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Background: Anterior cruciate ligament (ACL) injuries can be treated with or without ACL reconstruction (ACLR), and more high-quality studies evaluating outcomes after the different treatment courses are needed. The purpose of the present study was to describe and compare 5-year clinical, functional, and physical activity outcomes for patients who followed our decision-making and treatment algorithm and chose (1) early ACLR with preoperative and postoperative rehabilitation, (2) delayed ACLR with preoperative and postoperative rehabilitation, or (3) progressive rehabilitation alone. Early ACLR was defined as that performed ≤6 months after the preoperative rehabilitation program, and late ACLR was defined as that performed >6 months after the preoperative rehabilitation program., Methods: We included 276 patients from a prospective cohort study. The patients had been active in jumping, pivoting, and cutting sports before the injury and sustained a unilateral ACL injury without substantial concomitant knee injuries. The patients chose their treatment through a shared decision-making process. At 5 years, we assessed the International Knee Documentation Committee Subjective Knee Form (IKDC-SKF), Knee injury and Osteoarthritis Outcome Score (KOOS), Marx Activity Rating Scale, sports participation, quadriceps muscle strength, single-legged hop performance, and new ipsilateral and contralateral knee injuries., Results: The 5-year follow-up rate was 80%. At 5 years, 64% of the patients had undergone early ACLR, 11% had undergone delayed ACLR, and 25% had had progressive rehabilitation alone. Understandably, the choices that participants made differed by age, concomitant injuries, symptoms, and predominantly level-I versus level-II preinjury activity level. There were no significant differences in any clinical, functional, or physical activity outcomes among the treatment groups. Across treatment groups, 95% to 100% of patients were still active in some kind of sports and 65% to 88% had IKDC-SKF and KOOS scores above the threshold for a patient acceptable symptom state., Conclusions: Patients with ACL injury who were active in jumping, pivoting, and cutting sports prior to injury; who had no substantial concomitant knee injuries; and who followed our decision-making and treatment algorithm had good 5-year knee function and high sport participation rates. Three of 4 patients had undergone ACLR within 5 years. There were no significant differences in any outcomes among patients treated with early ACLR, delayed ACLR, or progressive rehabilitation alone., Level of Evidence: Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence., Competing Interests: Disclosure: The Delaware-Oslo ACL Cohort study is funded by the National Institutes of Health, grant R37HD37985. The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJS/G500)., (Copyright © 2021 by The Journal of Bone and Joint Surgery, Incorporated.)

Background: The anterolateral ligament (ALL) has been proposed as a primary restraint for knee rotational stability. However, the data remain inconclusive. The purpose of this study was to determine the effect of the ALL and the iliotibial band (ITB) on knee rotational stability., Methods: A 6-degrees-of-freedom robotic simulator was used to test 14 fresh-frozen cadaveric knee specimens. There were 4 testing conditions: intact, anterior cruciate ligament (ACL)-sectioned, ACL and ALL or ITB-sectioned (determined at random), and ACL and both ALL and ITB-sectioned. Lateral, central, and medial tibiofemoral compartment translations and internal tibial rotations were measured under 100-N anterior drawer (Lachman), 5-Nm internal rotation torque, and 2 pivot-shift simulations (Pivot Shift 1 was 5 Nm of internal rotation torque, and Pivot Shift 2 was 1 Nm of internal rotation torque). Statistical equivalence within 2 mm and 2° was defined as p < 0.05., Results: Sectioning the ACL alone produced increased pivot shift and Lachman compartment translations (p > 0.05). Further sectioning of either the ALL or the ITB separately produced minor added increases in pivot-shift compartment translations and tibial internal rotations (<2 mm or <3°) in the ACL-deficient knee. Sectioning both the ALL and ITB produced increases not equivalent to the ACL-deficient knee in pivot-shift lateral compartment translations (4.4 mm; 95% confidence interval [CI], 2.7 to 6.1 mm [p = 0.99] for Pivot Shift 1 and 4.3 mm; 95% CI, 2.6 to 6.0 mm [p = 0.99] for Pivot Shift 2), with 10 of 14 knees being converted to a corresponding Grade-3 pivot-shift (>20 mm of lateral translation). Increases in internal rotation after ALL and ITB sectioning occurred at 25°, 60°, and 90° (p = 0.99 for all) and ranged from 1° to 12°, with 21% of the knees having 8° to 12° increases., Conclusions: With ACL sectioning, a positive pivot-shift anterior subluxation occurred even with intact ALL and ITB structures, which indicates that the latter are not primary restraints but function together as anterolateral secondary restraints. With ACL deficiency, concurrent loss of the ALL and ITB resulted in conversion in a majority of knees (71%) to a Grade-3 pivot-shift subluxation, along with major increases of internal rotation in select knees., Clinical Relevance: With ACL rupture, major increases in rotational instability are not adequately resisted by native ALL or ITB structures. Therefore, anatomic ALL or ITB surgical reconstruction would not block a positive pivot shift. The potential protective effects of ACL graft-unloading from these structures require further study.

Background: The incidence of anterior cruciate ligament (ACL) injuries is two to eightfold greater in female compared with male athletes. Anatomic, hormonal, and neuromuscular factors have been associated with this disparity. This study compared gene expression and structural features in ruptured but otherwise normal ACL tissue from young female and male athletes., Methods: A biopsy sample of ruptured ACL tissue (which would normally have been discarded) was obtained intraoperatively from seven female and seven male athletes (12.7 to 22.6 years old). Each sample was divided into portions for histological and gene expression analyses. Specimens for gene analysis were frozen and ground, and RNA was extracted and purified. Microarray analysis was performed on RNA isolated from four female and three male study participants (13.9 to 18.5 years old) who had a noncontact injury. Genes with an expression level that differed significantly between these female and male athletes were grouped into functionally associated networks with use of IPA software (Qiagen). Three genes of interest were chosen for further validation by RT-qPCR (reverse transcription-quantitative polymerase chain reaction) analysis of the samples from all fourteen patients. Several statistical methods were used to examine sex-related differences., Results: Microarray analysis of the RNA isolated from the ruptured ACL tissue from the female and male athletes identified thirty-two genes with significant differential expression. Fourteen of these genes were not linked to the X or Y chromosome. IPA analysis grouped these genes into pathways involving development and function of skeletal muscle and growth, maintenance, and proliferation of cells. RT-qPCR confirmed significant differences in expression of three selected genes: ACAN (aggrecan) and FMOD (fibromodulin) were upregulated in female compared with male study participants, and WISP2 (WNT1 inducible signaling pathway protein 2) was downregulated. No morphological differences among the ruptured tissue from the various participants were apparent on histological examination., Conclusions: The genes identified in this study as differing distinctly according to sex produce major molecules in the ACL extracellular matrix. Significant upregulation of ACAN and FMOD (which regulate the matrix) and downregulation of WISP2 (which is involved in collagen turnover and production) may account for the weaker ACLs in female compared with male individuals., (Copyright © 2015 by The Journal of Bone and Joint Surgery, Incorporated.)

