Wei Chai

Background Robotic-assisted total knee arthroplasty (TKA) requires pin trackers fixed to the femur and tibia. The influence of femoral pin tracker placement (intra-incisional or extra-incisional) on fracture risk remains controversial, with limited clinical and biomechanical evidence. Methods A retrospective cohort study included 688 patients who underwent robotic-assisted TKA (505 in intra-incisional group, 183 in extra-incisional group). The incidence of femoral periprosthetic fractures was compared between the two groups within three months postoperatively. Finite-element analysis (FEA) simulated femoral biomechanical behaviour under compression, torsion, and bending loads in three models: control, intra-incisional, and extra-incisional groups. Results One fracture occurred in the extra-incisional group (1/183, 0.55%), whereas none occurred in the intra-incisional group (0/505), the difference was not statistically significant (Fisher's exact test, P = 0.266). In the FEA, ultimate loads and fracture patterns were similar among the control, intra-incisional, and extra-incisional models under all three loading conditions, and no simulated fracture initiated at nail channels. Conclusion Perioperative femoral fracture involving tracker nail channels was rare in this cohort, and its incidence did not differ significantly between intra-incisional and extra-incisional placement. When a standardized pin-placement protocol is followed, either location appears to have a limited effect on short-term fracture risk.

Total hip arthroplasty (THA) is the primary treatment for end-stage hip diseases, and its clinical outcomes mainly depend on the accuracy of prosthesis implantation. Robot-assisted THA (RTHA), with its advantages in prosthesis implantation, overcomes the uncertainty of component positioning in conventional surgery and has become a research hotspot in joint surgery in recent years. This article systematically reviews international RTHA systems such as ROBODOC and MAKO, as well as domestic RTHA systems including the ARTHROBOT Joint Replacement Surgical Robot and the LONGWELL THA Surgical Robot, comparing their technical characteristics and clinical application status. It also explores the medical application of industrial robotic arms such as WAM, KUKA, and UR and their innovative applications in THA, aiming to provide reference for the future development and clinical application of RTHA systems.

Purpose: Coronal plane alignment of the knee (CPAK) classification is widely used in total knee arthroplasty (TKA) planning, but its three‐dimensional (3D) relationship with sagittal and axial alignment remains unclear. This study aimed to investigate the association between the CPAK classification and 3D alignment parameters using EOS imaging. Methods: This single‐center retrospective cohort study included 1009 patients (511 non‐KOA; 498 KOA). All participants underwent EOS full‐body/lower‐limb biplanar radiographs with 3D reconstruction. The CPAK classification and sagittal/axial parameters were measured. Generalized linear models (GLMs) were used to compare parameters across CPAK types while controlling for age, sex, and BMI. Effect sizes were reported as partial eta‐squared ( η ²) with 95% confidence intervals obtained via bootstrap resampling. Associations between the arithmetic hip–knee–ankle angle (aHKA), joint line obliquity (JLO), and 3D parameters were assessed using partial Spearman correlation. Results: Most 3D parameters showed no statistically significant differences across CPAK types after adjusting for age, sex, and BMI. In the non‐KOA cohort, significant differences persisted for sagittal alignment ( p < 0.001; η ² = 0.116; 95% confidence interval [CI]: 0.069–1.000), the femoral torsion angle ( p < 0.001; η ² = 0.066; 95% CI: 0.029–1.000), and the femoro‐tibial rotation angle ( p < 0.001; η ² = 0.125; 95% CI: 0.078–1.000). In the KOA cohort, no parameters reached statistical significance after adjustment (all p > 0.05). The aHKA and JLO were significantly correlated with some 3D parameters, although all correlation coefficients were weak ( ρ < 0.30). Conclusion: The CPAK classification′s weak correlation with most 3D parameters confirms its inherent limitations, accounting for limited sagittal and axial variance. Future phenotyping should integrate kinematic and soft tissue assessments for personalized TKA planning. Level of Evidence: Level III, retrospective cohort study.

