Fracture of cementless femoral stems at the mid-stem junction in modular revision hip arthroplasty systems

Special aspects of total hip arthroplasty in patients with proximal femur pseudarthrosis

Introduction

The rate of proximal femur fractures (PFF) in the structure of musculoskeletal system injuries among all fractures of long bones ranges from 3.9 to 18%. According to Russian Ministry of Health 2020 data, the incidence of femoral fractures in Russia was up to 61 cases per 100,000 population (90,000 per year); and femoral neck fractures incidence was 4 times higher among people over 75 years of age. The choice of surgical technique and the fixator used depend on many factors, such as fracture location and its nature, the age of the patient, comorbidities, and the quality of bone tissue. Internal osteosynthesis, is the current treatment method of choice for extra-articular proximal femur fracture, but every treatment method has its limitations. a significant number of complications caused by technical errors, vicious union or nonunion with the subsequent development of false joints, the development of femoral head aseptic necrosis, which leads to coxarthrosis and persistent pain syndrome. To solve the above-described problems, it is necessary to use a conversion surgery - total hip replacement.

Objectives

long-term analysis of the results of total hip replacement in patients with proximal femur pseudarthrosis.

Methods

The study was based on clinical and laboratory data analysis and on the results of total hip arthroplasty (THA) in 45 patients aged 56-84 years (mean age 68.3), including 32 (71.1%) women and 13 (26.1%) men. 12 patients initially received conservative treatment, and 33 patients received initial surgical treatment using various metal osteosynthesis procedures. The time from osteosynthesis or from the moment of injury to admission to the hospital for hip arthroplasty ranged from 12 to 30 months. All patients, before conversion arthroplasty and after discharge, were repeatedly invited to the clinical diagnostic department for a clinical examination and for assessment using rating scales. 3, 6 and 12 months after the surgery, pain syndrome and patient quality of life were assessed using the following questionnaire scales: Harris Hip Score, MOS SF-36, VAS. The maximum follow-up period ranged from 12 to 60 months.

Results

Based on the results obtained, patients of all 4 groups after conversion arthroplasty noted a significant quality of life improvement, a decrease in pain severity and functional results improvement. This was probably due to the presence of a severe limitation of range of movements in the joint, intense pain, absence of support ability of the extremity, as well as low operative efficacy expectations.In 1 (2%) patient, acute PJI was diagnosed in the early postoperative period, followed by sepsis and death.In 4 patients (9%) the result was considered unsatisfactory. At 1 year of follow-up after surgery, they complained of pain and claudication in the operated joint.3 (6%) patients underwent reduction of dislocation.

Conclusions

Strict adherence to the recommended treatment algorithm for patients with proximal femur pseudarthrosis made it possible to achieve good treatment results in 90% of surgically treated patients. An important step in the treatment of this patients is a careful preoperative planning with thorough assessment of bone tissue quality and muscles condition in the proximal femur area, allowing to choose the optimal endoprosthesis components.

Outcomes of conversion total hip arthroplasty for failed fixation of intertrochanteric fractures with monoblock distal-loading reconstruction stem

PURPOSE

The aim of our study was to analyze the clinical and radiological outcomes of conversion total hip arthroplasty (THA) for failed fixation of proximal femur fractures with monoblock grit-blasted titanium reconstruction stem (Wagner self-locking stem, Zimmer).

PATIENTS AND METHODS

Thirty-nine patients were included in this retrospective analysis undergoing conversion THA for failed cephalomedullary nail or dynamic hip screw fixation for intertrochanteric fractures from January 2017 to January 2022. The clinical evaluation was done using Harris hip score. The radiological outcomes measured were subsidence, level of osteointegration, stem-canal fill ratio and heterotopic bone formation. The complications were noted postoperatively and during the follow-up.

RESULTS

The mean follow-up at the end of the study was 27.8 months (range, 14-72 months). There was a significant improvement in the Harris hip score over serial follow-ups (p < 0.001), but after 2 years, there was no statistically significant difference (p = 0.46). According to Engh's criteria, stable ingrowth was noted in 35 stems, fibrous stable ingrowth was noted in 4 stems and no patients had progressive subsidence and unstable stem. The mean stem-canal fill percentages were 91.8 ± 5.4% at the mid-stem and 80.3 ± 11.5% at the stem tip. Heterotopic ossification Brooker grade 2 was noted in 8 patients, and no patients had grade 3 or 4 heterotopic ossification. There were 7 (17.9%) intraoperative periprosthetic fractures, and greater trochanteric avulsion was noted in 2 patients in the follow-up.

CONCLUSION

Conversion THA using monoblock tapered distal loading stems bypasses the calcar deficiency and gives stable fixation in failed fixation of intertrochanteric fractures. It gives good radiological outcome and significant improvement in the clinical outcomes compared to the preoperative disability. However, caution should be noted for risk of intraoperative periprosthetic fractures in this subgroup of patients.

Long-term outcomes of revision total hip arthroplasty with the Zimmer Modular Revision hip system

Aims

There are limited long-term studies reporting on outcomes of the Zimmer Modular Revision (ZMR) stem, and concerns remain regarding failure. Our primary aim was to determine long-term survival free from all-cause revision and stem-related failure for this modular revision stem in revision total hip arthroplasty (THA). Secondary aims included evaluating radiological and functional outcomes.

Methods

We retrospectively identified all patients in our institutional database who underwent revision THA using the ZMR system from January 2000 to December 2007. We included 106 patients (108 hips) with a mean follow-up of 14.5 years (2.3 to 22.3). Mean patient age was 69.2 years (37.0 to 89.4), and 51.9% were female (n = 55). Indications for index revision included aseptic loosening (73.1%), infection (16.7%), fracture (9.3%), and stem fracture (0.9%). Kaplan-Meier analysis was used to determine the all-cause and stem-related failure revision-free survival. At most recent follow-up, Oxford Hip Scores (OHS) were collected, and radiological stem stability was determined using the Engh classification.

Results

A total of 17 hips (15.7%) underwent re-revision of any component. Indications for re-revision were stem failure (35.3%; n = 6), infection (29.4%; n = 5), instability (29.4%; n = 5), and acetabular aseptic loosening (5.9%; n = 1). The five- and 15-year all-cause survival was 89.7% (95% confidence interval (CI) 86.7 to 92.7) and 83.3% (95% CI 79.6 to 87.0), respectively. There were six re-revisions (5.6%) for stem failure; five for stem fracture and one for aseptic loosening. The five- and 15-year survival free from stem-related failure was 97.2% (95% CI 95.6 to 98.8) and 94.0% (95% CI 91.6 to 96.4), respectively. At final follow-up, the mean OHS was 36.9 (8.0 to 48.0) and 95.7% (n = 66) of surviving modular revision stems were well-fixed in available radiographs.

Conclusion

Femoral revision with the ZMR offers satisfactory long-term all-cause revision-free survival, good survival free of stem-related failure, and favourable clinical outcomes. Stem fracture was the most common reason for stem-related failure and occurred both early and late. This highlights the importance of both early and long-term surveillance for stem-related failure.

Minimum 2-Year Outcomes of a Modern Monoblock Titanium Fluted Tapered Revision Stem for Complex Primary and Revision Total Hip Arthroplasty

BACKGROUND

Modular titanium fluted tapered (TFT) stems have demonstrated excellent clinical success for femoral revision total hip arthroplasty (THA) surgery. This study reports the short-term outcomes of a novel modern monoblock TFT stem used for revision and complex primary THA with a minimum of 2 years of follow-up.

METHODS

We identified 126 patients who received a single monoblock TFT stem: 26 patients for complex THA (failed fracture fixation) and 100 patients for revision THA. The reasons for revision THA included 40 for previous periprosthetic joint infection, 42 for aseptic loosening, 9 for trunnionosis, and 9 for periprosthetic fractures. The Paprosky grading for femoral bone loss at the time of surgery and the measured subsidence of femoral stems at 3-month follow-up were determined. We evaluated the number and indications for reoperations.

RESULTS

The mean time from surgery was 3.9 years (range, 2.0 to 6.9). A paired t-test analysis showed significant improvement from preoperative versus postoperative clinical outcome scores (P < .001) for Harris Hip Score (38.76 ± 15.24 versus 83.42 ± 15.38), Western Ontario and McMaster Universities Arthritis Index (45.6 ± 19.0 versus 69.9 ± 21.3), Veterans RAND 12 Item Health Survey Physical component (31.7 ± 8.1 versus 37.8 ± 11.3), and Veterans RAND 12 Item Health Survey Mental component (48.2 ± 12.2 versus 51.6 ± 12.5). The Paprosky grading for femoral bone loss was Grade 1 (3.9%), Grade 2 (35.7%), Grade 3A (47.6%), Grade 3B (11.1%), and Grade 4 (1.6%) cases. There were 18 reoperations (14.7%), with 13 for periprosthetic joint infection (7 treated with implant retention and 6 treated with a 2-stage revision), 4 for instability, and 1 for acetabular aseptic loosening. There were no aseptic failures of the stem.

CONCLUSIONS

This novel modern monoblock TFT stem provided reliable femoral fixation and has increasingly supplanted the use of modular TFT stems for complex primary and revision surgery in our institution.

A rare case of taper junction corrosion in semi-constrained total knee arthroplasty

Metallosis is a known yet rare late complication of unicompartmental and total knee arthroplasty (TKA), usually secondary to either metal-backed patellar component failure, mobile-bearing polyethylene dislocation, or catastrophic polyethylene failure and wear through. The majority of literature surrounding metallosis has been published in relation to total hip arthroplasty (THA) metal on metal bearing wear or mechanically assisted crevice corrosion.This case report describes the development of metallosis in a 77-year-old male patient with advanced (Kellgren-Lawrence Grade 4) osteoarthritis with associated valgus deformity, who underwent index TKA with a semiconstrained revision knee system due to intraoperative medial collateral ligament laxity. The taper junction between the titanium alloy stem and cobalt chromium femoral component was the source of diffuse intra-articular metallosis.

