Effect of femoral head size on risk of revision for dislocation after total hip arthroplasty: a population-based analysis of 42,379 primary procedures from the Finnish Arthroplasty Register

The economical and reliable image free navigation system for acetabular cup implantation in total hip arthroplasty

Background

Achieving precise acetabular cup positioning is vital for the success of total hip arthroplasty (THA). Factors such as cup inclination and anteversion angles play a pivotal role in determining postoperative stability, limb length equality, and overall functional outcomes. Modern navigation systems and robotics have enhanced surgical precision but remain underutilized due to their high costs and complex training requirements.

Methods

We have designed an economical and compact image-free navigation device for acetabular cup placement. By employing computer vision techniques using OpenCV, the device was tested on artificial hip models to ensure precision. A total of 50 angle measurements were analyzed for accuracy.

Results

The tool demonstrated exceptional precision, with mean inclination angle errors of 0.15° (SD: 0.44°) and mean anteversion angle errors of -1.06° (SD: 0.34°), both statistically significant (p < 0.05).

Conclusion

Our navigation device, which is portable and cost-effective, offers reliable guidance for acetabular cup positioning. Its affordability and ease of use make it an excellent alternative for resource-constrained settings.

Short-term outcomes with routine use of size ≥40 femoral heads in THA: A retrospective cohort study

Background

Using larger femoral heads during total hip arthroplasty (THA) may result in a more stable hip. Greater volumetric wear and frictional torque, however, may result in increased postoperative complications. The purpose of this study was to compare outcomes of patients with femoral head size ≥40 mm compared to those with femoral head size <40 mm.

Materials and methods

A retrospective chart review of 504 THAs performed by a single surgeon at a single institution from 2009 to 2016 was conducted. Following exclusions, 131 THAs were identified with femoral heads ≥40 mm and 348 THAs were identified with femoral heads <40 mm. In addition to demographic data, all postoperative complications were recorded. Plain radiographs were used to rule out/in periprosthetic osteolysis and/or acetabular loosening. Chi-square tests and Student's t-tests were used to compare categorical and continuous variables, respectively.

Results

Mean follow-up period for the entire cohort was 5.5 years. Complications with ≥40 mm femoral heads included 1 superficial infection and 1 deep periprosthetic joint infection (PJI). There were no cases of dislocation, osteolysis, acetabular loosening, or trunnionosis. In contrast, complications with <40 mm femoral heads included 9 dislocations and 7 PJIs.

Conclusion

The routine use of large femoral heads (≥40-mm) during THA appears to be a safe option for patients at short-term clinical follow-up. Notably, 0 patients had a clinical course complicated by dislocation, osteolysis, acetabular loosening, or trunnionosis.

Level of evidence

Level III Retrospective Cohort Study.

Head size in Delta ceramic-on-ceramic total hip arthroplasty: a comparative registry study

INTRODUCTION

Optimal bearing size in total hip arthroplasty (THA) has not been clearly ascertained, but large diameter ceramic balls may improve function and implant stability, with minimal concerns for wear. Delta ceramic-on-ceramic (COC) THA were stratified based on head diameter (32, 36 and 40 mm), aiming to assess: 1) survival rates, reasons for revision and hazard ratios for failure; 2) survival rates and hazard ratios for aseptic loosening, dislocation/primary instability, liner failure.

MATERIALS AND METHODS

A regional arthroplasty registry was enquired about Delta COC THA performed for primary osteoarthritis, stratified by head size. 13,161 primary cementless THAs were included in the study, with a mean follow-up of 5.7 years (range: 0-17): 3980 (30.2%) 32 mm balls, 8327 (63.3%) 36 mm heads, 854 (6.5%) 40 mm heads.

RESULTS

The three cohorts achieved similar survival rates (p = 0.99) and adjusted hazard ratios (p > 0.05). No revisions for head breakage or metallosis occurred. When revision for cup aseptic loosening was the endpoint, the survival rates of three cohorts (p = 0.08) and the adjusted hazard ratios (p > 0.05) were similar. The three cohorts achieved comparable survival rates when revision for dislocation/primary instability was the endpoint (p = 0.08). When the endpoint was revision for liner breakage, 32 mm cohort showed higher rates of revision (p = 0.01). No liner failure was detected in the 40 mm cohort.

CONCLUSIONS

32 mm, 36 mm and 40 mm provided similar 10-year survival rates in Delta COC THA. 40 mm heads emerged as safe options but did not lower the revisions for dislocations/primary instability.

LEVEL OF EVIDENCE

IV (therapeutic study).

The impact of femoral head size on the wear evolution at contacting surfaces of total hip prostheses: A finite element analysis

Total Hip Arthroplasty has been a revolutionary technique in restoring mobility to patients with damaged hip joints. The introduction of modular components of the hip prosthesis allowed for bespoke solutions based on the requirements of the patient. The femoral stem is designed with a conical trunnion to allow for assembly of different femoral head sizes based on surgical requirements. The femoral head diameters for a metal-on-polyethylene hip prosthesis have typically ranged between 22 mm and 36 mm and are typically manufactured using Cobalt-Chromium alloy. A smaller femoral head diameter is associated with lower wear of the polyethylene, however, there is a higher risk of dislocation. In this study, a finite element model of a standard commercial hip arthroplasty prosthesis was modelled with femoral head diameters ranging from 22 mm to 36 mm to investigate the wear evolution and material loss at both contacting surfaces (acetabular cup and femoral stem trunnion). The finite element model, coupled with a validated in-house wear algorithm modelled a human walking for 10 million steps. The results have shown that as the femoral head size increased, the amount of wear on all contacting surfaces increased. As the femoral head diameter increased from 22 mm to 36 mm, the highly cross-linked polyethylene (XLPE) volumetric wear increased by 61% from 98.6 mm3 to 159.5 mm3 while the femoral head taper surface volumetric wear increased by 21% from 4.18 mm3 to 4.95 mm3. This study has provided an insight into the amount of increased wear as the femoral head size increased which can highlight the life span of these prostheses in the human body.

Lower Risk of Revision With 32- and 36-Millimeter Femoral Heads Compared With 28-mm Heads in Primary Total Hip Arthroplasty: A Comparative Single-Center Study (10,104 Hips)

BACKGROUND

We aimed to compare the clinical outcomes of different head sizes (28-, 32-, and 36- millimeter) in primary total hip arthroplasty (THA) at mean 6 years follow-up (range, 1 to 17.5 years).

METHODS

This was a retrospective consecutive study of primary THA at our institution (2003 to 2019). Demographic and surgical data were collected. The primary outcome measures were all-cause revision, revision for dislocation, and all-cause revision excluding dislocation. Continuous descriptive statistics used means, median values, ranges, and 95% confidence intervals, where appropriate. Kaplan-Meier survival curves were used to estimate time to revision. Cox proportional hazard regression analyses were used to compare revision rates between the femoral head size groups. Adjustments were made for age at surgery, sex, primary diagnosis, American Society of Anesthesiologists score, articulation type, and fixation methods. There were 10,104 primary THAs included; median age was 69 years (range, 13 to 101) with 61.5% women. A posterior approach was performed in 71.6%. There were 3,295 hips with 28-mm heads (32.6%), 4,858 (48.1%) with 32-mm heads, and 1,951 (19.3%) with 36-mm heads.

RESULTS

Overall rate of revision was 1.7% with the lowest rate recorded for the 36-mm group (2.7 versus 1.3 versus 1.1%). Cox regression analyses showed a decreased risk of all-cause revision for 32 and 36-mm head sizes as compared to 28-mm; this was statistically significant for the 32-mm group (P = .01). Risk of revision for dislocation was significantly reduced in both 32-mm (P = .03) and 36-mm (P = .03) head sizes. Analysis of all cause revision excluding dislocation showed no significant differences between head sizes.

CONCLUSIONS

We found a significantly reduced risk of revision for all causes, but particularly revision for dislocation with larger head sizes. Concerns regarding increased risk of early revision for aseptic loosening, polyethylene wear, or taper corrosion with larger heads appear to be unfounded in this cohort of 10,104 patients with up to 17 years follow-up.

Role of femoral head material on readmission and mortality rates following elective primary total hip arthroplasty in Medicare patients

INTRODUCTION

The role of different femoral head materials for total hip arthroplasty (THA) has been widely studied in the context of wear properties and corrosion. Cobalt chrome (CoCr) femoral heads are commonly used as a standard of comparison to other materials such as ceramic and oxidized zirconium (OxZi). This study aims to evaluate the impact of femoral head material on clinical outcomes in elective primary THA patients.

METHODS

Retrospective analysis of THA patients within the Medicare claims database between October 2017 and September 2020 using diagnosis-related group codes was conducted. Information collected included sex, age, Charlson Comorbidity Index, and femoral head type. Patients with CoCr femoral heads were compared against patients with either OxZi or ceramic femoral heads using 1:1 propensity score matching. Z-testing and Chi-square analysis were used to determine between-group significance.

RESULTS

In total, 112,960 elective THA patients were included, with 56,480 in OxZi or ceramic and 56,480 in CoCr. Readmission rates were lower in patients that received OxZi or ceramic femoral heads at 30-day (p < 0.0001), 60-day (p < 0.0001), and 90-day postoperatively (p < 0.0001) compared to CoCr. Mortality rates were also lower in patients that received OxZi or ceramic femoral heads at 30-day (p = 0.004), 60-day (p = 0.018), and 90-day postoperatively (p = 0.009) compared to CoCr.

CONCLUSION

CoCr femoral heads had higher rates of readmissions and mortality compared to OxZi or ceramic. Further analysis of bearing surface combinations and sub-group analyses to determine significance between-group differences is needed.

LEVEL III EVIDENCE

Retrospective analysis.

Increasing femoral head size from 32 mm to 36 mm does not increase the revision risk for total hip replacement: a New Zealand joint registry study

BACKGROUND

The use of larger femoral heads in total hip replacement (THR) has increased over the last decade. While the relationship between increasing head size and increased stability is well known, the risk of revision with increasing head size remains poorly understood. The aim of this study was to compare the outcome of total hip joint replacement with 32-mm and 36-mm heads.

METHODS

We carried out a 20-year retrospective analysis of prospective data from the New Zealand Joint Registry (NZJR). All primary total hip replacements registered between January 1999 and December 2018 were included. We compared the rate of revision of 32-mm and 36-mm heads in THR. Sub-group analysis included comparisons of bearing type and all-cause revision.

