HIP
A prospective comparative study of cementless total hip arthroplasty and hip resurfacing in patients under the age of 55 years A TEN-YEAR FOLLOW-UP F. S. Haddad, S. Konan, J. Tahmassebi From University College London Hospitals, London, United Kingdom
The aim of this study was to evaluate the ten-year clinical and functional outcome of hip resurfacing and to compare it with that of cementless hip arthroplasty in patients under the age of 55 years. Between 1999 and 2002, 80 patients were enrolled into the study: 24 were randomised (11 to hip resurfacing, 13 to total hip arthroplasty), 18 refused hip resurfacing and chose cementless total hip arthroplasty with a 32 mm bearing, and 38 insisted on resurfacing. The mean follow-up for all patients was 12.1 years (10 to 14). Patients were assessed clinically and radiologically at one year, five years and ten years. Outcome measures included EuroQol EQ5D, Oxford, Harris hip, University of California Los Angeles and University College Hospital functional scores. No differences were seen between the two groups in the Oxford or Harris hip scores or in the quality of life scores. Despite a similar aspiration to activity pre-operatively, a higher proportion of patients with a hip resurfacing were running and involved in sport and heavy manual labour after ten years. We found significantly higher function scores in patients who had undergone hip resurfacing than in those with a cementless hip arthroplasty at ten years. This suggests a functional advantage for hip resurfacing. There were no other attendant problems. Cite this article: Bone Joint J 2015; 97-B:617–22.
F. S. Haddad, BSc MD (Res), FRCS (Tr&Orth), Professor of Orthopaedic Surgery University College London Hospitals, 235 Euston Road, London, NW1 2BU, UK. S. Konan, MBBS, MD(res), MRCS, FRCS(Tr&Orth), Speciality Trainee, Department of Orthopaedics J. Tahmassebi, BSc, Physiotherapy Extended Scope Practitioner, Trauma and Orthopaedics University College London, 250 Euston Road, London, NW1 2BU, UK. Correspondence should be sent to Professor F. S. Haddad; e-mail: [email protected] ©2015 The British Editorial Society of Bone & Joint Surgery doi:10.1302/0301-620X.97B5. 34537 $2.00 Bone Joint J 2015;97-B:617–22. Received 29 May 2014; Accepted after revision 4 December 2014
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Total hip arthroplasty (THA) reliably relieves pain and improves the function of patients with end-stage hip disease.1 Hip resurfacing has emerged as an alternative procedure for this condition. Its suggested advantages are less linear wear, preservation of bone stock, and an excursion distance, which translates into improved stability, and restoration of the native anatomy and biomechanics. The concerns with resurfacing have centred on technique-specific complications such as fracture and avascular necrosis, and adverse reactions to the metal ions that are generated. This has led to a dramatic reduction in the use of hip resurfacing and to the withdrawal of some implants.2-6 However, the Birmingham Hip Resurfacing (BHR, Smith & Nephew, Warwick, United Kingdom) remains in use, has ten-year follow-up results, and has not been associated with the level of failure noted with some other resurfacing systems.7-9 In the United Kingdom, the Orthopaedic Data Evaluation Panel (ODEP)10 ranks the BHR as 10A (ten-year follow-up data with acceptable evidence to support its use). The senior author (FSH) started performing hip resurfacing surgery in 1999. As the
long-term results had then yet to be established, a study was set up to compare the longterm outcomes of resurfacing with those of THA. Because of the high expectations of this patient population and the known ceiling effects of well-established outcome measures, we also looked at functional outcome in order to assess the difference in hip function between the two types of implant.11 We hypothesised that there was no difference between the long-term functional outcome of hip resurfacing and that of uncemented primary THA in patients > 55 years, and that the two procedures were comparable in terms of operating time, analgesia requirement and post-operative recovery.
Patients and Methods Between 1999 and 2002, 80 patients were enrolled in the study. Each patient was reviewed in the senior author’s clinic for endstage osteoarthritis (OA) and placed on the waiting list. We excluded patients with a high body mass index (> 40 kg/m2), an American Society of Anesthesiologists12 (ASA) grade of 3 and above, or inflammatory arthritis. 617
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Table I. Patient demographics
Actual implants Gender (male/female) Mean age (range) (yrs)
Group 1 (BHR)
Group 2 (THA)
33 BHR, 7 THA 30/10 47.8 (29 to 55)
24 THA, 16 BHR 29/11 48.2 (31 to 55)
BHR, Birmingham hip resurfacing; THA, total hip arthroplasty
Table II. Head sizes used for Birmingham hip resurfacing Head size
Numbers used
38 42 46 50 54 58
1 7 13 17 9 2
Patients were informed about resurfacing and cementless THA. They were also given the option to participate in a randomised controlled trial. Patients who were willing to participate in the study and attend follow-up were included once they had been through the process of informed consent (Table I). After completing this, 18 patients refused to undergo hip resurfacing and chose cementless THA and 38 insisted on resurfacing. These patients were also followed up and included in the study. Of the 80 patients, 24 consented to be randomised. Randomisation was undertaken using sealed envelopes which were opened on the day of surgery. A total of 11 patients (11 hips) were randomised to hip resurfacing and 13 patients (13 hips) to THA. The results were analysed based on intention to treat. A single fellowship-trained arthroplasty surgeon with established competence performed all procedures. Our institutional review board approved the study. Surgical procedure and implants. The BHR was used for all patients undergoing resurfacing. The head sizes used are summarised in Table II. A cementless, tapered hydroxyapatite (HA)-coated stem (Synergy, Smith & Nephew, Memphis, Tennessee) with a 32 mm cobalt–chrome (CoCr) head was used for cementless THA in conjunction with a hemispherical porous-coated cementless acetabular shell with a polyethylene liner (Reflection, Smith & Nephew, Memphis, Tennessee). Surgery was carried out through a posterior approach, with full capsular repair using transosseous sutures in every case. A single drain was used and was removed 24 hours later. All patients were given antibiotics (cefuroxime) on induction and eight and 16 hours post-operatively. They were also given low molecular weight heparin (enoxaparin, Aventis Pharma, Dagenham, United Kingdom) until discharge. Blood transfusion was needed in eight patients in the resurfacing group and six in the THA group. All patients were allowed to mobilise fully weight-bearing
post-operatively, and were assessed by a physiotherapist blinded to the procedure. Clinical and radiographic assessment. All patients were followed up clinically and radiologically (two orthogonal views of the hip) at one, five and ten years. Acetabular component abduction angles were measured using PACS (Agfa HealthCare UK, Brentford, United Kingdom) tools on plain anteroposterior (AP) radiographs and anteversion angles using cross-table radiographs.13 The mean follow-up in all 80 patients enrolled in this study was 12.1 years (10 to 14). At the ten-year follow-up, MRI and metal ions studies were obtained for all patients, except eight who declined to be investigated. Outcome measures. These included EuroQol EQ-5D,14 the Oxford hip score (OHS),15 Harris hip score (HHS),16 University of California Los Angeles (UCLA) activity score,17 postoperative functional measures (detailed below) and the University College London Hospital (UCLH) function score.11 Post-operative recovery. In order to assess the postoperative function of both groups of patients, the patient’s earliest ability to achieve the following tasks was documented by a physiotherapist blinded to the intervention performed: knee flexion > 45º; straight leg raise; active abduction; standing; independent mobilisation out of bed; independent transfer into bed; stair climbing; walking > 20 metres; independent showering, and discharge from hospital. Primary outcome measures. Functional, quality of life and hip-specific outcome scores at the ten-year follow-up visit were set as the primary outcome measures. Secondary outcome measures included operating time, immediate postoperative functional recovery, clinical outcome and radiological outcome. Statistical analysis. The differences in primary and secondary endpoints were analysed using the Mann–Whitney U test on an intention to treat basis. A p-value < 0.05 was used as a threshold for significance.
