Cementless Unicompartmental Knee Replacement Research Articles

Preoperative proximal tibial bone density, bone microarchitecture, and bone turnover are not associated with postoperative tibial component migration in cemented and cementless medial unicompartmental knee replacements: secondary analyses from a randomized controlled trial.

Cementless arthroplasty fixation relies on early bone ingrowth and may be poor in patients with low proximal tibial bone density or abnormal bone turnover. We aimed first to describe the baseline bone properties in patients undergoing medial unicompartmental knee replacement (UKR), and second to investigate its association with cemented and cementless tibial component migration until 2 years. A subset investigation of 2 patient groups from a 3-armed randomized controlled trial was conducted. There were 26 cemented and 25 cementless medial UKRs with twin-pegged femoral components. Volumetric bone mineral density (vBMD) and microstructure of the excised medial tibial plateau were ascertained with µCT. Bone turnover was estimated using dynamic histomorphometry (eroded surface/bone surface = ES/BS, osteoid surface/bone surface = OS/BS, mineralizing surface/bone surface = MS/BS). Tibial component migration in 4 feature points was followed for 2 years with radiostereometry. At the 2-year follow-up, the cementless tibial components migrated 0.38 mm (95% confidence interval [CI] 0.14-0.62) total translation more than the cemented components at the posterior feature point. The greatest migration in the cementless group was subsidence at the posterior feature point of 0.66 mm (CI 0.48-0.84) until 6 weeks, and from 3 months the components were stable. Cemented tibial components subsided very little. Between 1- and 2-year follow-ups, no cementless but 4 cemented tibial components revealed continuous migration. OS/BS was half of the ES/BS. No µCT or histomorphometric parameters showed any clinically relevant correlation with tibial component migration at the posterior feature point for either cemented or cementless UKR at 6 weeks' or 2 years' follow-up after adjustment for age, BMI, and sex. Preoperative vBMD, bone turnover, and microstructure were not associated with postoperative tibial component migration of cemented and cementless medial UKR.

Less pain reported 5 years after cementless compared to cemented unicompartmental knee replacement: an analysis of pain, neuropathy, and co-morbidity scores

PurposeTo compare patient-reported pain scores and assess the influence of neuropathy and co-morbidity, on knee pain following cemented and cementless medial unicompartmental knee replacement (UKR) 5 years after surgery.MethodIn this longitudinal study, 262 cemented and 262 cementless Oxford UKR performed for the same indications and with the same techniques were recruited. Patients were reviewed at five years, evaluating patient-reported pain and association with clinical outcomes. Intermittent and Constant Osteoarthritis Pain (ICOAP), PainDETECT (PD), Charnley score, Oxford Knee Score (OKS) and American Knee Society Score (AKSS) were compared.ResultsIn both cohorts, intermittent pain was more common than constant pain (47% vs 21%). Cementless knees reported significantly less pain than cemented (ICOAP-Total 5/100 vs 11/100, p < 0.0001). A greater proportion of cementless knees experienced no pain at all (ICOAP = 0/100, 61% vs 43%, p < 0.0001) and 75% fewer experienced severe or extreme pain. Pain sub-scores in PD, OKS and AKSS follow this trend. Pain was unlikely to be neuropathic (PD positive: 5.26%), but patients reporting high levels of ‘strongest’ pain were three times more likely to be neuropathic. Patients with co-morbidities (Charnley C) experienced greater pain than those without (Charnley A+B) across all knee-specific scores, despite scores being knee specific.ConclusionBoth cemented and cementless UKR in this study had substantially less pain than that reported in literature following TKR. Cementless UKR had significantly less pain than cemented UKR in all scores. Two-thirds of patients with a cementless UKR had no pain at all at 5 years, and pain experienced was most likely to be mild and intermittent with no patients in severe or extreme pain. Patients with cementless UKR that had higher levels of pain were more likely to have co-morbidity or evidence or neuropathic pain. It is unclear why cementless UKR have less pain than cemented; further study is necessary.

