Adrian M. Nowitzke

Assessment of the Learning Curve for Lumbar Microendoscopic Discectomy

OBJECTIVE:An understanding of the learning curve of a new surgical procedure is essential for its safe clinical integration, teaching, and assessment. This knowledge is currently deficient for lumbar microendoscopic discectomy (MED). The present article aims to profile the learning curve for MED of an individual surgeon in a hospital not previously exposed to this procedure. METHODS:The first 35 cases of MED for posterolateral lumbar disc prolapse causing radiculopathy performed at the Princess Alexandra Hospital, Brisbane, Australia, were studied prospectively. The learning curve was assessed using surgery time, conversion rate, complication rate, surgeon “comfort,” and key learning steps. RESULTS:The duration of surgical operating time decreased over the course of the study, initially rapidly and then more gradually. There were three conversions to open discectomy in the first 7 cases and none in the next 28 cases. The complexity of cases increased over the series, and the complication rate decreased. The asymptote of the learning curve seems to be approximately 30 cases. The specific learning tasks of MED include lateral lamina radiology, scope vision, visuospatial orientation, smaller field of view, angle of approach and tube position, and care and handling of endoscope equipment. CONCLUSION:A learning curve for MED has been demonstrated. Further assessment of this curve for a population of surgeons is necessary before a clinical assessment of open discectomy versus MED can be embarked upon.

Promoting fusion in minimally invasive lumbar interbody stabilization with low-dose bone morphogenic protein-2—but what is the cost?

BACKGROUND Using bone morphogenic protein (BMP) to augment fusion in spine surgery is widespread and lends itself in particular to minimally invasive lumbar fusion, where the surface area for fusion is significantly less than the equivalent open procedure. PURPOSE Here we described the use of very low-dose BMP in promoting fusion in minimally invasive lumbar interbody fixation but also highlight some of the potential complications of BMP-2 use and techniques available to reduce or avoid them. STUDY DESIGN Prospective observational study of consecutive patients undergoing minimally invasive lumbar interbody fusion with percutaneous pedicle screws. PATIENT SAMPLE Thirty patients aged between 22 and 78 years (mean 53 years). OUTCOME MEASURES Thin-slice lumbar computed tomography scanning with multiplanar reconstruction at 6 and 12 months postoperative. METHODS Thirty-six spinal levels were instrumented in total, of which four underwent posterior lumbar interbody fusion and 32 underwent transforaminal lumbar interbody fusion. Bone graft harvested locally was placed in the disc space with low-dose BMP-2 (1.4 mg per level). RESULTS Thirty-three of 36 spinal levels showed complete fusion at a mean postoperative scan time of 7.1 months. Two levels demonstrated partial fusion at 6 months, which was complete at 12 months. There was one case of nonunion at 12 months, which also demonstrated vertebral body osteolysis. Despite very low-dose BMP-2, two cases of asymptomatic heterotopic ossification were observed, and there were two cases of perineural cyst formation, one of whom required revision of the interbody cage. CONCLUSIONS The use of BMP with autograft in the disc space during minimally invasive lumbar interbody fusion is associated with a high rate of early fusion. Even with very low-dose BMP used in this study, complications related to BMP usage were not avoided completely.

Safety and efficacy of intradural extramedullary spinal tumor removal using a minimally invasive approach.

