Minimally Invasive Posterior Approach for Hip Resurfacing Arthroplasty

Magnum metal-on-metal uncemented total hip replacement: 8- to 18-year outcomes of 211 cases

BACKGROUND

Reports of adverse reactions to metal debris contributed in part to a decline in use of large-bearing metal-on-metal total hip devices. We hypothesize an optimal trunnion design may reduce risk of this failure mode in large-bearing total hip arthroplasty systems. The purpose of this study is to report mid- to long-term outcomes for a single-surgeon series of 211 total hip arthroplasties using the large-bearing Biomet Magnum metal-on-metal system.

MATERIALS AND METHODS

Between December 2004 and January 2016, the primary surgeon performed 211 uncemented Magnum total hip arthroplasties in 181 patients. The average length of follow-up was 10.1 ± 3.5 years (range 8-18 years).

RESULTS

Using failure of any component as the endpoint, the overall survivorship rate was 98.1% at 10 years and 97.4% at 18 years. These eight failures (3.8% of cohort) included one case of adverse wear-related failure (0.5%), two cases of acetabular ingrowth failure (0.9%), three cases of trunnion corrosion (1.4%), one failure of late infection (0.5%), and one inappropriate revision of components for trochanteric nonunion without instability (0.5%). Excluding failed cases, all components were radiographically stable with no radiolucencies. Except for the one wear failure, ion testing revealed that 97.2% of cases were within optimal whole blood metal ion levels with the remaining ion test results within acceptable levels.

CONCLUSIONS

With the uncemented Magnum metal-on-metal total hip, we achieved 97.4% 18-year implant survivorship, exceeding the NICE criteria and registry benchmarks for implant survivorship. We observed a trunnion corrosion rate of 1.4% and no cases of instability. The single case of adverse wear-related failure was caused by acetabular component malposition.

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.

Comparison of Cemented and Bone Ingrowth Fixation Methods in Hip Resurfacing for Osteonecrosis

BACKGROUND

The optimal surgical treatment for osteonecrosis of the femoral head has yet to be elucidated. To evaluate the role of femoral fixation techniques in hip resurfacing, we present a comparison of the results for 2 consecutive groups: group 1 (75 hips) received hybrid hip resurfacing implants with a cemented femoral component; group 2 (103 hips) received uncemented femoral components. Both groups received uncemented acetabular components.

METHODS

We retrospectively analyzed our clinical database to compare failures, reoperations, complications, clinical results, metal ion test results, and X-ray measurements. Using consecutive groups caused time interval bias, so we required all group 2 patients to be at least 2 years out from surgery; we compared results from 2 years and final follow-up.

RESULTS

Patient groups matched similarly in age, body mass index, and percent female. Despite similar demographics, the uncemented, group 2 cases showed a lower raw failure rate (0% vs 16%; P < .0001), a lower 2-year failure rate (0% vs 7%; P = .04), and a superior 8-year implant survivorship (100% vs 91%; log-rank P = .0028; Wilcoxon P = .0026). In cases that did not fail, patient clinical (P = .05), activity (P = .02), and pain scores (P = .03), as well as acetabular component position (P < .0001), all improved in group 2, suggesting advancements in surgical management. There were no cases of adverse wear-related failure in either group.

CONCLUSION

This study demonstrates a superior outcome for cases of osteonecrosis with uncemented hip resurfacings compared to cases employing hybrid devices.

Reducing the failure rate of hip resurfacing in dysplasia patients: a retrospective analysis of 363 cases

BACKGROUND

Arthritis secondary to developmental hip dysplasia often mandates implant surgery at a relatively young age. Hip resurfacing arthroplasty (HRA), compared with standard stemmed total hip arthroplasty (THA), affords a more active lifestyle including extreme-motion activities but stimulates concerns pertaining to implant failure.

METHODS

We addressed the primary modes of failure through a series of interventions, including a new guideline for achieving proper implant alignment through intraoperative x-rays. We then compared two sequential cohorts in a single-surgeon practice: patients with developmental dysplasia who underwent HRA before (Group 1; 121 hips in 105 patients) and after (Group 2; 242 hips in 210 patients) June 2008, at which time the four interventions were all in place.

RESULTS

Implants in Group 2 failed less frequently within two years (0.8 % vs. 6.6 %, p = 0.002) and were more likely to have projected seven-year Kaplan-Meier survivorship (99 % vs. 89 %, p < 0.0001 by log-rank test). Patients in Group 2 were more likely to have normal metal ion levels (77 % vs. 56 %, p = 0.0008) and optimum metal ion levels (99 % vs. 86 %, p = 0.0008). Patients in Group 2 also benefited from a 19-min decrease in mean operation time, a 45 % decrease in mean estimated blood loss, and a 0.9-day decrease in mean hospital stay (p < 0.0001 in each instance).

