Difference In Ultimate Load Research Articles

Fixation strength in arthroscopic labral repair of the hip: A head-to-head comparison of the biomechanical performance of a biocompatible vs. all-suture anchor in the setting of acetabuloplasty.

Much is known about the biomechanical performance of various types of suture anchors commonly used for labral fixation in the shoulder; however, similar studies in the hip are less common. We sought to compare all-suture and polyether ether ketone small-diameter anchors in the setting of labral repair during hip arthroscopy, with and without acetabuloplasty. We hypothesized that the biomechanical properties of the all-suture group when compared to polyether ether ketone anchors would be similar amongst native acetabula and significantly less following acetabuloplasty and that pullout forces would be reduced in the anterior and inferior regions of the acetabulum compared to the superior region. Bone density was measured in nine matched pairs of fresh-frozen cadaveric acetabula in the superior, anterosuperior, and anterior regions. Acetabuloplasty was performed in all three regions, while the contralateral acetabulum was left in situ as a control. Suture anchors were placed such that one each of two different types was placed within each region. Specimens were tested in cyclic fatigue and loaded to failure. The all-suture group had significantly higher cyclic displacement compared to the polyether ether ketone, but there was no significant difference in ultimate load, regardless of acetabuloplasty. Amongst all non-resected specimens, the lowest bone density was observed consistently in the inferior region. Our results indicate that, with or without acetabuloplasty, a small-diameter polyether ether ketone anchor appears to be more stable than an all-suture anchor, which needs to be set first.

BIOMECHANICAL EVALUATION OF AN ALLOGRAFT FIXATION SYSTEM FOR ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION IN COMPARISON WITH THE INTERFERENCE SCREW

Screw fixation is an established method for anterior cruciate ligament (ACL) reconstruction, although with a high rate of implant-related complications. An allograft system for implant fixation in ACL reconstruction, the Shark Screw ACL (surgebright GmbH) could overcome some of the shortcomings of bioabsorbable screws, such as foreign body reaction, need for implant removal and imaging artefacts. However, it needs to provide sufficient mechanical stability. Therefore, the aim of this study was to investigate the biomechanical stability, especially graft slippage, of the novel allograft system versus a conventional bioabsorbable interference screw (BioComposite Interference Screw; Arthrex Inc.) for tibial implant fixation in ACL reconstruction.Twenty-four paired human proximal tibiae (3 female, 9 male, 72.7 ± 5.6 years) underwent ACL reconstruction. The quadrupled semitendinosus and gracilis tendon graft were fixed in one specimen of each pair using the allograft fixation system Shak Screw ACL and the contralateral one using an interference screw. All specimens were cyclically loaded at 1 Hz with peak load levels monotonically increased from 50 N at a rate of 0.1 N/cycle until catastrophic failure. Relative movements of the graft versus the tibia were captured with a stereographic optical motion tracking system (Aramis SRX; GOM GmbH).The two fixation methods did not demonstrate any statistical difference in ultimate load at graft slippage (p = 0.24) or estimated survival at slippage (p = 0.06). Both, the ultimate load and estimated survival until failure were higher in the interference screw (p = 0.04, and p = 0.018, respectively). Graft displacement at ultimate load reached values of up to 7.2 mm (interference screw) and 11.3 mm (Shark Screw ACL).The allograft screw for implant fixation in ACL reconstruction showed similar behavior in terms of graft slippage compared to the conventional metal interference screw but underperformed in terms of ultimate load. However, the ultimate load may not be considered a direct indicator of clinical failure.

Biomechanical Characterization of a New Locking Loop Stitch for Graft Fixation versus Krackow Stitch.

