Greater Failure Load Research Articles

Evaluation of Boron as a Feed Additive to Improve Musculoskeletal Health of Hy-Line W-36 Pullets

Boron supplementation may improve the musculoskeletal health of pullets before entering the lay phase. This study aimed to evaluate the effects of different boron amounts on the performance, muscle deposition, tibia cross-sectional area (CSA) and mineral density (BMD), ash percent, breaking strength, and bone mineralization (bone-specific alkaline phosphatase [BALP] and pro-collagen type 1 n-terminal propeptide [P1NP]) of a white-feathered strain of pullets. A total of 528 Hy-Line W-36 pullets were distributed across 24 pens and fed basal diets containing varying amounts of boron (C: 0 mg/kg; L: 50 mg/kg; M: 100 mg/kg; H: 150 mg/kg) for 17 weeks. Performance parameters (body weight, average daily weight gain/bird, and average daily feed intake/bird) were measured at weeks 4, 7, 10, 13, and 16, while all other measures were taken at 11 and 17 weeks of age. Performance was not impacted by boron supplementation. Pectoralis major weights were higher in H pullets at 11 weeks of age, and we also observed higher pectoralis major, minor, and leg muscle weights in H pullets at 17 weeks of age. Pullets fed the H diet had larger cortical CSA than the other treatment groups at 11 weeks of age. At 17 weeks of age, both the H and M groups had larger cortical CSA than the L and C groups, but the M group had slightly smaller cortical CSA. Pullets fed the H diet had higher BMD values than the other treatment groups at 11 weeks of age. At 17 weeks of age, pullets fed the H diet had the highest total BMD values compared to the other treatment groups, and cortical BMD increased with increasing boron inclusion. Pullets fed the H diet had the highest tibia ash percentages and concentrations of BALP and P1NP. Pullets fed the M and H diets had greater failure load and maximum bending moment than pullets fed the L or C diet at 11 weeks of age, with H pullets having greater stiffness values than other groups. At 17 weeks of age, pullets fed the H diet had greater failure load and maximum bending moment compared to all other treatment groups. Our results suggest that providing boron within the diet at 150 mg/kg can improve the musculoskeletal characteristics of Hy-Line W-36 pullets up to 17 weeks of age, without impacting performance parameters.

Enhanced Bone Size, Microarchitecture, and Strength in Female Runners with a History of Playing Multidirectional Sports.

Female runners have high rates of bone stress injuries (BSIs), including stress reactions and fractures. The current study explored multidirectional sports (MDS) played when younger as a potential means of building stronger bones to reduce BSI risk in these athletes. Female collegiate-level cross-country runners were recruited into groups: 1) RUN, history of training and/or competing in cross-country, recreational running/jogging, swimming, and/or cycling only, and 2) RUN + MDS, additional history of training and/or competing in soccer or basketball. High-resolution peripheral quantitative computed tomography was used to assess the distal tibia, common BSI sites (diaphysis of the tibia, fibula, and second metatarsal), and high-risk BSI sites (base of the second metatarsal, navicular, and proximal diaphysis of the fifth metatarsal). Scans of the radius were used as control sites. At the distal tibia, RUN + MDS ( n = 18) had enhanced cortical area (+17.1%) and thickness (+15.8%), and greater trabecular bone volume fraction (+14.6%) and thickness (+8.3%) compared with RUN ( n = 14; all P < 0.005). Failure load was 19.5% higher in RUN + MDS ( P < 0.001). The fibula diaphysis in RUN + MDS had an 11.6% greater total area and a 11.1% greater failure load (all P ≤ 0.03). At the second metatarsal diaphysis, total area in RUN + MDS was 10.4% larger with greater cortical area and thickness and 18.6% greater failure load (all P < 0.05). RUN + MDS had greater trabecular thickness at the base of the second metatarsal and navicular and greater cortical area and thickness at the proximal diaphysis of the fifth metatarsal (all P ≤ 0.02). No differences were observed at the tibial diaphysis or radius. These findings support recommendations that athletes delay specialization in running and play MDS when younger to build a more robust skeleton and potentially prevent BSIs.

