All authors have completed the Unified Competing Interest form at
Conceived and designed the experiments: SJ MR PG. Performed the experiments: SJ. Analyzed the data: SJ. Contributed reagents/materials/analysis tools: PB JM. Wrote the paper: SJ JM MR PB DD PG.
Hip replacement is one of the most commonly performed surgical procedures worldwide; hundreds of implant configurations provide options for femoral head size, joint surface material and fixation method with dramatically varying costs. Robust comparative evidence to inform the choice of implant is needed. This retrospective cohort study uses linked national databases from England and Wales to determine the optimal type of replacement for patients over 60 years undergoing hip replacement for osteoarthritis.
Implants included were the commonest brand from each of the four types of replacement (cemented, cementless, hybrid and resurfacing); the reference prosthesis was the cemented hip procedure. Patient reported outcome scores (PROMs), costs and risk of repeat (revision) surgery were examined. Multivariable analyses included analysis of covariance to assess improvement in PROMs (Oxford hip score, OHS, and EQ5D index) (9159 linked episodes) and competing risks modelling of implant survival (79,775 procedures). Cost of implants and ancillary equipment were obtained from National Health Service procurement data.
EQ5D score improvements (at 6 months) were similar for all hip replacement types. In females, revision risk was significantly higher in cementless hip prostheses (hazard ratio, HR = 2.22, p<0.001), when compared to the reference hip. Although improvement in OHS was statistically higher (22.1 versus 20.5, p<0.001) for cementless implants, this small difference is unlikely to be clinically important. In males, revision risk was significantly higher in cementless (HR = 1.95, p = 0.003) and resurfacing implants, HR = 3.46, p<0.001), with no differences in OHS. Material costs were lowest with the reference implant (cemented, range £1103 to £1524) and highest with cementless implants (£1928 to £4285).
Limitations include the design of the study, which is intrinsically vulnerable to omitted variables, a paucity of long-term implant survival data (reflecting the duration of data collection), the possibility of revision under-reporting, response bias within PROMs data, and issues associated with current outcome scoring systems, which may not accurately reflect level of improvement in some patients.
Cement fixation, using a polyethylene cup and a standard sized head offers good outcomes, with the lowest risks and at the lowest costs. The most commonly used cementless and resurfacing implants were associated with higher risk of revision and were more costly, while perceptions of improved function and longevity were unsupported.
Management of osteoarthritis (OA) of the hip is a significant global health burden. Hip replacement is an established and successful treatment of end-stage OA, with excellent quality of life improvement and cost-effectiveness [
Cemented hip replacements (which utilise a polymer known as ‘cement’ to secure the implant in place) with a metal-on-polyethylene (MoP) articulating (‘bearing’) surface account for one third of all hip replacements implanted in England and Wales since 2003. These devices show consistently good implant survival in long-term cohort studies and worldwide joint replacement registries [
Some patients with hip replacements will require a revision procedure to replace a failed or worn implant. The National Joint Registry (NJR) was established in 2003 to provide a record of hip replacements and any subsequent revisions performed in the pubic and private health systems in England and Wales. Patient Reported Outcomes Measures (PROMs) have been collected on hip replacement patients in the public system since 2008. Linkage of these national datasets allows the analysis of patient functional outcome following hip replacement and subsequent implant failure rates for specific implants. Taking the most commonly used cemented hip replacement as the reference implant for comparison, the objective of this study was to provide a summative evaluation of different implant types in order to determine the most cost-effective components for hip replacement, referencing patient reported outcomes and risk of implant revision. This study examines the eighty percent of all primary hip replacements that are performed in patients 60 years and over [
A retrospective cohort study design assessed prospectively collected patient-level PROMs and NJR data to compare outcomes and implant survival across different primary hip replacements, with supplementary material costs for specific implant combinations obtained through National Health Service (NHS) procurement.
