Purpose of the study: For medial osteoarthritis with chronic anterior laxity, we propose an original technique combining subtraction osteotomy and extra-articular ligmentoplasty using the lateral quarter of the patellar tendon. Material and methods: WE report a retrospective review of 29 patients (11 males/18 females) aged 29–51 years treated from May 1996 to October 2002. Time from rupture of the anterior cruciate ligament (ACL) and the operation was 17.5 years (range 13–22 years). These patients had had 52 prior operations (more than one per knee). All presented functional instability, a positive pivot test, and anterior laxity measured at 8 mm on average (range 5–10 mm) on KT1000. Pain in the medial compartment was observed in all patients with osteoarthritis noted grade II in 7, grade III in 18 and grade IV in 4. Radological varus measured 5–15°. Lateral subtraction osteotomy fixed with a plate was performed in combination with a patellar tendon autograft using the lateral quarter of the patellar tendon. Immediate mobilization with complete weight bearing was the rule. Results: A mean 5–year follow-up (range 18 months to 9 years). According to the IKDC subjective score, 26 patients were satisfied or very satisfied and 22 of them had resumed their sports activities. Instability persisted in one patient and pain in two. Varus was corrected in three patients but the medial degradation progressed. Anterior laxity measured with KT1000 was 1–6 mm (mean 2 mm). The pivot test was positive in one knee, negative in 18 and revealed slight displacement in 10. Excluding the radiological aspect, the overall IKDC score was 2A, 21B, 6C, 1D. Conclusion: This combined method is particularly interesting for stabilizing chronic ACL instability causing secondary medial degeneration. It treats two conditions with the same approach with an acceptable rate of satisfaction

Introduction. The management of young patients with painful medial compartment osteoarthritis remains controversial. Opening wedge medial high-tibial osteotomy using a locking plate has shown good results in selected patients. This cohort of patients has high physical demands and previous studies have warned against operating on patients with increased body mass index (BMI). Patients and Methods. Thirty-five patients undergoing valgus high tibial osteotomy between Oct 2004 and Feb 2010. Surgical outcome was assessed using Oxford Knee score, pre- and post-operative pain scores, change in employment and patient satisfaction. Results. Mean age at the time of surgery was 41 (22 to 62), mean BMI was 30.9 (21 to 43) and mean Oxford score was 37/48 (16 to 48). Patients rated their overall satisfaction as 7.9/10. Three patients were lost to follow-up, two patients died of unrelated disease. Fifteen (50%) patients had heavy manual jobs and of these 12 (80%) returned to their previous employment post-operatively within 6 months. Seven patients had a BMI > 35 (Mean 39) with a mean weight of 126 Kg (105Kg to 144Kg). These patients had a mean Oxford Score of 42/48 and overall satisfaction of 90%. Pain improved from 8.4/10 pre-op to 1.5/10 post-op (P < 0.0001). None had further procedures. Conclusion. Opening wedge high-tibial osteotomy offers a successful alternative treatment of medial osteoarthritis in young patients with high BMI who place high demands on their knees

Introduction. The management of young patients with painful medial compartment osteoarthritis remains controversial. Opening wedge medial high-tibial osteotomy using a locking plate has shown good results in selected patients. This cohort of patients has high physical demands and previous studies have warned against operating on patients with increased body mass index (BMI). Patients and Methods. Thirty five patients undergoing valgus high tibial osteotomy between Oct 2004 and Feb 2010. Surgical outcome was assessed using Oxford Knee score, pre- and post-operative pain scores, change in employment and patient satisfaction. Results. Mean age at the time of surgery was 41 (22 to 62), mean BMI was 30.9 (21 to 43) and mean Oxford score was 37/48 (16 to 48). Patients rated their overall satisfaction as 7.9/10. Three patients were lost to follow-up, two patients died of unrelated disease. Fifteen (50%) patients had heavy manual jobs and of these 12 (80%) returned to their previous employment post-operatively within 6 months. Seven patients had a BMI > 35 (Mean 39) with a mean weight of 126 Kg (105Kg to 144Kg). These patients had a mean Oxford Score of 42/48 and overall satisfaction of 90%. Pain improved from 8.4/10 pre-op to 1.5/10 post-op (P < 0.0001). None had further procedures. Conclusion. Opening wedge high-tibial osteotomy offers a successful alternative treatment of medial osteoarthritis in young patients with high BMI who place high demands on their knees

