Self-Tensioning Feature of Knotless Suture Anchor Provides Reproducible Knotless Fixation Independent of Initial Tension.

BACKGROUND: Anterior cruciate ligament (ACL) reconstruction with suture tape reinforcement has been shown to biomechanically reduce elongation and increase ultimate strength. However, the amount and consistency of the achieved tension after primary fixation using knotless suture anchors remains unclear. PURPOSE: To determine whether initial tensioning of suture tape before fixation with a knotless suture anchor significantly affects final tension of the suture tape. STUDY DESIGN: Controlled laboratory study. METHODS: We secured 15 pairs of Sawbones blocks with predrilled tunnels to a tensile testing machine. Suture tape was inserted through a suspensory fixation button on the representative femoral block and threaded top-down through the base of the tibial block over an attachable button system. The suture tape was attached with a knotless suture anchor in a predrilled and tapped hole on the tibial block under the following pretensioning conditions: (1) slight tension of 5 N, (2) no tension, and (3) initial slack. The suture anchor was inserted as the load-time data were recorded. After initial block testing, a porcine model of 24 tibias was used to test the same pretensioning conditions. The initial loads during anchor insertion and screw-in were measured, as well as final tension. RESULTS: During block testing, no difference in final tensioning was found when comparing the slight-tension, no-tension, and slack groups (42.3 ± 5.3, 37.7 ± 6.4, and 40.2 ± 7.0 N, respectively; P = .528). Similar to block testing, no difference in final tensioning was found when comparing the slight-tension, no-tension, and slack groups using the porcine model (43.64 ± 6.69, 48.09 ± 13.93, and 44.52 ± 6.84 N, respectively; P = .633). CONCLUSION: The final tension of the suture tape construct appears to be reproducible and consistent, independent of the initial tension introduced with suture anchor placement within the tested parameters. CLINICAL RELEVANCE: The results of the current study can help optimize the placement technique of independent suture tape reinforcement for ACL reconstruction, which is a promising strategy to help prevent ACL rerupture, particularly in the early phases of postoperative rehabilitation.

Posterior Cruciate Ligament Reconstruction With Independent Suture Tape Reinforcement: An In Vitro Biomechanical Full Construct Study.

BACKGROUND: Posterior cruciate ligament (PCL) reconstruction is commonly performed to restore joint stability and prevent posterior tibial translation at higher flexion angles. However, persistent knee laxity after reconstruction is often reported. PURPOSE: To biomechanically evaluate the effect of independent suture tape (ST) reinforcement on different PCL reconstruction techniques. STUDY DESIGN: Controlled laboratory study. METHODS: PCL reconstruction using porcine bones and quadrupled bovine tendons was performed using 2 techniques: (1) an all-inside method using suspensory adjustable loop devices (ALDs) in the tibia and femur and (2) a method using an interference screw on the tibial and an ALD on the femoral site. Both were tested with and without an additional ST for 4 groups (n = 8 per group). Each construct underwent biomechanical testing involving 3000 loading cycles in 3 stages. After position-controlled cycles simulating full range of motion, force-controlled loading from 10 to 250 N and then from 10 to 500 N were performed before pull-to-failure testing. Elongation, stiffness, and ultimate strength were evaluated. RESULTS: The highest ultimate load (1505 ± 87 N), a small total elongation (2.60 ± 0.97 mm), and stiffness closest to the native human ligament (156.3 ± 16.1 compared with 198.9 ± 33.5 N/mm; P = .192) was seen in the all-inside technique using ST. Intragroup comparison revealed that reinforcement with ST produced a smaller total elongation for the screw fixation (Screw-ALD, 6.06 ± 3.60 vs Screw-ALD ST, 2.50 ± 1.28 mm; P = .018) and all-inside techniques (ALD-ALD, 4.77 ± 1.43 vs ALD-ALD ST, 2.60 ± 0.97 mm; P = .077), albeit the latter was not significantly different. Elongation for constructs without ST increased more rapidly at higher loads compared with elongation for ST constructs. The ultimate strength was significantly increased only for constructs using the all-inside technique using ST (ALD-ALD, 1167 ± 125 vs ALD-ALD ST, 1505 ± 87 N; P = .010). CONCLUSION: Adding an independent ST to PCL reconstruction led to improvement in the studied metrics by reducing the total elongation and increasing the ultimate strength, independent of the technique used. CLINICAL RELEVANCE: PCL reconstruction using additional ST reinforcement was biomechanically favorable in this study. ST reinforcement in the clinical setting could decrease knee laxity after PCL reconstruction, providing better joint stability and improved functional outcomes.

