Electromyographic activity after latissimus dorsi transfer: testing of coactivation as a simple tool to assess latissimus dorsi motor learning.
BACKGROUND
The purpose of this study was to investigate coactivation (CoA) testing as a clinical tool to monitor motor learning after latissimus dorsi tendon transfer.


METHODS
We evaluated 20 patients clinically with the American Shoulder and Elbow Surgeons (ASES) and University of California-Los Angeles (UCLA) outcomes scores, visual analog scale, active external rotation (aER), and isometric strength testing in abduction and external rotation. Measurements of aER were performed while the latissimus dorsi was activated in its new function of external rotation with concomitant activation (coactivation) of its native functions (adduction and extension). Bilateral surface electromyographic (EMG) activity was recorded during aER measurements and the strength testing procedure (EMG activity ratio: with/without CoA). Patients were divided into two groups (excellent/good vs fair/poor) according to the results of the ASES and UCLA scores.


RESULTS
The mean follow-up was 57.8 ± 25.2 months. Subdivided by clinical scores, the superior outcome group lost aER with CoA, whereas the inferior outcome group gained aER (UCLA score: -2.2° ± 7.4° vs +4.3° ± 4.1°; P = .031). Patients with inferior outcomes in the ASES score showed higher latissimus dorsi EMG activity ratios (P = .027), suggesting an inadequate motor learning process. Isometric strength testing revealed that the latissimus dorsi transfer had significantly greater activity compared with the contralateral side (external rotation, P = .008; abduction, P = .006) but did not have comparable strength (external rotation, P = .017; abduction, P = .009).


CONCLUSIONS
Patients with inferior clinical results were more likely to be dependent on CoA to gain external rotation. Therefore, CoA testing may be used as a tool to evaluate the status of postoperative motor learning after latissimus dorsi transfer.
Department of Orthopaedic Sports Medicine, Klinikum rechts der Isar, Technische Universität München, Munich, Germany. Electronic address: johannes.plath@gmail.com.
Johannes E
JE
Plath
Department of Biomechanics in Sports, Technische Universität München, Munich, Germany.
Wolfgang
W
Seiberl
BG Center Murnau, Department of Trauma and Orthopaedic Surgery, Murnau, Germany.
Knut
K
Beitzel
Department of Orthopaedic Sports Medicine, Klinikum rechts der Isar, Technische Universität München, Munich, Germany.
Philipp
P
Minzlaff
Department of Biomechanics in Sports, Technische Universität München, Munich, Germany.
Ansgar
A
Schwirtz
Department of Orthopaedic Sports Medicine, Klinikum rechts der Isar, Technische Universität München, Munich, Germany.
Andreas B
AB
Imhoff
Department of Orthopaedic Sports Medicine, Klinikum rechts der Isar, Technische Universität München, Munich, Germany.
Stefan
S
Buchmann
D000368:Aged; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D016059:Range of Motion, Articular / Q000502:physiology; D012399:Rotation; D017006:Rotator Cuff / Q000503:physiopathology* / Q000601:surgery; D000070636:Rotator Cuff Injuries; D012782:Shoulder / Q000503:physiopathology* / Q000601:surgery; D064171:Superficial Back Muscles / Q000503:physiopathology* / Q000637:transplantation; D013709:Tendon Transfer; D016896:Treatment Outcome
Latissimus dorsi transfer; coactivation testing; electromyography; isometric strength; motor learning; muscle recruitment