The effect of activity on the outcome of cementless mobile bearing unicompartmental knee replacements

BackgroundMany surgeons consider high activity levels a contraindication to Unicompartmental Knee Replacement (UKR). Cementless fixation is of particular concern given the lack of cement to augment primary stability. We assessed the effect of pre and post-operative activity levels on the outcomes of cementless UKRs. MethodsA prospective cohort of 1000 medial cementless mobile bearing UKR were analysed. Patients were categorised by their pre-operative and highest post-operative Tegner Activity Score (TAS) and results compared between groups. Outcomes of interest included implant survival, Oxford Knee Score (OKS) and the American Knee Society Score – Objective/Functional (AKSS-O/F). ResultsIncreasing post-operative activity were not associated with higher revision rates. The 10-year survival of the high activity group (TAS ≥ 5, 96.7% (CI 91.3–98.8), and low/medium activity group (TAS ≤ 4, 98.1% (CI 96.5–99.0)) were not significantly different (p = 0.57). The mean 10-year OKS of the high activity group (46.5, SD 3.1) was significantly (p < 0.001) higher than that of the low/medium activity group (41.3, SD 7.7). There was a significant trend for increasing activity being associated with increasing AKSS-F at 5-years (p < 0.001) and 10 years (p = 0.01) and increasing AKSS-O at 5 years (p < 0.001). Higher pre-operative activity did not significantly increase revision rates and resulted in significantly higher 5-year post-operative scores. ConclusionsNeither higher pre-operative nor post-operative activity were associated with increased revision rates, but both were associated with better post-operative function. Therefore activity should not be considered a contraindication to cementless mobile bearing UKR and not be restricted post-operatively.

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.

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. 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. 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. 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. Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Clinical and Functional Results of Cementless Unicompartmental Knee Arthroplasty with a Minimum Follow Up of 5 Years—A Consecutive Cohort of 201 Patients

The number of unicompartmental knee replacements (UKR) is increasing. Alongside various advantages, the revision rate of cemented UKR is higher compared to total knee arthroplasty (TKR). In contrast, cementless fixation shows reduced revision rates, compared to the cemented UKR. However, most of the recent literature is based on designer-dependent studies. In this retrospective, single-center cohort study, we investigated patients who underwent cementless Oxford UKR (OUKR) between 2012 and 2016 in our hospital with a minimum follow-up of five years. Clinical outcome was evaluated using the OKS, AKSS-O, AKSS-F, FFbH-OA, UCLA, SF-36, EQ-5D-3L, FJS, ROM, pain, and satisfaction measures. Survival analysis was performed with reoperation and revision as endpoints. We included 201 patients (216 knees) for clinical evaluation. All outcome parameters increased significantly from pre- to postoperative stages. The five-year survival rate was 96.1% for revision surgery and 94.9% for reoperation. The main reasons for revision were the progression of osteoarthritis, inlay dislocation, and tibial overstuffing. Two iatrogenic tibial fractures appeared. Cementless OUKR shows excellent clinical outcome and high survival rates after five years. The tibial plateau fracture in cementless UKR represents a serious complication and requires modification of the surgical technique.

Impact of keel saw blade design and thickness on the incidence of tibial plateau fracture and tibial implant-loosening in cementless medial UKR

BackgroundTibial plateau fractures and tibial implant- loosening are severe complications in cementless unicompartmental knee replacement (UKR). The tibial keel preparation is particularly demanding and different saw blades can be used. It was hypothesized that different blade designs and thickness have an influence on the frequency of tibial plateau fractures and implant-loosening in cementless medial UKR.Methods1258 patients with cementless medial UKR were included in this retrospective study between 2013 and 2020. The tibial keel cut was performed either with a double keel saw blade (DKS; 2.8 mm) and added hand guided pick or a mono reciprocating saw blade (RKB) of different thickness (2.5 mm; 2.65 mm; 2.75 mm). Tibial plateau fracture and loosening were demonstrated by standard two-plane radiographs. Tibial implant-loosening was defined as complete radiolucency and implant migration. Fracture and loosening were combined with pain and loss of function.ResultsIn 126 patients (10%) the tibial keel was prepared with DKS, in 407 patients (32.4%) with RKB 2.5 mm, in 330 patients (26.2%) with RKB 2.65 mm and in 395 patients (31.4%) with 2.75 mm. In 4 patients (3.17%) with DKS tibial plateau fracture occurred, in 4 patients (0.99%) with 2.5 mm RKB, in 3 patients (0.92%) with 2.65 mm RKB and in 1 patient (0.25%) with 2.75 mm RKB. Significantly fewer fractures occurred with a RKB design (p = 0.007). A negative correlation between fracture incidence and RKB saw blade thickness was found (Spearman-r = − 0.93). No difference for tibial implant-loosening was shown (p = 0.51).ConclusionDifferent blade designs and thickness have a significant influence on the incidence of tibial plateau fractures and aseptic tibial implant-loosening. The incidence of tibial plateau fractures in cementless medial UKR can be reduced by changing the design and thickness of the tibial keel saw blade. Greater thickness of RKB leads to significantly fewer tibial plateau fractures while the incidence of implant-loosening is not increasing.Trial registration: This study was retrospectively registered and ethical approval was waived by the local ethical committee (No. 2020–1174).