Tibial component loosening is an important failure mode in unicompartmental knee arthroplasty (UKA) which may be due to the 6–8 mm of bone resection required or the limited surface area. To address component loosening and fixation, a new Early Intervention (EI) design is proposed which reverses the traditional material scheme between femoral and tibial components. That is, the EI design consists of a plastic inlay component for the distal femur and a thin metal plate for the proximal tibia. With this reversed materials scheme, the EI design requires minimal tibial bone resection compared to traditional UKA to preserve the dense and stiff bone in the proximal tibia. This study investigated, by means of finite element (FE) simulations, the potential advantages of a thin metal tibial component compared with traditional UKA tibial components, such as an all-plastic inlay or a metal-backed onlay. We hypothesized that an EI component would produce comparable stress, strain, and strain energy density characteristics to an intact knee and more favorable values than UKA components. Indeed, the finite element results showed that an EI design reduced stresses, strains and strain energy density in the underlying support bone compared to an all-plastic UKA component. Analyzed parameters were similar for an EI and a metal-backed onlay, but the EI component had the advantage of minimal resection of the stiffest bone.

Purpose: The management of degenerative arthritis of the knee in the younger, active patient often presents a challenge to the orthopaedic surgeon. Surgical treatment options include: high tibial osteotomy (HTO), uni-compartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA). The purpose of this study was to examine the long-term survival of closing wedge HTO in a large series of patients 8–19 years after surgery.

Method: The results of 458 consecutive patients undergoing lateral closing wedge HTO for medial compartment osteoarthritis (MCOA) between 1990 and 2001 were reviewed. Between 2008–2009, patients were contacted via telephone and assessment included: incidence of further surgery, Oxford Knee Score, and British Orthopaedic Association (BOA) Patient Satisfaction Scale. Failure was defined as the need for revision HTO or conversion to UKA or TKA. Survival analysis was completed using the Kaplan-Meier method.

Results: We were able to contact 400/458 (87%) patients for follow-up via telephone interview. Five patients (1%) who declined participation were excluded. Fifty-eight patients (13%) were lost to follow-up. Of the 395 patients, 12 (3%) had died of unrelated causes and 124 (31%) required further knee surgery. The remaining 259 (66%) completed the BOA patient satisfaction score and Oxford Knee Score. The probability of survival for HTO at 5, 10 and 15 years was 95%, 79% and 55% respectively. Multivariate regression analysis showed that only age < 50 years (p< 0.001) was associated with significantly longer survival. Mean Oxford Knee Score was 40/48 (range 17–60). Ninety-two percent (239/259 patients) were enthusiastic or satisfied and 90% (234/259 patients) would undergo HTO again at mean 11 years follow-up. Complications included: 5 pulmonary embolisms, 8 deep vein thromboses, 1 non-union, 1 post-operative subarachnoid hemorrhage and 1 transient peroneal nerve palsy.

Conclusion: To our knowledge, we have reported the long-term follow-up of lateral closing wedge HTO in the largest group of patients in the literature. We found that the results of HTO do deteriorate over time but that HTO can be effective for as long as 19 years. In appropriately selected patients and circumstances, HTO gives high patient satisfaction and affords patients unrestricted activity for many years.

Introduction: The long-term results of HTO depends on exact reconstruction of the weight bearing line. The lack of exact intraoperative real time control of the mechanical axis often results in postoperative malalignments. After preopertive planing and intraoperative measurement of the deformities, HTO is performed under navigation. The system shows the weight bearing line, the size of the osteotomy wedge and the tibial slope. Aim of the current study is to evaluate accuracy of intraoperative datas using the OrthoPilot in comparison to long standing radiographs including the center of the hip, knee and ankle joint.

Material and method: 54 patients with a mean age 49.7 years underwent HTO with navigation using the Ortho-Pilot. According to Ahlback’s staging 1 patient had I, 4 II, 21 III, 19 IV and 9 V osteoarthritis of the knee.