RESULTS

60,051 primary THRs met our inclusion criteria. The revision rate per 100 component years was significantly higher with a 36-mm head than with a 32-mm head (0.649 vs. 0.534, p < 0.001). Subgroup analysis of bearing type showed no significant differences in revision rates for all combinations of 36-mm heads when compared to 32-mm (p = 0.074-0.92), with the exception of metal-on-metal (MoM); p = 0.038. When MoM was removed there was no significant difference in revision rates per 100 component years between 32-mm and 36-mm heads, 0.528 versus 0.578 (p = 0.099).

CONCLUSIONS

Increasing head size from 32 mm to 36 mm results in no significant increase in revision in all bearing combinations except MoM.

Survivorship of the dual-mobility construct in elective primary total hip replacement: a systematic review and meta-analysis including registry data

INTRODUCTION

Dislocation is a common complication associated with total hip replacement (THR). Dual-mobility constructs (DMC-THR) may be used in high-risk patients and have design features that may reduce the risk of dislocation. We aimed to report overall pooled estimates of all-cause construct survival for elective primary DMC-THR. Secondary outcomes included unadjusted dislocation rate, revision for instability, infection and fracture.

METHODS

MEDLINE, EMBASE, Web of Science, Cochrane Library and National Joint Registry reports were systematically searched (CRD42020189664). Studies reporting revision (all-cause) survival estimates and confidence intervals by brand and construct including DMC bearings were included. A meta-analysis was performed weighting series by the standard error.

RESULTS

Thirty-seven studies reporting 39 case series were identified; nine (10,494 DMC-THR) were included. Fourteen series (23,020 DMC-THR) from five national registries were included. Pooled case series data for all-cause construct survival was 99.7% (95% CI 99.5-100) at 5 years, 95.7% (95% CI 94.9-96.5) at 10 years, 96.1% (95% CI 91.8-100) at 15 years and 77% (95% CI 74.4-82.0) at 20 years. Pooled joint registry data showed an all-cause construct survivorship of 97.8% (95% CI 97.3-98.4) at 5 years and 96.3% (95% CI 95.6-96.9) at 10 years.

CONCLUSIONS

Survivorship of DMC-THR in primary THR is acceptable according to the national revision benchmark published by National Institute for Clinical Excellence (NICE).

Did the dislocation risk after primary total hip arthroplasty decrease over time? A meta-analysis across six decades

BACKGROUND

While continuous optimization is attempted to decrease the incidence of dislocation after total hip arthroplasty (THA), dislocation remains a major complication. This meta-analysis aims to analyze the evolution of the dislocation risk after primary THA over the decades and to evaluate its potential publication bias.

PATIENTS AND METHODS

A systematic search was performed according to the PRISMA guidelines for this meta-analysis in the literature published between 1962 and 2020. MEDLINE, Cochrane and Embase databases were searched for studies reporting the dislocation risk and length of follow-up. Studies that reported on revision rates only and did not mention separate dislocations were excluded. All study designs were eligible. Study quality was assessed by existing quality assessment tools adjusted for arthroplasty research. Overall risk and yearly dislocation rates were calculated and related to historical time frame, study design, sample size and length of follow-up.

RESULTS

In total, 174 studies were included with an overall moderate quality. In total there were 85.209 dislocations reported in 5.030.293 THAs, showing an overall dislocation risk of 1.7%, with a median follow-up of 24 months. The overall dislocation risk classified per decade decreased from 3.7% in 1960-1970 to 0.7% in 2010-2020. The yearly dislocation rate decreased from 1.8 to 0.7% within these same decades. There was no significant correlation between the reported dislocation risk and the duration of follow-up (p = 0.903) or sample size (p = 0.755). The reported dislocation risk was higher in articles with registry data compared to other study designs (p = 0.021).

CONCLUSION

The dislocation risk in THA has been decreasing over the past decades to 0.7%. Non-selective registry studies reported a higher dislocation risk compared to studies with selective cohorts and RCTs. This indicates that the actual dislocation risk is higher than often reported and 'real-world data' are reflected better in large-scale cohorts and registries.

Mixed manufacturer dual mobility bearing and the Exeter V40 Stem: is it safe? Short-term results in primary and revision hip replacement

The aim is to review clinical and radiological outcomes for all cases of primary and revision THA, combining a cemented stem (Exeter V40) with a dual mobility component from a different manufacturer (SERF Novae), to evaluate whether concerns regarding mixing components from different manufacturers are justified. We identified 72 hip replacements performed between May 2010 and December 2015 using the SERF Novae dual mobility cup with an Exeter V40 stem, the majority of which were cemented (90%) and revisions (58%). Patients were evaluated clinically and radiologically at a minimum of two years. There were five (6.9%) dislocations; three (4.2%) requiring revision - one of which was an intra-prosthetic disarticulation and two infections. No cases were lost to follow-up and 49 surviving cases were reviewed at a mean of 4.0 (range 1.8-8.1) years following surgery. Pain and functional outcome scores all improved. There were no radiological failures and no revisions for aseptic loosening of stem or cup. The combination of Exeter cemented stem with a dual mobility bearing from a different manufacturer results in acceptable short-term outcomes in terms of hip stability, revision rates and patient-reported measures.

The Impact of Epilepsy on Complication Rates After Total Joint Arthroplasty: A Propensity Score-Matched Cohort Study

BACKGROUND

It is unclear how epilepsy may affect total joint arthroplasty outcomes. The purpose of this study is to analyze the impact of epilepsy on prosthesis-related complications following primary total hip arthroplasty (THA) and total knee arthroplasty (TKA).

METHODS

A retrospective cohort study was conducted using a national database. Patients who have epilepsy underwent a primary THA (n = 6,981) and TKA (n = 4,987) and were matched 1:4 (THA, n = 27,924; TKA, n = 19,948). Rates of low-energy falls and prosthesis-related complications within 2 years postoperatively were compared for patients who did and did not have epilepsy with multivariable logistic regression.

RESULTS

After primary TKA, patients who have epilepsy exhibited significantly higher rates of aseptic revision (4.3% versus 3.5%, odds ratio [OR] 1.21, P = .017) and revision for prosthetic joint infection (1.8% versus 1.3%, OR 1.29, P = .041). THA patients who have epilepsy exhibited significantly higher rates of prosthetic dislocation (3.2% versus 1.9%, OR 1.54, P < .001), periprosthetic fracture (2.2% versus 0.8%, OR 2.39, P < .001), and aseptic loosening (1.7% versus 1.1%, OR 1.40, P = .002). Rates of low-energy falls within 2 years after TKA (14.1% versus 6.4%, OR 2.19, P < .001) and THA (33.6% versus 7.5%, OR 5.95, P < .001) were also significantly higher for patients who have epilepsy.

CONCLUSION

Epilepsy was associated with significantly higher rates of falls (P < .001) and prosthesis-related complications after primary THA (P < .05) and TKA (P < .05). Precautions should be implemented in this population during intraoperative and perioperative decision-making to reduce complication risk.

LEVEL OF EVIDENCE

Level III.

Analysis of biomechanical gait parameters in patients after total hip replacement operated via anterolateral approach depending on size of the femoral head implant: retrospective matched-cohort study

INTRODUCTION

Total hip replacement (THR) is considered one of the most effective medical procedures in treatment of osteoarthritis. Since its introduction, there has been a worldwide debate over proper implant selection in terms of size, bearing type and shape. Following study was designed to assess the importance of femoral head size in long-term follow-up.

MATERIALS AND METHODS

A cohort of 30 patients with primary end stage osteoarthritis who underwent total hip replacement was analysed retrospectively. A homogenous group was chosen with no major differences in BMI. Patients' gait parameters were measured in a biomechanics laboratory using the 3D BTS Smart system. WOMAC and VAS questionnaires were used to assess patient reported outcome.

RESULTS

The subgroup with larger implant head size had several outcomes significantly superior to the subgroup with standard head size and non-inferior to healthy hips. Following variables were measured during this study: time of support phase, time of swing phase, double support time, walking hip extension angle.

CONCLUSIONS

Use of larger sized femoral heads during THR gives better results in terms of gait pattern. Since restoring the gait pattern is one of the aspects of rehabilitation and returning to daily activities it seems to be an important observation.

Analysis of New Orthopaedic Technologies in Large Database Research

Improvements in orthopaedic surgery go hand in hand with technological advances. The present article outlines the historical and current uses of large databases and registries for the evaluation of new orthopaedic technologies, providing insights for future utilization, with robotic-assisted surgery as the example technology.

Epidemiology of revision hip replacement in Italy: a 15-year study

Background

Over the past two decades, there has been an increase in the amount of primary total hip arthroscopies (THA) which in turn has increased the need for THA revision surgeries. The purpose of this study was to quantify the increase in THA revision in Italy, evaluate the causes and types of THA procedures performed.

Methods

The data regarding revision hip prosthetic replacements performed both in public and private structures between 2001 and 2015 was collected by the National Hospital Discharge reports (SDO) carried out by the Italian Ministry of Health.

Results

Overall, 109,746 Revision Hip Replacements (RHR) were performed in Italy from 2001 to 2015 in the adult population. The study shows a greater number of female patients underwent surgery between 2001 and 2015 and the 75- to 79-year age group had the highest incidence of THA revision. The main causes for THA revision were found to be “Mechanical complication of internal orthopedic device implant and graft” (31.5%), “Infection and inflammatory reaction due to internal joint prosthesis” (10.5%) and “Mechanical loosening of prosthetic joint” (8.3%).

Conclusions

Revision hip replacement is growing and heavily affecting the population between 65 and 89 years and the main causes of THA revision have been quantified. The average length of hospitalization (LOS) was found to have decreased over the 14-year study period. Understanding the causes and risk factors for revision is essential in identifying avoidable complications and improving preventative care for patients undergoing primary implantation to decrease the revision burden.

