Anterior Cruciate Ligament Graft Fixation Research Articles

Early outcome analysis of arthroscopic anterior cruciate ligament reconstruction using fixed closed loop and adjustable loop techniques: A prospective case series

CONTEXT: Anterior cruciate ligament (ACL) reconstruction has remained the gold standard for ACL injuries, especially for young individuals and athletes expose to high-level sporting activities aiming to return preinjury level of activity. Femoral cortical suspension devices have gained popularity. However, there are limited studies specifying a superior graft fixation technique. AIMS: To evaluate outcome of arthroscopic ACL reconstruction using fixed closed loop fixation (CLF) and adjustable loop fixation (ALF) techniques. SETTINGS AND DESIGN: Prospective case series. MATERIALS AND METHODS: 40 cases were included in the study, among of which 20 cases, underwent arthroscopic CLF and another group of 20, who were operated on using ALF. Clinical outcome was assessed using manual tests, i.e., Lachman and pivot shift, and results were graded using the International Knee Documentation Committee. Lysholm score was used to evaluate functional outcome up to 6 months. STATISTICAL ANALYSIS USED: Data were analyzed using SPSS version 21. RESULTS: There were no significant differences in manual Lachman and pivot shift grading in both groups. One case (5%) in CLF group and 15% in ALF group were showed Grade B clinically laxity by Lachman, and one case (5%) in CLF group and 10% in ALF group were showed Grade 2 + rotatory laxities by pivot shift. The study found no statistically significant differences in functional score between the groups (P = 0.245). CONCLUSIONS: In femoral fixation of ACL graft both CLF and ALF techniques may provide secure fixation, equal reduction of graft laxity, and similar functional outcome in ACL deficient knee.

Supercritical Carbon Dioxide–Sterilized Bone Allograft in the Treatment of Tunnel Defects in 2-Stage Revision Anterior Cruciate Ligament Reconstruction: A Histologic Evaluation

To examine the histologic properties of supercritical carbon dioxide (sCO2)-sterilized bone allograft for tunnel grafting and determine invivo graft quality, as well as graft incorporation and remodeling, in 2-stage revision anterior cruciate ligament (ACL) surgery. Histologic evaluation was performed in 12 subjects undergoing 2-stage revision ACL reconstruction. In the first stage, the femoral and tibial tunnels were debrided, tunnel dimensions were measured, and tunnels were grafted with sCO2-sterilized bone allograft. In the second stage, revision ACL reconstruction was performed and bone biopsy specimens were taken from the tibia. Tissue, bone, and graft volumes were measured, and histomorphometric analysis was performed. The mean time between the 2 stages was 8.8months (range, 5.6-21.3months). In the second stage, bone graft material was easily identified by its necrotic appearance comprising mature lamellar bone devoid of osteocyte nuclei within osteocyte lacunae. In all tissue samples, host-bone apposition of predominantly mature lamellar bone was noted on the surface of graft fragments in keeping with "creeping substitution." In several regions in 3 cases, osteoblastic and osteoclastic activity was evident in keeping with ongoing creeping substitution and remodeling. The mean bone volume over tissue volume was 68% (range, 33%-92%), and the mean graft volume over bone volume was 41% (range, 19%-70%). The mean graft volume (8 cases) harvested at less than 7months (44%; 95% confidence interval, 31.4%-56.8%) was not significantly different than the mean graft volume (4 cases) harvested at greater than 10months (34%; 95% confidence interval, 14.3%-54.2%; P= .214). The sCO2-sterilized bone allograft showed graft incorporation and remodeling through creeping substitution. The initial bone apposition and graft fragment bridging appear to provide a strong environment for ACL graft fixation resulting in technically successful 2-stage revision ACL reconstruction.

Three-Dimension-Printed Porous Poly(Propylene Fumarate) Scaffolds with Delayed rhBMP-2 Release for Anterior Cruciate Ligament Graft Fixation.