Results The two groups had comparable demographic features (Table I) and pre-operative scores (Table III). Intra-operative and immediate post-operative outcomes. The mean operating time (Fig. 1) was higher in the BHR group (69 minutes; 50 to 110) than in the THA group (60 minutes; 36 to 90). This difference was not statistically significant (p = 0.16). THE BONE & JOINT JOURNAL
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Table III. Comparison of the ten-year mean (standard deviation, (SD) outcome scores: Birmingham hip resurfacing (BHR) vs total hip arthroplasty (THA) THA
HHS WOMAC EQ5D UCLA OHS UCH F UCH D UCH P
BHR
Pre-op scores
SD
Post-op scores
SD
Post-op scores
SD
Post-op scores
SD
43.2 51.2 0.31 5 18.1 78.53 72.11 76.53
12.1 22 0.33 2 7 10.9 7.82 7.44
96 6.16 0.81 8 37.9 63 46.9 20.79
4.2 19.1 0.03 1 0.6 12.4 9.4 7.3
53.9 46.7 0.32 5 19.1 79.11 73.21 77.81
13.9 19.2 0.34 2 7.8 12.1 9.2 8.2
97.1 3.24 0.85 8.12 40.1 30.34 18 11.93
5.1 15 0.05 1 0.4 15.1 17.3 13.4
HHS, Harris Hip Score; WOMAC, Western Ontario and McMaster Universities Osteoarthritis Index; EQ-5D, EuroQol 5D; UCLA, University of California, Los Angeles; OHS, Oxford Hip score; UCH F, D, P, University College Hospital Function, Deformity, Pain
THA BHR
Straight leg raise
20 metre walk
0
20
40
60
80
100
120
THA
Time (mins) Fig. 1
BHR Stair climb
Box and whisker plots showing median comparison of operating time, Birmingham hip resurfacing (BHR) versus total hip arthroplasty (THA).
0
There were no immediate post-operative complications (infection, deep vein thrombosis, pulmonary embolism, nerve injury or fractures). There was one dislocation in the THA group, which was treated by closed reduction and a straight knee brace for six weeks, followed by routine physiotherapy. This patient’s subsequent recovery was unremarkable. The mean hospital stay was shorter in the BHR group (mean 4.3 days; 2 to 10) than in the THA group (mean 6 days; 3 to 10). This difference was not statistically significant (p = 0.21). Early post-operative functional outcome. In the immediate post-operative period, the BHR group were quicker to climb stairs and walk 20 metres but slower to achieve a straight leg raise (Fig. 2). Clinical assessment. Several patients showed a tendency to reduce their activity over the ten years of the study. At the ten-year follow-up, patients in the BHR group were more likely to be involved in higher-level activities than those who had undergone THA (Fig. 3). No failures or revisions occurred in this cohort. In particular, none of the BHR patients had metal ion-related complications. Radiological assessment. Radiological analysis of both cohorts of patients showed no evidence of change in VOL. 97-B, No. 5, MAY 2015
1
2
3
4
5
6
7
8
Number of days Fig. 2 Box and whisker plots showing comparison of early median functional parameters, Birmingham hip resurfacing (BHR) versus total hip arthroplasty (THA).
implant position or radiolucency. The THA group showed good osseointegration of stems with no signs of stem subsidence, and there was no osteolysis. In the BHR group, there was evidence of thinning of the femoral neck in six cases: this was not progressive, nor was impingement seen in any case. The mean abduction angle in the THA group was 47° (42 to 52) and 46° (41 to 51) in the BHR group. The mean anteversion angle was 21° (15 to 24) in the THA group and 20° (16 to 22) in the BHR group. Metal ions or MRI scans. Blood Co and Cr ion levels were available for 72 patients, 49 of whom had had THA and 23 BHR; eight patients refused the test. There were no significant differences between the two groups. Four patients (two with each type of prosthesis) had raised Co and Cr levels at five years, but these were below the 7 ppb threshold for concern.9 They remained static or reduced slightly between five and ten years after surgery. In addition, six
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120 THA
BHR
100
Operative time (mins)
THA
HHS
80 UCH F
60
UCH D
40 UCH F 20
UCH D WOMAC UCLA EQ5D 2 3 4 5 Number of scores
0
0
1
2
3
4
5
6
7
8
9
0
10
BHR
1
UCH P UCH P
6
7
8
UCLA scale Fig. 3
Fig. 4
Ten-year University of California Los Angeles (UCLA) scale comparing Birmingham hip resurfacing (BHR) with total hip arthroplasty (THA).
Graph showing the comparison of outcome scores between Birmingham hip resurfacing (BHR) and total hip arthroplasty (THA) (UCH F, D, P, University College Hospital Function, Deformity, Pain).
Table IV. Comparison of functional tasks at ten-year-follow up between Birmingham hip resurfacing (BHR) andtotal hip arthroplasty (THA) Group
Support for single leg stance (number of times)
Timed stair climb x 10 steps (s)
Lateral step-up balance assist (number of times)
THA BHR
4.4 0.6
8.47 4.19
0.8 0.3
patients (four BHR, two THA) had small non-progressive collections of trochanteric fluid. No adverse reactions to metal debris or pseudotumours were noted on any of the MRI scans in the 72 patients who had undergone testing for metal ions. No cross-sectional imaging was ordered in the remaining eight patients. Outcome measures. No significant differences in hip score were noted at one year or beyond between the two groups using conventional outcome measures. However, the UCH functional scale showed a difference in functional activity (Fig. 4) between the groups. There was no difference in quality of life scores at any stage. The ten-year results are summarised in Table III. Long-term functional differences between BHR and THA. In spite of similar aspirations to activity pre-operatively, a higher proportion of hip resurfacing patients were running and involved in sport and heavy manual work at long-term follow-up. At ten years, seven patients (19.4%) in the THA group were running compared with 26 patients (53.1%) in the BHR group (p = 0.1). With regard to involvement in any sport, 16 patients (51.6%) in the THA group were participating in the sport of their choice, compared with 49 (85.7%) in the BHR group (p = 0.09). A larger number of BHR patients (ten, 20.4%) were also involved in heavy or manual work than in the THA group (four, 12.9%; p = 0.19). We have found significantly better (p < 0.001) function scores using the UCH hip score (in the function, UCH F and difficulty, UCH D subgroups) in resurfacing patients than in THA patients (Table III).
