Effects of posterior distraction forces on anterior column intradiscal pressure in the dual growing rod technique.

BACKGROUND: Little evidence is available addressing biomechanical properties of posterior distraction forces and their effects on anterior spinal column in the growing rod technique. The question is often asked if posterior distraction forces may be kyphogenic. The goal of this study is to determine whether posterior distraction forces transmitted anteriorly through different foundation constructs (i.e., screws vs. hooks) affect intradiscal pressure. METHODS: Six skeletally immature porcine spines were harvested leaving soft tissues and rib heads intact. Pedicle screws served as the lower foundation on a L3-L4 motion segment while pedicle screws and laminar hooks were randomly used at T3-T4 levels. Proximal constructs (hook vs. screw) were switched after initial distraction testing. The dual rod distractor was instrumented with strain gauges and calibrated using a custom force transducer. During distraction, intradiscal pressures immediately inferior to the superior foundation and the level equidistant between foundations were measured using needle pressure transducers. Maximum distraction force and maximum anterior disc pressure change were compared between hook and pedicle screw anchors using one-way ANOVA (p < 0.05). RESULTS: Upper foundations with pedicle screws had significantly greater distraction forces (416 ± 101 N) than those with upper level hooks (349 ± 100 N). There were no significant differences in disc pressures between levels or between upper foundation constructs. Disc pressures adjacent to the upper foundation demonstrated greater reduction (disc expansion) than the level equidistant within the construct. Pedicle screw constructs demonstrated greater endplate separation (distraction) compared to hook constructs. CONCLUSIONS: Posterior distraction forces result in anterior disc separation (distraction) and are distributed across multiple levels rather than delivered to the disc immediately adjacent to a foundation. Constructs with upper foundation hooks had lower distraction forces possibly due to hook motion during distraction. The load distribution at multiple levels may assist with curve control and may affect vertebral growth. The distraction forces may not be kyphogenic as is commonly believed.

Get up, get out, get moving: an interactive tool for education at your local school.

BACKGROUND: Childhood obesity is a growing problem in America. Orthopaedic surgeons have an opportunity to interact with communities to educate children about healthy eating and physical activity. The American Academy of Orthopedic Surgeons (AAOS) Leadership Fellows Program [1] Class of 2012 created a presentation for AAOS members to bring to local schools. The goal was to teach the children about the potential complications of childhood obesity and the benefits of healthy living. QUESTIONS/PURPOSES: We describe a program in which orthopaedic surgeons gave presentations to elementary school students about healthy eating and activity and the effects that extra weight can have on their bones. METHODS: Each of the five members of the Leadership Fellows Program [1] 2012 class (JW, EM, MP, MR, MF) presented to a school in his or her hometown. The program was presented to 210 fifth grade children throughout the country. Before and after the presentation, students took a six-question multiple-choice quiz and answers compared to assess improvement in knowledge. RESULTS: The average number of answers correct before the presentation was 4.5 out of six, and the average after the presentation was six of six. The presentations were well received, and the students and their teachers invited each presenter back the next year. CONCLUSIONS: The improvement in quiz scores demonstrated interest among the students in that they paid attention and understood the content. The children appeared enthusiastic to learn about this subject, and the schools were enthusiastic to include the curriculum.

Effect of body mass index on patient outcomes of surgical intervention for the lumbar spine.

BACKGROUND: Conflicting findings exist on the effect of obesity on outcomes of lumbar spine surgery; results depend on the diagnosis studied, procedure evaluated, definition of obesity, and specific outcomes measured. The purpose of this retrospective cohort study is to examine the effect of increasing body mass index (BMI) on surgical-related, health-related, and long-term outcomes of lumbar spine surgery in a single representative patient sample. METHODS: Using a surgical registry from an integrated health care system, 8,049 instrumented lumbar spine cases were identified between 1/1/2009 and 09/30/2013. The sample was stratified into five BMI categories. Outcomes of interest included: (I) surgical-related factors and complications; (II) health-related complications; and (III) long-term complications. Mixed linear models, conditional logistic regressions, and survival analysis using a Cox regression model were conducted controlling for surgeon effects. Age, gender, diabetes status, smoking status, admitting diagnosis, and surgical approach were included as covariates. RESULTS: Every 5 kg/m2 increase in BMI was associated with a significant increase in surgical time (7.8 minutes), estimated blood loss (EBL) (36.5 mL), risk of deep infection (OR =1.7 times), and deep vein thrombosis (DVT) (OR =1.5). BMI was not associated with increased incidence of other intraoperative or health-related complications. Rate of re-operation was 1.1 times higher with every 5 kg/m2 increase in BMI, but rate of re-operation due to adjacent segment disease (ASD) was not associated with BMI. CONCLUSIONS: Obesity had an adverse effect on certain surgical-related, health-related and long-term surgical outcomes. The magnitude of this effect increased with increasing levels of obesity, which increases the medical burden associated with obesity.