Heterotopic ossification after hip arthroscopy

Abstract

Heterotopic ossification (HO) after hip arthroscopy is the abnormal formation of mature lamellar bone within extra skeletal soft tissues. HO may lead to pain, impaired range of motion and possibly revision surgery. There has been a substantial amount of recent research on the pathophysiology, prophylaxis and treatment of HO associated with open and arthroscopic hip surgery. This article reviews the literature on the aforementioned topics with a focus on their application in hip arthroscopy.

Fig. 1.

Heterotopic ossification is initiated local tissue damage leading to increased BMP-2 targeting of sensory nerves. Subsequently, a cascade of molecular mechanisms including the binding of SP and CGRP to mast cell and sympathetic signaling induces the remodeling of peripheral nerves. This remodeling initiates the production of chondro-osseous, glial, vascular and neural progenitor cells. These new cells respond to signals from transient brown adipocytes that regulate local oxygen content, vascularization and innervation to produce HO. (Reproduced with permission from reference [9].)

Fig. 2.

Follow up radiograph of a 20-year-old patient after bilateral hip arthroscopy. The radiograph was taken 9 months status post left and 3 months status post right hip arthroscopy. HO on the left side was evident on radiographs 10 weeks after the index procedure. NSAID prophylaxis using etodolac 600 mg once daily for 2 weeks was administered only after the operation on the right hip.

Fig. 3.

3D CT reconstruction of a 34-year-old triathlete showing grade 3 HO with acetabular origin and posterolateral location of the HO.