Anterior Cruciate Ligament Graft Fixation Research Articles

Biomechanical Analysis of Femoral Tunnel Pull-out Angles for Anterior Cruciate Ligament Reconstruction with Bioabsorbable and Metal Interference Screws

Background Fixation strength of metal and bioabsorbable interference screws has not been evaluated while varying the anterior cruciate ligament graft tension angle. Hypothesis There is no difference in fixation strength between 2 types of interference screws for anterior cruciate ligament graft fixation while the graft tension angle is varied relative to the femoral tunnel. Study Design Controlled laboratory study. Methods Forty-eight anterior cruciate ligament reconstructions were performed using immature porcine femurs stripped of soft tissue and doubled-over porcine flexor digitorum profundus tendon grafts. Specimens were randomized to bioabsorbable or titanium interference screw fixation. Specimens were randomized to one of three pull angles (0°, 30°, 60°) representing loading at different knee flexion angles (n = 8/group). Reconstructed ligaments were tensioned to 10 N followed by 200 loading cycles between 10 and 150 N and a final failure test. Construct elongation (mm) at 100 and 200 cycles and failure load (N) were analyzed using a 2-way analysis of variance (P < .05). Results Screw material interacted significantly with graft tension angle, as the bioabsorbable screw specimens demonstrated significantly greater fixation strength when tensioned at greater angles. Specimens fixed with bioabsorbable screws showed significantly less elongation at both 100 and 200 cycles and significantly greater failure load compared with titanium screws. Conclusion Bioabsorbable interference screws acutely have increased fixation strength compared with titanium interference screws for anterior cruciate ligament grafts loaded at greater tension angles. Clinical Relevance The strength of anterior cruciate ligament reconstruction fixation increases with increasing divergence between the tension angle and femoral tunnel, a condition seen when the knee approaches full extension.

Minimally Invasive Coracoclavicular Ligament Augmentation With a Flip Button/Polydioxanone Repair for Treatment of Total Acromioclavicular Joint Dislocation

Treatment of complete acromioclavicular joint disruption remains controversial and ranges from rehabilitation to extensive surgical reconstruction. However, high-grade injuries (type IV, V, and VI) are typically treated surgically. Most reconstruction techniques addressing these injuries selectively focus on coracoclavicular ligament augmentation because it has been shown to be the primary stabilizer of the acromioclavicular joint. The conventional coracoclavicular polydioxanone (PDS) loop, which is widely performed, has been detected to have some pivotal disadvantages, including anterior subluxation of the clavicle, extensive preparation of the coracoid, and bony avulsion of the clavicle as a result of rotational clavicle movement. Therefore we present an augmentation technique that reduces these complications by replicating the orientation of the native coracoclavicular ligament complex and providing a minimally invasive subcoracoid and clavicular fixation of a double PDS loop by use of 2 flip buttons, typically used for extracortical anterior cruciate ligament graft fixation. The key step of the procedure includes the anatomic, secure, and stable placement of the double PDS cerclage under the coracoid base transferring a flip button through a coracoid bone tunnel. Our clinical experience shows that the presented technique is easy to perform and has a comparable invasiveness to recently presented arthroscopic techniques.

Soft Tissue Tendon Graft Fixation in Serially Dilated or Extraction-Drilled Tibial Tunnels

Background Tibial tunnel preparation may contribute to improved soft tissue graft fixation. Hypothesis Step dilation produces greater tunnel wall bone volume than does extraction drilling and increases fixation strength. Bioabsorbable interference screw divergence decreases fixation strength, regardless of tunnel preparation method. Study Design Controlled laboratory study. Methods Twenty porcine tibias were divided into 2 groups of 10 with matching mean apparent bone mineral density. One group received 9-mm-diameter extraction-drilled tunnels, and the other group received 7-mm-diameter extraction-drilled tunnels followed by step dilation to 9 mm. High-resolution quantitative computerized tomography scans and voxel analysis techniques determined tunnel wall bone volume fraction. Screws secured 8.5-mm-diameter porcine grafts in the tunnels. Repeat scans were used to determine screw divergence. Cyclic loading was performed in a servohydraulic device before load to failure testing. Results The step dilation group had greater tunnel wall bone volume/total volume than did the extraction drilled group; however, a significant increase in fixation strength was not detected. Specimens with screw divergence angles less than 15° had superior fixation and insertion torques compared with specimens with angles 15° or more. Screw divergence correlated more strongly with fixation strength than did mean apparent bone mineral density or screw insertion torque. Conclusion Step dilation increased tunnel wall bone volume/total volume, but fixation strength did not improve. Screw divergence ≥15° decreases graft-bone tunnel fixation whether or not step dilation is performed. Clinical Relevance Screw alignment plays a greater role in anterior cruciate ligament graft fixation than does extraction drilling or step dilation tunnel preparation methods in healthy bone.

