A biomechanical comparison of four fixed-angle dorsal plates in a finite element model of dorsally-unstable radius fracture.

PURPOSE: To compare the finite element models of two different composite radius fracture patterns, reduced and stabilised with four different fixed-angle dorsal plates during axial, dorsal and volar loading conditions. METHODS: Eight different plastic models representing four AO/ASIF type 23-A3 distal radius fractures and four AO/ASIF 23-C2 distal radius fractures were obtained and fixed each with 1 of 4 methods: a standard dorsal non-anatomical fixed angle T-plate (3.5mm Dorsal T-plate, Synthes), anatomical fixed-angle double plates (2.4mm LCP Dorsal Distal Radius, Synthes), anatomical fixed angle T-plate (2.4mm Acu-Loc Dorsal Plate, Acumed) or anatomical variable-angle dorsal T-plate (3.5mm, Dorsal Plate, Zrinski). Composite radius with plate and screws were scanned with a 3D optical scanner and later processed in Abaqus Software to generate the finite element model. All models were axially loaded at 3 points (centrally, volarly and dorsally) with 50 N forces to avoid the appearance of plastic deformations of the models. Total displacements at the end of the bone and the stresses in the bones and plates were determined and compared. RESULTS: Maximal von Mises stress in bone for 3-part fracture models was very similar to that in 2-part fracture models. The biggest difference between models and the largest displacements were seen during volar loading. The stresses in all models were the highest above the fracture gap. The best performance in all parameters tested was with the Zrinski plate and the most modest results were with the Synthes T-plate. CONCLUSION: There was no significant difference between 2-part (AO/ASIF type 23-A3) and 3-part (AO/ASIF 23-C2) fracture models. Maximal stresses in the plates appeared above the fracture gap; therefore, it is worth considering the development of plates without screw holes above the gap.

Treatment of ruptured Achilles tendon: Operative or non-operative procedure?

PURPOSE: The aim of this study was to compare the efficiency of non-operative and surgical procedures in the treatment of ruptured Achilles tendon in athletes (professional and amateur). METHODS: Ninety professional or amateur athletes with rupture of the Achilles tendon were included in the study between 1998 and 2013. The athletes were aged between 25 and 40 years (mean 34.83±4.65). A total of 30 athletes underwent an open procedure, 30 were treated with a percutaneous method and 30 were treated non-operatively. All operated patients were tested one year after the surgical procedure. RESULTS: An isokinetic dynamometer was used to compare the open and percutaneous methods. The results for the patients who were treated using the percutaneous method were 15% better than those for the patients who underwent the open procedure; the results for the group treated conservatively were 20% better than those for the group treated percutaneously. DISCUSSION AND CONCLUSION: The percutaneous method was easier technically than the open method. Time spent in hospital was 14.5 times shorter with the percutaneous procedure compared with the open procedure (percutaneous procedure: range 0.5-2 days, mean 0.79±0.36; open procedure: range 10-24 days, mean 11.46±2.70; p<0.00). Return to sport activities was twice as fast with the percutaneous procedure compared with the open procedure. There were no postoperative infections or reruptured Achilles tendon in the group treated with the percutaneous procedure. One patient in the group treated with the open procedure had postoperative infection (4.2%). In the non-surgical (conservatively treated) group, there were three reruptures of the Achilles tendon within one year, and one patient developed adhesions that resulted in loss of function and had to undergo an operation. The percutaneous method is the best method of surgical treatment for Achilles tendon rupture.

Computer representation of osteosynthesis stability in locking plates used for the treatment of osteoporotic proximal humerus fractures.

BACKGROUND: Proximal humerus fractures are represented as 4-5% of all fractures, with incidence notably growing with age. Since surgical internal fixation in treatment of proximal humeral fractures is used, fractures of osteoporotic bone and choice of plate for their osteosynthesis represent particular problem. The aim of the study was to test two locking plates: Philos plate with locking screws with determinated direction, and Arthrex plate with poliaxial locking screws, using the finite element method. SUBJECTS AND METHODS: This study used version 6.10 of Abaqus FEA software package for simulation and fine element analysis of Philos and Artrex plates attached to the osteotomy models of proximal humerus with fracture gap at 0°, 10° and 20° in four types of static load: abduction, adduction, axial compression and flexion. Simulation results of loads in abduction, adduction, axial loads and flexion, were described with the total bone displacement (U) and maximum bone displacement in the fracture gap (Uf). RESULTS: When examining the Philos plate in axial load on the bone with fracture gap angle from 0°, 10° and 20° no significant differences between the results for the displacements were observed. Therefore, results for other loads are related to total displacements of the bone only at the angle of 0°. Given that the results of the total bone displacement and maximum bone displacement in the fracture gap with Artrex plate were mostly higher, for comparison with the results of bone displacement in Philos plate it was taken that total bone displacement and maximum displacement in the fracture gap in Artrex plate represent 100% of the total displacement. Philos plate showed 60.71% for abduction, 76.07% for adduction, 102.24% for axial loads and 79.59% for flexion of total bone displacement in Artrex plate, and 60.48% for abduction, 76.07% for adduction, 96.05% for axial load and 79.96% for flexion of maximum displacement in the fracture gap in Artrex plate. CONCLUSIONS: Osteosynthesis for osteoporotic fractures of proximal humerus with Philos plate in computer simulation proved to be more stable than with Arthrex plate.

