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✓ The hypothesis that cerebral arteriovenous difference of oxygen content (AVDO₂) can be used to predict cerebral blood flow (CBF) was tested in patients who were comatose due to head injury, subarachnoid hemorrhage, or cerebrovascular disease. In 51 patients CBF was measured daily for 3 to 5 days, and in 49 patients CBF was measured every 8 hours for 5 to 10 days after injury. In the latter group of patients, when a low CBF (≤ 0.2 ml/gm/min) or an increased level of cerebral lactate production (CMRL) (≤ −0.06 µmol/gm/min) was encountered, therapy was instituted to increase CBF, and measurements of CBF, AVDO₂, and arteriovenous difference of lactate content (AVDL) were repeated. When data from all patients were analyzed, including those with cerebral ischemia and those without, AVDO₂ had only a modest correlation with CBF (r = −0.24 in 578 measurements, p < 0.01). When patients with ischemia, indicated by an increased CMRL, were excluded from the analysis, CBF and AVDO₂ had a much improved correlation (r = −0.74 in 313 measurements, p < 0.01). Most patients with a very low CBF would have been misclassified as having a normal or increased CBF based on the AVDO₂ alone. However, when measurements of AVDO₂ were supplemented with AVDL, four distinct CBF patterns could be distinguished. Patients with an ischemia/infarction pattern typically had a lactate-oxygen index (LOI = −AVDL/AVDO₂) of 0.08 or greater and a variable AVDO₂. The three nonischemic CBF patterns had an LOI of less than 0.08, and could be classified according to the AVDO₂. Patients with a normal CBF (mean 0.42 ± 0.12 ml/gm/min) had an AVDO₂ between 1.3 and 3.0 µmol/ml. A CBF pattern of hyperemia (mean 0.53 ± 0.18 ml/gm/min) was characterized by an AVDO₂ of less than 1.3 µmol/ml. A compensated hypoperfusion CBF pattern (mean 0.23 ± 0.07 ml/gm/min) was identified by an AVDO₂ of more than 3.0 µmol/min. These studies suggest that reliable estimates of CBF may be made from AVDO₂ and AVDL measurements, which can be easily obtained in the intensive care unit.

✓ Intracranial compliance, as estimated from a computerized frequency analysis of the intracranial pressure (ICP) waveform, was continuously monitored during the acute postinjury phase in 55 head-injured patients. In previous studies, the high-frequency centroid (HFC), which was defined as the power-weighted average frequency within the 4- to 15-Hz band of the ICP power density spectrum, was found to inversely correlate with the pressure-volume index (PVI). An HFC of 6.5 to 7.0 Hz was normal, while an increase in the HFC to 9.0 Hz coincided with a reduction in the PVI to 13 ml and indicated exhaustion of intracranial volume-buffering capacity. The mean HFC for individual patients in the present study ranged from 6.8 to 9.0 Hz, and the length of time that the HFC was greater than 9.0 Hz ranged from 0 to 104.8 hours. The mortality rate increased concomitantly with the mean HFC, from 7% when the mean HFC was less than 7.5 Hz to 46% when the mean HFC was 8.5 Hz or greater. The length of time that the HFC was 9.0 Hz or greater was also associated with an increased mortality rate, which ranged from 16% if the HFC was never above 9.0 Hz to 60% if the HFC was 9.0 Hz or greater for more than 12 hours. In 12 patients who developed uncontrollable intracranial hypertension or clinical signs of tentorial herniation during the monitoring period, 75% were observed to have had an increase in the HFC to 9.0 Hz or more 1 to 36 hours prior to the clinical decompensation. The more rapid the increase in the HFC, the more likely the deterioration was to be caused by an intracranial hematoma. Continuous monitoring of intracranial compliance by computerized analysis of the ICP waveform may provide an earlier warning of neurological decompensation than ICP per se and, unlike PVI, does not require volumetric manipulation of intracranial volume.

✓ Although radical resection is the best treatment for malignant sacral tumors, total sacrectomy for such tumors has been performed in only a few instances. Total sacral resection requires reconstruction of the pelvic ring plus establishment of a bilateral union between the lumbar spine and iliac bone. This technique is illustrated in two patients harboring large, painful, sacral giant-cell tumors that were unresponsive to prior treatment. These patients were treated with complete en bloc resection of the sacrum and complex iliolumbar reconstruction/stabilization and fusion. Surgery was performed in two stages, the first consisting of a midline celiotomy, dissection of visceral/neural structures, and ligation of internal iliac vessels, followed by an anterior L5—S1 discectomy. The second stage consisted of mobilization of an inferiorly based myocutaneous rectus abdominis pedicle flap for wound closure, followed by an L-5 laminectomy, bilateral L-5 foraminotomy, ligation of the thecal sac, division of sacral nerve roots, and transection of the ilia lateral to the tumor and sacroiliac joints. Placement of the instrumentation required segmental fixation of the lumbar spine from L-3 down by means of pedicle screws and the establishment of a bilateral liaison between the lumbar spine and the ilia by using the Galveston L-rod technique. The pelvic ring was then reestablished by means of a threaded rod connecting left and right ilia. Both autologous (posterior iliac crest) and allograft bone were used for fusion, and a tibial allograft strut was placed between the remaining ilia. The patients were immobilized for 8 weeks postoperatively and underwent progressive rehabilitation. At the 1-year follow-up review, one patient could walk unassisted, and the other ambulated independently using a cane. Both patients controlled bowel function satisfactorily with laxatives and diet and could maintain continence but required self-catheterization for bladder emptying. The authors conclude that in selected patients, total sacrectomy represents an acceptable surgical procedure that can offer not only effective local pain control, but also a potential cure, while preserving satisfactory ambulatory capacity and neurological function.