Anterior cruciate ligament (ACL) ruptures reconstructed with tendon grafts are commonly fixed with bioabsorbable implants, which are frequently complicated by incomplete bone filling upon degradation. Bone regeneration after ACL reconstruction could be enhanced by utilizing tissue engineering techniques and three-dimensional (3D) printing to create a porous bioabsorbable scaffold with delayed delivery of recombinant-human bone morphogenetic protein 2 (rhBMP-2). The first aim of this study was to design a 3D poly(propylene fumarate) (PPF) porous scaffold that maintained suitable pullout strength for future testing in a rabbit ACL reconstruction model. Our second aim was to determine the release kinetics of rhBMP-2 from PPF scaffolds that utilized both calcium-phosphate coatings and growth factor delivery on microspheres, both of which have been shown to decrease the initial burst release of rhBMP-2 and increase bone regeneration. To determine the degree of scaffold porosity that maintained suitable pullout strength, tapered scaffolds were fabricated with increasing porosity (0%, 20%, 35%, and 44%) and pullout testing was performed in a cadaveric rabbit ACL reconstruction model. Scaffolds were coated with carbonate hydroxyapatite (synthetic bone mineral [SBM]), and radiolabeled rhBMP-2 was delivered in four different experimental groups as follows: Poly(lactic-co-glycolic acid) microspheres only, microspheres and collagen (50:50), collagen only, and saline solution only. rhBMP-2 release was measured at day 1, 2, 4, 8, 16, and 32. The microsphere delivery groups had a smaller burst release and released a smaller percentage of rhBMP-2 over the 32 days than the collagen and saline only groups. In conclusion, a porous bioabsorbable scaffold with suitable strength for a rabbit ACL reconstruction was developed. Combining a synthetic bone mineral coating with microspheres had an additive effect, decreasing the initial burst release and cumulative release of rhBMP-2. Future studies need to evaluate this scaffold's fixation strength and bone filling capabilities in vivo compared to traditional bioabsorbable implants.

Tibial fixation without hardware for anterior cruciate ligament reconstruction: a new technique

Introduction Tibial fixation is the weakest link in anterior cruciate ligament (ACL) reconstruction. Optimal or maximal ACL graft fixation in the tibia remains a challenging goal. Also, tibial fixation with implants for ACL reconstruction can be associated with a wide variety of problems such as graft-tunnel mismatch, graft damage, and poor graft fixation using metal or absorbable implants. Patients and methods A total of 15 male patients, average age 22.2 years (range: 18–36 years), were studied from December 2005 to December 2009. Eleven of our patients had associated medial meniscus injury. The causes of ACL injury were sport accidents in 12 patients and road traffic accidents in three patients. The right limb was affected in nine patients and the left limb was affected in six patients. Results Of the 15 patients, two patients were unwilling to or unable to return for assessment. These two patients were stable and had no complications or complaints at the sixth month for the first patient and at the ninth month for the second one. The results of these two patients were reported. but they were excluded from the evaluation, leaving 13 patients for the final assessment. The follow-up duration was 24 months. Subjectively, no patient complained of residual pain or instability and all patients were able to return to full activities as before injury before 12 months. The preoperative Lysholm Knee Score was poor, with a median of 61 (range: 7–95) as would be expected after injury. The median Lysholm Score at 24 months was 95 (range: 70–95). Objectively, all patients regained full extension and the flexion ranged from 120° to 140°. All patients had a solid end point on the Lachman test, with no positive pivot shift test. Conclusion This report describes a new technique for transosseous tibial fixation for ACL grafts of all varieties. This method secures the ACL graft to the tibial metaphyseal bone, followed by knot tying over a bone bridge and augmented with bone block impacted in the tibial tunnel. This technique is a simple, safe, inexpensive, and reproducible alternative for all types of grafts fixation in the tibial tunnel without hardware in ACL reconstruction.

Biomechanical Comparison of 2 Anterior Cruciate Ligament Graft Preparation Techniques for Tibial Fixation

