The science of reconstruction of the anterior cruciate ligament

A bioabsorbable plug in bone-tendon-bone reconstruction of the anterior cruciate ligament: Introduction of a novel fixation technique

PURPOSE

Our aim was to compare the fixation strength of a novel plugging technique with that of the conventional interference technique in bone-patellar tendon-bone reconstruction of the anterior cruciate ligament.

TYPE OF STUDY

Randomized experimental study.

METHODS

Twenty matched pairs of porcine knees were randomly assigned to 2 groups. The bone block of the graft was secured in the femoral drill hole with either the new bioabsorbable poly-L-lactide/D-lactide (PLA 96/4) copolymer plug (plugging technique) (n = 20) or a conventional interference screw (interference technique) (n = 20). Ten pairs were subjected to a single cycle loading test at a rate of 50 mm/min while the remaining 10 pairs underwent a cyclic loading test to further assess the quality of the fixation. The cyclic loading test consisted of 1,500 loading cycles between 50 and 200 N at half-hertz frequency, after which the specimens were loaded to failure at a rate of 50 mm/min.

RESULTS

In the single cycle loading test, the average ultimate failure load was 1,061 +/- 342 N in the plugging technique group and 971 +/- 260 N in the interference technique group (P =.57). Significant group differences were found neither in the yield loads nor in the stiffness of the fixations. In the cyclic loading, significant displacement difference was not observed between the 2 fixation techniques. There were neither significant group differences with regard to the ultimate failure load (plugging technique 994 +/- 376 N versus interference technique 1,001 +/- 343 N, P =.97) nor yield load of the fixations in the subsequent single cycle loading.

CONCLUSIONS

The results of this study indicate that, in anterior cruciate ligament reconstruction, the new plugging technique is a reasonable alternative for fixation of the femoral site of a bone-patellar tendon-bone graft.

Static and fatigue strength of a fixation device transducer for measuring anterior cruciate ligament graft tension

To determine which exercises do not overload the graft-fixation complex during intensive rehabilitation from reconstructive surgery of the anterior cruciate ligament (ACL), it would be useful to measure ACL graft loads during rehabilitative activities in vivo in humans. A previous paper by Ventura et al. (1998) reported on the design of an implantable transducer integrated into a femoral fixation device and demonstrated that the transducer could be calibrated to measure graft loads to better than 10 percent full-scale error in cadaveric knees. By measuring both the static and fatigue strengths of the transducer, the purpose of the present study was to determine whether the transducer could be safely implanted in humans without risk of structural failure. Eight devices were loaded to failure statically. Additionally, seven devices were tested using the up-and-down method to estimate the median fatigue strength at a life of 225,000 cycles. The average ultimate strength was 1856 +/- 74 N and the median fatigue strength was 441 N at a life of 225,000 cycles. The maximum graft load during normal daily activities is estimated to be 500 N and the 225,000 cycle life corresponds to that of the average healthy individual during a 12-week period. Considering that patients who have had an ACL reconstruction are less ambulatory than normal immediately following surgery and that biologic incorporation of the graft should be well developed by 12 weeks thus decreasing the load transmitted to the fixation device, the FDT can be safely implanted in humans without undue risk of structural failure.

Proprioceptive improvement in knees with anterior cruciate ligament reconstruction

The correlation between the prospective course of proprioceptive improvement and knee stability after anterior cruciate ligament reconstruction was investigated in 38 patients. Proprioception, on the basis of the patient's capacity to reposition the limb accurately, was evaluated at 3-month intervals for 24 months after hamstring graft anterior cruciate ligament surgery. Knee stability was evaluated concurrently with a KT-2000 knee arthrometer. Thirty patients experienced improvement in postoperative position sense in at least one of the examinations, although eight patients had no improvement at any time. Of the 30 patients who had improvement, 28 maintained improved position sense from 18 months to the final followup. Thirty patients maintained significantly better knee stability for a postoperative period of at least 24 months. These results indicated that a minimum of 18 months after anterior cruciate ligament reconstruction may be needed for complete restoration of the proprioceptive function in knees, although the mean position sense in all patients gradually improved from 9 months. Improvement in postoperative knee stability may have facilitated recovery of proprioception.

