Biomechanical Comparison of Anterior Cruciate Ligament Reconstruction Using a Single-Bundle Round or Ribbon-like Hamstring Tendon Graft.

BACKGROUND: Persistent instability of the knee is reported in up to 30% of patients after anterior cruciate ligament (ACL) reconstruction. Based on anatomic findings showing that ACL is a flat ribbon-like structure that twists during knee flexion, a new surgical ACL reconstruction technique using a ribbon-like graft has been developed. However the effect of this surgical technique on knee kinematics has not yet been evaluated. PURPOSE: To compare the anteroposterior and rotational stability of the knee after ACL reconstruction using single-bundle (SB) round and ribbon-like grafts in anterolateral-intact/deficient knees. STUDY DESIGN: Controlled laboratory study. METHODS: Twelve human fresh-frozen cadaveric knees were tested with a 6 degrees of freedom robotic system. Internal rotation and anterior translation of the knee were recorded from 0° to 90° of flexion. A full kinematic assessment was performed in each of the following conditions: (1) intact knee, (2) after sectioning of the ACL, (3) after ACL reconstruction using a SB hamstring tendon graft in a round configuration and a ribbon-like configuration, and (4) after sectioning of the anterolateral structures. One-way analysis of variance and post hoc Tukey tests were used for statistical analyses. RESULTS: When compared with the intact knee, the ACL-deficient knee demonstrated a mean ± SD increase in anterior translation and internal rotation of 6.3 ± 2.5 mm (P < .01) and 5.8°± 2.3° (P < .01), respectively. After ACL reconstruction using a SB ribbon-like graft, the mean difference in anterior translation and internal rotation as compared with the intact knee was -0.1 ± 1.5 mm (P = .842) and 0.0°± 1.1° (P = .999). These differences from the intact knee were also not significant after ACL reconstruction using a round graft (-0.1 ± 1.3 mm, P = .999; -0.5°± 1.5°, P = .401). In the ACL-reconstructed knee using either a ribbon-like or round graft, sectioning of the anterolateral structures did not induce a significant increase of anterior translation and internal rotation of the knee. CONCLUSION: ACL reconstruction using a SB ribbon-like or round graft restored the kinematics of the intact knee at time zero. Secondary sectioning of the anterolateral structures in the ACL-reconstructed knee using both types of graft did not significantly affect the anterior translation and internal rotation of the knee. CLINICAL RELEVANCE: This is the first biomechanical study on the new ACL reconstruction technique using a ribbon-like graft.

Knee Flexion and Daily Activities in Patients following Total Knee Replacement: A Comparison with ISO Standard 14243.

Walking is only one of many daily activities performed by patients following total knee replacement (TKR). The purpose of this study was to examine the hypotheses (a) that subject activity characteristics are correlated with knee flexion range of motion (ROM) and (b) that there is a significant difference between the subject's flexion/extension excursion throughout the day and the ISO specified input for knee wear testing. In order to characterize activity, the number of walking and stair stepping cycles, the time spent with dynamic and stationary activities, the number of activity sequences, and the knee flexion/extension excursion of 32 TKR subjects were collected during daily activity. Flexion/extension profiles were compared with the ISO 14243 simulator input profile using a level crossing classification algorithm. Subjects took an average of 3102 (range: 343-5857) walking cycles including 65 (range: 0-319) stair stepping cycles. Active and passive ROMs were positively correlated with stair walking time, stair step counts, and stair walking sequences. Simulated knee motion according to ISO showed significantly fewer level crossings at the flexion angles 20-40° and beyond 50° than those measured with the monitor. This suggests that implant wear testing protocols should contain more cycles and a variety of activities requiring higher knee flexion angles with incorporated resting/transition periods to account for the many activity sequences.

Osteochondral Tissue Cell Viability Is Affected by Total Impulse during Impaction Grafting.

OBJECTIVE: Osteochondral graft transplantation has garnered significant attention because of its ability to replace the lesion with true hyaline cartilage. However, surgical impaction of the graft to anchor it into the defect site can be traumatic and lead to cell death and cartilage degeneration. This study aimed to test the hypothesis that increasing impulse magnitude during impaction of osteochondral plugs has a direct effect on loss of cell viability. DESIGN: In this controlled laboratory study, the impaction force was kept constant while the impulse was varied. Ninety-six osteochondral plugs were extracted from the trochlea of bovine stifle joints and were randomly assigned into 3 experimental and 1 (nonimpacted) control group. The transferred impulse of the experimental groups reflected the median and the lower and upper quartiles of preceding clinical measurements. Data were obtained at day 0, day 4, and day 8; at each point, cell viability was assessed using the Live/Dead staining kit and histological assessments were performed to visualize matrix structural changes. RESULTS: After impaction, cartilage samples stayed intact and did not show any histological signs of matrix disruption. As expected, higher impulse magnitudes introduced more cell death; however, this relationship was lost at day 8 after impaction. CONCLUSION: Impulse magnitude has a direct effect on cell viability of the graft. Because impulse magnitude is mostly governed by the press-fit characteristics of the recipient site, this study aids in the definition of optimal insertion conditions for osteochondral grafts.