Aims. Knee joint distraction (KJD) is a relatively new, knee-joint preserving procedure with the goal of delaying total knee arthroplasty (TKA) in young and middle-aged patients. We present a randomised controlled trial comparing the two. Patients and Methods. The 60 patients ≤ 65 years with end-stage knee osteoarthritis were randomised to either KJD (n = 20) or TKA (n = 40). Outcomes were assessed at baseline, three, six, nine, and 12 months. In the KJD group, the joint space width (JSW) was radiologically assessed, representing a surrogate marker of cartilage thickness. Results. In total 56 patients completed their allocated treatment (TKA = 36, KJD = 20). All patient reported outcome measures improved significantly over one year (p < 0.02) in both groups. At one year, the TKA group showed a greater improvement in only one of the 16 patient-related outcome measures assessed (p = 0.034). Outcome Measures in Rheumatology-Osteoarthritis Research Society International clinical response was 83% after TKA and 80% after KJD. A total of 12 patients (60%) in the KJD group sustained pin track infections. In the KJD group both mean minimum (0.9 mm, standard deviation (. sd. ) 1.1) and mean JSW (1.2 mm, . sd. 1.1) increased significantly (p = 0.004 and p = 0.0003). Conclusion. In relatively young patients with end-stage knee osteoarthritis, KJD did not demonstrate inferiority of outcomes at one year when compared with TKA. However, there is a high incidence of pin track infection associated with KJD. Cite this article: Bone Joint J 2017;99-B:51–8

Knee joint distraction (KJD) is a joint-preserving treatment strategy for severe osteoarthritis (OA) that provides long-term clinical and structural improvement. Data from both human trials and animal models indicate clear cartilage regeneration from 6 months and onwards post-KJD. However, recent work showed that during distraction, the balance between catabolic and anabolic indicators is directed towards catabolism, as indicated by collagen type 2 markers, proteoglycan (PG) turnover and a catabolic transcription profile [unpublished data]. The focus of this study was to investigate the cartilage directly and 10 weeks after joint distraction in order to elucidate the shift from a catabolic to an anabolic cartilage state. Knee OA was induced bilaterally in 8 dogs according to the groove model. After 10 weeks of OA induction, all 8 animals received right knee joint distraction, employing the left knee as an OA control. After 8 weeks of distraction, 4 dogs were euthanized and after 10 weeks of follow-up the 4 other dogs. Macroscopic cartilage degeneration and synovial tissue inflammation was assessed using the OARSI canine scoring system. PG content was determined spectrometrically using Alcian Blue dye solution and the synthesis of newly formed PGs was determined using . 35. SO. 4. 2-. as a tracer, as was described before. Directly after KJD, macroscopic cartilage damage of the right tibial plateau was higher compared to the left OA control (OARSI score: 1.7±0.2 vs 0.6±0.3; p < 0.001). 10 weeks post-KJD this difference persisted (OARSI score: 1.4± 0.6 vs 0.6±0.3; p = 0.05). Directly after KJD, there was no difference in synovial inflammation between KJD and OA control (OARSI score: 1.4±0.5). At 10 weeks synovial inflammation increased significantly in the distracted knee (OARSI score: 2.1±0.3 vs 1.4±0.5; p < 0.05). Biochemical analysis of the tibia cartilage directly after KJD revealed a lower PG content (20.1±10.3 mg/g vs 23.7±11.7 mg/g). At 10 weeks post-KJD this difference in PG content was less (24.8±6.8 mg/g vs 25.4±7.8 mg/g). The PG synthesis rate directly after KJD appeared significantly lower vs. OA (1.4±0.6 nmol/h.g vs 5.9±4.4 nmol/h.g; p < 0.001)). However, 10 weeks post-KJD this difference was not detected (3.7±1.2 nmol/h.g vs 2.9±0.8 nmol/h.g), and the synthesis rate in the distracted knee was increased compared to directly after distraction (p < 0.01). Further in-depth investigation of the material is ongoing; these first results suggest that the shift from a catabolic to an anabolic state occurs within the first weeks after joint distraction, mostly reflected in the biochemical changes. As such, the post-distraction period seems to be essential in identifying key-players that support intrinsic cartilage repair

