1. Two cases of pseudomalignant osseous tumour of soft tissue are reported and added to the nineteen cases in the literature. 2. The clinical and histological features are described and distinguished from myositis ossificans, osteogenic sarcoma in soft tissue and parosteal fasciitis. 3. In one case the non-malignant nature of the lesion has been confirmed by its spontaneous regression

Ten patients with Charcot-Marie-Tooth disease have been reviewed at an average of 14 years after soft tissue procedures to correct foot deformities. No patient has so far required triple arthrodesis and the overall results as regards function, appearance and symptoms are satisfactory in all patients. It is concluded that soft tissue procedures can certainly postpone the need for triple arthrodesis and in many cases may obviate it altogether

We report a case of osteoclastoma of the distal radius originally treated by curettage, then by resection and bone replacement. There was a soft tissue recurrence of the tumor 13 years later

1. A case of pseudomalignant osseous tumour of soft tissue is reported. 2. The relationship between this condition and myositis ossificans is discussed and the importance of differentiating it from osteosarcoma is stressed

1. Five cases of pseudomalignant osseous tumour of soft tissue are reported. 2. Clinical and histological observations suggest that this lesion is a reactive condition initiated by an infection. 3. Tomography is helpful in demonstrating the characteristic peripheral ossification around non-ossified central regions of the lesion

Chondrosarcomas arising from soft tissues are rare. Two different varieties are described, myxoid and mesenchymal. We have collected nine cases of the tumour, five myxoid and four mesenchymal, from a review of 513 cases of chondrosarcoma seen between 1904 and 1988. We report the principal clinical, radiographical and histological differences between the two varieties and discuss their surgical treatment and prognosis

A total of seven patients (six men and one woman) with a defect in the Achilles tendon and overlying soft tissue underwent reconstruction using either a composite radial forearm flap (n = 3) or an anterolateral thigh flap (n = 4). The Achilles tendons were reconstructed using chimeric palmaris longus (n = 2) or tensor fascia lata (n = 2) flaps or transfer of the flexor hallucis longus tendon (n = 3). Surgical parameters such as the rate of complications and the time between the initial repair and flap surgery were analysed. Function was measured objectively by recording the circumference of the calf, the isometric strength of the plantar flexors and the range of movement of the ankle. The Achilles tendon Total Rupture Score (ATRS) questionnaire was used as a patient-reported outcome measure. Most patients had undergone several previous operations to the Achilles tendon prior to flap surgery. The mean time to flap surgery was 14.3 months (2.1 to 40.7). At a mean follow-up of 32.3 months (12.1 to 59.6) the circumference of the calf on the operated lower limb was reduced by a mean of 1.9 cm (. sd. 0.74) compared with the contralateral limb (p = 0.042). The mean strength of the plantar flexors on the operated lower limb was reduced to 88.9% of that of the contralateral limb (p = 0.043). There was no significant difference in the range of movement between the two sides (p = 0.317). The mean ATRS score was 72 points (. sd. 20.0). One patient who had an initial successful reconstruction developed a skin defect of the composite flap 12 months after free flap surgery and this resulted in recurrent infections, culminating in transtibial amputation 44 months after reconstruction. . These otherwise indicate that reconstruction of the Achilles tendon combined with flap cover results in a successful and functional reconstruction. Cite this article: Bone Joint J 2015;97-B:215–20

We treated 52 patients with impingement of the anterolateral soft tissues of the ankle by arthroscopic debridement. All had a history of single or multiple inversion injuries, without instability. One half had negative stress radiographs (stable group), while the others were positive (unstable group). Their mean age was 31 years and there were 35 men and 17 women. The results were assessed at a mean follow-up of 30 months. Three patients (6%) had a fair result, while 49 (94%) had an excellent or good outcome. No difference was found in the final results between the two groups (p > 0.05). We conclude that anterolateral impingement of the ankle should be considered in a patient with chronic anterolateral pain after an injury, regardless of the stability of the ankle

The usual causes of pain after total knee replacement are well known, but there are a small number of patients in whom its aetiology is obscure. We report three patients with a specific pain syndrome caused by hypertrophic fibrous tissue in the intercondylar notch. Excision of this tissue relieved the symptoms completely.

We describe the functional results in 14 patients (7 men, 7 women) after subtotal scapulectomy for primary bone and soft-tissue tumours at a specialist musculoskeletal oncology unit. Eight had chondrosarcomas, two Ewing’s sarcomas, one aggressive fibromatosis and three soft-tissue sarcomas. The mean follow-up was 52 months (6 to 120). Analysis of residual symptoms and of range and strength of movement by physicians used the Musculoskeletal Tumour Society rating scale (MSTS). Physical disability was measured by the patients using the Toronto Extremity Salvage Score (TESS).

All 14 patients are still alive, two with systemic disease. Nine had more than 80% of their scapula resected but the glenohumeral joint was preserved in all cases. Eight had full movement and another two achieved 90° of flexion. The mean functional results were good to excellent in all except three patients (mean MSTS = 71.6 and TESS = 79.9). Two of these three patients had considerable pain as a result of brachial neuropathy.

Scapulectomy gives an excellent functional result if the glenohumeral joint is preserved. The rotator cuff could be removed without a severe functional deficit provided that the deltoid was reattached to the scapular remnant and the trapezius.

Aims. The integrity of the soft tissue envelope is crucial for successful treatment of infected total knee arthroplasty (TKA). The purpose of this study was to evaluate the rate of limb salvage, infection control, and clinical function following microvascular free flap coverage for salvage of the infected TKA. Methods. We retrospectively reviewed 23 microvascular free tissue transfers for management of soft tissue defects in infected TKA. There were 16 men and seven women with a mean age of 61.2 years (39 to 81). The median number of procedures performed prior to soft tissue coverage was five (2 to 9) and all patients had failed at least one two-stage reimplantation procedure. Clinical outcomes were measured using the Knee Society Scoring system for pain and function. Results. In all, one patient was lost to follow-up prior to 12 months. The remaining 22 patients were followed for a mean of 46 months (12 to 92). At latest follow-up, four patients (18%) had undergone amputation for failure of treatment and persistent infection. For the other 18 patients, 11 patients (50%) had maintained a knee prosthesis in place while seven patients had undergone resections for persistent infection but retained their limbs (32%). Reoperations were common following coverage and reimplantation. The median number of additional procedures was two (0 to 6). Clinical function was poor in patients who underwent reimplantation and retained a knee prosthesis following free flap coverage with a mean KSS score for pain and function of 44 (0 to 70) and 30 (0 to 65), respectively. All patients required an assistive device. Extensor mechanism problems and extensor lag requiring bracing were common following limb salvage and prosthesis reimplantation. Conclusion. Microvascular tissue transfer for management of infected TKA can be successful in limb salvage (82%) but clinical outcomes in salvaged limbs were poor. Cite this article: Bone Joint J 2020;102-B(6 Supple A):176–180