Results: The mean preoperative deviation of the mechanical axis was 6.0 varus (3 to 14) on the x-ray and was confirmed by the OrthoPilot. The mean postoperative mechanical axis was 1.7 valgus (2 varus to 5 valgus) on the x-ray and was confirmed by the OrthoPilot with 1.4 valgus (0 to 3 valgus). The mean postoperative femorotibial angle was 7.1 (2–11). Complications related to the navigation procedure was one hematoma of the distal pin track.

Conclusion: By using an intraoperative navigation system, the outcome of the preoperative planned procedure becomes more predictable and more precision of the alignment can be achieved in HTO. Long-term studies will have to be carried out to verify whether this will lead to a lasting benefit for the patient.

On three occasions we have reviewed a series of knees after high tibial osteotomy for osteoarthritis: 99 were reviewed at one to two years; 81 at a mean of 5.7 years; and 65 at a mean of 11.9 years. At one to two years and at 5.7 years over 50% were good and over 75% acceptable. At 11.9 years, 43% were good and 60% acceptable. We determined the mechanical axis through the knee in maximum varus and maximum valgus; significantly better results were found if a mean angulation of 3 degrees to 7 degrees of valgus had been achieved at operation. We also measured intercondylar distances under varus and valgus stress, and found no significant lateral compartment narrowing. The best results were seen in knees with pre-operative grade I or grade II osteoarthritis and valgus deviation after osteotomy.

Aims

To compare time dependent functional improvement for patients with medial, respectively lateral knee osteoarthritis (OA) after treatment with opening wedge osteotomy relieving the pressure on the osteoarthritic part of the knee.

Introduction

The management of degenerative arthritis of the knee in the younger, active patient presents a challenge to the orthopaedic surgeon. Surgical treatment options include: high tibial osteotomy (HTO), unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA). The aim of this study was to examine the long-term survival of closing wedge HTO in a large series of patients up to 19 years after surgery.

Purpose of the study: Transposition of the anterior tibial tuberosisty (ATT) is often performed during the treatment of periodic dislocation of the patella. The purpose of this retrospective study was to evaluate the rate of medial femorotibial osteoarthritis and medial patellofemoral osteoarthritis after ATT transfer. Material and method: We reviewed 129 knees in 106 patients who underwent surgery from 1988 to 2004. The patients were reviewed at mean 9 years follow-up, minimum 2 years. Three groups were defined:. isolated descent (n=15),. isolated medial shift (n=19), and. descent and medial shift (n=95). The degree of the medial shift and the descent depended on the distance from the tibial tuberosity to the trochlear notch and the Caton-Deschamps index measured preoperatively. Patients who underwent surgery for chronic anterior laxity and/or meniscal lesions were excluded (n=3). All patients were free of osteoarthritis before surgery. A complete radiographic series was available for 102 knees. Unilateral periodic dislocation of the patella was present in 60 patients whose knee x-rays were obtained bilaterally. Results: All patients in group 2 were free of osteoarthritis. In group 2, the rate of medial femorotibial osteoarthritis was 10.5%; the rate of medial patellofemoral osteoarthritis was 21%. In group 3, the rate of medial femorotibial osteoarthritis was 7% and that of medial patellofemoral osteoarthritis 14%. For patients with unilateral periodic patellar dislocation, only the operated knees exhibited medial patellofemoral osteoarthritis (12%). The rate of medial patellofemoral osteoarthritis was significantly greater for knees with a medial shift of the ATT. The rate of medial femorotibial osteoarthritis was 6.8% for knees with medial shift versus 8.3% for the index knees. There was no significant difference between the medial shift knees and the index knees for medial femorotibial osteoarthritis. Discussion: Biomechanical studies have shown increased stress forces on the medial compartment after medial shift of the ATT. However, these studies were performed with normal knees free of the morphological anomalies generally present in knees exhibiting periodic patellar dislocation (abnormally high tibial tuberosity femoral notch distance, trochlear dysplasia. In our series, regarding the rate of medial femorotibial osteoarthritis, there was no significant difference between the knees which underwent a medial shift of the ATT and healthy knees. Consequently, medial shift of the ATT should be avoided when unnecessary; the morphology of the trochlea (depth, morphology of the medial component) can induce increased medial stress on the patellofemoral joint

