A Matched Comparison of Implant and Functional Outcomes of Cemented and Cementless Unicompartmental Knee Replacements: A Study from the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man and the Hospital Episode Statistics Patient Reported Outcome Measures Database.

BACKGROUND: Unicompartmental knee replacement (UKR) is an effective treatment for end-stage medial compartment osteoarthritis, but there can be problems with fixation. The cementless UKR was introduced to address this issue. It is unknown how its functional outcomes compare with those of the cemented version on a national scale. We performed a matched comparison of the clinical and functional outcomes of cementless and cemented UKRs. METHODS: Using the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man (NJR), 14,764 Oxford UKRs with linked data regarding patient-reported outcomes were identified. A total of 6,906 UKRs (3,453 cemented and 3,453 cementless) were propensity score matched on the basis of patient, surgical, and implant factors. RESULTS: The 10-year cumulative implant survival rate was 93.0% (95% confidence interval [CI], 90.0% to 95.1%) for cementless UKRs and 91.3% (95% CI, 89.0% to 93.0%) for cemented UKRs. The cementless UKR group had a significantly lower revision risk (hazard ratio [HR], 0.74; p = 0.02). Subgroup analyses showed a stronger effect size (HR, 0.66) among UKRs performed by high-caseload surgeons (i.e., surgeons performing ≥30 UKRs/year). In the overall cohort, the postoperative Oxford Knee Score (OKS) in the cementless group (mean and standard deviation, 39.1 ± 8.7) was significantly higher (p = 0.001) than that in the cemented group (38.5 ± 8.6). The cementless group gained a mean of 17.6 ± 9.3 points in the OKS postoperatively and the cemented group gained 16.5 ± 9.6 points, with a difference of 1.1 points between the groups (p < 0.001). The difference in OKS points gained postoperatively was highest among UKRs performed by high-caseload surgeons, with the cementless group gaining 1.8 points more (p < 0.001) than the cemented group. CONCLUSIONS: The cementless UKR demonstrated better 10-year implant survival and postoperative functional outcomes than the cemented UKR. The difference was largest among UKRs performed by high-caseload surgeons, with the cementless fixation group having an HR for revision of 0.66 and an approximately 2-point greater improvement in the OKS compared with the cemented fixation group. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Early radiological outcomes of a fully porous bridging collar in lower-limb endoprosthetic reconstructions: a case-matched retrospective series to assess osseointegration.

BACKGROUND: Limb-salvage surgery involving the utilization of endoprosthetic replacements is commonly employed following segmental bone resection for primary and secondary bone tumors. This study aimed to evaluate whether a fully porous bridging collar promotes early osseous integration in endoprosthetic replacements. METHODS: We undertook a retrospective review of all lower-limb endoprostheses utilizing a fully porous endosteal bridging collar design. We matched this cohort with a conventional extra-osteal non-porous fully hydroxyapatite-coated grooved collar cohort according to surgical indication, implant type, resection length, age, and follow-up time. At 6, 12, and 24 months post-implantation, radiographs were assessed for the number of cortices with or without osseointegration on orthogonal radiographs. Each radiograph was scored on a scale of -4 to + 4 for the number of cortices bridging the ongrowth between the bone and the collar of the prosthesis. Implant survival was estimated using the Kaplan-Meier method, and the mean number of osseointegrated cortices at each time point between the collar designs was compared using a paired t-test. RESULTS: Ninety patients were retrospectively identified and analyzed. After exclusion, 40 patients with porous bridging collars matched with 40 patients with conventional extra-osteal non-porous collars were included in the study (n = 80). The mean age was 63.4 years (range 16-91 years); there were 37 males and 43 females. The groups showed no difference in implant survival (P = 0.54). The mean number of cortices with radiographic ongrowth for the porous bridging collar and non-porous collar groups was 2.1 and 0.3, respectively, at 6-month (P < 0.0001), 2.4 and 0.5, respectively, at 12-month (P = 0.044), and 3.2 and -0.2, respectively, at 24-month (P = 0.18) radiological follow-up. CONCLUSION: These findings indicate that fully porous bridging collars increased the number of cortices, with evidence of bone ongrowth between 6 and 24 months post-implantation. By contrast, extra-osteal collars exhibited reduced evidence of ongrowth between 6 and 24 months post-implantation. In the medium term, the use of a fully porous bridging collar may translate to a reduced incidence of aseptic loosening.

Polyethylene bearing wear is comparable for cemented and cementless Oxford unicompartmental knee replacements: Ten-year results of a randomized controlled trial.

