The Journal of Bone and Joint Surgery 79:375-80 (1997)
© 1997 The Journal of Bone and Joint Surgery, Inc.
A Biomechanical Study of Replacement of the Posterior Cruciate Ligament with a Graft. Part I: Isometry, Pre-Tension of the Graft, and Anterior-Posterior Laxity*
KEITH L. MARKOLF, PH.D. ,
JAMES R. SLAUTERBECK, M.D. ,
KEVIN L. ARMSTRONG, M.D.,
MATTHEW S. SHAPIRO, M.D. and
GERALD A. M. FINERMAN, M.D., LOS ANGELES, CALIFORNIA
Investigation performed at the Biomechanics Research Section, Department of Orthopaedic Surgery, University of California at Los Angeles, Los Angeles
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Abstract
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Twelve fresh-frozen knee specimens from cadavera were subjected to anterior-posterior laxity testing with 200 newtons of force applied to the tibia; testing was performed before and after a femoral load-cell was connected to a mechanically isolated cylindrical cap of subchondral femoral bone containing the femoral origin of the posterior cruciate ligament. The posterior cruciate ligament then was removed, the proximal end of a thin trial isometer wire was attached to one of four points designated on the femur, and displacement of the distal end of the wire relative to the tibia was measured over a 120-degree range of motion. The potted end of a ten-millimeter-wide bone-patellar ligament-bone graft was centered over the femoral origin of the ligament and attached to the femoral load-cell. Isometry measurements were repeated with the wire attached to the bone block of the free end of the graft in the tibial tunnel. Force was recorded at the load-cell (representing force in the intra-articular portion of the graft) as pre-tension was applied, with use of a calibrated spring-scale, to the tibial end of the graft. A laxity-matched pre-tension of the graft was determined such that the anterior-posterior laxity of the reconstructed knee at 90 degrees of flexion was within one millimeter of the laxity that was measured after installation of the load-cell. Anterior-posterior testing was repeated after insertion of the graft at the laxity-matched pre-tension.
The least amount of change in the relative displacement of the trial wire over the 120-degree range of flexion occurred when the wire was attached to the proximal point on the femur (a point on the proximal margin of the femoral origin of the posterior cruciate ligament, midway between the anterior and posterior borders of the ligament). The greatest change in the relative displacement was associated with the anterior point (a point on the anterior margin of the femoral origin of the ligament, midway between the proximal and distal borders). The mean relative displacements of the trial wire when it was attached to a point at the center of the femoral origin of the ligament were not significantly different from the corresponding mean displacements of the distal end of the graft when the proximal end of the graft was centered at this point. At 90 degrees of flexion, the force recorded by the load-cell averaged 64 to 74 per cent of the force applied to the tibial end of the graft. The laxity-matched pre-tension of the graft at 90 degrees of flexion (as recorded by the load-cell) ranged from six to 100 newtons (mean and standard deviation, 43.0 ± 33.4 newtons). With the numbers available, the mean laxities after insertion of the graft were not significantly different, at any angle of flexion, from the corresponding mean values after installation of the load-cell.
CLINICAL RELEVANCE: Isometer readings from a trial wire attached to a point on the femur provided an accurate indication of the change in the length of a graft subsequently centered at that point. Anteriorly placed femoral tunnels should be avoided, as the isometer readings indicated increased tension, with flexion of the knee, in a graft placed in this region. The force in the intra-articular portion of the graft was always less than the force applied to the bone block in the tibial tunnel. Therefore, the femoral end of the graft should be tensioned to avoid frictional losses from the severe bend in the graft as it passes over the posterior tibial plateau. With correct pre-tensioning of a graft, normal anterior-posterior laxity at 0 to 90 degrees of flexion can be restored. However, because of the considerable range in the laxity-matched pre-tensions, we recommend that the pre-tension be greater than forty-three newtons for all patients to ensure that normal laxity is restored.
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Introduction
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It has been reported that injuries involving the posterior cruciate ligament (isolated and combined) account for 5 to 20 per cent of all injuries of the ligaments of the knee3,7,10,11,20,28. The objective and subjective outcomes of non-operative treatment of an isolated rupture of the posterior cruciate ligament have been reported to be good or excellent8,13,27,30,31. Unfortunately, combined injuries involving the posterior cruciate ligament are not uncommon5,17,25.
