The results of metal-on-metal hip resurfacing in patients under 30 years of age

Mid-term clinical and radiographic outcome of metal-on-metal hip resurfacing through an anterolateral approach

PURPOSE

The aim of this retrospective study was to evaluate the medium-term clinical and radiographic results of current generation metal-on-metal resurfacing prostheses performed through anterolateral approach.

MATERIALS AND METHODS

Fifty-seven hips in 52 patients underwent resurfacing arthroplasty. Two patients died from unrelated causes, leaving 55 hips in 35 males (3 bilateral) and 15 females (2 bilateral), with a mean age at surgery of 56.2 years (range, 27-70 years). Clinical and radiographic assessment was carried out preoperatively and at follow-up in all the survived cases. The cumulative survival rate was determined according to the method of Kaplan-Meier.

RESULTS

At a mean follow-up of 5.2 years (range, 1.8-9.1 years), 2 HRs of the same female patient were revised because of early loosening of the acetabular component. Deep venous thrombosis and transient femoral nerve palsy occurred both in 1 case. No specific complications of HR were observed. Average Harris hip score improved significantly from 59.8 points (range, 30.4-90.6) preoperatively to 93.7 points (range, 53-100) at the latest examination. Neck narrowing showed an average of 3.27%, but it never exceeded 10%. Nonprogressive acetabular radiolucencies and osteolysis were detected both in 2 hips. A high rate of patients (32, 60.4%) developed heterotopic ossifications, although low-grade in most cases (27, 84.4%). The cumulative survival rate at 9.1 years with revision for any reason as the end point was 93.0%.

CONCLUSIONS

The early clinical and radiographic results of modern metal-on-metal hip resurfacing performed through an anterolateral approach are promising, but longer-term follow-up studies are necessary.

Computational modelling of hip resurfacing arthroplasty investigating the effect of femoral version on hip biomechanics

Aim

How reduced femoral neck anteversion alters the distribution of pressure and contact area in Hip Resurfacing Arthroplasty (HRA) remains unclear. The purpose of this study was to quantitatively describe the biomechanical implication of different femoral neck version angles on HRA using a finite element analysis.

Materials and methods

A total of sixty models were constructed to assess the effect of different femoral neck version angles on three different functional loads: 0°of hip flexion, 45°of hip flexion, and 90° of hip flexion. Femoral version was varied between 30° of anteversion to 30° of retroversion. All models were tested with the acetabular cup in four different positions: (1) 40°/15° (inclination/version), (2) 40°/25°, (3) 50°/15°, and (4) 50°/25°. Differences in range of motion due to presence of impingement, joint contact pressure, and joint contact area with different femoral versions and acetabular cup positions were calculated.

Results

Impingement was found to be most significant with the femur in 30° of retroversion, regardless of acetabular cup position. Anterior hip impingement occurred earlier during hip flexion as the femur was progressively retroverted. Impingement was reduced in all models by increasing acetabular cup inclination and anteversion, yet this consequentially led to higher contact pressures. At 90° of hip flexion, contact pressures and contact areas were inversely related and showed most notable change with 30° of femoral retroversion. In this model, the contact area migrated towards the anterior implant-bone interface along the femoral neck.

Conclusion

Femoral retroversion in HRA influences impingement and increases joint contact pressure most when the hip is loaded in flexion. Increasing acetabular inclination decreases the area of impingement but doing so causes a reciprocal increase in joint contact pressure. It may be advisable to study femoral neck version pre-operatively to better choose hip resurfacing arthroplasty candidates.

