(782.15) The Pronator Quadratus Muscle – its Morphology and Functions

Poster Board Number: C65
Introduction: AAA has separate poster presentation times for odd and even posters.
Odd poster #s – 10:15 am – 11:15 am
Even poster #s – 11:15 am – 12:15 pm

Michel van Schaardenburgh (Norwegian University of Science and Technology, Trondheim (Norway), Vrije Universiteit Medisch Centrum, Amsterdam (the Netherlands)), Lucian Poliacu-Prose (Vrije Universiteit Medisch Centrum, Amsterdam (the Netherlands))

Knowledge of the architecture and nerve supply of the human pronator quadratus muscle (MPQ) appears to be rather scarce and is insufficient for a surgical approach of the muscle. In older French and more recent clinical studies it is stated that the MPQ consists of two or even three parts, each of them with an individual nerve supply and function. Former studies have described a superficial part that is active during pronation, and a deeper part which acts during supination. Furthermore, other authors described that the MPQ regulates the tension of the capsular complex at the distal radio-ulnar joint.

We studied the existence of subdivisions of the MPQ and their pattern of nerve supply from the anterior interosseous nerve in 15 cadaver forearms (8 M, 7 F, mean age 80 years). The dissection was carried out using a surgical microscope. In all 15 forearms the MPQ consisted of three parts: a superficial (pars superficialis; PQs), a deep proximal (pars profunda proximalis; PQpp) and a deep distal part (pars profunda distalis; PQpd).

Three primary nerve branches were identified (ramus proximalis, ramus intermedius and ramus distalis) as they originated from the anterior interosseous nerve and at entry of the individual parts of the MPQ.

We have not been able to conclude whether the ramus proximalis or the ramus intermedius supplies the superficial (PQs) or the deep proximal (PQpp) part of the MPQ. However, it could be established that the ramus distalis goes to the deep distal (PQpd) part of the MPQ. We could also confirm that only fibers of the deep distal part insert into the distal radio-ulnar joint. On the basis of the existing division of the MPQ in three different parts, functional considerations can be made with regard to the complex functions of MPQ, i.e. pronation by the superficial part of the MPQ, fine-tuning of motion of the radius during pronation and supination by the deep proximal part and capsular tension (stabilization) of the distal radio-ulnar joint by the deep distal part of the MPQ.

This study was supported by the medical faculty at the Vrije Universiteit Medisch Centrum in Amsterdam, Netherlands