Excessive posterior laxity at 90 degrees of flexion (3+ or more) often is found on physical examination of a knee with a ruptured posterior cruciate ligament, and the clinical course for such knees is not always benign6,9,18,27. Replacement of a ruptured posterior cruciate ligament with a graft has become increasingly popular for patients who have excessive posterior laxity2,6,12,23,24,28.
The primary biomechanical rationale for insertion of a graft is to restore normal posterior laxity and, when necessary, to repair torn secondary stabilizing structures. However, reports of residual excessive posterior laxity after reconstruction of the posterior cruciate ligament are becoming more frequent2,19,24. Gradual stretching of the graft is one explanation for increased laxity; however improper placement of the graft and failure to pre-tension the graft correctly are other possible explanations. The biomechanics of posterior cruciate reconstructions has received relatively little attention1,4,14,16,29.
There were several objectives of this study. The first was to compare the relative displacements of a trial isometer wire at four designated points on the femur and then to compare the displacement at one of these points with the displacement of the distal end of a graft that had its proximal end fixed at that point. Our second objective was to measure the force generated in the femoral end of the graft (that is, within the intra-articular portion of the graft) as a function of the amount of pre-tension applied directly to the bone block of the free end of the graft in the tibial tunnel. Third, we sought to determine the amount of pre-tensioning of the graft that is needed to restore normal anterior-posterior laxity at 90 degrees of flexion (the laxity-matched pre-tension). Finally, we compared the anterior-posterior laxity values at selected angles of knee flexion before and after section of the posterior cruciate ligament and after insertion of the graft at the laxity-matched pre-tension.
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Materials and Methods
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Twelve fresh-frozen normal, stable knees were obtained from cadavera of individuals who had been forty-nine to seventy-nine years old at the time of death. The ends of the femur and tibia were potted in cylindrical molds of polymethylmethacrylate so that they could be gripped in the fixtures of the testing apparatus. The skin and soft tissues around the knee were left intact during testing.
Testing Apparatus
An anterior-posterior force (±200 newtons) was applied manually to an undercarriage bar attached to the tibial fixture of the apparatus, and tibial displacement was recorded with use of a spring-loaded transducer22. The tibia was not allowed to rotate. Neutral rotation at each angle of flexion tested was defined as midway between the tibial rotations produced by five newton-meters of internal and external tibial torque. The force applied to the tibia, the resultant force in the posterior cruciate ligament or the graft, and the tibial displacement were recorded. Knee laxity was defined as the resultant anterior-posterior displacement of the tibia, relative to the femur, when a 200-newton anterior-posterior force was applied to the tibia.
In order to define 0 degrees of flexion, the potted end of the femur was clamped such that the femoral shaft was horizontal, with the patella facing down, and a 2.5-newton-meter extension moment was applied to the tibia. Isometer testing also was performed with the specimen in this inverted orientation to eliminate the posterior subluxation of the tibia that would have occurred if, after section of the posterior cruciate ligament, the tibia was extending upward against gravity during testing. A specially designed isometer containing a displacement transducer was used to record the displacement, relative to the tibia, of a trial wire connected to a femoral point (or to the tibial end of the graft). To begin the test, the electrical output of the instrumented isometer was set to zero when the knee was in 0 degrees of flexion. The knee was flexed slowly to 120 degrees while the displacement of the isometer wire and the angle of flexion were recorded. Isometer readings were recorded as positive when the wire retracted into the joint, which corresponded to lengthening of the graft.
Testing Procedures
First, the intact knee was subjected to anterior-posterior testing, with the tibia in neutral rotation, at 0, 10, 30, 45, 70, and 90 degrees of flexion. A cylindrical block of subchondral femoral bone containing the femoral origin of the posterior cruciate ligament was mechanically isolated and was attached to a miniature load-cell mounted on the femur (Fig. 1), which recorded the resultant force in the ligament32. Anterior-posterior testing was repeated, with the tibia locked in neutral rotation, after installation of the load-cell. The posterior cruciate ligament was removed, and anterior-posterior testing was performed again.
