Lower limb alignment and foot angle are related to stance phase knee adduction in normal subjects: a critical analysis of the reliability of gait analysis data.

Anatomic and mechanical factors that affect loading in the knee joint can contribute to pathologic changes seen at the knee in degenerative joint disease and should be considered in treatment planning. The objectives of this study were to quantify the relationships between the alignment of the bones of the lower extremity, foot progression angle, and knee adduction moment, and to determine the reliability of our gait measurements. Gait analysis and complete radiographic evaluation of the lower extremity were performed on 11 healthy subjects. The gait measurements were recorded with an optoelectronic digitizer and a multi-component force plate. The subjects who had radiographic measurements indicative of varus alignment of the lower extremity had statistically higher peaks in knee adduction moment in early stance. Conversely, those with valgus alignment of the lower extremity had statistically lower peaks in knee adduction moment in early stance. The subjects who had a large toe-out angle and low ankle inversion moment peaks in late stance had significantly lower peaks in knee adduction moment in late stance. These significant (low to moderate) correlations suggest that the limbs with more valgus alignment and those with a toe-out gait exhibited a reduced peak adduction moment at the knee. To verify the reproducibility of the data, gait analysis testing was performed on each lower limb on 2 separate days for each subject. Analysis of variance showed that there was no significant difference between test limbs or test days for each subject. Our results suggest that the alignment of the lower limb and the foot progression angle, which can be readily measured in a clinical setting, can serve as predictors of knee joint loading in healthy individuals. These findings may have important implications for both surgical and nonsurgical treatment of abnormalities of the knee joint.

Mechanical properties of primate vascularized vs. nonvascularized patellar tendon grafts; changes over time.

Mechanical properties of patellar tendon autografts used to replace the anterior cruciate ligament (ACL) in the cynomolgus monkey were measured at four time periods up to 1 year. The ACL was replaced in each knee with the medial half of the patellar tendon: as a vascularized graft (VG) on one side and as a nonvascularized or free graft (FG) on the other. Postoperative care consisted of 4 weeks of cast immobilization at 30 degrees flexion followed by unrestricted activity in a large cage. Both grafts showed low stiffness and maximum force at 7 weeks (24% and 16% of ACL control values, respectively), increasing to 57% of control ACL stiffness and 39% of control maximum force by 1 year. Corresponding material properties, modulus and maximum stress, also increased over time, but at 1 year were only 34% and 26% of ACL values, respectively. The results indicate that retaining vascularity does not prevent significant reduction in graft properties that occur postoperatively, nor does it accelerate the return in strength and stiffness. Tissue stiffness, which returns earlier than maximum force and joint anteroposterior (AP) force displacement data, should be routinely reported in any healing study. Finally, in studies of this kind, the large variation in the results makes sampling only one or two animals from each time period unreliable.

The correlation between anterior-posterior translation and cross-sectional area of anterior cruciate ligament reconstructions.

Total anterior-posterior translation is commonly used to assess the integrity of the cruciate ligaments and the success of reconstructive surgery. The purpose of this study was to determine, after surgical reconstruction of the anterior cruciate ligament with a biological graft, if total anterior-posterior translation correlated with graft length, cross-sectional area, or mechanical properties. These factors were investigated by analyzing data from three previous studies. These studies involved replacement of the anterior cruciate ligament in cynomolgus monkeys and goats, with free and vascularized patellar tendon autografts and both patellar tendon and anterior cruciate ligament allografts. Data were available at time periods of 6 and 12 months after surgery. We found statistically significant inverse correlations between the amount of anterior-posterior translation and cross-sectional area of a graft at the time of sacrifice. The Pearson correlation coefficients ranged from -0.966 (p < 0.002) to -0.830 (p < 0.05). We hypothesize that these correlations result from the following mechanism: the increased anterior translation reflects a slack graft; a slack graft is stress shielded by other structures about the knee; the reduced in vivo stresses on the graft modulate cellular metabolism in a way that over time produces a small cross-sectional area.

Effects of gamma irradiation on the initial mechanical and material properties of goat bone-patellar tendon-bone allografts.

