JBJS | The Effects of Tibial Rotation on Posterior Translation in Knees in Which the Posterior Cruciate Ligament Has Been Cut

The Journal of Bone & Joint Surgery, Volume 83, Issue 9

Scientific Articles | September 01, 2001

The Effects of Tibial Rotation on Posterior Translation in Knees in Which the Posterior Cruciate Ligament Has Been Cut

John A. Bergfeld, MD; David R. McAllister, MD; Richard D. Parker, MD; Antonio D. C. Valdevit, MSc; Helen Kambic, MS

Investigation performed at the Section of Sports Medicine, Department of Orthopaedic Surgery, The Cleveland Clinic Foundation, Cleveland, Ohio
John A. Bergfeld, MD
Richard D. Parker, MD
Antonio D.C. Valdevit, MSc
Helen Kambic, MS
Section of Sports Medicine, Department of Orthopaedic Surgery (J.A.B. and R.D.P.), and Department of Biomedical Engineering (A.D.C.V. and H.K.), The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195. Please address requests for reprints to Dr. Bergfeld.

David R. McAllister, MD
Department of Orthopaedic Surgery, University of California, Los Angeles, Center for Health Sciences, Box 956902, Los Angeles, CA 90095-6902

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. No funds were received in support of this study.

Presented at the Annual Meeting of the Orthopaedic Research Society, Orlando, Florida, March 12-15, 2000.

The Journal of Bone & Joint Surgery. 2001; 83:1339-1343

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Abstract

Background: One of the most useful clinical tests for diagnosing an isolated injury of the posterior cruciate ligament is the posterior drawer maneuver performed with the knee in 90° of flexion. Previously, it was thought that internally rotating the tibia during posterior drawer testing would decrease posterior laxity in a knee with an isolated posterior cruciate ligament injury. In this study, we evaluated the effects of internal and external tibial rotation on posterior laxity with the knee held in varying degrees of flexion after the posterior cruciate and meniscofemoral ligaments had been cut.

Materials and Methods: Twenty cadaveric knees were used. Each knee was mounted in a fixture with six degrees of freedom, and anterior and posterior forces of 150 N were applied. The testing was conducted with the knee in 90°, 60°, 30°, and 0° of flexion with the tibia in neutral, internal, and external rotation. All knees were tested with the posterior cruciate and meniscofemoral ligaments intact and transected. Repeated-measures analysis of variance was used for statistical analysis.

Results: At 30°, 60°, and 90° of flexion, there was a significant increase in posterior laxity following transection of the posterior cruciate and meniscofemoral ligaments. At 60° and 90° of flexion, there was significantly less posterior laxity when the tibia was held in internal compared with external rotation. At 0° and 30° of flexion, there was no significant difference in posterior laxity when the tibia was held in internal compared with external rotation.

Conclusions: After the posterior cruciate and meniscofemoral ligaments had been cut, posterior laxity was significantly decreased by both internal and external rotation of the tibia. Internal tibial rotation resulted in significantly less laxity than external tibial rotation did at 60° and 90° of knee flexion.

Clinical Relevance: An isolated injury of the posterior cruciate ligament is best detected when a posterior drawer test is performed with the knee in 90° of flexion. Repeating this test with the tibia internally rotated will result in a substantial decrease in the amount of posterior laxity at 60° and 90° of knee flexion.

Figures in this Article

Introduction

Introduction | Materials and Methods | Results | Discussion | References

The posterior cruciate ligament provides the primary restraint to posterior tibial translation in the intact knee¹. The most common cause of an isolated posterior cruciate ligament injury is a direct blow to the proximal aspect of the tibia while the knee is flexed. Posterior cruciate ligament injuries may be isolated or combined with other injuries involving the capsule and other ligaments in the knee. Whereas the diagnosis of a combined injury may be obvious in a knee that has been subjected to high-energy trauma, the diagnosis of an isolated injury is less obvious because isolated posterior instability is often asymptomatic.

