Heterotopic ossification around the hip with intramedullary nailing of the femur.

Heterotopic ossification (HO) at the proximal end of a reamed intramedullary femoral nail is a complication of the procedure. Kuntscher stated that these "callus caps" were due to the prominence of the nail above the greater trochanter. A study of patients undergoing locked intramedullary nailing of the femur to assess subsequent development of heterotopic ossification at the proximal end of the implant was done. The purpose was to study the clinical significance of the ectopic bone and identify etiologic factors of bone formation. This group consisted of 59 patients with 60 locked intramedullary nails who were reviewed after prospective clinical and radiologic followup. Ectopic bone around the proximal end of the nail was classified with respect to quantity and clinical importance. A number of parameters were evaluated and a multifactorial analysis was performed. There were 52 males and seven females. Heterotopic bone was graded as: none--32%; minimal--20%, mild--28%; moderate--15%; and severe--5%. There was a positive correlation between bone formation and head injury, Injury Severity Score, and ventilator and ICU days. Prominence of the nail was not significant.