The October 2023 Trauma Roundup. 360. looks at: Intramedullary nailing versus sliding hip screw in trochanteric fracture management: the INSITE randomized clinical trial; Five-year outcomes for patients with a displaced fracture of the distal tibia; Direct anterior versus anterolateral approach in hip joint hemiarthroplasty; Proximal humerus fractures: treat them all nonoperatively?; Tranexamic acid administration by prehospital personnel; Locked plating versus nailing for proximal tibia fractures: a multicentre randomized controlled trial; A retrospective review of the rate of septic knee arthritis after retrograde femoral nailing for traumatic femoral fractures at a single academic institution

Aims. The aim of this study was to compare the mid-term patient-reported outcome, bone remodelling, and migration of a short stem (Collum Femoris Preserving; CFP) with a conventional uncemented stem (Corail). Methods. Of 81 patients who were initially enrolled, 71 were available at five years’ follow-up. The outcomes at two years have previously been reported. The primary outcome measure was the clinical result assessed using the Oxford Hip Score (OHS). Secondary outcomes were the migration of the stem, measured using radiostereometric analysis (RSA), change of bone mineral density (BMD) around the stem, the development of radiolucent lines, and additional patient-reported outcome measures (PROMs). Results. There were no statistically significant differences between the groups regarding PROMs (median OHS (CFP 45 (interquartile range (IQR) 35 to 48); Corail 45 (IQR 40 to 48); p = 0.568). RSA showed stable stems in both groups, with little or no further subsidence between two and five years. Resorption of the femoral neck was evident in nine patients in the CFP group and in none of the 15 Corail stems with a collar that could be studied. Dual X-ray absorbiometry showed a significantly higher loss of BMD in the proximal Gruen zones in the CFP group (mean changes in BMD: Gruen zone 1, CFP -9.5 (95% confidence interval (CI) -14.8 to -4.2), Corail 1.0 (95% CI 3.4 to 5.4); Gruen zone 7, CFP -23.0 (95% CI -29.4 to -16.6), Corail -7.2 (95% CI -15.9 to 1.4). Two CFP stems were revised before two years’ follow-up due to loosening, and one Corail stem was revised after two years due to chronic infection. Conclusion. The CFP stem has a similar clinical outcome and subsidence pattern when compared with the Corail stem. More pronounced proximal stress-shielding was seen with the CFP stem, suggesting diaphyseal fixation, and questioning its femoral neck-sparing properties in the long term. Cite this article: Bone Joint J 2022;104-B(5):581–588

Aims. To determine the major risk factors for unplanned reoperations (UROs) following corrective surgery for adult spinal deformity (ASD) and their interactions, using machine learning-based prediction algorithms and game theory. Methods. Patients who underwent surgery for ASD, with a minimum of two-year follow-up, were retrospectively reviewed. In total, 210 patients were included and randomly allocated into training (70% of the sample size) and test (the remaining 30%) sets to develop the machine learning algorithm. Risk factors were included in the analysis, along with clinical characteristics and parameters acquired through diagnostic radiology. Results. Overall, 152 patients without and 58 with a history of surgical revision following surgery for ASD were observed; the mean age was 68.9 years (SD 8.7) and 66.9 years (SD 6.6), respectively. On implementing a random forest model, the classification of URO events resulted in a balanced accuracy of 86.8%. Among machine learning-extracted risk factors, URO, proximal junction failure (PJF), and postoperative distance from the posterosuperior corner of C7 and the vertical axis from the centroid of C2 (SVA) were significant upon Kaplan-Meier survival analysis. Conclusion. The major risk factors for URO following surgery for ASD, i.e. postoperative SVA and PJF, and their interactions were identified using a machine learning algorithm and game theory. Clinical benefits will depend on patient risk profiles. Cite this article: Bone Joint Res 2023;12(4):245–255