Implant breakage and revision factors for modular fluted tapered stems in revision total hip arthroplasty

PURPOSE

Modular stems in revision total hip arthroplasties allow diaphyseal fixation and optimal restoration of the architecture of the proximal femur. Several studies report metaphyseal implant breakage having a negative impact on survivorship. The aim of the study was to evaluate the outcome of an uncemented modular fluted tapered stem (MFT) in revision surgery.

METHODS

In a retrospective study, 316 patients who had revision surgery using the same design of MFT implant (Modular Revision Stem [MRS], Lima Corporate, Italy) between 2012 and 2017 were identified. Patients were male in 51% of cases and mean age was 74 years. Indications were 110 periprosthetic fractures, 98 periprosthetic joint infection, 97 aseptic loosening, 10 instability and 1 other cause. Survivorship, complications, clinical and radiographic outcomes, were assessed. Mean follow-up was 5 years.

RESULTS

There was no implant breakage. At 5-year follow-up, the survivorship, free from revision for aseptic loosening and free of revision for any reason were 96% and 87%, respectively. At last follow-up (8 years), these figures were 92% and 71%, respectively. 31 implants were revised. The risk of revision for any cause was higher for extreme length metaphyseal implants, hazard ratio was 3.7 (95% CI, 1.82-7.52). A mean stem subsidence of 9 mm was noted in 37 cases; 4 were revised for aseptic loosening. The Harris Hip Score at final follow-up was 82.

CONCLUSIONS

At 5-year follow-up, the MFT implant showed a good survivorship and outcomes with no specific complications. Unlike literature reports, no specific complications occurred with this design. Stem junction positioning and therefore metaphyseal length may be key to optimise long-term survivorship. However, a longer follow-up is needed as implant breakage is more often seen after long implantation times.

Is taper corrosion in modular revision hip stem junctions associated with patient or implant specific factors? A retrieval analysis

Implant modularity within revision total hip arthroplasty (THA) offers multiple implant configurations and allows surgeons a high intraoperative flexibility to restore functionality to the patients joint, even in complex revision cases. However, a rare but devastating complication for patients, clinicians and manufacturers presenting a breakage of the taper junction between the distal stem and the proximal implant part. Aside from implant and patient specific risk factors, corrosion and fretting at the stem junctions have been associated with taper failure. Whether corrosive processes are a precursor of failure or rather an accompaniment of material fatigue is thereby still unclear. Therefore, this study aims to investigate the incidence of taper corrosion in a collection of 17 retrievals from a single type (MRP-Titan, Peter Brehm GmbH) and on the correlation of taper corrosion to implant and patient specific factors. None of the implants was revised for problems related to the taper junction, corrosion or the implant itself. The modular stem junction of all retrievals was visually rated with respect to corrosion, fretting and surface contamination. Additionally, the stability of taper junctions of retrievals where the proximal part with the neck was still assembled to the stem was determined by measuring the loosening moment of the securing screw and the push-out-force for taper dissociation. There was no difference between the mean push-out-force of the retrievals (14 kN ± 1.2 kN) and new reference samples (12.6 kN ± 0.5 kN). Approximately one third of the investigated retrievals showed considerable taper corrosion. The extent of corrosion increased with time in vivo and contamination of the neck piece, while it decreased with the loosening moment of the locking screw. The parameters femoral head offset, neck piece length, lateralized neck pieces, obesity of patients and septic/aseptic revision were not correlated to taper corrosion. Taper corrosion seems to occur regularly in modular taper junctions and is not necessarily connected to taper failure. A correct assembly of the junction and avoiding taper surface contamination during revision surgery is mandatory.

Physicomechanical, morphological and tribo-deformation characteristics of lightweight WC/AZ31B Mg-matrix biocomposites for hip joint applications

Exploring high strength materials with a higher concentration of reinforcements in the alloy proves to be a challenging task. This research has explored magnesium-based composites (AZ31B alloy) with tungsten carbide reinforcements, enhancing strength for medical joint replacements via league championship optimisation. The primary objective is to enhance medical joint replacement biomaterials employing magnesium-based composites, emphasising the AZ31B alloy with tungsten carbide reinforcements. The stir casting method is utilised in the manufacture of magnesium matrix composites (MMCs), including varied percentages of tungsten carbide (WC). The mechanical characteristics, such as micro-hardness, tensile strength, and yield strength, have been assessed and compared with computational simulations. The wear studies have been carried out to analyse the tribological behaviour of the composites. Additionally, this study investigates the prediction of stress and the distribution of forces inside bone and joint structures, therefore offering significant contributions to the field of biomedical research. This research contemplates the use of magnesium-based MMCs for the discovery of biomaterials suitable for medical joint replacement. The study focuses on the magnesium alloy AZ31B, with particles ranging in size from 40 to 60 microns used as the matrix material. Moreover, the outcomes have revealed that when combined with MMCs based on AZ31B-magnesium matrix, the WC particle emerges as highly effective reinforcements for the fabrication of lightweight, high-strength biomedical composites. This study uses the league championship optimisation (LCO) approach to identify critical variables impacting the synthesis of Mg MMCs from an AZ31B-based magnesium alloy. The scanning electron microscopy (SEM) images are meticulously analysed to depict the dispersion of WC particulates and the interface among the magnesium (Mg) matrix and WC reinforcement. The SEM analysis has explored the mechanisms underlying particle pull-out, the characteristics of inter-particle zones, and the influence of the AZ31B matrix on the enhancement of the mechanical characteristics of the composites. The application of finite element analysis (FEA) is being used in order to make predictions regarding the distribution of stress and the interactions of forces within the model of the hip joint. This study has compared the physico-mechanical and tribological characteristics of WC to distinct combinations of 0%, 5%, 10% and 15%, and its impact on the performance improvements. SEM analysis has confirmed the findings' improved strength and hardness, particularly when 10%-15% of WC was incorporated. Following the incorporation of 10% of WC particles within Mg-alloy matrix, the outcomes of the study has exhibited enhanced strength and hardness, which furthermore has been evident by utilising SEM analysis. Using ANSYS, structural deformation and stress levels are predicted, along with strength characteristics such as additional hardness of 71 HRC, tensile strength of 140-150 MPa, and yield strength closer to 100-110 MPa. The simulations yield significant insights into the behaviour of the joint under various loading conditions, thus enhancing the study's significance in biomedical environments.

Survival and complications at a minimum 5years' follow-up of the modular Mark-2 Extreme™ cementless femoral stem: Does the reduced modularity resolve the mechanical issues of the Mark-I stem?

INTRODUCTION

The Extreme™ modular stem was developed for implant revision with metaphyseal-diaphyseal defect. Due to the high breakage rate, a new "reduced modularity" design has been introduced, but without reported results. We therefore conducted a retrospective assessment of (1) overall stem survival, (2) functional results, (3) osseointegration, and (4) the rate of complications, and notably of mechanical failure.

HYPOTHESIS

Reduced modularity reduces the risk of revision surgery for mechanical failure.

MATERIAL AND METHODS

Forty-five prostheses were implanted between January 2007 and December 2010 in 42 patients with severe bone defect (Paprosky≥III) or periprosthetic shaft fracture. Mean age was 69.6years (range: 44-91years). Minimum follow-up was 5years, for a mean 115.4months (range: 60-156months). The main study endpoint was femoral stem survival, counting all-cause explantation as event. Functional assessment comprised subjective rating of satisfaction, Postel Merle d'Aubigné (PMA) and Harris Hip scores, and Forgotten Joint Score (FJS). Whether the revision assembly was carried out in situ, in the patient's hip, or outside, on the operating table, was not known in 2 cases; in the other 43, assembly was in situ in 15 cases (35%) and on the operating table in 28 (65%).

RESULTS

Five-year stem survival was 75.7% (95% CI: 61.9-89.5%), taking all causes of change together. Seventeen patients (45.9%) had complications, 13 (35.1%) requiring revision surgery, including 10 (27.0%) for stem replacement. Five patients (13.5%) had steam breakage at the junction between the metaphysis and the diaphyseal stem, 4 of which occurred within 2 years of implantation or of fixation of a periprosthetic fracture. Mean preoperative Harris score was 48.4 [IQR (25-75% interquartile range): 37-58] and PMA score 11.1 (IQR: 10-12), compared to respectively 74 (IQR: 67-89) and 13.6 (IQR: 12.5-16) at follow-up. Mean FJS at follow-up was 71.5 (IQR: 61-94.5). In the 15 in situ assemblies, there were 3 breakages (20%), compared to 2 (7.1%) in the 28 table assemblies (p=0.21).

DISCUSSION

The stem breakage rate was high despite the reduced modularity, which concentrated all stress on a single junction but without reducing the risk of mechanical failure. Surgical technique was faulty in some cases, with in situ assembly of the metaphysis after implanting the diaphyseal stem, which does not respect the manufacturer's recommendations.

LEVEL OF EVIDENCE

IV; retrospective study.

Clinical and Functional Outcomes of Extended Trochanteric Osteotomy in 2-Stage Revision Total Hip Arthroplasty for Periprosthetic Joint Infection: A Systematic Review and Meta-Analysis

BACKGROUND

Extended trochanteric osteotomy (ETO) has long been used in 2-stage revision surgeries of the hip, for both aseptic and septic indications. The purpose of this systematic review is to summarize the cumulative occurrence rates of the clinical and functional outcomes associated with the use of ETO in 2-stage revision total hip arthroplasty for periprosthetic joint infection.

