Naotaka Mamizuka

Lumbar Intervertebral Disk Degeneration in Elite Competitive Swimmers A Case Control Study

Background The majority of orthopaedic problems experienced by competitive swimmers are related to pain in the shoulder, low back, and knee. Three of 39 national swim team members were hampered in their performance due to lumbar disk herniation at an international competition in 2001. There has been no previous research into lumbar disk degeneration in elite competitive swimmers. Hypothesis Excessive competitive swimming activities accelerate lumbar disk degeneration. Study Design Case control study; Level of evidence, 3. Methods Fifty-six elite swimmers (high-load group, 35 men and 21 women; mean age, 19.6 years) and a control group of 38 university recreational level swimmers (low-load group, 24 men and 14 women; mean age, 21.1 years) were evaluated for lumbar disk degeneration using magnetic resonance imaging. We compared the prevalence of disk degeneration and the disk level between the 2 groups and further investigated the relationship among their symptoms, swimming styles, and disk degeneration. Results Thirty-eight (68%) elite swimmers and 11 (29%) controls had degenerated disks at various disk levels, and the prevalence was significantly greater in the elite swimmers (P = .0002). Comparison between the 2 groups of the prevalence of disk degeneration at each level revealed that the disk level of L5-S1 was significantly more frequently degenerated in the high-load group (P = .026). There was no significant relationship observed among the variables of low back pain symptoms, swimming strokes, and disk degeneration. Conclusion Excessive competitive swimming activities might exaggerate lumbar intervertebral disk degeneration, especially in the L5-S1 intervertebral segment. Keywords lumbar intervertebral disk; disk degeneration; swimming; sports

High-resolution axial MR imaging of tibial stress injuries

PurposeTo evaluate the relative involvement of tibial stress injuries using high-resolution axial MR imaging and the correlation with MR and radiographic images.MethodsA total of 33 patients with exercise-induced tibial pain were evaluated. All patients underwent radiograph and high-resolution axial MR imaging. Radiographs were taken at initial presentation and 4 weeks later. High-resolution MR axial images were obtained using a microscopy surface coil with 60 × 60 mm field of view on a 1.5T MR unit. All images were evaluated for abnormal signals of the periosteum, cortex and bone marrow.ResultsNineteen patients showed no periosteal reaction at initial and follow-up radiographs. MR imaging showed abnormal signals in the periosteal tissue and partially abnormal signals in the bone marrow. In 7 patients, periosteal reaction was not seen at initial radiograph, but was detected at follow-up radiograph. MR imaging showed abnormal signals in the periosteal tissue and entire bone marrow. Abnormal signals in the cortex were found in 6 patients. The remaining 7 showed periosteal reactions at initial radiograph. MR imaging showed abnormal signals in the periosteal tissue in 6 patients. Abnormal signals were seen in the partial and entire bone marrow in 4 and 3 patients, respectively.ConclusionsBone marrow abnormalities in high-resolution axial MR imaging were related to periosteal reactions at follow-up radiograph. Bone marrow abnormalities might predict later periosteal reactions, suggesting shin splints or stress fractures. High-resolution axial MR imaging is useful in early discrimination of tibial stress injuries.

Discrete modeling of patellar-tendon-reflexes as logistic phenomena

The present paper proposes a logistic model to represent patellar-tendon-reflexes (PTR) from the release-angle of the tapping-hammer to the peak angular-speed of the knee joint. The experimental data obtained are discrete in nature and, thus, they are modeled as a discrete system. However, the model is formulated such that parameters of the underlying continuous model are directly obtained so that the discrete results can be related to continuous counterpart with ease. From the observation of PTR data, it was noticed that they resemble well some of the features exhibited by a system whose characteristics are governed by a logistic equation. For these reasons, a technique developed recently for exact time-discretization of nonlinear systems was applied to this non-temporal discrete system. A discrete logistic model was identified from the experimental data obtained from human reflexes. Furthermore, a method is presented to determine an appropriate initial condition to reproduce the data curve using the identified model. The overall scheme was found to give results that were closer to actual data than the popular forward difference method, even with a very large discrete interval. This is important since the modeling can be achieved using a small number of tapping on the patients.

