What Risk Factors Predict Recurrence of Heterotopic Ossification After Excision in Combat-related Amputations?

BACKGROUND: Heterotopic ossification (HO) is common after combat-related amputations and surgical excision remains the only definitive treatment for persistently symptomatic HO. There is no consensus in the literature regarding the timing of surgery, and recurrence frequency, reexcision, and complications have not been reported in large numbers of patients. QUESTIONS/PURPOSES: (1) What are the rates of symptomatic recurrence resulting in reexcision and other complications resulting in reoperation in patients with HO? (2) Is either radiographic or symptomatic recurrence dependent on timing and type of initial surgery, the experience of the surgeon in performing the procedure, the severity of preexcision HO, the presence of concomitant neurologic injury, or the use of postoperative HO prophylaxis?
METHODS: Between March 2005 and March 2013 our institution treated 994 patients with 1377 combat-related major extremity amputations; of those, 172 amputations underwent subsequent excision of symptomatic HO. The mechanism of injury resulting in nearly all amputations (n = 168) was blast-related trauma. We reviewed medical records and radiographs to collect initial grade of HO, radiographic recurrence, complete compared with partial excision, concomitant neurologic injury, timing to initial surgery, surgeon experience, and use of postexcision prophylaxis with our primary study outcome being a return to the operating room (OR) for repeat excision of symptomatic HO. All 172 combat-related amputations were considered for this study irrespective of followup, which was noted to be robust, with 157 (91%) amputations having at least 6 months clinical followup by an orthopaedic surgeon or physiatrist (median, 20 months; range, 0-88 months).
RESULTS: Eleven of 172 patients (6.5%) underwent reexcision of HO, and 67 complications resulting in return to the OR occurred in 53 patients (31%) of patients. Multivariate analysis of our primary outcome measure showed more frequent symptomatic recurrences requiring reexcision when initial excision was performed as a partial excision (p = 0.03; odds ratio [OR], 5.0; 95% confidence interval [CI], 1.2-29.6) or when the initial excision was performed within 180 days of injury (p = 0.047; OR, 4.1; 95% CI, 1.02-16.6). There was no association between symptomatic recurrence and HO grade, central nervous system injury, experience of the attending surgeon, or postoperative prophylaxis. Radiographic recurrence was observed when partial excisions (eight of 30 [27%]) were done compared with complete excisions (five of 77 [7%]; p = 0.008).
CONCLUSIONS: HO is common after combat-related amputations, and patients undergoing surgical excision of HO for this indication often have complications that result in repeat surgical procedures. Partial excisions of immature lesions more often resulted in both symptomatic and radiographic recurrence. The likelihood of a patient undergoing reexcision can be minimized by performing a complete excision at least 180 days from injury to surgery with no evidence of a reduced risk of reexcision by waiting longer than 270 days. LEVEL OF EVIDENCE: Level III, therapeutic study.