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1.  Fracture of the shoulder girdle in multiply injured patients - an imperative for a high level of suspicion for associated neurovascular injuries 
The combination of a bony injury to the shoulder girdle and damage to the brachial plexus and the subclavian vessels is a rare finding. The cases of this combined injury pattern described in the literature are most notably reported in multiply-injured patients after high velocity trauma.
Three cases were admitted to our hospital after motorcycle accidents resulting in a combination of severe bony injuries to the shoulder girdle, to the subclavian artery and a lesion to the brachial plexus. Based on these three clinical cases the patterns of injury, as well as primary and secondary treatment approaches are presented.
The early detection of these injuries can be difficult in given acute, life threatening injuries addressed first in these multiply injured patients. A high level of suspicion, in conjunction with standardized ATLS based institutional protocols for secondary and tertiary survey, should increase the likelihood of a timely detection and early management of these rare but potentially devastating injuries.
PMCID: PMC3717289  PMID: 23830143
Clavicle fractures; Scaphulothoracic dissociation; Multiply-injured patients; Associated injuries; Brachial plexus; Subclavian artery
2.  Embalmed and fresh frozen human bones in orthopedic cadaveric studies: which bone is authentic and feasible? 
Acta Orthopaedica  2012;83(5):543-547.
Background and purpose
The most frequently used bones for mechanical testing of orthopedic and trauma devices are fresh frozen cadaveric bones, embalmed cadaveric bones, and artificial composite bones. Even today, the comparability of these different bone types has not been established.
We tested fresh frozen and embalmed cadaveric femora that were similar concerning age, sex, bone mineral density, and stiffness. Artificial composite femora were used as a reference group. Testing parameters were pullout forces of cortex and cancellous screws, maximum load until failure, and type of fracture generated.
Stiffness and type of fracture generated (Pauwels III) were similar for all 3 bone types (fresh frozen: 969 N/mm, 95% confidence interval (CI): 897–1,039; embalmed: 999 N/mm, CI: 875–1,121; composite: 946 N/mm, CI: 852–1,040). Furthermore, no significant differences were found between fresh frozen and embalmed femora concerning pullout forces of cancellous screws (fresh frozen: 654 N, CI: 471–836; embalmed: 595 N, CI: 365–823) and cortex screws (fresh frozen: 1,152 N, CI: 894–1,408; embalmed: 1,461 N, CI: 880–2,042), and axial load until failure (fresh frozen: 3,427 N, CI: 2,564–4290; embalmed: 3,603 N, CI: 2,898–4,306). The reference group showed statistically significantly different results for pullout forces of cancellous screws (2,344 N, CI: 2,068–2,620) and cortex screws (5,536 N, CI: 5,203–5,867) and for the axial load until failure (> 7,952 N).
Embalmed femur bones and fresh frozen bones had similar characteristics by mechanical testing. Thus, we suggest that embalmed human cadaveric bone is a good and safe option for mechanical testing of orthopedic and trauma devices.
PMCID: PMC3488184  PMID: 22978564
3.  The benefit of wire cerclage stabilisation of the medial hinge in intramedullary nailing for the treatment of subtrochanteric femoral fractures: a biomechanical study 
International Orthopaedics  2011;35(8):1237-1243.
Reduction and intramedullary fixation of subtrochanteric fractures is often challenging. Osteosynthesis frequently fails and a higher rate of non-unions is found. The aim of this study was to evaluate the benefit of an additional cerclage to anatomically reduce and support the medial hinge. The application is based on the experience of the surgeon; as yet no biomechanical data are available.
Ten pairs of human cadaveric femora were used to determine the biomechanical and clinical advantage of an additional cerclage. All femora were tested in a materials testing system after osteotomy, osteosynthesis with the Gamma III nail and randomisation into two groups with or without additional cerclage.
After cyclic loading the compressive load to reach plastic deformation of 5 mm was 2,160 N on average in the group without cerclage vs 2,330 N on average in the group with cerclage. This biomechanical advantage showed no statistical significance (p = 0.2). Radiological examination when the abort criterion was reached revealed that use of the additional wire cerclage could significantly decrease the failure of osteosynthesis (100 vs 10%) after intramedullary nailing of subtrochanteric fractures (p < 0.05).
In view of the more invasive operative approach with additional soft tissue injuries, application of an additional cerclage should still be considered carefully. Nevertheless, a mini-open approach to difficult fractures could be helpful in reducing the fracture with a clamp and is sometimes essential. The damage to the soft tissue must be weighed against the benefits of the procedure. An additional cerclage in oblique subtrochanteric fractures is a good option to ensure the reposition and cortical medial support if appropriate and to decrease osteosynthesis failure and rates of non-unions.
PMCID: PMC3167430  PMID: 21258791
4.  Monoaxial versus polyaxial locking systems: a biomechanical analysis of different locking systems for the fixation of proximal humeral fractures 
International Orthopaedics  2011;35(8):1245-1250.
The development of locking plate systems has led to polyaxial screws and new plate designs. This study compares monoaxial head locking screws (PHILOS© by Synthes) and a new generation of polyaxial locking screws (NCB-LE© by Zimmer) with respect to biomechanical stability.
On nine pairs of randomised formalin fixed humerus specimens, standardised osteotomies and osteosyntheses with nine monoaxial (group A) und nine polyaxial (group B) plate/screw systems were performed. A material testing machine by Instron (M-10 14961-DE) was used for cyclic stress tests and crash tests until defined breakup criteria as endpoints were reached.
After axial cyclic stress 200 times at 90 N, plastic deformation was 1.02 mm in group A and 1.25 mm in group B. After the next cycle using 180 N the additional deformation averaged 0.23 mm in group A and 0.39 mm in group B. The deformation using 450 N was 0.72 mm in group A compared to 0.92 mm in group B. The final full power test resulted in a deformation average of 0.49 mm in group A and 0.63 mm in group B after 2,000 cycles using 450 N. When reaching the breakup criteria the plastic deformation of the NCB plate was 9.04 mm on average. The PHILOS plate was similarly deformed by 9.00 mm.
As a result of the crash test, in group A the screws pulled out of the humeral head four times whereas the shaft broke one time and another time the implant was ripped out. The gap was closed four times. In group B, there were three cases of screw cut-through, four shaft fractures/screw avulsions from the shaft and two cases of gap closure.
The two systems resist the cyclic duration tests and the increasing force tests in a similar manner. The considerable clinical benefits of the polyaxial system are enhanced by equal biomechanical performance.
PMCID: PMC3167442  PMID: 21301828

Results 1-5 (5)