Objectives. Unicompartmental knee replacement (UKR) is a conservative option for degenerative disease, with mobile (Oxford UKR) and fixed bearing (Physica ZUK) the most commonly used devices. The primary reasons for revising UKRs include disease progression (36.9%), loosening (31.7%), and pain (7.5%). Loosening typically occurs due to osteolysis caused by wear particles from the polyethylene (PE) inserts. There is limited published literature which has quantified volumetric material loss from the PE inserts of cemented fixed-bearing UKRs. This study aimed to quantify bearing wear and backside deformation of these PE components. Design and Methods. At our national retrieval centre, we measured changes volumetric bearing wear and backside deformation of 31 explanted fixed-bearing Physica ZUK UKR PE inserts using a peer-reviewed methodology based on coordinate measuring machine analysis. These explants had been revised for any indication [Females (19) and Males (12)]. The location of the wear scars was identified and mapped. We compared the volumetric wear from the bearing surface with contemporary total knee replacement (TKR) inserts. Results. The median (IQR) total volumetric wear of the UKR PEs [96(50-152) mm. 3. ] was significantly higher (p<0.001) than contemporary TKR PEs [40 (24-83) mm. 3. ]. The median (IQR) total volumetric wear of the PEs in males [148(122-200) mm. 3. ] was significantly higher(p=0.016) than in females [56(61-119) mm. 3. ]. The wear scars were situated in the anterior third in 61% of cases, with 26% located posteriorly. Examination of the PE backside surfaces exhibited damage in the area directly inferior to the bearing surface wear scar in the majority of cases. Conclusion. In conclusion, this study highlights significant PE wear of Physica ZUK UKR inserts, with higher wear rates compared to contemporary TKR inserts, particularly in males

Aims. Day-case knee and hip replacement, in which patients are discharged on the day of surgery, has been gaining popularity during the last two decades, and particularly since the COVID-19 pandemic. This systematic review presents the evidence comparing day-case to inpatient-stay surgery. Methods. A systematic literature search was performed of MEDLINE, Embase, and grey literature databases to include all studies which compare day-case with inpatient knee and hip replacement. Meta-analyses were performed where appropriate using a random effects model. The protocol was registered prospectively (PROSPERO CRD42023392811). Results. A total of 38 studies were included, with a total of 83,888 day-case procedures. The studies were predominantly from the USA and Canada, observational, and with a high risk of bias. Day-case patients were a mean of 2.08 years younger (95% CI 1.05 to 3.12), were more likely to be male (odds ratio (OR) 1.3 (95% CI 1.19 to 1.41)), and had a lower mean BMI and American Society of Anesthesiologists grades compared with inpatients. Overall, day-case surgery was associated with significantly lower odds of readmission (OR 0.83 (95% CI 0.73 to 0.96); p = 0.009), subsequent emergency department attendance (OR 0.62 (95% CI 0.48 to 0.79); p < 0.001), and complications (OR 0.7 (95% CI 0.55 to 0.89) p = 0.004), than inpatient surgery. There were no significant differences in the rates of reoperation or mortality. The overall rate of successful same-day discharge for day-case surgery was 85% (95% CI 81 to 88). Patient-reported outcome measures and cost-effectiveness were either equal or favoured day-case. Conclusion. Within the limitations of the literature, in particular the substantial risk of selection bias, the outcomes following day-case knee and hip replacement appear not to be inferior to those following an inpatient stay. The evidence is more robust for unicompartmental knee replacement (UKR) than for total knee replacement (TKR) or total hip replacement (THR). The rate of successful same-day discharge is highest in UKR, followed by TKR and comparatively lower in THR. Cite this article: Bone Joint J 2024;106-B(12):1385–1392