The single most commonly used brands of each type of hip replacement performed in England and Wales were chosen for the analysis, in order to control for brand heterogeneity within each type (the NJR annual report provides adequate analysis of the entire breadth of replacements available–our intention was to specifically analyse component options within brands, which would be impossible across all brands). Individual analyses of the same data on each individual hip replacement type have already defined component options within brand that confer the lowest revision risk (i.e. the longest survival) [
Type | Brand combination | Manufacturer | Market share, by type (England & Wales) |
---|---|---|---|
Cemented | Exeter V40 stem | Stryker Orthopaedics, Mahwah, New Jersey, United States | 23% |
Contemporary polyethylene cup | |||
Any Exeter stem | |||
Flanged version of Contemporary cup | |||
28mm or 32mm femoral head (metal or ceramic |
|||
Small heads (<28mm) | |||
Hooded version of Contemporary cup | |||
Cementless | Corail stem | DePuy Ltd, Leeds, United Kingdom | 31% |
Pinnacle modular (shell and liner) cup | |||
Medium/large Corail stem (size 11 or greater) | |||
Pinnacle cup / polyethylene liner (metal or ceramic head |
|||
Small Corail stems (<size 11) | |||
Pinnacle metal and ceramic liners |
|||
Hybrid | Exeter V40 stem | Stryker Orthopaedics, Mahwah, New Jersey, United States | 33% |
Trident modular (shell and liner) cup | |||
Any Exeter stem | |||
Solid shell Trident cup | |||
Ceramic bearing or a XLPE liner (metal or ceramic head |
|||
Cluster hole Trident shell | |||
Conventional polyethylene liner | |||
Resurfacing | Birmingham Hip Resurfacing (BHR) | Smith & Nephew, Memphis, Tennessee, United States | 55% |
Components with head size of 48mm or greater | |||
Components with head size <48mm |
*grouped together as no significant benefit of options was identified, XLPE–highly cross-linked polyethylene
All primary hip replacements performed using the specified implants on patients over 60 years and submitted to the NJR between 1st April 2003 and 31st December 2010 were initially included. Subsequently, exclusion criteria were employed as follows: all procedures with an indication other than OA; procedures with missing implant or patient data; and rarely used implant options [
The national PROMs project uses validated measures of hip-specific (Oxford hip score [OHS]) [
For this analysis PROMs of interest were improvements between the pre- and post-operative scores (the ‘change scores’) and self-reported readmission and reoperation in the post-operative period. Change scores, being approximately normally distributed, are analytically preferable to post-operative scores [
Implants were compared based on previously stratified revision risk within prosthesis types. Therefore, eight groups were compared (four ‘optimal’ groups and four ‘sub-optimal’ groups) (
Univariable analysis was performed initially to identify variables potentially influencing each outcome, based on statistical rejection criteria of p>0.10; these variables were then included in the multivariable models (see supplementary material for complete statistical methods). Due to the large population sizes and the questionable merits of statistically adjusting for gender, we chose to analyse data on males and females separately.
Implant survival times for patients who had not undergone revision were censored on the 31st December 2010. Competing risks models were used to adjust for potential differences in mortality across the implant groups, where patient death prior to either revision or censoring was the competing risk [
Results of the survival analysis were presented as hazard ratios (HRs). Statistical models for the change scores were evaluated with the margins function in STATA in order to provide predicted values separately for each of the implant groups. P-values are provided as statistical tests of the differences between the reference implant and the seven others. Significance was taken as p<0.05. All values are provided with 95% confidence intervals (CIs): ratios greater than one indicate that risk is higher when compared with the reference category. All models were fitted using STATA 12 (StataCorp LP, Texas, USA). Further supplementary information is available in
Costs for specific implant combinations were provided by NHS Wales (all seven hospital Trusts) and NHS supply chain (buyers on behalf of 30 hospital Trusts within the English NHS). Highest and lowest prices paid for implants during 2012 are provided for each of the implant components. A mode cost was also produced at source and provided. These costs represent actual prices paid, after discounts. In addition, the NJR levy fee (£20, which is included in the amount paid for each implant) and Value Added Tax (VAT, at 20%) were added for the total costs. The costs presented in this study also include acetabular screws (for cementless cup fixation) when used, the commonest cement used for each implant type, femoral cement restrictors and all equipment required to mix and perform pressurised cementation. Although it is acknowledged that hip replacement with cementless implants may result in slightly shorter operative time, for the purposes of this analysis it is assumed that theatre utilisation and length of stay was similar for all types of replacement, and that differences in specific implant costs approximated to incremental costs.
The National Joint Registry (England and Wales) Research Committee approved this study. Explicit patient consent is taken at the time of data collection for both the NJR and PROMs. Further ethical approval was not required for this study. Patient records/information was anonymized and de-identified prior to receipt of data and analysis.