The effects of 60Co gamma irradiation on the initial mechanical properties of the composite bone-patellar tendon-bone unit (CU) and the tendon midsubstance (TM) were studied. Frozen specimens were exposed to either 2 or 3 Mrad of gamma irradiation. Paired frozen specimens served as intraanimal controls. Treatment effects on the CU were assessed using four mechanical parameters. Effects on the TM were assessed using four material parameters measured using an optical surface-strain analysis system. The maximum force and strain energy to maximum force of the composite unit were significantly reduced 27% and 40%, respectively, after 3 Mrad of irradiation (p less than .05). Mechanical properties of the CU were not significantly altered, however, following 2 Mrad of irradiation. Based on individual paired contrasts between treatment and control, significant differences were also found in the material properties of the tendon midsubstance. The maximum stress, maximum strain, and strain energy density to maximum stress were significantly reduced following 3 Mrad, but not 2 Mrad, of irradiation. The results provide important "time zero" material property data, which will be useful for later anterior cruciate ligament reconstruction studies using irradiated allograft patellar tendons in the goat model and other animal models as well.

The effects of graft width and graft laxity on the outcome of caprine anterior cruciate ligament reconstruction.

We studied how initial graft size and initial graft laxity affected the biomechanics of anterior cruciate ligament (ACL) reconstruction at six months. Sixteen goats had bilateral reconstructions staged eight weeks apart. Autografts 4 and 7 mm wide were taken from the central patellar tendon (PT). Lax grafts were created by adding 4 mm slack to the graft before fixing. We reconstructed each joint using a combination of width and laxity treatments. Both factors were changed for the contralateral joint and all combinations appeared with equal frequency. At six months we measured the joint extension limit, anterior-posterior (AP) translation, and osteoarthritic changes. The grafts were then tested to failure to determine their mechanical properties. After six months the difference in initial treatments had disappeared: there was no difference in graft cross-section due to the different initial widths and there was no difference in joint AP translation due to the initial graft laxity. We did observe that wide grafts were associated with a block to extension, decreased joint AP translation, and increased articular cartilage damage and osteophyte formation. While AP translation was reduced, it was correlated with decreased extension, possibly indicating an increase in scar tissue formation rather than a more functional graft. Neither graft width nor graft laxity produced differences in any graft mechanical properties. This suggests that the use of larger grafts to prevent increased AP translation has undesirable complications. Ultimately, we conclude that neither of these surgical treatments strongly affects the biomechanical result of caprine ACL reconstruction.

Biomechanics of fascia lata ligament replacements: early postoperative changes in the goat.

Mechanical properties of fascia lata autografts used to replace the anterior cruciate ligament (ACL) in the goat were measured at 0, 2, 4, and 8 weeks after surgery. The ACL was replaced in the right knee of 50 animals divided equally into two groups according to graft fixation technique: (a) two smooth staples at each end, with the tissue pulled back toward the joint over the first staple and (b) reinforced fixation with a spiked bushing placed through the tissue and a 3-cm-long flat polypropylene braid sutured to each end of the graft. Eleven unoperated contralateral knees were tested as controls. All statistically significant effects of the reinforced versus staple fixation were observed at 0 weeks, with the reinforced group showing less anteroposterior (AP) translation of the joint and greater maximum force and stiffness of the femur-graft-tibia units. The reinforced group had increased AP translation and decreased strength and stiffness by 2 weeks after surgery. Increased AP translation resulted primarily from increases in the low-stiffness region of the force-displacement curve (primary AP translation) and to a lesser extent from increased translation in the high-stiffness region (secondary anterior translation). Failures at 0 weeks with the reinforced fixation occurred at the bushing or end of the reinforcing braid, while all but one of the later failures occurred in the tissue mid-substance. In the staple group, maximum force was greater at 8 weeks than at 0 weeks, as the failure locations changed from the fixation to the tissue mid-substance.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of tibial attachment location on the healing of the anterior cruciate ligament freeze model.