Background: Cortical button fixation at the femoral side and interference screws within the tibial bone tunnel are widely used for anterior cruciate ligament graft fixation. Using a bone socket instead of a full tunnel allows cortical button fixation on the tibial side as well. If adjustable-length loop cortical button devices are used for femoral and tibial fixation, the tendon graft has to be secured with sutures in a closed tendon loop. The increased distance of fixation points and potential slippage of the tendon strands at the securing sutures might lead to greater risk of postoperative graft elongation when compared with conventional graft preparation with tibial interference screw fixation. Hypothesis: Compared with an anterior cruciate ligament graft with tibial adjustable-length loop cortical button fixation, a graft with tibial interference screw fixation will show less graft elongation during cyclic loading and lower ultimate failure loads. Study Design: Controlled laboratory study. Methods: Grafts with tibial adjustable-length loop cortical button fixation and grafts with tibial interference screw fixation were biomechanically tested in calf tibiae (n = 10 per group). Femoral fixation was equivalent for both groups, using an adjustable-length loop cortical button. Specimens underwent cyclic loading followed by a load-to-failure test. Results: Grafts with screw fixation showed significantly less initial elongation (cycles 1-5: 1.46 ± 0.26 mm), secondary elongation (cycles 6-1000: 1.87 ± 0.67 mm), and total elongation (cycles 1-1000: 3.33 ± 0.83 mm) in comparison with grafts with button fixation (2.47 ± 0.26, 3.56 ± 0.39, and 6.03 ± 0.61 mm, respectively) (P < .001). While pull-out stiffness was significantly higher for grafts with screw fixation (309.5 ± 33.2 vs 185.6 ± 16.4 N/mm) (P < .001), grafts with button fixation were able to withstand significantly higher ultimate failure loads (908 ± 74 vs 693 ± 119 N) (P < .001). Conclusion: Grafts with tibial adjustable-length loop cortical button fixation resulted in higher graft elongation during cyclic loading and showed higher ultimate failure loads in comparison with conventional graft preparation with tibial interference screw fixation at time zero. Clinical Relevance: The results of this biomechanical study suggest that grafts with tibial interference screw fixation provide better knee stability at time zero because of reduced graft elongation and greater stiffness in comparison with grafts with tibial adjustable-length loop cortical button fixation.

Anterior Cruciate Ligament Reconstruction Using an Achilles Tendon Allograft Graft

Objectives:To compare femoral and tibial tunnel widening (TW) in patients undergoing anterior cruciate ligament (ACL) reconstruction using an interference screw (IS), or an EndoButton-Continuous Loop (EndoButton-CL®) on the femoral side, and an IS/staple on the tibial side.Methods:We retrospectively reviewed data on 46 patients who underwent arthroscopic ACL reconstruction with Achilles tendon allografting. Fixation was performed with a bioabsorbable IS (the IS group) in 24 patients (mean age 26.5 years), and with the EndoButton-CL device (the EB group) in 22 patients (mean age 28.1 years) on the femoral side. Evaluation included standardized anteroposterior (AP) and lateral radiography. The diameters of tunnels at the last follow-up visit (at a median time of 17 months postoperatively) were compared to those noted on radiographs taken 1 day postoperatively.Results:The two groups were similar in terms of age and gender distribution, the operated side, the size of the tunnel created, and the follow-up period (p>0.05). Femoral TW at the proximal and middle levels (on both anteroposterior and lateral views) in the IS group was significantly greater than in the EB group (p<0.050 for all comparisons). No significant difference in femoral TW at the distal level was evident between the groups, and tibial TW at all levels was similar in both groups (p>0.050).Conclusion:Femoral ACL graft fixation using an EndoButton-CL reduced femoral TW compared to use of an IS.

Intratunnel Versus Extratunnel Autologous Hamstring Double-Bundle Graft for Anterior Cruciate Ligament Reconstruction

Background: Anatomic double-bundle anterior cruciate ligament (ACL) reconstruction provides excellent results for restoring normal kinematics to the knee. Nevertheless, strong evidence supporting an ideal method for fixation of the ACL graft is lacking. Hypothesis: Intratunnel femoral fixation of the ACL graft via a cross-pin fixation technique would provide better clinical and objective results than the extratunnel femoral fixation with cortical buttons. Study Design: Randomized clinical trial; Level of evidence, 2. Methods: Seventy patients with a unilateral ACL-deficient knee were randomly assigned to 1 of 2 femoral fixation groups. Group A (35 patients) was fixed with 2 bioabsorbable Rigidfix pins, 1 cross-pin per bundle, while group B (35 patients) was secured with 1 EndoButton cortical button per bundle. All femoral tunnels were created via an anteromedial portal, and a bioabsorbable Biointrafix interference screw was used for tibial fixation for both groups. The evaluation of the patients was performed by history details, clinical examination findings, measurement of the joint laxity by KT-1000 arthrometer, and use of validated patient outcome questionnaires. Statistical analysis was carried out with Fisher exact and Mann-Whitney U tests, with P < .05 considered the cutoff level of significance. Results: At a mean follow-up of 30 months, 34 and 32 patients of group A and B, respectively, were available for evaluation. There were no statistically significant differences between the treatment groups regarding the subjective and objective outcomes, except for KT-1000 arthrometer values. The median KT-1000 value of patients in the cross-pin fixation group was 1.30 mm, while the median value in the cortical button fixation group was 1.95 mm (P < .001). Four patients with ACL grafts that were fixed with cortical buttons demonstrated failure of stability via the instrumented knee laxity testing, while patients from the other group had no failures. Conclusion: Intratunnel femoral fixation of the double-bundle ACL graft from the cross-pin fixation technique provided better instrumented knee laxity results than did the extratunnel femoral fixation with cortical buttons. Future larger studies comparing these 2 techniques should be conducted to ensure the availability of stronger evidence supporting the findings of this study.

