Epiphyseal Translation as a Predictor of Avascular Necrosis in Unstable Slipped Capital Femoral Epiphysis.

BACKGROUND: Physeal instability has been shown to be associated with a higher risk of avascular necrosis (AVN) in patients with slipped capital femoral epiphysis (SCFE). The purpose of this study was to identify additional preoperative factors associated with AVN in patients with unstable SCFE. METHODS: Basic demographic information, chronicity of symptoms, and estimated duration of nonambulatory status were noted. Preoperative radiographs were used to measure the Southwick slip angle, slip severity by Wilson criteria, and epiphyseal translation. Translation was measured by 3 distinct radiographic parameters in the position demonstrating maximal displacement. Postoperative radiographs at the time of most recent follow-up were assessed for the presence of AVN. Translation measurements were tested for inter-rater reliability. Patients who developed AVN were compared with those that did not by Fisher exact test and Wilcoxon tests. Logistic regression assessed the effect of translation on the odds of developing AVN. Receiver operating characteristic curve was plotted to assess any threshold effect. RESULTS: Fifty-one patients (55 hips) out of 310 patients (16%) treated for SCFE were considered unstable. Seventeen hips' unstable SCFE (31%) showed radiographic evidence of AVN. Slip severity by Wilson grade (P=0.009) and epiphyseal translation by all measurements (P< 0.05) were statistically significantly greater among patients who developed AVN. Superior translation had the best inter-rater reliability (intraclass correlation coefficient=0.84). Average superior translation in hips that developed AVN was 17.2 mm compared with 12.9 mm in those that did not (P<0.02). Although the receiver operating characteristic curve did not demonstrate a threshold effect for AVN, it did effectively rule out AVN in cases with <1 cm of superior translation. Age, sex, laterality, chronicity of prodromal symptoms or inability to bear weight, Southwick slip angle, and method of treatment did not vary with the occurrence of AVN. CONCLUSIONS: Epiphyseal translation, either by Wilson Grade or measured directly, is associated with AVN in patients with an unstable SCFE. LEVEL OF EVIDENCE: Level II-development of diagnostic criteria.

Terminal position of a tibial intramedullary nail: a computed tomography (CT) based study.

PURPOSE: The purpose of this study is to characterize the distal anatomic end-point of a tibial intramedullary nail placed using modern surgical techniques. The goal is to improve reduction of distal tibia fractures. METHODS: An intramedullary nail was placed in 14 skeletally mature legs. This included 8 patients with mid-shaft tibial fractures and 6 intact cadaveric legs. Each nail was a titanium cannulated tibial nail, size 10- or 11-mm. The nails were placed using a suprapatellar or transpatellar approach with an ideal starting point. All legs received post-nail insertion CT scans and fluoroscopy. The main outcome measure was the terminal location of the nail just proximal to the distal tibial physeal scar, as seen on axial CT and fluoroscopic views of the ankle (mortise and lateral). The end-point was measured as the (1) ratio of medial-lateral tibial width (ML ratio) and (2) ratio of anterior-posterior tibial width (AP ratio). Two-tailed Welch's t tests were used to compare the actual, observed position of the nail to the hypothesized center-center position (H0 = ML and AP ratio of 0.5). RESULTS: All enrolled patients (n = 8) and cadaveric legs were included (n = 6). On axial CT, the average distance from the medial tibial cortex to the nail center as a ratio of medial-lateral tibial width was 0.63, 95% CI 0.60-0.67, p < 0.001 (Patient = 0.60, 95% CI 0.55-0.64, p = 0.001) (Cadaver = 0.68, 95% CI 0.64-0.73, p < 0.001). On fluoroscopic mortise views, the distance from the medial cortex to the nail center as ratio of medial-lateral tibial width was 0.64, 95% CI 0.60-0.67, p < 0.001 (Patient = 0.61, 95% CI 0.56-0.65, p < 0.001) (Cadaver = 0.67, 95% CI 0.63-0.72, p < 0.001). The AP ratio was not significantly different from 0.5 on either axial CT or fluoroscopic mortise views (p > 0.05). CONCLUSION: The distal end-point of a tibial intramedullary nail is lateral (ML plane) and center (AP plane) in both cadaveric legs and patients with midshaft tibia fractures. These results suggest that the treatment of distal tibia fractures with intramedullary nails may be improved by positioning the nail slightly lateral in the distal segment. LEVEL OF EVIDENCE: Diagnostic level I.

Safety and pharmacokinetics of intravaginal rings delivering tenofovir in pig-tailed macaques.

Antiretroviral-based microbicides applied topically to the vagina may play an important role in protecting women from HIV infection. Incorporation of the nucleoside reverse transcriptase inhibitor tenofovir (TFV) into intravaginal rings (IVRs) for sustained mucosal delivery may lead to increased microbicide product adherence and efficacy compared with those of conventional vaginal formulations. Formulations of a novel "pod IVR" platform spanning a range of IVR drug loadings and daily release rates of TFV were evaluated in a pig-tailed macaque model. The rings were safe and exhibited sustained release at controlled rates over 28 days. Vaginal secretion TFV levels were independent of IVR drug loading and were able to be varied over 1.5 log units by changing the ring configuration. Mean TFV levels in vaginal secretions were 72.4 ± 109 µg ml(-1) (slow releasing) and 1.84 ± 1.97 mg ml(-1) (fast releasing). The mean TFV vaginal tissue concentration from the slow-releasing IVRs was 76.4 ± 54.8 µg g(-1) and remained at steady state 7 days after IVR removal, consistent with the long intracellular half-life of TFV. Intracellular tenofovir diphosphate (TFV-DP), the active moiety in defining efficacy, was measured in vaginal lymphocytes collected in the study using the fast-releasing IVR formulation. Mean intracellular TFV-DP levels of 446 ± 150 fmol/10(6) cells fall within a range that may be protective of simian-human immunodeficiency virus strain SF162p3 (SHIV(SF162p3)) infection in nonhuman primates. These data suggest that TFV-releasing IVRs based on the pod design have potential for the prevention of transmission of human immunodeficiency virus type 1 (HIV-1) and merit further clinical investigation.