Tensioning device increases biomechanical stability of tuberosity fixation technique with cerclage sutures in reverse shoulder arthroplasty for fracture.

BACKGROUND: Complex proximal humeral fractures in elderly patients are increasingly treated with primary reverse total shoulder arthroplasty. Many surgeons use cerclage sutures for tuberosity fixation in reverse total shoulder arthroplasty for proximal humeral fractures. In this study, we hypothesized that sutures fixated with a tensioning device would achieve higher initial fixation stability of the tuberosities compared with manually knotted cerclage sutures in a biomechanical model. METHODS: A 4-part fracture was created in 7-paired human cadaver proximal humeri. The tuberosities were reduced anatomically and fixed with 3 cerclage sutures in a standardized technique. Tightening was performed either manually (n = 7) or with a cerclage tensioning device with 50 Newton meter (N m) (n = 7). The humeri were placed in a custom-made test setup enabling internal and external rotation. Cyclic loading with gradually increasing load was applied with a material testing machine starting with 20 N m and increasing by 5 N m after each 100th cycle until failure (>15° rotation of the tuberosities). Motion of the tuberosities was measured with a 3-dimensional camera system. RESULTS: Overall, the knot group reached 1040 ± 152 cycles, and the device group reached 1820 ± 719 cycles (P = .035). Major fragment motion was detected in the humeral shaft axis and in the distal divergence of the tuberosities. After 900 cycles, the knot group showed increased rotation of both lesser and greater tuberosities in all 3 axes around the humeral shaft compared with the device group. CONCLUSION: Biomechanical stability of the reattached tuberosities is significantly increased, and rotational movement of the tuberosities is decreased after tightening of the applied cerclage sutures with a tensioning device compared with manual knotting. However, transferability of these promising biomechanical results and their clinical relevance have to be verified with clinical studies.

Higher primary stability of tuberosity fixation in reverse fracture arthroplasty with 135° than with 155° humeral inclination.

BACKGROUND: Proximal humeral fractures in elderly patients are frequently treated with reverse total shoulder arthroplasty, and tuberosity healing improves clinical outcome and patient satisfaction. So far reverse prostheses with different humeral inclination (HI) angles have been used. However, it has not been investigated yet if the HI angle affects the primary stability of the tuberosity fixation in primary reverse total shoulder arthroplasty for proximal humeral fractures in a biomechanical setting. METHODS: A 4-part fracture was created in 7-paired human cadaver proximal humeri after preceding power analysis. After randomization in a pairwise fashion, reverse prostheses with either 135° (n = 7) or 155° (n = 7) were implanted. The tuberosities were reduced anatomically to the metaphysis of the prostheses and were fixed with 3 suture cerclages in a standardized technique. Tightening was performed with a cerclage tension device with 50 Newton meter (N m). Before biomechanical testing, the initial vertical and horizontal gap formation was measured. The humeri were placed in a custom-made test setup enabling internal and external rotation. Cyclic loading with a gradually increasing load magnitude was applied with a material testing machine starting with 20 N m and increasing by 5 N m after each 100th cycle until failure (>15° rotation of the tuberosities). Any motion of the tuberosities was measured with a 3-dimensional camera system. RESULTS: Overall, the 155° group reached an average of 1460 ± 270 cycles and the 135° group of 1900 ± 271 cycles (P = .048). In contrast to the 135° group, in the 155° group, a mean initial vertical (0.3 ± 0.7 mm) and horizontal (2.7 ± 3.3 mm) gap formation could be observed before cyclic loading. After 1100 cycles, the 155° group showed increased rotation of both lesser and greater tuberosities in all 3 axes around the humeral shaft compared with the 135° group. CONCLUSION: Primary stability of the reattached tuberosities is significantly increased, whereas rotational movements are decreased in prostheses with an anatomic HI of 135° compared with a 155° HI according to the original Grammont design. In addition, a 135° HI allows an exact anatomic reposition of the tuberosities, whereas this was not possible for the 155° design. However, transferability and clinical relevance of these biomechanical results have to be verified with clinical studies.

Surgical Treatment of Meniscal Extrusion: A Biomechanical Study on the Role of the Medial Meniscotibial Ligaments With Early Clinical Validation.