Background: The purpose of the present retrospective study was to evaluate the influence of posterolateral corner reconstruction on anterior cruciate ligament (ACL) reconstruction in terms of anterior laxity and clinical outcomes. We hypothesized that the effects of combined ACL and posterolateral corner reconstruction would be less satisfactory than those of isolated ACL reconstruction in terms of anterior laxity and clinical outcomes., Methods: We retrospectively studied sixty-nine patients who underwent ACL reconstruction from February 2001 to December 2005. Forty-six patients underwent isolated ACL reconstruction (Group I), and twenty-three patients underwent combined ACL and posterolateral corner reconstruction (Group II). Clinical outcomes were determined from data obtained before surgery and at the time of the twenty-four-month follow-up examination., Results: Postoperatively, the mean side-to-side difference (and standard deviation) in anterior tibial translation, measured with a KT2000 arthrometer, was greater for Group I (2.2 ± 1.0 mm) than for Group II (1.6 ± 0.8 mm) (p = 0.031). Seven knees (15.2%) in Group I and two knees (8.7%) in Group II had grade-1 anterior translation. The mean Lysholm score was 93.2 in Group I and 90.1 in Group II (p = 0.392). Thirty-eight knees (82.6%) in Group I and twenty knees (87.0%) in Group II were classified as normal or nearly normal according to the International Knee Documentation Committee scoring system (p = 0.882)., Conclusions: On the basis of the evaluation of ligamentous laxity with use of the KT2000 arthrometer, we observed that combined ACL and posterolateral corner reconstruction allows less anterior translation than isolated ACL reconstruction. However, we could not identify significant differences between the two groups in terms of functional outcomes.

Background: Currently, a suitable and reliable noninvasive method to evaluate rotational stability in vivo in anterior cruciate ligament-deficient knees, particularly during sports movements, does not exist. We speculated that if there is a rotational instability, the patient would avoid reaching a high pivoting moment during pivoting activities as a defense mechanism, and that the ground reaction moment, as registered by dynamometric platforms, would be reduced. On the basis of this hypothesis, we developed a study using kinetic analysis to evaluate rotational stability under dynamic loading., Methods: Thirty recreationally active athletes, including fifteen healthy subjects and fifteen with an anterior cruciate ligament-deficient knee, were recruited for this study. Patients performed jumping with pivoting with internal tibial rotation and external tibial rotation on the dynamometric platform with both the healthy and the injured limb. The quantitative results were graphically plotted, and the following parameters were evaluated: loading moment, pivoting moment, torque amplitude, loading slope, pivoting slope, percentage of pivoting with load, loading impulse, pivoting impulse, and maximum body rotation angle., Results: There were no significant differences between the dominant and nondominant knees in the control group during the jumping with pivoting and external tibial rotation test with regard to the pivoting moment (p = 0.805), pivoting slope (p = 0.716), pivoting impulse 2 (p = 0.858), and pivoting impulse 3 (p = 0.873). In patients with a chronic tear of the anterior cruciate ligament, there was a significant decrease of the pivoting moment (p = 0.02), pivoting slope (p = 0.005), pivoting impulse 2 (p = 0.006), and pivoting impulse 3 (p = 0.035) during the jumping with pivoting and external tibial rotation test in the anterior cruciate ligament-deficient knee compared with the healthy, contralateral knee., Conclusion: Kinetic analysis with use of a dynamic platform can objectively detect alterations of rotational stability in anterior cruciate ligament-deficient knees, which may allow this to be a useful research tool for evaluating treatment strategies in patients with anterior cruciate ligament injuries.

Background: Successful anterior cruciate ligament reconstruction with use of soft-tissue grafts requires healing between tendon and bone. Little is known about the effect of mechanical load on the cellular and molecular cascade of tendon-to-bone healing. Understanding these mechanical influences has critical implications for postoperative rehabilitation following anterior cruciate ligament reconstruction. The purpose of this study was to test the hypothesis that, compared with perioperative immobilization, short-duration low-magnitude cyclic axial loading would result in impaired tendon-to-bone healing after anterior cruciate ligament reconstruction in a rat model., Methods: Fifty-two male Sprague-Dawley rats underwent anterior cruciate ligament reconstruction with use of a flexor digitorum longus autograft. The patellar tendon, capsule, and ligamentous structures were circumferentially released, and an external fixator parallel to the anterior cruciate ligament graft was placed across the knee. Mechanical loading, consisting of cyclic displacement of the femur and tibia constrained to axial translation parallel to the graft, was applied daily. The rats were randomly assigned to immobilization or daily loading, for fourteen or twenty-eight days. Biomechanical, micro-computed tomographic, and histomorphometric analysis was performed on the bone-tendon-bone complexes., Results: The load measured across the knees during cyclic displacement increased over time (p < 0.05). Load-to-failure testing of the isolated femur-anterior cruciate ligament graft-tibia specimens revealed no significant differences between groups at two or four weeks. By two weeks postoperatively, a greater number of ED1+ inflammatory macrophages (phagocytic cells involved in the initial injury response) were seen at the tendon-bone interface after loading in the cyclically loaded group than in the immobilized group (p = 0.01). Compared with the baseline values, the number of trabeculae was significantly lower after loading for four weeks (p = 0.02)., Conclusions: Short-duration low-magnitude cyclic axial loading of the anterior cruciate ligament graft in the postoperative period is not detrimental to the strength of the healing tendon-bone interface but appears to be associated with greater inflammation and less bone formation in the tunnel in this rat model.

Background: While the Lachman and pivot shift tests have been used clinically for decades to assess the anterior cruciate ligament, the relationship between the two has undergone limited experimental study. The goal of this study was to evaluate biomechanical relationships between the Lachman and pivot shift tests in anterior cruciate ligament-deficient and reconstructed knees., Methods: Knee kinematics during simulated pivot-shift testing and anteroposterior knee laxities were measured in seventeen knees in the intact condition, in the anterior cruciate ligament-deficient condition, and after anterior cruciate ligament reconstruction. Pivot shift magnitude was plotted against laxity for all knees with the grafts unfixed (the cruciate ligament-deficient condition). The grafts were then tensioned to match the laxities of the intact knees, and the change in pivot shift magnitude was plotted versus the change in laxity for all knees. In a separate series of tests for individual specimens, pivot shift magnitude was plotted versus laxity for each knee by incrementally loosening the anterior cruciate ligament graft., Results: Linear correlations between pivot shift magnitude and absolute laxity for anterior cruciate ligament-deficient knees were weak. When the unfixed grafts were tensioned to match anteroposterior laxities of the intact knees, changes in pivot shift were better correlated with corresponding changes in anteroposterior laxity (r(2) = 0.53 for tibial rotation and 0.73 for lateral tibial plateau displacement). When graft fixation was progressively loosened for each reconstructed knee, pivot shift magnitude increased linearly from the laxity of the intact knee up to an end point of the linear range, at which point the slope decreased abruptly. Between this end point and the anterior cruciate ligament-deficient condition, further increases in pivot shift were relatively small., Conclusions: Our findings suggest that the magnitude of laxity of an injured knee, when considered alone, may not accurately predict the magnitude of the pivot shift, but the difference in laxity between the injured knee and the normal knee (the injured-normal difference) could be a good clinical predictor of the injured-normal difference in the pivot shift. We demonstrated that an insufficiently tensioned anterior cruciate ligament graft could substantially reduce anterior laxity, while leaving the pivot shift evaluation virtually unchanged.