The effect of bone tunnel dilation versus extraction drilling on the initial fixation strength of press-fit anterior cruciate ligament reconstruction

Serial dilation of the bone tunnel has been reported to create a tighter graft-tunnel fit. It was hypothesized that a serial dilation of the femoral bone tunnel would increase the initial fixation strength in press-fit anterior cruciate ligament (ACL) reconstructive surgery. Initial fixation strength of the femoral press-fit fixation technique was investigated in 72 porcine specimens in an ex vivo study by varying the femoral tunnel preparation technique. Extraction-drilling, tunnel dilation by 1 mm and dilation by 2.5 mm were assessed. Initial fixation strength of press-fit fixated patellar tendon-bone grafts was tested within each preparation group conducting a single cycle (and cyclic) load to failure protocol. The resulting tunnel diameter and the porcine femoral bone mineral density were determined using microradiographs and peripheral quantitative CT scans, respectively. Dilating a previously extraction-drilled femoral bone tunnel by 1 mm significantly enhances initial press-fit fixation strength in both single cycle and cyclic load to failure testing when compared to extraction-drilling and tunnel dilation by 2.5 mm. Due to an initial spring-back effect the resulting diameter of the femoral tunnel was underestimated by 3.3% with drilling and 6.7 and 12.2% with dilation by 1 and 2.5 mm, respectively. Volumetric trabecular bone mineral density at the site corresponding to the area of tunnel placement averaged 318 mg/cm(3). Dilating a femoral tunnel that is underdrilled by 1 mm appears to be a reasonable technical procedure in order to enhance initial fixation strength of press-fit ACL graft fixation.

Comparison of volumetric bone mineral density in the tibial region of interest for ACL reconstruction

Adequate tibial bone mineral density (BMD) is essential to soft tissue graft fixation during anterior cruciate ligament (ACL) reconstruction. The purpose of this study was to compare volumetric bone plug density measurements at the tibial region of interest for ACL reconstruction using a standardized immersion technique and Archimedes' principle. Cancellous bone cores were harvested from the proximal, middle, and distal metaphyseal regions of the lateral tibia and from the standard tibial tunnel location used for ACL reconstruction of 18 cadaveric specimens. Proximal tibial cores displayed 32.6% greater BMD than middle tibial cores and 31.8% greater BMD than distal tibial cores, but did not differ from the BMD of the tibial tunnel cores. Correlational analysis confirmed that the cancellous BMD in the tibial tunnel related to the cancellous BMD of the proximal and distal lateral tibial metaphysis. In conjunction with its adjacent cortical bone, the cancellous BMD of the region used for standard tibial tunnel placement provides an effective foundation for ACL graft fixation. In tibia with poor BMD, bicortical fixation that incorporates cortical bone from the distal tibial tunnel region is recommended.

Bone Density and Insertion Torque as Predictors of Anterior Cruciateligament Graft Fixation Strength

Background Bone mineral density and interference screw insertion torque are thought to be useful predictors of anterior cruciate ligament graft fixation strength. Hypothesis Bone mineral density and insertion torque are reliable predictors of anterior cruciate ligament graft fixation strength. Study Design Randomized experimental study. Methods The volumetric bone mineral density, maximum insertion torque, and initial fixation strength (determined both as cyclic-loading-induced displacement and yield load) were recorded on 21 pairs of anterior cruciate ligament reconstructions. To assess the accuracy of bone mineral density and insertion torque in predicting the fixation strength, half of the specimens were first used to determine the regression equations between the variables, and then the data from the remaining specimens were used to validate the prediction equations. Results Despite the relatively high group correlations, the ability of bone mineral density and insertion torque to predict the strength of graft fixation was poor. Errors ranging from –150% to 92%, –22% to 50%, –56% to 121%, and –23% to 50% were observed when bone mineral density and insertion torque were used to predict individual cyclic-loading-induced displacement and yield load, respectively. Conclusions Neither bone mineral density nor insertion torque provides a sufficiently accurate prediction of the fixation strength of an individual soft tissue anterior cruciate ligament graft. Clinical Relevance Bone mineral density and insertion torque cannot be used to estimate the strength of interference screw fixation in anterior cruciate ligament reconstruction.