Objective: Subtrochanteric shortening osteotomy (SSO) with autogenous cortical plate grafting is a critical but technically demanding procedure in total hip arthroplasty for Crowe type IV developmental dysplasia of the hip. Conventional instruments often result in inaccurate osteotomies and unstable graft fixation. This study aimed to evaluate a novel surgical instrumentation system designed to address these challenges. Methods: A retrospective cohort study was conducted on 49 patients (60 hips) with Crowe type IV DDH who underwent primary THA with SSO. The control group included 25 patients (30 hips) treated with conventional instruments. The novel instrumentation group included 24 patients (30 hips) treated with the newly developed system. All surgeries were performed by a single senior surgeon. Demographic and clinical data were analyzed, and all patients completed the 24‐month postoperative follow‐up. Statistical analysis was performed using t ‐tests and chi‐squared tests as appropriate. Results: The mean operative time was significantly shorter in the novel instrumentation group than in the control group ( t = 2.123, p = 0.040). The novel instrumentation system was estimated to reduce the time required for the autogenous cortical plate technique by 43%. Patients in the novel instrumentation group also reported significantly less intraoperative blood loss ( t = 3.078, p = 0.003). The satisfaction rate regarding autogenous graft and wire positions was significantly higher in the novel instrumentation group ( χ ² = 5.455, p = 0.020). No significant differences were observed in clinical scores between the two groups during the 24‐month follow‐up. No severe perioperative or postoperative complications occurred in either group. Conclusion: The novel surgical instrumentation system demonstrated advantages over conventional devices in terms of operating time, blood loss, and satisfaction with autogenous graft and wire positioning. It represents an ideal set of surgical tools for Crowe type IV DDH patients undergoing THA with SSO. Level of Evidence: Level III, retrospective study.

Intraoperative frozen section histology is a cornerstone for diagnosing periprosthetic joint infection (PJI), yet its reported accuracy varies significantl

Aims: We developed a novel unicompartmental pressure sensor to measure intraoperative medial compartment pressureduring robotic arm-assisted unicompartmental knee arthroplasty (UKA) and conventional jig-based UKA in order to assess the effect and impact of soft-tissue balance. Methods: This retrospective study evaluated 80 patients who underwent medial compartment UKA at our institution between November 2022 and June 2023, including 40 patients in conventional jig-based (mobile bearing) UKA and 40 patients in robotic arm-assisted (fixed bearing) UKA. After intraoperative soft-tissue balancing, the medial compartment pressure at 10°, 45°, and 90° of knee flexion was measured using a new unicompartmental pressure sensor. The knee range of motion (ROM), Numerical Rating Scale, and American Knee Society scores were recorded at three months and one year of follow-up. Results: Conventional jig-based UKA did not achieve consistent medial compartment pressures at 10°, 45°, and 90° of knee flexion (p < 0.001), whereas robotic arm-assisted UKA achieved more balanced pressures at these angles (p-values between 10° vs 45°, 10° vs 90°, and 45° vs 90° were 0.132, 0.378, and > 0.999, respectively). In addition, robotic arm-assisted UKA showed better outcome scores and ROM at three months, but no significant clinical differences at the one-year follow-up. Conclusion: Intraoperative pressure measurements using the novel unicompartmental pressure sensor showed that robotic arm-assisted UKA was able to achieve more consistent pressure in the medial compartment than conventional jig-based UKA, which may improve early postoperative rehabilitation. Cite this article: Bone Joint J 2026;108-B(3):302–309.

Background: For robotic-assisted total knee arthroplasty (TKA), accurate identification of anatomical landmarks directly affects the displayed value for femoral component rotation. This study aimed to quantify the inter-surgeon consistency of the TEA-reference angle (the angle between the transepicondylar axis and the femoral component axis) and the PCA-reference angle (the angle between the posterior condylar axis and the femoral component axis). Methods: The anatomical data of 56 patients who underwent robotic-assisted TKA at our institution were analyzed. Two surgeons independently identified the transepicondylar axis (TEA) and posterior condylar axis (PCA) landmarks on the 3D femoral models generated by the MAKO TKA system. The TEA-reference angle was recorded as α with the PCA-reference angle standardized to 0°, and the PCA-reference angle was recorded as β with the TEA-reference angle standardized to 0°. The measured values were α ₁ β ₁ for Surgeon-1 and α ₂ β ₂ for Surgeon-2. The differences between surgeons for α (∆α = α₁ – α₂) and β (∆β = β₁ – β₂) were calculated. The values of α and β are defined as positive for external rotation and negative for internal rotation. Results: The inter-surgeon intraclass correlation coefficient (ICC) for α was 0.761 (95% CI: 0.592–0.860), and that for β was 0.943 (95% CI: 0.902–0.966). The absolute difference between surgeons (∆α) was > 2° in 15/56 (26.8%) patients and ≤ 1° in 24/56 (42.9%) patients. With respect to ∆β, 3/56 (5.4%) patients had a difference > 2°, whereas 45/56 (80.4%) patients had a difference ≤ 1°. Conclusion: The inter-surgeon consistency of the PCA was significantly greater than that of the TEA in robotic-assisted TKA planning. To mitigate the risk of inappropriate femoral component rotation, surgeons should verify landmark positions, particularly in patients with anatomical abnormalities of the distal femur, and consider cross-referencing both axes.