Koji Nawata

Correlation Between Operative Outcomes of Cervical Compression Myelopathy and Mri of the Spinal Cord

Study Design. Magnetic resonance images of cervical compression myelopathy were retrospectively analyzed in comparison with surgical outcomes. Objectives. To investigate which magnetic resonance findings in patients with cervical compression myelopathy reflect the clinical symptoms and prognosis, and to determine the radiographic and clinical factors that correlate with the prognosis. Summary of Background Data. Signal intensity changes of the spinal cord on magnetic resonance imaging in chronic cervical myelopathy are thought to be indicative of the prognosis. However, the prognostic significance of signal intensity change remains controversial. Methods. The participants in this study were 73 patients who underwent cervical expansive laminoplasty for cervical compression myelopathy. Their mean age was 64 years, and the mean postoperative follow-up period was 3.4 years. The pathologic conditions were cervical spondylotic myelopathy in 42 patients and ossification of the posterior longitudinal ligament in 31 patients. Magnetic resonance imaging (spin-echo sequence) was performed in all the patients. The transverse area of the spinal cord at the site of maximal compression was computed, and spinal cord signal intensity changes were evaluated before and after surgery. Three patterns of spinal cord signal intensity changes on T1-weighted sequences/T2-weighted sequences were detected as follows: normal/normal, normal/high-signal intensity changes, and low-signal/high-signal intensity changes. Surgical outcomes were compared among these three groups. The most useful combination of parameters for predicting prognosis was determined using a stepwise regression analysis. Results. The findings showed 2 patients with normal/normal, 67 patients with normal/high-signal, and 4 patients with low-signal/high-signal change patterns before surgery. Regarding postoperative recovery, the preoperative low-signal/high-signal group was significantly inferior to the preoperative normal/high-signal group. There was no significant difference between the transverse area of the spinal cord at the site of maximal compression in the normal/high-signal group and the low-signal/high-signal group. A stepwise regression analysis showed that the best combination of surgical outcome predictors included age (correlation coefficient R = −0.348), preoperative signal pattern, and duration of symptoms (correlation coefficient R = −0.231). Conclusions. The low-signal intensity changes on T1-weighted sequences indicated a poor prognosis. The authors speculate that high-signal intensity changes on T2 weighted images include a broad spectrum of compressive myelomalacic pathologies and reflect a broad spectrum of spinal cord recuperative potentials. Predictors of surgical outcomes are preoperative signal intensity change pattern of the spinal cord on radiologic evaluations, age at the time of surgery, and chronicity of the disease.

Development of the attachment zones in the rat anterior cruciate ligament: changes in the distributions of proliferating cells and fibrillar collagens during postnatal growth.

The development of the attachment zones of the anterior cruciate ligament (ACL) is an important consideration when examining the structural properties. The aim of this study was to elucidate the morphological changes and the distribution of proliferating cells and collagen types I, II and III at the attachment zones of the rat ACL during postnatal growth.

Anterior-posterior knee laxity increased by exercise: Quantitative evaluation of physiologic changes

To quantify physiologic changes in anterior-posterior laxity of the normal knee caused acutely by exercise, we evaluated the exercise level and the duration of exercise needed to cause changes in laxity, the magnitude of changes in laxity, and the time needed for laxity to return to the level before exercise, by continuously applying a fixed exercise load. After a 20-minute run at 7 km/hr, anterior laxity with a displacement force of 133 N increased by about one third, and the compliance increased by one half with anterior drawer between 0 and 67 N. These changes were maintained at a similar level during exercise. The levels before exercise were restored gradually over 1 hour after exercise. As the muscle strength showed no changes during exercise, we consider these changes in laxity are not associated with a decrease in muscle strength. Furthermore, since the changes in knee laxity after triathlon (in which the knee is subjected to prolonged excessive exercise) are similar to those after running at 7 km/hr, we believe that the magnitude of changes in laxity after exercise is fixed, regardless of the level of the exercise load. Moreover, the threshold of exercise that causes the maximum change is low.

