Ligamentum Teres

The ligamentum teres (Figure 8.16), or round ligament of the hip, arises from the posteroinferior portion of the acetabular fossa. Occasionally, it originates from both sides of the notch and blends with the transverse ligament. It runs across the notch, reaching the so-

called bare area on the apex of the femoral head (fovea) (Figure 8.17).

The ligament is a triangular flat band surrounded by a thin layer of synovium and, although it is intra-capsular, may thus be considered extrasynovial. It encloses the central artery of the femoral head, fatty tissue, and a complicated sensory nerve supply. These structures cannot normally be distinguished arthro-scopically, although occasional capillaries may be seen on its surface. Due to the course of this structure, it is not easy to palpate the ligament, at least at the femoral insertion, using a lateral approach; however, this may be accomplished with a curved hook if good distraction is obtained. The synovium around the base of the ligamentum teres extends across the floor of the acetabular fossa. It is in continuity with the synovium that passes beneath the transverse ligament arising from the inferior recess. Sometimes, through the synovium, it is possible to distinguish two different bands at the base of the ligament originating from the anterior and posterior margins of the acetabular notch.

The ligamentum does not constitute a mechanical block to inferior subluxation of any great degree. During hip arthroscopy, even if a high distractive force is applied to open the joint, the ligamentum teres never appears taut. The force used at hip arthroscopy serves to compress rather than distract the ligament. Physiologically, it is tense in adduction and relaxed in abduction.

Many theories exist as to the function of this structure, apart from its role as joint stabilizer. In this respect, if stability were its prime function, it does not act satisfactorily. It cannot, for example, prevent congenital dislocation. When traumatic dislocation of the hip occurs, frequently the proximal attachment of the ligament is torn from the fovea or in its midsubstance.

It is said to act as a windshield wiper, spreading synovial fluid across the articular surface during

FIGURE 8.17. Foveal insertion of the ligamentum teres.

FIGURE 8.16. The ligamentum teres.

FIGURE 8.17. Foveal insertion of the ligamentum teres.

CHAPTER 8: ARTHROSCOPIC ANATOMY OF THE HIP

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