Original Article
Arthroscopic Repair of the Acetabular Labrum: A Histologic Assessment of Healing in an Ovine Model

https://doi.org/10.1016/j.arthro.2007.01.017Get rights and content

Purpose: Recently, arthroscopic repair has been advocated for the treatment of labral tears. The purpose of this study was to document the histologic healing process in an arthroscopically repaired acetabular-labral detachment in an ovine model. Methods: A total of 10 skeletally mature female sheep underwent unilateral arthroscopic labral repair. A 1.5-cm-long incision was made at the junction of the labrum and acetabulum. The labral detachment was then repaired arthroscopically with a single suture anchor. Postoperatively, the animals were confined to small indoor pens, and no form of immobilization was used. After 12 weeks, the animals were killed and the labral repair evaluated via routine histology. Normal labra from 3 nonoperative animals were also processed for histology. Results: The acetabular labrum of the sheep is an avascular, fibrocartilaginous structure similar in anatomic design to that of human beings. All arthroscopically repaired labra appeared stable and grossly healed at 12 weeks. Histologically, labral healing appeared to occur via fibrovascular scar tissue originating from the joint capsule or the exposed bony attachment of the labrum (or both). However, the labral healing was incomplete in all specimens, with a shallow, superficial cleft remaining at the junction of the labrum and the articular surface of the acetabulum. Conclusions: Arthroscopically repaired acetabular-labral lesions in sheep are capable of healing via fibrovascular repair tissue or direct reattachment via new bone formation (or both). Clinical Relevance: The ability of labral detachments to heal in this animal model provides the rationale for additional investigations into the clinical efficacy of arthroscopic labral repair in human beings.

Section snippets

Methods

After institutional animal care and use committee approval was obtained, the left hip joint of 10 adult female sheep was accessed via arthroscopy under general anesthesia and by use of sterile surgical technique. The animals were positioned on the right side in a semisupine position, and the left rear limb was distracted in a caudal direction with approximately 15° of abduction against a padded post. Arthroscopic access to the hip joint was made under fluoroscopic control by use of two portals:

Results

As in human beings, the results of this study show that the acetabular labrum of the sheep is a fibrocartilaginous extension of the acetabulum.[21, 22 It varies in width as it courses anterior (cranial) to posterior (caudal) along the peripheral rim of the acetabulum. It is a fibrocartilaginous structure similar in histologic structure to that of human beings and is intimately attached to the acetabulum (Fig 1). Like the human acetabular labrum, that of the sheep has a poor vascular supply,

Discussion

The contribution of the acetabular labrum to normal biomechanical function of the hip joint is well known.[10, 14, 15, 16, 17 Although a previous animal study has suggested that a partially resected acetabular labrum can spontaneously regenerate,[25 the ability of a resected human acetabular labrum to regenerate functional and biomechanically competent replacement tissue has not been proved. A recent study has suggested that at 2 years, patients who have undergone labral repair had results that

Conclusions

The results of this study support the concept that surgically created acetabular-labral lesions in sheep that are repaired via a minimally invasive arthroscopic technique are capable of partial healing by 12 weeks. Depending on the location of the lesion, the labrum appears to heal by way of fibrovascular repair tissue that originates from the capsular tissues (for intra-labral lesions) or reattachment by direct new bone formation (for labral lesions that are repaired to exposed acetabular

Acknowledgment

The authors thank Simon Turner, D.V.M., and Troy Trumble, D.V.M., Ph.D., from Colorado State University, Fort Collins, Colorado, and Brian T. Kelly, M.D., from the Hospital for Special Surgery, New York, New York, for their contributions to this study.

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    Supported by Smith & Nephew Endoscopy. Research performed at Colorado State University, Fort Collins, Colorado, and Michigan State University, East Lansing, Michigan. Drs. Philippon and Arnoczky are paid consultants for Smith & Nephew Endoscopy, and Mr. Torrie is an employee of Smith & Nephew Endoscopy.

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