Isocentric reattachment of ligamentum teres: a porcine study

Abstract

Background: Recent reports reveal interest in the mechanical importance of ligamentum teres (LT) in hip dislocation. In the previously established procedure of anteroinferior acetabular LT reattachment in developmental dysplasia of the hip, the LT functions as a check-rein, showing promising results. However, this position of reattachment could potentially limit motion. The purpose of this study was to evaluate the feasibility of an isocentric point for reattachment of the LT and to study its impact on hip function using a young porcine model.

Methods: Pelvic specimens with intact anatomy were obtained from 6 skeletally immature pigs (12 hips). Through a careful anteromedial capsulotomy, the LT was detached from its acetabular insertion then reattached to 1 of 2 positions: (1) anteroinferior lip of the acetabulum; (2) proposed isocentric position. Intra-articular stress distribution was measured through a complete range of motion with a prescale Fuji pressure film. Tension was then applied to the LT and the stresses were recorded again. In addition, radioopaque solution was injected into the substance of the LT, then floroscopy tracked the LT location initially and after the 2 reattachment positions through a full hip range of motion.

Results: Reattachment of the LT at an isocentric point is feasible in a pig model. With careful physiologic tensioning of this reattachment, hip can maintain full motion with no excessive pressure areas created within the joint. On the contrary, the initial technique of anteroinferior extra-articular attachment limits external rotation and extremes of abduction. We found this LT tracking technique (with radioopaque dye injection) to be reliable and reproducible.

Conclusions: The isocentric reattachment of the LT is feasible in this pig model and serves as a natural check-rein to dislocation without limiting joint motion or causing abnormal cartilage pressures.

Clinical relevance: Isocentric LT reattachment may provide a method for improving stability of open reductions when treating children with such conditions.