High prevalence of generalized ligamentous laxity in patellar dislocation with posterior weight-bearing lateral femoral condyle osteochondral fractures: an observational study and treatment outcomes.

objectiveTo investigate the high incidence of multiple ligament laxity signs in a highly selected cohort of patients with patellar dislocation complicated by osteochondral fractures in the posterior weight-bearing zone of the femoral condyle, evaluate the therapeutic efficacy of absorbable cartilage pins, and further analyze the causes of such injuries.

methodsA retrospective review was performed using clinical data from 40 patients with patellar dislocation complicated by osteochondral fractures involving the posterior weight-bearing zone of the lateral femoral condyle who were admitted to the Second Hospital of Lanzhou University between January 2021 and August 2024. Demographic and clinical characteristics (age, sex, osteochondral fracture size, affected side, and follow-up duration) as well as baseline anatomical parameters, including patellar height (Caton-Deschamps index), tibial tubercle-trochlear groove (TT-TG) distance, and femoral anteversion angle, were recorded. Systemic ligamentous laxity was evaluated preoperatively using the Beighton score, and a Beighton score ≥ 4 was used to define multiple ligament laxity. Patellar tilt (PT) and patellar shift (PS) were measured on magnetic resonance imaging (MRI), whereas TT-TG was primarily assessed on computed tomography (CT), supplemented by MRI when necessary. All patients underwent osteochondral fragment reduction and fixation using absorbable cartilage pins in conjunction with medial patellofemoral ligament (MPFL) reconstruction.The prevalence of multiple ligament laxity in this cohort was described using a one-sample proportion test (exact binomial test) with literature-reported proportions as reference. The primary outcome was the Lysholm score at the final follow-up. A multivariable linear regression model was constructed with adjustment for baseline Lysholm score, age, sex, follow-up duration, and preoperative TT-TG distance. In addition, paired-sample t-tests were used to compare clinical outcomes (range of motion [ROM], Lysholm, International Knee Documentation Committee [IKDC], Tegner, and visual analog scale [VAS]) and radiological parameters (PT, PS, and TT-TG) between the preoperative assessment and the final follow-up. The clinical efficacy and postoperative complications associated with the combined absorbable cartilage pin fixation and MPFL reconstruction were subsequently evaluated.

resultsAll 40 patients completed follow-up (9-24 months; mean, 14.18 ± 4.9 months). All incisions healed primarily, and no predefined complications were observed. Follow-up imaging demonstrated fracture-site healing and stable fixation in all cases. Multiple ligament laxity (Beighton score ≥ 4) was present in 38 of 40 patients (95.0%); compared with literature-reported prevalence (approximately 20-30%), a one-sample exact binomial test showed a statistically higher proportion (P < 0.001), which should be interpreted as an enriched prevalence in this selected cohort. In multivariable linear regression, the Lysholm score at final follow-up was independently associated with baseline Lysholm score (β = 0.984, 95% CI 0.798-1.170; P < 0.001), whereas age, sex, follow-up duration, and preoperative TT-TG were not significant predictors (all P > 0.05). Significant improvements were observed from preoperative assessment to final follow-up in radiological parameters-PT (12.4 ± 2.5 vs. 5.7 ± 1.2), PS (9.7 ± 1.2 vs. 1.3 ± 0.5), and TT-TG (18.1 ± 2.3 vs. 14.6 ± 1.6)-and in clinical outcomes, including ROM (112.7 ± 5.3 vs. 128.4 ± 1.9), Lysholm (51.9 ± 2.6 vs. 82.7 ± 3.1), IKDC (43.1 ± 13.2 vs. 83.8 ± 6.8), Tegner (4.1 ± 1.2 vs. 5.9 ± 1.6), and VAS (7.23 ± 1.3 vs. 1.97 ± 0.62) (all P < 0.001).

conclusionIn the selective cohort of "patellar dislocation with concomitant osteochondral lesions in the posterior weight-bearing zone of the lateral femoral condyle" included in this study, multiple ligament laxity signs exhibited a high incidence rate. Although the current study design precludes exploration of the underlying mechanisms, the coexistence of ligament laxity with baseline anatomical features supports a plausible hypothesis: patients with multiple ligament laxity syndrome may exhibit altered patellofemoral kinematics and energy transfer pathways under dynamic loading. And early surgical intervention involving reduction and fixation with resorbable cartilage pins combined with medial patellofemoral ligament (MPFL) reconstruction may represent a reliable and feasible treatment strategy.