Background: Mechanical instability, neurosensory deficits, and/or modified coactivation strategies following anterior cruciate ligament injury and surgery might compromise the ability of the knee extensors to exert a precise force during isokinetic knee extension with maximal effort. The purpose of this study was to examine the effects of an anterior cruciate ligament deficiency and reconstruction on knee extensor torque-time curve smoothness and to elucidate its association with hamstring (antagonist) activation and physical performance., Methods: Thirteen subjects who had a unilateral deficiency of the anterior cruciate ligament, twenty-five matched subjects with a unilateral reconstructed anterior cruciate ligament, and thirty-three control subjects performed knee extension and flexion repetitions bilaterally with maximal effort at 180 degrees/sec on a Cybex dynamometer. For the subjects with a deficient or a reconstructed anterior cruciate ligament, hamstring activation was measured electromyographically. Physical performance was measured by requiring subjects to perform single-limb timed hopping on the involved limb., Results: In the subjects with a reconstructed or a deficient anterior cruciate ligament, wavelet-derived mean instantaneous frequency of the extensor torque-time curves was significantly (p < 0.001) higher in the involved limb than in the noninvolved limb and the limbs of the control subjects. Furthermore, for the subjects with a reconstructed or deficient anterior cruciate ligament, the mean instantaneous frequency of the extensor torque-time curves was positively associated with the level of hamstring antagonist activity (r = 0.580, p < 0.001) and with hopping performance (b = -0.943, p = 0.019), whereas isokinetic peak torque was not (b = -0.001, p = 0.797)., Conclusions: For individuals who have a deficient or a reconstructed anterior cruciate ligament, an increased frequency content of the knee extensor torque is not, as previously and commonly assumed, a deleterious manifestation of the neuromuscular system. Rather, our results suggest that torque smoothness reduces as hamstring activation increases-a positive neuromuscular adaptation that enhances joint stability and, hence, optimizes physical performance. Wavelet-derived measures of extensor torque smoothness may provide valuable clinical information regarding joint function that conventional isokinetic torque measures cannot.

Measuring knee biomechanics in six degrees of freedom with acceptable accuracy has been proven to be technically challenging. At our bioengineering laboratory, we have employed both an in vitro robotic testing system and an in vivo combined dual fluoroscopic and magnetic resonance imaging technique to analyze the impact of anterior cruciate ligament rupture on the knee joint. When measuring the tibiofemoral kinematics of nine cadavers with the robotic testing system, we found that anterior cruciate ligament deficiency not only altered anterior translation and axial rotation of the tibia, but it also increased the medial translation of the tibia as well. The in vivo dual fluoroscopic imaging analysis of tibiofemoral kinematics in ten anterior cruciate ligament-deficient patients revealed analogous findings: an increased medial translation of the tibia of approximately 1 mm between 15 degrees and 90 degrees of flexion was found in anterior cruciate ligament-deficient knees, in addition to an increased anterior translation (approximately 3 mm) and internal rotation (approximately 2 degrees) of the tibia at low flexion angles. In a subsequent study of tibiofemoral cartilage contact, we found that the cartilage contact points shifted posteriorly--as was expected on the basis of the increased anterior tibial translation--as well as laterally on the surface of the tibial plateau. The data demonstrate how rupture of the anterior cruciate ligament initiates a cascade of events that eventually results in abnormal tibiofemoral cartilage contact in both the anteroposterior and mediolateral directions. If the restoration of normal knee homeostasis is the ultimate goal of ligament reconstruction, the normal function of the anterior cruciate ligament should be restored as closely as possible in all degrees of freedom.

In our research center, we have developed and utilized a novel robotic/universal force-moment sensor testing system to gain quantitative data on multiple-degree-of-freedom kinematics of the knee simultaneously with data on the in situ forces in normal and repaired soft tissues. In particular, we have investigated the complex interaction of the anteromedial and posterolateral bundles of the anterior cruciate ligament as well as several key biomechanical variables in anterior cruciate ligament reconstruction, such as graft selection and femoral tunnel placement (both of which impact knee stability). For example, both the bone-patellar tendon-bone and quadrupled hamstrings tendon autografts restored anterior stability but were insufficient in gaining rotatory stability. In a follow-up study, we have shown that a more laterally placed graft was beneficial and could improve these outcomes. Such findings led to additional investigation in which the biomechanical advantages of double-bundle anterior cruciate ligament reconstruction were demonstrated. However, a more laterally placed autograft at the femoral insertion of the posterolateral bundle also worked well, especially when the knee was nearly at full extension (a position in which the anterior cruciate ligament is needed most). At present, we are moving forward by obtaining in vivo kinematics data and then repeating those kinematics exactly to obtain new data with use of the robotic/universal force-moment sensor testing system in order to gain further insight regarding the function of the anterior cruciate ligament and anterior cruciate ligament replacement grafts in vivo. In parallel, we are developing a mathematical model of the knee and validating the computational model with experimental data. The combined approach will yield new and relevant information, including the stress and strain distribution in the anterior cruciate ligament and anterior cruciate ligament grafts. This will facilitate a better understanding of the function of the anterior cruciate ligament and a scientifically based design of surgical procedures and postoperative rehabilitation protocols that will lead to better patient outcomes.

Osteoarthritis is widely believed to result from local mechanical factors acting within the context of systemic susceptibility. Previous studies have demonstrated that malalignment is a potent predictor of disease progression in patients with osteoarthritis of the knee. Malalignment also mediates the effects of other risk factors, including obesity, quadriceps strength, laxity, and stage of disease. Recent studies have had conflicting results regarding whether malalignment increases the risk of incident tibiofemoral osteoarthritis. While the evidence is conflicting, malalignment appears to play a smaller role in incident disease. Certain local factors within the joint, such as tibiofemoral congruence, integrity of the anterior cruciate ligament, and meniscal degeneration and position, appear to play a role in determining alignment. It is also apparent that malalignment changes with disease progression and is itself possibly influenced by structural changes within the joint.