METHODS

PubMed/MEDLINE and the Cochrane Database of Systematic Reviews databases were searched for articles published from January 1980 to January 2022 using the following keywords: "extended" AND "trochanteric" AND "osteotomy" AND "infection." Cumulative occurrence rates of outcomes and complications were calculated. A fixed-effects model and a 95% CI were applied. A P value of .05 was considered the significance threshold.

RESULTS

Nine studies were in full compliance with the inclusion criteria, with a total population size across all studies of 378. Union and infection eradication rates among studies were 95.1% (95% CI, 92.7-97.1, P = .018) and 94.0% (95% CI, 91.1-96.4, P = .089), respectively. Postoperation complications occurred in 15.34% of patients (95% CI, 10.34-21.22, P = .066). Occurrence rates for stem subsidence, dislocation, and femoral fractures were 6.2% (95% CI, 3.3-9.9, P = .187), 7.6% (95% CI, 4.8-10.9, P = .075), and 9.1% (95% CI, 5.8-13, P = .106), respectively.

CONCLUSION

With high rates of union and infection eradication, and low rates of postoperation complications, this study concludes the use of ETO in performing 2-stage revision total hip arthroplasty for the septic hip to be effective and safe.

Accuracy of Positioning and Risk Factors for Malpositioning Custom-Made Femoral Stems in Total Hip Arthroplasty-A Retrospective Multicenter Analysis

Total hip arthroplasty (THA) is commonly performed using off-the-shelf implants. In the case of a severe mismatch between the anatomy of the proximal femur and the geometry of the stem, the use of custom-made stems might become necessary. The goal of this study was to investigate the precision of the implantation of custom-made stems of one manufacturer (CTX stem, AQ Implants) and to determine risk factors for malpositioning. All patients receiving a custom-made CTX stem between 2014 and 2020 at six high-volume academic centers were retrospectively recruited. The achieved position of the stem, as determined by stem version, stem coronal angle, and implantation depth on radiographs, was compared to the plan. The influence of radiographic and demographic parameters on the position was investigated. The results revealed a high variability of the achieved implant position in relation to the preoperative plan. While the stem coronal angle only differed slightly from the intended position, the stem version and the implantation depth showed a high frequency and amount of deviation. Right stems showed significantly higher positions than planned. Surgeons must be aware of this potential problem when implanting custom-made stems.

Monoblock tapered stems in management of UCS B2 and B3 periprosthetic fractures in revision total hip arthroplasty

Aims

United Classification System (UCS) B2 and B3 periprosthetic fractures in total hip arthroplasties (THAs) have been commonly managed with modular tapered stems. No study has evaluated the use of monoblock fluted tapered titanium stems for this indication. This study aimed to evaluate the effects of a monoblock stems on implant survivorship, postoperative outcomes, radiological outcomes, and osseointegration following treatment of THA UCS B2 and B3 periprosthetic fractures.

Methods

A retrospective review was conducted of all patients who underwent revision THA (rTHA) for periprosthetic UCS B2 and B3 periprosthetic fracture who received a single design monoblock fluted tapered titanium stem at two large, tertiary care, academic hospitals. A total of 72 patients met inclusion and exclusion criteria (68 UCS B2, and four UCS B3 fractures). Primary outcomes of interest were radiological stem subsidence (> 5 mm), radiological osseointegration, and fracture union. Sub-analysis was also done for 46 patients with minimum one-year follow-up.

Results

For the total cohort, stem osseointegration, fracture union, and stem subsidence were 98.6%, 98.6%, and 6.9%, respectively, at latest follow-up (mean follow-up 27.0 months (SD 22.4)). For patients with minimum one-year of follow-up, stem osseointegration, fracture union, and stem subsidence were 97.8%, 97.8%, and 6.5%, respectively.

Conclusion

Monoblock fluted stems can be an acceptable modality for the management of UCS B2 periprosthetic fractures in rTHAs due to high rates of stem osseointegration and survival, and the low rates of stem subsidence, and revision. Further research on the use of this stem for UCS B3 periprosthetic fractures is warranted to determine if the same conclusion can be made for this fracture pattern.

Breakage of Tapered Junctions of Modular Stems in Revision Total Hip Arthroplasty—High Incidence in a Consecutive Series of a Single Institution

Background: Modularity in revision THA (RTHA) has become accepted during the last three decades. Nevertheless, specific risks of modularity of current revision devices such as breakage of taper junctions occur during follow-up. Data reporting failure rates are predominantly given by the manufacturers but independent data acquisition is missing so far. Questions/Purposes: 1. What time-related risk of breakage of taper junction between neck and body of an established modular revision device can be expected in a consecutive single institutional series and a mid-term follow-up? 2. Are there specific factors influencing breakage in this cohort? Materials and Methods: A retrospective analysis was performed of a consecutive series of 89 cases after femoral revision using a tapered modular revision stem. Mean follow-up period was 7.1 (range: 3.0–13.7) years. Breakage of stem as failure criteria of the implant was investigated with a Kaplan–Meier analysis. Results: Breakage of taper junctions occurred in four patients during follow-up showing a time-depending implant survival of 94.2 (95% CI: 88.6–100%) after 13.7 years. Implant survival of stems with lateralized necks of 87.4 (95% CI: 75.6–100%) after 13.7 years was significantly lower compared to the standard offset variant with 100% after 13.5 years (log rank test p = 0.0283). Chi square test also revealed a significantly higher risk of breakage of lateralized necks compared to standard offset pieces (p = 0.0141). Three of four patients were obese with a mean BMI of 37.9 kg/m2. Grade of obesity (grade 1 or higher) had significant influence on risk of breakage. Survival of the implant was significantly lower in obese patients with at least grade 1 obesity compared to patients with a BMI < 30 kg/m2 (82.9 (95% CI: 64.9–100%) after 11.6 years vs. 98.4 (95% CI: 95.3–100%) after 13.7 years; log-rank p = 0.0327). Conclusions: Cumulative risk for failure of taper junctions was high in this consecutive single institutional cohort and may further increase during follow-up. As independent data acquisition in registries is missing, failure rate may be higher than reported data of the manufacturers. The use of lateralized offset necks in obese patients of at least grade 1 obesity showed a significantly higher risk of breakage. The use of monobloc revision devices may be an option, but randomized control trials are currently missing to establish standardized treatment protocols considering individual risks for both monobloc and/or modular implants.

Wear estimation of hip implants with varying chamfer geometry at the trunnion junction: a finite element analysis

The hip joint helps the upper body to transfer its weight to lower body. Along with age, there are various reasons for the degeneration of the hip joint. The artificial hip implant replaces the degenerated hip. Wear between the joints is the primary cause of the hip implant becoming loose. The wear can occur due to various reasons. Due to this revision surgery are most common in young and active patients. In the design phase of the implant if this is taken care then life expectancy of the implant can be improved. Small design changes can significantly enhance the implant's life. In this work, elliptical-shaped hip implant stem is designed, and linear wear is estimated at trunnion junction. In this work, a 28 mm diameter femoral head with a 4 mm thick acetabular cup and a 2 mm thick backing cup is used. The top surface taper radiuses are changed. Solid works was used to create the models. Ansys was used to perform the analysis. It was found that as the radius of the TTR decreased, the wear rate decreased. The least wear rate was found in 12/14 mm taper with a value of 1.15E^-02mm year^-1for the first material combination and with a value of 1.23E^-02mm year^-1for the second material combination. In the comparison between the models with 1 mm chamfer and no chamfer, it was found that the wear rate was lower for the models with 1 mm chamfer. When the chamfer was increased (more than 1 mm), the linear wear increased. Wear is the main reason for the loosening of hip implants, which leads to a revision of an implant. It was found that with a decrease in TTR, there was a small increase in the linear wear rate. Overall, the implant with TTR 6 mm and a chamfer of 1 mm was found to have the least wear rate. To validate these results, the implant can be 3D printed and tested on a hip simulator.

Long-Term Outcomes of Revision Total Hip Arthroplasty Using a Tapered and Fluted Modular Stem: A Mean Follow-Up of 16 Years

BACKGROUND

Tapered modular stems are increasingly used in revision total hip arthroplasty (THA) with deficient femoral bone stock. This study aimed to report the long-term outcomes of revision THA using a tapered and fluted modular stem.

METHODS

Between December 1998 and February 2006, 113 revision THAs (110 patients) were performed with a tapered and fluted modular stem at a single institution. Hip radiographs were used to identify stem subsidence, stability, and femoral radiolucency. Final outcomes were assessed in 72 hips (70 patients), with a minimum follow-up of 10 years.

RESULTS

The mean follow-up duration was 16 years (range, 10-23). At the final evaluation, the Harris Hip Score improved from a mean of 41 points (range, 10-72) preoperatively to 83 points (range, 56-100) (P < .001). Six femoral re-revisions were performed for the following reasons: 1 aseptic loosening, 2 stem fractures, and 3 infections. One stem fracture occurred at the modular junction after 14 years, and the other at a more distal location after 15 years. Stem subsidence was >5 mm in 6 hips (9.1%), but secondary stability was achieved in all stems. Osseointegration was observed in 63 (95.5%) hips. Stem survivorship was 91.1% with an end point of any re-revision and 94.6% for aseptic re-revision.

CONCLUSION

A tapered and fluted modular stem demonstrated excellent implant survivorship with reliable bony fixation at a mean follow-up of 16 years. This type of stem can be a durable option for revision THA in patients who have femoral defects.

Stay Short or Go Long in Revision Total Hip Arthroplasty With Paprosky Type II Femoral Defects: A Comparative Study With the Use of an Uncemented Distal Fixating Modular Stem and a Primary Monobloc Conical Stem With 5-Year Follow-Up

BACKGROUND

In the revisions for Paprosky type II femoral defects, diaphyseal fixating femoral stems are commonly used. To preserve bone stock, the use of a shorter primary conical stem could be an adequate alternative. The objective of this study is to compare the results of a primary conical stem to the more commonly used diaphyseal fixating modular revision stem in revision total hip arthroplasty surgery with Paprosky type II femoral defects.

