Sciatic nerve compression by neurogenic heterotopic ossification: use of CT to determine surgical indications

To describe the characteristics of neurogenic heterotopic ossification (NHO) based on clinical tests, electroneuromyography (ENMG) and CT in a database of patients with lesions of the central nervous system who required sciatic nerve neurolysis along with posterior hip NHO resection, and to determine the respective roles of ENMG and CT in the management of posterior hip NHOs in patients who are unable to communicate or express pain.

The consistency of the ENMG results with clinical findings, CT results and macroscopic signs of lesions was retrospectively assessed after sciatic nerve neurolysis and ablation of 55 posterior hip NHOs.

Sciatic nerve neurolysis was necessary in 55 cases (47.4%; 55 out of 116). CT showed contact of the NHO with the nerve in all cases: 5 in contact with no deflection, 3 in contact with deflection, 21 moulded into a gutter and 26 entrapped in the NHO. There were clinical signs of sciatic nerve lesion in 21.8% of cases (12 out of 55). ENMG showed signs of sciatic nerve lesions in only 55.6% (10 out of 18), only 4 of whom presented with clinical signs of a nerve lesion. No significant relationship was found between clinical symptoms and ENMG findings of sciatic nerve compression (n = 13, p = 0.77).

Nerve compression by NHO is likely an underdiagnosed condition, particularly in patients who are unable to communicate. Diagnosis of sciatic compression by NHO should be based on regular clinical examinations and CT. ENMG is not sufficiently sensitive to be used alone for surgical decision-making.