Distal femoral varus osteotomy is a procedure intended to relieve pain, correct valgus deformity, and delay or possibly prevent the progression of lateral compartment osteoarthritis in the knee. It is indicated in patients who are considered too young or are too active to be considered candidates for total knee arthroplasty. It also allows protection of the lateral compartment in cases of meniscal or cartilage allograft. In patients who are a good candidate for total knee replacement, TKR is the procedure of choice. A sloping joint line requires that the correction be performed above the knee. Several methods of distal femoral varus osteotomy have been proposed. These include a medial closing wedge, a lateral opening wedge, and a dome osteotomy. In the author's experience, the medial closing wedge has proven reliable. This technique uses a 90-degree blade plate, and does not require any angle measurements during surgery. Fixation is secure, allowing early motion. Healing proceeds rapidly in the metaphyseal bone, and non-unions have not occurred. The desired final alignment was zero degrees, which was reliably achieved using this method. Medium to long-term results are generally satisfactory. When conversion to total knee replacement is required, standard components may generally be used, and function was not compromised by the prior osteotomy. Distal femoral varus osteotomy is a successful procedure for lateral compartment osteoarthritis in a valgus knee. It is indicated in patients who are too young or active for total knee arthroplasty, and provides an excellent functional and cosmetic result

INTRODUCTION. Controversy exists regarding the ability of unicompartmental knee arthroplasty (UKA) to restore native knee kinematics, with some studies suggesting native kinematics are restored in most or all patients after UKA. 1–3. , while others indicate UKA fails to restore native knee kinematics. 4,5. Previous analysis of UKA articular contact kinematics focused on the replaced compartment. 2,5. , neglecting to assess the effects of the arthroplasty on the contralateral compartment which may provide insight to future pathology such as accelerated degeneration due to overload. 6. or a change in the location of cartilage contact. 7. The purpose of this study was to assess the ability of medial UKA to restore native knee kinematics, contact patterns, and lateral compartment dynamic joint space. We hypothesized that medial UKA restores knee kinematics, compartmental contact patterns, and lateral compartment dynamic joint space. METHODS. Six patients who received fixed-bearing medial UKA consented to participate in this IRB-approved study. All patients (4 M, 2 F; average age 62 ± 6 years) completed pre-surgical (3 weeks before) and post-surgical (7±2 months) testing. Synchronized biplane radiographs were collected at 100 images per second during three repetitions of a chair rise movement (Figure 1). Motion of the femur, tibia, and implants were tracked using an automated volumetric model-based tracking process that matches subject-specific 3D models of the bones and prostheses to the biplane radiographs with sub-millimeter accuracy. 8. Anatomic coordinate systems were created within the femur and tibia. 9. and used to calculate tibiofemoral kinematics. 10. Additional outcome measures included the center of contact in the medial and lateral compartments, and the lateral compartment dynamic joint space (i.e. the distance between subchondral bone surfaces). 11. The results of the three movement trials were averaged for each knee in each test session. All outcome measures were interpolated at 5° increments of knee extension (Figure 2). The average differences between knees at corresponding flexion angles were analyzed using paired t-tests with significance set at p < 0.05. RESULTS. The UKA knee was in 5.3° more varus than the contralateral knee prior to surgery (p=0.005). After surgery, the UKA knee was in 4.9° more valgus than before surgery (p=0.005). The UKA knee was 4.3° more externally rotated than the contralateral knee post-surgery (p=0.05) (Table 1). No significant differences were observed between knees or pre- to post-surgery in lateral compartment dynamic joint space or the center of contact in the medial and lateral tibia compartments (Table 1). DISCUSSION. These results suggest that medial UKA can restore native knee varus without significantly altering lateral compartment joint space or contact location during the chair rise movement. For any figures or tables, please contact the authors directly

