Quadriceps/anterior cruciate graft interaction. An in vitro study of joint kinematics and anterior cruciate ligament graft tension.

The Oxford Rig, a device that simulates active knee extension during stance, was used to study the effects of quadriceps force on AP tibial displacement and axial tibial rotation in vitro. Human anatomic specimen knees were tested with the anterior cruciate ligament (ACL) intact, sectioned, and reconstructed. Patellar tendon grafts used in the ACL-reconstructed state were attached distally to a load cell, allowing direct measurement of graft tension. Both ACL status and quadriceps force had significant effects on anterior tibial displacement, limits of AP displacement, axial tibial rotation, and graft tension, as shown by analysis of variance. Anterior cruciate ligament sectioning led to anterior tibial displacement in the absence of quadriceps force, whereas ACL reconstruction led to posterior tibial displacement. In the ACL-intact, quadriceps-stabilized state, anterior displacement of the tibia was observed between 95 degrees flexion and full extension, with a maximum displacement (3.5 +/- 0.2 mm) between 30 degrees and 45 degrees flexion. After ACL sectioning, anterior tibial displacement resulting from quadriceps force was accentuated relative to the intact state by as much as 4.5 mm +/- 0.9 mm at 20 degrees and 25 degrees flexion. Anterior tibial displacement in the ACL-intact and reconstructed specimens was similar when quadriceps force was present. In the quadriceps-stabilized state, graft tension increased between 5 degrees and 80 degrees flexion. The maximum increase in graft tension due to quadriceps force was at 35 degrees flexion.

Effects of fibrin sealant on incorporation of autograft and xenograft tendons within bone tunnels. A preliminary study.

The anterior and posterior tibialis tendons in both hindlimbs of six adult dogs were rerouted through extraarticular bone holes created in the distal tibial metaphysis. Xenograft tendons of comparable dimensions were used in an additional six dogs. Fibrin Sealant System (FSS) was applied to the bone tendon interface in the right legs, whereas the left legs were used as controls. The animals were sacrificed at 5, 9, and 28 days. Coronal sections of the distal tibias were studied histologically and microangiographically. The autogenous tendons appeared to incorporate by means of fibrous ingrowth, whereas spicules of new bone in direct opposition to the xenografts were observed at 28 days. FSS promoted organization and maturation of fibrous connective tissue surrounding both implants at early sacrifice but did not appreciably alter incorporation at 28 days.

Tibial torque generation in a flexed weight-bearing stance.

Internal and external torque generated about the long axis of the lower extremity was measured in 18 male subjects who were instructed to twist with maximal effort against a fixed footplate containing an instrumented torque cell. Mean torque values ranged from 30 to 71 newton meters (Nm) depending upon the test conditions. Torques recorded during the flexed single-leg stance were 19% to 49% higher than those measured while seated. Values at 45 degrees of knee flexion were 11% to 16% greater than those at 20 degrees. Torques generated while wearing a ski boot were 8% to 11% greater than those recorded in an athletic shoe. When movement of the pelvis and upper torso was allowed, torque values were 17% to 49% higher than those recorded when the hips and shoulders were restrained which allowed only lower leg musculature to act in an isolated fashion. There were no differences between internal versus external generated torques when the hips and torso were restrained. When the hips and shoulders were unrestrained, internal torque was 12% greater than external torque. There were no strong correlations between generated torque and body weight or height. These generated torque values suggest that if ski bindings are set to American Society for Testing and Materials (ASTM) standards for twist-release torque, then upper torso and pelvic movement in conjunction with tensed knee musculature (i.e., a "locked knee") may be necessary to accomplish binding release. Use of the lower leg musculature alone (i.e., ankle twist) may not generate sufficient torque for release.

The role of the meniscus in the anterior-posterior stability of the loaded anterior cruciate-deficient knee. Effects of partial versus total excision.

The effects of progressive removal of the menisci on the anterior-posterior force-versus-displacement response of the anterior cruciate-deficient knee were studied in fresh cadaver specimens at 20 degrees of flexion without and with tibial-femoral contact force (joint load). In the absence of joint load, removal of the medial meniscus increased total anterior-posterior laxity measured at 200 newtons of applied tibial force by 10 per cent, and subsequent lateral meniscectomy produced an additional 10 per cent increase. When a bucket-handle tear of the medial meniscus was removed, the application of joint load caused the tibia to displace (subluxate) forward on the femur, thereby changing the balance condition of the knee. Subsequent removal of the remainder of the medial meniscus and complete lateral meniscectomy both produced additional smaller anterior tibial subluxations. Changes in total anterior-posterior laxity due to progressive meniscectomy in the loaded knee were dependent on both the amount of applied anterior-posterior force and the level of compressive force. At 200 newtons of anterior-posterior tibial force, increases in laxity in the loaded knee due to progressive meniscal removal were not significantly different than those recorded in the unloaded condition. At applied forces of fifty newtons or less, the laxities for loaded specimens were always significantly less than those for unloaded specimens at comparable stages of meniscal removal. Bilateral meniscectomy had no significant effect on the posterior response curve, as posterior tibial translation was effectively checked by the intact posterior cruciate ligament.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of joint load on the stiffness and laxity of ligament-deficient knees. An in vitro study of the anterior cruciate and medial collateral ligaments.

