STRUCTURE-BASED PREDICTIONSTRUCTURE-BASED PREDICTIONOF JOINT MOTIONOF JOINT MOTION

P.V. Loubert1, T.J. Masterson2, A. Saltarelli2

1School of Rehabilitation and Medical Sciences2School of Health Sciences

Central Michigan University, Mt. Pleasant, MI 48859

INTRODUCTIONINTRODUCTION

INTRODUCTIONINTRODUCTION

Our hypothesis states that for any given synovial joint, the range of motion (ROM) can be predicted by subtracting the concave arc from the convex arc of the respective articular surfaces in a joint (see Figure 1).

Convex Arc

Concave Arc

Convex Arc – Concave Arc = ROM

Figure 1. ROM - Arc Relationship.Figure 1. ROM - Arc Relationship.

Convex Arc - Concave Arc = Predicted ROM

180 deg. - 60 deg. = 120 deg.

INTRODUCTION Cont.INTRODUCTION Cont.

This hypothesis is based on two assumptions:

(1) The entire dimension of an articular surface is utilized in some part of the ROM, and

(2) There is no part of the ROM where there would not be contact between articular surfaces.

Violations of these assumptions will require consideration of additional variables in the application of our hypothesis.

METHODSMETHODS

We used the procedure developed by Lee et. al. (1998) to test our hypothesis.

1. Restraining soft tissues were removed or released for the cadaver specimens.

2. Passive ROM was measured using a standard clinical gonimeter on each specimen and recorded.

3. Twenty-one joints were transected in the same plane as the measured ROM using a band saw. Joints studied include:

- 5 glenohumoral joints - 5 ulnohumoral joints

- 3 radiohumoral joints - 4 knee joints

- 2 radioulnar joints - 1 ankle joint

- 1 proximal interphalangeal joint.

Figure 2. Determining center of curvature.Figure 2. Determining center of curvature.

Figure 3. Measuring predicted ROM.Figure 3. Measuring predicted ROM.

CALCULATIONSCALCULATIONS

1. Rom was predicted by subtracting the concave arc from the convex arc.

2. Correlations were calculated between the:

a. Predicted ROM and measured ROM

b. Predicted ROM and published ROM (Rothstein et. al., 1998)

RESULTSRESULTS

Section Joint Published ROM

Measured ROM

Convex ARC

Predicted ROM

Difference

Sagittal Talocural 50.00 46.00 77.40 52 6.00

Sagittal 3rd PIP 110.00 86.00 157.40 80.30 5.70

RESULTSRESULTS

DISCUSSIONDISCUSSION

WHAT DOES IT ALL MEAN?

Our results indicate that there is a moderate correlation, r = 0.77, between the measured and predicted ROM, as well as between the published and predicted ROM, r = 0.77.

Several kinematic relationships were observed between articular

surfaces during movement that suggest additional considerations that must be taken into account in order to achieve a higher correlation between joint structure and function. These included:

1) Violations of the assumption that the articular surfaces would be in contact during the entire movement, and2) The transection of the joint must be in the true plane of movement.

CHANGES IN GEOMETRIC AXES OF CHANGES IN GEOMETRIC AXES OF ROTATIONROTATION

AB A + B = ROM

CONCLUSIONCONCLUSION

WHY STUDY ARTHROKINEMATICS?

The relationship tested in this study may be used by:

1)Paleontologists to refine predictions of functional motion in fossil primates as well as other organisms, and

2) Practicing medical clinicians who treat joint dysfunction and help in the design and fabrication of prosthetic devices for humans

REFERENCESREFERENCES

• Lee KJ, RJ Kranich, PV Loubert: Qualitative Analysis of the Convex-Concave Rule as it Applies to the Glenohumeral Joint. Phys Ther 78:S65 1998.

• Loubert PV: The Theoretical Foundations for Joint Mobilization. Physical Therapy ’98 Course Materials: A Compendium of Conference Handouts, American Physical Therapy Association, pp354-359 1998.

• Rothstein JM, SH ROY, SL Wolf: The Rehabilitation Specialist’s Handbook, Second Edition. F.A. Davis, Philadelphia, 1998.

• Paint Shop Pro 7.0, JASC Software (www.jasc.com).

• Scion Image (beta 4.02), Scion Corporation (www.scioncorp.com).

THANKSTHANKS

Dr. Loubert, Dr. Masterson