Distal femoral varus osteotomy is a procedure intended to relieve pain, correct valgus deformity, and delay or possibly prevent the progression of lateral compartment osteoarthritis in the knee. It is indicated in patients who are considered too young or are too active to be considered candidates for total knee arthroplasty. It also allows protection of the lateral compartment in cases of meniscal or cartilage allograft. In patients who are a good candidate for total knee replacement, TKR is the procedure of choice. A sloping joint line requires that the correction be performed above the knee. Several methods of distal femoral varus osteotomy have been proposed. These include a medial closing wedge, a lateral opening wedge, and a dome osteotomy. In the author's experience, the medial closing wedge has proven reliable. This technique uses a 90-degree blade plate, and does not require any angle measurements during surgery. Fixation is secure, allowing early motion. Healing proceeds rapidly in the metaphyseal bone, and non-unions have not occurred. The desired final alignment was zero degrees, which was reliably achieved using this method. Medium to long-term results are generally satisfactory. When conversion to total knee replacement is required, standard components may generally be used, and function was not compromised by the prior osteotomy. Distal femoral varus osteotomy is a successful procedure for lateral compartment osteoarthritis in a valgus knee. It is indicated in patients who are too young or active for total knee arthroplasty, and provides an excellent functional and cosmetic result

Introduction:. The number of medial unicompartmental knee arthroplasties (UKA) performed over the last decade has increased by 30%, as studies have demonstrated improved knee kinematics, range of motion, and decreased perioperative morbidity versus total knee arthroplasty. However, concerns remain regarding the future risk of revision due to lateral compartment degeneration. In patients with a varus mechanical alignment and tibiofemoral subluxation secondary to medial compartment osteoarthritis, the femoral and tibial articular surfaces of the lateral compartment subsequently become incongruous, potentially increasing the focal contact stresses seen with loading. The purpose of this study is to evaluate whether the tibiofemoral congruence of the lateral compartment of the knee is improved following a medial UKA. Methods:. This study is a retrospective review of 192 consecutive medial UKAs included in an IRB-approved, single-surgeon database. All UKAs were performed using a robot-assisted surgical technique. Preoperative and postoperative standing, anteroposterior hip-to-ankle radiographs controlling for lower extremity rotation were performed from which the congruence of the lateral compartment was measured. The preoperative and postoperative degree of articular congruence (congruence index, CI) was calculated using an iterative closest point (ICP)-based software code (Matlab, MathWorks Inc., Natick, MA), specially developed to evaluate congruence of knee compartments. Following digitization of the articular surfaces of the femur and tibia, the code performs a rigid transformation that best aligns the articular surfaces and evaluates the current degree of articular congruence. A congruence index (CI) is then calculated, with a value of 1 indicating complete congruence, and a value of 0 indicating a 100% dislocation of the articular surfaces. A student's t-test was used to compare the preoperative and postoperative values of lateral compartment congruence. Results:. The mean, preoperative congruence index of the lateral compartment was 0.88 (± 0.1), which was improved to 0.93 (± 0.07), following implantation of a medial UKA (p < 0.001). Congruence of the lateral compartment was improved in 158 of the UKAs (83%), while 34 (17%) demonstrated a decrease in the congruence index postoperatively. Conclusion:. Implantation of a medial unicompartmental knee arthroplasty improves the articular surface congruence of the lateral compartment in the majority of patients with isolated, medial compartment osteoarthritis (Figure 1). We hypothesize that this factor, combined with a controlled undercorrection of the overall mechanical alignment, will improved load distribution across the lateral compartment, reduce the risk of focal contact stress points, and decrease the risk of subsequent osteoarthritic degeneration of the lateral compartment. Medial UKA not only resurfaces the medial compartment, but also may treat potential lateral compartment degeneration by improving congruence and load distribution