There were 79,775 procedures available for implant survival analysis within the NJR dataset. Significant baseline differences were seen in age, ASA grade, proportions of females and BMI for the type of implant received (
Cemented | Hybrid | Cementless | Resurfacing | Difference | |||||
---|---|---|---|---|---|---|---|---|---|
Optimal | Sub-opt. | Optimal | Sub-opt. | Optimal | Sub-opt. | Optimal | Sub-opt. | ||
Number (%) | 19815 (24.8) | 13673 (17.1) | 2388 (3.0) | 9768 (12.2) | 9867 (12.4) | 19726 (24.7) | 3317 (4.2) | 1221 (1.5) | |
Age, median years (range) | 74.8 (60 to 100) | 74.8 (60 to 97) | 67.6 (60 to 97) | 71.7 (60 to 103) | 72.2 (60 to 98) | 68.7 (60 to 106) | 63.8 (60 to 89) | 63.3 (60 to 88) | p<0.001 |
Female | 12788 (64.5) | 9163 (67.0) | 1238 (51.8) | 6142 (62.9) | 5303 (53.7) | 11559 (58.6) | 166 (5.0) | 872 (71.4) | p<0.001 |
ASA | |||||||||
1 | 2461 (12.4) | 1822 (13.3) | 508 (21.3) | 1336 (13.7) | 1219 (12.4) | 2921 (14.8) | 1343 (40.5) | 542 (44.4) | p<0.001 |
2 | 13835 (69.8) | 9496 (69.5) | 1637 (68.6) | 6888 (70.5) | 7186 (72.8) | 14280 (72.4) | 1833 (55.3) | 644 (52.7) | |
3+ | 3519 (17.8) | 2355 (17.2) | 243 (10.2) | 1544 (15.8) | 1462 (14.8) | 2525 (12.8) | 141 (4.3) | 35 (2.9) | |
BMI, mean kg/m2(sd, range) | 28.3 (5.0, 15 to 63) | 27.9 (5.0, 15 to 65) | 28.4 (5.1 16 to 56) | 28.1 (5.1, 15 to 61) | 28.4 (5.1, 15 to 64) | 28.5 (5.2, 15 to 64) | 27.8 (4.3, 18 to 64) | 27.3 (4.2, 18 to 40) | p = 0.015 |
ASA–American Society of Anesthesiologists, BMI–body mass index (data based on 34756 procedures [44%])
Statistical notes: one-way analysis of variance (ANOVA) used for parametric data, Kruskal-Wallis test for non parametric data, Chi squared test for proportions
Cemented | Hybrid | Cementless | Resurfacing | Difference | |||||
---|---|---|---|---|---|---|---|---|---|
Optimal | Sub-opt. | Optimal | Sub-opt. | Optimal | Sub-opt. | Optimal | Sub-opt. | ||
Number (%) | 2369 (25.9) | 1133 (12.4) | 300 (3.3) | 1168 (12.8) | 1582 (17.3) | 2485 (27.2) | 97 (1.1) | 15 (0.2) | |
Age, median years (range) | 74.0 (60 to 93) | 75.2 (60 to 94) | 68.1 (60 to 91) | 71.6 (60 to 93) | 72.0 (60 to 95) | 67.8 (60 to 96) | 64.2 (60 to 75) | 62.8 (60 to 67) | p<0.001 |
Female | 1463 (61.8) | 747 (65.9) | 164 (54.7) | 744 (63.7) | 776 (49.1) | 1425 (57.3) | 1 (1.0) | 13 (86.7) | p<0.001 |
ASA | |||||||||
1 | 213 (9.0) | 96 (8.5) | 53 (17.7) | 122 (10.5) | 162 (10.2) | 345 (13.9) | 35 (36.1) | 5 (33.3) | p<0.001 |
2 | 1709 (72.1) | 829 (73.2) | 217 (72.3) | 888 (76.0) | 1201 (75.9) | 1897 (76.3) | 59 (60.8) | 10 (66.6) | |
3+ | 447 (18.9) | 208 (18.4) | 30 (10.0) | 158 (13.5) | 219 (13.8) | 243 (9.8) | 3 (3.1) | 0 (0) | |
BMI, mean kg/m (sd, range) | 28.6 (5.0, 16 to 55) | 28.1 (4.7, 15 to 46) | 28.4 (4.6 17 to 44) | 28.2 (4.8, 17 to 43) | 28.5 (4.9, 16 to 56) | 28.6 (5.2, 15 to 50) | 28.0 (4.0, 20 to 38) | 27.8 (2.9, 23 to 32) | p = 0.679 |
PROMs–patient reported outcome measures, ASA–American Society of Anesthesiologists, BMI–body mass index (data based on 5843 procedures [64%])
Statistical notes: one-way analysis of variance (ANOVA) used for parametric data, Kruskal-Wallis test for non parametric data, Chi squared test for proportions
Cemented | Hybrid | Cementless | Resurfacing | p value | |||||
---|---|---|---|---|---|---|---|---|---|
Optimal | Sub-optimal | Optimal | Sub-optimal | Optimal | Sub-optimal | Optimal | Sub-optimal | ||
Females (n, %) | 1463 (27.4) | 747 (14.0) | 164 (3.1) | 744 (14.0) | 776 (14.6) | 1425 (26.7) | 1 (0.0) | 13 (0.2) | |
