Aims. Treatment of end-stage anteromedial osteoarthritis (AMOA) of the knee is commonly approached using one of two surgical strategies: medial unicompartmental knee arthroplasty (UKA) or total knee arthroplasty (TKA). In this study we aim to investigate if there is any difference in outcome for patients undergoing UKA or TKA, when treated by high-volume surgeons, in high-volume centres, using two different clinical guidelines. The two strategies are ‘UKA whenever possible’ vs TKA for all patients with AMOA. Methods. A total of 501 consecutive AMOA patients (301 UKA) operated on between 2013 to 2016 in two high-volume centres were included. Centre One employed clinical guidelines for the treatment of AMOA allowing either UKA or TKA, but encouraged UKA wherever possible. Centre Two used clinical guidelines that treated all patients with a TKA, regardless of wear pattern. TKA patients were included if they had isolated AMOA on preoperative radiographs. Data were collected from both centres’ local databases. The primary outcome measure was change in Oxford Knee Score (OKS), and the proportion of patients achieving the patient-acceptable symptom state (PASS) at one-year follow-up. The data were 1:1 propensity score matched before regression models were used to investigate potential differences. Results. The matched cohort included 400 patients (mean age 67 years (SD 9.55), 213 (53%) female, mean BMI 30.2 kg/m. 2. , 337 (84%) American Society of Anesthesiologists grade ≤ 2). We found a mean adjusted difference in change score of 3.02 points (95% confidence interval (CI) 1.41 to 4.63; p < 0.001) and a significantly larger likeliness of achieving PASS (odds ratio 3.67 (95% CI 1.73 to 8.45); p = 0.001) both in favour of the UKA strategy. Conclusion. UKA and TKA are both good strategies for treating end-stage AMOA. However, when compared as a strategy, UKA achieved larger improvements in OKS, and were more likely to reach the PASS value at one-year follow-up. Cite this article: Bone Jt Open 2022;3(5):441–447

A sibling risk study that shows a statistically significant increase in risk for anteromedial osteoarthritis of the knee. Anteromedial osteoarthritis is a distinct phenotype of osteoarthritis. Previous studies have shown a genetic aetiology to both hip and knee osteoarthritis. The aim of this study was to determine the sibling risk of antero-medial osteoarthritis of the knee. We conducted a retrospective cohort study of 132 probands with primary anteromedial osteoarthritis, who had undergone unicompartmental arthroplasty. Sibling were identified as having symptomatic knee problems by postal Oxford Knee Score (OKS). A positive OKS was defined as an OKS+/− 2SD of the mean of the proband group. Sibling spouses were used as controls. Those siblings & spouses that were symptomatic from the OKS were invited to undergo Knee X-rays, to look for radiological signs of osteoarthritis. Osteoarthritis was diagnosed as greater than Grade II on the Kell-gren Lawrence classification. The pattern of disease was noted and it was considered if the sibling were suitable for a unicompartmental knee arthroplasty. The prevalence and sibling risk of anteromedial osteoarthritis was determined using a randomly selected single sibling per proband family. The prevalence was determined in the 103 single proband sibling pairs. There was a statistically significant risk within the sibling group P= 0.024 using the Chi square test. The relative risk of anteromedial osteoarthritis was. 3.21(95% CI 1.08 to 9.17). Genetic factors play a major role in the development of anteromedial osteoarthritis