Objectives. Patient-specific (PS) implantation surgical technology has been introduced in recent years and a gradual increase in the associated number of surgical cases has been observed. PS technology uses a patient’s own geometry in designing a medical device to provide minimal bone resection with improvement in the prosthetic bone coverage. However, whether PS unicompartmental knee arthroplasty (UKA) provides a better biomechanical effect than standard off-the-shelf prostheses for UKA has not yet been determined, and still remains controversial in both biomechanical and clinical fields. Therefore, the aim of this study was to compare the biomechanical effect between PS and standard off-the-shelf prostheses for UKA. Methods. The contact stresses on the polyethylene (PE) insert, articular cartilage and lateral meniscus were evaluated in PS and standard off-the-shelf prostheses for UKA using a validated finite element model. Gait cycle loading was applied to evaluate the biomechanical effect in the PS and standard UKAs. Results. The contact stresses on the PE insert were similar for both the PS and standard UKAs. Compared with the standard UKA, the PS UKA did not show any biomechanical effect on the medial PE insert. However, the contact stresses on the articular cartilage and the meniscus in the lateral compartment following the PS UKA exhibited closer values to the healthy knee joint compared with the standard UKA. Conclusion. The PS UKA provided mechanics closer to those of the normal knee joint. The decreased contact stress on the opposite compartment may reduce the overall risk of progressive osteoarthritis. Cite this article: K-T. Kang, J. Son, D-S. Suh, S. K. Kwon, O-R. Kwon, Y-G. Koh. Patient-specific medial unicompartmental knee arthroplasty has a greater protective effect on articular cartilage in the lateral compartment: A Finite Element Analysis. Bone Joint Res 2018;7:20–27. DOI: 10.1302/2046-3758.71.BJR-2017-0115.R2

Goodfellow & Bullough (1968) first described the pattern of articular cartilage wear in the elbow. More recent post mortem studies have shown that advanced degenerative changes can develop in the radio-capitellar (lateral) compartment of elbow joints of elderly subjects in which the humeroulnar (medial) compartment remains remarkably well preserved. We have reviewed the findings in a consecutive series of 117 elbow arthroscopies performed on patients with elbow pain resistant to conservative treatments (age range 21–80 years: mean age 51 years). We documented established degenerative changes involving articular cartilage in 68 patients (59%). In this group we found that in 60 patients (88%) the degenerative changes were confined to the lateral compartment and contrasted with normal appearances of the articular cartilage of the medial compartment. The post mortem studies carried out on mainly elderly subjects demonstrated that the degree of degenerative change in the elbow is age dependant and involves predominantly the lateral compartment of the joint. Our study would support these observations, but indicates that symptomatic degenerative change occurs at a much earlier age than had previously been thought. We consider that lateral compartment degenerative change is a distinct clinical entity. It begins in relatively young patients in whom the x ray appearance may be normal or near normal and is often diagnosed as lateral epicondylitis. Our observations taken together with the reported post mortem studies indicate that primary osteoarthritis of the elbow begins in the lateral compartment of the joint and may remain confined to the lateral compartment throughout life. We believe that new treat ment strategies need to be developed specifically for patients with primary osteoarthritis as opposed to degenerative joint disease due to other causes

The aim of this study was to assess the distribution of wear down to bone in lateral compartment osteoarthritis and to analyse the effect of ACL condition and Ahlbach grading on this distribution. Background: The distribution of medial compartment wear is now well described and shows posterior progression and increased area of wear with worsening AhIback grade and ACL condition (Porteous 2000). Harman (1998) described wear situated more posteriorly in the lateral compartment but did not show any change to this with altering ACL function, and did not assess the severity of the arthritis. Method: Forty two tibial plateaus resected at total or unicompartmental replacement for lateral compartment osteoarthritis were analysed for the anterior and posterior extent of wear, as well as the point of deepest wear and the size of lesion. The plateau was divided into five zones from anterior to posterior. The ACL condition at surgery was graded as Normal, Frayed or Absent. Radiographs were classified by Ahlbach grade. Analysis using Mann-Whitney U-test, Fisher’s exact test and Spearman’s rank correlation were performed. Results: The significant changes with increasing Ahlbach grade were that: the point of deepest wear moved posteriorly, the posterior extent of wear moved posteriorly and the size of the lesion increased. With ACL deterioration and rupture, the anterior extent of the wear moved forward and the size of lesion increased, but this did not occur through posterior migration of the posterior extent of the wear. There was a significant difference between the Ahlbach grade of ACL Normal and Absent knees. Conclusion: In early disease, the wear is situated more posteriorly than in medial disease. The wear size increases with ACL insufficiency, but the further posterior progression of wear associated with posterior femoral subluxation seen in advanced disease seems to be more dependant on the loss of bone reflected in the Ahlbach grading