The effect of femoral head size on edge loading in metal-on-metal hip joint replacement under dynamic separation conditions

Edge loading that occurs in hip joint replacements due to dynamic separation of the joint bearings has been shown to cause severe wear for meal-on-metal bearings. In the present study, the multibody dynamics model for metal-on-metal (MoM) hip joints with a medial-lateral translational mismatch in the centers of rotation of the cup and head has been developed to predict the dynamic separation and contact force of edge loading under gait loading conditions. The effects of larger head diameters (28-55 mm), in combination with the translational mismatch (0-4 mm) and varied cup inclination angles (45°-65°), on edge loading of MoM bearings have been computationally investigated. For the given translational mismatch, increasing head diameters results in negligible effects on the dynamic separation, contact force and severity of edge loading. Increasing head size also leads to increased offset loading torque which has been found to reach at the level that may cause cup loosening under larger translational mismatch at 4 mm. The result highlights the importance of the cup inclination angle of 45° and a lower translational mismatch to avoid severe edge loading.

Metal on Metal Hip Resurfacing in Patients 45 Years of Age and Younger at Minimum 5-Year Follow-Up

BACKGROUND

Metal on metal hip resurfacing (MoM-HR) is an alternative to total hip arthroplasty in young and active patients. The purpose was to determine the survivorship of MoM-HR procedures performed in patients aged 45 years and younger assessing patient-reported outcome measures (PROMs) at minimum 5-year follow-up.

METHODS

All 217 patients equal to or younger than 45 years of age at the time of surgical intervention presenting to our center with MoM-HR between May 2002 and May 2011 were prospectively followed. Baseline demographic data, preoperative and postoperative radiographic measurements, and validated PROMs were obtained (Hip Disability and Osteoarthritis Outcome Score, Western Ontario and McMaster Universities Osteoarthritis Index, and University of California, Los Angeles Activity Score). Survivorship was calculated using Kaplan-Meier analysis, and risk factors for failure were identified using multivariate regression analysis.

RESULTS

The overall survivorship excluding septic failures was 94.6% and 93.8% at 5 and 10 years, respectively. Aseptic loosening of the acetabular component was the most common mode of failure (11/20 cases). Gender, head size, and acetabular abduction angle had no significant effect on survivorship. Significant improvements in PROMs were seen for Hip Disability and Osteoarthritis Outcome Score, Western Ontario and McMaster Universities Osteoarthritis Index, and University of California, Los Angeles Activity Scale (P < .001).

CONCLUSION

This study indicates that MoM-HR is a suitable option for young individuals, as demonstrated through improved functional scores and low revision rates. The survivorship of HR in the younger than 45 age-group was similar to that of total hip arthroplasty, as well as HR in older patients. Given the proposed benefits of HR, this procedure may be viewed as a viable option in patients aged younger than 45 years.

Metal-on-metal hip resurfacing in patients younger than 50 years: a retrospective analysis : 1285 cases, 12-year survivorship

BACKGROUND

The Nordic registry reports patients under 50 years old with total hip replacements realize only 83% 10-year implant survivorship. These results do not meet the 95% 10-year survivorship guideline posed by the UK's National Institute for Health and Care Excellence (NICE) in 2014.

METHODS

The purpose of this study is threefold: First, we evaluate if metal-on-metal hip resurfacing arthroplasty meets these high standards in younger patients. Next, we compare outcomes between age groups to determine if younger patients are at higher risk for revision or complication. Lastly, we assess how outcomes between sexes changed over time. From January 2001 to August 2013, a single surgeon performed 1285 metal-on-metal hip resurfacings in patients younger than 50 years old. We compared these to an older cohort matched by sex and BMI.

RESULTS

Kaplan-Meier implant survivorship was 96.5% at 10 years and 96.3% at 12 years; this did not differ from implant survivorship for older patients. Implant survivorship at 12 years was 98 and 93% for younger men and women, respectively; survivorship for women improved from 93 to 97% by using exclusively Biomet implants. There were four (0.3%) adverse wear-related failures, with no instances of wear or problematic ion levels since 2009. Activity scores improved from 5.4 ± 2.3 preoperatively to 7.6 ± 1.9 postoperatively (p < 0.0001), with 43% of patients reporting a UCLA activity score of 9 or 10.

CONCLUSIONS

Hip resurfacing exceeds the stricter 2014 NICE survivorship criteria independently in men and women even when performed on patients under 50 years old.