At ten years, comparison of specific functional tasks (Table IV) showed that the BHR group had better single leg stance and hop, and better stair climbing endurance (anterior and lateral).
Discussion Although our primary aim was to conduct a randomised controlled trial comparing hip resurfacing and THA, this was only possible in 24 patients. The other 56 insisted on choosing the type of prosthesis before surgery and were included in the study. Activity measures in this small cohort of patients comparing THA and BHR suggest an advantage to hip resurfacing. In this group of patients we have not seen the dramatic problems reported elsewhere3,18 with hip resurfacing. Our data suggest that BHR is definitely not a ‘lesser’ operation than THA, as shown by the higher mean operating time and the time lag in achieving a straight leg raise in the BHR cohort. However, BHR patients recovered quickly, were discharged from hospital earlier and had better long-term function with a greater involvement in sports and heavy manual work. However, our patients were young (< 55 years), and this may account for the results we observed. There was no loss to follow-up. Our study suggests that function after BHR is probably better than that after cementless THA, but this is only seen with functional tasks and activity-specific measures, not in the conventional quality of life or hip outcome questionnaires. There has been recent concern over the use of metal-onmetal articulations and this has resulted in a decline in the THE BONE & JOINT JOURNAL
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Table V. Summary of studies comparing hip resurfacing (HR) and total hip arthroplasty (THA) n (hips) Author
HR
THA
Mean follow-up (range)
Outcome measures
Better outcome in HR
Mont Pollard24 Vail25
54 54 57
54 54 93
40 mths (24 to 60) 5 to 7 yrs min 2 yrs, mean 3 yrs
HHS, activity levels OHS, UCLA, EurQol HHS, function, pain scores
Fowble26 Lingard27 Zyweil28
50 132
44 214 33
HHS, UCLA, function, SF-12 WOMAC, SF-36 Activity scores, HHS, Patient satisfaction score, pain scores PAT-5D index, WOMAC, SF-36, and UCLA OHS, WOMAC HHS, activity score WOMAC
Higher activity scores Higher UCLA & EuroQol Higher activity scores and range of movement scores Higher function, UCLA, SF-12 Higher SF-36 & WOMAC pain Higher activity levels
HHS OHS, HHS, QoL, disability rating, physical activity level HHS, UCLA
23
Garbuz31 Sandiford32 Venditolli29
33 48 141 109
56 141 100
2 to 4 yrs 1 yr HR 42 mths (25 to 68) THA 45 mths (24 to 67) 1.1 yrs (0.8 to 2.2) HR 19.2 mths, THA 13.4 mths 56 mths (36 to 72)
Costa33 Costa34
73 60
137 66
min 2 yrs 12 mths
Issa30
120
120
42 mths (24 to 55)
No difference No difference Higher WOMAC functional at 1 and 2 years No difference No difference Higher UCLA
HHS, Harris Hip score; SF, short form; WOMAC, Western Ontario and McMaster Universities Osteoarthritis Index; UCLA, University of California Los Angeles; QoL, quality of life; OHS, Oxford Hip Score; PAT-5D: paper adaptive test
number of resurfacing arthroplasties undertaken.19 However, with appropriate selection of both patient and implant, and precise positioning of the implant, others have reported excellent long-term outcomes for hip resurfacing.20 The BHR has not failed for the same reasons as other metal-on-metal bearings,9,21 but as a result of wear and edge loading, which are technique-specific. This is in contrast to large head metal-on-metal hip arthroplasties, where corrosion and taper-related complications are welldocumented concerns.22 Summary of other studies. Table V summarises some of the studies that have compared hip resurfacing with THA. Most of these report the results of early follow-up. A functional or quality-of-life advantage was noted by several of these.23-30 Some studies, however,31-34 reported no difference between resurfacing and THA: two of these were randomised controlled trials.31,34 However, both of these studies looked at early follow-up and did not use physical activity-specific outcome measures. Garbuz et al31 randomised 107 patients deemed eligible for resurfacing arthroplasty to have either a resurfacing or a large head metal-on-metal THA. Of the 73 patients followed for at least one year, both groups reported an improvement in quality of life on all outcome measures using quality of life and activity scores. The authors cautioned against the use of large-head THAs due to the excessively high metal ion levels compared with the resurfacing group. Costa et al34 compared 60 hip resurfacings with 66 THAs. Intention-to-treat analysis showed no evidence for a difference in hip function (HHS) between the treatment groups at 12 months, but once again no activity-specific measures were used. The strengths of our study are the long-term follow-up (ten years) and no loss to follow-up. Only 24 patients were randomised, but this highlights the difficulty with clinical studies comparing resurfacing with arthroplasty. A single
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surgeon who is a fellowship-trained, high-volume hip surgeon performed all the procedures, and consequently these results may not be reproducible. We acknowledge that our study probably represents the ‘best-case scenario’, with a preponderance of young male patients with large femoral heads. We were also at a clinical ‘advantage’ by having chosen one of the better-performing hip resurfacing implants. We acknowledge that the use of hip resurfacing remains controversial with conflicting reports in the literature.20,35 However, based on our study, the functional advantage of the BHR is apparent, but the economic and quality-of-life sequelae of these results are more difficult to assess. Supplementary material An appendix explaining the five tasks tested by the University College London Hospitals Functional Outcome Assessment System is available alongside the online version of this article at www.bjj.boneandjoint.org.uk Author contributions: F. S. Haddad: Hypothesis generation, Data interpretation and presentation, manuscript preparation. S. Konan: Data Analysis, Manuscript preparation. J. Tahmassebi: Data collection. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. This article was primary edited by A. Ross and first proof edited by G. Scott.
