Removal of volar locking plates after healing of a distal radius fracture is becoming increasingly common. However, it is unclear how the fracture healing proceeds and which defects remain. The aim of this study was to assess changes in bone microarchitecture and biomechanical properties in surgically treated radius fracture after volar locking plate removal.

Twelve patients were recruited after undergoing plate removal. High Resolution Quantitative Computed Tomography (HR-pQCT) was used to perform scans of the fractured and contralateral distal radius on average one (M1) and 16 months (M2) after plate removal. Parameters measured were cortical- (Dcomp), trabecular- (Dtrab) and total bone density (D100), as well as cortical thickness (Ct.Th). Axial bone stiffness (FE.Kaxial) was determined through linear micro-finite element analysis (µFEA).

At M1, no significant differences between fractured and contralateral side were detected except for Dcomp. At the fractured side, all parameters except for Dtrab increased significantly between M1 and M2. At M2, Ct.Th and FE.Kaxial were significantly higher at the fractured side compared to the contralateral side, but Dcomp remained significantly lower. Qualitatively, closure of the screw holes was observed between M1 and M2, while large trabecular defects remained.

Bone (re)modeling at the distal radius is an ongoing process even after plate removal and leads to a partial exaggeration of the bone properties relative to the intact contralateral side. It seems that the bone regains its biomechanical competence by closing screw holes and increasing cortical thickness, which compensates for trabecular defects that cannot be repaired.

III.

Far cortical locking (FCL) is a concept of locking plate fixation with reduced stiffness and symmetric micromotion to improve callus formation. The goal of our study was to review biomechanical data evaluating FCL plate and screw fixation versus standard locking (SL) plate and screw fixation by analyzing studies of cadaveric and synthetic bone models to draw biomechanical conclusions.

Biomechanical studies that compared FCL and SL plate fixation for simulated femoral fractures were reviewed for construct stiffness, load to failure, axial motion at the near and far cortices, and the difference between near and far cortical axial motion to demonstrate motion symmetry.

FCL decreased stiffness by 1.069 kN/mm compared to SL (95 % CI 0.405 to 1.732, p = 0.002). FCL demonstrated greater axial motion than SL in the near cortex by 0.425 mm (95 % CI 0.359 to 0.491, p < 0.001) and in the far cortex by 0.456 mm (95 % CI 0.378 to 0.534, p < 0.001). FCL resulted in symmetric motion with no significant difference between far and near cortices with the far cortex displacing 0.347 mm more than near (95 % CI -0.038 to 0.731, p = 0.78). SL resulted in asymmetric motion favoring the far cortex by 0.270 mm (0.096-0.443, p = 0.002). Construct strength was not significantly different with FCL load to failure 0.367 kN greater than SL (95 % CI -0.762 to 1.496, p = 0.524).

FCL screw fixation in femoral fractures achieves the goals of reducing construct stiffness and promoting more symmetric axial motion while maintaining construct strength. These results support the overall biomechanical goals of far cortical locking and should encourage investigation into its effects on clinical and radiographic outcomes.

This study aimed to compare the mechanical responses, including the stability and implant stress, of different proximal femoral fractures stabilized with an intramedullary system by finite element simulation. Furthermore, the effect of number of the lag screws, including one and two screws, was also investigated.

A numerical hip model was created first, and then four different types of proximal femoral fractures-namely femoral neck, intertrochanteric, reverse intertrochanteric, and subtrochanteric fractures-were employed in this study. An intramedullary nail system was used to fix the four fracture types. Furthermore, two different number of lag screws, either one bigger or two smaller, was also compared. The peak loading of the femur in level walking was used for comparison.

The results showed that both the peak displacement and the gap opening distance in the reversed intertrochanteric fracture were obviously higher than in the other fractures. Additionally, the peak equivalent stress of the intramedullary nail in the reversed intertrochanteric fracture was the highest among all the fractures. The stress on the nail in cases of reversed intertrochanteric fracture was 4.6 times (ranging from 132.9 to 616.8 MPa) and 4.4 times (ranging from 126 to 556 MPa) higher than in intertrochanteric fractures with one and two lag screws, respectively.

The intramedullary nail is a mechanically effective device for the fixation of proximal femoral fractures. However, to avoid the nail breakage the postoperative rehabilitation process for reversed intertrochanteric fracture should be slower compared to the neck, intertrochanteric and subtrochanteric fractures.

The "2 to 10% strain rule" for fracture healing has been widely interpreted to mean that interfragmentary strain greater than 10% predisposes a fracture to nonunion. This interpretation focuses on the gap-closing strain (axial micromotion divided by gap size), ignoring the region around the gap where osteogenesis typically initiates. The aim of this study was to measure gap-closing and 3D interfragmentary strains in plated ovine osteotomies and associate local strain conditions with callus mineralization.

MicroCT scans of eight female sheep with plated mid-shaft tibial osteotomies were used to create image-based finite element models. Virtual mechanical testing was used to compute postoperative gap-closing and 3D continuum strains representing compression (volumetric strain) and shear deformation (distortional strain). Callus mineralization was measured in zones in and around the osteotomy gap.

Gap-closing strains averaged 51% (mean) at the far cortex. Peak compressive volumetric strain averaged 32% and only a small tissue volume (average 0.3 cm3) within the gap experienced compressive strains > 10%. Distortional strains were much higher and more widespread, peaking at a mean of 115%, with a mean of 3.3 cm3 of tissue in and around the osteotomy experiencing distortional strains > 10%. Callus mineralization initiated outside the high-strain gap and was significantly lower within the fracture gap compared to around it at nine weeks.

Ovine osteotomies can heal with high gap strains (> 10%) dominated by shear conditions. High gap strain appears to be a transient local limiter of osteogenesis, not a global inhibitor of secondary fracture repair.

Axial micromotion between bone fragments can stimulate callus formation and fracture healing. In this study, we propose a novel mechanically compliant locking plate which achieves up to 0.6 mm of interfragmentary motion as flexures machined into the plate elastically deflect under physiological load. We investigated the biomechanical performance of three compliant plate variations in comparison to rigid control plates with small and large working lengths in a comminuted bridge plating scenario using humeral diaphysis surrogates. Under static axial loading, average interfragmentary motion was 6 times larger at 100 N (0.38 vs. 0.05 mm) and nearly three times larger at 350 N (0.58 vs. 0.2 mm) for compliant plates than rigid plates, respectively. Compliant plates delivered between 2.5 and 3.4 times more symmetric interfragmentary motion than rigid plates (p < 0.01). The bi-phasic stiffness of compliant pates provided 74%-96% lower initial axial stiffness up to approximately 100 N (p < 0.01), after which compliant plate stiffness was similar to rigid plates with increased working length (p > 0.3). The strength to failure of compliant plates under dynamic loading was on average 48%-55% lower than rigid plate groups (p < 0.01); however, all plates survived cyclic fatigue loading of 100,000 cycles at 350 N. This work characterizes the improvement in interfragmentary motion and the reduction in strength to failure of compliant plates compared to control rigid plates. Compliant plates may offer potential in comminuted fracture healing due to their ability to deliver symmetric interfragmentary motion into the range known to stimulate callus formation while surviving moderate fatigue loading with no signs of failure.

