Harish S. Hosalkar

The British Editorial Society of Bone & Joint Surgery

Recent biplanar radiographic studies have demonstrated acetabular retroversion and increased superolateral femoral head coverage in hips with slipped capital femoral epiphysis (SCFE), seemingly divergent from earlier CT-based studies suggesting normal acetabular version. We therefore asked: Are there differences in (1) acetabular version at the superior ¼ of the acetabular dome (AV_sup), (2) acetabular version at the center of the femoral head (AV_cen), and (3) superolateral femoral head coverage (lateral center-edge angle [LCEA]) among affected SCFE hips, unaffected hips, and normal controls? We identified 32 patients with SCFE who underwent CT between 2007 and 2012. Twenty-three met our inclusion criteria. Seventy-six age- and sex-matched normal patients comprised the control group. Pelvic rotation, tilt, and inclination were corrected on each CT. AV_sup, AV_cen, and LCEA were measured. The mean AV_sup of the affected hips (−1.71°) demonstrated retroversion compared to the unaffected hips and the control group; the mean AV_sup of the unaffected hips was similar to that of the normal controls. Mean AV_cen was similar among the three groups. The LCEA was higher in affected and unaffected SCFE hips than in the control group (34.3° versus 34.5° versus 28.9°, respectively), but we found no difference between affected and unaffected hips. Our data suggest an association of superior acetabular retroversion and increased superolateral femoral head coverage in SCFE. Whether this represents a primary abnormal morphology or a secondary pathologic response remains unclear. Further studies investigating the role of acetabular morphology in SCFE and its implications for development of symptomatic femoroacetabular impingement are warranted.

Lateral center-edge angle (LCEA), originally described and validated on AP radiographs, has been used increasingly in CT-based studies, but it is unclear whether the measure is reliable and whether it correlates with that on AP radiographs. We therefore determined: (1) the interobserver and intraobserver reliabilities of the LCEA measured on AP radiographs; (2) the interobserver and intraobserver reliabilities of the LCEA measured on CT scans; and (3) the intermodality correlation of the LCEA between CT and AP radiography. We reviewed the AP radiographs and CT scans of 22 patients treated for slipped capital femoral epiphyses. CT scans were reoriented to a neutral pelvic tilt and inclination. Three evaluators measured the LCEA on the unaffected hip on the AP and CT coronal images that corresponded to the center of the acetabulum on the axial slice. We found an interobserver intraclass correlation (ICC) analysis of 0.84 for the AP radiographs and 0.88 for the CT scans. The intraobserver ICC for the AP radiographs was 0.96, and for the CT scans 0.98. The intermodality ICC for the CT scans and AP radiographs was 0.79, with a lower bound of 0.61 and an upper bound of 0.87. Our data suggest the LCEA measured on a CT scan is reliable and correlates with the LCEA on AP radiographs.

Injuries to the physis continue to be a source of concern for the pediatric orthopaedic surgeon. Bries et al. examined the effect of a compressive load on the proximal tibial physis of rabbits to determine if changes in gene expression, cells, and extracellular components that promote physeal resilience and strength (type-II collagen and aggrecan) and cartilage hypertrophy (type-X collagen and matrix metalloprotease-13) were produced³. The authors found that the proximal tibial physes that were loaded in compression had decreased thickness, structurally disorganized chondrocyte columns, a decreased extracellular matrix, and less intense type-II and type-X collagen immunohistochemical staining. Gene expression of aggrecan and type-II and type-X collagen was decreased, with no significant changes in matrix metalloprotease-13 expression. Genetics continue to play a large role in our understanding of clinical conditions such as clubfoot and congenital scoliosis. Alvarado et al. examined the role of PITX1 (a bicoid homeodomain transcription factor) in the development of lower limb abnormalities, particularly clubfoot^{4 …}

Background: Assessment of lower extremity (LE) torsional profile using computed tomography (CT) imaging is a well-recognized imaging method that supplements the clinical examination. Magnetic resonance imaging (MRI) is another advanced imaging modality that can be used as an alternative, since there are many growing concerns of radiation exposure with traditional CT studies, particularly in the skeletally immature population. Methods: Sixty-two patients between the ages of 7 and 19 years were included. Thirty-four had CT and 28 had MRI for assessment of LE torsional profile. All patients had clinical evidence of torsional malalignment. CT and MR images were randomized and de-identified. Two observers measured femoral anteversion and tibial torsion based on previously published methodologies. This exercise was repeated 2 weeks later and the data were tabulated and statistical analysis was performed. Radiation exposure for the patients studied by CT was estimated. Results: The mean age of the patients was 14.4 years (range 9.5–18.9 years) and 13.8 years (range 7.3–18.9 years) for the CT and MRI groups, respectively. Inter-observer reliability for both CT and MRI studies were excellent. The intra-class correlation coefficient (ICC) for femoral anteversion and tibial torsion studied by CT and MRI for both observers at both times were excellent. The radiation exposure for CT examination averaged 0.3–0.5 mSv, compared to none with the MRI method. Conclusions: MRI provides a reproducible method for assessing the torsional profile in children and adolescents using similar anatomic landmarks for measurements as those used on CT torsional profile. In circumstances where MRI methods are readily available (and affordable), the CT torsional profile can be replaced with MRI methods, in the current era of growing concerns of radiation hazards and increasing awareness about radiation safety. Level of evidence: Diagnostic Level III.

Stages III and IV of LCPD; (2) whether the center-edge (CE) angle, acetabular roof arc angle (ARA), and Sharp’s angle changed during the growing years; and (3) what percentage of patients had radiographic evidence of pincer impingement beyond a minimum followup of 3 years. Methods We identified 19 children who had 20 TIOs performed for Catterall Stages III and IV LCPD. Two blinded observers assessed sequential radiographs. Each observer made two sets of readings more than 2 weeks apart. Femoral head extrusion index, CE angle of Wiberg, ARA, and Sharp’s angle were measured. Minimum followup was 3 years to document continued acetabular growth (mean, 3.8 years; range, 3-7 years). Results All patients exhibited femoral head containment at last followup. Eleven of 20 hips demonstrated no radiographic evidence of pincer morphology beyond a minimum followup of 3 years (mean, 3.8 years). Patients with CE angle corrected to 44° or less and an ARA of greater than −6° after TIO did not demonstrate a pincer morphology at last followup. Conclusions TIO resulted in femoral head containment in all cases. Lateral acetabular coverage changed during the growing years in all patients. Surgical correction beyond 44° of CE angle and −6° of ARA should be avoided to prevent pincer morphology later. Level of Evidence Level IV, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence....