Travis Lee Turnbull

The Anterolateral Ligament An Anatomic, Radiographic, and Biomechanical Analysis

Background: Recent publications have described significant variability in the femoral attachment and overall anatomy of the anterolateral ligament (ALL). Additionally, there is a paucity of data describing its structural properties. Purpose: Quantitative data characterizing the anatomic and radiographic locations and the structural properties of the ALL may be used to guide graft selection and placement and to facilitate the future development of an evidence-based approach to ALL reconstructions. Study Design: Descriptive laboratory study. Methods: Identification of the ALL was performed by a combined outside-in and inside-out anatomic dissection of 15 nonpaired fresh-frozen cadaveric knees. Quantitative anatomic relationships were calculated using a 3-dimensional coordinate measuring device. Measurements on anteroposterior (AP) and lateral radiographs were obtained by use of a picture archiving and communications system program. Structural properties were characterized during a single pull-to-failure test using a tensile testing machine. All anatomic, radiographic, and biomechanical measurements were reported as mean values and 95% CIs. Results: The ALL was identified as a thickening of the lateral capsule coming under tension with an applied internal rotation at 30° of flexion. Its femoral attachment was located 4.7 mm (95% CI, 3.5-5.9 mm) posterior and proximal to the fibular collateral ligament attachment and coursed anterodistally to its anterolateral tibial attachment approximately midway between the center of the Gerdy tubercle and the anterior margin of the fibular head; the tibial attachment was located 24.7 mm (95% CI, 23.3-26.2 mm) and 26.1 mm (95% CI, 23.9-28.3 mm) from each structure, respectively. On the AP radiographic view, the ALL originated on the femur 22.3 mm (95% CI, 20.7-23.9 mm) proximal to the joint line and inserted on the tibia 13.1 mm (95% CI, 12.3-13.9 mm) distal to the lateral tibial plateau. On the lateral view, the femoral attachment was 8.4 mm (95% CI, 6.8-10.0 mm) posterior and proximal to the lateral epicondyle. The tibial attachment was 19.0 mm (95% CI, 17.1-20.9 mm) posterior and superior to the center of the Gerdy tubercle. The mean maximum load was 175 N (95% CI, 139-211 N) and the stiffness was 20 N/mm (95% CI, 16-25 N/mm). Failure occurred by 4 distinct mechanisms: ligamentous tear at the femoral (n = 4) or tibial (n = 1) attachment, midsubstance tear (n = 4), and bony avulsion of the tibial attachment (Segond fracture; n = 6). Conclusion: Defined ALL attachment locations can be reproducibly identified with intraoperative landmarks or radiographs. The biomechanical analysis suggests that most traditional soft tissue grafts are sufficient for ALL reconstruction. Clinical Relevance: The ALL was consistently found in all knees. Segond fractures appear to occur primarily from the avulsion of the ALL.

A Biomechanical Comparison of Femoral Cortical Suspension Devices for Soft Tissue Anterior Cruciate Ligament Reconstruction Under High Loads

Background: Graft healing after soft tissue anterior cruciate ligament (ACL) reconstruction requires rigid fixation to allow for soft tissue healing. Cortical suspension devices for femoral fixation should be biomechanically tested under high loads representative of early rehabilitation to evaluate whether they provide sufficient fixation. Purpose/Hypothesis: To biomechanically compare current fixed-loop and adjustable-loop cortical suspension devices for soft tissue femoral fixation under high loads. The hypotheses were that there would be significant differences in cyclic displacement between devices, independent of loop type, and that retensioning of the adjustable-loop devices would not significantly alter the biomechanical properties of these devices. Study Design: Controlled laboratory study. Methods: Five different femoral ACL graft cortical suspension devices (3 fixed and 2 adjustable) were compared under high cyclic forces (100-400 N for 1000 cycles) and then pulled to failure at 50 mm/min. In addition, the effect of retensioning after simulated preconditioning was evaluated for the 2 adjustable-loop devices. Results: On average, the least amount of cumulative peak cyclic displacement (mean ± SD) was observed for the ENDOBUTTON (1.05 ± 0.05 mm), followed by the RIGIDLOOP (1.09 ± 0.16 mm), XO Button (1.65 ± 0.43 mm), TightRope with retensioning (1.81 ± 0.51 mm), TightRope without retensioning (2.20 ± 0.62 mm), ToggleLoc with retensioning (3.22 ± 1.41 mm), and ToggleLoc without retensioning (3.69 ± 2.39 mm). The ENDOBUTTON displaced significantly less after cyclic loading than all adjustable-loop devices (TightRope and ToggleLoc, both with and without retensioning) and the XO Button. The RIGIDLOOP displaced significantly less than the TightRope without retensioning and ToggleLoc with and without retensioning. There was no significant difference in biomechanical properties after retensioning for both adjustable-loop devices. Conclusion: Significant differences were observed between current fixed-loop and adjustable-loop cortical suspension devices for soft tissue femoral fixation when subjected to high loads experienced during rehabilitation. Retensioning did not significantly alter the biomechanical properties of adjustable-loop devices. Clinical Relevance: Early rehabilitation protocols subject the graft construct to higher forces than what has been previously tested biomechanically. Biomechanical testing of cortical suspension devices under simulated high rehabilitation loads demonstrated significant differences between devices. Future studies should investigate the clinical implications of these time zero results.

Biomechanical Consequences of a Nonanatomic Posterior Medial Meniscal Root Repair

Background: Posterior medial meniscal root tears have been reported to extrude with the meniscus becoming adhered posteromedially along the posterior capsule. While anatomic repair has been reported to restore tibiofemoral contact mechanics, it is unknown whether nonanatomic positioning of a meniscal root repair to a posteromedial location would restore the loading profile of the knee joint. Purpose/Hypothesis: The purpose of this study was to compare the tibiofemoral contact mechanics of a nonanatomic posterior medial meniscal tear with that of the intact knee or anatomic repair. It was hypothesized that a nonanatomic root repair would not restore the tibiofemoral contact pressures and areas to that of the intact or anatomic repair state. Study Design: Controlled laboratory study. Methods: Tibiofemoral contact mechanics were recorded in 6 male human cadaveric knee specimens (average age, 45.8 years) using pressure sensors. Each knee underwent 5 testing conditions for the posterior medial meniscal root: (1) intact knee; (2) root tear; (3) anatomic transtibial pull-out repair; (4) nonanatomic transtibial pull-out repair, placed 5 mm posteromedially along the edge of the articular cartilage; and (5) root tear concomitant with an ACL tear. Knees were loaded with a 1000-N axial compressive force at 4 flexion angles (0°, 30°, 60°, 90°), and contact area, mean contact pressure, and peak contact pressure were calculated. Results: Contact area was significantly lower after nonanatomic repair than for the intact knee at all flexion angles (mean = 44% reduction) and significantly higher for anatomic versus nonanatomic repair at all flexion angles (mean = 27% increase). At 0° and 90°, and when averaged across flexion angles, the nonanatomic repair significantly increased mean contact pressures in comparison to the intact knee or anatomic repair. When averaged across flexion angles, the peak contact pressures after nonanatomic repair were significantly higher than the intact knee but not the anatomic repair. In contrast, when averaged across all flexion angles, the anatomic repair resulted in a 17% reduction in contact area and corresponding increases in mean and peak contact pressures of 13% and 26%, respectively, compared with the intact knee. Conclusion: For most testing conditions, the nonanatomic repair did not restore the contact area or mean contact pressures to that of the intact knee or anatomic repair. However, the anatomic repair produced near-intact contact area and resulted in relatively minimal increases in mean and peak contact pressures compared with the intact knee. Clinical Relevance: Results emphasize the importance of ensuring an anatomic posterior medial meniscal root repair by releasing the extruded menisci from adhesions and the posteromedial capsule. Similar caution toward preventing displacement of the meniscal root repair construct should be emphasized.

A Biomechanical Comparison of an Open Repair and 3 Minimally Invasive Percutaneous Achilles Tendon Repair Techniques During a Simulated, Progressive Rehabilitation Protocol

Background: While the nonoperative management of Achilles tendon ruptures is a viable option, surgical repair is preferred in healthy and active populations. Recently, minimally invasive percutaneous repair methods with assistive devices have been developed. Hypothesis/Purpose: The purpose of this study was to biomechanically analyze 3 commercially available, minimally invasive percutaneous techniques compared with an open Achilles repair during a simulated, progressive rehabilitation program. It was hypothesized that no significant biomechanical differences would exist between repair techniques. Study Design: Controlled laboratory study. Methods: A simulated, midsubstance Achilles rupture was created 6 cm proximal to the calcaneal insertion in 33 fresh-frozen cadaveric ankles. Specimens were then randomly allocated to 1 of 4 different Achilles repair techniques: (1) open repair, (2) the Achillon Achilles Tendon Suture System, (3) the PARS Achilles Jig System, or (4) an Achilles Midsubstance SpeedBridge Repair variation. Repairs were subjected to a cyclic loading protocol representative of progressive postoperative rehabilitation: 250 cycles at 1 Hz for each loading range: 20-100 N, 20-200 N, 20-300 N, and 20-400 N. Results: The open repair technique demonstrated significantly less elongation (5.2 ± 1.1 mm) when compared with all minimally invasive percutaneous repair methods after 250 cycles (P < .05). No significant differences were observed after 250 cycles between the Achillon, PARS, or SpeedBridge repairs, with mean displacements of 9.9 ± 2.2 mm, 12.2 ± 4.4 mm, and 10.0 ± 3.9 mm, respectively. When examined over smaller cyclic intervals, the majority of elongation, regardless of repair, occurred within the first 10 cycles. Within the first 10 cycles, open repairs achieved 71.2% of the total elongation observed after 250 cycles. Corresponding values for the Achillon, PARS, and SpeedBridge repairs were 81.8%, 77.9%, and 69.0%, respectively. No significant differences were observed in the total number of cycles to failure between minimally invasive percutaneous repairs and open repairs. Minor differences in the mechanism of failure were noted; however, the majority of all repairs failed at the suture-tendon interface. Conclusion: Minimally invasive percutaneous repair techniques demonstrated a susceptibility to significant early repair elongation when compared with open repairs. However, the ultimate strengths of repairs (cycles to failure) were comparable across all techniques. Clinical Relevance: The reduced early elongation of open repairs suggests that patients treated with this technique may be able to progress through an earlier and/or more aggressive postoperative rehabilitation protocol with a lower risk of early irrevocable repair elongation or gapping about the repair site. However, in cases where cosmesis or wound-healing complications are of significant concern, minimally invasive percutaneous techniques provide a biomechanically reasonable alternative based on their repair strengths (cycles to failure). These repairs may need to be protected longer postoperatively to allow for biological healing and avoid early repair elongation and potential gapping between the healing tendon ends.

Cyclic displacement after meniscal root repair fixation: a human biomechanical evaluation.

Background: Recent biomechanical evidence suggests that the meniscus-suture interface contributes the most displacement to the transtibial pull-out repair for meniscal root tears. Therefore, optimization of surgical technique at the meniscus-suture interface may minimize displacement and improve the strength of meniscal root repairs. Purpose/Hypothesis: The purpose of this study was to investigate the cyclic displacement and ultimate failure loads of 4 different meniscus-suture fixation techniques for posterior medial meniscal root repairs in human meniscus tissue. The hypothesis was that there would be no significant difference between the two simple sutures (TSS) technique and 3 other techniques in cyclic displacement or ultimate failure load. Study Design: Controlled laboratory study. Methods: A total of 32 fresh-frozen, human, medial meniscal transplant specimens were randomly assigned to 4 meniscus-suture fixation techniques used for transtibial pull-out repair in posterior medial meniscal root tears (n = 8 per group). The suture techniques studied were (1) TSS, (2) modified Mason-Allen (MMA), (3) single double-locking loop (S-DLL), and (4) double double-locking loop (D-DLL). The menisci were subjected to a cyclic tensioning protocol representative of postoperative rehabilitation (10-30 N for 1000 cycles) and pulled to failure at a rate of 0.5 mm/s. Results: After 1000 cycles, the TSS group displaced the least (mean ± SD, 1.78 ± 0.64 mm), followed by the MMA (2.14 ± 0.65 mm), D-DLL (2.97 ± 0.57 mm), and S-DLL (3.81 ± 0.78 mm) groups. After 100, 500, and 1000 cycles, suture displacements using the TSS and MMA techniques were not significantly different (P > .13), while the TSS technique resulted in significantly less displacement than the S-DLL and D-DLL (P < .03) techniques. The ultimate failure loads of the MMA (325 ± 77 N) and D-DLL (320 ± 50 N) techniques were significantly greater than those of the TSS (192 ± 52 N) and S-DLL (217 ± 51 N) techniques (P < .05). Conclusion: The TSS and MMA fixation techniques were not significantly different, while the TSS was significantly better at resisting displacement when compared with the S-DLL and D-DLL stitch configurations. The MMA and D-DLL techniques exhibited significantly greater failure loads than did the TSS and S-DLL techniques; however, all techniques demonstrated ultimate failure loads above the currently accepted rehabilitation force threshold. Clinical Relevance: The TSS fixation technique combines the lowest technical difficulty and the ability to resist displacement at time zero. The MMA technique, although more technically challenging, may provide an alternative means to resist displacement while enhancing the failure load.

Biomechanical Evaluation of the Transtibial Pull-Out Technique for Posterior Medial Meniscal Root Repairs Using 1 and 2 Transtibial Bone Tunnels

Background: Current methods of the transtibial pull-out meniscal root repair significantly displace under cyclic loading in porcine models but have not been evaluated in human models. One potential explanation for the displacement is that a single transtibial tunnel may not fully restore the attachment of the entire posterior medial meniscal root. Purpose/Hypothesis: The purpose of this study was to biomechanically evaluate the transtibial pull-out technique in a human cadaveric model using either 1 or 2 transtibial bone tunnels. The hypothesis was that a transtibial pull-out technique using 2 transtibial bone tunnels would confer superior biomechanical properties in comparison to an iteration using 1 transtibial bone tunnel. Study Design: Controlled laboratory study. Methods: Ten matched pairs of male human cadaveric knees (average age, 52.7 years) were randomly assigned (1 each of the pair) to 2 groups consisting of a transtibial pull-out technique using either 1 or 2 transtibial bone tunnels. The knees were cyclically loaded for 1000 cycles from 10 to 30 N at 0.5 Hz, representing the loads experienced during a typical meniscal root repair postoperative rehabilitation program, and then pulled to failure at a rate of 0.5 mm/s. Results: Differences between 1- and 2-tunnel repair groups were neither statistically nor clinically significant with respect to displacement or ultimate failure load. On average, the 1- and 2-tunnel repair groups resulted in 3.32 mm and 3.23 mm of displacement, respectively, after 1000 testing cycles. At 1, 100, 500, and 1000 testing cycles, displacement was not significantly different between groups (P > .799). The 2-tunnel repair technique resulted in a 10.2% higher ultimate failure load (135 N vs 123 N); however, this was not significant (P = .333). Conclusions: Similar biomechanical properties were seen between transtibial pull-out repairs using either 1 or 2 transtibial bone tunnels in a human cadaveric model. Both repair groups exceeded the 3-mm threshold for nonanatomic displacement. Clinical Relevance: This study indicates that a newly proposed iteration of the transtibial pull-out repair technique using a second transtibial tunnel, which theoretically restores more of the posterior medial meniscal root, was almost identical to the current clinical standard involving a single transtibial tunnel. As the importance of repairing meniscal root tears is increasingly recognized, further studies on new iterations of both techniques are warranted to minimize the risk of displacement caused by early motion in the initial postoperative rehabilitation period.

Biomechanical Analysis of an Arthroscopic Broström Ankle Ligament Repair and a Suture Anchor–Augmented Repair

Background: Secondary surgical repair of ankle ligaments is often indicated in cases of chronic lateral ankle instability. Recently, arthroscopic Broström techniques have been described, but biomechanical information is limited. The purpose of the present study was to analyze the biomechanical properties of an arthroscopic Broström repair and augmented repair with a proximally placed suture anchor. It was hypothesized that the arthroscopic Broström repairs would compare favorably to open techniques and that augmentation would increase the mean repair strength at time zero. Methods: Twenty (10 matched pairs) fresh-frozen foot and ankle cadaveric specimens were obtained. After sectioning of the lateral ankle ligaments, an arthroscopic Broström procedure was performed on each ankle using two 3.0-mm suture anchors with #0 braided polyethylene/polyester multifilament sutures. One specimen from each pair was augmented with a 2.9-mm suture anchor placed 3 cm proximal to the inferior tip of the lateral malleolus. Repairs were isolated and positioned in 20 degrees of inversion and 10 degrees of plantarflexion and loaded to failure using a dynamic tensile testing machine. Maximum load (N), stiffness (N/mm), and displacement at maximum load (mm) were recorded. Results: There were no significant differences between standard arthroscopic repairs and the augmented repairs for mean maximum load and stiffness (154.4 ± 60.3 N, 9.8 ± 2.6 N/mm vs 194.2 ± 157.7 N, 10.5 ± 4.7 N/mm, P = .222, P = .685). Conclusions: Repair augmentation did not confer a significantly higher mean strength or stiffness at time zero. Clinical Relevance: Mean strength and stiffness for the arthroscopic Broström repair compared favorably with previous similarly tested open repair and reconstruction methods, validating the clinical feasibility of an arthroscopic repair. However, augmentation with an additional proximal suture anchor did not significantly strengthen the repair.

Structural Properties of the Native Ligamentum Teres.

Background: A majority of studies investigating the role of the ligamentum teres (LT) have focused primarily on anatomical and histological descriptions. To date, however, the structural properties of the LT have yet to be fully elucidated. Purpose: To investigate the structural properties of the native LT in a human cadaveric model. Study Design: Descriptive laboratory study. Methods: A total of 12 human cadaveric hemipelvises (mean age, 53.6 years; range, 34-63 years) were dissected free of all extra-articular soft tissues to isolate the LT and its acetabular and femoral attachments. A dynamic tensile testing machine distracted each femur in line with the fibers of the LT at a displacement-controlled rate of 0.5 mm/s. The anatomic dimensions, structural properties, and modes of failure were recorded. Results: The LT achieved a mean yield load of 75 N and ultimate failure load of 204 N. The LT had mean lengths of 38.0 and 53.0 mm at its yield and failure points, respectively. The most common (75% of specimens) mechanism of failure was tearing at the fovea capitis. On average, the LT had a linear stiffness of 16 N/mm and elastic modulus of 9.24 MPa. The mean initial length and cross-sectional area were 32 mm and 59 mm2, respectively. Conclusion: The human LT had a mean ultimate failure load of 204 N. Therefore, the results of this investigation, combined with recent biomechanical and outcomes studies, suggest that special consideration should be given to preserving the structural and corresponding biomechanical integrity of the LT during surgical intervention. Clinical Relevance: The LT may be more important as a static stabilizer of the hip joint than previously recognized. Further studies are recommended to investigate the appropriate indications to perform surgical repair or reconstruction of the LT for preservation of hip stability and function.

Structural Properties of the Intact Proximal Hamstring Origin and Evaluation of Varying Avulsion Repair Techniques An In Vitro Biomechanical Analysis