Background: Medial opening wedge high tibial osteotomy (HTO) treats medial knee osteoarthritis by realigning the knee joint, though it still carries quite a high risk of complications. A new Variable Fixation Locking Screw technology, designed to gradually reduce construct stiffness and promote bone healing, aims to address these issues. This observational study evaluates the safety and effectiveness of this innovative approach in improving clinical outcomes. Methods: Data were prospectively collected on a cohort of the first ten consecutive patients (over 18 years of age) who underwent corrective medial opening wedge high tibial osteotomy using Variable Fixation Locking Screws (VFLSs). The procedure followed the standard surgical technique, with osteotomies stabilized using a Tomofix plate and a combination of standard locking screws and VFLSs. This study aimed to evaluate outcomes such as fracture healing, patient safety, and procedural success at 6 and 12 weeks and at 6 months. Results: No complications, side effects, or need for implant removal were observed. By six months, 70% of patients showed radiographic and clinical healing, and 100% of patients achieved full functional recovery without any issues like length discrepancy, instability, pain, or joint stiffness. Conclusions: This first clinical observation study indicates that Variable Fixation Locking Screws are safe and effective for medial opening wedge high tibial osteotomies, showing promising results in reducing the risk of delayed closure or non-closure of the wedge. Further studies with a larger patient population are needed to confirm their effectiveness.

Both initial mechanical stability and subsequent axial interfragmentary micromotion at fracture ends play crucial roles in fracture healing. However, the conversion timing of variable fixation and its effect on and mechanism of fracture healing remain inadequately explored.

A magnesium degradation-induced variable fixation plate (MVFP) for femurs was designed, and its conversion timing was investigated both in vitro and in vivo. Then, locking plates and MVFPs with and without a magnesium shim were implanted in rabbit femur fracture models. X-ray photography and micro computed tomography (micro-CT) were performed to observe the healing of the fracture. Toluidine blue and Masson's trichrome staining were performed to observe new bone formation. The torsion test was used to determine the strength of the bone after healing. Finally, reverse transcription-polymerase chain reaction (RT-PCR) and western blotting were used to detect the expression of osteogenesis-related genes in the three groups.

The MVFP with sample 3 magnesium shim showed greater axial displacement within 15 days in vitro, and its variable capability was likewise confirmed in vivo. X-ray photography and micro-CT indicated increased callus formation in the variable fixation group. Toluidine blue and Masson's trichrome staining revealed less callus formation on the rigid fixation side of the locking plate, whereas the variable fixation group presented more callus formation, more symmetrical intraosseous calli, and greater maturity. The torsion test indicated greater torsional resistance of the healed bone in the variable fixation group. RT-PCR and western blotting revealed that the expression levels of BMP2 and OPG increased during early fracture stages but decreased in late fracture stages, whereas RANKL expression showed the opposite trend in the variable fixation group.

MVFP promoted faster and stronger bone healing in rabbits, potentially by accelerating the expression of BMP2 and modulating the OPG/RANKL/RANK signaling axis. This study offers valuable insights for the clinical application of variable fixation technology in bone plates and contributes to the advancement of both internal fixation technology and theory.

level V.

Comminuted proximal humerus fractures are often repaired by metal plates, but potentially still experience bone refracture, bone "stress shielding," screw perforation, delayed healing, and so forth. This "proof of principle" investigation is the initial step towards the design of a new plate using alternative materials to address some of these problems. Finite element modeling was used to create design graphs for bone stress, plate stress, screw stress, and interfragmentary motion via three different fixations (no, 1, or 2 "kickstand" [KS] screws across the fracture) using a wide range of plate elastic moduli (EP = 5-200 GPa). Well-known design optimization criteria were used that could minimize bone, plate, and screw failure (i.e., peak stress < ultimate tensile strength), reduce bone "stress shielding" (i.e., bone stress under the new plate ≥ bone stress for an intact humerus, titanium plate, and/or steel plate "control"), and encourage callus growth leading to early healing (i.e., 0.2 mm ≤ axial interfragmentary motion ≤ 1 mm; shear/axial interfragmentary motion ratio <1.6). The findings suggest that a potentially optimal configuration involves the new plate being manufactured from a material with an EP of 5-41.5 GPa with 1 KS screw; but, using no KS screws would cause immediate bone fracture and 2 KS screws would almost certainly lead to delayed healing. A prototype plate might be fabricated using alternative materials suggested for orthopedics and other industries, like fiber-metal laminates, fiber-reinforced polymers, metal foams, pure polymers, shape memory alloys, or 3D-printed porous metals.

Osteoporosis is a major risk factor for fragility fractures. The British Orthopaedics Association Standards for Trauma and Orthopaedics (BOAST) and Getting it Right First Time (GIRFT) guidelines on fragility fracture management highlight the need to initiate prompt, coordinated multidisciplinary care with a focus on early mobilisation to improve patient outcomes. Medical management of fragility fractures focuses on the prevention of progressive frailty. Advancements in medical therapy include romosozumab, recommended by the National Institute for Health and Care Excellence guidance in patients with imminent fracture risk, which improves overall bone mineral density. Regional nerve blocks are an increasingly common form of perioperative anaesthesia with fewer side effects than opioids and rates of postoperative delirium. Surgical management of osteoporotic fractures poses unique challenges, such as complex fracture patterns and increased risk of implant failure. The surgical approach to fragility fractures has undergone major advancements over the past 20 years, with developments such as polyaxial locking and far cortical locking systems that achieve secondary bone healing, as well as cement augmented screw fixation to provide stable fixation in osteoporotic bone. The development of minimally invasive surgical approaches has led to improved periosteal blood flow around a fracture site, as well as reduced operating time, hospital stay, and time to pain-free weight-bearing. In the future, we are likely to see a focus on minimally invasive surgical techniques for vertebral and pelvic fragility fractures to improve patients' mobility and independence before discharge, subsequently improving quality of life and preventing progressive frailty.

Fixation of distal femoral fractures remains a challenge, and nonunions are common with standard constructs. Far cortical locking (FCL) constructs have been purported to lead to improved fracture-healing as compared with that achieved with traditional locking bridge plates. We sought to test this hypothesis in a comparative effectiveness clinical trial.