The Results of Internal Fixation of Proximal Humeral Osteoporotic Fractures with PHILOS Locking Plate.

BACKGROUND: In the last fifty years since plate and screw osteosynthesis has been implemented in fracture treatment, osteosporotic bone fractures were observed as a special problem. Due to special histologic, anatomic, physical and biomehanic properties of osteoporotic changed bone the laws of biomechanics suggest that stable osteosynthesis for osteoporotic bone is necessary to increase the contact surface of metallic implants and bone and the stability of the screw-plate-bone compound. There are numerous surgical techniques and methods for treatment of osteoporotic proximal humeral fractures. Every surgical procedure has to establish anatomical reduction and stable fixation that will enable early mobilisation. SUBJECTS AND METHODS: The aim of this study was to present results of internal fixation of proximal humeral osteoporotic fractures with PHILOS locking plate. Between 2007 and 2012, a total of 67 patients older than 65 years with closed proximal humerus fractures underwent surgical treatment with PHILOS plate system (Synthes, Switzerland). 42 patients were operated with deltopectoral approach and 25 with deltoid split approach. After a mean follow up period of 14.68 (6-28) months functional and radiologic results were assessed. RESULTS: We noted 9 postoperative complications related to surgical technique (1 intraarticular screw placement, 1 displacement in major tuberculum fragment, 1 displacement in major tuberculum fragment along with oblique placement of the plate, 2 cases of inadequate reduction, 1 case of humeral head avascular necrosis, varus humeral head fixation in 3 cases). None of the patients developed superficial or deep surgical infection. There was no nonunions. In the final evaluation, the Constant shoulder score was 91.75 (72-100). CONCLUSIONS: In this study PHILOS locking plate showed good applicability, respecting bone biologic properties because of negligible interference with blood supply of the humeral head. There was no requirement to shape the plate enabling stabilization at constant angles as clear benefit of this plate. All that enables early mobilisation, and no implant insufficiency resulting in satisfactory treatment results and high Constant shoulder scores.

Is experimentally induced pain associated with socioeconomic status? Do poor people hurt more?

BACKGROUND: The association of pain and socioeconomic status is widely reported, yet much less clearly understood. The aim of this study was to investigate the association of experimentally induced pain threshold and tolerance with socioeconomic status. MATERIAL/METHODS: The study sample consisted of 319 adult subjects from the population of the island of Vis, Croatia, which was previously shown to have a high level of social homogeneity. A manual dolorimeter was used to measure mechanical pressure pain threshold (least stimulus intensity) and pain tolerance (maximum tolerance stimulus intensity) on both hands. Pain tolerance interval was defined as the difference between pain tolerance and threshold. Years of schooling and material status were used as socioeconomic estimates. RESULTS: Both of the socioeconomic estimates were significantly correlated with pain threshold, tolerance, and tolerance interval (P<0.001). The mixed modeling analysis, controlled for the effects of age, gender, and 4 psychological variables, indicated that education was not a significant predictor in any of the 3 models. However, lower material status was significantly associated with lower pain tolerance (P=0.038) and narrower pain tolerance interval (P=0.032), but not with pain threshold (P=0.506). The overall percentages of explained variance were lower in the tolerance interval model (20.2%) than in pain tolerance (23.1%) and threshold (33.1%), suggesting the increasing share of other confounding variables in pain tolerance and even more so in tolerance interval model. CONCLUSIONS: These results suggest a significant association between experimentally induced pain tolerance and tolerance interval with material status, suggesting that poor people indeed do hurt more.

Novel external fixation fracture method with circular locking mechanism compared with the application of dynamic axial external fixator on experimental tibial model ensures better stability in bending and favourable performance in dynamic loads.