Aims. Several previously identified patient-, injury-, and treatment-related factors are associated with the development of nonunion in distal femur fractures. However, the predictive value of these factors is not well defined. We aimed to assess the predictive ability of previously identified risk factors in the development of nonunion leading to secondary surgery in distal femur fractures. Methods. We conducted a retrospective cohort study of adult patients with traumatic distal femur fracture treated with lateral locking plate between 2009 and 2018. The patients who underwent secondary surgery due to fracture healing problem or plate failure were considered having nonunion. Background knowledge of risk factors of distal femur fracture nonunion based on previous literature was used to form an initial set of variables. A logistic regression model was used with previously identified patient- and injury-related variables (age, sex, BMI, diabetes, smoking, periprosthetic fracture, open fracture, trauma energy, fracture zone length, fracture comminution, medial side comminution) in the first analysis and with treatment-related variables (different surgeon-controlled factors, e.g. plate length, screw placement, and proximal fixation) in the second analysis to predict the nonunion leading to secondary surgery in distal femur fractures. Results. We were able to include 299 fractures in 291 patients. Altogether, 31/299 fractures (10%) developed nonunion. In the first analysis, pseudo-R. 2. was 0.27 and area under the receiver operating characteristic curve (AUC) was 0.81. BMI was the most important variable in the prediction. In the second analysis, pseudo-R. 2. was 0.06 and AUC was 0.67. Plate length was the most important variable in the prediction. Conclusion. The model including patient- and injury-related factors had moderate fit and predictive ability in the prediction of distal femur fracture nonunion leading to secondary surgery. BMI was the most important variable in prediction of nonunion. Surgeon-controlled factors had a minor role in prediction of nonunion. Cite this article: Bone Jt Open 2023;4(8):584–593

The October 2024 Children’s orthopaedics Roundup. 360. looks at: Cost-effectiveness analysis of soft bandage and immediate discharge versus rigid immobilization in children with distal radius torus fractures: the FORCE trial; Percutaneous Achilles tendon tenotomy in clubfoot with a blade or a needle: a single-centre randomized controlled noninferiority trial; Treatment of hip displacement in children with cerebral palsy: a five-year comparison of proximal femoral osteotomy and combined femoral-pelvic osteotomy in 163 children; The Core outcome Clubfoot (CoCo) study: relapse, with poorer clinical and quality of life outcomes, affects 37% of idiopathic clubfoot patients; Retention versus removal of epiphyseal screws in paediatric distal tibial fractures: no significant impact on outcomes; Predicting the resolution of residual acetabular dysplasia after brace treatment in infant DDH; Low prevalence of acetabular dysplasia following treatment for neonatal hip instability: a long-term study; How best to distract the patient?

Aims. This study reports the results of 38 total hip arthroplasties (THAs) in 33 patients aged less than 50 years, using the JRI Furlong hydroxyapatite ceramic (HAC)-coated femoral component. Methods. We describe the survival, radiological, and functional outcomes of 33 patients (38 THAs) at a mean follow-up of 27 years (25 to 32) between 1988 and 2018. Results. Of the surviving 30 patients (34 THAs), there were four periprosthetic fractures: one underwent femoral revision after 21 years, two had surgical fixation as the stem was deemed stable, and one was treated nonoperatively due to the patient’s comorbidities. The periprosthetic fracture patients showed radiological evidence of change in bone stock around the femoral stem, which may have contributed to the fractures; this was reflected in change of the canal flare index at the proximal femur. Two patients (two hips) were lost to follow-up. Using aseptic loosening as the endpoint, 16 patients (18 hips; 48%) needed acetabular revision. None of the femoral components were revised for aseptic loosening, demonstrating 100% survival. The estimate of the cumulative proportion surviving for revisions due to any cause was 0.97 (standard error 0.03). Conclusion. In young patients with high demands, the Furlong HAC-coated femoral component gives excellent long-term results. Cite this article: Bone Jt Open 2024;5(4):286–293

Aims. For rare cases when a tumour infiltrates into the hip joint, extra-articular resection is required to obtain a safe margin. Endoprosthetic reconstruction following tumour resection can effectively ensure local control and improve postoperative function. However, maximizing bone preservation without compromising surgical margin remains a challenge for surgeons due to the complexity of the procedure. The purpose of the current study was to report clinical outcomes of patients who underwent extra-articular resection of the hip joint using a custom-made osteotomy guide and 3D-printed endoprosthesis. Methods. We reviewed 15 patients over a five-year period (January 2017 to December 2022) who had undergone extra-articular resection of the hip joint due to malignant tumour using a custom-made osteotomy guide and 3D-printed endoprosthesis. Each of the 15 patients had a single lesion, with six originating from the acetabulum side and nine from the proximal femur. All patients had their posterior column preserved according to the surgical plan. Results. Postoperative pathological assessment revealed a negative surgical margin was achieved in all patients. At final follow-up, 13.3% (2/15) died and no recurrence occurred. The overall survival was 81.7% at five years. None of the patients showed any signs of aseptic loosening, and no wound healing issues were observed. In total, 20% (3/15) developed complications, with two cases of early hip dislocation and one case of deep infection. The cumulative incidence of mechanical and non-mechanical failure in this series was 13.7% and 9.3%, respectively, at five years. In this cohort, the mean time to full weightbearing was 5.89 (SD 0.92) weeks and the mean Musculoskeletal Tumor Society score was 24.1 (SD 4.4). Conclusion. For patients with a hip joint tumour who met the inclusion criteria and were deemed suitable for posterior column preservation, a custom-made osteotomy guide combined with 3D-printed endoprosthesis is worth performing when treating patients who require extra-articular resection of the hip joint, as it can achieve adequate margin for local control, maximize bone preservation to maintain pelvic ring integrity, reduce the risk of complications by simplifying the surgical procedure, and allow for more precise reconstruction for better function. Cite this article: Bone Jt Open 2024;5(11):1027–1036

