Comparison of Functional Results of Hip Resurfacing and Total Hip Replacement: A Review of the Literature

Total hip arthroplasty (THA) results in good outcomes in function and risk for revision in older patients. However, in young, active patients, it results in an increased rate of revision and poorer outcomes. Modern metal-on-metal hip resurfacing arthroplasty (HRA) is described as an appropriate treatment of hip osteoarthritis in young, active patients. The selection of an appropriate prosthesis is critical for this patient demographic. This review compares the functional results of THA and HRA and focuses on range of motion, activity level, groin pain, patient satisfaction, restoration of normal hip anatomy, and gait.

Total hip arthroplasty (THA) has long been considered the treatment of choice for osteoarthritis of the hip in older patients. This procedure results in consistently good outcomes in function and risk for revision in this patient demographic. However, the same procedure performed in young, active patients results in an increased rate of revision and less favorable outcome of those revision proceedures.

Modern metal-on-metal hip resurfacing arthroplasty (HRA), despite having a higher overall rate of revision and less evidence-based literature supporting its use in all demographics, is perceived by patients as being a safer, more effective treatment that results in a greater range of motion than THA. In the literature, HRA is often described as an appropriate treatment of hip osteoarthritis in young, active patients. In Australia, 50% of HRA is performed in patients who are less than 55 years of age.

The active lifestyle of younger patients places additional stresses on hip prostheses for a prolonged period of time that are not encountered in older patients. Furthermore, young active patients are less tolerant of compromised function and, therefore, selection of an appropriate prosthesis that provides good functionality and durability is critical in these patients. Data that compare the functional results of HRA and THA across different patient demographics and activity levels give surgeons the ability to make adequately informed, patient-based decisions regarding prosthesis selection.

We have examined the literature to prepare a review of published studies that compare the functional results of THA and HRA. Specific outcomes such as range of motion, activity level, groin pain, patient satisfaction, and restoration of normal hip anatomy and gait are addressed separately.

Methods

The authors systematically reviewed the literature on hip resurfacing outcomes using the PubMed bibliographic database. An initial search was performed to identify all articles that might be relevant to the review by collecting all entries with the keywords “hip resurfacing,” “resurfacing arthroplasty,” “hip resurfacing versus total hip” and “functional outcome hip resurfacing.” The initial keyword search yielded 713 articles. The abstracts of these articles were searched to determine whether they were suitable for inclusion in this review. In examining the references generated by this process, articles were selected that discussed the functional outcome of HRA compared with the functional outcome of conventional total hip replacement, with preference given to studies in which patients were matched for age, gender, and preoperative function. Of the 713 articles found using the keyword search, 46 articles were selected for further evaluation. No preference was given to articles in which a specific femoral head size was used for either HRA or conventional THA. Review articles and the bibliographies of each reference were also searched to find additional articles that appeared relevant.

Results

Range of Motion

Range of motion (ROM) is particularly important for younger patients who wish to return to a highly active lifestyle following joint replacement. Limited ROM may be a consequence of impingement, which may cause subluxation and hence high levels of wear and early failure.

In vitro studies including both cadaver and computer simulation studies consistently show that HRA results in reduced ROM when compared with conventional THA. Bengs and colleagues evaluated 3 contemporary hip resurfacing systems and compared 20 different movements (10 with zero femoral anteversion, and 10 with 20 degrees femoral anteversion) with those of 5 conventional hip replacement systems. Overall, the hip resurfacing systems resulted in less ROM than the conventional THA systems, with the conventional THA having significantly more ROM in 12 of the 20 movements tested. The summed mean arcs of motion in the sagittal, coronal, and axial planes for the HRA group were 135, 78, and 115 degrees, compared with 174, 87, and 150 degrees for the zero anteversion group, and 158, 90, and 147 degrees for the groups with 20 degrees of anteversion. These findings are consistent with those of Kluess and colleagues, who showed that ROM for 8 designs of hip resurfacing prosthesis tested in 3 different leg positions were on average 31 to 48 degrees less than for conventional hip replacements using a 32-mm head diameter. In both studies, neck-on-cup impingement was the cause of the observed reduction in ROM. Incavo and colleagues attempted to eliminate all patient-related variables by using a combination cadaver/computer simulation. The investigators found that, with controlled patient variables, THA was able to restore normal ROM more effectively than HRA. Surface replacement showed minor deficits in extension and significant reductions in flexion and internal rotation at 90° compared with the natural hip. The investigators concluded that decreased ROM for the HRA group was attributed to a smaller head-neck ratio or head-neck offset at points of impingement.