This randomized trial was performed across 16 centers and included adult patients with an AO/OTA type 33A or 33C distal femoral fracture that was suitable for bridging fixation. We excluded patients with periprosthetic fractures. Participants were randomly assigned to either FCL fixation or standard locking plate fixation. The primary outcome was a hierarchical composite of radiographic and clinical fracture-healing at 3 months after fixation. We estimated between-group differences with use of the win ratio approach. Secondary outcomes included radiographic healing, clinical fracture-healing, complications, reoperations, and health-related quality of life (Short Form-36 Health Survey Version 2 [SF-36] Physical Component Summary and Mental Component Summary scores) at 3, 6, and 12 months after fixation.

We randomly assigned 193 patients to treatment with either FCL screws (96 patients) or standard screws (97 patients). The study population had a mean age of 63.4 years, consisted predominantly of women (68%), and was well-balanced between AO/OTA 33A and 33C fractures. Based on 4,355 pairwise comparisons, the calculated win ratio was 1.18 (95% confidence interval [CI], 0.77 to 1.79; p = 0.45), indicating that patients assigned to FCL screws had better outcomes in 51% of the comparisons. Radiographic healing did not differ significantly between the groups (odds ratio, 1.36; 95% CI, 0.69 to 2.72; p = 0.38), nor did Function IndeX for Trauma (FIX-IT) scores (p = 0.41). There were no significant differences between the groups in terms of SF-36 Physical Component Summary scores at 3 months or in the change in scores at 12 months after fixation.

In this multicenter randomized trial of adult patients with an AO/OTA type 33A or 33C distal femoral fracture, similar clinical and radiographic healing outcomes were observed in the FCL and standard fixation groups.

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Distal femoral fractures account for less than 1% of all fractures. The therapy of choice is usually surgical stabilization. Despite advances in implant development over the past few years, complication rate remains comparatively high. The aim of this study is to analyze our results with plate fixation of distal femoral fractures with a focus on complication and fracture healing rates.

In this retrospective cohort study, patients (> 18 years) with distal femoral fractures treated at an urban level I trauma center between 2015 and 2022 were analyzed.

In total, 206 patients (167 female, 39 male) with an average age of 75 (SD 16) years were diagnosed with a fracture of the distal femur. One hundred fourteen of these patients were treated surgically by means of plate osteosynthesis. In 13 cases (11.41%), a revision procedure had to be performed. The indication for surgical revision was mechanical failure in eight cases (7.02%) and septic complication in five cases (4.39%). Periprosthetic fractures were more likely to cause complications overall (19.6% versus 4.76%) and further included all documented septic complications. The analysis of modifiable surgical factors in the context of plate osteosynthesis showed higher complication rates for cerclage in the fracture area compared with plate-only stabilizations (44.44% versus 22.22%).

The data show an increased amount of revisions and a significantly higher number of septic complications in the treatment of periprosthetic fractures of the distal femur compared with non-periprosthetic fractures. The detected combination of plates together with cerclage was associated with higher complication rates. Level of evidence Level III retrospective comparative study.

 The aim of this study was to evaluate the stress changes in the radii beneath the locking plates (LP) of dogs implanted with LP using finite element analysis (FEA).

 The study included radii harvested from eight dogs. After computed tomography (CT) scans of the forelimb, the articular surface of the radius was fixed using resin. Material tests were conducted to identify the yield and fracture points and for verification with FEA. The CT data of the radius were imported into FEA software. The radii were classified into three groups based on the placement of the LP (nonplate placement, intact group; 1 mm above the radial surface, LP + 1 mm group; 3 mm above the radial surface, LP + 3 mm group). Equivalent, maximum, and minimum principal stresses and minimum principal strain were measured after FEA at the radial diaphysis beneath the plate.

 In shell elements, the LP + 1 mm and LP + 3 mm groups showed a significantly lower maximum principal stress compared with the intact group. In solid elements, the LP + 1 mm and LP + 3 mm groups showed a significantly higher equivalent stress and a significantly lower maximum principal stress compared with the intact group.

 When an axial load is applied to the radius, LP placement reduces the tension stress on the cortical bone of the radius beneath the plate, possibly related to implant-induced osteoporosis and bone formation in the cortical bone beneath the plate.

With the introduction and continuous improvement in operative fracture fixation, even the most severe bone fractures can be treated with a high rate of successful healing. However, healing complications can occur and when healing fails over prolonged time, the outcome is termed a fracture non-union. Non-union is generally believed to develop due to inadequate fixation, underlying host-related factors, or infection. Despite the advancements in fracture fixation and infection management, there is still a clear need for earlier diagnosis, improved prediction of healing outcomes and innovation in the treatment of non-union.

This review provides a detailed description of non-union from a clinical perspective, including the state of the art in diagnosis, treatment, and currently available biomaterials and orthobiologics.Subsequently, recent translational development from the biological, mechanical, and infection research fields are presented, including the latest in smart implants, osteoinductive materials, and in silico modeling.

The first challenge for future innovations is to refine and to identify new clinical factors for the proper definition, diagnosis, and treatment of non-union. However, integration of in vitro, in vivo, and in silico research will enable a comprehensive understanding of non-union causes and correlations, leading to the development of more effective treatments.

This study experimentally validated a computationally optimized screw number and screw distribution far cortical locking distal femur fracture plate and compared the results to traditional implants.

24 artificial femurs were osteotomized with a 10 mm fracture gap 60 mm proximal to the intercondylar notch. Three fixation constructs were used. (i) Standard locking plates secured with three far cortical locking screws inserted according to a previously optimized distribution in the femur shaft (n = 8). (ii) Standard locking plates secured with four standard locking screws inserted in alternating plate holes in the femur shaft (n = 8). (iii) Retrograde intramedullary nail secured proximally with one anterior-posterior screw and distally with two oblique screws (n = 8). Axial hip forces (700 and 2800 N) were applied while measuring axial interfragmentary motion, shear interfragmentary motion, and overall stiffness.

Experimental far cortical locking plate results compared well to published computational findings. Far cortical locking femurs contained the highest axial motion within the potential ideal range of 0.2-1 mm and a sheer-to-axial motion ratio < 1.6 at toe-touch weight-bearing (700 N). At full weight-bearing (2800 N), Standard locking-plated femurs had the only axial motion within 0.2-1 mm but had an excess shear-to-axial motion ratio. Nail-implanted femurs underperformed at both forces.

For toe-touch weight-bearing, the far cortical locking construct provided optimal biomechanics to allow moderate motion, which has been suggested to encourage early callus formation. Conversely, at full weight-bearing, the standard locking construct offered the biomechanical advantage on fracture motion.

