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No evidence of active denervation seen 1 year after total shoulder arthroplasty
Patients who underwent shoulder arthroplasty had improved patient outcome scores at 1 year.
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While half of patients who underwent total shoulder arthroplasty showed evidence of chronic denervation and reinnervation changes across five muscle groups with electromyographic evaluation, active denervation of the subscapularis was not evident in any patient at least 1 year after surgery, according to study results.
Evidence of denervation
April D. Armstrong, BSc (PT), MD, MSc, FRCSC, and her colleagues performed physical examination, ultrasound evaluation and electromyographic (EMG) evaluation on 30 patients with a diagnosis of primary osteoarthritis (OA) who underwent an anatomic total shoulder arthroplasty (TSA) with subscapularis tenotomy 1 year prior. Patients completed the American Shoulder and Elbow Surgeons (ASES) questionnaire, the Simple Shoulder Test and the SF-12 Health Survey postoperatively.
Results showed an improvement in ASES scores from 45.3 preoperatively to 76.8 postoperatively, as well as improvements in the Simple Shoulder Test from 3.9 preoperatively to 9 postoperatively. Researchers also noted an increase in the average mental preoperative score and the average physical preoperative score from 52 to 55.1 postoperatively and from 33.9 to 42.8 postoperatively, respectively.
Patients experienced improvements in average forward elevation from 108° preoperatively to 146° postoperatively and in active external rotation from 27° preoperatively to 59° postoperatively. Researchers noted six patients had positive lift-off test results, while all patients had negative belly-press test results. Ultrasound revealed subscapularis ruptures in two patients. Overall, 15 patients had a normal postoperative EMG finding. However, researchers found evidence of chronic denervation with reinnervation changes in 15 patients with 30% in the subscapularis, 27% in the infraspinatus, 20% in the supraspinatus, 20% in the teres minor and 13% in the rhomboids.
“The fact we were seeing that there was some denervation of the muscle belly of the subscapularis [was surprising], and it is still unclear if this could be related to surgical exposure or the use of regional anesthesia,” Armstrong said. “We also found denervation in other muscle bellies around the shoulder, but they all showed reinnervation, so it was a temporary finding.”
Anatomical studies
Armstrong is currently working on an anatomical study looking at the nerves around the subscapularis muscles to see where these are in relation to the subscapularis to get a better understanding of how surgical exposure may affect the nerves around the shoulder.
“I am also considering repeating this study without using regional blocks [to] see if this would change our findings. If we saw less denervation without using regional blocks then there could be a relationship to regional anesthesia,” she said.
“[This study] makes us critically on our surgical and pain control techniques,” Armstrong said. – by Casey Tingle
- Reference:
- Armstrong AD, et al. J Shoulder Elbow Surg. 2016;doi:10.1016/j.jse.2016.02.018.
- For more information:
- April D. Armstrong, BSc (PT), MD, MSc, FRCSC, can be reached at Penn State Health Milton S. Hershey Medical Center, 30 Hope Dr., Building A, EC089, Hershey, PA 17033; email: aarmstrong@hmc.psu.edu.
Disclosure: Armstrong reports she is a consultant for Zimmer Biomet.