Pre-operative, mean (sd,range) | 17.4 (8.0, 0 to 44) | 16.8 (8.0, 0 to 42) | 19.7 (7.8, 4 to 37) | 18.3 (8.0, 1 to 38) | 17.3 (7.7, 1 to 43) | 18.5 (8.1, 0 to 44) | 13 | 25.9 (4.5,18 to 33) | <0.001 |
Post-operative, median (range) | 40 (4 to 48) | 38 (2 to 48) | 43 (13 to 48) | 42 (5 to 48) | 42 (6 to 48) | 42 (2 to 48) | 48 | 46 (21 to 48) | <0.001 |
Pre-operative, mean (sd, range) | 0.342 (0.313, -0.43 to 1) | 0.319 (0.325, -0.48 to 1) | 0.432 (0.301, -0.24 to 0.88) | 0.356 (0.323, -0.59 to 1) | 0.346 (0.317, -0.35 to 1) | 0.366 (0.318, -0.59 to 1) | 0.516 | 0.586 (0.192, 0.09 to 0.76) | 0.008 |
Post-operative, median (range) | 0.796 (-0.24 to 1) | 0.760 (-0.24 to 1) | 0.850 (-0.18 to 1) | 0.814 (-0.24 to 1) | 0.812 (-0.13 to 1) | 0.796 (-0.32 to 1) | 1 | 1 (0.52 to 1) | <0.001 |
208.8 (29.0, 183 to 358) | 209.5 (29.2, 183 to 358) | 209.5 (30.6, 184 to 360) | 209.4 (28.5, 183 to 364) | 207.2 (25.8, 185 to 357) | 208.3 (28.4, 183 to 360) | 193 | 258.8 (46.8, 192 to 316) | 0.323 | |
Males (n, %) | 906 (23.7) | 386 (10.1) | 136 (3.6) | 424 (11.1) | 806 (21.1) | 1060 (27.8) | 96 (2.5) | 2 (0.1) | |
Pre-operative, mean (sd,range) | 19.8 (7.9, 0 to 44) | 19.1 (8.1, 2 to 48) | 22.1 (7.9, 4 to 41) | 20.4 (8.5, 2 to 42) | 19.9 (8.0, 2 to 42) | 20.4 (8.3, 3 to 44) | 25.7 (8.2, 4 to 43) | 21.5 (0.7,21 to 22) | 0.001 |
Post-operative, median (range) | 43 (7 to 48) | 41 (12 to 48) | 44 (14 to 48) | 43 (11 to 48) | 43 (2 to 48) | 44 (1 to 48) | 45 (13 to 48) | 48 | <0.001 |
Pre-operative, mean (sd, range) | 0.425 (0.300, -0.32 to 1) | 0.439 (0.288, -0.48 to 0.88) | 0.439 (0.288, -0.07 to 0.80) | 0.422 (0.302, -0.35 to 1) | 0.418 (0.301, -0.35 to 1) | 0.425 (0.311, -0.35 to 1) | 0.551 (0.253, -0.18 to 81) | 0.516 | 0.016 |
Post-operative, median (range) | 0.814 (-0.18 to 1) | 0.814 (-0.18 to 1) | 0.883 (0.88 to 1) | 1 (-0.24 to 1) | 0.850 (-0.18 to 1) | 0.883 (-0.59 to 1) | 1 (-0.02 to 1) | 1 | <0.001 |
208.2 (28.5, 183 to 363) | 207.6 (27.2, 183 to 355) | 208.5 (27.1, 183 to 336) | 205.0 (22.3, 184 to 355) | 207.9 (28.7, 183 to 363) | 207.2 (27.5, 183 to 362) | 272.4 (44.3, 184 to 336) | 195.5 (3.5, 193 to 198) | 0.192 |
SD–standard deviation, PROMs–patient reported outcome measures
Statistical notes: one-way analysis of variance (ANOVA) used for parametric data, Kruskal-Wallis test for non parametric data, Chi squared test for proportions
In females OHS change was significantly higher (22.1 versus 20.5, p<0.001) in the optimal cementless group when compared with the reference implant. No other implant combination had a significantly better OHS improvement. There were no significant OHS improvement benefits across the implant types in males. No implant combination displayed an EQ5D index improvement significantly greater than the reference, in either sex (
Simple | Multivariable | |||||
---|---|---|---|---|---|---|
Value | 95% CI | P value | Value | 95% CI | P value | |
Optimal cemented (n = 1463) | 20.2 | 19.7 to 20.7 | Reference | 20.5 | 20.1 to 21.0 | Reference |
Sub-optimal cemented (n = 747) | 19.2 | 18.4 to 19.9 | 0.029 | 19.7 | 19.0 to 20.5 | 0.075 |
Optimal hybrid (n = 164) | 20.4 | 18.9 to 21.9 | 0.773 | 21.7 | 20.0 to 23.4 | 0.207 |
Sub-optimal hybrid (n = 744) | 20.7 | 20.0 to 21.4 | 0.227 | 20.9 | 20.1 to 21.6 | 0.463 |
Optimal cementless (n = 776) | 21.9 | 21.2 to 22.6 | <0.001 | 22.1 | 21.3 to 22.8 | <0.001 |
Sub-optimal cementless (n = 1425) | 20.7 | 20.2 to 21.2 | 0.169 | 21.0 | 20.4 to 21.5 | 0.270 |