Comparison of five-year clinical outcomes of 524 cemented and cementless medial unicompartmental knee replacements

AimTo compare the outcomes of cemented and cementless Unicompartmental Knee Replacements (UKR) at 5 years after surgery. Methods262 cemented and 262 cementless medial mobile-bearing UKR, implanted by four high-volume surgeons using identical indications and surgical techniques, were reviewed by independent physiotherapists at 5 years. Survival, Oxford Knee Score (OKS), American Knee Society Score (AKSS), and EQ-5D-5L were assessed. The cementless cohort was mainly implanted after the cemented. Each cohort was divided into early and late sub-groups and compared, to assess if any differences were due to progressive improvement in surgical practice over time. ResultsThere were no significant differences between the cohorts for demographics, pre-operative scores, and 5-year revision (0.8%), re-operation (1.5%), and complication rates (5%). The cementless cohort had significantly better 5-year OKS (43v41, p = 0.008), AKSS-Objective (94v90, p = 0.049) and EQ-5D-5L (0.81v0.87, p = 0.0001). Pain sub-scores within OKS, AKSS, and EQ-5D-5L were also significantly better in the cementless cohort, and the differences were proportionally much greater and more significant than differences in their respective overall scores. There was no significant improvement in scores between the early and late subgroups of the cohorts, whereas the ‘early-cementless’ cohort had significantly better scores than the contemporaneously implanted ‘late-cemented’ cohort. This suggests that differences found were due to implant type, instead of improved surgical practice over time. ConclusionCementless UKR is associated with better clinical outcomes than cemented UKR, which is primarily due to improved pain relief. Both cemented and cementless UKR are safe with low reoperation and complication rates, and a 5-year survival of 99%.

Five-year results of a randomised controlled trial comparing cemented and cementless Oxford unicompartmental knee replacement using radiostereometric analysis

BackgroundCementless fixation is an alternative to cemented unicompartmental knee replacement (UKR). The aim of this study was to determine if cementless UKR fixation is as good as cemented by comparing the five-year migration measured radiostereometric analysis (RSA) in a randomised controlled trial. MethodsThirty-nine patients were randomised to receive either a cemented or a cementless Oxford UKR and were studied at intervals up to five years to assess migration with RSA and radiolucencies with radiographs. ResultsDuring the first year there was a small and significant amount of migration, predominantly in an anterior direction, of both the cemented (0.24 mm, SD 0.32, p = 0.01) and cementless (0.26 mm, SD 0.31, p = 0.00) femoral components. Thereafter there was no significant migration in any direction. At no stage was there any significant difference between the migrations of the cemented or cementless femoral components. During the first year, particularly the first three months, the cementless tibial components subsided 0.28 mm (SD 0.19, p = 0.00). This was significantly (p = 0.00) greater than the subsidence of the cemented tibial component (0.09, SD 0.19, p = 0.28). Between the second and fifth years there was no significant migration of either cemented or cementless tibial components.At five years radiolucent lines occurred significantly less with cementless (one partial) compared to cemented (six partial and one complete) tibial components. ConclusionsAs, between two and five years, there was no significant migration of cemented or cementless components, and no significant difference between them, we conclude that cementless fixation is as reliable as cemented. It may be better as there are fewer radiolucent lines.

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

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). Databases Medline, Embase and Cochrane Central of Controlled Trials were searched to identify all UKR studies reporting the ≥ 10year 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 wereperformed. Mechanisms of failure and patient reported outcome measures are reported. 25 studies were eligible for inclusion with a total of 10,736UKRs, inwhich 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). 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. III.

Cementless Oxford Medial Unicompartmental Knee Replacement-Clinical and Radiological Results of 228 Knees with a Minimum 2-Year Follow-Up.

