Recurrent patellar dislocation is a commonly encountered patellofemoral disease. Prompt surgical intervention is indicated for recurrent dislocation to restore patellofemoral stability. As one of the most preferred procedures, medial patellofemoral ligament (MPFL) reconstruction has been implemented on a large scale. Femoral tunnel placement remains a crucial technical issue during MPFL reconstruction and is critical to ensure the isometry and proper tension of the graft. Currently, visual–palpatory anatomic landmarks and fluoroscopy-guided radiographic landmarks comprise the main approaches to intraoperative femoral tunnel positioning. However, the accuracy of both methods has been questioned. This article introduces an arthroscopic femoral tunnel placement technique. Apart from traditional anteromedial and anterolateral portals, two auxiliary arthroscopic portals are specially designed. The adductor tubercle, the medial epicondyle and the posterior edge are selected as main anatomic landmarks and are directly visualized in sequence under arthroscope. The relative position between the femoral attachment of the MPFL and the three landmarks is measured on preoperative three-dimensional computed tomography, providing semi-quantified reference for intraoperative localization. This technique achieves minimally invasive tunnel placement without X-ray exposure, and especially suits obese patients for whom palpatory methods are difficult to perform.

Background: Femoral torsion can be evaluated from different femoral segments. The pathological thresholds for femoral torsion of different segments and the influence of segmental femoral torsion on patellofemoral alignment remain unknown. Purpose: To compare femoral torsion between patients with recurrent patellar dislocation and healthy individuals, to determine the statistical physiological range and pathological thresholds of femoral torsion in different segments, and to investigate the influence of femoral torsion on patellofemoral malalignment. Study Design: Cross-sectional study; Level of evidence, 3. Methods: We retrospectively reviewed the records of patients with patellar dislocation who received surgical treatment in our department between 2019 and 2020. Healthy participants were recruited as the control group. The control patients were asymptomatic and had no history of lower extremity disorders. The differences in femoral torsion between the study and control groups were compared. The diagnostic capacity of femoral torsion in different segments and their correlation with patellar tilt were investigated. The mean value and 95% CI of femoral torsion in different segments were established using data from healthy volunteers. Results: A total of 60 patients with patellar dislocation and 100 healthy volunteers were included in this study. The total, mid, and distal femoral torsion values differed significantly between the study and control groups ( P < .01). Total femoral torsion had the highest diagnostic value (area under the receiver operating curve = 0.733). Total torsion ( r = 0.432; P < .001), mid torsion ( r = 0.242; P = .002), and distal torsion ( r = 0.324; P < .001) showed significant correlations with patellar tilt. The pathological thresholds of excessive femoral torsion of the total, proximal, mid, and distal femoral segments were 24.73°, 46.68°, –6.55°, and 14.92°, respectively. Conclusion: Patients with patellar dislocation had greater femoral torsion than healthy individuals in multiple femoral segments. Excessive mid, distal, and total torsion was associated with more significant patellar tilt.

Purpose: The purpose of this study was to evaluate the accuracy of femoral tunnel location, post‐operative pain management, functional rehabilitation and clinical outcomes in medial patellofemoral ligament (MPFL) reconstruction using all‐arthroscopic technique.Methods: Between 2020 and 2021, 160 patients with recurrent patellar dislocation undergoing MPFL reconstruction were categorized into control (traditional surgery) and study (all‐arthroscopic technique) groups. Femoral tunnel accuracy was assessed via computed tomography scans, pain management, functional rehabilitation, knee range of motion and daily activities were evaluated up to 6 months post‐operatively. Knee function was assessed using Kujala and Lysholm scores at post‐operative 12 months.Results: Seventy‐one patients in the control group and 69 patients in the study group reached the final follow‐up with no demographic differences. Follow‐up duration was 12.65 ± 0.68 vs 12.77 ± 0.73 months in the control and study groups (p = 0.3145). The intra‐class correlation coefficient was excellent (r = 0.97). In femoral tunnels, 93.5% in the control group and 92.4% in the study group were correctly localized. In patellar tunnels, 96.1% in the control group and 96.2% in the study group were correctly localized (p > 0.9999). Post‐operative strong opioid analgesics were used 25.9 ± 31.0 versus 12.0 ± 22.2 mg/day in the control and study groups (p = 0.0016). The pain score was 3.4 ± 1.1 versus 2.7 ± 1.2 in the control and study groups (p = 0.0006) during post‐operative functional rehabilitation. Time to resume daily living was 8.2 ± 0.6 versus 7.6 ± 0.6 weeks in the control and study groups (p < 0.0001). Time to resume low‐intensity exercise was 12.3 ± 0.6 versus 11.7 ± 0.6 weeks in the control and study groups (p < 0.0001). In the more than 1‐year follow‐up, no significant difference was found in the Kujala and Lysholm scores.Conclusions: The all‐arthroscopic technique for MPFL reconstruction in recurrent patellar dislocation ensures precise femoral tunnel placement. It offers advantages in early post‐operative pain management and functional recovery, enabling faster rehabilitation compared to traditional non‐all‐arthroscopic techniques.Level of Evidence: Level III.

Anterior cruciate ligament (ACL) rupture and patellar dislocation (PD) are common knee injuries. Dual-energy X-ray absorptiometry (DXA) and computed tomography (CT) are widely used clinical diagnostic tools. The aim was to investigate the characteristics of knee bone mineral density (BMD) in patients with ACL rupture and PD and to explore the relationship between BMD and Hounsfield unit (HU) values. This prospective cross-sectional study included 32 ACL rupture and 32 PD patients assessed via DXA and CT. BMD and CT measurements were taken from regions of interest in the femoral and tibial condyles. Statistical analyses included t-tests and mixed-effects models. The results showed that BMD in the PD group was significantly lower than in the ACL group (p < 0.05). The HU values of cortical bone in the femur and tibia differed significantly between the ACL group and the PD group (p < 0.05). The BMD of the femur and tibia showed significant correlations with the HU values of cancellous bone and cortical bone (p < 0.05). The conclusion was that PD patients had lower BMD and HU values in the femur and tibia compared to patients with ACL ruptures, particularly in the cortical bone of the tibia, and there was a strong correlation between HU value and BMD.

The inheritance of recurrent patellar dislocation (RPD) is known, but the susceptible gene remains unidentified. Here, we performed the first whole exome sequencing (WES) cohort study to identify the susceptible genes. The results showed eight genes were associated with this disease. Notably, the carboxypeptidase D (CPD) gene showed the highest relevance based on its gene function and tissue expression. Single-cell sequencing results indicate that the CPD gene is involved in the pathophysiological process of RPD through granulocytes. Implicated pathways include nuclear factor kappa B (NF-κB), mitogen-activated protein kinase (MAPK), and Wnt/β-catenin signaling, potentially influencing CPD’s role in RPD pathogenesis. This study identified the susceptible gene and investigates the potential pathogenesis of RPD, which provided a new prospect for the understanding of RPD. Besides, it would offer the theoretical basis for disease prevention and genetic counseling.