One of the most useful clinical tests for diagnosing a torn posterior cruciate ligament is the posterior drawer maneuver performed with the knee in 90° of flexion and the tibia held in neutral rotation. Additional information can be obtained by repeating this test with the tibia held in internal and external rotation. Clancy et al.² noted decreased posterior translation when the tibia was internally rotated, and they attributed this effect to tightening of the meniscofemoral ligaments. Ritchie et al.³ demonstrated decreased posterior tibial translation in cadaveric knees when the tibia was internally rotated with the knee in 90° of flexion. Furthermore, they identified the tibial collateral ligament as the structure responsible for the observed decrease in posterior translation. Internal rotation of the tibia during the posterior drawer test has been thought to decrease posterior laxity in a knee that has an isolated posterior cruciate ligament injury. Although this effect has been observed in previous clinical studies^4,5, it has not been confirmed in an in vitro biomechanical study, to our knowledge. In the present study, we evaluated the effects of internal and external tibial rotation on posterior laxity with the knee held in various angles of flexion after the posterior cruciate ligament and meniscofemoral ligaments had been cut.

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Fig. 1:: Graph illustrating anterior-posterior (A-P) laxity with the knee in 0°, 30°, 60°, and 90° of flexion. The test was performed under four conditions: with the posterior cruciate and meniscofemoral ligaments intact (diamonds), with the ligaments transected and the tibia in neutral rotation (squares), with the ligaments transected and the tibia in internal rotation (circles), and with the ligaments transected and the tibia in external rotation (triangles). A double asterisk indicates a significant difference at p £ 0.001, a single asterisk indicates a significant difference at p £ 0.05, and NS indicates no significant difference (p > 0.05) compared with the laxity measured with the ligaments transected and the tibia in neutral rotation.

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TABLE I: Anterior-Posterior Laxity for Each Condition at Each Knee-Flexion Angle

*PCL = posterior cruciate ligament, and MFL = meniscofemoral ligament. †a, b, and c indicate p £ 0.001, p £ 0.05, and p > 0.05, respectively, compared with the intact condition. d and e indicate p £ 0.05 and p > 0.05, respectively, compared with the test performed with the ligaments transected and the tibia in external rotation.

Condition*	Anterior-Posterior Laxity† (mm)
0° of Flexion	30° of Flexion	60° of Flexion	90° of Flexion
PCL and MFL intact	?9.4	13.5	11.5	10.2
PCL and MFL transected
Neutral tibial rotation	12.1c	20.8a	23.3a	25.5a
Internal tibial rotation	?9.3c,e	11.8c,e	13.2c,d	13.2b,d
External tibial rotation	?9.0c	11.7c	16.1a	15.7a

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TABLE I: Anterior-Posterior Laxity for Each Condition at Each Knee-Flexion Angle

Condition*	Anterior-Posterior Laxity† (mm)
0° of Flexion	30° of Flexion	60° of Flexion	90° of Flexion
PCL and MFL intact	?9.4	13.5	11.5	10.2
PCL and MFL transected
Neutral tibial rotation	12.1c	20.8a	23.3a	25.5a
Internal tibial rotation	?9.3c,e	11.8c,e	13.2c,d	13.2b,d
External tibial rotation	?9.0c	11.7c	16.1a	15.7a

Materials and Methods

Introduction | Materials and Methods | Results | Discussion | References

Twenty apparently normal, fresh-frozen cadaveric knees were used. Knees that had evidence of prior surgery, abnormal laxity, or obvious degenerative joint disease were excluded. Specimens were amputated at the middle of the femur and the middle of the tibia.

Specimen Preparation and Testing

The knees were thawed, and soft tissue was removed from the tibia and the femur to within 10 cm of the joint line. Skin, subcutaneous fat, and muscle around the knee joint were excised, leaving only the joint capsule, ligaments, popliteus muscle, and extensor mechanism intact. The portion of the fibula distal to the fibular neck was resected, and the proximal tibiofibular joint was fixed to the tibia with use of a 4.5-mm cortical screw (Synthes, Paoli, Pennsylvania). The proximal end of the femur and the distal end of the tibia were potted in aluminum tubes with polymethylmethacrylate. Transfixion pins within the tubing were used to eliminate rotation at the polymethylmethacrylate-tube interface. We used a previously described custom-designed testing apparatus with six degrees of freedom⁶. A Bionix 858 MTS machine with TestStar software (MTS, Eden Prairie, Minnesota) was used to apply anterior and posterior shear forces to the knee while displacements were measured. The potted femoral end of the specimen was clamped into a yoke that was attached to the load ram of the machine. The epicondylar axis of the knee joint was placed at the pivot axis of the femoral yoke. The knee-flexion angle was adjusted with the yoke and was locked at the desired angle prior to testing. A bearing system allowed free motion of angulation in valgus and varus directions. The potted tibial end of the specimen was mounted in a clamp housed within a bearing mechanism that allowed axial rotation and could be locked if desired. The tibial bearing mechanism was mounted on the plate of an X-Y table, allowing free translation of the tibia in the coronal plane.