Aims. To investigate the risk factors for unsuccessful radial head reduction (RHR) in children with chronic Monteggia fractures (CMFs) treated surgically. Methods. A total of 209 children (mean age 6.84 years (SD 2.87)), who underwent surgical treatment for CMFs between March 2015 and March 2023 at six institutions, were retrospectively reviewed. Assessed risk factors included age, sex, laterality, dislocation direction and distance, preoperative proximal radial metaphysis width, time from injury to surgery, reduction method, annular ligament reconstruction, radiocapitellar joint fixation, ulnar osteotomy, site of ulnar osteotomy, preoperative and postoperative ulnar angulation, ulnar fixation method, progressive ulnar distraction, and postoperative cast immobilization. Independent-samples t-test, chi-squared test, and logistic regression analysis were used to identify the risk factors associated with unsuccessful RHR. Results. Redislocation occurred during surgery in 48 patients (23%), and during follow-up in 44 (21.1%). The mean follow-up of patients with successful RHR was 13.25 months (6 to 78). According to the univariable analysis, time from injury to surgery (p = 0.002) and preoperative dislocation distance (p = 0.042) were identified as potential risk factors for unsuccessful RHR. However, only time from injury to surgery (p = 0.007) was confirmed as a risk factor by logistic regression analysis. Receiver operating characteristic curve analysis and chi-squared test confirmed that a time from injury to surgery greater than 1.75 months increased the rate of unsuccessful RHR above the cutoff (p = 0.002). Conclusion. Time from injury to surgery is the primary independent risk factor for unsuccessful RHR in surgically treated children with CMFs, particularly in those with a time from injury to surgery of more than 1.75 months. No other factors were found to influence the incidence of unsuccessful RHR. Surgical reduction of paediatric CMFs should be performed within the first two months of injury whenever possible. Cite this article: Bone Jt Open 2024;5(7):581–591

The April 2023 Trauma Roundup. 360. looks at: Displaced femoral neck fractures in patients aged 55 to 70 years: internal fixation or total hip arthroplasty?; Tibial plateau fractures: continuous passive motion approves range of motion; Lisfranc fractures: to fuse or not to fuse, that is the question; Is hardware removal after clavicle fracture plate fixation beneficial?; Fixation to coverage in Grade IIIB open fractures – what’s the time window?; Nonoperative versus locking plate fixation in the proximal humerus; Retrograde knee nailing or lateral plate for distal femur fractures?

Aims. The aim of this study was to analyze how proximal radial neck resorption (PRNR) starts and progresses radiologically in two types of press-fit radial head arthroplasties (RHAs), and to investigate its clinical relevance. Methods. A total of 97 patients with RHA were analyzed: 56 received a bipolar RHA (Group 1) while 41 received an anatomical implant (Group 2). Radiographs were performed postoperatively and after three, six, nine, and 12 weeks, six, nine, 12, 18, and 24 months, and annually thereafter. PRNR was measured in all radiographs in the four radial neck quadrants. The Mayo Elbow Performance Score (MEPS), the abbreviated version of the Disabilities of the Arm, Shoulder, and Hand questionnaire (QuickDASH), and the patient-assessed American Shoulder and Elbow Surgeons score - Elbow (pASES-E) were used for the clinical assessment. Radiological signs of implant loosening were investigated. Results. The mean follow-up was six years (2 to 14). PRNR started after a mean of 7.5 weeks (SD 2.1) and progressed significantly during the first two years, by the end of which the bone resorption stabilized. PRNR was detected in 81% (n = 45) of patients in Group 1 and 88% (n = 36) in Group 2. The final mean PRNR was 3.0 mm (SD 2.3) in Group 1 and 3.7 mm (SD 2.5) in Group 2. The mean MEPS, QuickDASH, and pASES-E were 95.9 (SD 11.5), 4.4 (SD 9.2), and 94.8 (SD 10.9) in Group 1 and 92.2 (SD 16.2), 9.9 (SD 21.5), and 90.8 (SD 15) in Group 2, respectively. No significant differences were observed between groups in the clinical and radiological outcomes. No correlations were found between PRNR and the clinical results. Conclusion. PRNR after press-fit RHA is a common radiological finding that develops in the first 24 months before stabilizing definitively. PRNR does not affect the clinical results or implant survival in the mid term. Cite this article: Bone Joint J 2023;105-B(8):905–911