We studied the healing response of a devitalized anterior cruciate ligament to a treatment of initial anterior-posterior joint translation in goats. Devitalization and devascularization were achieved by five successive freeze-thaw cycles. Anterior-posterior translation was surgically altered by an osteotomy of the tibial attachment of the devitalized ligament and its reattachment either in the anatomical position or in a position 5 mm posterior. Six weeks after the first surgery, the same procedure was performed on the contralateral limb, except that the ligament was reattached in the alternate position. Six months after the initial surgery, femur-anterior cruciate ligament-tibia specimens were tested to determine their structural and mechanical material properties. Anatomic ligament placement resulted in reduced anterior-posterior translation (p < 0.05) and greater anterior joint stiffness (p < 0.05). Maximum load (p < 0.05) and ligament stiffness (p < 0.01) also were greater for the anatomically placed anterior cruciate ligaments. The maximum load for anatomically placed ligaments averaged 1.625 +/- 211 N (SEM). The strength of the posteriorly placed anterior cruciate ligament, 895 +/- 164 N was similar to results of historical anterior cruciate autograft reconstructions. Ligament failure occurred near the tibial insertion in the posteriorly placed ligaments more often than in the anatomically placed ligaments (four of five times compared with one of five times). Ligament failure near the tibial insertion occurred with lower mean maximum load than failure at the midsubstance or by bone avulsion (796 compared with 1.592 N: p < 0.05). These data support the hypothesis that ligament laxity is important to the healing and remodeling of anterior cruciate ligament grafts.

Assessment of sports participation levels following knee injuries.

Although there are many published instruments designed to determine outcome following the treatment of knee injuries, only a few incorporate specific assessments of sports activity level and participation into the evaluation. This article reviews 3 of the most commonly used sports activity outcome instruments: the scales devised by Tegner and Lysholm, the Hospital for Special Surgery and the International Knee Documentation Committee. Problems and potential study biases that can arise with improper questionnaire design and data reduction techniques are reviewed, and recommendations are made to correct these problems. The problems identified include: (i) the failure to precisely define sports activity levels according to a specific sport and intensity of participation; (ii) the failure to sort populations according to overall intensity of athletic participation both before and after treatment; (iii) the failure to detect and sort from the population patients who return to sports and experience significant symptoms; (iv) the combination of work and sports activities into the same scale; and (v) the failure to detect alterations in sports participation caused by changes in lifestyle or non-knee-related factors. We have developed a sports assessment instrument, the Cincinnati Sports Activity Scale (CSAS). The methodology used to create this scale, its use in the assessment of return to or change in sports activities, and the assessment of specific functions of daily and sports activities, are briefly reviewed. The CSAS is based on 2 criteria: (i) the frequency of participation; and (ii) the general types of forces experienced by the lower extremity during the sport. The assessment of change in sports activities accounts for modifications in lifestyle and can also detect patients who have returned to sports but are experiencing significant symptoms and problems. Examples of data reduction and reporting are provided to represent practical situations from a prior investigation.

Functional disability in the anterior cruciate insufficient knee syndrome. Review of knee rating systems and projected risk factors in determining treatment.

The complete tear of the anterior cruciate ligament initiates the clinical syndrome represented by continued functional disability. The precise degree of functional disability is highly debated. Agreement is elusive due to the lack of uniform and scientific methodology. An historical review and analysis of functional and subjective rating systems is reported, and the strengths of previous systems are identified. A subjective and functional rating system is proposed in which 6 activity levels are related to pain, swelling, giving-way and overall activity. This is important because of the marked dependence of the functional disability of the anterior cruciate insufficient knee on the activity level of the patient. Thus, activity levels must be rigorously and comprehensively defined. In addition, we propose the utilisation of a risk factor checklist, based on the statistics drawn from our previous articles, to identify those patients at significant risk for future joint arthrosis. Risk factors are grouped under the categories of activity level, symptoms, clinical laxity, meniscal damage, lower limb alignment, tibiofemoral crepitus, patellofemoral factors, rehabilitation and patient compliance. Thirdly, we examine controversial aspects of the anterior cruciate ligament syndrome existing in the literature today and demonstrate why contrasting opinions are not mutually exclusive. Finally we propose our treatment guidelines for management of the acute and chronic anterior cruciate ligament insufficient knee.

Advances in the understanding of knee ligament injury, repair, and rehabilitation.

Knee injuries continue to present a complex set of clinical problems. The answers to these problems have recently been redefined by the application of sophisticated biomechanical research methods to the study of knee ligaments and joint function. This manuscript reviews contributions which our laboratory has made to the understanding of knee injury, highlighting those research findings which form the basis for our clinical treatment of knee ligament injuries. High strain-rate techniques for studying knee ligament failure have replaced the previous low strain-rate methods and distinguish the failure mechanism of ligaments from that of bone. Ligament function is now further defined by measuring the restraining force provided by specific ligaments, adding to the information provided by cutting studies. The development of the 6-degrees-of-freedom concept and the instrumented kinematic chain now permit precise analysis of joint position, motion, and laxity. Biomechanical evaluation of intra-articular anterior cruciate ligament substitution has emphasized the importance of selection of a high-strength graft material, meticulous surgical technique with attention to graft vascularity, precise location of graft fixation sites, judicious adjustment of graft tension, post-operative protection during tissue remodelling, and a carefully conceived rehabilitation program. Newer biomechanical research methods have provided a sound scientific foundation on which to base clinical decisions concerning the care of knee ligament injuries.