(1) Background: Studies show several advantages of unicompartmental knee replacement (UKR) over total knee replacements (TKR), whereas registry based revision rates of UKR are significantly higher than for TKA. Registry data report lower revision rates for cementless UKR compared to cemented UKR. The aim of this study was to assess clinical and radiological results of cementless Oxford UKR (OUKR) in an independent cohort. (2) Methods: This retrospective cohort study examines a consecutive series of 228 cementless OUKR. Clinical outcome was measured using functional scores (Oxford Knee Score (OKS), American Knee Society Score (AKSS), Hannover Functional Ability Questionnaire for Osteoarthritis (FFbH-OA), range of motion (ROM)), pain and satisfaction. Radiographs were analyzed regarding the incidence of radiolucent lines (RL), implant positioning, and their possible impact on clinical outcome. (3) Results: At a mean follow-up of 37.1 months, the two and three year revision free survival-rates were 97.5% and 96.9%. Reasons for revision surgery were progression of osteoarthritis, inlay dislocation and pain. All clinical outcome scores showed a significant improvement from pre- to postoperative. The incidence of RL around the implant was highest within the first year postoperatively (36%), and decreased (5%) within the second year. Their presence was not correlated with inferior clinical outcome. Implant positioning showed no influence on clinical outcome. (4) Conclusion: Cementless OUKR showed excellent clinical outcome and survival rates, with reliable osteointegration. Neither the incidence of radiolucent lines nor implant positioning were associated with inferior clinical outcome.

Should We Do More Unicompartmental Knee Replacements?: Commentary on an article by Hasan R. Mohammad, MBChB, MRCS, MRes(Dist), et al.: "The Effect of Surgeon Caseload on the Relative Revision Rate of Cemented and Cementless Unicompartmental Knee Replacements. An Analysis from the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man".

Should We Do More Unicompartmental Knee Replacements?: Commentary on an article by Hasan R. Mohammad, MBChB, MRCS, MRes(Dist), et al.: "The Effect of Surgeon Caseload on the Relative Revision Rate of Cemented and Cementless Unicompartmental Knee Replacements. An Analysis from the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man".

Fast Return to Sports and High Level of Activity after Cementless Oxford Unicompartmental Knee Arthroplasty.

Physical activity is essential for overall health. For patients undergoing knee arthroplasty, questions about the implant's suitability for sports arise. The general recommendations for physical activity with knee replacements are often based upon experts' opinions, with a lack of scientific data. This study was performed at an independent high-volume center and aimed to investigate what level of activity patients can achieve and how they perform with a well-functioning cementless unicompartmental knee replacement (UKR). Possible differences in outcome in regards to patients' body mass index (BMI) were also examined. A total of 228 knees treated with cementless Oxford UKR (OUKR) were followed up after a mean of 37.1 months. Tegner's and UCLA (University of California, Los Angeles) scores were obtained to assess the level of physical activity. The Schulthess Clinical Activity Questionnaire was assessed for detailed information on practiced sports, and the SF-36 questionnaire was evaluated to analyze patients' quality of life. The return to activity rate was 92.9%. In total, 64% of the physically active patients had already taken up sports within 3 months after surgery. Mean Tegner's score was at 3.5, and mean UCLA score was at 6.3. High impact sports were not performed very often after surgery. Higher BMI showed a negative correlation with the numbers of sports (rsp = -0.289) as well as Tegner's (rsp = -0.222) and UCLA (rsp = -0.383) scores. The SF-36 scores were comparably good to those in an age-equivalent standard reference group. In conclusion, cementless OUKR allows a fast return to activity with a high level of physical exercise. Patients with increased BMI tend to practice less types of sports with decreased activity scores.

The Effect of Surgeon Caseload on the Relative Revision Rate of Cemented and Cementless Unicompartmental Knee Replacements: An Analysis from the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man.

