Total knee arthroplasty ligament balancing and gap kinematics with posterior cruciate ligament retention and sacrifice

This cadaver study was undertaken to gain insight into the effects that posterior cruciate ligament retention and sacrifice would have on the amount of deformity correction obtained with medial and lateral structure release during total knee arthroplasty. Twenty-seven cadaveric specimens were used to sequentially release medial and lateral structures with and without posterior cruciate support. Each release sequence was tested in full extension and 90 degrees flexion. In full extension, the resulting change into valgus after release of the posterior cruciate ligament, posteromedial capsule/oblique ligament complex, superficial medial collateral ligament, and pes anserinus and semimembranosus tendons was 6.9 degrees, and it increased to 13.4 degrees in 90 degrees flexion. With preservation of the posterior cruciate ligament this decreased to 5.2 degrees in extension and 8.7 degrees in flexion. Changes seen in 90 degrees flexion were significantly greater than those in full extension. For the valgus knee model with release of the posterior cruciate ligament, posterolateral capsule, lateral collateral ligament, iliotibial band, popliteus tendon, and lateral head of the gastrocnemius, 8.9 degrees of change into varus was seen in extension and 18.1 degrees in 90 degrees flexion. With posterior cruciate ligament retention 5.4 degrees and 4.9 degrees of change into varus was seen in extension and flexion, respectively. Significantly less change with retention of the posterior cruciate ligament was seen with both medial and lateral release and more opening of the flexion gap was seen on the release side of the joint for all groups except those with lateral release with sacrifice of the posterior cruciate ligament.     

In vivo strain patterns in the four major canine knee ligaments

Using mercury gauges, we measured strains in vivo in the four major ligaments of the canine knee joint as the tibia was loaded in valgus or varus at fixed angles of knee flexion. Free axial rotation of the tibia on the femur was allowed. Forces up to 78.4 N were applied to the tibia, producing moments of approximately 9 N-m. We found that with valgus loading, significant strains were observed in the medial collateral ligament at extension. At 45 degrees of flexion, the medial collateral, posterior cruciate, and anterior cruciate were strained. At 90 degrees of flexion, all four ligaments were strained. With varus loading, significant strains were found in the lateral collateral and anterior cruciate at extension. The lateral collateral and anterior cruciate ligaments were strained at 45 degrees of flexion. At 90 degrees of flexion, the lateral collateral, anterior cruciate, and posterior cruciate ligaments were strained. With valgus loading, the tibia rotated internally and the degree of axial rotation increased with flexion. External rotation of the tibia resulted from varus loading, and was relatively constant through the range of flexion. Thus when axial rotation is allowed, stability of the knee in response to valgus and varus loads is maintained by the cruciates as well as the collaterals, and the role of the cruciates increases with flexion and axial rotation.     

Strain in the human medial collateral ligament during valgus loading of the knee

The medial collateral ligament is one of the most frequently injured ligaments in the knee. Although the medial collateral ligament is known to provide a primary restraint to valgus and external rotations, details regarding its precise mechanical function are unknown. In this study, strain in the medial collateral ligament of eight knees from male cadavers was measured during valgus loading. A material testing machine was used to apply 10 cycles of varus and valgus rotation to limits of +/- 10.0 N-m at flexion angles of 0 degrees, 30 degrees, 60 degrees, and 90 degrees. A three-dimensional motion analysis system measured local tissue strain on the medial collateral ligament surface within 12 regions encompassing nearly the entire medial collateral ligament surface. Results indicated that strain is significantly different in different regions over the surface of the medial collateral ligament and that this distribution of strain changes with flexion angle and with the application of a valgus torque. Strain in the posterior and central portions of the medial collateral ligament generally decreased with increasing flexion angle, whereas strain in the anterior fibers remained relatively constant with changes in flexion angle. The highest strains in the medial collateral ligament were found at full extension on the posterior side of the medial collateral ligament near the femoral insertion. These data support clinical findings that suggest the femoral insertion is the most common location for medial collateral ligament injuries.     