Background: Although surgical repair has been reported to provide improved outcomes compared with nonoperative treatment in the management of complete proximal hamstring origin avulsions, no intact or avulsion repair biomechanical data exist to support various repair strategies or guide postoperative rehabilitation. Purpose: To compare failure load among 4 proximal hamstring tendon conditions: (1) intact, (2) repair with 2 small anchors (2S), (3) repair with 2 large anchors (2L), and (4) repair with 5 small anchors (5S). Study Design: Controlled laboratory study. Methods: Twenty-four human cadaveric hemipelvises were randomly allocated to 1 of the 4 testing groups. Intact and repaired specimens were subjected to cyclic loading at 1 Hz between 25 N and a progressively increasing maximum load that was incremented by 200 N every 50 cycles, beginning at 200 N and increasing to 1600 N. Displacement, maximum load, stiffness, number of cycles to failure, and mode of failure during cyclic loading were recorded and analyzed. Results: The intact proximal hamstring tendons failed at the highest cyclic force of all tested groups, yet no significant differences existed between the intact (1405 ± 157 N) and 5S repair (1164 ± 294 N) conditions. Both the 2S and the 2L repair groups failed at a level significantly lower than the intact hamstring (474 ± 145 N [P < .001] and 543 ± 245 N [P < .001], respectively). The maximum load attained by the 5S repairs was significantly greater than the loads attained by the 2S (P = .005) and 2L (P = .013) repairs. Conclusion: Repairs using 5 small anchors were similar to the intact tendon and were significantly stronger than repairs using only 2 large or 2 small anchors in the repair of complete avulsions of the proximal hamstring tendons. Additionally, no significant differences in strength were observed when only anchor size differed. Clinical Relevance: This finding supports the clinical investigation of postoperative range of motion rehabilitation protocols that permit full flexion and extension of the hip and knee when a 5-anchor repair construct is used.

Biomechanical Evaluation of the Medial Stabilizers of the Patella

Background: Quantification of the biomechanical properties of each individual medial patellar ligament will facilitate an understanding of injury patterns and enhance anatomic reconstruction techniques by improving the selection of grafts possessing appropriate biomechanical properties for each ligament. Purpose: To determine the ultimate failure load, stiffness, and mechanism of failure of the medial patellofemoral ligament (MPFL), medial patellotibial ligament (MPTL), and medial patellomeniscal ligament (MPML) to assist with selection of graft tissue for anatomic reconstructions. Study Design: Descriptive laboratory study. Methods: Twenty-two nonpaired, fresh-frozen cadaveric knees were dissected free of all soft tissue structures except for the MPFL, MPTL, and MPML. Two specimens were ultimately excluded because their medial structure fibers were lacerated during dissection. The patella was obliquely cut to test the MPFL and the MPTL-MPML complex separately. To ensure that the common patellar insertion of the MPTL and MPML was not compromised during testing, only one each of the MPML and MPTL were tested per specimen (n = 10 each). Specimens were secured in a dynamic tensile testing machine, and the ultimate load, stiffness, and mechanism of failure of each ligament (MPFL = 20, MPML = 10, and MPTL = 10) were recorded. Results: The mean ± SD ultimate load of the MPFL (178 ± 46 N) was not significantly greater than that of the MPTL (147 ± 80 N; P = .706) but was significantly greater than that of the MPML (105 ± 62 N; P = .001). The mean ultimate load of the MPTL was not significantly different from that of the MPML (P = .210). Of the 20 MPFLs tested, 16 failed by midsubstance rupture and 4 by bony avulsion on the femur. Of the 10 MPTLs tested, 9 failed by midsubstance rupture and 1 by bony avulsion on the patella. Finally, of the 10 MPMLs tested, all 10 failed by midsubstance rupture. No significant difference was found in mean stiffness between the MPFL (23 ± 6 N/mm2) and the MPTL (31 ± 21 N/mm2; P = .169), but a significant difference was found between the MPFL and the MPML (14 ± 8 N/mm2; P = .003) and between the MPTL and MPML (P = .028). Conclusion: The MPFL and MPTL had comparable ultimate loads and stiffness, while the MPML had lower failure loads and stiffness. Midsubstance failure was the most common type of failure; therefore, reconstruction grafts should meet or exceed the values reported herein. Clinical Relevance: For an anatomic medial-sided knee reconstruction, the individual biomechanical contributions of the medial patellar ligamentous structures (MPFL, MPTL, and MPML) need to be characterized to facilitate an optimal reconstruction design.