Aims. The treatment of tibial aplasia is controversial. Amputation represents the gold standard with good functional results, but is frequently refused by the families. In these patients, treatment with reconstructive limb salvage can be considered. Due to the complexity of the deformity, this remains challenging and should be staged. The present study evaluated the role of femoro-pedal distraction using a circular external fixator in reconstructive treatment of tibial aplasia. The purpose of femoro-pedal distraction is to realign the limb and achieve soft tissue lengthening to allow subsequent reconstructive surgery. Methods. This was a retrospective study involving ten patients (12 limbs) with tibial aplasia, who underwent staged reconstruction. During the first operation a circular hexapod external fixator was applied and femoro-pedal distraction was undertaken over several months. Subsequent surgery included reconstruction of the knee joint and alignment of the foot. Results. The mean follow-up was 7.1 years (2 to 10). The mean age of the patients at the time of the application of the fixator was 2.3 years (1.1 to 5.0). The mean time under distraction was 139.7 days (81.0 to 177.0). A mean fibular distalization of 38.7 mm (14.0 to 67.0) was achieved. Pin infections occurred in four limbs (33.3%) and osteitis in one. A femoral fracture occurred in one patient. Premature removal of the frame was not required in any patient. Sufficient realignment of the leg as well as soft tissue lengthening was achieved in all patients, allowing subsequent reconstruction. All patients were able to mobilize fully weight bearing after reconstruction. Functional outcome was limited in all limbs, and five patients (50.0%) required additional reconstructive operations. Conclusion. Regarding the functional results in the treatment of tibial aplasia, amputation remains superior to limb salvage. The latter procedure should only be performed in patients whose parents refuse amputation. Femoro-pedal distraction efficiently prepares the limb by realigning the leg and soft tissue lengthening. Minor complications are frequent, but usually do not hinder the continuation of distraction. Even though a fully weight-bearing limb is achieved, the functional outcome of reconstructive treatment remains limited. Recurrent deformities frequently occur and may require further operations. Cite this article: Bone Joint J 2020;102-B(9):1248–1255

Aims. The aims of this study were to determine the effect of osteophyte excision on deformity correction and soft tissue gap balance in varus knees undergoing computer-assisted total knee arthroplasty (TKA). Methods. A total of 492 consecutive, cemented, cruciate-substituting TKAs performed for varus osteoarthritis were studied. After exposure and excision of both cruciates and menisci, it was noted from operative records the corrective interventions performed in each case. Knees in which no releases after the initial exposure, those which had only osteophyte excision, and those in which further interventions were performed were identified. From recorded navigation data, coronal and sagittal limb alignment, knee flexion range, and medial and lateral gap distances in maximum knee extension and 90° knee flexion with maximal varus and valgus stresses, were established, initially after exposure and excision of both cruciate ligaments, and then also at trialling. Knees were defined as ‘aligned’ if the hip-knee-ankle axis was between 177° and 180°, (0° to 3° varus) and ‘balanced’ if medial and lateral gaps in extension and at 90° flexion were within 2 mm of each other. Results. Of 50 knees (10%) with no soft tissue releases (other than cruciate ligaments), 90% were aligned, 81% were balanced, and 73% were aligned and balanced. In 288 knees (59%) only osteophyte excision was performed by subperiosteally releasing the deep medial collateral ligament. Of these, 98% were aligned, 80% were balanced, and 79% were aligned and balanced. In 154 knees (31%), additional procedures were performed (reduction osteotomy, posterior capsular release, and semimembranosus release). Of these, 89% were aligned, 68% were balanced, and 66% were aligned and balanced. The superficial medial collateral ligament was not released in any case. Conclusion. Two-thirds of all knees could be aligned and balanced with release of the cruciate ligaments alone and excision of osteophytes. Excision of osteophytes can be a useful step towards achieving deformity correction and gap balance without having to resort to soft tissue release in varus knees while maintaining classical coronal and sagittal alignment of components. Cite this article: Bone Joint J 2020;102-B(6 Supple A):49–58

Aims. The objectives of this study were to assess the effect of anterior cruciate ligament (ACL) resection on flexion-extension gaps, mediolateral soft tissue laxity, maximum knee extension, and limb alignment during primary total knee arthroplasty (TKA). Methods. This prospective study included 140 patients with symptomatic knee osteoarthritis undergoing primary robotic-arm assisted TKA. All operative procedures were performed by a single surgeon using a standard medial parapatellar approach. Optical motion capture technology with fixed femoral and tibial registration pins was used to assess study outcomes pre- and post-ACL resection with knee extension and 90° knee flexion. This study included 76 males (54.3%) and 64 females (45.7%) with a mean age of 64.1 years (SD 6.8) at time of surgery. Mean preoperative hip-knee-ankle deformity was 6.1° varus (SD 4.6° varus). Results. ACL resection increased the mean extension gap significantly more than the flexion gap in the medial (mean 1.2 mm (SD 1.0) versus mean 0.2 mm (SD 0.7) respectively; p < 0.001) and lateral (mean 1.1 mm (SD 0.9) versus mean 0.2 mm (SD 0.6) respectively; p < 0.001) compartments. The mean gap differences following ACL resection did not create any significant mediolateral soft tissue laxity in extension (gap difference: mean 0.1 mm (SD 2.4); p = 0.89) or flexion (gap difference: mean 0.2 mm (SD 3.1); p = 0.40). ACL resection did not significantly affect maximum knee extension (change in maximum knee extension = mean 0.2° (SD 0.7°); p = 0.23) or fixed flexion deformity (mean 4.2° (SD 3.2°) pre-ACL release versus mean 3.9° (SD 3.7°) post-ACL release; p = 0.61). ACL resection did not significantly affect overall limb alignment (change in alignment = mean 0.2° valgus (SD 1.0° valgus; p = 0.11). Conclusion. ACL resection creates flexion-extension mismatch by increasing the extension gap more than the flexion gap. However, gap differences following ACL resection do not create any mediolateral soft tissue laxity in extension or flexion. ACL resection does not affect maximum knee extension or overall limb alignment. Cite this article: Bone Joint J 2020;102-B(4):442–448

