Arthroscopic Lower Trapezius Tendon Transfer for a Patient with Axillary Nerve Injury and Concomitant Rotator Cuff Tear: A Case Report and Technical Notes.

Introduction: Concomitant nerve injuries with musculoskeletal injuries present a challenging problem. The goals of nerve reconstruction for the shoulder include shoulder abduction and external rotation. When patients fail to achieve acceptable shoulder external rotation and shoulder abduction, tendon transfers such as trapezius transfer offer a reliable option in the subsequent stage. Case Presentation: A 32-year-old male presented with weak external rotation in his left shoulder, after previous axillary nerve reconstruction. He received the ipsilateral lower trapezius transfer with the aim of improving the external rotation. Discussion: The lower trapezius restores a better joint reaction force in both the compressive-distractive and anterior-posterior balancing and provides a centering force through the restoration of the anterior-posterior force couple. Conclusion: We believe that the ipsilateral lower trapezius transfer to the infraspinatus is a good outcome and is effective in improving overall shoulder stability and the shoulder external rotation moment arm or at least maintaining in neutral position with the arm fully adducted in patients with post axillary nerve injuries post unsatisfactory nerve reconstruction to increase the quality of life and activities of daily living.

Can an injured nerve be used as a donor nerve for distal nerve transfer?-An experimental study in rats.

BACKGROUND: Distal nerve transfer has proven efficacy. The purpose of this study was to investigate if an injured nerve can be used as a donor nerve for transfer, and to determine the threshold of injury. MATERIALS AND METHODS: Rat's left ulnar-nerves in the axilla with different degrees of injury were selected as the donor nerves for transfer, and the musculocutaneous-nerves the target nerves for being re-innervated. Six rats each served as positive and negative controls: Group A, intact ulnar-nerve transfer; and Group E, the ulnar-nerve was cut but no transfer. Ten rats each were assigned to Group B to Group D with 25%, 50%, and 75% transected ulnar-nerve, respectively and all were transferred to the musculocutaneous-nerve. After a 12-week recovery period, outcomes were evaluated. RESULTS: Biceps muscle weight measurements showed all experimental groups-D 0.28 ± 0.02 g/72%, C 0.28 ± 0.03 g/73%, B 0.29 ± 0.04 g/74%, and A 0.29 ± 0.04 g/80%-were lighter than group H 0.36 ± 0.04 g, which were all statistically significant (P < 0.001). Muscle tetanus contraction force measurements were the lowest in group D35 ± 8.6 g/69%. Groups C and B measured 41 ± 8.5 g/75% and 40 ± 2.2 g/77% and group A 41 ± 9.4 g/95%, respectively. Group H showed muscle contraction force of 52 ± 7.2 g, which was statistically significant when compared to experimental groups (P < 0.05-0.001). EMG measurements of the biceps muscles showed: group D was 3.6 ± 0.7 mV/69%, group C was 3.6 ± 0.6 mV/75%, and group B was 4.2 mV ± 0.7/81%. Group H was5.1 ± 0.7 mV and statistically significant different when compared with experimental groups (P < 0.05-0.001).Axon counts of healthy ulnar-nerve (Group H) were 1849 ± 362. Axon counts of the injured ulnar-nerve were in group B 1447 ± 579/78%, group C 1051 ± 367/57% and group D 567 ± 230/31%. CONCLUSION: The donor nerve should be healthy in order to provide optimal result. A big nerve (e.g., ulnar nerve) but injured with at least 75% axon spared is still potentially effective for transfer. In contrast, a small nerve (e.g., intercostal nerve) once injured with 75%axon spared would be considered a suboptimal donor nerve.