PURPOSE: There is concern that using cementless components may increase polyethylene wear of the Oxford unicompartmental knee replacement (OUKR). Therefore, this study aimed to measure bearing wear at 10 years in patients from a randomized trial comparing Phase 3 cemented and cementless OUKRs and to investigate factors that may affect wear. It was hypothesized that there would be no difference in wear rate between cemented and cementless OUKRs. METHODS: Bearing thickness was determined using radiostereometric analysis at postoperative, 3-month, 6-month, 1-year, 2-year, 5-year and 10-year timepoints. As creep occurs early, wear rate was calculated using linear regression between 6 months and 10 years for 39 knees (20 cemented, 19 cementless). Associations between wear and implant, surgical and patient factors were analysed. RESULTS: The linear wear rate of the Phase 3 OUKR was 0.06 mm/year with no significant difference (p = 0.18) between cemented (0.054 mm/year) and cementless (0.063 mm/year) implants. Age, Oxford Knee Score, component size and bearing thickness had no correlation with wear. A body mass index ≥ 30 was associated with a significantly lower wear rate (p = 0.007) as was having ≥80% femoral component contact area on the bearing (p = 0.003). Bearings positioned ≥1.5 mm from the tibial wall had a significantly higher wear rate (p = 0.002). CONCLUSIONS: At 10 years, the Phase 3 OUKR linear wear rate is low and not associated with the fixation method. To minimize the risk of wear-related bearing fracture in the very long-term surgeons should consider using 4 mm bearings in very young active patients and ensure that components are appropriately positioned, which is facilitated by the current instrumentation. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

A Comparison of the Periprosthetic Fracture Rate of Cemented and Cementless Mobile Bearing Unicompartmental Knee Arthroplasties: An Analysis of Data From the National Joint Registry for England, Wales, Northern Ireland, and the Isle of Man.

BACKGROUND: Periprosthetic fractures are rare but serious complications of unicompartmental knee arthroplasty (UKA). Although cementless UKA has a lower risk of loosening than cemented, there are concerns that tibial fracture risk may be higher given the reliance on interference fit for primary stability. The risk of fracture and the effect of surgical fixation are currently unknown. We compared the periprosthetic fracture rate following cemented and cementless UKA surgery. METHODS: A total of 14,122 medial mobile-bearing UKAs (7,061 cemented and 7,061 cementless) from the National Joint Registry and Hospital Episodes Statistics database were propensity score-matched. Cumulative fracture rates were calculated and Cox regressions were used to compare fixation groups. RESULTS: The three-month periprosthetic fracture rates were similar (P = .80), being 0.10% in the cemented group and 0.11% in the cementless group. The fracture rates were highest during the first three months postoperatively, but then decreased and remained constant between one and 10 years after surgery. The one-year cumulative fracture rates were 0.2% (confidence interval [CI]: 0.1 to 0.3) for cemented and 0.2% (CI: 0.1 to 0.3) for cementless cases. The 10-year cumulative fracture rates were 0.8% (CI: 0.2 to 1.3) and 0.8% (CI: 0.3 to 1.3), respectively. The hazard ratio during the whole study period was 1.06 (CI: 0.64 to 1.77; P = .79). CONCLUSIONS: The periprosthetic fracture rate following mobile bearing UKA surgery is low, being about 1% at 10 years. There were no significant differences in fracture rates between cemented and cementless implants after matching. We surmise that surgeons are aware of the higher theoretical risk of early fracture with cementless components and take care with tibial preparation. LEVELS OF EVIDENCE: III.

A Comparison of the Periprosthetic Fracture Rate of Cemented and Cementless Total Knee Arthroplasties: An Analysis of Data From the National Joint Registry.

BACKGROUND: Periprosthetic fractures are serious complications of knee arthroplasty often requiring complex surgery. There is concern of increased periprosthetic fracture risk with cementless components given the reliance on interference fit for primary stability. It is unknown how the periprosthetic fracture risk compares between cemented and cementless total knee arthroplasties (TKAs). METHODS: A total of 22,477 cemented and 22,477 cementless TKAs from the National Joint Registry and Hospital Episodes Statistics database were propensity score matched on patient and surgical factors. Cumulative periprosthetic fracture rates were calculated using Kaplan-Meier analyses and compared with Cox regressions. Subgroup analyses were performed in different age, body mass index, and sex groups. RESULTS: The 3-month fracture rate in the cemented and cementless TKA groups were 0.02% and 0.04%, respectively. At 10 years, the cumulative fracture rate after cemented TKA was 1.2%, and after cementless was 1.4%. During the study period, there were no significant differences in fracture rates between cemented and cementless TKAs with a hazards ratio 1.14 (confidence interval 0.94 to 1.37, P = .20) at 10 years postoperatively. There were no significant differences in fracture rates between fixation types on subgroup analyses of sex, body mass index, and age groups. Female sex was a risk factor for fracture in both cemented (odds ratio 2.35, P < .001) and cementless TKAs (odds ratio 2.97, P < .001). CONCLUSIONS: The periprosthetic fracture rates following cemented and cementless TKA surgery are low being approximately 1.2% and 1.4%, respectively at 10 years. There were no significant differences in periprosthetic fracture rates requiring readmission between cemented and cementless TKAs. LEVEL OF EVIDENCE: III.