Aims. Surgical limb sparing for knee-bearing paediatric bone sarcoma is considered to have a clinically significant influence on postoperative function due to complications and leg-length discrepancies. However, researchers have not fully evaluated the long-term postoperative functional outcomes. Therefore, in this study, we aimed to elucidate the risk factors and long-term functional prognosis associated with paediatric limb-sparing surgery. Methods. We reviewed 40 patients aged under 14 years who underwent limb-sparing surgery for knee bone sarcoma (15 cases in the proximal tibia and 25 in the distal femur) between January 2000 and December 2013, and were followed up for a minimum of five years. A total of 35 patients underwent reconstruction using artificial materials, and five underwent biological reconstruction. We evaluated the patients’ postoperative complications, survival rate of reconstruction material, and limb, limb function, and leg-length discrepancy at the final follow-up, as well as the risk factors for each. Results. Complications were observed in 55% (22/40) of patients. The limb survival and reconstruction material rates at five and ten years were 95% and 91%, and 88% and 66%, respectively. Infection was the only risk factor in both survivals (p < 0.001, p = 0.019). In the 35 patients with limb preservation, the median International Society of Limb Salvage (ISOLS) score at the final follow-up was 80 (47% to 97%). Younger age (p = 0.027) and complications (p = 0.005) were poor prognostic factors. A negative correlation was found between age and leg-length discrepancy (R = −0.426; p = 0.011). The ISOLS scores were significantly lower in patients with a leg-length discrepancy of more than 5 cm (p = 0.005). Conclusion. Young age and complications were linked to an unfavourable functional prognosis. Leg-length correction was insufficient, especially in very young children, resulting in decreased function of the affected limb. Limb-sparing surgery for these children remains a considerable challenge. Cite this article: Bone Jt Open 2024;5(10):868–878

Aims. Acute and chronic injuries of the interosseus membrane can result in longitudinal instability of the forearm. Reconstruction of the central band of the interosseus membrane can help to restore biomechanical stability. Different methods have been used to reconstruct the central band, including tendon grafts, bone-ligament-bone grafts, and synthetic grafts. This Idea, Development, Exploration, Assessment, and Long-term (IDEAL) phase 1 study aims to review the clinical results of reconstruction using a synthetic braided cross-linked graft secured at either end with an Endobutton to restore the force balance between the bones of the forearm. Methods. An independent retrospective review was conducted of a consecutive series of 21 patients with longitudinal instability injuries treated with anatomical central band reconstruction between February 2011 and July 2019. Patients with less than 12 months’ follow-up or who were treated acutely were excluded, leaving 18 patients in total. Preoperative clinical and radiological assessments were compared with prospectively gathered data using range of motion and the abbreviated version of the Disabilities of the Arm, Shoulder and Hand questionnaire (QuickDASH) functional outcome score. Results. Of the 18 patients (nine male, nine female) who met the inclusion criteria, the median follow-up was 8.5 years (interquartile range (IQR) 5.6 to 10). Their mean age was 49 years (SD 11). The mean extension improved significantly from 38° (SD 15°) to 24° (SD 9°) (p = 0.027), with a mean flexion-extension arc change from 81° (SD 27°) to 93° (SD 30°) (p = 0.172) but with no forearm rotational improvement (p = 0.233) at latest follow-up. The QuickDASH functional score improved significantly from 80 (SD 14) to 52 (SD 26) following reconstruction (p = 0.031), but generally the level of disability remains high. Radiological assessment showed no progression of proximal migration of the radius, with a stable interbutton distance and ulnar variance from immediate postoperative radiograph to the latest follow-up. Conclusion. Central band interosseus membrane reconstruction using a synthetic braided cross-linked graft can improve patient-rated arm function and range of motion, but significant functional deficits remain in patients with chronic injuries. Cite this article: Bone Joint J 2024;106-B(2):182–188

