Higher Ultimate Failure Load Research Articles

Biomechanical strength of triceps tendon repairs: systematic review and meta-regression analysis of human cadaveric studies.

It is unclear which triceps tendon repair constructs and techniques produce the strongest biomechanical performance while minimizing the risk of gap formation and repair failure. We aimed to determine associations of construct and technique variables with the biomechanical strength of triceps tendon repairs. PubMed, Embase, Cochrane Library, Web of Science, Scopus, and ClinicalTrials.gov were systematically searched for peer-reviewed studies on biomechanical strength of triceps tendon repairs in human cadavers. 6 articles met the search criteria. Meta-regression was performed on the pooled dataset (123 specimens). Outcomes of interest included gap formation, failure mode, and ultimate failure load. Covariates were fixation type; number of implants; and number of sutures. Stratification by covariates was performed. We found no association between fixation type and ultimate failure load; however, suture anchor fixation was associated with less gap formation compared with transosseous direct repair (β = - 1.1; 95% confidence interval [CI]:- 2.2, - 0.04). A greater number of implants was associated with smaller gap formation (β = - 0.77; 95% CI: - 1.3, - 0.28) while a greater number of sutures was associated with higher ultimate failure load ( β= 3; 95% CI: 21, 125).In human cadaveric models, the number of sutures used in triceps tendon repairs may be more important than the fixation type or number of implants for overall strength. If using a transosseous direct repair approach to repair triceps tendon tears, surgeons may choose to use more sutures in their repair in order to balance the risk of larger gap formation when compared to indirect repair techniques. Level III.

The double-lasso loop technique of Biceps tenodesis has lower displacement after cyclic loading, compared to interference screw fixation: Biomechanical analysis in an ovine model.

Biceps tenodesis is an effective treatment for symptomatic long head of biceps tendon pathology. Recently the arthroscopic "double lasso-loop" suture anchor (DLSA) technique was described, advantaged by reduced cost, complexity, and operative time. We aimed to compare the in vitro strength of DLSA with conventional interference screws (IS). A biomechanical analysis was conducted on 14 sheep shoulders (8 DLSA, 6 IS), consisting of a 500-cycle cyclic loading experiment of 5-70 N and ultimate failure load (UFL) test where each specimen was pulled until failure. Displacement (mm) was recorded every 100 cycles, while stiffness and UFL were observed. Cyclic displacement was significantly lower with DLSA at 100 cycles, but not above. During the UFL test, IS was stiffer (27.68 ± 6.56 N/mm versus 14.10 ± 5.80 N/mm, p = .005) and had higher UFL (453.67 ± 148.55 N versus 234.22 ± 44.57 N, p = .001) than DLSA. All DLSA failures occurred with suture/anchor pull-out, while all IS constructs failed at the muscle/tendon. Comparison of the novel DLSA technique with a traditional IS method found lower initial displacement. While our IS constructs could withstand higher UFL, peak load characteristics of DLSA were similar to previous ovine studies. Hence, the DLSA technique is a viable alternative to IS for biceps tenodesis with its purported non-biomechanical advantages.

Outcomes After Hamstring ACL Reconstruction With Suture Tape Reinforcement in Adolescent Athletes.