References 1. Bellamy N, Buchanan WW, Goldsmith CH, Campbell J, Stitt LW. Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee. J Rheumatol 1988;15:1833–1840. 2. Kwon YM, Thomas P, Summer B, et al. Lymphocyte proliferation responses in patients with pseudotumors following metal-on-metal hip resurfacing arthroplasty. J Orthop Res 2010;28:444–450. 3. Pandit H, Glyn-Jones S, McLardy-Smith P, et al. Pseudotumours associated with metal-on-metal hip resurfacings. J Bone Joint Surg [Br] 2008;90-B:847–851.
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4. Kwon YM, Ostlere SJ, McLardy-Smith P, et al. "Asymptomatic" pseudotumors after metal-on-metal hip resurfacing arthroplasty: prevalence and metal ion study. J Arthroplasty 2011;26:511–518. 5. Malviya A, Holland JP. Pseudotumours associated with metal-on-metal hip resurfacing: 10-year Newcastle experience. Acta Orthop Belg 2009;75:477–483. 6. Anderson H, Toms AP, Cahir JG, et al. Grading the severity of soft tissue changes associated with metal-on-metal hip replacements: reliability of an MR grading system. Skeletal Radiol 2011;40:303–307. 7. Matharu GS, McBryde CW, Pynsent WB, Pynsent PB, Treacy RB. The outcome of the Birmingham Hip Resurfacing in patients aged < 50 years up to 14 years postoperatively. Bone Joint J 2013;95-B:1172–1177. 8. Treacy RB, McBryde CW, Shears E, Pynsent PB. Birmingham hip resurfacing: a minimum follow-up of ten years. J Bone Joint Surg [Br] 2011;93-B:27–33. 9. Haddad FS, Thakrar RR, Hart AJ, et al. Metal-on-metal bearings: the evidence so far. J Bone Joint Surg [Br] 2011;93-B:572–579. 10. No authors listed. Orthopaedic Data Evaluation Panel. http://www.odep.org.uk/ product.aspx?pid=149 (date last accessed 17 March 2015). 11. Konan S, Tahmassebi J, Haddad FS. The development and validation of a more discriminating functional hip score for research. HSS J 2012;8:198–205. 12. Saklad M. Grading of patients for surgical procedures. Anesthesiol 1941;2:281–284. 13. Woo RY, Morrey BF. Dislocations after total hip arthroplasty. J Bone Joint Surg [Am] 1982;64-A:1295–1306. 14. Brooks R. EuroQol: the current state of play. Health Policy 1996;37:53–72. 15. Dawson J, Fitzpatrick R, Carr A, Murray D. Questionnaire on the perceptions of patients about total hip replacement. J Bone Joint Surg [Br] 1996;78-B:185–190. 16. Harris WH. Traumatic arthritis of the hip after dislocation and acetabular fractures: treatment by mold arthroplasty: an end-result study using a new method of result evaluation. J Bone Joint Surg [Am] 1969;51-A:737–755. 17. Zahiri CA, Schmalzried TP, Szuszczewicz ES, Amstutz HC. Assessing activity in joint replacement patients. J Arthroplasty 1998;13:890–895. 18. Bisschop R, Boomsma MF, Van Raay JJ, et al. High prevalence of pseudotumors in patients with a Birmingham Hip Resurfacing prosthesis: a prospective cohort study of one hundred and twenty-nine patients. J Bone Joint Surg [Am] 2013;95-A:1554– 1560. 19. No authors listed. National Joint Registry 11th annual report. http://www.njrreports.org.uk/ (date last accessed 17 March 2015). 20. Daniel J, Pradhan C, Ziaee H, Pynsent PB, McMinn DJW. Results of Birmingham hip resurfacing at 12 to 15 years: a single-surgeon series. Bone Joint J 2014;96B:1298–1306. 21. Carrothers AD, Gilbert RE, Jaiswal A, Richardson JB. Birmingham hip resurfacing: the prevalence of failure. J Bone Joint Surg [Br] 2010;92:1344–1350.
22. Cooper HJ, Della Valle CJ. Large diameter femoral heads: is bigger always better? Bone Joint J 2014;96-B(11 Supple A):23–26. 23. Mont MA, Marker DR, Smith JM, Ulrich SD, McGrath MS. Resurfacing is comparable to total hip arthroplasty at short-term follow-up. Clin Orthop Relat Res 2009;467:66–71. 24. Pollard TC, Baker RP, Eastaugh-Waring SJ, Bannister GC. Treatment of the young active patient with osteoarthritis of the hip; a five- to seven-year comparison of hybrid total hip arthroplasty and metal-on-metal resurfacing. :J Bone Joint Surg [Br] 2006;88-B:592–600. 25. Vail TP, Mina CA, Yergler JD, Pietrobon R. Metal-on-metal hip resurfacing compares favorably with THA at 2 years follow up. Clin Orthop Relat Res 2006;453:123– 131. 26. Fowble VA, dela Rosa MA, Schmalzried TP. A comparison of total hip resurfacing and total hip arthroplasty - patients and outcomes. Bull NYU Hosp Jt Dis 2009;67:108–112. 27. Lingard EA, Muthumayandi K, Holland JP. Comparison of patient-reported outcomes between hip resurfacing and total hip replacement. J Bone Joint Surg [Br] 2009;91-B:1550–1554. 28. Zywiel MG, Marker DR, McGrath MS, Delanois RE, Mont MA. Resurfacing matched to standard total hip arthroplasty by preoperative activity levels - a comparison of postoperative outcomes. Bull NYU Hosp Jt Dis 2009;67:116–119. 29. Vendittoli PA, Ganapathi M, Roy AG, Lusignan D, Lavigne M. A comparison of clinical results of hip resurfacing arthroplasty and 28 mm metal on metal total hip arthroplasty: a randomised trial with 3-6 years follow-up. Hip Int 2010;20:1–13. 30. Issa K, Palich A, Tatevossian T, et al. The outcomes of hip resurfacing compared to standard primary total hip arthroplasty in Men. BMC Musculoskelet Disord 2013;14:161. 31. Garbuz DS, Tanzer M, Greidanus NV, Masri BA, Duncan CP. The John Charnley Award: metal-on-metal hip resurfacing versus large-diameter head metal-on-metal total hip arthroplasty: a randomized clinical trial. Clin Orthop Relat Res 2010;468:318– 325. 32. Sandiford NA, Muirhead-Allwood SK, Skinner JA, Hua J. Metal on metal hip resurfacing versus uncemented custom total hip replacement--early results. J Orthop Surg Res 2010;5:8. 33. Costa CR, Johnson AJ, Naziri Q, Mont MA. The outcomes of Cormet hip resurfacing compared to standard primary total hip arthroplasty. Bull NYU Hosp Jt Dis 2011;69(Suppl1):S12–S15. 34. Costa ML, Achten J, Parsons NR, et al. Total hip arthroplasty versus resurfacing arthroplasty in the treatment of patients with arthritis of the hip joint: single centre, parallel group, assessor blinded, randomised controlled trial. BMJ 2012;344:2147. 35. Dunbar MJ, Prasad V, Weerts B, Richardson G. Metal-on-metal hip surface replacement: the routine use is not justified. Bone Joint J 2014;96-B:17–21.
