Milbrandt, Todd A.

The growth plate (physis) is responsible for enabling and regulating longitudinal growth of upper and lower limbs. This regulation occurs through interaction of the cells in the growth plate with systemic and locally produced factors. This complex interaction leads to precisely controlled changes in chondrocyte size, receptors, and matrix, which ultimately result in endochondral bone formation. With advances in cellular and molecular biology, our knowledge about these complex interactions has increased significantly over the past decade. Deficiency of any of the regulating factors or physeal injury during childhood can alter this well-orchestrated sequence of events and lead to abnormalities in growth. This review highlights the histology of the normal physis, including recent findings at the cellular and molecular levels, mechanics and mechanobiology of the growth plate, pathologies that can affect the physis, and treatment options, including interposition materials.

Background: Intraoperative C-arm fluoroscopy and low-dose O-arm are both reasonable means to assist in screw placement for idiopathic scoliosis surgery. Both using pediatric low-dose O-arm settings and minimizing the number of radiographs during C-arm fluoroscopy guidance decrease patient radiation exposure and its deleterious biological effect that may be associated with cancer risk. We hypothesized that the radiation dose for C-arm-guided fluoroscopy is no less than low-dose O-arm scanning for placement of pedicle screws. Methods: A multicenter matched-control cohort study of 28 patients in total was conducted. Fourteen patients who underwent O-arm-guided pedicle screw insertion for spinal fusion surgery in 1 institution were matched to another 14 patients who underwent C-arm fluoroscopy guidance in the other institution in terms of the age of surgery, body weight, and number of imaged spine levels. The total effective dose was compared. A low-dose pediatric protocol was used for all O-arm scans with an effective dose of 0.65 mSv per scan. The effective dose of C-arm fluoroscopy was determined using anthropomorphic phantoms that represented the thoracic and lumbar spine in anteroposterior and lateral views, respectively. The clinical outcome and complications of all patients were documented. Results: The mean total effective dose for the O-arm group was approximately 4 times higher than that of the C-arm group (P<0.0001). The effective dose for the C-arm patients had high variability based on fluoroscopy time and did not correlate with the number of imaged spine levels or body weight. The effective dose of 1 low-dose pediatric O-arm scan approximated 85 seconds of the C-arm fluoroscopy time. All patients had satisfactory clinical outcomes without major complications that required returning to the operating room. Conclusions: Radiation exposure required for O-arm scans can be higher than that required for C-arm fluoroscopy, but it depends on fluoroscopy time. Inclusion of more medical centers and surgeons will better account for the variability of C-arm dose due to distinct patient characteristics, surgeon’s preference, and individual institution’s protocol. Level of Evidence: Level III–case-control study.

Background: Peripheral nerve blocks (PNBs) have the potential to reduce postoperative pain. The use of ultrasound (US) to guide PNBs may be more beneficial than nerve stimulation (NS); however, very few studies have studied this technique in children. The objective of this study was to compare postoperative pain control in pediatric patients who had general anesthesia (GA) alone compared with those who had PNB performed by NS, or PNB with both NS and US guidance. Our hypothesis was that compared with NS, the US-guided PNB would result in reduced postoperative pain and opioid use, and that both PNB conditions would have improved outcomes compared with GA. Methods: A retrospective chart review of foot and ankle surgery included 103 patients who were stratified into 3 groups: GA, PNB with NS, and PNB with NS and US. Pain levels were measured with visual pain scales at 2, 4, 6, 8, 12, and 24 hours postoperatively. Days of hospitalization, morphine and oxycodone use by weight, and time to first PRN opioid use were also recorded. A repeated measure analysis of variance was used to compare the groups, and the proportion of patients who reported a visual analog scale score of 0 was calculated for each time point. Results: There were no significant differences in pain levels between groups for the first 12 hours, but the US group had higher pain levels at 24 hours. Both US and NS groups had a longer time to PRN opioid use and used significantly less morphine compared with GA. The US group had a significantly greater proportion of pain-free patients than the other 2 groups for the first 6 hours. Conclusions: The use of US guidance is beneficial in postoperative pain control. Both US-guided and NS-guided PNB are preferable to GA alone for lower extremity orthopaedic surgery in the pediatric population. Level of Evidence: III, retrospective comparative study.