An in vitro study of anterior cruciate ligament strain induced by quadriceps and hamstrings forces

Strain in the anteromedial fibers of the anterior cruciate ligament [ACL(am)] was studied in six cadaver knees. ACL(am) strain was measured in five knees during the application of isometric quadriceps forces alone and simultaneously applied isometric quadriceps and hamstrings forces at 10 degrees increments from 0 degrees to 90 degrees of knee flexion. ACL(am) strain during muscle loading was measured with respect to the ACL(am) strain measured with the knee in its resting position (neutral or near neutral position). A sixth knee was used to investigate the reproducibility of the resting position and quadriceps-induced ACL(am) strains. The strains induced in the ACL(am) by the quadriceps were significantly greater than 0 at knee flexion angles from 0 to 40 degrees and not significantly different from 0 for 50 to 90 degrees. The ACL(am) strains induced by simultaneously applied hamstrings and quadriceps forces were not significantly different from 0 at any of the knee flexion angles tested. Simultaneously applied hamstrings and quadriceps forces significantly reduced ACL(am) strain at 10, 20, and 90 degrees of knee flexion compared to the ACL(am) strain induced by quadriceps forces alone. The hamstrings are potentially capable of both significantly reducing and negating quadriceps-induced ACL(am) strain at 10 and 20 degrees of knee flexion.     

Replacement of the anterior cruciate ligament using a patellar tendon allograft. An experimental study

The anterior cruciate ligament of twenty-five adult dogs was replaced using fresh or deep-frozen patellar-tendon allografts. The morphology of these transplanted allografts was then evaluated using routine histological studies and a vascular-injection (Spalteholz) technique at various intervals from two weeks to one year postoperatively. The fresh patellar-tendon allografts incited a marked inflammatory and rejection response which was characterized by perivascular cuffing and lymphocyte invasion. Deep-frozen patellar-tendon allografts appeared to be benign within the joint and underwent alterations that were comparable with those observed in autogenous patellar-tendon grafts. These included avascular necrosis followed by revascularization and cellular proliferation. At one year, the gross and histological appearance of the patellar tendon allograft resembled that of a normal anterior cruciate ligament.     

Replacement of the anterior cruciate ligament using a deep-frozen bone-Lca- Bone Allograft. An experimental study

Summary One ACL in each of 17 mature sheep was replaced with a deep-frozen bone – an ACL bone allograft. Allografts were obtained from skeletally mature sheep using a standard aseptic technique and stored deep frozen for at least 6 days (mean 21 days). Macroscopical, biomechanical, and histological changes were evaluated 12, 24, and 52 weeks following implantation. At autopsy all allograft ligaments were present and demonstrated no evidence of infection or immune reaction. We found slight arthrotic changes in 3 knees after 12 weeks, in 4 knees after 24 weeks, and in 3 knees after 52 weeks. Twelve weeks after the operation the maximum load of the allografts was 17.5 % of the contralateral controls and increased to 20.9 % after 24 weeks and to 32 % of controls after 52 weeks. Ligament stiffness in the linear region also increased from 18.9 % of controls (12 weeks) to 32.5 % after 52 weeks, whereas maximum load decreased from 112.2 % of controls (12 weeks) to 98 % of controls (52 weeks). Histologically, the allografts progressively matured with time, becoming nearly identical to normal ligaments at 52 weeks.      

Radiological assessment of anterior cruciate ligament deficiency. A new technique

A new method of demonstrating sagittal laxity in the anterior cruciate-deficient knee is described. Seventy such knees were compared to 70 normal knees. Sagittal laxity was recorded as the average displacement of the medial and lateral femoral condyles. This displacement index was significantly different between the two groups of knees (P less than 0.0001). A range for normal and abnormal knees is discussed. Quantitative assessment of the degree of sagittal laxity by clinical evaluation is shown to be unreliable. Only the pivot-shift test demonstrated any significant correlation with the amount of sagittal displacement (P less than 0.05).     

Aplasia of the anterior cruciate ligament with a compensating posterior cruciate ligament.

Aplasia of the anterior cruciate ligament is a rare condition and is usually associated with other abnormalities of the lower extremities. We report aplasia of the anterior cruciate ligament with a compensating posterior cruciate ligament in a 15-year-old boy.     