Purpose: The purpose of this study was to determine what differences exist in the knee flexion, rotation and adduction moments and periarticular knee muscle activation patterns between subjects with medial compartment knee osteoarthritis (OA) and those with lateral compartment knee OA. Method: Forty eight individuals with knee OA were studied. The group was divided into those with predominantly medial compartment involvement (38 subjects, age 63 ± 8 years) and those with lateral involvement (10 subjects, age 63 ± 9 years). Three-dimensional motion (Optotrak) and ground reaction force (AMTI) data were collected while the subjects walked at a self-selected velocity. The knee flexion, rotation and adduction moments, time normalized to the percentage of one gait cycle, were calculated using an inverse dynamics approach. Electromyograms (EMG) were also collected from the rectus femoris, vastus lateralis, vastus medialis, medial and lateral hamstrings, and medial and lateral gastrocnemius and normalized to maximum voluntary isometric contractions. Knee moments and waveforms for each muscle for one complete gait cycle were analyzed for group differences using principal component analysis (PCA) followed by Student’s t-tests (alpha-adj = 0.017) for the PCA scores. Results: The two groups were statistical similar in terms of age, height, weight, and walking velocity (p> 0.05). PCA analysis revealed statistically significant differences (p< 0.017) in patterns for the knee adduction moment, medial gastrocnemius, and lateral hamstrings between the two groups. Conclusion: As expected, there was a difference in the knee adduction moment between the two groups. What is novel is that the muscle activation patterns from the lateral site group are consistent with an attempt to unload that compartment. The results of this study provide evidence that biomechanical and neuromuscular differences do exist, depending on the OA site. This could have implications for developing site-specific conservative management approaches

Soft tissue balancing in fixed genu valgum can be challenging and may lead to instability in flexion. Current techniques involve release of the tight secondary structures initially, with the fascia lata and the lateral capsule usually addressed first, and then the posterior capsule if necessary. If ligament testing does not permit neutral alignment in extension, release of the lateral collateral ligament becomes necessary.

The most common way of achieving neutral alignment is by lengthening the lateral structures through elevation of the proximal insertion of the lateral collateral ligament (LCL). This technique has two drawbacks: the lengthening affects both extension and flexion gaps and may give rise to excessive external rotation of the femoral implant, with too much offset of the rotational centre. Particularly when non-constrained prostheses are used, the resulting lateral instability in flexion can be a problem.

An alternative is to perform a release at the level of the distal insertion of the LCL, as advocated by Keblish and Buechel. However, this still induces undue external rotation of the femoral implant.

We think that if the situation in flexion before any release is satisfactory in terms of the patella, it should not be changed. This means that in order to maintain optimal patellofemoral function, the flexion gap should be addressed before any release. The task is then to achieve a good extension gap with a well-aligned knee. In fixed valgus deformities, this means distal translocation of the femoral insertion of the LCL by distal sliding lateral condylar osteotomy. This procedure aims to preserve the flexion condition and to allow distal slide of the lateral condylar osteotomised fragment. In doing the osteotomy, it is important to make the lateral fragment sufficiently large to allow relocation of the osteotomised fragment inside the prosthesis. This provides the immediate stability necessary for good healing. We have been using two simple cortical screws to ensure stability of the fragment.

This paper reports our experience in 100 cases.