The purpose of this study was to quantify and compare the biomechanical characteristics of a new locking loop stitch (LLS), developed utilizing the concepts of both running locking stitch and needleless stitch, to the traditional Krackow stitch. The Krackow stitch with No.2 braided suture and the LLS with 1.3-mm augmented polyblend suture tape were compared biomechanically. The LLS was performed with single strand locking loops and wrapping suture around the tendon, resulting in half the needle penetrations through the graft compared to the Krackow stitch. Twenty bovine extensor tendons were divided randomly into two groups. The tendons were prepared to match equal thickness and cross-sectional area. Each suture-tendon was stitched and preloaded to 5 N for 60 seconds, cyclically loaded to 20 N, 40 N, and 60 N for 10 cycles each, and then loaded to failure. The deformation of the suture-tendon construct, stiffness, yield load, and ultimate load were measured. The LLS had significantly less deformation of the suture-tendon construct at 100 N, 200 N, 300 N, and at ultimate load compared to the Krackow stitch (Krackow stitch and LLS at 100 N: 1.3 ± 0.1 mm and 1.0 ± 0.2 mm, p < 0.001; 200 N: 3.0 ± 0.3 mm and 1.9 ± 0.2 mm, p < 0.001; 300 N: 5.1 ± 0.6 mm and 2.9 ± 0.4 mm, p < 0.001; ultimate load: 12.8 ± 2.8 mm and 5.0 ± 1.2 mm, p < 0.001). The LLS had significantly greater stiffness (Krackow stitch and LLS: 97.5 ± 6.9 N/mm and 117.2 ± 13.9 N/mm, p < 0.001) and yield load (Krackow stitch and LLS: 66.2 ± 15.9 N and 237.9 ± 93.6 N, p < 0.001) compared to the Krackow stitch. There was no significant difference in ultimate load (Krackow stitch: 450.2 ± 49.4 N; LLS: 472.6 ± 59.8 N; p = 0.290). The LLS had significantly smaller deformation of the suture-tendon construct compared to the Krackow stitch. The LLS may be a viable surgical alternative to the Krackow stitch for graft fixation when secure fixation is necessary.

Superior Capsule Reconstruction With Fascia Lata Allograft Has Initial Stiffness and Ultimate Load Comparable to the Native Shoulder Superior Capsule: A Cadaveric Biomechanical Study

The purpose of this study was to compare the biomechanical characteristics of a fascia lata superior capsule reconstruction (FL-SCR) to the native superior capsule. The native superior capsule of 8 cadaveric shoulders was tested with cyclic loading from 10 to 50 N for 30 cycles in 20° of glenohumeral abduction followed by load to failure at 60 mm/min. Following native superior capsule testing, FL-SCR was performed, which was tested as described for the native capsule. Paired t test was used for statistical analyses with P < .05 for significance. The stiffness for cycle 1 to 50 N was significantly higher for the native superior capsule compared to the FL-SCR (P= .001). By cycle 30, the stiffness between the two was not statistically different (P= .734). During load to failure, the initial stiffness to 2 mm for the FL-SCR and the native superior capsule was not statistically different (P= .262). The linear stiffness and yield load of the native superior capsule were significantly greater than that of the FL-SCR (94.5 vs 28.0 N/mm, P= .013; 386.9 vs 123.8 N, P= .029). There was no significant difference in ultimate load between the native superior capsule and the FL-SCR (444.9 vs 369.0 N, P= .413). FL-SCR has initial stiffness and ultimate load similar to the native superior capsule. The biomechanical properties of FL allograft make it an appealing option as a graft choice for superior capsule reconstruction.

Failure Rates of Suture Anchor Fixation Versus Transosseous Tunnel Technique for Patellar Tendon Repair: A Systematic Review and Meta-analysis of Biomechanical Studies.

Background:Transosseous tunnel (TO) repair is considered the gold standard for patellar tendon rupture; however, suture anchor (SA) repair has emerged as a viable alternative in recent years. Although both these techniques are used widely in clinical practice, the most biomechanically optimal construct for patellar tendon repair remains unknown.Purpose:To examine published studies on the biomechanical properties of TO and SA fixation for patellar tendon repair in terms of ultimate load to failure and cyclic gap formation. The null hypothesis was that there would be no significant difference in either outcome measure between the groups.Study Design:Systematic review.Methods:A systematic review using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines was performed by searching PubMed, the Cochrane Library, and Embase to identify studies that analyzed the biomechanical properties of SA and TO techniques for repair of a ruptured patellar tendon. The search phrase implemented was “patellar tendon repair.” Meta-analysis was performed to provide a quantitative comparison of the 2 techniques with regard to ultimate load to failure and cyclic gap displacement. Weighted averages were calculated for all quantitative outcomes, and outcomes were summarized in a forest plot. A random-effects model was used to account for the heterogeneity among the included studies in the final statistical analysis.Results:Of 875 studies initially screened, the inclusion criteria were met by 7 studies, including 128 cadaveric specimens (66 SA, 62 TO). The pooled analysis from 6 studies reporting on gap displacement revealed a statistically significant difference in favor of SA versus TO fixation (P < .001). Pooled analysis from 7 studies reporting on ultimate load to failure did not reveal a statistically significant difference between the use of SA and TO for tendon repair (P = .465).Conclusion:Our systematic review revealed that the use of SA fixation for patellar tendon repair was associated with lower cyclic gap displacement when compared with TO fixation. There was no significant difference in ultimate load to failure between the repair techniques.

