Yusaku Kamata

Keio University · Department of Orthopedic Surgery

Introduction Osteoporosis can affect the surgical outcomes of proximal humeral fractures in older people. Recently, the cortical bone thickness of the proximal humerus on plain radiograph has been proposed to reflect local osteoporosis of the proximal humerus; however, its effect on the surgical outcome of proximal humeral fractures remains unclear...

Background Inferior subluxation of the humeral head is frequently observed immediately after surgery for proximal humerus fractures; however, the incidence and risk factors of inferior subluxation after osteosynthesis for isolated greater tuberosity fractures remain unsolved. Additionally, the postoperative course of inferior subluxation has not be...

Surgical treatment for humeral shaft fractures has been reported to yield satisfactory results; however, there may be complications, such as delayed bone union, nonunion, iatrogenic radial nerve injury, and infection. The risk factors for postoperative complications remain largely unknown. This study aimed to investigate the influence of timing of...

Triceps tendon avulsion is a rarely occurring tendinous injury. Various surgical procedures, such as repair using sutures through the transosseous tunnel or suture anchors, have been reported for treating triceps tendon avulsion. However, standard surgical treatment has not yet been established. Here, we present a case of triceps tendon avulsion tr...

Background: Humeral head inferior subluxation often occurs immediately after osteosynthesis for proximal humeral fracture; however, the underlying cause remains largely unknown. In addition, the prognosis of postoperative inferior subluxation has not been fully investigated. This study aimed to clarify the predictive factors that affected the onse...

In inferior shoulder dislocation (ISD) cases, closed reduction usually achieves reduction and irreducible ISD is extremely rare. To date, only two cases requiring open reduction have been reported. Herein, we describe a case of an irreducible ISD that required open reduction. A 90-year-old woman fell at home and presented to our hospital. Plain rad...

Background Calcific tendinitis of the rotator cuff is a disorder that causes acute onset of shoulder pain when spontaneous resorption of the calcification occurs. However, factors that trigger calcium resorption have not been clarified. The present study aimed to investigate the association between the onset of calcium resorption in calcific tendin...

Background Although anterior glenohumeral dislocations are common, the reduction procedure is often difficult, requiring sedation or anesthesia. To date, the risk factors for reduction failure without sedation has not been fully investigated. The present study aimed to clarify the predictive factors that render the reduction of anterior glenohumera...

Background Calcific tendinitis of the rotator cuff is a common disorder that causes acute onset of shoulder pain when spontaneous resorption of the calcification occurs.However, factors that triggercalcium resorption have not been clarified. The present study aimed to investigate the association between the onset of calcium resorption in calcific t...

Background Calcific tendinitis of the rotator cuff is a disorder that causes acute onset of shoulder pain when spontaneous resorption of the calcification occurs. However, factors that trigger calcium resorption have not been clarified. The present study aimed to investigate the association between the onset of calcium resorption in calcific tendin...

Background Calcific tendinitis of the rotator cuff is a disorder that causes acute onset of shoulder pain when spontaneous resorption of the calcification occurs. However, factors that trigger calcium resorption have not been clarified. The present study aimed to investigate the association between the onset of calcium resorption in calcific tendin...

Background: Plate fixation is an established method for treating unstable distal clavicle fractures. However, the appropriate timing of surgery for acute distal clavicle fractures remains unclear. The present study aimed to evaluate the clinical outcomes of osteosynthesis using a Scorpion plate and to assess the influence of surgery timing on the...

Background Plate fixation is an established method for treating unstable distal clavicle fractures. However, the appropriate timing of surgery for acute distal clavicle fractures remains unclear. The present study aimed to evaluate the clinical outcomes of osteosynthesis using a Scorpion plate and to assess the influence of surgery timing on the su...

The association between carpal tunnel syndrome (CTS) and remitting seronegative symmetrical synovitis with pitting edema (RS3PE) syndrome, an elderly onset rheumatic disease, is not fully understood. Here, we describe a case of acute CTS caused by RS3PE syndrome. An 84-year-old man visited the hospital with sudden onset of severe neuralgia in the m...

Background Plate fixation is the established method of treating unstable distal clavicle fractures. However, the appropriate timing of surgery for acute distal clavicle fractures remains unclear. The present study aimed to evaluate the clinical outcomes of osteosynthesis using a Scorpion plate and to assess the influence of surgery timing on the su...

We present a 70-year-old woman with severe diabetes mellitus, who experienced low back pain and left lower leg paralysis. Computed tomography showed air in the spinal canal from C4 to S5, and magnetic resonance imaging revealed an epidural abscess from Th11 to L1. Laboratory findings showed increases in inflammatory indicators and blood culture ind...

Case: A 63-year-old man with a cardiac pacemaker presented with a left shoulder dislocation. His heart rate was 46 beats per minute, and pacemaker testing demonstrated an elevated pacing threshold, a decreased sensing threshold, and stable pacemaker lead impedance. Lead dislodgement due to the shoulder dislocation was suspected, and the patient un...

Background: It remains unclear whether early surgical intervention can reduce mortality after surgery in hip fracture patients. The aim of this study was to investigate the association between time from injury to surgery and mortality rate within 90 days after hip fracture surgery. Methods: We retrospectively identified 1827 patients who underwe...

The TightRope RT (Arthrex, Naples, FL) is a suspensory device for anterior cruciate ligament reconstruction. However, there is a potential risk of the button being pulled too far off the lateral femoral cortex into the soft tissue because the adjustable loop is long. The purpose of this article is to present an easy and safe technique for self-flip...

Three-dimensional fingertip trajectory was examined under different force levels of the lumbrical muscle to clarify the function of the lumbrical muscle in free index finger motion. The metacarpophalangeal joint balancing effect of the lumbrical muscle in the thumb-up position was also examined. The motions of the finger bones were recorded during...

In this study, we investigate the pattern of coordination between motions of two joints generated by intrinsic and extrinsic muscles. The joint motions were created by excursion controller that pulled seven muscle tendons independently according to manually designed four excursion patterns. The result of the experiment clearly showed linear relatio...

We present a new apparatus, excursion controller, to measure and analyze musculoskeletal motion of cadaveric fingers. The result of the preliminary experiment clearly shows that the range of excursion of the interosseous for abduction-adduction and that of the extensors for hyperextension were estimated to be 5 to 8mm, while that of the flexors for...

The contribution of lumbrical muscles for the articulated finger motion is yet to be clarified. In this paper we analyze the role of the lumbrical muscle by using excursion controller and cadaver specimens. The result of the experiment clearly shows that the activation of the lumbrical muscle enlarges the arc of the fingertip trajectory except in t...

Desmoplastic fibroblastoma (collagenous fibroma) is a recently described tumor thought to arise predominantly from subcutaneous tissue or skeletal muscle. The natural evolution of this tumor on magnetic resonance imaging has never been described, to the best of our knowledge. We herein report a case of desmoplastic fibroblastoma arising in the thig...