The controlled dynamization of fractures can promote natural fracture healing by callus formation, while overly rigid fixation can suppress healing. The advent of locked plating technology enabled new strategies for the controlled dynamization of fractures, such as far cortical locking (FCL) screws or active plates with elastically suspended screw holes. However, these strategies did not allow for the use of non-locking screws, which are typically used to reduce bone fragments to the plate. This study documents the first in vivo study on the healing of ovine tibia osteotomies stabilized with an advanced active plate (AAP). This AAP allowed plate application using any combination of locking and non-locking screws to support a wide range of plate application techniques. At week 9 post-surgery, tibiae were harvested and tested in torsion to failure to assess the healing strength. The five tibiae stabilized with an AAP regained 54% of their native strength and failed by spiral fracture through a screw hole, which did not involve the healed osteotomy. In comparison, tibiae stabilized with a standard locking plate recovered 17% of their strength and sustained failure through the osteotomy. These results further support the stimulatory effect of controlled motion on fracture healing. As such, the controlled dynamization of locked plating constructs may hold the potential to reduce healing complications and may shorten the time to return to function. Integrating controlled dynamization into fracture plates that support a standard fixation technique may facilitate the clinical adoption of dynamic plating.

Delayed union and non-union of fractures continue to be a major problem in trauma and orthopedic surgery. These cases are challenging for the surgeon. In addition, these patients suffer from multiple surgeries, pain and disability. Furthermore, these cases are a major burden on healthcare systems. The scientific community widely agrees that the stability of fixation plays a crucial role in determining the outcome of osteosynthesis. The extent of stabilization affects factors like fracture gap strain and fluid flow, which, in turn, influence the regenerative processes positively or negatively. Nonetheless, a growing body of literature suggests that during the fracture healing process, there exists a critical time frame where intervention can stimulate the bone's return to its original form and function. This article provides a summary of existing evidence in the literature regarding the impact of different levels of fixation stability on the strain experienced by newly forming tissues. We will also discuss the timing and nature of this "window of opportunity" and explore how current knowledge is driving the development of new technologies with design enhancements rooted in mechanobiological principles.

Distal femur fractures are challenging injuries to manage, and complication rates remain high. This article summarizes the international and basic science perspectives regarding distal femoral fractures that were presented at the 2022 Orthopaedic Trauma Association Annual Meeting. We review a number of critical concepts that can be considered to optimize the treatment of these difficult fractures. These include biomechanical considerations for distal femur fixation constructs, emerging treatments to prevent post-traumatic arthritis, both systemic and local biologic treatments to optimize nonunion management, the relative advantages and disadvantages of plate versus nail versus dual-implant constructs, and finally important factors which determine outcomes. A robust understanding of these principles can significantly improve success rates and minimize complications in the treatment of these challenging injuries.

Treatment of osteoporotic distal femur fractures is often complicated by a high rate of nonunion and varus collapse. For such fractures, lateral plating with lateral incision and double plating with anterior paramedial incision have shown promising results in the recent literature. The hypothesis of this study was that bilateral plating of comminuted distal femur fractures in osteoporotic patients would result in higher union rates and lower revision rates compared to an isolated lateral locking plate. The study included 56 patients (23 males, 33 females) with supracondylar femur fracture. According to the OA/OTA classification, 9 were type A3, 8 were A2, 13 were C1, 16 were C2, and 10 were C3. The mean follow-up period was 12 months, with 29 patients treated using lateral mini-incision, lateral locking plate, and 27 patients treated with anterior paramedial incision, dual plating. The clinical and radiological results were evaluated. The mean duration of radiological union in the studied population was 15 ± 2.1 months (range, 11-21 months) in the single plate group (Group A), and 13.5 ± 2.6 months (range, 9-19 months) in the double plate group (Group B). Mean ROM was 112.3° and flexion contracture 4° in Group A, and ROM 108.3° and flexion contracture 6.7° in Group B. (P = .15). The average Western Ontario and McMaster Universities Arthritis Index (WOMAC) score was 85.6 points in Group A and 83.5 points in Group B (P = .2278). The postoperative anteversion measurement in the operated extremity ranged from -15 to 19 in Group A, and from 5 to 18 in Group B. When the anteversion degrees were compared between the injured and uninjured extremities in the postoperative period, a significant difference was observed within Group A (P = .0018), but no significant difference was observed in Group B (P = .2492). Dual plate fixation using the anterior paramedial approach is an effective operative method for osteoporotic distal femur fractures. This has many advantages such as precise exposure, easy manipulation, anatomic reduction, and stable fixation. However, for surgical indications and medial bone defects > 1 cm, grafting should be performed.

(1) Background: Bone healing is influenced by various mechanical factors, such as stability, interfragmentary motion, strain rate, and direction of loading. Far cortical locking (FCL) is a novel screw design that promotes bone healing through controlled fracture motion. (2) Methods: This study compared the outcome of distal femur fractures treated with FCL or SL (standard locking) screws and an NCB plate in a randomised controlled prospective multicentre trial. The radiographic union scale (RUST) and healing time was used to quantify bone healing on follow-up imaging. (3) Results: The study included 21 patients with distal femur fractures, 7 treated with SL and 14 treated with FCL screws. The mean working length for patients with SL screws was 6.1, whereas for FCL screws, it was 3.9. The mean RUST score at 6 months post fracture was 8.0 for patients with SL plates and 7.3 for patients with FCL plates (p value > 0.05). The mean healing time was 6.5 months for patients with SL plates and 9.9 months for patients with FCL plates (p value < 0.05). (4) Conclusions: Fractures fixed with SL plates had longer working lengths and faster healing times when compared to FCL constructs, suggesting that an adequate working length is important for fracture healing regardless of screw choice.

Osteoporotic supracondylar femoral fractures (OSFF) have historically been managed by the lateral anatomical locking plate with reasonable success. However, for some kinds of unstable and osteoporotic supracondylar femoral fractures (UOSFF), especially with bone defects, unilateral locking plate (ULLP) fixation failed or resulted in implant breakage. This paper is going to explore what is the stable internal fixation for UOSFF by adding the bilateral locking plate (BLLP) fixation.

OSFF models were divided into two groups according to the fracture line type, which would be further subdivided according to their angle of fracture line, presence of bone defect, location, and degree of bone defect. Thereafter, kinds of locking plate fixation were constructed. A 2010-N load was applied to the femoral head, and a 1086-N load was applied to the greater trochanter. In this condition, the maximum von Mises stress distribution of models were investigated.

Firstly, it was obviously found that the stress concentration in the BLLP group was more dispersed than that in the ULLP group. Secondly, according to the fracture line analysis, the stress value of fracture line type in "\" model group was higher than that of "/" model group. Moreover, with the increase in fracture line angle, the stress value of the model increased. Thirdly, from the bone defect analysis, the stress value of the medial bone defect (MBD) model group was higher than that of the lateral bone defect (LBD) model group. And as the degree of bone defect increased, the stress value increased gradually in the model group.

In the following four cases, lateral unilateral locking plate fixation cannot effectively stabilize the fracture end, and double locking plate internal fixation is a necessary choice. First, when the angle of the fracture line is large (30, 45). Second, when the fracture line type is "/." Third, when the bone defect is large. Fourth, when the bone defect is medial.