Optimal cemented (n = 1463) | 0.421 | 0.402 to 0.439 | Reference | 0.426 | 0.414 to 0.439 | Reference |
Sub-optimal cemented (n = 747) | 0.429 | 0.403 to 0.454 | 0.619 | 0.418 | 0.398 to 0.439 | 0.502 |
Optimal hybrid (n = 164) | 0.373 | 0.320 to 0.427 | 0.103 | 0.452 | 0.404 to 0.499 | 0.312 |
Sub-optimal hybrid (n = 744) | 0.433 | 0.408 to 0.459 | 0.421 | 0.436 | 0.416 to 0.457 | 0.430 |
Optimal cementless (n = 776) | 0.446 | 0.421 to 0.471 | 0.100 | 0.447 | 0.427 to 0.467 | 0.086 |
Sub-optimal cementless (n = 1425) | 0.417 | 0.398 to 0.435 | 0.765 | 0.420 | 0.404 to 0.435 | 0.182 |
Optimal cemented (n = 906) | 20.1 | 19.5 to 20.7 | Reference | 20.3 | 19.7 to 20.9 | Reference |
Sub-optimal cemented (n = 386) | 20.4 | 19.5 to 21.4 | 0.553 | 19.9 | 18.9 to 20.9 | 0.521 |
Optimal hybrid (n = 136) | 20.0 | 18.3 to 21.6 | 0.882 | 18.9 | 17.2 to 20.6 | 0.140 |
Sub-optimal hybrid (n = 424) | 20.5 | 19.6 to 21.4 | 0.488 | 20.6 | 19.7 to 21.5 | 0.603 |
Optimal cementless (n = 806) | 20.7 | 20.0 to 21.3 | 0.222 | 20.6 | 19.9 to 21.3 | 0.521 |
Sub-optimal cementless (n = 1060) | 20.2 | 19.6 to 20.8 | 0.820 | 19.8 | 19.1 to 20.5 | 0.295 |
Optimal resurfacing (n = 96) | 17.1 | 15.2 to 19.0 | 0.004 | 19.1 | 17.2 to 21.1 | 0.282 |
Optimal cemented (n = 906) | 0.379 | 0.357 to 0.401 | Reference | 0.390 | 0.374 to 0.407 | Reference |
Sub-optimal cemented (n = 386) | 0.417 | 0.384 to 0.450 | 0.060 | 0.391 | 0.364 to 0.418 | 0.988 |
Optimal hybrid (n = 136) | 0.377 | 0.322 to 0.432 | 0.941 | 0.364 | 0.316 to 0.411 | 0.302 |
Sub-optimal hybrid (n = 424) | 0.419 | 0.387 to 0.450 | 0.044 | 0.415 | 0.389 to 0.441 | 0.121 |
Optimal cementless (n = 806) | 0.395 | 0.371 to 0.418 | 0.345 | 0.401 | 0.381 to 0.421 | 0.428 |
Sub-optimal cementless (n = 1060) | 0.390 | 0.370 to 0.410 | 0.482 | 0.358 | 0.340 to 0.377 | 0.011 |
Optimal resurfacing (n = 96) | 0.340 | 0.273 to 0.406 | 0.270 | 0.398 | 0.343 to 0.453 | 0.790 |
OHS–Oxford Hip Score, CI–confidence interval
Note: No predicted values are available for resurfacings in females (14 PROMs available only) and others resurfacing in males (2 PROMs only)
Simple | Multivariable | ||||||
---|---|---|---|---|---|---|---|
Number (%) | OR | 95% CI | P value | OR | 95% CI | P value | |
Optimal cemented (n = 1463) | 92 (6.3) | 1 | 1 | ||||
Sub-opt. cemented (n = 747) | 67 (8.9) | 1.47 | 1.06 to 2.04 | 0.022 | 1.67 | 1.11 to 2.51 | 0.013 |
Optimal hybrid (n = 164) | 8 (4.9) | 0.76 | 0.36 to 1.60 | 0.477 | 1.76 | 0.23 to 2.50 | 0.651 |
Sub-optimal hybrid (n = 744) | 47 (6.3) | 1.00 | 0.70 to 1.44 | 0.979 | 1.24 | 0.77 to 2.00 | 0.379 |
Optimal cementless (n = 776) | 56 (7.2) | 1.16 | 0.82 to 1.64 | 0.401 | 1.25 | 0.79 to 1.98 | 0.340 |
Sub-opt cementless (n = 1425) | 82 (5.8) | 0.91 | 0.67 to 1.24 | 0.547 | 1.18 | 0.78 to 1.78 | 0.423 |
Optimal cemented (n = 1463) | 29 (2.0) | 1 | 1 | ||||
Sub-opt. cemented (n = 747) | 20 (2.7) | 1.36 | 0.76 to 2.42 | 0.296 | 1.22 | 0.67 to 2.22 | 0.522 |
Optimal hybrid (n = 164) | 3 (1.8) | 0.92 | 0.28 to 3.06 | 0.894 | 0.99 | 0.29 to 3.31 | 0.982 |
Sub-optimal hybrid (n = 744) | 15 (2.0) | 1.02 | 0.54 to 1.91 | 0.957 | 0.95 | 0.50 to 1.82 | 0.879 |
Optimal cementless (n = 776) | 6 (0.8) | 0.39 | 0.16 to 0.93 | 0.034 | 0.46 | 0.16 to 1.35 | 0.156 |
Sub-opt cementless (n = 1425) | 27 (1.9) | 0.96 | 0.56 to 1.62 | 0.865 | 0.83 | 0.47 to 1.46 | 0.519 |
Optimal cemented (n = 906) | 88 (9.7) | 1 | 1 | ||||
Sub-opt. cemented (n = 386) | 32 (8.3) | 0.84 | 0.55 to 1.28 | 0.420 | 0.97 | 0.57 to 1.63 | 0.894 |