Aims. A comprehensive classification for coronal lower limb alignment with predictive capabilities for knee balance would be beneficial in total knee arthroplasty (TKA). This paper describes the Coronal Plane Alignment of the Knee (CPAK) classification and examines its utility in preoperative soft tissue balance prediction, comparing kinematic alignment (KA) to mechanical alignment (MA). Methods. A radiological analysis of 500 healthy and 500 osteoarthritic (OA) knees was used to assess the applicability of the CPAK classification. CPAK comprises nine phenotypes based on the arithmetic HKA (aHKA) that estimates constitutional limb alignment and joint line obliquity (JLO). Intraoperative balance was compared within each phenotype in a cohort of 138 computer-assisted TKAs randomized to KA or MA. Primary outcomes included descriptive analyses of healthy and OA groups per CPAK type, and comparison of balance at 10° of flexion within each type. Secondary outcomes assessed balance at 45° and 90° and bone recuts required to achieve final knee balance within each CPAK type. Results. There was similar frequency distribution between healthy and arthritic groups across all CPAK types. The most common categories were Type II (39.2% healthy vs 32.2% OA), Type I (26.4% healthy vs 19.4% OA) and Type V (15.4% healthy vs 14.6% OA). CPAK Types VII, VIII, and IX were rare in both populations. Across all CPAK types, a greater proportion of KA TKAs achieved optimal balance compared to MA. This effect was largest, and statistically significant, in CPAK Types I (100% KA vs 15% MA; p < 0.001), Type II (78% KA vs 46% MA; p = 0.018). and Type IV (89% KA vs 0% MA; p < 0.001). Conclusion. CPAK is a pragmatic, comprehensive classification for coronal knee alignment, based on constitutional alignment and JLO, that can be used in healthy and arthritic knees. CPAK identifies which knee phenotypes may benefit most from KA when optimization of soft tissue balance is prioritized. Further, it will allow for consistency of reporting in future studies. Cite this article: Bone Joint J 2021;103-B(2):329–337

Dissatisfaction following total knee arthroplasty is a well-documented phenomenon. Although many factors have been implicated, including modifiable and nonmodifiable patient factors, emphasis over the past decade has been on implant alignment and stability as both a cause of, and a solution to, this problem. Several alignment targets have evolved with a proliferation of techniques following the introduction of computer and robotic-assisted surgery. Mechanical alignment targets may achieve mechanically-sound alignment while ignoring the soft tissue envelope; kinematic alignment respects the soft tissue envelope while ignoring the mechanical environment. Functional alignment is proposed as a hybrid technique to allow mechanically-sound, soft tissue-friendly alignment targets to be identified and achieved. Cite this article: Bone Joint J 2020;102-B(3):276–279

Aims. Survival rates and local control after resection of a sarcoma of the pelvis compare poorly to those of the limbs and have a high incidence of complications. The outcome for patients who need a hindquarter amputation (HQA) to treat a pelvic sarcoma is poor. Our aim was to evaluate the patient, tumour, and reconstructive factors that affect the survival of the patients who undergo HQA for primary or recurrent pelvic sarcoma. Methods. We carried out a retrospective review of all sarcoma patients who had undergone a HQA in a supraregional sarcoma unit between 1996 and 2018. Outcomes included oncological, surgical, and survival characteristics. Results. A total of 136 patients, with a mean age of 51 (12 to 83) underwent HQA, 91 for a bone sarcoma and 45 for a soft tissue sarcoma. The overall survival (OS) after primary HQA for a bone sarcoma was 90.7 months (95% confidence interval (CI) 64.1 to 117.2). In patients undergoing a secondary salvage HQA it was 90.3 months (95% CI 58.1 to 122.5) (p = 0.727). For those treated for a soft tissue sarcoma (STS), the mean OS was 59.3 months (95% CI 31.1 to 88.6) for patients with a primary HQA, and 12.5 months (95% CI 9.4 to 15.5) for those undergoing a secondary salvage HQA (p = 0.038). On multivariate analysis, high histological grade (hazard ratio (HR) 2.033, 95% CI 1.127 to 3.676; p = 0.018) and a diagnosis of STS (HR 1.653, 95% CI 1.027 to 2.660; p = 0.039) were associated with a poor prognosis. The 30-day mortality for patients with curative intent was 0.8% (1/128). For those in whom surgery was carried out with palliative intent it was 33.3% (2/6) (p = 0.001). In total, 53.7% (n = 73) of patients had at least one complication with 23.5% (n = 32) requiring at least one further operation. Direct closure was inferior to flap reconstruction in terms of complete primary wound healing (60.0% (3/5) vs 82.0% (82/100); p = 0.023). Conclusion. In carefully selected patients HQA is associated with satisfactory overall survival, with a low risk of perioperative mortality, but considerable morbidity. However, caution must be exercised when considering the procedure for palliation due to the high incidence of early postoperative mortality. Cite this article: Bone Joint J 2020;102-B(6):788–794