Introduction. This study assessed outcomes of total knee joint replacements (TKJR) in patients who had undergone previous periarticular osteotomy compared with unicompartmental knee replacement (UKR). Establishing a difference in the results of total knee joint replacements following these operations may be an important consideration in the decision-making and patient counselling around osteotomy versus UKR for the management of single-compartment osteoarthritis. Method. Using data from the New Zealand Joint Registry, we identified 1,895 total knee joint replacements with prior osteotomy and 1,391 with prior UKR. Revision rates and patient-reported outcomes, as measured by the Oxford Knee Score (OKS), between these two groups were compared. Adjusted hazard ratios were also calculated to compare the groups. Results. The revision rate for total knee joint replacement following osteotomy was significantly lower than TKJR following UKR (0.88 per 100 component years versus 1.38 per 100 component years, respectively). Adjusted hazard ratio calculations found that those with TKJR with prior UKR had more than double the risk of requiring revision than those with prior osteotomy. Additionally, there was a statistically significant difference in the mean adjusted OKS scores between the two groups, with improved outcomes in the group with prior osteotomy. Conclusion. Our findings suggest that total knee joint replacement following periarticular osteotomy have a lower risk of revision and improved OKS when compared to those with prior UKR. Previous studies assessing New Zealand Joint Registry have not found a statistically significant difference between the two groups however, these results are no longer in keeping with more contemporary literature. Our study confirms the New Zealand population to be comparable with international studies with TKJR after osteotomy performing significantly better compared with prior UKR

Abstract. Introduction. In cementless UKR, early post-operative tibial fractures are 7x more common in very small tibias. A smaller keel has been shown to reduce this fracture risk, but its effect on fixation is unassessed. This mechanical study assesses the effect of keel interference and size on sagittal micromotion of the tibial component in physiological loading positions. Method. A high-resolution Digital Image Correlation setup was developed and validated to an accuracy of 50 micrometres. Variants of tibial components were 3D-printed: standard, no-interference, no-keel, and a new small keel. Components were implanted into bone-analogue foam which was machined to a CT-reconstructed small tibia, using surgical technique. Tibias were loaded to 200N in physiological loading positions: 8mm (step-up) and 15mm (lunge) posterior to midpoint, and micromotion was assessed. Results. In all tests, anterior lift-off was the largest micromotion observed. In ‘step-up’, a standard keel moved more than the no-interference and no-keel variants (340μm-vs-63μm-vs-30μm, p=0.002). In ‘lunge’ loading, the no-interference and no-keel variants moved more than the standard (826μm-vs-1003μm-vs-521μm, p=0.039). The small keel experienced less micromotion in ‘step-up’ (245μm-vs-340μm p=0.233, overall p=0.009) and ‘lunge’ (378μm-vs-521μm p=0.265, overall p=0.006) than the standard keel. Conclusion. The keel protects against large tibial micromotion during lunge movement. Counterintuitively, interference increases micromotion during step-up movement, likely due to implant pivoting around the bone-keel interface. Results suggest patients should be advised against lunge movements early post-operatively. The new smaller keel fixes similarly or better than the standard keel, making it viable for replacing the standard keel to potentially reduce fracture risk

Abstract. Background. Daycase pathways which aim to discharge patients the same day following Unicompartmental Knee Replacement have been introduced in some centres, though most continue with Standard pathways. While Daycase pathways have cost savings, recovery data comparing pathways is limited. This study aims to compare patient-reported early recovery between Daycase and Standard pathways following UKR. Method. This study was carried out in two centres that originally used the same Standard recovery pathway for UKR. In one centre, the Standard pathway was modified into a Daycase pathway. 26 Daycase-Outpatient, 11 Daycase-Inpatient, and 18 Standard patients were recruited. Patients completed the Oxford Arthroplasty Early Recovery Score (OARS) and SF-36 (Acute) measure between Days 1–42. Results. Standard patients had significantly better Day-1 scores than Daycase patients, but this difference rapidly diminished, and from Day-3 onwards both groups had near-identical scores (OARS Day-1, 59 vs 37, p=0.002, stemming from differences in Pain, Nausea/Feeling-Unwell, Function/Mobility subscores p=0.003,0.014,0.011. OARS Day-3 48 vs 49, p=0.790). Daycase-Outpatients had a higher overall OARS (p=0.002), recovering 1–2 weeks faster than Daycase-Inpatients. OARS subscores demonstrated that Daycase-Outpatients had better Pain, Nausea/Feeling-Unwell, Fatigue/Sleep scores (p=0.020,0.0004,0.019 respectively). SF-36 scores corroborate OARS scores. Conclusion. The Standard cohort had better Day-1 scores than the Daycase cohort, likely due to later mobilisation and stronger inpatient analgesia; these differences diminished by Day-3. Daycase-Outpatients recovered substantially faster than Daycase-Inpatients – likely due to the factors that delayed their discharge. The convergence of scores at 6 weeks demonstrates that both pathways have similar early recovery outcomes

