Aim: The aim of this study was to evaluate the functional results and ease of performing revision surgery after a primary unicompartmental arthroplasty versus primary total knee arthroplasty. Method: 114 revision TKRs had data collected prospectively as part of our unit’s Knee Database. 45 were revisions of UKR’s and 79 revisions of TKR’s. This data included Bristol Knee Scores (BKS), reason for revision, use of implant augments and bone graft. Measurements were also made of the ability to restore joint-line after revision. Results: In both groups there was a significant improvement in BKS post-operatively. In the UKR group the commonest reason for revision was progression of disease, while in the TKR group it was aseptic loosening. Bone graft was required in significantly fewer UKR cases (20% vs 40%, P< 0.05). Distal femoral augments were used in 45% of the TKR revisions but in none of the revisions from UKR. The joint line was elevated in a significantly higher proportion of revision from TKR cases versus revision from UKR cases (P< 0.001). Revisions from UKR had higher Total BKS and Functional BKS score than revisions from TKR. Conclusions: Revision TKR after a primary UKR requires less bone graft, fewer augments, restores the joint line more frequently and gives improved functional results over revisions after primary TKR

Introduction. There has been a recent major increase in the use of unicompartmental knee replacement (UKR) but few studies exist comparing its long term efficiency with total knee replacement (TKR). Method. Ethical approval was obtained. Between 1989 and 1992 a randomised prospective study was undertaken in which 102 cases adjudged suitable for UKR were allocated to receive either a St Georg Sled UKR or a Kinematic Modular TKR. Both cohorts had a median age of 68 and a similar sex distribution and preoperative knee score. Regular follow up has been maintained. As reported the early results favoured UKR. All cases have now been assessed after a minimum of 10 years using modified WOMAC, Oxford and Bristol Knee Scores (BKS) as well as radiographs. Results. 28 cases had died with their knees known to be intact, 2 cases were untraceable. 33 knees in each group were reviewed. 3 in each group had been revised, no impending failures were identified on the radiographs. At 10 years the UKR group had better Oxford and WOMAC scores as well as significantly more excellent results (19:14) and fewer fair and poor results on the BKS. Both groups averaged over 105′ of flexion but 61% of the UKR and only 15% of the TKR group had 120′ or more of flexion. Conclusion. The faster rehabilitation and better early results with UKR are maintained for 10 years with few failures occurring. The average BKS of the UKR group only fell from 91 to 88 between 5 and 10 years suggesting minimal evidence of functional deterioration in either the prosthesis or the remainder of the joint

A cementless version of the Phase 3 Oxford UKR has been used in our unit since mid 2005. We report on our early experience with this implant, reviewing the National Joint Register (NJR) data on UKR in general and Oxford specifically, with respect to six month Oxford Knee Scores (OKS) and revision rates. A single surgeon review of 170 cementless and 132 cemented cases revealed a mean 6 month OKS of 41.5 and revision rate per 100 component years of 0 for the cementless group, and mean 6 month OKS of 40.0 and revision rate of 1.05 for the cemented group. The equivalent results from the NJR for UKR are 38.75 and 1.44. Radiological review of the 170 cementless cases showed no concerns regarding subsidence and encouraging features with respect to ingrowth. There were no radiolucent lines at one year. The cementless components appear to be strongly osteophilic. The NZ experience with the Cementless Oxford is single centre, comprising a small number of high volume surgeons, and the OKS and revision rates are presented. To date, there have been 346 cases with a revision rate per 100 component years of 0.30. In summary, single surgeon and national early experience of the Cementless Oxford UKR from clinical and radiological evidence is encouraging