A Comparison of Revision Rates and Dislocation After Primary Total Hip Arthroplasty with 28, 32, and 36-mm Femoral Heads and Different Cup Sizes: An Analysis of 188,591 Primary Total Hip Arthroplasties

This article was updated on August 17, 2022, because of previous errors, which were discovered after the preliminary version of the article was posted online. On page 1462, in the first sentence of the Abstract section entitled "Results," the phrase that had read "and 36-mm heads had fewer dislocations than 28-mm (HR = 0.33 [95% CI, 0.16 to 0.68]; p = 0.003), but more dislocations than 32-mm heads (HR for >2 weeks = 2.25 [95% CI, 1.13 to 4.49]; p = 0.021)" now reads "and 36-mm heads had fewer dislocations than 28-mm (HR = 0.33 [95% CI, 0.16 to 0.68]; p = 0.003) and 32-mm heads (HR for ≥2 weeks = 0.44 [95% CI, 0.22 to 0.88]; p = 0.021)." On page 1468, in the last sentence of the section entitled "Acetabular Components with a Diameter of <51 mm," the phrase that had read "and HR for ≥2 weeks = 2.25 [95% CI, 1.13 to 4.49; p = 0.021]) ( Fig. 3 )" now reads "and HR for ≥2 weeks = 0.44 [95% CI, 0.22 to 0.88; p = 0.021]) ( Fig. 3 )." Finally, on page 1466, in the upper right corner of Figure 3 , under "32mm vs 36mm," the second line that had read "2Wks+: HR=2.25 (1.13, 4.49), p=0.021" now reads "2Wks+: HR=0.44 (0.22, 0.88), p= 0.021."

Safety of vitamin E-infused highwall liners for routine use in primary total hip arthroplasty: single centre, short-term follow-up of 1221 cases

BACKGROUND

Introduction of new implants should be monitored closely to capture any signs of compromising patient safety. Vitamin E infused highly-crosslinked polyethylene liners (VEPE) offer the potential for reduced wear. Highwall liners have been hypothesised to result in increased wear and potential liner fractures. The aim of this study was to determine the 3-7-year follow-up of highwall VEPE for primary total hip arthroplasty (THA), focusing on liner-related complications.

METHODS

We included 1221 consecutive THA operations from July 2010 to May 2014 with minimum follow-up of 3 (3.1-6.8) years Data collected included demographics, implant data, complications, reoperations, and deaths. Data were cross-referenced with the Danish Hip Arthroplasty Registry in order to ensure validity and completeness. Acetabular shell position was measured using Martell Hip Analysis Suite in a subgroup of 931 THAs.

RESULTS

Cumulative stem revision and shell revision at 3-year follow-up was 3.4% and 0.4% respectively. There were no revisions due to liner failure. Reason for revision included 11 dislocations, 15 soft-tissue revisions for infection, 44 stem revisions of which 34 were periprosthetic fractures and 13 shell revisions of which 6 were combined shell and stem revisions.

CONCLUSION

Early follow-up of VEPE liners for primary THA have not shown any revisions associated with liner failure. Continued monitoring of new materials are necessary to capture any signs of compromised patient safety.

Implant survival of 662 dual-mobility cups and 727 constrained liners in primary THA: small femoral head size increases the cumulative incidence of revision

Background and purpose - In total hip arthroplasty (THA), the risk for dislocation can be reduced using either dual-mobility cups (DMCs) or constrained liners (CLs). There are few studies comparing these concepts in primary THA. Therefore, we compared the cumulative incidence of revision in primary THA patients treated with DMC or CL with varying head sizes with conventional THA patients as reference group.Patients and methods - We performed a cohort study based on the Finnish arthroplasty register, comparing DMCs and CLs operated over the period 2000-2017. DMCs were divided into 2 groups based on the implant design: "DMC Trident" group (n = 399) and "DMC Others" group (n = 263). CLs were divided based on the femoral head size: "CL 36 mm" group (n = 425) and "CL < 36 mm" group (n = 302). All conventional primary THAs operated on in 2000-2017 with 28-36 mm femoral head were included as control group ("Conventional THA" group, n = 102,276). Implant survival was calculated by the corresponding cumulative incidence function with revision as the endpoint and death as competing event. Also, the prevalence of different reasons for revision was compared.Results - The 6-year cumulative incidence function estimates for the first revision were 6.9% (95% CI 4.0-9.7) for DMC Trident, 5.0% (CI 1.5-8.5) for DMC Others, 13% (CI 9.3-17) for CL < 36 mm, 6.3% (3.7-8.9) for CL 36 mm, and 4.7% (CI 4.5-4.8) for control group (conventional THA). The prevalence of dislocation revision was high (5.0%, CI 2.9-8.2) in the CL < 36 mm group compared with other groups.Interpretation - The DMC and CL 36 mm groups had promising mid-term survival rates, comparable to those of primary conventional THA group. The revision rate of CLs with < 36 mm head was high, mostly due to high prevalence of dislocation revisions. Therefore, CLs with 36 mm femoral head should be preferred over smaller ones.

Revision hip arthroplasty using a porous tantalum acetabular component

INTRODUCTION

Reconstruction of acetabulum in case of bone defects can be challenging. The aim of this retrospective study was to investigate the 10-year survival of trabecular tantalum metal (TM) acetabulum component in revision hip arthroplasty operations and to evaluate complications.

METHODS

A total of 100 consecutive acetabulum revision hip arthroplasties (100 patients) were operated on between May 2004 and October 2006 at Kuopio University Hospital. The mean follow-up time was 9.4 years and the median was 11.5 years (SD 4.118; range 0.1-13.4 years). Kaplan-Meier survival analysis was performed to study the survival of patients to re-revision surgery. Intra- and postoperative complications and reasons for re-revision were evaluated.

RESULTS

The Kaplan-Meier analysis showed a cumulative proportion of revision hip survivorship of 66% at 13.4 years (SE 0.403, 95% CI, 10.886-12.466) based on the need for further re-revision surgery for any major reason. The Kaplan-Meier survival analysis of time to re-revision surgery due acetabular component loosening showed a cumulative proportion of survivorship of 98.9% at 13.4 years (SE 0.136; 95% CI, 12.998-13.529). There were a total of 41/100 complications and the most common complication was dislocation (24/100). Re-revision for any major reason was performed on 18/100 of the revision arthroplasties. The mean time to re-revision was 4.9 years (SD 5.247; range 0.1-13.2 years).

DISCUSSION

The trabecular TM acetabular component gives excellent outcomes regarding stability and fixation to the acetabulum in acetabulum revision hip arthroplasty at a minimum of ten years of follow-up. However, acetabular component malposition and the small head size (28 mm) are risk factors for dislocation.

Usefulness of intraoperative C-arm image intensifier in reducing errors of acetabular component during primary total hip arthroplasty: an application of Widmer's method

Background

Acetabular prosthesis positioning in total hip arthroplasty (THA) is crucial in reducing the risk of dislocation. There has been minimal research on the proper way to put the acetabular components into the safe zone intraoperatively. Assessment of version by intraoperative imaging intensifier is very valuable. The value of Widmer’s method, using the intraoperative C-arm available to determine cup anteversion was assessed.

Methods

One hundred one hips in 91 patients who underwent primary THA were eligible for inclusion. Utilizing intraoperative C-arm images, measurement was performed using the technique described by Widmer. The values obtained using 3D computed tomography postoperatively, which determined the anteversion of the acetabular component, were regarded as the reference standard.

Results

The method of Widmer obtained values similar to those obtained using 3D computed tomography and was considered accurate (n.s.). All 101 hips were positioned in the set target zone. Among the 101 hips, the cup position in nine hips (8.9%) was changed. The dislocation rate in our study was 1.0% with all dislocations occurring in hips placed in the target zone. The mean Harris hip score after THA in 1 year was 94.2 (82-98).

Conclusions

The method of Widmer was accurate using intraoperative imaging intensifier for the measurement of the anteversion of the acetabular component during THA, with reference to the anteversion obtained from the 3D computed tomography. Also, utilizing intraoperative C-arm imaging was very useful because it allowed for correction of the position of the acetabular cup.

Can we trust combined anteversion and Lewinnek safe zone to avoid hip prosthesis dislocation?

INTRODUCTION

Dislocation is one of the most common complications after primary total hip arthroplasty (THA). Combined anteversion (CA) is currently considered one of the most important measures of stability for THA. Thus, the aim of this study is to determine the association between a correct CA after THA and hip prosthesis dislocation, and to analyze the reliability of the Lewinnek safe zone parameters.

MATERIAL AND METHODS

This is a non-interventional retrospective study, carried out at a tertiary hospital in Spain. 2489 primary THA in 2147 patients between January 2008 and December 2014 were identified. Clinical, biological and radiographic data, including cup inclination and cup and femoral anteversion, were analyzed of all patients who developed a hip prosthesis dislocation.

RESULTS

Thirty-four patients met the eligibility criteria to be analyzed. In 73.5% (25/34) of cases, acetabular anteversion (AV) was correct, with a mean AV of 15.1° ± 9.4°. Femoral anteversion (FA) was considered correct only in 38.2% (13/34) of the dislocated THA, with a mean FA of 8.4° ± 17.2°. Sixteen of these 34 patients (47.0%) presented a correct CA, with a mean CA of 24.2° ± 21.0°. Nineteen hips (55.8%) were within the Lewinnek safe zone. Moreover, eleven patients (32.3%) developed a dislocation even though components were within the Lewinnek safe zone and presented a correct CA.

CONCLUSION

Our findings suggest that even when the THA components are positioned within a correct CA and in the Lewinnek safe zone, hip prosthesis dislocations can occur in a not inconsiderable percentage of the cases. Thus, further radiological and clinical analysis should be done to identify potential reasons for hip prosthesis dislocation.

