2015 ISAKOS Biennial Congress ePoster #1299

Which Technical Variables of Surgical ACL Reconstruction Mainly Affect Postoperative Static Laxity?

Stefano Zaffagnini, MD, Prof., Bologna ITALY
Cecilia Signorelli, PhD, Bologna, BO ITALY
Tommaso Bonanzinga, MD, Bologna ITALY
Nicola Francesco Lopomo, PhD, MSc Eng, Bologna ITALY
Giulio Maria Marcheggiani-Muccioli, MD, PhD, Bologna ITALY
Alberto Grassi, MD, Bologna ITALY
Federico Raggi, MD, Bologna ITALY
Alessandro Russo, MD, PhD, Bologna ITALY
Maria P. Neri, Bologna ITALY
Maurilio Marcacci, MD, Milano, Milano ITALY

Istituto Ortopedico Rizzoli, Bologna, BO, ITALY

FDA Status Not Applicable

Summary: The relationship among different details of surgical ACL reconstruction and the post-reconstruction knee laxities, has not yet been clearly characterized. The goal of this study was to define by a multivariate model, the correlation between post-operative static laxity parameters and specific technical variables of the surgical procedure evaluating in-vivo data acquired by a navigation system.

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Abstract:

Introduction

The most appropriate details of an ACL reconstruction are still under discussion. Our purpose is to evaluate the presence of any relationship between different details of the surgical techniques, concerning both tibial tunnel and femoral portion of the graft, and the postoperative knee laxity.

Methods

17 patients who underwent navigated primary Single Bundle plus Lateral Plasty (SBLP) ACL reconstruction [1] included. Kinematics data were acquired by a surgical navigation system. All the kinematics tests were performed just after graft fixation. The analyzed laxity parameters were defined as the value of Internal/External rotation at 30° (IE30) and 90° (IE90) of flexion, Varus/Valgus rotation at 0° (VV0) and 30° (VV30) of flexion and Anterior/Posterior displacement at 30° (AP30) and 90° (AP90) of flexion. As surgical details the angles between the tibial tunnel and the three planes were defined as well as the lengths of the tunnel and the relationship between native footprints and tunnels. The same analysis was performed for the femoral side. The technical details were combined in a multivariated analysis in order to assess for predictive factors between features of surgery and postoperative laxities. Evaluation of normal distribution of the variables was conducted with Lilliefors test. Selection method of backward was used to assess those factors that optimize the model. The multivariate analysis defined the following models: AP30estimate, AP90estimate, IE30estimate, IE90estimate, VV0estimate, VV30estimate. In order to quantify the performance of each multivariate model, the correlation ratio (R2) and the corresponding P-value (P) have been evaluated. Significance was set at P <0.050.

Results

All the analyzed variables could be considered normally distributed. The performed multivariate analysis underlined statistically significant models for: AP30estimate (R2= 0.987; P=0.014 ), IE30estimate (R2= 0.995; P=0.005), IE90estimate (R2=0.568; P=0.010 ), VV0estimate (R2=0.932; P=0.003). The three parameters that greatly affect the identified models are the orientation of the tibial tunnel respect to the three anatomical planes, except the second relevant AP30estimate parameter which is the femoral graft orientation respect to the sagital plane. Specifically, AP30estimate, IE30estimate and IE90estimate get lower value as the orientation of the tibial tunnel respect to transverse plane decreases. Considering the orientation to sagittal (ThetaTSAG) and coronal (ThetaTCOR) plane, we found that their reduction provoke a AP30estimate, IE30estimate, IE90estimate decrease (except ThetaTSAG that do not appear in AP30estimate). About VV0estimate it is an increase of ThetaTSAG, and ThetaTCOR which leads to a laxity reduction. Moreover, the more the intrarticular point of the tibial tunnel results medial respect native ACL-insertion, the more the AP30estimate, IE30estimate, VV0estimate, decrease.

Discussion

The identified model were able to predict postoperative static laxity combining different technical features of ACL-reconstruction technique. In particular has been defined the conditions that minimize the different aspect of static laxity. Future relevant application of the study can be the embedding of the obtained results in a navigation system which optimizes the surgical variables considering the estimation models with the aim to control the postoperative laxity basing the choice on the patient specificity.


References:
[1] Marcacci M et al. Knee Surg Sports Traumatol Arthrosc. 1998;6(2):68-75.