Motoyuki Horii

Coverage of the femoral head by the acetabular labrum in dysplastic hips Quantitative analysis with radial MR imaging

Hip dysplasia is an important cause of osteoarthrosis of the hip, especially in Japanese. Recently, the role of the acetabular labrum in hip diseases has attracted the attention of researchers, but the condition of the labrum in the dysplastic hips has not ben described. We used radial MRI to measure the degree of coverage of the femoral head by the acetabu-lum and the labrum, corresponding to 7 positions on the acetabular rim at every 15° from anterosuperior 45° via midsuperior to posterosuperior 45°. 38 Japanese patients (51 hips) with dysplasia, and 11 healthy controls (22 hips) were studied. In the dysplastic hips, the labrum was larger than in the controls. We found no correlation between the coverage of the acetabulum in the anterosuperior positions and the size of the labrum among the dysplastic hips.

Effects of alternating current electrical stimulation on lengthening callus.

Limb lengthening by the callotasis method has been clinically applied to patients who suffered from limb length inequality, micromelia, angular deformation and partial bone defect on long bones. However, this technique was time consuming and led to various complications, such as infection at the pin insertion sites, limitation of the range of motion in adjacent joints, muscular weakness and peripheral neuroparalysis. This study was undertaken to investigate whether alternating current electric (AC) stimulation could shorten the maturation period during callotasis. The tibiae of 20 immature male Japanese white rabbits were osteotomized and fixed with external lengthener (Orthofix M100; Orthofix Srl, Bussolengo, Italy). The experimental schedule lasted 5 weeks consisting of 1 week for the latency period, 2 weeks for distraction and 2 weeks for maturation. Twenty rabbits were equally divided into two groups: the control group and the electrical stimulation (ES) group. The control group was not stimulated with an AC stimulator. The ES group was stimulated for 5 weeks just after osteotomy. The obtained results revealed radiologically, electrophysiologically and histologically that AC stimulation accelerated the maturation of lengthened callus and that it could shorten the time course of callus lengthening.

Development of the acetabulum and the acetabular labrum in the normal child: analysis with radial-sequence magnetic resonance imaging.

The degree of acetabular and labral coverage was clarified in children at different positions using radial-sequence magnetic resonance imaging. Scans were performed on 40 hips in 20 normal children (group A, 6–8 years old; group B, 9–11 years old; group C, 12–13 years old) and on 19 hips of 10 healthy adults as controls. The degrees of coverage of the femoral head by acetabulum, acetabular labrum, and both were measured at seven positions at every 15° from anterosuperior 45° via midsuperior to posterosuperior 45°. Coverage of the femoral head by the acetabulum in young children was less than in adults at all positions, but the total coverage including the labrum was greater than in adults. Development of the acetabulum and the acetabular labrum showed differences by position.

Diagnostic accuracy of magnetic resonance imaging for subscapularis tendon tears using radial-slice magnetic resonance images

BACKGROUND Magnetic resonance imaging has low diagnostic accuracy for subscapularis tendon tears. This study investigated the utility of radial-slice magnetic resonance images for diagnosing subscapularis tendon tears. MATERIALS AND METHODS We investigated 55 shoulders in 54 patients with rotator cuff tears evident during arthroscopic shoulder surgery. The intraoperative finding of a subscapularis tendon tear was compared with the identification of a subscapularis tendon tear on preoperative radial, transverse, and oblique sagittal images using a 3.0-T system. The sensitivity and specificity of diagnostic images generated using different imaging methods for subscapularis tendon tears were investigated. RESULTS A subscapularis tendon tear was present in 38 shoulders (69.1%). When the diagnostic accuracy of the magnetic resonance images was compared with the arthroscopic findings, the radial images had 94.7% sensitivity and 82.4% specificity, the transverse images had 57.9% sensitivity and 100% specificity, and the oblique sagittal images had 60.5% sensitivity and 100% specificity. CONCLUSION Radial-slice magnetic resonance images have high sensitivity for subscapularis tendon tears and are useful for diagnosing these lesions. In particular, the sensitivity for tears in the superior part of the subscapularis tendon is higher than that of conventional methods.

Radial magnetic resonance imaging and pathological findings of acetabular labrum in dysplastic hips

Radial MRI findings and pathological changes were comparatively examined in the acetabular labrum of 11 hips of 11 patients, who underwent total hip arthroplasty for osteoarthritis due to acetabular dysplasia. Diffuse high signal pattern on the radial MR images corresponded to histological degeneration of the labrum. High signal pattern which was equivalent to the synovial fluid, showed an intralabral tear. In the obscure areas of MR images, severe impairment of the labrum such as rupture, detachment, and displacement were found.

Characteristic features of the acetabular labrum in healthy children.

Radial magnetic resonance images of the acetabular labrum were obtained on 40 hips of healthy children. There were no right-left or male-female differences. In children aged 11 years or younger, the labrum on the antero-superior weightbearing portion was triangular in shape, and there was an insular-shaped or linear high-intensity area inside; on the mid-superior portion, the labrum appeared as a regular triangular, low-intensity area; and on the postero-superior portion, it was flat. In children aged 12 and 13 years, the shape of the labrum in each portion was similar to that of the younger children, but the high signal intensity area on the antero-superior portion appeared less frequently. The size of the labrum relative to the femoral head was greater in younger children.