The aim of this retrospective study was to assess the long-term results (minimum ten years) following treatment of medial compartment osteoarthrosis of the knee with high tibial osteotomy using a simple, reproducible technique with minimal internal fixation and early mobilisation. Between 1980 and 1993, seventy-five lateral, closing wedge osteotomies were performed in sixty-five patients by a single surgeon (ALP). A lateral approach was utilised, with stabilisation achieved using two staples and no use of external splints. Twenty-three patients had died prior to this review (twenty-six knees) and the remaining forty-two patients were invited to attend for independent review. The patients were assessed using the Knee Society Knee Score, Tegner and Lysholm activity score, a patient self-assessment questionnaire and radiological review. The average age of the patients at surgery was sixty-two years (range twenty-six to seventy-seven years), reviewed between ten and twenty-three years (average seventeen years) following the procedure. Results will be presented with end-points of conversion to arthroplasty and patient dissatisfaction and complications discussed. There were no major complications observed during conversion to total knee joint replacement. The current role of high tibial osteotomy for the treatment of medial compartment osteoarthrosis will be discussed

Purpose of the study: The purpose of this study was to confirm long-term changes in frontal alignment after wedge osteotomy(even for with an «ideal» postoperative wedge angle of 3–6°), that the frontal alignment is correlated with functional degradation and also with femorotibial skeletal torsion.

Material and methods: A non-consecutive retrospective series of 70 patients aged 57.5 on average at surgery for medial open-wedge tibial osteotomy were reviewed at 10–25 years. Goniometry measurements were obtained in the upright position after healing. Tibial and femoral torsion values were measured on the CT scan. Functional outcome at last follow-up was noted good, fair or poor.

Results: Postoperatively 80% percent of the knees presented frontal realignment within the 3–6° range. At last follow-up frontal alignment had changed on average 10° for 40% of knees. The change in frontal alignment resulted from a deterioration of the medial or lateral joint space and in 80% was associated with poor functional outcome. Knees which preserved valgus of 3–6° at last follow-up had statistically better results than the rest of the series. There was a correlation between valgus frontal misalignment and femoral torsion greater than 14° (anteversion) and between varus frontal misalignment and femoral torsion less than 14°. There thus appeared to be a linear correlation between postoperative changes in the correction and femoral torsion.

Conclusion: Good functional outcome of open wedge tibial osteotomy is correlated with stability of the axial correlation over time. Achieving postoperative valgus of 3–6° does not appear to be sufficient for stable axial correction. To achieve long-term preservation of the axial correction, it would be preferable to modulate the postoperative correction according to the degree of femoral torsion.

Aims

Medial unicompartmental knee arthroplasty (UKA) is undertaken in patients with a passively correctable varus deformity. Our hypothesis was that restoration of natural soft tissue tension would result in a comparable lower limb alignment with the contralateral normal lower limb after mobile-bearing medial UKA.

Objective. To analyze the short-term outcome after medial open-wedge high tibial osteotomy with a 3D-printing technology in early medial keen osteoarthritis and varus malalignment. Design and Method. 32 knees(28 cases) of mOWHTO (fixation with an angular-stable TomoFix implant(Synthes)) with a 3D-printing technology combined with arhtroscopy were prospectively surveyed with regard to functional outcome(Hospital for special knee score [HSS] score). Pre- and postoperative tibial bone varus angle (TBVA), mechanical medial proximal tibial angle (MPTA), and alignment were analyzed with regard to the result. Results. 32 knees were included (28 patients; mean age 46.5±9.3 years). The follow-up rate was 100% at 1.7±0.6 years (range, 1.2–3.2 years). Pre- and postoperative mechanical tibiofemoral axis were 6.8°±2°of varus and 1.2°± 3.4° of valgus, respectively. HSS score significantly improved from 46.0±18.3 preoperatively to 84±12 at one, 80±7 at two years (P<0.01). Conclusions. Medial open-wedge high tibial osteotomy with a 3D-printing technology combined with arthroscopy in medial keen osteoarthritis and varus malalignment is an accurate and good treatment option. High preoperative TBVA and appropriate corrected angle(0–3° of valgus)) was associated with better functional outcome at final follow-up

