David N.M. Caborn

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.

Femoral anteversion influences vastus medialis and gluteus medius EMG amplitude: composite hip abductor EMG amplitude ratios during isometric combined hip abduction-external rotation

This prospective study evaluated differences in vastus medialis (VM) and gluteus medius (GM) EMG amplitude:composite hip abductor (gluteus maximus, gluteus medius, tensor fascia lata) EMG amplitude ratios among subjects with low or high relative femoral anteversion. Data were collected during the performance of a non-weight bearing, non-sagittal plane maximal volitional effort isometric combined hip abduction-external rotation maneuver. Eighteen nonimpaired athletically active females participated in this surface EMG study. Medial hip rotation (relative femoral anteversion estimate) was measured with a handheld goniometer. Subjects were grouped by medial hip rotation displacement (group 1 < or = 42 degrees =36.1+/-7 degrees and group 2 > 42 degrees =52.7+/-7 degrees ) for statistical analysis (Mann Whitney U-tests, p < 0.05). Group 2 had decreased VM (42+/-23% vs. 69+/-30%, U=19, p=0.034) and GM (62+/-25% vs. 96+/-39%, U=19, p=0.034) normalized mean peak EMG amplitude:composite mean peak hip abductor EMG amplitude ratios compared to group 1. Decreased normalized VM (-27%) and GM (-34%) EMG amplitudes among subjects with increased relative femoral anteversion suggest reduced dynamic frontal and transverse plane femoral control from these muscles, possibly contributing to the increased incidence of non-contact knee injury observed among athletic females.

Biomechanical Evaluation of Meniscal Repair Systems A Comparison of the Meniscal Viper Repair System, the Vertical Mattress FasT-Fix Device, and Vertical Mattress Ethibond Sutures

Background The biomechanical characteristics of the Meniscal Viper Repair System have not been previously studied. Hypothesis Comparable meniscal lesion fixation standards will exist among the Meniscal Viper Repair System, the vertical FasT-Fix device, and vertical mattress sutures. Study Design Controlled laboratory study. Methods Porcine menisci (3 groups of 7 menisci each) were repaired using different devices. A servohydraulic device cycled each construct between 5 N and 50 N for 500 cycles before load to failure (5 mm/min). Group differences were evaluated with 1-way analysis of variance and Tukey post hoc tests. Results During cyclic testing, the vertical mattress suture group (2.3 ± 0.2 mm) showed less mean displacement than did the vertical FasT-Fix or the Viper system groups (3.9 ± 0.7 mm and 3.9 ± 0.5 mm, respectively); the vertical mattress suture group (21.8 ± 2 N/mm) also displayed superior mean stiffness to the vertical FasT-Fix or the Viper system groups (13.2 ± 2 N/mm and 13.1 ± 1.8 N/mm, respectively). During load-to-failure testing, the vertical FasT-Fix group (145.9 ± 9 N) withstood greater mean loads than did the Viper system group (111.2 ± 30 N), but it did not differ significantly from loads withstood by the vertical mattress suture group (133.4 ± 10 N). The Viper system and vertical FasT-Fix groups (14.6 ± 2 N/mm and 12.1 ± 1 N/mm, respectively) displayed superior mean stiffness to the vertical mattress suture group (9.8 ± 0.5 N/mm) during load-to-failure testing. Clinical Relevance Standard vertical mattress sutures provided superior fixation during cyclic loading compared with the 2 all-inside methods of suture fixation, suggesting a potential for better meniscal lesion healing with vertical mattress sutures when confronted with the stresses associated with early, progressive rehabilitation activities. Stronger sutures and less meniscal segment purchase in tears located 3 to 4 mm from the periphery may contribute to the failure of the Viper repair system.