A Comparison of the Periprosthetic Fracture Rate of Unicompartmental and Total Knee Replacements: An Analysis of Data of >100,000 Knee Replacements from the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man and Hospital Episode Statistics.

BACKGROUND: Periprosthetic fractures are rare but devastating complications of knee replacement, often requiring complex surgery with substantial morbidity and mortality. It is not known how the fracture rates after total knee replacement (TKR) and unicompartmental knee replacement (UKR) compare. We performed the first matched study comparing TKR and UKR periprosthetic fracture rates. METHODS: This study involved 54,215 UKRs and 54,215 TKRs, identified in the National Joint Registry and Hospital Episodes Statistics database, which were propensity score-matched on patient and surgical factors. The International Classification of Diseases, Tenth Revision, (ICD-10) code M96.6 was used to identify periprosthetic fractures at ≤3 and >3 months postoperatively, as well as estimate rates at up to 10 years. Subgroup analyses were performed in different age groups (<55, 55 to 64, 65 to 74, and ≥75 years), body mass index (BMI) categories (normal, 18.5 to <25 kg/m 2 ; overweight, 25 to <30 kg/m 2 ; obese, 30 to <40 kg/m 2 ; and morbidly obese, ≥40 kg/m 2 ), and sexes. RESULTS: The 3-month fracture rate was 0.09% (n = 50) in the UKR group and 0.05% (n = 25) in the TKR group, with this difference being significant (odds ratio [OR], 2.0; p = 0.004). The rate of fractures occurring at >3 months was 0.32% (n = 171) in the UKR group and 0.61% (n = 329) in the TKR group (OR, 0.51; p < 0.001). At 10 years, the cumulative incidence of fractures was 0.6% after UKR versus 1% after TKR (OR, 0.68; p < 0.001). Fracture rates increased with increasing age, decreasing BMI, and female sex for both UKRs and TKRs. CONCLUSIONS: The fracture risk was small after both UKR and TKR, with small absolute differences between implant types. During the first 3 postoperative months, the fracture rate after UKR was 0.1% and was about twice as high as that after TKR. However, over the first 10 years, the cumulative fracture rate after TKR was 1% and was almost twice as high as that after UKR. Fracture rates after both UKR and TKR were higher in women, patients ≥75 years of age, and patients with normal weight. LEVEL OF EVIDENCE: Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

The Effect of Body Mass Index on the Relative Revision Rates of Cemented and Cementless Unicompartmental Knee Replacements: An Analysis of Over 10,000 Knee Replacements from National Databases.

BACKGROUND: Unicompartmental knee replacements (UKRs) are being performed in an increasingly overweight population. There are concerns that cemented fixation will not last. Cementless fixation may offer a solution, but the relative performance in different body mass index (BMI) groups remains unknown. METHODS: Ten thousand, four hundred and forty cemented and cementless UKRs were propensity matched. Patients were stratified into 4 BMI groups: underweight (<18.5 kg/m 2 ), normal weight (18.5 to <25 kg/m 2 ), overweight (25 to <30 kg/m 2 ), and obese (≥30 kg/m 2 ). The effect of BMI on the relative performance of UKR fixation groups was studied. Cox regression was used to compare revision and reoperation rates. RESULTS: The revision rate per 100 component-years significantly increased (p < 0.001) with BMI for the cemented UKRs. Revision rates per 100 component-years for the normal, overweight, and obese groups were 0.92 (95% confidence interval [CI], 0.91 to 0.93), 1.15 (95% CI, 1.14 to 1.16), and 1.31 (95% CI, 1.30 to 1.33), respectively. This was not observed for the cementless UKR, with revision rates of 1.09 (95% CI, 1.08 to 1.11), 0.70 (95% CI, 0.68 to 0.71), and 0.96 (95% CI, 0.95 to 0.97), respectively. The 10-year implant survival rates for the matched cemented and cementless UKRs in the normal, overweight, and obese groups were 93.8% (95% CI, 89.1% to 96.5%) and 94.3% (95% CI, 90.9% to 96.5%) (hazard ratio [HR], 1.17; p = 0.63), 88.5% (95% CI, 84.2% to 91.7%) and 93.8% (95% CI, 90.2% to 96.2%) (HR, 0.61; p = 0.005), and 90.7% (95% CI, 88.2% to 92.6%) and 91.8% (95% CI, 88.9% to 94.0%) (HR, 0.74; p = 0.02), respectively. There were insufficient numbers in the underweight group for analysis (n = 13). Obese patients had less than half the rates of aseptic loosening (0.46% vs. 1.31%; p = 0.001) and pain (0.60% vs. 1.20%; p = 0.02) in the cementless group as compared with the cemented group. CONCLUSIONS: Higher-BMI groups had higher revision rates for the cemented UKRs but not for the cementless UKRs. Cementless fixation was associated with reduced long-term revision rates compared with cement fixation in the overweight and obese groups. In the obese group, the rates of aseptic loosening and pain were at least 50% lower in the cementless UKR group. LEVEL OF EVIDENCE: Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

The Effect of Age on the Relative Outcomes of Cemented and Cementless Mobile-Bearing Unicompartmental Knee Arthroplasty, Based on Data From National Databases.

