Intraoperative application of three-dimensional printed guides in total hip arthroplasty: A systematic review

Abstract

BACKGROUND

Acetabular component positioning in total hip arthroplasty (THA) is of key importance to ensure satisfactory post-operative outcomes and to minimize the risk of complications. The majority of acetabular components are aligned freehand, without the use of navigation methods. Patient specific instruments (PSI) and three-dimensional (3D) printing of THA placement guides are increasingly used in primary THA to ensure optimal positioning.

AIM

To summarize the literature on 3D printing in THA and how they improve acetabular component alignment.

METHODS

PubMed was used to identify and access scientific studies reporting on different 3D printing methods used in THA. Eight studies with 236 hips in 228 patients were included. The studies could be divided into two main categories; 3D printed models and 3D printed guides.

RESULTS

3D printing in THA helped improve preoperative cup size planning and post-operative Harris hip scores between intervention and control groups (P = 0.019, P = 0.009). Otherwise, outcome measures were heterogeneous and thus difficult to compare. The overarching consensus between the studies is that the use of 3D guidance tools can assist in improving THA cup positioning and reduce the need for revision THA and the associated costs.

CONCLUSION

The implementation of 3D printing and PSI for primary THA can significantly improve the positioning accuracy of the acetabular cup component and reduce the number of complications caused by malpositioning.

Key Words: Total hip arthroplasty; Three-dimensional printing; Hip replacement surgery; Three-dimensional planning; Surgical guides

Core Tip: This study aimed to assess and summarize the current use of three-dimensional (3D) printing in total hip arthroplasty (THA) surgery. Eight studies discussing different implementations of 3D printing in THA were included and analyzed. The implementation of 3D printing and patient specific instruments for primary THA can significantly improve the positioning accuracy of the acetabular cup component and reduce the number of complications caused by malpositioning.

INTRODUCTION

Total hip arthroplasty (THA) significantly improves the quality of life in patients with end stage hip osteoarthritis[1]. Acetabular component positioning is of key importance to ensure satisfactory post-operative outcomes and to minimize the risk of complications[2,3]. Malalignment of the acetabular component in any particular way can increase the risk of dislocation, wear, loosening, impingement and overall patient dissatisfaction[2,4]. Malpositioning of the implants through freehand component positioning, even with an aiming device or navigation, can result in premature implant failure requiring revision[5,6]. To prevent hip dislocation and subsequent revision arthroplasty, surgeons strive for optimal acetabular component positioning, for which use of the “Lewinnek safe zone” was formerly advised. This safe zone is set at an anteversion angle of 15° ± 10° and an inclination angle of 40° ± 10°, with a reported increased chance of dislocation outside this range[7]. Several studies have recently shown that this generalized safe zone is non-existent, and that the safe zone for acetabular alignment is patient specific and dependent on multiple factors[8,9]. Moreover, the angle measurements of the acetabular component are highly dependent on spinopelvic mobility and the position of the patient[10,11].

Currently the majority of acetabular components are aligned freehand, without the use of navigation methods[3]. The position of the acetabular component is estimated using anatomical landmarks such as the transverse acetabular ligament and the posterior acetabular wall[12]. Callanan et al[13] reported that only 50% of acetabular components were positioned within 10 degrees of the surgeons’ aimed acetabular position. The use of surgical navigation has shown to significantly improve accuracy of acetabular component positioning and to reduce the number and severity of outliers during acetabular component positioning in primary THA[14,15].

Bishi et al[16] and Moralidou et al[17] compared the accuracy of two-dimensional (2D) preoperative planning methods with three-dimensional (3D) preoperative planning methods and concluded that 3D preoperative planning helps the surgeons to visualize the pelvic anatomy and accurately plan the required implant size and orientation. With the rise of these 3D planning methods and the increase of computational power, various intraoperative navigational systems have been introduced over the years with the aim of improving the accuracy of acetabular component positioning and reducing postoperative complications from cup malalignment in primary and revision THA. 3D printed patient specific instruments (PSIs) are modelled after computed tomography (CT) or magnetic resonance imaging scans of a patient and can be designed in whichever way the surgery requires. PSIs are generally made of polylactic acid and are designed to precisely fit the bone structure at or around the surgical region of interest, in order to guide screw placement, saw or drill direction or implant positioning[18]. PSIs have already been used as guides during various types of surgical procedures, including osteotomy and/or arthroplasty of the knee, shoulder, wrist, ankle, and spine[19,20]. However, it has not yet been determined how the use of PSI improves cup positioning accuracy and clinical outcomes.

The aim of this systematic review was to summarize the existing literature on the use of PSI and 3D printing of THA placement guides in primary THA and how they contribute to improved acetabular component alignment accuracy. We hypothesize that the use of 3D guides leads to an improved accuracy of acetabular component positioning with less outliers compared to free-hand component positioning.