Abstract. Unicompartment knee replacement (UKR) has been an effective treatment of isolated medial compartment osteoarthritis (OA). There has been several studies which suggest that patellofemoral (PFJ) wear may not be a relative contraindication for UKR with no statistical difference in failure rates. There is currently conflicting evidence on the role of BMI. We will review if BMI and PFJ wear impacts on the post operative functional scores following UKR. A retrospective review of a prospectively collected database was performed. Data was collected between 26/6/2014 and 25/8/2022. 159 UKR procedures were identified. BMI and PFJ cartilage wear were collected. Oxford knee scores (OKS) were collected at > 2 years. PFJ wear was split into International Cartilage Research Society (ICRS) grades I&II and III&IV. 159 UKR procedures were identified, of these 115 had 2 year follow up. There were 77 who had OKS recorded at 2 years. For PFJ wear there was no statistical difference in the median OKS at 2 years 45 vs 43.5 (p=0.408). Assessing the BMI the median was 29kg/m. 2. , range 20–43kg/m. 2. Spearman's rank was performed to assess the correlation between BMI and >2 year OKS, this demonstrated a moderately negative correlation p(df)=−0.339 (CI 95% −0.538, −0.104) p=0.004. There is no statistically significant difference in >2 year OKS following UKR regardless of PFJ wear. There is a moderately negative correlation between BMI and >2 year OKS which was significant p=0.004. Therefore BMI is a more important consideration when counselling patients for UKR

Abstract. Introduction. Uni-compartmental knee replacement (UKR) has become popularised due to quicker recovery times, reduced postoperative pain, and blood loss. The desire to increase bed capacity and reduce costs, while preserving safety and patient satisfaction, has led to increased interest in day-case arthroplasty. This study observes the feasibility of UKR as a day-case procedure and whether this affects short and long-term postoperative outcomes. Methodology. Between 2018 and 2021, at a single institution and operated by a single orthopaedic surgeon, seventy-seven patients received a UKR on an elective basis. The patients were divided into two groups: ‘day-case’ for those discharged on the same day, and ‘non day-case’ group. Results. 31 patients were identified as day case procedures with the remaining 46 requiring between one to three days before discharge. Mean age, sex, modal ASA score, BMI, Charlson co-morbidity index, and pre-op oxford knee score showed no statistically significant difference between the two groups (p>0.05). No significant difference between the post-op oxford knee score at 1 year was found for patients treated and discharged as a day case procedure (37.8 +/− 6.88) and those who remained as an inpatient postoperatively (37.8 +/− 10.7); t(df) = −0.0007, p=0.994. No patients in either group suffered any complications beyond the peri-operative period. 30-day and 90-day readmission rates were equal. Conclusions. With no significant differences in post-op knee scores, complication, and readmission rates, we feel UKR can be performed as a viable day case procedure in a planned elective setting. This will result in significant cost savings

The development and implementation of Enhanced Recovery After Surgery (ERAS) protocols are of particular interest in elective orthopaedics due to clinical benefits and cost effectiveness. The Wycombe Arthroplasty Rapid-Recovery Pathway (WARP) was designed to streamline hip and knee joint arthroplasty to reduce time spent in hospital whilst optimising outcomes in an NHS District General Hospital. 966 patients were admitted to Wycombe General Hospital for primary elective joint replacement (60 UKR, 446 THR, 460 TKR) during the period 1st September 2020 to 31st September 2022. The WARP pathway was used for 357 (37%) patients (32 UKR, 155 THR, 170 TKR) and the standard “non-WARP” pathway was used for 609 (63%) patients (28 UKR 291 THR, 290 TKR). Data was collected on length of stay, time of mobilisation, number of physiotherapy sessions, and inpatient morbidity. Average length of stay following UKR was 0.75 days for WARP vs 2.96 for non-WARP patients, following THR was 2.17 days for WARP vs 4.17 for non-WARP patients, following TKR was 3.4 days for WARP vs 3.92 for non-WARP patients. Day-0 mobilisation after UKR was achieved in 97% of WARP vs 12% of non-WARP patients, after THR in 43% of WARP vs 14% of non-WARP patients, after TKR in 33% of WARP vs 11% of non-WARP patients. Same-day discharge was achieved in the WARP cohort in 63% of UKR, 10% of THR, 2% of TKR patients. There were no same-day discharges in the non-WARP cohort. Complications delaying mobilisation (pain, nausea/vomiting, dizziness/low BP) were identified in 8.4% of WARP vs 25% of non-WARP patients. Our cohort study shows that the initiation of WARP Rapid Recovery pathway for joint arthroplasty decreased the average length of stay after UKR by 2.21 days, after THR by 2 days, after TKR by 0.52 days. Time to first mobilisation was decreased significantly by increased rates of same-day mobilisation and reduced rates of postoperative anaesthetic-related complications

