Department of Orthopedics, Hospital for Special Surgery, New York, New York, USA.
Am J Sports Med. 2011 Jul;39(7):1444-9. doi: 10.1177/0363546510397174. Epub 2011 Mar 3.
Patellar dislocation is a common traumatic injury in the pediatric and adolescent population. The primary constraint to lateral subluxation and dislocation of the patella is the medial patellofemoral ligament (MPFL), which serves to resist lateral translation of the patella. Injury to the MPFL may predispose to recurrent dislocation but the anatomic site of injury is poorly characterized in children and adolescents.
The authors addressed 2 questions: (1) What is the zone of injury to the MPFL in a pediatric/adolescent population after primary patellar dislocation? (2) What is the location of the femoral attachment of the MPFL with respect to the growth plate?
Cohort study (prevalence); Level of evidence, 2.
Patients were eligible if they were ≤18 years of age and suffered a recent patellar dislocation characterized by magnetic resonance imaging (MRI) findings of high T2-signal intensity in the lateral femoral condyle. Patients were excluded if they had a history of prior dislocations, prior knee surgery, or congenital dislocation. Two musculoskeletal radiologists and an orthopaedic resident reviewed MRI scans of 43 children. The MPFL was divided into 3 zones: patellar insertion, femoral insertion, and midsubstance. The zone of injury was confirmed by the presence of associated soft tissue edema on short tau inversion recovery sequences and the distance from the MPFL insertion to the medial distal femoral growth plate was measured. Associated injuries were noted and the Insall-Salvati ratio was measured.
The MPFL injury was isolated to the patellar attachment in 61% of patients and to the femoral attachment in 12%. Twelve percent of patients had injury at both the patellar and femoral attachments. Six percent had no identifiable MPFL injury and 9% had combinations of midsubstance and either patellar or femoral attachment injuries. The kappa value for injury determinations was 0.71, indicating substantial concordance. The MPFL insertion site averaged 5 mm distal to the medial physis. Eighty-six percent of patients had an MPFL insertion distal to the growth plate, 7% had an insertion at the physis, while only 7% had a proximal insertion. The incidence of associated chondral injuries, the value of the Insall-Salvati ratio, and the location of MPFL insertion did not vary significantly with location of MPFL injury. Sixteen patients (36%) had MPFL insertions that were within 5 mm (either proximal or distal) of the growth plate.
The zone of MPFL injury in a pediatric population after primary patellar dislocation was predominantly isolated to the patellar attachment (61%), in contrast to previous literature. Twelve percent of patients had injury only at the femoral attachment, while 12% of patients had injury to both the patellar and femoral attachments. The remaining 15% had injury at multiple locations or no identifiable injury. The MRI finding that the anatomic insertion of the MPFL is distal to the physis in 93% of patients and that the MPFL is more likely to be injured at the patellar attachment has important implications in the surgical reconstruction of the MPFL in pediatric or adolescent patients.
髌骨脱位是儿童和青少年中常见的创伤性损伤。髌骨外侧半脱位和脱位的主要限制因素是内侧髌股韧带（MPFL），它可以抵抗髌骨的外侧平移。MPFL 的损伤可能导致复发性脱位，但在儿童和青少年中，MPFL 的损伤部位描述不佳。
作者提出了 2 个问题：（1）在初次髌骨脱位后，儿童和青少年的 MPFL 损伤部位在哪里？（2）MPFL 的股骨附着点相对于生长板的位置在哪里？
队列研究（患病率）；证据水平，2 级。
如果患者≤18 岁且符合 MRI 发现外侧股骨髁高 T2 信号强度的近期髌骨脱位，则有资格入选。如果患者有既往脱位史、既往膝关节手术或先天性脱位，则排除在外。两名肌肉骨骼放射科医生和一名骨科住院医师对 43 名儿童的 MRI 扫描进行了回顾。MPFL 分为 3 个区：髌骨附着、股骨附着和中体。通过短反转时间反转恢复序列上的相关软组织水肿以及 MPFL 附着到内侧远端股骨生长板的距离来确认损伤区域。注意到相关损伤，并测量 Insall-Salvati 比。
61%的患者 MPFL 损伤仅限于髌骨附着处，12%的患者仅限于股骨附着处。12%的患者髌骨和股骨附着处均有损伤。6%的患者没有可识别的 MPFL 损伤，9%的患者有中体和髌骨或股骨附着处损伤的组合。损伤判断的kappa 值为 0.71，表明有实质性一致性。MPFL 附着点平均距离内侧骺板 5mm 远。86%的患者 MPFL 附着点位于生长板远端，7%的患者附着点位于骺板，只有 7%的患者附着点位于近端。软骨损伤的发生率、Insall-Salvati 比的数值以及 MPFL 附着点的位置与 MPFL 损伤的位置无显著差异。16 名患者（36%）的 MPFL 附着点距离生长板 5mm 以内（无论是近端还是远端）。
与先前的文献相比，初次髌骨脱位后儿童人群中 MPFL 损伤的区域主要局限于髌骨附着处（61%）。12%的患者仅在股骨附着处有损伤，而 12%的患者在髌骨和股骨附着处均有损伤。其余 15%的患者有多个部位的损伤或无明显损伤。93%的患者 MRI 发现 MPFL 的解剖附着点位于骺板远端，MPFL 更可能在髌骨附着处受伤，这对儿童或青少年患者的 MPFL 重建手术具有重要意义。