Aims. To compare patients undergoing total knee arthroplasty (TKA) with ≤ 80° range of movement (ROM) operated with a 2 mm increase in the flexion gap with matched non-stiff patients with at least 100° of preoperative ROM and balanced flexion and extension gaps. Methods. In a retrospective cohort study, 98 TKAs (91 patients) with a preoperative ROM of ≤ 80° were examined. Mean follow-up time was 53 months (24 to 112). All TKAs in stiff knees were performed with a 2 mm increased flexion gap. Data were compared to a matched control group of 98 TKAs (86 patients) with a mean follow-up of 43 months (24 to 89). Knees in the control group had a preoperative ROM of at least 100° and balanced flexion and extension gaps. In all stiff and non-stiff knees posterior stabilized (PS) TKAs with patellar resurfacing in combination with adequate soft tissue balancing were used. Results. Overall mean ROM in stiff knees increased preoperatively from 67° (0° to 80°) to 114° postoperatively (65° to 135°) (p < 0.001). Mean knee flexion improved from 82° (0° to 110°) to 115° (65° to 135°) and mean flexion contracture decreased from 14° (0° to 50°) to 1° (0° to 10°) (p < 0.001). The mean Knee Society Score (KSS) improved from 34 (0 to 71) to 88 (38 to 100) (p < 0.001) and the KSS Functional Score from 43 (0 to 70) to 86 (0 to 100). Seven knees (7%) required manipulations under anaesthesia (MUA) and none of the knees had flexion instability. The mean overall ROM in the control group improved from 117° (100° to 140°) to 123° (100° to 130°) (p < 0.001). Mean knee flexion improved from 119° (100° to 140°) to 123° (100° to 130°) (p < 0.001) and mean flexion contracture decreased from 2° (0° to 15°) to 0° (0° to 5°) (p < 0.001). None of the knees in the control group had flexion instability or required MUA. The mean KSS Knee Score improved from 48 (0 to 80) to 94 (79 to 100) (p < 0.001) and the KSS Functional Score from 52 (5 to 100) to 95 (60 to 100) (p < 0.001). Mean improvement in ROM (p < 0.001) and KSS Knee Score (p = 0.017) were greater in knees with preoperative stiffness compared with the control group, but the KSS Functional Score improvement was comparable (p = 0.885). Conclusion. TKA with a 2 mm increased flexion gap provided a significant improvement of ROM in knees with preoperative stiffness. While the improvement in ROM was greater, the absolute postoperative ROM was less than in matched non-stiff knees. PS TKA with patellar resurfacing and a 2 mm increased flexion gap, in combination with adequate soft tissue balancing, provides excellent ROM and knee function when stiffness of the knee had been present preoperatively. Cite this article: Bone Joint J 2020;102-B(4):426–433

Aims. Patients with soft-tissue sarcoma (STS) who undergo unplanned excision (UE) are reported to have worse outcomes than those who undergo planned excision (PE). However, others have reported that patients who undergo UE may have similar or improved outcomes. These discrepancies are likely to be due to differences in characteristics between the two groups of patients. The aim of the study is to compare patients who underwent UE and PE using propensity score matching, by analyzing data from the Japanese Bone and Soft Tissue Tumor (BSTT) registry. Methods. Data from 2006 to 2016 was obtained from the BSTT registry. Only patients with STS of the limb were included in the study. Patients with distant metastasis at the initial presentation and patients with dermatofibrosarcoma protuberans and well-differentiated liposarcoma were excluded from the study. Results. A total of 4,483 patients with STS of the limb were identified before propensity score matching. There were 355 patients who underwent UE and 4,128 patients who underwent PE. The five-year disease-specific survival (DSS) rate was significantly better in the patients who received additional excision after UE than in those who underwent PE. There was no significant difference in local recurrence-free survival (LRFS) between the two groups. After propensity score matching, a new cohort of 355 patients was created for both PE and UE groups, in which baseline covariates were appropriately balanced. Reconstruction after tumour excision was frequently performed in patients who underwent additional excision after UE. There were no significant differences in DSS and LRFS between the patients who underwent PE and those who had an additional excision after UE. Conclusion. Using propensity score matching, patients with STS of the limb who underwent additional excision after UE did not experience higher mortality and local failure than those who underwent PE. Reconstruction may be necessary when additional excision is performed. Cite this article: Bone Joint J 2021;103-B(12):1809–1814

Aims. Local recurrence remains a challenging and common problem following curettage and joint-sparing surgery for giant cell tumour of bone (GCTB). We previously reported a 15% local recurrence rate at a median follow-up of 30 months in 20 patients with high-risk GCTB treated with neoadjuvant Denosumab. The aim of this study was to determine if this initial favourable outcome following the use of Denosumab was maintained with longer follow-up. Methods. Patients with GCTB of the limb considered high-risk for unsuccessful joint salvage, due to minimal periarticular and subchondral bone, large soft tissue mass, or pathological fracture, were treated with Denosumab followed by extended intralesional curettage with the goal of preserving the joint surface. Patients were followed for local recurrence, metastasis, and secondary sarcoma. Results. A total of 25 patients with a mean age of 33.8 years (18 to 67) with high-risk GCTB received median six cycles of Denosumab before surgery. Tumours occurred most commonly around the knee (17/25, 68%). The median follow-up was 57 months (interquartile range (IQR) 13 to 88). The joint was salvaged in 23 patients (92%). Two required knee arthroplasty due to intra-articular fracture and arthritis. Local recurrence developed in 11 patients (44%) at a mean of 32.5 months (3 to 75) following surgery, of whom four underwent repeat curettage and joint salvage. One patient developed secondary osteosarcoma and another benign GCT lung metastases. Conclusion. The use of Denosumab for joint salvage was associated with a higher than expected rate of local recurrence at 44%. Neoadjuvant Denosumab for joint-sparing procedures should be considered with caution in light of these results. Cite this article: Bone Joint J 2021;103-B(1):184–191

Aims. The primary aim of this study was to compare the postoperative systemic inflammatory response in conventional jig-based total knee arthroplasty (conventional TKA) versus robotic-arm assisted total knee arthroplasty (robotic TKA). Secondary aims were to compare the macroscopic soft tissue injury, femoral and tibial bone trauma, localized thermal response, and the accuracy of component positioning between the two treatment groups. Methods. This prospective randomized controlled trial included 30 patients with osteoarthritis of the knee undergoing conventional TKA versus robotic TKA. Predefined serum markers of inflammation and localized knee temperature were collected preoperatively and postoperatively at six hours, day 1, day 2, day 7, and day 28 following TKA. Blinded observers used the Macroscopic Soft Tissue Injury (MASTI) classification system to grade intraoperative periarticular soft tissue injury and bone trauma. Plain radiographs were used to assess the accuracy of achieving the planned postioning of the components in both groups. Results. Patients undergoing conventional TKA and robotic TKA had comparable changes in the postoperative systemic inflammatory and localized thermal response at six hours, day 1, day 2, and day 28 after surgery. Robotic TKA had significantly reduced levels of interleukin-6 (p < 0.001), tumour necrosis factor-α (p = 0.021), ESR (p = 0.001), CRP (p = 0.004), lactate dehydrogenase (p = 0.007), and creatine kinase (p = 0.004) at day 7 after surgery compared with conventional TKA. Robotic TKA was associated with significantly improved preservation of the periarticular soft tissue envelope (p < 0.001), and reduced femoral (p = 0.012) and tibial (p = 0.023) bone trauma compared with conventional TKA. Robotic TKA significantly improved the accuracy of achieving the planned limb alignment (p < 0.001), femoral component positioning (p < 0.001), and tibial component positioning (p < 0.001) compared with conventional TKA. Conclusion. Robotic TKA was associated with a transient reduction in the early (day 7) postoperative inflammatory response but there was no difference in the immediate (< 48 hours) or late (day 28) postoperative systemic inflammatory response compared with conventional TKA. Robotic TKA was associated with decreased iatrogenic periarticular soft tissue injury, reduced femoral and tibial bone trauma, and improved accuracy of component positioning compared with conventional TKA. Cite this article: Bone Joint J 2021;103-B(1):113–122