Technical note: alternative soft-tissue graft preparation technique for cruciate ligament reconstruction

Reconstruction of both the anterior cruciate ligament and posterior cruciate ligament has become increasingly common in orthopaedic practice. Once the gold standard for graft choice, the bone-patellar tendon-bone autograft has lost favor because of complications associated with its use. Attention has turned to other graft sources that lack a bone plug on 1 or both sides, such as hamstring autograft, and allografts including quadriceps, Achilles, and tibialis anterior tendons. We have developed a technique for graft preparation that can be used for a wide range of graft choices that has been shown both to provide better protection of the graft from interference screw damage, and to increase sequential compression of the graft in the bony tunnel, enhancing pull-out strength.

The menisci: basic science and advances in treatment

Once described as a muscle remnant, and therefore treated with disrespect, the meniscus is now known to be a vital structure within the knee. Minimal partial meniscectomy performed arthroscopically, or meniscal repair when practical, have become the standard treatments. In spite of the advancements in understanding meniscal function and its preservation, much remains to be studied. In the future, availability of better repair techniques and the option of meniscal replacement with allograft or prosthetic menisci are expected to improve outcomes.

Internal and external tibial rotation strength after anterior cruciate ligament reconstruction using ipsilateral semitendinosus and gracilis tendon autografts

The internal and external tibial rotation torques of subjects who had undergone anterior cruciate ligament reconstruction using semitendinosus and gracilis tendon grafts were measured to determine whether harvest of the tendons results in weakness of tibial internal and external rotation. Cybex NORM dynamometer examinations were performed to measure internal and external tibial torque at angular velocities of 60, 120, and 180 deg/sec in 23 subjects. The sex-specific average torque data of the reconstructed limbs were compared with those of the contralateral limbs. Relative internal and external torque scores were calculated for each subject by subtracting the peak torque of the reconstructed knee from that of the contralateral knee. These relative scores were averaged and compared with the null hypothesis that each score should be statistically similar to zero. Subjects were evaluated at an average of 51 +/- 40 months postoperatively. The mean relative internal torque scores of the reconstructed limbs showed a statistically significant decrease from those of the contralateral limbs at all angular velocities. The mean relative external torque scores of the reconstructed limbs were statistically similar to those of the contralateral limbs at all angular velocities. Subjects who had undergone ligament reconstruction using semitendinosus and gracilis tendons demonstrated internal tibial rotation weakness in their reconstructed knees compared with their contralateral knees at all angular velocities tested. These results suggest that semitendinosus and gracilis tendon harvest causes weakness of internal tibial rotation.

Noncontact anterior cruciate ligament injuries: risk factors and prevention strategies

An estimated 80,000 anterior cruciate ligament (ACL) tears occur annually in the United States. The highest incidence is in individuals 15 to 25 years old who participate in pivoting sports. With an estimated cost for these injuries of almost a billion dollars per year, the ability to identify risk factors and develop prevention strategies has widespread health and fiscal importance. Seventy percent of ACL injuries occur in noncontact situations. The risk factors for non-contact ACL injuries fall into four distinct categories: environmental, anatomic, hormonal, and biomechanical. Early data on existing neuromuscular training programs suggest that enhancing body control may decrease ACL injuries in women. Further investigation is needed prior to instituting prevention programs related to the other risk factors.

The '3 in 1' lumbar plexus block following anterior cruciate ligament reconstruction with autologous hamstring tendons

We have reviewed 33 patients undergoing primary reconstruction of the anterior cruciate ligament with a four-strand hamstring graft to assess the analgesic effect of a '3 in 1' lumbar plexus block. Patients were randomised into two groups to determine whether or not they received a catheter infusion of bupivacaine for 24 h after operation. Pain scores and additional analgesic requirements were assessed at 4, 8, 12, 16, 20 and 24 h after surgery. No difference was found between the two groups in terms of pain scores (P=0.884) and the numbers requiring morphine were similar (5/16 and 7/17). There was a trend (2.0 vs. 3.4 tablets) towards a greater coproxamol requirement for the non-block group, although not quite statistically significant (P=0.06). We conclude that the additional risk and cost of '3 in 1' lumbar plexus blockade is not justifiable after this procedure.