Degradation of poly-d-l-lactide (PDLLA) interference screws (Megafix®)

Interference screw fixation is a standard procedure in anterior cruciate ligament (ACL) replacement. Aim of this study was to evaluate the degradation process of Poly-D-L-lactide (PDLLA) interference screws used for tibial ACL graft fixation. We evaluated magnetic resonance imaging (MRI) scans of 18 patients who underwent ACL revision surgery at different time points after anatomic ACL reconstruction. At primary surgery, a tibial hybrid fixation was performed with a degradable interference (IF) screw made of PDLLA (Megafix(®)) and a button. MRI revealed three different phases of degradation of the PDLLA screw. 6-8 months after surgery the IF screw was clearly visible as a well-defined structure on MRI and CT scan. After 12-16 months, the screws appeared less defined with central ingrowths' of connective tissue. In some cases only fragmented screw material was visible. At these time points, there was a slight edema surrounding the tunnel visible on MRI. After 22 months and later, the mean screw site densities were comparable with the surrounding bone density. There was no edema or signs of inflammation around the bone tunnels visible. Presence of cystic or osteolytic changes was not detected. After 22 months, a PDLLA screw may not interfere with ACL revision surgery. Regarding the degradation process of PDLLA screws, we noted three different phases. Furthermore, the degradation process observed by MRI resembles to that described by animal studies. The PDLLA screws fully absorb and are partially replaced by bone. The degradation process in humans seems to be longer than that described in animals.

Pediatric anterior cruciate ligament reconstruction using low-profile hybrid tibial fixation.

The authors introduce the application of a low-profile hybrid fixation technique for pediatric anterior cruciate ligament graft fixation into the tibia using both an interference screw and knotless anchors. This technique allows for physeal avoidance while maintaining fixation strength.

Implant-free ACL reconstruction: a review

Implant-free anterior cruciate ligament (ACL) reconstruction is the fixation of ACL grafts without the need for artificial implants. Our aim was to study the evolution of this technique, review the biomechanical evidence and summarise the results. Implant-free graft fixation for bone patella tendon ACL reconstruction was first described in 1987. This concept of implant-free graft fixation was adapted for hamstring and quadriceps tendons as alternative graft sources. Various biomechanical studies have reported that by adhering to certain technical details, this technique provides comparable fixation strength as conventional ACL fixation. The outcome studies of implant-free ACL reconstruction also report clinical results similar to ACL reconstruction with conventional implants.

Metallic or bioabsorbable interference screw for graft fixation in anterior cruciate ligament (ACL) reconstruction?

Approximately 100,000 anterior cruciate ligament (ACL) reconstructions are performed in the USA each year. Interference screw fixation is considered the standard for rigid fixation of the graft and provides higher fixation strength compared with other devices such as staples or buttons. The present study summarizes the latest evidence comparing the effectiveness of the available classes of interference screws for fixation of ACL grafts. A comprehensive search of the CINAHL, PubMed, Google Scholar, Embase Biomedical databases and the Cochrane Central Registry of Controlled Trials was performed in March 2013. Twelve studies met our inclusion criteria. Most studies showed no intergroup difference in terms of outcomes measured with validated clinical scores such as IKDC (International Knee Documentation Committee), Lysholm score and Tegner activity level. There was no significant difference regarding range of motion. Knee stability as evaluated with pivot shift and KT arthrometer showed a significant difference only in one study, favouring metallic interference screws. Tunnel widening is much more evident and marked patients who underwent ACL reconstruction with bioabsorbable screws, with no influence on the final clinical results achieved. Complication rates between the two screw classes were similar. The average modified Coleman methodology score was 74.67. AREAS OF UNCERTAINTY/RESEARCH NEED: The data comparing the outcomes achieved by two different materials for fixation, bioabsorbable and metallic, to be used during single-bundle ACL reconstruction, showed no significant difference in the final patient outcomes, in terms of clinical scores, clinical evaluation and imaging.

