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Joint stability, any standard definition?

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  • Joint stability, any standard definition?

    Dear Biomech-l subscribers, I was wondering if any of you is aware of an objective test to assess joint stability. According to my literature research neither a standard definition of joint stability nor standard evaluation tests to determine the degree of instability at joints have been established In most cases the level of instability is subjectively assessed by clinicians by applying dislocating forces to the joint. When more scientifically-objective approaches were taken, joint rotations to triplanar joint displacements (or rotations) are normally shown. However, although differences to the normal/stable joint are graphically presented, when/if the joint can objectively be considered unstable is not reported.

    As far as our specific case, we are trying to quantify the level of instability at the proximal interphalangeal joint of the finger in-vitro through active flexion/extension of the joint following the release of supporting ligaments and the disruption of the joint by systematic resection of bone at its proximal aspect. We are indeed finding significant differences in the flex/ext rotation to joint displacement curves across different configurations (intact, disrupted..) but we are now facing the issue of establishing some kind of objective index for joint-stability. In other words, which variable is more relevant here and how far from the normal/non-pathological configuration a joint can still be considered to be stable?

    Any suggestions and/or further comments on this matter are welcome.


    Paolo Caravaggi, PhD
    Joint Biomechanics Lab, Orthopedics dep.
    University of Medicine and Dentistry of New Jersey
    185 South Orange Avenue, Newark, NJ 07103
    Tel. +1 973 972 1426