Strength and function before and after anterior cruciate ligament reconstruction

Rehabilitation of patients with anterior cruciate ligament injury is a topic of interest among clinicians. Although numerous studies report the deficits after anterior cruciate ligament reconstruction, there are no data available on the changes in strength and functional performance before and 6 months after reconstruction surgery. This is when most patients are returning to sports activities. In the current study 31 patients with complete unilateral anterior cruciate ligament ruptures followed a controlled rehabilitation program emphasizing early range of motion after surgery and quadriceps strengthening before and after undergoing bone-patellar tendon-bone reconstruction. Strength of the hamstrings and quadriceps and five functional activities were assessed at 1 week before and 6 months after surgery. Preoperative strength assessments using a Cybex II dynamometer showed a 12% quadriceps deficit at 60 degrees per second and 9% deficit at 120 degrees per second with no hamstring deficit in the injured leg compared with the uninjured leg. Despite intensive quadriceps training, the postoperative quadriceps deficit increased to 28% at 60 degrees per second and 22% at 120 degrees per second in comparison with the uninjured leg. There was no change in hamstring strength in the injured leg. Most functional measures improved after surgery. The shuttle run improved by 10%, the side step test results improved by 17%, and the carioca test results improved by 23%. No significant difference was found in the results of the hop test. This study highlights the extent of the quadriceps deficits despite functional improvement and the difficulty in restoring quadriceps strength after bone-patellar tendon-bone reconstruction. It also questions the relationship of current functional tests to quadriceps strength and the role of maximum strength testing as a predictor of function and of safe sporting performance.

Biological fixation of the graft within bone after anterior cruciate ligament reconstruction in rabbits: effects of the duration of postoperative immobilization

To investigate the effects of the duration of postoperative immobilization on the biological fixation of the graft within bone after anterior cruciate ligament (ACL) reconstruction, we performed ACL reconstruction in 27 rabbits, which were divided into five groups - no immobilization and 1-, 2-, 4-, and 6-week immobilization. All animals were killed 6 weeks postoperatively, and the graft-bone tunnel interface was examined biomechanically and histologically. In the groups with immobilization, in tensile failure tests, most specimens failed through the intraarticular portion of the grafts. There was no significant difference in the maximum load between these groups. In the no-immobilization group, all specimens failed through pulling of the grafts out of the femoral tunnel, with a lower maximum load than in the other groups. Histologically, new bone formation and occasional collagen fiber continuity were observed at the interface; which consisted of a fibrous tissue. In the no-immobilization group, the graft was partly separated from the fibrous tissue covering the bony wall. It is concluded that no immobilization delays the biological fixation process in the bone tunnel after ACL reconstruction, and that a certain period of immobilization is necessary for the fixation to proceed smoothly.

Current trends in anterior cruciate ligament reconstruction. Part II. Operative procedures and clinical correlations

Surgical management of the anterior cruciate ligament-deficient knee has evolved from primary repair to extracapsular augmentation to anterior cruciate ligament reconstruction using biologic tissue grafts. The technique of anterior cruciate ligament reconstruction has improved over the last few decades with the aid of knowledge gained from basic science and clinical research. The biology and biomechanics of anterior cruciate ligament reconstruction were analyzed in the previously published first part of this article. In this second part, current operative concepts of anterior cruciate ligament reconstruction as well as clinical correlations are discussed. The latest information regarding anterior cruciate ligament reconstruction is presented with a goal of demonstrating the correlation between the application of basic science knowledge and the improvement of clinical outcomes.

Anterior cruciate injuries in the skeletally immature athlete: a review of treatment outcomes

The documentation of anterior cruciate ligament (ACL) injuries in the skeletally immature athlete has significantly increased over the past decade, primarily due to increased awareness of these injuries within this younger athletic population. The evaluation of these injuries are similar to that in the adult population. Diagnostic studies such as plain radiographs, as well as magnetic resonance imaging, can delineate the location of the ACL failure. Physical presentation most commonly includes an acute haemarthrosis and ligamentous insufficiency. Several studies have demonstrated that the diagnostic reliability of the physical examination is poor in children, especially in patients less than 12 years old. The site of ACL failure in this adolescent population is most commonly at the tibial insertion. We recommend arthroscopic or arthroscopically assisted open reduction and internal fixation with nonabsorbable sutures for all displaced tibial eminence fractures. Mid-substance ACL failures also occur in this athletic age group. The association of meniscal injuries with these ACL failures appears to be greater than 50%. Historically, poor subjective and objective outcomes have been associated with primary and extra-articular repairs. Intra-articular reconstruction is the gold standard. The issue of placing the graft across open physeal plates is under investigation. Recent animal studies as well as human clinical series have demonstrated safety in placing soft tissue, i.e. hamstring grafts, across open growth plates without subsequent angular or leg length discrepancy. Historically, non-operatively treated ACL failures are associated with poor functional outcomes as well as a high incidence of meniscal re-injury. If the treatment of an adolescent athlete with an ACL failure is to be rehabilitation until skeletal maturity, close follow-up is essential to detect functional instability, which may prompt earlier surgical reconstruction.

