2015 ISAKOS Biennial Congress ePoster #1104

Minimum 12 Months Follow-Up Assessment of Rotatory Knee Laxity by Means of Inertial Sensors

Giulio Maria Marcheggiani-Muccioli, MD, PhD, Bologna ITALY
Nicola Francesco Lopomo, PhD, MSc Eng, Bologna ITALY
Cecilia Signorelli, PhD, Bologna, BO ITALY
Tommaso Bonanzinga, MD, Bologna ITALY
Alberto Grassi, MD, Bologna ITALY
Federico Raggi, MD, Bologna ITALY
Tommaso Roberti Di Sarsina, MD, Bologna ITALY
Dario Giunchi, MD, Bologna ITALY
Maurilio Marcacci, MD, Milano, Milano ITALY
Stefano Zaffagnini, MD, Prof., Bologna ITALY

Istituto Ortopedico Rizzoli, Bologna, ITALY

The FDA has not cleared the following pharmaceuticals and/or medical device for the use described in this presentation. The following pharmaceuticals and/or medical device are being discussed for an off-label use: Orthokey, KIRA

Summary: Acceleration measurements during pivot-shift test by inertial sensors show good correlation with IKDC clinical grading of this test.




Recently, noninvasive systems have been developed to quantitatively measure the pivot shift (PS) test, which is the benchmark to assess the rotatory laxity of the knee. Some of these systems have been proved to be reliable in the measurements of the acceleration of the tibia during the PS test and one of them (KiRA, Orthokey LLC, Delaware, USA), based on inertial sensors, was validated for in office evaluation of ACL injury compared to the contralateral limb [1]. At present, there is a lack of validation of this system at follow-up, compared to the objective International Knee Documentation Committee (IKDC) score system. The purpose of this study was therefore to analyze the differences in the acceleration values acquired by KiRA at pre-operative and at 12 months follow-up conditions. Moreover the acceleration values were compared to the objective IKDC clinical grading. We specifically hypothesize the existence of a strong correlation between the side-to-side difference in the measured acceleration range and the objective IKDC clinical grading of the PS.


Between 2010 and 2011, a total of 21 patients with anterior cruciate ligament (ACL) lesion were enrolled. They underwent over-the-top surgical reconstruction of the ACL plus lateral extra-articular tenodesis [2]. Power analysis based on previous study [1] highlighted a minimum sample size of 15 patients. All the patients were evaluated before the reconstruction and re-evaluated 12 months after the surgery. Each patient underwent a clinical examination and then was subjected to the instrumental pivot-shift examination by KiRA. The differences in the acceleration range between the injured and the contralateral limb were used in the analysis. The correlations between the differences in the acceleration ranges and the corresponding IKDC score were calculated using Spearman correlation analysis. Correlation coefficients (rs) were interpreted according to following guidelines; poor(r > 0.3), moderate (0.3< r < 0.6), good (0.6 < r < 0.8) [3].



IKDC clinical grading of the PS improved from 17 C and 4 D to 18 A, 2B and 1C (p<0.0001). The side-to-side difference in acceleration range measured by KIRA improved from 2.0 +/-1.2 to 0.3+/-0.3 m/s2 (p < 0.0001). Good correlation was displayed between the overall side-to-side difference in acceleration range measured by KiRA and overall objective IKDC clinical grading of the PS (rs=0.82, p<0.0001).


Acceleration measurements during PS test by KiRA show good correlation with IKDC clinical grading of this test. The advantage of using this non-invasive system with respect to the only objective clinical PS examination relies in the in vivo quantification of dynamic rotatory knee laxity (a patient-specific parameter useful to customize the surgery).

1. Lopomo et al, Comput Methods Biomech Biomed Engin. 2012;15(12):1323-8.
2. Marcacci et al, Am J Sports Med. 2009 Apr;37(4):707-14.
3. Bellamy et al, Clin Rheumatol. 1991 Jun;10(2):138-43.