Aims. Inadvertent soft tissue damage caused by the oscillating saw during total knee arthroplasty (TKA) occurs when the sawblade passes beyond the bony boundaries into the soft tissue. The primary objective of this study is to assess the risk of inadvertent soft tissue damage during jig-based TKA by evaluating the excursion of the oscillating saw past the bony boundaries. The second objective is the investigation of the relation between this excursion and the surgeon’s experience level. Methods. A conventional jig-based TKA procedure with medial parapatellar approach was performed on 12 cadaveric knees by three experienced surgeons and three residents. During the proximal tibial resection, the motion of the oscillating saw with respect to the tibia was recorded. The distance of the outer point of this cutting portion to the edge of the bone was defined as the excursion of the oscillating saw. The excursion of the sawblade was evaluated in six zones containing the following structures: medial collateral ligament (MCL), posteromedial corner (PMC), iliotibial band (ITB), lateral collateral ligament (LCL), popliteus tendon (PopT), and neurovascular bundle (NVB). Results. The mean 75. th. percentile value of the excursion of all cases was mean 2.8 mm (SD 2.9) for the MCL zone, mean 4.8 mm (SD 5.9) for the PMC zone, mean 3.4 mm (SD 2.0) for the ITB zone, mean 6.3 mm (SD 4.8) for the LCL zone, mean 4.9 mm (SD 5.7) for the PopT zone, and mean 6.1 mm (SD 3.9) for the NVB zone. Experienced surgeons had a significantly lower excursion than residents. Conclusion. This study showed that the oscillating saw significantly passes the edge of the bone during the tibial resection in TKA, even in experienced hands. While reported neurovascular complications in TKA are rare, direct injury to the capsule and stabilizing structures around the knee is a consequence of the use of a hand-held oscillating saw when making the tibial cut. Cite this article: Bone Joint J 2020;102-B(10):1324–1330

Aims. The aim of this study was to determine the differences in spinal imaging characteristics between subjects with or without lumbar developmental spinal stenosis (DSS) in a population-based cohort. Methods. This was a radiological analysis of 2,387 participants who underwent L1-S1 MRI. Means and ranges were calculated for age, sex, BMI, and MRI measurements. Anteroposterior (AP) vertebral canal diameters were used to differentiate those with DSS from controls. Other imaging parameters included vertebral body dimensions, spinal canal dimensions, disc degeneration scores, and facet joint orientation. Mann-Whitney U and chi-squared tests were conducted to search for measurement differences between those with DSS and controls. In order to identify possible associations between DSS and MRI parameters, those who were statistically significant in the univariate binary logistic regression were included in a multivariate stepwise logistic regression after adjusting for demographics. Odds ratios (ORs) and 95% confidence intervals (CIs) were reported where appropriate. Results. Axial AP vertebral canal diameter (p < 0.001), interpedicular distance (p < 0.001), AP dural sac diameter (p < 0.001), lamina angle (p < 0.001), and sagittal mid-vertebral body height (p < 0.001) were significantly different between those identified as having DSS and controls. Narrower interpedicular distance (OR 0.745 (95% CI 0.618 to 0.900); p = 0.002) and AP dural sac diameter (OR 0.506 (95% CI 0.400 to 0.641); p < 0.001) were associated with DSS. Lamina angle (OR 1.127 (95% CI 1.045 to 1.214); p = 0.002) and right facet joint angulation (OR 0.022 (95% CI 0.002 to 0.247); p = 0.002) were also associated with DSS. No association was observed between disc parameters and DSS. Conclusion. From this large-scale cohort, the canal size is found to be independent of body stature. Other than spinal canal dimensions, abnormal orientations of lamina angle and facet joint angulation may also be a result of developmental variations, leading to increased likelihood of DSS. Other skeletal parameters are spared. There was no relationship between DSS and soft tissue changes of the spinal column, which suggests that DSS is a unique result of bony maldevelopment. These findings require validation in other ethnicities and populations. Level of Evidence: I (diagnostic study). Cite this article: Bone Joint J 2021;103-B(4):725–733

Aims. This study presents patient-reported quality of life (QoL) over the first year following surgical debridement of long bone osteomyelitis. It assesses the bone involvement, antimicrobial options, coverage of soft tissues, and host status (BACH) classification as a prognostic tool and its ability to stratify cases into ‘uncomplicated’ or ‘complex’. Methods. Patients with long-bone osteomyelitis were identified prospectively between June 2010 and October 2015. All patients underwent surgical debridement in a single-staged procedure at a specialist bone infection unit. Self-reported QoL was assessed prospectively using the three-level EuroQol five-dimension questionnaire (EQ-5D-3L) index score and visual analogue scale (EQ-VAS) at five postoperative time-points (baseline, 14 days, 42 days, 120 days, and 365 days). BACH classification was applied retrospectively by two clinicians blinded to outcome. Results. In total, 71 patients with long-bone osteomyelitis were included. There was significant improvement from time of surgery to one year postoperatively in mean EQ-VAS (58.2 to 78.9; p < 0.001) and mean EQ-5D-3L index scores (0.284 to 0.740; p < 0.001). At one year following surgery, BACH ‘uncomplicated’ osteomyelitis was associated with better QoL compared to BACH ‘complex’ osteomyelitis (mean EQ-5D-3L 0.900 vs 0.685; p = 0.020; mean EQ-VAS 87.1 vs 73.6; p = 0.043). Patients with uncomplicated bone involvement (BACH type B1, cavitary) reported higher QoL at all time-points when compared to complex bone involvement (B2, segmental or B3, osteomyelitis involving a joint). Patients with good antimicrobial options (Ax or A1) gave higher outcome scores compared to patients with multidrug-resistant isolates (A2). The need for microvascular tissue transfer (C1 and C2) did not impact significantly on QoL. Patients without major comorbidities (uncomplicated, H1) reported higher QoL compared to those with significant disease (complex, H2). Conclusion. Uncomplicated osteomyelitis, as defined by BACH, gave higher self-reported QoL when compared to complex cases. The bone involvement, antimicrobial options, and host status variables were able to stratify patients in terms of QoL. These data can be used to offer prognostic information to patients who are undergoing treatment for long bone osteomyelitis. Cite this article: Bone Joint J 2020;102-B(11):1587–1596