Limits of movement in the human knee. Effect of sectioning the posterior cruciate ligament and posterolateral structures

We applied specific forces and moments to the knees of fifteen whole lower limbs of cadavera and measured, with a six degrees-of-freedom electrogoniometer, the position of the tibia at which the ligaments and the geometry of the joint limited motion. The limits were determined for anterior and posterior tibial translation, internal and external rotation, and varus and valgus angulation from zero to 90 degrees of flexion. The limits were measured in the intact knee and then the changes that occurred with removal of the posterior cruciate ligament, the lateral collateral ligament, the popliteus tendon at its femoral attachment, and the arcuate complex were measured. The cutting order was varied, allowing us to determine the changes in the limits that occurred when each structure was cut alone and the amount of motion of the joint that was required for each structure to become taut and to limit additional motion when the other supporting structures had been removed. Removal of only the posterior cruciate ligament increased the limit for posterior tibial translation, with no change in the limits for tibial rotation or varus and valgus angulation. The additional posterior translation was least at full extension and increased progressively, reaching 11.4 millimeters at 90 degrees of flexion. The progressive increase in posterior translation with flexion was apparently due to slackening of the posterior portion of the capsule, as the translation nearly doubled when the posterolateral structures subsequently were removed. Removal of only the posterolateral extra-articular restraints increased the amount of external rotation and varus angulation. The average increase in external rotation depended on the angle of flexion; it was greatest at 30 degrees of flexion and decreased with additional flexion. At 90 degrees of flexion, the intact posterior cruciate ligament limited the increase in external rotation to only 5.3 degrees, less than one-half of the 13.0-degree increase that occurred at 30 degrees of flexion. Subsequent removal of the posterior cruciate ligament markedly increased external rotation at 90 degrees of flexion, resulting in a total increase of 20.9 degrees. The limit for varus angulation was normal as long as the lateral collateral ligament was intact. When the lateral collateral ligament was cut, the limit increased 4.5 degrees (approximately 4.5 millimeters of additional joint opening) when the knee was partially flexed (to 15 degrees).(ABSTRACT TRUNCATED AT 400 WORDS)     

Functional medical ligament balancing in total knee arthroplasty

Function of the anterior and posterior oblique portions of the medial collateral ligament and the posterior capsule in flexion and extension was evaluated in eight knee specimens after posterior cruciate retaining total knee arthroplasty. The posterior oblique portion of the medial collateral ligament was released subperiosteally in four specimens, and the anterior portion was released in four specimens. The medial posterior capsule was released in each group, then the remaining portion of the medial collateral ligament was released. Release of the posterior oblique portion produced moderate laxity at full extension and at 30 degrees flexion, and posterior capsule release produced additional laxity in full extension. Release of the anterior portion produced major laxity at 60 degrees and 90 degrees flexion. Complete medial collateral ligament release increased laxity significantly in both groups in flexion and extension. This rationale was tested in a clinical study of 82 knees (76 patients) in which 62 (76%) required medial collateral ligament release to correct varus deformity during posterior cruciate retaining total knee arthroplasty. Twenty-two knees (35.5%) were tight medially in extension only, and were corrected by releasing the posterior oblique portion. Thirty-one knees (50%) were tight medially in flexion only, and were corrected by releasing the anterior portion. Nine knees (14.5%) were tight medially in flexion and extension and required complete medial collateral ligament release, but three knees (4.8%) remained tight in extension and required medial posterior capsule release to correct flexion contracture and medial ligament contracture. Seventeen (27%) had partial posterior cruciate ligament release to correct excessive rollback of the femoral component on the tibial surface.     

