Vial Irarrazaval Raimundo, Turkula Stefan, Tompkins Marc, Agel Julie, Arendt Elizabeth
Department of Orthopedic Surgery, Pontifical Catholic University of Chile, Santiago, Chile.
Teton Valley Health Care, Driggs, Idaho, USA.
Am J Sports Med. 2025 Apr 30:3635465251336162. doi: 10.1177/03635465251336162.
The J-sign is a marker of abnormal patellar tracking and is associated with bony abnormalities. When patella alta is present, distal tibial tubercle osteotomy (dTTO) can enable the patella to engage in a more distal/deeper groove, often eliminating the J-sign.
To determine which anatomic findings are associated with a persistent J-sign after medial patellofemoral ligament reconstruction (MPFL-R) and dTTO in patients with recurrent lateral patellar dislocations and patella alta.
Cohort study; Level of evidence, 4.
A retrospective cohort study of 93 knees (77 patients) with recurrent lateral patellar dislocations and the J-sign, treated by a single surgeon with MPFL-R and dTTO without trochleoplasty, was conducted. Demographic, imaging, and surgical data were obtained from medical records. The following measurements were obtained: Caton-Deschamps index (CDI), patellotrochlear index, tibial tubercle-trochlear groove (TT-TG) distance, patellar tendon-lateral trochlear ridge (PT-LTR) distance, lateral patellar tilt, tibiofemoral joint rotation (TFJR), lateral trochlear inclination (LTI), trochlear depth, sulcus angle, and sagittal bump height. The postoperative J-sign was assessed. Patients were categorized into the resolved J-sign group or persistent J-sign group. Binary logistic regression was performed to identify significant predictors of a postoperative J-sign. Cutoff values were determined by receiver operating characteristic curve analysis using the Youden index. The Fisher exact test was used to compare frequencies.
The J-sign was not observed postoperatively in 56 cases (60.2%) and was thus considered resolved. Preoperative characteristics revealed differences between the resolved J-sign and persistent J-sign groups for mean lateral patellar tilt, PT-LTR distance, TFJR, sulcus angle, trochlear depth, TT-TG distance, sagittal bump height, and LTI. The mean amount of distalization, patellotrochlear index, and preoperative and postoperative CDI were similar between the groups. Logistic regression identified TFJR, PT-LTR distance, and LTI as significant predictors of a persistent J-sign. An increased risk of a persistent J-sign was found for a TFJR ≥6° (odds ratio [OR], 14.9 [95% CI, 5.4-41.6]), PT-LTR distance ≥13 mm (OR, 12.3 [95% CI, 4.3-35.5]), and LTI ≤10° (OR, 4.1 [95% CI, 1.6-10.4]). The frequency of a persistent J-sign was 3.8% for cases with no risk factors above the threshold value, 10.5% with 1 risk factor, 63.0% with 2 risk factors, and 87.5% with all 3 risk factors present.
A persistent J-sign was associated with imaging measurements of a more lateralized extensor mechanism (greater PT-LTR distance), trochlear dysplasia (lower LTI), and increased external TFJR.
J征是髌股轨迹异常的一个标志，与骨骼异常相关。当存在高位髌骨时，胫骨结节远端截骨术（dTTO）可使髌骨嵌入更靠远端/更深的滑车沟，常可消除J征。
确定在复发性髌骨外侧脱位和高位髌骨患者中，哪些解剖学发现与内侧髌股韧带重建术（MPFL-R）和dTTO术后持续存在的J征相关。
队列研究；证据等级，4级。
对93例（77例患者）复发性髌骨外侧脱位且有J征的膝关节进行回顾性队列研究，这些患者均由同一位外科医生采用MPFL-R和dTTO治疗，未行滑车成形术。从病历中获取人口统计学、影像学和手术数据。进行以下测量：卡顿-德尚指数（CDI）、髌股指数、胫骨结节-滑车沟（TT-TG）距离、髌腱-外侧滑车嵴（PT-LTR）距离、髌骨外侧倾斜度、胫股关节旋转（TFJR）、外侧滑车倾斜度（LTI）、滑车深度、沟角和矢状隆起高度。评估术后J征。将患者分为J征消失组或持续存在J征组。进行二元逻辑回归以确定术后J征的显著预测因素。通过使用约登指数的受试者工作特征曲线分析确定截断值。采用Fisher精确检验比较频率。
56例（60.2%）术后未观察到J征，因此认为J征消失。术前特征显示，J征消失组和持续存在J征组在平均髌骨外侧倾斜度、PT-LTR距离、TFJR、沟角、滑车深度、TT-TG距离、矢状隆起高度和LTI方面存在差异。两组之间的平均远端化量、髌股指数以及术前和术后CDI相似。逻辑回归确定TFJR、PT-LTR距离和LTI是持续存在J征的显著预测因素。发现TFJR≥6°（比值比[OR]，14.9[95%可信区间，5.4-41.6]）、PT-LTR距离≥13 mm（OR，12.3[95%可信区间，4.3-35.5]）和LTI≤10°（OR，4.1[95%可信区间，1.6-10.4]）时，持续存在J征的风险增加。对于无高于阈值危险因素的病例，持续存在J征的频率为3.8%；有1个危险因素时为10.5%；有2个危险因素时为63.0%；有所有3个危险因素时为87.5%。
持续存在的J征与伸膝机制更偏外侧（更大的PT-LTR距离）、滑车发育不良（更低的LTI）以及增加的外侧TFJR的影像学测量结果相关。