Locking a compression plate is a more favorable surgical technique than intramedullary nailing in the treatment of distal femur fractures. This study analyzed the risk factors of proximal screw breakage retrospectively, which was confirmed in the patients with plate removal after bony union.

A total of 140 patients who were fixed by MIPO using ZPLP from 2009 to 2019 were identified. A total of 42 patients met the inclusion criteria and were included. The screw breakage group (12 patients) and the non-breakage group (30 patients) were compared.

Approximately 12 (28.6%) of 42 plate-removal patients showed proximal screw breakage. The breakage of proximal screws developed at the junction of the screw head and neck. The number of broken proximal screws averaged 1.4 (1~4). The breakage of the proximal screw even after the bony union is more frequent in older patients (p = 0.023), the dominant side (p = 0.025), the use of the cortical screw as the proximal uppermost screw (p = 0.039), and the higher plate-screw density (p = 0.048).

Advanced age, dominant side, use of the cortical screw as the uppermost screw, and higher plate-screw density were related to proximal screw breakage. When the plate is removed after bony union or delayed union is shown in these situations, the possibility of proximal screw breakage should be kept in mind.

Secondary bone healing requires an adequate level of mechanical stimulation expressed by the extent of interfragmentary motion in the fracture. However, there is no consensus about when the mechanical stimulation should be initiated to ensure a timely healing response. Therefore, this study aims to compare the effect of the immediate and delayed application of mechanical stimulation in a large animal model.

Twelve Swiss White Alpine sheep underwent partial osteotomy of a tibia that was stabilised with an active fixator inducing well-controlled mechanical stimulation. Animals were randomly assigned into two groups with different stimulation protocols. The immediate group received daily stimulation (1000 cycles/day) from the first day post-operation, while in the delayed group, stimulation began only on the 22nd day post-operation. Healing progression was evaluated daily by measuring the in vivo stiffness of the repair tissue and by quantifying callus area on weekly radiographs. All animals were euthanised five weeks post-op. Post-mortem callus volume was determined from high-resolution computer tomography (HRCT).

Fracture stiffness (p < 0.05) and callus area (p < 0.01) were significantly larger for the immediate group compared to the delayed stimulation group. In addition, the callus volume measured on the post-mortem HRCT showed 319 % greater callus volume for the immediate stimulation group (p < 0.01).

This study demonstrates that a delay in the onset of mechanical stimulation retards fracture callus development and that mechanical stimulation already applied in the early post-op phase promotes bone healing.

To determine whether deficient early callus formation can be defined objectively based on the association with an eventual nonunion and specific patient, injury, and treatment factors.

Final healing outcomes were documented for 160 distal femur fractures treated with locked bridge plate fixation. Radiographic callus was measured on postoperative radiographs until union or nonunion had been declared by the treating surgeon. Deficient callus was defined at 6 and 12 weeks based on associations with eventual nonunion through receiver-operator characteristic analysis. A previously described computational model estimated fracture site motion based on the construct used. Univariable and multivariable analyses then examined the association of patient, injury, and treatment factors with deficient callus formation.

There were 26 nonunions. The medial callus area at 6 weeks <24.8 mm 2 was associated with nonunion (12 of 39, 30.8%) versus (12 of 109, 11.0%), P = 0.010. This association strengthened at 12 weeks with medial callus area <44.2 mm 2 more closely associated with nonunion (13 of 28, 46.4%) versus (11 of 120, 9.2%), P <0.001. Multivariable logistic regression analysis found limited initial longitudinal motion (OR 2.713 (1.12-6.60), P = 0.028)) and Charlson Comorbidity Index (1.362 (1.11-1.67), P = 0.003) were independently associated with deficient callus at 12 weeks. Open fracture, mechanism of injury, smoking, diabetes, plate material, bridge span, and shear were not significantly associated with deficient callus.

Deficient callus at 6 and 12 weeks is associated with eventual nonunion, and such assessments may aid future research into distal femur fracture healing. Deficient callus formation was independently associated with limited initial longitudinal fracture site motion derived through computational modeling of the surgical construct but not more routinely discussed parameters such as plate material and bridge span. Given this, improved methods of in vivo assessment of fracture site motion are necessary to further our ability to optimize the mechanical environment for healing.

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

The optimal balance between mechanical environment and biological factors is crucial for successful bone healing, as they synergistically affect bone development. Any imbalance between these factors can lead to impaired bone healing, resulting in delayed union or non-union. To address this bone healing disorder, clinicians have adopted a technique known as "dynamization" which involves modifying the stiffness properties of the fixator. This technique facilitates the establishment of a favorable mechanical and biological environment by changing a rigid fixator to a more flexible one that promotes bone healing. However, the dynamization of fixators is selective for certain types of non-union and can result in complications or failure to heal if applied to inappropriate non-unions. This review aims to summarize the indications for dynamization, as well as introduce a novel dynamic locking plate and various techniques for dynamization of fixators (intramedullary nails, steel plates, external fixators) in femur and tibial fractures. Additionally, Factors associated with the effectiveness of dynamization are explored in response to the variation in dynamization success rates seen in clinical studies.

Objective: To evaluate the biomechanical effects of Poller screws (PS) combined with small-diameter intramedullary nails in the treatment of distal tibial fractures at different locations and on different planes. Methods: Nine finite element (FE) models were used to simulate the placement of the intramedullary nail (IMN) and the PS for distal tibial fractures. Structural stiffness and interfragmentary motion (IFM) through the fracture were investigated to assess the biomechanical effects of the PS. The allowable stress method was used to evaluate the safety of the construct. Results: With the axial load of 500 N, the mean axial stiffness of IMN group was 973.38 ± 95.65 N/mm, which was smaller than that at positions A and B of the coronal group and sagittal group (p < 0.05). The shear IFM of the IMN group was 2.10 ± 0.02 mm, which were smaller than that at positions A and B of the coronal group and sagittal group (p < 0.05). Under physiological load, the stresses of all internal fixation devices and the nail-bone interface were within a safe range. Conclusion: In the treatment of distal tibial fractures, placing the PS in the proximal fracture block can obtain better biomechanical performance. The IMN fixation system can obtain higher structural stiffness and reduce the IFM of the fracture end by adding PS.

The extramedullary locking plate system was the common internal fixation method for hip fractures. However, common plates were poorly matched to femur, which was because they were designed based on anatomical parameters of the Western populations. Therefore, the aim was to design an end-structure of the anatomical proximal femoral locking plate that closely matched the anatomy of the Chinese population.

From January 2010 to December 2021, consecutive patients aged 18 years and older who underwent a full-length computed tomography scan of the femur were included. The end-structure (male and female model) of the anatomical proximal femoral locking plate was designed based on anatomical parameters of femurs that were measured in three-dimensional space using computer-assisted virtual technology. The match degree between the end-structure and femur were evaluated. Inter-observer and intra-observer agreement for the evaluation of match degree was assessed. The matching evaluation based on a three-dimensional printing model was regarded as the gold standard to assess the reliability.