Background: Some surgeons presently reconstruct both the anteromedial and posterolateral bundles of the anterior cruciate ligament. The purposes of this study were to measure the abilities of single-bundle and anatomic double-bundle reconstructions to restore anteroposterior laxities and rotational kinematics to intact knee levels and to compare graft forces in reconstructed knees with forces in the native anterior cruciate ligament for the same loading conditions., Methods: Native anterior cruciate ligament force and tibial rotations were recorded during passive knee extension tests with and without applied tibial loads. The anteromedial and posterolateral bundles were reconstructed with patellar tendon tissue sized to fit tightly within 7-mm femoral tunnels. Testing was repeated with the anteromedial graft alone (single bundle), tensioned to restore anteroposterior laxity at 30 degrees of flexion, and with double-bundle grafts. For double-bundle reconstructions, the anteromedial graft was first tensioned as above and then the posterolateral graft was tensioned with use of one of four protocols: posterolateral tension = anteromedial tension at 10 degrees (DB1), posterolateral tension = anteromedial tension at 30 degrees (DB2), posterolateral tension = (anteromedial tension + 30 N) at 10 degrees (DB3), and posterolateral tension = (anteromedial tension + 30 N) at 30 degrees (DB4)., Results: The posterolateral graft underwent a greater length change than the anteromedial graft between 0 degrees and 90 degrees . This difference in elongation patterns produced high forces in the posterolateral graft at 0 degrees when both grafts were tensioned and fixed at 30 degrees . The mean laxities for single-bundle reconstructions were within 1.1 mm of those of the intact knee between 0 degrees and 90 degrees ; the mean graft force at 0 degrees was 76 N. The mean laxities for DB4 reconstructions were from 0.9 to 2.8 mm less than those of the intact knee, and the mean graft force at 0 degrees was 264 N. Coupled internal tibial rotations from valgus moment were normal with the single-bundle graft. Internal rotations from tibial torque were approximately 2 degrees to 4 degrees greater than normal with a single-bundle graft. DB3 and DB4 reconstructions overcorrected the coupled tibial rotations from valgus moment and restored tibial rotations from internal torque to normal from 0 degrees to 45 degrees . The graft forces from tibial torque and valgus moment were normal with the single-bundle graft. The mean double-bundle graft forces at 0 degrees were 57 N to 143 N and 34 N to 171 N greater than normal for internal torque and valgus moment, respectively., Conclusions: The single-bundle reconstruction produced graft forces, knee laxities, and coupled tibial rotations that were closest to normal. Adding a posterolateral graft to an anteromedial graft tended to reduce laxities and tibial rotations, but the reductions were accompanied by markedly higher forces in the posterolateral graft near 0 degrees that occasionally caused it to fail during tests with internal torque or anterior tibial force.

Background: One of the principal rationales for performing a double-bundle reconstruction of the anterior cruciate ligament is the suggestion that it may be superior to a single-bundle reconstruction in restoring a normal pivot-shift sign. The purpose of this study was to measure the abilities of single-bundle and anatomic double-bundle reconstructions to restore normal knee kinematics and graft forces during a simulated pivot-shift test., Methods: Graft force and knee kinematics were recorded during a simulated pivot-shift event with and without the anterior cruciate ligament and after graft reconstructions. With a single bundle, the graft was tensioned to restore anterior-posterior laxity at 30 degrees of flexion. With double-bundle reconstructions, the anteromedial graft was first tensioned as above and then the posterolateral graft tension was set with use of one of four protocols: posterolateral tension = anteromedial tension at 10 degrees of flexion (DB1); posterolateral tension = anteromedial tension at 30 degrees (DB2); posterolateral tension = (anteromedial tension + 30 N) at 10 degrees (DB3); and posterolateral tension = (anteromedial tension + 30 N) at 30 degrees (DB4)., Results: A single-bundle reconstruction restored all displacements and rotations during the pivot shift to the intact knee levels. The mean tibial rotations and lateral plateau displacements during the pivot shift with DB2, DB3, and DB4 reconstructions were less than those in the intact knee and also less than those in a single-bundle reconstruction. Before the pivot shift, the mean graft forces with all reconstructions were greater than that of the intact knee; the mean graft forces with the DB3 and DB4 reconstructions were also greater than that of a single-bundle reconstruction. After the pivot shift, the mean graft forces for all reconstructions were less than the levels before the pivot shift with single-bundle forces lower than intact knee levels and DB4 forces higher than intact knee levels., Conclusions: Reduction or elimination of the pivot-shift sign is an important goal for anterior cruciate ligament reconstruction. In our model, the results show that a single-bundle reconstruction was sufficient to restore intact knee kinematics during a simulated pivot-shift event. The higher graft forces with some double-bundle graft-tensioning protocols reduced the coupled rotations and displacements from an applied valgus moment to less than the intact levels. This overcorrection should theoretically make the knee less likely to pivot but could have unknown clinical consequences.

Background: Macrophages accumulate following tendon-to-bone repair and may contribute to the formation of a scar-tissue interface rather than to the reformation of a normal insertion site. We hypothesized that macrophage depletion may lead to improved insertion site regeneration, in a form of "scar-less" healing rather than reactive scar-tissue formation., Methods: One hundred and ninety-two Sprague-Dawley rats underwent anterior cruciate ligament reconstruction with use of a flexor tendon autograft and were divided into a control group (ninety-six rats) and a liposomal clodronate-injected group (ninety-six rats). Clodronate is a bisphosphonate that selectively induces macrophage apoptosis. Animals in the liposomal clodronate group received weekly intraperitoneal injections of liposomal clodronate (1.33 mL/100 g of body weight). Rats were killed at serial time points from three to forty-two days. Immunostaining identified macrophages and transforming growth factor-beta (TGF-beta) at the tendon-bone interface. Fibrous interface width, osteoid formation, and collagen fiber continuity were evaluated with use of histomorphometry. Serial fluorochrome labeling was used to measure mineral apposition rate. Additional rats were killed for biomechanical testing at seven, fourteen, twenty-eight, and forty-two days., Results: Liposomal clodronate significantly decreased macrophages and TGF-beta accumulation at the tendon-bone interface (p < 0.05). Specimens from rats that received liposomal clodronate exhibited a significantly narrower fibrous tissue interface between tendon and bone at all time points compared with specimens from controls (p < 0.05). In specimens from the liposomal clodronate group, healing proceeded at an accelerated rate, characterized by enhanced collagen fiber continuity and a greater degree of interface remodeling between tendon and bone. There were significant increases in osteoid formation (p < 0.05) and mineral apposition rates (p < 0.05) among experimental specimens. At forty-two days, the specimens from the liposomal clodronate group had significantly greater increases than the control specimens with respect to load to failure (mean and standard deviation, 13.5 +/- 4.2 N and 9.7 +/- 3.9 N, respectively; p < 0.05) and stiffness (mean, 11.5 +/- 5.0 N/mm and 7.5 +/- 3.2 N/mm; p < 0.05)., Conclusions: Macrophage depletion following anterior cruciate ligament reconstruction resulted in significantly improved morphologic and biomechanical properties at the healing tendon-bone interface, which we hypothesize are due to diminished macrophage-induced TGF-beta production.