Sandwich concrete beams with GFRP side faces tested and modeled in flexure

The flexural behavior of sandwich concrete beams reinforced with Glass Fiber-Reinforced Polymer (GFRP) side faces is studied. The GFRP faces are commercially available as pultruded sections consisting of flat plates with integrated T-shaped ribs and are used as stay-in-place (SIP) structural forms with the ribs embedded longitudinally into the concrete beam. Nine beams, 170 ×245 mm in cross-section and 1.06 to 1.945 m in length were tested in three-point bending to failure. Five of the beams included GFRP splices at mid-height along the length to simulate sections of continuous wall applications with spliced panels. The main parameters studied were splice method (adhesive and mechanical fasteners at spacing of 3.7%–16.7% the shear span), GFRP reinforcement ratio (7.6 and 10%) which was controlled by rib spacing, and shear span-to-depth (a/d) ratio (1.8–3.7). The test results have shown that the adhesively spliced beams reached 92%–96% the strength of their un-spliced counterparts. As the fasteners spacing reduced from 16.7%–3.7% of shear span, the strength increased from 86 to 92% the strength of the un-spliced counterpart. As a/d ratio reduced from 3.7 to 1.8, the ultimate moment increased by 17%. The beam with 7.6% GFRP reinforcement ratio had the same flexural strength as a conventional reinforced concrete section of the same size with a total steel reinforcement ratio of 3%. A three-dimensional finite element model is also developed and validated using test results and was able to predict all responses and failure modes, within 5%–8% difference in ultimate load. It was then implemented in a parametric study using 10 additional models to investigate the effects of adding a bottom facing and corner connections.

Biomechanical Comparison of Meniscal Allograft Root Fixation Techniques: Anterograde Interference Bone Plug Fixation Yields Favorable Results Compared to Transosseous Suture Fixation Alone

PurposeTo compare the biomechanical properties of 2 different fixation techniques (interference bone plug fixation vs transosseous suture fixation) of the posterior horn of the medial meniscus using a porcine model.MethodsTwenty-six matched pairs of fresh-frozen juvenile domestic porcine knees were used in this study. Specimens were randomly distributed among 3 groups: (1) native meniscus groups, (2) interference fixation, and (3) transosseous suture fixation. In each group, the posterior segments of the tested medial menisci were gripped with the freeze clamps and fixed to the tensile testing machine. Samples were preconditioned, followed by cyclic tension-relaxation for 1000 cycles between 10 and 30 N at 0.5 Hz and finally pulled to failure at a rate of 0.55 mm/s. The cyclic elongation, stiffness to failure, mode, and ultimate load to failure were recorded.ResultsThere was no significant difference in ultimate load to failure between the interference fixation (169.71 ± 71.98 N) and transosseous suture fixation (222.73 ± 72.40 N) groups (P = .118), both were significantly less than that of the native meniscus (405.46 ± 95.62) (P < .001). Interference fixation displayed cyclic elongation (1.04 ± 0.71 mm) and stiffness (69.10 ± 25.8 N/mm) that were not significantly different from the native meniscus tissue (0.78 ± 0.53 mm and 83.1 ±26.28 N/mm) (P = .359 and P = .224), in comparison to transosseous suture fixation, which did show increased cyclic elongation (1.85 ± 1.44 mm) (P = .047) and decreased stiffness (34.72 ± 10.2 N/mm) (P < .001).ConclusionInterference fixation of the posterior horn of the medial meniscus has superior cyclic elongation and stiffness when compared to transosseous suture fixation. Interference fixation and the native meniscus model have a similar stiffness and cyclic elongation.Clinical RelevanceThe significance of our study is that using interference fixation for meniscal allograft transplantation has the potential to reduce short term surgical failures as well as long term complication rates.

Continuous-Loop Tape Technique Has Greater Stiffness and Less Elongation Compared With Tied-Suture Fixation of Full-Thickness All-Soft Tissue Quadriceps Tendon Autografts.

