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Several methods have been used to describe the pivot-shift phenomenon in anterior cruciate ligament (ACL)-deficient knees; in this study we analyzed this test intraoperatively with a navigation system, to quantify its components and to highlight its clinical relevance, correlating it with the laxity test (Lachman and I/E rotation at 30°) and a clinical score (ie, the International Knee Documentation Committee [IKDC]). Eighteen consecutive patients who had undergone anatomic double-bundle ACL reconstruction were included in this study. A commercial navigation system (BLU-IGS, Orthokey, Lewes, DE) was used for kinematic acquisitions. For the pivot-shift test anteroposterior translation and internal/external (IE) rotation with respect to flexion/extension (FE) angle were analyzed by the evaluation of the areas included by the curves and the corresponding peaks. Each parameter was correlated with static laxities and preoperative IKDC score. Maximum peaks during pivot-shift test were reached between 20° and 30° of flexion. Both the AP and IE areas demonstrated a statistically significant reduction. There was no correlation between the Lachman test and the AP Peak or between IE rotation at 30° and the IE peak during the pivot-shift test. Preoperatively, patients with an IKDC grade “D” had significantly larger AP and IE areas compared with patients with IKDC grade “C”; after anatomic double bundle ACL reconstruction, there was no more difference in areas. A strictly relationship between AP and IE areas and the preoperative IKDC score was demonstrated. The presented quantification results extremely helpful in characterizing patient-specific laxity and ACL reconstruction performance, thus quantifying and improving the clinical relevance of pivot-shift test. [Copyright &y& Elsevier]

Background: The hip joint center is a fundamental landmark in the identification of lower limb mechanical axis; errors in its location lead to substantial inaccuracies both in joint reconstruction and in gait analysis. Actually in Computer Aided Surgery functional non-invasive procedures have been tested in identifying this landmark, but an anatomical validation is scarcely discussed. Methods: A navigation system was used to acquire data on eight cadaveric hips. Pivoting functional maneuver and hip joint anatomy were analyzed. Two functional methods – both with and without using the pelvic tracker – were evaluated: specifically a sphere fit method and a transformation techniques. The positions of the estimated centers with respect to the anatomical center of the femoral head, the influence of this deviation on the kinematic assessment and on the identification of femoral mechanical axis were analyzed. Findings: We found that the implemented transformation technique was the most reliable estimation of hip joint center, introducing a – Mean (SD) – difference of 1.6 (2.7) mm from the anatomical center with the pelvic tracker, whereas sphere fit method without it demonstrated the lowest accuracy with 25.2 (18.9) mm of deviation. Otherwise both the methods reported similar accuracy (<3mm of deviation). Interpretation: The functional estimations resulted in the best case to be in an average of less than 2mm from the anatomical center, which corresponds to angular deviations of the femoral mechanical axis smaller than 1.7 (1.3)° and negligible errors in kinematic assessment of angular displacements. [Copyright &y& Elsevier]

Significantly better stability may be achieved with a Single Bundle Lateral Plasty (SBLP) reconstruction compared with the Single Bundle (SB) and Double Bundle (DB) procedures. The study included 42 patients who underwent ACL reconstruction. Patients were randomly selected for one of the following surgical procedure defining three study groups: Single-Bundle-Lateral-Plasty, Single-Bundle and Double-Bundle procedures. Laxity evaluation was performed with an intraoperative navigation system. Lachman test (AP30), Drawer test (AP90), Varus-Valgus stress test at 0° and 30° knee flexion (VV0, VV30), Internal-External rotation (IE30, IE90), and pivot shift (PS) test are the clinical test executed for the laxity evaluation. Laxity reduction was defined as the difference between laxity before the fixation of the graft used for the reconstruction and the laxity just after its fixation. For all the analyzed surgical techniques, the pre-reconstruction laxity values were statistically higher (P < 0.05) than the post-reconstruction values for all the analyzed tests. The analysis of the Drawer test and Internal-External rotation at 30° and 90° of knee flexion, highlighted a significant difference at time zero after surgery among the three study groups. The results showed that the SBLP technique had the highest reduction values compared to SB (P IE90 = 0.001) and DB (P AP90 = 0.012; P IE30 = 0.021; P IE90 = 0.003) techniques. SBLP technique showed significantly superior results in terms of antero-posterior and internal-external laxity reduction at time-zero after ACL reconstruction. • Contrasting findings in short- and long- term results have not identified which surgical procedure is superior to the others • SBLP is more effective in controlling AP translation at 90°, and IE tibial rotation at 30° and 90° than the other techniques. • No differences were found regard to varus-valgus rotation and pivot shift test among the different ACL reconstruction approaches. [ABSTRACT FROM AUTHOR]

Background: This study describes a novel method for accurate evaluations of knee kinematics during arthroscopic reconstructions of anterior cruciate ligament (ACL). Methods: Quantitative evaluation of knee stability was estimated by experimental validation on 30 volunteers and by statistical analysis of test repeatability. Results: Proposed method present short learning time, is minimally invasive and thus suitable for arthroscopic techniques. Computed laxity showed a repeatability of 1. 5° for varus–valgus, 3° for internal–external, and 2mm for antero–posterior tests. Conclusions: This method represents a reliable quantification of knee kinematics in surgery, able to improve present intra-operative assessment of knee stability. [Copyright &y& Elsevier]