Background:Medial meniscus root tear (MMRT) is a recently recognized yet frequently missed meniscal tear pattern that biomechanically creates an environment approaching meniscal deficiency.Hypothesis/Purpose:The purpose of this study was to assess the effect of MMRT on tibiofemoral kinematics and arthrokinematics during daily activities by comparing the injured knees of subjects with isolated MMRT to their uninjured contralateral knees. The hypothesis was that the injured knee will demonstrate significantly more lateral tibial translation and adduction than the uninjured knee, and that the medial compartment will exhibit significantly different arthrokinematics than the lateral compartment in the affected limb.Study Design:Cross-sectional study; Level of evidence, 3.Methods:Seven subjects with isolated MMRT were recruited and volumetric, density-based 3-dimensional models of their distal femurs and proximal tibia were created from computed tomography scans. High-speed, biplane radiographs were obtained of both their affected and unaffected knees. Moving 3-dimensional models of tibiofemoral kinematics were calculated using model-based tracking to assess overall kinematic variables and specific measures of tibiofemoral joint contact. The affected knees of the subjects were then compared to their unaffected contralateral knees.Results:Affected knees demonstrated significantly more lateral tibial translation than the uninjured contralateral limb in all dynamic activities. Additionally, the medial compartment displayed greater amounts of mobility than the lateral compartment in the injured limbs.Conclusion:This study suggests that MMRT causes significant changes in in vivo knee kinematics and arthrokinematics and that the magnitude of these changes is influenced by dynamic task difficulty.Clinical Relevance:Medial meniscus root tears lead to significant changes in joint arthrokinematics, with increased lateral tibial translation and greater medial compartment excursion. With complete root tears, essentially 100% of circumferential fibers are lost. This study will further our knowledge of meniscal deficiency and osteoarthritis and provide a baseline for more common forms of medial meniscal injuries (vertical, horizontal, radial), with various degrees of circumferential fiber function remaining.
Purpose Femoral tunnel angle (FTA) has been proposed as a metric for evaluating whether ACL reconstruction was performed anatomically. In clinic, radiographic images are typically acquired with an uncertain amount of internal/external knee rotation. The extent to which knee rotation will influence FTA measurement is unclear. Furthermore, differences in FTA measurement between the two common positions (0° and 45° knee flexion) have not been established. The purpose of this study was to investigate the influence of knee rotation on FTA measurement after ACL reconstruction. Methods Knee CT data from 16 subjects were segmented to produce 3D bone models. Central axes of tunnels were identified. The 0° and 45° flexion angles were simulated. Knee internal/external rotations were simulated in a range of ±20°. FTA was defined as the angle between the tunnel axis and femoral shaft axis, orthogonally projected into the coronal plane. Results Femoral tunnel angle was positively/negatively correlated with knee rotation angle at 0°/45° knee flexion. At 0° knee flexion, FTA for anterio-medial (AM) tunnels was significantly decreased at 20° of external knee rotation. At 45° knee flexion, more than 16° external or 19° internal rotation significantly altered FTA measurements for single-bundle tunnels; smaller rotations (±9° for AM, ±5° for PL) created significant errors in FTA measurements after double-bundle reconstruction. Conclusion Femoral tunnel angle measurements were correlated with knee rotation. Relatively small imaging malalignment introduced significant errors with knee flexed 45°. This study supports using the 0° flexion position for knee radiographs to reduce errors in FTA measurement due to knee internal/external rotation. Level of evidence Case–control study, Level III.
ACL reconstruction (ACLr) has been found to restore the functionality and mobility of those afflicted with ACL tears. In the process of this restoration, previous work has shown alterations in the activity of the musculature surrounding the reconstructed knee [1]. Specifically, at 5 months post-op, the gastrocnemius, vastus lateralis, and rectus femoris demonstrate significantly different activation patterns. These differences raise the question if the reconstructed leg is the only limb affected by ACLr.
Injury to the anterior cruciate ligament (ACL) occurs 200,000 times per year in the United States. About half of these patients opt for ACL reconstruction (ACLr), while the other half choose non-surgical, conservative treatment. ACLr has been found to result in altered kinematics, namely external tibial rotation and knee adduction, during downhill running 1. ACLr also contributes to alterations in muscle activity after surgery. Leg muscles of the affected limb are weakened and contract in different muscle activation patterns when compared to healthy, uninjured patients 2.
Meniscal injury has been found to leave patients at high risk for the development of knee osteoarthritis (OA). Partial meniscectomy is often used to treat meniscal tears, and while this procedure adequately addresses pain and the restoration of function, it does not prevent the progression of OA in the injured knee. Often during arthroscopy, surgeons identify areas of “softened” cartilage, which do not always correlate with visible signs of surface damage or cartilage loss. This softening has been related to changes in the cartilage matrix, which could represent early structural damage that can lead to irreversible cartilage damage and OA.
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