Background:Many graft fixation techniques are utilized for full-thickness soft tissue quadriceps tendon autografts during anterior cruciate ligament reconstruction (ACLR).Purpose:To determine the tensile properties of all–soft tissue quadriceps tendon graft fixation using a tied-suture versus continuous-loop tape technique. It was hypothesized that the continuous-loop tape technique would have less cyclic elongation and greater ultimate load to failure and stiffness compared with a commonly used tied-suture technique.Study Design:Controlled laboratory study.Methods:Sixteen fresh-frozen human knee specimens were used to harvest a full-thickness all–soft tissue quadriceps tendon graft; half were secured using a Krackow suture technique with 2 braided sutures, and half were secured using a continuous-loop tape suspensory fixation button with a rip-stop stitch. Cyclic and permanent elongation, toe- and linear-region stiffness, and ultimate load were determined. Statistical analysis was performed at P <.05.Results:The tied-suture fixation group demonstrated significantly higher permanent elongation (11.7 ± 3.6 vs 4.2 ± 1.0 mm, P < .001) and cyclic elongation (5.9 ± 1.3 vs 2.0 ± 0.4 mm, P < .001) compared with the continuous-loop tape fixation group. There was a significantly higher linear-region stiffness with continuous-loop tape fixation compared with tied-suture fixation (98.8 ± 12.7 vs 85.5 ± 7.5 N/mm, P = .022). No significant difference in ultimate load between groups (517.1 ± 149.2 vs 465.6 ± 64.6 N) was found. The mode of failure was tendon pull-through for the continuous-loop tape group and suture breakage in the tied-suture group (P < .001).Conclusion:Continuous-loop tape fixation is superior to tied-suture fixation in regard to elongation and stiffness for all–soft tissue quadriceps tendon grafts, but there was no significant difference in ultimate load.Clinical Relevance:Continuous-loop tape fixation of all–soft tissue quadriceps tendon grafts for ACLR is a valid technique with superior tensile properties.

Biomechanical Comparison of 2 Common Techniques of Minimally Invasive Hallux Valgus Correction.

Hallux valgus is one of the most common surgically corrected forefoot deformities. Compared to open procedures, minimally invasive (MIS) treatment of hallux valgus has resulted in decreased operative time, reduced complication rates, and greater patient satisfaction. Historically, distal chevron osteotomies are the standard for moderate hallux valgus correction. To our knowledge, no studies have evaluated biomechanical strength of transverse and chevron distal first metatarsal osteotomy (DMO) constructs. The purpose of this study was to evaluate the biomechanical strength of these techniques. Eighteen cadaveric specimens (9 matched pairs) were randomized to transverse or chevron DMO. Each technique was performed by a separate fellowship-trained orthopedic foot and ankle surgeon. Radiographic images were analyzed. Biomechanical testing was performed using Instron Mechanical System. Ultimate load to failure, yield load, and stiffness were assessed. A 10-N preload was applied to the sesamoid bones for stability. A coaxial compression rate (10 mm/min) was applied until failure was observed. Mean and standard deviations were compared. All cadaveric specimens were male. There was no significant difference in percent metadiaphyseal shift between osteotomies (P = .453). The most common mode of failure was fracture at screw insertion site (55.6%), followed by failure at osteotomy site (44.4%). A trend toward increased ultimate load to failure (P = .480), yield load (P = .054), and stiffness (P = .438) among transverse compared to chevron osteotomy was observed, but this difference was not statistically significant. Biomechanical testing demonstrated no significant difference in ultimate load, yield load, and stiffness between MIS transverse and chevron osteotomy constructs; a trend toward increased strength in the transverse osteotomy cohort was observed. Chevron osteotomies may result in early failure by relative ease of cutout through cancellous bone compared to transverse osteotomies in which failure requires cortical cutout. Use of MIS techniques for hallux valgus correction is gaining clinical traction. Although various clinical studies have evaluated outcomes of these MIS techniques, biomechanical studies have been minimal. Specifically, the potential biomechanical benefits of various MIS hallux valgus osteotomy techniques have not been delineated to date. The content of this manuscript is quite timely, given the rise in use of these MIS techniques.

Biomechanical Comparison of All-Soft Suture Anchor Single-Row vs Double-Row Bridging Construct for Insertional Achilles Tendinopathy.

Two common operative fixation techniques for insertional Achilles tendinopathy are the use of all-soft suture anchors vs synthetic anchors with a suture bridge. Despite increasing emphasis on early postoperative mobilization, the biomechanical profile of these repairs is not currently known. We hypothesized that the biomechanical profiles of single-row all-soft suture anchor repairs would differ when compared to double-row suture bridge repairs. Achilles tendons were detached from their calcaneal insertions on 6 matched-pair, fresh-frozen cadaver through-knee amputation specimens. Group 1 underwent a single-row repair with all-soft suture anchors. Group 2 was repaired with a double-row bridging suture bridge construct. Achilles-calcaneal displacement was tracked while specimens were cyclically loaded from 10 to 100 N for 2000 cycles and then loaded to failure. Linear mixed models were used to analyze the independent effects of age, body mass index, tendon morphology, repair construct, and footprint size on clinical and ultimate failure loads, Achilles-calcaneal displacement, and mode of failure. The suture bridge group was independently associated with an approximately 50-N increase in the load to clinical failure (defined as more than 5 mm tendon displacement). There was no difference in ultimate load to failure or tendon/anchor displacement between the 2 groups. This cadaveric study found that a double-row synthetic bridge construct had less displacement during cyclic loading but was not able to carry more load before clinical failure when compared to a single-row suture anchor construct for the operative repair of insertional Achilles tendinopathy. Our data suggest that double-row suture bridge constructs increase the load to clinical failure for operative repairs of insertional Achilles tendinopathy. It must be noted that these loads are well below what occurs during gait and the repair must be protected postoperatively without early mobilization. This study also identified several clinical factors that may help predict repair strength and inform further research.