Object. Anterior approaches to the spine for the treatment of spinal tumors have gained acceptance; however, in most published reports, patients with primary, metastatic, or chest wall tumors involving cervical, thoracic, or lumbar regions of the spine are combined. The purpose of this study was to provide a clear perspective of results that can be expected in patients who undergo anterior vertebral body resection, reconstruction, and stabilization for spinal metastases that are limited to the thoracic region.

Methods. Outcome is presented for 72 patients with metastatic spinal tumors who were treated by transthoracic vertebrectomy at The University of Texas M. D. Anderson Cancer Center. The predominant primary tumors included renal cancer in 19 patients, breast cancer in 10, melanoma or sarcoma in 10, and lung cancer in nine patients. The most common presenting symptoms were back pain, which occurred in 90% of patients, and lower-extremity weakness, which occurred in 64% of patients. All patients underwent transthoracic vertebrectomy, decompression, reconstruction with methylmethacrylate, and anterior fixation with locking plate and screw constructs. Supplemental posterior instrumentation was required in seven patients with disease involving the cervicothoracic or thoracolumbar junction, which was causing severe kyphosis. After surgery, pain improved in 60 of 65 patients. This improvement was found to be statistically significant (p < 0.001) based on visual analog scales and narcotic analgesic medication use. Thirty-five of the 46 patients who presented with neurological dysfunction improved significantly (p < 0.001) following the procedure. Thirty-three patients had weakness but could ambulate preoperatively. Seventeen of these 33 regained normal strength, 15 patients continued to have weakness, and one patient was neurologically worse postoperatively. Of the 13 preoperatively nonambulatory patients, 10 could walk after surgery and three were still unable to walk but showed improved motor function. Twenty-one patients had complications ranging from minor atelectasis to pulmonary embolism. The 30-day mortality rate was 3%. The 1-year survival rate for the entire study population was 62%.

Conclusions. These results suggest that transthoracic vertebrectomy and spinal stabilization can improve the quality of life considerably in cancer patients with spinal metastasis by restoring or preserving ambulation and by controlling intractable spinal pain with acceptable rates of morbidity and mortality.

Object. Primary chondrosarcoma of the spine is extremely rare. During the last 43 years only 21 patients with this disease were registered at The University of Texas M. D. Anderson Cancer Center. The purpose of this study was to examine the demographic characteristics, treatments, and outcomes of this set of patients.

Methods. Medical records for 21 patients were reviewed. Age, sex, race, clinical presentation, tumor histology, tumor location in the spinal column, treatments, surgical details, and response to treatment were recorded. Surgical procedures were categorized as either gross-total resection or subtotal excision of tumor. Neurological function was assessed using Frankel's functional classification. Time to recurrence and survival analyses were performed using the Kaplan—Meier method. The median age of patients was 51 years, with fairly equal gender representation. Eighteen patients underwent at least one surgical procedure for a total of 28 surgical procedures: seven radical resections and 21 subtotal excisions. Radiation therapy was used in conjunction with 10 of the 28 surgical procedures. The median Kaplan—Meier estimate of overall survival for the entire group was 6 years (range 6 months–17 years). Tumors recurred after 18 of the 28 procedures. Kaplan—Meier analysis revealed a statistically significant difference in the per-procedure disease-free interval after gross-total resection relative to subtotal excision (exact log rank 3.39; p = 0.04). The addition of radiation therapy prolonged the median disease-free interval from 16 to 44 months, although this was not statistically significant (exact log rank 2.63; p = 0.16).

Conclusions. Our results suggest that gross-total resection of the chondrosarcoma provides the best chance for prolonging the disease-free interval in patients. Subtotal excision should be avoided whenever possible. Addition of radiation therapy does not appear to lengthen significantly the disease-free interval in this patient population.

Object. Occipitocervicothoracic (OCT) fixation and fusion is an infrequently performed procedure to treat patients with severe spinal instability. Only three cases have been reported in the literature. The authors have retrospectively reviewed their experience with performing OCT fixation in patients with neoplastic processes, paying particular attention to method, pain relief, and neurological status.