Top tips for RIGIDfix femoral fixation.

The use of pin fixation for grafts in the femoral tunnel in anterior cruciate ligament (ACL) reconstruction is becoming more popular. The transtibial stiff femoral guides are necessary to ensure that the pins fix the graft. However, the cross pins can sometimes miss the femoral tunnel. As a result of some technical problems that we encountered, we introduced an extra step in the technique of the Mitek RIGIDfix ACL Graft Fixation System (Mitek Products, Ethicon, Edinburgh, UK). This article suggests some tips for fixing problems that arise in cases in which the graft is accidentally missed with the cross pins.

Porcine Tibia is a Poor Substitute for Human Cadaver Tibia for Evaluating Interference Screw Fixation

Background Animal tissues are commonly used in anterior cruciate ligament graft fixation studies. Hypothesis Porcine bones and tendons provide good surrogates for human cadaver tissues in the biomechanical evaluation of anterior cruciate ligament reconstruction. Study Design Randomized experimental study. Method Three different tissue models—pure porcine (porcine graft fixed in porcine tibia, group 1), combination (human hamstring graft and porcine tibia, group 2), and pure human (human graft and tibia, group 3)—were compared using both cyclicloading and subsequent single-cycle load-to-failure tests to assess the effect of graft and bone tissue source (porcine vs human) on the fixation strength of anterior cruciate ligament reconstruction. Results In the cyclic-loading test, the displacement (slippage) after 1500 cycles was 2.0 mm ± 0.7 mm, 1.6 mm ± 0.4 mm, and 4.4 mm ± 1.9 mm for groups 1, 2, and 3, respectively (P< .001 between 1 and 2 vs 3). In the subsequent single-cycle load-tofailure test, the corresponding average yield loads were 668 N ± 157 N, 962 N ± 238 N, and 448 N ± 98 N, all differences being statistically significant. Conclusions In comparison to young human cadaver tibia, porcine tibia underestimate graft slippage and overestimate the failure load of the soft tissue graft in anterior cruciate ligament reconstruction. Clinical Relevance Porcine tibia does not provide a reasonable surrogate for human cadaver tibia for evaluating ACL reconstructions.

Valgus osteotomy of the tibia with a Puddu plate combined with anterior cruciate ligament reconstruction

Anterior knee instability associated with a varus deformity is a complex condition with several treatment possibilities. Among these, anterior cruciate ligament (ACL) associated to a simultaneous valgus tibial osteotomy is a increasing indication. This simultaneous procedure adds technical issues to those related to the isolated surgeries. Thus, the osteotomy plane and location of fixation hardware shouldn’t conflict with tibial tunnel and ACL graft fixation. Authors analyze the relations between a opening tibial valgus osteotomy stabilized with a Puddu plate and ACL reconstruction with a patellar tendon graft fixated with interference screws in 10 human cadaver knees. A straight oblique tibial osteotomy starting on the medial tibial cortex and oriented laterally and proximally was performed on all knees with a 10mm opening medially and stabilized with a Puddu plate on the most posterior aspect of the medial tibia, and a tibial tunnel drilled 50° to tibial plateau. With this technique there was no intersection between tibial tunnel or interference screw and the osteotomy or the plate fixation screws.

Intra-articular migration of anterior cruciate ligament graft fixation presenting as a locked knee

∗ Corresponding author. Present address: 3 Stanbury Avenue, Crownhill, Plymouth, Devon PL6 5AT, UK. Tel.: +44-1752-705-450. E-mail address: markbrinsden@doctors.org.uk (M.D. Brinsden). walking down a slight incline when the knee gave way. On standing he found that he was unable to straighten the knee. Twelve years previously he had a right anterior cruciate ligament (ACL) reconstruction using a Dacron® graft and an

Histologic findings with a bioabsorbable anterior cruciate ligament interference screw explant after 2.5 years in vivo

