The influence of nerve surgical techniques at time of amputation on the prevalence of heterotopic ossification in transtibial amputees

Background: Heterotopic ossification (HO) can form after amputation and may cause pain and functional impairment. We aimed to describe the prevalence of HO in a civilian population of transtibial amputees. We hypothesized that the decreased rate of symptomatic neuroma following active nerve surgery (Targeted Muscle Reinnervation (TMR) or Regenerative Peripheral Nerve Interface (RPNI)) may subsequently lead to a lower prevalence of HO compared to passive nerve surgery (i.e. traction neurectomy) performed at the time of amputation. Methods: Adult patients undergoing transtibial amputation at a tertiary care center between 2000 and 2023 were included. Patient data were collected through chart review. The most recent post-amputation X-ray of the residual limb was assessed for HO presence, according to the Walter Reed classification. A random subset of X-rays (10.0 %) was independently assessed by five clinicians and two radiologists, and inter-rater reliability (IRR) was calculated using Cohen's kappa (κ). Multivariable logistic regression was conducted to identify factors associated with HO presence. Results: In total, 665 limbs of 632 patients were included. The median time between amputation and X-ray was 1.7 years (IQR: 0.3–6.2). HO was identified in 326 X-rays (49.0 %) and was commonly present on the distal residual tibia (68.1 %) and fibula (69.0 %). Traditional amputations (i.e. those without TMR or RPNI (OR: 2.0, p = 0.014)), and the presence of a symptomatic neuroma (OR: 2.3, p < 0.001), were independently associated with a higher prevalence of HO. The IRR of the two radiologists was κ = 0.99, the overall IRR of all evaluators was κ = 0.92. Conclusions: HO is a common finding in transtibial amputees. Peripheral nerve surgerical techniques that actively address amputated nerve endings to reduce symptomatic neuroma formation may decrease the prevalence of HO.