Knee joint distraction (KJD) has been associated with clinical and structural improvement and synovial fluid (SF) marker changes. However, structural changes have not yet been shown satisfactorily in regular care, since radiographic acquisition was not fully standardized. AI-based modules have shown great potential to reduce reading time, increase inter-reader agreement and therefore function as a tool for treatment outcome assessment. The objective was to analyse structural changes after KJD in patients using this AI-based measurement method, and relate these changes to clinical outcome and SF markers. 20 knee OA patients (<65 years old) were included in this study. KJD treatment was performed using an external fixation device, providing 5 mm distraction for 6 weeks. SF was aspirated before, during and immediately after treatment. Weight-bearing antero-posterior knee radiographs and WOMAC questionnaires were collected before and ~one year after treatment. Radiographs were analysed with the Knee Osteoarthritis Labelling Assistant (KOALA, IB Lab GmbH, Vienna, Austria), and 10 pre-defined biomarker levels in SF were measured by immunoassay. Radiographic one-year changes were analysed and linear regression was used to calculate associations between changes in standardized joint space width (JSW) and WOMAC, and changes in JSW and SF markers. After treatment, radiographs showed an improvement in Kellgren-Lawrence grade in 7 of 16 patients that could be evaluated; 3 showed a worsening. Joint space narrowing scores and continuous JSW measures improved especially medially. A greater improvement in JSW was significantly associated with a greater improvement in WOMAC pain (β=0.64;p=0.020). A greater increase in MCP1 (β=0.67;p=0.033) and lower increase in TGFβ1 (β=-0.787;p=0.007) were associated with JSW improvement. Despite the small number of patients, also in regular care KJD treatment shows joint repair as measured automatically on radiographs, significantly associated with certain SF marker change and even with clinical outcome

Introduction: Previous investigation showed that joint distraction (arthrodiastasis) is able to reduce intraarticular pressure and to have a positive effect on the regeneration of bone and cartilage on both sides of the joint. Many reports have been published about the results of arthrodiastasis in the treatment of femoral head necrosis in young children, pointing out good reconfiguration of the femoral head and improved range of motion. In contrast to that, -to our knowledge- there is so far no study showing the effect of hip joint distraction in older children with femoral head avascular necrosis. Question: In the present study the outcome of the treatment of femoral head avascular necrosis in older children by hip joint distraction was investigated. Methods: The hip joint distraction method was performed in three patients with necrosis of the femoral head. The causes of avascular necrosis were: Late onset Perthes’ disease in two patients and slipped capital femoral epiphysis (ECF) in one patient. The average age of the patients was 13.4 years. They all suffered from persistent severe pain and mostly limited range of motion of the hip joint. The plain radiographs revealed a Catterall IV, Herring C stade in both patients with late onset Perthes’disease. In the radiograph of the ECF patient a severe deformity of the femoral head was visible. After intraoperative soft tissue release, joint distraction was performed with an Ilizarov-ring fixation and immediately distracted 4–5 mm under image control. Distraction was continued 1 mm per day until the Shenton line was overcorrected. At this time the fixator was changed so that flexion-extension exercises were encouraged with the fixator in place. The patients were kept non-weight bearing. After 4 weeks the fixator was changed, so that in addition abduction up to 30° was possible. In total fixator duration time was 3.5 months. (In one case due to a fracture, the fixator was left for further 3 months) During distraction period with the fixator two patients suffered a femoral fracture without a causal adequate trauma. Due to these major complications further investigations on additional patients have been stopped. Results: The outcomes after 2.5 years showed in two patients an ankylosis of the hip joint with adductionflexion contracture and radiographical no reshaping of the femoral head. The third patient had a poor range of motion while radiographic findings showed a good reconfiguration of the femoral head. Nevertheless even in this patient advanced arthrosis was evident. Conclusion: In conclusion, due to the major complications and the unsatisfactory “middle-term”-results, arthrodiastasis as a therapy of avascular necrosis of the femoral head in older children has failed in our study. In our opinion fracture was as a result of immobilisation osteopenie

We have previously shown that joint distraction and movement with a hinged external fixation device for 12 weeks was useful for repairing a large articular cartilage defect in a rabbit model. We have now investigated the results after six months and one year. The device was applied to 16 rabbits who underwent resection of the articular cartilage and subchondral bone from the entire tibial plateau. In group A (nine rabbits) the device was applied for six months. In group B (seven rabbits) it was in place for six months, after which it was removed and the animals were allowed to move freely for an additional six months. The cartilage remained sound in all rabbits. The areas of type II collagen-positive staining and repaired soft tissue were larger in group B than in group A. These findings provide evidence of long-term persistence of repaired cartilage with this technique and that weight-bearing has a positive effect on the quality of the cartilage

