Heterotopic ossification (HO) is a frequent complication after damage to the central nervous system (CNS), with an estimated prevalence of up to 76%. The primary site of HO is the hip joint (60,9%). The only effective treatment of troublesome HO is surgery. The main purpose of this study was to identify the relationship between the location of troublesome hip HO treated by surgery and the etiology of the cerebral damage. The secondary aim was to identify risk factor of sepsis and recurrences after the surgery.

We retrospectively analyzed data from an anonymous prospective survey of patients undergoing surgery for troublesome HO from 1993 to 2016 (417 patients, 609 surgeries).

The sites of HO on the hip joint were associated with its etiology (P<0.01): for brain damaged patients, the hip HO was most frequently anterior and internal with a rate of 40.0% whereas it was anterior for patients with spinal cord injury (SCI), with a rate of 54.4%. The main side effect after surgery of troublesome HO was sepsis, with a rate of revision surgery of 8.2%. SCI patients were more affected (18.3%) than traumatically brain injured patients (TBI) (4.4%) or stroke patients (8.7%). Sepsis seemed to occur most frequently on hip surgeries, but no statistically significant relationship was found. The rate of recurrence was 2.8% for the whole population. It occurred most frequently after TBI (3.6%) rather than after stroke (1.9%) or SCI (1.5%).

The sites of hip HO, their recurrences and sepsis were associated with its etiology. The patients with SCI will develop most frequently anterior hip HO, with a risk of sepsis that is more frequent than in the other etiologies.