Rat model of distraction osteogenesis

Prior studies of distraction osteogenesis in dog and rabbit models have shown predominantly intramembranous bone formation. Other models of fracture healing normally display mixtures of both endochondral and intramembranous bone formation. We have established a rat model of tibial lengthening that reliably reproduces the pattern of zonal osteogenesis previously observed in dog and rabbit models. A distraction rate of 0.25 mm twice a day with a 0-day latency period produced intramembranous bone with zones of progressive mineralization from collagen. With this protocol, rats bridged the distraction gap with a 25% increase in the tibial bone length. After 20 days of distraction and 50 days of consolidation, the three-point bending stiffness, as a percentage of the contralateral control, reached a level equivalent to that measured in the canine model for a 15% lengthening (28-day distraction and 84-day consolidation). Radiodensitometric analysis of the regenerate bones measured 97% of the unaffected contralateral tibial densities, and mineral analyses demonstrated that calcium and phosphorus levels in the regenerate bone reached 78% of contralateral tibial levels by day 70. We concluded that a rat model of distraction ostegenesis will be useful for a wide range of studies involving rapid intramembranous bone formation.     

Short-Ti inversion-recovery pulse sequence: analysis and initial experience in cancer imaging

Inversion recovery (IR), commonly considered a pulse sequence capable of producing T1-weighted images with excellent display of normal anatomy, is versatile: The null point and peak time provide a useful, succinct summary of the properties of IR and its capacity for producing both T1- and T2-weighted images. Shortening of the inversion time (TI) and creation of a short-TI inversion-recovery (STIR) pulse sequence increases sensitivity to malignancy and other abnormalities by making the effects of prolonged T1 and T2 on signal intensity additive and by nulling the signal from fat. The authors examined over 300 patients with various malignancies and compared STIR images with T1- and T2-weighted images obtained at 0.5 T. In 43 cases, signal-difference-to-noise ratios (SD/Ns) were calculated between tumor, fat, and muscle. In general, STIR images demonstrated tumor as a conspicuously high-intensity area in a background of muted, discernible anatomic detail. The good contrast achieved with STIR sequences between tumor and fat (SD/N = 18.1) and tumor and muscle (SD/N = 12.9) consolidated into a single image the information contained separately on T1- and T2-weighted images, which facilitates efficient detection and localization of malignancy.     

Rizatriptan in the treatment of migraine

Migraine is a common, disabling disorder associated with considerable personal and societal burden. Current guidelines recommend triptans for the acute treatment of migraine unlikely to respond to less effective therapies. Rizatriptan is a second-generation triptan available in tablet or orally disintegrating tablet (wafer) formulations that offers several advantages over other members of its class. Rizatriptan is rapidly absorbed from the gastrointestinal tract and achieves maximum plasma concentrations more quickly than other triptans, providing rapid pain relief. Clinical trials have shown that rizatriptan is at least as effective or superior to other oral migraine-specific agents in the acute treatment of migraine, and has more consistent long-term efficacy across multiple migraine attacks. Rizatriptan has a favorable tolerability profile, and patients have reported greater satisfaction and a preference for rizatriptan over other migraine-specific agents. Improvements in quality of life reported with rizatriptan are consistent with its favorable efficacy and tolerability profiles. Notably, multi-attribute decision models that combine clinical data with patient- and physician-reported treatment preferences have identified rizatriptan as one of three triptans closest to a hypothetical “ideal”. The efficacy and tolerability of rizatriptan for the acute treatment of migraine have thus been well established.     

Seasonal variation of slipped capital femoral epiphysis

To correlate the season of the year with the prevalence of slipped capital femoral epiphysis, we reviewed the cases of 177 patients who had 243 slips during an eleven-year period. We assessed the month when the patient was seen and the implied time of onset of the slip and found a statistically significant variation for both. The average time of onset was mid-June, with a standard deviation of 2.5 months, and was not significantly different for race, sex, or laterality. We attributed the increased incidence of slipped capital femoral epiphysis during the summer to increased physical activity in that season.     

Case Report: Giant choledochal cyst

We report an adult female with a rare giant choledochal cyst. The patient presented following a normal pregnancy with the classical triad of an abdominal mass associated with jaundice and right upper quadrant abdominal pain. The cyst was excised using an intramural technique and biliary reconstruction achieved with a Roux-en-Y hepaticojejunostomy. Our patient has remained well with no evidence of malignancy over a 12 year review period. The aetiology and current management of this condition are discussed.