Long-term follow-up result of short metaphyseal femoral stem in primary total hip arthroplasty: A retrospective study

Abstract

BACKGROUND

Total hip arthroplasty (THA) has increased along with an increasing demand for improved quality of life. Combined with prolonged life expectancy, the number of revision surgeries is expected to increase. Stress shielding is a significant issue with traditional femoral stems used in THA, making revision surgeries particularly challenging in younger patients. This has sparked renewed interest in studying safety and functional outcomes of short metaphyseal femoral stems, which have the potential to alleviate these challenges and simplify revision surgeries.

AIM

To evaluate the long-term outcomes of short-stem THA.

METHODS

A total of 124 hips that underwent THA using the short femoral stem (TRILOCK^® Depuy) between May 2006 and November 2008 were included in this study. Patients were followed for a period of 15 years. Outcomes were assessed in terms of pain relief, hip joint range of motion, improvement in mobility, and functional outcomes using the modified Harris Hip Score, Oxford hip score, and Western Ontario and McMaster Universities Osteoarthritis index score.

RESULTS

A total of 124 hips in 98 patients were evaluated. Significant improvements in functional outcomes were observed over the 15-year follow-up period, with no cases of subsidence, implant loosening, or complications necessitating revision surgery. The only complication reported was heterotopic ossification in 1 patient.

CONCLUSION

Short metaphyseal stems provide better functional outcomes with early mobilization, and its long-term follow-up without subsidence, implant loosening, or proximal femoral bone loss simplifies revision surgery in younger patients.

Key Words: Short stem total hip replacement; Short metaphyseal stem; Uncemented hip replacement; Proximal femur osteolysis; Proximal femur bone loss

Core Tip: As the demand for an improved quality of life increases, so does the trend for total hip arthroplasty (THA). This, coupled with longer life expectancy, is expected to lead to more revision surgeries. One of the major issues with traditional femoral stems in THA is stress shielding, which makes revision surgeries particularly difficult in younger patients. Short metaphyseal femoral stems may address this issue, simplifying revision surgeries and improving patient outcomes. This study assessed the long-term results of short-stem THA.

INTRODUCTION

The increasing demand for an improved quality of life has led to the extension of total hip arthroplasty (THA) in younger patients. However, prolonged life expectancy and enhanced quality of life in recent years have necessitated multiple revision surgeries for these younger patients. These revision surgeries present numerous technical challenges due to bone and soft tissue loss, distorted anatomy, or complications from previous surgeries. In THA using a conventional femoral stem, there is greater bone loss due to stress shielding, which particularly complicates revision surgeries in younger patients who may require more surgeries in the future[1,2].

As a result, the search for alternative options has prompted modifications in implants, procedural techniques, and patient selection. One advancement involves achieving more proximal femoral load transfer to reduce proximal stress shielding, thereby preserving bone stock for potential future revision surgeries. One method of achieving this is through the use of short-stem femoral components[3]. Since many of these short stems are relatively new, there is limited long-term evidence regarding their clinical and radiological outcomes. Given this, it is considered worthwhile to study the long-term functional outcomes and complications of THA with short stems.

MATERIALS AND METHODS

This study included retrospective cases of patients who underwent total hip replacement using a short femoral stem (TRILOCK^®; Depuy Synthes, Johnson & Johnson, Warsaw, IN, United States) between May 2006 and November 2008 at the Department of Orthopaedic Surgery, Indira Gandhi Medical College (Shimla, India). All surgeries were performed by the same senior orthopedic surgeon experienced in arthroplasty procedures, using a posterior approach and consistent surgical techniques. The same preoperative and postoperative protocols were followed for all patients by the treating team.

Data collection

Institutional records were meticulously reviewed, and relevant information was noted, including demographic data, diagnosis, radiology, preoperative functional scores [modified Harris Hip Score, Oxford hip score, and Western Ontario and McMaster Universities Osteoarthritis index (WOMAC) score], pain scores (measured using the visual analog scale documented in the records), and any complications noted during follow-up. Patients were contacted via post or telephone for follow-up visits, during which data were collected on pain relief (using the visual analog scale), range of motion in the hip joint, improvements in mobility, and functional outcomes assessed by the modified Harris Hip Score, Oxford hip score, and WOMAC score. Complications and radiological outcomes such as subsidence, stress shielding/proximal femoral bone loss, and loosening were also evaluated at the final follow-up.

Radiological evaluation

X-rays were taken with a tube-to-film distance of 40 inches to ensure standard magnification and included both hips and the upper half of the femur. Anteroposterior views were taken in a neutral position, followed by X-rays with 15° internal rotation and lateral views of both hips and the upper half of the thigh. Radiological features such as subsidence, stress shielding/proximal femoral bone loss, and loosening were noted.

Statistical analysis

Statistical analysis was conducted using the Statistical Package for Social Science version 17.0 (IBM Corp., Armonk, NY, United States). The power of the study was calculated through post hoc power analysis. Continuous variables were represented as mean ± SD or as median (interquartile range) for non-normally distributed data, while categorical variables were expressed as frequencies and percentages.

RESULTS

Demographics

A total of 124 hips in 98 patients were included in the study, with a mean age of 44 years. The most common age group receiving THA was between 30-60 years and were predominately male. Avascular necrosis with secondary osteoarthritis (60%) was the most frequent indication for surgery. The mean duration of surgery was 140 minutes, and the average blood loss was 160 mL. The demographic data, intraoperative details, and diagnoses of the patients are summarized in Table 1.