THE BONE & JOINT JOURNAL
A prospective comparative study of cementless total hip arthroplasty and hip resurfacing in patients under the age of 55 years A TEN-YEAR FOLLOW-UP F. S. Haddad, S. Konan, J. Tahmassebi From University College London Hospitals, London, United Kingdom
The aim of this study was to evaluate the ten-year clinical and functional outcome of hip resurfacing and to compare it with that of cementless hip arthroplasty in patients under the age of 55 years. Between 1999 and 2002, 80 patients were enrolled into the study: 24 were randomised (11 to hip resurfacing, 13 to total hip arthroplasty), 18 refused hip resurfacing and chose cementless total hip arthroplasty with a 32 mm bearing, and 38 insisted on resurfacing. The mean follow-up for all patients was 12.1 years (10 to 14). Patients were assessed clinically and radiologically at one year, five years and ten years. Outcome measures included EuroQol EQ5D, Oxford, Harris hip, University of California Los Angeles and University College Hospital functional scores. No differences were seen between the two groups in the Oxford or Harris hip scores or in the quality of life scores. Despite a similar aspiration to activity pre-operatively, a higher proportion of patients with a hip resurfacing were running and involved in sport and heavy manual labour after ten years. We found significantly higher function scores in patients who had undergone hip resurfacing than in those with a cementless hip arthroplasty at ten years. This suggests a functional advantage for hip resurfacing. There were no other attendant problems. Cite this article: Bone Joint J 2015; 97-B:617–22.
F. S. Haddad, BSc MD (Res), FRCS (Tr&Orth), Professor of Orthopaedic Surgery University College London Hospitals, 235 Euston Road, London, NW1 2BU, UK. S. Konan, MBBS, MD(res), MRCS, FRCS(Tr&Orth), Speciality Trainee, Department of Orthopaedics J. Tahmassebi, BSc, Physiotherapy Extended Scope Practitioner, Trauma and Orthopaedics University College London, 250 Euston Road, London, NW1 2BU, UK. Correspondence should be sent to Professor F. S. Haddad; e-mail: [email protected] ©2015 The British Editorial Society of Bone & Joint Surgery doi:10.1302/0301-620X.97B5. 34537 $2.00 Bone Joint J 2015;97-B:617–22. Received 29 May 2014; Accepted after revision 4 December 2014
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Total hip arthroplasty (THA) reliably relieves pain and improves the function of patients with end-stage hip disease.1 Hip resurfacing has emerged as an alternative procedure for this condition. Its suggested advantages are less linear wear, preservation of bone stock, and an excursion distance, which translates into improved stability, and restoration of the native anatomy and biomechanics. The concerns with resurfacing have centred on technique-specific complications such as fracture and avascular necrosis, and adverse reactions to the metal ions that are generated. This has led to a dramatic reduction in the use of hip resurfacing and to the withdrawal of some implants.2-6 However, the Birmingham Hip Resurfacing (BHR, Smith & Nephew, Warwick, United Kingdom) remains in use, has ten-year follow-up results, and has not been associated with the level of failure noted with some other resurfacing systems.7-9 In the United Kingdom, the Orthopaedic Data Evaluation Panel (ODEP)10 ranks the BHR as 10A (ten-year follow-up data with acceptable evidence to support its use). The senior author (FSH) started performing hip resurfacing surgery in 1999. As the
long-term results had then yet to be established, a study was set up to compare the longterm outcomes of resurfacing with those of THA. Because of the high expectations of this patient population and the known ceiling effects of well-established outcome measures, we also looked at functional outcome in order to assess the difference in hip function between the two types of implant.11 We hypothesised that there was no difference between the long-term functional outcome of hip resurfacing and that of uncemented primary THA in patients > 55 years, and that the two procedures were comparable in terms of operating time, analgesia requirement and post-operative recovery.
Patients and Methods Between 1999 and 2002, 80 patients were enrolled in the study. Each patient was reviewed in the senior author’s clinic for endstage osteoarthritis (OA) and placed on the waiting list. We excluded patients with a high body mass index (> 40 kg/m2), an American Society of Anesthesiologists12 (ASA) grade of 3 and above, or inflammatory arthritis. 617
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Table I. Patient demographics
Actual implants Gender (male/female) Mean age (range) (yrs)
Group 1 (BHR)
Group 2 (THA)
33 BHR, 7 THA 30/10 47.8 (29 to 55)
24 THA, 16 BHR 29/11 48.2 (31 to 55)
BHR, Birmingham hip resurfacing; THA, total hip arthroplasty
Table II. Head sizes used for Birmingham hip resurfacing Head size
Numbers used
38 42 46 50 54 58
1 7 13 17 9 2
Patients were informed about resurfacing and cementless THA. They were also given the option to participate in a randomised controlled trial. Patients who were willing to participate in the study and attend follow-up were included once they had been through the process of informed consent (Table I). After completing this, 18 patients refused to undergo hip resurfacing and chose cementless THA and 38 insisted on resurfacing. These patients were also followed up and included in the study. Of the 80 patients, 24 consented to be randomised. Randomisation was undertaken using sealed envelopes which were opened on the day of surgery. A total of 11 patients (11 hips) were randomised to hip resurfacing and 13 patients (13 hips) to THA. The results were analysed based on intention to treat. A single fellowship-trained arthroplasty surgeon with established competence performed all procedures. Our institutional review board approved the study. Surgical procedure and implants. The BHR was used for all patients undergoing resurfacing. The head sizes used are summarised in Table II. A cementless, tapered hydroxyapatite (HA)-coated stem (Synergy, Smith & Nephew, Memphis, Tennessee) with a 32 mm cobalt–chrome (CoCr) head was used for cementless THA in conjunction with a hemispherical porous-coated cementless acetabular shell with a polyethylene liner (Reflection, Smith & Nephew, Memphis, Tennessee). Surgery was carried out through a posterior approach, with full capsular repair using transosseous sutures in every case. A single drain was used and was removed 24 hours later. All patients were given antibiotics (cefuroxime) on induction and eight and 16 hours post-operatively. They were also given low molecular weight heparin (enoxaparin, Aventis Pharma, Dagenham, United Kingdom) until discharge. Blood transfusion was needed in eight patients in the resurfacing group and six in the THA group. All patients were allowed to mobilise fully weight-bearing
post-operatively, and were assessed by a physiotherapist blinded to the procedure. Clinical and radiographic assessment. All patients were followed up clinically and radiologically (two orthogonal views of the hip) at one, five and ten years. Acetabular component abduction angles were measured using PACS (Agfa HealthCare UK, Brentford, United Kingdom) tools on plain anteroposterior (AP) radiographs and anteversion angles using cross-table radiographs.13 The mean follow-up in all 80 patients enrolled in this study was 12.1 years (10 to 14). At the ten-year follow-up, MRI and metal ions studies were obtained for all patients, except eight who declined to be investigated. Outcome measures. These included EuroQol EQ-5D,14 the Oxford hip score (OHS),15 Harris hip score (HHS),16 University of California Los Angeles (UCLA) activity score,17 postoperative functional measures (detailed below) and the University College London Hospital (UCLH) function score.11 Post-operative recovery. In order to assess the postoperative function of both groups of patients, the patient’s earliest ability to achieve the following tasks was documented by a physiotherapist blinded to the intervention performed: knee flexion > 45º; straight leg raise; active abduction; standing; independent mobilisation out of bed; independent transfer into bed; stair climbing; walking > 20 metres; independent showering, and discharge from hospital. Primary outcome measures. Functional, quality of life and hip-specific outcome scores at the ten-year follow-up visit were set as the primary outcome measures. Secondary outcome measures included operating time, immediate postoperative functional recovery, clinical outcome and radiological outcome. Statistical analysis. The differences in primary and secondary endpoints were analysed using the Mann–Whitney U test on an intention to treat basis. A p-value < 0.05 was used as a threshold for significance.