A Biomechanical Comparison of Initial Soft Tissue Tibial Fixation Devices The Intrafix Versus a Tapered 35-mm Bioabsorbable Interference Screw

Background Biomechanical testing of the Intrafix device has not been performed using human tibiae. Hypothesis The Intrafix device would provide comparable or superior tibial fixation of a quadrupled hamstring tendon graft to a 35-mm-long bioabsorbable interference screw. Study Design In vitro, biomechanical study. Methods Eight paired human tibiae and 16 quadrupled hamstring tendon grafts were divided into 2 groups. Each quadrupled hamstring tendon graft was fixed in a tunnel sized to 0.5 mm graft diameter with either an Intrafix device or a screw. Results Displacement at failure was greater in the Intrafix group (17.3 ± 4.6 mm versus 10.9 ± 4.4 mm, P = .002). Load at failure (796 ± 193 N versus 647 ± 269 N), stiffness (49.2 ± 21.9 N/mm versus 64.5 ± 22 N/mm), and bone mineral density (0.74 ±0.15 gm/cm3 versus 0.74 ± 0.14 gm/cm3) did not display significant differences for the Intrafix device and the screw, respectively (P > .05). Conclusions Displacement at failure was greater for the Intrafix device. Clinical Relevance Increased displacement at failure for the Intrafix group suggests slippage from sheath channel deployment. Concentric fixation may not occur when less than optimal tibial bone mineral density increases the difficulty of attaining precise sheath deployment and quadrupled hamstring tendon graft strand alignment.

Shoulder proprioception: latent muscle reaction times.

PURPOSE The purpose of this study was to identify electromyographic (EMG) differences in the latent muscle reaction timing (LMRT) of the rotator cuff between trained overhead throwers and control subjects in response to sudden internal rotation perturbation (P < or = 0.05). METHODS Subjects included 15 trained overhead throwers (male intercollegiate baseball players) and 15 untrained subjects (males not active in competitive throwing sports). Subjects were tested while seated, with their dominant glenohumeral joint positioned in 90 degrees abduction/external rotation (scapular plane), their elbow flexed to 90 degrees, and their forearm placed in the perturbation device. Rotator cuff LMRT was assessed as they tried to decelerate a variably timed, sudden internal rotation force. EMG sampling (2000 Hz, 2-s duration) began immediately before perturbation. RESULTS Trained throwers had slower infraspinatus (P = 0.011) and teres minor (P = 0.024) LMRT and decreased supraspinatus (P = 0.001) and posterior deltoid (P = 0.0001) muscle activation duration compared with control subjects. CONCLUSIONS These results suggest that the rotator cuff muscles of trained throwers may be downregulated in response to sudden internal rotation perturbation. Although these adaptations would enable greater internal rotation velocities during overhead throwing, they may also contribute to glenohumeral joint pathology. The identification of changes in rotator cuff LMRT in response to sudden internal rotation perturbation suggests an area of acquired neuromuscular imbalance warranting consideration by those involved in the rehabilitation and conditioning of the overhead throwing athlete.

Lower Extremity Compensatory Neuromuscular and Biomechanical Adaptations 2 to 11 Years After Anterior Cruciate Ligament Reconstruction

PURPOSE To determine whether compensatory neuromuscular and biomechanical adaptations exist after successful anterior cruciate ligament reconstruction and rehabilitation. METHODS Seventy subjects, 5.3 +/- 3 years after surgery, participated in this study. Sagittal-plane lower extremity kinematic, gluteus maximus, vastus medialis, medial hamstring, and gastrocnemius electromyography (EMG) and vertical ground reaction force data were collected during single-leg countermovement jump (CMJ) performance. RESULTS Women had lower propulsive and landing forces, lower CMJ heights, less hip and knee flexion, and greater angular hip, knee, and ankle velocities than men (P < or = .014). The involved lower extremity of men and women had decreased landing forces (P = .008). During propulsion, men and women had increased involved-lower extremity gluteus maximus (P < .0001) and decreased vastus medialis (P = .013) EMG amplitudes, whereas women had bilaterally increased gastrocnemius EMG amplitudes compared with men (P = .003). During propulsion, men had longer gluteus maximus and vastus medialis EMG durations than women (P < .0001). During landing, both men and women had increased gluteus maximus EMG amplitudes at the involved lower extremity (P < .0001). Women had increased vastus medialis (P = .01) and gastrocnemius (P < .0001) EMG amplitudes compared with men. During landing, men had longer gluteus maximus (P = .004), vastus medialis (P = .012), and gastrocnemius (P = .007) EMG durations than women and the involved-lower extremity vastus medialis EMG durations of both men and women were shorter than at the noninvolved lower extremity (P = .011). CONCLUSIONS Decreased involved-lower extremity landing forces, decreased vastus medialis activation, and increased gluteus maximus and gastrocnemius activation suggest a protective mechanism to minimize knee loads that increase anterior translatory knee forces during single-leg jumping. Women showed more balanced gluteus maximus, vastus medialis, and gastrocnemius contributions to dynamic knee stability than men during CMJ landings but used shorter activation durations. LEVEL OF EVIDENCE Level IV, therapeutic case series.

