Emin Sunbuloglu

A comparison of single-versus double-row suture anchor techniques in a simulated repair of the rotator cuff: AN EXPERIMENTAL STUDY IN RABBITS

We compared time-dependent changes in the biomechanical properties of single-and double-row repair of a simulated acute tear of the rotator cuff in rabbits to determine the effect of the fixation techniques on the healing process. A tear of the supraspinatus tendon was created in 80 rabbits which were separated into two equal groups. A single-row repair with two suture anchors was conducted in group 1 and a double-row repair with four suture anchors in group 2. A total of ten intact contralateral shoulder joints was used as a control group. Biomechanical testing was performed immediately post-operatively and at four and eight weeks, and histological analysis at four and eight weeks. The mean load to failure in group 2 animals was greater than in group 1, but both groups remained lower than the control group at all intervals. Histological analysis showed similar healing properties at four and eight weeks in both groups, but a significantly larger number of healed tendon-bone interfaces were identified in group 2 than in group 1 at eight weeks (p < 0.012). The ultimate load to failure increased with the number of suture anchors used immediately post-operatively, and at four and eight weeks. The increased load to failure at eight weeks seemed to be related to the increase in the surface area of healed tendon-to-bone in the double-row repair group.

Time-Dependent Changes in Failure Loads of 3 Biceps Tenodesis Techniques In Vivo Study in a Sheep Model

Background Failure load of the tendon–fixation material–bone unit has a crucial importance for the rehabilitation protocol after tenodesis procedures. Purpose To investigate and compare the time-dependent changes in fixation strengths of 3 proximal biceps tenodesis techniques. Study Design Controlled laboratory study. Methods Two intraosseous techniques (suture sling and tenodesis screw) and 1 extraosseous technique (2 suture anchors) were investigated. Biceps tenodesis was performed on 45 shoulders of 26 sheep, 15 shoulders for each technique. Twelve similar cadaveric sheep shoulders (4 for each technique) provided the day 0 results. Sheep were sacrificed at 3, 6, and 9 weeks, and specimens were tested for the failure load of the tenodeses. Results All 3 tenodesis techniques were found to have similar failure loads at all time intervals tested. All 3 curves remained below the failure load of the intact tendon (862 ± 96 N) and above their day 0 results for the study period; similarly, at each time interval, results tended to be better compared to the previous test. The tenodesis screw group exhibited significantly higher failure loads at week 3 (419 ± 53 N) compared to day 0 values (164 ± 45 N) (P=. 009). The same level of significance was observed at week 6 in the remaining 2 groups. Conclusion Tenodesis of the biceps tendon on the proximal humerus at an extra-articular site does not weaken after surgery. The tenodesis screw group had a significantly higher increase in the fixation strength within the first 3 weeks. Clinical Relevance No significant differences could be found between the failure loads of all 3 investigated tenodeses for the first 9 weeks.

Biomechanical Comparison of Fixation Techniques in Midshaft Clavicular Fractures

Objectives: The purpose of this study is to evaluate the biomechanical properties and the stability among a locking clavicle plate (LCP), a dynamic compression plate (DCP) and an external fixator (Ex-fix) in an unstable displaced clavicle fracture model under torsional and three-point bending loading. Materials and Methods: Forty-eight human adult formalin-fixed clavicles were paired according to their bone mineral density homogeneously into three groups: LCP, DCP, and Ex-fix. Each specimen was osteotomized at the midshaft. Torsional and three-point bending forces were performed for 1000 cycles with stiffness recorded at 10 cycles (initial) and then at 100-cycle intervals thereafter. Initial stiffness, failure loads, and the percentage of initial stiffness at the various intervals were compared using analysis of variance. Results: The mean initial stiffness values (Nmm/deg) for torsion were 703.2 (LCP), 448.1 (DCP), and 365.2 (Ex-fix). The mean failure moments (Nmm) for torsion were 7671.7 (LCP), 4370.3 (DCP), and 2999.7 (Ex-fix). The mean initial stiffness (Nmm) for bending were 32.6 (LCP), 23.4 (DCP), and 20.6 (Ex-fix). The mean failure loads (N) for bending were 213.2 (LCP), 131.1 (DCP), and 102.7 (Ex-fix). For both torsion and bending, an overall significant difference among the three constructs in terms of failure loads and also a significant difference between the locking plate and the other two models only in terms of initial stiffness was seen. For torsion and bending, at all cyclic intervals, there was a significant difference between the locking plate and the other two models. After 700 cycles, a significant difference was also detected between the DCP and Ex-fix in torsion, but no difference was found between these groups at any cyclic interval in bending. Conclusions: The locking plate is significantly more stable than DCP and Ex-fix under torsional and bending cyclic loading in a displaced fracture clavicle model.