Hallux Valgus Correction: Comparison of Minimally Invasive Transverse and Chevron Distal Metatarsal Osteotomy Constructs

Category:Basic Sciences/Biologics; BunionIntroduction/Purpose:Hallux valgus is one of the most common surgically corrected forefoot deformities. Compared to open procedures, minimally invasive treatment of hallux valgus has resulted in decreased operative time, reduced complication rates, and greater patient satisfaction. Until recently in the United States, distal chevron osteotomies have been the standard for hallux valgus correction of moderate deformity. To the best of the authors’ knowledge, no studies have evaluated biomechanical strength of transverse and chevron distal metatarsal osteotomy constructs. The purpose of this study was to evaluate the biomechanical strength of transverse and chevron minimally invasive osteotomy techniques using 9 matched cadaveric pairs.Methods:A total of nine matched cadaveric specimens were randomized to transverse or chevron distal metatarsal osteotomies. Each minimally invasive surgical technique was performed by a fellowship trained orthopedic foot and ankle surgeon. Anterior- posterior and lateral radiographic images were obtained following surgical fixation. Biomechanical testing was performed on an Instron Mechanical System. Ultimate load to failure, yield load, and stiffness were assessed across the fixation construct with fulcrum within the metatarsal shaft proximal to screw fixation and compression load at the sesamoid bones. A pre-load of 10N was applied to the sesamoid bones by the compression post to stabilize the sample. Subsequently, a compression rate was applied to the sample at 10mm/min until failure was observed. Mean and standard deviations were assessed and compared across cohorts.Results:All nine cadaveric specimens were male. There was no difference in average percent metadiaphyseal shift among transverse (36%) and chevron (38%) osteotomies. The most common mode of failure among transverse and chevron osteotomies was fracture at screw insertion site (55.6%), followed by failure at osteotomy site (44.4%). One paired sample was noted to have poor bone quality prior to biomechanical testing. There was a trend towards increased ultimate load to failure (p=0.480) and stiffness (p=0.438) among transverse osteotomy compared to chevron osteotomy, however, no statistically significant difference was observed.Conclusion:Biomechanical testing demonstrates no statistical difference in ultimate load to failure and stiffness between minimally invasive transverse and chevron distal metatarsal osteotomy constructs. A trend towards increased ultimate load and stiffness in the transverse osteotomy cohort was observed. Chevron osteotomies violate the entire plantar cortex and may result in early failure by relative ease of cutout through cancellous bone compared to transverse osteotomies in which failure would require cortical bone cutout. Future studies are required to evaluate strength of construct in a larger sample. Analysis is limited, healing may provide additional strength that is not simulated in cadaveric studies.

Nonlinear Finite Element Analysis of Reinforced Concrete Beam-Column Connection with Interface Elements under Cyclic Loading

To study the nonlinear response of corner beam-column junctions with inclusion of the effect of construction joint between the column and the beam cast at different times and subjected to cyclic and repeated loads, a computer program of three dimensional nonlinear finite element analysis, written by Al-Shaarbaf[1], (P3DNFEA)has been extended to account for the effect of construction joints on the behavior and to deal with concrete behavior under cyclic loads.The 20-node isoperimetric brick elements have been used to model the concrete, while the reinforcing bars are modeled as axial members embedded within the brick elements. A nonlinear cyclic behavior model for concrete is developed in uniaxial and multiaxial states of stress. Also, a nonlinear cyclic behavior model for reinforcing bars is presented.In completion, the behavior of concrete under cyclic loads is simulated by an elasto-plastic work hardening model followed by a perfectly plastic response. In tension, affixed smeared crack modeled has been used to simulate the behavior of concrete with a tension-stiffening model to represent the retained post-cracking tensile stresses in concrete. Closing and reopening of cracks during cyclic loading has been taken into consideration.The nonlinear equations of equilibrium have been saved using an incremental-iterative technique based on the modified Newton-Raphson method. The convergence of the solution was controlled by a force convergence criterion. The numerical integration has been conducted by using 27-point Gaussian rule.To represent the shear transfer between two concretes cast at different times, 20-noded interface layer brick elements are used with Fronteddu’s and Millard’s models to represent the aggregate interlock and the dowel stiffness, respectively.Comparison between the results obtained from the finite elements and the available experimental results is made for a corner beam-column junction with inclusion of the effect of a construction joint. Good agreement is obtained. The maximum difference in ultimate load is 3.9%.A parametric study dealing with construction joint is presented by taking various conditions of the junction. These include the axial load on the column, strength of concrete in the second cast.