Avoiding graft-tunnel mismatch in endoscopic anterior cruciate ligament reconstruction: a new technique.

A common problem encountered in endoscopic anterior cruciate ligament reconstruction is graft-tunnel mismatch. A technique not previously described in the literature is illustrated. This technique provides direct measurement of the tibial tunnel length plus the intra-articular distance. This allows direct calculation of the length of the femoral tunnel necessary to avoid a graft-tunnel mismatch. This technique has been used very effectively in our institution with excellent, reproducible results.     

The effects of in situ freezing on the anterior cruciate ligament. An experimental study in goats

We developed an in situ freeze-thaw model designed to simulate an ideally placed and oriented autogenous graft of the anterior cruciate ligament. In this model, the anterior cruciate ligament was exposed, and the femoral insertion, tibial insertion, and body of the anterior cruciate ligament were frozen in situ with specially designed freezing probes. Freeze-thaw cycles were repeated five times. We used the technique in thirty-three mature goats to study the biological and biomechanical outcomes of the devitalized and devascularized anterior cruciate ligament at zero, six, and twenty-six weeks after treatment. Thus, the collagen fibers of the simulated autogenous graft remain in normal anatomical position and the simulated graft is fixed under physiological tension. At twenty-six weeks, no statistically significant differences were noted between treated and contralateral control (untreated) ligaments relative to anterior-posterior translation, maximum force to rupture, stiffness in the linear region of the force-length curve, modulus of elasticity in the linear region, strain to maximum stress, or maximum stress. The only statistically significant difference was an increase in cross-sectional area of the ligament. This increase was 22 and 42 per cent greater than that in the control ligaments at six weeks and six months. At six months, the ligaments in the control group had an average mid-cross-sectional area of 17.7 +/- 1.2 square millimeters and the ligaments in the experimental group, 25.2 +/- 3.1 square millimeters. Changes in the size and density of the collagen fibrils also were demonstrated at six months. These observations are in sharp contrast to our previous studies of replacement of the anterior cruciate ligament, in which an allograft of the ligament or an allograft supplemented with a 3M ligament augmentation device (LAD; 3M, St. Paul, Minnesota) was used. In those studies, an average reduction in maximum strength of 75 per cent for the allografts and 50 per cent for the allografts that had a ligament-augmentation device was found at one year. We concluded that devitalized, devascularized anterior cruciate ligaments do not lose strength if the anatomical position and the orientation of the collagen fibers are not altered.     

Replacement of the anterior cruciate ligament with a bone-ligament-bone anterior cruciate ligament allograft in dogs

Acute replacement of the canine anterior cruciate ligament (ACL) with a frozen, bone-ligament-bone anterior cruciate ligament preparation was studied using biochemical, immunologic, and biomechanical testing methods. Nine dogs were used for the study, six dogs received allografts and three received autografts. No tissue antigen matching was performed. All nine dogs were killed nine months after surgery. Necropsy examination revealed that the ACL was not present in three joints (one autograft, two allografts). The two autograft and four allograft ligaments available for mechanical testing sustained mean maximum loads that were 10% and 14%, respectively, of the mean maximum loads sustained by the contralateral ACL. Autoradiography indicated that cellular activity was more pronounced in the autograft specimens. Hydroxyproline uptake was 200% and 45% of normal in the autograft and allograft ligaments, respectively. Both autograft and allograft specimens were producing Type I collagen at the time of killing. Antidonor dog leukocyte antigen (DLA) antibody was detected in the synovial fluid taken at the time of killing from six of six dogs that received allografts and in zero of three dogs that received autografts.     

Notchplasty in anterior cruciate ligament reconstruction: an experimental animal study.

The purpose of this study was to evaluate the effects of a notchplasty on the biomechanical and histological properties of the anterior cruciate ligament (ACL) and changes in patellar articular cartilage. We used an in situ freeze-thaw model for the ACL reconstruction performed with or without notchplasty in 36 Japanese white rabbits. The cross-sectional area of the regenerated ACLs without a notchplasty (6.4 +/- 0.4 mm(2)) was statistically smaller than that of the ACLs with a notchplasty (7.0 +/- 0.3 mm(2)), and the cross-sectional area of the normal ACLs (5.4 +/- 0.5 mm(2)) was statistically smaller than that of both other types. However, the mechanical strength of the ACL with the notchplasty was identical to that of the ACL without a notchplasty. Although the notchplasty areas were covered with fibrous scar tissue, caliper measurement and histological examination showed no obvious osteochondral reconstitution in the notchplasty sites of any of the specimens. Regarding the deleterious effect of notchplasty on patellar articular cartilage, the extent of the slight degenerative changes was about the same in the group with a 1-mm notchplasty and in the control group.     

