Biomechanical Study of Cervical Posterior Decompression.

STUDY DESIGN: Biomechanical study. PURPOSE: We examined the dynamic characteristics of different operative procedures using three-dimensional finite-element models. OVERVIEW OF LITERATURE: Cervical laminoplasty is often selected for patients requiring multilevel spinal decompression. Many laminoplasty techniques have been developed and are continually being improved. METHODS: Images were extracted for the two intervertebral joints between C3 and C5 in domestic rabbits. The following models were created: preoperative, laminectomy, Z-plasty, open door laminoplasty, French open door laminoplasty, en-bloc laminoplasty, and double-door laminoplasty. The loads required for sagittal rotation of 2.5°, 5°, and 7.5° were measured in vitro and respectively placed at the bottom of the C5 model. Displacement of the plate in the X, Y, and Z coordinates was measured and the rotational angles of the plate were determined. RESULTS: The sagittal rotation angle was greater in the laminectomy model than in the preoperative model, but was almost the same in the preoperative and Z-plasty models. Compared with the preoperative model, sagittal rotation angles were smaller in the French open door, open door, en-bloc, and double-door laminoplasty models. CONCLUSIONS: Laminectomy and various types of laminoplasty are associated with different mechanical features, such as stability and mobility, allowing for selection of the most appropriate surgical procedure for each case.

[Case of tracheal agenesis found during surgery].

We reported a case of tracheal agenesis (TA) that was diagnosed during surgery. A female infant, weighing 1,104 g, was born at the 29 weeks of gestation. She showed severe respiratory distress without crying. Oxygenation was improved by mask ventilation, but tracheal intubation was very difficult. Tracheoesophageal fistula (TEF) was suspected because significant amount of air from nasogastric tube was noticed. Physical examination and X-ray findings suggested Gross E type TEF, duodenal atresia and cloaca. On the second day of life, ligation of TEE gastrostomy and colostomy were scheduled. Although operation was started without problems, ventilation became impossible when TEF was clamped and release of clamping made it possible. Bronchoscopic investigation revealed that tracheal tube was located in the esophagus. We have never doubted the esophageal intubation, because patient was ventilated preoperatively and signs of respiratory distress syndrome were successfully treated by the surfactant replacement therapy through tracheal tube. Type II TA according to Floyd's classification was diagnosed by bronchoscopic and echographic investigations. Distal esophageal ligation, gastrostomy and esophagostomy were performed. She died on the 12th day of life in spite of vigorous ventilatory and cardiovascular support.

Investigation of motor dominant C5 paralysis after laminoplasty from the results of evoked spinal cord responses.

BACKGROUND: Postoperative motor dominant C5 paralysis was known as one of several complications after laminoplasty. Several theories have been proposed for postoperative segmental paralysis after laminoplasty, but its etiology remains unclear. OBJECTIVE: To investigate the possible mechanism for postoperative motor dominant C5 paralysis from intraoperative electrophysiological studies using evoked spinal cord potentials (ESCPs). METHODS: A total of 66 patients who had undergone laminoplasty due to compressive cervical myelopathy were studied retrospectively. In all patients, the symptomatic intervertebral levels of cervical myelopathy were identified by several types of the ESCPs. Motor dominant C5 paralysis was determined as at least 1 level down compared with pre-operative shoulder abduction according to the manual muscle testing. RESULTS: Five patients (7.6%) showed postoperative motor dominant C5 paralysis. C5 paralysis occurred from 1 to 3 days after surgery and compromised unilaterally in all 5 patients. The causes of cervical myelopathy were cervical spondylosis in 3 patients and ossification of the posterior longitudinal ligament in 2 patients. One patient with severe impairment (2 in manual muscle-testing [MMT] scale) did not show clinical recovery. The other 4 patients recovered to 4 or 5 on the MMT score from 3 to 6 months after the onset. Based on the findings of ESCPs, the C4-5 level was affected by cervical myelopathy in all 5 patients with postoperative motor dominant C5 paralysis (C4-5 level in 3 patients, both C4-5 and C5-6 levels in 2 patients). A high signal intensity area on T2-weighted magnetic resonance imaging (MRI) was observed in all patients who showed apparent motor dominant C5 paralysis in this study. CONCLUSIONS: Cervical myelopathy at the C4-5 level is a potential risk for motor dominant C5 paralysis. Although it is merely a speculation, when C5 radiculopathy occurs after laminoplasty, C5 paralysis becomes clinically apparent because the deltoid muscle gets predominantly innervated by C5 root due to intramedullary spinal cord damage on the C6 segment in C4-5 myelopathy before surgery. It may represent the high signal intensity area on T2-weighted MRI at the C4-5 level.

[Anesthesia for cesarean section in a patient with transient diabetes insipidus].

A 32-year-old pregnant female was admitted to our hospital at 32 week gestation and was scheduled for emergent cesarean section because of fetal distress. She had been suffering hydrodipsia and dry mouth, and had lost 4 kg in 2 weeks. Hypernatremia, hyperchloremia, and lower urinary specific gravity were preoperatively noted. Her electrolyte imbalance was partially corrected by the infusion of 1400 ml of 5% glucose solution and 500 ml of acetated Ringer's solution, but unexpected hyperglycemia; 440 mg.dl-1, appeared before surgery. Cesarean section was successfully performed with spinal anesthesia. A 1566 g male infant was delivered with 1 and 5 min Apgar scores of 2 and 1. Hyperglycemia and secondary hypoglycemia occurred in the infant in the neonatal ICU. The mother's fluid loss, including blood and amniotic fluid, was estimated at 784 ml. Five hundred milliliters of acetated Ringer's solution and 1000 ml of half saline solution with 2.5% glucose were infused before delivery, followed by the glucose solution containing a low concentration of sodium after delivery. After surgery, high serum osmotic pressure and paradoxically low urinary osmotic pressure were found. The plasma antidiuretic hormone level was normal against the high serum osmotic pressure. The electrolyte imbalance and urinary osmotic pressure were improved by using I-deamino-8-d-arginine vasopressin, and DI was finally diagnosed. Hormonal therapy was discontinued on day 20, and the patient was discharged on day 21. Some pregnancies are complicated by transient DI. Anesthesiologists have to consider DI when a pregnant female has symptoms of dehydration and a significant electrolyte imbalance.