Impact of Screw Length on Proximal Scaphoid Fracture Biomechanics.

Background Proximal scaphoid fractures display high nonunion rates and increased revision cases. Waist fracture fixation involves maximizing screw length within the cortex; however, the optimal screw length for proximal scaphoid fractures remains unknown. Purpose The main purpose of this article is to compare stiffness and ultimate load for proximal scaphoid fracture fixation of various headless compression screw lengths. Methods Eighteen scaphoids underwent an osteotomy simulating a 7 mm oblique proximal fracture. Screws of three lengths (10, 18, and 24 mm) were randomly assigned for fixation. Each specimen underwent cyclic loading with stiffness calculated during the last loading cycle. Specimens that withstood cyclic loading were loaded to failure. Results No significant difference in stiffness between screw lengths was found. Ultimate load was significantly impacted by the screw length. A significant difference in ultimate load between a 10 and 24 mm screw was found; however, no significant difference occurred in ultimate load between an 18 and 24 mm screw. Conclusions No significant difference in stiffness between all groups could be due to similarities in purchase in the proximal aspect. The 10 mm screw withstanding less ultimate load compared to the 24 mm screw could be due to the 10 mm screw gaining less purchase on either side of the fracture site compared to the 24 mm screw. Lack of significant difference in ultimate load between the 18 and 24 mm screw could be occurring because the fracture site is closer to the 18 mm screw midpoint, as distal threads are engaged closer to the fracture. Clinical Relevance Maximizing screw length may not provide superior fixation biomechanically compared with fixation utilizing a 6 mm shorter screw for proximal scaphoid fractures.

Experimental and Numerical Investigation on Cold-formed Steel C Back-to-Back Beams

Investigation on flexural behavior of cold-formed steel (CFS) C back-to-back beam has been conducted in this study. In North American Specification for the Design of Cold-Formed Steel Structural Members, there is only the information on the spacing condition of C back-to-back beam. In the present experiment, twelve C back-to-back beam specimens with different connection spacing and cross-sectional dimension were tested under four-point loading. Bolts were used for connecting two C section beams. From the experimental result, the influence of the thickness and connection spacing of the C back-to-back beams were observed. Nonlinear finite element analysis of the beam specimens are performed, and compared with experimental result. It was found that the difference in ultimate load obtained from experimental and numerical result, are less than 30 percent.

A new femoral fixation device for anterior cruciate ligament reconstruction using the outside-in technique and hamstring tendon graft: A comparison between two devices in cadaveric human knee models

BackgroundA new device (T-anchor) was developed for ACL reconstruction and is implanted via the outside-in technique using hamstring grafts. The purpose of this study was to compare the T-anchor with the EndoButton Direct. MethodsThis study was conducted on 30 cadaveric knees (15 matched pairs). There were two groups of 15 each in the T-anchor and EndoButton Direct groups. After the harvest of grafts, fixation site profile and graft length were measured by loading the grafts onto both devices. They were then tested on a universal testing machine to assess elongation after cyclic loading, load to failure, ultimate load, and mode of failure. ResultsThe fixation site profile was lower in the T-anchor group than in the EndoButton Direct group (2.3±0.4mm vs. 4.7±1.0mm, P<0.001). The length of the graft-device complex of the T-anchor specimens was longer than that of the EndoButton Direct specimens (125.0±8.9mm vs. 115.0±8.7mm, P<0.001). The mean cyclic elongation was lower for the T-anchor group when compared with the EndoButton Direct group (2.4±0.6mm vs. 3.9±2.6mm, P=0.015). There was no statistically significant difference in ultimate load and load to failure between the T-anchor and EndoButton Direct groups. For mode of failure, the T-anchor fared better (P=0.013) with all failures attributed to specimens. ConclusionsIn this cadaveric study, the new device, T-anchor, performed better than the EndoButton Direct with respect to the above-mentioned study parameters except for ultimate load and load to failure.

Biomechanical Comparison of a First- and a Second-Generation All-Soft Suture Glenoid Anchor.