METHODS

A total of 59 consecutive patients with Paprosky type II femoral defects from our prospective revision registry were included. Thirty patients who received a long distal fixating modular stem (Revision Stem, Lima Corporate) and 29 patients who received a primary conical short stem (Wagner Cone, Zimmer) were prospectively followed. Minimal follow-up time was 2 years for subsidence and patient-reported outcome measures and 5 years for complications, reoperation, and revision. We compared subsidence, perioperative complications, reoperations, femoral component survival, Oxford Hip Score, EuroQol 5 Dimension, visual analog scale (VAS) for pain at rest, and VAS for pain during activity between stems.

RESULTS

Both groups were comparable regarding demographic, clinical, and surgery-related characteristics. We found more perioperative complications and stem revisions with the modular revision stem than with the primary conical stem. There were no statistical differences in subsidence, EuroQol 5 Dimension, Oxford Hip Score, and VAS for pain at rest or during activity between both stems.

CONCLUSION

In revision total hip arthroplasty with Paprosky type II femoral defects, uncemented primary monobloc conical femoral stems showed the same clinical result as distal fixating modular stems with fewer complications and fewer stem revisions.

EBRA Migration Analysis of a Modular, Distally Fixed Stem in Hip Revision Arthroplasty: A Clinical and Radiological Study

Background: Massive osteolysis of the proximal femur makes stem revision a challenging procedure. EBRA-FCA provides the opportunity to determine stem migration, which is considered a predictive factor for implant survival. In this study, we aimed to analyze the migration behavior of a modular, distally fixed reconstruction prosthesis. Methods: Applying a retrospective study design, we reviewed all consecutive patients who received a cementless MP reconstruction prosthesis (Waldemar Link GmbH & Co. KG, Hamburg, Germany) at our Department between 2005 and 2019. We reviewed medical histories and performed radiological measurements using EBRA-FCA software. Results: A total of 67 stems in 62 patients (female 26; male 36) fulfilled our inclusion criteria. Mean age at surgery was 68.0 (range 38.7−88.44) years. EBRA migration analysis showed a median subsidence of 1.6 mm (range 0.0−20.6) at 24 months. The angle between stem and femur axis was 0.3° (range 0.0°−2.9°) at final follow-up. No correlation between body mass index and increased subsidence was found (p > 0.05). Overall revision-free rate amounted to 92.5% and revision-free rate for aseptic loosening to 98.5%. Furthermore, no case of material breakage was detected. Conclusions: In summary, the MP reconstruction prosthesis showed low subsidence and reduction in the migration rate over the investigated follow-up. Based on this, the modular stem can be considered as a good therapy option in challenging stem revisions offering various options to address the individual anatomical situation.

Fully hydroxyapatite-coated distal locking cementless femoral modular implant for revision total hip arthroplasty: A retrospective study of 94 Renaissance™ stems at a minimum 10 years' follow-up

INTRODUCTION

Modular locking revision total hip arthroplasty femoral implants have been little assessed over the long term. We therefore conducted a retrospective assessment of the Renaissance™ fully hydroxyapatite-coated distal locking cementless femoral modular revision implant at a minimum 10 years' follow-up, analyzing: 1) survivorship, 2) complications, 3) radiologic and functional results, and 4) prevalence of thigh pain.

HYPOTHESIS

This implant shows more than 90% 10-year survival.

MATERIAL AND METHOD

Between December 2002 and December 2008, 213 implant exchanges were performed in 206 patients, including 97 Renaissance™ stems in 93 patients. Three patients were excluded for missing data. Survival was analyzed for 94 stems in 90 patients at a mean 11.2±3 years' follow-up; radiographic and clinical assessment was performed for 48 stems in 45 patients. The survival criterion was implant fracture and/or femoral stem removal.

RESULTS

Survival was 93.5% at 10 years (95% CI: 86-97) and 91.3% at 15 years (95% CI: 82.9-96). Eight stems (8.5%) were exchanged or removed by last follow-up: 5 for infection (5.3%) and 3 for implant breakage (3.2%). The complications rate was 18.1% (N=17, including the 8 stem revisions): 3 stem exchanges for breakage (3.2%), 9 stem infections (9.6%), 3 dislocations (3.2%), and 2 traumatic greater trochanter fractures (2.1%). For the 45 patients with long-term clinical assessment, the mean Postel Merle d'Aubigné and Harris Hip scores were respectively 15±3 and 80 ±19 at last follow-up. Metaphysis reconstruction was satisfactory in 36/48 cases (75.0%). Seven of the 48 stems (14.6%) assessed at longest follow-up, in 45 patients, were causing thigh pain, unrelated to stress-shielding, distal locking screws or metaphyseal filling index.

DISCUSSION

The Renaissance™ fully hydroxyapatite-coated modular locking stem with curved nail showed 90% 10-year survival, with satisfactory functional results and little thigh pain.

LEVEL OF EVIDENCE

IV; case study without control group.

[Partial or full component exchange in hip revision? : The relevance of off-label use and mix & match]

Off-label use is frequently practiced in hip revision arthroplasty, as there may be indications for the application of implants for purposes outside the one the manufacturers intended (i.e. large bone and soft tissue defects, obesity). Patients may also benefit from selective application of mix & match in hip revision, when the exchange of one component only is necessary and the invasiveness of surgery can be reduced. Currently, there are no formal guidelines for these situations. Therefore, within a recent EFORT initiative, evidence- and consensus-based recommendations have been developed for the safe application of off-label use and mix & match in revision hip and knee arthroplasty.

The survivorship of revision total hip replacement with severe proximal bone deficiency using a modular taper fluted prosthesis

Contemporary uncemented femoral revision hip systems have become commonly used over the past decade and have enabled the reconstruction of leg length, offset and anteversion as independent variables through the use of modular junctions. Modular junction failures between the proximal body and distal stem have been described with revision systems, although this is rare. We sought to identify the survivorship of one revision system in a salvage arthroplasty scenario where no host bone support of the modular junction was present. From a series of 136 patients, 15 patients (16 hips) were identified without host bone support of the modular junction with a mean radiological follow up of over 6 years (76 months +/- 35 months). There have been no cases of prosthetic fracture over the follow-up duration, with two revisions performed for reasons of aseptic loosening and infection. The mean BMI of the study group was 30.2 with 78% of the cohort classified as overweight or obese. It is well recognised that, host bone support of the modular junction is preferable, however the satisfactory outcomes over the midterm in these complex patients suggests that modular revision systems remain an option.

EFORT recommendations for off-label use, mix & match and mismatch in hip and knee arthroplasty

Off-label use is frequently practiced in primary and revision arthroplasty, as there may be indications for the application of implants for purposes outside the one the manufacturers intended.

Under certain circumstances, patients may benefit from selective application of mix & match. This can refer to primary hip arthroplasty (if evidence suggests that the combination of devices from different manufacturers has superior results) and revision hip or knee arthroplasty (when the exchange of one component only is necessary and the invasiveness of surgery can be reduced).

Within the EFORT ‘Implant and Patient Safety Initiative’, evidence- and consensus-based recommendations have been developed for the safe application of off-label use and mix & match in primary as well as revision hip and knee arthroplasty.

Prior to the application of a medical device for hip or knee arthroplasty off-label and within a mix & match situation, surgeons should balance the risks and benefits to the patient, obtain informed consent, and document the decision process appropriately.

Nevertheless, it is crucial for surgeons to only combine implants that are compatible. Mismatch of components, where their sizes or connections do not fit, may have catastrophic effects and is a surgical mistake.

Surgeons must be fully aware of the features of the components that they use in off-label indications or during mix & match applications, must be appropriately trained and must audit their results.

Considering the frequent practice of off-label and mix & match as well as the potential medico-legal issues, further research is necessary to obtain more data about the appropriate indications and outcomes for those procedures.

Cite this article: EFORT Open Rev 2021;6:982-1005. DOI: 10.1302/2058-5241.6.210080

Mid- to long-term results of the Cone-Conical modular system in revision hip arthroplasty

BACKGROUND

Modular design in revision hip surgery allows some flexibility intra-operatively to address leg length discrepancy, version, and offset while allowing the surgeon to bypass a deficient proximal femur and achieve axial and rotational stability distally. The purpose of this study was to analyze the mid-term to long-term survival and clinical and radiological outcomes using a conical fluted stem and a cone-shaped hydroxyapatite-coated proximal body "The Cone-Conical modular system (Stryker)" in revision hip surgery.

METHODS

We retrospectively reviewed all the patients who underwent hip revision surgery using Cone-Conical modular system between January 2006 and January 2015 at our institution. Seventy patients (72 hips) were included with a mean age of 71.3 years. We had a mean follow-up period of 8.6 years (range 5-15). All patients had a minimum follow-up of five years. A Kaplan-Meier analysis was used to determine the survival of the implant. Functional outcomes were assessed using Oxford Hip Score. Plain radiographs were performed to assess implant fixation and osseointegration.

RESULTS

The mean OHS improved significantly from 12 pre-operatively to 34 at the final follow-up (P < .001). The Cone-Conical system survivorship for aseptic loosening as an end point was 100%. The all-cause survivorship was 97.2%. Two hips had revisions for recurrence of infection.

CONCLUSIONS

The Cone-Conical femoral modular revision system has demonstrated excellent mid-term to long-term clinical and radiographic results with low failure rate and minimal complications. Longer-term follow-up would be of value to assess the ongoing survival of this implant.

A New Type of Periprosthetic Fracture: Is It the Time to Update the Unified Classification System?

INTRODUCTION

Increased number of primary and revision arthroplasties performed globally has led to a surge in the numbers of periprosthetic fractures. The Unified Classification System (UCS) advocated a rational approach towards the classification of periprosthetic fractures. We present here an update to the UCS with addition of new fracture pattern encountered in orthopedic practice.