Anterior-posterior laxity was defined as the amount of translation of the tibia relative to the femur in the midsagittal plane. Anterior and posterior forces of 150 N were applied to the femur and measured with the MTS load-cell. The amount of displacement of the femur was measured by the linear variable displacement transducer of the MTS machine. Tibial rotation was locked during the laxity testing. Neutral rotation was defined as a position that was midway between the tibial rotations produced by 5 Nm of internal and external tibial torque, as previously described by Markolf et al.⁷. Positions of internal and external rotation were defined as those resulting from the application of 5 Nm of internal and external tibial torque, respectively. The yoke of the testing apparatus held the knee in various degrees of knee flexion while anterior and posterior forces were applied with the MTS machine.

Testing Procedures

Each intact knee was mounted on the apparatus and subjected to anterior-posterior loading at 0°, 30°, 60°, and 90° of flexion in neutral, internal, and external rotation. Anterior and posterior forces of 150 N were applied, at a rate of 0.2 Hz, to the femoral yoke at the level of the joint line. Tibial rotation was unlocked between tests during changing of the knee-flexion angle, and neutral rotation was redefined at each knee-flexion angle. During anterior-posterior loading, tibial rotation was locked but the joint was free to angulate in the valgus and varus directions and the tibia was allowed to translate in the coronal plane. The knee was loaded six times under each testing condition. The first three loading cycles were used to precondition the knee, and the last three loading cycles were used for data collection. In all testing conditions, the load-deformation curve became reproducible after two loading cycles. Anterior-posterior knee laxity was defined as the displacement of the tibia relative to the femur that occurred between the limits of anterior and posterior loads of 150 N. This convention was chosen to load the anterior cruciate ligament and use it as a reference. Since the anterior cruciate ligament was not cut in the experiment, it is reasonable that the reference for displacement measurement was an anteriorly applied load to the tibia that loaded the anterior cruciate ligament. These tests were performed with use of the load-defined feedback loop option on the MTS system. The neutral position for anterior-posterior translation was identified as the inflection point of the load-displacement data generated during anterior-posterior loading. This zero-load position was maintained while the knee-flexion angle and tibial rotation were changed between testing cycles.

Sectioning of the Posterior Cruciate Ligament

After laxity data had been obtained for the intact knee, a posterior arthrotomy was performed and the posterior cruciate and meniscofemoral ligaments were transected. The posterior part of the capsule was repaired, and anterior-posterior loading was repeated under the previously listed testing conditions. Because the specimen was not removed from the testing jig between the loading conditions, the zero-load neutral position could be maintained throughout the testing sequence.

Evaluation of the Internal Rotation Posterior Drawer Test

The difference in posterior laxity between the internal rotation condition and the neutral rotation condition was calculated for each knee at 90° of flexion. A change in laxity of 10 mm or more signified a positive test result, and the sensitivity and specificity of the internal rotation posterior drawer test were determined.

Statistical Analysis

The data consisted of the laxity measurements (in millimeters) for each knee under different loading conditions and at several different angles. Therefore, repeated-measures analysis of variance was used for statistical analysis. Pairwise comparisons between different conditions were performed with a Bonferroni adjustment for multiple comparisons.

Results

Introduction | Materials and Methods | Results | Discussion | References

Total anterior-posterior laxity was measured at 0°, 30°, 60°, and 90° of knee flexion under each condition (Fig. 1). At 30°, 60°, and 90° of flexion, significantly more laxity was measured with the posterior cruciate and meniscofemoral ligaments transected and the tibia held in neutral rotation than was measured under the other three conditions. At 0° of flexion, only the laxity that was measured with the ligaments transected and the tibia held in external rotation was significantly different from that measured with the ligaments transected and the tibia held in neutral rotation.

Table I shows the anterior-posterior laxity for each condition at each knee-flexion angle. At 90° of flexion, there was significantly more laxity with the posterior cruciate and meniscofemoral ligaments transected, regardless of rotation, compared with the intact condition. At 60° and 90° of flexion, there was significantly less laxity with the ligaments transected and the tibia internally rotated than with the ligaments transected and the tibia externally rotated. At 60° of flexion, there was significantly more laxity with the ligaments transected and the tibia externally rotated, but not internally rotated, compared with the intact condition. At 30° of flexion, there was significantly more laxity with the ligaments transected and the tibia held in neutral rotation, but not in internal or external rotation, compared with the intact condition.