Aim of the study: To evaluate the final outcome following joint distraction and reconstruction in patients with complex knee contractures in a select group with varied aetiology. Materials and methods: Retrospective study of six patients (nine knees, 3 bilateral) with severe knee flexion contractures treated by gradual distraction using ring fixators. Most cases were syndromic or arthrogrypotic.. Case notes and radiographs were reviewed to assess the mobility and functional range of motion before and after the procedure. Results: Staged procedures was carried out in 6 out of 9 knees accompanied by soft tissue releases, realignment of extensor mechanism and bony and joint realignment. The average age at operation was nine years and nine months and the mean follow up was 53 months. The average time spent in frame was 20 weeks. The correction was graded as good to excellent in 5 knees, fair in 1 and poor in 3 knees. The total arc of motion remained unchanged though the functional range of movement improved. The mobility improved significantly in most patients who were independent walkers with or without splints. Complications were of rebound phenomenon after frame removal in arthrogrypotic children, transient neuropraxia of common peroneal nerve in 2 epiphyseal separation in one and 3 sustained undisplaced fractures during mechanical distraction. Conclusion: Syndromic and arthrogrypotic knee contractures are difficult to treat due to their severity and complexity. Planned staged procedures with joint distraction, patellar and bony realignment can produce satisfactory outcome in most making them functional independent ambulators

We present the outcome of the treatment of chronic post-traumatic contractures of the proximal interphalangeal joint by gradual distraction correction using an external fixator. A total of 30 consecutive patients with a mean age of 34 years (17 to 54) had distraction for a mean of 16 days (10 to 22). The fixator was removed after a mean of 29 days (16 to 40). Assessment at a mean of 34 months (18 to 54) after completion of treatment showed that the mean active range of movement had significantly increased by 63° (30° to 90°; p < 0.001). The mean active extension gained was 47° (30° to 75°). Patients aged less than 40 years fared slightly better with a mean gain in active range of movement of 65° (30° to 90°) compared with those aged more than 40 years, who had a mean gain in active range of movement of 55° (30° to 70°) but the difference was not statistically significant (p = 0.148). The use of joint distraction to correct chronic flexion contracture of the proximal interphalangeal joint is a minimally-invasive and effective method of treatment

Osteoarthritis (OA) is a disease of the joints stemming from a variety of factors, including joint injuries and abnormally high mechanical loading. Although the traditional treatment alternatives for end-stage OA are arthroplasty in the case of the hip and knee, and arthroplasty or arthrodesis in the case of the ankle, these options are not ideal for younger, more active patients. For these patients, joint prostheses would be expected to fail relatively quickly, and ankle fusion is not amenable to maintaining their active lifestyles. In these cases, joint distraction has attracted investigative attention as a conservative OA treatment for younger patients. 9-14. . Based on the principle that decreasing the mechanical load on cartilage stimulates its regeneration. 15. , distraction treatment calls for reduced loading of the joint during a period of typically 3 months, during which time the load customarily passing through the joint is taken up by an external fixator spanning the joint . By mounting the fixator components to the bone on each side of the joint, and then lengthening the rods connecting the proximal and distal portions of the fixator, the joint is distracted. Assuming the fixation is appropriately stiff, any load passes through the fixator instead of the joint, and the two articular surfaces will not be allowed to contact each other under physiologic loading. The exact mechanisms leading to cartilage regeneration during distraction are not yet understood. A possible negative consequence of joint fixation is cartilage degeneration due to immobilization during the treatment. It has been shown by Haapala et al. and others that long-term immobilization can be detrimental to articular cartilage. 16-18. . Conversely, joint motion during fixation (even passive motion) is thought to stimulate or encourage cartilage regeneration. 19-22. Toward this end, considerable effort has been invested in the application of hinges to external fixation for joints Joint motion has also been suggested as a potentially beneficial factor in distraction treatment, as well. 10. This is borne out by data from an RCT comparing the use of a rigid vs motion external fixator. Change in joint biology due to resorption of cysts may be responsible for reversal of symptoms