Aims. To assess the effect of age on clinical outcome and revision rates in patients who underwent total ankle arthroplasty (TAA) for end-stage ankle osteoarthritis (OA). Methods. A consecutive series of 811 ankles (789 patients) that underwent TAA between May 2003 and December 2013 were enrolled. The influence of age on clinical outcome, including the American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot score, and pain according to the visual analogue scale (VAS) was assessed. In addition, the risk for revision surgery that includes soft tissue procedures, periarticular arthrodeses/osteotomies, ankle joint debridement, and/or inlay exchange (defined as minor revision), as well as the risk for revision surgery necessitating the exchange of any of the metallic components or removal of implant followed by ankle/hindfoot fusion (defined as major revision) was calculated. Results. A significant improvement in the AOFAS hindfoot score and pain relief between the preoperative assessment and the last follow-up was evident. Age had a positive effect on pain relief. The risk for a minor or major revision was 28.7 % at the mean follow-up of 5.4 years and 11.0 % at a mean follow-up of 6.9 years respectively. The hazard of revision was not affected by age. Conclusion. The clinical outcome, as well as the probability for revision surgery following TAA, is comparable between younger and older patients. The overall revision rate of the Hintegra total ankle is comparable with other three component designs. TAA should no longer be reserved for low demand elderly patients, but should also be recognized as a viable option for active patients of younger age. Cite this article: Bone Joint J 2020;102-B(7):925–932

Aims. Previous research has demonstrated increased early complication rates following total hip arthroplasty (THA) in obese patients, as defined by body mass index (BMI). Subcutaneous fat depth (FD) has been shown to be an independent risk factor for wound infection in cervical and lumbar spine surgery, as well as after abdominal laparotomy. The aim of this study was to investigate whether increased peritrochanteric FD was associated with an increased risk of complications in the first year following THA. Methods. We analyzed prospectively collected data on a consecutive series of 1,220 primary THAs from June 2013 until May 2018. The vertical soft tissue depth from the most prominent part of the greater trochanter to the skin was measured intraoperatively using a sterile ruler and recorded to the nearest millimetre. BMI was calculated at the patient’s preoperative assessment. All surgical complications occuring within the initial 12 months of follow-up were identified. Results. Females had a significantly greater FD at the greater trochanter in comparison to males (median 3.0 cm (interquartile range (IQR) 2.3 to 4.0) vs 2.0 cm (IQR 1.7 to 3.0); p < 0.001) despite equivalent BMI between sexes (male median BMI 30.0 kg/m. 2. (IQR 27.0 to 33.0); female median 29.0 kg/m. 2. (IQR 25.0 to 33.0)). FD showed a weak correlation with BMI (R² 0.41 males and R² 0.43 females). Patients with the greatest FD (upper quartile) were at no greater risk of complications compared with patients with the lowest FD (lower quartile); 7/311 (2.3%) vs 9/439 (2.1%); p = 0.820 . Conversely, patients with the highest BMI (≥ 40 kg/m. 2. ) had a significantly increased risk of complications compared with patients with lower BMI (< 40 kg/m. 2. ); 5/60 (8.3% vs 18/1,160 (1.6%), odds ratio (OR) 5.77 (95% confidence interval (CI) 2.1 to 16.1; p = 0.001)). Conclusion. We found no relationship between peritrochanteric FD and the risk of surgical complications following primary THA. Cite this article: Bone Joint J 2020;102-B(9):1146–1150

Aims. The existing clinical guidelines do not describe a clear indication for adjuvant radiotherapy (RT) in the treatment of superficial soft tissue sarcomas (STSs). We aimed to determine the efficacy of adjuvant RT for superficial STSs. Methods. We retrospectively studied 304 patients with superficial STS of the limbs and trunk who underwent surgical resection at a tertiary sarcoma centre. The efficacy of RT was investigated according to the tumour size and grade: group 1, ≤ 5 cm, low grade; group 2, ≤ 5cm, high grade; group 3, > 5 cm, low grade; group 4, > 5 cm, high grade. Results. The five- and ten-year local recurrence-free survival (LRFS) for all patients was 88% and 81%, respectively. While the efficacy of adjuvant RT was not proven in local control of all patients (five-year LRFS; RT+, 90% versus RT-, 83%; p = 0.074), the LRFS was significantly improved by adjuvant RT in group 2 (five-year LRFS; RT+, 96% versus RT-, 82%; p = 0.019), and group 4 (five-year LRFS; RT+, 87% versus RT-, 73%; p = 0.027). In groups 2 and 4, adjuvant RT significantly reduced the LR risk if the resection margin was clear but less than 5 mm; the LR rate was 7% with adjuvant RT compared with 26% with surgery alone (p = 0.003). There was no statistical relationship with the use of adjuvant RT and survival in every group. Conclusion. Adjuvant RT reduces the risk of local recurrence in patients with superficial high-grade STS regardless of tumour size, especially when resection margin is less than 5 mm. Cite this article: Bone Joint J 2020;102-B(8):1088–1094

Aims. The aim of this study was to establish the results of isolated exchange of the tibial polyethylene insert in revision total knee arthroplasty (RTKA) in patients with well-fixed femoral or tibial components. We report on a series of RTKAs where only the polyethylene was replaced, and the patients were followed for a mean of 13.2 years (10.0 to 19.1). Patients and Methods. Our study group consisted of 64 non-infected, grossly stable TKA patients revised over an eight-year period (1998 to 2006). The mean age of the patients at time of revision was 72.2 years (48 to 88). There were 36 females (56%) and 28 males (44%) in the cohort. All patients had received the same cemented, cruciate-retaining patella resurfaced primary TKA. All subsequently underwent an isolated polyethylene insert exchange. The mean time from the primary TKA to RTKA was 9.1 years (2.2 to 16.1). Results. At final follow-up, 13 patients had died, leaving 51 patients for study. Only seven of these patients had required re-operation. Knee Society scores (KSS) prior to RTKA were a mean of 78.4 (24 to 100). By six weeks post-revision, the mean total KSS was 93.5 (38 to 100) and at final follow-up, they had a mean of 91.6 (36 to 100). Conclusion. In appropriate circumstances, where the femoral and tibial components are satisfactorily aligned and well fixed, and where the soft tissues can be balanced, a polyethylene exchange alone can provide a durable solution for these RTKA patients. Cite this article: Bone Joint J 2019;101-B(7 Supple C):104–107