We retrieved a high-molecular-weight poly-L-lactic) (PLLA) anterior cruciate ligament (ACL) interference screw (Arthrex, Naples, FL) after 30 months in vivo during revision ACL surgery. Gross, histologic, histomorphometric, and molecular weight measurements were carried out on the implant and the surrounding bone. These studies showed a 75% decrease in the molecular weight of the screw, with implant fragmentation and new bone formation adjacent to the screw and graft. Healing of the graft within the bony tunnel with no significant inflammatory reaction had occurred. The clinical implications of these findings are that this implant dissolves slowly, and it was physically present at 30 months in vivo. It is a safe, nonreactive alternative to traditional metal interference screws used for ACL graft fixation. It will eventually be substituted by bone and will eliminate some of the problems associated with metallic devices.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 18, No 9 (November-December), 2002: E47–E47

Modified cross-pin femoral fixation using long needles, polydioxanone suture, and traction suture for hamstring anterior cruciate ligament reconstruction

The use of cross-pin femoral fixation in anterior cruciate ligament (ACL) reconstruction using semitendinosus and gracilis (ST/G) tendons has been shown to be biomechanically sound. As a result of some technical problems that we encountered, we modified the technique of the DePuy OrthoTech Xact ACL Graft Fixation System (DePuy, Warsaw, IN) using No. 2/0 polydioxanone suture (PDS) with long needles normally used for inside-out meniscal repair. In addition, a No. 5 Ethibond suture loop (Ethicon, Somerville, NJ) is used for traction of the ST/G graft up the femoral tunnel. Using a 2-suture loops technique, the traction suture loop offers a more effective in-line pull for the graft and it pulls the ST/G loops slightly higher than the alignment PDS. By so doing, it lessens the chance of kinking the alignment guidewire or even amputating the graft. Although not reported in literature, this type of graft complication is possible in other single-alignment suture or guidewire techniques.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 17, No 3 (March), 2001: pp 324–328

A new interference nail fixation for anterior cruciate ligament soft tissue grafts.

We present a new device for femoral and tibial fixation in anterior cruciate ligament reconstruction using soft tissue. We evaluated the method biomechanically in pullout tests using human cadaver knee joints. Fixation strengths ranged from 300 +/- 60 to 600 +/- 50 N (mean 400 +/- 50 N). This corresponds to loads in the graft during aggressive rehabilitation although cadaveric specimens were used. With respect to primary fixation strength this implant is a reasonable alternative for anterior cruciate ligament graft fixation.

The contribution of the anterior cruciate ligament to knee joint kinematics: Evaluation of its in situ forces using a robot/universal force-moment sensor test system

Damage to one of the major soft tissue structures of the knee joint, namely, the anterior cruciate ligament (ACL), can lead to significant changes in joint kinematics, which the patient perceives as instability. In this manuscript, we illustrate the importance of the anatomical complexity and biomechanical function of the ACL in knee joint kinematics. Further, we introduce a new test system whereby the in situ forces of the ACL and multiple-degree of freedom (DOF) knee kinematics are determined. Using a robotic manipulator coupled with a universal force-moment sensor (UFS), these forces can be determined directly and without making mechanical contact with the tissue. We have found that the in situ force in the human ACL in response to 110N of anterior tibial load decreases significantly with knee flexion, changing from 110.6 ± 14.8N at 15° of flexion to 71.1 ± 29.5N at 90° of flexion. Distribution of the in situ force within the human ACL was determined by consistently defining its distribution in anteromedial (AM) and posterolateral (PL) bundles of the ACL. In situ forces in the PL bundle in response to 110N of anterior tibiat load showed a maximum of 75.2 ± 18.3N at 15°, and were significantly larger than those in the AM bundle. On the contrary, in situ forces in the AM bundle varied from a maximum of 47.4 ± 34.2N at 60° to a minimum of 32.6 ± 13.3N at 0° In the porcine ACL, the magnitude of in situ force was not significantly affected as the constraints varied from 1-DOF to 5-DOF. However, the directions of the force were significantly different between 1-DOF and 5-DOF conditions. The ACL reconstruction study has shown that anatomical (proximal) ACL graft fixation in the tibial tunnel more closely reproduced the knee kinematics and in situ force of the native ACL than those in central and distal fixations. These findings have important implications in terms of the mechanisms of ACL injuries, complexity of the ACL function, and anatomy- and biomechanics-based approaches to ACL reconstruction.