A total of 1672 patients were included, with 701 men and 971 women. Significant differences were seen between male and female for all parameters of the proximal femur (all P <0.001). All match degree of end-structure was over 90%. Inter-observer and intra-observer agreement was almost perfect (all kappa value, >0.81). The sensitivity, specificity, and percentage of correct interpretation of matching evaluation in the computer-assisted virtual model was all greater than 95%. From femur reconstruction to completion of internal fixation matching, the process takes about 3 min. Moreover, reconstruction, measurement, and matching were all completed in one system.

The results showed that based on the larger sample of femoral anatomical parameters, a highly matching end-structure of anatomical proximal femoral locking plate for Chinese population could be designed with use of computer-assisted imaging technology.

Early therapeutic exercises are vital for the healing of distal radius fractures (DRFs) treated with the volar locking plate. However, current development of rehabilitation plans using computational simulation is normally time-consuming and requires high computational power. Thus, there is a clear need for developing machine learning (ML) based algorithms that are easy for end-users to implement in daily clinical practice. The purpose of the present study is to develop optimal ML algorithms for designing effective DRF physiotherapy programs at different stages of healing.

First, a three-dimensional computational model for the healing of DRF was developed by integrating mechano-regulated cell differentiation, tissue formation and angiogenesis. The model is capable of predicting time-dependant healing outcomes based on different physiologically relevant loading conditions, fracture geometries, gap sizes, and healing time. After being validated using available clinical data, the developed computational model was implemented to generate a total of 3600 clinical data for training the ML models. Finally, the optimal ML algorithm for each healing stage was identified.

The selection of the optimal ML algorithm depends on the healing stage. The results from this study show that cubic support vector machine (SVM) has the best performance in predicting the healing outcomes at the early stage of healing, while trilayered ANN outperforms other ML algorithms in the late stage of healing. The outcomes from the developed optimal ML algorithms indicate that Smith fractures with medium gap sizes could enhance the healing of DRF by inducing larger cartilaginous callus, while Colles fractures with large gap sizes may lead to delayed healing by bringing excessive fibrous tissues.

ML represents a promising approach for developing efficient and effective patient-specific rehabilitation strategies. However, ML algorithms at different healing stages need to be carefully chosen before being implemented in clinical applications.

The purpose of this historical review is to illustrate the progression and evolution of treatment for distal femur fractures.

Scientific literature was searched for descriptions of treatment for distal femur fractures to provide an in-depth overview of the topic, with emphasis on the evolution of surgical constructs used to treat these fractures.

Prior to the 1950s, distal femur fractures were treated nonoperatively, resulting in considerable morbidity, limb deformity, and limited function. As principles of surgical intervention for fractures emerged in the 1950s, surgeons developed conventional straight plates to better stabilize distal femur fractures. Angle blade plates and dynamic condylar screws emerged out of this scaffolding to prevent post-treatment varus collapse. Meanwhile, intramedullary nails, and later, in the 1990s, locking screws, were introduced to minimize soft tissue disruption. Treatment failure led to the development of locking compression plates with the advantage of accommodating either locking or nonlocking screws. Despite this advancement, the rare but significant incidence of nonunion has not been eliminated, leading to the recognition of the biomechanical environment as important for prevention and the development of active plating techniques.

Emphasis for the surgical treatment of distal femur fractures has incrementally progressed over time, with initial focus on complete stabilization of the fracture while the biological environment surrounding the fracture was ignored. Techniques slowly evolved to minimize soft tissue disruption, allow more ease of implant placement at the fracture site, and attend to the systemic health of the patient, while simultaneously ensuring appropriate fracture fixation. Through this dynamic process, the desired results of complete fracture healing and maximization of functional outcomes have emerged.

A lot of evidence has shown the importance of stimulating cell mechanically during bone repair. In this study, we modeled the challenging fracture healing of a large bone defect in tibial diaphysis. To fill the fracture gap, we considered the implantation of a porous osteoconductive biomaterial made of poly-lactic acid wrapped by a hydrogel membrane mimicking osteogenic properties of the periosteum. We identified the optimal loading case that best promotes the formation and differentiation into bone tissue. Our results support the idea that a patient's rehabilitation program should be adapted to reproduce optimal mechanical stimulations.

A locking compression plate (LCP) of the distal femur is used as an external fixator for lower tibial fractures. However, in clinical practice, the technique lacks a standardized approach and a strong biomechanical basis for its stability.

In this paper, internal tibial LCP fixator (Group IT-44), external tibial LCP fixator (Group ET-44), external distal femoral LCP fixator (Group EF-44, group EF-33, group EF-22), and conventional external fixator (Group CEF-22) frames were used to fix unstable fracture models of the lower tibial segment, and anatomical studies were performed to standardize the operation as well as to assess the biomechanical stability and adjustability of the distal femoral LCP external fixator by biomechanical experiments.

It was found that the torsional and flexural stiffnesses of group EF-44 and group EF-33 were higher than those of group IT-44 and group ET-44 (p < 0.05); the flexural stiffness of group EF-22 was similar to that of group IT-44 (p > 0.05); and the compressive stiffness of all three EF groups was higher than that of group ET-44 (p < 0.05). In addition, the flexural and compressive stiffnesses of the three EF groups decreased with the decrease in the number of screws (p < 0.05), while the torsional stiffness of the three groups did not differ significantly between the two adjacent groups (p > 0.05). Group CEF-22 showed the highest stiffnesses, while group ET-44 had the lowest stiffnesses (P < 0.05).

The study shows that the distal femoral LCP has good biomechanical stability and adjustability and is superior to the tibial LCP as an external fixator for distal tibial fractures, as long as the technique is used in a standardized manner according to the anatomical studies in this article.

Understanding factors that affect bone response to trauma is integral to forensic skeletal analysis. It is essential in forensic anthropology to identify if impaired fracture healing impacts assessment of post-traumatic time intervals and whether a correction factor is required. This paper presents a synthetic review of the intersection of the literature on the immune system, bone biology, and osteoimmunological research to present a novel model of interactions that may affect fracture healing under autoimmune conditions. Results suggest that autoimmunity likely impacts fracture healing, the pathogenesis however, is under researched, but likely multifactorial. With autoimmune diseases being relatively common, significant clinical history should be incorporated when assessing skeletal remains. Future research includes the true natural healing rate of bone; effect of autoimmunity on this rate; variation of healing with different autoimmune diseases; and if necessary, development of a correction factor on the natural healing rate to account for impairment in autoimmunity.