Unicompartmental knee replacement (UKR) offers substantial benefits compared with total knee replacement (TKR) but is associated with higher revision rates. Data from registries suggest that revision rates for cementless UKR implants are lower than those for cemented implants. It is not known how much of this difference is due to the implant or to other factors, such as a greater proportion of high-volume surgeons using cementless implants. We aimed to determine the effect of surgeon caseload on the revision rate of matched cemented and cementless UKRs. From a group of 40,522 Oxford (Zimmer Biomet) UKR implants (30,814 cemented, 9,708 cementless) recorded in the National Joint Registry, 14,814 (7,407 cemented, 7,407 cementless) were propensity-score matched. Surgeons were categorized into 3 groups: low volume (<10 cases/year), medium volume (10 to <30 cases/year), and high volume (≥30 cases/year). The effect of caseload on the relative risk of revision was assessed with use of Cox regression. The 10-year survival rates for unmatched cementless and cemented UKR implants were 93.3% (95% confidence interval [CI] = 89.8% to 95.7%) and 89.1% (95% CI = 88.6% to 89.6%), respectively, with the difference being significant (hazard ratio [HR] = 0.59; p < 0.001). Cementless UKR implants had a greater proportion of high-volume surgeon users than cemented implants (30.4% compared with 15.1%). Following matching, the 10-year survival rates were 93.2% (95% CI = 89.7% to 95.6%) and 90.2% (95% CI = 87.5% to 92.3%), which were still significantly different (HR = 0.76; p = 0.002). The 10-year survival rates for matched cementless and cemented UKR implants were 86.8% (95% CI = 73.6% to 93.7%) and 81.8% (95% CI = 73.0% to 88.0%) for low-volume surgeons, 94.3% (95% CI = 92.2% to 95.9%) and 92.5% (95% CI = 89.9% to 94.5%) for medium-volume surgeons, and 97.5% (95% CI = 96.5% to 98.2%) and 94.2% (95% CI = 90.8% to 96.4%) for high-volume surgeons. The revision rate for cementless implants was lower for surgeons in all 3 caseload groups (HR = 0.74, 0.79, 0.80, respectively). Cementless fixation decreased the revision rate by about a quarter, whatever the surgeon caseload. Caseload had a profound effect on implant survival. Low-volume surgeons had a high revision rate with cemented or cementless fixation and therefore should consider either stopping or doing more UKR procedures. High-volume surgeons performing cementless UKR demonstrated a 10-year survival rate of 97.5%, which was similar to that reported in registries for the best-performing TKRs. Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

The clinical outcomes of cementless unicompartmental knee replacement in patients with reduced bone mineral density

BackgroundOsteoporosis and osteopenia are conditions characterised by reduced bone mineral density (BMD). There is concern that bone with reduced BMD may not provide sufficient fixation for cementless components which primarily rely on the quality of surrounding bone. The aim of our study was to report the midterm clinical outcomes of patients with reduced BMD undergoing cementless unicompartmental knee replacements (UKR). Our hypothesis was that there would be no difference in outcome between patients with normal bone and those with reduced BMD.MethodsFrom a prospective cohort of 70 patients undergoing cementless UKR surgery, patients were categorised into normal (n = 20), osteopenic (n = 38) and osteoporotic groups (n = 12) based on their central dual-energy X-ray absorptiometry (DEXA) scans according to the World Health Organization criteria. Patients were followed up by independent research physiotherapists and outcome scores; Oxford Knee Score (OKS), Tegner score, American Knee Society Score Functional (AKSS-F) and Objective (AKSS-O) were recorded preoperatively and at a mean of 4 years postoperatively. The prevalence of reoperations, revisions and mortality was also recorded at a mean of 5 years postoperatively.ResultsThere were no significant differences in the midterm postoperative OKS (P = 0.83), Tegner score (P = 0.17) and AKSS-O (P = 0.67). However, the AKSS-F was significantly higher (P = 0.04) in normal (90, IQR 37.5) compared to osteoporotic (65, IQR 35) groups. There were no significant differences (P = 0.82) between normal and osteopenic bone (80, IQR 35). The revision prevalence was 5%, 2.6% and 0% in the normal, osteopenic and osteoporotic groups respectively. The reoperation prevalence was 5%, 7.9% and 0% respectively. There were no deaths in any group related to the implant.ConclusionsWe found that patients with reduced BMD could safely undergo cementless UKR surgery and have similar clinical outcomes to those with normal BMD. However, larger studies with longer follow-up are needed to confirm our findings and ensure that cementless fixation is safe in patients with reduced BMD.

