[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: The goals of this study were to determine the precision of femoral component placement using a novel computes assisted surgery (CAS)-enabled 8-in-1 cutting guide in cadaver limbs and to identify errors generated at various stages of the cutting process. The cutting guide placement was on average within 1 degrees or millimeter of the target position in the varus/valgus, axial rotation, and cut height directions and within 2 degrees or millimeters, in all other directions. The difference between the desired femoral component and the impacted trial component position, defined as the execution error, averaged 0.9 degrees +/- 1.7 degrees of varus rotation, 0.8 +/- 2.3 mm of lateral translation, and 0.3 +/- 1 mm of proximal translation in the coronal plane (+/-SD). In the sagittal and axial planes, the execution error averaged 2.8 degrees +/- 2.5 degrees of flexion, 3.4 +/- 1.3 mm of anterior translation, and 0.7 degrees +/- 2.7 degrees of external rotation. CAS permits accurate placement of 8-in-1 jigs for valgus/varus, axial rotation, and cut height but is less accurate in the sagittal plane. Care should be taken when executing the cuts, which can affect precision in the sagittal plane more than actual positioning of the jig.
The Journal of arthroplasty 01/2009; 25(1):138-45. · 1.79 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
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.
Controlled laboratory study.
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.
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.
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.
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.
The American journal of sports medicine 08/2008; 36(11):2196-203. · 3.61 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Surgical navigation allows continuous intraoperative monitoring of ACL graft anisometry and 3-dimensional obliquity. However, normative anisometry and obliquity measurements for different single-bundle anterior cruciate ligament graft positions are not well described.
ACL Grafts placed in anteromedial and posterolateral bundle positions will have distinct anisometric profiles and 3-dimensional obliquities. A graft placed centrally in anterior cruciate ligament insertion sites will have different obliquity and anisometry than a conventional (single-bundle) graft extending from the tibia's posterolateral aspect to the femur's anteromedial aspect.
Controlled laboratory study.
Five cadaveric knees were tested. A surgical navigation system was used to create 4 virtual graft positions in the anterior cruciate ligament footprint: (1) anteromedial, (2) posterolateral, (3) central, and (4) posterolateral tibia to anteromedial femur (conventional). Obliquity at various flexion angles and anisometry of each virtual graft's central fiber were determined.
Anteromedial and posterolateral fibers are relatively parallel up to 30 degrees of flexion. At higher degrees of flexion, the anteromedial position is more oblique in the sagittal plane, while the posterolateral position is more oblique in the axial plane. The conventional single-bundle position is significantly more vertical than the central position in multiple planes throughout the range of motion. The anteromedial fiber is most isometric, while the posterolateral fiber is the least isometric at all flexion angles. There is no significant difference in the anisometry between the central or conventional positions at any flexion angle. The posterolateral, central, and conventional fibers were longest at full extension and slackened with progressive flexion.
Anteromedial and posterolateral graft positions can be distinguished by sagittal and axial plane obliquity at flexion angles >30 degrees and by anisometry measurements. Conventional positioning produces a relatively vertical graft placement compared with the central position but has similar anisometry characteristics. Our data suggest that posterolateral, central, and conventional grafts should be fixed at or near full extension to avoid excessive tightening during motion.
This study provides anisometry and 3-dimensional obliquity data for various graft positions using surgical navigation. The failure of single-bundle anterior cruciate ligament reconstruction to restore intact knee kinematics may be partly due to the relative vertical placement of conventional grafts compared with the central anterior cruciate ligament footprint position.
The American journal of sports medicine 04/2008; 36(8):1534-41. · 3.61 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The synergistic functions of the anteromedial and posterolateral bundles of the anterior cruciate ligament in restraining anterior laxity are known. Cadaveric experiments have also suggested different functions of the 2 bundles in controlling a combined rotatory load simulating the pivot shift.
The posterolateral bundle is important in controlling the coupled tibial axial rotation laxity occurring during clinical laxity tests performed in vivo, particularly the pivot-shift maneuver.
Cohort study; Level of evidence, 2.
Twenty-one patients underwent navigated 2-bundle anterior cruciate ligament reconstruction. The navigation was additionally used to measure the knee kinematics in response to the anterior drawer test (performed at 90 degrees ), Lachman test (performed at 20 degrees of flexion), and pivot-shift test. Two sequential reconstruction protocols were used to assess the contribution of the anteromedial and posterolateral bundles to restraining tibial translations and coupled axial rotation occurring with the manually performed clinical laxity tests.
Anterior tibial translation during the anterior drawer test was better restrained by anteromedial bundle reconstruction than by posterolateral bundle reconstruction. Conversely, posterolateral bundle reconstruction better restrained anterior tibial translation during the Lachman test. Both bundles contributed to the control of anterior laxity during the pivot shift. However, the posterolateral bundle was more important than was the anteromedial bundle in controlling the tibial rotational component (posterolateral bundle reconstruction caused a 53% reduction in tibial rotation laxity compared with a 42% reduction with anteromedial bundle reconstruction, P< .0001).
This study provides objective, in vivo data about how the anteromedial and posterolateral bundles act differentially to stabilize the knee, particularly during the pivot shift. The posterolateral bundle was important in controlling not only anterior laxity toward knee extension but the rotational component of the pivot shift.
The American journal of sports medicine 12/2007; 35(12):2006-13. · 3.61 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
An image-free navigation system can reliably register and collect multiplanar knee kinematics during knee stability examination.
Controlled laboratory study.
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.
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.
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.
Surgical navigation may refine the diagnostic evaluation of knee instability.
The American Journal of Sports Medicine 09/2007; 35(8):1315-20. · 4.44 Impact Factor