Quantitative assessment of pivot-shift using inertial sensors.
OBJECTIVE
The pivot-shift phenomenon has been identified to be one of the essential signs of functional anterior cruciate ligament (ACL) insufficiency. However, the pivot-shift test remains a surgeon-subjective examination, lacking a general recognized quantitative measurement. The goal of the present study was to validate the use of an inertial sensor for quantifying the pivot-shift test, using a commercial navigation system.


METHODS
An expert surgeon intra-operatively performed the pivot-shift test on 15 consecutive patients before ACL reconstruction. A single accelerometer and a commercial navigation system simultaneously acquired limb kinematics. An additional optical tracker mounted on the accelerometer allowed following sensor movements. Anteroposterior (a-p) tibial acceleration obtained with the navigation system was compared with three-dimensional (3D) acceleration acquired by the accelerometer. The effect of skin artifacts and test-retest positioning were estimated. Repeatability of the acceleration parameter and waveform was analyzed. Correlation between the two measurements was also assessed.


RESULTS
Average root mean square (RMS) error in test-retest positioning reported a good value of 5.5 ± 2.9 mm. Mean RMS displacement due to soft tissue artifacts was 4.9 ± 2.6 mm. The analysis of acceleration range repetitions reported a good intra-tester repeatability (Cronbach's alpha = 0.86). Inter-patients similarity analysis showed a mean acceleration waveform correlation of 0.88 ± 0.14. The acceleration ranges demonstrated a good positive correlation between the two measurements (rs = 0.72, P < 0.05).


CONCLUSIONS
This study showed good reliability of the new device and good correlation with the navigation system results. Therefore, the accelerometer is a valid method to assess dynamic joint laxity.


METHODS
II.
Laboratorio di Biomeccanica e Innovazione Tecnologica, Istituto Ortopedico Rizzoli, Via Di Barbiano, 1/10, 40136 Bologna, Italy. n.lopomo@biomec.ior.it
Nicola
N
Lopomo
Cecilia
C
Signorelli
Tommaso
T
Bonanzinga
Giulio Maria
GM
Marcheggiani Muccioli
Andrea
A
Visani
Stefano
S
Zaffagnini
D000054:Acceleration; D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods; D053587:Arthrometry, Articular / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D015331:Cohort Studies; D005069:Evaluation Studies as Topic; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000175:diagnosis* / Q000601:surgery; D007718:Knee Injuries / Q000175:diagnosis / Q000601:surgery; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D009983:Orthopedic Equipment; D011446:Prospective Studies; D016059:Range of Motion, Articular / Q000502:physiology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome; D055815:Young Adult