Treatment of distal femur fractures have reported high fracture healing complications in several studies. The development of far cortical locking (FCL) technology results in improved fracture healing outcomes. There are biomechanical and animal studies demonstrating that the locked plating incorporating FCL screws provides a more flexible form of fixation compared to traditional locking plates (LP). Clinical studies have shown that the commercially available Zimmer Motionloc system with FCL screws provide good results in distal femur fractures and periporsthetic distal femur fractures. FCL constructs may help resolve fracture healing problems in the future. However, there is not enough available clinical evidence to conclusively indicate whether clinical healing rates are improved with FCL screw constructs compared to traditional LP's. Therefore, further prospective study designs are needed to compare FCL to LP constructs and to investigate the role of interfragmentary motion on callus formation. Level of Evidence: V.

Locking plate technology was developed approximately 25-years-ago and has been successfully used since. Newer designs and material properties have been used to modify the original design, but these changes have yet to be correlated to improved patient outcomes. The purpose of this study was to evaluate the outcomes of first-generation locking plate (FGLP) and screw systems at our institution over an 18 year period.

Between 2001 to 2018, 76 patients with 82 proximal tibia and distal femur fractures (both acute fracture and nonunions) who were treated with a first-generation titanium, uniaxial locking plate with unicortical screws (FGLP), also known as a LISS plate (Synthes Paoli Pa), were identified and compared to 198 patients with 203 similar fracture patterns treated with 2nd and 3rd generation locking plates, or Later Generation Locking Plates (LGLP). Inclusion criteria was a minimum of 1-year follow-up. At latest follow-up, outcomes were assessed using radiographic analysis, Short Musculoskeletal Functional Assessment (SMFA), VAS pain scores, and knee ROM. All descriptive statistics were calculated using IBM SPSS (Armonk, NY).

A total of 76 patients with 82 fractures had a mean 4-year follow-up available for analysis. There were 76 patients with 82 fractures fixed with a First-generation locking plate. The mean age at time of injury for all patients was 59.2 and 61.0% were female. Mean time to union for fractures about the knee fixed with FGLP was by 5.3 months for acute fractures and 6.1 months for nonunions. At final follow-up, the mean standardized SMFA for all patients was 19.9, mean knee range of motion was 1.6°-111.9°, and mean VAS pain score was 2.7. When compared to a group of similar patients with similar fractures and nonunions treated with LGLPs there were no differences in outcomes assessed.

Longer-term outcomes of first-generation locking plates (FGLP) demonstrate that this construct provides for a high rate of union and low incidence of complications, as well as good clinical and functional results. Level of Evidence: III.

To report the peri-implant fracture rates after locked plating of distal femur fractures and examine risk factors.

Over a 7 year period, 89 AO/OTA 33A/C distal femur fractures were identified and reviewed. After excluding treatment with intramedullary nails, age under 50, those with the proximal femur protected, or those without 6 months of follow-up, 42 distal femur fractures in 41 patients, mean age 72.3 were studied. All were treated with lateral locked plating of distal femur fractures. The details of the constructs were recorded. Mean follow-up was 562 days (18.7 months).

3/42 were open injuries, 9/42 were type C, 16/42 were type A, and 17 were periprosthetic above a knee arthroplasty. Two patients were treated with a dynamic plating construct using all far-cortical locking (FCL) screws in the diaphysis. 40 patients were treated with a variety of non-dynamic diaphyseal constructs including locking, non-locking, and four with 1-2 FCL screws distally. There was one asymptomatic nonunion. 2/2 patients in the dynamically plated group experienced a peri-implant fracture versus 1/40 in the non-dynamically plated group (p = 0.001). 3/9 with an all-locked construct versus 0/25 patients with a most proximal non-locking screw experienced a fracture.

The overall peri-implant fracture risk was 7.1% (3/42), 3/17 patients with a locking screw most proximal experienced a peri-implant fracture, 3/9 with an all-locking construct, and 2/2 patients with a dynamic construct experienced a fracture. These findings merit additional clinical and biomechanical study.

Significant work has been done in recent years on treatment strategies for distal femur fractures. Inclusive reviews on periprosthetic fractures of distal femur have been carried out recently, but there is a lack of such reviews on the subject of native distal femur fractures in the recent literature. In this narrative review, we are set out to address the latest updates on geriatric non-periprosthetic distal femur fractures, and perform a rapid review over different treatment options, arriving at a summarized proposed treatment algorithm.

 The aim of this study was to evaluate the influence of near-cortical over-drilling holes on the mechanical behaviour of locking plate constructs applied in maned wolf's femur by using mechanical testing and finite element method (FEM).

 Seven pairs of adult maned wolves (Chrysocyon brachyurus) femur bones were randomly distributed into four groups. In all groups, a 3.5 mm locking compression plate, designed with 12 combi-holes and one locked, was applied to the lateral surface of the femur. G1 (n = 4) received bicortical locking screws placed in holes 1, 3, 5, 8, 10 and 12. In G2 (n = 5), the plate was applied as used in G1, but the application of the locked screws involved the near-cortical over-drilling technique. In G3 (n = 4), the plate was applied as used in G2, but the size of the near-cortical over-drilling was larger. The combi-holes 6 and 7 were maintained over a 10 mm fracture gap without screws. All constructs were tested for failure in the axial load. The axial load was applied eccentrically to the femoral head.

 Statistical differences were observed in the maximum load with G3 > G1 and G3 > G2, and in the deflection with G2 > G1 and G2 > G3. The FEM showed the lowest total displacement of the bone-plate constructs as well as of the plate in G1 compared with G2 and G3.

 The near-cortical over-drilling technique used in unstable fractures induced in the maned wolf's femur showed by static axial compression test that maximum load and deflection are dependent on drill hole size induced in the near-cortex. Based on FEM, the lowest total displacement of the bone-plate constructs was observed in Group 1.

To determine the clinical outcome of patients who had been treated with bone allografts during open reduction and internal fixation (ORIF) of tibial head fractures.

Patients who suffered a medial, lateral, or bicondylar fracture of the tibial plateau and underwent surgical treatment by open reduction and internal fixation (ORIF) using human femoral head bone allografts were included. Patients were invited to provide information for the following: Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), EuroQol Five Dimension score (EQ-5D), Lower Extremity Functional Scale (LEFS) and Parker Mobility Score. Bone mineral density (BMD) of the allograft area and the healthy human bone tissue were measured by quantitative computed tomography.