Results The two groups had comparable demographic features (Table I) and pre-operative scores (Table III). Intra-operative and immediate post-operative outcomes. The mean operating time (Fig. 1) was higher in the BHR group (69 minutes; 50 to 110) than in the THA group (60 minutes; 36 to 90). This difference was not statistically significant (p = 0.16). THE BONE & JOINT JOURNAL
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Table III. Comparison of the ten-year mean (standard deviation, (SD) outcome scores: Birmingham hip resurfacing (BHR) vs total hip arthroplasty (THA) THA
HHS WOMAC EQ5D UCLA OHS UCH F UCH D UCH P
BHR
Pre-op scores
SD
Post-op scores
SD
Post-op scores
SD
Post-op scores
SD
43.2 51.2 0.31 5 18.1 78.53 72.11 76.53
12.1 22 0.33 2 7 10.9 7.82 7.44
96 6.16 0.81 8 37.9 63 46.9 20.79
4.2 19.1 0.03 1 0.6 12.4 9.4 7.3
53.9 46.7 0.32 5 19.1 79.11 73.21 77.81
13.9 19.2 0.34 2 7.8 12.1 9.2 8.2
97.1 3.24 0.85 8.12 40.1 30.34 18 11.93
5.1 15 0.05 1 0.4 15.1 17.3 13.4
HHS, Harris Hip Score; WOMAC, Western Ontario and McMaster Universities Osteoarthritis Index; EQ-5D, EuroQol 5D; UCLA, University of California, Los Angeles; OHS, Oxford Hip score; UCH F, D, P, University College Hospital Function, Deformity, Pain
THA BHR
Straight leg raise
20 metre walk
0
20
40
60
80
100
120
THA
Time (mins) Fig. 1
BHR Stair climb
Box and whisker plots showing median comparison of operating time, Birmingham hip resurfacing (BHR) versus total hip arthroplasty (THA).
0
There were no immediate post-operative complications (infection, deep vein thrombosis, pulmonary embolism, nerve injury or fractures). There was one dislocation in the THA group, which was treated by closed reduction and a straight knee brace for six weeks, followed by routine physiotherapy. This patient’s subsequent recovery was unremarkable. The mean hospital stay was shorter in the BHR group (mean 4.3 days; 2 to 10) than in the THA group (mean 6 days; 3 to 10). This difference was not statistically significant (p = 0.21). Early post-operative functional outcome. In the immediate post-operative period, the BHR group were quicker to climb stairs and walk 20 metres but slower to achieve a straight leg raise (Fig. 2). Clinical assessment. Several patients showed a tendency to reduce their activity over the ten years of the study. At the ten-year follow-up, patients in the BHR group were more likely to be involved in higher-level activities than those who had undergone THA (Fig. 3). No failures or revisions occurred in this cohort. In particular, none of the BHR patients had metal ion-related complications. Radiological assessment. Radiological analysis of both cohorts of patients showed no evidence of change in VOL. 97-B, No. 5, MAY 2015
1
2
3
4
5
6
7
8
Number of days Fig. 2 Box and whisker plots showing comparison of early median functional parameters, Birmingham hip resurfacing (BHR) versus total hip arthroplasty (THA).
implant position or radiolucency. The THA group showed good osseointegration of stems with no signs of stem subsidence, and there was no osteolysis. In the BHR group, there was evidence of thinning of the femoral neck in six cases: this was not progressive, nor was impingement seen in any case. The mean abduction angle in the THA group was 47° (42 to 52) and 46° (41 to 51) in the BHR group. The mean anteversion angle was 21° (15 to 24) in the THA group and 20° (16 to 22) in the BHR group. Metal ions or MRI scans. Blood Co and Cr ion levels were available for 72 patients, 49 of whom had had THA and 23 BHR; eight patients refused the test. There were no significant differences between the two groups. Four patients (two with each type of prosthesis) had raised Co and Cr levels at five years, but these were below the 7 ppb threshold for concern.9 They remained static or reduced slightly between five and ten years after surgery. In addition, six
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120 THA
BHR
100
Operative time (mins)
THA
HHS
80 UCH F
60
UCH D
40 UCH F 20
UCH D WOMAC UCLA EQ5D 2 3 4 5 Number of scores
0
0
1
2
3
4
5
6
7
8
9
0
10
BHR
1
UCH P UCH P
6
7
8
UCLA scale Fig. 3
Fig. 4
Ten-year University of California Los Angeles (UCLA) scale comparing Birmingham hip resurfacing (BHR) with total hip arthroplasty (THA).
Graph showing the comparison of outcome scores between Birmingham hip resurfacing (BHR) and total hip arthroplasty (THA) (UCH F, D, P, University College Hospital Function, Deformity, Pain).