We measured the effects of serial section of the medial collateral ligament and anterior cruciate ligament and of the anterior cruciate ligament and medial collateral ligament on anterior-posterior force-versus-displacement and tibial torque-versus-rotation response curves for seven fresh frozen cadaver knees at zero and 20 degrees of flexion before and after application of as much as 925 newtons of compressive load on the tibiofemoral joint. Section of the anterior cruciate ligament always increased anterior laxity in an unloaded specimen; joint load reduced this increase by a greater amount at zero degrees than at 20 degrees of flexion. Joint load was more effective in limiting anterior laxity in anterior cruciate-deficient specimens at low levels of applied anterior force; at higher levels of applied force, the effects of joint congruency were overcome and ligament restraints came into play. Section of the medial collateral ligament increased anterior laxity in an unloaded knee only for specimens in which the anterior cruciate ligament had been previously sectioned; joint load eliminated this increase at full extension but did not do so at 20 degrees of flexion. The medial collateral ligament was the more important of the two ligaments in controlling torsional laxity. Secondary section of either ligament (the other ligament having been sectioned first) produced a greater increase in laxity than did primary section of that ligament in an intact knee. Increases in torsional laxity due to primary section of either ligament were unaffected by the application of joint load. Joint load reduced increases in laxity that were due to secondary section of the medial collateral ligament.

The effects of exercise, ice, and ultrasonography on torsional laxity of the knee.

Changes in torsional knee laxity, after subjects ran 3.5 miles during a 30-minute period, were studied in 13 subjects. The effects of ice and ultrasonographic treatments on these laxity changes were then investigated. Knee laxity was determined by measuring torque versus rotation responses of the tibia at 90 degrees of knee flexion. Total rotational laxity of the tibia was tabulated at +/- 10 newton-meters of applied torque. There were significant increases in postexercise laxities over preexercise levels for internal and external tibial rotation. Postexercise laxity changes followed a uniform time course of recovery. The maximum postexercise laxity represented a mean increase of 14% over pre-exercise levels, with a mean recovery time of 52.4 minutes and a standard deviation of 17.8 minutes. The application of ten-minute treatments of either ice or ultrasonography significantly reduced postexercise recovery times, to 20.0 +/- 4.6 SD and 20.9 +/- 6.4 SD, respectively. A common clinical assumption, that cold and heat have opposite effects on knee laxity, was found invalid. In the authors' study, ice and ultrasonography had equivalent effects in accelerating the return to pre-exercise laxities. No laxity changes were observed in unexercised subjects, with either ice or ultrasonographic treatments. The time course of laxity recovery and the subsequent effects of heat and ice are important clinically. Immediately after injury, both knees are more lax than normal, and after approximately one hour, recovery to pre-exercise laxity levels will be complete for the uninjured leg. Ice (or ultrasonography) will shorten this time to 20 minutes. If these recovery time courses are recognized and taken into account, a more accurate diagnosis can be made during this "golden opportunity" period before pain and swelling ensue. The fact that ice and ultrasonography have identical effects on the time course of recovery in the exercised knee raises new questions and suggests additional areas for future work in the recently developing field of sports medicine biomechanics.

The effect of tibia-foot rotatory position on the anterior drawer test.

The effect of the position of the foot and tibia on the anteroposterior drawer test was quantified using a clinical testing device. Maximum laxity occurred at 15 degrees of external rotation of the foot. Extreme rotation of the foot and tibia resulted in reductions of anteroposterior laxity of 63% for internal rotation and 50% for external rotation. The ratio of foot rotation to tibia rotation was approximately 2:1. Medial meniscectomy alone did not result in increased anteroposterior laxities when compared with normal knees. Medial meniscectomy with an unrepaired anterior cruciate ligament tear resulted in increased anteroposterior laxities at 15 degrees, 30 degrees, and maximum external rotation of the foot.

In vivo rotatory knee stability. Ligamentous and muscular contributions.

Active and passive components of torsional stability of the knee were measured with an instrumented clinical knee-testing apparatus. Torque-versus-rotation response curves were recorded in the non-weight-bearing condition with muscles relaxed for twenty normal subjects who were tested at 20 and 90 degrees of knee flexion with the hips flexed and extended. At applied torque levels as high as +/-10 newton-meters, tibial rotation averaged approximately one-half the foot rotation. The mean algebraic right-left rotation difference for the group was nearly zero; however, sizable standard deviations for this difference indicated considerable right-left variations between individuals in the test group. Maximum isometrically generated tibial torques were measured by asking the subjects to twist with an explosive effort against a locked torque-cell. No significant differences in generated torque were measured between preferred and non-preferred lower limbs, with only one minor exception. Subjects generally were able to generate greater internal torque than external torque. When the foot was locked in a position of internal or external rotation, an individual was able to generate increased tibial torque in the direction that would tend to return the foot to the neutral position. Flexion of the knee from 20 to 90 degrees increased externally generated torque, while internal torque was affected to a lesser degree. Flexion of the hip had little effect on generated torque. Six cadaver knees without menisci that were tested to failure in external rotation showed torque levels for ligament failure to be similar in magnitude to the maximum generated isometric torque that acts to protect the knee ligaments.

In vivo stability testing of post-meniscectomy knees.

Post-meniscectomy knees examined with an instrumented clinical testing device reveal that meniscectomy alone does not cause a measurable degree of instability. If meniscectomy causes a minor degree of instability, the degree is within the right-left variation for a normal population. Medical meniscectomy in combination with a torn anterior cruciate results in an increased anterior-posterior instability at 20 degrees knee flexion. The device used in this study was more reliable in diagnosing increased anterior-posterior instability secondary to anterior-cruciate tear than was a clinical examiner.