A predictive model for outcome after conservative decompression surgery for lumbar spinal stenosis.

This study was designed to develop predictive models for surgical outcome based on information available prior to lumbar stenosis surgery. Forty patients underwent decompressive laminarthrectomy. Preop and 1-year postop evaluation included Waddell's nonorganic signs, CT scan, Waddell disability index, Oswestry low back pain disability questionnaire, low back outcome score (LBOS), visual analog scale (VAS) for pain intensity, and trunk strength testing. Statistical comparisons of data used adjusted error rates within families of predictors. Mathematical models were developed to predict outcome success using stepwise logistic regression and decision-tree methodologies (chi-squared automatic interaction detection, or CHAID). Successful outcome was defined as improvement in at least three of four criteria: VAS, LBOS, and reductions in claudication and leg pain. Exact logistic regression analysis resulted in a three-predictor model. This model was more accurate in predicting unsuccessful outcome (negative predictive value 75.0%) than in successful outcome (positive predictive value 69.6%). A CHAID model correctly classified 90.1% of successful outcomes (positive predictive value 85.7%, negative predictive value 100%). The use of conservative surgical decompression for lumbar stenosis can be recommended, as it demonstrated a success rate similar to that of more invasive techniques. Given its physiologic and biomechanical advantages, it can be recommended as the surgical method of choice in this indication. Underlying subclinical vascular factors may be involved in the complaints of spinal stenosis patients. Those factors should be investigated more thoroughly, as they may account for some of the failures of surgical relief. The CHAID decision tree appears to be a novel and useful tool for predicting the results of spinal stenosis surgery

A prospective study on CT scan outcomes after conservative decompression surgery for lumbar spinal stenosis.

This is a prospective study analyzing CT scan imaging outcomes after conservative decompression in patients with lumbar spinal stenosis. Forty patients (18 males and 22 females) initially underwent a laminarthrectomy surgical procedure to decompress the central canal as well as the neuroforamina and nerve root canals while respecting the integrity of the neural arches, facet joints, and most muscle attachments. Morphologic features of preoperative CT scan images were compared with postoperative CT scans of the operative levels, obtained for 36 patients (17 males and 19 females) after a minimum follow-up of 1 year (mean 1.7 years). Successful surgical outcome was defined as an improvement in at least three of the following four criteria: self-reported pain on a visual analog scale, self-reported functional status measured by LBOS, reduction of pain while walking, and reduction of leg pain. Fifty-five percent of patients met the successful surgical outcome criteria, including 14 subjects who met all four success criteria. Overall, there was a statistically significant increase in the interfacet bony canal diameter of the operated levels (3.9 mm, p < 001). However, patients categorized as successful surgical outcomes had a substantially, but not significantly, lower interfacet canal diameter increase postsurgically (mean 3.41 mm) in comparison with patients categorized as failures (mean postoperative increase 4.52 mm). Midsagittal canal diameters remained unchanged in the failure group but increased in the success group. The CT scan canal measures used in this study cannot be advocated for evaluation of outcome in conservative lumbar spinal canal decompression.

Clinical and psychofunctional measures of conservative decompression surgery for lumbar spinal stenosis: a prospective cohort study.

Less invasive decompressive surgery has emerged as a logical surgical treatment alternative to wide decompression of spinal stenosis. The clinical outcomes of such conservative surgical treatment, however, are not well known. The aim of the study was to evaluate short-term psychometric and functional outcomes after conservative decompressive surgery for lumbar canal stenosis. Forty patients had a lumbar laminectomy procedure, which preserved the integrity of the neural arches, facet joints and most muscle attachments. Pre-operative clinical evaluation of the patients included: Waddell's non-organic signs (NOS) performed by an independent surgeon observer; three self-report questionnaires--the Waddell Disability Index (WDI), the Oswestry Low Back Pain Disability Questionnaire (ODI), and the Low Back Outcome Score (LBOS); and a general questionnaire that included a visual analog pain intensity scale (VAS). Post-operative clinical evaluations and questionnaires were obtained in 36 subjects (mean age 59.8 years) after a 1.7-year follow-up (range 1-2.6 years). Pre-operative versus post-operative statistical comparisons of the data were performed using adjusted error rates within families of predictors. Successful surgical outcome was defined as an improvement in at least three of the following four criteria: self-reported pain on a VAS, self-reported functional status measured by LBOS, reduction of pain during walking and reduction of leg pain. At follow-up, there was a statistically significant improvement in VAS pain intensity, ODI, WDI, and LBOS. Patients classified as having mixed stenosis had a higher incidence of continuous pain symptoms in comparison with acquired stenosis, but there was no differential improvement with treatment depending upon stenosis classification and/or number of operative levels. Overall, 58% (21/36) of patients met the successful surgical outcome criteria, including 14 subjects who met all four success criteria. Based upon a stringent definition of successful surgical outcome, the results of a conservative laminectomy were as good as those of more aggressive decompressive procedures presented in the literature. Our findings indicate that, even in a highly organic disorder such as spinal stenosis, illness behavior plays an important role in predicting surgical outcome.

Neurophysiologic response to intraoperative lumbosacral spinal manipulation.

BACKGROUND: Although the mechanisms of spinal manipulation are poorly understood, the clinical effects are thought to be related to mechanical, neurophysiologic, and reflexogenic processes. Animal studies have identified mechanosensitive afferents in animals, and clinical studies in human beings have measured neuromuscular responses to spinal manipulation. Few, if any, studies have identified the basic neurophysiologic mechanisms of spinal manipulation in human beings or animals. OBJECTIVES: The purpose of this clinical investigation was to determine the feasibility of obtaining intraoperative neurophysiologic recordings and to quantify mixed-nerve root action potentials in response to lumbosacral spinal manipulation in a human subject undergoing lumbar spinal surgery. METHODS: An L4-L5 laminectomy was performed in a 62-year-old man. Short-duration (<0.1 ms) mechanical force, manually assisted spinal manipulative thrusts (150 N) were delivered to the lumbosacral spine with an Activator II Adjusting Instrument. With the spine exposed, spinal manipulative thrusts were delivered internally to the L5 mammillary process, L5-S1 joint, and the sacral base with various force vectors. This protocol was repeated by contacting the skin overlying respective anatomic landmarks. Mixed-nerve root recordings were obtained from gas-sterilized platinum bipolar hooked electrodes attached to the S1 nerve root at the level of the dorsal root ganglion during the spinal manipulative thrusts and during a 30-second baseline period during which no spinal manipulative thrusts were applied. RESULTS: During the active trials, mixed-nerve root action potentials were observed in response to both internal and external spinal manipulative thrusts. Differences in the amplitude and discharge frequency were noted in response to varying segmental contact points and force vectors, and similarities were noted for internally and externally applied spinal manipulative thrusts. Amplitudes of mixed-nerve root action potentials ranged from 200 to 2600 mV for internal thrusts and 800 to 3500 mV for external thrusts. CONCLUSIONS: Monitoring mixed-nerve root discharges in response to spinal manipulative thrusts in vivo in human subjects undergoing lumbar surgery is feasible. Neurophysiologic responses appeared sensitive to the contact point and applied force vector of the spinal manipulative thrust. Further study of the neurophysiologic mechanisms of spinal manipulation in humans and animals is needed to more precisely identify the mechanisms and neural pathways involved.