Introduction. The pathogenesis of primary knee osteoarthritis is due to excess mechanical loading of the articular cartilage. Previous studies have assessed the impact of muscle forces on tibiofemoral kinematics and force distribution. A cadaveric study was performed to evaluate the effect of altering the moment arm of the iliotibial band (ITB) on knee biomechanics. Method. A robotic system consisting of a 6-DOF manipulator capable of measuring forces on the medial and lateral condyle of a cadaveric knee at various flexion angles and muscle forces was utilized [1]. The system measured the compartment forces at flexion angles between 0° and 30° under 3 simulated loading conditions (300N quadriceps, 100N hamstrings and: i. 0N ITB; ii. 50N ITB; iii. 100N ITB). Eight fresh frozen human cadaver knee specimens (4 males, 4 females); age range 36 – 50 years; weight range 49 – 90 kg; height range 154 – 190 cm were used in the study. The ITB and associated lateral soft tissue structures were laterally displaced from the lateral femoral condyle by fixing a metal implant (like in Figure 1) to the distal lateral femur. Mechanical loads on the medial and lateral compartments (with and without the implant) were measured using piezoelectric pressure sensors. Results. For each specimen, lateral displacement of the ITB due to the implant was measured (15 – 20 mm). The % average unloading of the medial compartment for all the specimens ranged from 34% – 65% (Figure 2). Also observed was a concomitant increase in lateral compartment load. Medial unloading was even observed with no ITB force (0N) which indicates a role for other lateral structures attached to the ITB in unloading the medial compartment [2]. In addition, under these non-weight bearing conditions, on average, there was an increase in valgus tibial angulation through the flexion range. Discussion. Increasing mechanical leverage of muscles across a joint is accomplished in nature through sesamoid bones (e.g., patella) which increase the muscle moment arm. By increasing the moment arm of the ITB and lateral soft tissue structures by lateralizing these structures, our model demonstrates a 34–65% unloading of the medial compartment. Studies of knee braces and weight loss have shown that reducing mechanical load on the medial condyle by even 10% provides clinical benefits in terms of reduced pain and improved function. Based on the results of this study, unloading the medial compartment by displacing the ITB laterally may be a means of treating medial osteoarthritis (Figure 3). A prospective, multi-center, non-randomized, open label, single-arm study is currently underway to establish the safety and efficacy of providing medial osteoarthritis pain relief by displacing the ITB using Cotera, Inc.'s Latella™ Knee Implant

Aims. The patient-acceptable symptom state (PASS) is a level of wellbeing, which is measured by the patient. The aim of this study was to determine if the proportion of patients who achieved an acceptable level of function (PASS) after medial unicompartmental knee arthroplasty (UKA) was different based on the status of the anterior cruciate ligament (ACL) at the time of surgery. Methods. A total of 114 patients who underwent UKA for isolated medial osteoarthritis (OA) of the knee were included in the study. Their mean age was 65 years (SD 10). No patient underwent a bilateral procedure. Those who had undergone ACL reconstruction during the previous five years were excluded. The Knee injury Osteoarthritis Outcome Score Activities of Daily Living (KOOS ADL) function score was used as the primary outcome measure with a PASS of 87.5, as described for total knee arthroplasty (TKA). Patients completed all other KOOS subscales, Lysholm score, the Western Ontario and McMaster Universities Osteoarthritis Index, and the Veterans Rand 12-item health survey score. Failure was defined as conversion to TKA. Results. Survivorship at ten years was 97% in both the ACL-deficient and ACL-intact groups. The mean survival was 16.1 years (95% confidence interval (CI) 15.3 to 16.8) for the ACL-deficient group and 15.6 years (95% CI 14.8 to 16.361) for the ACL-intact group (p = 0.878). At a mean of nine years (SD 3.5) in the ACL-deficient group, 32 patients (87%) reached the PASS for the KOOS ADL. In the ACL-intact group, at a mean of 8.6 years (SD 3) follow-up, 63 patients (85%) reached PASS for the KOOS ADL. There was no significant difference in the percentage of patients who reached PASS for all KOOS subscales and Lysholm between the two groups. Conclusion. PASS was achieved in 85% of all UKAs for KOOS ADL, similar to reports for TKA. Fixed-bearing, medial, non-robotically-assisted UKA resulted in 97% survival at ten years in both the ACL-deficient and ACL-intact groups. There was no significant difference in all outcomes between the two groups. Understanding PASS will allow better communication between surgeons and patients to improve the surgical management of patients with single compartment OA of the knee. This study provides mid- to long-term data supporting the use of PASS to document outcomes following UKA. PASS was met in more than 85% of patients with no differences between ACL-deficient and ACL-intact knees at a mean follow-up of nine years. Cite this article: Bone Joint J 2021;103-B(8):1367–1372