Comparison of the 10-year outcomes of cemented and cementless unicompartmental knee replacements: data from the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man

Background and purpose — Unicompartmental knee replacement (UKR) offers advantages over total replacement but has higher revision rates, particularly for aseptic loosening. The cementless Oxford UKR was introduced to address this. We undertook a registry-based matched comparison of cementless and cemented UKRs.Patients and methods — From 40,552 Oxford UKRs identified by the National Joint Registry for England, Wales, Northern Ireland and Isle of Man (NJR) we propensity score matched, based on patient, surgical, and implant factors, 7,407 cemented and 7,407 cementless UKRs (total = 14,814).Results — The 10-year cumulative implant survival rates for cementless and cemented UKRs was 93% (95% CI 90–96) and 90% (CI 88–92) respectively, with this difference being significant (HR 0.76; p = 0.002). The risk of revision for aseptic loosening was less than half (p < 0.001) in the cementless (0.42%) compared with the cemented group (1.00%), and the risk of revision also decreased for unexplained pain (to 0.46% from 0.74%; p = 0.03) and lysis (to 0.04% from 0.15%; p = 0.03). However, the risk of revision for periprosthetic fracture increased significantly (p = 0.01) in the cementless (0.26%) compared with the cemented group (0.09%). 10-year patient survival rates were similar (HR 1.2; p = 0.1).Interpretation — The cementless UKR has improved 10-year implant survival compared with the cemented UKR, independent of patient, implant, and surgical factors. This improved survival in the cementless group was primarily the result of lower revision rate for aseptic loosening, unexplained pain, and lysis, suggesting the fixation of the cementless was superior. However, there was a small increased risk of revision for periprosthetic fracture with the cementless implant.

Mid- to long-term function and implant survival of ACL reconstruction and medial Oxford UKR

PurposeThe purpose of this study was to describe mid- to long-term outcomes of anterior cruciate ligament (ACL) reconstruction with simultaneous or staged medial unicompartmental knee replacement (UKR), and compare outcomes between (1) young patients aged younger than 55 at surgery and those older, (2) those with long-term follow-up greater than 10 years, (3) cemented and cementless UKR, and (4) compare outcomes to those with an intact ACL. Patients and methodsWe identified knees with staged or simultaneous ACL reconstruction and medial UKR from a prospectively followed designer UKR cohort, and describe mean Oxford Knee Score (OKS), mean Tegner activity score and Kaplan–Meier survival estimates. We matched these knees to ACL-intact knees. ResultsSeventy-six consecutive UKR with staged or simultaneous ACL reconstruction were identified with mean six-year follow-up (range 1–15). There was significant improvement in OKS and Tegner score with surgery. At most recent follow-up, OKS was 41.0 (range 11 to 48), and Tegner score 3.6 (0 to 8). There were three revisions occurring at a mean of five years post-operatively. The five-, 10- and 15-year survival estimates were 97% (95% confidence interval [CI] 93–100), 92% (83–100), and 92% (83–100). There was no difference in functional scores or implant survival in young patients, those with long-term follow-up (>10 years), those with cementless fixation, or when compared to ACL intact knees. ConclusionThese results demonstrate excellent mid- to long-term function and survival of selected patients who have undergone ACL reconstruction and medial UKR. Their outcome was similar to those with intact ACLs.

Instruments to reduce the risk of tibial fracture following cementless unicompartmental knee replacement

BackgroundTibial plateau fracture is an important complication of cementless Oxford unicompartmental knee replacement. The press fit between the keel and the bone's keel slot is responsible for primary fixation and also contributes to fracture risk. This study investigates whether the fracture risk could be reduced without compromising primary fixation, by using different instruments to widen the keel slot. MethodsKeel slots were made in polyurethane blocks (n = 60) using the standard keel cut saw blade or a new blade that was 0.2 mm wider, with adjuvant use of the cemented pick or a prototype rasp. A tibial component was pushed into and pulled out of the slots using a Dartec materials testing machine. It was assumed that the ‘push-in’ force was related to the risk of fracture and ‘pull-out’ force was related to fixation. Reproducibility studies with 10 different tibial components were undertaken. ResultsThe new blade required significantly lower push-in forces than the standard blade (789 N SD 130, 1411 N SD 180; P < 0.001), but the pull-out forces were not different (240 N SD 47, 230 N SD 56; P > 0.999). With the standard blade the pick decreased the push-in (818 N SD 318; P < 0.001) and pull-out (128 N SD 58; P < 0.001) forces, but the rasp had no effect. With the new blade the pick had no effect, but the rasp increased the push-in force (1390 N SD 202; P < 0.001). ConclusionsThis study suggests the fracture risk will be reduced with the new blades, with no compromise in fixation. If the new blades are used routine use of the cemented pick appears to be of no benefit.