Abstract. Introduction. Patient selection is key to the success of medial unicondylar knee arthroplasty (UKA). Progression of arthritis is the most common indication for revision. Various methods of assessing the lateral compartment have been used including stress radiography, radioisotope bone scanning, MRI, and visualisation at the time of surgery. Arthroscopy is another means of assessing the integrity of the lateral compartment. Methods. We used per-operative arthroscopy as a means to confirm suitability for UKA in a consecutive series of 279 Oxford medial UKA. This study reports the long-term results of a previously published cohort of knees. Our series of UKA with per-operative arthroscopy (Group 1) was compared to all Oxford UKA (Group 2) and all UKA in the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) (Group 3). Results. The 14-year cumulative percentage revision (CPR) was 18.5% (95% CI 12.7, 26.4) for group 1, 19.7% (95% CI 18.8, 20.6) for group 2, and 19.2% (95% CI 18.5, 19.8) for group 3. There was no statistically significant difference in the (CPR) for the entire period when group 1 was compared to groups 2 or 3. Progression of arthritis was the indication for revision in similar proportions for the three groups (Group 1: 32.3%, Group 2: 35.7% and Group 3: 33.5%). Following per-operative arthroscopy 21.6% (77/356) of knees underwent a change of surgical plan from UKA to TKA. Conclusion. Per-operative arthroscopy may improve medium-term medial unicompartmental knee survivorship but does not improve long-term survivorship nor reduce revision due to progression of arthritis

Biplane video X-ray (BVX) – with models segmented from magnetic resonance imaging (MRI) – is used to directly track bones during dynamic activities. Investigating tibiofemoral kinematics helps to understand effects of disease, injury, and possible interventions. Develop a protocol and compare in-vivo kinematics during loaded dynamic activities using BVX and MRI. BVX (60 FPS) was captured whilst three healthy volunteers performed three repeats of lunge, stair ascent and gait. MRI scans were performed (Magnetom 3T Prisma, Siemens). 3D bone models of the tibia and femur were segmented (Simpleware Scan IP, Synopsis). Bone poses were obtained by manually matching bone models to X-rays (DSX Suite, C-Motion Inc.). Mean range of motion (ROM) of the contact points on the medial and lateral tibial plateau were calculated using custom MATLAB code (MathWorks). Results were filtered using an adaptive low pass Butterworth filter (Frequency range: 5-29Hz). Gait and Stair ascent activities from one participant's data showed increased ROM for medial-lateral (ML) translation in the medial compartment but decreased ROM in anterior-posterior (AP) translation when comparing against the same translations on the lateral compartment of the tibial plateau. Lunge activity showed increased ROM for both ML and AP translation in the medial compartment when compared with the lateral compartment. These results highlight the variability in condylar translations between different activities. Understanding healthy in-vivo kinematics across different activities allows the determination of suitable activities to best investigate the kinematic changes due to disease or injury and assess the efficacy of different interventions. Acknowledgements: This research was supported by the Engineering and Physical Sciences Research Council (EPSRC) doctoral training grant (EP/T517951/1)

Aims. Micromotion of the polyethylene (PE) inlay may contribute to backside PE wear in addition to articulate wear of total knee arthroplasty (TKA). Using radiostereometric analysis (RSA) with tantalum beads in the PE inlay, we evaluated PE micromotion and its relationship to PE wear. Methods. A total of 23 patients with a mean age of 83 years (77 to 91), were available from a RSA study on cemented TKA with Maxim tibial components (Zimmer Biomet). PE inlay migration, PE wear, tibial component migration, and the anatomical knee axis were evaluated on weightbearing stereoradiographs. PE inlay wear was measured as the deepest penetration of the femoral component into the PE inlay. Results. At mean six years’ follow-up, the PE wear rate was 0.08 mm/year (95% confidence interval 0.06 to 0.09 mm/year). PE inlay external rotation was below the precision limit and did not influence PE wear. Varus knee alignment did not influence PE wear (p = 0.874), but increased tibial component total translation (p = 0.041). Conclusion. The PE inlay was well fixed and there was no relationship between PE stability and PE wear. The PE wear rate was low and similar in the medial and lateral compartments. Varus knee alignment did not influence PE wear. Cite this article: Bone Joint Res 2024;13(5):226–236