We applied joint distraction using an Ilizarov apparatus in 11 patients with post-traumatic osteoarthritis of the ankle to try to delay the need for an arthrodesis. Distraction for three months resulted in clinical improvement in pain and mobility for a mean of two years, with an increase in the joint space. We considered that these effects may be produced by the absence of mechanical stress on the cartilage combined with the intra-articular hydrostatic pressures during distraction. We measured these pressures during walking with distraction, and found levels very similar to those reported to improve osteoarthritic cartilage when applied in vitro

Purpose: Instability of the injured elbow early after repair can lead to recurrent dislocation or failed fixation. Complementary immobilisation increases the risk of stiffness. The purpose of this study was to assess the contribution of dynamic external fixation which allows protected mobilisation and controlled distraction. We wanted to determine feasibility and appropriate indications.

Material and methods: We used the Pennig articulated elbow fixator in twelve trauma victims. Most had complex injuries: five dislocations with lesions of the medial ligaments and fractures of the radial head, including two with early recurrent dislocation; five joint fractures (involving to various degrees the lateral condyle, the head of the radius, the olecranon, and the humeral surface). This fixation method was also used for old or sequelar lesions to achieve reconstruction of the humeral surface (n=3) or after extensive arthrolysis (n=2). Mobilisation was started on day five postop.

Results: For the fresh injuries, the humero-ulnar articulation was centred in all cases. In these patients, mean final flexion was 0.35.130° and pronation-supination was 0.10.155°. One purely lateral dislocation was observed. Radio-ulnar synostosis after fracture of the ulna (n=1) and osteoma (n=1) were also observed.

Discussion: This dynamic external fixation system is a simple and safe procedure if a rigorous technique is applied. This method enabled early rehabilitation without secondary displacement and also enabled reliable contention particularly important in these multiple injury patients. The patients experienced very little pain during rehabilitation exercises, probably due to the distraction which did not appear to provoke reflex dystrophy. For complex instability of the elbow, the reduction of stress forces during mobilisation movements enables an extension of the indications for preservation of the joint fragments. Less reliable results are obtained for stiff elbows with old lesions.

Introduction. Intra articular distal tibia fractures can lead to post-traumatic osteoarthritis. Joint distraction has shown promise in elective cases. However, its application in acute fractures remains unexplored. This pilot study aims to fill this knowledge gap by investigating the benefits of joint distraction in acute fractures. Materials & Methods. We undertook a restrospective cohort study comprising patients with intra-articular distal tibia and pilon fractures treated with a circular ring fixator (CRF) at a single center. Prospective data collection included radiological assessments, Patient-Reported Outcome Measures (PROM), necessity for additional procedures, and Kellgren and Lawrence grade (KL) for osteoarthritis (OA). 137 patients were included in the study, 30 in the distraction group and 107 in the non-distraction group. There was no significant difference between the groups. Results. Mean follow-up was 3.73 years. There was no significant difference between the groups in overall complications or need for further procedures. There was no significant difference in progression of KL between the groups (1.81 vs 2.0, p=0.38) mean follow up 1.90 years. PROM data was available for 44 patients (6 distraction, 38 non-distraction) with a mean follow-up of 1.71 years. There was no significant difference in EQ5D (p=0.32) and C Olerud-H Molander scores (p=0.17). Conclusions. This pilot study suggests that joint distraction is safe in the acute setting. However, the study's impact is constrained by a relatively small patient cohort and a short-term follow-up period. Future investigations should prioritise longer-term follow-ups and involve a larger patient population to more comprehensively evaluate the potential benefits of joint distraction in acute fractures

Aims. The aim of this study was to evaluate the kinematics of the elbow following increasing length of the radius with implantation of radial head arthroplasties (RHAs) using dynamic radiostereometry (dRSA). Methods. Eight human donor arms were examined by dRSA during motor-controlled flexion and extension of the elbow with the forearm in an unloaded neutral position, and in pronation and supination with and without a 10 N valgus or varus load, respectively. The elbows were examined before and after RHA with stem lengths of anatomical size, + 2 mm, and + 4 mm. The ligaments were maintained intact by using a step-cut lateral humeral epicondylar osteotomy, allowing the RHAs to be repeatedly exchanged. Bone models were obtained from CT scans, and specialized software was used to match these models with the dRSA recordings. The flexion kinematics of the elbow were described using anatomical coordinate systems to define translations and rotations with six degrees of freedom. Results. The greatest kinematic changes in the elbows were seen with the longest, + 4 mm, implant, which imposed a mean joint distraction of 2.8 mm in the radiohumeral joint and of 1.1 mm in the ulnohumeral joint, an increased mean varus angle of up to 2.4° for both the radius and the ulna, a mean shift of the radius of 2.0 mm in the ulnar direction, and a mean shift of the ulna of 1.0 mm posteriorly. Conclusion. The kinematics of the elbow deviated increasingly from those of the native joint with a 2 mm to a 4 mm lengthening of the radius. This confirms the importance of restoring the natural length of the radius when undertaking RHA. Cite this article: Bone Joint J 2024;106-B(10):1165–1175