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Fig. 1 The femoral load-cell was connected to a bracket anchored to the femur by an acrylic construct. The mechanically isolated cap of subchondral femoral bone encompassed the entire femoral origin of the posterior cruciate ligament. The trial isometer wire was attached to points on the anterior, distal, central, and proximal margins of the border of the ligament.
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The knee was mounted for isometer testing with the trial wire attached to the femur at one of four designated points. The femoral origin of the posterior cruciate ligament could be considered as approximately elliptical in shape, with the major axis of the ellipse oriented approximately in the anterior-posterior direction and the minor axis, in the proximal-distal direction (Fig. 1). The location that we designated as the central point was at the center of the ellipse. The axis of the cylindrical cap of bone and of the load-cell also passed through this point. The proximal and distal points were on the minor axis of the ellipse at the proximal and distal margins, respectively, of the femoral origin of the ligament. The anterior point lay on the major axis of the ellipse at the anterior margin of the femoral origin of the ligament, near the femoral trochlea. A point on the posterior margin of the femoral origin of the ligament was not tested because this location is never considered for attachment of a graft in the clinical setting. A small screw with an attachment hook was inserted at each point for connection of the isometer trial wire. Slight tension of the trial wire was maintained by a spring within the plunger of the isometer.
After the measurements made with the isometer trial wire had been recorded, an eleven-millimeter hole for a tibial tunnel was created with use of a drill and a drill-guide. The posterior (target) point of the drill-guide was placed at the center of the tibial insertion of the posterior cruciate ligament, approximately one centimeter distal to the tibial plateau. The included angle between the drill and the tibial plateau was approximately 50 degrees.
The grafts were prepared from whole bone-patellar ligament-bone specimens obtained from a tissue bank; each specimen was split longitudinally into two halves, yielding two grafts. A ten-millimeter-wide section of tissue was prepared from the central portion of each half. The bone at the patellar end was reinforced with wire loops and was potted in a small cylinder of polymethylmethacrylate to make a cap on the graft identical in size to the isolated cap of bone that contained the posterior cruciate ligament; the femoral load-cell was attached to this cap. The bone block at the tibial end of the graft was interwoven with four strands of high-strength Dacron line and was passed over and around the posterior edge of the tibial plateau and into the tibial tunnel. The bone block was free in the tunnel because of a 0.5-millimeter difference between its diameter and that of the hole to the tunnel. The Dacron lines exited the tunnel distally and passed through a split clamp mounted to the tibia. The lines were clamped when the desired level of pre-tension of the graft had been achieved. The graft was oriented such that its wide dimension was aligned with the wide dimension of the intact posterior cruciate ligament. The acrylic surface (at which the graft fibers exited the acrylic cap on the graft) was flush with the surface of the intercondylar notch. This placement simulated as closely as possible the geometric configuration of a graft located at the center of the femoral attachment of the intact posterior cruciate ligament.
With the tibia free to rotate, a calibrated spring-scale was used to apply tension to the Dacron lines with the knee flexed 90 degrees while force was recorded simultaneously by the femoral load-cell. Four levels of tension were applied to the graft: forty-five, ninety, 134, and 189 newtons. Three trials were performed with each level of tension, and the average of the load-cell readings was determined.
Next, the spring-scale was used to apply a trial level of pre-tension to the Dacron lines with the knee in 90 degrees of flexion while an anterior force (approximately twenty-two newtons) was applied to the tibia (as is done commonly at an operation). The Dacron lines were clamped to maintain the level of pre-tension of the graft during anterior-posterior testing with the tibia in neutral rotation. Through trial and error, we found a level of pre-tension that, with a 200-newton force applied to the tibia, produced the same anterior-posterior laxity (within one millimeter) at 90 degrees of flexion as that recorded after installation of the load-cell on the posterior cruciate ligament. This pre-tension was designated the laxity-matched pre-tension. Anterior-posterior testing with the tibia in neutral rotation was repeated after the insertion of the graft at the laxity-matched pre-tension.