Table IV. Comparison of functional tasks at ten-year-follow up between Birmingham hip resurfacing (BHR) andtotal hip arthroplasty (THA) Group
Support for single leg stance (number of times)
Timed stair climb x 10 steps (s)
Lateral step-up balance assist (number of times)
THA BHR
4.4 0.6
8.47 4.19
0.8 0.3
patients (four BHR, two THA) had small non-progressive collections of trochanteric fluid. No adverse reactions to metal debris or pseudotumours were noted on any of the MRI scans in the 72 patients who had undergone testing for metal ions. No cross-sectional imaging was ordered in the remaining eight patients. Outcome measures. No significant differences in hip score were noted at one year or beyond between the two groups using conventional outcome measures. However, the UCH functional scale showed a difference in functional activity (Fig. 4) between the groups. There was no difference in quality of life scores at any stage. The ten-year results are summarised in Table III. Long-term functional differences between BHR and THA. In spite of similar aspirations to activity pre-operatively, a higher proportion of hip resurfacing patients were running and involved in sport and heavy manual work at long-term follow-up. At ten years, seven patients (19.4%) in the THA group were running compared with 26 patients (53.1%) in the BHR group (p = 0.1). With regard to involvement in any sport, 16 patients (51.6%) in the THA group were participating in the sport of their choice, compared with 49 (85.7%) in the BHR group (p = 0.09). A larger number of BHR patients (ten, 20.4%) were also involved in heavy or manual work than in the THA group (four, 12.9%; p = 0.19). We have found significantly better (p < 0.001) function scores using the UCH hip score (in the function, UCH F and difficulty, UCH D subgroups) in resurfacing patients than in THA patients (Table III).
At ten years, comparison of specific functional tasks (Table IV) showed that the BHR group had better single leg stance and hop, and better stair climbing endurance (anterior and lateral).
Discussion Although our primary aim was to conduct a randomised controlled trial comparing hip resurfacing and THA, this was only possible in 24 patients. The other 56 insisted on choosing the type of prosthesis before surgery and were included in the study. Activity measures in this small cohort of patients comparing THA and BHR suggest an advantage to hip resurfacing. In this group of patients we have not seen the dramatic problems reported elsewhere3,18 with hip resurfacing. Our data suggest that BHR is definitely not a ‘lesser’ operation than THA, as shown by the higher mean operating time and the time lag in achieving a straight leg raise in the BHR cohort. However, BHR patients recovered quickly, were discharged from hospital earlier and had better long-term function with a greater involvement in sports and heavy manual work. However, our patients were young (< 55 years), and this may account for the results we observed. There was no loss to follow-up. Our study suggests that function after BHR is probably better than that after cementless THA, but this is only seen with functional tasks and activity-specific measures, not in the conventional quality of life or hip outcome questionnaires. There has been recent concern over the use of metal-onmetal articulations and this has resulted in a decline in the THE BONE & JOINT JOURNAL
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Table V. Summary of studies comparing hip resurfacing (HR) and total hip arthroplasty (THA) n (hips) Author
HR
THA
Mean follow-up (range)
Outcome measures
Better outcome in HR
Mont Pollard24 Vail25
54 54 57
54 54 93
40 mths (24 to 60) 5 to 7 yrs min 2 yrs, mean 3 yrs
HHS, activity levels OHS, UCLA, EurQol HHS, function, pain scores
Fowble26 Lingard27 Zyweil28
50 132
44 214 33
HHS, UCLA, function, SF-12 WOMAC, SF-36 Activity scores, HHS, Patient satisfaction score, pain scores PAT-5D index, WOMAC, SF-36, and UCLA OHS, WOMAC HHS, activity score WOMAC
Higher activity scores Higher UCLA & EuroQol Higher activity scores and range of movement scores Higher function, UCLA, SF-12 Higher SF-36 & WOMAC pain Higher activity levels
HHS OHS, HHS, QoL, disability rating, physical activity level HHS, UCLA
23
Garbuz31 Sandiford32 Venditolli29
33 48 141 109
56 141 100
2 to 4 yrs 1 yr HR 42 mths (25 to 68) THA 45 mths (24 to 67) 1.1 yrs (0.8 to 2.2) HR 19.2 mths, THA 13.4 mths 56 mths (36 to 72)
Costa33 Costa34
73 60
137 66
min 2 yrs 12 mths
Issa30
120
120
42 mths (24 to 55)
No difference No difference Higher WOMAC functional at 1 and 2 years No difference No difference Higher UCLA
HHS, Harris Hip score; SF, short form; WOMAC, Western Ontario and McMaster Universities Osteoarthritis Index; UCLA, University of California Los Angeles; QoL, quality of life; OHS, Oxford Hip Score; PAT-5D: paper adaptive test
number of resurfacing arthroplasties undertaken.19 However, with appropriate selection of both patient and implant, and precise positioning of the implant, others have reported excellent long-term outcomes for hip resurfacing.20 The BHR has not failed for the same reasons as other metal-on-metal bearings,9,21 but as a result of wear and edge loading, which are technique-specific. This is in contrast to large head metal-on-metal hip arthroplasties, where corrosion and taper-related complications are welldocumented concerns.22 Summary of other studies. Table V summarises some of the studies that have compared hip resurfacing with THA. Most of these report the results of early follow-up. A functional or quality-of-life advantage was noted by several of these.23-30 Some studies, however,31-34 reported no difference between resurfacing and THA: two of these were randomised controlled trials.31,34 However, both of these studies looked at early follow-up and did not use physical activity-specific outcome measures. Garbuz et al31 randomised 107 patients deemed eligible for resurfacing arthroplasty to have either a resurfacing or a large head metal-on-metal THA. Of the 73 patients followed for at least one year, both groups reported an improvement in quality of life on all outcome measures using quality of life and activity scores. The authors cautioned against the use of large-head THAs due to the excessively high metal ion levels compared with the resurfacing group. Costa et al34 compared 60 hip resurfacings with 66 THAs. Intention-to-treat analysis showed no evidence for a difference in hip function (HHS) between the treatment groups at 12 months, but once again no activity-specific measures were used. The strengths of our study are the long-term follow-up (ten years) and no loss to follow-up. Only 24 patients were randomised, but this highlights the difficulty with clinical studies comparing resurfacing with arthroplasty. A single
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surgeon who is a fellowship-trained, high-volume hip surgeon performed all the procedures, and consequently these results may not be reproducible. We acknowledge that our study probably represents the ‘best-case scenario’, with a preponderance of young male patients with large femoral heads. We were also at a clinical ‘advantage’ by having chosen one of the better-performing hip resurfacing implants. We acknowledge that the use of hip resurfacing remains controversial with conflicting reports in the literature.20,35 However, based on our study, the functional advantage of the BHR is apparent, but the economic and quality-of-life sequelae of these results are more difficult to assess. Supplementary material An appendix explaining the five tasks tested by the University College London Hospitals Functional Outcome Assessment System is available alongside the online version of this article at www.bjj.boneandjoint.org.uk Author contributions: F. S. Haddad: Hypothesis generation, Data interpretation and presentation, manuscript preparation. S. Konan: Data Analysis, Manuscript preparation. J. Tahmassebi: Data collection. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. This article was primary edited by A. Ross and first proof edited by G. Scott.