Introduction: This study explores whether modern magnetic resonance imaging (MRI) with improved cartilage sequencing is able to show a more detailed view of anteromedial osteoarthritis of the knee (AMOA). Preoperative assessment of patients and selection of intervention is very important and preoperative imaging forms an integral part of this. Modern MRI technology may allow us to visualize in great detail the structures and cartilage within the knee, providing a better understanding of the pathoanatomy of AMOA. This will be useful in preoperative assessment and surgical management of patients. Methods: 50 patients with a radiographic diagnosis of anteromedial osteoarthritis of the knee and had been listed for unicompartmental knee arthroplasty (UKA) had MRI as part of their pre-op workup. At operation all were deemed suitable for UKA using the current Oxford indications. The image sequences were coronal, axial and sagittal with a predetermined cartilage protocol. The state of the ACL, cartilage wear location and pattern, presence of osteophytes and subchondral high signal were assessed. Results: All the ACLs were visualized and in continuity, however 40% showed intrasubstance high signal. 100% of medial compartments showed full thickness anteromedial loss with preservation of the posteromedial cartilage. When present, the meniscus was extruded in 96% of cases. 90% of lateral compartments were normal and none had full thickness cartilage loss. However 10% showed high signal in the tibial plateau. There was a highly reproducible pattern of osteophyte formation; 94% posteromedial and posterolateral aspect of medial femoral condyle; 90% medial tibial; 80% medial femoral and 84% lateral intercondylar notch. Discussion: This study maps the pattern of anteromedial osteoarthritis using modern MRI techniques. This has importance in determining preoperative indications (preservation of ACL and posteromedial cartilage); surgical technique (determine pattern of osteophytes requiring resection) and potentially important for long-term outcome (early lateral compartment changes)

Introduction: This study explores whether modern magnetic resonance imaging (MRI) with improved cartilage sequencing is able to show a more detailed view of antero-medial osteoarthritis of the knee (AMOA) than previously, so enabling a radiographic description of this common phenotype of disease. Modern MRI technology allows us to visualize in great detail the structures and cartilage within the knee, providing a better understanding of the pathoanatomy of AMOA. This description of the end stage of disease is useful as a baseline when investigating the progression of arthritis through the knee. Preoperative assessment of patients and selection of intervention is very important and preoperative imaging forms an integral part of this. This will also be useful in preoperative assessment and surgical management of patients. Methods: 50 patients with a radiographic diagnosis of anteromedial osteoarthritis of the knee and had been listed for unicompartmental knee arthroplasty (UKA) had MRI as part of their pre-op workup. At operation all were deemed suitable for UKA using the current Oxford indications. The image sequences were coronal, axial and sagittal with a predetermined cartilage protocol. The state of the ACL, cartilage wear degree and location, presence and pattern of osteophytes, meniscal anatomy and subchondral high signal were assessed. Results: All the ACLs were visualized and in continuity, however 40% showed intrasubstance high signal. 100% of medial compartments showed full thickness anteromedial loss with preservation of the posteromedial cartilage. When present, the meniscus was extruded in 75% of cases. 90% of lateral compartments were normal and none had full thickness cartilage loss. However 10% showed high signal in the tibial plateau. There was a highly reproducible pattern of osteophyte formation; 94% posteromedial and posterolateral aspect of medial femoral condyle; 90% medial tibial; 80% medial femoral and 84% lateral intercondylar notch. Discussion: This study maps the pattern of anteromedial osteoarthritis using modern MRI techniques. This creates a baseline description of disease which is useful when investigating disease progression. This also has importance in determining preoperative indications (preservation of ACL and posteromedial cartilage); surgical technique (determine pattern of osteophytes requiring resection) and potentially important for long-term outcome (early lateral compartment changes)

Anteromedial Osteoarthritis of the Knee (AMOA) is a distinct phenotype of OA. Within this pattern of disease, the anterior third of the medial tibial plateau exhibits full thickness cartilage loss. The middle third has damaged partial thickness cartilage, and the posterior third has retained cartilage, which is seen on macroscopic visual assessment to be normal. This study investigates the molecular features of progressive severities of cartilage damage within this phenotype. Ten medial tibial plateau specimens were collected from patients undergoing unicompartmental knee replacements. The cartilage within the area of macroscopic damage was divided into equal thirds: T1(most damaged), to T3 (least damaged). The area of macroscopically undamaged cartilage was taken as a 4th sample, N. The specimens were prepared for histological (Safranin-O) and immunohistochemical analysis (Type I and II Collagen, proliferation and apoptosis). Immunoassays were undertaken for Collagens I and II and GAG content. Real time PCR compared gene expression between areas T and N. There was a decrease in OARSI grade across the four areas, with progressively less fibrillation between areas T1, T2 and T3. Area N had a grade of 0 (normal). The GAG immunoassay showed decreased levels with increasing severity of cartilage damage (p< 0.0001). Proliferation and apoptosis, as expected, were increased in the more damaged areas. There was no significant difference in the Collagen II content or gene expression between areas. The Collagen I immunohistochemistry showed increased staining within chondrocyte pericellular areas in the undamaged region (N) and immunoassays showed that the Collagen I content of this macroscopically and histologically normal cartilage, was significantly higher than the damaged areas (p< 0.0001). Furthermore, real time PCR showed a significant increase in Collagen I expression in the macroscopically normal areas compared to the damaged areas (p=0.04). We conclude that in this phenotype the Collagen I increase, in areas of macroscopically and histologically normal cartilage, may represent very early changes of the cartilage matrix within the osteoarthritic disease process. This may be able to be used as an assay of early disease and as a therapeutic target for disease modification or treatment