Low revision rate of dual mobility cups after arthroplasty for acute hip fractures: report of 11,857 hip fractures in the Dutch Arthroplasty Register (2007-2019)

Background and purpose - Dislocation is one of the most frequent reasons for cup revision after total hip arthroplasty (THA) for an acute fracture. A dual mobility cup (DMC) might reduce this risk. We determined the cup revision rate after THA for an acute fracture according to type of cup.Patients and methods - All THAs for an acute fracture registered in the Dutch Arthroplasty Register (LROI) during 2007-2019 were included (n = 11,857). Type of cup was divided into DMC and unipolar cup (UC). Competing risk analyses were performed with cup revision for any reason as endpoint. Multivariable Cox regression analyses with outcome cup revision were performed adjusted for sex, age, ASA class, and surgical approach, stratified for UC THA with femoral head size of 32 mm and 22-28 mm.Results - A DMC was used in 1,122 (9%) hips. The overall 5-year cup revision rate for any reason after THA for acute fracture was 1.9% (95% CI 1.6-2.2). Cup revision for dislocation within 5 years was performed in 1 of 6 DMC THAs versus 108 of 185 (58%) UC THAs. Univariable Cox regression analyses showed no statistically significant difference in cup revision rate between DMC and UC (HR = 0.8; CI 0.4-1.5). Multivariable Cox regression analyses showed lower risk of cup revision in DMC THA (n = 1,122) compared with UC THA with 22-28 mm femoral head size (n = 2,727) (HR = 0.4; CI 0.2-0.8).Interpretation - The 5-year cup cumulative incidence of revision after THA for acute fracture was comparable for DMC and UC THA. However, DMC THA had a lower risk of cup revision than UC THA with 22-28 mm femoral head.

Impact of Acetabular Implant Design on Aseptic Failure in Total Hip Arthroplasty

Background

Failure of cementless acetabular osseointegration is rare in total hip arthroplasty. Nevertheless, new fixation surfaces continue to be introduced. Novel implants may lack large diameter, constrained bearings, or dual mobility (DM) bearings to address instability. We compared clinical and radiographic outcomes for acetabular components with differing fixation surfaces and bearing options, focusing on the relationship between fixation surface and osseointegration and the relationship between bearing options and dislocation rate.

Methods

We retrospectively reviewed 463 total hip arthroplasties implanted with 3 different acetabular components between 2012 and 2016. Records were reviewed for demographics, clinical scores, and complications. Radiographs were examined for evidence of acetabular osteointegration. Analysis of variance and chi-square tests were used to compare cohorts.

Results

All cohorts had 100% survivorship free of acetabular fixation failure with no differences in clinical scores. Dislocation occurred in 1.3% of cases (n = 6). Analysis of the “transition” sizes, for which brand determined the maximum bearing diameter, revealed a significantly higher dislocation rate (3/50, 6%) in implants with limited bearing options. All 4 revisions for recurrent dislocation involved well-positioned components that did not accept large diameter, constrained bearings, or DM bearings, resulting in 3 shell revisions to expand bearing options. Femoral revisions were associated with dislocation risk but did not vary between cohorts.

Conclusion

Dislocation was the primary mechanical cause for acetabular revision, while acetabular fixation failure was not encountered. We caution against selecting “new and improved” acetabular components without options for large diameter, constrained bearings, or DM bearings, even when enabling technology makes component positioning reliable.

Survival analysis for all-cause revision following primary total hip arthroplasty with a medial collared, triple-tapered primary hip stem versus other implants in real-world settings

OBJECTIVE

Patients that undergo total hip replacement (THA) are at risk of revision surgery. This study evaluated the cumulative incidence of revision following a medial collared, triple tapered (MCTT) primary hip stem versus other implants in real-world settings using electronic medical records.

METHODS

This was a retrospective cohort study that used the Mercy Healthcare Systems - Orthopedics Database (MHSOD) to identify ACTIS total hip system, a MCTT primary hip stem for THA, and any other primary THA between 2016 and 2020. A Kaplan-Meier analysis was conducted to evaluate the risk of revision over time between the MCTT hip stem and other implants. In order to control for the confounding, a multivariable Cox model was developed to evaluate the risk of revision between the two groups.

RESULTS

There were 1213 patients treated with MCTT hip stem and 6916 patients treated with other implants. The Kaplan-Meier analysis showed statistically significant difference (p value = .006) in cumulative incidences for all-cause revisions between the MCTT hip stem and other implants. The cumulative incidence at 3 years was 1.08% (0.43-2.72%) for the MCTT hip stem, while it was 2.63% (2.19-3.16%) for other implants. After adjusting for patient demographics, clinical characteristics, prescribed medications, and surgeon characteristics, the multivariable Cox proportional hazard model showed the MCTT hip stem was statistically significantly associated with 57% lower risk of revisions compared with other implants (HR, 0.43; 95% CI, 0.19-0.97; p-value = .042).

CONCLUSIONS

This real-world study found that the incidence of revision after treatment with MCTT primary hip stem was significantly lower than for other implants.

Global diversity in bearings in primary THA

Choice of articulating materials, head size and the design of the articulation will become decisive for the long-term performance of a total hip arthroplasty (THA) and especially in terms of risk for dislocation and wear-related problems. Here we account for common alternatives based on available studies and the evidence that can be derived from them.Metal or ceramic femoral heads articulating against a liner or cup made of highly cross-linked polyethylene and ceramic-on-ceramic articulations have about similar risk for complications leading to revision, whereas the performance of metal-on-metal articulations, especially with use of big heads, is inferior. The clinical significance of problems related to ceramic-on-ceramic articulations such as squeaking remains unclear. With use of current technology ceramic fractures are rare.Large femoral heads have the potential to increase the range of hip movement before impingement occurs and are therefore expected to reduce dislocation rates. On the other hand, issues related to bearing wear, corrosion at the taper-trunnion junction and groin pain may arise with larger heads and jeopardize the longevity of THA. Based on current knowledge, 32-mm heads seem to be optimal for metal-on-polyethylene bearings. Patients with ceramic-on-ceramic bearings may benefit from even larger heads such as 36 or 40 mm, but so far there are no long-term reports that confirm the safety of bearings larger than 36 mm.Assessment of lipped liners is difficult because randomized studies are lacking, but retrospective clinical studies and registry data seem to indicate that this liner modification will reduce the rate of dislocation or revision due to dislocation without clear evidence of clinically obvious problems due to neck-liner impingement.The majority of studies support the view that constrained liners and dual mobility cups (DMC) will reduce the risk of revision due to dislocation both in primary and revision THA, the latter gaining increasing popularity in some countries. Both these devices suffer from implant-specific problems, which seem to be more common for the constrained liner designs. The majority of studies of these implants suffer from various methodological problems, not least selection bias, which calls for randomized studies preferably in a multi-centre setting to obtain sufficient power. In the 2020s, the orthopaedic profession should place more effort on such studies, as has already been achieved within other medical specialties, to improve the level of evidence in the choice of articulation when performing one of the most common in-hospital surgical procedures in Europe. Cite this article: EFORT Open Rev 2020;5:763-775. DOI: 10.1302/2058-5241.5.200002.

Dual mobility acetabular construct with freedom constrained liner for treatment of recurrent dislocations after total hip arthroplasty: A case report and literature review

•

Dual-mobility bearings improve stability in total hip arthroplasty (THA) but may fail to prevent postoperative dislocation.

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Dry revision with a compatible constrained liner system can provide an effective salvage option for instability after THA.

•

The unique G7 constrained liner system offers good short-term stability and range of motion.

Introduction

Recurrent dislocation after total hip arthroplasty (THA) using the dual mobility cup system can present challenges, while dual-mobility THA bearings can improve stability in both primary and revision total hip arthroplasties.

Presentation of case

A 72-year-old woman with a history of schizophrenia underwent a left primary THA using the G7 dual mobility system. Two postoperative posterior dislocations occurred within 2 months post-surgery. The patient underwent revision surgery in which the metal liner and dual mobility head were exchanged using the Freedom constrained liner system without revision of the cup and stem. As of this writing, 28 months after the revision surgery, no further dislocations have occurred. The implants are stable, and the patient has good range of motion.

Discussion

Dual-mobility bearings are utilized to improve stability in both primary and revision total hip arthroplasties, but even if the dual mobility system is chosen, it sometimes fails to prevent postoperative dislocation. Although a relatively high failure rate has been reported in THA using the constrained liner system, this patient’s clinical course suggests that the G7 Freedom constrained liner system can be an efficacious option for some patients with unstable hip joints who undergo THA using the dual mobility system.

Conclusion

A modern constrained liner system such as the G7 Freedom liner may provide an improved salvage solution for joint instability in dual mobility THA.

Following total hip arthroplasty: femoral head component diameter of 32 mm or larger is associated with lower risk of dislocation in patients with a prior lumbar fusion

Aims

There is evidence that prior lumbar fusion increases the risk of dislocation and revision after total hip arthroplasty (THA). The relationship between prior lumbar fusion and the effect of femoral head diameter on THA dislocation has not been investigated. We examined the relationship between prior lumbar fusion or discectomy and the risk of dislocation or revision after THA. We also examined the effect of femoral head component diameter on the risk of dislocation or revision.

Methods

Data used in this study were compiled from several Finnish national health registers, including the Finnish Arthroplasty Register (FAR) which was the primary source for prosthesis-related data. Other registers used in this study included the Finnish Health Care Register (HILMO), the Social Insurance Institutions (SII) registers, and Statistics Finland. The study was conducted as a prospective retrospective cohort study. Cox proportional hazards regression and Kaplan-Meier survival analysis were used for analysis.

Results

Prior lumbar fusion surgery was associated with increased risk of prosthetic dislocation (hazard ratio (HR) = 2.393, p < 0.001) and revision (HR = 1.528, p < 0.001). Head components larger than 28 mm were associated with lower dislocation rates compared to the 28 mm head (32 mm: HR = 0.712, p < 0.001; 36 mm: HR = 0.700, p < 0.001; 38 mm: HR = 0.808, p < 0.140; and 40 mm: HR = 0.421, p < 0.001). Heads of 38 mm (HR = 1.288, p < 0.001) and 40 mm (HR = 1.367, p < 0.001) had increased risk of revision compared to the 28 mm head.

Conclusion

Lumbar fusion surgery was associated with higher rate of hip prosthesis dislocation and higher risk of revision surgery. Femoral head component of 32 mm (or larger) associates with lower risk of dislocation in patients with previous lumbar fusion. Cite this article: Bone Joint J 2020;102-B(8):1003–1009.

Is there a reduction in risk of revision when 36-mm heads instead of 32 mm are used in total hip arthroplasty for patients with proximal femur fractures?

