Examining the “revisability” benefit of hip resurfacing arthroplasty

Abstract

BACKGROUND

Hip resurfacing arthroplasty (HRA) is an alternative to total hip arthroplasty (THA) that is typically reserved for young active patients because it preserves bone. However, the benefits of HRA only hold true if conversion THA after failed HRA provides acceptable outcomes.

AIM

To compare patient reported outcomes for conversion THA after HRA failure to primary THA.

METHODS

A retrospective review of 36 patients (37 hips) that underwent conversion THA for failed HRA between October 2006 and May 2019 by a single surgeon was performed. Patient reported outcomes [modified Harris Hip Score (mHHS), University of California Los Angeles (UCLA) activity score] were obtained via an email-based responder-anonymous survey. Outcomes were compared to normative data of a primary THA cohort with similar demographics. Subgroup analysis was performed comparing outcomes of conversion THA for adverse local tissue reaction (ALTR) vs all other causes for failure.

RESULTS

The study group had a lower mHHS than the control group (81.7 ± 13.8 vs 90.2 ± 11.6, P < 0.01); however, both groups had similar UCLA activity levels (7.5 ± 2.3 vs 7.2 ± 1.6, P = 0.51). Patients that underwent conversion for non-ATLR causes had similar mHHS (85.2 ± 11.5 vs 90.2 ± 11.6, P = 0.11) and higher UCLA activity levels (8.5 ± 1.8 vs 7.2 ± 1.6, P < 0.01) compared to the control group. Patients that underwent conversion for ATLR had worse mHHS (77.1 ± 14.5 vs 90.2 ± 11.6, P < 0.01) and UCLA activity levels (6.1 ± 2.3 vs 7.2 ± 1.6, P = 0.05) when compared to the control group.

CONCLUSION

Patient outcomes equivalent to primary THA can be achieved following HRA conversion to THA. However, inferior outcomes were demonstrated for ALTR-related HRA failure. Patient selection and perhaps further studies examining alternative HRA bearing surfaces should be considered.

Key Words: Total hip arthroplasty; Hip resurfacing arthroplasty; Conversion total hip arthroplasty; Adverse local tissue reaction; Patient reported outcome measures

Core Tip: We aim to examine the “revisability” benefit of hip resurfacing arthroplasty (HRA): Are outcomes of conversion to total hip arthroplasty (THA) after failed metal-on-metal-HRA worse compared to primary THA? This study expands the literature by examining patient reported outcomes between HRA revision and primary THA, and outcomes between HRA revision and revision THA. HRA patients revised to THA have worse clinical outcomes compared to primary THA and the outcome is dependent on the etiology of failure.

INTRODUCTION

Hip resurfacing arthroplasty (HRA) has been an alternative to total hip arthroplasty (THA) in young and/or active patients to accommodate higher activity and ease of revision[1-3]. With near-physiologic stress transfer to the femoral neck, HRA preserves the quality of bone in the proximal femur, simplifying revision to THA[4-7], the so-called revisability benefit. With a metal-on-metal (MoM) bearing, HRA has the potential for low wear, but also the potential for metal-related pathologies (MRP) which negatively impact outcomes[3-6,8].

The purpose of the current study is to examine the “revisability” benefit of HRA: How do outcomes of conversion to THA after failed MoM-HRA compare to a primary THA? Further, how do the outcomes of HRA revision to THA compare to primary THA when patients are stratified for MRP vs all other causes? Although MoM-HRA is now < 2% of all primary hip arthroplasties worldwide, bearing surfaces and HRA technology will continue to evolve[8]. For these reasons, knowledge of patient reported outcomes of THA after failed MoM-HRA has value.

MATERIALS AND METHODS

After obtaining institutional review board approval, retrospective review was performed of all patients that underwent conversion THA for failed HRA between October 2006 and May 2019 by a single surgeon (TPS). Patients were contacted via email for an invitation to participate in a responder-anonymous voluntary survey. Each patient was sent an identical e-mail with a link to the patient survey which was conducted via SurveyMonkey^® (San Mateo, CA, United States). The survey included standardized functional outcome measures including modified Harris Hip Score (mHHS)[4], University of California Los Angeles (UCLA) activity scores[5], and the Short-Form Health Survey (SF-12)[6]. No identifying patient information was included in the survey and the survey did not obtain or record the individual’s IP address to maintain patient privacy and anonymity. Two follow-up emails were sent in 2-wk intervals after initial contact to increase participation.

Study group

A total of 48 patients (49 hips), were identified. Of these, a total of 41 patients responded to the survey with 36 patients (37 hips) [17 (47%) male, 19 (53%) female] stating they would participate (Table 1), with an average age of 53 years (range, 20-79 years). Diagnoses for the initial HRA in the study group included osteoarthritis in 33 patients and avascular necrosis in 4 patients. The average time from HRA to conversion THA was 81.6 months (range, 4.1 months-18 years). Sixteen hips (43%) underwent conversion for MRP while 21 hips (57%) underwent conversion for other causes.