MATERIALS AND METHODS

Search strategy and study design

This systematic review was conducted according to the preferred reporting items for systematic reviews and meta-analysis guidelines. PubMed was used to identify and access scientific studies reporting on different 3D printing methods used in THA. The systematic search was performed on 30 March 2023, with the following search query:

["Arthroplasty, Replacement, Hip" (mj) or Hip-Replacement (ti) or Hip Prosthe (ti) or Prosthetic-Hip (ti) or Hip Arthroplast (ti) or tha (ti)] and ["Printing, Three-Dimensional" (mj) or Three-Dimension (ti) or 3-Dimension (ti) or 3d (ti) or 3-d (ti)] and ["Patient-Specific Modeling" (mj) or "Surgical Navigation Systems" (mj) or Patient-specific (ti) or navigat (ti) or guide (ti) or templat (ti) or planning (ti) and 2010:2023 (dp)] not [animals (mh) not humans(mh) and English (la)].

All papers reporting on 3D printing for clinical use during THA performed in adult humans were included in the study. Each study was analyzed for inclusion eligibility by the first and last author, based on title, abstract and full text analysis. The lists of references of retrieved publications were manually checked for additional studies potentially meeting the inclusion criteria and not found by the electronic search.

Studies that did not report postoperative cup angles or cup position were excluded as the accuracy could not be reported on. Studies regarding different, non-3D printed preoperative planning techniques were excluded as these planning techniques are not regarded as intraoperative surgical navigation techniques, and therefore do not add to the subject of this study.

An adaptation of the QUADAS-2 quality assessment tool[21] was used to assess the quality of the included studies.

RESULTS

Search results

The literature search resulted in 86 studies, of which 8 studies including 236 hips in 228 patients could be included[22-29]. Figure 1 depicts a detailed overview of the selection procedure.

Figure 1 PRISMA Flowchart of study inclusion. 2D: Two-dimensional; 3D: Three-dimensional.

Table 1 provides a detailed overview of the study characteristics of the included studies. The studies can be divided into two main categories, based on the 3D print application used. Table 2 provides the quality assessment of each study.

Table 1 Study characteristics of included studies.

Ref.	Year	Study design	Navigation type	Patients, n	Hips, n
Dos Santos-Vaquinhas et al[22]	2022	Comparative study with retrospective cohort	3D model print	45	45
Xu et al[23]	2015	Retrospective cohort	3D model print	10	14
Zhang et al[24]	2022	Retrospective cohort	3D model print	17	21
Chen et al[25]	2022	RCT	3D printed Guides	60	60
Kida et al[26]	2023	Prospective cohort	3D printed Guides	23	23
Mishra et al[27]	2020	RCT	3D printed Guides	36	36
Tu et al[28]	2022	Prospective cohort	3D printed Guides	12	12
Yan et al[29]	2020	RCT	3D printed Guides	25	25

3D: Three-dimensional; RCT: Randomized controlled trial.

Table 2 Tubular presentation of QUADAS-2 results for included studies.

Ref.	Risk of bias				Applicability concerns
	Patient selection	Index test	Reference standard	Flow and timing	Patient selection	Index test	Reference standard
Dos Santos-Vaquinhas et al[22]	+	+	+	+	+	+	+
Xu et al[23]	+	+	+	+	+	+	+
Zhang et al[24]	+	-	-	-	+	+	+
Chen et al[25]	+	+	+	+	+	+	+
Kida et al[26]	+	+	+	+	+	+	+
Mishra et al[27]	+	+	+	+	+	+	+
Tu et al[28]	?	-	-	-	+	+	+
Yan et al[29]	+	+	+	+	+	+	+
	+	Low risk	-	High risk	?	Unknown risk

3D printed models

Three studies analyzed the use of 3D printed models as a method of preoperative planning of THA. The models were based on CT scans and used by surgeons to make a surgical plan ahead of THA and intraoperatively as a reference tool for anatomical landmarks. Table 3 provides an overview of the outcome measures of the three studies.

Table 3 Outcome measures of articles reporting three-dimensional printed models.