Valgus knee deformity can present a number of unique surgical challenges for the total knee arthroplasty (TKA) surgeon. Understanding the typical patterns of bone and soft-tissue pathology in the valgus arthritic knee is critical for appropriate surgical planning. This review aims to provide the knee arthroplasty surgeon with an understanding of surgical management strategies for the treatment of valgus knee arthritis. Lateral femoral and tibial deficiencies, contracted lateral soft tissues, attenuated medial soft tissues, and multiplanar deformities may all be present in the valgus arthritic knee. A number of classifications have been reported in order to guide surgical management, and a variety of surgical strategies have been described with satisfactory clinical results. Depending on the severity of the deformity, a variety of TKA implant designs may be appropriate for use. Regardless of an operating surgeon’s preferred surgical strategy, adherence to a step-wise approach to deformity correction is advised. Cite this article: Bone Joint J 2017;99-B(1 Supple A):60–4

Ten acetabular cups coated with hydroxyapatite (HA) had originally been inserted in five primary and five revision total hip replacements. The thickness of the HA was 155 ± 35 μm. The cups, which were well-fixed, were retrieved, with their adherent tissue, at reoperation after 0.3 to 5.8 years because of infection (five hips), wear of polyethylene (three hips), and instability (two hips). Undecalcified sections showed a direct contact between bone and osteoid-like tissue which had formed directly onto the HA coating. The area within the threads and their mirror images, as well as the implant-tissue interfaces consisted of similar amounts of bone and soft tissue. Degradation of HA was seen in all hips. The mean thickness of the remaining HA coating was 97 μm (95% CI 94 to 101). The metal interface comprised 66% HA. The HA-tissue interface contained more bone than soft tissue (p = 0.001), whereas the metal-tissue interface included more soft tissue than bone (p = 0.019). Soft tissue at the implant interface and poor replacement of HA by bone may interfere with long-term fixation

Aims. The Intraosseous Transcutaneous Amputation Prosthesis (ITAP) may improve quality of life for amputees by avoiding soft-tissue complications associated with socket prostheses and by improving sensory feedback and function. It relies on the formation of a seal between the soft tissues and the implant and currently has a flange with drilled holes to promote dermal attachment. Despite this, infection remains a significant risk. This study explored alternative strategies to enhance soft-tissue integration. Materials and Methods. The effect of ITAP pins with a fully porous titanium alloy flange with interconnected pores on soft-tissue integration was investigated. The flanges were coated with fibronectin-functionalised hydroxyapatite and silver coatings, which have been shown to have an antibacterial effect, while also promoting viable fibroblast growth in vitro. The ITAP pins were implanted along the length of ovine tibias, and histological assessment was undertaken four weeks post-operatively. Results. The porous titanium alloy flange reduced epithelial downgrowth and increased soft-tissue integration compared with the current drilled flange. The addition of coatings did not enhance these effects. Conclusion. These results indicate that a fully porous titanium alloy flange has the potential to increase the soft-tissue seal around ITAP and reduce susceptibility to infection compared with the current design. Cite this article: Bone Joint J 2017;99-B:393–400

Aims. The aims of this study were to evaluate the long-term outcome of surgery for bone or soft-tissue metastases from renal cell carcinoma (RCC) and to determine factors that affect prognosis. Patients and Methods. Between 1993 and 2014, 58 patients underwent surgery for bone or soft-tissue metastases from RCC at our hospital. There were 46 men and 12 women with a mean age of 60 years (25 to 84). The mean follow-up period was 52 months (1 to 257). The surgical sites included the spine (33 patients), appendicular skeleton (ten patients), pelvis (eight patients), thorax (four patients), and soft tissue (three patients). The surgical procedures were en bloc metastasectomy in 46 patients (including 33 patients of total en bloc spondylectomy (TES)) and intralesional curettage in 12 patients. These patients were retrospectively evaluated for factors associated with prognosis. Results. The one-, three-, five-, ten-, and 15-year overall survival (OS) rates were 89%, 75%, 62%, 48%, and 25%, respectively. The median survival time (MST) was 127 months for en bloc metastasectomy and 54 months for intralesional curettage and bone grafting. The median survival time was 127 months for the spine, 140 months for lesions of the appendicular skeleton, and 54 months for the pelvis. Multivariate analysis showed that non-clear cell type RCC and metastases to more than two sites were independent risk factors for a poor prognosis. Conclusion. Patients with bone or soft-tissue metastases from a RCC have a reasonable prognosis, making surgical resection a viable option even in patients in whom the metastases are advanced. Cite this article: Bone Joint J 2018;100-B:1241–8

Aims. In patients undergoing medial opening wedge high tibial osteotomy (MOWHTO), soft tissue opening on the medial side of the knee is difficult to predict. When the load bearing axis is corrected beyond a certain point, the knee joint tilts open on the medial side. We therefore hypothesised that there is a tipping point and defined this as the coronal hypomochlion. Patients and Methods. In this prospective study of 150 navigated MOWHTOs (144 consecutive patients), data were collected before surgery and at three months post-operatively. In order to calculate the hypomochlion, we compared the respective changes to the joint line convergence angle (JLCA) with the post-operative axis of the leg. The change to the medial proximal tibial angle accounts for only about 80% of the change to the femorotibial angle; 20% of the correction can therefore be attributed to non-osseous, soft-tissue changes. Results. We were able to demonstrate a linear change of JLCA in a range of 0° to 5° of valgus which started when the post-operative long-leg axis was corrected beyond 2° of valgus. Conclusion. We found that the coronal hypomochlion occurs at 2° of valgus. Take home message: It is recommended to plan realignment for medial open wedge high tibial osteotomy at a maximum of 2° valgus. Cite this article: Bone Joint J 2016;98-B:628–33