Introduction. Cementless unicondylar knee implants are intended to offer surgeons the potential of a faster and less invasive surgery experience in comparison to cemented procedures. However, initial 8 week fixation with micromotion less than 150µm is crucial to their survivorship1 to avoid loosening2. Methods. Test methods by Davignon et al3 for micromotion were used to assess fixation of the MAKO UKR Tritanium (MAKO) (Stryker, NJ) and the Oxford Cementless UKR (Biomet, IN). Data was analyzed to determine the activities of daily living (ADL) that generate the highest forces and displacements4, 5. Stair ascent with 3.2BW compressive posterior tibial load was identified to be an ADL which may cause the most micromotion5. Based on previous studies6, 10,000 cycles was set as the run-time. The AP and IE profiles were scaled back to 60% for the Oxford samples to prevent the congruent insert from dislocating. A four-axis test machine (MTS, MN) was used. The largest size UKRs were prepared per manufacturer's surgical technique. Baseplates were inserted into Sawbones (Pacific Research, WA) blocks1. Femoral components were cemented to arbors. The medial compartment was tested, and the lateral implants were attached to balance the loads. Five tests were conducted for each implant with a new Sawbones and insert for each test per the test method3. The ARAMIS System (GOM, Germany) was used to measure relative motion between the baseplate and the Sawbones at three anteromedial locations (Fig. 1). Peak-Peak (P-P) micromotion was calculated in the compressive and A/P directions. FEA studies replicating the most extreme static loading positions for MAKO micromotion were conducted to compare with the physical test results using ANSYS14.5 (ANSYS, PA). Results. MAKO had a maximum axial motion of 36µm (SD=5.28) at gage 2. Oxford had an average gage 1 axial and A/P motion of 109µm (SD=31.77) and 44mm (SD=28.62) respectively (Fig. 2A). FEA correlated well with the MAKO results (Fig. 2B). Discussion. Oxford has been shown to have microseparation in lab testing conditions and the studies by Liddle et al7 under the same stair ascent activity. However, based on our results, MAKO and Oxford are both expected to allow interdigitation for long-term fixation. The Sawbones model does not allow plastic deformation in axial compression and subsequent stabilization, which could allow Oxford to achieve the fixation and clinical success shown in outcome studies. A/P prep for Oxford allows for 3mm gap between the keel and the bone which may explain the variability in the X direction. Distal flatness of the Oxford varied by 0.5mm as shown on Figure 3. The flatness of the boundary of the implant may explain the elevated micromotion observed for Oxford implant. Future studies will concentrate on FEA of manufactured Oxford components to take into account the geometric discrepancies from a perfectly flat model. Davignon et al3 and this study show that the MAKO is expected to achieve long-term fixation in the initial fixation stages similar to the clinically successful Oxford cementless UKR

NavioPFS™ unicondylar knee replacement (UKR) system combines CT-free planning and navigation with robotically assisted bone preparation. In the planning procedure, all relevant anatomic information is collected under navigation, either directly with the point probe or by kinematic manipulation. In addition to key anatomic landmarks and the maps of the articulating surfaces of the femur and tibia, kinematic assessment of the joint laxity is performed. Relative positions of femur and tibia are collected through the flexion/extension range, with the pressure applied to fully stretch the collateral ligament on the operative side. The planning procedure involves three stages: (1) the implant sizing and initial placement,(2) balancing of the gap on the operative side and (3) evaluating the contact points for the recorded flexion data and the planned placement of implants. In the gap balancing stage, the implants are repositioned until they allow for a positive gap, preferably uniform, throughout the entire range of flexion. UKR was planned and prepared on six cadaver knees with the help of NavioPFS system. All knees were normal without any signs of osteoarthritis. Two surgeons have performed medial UKR (4+2), and the bones were prepared using the NavioPFS handheld robotic tool. Postoperatively, we have re-used the data collected during the planning procedure to compare the kinematic (gap balancing) performance of the used implant with three different commercial implant designs. All implants were placed in the orientation recommended by the respective manufacturer, sized to best fit the original bone geometry, and repositioned optimally balance the gap curve through the entire flexion range, without any negative gaps (overlaps). Since these were nonarthritic cadaver knees, the intent was to restore the original preoperative varus/valgus in neutral (zero) flexion. The three implant designs demonstrated variable degree of capability to uniformly balance the knee gap over the entire range of flexion. The first implant (A) required a gap larger than 2 mm in one case out of six, the second (B) was capable of producing the positive gap curve under 2mm of gap in all six cases, and the third (C) required a gap larger than 2 mm in 3 (50%) of cases. All three designs exhibit the reduced gap space in mid (30°–90°) flexion. Despite the best attempts, the artificial implants do not fully replicate the healthy knee kinematics. This is manifested by increased tightness in the mid flexion. In order to balance the gap in mid flexion, additional laxity has to be allowed in full flexion, extension, or both. NavioPFS allows for patient specific planning that takes into account this information, only available intraoperatively. This kind of evaluation on a patient specific basis is a very important planning tool and it allows the insight on the implant performance in mid flexion, typically not available using conventional planning techniques. It can also help in improving kinematic performance of future implant designs