A total of 22 patients with a mean follow-up time of 2.88 ± 2.46 years were included in our study. The most common fractures observed in this study were classified as Schatzker II (11 patients, 50.0%) or AO/OTA 41.B3 (12 patients, 54.5%) fractures. Postoperative WOMAC total was 13.0 (IQR = 16.3, range 0-33). Median quality of life (EQ-5D) score was 0.887 ± 0.121 (range 0.361-1.000). Median Lower Extremity Functional Scale (LEFS) score was 57.5 ± 19.0 (range 33-79). Mean Parker Mobility Score was 9 (range 6-9). Median bone mineral density (BMD) for the whole group was 300.04 ± 226.02 mg/cm³ (range - 88.68 to 555.06 mg/cm³) for region of interest (ROI 5) (central), 214.80 ± 167.45 mg/cm³ (range - 7.16 to 597.21 mg/cm³) for ROI 1-4 (marginal zones: medial, lateral, ventral, dorsal) and 168.14 ± 65.54 mg/cm³ (range 17.47-208.97 mg/cm³) for healthy bone tissue (femur and tibia).

Based on WOMAC scores, LEFS, ambulatory status, and quality of life findings, it can be concluded that following tibial head ORIF with allograft bone patients has promising results.

 The aim of this study was to measure and compare the stiffness and cyclic fatigue of two plate-bone model constructs, with either two or three locking screws per fragment, under cyclic compression.

 A 10-hole 3.5 mm stainless steel locking compression plate (LCP) was fixed 1 mm from a synthetic bone model in which the fracture gap was 47 mm. Two groups of 10 constructs, prepared with either two or three bicortical locking screws placed at the extremities of each fragment, were tested in a load-controlled compression test until failure.

 The three-screw constructs were stiffer than the two-screw constructs (196.75 ± 50.48 N/mm and 102.43 ± 22.93 N/mm, respectively) and the actuator displacements of the two-screw constructs were higher (18.02 ± 1.07 mm) than those of the three-screw constructs (14.48 ± 2.25 mm). The number of cycles to failure of the two-screw constructs was significantly lower (38,337.50 ± 2,196.98) than the that of the three-screw constructs (44,224.00 ± 1,515.24). Load at irreversible deformation was significantly lower in the two-screw constructs (140.93 ± 13.39 N) than in the three-screw constructs (184.27 ± 13.17 N). All constructs failed by plate bending at the gap between the two cylinders.

 Omission of the third innermost locking screw during bridging osteosynthesis subjected to compression forces led to a 13.3% reduction in the number of cycles to failure and a 23.5% reduction of the load withstood by the plate before plastic deformation occurred.

Current surgical fracture treatment paradigms, which use rigid metallic constructs to heal bones, provide reasonable clinical outcomes; however, they do not leverage recent advances in our understanding of bone healing and mechanotransduction throughout bone healing. The objective of this review was to investigate the efficacy and potential clinical applicability of surgical techniques and implants that deliberately introduce interfragmentary motion throughout the healing process.

The authors searched PubMed and Google Scholar databases for articles reporting on fracture repair using dynamic locking plates, dynamized surgical techniques, and reverse dynamization. Data collection also included assessment of additively manufactured (AM) implants that provide dynamic mechanical behaviors.

Forty articles were included for final review. It was found that accelerated rates of fracture healing can be achieved with staged 2-part surgeries or dynamic implant designs. Temporal dynamization, where static fixation of bones is followed by the introduction of micromotion and controlled loading, has been shown to improve callus volume and accelerate the healing response. Reverse dynamization, where micromotion is encouraged during early callus formation and arrested later, may represent a significant advance for the treatment of critical defect injuries. Advances in AM techniques will likely provide the ability to create high-resolution implants capable of dynamized and reverse dynamized modalities.

There is no one-size-fits-all approach to optimization of fracture healing. However, it has been clearly demonstrated that fracture treatment can be enhanced by systematically altering the construct stiffness throughout the different phases of healing, which may be achieved with AM implant designs.

Therapeutic exercises could potentially enhance the healing of distal radius fractures (DRFs) treated with volar locking plate (VLP). However, the healing outcomes are highly dependant on the patient-specific fracture geometries (e.g., gap size) and the loading conditions at the fracture site (e.g., loading frequency) resulted from different types of therapeutic exercises. The purpose of this study is to investigate the effects of different loading frequencies induced by therapeutic exercises on the biomechanical microenvironment of the fracture site and the transport of cells and growth factors within the fracture callus, ultimately the healing outcomes. This is achieved through numerical modelling and mechanical testing.

Five radius sawbones specimens (Pacific Research Laboratories, Vashon, USA) fixed with VLP (VRP2.0+, Austofix) were mechanically tested using dynamic test instrument (INSTRON E3000, Norwood, MA). The loading protocol used in mechanical testing involved a series of cyclic axial compression tests representing hand and finger therapeutic exercises. The relationship between the dynamic loading rate (i.e., loading frequency) and dynamic stiffness of the construct was established and used as inputs to a developed numerical model for studying the dynamic loading induced cells and growth factors in fracture site and biomechanical stimuli required for healing.

There is a strong positive linear relationship between the loading rate and axial stiffness of the construct fixed with VLP. The loading rates induced by the moderate frequencies (i.e., 1-2 Hz) could promote endochondral ossification, whereas relatively high loading frequencies (i.e., over 3 Hz) may hinder the healing outcomes or lead to non-union. In addition, a dynamic loading frequency of 2 Hz in combination of a fracture gap size of 3 mm could produce a better healing outcome by enhancing the transport of cells and growth factors at the fracture site in comparison to free diffusion (i.e. without loading), and thereby produces a biomechanical microenvironment which is favourable for healing.

The experimentally validated numerical model presented in this study could potentially contribute to the design of effective patient-specific therapeutic exercises for better healing outcomes. Importantly, the model results demonstrate that therapeutic grip exercises induced dynamic loading could produce a better biomechanical microenvironment for healing without compromising the mechanical stability of the overall volar locking plate fixation construct.

Elastic stable intramedullary nailing (ESIN) is the current preferred method for treating diaphyseal femur fractures in children. Introduction of the submuscular locked plate (SMP) fixation construct has opened the debate on treatment options for pediatric diaphyseal femur fractures in the older children and adolescents. A randomized controlled trial (RCT) protocol was designed to compare ESIN and SMP for diaphyseal femur fractures in children. An open-labelled RCT comparing SMP with ESIN was conducted from January 2013 to June 2016, for children aged 6-15 years with closed, acute femoral diaphyseal fractures. Randomization was done through computer-generated randomization sequence and opaque-sealed envelopes. Rate of adverse surgical events including unplanned re-operations was assessed as the primary outcome and secondary analysis was done for time to union, degree of malunion, limb length discrepancy, functional outcome at 2 years, surgical duration and blood loss, radiation exposure, hospital stay, cost incurred and secondary implant removal procedure. Forty children were randomized with allocation concealment. There were three adverse events in the SMP arm and five in the ESIN arm. Fifteen children with SMP underwent routine implant removal compared to only three children with ESIN (P < 0.001). Both ESIN and SMP are equally safe, viable and effective options for treating pediatric diaphyseal femoral fractures. However, the additional cost of secondary surgery for implant removal in the SMP group proved to be a deterrent factor, which led to ESIN being the preferred option in our resource-limited setting.