Aims. When performing revision total hip arthroplasty using diaphyseal-engaging titanium tapered stems (TTS), the recommended 3 to 4 cm of stem-cortical diaphyseal contact may not be available. In challenging cases such as these with only 2 cm of contact, can sufficient axial stability be achieved and what is the benefit of a prophylactic cable? This study sought to determine, first, whether a prophylactic cable allows for sufficient axial stability when the contact length is 2 cm, and second, if differing TTS taper angles (2° vs 3.5°) impact these results. Methods. A biomechanical matched-pair cadaveric study was designed using six matched pairs of human fresh cadaveric femora prepared so that 2 cm of diaphyseal bone engaged with 2° (right femora) or 3.5° (left femora) TTS. Before impaction, three matched pairs received a single 100 lb-tensioned prophylactic beaded cable; the remaining three matched pairs received no cable adjuncts. Specimens underwent stepwise axial loading to 2600 N or until failure, defined as stem subsidence > 5 mm. Results. All specimens without cable adjuncts (6/6 femora) failed during axial testing, while all specimens with a prophylactic cable (6/6) successfully resisted axial load, regardless of taper angle. In total, four of the failed specimens experienced proximal longitudinal fractures, three of which occurred with the higher 3.5° TTS. One fracture occurred in a 3.5° TTS with a prophylactic cable yet passed axial testing, subsiding < 5 mm. Among specimens with a prophylactic cable, the 3.5° TTS resulted in lower mean subsidence (0.5 mm (SD 0.8)) compared with the 2° TTS (2.4 mm (SD 1.8)). Conclusion. A single prophylactic beaded cable dramatically improved initial axial stability when stem-cortex contact length was 2 cm. All implants failed secondary to fracture or subsidence > 5 mm when a prophylactic cable was not used. A higher taper angle appears to decrease the magnitude of subsidence but increased the fracture risk. The fracture risk was mitigated by the use of a prophylactic cable. Cite this article: Bone Jt Open 2023;4(7):472–477

Aims. Perthes’ disease (PD) often results in femoral head deformity and leg length discrepancy (LLD). Our objective was to analyze femoral morphology in PD patients at skeletal maturity to assess where the LLD originates, and evaluate the effect of contralateral epiphysiodesis for length equalization on proximal and subtrochanteric femoral lengths. Methods. All patients treated for PD in our institution between January 2013 and June 2020 were reviewed retrospectively. Patients with unilateral PD, LLD of ≥ 5 mm, and long-leg standing radiographs at skeletal maturity were included. Total leg length, femoral and tibial length, articulotrochanteric distance (ATD), and subtrochanteric femoral length were compared between PD side and the unaffected side. Furthermore, we compared leg length measurements between patients who did and who did not have a contralateral epiphysiodesis. Results. Overall, 79 patients were included, of whom 21 underwent contralateral epiphysiodesis for leg length correction. In the complete cohort, the mean LLD was 1.8 cm (95% confidence interval (CI) 1.5 to 2.0), mean ATD difference was 1.8 cm (95% CI -2.1 to -1.9), and mean subtrochanteric difference was -0.2 cm (95% CI -0.4 to 0.1). In the epiphysiodesis group, the mean LLD before epiphysiodesis was 2.7 cm (95% CI 1.3 to 3.4) and 1.3 cm (95% CI -0.5 to 3.8) at skeletal maturity. In the nonepiphysiodesis group the mean LLD was 2.0 cm (95% CI 0.5 to 5.1; p = 0.016). The subtrochanteric region on the PD side was significantly longer at skeletal maturity in the epiphysiodesis group compared to the nonepiphysiodesis group (-1.0 cm (95% CI -2.4 to 0.6) vs 0.1 cm (95% CI -1.0 to 2.1); p < 0.001). Conclusion. This study demonstrates that LLD after PD originates from the proximal segment only. In patients who had contralateral epiphysiodesis to balance leg length, this is achieved by creating a difference in subtrochanteric length. Arthroplasty surgeons need to be aware that shortening of the proximal femur segment in PD patients may be misleading, as the ipsilateral subtrochanteric length in these patients can be longer. Therefore, we strongly advise long-leg standing films for THA planning in PD patients in order to avoid inadvertently lengthening the limb. Cite this article: Bone Joint J 2021;103-B(11):1736–1741