Purpose. Unicompartmental knee replacement (UKR) is an established, bone preserving surgical treatment option for medial compartment osteoarthritis (OA). Early revision rates appear consistently higher than those of total knee replacement (TKR) in many case series and consistently in national registry data. Failure with progression of OA in the lateral compartment has been attributed, in part, to surgical technical errors. In this study we used navigation assisted surgery to investigate the effects of improper sizing of the mobile bearing and malrotation of the tibial component on alignment and lateral compartment loading. Method. A total of eight fresh frozen cadaveric lower limbs were used in the study. After thawing overnight, a Brainlab navigation system with an Oxford (Biomet, Inc) medial UKR module was used to capture the native knee anatomy and alignment using a digitizing probe. Following registration, the case was performed with navigation verified neutral cuts and an ideal insert size was selected to serve as a baseline. The bearing thickness was subsequently increased by 2 mm increments to simulate progressive medial joint overstuffing. Excessive tibial internal rotation of 12 was also simulated at each of the intervals. Knee alignment in varus or valgus was recorded in real time for each surgical scenario with the knee in full extension and at 20 of flexion. Lateral compartment peak pressure was measured using a Tekscan pressure map. Results. Incremental overstuffing of the medial compartment with inserts of increasing thickness resulted in a progressive shift to more valgus knee alignment. Internally rotated sagittal cuts at 12 resulted in a further valgus shift for a given insert size. The valgus shift was detectable at full extension however it was more pronounced at 20 of flexion. Conclusion. The intentional technical errors of overstuffing and malrotation in UKR produced coronal valgus knee alignment and a greater load shift to the lateral compartment. These errors can be construed to contribute to the higher early failure rates associated with UKR when compared to TKR. Special care should be taken to ensure a neutral sagittal tibia cut and appropriate bearing selection. The Intra operative verification of knee alignment should be conducted at 20 of flexion where such errors will be easier for the surgeon to detect and rectify

Purpose. Patients with anterior cruciate ligament (ACL) deficiency and symptomatic medial compartment osteoarthritis (OA) present a challenge in management. These are often younger than typical primary OA patients and aspire to remain athletically active beyond simple ADLs. Combined ACL reconstruction and valgus tibial osteotomy (ACLHTO) is a well documented surgical option for patients deemed wither too young or too active for total knee arthroplasty. Unicompartmental knee arthroplasty (UKA) is an established surgical treatment for symptomatic medial osteoarthritis of the knee refractory to conservative management. A commonly cited contraindications is symptomatic ACL deficiency because of previous reports detailing premature failure through loosening of the tibial component. Improved results and endoscopic ACL reconstructive procedures have led to an enticing concept of combining ACL reconstruction with medial unicompartmental knee arthroplasty (ACLUKR) for those ACL-deficient medial osteoarthritic (OA) knees. We sought to compare the outcomes in 2 cohorts of patients who underwent either ACLHTO or ACLUKR for this clinical problem. Method. Patients presenting with symptomatic bone on bone medial compartment OA and concomitant ACL deficiency (clinical or asymptomatic) were evaluated for surgery after exhausting non operative management. Patients who were under 40 or had plans to return to high impact loading sports and/or who had more moderate OA were offered combined ACL – medial opening wedge tibia osteotomy as a surgical procedure of choice. Patients were considered for combined ACL Oxford replacement if they were primarily seeking pain relief and were not engaged or aspiring to return to high impact or pivoting sports. All cases but one were concurrent ACL with either HTO or UKR with autogenous hamstring grafts used in all but 2 cases. Results. Thirty of 34 consecutive cases were available for follow-up for a rate of 88%. The median ages for 14 cases of ACLUKR was 51 (range 43 60) whereas 16 patients with ACLHTO had median age 43.4 (range 32 −59). Median FU was 4.65 yrs with minimum 2 year follow up (range 2–8.3). Three of the cases were revision ACL cases all from previous Gore-Tex reconstructions. All but the first patient had concomitant ACL and Oxford unicompartmental knee replacement at 1 surgical sitting and are the subject of this report. The first patient had an autogenous patella bone tendon bone graft performed 6 months prior to the UKA. There were similar change scores for patients in both groups. For ACLUKR, WOMAC pain improvements from 48.1 10.2 SD preoperatively to 79.0 17 SD postop. For ACLHTO, WOMAC improvements from 55.1 13.2 SD preoperatively to 85.0 17 SD postop. To date there have been no cases of infection or bearing dislocation in the ACLUKR group. One patient in the ACLHTO group was revised to TKR for ongoing pain and postoperative flexion contracture. Patient activities ranged from ambulation to vigorous hiking, tennis, and downhill skiing in the UKR group whereas a few in the ACLHTO group were also running mid distances. Overall satisfaction was similar in both groups. Conclusion. ACL reconstruction can safely be combined with medial UKR. The procedure has been used in younger patients with a view toward bone preservation while anticipating need for future revision. Both cohorts showed similar improvements and can be considered. The choice should be geared toward patient athletic demand. While short term results are encouraging though longer term data are necessary to thoroughly evaluate the role of this procedure in patients with medial compartment osteoarthritis and ACL deficiency