Statistical Analysis
A two-way analysis-of-variance model with repeated measures was used to determine the significance of differences among the mean anterior-posterior laxities for the various conditions: the intact knee, after installation of the load-cell, after section of the posterior cruciate ligament, and after insertion of the graft at the laxity-matched pre-tension. Multiple pairwise comparisons between the means at specific angles of flexion of the knee were made with use of the Student-Newman-Keuls procedure. Similar analysis-of-variance models (with pairwise comparisons) were used to compare the isometer measurements associated with the four different points on the femur and to compare the pre-tensioning force ratios (ratio of the force recorded by the load-cell to the force applied to the distal end of the graft) at 30 and 90 degrees of flexion. The level of significance was p  0.05.
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Results
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Isometry: The least amount of change in the relative displacement of the trial wire over the 120-degree range of flexion occurred when the wire was attached to the proximal point on the femur, and the greatest change occurred when the wire was attached to the anterior point (Fig. 2). The mean relative displacements associated with the central and distal points on the femur were not significantly different, with the numbers available, from each other at any angle of flexion, but the mean values associated with each of these points at flexion of more than 50 degrees were significantly greater (p 0.05) than the corresponding mean displacements associated with the proximal point. The mean relative displacements of the trial wire attached to the central point were not significantly different, with the numbers available, from the corresponding values for the distal end of the graft when the proximal end of the graft was centered at this point.
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Fig. 2 Graph of the mean relative displacement of the trial wire according to the angle of flexion of the knee when the proximal end of the trial wire was attached to one of four points on the femur. Positive values indicate that the trial wire retracted into the joint. The mean values associated with the central and distal points were not significantly different, with the numbers available, from each other at any angle of flexion. The error bars indicate one standard deviation of the sample mean. ns = non-significant difference at the p 0.05 level.
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Pre-tension of the graft: The force recorded by the load-cell on the posterior cruciate ligament (which represented the force in the intra-articular portion of the graft) was a mean of 64 to 74 per cent that of the force applied to the tibial end of the graft at 90 degrees of flexion; the force averaged 58 to 63 per cent at 30 degrees of flexion (Fig. 3). The mean force ratio was significantly greater (p 0.05) at 90 degrees of flexion than at 30 degrees of flexion for all four levels of applied force. The level of pre-tension of the graft (as recorded by the load-cell on the posterior cruciate ligament) that was needed to restore normal anterior-posterior laxity at 90 degrees of flexion ranged from six to 100 newtons (mean and standard deviation, 43.0 ± 33.4 newtons).
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Fig. 3 Graph of the mean ratios of the force in the intra-articular portion of the graft (FI) to the force applied to the bone block in the tibial tunnel (FT). Four levels of force were applied at two angles of flexion of the knee. The mean force ratios at 30 and 90 degrees of flexion were significantly different (p 0.05) from each other at all levels of applied force. The error bars indicate one standard deviation of the sample mean.
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Anterior-posterior laxity: After installation of the load-cell, the mean anterior-posterior laxities were significantly greater (p 0.05) than the corresponding mean values for the intact knees only at 70 and 90 degrees of flexion (Fig. 4). With the numbers available, there were no significant differences between the mean laxities after insertion of the graft and the corresponding values after installation of the load-cell at any angle of flexion. The mean laxity increased at all angles of flexion after section of the posterior cruciate ligament (p 0.05).
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Discussion
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Isometry
The isometry measurements that we recorded with use of a trial wire are in general agreement with those reported by Ogata and McCarthy26, who also found that use of an anterior point of attachment for a trial wire increased the relative displacement of that wire (that is, the wire was drawn into the joint) during flexion of the knee. We believe that the proximal, distal, and central points of attachment were associated with acceptable changes in the relative displacement of the wire over the range of motion that was tested.
Our results contrast with those of Grood et al.15, who concluded that errors in the placement of the femoral tunnel in the anterior-posterior direction would be more acceptable than those in the proximal-distal direction. However, those authors performed tests on knees with an intact posterior cruciate ligament and applied a 100-newton posterior force to the tibia throughout the range of motion, whereas we performed testing on posterior-cruciate-deficient knees (as would be done at an operation) and made a special effort to eliminate posterior loading of the tibia during isometer testing.