BACKGROUND: Unicompartmental knee arthroplasty (UKA) is an effective treatment for medial compartment arthritis. A challenge is that patients requiring knee arthroplasty are becoming younger. It is currently unknown what the relative performances of cemented and cementless UKAs are, in different age groups. METHODS: A total of 12,882 cemented and cementless UKAs from the National Joint Registry and Hospital Episodes Statistics databases were matched on patient and surgical factors. Patients were stratified into 3 groups: (1) <60 years; (2) 60-69 years; and (3) ≥70 years. Revision and reoperation rates were compared using Cox regression analyses. RESULTS: The 10-year implant survival for the matched cemented and cementless UKAs for (1) <60 years were 81.4% (CI 73.6-87.0) and 86.7% (CI 80.7-90.9) (hazard ratio [HR] 0.73, CI 0.56-0.94, P = .02); (2) for 60-69 years were 91.8% (CI 88.9-94.0) and 94.5% (CI 92.9-95.7) (HR 0.90, CI 0.67-1.22, P = .51); and (3) ≥70 years were 93.5% (CI 91.1-95.3) and 94.2% (CI 92.0-95.8) (HR 1.0, CI 0.71-1.40, P = .99). The same trend was observed for reoperations. In the <60 years and 60-69 years groups there were significantly fewer revisions for aseptic loosening in the cementless group (0.5% versus 1.6% [P < .001] and 0.4% versus 1.3% [P = .002], respectively). CONCLUSION: Younger ages were associated with higher revision rates in both cemented and cementless UKA groups. Cementless fixation has reduced long-term revision rates compared to cemented fixation in the <60 years group with aseptic loosening rates 3 times lower. LEVEL OF EVIDENCE: III.

The Influence of Surgeon Caseload and Usage on the Long-Term Outcomes of Mobile-Bearing Unicompartmental Knee Arthroplasty: An Analysis of Data From the National Joint Registry for England, Wales, Northern Ireland, and the Isle of Man.

BACKGROUND: Unicompartmental knee arthroplasty (UKA) revision rates are variable and known to be influenced by a surgeon's caseload (number of UKAs performed annually) and usage (UKA as a proportion of overall knee arthroplasty practice). It is not known which is more important. We explored the influence of caseload and usage on cemented and cementless UKA. METHODS: A total of 34,277 medial Oxford UKAs (23,707 cemented and 10,570 cementless) from the National Joint Registry were analyzed. UKAs were subdivided by the following: (1) surgeon caseload, into low (<10 UKAs/y) and high (≥10 UKAs/y) categories; and (2) usage, into low (<20%) and high (≥20%) categories. The 10-year revision rates were compared. RESULTS: The 10-year survival of the low-caseload/low-usage cemented and cementless UKA was 82.8% (CI 81.6-83.9) and 86.2% (CI 72.1-93.4), respectively. The 10-year survival of the high-caseload/high-usage cemented and cementless UKA was 90.0% (CI 89.2-90.6) and 93.3% (CI 91.3-94.8), respectively. For cemented UKA, the high-caseload/high-usage group had lower revision rates (hazard ratio [HR] 0.57, CI 0.52-0.63, P < .001) compared to the low-caseload/low-usage group. The high-caseload/low-usage (HR 0.74, CI 0.66-0.83, P < .001) and the low-caseload/high-usage (HR 0.86, CI 0.74-0.99, P = .04) groups also had lower revision rates than the low-caseload/low-usage group. CONCLUSION: Mobile-bearing UKA revision rates improve with both increasing surgeon UKA caseload and usage. Surgeons using cemented UKA who have usage ≥20% and caseload ≥10/year had a 10-year survival of 90%. Higher survivorship was associated with higher caseload, higher usage, and cementless fixation. LEVELS OF EVIDENCE: III.

How long does an elbow replacement last? A systematic review and meta-analysis of case-series and national registry reports with more than 10 years of follow-up.