CONCLUSIONS

We believe the interventions reported here, combined with sufficient surgeon experience and properly designed implants, afford patients with mild developmental dysplasia a more active lifestyle with favorable implant survival.

High incidence of pseudotumours after hip resurfacing even in low risk patients; results from an intensified MRI screening protocol

We intensified our screening protocol for the presence of pseudotumours in a consecutive series of patients with a hip resurfacing arthroplasty (HRA), to establish whether we should be alert to the presence of 'silent' pseudotumours. Patients categorised with high risk (11 hips) and low risk (10 hips) for pseudotumour development and a control group (23 hips) were screened with metal artefact reduction sequence (MARS) magnetic resonance imaging (MRI). The Anderson classification to grade any metal-on-metal (MoM) disease present on MARS-MRI images was used. In 15 out of 44 MRI scans pseudotumours were observed (34.1%), of which six were graded with mild (13.6%), eight with moderate (18.2%) and one with severe MoM disease (2.3%). Twelve pseudotumours were present in asymptomatic patients (27.3%). Metal ion levels were normal in 80% of the MARS-MRI screened patients. As a consequence of our intensified screening protocol, one patient was revised for pseudotumour formation and another patient was scheduled for revision. Silent pseudotumours were observed in all three groups. Before our intensified screening protocol was initiated, no pseudotumours were encountered in our cohort of 289 HRAs. We concluded that clinical outcomes and plain radiographs for screening MoM patients underestimates the presence of pseudotumours in MoM patients. The true clinical relevance of these pseudotumours is still unclear.

Current status of modern fully porous coated metal-on-metal hip resurfacing arthroplasty

Between March 2007 and July 2010, 1000 consecutive fully porous coated hip resurfacing arthroplasties (HRA) were performed by a single surgeon in 871 patients. The average length of follow-up was 3 ± 1 years. Three cases (0.3%) in three patients showed adverse wear related failures. Another 17 (1.7%) failures were identified at the time of this study. Using any failure of any component as the endpoint, the survivorship rate was 98.8% at two years and 97.4% at five years. Excluding the failed cases, all components were radiographically stable; there was only one partial femoral radiolucency seen. The clinical and radiological outcomes of this fully porous coated hip resurfacing were comparable to, if not better than, those reported by others using hybrid fixation methods at five years post-operatively.

Hip resurfacing with the Biomet Hybrid ReCap-Magnum system: 7-year results

The purpose of this study was to report our clinical outcome of a large series of metal-on-metal hip resurfacing arthroplasty (HRA) using the hybrid Biomet ReCap-Magnum system. This is a single-designer surgeon series with an average of 5 ± 1 years. Seven hundred forty consecutive hybrid HRAs were performed in 653 patients. Kaplan-Meier survivorship with any revision as an end point was 96.4% at 7 years. Twenty-five (3.4%) cases were revised: 8 due to acetabular component loosening, 6 due to femoral neck facture, 4 due to failure of femoral component fixation, 2 due to deep infection, 2 due to adverse wear, 1 due to psoas tendonitis, 1 due to recurrent dislocation, and 1 due to unexplained pain. Biomet ReCap and Magnum HRA components with hybrid fixation methods showed excellent survivorship for a minimally selected young patient cohort at 7 years.

Clinical outcome of the metal-on-metal hybrid Corin Cormet 2000 hip resurfacing system: an up to 11-year follow-up study

This report extends the follow-up for the largest center of the first multicenter US Food and Drug Administration investigational device exemption study on metal-on-metal hip resurfacing arthroplasty up to 11 years. A single surgeon performed 373 hip resurfacing arthroplasties using the hybrid Corin Cormet 2000 system. The Kaplan-Meier survivorship at 11 years was 93% when revision for any reason was used as an end point and 91% if radiographic failures were included. The clinical results demonstrate an acceptable failure rate with use of this system. Loosening of the cemented femoral components was the most common source of failure and occurred at all follow-up intervals. A learning curve that persisted for at least 200 cases was confirmed. All femoral neck fractures occurred before 6 months postoperatively.

Risk factor analysis for early femoral failure in metal-on-metal hip resurfacing arthroplasty: the effect of bone density and body mass index

Background

The importance of appropriately selecting patients based on factors such as bone mineral density, body mass index, age, gender, and femoral component size has been demonstrated in many studies as an aid in decreasing the rate of revisions and improving the outcomes for patients after hip resurfacing arthroplasty (HRA); however, there are few published studies quantitatively specifying the potential risk factors that affect early femoral component failures. Therefore, the purpose of this study was to investigate the specific causes of early femoral component failures in hip resurfacing separately and more carefully in order to develop strategies to prevent these failures, rather than excluding groups of patients from this surgical procedure.

Methods

This retrospective study included 373 metal-on-metal HRAs performed by a single surgeon using the vascular sparing posterior minimally invasive surgical approach. The average length of follow-up was 30 ± 6 months. In order to understand the causes of early femoral failure rate, a multivariable logistic regression model was generated in order to analyze the effects of bone mineral density (T-score), gender, diagnosis, body mass index, femoral implant fixation type, age, and femoral component size.

