Erisa S Mwaka

Publications (6)8.33 Total impact

• Article: Metaphyseal-loading anterolaterally-flared femoral stem in cementless total hip arthroplasty: five- to eleven-year follow-up evaluation.

  Hideo Kawahara, Yasuo Kokubo, Takafumi Yayama, Kenzo Uchida, Shigeru Kobayashi, Hideaki Nakajima, Hisashi Oki, Kohei Negoro, Erisa S Mwaka, Norbert T Orwotho, Hisatoshi Baba
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  ABSTRACT: Using a nonlinear three-dimensional finite element analysis simulating loading conditions, we designed a new type of proximal-fitting, anterolaterally-flared, arc-deposit hydroxyapatite-coated anatomical femoral stem (FMS-anatomic stem; Japan Medical Materials, Osaka, Japan) for cementless total hip arthroplasty (THA) for Japanese patients with dysplastic hip osteoarthritis. The aim of the present study was to analyze the clinical and radiographic outcomes of the new stem. We reviewed 143 consecutive patients (164 hips; 13 men, 14 hips; 130 women, 150 hips; age at surgery, 56.6 +/- 7.6 years, mean +/- SD, range, 30-74) who underwent cementless THA using the FMS-anatomic stem at a single institution, with a follow-up period of 7.6 +/- 1.6 years (range, 5.3-11.0). Harris Hip score improved from 46.1 +/- 12.6 before surgery to 90.0 +/- 8.9 points post-THA. The 7.6-year survival rate of the stem was 99.0% after revision for aseptic loosening. Radiographs at follow-up confirmed the stability of the femoral stems within the femoral canal in all cases, with sufficient bone ingrowth. None of the patients had subsidence of the stem exceeding 2.0 mm within the femoral canal or changes in varus or valgus position of more than 2.0 degrees . The FMS-anatomic stem provided excellent results in patients with dysplastic hip osteoarthritis. Our analysis confirmed reduced radiolucency around the stem in Gruen zones, minimal subsidence, appropriate stress shielding, and promising medium-term stability within the femoral canal in our patients.
  Artificial Organs 05/2010; 34(5):377-83. · 2.00 Impact Factor
• Article: Effects of graded mechanical compression of rabbit sciatic nerve on nerve blood flow and electrophysiological properties.

  Takafumi Yayama, Shigeru Kobayashi, Yoshitaka Nakanishi, Kenzo Uchida, Yasuo Kokubo, Tsuyoshi Miyazaki, Kenichi Takeno, Kosuke Awara, Erisa S Mwaka, Yukihide Iwamoto, Hisatoshi Baba
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  ABSTRACT: Entrapment neuropathy is a frequent clinical problem that can be caused by, among other factors, mechanical compression; however, exactly how a compressive force affects the peripheral nerves remains poorly understood. In this study, using a rabbit model of sciatic nerve injury (n=12), we evaluated the time-course of changes in intraneural blood flow, compound nerve action potentials, and functioning of the blood-nerve barrier during graded mechanical compression. Nerve injury was applied using a compressor equipped with a custom-made pressure transducer. Cessation of intraneural blood flow was noted at a mean compressive force of 0.457+/-0.022 N (+/-SEM), and the compound action potential became zero at 0.486+/-0.031 N. Marked extravasation of Evans blue albumin was noted after 20 min of intraneural ischemia. The functional changes induced by compression are likely due to intraneural edema, which could subsequently result in impairment of nerve function. These changes may be critical factors in the development of symptoms associated with nerve compression.
  Journal of Clinical Neuroscience 04/2010; 17(4):501-5. · 1.25 Impact Factor
• Article: Cervical spondylotic myelopathy associated with kyphosis or sagittal sigmoid alignment: outcome after anterior or posterior decompression.

  Kenzo Uchida, Hideaki Nakajima, Ryuichiro Sato, Takafumi Yayama, Erisa S Mwaka, Shigeru Kobayashi, Hisatoshi Baba
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  ABSTRACT: The effects of sagittal kyphotic deformities or mechanical stress on the development of cervical spondylotic myelopathy, or the reduction and fusion of kyphotic sagittal alignment have not been consistently documented. The aim in this study was to determine the effects of kyphotic sagittal alignment of the cervical spine in terms of neurological morbidity and outcome after 2 types of surgical intervention. The authors retrospectively reviewed the records of 476 patients who underwent cervical spine surgeries for spondylotic myelopathy between 1993 and 2006 at their university medical center. Among these were identified 43 patients-30 men and 13 women, with a mean age of 58.8 years-who had cervical kyphosis exceeding 10 degrees on preoperative sagittal lateral radiographs obtained in the neutral position, and their cases were analyzed in this study. Anterior decompression with interbody fusion was conducted in 28 patients, and en bloc open-door C3-7 laminoplasty in 15 patients. Both pre- and postoperative neurological, radiographic, and MR imaging findings were assessed in both surgical groups. The mean preoperative kyphotic angle in all 43 patients was 15.9 +/- 5.9 degrees in the neutral position. Segmental instability was noted in 26 patients (61%) and reversed dynamic spinal canal stenosis at the level above the local kyphosis in 22 (51%). Preoperative T2-weighted MR images showed high-intensity signal within the cord at and around the level of maximal compression or segmental instability in 28 patients (65%). The mean kyphotic angle in both the neutral and flexion positions was significantly smaller at 4-6 weeks after surgery in the anterior spondylectomy group than in the laminoplasty group (p < 0.001). Furthermore, the angle in the neutral position was significantly smaller on follow-up in the anterior spondylectomy group than in the laminoplasty group (p = 0.034). The transverse area of the spinal cord was significantly larger in the anterior spondylectomy group than in the laminoplasty group on follow-up (p = 0.037). Preoperative neurological scores (assessed using the Japanese Orthopaedic Association scale) and improvement on follow-up > or = 2 years after treatment (average 3.3 years) were not significantly different between the 2 groups; however, there was a significant difference in Japanese Orthopaedic Association score at 4-6 weeks postoperatively (p = 0.047). Kyphotic deformity and mechanical stress in the cervical spine may play an important role in neurological dysfunction. In a select group of patients with kyphotic deformity > or = 10 degrees , adequate correction of local sagittal alignment may help to maximize the chance of neurological improvement.
  Journal of neurosurgery. Spine 11/2009; 11(5):521-8. · 1.61 Impact Factor
• Article: Anterior and posterior decompressive surgery for progressive amyotrophy associated with cervical spondylosis: a retrospective study of 51 patients.