BACKGROUND AND PURPOSE: This study aims to determine, for the first time, generalizable data on the longevity and long-term function of elbow replacements. METHODS: In this systematic review and meta-analysis, we searched MEDLINE and Embase for articles reporting 10-year or greater survival of total elbow replacements (TERs) and distal humeral hemiarthroplasty. Implant survival and patient reported outcome measures (PROMs) data were extracted. National joint replacement registries were also analyzed. We weighted each series and calculated a pooled survival estimate at 10, 15, and 20 years. For PROMs we pooled the standardized mean difference (SMD) at 10 years. FINDINGS: Despite its widespread use, we identified only 9 series reporting all-cause survival of 628 linked TERs and 610 unlinked TERs and no series for distal humeral hemiarthroplasty. The studied population was treated for rheumatoid arthritis in over 90% of cases. The estimated 10-year survival for linked TERs was 92% (95% CI 90-95) and unlinked TERs 84% (CI 81-88). 2 independent registries contributed 32 linked TERs and 530 unlinked TERs. The pooled registry 10-year survival for unlinked TERs was 86% (CI 83-89). Pooled 10-year PROMs from 164 TERs (33 linked and 131 unlinked), revealed a substantial improvement from baseline scores (SMD 2.7 [CI 1.6-3.8]). INTERPRETATION: Over 80% of all elbow replacements and over 90% of linked elbow replacements can last more than 10 years with sustained patient-reported benefits. This information is long overdue and will be particularly useful to patients as well as healthcare providers.

A matched comparison of cementless unicompartmental and total knee replacement outcomes based on the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man.

BACKGROUND AND PURPOSE: The main treatments for severe medial compartment knee arthritis are unicompartmental (UKR) and total knee replacement (TKR). UKRs have higher revision rates, particularly for aseptic loosening, therefore the cementless version was introduced. We compared the outcomes of matched cementless UKRs and TKRs. PATIENTS AND METHODS: The National Joint Registry was linked to the English Hospital Episode Statistics and Patient Reported Outcome Measures (PROMs) databases. 10,552 cementless UKRs and 10,552 TKRs were propensity matched and regression analysis used to compare revision/reoperation risks. 6-month PROMs were compared. UKR results were stratified by surgeon caseload into low- (< 10 UKRs/year), medium- (10 to < 30 UKRs/year), and high-volume (≥ 30 UKRs/year). RESULTS: 8-year cementless UKR revision survival for the 3 respective caseloads were 90% (95% CI 87-93), 93% (CI 91-95), and 96% (CI 94-97). 8-year reoperation survivals were 76% (CI 71-80), 81% (CI 78-85), and 84% (CI 82-86) respectively. For TKR the 8-year implant survivals for revision and reoperation were 96% (CI 95-97) and 81% (CI 80-83). The HRs for the 3 caseload groups compared with TKR for revision were 2.0 (CI 1.3-2.9), 2.0 (CI 1.6-2.7), and 1.0 (CI 0.8-1.3) and for reoperation were 1.2 (CI 1.0-1.4), 0.9 (CI 0.8-1.0), and 0.6 (CI 0.5-0.7). 6-month Oxford Knee Score (OKS) (39 vs. 37) and EQ-5D (0.80 vs. 0.77) were higher (p < 0.001) for the cementless UKR. INTERPRETATION: Cementless UKRs have higher revision and reoperation rates than TKR for low-volume UKR surgeons, similar reoperation but higher revision rates for mid-volume surgeons, and lower reoperation and similar revision rates for high-volume surgeons. Cementless UKR also had better PROMs.

A matched comparison of the patient-reported outcome measures of cemented and cementless total knee replacements, based on the National Joint Registry of England, Wales, Northern Ireland, and Isle of Man and England's National PROM collection programme.

Background and purpose - Total knee replacement (TKR) can be implanted with or without bone cement. It is currently unknown how the functional outcomes compare. Therefore, we compared the patient-reported outcome measures (PROMS) of both fixation methods. Patients and methods - We performed a propensitymatched comparison of 14,404 TKRs (7,202 cemented and 7,202 cementless) enrolled in the National Joint Registry and the English National PROMs collection programme. Subgroup analyses were performed in different age groups (1) < 55 years; (2) 55-64 years; (3) 65-74 years; (4) ≥ 75 years. Results - The 6-month postoperative Oxford Knee Score (OKS) was significantly (p < 0.001) higher for cemented TKR (35, SD 9.7) than cementless TKR (34, SD 9.9). The OKS was also significantly higher for the cemented TKR in all age groups, except the 55-64-year group. A significantly higher proportion of cemented TKRs had an excellent OKS (≥ 41) compared with cementless (32% vs. 28%, p < 0.001) and a lower proportion of poor (< 27) scores (19% vs. 22%, p = 0.001). This was also observed for all age subgroups. There were no significant differences in EQ-5D points gained postoperatively between the groups respectively (0.31 vs. 0.30, p = 0.1). Interpretation - Cemented TKRs had a greater proportion of excellent OKS scores and lower proportion of poor scores both overall and across all age groups. However, the absolute differences are small and below the minimally clinically important difference, making both fixation types acceptable. Currently the vast majority of TKRs are cemented and the results from this study suggest that this is appropriate.

A Matched Comparison of Long-Term Outcomes of Total and Unicompartmental Knee Replacements in Different Ages Based on National Databases: Analysis of Data From the National Joint Registry for England, Wales, Northern Ireland, and the Isle of Man.