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

Numerous papers present in-vivo knee kinematics data following total knee arthroplasty (TKA) from fluoroscopic testing. Comparing data is challenging given the large number of factors that potentially affect the reported kinematics. This paper aims at understanding the effect of following three different factors: implant geometry, performed activity and analysis method. A total of 30 patients who underwent TKA were included in this study. This group was subdivided in three equal groups: each group receiving a different type of posterior stabilized total knee prosthesis. During single-plane fluoroscopic analysis, each patient performed three activities: open chain flexion extension, closed chain squatting and chair-rising. The 2D fluoroscopic data were subsequently converted to 3D implant positions and used to evaluate the tibiofemoral contact points and landmark-based kinematic parameters. Significantly different anteroposterior translations and internal-external rotations were observed between the considered implants. In the lateral compartment, these differences only appeared after post-cam engagement. Comparing the activities, a significant more posterior position was observed for both the medial and lateral compartment in the closed chain activities during mid-flexion. A strong and significant correlation was found between the contact-points and landmarks-based analyses method. However, large individual variations were also observed, yielding a difference of up to 25% in anteroposterior position between both methods. In conclusion, all three evaluated factors significantly affect the obtained tibiofemoral kinematics. The individual implant design significantly affects the anteroposterior tibiofemoral position, internal-external rotation and timing of post-cam engagement. Both kinematics and post-cam engagement additionally depend on the activity investigated, with a more posterior position and associated higher patella lever arm for the closed chain activities. Attention should also be paid to the considered analysis method and associated kinematics definition: analyzing the tibiofemoral contact points potentially yields significantly different results compared to a landmark-based approach

Abstract. INTRODUCTION. A paucity of literature exists regarding efficacy of lateral unloader bracing in treatment for pathologies effecting the lateral compartment of the knee. We evaluate patient outcomes following customised lateral unloader bracing (cLUB) in treatment of lateral compartment osteoarthritis (LCOA), lateral tibial plateau fractures (LTPF) and spontaneous osteonecrosis of knee (SONK). METHODS. Institutional study approval was obtained. All patients undergoing cLUB between January 2013 and January 2021 were included, and prospectively followed-up. Visual Analogue Scales (VAS), Oxford Knee Scores (OKS) and Knee Injury and Osteoarthritis Outcome Scores (KOOS) were assessed at brace fitting and final follow-up. Brace compliance, complications and surgical interventions were also collected. Statistical analysis utilised paired t-test. RESULTS. 71 patients (LCOA n=47, LTPF n=21, SONK n=3) were analysed. VAS, OKS and KOOS scores show significant improvements after bracing (p<0.05). Brace compliance was 90.5%. One patient developed a deep-vein thrombosis, 12.7% suffered skin irritation (n=5 LTPF/n=4 LCOA) managed with bio-skin calf sleeves, and brace intolerance occurred in 8.5% (n=6). Brace survivorship was 64.8% (n=46). Twenty-five patients underwent post-bracing surgery; LTPF n=2, LCOA n=22, SONK n=1. The mean time interval between brace fitting and arthroplasty for LKOA patients was 2.1 (range 0.5-4) years. CONCLUSION. Our cohort demonstrates good compliance and significant improvements with cLUB across acute and chronic pathologies. Surgery and associated risks were avoided in certain cases. Further research is required alongside a cost-analysis. However, with increasing disease burden and surgical waiting times cLUB could be a crucial component of management in selected knee pathology cases