Contemporary indications for unicompartmental knee replacement (UKR) include bone on bone radiographic changes in the medial compartment with relatively preserved lateral and patellofemoral compartments. The role of MRI in identifying candidates for UKR is commonplace. The aim of this study was to assess the relationship between radiographic and MRI pre-operative grade and outcome following UKR. A retrospective analysis of medial UKR patients from 2017 to 2021. Inclusion criteria were medial UKR for osteoarthritis with pre-operative and post-operative Oxford Knee Scores (OKS), pre-operative radiographs and MRI. 89 patients were included. Whilst all patients had grade 4 ICRS scores on MRI, 36/89 patients had grade 3 KL radiographic scores in the medial compartment, 50/89 had grade 4 KL scores on the medial compartment. Grade 3 KL with grade 4 IRCS medial compartment patients had a mean OKS change of 17.22 (Sd 9.190) meanwhile Grade 4 KL had a mean change of 17.54 (SD 9.001), with no statistical difference in the OKS change score following UKR between these two groups (p=0.873). Medial bone oedema was present in all but one patient. Whilst lateral compartment MRI ICRS scores ranged from 1 to 4 there was no association with MRI score of the lateral compartment and subsequent change in oxford score (P value 0.458). Patellofemoral Compartment (PFC) MRI ICRS ranged from 0 to 4. There was no association between PFC ICRS score and subsequent change in oxford knee score (P value .276). Radiographs may under report severity of some medial sided knee osteoarthritis. We conclude that in patients with grade 3 KL score that would normally not be considered for UKR, pre-operative MRI might identify grade 4 ICRS scores and this subset of patients have equivalent outcomes to patients with radiographic Grade 4 KL medial compartment osteoarthritis

Due to shorter hospital stays and faster patient rehabilitation Unicompartmental Knee Replacements (UKR) are now considered more cost effective than Total Knee Joint Replacements (TKJR). Obesity however, has long been thought of as a relative contraindication to UKR due to an unproven theoretical concern of early loosening. This study is a retrospective review of patient reported outcome scores and revision rates of all UKR with recorded BMI performed by the Canterbury District Health Board (CDHB) from January 2011 and September 2021. Patient reported outcome scores were taken preoperatively, at 6 months, 1 year, 5 years and 10 years post operatively. These included WOMAC, Oxford, HAAS, UCLA, WHOQOL, normality, pain and patient satisfaction. 873 patients had functional scores recorded at 5 years and 164 patients had scores recorded at 10 years. Further sub-group analysis was performed based on patient BMI of <25, 25–30, 30–35 and >35. Revision data was available for 2377 UKRs performed in Christchurch during this period. Both obese (BMI >30) and non-obese (BMI <30) patients had significantly improved post-operative scores compared to preoperative. Pre-operatively obese patients had significantly lower functional scores except for pain and UCLA. All functional scores were lower in obese patients at 5 years but this did not meet minimum clinical difference. At 10 years, there was significantly lower HAAS, satisfaction and WOMAC scores for obese patients but no difference in Oxford, normality, WHOQOL, UCLA and pain scores. There was no significant difference in the improvement from pre-operative scores between obese and non-obese patients. All cause revision rate for obese patients at 10 years was 0.69 per 100 observed component years compared to 0.76 in non-obese. This was not statistically significant. Our study proves that UKR is an excellent option in obese patients with post-operative improvement in functional scores and 10 year survivorship equivalent to non-obese patients

The purpose of this study is to assess the long term results of combined ACL reconstruction and unicompartmental knee replacements (UKR). These patients have been selected for this combined operation due to their combination of instability symptoms from an absent ACL and unicompartmental arthritis. Retrospective review of 44 combined UKR and ACL reconstruction by a single surgeon. Surgeries included both medial and lateral UKR combined with either revision ACL reconstruction or primary ACL reconstruction. Patient reported outcomes were obtained preoperatively, at one year, 5 years and 10 years. Revision rate was followed up over 13 years for a mean of 7.4 years post-surgery. The average Oxford score at one year was 43 with an average increase from pre-operation to 1 year post operation of 15. For the 7 patients with 10 year follow up average oxford score was 42 at 1 year, 43 at 5 years and 45 at 10 years. There were 5 reoperations. 2 for revision to total knee arthroplasty and 1 for an exchange of bearing due to wear. The other 2 were the addition of another UKR. For those requiring reoperation the average time was 8 years. Younger more active patients presenting with ACL deficiency causing instability and unicompartmental arthritis are a difficult group to manage. Combining UKR and ACL reconstruction has scant evidence in regard to long term follow up but is a viable option for this select group. This paper has one of the largest cohorts with a reasonable follow up averaging 7.4 years and a revision rate of 11 percent. Combined unilateral knee replacements and ACL reconstruction can be a successful operation for patients with ACL rupture causing instability and unicompartmental arthritis