Background: Loss of knee extension has been reported by many authors to be the most common complication following anterior cruciate ligament reconstruction. The objective of this in vitro study was to determine the effect, on loss of knee extension, of the knee flexion angle and the tension of the bone-patellar tendon-bone graft during graft fixation in a reconstruction of an anterior cruciate ligament., Methods: The anterior cruciate ligament was reconstructed with use of tibial and femoral bone tunnels placed in the footprint of the native anterior cruciate ligament in ten cadavers. The graft was secured with an initial tension of either 44 N (10 lb) or 89 N (20 lb) applied with the knee at 0 degrees or 30 degrees of flexion. The knee flexion angle was measured with use of digital images following graft fixation., Results: Tensioning of the graft at 30 degrees of knee flexion was associated with loss of knee extension in this cadaver model. Graft tension did not affect knee extension under the conditions tested., Conclusions: The results suggest that one of the common causes of the loss of full knee extension may be diminished if the graft is secured in full knee extension when the tibial and femoral tunnels are placed in the footprint of the native anterior cruciate ligament. More importantly, even when the femoral and tibial tunnels are placed in the femoral and tibial footprints of the native anterior cruciate ligament, fixing a graft in knee flexion can result in the loss of knee extension.

Background: Quantifying the effects of anterior cruciate ligament deficiency on joint biomechanics is critical in order to better understand the mechanisms of joint degeneration in anterior cruciate ligament-deficient knees and to improve the surgical treatment of anterior cruciate ligament injuries. We investigated the changes in position of the in vivo tibiofemoral articular cartilage contact points in anterior cruciate ligament-deficient and intact contralateral knees with use of a newly developed dual orthogonal fluoroscopic and magnetic resonance imaging technique., Methods: Nine patients with an anterior cruciate ligament rupture in one knee and a normal contralateral knee were recruited. Magnetic resonance images were acquired for both the intact and anterior cruciate ligament-deficient knees to construct computer knee models of the surfaces of the bone and cartilage. Each patient performed a single-leg weight-bearing lunge as images were recorded with use of a dual fluoroscopic system at full extension and at 15 degrees , 30 degrees , 60 degrees , and 90 degrees of flexion. The in vivo knee position at each flexion angle was then reproduced with use of the knee models and fluoroscopic images. The contact points were defined as the centroids of the areas of intersection of the tibial and femoral articular cartilage surfaces., Results: The contact points moved not only in the anteroposterior direction but also in the mediolateral direction in both the anterior cruciate ligament-deficient and intact knees. In the anteroposterior direction, the contact points in the medial compartment of the tibia were more posterior in the anterior cruciate ligament-deficient knees than in the intact knees at full extension and 15 degrees of flexion (p < 0.05). No significant differences were observed with regard to the anteroposterior motion of the contact points in the lateral compartment of the tibia. In the mediolateral direction, there was a significant lateral shift of the contact points in the medial compartment of the tibia toward the medial tibial spine between full extension and 60 degrees of flexion (p < 0.05). The contact points in the lateral compartment of the tibia shifted laterally, away from the lateral tibial spine, at 15 degrees and 30 degrees of flexion (p < 0.05)., Conclusions: In the presence of anterior cruciate ligament injury, the contact points shift both posteriorly and laterally on the surface of the tibial plateau. In the medial compartment, the contact points shift toward the medial tibial spine, a region where degeneration is observed in patients with chronic anterior cruciate ligament injuries.

Background: The use of soft-tissue grafts for anterior cruciate ligament reconstruction delays the healing process. This delay may be due to biochemical and/or biomechanical insults. We hypothesized that the blocking effect of alpha2-macroglobulin on synovial matrix metalloproteinase activity may enhance the healing of tendon graft in a bone tunnel., Methods: The study was performed on twenty-eight healthy, skeletally mature New Zealand White rabbits. Each rabbit underwent bilateral anterior cruciate ligament reconstruction with use of the ipsilateral semitendinosus tendon. Alpha-2-macroglobulin (alpha2-macroglobulin) was injected into the knee joint in one limb, and the contralateral limb served as a control. The rabbits were killed two weeks (fourteen rabbits) or five weeks (fourteen rabbits) after the operative procedures. The presence of matrix metalloproteinases in synovial fluid, and the blocking effect of alpha2-macroglobulin on them, were determined with enzymatic assays. Healing between the tendon and the bone tunnel was assessed morphologically by determining the presence of fibrovascular tissue and collagen fibers. Healing also was assessed quantitatively by measuring the ultimate load to failure of the reconstructed complex., Results: There was an increase in matrix metalloproteinases in the control group; in contrast, there was a decrease in the study group (p < 0.05). In the control specimens, the fibrovascular tissue at the bone-tendon interface had developed into dense connective tissue with poor vascularization. In the treated specimens, the bone tunnel had more areas of denser connective-tissue ingrowth. The interface tissue was more mature and contained numerous perpendicular collagen bundles (Sharpey fibers). The ultimate load to failure was significantly greater in the alpha2-macroglobulin-treated specimens than in the untreated controls at both two and five weeks., Conclusions: The present study demonstrated that alpha2-macroglobulin blockade of matrix metalloproteinases can enhance bone-tendon healing. This effect of alpha2-macroglobulin could occur through its effect solely on collagenase or on a subset of matrix metalloproteinases that are present at the healing interface.

Background: The tensile force applied to an anterior cruciate ligament graft determines the maximal anterior translation; however, it is unknown whether the tensile force is transferred to the intra-articular portion of the graft and whether the intra-articular tension and maximal anterior translation are maintained shortly after ligament reconstruction., Methods: Ten cadaveric knees were reconstructed with a double-looped tendon graft. The graft was looped through a femoral fixation transducer that measured the resultant force on the proximal end of the graft. A pneumatic cylinder applied a tensile force of 110 N to the graft exiting the tibial tunnel with the knee in full extension. The graft was fixed sequentially with four tibial fixation devices (a spiked metal washer, double staples, a bioabsorbable interference screw, and a WasherLoc). Three cyclic loading treatments designed to conservatively load the graft and its fixation were applied., Results: The combined loss in intra-articular graft tension from friction, insertion of the tibial fixation device, and three cyclic loading treatments was 50% for the spiked washer (p = 0.0004), 100% for the double staples (p < 0.0001), 64% for the interference screw (p = 0.0001), and 56% for the WasherLoc (p < 0.0001). The tension loss caused an increase in the maximal anterior translation from that of the intact knee of 2.0 mm for the spiked washer (p = 0.005), 7.8 mm for the double staples (p < 0.0001), 2.7 mm for the interference screw (p = 0.001), and 2.1 mm for the WasherLoc (p < 0.0001)., Conclusions: The tensile force applied to a soft-tissue anterior cruciate ligament graft is not transferred intra-articularly and is not maintained during graft fixation. The loss in tension is caused by friction in the tibial tunnel and wrapping the graft around the shank of the screw of the spiked washer, insertion of the tibial fixation device, and cyclical loading of the knee. The amount of tension loss is sufficient to increase the maximal anterior translation.