We think our findings are encouraging for a clinician contemplating the intraoperative use of an isometer, as the measurements that were recorded with the trial wire were an accurate indicator of the behavior of the graft in situ.
Pre-Tensioning of the Graft
We pre-tensioned the graft at 90 degrees of flexion because this is the position used clinically for the posterior drawer test and it is the position of maximum laxity for a knee with a ruptured posterior cruciate ligament.
We found that the resultant force measured at the femoral load-cell (which represented force in the intra-articular portion of the graft) was always less than the tension that was applied to the tibial end of the graft. This finding is probably due to frictional loss as the graft passes up and over the posterior tibial plateau and into the joint. We believe that the tibial end of the graft should be fixed and the femoral end should be pre-tensioned before fixation. This ensures that the pre-tension force is transmitted directly to the intra-articular portion of the graft.
The laxity-matched pre-tension varied a great deal. Although the mean value for the twelve knees was 43.0 newtons, pre-tension of eighty-nine newtons or more was needed in three knees. We believe that the surgeon should apply more than forty-three newtons to the femoral end of the graft with the knee flexed 90 degrees in order to ensure that laxity will be restored in all patients. The potential consequences of over-tensioning with respect to the forces in the graft is discussed in Part II of this study21.
Anterior-Posterior Laxity
The two to three-millimeter increase in laxity at 70 and 90 degrees after installation of the load-cell is best explained by considering the angle of pull of the intact ligament on the cap of bone during an applied posterior-drawer force. At angles of flexion near 90 degrees, the fibers of the ligament are pulling almost perpendicular to the axis of the load-cell. This subjects the cap of bone to the maximum amount of cantilever deflection and produces additional posterior laxity. At smaller angles of flexion, the collateral ligaments and the capsule help to resist posterior force, and the component of ligament-pull acting at right angles to the load-cell is diminished.
The coring cutter used to isolate the cap of bone produced a gap of about three millimeters, which is approximately equal to the mean increase in anterior-posterior laxity at 70 to 90 degrees after installation of the load-cell. When a posterior tibial force is applied at an angle of flexion near 90 degrees, theoretically the cap of bone could come into contact with the wall of the tunnel and reduce the recorded load. Although we could not be certain that a gap remained during all of the anterior-posterior tests, periodic visual checks of the gap demonstrated that the cap of bone clearly was deflected but did not touch the wall. Even if contact had occurred, it would not have explained the scatter in the pre-tension values, as they were relatively low.
After section of the posterior cruciate ligament, the mean increase in anterior-posterior laxity at 90 degrees of flexion was approximately 58 per cent greater than the increase at 30 degrees of flexion (the angle at which the Lachman test is normally performed to test for rupture of the anterior cruciate ligament) (Fig. 3). This finding reinforces the accepted clinical practice of performing the posterior drawer test at 90 degrees of flexion to establish the diagnosis of rupture of the posterior cruciate ligament.
NOTE: The authors thank Steve Jackson, for his assistance in the testing and the data analysis, and Stephen Liu, M.D., for his guidance in the initial phases of the work. The tissues used for the patellar ligament grafts were kindly provided by the Musculoskeletal Transplant Foundation.
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Footnotes
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*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Funds were received in total or partial support of the research or clinical study presented in this article. The funding sources were National Institutes of Health Grant RO1 AR40330 and the Dorothy and Leonard Straus Fund.
Biomechanics Research Section, Department of Orthopaedic Surgery, Rehabilitation Center, University of California at Los Angeles, 1000 Veteran Avenue, Los Angeles, California 90024-1795. E-mail address for Dr. Markolf: kmarkolf@ortho.medsch.ucla.edu.
Department of Orthopaedic Surgery, Texas Tech University Health Sciences Center, Lubbock, Texas 79301.
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July 1, 2006;
34(7):
1126 - 1133.
