# The Shoulder Arm Model¶

The ShoulderArm model contains data from two different persons. Most of this data comes from the Dutch Shoulder Group and their shoulder model available online

New in version 2.2: A new wrapping implementation of the deltoid muscles was recently added by Marta Strzelczak from École de technologie supérieure, Montreal, CA. See :ref:DeltoidWrapping below.

The model is built using data from subject 2 from the VU study and subject 2 from the MAYO study. The files, which contains the name “forearm”, are built on data from the MAYO study

The shoulder is the site of complex, mutually coupled motions of the scapula, clavicle and the humerus. To balance realism with model simplicity, the model defines motions of the scapula and clavicle as mathematical functions of the glenohumeral joint angles, also known as a “Shoulder rhythms”.

The AnyBody shoulder model’s rhythm can be switched on and off, the full details of which can be seen in this report Shoulder Rhythm Report.

## Example Configuration¶

Short example of how to configure the Shoulder Arm model:

#define BM_ARM_RIGHT ON
#define BM_ARM_LEFT ON
#define BM_ARM_SHOULDER_RHYTHM ON

#define BM_ARM_MUSCLE _MUSCLES_3E_HILL_


See Arm configuration parameters for a full list of configuration parmaeters or configuration section for more information on BM parameters.

The model consists of the following joints:

## Deltoid wrapping¶

A new implementation of the deltoid muscles have been added. The implementation uses multiple wrapping cylinders for each element of the deltoid muscle. The new approach ensures a more realistic path of the muscle fibers compared to the previous implementaiton which used a dedicated rake segment to hold the detoid fibers in place.

New deltoid wrapping can be disabled/enabled with the switch BM_ARM_DELTOID_WRAPPING.

The new deltoid wrapping was developed by Marta Strzelczak from Département de génie de la production automatisée, École de technologie supérieure, Montreal, CA. Please cite the following work if you need it:

Strzelczak, M., Lund, M. E., Sins, L., Mickael, B. & Hagemeister, N. A new wrapping approach for the deltoid muscle modelling. in The Proceedings of the 20th Biennial Meeting of theCanadian Society for Biomechanics (2018).

## Degrees of freedom¶

The arm has the following basic dof, which can be controlled by combinations joint drivers directly or indirectly through connections to the environment

• SternoClavicularProtraction

• SternoClavicularElevation

• SternoClavicularAxialRotation

• GlenohumeralFlexion

• GlenohumeralAbduction

• GlenohumeralExternalRotation

• ElbowFlexion

• ElbowPronation

• WristFlexion

• WristAbduction

## Joint terminology¶

Joints and kinematic contraints of the arm model

Name

Description

Joint/Constraint Type

SternoClavicularJoint

SternoClavicular

Spherical joint

AcromioClavicularJoint

AcromioClavicular

Spherical joint

GlenoHumeralJoint

Glenohumeral joint

Spherical joint (The default joint reactions are disabled, since they do not automatically ensure that the net force vector passes through the glenoid cavity. The special force elements providing these biofidelic reaction forces are contained in the file “GHReactions.any”)

AI

One DOF constraint requiring the bony landmark AI on the scapula, to stay in contact with the thorax

AA

One DOF constraint requiring the bony landmark AA on the scapula, to stay in contact with the thorax

ConoideumLigament

The length of this ligament is driven to always remain constant

HumeroUlnarJoint

Flexion-extension of the elbow

Revolute joint

Pronation-supination

Single linear constraint (5 DOF joint) between radius and humerus

Pronation-supination

Trans Spherical joint between radius and ulna at the proximal part.

Pronation-supination

Trans Spherical joint between radius and ulna at the proximal part. The HumeroRadialJoint, ProximalRadioUlnarJoint DistalRadioUlnarJoint leaves one DOF free which is pronation/supination of the forearm

Wrist joint

Two successive revolute joints where the axes of rotations are not coincident

## Resources¶

More details on the ShoulderArm model can be found online:

## Anatomy References¶

• F.C.T. van der Helm and R. Veenbaas, Modeling the mechanical efect of muscles with large attachment sites: aplication to the shoulder mechanism. Journal of Biomechanics, vol. 24, no. 12, pp. 1151-1163, 1991

• H.E.J. Veeger, F.C.T. van der Helm, L.H.V. van der Woude, G.M. Pronk and R.H. Rozendal, Inertia and muscle contraction parameters for musculoskeletal modelling of the shoulder mechanism. Journal of Biomechanics, vol. 24, no. 7, pp. 615-629, 1991

• F.C.T. van der Helm, A finite element musculoskeletal model of the shoulder mechanism. Journal of Biomechanics, vol. 27, no. 5, pp. 551-569, 1994

• R. Happee and F.C.T. Van der Helm, The control of shoulder muscles during goal directed movements, an inverse dynamic analysisJ. Biomechanics, vol. 28, no. 10, pp. 1179-1191, 1995

• Van der Helm FC, Veeger HE, Pronk GM, Van der Woude LH, Rozendal RH. Geometry parameters for musculoskeletal modeling of the shoulder system Journal of biomechanics Vol. 25 no. 2, pp. 129-144, 1992 Note: this reference is used for the geometry used for the definition of many of the geometries which are used for muscle wrapping

• DirkJan (H.E.J.) Veeger, Bing Yu, Kai Nan An, Orientation of axes in the elbow and forearm for biomechanical modeling Proceedings of the first conference of the ISG,1997

• The segment coordinatesystem are according to the ISB proposal, please see http://internationalshouldergroup.org/files/standards97.pdf

• H.E.J. Veeger, Bing Yu, Kai-Nan An and R.H. Rozendal, Parameters for modeling the upper extremity, Journal of Biomechanics, Vol. 30, No. 6, pp. 647-652, 1997

• H.E.J. Veeger, F.C.T. van der Helm, L.H.V. van der Woude, G.M. Pronk and R.H. Rozendal,Inertia and muscle contraction parameters for musculoskeletal modelling of the shoulder mechanism. Journal of Biomechanics, vol. 24, no. 7, pp. 615-629, 1991

## Muscle References¶

• Jacobson, M. D., R. Raab, B. M. Fazeli, R. A. Abrams, M. J. Botte, and R. L. Lieber. Architectural design of the human intrinsic hand muscles. J. Hand Surg. [Am.] 17:804809, 1992.

• Lieber, R. L., M. D. Jacobson, B. M. Fazeli, R. A. Abrams, and M. J. Botte. Architecture of selected muscles of the arm and forearm: Anatomy and implications for tendon transfer. J. Hand Surg. [Am.] 17:787-798, 1992.

• Lieber, R. L., B. M. Fazeli, and M. J. Botte. Architecture of selected wrist flexor and extensor muscles. J. Hand Surg. [Am.] 15:244-250, 1990.

• Muray, W.M.,T.S. Buchanan, and S.L. Delp. Scaling of peak moment arms with the elbow and forearm position J. Biomech. Vol. 28, pp. 513-525, 1995