Background: The purpose of this study was to identify the determinants of patient satisfaction with the outcome after reconstruction of the anterior cruciate ligament., Methods: A cohort of 201 patients undergoing primary reconstruction of the anterior cruciate ligament was studied prospectively. All patients were followed for a minimum of two years (mean, 35.9 months). The dependent variable was patient satisfaction with the outcome, graded ordinally on a scale of 1 to 10. Nonparametric univariate analysis and multivariable modeling were performed to identify determinants of satisfaction., Results: The demographic variables were not found to have a significant association (p > 0.05) with patient satisfaction. The variables at surgery demonstrated a significant association (p < 0.05) with patient satisfaction only with respect to the status of the lateral meniscus, the presence of osteophytes, and concurrent plica excision. The objective variables at follow-up revealed that patients were significantly less satisfied (p < 0.05) if they had a flexion contracture, increased laxity of the involved leg on the manual maximum test as measured on a KT-1000 device, an abnormal result on the pivot-shift examination, effusion, or tenderness at the medial joint line or patella. With regard to the subjective symptoms at follow-up, patients were found to be significantly (p < 0.05) less satisfied with the outcome if they had symptoms of pain, swelling, partial giving-way, full giving-way, locking, noise, stiffness, or a limp. Analysis of the subjective function at follow-up demonstrated that patients were significantly less satisfied (p < 0.05) with the outcome if they had a lower level of activity, sports activity, strenuous work, activities of daily living, overall knee function, sports participation, or symptom-free activity; if they were unemployed; or if they had difficulty with walking, squatting, ascending or descending stairs, running, jumping, cutting, or twisting. Patient satisfaction was significantly associated (p < 0.05) with the Lysholm knee score, overall International Knee Documentation Committee (IKDC) knee score, IKDC subjective subscore, IKDC symptoms subscore, and IKDC range-of-motion subscore. The seven independent multivariate determinants (adjusted R (2) = 0.83, p < 0.001) of patient satisfaction included the Lysholm score, overall subjective knee function, IKDC range-of-motion subscale, patellar tenderness, full giving-way, flexion contracture, and swelling., Conclusions: Univariate and multivariate determinants of patient satisfaction with the outcome after reconstruction of the anterior cruciate ligament were established. Although some specific surgical and objective variables were important, subjective variables of symptoms and function had the most robust associations with patient satisfaction. In assessing the outcome of reconstruction from the perspective of patient satisfaction with the outcome, we should emphasize patient-derived subjective assessment of symptoms and function, particularly those involving issues of stiffness, giving-way, swelling, and patellofemoral symptoms.

Background: The purpose of this investigation was to evaluate replacement of a torn anterior cruciate ligament with either a bone-patellar tendon-bone autograft or a two-strand semitendinosus-gracilis autograft to compare the results of clinical testing, patient satisfaction, activity level, functional status, and muscle strength., Methods: Fifty-six patients with a torn anterior cruciate ligament were enrolled in a prospective, randomized, controlled study. Twenty-eight underwent reconstruction with a bone-patellar tendon-bone autograft, and twenty-eight were treated with a two-strand semitendinosus-gracilis autograft. Patients were followed for an average of thirty-nine months (range, thirty-six to fifty-seven months). At the time of final follow-up, twenty-two patients in each group were evaluated in terms of clinical test findings, patient satisfaction, activity level, functional status, and isokinetic muscle strength., Results: The objective outcome of replacement of the torn anterior cruciate ligament with a bone-patellar tendon-bone graft was superior to that obtained with a two-strand semitendinosus-gracilis graft. At the three-year follow-up interval, the patients in whom a hamstring graft had been used had an average of 4.4 mm of increased anterior knee laxity compared with the laxity of the contralateral, normal knee, whereas the patients in whom a bone-patellar tendon-bone graft had been used had an average of 1.1 mm of increased knee laxity. Fourteen percent (three) of the twenty-two patients with a hamstring graft had a mild pivot shift, and 27% (six) had a moderate pivot shift. Only 14% (three) of the twenty-two patients with a bone-patellar tendon-bone graft had a mild pivot shift, and none had a moderate pivot shift. At the same follow-up interval, the patients in whom a hamstring graft had been used had significantly lower peak knee-flexion strength than those who had a bone-patellar tendon-bone graft (p = 0.039). In contrast, the two treatments produced similar outcomes in terms of patient satisfaction, activity level, and knee function (ability to perform a one-legged hop, bear weight, squat, climb stairs, run in place, and duckwalk)., Conclusions: After three years of follow-up, the objective results of anterior cruciate ligament replacement with a bone-patellar tendon-bone autograft were superior to those of replacement with a two-strand semitendinosus-gracilis graft with regard to knee laxity, pivot-shift grade, and strength of the knee flexor muscles. However, the two groups had comparable results in terms of patient satisfaction, activity level, and knee function.

Background: The objective of this study was to evaluate the effectiveness of reconstructions of the anterior cruciate ligament to resist anterior tibial and rotational loads. We hypothesized that current reconstruction techniques, which are designed mainly to provide resistance to anterior tibial loads, are less effective in limiting knee instability in response to combined rotational loads., Methods: Twelve fresh-frozen young human cadaveric knees (from individuals with a mean age [and standard deviation] of 37 +/- 13 years at the time of death) were tested with use of a robotic/universal force-moment sensor testing system. The loading conditions included (1) a 134-N anterior tibial load with the knee at full extension and at 15 degrees, 30 degrees, and 90 degrees of flexion, and (2) a combined rotational load of 10 N-m of valgus torque and 10 N-m of internal tibial torque with the knee at 15 degrees and 30 degrees of flexion. The kinematics of the knees with an intact and a deficient anterior cruciate ligament, as well as the in situ force in the intact anterior cruciate ligament, were determined in response to both loads. Each knee then underwent reconstruction of the anterior cruciate ligament with use of a quadruple semitendinosus-gracilis tendon graft and was tested. A second reconstruction was performed with a bone-patellar tendon-bone graft, and the same knee was tested again. The kinematics of the reconstructed knees and the in situ forces in both grafts were determined., Results: The results demonstrated that both reconstructions were successful in limiting anterior tibial translation under anterior tibial loads. Furthermore, the mean in situ forces in the grafts under a 134-N anterior tibial load were restored to within 78% to 100% of that in the intact knee. However, in response to a combined rotational load, reconstruction with either of the two grafts was not as effective in reducing anterior tibial translation. This insufficiency was further revealed by the lower in situ forces in the grafts, which ranged from 45% to 65% of that in the intact knee., Conclusions: In current reconstruction procedures, the graft is placed close to the central axis of the tibia and femur, which makes it inadequate for resisting rotational loads. Our findings suggest that improved reconstruction procedures that restore the anatomy of the anterior cruciate ligament may be needed.