METHODS

A retrospective study was conducted to review the service arthroplasty register for the cases with unique fracture pattern where the periprosthetic fracture around total hip arthroplasty was also associated with fracture of the prosthetic component. The details were retrieved from the medical record and the patients were called for a review. The radiological assessment was done with X-rays and clinical assessment with Harris Hip Scores at the latest follow-up.

RESULTS

Between 2012 and 2019, 11 patients (7 males and 4 females) were operated for peri-prosthetic fracture with a unique pattern where the fracture of femur was associated with fracture of the femoral stem as well. The mean age of the patient at the time of fracture was 56.8 years (range 42-71 years). All patients were managed with revision hip surgery. One patient died due to malignancy after 7 years of revision surgery. All the surviving patients are doing well with a mean Harris Hip Score of 86.8 at the latest follow-up of 2-9 years (mean 5.0 years).

CONCLUSION

With emergence of this new fracture pattern, it is recognition as a separate entity would help in better understanding and augmentation of the existing classification system of periprosthetic fractures.

Modular or Monolithic Tapered Fluted Prostheses for Periprosthetic Fractures: Which One Could Work for You?

Periprosthetic fracture around a femoral component is a potentially devastating complication after total hip arthroplasty. Surgical treatment is often technically demanding and requires a thorough understanding of fracture care and revision joint reconstruction. Advancements in femoral component designs for revision total hip arthroplasty have improved management of this challenging complication. It is important for surgeons to understand which femoral component design might best suit their needs. We present an overview of revision total hip arthroplasty in the setting of periprosthetic fracture, focusing on comparing the 2 most popular femoral component revision models, the modular and monolithic tapered fluted conical prostheses.

A Role for Modern Primary Cementless Femoral Stems in Revision Hip Arthroplasty

BACKGROUND

In revision total hip arthroplasty (THA) cases with preserved femoral metaphyseal bone, tapered proximally porous-coated "primary" femoral stems may be an option. The objective of this study was to compare outcomes of patients with Paprosky I or II femoral bone loss undergoing revision THA with either a primary metaphyseal-engaging cementless stem or a revision diaphyseal-engaging stem.

METHODS

This was a retrospective analysis of 70 patients with Paprosky I or II femoral bone loss who underwent femoral revision. 35 patients who were revised using a primary cementless femoral stem were compared with 35 patients who underwent femoral revision using a revision diaphyseal-engaging stem. The groups were similar regarding age, gender, body mass index, and American Society of Anesthesiologists. Clinical and radiographic outcomes and complications were compared over an average follow-up of 2.9 years (SD 1.4).

RESULTS

Revision THA was most commonly performed for periprosthetic joint infection (N = 27, 38.6%). The groups were similar with regards to Paprosky femoral classification (P = .56), length of stay (P = .68), discharge disposition (P = .461), operative time (P = .20), and complications (P = .164). There were no significant differences between primary and revision femoral stem subsidence (0.12 vs. 0.75 mm, P = .18), leg length discrepancy (2.3 vs. 4.05 mm, P = .37), and Hip Disability and Osteoarthritis Outcome Score Jr (73.1 [SD 21.1] vs. 62.8 [SD 21.7], P = .088). No patient underwent additional revision surgery involving the femoral component.

CONCLUSION

Use of modern primary cementless femoral stems is a viable option for revision hip arthroplasty in the setting of preserved proximal femoral metaphyseal bone. Outcomes are not inferior to those of revision stems and offer potential benefits.

Tapered, fluted, modular, titanium stems in Vancouver B periprosthetic femoral fractures: an analysis of 87 consecutive revisions

AIMS

One of the instruments in the orthopaedic surgeon's armamentarium to face the challenges associated with periprosthetic fracture around the stem of a hip replacement is the tapered, fluted, modular, titanium (TFMT) stem. Our aim was to study its clinical and radiological outcomes.

PATIENTS AND METHODS

During the period 2010-2016 86 patients (55 females; median age 78.2 years; mean BMI 26.3 kg/m²; median ASA classification 2) underwent 87 revisions for a Vancouver B periprosthetic fracture using a Stryker Restoration Cone-Conical stem.

RESULTS

After a median follow-up of 2.9 years no stem had to be revised and no case of stem fracture was found. Dislocation was the most common complication and occurred in 18% of patients. Other major complications were deep infection (n = 4), subsidence >5 mm (n = 7), and nonunion (n = 5). 3-month and 1-year mortality was 10% and 15% respectively and was strongly correlated with age, deep infection, and ASA classification. The median EQ-5D health state index at final follow-up was 0.78 and all patients were ambulatory.

CONCLUSIONS

The complication most commonly encountered was dislocation and can likely be prevented by the use of large heads, adequate reduction and fixation of the trochanteric area and restoration of the native anatomy. Contrary to previous concerns, fracture and subsidence of these modular stems do not appear to be a significant problem in this geriatric population.

Early clinical and radiological outcomes of a new tapered fluted titanium monobloc revision stem in hip arthroplasty

PURPOSE

A new fluted, titanium, monobloc stem with a three degree taper has been designed in an attempt to overcome the challenges associated with femoral reconstruction in the setting of extensive bone loss. The aim of this study was to report its early clinical and radiographic outcomes.

METHODS

This is a retrospective review of prospectively collected data carried out at a single institution between Jan 2017 and Dec 2019. Forty-three femoral revisions were performed using a new tapered, fluted, titanium, monobloc (TFTM) revision stem. Complications, clinical and radiographic data were obtained from medical records and a locally maintained database. Clinical outcomes were assessed using the Oxford Hip Score (OHS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). All post-operative radiographs were analysed for subsidence, osteolysis and femoral cortical bone remodelling.

RESULTS

Mean follow-up was 24 months (range 8-42 months). Subsidence of 1.2 mm was noted in one patient. No cases of clinically significant subsidence (> 10 mm) were observed. At final follow-up, a statistically significant improvement was noted in functional outcome scores. The mean OHS preoperatively and at final follow-up were 24 (SD 13) and 42 (SD15). p = 0.04 mean difference 18 (95% CI 15-22). The mean WOMAC scores preoperatively and at final follow-up were 62 (SD23) and 88 (SD7) respectively (p < 0.001, mean difference 26; 95% CI 21-34). No stem fractures were noted within the follow-up period.

CONCLUSION

Positive early clinical and radiological outcomes have been observed with this tapered, fluted, titanium, monobloc stem. Based on these results, this implant may be considered as a viable option in the majority of uncemented femoral revisions.

Short proximal components in modular revision stems carry a higher risk for stem fractures

INTRODUCTION

Fractures of modular hip revision stems are not uncommon. The current study examined implant-related factors on stem fracture. We hypothesised that in a modular stem the fracture risk is increased with the use of a short proximal implant component.

MATERIALS AND METHODS

Anonymised data of all 32 patients in Switzerland with a Revitan modular hip system who had a stem fracture were obtained from the manufacturer. Implant and patient data were compared with all components implanted in Switzerland during the same time interval.

RESULTS

Between 2002 and 2017, 4834 Revitan stems were implanted, of which 32 fractured. A smaller size of the proximal stem component was significantly associated with a higher fracture risk (p < 0.001). Compared with the control group, the proportion of male patients was higher among the fracture cases, patients were younger, and they had a higher body weight (p < 0.001, respectively).

CONCLUSIONS

The present study suggests that small proximal stem components increase the load at the modular junction due to size and lack of bony support. Surgeons should therefore avoid short proximal components so that the mid-stem junction lies as distally as possible and the risk of fracture is minimised.

Femoral Stem Fracture in Hip Revision Arthroplasty: A Systematic Literature Review of the Real-World Evidence

Background Total hip arthroplasty (THA) presents as an excellent treatment for the osteoarthritic hip, demonstrating good survival rates. However, aseptic loosening and infection are the main causes of operative revision. The methods used in revision surgery are non-modular or modular THA implants. In addition to the abovementioned revision reasons for THA, this treatment could be associated with the possibility of femoral stem fracture, especially in the modular system. The topic of material failure has been focused on in the public media. The question arises as to how such media reports correlate with the published literature. The observed mentioned number of cases concerning a femoral stem fracture vary between one single case and up to 18.5% within a clinical study, thus presenting an inhomogeneous data situation with a large span. The specific aim of this systematic review is to establish facts and clarify the number of unforeseen events of a femoral stem fracture based on peer review articles and registry data. This clarification is important to us, as these media reports have led to uncertainty among patients.

Methods A systematic review was performed in accordance with the PRISMA statement. Peer review articles in English and German, presenting original articles, meta-analyses, or case reports, were searched from the turn of the millennium up to December 2019. Only articles that reported a femoral stem component fracture, with content of clinical data as well as register data, were included. Relevant papers published after the defined research time frame were taken into account within the discussion.

Results In total, 218 fractures of a femoral stem (141 primary and 77 revision THA) component could be identified within the selected literature. Most cases of a femoral stem fracture occurred in the modular THA implants compared to the non-modular stems. Regarding revision THA, in summary, 77 implants, presenting 23 non-modular and 54 modular implants, failed by means of femoral stem fracture. A review of 11 National Joint Registries shows a revision rate between 0.04 and 0.05% in only 2 registers according to the specific subject of a femoral stem fracture. For the remaining 9 registers, however, detailed information is lacking and only nonspecific information such as a generic “implant failure” or “other reason” (which can cover a multitude of causes) is supplied.