We produced large full-thickness articular cartilage defects in 33 rabbits in order to evaluate the effect of joint distraction and autologous culture-expanded bone-marrow-derived mesenchymal cell transplantation (ACBMT) at 12 weeks. After fixing the knee on a hinged external fixator, we resected the entire surface of the tibial plateau. We studied three groups: 1) with and without joint distraction; 2) with joint distraction and collagen gel, and 3) with joint distraction and ACBMT and collagen gel. The histological scores were significantly higher in the groups with ACBMT collagen gel (p < 0.05). The area of regenerated soft tissue was smaller in the group allowed to bear weight (p < 0.05). These findings suggest that the repair of large defects of cartilage can be enhanced by joint distraction, collagen gel and ACBMT

Management of ankle arthritis in young patients is challenging. Although ankle arthrodesis gives consistent pain relief, it leads to loss of function and adjacent joint arthritis. Ankle joint distraction (AJD) has been shown to give good outcomes in adults with osteoarthritis or post-traumatic arthritis. The efficacy in children or young adults and those with juvenile idiopathic arthritis is less well evidenced. Clinical notes and radiographs of all patients (n=6) managed with AJD in one tertiary referral centre were retrospectively reviewed. Radiographs were taken pre-surgery, intra-operatively, 1 month following frame removal and at the last follow up, tibiotalar joint space was assessed using ImageJ software. Measurements were taken at the medial, middle and lateral talar dome using frame components as reference. Radiographic data for patients with a good clinical outcome was compared with those who did not. At time of surgery mean age was 16.1 years (12 – 25 years). Mean follow up was 3.4 years (1.5 – 5.9 years). Indications were juvenile idiopathic arthritis (4) post-traumatic (1) and post-infective arthritis (1). Three patients at last follow up had a good clinical outcome. Two patients required revision to arthrodesis (1.3 and 2.4 years following distraction). One patient had spontaneous fusion. One patient required oral antibiotics for pin site infection. Inter-observer reliability was 95%. Mean joint space was 1.17mm (SD = 0.87mm) pre-operatively which increased to 6.72mm (SD = 2.23mm) at the time of distraction and 2.09mm (SD = 1.14mm) at the time of removal. At one-year follow up, mean joint space was 1.96mm (SD = 1.97mm). Outcomes following AJD in this population are variable although significant benefits were demonstrated for 50% of the patients in this series. Radiographic joint space preoperatively did not appear to be associated with need for arthrodesis. Further research in larger groups of young patients is required

