Anterolateral Ligament of the Knee Shows Variable Anatomy in Pediatric Specimens

Abstract

Background: Anterior cruciate ligament (ACL) reconstruction failure rates are highest in youth athletes. The role of the anterolateral ligament in rotational knee stability is of increasing interest, and several centers are exploring combined ACL and anterolateral ligament reconstruction for these young patients. Literature on the anterolateral ligament of the knee is sparse in regard to the pediatric population. A single study on specimens younger than age 5 years demonstrated the presence of the anterolateral ligament in only one of eight specimens; therefore, much about the prevalence and anatomy of the anterolateral ligament in pediatric specimens remains unknown.

Questions/purposes: We sought to (1) investigate the presence or absence of the anterolateral ligament in prepubescent anatomic specimens; (2) describe the anatomic relationship of the anterolateral ligament to the lateral collateral ligament; and (3) describe the anatomic relationship between the anterolateral ligament and the physis.

Methods: Fourteen skeletally immature knee specimens (median age, 8 years; range, 7-11 years) were dissected (12 male, two female specimens). The posterolateral structures were identified in all specimens, including the lateral collateral ligament and popliteus tendon. The presence or absence of the anterolateral ligament was documented in each specimen, along with origin, insertion, and dimensions, when applicable. The relationship of the anterolateral ligament origin to the lateral collateral ligament origin was recorded.

Results: The anterolateral ligament was identified in nine of 14 specimens. The tibial attachment point was consistently located in the same region on the proximal tibia, between the fibular head and Gerdy's tubercle; however, the femoral origin of the anterolateral ligament showed considerable variation with respect to the lateral collateral ligament origin. The median femoral origin of the anterolateral ligament was 10 mm (first interquartile 6 mm, third interquartile 13) distal to the distal femoral physis, whereas its median insertion was 9 mm (first interquartile 5 mm, third interquartile 11 mm) proximal to the proximal tibial physis.

Conclusions: The frequency of the anterolateral ligament in pediatric specimens we observed was much lower than other studies on adult specimens; future studies might further investigate the prevalence, development, and functional role of the anterolateral ligament of the knee.

Clinical relevance: This study expands our understanding of the anterolateral ligament and provides important anatomic information to surgeons considering anterolateral ligament reconstruction concomitantly with primary or revision ACL reconstruction in pediatric athletes.

Fig. 1

The figure shows merged CT images to replicate the view available by intraoperative fluoroscopy. A digital marker (black bull’s eye) has been drawn over the signal produced by the metallic pin. Line A represents the condylar depth; Line B represents the condylar height. Line B extends perpendicularly from Line A at the most posterior aspect of the femoral condyle to the most proximal aspect of the posterior physis.

Fig. 2

Line A shows the total depth of the lateral femoral condyle. Line B shows the distance from a ligament origin to the most posterior aspect of the lateral femoral condyle. Length of Line B was divided by the length of Line A and multiplied by 100 to determine % AP. Point shown in figure measures approximately 30% AP.

Fig. 3

Line A shows the total height of the lateral femoral condyle. Line B shows the distance from the ligament origin to the posterosuperior aspect of the lateral femoral condyle. Height of Line B was divided by the height of Line A and multiplied by 100 to determine % proximal distal. Point shown in figure measures approximately 30% proximal distal.

Fig. 4A–D

The figure demonstrates that the structural appearance of the anterolateral ligament (ALL) varied in pediatric specimens. (A) Left knee, 8-year-old boy; anterolateral ligament origin is proximal and posterior to the lateral collateral ligament (LCL) origin. The femoral attachment points of the lateral collateral ligament and anterolateral ligament are on the right in this photograph. (B) Right knee, 11-year-old boy; anterolateral ligament origin is proximal and posterior to the lateral collateral ligament. The femoral attachments of the lateral collateral ligament and anterolateral ligament are in the upper region of the photo. (C) Left knee, 10-year-old boy; anterolateral ligament and lateral collateral ligament share the same origin. The femoral attachment point of the lateral collateral ligament and anterolateral ligament are on the right in this photograph. (D) Right knee, 11-year-old boy; anterolateral ligament origin is proximal and anterior to the lateral collateral ligament. The femoral attachments of the lateral collateral ligament and anterolateral ligament are in the upper left region of the photograph.

Fig. 5

Variations observed in the relationship between the lateral collateral ligament (LCL) and anterolateral ligament in nine pediatric knee specimens are shown in the figure. The anterolateral ligament was proximal and anterior to the lateral collateral ligament in one specimen, directly anterior to the lateral collateral ligament in one, distal and anterior to the lateral collateral ligament in three, proximal and posterior to the lateral collateral ligament in two, and shared the same origin as the lateral collateral ligament in two.

Fig. 6

Lateral collateral ligament (LCL) and anterolateral ligament (ALL) origin distribution as % AP and % proximal distal. Lateral collateral ligament origins of specimens without an anterolateral ligament are not shown in the figure. Points are labeled with specimen numbers.