Ref.	Outcomes
	Number of hips	Mean (range) follow-up in months	Cup size planning accuracy1	Mean operating time in min	HHS2	Complications1	Vertical distance in mm3	Horizontal distance in mm3
Dos Santos-Vaquinhas et al[22]	45	32.4 (12-60)	19/21 vs 14/24 (P = 0.045)	156.15 ± 43.03 vs 187.5 ± 54.38 (P = 0.045)	57.15 ± 15.41–83.74 ± 8.49 vs 53.12 ± 15.62–75.59 ± 11.46 (P = 0.019)	Intraoperative 4/21 vs 10/24 (P = 0.003)	0.7 [(-5.0)-15] vs -3.3 [(-32.0)-8.0] (P = 0.102)	1.2 [(-9.0)-7.0)] vs 1.0 [(-8.0)-15.0] (P = 0.884)
Xu et al[23]	14	23.1 ± 5.9 (14-30)	10/14 (3/14 < 2 mm diff) vs 1/14 (5/14 < 2 mm diff)		37.7 ± 6.8–83.3 ± 5.7 (P < 0.01)		18.8 (11.5-25.8)	21.7 (15.0-31.2)
Zhang et al[24]	21	18.35 ± 6.86 (12-36)	15/17 (ICC = 0.930)		38.33 ± 6.07–88.61 ± 3.44 (P < 0.05)		40.48 ± 8.42–15.12 ± 1.25 (P < 0.05)	41.49 ± 5.17–32.49 ± 2.83 (P < 0.05)

¹Intervention vs control.

²Harris hip score (preoperative–postoperative; intervention vs control; P value between postoperative values for intervention vs control or preoperative-postoperative when no control group was used).

³Distance to center of rotation of the hip (preoperative–postoperative; intervention vs control).

ICC: Intraclass correlation coefficient.

Dos Santos-Vaquinhas et al[22] compared the use of 3D models with conventional free hand component positioning and found superior outcome for THA after preoperative planning with 3D printed models (Table 3). They reported a significantly shorter operating time between groups, a significant increase in post-operative Harris hip scores (HHS), and a significant decrease in intraoperative complications.

All studies found higher correspondence between the 3D planned cup size and the implanted cup than for the cup size planned on 2D X-ray imaging. However, the included studies did not find any significant improvement in horizontal or vertical distance, in relation to the teardrop, between the cup and the original center of rotation between the intervention and control groups.

3D printed guides

Five studies reported on the use of 3D printed surgical guides, which are patient specific devices that use the anatomical landmarks of the acetabulum to guide intraoperative positioning of the cup component. The studies provide heterogeneous outcome measures and are provided in Table 4.

Table 4 Outcome measures of articles reporting three-dimensional printed acetabular guides.

Ref.	Outcomes
	Number of hips	Mean (range) follow-up in months	Cup size planning accuracy1	Postoperative cup inclination angle as °1	Postoperative cup anteversion angle as °1	Mean operating time in min1	HHS2	Intraoperative blood loss in mL1
Chen et al[25]	60	3	83.3% (93.3% < 2 mm) vs 73.3% (80% < 2 mm) (P = 0.532)	Absolute error: 2.6 (0-8.0) vs 5.0 (0-15.0) (P = 0.004)	Absolute error: 2.5 (0.3-7.3) vs 5.2 (0.1-14.0) (P < 0.001)	100.2 ± 13.4 vs 106.7 ± 24.4		290 ± 70.3 vs 251.7 ± 93.3
Kida et al[26]	23	0.5		39.37 ± 8.18	25.86 ± 7.87
Mishra et al[27]	36		18/18 vs 6/18	43.28 (38-46) vs 44.11 (34-50)	14.22 (8-27) vs 13.42 (5-36)	99.39 vs 92.33		519.44 vs 495.56
Tu et al[28]	12	72.42 (38–135)		42.6 ± 4.2	12.5 ± 3.6	280.8 ± 106.8	34.2 ± 3.7- 85.2 ± 4.2 (P < 0.001)	590.35 ± 112.47
Yan et al[29]	25	19.2 (14.4–45.6)		42.25 ± 4.55 vs 38.60 ± 3.25	17.30 ± 5.12 vs 15.01 ± 5.68	57.8 ± 3.73 vs 62.1 ± 4.19 (P = 0.008)	93.9 ± 2.87 vs 91.8 ± 3.69 (P = 0.009)	169 ± 34.1 vs 219 ± 38.0 (P = 0.002)

¹Intervention vs control.

²Harris hip score (preoperative–postoperative; intervention vs control; P value between postoperative values). P values are displayed for all studies that provided P values in their comparisons.

Cup angles were either provided as absolute angles with the range/SD or as absolute error of the angle and were measured on 2D X-ray images, by 3D matching using ZedView, or with CT images. Chen et al[25] reported a significant difference in absolute error of the cup inclination angles and the cup anteversion angles between both groups. The other studies found no significant differences in cup angles between intervention and control. Yan et al[29] found that the intervention group reported higher HHS postoperatively, significantly shorter operating time and significantly lower intraoperative blood loss compared to the control group. However, these significant results for mean operating time and intraoperative blood loss were not found by the other studies.

DISCUSSION

This study aimed to review the literature on the use of PSI and 3D printing for component positioning in THA. Only a limited number of studies were eligible for inclusion as the use of PSI in acetabular component positioning has not yet been frequently described.