Background and purpose - 32-mm heads are widely used in total hip arthroplasty (THA) in Scandinavia, while the proportion of 36-mm heads is increasing as they are expected to increase THA stability. We investigated whether the use of 36-mm heads in THA after proximal femur fracture (PFF) is associated with a lower risk of revision compared with 32-mm heads.Patients and methods - We included 5,030 patients operated with THA due to PFF with 32- or 36-mm heads from the Nordic Arthroplasty Register Association database. Each patient with a 36-mm head was matched with a patient with a 32-mm head, using propensity score. The patients were operated between 2006 and 2016, with a metal or ceramic head on a polyethylene bearing. Cox proportional hazards models were fitted to estimate the unadjusted and adjusted hazard ratio (HR) with 95% confidence intervals (CI) for revision for any reason and revision due to dislocation for 36-mm heads compared with 32-mm heads.Results - 36-mm heads had an HR of 0.9 (CI 0.7-1.2) for revision for any reason and 0.8 (CI 0.5-1.3) for revision due to dislocation compared with 32-mm heads at a median follow-up of 2.5 years (interquartile range 1-4.4).Interpretation - We were not able to demonstrate any clinically relevant reduction of the risk of THA revision for any reason or due to dislocation when 36-mm heads were used versus 32-mm. Residual confounding due to lack of data on patient comorbidities and body mass index could bias our results.

Posterior approach, fracture diagnosis, and American Society of Anesthesiology class III-IV are associated with increased risk of revision for dislocation after total hip arthroplasty: An analysis of 33,337 operations from the Finnish Arthroplasty Register

Background and objective:

Dislocation is one of the most common reasons for revision surgery after primary total hip arthroplasty. Both patient related and surgical factors may influence the risk of dislocation. In this study, we evaluated risk factors for dislocation revision after total hip arthroplasty based on revised data contents of the Finnish Arthroplasty Register.

Methods:

We analyzed 33,337 primary total hip arthroplasties performed between May 2014 and January 2018 in Finland. Cox proportional hazards regression was used to estimate hazard ratios with 95% confidence intervals for first dislocation revision using 18 potential risk factors as covariates, such as age, sex, diagnosis, hospital volume, surgical approach, head size, body mass index, American Society of Anesthesiology class, and fixation method.

Results:

During the study period, there were 264 first-time revisions for dislocation after primary total hip arthroplasty. The hazard ratio for dislocation revision was 3.1 (confidence interval 1.7–5.5) for posterior compared to anterolateral approach, 3.0 (confidence interval 1.9–4.7) for total hip arthroplasties performed for femoral neck fracture compared to total hip arthroplasties performed for osteoarthritis, 2.0 (confidence interval 1.0–3.9) for American Society of Anesthesiology class III–IV compared to American Society of Anesthesiology class I, and 0.5 (0.4–0.7) for 36-mm femoral head size compared to 32-mm head size.

Conclusions:

Special attention should be paid to patients with fracture diagnoses and American Society of Anesthesiology class III–IV. Anterolateral approach and 36-mm femoral heads decrease dislocation revision risk and should be considered for high-risk patients.

Large Diameter Head in Primary Total Hip Arthroplasty: A Systematic Review

INTRODUCTION

The literature around use of Large Diameter Heads (LDH) is abundantly available for revision Total Hip Arthroplasty (THA) but is lacking for primary uncomplicated THA. This systematic review was undertaken to synthesize data around primary THA involving LDH and analyze the associated complications (dislocation, volumetric wear, implant survivorship and functional score) along with reported effects on range of motion (ROM), patient reported outcomes and impingement rate/groin pain.

METHODS

A PRISMA compliant systematic review was done using extensive search in PubMed database, along with offline search looking for the literature published in English language between 2008 and 2018. The articles providing data on the use of large diameter heads (LDH) (36 mm or larger) on various bearing surfaces were collected. This included robust national joint registries of different countries. Narrative approach to data synthesis was used.

RESULTS

A total of 23 papers met our inclusion criteria, including six national joint registries. It was observed that LDH had significantly low dislocation rates, excellent implant survival rate as per Kaplan-Meier survivorship (> 90% at five years). Surgical approaches, except Minimally Invasive Surgery (MIS), did not increase any risk of dislocation as long as it was meticulously repaired. There was no significant improvement in any functional scores or improved ROM.

CONCLUSIONS

LDH of 32-36 mm are now commonly used in primary THA and is accepted as a popular size. The beneficial effects of a large head size are negated beyond 38 mm. The most favored size for LDH THA, therefore, is 36 mm contrary to the older literature favoring 28 mm.

Combined Application of Dexamethasone and Tranexamic Acid to Reduce the Postoperative Inflammatory Response and Improve Functional Outcomes in Total Hip Arthroplasty

Objective

To evaluate the efficacy and safety of combined use of tranexamic acid (TXA) and dexamethasone (DEX) for anti‐inflammatory and clinical outcomes after total hip arthroplasty (THA).

Methods

A total of 100 patients were included in this randomized, controlled study. Patients in the TXA + DEX group were administered TXA at a dose of 15 mg/kg, which was repeated 3 h after THA, and received 20 mg DEX. In contrast, patients in the TXA group were administered TXA at a dose of 15 mg/kg, which was repeated at 3 h postoperatively. C‐reactive protein (CRP), interleukin‐6 (IL‐6) and pain levels, incidence of postoperative nausea and vomiting (PONV), total blood loss and transfusion rates, postoperative fatigue, range of motion (ROM), length of hospital stay (LOS), analgesic rescue and antiemetic rescue consumption, and complications were compared in both groups.

Results

The CRP and IL‐6 levels were lower in the TXA + DEX group than in the TXA group (all P < 0.001) at 24 h, 48 h, and 72 h postoperatively. Patients in the TXA + DEX group had lower pain scores at rest and walking at 24 h postoperatively (all P < 0.001). In the TXA + DEX group, the incidence of PONV was lower (P = 0.005), postoperative fatigue (P < 0.001) was reduced, and analgesia and antiemetic rescue consumption were also reduced. The total blood loss, transfusion rate, LOS and hip ROM were similar in the two groups. There was no thrombosis, infection, or gastrointestinal bleeding in either group.

Conclusion

Compared to TXA alone, the combination of TXA + DEX can reduce postoperative inflammatory response, relieve pain, and reduce PONV and fatigue, without increasing the risk of complications. Therefore, the present study suggested that the combination of TXA + DEX is an effective and safe accelerated rehabilitation strategy for patients receiving primary unilateral THA.

Survival and revision causes of hip resurfacing arthroplasty and the Mitch proximal epiphyseal replacement: results from the Danish Hip Arthroplasty Register

Background and purpose - The Mitch proximal epiphyseal replacement (PER) was developed to preserve proximal femoral bone and minimize femoral neck fracture associated with hip resurfacing arthroplasty (HRA). We studied the survival and risk of revision of HRA compared with cementless metal-on-polyethylene (MoP) total hip arthroplasty (THA) and the survival and risk of revision of the Mitch PER compared with MoP THA.Patients and methods - Using propensity score, we matched 1,057 HRA to 1,057 MoP THA and 202 Mitch PER to 1,010 MoP THA from the Danish Hip Arthroplasty Register. To estimate the relative risk (RR) of revision, we used regression with the pseudo-value approach and treated death as a competing risk.Results - The cumulative incidence for any revision of HRA at 10 years' follow-up was 11% (95% confidence interval [CI] 9.1-13) and 6.4% (CI 5.8-7.0) for MoP THA. The RR of any revision was 1.5 (CI 1.1-2.1) for HRA at 10 years' follow-up. By excluding the ASR components, the RR of revision at 10 years was 1.2 (CI 0.8-1.7). The cumulative incidence of revision was 9.6% (CI 4.2-18) for Mitch PER and 5.4% (CI 5.1-5.7) for MoP THA at 8 years. The RR of revision was 2.0 (CI 0.9-4.3) for Mitch PER at 8 years' follow-up.Interpretation - The HRA had increased risk of revision compared with the MoP THA. When excluding ASR, the HRA group had similar risk of revision compared with MoP THA. The Mitch PER did not have a statistically significant increased risk of revision compared with MoP THA.

The risk of revision after total hip arthroplasty in young patients depends on surgical approach, femoral head size and bearing type; an analysis of 19,682 operations in the Dutch arthroplasty register

Background

Total hip arthroplasty (THA) is used increasingly in younger patients. There is little knowledge about the effect of THA characteristics on risk of revision, especially in young patients. Therefore, we studied the influence of both patient-related and surgical factors on the risk of revision using data from the Dutch Arthroplasty Registry (LROI).

Methods

All patients younger than 55 years with a primary THA implanted in the Netherlands between 2007 and 2017 were selected (n = 19,682). The covariates age, sex, primary diagnosis, ASA-classification, surgical approach, fixation method, bearing type, head size and year of surgery were entered into Cox proportional hazards models to calculate hazard ratios for the risk of revision.

Results

The overall 5-year survival of primary THA was 95.3% (95% CI, 94.9–95.6). Use of the anterior approach resulted in a lower risk of revision than the use of the posterolateral approach (HR: 0.66, 95% CI: 0.47–0.92). THAs with a head diameter ≥ 38 mm had a higher risk of revision (HR: 1.90, 95% CI: 1.33–2.72) than THAs with 32 mm heads. Use of MoM bearings resulted in an increased risk when compared to C-PE (HR: 1.76, 95% CI: 1.27–2.43).

Conclusion

The risk of revision in patients younger than 55 years depends on surgical approach, head size and bearing type. The anterior approach resulted in a decreased risk of revision, whereas use of ≥38 mm heads and MoM bearings resulted in an increased risk of revision for any reason.

Are Hooded, Crosslinked Polyethylene Liners Associated with a Reduced Risk of Revision After THA?

BACKGROUND

Hooded acetabular liners and head sizes ≥ 32 mm have both shown to have a beneficial effect on the revision rate for dislocation in THA. Experience with noncrosslinked polyethylene (nonXLPE) raised concerns regarding the risk of impingement damage, loosening, and osteolysis with hooded liners; however, the evidence for this in crosslinked polyethylene (XLPE) is inconclusive. The interaction between different femoral head sizes and hooded liners is not well understood, and it is unclear whether hooded XLPE liners have a beneficial effect on overall long-term survivorship.

QUESTIONS/PURPOSES

We analyzed a large national joint registry to ask: (1) Is the use of hooded XLPE liners associated with a reduced revision rate for dislocation compared with nonhooded liners? (2) Is there a difference in the revision rate for aseptic loosening/osteolysis? (3) Is head size associated with any difference in the revision rate between hooded and nonhooded liners?