Objectives. Unicompartmental knee arthroplasty (UKA) is one surgical option for treating symptomatic medial osteoarthritis. Clinical studies have shown the functional benefits of UKA; however, the optimal alignment of the tibial component is still debated. The purpose of this study was to evaluate the effects of tibial coronal and sagittal plane alignment in UKA on knee kinematics and cruciate ligament tension, using a musculoskeletal computer simulation. Methods. The tibial component was first aligned perpendicular to the mechanical axis of the tibia, with a 7° posterior slope (basic model). Subsequently, coronal and sagittal plane alignments were changed in a simulation programme. Kinematics and cruciate ligament tensions were simulated during weight-bearing deep knee bend and gait motions. Translation was defined as the distance between the most medial and the most lateral femoral positions throughout the cycle. Results. The femur was positioned more medially relative to the tibia, with increasing varus alignment of the tibial component. Medial/lateral (ML) translation was smallest in the 2° varus model. A greater posterior slope posteriorized the medial condyle and increased anterior cruciate ligament (ACL) tension. ML translation was increased in the > 7° posterior slope model and the 0° model. Conclusion. The current study suggests that the preferred tibial component alignment is between neutral and 2° varus in the coronal plane, and between 3° and 7° posterior slope in the sagittal plane. Varus > 4° or valgus alignment and excessive posterior slope caused excessive ML translation, which could be related to feelings of instability and could potentially have negative effects on clinical outcomes and implant durability. Cite this article: K. Sekiguchi, S. Nakamura, S. Kuriyama, K. Nishitani, H. Ito, Y. Tanaka, M. Watanabe, S. Matsuda. Bone Joint Res 2019;8:126–135. DOI: 10.1302/2046-3758.83.BJR-2018-0208.R2

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

Background. Medial open wedge high tibial osteotomy (MOWHTO) has been accepted as a highly effective option for the treatment of medial unicompartmental osteoarthritis of the knee. Although pain in the medial joint line is significantly relieved after MOWHTO, some patients complain of pain over pes anserinus after the osteotomy, necessitating implant removal for pain relief. Purpose. The purpose of this study is to define the implant removal rate after MOWHTO due to patient complaints. Methods. 103 knees of 72 patients who underwent MOWHTO for medial unicompartmental osteoarthritis between 2010 and 2018 with a follow-up of at least 24 months were enrolled in the study. Patients were evaluated with the Knee Injury and Osteoarthritis Outcome Score (KOOS), Oxford Knee Score (OKS) and Visual Analogue Score (VAS) for pain in the medial knee joint (VAS-MJ). All tests were performed before the surgery, at 12 months after surgery. VAS value for pain over pes anserinus (VAS-PA) was recorded at 12 months after MOWHTO and at 3 months after implant removal. Results. Mean follow-up was 31±5.4 months. TomoFix® medial high tibia plate (DePuy Synthes, Raynham, MA, USA) was used for the fixation of osteotomy in all cases. Significant improvement in KOOS, OKS and VAS-MJ were observed 12 months after MOWHTO. Average values of VAS-MJ and VAS-PA were 21.7±7.1 and 34±8.4, respectively. Implant removal was needed for 65 (63.1%) knees. There were no significant differences in regard of postoperative KOOS (p=0.134), OKS (p=0.287) and VAS-MJ (p=0.416) scores between patients for which implant removal was needed or not. VAS-PA value decreased significantly at 3 months after implant removal (p<0.001). Conclusion. A large portion of patients needed implant removal after MOWHTO to relieve pain over pes anserinus even if knee function was significantly improved. Lower profile plates may be preferred to avoid secondary implant removal surgery after MOWHTO

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