Supplemental bio-tenodesis improves tibialis anterior allograft yield load in extremely low density tibiae

Improved soft tissue tendon graft mechanical properties have led to their increased use for anterior cruciate ligament (ACL) reconstruction. Because they do not have an osseous component; however, there are greater concerns regarding tibial graft slippage during early postoperative rehabilitation and activities of daily living, particularly in patients with poor bone mineral density (BMD), such as older patients, women, smokers, and patients undergoing revision ACL reconstruction surgery. This in vitro biomechanical study attempted to determine the effectiveness of supplemental ACL graft fixation in low BMD tibiae. Eight paired knees (16 specimens) were harvested from female cadavers (mean age=76, range=60-88years). Tibiae were assigned to either a combination bioabsorbable interference screw, bio-tenodesis screw group (Group 1, n=8, apparent BMD=0.44±0.13g/cm(2)) or a bioabsorbable interference screw group (Group 2, n=8, apparent BMD=0.44±0.14g/cm(2)). Double-strand (single loop) tibialis anterior tendon allografts were fixed in matched diameter tibial tunnels. Using a custom 6° of freedom jig, potted constructs were mounted on to a servo hydraulic device with the axial loading force aligned directly with the tibial tunnel. Constructs underwent progressive cyclic tensile loading from 10 to 150N with a 25N load increase every 20 cycles. This was followed by yield load to failure testing (20mm/min). Groups did not display displacement differences during progressive cyclic loading. Group 1 (312.7±67.5N) displayed 25% greater yield load at failure than Group 2 (235.0±47.6N), P=0.045. Both groups displayed fixation levels well below the previously reported minimal safe threshold estimate for early unrestricted weight bearing, accelerated rehabilitation and activities of daily living. Supplemental bio-tenodesis fixation may improve early tibial-soft tissue tendon graft fixation in patients that have poor tibial BMD, but study results suggest that both methods may require weightbearing, rehabilitation, and activity of daily living restrictions during the early postoperative period to prevent graft slippage.

Tibial Tunnel Aperture Irregularity After Drilling With 5 Reamer Designs

Background: There is limited information in the literature on comparisons of antegrade versus retrograde reaming techniques and the effect on the creation of anterior cruciate ligament (ACL) tibial tunnel entry and exit apertures. Hypothesis: Proximal and distal apertures of ACL tibial tunnels, as created with different reamers, will be affected by type of reamer design. Study Design: Controlled laboratory study. Methods: Forty skeletally mature porcine tibias with bone mineral density values comparable with a young athletic population were included in this study. Five 9-mm reamer models were used (3 antegrade: A1, smooth-bore reamer; A2, acorn-head reamer; A3, flat-head reamer; 2 retrograde: R1, retrograde acorn reamer; R2, single-blade retrograde reamer), and a new reamer was used for each tibia (8 reamer-tibia pairs per reamer model). All specimens underwent micro–computed tomography scanning, and images were reconstructed and analyzed using 3-dimensional image analysis software. Aperture rim fractures were graded on a 0-IV scale that described the proportion of the fractured aperture circumference. Specimens with incomplete apertures were also recorded. Because of the unique characteristics of various tunnels, intratunnel characteristics were observed and recorded. Results: In sum, 1 proximal and 7 distal aperture rim fractures were found; 3, 0, and 4 distal aperture rim fractures were found with groups A1, A2, and A3, respectively. Incomplete apertures were more commonly found at the distal aperture (n = 15) than the proximal aperture (n = 8); there were no tibias with this finding at both apertures. All incomplete distal apertures occurred with the retrograde technique, and all incomplete proximal apertures occurred with the antegrade technique, most commonly with reamer design A3. An added finding of tunnel curvature at the distal aspect of the tunnel was observed in all 8 tibias with R1 reamers and 5 tibias with R2 reamers. This phenomenon was not observed in any of the tibias reamed with the antegrade technique. Conclusion: Anterior cruciate ligament tibial tunnel aperture characteristics were highly dependent on reamer design. Optimal proximal aperture characteristics were produced by the retrograde reamers, whereas optimal distal aperture characteristics were obtained with the antegrade reamers. In addition, a phenomenon of tunnel curvature in retrograde-type reamers was found, which may have effects on ACL graft or screw fixation. Clinical Relevance: Differences in tunnel aperture shapes and fractures depend on reamer design. This information is important for the creation of ACL reconstruction tunnels with different reamer designs.