Cyclic pull-out strength of hamstring tendon graft fixation with soft tissue interference screws. Influence of screw length

Blunt-threaded interference screws used for fixation of hamstring tendons in anterior cruciate ligament reconstructions provide aperture fixation and may provide a biomechanically more stable graft than a graft fixed further from the articular surface. It is unknown if soft tissue fixation strength using interference screws is affected by screw length. We compared the cyclic and time-zero pull-out forces of 7 x 25 mm and 7 x 40 mm blunt-threaded metal interference screws for hamstring graft tibial fixation in eight paired human cadaveric specimens. A four-stranded autologous hamstring tendon graft was secured by a blunt-threaded interference screw into a proximal tibial tunnel with a diameter corresponding to the graft width. Eight grafts were secured with a 25-mm length screw while the other eight paired grafts were secured with a 40-mm length screw. During cyclic testing, slippage of the graft occurred as the force of pull became greater with each cycle until the graft-screw complex ultimately failed. All grafts failed at the fixation site, with the tendon being pulled past the screw. There were no measurable differences in the mean cyclic failure strength, pull-out strength, or stiffness between the two sizes of screws. Although use of the longer screw would make removal technically easier should revision surgery be necessary, it did not provide stronger fixation strength than the shorter, standard screw as had been postulated.

Patella fracture and proximal patellar tendon rupture following arthroscopic anterior cruciate ligament reconstruction

The central one-third bone-patella tendon-bone graft is a popular choice for arthroscopic anterior cruciate ligament reconstruction. Complications following graft harvesting are unusual, but several reports have been published. We report an unusual case involving a simultaneous patella fracture and patellar tendon rupture that occurred 6 weeks postoperatively.

Incorporating a statistically based shape model into a system for computer-assisted anterior cruciate ligament surgery

This paper addresses the problem of extrapolating very sparse three-dimensional (3-D) data to obtain a complete surface representation. A new method that uses statistical shape models is proposed and its application to computer-assisted anterior cruciate ligament (ACL) reconstruction is detailed. The rupture of the ACL has become one of the most common knee injuries. One problem during reconstruction is to find the optimal attachment points for the graft. Therefore a system for computer-assisted reconstruction of the ACL has been proposed by TIMC laboratory. During surgery the surgeon collects several data points on the tibial and femoral joint surface with a 3-D localizer system. These 3-D data are used to find those attachment points resulting in a low anisometry of the graft, while preventing impingement between the graft and the femoral notch. As the collected data points only cover a small surface patch of the femur, it is desirable to extrapolate these data to also have a visualization in those areas where no data points are available. A sufficiently good approximation of the actual femur by the model would further allow us to better deal with the notch impingement problem of the graft. The chosen approach is to fit a deformable model to the data points, it can be subdivided into two steps, constructing the model and fitting this model to the data. To incorporate a priori knowledge into the model, the allowed deformations are determined by the statistics of the shape variation of a set of training objects. Matching the training objects together is obtained by elastic registration of surface points using octree splines. The fitting process of the sparse intra-operative data with the statistical model results in a non-linear multi-dimensional function minimization. A hybrid search strategy combining local and global methods is used to avoid local minima. First experimental results with a model generated from 10 femurs are presented, including fitting of the model with both simulated and real intra-operative data.

Musculoskeletal rehabilitation and sports medicine. 3. Knee and lower extremity injuries

This self-directed learning module discusses classic concepts and highlights new advances in the diagnosis and management of knee and lower extremity injuries that commonly occur during athletic competition. It is part of the chapter on musculoskeletal rehabilitation and sports medicine in the Self-Directed Physiatric Education Program for practitioners and trainees in physical medicine and rehabilitation.

The gross morphology of torn human anterior cruciate ligaments in unstable knees

To evaluate the presence and incidence of reattachments of torn human anterior cruciate ligaments (ACL), we prospectively investigated 101 patients undergoing arthroscopic ACL reconstruction to study the intra-articular morphology of ACLs under circumstances in which functional healing had failed. Results showed that roughly 72% of these unstable knees had reattachment of the torn ACL to the posterior cruciate ligament (PCL). Eighteen percent had no signs of ACL reattachment but only 2% of previously torn ACLs were absent. These results suggest that even in chronic situations in which the knee remains functionally unstable, human ACLs rarely resorb. It also suggests that torn human ACLs commonly reattach in the knee, mainly to the PCL via a process that is consistent with scarring. While the function of these reattachments is clearly inadequate in people with unstable knees because of a combination of reattachment location, scar quantity, or quality, these results nonetheless show that the intra-articular environment in humans often maintains ACL stumps and it is not totally inhibitory to ACL reattachment via some biological process.