Background. Post-operative (postop) lower limb alignment in unicompartmental knee arthroplasty (UKA) has been reported to be an important factor for postop outcomes. Slight under-correction of limb alignment has been recommended to yield a better clinical outcomes than neutral alignment. It is useful if the postop limb alignment can be predicted during surgery, however, little is known about the surgical factors affecting the postop limb alignment in UKA. The purpose of this study was to examine the influence of the medial tibial joint line elevation on postop limb alignment in UKA. Methods. Seventy-four consecutive medial UKAs were enrolled in this study. All the patients received a conventional fixed bearing UKA. Pre-operative (preop) and postop limb alignment was examined using long leg radiograph and lower limb alignment changes were calculated. Femoral and tibial osteotomy thickness were measured during surgery. Medial tibial joint line change was defined as polyethylene thickness minus tibial osteotomy thickness and sawblade thickness (1.27mm). Positive values indicated a tibial joint line elevation. Medial femoral joint line change was defined as femoral distal component thickness (6.5mm) minus femoral distal osteotomy thickness and sawblade thickness. Positive values indicated a femoral joint line reduction. Medial joint distraction width was also calculated by tibial joint line elevation plus femoral joint line reduction. The correlation of lower limb alignment change with polyethylene insert thickness, the medial tibial joint line elevation, femoral joint line reduction, or joint distraction width were analyzed. Results. The mean preop hip-knee-ankle (HKA) angle was 7.1 ± 3.3° in varus and postop was 2.1 ± 3.0° in varus. The mean lower limb alignment change was 5.0 ± 2.6°. The mean polyethylene insert thickness was 8.5 ± 0.8mm, the tibial joint line elevation was 4.4 ± 1.3mm and the medial femoral joint line reduction was 0.0 ± 1.1mm, the joint distraction width was 4.5 ± 1.5mm. The polyethylene insert thickness, the medial tibial joint line elevation, and the joint distraction width were positively correlated with the lower limb alignment change (R=0.27; P<0.05, R=0.47; P<0.001, R=0.53; P<0.001, respectively) (Figure 1a,b,d). There was no correlation between the medial femoral joint line reduction and the lower limb alignment change (Figure 1c). Discussion. The postop limb alignment in total knee arthroplasty (TKA) is determined by the osteotomy angle of the femur and tibia. On the other hand, it has been reported that the postop alignment in UKA is not influenced by the osteotomy angle but by the insert thickness. Our results indicated that the medial tibial joint line elevation and the joint distraction width were more useful to predict lower limb alignment change than the insert thickness itself. Measuring the medial tibial osteotomy thickness during surgery will help surgeon to predict postop lower limb alignment in UKA. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Introduction. Accurate soft tissue balancing in knee arthroplasty is essential in order to attain good postoperative clinical results. In mobile-bearing UKA (Oxford Partial Knee unicompartmental knee arthroplasty, Biomet), since determination of the thickness of the spacer block depends on the individual surgeon, it will vary and it will be difficult to attain appropriate knee balancing. The first objective of the present study was to investigate flexion and extension medial unicompartmental knee gap kinematics in conjunction with various joint distraction forces. The second objective of the study was to investigate the accuracy of gap measurement using a spacer block and a tensor device. Methods. A total of 40 knees in 31 subjects (5 men and 26 women) with a mean age of 71.5 years underwent Oxford UKA for knee osteoarthritis and idiopathic osteonecrosis of the medial compartment. According to instructions of Phase 3 Oxford UKA, spacer block technique was used to make the extension gap equal to the flexion gap. Adequate thickness of the spacer block was determined so that the surgeon could easily insert and remove it with no stress. Following osteotomy, the tensor devise was used to measure the medial compartmental gap between the femoral trial prosthesis and the tibial osteotomy surface (joint component gap) (Fig. 1 and 2). The medial gap was measured at 20° of knee flexion (extension gap) and 90° of knee flexion (flexion gap) with 25N, 50N, 75N, 100N, 125N, 150N of joint distraction force. Corresponding size of bearing was determined for the prosthesis. The interplay gap was calculated by subtracting the thickness of the tibial prosthesis and the thickness of the selected size of bearing from the measured extension and flexion gaps. Results. The selected bearing size was 3 mm: 3 knees, 4 mm: 20 knees, 5 mm: 15 knees and 6 mm: 2 knees. The mean flexion gap in the medial compartment was 25N: 8.4 ± 1.6 mm, 50N: 9.4 ± 1.6 mm, 75N: 10.4 ± 1.5 mm, 100N: 11.0 ± 1.4 mm, 125N: 11.6 ± 1.5 mm, 150N: 11.9 ± 1.4 mm. The mean extension gap was 25N: 7.8 ± 1.6 mm, 50N: 8.8 ± 1.6 mm, 75N: 9.7 ± 1.6 mm, 100N: 10.4 ± 1.5 mm, 125N: 11.1 ± 1.5 mm, 150N: 11.4 ± 1.5 mm. The mean flexion interplay gap was 25N: 0.5 ± 1.2 mm, 50N: 1.5 ± 1.2 mm, 75N: 2.4 ± 1.1 mm, 100N: 3.1 ± 1.0 mm, 125N: 3.6 ± 1.1 mm, 150N: 4.0 ± 1.1 mm. The mean extension interplay gap was 25N: −0.2 ± 1.2 mm, 50N: 0.8 ± 1.1 mm, 75N: 1.7 ± 1.2 mm, 100N: 2.5 ± 1.2 mm, 125N: 3.1 ± 1.2 mm, 150N: 3.5 ± 1.2 mm. When flexion and extension of the interplay gap were compared, the extension interplay gap was shown to be significantly smaller compared with the flexion interplay gap at every joint distraction force (p < 0.05). Conclusion. The mean extension interplay gap was shown to be significantly smaller compared with the flexion interplay gap at every joint distraction force even though the extension gap was adjusted to the flexion gap using the spacer block. This suggests that in the actual UKA operative technique using a spacer block there is a potential that the extension gap will be smaller than the flexion gap. Surgeons should be aware of this fact and adjust the flexion and extension gaps with caution when performing mobile-bearing UKA