Seventeen fresh-frozen knee specimens from cadavera were instrumented with a load-cell attached to a mechanically isolated cylinder of subchondral bone containing the tibial insertion of the anterior cruciate ligament. The forces in the intact anterior cruciate ligament were recorded as the knee was passively extended from 90 degrees of flexion to 5 degrees of hyperextension without and with several constant tibial loads: 100 newtons of anterior tibial force, ten newton-meters of internal and external tibial torque, and ten newton-meters of varus and valgus moment. The anterior cruciate ligament was resected, and a bone-patellar ligament-bone graft was inserted. The knee was flexed to 30 degrees, and the graft was pre-tensioned to restore normal anterior-posterior laxity. The knee-loading experiments were repeated at this level of pre-tension (laxity-matched pre-tension) and at a level that was forty-five newtons greater than the laxity-matched pre-tension (over-tension). During passive extension of the knee, the forces in the graft were always greater than the corresponding forces in the intact anterior cruciate ligament. Over-tensioning of the graft increased the forces in the graft at all angles of flexion. At full extension, the mean force in the anterior cruciate ligament was fifty-six newtons; the mean force in the graft at laxity-matched pre-tension was 168 newtons, and it was 286 newtons in the over-tensioned graft. Greater pre-tensioning may be required when the knee demonstrates apparent tightening of the graft in flexion. The mean forces in the graft generated during all constant loading tests were greater than those for the intact anterior cruciate ligament over the range of flexion. When the graft was over-tensioned, the forces generated by the anterior tibial force and by varus and valgus moment increased but those generated by internal and external tibial torque did not. There was no significant change in the mean tibial rotation as a function of the angle of flexion of the knee after insertion of the graft; normal tibial rotation of the knee during passive extension (the so-called screw home mechanism) was eliminated.

Nineteen fresh-frozen knee specimens from cadavera were tested for anterior-posterior laxity with 200 newtons of force applied to the tibia. A cylindrical cap of subchondral bone containing the tibial insertion of the anterior cruciate ligament was isolated with a coring cutter and was potted in acrylic. A thin wire was connected to the undersurface of the cap, and relative displacement between the cap and the tibia was measured with an isometer as the knee was extended. The cap of bone was connected to a load-cell that recorded force in the intact ligament during anterior-posterior testing with the tibia locked in neutral, internal rotation, and external rotation. The anterior cruciate ligament was then resected, and a femoral tunnel was drilled at the site where the isometer readings from the wire were the same as those obtained for the intact anterior cruciate ligament. A bone-patellar ligament-bone graft was used to reconstruct the anterior cruciate ligament, and the isometer measurements were repeated with the graft in place. The graft was pre-tensioned at 30 degrees of flexion to restore normal anterior-posterior laxity. Anterior-posterior laxity tests were repeated at this level of pre-tension (laxity-matched pre-tension) as well as at a level that was forty-five newtons greater (over-tension). The moment required to extend the knee was measured before and after insertion of the graft at both levels of pre-tension. When the tibia was locked in positions of internal and external rotation, the anterior-posterior laxities and the forces in the anterior cruciate ligament (generated by an anterior force applied to the tibia) were significantly less than the corresponding values with the tibia in neutral rotation at 20, 30, and 45 degrees of flexion (p < or = 0.05). Isometer readings for the intact anterior cruciate ligament indicated that the cap of bone retracted into the joint a mean and standard deviation of 3.1 +/- 0.8 millimeters as the knee was extended from 30 degrees of flexion to full extension. For each specimen, the isometer measurements for the trial wire and for the graft were within 1.5 millimeters of those for the intact anterior cruciate ligament. At laxity-matched pre-tension (mean, 28.2 +/- 16.8 newtons), the mean anterior-posterior laxities of the reconstructed knees were within 1.0 millimeter of the corresponding means for the intact knees between 0 and 45 degrees of flexion. Over-tensioning of the graft by forty-five newtons decreased the anterior-posterior laxity a mean of 1.2 millimeters at 30 degrees of flexion. Over-tensioning of the graft did not change the moment required to bring the knee to full extension.

One hundred and twenty-seven patients who had a rupture of the anterior cruciate ligament agreed to participate in a prospective, randomized study of three arthroscopically assisted reconstruction techniques. One hundred and twenty-five patients (125 reconstructions) were evaluated after a mean duration of follow-up of forty-two months (range, two to five years). Group I included forty patients who had a two-incision reconstruction with use of an autogenous semitendinosus-gracilis graft, group II consisted of forty patients who had a two-incision reconstruction with use of an autogenous patellar-ligament graft, and group III included forty-five patients who had a single-incision reconstruction (endoscopic technique) with use of an autogenous patellar-ligament graft. The male-female ratio, age range, level of athletic activity, interval between the injury and the reconstruction, previous operative procedures, and associated injuries were similar in all three groups. The same postoperative rehabilitation protocol was followed for all patients. Testing with a KT-2000 arthrometer at maximum manual force was done at the follow-up evaluation; the difference in laxity between the involved knee and the contralateral knee was three millimeters or less in thirty-three patients (83 per cent) in group I, thirty-seven patients (93 per cent) in group II, and thirty-nine patients (87 per cent) in group III. A difference of two millimeters or less was found in thirty patients (75 per cent) in group I, thirty-one patients (78 per cent) in group II, and thirty-five patients (78 per cent) in group III. Thirty-five patients (88 per cent) in group I, thirty-eight patients (95 per cent) in group II, and forty patients (89 per cent) in group III returned to at least the same level of athletic activity. Four grafts (two in group I and two in group II) failed as a result of trauma. There was one additional failure in groups I and III, as evidenced by a difference of nine and seven millimeters, respectively, on instrumented testing of laxity. The significant findings were that no knee was rated D according to the system of the International Knee Documentation Committee (p < 0.002, 94 per cent confidence level) and that fewer additional operative procedures were done on patients in group III (p < 0.08). Also, it was found that the patients in group II returned to a greater level of athletic activity (p < 0.02) and that a higher percentage of the patients in this group had a difference of three millimeters or less on testing with the KT-2000 arthrometer than in the other two groups (p < 0.08). However, with the numbers available, there were no significant differences in the over-all outcome among the three groups (p > 0.1). Importantly, the rate of failure was not greater and the outcomes were not less satisfactory for the late reconstructions than they were for the acute reconstructions (those performed less than three weeks after the injury), including those done with an autogenous semitendinosus-gracilis graft in a chronically unstable knee.

Forty-one patients in whom operative reconstruction of a torn anterior cruciate ligament had been performed by one surgeon with use of a double-looped semitendinosus and gracilis hamstring graft were studied to determine (1) if a brace-free rehabilitation program compromised the early stability of the knee; (2) if the stability of the knee deteriorated between four months, when the patient returned to unrestricted activities, and two years; and (3) if the function of the treated knee was completely restored by four months after the operation. The graft was placed arthroscopically, without impingement by the intercondylar roof, and was fixed within the tibial tunnel to conserve the length of the graft. The stability and function of thirty-seven of the knees were assessed at four months as part of a larger prospective study. Four patients chose not to return for the four-month evaluation. The patients returned to unrestricted sports and work activities after the four-month evaluation. At two years, all forty-one patients were evaluated. At four months, after completion of the brace-free rehabilitation program, thirty-three (82 per cent) of the thirty-seven patients had an absent pivot shift and a normal Lachman test. Twenty-eight (88 per cent) of thirty-four knees had less than three millimeters of difference in laxity compared with the contralateral knee, as determined by testing at the maximum manual force with use of a KT-1000 arthrometer. Stability remained unchanged at two years, justifying the early return to vigorous activities at four months. The girth of the thigh, the extension of the knee, and the Lysholm and Gillquist score were the same at four months as at two years, verifying the success of the brace-free intensive rehabilitation program in the restoration of early function to the treated knee. However, some continued improvement was observed in the performance of the one-leg-hop for distance test between four months and two years.