The effect of section of the medial collateral ligament on force generated in the anterior cruciate ligament

Ten fresh-frozen knees from cadavera were instrumented with a specially designed transducer that measures the force that the anterior cruciate ligament exerts on its tibial attachment. Specimens were subjected to tibial torque, anterior tibial force, and varus-valgus bending moment at selected angles of flexion of the knee ranging from 0 to 45 degrees. Section of the medial collateral ligament did not change the force generated in the anterior cruciate ligament by applied varus moment. When valgus moment was applied to the knee, force increased dramatically after section of the medial collateral ligament; the increases were greatest at 45 degrees of flexion. Section of the medial collateral ligament had variable effects on the force generated in the anterior cruciate ligament during internal rotation but dramatically increased that generated during external rotation; these increases were greatest at 45 degrees. Section of the medial collateral ligament increased mean total torsional laxity by 13 degrees (at 0 degrees of flexion) to 20 degrees (at 45 degrees of flexion). Application of an anteriorly directed force to the tibia of an intact knee increased the force generated in the anterior cruciate ligament; this increase was maximum near the mid-part of the range of tibial rotation and minimum with external rotation of the tibia. Section of the medial collateral ligament did not change the force generated in the anterior cruciate ligament by straight anterior tibial pull near the mid-part of the range of tibial rotation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Instability of cadaver knees after transection of capsule and ligaments

The importance of the medial collateral ligament and the anterior cruciate ligament of the knee in relation to valgus and varus instability was investigated. Mobility patterns were drawn from ten osteoligamentous knee preparations after successive transections of the structures. Cutting the entire collateral medial ligament caused only slight valgus instability, even when the knee was flexed. Further transection of the anterior cruciate ligament increased the instability considerably, but the knee remained stable in extension. The valgus instability after the transections was maximal at about 60 degrees of flexion.     

Effects of posterior cruciate ligament resection on the tibiofemoral joint gap

The effect of posterior cruciate ligament resection on the tibiofemoral joint gap was analyzed in 30 patients with varus osteoarthritis of thee knee who underwent total knee replacement. The medial soft tissue was released and the bone cut was made without preserving the bone segment of the tibia to which the posterior cruciate ligament was attached. Then the medial and lateral joint gaps in full extension and 90 degrees flexion were measured before and after the posterior cruciate ligament was resected using a tensioning device. After the resection, the flexion gap significantly increased in the medial and the lateral sides (4.8 +/- 0.4 and 4.5 +/- 0.4 mm, respectively, mean +/- standard error) compared with those seen in the extension gap (0.9 +/- 0.2 and 0.8 +/- 0.2 mm). There was no significant difference between the changes in the medial and lateral gaps. The mean value of the flexion gap was 2 mm smaller than the extension gap before the resection and 1.7 mm larger after the sacrifice. Overall, posterior cruciate ligament resection resulted in an increase in the flexion gap and made space for approximately 3-mm thicker polyethylene. The flexion gap can be controlled selectively with posterior cruciate ligament release.     

Effect of tibial slope or posterior cruciate ligament release on knee kinematics

An experimental study using fresh human cadaver knees was designed to evaluate the effect of partial posterior cruciate ligament release or posterior tibial slope on knee kinematics after total knee arthroplasty. Varus and valgus laxity, rotational laxity, anteroposterior laxity, femoral rollback, and maximum flexion angle were evaluated in a normal knee, an ideal total knee arthroplasty, and a total knee arthroplasty in which the ligaments were made to be too tight in flexion. The total knee arthroplasty specimens then were subjected to either partial posterior cruciate ligament release or increased posterior tibial slope, and the tests were repeated. Posterior tibial slope increased varus and valgus laxity, anteroposterior laxity, and rotational laxity in the knee that had flexion tightness. Posterior cruciate ligament release corrected only anteroposterior tightness, and had no effect on the abnormal collateral ligament tightness. Increased posterior tibial slope significantly improved varus and valgus laxity and rotational laxity in the knee that was tight in flexion more than with release of the posterior cruciate ligament. Therefore increasing posterior tibial slope is preferable for a knee that is tight in flexion during total knee arthroplasty.     

Selective ligament release in total knee arthroplasty of the knee in valgus.