Purpose. The purpose of this study was to elucidate kinematic change according to the implant's specific femoral rotation by using orthosensor (Verasense) implant with three degrees external rotation of femoral rotation rebuilt (Genesis-II) and traditional TKA implant without rebuilt of the femoral rotation (Anthem). Methods. Twenty-eight patients (34 knees) underwent TKA using Anthem (Smith & Nephew, Memphis, TN, USA) and 16 patients (22 knees) underwent TKA using Genesis-II (Smith & Nephew, Memphis, TN, USA). Patients were followed up for at least 1 year. Mean age of patients was 71.1 years (range, 60 to 80 years) at the time of surgery. After implantation of femur and tibial components, we applied Verasense, the orthosensor system, to evaluate femoral rollback of the new artificial joint. Femoral rollback was analyzed using digitized screenshot function of Verasense. Results. Overall femoral tracking proportion regardless of implants was significantly higher on the medial compartment compared to that on the lateral compartment (13.3 ± 8.4% vs. 6.3 ± 5.0%, p < 0.001). Regarding femoral tracking according to each compartment, Genesis-II and Anthem showed 12.1 ± 8.2% and 14.2 ± 8.6% (p = 0.371) on the medial compartment and 8.0 ± 5.8% and 5.2 ± 4.2% (p = 0.059) on the lateral compartment, respectively. Conclusion. Our study showed reverse femoral roll-back movement with higher tracking distance on the lateral compartment during TKA. Genesis-II TKA system with femoral component 3-degree rebuilt showed less roll-back difference between medial and lateral compartments compared to traditional TKA system. Fortunately, both TKA systems had excellent short-term clinical outcomes without having significant difference between the two. With longer follow-up and larger cohort, the advantage and effectiveness of femoral component rotation can be elucidated in the future

Aims. Distal femoral osteotomies (DFOs) are commonly used for the correction of valgus deformities and lateral compartment osteoarthritis. However, the impact of a DFO on subsequent total knee arthroplasty (TKA) function remains a subject of debate. Therefore, the purpose of this study was to determine the effect of a unilateral DFO on subsequent TKA function in patients with bilateral TKAs, using the contralateral knee as a self-matched control group. Methods. The inclusion criteria consisted of patients who underwent simultaneous or staged bilateral TKA after prior unilateral DFO between 1972 and 2023. The type of osteotomy performed, osteotomy hardware fixation, implanted TKA components, and revision rates were recorded. Postoperative outcomes including the Forgotten Joint Score-12 (FJS-12), Tegner Activity Scale score, and subjective knee preference were also obtained at final follow-up. Results. A total of 21 patients underwent bilateral TKA following unilateral DFO and were followed for a mean of 31.5 years (SD 11.1; 20.2 to 74.2) after DFO. The mean time from DFO to TKA conversion was 13.1 years (SD 9.7) with 13 (61.9%) of DFO knees converting to TKA more than ten years after DFO. There was no difference in arthroplasty implant systems employed in both the DFO-TKA and TKA-only knees (p > 0.999). At final follow-up, the mean FJS-12 of the DFO-TKA knee was 62.7 (SD 36.6), while for the TKA-only knee it was 65.6 (SD 34.7) (p = 0.328). In all, 80% of patients had no subjective knee preference or preferred their DFO-TKA knee. Three DFO-TKA knees and two TKA-only knees underwent subsequent revision following index arthroplasty at a mean of 12.8 years (SD 6.9) and 8.5 years (SD 3.8), respectively (p > 0.999). Conclusion. In this self-matched study, DFOs did not affect subsequent TKA function as clinical outcomes, subjective knee preference, and revision rates were similar in both the DFO-TKA and TKA-only knees at mean 32-year follow-up. Cite this article: Bone Jt Open 2024;5(11):1013–1019

Intro/Purpose. Lateral partial knee replacement is indicated as an alternative to total knee replacement for isolated end stage lateral compartment degenerative joint disease. The purpose of this study is to report the surgical technique and clinical results of a large series of lateral partial knee replacements from two institutions. Methods. A retrospective review identified 205 lateral unicompartmental arthroplasty procedures performed in two practices over a six-year period (Aug 2011 – June 2017). Patients indicated for surgery met specific preoperative clinical and radiographic criteria confirming lateral compartment arthritic disease with a correctable deformity, intact full-thickness medial cartilage, competent anterior cruciate ligament, and minimal disease in the patellofemoral compartment. A single cemented fixed bearing tibial component design was used in all cases specifically designed for lateral compartment anatomy. Results. The average age was 65 years old and 76% were female. Average follow-up in the lateral partials was 1.7 years (range 0.5 years to 6 years). Knee Society Scores improved from 45 (pre-op) to 88 points (post-op). Range of motion improved from 6–115o (pre-op) to 0–122 o (post-op). No knees were revised to a TKA. One knee had an additional medial partial knee placed at 1.1 years post lateral partial knee replacement for medial disease progression. Two knees required an irrigation and debridement for traumatic wound dehiscence. Conclusion. This is the largest series of lateral partial knee replacements reported. Clinical improvements, range of motion, and survivorship were excellent at short-term follow-up. Long-term follow-up is needed for additional understanding of a novel implant designed specifically for the lateral compartment and the survivorship of the unreplaced compartments. We believe the lateral partial knee replacement to be a viable option for isolated lateral compartment disease in approximately 4% of patients