The Plug-Type Patch Results in Immediate and Postoperative Advantages in Graft-to-Bone Integration for Bridging Massive Rotator Cuff Tears in a Chronic Rabbit Model

Background: Various patches have been used to bridge massive rotator cuff tears (MRCTs) by reconnecting the cuff tendons to the humeral head, but the outcomes continue to be suboptimal. Notably, the graft-bone junction is a vulnerable site for failure, which requires optimization in patch design and techniques to enhance initial and postoperative fixation strength at the graft-bone interface. Hypothesis: The plug-type patch (Plug-Pat) through intratunnel fixation would optimize mechanical characteristics in initial graft-to-bone fixation and subsequently improve postoperative biomechanical and histological properties in graft-to-bone healing when compared with the routine rectangular patch (Rect-Pat). Study Design: Controlled laboratory study. Methods: A total of 60 mature male New Zealand White rabbits underwent acute rotator cuff defects to create chronic models with MRCTs. The fascia lata autograft was then harvested to prepare a Plug-Pat, which was distally rooted in the bone tunnel and proximally sutured to native tendons in a horizontal mattress fashion to reconnect the humeral head and cuff tendons. The control group was repaired with a routine Rect-Pat that was secured onto the bone surface for graft-bone fixation. After surgery, the cuff-graft-bone complexes of rabbits in both groups were harvested immediately (0 weeks) for time-zero initial fixation strength and refreshed contact area assessment, and at 6 or 12 weeks for postoperative biomechanical and histological evaluation. Results: The Plug-Pat significantly enhanced initial fixation strength in comparison with the Rect-Pat (mean ± SD; failure load, 36.79 ± 4.53 N vs 24.15 ± 2.76 N; P < .001) and decreased failure at the graft-bone interface of the construct at 0 weeks, with a significantly increased refreshed bone bed contact area (52.63 ± 2.97 mm2 vs 18.28 ± 1.60 mm2; P < .001) between the graft and bone. At 6 and 12 weeks postoperatively, the Plug-Pat similarly resulted in greater failure load (43.15 ± 4.53 N vs 33.74 ± 2.58 N at 6 weeks; P = .001; 76.65 ± 5.04 N vs 58.17 ± 5.06 N at 12 weeks; P < .001) and stiffness (10.77 ± 2.67 N/mm vs 8.43 ± 0.86 N/mm at 6 weeks; P = .066; 16.98 ± 2.47 N/mm vs 13.21 ± 1.66 N/mm at 12 weeks; P = .011), with less specimen failure at the graft-bone interface than the Rect-Pat. In histological analyses, the Plug-Pat had a higher postoperative graft-bone integration score than the Rect-Pat, showing a more mature intratunnel healing interface with fibrocartilage tidemark formation, improved collagen properties, and more oriented cells when compared with those at the surface healing interface in the Rect-Pat. Conclusion: The Plug-Pat enhanced initial fixation strength and enlarged the refreshed contact area for graft-bone connection at time zero and subsequently improved postoperative biomechanical properties and graft-bone integration at the graft-bone healing interface when compared with the Rect-Pat. Clinical Relevance: The Plug-Pat using intratunnel fixation may be a promising strategy for patch design to optimize its initial and postoperative graft-bone connection for bridging reconstruction of MRCTs.

The Biomechanical and Histological Processes of Rerouting Biceps to Treat Chronic Irreparable Rotator Cuff Tears in a Rabbit Model