Table 1 Demographic information of study and control groups.

	Study group (n = 37)	Control group (n = 37)
Age (yr)	53.0	42.1
Male/female ratio (%)	47.2/55.5	33.0/67.0
BMI (kg/m2)	26.4	29.0
Indication for revision surgery, n (%)
Adverse local tissue reaction	16 (43)	-
Infection	2 (5)	-
Loose femoral component	6 (16)	-
Loose acetabular component	9 (24)	-
Femoral neck fracture	1 (3)	-
Other	3 (8)	-

BMI: Body mass index.

Control group

To compare the outcomes of conversion THA after failed HRA to primary THA in a similar patient population, normative data on primary THA was obtained from Kuhn et al[7]. This study had patient reported outcomes for 37 patients with an average age of 42.1 years (range, 17.8 years to 50.3 years) before and after primary THA[7]. Diagnoses for the control group included osteoarthritis in 32 patients, avascular necrosis in 4 patients, and rheumatoid arthritis in 1 patient. All surgeries were performed by a single surgeon between January 2008 to July 2010. Demographic information for the patients is summarized in Table 1.

Statistical analysis

The statistical analysis was performed with the online software EasyMedStat (France). Statistical analysis for patient reported outcomes between the study and control groups was calculated using an unpaired student t-test. The difference in functional outcome scores between patients that underwent conversion THA due to MRP vs all other causes was calculated using paired student t-tests with a two-sided significance level of 0.05. Kaplan-Meier survivorship analysis [with a 95% confidence interval (95%CI)] was performed with revision surgery as the endpoint.

RESULTS

Overall outcomes

The mean mHHS was significantly better for the primary THA control group when compared to the revision HRA group (90.2 ± 11.6 vs 81.7 ± 13.8, P = 0.005) (Table 2). There was no statistically significant difference in the mean UCLA activity level between the control and study groups (7.2 ± 1.6 vs 7.5 ± 2.3, P = 0.51). Four patients underwent re-revision at an average of 2.5 years after the first revision. Using the time to re-revision as the endpoint, the Kaplan-Meier survivorship was 88.9% at 10 years (95%CI: 73.0%-95.7%).

Table 2 Patient reported outcomes between study and control groups.

	Study group	Control group	P value
Visual Analog Scale Pain Score	1.5 ± 1.6	-
Modified Harris Hip Score	81.7 ± 13.8	90.2 ± 11.6	< 0.01a
UCLA activity level	7.5 ± 2.3	7.2 ± 1.6	0.51
Short-form 12
Physical	51 ± 8.1	-
Mental	53 ± 10.8	-

^aP < 0.05.

UCLA: University of California Los Angeles.

Stratified outcome measures

Comparing patient reported outcomes for HRA revision due to MRP vs all other causes, there was a significant decrease in mHHS (77.1 ± 14.5 vs 85.2 ± 11.5, P = 0.04), UCLA activity level (6.1 ± 2.3 vs 8.5 ± 1.8, P < 0.01), and the physical component of the SF-12 (45.6 ± 8.9 vs 55.2 ± 4.3, P < 0.01) for the MRP group (Table 3). Patients that underwent HRA revision for MRP had significantly worse mHHS than primary THA patients (77.1 ± 14.5 vs 90.2 ± 11.6, P < 0.01) and worse UCLA activity scores (6.1 ± 2.3 vs 7.2 ± 1.6, P = 0.05) (Table 4). Patients that underwent HRA revision for non-MRP had similar mHHS compared to primary THA patients (85.2 ± 11.5 vs 90.2 ± 11.6, P = 0.11) and better UCLA activity level scores (8.5 ± 1.8 vs 7.2 ± 1.6, P < 0.01).

Table 3 Patient reported outcomes between metal-related pathologies revision and non-metal-related pathologies revision compared to the control group.

	Control	MRP (P value)	Non-MRP (P value)
Modified Harris Hip Score	90.2 ± 11.6	77.1 ± 14.5 (< 0.01a)	85.2 ± 11.5 (0.11)
UCLA activity level	7.2 ± 1.6	6.1 ± 2.3 (0.05)	8.5 ± 1.8 (< 0.01a)

^aP < 0.05.

MRP: Metal-related pathologies; UCLA: University of California Los Angeles.

Table 4 Patient reported outcomes for metal-related pathologies versus non-metal-related pathologies groups.