Abstract. Introduction. In cementless UKR, primary fixation of the tibial component is achieved by press-fitting a keel (i.e. with interference) into a vertical slot cut into the proximal tibia. This may adversely affect the structural integrity of surrounding bone. Early post-operative peri-prosthetic tibial fractures are 7x more common in very small knees, but the aetiology of these fractures is unknown - such sizes are rarely used in the UK but more common in Asian populations. This study explores the effect of keel-related features in fracture risk of these very small tibias. Method. This in vitro study compares the effect of keel and slot depth (standard vs 33% shallower vs nil) and loading position (anterior/posterior gait range limits: mid-tibia vs 8mm posterior) on fracture load and path. 3D-printed titanium components were implanted using surgical instrumentation/technique, in bone-analogue foam machined to a CT-reconstructed very small tibia which subsequently experienced a peri-prosthetic fracture. Results. Introducing a standard slot reduces load-to-fracture by 50% (1421N-vs-710N, p<0.0001). Press-fitting a standard keel further reduces load-to-fracture by 40% (710N-vs-423N, p=0.0001). A shallower slot/keel increases load-to-fracture substantially (slot: 27% increase, 904N-vs-710N p=0.0003, slot+keel: 60% increase, 683N-vs-423N p=0.0004). Deeper keels fractured more vertically (current 8.2° vs shallow 15.5° vs nil 21°, degrees-to-vertical, p<0.0001). There was no difference caused by loading position. Conclusion. In very small tibias, a standard cementless keel significantly weakens the bone and may contribute to fractures. Therefore, decreasing interference or using a shallower keel should decrease the risk of fracture, although it might compromise fixation

Abstract. Introduction. Medial fix bearing unicompartmental knee replacement (UKR) designs are consider safe and effective implants with many registries data and big cohort series showing excellent survivorship and clinical outcome comparable to that reported for the most expensive and surgically challenging medial UKR mobile bearing designs. However, whether all polyethylene tibial components (all-poly) provided comparable results to metal-backed modular components during medial fix bearing UKR remains unclear. There have been previous suggestions that all-poly tibia UKR implants might show unacceptable higher rates of early failure due to tibial component early loosening especially in high body max index (BMI) patients. This study aims to find out the short and long-term survival rate of all-poly tibia UKR and its relationship with implant thickness and patient demographics including sex, age, ASA and BMI. Material and Methods. we present the results of a series of 388 medial fixed bearing all-polly tibia UKR done in our institution by a single surgeon between 2007–2019. Results. We found out excellent implant survival with this all-poly tibia UKR design with 5 years survival rate: 96.42%, 7 years survival rate: 95.33%, and 10 years survival rate: 91.87%. Only 1.28% had early revision within 2 years. Conclusion. Fixed bearing medial all-poly tibia UKR shows excellent survivor rate at 2, 5, 7 and 10 years follow up and the survival rate is not related with sex, age, BMI, ASA grade or implant thickness. Contrary to the popular belief, we found out that only 1.71% of all implants was revised due to implant loosening