BACKGROUND: The 2 main treatment options for end-stage single compartment knee arthritis are unicompartmental (UKR) or total knee replacement (TKR). We compared the long-term outcomes in different age groups. METHODS: In total, 54,215 UKRs and 54,215 TKRs from the National Joint Registry and Hospital Episode Statistics database were propensity score matched and Kaplan-Meier and regression analysis used to compare revision, reoperation, mortality, and 3-month complications. RESULTS: UKR had higher 10-year revision rates (12% vs 5%, hazard ratio [HR] 2.31, P < .001) and 10-year reoperation rates (25% vs 21%, HR 1.12, P < .001). UKR had lower 10-year mortality rates (13.6% vs 15.5%, HR 0.86, P < .001). UKR had lower rates of medical (P < .001) and procedure related (P < .001) complications and deaths (HR 0.61, P = .02). If 100 patients had a UKR instead of a TKR then over 10 years, if they were <55 years old there would be 7 more reoperations and 1 less death; if they were 55-64 years old there would be 6 more reoperations and 2 more deaths; if they were 65-74 years old there would be 4 more reoperations and 2 less deaths; and if they were ≥75 years old there would be 3 more reoperations and 4 less deaths. CONCLUSION: UKR has higher revision and slightly higher reoperation rates but lower mortality rates than matched TKR. The decision to do a UKR should, in part, be based on the balance of these risks, which are influenced by patient age. In the elderly group (>75 years) the data suggests that UKR compared to TKR has a greater absolute reduction in mortality than the increase in reoperation rate. LEVELS OF EVIDENCE: III.

A Matched Comparison of the Long-Term Outcomes of Cemented and Cementless Total Knee Replacements: An Analysis from the National Joint Registry of England, Wales, Northern Ireland and the Isle of Man.

BACKGROUND: Total knee replacements (TKRs) can be implanted with or without the use of cement. It is currently uncertain how cemented and cementless TKRs compare overall and in different age groups of the population in the long term. METHODS: The National Joint Registry collects information on knee replacements inserted in England, Wales, Northern Ireland, and the Isle of Man and was linked for multiple confounders to the National Health Service Hospital Episode Statistics database. With use of propensity score matching techniques, 44,954 cemented and cementless TKRs were compared. Regression models were used to compare the outcomes of revision, reoperation, and mortality both overall and in different age strata. RESULTS: The 10-year implant survival rate with revision as the end point for cemented and cementless TKRs was 96.0% and 95.5%, respectively (hazard ratio [HR] = 1.14; p = 0.01). The 10-year survival rate with reoperation as the end point was 82.7% and 81.4%, respectively (HR = 1.08; p = 0.001). The rate of revision for pain was higher for cementless TKRs (0.5% [cemented] compared with 0.7% [cementless]; p = 0.002), but the rate of revision for infection was lower (0.7% [cemented] compared with 0.5% [cementless]; p = 0.003). No significant interactions with age existed for the outcomes of revision (p = 0.24), reoperation (p = 0.30), or mortality (p = 0.58). CONCLUSIONS: We found that matched cemented and cementless TKRs both have 10-year implant survival rates of >95%. Cementless TKRs had a higher revision rate (absolute difference, 0.5%) and reoperation rate (absolute difference, 1.3%). The rate of revision for infection was lower in the cementless group, although the rate of revision for pain was higher. Age did not significantly affect the relative performances. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

A matched comparison of the patient-reported outcome measures of 38,716 total and unicompartmental knee replacements: an analysis of linked data from the National Joint Registry of England, Northern Ireland and Isle of Man and England's National PROM collection programme.

Background and purpose - The surgical treatment options for severe knee osteoarthritis are unicompartmental (UKR) and total knee replacement (TKR). For patients, functional outcomes are more important than revision rate. We compared the patient-reported outcome measures (PROMs) of both implant types using a large PROMs dataset.Patients and methods - We analysed a propensity-matched comparison of 38,716 knee replacements (19,358 UKRs and 19,358 TKRs) enrolled in the National Joint Registry and the English National PROM collection programme. Subgroup analyses were performed in different age groups.Results - 6-month postoperative Oxford Knee Score (OKS) for UKR and TKR were 38 (SD 9.4) and 36 (SD 9.4) respectively. A higher proportion of UKRs had an excellent OKS (≥ 41) compared with TKR (47% vs 36%) and a lower proportion of poor OKS (< 27) scores (13% vs. 16%). The 6-month OKS was higher in all age groups for UKR compared with TKR, with the difference increasing in older age groups. The mean 6-month EQ-5D score was 0.78 (SD 0.25) and 0.75 (SD 0.25) respectively. The improvement in EQ-5D resulting from surgery was higher for UKR than TKR both overall and in all age groups. All comparisons were statistically significant (p < 0.05).Interpretation - UKR had a greater proportion of excellent OKS scores and lower proportion of poor scores than TKR. Additionally, the quality of life was higher for UKR compared with TKR. These factors should be balanced against the higher revision rate for UKR when choosing which procedure to perform.