[Abstract]
[Full Text]
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K. L. Markolf, B. T. Feeley, S. R. Jackson, and D. R. McAllister
Where Should the Femoral Tunnel of a Posterior Cruciate Ligament Reconstruction Be Placed to Best Restore Anteroposterior Laxity and Ligament Forces?
Am. J. Sports Med.,
April 1, 2006;
34(4):
604 - 611.
[Abstract]
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J. A. Bergfeld, S. M. Graham, R. D. Parker, A. D. C. Valdevit, and H. E. Kambic
A Biomechanical Comparison of Posterior Cruciate Ligament Reconstructions Using Single- and Double-Bundle Tibial Inlay Techniques
Am. J. Sports Med.,
July 1, 2005;
33(7):
976 - 981.
[Abstract]
[Full Text]
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C. A. Fontbote, T. C. Sell, K. G. Laudner, M. Haemmerle, C. R. Allen, F. Margheritini, S. M. Lephart, and C. D. Harner
Neuromuscular and Biomechanical Adaptations of Patients With Isolated Deficiency of the Posterior Cruciate Ligament
Am. J. Sports Med.,
July 1, 2005;
33(7):
982 - 989.
[Abstract]
[Full Text]
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F. R. Noyes and S. D. Barber-Westin
Posterior Cruciate Ligament Revision Reconstruction, Part 1: Causes of Surgical Failure in 52 Consecutive Operations
Am. J. Sports Med.,
May 1, 2005;
33(5):
646 - 654.
[Abstract]
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S. E. Park, B. D. Stamos, L. E. DeFrate, T. J. Gill, and G. Li
The Effect of Posterior Knee Capsulotomy on Posterior Tibial Translation During Posterior Cruciate Ligament Tibial Inlay Reconstruction
Am. J. Sports Med.,
September 1, 2004;
32(6):
1514 - 1519.
[Abstract]
[Full Text]
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K. L. Markolf, G. O'Neill, S. R. Jackson, and D. R. McAllister
Effects of Applied Quadriceps and Hamstrings Muscle Loads on Forces in the Anterior and Posterior Cruciate Ligaments
Am. J. Sports Med.,
July 1, 2004;
32(5):
1144 - 1149.
[Abstract]
[Full Text]
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L. E. DeFrate, A. van der Ven, T. J. Gill, and G. Li
The Effect of Length on the Structural Properties of an Achilles Tendon Graft as Used in Posterior Cruciate Ligament Reconstruction
Am. J. Sports Med.,
June 1, 2004;
32(4):
993 - 997.
[Abstract]
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F. Margheritini, C. S. Mauro, J. A. Rihn, K. J. Stabile, S. L-Y. Woo, and C. D. Harner
Biomechanical Comparison of Tibial Inlay Versus Transtibial Techniques for Posterior Cruciate Ligament Reconstruction: Analysis of Knee Kinematics and Graft In Situ Forces
Am. J. Sports Med.,
April 1, 2004;
32(3):
587 - 593.
[Abstract]
[Full Text]
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T. J. Gill, L. E. DeFrate, C. Wang, C. T. Carey, S. Zayontz, B. Zarins, and G. Li
The Effect of Posterior Cruciate Ligament Reconstruction on Patellofemoral Contact Pressures in the Knee Joint Under Simulated Muscle Loads
Am. J. Sports Med.,
January 1, 2004;
32(1):
109 - 115.
[Abstract]
[Full Text]
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K. L. Markolf, G. O'Neill, S. R. Jackson, and D. R. McAllister
Reconstruction of Knees with Combined Cruciate Deficiencies: A Biomechanical Study
J. Bone Joint Surg. Am.,
September 1, 2003;
85(9):
1768 - 1774.
[Abstract]
[Full Text]
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D. A. Oakes, K. L. Markolf, J. McWilliams, C. R. Young, and D. R. McAllister
The Effect of Femoral Tunnel Position on Graft Forces During Inlay Posterior Cruciate Ligament Reconstruction
Am. J. Sports Med.,
September 1, 2003;
31(5):
667 - 672.