Background:All–soft tissue suture anchors provide advantages of decreased removal of bone and decreased glenoid volume occupied compared with traditional tap or screw-in suture anchors. Previous published data have led to biomechanical concerns with the use of first-generation all-soft suture anchors.Purpose/Hypothesis:The purpose of this study was to evaluate the load to 2-mm displacement and ultimate load to failure of a second-generation all-soft suture anchor, compared with a first-generation anchor and a traditional PEEK (polyether ether ketone) anchor. The null hypothesis was that the newer second-generation anchor will demonstrate no difference in loads to 2-mm displacement after cycling compared with first-generation all-soft suture anchors.Study Design:Controlled laboratory study.Methods:Twenty human cadaveric glenoids were utilized to create 97 total suture anchor sites, and 1 of 3 anchors were randomized and placed into each site: (1) first-generation all-soft suture anchor (Juggerknot; Biomet), (2) second-generation all-soft suture anchor (Suturefix; Smith & Nephew), and (3) a control PEEK anchor (Bioraptor; Smith & Nephew). After initial cyclic loading, load to 2 mm of displacement and ultimate load to failure were measured for each anchor.Results:After cyclic loading, the load to 2-mm displacement was significantly less in first-generation anchors compared with controls (P < .01). However, the load to 2-mm displacement was significantly greater in second-generation anchors compared with controls (P < .01). There was no difference in ultimate load to failure between the first- and second-generation all-soft suture anchors (P > .05).Conclusion:The newer generation all-soft suture anchors with a theoretically more rigid construct and deployment configuration demonstrate biomechanical characteristics (specifically, with load to 2-mm displacement after cyclic loading) that are improved over first-generation all-soft suture anchors and similar to a traditional solid tap-in anchor. The configuration of these newer generation all-soft suture anchors appears to mitigate the biomechanical concerns of decreased load to failure with first-generation all–soft tissue suture anchors.Clinical Relevance:The theoretical advantages of all-soft anchors may be particularly valuable in revision surgery or in cases where multiple anchors are being placed into a small anatomic area.

Biomechanical Comparison of Standard and Linked Single-Row Rotator Cuff Repairs in a Human Cadaver Model

The purpose of this study was to evaluate the time zero cyclic and failure loading properties of a linked single-row rotator cuff repair compared with a standard simple suture single-row repair using triple-loaded suture anchors. Eighteen human cadaveric shoulders from 9 matched pairs were dissected, and full-thickness supraspinatus tears were created. The tendon cross-sectional area was recorded. In each pair, one side was repaired with a linked single-row construct and the other with a simple suture single-row construct, both using 2 triple-loaded suture anchors. After preloading, specimens were cycled to 1MPa of effective stress at 1Hz for 500 cycles, and gap formation was recorded with a digital video system. Samples were then loaded to failure, and modes of failure were recorded. There was no statistical difference in peak gap formation between the control and linked constructs (3.6 ± 0.9mm and 3.6 ± 1.2mm, respectively; P= .697). Both constructs averaged below a 5-mm cyclic failure threshold. There was no statistical difference in ultimate load to failure between the control and linked repair (511.1 ± 139.0N and 561.2 ± 131.8N, respectively; P=.164), and both groups reached failure at loads similar to previous studies. Constructs failed predominantly via tissue tearing parallel to the medial suture line. The linked repair performed similarly to the simple single-row repair. Both constructs demonstrated high ultimate load to failure and good resistance to gap formation with cyclic loading, validating the time zero strength of both constructs in a human cadaveric model. The linked repair provided equivalent resistance to gap formation and failure loads compared with simple suture single-row repairs with triple-loaded suture anchors. This suggests that the linked repair is a simplified rip-stop configuration using the existing suture that may perform similarly to current rotator cuff repair techniques.

Biomechanical Evaluation of Posterior Cruciate Ligament Reconstruction With Quadriceps Versus Achilles Tendon Bone Block Allograft.

