Biomechanical determination of the relationship between femoral neck lesion size and the risk of pathological fracture.

PURPOSE: Half of the pathological fractures of the proximal femur occur in the neck region. We evaluate the relationship between the defect size within the femoral neck and the risk of pathological fracture. METHODS: After creating metastasis-like lesions in the neck regions of 21 human cadaver femurs, compression was applied to simulate single-limp stance type loading. First, a loading of 600 Newtons (N) was applied to the 35%-defected femoral necks. If the bone fracture did not occur, the defect size was increased to 45% and the 600 N force was applied again. If no fracture was observed then the defect size was increased to 55% and the bones were loaded again. The 55%-defected bones with no fractures were loaded until a fracture was detected. RESULTS: There were no fractures with the 35%- and 45%-defected femurs until 600 N was applied. However, when the defect size was increased to 55%, 3 bones were fractured before reaching 600 N. The fractures occurred at an average of 455 N in the 3 bones. At a compression of 600 N, 18 bones (84%) were intact, and the loading was continued. 18 femurs with 55%-defected neck regions had an average endurance of 1270 N compression (range 750-2800 N). CONCLUSIONS: This study showed that even very osteoporotic bones with large metastases can withstand high forces of compressive loading.

Mid-term radiological and functional results of biological reconstructions of extremity-located bone sarcomas in children and young adults.

Biological reconstruction is a useful option for reconstruction following bone sarcoma resection in children. The mid-term functional and radiological outcomes of biological reconstructions after resection of bone sarcomas in children are presented in this study. Eighteen patients [average age 12.5 years (range 4-22 years)] with primary sarcomas of long bones underwent wide surgical resection and biological reconstruction. The bone defects were managed by intercalary (n=14), osteoarticular (n=3) reconstructions and arthrodesis (n=1) with a vascularized fibular graft (VFG). VFG was combined with a massive allograft in seven lower extremity reconstructions. The average follow-up was 45.7 months (range 25-78 months). Graft union and graft hypertrophy was observed in 17 (94.4%) of 18 patients at 12 months. The VFG-allograft osteointegration rate was 100% at 24 months. The average final follow-up Musculoskeletal Tumor Society (MSTS) scores for lower and upper extremity reconstructions were 79.7% (range 66.6-90%) and 80.9% (range 53.3-100%), respectively. Four (22.2%) complications, including nonunion (n=1), implant failure (n=1), infection (n=1) and skin necrosis (n=1), required reoperation. The disease relapsed in three (16.6%) patients. Defect size and VFG length did not correlate with MSTS scores and radiological parameters (P>0.05). Biological reconstruction with VFG can provide permanent stability and progressively increasing functional and radiological results.

Tendon-holding capacities of two newly designed implants for tendon repair: an experimental study on the flexor digitorum profundus tendon of sheep.

BACKGROUND: Two main factors determine the strength of tendon repair; the tensile strength of material and the gripping capacity of a suture configuration. Different repair techniques and suture materials were developed to increase the strength of repairs but none of techniques and suture materials seem to provide enough tensile strength with safety margins for early active mobilization. In order to overcome this problem tendon suturing implants are being developed. We designed two different suturing implants. The aim of this study was to measure tendon-holding capacities of these implants biomechanically and to compare them with frequently used suture techniques. MATERIALS AND METHODS: In this study we used 64 sheep flexor digitorum profundus tendons. Four study groups were formed and each group had 16 tendons. We applied model 1 and model 2 implant to the first 2 groups and Bunnell and locking-loop techniques to the 3rd and 4th groups respectively by using 5 Ticron sutures. RESULTS: In 13 tendons in group 1 and 15 tendons in group 2 and in all tendons in group 3 and 4, implants and sutures pulled out of the tendon in longitudinal axis at the point of maximum load. The mean tensile strengths were the largest in group 1 and smallest in group 3. CONCLUSION: In conclusion, the new stainless steel tendon suturing implants applied from outside the tendons using steel wires enable a biomechanically stronger repair with less tendon trauma when compared to previously developed tendon repair implants and the traditional suturing techniques.

Effects of the grade, stability, chronological classification and being either unilateral or bilateral of the slip on the treatment by in situ single screw fixation of patients with slipped capital femoral epiphysis.

PURPOSE: The effects of the grade, stability, chronological classification and being either unilateral or bilateral of the slip on the outcomes of the treatment by in situ single screw fixation of the Slipped capital femoral epiphysis were investigated. METHODS: 34 hips of 24 patients (7 girls, 17 boys; mean age 12.04 years; range 9-14; 14 slips acute, 7 slips acute on chronic, 13 slips chronic; 22 slips stable, 12 slips unstable; 20 slips Grade 1, 13 slips Grade 2, 1 slips Grade 3) between 2003 and 2009 were involved in the study. During the controls; range of motion, walking abnormalities, Trendelenburg test, use of assistive devices during mobilization, existence of pain and complications were evaluated. The evaluation of clinical results was made according to the average Harris Hip Score. RESULTS: 10 of 24 patients showed evidence of a slip of the contralateral hip on average 10.6 (6-16) months after the initial operation. At mean 41.52 ± 8.08 months controls, the Harris Hip Score was found 77.41 ± 14.66, hip-joint motions, flexion 120° (70°-140°), abduction 40° (20°-60°), internal rotation 25° (10°-40°). Evaluation at the last follow-up showed significant differences between single hip slip than both hip slip, stable slip than unstable slip and Grade 1 slip than Grade 2 slip. In the last control of one patient with a Grade 3 slip, avascular necrosis has been observed. Considering the effect on the clinical results of the chronological classification of the no slip, significant differences have been seen between the clinical outcomes of the acute, chronic or acute on chronic slips. DISCUSSION: The outcomes of the treatment by in situ single screw fixation are negatively affected by increase in the grade of slip, instability of the slip and existence of slip at both hips.