Biomechanical Comparison of Tibial Eminence Fracture Fixation With High-Strength Suture, EndoButton, and Suture Anchor

PURPOSE To biomechanically compare anterior cruciate ligament (ACL) tibial bony avulsion fixation by suture anchors, EndoButtons (Smith & Nephew, Andover, MA), and high-strength sutures subjected to cyclic loading. METHODS Type III tibial eminence fractures were created in 49 ovine knees, and 7 different types of repairs were performed. Each repair group contained 7 specimens. The repair groups were as follows: No. 2 FiberWire (Arthrex, Naples, FL); No. 2 UltraBraid (Smith & Nephew); No. 2 MaxBraid (Arthrotek, Warsaw, IN); No. 2 Hi-Fi (ConMed Linvatec, Largo, FL); No. 2 OrthoCord (DePuy Mitek, Raynham, MA); Ti-Screw suture anchor (Arthrotek); and titanium EndoButton. These constructs were cyclically loaded (500 cycles, 0 to 100 N, 1 Hz) in the direction of the native ACL and loaded to failure (100 mm/min). Endpoints included ultimate failure load (in Newtons); pullout stiffness (in Newtons per millimeter); cyclic displacement (in millimeters) after 100 cycles, between 100 and 500 cycles, and after 500 cycles; and mode of failure. Bone density testing was performed in all knees. RESULTS Bone density was not different among the groups. The EndoButton group had a higher ultimate failure load than the FiberWire, UltraBraid, Hi-Fi, and suture anchor groups (P < .05). The MaxBraid and OrthoCord groups had higher failure loads than the suture anchor group (P < .05). The MaxBraid group also had a higher failure load than the Hi-Fi group (P < .05). Stiffness was not statistically different for the various tested constructs. After 100 cycles, the EndoButton group had less displacement than the FiberWire, UltraBraid, MaxBraid, and Hi-Fi groups (P < .05). The suture anchor group had less displacement than the Hi-Fi and FiberWire groups (P < .05). The displacements of the different tested constructs between 100 and 500 cycles and total displacements after 500 cycles were not statistically different. The predominant failure mode was suture rupture. CONCLUSIONS Under cyclic loading conditions in an ovine model, EndoButton fixation of tibial eminence fractures provided greater initial fixation strength than suture anchor fixation or fixation with various high-strength sutures except for OrthoCord. CLINICAL RELEVANCE During initial cyclic loading of ACL tibial eminence fractures, the strength of the repair construct should be taken into consideration because conventional suture repair even with ultrahigh-molecular-weight polyethylene sutures may not provide enough strength.

Railroad passenger car collision analysis and modifications for improved crashworthiness

In this study, crashworthiness assessment and suggestions for the modification of a railroad passenger car are presented. To assess the crashworthiness, collision of the railroad passenger car onto a rigid wall is simulated by using finite element (FE) methods. A full-length, detailed passenger car model is used in FE analyses. In order to validate the FE model, simulation results obtained for different types of static loading conditions in compliance with various scenarios defined in UIC CODE OR 577 are compared with experimental measurements before running collision analyses of the railroad passenger car. The good agreement between static tests and FE analyses results indicates that the FE model accurately represents the real structure. Following the FE model validation, analysis of the collision behaviour of the railroad passenger car consists of two stages. In the first stage, the crashworthiness of the initial concept design of the railroad passenger car is analysed. It was observed that local buckling takes place at various points, which prevents the desired progressive damage behaviour in the railroad car body. Having revealed the structural weaknesses, the initial design was modified and simulated again under the same conditions. Using size optimisation, thickness of some sheet metal components is changed in order to obtain the intended progressive damage behaviour. As a result of the modifications, the passenger car design with better crashworthiness properties was obtained, in which large plastic deformations occur around the collision side of the car while mainly elastic deformations occur in the cars body away from the bumpers.

The effect of strut allograft and its position on Vancouver type B1 periprosthetic femoral fractures: a biomechanical study.

The aim of this study is to assess the biomechanical advantage of adding strut allograft and the effect of its position on the construct in Vancouver type B1 fractures. Fifteen forth-generation synthetic femurs were used and created a fracture model at the tip of prosthesis, and subsequently fixated with a lateral plate only, lateral plate and medial strut, lateral plate and anterior strut. Rotational and axial tests were performed. In all loading tests, the plate with medial strut group was stiffer than the other constructs and had higher failure load values and had less displacement in the fracture site. A combination of a plate with a medial strut allograft provides more mechanical stability on periprosthetic femoral fractures near the tip of a total hip arthroplasty.

