Reconstruction of elbow flexion in arthrogryposis multiplex congenita type I. Part I: surgical anatomy and vascular and nerve supply of the pectoralis major muscle as a basis for muscle transfer.

Purpose: The anatomy and neurovascular supply of the pectoralis major muscle was studied in order to establish the safe and functional muscle transfer for the reconstruction of elbow flexion in patients with arthrogryposis multiplex congenita (AMC).

Methods: Twenty pectoralis major muscles were dissected in 11 adult cadavers. The distribution of the motor end plates was studied in five pectoralis major muscles in foetuses by the detection of esterases.

Results: The pectoralis major muscle consists of clavicular, manubrial, sternocostal, costal and abdominal parts. Each part has a distinct vascular and nerve supply. The motor nerves arise from the medial and lateral pectoral nerves. The motor end plates are localised in one zone in the clavicular and manubrial parts and in two oblique zones in the distal parts of the muscle. In 15 cases, each of the muscle parts were supplied by one nerve branch. In four cases, six nerves were distinguished and the clavicular part was supplied by two nerves. In one case, four nerves were found, with the clavicular and manubrial parts supplied by one common nerve. Three branches (13 cases) or two arterial branches (seven cases) supplied the muscle, arising from thoracoacromial and lateral thoracic arteries, respectively. The superior branch supplied the clavicular and manubrial parts, whereas the dominant pectoral branch supplied the manubrial, sternocostal and costal parts of the muscle. The inferior branch of the lateral thoracic artery supplied the abdominal part in 13 cases. In seven cases, the inferior branch failed and the abdominal part was supplied from the dominant branch.

Conclusion: This study presents guidelines for the transfer of the distal parts of the pectoralis major muscle for the reconstruction of elbow flexion. The sternocostal, costal and abdominal parts of the muscle can be released as a unit from the chest wall after dissection between the second and third rib and be transferred to the brachium. They are sufficiently supplied from the dominant pectoral branch of the thoracoacromial artery in all cases and inconstantly from the inferior branch of the lateral thoracic artery and from three motor nerves.