The effect of an extra-articular procedure on allograft reconstructions for chronic ruptures of the anterior cruciate ligament.

A study was performed on the effect of the addition of an extra-articular procedure involving tenodesis of the iliotibial band to a reconstruction with a bone-patellar ligament-bone allograft for the treatment of chronic rupture of the anterior cruciate ligament. One hundred and four patients were divided into two groups for comparison: Group 1 (sixty-four patients) was treated with only an intra-articular replacement with an allograft and Group 2 (forty patients), with both an intra-articular replacement with an allograft and the extra-articular procedure. Preoperatively, there were no statistically significant differences between the two groups in terms of twenty variables, including body weight, level of activity, anterior-posterior displacements, number of previous operations, and duration of follow-up. All of the patients returned for follow-up evaluation twenty-three to fifty-four months (mean, thirty-five months) postoperatively. All were treated with the same postoperative program of immediate motion of the knee and rehabilitation. The results were evaluated with the use of a comprehensive subjective and objective system that rated the twenty factors. Both procedures proved to be effective in decreasing functional limitations and symptoms and in improving the level of sports activity and the over-all scores. The results in Group 2 were significantly better than those in Group 1, as measured with tests done with the KT-1000 arthrometer (p less than 0.01) and with regard to the level of sports activity (p less than 0.05) and the over-all scores (p less than 0.01). There was no postoperative difference between the two groups in terms of the results on pivot-shift or isokinetic testing, patellofemoral crepitus, functional limitations, or symptoms. The program of rehabilitation effectively restored 0 to 135 degrees of motion to all but four knees, which lacked 5 degrees of extension at the most recent follow-up. The over-all rate of failure for both groups was 11 per cent. However, the rate of failure was 16 per cent (ten of sixty-four knees) in Group 1 and only 3 per cent (one of forty knees) in Group 2. This difference was significant (p less than 0.05). The extra-articular procedure appeared to provide support to the healing intra-articular allograft by reducing deleterious forces and tibial displacements, and to restore the secondary restraints provided by the lateral iliotibial band. The results suggest that the combination of the procedures is of value in young, athletically active people who have chronic rupture of the anterior cruciate ligament.(ABSTRACT TRUNCATED AT 400 WORDS)

The effect of a ligament-augmentation device on allograft reconstructions for chronic ruptures of the anterior cruciate ligament.

A prospective study was performed to determine the effect of a combination of a ligament-augmentation device with a bone-patellar ligament-bone allograft for the treatment of chronic rupture of the anterior cruciate ligament. One hundred and fifteen knees in 110 patients were divided into two groups. Group BLB consisted of sixty-six knees in sixty-four patients who were managed with a bone-patellar ligament-bone allograft only, and Group BLB-LAD consisted of forty-nine knees in forty-six patients who were managed with both the allograft and a ligament-augmentation device. Preoperatively, there were no statistically significant differences between the two groups with regard to fifteen variables. All patients were managed with the same postoperative program of immediate motion and rehabilitation of the knee. All patients returned for evaluation at a mean of thirty-four months (range, twenty-three to fifty-three months) postoperatively. The results were evaluated with a comprehensive rating system that assessed twenty factors. Both of these procedures significantly decreased functional limitations and symptoms and improved the level of sports activity and the over-all score. However, the use of the ligament-augmentation device did not improve the efficacy of the reconstruction with regard to any of the individual variables that were assessed or in terms of the over-all score. All but one of the patients regained an arc of 0 to 135 degrees of motion. Although the augmentation device reduced anterior-posterior displacement effectively for the first twenty weeks postoperatively (p less than 0.05), there was no difference between the groups in terms of the percentage of knees that had abnormal displacement at the latest follow-up. A new classification system was developed to determine rates of failure. The over-all rate of failure was 28 per cent (thirty-two) of the 115 knees: 29 per cent (nineteen) of the sixty-six knees in Group BLB and 27 per cent (thirteen) of the forty-nine knees in Group BLB-LAD. The difference between the two groups was not statistically significant. The addition of the ligament-augmentation device did not improve the results of allograft reconstruction in the treatment of chronic rupture of the anterior cruciate ligament. The use of either an allograft alone or an allograft combined with a ligament-augmentation device did not reduce the amount of anterior-posterior displacement satisfactorily in all of the knees.