Background:Previous studies have suggested that suture tape-reinforced anterior cruciate ligament (ACL) grafts may have higher ultimate failure loads without stress-shielding. In patients at high risk for graft failure, such as adolescents, the addition of suture tape could have beneficial outcomes.Hypothesis:Suture tape reinforcement (STR) of ACL grafts in adolescent patients would lead to fewer graft ruptures during early recovery, without hindering subjective outcomes.Study Design:Cohort study; Level of evidence, 3.Methods:A retrospective review was performed on adolescent patients with a minimum 2-year follow-up after hamstring tendon autograft ACL reconstruction; enrolled were patients from both before (n = 40) and after (n = 40) a shift in surgical technique that added STR. Both the no-STR and the STR cohorts were contacted yearly to obtain patient-reported outcome data for visual analog scale (VAS; range, 0-10) for pain score, Single Assessment Numeric Evaluation, Lysholm score, Tegner activity score, patient satisfaction score (range, 0-100), and return to previous level of sport (yes/no). The cohorts were then matched based on follow-up duration, excluding those with follow-up of <2 years and >3 years to maintain consistency in duration of follow-up. Graft failure was defined as either graft rupture or recurrent instability symptoms, and failures occurring from index procedure to the 3-year mark were recorded for calculations of failure rate.Results:There were no differences between cohorts in mean age [STR, 15.7 years (range, 9.5-18.7 years); no STR, 14.9 years (range, 9.3-18.8 years)], follow-up duration, laterality, or graft size. While not statistically significant, 2 (5%) patients in the STR cohort experienced graft rupture compared with 7 (17.5%) patients in the no-STR cohort. The Tegner score was significantly higher in the STR cohort (P = .017); no between-group differences were seen on the other outcome scores. A subanalysis of the STR cohort comparing small-diameter grafts (<8 mm) with grafts ≥8 mm also demonstrated no difference in outcome measures, with 1 graft failure in each cohort.Conclusion:Study outcomes indicated that patients treated with ACL reconstruction and STR experienced a significant improvement in Tegner scores while at the same time maintaining the other subjective outcomes.

Effect of a Porous Suture Containing Transforming Growth Factor Beta 1 on Healing After Rotator Cuff Repair in a Rat Model

Background: The healing failure rate after rotator cuff repair is considerably high. Purpose: To evaluate the effect of a porous suture containing transforming growth factor beta 1 (TGF-β1) on the sustained release of TGF-β1 and rotator cuff healing in a rat model. Study Design: Controlled laboratory study. Methods: A porous suture was developed, and its tensile strength was measured. TGF-β1 was delivered using the porous suture, and a TGF-β1 release test and human fibroblast proliferation assay were performed. For the animal experiment, 30 rats were randomly allocated into 3 groups (n = 10 each). A bilateral supraspinatus tendon tear was made in all the rats, and repair was performed. Group 1 received repair only; group 2, repair and a single injection of TGF-β1; and group 3, repair using the porous suture containing TGF-β1. Eight weeks after repair, biomechanical and histological analyses were performed. Results: The porous suture was successfully developed with mechanical properties compatible with the conventional suture, and the sustained release of TGF-β1 from the porous suture was confirmed. In addition, the cell proliferation assay confirmed the biological safety of the porous suture. In the animal experiment, group 3 biomechanically exhibited the largest cross-sectional area and the highest ultimate failure load and ultimate stress (all P < .05). Histological examination revealed that group 3 showed significantly better collagen fiber density and tendon-to-bone maturation than did groups 1 and 2 (all P < .05). Conclusion: The porous suture containing TGF-β1 could sustainedly and safely release TGF-β1, and its use during rotator cuff repair could improve rotator cuff healing, as assessed on the basis of the biomechanical and histological changes in the rat model in this study. Considering the effectiveness, safety, and convenience of the porous suture without extra effort in surgery, the findings of the present study will have a far-reaching effect on the treatment of rotator cuff tears. Clinical Relevance: The porous suture containing TGF-β1 might improve healing after rotator cuff repair.

Factors affecting biomechanical strength of Latarjet constructs: A systematic review and meta-regression.

The Latarjet procedure reduces recurrent glenohumeral instability but has potential hardware and graft complications. The procedure has been modified to use various screw types as well as suture buttons. Biomechanical studies have evaluated the effect of these implants on construct strength. With varying results it is unclear whether there is an optimal implant to use. We conducted a systematic review of human cadaveric biomechanical studies evaluating Latarjet ultimate failure load. Two independent reviewers screened articles and included them after full text review. Additional factors including implants used, graft orientation, cortices engaged, drill diameter, and screw characteristics were recorded. Meta-regression was performed on the 145 specimens from eight studies that met inclusion criteria. Screw fixation resulted in a 396.8 N (95% CI, 149.8-643.7) N higher ultimate failure load against shear stresses than suture buttons (p = 0.002). There were no differences between implants for ultimate failure load against tensile forces. Tensile strength was significantly affected by drill diameter with each millimeter of increase reducing the mean ultimate failure load by 127.4 N (95% CI, 41.2-213.6) N (p = 0.004). These results suggest that using screw fixation and minimizing drill diameter can obtain the maximum ultimate failure load against both shear and tensile forces in a Latarjet construct.