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4. Kwon YM, Ostlere SJ, McLardy-Smith P, et al. "Asymptomatic" pseudotumors after metal-on-metal hip resurfacing arthroplasty: prevalence and metal ion study. J Arthroplasty 2011;26:511–518. 5. Malviya A, Holland JP. Pseudotumours associated with metal-on-metal hip resurfacing: 10-year Newcastle experience. Acta Orthop Belg 2009;75:477–483. 6. Anderson H, Toms AP, Cahir JG, et al. Grading the severity of soft tissue changes associated with metal-on-metal hip replacements: reliability of an MR grading system. Skeletal Radiol 2011;40:303–307. 7. Matharu GS, McBryde CW, Pynsent WB, Pynsent PB, Treacy RB. The outcome of the Birmingham Hip Resurfacing in patients aged < 50 years up to 14 years postoperatively. Bone Joint J 2013;95-B:1172–1177. 8. Treacy RB, McBryde CW, Shears E, Pynsent PB. Birmingham hip resurfacing: a minimum follow-up of ten years. J Bone Joint Surg [Br] 2011;93-B:27–33. 9. Haddad FS, Thakrar RR, Hart AJ, et al. Metal-on-metal bearings: the evidence so far. J Bone Joint Surg [Br] 2011;93-B:572–579. 10. No authors listed. Orthopaedic Data Evaluation Panel. http://www.odep.org.uk/ product.aspx?pid=149 (date last accessed 17 March 2015). 11. Konan S, Tahmassebi J, Haddad FS. The development and validation of a more discriminating functional hip score for research. HSS J 2012;8:198–205. 12. Saklad M. Grading of patients for surgical procedures. Anesthesiol 1941;2:281–284. 13. Woo RY, Morrey BF. Dislocations after total hip arthroplasty. J Bone Joint Surg [Am] 1982;64-A:1295–1306. 14. Brooks R. EuroQol: the current state of play. Health Policy 1996;37:53–72. 15. Dawson J, Fitzpatrick R, Carr A, Murray D. Questionnaire on the perceptions of patients about total hip replacement. J Bone Joint Surg [Br] 1996;78-B:185–190. 16. Harris WH. Traumatic arthritis of the hip after dislocation and acetabular fractures: treatment by mold arthroplasty: an end-result study using a new method of result evaluation. J Bone Joint Surg [Am] 1969;51-A:737–755. 17. Zahiri CA, Schmalzried TP, Szuszczewicz ES, Amstutz HC. Assessing activity in joint replacement patients. J Arthroplasty 1998;13:890–895. 18. Bisschop R, Boomsma MF, Van Raay JJ, et al. High prevalence of pseudotumors in patients with a Birmingham Hip Resurfacing prosthesis: a prospective cohort study of one hundred and twenty-nine patients. J Bone Joint Surg [Am] 2013;95-A:1554– 1560. 19. No authors listed. National Joint Registry 11th annual report. http://www.njrreports.org.uk/ (date last accessed 17 March 2015). 20. Daniel J, Pradhan C, Ziaee H, Pynsent PB, McMinn DJW. Results of Birmingham hip resurfacing at 12 to 15 years: a single-surgeon series. Bone Joint J 2014;96B:1298–1306. 21. Carrothers AD, Gilbert RE, Jaiswal A, Richardson JB. Birmingham hip resurfacing: the prevalence of failure. J Bone Joint Surg [Br] 2010;92:1344–1350.
22. Cooper HJ, Della Valle CJ. Large diameter femoral heads: is bigger always better? Bone Joint J 2014;96-B(11 Supple A):23–26. 23. Mont MA, Marker DR, Smith JM, Ulrich SD, McGrath MS. Resurfacing is comparable to total hip arthroplasty at short-term follow-up. Clin Orthop Relat Res 2009;467:66–71. 24. Pollard TC, Baker RP, Eastaugh-Waring SJ, Bannister GC. Treatment of the young active patient with osteoarthritis of the hip; a five- to seven-year comparison of hybrid total hip arthroplasty and metal-on-metal resurfacing. :J Bone Joint Surg [Br] 2006;88-B:592–600. 25. Vail TP, Mina CA, Yergler JD, Pietrobon R. Metal-on-metal hip resurfacing compares favorably with THA at 2 years follow up. Clin Orthop Relat Res 2006;453:123– 131. 26. Fowble VA, dela Rosa MA, Schmalzried TP. A comparison of total hip resurfacing and total hip arthroplasty - patients and outcomes. Bull NYU Hosp Jt Dis 2009;67:108–112. 27. Lingard EA, Muthumayandi K, Holland JP. Comparison of patient-reported outcomes between hip resurfacing and total hip replacement. J Bone Joint Surg [Br] 2009;91-B:1550–1554. 28. Zywiel MG, Marker DR, McGrath MS, Delanois RE, Mont MA. Resurfacing matched to standard total hip arthroplasty by preoperative activity levels - a comparison of postoperative outcomes. Bull NYU Hosp Jt Dis 2009;67:116–119. 29. Vendittoli PA, Ganapathi M, Roy AG, Lusignan D, Lavigne M. A comparison of clinical results of hip resurfacing arthroplasty and 28 mm metal on metal total hip arthroplasty: a randomised trial with 3-6 years follow-up. Hip Int 2010;20:1–13. 30. Issa K, Palich A, Tatevossian T, et al. The outcomes of hip resurfacing compared to standard primary total hip arthroplasty in Men. BMC Musculoskelet Disord 2013;14:161. 31. Garbuz DS, Tanzer M, Greidanus NV, Masri BA, Duncan CP. The John Charnley Award: metal-on-metal hip resurfacing versus large-diameter head metal-on-metal total hip arthroplasty: a randomized clinical trial. Clin Orthop Relat Res 2010;468:318– 325. 32. Sandiford NA, Muirhead-Allwood SK, Skinner JA, Hua J. Metal on metal hip resurfacing versus uncemented custom total hip replacement--early results. J Orthop Surg Res 2010;5:8. 33. Costa CR, Johnson AJ, Naziri Q, Mont MA. The outcomes of Cormet hip resurfacing compared to standard primary total hip arthroplasty. Bull NYU Hosp Jt Dis 2011;69(Suppl1):S12–S15. 34. Costa ML, Achten J, Parsons NR, et al. Total hip arthroplasty versus resurfacing arthroplasty in the treatment of patients with arthritis of the hip joint: single centre, parallel group, assessor blinded, randomised controlled trial. BMJ 2012;344:2147. 35. Dunbar MJ, Prasad V, Weerts B, Richardson G. Metal-on-metal hip surface replacement: the routine use is not justified. Bone Joint J 2014;96-B:17–21.
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