Toshihito Naito

Gravitational unloading inhibits the regenerative potential of atrophied soleus muscle in mice

Aim:  The present study was performed to investigate the influence of unloading on the regeneration of atrophied and injured skeletal muscle.

Functional Overloading Facilitates the Regeneration of Injured Soleus Muscles in Mice

The effect of functional overloading on the regenerating process of injured skeletal muscle was investigated in 10-week-old male mice (C57BL/6J). Functional overloading on soleus of both hindlimbs was performed by cutting the distal tendons of plantaris and gastrocnemius muscles for 2 weeks before cardiotoxin (CTX) injection as the preconditioning and also during 10 weeks of recovery. To activate the necrosis-regeneration cycle, 0.1 ml of 10-microM CTX was injected into soleus muscle. The mean values of absolute muscle weight and the percentage of Pax7-positive nuclei in soleus were increased by the preconditioning. These values, as well as total muscle protein content, in the group with CTX injection plus overloading were larger than in the group with CTX injection alone. Fibers with central nucleus were noted in the group with CTX injection with or without overloading. The rate of disappearance of fibers having central nucleus during recovery was stimulated by overloading. Histological analyses revealed that the regeneration of injured soleus muscle with overloading proceeded more rapidly than the muscle without overloading. These results, in combination with previous lines of evidence, strongly suggest that functional overloading may facilitate the regeneration of injured skeletal muscles.

Clinical outcomes of hook of hamate fractures and usefulness of the hook of hamate pull test.

We report the usefulness of hook of hamate pull test (HHPT), described by Wright et al. in 2010, along with therapeutic outcomes of hook of hamate fractures. Eleven patients (two with fresh fractures and nine with nonunion) were studied. The fractures were diagnosed with HHPT for recently encountered 4 patients and a definitive diagnosis was made by a carpal canal view and a computed tomography (CT) scan. Treatment involved cast immobilization for one fresh fracture case, and bone fragment removal immediately over the hook for ten others. HHPT was positive in all the four cases. Union was achieved by conservative treatment, and hypothenar pain disappeared after surgery. Patients returned to work/sports two months postoperatively. HHPT was useful for diagnosing both fresh fractures and nonunion. If HHPT is positive, CT should be performed even if the fracture is obscure on a carpal canal view.

Ultrasonographic Diagnosis for Tenosynovitis of Extensor Carpi Ulnaris

We investigated the usefulness of ultrasound imaging and treatments for tenosynovitis of the extensor carpi ulnaris (ECU), based on clinical findings. Ultrasonography for diagnostic imaging of ECU tenosynovitis has not been previously reported. This study included 29 patients who were diagnosed as having ECU tendinitis and underwent ultrasonography. The short-axis view ultrasound images were characterized by an oval hyperechoic area in the ECU tendon from the distal to the peripheral end of the ulna on the affected side in all patients and a hypoechoic area suggesting a thickened synovial membrane of the tendon sheath around the ECU tendon. Patients with the most pronounced findings showed the greatest resistance to conservative therapy. Ultrasound images can be an indicator for differentiating ECU tendinitis from other diseases and determining therapeutic strategies. In cases with ulnar-sided wrist pain without these characteristic ultrasound imaging findings, injury of the triangular fibro cartilage complex should be suspected.

Ultrasonographic Evaluation and Treatment for Dequervain’s Disease

We performed ultrasonography in patients with de Quervain’s disease to examine the presence or absence of a septum and the extent of hypoechoic areas around tendons. We also compared the ultrasonographic findings with therapeutic outcomes. The subjects were 151 hands (96 conservatively-treated hands, 55 surgically-treated hands) of 146 patients who underwent ultrasonography at the time of initial examination or during treatment. We evaluated the presence or absence of a septum mainly on short axial images and the degree of tendon sheath thickening based on hypoechoic areas around the extensor pollicis brevis and abductor pollicis longus tendons. Among those with a septum and hypoechoic areas around these tendons, more hands were treated surgically, more injections were given, and the time-to-remission tended to be longer. Among those without a septum but with hypoechoic areas, there were more hands responding to conservative therapy. Among those with neither a septum nor a hypoechoic area, there were no surgically treated cases, and remission was obtained in the early stage. According to ultrasonographic findings indicating the presence or absence of a septum and hypoechoic areas, the subjects were classified into 4 types, and these types reflected the therapeutic effects.