Alginate Nonwoven-Sponge Composite Scaffold for Rotator Cuff Tendon Repair

Growth factor-mediated healing of rotator cuff tendon requires to develop a clinically applicable biomaterial playing roles of mechanical support and growth factor release in vivo. In this study, the alginate (AG) nonwoven-sponge composite scaffold (AGNWSP) was fabricated through the formation of an AG sponge layer on the AG nonwoven scaffold (AGNW) surface, and rotator cuff repair with the AG-based scaffolds containing transforming growth factor-beta 1 (TGF-β1) was investigated with a rabbit model. AGNWSP had higher tensile strength, lower bioabsorbability, and higher sustained TGF-β1 release capacity than AGNW, which were highly correlated with tendon regeneration. AGNW and AGNWSP were fixed to the ruptured tendon-to-bone sites, and fresh solutions of TGF-β1 were injected into the scaffolds. When AGNWSP was applied, the repaired supraspinatus tendon had higher ultimate failure load and stress. In addition, well-organized collagen fibers and fibrocartilages were observed at the tendon-to-bone interface in this case. It is suggested that high degree of ruptured rotator cuff healing could be achieved with AGNWSP in combination with TGF-β1.

In-vitro fatigue and fracture performance of three different ferrulized implant connections used in fixed prosthesis

Background/purposeThe aim of the present in vitro study was to evaluate fatigue resistance of dental fixtures in three different types of fixture/abutment finishing line.Materials and methodsTransmucosal dental implants, with or without ferrulized neck, underwent fatigue tests (static and dynamic load) using the following standard protocol: UNI EN ISO 14801:2016. Two types of loading devices (screw- or cement-retained restoration) were also tested, and fatigue cycle tests were run to failure. Data of static and dynamic load tests were analyzed by proper statistical methods.ResultsFollowing standard protocol for fatigue testing, the ILC type (Implant Level with ferrulized neck and cement-retained crown) showed a non-significant but higher Ultimate Failure Load (UFL = 445.7 N) compared to AL type (Abutment Level without ferrule effect, 421.6 N) and ILS type (Implant Level with ferrulized neck and Screw-retained crown, 362.8 N). No fracture of the titanium-base was registered in the tested specimens during the static loadings. Permanent deformations of the materials were observed.ConclusionThe number of cycles to either fracture or deformation (higher than 4 mm) occurring during fatigue tests showed that the stress rupture curve of the materials in group ILS appeared to be significantly different from those of the ILC and AL groups (p-values < 0.01): much higher life of one-half order of magnitude.

Comportement biomécanique de différents types de suture des tendons ischio-jambiers dans la reconstruction trois brins « tout en dedans » du ligament croisé antérieur

BackgroundIn all-inside anterior cruciate ligament (ACL) reconstruction, it is usually difficult to obtain sufficient autologous semitendinosus tendon length for quadruple stranded graft in Asians, females, and those with short stature. The purpose of this study was to compare biomechanical properties of three different types of suture preparations for tripled graft and determine which method could achieve sufficient strength for ACL through in vitro study. HypothesisThe hypothesis of this study was that suturing with a rip-stop (RS) stitch for tripled-strand graft would lead to stronger mechanical properties than suturing with buried-knot four sutures. MethodsTwenty-four bovine digital extensor tendons harvested from forelimbs were prepared for tripled-strand graft in three different ways: 1) buried-knot four sutures, 2) two RS sutures, and 3) four RS sutures. These grafts were directly connected to cylindrical metal rods of a tensile testing machine. All specimens underwent cyclic loading followed by a load-to-failure test. Preparation time, elongation, stiffness, and ultimate failure load were compared. ResultsFor biomechanical comparison, the group with buried-knot four sutures was excluded because six (75%) specimens failed during the cycle load test. The group with four RS sutures showed lower total elongation (two RS sutures: 8.42±5.28mm; four RS sutures: 3.86±0.83mm, p=0.030), higher stiffness (two RS sutures: 247.28±53.39N/mm; four RS sutures: 329.27±55.56N/mm, p<0.001), and higher ultimate failure load (two RS sutures: 567.74±60.50N; four RS sutures: 736.46±32.50N, p=0.009). The most common failure mechanism of triple stranded graft was tendon split across sutures. ConclusionThe method with four RS sutures showed sufficient strength for triple stranded graft for all-inside ACL reconstruction without increasing preparation time. Level of evidenceIII, controlled laboratory study.