OBJECTIVE: The aim of this study was to compare the biomechanical properties of a novel tibial external bone fracture fixator with a circular locking mechanism with standard dynamic axial external fixator. MATERIAL AND METHODS: In order to investigate the prototype usability in experimental conditions, a biomechanical study was performed in which 42 polyacetal tubes set in 14 experimental groups and subgroups represented the fractured tibia that were fixed by a standard dynamic axial external fixator and a novel fixator. Displacements under static and dynamic loads were measured, with static ones corresponding to three directions of fragment movement and dynamic simulating the human gait. Analysis was performed in SPSS v13, with significance set at P<0.05. RESULTS: The novel fixator showed biomechanical superiority in "fragments apart" study groups, while the standard dynamic axial external fixator outperformed the novel one in the situations of bending with "fragments in contact" study groups. There were no significant differences in dynamic load, despite better numerical result of the novel fixator. CONCLUSION: The novel fixator is expectedly faster applicable and offers greater extent of external fixation flexibility. Further developments of this model thus seems justified in both construction improvement and on clinical application.

Comparative study of three models of extra-articular distal humerus fracture osteosynthesis using the finite element method on an osteoporotic computational model.

INTRODUCTION: The biomechanical properties of extra-articular fractures of the distal humerus have not been researched sufficiently. The aim of the study was to examine three different models of osteosynthesis for extra-articular distal humerus fractures. Osteosynthesis with two parallel or perpendicular plates is a common method of osteosynthesis for those fractures. We wanted to examine the biomechanical performance of a newly designed Y plate, and compare it to the previously used osteosynthesis methods. MATERIALS AND METHODS: On an osteoporotic computational model of the distal humerus, a 10 mm gap was made, 25 mm above the olecranon fossa, and osteosynthesis was performed with the newly designed Y-shaped plate and with 3.5 reconstruction plates in parallel and perpendicular configuration. The numerical simulations in axial compression, bending and varus loading were conducted using the finite element method. RESULTS: On all models the largest displacements in the area of the fracture gap appear around the lower anterior edge. The parallel plate construct had the highest stiffness among the three plating techniques in axial compression. In bending and varus loading the construct with the newly designed plate had the highest stiffness, but in axial compression demonstrated the lowest. The parallel plate configurations had higher stiffness than the perpendicular ones in all three loading directions and the difference is most pronounced in axial compression. CONCLUSION: The displacements that appeared in all three plating systems are minimal and within the limits that meet the requirements of sufficient biomechanical stability in the usual time for the healing of fractures in that region. The newly designed Y-shaped plate for extra-articular fractures of the distal humerus is a possible alternative to the usual method of osteosynthesis with two plates in the case of an extra-articular fracture of the distal humerus. Further biomechanical studies are needed for a decisive conclusion.

Can genetics aggravate the health of isolated and remote populations? The case of gout, hyperuricaemia and osteoarthritis in Dalmatia.

INTRODUCTION: The aim of this study was to investigate whether genetics may be considered an additional risk factor for health in isolated and remote populations, compared with their populations of origin. In this study, two remote island population samples from Croatia (from the islands of Vis and the Korcula) were compared with mainland controls from the coastal city of Split. The analyses focused on gout, hyperuricaemia and osteoarthritis, as examples of complex, multifactorial diseases. METHODS: A total of 3006 examinees from all three sites in Dalmatia, Croatia were included in the descriptive part of the study, within a large-scale project of 10,001 Dalmatians. Additionally, a subset of 2428 subjects was genotyped and information on three genomic loci was used in this study. All three loci belong to SLC2A9 gene, considered to have a major role in the regulation of serum uric acid concentration (rs6449213, rs1014290 and rs737267). RESULTS: There was a much a higher prevalence of gout in the isolated populations compared with the mainland sample (3.3% in Vis, 2.2% in Korcula and 1.7% in Split, after age standardization). Furthermore, standardized prevalence of hyperuricaemia (defined as serum uric acid ≥403 mmol/L) was 9.9% in Vis, 5.6% in Korcula and 6.1% in Split. Analysis of the allele frequencies for the three loci of SLC2A9 suggested that in all three instances the prevalence of deleterious genotypes was highest in Vis, followed by Korcula, which had higher or comparable prevalence to the city of Split. Multivariate analysis, adjusted for the main confounder effects indicated that those on the island of Vis, which has the higher degree of isolation, had significantly higher odds ratio for both hyperuricaemia (odds ratio 1.90 95% confidence intervals [1.36-2.64]) and osteoarthritis, but not gout (3.37 [2.14-5.32]). The difference between Split and Korcula included only greater odds for osteoarthritis (1.92 [1.20-3.06]). CONCLUSIONS: Isolated and remote populations that maintain a sufficient level of genetic isolation may suffer not only from consequences of geographic and social isolation, but their population genetic structure may also further contribute to poorer health status and outcomes.