A three-dimensional model of the shoulder girdle. Forces developed in deltoid and supraspinatus muscles during abduction

Surg Radiol Anat (2004) 26: 290296DOI 10.1007/s00276-004-0225-3ORIGINAL ARTICLEM. Scepi J.-P. Faure N. Ridoux P. KaminaJ.-P. RicherA three-dimensional model of the shoulder girdle. Forces developed

in deltoid and supraspinatus muscles during abductionReceived: 7 April 2003 / Accepted: 9 September 2003 / Published online: 24 March 2004

Springer-Verlag 2004Abstract The aim of this study was to design a threedimensional model of the human shoulder girdle.

Fourteen muscles were modelled geometrically using

robotics software (Solid Dynamics System). A static

study in reverse dynamics allowed the forces developed

in seven muscles to be studied, particularly in the deltoid

and supraspinatus during abduction of the arm with the

forearm bent at 90, the scapula being xed. After

optimization by Excel, this model allowed simultaneous

curves of forces developed in every modelled muscular

bundle to be obtained during various degrees of

abduction of the arm from 0 to 100, in the scapular

plane. The analysis of supraspinatus and deltoid curves

revealed an interesting chronology of action. The rst

muscle developed eorts estimated at 140 N, quickly

relieved by the deltoid. It is also interesting to note that a

constant action of supraspinatus was found throughout

abduction of the arm. Clinical applications seem to be in

simulation of muscular pathology of the shoulder girdle.

This study is continuing by releasing the xed scapula

and by simulating muscle transfers proposed for massive

ruptures of the rotator cu.Keywords Three-dimensional model Shoulder

Deltoid Supraspinatus Abduction22]. A three-dimensional (3D) model is proposed, which

allows one to obtain, simultaneously, forces in muscles

modelled during abduction of the arm in the scapular

plane. Results compared with those in the literature [8,

9, 11, 16, 19, 21, 22] seem interesting and suggest future

clinical applications.Material and methodsAnatomical studyIn this study 20 freshly embalmed human shoulder girdles were

dissected and all measurements were made with calipers. Each

muscle of the shoulder girdle was studied in the following way: measurement of the distal and proximal bony attachments

according to a stationary bony reference point (e.g., greater

tuberosity of the humerus); measurement of the length of the muscle, the upper limb in

anatomical position along the body and at 30of abduction; measurement of the thickness in the middle body for the long

muscles, and near their bony attachments for the at muscles