Low polyethylene creep and wear following mobile-bearing unicompartmental knee replacement.

PURPOSE: The Oxford unicompartmental knee replacement (UKR) has a fully congruent mobile bearing to minimise wear. However, with younger higher demand patients, wear remains a concern. The aim of this study was to quantify the wear rate of Phase 3 Oxford UKR bearings over the course of 5 years and to identify the factors that influence it. METHODS: 40 medial Oxford UKRs recruited for a randomised study of cemented and cementless fixation were studied with Radiostereometric analysis (RSA) at 1 week, 3 months, 6 months, 1 year, 2 years, and 5 years post-operatively and bearing thickness was calculated. Penetration, defined as the change in thickness compared to the 1-week measurement, was determined. Creep (early penetration) and wear (late penetration at a constant rate) were calculated. The influence of demographic factors, Oxford Knee Score (OKS), Tegner score, fixation and bearing overhang (determined by RSA) on wear was analysed. RESULTS: After 6 months the penetration rate was constant, indicating that wear alone was occurring. The wear rate was 0.07 mm/year (SD 0.03). The creep was 0.06 mm with about 95% occurring during the first 3 months. There was no significant relationship between fixation (cemented/cementless), age, component size, OKS and Tegner score with wear rate. Increasing BMI was associated with decreasing wear (p = 0.042). 37/40 bearings overhung the tibia to some extent and 23/40 overhung the tibia medially. An increase in the area of overhang (p = 0.036), amount of medial overhang (p = 0.028) and distance between the bearing and tibial wall (p = 0.019) were associated with increased wear. Bearings that did not overhang (0.06 mm/year) had less wear (p = 0.025) than those that did (0.08 mm/year). There was no relationship (p = 0.6) between the femoral contact area and wear. CONCLUSION: During the first three to six months after implantation, the bearing becomes 0.06 mm thinner due to creep. The combined wear rate of the upper and lower surfaces of the bearing is constant (0.07 mm/year). The wear is lower if the bearing does not overhang the tibia so surgeons should aim for the bearing to be close to the tibial wall. The orientation of the femoral component does not influence wear. LEVEL OF EVIDENCE: Retrospective Study, Level III.

Cementless unicompartmental knee replacement achieves better ten-year clinical outcomes than cemented: a systematic review.

PURPOSE: The aim of this study was to report and compare the long-term revision rate, revision indications and patient reported outcome measures of cemented and cementless unicompartmental knee replacements (UKR). METHODS: Databases Medline, Embase and Cochrane Central of Controlled Trials were searched to identify all UKR studies reporting the ≥ 10 year clinical outcomes. Revision rates per 100 component years [% per annum (% pa)] were calculated by fixation type and then, subgroup analyses for fixed and mobile bearing UKRs were performed. Mechanisms of failure and patient reported outcome measures are reported. RESULTS: 25 studies were eligible for inclusion with a total of 10,736 UKRs, in which there were 8790 cemented and 1946 cementless knee replacements. The revision rate was 0.73% pa (CI 0.66-0.80) and 0.45% pa (CI 0.34-0.58) per 100 component years, respectively, with the cementless having a significantly (p < 0.001) lower overall revision rate. Therefore, based on these studies, the expected 10-year survival of cementless UKR would be 95.5% and cemented 92.7%. Subgroup analysis revealed this difference remained significant for the Oxford UKR (0.37% pa vs 0.77% pa, p < 0.001), but for non-Oxford UKRs there were no significant differences in revision rates of cemented and cementless UKRs (0.57% pa vs 0.69% pa, p = 0.41). Mobile bearing UKRs had significantly lower revision rates than fixed bearing UKRs in cementless (p = 0.001), but not cemented groups (p = 0.13). Overall the revision rates for aseptic loosening and disease progression were significantly lower (p = 0.02 and p = 0.009 respectively) in the cementless group compared to the cemented group (0.06 vs 0.13% pa and 0.10 vs 0.21% pa respectively). CONCLUSIONS: Cementless fixation had reduced long-term revision rates compared to cemented for the Oxford UKR. For the non-Oxford UKRs, the revision rates of cementless and cemented fixation types were equivalent. Therefore, cementless UKRs offer at least equivalent if not lower revision rates compared to cemented UKRs. LEVEL OF EVIDENCE: III.

The Mid- to Long-Term Outcomes of the Lateral Domed Oxford Unicompartmental Knee Replacement: An Analysis From the National Joint Registry for England, Wales, Northern Ireland, and the Isle of Man.