An anterior cruciate ligament and medial collateral ligament tear in a skeletally immature patient: a new technique to augment primary repair of the medial collateral ligament and an allograft reconstruction of the anterior cruciate ligament

The goal of this case report is to fill a dual purpose. We describe a case involving a tear of the anterior cruciate ligament (ACL) and medial collateral ligament (MCL) in a skeletally immature athlete. At the same time, we describe a new technique with which we repaired the ACL with an allograft posterior tibialis tendon through intra-articular tunnels. A trial of conservative therapy for the MCL was performed. During surgery, its instability was assessed. No improvement was seen in stability, so a primary repair of the MCL was performed and augmented with an autograft gracilis tendon. The patient did well postoperatively, subsequently achieving equal stability and range of motion when compared with the opposite limb. He was back to competitive sports at 6 months.     

An experimental study on tissue induction in anterior cruciate ligament reconstruction with the scaffold-type polyester artificial ligament (Leeds-Keio)]

The effect of experimental autogenous tissue implantation (infrapatellar fat pad, fascia lata) together with scaffold type artificial ligament (Leeds-Keio) in ACL reconstruction was studied in 56 mongrel adult dogs. Specimens were examined macroscopically, histologically and by means of microangiography. The results were compared with those in which the artificial ligament was used alone. When infrapatellar fat pad was transferred on artificial ligament, tissue induction was observed 2 weeks after reconstruction. When ACL was reconstructed using a combination of artificial ligament and a small piece of fascia lata, maturated dense collagen fibers were observed 24 weeks after reconstruction. These results indicated that quicker tissue induction could be obtained in ACL reconstruction using an artificial ligament together with a infrapatellar fat pad, and that collagen fiber maturation was accelerated when ACL was reconstructed using an artificial ligament together with a small piece of fascia lata.     

In vitro comparison of elongation of the anterior cruciate ligament and single- and dual-tunnel anterior cruciate ligament reconstructions.

This study evaluated strain in the normal anterior cruciate ligament (ACL) and compared it to four different double-strand hamstring tendon reconstructive techniques. Seventeen fresh-frozen knees from 11 cadavers were tested. The strain in the anteromedial and posterolateral bands of the native ACL and their equivalents in four autograft techniques were measured using differential variable reluctance transducers. The anteromedial band of the intact ACL shortened from 0 degree -30 degrees of flexion, then lengthened to 120 degrees; the posterolateral band of the intact ACL shortened from 0 degree - 120 degrees of flexion. Following ACL excision, these knees underwent reconstruction with double-strand hamstring tendons with either single tibial and femoral tunnels, single tibial and dual femoral tunnels, dual tibial and single femoral tunnels, or dual tibial and dual femoral tunnels. With the exception of the dual-band, dual-tunnel technique, all of the procedures placed greater strain on the reconstructive tissues than was observed on the native ACL, after approximately 30 degrees of flexion. These results indicate that dual-band hamstring tendon reconstructions placed with single tibial and femoral tunnels do not address the complexity of the entire ACL. Rather, these procedures appear to only duplicate the effect of the anteromedial band, while perhaps overconstraining the joint as a result of its inability to reproduce the function of the posterolateral band. During rehabilitation following ACL reconstruction, therefore, only from 0 degree - 30 degrees of the graft tissues are not significantly strained. Dual tibial and femoral tunnel techniques should be evaluated further to more closely recreate knee kinematics following ACL reconstruction.     

Devascularization of the anterior cruciate ligament by synovial stripping in rabbits. An experimental model.

In rabbits, synovial stripping of the anterior cruciate ligament was performed, and histologic and mechanical changes were followed up to 2 months. The operation did not immediately affect the strength of the ligament or its histological structure. However, a gradual deterioration of mechanical properties, associated with collagen necrosis and an ineffectual reparative response, was evident. Thus, synovial stripping of the ligament with the attendant concomitant devascularization leads to ligamentary insufficiency despite the lack of structural damage to the ligament by the contusion itself.     

