Effects of acute femoral head ischemia on the growth plate and metaphysis in a piglet model of Legg-Calvé-Perthes disease.

OBJECTIVE: To determine the effects of acute (≤7 days) femoral head ischemia on the proximal femoral growth plate and metaphysis in a piglet model of Legg-Calvé-Perthes disease (LCPD). We hypothesized that qualitative and quantitative histological assessment would identify effects of ischemia on endochondral ossification. DESIGN: Unilateral femoral head ischemia was surgically induced in piglets, and femurs were collected for histological assessment at 2 (n = 7) or 7 (n = 5) days post-ischemia. Samples were assessed qualitatively, and histomorphometry of the growth plate zones and primary spongiosa was performed. In a subset of samples at 7 days, hypertrophic chondrocytes were quantitatively assessed and immunohistochemistry for TGFß1 and Indian hedgehog was performed. RESULTS: By 2 days post-ischemia, there was significant thinning of the proliferative and hypertrophic zones, by 63 µm (95% CI -103, -22) and -19 µm (95% CI -33, -5), respectively. This thinning persisted at 7 days post-ischemia. Likewise, at 7 days post-ischemia, the primary spongiosa was thinned to absent by an average of 311 µm (95% CI -542, -82) in all ischemic samples. TGFß1 expression was increased in the hypertrophic zone at 7 days post-ischemia. CONCLUSIONS: Alterations to the growth plate zones and metaphysis occurred by 2 days post-ischemia and persisted at 7 days post-ischemia. Our findings suggest that endochondral ossification may be disrupted at an earlier time point than previously reported and that growth disruption may occur in the piglet model as occurs in some children with LCPD.

Quantitative T2 and T1ρ mapping are sensitive to ischemic injury to the epiphyseal cartilage in an in vivo piglet model of Legg-Calvé-Perthes disease.

OBJECTIVE: To determine if the quantitative MRI techniques T2 and T1ρ mapping are sensitive to ischemic injury to epiphyseal cartilage in vivo in a piglet model of Legg-Calvé-Perthes disease using a clinical 3T MRI scanner. We hypothesized that T2 and T1ρ relaxation times would be increased in the epiphyseal cartilage of operated vs contralateral-control femoral heads 1 week following onset of ischemia. DESIGN: Unilateral femoral head ischemia was surgically induced in eight piglets. Piglets were imaged 1 week post-operatively in vivo at 3T MRI using a magnetization-prepared 3D fast spin echo sequence for T2 and T1ρ mapping and a 3D gradient echo sequence for cartilage segmentation. Ischemia was confirmed in all piglets using gadolinium contrast-enhanced MRI. Median T2 and T1ρ relaxation times were measured in the epiphyseal cartilage of the ischemic and control femoral heads and compared using paired t-tests. Histological assessment was performed on a subset of five piglets. RESULTS: T2 and T1ρ relaxation times were significantly increased in the epiphyseal cartilage of the operated vs control femoral heads (ΔT2 = 11.9 ± 3.7 ms, 95% CI = [8.8, 15.0] ms, P < 0.0001; ΔT1ρ = 12.8 ± 4.1 ms, 95% CI = [9.4, 16.2] ms, P < 0.0001). Histological assessment identified chondronecrosis in the hypertrophic and deep proliferative zones within ischemic epiphyseal cartilage. CONCLUSIONS: T2 and T1ρ mapping are sensitive to ischemic injury to the epiphyseal cartilage in vivo at clinical 3T MRI. These techniques may be clinically useful to assess injury and repair to the epiphyseal cartilage to better stage the extent of ischemic damage in Legg-Calvé-Perthes disease.

Optimization of histologic grading schemes in spontaneous and surgically-induced murine models of osteoarthritis.

OBJECTIVE: To compare the Osteoarthritis Research Society International (OARSI) and Articular Cartilage Structure (ACS) grading schemes applied to multiple and single sections, along with additional histologic measures, in two mouse models of Osteoarthritis (OA). METHODS: Six coronal histologic stifle joint sections were collected from 40 C57BL/6J mice, including aged mice with spontaneous OA (approximately 18 months of age; n = 15) and young (12-week-old) mice that either underwent destabilization of the medial meniscus (DMM) surgery (n = 15) or sham surgery (n = 10). Sections were evaluated with the standard OARSI (0-6) scheme, a modified OARSI scheme, the ACS (0-12) scheme, histomorphometry of cartilage and bone, and scoring of osteophytes (0-3) and synovial hyperplasia (0-3). Principal components analysis (PCA) was used to determine the features explaining the greatest variability among the sections. RESULTS: The grading schemes performed similarly when applied to a single mid-coronal section or six total coronal sections per joint. OARSI grading produced similar results when applied to hematoxylin and eosin or toluidine blue-stained sections. Aged mice had higher severity scores in the LTP than DMM mice (mid-coronal OARSI grade aged = 2.3 and DMM = 1.1, p = 0.0006; ACS grade aged = 4.1 and DMM = 1.6, p = 0.0024). PCA resulted in retention of four factors that accounted for 78.4% of the total variance. Factor 1 (36.4%) included the OARSI grade, ACS grade, Toluidine blue grade, articular cartilage area and thickness and the osteophyte grade. CONCLUSIONS: Grading of a single mid-coronal section using either the OARSI or ACS schemes combined with osteophyte and histomorphometric measures can consistently define OA severity in mice.

The prevalence in Canada of drug-resistant tubercle bacilli in newly discovered untreated patients with tuberculosis.

During the period February 1963 to September 1964, the incidence of strains of tubercle bacilli excreted by newly diagnosed, previously untreated patients with tuberculosis in Canada that were resistant to the major antituberculosis drugs, viz. streptomycin, para-aminosalicylic acid and isoniazid, was 4.8%. Resistance to a single drug (3.8%) was observed more commonly than was resistance to two drugs (0.9%) or to all three drugs (0.3%), and the drug most frequently involved in this regard was streptomycin (1.8%). Data for the province of Ontario were almost the same as those for Canada. These data are compared with results of surveys in other countries and it is concluded that while drug-resistant tubercle bacilli do not constitute a major problem in Canada at present, awareness of this potential hazard should be maintained.