Objective. Mobile bearing unicompartmental knee arthroplasty (UKA) is an effective and safe treatment for osteoarthritis of the medial compartment. However, mobile-bearing UKA needs accurate ligament balancing of flexion and extension gaps to prevent dislocation of the mobile meniscal bearing. Instability can lead to dislocation of the insert. The phase 3 instruments of the Oxford UKA use a balancing technique for the flexion gap (90° of flexion) and extension gap (20° of flexion), thereby focusing attention on satisfactory soft tissue balancing. With this technique, spacers are used to balance the flexion and extension gap. However, gap kinematics in another flexion angle of mobile-bearing UKA is unclear. We developed UKA tensor for mobile-bearing UKA and we assessed the accurate gap kinematics of UKA. Materials and Methods. Between 2012 and 2013, The Phase 3 Oxford Partial Knee UKA (Biomet Inc., Warsaw, IN) were carried out in 48 patients (71 knees) for unicompartmental knee osteoarthritis or spontaneous osteonecrosis of the medial compartment. The mean age of patients at surgery was 71.6 years and the mean follow-up period was 1.7 years. The mean preoperative coronal plane alignment was 7.4° in varus. The indications for UKA included disabling knee pain with medial compartment disease; intact ACL and collateral ligaments; preoperative contracture of less than 15°; and preoperative deformity of <15°. Each surgery was performed by using different spacer block with 1-mm increments and the meniscal bearing lift-off tests according to surgical technique. We developed newly tensor for mobile bearing UKA which designed to permit surgeons to measure multiple range of the joint medial compartment/joint component gap, while applying a constant joint distraction force (Figure 1). We assessed the intra-operative joint gap measurements at 0, 20, 60, 90 and 120 of flexion with 100N, 125N and 150N of joint distraction forces. Results. The gaps measured were 0°: 8.6 ± 1.6, 20°: 9.2 ± 1.4, 60°: 9.6 ± 1.2, 90°: 11.1 ± 1.3, 120°: 11.6 ± 1.8 in 100 N, 0°: 9.7 ± 1.7, 20°: 11.2 ± 1.3, 60°: 11.4 ± 1.3, 90°: 11.9 ± 1.5, 120°: 10.4 ± 1.6 in 125 N, 0°: 11.3±1.4, 20°: 11.8 ± 1.3, 60°: 11.1 ± 1.2, 90°: 12.5 ± 1.3, 120°: 11.9 ± 1.6 in 150N (Figure 2). There was a significant difference between full extension to extension (20° of flexion) and flexion (90° of flexion) to full flexion (120° of flexion). Conclusion. Mobile bearing UKA instrumentation using a balancing technique by spacer block for the flexion gap (90° of flexion) and extension gap (20° of flexion), full extension gap was significantly smaller than extension gap and flexion gap was significantly smaller than full flexion gap in 100N, 125N and 150N of joint distraction forces