Results

The average post-operative Harris hip score was 92 ± 11 points and the average post-operative UCLA score was 7 ± 2 points. There were three revisions due to femoral neck fracture and two for femoral component loosening. These occurred in two female and three male patients. In the multi-variable regression model, only T-score and body mass index showed significant effects on the failure rate of femoral components. Patients with a lower T-score and a higher body mass index had a significantly increased risk of early femoral component failure.

Conclusion

We recommend that dual energy x-ray absorptiometry scan T-score tests should be routinely performed on all hip resurfacing patients pre-operatively. If a patient has a low T-score (≤ -1.5), consideration should be given to additional precautions or treatments to alleviate his or her risk, especially when the patient has a higher body mass index (≥ 29 kg/m²).

Is there added risk in resurfacing a femoral head with cysts?

Background

Femoral head cysts have been identified as a risk factor for early femoral failures after metal-on-metal hip resurfacing arthroplasty (HRA) based on limited scientific data. However, we routinely performed HRA if less than 1/3 of the femoral head appeared destroyed by cysts on the preoperative radiograph. This study was undertaken to analyze whether there was an added risk of early femoral failures in HRA when femoral head cysts were present.

Methods

This retrospective case-control study included 939 MOM HRAs operated by a single surgeon with use of the posterior minimally invasive surgical (MIS) approach between November 2005 and January 2009. Patients with all diagnoses except osteonecrosis were included. Among them, 117 HRAs had femoral head cysts ≥ 1 cm identified in surgery. All cysts were treated with bone grafting using acetabular reamings packed into the cavitary defect (instead of filling the cysts with cement). The control group, which had no cyst observed at the time of surgery, was randomly selected from our database using computer algorithms to match those cases in the study group for the parameters of surgical date, age, gender, body mass index, diagnosis, femoral fixation method, and the size of the femoral component.

Results

The minimum follow-up was 24 months for both groups. The early femoral failure rate in the study group was 3/117 (2.6%) and 0/117 in the control group; there was no statistical difference between these two groups (P = 0.08). In the study group, there were two femoral neck fractures (revised): both occurred in patients having a cyst size of 1 cm³; and there was one femoral component loosening at 3-year follow up in a patient having a cyst size of 2 cm³.

Conclusion

Although the risk of early femoral failures among the group with cysts appeared higher than the group without cysts, we could not demonstrate a significant statistical difference between the two groups. It is possible that bone grafting cysts rather than cementing them may account for the low failure rate, and that this technique may minimize the risk of resurfacing a femoral head with cysts.

Prevalence of dysplasia as the source of worse outcome in young female patients after hip resurfacing arthroplasty

PURPOSE

Smaller femoral component size has been implicated as underlying the risk factor that explains the higher failure rate in women who have a hip resurfacing arthroplasty (HRA). We suspect that the diagnosis of dysplasia may be a more important causative risk factor than either small component size or female gender.

METHODS

From January 2002 to July 2008, a total of 1,216 HRA cases, 1,082 with the primary diagnosis of osteoarthritis and 134 with dysplasia, were included in this study. Of them, 867 cases were performed in men and 349 performed in women. The average femoral component size was 51 ± 4 mm. Cox proportional hazard regression models were used to evaluate the significance of each variable and determine the causative risk factors for failure.

RESULTS

The average follow-up was 5 ± 2 years. Thirty-nine cases failed (20 in men vs. 19 in women). The failure rate for the whole group was 3.2% (2.3% in men vs. 5.4% in women; P = 0.01). Dysplasia (P = 0.05) was identified as the only significant risk factor in our multi-variable analysis; small femoral component size (P = 0.09) and gender (P = 0.76) were not significant risk factors. Women with the primary diagnosis of dysplasia had a survivorship rate of only 75% compared to 93% for the entire group at eight-year follow-up post-operatively.

CONCLUSIONS

In our study, we found that the high incidence of dysplasia in young women undergoing HRA was the reason that women had a higher failure rate after HRA. In dysplasia, 70% of failures were due to acetabular problems, of which 50% were due to failure of fixation and 20% due to adverse wear.

Comparison of fully porous-coated and hybrid hip resurfacing: a minimum 2-year follow-up study

The purpose of this study was to compare clinical and radiological outcomes of the first 191 fully porous-coated hip resurfacing arthroplasties with 96 hybrid hip resurfacing arthroplasties performed during the same period at a minimum 2-year follow-up to evaluate the initial fixation of uncemented femoral resurfacing components. The results of this study indicate that fully porous-coated femoral resurfacing components can routinely achieve reliable fixation and provide similar initial results as have been achieved with cemented fixation. Long-term results are needed to determine which type of fixation is superior for the femoral hip resurfacing component.