Methods. From July 1994 through July 1998, 13 of 552 patients who underwent a total of 722 spinal operations at the M. D. Anderson Cancer Center have required OCT fixation for spinal instability caused by neoplastic processes (12 of 13 patients) or rheumatoid arthritis (one of 13 patients). Fixation was achieved by attaching two intraoperatively contoured titanium rods to the occiput via burr holes and Luque wires or cables; to the cervical spinous processes with Wisconsin wires; and to the thoracic spine with a combination of transverse process and pedicle hooks. Crosslinks were used to attain additional stability. In all patients but one arthrodesis was performed using allograft.

At a follow-up duration of 1 to 45 months (mean 14 months), six of the 12 patients with neoplasms remained alive, whereas the other six patients had died of malignant primary disease. There were no deaths related to the surgical procedure. Postoperatively, one patient experienced respiratory insufficiency, and two patients required revision of rotational or free myocutaneous flaps. All patients who presented with spine-based pain experienced a reduction in pain, as measured by a visual analog scale for pain. All patients who were neurologically intact preoperatively remained so; seven of seven patients with neurological impairment improved; and six of seven patients improved one Frankel grade. There were no occurrences of instrumentation failure or hardware-related complications. In one patient a revision of the instrumentation was required 13.5 months following the initial surgery for progression of malignant fibrous histiosarcoma.

Conclusions. In selected patients, OCT fixation is an effective means of attaining stabilization that can provide pain relief and neurological preservation or improvement.

Object. Primary and metastatic neoplasms of the lumbosacral junction frequently pose a complex problem for the surgical management and stabilization of the spine because of the anatomical and biomechanical factors of this transition zone between spine and pelvis. The authors have used a modification of the Galveston technique, originally described by Allen and Ferguson in the treatment of scoliosis, to achieve rigid spinal—pelvic fixation in patients with lumbosacral neoplasms. The authors retrospectively reviewed their experience, with particular attention to method, pain relief, and neurological status.

Methods. From July 1994 through December 1998, 13 patients at the authors' institution have required spinal—pelvic fixation secondary to instability caused by primary (eight cases) or metastatic (five cases) neoplasms. Previous treatment included spinal surgery in 10 (77%), radiation therapy in seven (54%), and/or chemotherapy in six (46%). Following tumor resection, fixation was achieved by intraoperative placement of contoured titanium rods bilaterally into the ilium. These rods were attached to the lumbar spine with pedicle screws and subsequently crosslinked. Arthrodesis was performed.

In the follow-up period of 3 to 50 months (average 20 months), nine (69%) of 13 patients were still alive. There were no cases of surgery-related death. Seven weeks postoperatively instrumentation failure occurred in one patient and was corrected by performing double L-rod spinal—pelvic fixation. Two patients experienced neurological dysfunction (ankle weakness and neurogenic bladder) that was thought to be related to tumor resection rather than the fixation procedure. Neurological status improved in four patients and remained unchanged in seven patients. Ambulatory status improved in 62% (eight patients), remained unchanged in 23% (three patients), and worsened in 15% (two patients). Spinal pain, as measured by a visual analog pain scale and determined by medication consumption was significantly reduced in 85% (11 cases).

Conclusions. In selected patients with primary or metastatic lumbosacral tumors, resection followed by modified Galveston L-rod spinal—pelvic fixation is an effective means of achieving stabilization that can provide significant pain relief and preserve ambulatory capacity.

Object. A unique method of anterior spinal reconstruction after decompressive surgery was used to prevent methylmethacrylate—dural contact in cancer patients who underwent corpectomy. The purpose of this study was to assess the efficacy and stability of polymethylmethacrylate (PMMA) anterior surgical constructs in conjunction with anterior cervical plate stabilization (ACPS) in these patients.

Methods. Approximately 700 patients underwent spinal surgery at The University of Texas M. D. Anderson Cancer Center over a 4-year period. The authors conducted a retrospective outcome study for 29 of these patients who underwent anterior cervical or upper thoracic tumor resections while in the supine position. These patients were all treated using the coaxial, double-lumen, PMMA technique for anterior spinal reconstruction with subsequent ACPS. No postoperative external orthoses were used. Twenty-seven patients (93%) harbored metastatic spinal lesions and two (7%) harbored primary tumors. At 1 month postsurgery, significant improvement was seen in spinal axial pain (p < 0.001), radiculopathy (p < 0.00 1), gait (p = 0.008), and Frankel grade (p = 0.002). A total of nine patients (31%) underwent combined anterior—posterior 360° stabilization. Twenty-one patients (72%) experienced no complications. Complications related to instrumentation failure occurred in only two patients (7%). There were no cases in which the patients' status worsened, and there were no neurological complications or infections. The median Kaplan—Meier survival estimate for patients with spinal metastases was 9.5 months. At the end of the study, 13 patients (45%) had died and 16 (55%) were alive. Postoperative magnetic resonance images consistently demonstrated that the dura and PMMA in all patients remained separated.

Conclusions. The anterior, coaxial, double-lumen, PMMA reconstruction technique provides a simple means of spinal cord protection in patients in the supine position while undergoing surgery and offers excellent results in cancer patients who have undergone cervical vertebrectomy.