MRI evaluation of the inferior glenohumeral ligament: Comparison with arthroscopic findings in 81 shoulders

Arthroscopic Bankart repair, using staples, requires a thick and wide anterior band of the inferior glenohumeral ligament. We compared MRI and arthroscopic findings of the ligament in 81 shoulders with traumatic anterior glenohumeral instability. When fluid was present in the shoulder, sensitivity and specificity of the MRI evaluation for the presence of a thick and wide ligament were 82% and 100%, respectively. In shoulders without joint fluid, the condition of the ligament was evaluated according to the presence of a low- or moderate-signal triangle structure on the anterior margin of the glenoid cavity in the 3 MR images obtained from the inferior 2 cm of the glenoid. Sensitivity and specificity of the MRI evaluation in cases without fluid were 84% and 93%, respectively. The MR technique needs to be further improved to achieve better sensitivity for preoperative selection of shoulders suitable for Bankart repair with staples.

Usefulness of epiphyseal quotient measurement on magnetic resonance images for outcome prediction in patients with early-stage Legg-Calve-Perthes disease.

To investigate the usefulness of epiphyseal quotient (EQ) measurement for outcome prediction in patients with Legg–Calvé–Perthes disease (LCPD), magnetic resonance (MR) imaging was performed in 26 patients with unilateral LCPD within 6 months of the disease onset and subsequently once every 3 months. All the patients were treated conservatively in our institute between 1990 and 1999. The mean follow-up period was 80 months. Clinical outcome was evaluated based on the plain radiograms of the femoral head at the final examination according to Stulbergs classification: the patients whose outcome was class I were regarded as ‘excellent’ (excellent group), class II as ‘good’ (good group), and classes III, IV and V as ‘poor’ (poor group). The excellent group consisted of 10 patients, the good group of 12, and the poor group of four. The EQ measured on MR images (MR-EQ) decreased remarkably in the poor group chronologically, whereas there was no decrease in the excellent group and a slow decrease in the good group. The mean MR-EQ at or before the sixth month (range, 2–6 months; mean, 4.9 months) was 86.2 (range, 76.8–94.8) in the excellent group, 78.3 (57.0–93.4) in the good group, and 67.4 (57.8–74.5) in the poor group (P<0.05 among the three groups). According to our results, because all patients having an MR-EQ at or before the sixth month of 75 or higher were classified in the excellent or good groups, it is thought that the ongoing method of treatment can be continued. On the other hand, since half of the patients having an MR-EQ at or before the sixth month of lower than 75 were classified in the poor group and had a high potential for a poor outcome, it is thought that these patients require strict containment therapy, and altering the surgical procedure could be considered depending on the particular patient. It was thought that the MR-EQ is a useful predictive factor of LCPD prognosis.

Association between loss of bone mass due to short sleep and leptin-sympathetic nervous system activity

BACKGROUND Sleep has been reported to be an important factor in bone metabolism, and sympathetic nervous system activity has been reported to regulate bone metabolism. In this study, we evaluated the association between sleep, sympathetic nervous system activity, and bone mass. METHODS The study subjects were 221 individuals (108 males; 113 females; mean age: 55.1±7.0years) divided into two groups: those who slept for less than 6h a day (short sleep [SS] group), and those who slept 6h or longer (normal sleep [NS] group). The groups were compared with regard to lifestyle, cortical bone thickness, cancellous bone density, bone metabolism markers, blood leptin levels, and sympathetic nervous system activity as evaluated by heart rate variability analysis. RESULTS Significant differences were observed between the two groups in cortical bone thickness, blood TRACP-5b, and leptin levels. The L/H ratio (an index of sympathetic nervous system activity) was higher in the SS group than in the NS group. Significant negative correlations were observed between cortical bone thickness and both the L/H ratio and leptin levels, and a significant positive correlation was observed between the L/H ratio and leptin levels. CONCLUSIONS Short sleep was associated with a decline in cortical bone thickness due to the promotion of bone resorption and sympathetic nervous system hyperactivity in the middle-aged group. Leptin levels and cortical bone thickness were found to be closely related, suggesting that cortical bone mass may be regulated via interaction with the leptin-sympathetic nervous system.

Clinical application of radial magnetic resonance imaging for evaluation of rotator cuff tear

BACKGROUND Magnetic resonance imaging is useful for evaluating the rotator cuff, but some tendinous insertions cannot be assessed using oblique sagittal, oblique coronal, and axial magnetic resonance (MR) images because of the presence of the partial volume effect. HYPOTHESIS The purpose of this study was to determine whether radial-slice MR images could reveal normal rotator cuff insertions and rotator cuff tears more clearly than conventional MR images. PATIENTS AND METHODS The study included 18 subjects with normal rotator cuffs and 30 with rotator cuff tears. MR images of rotator cuff insertions sliced into radial, oblique coronal, and axial sections were obtained. The extent to which normal rotator cuff insertions and rotator cuff tears were visualized in each of the three MR images was evaluated. RESULTS The top to posterior portions of the rotator cuff insertions from 0° to 120° could be visualized in the radial MR images. In comparison, the posterior portions of the rotator cuff insertions could not be visualized around 45° in both the oblique coronal and axial MR images. DISCUSSION These findings demonstrate that radial MR images are superior to the oblique coronal and axial MR images regarding their ability to accurately visualize rotator cuff insertions. Radial MR images also revealed greater detail around 45° in the posterior area of the rotator cuff tears than the oblique coronal and axial MR images. Radial MR images are particularly useful for visualizing clinically important posterosuperior rotator cuff tears. LEVEL OF EVIDENCE Level III - Diagnostic study.