2015 ISAKOS Biennial Congress ePoster #1382

Non-Invasive Quantification of the Pivot Shift by Directly Measuring Translation and Acceleration of the Joint before ACL Reconstruction and at 6 Months Follow-up: A Multicenter International Study

Nicola Francesco Lopomo, PhD, MSc Eng, Bologna ITALY
Yuichi Hoshino, MD, PhD, Kobe, Hyogo JAPAN
Kristian Samuelsson, MD, PhD, MSc, Prof., Mölndal SWEDEN
James J. Irrgang, PT, PhD, FAPTA, Pittsburgh, PA UNITED STATES
Volker Musahl, MD, Pittsburgh, PA UNITED STATES
Ryosuke Kuroda, MD, PhD, Kobe, Hyogo JAPAN
Jon Karlsson, Prof., Mölndal SWEDEN
Stefano Zaffagnini, MD, Prof., Bologna ITALY
The Pivot Study Group, Pittsburgh, Bologna, Kobe, Göteborg UNITED STATES

Istituto Ortopedico Rizzoli, Kobe University, University of Pittsburgh, University of Gothenburg, Bologna, Kobe, Pittsburgh, Gothenburg, Italy, Japan, USA, Sweden, ITALY

FDA Status Not Applicable

Summary: Pivot shift was quantified before ACL reconstruction and at 6 months follow-up by using an acceleration sensor and an image-based application for tablet computer. At follow-up, both acceleration and translation were reduced in terms of absolute values and with respect to the contralateral limb. Both the non-invasive methods were able to detect reduced rotational laxity at follow-up.

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Abstract:

Background

& Objectives: Up to now, the pivot shift (PS) test has been reported to be the basis for assessing rotational knee laxity that is associated with anterior cruciate ligament (ACL) functional insufficiency [1]. The main objective of this study was to non-invasively quantify acceleration and translation of the lateral compartment during the PS performed with the patient awake just before surgery and at 6 months follow-up. Methods: Seventy-three patients undergoing anatomic single-bundle ACL reconstruction in 4 different centers were included in this analysis. To measure acceleration range, an inertial sensor was affixed to the skin close to the knee with an elastic strap [2]. To measure the relative translation between the lateral compartment of tibia and femur, 3 skin markers were placed on Gerdy’s tubercle, the fibular head and lateral epicondyle and tracked by an image-based tracking application [3]. A standardized PS test was performed by the senior surgeon at each center at 2 different times: before surgery with the patient awake (PRE-OP); at 6 months follow-up with the patient awake (6mFU). Paired t-tests were used to compare acceleration and translation of the injured limb and side-to-side difference from PRE-OP to 6mFU. The level of significance was set at p<0.05. Results: For the side-to-side comparison, both acceleration (0.9 +/- 1.4 m/s2 vs. 0.2 +/- 1.3 m/s2, p=0.001) and translation (1.2 +/- 1.6 mm vs. 0.0 +/- 1.4 mm, p=0.002) were significant reduced at the 6mFU compared to the PRE-OP values. For the injured limb, a statistically significant difference was found from the PRE-OP to 6mFU time points for the acceleration (3.5 +/- 1.9 m/s2 vs. 2.8 +/- 1.4 m/s2, p=0.002) and translation (2.0 +/- 1.5 mm vs. 1.2 +/- 1.2 mm, p=0.002). Conclusions: Both acceleration and the translation of the lateral compartment were able to detect the reduction in knee rotational laxity from before surgery to follow-up at 6 months. From a clinical point of view, this study suggests the possibility of quantifying the dual nature of the pivot shift phenomenon by means of non-invasive specific systems, thus to evaluate the reconstruction outcome, even during follow-ups. In particular, at 6 months follow-up the reconstructed knee reported no differences from both translations and acceleration when compared to the contralateral knee. This outcome represents the main goal of optimal ACL surgery. References: [1] Musahl V et al. Knee Surg Sports Traumatol Arthrosc. 2012; 20(4):724-31. [2] Lopomo N et al. Comput Methods Biomech Biomed Engin. 2012;15(12):1323-8. [3] Hoshino Y et al. Knee Surg Sports Traumatol Arthrosc. 2013; 21(4):975-80.