Introduction. Unicompartmental Knee Replacement (UKR) is an appealing alternative to Total Knee Replacement (TKR) when the patient has isolated compartment osteoarthritis (OA). A common observation post-operatively is radiolucency between the tibial tray wall and the bone. In addition, some patients complain of persistent pain following implantation with a UKR; this may be related to elevated bone strains in the tibia. The aim of this study was to investigate the mechanical environment of the tibia bone adjacent to the tray wall, following UKR, to determine whether this region of bone resorbs, and how altering the mechanical environment affects tibia strains. Materials and methods. A finite element (FE) model of a cadaver tibia implanted with an Oxford UKR was used in this study, based on a validated model. A single static load, measured in-vivo during a step-up activity was used. There was a 1 mm layer of cement surrounding the keel in the cemented UKR, and the cement filled the cement pocket. In accordance with the operating procedure, no cement was used between the tray wall and bone. For the cementless UKR a layer of titanium filled the cement pocket. An intact tibia was used to compare to the cemented and cementless UKR implanted tibiae. The tibia was sectioned by the tray wall, defining the radiolucency zone (parallel to the vertical tray wall, 2 mm wide with a volume of 782.5 mm. 3. ), corresponding to the region on screened x-rays where radiolucencies are observed. Contact mechanics algorithms were used between all contacting surfaces; bonded contact was also introduced between the tray wall and adjacent bone, simulating a mechanical tie between them. Strain energy density (SED), was compared between the intact and implanted tibia for the radiolucency zone. Equivalent strains were compared on the proximal tibia between the intact and implanted tibia models. Forty patients (20 cemented, 20 cementless) who had undergone UKR were randomly selected from a database, and assessed for radiolucency. Results. The SED in the radiolucency zone was 80% lower in the cemented and cementless tibia, compared to the intact tibia, without a mechanical tie between the tibial tray wall and adjacent bone. When a mechanical tie was introduced the SED in the radiolucency zone was 35% higher in the cemented and cementless tibia, compared to the intact tibia. The strain on the proximal tibia was reduced by 20% when a mechanical tie was used between the tray wall and adjacent bone. Radiolucency at the tray wall was observed in all forty radiographs examined. Discussion. This work has presented a static snapshot of the load being carried through the proximal tibia following implantation with an Oxford UKR. It has been shown that by introducing a mechanical tie between the tibial tray wall and the adjacent bone, the SED in the region observed to have radiolucency is increased; this has the potential of reducing the likelihood of a radiolucency occurring in that region. Moreover, the strain observed in the proximal tibia was reduced when a mechanical tie was introduced, which may reduce the incidence of pain following implantation with a UKR. It is recommended that integration between the bone and the tray wall is important for UKR

Introduction: The Oxford unicompartmental knee replacement (UKR) use in the lateral compartment has been associated with a reduced flexion range and increased medial compartment pain than seen with its medial counterpart due to, in part, the inadequacy of a flat tibial tray replacing the domed anatomy of the lateral tibia. A new design incorporating a domed tibial component and a biconcave meniscal bearing has been developed to overcome these problems. This study reports a clinical comparison of new and old establishing whether this modified implant has maintained the established normal kinematic profile of the Oxford UKR. Method: Patients undergoing lateral UKR for OA were recruited for the study. Fifty one patients who underwent UKR with the domed design were compared to 60 patients who had lateral UKR with a flat inferior bearing surface. Kinematic evaluation was performed on 3 equal subgroups (n = 20); Group 1-Normal volunteer knees, Group 2-Flat Oxford Lateral UKR’s and Group 3-Domed Oxford Lateral UKR’s. The sagittal plane kinematics of each knee was assessed using videofluoroscopic analysis whilst performing a step up and deep knee bend activity. The fluoroscopic images were recorded digitally, corrected for distortion using a global correction method and analysed using specially developed software to identify the anatomical landmarks needed to determine the Patella Tendon Angle (PTA) (the angle the patella tendon and the tibial axis). Knee kinematics were assessed by analysing the movement of the femur relative to the tibia using the PTA. Results: PTA/KFA values, for both devices, from extension to flexion did not show any significant difference in PTA values in comparison to the normals as measured by a 3-way ANOVA. The Domed implant achieved higher maximal active flexion during the lunge exercise than those with a flat implant. Only 33% of the flat UKR’s achieved KFA of 130° or more under load whilst performing a lunge, compared with 75% of domed UKR’s and 90% of normal knees. No flat UKR achieved a KFA of 140° or more, yet 50% of all domed UKR’s did, as did 60% of all normal knees. Conclusions: There was no significant difference in sagittal plane kinematics of the domed and flat Oxford UKR’s. Both designs had favorable kinematic profiles closely resembling that of the normal knee, suggesting normal function of the cruciate mechanism. The domed knees had a greater range of motion under load compared to the flats, approaching levels seen with the normal knee, suggesting that limited flexion for the flat plateau results from over tightening in high flexion and that this is corrected with the domed plateau. Problems with the second generation of lateral Oxford UKA have been rectified by a new bi-concave bearing without losing bearing stability and normal kinematics