Aims. Unicompartmental and total knee arthroplasty (UKA and TKA) are successful treatments for osteoarthritis, but the solid metal implants disrupt the natural distribution of stress and strain which can lead to bone loss over time. This generates problems if the implant needs to be revised. This study investigates whether titanium lattice UKA and TKA implants can maintain natural load transfer in the proximal tibia. Methods. In a cadaveric model, UKA and TKA procedures were performed on eight fresh-frozen knee specimens, using conventional (solid) and titanium lattice tibial implants. Stress at the bone-implant interfaces were measured and compared to the native knee. Results. Titanium lattice implants were able to restore the mechanical environment of the native tibia for both UKA and TKA designs. Maximum stress at the bone-implant interface ranged from 1.2 MPa to 3.3 MPa compared with 1.3 MPa to 2.7 MPa for the native tibia. The conventional solid UKA and TKA implants reduced the maximum stress in the bone by a factor of 10 and caused > 70% of bone surface area to be underloaded compared to the native tibia. Conclusion. Titanium lattice implants maintained the natural mechanical loading in the proximal tibia after UKA and TKA, but conventional solid implants did not. This is an exciting first step towards implants that maintain bone health, but such implants also have to meet fatigue and micromotion criteria to be clinically viable. Cite this article: Bone Joint Res 2022;11(2):91–101

Aims. Perthes' disease (PD) is a relatively rare syndrome of idiopathic osteonecrosis of the proximal femoral epiphysis. Treatment for Perthes' disease is controversial due to the many options available, with no clear superiority of one treatment over another. Despite having few evidence-based approaches, many patients with Perthes' disease are managed surgically. Positive outcome reporting, defined as reporting a study variable producing statistically significant positive (beneficial) results, is a phenomenon that can be considered a proxy for the strength of science. This study aims to conduct a systematic literature review with the hypothesis that positive outcome reporting is frequent in studies on the treatment of Perthes' disease. Methods. We conducted a systematic review of all available abstracts associated with manuscripts in English or with English translation between January 2000 and December 2021, dealing with the treatment of Perthes' disease. Data collection included various study characteristics, surgical versus non-surgical management, treatment modality, mean follow-up time, analysis methods, and clinical recommendations. Results. Our study included 130 manuscripts. Overall, 110 (85%) reported positive (beneficial) results, three (2%) reported negative results, and 17 (13%) reported no significant difference. Despite only 10/130 studies (8%) having a testable hypothesis, 71 (55%) recommended the use of their studied treatment methods for the patients, five (4%) made recommendations against the use of the studied treatment modality, and 54 (42%) did not make any recommendations. Conclusion. The overall rate for positive outcomes among included manuscripts regarding different treatment methods for Perthes' disease (85%) is higher than the 74% positive outcome rate found among studies for other surgically treated disorders and significantly higher than most scientific literature. Despite the lack of testable hypotheses, most manuscripts recommended their studied treatment method as a successful option for managing patients solely based on the reporting of retrospective data. Cite this article: Bone Joint J 2024;106-B(2):121–127

Aims. In order to release the contracture band completely without damaging normal tissues (such as the sciatic nerve) in the surgical treatment of gluteal muscle contracture (GMC), we tried to display the relationship between normal tissue and contracture bands by magnetic resonance neurography (MRN) images, and to predesign a minimally invasive surgery based on the MRN images in advance. Methods. A total of 30 patients (60 hips) were included in this study. MRN scans of the pelvis were performed before surgery. The contracture band shape and external rotation angle (ERA) of the proximal femur were also analyzed. Then, the minimally invasive GMC releasing surgery was performed based on the images and measurements, and during the operation, incision lengths, surgery duration, intraoperative bleeding, and complications were recorded; the time of the first postoperative off-bed activity was also recorded. Furthermore, the patients’ clinical functions were evaluated by means of Hip Outcome Score (HOS) and Ye et al’s objective assessments, respectively. Results. The contracture bands exhibited three typical types of shape – feather-like, striped, and mixed shapes – in MR images. Guided by MRN images, we designed minimally invasive approaches directed to each hip. These approaches resulted in a shortened incision length in each hip (0.3 cm (SD 0.1)), shorter surgery duration (25.3 minutes (SD 5.8)), less intraoperative bleeding (8.0 ml (SD 3.6)), and shorter time between the end of the operation and the patient’s first off-bed activity (17.2 hours (SD 2.0)) in each patient. Meanwhile, no serious postoperative complications occurred in all patients. The mean HOS-Sports subscale of patients increased from 71.0 (SD 5.3) to 94.83 (SD 4.24) at six months postoperatively (p < 0.001). The follow-up outcomes from all patients were “good” and “excellent”, based on objective assessments. Conclusion. Preoperative MRN analysis can be used to facilitate the determination of the relationship between contracture band and normal tissues. The minimally invasive surgical design via MRN can avoid nerve damage and improve the release effect. Cite this article: Bone Jt Open 2024;5(9):776–784

