Todd Alamin

A Gold Standard Evaluation of the "Discogenic Pain" Diagnosis as Determined by Provocative Discography

Study Design. This is a prospective study of the validity of a positive test result in provocative lumbar discography for the diagnosis of “discogenic pain.” Objective. To investigate the hypothesis that provocative discography by strict criteria accurately identifies a low back pain illness due to a primary disc lesion. Summary and Background Data. According to the Sackett and Haynes criteria for establishing diagnostic test validity, no test without a gold standard external standard can be meaningfully applied. Provocative discography as a test for determining “discogenic pain” has, to date, not been compared against a gold standard. Absent a gold standard reference, there can be no validity assessment or systematic improvement of test accuracy. This is the first study to apply an external gold standard evaluation of the diagnostic validity of discography in any manner. Methods. Over a 5-year period using a strict enrollment protocol, 32 patients with low back pain and a positive single-level low-pressure provocative discogram, underwent spinal fusion. Subjects with known patient selection comorbidities were excluded. Generic surgical limitations/morbidity were controlled by comparison to the clinical outcomes of a strictly-matched cohort of 34 patients having a well-accepted single-level lumbar pathology (unstable spondylolisthesis). Treatment success was compared between groups. Results. In the control-spondylolisthesis group, 23 of 32 patients (72%) met the highly effective success criteria compared with 8 of 30 in the presumed discogenic pain cohort (27%). The proportion of patients who met the “minimal acceptable outcome” was 29 of 32 (91%) in the spondylolisthesis group and 13 of 30 (43%) in the presumed discogenic pain group. Adjusting for surgical morbidity and dropout failure, by either criteria of success, the best-case positive predictive value of discography was calculated to be 50% to 60%. Conclusions. Positive discography was not highly predictive in identifying bona fide isolated intradiscal lesions primarily causing chronic serious LBP illness in this first study comparing discography results to a gold standard.

A prospective controlled study of limited versus subtotal posterior discectomy: short-term outcomes in patients with herniated lumbar intervertebral discs and large posterior anular defect.

Study Design. Prospective observational study with historical control. The prospective study population consisted of 30 patients undergoing a posterior lumbar subtotal discectomy for lumbar disc herniation. This group was compared to a historical cohort of 46 patients treated with limited discectomy alone. Objective. To compare clinical outcomes after limited versus subtotal discectomy for lumbar disc herniations. Summary of Background Data. Large posterior anular defects found at posterior discectomy have been associated with more frequent reherniation when treated with limited discectomy (i.e., removing only extruded or loose intervertebral fragments). A trial of more aggressive discectomy (subtotal) was undertaken to determine if the rate of reherniation could be decreased with this technique. Methods. A total of 30 patients undergoing a posterior lumbar discectomy for lumbar disc herniation were treated with an aggressive (subtotal) resection of intervertebral disc material after removal of the extruded or protruded fragments. This group was compared against a historical cohort of 46 patients treated with limited discectomy alone. Reherniation rates and clinical outcomes were determined by independent evaluation at 6, 12, and 24 months after surgery. Results. The reherniation rate in the limited discectomy group was 18% versus 9% in the subtotal discectomy group at follow-up (P = 0.1). However, the back pain (visual analog scale) (P = 0.02) and Oswestry scores (P = 0.06) were worse in the subtotal discectomy group at 12-month follow-up. Time to return to work was longer, and pain medication usage was higher in the subtotal discectomy group at 12-month follow-up. Despite a trend toward a higher reherniation rate, the patient satisfaction at 2-year follow-up was higher in the limited discectomy group. Conclusions. The more aggressive removal of remaining intervertebral disc material may decrease the risk of reherniation, but the overall outcome was less satisfactory, especially during the first year after surgery.

Comparison of minimally invasive and conventional open posterolateral lumbar fusion using magnetic resonance imaging and retraction pressure studies.

Objective To determine whether minimally invasive lumbar spinal fusion results in less paraspinal muscle damage than conventional open posterior fusion. Methods The maximum intramuscular pressure (IMP) generated by a minimally invasive and standard open retractor was compared in cadavers using an ultra-miniature pressure transducer. In a second clinical study, eight patients with either minimally invasive or open posterolateral lumbar spinal fusion underwent magnetic resonance imaging (MRI) scanning approximately 6 months post surgery. MRI was used to estimate edema and atrophy within multifidus, with T2 mapping and diffusion-weighted imaging allowing quantification of differences between the two surgical techniques. Results IMP measured with the minimally invasive retractor was 1.4 versus 4.7 kPa with the open retractor (P<0.001). The minimally invasive retractor produced a transient maximal IMP only on initial expansion. Maximum IMP was constant throughout open retractor deployment. Striking visual differences in muscle edema were seen between open and minimally invasive groups on MRI. The mean T2 relaxation time at the level of fusion was 47 milliseconds in the minimally invasive and 90 milliseconds in the open group (P=0.013). The mean apparent diffusion coefficient was 1357×10−6 mm2/s and 1626×10−6 mm2/s (P=0.0184), respectively. Conclusions The peak IMP generated by the minimally invasive retractor was significantly less than with the open retractor. Postoperatively, less muscle edema was demonstrated after the minimally invasive lumbar spinal fusion, with lower mean T2 and apparent diffusion coefficient measurements supporting the hypothesis that less damage occurs using a minimally invasive approach.

