Proof of concept: hip joint damage occurs at the zone of femoroacetabular impingement (FAI) in an experimental FAI sheep model

Abstract

Objective: In ovine hips chondrolabral damage as seen in cam-type femoroacetabular impingement (FAI) can be induced via an intertrochanteric varus osteotomy. However, it is yet to proven whether the observed cartilage damage is caused by a dynamic cam type impingement. Thus we asked, (1) whether actual cartilage damage observed after FAI induction in ovine hips occurs at the predicted, computed zone of FAI; (2) whether the extent of cartilage damage increases with ambulation time in this animal model? Design: In this experimental, controlled, comparative study 20 sheep underwent unilateral FAI induction through an intertrochanteric varus osteotomy. Preoperatively sheep underwent computed tomography to generate three-dimensional models of the osseous pelvis and femur. The models were used to predict impingement zones before and after simulated varus osteotomy using range of motion (ROM) analysis. Sheep were sacrificed after 14e40 weeks of ambulation. At sacrifice cartilage was inspected and (1) location of actual damage and computed impingement zones were compared; (2) Cartilage damage was compared between short-and long ambulation groups. Results: (1) The average location and the extent of peripheral and central cartilage lesions did not differ with the computed impingement zones (all P > 0.05). (2) Grades of central, posterior cartilage damage were more severe in the long-compared to the short ambulation group (2.2 ± 1.8 vs 0.4 ± 0.5; P ¼ 0.030). Conclusions: In this experimental ovine FAI model the surgical induction of an osseous impingement conflict between the femur and acetabulum causes cartilage damage at the zone of simulated FAI.

How Does Chondrolabral Damage and Labral Repair Influence the Mechanics of the Hip in the Setting of Cam Morphology? A Finite-Element Modeling Study

“…Delamination injuries are commonly observed at the anterosuperior chondrolabral junction and adjacent articular cartilage in individuals with FAIS [43]. Investigators have attempted to elucidate the cause of the initial damage using motion tracking of individuals during activities of daily living [53], experimental testing [14,55,61], and computational models [6,25,44,50], but the specific mechanical factors responsible for the initial injury and those driving the progression to more severe damage, such as rupture of the chondrolabral junction and a full-thickness defect (seen in 20% and 6% of individuals with symptomatic FAIS, respectively) are unknown [35].…”

A Novel Model of Hip Femoroacetabular Impingement in Immature Rabbits Reproduces the Distinctive Head-Neck Cam Deformity

“…The difference in location is explained by the upright walking pattern in humans as opposed to the quadrupedal motion pattern in sheep. 34 We believe that in a rabbit model, induced FAI impingement will result in a similar pattern of intra–articular disease as observed in sheep. A future long–term follow-up is needed to confirm the intra–articular pattern of disease.…”

Acetabular Cartilage Thickness Differs Among Cam, Pincer, or Mixed-Type Femoroacetabular Impingement: A Descriptive Study Using In Vivo Ultrasonic Measurements During Surgical Hip Dislocation

“…These locations for cartilage thickness measurements were chosen since FAI and early joint degeneration typically occur in the anterosuperior aspect and the acetabulum. 21,22 The in vivo cartilage thickness measurements were performed with a validated ultrasonic device. 13 Specifically, an A-mode 20-MHz hand-held ultrasonic probe with a speed of sound of 1580 m/s was used.…”