Anteromedial osteoarthritis is a distinct phenotype of osteoarthritis. The arthritic lesion on the tibia is localised to the anteromedial quadrant with an intact ACL. Deficiency of the ACL leads to a progression to tricompartmental disease. Within the spectrum of intact ACL a varying degree of ligament damage is seen. Our aim was to correlate the progression of ACL damage to the geographical extent of disease and the degree of cartilage loss on the tibial plateau. We systematically digitally mapped 50 tibial plateau resection specimens from clinical photographs of patients undergoing unicompartmental arthroplasty, additionally the damage to their ACL was graded (0: normal, 1:synovium loss, 2:longitudinal splits). These images were imported into image analysis software. Accurate measurements were made of the dimensions of the specimen. Measurements included the AP distance to the anterior and posterior aspect of the lesion, and the distance to the start of the macroscopically non damaged cartilage. The areas of cartilage damage and full thickness loss were also recorded. The results were represented as a % of total area to account for variation in size of the resection specimens. We compared % of full thickness loss in patients with normal to those with damaged, but functionally intact ligaments. All specimens had a similar macroscopic appearance. A significant difference was seen with the progression of ACL damage and area of eburnation of bone. Using an unpaired t test, a significant difference in area of % full thickness cartilage loss (P=0.047) was seen between patients with a normal and longitudinal splits within their ACL. No correlation between the clinical status of the ACL and start or finish point of cartilage loss on the tibial plateau. We surmise that the progression from anteromedial to tricompartmental osteoarthritis of the knee may be related to the graduated damage of the ACL

Aim: To investigate the molecular features of progressive severities of cartilage damage, within the phenotype of Anteromedial Osteoarthritis of the Knee (AMOA). Methods: Ten medial tibial plateau specimens were collected from patients undergoing unicompartmental knee replacements. The cartilage within the area of macroscopic damage was divided into equal thirds: T1(most damaged), to T3 (least damaged). The area of macroscopically undamaged cartilage was taken as a 4th sample, N. The specimens were prepared for histological (Safranin-O and H& E staining) and immunohistochemical analysis (Type I and II Collagen, proliferation and apoptosis). Immunoassays were undertaken for Collagens I and II and GAG content. Real time PCR compared gene expression between areas T and N. Results: There was a decrease in OARSI grade across the four areas, with progressively less fibrillation between areas T1, T2 and T3. Area N had an OARSI grade of 0 (normal). The GAG immunoassay showed decreased levels with increasing severity of cartilage damage (ANOVA P< 0.0001). There was no significant difference in the Collagen II content or gene expression between areas. The Collagen I immunohistochemistry showed increased staining within chondrocyte pericellular areas in the undamaged region (N) and immunoassays showed that the Collagen I content of this macroscopically and histologically normal cartilage, was significantly higher than the damaged areas (ANOVA P< 0.0001). Furthermore, real time PCR showed that there was a significant difference in Collagen I expression between the damaged and macroscopically normal areas (p=0.04). Conclusion: In AMOA there are distinct areas, demonstrating progressive cartilage loss. We conclude that in this phenotype the Collagen I increase, in areas of macroscopically and histologically normal cartilage, may represent very early changes of the cartilage matrix within the osteoarthritic disease process. This may be able to be used as an assay of early disease and as a therapeutic target for disease modification or treatment