A Magnetic Resonance Imaging–Based Staging System for Osteochondritis Dissecans of the Elbow: A Validation Study Against the International Cartilage Repair Society Classification

Background: Evaluations of the stability of osteochondritis dissecans (OCD) lesions of the elbow using magnetic resonance imaging (MRI) have resulted in reports with variable accuracy. Therefore, the International Cartilage Repair Society (ICRS) classification remains the gold standard to determine OCD lesion stability. Because OCD commonly occurs in pediatric patients, a noninvasive method comparable with the ICRS classification is desired. Hypothesis/Purpose: Based on the previous literature, the capitellum of unstable OCD lesions has an irregular outline on MRI because of displacement or dislocation of the lesion via synovial fluid inflow. Therefore, we defined a 4-stage classification, similar to the ICRS classification, which focused on the outline of the capitellum and articular cartilage status on MRI without subchondral bone information. The purpose of this study was to validate this MRI-based staging system against the ICRS classification and to verify its accuracy in diagnosing unstable OCD lesions of the elbow. Study Design: Cohort study (diagnosis); Level of evidence, 2. Methods: A total of 81 patients with OCD of the elbow who were surgically treated were evaluated. The MRI-based stages were as follows: stage 1, normal-shaped capitellum and articular cartilage without signal intensity change; stage 2, normal-shaped capitellum and articular cartilage with signal intensity change; stage 3, irregular-shaped capitellum and discontinuity of the articular cartilage; and stage 4, dislocated lesion with an articular cartilage defect. Agreement between the MRI and ICRS classifications was evaluated, and the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for lesion instability were determined. The intraclass correlation coefficient (ICC) for intrarater and interrater reliability of the MRI-based staging system was calculated. Results: Agreement between the MRI-based staging system and the ICRS classification was 88.9%, with a sensitivity of 98.4%, specificity of 84.2%, PPV of 95.3%, and NPV of 94.1% for diagnosing an unstable lesion. The ICC was high for both intrarater (0.925) and interrater (0.915-0.939) reliability. Conclusion: The MRI-based staging system corresponded well with the ICRS classification, providing an accurate preoperative assessment of OCD lesions of the elbow, even with minimal subchondral bone information.

Gait characterization of pre- and postoperative patients with lumbar spinal stenosis utilizing a body-mounted inertial measurement unit

This report presents a quantitative evaluation of gait characteristics in patients with lumbar spinal stenosis (LSS). Our method used a miniature three-dimensional inertial measurement unit (IMU) attached on the cervical back of the upper trunk. Our experiment examined 18 LSS subjects (70±8 years) before surgery and after surgery at three months. Their gait performance was examined using a six-minute walking test shuttling between 30 m straight walkways in a hospital. Spatiotemporal gait factors including step counts, cadence, and mean step lengths were estimated from the IMU measures for every walking path. Transition periods of walking around turns were excluded from the data. Subsequently, three-dimensional rotation angles of the upper body were calculated to evaluate the degree of postural sway during walking. It was assumed that variations in gait factors or postural performance involving consecutive walking time were observed as an expression of pain or intermittent claudication of LSS. Experimental results showed remarkable changes in the maximum walking distance and walking time postoperatively. Postoperative subjects walked with greater step length, fewer steps, and less step interval variety on a walking path. Moreover, analysis of postural sway revealed that postoperative subjects had decreased sway range mainly in an anterior-posterior direction, maintaining their upper body steadiness and their walking smoothness. Results show that our method of gait characterization, combining validated clinical walking test with the use of wearable IMU, is useful for evaluating the curative effects on LSS patients before and after surgery in terms of their walking performance.