Is a Local Administration of Parathyroid Hormone Effective to Tendon-to-Bone Healing in a Rat Rotator Cuff Repair Model?

To evaluate the effect of local parathyroid hormone (PTH) administration on rotator cuff tendon-to-bone healing in a rat model compared with systemic PTH injection and untreated controls. PTH-alginate scaffold was prepared and sustained release of PTH was confirmed. Bilateral supraspinatus tendon repairs were performed in 39 rats (group 1, supraspinatus repair only; group 2, supraspinatus repair with systemic PTH injection; group 3, supraspinatus repair with local PTH administration via an absorbable scaffold; n = 13 each). Biomechanical (cross-sectional area, mode of failure, load to failure, and ultimate stress: right side) and histological analyses (hematoxylin and eosin stain, Masson's Trichrome stain Picrosirius red stain, Immunohistochemistry for BMP2, PTH1R, ColI, and ColIII: Left side) were performed to evaluate tendon-to-bone healing quality at 8 weeks after repair, and blood test (osteocalcin and procollagen type I N-terminal pro-peptide [PINP] levels) was performed in all rats. There was no intergroup difference in the healing failure rate (p = 0.910) or failure mode (p = 0.585). Biomechanically, subjects in groups 2 and 3 exhibited significantly larger cross-sectional areas and higher ultimate failure loads and ultimate stress than those in group 1 (all p < 0.05); however, no differences were noted between groups 2 and 3 (all p > 0.05). Histologically, groups 2 and 3 exhibited more organized tendon-to-bone interface structures with higher density, parallel orientation, and collagen fiber continuity than group 1 (all p < 0.05 except collagen fiber continuity in group 1 vs. 2); however, no differences in histological parameters between groups 2 and 3 (all p > 0.05). The protein levels of bone morphogenic protein 2, PTH 1 receptor, and collagen I and III and the serum level of PINP were increased in groups 2 and 3 versus group 1 (all p < 0.05) without showing differences between groups 2 and 3 (all p > 0.05). Local PTH administration using an absorbable scaffold improved the biomechanical and histological outcomes of rotator cuff tendon-to-bone healing comparable with systemic PTH injection at 8 weeks after repair in a rat model. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:82-91, 2020.

Biomechanical properties of off-axis screw in Pauwels III femoral neck fracture fixation: Bicortical screw construct is superior to unicortical screw construct

ObjectivesThe purpose of this study is to determine the biomechanical properties of the bicortical off-axis screw fixation for stabilizing of Pauwels III femoral neck fractures compared with other fixation methods. MethodsEighteen synthetic femurs (Sawbones Pacific Research Laboratories, Vashon, WA) were divided into three groups. The osteotomy was made vertically to mimic the Pauwels type III femoral neck fracture. Group A (n = 6) was fixed with traditional inverted triangle cannulated screws. Group B (n = 6) was fixed with a unicortical off-axis screw and two parallel cannulated screws. Group C (n = 6) was fixed with a bicortical off-axis screw and two parallel cannulated screws. Each group was tested with a nondestructive axial compression test at a 7° of valgus followed with 1000 cycles of cyclic loading test from 100 N to 1000 N. Finally, a destructive axial compression test was applied until catastrophic failure. ResultsThe average axial stiffness from group A to group C was 856.5, 934, and 1340 N/mm, respectively. The average ultimate failure load from group A to group C was 2612.7, 2508.8, and 3706 N, respectively. Group C exhibited significantly greater axial stiffness and a higher ultimate failure load than the other two groups (P < 0.05). Regarding the interfragmental displacement, the values from group A to group C were 0.41, 0.83, 0.36, respectively, and group B exhibited significantly larger fracture gap formation after the cyclic loading test. ConclusionsThe results of this biomechanical study show statistically significant increases in axial stiffness and ultimate failure load for the off-axis screw placed in bicortical fashion. Once the off-axis screw was positioned unicortically, the largest fracture diastasis was observed as compared to the other two methods.