The aim of this study was to investigate the molecular features of progressive severities of cartilage damage, within the phenotype of Anteromedial Osteoarthritis of the Knee (AMOA). Ten medial tibial plateau specimens were collected from patients undergoing unicompartmental knee replacements. The cartilage within the area of macroscopic damage was divided into equal thirds: T1(most damaged), to T3 (least damaged). The area of macroscopically undamaged cartilage was taken as a 4th sample, N. The specimens were prepared for histological (Safranin-O and H& E staining) and immunohistochemical analysis (Type I and II Collagen). Immunoassays were undertaken for Collagens I and II and GAG content. Real time PCR compared gene expression between areas T and N. There was a decrease in OARSI grade across the four areas, with progressively less fibrillation between areas T1, T2 and T3. Area N had an OARSI grade of 0 (normal). The GAG immunoassay showed decreased levels with increasing severity of cartilage damage (ANOVA P< 0.0001). There was no significant difference in the Collagen II content or gene expression between areas. The Collagen I immunohistochemistry showed increased staining within chondrocyte territorial areas in the undamaged region (N) and immunoassays showed that the Collagen I content of this macroscopically and histologically normal cartilage, was significantly higher than the damaged areas (ANOVA P< 0.0001). Furthermore, real time PCR showed that there was a significant increase in Collagen I expression in the macroscopically normal areas (p=0.04). In AMOA there are distinct areas, demonstrating progressive cartilage loss. We conclude that in this phenotype the Collagen I increase, in areas of macroscopically and histologically normal cartilage, may represent very early changes of the cartilage matrix within the osteoarthritic disease process. This may be able to be used as an assay of early disease and as a therapeutic target for disease modification or treatment

Our aim was to investigate the molecular features of progressive severities of cartilage damage, within the phenotype of Anteromedial Gonarthrosis (AMG).

Ten medial tibial plateau specimens were collected from patients undergoing unicompartmental knee replacements. The cartilage within the area of macroscopic damage was divided into equal thirds: T1(most damaged), to T3 (least damaged). The area of macroscopically undamaged cartilage was taken as a 4th sample, N. The specimens were prepared for histological (Safranin-O and H& E staining) and immunohistochemical analysis (Type I and II Collagen, proliferation and apoptosis). Immunoassays were undertaken for Collagens I and II and GAG content. Real time PCR compared gene expression between areas T and N.

There was a decrease in OARSI grade across the four areas, with progressively less fibrillation between areas T1, T2 and T3. Area N had an OARSI grade of 0 (normal). The GAG immunoassay showed decreased levels with increasing severity of cartilage damage (p< 0.0001). There was no significant difference in the Collagen II content or gene expression between areas. The Collagen I immunohistochemistry showed increased staining within chondrocyte pericellular areas in the undamaged region (N) and immunoassays showed that the Collagen I content of this macroscopically and histologically normal cartilage, was significantly higher than the damaged areas (p< 0.0001). Furthermore, real time PCR showed a significant increase in Collagen I expression in the macroscopically normal areas compared to the damaged areas (p=0.04).

In AMG there are distinct areas, demonstrating progressive cartilage loss. We conclude that in this phenotype the Collagen I increase, in areas of macroscopically and histologically normal cartilage, may represent very early changes of the cartilage matrix within the osteoarthritic disease process. This may be able to be used as an assay of early disease and as a therapeutic target for disease modification or treatment.

Abstract. Background. Since 2012 we have routinely used the cementless Oxford medial unicompartmental knee arthroplasty (mUKA), with microplasty instrumentation, in patients with anteromedial osteoarthritis (AMOA) meeting modern indications. We report the 10-year survival of 1000 mUKA with minimum 4-year follow-up. Methods. National Joint Registry (NJR) surgeon reports were interrogated for each senior author to identify the first 1,000 mUKAs performed for osteoarthritis. A minimum of 4 years follow-up was required. There was no loss to follow-up. The NJR status of each knee was established. For each mUKA revision the indication and mechanism of failure was determined using local patient records. The 10-year implant survival was calculated using life-table analysis. Results. The 1,000 mUKA cohort represented 55% of all primary knee replacements in the period, with an average age of 67.7 years and a 54%/46% male/female split. There were 17 revisions (11 for arthritis progression, 4 infections, 1 dislocation and 1 aseptic loosening). The 10-year survival was 98% (44 at risk in 10th year). One patient sustained a periprosthetic fracture at 3 weeks, treated with buttress plate fixation. Discussion. This is the first detailed series reporting the long-term outcome of the cementless Oxford mUKA implanted using microplasty instrumentation. There was a low failure rate, with only one revision for aseptic loosening. Lateral progression was the commonest cause for revision, with an incidence of 1%. This report provides evidence that the combination of evidence-based indications, well-designed instrumentation and cementless fixation can provide excellent long-term survival for the Oxford mUKA in treating AMOA

