The deficit of joint position sense in the chronic unstable ankle as measured by inversion angle replication error.
BACKGROUND
Functional instability is defined as a repeated ankle inversion sprain and a giving way sensation. Previous studies have described the damage of sensori-motor control in ankle sprain as being a possible cause of functional instability. The aim of this study was to evaluate the inversion angle replication errors in patients with functional instability after ankle sprain.


METHODS
The difference between the index angle and replication angle was measured in 12 subjects with functional instability, with the aim of evaluating the replication error. As a control group, the replication errors of 17 healthy volunteers were investigated. The side-to-side differences of the replication errors were compared between both the groups, and the relationship between the side-to-side differences of the replication errors and the mechanical instability were statistically analyzed in the unstable group.


RESULTS
The side-to-side difference of the replication errors was 1.0 +/- 0.7 degrees in the unstable group and 0.2 +/- 0.7 degrees in the control group. There was a statistically significant difference between both the groups. The side-to-side differences of the replication errors in the unstable group did not statistically correlate to the anterior talar translation and talar tilt.


CONCLUSIONS
The patients with functional instability had the deficit of joint position sense in comparison with healthy volunteers. The replication error did not correlate to the mechanical instability. The patients with functional instability should be treated appropriately in spite of having less mechanical instability.
Nakasa
Tomoyuki
T
Department of Orthopaedic Surgery, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima, 734-8551, Japan. tnakasa@hiroshima-u.ac.jp
Fukuhara
Kohei
K
Adachi
Nobuo
N
Ochi
Mitsuo
M
D000293:Adolescent; D000328:Adult; D016512:Ankle Injuries / Q000150:complications / Q000503:physiopathology*; D000843:Ankle Joint / Q000503:physiopathology*; D001265:Athletic Injuries / Q000503:physiopathology*; D002908:Chronic Disease; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D015203:Reproducibility of Results; D012677:Sensation; D013180:Sprains and Strains / Q000150:complications