Abstract. Introduction. After remodelling, loss of bone density beside the keel of cementless UKR tibial components has been observed as a potential cause of concern. How this affects patient-reported outcomes, and further clinical implications, is unclear. This study aims to assess the effect of cementless UKR implantation on tibial bone density, and to explore its relationship to patient demographics and outcomes. Method. This prospective study assesses 115 anterior-posterior radiographs from cementless UKR postoperatively and five years after surgery. Grey values from nine regions around each keel were collected and standardised to enable inter-radiograph comparison. Change between the post-operative and 5-year radiographs (indicating bone density) was calculated, and effect on 5-year patient demographics and pain and functional outcomes was assessed. Repeat measurements were performed by two operators to assess reliability. Results. There was excellent inter-operator correlation. There was increased bone density directly below the keel (9.1% vs 3.3%: p<0.0001), and reduced density beside the keel (−5.9% vs -1.0%, p<0.0001); comparisons to adjacent regions. Overall remodelling was significantly greater in smaller tibias (p=0.006), and females (p=0.01). Remodelling was unrelated to outcomes (OKS, ICOAP-A/B, TAS), age, and BMI. Conclusion. Remodelling patterns suggest increased loading below and decreased loading adjacent to the tibial keel. Remodelling is greater in smaller tibias and females. Remodelling is not related to any patient-reported pain or function five years after surgery, suggesting that remodelling is successful in removing any mechanical source of bone pain. Therefore, clinicians viewing such remodelling patterns can ignore them as they are of no consequence

There has been significant interest in day-case and rapid discharge pathways for unicompartmental knee replacements (UKR). Pathways to date have shown this to be a safe and feasible option; however, no studies to date have published results of rapid-discharge pathways using the NAVIO robotic system. To date there is no published experience with rapid discharge UKR patients using the NAVIO robotic system. We report an initial experience of 11 patients who have safely been discharged within 24 hours. With the primary goal of investigating factors that led to rapid discharge and a secondary goal of evaluating the safety of doing so. All patients were discharged within 24 hours; there were no post-operative complications and no readmissions to hospital. The mean length of stay was 16.9 hours (SD=7.3), with most patients seen once on average by physiotherapy. Active range of motion at 6 weeks was 0.7o to 130.5 o, with all patients mobilising independently. The average 6-month post-operative Oxford Knee Score was 43.5 out of 48. There were no readmission or complications in any of our patients. This initial feasibility study identified that patients could be safely discharged within 24 hours after UKR using the NAVIO robotic system. With growing uptake of robotic procedures, with longer operative durations than traditional procedures, it is essential to ensure a rapid discharge to reduce healthcare cost whilst ensuring that patients are discharged home in a safe manner

Background. There are advantages and disadvantages of Unicompartmental (UKR) and Total Knee Replacement, with UKR having better functional outcomes with fewer complications but a higher revision rate. The relative merits depend on patient characteristics. The aim was to compare UKR and TKR risk-benefits and cost-effectiveness in patients with severe systemic morbidity. Methods. Data from the National Joint Registry for England, Wales and Northern Ireland was linked to hospital inpatient and patient-reported outcomes data. Patients with American Society of Anesthesiologists (ASA) grade ≥3 undergoing UKR or TKR were identified. Propensity score stratification was used to compare 90-day complications and 5-year revision and mortality of 2,256 UKR and 57,682 TKR, and in a subset of 145 UKR and 23,344 TKR Oxford Knee Scores (OKS). A health-economic analysis was based on EQ-5D and NHS hospital costs. Results. The OKS was significantly better following UKR than TKR with a difference of 1.83 (95%CI 0.10–3.56). UKR was associated with lower relative risks of venous thromboembolism (0.33, CI0.15–0.74), myocardial infarction (0.73, CI0.36–1.45) and early joint infection (0.85, CI0.33–2.19) but only the decrease in venous thromboembolism was significant. The revision risk following UKR was significantly higher than following TKR (hazard ratio 2.70, CI2.15–3.38) and the mortality was significantly lower (0.52, CI0.36–0.74). At five years the cumulative incidence of revision was 8% higher with UKR, and the cumulative incidence of death was 13% lower. The health economic analysis found that UKR dominated TKR having lower costs (£359, CI340-378) and higher quality-of-life gains (0.33, CI-0.31–0.970). Conclusions. For patients with ASA ≥3, UKR was safer and more cost-effective than TKR. In particular if UKR was used instead of TKR the number of lives saved was higher than the number of extra revisions. UKR should be considered the first option for suitable patients with severe co-morbidity

Background. Lateral Unicompartmental Knee Arthroplasty (UKA) is a recognised treatment option in the management of lateral Osteoarthritis (OA) of the knee. Whilst there is extensive evidence on the indications and contraindcations in Medial UKA there is limited evidence on this topic in Lateral UKA. The aim of this study was to assess our experience of mobile lateral UKR and to look specifically at the effect of Contraindications on the outcome. Method. 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 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%). In total, 14 (4%) were for dislocation, of which 12 had no recurrence following insertion of a new bearing. In all, 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. Mobile (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. Younger age, heavier weight, high activity, and patellofemoral erosions did not detrimentally affect outcome, so should not be considered contraindications