Cementless unicompartmental knee replacement allows early return to normal activity

BackgroundPhysical activity and regular participation in recreational sports gain importance in patients’ lifestyle after knee arthroplasty. Cementless unicompartimental Knee replacement with the Oxford System has been introduced into clinical routine. Currently there is no data reporting on the physical activity, return to sports rate and quality of live after medial cementless Oxford Unicompartimental Knee Replacement (OUKR).MethodsThis retrospective cohort study reports on the functional outcome of the first 27 consecutive patients (30 knees) that were consecutively treated with a cementless medial OUKR between 2007 and 2009 in our hospital. Physical activity and quality of life were measured using the Tegner-Score, the UCLA-Activity Score, the Schulthess Clinical Activity Questionnaire and the SF-36 Score. The patients’ satisfaction with the outcome was measured using a visual analogue scale.ResultsMean age at surgery was 62.5 years. Patients showed a rapid recovery with 17 out of 27 patients returning to sports within 3 months, 24 within 6 months after surgery. The Return-to-activity-rate was 100%. 10 out of 27 patients showed a high activity level (UCLA ≥7 points) with a mean postoperative UCLA-Score of 6.1 points.ConclusionsPatients recover rapidly after cementless OUKR with a return to sports rate of 100% and patients are able to participate in high impact sports disciplines.

Cementless Oxford medial unicompartimental knee replacement: an independent series with a 5-year-follow-up.

Cemented unicompartmental knee replacement (UKR) has proven excellent long-term survival rates and functional scores in Price et al. (Clin Orthop Relat Res 435:171-180, 2005), Price and Svard (Clin Orthop Relat Res 469(1):174-179, 2011) and Murray et al. (Bone Joint Surg Br 80(6):983-989, 1998). The main causes for revision, aseptic loosening and pain of unknown origin might be addressed by cementless UKR in Liddle et al. (Bone Joint J 95-B(2):181-187, 2013), Pandit et al. (J Bone Joint Surg Am 95(15):1365-1372, 2013), National Joint Registry for England, Wales and Northern Ireland: 10th Annual Report 2013 ( http://www.njrcentre.org.uk/njrcentre/Portals/0/Documents/England/Reports/10th_annual_report/NJR%2010th%20Annual%20Report%202013%20B.pdf , 2013), Swedish Knee Arthroplasty Register: Annual Report 2013 ( http://www.myknee.se/pdf/SKAR2013_Eng.pdf , 2013). This single-centre retrospective cohort study reports the 5-year follow-up results of our first 30 consecutively implanted cementless Oxford UKR (OUKR). Clinical outcome was measured using the OKS, AKSS, range of movement and level of pain (visual analogue scale). The results were compared to cemented OUKR in a matched-pair analysis. Implant survival was 89.7%. One revision each was performed due to tibial fracture, progression of osteoarthritis (OA) and inlay dislocation. The 5-year survival rate of the cementless group was 89.7% and of the cemented group 94.1%. Both groups showed excellent postoperative clinical scores. Cementless fixation shows good survival rates and clinical outcome compared to cemented fixation.

Five-year experience of cementless Oxford unicompartmental knee replacement.

Cementless unicompartmental knee replacement (UKR) was introduced to address someof the problems that can occur following cemented UKR. The aim of this study was to report the 5-year experience of the first 512 medial cementless Oxford UKR implanted by two surgeons for the recommended indications. The first consecutive 512 cementless Phase 3 Oxford UKRs implanted by two surgeons for the recommended indications between June 2004 and October 2013 were prospectively identified and followed up independently. All the procedures were carried out through a minimally invasive approach without eversion or dislocation of the patella. Patients were assessed clinically pre-operatively and at 1, 2, 5, 7 and 10years after surgery with functional outcome scores and radiographs. There were eight reoperations of which six were revisions giving a 5-year survival of 98% (95% CI 94-100%). At a mean follow-up of 3.4years (1.0-10.2), the mean OKS was 43 (SD 7), AKSS (objective) was 81 (SD 13), and AKSS (functional) was 86 (SD 17). The first 120 cases had a minimum follow-up of 5years (mean 5.9; range 5-10.2). In these patients, the mean OKS was 41 (SD 8), AKSS (objective) was 81 (SD 14), and AKSS (functional) was 82 (SD 18). There were no femoral radiolucencies and no complete tibial radiolucencies. 11% of tibial components had partial radiolucent lines; the remaining 89% had no radiolucencies. The clinical results are as good as or better than those previously reported for cemented fixation. The radiographic results are better with secure bony attachment to the implants in every case. IV.