Postoperative Loss of Midline Function in Brachial Plexus Birth Palsy.

PURPOSE: To identify the rate of and predictive variables for functionally limited shoulder internal rotation in postoperative patients with brachial plexus birth palsy. METHODS: Records of patients with brachial plexus birth palsy who had surgery on the affected upper extremity during a 10-year period were retrospectively reviewed. Patient demographics, physical examinations, and all upper extremity procedures were recorded. Loss of midline function (LOM) was defined as a Modified Mallet Scale or Active Movement Scale (AMS) internal rotation score <3. Exclusion criteria were <1-year follow-up after the most recent procedure, insufficient documentation, or preexisting LOM. Multivariable logistic regression was performed on 3 different scenarios of candidate variables to identify those associated with LOM. All scenarios included each procedure as a candidate variable. Scenario A additionally analyzed preprocedural AMS scores. Scenario B additionally analyzed preprocedural Modified Mallet Scale scores. Scenario C isolated the surgical pathway without preprocedural examination scores. RESULTS: Among 172 included patients, 34 (19.8%) developed LOM. Predictive variables associated with LOM included severity of initial palsy (C5-7, odds ratio 3.6; C5-T1, odds ratio 4.9), poor recovery of upper trunk motor function before the patient's first surgery (specifically Modified Mallet Scale abduction < 4, AMS elbow flexion < 3, and AMS wrist extension < 3), and patients who ultimately required surgical glenohumeral reduction (odds ratio 3.6). Age, number of procedures, closed shoulder reduction with casting, shoulder tendon transfers, and external rotation humeral osteotomies were not predictive of LOM. CONCLUSIONS: Approximately 1 in every 5 patients with brachial plexus birth palsy will develop LOM after entering a surgical algorithm designed to improve shoulder external rotation. Patients with a more severe initial palsy (C5-7 or global), poor spontaneous recovery of upper trunk motor function (elbow flexion or wrist extension) before their first procedure, and those who ultimately require surgical glenohumeral joint reduction should be counseled as having a higher odds of LOM development. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.