The translation of the results from these in vitro studies to the clinical situation is limited because they do not accurately mimic the complex nature of the in vivo implanted hip. Differences may be expected because of variation in hip anatomy and musculotendinous attachments, as well as subtle differences in surgical approach. Furthermore, fear of instability for hips treated with THA and the benefits of complete capsular release in HRA that overcomes preoperative soft tissue contracture may also cause discrepancies between the results of in vitro and in vivo studies.

Clinical studies report that the ROM for THA and HRA is similar or even better for HRA ( Table 1 ). Vail and colleagues, in a study of 52 patients (57 hips) with resurfacing and 84 patients (93 hips) with cementless THAs, found that, after controlling for age, gender, and preoperative differences, the resurfacing group had significantly higher ROM scores than did the cementless THA group after a mean follow-up of 3 years. However, Lavigne and colleagues, in a single-blind randomized study using digital photography of hip motion, failed to find a difference between patients assigned to the HRA group and the THA group at 1-year follow-up. In this study, patient demographics and preoperative ROM were similar. Le Duff and colleagues also found no difference in ROM between patients treated bilaterally, with an HRA on one side and a conventional THA in the contralateral limb to control patient variability. The investigators reported that the ROM for both implant types was consistent with the ROM seen in normal, undiseased hips. It is possible that, although THA can result in significantly greater ROM in the laboratory setting, this increased ROM is unable to be achieved in patients with normal to average flexibility, thereby resulting in a similar clinical ROM for THA and HRA.

Table 1

Ranges of motion reported in the literature for patients treated with HRA and conventional THA

Study	No. of Patients	Mean Follow-up (mo)	Type of Evaluation	HRA	THA	P Value
Lavigne et al, 2010	24 HRA 24 THA	12	Total arc of motion Arc of rotation Flexion-extension arc Abduction/adduction arc	204.2 47.7 118.1 43.1	196.5 44.3 120.1 42.9	>.05
Le Duff et al, 2009	35 HRA 35 THA	88	Abduction/adduction Angle Flexion arc Rotation arc	71 (45–85) 121 (80–140) 75 (30–115)	70 (50–95) 119 (70–140) 72 (30–110)	.6477 .4322 .5420
Vail et al, 2006	52 HRA 84 THA	24	ROM score	5.0	4.8	<.001

In summary, although the geometry of hip resurfacing components may limit their ROM in the laboratory setting, clinically patients may expect to achieve equivalent, if not better, ROM following HRA. If patients do experience a decreased ROM as a consequence of impingement, then subluxation and edge loading may occur, which can lead to a higher wear rate and early failure.

Activity Level

Many young patients, once relieved of their arthritic pain, may return to a physically active lifestyle after hip arthroplasty.

Most clinical studies report that patients return to high levels of activity after surgery. Six out of 7 studies that compare postoperative activity levels between HRA and THA report that patients have significantly increased activity levels when treated with HRA compared with THA. A summary of postoperative activity scores is presented in Table 2 . Vail and colleagues found significantly higher postoperative UCLA activity scores for patients in the HRA group compared with the THA group. Although the outcomes were controlled for age, gender, and preoperative clinical scores, there was variation in the demographic profile and preoperative hip score. Mont and colleagues, in a comparison of 54 consecutive HRAs and 54 consecutive THAs, found significantly higher postoperative activity levels in the HRA group (see Table 2 ). In the study by Mont and colleagues, the patients were matched according to demographics and preoperative Harris hip score; however, patients were not matched according to preoperative activity level. It was subsequently found that, before surgery, patients treated with HRA had a significantly higher weighted activity score, which, given that preoperative activity level has a positive influence on functional outcome, makes interpretation of these findings challenging. Pollard and colleagues, in a study comparing the outcome of hip resurfacing with THA in patients that were matched for age, gender, body mass index (BMI, calculated as weight in kilograms divided by the square of height in meters), and preoperative activity score, found higher University of California, Los Angeles (UCLA) activity scores in the resurfaced patients (see Table 2 ). Significantly more patients treated with HRA ran, participated in sport, or performed heavy manual labor than those treated with THA, a finding that is also reported by Vendittoli and colleagues and Pattyn and De Smet. These findings are further supported by Zywiel and colleagues, who evaluated patients that were matched in age, gender, BMI, and preoperative activity level. Pre- and postoperative activity levels were measured using a weighted activity questionnaire. At follow-up, the resurfacing patients had a significantly higher mean weighted activity score than those treated with THA (10.0 points, range 1.0–27.5 points, compared with 5.3 points, range 0–12.0 points).

