Influence of etiology in heterotopic bone formation of the hip

Heterotopic ossification (HO) in periarticular tissue can appear after brain or local joint trauma. The aim of this study was to investigate differences of manifestation and outcome after surgical therapy of patients suffering from HO of the hip after isolated brain injury (n = 18), local hip trauma (n = 21), or the combination of both (n = 25). HO can cause progressive lost of joint movement; once mature, the only therapy to improve joint mobility is the excision.

All patients underwent surgical removal of HO and postoperative irradiation therapy. On the basis of plain radiographic findings, we evaluated the recurrent ossification after 1-year and 5-year follow-up periods. Within this prospective study, clinical performance status was scored according to the classification of d'Aubigne and a planimeter was used to evaluate the area of heterotopic bone formation in standard x-rays films.

The severity of brain trauma observed by Glasgow Coma Scale correlated with the ossification size (square centimeters). Correlation was noticed as well between severity of brain injury and functional outcome. The evaluation of an average 1-year and 5-year follow-up period showed relief of pain and clear improvement of range of motion in all patients. There was mild recurrence of heterotopic bone growth within the first postoperative year without deterioration of the functional results.

The severity of brain trauma has an influence on the extent of HO near the hip joint and also on the rehabilitation process. The histologic findings and recurrence of HO after excision were not affected by the localization of initial trauma. There was only mild recurrence of heterotopic bone growth between the first and fifth postoperative year. For objective evaluation of heterotopic bone formation in standard x- ray films, planimetric measurement is a useful method.