Predictors of wrist extensor muscle recovery following acute traumatic spinal cord injury: A model systems replication study.

Background: After high-level spinal cord injury (SCI), motor recovery of wrist extensors has significant functional consequences as it can facilitate grasp through tenodesis. A small seminal study from 1993 established widely used prognostic rules for wrist extensor recovery, though these have not been replicated with larger, real-world samples since inception.

Objective: To determine the prognostic value of initial C5 sharp-dull discrimination, C5 motor strength, and C6 motor strength on predicting 1-year ipsilateral wrist extensor motor recovery for patients with SCI with neurological level of C4 or C5.

Design: Retrospective cohort replication study.

Setting: SCI Model Systems.

Participants: 35,675 total individuals with acute traumatic SCI with 219 cases of initial wrist extensor weakness (0/5-2/5) meeting inclusion criteria.

Intervention: Not applicable.

Main outcome measure: Recovery of wrist extensor strength to ≥3/5 at 1 year.

Results: The positive predictive and negative predictive values were 57% (95% CI, 47.4%-66.1%) and 66% (56.0%-75.1%) if initial C5 sharp-dull discrimination was present, 61% (52.7%-69.3%) and 82% (71.4%-89.7%) if initial C5 myotome strength was at least antigravity, and 74% (63.7%-82.5%) and 74% (65.5%-81.4%) if initial C6 myotome strength was at least a 1/5 or 2/5. Synthesizing these three rules, an updated branched nomogram for functional wrist extensor recovery prediction was created.

Conclusions: In isolation, none of the previously established wrist extensor motor recovery predictive rules had as high of a prognostic value when using a larger dataset. As such, singular reliance on these prediction rules to identify who will gain 1-year antigravity wrist extension should be approached with decreased certainty. The best positive and negative predictors were trace C6 strength and absent C5 strength, respectively. An updated nomogram provides more nuanced prognostic information to guide clinical care following acute SCI.