Orthopaedic Surgery, Traumacor Clinic, La Coruña, Spain

Rehabilitation Physical Medicine, Traumacor Clinic, La Coruña, Spain

Orthopaedic, Hospital Cuf Descobertas, Lisbon, Portugal

Fisioterapia, Fisioroma Lisbon, Lisbon, Portugal

Traumatology Orthopaedic Surgery, Hospital de Cabueñes, Gijón, Spain

Purpose: The aim of this multicenter study is to evaluate by superficial electromyography (EMGs) the muscular activation of the deltoid and trapezius muscles after the implantation of a reverse prosthesis (RP) by transdeltoid approach.

Material and Methods: The study involved 31 reverse arthroplasties (10 men -21 women) by transdeltoid approach and was performed between12 and 30 months after operation. The indication was massive cuff rupture in 27 and proximal humerus fracture in 4 (1 acute, 3 fracture sequelae). An EMGs of the 3 portions of deltoid and superior-inferior trapezius was performed on both limbs with 90º of scaption movements. We evaluated Constant score and X-ray deltoid elongation-postoperative acromiohumeral distance. The non operated shoulder was used as control group.

Results: The medium portion of deltoid showed the higher values of EMG activation in both shoulders (RP 30% ; control 24%) ;posterior deltoid activation was similar in both groups, and anterior deltoid showed higher values in control group, although not statistical significant. No deltoid fatigue was recorded. Increased activation was recorded in the trapezius, higher in its superior portion (RP 17% ; control 16%) than the inferior (RP 13% ; control 12%). Average acromiohumeral distance was 3,2 cms. Adjusted Constant score was 76.

Conclusion

The EMG function parameters of deltoid muscle after implantation of a reverse shoulder arthroplasty by transdeltoid approach are not statistically different from non operated shoulder after 1 year postoperative time, and particularly are not affected by the increased elongation. Trapezius muscle demonstrates an increased bilateral activation, higher in the superior part. These data may be valuable in the postoperative rehabilitation of patients operated with reverse prosthesis.