Conclusion A femoral stem fracture presents a devastating complication for the patient, the surgeon as well as for the manufacturer of the implant. Modular THA implants play an increasingly valuable role concerning restoration of individual anatomy in modern THA revision surgery, especially within complex cases. Regarding revision procedures, data suggests a lower risk of femoral stem fracture for modular implants compared to primary procedures, while the risk of fracture for non-modular implants seems to increase during revision. Ultimately, it cannot be proven whether this is actually applicable, since the absolute number of implanted prosthesis systems is not known. Various implant-, patient-, and surgeon-related factors may lead to these reported femoral stem fractures. However, this systematic review suggests that this is, in general, a rare complication.

Mid- to Long-Term Outcomes of Cementless Modular, Fluted, Tapered Stem for Massive Femoral Bone Loss in Revision Total Hip Arthroplasty

OBJECTIVE

To evaluate mid- to long-term results of revision total hip arthroplasty for massive femoral bone loss using a cementless modular, fluted, tapered stem.

METHODS

This is a retrospective study performed at a single hospital. During the period of January 2007 to January 2015, 33 patients (34 hips) underwent primary revision surgery with cementless modular, fluted, tapered stems due to femoral bone loss. Sixteen men and 17 women were included in the study, with an average age of 63.9 ± 11.7 years (range, 27 to 88 years). Operative data including operative duration, length of incision, drainage volume and duration, blood loss and transfusion, cases of bone graft and extended trochanteric osteotomy were recorded. Clinical evaluation was performed using Harris hip score (HHS), visual analogue scale (VAS), and patients' satisfaction. Radiographic data including femoral stem fixation, subsidence, integrin of allograft bone, and leg length discrepancy were assessed. Complications and survivorship were evaluated using Kaplan-Meier survival rate.

RESULTS

The mean follow-up was 9.1 ± 2.5 years (range, 5-13 years). The Harris hip score was 43.6 ± 11.5 preoperatively and maintained at 86.5 ± 6.6 at the time of latest follow-up (P < 0. 05). The X-ray showed bone ingrowth fixation in 30 hips (88%), fibrous stable fixation in three hips (9%), and instability in one hip (3%). The average stem subsidence was 3.9 ± 2.2 mm (range, 1 to 10 mm). The mean difference in leg length in our study was 3.3 ± 2.7 mm (range, 0 to 10 mm), and the leg length discrepancy in 28 (82%) patients was within 5 mm. No case of junction fracture was observed. Seven (21%) intraoperative fractures occurred in our study. Three (9%) cases with infection were observed after revision. Six (18%) patients had lower limb vein thrombosis. The survivorship of prostheses with re-revision for any reason was 95% (95% CI, 12.0 to 13.0) at the 10-year follow-up. Three (9%) re-revisions were needed, including one for aseptic loosening, one for dislocation, and one for infection.

CONCLUSION

The mid- to long-term results of revision total hip arthroplasty with the cementless modular, fluted, tapered stems are encouraging for massive femoral bone loss.

Medium Term Radiographic and Clinical Outcomes Using a Modular Tapered Hip Revision Implant

Background

The rate of revision hip arthroplasty surgery is rising. Surgeons must use implants with proven outcomes to help overcome the technical challenges faced during revision surgery. However, outcome studies using these implants are limited. The aim of this study is to investigate the radiographic and clinical outcomes of the Stryker Restoration stem, the most commonly used hip revision stem in the United Kingdom (UK).

Methods

A retrospective review of a single surgeon case series was performed. Immediate postoperative radiographs were analyzed for offset and leg length discrepancy. Radiographic evidence of subsidence was assessed using follow-up radiographs. Kaplan-Meier survival analysis was applied using explantation and reoperation as endpoints. Patient-reported outcomes were measured using the Oxford Hip Score and EQ-5D-5L.

Results

One hundred ninety-eight cases were identified. Mean follow-up duration was 51.8 months (range: 24-121). Stem survival during this period was 98%. Reoperation for any reason was 13%. Mean subsidence was 4.18 mm. Analysis of variance testing showed no difference in mean subsidence between revision indications. Mean offset and leg length discrepancies were measured at 4.5 mm and 4.3 mm, respectively. The mean Oxford Hip Score for participants was 27.6.

Conclusions

This series demonstrates excellent implant survival, with radiographic parameters for reconstruction and subsidence levels comparable to those in the existing literature. The tapered modular hip revision stem provides surgeons with the intraoperative flexibility to overcome some of the anatomical difficulties encountered during revision surgery; this is reflected in the radiographic and clinical outcomes of the cohort in this study.

High Incidence of Irradiated Cortical Strut Allograft Resorption Following Revision of Femoral Stems

BACKGROUND

Despite the widespread use of revision total hip arthroplasties using cementless stems and cortical strut allografts, graft resorption has not been explicitly studied.

METHODS

Between 2010 and 2018, 40 femoral strut grafts were used in the revision of femoral stems of 36 patients (18 males and 18 females; average age, 51.9 ± 12.9 years). The mean follow-up was 78.9 ± 37.3 months. Failure was defined as revision surgery for any reason and subsidence of greater than 5 mm.

RESULTS

The survival rate of the stem without the need for revision at 5 years was 95% (mean graft survival time, 10.8 [95% CI, 9.414-12.234] years). Overall survival with graft resorption as the endpoint was 90% at 5 years (mean graft survival time, 8.8 [95% CI, 7.5-10.2] years). Survival with graft nonunion as the endpoint was 90% at 3 years (mean survival time, 11.7 [95% CI, 10.5-12.8] years).

CONCLUSION

The resorption rate increases proportionally to the follow-up duration and can be very severe in a high percentage of cases. Long-term multicenter studies are required to assess the effect of resorption on prosthesis longevity.

Anterolateral Bone Window for Revision Broken Cemented Stem of Unipolar Hemiarthroplasty

Background

Fractured stem of the hip prosthesis is well documented in the literature. Although it is rare, it is considered as a challenging problem. Many techniques have been described to solve this problem. Purpose of the Study. Evaluation of the effect of anterolateral bone window for extraction of the cemented femoral stem of hemiarthroplasty in revision total hip replacement.

Methods

The study included eight revision hip arthroplasties in eight patients, with a broken stem of cemented (Thompson) hemiarthroplasty, which has been revised by the anterolateral proximal femoral window. All cases received cemented cups and cement-in-cement stems, except one case who received cementless long stem. Clinical follow-up of cases by Harries hip score (HHS) and X-ray.

Results

Functional improvement of HHS of all cases, with no signs of loosening, after a mean follow-up period of 1.5 years.

Conclusion

Extraction of broken stem is a challenging procedure. Many techniques have been described for revision of cases with a fractured stem of hip prosthesis, but we think that the anterolateral femoral bone window is a reproducible technique due to the characteristics of simplicity, short-time procedure, less invasive, not requiring extra instruments, and can be successful for most patients.

Revision Hip Arthroplasty Using a Porous-coated or Taper ZMR Implant: Minimum 10-year Follow-up of Implant Survivorship

INTRODUCTION

The Zimmer Modular Revision hip (ZMR) system is available in two stem options, a porous-coated cylindrical (PCM) and a taper (TM) stem. Several concerns have been reported regarding modular implants. Specifically, because of early junctional fractures, the ZMR system was redesigned with a wider modular interface. As such, we designed a study assessing long-term ZMR survivorship and functional and radiographic outcomes.

METHODS AND MATERIALS

A search of our institutional research database was performed. A minimum 10-year follow-up was selected. The following two cohorts were created: PCM and TM stems. The Kaplan-Meier survival analysis was performed, and causes of stem failure requiring revision surgery were collected. Functional outcomes as per the Harris Hip Score and radiographic stem stability were assessed as per the Engh classification.

RESULTS

A total of 146 patients meeting the inclusion criteria were available for follow-up (PCM = 68, TM = 78). The mean follow-up was 13.4 years clinically and 11.1 years radiographically for the PCM cohort. Similarly, the TM cohort had a follow-up of 11.1 years clinically and 10.5 years radiographically. The Kaplan-Meier survivorships were 87.1% and 87.8% at 15 years for the PCM and TM cohorts, respectively. The most common cause of failure requiring revision surgery overall was aseptic loosening (PCM = 1.4%, TM = 5.6%). The mean postoperative Harris Hip Score was as follows: PCM = 71.2 and TM = 64.7. Engh type I or II stem ingrowth was as follows: PCM = 85% and TM = 68%.

DISCUSSION

Good survivorship using the ZMR stem system can be expected at up to 15 years. Aseptic loosening remains the most commonly encountered problem for both PCM and TM stems. Previously identified modular junctional weakness seem to have been addressed.

The Role of Stem Modularity in the Failure of Internal Fixation in Geriatric Patients With Distally Fixed Hemiarthroplasty

The aim of this study was to compare the radiological and clinical outcomes of the same make of modular and monoblock tapered fluted stems in patients with failure of internal fixation following osteoporotic intertrochanteric fracture. This retrospective, comparative study included patients older than 65 years who underwent hemiarthroplasty with a modular or monoblock distally fixed fluted stem and had failed treatment with proximal femoral nailing between 2012 and 2017, with at least a 2-year follow-up period. Radiographic and clinical evaluations of the groups were compared. The modular group comprised 22 males and 18 females with a mean age of 85.05±7.1 years, and the monoblock group comprised 27 males and 17 females with a mean age of 83.27±7.0 years. No significant difference was observed between the groups regarding the preoperative and final-visit Harris Hip Score and Parker and Palmer Mobility Score values (P>.05 for both). More patients showed osseous restoration in the monoblock group, but not to a significant level. The groups were similar regarding mortality rates. Stem length was greater in the modular group, but the proximal femoral part and stem size were similar in the groups (P<.05 for all). Canal filling at levels A, B, and C was negatively correlated (weak) with the proximal femoral bone restoration (P<.001 for all). Canal filling at level B was negatively correlated (weak) with the stress shielding of the femur (P<.05 for all). When comparing the modularity of the stem by minimizing the variations of both prostheses, such as brand and geometric design, there was no significant difference in either clinical or radiological evaluations. [Orthopedics. 2021;44(1):e119-e124.].