METHODS

The Australian Orthopaedic Association National Joint Replacement Registry longitudinally maintains data on all primary and revision joint arthroplasties with nearly 100% capture. We analyzed all conventional primary THAs performed from registry inception in September 1999 until December 31, 2016 in patients with a diagnosis of osteoarthritis who had nonhooded or hooded XLPE bearings in a cementless acetabular shell. The study group included 192,659 THA procedures with XLPE liners, of which 67,904 were nonhooded and 124,755 were hooded. The mean age of patients receiving nonhooded liners was 70 years (range, 11-100 years); 44% were males. This was similar to the patients with hooded liners, who had a mean age of 70 years (range, 16-100 years); 45% were males. The main outcome measure was the cumulative percent revision at 15 years of the THA using Kaplan-Meier estimates of survivorship. We examined reasons for revision and and performed multivariable analysis to control for the confounding factors of three head size groups (< 32mm, 32mm, and > 32mm) and for the method of femoral fixation.

RESULTS

There was a higher revision rate for dislocation for patients with nonhooded liners at all times to 15 years (HR, 1.31; 95% CI, 1.17-1.47; p < 0.001). There was a higher revision rate for the diagnosis of aseptic loosening/osteolysis with patients with nonhooded liners compared with hooded liners (HR, 1.19; 95% CI, 1.05-1.34; p = 0.006). Head sizes of 32 mm or larger were independently associated with a lower comparative revision rate between hooded and nonhooded liners, but this was not apparent for head sizes smaller than 32 mm. It appeared that the main driver of the finding in larger heads was a reduced dislocation risk with hooded liners for 32 mm heads (HR, 1.50; 95% CI, 1.23-1.80; p < 0.001) and for heads larger than 32 mm (HR, 1.50; 95% CI, 1.20-1.89; p < 0.001).

CONCLUSIONS

Prior research has suggested that hooded acetabular liners may be associated with impingement, loosening, and osteolysis; however, in this large, registry-based report we found that XLPE hooded liners are not associated with an increased revision rate for aseptic loosening/osteolysis. Although there are many potential confounding variables in this registry analysis, if anything, surgeons using larger femoral heads and hooded liners likely did so in patients with a higher perceived dislocation risk. Patients with larger heads and XLPE hooded liners were, however, less likely to experience revision for dislocation. These liners therefore appear reasonable to use in primary THA at the surgeon's discretion.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Dislocation of large-diameter head metal-on-metal total hip arthroplasty and hip resurfacing arthroplasty

INTRODUCTION

Dislocation of large-diameter head (LDH) metal-on-metal (MoM) total hip arthroplasty (THA) or hip resurfacing arthroplasty (HRA) is a rare complication. This study aimed to determine the incidence and risk factors for dislocation of LDH MoM THAs and HRAs.

METHODS

This retrospective analysis considered 4038 cementless LDH MoM THAs and HRAs, 3207 THAs in 2912 patients and 831 HRAs in 757 patients. The end of follow-up was revision due to dislocation. Incidence of dislocation was evaluated from this study population of 4038, and study groups were formed. The study was designed as a case-control study, and a threefold stratified randomised control group was formed. Demographic data were collected and radiological analyses were performed in the study groups.

RESULTS

There were 26/3207 (0.8%) early dislocations in the THA group, and 6/831 (0.7%) in the HRA group ( p = 0.9). Most LDH THA dislocations occurred in a group with head size ⩽ 38 mm (18/26) ( p < 0.001). In dislocated hips, there were more dysplastic acetabula and post-traumatic hips than in the control group ( p = 0.036). In the dislocation group, the mean acetabulum component anteversion angle was 19.6° (standard deviation [SD] 13.4°) and in the control group it was 23.2° (SD 10.4°) ( p = 0.006); 7/32 (21.8%) of dislocated THAs needed revision surgery, and mean time to revision from the index surgery was 1.2 (SD 2.6) years.

DISCUSSION

Dislocations occurred more often in THAs of head size ⩽ 38 mm and with a smaller anteversion angle of the acetabulum component. Hip dysplasia and post-traumatic osteoarthritis were more common in patients with dislocation.

No Increase in Survival for 36-mm versus 32-mm Femoral Heads in Metal-on-polyethylene THA: A Registry Study

BACKGROUND

During the past decade, the 32-mm head has replaced the 28-mm head as the most common head size used in primary THA in many national registries, and the use of 36-mm heads has also increased. However, it is unclear whether 32-mm and 36-mm heads decrease the revision risk in metal-on-polyethylene (MoP) THA compared with 28-mm heads.

QUESTIONS/PURPOSES

(1) In the setting of the Nordic Arthroplasty Register Association database, does the revision risk for any reason differ among 28-, 32-, and 36-mm head sizes in patients undergoing surgery with MoP THA? (2) Does the revision risk resulting from dislocation decrease with increasing head diameter (28-36 mm) in patients undergoing surgery with MoP THA in the same registry?

METHODS

Data were derived from the Nordic Arthroplasty Register Association database, a collaboration among the national arthroplasty registries of Denmark, Finland, Norway, and Sweden. Patients with primary osteoarthritis who had undergone primary THA with a 28-, 32-, or 36-mm MoP bearing from 2003 to 2014 were included. Patients operated on with dual-mobility cups were excluded. In patients with bilateral THA, only the first operated hip was included. After applying the inclusion criteria, the number of patients and THAs with a complete data set was determined to be 186,231, which accounted for 51% of all hips (366,309) with primary osteoarthritis operated on with THA of any head size and bearing type during the study observation time. Of the included patients, 60% (111,046 of 186,231) were women, the mean age at surgery was 70 (± 10) years, and the median followup was 4.5 years (range, 0-14 years). A total of 101,094 patients had received a 28-mm, 57,853 a 32-mm, and 27,284 a 36-mm head with 32 mm used as the reference group. The revision of any component for any reason was the primary outcome and revision for dislocation was the secondary outcome. Very few patients are estimated to be lost to followup because emigration in the population of interest (older than 65-70 years) is rare. A Kaplan-Meier analysis was used to estimate THA survival for each group, whereas Cox regression models were fitted to calculate hazard ratios (HRs) with 95% confidence intervals (CIs) for THA revision comparing the 28- and 36-mm head diameters with the 32-mm head diameters adjusting for age, sex, year of surgery, type of cup and stem fixation, polyethylene type (crosslinked versus conventional), and surgical approach.

RESULTS

In the adjusted Cox regression model, there was no difference in the adjusted risk for revision for any reason between patients with 28-mm (HR, 1.06; 95% CI, 0.97-0.16) and 32-mm heads, whereas the risk of revision was higher for patients with 36-mm heads (HR, 1.14; 95% CI, 1.04-1.26) compared with patients with 32-mm heads. Patients with 28-mm heads had a higher risk of revision for dislocation (HR, 1.67; 95% CI, 1.38-1.98) compared with 32 mm, whereas there was no difference between patients with 36-mm (HR, 0.85; 95% CI, 0.70-1.02) and 32-mm heads.

CONCLUSIONS

After adjusting for relevant confounding variables, we found no benefits for 32-mm heads against 28 mm in terms of overall revision risk. However, when dislocation risk is considered, 32-mm heads would be a better option, because they had a lower risk of revision resulting from dislocation. There were no benefits with the use of 36-mm heads over 32 mm, because the transition from 32 to 36 mm was associated with a higher risk of revision for all reasons, which was not accompanied by a decrease in the risk of revision resulting from dislocation. The use of 32-mm heads appears to offer the best compromise between joint stability and other reasons for revision in MoP THA. Further studies with longer followup, especially of 36-mm heads, as well as better balance of confounders across head sizes and better control of patient-related risk factors for THA revision are needed.

LEVEL OF EVIDENCE

Level III, therapeutic study.

A Survey of the Prevalence of and Techniques to Prevent Trunnionosis

Trunnionosis of total hip arthroplasty (THA) components has been an increasingly reported complication. Consensus is lacking regarding preventive practices and the overall incidence of trunnionosis. In this study, fellowship-trained adult reconstruction orthopedic surgeons were surveyed to identify expert opinions. A 25-question, web-based survey regarding trunnionosis incidence, prevention, and biomaterials was sent to 345 fellowship-trained adult reconstruction orthopedic surgeons in North America. The survey yielded 151 (43.8%) responses from surgeons with a mean of 11.97±9.49 years of experience. These surgeons believe that the material composite of the head-neck junction is the most important contributor to trunnionosis. They often choose a ceramic head with a metal alloy stem to reduce trunnionosis. They more commonly impact the femoral head 3 times than once. Fifty-one percent believe that trunnionosis leads to THA failure for between 0% and 2% of all THA revisions, whereas 48.3% believe that the failure rate is greater than 2%. More than half (53.6%) of these surgeons recommend a revision THA if a patient's serum cobalt level is greater than 10 µg/L, regardless of symptom presence. The incidence of trunnionosis appears to be increasing due to changes in implants and/or an increased awareness of the problem, with 48.3% of these surgeons believing that trunnionosis is the primary cause of THA failure for more than 1 in 50 patients. Some suggested preventive measures include cleaning and drying the trunnion, using ceramic femoral heads, matching THA components, and adding titanium sleeves on well-fixed stems that are retained during revision surgery. [Orthopedics. 2018; 41(4):e557-e562.].

Nationwide multicenter follow-up cohort study of hip arthroplasties performed for osteonecrosis of the femoral head

PURPOSE

To identify modifiable factors related to post-operative dislocation and reoperation in patients with osteonecrosis of the femoral head (ONFH) in a large cohort.

METHODS

We studied 4995 hip arthroplasties: total hip arthroplasty (THA) was performed in 79% of patients; bipolar hemiarthroplasty (BP), 17%; total resurfacing arthroplasty (tRS), 3%; and hemi-resurfacing arthroplasty (hRS), 1%. A new type of BP (accounting for 49% of BPs) comprised a femoral component with a polished or smooth, small-diameter (approximately 10 mm) neck with a round or oval axial cut surface and no sharp corners.