The strength of the anterior cruciate ligament in humans and Rhesus monkeys.

The mechanical properties of anterior cruciate bone-ligament-bone specimens from humans and rhesus monkeys were determined in tension to failure under high strain-rate conditions. The age range of the human specimens was from sixteen to eighty-six years. The values fro human specimens obtained from young adults with regard to elastic modulus, ultimate tensile stress, and strain energy to failure were approximately two to three times those for specimens from humans in the sixth decade and older. The major mode of failure was ligament disruption in the specimens from young adult humans and avulsion of bone beneath the ligament insertion site in the specimens from older humans. The difference in mode of failure correlated with histological observations of decreased bone mass at the site of ligament attachment in the specimens from older humans. Rhesus monkey specimens had higher values for elastic modulus, failure stress, and strain energy. Significant reductions in strength and stiffness properties of ligament units were shown to occur with advancing age to a greater degree than expected. All experiments in which specimens from older human cadavera are used should be interpreted with caution when the results are applied to mechanisms of ligament failure for younger or athletic individuals.

Cruciate ligament prosthesis: strength, creep, and fatigue properties.

The mechanical properties of the Richards polyethylene ligament implant were studied and compared with the strength of human cruciate ligament preparations. The implant yields and plastically deforms at a force of 420 newtons (ninety-four pounds) and approximately 10 per cent elongation when tested at a strain rate of 100 per second. This is one-fourth the average tensile strength of the human anterior curciate ligament preparations. When tested at a strain rate of 1 per cent per second the implant's yield-point force was lowered by 15 per cent. The implant exhibits considerable viscoelastic behavior and will progressively elongate under repetitive loads when insufficient time is allowed for it to return to its original length. In bending, the implant did not fail after eighty million stress reversals (forty million revolutions) when tested while immersed in saline solution at body temperature. The tests indicate that the tensile strength of the implant is low in comparison with both the strength of human preparations and estimates of actual in vivo functional loads. We conclude that caution is required in the use of this implant.

Reconstruction of the anterior cruciate ligament with human allograft. Comparison of early and later results.

Sixty-eight patients who had had reconstruction of an acute rupture of the anterior cruciate ligament with either a fascia lata or a bone-patellar ligament-bone allograft returned for two follow-up evaluations, at two to four years and at five to nine years (mean, seven years) postoperatively. The early (two to four-year) results in these patients have been reported previously. The mean time between the early and the later evaluation was fifty-six months (range, twenty to ninety-six months). At the early evaluation, fifty-two (78 per cent) of the sixty-seven patients who were tested with an arthrometer at eighty-nine newtons had less than three millimeters of increased anterior-posterior displacement compared with that of the contralateral limb; at the later evaluation, fifty-four (79 per cent) of the sixty-eight patients had this finding (p=0/97). With use of arthrometric and pivot-shift-test data, forty-eight (75 per cent) of sixty-four grafts were classified as functional at the early evaluation and fourteen (22 per cent), as partially functional; two (3 per cent) had failed. (Four grafts could not be classified because of incomplete data.) At the later examination, fifty (74 per cent) of the sixty-eight grafts were functional, thirteen (19 per cent) were partially functional, and five (7 per cent) had failed. At the early evaluation, sixty-two (93 percent) of sixty-seven patients had no palpable patellofemoral crepitus and five (7 per cent) had moderate crepitus. At the later evaluation, fifty-one (75 per cent) of the sixty-eight patients continued to have no crepitus, sixteen (24 per cent) had moderate crepitus, and on (1 per cent) had severe crepitus. An increase in crepitus between the early and the later evaluation was found in twelve (19 per cent) of the sixty-two patients who had normal crepitus at the early evaluation. With the numbers available, no factor, such as the type of graft, associated ligamentous injury, or meniscal repair, correlated significantly with the amount of patellofemoral crepitus at either follow-up evaluation. At the early evaluation, the result was rated excellent or good for thirty-eight (60 per cent) of sixty-three patients, fair for twenty-one (33 per cent), and poor for four (6 per cent). (The result could not be rated for four patients because of incomplete data.) At the later evaluation, the result was rated excellent or good for forty-five (66 per cent) of the sixty-eight patients, fair for eighteen (26 per cent), and poor for five (7 per cent). For nine patients (13 per cent), the over-all rating deteriorated from excellent or good at the early evaluation to fair or poor at the later examination. For six patients (9 per cent), the rating improved from fair at the early evaluation to excellent or good at the later evaluation. With the numbers available, we could detect no significant decrease in anterior-posterior displacement of the knee, patellofemoral crepitus, the pain or the jumping score, or the over-all knee rating over the time-period studied. While we currently recommend arthroscopically assisted reconstruction with a bone-patellar ligament-bone autogenous graft as the first choice for an acute rupture of the anterior cruciate ligament, our study shows that favorable results can be obtained with allografts and justifies their use when the surgeon and patient choose this approach.