Functional outcomes of total hip arthroplasty in patients aged 30 years or less: a systematic review and meta-analysis

INTRODUCTION

Young adult hip surgery is a growing subspecialty. Increasingly total hip arthroplasty (THA) is offered to patients aged 30 or less suffering from end-stage hip arthropathy from a variety of congenital, developmental and acquired conditions. There is a paucity of evidence to advise such patients and surgeons alike on the functional outcomes of THA in this age group, as individual studies tend to include small cohorts.

METHODS

A systematic review and meta-analysis was performed to assess whether THA in patients aged 30 years or less provides significant functional improvement. The primary outcome measure was change in Harris Hip Score. Secondary outcome measures were implant survivorship and the effect of fixation type and bearing surface.

RESULTS

The results of 743 primary THA procedures were included. Weighted mean patient age was 22.7 years. Harris Hip Score improved by a weighted mean difference of 42.17 points out of 100 (95% confidence interval, 36.48-47.86 points, p&lt;0.001) after THA at a weighted mean follow-up of 8.4 years. Pooled revision rate was 5.0% for the same time period.

CONCLUSIONS

This is the largest review to date of THA in patients aged 30 or less. The results show significant functional improvement measured by Harris Hip Score. The revision rate of 5% at 8.4 years is comparable to the general THA population. This contrasts high revision rates reported in older reviews of the literature, suggesting adoption of improved techniques and implants in the more recent literature.

Prevalence of Failure due to Adverse Reaction to Metal Debris in Modern, Medium and Large Diameter Metal-on-Metal Hip Replacements--The Effect of Novel Screening Methods: Systematic Review and Metaregression Analysis

Metal-on-metal (MoM) hip replacements were used for almost a decade before adverse reactions to metal debris (ARMD) were found to be a true clinical problem. Currently, there is a paucity of evidence regarding the usefulness of systematic screening for ARMD. We implemented a systematic review and meta-analysis to establish the prevalence of revision confirmed ARMD stratified by the use of different screening protocols in patients with MoM hip replacements. Five levels of screening were identified: no screening (level 0), targeted blood metal ion measurement and/or cross-sectional imaging (level 1), metal ion measurement without imaging (level 2), metal ion measurement with targeted imaging (level 3) and comprehensive screening (both metal ions and imaging for all; level 4). 122 studies meeting our eligibility criteria were included in analysis. These studies included 144 study arms: 100 study arms with hip resurfacings, 33 study arms with large-diameter MoM total hip replacements (THR), and 11 study arms with medium-diameter MoM THRs. For hip resurfacing, the lowest prevalence of ARMD was seen with level 0 screening (pooled prevalence 0.13%) and the highest with level 4 screening (pooled prevalace 9.49%). Pooled prevalence of ARMD with level 0 screening was 0.29% and with level 4 screening 21.3% in the large-diameter MoM THR group. In metaregression analysis of hip resurfacings, level 4 screening was superior with regard to prevalence of ARMD when compared with other levels. In the large diameter THR group level 4 screening was superior to screening 0,2 and 3. These outcomes were irrespective of follow-up time or study publication year. With hip resurfacings, routine cross-sectional imaging regardless of clinical findings is advisable. It is clear, however, that targeted metal ion measurement and/or imaging is not sufficient in the screening for ARMD in any implant concepts. However, economic aspects should be weighed when choosing the preferred screening level.

The Role of Hip Arthroscopy in Investigating and Managing the Painful Hip Resurfacing Arthroplasty

PURPOSE

To determine the safety and efficacy of hip arthroscopy performed in the peripheral compartment as a diagnostic and therapeutic treatment option for patients with hip pain after hip resurfacing surgery.

