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Posterior thoracic skeletal structures involved in upper instrumented vertebra exposure andanchor placement were found to contribute to adjacent segment flexion stiffness. Although stiffness loss was small after individual procedures, the effects were additive for routinely used combinations.

Study Design A retrospective historical cohort design. Objective To determine what effect the addition of intrawound vancomycin powder to the prophylactic regimen of posterior instrumented spinal arthrodesis procedures has had on acute surgical site infections. Summary of Background Data Surgical site infections (SSI) are known complications in instrumented spinal arthrodesis procedures, and are predominately caused by Staphylococcus aureus. Recent reports have suggested that placing vancomycin powder into the surgical wound prior to closure prevents surgical site infections in spinal surgery. Risk factors for SSIs in the setting of intrawound vancomycin powder use have not been previously reported on. Methods Surgical site infection rates following 342 posterior instrumented spinal arthrodeses (Oct. 2008 to Sept. 2011) in which intrawound vancomycin powder was used in addition to the standard antimicrobial prophylaxis (Vanco cohort) were compared to 341 posterior instrumented spinal arthrodeses (Apr. 2005 to Oct. 2008) in which no vancomyin powder was added (Non-Vanco cohort). Both two sample t-test and Chi-square test (Fisher’s where appropriate) were used for group comparisons. A sub-analysis of the Vanco cohort was undertaken to identify risk factors for SSIs despite intrawound vancomycin use. Results There was a significant reduction in the number of acute staphylococcal SSIs in the Vanco cohort (1.1%) compared to the Non-Vanco cohort (3.8%) (p=0.029). Deep staphylococcal infections decreased to 0 compared to 7 in the Non-Vanco cohort (2.1%) (p=0.008). Deep MRSA infections decreased to 0 compared to 5 in the Non-Vanco cohort (1.5%) (p=0.031). Sub-analysis of the Vanco cohort identified that being discharged to an inpatient rehabilitation or skilled nursing facility was associated with developing a SSI. Conclusions Intrawound vancomycin powder use has decreased the rate of acute staphylococcal SSIs in our posterior instrumented spine arthrodesis surgeries. Patients who are discharged to skilled nursing or rehabilitation facilities are at increased risk for developing SSIs despite intrawound vancomycin use.

When performing the Scandinavian Total Ankle Replacement (STAR), the positioning of the talar component and the selection of mobile-bearing thickness are critical. A biomechanical experiment was undertaken to establish the effects of these variables on the range of movement (ROM) of the ankle. Six cadaver ankles containing a specially-modified STAR prosthesis were subjected to ROM determination, under weight-bearing conditions, while monitoring the strain in the peri-ankle ligaments. Each specimen was tested with the talar component positions in neutral, as well as 3 and 6 mm of anterior and posterior displacement. The sequence was repeated with an anatomical bearing thickness, as well as at 2 mm reduced and increased thicknesses. The movement limits were defined as 10% strain in any ligament, bearing lift-off from the talar component or limitations of the hardware. Both anterior talar component displacement and bearing thickness reduction caused a decrease in plantar flexion, which was associated with bearing lift-off. With increased bearing thickness, posterior displacement of the talar component decreased plantar flexion, whereas anterior displacement decreased dorsiflexion.

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To compare the biomechanical properties of the superficial (human acellular dermis); (AlloDerm; LefeCell Corp, Branchburg, NJ) and deep layers of cadaveric dermis and expanded polytetrafluoroethylene (ePTFE); (Gore-Tex; W. L. Gore & Associates, Flagstaff, Ariz). Methods: Sixteen samples of superficial dermis (Allo-Derm), 12 samples of deep dermis, and 12 samples of ePTFE were axial loaded on a materials testing machine. Maximum load to failure and stiffness were calculated and statistical analysis was performed to compare the materials. Results: Dermis samples had statistically greater mean stiffness compared with ePTFE samples. There was no statistical difference of maximum load to failure comparing ePTFE with superficial dermis. There was a statistical difference in maximum load to failure between ePTFE and deep dermis. There was no statistical difference between the superficial and deep layers of the dermis with respect to stiffness or maximum load to failure. Conclusions: Cadaveric dermis has some biomechanical properties to be a superior material for static facial suspension. There was larger than expected variability in both parameters (stiffness and maximum load to failure) tested in dermis samples, which may correlate with occasional clinical failure.

Both the relative volume of liquid monomer and the timing of antibiotic addition have substantial effects on the elution of antibiotic from bone cement.