Nobuhiko Samoto

Diagnosis of discoid lateral meniscus of the knee on MR imaging.

To establish the quantitative MR diagnostic criteria for discoid lateral meniscus, MR imaging of 60 knees with arthroscopically confirmed discoid lateral menisci and 134 knees with semilunar lateral menisci were analyzed. Following four quantitative parameters were measured. (1) Meniscal width (MW): The minimum meniscal width on the coronal slice. (2) Ratio of the meniscus to the tibia (RMT): The ratio of minimum meniscal width to maximum tibial width on the coronal slice. (3) Percent coverage of the meniscus (PCM): The ratio of the sum of the width of the anterior and posterior horns to the meniscal diameter on the sagittal slice showing the maximum meniscal diameter. (4) Continuity of the anterior and posterior horns (CAPH): The number of consecutive sagittal slices showing continuity between the anterior and posterior horns of the meniscus on the sagittal slice. The cut-off values of each parameter to discriminate between the discoid and semilunar meniscus were calculated based on a univariate logistic regression analysis. The sensitivity and specificity were also calculated for each of 4 parameters and combinations of these parameters. The cut-off value was 15 mm for the MW, 20% for the RMT, 75% for the PCM, and 3 slices for the CAPH. The sensitivity and specificity of the four parameters ranged between 87% and 50% and between 99% and 92%, respectively. The most accurate diagnostic criterion was either the RMT > or = 20% or the PCM > or = 75%, and the sensitivity and specificity were 95% and 97%, respectively, even when torn menisci were included.

Acetabular Diameter Measurement Determines Proper Prosthetic Head Size in Hemiarthroplasty for Femoral Head Osteonecrosis

In hemiarthroplasty for femoral head osteonecrosis, collapse and deformity may make femoral head measurement difficult, thus, precluding the selection of an appropriate prosthetic head. We describe a method for measuring the acetabular diameter using acetabular sizing gauges to estimate the prosthetic head size. We evaluated the precision of this method and found it to be highly accurate and reliable.

Osteomyelitis Forming A Broad Subperiosteal Abscess Followed up by MRI: A Case Report

There are only a few reports following the osteomyelitis using MRI. We experienced a case of bacterial osteomyelitis of the femur which formed a broad subperiosteal abscess.We used MRI for the diagnosis and follow up and found it to be useful.The case was a 12 year old male, who presented with a 40°C fever and swelling and local heat of his right thigh were observed. On blood examination, WBC number was decreased, with a shift to the left, and CRP was strongly positive. MRI T2WI showed a broad high intensity area in the subperiosteal space. Puncture showed bloody abscess and the patient was hospitalized for examination and treatment. Bacterial culture of the abscess and blood were performed and both of which were positive for Staphylocossus aureus.We performed an irrigatim of the abcsess fenestration of the bone, and continuos intramedullary drip infusion of antibiotics. MRI was also useful for observation of the recovery stage.