An approach to the valgus knee based on anatomic function of ligaments in flexion and extension consistently yields a knee that is balanced in flexion and extension when the implants have been positioned correctly. Two hundred thirty-one knees had a valgus deformity (range, 12 degrees-45 degrees) and were corrected with valgus alignment to 5 degrees by resecting the intact joint surfaces to match implant thickness. Femoral joint surfaces were aligned in 5 degrees valgus to the long axis of the femur and parallel to the epicondylar axis of the femur in flexion and extension. The tibial surfaces were aligned perpendicular to the long axis of the tibia. For knees that were tight in flexion and extension, the lateral collateral ligament and popliteus tendon were released. Those knees that remained tight only in extension had release of the iliotibial band. Posterior capsular release was done only when necessary for persistent lateral ligament tightness. Neither ligament advancement procedures nor varus or valgus stabilized implant systems were needed to achieve stability with this procedure. The knees with ligament releases all fell within a range of 4 degrees to 7 degrees mean varus and valgus laxity, and were not significantly different from one another. No cases of clinical instability occurred, and joint stability did not deteriorate with time.     

Soft tissue release in total knee arthroplasty. Cadaver study using knees without deformities

Soft tissue releases are performed to correct fixed deformities in total knee arthroplasty. The goal of this in vitro study was to investigate the relationship between the individual steps in a medial (eight anatomic specimen knees) or lateral (four anatomic specimen knees) soft tissue release sequence, the resulting change in the medial and lateral tibiofemoral gaps, and the change in coronal angulation caused by 10 Nm varus and valgus moments in extension and 90 degrees flexion. An optical encoder was used to measure the coronal angulation. The tibiofemoral gaps were measured with calipers with the knee distracted by a 53-N load. In the medial release sequence, a significant increase in coronal angulation and medial gap occurred after the release of the anteromedial sleeve 8 cm from the medial joint line. In the lateral release sequence, there was a significant increase in the coronal angle and lateral gap after the lateral collateral ligament and popliteus tendon were released from the femur. Release of the posterior cruciate ligament led to a significant increase in angle and gap in medial and lateral release sequences. These results are specific for the particular release sequences studied, with release of the posterior cruciate being the final step in each sequence.     

Quantification of effect of sequential posteromedial release on flexion and extension gaps: a computer-assisted study in cadaveric knees

A novel sequence of posteromedial release consistent with surgical technique of total knee arthroplasty was performed in 15 cadaveric knees. Medial and lateral flexion and extension gaps were measured after each step of the release using a computed tomography-free computer navigation system. A spring-loaded distractor and a manual distractor were used to distract the joint. Posterior cruciate ligament release increased flexion more than extension gap; deep medial collateral ligament release had a negligible effect; semimembranosus release increased the flexion gap medially; reduction osteotomy increased medial flexion and extension gaps; superficial medial collateral ligament release increased medial joint gap more in flexion and caused severe instability. This sequence of release led to incremental and differential effects on flexion-extension gaps and has implications in correcting varus deformity.     

The effect of medial release on flexion and extension gaps in cadaveric knees: implications for soft-tissue balancing in total knee arthroplasty

This cadaver study examined the effects of medial structure release for varus deformity correction during total knee arthroplasty. Twelve specimens were used to investigate the amount of varus correction achieved with sequential release of medial structures. Varus-valgus and internal-external rotation angles were measured using the Isotrack II motion tracking system. Each release sequence was tested at full extension and 45 degrees and 90 degrees of flexion to compare any differences obtained in the joint gaps. After release of the posteromedial capsule oblique ligament complex, superficial medial collateral ligament (MCL), pes anserinus, and semimembranosus tendons, valgus rotation increased to 6.9 degrees in full extension and 13.4 degrees in 90 degrees of flexion. The largest increase (3.2 degrees) in valgus rotation occurred after the superficial MCL was released. Initial release of the superficial MCL led to a more gradual correction with release of subsequent structures. Changes seen in 90 degrees flexion were significantly greater than those in full extension. While the cadaveric model is limited by the lack of deformity in the specimens, the data provide several clinically relevant conclusions. In many cases requiring major medial release for severe varus deformity, potential flexion-extension differences in the resulting tibiofemoral gaps may require new consideration. These data may help explain the heightened interest in and variety of approaches for addressing femoral component rotation and issues of flexion stability since a significantly larger correction is obtained in flexion. Minimal changes in internal-external rotation of the tibia occurred until both the pes anserinus and semimembranosus tendons were released (4 degrees of external rotation).     