BACKGROUND: Although minimally invasive surgery for intradural tumors offers the potential benefits of less postoperative pain, a quicker recovery, and the avoidance of long-term instability from multilevel laminectomy, there are concerns over whether one can safely and effectively remove intradural extramedullary tumors in a fashion comparable to open techniques and whether the advantages of minimally invasive surgery are clinically significant. OBJECTIVE: To review our early experience with minimally invasive techniques for intradural extramedullary tumors of the spine. METHODS: Thirteen intradural tumors (1 cervical, 6 thoracic, 6 lumbar) in 11 patients were operated on using a muscle-splitting, tube-assisted paramedian oblique approach with hemilaminectomy to access the spinal canal while preserving the spinous process and ligaments. Fluoroscopy and navigation were used to determine the surgical level in all thoracic and lumbar cases. RESULTS: Satisfactory tumor resection using standard microsurgical techniques was achieved in all but 1 case using a minimally invasive approach. Surgical time and intraoperative blood loss were favorable compared with our open technique cases. There was no postoperative morbidity with the minimally invasive approach, although in 2 patients with tumors in the mid- and upper thoracic spine, the surgical incision was inaccurately placed by 1 level. In 1 case, the approach was converted to open when the tumor could not be found, and postoperatively there was a cerebrospinal fluid leak with infection that required readmission. CONCLUSION: Intradural extramedullary tumors can be safely and effectively removed using minimally invasive techniques. The pros and cons of minimally invasive vs open surgery are discussed.

Minimally invasive lumbar decompression: long-term outcome, morbidity, and the learning curve from the first 50 cases.

Study Design Prospective observational study. Objective To describe our experience with the first 50 cases of minimally invasive lumbar canal decompression in terms of patient outcome up to 2 years, the learning curve incurred, and complications when compared with our most recent 50 cases. Summary of Background Data Lumbar canal stenosis is a common condition in the elderly population, the symptoms of which respond well to surgical decompression. A minimally invasive approach offers potential short and long-term benefits to patients but the technique is associated with a learning curve and equivalence to open surgery regarding efficacy and complications needs to be demonstrated. Methods Fifty patients (mean age 70 y) who presented with clinical and radiological features of lumbar canal stenosis and who had failed a period of conservative management underwent lumbar canal decompression through a paramedian oblique, muscle splitting approach using a 16 to 18 mm operating tube and microscope. Outcome was assessed using the Oswestry Disability Index and Short Form-36 at 3 months, 1 year, and 2 years. Results Significant clinical improvements were seen at 3 months that were sustained at 1 and 2 years. Clinical outcome improved whereas operative time and complications fell as experience increased, helping to define the learning curve with this technique. Conclusions Minimally invasive lumbar decompression seems to offer patients a clinical benefit comparable to that observed in published open series, with potential advantages in terms of postoperative pain and recovery. However, there is a learning curve and whether this technique offers long-term benefits with regard to a reduction in back pain or postoperative spondylolisthesis is not yet known.

Epidemiological aspects of spontaneous subarachnoid haemorrhage in Queensland, Australia.

AIMS To examine the epidemiology of spontaneous subarachnoid haemorrhage (SAH) within the population of Queensland, Australia in 2002. METHODS A retrospective population and hospital-based survey of all cases of spontaneous SAH occurring within the population of Queensland (3.7 million) during the calendar year 2002 was performed. Cases were identified from hospital separation coding data and the register of births, deaths and marriages. Standard demographic data was recorded for each case identified. RESULTS The annual incidence of SAH in our population was 9.4 cases per 100,000. There was a steady increase in the incidence of SAH with increasing age, with the incidence rising to 38.8 per 100,000 in those aged greater than 80. The overall mortality rate was 33.1%, with 6% of all cases dying before reaching hospital care. The annual incidence in the indigenous population of Queensland was 8.9 /100,000.

Rapid fluctuations in conscious state in a patient with an extensive spinal dural fistula

A man with a spontaneous spinal dural fistula and significant fluctuations in level of consciousness is discussed. The presentation was that of headache and vomiting followed by an initially enigmatic acute reduction in the level of consciousness. This required urgent evacuation of bilateral chronic subdural haematomas, believed to be causative. Following mobilisation, several episodes of presumed orthostatic intracranial hypotension occurred rendering the patient rapidly unconscious. A large spinal extradural CSF collection extending through the full length of the vertebral canal was later diagnosed however, the precise location of the fistulous leak could not be found radiologically. Non-operative management was successful. To the best of our knowledge, this is the first description of a spontaneous spinal cerebrospinal fluid leak of this magnitude. The case, pathogenesis, investigations and management of this rare entity are considered and the literature reviewed.