	MRP	Non-MRP	P value
Visual Analog Scale Pain Score	1.7 ± 1.6	1.3 ± 1.7	0.22
Modified Harris Hip Score	77.1 ± 14.5	85.2 ± 11.5	0.04a
UCLA activity level	6.1 ± 2.3	8.5 ± 1.8	< 0.01a
Short-form 12
Physical	45.6 ± 8.9	55.2 ± 4.3	< 0.01a
Mental	50.1 ± 12.6	55.3 ± 8.7	0.07

^aP < 0.05.

MRP: Metal-related pathologies; UCLA: University of California Los Angeles.

DISCUSSION

In this study, the overall patient reported outcomes of THA following failed MoM-HRA are inferior to primary THA. Additionally, the outcomes were related to the cause for revision. Patients who underwent revision to THA for MRP had inferior outcomes compared to patients with other etiologies.

Amstutz and Le Duff[9] reported that THA for failed MoM-HRA provides function and quality of life similar to that of primary THA and noted no trend towards worse outcomes with any specific reason for revision. This is in contrast to our results as well as the results of other studies in the literature that show revision due to MRP has worse outcomes[10-12].

Su et al[11] demonstrated that unexplained pain and metal sensitivity, categorized together, were the worst prognostic factors for the clinical scores of THA after MoM-HRA. Similarly, Grammatopoulos et al[12] found that patients undergoing revision for MRP after HRA had worse outcomes and higher rates of major complications. The etiology of inferior outcomes due to MRP is likely related to the invasive and destructive potential of MRP[12]. Patients that undergo HRA revision to THA for MRP may have extensive damage to the soft tissues and bone leading to complications including dislocations, infection, component loosening, recurrent MRP, and re-revision[10]. Even when extensive tissue damage is not present with MRP, patients still do not perform as well and this may be due to retained metal debris and persistent inflammation[11].

Outcomes after revision THA are generally inferior to those of primary THA[13-21]. In the current series, the clinical outcomes of all-cause HRA revision to THA were comparable to revision THA (Table 5)[18,20,21]. When stratifying patients who underwent HRA revision to THA for non-MRP etiologies, the outcomes were superior to revision THA. Our 10-year survival results of 88.9% are similar to the results of Amstutz and Le Duff with 85.3% survival at 13 years. These compare favorably to the 10-year survivorship of revision THA in patients under 50 years old which has been reported as low as 71.0%[15].

Table 5 Patient reported outcomes between all cause conversion total hip arthroplasty, metal-related pathologies, and non-metal-related pathologies revision compared to revision total hip arthroplasty.

Ref.	Patient reported outcome	Revision THA	Conversion THA (P value)	Non-MRP (P value)	MRP (P value)
Lübbeke et al[18], 2012	HHS	76.7 ± 18.1	81.7 ± 13.8 (0.12)	85.2 ± 11.5 (0.04a)	77.1 ± 14.5 (0.93)
	SF-12 PCS	36.5 ± 8.6	51.0 ± 8.1 (< 0.01a)	55.2 ± 4.3 (< 0.01a)	45.6 ± 8.9 (< 0.01a)
	SF-12 MCS	46.5 ± 11.2	53.0 ± 10.8 (< 0.01a)	55.3 ± 8.7 (< 0.01a)	50.1 ± 12.6 (0.23)
Postler et al[20], 2017	UCLA	4.1 ± 1.6	7.5 ± 2.3 (< 0.01a)	8.5 ± 1.8 (< 0.01a)	6.1 ± 2.3 (< 0.01a)

^aP < 0.05.

MRP: Metal-related pathologies; THA: Total hip arthroplasty; mHHS: Modified Harris Hip Score; HHS: Harris Hip Score; UCLA: University of California Los Angeles activity level; SF-12 PCS: Short-Form 12 Physical Component Score; SF-12 MCS: Short-Form 12 Mental Component Score.

Considering the outcomes and survival that can be obtained with contemporary THA, it is reasonable to debate the role of HRA. Although there is certainly a risk of selection bias, increases in walking speed, range of motion, and greater return to sport compared to primary THA makes HRA an attractive option for young and/or active patients[22,23]. As materials technology and manufacturing evolve, other HRA bearing surfaces are being investigated. Treacy et al[24] reported excellent early outcomes with metal-on-highly-crosslinked-polyethylene HRA while Ul Haq et al[25] are evaluating a ceramic-on-ceramic HRA. Such bearings may deliver the benefits of HRA without the complications of MRP.

The limitations of our study include the retrospective survey-based design, which could result in respondent selection bias. With normative control data, we were unable to fully match group and surgeon-related variables. The average age of the control group was 10 years younger than the study group, which generally provides a relatively active and functional control group[7].

This study expands the literature by examining patient reported outcomes between all-cause HRA revision and primary THA, and outcomes between HRA revision and revision THA. Our data supports non-MoM HRA in select patients.

CONCLUSION

HRA patients revised to THA have worse clinical outcomes compared to primary THA. The outcomes of patients who undergo THA for failed HRA outcome is dependent on the etiology of failure.