Table 2

Functional outcome scores reported in the literature for patients treated with HRA and conventional THA

Study	No. of Patients	Mean Follow-up (mo)	WOMAC		OHS		HHS		UCLA/Activity Score
Study	No. of Patients	Mean Follow-up (mo)	Preop	Postop	Preop	Postop	Preop	Postop	Preop	Postop
Mont et al, 2009	54 HRA 54 THA	39 (24–60) 39 (24–56)	—	—	—	—	52 (33–71) 50 (32–73)	90 (50–100) 91 (62–100)	3 (0–15) ^a 2 (0–6) ^a	11.5 (0–32) ^a 7 (0–21) ^a
Killampalli et al, 2009	58 HRA 58 THA	5 y (4–7)	—	—	44.4 (31–57) 46.1 (16–60)	16.6 (12–31) 18.8 (12–45)	—	—	4.2 (1–8) 3.4 (1–7)	6.7 (3–10) 5.8 (3–10)
Hall et al, 2009	33 HRA 99 THA	6	—	—	38.1 (36.0–40.2) 41.7 (40.1–43.4)	18.6 (16.3–20.8) 21.5 (19.2–23.1)	—	—	—	—
Vendittoli et al, 2010	109 HRA 100 THA	2 y	52.7±15.4 54.4±18.3	5.7±8.6 9.0±11.9	—	—	—	—	—	7.5±1.8 7.1±1.6
Sandiford et al, 2010	141 HRA 141 THA	19.2 13.4	45.9 50.9 (3–96)	6.1 (0–56) 5 (0–39)	37 (13–57) 41.1 (16–75)	15 (12–35) 14.8 (12–33)	54.1 (7–97) 46.4 (7–87)	96.8 (59–100) 95.8 (65–100)	3 2	9 9
Lavigne et al, 2010	24 HRA 24 THA	12	46.5 (26–79) 54.3 (30–80)	3.0 (0–12) 2.7 (0–16)	—	—	—	—	—	8.0 (5–10) 8.3 (6–10)
Rahman et al, 2010	329 HRA	6.6 y (5–9.2)	47.9 (5–96)	6.9 (0–58)	38.3 (16–60)	15.9 (12–46)	51.3 (7–91)	94.3 (24–100)	4.7 (1–9)	7.5 (3–10)
Pollard et al, 2006	54 HRA 54 THA	61 (52–71) 80 (42–120)	—	—	—	15.9 (12–42) 18.5 (12–41)	—	—	9 (6–10) 8.9 (6–10)	8.4 (4–10) 6.8 (3–10)
Fowble et al, 2009	50 HRA 44 THA	38 (24–50) 30 (24–48)	—	—	—	—	46 (25–59) 52 (30–73)	97 (81–100) 96 (66–100)	4.2 (2–7) 3.6 (2–7)	8.2 (4–10) 5.9 (3–10)
Zywiel et al, 2009	33 HRA 33 THA	42 (25–68) 45 (24–67)	—	—	—	—	52 (28–71) 49 (20–69)	91 (32–100) 90 (50–100)	2.1 (0–6) ^a 2.3 (0–6) ^a	10 (1–27.5) ^a 5.3 (0–12) ^a