Background: Recently, the biceps was rerouted into a newly fabricated bicipital groove for in situ superior capsular reconstruction (SCR), resulting in promising time-zero cadaveric and clinical outcomes. However, no studies have determined the in vivo biomechanical and histological processes after the biceps is transposed to a nonanatomic position. Purpose: To explore the in vivo biomechanical and histological processes of the rerouting biceps tendon to treat chronic irreparable rotator cuff tears (IRCTs) in a rabbit model. Study Design: Controlled laboratory study. Methods: A total of 94 skeletally mature male rabbits were used to create a chronic IRCT model in the supraspinatus tendon. Then, the biceps rerouting procedures were performed in rabbits with chronic IRCT. Eighteen rabbits were sacrificed at 1, 3, 6, 9, and 12 weeks postoperatively for biomechanical testing, micro—computed tomography scanning, and histological analysis. The biomechanical and histological changes of intra- and extra-articular portions of the rerouting biceps were evaluated at each time point, with the contralateral native superior capsule (NSC) and the native biceps (NB) as controls, respectively. The morphology and bone formation of the fabricated bicipital grooves were evaluated, with native grooves as controls. Results: The intra-articular rerouting biceps tendon was progressively remodeled over time, displaying denser fibers and more mature collagen than those of the NSC, with gradual improvements in the tendon-to-bone healing interface from 6 to 12 weeks. Consequently, the failure load and stiffness of the intra-articular rerouting biceps portion increased with time and were significantly higher than those of the NSC from 9 weeks. Similarly, the extra-articular portion of the rerouting biceps progressively healed into a new bicipital groove, as demonstrated by a smaller tendon-to-bone interface from 6 to 12 weeks, resulting in greater failure load and stiffness at 9 and 12 weeks than those of the NB attachment. The newly fabricated bicipital groove showed similar morphology to that of the native groove with sufficient trabecular bone formed underneath. Conclusion: The rerouting biceps could progressively remodel and heal into the newly fabricated bicipital groove over time, resulting in greater biomechanical performances in intra- and extra-articular portions than the NSC and the NB attachment. Clinical Relevance: The biceps rerouting technique may be a feasible procedure to perform in situ SCR to treat IRCT in the future clinical practice; however, more clinical evidence is required.

A pilot study to assess the healing of meniscal tears in young adult goats

Meniscal tears are a common orthopedic injury, yet their healing is difficult to assess post-operatively. This impedes clinical decisions as the healing status of the meniscus cannot be accurately determined non-invasively. Thus, the objectives of this study were to explore the utility of a goat model and to use quantitative magnetic resonance imaging (MRI) techniques, histology, and biomechanical testing to assess the healing status of surgically induced meniscal tears. Adiabatic T1ρ, T2, and T2* relaxation times were quantified for both operated and control menisci ex vivo. Histology was used to assign healing status, assess compositional elements, and associate healing status with compositional elements. Biomechanical testing determined the failure load of healing lesions. Adiabatic T1ρ, T2, and T2* were able to quantitatively identify different healing states. Histology showed evidence of diminished proteoglycans and increased vascularity in both healed and non-healed menisci with surgically induced tears. Biomechanical results revealed that increased healing (as assessed histologically and on MRI) was associated with greater failure load. Our findings indicate increased healing is associated with greater meniscal strength and decreased signal differences (relative to contralateral controls) on MRI. This indicates that quantitative MRI may be a viable method to assess meniscal tears post-operatively.

Axial wall height effect on failure of adhesively luted computer assisted design/computer assisted manufactured ceramic crowns on preparations containing advanced total occlusal convergence

Computerized dentistry advocates promote that CAD/CAM adhesive technology compensates for traditional crown preparation recommendations. This study was to investigate the effect of preparation axial wall height on retention of adhesively-luted, all ceramic crowns manufactured by computerized methods. Maxillary molars were prepared with a 20 ° total occlusal convergence with preparation axial wall heights of 4, 3, 2, and 1 mm as well as an additional group containing a flat surface. The preparations were scanned with a computer acquisition device with crowns milled and prepared from a lithium disilicate ceramic material. The crowns were adhesively luted to the prepared tooth surfaces and then tested under static loading at a 45 ° angle to the tooth long axis on a universal testing machine until failure. Analysis with Kruskal-Wallis/Dunn’s found that crowns with 2, 3, and 4 mm preparation axial wall height had similar failure loads and demonstrated significantly greater failure load resistance than the zero and 1 mm axial wall height groups. However, failure mode analysis revealed that the 2 mm axial wall height group demonstrated universal adhesive failures as the zero and 1 mm axial wall height groups. Under the conditions of this study, some evidence is provided that adhesive technology may provided some compensation for less than optimal preparation features as the 3 mm axial wall height preparations demonstrated equivalent failure mode as the recommended 4 mm axial wall height preparations. However, further fatigue studies are warranted.