Clinical, radiographic, and survivorship analysis of a modular fluted tapered stem in revision hip arthroplasty

PURPOSE

Modular fluted tapered stems are one of the most commonly used implants in femoral revision surgery. Due to the relative lack of studies on the Restoration modular fluted tapered stem, we conducted a study to evaluate its short- to mid-term clinical, radiographic, and survival outcomes.

METHODS

We identified all 45 patients treated with this revision stem at our institution. Five patients did not complete the minimum 2-year follow-up, leaving 40 patients (41 hips) for assessment. Mean follow-up was 5.1 years (range 2-11 years). Clinical outcomes were assessed using the Harris hip score (HHS). Radiographs were evaluated for subsidence and loosening. Kaplan-Meier survival analysis was performed using revision of the stem for any reason as end point.

RESULTS

The mean HHS improved from 44.6 points preoperatively to 78.4 points at the most recent follow-up (p < 0.0001). Nonprogressive subsidence occurred in 83% of the hips (mean 2.8 mm; range 1-7 mm). One stem (2.4%) showed progressive subsidence (20 mm) and was considered loose. The most common cause for reoperation was dislocation (three hips, 7.3%). The 10-year survivorship with revision of the stem for any reason as the end point was 93.5% (95% CI, 84.9-100%).

CONCLUSION

There was a significant improvement in the HHS and a low likelihood of revision at short- to mid-term follow-up, adding to the current evidence base for use of this implant in revision surgery. A longer follow-up and a larger number of cases are necessary to fully evaluate its role and performance.

Modular Fluted Tapered Stems in Aseptic Oncologic Revision Total Hip Arthroplasty: A Game Changer?

BACKGROUND

Modular fluted tapered (MFT) stems are the most frequently used femoral component in revision total hip arthroplasties (THAs). Despite this, no data are available on how they perform in revision THA for oncologic salvage. This is a unique population, often with severe bone loss and prior radiation that extends the limits of uncemented femoral reconstruction. The aims of this study were to evaluate the implant survivorship, radiographic results, and clinical outcomes of MFT stems used for revision oncologic salvage.

METHODS

We identified 17 patients treated initially with primary THA for an oncologic diagnosis (15 primary oncologic, 2 metastatic disease) who underwent subsequent femoral revision with an MFT stem. Mean age at revision was 66 years and 35% of patients were female. Mean follow-up was 4 years. Before revision, 5 of 17 had undergone local radiation.

RESULTS

Ten-year survivorship free from aseptic loosening was 100%. The survivorship free of any reoperation was 76%. There were no femoral component fractures. Three patients were revised for recurrent instability, and 1 patient underwent irrigation and debridement for an acute infection. At most recent follow-up, no patient had radiographic evidence of progressive femoral component subsidence or failure of osteointegration. The mean Harris Hip Score improved from 29 preoperatively to 76 postoperatively (P < .0001).

CONCLUSION

In this series of patients with cancer, many of whom had severe bone loss and/or prior local radiation, being treated with revision THA, there were no revisions for femoral component loosening and no cases of implant fracture.

LEVEL OF EVIDENCE

III.

A new perspective towards failure of gamma nail systems

Uncommon causes of nail failures and surgical reinterventions were determined. The study included 23 osteoporotic patients, 13 of whom followed a fast recovery program with early walking (FWB group). The other 10 patients were not allowed full weight bearing until 6 weeks (NFWB group). The T-score was determined before surgery for all cases. A case with a nail breakage after a failed DCS implant fixed in another clinic was also analyzed. The nail was revised and the broken implant underwent a metallurgic and microscopic examination. The average T-score was 2.5 for the patients that followed the fast recovery program and 2.7 for the patients from non-full weight bearing. Four patients, 1 from the NFWB group and 3 from FWB group, presented a screw cut-out. It was found that the errors of the guiding instruments may create dents, scratches or micro-fractures on the titanium coating that lead to an early implant failure. Imperfect reduction leads to incorrect implant placement and a high incidence of failure. Damaging the titanium protective coating, in a low force, high cycles scenario can cause structural failure. Delays in fracture healing and material fatigue are the most common causes of nail failure and can lead to catastrophic complications.

Femoral stem fractures after primary and revision hip replacements: A single-center experience

Objectives

This study aims to present our experience in the management of fractured femoral stems after primary and revision hip replacements by evaluating the clinical and radiographic characteristics and determining the effectiveness of the extraction methods.

Patients and methods

A total of 15 patients (5 males, 10 females; mean age 65.9 years; range, 49 to 87 years) who underwent revision hip replacement due to a fractured femoral stem between January 2005 and December 2019 were included in this retrospective study. The mechanisms and risk factors for failure as well as methods applied to extract fractured stem were analyzed through clinical and radiographic data.

Results

Nine patients had fractured cemented femoral stems, while six patients had fractured fully porous coated cementless revision stems. Lack of proximal buttress in distally fixed femoral stems was detected in 11 patients and identified as the predominant mechanism resulting in fracture. The proximal extraction method with conventional revision instrumentation, the cortical window technique, and extended trochanteric osteotomy (ETO) were used in three, seven, and five cases, respectively.

Conclusion

Our results demonstrated that the lack of proximal buttress is the most common reason for femoral stem fracture. Moreover, the proximal extraction method was mostly ineffective in fully porous femoral stems. A step-by-step approach should be considered for the extraction of a broken stem. The cortical window method can be considered as the second step if proximal extraction methods fail, and ETO should be considered at the last step if all techniques fail.

Conversion total hip arthroplasty with a proximally modular, distal fixation reconstruction prosthesis following cephalomedullar nail failure

BACKGROUND

The goals of intertrochanteric hip fracture (IHF) treatment are stable fixation, early mobilisation and function restoration. If the attempt to reduce, stabilise and fracture healing utilising a femoral cephalomedullar nail (CMN) fails, options for subsequent attempts are limited.

PURPOSE

Evaluate the clinical and radiographic outcomes of conversion total hip arthroplasty (THA) using a modular stem following a CMN failure.

MATERIALS AND METHODS

We retrospectively reviewed a consecutive series of patients with an IHF between 2012 and 2014 to identify CMN patients that went on to the subsequent failure and conversion to THA utilising a modular femoral stem (MFS). In all cases, MP Reconstruction Prosthesis (Waldemar Link, Hamburg, Germany) was implanted. Primary clinical outcomes were assessed using Harris Hip Score (HSS) before conversion procedure, 3 months, 6 months and recent office visit post-conversion THA thereafter. The secondary outcome was to analyse intra and postoperative complications. Serial radiographs at each follow-up interval were assessed for clinical success or to confirm adverse events.

RESULTS

28 patients were included in the study; 17 were females. The average age was 72.7 years (SD ± 10.5); the average time from the index procedure to conversion THA was 12.6 months (SD ± 3.5). At baseline, average HHS was 42.1 (SD ± 3.6), improved to 80.7 (SD ± 5.1) at 3 months, 86.0 (SD ± 3.9) at 6-months which levelled off to 86.1 (SD ± 4.0) at final follow-up. There were 4 (14%) post-conversion complications: 2 dislocations, 1 superficial wound infection, 1 patient with symptomatic abductor deficiency. All 4 cases were conservatively treated successfully, the implants were retained, and the patients progressed without further issue.

CONCLUSIONS

MFSs allow to successfully treat failed CMN and adverse variations in femoral anatomy with a device that will permit simultaneous correction of leg length, offset and version to relieve pain, restore function and create a durable prosthetic to host composite.

Promising results of revision total hip arthroplasty using a hexagonal, modular, tapered stem in cases of aseptic loosening

Background

Modular stems are widely used in revision total hip arthroplasty (THA) with aseptic loosening being a common reason for revision. Despite the good results reported on the use of modular stem designs, there are only few studies focusing on aseptic revisions and few studies on a hexagonal stem design. The goal of this study is to determine stem survival, clinical and functional outcome along with possible risk factors for implant failure in aseptic revision THA.

Methods

We retrospectively identified 53 patients with aseptic THA revision using a modular hexagonal stem with a minimum follow-up of two years. Femoral bone loss, radiographic and clinical outcomes as well as function measured using the Harris Hip Score (HHS) was assessed. Patients’ previous medical history was analyzed for comorbidities and the body mass index. Stem survival was calculated using the Kaplan-Meier method. Possible risk factors for implant failure were analyzed using the log-rank test. The median age at revision was 69 (IQR 62–73) with a median follow up of 74 months.

Results

Implant survival rates amounted to 90.4% at 3 and 5 years. The median HHS improved by 47 points (34 (IQR 22–47) vs 81 (IQR 59–90) p<0.001). There was a reduced implant survival after 5 years when the revision stem was used following a previous cemented stem (83.4% vs 100%, p = 0.04).

Conclusion

A modular, hexagonal stem can be successfully used in aseptic revision THA with remarkable functional results and excellent survivorship. Revision of a cemented stem using this implant might result in reduced survival which must be considered when planning treatment.

Revision of a Fractured Titanium Modular Revision Hip Stem Without Removal of the Well-Fixed Part of the Stem: A New Approach Using a Cemented Tube

Component fracture is a rare cause for revision in total hip arthroplasty. For a fractured well-fixed long femoral stem, the options are limited. We sought to develop a technique to address this problem with lower morbidity. A newly developed cemented tube was constructed and cemented onto a fractured Revitan revision hip femoral stem to retain the distal well-fixed component. At the 2-year follow-up, the Harris Hip Score, pain level, and radiographic images were analyzed. At the 2-year follow-up, no radiological signs of loosening or failure could be observed. The patient's preoperative Harris Hip Score improved from 42.8 to 97 points. The pain level improved from 7/10 to 0/10. Our case report depicts excellent clinical and radiographic outcomes at 2-year follow-up by a newly developed cemented tube technique. This technique is a potential new option for revision of fractured well-fixed diaphyseal stems without major bone loss. Our successful results suggest this technique is worthy of consideration and further study.