Coordination of the anterior and posterior cruciate ligaments in constraining the varus–valgus and internal–external rotatory instability of the knee

 Tension along both cruciate ligaments was measured simultaneously under various loading conditions, and the interaction of these ligaments as constraints on knee instability was analyzed. Six fresh cadaveric knees were used. The attachments for both cruciate ligaments were detached from the femur and reattached to their original positions using metal plates equipped with 12 strain gauges. Each knee was moved under various loading conditions, and changes in tension along the cruciate ligaments were recorded simultaneously using the output of the strain gauges. Under varus torque, tension along the anterior cruciate ligament increased near full extension whereas that along the posterior cruciate ligament increased near 90° of flexion. Similar results were obtained under valgus torque. Under internal rotatory torque, a pattern similar to that under varus torque was also observed. Under external rotatory torque, no remarkable changes in tension were observed along either cruciate ligament. Thus, we conclude that both the anterior cruciate ligament and the posterior cruciate ligament cooperate to control varus–valgus and internal rotatory instabilities of the knee, and that the constraining function is transferred from the anterior cruciate ligament to the posterior cruciate ligament as the knee joint is flexed. Received: July 30, 2001 / Accepted: January 7, 2002     

No need for routine closed suction drainage in elective arthroplasty of the hipA prospective randomized trial in 104 operations

The importance of the medial collateral ligament and the anterior cruciate ligament of the knee in relation to valgus and varus instability was investigated. Mobility patterns were drawn from ten osteoligamentous knee preparations after successive transections of the structures. Cutting the entire collateral medial ligament caused only slight valgus instability, even when the knee was flexed. Further transection of the anterior cruciate ligament increased the instability considerably, but the knee remained stable in extension. The valgus instability after the transections was maximal at about 60° of flexion.     

Instability of cadaver knees after transection of capsule and ligaments

The importance of the medial collateral ligament and the anterior cruciate ligament of the knee in relation to valgus and varus instability was investigated. Mobility patterns were drawn from ten osteoligamentous knee preparations after successive transections of the structures. Cutting the entire collateral medial ligament caused only slight valgus instability, even when the knee was flexed. Further transection of the anterior cruciate ligament increased the instability considerably, but the knee remained stable in extension. The valgus instability after the transections was maximal at about 60° of flexion.     

Effects of combined knee loadings on posterior cruciate ligament force generation

Resultant forces in the posterior cruciate ligament were measured under paired combinations of posterior tibial force, internal and external tibial torque, and varus and valgus moment. The force generated in the ligament from a straight 100 N posterior tibial force was highly sensitive to the angle of knee flexion. For example, at 90 of flexion the mean resultant force in the posterior cruciate ligament was 112% of the applied posterior tibial force, whereas at 0°, only 16% of the applied posterior force was measured in the ligament. When the tibia was preloaded by 10 Nm of external torque, only 9–13% of the 100 N posterior tibial force was transmitted to the posterior cruciate ligament at flexion angles less than 60° at 90° of flexion, 61% was carried by the ligament. This “off-loading” of the posterior cruciate ligament also occurred when the tibia was preloaded by 10 Nm or internal torque, but only at knee flexion angles between 20 and 40°. The addition of 10 Nm of valgus moment to a knee loaded by a 100 N posterior tibial force increased the mean force in the posterior cruciate ligament at all flexion angles except hyperextension: this represents a common and potentially dangerous loading combination. The addition of 10 Nm of varus moment to a knee loaded by a 100 N posterior tibial force increased the mean force in the posterior cruciate ligament at all flexion angles except hyperextension; this represents a common and potentially dangerous loading combination. The addition of 10 Nm of varus moment to a knee loaded by a 100 N posterior tibial force decreased the mean force in the ligament between 10 and 70° of flexion. External tibial torque (alone or combined with varus or valgus moment) was not an important loading mechanism in the posterior cruciate ligament. The application of internal torque plus varus moment at 90° of flexion produced the greatest posterior cruciate ligament forces in our study and represented the only potential injury mechanism that did not involve posterior tibial force.     

