Akbar Nawab

Anatomic double bundle ACL reconstruction: a literature review

With the abundance of anatomic double bundle ACL reconstruction techniques that currently exist and limited patient outcome data, one has to ask whether or not they should be used and if so, which one, and what is the learning curve for the average knee surgeon to become competent with the technique that they select? The purpose of this literature review is to summarize existing anatomic double bundle ACL reconstruction surgical and rehabilitation techniques and the clinical and biomechanical study evidence that currently exists. In choosing to perform anatomic double bundle ACL reconstruction we suggest that the knee surgeon should look for evidence of: (1) control of the pivot shift phenomenon, (2) improved transverse plane rotatory knee control during the performance of sports type movements, (3) a decreased likelihood of revision procedures either for ACL reconstruction or for treatment of associated primary or recurrent meniscal injuries, (4) improved patient self-reports of perceived function, satisfaction, and quality of life, and (5) radiographic evidence of a lower incidence and/or magnitude of osteoarthritic changes compared to conventional single bundle ACL reconstruction.

Biomechanical comparison of the bioabsorbable retroscrew system, bioscrew XtraLok with stress equalization tensioner, and 35-mm delta screws for tibialis anterior graft-tibial tunnel fixation in porcine tibiae

Background Achieving effective soft tissue graft-tibial tunnel fixation remains problematic. Hypothesis No differences would exist for tibialis anterior graft-tibial tunnel fixation when comparing the RetroScrew System (20-mm retrograde screw, 17-mm antegrade screw), the 35-mm tapered Delta Screw (manual tensioning), and the 35-mm BioScrew XtraLok (applied using an instrumented tensioner). Study Design Controlled laboratory study. Methods Porcine tibiae (apparent bone mineral density, 1.3 g/cm2) and human tendon allografts were divided into 3 matched groups of 6 specimens each before cyclic (500 cycles, 50-250 N, 1 Hz) and load-to-failure (20 mm/min) tests. Results The BioScrew XtraLok (210.9 ± 54.9 N/mm) and the 35-mm Delta Screw (224.3 ± 43.7 N/mm) displayed superior stiffness to the RetroScrew System (114.1 ± 23.3 N/mm) (P =. 0004) during cyclic testing. The BioScrew XtraLok (1.0 ± 0.2 mm) and the Delta Screw (0.9 ± 0.2 mm) also displayed less displacement during cyclic testing than the RetroScrew System (1.8 ± 0.5 mm) (P =. 001). During load-to-failure testing, the BioScrew XtraLok withstood greater loads (1436.3 ± 331.3 N) (P =. 001) and displayed greater stiffness (323.6 ± 56.8 N/mm) (P =. 002) than the 35-mm Delta Screw (load, 1042.2 ± 214.4 N; stiffness, 257.2 ± 22.2 N/mm) and the RetroScrew System (load, 778.7 ± 177.5 N; stiffness, 204.4 ± 52.9 N/mm). Conclusion The BioScrew XtraLok with instrumented tensioning displayed superior fixation to the RetroScrew System and the 35-mm Delta Screw applied with manual tensioning. Clinical Relevance The BioScrew XtraLok may provide superior soft tissue graft-tibial tunnel fixation. Further in vitro studies using human tissue and in vivo clinical studies are needed.

Tendon graft fixation in ACL reconstruction: in vitro evaluation of bioabsorbable tenodesis screw.

BACKGROUND Conventional ACL reconstruction requires sufficient tibial bone quality for secure graft fixation. We evaluated the mechanical characteristics of a supplemental tenodesis screw in cadaveric specimens. MATERIAL AND METHODS One group of 7 specimens from 7-paired tibiae was randomly assigned to undergo tibialis anterior tendon graft-bone tunnel fixation with a bioabsorbable interference screw, using conventional ACL reconstruction techniques. The other group of 7 specimens underwent the same procedure supplemented with a bioabsorbable tenodesis screw. All specimens were subjected to pullout testing on a servo hydraulic device. RESULTS Specimens in the supplemental fixation group had double the load to failure (tenodesis = 467 (SD 184) N, control group = 223 (SD 66) N, p = 0.02) and were also one-third stiffer (tenodesis = 31 (SD 13) N/mm, control group = 21 (SD 6) N/mm, p = 0.03) than the specimens in the conventional fixation group. INTERPRETATION Supplemental bioabsorbable tenodesis screw fixation may be advantageous for primary reconstruction in patients with low tibial bone mineral density or during revision procedures. By providing secure soft tissue graft-tibia fixation during the early phase after ACL reconstruction, supplemental tenodesis fixation may enable patients to participate safely in more intense, early rehabilitation.

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.

Anatomical Double-Bundle Anterior Cruciate Ligament Reconstruction: Maximizing Benefits While Minimizing Complexity: A Balanced Potential Approach

The rapid development of anatomical double-bundle anterior cruciate ligament (ACL) reconstruction techniques is unprecedented, especially given the 80% to 90% success rate that has been reported for conventional single-bundle ACL reconstruction. However, in vitro and in vivo biomechanical evidence of poor transverse plane rotatory knee control and 10% to 30% complication rates associated with conventional single-bundle ACL reconstruction techniques suggest that a better method of restoring ACL function and improving patient outcomes is needed. Selection of which technique to use and its associated learning curve may decrease its desirability for the average knee surgeon who performs fewer than 10 ACL reconstruction procedures a year. This article describes an anatomical double-bundle ACL reconstruction technique that provides reciprocating double-bundle ACL function and that can be performed using a modified conventional single-bundle ACL reconstruction approach. The double-bundle function provided by this ACL reconstruction technique simulates the native ACL more closely than conventional single-bundle ACL reconstruction techniques. In addition to the aforementioned surgical innovations, there is a dire shortage of well-designed patient outcome studies regarding any of these anatomical double-bundle ACL reconstruction techniques. When considering use of a particular anatomical double-bundle ACL reconstruction technique, the knee surgeon must consider its complexity, how the procedure would influence revision surgery should it be needed, appropriate selection of patients who would benefit the most, additional patient education and behavioral change needs, rehabilitation and conditioning program modifications, and how this procedure may better protect the menisci and mitigate the onset and progression of knee osteoarthritis better than conventional single-bundle ACL reconstruction.