Hiroaki Takai

Osteochondritis dissecans of the femoral condyle in the growth stage

The site of lesion, spontaneous healing, onset mechanism, and magnetic resonance imaging findings of 51 knees in 38 patients with osteochondritis dissecans involving the femoral condyle in the growth stage were investigated. Half of the lesions were found in the center of the lateral condyle, 1/4 were in the medial in tercondylar site, and the remaining 1/4 were in other sites. Compared with those in the other sites, the lesions in a medial intercondylar site had a lower healing rate and required a longer time to heal. T2 weighted images of the lesions showed a progression from low signal areas to the appearance of a high signal line at the fragment to parent to bone interface, to a high signal double line at the interface and parentbone surface, or to disappearance of the line. Magnetic resonance imaging often revealed discoid menisci or meniscal tears in patients with lesions in the lateral condyle, suggesting that endogenous forces play an important role in the onset of osteochondritis dissecans.

Effect of peripheral nerve injury on nuclear magnetic resonance relaxation times of rat skeletal muscle.

RATIONALE AND OBJECTIVES The authors evaluate the changes in magnetic resonance (MR) relaxation times of rat skeletal muscles in vivo after nerve injury and during neural recovery, and determine the major determinants of relaxation times. MATERIALS Magnetic resonance relaxation times, blood volume, and water and fat content were examined after nerve injury and during recovery with time course. RESULTS Nerve injury led to longer T2 values compared with controls, but there were no significant changes in T1 values. After the initial prolongation of T2 after nerve injury, no changes were observed. Neural recovery resulted in a return of T2 values to normal. The time course of changes in blood volume was similar to that of changes in T2, and T2 values were correlated strongly with 19-fluorine-MR spectroscopy estimates of blood volume (r2 = 0.94). CONCLUSIONS T2 values may be useful to monitor recovery after nerve injury and may be related to the blood volume in skeletal muscle.

Observation of fatigue unrelated to gross energy reserve of skeletal muscle during tetanic contraction ― an application of 31P-MRS

The mechanism of muscle fatigue was studied by 31P-MRS. During tetanic contraction for 2 minutes(min), the tension measured with a strain gauge and Phosphocreatine(PCr)/Inorganic phosphate(Pi)+ Phosphomonoester(PME) ratio decreased to 31.5 +/- 4.4% of the control value and 0.6 +/- 0.1, respectively. The intracellular pH(pH) also decreased to 6.62 +/- 0.04. Toward the end of the stimulation, the tension decreased to 25.3 +/- 1.9% of the control value. However, during 20min stimulation, the PCr/(Pi+PME) ratio increased to 2.5 +/- 0.5 and the pH to 6.91 +/- 0.04. These results show that muscular fatigue is ascribable not to a decreased level of high energy metabolites required for actomyosin ATPase, but to an increase in the threshold intensity of excitation in excitation-contraction coupling.

Locking of the metacarpophalangeal joint caused by idiopathic intrinsic muscle atrophy of the hand: report of three cases

The incidence of eating disorders is growing and is twice as common among women as men. Atrophy of the intrinsic muscles causes the fingers to stiffen and the hand to become deformed and functionally disabled. Trauma limited to the hand, inflammation, spasticity, central nervous system disease, prolonged spasm, and excessive immobilization can cause such muscle contracture [1, 2, 4, 5, 7–9, 12]. Metacarpophalangeal (MP) joint locking is known to be caused by muscular contracture or trauma, collateral ligament, or volar plate tethering on a prominent MP head or osteophyte, a torn palmar plate, metacarpal head fracture, a loose body, or abnormal sesamoids [10, 11]. We report the very rare cause of MP joint snapping with intrinsic plus deformity, which finally became locked.

Swan neck deformity due to chronic radial collateral ligament injury of the little finger proximal interphalangeal joint

We present seven cases of a relatively rare swan neck deformity resulting from chronic radial collateral ligament (RCL) injury of the proximal interphalangeal (PIP) joint in the little finger. All patients were middle-aged women (mean 51 years old, range 42–55), and the duration between the initial injury and surgery was 20 years (range 5–40). The chief complaint was painful snapping of the PIP joint. All patients had hyperextension and ulnar deviation of the PIP joint with mobile swan neck deformities that had not improved with conservative treatment. Radiographs revealed osteoarthritis and ulnar deviation of the PIP joints in all cases. We describe a method for reconstruction of both the palmar plate and the RCL of the affected PIP joint using a distally-based ulnar slip of flexor superficialis tendon. The prevention of PIP joint hyperextension was critical for successful resolution of symptoms; the aim of RCL augmentation was to prevent the recurrence of the deformity. Level of evidence: IV