When the difference in posterior laxity between the internal rotation condition and the neutral rotation condition was 10 mm at 90° of knee flexion, the internal rotation posterior drawer test had a sensitivity of 0.8 and a specificity of 1.0 for detecting knees in which the posterior cruciate and the meniscofemoral ligaments had been cut.

Discussion

Introduction | Materials and Methods | Results | Discussion | References

We found that isolated sectioning of the posterior cruciate and the meniscofemoral ligaments led to an increase in anterior-posterior laxity at 30°, 60°, and 90° of knee flexion. It has been reported that laxity increases as the knee is flexed and is greatest at 90° of knee flexion^8-10. These observations provide the rationale for performing the posterior drawer test with the knee in 90° of flexion.

After the posterior cruciate and meniscofemoral ligaments had been cut, we found that anterior-posterior laxity was significantly decreased by both internal and external rotation of the tibia with the knee in 30°, 60°, and 90° of flexion. Internal tibial rotation resulted in significantly less anterior-posterior laxity than external rotation did at 60° and 90° of flexion. At 90° of flexion, the internal rotation posterior drawer test had a sensitivity of 0.8 and a specificity of 1.0 for detecting knees in which the posterior cruciate and meniscofemoral ligaments had been cut.

Clancy et al.² observed decreased posterior laxity in eight of ten patients with acute posterior cruciate ligament injuries when the posterior drawer test was repeated with the tibia held in internal rotation. An intact ligament of Humphrey or Wrisberg was identified at the time of surgery in all ten of these patients. The authors concluded that internal rotation of the tibia caused tightening of these ligaments, resulting in the observed decrease in posterior laxity. One of us (J.A.B.) and colleagues³ performed a selective cutting experiment in cadaveric knees held in 90° of knee flexion only. There was no increase in posterior laxity after sectioning the meniscofemoral ligament alone, but, after sectioning both the meniscofemoral ligament and the posterior cruciate ligament, there was a significant increase in posterior laxity. It was concluded that the tibial collateral ligament was the structure that was responsible for decreased posterior laxity in knees in which the posterior cruciate and meniscofemoral ligaments had been cut. In the current study, we did not attempt to identify the structure responsible for the observed decrease in posterior laxity with internal rotation of the tibia. Because the ligaments of Humphrey and Wrisberg were cut in all of the knees that we tested, our results suggest that a structure other than the meniscofemoral ligament is responsible for the decreased laxity that is observed when the tibia is internally rotated.

We did not observe a significant increase in anterior-posterior laxity at 0° of knee flexion after transection of the posterior cruciate and meniscofemoral ligaments. This finding is contrary to those of other investigators^1,7,9,10 and may be best explained by differences in methodology. The testing jig that we constructed aligned the knee according to the angle between the tibia and the femur and did not take into account individual variability among the specimens. Many cadaveric knees from older donors have slight flexion contractures. Forcibly extending the knee to 0° probably was beyond the normal physiological limit of some of our specimens and could have led to tightening of the capsule and to other secondary restraints, resulting in less laxity.

The present study had other limitations as well. It is unclear whether the injury that was created (an isolated transection of the posterior cruciate and meniscofemoral ligaments without substantial capsular injury) accurately simulated an isolated posterior cruciate ligament injury, which may also be associated with capsular injury. We used cadaveric knees from an elderly population, and it is possible that these knees were stiffer than the knees in younger individuals, who are more likely to sustain a posterior cruciate ligament injury. No muscle loads were applied in this model, negating the potential dynamic stabilizing effects of the quadriceps, hamstring, and gastrocnemius muscles.

We conclude that an isolated injury of the posterior cruciate and meniscofemoral ligaments is best detected when a posterior drawer test is performed with the knee flexed to 90°. Repeating this test with the tibia internally rotated will result in a substantial decrease in the amount of posterior laxity.