Strain gauge analysis of knee ligaments

Mercury strain gauges were sutured onto the tibial collateral anterior and posterior cruciate ligaments to quantitatively determine the relative strain or deformation of each of these ligaments as a function of joint position. The results were obtained on 5 amputation specimens by subjecting them to flexion, extension, rotation, valgus--varus and anteroposterior forces. The tibial collateral ligament is most lax in full flexion and stretches with extension, valgus and external rotation. The cruciate ligaments are most lax at 35 degrees flexion and stretch with both flexion and extension. Internal rotation and varus stretch and anterior cruciate ligament. These principles allow us a better understanding of injury patterns. The most advantageous position for immobilization following acute injuries or reconstructions is better understood knowing that minimal tension on ligamentous fibers occurs as follows: Anterior cruciate, 35 degrees; Posterior cruciate, 35 degrees; Tibial collateral ligament, 45--90 degrees (or as much flexion as the patient will tolerate).     

The role of the posterolateral and cruciate ligaments in the stability of the human knee. A biomechanical study

Injury to the posterolateral structures of the knee, including the popliteus tendon and arcuate complex, frequently results in poorly understood patterns of instability. To evaluate the static function of these tissues, we used a mechanical testing apparatus that allowed five degrees of freedom to test seventeen specimens from human cadavera at angles of flexion that ranged from zero to 90 degrees. Selective section of the lateral collateral ligament, popliteus-arcuate (deep) ligament complex, anterior cruciate ligament, and posterior cruciate ligament was performed. At all angles of flexion, the lateral collateral ligament and deep ligament complex functioned together as the principal structures preventing varus rotation and external rotation of the tibia, while the posterior cruciate ligament was the principal structure preventing posterior translation. However, at angles of flexion of 30 degrees or less, the amount of posterior translation after section of only the lateral collateral ligament and the deep structures was similar to that noted after isolated section of the posterior cruciate ligament. Isolated section of the posterior cruciate ligament did not affect varus or external rotation of the tibia at any position of flexion of the knee. When the posterior cruciate ligament was sectioned after the lateral collateral ligament and deep ligament complex had been cut, a large increase in posterior translation and varus rotation resulted at all angles of flexion. In addition, at angles of flexion of more than 30 degrees, external rotation of the tibia also increased. The application of internal tibial torque resulted in no increase in tibial rotation after isolated section of the anterior cruciate ligament or combined section of the lateral collateral ligament and deep ligament complex. However, combined section of all three structures increased internal rotation at 30 and 60 degrees of flexion. The increases in external rotation that were produced by section of the lateral collateral ligament and deep ligament complex were not changed by the addition of the section of the anterior cruciate ligament.     

The posterior cruciate ligament and rotatory knee instability. An experimental study

The importance of the posterior cruciate ligament in relation to valgus-varus and axial rotatory stability in the knee joint was investigated. Mobility patterns were drawn from 20 osteoligamentous preparations after successive transection of the posterior cruciate ligament (PCL), the medial and lateral collateral ligaments, and the posterior joint capsule. The knee joint remained grossly stable after isolated transection of the PCL, and further cutting of either one of the collateral ligaments or of the posterior capsule yielded no greater instability than one should expect from isolated cutting of each of these structures. The posterior cruciate ligament was the stabilizing factor in flexion and external rotation after injury to the lateral collateral ligament and the posterolateral capsule, and it restricted internal rotation after cutting of the medial cruciate ligament and the posteromedial capsule. Valgus instability was markedly increased during the whole range of movement when PCL was included in injury to the medial compartment ligaments, and when included in a lateral compartment injury a further varus instability was found, though only in the flexed or semiflexed knee. No hyperextension could be demonstrated after these injuries.