RESULTS

The infection rate was relatively low (0.56%) even though 58% of cases of ONFH were associated with systemic steroid use, a known risk factor for infection. Post-operative dislocation occurred in 4.3% of cases, with re-operation needed in 3.9%. The dislocation rate was related to surgery type: 5.2% in THA, 0.9% in BP, and 0% in tRS and hRS. Among total arthroplasties with six month or longer follow-up (3670 THAs and 159 tRSs), the risk factors for post-operative dislocation were younger (≤ 40 years) or older (≥ 62 years) age, higher body weight, posterolateral approach, and smaller prosthetic head diameter. Regarding the need for re-operation, higher body weight and surgery type were identified as risk factors.

CONCLUSIONS

The relatively high dislocation rate of 5.2% in THA is a cause for concern. The identified risk factors for dislocation should be considered when selecting THA for treatment. Prosthesis survivorship in hRSs was inferior to that in BPs or THAs. Body weight also affected the survivorship of hip arthroplasties.

Head size in primary total hip arthroplasty

The use of larger femoral head size in total hip arthroplasty (THA) has increased during the past decade; 32 mm and 36 mm are the most commonly used femoral head sizes, as reported by several arthroplasty registries.The use of large femoral heads seems to be a trade-off between increased stability and decreased THA survivorship.We reviewed the literature, mainly focussing on the past 5 years, identifying benefits and complications associated with the trend of using larger femoral heads in THA.We found that there is no benefit in hip range of movement or hip function when head sizes > 36 mm are used.The risk of revision due to dislocation is lower for 36 mm or larger bearings compared with 28 mm or smaller and probably even with 32 mm.Volumetric wear and frictional torque are increased in bearings bigger than 32 mm compared with 32 mm or smaller in metal-on-cross-linked polyethylene (MoXLPE) THA, but not in ceramic-on-XLPE (CoXLPE).Long-term THA survivorship is improved for 32 mm MoXLPE bearings compared with both larger and smaller ones.We recommend a 32 mm femoral head if MoXLPE bearings are used. In hips operated on with larger bearings the use of ceramic heads on XLPE appears to be safer. Cite this article: EFORT Open Rev 2018;3 DOI: 10.1302/2058-5241.3.170061.

Application of a Causal Discovery Algorithm to the Analysis of Arthroplasty Registry Data

Improving the quality of care for hip arthroplasty (replacement) patients requires the systematic evaluation of clinical performance of implants and the identification of "outlier" devices that have an especially high risk of reoperation ("revision"). Postmarket surveillance of arthroplasty implants, which rests on the analysis of large patient registries, has been effective in identifying outlier implants such as the ASR metal-on-metal hip resurfacing device that was recalled. Although identifying an implant as an outlier implies a causal relationship between the implant and revision risk, traditional signal detection methods use classical biostatistical methods. The field of probabilistic graphical modeling of causal relationships has developed tools for rigorous analysis of causal relationships in observational data. The purpose of this study was to evaluate one causal discovery algorithm (PC) to determine its suitability for hip arthroplasty implant signal detection. Simulated data were generated using distributions of patient and implant characteristics, and causal discovery was performed using the TETRAD software package. Two sizes of registries were simulated: (1) a statewide registry in Michigan and (2) a nationwide registry in the United Kingdom. The results showed that the algorithm performed better for the simulation of a large national registry. The conclusion is that the causal discovery algorithm used in this study may be a useful tool for implant signal detection for large arthroplasty registries; regional registries may only be able to only detect implants that perform especially poorly.

Intraoperative Complications and Mid-Term Follow-Up of Large-Diameter Head Metal-on-Metal Total Hip Arthroplasty and Hip Resurfacing Arthroplasty

BACKGROUND AND AIMS

Large-diameter head total hip arthroplasty and hip resurfacing arthroplasty were popular in Finland from 2000 to 2012 for the treatment of hip osteoarthritis. The aim of this retrospective study was to investigate the mid-term survival of large-diameter head total hip arthroplasty patients operated on in three university hospitals and to compare these results to the survival of hip resurfacing arthroplasty patients.

MATERIAL AND METHODS

A total of 3860 hip arthroplasties (3029 large-diameter head total hip arthroplasties in 2734 patients and 831 hip resurfacing arthroplasties in 757 patients) were operated on between January 2004 and December 2009. The mean follow-up was 4.3 years (range: 0.3-8.0 years) in the total hip arthroplasty group and 5.1 years (range: 1.7-7.9 years) in the hip resurfacing arthroplasty group. Cox multiple regression model and Kaplan-Meier survival analysis were used to study the survival of the total hip arthroplasties and the hip resurfacing arthroplasties. Intraoperative complications and reasons for revisions were also evaluated.

RESULTS

In Cox regression analysis, the hazard ratio for revision of hip resurfacing arthroplasty was 1.5 compared with large-diameter head total hip arthroplasty (95% confidence interval: 1.0-2.2) ( p = 0.029). The cumulative Kaplan-Meier survival rate was 90.7% at 7.7 years for the large-diameter head total hip arthroplasty (95% confidence interval: 86.8-94.6) and 92.2% at 7.6 years for hip resurfacing arthroplasty (95% confidence interval: 89.9-94.6). There were a total of 166/3029 (5.5%) intraoperative complications in the large-diameter head total hip arthroplasty group and 20/831 (2.4%) in the hip resurfacing arthroplasty group ( p = 0.001). Revision for any reason was performed on 137/3029 (4.5%) of the arthroplasties in the large-diameter head total hip arthroplasty group and 52/831 (6.3%) in the hip resurfacing arthroplasty group ( p = 0.04).

CONCLUSION

The mid-term survival of both of these devices was poor, and revisions due to adverse reactions to metal debris will most likely rise at longer follow-up. There were more intraoperative complications in the large-diameter head total hip arthroplasty group than in the hip resurfacing arthroplasty group.

A multimodal approach prevents instability after total hip arthroplasty: A 1 year follow-up prospective study

INTRODUCTION

Joint dislocation is one of the most frequent complications after hip arthroplasty. Multiple strategies have demonstrated ability to prevent instability when used in isolation, but the effect when more than one intervention is implemented has not been measured. The purpose of this study is to assess the rate of dislocation after implementation of a protocol of combined strategies for prevention of instability.

MATERIALS AND METHODS

Consecutive patients undergoing primary total hip replacement for hip osteoarthritis between February 2012 and June 2014 were included. A multimodal protocol including patient education, use of large femoral heads, posterior soft-tissue repair, and intraoperative adjustment of limb length and hip offset was applied. Dislocation episodes were documented trough medical records review and a telephonic follow-up at 3 and 12 months after surgery.

RESULTS

During the period of study 331 patients were included, mean age was 66 years and 68.8% were females. Only 0.91% of patients were lost to follow-up. Eighty-nine percent of patients received all interventions. Cumulative dislocation rate at 3 months was 0.60% and 0.90% at 12 months.

CONCLUSIONS

The implementation of a multimodal protocol for prevention of prosthesis instability produces a low rate of dislocation, which compares favorably with benchmarks. We recommend the use of a combination of multiple interventions to prevent this complication.

Can Surgeons Reduce the Risk for Dislocation After Primary Total Hip Arthroplasty Performed Using the Posterolateral Approach?

BACKGROUND

Hip dislocation is one of the most common postoperative complications after total hip arthroplasty (THA). Potential contributors include patient- and surgical-related factors. We performed a retrospective cohort study to identify risk factors for postoperative dislocation in patients receiving THA via the posterolateral approach.

METHODS

We assessed 1326 consecutive primary THAs performed between 2010 and 2015. Patient information was documented, and plain radiographic films were used to evaluate cup positioning, hip offset, and hip length change. A multiple logistic regression was used to identify risk factors for dislocation. Follow-up was coordinated by the Danish National Patient Registry.

RESULTS

Age and American Society of Anesthesiologists scores were higher in dislocating THA compared with those in the nondislocating THA. Cup anteversion was less in dislocating THA compared with that in nondislocating THA. Independent risk factors for cup dislocation were increased age, body mass index <25 and >30 kg/m², and leg shortening of >5 mm.

CONCLUSION

Surgeons should aim for a shortening of leg length <5 mm to reduce the risk of postoperative dislocation in primary THA. Although anteversion was reduced for dislocating THA, there is likely no universal safe zone for cup positioning. Hip stability is multifactorial, and optimal cup positioning may vary from patient to patient.

Effect of femoral head size and surgical approach on risk of revision for dislocation after total hip arthroplasty

Background and purpose - Recurrent dislocation is the commonest cause of early revision of a total hip arthropasty (THA). We examined the effect of femoral head size and surgical approach on revision rate for dislocation, and for other reasons, after total hip arthroplasty (THA). Patients and methods - We analyzed data on 166,231 primary THAs and 3,754 subsequent revision THAs performed between 2007 and 2015, registered in the Dutch Arthroplasty Register (LROI). Revision rate for dislocation, and for all other causes, were calculated by competing-risk analysis at 6-year follow-up. Multivariable Cox proportional hazard regression ratios (HRs) were used for comparisons. Results - Posterolateral approach was associated with higher dislocation revision risk (HR =1) than straight lateral, anterolateral, and anterior approaches (HR =0.5-0.6). However, the risk of revision for all other reasons (especially stem loosening) was higher with anterior and anterolateral approaches (HR =1.2) and lowest with posterolateral approach (HR =1). For all approaches, 32-mm heads reduced the risk of revision for dislocation compared to 22- to 28-mm heads (HR =1 and 1.6, respectively), while the risk of revision for other causes remained unchanged. 36-mm heads increasingly reduced the risk of revision for dislocation but only with the posterolateral approach (HR =0.6), while the risk of revision for other reasons was unchanged. With the anterior approach, 36-mm heads increased the risk of revision for other reasons (HR =1.5). Interpretation - Compared to the posterolateral approach, direct anterior and anterolateral approaches reduce the risk of revision for dislocation, but at the cost of more stem revisions and other revisions. For all approaches, there is benefit in using 32-mm heads instead of 22- to 28-mm heads. For the posterolateral approach, 36-mm heads can safely further reduce the risk of revision for dislocation.

Sports activities after total hip arthroplasty

Performing sports after total hip arthroplasty (THA) may be associated with a risk of

Trauma (fracture and dislocation)

Shorter implant survival

There is no proof that trauma occurs more often than in healthy individuals, but sequelae may be more severe.

Shorter implant survival due to repetitive high contact forces is a fact, due to increased wear. The 15 year survival in highly active patients seems to be around 80%.

Surgeons can address the needs of active patients by using bearings with low wear rates, and femoral heads up to 36 mm in diameter.