[Abstract]
[Full Text]
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K. Markolf, M. Davies, B. Zoric, and D. McAllister
Effects of Bone Block Position and Orientation Within the Tibial Tunnel for Posterior Cruciate Ligament Graft Reconstructions: A Cyclic Loading Study of Bone-Patellar Tendon-Bone Allografts
Am. J. Sports Med.,
September 1, 2003;
31(5):
673 - 679.
[Abstract]
[Full Text]
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T. J. Gill, L. E. DeFrate, C. Wang, C. T. Carey, S. Zayontz, B. Zarins, and G. Li
The Biomechanical Effect of Posterior Cruciate Ligament Reconstruction on Knee Joint Function: Kinematic Response to Simulated Muscle Loads
Am. J. Sports Med.,
July 1, 2003;
31(4):
530 - 536.
[Abstract]
[Full Text]
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E. A. Mejia, F. R. Noyes, and E. S. Grood
Posterior Cruciate Ligament Femoral Insertion Site Characteristics: Importance for Reconstructive Procedures
Am. J. Sports Med.,
September 1, 2002;
30(5):
643 - 651.
[Abstract]
[Full Text]
[PDF]
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D. A. Oakes, K. L. Markolf, J. McWilliams, C. R. Young, and D. R. McAllister
Biomechanical Comparison of Tibial Inlay and Tibial Tunnel Techniques for Reconstruction of the Posterior Cruciate Ligament : Analysis of Graft Forces
J. Bone Joint Surg. Am.,
June 1, 2002;
84(6):
938 - 944.
[Abstract]
[Full Text]
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D. R. McAllister, K. L. Markolf, D. A. Oakes, C. R. Young, and J. McWilliams
A Biomechanical Comparison of Tibial Inlay and Tibial Tunnel Posterior Cruciate Ligament Reconstruction Techniques: Graft Pretension and Knee Laxity
Am. J. Sports Med.,
May 1, 2002;
30(3):
312 - 317.
[Abstract]
[Full Text]
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J. A. Bergfeld, D. R. McAllister, R. D. Parker, A. D. C. Valdevit, and H. Kambic
The Effects of Tibial Rotation on Posterior Translation in Knees in Which the Posterior Cruciate Ligament Has Been Cut
J. Bone Joint Surg. Am.,
September 1, 2001;
83(9):
1339 - 1343.
[Abstract]
[Full Text]
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J. A. Bergfeld, D. R. McAllister, R. D. Parker, A. D. C. Valdevit, and H. E. Kambic
A Biomechanical Comparison of Posterior Cruciate Ligament Reconstruction Techniques
Am. J. Sports Med.,
March 1, 2001;
29(2):
129 - 136.
[Abstract]
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D. A. Mannor, J. T. Shearn, E. S. Grood, F. R. Noyes, and M. S. Levy
Two-Bundle Posterior Cruciate Ligament Reconstruction: An In Vitro Analysis of Graft Placement and Tension
Am. J. Sports Med.,
November 1, 2000;
28(6):
833 - 845.
[Abstract]
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C. D. Harner, M. A. Janaushek, A. Kanamori, M. Yagi, T. M. Vogrin, and S. L.-Y. Woo
Biomechanical Analysis of a Double-Bundle Posterior Cruciate Ligament Reconstruction
Am. J. Sports Med.,
March 1, 2000;
28(2):
144 - 151.
[Abstract]
[Full Text]
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C. D. Harner, T. M. Vogrin, J. Hoher, C. B. Ma, and S. L-Y. Woo
Biomechanical Analysis of a Posterior Cruciate Ligament Reconstruction: Deficiency of the Posterolateral Structures as a Cause of Graft Failure
Am. J. Sports Med.,
January 1, 2000;
28(1):
32 - 39.
[Abstract]
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K. L. MARKOLF, J. R. SLAUTERBECK, K. L. ARMSTRONG, M. S. SHAPIRO, and G. A. M. FINERMAN
A Biomechanical Study of Replacement of the Posterior Cruciate Ligament with a Graft. Part II: Forces in the Graft Compared with Forces in the Intact Ligament
J. Bone Joint Surg. Am.,
March 1, 1997;
79(3):
381 - 6.
[Abstract]
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Top
Abstract
Introduction