No abstract

This study evaluated the effect of pre-bending dynamic compression plates on fracture site compression. Recommendations of 1 to 2 mm of pre-bend have been proposed, but there does not appear to be experimental data to confirm the optimal pre-bend magnitude. Dynamic compression plating was performed on the lateral convex surface of 18 femoral analogs to fixate a simulated mid-shaft fracture. Plates with 0 mm (flat plate), 1 mm, and 2 mm of pre-bend were evaluated for their production of compression by determining the strain magnitudes for 10 equal-sized zones across the anterior cortex at the osteotomy site using digital imaging correlation. The 0 and 1 mm plates produced significantly more compression at the near cortex (p = 0.001 and p = 0.003, respectively) than the 2 mm plate. However, the 0 and 1 mm plates also created visible diastasis at the far cortex, while the 2 mm plate exhibited compression across all zones. The strain magnitudes for the 0 mm (R2 = 0.62) and 1 mm (R2 = 0.86) plates linearly and significantly decreased from the region adjacent to the plate until a region 50%–60% across the analog diameter. In contrast, the 2 mm plate exhibited uniform strains across the osteotomy site. This study demonstrates that pre-bending a dynamic compression plate 2 mm prior to fixation on a convex lateral femur provides the most compression at the far cortex. It also produces more uniform compression across the fracture when compared to 0 and 1 mm of pre-bend.

Background: Equipment used to guide surgical incisions has been shown to be a source of bacterial contamination during surgery. Purpose/Hypothesis: To compare the culture-positive rates of sterile marking pens used before and after skin preparation for shoulder surgery. It was hypothesized that there will be no difference in culture-positive rates from marking pens used after skin preparation compared with before skin preparation. Study Design: Controlled laboratory study. Methods: Overall, 43 consecutive patients undergoing elective shoulder surgery were enrolled prospectively into this study. Each patient provided 2 samples: study pens (from marking the surgical site incision after skin preparation) and positive control pens (from marking the surgical site incision before skin preparation). In addition, there were 43 negative control pens evaluated (straight from the packaging without any patient contact). Cultures were evaluated at 4 and 21 days, and all positive cultures were further evaluated for speciation, if able. Standard descriptive summaries and Fisher exact tests were used to compare the study samples. Results: The average age of the 43 patients was 54 years (range, 18-76 years). There were 29 (67%) female patients, and 30 (70%) procedures were on the right shoulder. Of the 43 procedures performed, 29 (67.4%) were arthroscopic, 12 (27.9%) were open, and 2 (4.7%) were closed. Of the 43 study pens, 1 culture was positive for Propionibacterium acnes (2.3%). Of the 43 positive control pens, 2 cultures were positive for bacterial growth (4.7%): P. acnes and Gram-positive bacilli (no speciation could be obtained). Of the 43 negative control pens, none of the cultures were positive for bacterial growth (0%). There was no statistical difference in the culture-positive rate between the study pens and the positive or negative control pens ( P ≥ .999). Conclusion: Study results indicated that sterile surgical marking pens used to plan incisions and to outline anatomic landmarks did not have a higher culture-positive rate compared with pens used on unprepared skin or pens straight from the packaging. Clinical Relevance: As a precaution, sterile surgical marking pens should be discarded after use on the skin surface and not placed on the sterile field.