Treatment With a Soluble Bone Morphogenetic Protein Type 1A Receptor (BMPR1A) Fusion Protein Increases Bone Mass and Bone Formation in Mice Subjected to Hindlimb Unloading.

ABSTRACTPrevious work has shown that the soluble murine BMPR1A–fusion protein (mBMPR1A‐mFc) binds to BMP2 and BMP4 with high affinity, preventing downstream signaling. Further, treatment of intact and ovariectomized mice with mBMPR1A‐mFc leads to increased bone mass, and improved bone microarchitecture and strength, via increased bone formation and reduced resorption. In this study, we tested the effects of mBMPR1A‐mFc on disuse‐induced bone loss caused by 21 days of hindlimb unloading (HLU) via tail suspension versus cage controls (CONs). Adult female C57BL/6J mice (12 weeks old) were assigned to one of four groups (n = 10 each): CON‐VEH; CON‐mBMPR1A‐mFc; HLU‐VEH; and HLU‐mBMPR1A‐mFc. Mice were injected subcutaneously with VEH or mBMPR1A‐mFc (4.5 mg/kg, 2×/week). Leg BMD declined in the HLU‐VEH group (–5.3% ± 1.3%), whereas it was unchanged in HLU‐mBMPR1A‐mFc (–0.3% ± 0.9%, p < 0.05 versus HLU‐VEH). Leg BMD increased significantly more in CON‐mBMPR1A‐mFc than CON‐VEH (10.2% ± 0.6% versus 4.4% ± 0.8%). In the femur, trabecular, and cortical bone microarchitecture was worse in the HLU‐VEH compared to CON‐VEH mice, whereas mBMPR1A‐mFc treatment for 3 weeks led to greater Tb.BV/TV, Tb.Th, and midshaft Ct.Th in both the HLU and CON groups compared to comparable VEH‐treated counterparts (p < 0.05). HLU‐mBMPR1A‐mFc mice also had 21% greater failure load (p < 0.05) compared to their VEH‐treated counterparts. Dynamic histomorphometry indicated that treatment with mBMPR1A‐mFc led to significantly greater mineralizing surface and mineral apposition rate, resulting in a 3.5‐fold and fivefold higher bone formation rate in the mBMPR1A‐mFc‐treated CON and HLU animals versus VEH groups, respectively. mBMPR1A‐mFc‐treated mice had a similar osteoblast surface but significantly lower osteoclast surface than VEH‐treated animals in both the CON and HLU groups. Altogether, these findings suggest that treatment with the soluble BMPR1A fusion protein may be useful for maintenance of skeletal integrity in the setting of disuse‐induced bone loss. © 2017 The Authors JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Mechanical aspects of degree of cement bonding and implant wedge effect

Background The degree of bonding between the femoral stem and cement in total hip replacement remains controversial. Our objective was to determine the wedge effect by debonding and stem taper angle on the structural behavior of axisymmetric stem–cement–bone cylinder models. Methods Stainless steel tapered plugs with a rough (i.e. bonded) or smooth (i.e. debonded) surface finish were used to emulate the femoral stem. Three different stem taper angles (5°, 7.5°, 10°) were used for the debonded constructs. Non-tapered and tapered (7.5°) aluminum cylindrical shells were used to emulate the diaphyseal and metaphyseal segments of the femur. The cement–aluminum cylinder interface was designed to have a shear strength that simulated bone–cement interfaces (∼8 MPa). The test involved applying axial compression at a rate of 0.02 mm/s until failure. Six specimens were tested for each combination of the variables. Finite element analysis was used to enhance the understanding of the wedge effect. Findings The debonded stems sustained about twice as much load as the bonded stem, regardless of taper angle. The metaphyseal model carried 35–50% greater loads than the diaphyseal models and the stem taper produced significant differences. Based on the finite element analysis, failure was most probably by shear at the cement–bone interface. Interpretation Our results in this simplified model suggest that smooth (i.e. debonded) stems have greater failure loads and will incur less slippage or shear failure at the cement–bone interface than rough (i.e. bonded) stems.