Introduction. The authors performed a short term prospective study of unicompartmental knee replacement (UKR) associated to patella-femoral arthroplasty (PFA) for the treatment of bicompartmental symptomatic knee arthritis. At the latest follow-up all the implants were matched to a similar computer assisted Total Knee Replacements (CAS-TKR) group implanted for the same indications. Hypothesis of the study was that this bicompartimental implants could achieve comparable outcomes to TKR with a more conservative surgery and a higher joint function. Materials and Methods. 19 cases of anteriomedial (12) or anterolateral (7) arthritis in 19 stable knees were prospectively involved in the study. All the knees underwent to a selective reconstruction using simultaneously both UKR and PFR using the same surgical technique. All bicompartmental implants were performed by the same surgeon. Surgical time, hospital staying and all intra and post operative complications were registered. At a minimum follow-up of 20 months, every single case was marched to a similar case where had been implanted a computer assisted cruciate retaining TKR. Criteria of matching were: sex, age, pre-operative range of motion and arthritis grade. In both the groups all the cases were assessed clinically using WOMAC, KKS and GIUM scores. All the knees were radiologically investigated using the same radiological protocol. Results. Intra operatively we did not registered any complication. No revision in both groups. The mean surgical time was 86 minutes (range: 78–121) in UKR+PFR group and 81 minutes (range: 71–112) in CAS-TKR group. There were no statistical significant differences in the hospital stay. No statistically significant difference was seen for the Knee Society, Functional and GIUM scores between the 2 groups. Statistically significant better WOMAC Function/Stiffness indexes were registered for the UKR+PFR group. CAS-TKR implants achieved a statistically better aligned mechanical axes. Conclusions. The results of this prospective short term prospective study suggest that UKR+PFR implant is a viable option for bicompartmental anteromedial arthritis at least as well as TKR but maintaining an higher level of function

Background. The reported outcomes of unicompartmental knee replacement (UKR) for spontaneous osteonecrosis of the knee (SPONK) often derive from small series with an average followup of 5 years, enabling to generate meaningful conclusions. Therefore, we determined the long-term functional results and the 10-years survivorship of the implant in all patients with advanced SPONK of the medial tibio-femoral compartment treated with a unicompartmental knee arthroplasty at our institute. Methods. We retrospectively evaluated 84 consecutive patients with late stage SPONK. All patients received a pre-operative MRI to confirm the diagnosis, to exclude any metaphyseal involvement and to assess the absence of significative degenerative changes in the lateral and PF compartment. Mean age at surgery was 66 years and mean body mass index (BMI) was 28.9. In all cases, SPONK involved the medial compartment; in 77 cases the medial femoral condyle (MFC) was involved, while in 7 cases the pathology site was the medial tibial plateau (MTP). Radiological evaluation was conducted by 3 different radiologists and clinical evaluation according to KSS and WOMAC score was performed by 3 fellows from outside institutions, with no previous clinical contact with the patients, at a mean followup of 98 months. Results. We found a significant improvement in VAS score for residual pain self-assessment and maximum knee flexion (p<0.0001). The 10-year Kaplan-Meier survivorship with revision for any reason as endpoint was 89%. Mean results at final observation point for global KSS and WOMAC score were 87.1 (range 45–100; standard deviation 13.8) and 12 (range 0–44; standard deviation 10.3), respectively. No patient had significant radiographic signs of osteoarthritis progression in the lateral compartment or in the patello-femoral compartment at final evaluation. Conclusions. Our findings suggest that medial UKR performed for late stage SPONK of the medial tibio-femoral compartment in selected patients provides satisfactory long term clinical and radiographical results, with a 10-years Kaplan-Meier survivorship of the implant of 89%

Introduction

Precision Freehand Sculpting(PFS), is a hand-held semi-active robotic technology for bone shaping that works within the surgical navigation framework. PFS can alternate between two control modes – one based on control of exposure of the cutting bur (“Exposure Control”) and another based on the control of the speed of the cutting bur (“Speed Control”). In this study we evaluate the performance of PFS in preparing the femoral bone surface for unicondylar knee replacement (UKR).

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

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

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

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

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

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. 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

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