BACKGROUND: Lateral unicompartmental knee replacement (UKR) is an alternative to total knee replacement for isolated lateral unicompartmental knee arthritis. The geometry and mechanics of the lateral compartment differ to the medial compartment with the Lateral Domed Oxford UKR designed to address this. We used the National Joint Registry (NJR) data to report the mid- to long-term outcomes of this device. METHODS: We performed a retrospective observational study using NJR data on 992 Lateral Domed Oxford UKRs implanted between 1st January 2005 and 31st December 2017. Outcomes of interest were implant survival and revision indications. RESULTS: The 10 year cumulative implant survival rates were 88.6% (CI 85.3-91.2). When compared with <55 year age group, the 55-64, 65-74 and ≥75 groups had significantly lower revision rates (hazard ratio (HR) = 0.56 (CI 0.32-0.98, P = .04), HR 0.40 (CI 0.22-0.72, P = .003), and HR 0.27 (CI 0.12-0.58, P = .001), respectively). The obese group had significantly (P = .04) increased revision risk compared with normal BMI (HR 2.33, CI 1.06-5.12). The commonest reasons for revision surgery were dislocation (n = 23, 2.3%), pain (n = 15, 1.5%), and aseptic loosening (n = 14, 1.4%). CONCLUSION: The Lateral Domed Oxford UKR provides a good option for isolated lateral compartment osteoarthritis. However, dislocation of the mobile bearing remains a problem, occurring in 2.3% of the patients and accounting for 30% of the revisions. To help prevent dislocation, it is now possible to assess bearing stability intraoperatively and if very unstable to implant a compatible fixed bearing tibial component, without the need for further bone preparation.

Oxford domed lateral unicompartmental knee arthroplasty.

AIMS: To report mid- to long-term results of Oxford mobile bearing domed lateral unicompartmental knee arthroplasty (UKA), and determine the effect of potential contraindications on outcome. METHODS: A total of 325 consecutive domed lateral UKAs undertaken for the recommended indications were included, and their functional and survival outcomes were assessed. The effects of age, weight, activity, and the presence of full-thickness erosions of cartilage in the patellofemoral joint on outcome were evaluated. RESULTS: Median follow-up was seven years (3 to 14), and mean age at surgery was 65 years (39 to 90). Median Oxford Knee Score (OKS) was 43 (interquartile range (IQR) 37 to 47), with 260 (80%) achieving a good or excellent score (OKS > 34). Revisions occurred in 34 (10%); 14 (4%) were for dislocation, of which 12 had no recurrence following insertion of a new bearing, and 12 (4%) were revised for medial osteoarthritis (OA). Ten-year survival was 85% (95% confidence interval (CI) 79 to 90, at risk 72). Age, weight, activity, and patellofemoral erosions did not have a significant effect on the clinical outcome or survival. CONCLUSION: Domed lateral UKA provides a good alternative to total knee arthroplasty (TKA) in the management of lateral compartment OA. Although dislocation is relatively easy to treat successfully, the dislocation rate of 4% is high. It is recommended that the stability of the bearing is assessed intraoperatively. If the bearing can easily be displaced, the fixed rather than the mobile bearing version of the Oxford lateral tibial component should be inserted instead. Younger age, heavier weight, high activity, and patellofemoral erosions did not detrimentally affect outcome, so should not be considered contraindications. Cite this article: Bone Joint J 2020;102-B(8):1033-1040.

A matched comparison of revision rates of cemented Oxford Unicompartmental Knee Replacements with Single and Twin Peg femoral components, based on data from the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man.

Background and purpose - Registries report high revision rates after unicompartmental knee replacement (UKR) due, in part, to aseptic loosing. In an attempt to improve Oxford UKR femoral component fixation a new design was introduced with a Twin rather than a Single peg. We used the National Joint Registry (NJR) to compare the 5-year outcomes of the Single and Twin Peg cemented Oxford UKRs.Patients and methods - We performed a retrospective observational study using NJR data on propensity score matched Single and Twin Peg UKRs (matched for patient, implant and surgical factors). Data on 2,834 Single Peg and 2,834 Twin Peg were analyzed. Cumulative implant survival was calculated using the Kaplan-Meier method and comparisons between groups performed using Cox regression models.Results - In the matched cohort, the mean follow up for both Single and Twin Peg UKRs was 3.3 (SD 2) and 3.4 years (SD 2) respectively. The 5-year cumulative implant survival rates for Single Peg and Twin Peg were 94.8% (95% CI 93.6-95.8) and 96.2% (CI 95.1-97.1) respectively. Implant revision rates were statistically significantly lower in the Twin Peg (hazard ratio [HR)] = 0.74; p = 0.04). The revision rate for femoral component aseptic loosening decreased significantly (p = 0.03) from 0.4% (n = 11) with the Single Peg to 0.1% (n = 3) with the Twin Peg. The revision rate for pain decreased significantly (p = 0.01) from 0.8% (n = 23) with the Single Peg to 0.3% (n = 9) with the Twin Peg. No other reasons for revision had significant differences in revision rates.Interpretation - The revision rate for the cemented Twin Peg Oxford UKR was 26% less than the Single Peg Oxford UKR. This was mainly because the revision rates for femoral loosening and pain more than halved. This suggests that the Twin Peg component should be used in preference to the Single Peg design.