Isometry of medial collateral ligament reconstruction.

The purpose of this study was to determine the femoral and tibial fixation sites that would result in the most isometric MCL reconstruction technique. Seven cadaveric knees were used in this study. A navigation system was utilized to determine graft isometry continuously from 0 masculine to 90 masculine. Five points on the medial side of the femur and four on the tibia were tested. A graft positioned in the center of the MCL femoral attachment (F(C)) and attached in the center of the superficial MCL attachment on the tibia led to the best isometry (2.7 +/- 1.1 mm). Movement of the origin superiorly only 4 mm (F(S)) led to graft excursion of greater than 10 mm (P < 0.01). MCL reconstruction performed with the origin of the MCL within the femoral footprint and the insertion in tibial footprint of the superficial MCL results in the least graft excursion when the knee is cycled between 0 masculine and 90 masculine. Although the MCL often heals without surgical intervention, surgical reconstruction is occasionally in Grade III MCL and combined ligamentous injuries to the knee. This study demonstrates the optimal position of the MCL reconstruction to reproduce the kinematics of the native knee.

Changes in the length of virtual anterior cruciate ligament fibers during stability testing: a comparison of conventional single-bundle reconstruction and native anterior cruciate ligament.

BACKGROUND: Conventional tunnel positions for single-bundle (SB) transtibial anterior cruciate ligament (ACL) reconstruction are located in the posterolateral (PL) tibial footprint and the anteromedial (AM) femoral footprint, resulting in an anatomic mismatch graft that is more vertical than native fibers. This vertical mismatch position may significantly influence the ability of an ACL graft to stabilize the knee. HYPOTHESIS: Anatomic ACL fibers undergo a greater change in length during anterior translation and internal rotation than a conventional SB reconstruction from the PL tibial footprint to the AM femoral footprint. STUDY DESIGN: Controlled laboratory study. METHODS: The Praxim ACL Surgetics navigation system was used to acquire kinematic data during a flexion/extension cycle and to register all points within the ACL footprint from 5 fresh-frozen cadaveric knees. Virtual fibers were placed in the center of the AM and PL bundles as well as central and conventional SB positions. After transection of the ACL, the absolute length change and apparent strain of the fibers were computed for each knee during the Lachman and anterior drawer tests and internal rotation at 0 degrees and 30 degrees of flexion. RESULTS: Each of the anatomic fibers (AM, PL, and central) had more elongation and apparent strain than the conventional SB fiber during the Lachman maneuver. During the anterior drawer test, the AM and central (but not the PL) fibers lengthened significantly more and the AM had more apparent strain than the conventional SB fiber. During internal rotation at 0 degrees and 30 degrees of flexion, anatomic fibers elongated significantly more than the conventional fiber. Except for the AM fiber with the knee at full extension, apparent strain was greater in all anatomic fibers than in the conventional SB fiber during internal rotation maneuvers. CONCLUSION: In ACL-deficient cadaveric knees, anatomic fibers undergo greater elongation and apparent strain in response to anterior translation and internal rotation maneuvers than a conventional SB graft. Because of their optimal orientation, anatomic fibers may resist pathologic anterior translation and internal rotation more than the conventional SB position. CLINICAL RELEVANCE: Conventional placement of a single-bundle graft results in suboptimal changes in fiber length and strain, suggesting that alternatives such as anatomic placement of an SB graft or double-bundle reconstruction may result in greater control of translation and rotation.

Reliability of navigated knee stability examination: a cadaveric evaluation.

BACKGROUND: Clinical examination remains empirical and may be confusing in the setting of rotatory knee instabilities. Computerized navigation systems provide the ability to visualize and quantify coupled knee motions during knee stability examination. HYPOTHESIS: An image-free navigation system can reliably register and collect multiplanar knee kinematics during knee stability examination. STUDY DESIGN: Controlled laboratory study. METHODS: Coupled knee motions were determined by a robotic/UFS testing system and by an image-free navigation system in 6 cadaveric knees that were subjected to (1) isolated varus stress and (2) combined varus and external rotation force at 0 degrees, 30 degrees, and 60 degrees. This protocol was performed in intact knees and after complete sectioning of the posterolateral corner (lateral collateral ligament, popliteus tendon, and popliteofibular ligament). The correlation between data from the surgical navigation system and the robotic positional sensor was assessed using the intraclass correlation coefficient. The 3-dimensional motion paths of the intact and sectioned knees were assessed qualitatively using the navigation display system. RESULTS: Intraclass correlation coefficients between the robotic sensor and the navigation system for varus and external rotation at 0 degrees, 30 degrees, and 60 degrees were all statistically significant at P < .01. The overall intraclass correlation coefficient for all tests was 0.9976 (P < .0001). Real-time visualization of the coupled motions was possible with the navigation system. Post hoc analysis of the knee motion paths during loading distinguished distinct rotatory patterns. CONCLUSION: Surgical navigation is a precise intraoperative tool to quantify knee stability examination and may help delineate pathologic multiplanar or coupled knee motions, particularly in the setting of complex rotatory instability patterns. Repeatability of load application during clinical stability testing remains problematic. CLINICAL RELEVANCE: Surgical navigation may refine the diagnostic evaluation of knee instability.