METHODS

Indications for hip arthroscopy after hip resurfacing included patients with a symptomatic hip-resurfaced arthroplasties who did not respond to nonoperative treatment. Patients who underwent a hip arthroscopy after a painful hip resurfacing were included with a minimum of 1 year follow-up. Subgroup analysis was performed according to whether an established diagnosis was made before arthroscopic intervention or not. Subjective measures were based on Western Ontario and McMaster Universities Arthritis Index (WOMAC) scores, and results were calculated and analyzed.

RESULTS

We included 68 patients (26 male [38%] and 42 female [62%]) who underwent subsequent hip arthroscopy from a population of 978 consecutive hip-resurfaced arthroplasties performed between 1999 and 2010. The average age was 58 (range, 37 to 78 years). The mean follow-up after hip arthroscopy was 3.4 years (range, 12 months to 5.8 years). Patients who had an established diagnosis (n = 41) before hip arthroscopy showed statistical improvement in their WOMAC scores (7 to 2, P < .001). Only 3 (7%) of these 41 patients failed and were converted to a total hip replacement (THR); however, patients who did not have an established diagnosis (n = 27) before undergoing hip arthroscopy showed statistical worsening of the WOMAC (15 to 21, P = .002). Ten (37%) of these 27 patients without a diagnosis failed and needed to be converted to a THR. A significant correlation was found between the collections found on ultrasound (psoas bursa and/or in the hip joint) and the need for synovectomy (P = .01). The overall revision rate to THR after hip resurfacing in our group of patients was 1.3% (n = 13). Female patients were more likely to require postresurfacing hip arthroscopy with 42 (60%) female to only 26 (40%) male patients undergoing this procedure. In our study population, 70% (14/21, P < .05) of patients with hip pain caused by severe metal synovial reaction or metal-on-metal reaction were women. A total of 5 (7%) patients had minor-to-mild complications after hip arthroscopy.

CONCLUSIONS

Hip arthroscopy is a safe surgical treatment option for those patients with a painful hip resurfacing arthroplasty. Having an accurate diagnosis before hip arthroscopy improves the likelihood a good outcome.

LEVEL OF EVIDENCE

Level IV - therapeutic case series.

Current indications for hip resurfacing arthroplasty in 2016

Hip resurfacing arthroplasty (HRA) is an alternative to conventional, stemmed total hip arthroplasty (THA). The best reported results are young, active patients with good bone stock and a diagnosis of osteoarthritis. Since the 1990s, metal-on-metal (MoM) HRA has achieved excellent outcomes when used in the appropriate patient population. Concerns regarding the metal-on-metal bearing surface including adverse local tissue reaction (ALTR) to metal debris have recently lead to a decline in the use of this construct. The current paper aims to provide an updated review on HRA, including a critical review of the most recent literature on HRA.

Hip Resurfacing Implants

EDUCATIONAL OBJECTIVES As a result of reading this article, physicians should be able to: 1. Describe the advantages of hip resurfacing. 2. Describe the disadvantages of hip resurfacing. 3. Identify the population in which hip resurfacing is most often indicated. 4. Demonstrate how to properly postoperatively manage patients with metal-on-metal prostheses. Hip resurfacing offers a suitable solution for young patients affected by hip disease who have high function demands and good bone quality. Bone stock preservation, restoration of the normal proximal femur anatomy, the lack of stress shielding, and the possibility of resuming sporting activity are proven advantages of hip resurfacing. However, there are some disadvantages, such as fracture of the femoral neck, onset of neck narrowing, and possible complications due to the metal-on-metal bearings, including pseudotumors, peri-implant osteolysis, and chronic elevation of metal ions in serum levels. Recent data suggest that the ideal candidate for hip resurfacing is an active male, younger than 65 years, with primary or posttraumatic osteoarthritis, and with a femoral head diameter larger than 50 to 54 mm. Based on these selection criteria, the literature reports implant survival to be similar to that of total hip arthroplasty. The current authors' experience confirms a low failure rate and excellent functional outcomes, with metal ion serum levels becoming stable over time in well-functioning implants. Proper surgical technique, correct patient selection, and the right choice of a well-established prosthetic model are essential elements for the long-term success of these implants.