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.

Electromyographic timing analysis of forward and backward cycling.

PURPOSE Backward walking to running progressions are becoming a popular, nontraditional component of functional knee rehabilitation programs. The purpose of this electromyographic (EMG) and motion analysis study was to compare the activation duration of the vastus medialis, vastus lateralis, rectus femoris, medial hamstrings, lateral hamstring, tibialis anterior, and gastrocnemius muscles during forward and backward cycling. We hypothesized that the hamstrings would demonstrate greater activation duration during backward cycling. METHODS The right lower extremity of 12 healthy subjects (6 male and 6 female) was instrumented with surface EMG electrodes and retroreflective markers to confirm lower extremity kinematic consistency between conditions. RESULTS Statistical analysis of hip, knee, and ankle kinematics (200 Hz sampling rate) and gender failed to reveal significant differences between conditions (P > 0.05). Quadrant analysis of muscle activation duration with Bonferroni corrections for multiple comparisons revealed that medial and lateral hamstring activation duration was greater during the early recovery phase (quadrant III) of backward cycling than forward cycling (P < 0.00156). Rectus femoris activation duration was greater in the early propulsive phase of backward cycling (quadrant 1) (P < 0.00156) and in the early recovery phase of forward cycling (quadrant III) (P < 0.00156). CONCLUSIONS These findings lend support for the use of backward cycling during the early recovery phase (quadrant III) to achieve a selective hamstring muscle response of relatively decreased patellofemoral stress and anterior cruciate ligament strain.

Anatomic Graft Fixation Using a Retrograde Biointerference Screw for Endoscopic Anterior Cruciate Ligament Reconstruction: Single-Bundle and 2-Bundle Techniques

Summary: This article describes a simple technique for anatomic anterior cruciate ligament (ACL) tibial graft fixation at the level of the intercondylar floor within a standard endoscopic tibial tunnel. Fixation is achieved with a retrograde positioned, cannulated biointerference screw delivered over a No. 2 permanent suture from a standard anteromedial portal. Routine interference screw fixation on the femur is carried out. For the tibia, the screw is inserted into the tibial tunnel in an inside–out position so that the head of the screw is flush with the intraarticular orifice of the tibial tunnel. Recent experimental, animal, and clinical studies have reported that the advantages of this type of anatomic graft fixation over nonanatomic tibial graft fixation include increased fixation strength, a more stable reconstruction through full knee range of motion, absence of postoperative tunnel expansion, and final biologic graft incorporation at or near the native ACL tibial insertion. Also evolving from this concept is a simplified technique for a 2-bundle ACL reconstruction using single-socket tunnel preparation on the femoral and tibial sides, specific notch preparation on the femoral side to accommodate separate anteromedial and posterolateral bundles, allowing a single-stranded soft tissue graft to be secured with concentric placement of a single femoral interference screw on the femoral surface followed by securing the anteromedial and posterolateral bundles anatomically on the tibia surface using the retrograde interference screw.

Soft Tissue Tendon Graft Fixation in Serially Dilated or Extraction-Drilled Tibial Tunnels: A Porcine Model Study Using High-Resolution Quantitative Computerized Tomography

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.