Aims. The surgical target for optimal implant positioning in robotic-assisted total knee arthroplasty remains the subject of ongoing discussion. One of the proposed targets is to recreate the knee’s functional behaviour as per its pre-diseased state. The aim of this study was to optimize implant positioning, starting from mechanical alignment (MA), toward restoring the pre-diseased status, including ligament strain and kinematic patterns, in a patient population. Methods. We used an active appearance model-based approach to segment the preoperative CT of 21 osteoarthritic patients, which identified the osteophyte-free surfaces and estimated cartilage from the segmented bones; these geometries were used to construct patient-specific musculoskeletal models of the pre-diseased knee. Subsequently, implantations were simulated using the MA method, and a previously developed optimization technique was employed to find the optimal implant position that minimized the root mean square deviation between pre-diseased and postoperative ligament strains and kinematics. Results. There were evident biomechanical differences between the simulated patient models, but also trends that appeared reproducible at the population level. Optimizing the implant position significantly reduced the maximum observed strain root mean square deviations within the cohort from 36.5% to below 5.3% for all but the anterolateral ligament; and concomitantly reduced the kinematic deviations from 3.8 mm (SD 1.7) and 4.7° (SD 1.9°) with MA to 2.7 mm (SD 1.4) and 3.7° (SD 1.9°) relative to the pre-diseased state. To achieve this, the femoral component consistently required translational adjustments in the anterior, lateral, and proximal directions, while the tibial component required a more posterior slope and varus rotation in most cases. Conclusion. These findings confirm that MA-induced biomechanical alterations relative to the pre-diseased state can be reduced by optimizing the implant position, and may have implications to further advance pre-planning in robotic-assisted surgery in order to restore pre-diseased knee function. Cite this article: Bone Joint J 2024;106-B(11):1231–1239

Aims. Intra-articular (IA) tumours around the knee are treated with extra-articular (EA) resection, which is associated with poor functional outcomes. We aim to evaluate the accuracy of MRI in predicting IA involvement around the knee. Methods. We identified 63 cases of high-grade sarcomas in or around the distal femur that underwent an EA resection from a prospectively maintained database (January 1996 to April 2020). Suspicion of IA disease was noted in 52 cases, six had IA pathological fracture, two had an effusion, two had prior surgical intervention (curettage/IA intervention), and one had an osseous metastasis in the proximal tibia. To ascertain validity, two musculoskeletal radiologists (R1, R2) reviewed the preoperative imaging (MRI) of 63 consecutive cases on two occasions six weeks apart. The radiological criteria for IA disease comprised evidence of tumour extension within the suprapatellar pouch, intercondylar notch, extension along medial/lateral retinaculum, and presence of IA fracture. The radiological predictions were then confirmed with the final histopathology of the resected specimens. Results. The resection histology revealed 23 cases (36.5%) showing IA disease involvement compared with 40 cases without (62%). The intraobserver variability of R1 was 0.85 (p < 0.001) compared to R2 with κ = 0.21 (p = 0.007). The interobserver variability was κ = 0.264 (p = 0.003). Knee effusion was found to be the most sensitive indicator of IA involvement, with a sensitivity of 91.3% but specificity of only 35%. However, when combined with a pathological fracture, this rose to 97.5% and 100% when disease was visible in Hoffa’s fat pad. Conclusion. MRI imaging can sometimes overestimate IA joint involvement and needs to be correlated with clinical signs. In the light of our findings, we would recommend EA resections when imaging shows effusion combined with either disease in Hoffa’s fat pad or retinaculum, or pathological fractures. Cite this article: Bone Joint J 2023;105-B(6):696–701