Hyperselective neurectomy of thoracodorsal nerve for treatment of the shoulder spasticity: anatomical study and preliminary clinical results

Background Hyperselective neurectomy is a reliable treatment for spasticity. This research was designed to quantify the surgical parameters of hyperselective neurectomy of thoracodorsal nerve for shoulder spasticity through anatomical studies, as well as to retrospectively assess patients who underwent this procedure to provide an objective basis for clinical practice. Methods On nine embalmed adult cadavers (18 shoulders), we dissected and observed the branching patterns of thoracodorsal nerve, counted the number of nerve branches, measured the distribution of branch origin point, and determined the length of the surgical incision. Next, we selected five patients who underwent this procedure for shoulder spasticity and retrospectively evaluated (ethic committee: 2022–37) their shoulder function with active/passive range of motion (AROM/PROM) and modified Ashworth scale (MAS). Results The anatomical study revealed that the main trunk of thoracodorsal nerve sends out one to three medial branches, with the pattern of only one medial branch being the most common (61.1%); there were significant variations in the branch numbers and nerve distributions; the location of thoracodorsal nerve branches’ entry points into the muscle varied from 27.2 to 67.8% of the length of the arm. Clinical follow-up data showed significant improvement in shoulder mobility in all patients. AROM of shoulder abduction increased by 39.4° and PROM increased by 64.2° ( P < 0.05). AROM and PROM of shoulder flexion increased by 36.6° and 54.4°, respectively ( P < 0.05). In addition, the MAS of shoulder abduction (1.8) and flexion (1.2) was both significantly reduced in all patients ( P < 0.05). Conclusion Hyperselective neurectomy of thoracodorsal nerve is effective and stable in the treatment of shoulder spasticity. Intraoperative attention is required to the numbers of the medial branch of thoracodorsal nerve. We recommend an incision in the mid-axillary line that extends from 25 to 70% of the arm length to fully expose each branch.