BACKGROUND: Meniscal extrusion refers to meniscal displacement out of the joint space and over the tibial margin, altering knee mechanics and increasing the risk of osteoarthritis. The meniscotibial ligaments have been shown to have an important role in meniscal stability. However, it remains unclear whether an isolated lesion of the medial meniscotibial ligaments will result in meniscal extrusion and whether repairing the detached ligament will reduce extrusion. HYPOTHESIS: A lesion of the medial meniscotibial ligament will result in meniscal extrusion, and repairing the joint capsule will eliminate the extrusion by returning the meniscus back to its original position. STUDY DESIGN: Controlled laboratory study. METHODS: Fresh-frozen human cadaveric knees (N = 6) were used for biomechanical testing. The test protocol involved 100 flexion-extension cycles. In full extension, meniscal extrusion was measured using ultrasound, in both an otherwise unloaded state and while subjected to a 10-N·m varus load. Each knee was tested in its native condition (baseline), after creating a detachment of the medial meniscotibial ligament, and finally with the joint capsule repaired using 3 knotless SutureTak anchors. We also performed a retrospective review of 15 patients who underwent meniscotibial ligament repair with a minimal follow-up of 5 weeks (mean, 14 weeks; range, 5-35 weeks). RESULTS: During biomechanical testing, the mean absolute meniscal extrusion at baseline was 1.5 ± 0.6 mm. After creation of the meniscotibial ligament lesion, the mean absolute meniscal extrusion was significantly increased (3.4 ± 0.7 mm) (P < .001). After repair, the extrusion was reduced to 2.1 ± 0.4 mm (P < .001). Clinically, a reduction in absolute meniscal extrusion of approximately 48% was reached (1.2 ± 0.6 vs 2.4 ± 0.5 mm preoperatively; P < .001). CONCLUSION: This study indicates that the medial meniscotibial ligaments contribute to meniscal stability as lesions cause the meniscus to extrude and that repair of those ligaments can significantly reduce extrusion. Early clinical results using this meniscotibial ligament repair technique support our biomechanical findings, as a significant reduction in meniscal extrusion was achieved. CLINICAL RELEVANCE: Our biomechanical findings suggest that repair of medial meniscotibial ligaments reduces meniscal extrusion and clinically may improve meniscal function, with the possible long-term benefit of reducing the risk for osteoarthritis.

Biomechanical Testing of Three Alternative Quadrupled Tendon Graft Constructs With Adjustable Loop Suspensory Fixation for Anterior Cruciate Ligament Reconstruction Compared With Four-Strand Grafts Fixed With Screws and Femoral Fixed Loop Devices.

BACKGROUND: Quadrupled semitendinosus (ST) grafts for anterior cruciate ligament (ACL) reconstruction have advantages of greater graft diameter and gracilis (G) preservation compared with doubled ST-G grafts. However, a paucity of biomechanical data are available regarding different preparation techniques for these constructs. PURPOSE: To biomechanically analyze 3 alternative tendon constructs fixed with adjustable suspensory fixation devices on the femur and tibia compared with a matched 4-strand construct fixed with a tibial screw and femoral fixed loop device. STUDY DESIGN: Controlled laboratory study. METHODS: Three alternative quadrupled tendon preparation techniques with suspensory fixation (grafts constructs A, B, and C) were compared with a 4-strand screw-fixed loop device construct (graft construct D) in matched diameter bovine tendon graft and porcine tibia models. Graft constructs were tested with a 3-stage cyclic loading protocol (1000 cycles in position control and 1000 cycles each from 10 to 250 N and from 10 to 400 N), followed by a pull to failure. In graft construct A, the graft ends were whipstitched and tied over the tibial button; in graft construct B, the graft ends functioned as pulleys; and in graft construct C, a continuous loop was created. Initial, dynamic, and total elongation, stiffness, and ultimate failure load were recorded. RESULTS: Graft construct D had the highest initial (0.51 ± 0.29 mm) and total (3.53 ± 0.98 mm) elongation compared with the 3 quadrupled constructs ( P < .001 each). Graft construct B had lower total elongation (2.13 ± 0.31 mm) compared with graft construct A (2.40 ± 0.30 mm) ( P = .004) and graft construct C (2.53 ± 0.21 mm) ( P = .007). Graft construct C had a higher ultimate failure load (1097 ± 79 N) compared with graft construct A (988 ± 112 N) ( P = .001), graft construct B (973 ± 137 N) ( P = .022), and graft construct D, which had the lowest failure load (767 ± 182 N) ( P < .001). CONCLUSION: The 3 quadrupled tendon suspensory fixation constructs exhibited small yet statistically significant biomechanical differences among each other. Constructs that used tibial screw fixation had lower ultimate failure load and higher total elongation compared with the quadrupled tendon constructs. CLINICAL RELEVANCE: Total elongation for the screw fixation group was higher than the threshold of clinical failure, which may allow for graft construct elongation during the postoperative rehabilitation phase. Biomechanical properties of the 3 quadrupled tendon suspensory graft constructs may be clinically comparable, albeit statistically different.