Background:Long-term studies of posterior cruciate ligament (PCL) reconstruction suggest that normal stability is not restored in the majority of patients. The Achilles tendon allograft is frequently utilized, although recently, the quadriceps tendon has been introduced as an alternative option due to its size and high patellar bone density.Purpose/Hypothesis:The purpose of this study was to compare the biomechanical strength of PCL reconstructions using a quadriceps versus an Achilles allograft. The hypothesis was that quadriceps bone block allograft has comparable mechanical properties to those of Achilles bone block allograft.Study Design:Controlled laboratory study.Methods:Twenty-nine fresh-frozen cadaveric knees were assigned to 1 of 3 groups: (1) intact PCL, (2) PCL reconstruction with Achilles tendon allograft, or (3) PCL reconstruction with quadriceps tendon allograft. After reconstruction, all supporting capsular and ligamentous tissues were removed. Posterior tibial translation was measured at neutral and 20° external rotation. Each specimen underwent a preload, 2 cyclic loading protocols of 500 cycles, then load to failure.Results:Construct creep deformation was significantly lower in the intact group compared with both Achilles and quadriceps allograft (P = .008). The intact specimens reached the greatest ultimate load compared with both reconstructions (1974 ± 752 N, P = .0001). The difference in ultimate load for quadriceps versus Achilles allograft was significant (P = .048), with the quadriceps group having greater maximum force during failure testing. No significant differences were noted between quadriceps versus Achilles allograft for differences in crosshead excursion during cyclic testing (peak-valley [P-V] extension stretch), creep deformation, or stiffness. Construct stiffness measured during the failure test was greatest in the intact group (117 ± 9 N/mm, P = .0001) compared with the Achilles (43 ± 11 N/mm) and quadriceps (43 ± 7 N/mm) groups.Conclusion:While the quadriceps trended to be a stronger construct with a greater maximum load and stiffness required during load to failure, only maximum force in comparison with the Achilles reached statistical significance. Quadriceps and Achilles tendon allografts had similar other biomechanical characteristics when used for a PCL reconstruction, but both were inferior to the native PCL.Clinical Relevance:The quadriceps tendon is a viable graft option in PCL reconstruction as it exhibits a greater maximum force and is otherwise comparable to the Achilles allograft. These findings expand allograft availability in PCL reconstruction.

Healing of rotator cuff tendons using botulinum toxin A and immobilization in a rat model.

BackgroundWe evaluated effects of botulinum toxin A (Botox) and cast immobilization on tendon healing in a rat model. Injection of Botox into rat supraspinatus was hypothesized to reduce muscle active force and improved healing.MethodsEighty-four supraspinatus tendons were surgically transected and repaired in 42 Sprague-Dawley rats (transosseous technique). After repair, supraspinatus muscle was injected with saline or Botox (3 or 6 U/kg). Half the shoulders were cast-immobilized for the entire postoperative period; half were allowed free cage activity. Histology was examined at 2, 4, 8, and 12 weeks. A healing zone cross-sectional area was measured, and biomechanical testing of repair strength and tendon viscoelastic properties was conducted at 4 and 12 weeks.ResultsBotox alone and cast immobilization alone exhibited increased ultimate load compared with controls (saline injection, no immobilization) at 4 weeks. No difference in ultimate load occurred between Botox-only and cast-only groups. At 12 weeks, the Botox (6 U/kg) plus cast immobilization group was significantly weakest (p < 0.05). A trend was shown toward decreased healing zone cross-sectional areas in casted groups.ConclusionsSupraspinatus Botox injection after rotator cuff repair might help protect the repair. However, cast immobilization plus Botox administration is harmful to rotator cuff healing in a rat tendon model.

Biomechanical Evaluation of Suture Anchor Versus Transosseous Tunnel Quadriceps Tendon Repair Techniques

To evaluate the biomechanical fixation strength of suture anchor and transosseous tunnel repair of the quadriceps tendon in a standardized cadaveric repair model. Twelve "patella-only" specimens were used. Dual-energy X-ray absorptiometry measurement was performed to ensure equal bone quality amongst groups. Specimens were randomly assigned to either a suture anchor repair of quadriceps tendon group (n= 6) or a transosseous tunnel repair group (n= 6). Suture type and repair configuration were equivalent. After the respective procedures were performed, each patella was mounted into a gripping jig. Tensile load was applied at a rate of 0.1mm/s up to 100N after which cyclic loading was applied at a rate of 1Hz between magnitudes of 50 to 150N, 50 to 200N, 50 to 250N, and tensile load at a rate of 0.1mm/s until failure. Outcome measures included load to failure, displacement at 1st 100N load, and displacement after each 10th cycle of loading. The measured cyclic displacement to the first 100N, 50 to 150N, 50 to 200N, and 50 to 250N was significantly less for suture anchors than transosseous tunnels. There was no statistically significant difference in ultimate load to failure between the 2 groups (P= .40). Failure mode for all suture anchors except one was through the soft tissue. Failure mode for all transosseous specimens but one was pulling the repair through the transosseous tunnel. Suture anchor quadriceps tendon repairs had significantly decreased gapping during cyclic loading, but no statistically significant difference in ultimate load to failure when compared with transosseous tunnel repairs. Although suture anchor quadriceps tendon repair appears to be a biomechanically superior construct, a clinical study is needed to confirm this technique as a viable alternative to gold standard transosseous techniques. Although invivo studies are needed, these results support the suture anchor technique as a viable alternative to transosseous repair of the quadriceps tendon.