Biomechanical comparison of different tendon suturing techniques for three-stranded all-inside anterior cruciate ligament grafts

ObjectiveIn all-inside anterior cruciate ligament (ACL) reconstruction, it is usually difficult to obtain sufficient autologous semitendinosus tendon length for quadruple stranded graft in Asians, females, and those with short stature. The purpose of this study was to compare biomechanical properties of three different types of suture preparations for tripled graft and determine which method could achieve sufficient strength for ACL through in vitro study. The hypothesis of this study was that suturing with a rip-stop (RS) stitch for tripled-strand graft would lead to stronger mechanical properties than suturing with buried-knot four sutures. MethodsTwenty-four bovine digital extensor tendons harvested from forelimbs were prepared for tripled-strand graft in three different ways: (1) buried-knot four sutures, (2) two RS sutures, and (3) four RS sutures. These grafts were directly connected to cylindrical metal rods of a tensile testing machine. All specimens underwent cyclic loading followed by a load-to-failure test. Preparation time, elongation, stiffness, and ultimate failure load were compared. ResultsFor biomechanical comparison, the group with buried-knot four sutures was excluded because six (75%) specimens failed during the cycle load test. The group with four RS sutures showed lower total elongation (two RS sutures: 8.42±5.28mm; four RS sutures: 3.86±0.83mm, p=0.030), higher stiffness (two RS sutures: 247.28±53.39N/mm; four RS sutures: 329.27±55.56N/mm, p<0.001), and higher ultimate failure load (two RS sutures: 567.74±60.50N; four RS sutures: 736.46±32.50N, p=0.009). The most common failure mechanism of triple stranded graft was tendon split across sutures. ConclusionThe method with four RS sutures showed sufficient strength for triple stranded graft for all-inside ACL reconstruction without increasing preparation time. Level of evidenceIII, controlled laboratory study.

Biomechanical analysis of four different medial row configurations of suture bridge rotator cuff repair

BackgroundRotator cuff tendon rupture after suture bridge repair occasionally occurs at the medial row, with remnant tendon tissue remaining at the footprint. While concentrated medial row stress is suspected to be involved in such tears, the optimal suture bridge technique remains controversial. MethodsThis study aimed to investigate the construct strength provided by suture bridge techniques having four different medial row configurations using artificial materials (n = 10 per group): Group 1, four-hole (two stitches per hole) knotless suture bridge; Group 2, eight-hole (one stitch per hole) parallel knotless suture bridge; Group 3, eight-hole non-parallel knotless suture bridge; and Group 4, eight-hole knot-tying suture bridge. Each construct underwent cyclic loading from 5 to 30 N for 20 cycles, followed by tensile testing to failure. The ultimate failure load and linear stiffness were measured. FindingsGroup 2 had the highest ultimate failure load (mean 160.54 N, SD 6.40) [Group 4 (mean 150.21 N, SD 9.76, p = 0.0138), Group 3 (mean 138.80 N, SD 7.18, p < 0.0001), and Group 1 (mean 129.35 N, SD 4.25, p < 0.0001)]. The linear stiffness of Group 2 (mean 9.32 N/mm, SD 0.25) and Group 4 (mean 9.72 N/mm, SD 0.40) was significantly higher (p = 0.0032) than that of Group 1 (mean 8.44 N/mm, SD 0.29) and Group 3 (mean 8.61 N/mm, SD 0.31). InterpretationIn conclusion, increasing the number of suture-passed holes, arranging the holes in parallel, and a knotless technique improved the failure load following suture bridge repair.