The use of 3D printed models for preoperative planning and intraoperative referencing enables the surgeon to plan the required implant sizes more accurately than based on conventional x-ray imaging. However, the included studies did not find a significant improvement in horizontal or vertical distance of the cup from the center of ration between the intervention and control groups. Zhang et al[24] did report significant postoperative improvements in horizontal and vertical distance within their population, with the aid of their self-developed acetabular center locator. The HHS improved significantly in all study populations that used the 3D models, but only Dos Santos-Vaquinhas et al[22] compared the postoperative HHS of the intervention group with a control group and found a significant improvement there.

As mentioned prior, the 3D printed acetabular cutting and positioning guides use heterogeneous outcome measures. Kida et al[26] and Tu et al[28] do not compare the results with any control groups. Despite these limitations, PSIs seemingly improve component position, based on the significant difference in absolute error found by Chen et al[25] and the smaller positioning ranges reported by Mishra et al[27]. Furthermore, the use of PSI significantly increases the HHS, as found by Yan et al[29]. Yan et al[29] performed THA on unilateral developmental dysplasia of the hip patients and did not directly compare both groups with each other, but they compared the anteversion angle, abduction angle and the distance from the rotation center to the ischial tuberosity connection of the ipsilateral side with the contralateral side. When comparing these values they found no significant differences between both sides within the intervention group, but they did find significantly smaller anteversion angles (P = 0.015) and a larger distance from center of rotation (P = 0.002) between both sides within the control group. This suggests that component positioning in the intervention group is more similar to the natural anatomy of the healthy contralateral hip of the patient and thus better than component positioning in the control group. Outcome measures such as mean operating time and intraoperative blood loss varied widely between studies and therefore it is difficult to predict, based on these studies alone, if and how the use of PSI will improve these outcome measures.

The overarching conclusion between the studies is that the use of 3D guidance tools can assist in improving THA cup positioning. Henckel et al[30] performed a literature study regarding 3D printed PSI in THA and found similar results supporting the superiority of THA performed with PSI, albeit most of their included studies consist of THA performed on dry bone models or cadavers. Additionally, they analyzed the cost of producing PSIs and they concluded that it would add approximately $371 per surgical procedure. However, as the THA positioning improved, these additional costs would be relatively small compared to potential additional costs of possible revision surgery caused by early failure or poor positioning of freehand THA. Similarly with our findings, Henckel et al[30] could not find significant differences in intraoperative blood loss between PSI and conventional THA groups. They found one complication in a total of 128 patients in whom PSI was used during THA.

Constantinescu et al[31] also conducted a literature study on PSI in THA and supported previous results regarding the efficacy of PSI in THA. However, they found PSI to be most useful in patients with larger acetabular defects where traditional landmarks were difficult to identify.

While the focus of this study was on the use of 3D printing in THA, other navigation methods such as imageless navigation and surgical robots are also available. The use of navigation and/or robotic assistance during THA has shown to improve accuracy of acetabular component positioning[14,32]. However, these devices often require a major investment and are not yet widely used for THA[33]. When 3D planning software, knowledge and printers are readily available in-house, the use of 3D printed models can be a relatively cheap method of improving surgical outcome without needing major investment in navigational devices such as robots or imageless navigation.

Despite the promising postoperative results of PSI assisted THA, this review does not report on long-term functional outcome, complications and patient satisfaction. Also, this review focusses only on the positioning of the acetabular cup component and one could argue that accurate positioning of the femoral component is as important as the accuracy of the cup position and should therefore be analyzed together to find the optimal methodology. Furthermore, only eight studies were included and subcategorized into different 3D print applications that did not use uniform outcome measures. On the other hand, the limited existing literature on PSI and 3D printing for THA, with promising improved outcome for patients, underscores the significance and amplifies the importance of this systematic literature review. What is more, this review summarizes existing knowledge and provides insight into combining different applications of 3D printing. The use of 3D printed models for preoperative planning can easily be combined with 3D printed acetabular cutting and positioning guides to improve the preoperative planning, understanding of the anatomical landmarks and finding the optimal position of the cup component.

In revision arthroplasty, the anatomical landmarks used for free-hand acetabular component alignment are more difficult to use or absent due to bone loss and scar tissue formation. Acetabular component positioning can be very difficult, as there can be little anatomical landmarks to use as feedback during surgery. The most frequently used commercially available navigation systems are not yet officially available for revision THA, or lack a revision module. In these cases, 3D printed guides could provide the necessary aid to improve acetabular component positioning, however to date this has not yet been described.

CONCLUSION

In conclusion, the implementation of 3D printing and PSI for primary THA can significantly improve the positioning accuracy of the acetabular cup component and reduce the number of complications caused by malpositioning. Future studies should further explore the possibilities of implementing PSIs in primary and revision THA with a focus on patient reported outcome and postoperative complication rate reduction.