24. Radial Nerve Recovery After Humerus Fracture Using Frequentist and Bayesian Statistics

PURPOSE: Humerus fractures are among the most common fractures and are accompanied by radial nerve injury in approximately 1 in 8 patients. Nerve transfers have gained popularity as a treatment option when spontaneous recovery does not occur, but they need to be performed early and therefore carry the risk of overtreatment. Since most radial nerve injuries are likely to recover spontaneously, the optimal timing of surgery - the moment the probability of neurotmesis outweighs the iatrogenic harm from surgery - is unclear. We asked: (1) What is the probability of recovery of radial nerve paralysis after humerus fracture accounting for time passed after injury? (2) What factors are independently associated with timing of radial nerve recovery? METHODS: We retrospectively re-screened records from a previously established patient cohort of 374 adults with surgically treated humerus fractures for patients with a radial nerve palsy. We included 53 patients with a radial nerve palsy in addition to their traumatic humerus fracture. The median age was 43 years (range 18 to 94), and 49% were male. Most palsies were present preoperatively (83%) and median time from injury to surgery was 2 days (range 0 to 64). We collected data on motor recovery (Medical Research Council 3 or higher) of the wrist and digits. RESULTS: (1) Although the Kaplan-Meier function shows that after 4 months more than 50% of patients recovered motor function, the probability that a patient is going to recover, assessed with Bayesian statistics, remains above 50% up to 8 months. If a patient has not yet recovered, the probability that a patient is going to recover is 45% at 8 months, 29% at 10 months, and 17% at 12 months. (2) Obese patients have a higher rate of recovery at any given time (HR 5.7 [95% CI 2.2 to 15, p<0.0001]. Patients seem to regain wrist function before regaining digital function. CONCLUSION: Early exploration or nerve transfers for radial nerve injury after humerus fractures seem to carry a significant risk of overtreatment, as patients still have a substantial chance of spontaneous recovery at that time. Awaiting recovery for at least one year and performing tendon transfers seems to result in the lowest amount of overtreatment and unnecessary iatrogenic harm.