Anomalies of ossification in the posterolateral femoral condyle: assessment by MRI

Background. Anomalies of ossification in the lower femoral epiphysis are often radiographically indistinguishable from juvenile osteochondritis dissecans. Objective. To clarify the MRI characteristics of the anomalies of ossification in the posterolateral femoral condyle that distinguish it from juvenile osteochondritis dissecans. Materials and methods. We retrospectively examined the medical records, plain radiographs (n = 4), MRI (n = 4) and follow-up MRI (n = 2) of four boys (age 8–11 years) with anomalies of ossification in the posterolateral femoral condyle. Results. Plain radiography showed symmetrical marginal irregularity of the posterolateral femoral condyles of both knees. These lesions were asymptomatic, and the areas of irregular radiographic appearances reduced in size or disappeared without treatment within a mean observation period of 3.5 months. MRI showed a clearly demarcated low-intensity islet with the same signal intensity as subchondral bone (which was considered to be an accessory ossification nucleus) in a high-signal area in which the signal intensity was equal to that of normal articular cartilage. The areas observed as radiolucent zones on plain radiography were visualised at the same signal intensity as articular cartilage, and were continuous with articular cartilage on MRI; thus they were regarded as uncalcified cartilage. These MR findings are different from MR images of osteochondritis dissecans. Conclusions. MRI is considered to be the most effective non-invasive diagnostic method for these two conditions.

Osseous lesions associated with anterior cruciate ligament injuries

In 56 patients with anterior cruciate ligament (ACL) rupture, we retrospectively examined osseous lesions secondary to the rupture using magnetic resonance imaging (MRI). Depending on the time from their ligamentous injury to the performance of MRI, the patients were divided into three groups: the acute group (less than 1 month, n = 20), the subacute group (between 1 and 12 months, n = 16), and the chronic group (12 months or more, n = 20). Occult osseous lesions which were not detected by roentgenography were revealed by MRI in 14 patients in the acute group (70.0%), 5 in the subacute group (31.3%), and 1 in the chronic group (5%). The detection rate of osseous lesions by MRI was significantly higher in the acute group than in the other groups (P < 0.001). Osseous lesions were always detected in the same locations of the lateral compartment of the knee joint. When examined by arthroscopy, these lesions were often found to be accompanied by articular cartilage injuries. In the acute group, osseous lesions were visible in the high signal intensity area of T2-weighted images and in the low signal intensity area of proton density images. They were interpreted as representing hemorrhage and edema within the bone marrow. In the subacute and chronic groups, the osseous lesions were smaller, and their signal intensity on T2-weighted images was lower than that in the acute group, probably reflecting the ongoing resorption of the hemorrhage and healing of the lesions. These results suggest that osseous lesions develop following injury to the ACL.

Effects of weight bearing on the tidemark and osteochondral junction of articular cartilage: Histomorphometric analyses of 7 normal femoral heads

To study the effect of weight bearing on the tidemark and osteochondral junction, we compared the morphology of these two boundaries in weight-bearing and less weight-bearing regions of normal human femoral heads. We measured the irregularities of the boundaries in the two regions using an X-Y digitizer connected to a computer in histological whole sections of femoral heads in 7 subjects without joint diseases. The irregularity of the tidemark was small, showing no difference between the two regions. However, the irregularity of the osteochondral junction in the weight-bearing region was greater than in the less weight-bearing region, which was confirmed by three-dimensional reconstructed images. Our findings suggest that mechanical stresses greatly influence the morphology of the osteochondral junction compared to the influence of such stresses on the tidemark, and that the marked irregularity of the osteochondral junction in the weight-bearing region is a reactive phenomenon against mechanical fragility due to simple contact between calcified cartilage and subchondral bone without fibrous connections.

Magnetic resonance imaging of meniscal degeneration in torn menisci: a comparison between anterior cruciate ligament deficient knees and stable knees.

Abstract Signal anomalies observed in magnetic resonance imaging of the intrameniscal tissue adjacent to the tear were compared between stable knees (group 1, 54 menisci) and anterior cruciate ligament (ACL) deficient knees (group 2, 98 menisci). The histological significance of these signal anomalies was also studied (n = 25). The frequency of intrameniscal signal anomalies adjacent to the tear was significantly lower in ACL-deficient knees than in ACL-stable knees (P = 0.0022). There was a close correlation between the imaging anomalies and the presence of histological lesions (fissures, degeneration) within meniscal tissues adjacent to the tear (sensitivity: 0.95, specificity: 0.60). Our results suggest that the severity of intrameniscal degenerative changes adjacent to the tear are lower in ACL-deficient knees than in ACL-stable knees.