References

Introduction | Materials and Methods | Results | Discussion | References

Butler DL, Noyes FR,Grood ES. Ligamentous restraints to anterior-posterior drawer in the human knee. A biomechanical study. J Bone Joint Surg Am,1980;62: 259-70. 62259 1980 [PubMed]

Clancy WG Jr, Shelbourne KD, Zoellner GB, Keene JS, Reider B,Rosenberg TD. Treatment of knee joint instability secondary to rupture of the posterior cruciate ligament. Report of a new procedure. J Bone Joint Surg Am,1983;65: 310-22. 65310 1983 [PubMed]

Ritchie JR, Bergfeld JA, Kambic H,Manning T. Isolated sectioning of the medial and posteromedial capsular ligaments in the posterior cruciate ligament-deficient knee. Influence on posterior tibial translation. Am J Sports Med,1998;26: 389-94. 26389 1998 [PubMed]

Parolie JM,Bergfeld JA. Long-term results of nonoperative treatment of isolated posterior cruciate ligament injuries in the athlete. Am J Sports Med,1986;1: 35-8.. 135 1986

Shelbourne KD, Davis TJ,Patel DV. The natural history of acute, isolated, nonoperatively treated posterior cruciate ligament injuries. A prospective study. Am J Sports Med,1999;27: 276-83. 27276 1999 [PubMed]

Bergfeld JA, McAllister DR, Parker RD, Valdevit AD,Kambic HE. A biomechanical comparison of posterior cruciate ligament reconstruction techniques. Am J Sports Med,2001;29: 129-36. 29129 2001 [PubMed]

Markolf KL, Slauterbeck JR, Armstrong KL, Shapiro MS,Finerman GA. A biomechanical study of replacement of the posterior cruciate ligament with a graft. Part 1: Isometry, pre-tension of the graft, and anterior-posterior laxity. J Bone Joint Surg Am,1997;79: 375-80.. 79375 1997 [PubMed]

Fukubayashi T, Torzilli TA, Sherman MF,Warren RF. An in vitro biomechanical evaluation of anterior-posterior motion of the knee. Tibial displacement, rotation, and torque. J Bone Joint Surg Am,1982;6: 258-64.. 6258 1982

Gollehon DL, Torzilli PL,Warren RF. The role of the posterolateral and cruciate ligaments in the stability of the human knee. A biomechanical study. J Bone Joint Surg Am,1987;69: 233-42. 69233 1987 [PubMed]

Grood ES, Stowers SF,Noyes FR. Limits of movement in the human knee. Effect of sectioning the posterior cruciate ligament and posterolateral structures. J Bone Joint Surg Am,1988;70: 88-97. 7088 1988 [PubMed]

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TABLE I: Anterior-Posterior Laxity for Each Condition at Each Knee-Flexion Angle

Condition*	Anterior-Posterior Laxity† (mm)
0° of Flexion	30° of Flexion	60° of Flexion	90° of Flexion
PCL and MFL intact	?9.4	13.5	11.5	10.2
PCL and MFL transected
Neutral tibial rotation	12.1c	20.8a	23.3a	25.5a
Internal tibial rotation	?9.3c,e	11.8c,e	13.2c,d	13.2b,d
External tibial rotation	?9.0c	11.7c	16.1a	15.7a

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TABLE I: Anterior-Posterior Laxity for Each Condition at Each Knee-Flexion Angle

Condition*	Anterior-Posterior Laxity† (mm)
0° of Flexion	30° of Flexion	60° of Flexion	90° of Flexion
PCL and MFL intact	?9.4	13.5	11.5	10.2
PCL and MFL transected
Neutral tibial rotation	12.1c	20.8a	23.3a	25.5a
Internal tibial rotation	?9.3c,e	11.8c,e	13.2c,d	13.2b,d
External tibial rotation	?9.0c	11.7c	16.1a	15.7a

Butler DL, Noyes FR,Grood ES. Ligamentous restraints to anterior-posterior drawer in the human knee. A biomechanical study. J Bone Joint Surg Am,1980;62: 259-70. 62259 1980 [PubMed]

Parolie JM,Bergfeld JA. Long-term results of nonoperative treatment of isolated posterior cruciate ligament injuries in the athlete. Am J Sports Med,1986;1: 35-8.. 135 1986

Bergfeld JA, McAllister DR, Parker RD, Valdevit AD,Kambic HE. A biomechanical comparison of posterior cruciate ligament reconstruction techniques. Am J Sports Med,2001;29: 129-36. 29129 2001 [PubMed]

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John A. Bergfeld, David R. McAllister, Richard D. Parker, Antonio D. C. Valdevit, Helen Kambic; The Effects of Tibial Rotation on Posterior Translation in Knees in Which the Posterior Cruciate Ligament Has Been Cut. The Journal of Bone & Joint Surgery. 2001 Sep;83(9):1339-1343.

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