  Kenzo Uchida, Hideaki Nakajima, Takafumi Yayama, Ryuichiro Sato, Shigeru Kobayashi, Yasuo Kokubo, Erisa S Mwaka, Hisatoshi Baba
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  ABSTRACT: The aims of this study were to review the clinicoradiological findings in patients who underwent decompressive surgery for proximal and distal types of muscle atrophy caused by cervical spondylosis and to discuss the outcome and techniques of surgical intervention. Fifty-one patients (43 men and 8 women) with proximal (37, with arm drop) and distal muscle atrophy (14, with wrist drop) underwent cervical decompression (39 anterior decompressions and 12 open-door C3-7 laminoplasties with microsurgical foraminotomy) for muscle weakness in the upper extremities. The clinical course, type of spinal cord compression, abnormal signal intensity on high-resolution MR imaging, and postdecompression improvement in muscle power were reviewed at a mean follow-up of 2.6 years (range 0.8-9.4 years). The most commonly affected vertebrae were C4-5 and C5-6, and C5-6 and C6-7 in patients with proximal or distal muscle atrophy, respectively; the respective numbers of affected vertebrae were 1.5 and 2.2. Transaxial MR imaging showed medial compression of the spinal cord in 20 patients (in 12 with proximal and 8 with distal muscle atrophy), paramedial compression in 22 (17 and 5 patients, respectively), and foraminal compression in 9 (8 and 1 patient, respectively). Increased signal intensity on MR imaging was observed in 85.0, 22.7, and 11.1% of cases of medial, paramedial, and foraminal compression, respectively. Increased signal intensity at the affected muscle segment level was observed in 52.9, 40.0, and 0% of cases, respectively. Sixty-two percent of patients with proximal muscle atrophy gained 1 or more grades of muscle power on manual muscle testing (MMT), whereas 64.3% with distal muscle atrophy failed to gain even 1 grade of improvement. The recovery of muscle power correlated with disease duration and the percent voltage of Erb point or wrist-stimulated muscle evoked potentials but not with preoperative MMT, longitudinal range of spinal cord compression, signal change on T2-weighted MR imaging, or surgical procedure. Surgical outcome in patients with distal muscle atrophy was inferior to that in patients with proximal atrophy. The distal type was characterized by a long preoperative period, a greater number of cervical spine misalignments, a narrow spinal canal, and increased signal intensity on T2-weighted MR imaging. It is essential to perform a careful neurological evaluation, including sensory examination of the lower limbs, as well as neuroradiological and neurophysiological assessments to avoid confusion with motor neuron disease and to detect the coexistence of amyotrophic lateral sclerosis, especially when surgical treatment of cervical spondylosis is planned. The results of careful physical examination, MR imaging studies, and electromyography studies should be comprehensively evaluated to ascertain the pathophysiology of the muscle atrophy. It is very important to distinguish the pathophysiology caused by nerve root impingements from anterior horn dysfunction when making decisions about treatment strategy. Surgical treatment--with or without foraminotomy--for amyotrophy in cervical spondylosis requires urgent action with regard to human neuroanatomy and neural innervation of the paralyzed muscles.
  Journal of Neurosurgery Spine 09/2009; 11(3):330-7. · 1.53 Impact Factor
• Article: Immunohistochemical findings of multiple ossified en plaque meningiomas in the thoracic spine

  Kenzo Uchida, Hideaki Nakajima, Takafumi Yayama, Ryuichiro Sato, Shigeru Kobayashi, Erisa S. Mwaka, Yoshiaki Imamura, Hisatoshi Baba
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  ABSTRACT: We describe a 76-year-old woman who presented with painful muscle weakness and numbness in both legs secondary to grossly ossified meningiomas at the T8 and T11–T12 vertebral levels. Midline durotomy followed by en bloc excision of the tumours, together with partial resection of the dura mater and the arachnoid, was performed. Histopathological examination showed both tumours consisted of three different histological patterns: psammomatous, fibrous, and metaplastic subtypes. Immunostaining for bone morphogenetic protein-2 and vascular endothelial growth factor was significantly positive in the areas surrounding mature bone tissues in the metaplastic and psammomatous subtypes.
  Journal of Clinical Neuroscience.
• Article: Alveolar rhabdomyosarcoma arising from the infraspinatus muscle in a child treated with subtotal scapulectomy and chemoradiotherapy: a case study.

  Kenzo Uchida, Kohei Negoro, Hideaki Nakajima, Tomoo Inukai, Takafumi Yayama, Erisa S Mwaka, Teruhiko Tanizawa, Yoshiaki Imamura, Hisatoshi Baba
  Journal of shoulder and elbow surgery / American Shoulder and Elbow Surgeons ... [et al.] 18(4):e21-6. · 1.93 Impact Factor