Optimal hybrid (n = 136) | 14 (4.5) | 1.07 | 0.59 to 1.93 | 0.832 | 0.74 | 0.29 to 1.93 | 0.542 |
Optimal cementless (n = 806) | 69 (8.6) | 0.87 | 0.63 to 1.21 | 0.410 | 0.82 | 0.53 to 1.27 | 0.381 |
Sub-opt cementless (n = 1060) | 68 (6.4) | 0.64 | 0.46 to 0.87 | 0.007 | 0.77 | 0.50 to 1.19 | 0.238 |
Optimal resurfacing (n = 96) | 4 (4.2) | 0.40 | 0.15 to 1.13 | 0.083 | 0.60 | 0.18 to 2.03 | 0.411 |
Optimal cemented (n = 906) | 21 (2.3) | 1 | 1 | ||||
Sub-opt. cemented (n = 386) | 6 (1.6) | 0.67 | 0.27 to 1.66 | 0.383 | 0.85 | 0.31 to 2.34 | 0.749 |
Optimal hybrid (n = 136) | 5 (3.7) | 1.61 | 0.59 to 4.34 | 0.348 | 1.34 | 0.37 to 4.83 | 0.658 |
Sub-optimal hybrid (n = 424) | 6 (1.4) | 0.60 | 0.24 to 1.51 | 0.281 | 0.55 | 0.18 to 1.68 | 0.297 |
Optimal cementless (n = 806) | 17 (2.1) | 0.91 | 0.48 to 1.73 | 0.770 | 0.47 | 0.18 to 1.21 | 0.116 |
Sub-opt cementless (n = 1060) | 18 (1.7) | 0.73 | 0.39 to 1.37 | 0.328 | 0.72 | 0.33 to 1.56 | 0.409 |
Optimal resurfacing (n = 96) | 1 (1.0) | 0.44 | 0.06 to 3.33 | 0.430 | 1 | - |
OR–odds ratio, CI–confidence interval
Note: No predicted values are available for resurfacings in females (14 PROMs available only) and others resurfacing in males (2 PROMs only)
When compared to the reference hip in females, the following had significantly higher revision risks: sub-optimal cemented (HR = 1.85, p<0.001), sub-optimal hybrid (HR = 1.68, p = 0.012), optimal cementless (HR = 2.22, p<0.001), sub-optimal cementless (HR = 3.60, p<0.001), and sub-optimal resurfacing (HR = 8.74, p<0.001). Optimal hybrid and optimal resurfacing had similar implant survival, but confidence intervals were wide for resurfacing (
Simple | Multivariable | |||||
---|---|---|---|---|---|---|
HR | 95% CI | P value | HR | 95% CI | P value | |
Optimal cemented (n = 12788) | 1 | 1 | ||||
Sub-optimal cemented (n = 9163) | 1.77 | 1.28 to 2.44 | 0.001 | 1.85 | 1.31 to 2.61 | <0.001 |
Optimal hybrid (n = 1238) | 1.30 | 0.60 to 2.85 | 0.507 | 1.26 | 0.56 to 2.81 | 0.578 |
Sub-optimal hybrid (n = 6142) | 1.73 | 1.19 to 2.52 | 0.004 | 1.68 | 1.12 to 2.52 | 0.012 |
Optimal cementless (n = 5303) | 2.15 | 1.47 to 3.14 | <0.001 | 2.22 | 1.48 to 3.34 | <0.001 |
Sub-optimal cementless (n = 11559) | 3.62 | 2.70 to 4.85 | <0.001 | 3.60 | 2.63 to 4.94 | <0.001 |
Optimal resurfacing (n = 166) | 1.98 | 0.49 to 8.07 | 0.339 | 2.31 | 0.57 to 9.41 | 0.244 |
Sub-optimal resurfacing (n = 872) | 7.66 | 5.21 to 11.3 | <0.001 | 8.74 | 5.81 to 13.2 | <0.001 |
Optimal cemented (n = 7027) | 1 | 1 | ||||
Sub-optimal cemented (n = 4510) | 2.03 | 1.36 to 3.04 | 0.001 | 2.09 | 1.37 to 3.18 | 0.001 |
Optimal hybrid (n = 1150) | 0.94 | 0.40 to 2.21 | 0.882 | 0.68 | 0.26 to 1.76 | 0.425 |
Sub-optimal hybrid (n = 3626) | 1.47 | 0.92 to 2.37 | 0.108 | 1.28 | 0.78 to 2.11 | 0.327 |
Optimal cementless (n = 4564) | 2.08 | 1.36 to 3.16 | 0.001 | 1.95 | 1.25 to 3.05 | 0.003 |
Sub-optimal cementless (n = 8167) | 2.79 | 1.95 to 3.98 | <0.001 | 2.53 | 1.74 to 3.68 | <0.001 |
Optimal resurfacing (n = 3151) | 3.30 | 2.23 to 4.88 | <0.001 | 3.46 | 2.28 to 5.26 | <0.001 |
Sub-optimal resurfacing (n = 349) | 6.13 | 3.37 to 11.2 | <0.001 | 6.21 | 3.36 to 11.5 | <0.001 |
HR–hazard ratio, CI–confidence interval
For males, all implants except hybrids had significantly higher revision risk: sub-optimal cemented (HR = 2.09, p = 0.001), optimal cementless (HR = 1.95, p = 0.003), sub-optimal cementless (HR = 2.53, p<0.001), optimal resurfacing (HR = 3.46, p<0.001) and sub-optimal resurfacing (HR = 6.21, p<0.001) (