Objectives. The medially spherical GMK Sphere (Medacta International AG, Castel San Pietro, Switzerland) total knee arthroplasty (TKA) was previously shown to accommodate lateral rollback while pivoting around a stable medial compartment, aiming to replicate native knee kinematics in which some coronal laxity, especially laterally, is also present. We assess coronal plane kinematics of the GMK Sphere and explore the occurrence and pattern of articular separation during static and dynamic activities. Methods. Using pulsed fluoroscopy and image matching, the coronal kinematics and articular surface separation of 16 well-functioning TKAs were studied during weight-bearing and non-weight-bearing, static, and dynamic activities. The closest distances between the modelled articular surfaces were examined with respect to knee position, and proportions of joint poses exhibiting separation were computed. Results. Overall, 1717 joint poses were analyzed. At a 1.0 mm detection threshold, 37 instances of surface separation were observed in the lateral compartment and four medially (p < 0.001). Separation was activity-dependent, both laterally and medially (p < 0.001), occurring more commonly during static deep flexion in the lateral compartment, and during static rotation in the medial compartment. Lateral separation occurred more frequently than medial during kneeling (7/14 lateral vs 1/14 medial; p = 0.031) and stepping (20/1022 lateral vs 0/1022 medial; p < 0.001). Separation varied significantly between individuals during dynamic activities. Conclusion. No consistent association between closest distances of the articular surfaces and knee position was found during any activity. Lift-off was infrequent and depended on the activity performed and the individual knee. Lateral separation was consistent with the design rationale. Medial lift-off was rare and mostly in non-weight-bearing activities. Cite this article: S. Key, G. Scott, J. G. Stammers, M. A. R. Freeman†, V. Pinskerova, R. E. Field, J. Skinner, S. A. Banks. Does lateral lift-off occur in static and dynamic activity in a medially spherical total knee arthroplasty? A pulsed-fluoroscopic investigation. Bone Joint Res 2019;8:207–215. DOI: 10.1302/2046-3758.85.BJR-2018-0237.R1

Purpose. The purpose of the present study was to evaluate the intercompartmental loads with a sensor placed on implants after conventional gap balancing during total knee arthroplasty (TKA) with a tensiometer. Methods. Fifty sensor-assisted TKA procedures were performed prospectively between August and September 2018 with a cruciate-retaining prosthesis. After applying a modified measured technique, conventional balancing between the resected surfaces was achieved. The equal and rectangular flexion–extension gaps were confirmed using a tensiometer. Then, the load distribution was evaluated with a sensor. Results. The average load of the medial compartment was greater than that of the lateral compartment in both the flexion and extension of the knee. The proportion of medial–tight coronal load imbalance (medial load – lateral load ≥ 15 lb) was 50% in the extension and 28% in the flexion positions, respectively (p = 0.035). The loads in each medial and lateral compartment increased with extension of the knee; of note, the amount of increase was higher in the medial compartment (9.7 lb vs. 4.0 lb; p < 0.001). The proportion of the extension–tight sagittal load imbalance (extension load – flexion load ≥ 15lbs) was 34% in the medial compartment and 4% in the lateral compartment (p < 0.001). Conclusions. Coronal and sagittal load imbalances existed as determined by the sensor even after the achievement of appropriate conventional gap balance. The use of an intraoperative load sensor offers the advantage of being able to directly evaluate the load on TKA implants following surgery