The data provided in this review may help to fully inform active patients of the risks. The patient has to balance the pros and cons of sports after THA and to decide the best way for themselves.

Cite this article: EFORT Open Rev 2017;2. DOI: 10.1302/2058-5241.2.160059. Originally published online at www.efortopenreviews.org

Is There a Difference in Revision Risk Between Metal and Ceramic Heads on Highly Crosslinked Polyethylene Liners?

BACKGROUND

The most common bearing surface used among primary THAs worldwide is a metal or ceramic femoral head that articulates against a highly crosslinked ultrahigh-molecular-weight polyethylene (HXLPE) acetabular liner. Despite their widespread use, relatively little is known about the comparative effectiveness of ceramic versus metal femoral heads with respect to risk of revision and dislocation as well as the role of head size in this relationship.

QUESTIONS/PURPOSES

The purpose of this study was to evaluate the risk of (1) all-cause revision in metal versus ceramic femoral heads when used with an HXLPE liner, including an evaluation of the effect of head size; and (2) dislocation in metal versus ceramic femoral heads when used with an HXLPE liner as well as an assessment of the effect of head size.

METHODS

Data were collected as part of the Kaiser Permanente Total Joint Replacement Registry between 2001 and 2013. Patients in this study were on average overweight (body mass index = 29 kg/m²), 67 years old, mostly female (57%), and had osteoarthritis (93%) as the primary indication for surgery. The material of the femoral head (metal, ceramic) was crossed with head size (< 32, 32, 36, > 36 mm), yielding eight device groupings. Only uncemented devices were evaluated. The primary outcome was all-cause revision (n = 28,772) and the secondary outcome was dislocation within 1 year (n = 19,623). Propensity scores were used to adjust for potential confounding at the implant/patient level using between-within semiparametric survival models that control for surgeon and hospital confounding and adjust estimates for the within-cluster correlation among observations on the response.

RESULTS

For all-cause revision, there was no difference between ceramic versus metal (reference) heads in combination with an HXLPE liner (hazard ratio [HR] = 0.82 [0.65-1.04], p = 0.099). Smaller metal head sizes of < 32 mm were associated with increased risk of revision relative to 36 mm (HR = 1.66 [1.20-2.31], p = 0.002, adjusted p = 0.025). For dislocation, ceramic heads increased risk relative to metal at < 32 mm only (HR = 4.39 [1.72-11.19], p = 0.002, adjusted p = 0.020). Head sizes < 32 mm were associated with increased risk of dislocation relative to 36 mm for metal (HR = 2.99 [1.40-6.39], p = 0.005, adjusted p = 0.047) and ceramic heads (HR = 15.69 [6.07-40.55], p < 0.001, adjusted p < 0.001).

CONCLUSIONS

The results did not provide evidence for use of one femoral head material over another when used with HXLPE liners for the outcome of revision, but for dislocation, metal performed better than ceramic with < 32-mm heads. Overall, the findings suggest increased risk of revision/dislocation with head sizes < 32 mm.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Accuracy of the modified Hardinge approach in acetabular positioning

BACKGROUND

The surgical approach chosen for total hip arthroplasty (THA) may affect the positioning of the acetabular component. The purpose of this study was to examine the accuracy in orienting the acetabular component using the modified Hardinge approach.

METHODS

We used our institutional arthroplasty database to identify patients with primary, press-fit, hemispherical acetabular components of a metal-on-polyethylene THA performed between 2003 and 2011. Patients with radiographs obtained 1-3 years after the index procedure were included for measurement of anteversion and inclination angles. Acceptable values of anteversion and abduction angles were defined as 15° ± 10° and 40° ± 10°, respectively.

RESULTS

We identified 1241 patients from the database, and the modified Hardinge approach was used in 1010 of the patients included in our analysis. The acetabular component was anteverted in the acceptable zone in 54.1% of patients. The abduction angle was within the defined range in 79.2% of patients. Combined anteversion and abduction angles within the defined zone were present in 43.6% of patients.

CONCLUSION

Consistent with studies examining accuracy from other approaches, our study reveals that the modified Hardinge approach was only moderately accurate in positioning the acetabular component in the acceptable zone.

Characterization of Femoral Head Taper Corrosion Features Using a 22-Year Retrieval Database

BACKGROUND

Modularity in total hip arthroplasty has been used for decades with great success, but new findings regarding corrosion artifacts have caused a resurgence in tapered junction research. Mechanically assisted crevice corrosion (MACC) is thought to be the mechanism by which corrosive attack occurs. Myriad multi-factorial variables are known to influence the susceptibility of a modular taper junction to MACC. Some of these variables are design and manufacture related and others can be controlled by the surgeon.

QUESTIONS/PURPOSES

This study was performed to assess a 22-year retrieval database to determine if correlations exist between severity of corrosion artifacts and head size, time in vivo, head offset, or head material. Secondarily, the agreement of visual and semi-quantitative scoring methods was assessed using the retrieved components.

METHODS

A total of 210 femoral head tapers were scored and heads receiving high scores were measured to quantify material loss due to MACC.

RESULTS

Increased head size and increased time in vivo did not correlate to higher corrosion scores. Contrarily, there were differences in corrosion scores based on femoral head offset and material. Deviations away from a neutral offset (where neutral is defined as the alignment of femoral head center and stem taper gage point) resulted in higher scores. Cobalt-chromium-molybdenum heads were associated with higher corrosion scores and higher material loss as compared to oxidized zirconium heads.

CONCLUSION

Reducing the moment arm at the head-neck junction and choosing a more inert material appears to provide greater resistance to corrosion.

Acetabular cup position and risk of dislocation in primary total hip arthroplasty

Background and purpose - Hip dislocation is one of the most common complications following total hip arthroplasty (THA). Several factors that affect dislocation have been identified, including acetabular cup positioning. Optimal values for cup inclination and anteversion are debatable. We performed a systematic review to describe the different methods for measuring cup placement, target zones for cup positioning, and the association between cup positioning and dislocation following primary THA. Methods - A systematic search of literature in the PubMed database was performed (January and February 2016) to identify articles that compared acetabular cup positioning and the risk of dislocation. Surgical approach and methods for measurement of cup angles were also considered. Results - 28 articles were determined to be relevant to our research question. Some articles demonstrated that cup positioning influenced postoperative dislocation whereas others did not. The majority of articles could not identify a statistically significant difference between dislocating and non-dislocating THA with regard to mean angles of cup anteversion and inclination. Most of the articles that assessed cup placement within the Lewinnek safe zone did not show a statistically significant reduction in dislocation rate. Alternative target ranges have been proposed by several authors. Interpretation - The Lewinnek safe zone could not be justified. It is difficult to draw broad conclusions regarding a definitive target zone for cup positioning in THA, due to variability between studies and the likely multifactorial nature of THA dislocation. Future studies comparing cup positioning and dislocation rate should investigate surgical approach separately. Standardized tools for measurement of cup positioning should be implemented to allow comparison between studies.

3-year follow-up of a long-term registry-based multicentre study on vitamin E diffused polyethylene in total hip replacement

PURPOSE

Preclinical studies of vitamin E diffused highly cross-linked polyethylene (E-XLPE) has shown enhanced mechanical properties with less wear. The purpose of our study was to document the early clinical outcome of E-XLPE to ensure, for the safety of patients, that there are no unforeseen early adverse events from using this new biomaterial.

METHODS

The enrolled patients (n = 977) have received either a porous titanium coated or porous plasma sprayed acetabular shell with either a E-XLPE liner or a medium cross-linked (AXL) liner. At each follow-up 5 patient-reported outcome measures (PROMs) were completed: Harris Hip Score, Case Mix Indicator, UCLA Activity Score, SF-36, and EQ-5D. Radiographs were measured for cup and stem position, as well as femoral head penetration into the liner (wear). Postoperative complications and revisions were collected.

RESULTS

At 3 years follow-up, there were 13 revisions due to: 4 periprosthetic fractures; 1 sepsis; 6 instabilities; and 2 implant mismatches at surgery. Wear of the hip implant, calculated by software analysis of pelvis x-rays, from the postoperative interval to 3 years showed a liner penetration rate of 0.027 mm/year for AXL and 0.005 mm/year for E-XLPE with no significant difference between the 2 (p = 0.24). Improvement was seen in all PROMs from the preoperative interval to 3 years after surgery (p&lt;0.0001).

CONCLUSIONS

Early follow-up of the E-XLPE and AXL liners show low penetration. PROMs indicate improvement after total hip arthroplasty in functionality and quality of life across the centers. We have not observed any early in vivo adverse effects from diffusing the liners with vitamin E.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT00545285.

An Assessment of Gender-Specific Risk of Implant Revision After Primary Total Hip Arthroplasty: A Systematic Review and Meta-analysis

BACKGROUND

Total hip arthroplasty (THA) has been a successful reconstructive procedure to mitigate pain associated with diseases of the hip joint. However, some THA procedures require revision due to mechanical or biological failure. The purpose of this study was to synthesize and examine the evidence on the relative risk of revision in men and women after primary THA procedures.

METHODS

We conducted a systematic literature review of cohort studies reporting THA revision risk estimate by gender. Study quality scoring and a random effects meta-analysis were performed to estimate the meta-relative risk (meta-RR) and corresponding 95% confidence interval (95% CI) of revision, comparing men to women.

RESULTS

Males had a statistically significant increased risk of revision after primary THA (meta-RR = 1.33 [95% CI: 1.13-1.57]), when compared to females. When stratified by cause of revision, males had a statistically significant increased risk of revision due to any cause (meta-RR = 1.16 [95% CI: 1.01-1.33]), aseptic loosening (meta-RR = 1.54 [95% CI: 1.05-2.25]), and infection (meta-RR = 1.55 [95% CI: 1.11-2.15]). For primary THA operations performed during the 2000s, males in Europe had a statistically significant increased risk of revision (meta-RR 1.42 [95% CI: 1.25-1.61]) while males in the United States had a statistically significant decreased risk of revision (meta-RR 0.80 [95% CI: 0.72-0.89]).

CONCLUSION

These results provide evidence for an increased risk of revision after THA among males, which may be impacted by geographic location and time period of operation. Findings suggest that a better understanding of the underlying drivers of gender-specific risks would help reduce postsurgery complications.