Revision anterior cruciate ligament surgery

Tensile properties of an anterior cruciate ligament graft after bone-patellar tendon-bone press-fit fixation

Hardware used for fixation of ACL autografts in bone tunnels frequently complicates revision surgery, requiring two-stage procedures when a bone-patellar tendon-bone (B-PT-B) autograft is used for ACL reconstruction. Therefore alternative procedures that eliminate hardware have been advocated. This study compared the mechanical behavior of two fixation procedures: a widely used interference screw (IFS) fixation and a press-fit fixation that is hardware free. Twenty hind limbs from skeletally mature Saanen breed goats were used in this study, ten each in IFS and press-fit groups. After ACL reconstruction the specimens were dissected, leaving a femur-ACL graft-tibia complex (FATC) for uniaxial tensile testing. The tests included a series of three cyclic creep tests (C1-C3) for the evaluation of residual elongation followed by a tensile load to failure test to obtain linear stiffness and ultimate load of the FATCs. Four of ten specimens failed during the cyclic creep test for the press-fit group, compared to one for the IFS group. For the remaining specimens residual elongation following three cyclic creep tests (C1-C3) was 1.7+/-0.5 mm in the press-fit group compared to 1.3+/-0.6 mm in the IFS group, and there was no statistical significant difference between the two fixations. In the load to failure test there was also no statistical significant difference in linear stiffness between the two fixations. However, the ultimate load for the press-fit group (215+/-75 N) was significantly lower than that for the IFS group (328+/-103 N). These results provide the basis for future studies involving the time course of healing of these two procedures using the goat model.

Arthroscopic anterior cruciate ligament reconstruction: a metaanalysis comparing patellar tendon and hamstring tendon autografts

BACKGROUND

The best choice of graft tissue for use in anterior cruciate ligament reconstruction has been the subject of debate.

HYPOTHESIS

Anterior cruciate ligament reconstruction with patellar tendon autograft leads to greater knee stability than reconstruction with hamstring tendon autograft.

STUDY DESIGN

Metaanalysis.

METHODS

A Medline search identified articles published from January 1966 to May 2000 describing arthroscopic anterior cruciate ligament reconstruction with either patellar tendon or hamstring tendon autograft and with a minimum patient follow-up of 24 months.

RESULTS

There were 1348 patients in the patellar tendon group (21 studies) and 628 patients in the hamstring tendon group (13 studies). The rate of graft failure in the patellar tendon group was significantly lower (1.9% versus 4.9%) and a significantly higher proportion of patients in the patellar tendon group had a side-to-side difference of less than 3 mm on KT-1000 arthrometer testing than in the hamstring tendon group (79% versus 73.8%). There was a higher rate of manipulation under anesthesia or lysis of adhesions (6.3% versus 3.3%) and of anterior knee pain in the patellar tendon group (17.4% versus 11.5%) and a higher incidence of hardware removal in the hamstring tendon group (5.5% versus 3.1%).

CONCLUSIONS

Patellar tendon autografts had a significantly lower rate of graft failure and resulted in better static knee stability and increased patient satisfaction compared with hamstring tendon autografts. However, patellar tendon autograft reconstructions resulted in an increased rate of anterior knee pain.

Revision anterior cruciate ligament reconstruction

Revision ACL surgery is indicated in patients who present with pathologic anterior laxity on clinical examination that reproduces their symptoms of instability during activities of daily living or athletic activities. The goals of the revision ACL surgery are to stabilize the knee, prevent further injury to the articular cartilage and menisci, and maximize the patient's function. Successful revision ACL surgery requires a thorough preoperative evaluation, including a detailed history, physical examination, and radiographic evaluation. Preoperative planning begins with a determination of the mechanisms of failure for the initial ACL reconstruction. Often a primary, as well as secondary cause, for failure can be identified. The determination of the cause of failure is the first step in a carefully-constructed treatment plan, which includes consideration of skin incisions to be used, method of graft removal, hardware removal, the need for a staged procedure or concomitant surgery, graft material selection, tunnel placement, graft fixation, and postoperative rehabilitation protocol. Despite the most meticulous planning, unanticipated findings may be encountered in the operating room, and the preoperative plan should have enough flexibility to accommodate these developments. Finally, it is crucial to counsel the patient preoperatively to limit his or her expectations regarding their surgical outcome. Given the complexity of revision ACL reconstruction, patient expectations must be adjusted to realistically match the potential for success. With proper planning, attention to detail, and appropriate patient expectations, revision ACL surgery can result in a beneficial and satisfying patient outcome.