Table 1 Demographic data.

Demographic variable	Result
Age (year), mean ± SD	44 ± 7.5
Side of surgery as left/right/bilateral	72/52/26
Indication	Avascular necrosis with secondary arthritis (n =65); femoral neck fracture (n = 22); ankylosing spondylitis (n = 13); psoriatic arthritis (n = 12); post-infection sequelae (n = 12)
Mean duration of surgery (minute), mean ± SD	140 ± 25
Average blood loss (mL), mean ± SD	160 ± 50
Follow-up (year)	15

Functional outcome

The preoperative and postoperative functional outcome scores are tabulated in Table 2. We observed significant improvement in the modified Harris Hip Score at the last follow-up compared to the preoperative score. The mean modified Harris Hip Score increased from 19.75 preoperatively to 91.66 at the final follow-up, with almost 80% of patients showing excellent outcomes. The mean Oxford hip score and WOMAC score also improved from 12.04 to 40.54 and from 85.16 to 19.16, respectively, at the final follow-up. The pain score significantly improved from 7.1 ± 2.7 to 1.4 ± 0.7 at the final follow-up, with a P value < 0.05.

Table 2 Preoperative and postoperative functional scores at last follow-up.

Functional score	Preoperative score	Postoperative score at final follow-up
Modified Harris Hip Score, mean ± SD	< 70 (poor): 100%; mean score: 19.75 ± 15.00	90-100 (excellent): 80%; 80-89 (good): 16%; 70-79 (fair): 4%; mean score: 91.66 ± 7.50
Oxford hip score, mean ± SD	12.04 ± 3.00	40.54 ± 4.50
WOMAC score	85.16	19.16
Visual analogue score, mean ± SD	7.1 ± 2.7	1.4 ± 0.7

WOMAC: Western Ontario and McMaster Universities Osteoarthritis index.

Radiological evaluation

The 15-year final follow-up revealed no evidence of component malpositioning or significant subsidence of the implant in any of the patients. However, 1 patient showed aseptic loosening, and another patient had a prosthetic joint infection and loosening. Six patients exhibited heterotopic ossification, though without significant functional limitations. Figure 1 shows representative preoperative and follow-up X-rays of a patient, while Figure 2 displays an X-ray of a patient with heterotopic ossification. No significant limb length discrepancy, varus malposition of the component, or sciatic nerve palsy was noted. Table 3 outlines the complications observed among the patients.

Figure 1 Preoperative and follow-up X-rays of a patient. A: Preoperative; B: Postoperative, at final follow-up.

Figure 2 Heterotopic ossification in both the hips.

Table 3 Complications.

Type of complication	Patients (n)
Heterotopic ossification	6
Varus malposition	0
Infection	1
Aseptic loosening	1
Limb length discrepancy > 1.5 cm	0
Sciatic nerve palsy	0

DISCUSSION

Short-stem THA has been proposed as a bone-preserving procedure for younger, more active patients undergoing THA. This concept was first introduced by Judet in the 1940s[3]. Short-stem prostheses conserve more bone stock for potential future revisions, which is especially beneficial for young, active patients with a longer life expectancy and higher activity levels who are more likely to require revisions[4]. These stems offer the advantage of enabling future revisions using conventional primary stems[5]. Other benefits include a lower incidence of thigh pain[6] and the ease of minimally invasive surgery, owing to the more medial entry point of the stem in the femoral neck[7]. The lateral flare geometry of these short stems rests on the lateral column of the proximal femur, leading to physiological load distribution, osteointegration of the implant with the metaphysis of the proximal femur, and avoidance of stress shielding[8,9]. However, like all surgical procedures, THA with a short stem comes with limitations and potential complications, including perioperative morbidity and mortality, postoperative infections, dislocation/instability, heterotopic ossification, and implant-related issues. Still, the benefits of THA generally outweigh the risks[10]. The rates of aseptic loosening, intraoperative fractures, and periprosthetic fractures were found to be similar to those of standard stems[11].

Considering the advantages of short stems in THA, it is expected that these implants will be increasingly used in clinical practice, although this must be supported by long-term studies. The longest follow-up period found in the literature was 10 years[12]. In our study, short-stem prostheses for THA were associated with improved patient outcomes, with no significant subsidence of the implant or other complications observed at the 15-year follow-up. These results are consistent with previous studies by Kim et al[13], Floerkemeier et al[14], Thorey et al[15], and Sperati and Ceri[16]. We also found that patients had better functional outcomes and were mobilized earlier, consistent with Wroblewski[17]. At the 15-year follow-up, we observed no radiolucent lines in any of the Gruen zones or implant subsidence, and good osteointegration was evident on plain radiography in two orthogonal views, consistent with the available literature[18]. The strengths of this study included its prospective nature, adequate sample size, and long follow-up period. It also provides insight into the long-term outcomes of relatively new short metaphyseal femoral stems in THA. However, a limitation of the study is that it was conducted at a single center.

CONCLUSION

THA with a short metaphyseal stem can be safely used in patients with adequate bone support, preserving bony and soft tissue anatomy and yielding better functional outcomes. In this 15-year follow-up, we observed minimal complications such as subsidence, implant loosening, or proximal femoral bone loss due to stress shielding. Short-stem THR also simplifies revision surgeries by preserving bone stock, if needed. This approach can be preferred, especially in younger patients with good bone stock.

ACKNOWLEDGEMENTS

We thank all the patients and their families for their support.