Finite element simulation of the behavior of the periodontal ligament: A validated nonlinear contact model

Due to its significance in tooth movement, the stress/deformation field of periodontium and the alveolar bone remodeling process, periodontal ligament (PDL) cannot be excluded from the studies investigating dental biomechanics regarding its excessive deformability. Therefore, many analytical and numerical researches are carried out to simulate its response and to create a constitutive model via experiments intending to discover the material properties of PDL. The aim of this study is to formulate a user specified contact model that can be used in conjunction with finite element (FE) software and reflects PDLs influence on neighboring structures based on the currently available information, without requiring an actual volumetric finite element mesh of ligament. The results show good agreement with available experimental tooth mobility data. Smooth stress fields are obtained on the tooth root and alveolar bone, which is a significant aspect in bone-remodeling studies. The advantage of simulating PDL as a contact model at the interface of tooth root and the alveolar process instead of a solid-meshed FE model with poor geometric morphology and/or very dense mesh is expected to save pre/post-processing workforce, to increase the accuracy and to contribute to the smoothness of interface stress distributions.

Crash and structural analyses of an aluminium railroad passenger car

Crashworthiness, strength and vibrational features of a railroad passenger car, which is originally made of steel members and then converted to an aluminium design, are studied. The finite element (FE) method is utilised for the static analysis in compliance with various scenarios defined in UIC CODE OR 577, modal analysis and simulation of the crash into a rigid wall. Firstly, a full-length, detailed passenger car model made of steel is used in FE analyses and the model is verified for the steel car body by comparisons with strain measurements and experimental evaluation of natural frequencies. The agreement between test measurements and FE results indicates that the FE model of the railroad car accurately represents the original structure. Following, effects of material change on the structural behaviour can be accurately judged based on the outcomes of the analyses. It is observed that the stress values and natural frequencies of the aluminium structure are almost equal to those of the original steel structure. Moreover, the crash energy absorption characteristics are within the acceptable tolerances for both cases. The final aluminium design is found to be about one-third of the weight of the initial steel structure while it preserves stiffness values within acceptable limits. In addition, an equivalent spring-mass system is developed to model the crash of both steel and aluminium passenger cars, which can be used for occupant safety investigations in future.

Effect of decortication on laminar strength during sublaminar wiring: an experimental study.

Eighty lumbar segments from 16 female sheep were used to investigate the effect of laminar decortication on the strength of the lamina during sublaminar wiring procedure. Sheep were 12-14 months old. Forty vertebrae from eight animals were decorticated before loading with sublaminar wire to failure, and 40 vertebrae from the remaining eight sheep were tested with the same procedure but intact. The effects of bone mineral density (BMD) and laminar dimensions on laminar strength in both decorticated and nondecorticated groups were also investigated. The failure force values of the laminae for decorticated and nondecorticated groups were 881.15 ± 36.86 and 298.48 ± 21.99 N, respectively (P < 0.001). There was a positive linear relationship between BMD and laminar strength in an intact lamina. In a decorticated lamina, no significant relationship existed between these variables. There was a negative linear relationship between mediolateral length of hemilamina and laminar strength in both intact and decorticated vertebra. Laminar strength after decortication was positively related to dorsoventral length of the remaining portion of the lamina. Decortication leads to a statistically significant decrease in laminar strength.

The impact of frenulum height on strains in maxillary denture bases

PURPOSE The midline fracture of maxillary complete dentures is a frequently encountered complication. The purpose of this study was to assess the effect of frenulum height on midline strains of maxillary complete dentures. MATERIALS AND METHODS A removable maxillary complete denture was fabricated and duplicated seven times. Four different labial frenulum heights were tested for stresses occurring on the palatal cameo surface. The strains were measured with strain gauges placed on 5 different locations and the stresses were calculated. To mimic occlusal forces bilaterally 100 N of load was applied from the premolar and molar region. RESULTS A statistically significant association between the height of the labial frenulum and the calculated stresses and strains was shown (P<.05) predominantly on the midline and especially on the incisive papilla. The results showed that stress on the anterior midline of the maxillary complete denture increases with a higher labial frenulum. CONCLUSION Within the limitations of this in vitro study, it can be concluded that the stress on the anterior midline of the maxillary complete denture increases with a higher labial frenulum. Surgical or mechanical precautions should be taken to prevent short-term failure of maxillary complete dentures due to stress concentration and low cycle fatigue tendency at the labial frenulum region.