The purpose of this study was to establish the long-term clinical outcome of the Oxford Medial Unicompartmental Knee Arthroplasty (UKA). Methods: A continuous series of 420 patients underwent medial Oxford UKA. Indications were anteromedial osteoarthritis with full thickness lateral compartment cartilage, a functioning anterior cruciate ligament and correctable varus deformity. Survival analysis with all cause revision as the endpoint was carried out for the entire group. At the time of this study 121 were still alive at 10 years and pre/post-operative 10-year clinical data had been prospectively recorded for them from which the AKS and HSS scores were calculated. Results: Seventeen patients required revision (4%) and the fifteen year survival rate was 94.3% (95% CI 85.6 - 100%). At ten years AKS and HSS scores were: AKSS (Knee) pre 30 / post 90, AKSS (Function): pre 42/ post 69 and HSS pre 56/ post 86. The differences were statistically significant (p< 0.01). Discussion and Conclusion: We conclude that providing careful patient selection is maintained, meniscal bearing medial unicompartmental knee arthroplasty has clinical and survival results comparable to modern total knee arthroplasty. The advantages of lower morbidity and earlier return to function, enhanced by the introduction of minimally invasive techniques may make this the treatment of choice for suitable patients with anteromedial osteoarthritis of the knee

Introduction: The use of the Oxford Phase 3 unicompartmental knee arthroplasty (UKA) in the treatment of anteromedial osteoarthritis of the knee in elderly patients is controversial. The aim of this study was to analyse the performance of patients 75 years of age or older after surgery with the Oxford Phase 3 prosthesis by a minimally invasive technique. Material and methods: Between January 1999 and September 2004, 128 Oxford Phase 3 prostheses were implanted by a single surgeon. Patients with a minimal follow up (FU) of one year were divided in two groups depending on age. (Group A less than 75 years, group B 75 years or more.) Loss to FU was documented. The pre and postoperative clinical outcome of the patient with the new implant was objectively evaluated by a visual analog pain and satisfaction score, the WOMAC Score, Oxford score, the Knee Society knee score and Knee Society function score. The range of motion (ROM) was documented. Results: Fourty-five patients were under the age of 75 (group A). Thirty patients were 75 or older (group B). In the second group 4 patients were lost to FU: two deceased and two due to severe illness. Mean age (range) in the first and second group was 67 (47–74 yrs) and 79 (76–87) years respectively. Both groups had a mean FU time of 29 months. In the preoperative scores there was a significant difference in the WOMAC function score (49.7 A vs 42.4 B), Knee Society knee score (51.2 A vs 45.5 B) and the Knee Society function score (51.7 A vs 41.4 B).The pre-operative ROM was 120.1 (A) vs 122.7 (B) degrees. Comparing the postoperative scores a significant difference was found in the Knee Society knee score (89.1 A vs 78.0 B) and in the WOMAC function score (77.8 A vs 74.0 B). The Oxford score and the postoperative VAS for pain and satisfaction were slightly in favour for the younger group, but did not differ significantly. The postoperative ROM was 126 degrees in both groups. Conclusions: This study shows that in both groups the scores are good to excellent but slightly in favour for the younger group of patients operated for anteromedial osteoarthritis using a minimally invasive approach. Patients’ satisfaction is high in both groups. The slight difference in scores may be due to the presence of comorbidity in the older patient. Although the follow up in this study is the shortterm we advocate the use of the Oxford Phase 3 prosthesis in the elderly patient. The minimally invasive technique will lead to better range of movement, a quicker recovery of the older patient with less risk of complications and will be in our opinion more cost-effective than total knee replacement