Measurement of stability of the knee and ligament force after implantation of a synthetic anterior cruciate ligament. In vitro measurement

A Gore-Tex prosthetic ligament was inserted, with an over-the-top femoral placement, into thirteen fresh-frozen cadaver knees as a substitute for the anterior cruciate ligament. The femoral eyelet was screwed into bone and the tibial eyelet was attached to a force-transducer, which was positioned and locked on a tibial slider track to record forces in the ligament as the tibia was externally loaded. A reference position was established for the tibial eyelet so that, after the Gore-Tex ligament was implanted, the total anterior-posterior laxity of the knee (at 200 newtons of applied tibial force) matched that of the intact knee (that is, before the anterior cruciate ligament had been cut) at 20 degrees of flexion. With both ends of the ligament secured in the knee, repeated 200-newton anterior-posterior load cycles produced an increase of five to seven millimeters in the total laxity. This apparent stretch-out of the ligament could be worked out of the knee by manually flexing and extending the knee thirty times between zero and 90 degrees of flexion while a constant 200-newton force was applied to the tibial eyelet. After implantation of the Gore-Tex ligament, the laxity of the knee matched that of the intact specimen at 20 degrees of flexion and matched it within one millimeter at zero, 5, and 10 degrees of flexion. For each millimeter that the tibial eyelet was moved distally, the total anterior-posterior laxity decreased by the same amount. The anterior stiffness of the knee after implantation of the Gore-Tex ligament was always less than that of the intact specimen. With an applied extension moment of ten newton-meters, section of the anterior cruciate ligament increased hyperextension of the knee by 2.3 degrees; implantation of the Gore-Tex ligament did not restore full extension, even when the ligament was over-tightened by using a distal location for the tibial eyelet. When the eyelet was in the reference position, the ligament forces ranged from three to 319 newtons when the knee was in full extension, they rose dramatically as the knee was hyperextended, and they decreased to zero in most specimens as the knee was flexed more than 15 degrees. The pull of the quadriceps tendon against fixed resistance always increased the ligament forces. The application of tibiofemoral contact force reduced the ligament forces that were generated during a straight anterior tibial pull.(ABSTRACT TRUNCATED AT 400 WORDS)     

A new technique of harvesting patellar tendon autografts for anterior cruciate ligament reconstruction.

A new surgical technique to uniformly harvest the middle one-third of the patellar tendon for anterior cruciate ligament reconstruction is described. The technique uses a guide system of 8 templates of varying widths to guide the saw cuts and "collared," depth-controlled saw blades and drill bits to produce a standard cutting and drilling depth. This kind of template system lessens the risks of graft harvesting complications such as patella fracture, bone graft fragmentation, suture pull out, and judgment errors pertaining to graft depth, length, or width. The Patellar Tendon Graft Guide was used to obtain a patellar tendon graft in 65 patients. Fifty-nine arthroscopic-assisted and 6 open anterior cruciate ligament reconstructions were performed. Of the 65 grafts harvested, 63 consistently demonstrated bone portions 20 mm in length, 7 mm in depth, and a width corresponding to the template chosen (usually 10 mm). Two grafts supposed to be 10 mm in width turned out to be 9 mm in width because of a technique related problem.     

Comparison of femoral and tibial pullout forces in bone-patellar tendon-bone anterior cruciate ligament reconstructions with a new interference fixation device.

Interference screws have become the standard method for fixing bone-patellar tendon-bone (BPTB) grafts. To avoid the inherent pitfalls and complications of interference screws, a 28-mm long and from 5 to 7 mm spreadable metal bolt with nontapping threads was developed for this study. The technical applicability and biomechanical characteristics of this new BPTB interference fixation device were investigated by dissection or tensile testing of 48 cadaveric knee specimens from young donors. No problems occurred with respect to bone plug anchoring during insertion of the spreading bolts. The clinically important linear load was 920+/-283 N for the femoral and 635+/-247 N for the tibial fixation site. Bone plug pullout was the mode of failure in all specimens. The results of this study indicate that the spreading bolt is a reasonable alternative to interference screws.     

