Ergun Bozdag

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.

Influence of surgical technique, implant shape and diameter on the primary stability in cancellous bone

Achievement of primary stability during surgical placement of dental implants is one of the most important factors for successful osseointegration depending on various anatomical, surgical and implant-related factors. Resonance frequency analysis (RFA) has been shown as a non-invasive and objective technique for measuring the stability of implants. The aim of this study was to evaluate the effect of some surgical and implant-related factors in enhancing primary stability and to estimate a correlation between RFA and insertion torque (IT) in proximal regions of cow ribs representing cancellous bone. Fifteen implant beds were prepared in the most proximal region of six fresh cow ribs. Ninety implants with three different shapes and two different diameters were placed with two different surgical techniques, and the primary stability was compared using RFA and IT. Significantly higher RFA and IT values were achieved when under-dimensioned drilling was used as the surgical method (P<0·01); significantly higher IT values were obtained with the use of wider implants (P<0·01) and partially conical Astra Tech implants showed the highest IT values (P<0·01). When all the implants were considered, significant correlations between the IT and RFA values were noted (%40·6, P<0·05). Partially conical implants with a wide diameter to be placed with the modified surgical technique proposed appear to be useful in enhancing the primary stability in cancellous bone.

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.

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.

In vivo comparison of biomechanical, histological, and radiological properties of three techniques for tendon lengthening: An experimental study in rabbits

Biomechanical, histological, and radiological properties of three different techniques of tendon lengthening – Z-plasty, modified Vulpius, and modified Baker – were investigated and compared. Sixty white female Angora rabbits (mean weight 4.1 kg, range 3.9 kg- 4.2 kg) were randomly divided into three groups: Z-plasty, V-Y plasty (modified Vulpius technique), and U-T plasty (modified Baker technique). Histopathological, radiological, and biomechanical properties were evaluated at the third and sixth postoperative week. Qualitative analysis of ultrasound examination showed that Z-plasty had the most irregular echo pattern at the third postoperative week, and had less echogenic areas at the sixth postoperative week. Histological evaluation showed that Z-plasty had significantly more formation of fibrosis and adhesion and less parallel homogeneous collagen fibres at the sixth postoperative week (p<0.05). U-T plasty had a significantly higher mean (SD) failure load (15.35 (1.89) N) than the other two methods during the third postoperative week (p<0.05). There was no significant difference in failure load between the groups at the sixth postoperative week. U-T plasty is a good alternative to Z-plasty technique for lengthening tendons, and it may be the first choice in those who need moderate lengthening of tendons and early rehabilitation because it is easy to do, heals better, and has good biomechanical properties.

The influence of implant number and attachment type on maximum bite force of mandibular overdentures: a retrospective study

AIM Assessment of the influence of such factors as attachment type, number of implants, gender and age of patients on maximum bite force (MBF). MATERIAL AND METHODS Sixty-two edentulous patients (32 females, 30 males; aged 64.03 ± 10.07 years, range 42-90 years) with mandibular implant overdentures with various attachment types were included in the study and their MBFs were recorded. The results were evaluated statistically at a significance level of p < 0.05. RESULTS The MBF in male patients was found to be statistically significantly (p < 0.05) higher than in female patients. No statistically significant differences (p > 0.05) were found with respect to age groups, attachment types and number of implants supporting the mandibular overdentures. CONCLUSION Within the limitations of this study, it is concluded that independent of the number applied, dental implants increase MBF in edentulous patients. While males show higher bite force, patient age and attachment type seem not to play an important role.

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.