This is a study of the quality of outcome of the first 100 patients who received the Twin Peg Oxford Partial knee replacement; which has been designed with a 15 degree extra surface for contact in deep flexion, and two pins for more secure fixation. We measured the outcome in patients with anteromedial osteoarthritis at 2 years after implantation using patient perception outcome measures: the OKS (Oxford Knee Score) and a patient satisfaction questionnaire. We also measured range of motion, the AKS (American Knee Society Score-Objective), the AFS (American Knee Society Score-Functional), and carried out a radiological assessment. The results showed a mean OKS of 41, a mean AKS of 93, a mean AFS of 84, a mean range of motion of 130 degrees and a 97% satisfaction rate. Results were significantly better in male patients. There were no deaths, infections, dislocations, fractures or revisions. There were no radiolucent lines of 2 mms or more at the femoral bone-cement interfaces. The introduction of this new version of the Oxford knee shows excellent clinical and radiological results which are at least as good as those seen with the Phase 3 Oxford Partial knee replacement. Small adjustments were made to the minimally invasive approach: a reduced invasive incision for ease of implantation. For those surgeons who are concerned over the risks of femoral loosening with the Phase 3 implant, or desire an improved surface area of contact at high angles of flexion, this Twin Peg Oxford Partial knee replacement offers an excellent alternative

Enhanced appreciation of normal knee kinematics and the inability to replicate these in the replaced total knee has led to increased enthusiasm for partial knee arthroplasty by some. These arthroplasties more closely replicate normal kinematics since they inherently preserve the anterior cruciate ligament (ACL). Indications for medial UKA are: anteromedial osteoarthritis with an intact ACL, posterior cruciate ligament, and medial collateral ligament (MCL), full thickness cartilage loss, and correctable deformity demonstrated radiographically with valgus stress view; full thickness cartilage laterally with no central ulcer; <15 degrees of flexion contracture, < 15 degrees varus and > 90 degrees flexion. The state of the patellofemoral joint, chondrocalcinosis, obesity, age and activity level are NOT contraindications to medial mobile-bearing UKA. The only certain contraindications are the presence of inflammatory arthritis or a history of previous high tibial osteotomy (HTO). Advantages of medial UKA are that it preserves undamaged structures, it is a minimally invasive technique with low incidence of perioperative morbidity, preservation of the cruciate mechanism results in more “normal” kinematics versus TKA, it normalises contact forces and pressures in the patellofemoral joint, and it provides better range of motion than TKA. Furthermore, medial UKA results in better function than TKA in gait studies, with demanding activities, such as climbing stairs, having a better “feel”. Pain relief with medial UKA is equivalent or better than TKA, and morbidity and mortality are decreased compared with TKA, as well as venous thromboembolism. Recommended preoperative imaging studies consist of plain radiographs with the following views obtained: standing AP, PA flexed, lateral, Merchant or axial, and valgus stress. There are several surgical perils associated with performing medial UKA. First, in regard to patient selection, avoid medial UKA in patients with residual hyaline cartilage – the joint must be bone on bone. Second, perform a conservative tibial resection with respect to depth to prevent tibial collapse as well as excessive overload of weakened bone, and avoid excessive posterior slope. Perform the tibial resection coplanar with tibial spine/ACL insertion to maximise tibial coverage. Avoid overcorrection of deformity. Do not perform a medial release. Balance flexion/extension gaps meticulously. For mobile-bearing designs, remove all impinging osteophytes. Over 55 published studies report results with mobile-bearing medial UKA, with survival ranging 63.2–100% at mean follow-up ranging from 1 to 17.2 years

