Analysis of ankle-hindfoot stability in patients with ankle instability and normals.
OBJECTIVE
We devised a testing apparatus for in vivo analysis of ankle stability. The purpose of the study was to test the reliability of this apparatus and to determine the stability pattern of the ankle-hindfoot complex in healthy, asymptomatic volunteers and in patients with ankle instability.


METHODS
Ten healthy individuals were studied, and testing was repeated on the same day and different days. Three patients with symptomatic, unstable ankles were also tested on both involved and uninvolved sides. Constant inversion torque was applied, then internal rotation torque, while moving the ankle throughout the range of sagittal motion. Three-dimensional kinematics of the ankle-hindfoot complex were measured by an electromagnetic tracking system.


RESULTS
Measurements were repeatable, with intraclass correlation coefficients 0.9 or better. Variability was observed among controls, but motion curve patterns were consistent. Motion curve slopes were sensitive in differentiating between unstable and stable ankles.


CONCLUSIONS
Most previous reports are in vitro studies conducted with the ankle in one position, manual stress applied, or joint positions estimated with planar radiographs. Our study indicated that more accurate diagnosis of severity of ankle ligament injuries may be possible.
Orthopaedic Biomechanics Laboratory, Mayo Clinic, Rochester, MN 55905, USA.
Kota
K
Watanabe
Tadashi
T
Fujii
Harold B
HB
Kitaoka
Brian R
BR
Kotajarvi
Zong-Ping
ZP
Luo
Kai-Nan
KN
An
D000328:Adult; D000842:Ankle / Q000503:physiopathology*; D000843:Ankle Joint / Q000503:physiopathology*; D058070:Asymptomatic Diseases; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D007866:Leg / Q000503:physiopathology*; D008023:Ligaments, Articular / Q000503:physiopathology*; D008297:Male; D016059:Range of Motion, Articular; D012016:Reference Values; D015203:Reproducibility of Results; D012399:Rotation; D019415:Torque