Effect of Femoral Tunnel Length on the Safety of Anterior Cruciate Ligament Graft Fixation Using Cross-Pin Technique

Background: A more oblique placement of the anterior cruciate ligament (ACL) graft has been related to better control of rotatory knee stability. Femoral fixation with a transverse system might injure its posterolateral structures. Hypothesis: A cross-pin system, originally developed for transtibial reconstruction of the ACL, can safely be used when creating a lower femoral tunnel through the anteromedial portal. However, a long femoral tunnel must be created to protect the posterolateral structures of the knee. Study Design: Controlled laboratory study. Methods: An ACL was arthroscopically reconstructed with a hamstring graft in 22 fresh cadaveric knees. The femoral tunnel was anatomically drilled in all cases. Knee flexion angle was set at 110°. Femoral fixation was performed with a cross-pin system. A 30-mm-long femoral tunnel was created in 11 knees (group A). In the remaining 11 knees, the femoral tunnel was drilled as long as each lateral condyle permitted (group B). For both groups, the relationships were compared between the cross-pin and the lateral collateral ligament (LCL), popliteus tendon, articular cartilage, and peroneal nerve. Results: In 5 cases of group A, the cross-pin was placed either through the LCL or between the LCL and popliteus tendon, whereas in group B it was always posterior to the LCL (P = .035). The cross-pin was closer to the articular cartilage in group A than in group B (7.14 mm versus 16.9 mm; P < .001). The minimal distance to the peroneal nerve in all specimens was 23.89 mm. Conclusion: Hamstring graft fixation with a cross-pin system from the anteromedial portal with a 30-mm femoral tunnel presents a higher risk of injury to the LCL. The femoral tunnel should be drilled as long as possible. Clinical Relevance: A long femoral tunnel is required for safe transverse femoral fixation in an anatomical ACL reconstruction.

Anterior Cruciate Ligament Graft Fixation—A Myth Busted?

Anterior cruciate ligament graft fixation has become one of the most investigated topics in the sports traumatology literature. With over 400 publications within the past decade, a plausible explanation for the popularity of the topic would be that anterior cruciate ligament graft fixation represents an obvious clinical problem. Yet this does not seem to be the case. We set out to analyze the veracity of the notion that the fixation site is the weak link in a reconstructed knee in the early postoperative period. A mere temporal association is found between the first clinical reports on increased anterior tibial translation relative to the femur with soft-tissue grafts and the first pullout studies reporting lower ultimate failure loads with such grafts. This association was sufficient to convince the orthopaedic community at large that actual causality exists between soft-tissue graft fixation failure and increased knee laxity during healing. Thus the concept of “graft slippage” was born. Even with the imminent risk of being misconstrued as contentious, we submit that the entire concept of graft slippage is a myth, founded on poor scientific practice and affected by commercial bias. As a way forward, clinically important phenomena should be demonstrated through experiments with clear and sound clinical endpoints. As for preclinical studies, although they are indisputably helpful in the elaboration of such phenomena, serious hazards lie in declaring them a sufficient scientific basis for new research or, worse, for clinical standards of care. More importantly, no matter how sophisticated or fascinating their methodology, preclinical studies do not relieve us from the necessity and duty of proving our theories, whenever possible, with randomized controlled trials.