The reference (cemented) replacement in this analysis was the cheapest (most commonly paid total price £1138). Resurfacing implants ranged in total cost from £2018 to £2991. A cementless 36mm CoC implant cost the NHS between £2500 and £4285 (
Implant description | Stem | Femoral head | Cup | Ancillary items | Cost, mode / range (£) | Total cost* (£) | |||||
---|---|---|---|---|---|---|---|---|---|---|---|
Description | Cost (£) | Description | Cost (£) | Description | Cost (£) | Description | Cost (£) | ||||
Most commonly used ‘optimal’ component set | Flanged cup / 28mm metal head | 44/size 1 | 397.90 to 547.40 | Stainless steel (Orthinox) V40 standard offset 28mm | 145.00 to 257.60 | Flanged cup | 138.40 to 227.50 | Heraeus Palacos R+Gentamycin antibiotic cement (4 mixes required) | 26.75 /mix | ||
Alternative ‘optimal’ | Flanged cup / 32mm ceramic head | 44/size 1 | 397.90 to 547.40 | Ceramic (Alumina) V40 standard offset 32mm | 415.00 to 588.00 | Flanged cup | 138.40 to 227.50 | DePuy Hardinge restrictor | 22.00 | ||
Most commonly used ‘sub-optimal’ | Hooded cup/26mm head | 44/ size 1 | 397.90 to 547.40 | Stainless steel (Orthinox) standard offset 26mm | 138.40 to 227.50 | Hooded cup | 138.40 to 227.50 | Biomet Optivac vacuum mixing and delivery system (2 required) | 44.29 /kit | ||
Most commonly used ‘optimal’ component set | Solid shell/ 36mm CoC | 44/ size 1 | 397.90 to 547.40 | Ceramic (Alumina) V40 standard offset 36mm | 415.00 to 588.00 | Ceramic 36mm liner plus PSL solid back shell | 415.00 to 717.50 plus 432.40 to 646.10 | Heraeus Palacos R+Gentamycin antibiotic cement (2 mixes required)DePuy Hardinge restrictorBiomet Optivac vacuum mixing and delivery system (1 required) | 26.75 /mix22.0044.29 | ||
Alternative ‘optimal’ | Solid shell/32mm MoXLP | 44/ size 1 | 397.90 to 547.40 | Cobalt-chrome (Vitallium) V40 standard offset 32mm | 145.00 to 271.60 | X3 XLPE 32mm 10 degree liner plus PSL solid back shell | 345.14 to 506.80 plus 432.40 to 646.10 | ||||
Most commonly used ‘sub-optimal’ | Multi-hole shell/28mm MoP | 44/ size 1 | 397.90 to 547.40 | Cobalt-chrome (Vitallium) V40 standard offset 28mm | 145.00 to 271.60 | Conventional Polyethylene 28mm liner plus PSL 5-hole | 230.09 to 375.20 plus 432.40 to 646.10 | As above, plus 2 Stryker acetabular screws | 40.00 to 51.10 | ||
Optimal | Head size ≥48mm | - | - | BHR head | 540.00 to 865.52 | BHR cup | 1050.00 to 1534.81 | Stryker Antibiotic Simplex cement (1 mix required) | 27.72 | ||
Sub-optimal | Head size <48mm | - | - | BHR head | 540.00 to 865.52 | BHR cup | 1050.00 to 1534.81 | ||||
Most commonly used ‘optimal’ component set | 28mm MoP | Size 11 KS | 642.85 to 1118 | Metal standard offset 28mm | 130.53 to 227.00 | Marathon 28mm PE neutral lip liner plus cluster-hole Duofix | 252.43 to 439.00 plus 510.03 to 887.00 | 1 DePuy acetabular screw included | 54.05 | ||
Commonly used ‘sub-optimal’ | 36mm MoM | Size 11 KS | 642.85 to 1118 | Ultamet standard offset 36mm | 249.55 to 434.00 | Metal liner plus Sector cluster-hole Duofix | 249.55 to 434.00 plus 510.03 to 887.00 | ||||
Commonly used ‘sub-optimal’ | 36mm CoC | Size 11 KS | 642.85 to 1118 | Ceramic 36mm standard offset | 431.25 to 750.00 | Ceramic liner plus Sector cluster-hole Duofix | 428.38 to 745.00 plus 510.03 to 887.00 |
CoC–ceramic-on-ceramic, MoXLP–metal-on-highly cross-linked polyethylene, MoP–metal-on polyethylene, MoM–metal-on-metal, PE–polyethylene.