Obtaining intra-articular bone grafts arthroscopically for intra-articular grafting

Autogenous bone graft is frequently necessary for arthroscopic procedures and even small open procedures that involve cruciate revision, osteochondritis dissecans repair, and fracture reduction and internal fixation. Currently used sites to obtain bone graft are the iliac crest and Gerdy's tubercle. This article describes an arthroscopic technique for harvest of small amounts of bone graft from the distal femur. This avoids the morbidity of the extra-articular harvest. Tube harvesters frequently used for osteochondral autografts are the primary tool required for this technique. However, as described, the obtaining of bone graft is much less technically exacting than when procuring osteochondral bone plugs. This provides a safe, simple way to obtain extra autogenous bone at minimal additional operative morbidity.

Initial fixation strength of bioabsorbable and titanium interference screws in anterior cruciate ligament reconstruction. Biomechanical evaluation by single cycle and cyclic loading

We evaluated the initial bone-patellar tendon-bone graft fixation strength of bioabsorbable as compared with titanium interference screws in anterior cruciate ligament reconstruction using matched pairs of porcine knees. Ten pairs underwent single-cycle failure loading at a rate of 50 mm/min, and 10 pairs underwent cyclic loading at half-hertz frequency. The cyclic loading started with 100 load cycles between 50 and 150 N. We then progressively increased loads in 50-N increments after each set of 100 cycles. After 100 cycles at 850 N, the specimens were loaded to failure at a rate of 50 mm/min. In the single-cycle failure loading test, the mean ultimate failure loads (+/-SD) for the bioabsorbable (837 +/- 260 N) and titanium interference screws (863 +/- 192 N) were not significantly different, nor were the mean yield loads or the stiffness of the fixation. In the cyclic loading test, the yield loads were 605 +/- 142 N and 585 +/- 103 N for the bioabsorbable and titanium interference screws, respectively (no significant difference). Although there was no significant difference in the ultimate failure load, more bone block fractures were found in the grafts fixed with a titanium interference screw. Bioabsorbable interference screw fixation thus seems to provide a reasonable alternative to titanium screws.

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.

Magnetic resonance imaging at different time periods following hamstring harvest for anterior cruciate ligament reconstruction

PURPOSE

The purpose of this study was to evaluate the magnetic resonance imaging (MRI) appearance of the hamstring graft harvest site after harvesting the hamstring tendons to reconstruct a torn anterior cruciate ligament (ACL).

TYPE OF STUDY

Case series.

METHODS

We performed MRI on 21 patients who had previously undergone hamstring harvest and ACL reconstruction. Twenty of the patients (7 female and 13 male; mean age, 37 years; range, 16 to 84 years), all volunteers, were selected from a series of 45 ACL reconstructions performed by the senior author during a 20-month period. Another patient, a 32-year-old man, underwent ACL reconstruction elsewhere 32 months before. Both the semitendinosus and gracilis tendons were harvested in all cases. All MRIs were obtained on a 1.5-T magnet and were prospectively evaluated by 2 experienced musculoskeletal radiologists who were blinded to the time interval between graft harvest and MRI.

RESULTS

Two weeks after graft harvest, MRI showed ill-defined intermediate signal on T1-weighted images and increased signal on T2-weighted images, consistent with fluid in the harvest site, with no discernable tendon. At 6 weeks, structures were seen at the level of the superior pole of the patella that had morphology and signal characteristics similar to native tendon. By 3 months, structures with normal morphology and signal characteristics were seen to the level of the joint line, and by 12 months, to the level of 1 to 3 cm above that of the tibial attachment. At 32 months, the tendons appeared on MRI to normalize to a level of 1 to 2 cm above their tibial attachment.

CONCLUSION

Following hamstring tendon harvest, MRI demonstrates an apparent regeneration of tendons beginning proximally and extending distally over time.