Muscle localization of heterotopic ossification following spinal cord injury

Background context: Heterotopic ossification (HO) is a known complication especially in people with traumatic spinal cord injury (SCI). Although some risk factors have already been described, the pathophysiology of HO is still unknown. The pelvis is the most common region for HO occurrence. However, the prevalence of HO by muscle groups about the hip is not well described.

Purpose: To analyze the prevalence of early HO in muscle groups about the hip in 267 patients with SCI.

Patient sample: 267 patients with traumatic SCI and pelvic HO.

Methods: Between January 2001 and December 2014, 267 patients with SCI were treated in our university hospital and were included in the study. Patients were routinely screened for HO using ultrasound. The diagnosis of HO was validated using magnetic resonance imaging (MRI) or computed tomography (CT). The primary outcome measure was the prevalence of HO by muscle groups around the hip. The following muscle groups around the hip were defined: (1) gluteal group, (2) adductor group, (3) iliopsoas group, and (4) deep muscle group. Additionally, the prevalence of concomitant trochanteric bursitis was recorded in all cases.

Results: The gluteal group showed the highest HO prevalence with 55.8%, followed by the deep muscle group with 31.1%. Concomitant trochanteric bursitis was found in 62 patients (23.2%). No association between pelvic trauma and HO development was observed (n=16, 11%).

Conclusions: The most common muscular location for the occurrence of HO about the hip was the gluteal muscle group. Considering that no laboratory parameters are currently available for screening for HO, highly sensitive ultrasound screening examinations should be routinely performed, with particular attention paid to the gluteal muscles. Additionally, routine range of motion examination for extension and external rotation of the hip joint is warranted.