Comparison of Patient-Reported Outcome from Neck-Preserving, Short-Stem Arthroplasty and Resurfacing Arthroplasty in Younger Osteoarthritis Patients

Hip resurfacing has been considered a good treatment option for younger, active osteoarthritis patients. However, there are several identified issues concerning risk for neck fractures and issues related to current metal-on-metal implant designs. Neck-preserving short-stem implants have been discussed as a potential alternative, but it is yet unclear which method is better suited for younger adults. We compared hip disability and osteoarthritis outcome scores (HOOS) from a young group of patients (n = 52, age 48.9 ± 6.1 years) who had received hip resurfacing (HR) with a cohort of patients (n = 73, age 48.2 ± 6.6 years) who had received neck-preserving, short-stem implant total hip arthroplasty (THA). Additionally, durations for both types of surgery were compared. HOOS improved significantly preoperatively to last followup (>1 year) in both groups (p < 0.0001, η (2) = 0.69); there were no group effects or interactions. Surgery duration was significantly longer for resurfacing (104.4 min ± 17.8) than MiniHip surgery (62.5 min ± 14.8), U = 85.0, p < 0.0001, η (2) = 0.56. The neck-preserving short-stem approach may be preferable to resurfacing due to the less challenging surgery, similar outcome, and controversy regarding resurfacing implant designs.

Do hardened femoral heads reduce blood metal ion concentrations after hip resurfacing?

BACKGROUND

Elevated cobalt and chromium ion concentrations have been associated with the use of metal-on-metal bearings in hip arthroplasty. The use of a differential hardness bearing may reduce metal particle release. The aim of our study was to compare circulating cobalt (Co) and chromium (Cr) ion levels between patients treated with a standard all 'as-cast' heat treated bearing and a differential hardness bearing.

MATERIALS AND METHODS

One hundred and thirty-two patients implanted with unilateral hip resurfacing arthroplasties and having had blood metal ion studies performed between one and six years after surgery were retrospectively selected. There were 73 patients in the standard all 'as cast' heat treated bearing group (group 1) and 59 in the differential hardness bearing group (group 2).

RESULTS

Clinical and quality of life scores were comparable between groups. The median Co in group 1 was 1.01 µg/L and 1.23 µg/L in group 2 (p = 0.0566). The median Cr in group 1 was 1.60 µg/L and 1.34 µg/L in group 2 (p = 0.0505).

CONCLUSION

Compared with conventional heat-treated CoCr bearings, differential hardness metal-on metal bearings do not confirm in vivo the hopes of a substantial reduction in circulating metal ions concentrations suggested by in vitro wear studies.

Effect of microseparation on contact mechanics in metal-on-metal hip replacements-A finite element analysis

Some early failures of metal‐on‐metal (MoM) hip replacements associated with elevated wear have caused concerns for the use of this bearing combination. Simulator studies have shown that microseparation and its associated rim contact and edge loading may produce the most severe wear in MoM bearings. It is generally recognized that this high wear can be attributed to the high contact stress of the head on the rim of the cup. In this study, an improved finite element contact model that incorporates an elastic‐perfectly plastic material property for cobalt‐chrome alloy of the metal bearing was developed in an attempt to provide an accurate prediction of the stress and strain for the rim contact. The effects of the microseparation displacement (0.1−2 mm), cup inclination angle (25−65°) and cup rim radius (0.5−4 mm) on the contact stress/strain were investigated. The results show that a translational displacement >0.1 mm under a load >0.5 kN can produce a highly concentrated contact stress at the surface of the cup rim which can lead to plastic deformation. This study also suggests that the magnitude of translational displacement was the major factor that determined the severity of the contact conditions and level of stress and strain under microseparation conditions. Future studies will address the effect of surgical translational and rotational malposition and component design on the magnitude of microseparation, contact stress and strain and severity of wear. © 2014 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 1312–1319, 2015.