The treatment of medial knee osteoarthritis (OA) in conjunction with anterior knee laxity is an issue of debate. Current treatment options include knee joint distraction, unicompartmental knee replacement (UKR) or high tibial osteotomy with anterior cruciate ligament (ACL) reconstruction or total knee replacement. Bone-conserving options are preferred for younger and active patients with intact lateral and patello-femoral compartment. However, still limited experience exists in the field of combining medial UKR and ACL reconstruction. The aim of this study is to retrospectively evaluate the results of combined fixed-bearing UKR and ACL reconstruction, specifically with regard to patient satisfaction, activity level, and postoperative functional outcomes. The hypothesis was that this represents a safe and viable procedure leading to improved stability and functional outcome in patients affected by isolated unicompartmental OA and concomitant ACL deficiency. Fourteen patients with ACL deficiency and concomitant medial compartment symptomatic osteoarthritis were treated from 2006 to 2010. Twelve of them were followed up for an average time of 7.8 year (range 6–10 years). Assessment included Knee Osteoarthritis Outcome Score (KOOS), Oxford Knee score (OKS), American Knee Society scores (AKSS), WOMAC index of osteoarthritis, Tegner activity level, objective examination including instrumented laxity test with KT-1000 arthrometer and standard X-rays. Wilcoxon test was utilized to compare the pre-operative and follow-up status. Differences with a p value <0.05 were considered statistically significant. KOOS score, OKS, WOMAC index and the AKSS improved significantly at follow-up (p < 0.05). There was no clinical evidence of instability in any of the knees as evaluated with clinical an instrumented laxity testing (p < 0.05). No pathologic radiolucent lines were observed around the components. In one patient a total knee prosthesis was implanted due to the progression of signs of osteoarthritis in the lateral compartment 3 years after primary surgery. UKR combined with ACL reconstruction is a valid therapeutic option for young and active patients with a primary ACL injury who develop secondary OA and confirms subjective and objective clinical improvement up to 8 years after surgery

Introduction. The commonest causes of revision of Unicompartmental Knee Replacement (UKR) in National Registers are loosening and pain. Cementless UKR was introduced to address loosening and was found, in small randomised studies, to have better radiographic fixation than Cemented UKR. Although non-significant these studies also suggested the clinical outcome was better with cementless. The aim of this larger study was to compare the pain and function of cementless and cemented UKR at five years. Methods. 263 Cemented and 266 Cementless UKR of identical design, implanted by four high volume surgeons for the same indications, were reviewed by independent physiotherapists at five years. Revision, re-operation, Oxford Knee Score (OKS), American Knee Society score (AKSS) and EQ-5D were assessed. Two pain specific scores were also used: Pain Detect (PD) and Intermittent and Constant Osteoarthritis Pain (ICOAP). The pain scores were normalised onto a scale of 0 to 100 with 100 being the best. The cemented cohort was mainly implanted before the cementless, although there was considerable overlap. To explore whether differences were due to progressive improvement in surgical practice with time each cohort was divided into early and late subgroups. Results. Pre-operatively there were no differences between the devices in patient demographics or scores. At 5 years there were no differences in revision rate (0.8%), re-operation rate (2.2%) or medical complication rate (4%). The Cementless had significantly (p<0.05) better OKS (43 v 41), AKSS and EQ5D. There were significantly (p=0.03) fewer cementless cases with unexplained pain (2.3% v 6%). The cementless had significantly (p<0.002), less ‘strongest’ (84 v 76) and ‘average’ (90 v 85) pain as assessed by PD and less chronic (97 v 92) and intermittent (93 v 86) pain as assessed by ICOAP. Subgroup analysis found no significant differences in outcome between the early and late subgroups within the cohorts, whereas there were significant differences in outcomes between the late subgroup of the cemented cohort and the early subgroup of the cementless cohort. Discussion and Conclusion. Almost all outcome scores were significantly better following cementless compared to cemented UKR, suggesting that the cementless is better than cemented. However, as the cemented cases were mainly implanted before the cementless, it could be the difference was due to other factors, such as surgical technique or rehabilitation, that improved with time. This is unlikely to be the case as there were no differences between the early and late subgroups within the cohorts whereas there were differences between the late subgroup of the cemented cohort and the early subgroup of the cementless cohort which were implanted at a similar time. Although the functional scores following cementless are significantly better than cemented, the differences are similar to or smaller than the minimally clinical important difference (MCID) for these scores. In contrast there is significantly less pain following the cementless and the differences tended to be greater than the MCID. This suggests that Cementless UKR is associated with appreciably less pain and slightly better function than Cemented UKR. For figures, tables, or references, please contact authors directly