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.

Kartogenin Enhances Collagen Organization and Mechanical Strength of the Repaired Enthesis in a Murine Model of Rotator Cuff Repair

To investigate the use of kartogenin (KGN) in augmenting healing of the repaired enthesis after rotator cuff repair in a murine model. Seventy-two C57BL/6 wild-type mice underwent unilateral detachment and transosseous repair of the supraspinatus tendon augmented with either fibrin sealant (control group; n= 36) or fibrin sealant containing 100μmol/L of KGN (experimental group; n= 36) applied at the repair site. Postoperatively, mice were allowed free cage activity without immobilization. Mice were humanely killed at 2 and 4weeks postoperatively. Repair site integrity was evaluated histologically through fibrocartilage formation and collagen fiber organization and biomechanically through load-to-failure testing of the supraspinatus tendon-bone construct. At 2weeks, no differences were noted in percent area of fibrocartilage, collagen organization, or ultimate strength between groups. At 4weeks, superior collagen fiber organization (based on collagen birefringence [17.3 ± 2.0 vs 7.0 ± 6.5 integrated density/μm2; P<.01]) and higher ultimate failure loads (3.5 ± 0.6N vs 2.3 ± 1.1N; P= .04) were seen in the KGN group. The percent area of fibrocartilage (13.2 ± 8.4% vs 4.4 ± 5.4%; P= .04) was higher in the control group compared with the KGN group. Rotator cuff repair augmentation with KGN improved the collagen fiber organization and biomechanical strength of the tendon-bone interface at 4weeks in a murine model. These findings have implications for improving the structural integrity of the repaired enthesis and potentially reducing the retear rate after rotator cuff repair, which can ultimately lead to improvements in clinical outcomes.

Biomechanical Strength of Rotator Cuff Repairs: A Systematic Review and Meta-regression Analysis of Cadaveric Studies

Background: Biomechanical cadaveric studies of rotator cuff repair (RCR) have shown that transosseous equivalent and double-row anchored repairs are stronger than other repair constructs. Purpose: To identify technical and procedural parameters that most reliably predict biomechanical performance of RCR constructs. Study Design: Systematic review. Methods: The authors systematically searched the EMBASE and PubMed databases for biomechanical studies that measured RCR performance in cadaveric specimens. The authors performed a meta-regression on the pooled data set with study outcomes (gap formation, failure mode, and ultimate failure load) as dependent variables and procedural parameters (eg, construct type, number of suture limbs) as covariates. Stratification by covariates was performed. An alpha level of .05 was used. Results: Data from 40 eligible studies were included. Higher number of suture limbs correlated with higher ultimate failure load (β = 38 N per limb; 95% CI, 28 to 49 N) and less gap formation (β = −0.6 mm per limb; 95% CI, −1 to −0.2 mm). Other positive predictors of ultimate failure load were number of sutures, number of mattress stitches, and use of wide suture versus standard suture. When controlling for number of suture limbs, we found no significant differences among single-row anchored, double-row anchored, transosseous equivalent, and transosseous repairs. Higher number of suture limbs and transosseous equivalent repair both increased the probability of catastrophic construct failure. Conclusion: This study suggests that the number of sutures, suture limbs, and mattress stitches in a RCR construct are stronger predictors of overall strength than is construct type. There is a need to balance increased construct strength with higher risk of type 2 failure.

Biomechanical properties of suprapectoral biceps tenodesis: double knotless screw fixation is superior to single knotless screw fixation.