Revision anterior cruciate surgery with use of bone-patellar tendon-bone autogenous grafts.

BACKGROUND: A prospective study was done to determine the functional results, patient satisfaction, and graft failure rate after fifty-seven consecutive revision replacements of the anterior cruciate ligament with use of a bone-patellar tendon-bone autogenous graft. METHODS: Fifty-four patients (fifty-five operations) were followed in this study. Concurrent operative procedures were performed during the revision procedure in thirty-seven knees (67%). These procedures included repair of a meniscal tear in twenty knees (36%) and reconstruction of deficient posterolateral or medial ligament structures in seventeen knees (31%). Nine knees (16%) had a high tibial osteotomy to correct varus malalignment before the revision operation. The results were evaluated with the Cincinnati Knee Rating System. RESULTS: There were significant improvements in the scores for pain (p < 0.0001), activities of daily living (p < 0.01), sports participation (p < 0.001), patient satisfaction (p < 0.0001), and overall rating of the knee (p < 0.0001). Thirty-three (60%) of the replaced ligaments were functional, nine (16%) were partially functional, and thirteen (24%) had failed. CONCLUSIONS: Many knees (93%) had compounding problems, including articular cartilage damage, prior meniscectomy, loss of secondary ligament restraints, varus malalignment, and concomitant ligament replacement or meniscal repair. Therefore, the results were generally less favorable than those following primary operations. The rate of graft failure was three times higher than our previously reported failure rate after primary replacements of the anterior cruciate ligament with a bone-patellar tendon-bone autogenous graft. Even so, symptoms and functional limitations with regard to daily and sports activities were found to have decreased and patient satisfaction improved. We advocate correction of varus malalignment prior to anterior cruciate procedures. Associated posterolateral ligament deficiencies should be surgically corrected during anterior cruciate procedures to prevent excessive loading on the graft from abnormal lateral tibiofemoral joint opening. Meniscal tears, including complex tears that extend into the avascular zone, can be concurrently repaired successfully during the revision.

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)

Bone-patellar ligament-bone and fascia lata allografts for reconstruction of the anterior cruciate ligament.

A prospective study was performed of the first forty-seven consecutive patients who had repair of a ruptured anterior cruciate ligament and replacement with an allograft. Patients who had a rupture of another ligament were excluded, to provide a homogeneous group. Twenty-two patients received a fascia lata allograft and twenty-five patients received a bone-patellar ligament-bone allograft. All patients were enrolled in an exercise program to facilitate motion of the knee immediately after the operation, and all patients returned for postoperative evaluation (mean, forty months; range, twenty-five to sixty-seven months). The results were based on a comprehensive subjective and objective rating system, which assessed twenty factors. On testing with the KT-1000 arthrometer, 69 per cent of the patients had less than three millimeters of increased anterior-posterior displacement of the knee that had been operated on compared with the contralateral knee, 26 per cent had three to five millimeters, and 5 per cent had more than five millimeters. The knees that had a bone-patellar ligament-bone allograft had significantly lower values for anterior-posterior displacement than did those that had a fascia lata allograft (p less than 0.05). Just one patient, the only one in whom the fascia lata graft failed, had giving-way. There were no infections, and there was no evidence of rejection of the allograft or documented transmission of disease at the time of writing. A strict rating system was used. Eighteen patients (38 per cent) had an excellent result, twenty-four (51 per cent) had a good result, and five (11 per cent) had a fair or poor result. Motion of the knee immediately postoperatively was not deleterious to the allograft, and, because limitations of motion were identified and treated in the early postoperative period, full motion (0 to 135 degrees) was restored in all knees.