Introduction. The number of medial unicompartmental knee replacements (UKR) performed for arthritis has increased and as such, revisions to total knee replacement (TKR) is increasing. Previous studies have investigated survivorship of UKR to TKR revision and functional outcomes compared to TKR to TKR revision, but have failed to detail the surgical considerations involved in these revisions. Our objectives are to investigate the detailed surgical considerations involved in UKR to TKR revisions. Methods. This study is a retrospective comparative analysis of a prospectively collected database. From 2005 to 2017, 61 revisions of UKR to TKR were completed at a single center. Our inclusion criteria included: revision of UKR to TKR or TKR to TKR with minimum 1 year follow-up. Our exclusion criteria include: single component and liner revisions and revision for infection. The 61 UKR to TKR revisions were matched 2:1 with respect to age, ASA and BMI to a group of 122 TKR to TKR revisions. The following data was collected: indication for and time to revision, operative skin to skin surgical time, the use of specialized equipment (augment size/location, stem use), intraoperative and postoperative complications, re-operations and outcome scores (WOMAC, Oxford 12, SF 12, satisfaction score). Results. There were no statistical differences between the demographic data from either group (age, BMI, ASA, sex and follow-up range). Progression of arthritis was the most common reason for revision in the UKR to TKR group (30/61, 49%, p < 0.001). Aseptic loosening was the most common reason for revision in the TKR to TKR group (73/122, 60%,) and was encountered more often than aseptic loosening in the UKR to TKR group (21/61, 35%, p=0.002). The operative time was longer in the TKR to TKR group (77 vs 112 min, p< 0.001). Femoral augmentation was required for one 1/61 (1.64%) UNI and 92/122 (75%) TKR revisions, respectively (p <0.001). Medial tibial augments were required in 9/61 (14.8%) of the UKR to TKR group while 12/122 (10%) and 10/122 (8%) of the TKR to TKR group required medial and full tibial augments, respectively (p=0.7). UKR to TKR revisions never required femoral stems while 120/122 (98%) of the TKR to TKR group did (p<0.001). Tibial stems were required in 19/61 (31%) and 122/122 (100%) of UKR to TKR and TKR to TKR groups, respectively (p<0.001). There was no statistical difference in the overall complication rate of either group (15% in the UKR to TKR group and 13% in the TKR to TKR group, p = 0.9). Stiffness was a common complication of UKR to TKR and TKR to TKR re-revisions at 2/61 (3%), and 6/122 (5%), respectively (P = 0.6). Aseptic loosening was also a common complication of in both groups at 2/61 (3%) and 4/122 (3%) in the UKR to TKR and TKR to TKR groups, respectively (p = 0.7). There was no statistical difference in the re-operation rate of either group (10% in the UKR to TKR group and 7% in the TKR to TKR group, P = 1). Stiffness was the most common indication for re-operation in the UKR to TKR group (2/61, 3%, p = 0.11) while aseptic loosening was the most common in the TKR to TKR group (4/122, 3.2%, p = 0.7). The survivorship in the UKR to TKR was 93% and 90% at 5 and 9 years, respectively. The survivorship in the TKR to TKR group was 95% and 94% at 5 and 9 years, respectively, which was not statistically different from the UKR group. Discussion. The most common reason for revision was different between the two groups (p < 0.001) while the skin to skin time was longer in the TKR to TKR group. In terms of revision components, femoral stems were never required in the UKR to TKR group while tibial stems were only required in 31%. Similarly, medial tibial augments were only required in 15% of the UKR to TKR group. While the surgeon must be prepared to use augmentation and stems in UKR to TKR revisions, they can often be completed with primary components and therefor will have an overall lower cost to the health care system. Furthermore, the survivorship and re-operation between the two groups was similar which supports previous literature. The results of this study will allow for a more in-depth cost-effectiveness analysis of UKR to TKR vs TKR to TKR in arthroplasty decision making. Unicompartmental knee replacements should be considered in appropriate patients to decrease the lifetime cost of arthroplasty intervention and potentially decrease the burden on the health care system. For figures, tables, or references, please contact authors directly