Bone Tunnel Widening After Anterior Cruciate Ligament Reconstruction Using EndoButton or EndoButton Continuous Loop

This study investigated the effect of the EndoButton CL (Smith & Nephew, Andover, MA) used for femoral graft fixation during anterior cruciate ligament reconstruction compared with an EndoButton with knot-fixed polyester tape on femoral and tibial bone tunnel widening and clinical outcome. A retrospective case-control study design was used. We compared 120 patients with EndoButton CL femoral fixation with 120 patients with an EndoButton with knot-fixed polyester tape. All patients had hamstring grafts and EndoButton femoral fixation and tibial fixation with a 7 x 30-mm metal interference screw. Tunnel widening was measured on anteroposterior (AP) and lateral radiographs at 12 months' follow-up. The largest tunnel width was measured for the femoral tunnel and in the tibial tunnel above the interference screw. Clinical outcome was assessed by objective and subjective International Knee Documentation Committee scores and KT-1000 (MEDmetric, San Diego, CA) knee laxity measurements. Femoral tunnel widening in the EndoButton group was 46.2% and 38.5% on the AP and lateral radiographs, respectively, and tibial tunnel widening was 24.9% and 33.2%, respectively. Femoral tunnel widening in the EndoButton CL group was 38.7% and 28.2% on the AP and lateral radiographs, respectively, and tibial tunnel widening was 10.9% and 23%, respectively. The EndoButton CL widening was lower for both femoral and tibial tunnels (P < .01). There were no differences between the groups for any of the clinical scores or KT-1000 knee laxity. This study showed that femoral anterior cruciate ligament graft fixation with an EndoButton and continuous polyester loop compared with an EndoButton with knot-fixed polyester tape reduced the radiographic tunnel widening at 1 year for both the femur and tibia. The reduction in tunnel widening was not associated with differences in clinical outcome with respect to International Knee Documentation Committee scores or KT-1000 knee laxity measurement. Level III, retrospective comparative study.

Tension Degradation of Anterior Cruciate Ligament Grafts With Dynamic Flexion-Extension Loading: A Biomechanical Model in Porcine Knees

This study investigates the influence of various femoral anterior cruciate ligament graft fixation methods on the amount of tension degradation and the initial fixation strength after cyclic flexion-extension loading in a porcine knee model. One hundred twenty porcine digital extensor tendons, used as 4-stranded free tendon grafts, were fixated within porcine femoral bone tunnels by use of extracortical button, cross-pin, or interference screw fixation. One hundred twenty porcine patellar tendon-bone grafts were fixated by use of cross-pin, interference screw, or press-fit fixation. Each femur-graft complex was submitted to cyclic flexion-extension loading for 1,000 cycles throughout different loading ranges, and the total loss of tension was determined. After cyclic testing, the grafts were loaded to failure, and the data were compared with a pullout series without cyclic loading. Tension degradation after 1,000 cycles of flexion-extension loading averaged 62.6% +/- 10.0% in free tendon grafts and 48.9% +/- 13.35% in patellar tendon-bone grafts. There was no influence of the loading range on the total amount of tension degradation. The total amount of tension degradation was the highest with interference screw fixation of free tendon and patellar tendon-bone grafts. Despite excessive loss of tension, the initial fixation strength of the femur-graft complex was not reduced. The method of femoral graft fixation significantly influenced tension degradation during dynamic flexion-extension loading. Femoral graft fixation methods that secure the graft close to the tunnel entrance and that displace the graft substance from the center of the bone tunnel show the largest amount of tension degradation during cyclic flexion-extension loading. The graft substance, not the fixation site, was the weakest link of the graft complex within this investigation. We believe that the graft fixation method should be considered when aiming to improve the precision of femoral graft placement in anterior cruciate ligament reconstruction.

Microporous Pure β–Tricalcium Phosphate Implants for Press-Fit Fixation of Anterior Cruciate Ligament Grafts: Strength and Healing in a Sheep Model

A sheep study was conducted to test a press-fit technique using microporous pure beta-tricalcium phosphate (beta-TCP) dowels for fixation of the anterior cruciate ligament (ACL) graft. Microporous (5 mum) cylindrical plugs of beta-TCP (diameter, 7 mm; length, 25 mm) with interconnecting pores were used. The material featured a novel configuration of structure and surface geometry. Implants were tested by use of press-fit fixation of ACL grafts with and without bone blocks in 42 sheep over a period of 24 weeks. Biomechanical, radiologic, histologic, and immunohistochemical evaluations were performed. In load-to-failure tests at 6, 12, and 24 weeks after surgery, the intra-articular graft always failed, not the fixation. Grafts showed bony fixation in the tunnel at 6 weeks and primary healing at the junction of the tunnel and joint after 24 weeks. Tricalcium phosphate was resorbed and simultaneously replaced by bone. Remodeling was still incomplete at 24 weeks. In the sheep model microporous beta-TCP implants used with press-fit fixation of ACL grafts permit early functional rehabilitation. After 6 weeks, the graft is fixed by woven bone or bony integration. Implanted microporous tricalcium phosphate is resorbed and replaced by bone. In a sheep model we showed that primary healing of ACL grafts with resorption and bony replacement of the fixating implant can be achieved by means of press-fit fixation with pure beta-TCP.