Figures based on actual implant costs paid to manufacturers by NHS Wales (seven Trusts) and NHS Supply chain (30 Trusts in England). *Total cost is calculated using the mode cost plus NJR levy costs (£20) and Value Added Tax (20%). Note–very large Exeter stems (offset 44 sizes 4 and 5, and all 50 offset stems) increase cost by £614.27 (this represents less than 5% of all Exeter stems used) [
The reference implant (fully cemented, standard head size and conventional polyethylene cup) offered the lowest risk of implant failure at the lowest cost in patients over 60 years. No functional benefit of any implant was found in males relative to the reference implant; some differences for females were statistically significant but of unclear clinical importance. Readmission and reoperation rates were similar across all groups, suggesting there are no large variations in dislocation risk across implants. Notably higher costs and poorer implant survival was found when resurfacing and cementless implants were used. The findings of this summative evaluation of a range of hip replacements are contrary to current trends in surgery and may be useful for healthcare providers, surgeons and those commissioning hip replacement services.
As with all database analyses, the study design is observational and thus vulnerable to omitted variables. Implant choices in this cohort result from the interplay of patient, surgical and provider factors, and are not assigned randomly. Potentially important variables that were unavailable, such as radiological data, race, socioeconomic status, patient experiences, levels of perioperative pain and preoperative expectations, are known to influence outcome [
The numbers within comparison groups were adequate in order to identify meaningful differences in PROMs, despite limiting to specific brands (to reduce the confounding effect of implant heterogeneity) [
This analysis covers an entire nation of surgeons and surgical units providing hip replacement, and therefore provides strong external validity. However, NJR data validity has been questioned; data loss and under-reporting of revision numbers remains a concern (although this should affect comparison groups equally). PROMs data are currently recorded only once post-operatively, at around six months following surgery, which may be too early to determine success of a joint replacement. Nevertheless, the greatest improvement in OHS occurs in the first three months, with no improvements seen beyond 12 months; results from this current study are therefore a reliable indication of longer-term outcome [
Pennington et al recently published a cost effectiveness paper using NJR, PROMs and implant cost data to compare types of hip replacement [
Although hybrid implants have good implant survival in this current study, it must be stressed these results rely on rigid press-fit of the acetabular component into the bony socket without the need for supplementary screws to aid fixation. The use of multi-hole shells to allow supplementary screw fixation (as apposed to ‘solid’ shells, without holes) have a 37% higher risk of revision [
The fully cementless implant analysed here has a 1.9 to 3.6 times higher revision risk than the standard cemented implant. Although there was a higher OHS improvement (1.6 points) in females, this is below the clinical important threshold of 3 to 5 points suggested by the OHS designers [
This study demonstrates no benefit of a resurfacing procedure in patients over 60 years across any of the domains studied in this analysis. Given the high failure rates, the risks of local and systemic complications, and the long-term concerns surrounding these implants, including a medical device warning and mandatory annual follow-up, there appears to be no routine place for a resurfacing procedure in patients over 60 years [
Long-term observational studies of mortality after hip replacement suggest a higher risk of death when cement is used, but these fail to account for the confounding effect of true patient differences and provide no logical reason for the increased death rate many years after cementation [
In the past decade hip surgeons have been guilty of using implants with limited long-term evidence at great expense to the NHS and other healthcare providers (as a result of costs incurred initially and at revision surgery), and with significant adverse impact on patient outcomes [
The proliferation of hip replacement options has meant that any analysis aiming to determine ‘optimal’ hip replacement is inherently complex. However, the intention of this study was to provide a summative evaluation of a range of hip replacements for the patient over 60 years with hip OA. This type of evaluation is crucial to inform commissioning decisions by helping to answer the question 'what is the most cost-effective hip replacement?’ We believe the findings of this paper will appeal to commissioners, surgeons, healthcare management and the broader medical community striving to delivery high quality and cost effective healthcare.
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We thank the patients and staff of all the hospitals in England and Wales who have contributed data to the National Joint Registry. We are grateful to the Healthcare Quality Improvement Partnership (HQIP), the NJR steering committee and the staff at the NJR centre for facilitating this work.
We also thank Andrew Smallwood (NHS Wales) and Philip Lewis (NHS Supply chain) for their provision of, and help with, implant costs data.
This study was carried out in accordance with the STROBE checklist.