Use of allografts after failed treatment of rupture of the anterior cruciate ligament.

A prospective study was done of the use of allogeneic tissue to reconstruct the anterior cruciate ligament in knees in which an intra-articular or an extra-articular operation had failed. Sixty-six consecutive patients (sixty-six knees) had such an operation with use of bone-patellar ligament-bone allografts; all but one returned for follow-up evaluation twenty-three to seventy-eight months (mean, forty-two months) after the operation. A total of 235 previous operations had been performed in these sixty-six knees, including eighty-one procedures for rupture of the anterior cruciate ligament. The results of the allograft procedure were evaluated with a subjective and objective system that rated twenty factors. The anterior-posterior displacement was substantially improved in most of the patients. According to data derived from arthrometric studies and pivot-shift tests of the fifty-seven patients who were so evaluated and in whom the condition was unilateral, 53 per cent (thirty) of the reconstructed ligaments were determined to be functional; 21 per cent (twelve ligaments), partially functional; and 26 per cent (fifteen ligaments), a failure. When we calculated the rate of failure by including ten failures that had occurred within two years after the operation with the fifteen that occurred in patients who had been followed for at least two years, the over-all rate of failure was 33 per cent (twenty-five of seventy-five operations). There was significant improvement in the subjective ratings of functional limitations and symptoms (p < 0.01) and in the over-all rating score (p < 0.0001). However, there was a significant difference between the scores of the patients in whom the surfaces of the articular cartilage had appeared normal at the index operation and those of the patients in whom there had been noteworthy fissuring and fragmentation or exposure of subchondral bone. After the program of rehabilitation, which included immediate motion of the knee, a range of motion of 0 to 135 degrees was restored in all but five knees, four of which lacked only 5 degrees of this extent of flexion or extension. The results demonstrate that bone-patellar ligament-bone allografts may be used when proper autogenous tissues are not available and that symptoms and abnormal displacement were reduced in most of our patients.

Biomechanics of the knee-extension exercise. Effect of cutting the anterior cruciate ligament.

UNLABELLED: We conducted this study to determine the effective moment arm of the knee extensor mechanism and the conditions under which the anterior cruciate ligament is loaded during knee-extension exercises. The moment arm was calculated from measurement of the quadriceps force required to extend the knee with and without resistive weights placed at the foot, the leg weight, and the location of its center of gravity. Changes in three-dimensional joint motion after the anterior cruciate ligament was removed were considered to be an indication that the ligament was loaded. The quadriceps force rose during the initial phase of knee extension and remained nearly constant at an average value of 177 newtons between 50 and 15 degrees. With extension past 15 degrees it rose rapidly, reaching an average of 350 newtons at zero degrees of extension, and continued to increase with hyperextension. The addition of thirty-one newtons (seven pounds) at the foot approximately doubled the quadriceps force that was required to extend the knee. The effective moment arm of the extensor mechanism increased with knee extension, peaked at approximately 20 degrees, and rapidly decreased with further extension. No change was found in the quadriceps force or its effective moment arm when the anterior cruciate ligament was sectioned except in hyperextension, where the quadriceps force decreased in two of five specimens. There was, however, an increased anterior tibial displacement in the range of 30 degrees to full extension, suggesting that the anterior cruciate ligament is loaded in that flexion arc. CLINICAL RELEVANCE: This study demonstrates that very large quadriceps forces are required to accomplish the last 15 degrees of extension during leg-raising exercises, typically twice those required to reach 30 degrees of flexion. The large forces that are required to obtain full extension explain why an extensor lag occurs with quadriceps weakness even though a full passive range of motion is possible. Since thirty-one newtons (seven pounds) of resistive weight added at the foot approximately doubles the quadriceps forces required to extend the leg alone, using such weights can produce very large quadriceps forces and concurrent patellofemoral and tibiofemoral contact forces. Because the quadriceps force increases little as the leg is extended from 50 to 15 degrees, in patients with patellofemoral chondroses for whom a full range of joint motion is not desired, quadriceps exercises can be limited to the amount of extension without decreasing quadriceps force.(ABSTRACT TRUNCATED AT 400 WORDS)