About ten years ago we introduced sophisticated instrumentation and an increased range of component sizes for the Oxford unicompartmental knee replacement (UKR) to facilitate a minimally invasive surgical (MIS) approach. The device is now routinely implanted through an incision from the medial pole of the patella to the tibial tuberosity. This has resulted in a more rapid recovery and an improved functional result. As the access to the knee is limited there is a concern that the long term results may be compromised. The aim of this study was to determine the 10 year survival. A prospective follow up of all Phase 3 minimally invasive Oxford UKR implanted by two senior authors (DWM & CAFD) has been undertaken. So far 1015 UKRs have been implanted for anteromedial osteoarthritis. All patients received a cemented implant through a MIS approach and were followed up prospectively by an independent observer. The data was collected prospectively regarding pre-operative status, complications and clinical as well as functional outcome at predetermined intervals. The average age of patients was 66.4 years (range: 33 – 88) with mean Oxford Knee Score 41 (SD: 7.9) at the time of last follow up, Knee Society Score (objective) of 84 (SD: 13) and Knee Society Score (functional) of 83 (SD: 21). At ten years the survival of this cohort is 96%. There were 22 revisions including 7 for progression of arthritis, 5 for infection, 5 for bearing dislocation, 4 for unexplained pain and one for rupture of ACL secondary to trauma. We conclude that the Oxford Knee can be implanted reliably through a minimally invasive approach, giving excellent long term results

Aims: To evaluate the outcome of 135 Oxford Unicompartmental Knee replacements with regards to knee function and implant survival. Methods: 135 Oxford unicompartmental knee replacements were performed by a single surgeon between 1989–2000. Indication was anteromedial knee osteoarthritis with a correctable varus deformity and intact anterior cruciate ligament. The patients were evaluated in clinic both clinically & radiologically. Modiþed Knee Society Score was used to evaluate knee function. X-rays were performed to look for implant loosening and progression of arthritis. Results: 29 patients died and 5 were too ill to attend clinic. A total of 5 revisions were carried out. There were 53 male and 43 females. 74% patients were betweem 60 Ð 80 yrs. Follow up ranged from 1–11 yrs with a mean follow up of 5.2 yrs. 88% patients had range of movement of more than 105 degrees. The mean Total Knee Score was 92 and the mean functional knee score was 76. Blood transfusion was not necessary in 90% of patients. Superþcial wound infection was noted in 2 cases and hematoma formation in 4 cases. Tibial component loosening was the cause for revision. Conclusions: 1. With appropriate patient selection Oxford unicompartmental knee is a reliable treatment option for anteromedial osteoarthritis of the knee. 2. It offers long term relief of symptoms and good knee function in a high percentage of cases. 3. Implant survival is comparable to total knee replacement and to the series reported by the designers

Purpose: This study was designed to establish the poly-ethylene wear rates in the Oxford medial unicompert-mental knee replacement. Introduction: The Oxford meniscal bearing knee was introduced as a design to reduce polyethylene wear. There has been one previous retrieval study of the Oxford UKA, which reported very low wear rates in some specimens, but abnormal patterns of wear in others, including impingement. There has been no further investigation of these abnormal wear patterns. Methods: Forty-seven bearings were retrieved from patients who had received a medial Oxford UKA for anteromedial osteoarthritis of the knee, none of which had previously been studied. Mean time to revision was 8.4 years (SD 4.1) and 20 had been implanted for over 10 years. The macroscopic pattern of polyethylene wear and the linear penetration (dial gauge measurement) was recorded for each bearing. Results: The mean linear penetration rate (LPR) was 0.07mm/year. The patterns of wear fell into 4 categories, each with a different LPR; 1) No abnormal macroscopic appearance, n=16 (LPR = 0.01mm/year), 2) Abnormal macroscopic wear with extra-articular impingement, n=16 (LPR = 0.05mm/year), 3) Abnormal macroscopic wear with intra-articular impingement, n=6 (LPR = 0.10mm/year), 4) Abnormal macroscopic wear with impingement and signs of incongruous articulation, n=9 (LPR = 0.14mm/year). The differences in LPR were statistically significant (p< 0.05). Conclusion: The results show that very low polyethylene wear rates are possible if the device functions normally. However if the bearing displays abnormal function (extra-articular, intra-articular impingement or incongruous articulation) wear rates increase significantly