The purpose of this study is to biomechanically evaluate a new technique of double knotless screw fixation for suprapectoral biceps tenodesis and compare the results with that of the single knotless screw fixation as well as the interference screw fixation. 24 fresh-frozen human cadaveric shoulders with a mean age of 68.3 ± 9years were studied. The specimens were randomly divided into three experimental biceps tenodesis groups (n = 8): single knotless screw, double knotless screw and interference screw. Each tenodesis specimen was mounted on a mechanical testing machine, preloaded for 2min at 5N, tested with cyclic loading from 5 to 70N for 500 load cycles and subjected to an axial load to failure test (1mm/s). The ultimate failure load, stiffness, cyclic displacement and mode of failure were evaluated. The interference screw fixation had the highest ultimate failure load (215.8 ± 43.1N) and stiffness (25.7 ± 5.2N/mm) which were significantly higher than the corresponding results for the single and double knotless screw groups (P = 0.0029). The double knotless screw group had the second highest ultimate failure load (162.8 ± 13.8N) and stiffness (15.1 ± 4.1N/mm) which were significantly higher than the corresponding results for the single knotless screw technique (P = 0.0002). The most common mode of failure was suture slippage for both the double (7/8) and single knotless screw (6/8) groups while biceps tendon tearing occurred most often for the interference screw group (6/8). In this biomechanical study, the double knotless screw fixation was found to have a significantly greater ultimate failure load and stiffness than the single knotless screw fixation but lower values than the interference screw fixation.

Arthroscopic Fixation of Tibial Eminence Fractures: A Biomechanical Comparative Study of Screw, Suture, and Suture Anchor

To compare biomechanical outcomes of 4 different arthroscopic techniques for fixation of tibial eminence fractures. Twenty-four skeletally mature, fresh-frozen cadaveric knees were divided into 4 comparison groups based on the fixation method: screw fixation (group A), traditional sutures fixation with 2 FiberWire sutures (group B), a modified suture technique with 2 FiberWire sutures that created neckwear knots to firmly trap the fracture fragment (group C), or suture anchors which was based on the suture bridge technique primarily used in the shoulder for repair of rotator cuff tears and greater tuberosity fractures (group D). A tibial eminence fracture was created in each knee for subsequent fixation. After fixation, each knee underwent cyclic loading of 100N to assess the displacement change after500 cycles of the fixation construct. Afterward, a single tensile failure test load was performed to assess the ultimate failure load, stiffness, and failure mode for each specimen. All specimens survived cyclic testing and were subsequently loaded to failure. Group C had the highest ultimate failure load (P < .05) and group D had the lowest displacement compared with the other 3 groups (P < .05). Different failure modes were found among the 4 groups. Suture fixation using the neckwear knots technique provides superior fixation with regard to higher ultimate failure load, and absorbable suture anchor fixation with the suture bridge technique provides less displacement under cyclic loading conditions. Both techniques exhibited superior biomechanical properties compared with traditional screw and suture fixation. The new techniques showed satisfactory biomechanical properties and provided more choice for surgeons in the treatment of tibial eminence fractures.

Independent Suture Tape Reinforcement of Small and Standard Diameter Grafts for Anterior Cruciate Ligament Reconstruction: A Biomechanical Full Construct Model

To compare the dynamic elongation, stiffness behavior, and ultimate failure load of standard with small diameter soft tissue grafts for anterior cruciate ligament (ACL) reconstruction with and without high-strength suture tape reinforcement. Both a tripled "small" diameter and a "standard" quadrupled tendon graft with and without suture tape reinforcement were tested using suspensory fixation (n= 8 each group). The suture tape was passed through the suspensory fixation button on the femur and tibia to ensure independent (safety belt) fixation from the graft invitro. The testing of the constructs included position-controlled cyclic loading, force-controlled cyclic loading at 250N and 400N as well as pull to failure (50mm/min). Reinforcement of a small diameter graft significantly reduced dynamic elongation of 38% (1.46 ± 0.28mm vs 2.34 ± 0.44mm, P < .001) and 50% (2.55 ± 0.44mm vs 5.06 ± 0.67mm, P < .001) after the 250N and 400N load protocol, respectively. Reinforcement of a standard diameter tendon graft decreased dynamic elongation of 15% (1.59 ± 0.34mm vs 1.86 ± 0.17mm, P= .066) and 26% (2.62 ± 0.44mm vs 3.55 ± 0.44mm, P < .001). No significant difference was found between both reinforced models. The ultimate failure loads of small and standard diameter reinforced grafts were 1592 ± 105N and 1585 ± 265N, resulting in a 64% (P < .001) and 40% (P < .001) increase compared with their respective controls. Independent suture tape reinforcement of soft tissue grafts for ACL reconstruction leads to significantly reduced elongation and higher ultimate failure load according to invivo native ACL function data without stress-shielding the soft tissue graft. If invitro results are translational to human knees invivo, the suture tape reinforcement technique for ACL reconstruction may decrease the risk of graft tears, particularly in the case of small diameter soft tissue grafts.

