The effect of botulinum toxin application on latissimus dorsi and teres major muscles in patients with brachial plexus birth palsy: An electron microscopic and clinical study

BACKGROUND: In brachial plexus birth palsy (BPBP), botulinum toxin may be utilized to prevent glenohumeral dysplasia and to maintain the stable growth of the glenohumeral joint. Repeated injections may cause muscular atrophy and their functional effects are uncertain. The aim of this study was to compare the microstructure and the function of the muscles that received two injections before transfer with the muscles that were not injected. METHODS: BPBP patients that were operated between January 2013 and December 2015 were included in the study. Latissimus dorsi and teres major muscles were transferred to humerus in standard fashion. Patients were divided in two groups according to botulinum toxin status. Group 1 was toxin negative whereas Group 2 was toxin positive. For each patient, mean latissimus dorsi myocyte thickness (LDMT) was measured with electron microscopy and pre-operative and post-operative active shoulder abduction, flexion, external and internal rotation, and Mallet scores were evaluated with goniometry. RESULTS: Fourteen patients (seven patients per group) were evaluated. Five patients were female whereas nine were male. Mean LDMT was not affected significantly (p>0.05). The operation improved shoulder abduction, flexion, and external rotation significantly (p<0.05), independent of the toxin status. The internal rotation decreased significantly only in Group 2 (p<0.05). The Mallet score increased in both groups, but it was not significant (p>0.05), independent of the toxin status. CONCLUSION: Botulinum toxin that was applied twice prevented glenohumeral dysplasia and it did not cause permanent latissimus dorsi muscle atropy and function loss in late period. It augmented upper extremity functions by alleviating internal rotation contracture.