Unicompartmental knee replacement (UKR) is an established treatment for single compartment end-stage arthrosis with good recorded survivorship. UKRs are often implanted into more active younger patients, but patient selection remains controversial. A recent study, led by the Royal College of Surgeons Clinical Effectiveness Unit, demonstrated that prosthesis revision rates decrease strongly with age (Van Der Meulen et al 2008). It has therefore been suggested that UKR should only be considered in elderly patients. This contrasts our observed experience of early revision cases leading us to compare these patients with a control group. Between September 2002 and 2008, 812 Oxford Mobile Bearing Medial UKRs were implanted. We compared all patients who underwent UKR revision to Total Knee Replacement (TKR) against a control group of 50 consecutive UKR patients. 20 implants have required revision to TKR in 19 patients since 2002. Median age at index surgery was 68 (range 48-81), median BMI was 31 (range 25-41.5), 17 patients were female (85%), and median implant survival was 25 months (range 6-57). Control group median age at index surgery was 66 (range 46-81), median BMI was 30 (range 22-51), and 27 patients were female (54%). Median Oxford Knee Score recorded in September 2009 was 36 (range 14-54) for revision patients and 21 (range 14-39) for the control group (p=0.021). Our UKR patients with early failure requiring revision are far more likely to be female (p=0.015), as well as older and with a higher BMI than the control group. We feel this is a subset of patients at high risk of failure, despite meeting all criteria for UKR. The underlying causes are likely to be multifactorial, but a key factor may be that this group has varus tricompartment osteoarthritis rather than classical anteromedial osteoarthritis. Our data counters recent advice based on National Joint Registry data

To report a 15-year survival analysis of the Oxford Medial Unicompartmental Knee Arthroplasty (Oxford UKA) in an independent series. We report the results of a series of 420 Oxford UKAs performed between 1983 and 2000. Indications for surgery were primary antero-medial osteoarthritis of the knee with an intact ACL, correctable varus deformity of < 15° and < 15° fixed flexion deformity. The state of the patello-femoral joint was not used as a selection criterion. Patients were contacted by a postal questionnaire or by telephone. The outcome of all 420 knees was established, with none lost to follow-up. Seventy-six knees were in patients who had died and the state of each arthroplasty was determined from hospital and GP records. Seventeen patients (4%) had required revision. Indications for revision were lateral compartment arthrosis (7), component loosening (4), bearing dislocation (4) and infection (2). There were no failures for polyethylene wear. Cumulative survival at 15 years was 94.3% [95% CI 3.8%]. The worst case scenario was 94.3% as none were lost to follow-up. The results from an independent series are important, as they avoid bias. The 15-year results of this independent series are better than any other reported series of unicompartmental device at 15 years and as good as the published independent 15 year survival results for total knee arthroplasty. The data illustrates that excellent long-term survival can be achieved with the Oxford UKA, allowing patients to benefit from the advantages that unicompartmental arthroplasty offers. We believe that provided patients are selected appropriately, this device provides the treatment of choice for anteromedial osteoarthritis of the knee

We report the outcome of 58 knees with anteromedial osteoarthritis in which the Oxford unicompartmental arthroplasty was inserted. These were performed in a district general hospital by three surgeons. All the knees had only anteromedial disease, an intact anterior cruciate ligament and correctable varus. The indication for replacement in all cases was pain. The mean follow up was 24.5 months (6–48). Outcome was assessed by patient satisfaction and the Oxford knee score. Complications, revisions, time to mobility and time to return to work were also noted. The average age of the 26 women and 23 men at time of operation was 65 years. 31 of the patients were very happy with the outcome, 12 were happy, 5 were unhappy, and one was very unhappy. Mean pre-operative Oxford knee score was 43 (27–53) this improved post-operatively to 18 (12–45) a significant improvement (p< 0.005, paired t-test). Time taken to mobility was an average of 36 hours (24–72), 24 of the patients were in full or part time employment at the time of operation, all returned to their former posts at an average of 6 weeks (2–24). Three patients have ongoing pain and are booked for revision to TKR. One patient had a dislocated femoral component and required this to be revised twice with a meniscus change at the same time; this patient is now happy. 2 further patients had revision of the meniscus to a larger size for meniscal dislocation. One patient had an infection treated with debridement and antibiotics; infection settled. Our results show that there is a learning curve; all of the insert revision occurred early in the series. Patient selection is important, those with disease in other compartments have continuing pain. Appropriate selection of patients and good surgical technique are the key to obtaining a good outcome