"Cigar Wrap" technique for gracilis augmentation in hamstring anterior cruciate ligament reconstruction

The use of Hamstring grafts for anterior cruciate ligament reconstruction is becoming increasingly popular. Most surgeons use a four-stranded graft consisting of double-stranded semitendinosus and gracilis tendons. The gracilis tendon, in addition to being smaller in diameter, is often shorter and more diminutive at its muscular end. We developed a technique for supplementing this tendon using excess semitendinosus tendon. This allows enhanced tibial tunnel fit and improved graft fixation.

Structural properties of six tibial fixation methods for anterior cruciate ligament soft tissue grafts

This study compared the stiffness (K), yield load (YL), and slippage (SL) of six tibial fixation methods. These properties were determined from load-to-failure and cyclic tests of double-looped tendon grafts fixed to both animal and young human tissue. Tandem washers (K = 259 N/mm, YL = 1159 N, SL = 0.5 mm) and the Washerloc (K = 248 N/mm, YL = 905 N, SL = 2.0 mm) were the two best fixations. At 500 N of load, which is the estimated daily tension of an anterior cruciate ligament graft during intensive rehabilitation, slippage was significantly greater in either of the other two methods for sutures tied to a post (4.9 mm), double staples (3.3 mm), and a 20-mm spiked metal washer (3.5 mm). Interference screw fixation performed well in animal tissue (YL = 776 N), but was significantly worse in young human tissue (YL = 350 N), with 57% of the fixations failing before 500 N of load. Animal tissue should not be used to estimate the performance of interference screw fixation in human tissue. Because 57% of the interference screw fixations using human tissue failed at loads below 500 N, their ability to provide adequate fixation during intensive rehabilitation should be questioned. However, both the Washerloc and tandem washers and screws provide fixation structural properties in young human tibia that should be appropriate for intensive rehabilitation.

Gait biomechanics are not normal after anterior cruciate ligament reconstruction and accelerated rehabilitation

PURPOSE

Accelerated rehabilitation for anterior cruciate ligament (ACL) injury and reconstruction surgery is designed to return injured people to athletic activities in approximately 6 months. The small amount of empirical data on this population suggests, however, that the torque at the knee joint may not return until 22 months after surgery during walking and even longer during running. Although the rehabilitation has ended and individuals have returned to preinjury activities, gait mechanics appear to be abnormal at the end of accelerated programs. The purpose of this study was to compare lower extremity joint kinematics, kinetics, and energetics between individuals having undergone ACL reconstruction and accelerated rehabilitation and healthy individuals.

METHODS

Eight ACL-injured and 22 healthy subjects were tested. Injured subjects were tested 3 wk and 6 months (the end of rehabilitation) after surgery. Ground reaction force and kinematic data were combined with inverse dynamics to predict sagittal plane joint torques and powers from which angular impulse and work were derived.

RESULTS

The difference in all kinematic variables between the two tests for the ACL group averaged 38% (all P < 0.05). The kinematics were not different between the ACL group after rehabilitation and healthy subjects. Angular impulses and work averaged 100% difference for all joints (all P < 0.05) between tests for the ACL group. After rehabilitation, the differences between injured and healthy groups in angular impulse and work at both the hip and knee remained large and averaged 52% (all P < 0.05).

CONCLUSIONS

Results indicated that after reconstruction surgery and accelerated rehabilitation for ACL injury, humans walk with normal kinematic patterns but continue to use altered joint torque and power patterns.

Computer assisted reconstruction of the anterior cruciate ligament

Reconstruction of the anterior cruciate ligament is a delicate task for which many different techniques have been proposed. A system consisting of a computer and a three-dimensional optical sensor is proposed to help the surgeon control the placement of a graft. This system can be used to minimize anisometry of the graft and avoid notch impingement. The same system, which had been validated by previous testing on 20 fresh human anatomic specimen knees, was tested on 23 patients who had an anterior cruciate ligament injury. Tunnel placement was performed using the standard technique of Morgan et al and was measured with the computer based system. It was found that all cases had different configurations of tibial and femoral placement. The computer based anisometry measurements ranged from 1.9 mm to 8.8 mm in the anterior part of the graft, and from 1 mm to 13 mm in the centers of the tunnels. Using the computer retrospectively, it was possible to find configurations of the graft in all cases that avoid notch impingement, with anisometry values ranging from 1.3 mm to 3.7 mm. This study shows that a computer based system can be a useful tool for routine anterior cruciate ligament reconstruction and can be useful for research purposes.