Ligamentum teres injury

To recap, the ligamentum teres (LT) is an intra-articular ligament extending from the fovea capitis of the femoral head to the acetabular notch and transverse acetabular ligament. The biomechanical role of the LT remains incompletely defined. Cadaveric studies suggest that it becomes taut in specific combinations of flexion, adduction, and rotation and functions primarily as an end-range restraint to hip rotation 1,2. The LT should therefore be considered a secondary rather than primary stabilizer of the native hip.

LT injury encompasses partial tearing, complete rupture, and degenerative disruption of the ligament. Injury should not automatically be considered an isolated lesion: LT abnormalities are frequently encountered alongside femoroacetabular impingement, acetabular dysplasia, capsular laxity, labral injury, and chondral damage.

LT injury may result from major trauma, repetitive mechanical overload, instability, impingement, or degeneration. Acute complete rupture is classically associated with traumatic dislocation or subluxation, in which excessive translation places the ligament under sudden tensile load 3. Partial tears are more commonly encountered arthroscopically and may develop through repetitive loading without a single major traumatic event.

Structural abnormalities can predispose the ligament to chronic injury. In acetabular dysplasia or capsular laxity, deficient osseous or soft-tissue restraint permits increased femoral head motion, increasing demand on the LT as a secondary stabilizer. Complete LT tears have been associated with reduced acetabular coverage and capsular laxity, supporting an important relationship between LT pathology and instability 4. Femoroacetabular impingement may also coexist with LT injury; abnormal terminal motion and altered femoral head movement may repetitively tension or impinge the ligament, although the exact contribution of impingement versus instability varies between hips 4.

The commonly cited Gray and Villar classification divides LT pathology into three broad patterns 3:

More detailed arthroscopic grading systems describe the extent of ligament involvement and are primarily descriptive. The Gray and Villar classification is the most widely cited system and categorizes ligamentum teres pathology as complete rupture, partial tear, or degenerative tear 3. Botser and colleagues subsequently proposed a more detailed arthroscopic classification based on the proportion of ligament fibers involved: Grade 0, an intact ligament; Grade 1, synovitis or fraying involving less than 50% of the ligament; Grade 2, partial tearing involving more than 50% but less than 100% of the fibers; and Grade 3, complete rupture of the ligament 5.

LT tears commonly coexist with labral and articular cartilage pathology. In an arthroscopic series of 2,761 hips, ligamentum teres tears were identified in 1,090 hips (39.5%). Compared with hips without ligamentum teres tears, affected hips had a higher prevalence of labral tears (98.3% vs 91.2%) and acetabular chondral lesions (72.8% vs 58.4%) 5. Among patients undergoing arthroscopy for femoroacetabular impingement, complete ligamentum teres tears were associated with femoral head chondral defects in 50% of hips compared with 18% of hips without complete tears, and with capsular laxity in 75% compared with 24%, respectively 4.

These associations are mechanically plausible. Instability may simultaneously overload the LT and labrum, while repetitive abnormal translation can increase cartilage stress. Conversely, loss of LT integrity may remove a secondary restraint and further increase demand on the remaining stabilizing structures. Thus, LT injury may function both as a marker of abnormal hip mechanics and, in selected unstable hips, a contributor to those mechanics.