Introduction. Both measured resection technique and gap balancing technique have been important surgical concepts in total knee arthroplasty (TKA). Modified gap technique has been reported to be beneficial for the intra-operative soft tissue balancing in posterior-stabilizing (PS) -TKA. On the other hand, we have found joint distraction force changed soft tissue balance measurement and medial knee instability would be more likely with aiming at perfect ligament balance at extension in modified gap technique. The medial knee stability after TKA was reported to essential for post-operative clinical result. We have developed a new surgical concept named as “medial preserving gap technique” for varus type osteoarthritic (OA) knees to preserve medial knee stability and provide quantitative surgical technique using tensor device. The purpose of this study was to compare post-operative knee stability between medial preserving gap technique (MPGT) and measured resection technique (MRT) in PS-TKA. Material & Method. The subjects were 140 patients underwent primary unilateral PS-TKA for varus type OA knees. The surgical technique was MPGT in 70 patients and MRT in 70 patients. There were no significant differences between two groups in the pre-operative clinical features including age, sex, ROM and deformity. Originally developed off-set type tensor device was used to evaluate both center gap and varus angle with 40 lbs. of joint distraction force. The extension gap preparation was identical in both group. In MPGT group, femoral component size and external rotation angle were adjusted depending on the differences of center gaps and varus angles between extension and flexion before posterior femoral condylar osteotomy. The knee stabilities at extension and flexion were assessed by stress radiographies; varus-valgus stress test with extension and stress epicondylar view with flexion, at one-month and one-year after TKA. We measured joint opening distance (mm) at medial and lateral compartment at both knee extension and flexion. Joint opening distances were compared between two groups using unpaired t-test, and the difference between medial and lateral compartment in each group was compared using paired t- test (p<0.05). Results. Joint opening distances at medial compartments with both extension and flexion were significantly smaller than lateral in both groups. There were no significant differences in join opening distance between two groups at medial compartment, but those at lateral were significantly smaller in MPGT than MRT with both knee extension and flexion. Discussion. In the present study, we found MPGT resulted in equal postoperative medial knee stability as in MRT, and superior to MRT as for the lateral knee stability. This finding would be the result of different femoral external rotation angle and femoral component size selection between two groups. We used the difference of varus angle and center gap between flexion and extension for the femoral component size selection and external rotation angle in MPGT. Quantitative surgical concept; MPGT, was found to be safer and feasible gap technique in PS-TKA to preserving medial knee stability and control lateral laxity in varus type OA knee. MPGT would be an advantageous gap technique to enhance clinical outcome

Introduction. Although gap balancing technique has been reported to be beneficial for the intra-operative soft tissue balancing in posterior-stabilized (PS)-TKA, excessive release of medial structures for achieving perfect ligament balance would be more likely to result in medial instability, which would deteriorate post-operative clinical results. We have modified conventional gap balancing technique and devised a new surgical concept; named as “medial gap technique” aiming at medial stability with permitting lateral looseness, as physiologically observed in normal knee. Objective. We compared intra-operative soft tissue balance between medial gap technique (MGT) and measured resection technique (MRT) in PS-TKAs. Materials and Methods. The subjects were 210 female patients with varus type osteoarthritic knees, underwent primary PS TKA. The surgical techniques were MGT in 96 patients and MRT in 114 patients. The extension gap was made in the same manners in both groups with medial releases limited until the spacer block could be easily inserted. The residual lateral laxity was permitted. In the MGT group, before posterior femoral osteotomies, varus angles (°) and center gaps (mm) at extension and flexion were measured using an offset type tensor with applying 40 lbs. (177.9N) of joint distraction force. The level and external rotation angle of posterior femoral osteotomies were determined based on the difference of center gaps and varus angles between extension and flexion respectively. Intra-operative joint gap kinematics was measured with femoral trial in place and patello-femoral joint reduced. We measured varus angle and component gap at 8 different knee flexion angles from 0° to 135°. From these component gaps and varus angles, we calculated a medial and lateral compartment gaps (MCG and LCG) by using a trigonometric function. Also we calculated the increase of both compartment gaps from those at full extension, named as joint gap loosening (mm). Both compartment gaps and joint gap loosening were compared between 2 groups using unpaired t-test, and the difference between MCG and LCG in each group were compared using paired t- test (p<0.05). Results. The mean MCGs showed significantly smaller value than LCGs at all flexion angles in both groups (Fig.1). Both medial and lateral joint gap loosening were significantly smaller in MGT group than MRT group from mid-flexion to deep flexion (Fig. 2, 3). Discussion. We have reported the joint distraction force affected varus imbalance due to the stiffness difference between medial and lateral structures. This might be a reason why gap technique was performed less quantitatively and with higher risk of medial instability. In MGT, we allowed persistent lateral looseness and applied the difference in varus angle between extension and flexion to the external rotation angle of femoral component. Results showed no medial looseness were observed in MGT like in MRT. The less joint gap loosening with knee flexion were achieved by MGT because the advantage of conventional gap balancing was also incorporated. We found “medial gap technique” was effective for quantitative soft tissue balancing with more stable joint gap kinematics and no medial looseness

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