Is There a Benefit to Modularity for Femoral Revisions When Using a Splined, Tapered Titanium Stem?

BACKGROUND

Proposed benefits of modularity for femoral revisions in total hip arthroplasty (THA) include more precise biomechanical restoration and improved stability, but this has not been proven with use of a splined, tapered design. This study's purpose is to compare (1) complication rates, (2) functional outcomes, and (3) radiographic measures of subsidence, offset, and leg length discrepancy with the use of modular vs monoblock splined, tapered titanium stems in revision THA.

METHODS

We retrospectively reviewed 145 femoral revisions with minimum 2-year follow-up (mean, 5.12 years; range, 2-17.3 years). Patients receiving a modular (67) or monoblock (78) splined, tapered titanium stem for femoral revision were included.

RESULTS

There were no statistically significant differences in rates of reoperation (22.3% vs 17.9%; P = .66), intraoperative fracture (9.0% vs 3.8%; P = .30), postoperative fracture (3.0% vs 1.3%; P = .47), dislocation (11.9% vs 5.1%; P = .23), or aseptic loosening (4.5% vs 6.4%; P = .73) between the modular and monoblock cohorts, respectively. There were similar results regarding subsidence >5 mm (10.4% vs 12.8%; P = .22), LLD >1 cm (35.8% vs 38.5%; P = .74), restoration of hip offset (-5.88 ± 10.1 mm vs -5.07 ± 12.1 mm; P = .67), and Harris Hip Score (70.7 ± 17.9 vs 73.9 ± 19.7; P = .36) between groups. Multivariate regression showed no differences in complications (P = .44) or reoperations (P = .20) between groups.

CONCLUSION

Modular and monoblock splined, tapered titanium stems demonstrated comparable complication rates, functional outcomes, and radiographic parameters for femoral revisions. However, a limited number of patients with grade IIIB or IV femoral bone loss received a monoblock stem. Future investigations are required to determine whether modularity is beneficial for more complex femoral defects.

Subsidence Following Revision Total Hip Arthroplasty Using Modular and Monolithic Components

BACKGROUND

The ideal femoral component in revision total hip arthroplasty (rTHA) remains undetermined; however, tapered, fluted, titanium (TFT) stems are now widely used with favorable results in all types of revision scenarios. With both modular and monoblock TFT stem options, neither has been proven to be superior. Femoral stem subsidence has been linked to aseptic loosening, instability, and leg length discrepancy. This study aims to assess stem subsidence of modular and monoblock TFT stems at a single urban orthopedic specialty hospital within a tertiary academic medical center.

METHODS

Electronic medical records of rTHAs performed between January 2013 and March 2018 utilizing modular and monoblock TFT stems were examined. Data collected included baseline demographics, surgical indication, femoral Paprosky classification, and stem subsidence at most recent follow up (3 months to 3 years). Two-sample t-tests and chi-squared tests were used for statistical analysis.

RESULTS

A total of 186 patients (106 modular, 80 monoblock) were included in the analysis. Modular stems underwent significantly greater subsidence than monoblock stems at latest radiographic follow-up (3.9 ± 2.6 vs 2.3 ± 2.5 mm, P < .001). A significantly greater proportion of modular stems underwent >5 mm of subsidence at latest follow-up (29.2% vs 11.3%, P < .001).

CONCLUSION

Monoblock TFT stems have displayed promising clinical results in prior studies, and now have been shown to decrease the incidence of postoperative subsidence. With the potential for stem subsidence to lead to aseptic loosening, limb length discrepancy, and instability, the orthopedic surgeon should weigh the risks and benefits of utilizing modular vs monoblock TFT stems in rTHA.

Survivorship and Radiological Analysis of a Monoblock, Hydroxyapatite-Coated Titanium Stem in Revision Hip Arthroplasty

BACKGROUND

We evaluated the survivorship, incidence of complications, radiological subsidence, proximal stress shielding, and patient-reported outcomes of a conservative, monoblock, hydroxyapatite-coated femoral stem.

METHODS

This retrospective cohort study reports on 254 revision hip arthroplasties between January 2006 and June 2016. The mean age of patients was 71 years. The mean length of follow-up was 62 months (range 12-152).

RESULTS

There were 13 stem re-revisions: infection (4), periprosthetic fracture (4), aseptic stem loosening (3), stem fracture (1), and extended trochanteric osteotomy nonunion (1). Kaplan-Meier aseptic stem survivorship was 97.33% (confidence interval 94-100) at 6 years. There were 29 intraoperative fractures. There were 6 cases of subsidence greater than 10 mm; however, none required revision. Ninety-six percent of cases showed no proximal stress shielding. Thigh pain was reported in 3% of cases.

CONCLUSION

This study confirms that this stem provides good survivorship at 6 years, acceptable complication rates, adequate proximal bone loading, low incidences of thigh pain, and reliable clinical performance in revision hip arthroplasty.

KEY MESSAGE

A monoblock, fully hydroxyapatite-coated titanium stem is reliable in revision arthroplasty with mild-moderate femur deficiencies.

Mechanical failure of 113 uncemented modular revision femoral components

Aims

We evaluated a large database with mechanical failure of a single uncemented modular femoral component, used in revision hip arthroplasty, as the end point and compared them to a control group treated with the same implant. Patient- and implant-specific risk factors for implant failure were analyzed.

Methods

All cases of a fractured uncemented modular revision femoral component from one manufacturer until April 2017 were identified and the total number of implants sold until April 2017 was used to calculate the fracture rate. The manufacturer provided data on patient demographics, time to failure, and implant details for all notified fractured devices. Patient- and implant-specific risk factors were evaluated using a logistic regression model with multiple imputations and compared to data from a previously published reference group, where no fractures had been observed. The results of a retrieval analysis of the fractured implants, performed by the manufacturer, were available for evaluation.

Results

There were 113 recorded cases with fracture at the modular junction, resulting in a calculated fracture rate of 0.30% (113/37,600). The fracture rate of the implant without signs of improper use was 0.11% (41/37,600). In 79% (89/113) of cases with a failed implant, either a lateralized (high offset) neck segment, an extralong head, or the combination of both were used. Logistic regression analysis revealed male sex, high body mass index (BMI), straight component design, and small neck segments were significant risk factors for failure. Investigation of the implants (76/113) showed at least one sign of improper use in 72 cases.

Conclusion

Implant failure at the modular junction is associated with patient- and implant-specific risk factors as well as technical errors during implantation. Whenever possible, the use of short and lateralized neck segments should be avoided with this revision system. Implantation instructions and contraindications need to be adhered to and respected. Cite this article: Bone Joint J 2020;102-B(5):573–579.

Fractured Femoral Stems in Primary and Revision Hip Arthroplasties Revisited: Wrightington Experience

BACKGROUND

The aim of this study is to present our experience in managing fractured femoral stems over the last 10 years for both primary and revision stems at our tertiary unit focusing on modes of failure and operative techniques.

METHODS

This is a retrospective consecutive study of all patients with fractured femoral stems that were operatively managed in our unit between 2008 and 2018. Detailed radiographic evaluation (Paprosky classification) was undertaken and data collected on operative techniques used to extract distal fractured stem fragments.

RESULTS

Thirty-five patients (35 hips) were included (25 men/10 women) with average age at time of presentation of 68 years (range, 29-93). Average body mass index was 30 (standard deviation, 3.8; range, 22.5-39). There were variety of stems both contemporary and historical, primary and revision cases (15 hips polished tapered cemented stems, 10 hips composite beam and miscellaneous stems, and 10 revision hip stems). The predominant mechanism of failure was fatigue due to cantilever bending in distally fixed stems. Surgical techniques used to extract distal fragment were drilling technique in 2 hips, cortical window in 13 hips, extended trochanteric osteotomy (ETO) in 5 hips, and proximal extraction in 15 hips.

CONCLUSION

When faced with a contemporary fractured stem, drilling techniques into the distal fragment are unlikely to succeed. If a trochanteric osteotomy had been used at time of index surgery, this could be used again to aid proximal extraction with conventional revision instrumentations. The cortical window technique is useful but surgically demanding technique that is most successful in extracting polished tapered fractured stems particularly when an ETO is not planned for femoral reconstruction. Use of trephines can be useful for removal of longer, uncemented stems. Finally, an ETO might be necessary when other techniques have failed.

Single 3° tapered fluted femoral stems demonstrate low subsidence at mid-term follow-up in severe bony deficiency

Background

Tapered femoral stems have become popular in revision total hip arthroplasty (rTHA). Increasing the distal taper angle may mitigate subsidence. This study reports osseointegration of a new 3 degree distal taper revision stem at minimum 4 years post-operatively.

Methods

Indication for surgery, pre-operative bony deficiency and latest clinical, tribological and radiological follow-up were analysed. Radiographs were assessed by two blinded observers for preoperative femoral bone stock according to Paprosky, postoperative subsidence according to Callaghan and restoration of femoral bone stock over time according to Kolstad. Stem integration was determined using the Rodriguez classification.

Results

Twenty-three cases were analyzed at 5.9±1.0 years. All patients presented with Paprosky III defects. All stems met the criteria for osseointegration. Spot welds occurred distal to the proximal modular junction and at the tip. Two femora with severe proximal femoral bone loss recovered bone stock by final follow-up but two demonstrated stress shielding. No intraoperative fractures occurred. One stem subsided early but remained stable and osseointegrated at final follow up. There were no stem failures due to taper corrosion or modular junctional failure.

Conclusions

This study reports good osseointegration and low subsidence with a novel fluted, 3-degree tapered femoral stem demonstrates at medium-term follow-up in cases with severe femoral bone deficiency.