A CT-free, intra-operative planning and navigation system for minimally invasive anterior spinal surgery - an accuracy study.

OBJECTIVE: A comprehensive study was performed to evaluate the accuracy of a newly developed CT-free, intra-operative planning and navigation system for anterior spine surgery. MATERIALS AND METHODS: Instruments and an image intensifier were tracked using the SurgiGATE navigation system. A laboratory study was performed on 27 plastic vertebrae. Fiducial markers were implanted in the vertebrae for accuracy evaluation purposes, and a dynamic reference base was placed on the vertebrae to establish a patient coordinate system (P-COS). Two fluoroscopic images were used for intra-operative planning. The graft bed plan was recorded in P-COS, followed by surgical formation of the graft bed, which was visualized. To evaluate the accuracy, the vertebrae were scanned with CT, and the markers were used to calculate an accurate paired-point registered transformation between the CT coordinate system and P-COS. RESULTS: Using the new SPO module, accurate planning and navigation of a resection of the vertebral body is possible using two fluoroscopic images. The overall mean error between the planned resection volume and the actual resection was 0.98 mm. In addition, the module can serve as an educational tool for training spine surgeons. CONCLUSIONS: The new fluoroscopy-based system can be used safely for accurate performance of anterior resection during spondylodesis. New methods for safe and accurate registration during anterior spine surgery need to be developed.     

The changes of the interspace angle after anterior correction and instrumentation in adolescent idiopathic scoliosis patients

Background  

In idiopathic scoliosis patients, after anterior spinal fusion and instrumentation, the discs (interspace angle) between the lowest instrumented vertebra (LIV) and the next caudal vertebra became more wedged. We reviewed these patients and analyzed the changes of the angle.     

Obesity: determinants and therapeutic initiatives.

There are several possible determinants of obesity, including impaired thermogenesis and the differential utilization of fuels in different tissues. Whereas hypometabolism may initiate obesity in some people, once obese, individuals tend to manifest a higher resting metabolic rate because of their greater fat-free mass, exhibit an impaired thermic response to food, and expend more calories than lean individuals for equivalent amounts of activity. As a result, over a 24-h period, obese people generally expend more energy than lean people. A second determinant of obesity is related to fuel utilization and suggests that those predisposed to be obese may have an innate insulin resistance in muscle, leading to decreased uptake, oxidation, and storage of glucose in this tissue. As a result, the glucose is shunted to adipose tissue, where it is stored. With regard to treatment of obesity, emphasis on increased energy expenditure through the inclusion of reasonable amounts of activity is essential. However, this must always be combined with restraint in caloric intake.     

Revascularization of the renal artery in renovascular hypertension with progressive renal insufficiency

Sixteen patients underwent surgical treatment for severe renovascular hypertension with rapidly progressive renal failure. These patients were assessed preoperatively with the measurement of serum creatinine and blood-urea levels (means 271 +/- 204 mumol/l and 15.6 +/- 10.3 mmol/l respectively), and renal clearances. 5 patients underwent aorto-renal bypass (bilateral in one case) and 11 patients were treated by autotransplantation of the kidney. Operative mortality was 6.2%. Early results were assessed at 1 and 6 months postoperatively. Renal function was normal in 8 patients, improved in 5 (p less than 0.05), unchanged in 1 and worse in 1 by aorto-renal bypass thrombosis. At long-term with a minimum follow-up of 12 months (mean 31 +/- 12 months), the initial improvement in renal function remained steady in 12 patients whilst 1 patient has gone on to hemodialysis. At middle and long-term, 81% of the patients were normotensive without medication or had improved blood pressure (p less than 0.001). These good results confirm the reversibility of renal ischemic lesions and support an aggressive attitude towards the use of revascularization in the surgical treatment of such patients with renovascular hypertension and renal failure.     

Enhanced myocardial necrosis induced in rats by the combined administration of hydralazine and prenalterol

The cardiotoxic effects of hydralazine and prenalterol, given alone and in combination, were assessed in rats and rabbits. Acute myocardial necrosis was induced by a single administration of each drug alone in rats. However, the incidence and severity of lesions were markedly enhanced when both drugs were given in combination. Rats that received the same treatment for 10 consecutive days showed minimal or no acute necrosis, demonstrating the development of a resistance to further cardiotoxic effects of the drugs. Rabbits showed only minimal lesions when either drug was used alone and no enhancement of lesions when they were given in combination. From these data, it is concluded that the possibility of a cardiotoxic interaction exists when these drugs are used in combination and that the heavy rat (500-600 g) is a more sensitive model than the rabbit for studies of this nature.     

Comparison of morphologic and immunohistochemical features of cervical microglandular hyperplasia with low-grade mucinous adenocarcinoma of the endometrium.

Twenty cases of microglandular hyperplasia (MGH) of the uterine cervix and 14 cases of low-grade (nuclear) mucinous adenocarcinoma of the endometrium (MA) were compared morphologically and immunohistochemically. Subnuclear vacuoles were seen in 10 cases of MGH but were absent in all MA. Luminal squamous metaplasia was seen in only 10% of MGH cases versus 65% of MA cases. Stromal foam cells were present in 36% of MA but were absent in MGH cases. Both MGH and MA had minimal variation in nuclear size and inconspicuous nucleoli. As many as 8 mitoses/10 high-power fields (MF/10 HPF) were found in MA compared with 3 or fewer MF/10 HPF in MGH. Vimentin was expressed in 90% of MA but was absent in MGH. A significantly higher percentage of MA cells stained with MIB-1 than did those of MGH (mean 11% versus 0.5%). Both MA and MGH lacked CEA and p53 staining, whereas both had variable expression of ER and PR with no significant differences except that PR was absent in 40% of MGH cases. Our findings indicate that in the differential diagnosis of MGH versus MA, the presence of subnuclear vacuoles favors the former, whereas luminal squamous metaplasia, stromal foam cells, mitotic activity, vimentin expression, and MIB-1 expression favor the latter.