Decellularized Versus Fresh-Frozen Allografts in Anterior Cruciate Ligament Reconstruction

Background: The common fresh-frozen allografts that are used for anterior cruciate ligament (ACL) reconstructions behave slower during the remodeling process and produce weaker tendon-bone integrations than do autografts. Decellularization of allogenic tendons results in a clean and porous collagen scaffold with low antigenicity and high compatibility, which may be more suitable for ACL reconstructions. Hypothesis: Allograft decellularization will result in a tissue structure with suitable mechanical characteristics for ACL reconstruction, thereby promoting graft remodeling and enhancing tendon-bone healing. Study Design: Controlled laboratory study. Methods: Decellularized allograft tissues were prepared with a pH-modified decellularization process and evaluated for their biocompatibility and biomechanical character in vitro. Eighty New Zealand White rabbits were divided into 2 groups, with 40 in each group, to receive ACL reconstruction with either fresh-frozen (common) allografts or decellularized allografts on both knees. At 2, 4, 8, and 12 weeks postoperatively, the rabbits were euthanized for biomechanical testing, micro–computed tomography analysis, and histologic analysis. Results: The pH-modified decellularized allograft tissues kept excellent biocompatibility and biomechanical character during the in vitro study. Biomechanical testing indicated that the decellularized allograft had significantly higher ultimate load (P = .02) and stiffness (P = .01) levels than the common allograft at 12 weeks, and there was no significant difference between the 2 groups at any other time point. The micro-CT evaluation determined significantly higher bone mineral density (P < .01) in the decellularized allograft group than that in the common allograft group at 12 weeks, but no difference between the 2 groups was observed at any other time point. Regarding bone volume/total volume, there was no difference between the 2 groups at any time point. Fibroblast ingrowths, vascular formation, and connective tissue formation in the tendon-bone interface were better in the decellularized group within 8 weeks. New bone formation was more common in the decellularized allograft group. The collagen birefringence was restored more quickly in the decellularized allograft group than in the common allograft group at all time points. Conclusion: The use of pH-modified decellularized allografts compared with the common allografts resulted in better cellularity, vascularity, collagen matrix remolding, new bone formation around the graft, enhanced tendon-bone healing, and higher ultimate failure load and stiffness of the graft after ACL reconstruction in the rabbit model. Clinical Relevance: The pH-modified decellularized allograft may be a better graft option than the common fresh-frozen allograft for knee ligament reconstructions.

Biomechanical Comparison of Single- Double- and Novel Triple- Row Rotator Cuff Repairs in a Porcine Model Using Generic Anchors

Comparison of a novel triple-row (NTR) rotator cuff repair (RCR) was made to single row (SR) and double row (DR) repairs as measured by gap formation, Ultimate Failure Load (UFL), and mode of failure. Porcine humeri were divided into three groups of forty and the infraspinatus tendons were completely released and then repaired using generic (PEEK) anchors. Biomechanical testing of RCRs consisted of 3500 cycles of a load varied from 10 to 180 Newtons (N). Gap size at all cycle counts was significantly larger for SR and DR than NTR RCRs. 84% of NTR repairs completed the 3500 cycle test versus 66% of DR and 61% of SR repairs. The tendon pulled from the sutures 60%, 49% and 33% of the time for SR, DR and NTR RCRs respectively. UFLs were 464 N for the NTR repairs, 394 N for DR and 414 N for SR repairs. In summary, NTR repairs resulted in smaller gap formation, higher UFLs, and fewer instances of tendons tearing at the sutures than SR or DR repairs. Results of NTR repairs demonstrate that the tendon footprint is securely restored with small gap formation for the range of forces that a shoulder will be subjected to in normal use.