Tibial bone tunnel widening is reduced by polylactate/hydroxyapatite interference screws compared to metal screws after ACL reconstruction with hamstring grafts

Composite interference screws containing calcium phosphate for anterior cruciate ligament graft fixation could improve implant/bone integration and thereby reduced tunnelwidening and graft slippage. The present study investigated the effect of polylactate/hydroxyapatite interference screw (HA/PLLA) screw used for tibial graft fixation on tunnel widening and clinical outcomes compared with a metal interference screw. We hypothesized less tibial tunnelwidening with HA/PLLA screws compared to metal screws. Hundred patients with HA/PLLA screw tibial fixation was compared with 100 patients with metal screw tibial fixation. Tibial tunnel widening was measured on AP and lateral radiographs taken at 12 months follow-up. Clinical outcome was assessed by objective and subjective international Knee Documentation Committee (IKDC) scores, Noyes Sports Activity and Occupational Rating scores and KT-1000 knee laxity measurements. Tibial tunnel widening at the level of the metal screw group was 36% and 38% on AP and lateral radiographs respectively. Tunnel widening was lower in the HA/PLLA group with mean tunnel widening of 30% and 32% ( p = 0.012 and 0.018) on AP and lateral radiographs respectively. No differences were found for any of the clinical scores or for anterior knee laxity. The use of a polylactate/hydroxyapatite interference screw resulted in less tibial tunnel widening than a metal screw around the screw but did not affect clinical outcome or objective knee laxity.

The Influence of Femoral Technique for Graft Placement on Anterior Cruciate Ligament Reconstruction Using a Skeletally Immature Canine Model With a Rapidly Growing Physis

The purpose of this study was to evaluate 3 different femoral techniques of anterior cruciate ligament (ACL) reconstruction using a skeletally immature canine model. A soft-tissue autograft ACL reconstruction was performed in 25 ten-week-old canines via a central transphyseal tibial tunnel and 1 of 3 femoral techniques: epiphyseal, over the top, or transphyseal. The contralateral hind limbs served as controls. The canines were killed at 16 weeks postoperatively and evaluated by gross inspection, plain radiographs, photography, magnetic resonance imaging, and histomorphometry. There were no significant differences in femoral longitudinal growth; however, tibial growth was significantly greater on the experimental side relative to controls (P = .001). Angular and rotational deformities were noted on the femoral side but not on the tibial side. The epiphyseal technique resulted in less angular deformity and most closely maintained the anatomic position of the ACL graft with growth; however, this technique exhibited increased femoral rotational deformity. All techniques exhibited a high rate of graft failure. Magnetic resonance imaging revealed chondral and subchondral injuries to the lateral femoral condyle, most frequently in the epiphyseal group. From the results of our study, we cannot advocate any single femoral reconstructive technique. An epiphyseal femoral technique may reduce the risk of angular deformity and allow a more optimal femoral graft position after growth as opposed to transphyseal and over-the-top techniques. However, the epiphyseal technique may possess an increased risk for rotational deformity, physeal injury, and articular surface injury. Metaphyseal fixation of ACL grafts traversing rapidly growing physes may be responsible for the observed abnormalities in graft integrity, femoral graft position, and femoral angulation and rotation. ACL reconstruction in the skeletally immature individual is complicated by the presence of active physeal and epiphyseal cartilage surrounding the growing knee, the pathophysiologic consequences of injury to these developing structures, and the final effect on the anatomy and function of the graft, bone, and articular surface. Animal models can provide insight and direction as we develop and evaluate our treatment methods for this clinical problem, but these animal models have anatomic and physiologic differences that limit direct comparison to humans.