Improved technique of anterior cruciate ligament replacement with a patellar tendon graft

Surgical Principles Diagnostic arthroscopy and arthroscopic treatment of all meniscal lesions. Anteromedial “mini”-arthrotomy and small lateral incision for the placement of the bone tunnels and the passage of the graft. Use of a drill guide system with a “test prosthesis” to improve the precision of the graft placement. Immediate high fixation strength of the graft through screw fixation. Revised Version from: Operat. Orthop. Traumatol. 4 (1991), 238–253 (German Edition).     

The measurement of anterior cruciate ligament strain in vivo

Summary This article describes the use of the Hall Effect strain transducer (HEST) in a new arthroscopic technique to study the normal anterior cruciate ligament (ACL) in-vivo. Study participants were patient volunteers with normal ACLs undergoing diagnostic arthroscopic or meniscal surgery under local anaesthesia. The HEST was implanted into the Anterior Medial Band (AMB) of the ACL. Anterior shear loading of the tibia in relation to the fixed femur at 30° of knee flexion (Lachman test), produced significantly greater strain values in comparison to anterior shear loading at 90° (Anterior Drawer test). During isometric quadriceps contraction a significant increase in AMB strain was measured with the knee flexed to 30°, while no significant change was measured at 90°. For quadriceps contraction there were significantly higher values of AMB strain measured at 30° of knee flexion in comparison to that observed at 90°. For active range of motion (AROM) the AMB was strained between 10° and 48°, and unstrained between 48° and 110°. During passive range of motion (PROM) the AMB remained unstrained until the joint was brought into extension. There were significant differences in strain values found between AROM and PROM at the flexion angles 10°, 20°, 30° and 40°, while between 50° and 110° there were no significant differences. These results confirm previous studies that the Lachman test is a superior technique in comparison to the classic anterior drawer test for evaluating the AMB. They suggest that isometric quadriceps activity at 90° of knee flexion can be prescribed for rehabilitation immediately after ACL reconstruction. These data indicate that AROM (between the limits of 50° and 110°) and PROM may also be performed with minimal risk of strain to a reconstructive replacement. The PROM data may also serve as an important standard for the reconstruction of the ACL.

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Résumé Cet article décrit l'utilisation du transducteur de tension par effet Hall (TTEH) dans une nouvelle technique arthroscopique pour étudier le ligament croisé antérieur (LCA) normal in vivo. Les participants à l'étude étaient des patients volontaires avec LCA normal, soumis à une arthroscopie à visée diagnostique ou à une intervention sur un ménisque, sous anesthésie locale. Le TTEH fut implanté dans la bande médiane antérieure (BMA) du LCA. La translation antérieure du tibia, le fémur étant fixé et le genou fléchi à 30° (test de Lachman), donne des chiffres de tension sensiblement plus élevés par rapport à ceux obtenus en flexion à 90° (épreuve de tiroir antérieur). Lors de la contraction isométrique du quadriceps, une augmentation significative de la tension de la BMA a été notée, le genou fléchi à 30°, alors qu'aucune modification n'était mesurable à 90°. Lors des contractions du quadriceps, les chiffres de tension de la BMA, le genou fléchi à 30° étaient notablement supérieurs à ceux enregistrés à 90°. Dans le secteur de mobilité active, la BMA était sous tension entre 10° et 48° et ne l'était pas de 48° à 110°. Durant la mobilisation passive la BMA restait détendue jusqu'à ce que l'articulation soit mise en extension complète. On a trouvé des différences significatives entre les tensions mesurées lors des mobilisations actives et passives aux angles de flexion de 10°, 20°, 30° et 40°, alors qu'il n'y en avait pas de 50° à 110°. Ces résultats confirment les études antérieures selon lesquelles le test de Lachman est une technique d'examen plus sensible que la classique recherche du tiroir antérieur pour évaluer la BMA. Ces résultats laissent à penser que l'activité isométrique du quadriceps, le genou fléchi à 90°, peut être prescrite pour la réeducation, immédiatement après reconstruction du LCA. Ces données indiquent également que la mobilisation active (entre 50° et 110°) et la mobilisation passive peuvent être effectuées avec des risques mineurs après reconstruction. Les données concernant la mobilité passive peuvent aussi fournir des repères valables pour la reconstruction du LLA.