Aims. The aims of this study were to establish whether composite fixation (rail-plate) decreases fixator time and related problems in the management of patients with infected nonunion of tibia with a segmental defect, without compromising the anatomical and functional outcomes achieved using the classical Ilizarov technique. We also wished to study the acceptability of this technique using patient-based objective criteria. Patients and Methods. Between January 2012 and January 2015, 14 consecutive patients were treated for an infected nonunion of the tibia with a gap and were included in the study. During stage one, a radical debridement of bone and soft tissue was undertaken with the introduction of an antibiotic-loaded cement spacer. At the second stage, the tibia was stabilized using a long lateral locked plate and a six-pin monorail fixator on its anteromedial surface. A corticotomy was performed at the appropriate level. During the third stage, i.e. at the end of the distraction phase, the transported fragment was aligned and fixed to the plate with two to four screws. An iliac crest autograft was added to the docking site and the fixator was removed. Functional outcome was assessed using the Association for the Study and Application of Methods of Ilizarov (ASAMI) criteria. Patient-reported outcomes were assessed using the Musculoskeletal Tumor Society (MSTS) score. Results. The mean age of patients was 38.1 years (. sd. 12.7). There were 13 men and one woman. The mean size of the defect was 6.4 cm (. sd. 1.3). the mean follow-up was 33.2 months (24 to 50). The mean external fixator index was 21.2 days/cm (. sd. 1.5). The complication rate was 0.5 (7/14) per patient. According to the classification of Paley, there were five problems and two obstacles but no true complications. The ASAMI bone score was excellent in all patients. The functional ASAMI scores were excellent in eight and good in six patients. The mean MSTS composite score was 83.9% (. sd. 7.1), with an MSTS emotional acceptance score of 4.9 (. sd. 0.5; maximum possible 5). Conclusion. Composite fixation (rail-plate) decreases fixator time and the associated complications, in the treatment of patients of infected nonunion tibia with a segmental defect. It also provides good anatomical and functional results with high emotional acceptance. Cite this article: Bone Joint J 2018;100-B:1094–9

In this in vitro study of the hip joint we examined which soft tissues act as primary and secondary passive rotational restraints when the hip joint is functionally loaded. A total of nine cadaveric left hips were mounted in a testing rig that allowed the application of forces, torques and rotations in all six degrees of freedom. The hip was rotated throughout a complete range of movement (ROM) and the contributions of the iliofemoral (medial and lateral arms), pubofemoral and ischiofemoral ligaments and the ligamentum teres to rotational restraint was determined by resecting a ligament and measuring the reduced torque required to achieve the same angular position as before resection. The contribution from the acetabular labrum was also measured. Each of the capsular ligaments acted as the primary hip rotation restraint somewhere within the complete ROM, and the ligamentum teres acted as a secondary restraint in high flexion, adduction and external rotation. The iliofemoral lateral arm and the ischiofemoral ligaments were primary restraints in two-thirds of the positions tested. Appreciation of the importance of these structures in preventing excessive hip rotation and subsequent impingement/instability may be relevant for surgeons undertaking both hip joint preserving surgery and hip arthroplasty. Cite this article: Bone Joint J 2015; 97-B:484–91

Primary giant-cell tumour of soft tissue arising in the ligamentum teres has not been previously described. We report a case of such a tumour in a 46-year-old woman. The lesion was only detected at the time of hip arthroscopy despite pre-operative MRI being performed. It was successfully excised arthroscopically with resolution of the symptoms

We retrospectively reviewed the outcomes of 33 consecutive patients who had undergone an extra-articular, total or partial scapulectomy for a malignant tumour of the shoulder girdle between 1 July 2001 and 30 September 2013. Of these, 26 had tumours which originated in the scapula or the adjacent soft tissue and underwent a classic Tikhoff–Linberg procedure, while seven with tumours arising from the proximal humerus were treated with a modified Tikhoff-Linberg operation. We used a Ligament Advanced Reinforcement System for soft-tissue reconstruction in nine patients, but not in the other 24. The mean Musculoskeletal Tumor Society score (MSTS) was 17.6 (95% confidence interval (CI) 15.9 to 19.4); 17.6 (95% CI 15.5 to 19.6) after the classic Tikhoff–Linberg procedure and 18.1 (95% CI 13.8 to 22.3) after the modified Tikhoff–Linberg procedure. Patients who had undergone a LARS soft-tissue reconstruction had a mean score of 18.6 (95% (CI) 13.9 to 22.4) compared with 17.2 (95% CI 15.5 to 19.0) for those who did not. The Tikhoff–Linberg procedure is a useful method for wide resection of a malignant tumour of the shoulder girdle which helps to preserve hand and elbow function. The method of soft-tissue reconstruction has no effect on functional outcome. . Cite this article: Bone Joint J 2014;96-B:684–90

The treatment of peri-prosthetic joint infection (PJI) of the ankle is not standardised. It is not clear whether an algorithm developed for hip and knee PJI can be used in the management of PJI of the ankle. We evaluated the outcome, at two or more years post-operatively, in 34 patients with PJI of the ankle, identified from a cohort of 511 patients who had undergone total ankle replacement. Their median age was 62.1 years (53.3 to 68.2), and 20 patients were women. Infection was exogenous in 28 (82.4%) and haematogenous in six (17.6%); 19 (55.9%) were acute infections and 15 (44.1%) chronic. Staphylococci were the cause of 24 infections (70.6%). Surgery with retention of one or both components was undertaken in 21 patients (61.8%), both components were replaced in ten (29.4%), and arthrodesis was undertaken in three (8.8%). An infection-free outcome with satisfactory function of the ankle was obtained in 23 patients (67.6%). The best rate of cure followed the exchange of both components (9/10, 90%). In the 21 patients in whom one or both components were retained, four had a relapse of the same infecting organism and three had an infection with another organism. Hence the rate of cure was 66.7% (14 of 21). In these 21 patients, we compared the treatment given to an algorithm developed for the treatment of PJI of the knee and hip. In 17 (80.9%) patients, treatment was not according to the algorithm. Most (11 of 17) had only one criterion against retention of one or both components. In all, ten of 11 patients with severe soft-tissue compromise as a single criterion had a relapse-free survival. We propose that the treatment concept for PJI of the ankle requires adaptation of the grading of quality of the soft tissues. Cite this article: Bone Joint J 2014;96-B:772–7

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