Optimal internal fixation of anatomically shaped synthetic bone grafts for massive segmental defects of long bones.

BACKGROUND: Large segmental bone defects following tumor resection, high-energy civilian trauma, and military blast injuries present significant clinical challenges. Tissue engineering strategies using scaffolds are being considered as a treatment, but there is little research into optimal fixation of such scaffolds. METHODS: Twelve fresh-frozen paired cadaveric legs were utilized to simulate a critical sized intercalary defect in the tibia. Poly-ε-caprolactone and hydroxyapatite composite scaffolds 5 cm in length with a geometry representative of the mid-diaphysis of an adult human tibia were fabricated, inserted into a tibial mid-diaphyseal intercalary defect, and fixed with a 14-hole large fragment plate. Optimal screw fixation comparing non-locking and locking screws was tested in axial compression, bending, and torsion in a non-destructive manner. A cyclic torsional test to failure under torque control was then performed. FINDINGS: Biomechanical testing showed no significant difference for bending or axial stiffness with non-locking vs. locking fixation. Torsional stiffness was significantly higher (P=0.002) with the scaffold present for both non-locking and locking compared to the scaffold absent. In testing to failure, angular rotation was greater for the non-locking compared to locking constructs at each torque level up to 40 N-m (P<0.05). The locking constructs survived a significantly higher number of loading cycles before reaching clinical failure at 30 degrees of angular rotation (P<0.02). INTERPRETATION: The presence of the scaffold increased the torsional stiffness of the construct. Locking fixation resulted in a stronger construct with increased cycles to failure compared to non-locking fixation.

Investigation of the preservation of the fluid seal effect in the repaired, partially resected, and reconstructed acetabular labrum in a cadaveric hip model.

BACKGROUND: Debate exists on whether hip labral tears should be surgically repaired, partially resected, or reconstructed. Furthermore, limited data exist regarding the fluid seal properties of hip labrum repair and/or reconstruction with iliotibial band autograft when compared with the labrum-intact condition. Hypothesis/ PURPOSE: The purpose of this study was to investigate the fluid seal properties of hip labral repair and reconstruction techniques. We hypothesized that hip labral repair preserves the acetabular labral fluid seal greater than labral tear, partial-resection, and reconstruction conditions. STUDY DESIGN: Controlled laboratory study. METHODS: Six human cadaveric hemipelvises were dissected of all soft tissue, leaving the hip capsule intact. Fluid efflux was measured under 5 conditions using a custom fluid infusion device: (1) hip labrum intact, (2) labral tear, (3) labral repair with suture anchors, (4) partial labral resection, and (5) labral reconstruction using ipsilateral iliotibial band autograft. Joint fluid expression was measured as flow rate under 3 different pressure settings (2, 3, and 4 psi). Statistical differences between conditions were assessed using 2-way, repeated-measures analysis of variance. The Student-Newman-Keuls (SNK) multiple comparison test was used to determine differences between levels. RESULTS: There was a significant increase in fluid efflux with a simulated labral tear (0.54 ± 0.3 mL/sec) when compared with the intact hip labrum condition (0.006 ± 0.008 mL/sec, P < .05). The labrum-repaired condition (0.21 ± 0.2 mL/sec) demonstrated significantly less fluid efflux when compared with the labral-tear condition. Hip labral repair significantly prevented greater fluid efflux when compared with partial labral resection (0.60 ± 0.4 mL/sec) and reconstruction with iliotibial band autograft (0.54 ± 0.3 mL/sec; P < .05). Labral repair did not preserve fluid efflux as effectively as in the labrum-intact condition (0.21 ± 0.2 > 0.006 ± 0.008 mL/sec; P < .05). There was no difference observed in fluid efflux between the labral reconstruction, tear, or resection conditions (P > .05). CONCLUSION: In this human cadaveric model, hip labral repair outperforms partial labral resection and reconstruction in preserving the joint fluid seal; however labral repair does not restore fluid seal characteristics as effectively as in the labrum-intact condition. CLINICAL RELEVANCE: Further prospective studies are needed to determine whether hip labral repair outperforms partial labral resection and/or reconstruction in clinical practice.

Improving bone density at the rotator cuff footprint increases supraspinatus tendon failure stress in a rat model.

The purpose of this study was to investigate whether supraspinatus tendon failure stress at the footprint can increase by improving the bone density at the rotator cuff footprint in a rat model. Bilateral ovariectomies were performed in twenty-four 4-month-old Sprague-Dawley rats. Half received bisphosphonate (zoledronic acid) and the other half received no treatment (OVX + ZOM and OVX, respectively). Twelve additional rats did not undergo ovariectomy or receive bisphosphonate treatment (CON). All rats were sacrificed at 7 months of age. Quantitative micro-computed tomography was used to assess bone density in the proximal humerus. A series of stress-relaxation tests were performed to assess stiffness and failure stress of the supraspinatus tendon. Bone density in OVX + ZOM was significantly higher at the rotator cuff footprint when compared to CON and OVX rats (p < 0.0001). The supraspinatus tendons in the OVX group were significantly stiffer when compared to the CON and OVX + ZOM groups (p < 0.05). The failure stress of the OVX + ZOM group was significantly greater than the CON and OVX groups (22.89 +/- 4.43 MPa vs. 18.36 +/- 3.16 and 17.70 +/- 4.92, respectively). In conclusion, improving the bone density at the rotator cuff footprint enhances failure stress of the suprapinatus tendon.

The use of herbal and over-the-counter dietary supplements for the prevention of prostate cancer.

Having a high probability of experiencing prostate cancer during their lifetime, men are increasingly seeking protection against this disease with the use of over-the-counter dietary supplements containing herbs, vitamins, or plant-derived biochemical agents. The use of these agents for prostate cancer prevention is driven by epidemiology supporting the idea that regional diets and consumption of specific dietary components (certain herbs, vitamins, isoflavones, and polyphenols) are associated with a lower risk for prostate cancer, in conjunction with basic research that is defining molecules within food substances that kill or suppress growth of cultured human prostate cancer cells. Moreover, there is a sense that these dietary agents lack side effects, although this assumption often is faulty. Unfortunately, at this time, there is insufficient clinical evidence to support the widespread use of these dietary supplements for chemoprevention of prostate cancer, although ongoing clinical trials of the most promising vitamins and minerals are approaching conclusion.

The use of herbal and over-the-counter dietary supplements for the prevention of prostate cancer.

Having a high probability of experiencing prostate cancer during their lifetime, men are increasingly seeking protection against this disease with the use of over-the-counter dietary supplements containing herbs, vitamins, or plant-derived biochemical agents. The use of these agents for prostate cancer prevention is driven by epidemiology supporting the idea that regional diets and consumption of specific dietary components (certain herbs, vitamins, isoflavones, and polyphenols) are associated with a lower risk for prostate cancer, in conjunction with basic research that is defining molecules within food substances that kill or suppress growth of cultured human prostate cancer cells. Moreover, there is a sense that these dietary agents lack side effects, although this assumption often is faulty. Unfortunately, at this time, there is insufficient clinical evidence to support the widespread use of these dietary supplements for chemoprevention of prostate cancer, although ongoing clinical trials of the most promising vitamins and minerals are approaching conclusion.