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.

We retrospectively reviewed the records of fifty-two patients who had had a rupture of the anterior cruciate ligament between the ages of forty and sixty years, to determine the results of aggressive non-operative treatment. We were able to locate and re-examine thirty of these patients (mean age, forty-six years) after a mean duration of follow-up of seven years (range, five to thirteen years), and to assess the clinical, radiographic, and functional results. The mean score, according to the scale of Lysholm and Gillquist, was 82 points; eight of the eleven patients who had combined ligamentous injuries had a score of less than 84 points (symptoms with daily activities). Thirteen substantial reinjuries had occurred in eleven patients (37 per cent) during the follow-up period. Twenty-nine patients (97 per cent) had a grade-2 or 3 Lachman test, and a positive pivot-shift test was elicited in twenty-five patients (83 per cent). Plain radiographs revealed minimum or no changes in twenty-six patients (87 per cent). Magnetic resonance imaging in nine patients revealed scarring of the remnant of the anterior cruciate ligament to the posterior cruciate ligament in six. The mean difference in anterior-posterior laxity between the injured knee and the normal, contralateral knee, as measured with the KT-1000 arthrometer, was five millimeters at twenty pounds (eighty-nine newtons). Twenty-five (83 per cent) of these thirty middle-aged patients, who had had guided rehabilitation and had modified activity, had a satisfactory outcome without an operation. However, a few patients, who had combined instabilities and who wished to resume competitive sports activity that required pivoting, were dissatisfied. Such patients may need operative reconstruction to achieve their goals.

Functional knee-braces are widely used to protect injured or reconstructed anterior cruciate ligaments, despite the fact that few scientific data support their efficacy. We studied seven functional braces, representative of both the typical custom-fit and off-the-shelf designs. The braces were tested on subjects who had a normal anterior cruciate ligament and were scheduled for arthroscopic meniscectomy or exploration of the knee under local anesthesia. After the operative procedure, a Hall-effect strain-transducer was applied to the anterior cruciate ligament. Under low anterior shear loads, two braces provided some protective strain-shielding effect compared with no brace, but this strain-shielding effect did not occur at the higher anterior shear loads expected during the high-stress activities common to athletic events. The DonJoy, Townsend, C.Ti., and Lenox Hill braces demonstrated a strain-shielding effect on the anterior cruciate ligament with an internal torque of five newton-meters applied to the tibia. None of the braces had any effect on strain on the anterior cruciate ligament during active range of motion of the knee from 10 to 120 degrees or during isometric contraction of the quadriceps. Wearing of a brace did not produce an increase in the value for strain on the anterior cruciate ligament. For the activities that were evaluated in this study, none of the braces produced adverse effects on the anterior cruciate ligament, and there were no significant differences in the strain on the anterior cruciate ligament between the use of a custom-fit or an off-the-shelf brace design. There were no apparent advantages of the more expensive custom-made braces compared with the off-the-shelf designs.

Healing of the anterior cruciate ligament was studied in 170 male rabbits. One group included immature animals that had open epiphyses, and a second group consisted of only mature animals. In one knee of each animal, the anterior cruciate ligament was transected either completely or partially, and in the contralateral knee a sham operation was carried out. Mechanical testing and histological studies of the ligaments were done immediately postoperatively and at two weeks, six weeks, three months, and one year. As we expected, there was no regeneration after complete transection of the anterior cruciate ligament, and all of the animals in which this procedure was done had severe osteoarthrosis of the joint at three months. Postoperatively, the partially sectioned ligaments exhibited one-third of the strength of the ligaments on the side on which the sham operation had been done in the immature animals and one-fourth of the strength of the ligaments on the side on which the sham operation had been done in the mature animals. Subsequently, there was secondary complete rupture of 20 per cent of the partially sectioned ligaments. The remaining 80 per cent of the partially sectioned ligaments were clearly weaker two weeks after the operation than immediately postoperatively, but this was also true on the side on which the sham operation had been done. At six weeks, the initial postoperative strength of the partially sectioned ligaments had been regained. At one year, the ligaments of the immature animals were two-thirds as strong as those on the contralateral side, and those of the mature animals were three-fourths as strong as those on the contralateral side. The ligaments were markedly elongated, especially in the mature animals. At three months, stiffness of the ligaments returned to normal. Histologically, the defect was filled with tissue that was still somewhat different from normal ligamentous tissue.

We compared the results of a radiographic technique for the measurement of instability of the knee with those obtained with a KT-1000 arthrometer. The study was conducted on both knees of sixty patients who had a ruptured anterior-cruciate ligament in one knee, as well as in ten control subjects. The radiographic technique included the examination of a true lateral radiograph, made while the knee was in full extension and the quadriceps was maximally contracted, with a 66.7-newton downward force produced by a 6.8-kilogram weight suspended from the ankle. As demonstrated by both techniques, the maximum difference between the displacements of the right and left knees in the control subjects was 2.5 millimeters and the mean difference between the displacements in the two knees in the patients was 7.5 millimeters. In fourteen of the sixty knees in which the ligament was ruptured, the injury was acute. The forward translation of the medial side in these fourteen knees was compared with that in the forty-six knees in which the injury was chronic. The mean difference in the displacement of the medial side in the right and left knees was 3.5 millimeters in the fourteen patients who had an acute injury and 5.0 millimeters in the forty-six patients who had a chronic injury. Thirteen of the sixty patients had disruption of the posteromedial corner of the injured knee, and the translation of the medial side in these knees was significantly increased compared with that in the intact knees of the same patients.(ABSTRACT TRUNCATED AT 250 WORDS)

We used the KT-1000 arthrometer to test the knees of 107 patients who had an acute tear of the anterior cruciate ligament, 153 patients who had a chronic tear, and 141 control subjects, for a total of 401 individuals. The three testing parameters were the extent of anterior translation at eighty-nine newtons of force and at maximum manual force, and the compliance index. The differences between the involved and the uninvolved knees were calculated. At eighty-nine newtons, all but one of the control subjects had anterior translation of ten millimeters or less, compared with 58 per cent of the patients who had a chronic tear. At maximum manual force, all but two of the control subjects had translation of ten millimeters or less, compared with 20 per cent of the patients who had an acute or a chronic tear. Analysis of variance showed that the clinical diagnosis correlated well with the results for all tests (p less than 0.001). However, when the uninjured knees of patients who had an acute or a chronic tear were compared with the knees of the control subjects, significant differences were noted (p less than 0.001 to 0.006). In the patients who had a chronic tear, there was no relationship between the time from injury to operation and the extent of anterior translation. The arthrometric test at maximum manual force was the strongest discriminant; it differentiated normal from abnormal knees (p less than 0.001) with high sensitivity (92 per cent), high specificity (95 per cent), and high positive predictive accuracy; the cut-off point was eleven millimeters or less.(ABSTRACT TRUNCATED AT 250 WORDS)