Adjustable- Versus Fixed-Loop Devices for Femoral Fixation in ACL Reconstruction: An In Vitro Full-Construct Biomechanical Study of Surgical Technique-Based Tibial Fixation and Graft Preparation.

BACKGROUND: Femoral suspensory fixation for anterior cruciate ligament (ACL) reconstruction has evolved from fixed- to adjustable-loop devices. However, there are still controversies regarding undesired lengthening of adjustable-loop devices. HYPOTHESIS: Adjustable-loop fixation will achieve similar elongation to that of fixed-loop devices, and intraoperative preconditioning will reduce initial elongation for adjustable-loop constructs. STUDY DESIGN: Controlled laboratory study. METHODS: Three adjustable-loop devices (GraftMax, TightRope, and Ultrabutton) and 2 fixed-loop devices (Endobutton and RetroButton) were used in an intraoperative surgical technique workflow according to an in vitro model with porcine bone and bovine tendons (8 specimens per device; N = 40 constructs tested). Each construct underwent 1000 cycles of position- and force-controlled dynamic loading, whereby a total elongation threshold of 3 mm was defined as clinical failure. Constructs were finally pulled to failure at 50 mm/min. RESULTS: There were no statistically significant differences among the devices for total or dynamic elongation. Total elongation (mean ± SD) for adjustable-loop constructs was 4.13 ± 1.46 mm for GraftMax, 2.78 ± 0.85 mm for TightRope, and 2.76 ± 0.45 mm for Ultrabutton; for the fixed-loop devices, total elongation was 2.85 ± 0.74 mm for Endobutton and 2.85 ± 1.03 mm for RetroButton. The GraftMax had a significantly lower initial force (95.5 ± 58.0 N) after retensioning, with the highest initial elongation (0.99 ± 0.60 mm). The Ultrabutton showed the greatest force loss (-105.9 ± 13.5 N) during position control cycling, which was significantly different from the GraftMax (-22.3 ± 28.2 N), with the smallest force loss (P < .001). The TightRope construct had a significantly smaller initial elongation (-0.36 ± 0.22 mm) and the greatest pull-to-failure load (958 ± 40 N) as compared with all of the other devices. CONCLUSION: Adjustable- and fixed-loop configurations achieved statistically comparable fixation strength for total elongation. However, the GraftMax construct exceeded the total elongation threshold of clinical failure. The Ultrabutton produced the greatest loss of force during position control cycling, and the GraftMax button design prevented proper retensioning. The TightRope had a significant greater ultimate strength when compared with all other devices. CLINICAL RELEVANCE: Biomechanical testing according to a surgical technique workflow suggests that adjustable-loop devices can be considered a safe alternative to fixed-loop devices in ACL reconstruction.

Knotless Fixation Is Stronger and Less Variable Than Knotted Constructs in Securing a Suture Loop.

BACKGROUND: Historically, tendon-to-bone fixation has relied on knot tying. However, considerable variability exists in knot-tying strength among surgeons. PURPOSE/HYPOTHESIS: The purpose of this study was to compare the biomechanical properties of knotted and knotless fixation and to evaluate variability among surgeons. The hypothesis was that knotless constructs would be stronger and have less variability as compared with knotted constructs. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 34 orthopaedic surgeons participated in a laboratory study to compare knotted and knotless constructs, where 104 knotted constructs were performed with No. 2 suture, 21 knotless constructs with No. 2 suture (K2 group), and 79 knotless constructs with suture tape (KT group). Mechanical testing was performed to compare load at 3 mm of displacement, load to failure, and stiffness of each construct. RESULTS: The mean load at 3 mm of displacement was greatest in the KT group, with significant differences among all 3 groups (P < .001). Load to failure was significantly greater in the KT group as compared with the K2 group and the knotted group (P < .001), but there was no difference between the K2 and knotted groups (P ≥ .999). Stiffness and displacement were also greatest in the KT group. Based on the F test, the variance in load to failure was significantly different between the knotted and knotless constructs, with the knotted group demonstrating greater variability (SD, 94 N) than the KT (SD, 38 N) and K2 (SD, 17 N) groups (P < .001). CONCLUSION: Knotless fixation with suture tape had improved biomechanical performance as compared with knots or knotless fixation with No. 2 suture. In addition, knotless fixation had less variability in biomechanical properties among multiple surgeons. CLINICAL RELEVANCE: This study may be relevant for surgeons choosing between knotted and knotless constructs as well as for considerations in the design of rotator cuff repair constructs.