Low-pressure positive Discography in subjects asymptomatic of significant low back pain illness.

Study Design. Retrospective data review of positive disc injections at low pressures among subjects without chronic low back pain (LBP) illness compared to patients with chronic LBP undergoing Discography. Objective. To test the hypothesis that false-positive injections during Discography can effectively be eliminated by defining the positive injection criteria to include only those discs in which pain is produced with low injection pressure injections. Summary of Background Data. The use of lumbar Discography as a diagnostic tool remains controversial. Studies have shown that disc injections among subjects asymptomatic of clinical LBP will produce painful injections in a significant proportion of subjects, rendering the interpretation of positive diskograms in clinical practice problematic. It has been argued that lumbar disc injections at low pressure may be clinically different from those at higher pressure and that a guideline accepting only of low-pressure injections will effectively eliminate false positives. Methods. A total of 69 volunteers with no clinically significant LBP undergoing experimental lumbar Discography were analyzed. There were 4 subgroups of this study cohort: no LBP, no chronic pain (n = 10); no LBP, chronic pain (n = 14); no LBP, previous lumbar discectomy (n = 20); and minor benign “backache” (n = 25). Pressure measurements during injection were made, and the pressure at which a significant pain response was elicited was recorded. This result was compared to the pain response and pressure profiles of 52 patients undergoing Discography for chronic LBP illness in consideration of treatment. Raters who were blinded to the subject’s study group scored the studies. Diskogram morphology, pain response, and concordance, as well as magnetic resonance imaging, plain radiographs, psychometric testing (Distress and Risk Assessment Method), and compensation history were documented for each group. A low-pressure positive was defined as significant pain elicited less than 22 psi more than opening pressure. Results. The number and percent of individuals with at least 1 low-pressure positive disc in the experimental group were 17 of 69 (25%) and in the clinical LBP group 14 of 52 (27%). The percentage of subjects with positive pain in the different experimental subgroups was: no LBP, no chronic pain 0/10 (0%); no LBP, chronic pain 5/14 (36%); no LBP, previous lumbar discectomy 5/20 (25%); and minor benign “backache” 7/25 (28%). Positive injections correlated with anular disruption, abnormal psychometric findings, and chronic pain states. Conclusions. The analysis shows that the rate of low-pressure painful injections in subjects without chronic LBP illness is approximately 25%, and correlates with both anatomic and psychosocial factors. In certain subgroups, this may represent an unacceptable risk of false-positive results.

Prospective Controlled Study of the Development of Lower Back Pain in Previously Asymptomatic Subjects Undergoing Experimental Discography

Study Design. A prospective controlled longitudinal study. Objectives. To determine whether subjects, asymptomatic for lower back problems, who undergo experimental discography, will develop lower back problems during the medium term to the full term. Summary of Background Data. Previous work has shown significant pain on discographic injection in approximately 40% of asymptomatic subjects. It has been suggested that those subjects with painful injections would soon develop lower back pain (LBP) syndromes in the near future: that is, the experimental discography was detecting an imminent “pain generator” before clinically symptomatic. Methods. Fifty subjects without low back pain were recruited for clinical and psychometric testing, MRI scanning, and experimental lumbar discography to determine the rate of painful lumbar disc injections in select subjects without LBP history. After determining which subjects had painful injections, all subjects completing the discography protocol were prospectively followed at yearly intervals to determine the occurrence of LBP and LBP disability over time. Statistical methods were then used to determine the correlation, if any, between the asymptomatic subjects’ clinical, MRI, and discography findings, and the subsequent LBP measures. Controls, not participating in the lumbar discography study, were also followed. Controls were matched for clinical features, sex, age, and occupational/recreational exposure. Follow-up examinations were performed at yearly intervals by blinded researchers using a scripted interview and completing standard questionnaires. Results. A total of 46 of 50 completed the discogram, and all 46 subjects completed the final 4-year follow-up examination. There was a low incidence of LBP episodes in the experimental groups and control. A painful disc injection, independent of psychological profile, did not predict LBP or any other functional outcome measure at follow-up on multivariate analysis. The presence of an anular fissure seen on discography was weakly associated with the cumulative incidence of LBP episodes after discography (P = 0.08). The presence of high intensity zone on MRI in any disc was also weakly associated with the development of LBP episodes (P = 0.09). Psychometric profiles at the start of the study strongly and independently predicted future back pain (P = 0.01), medication usage (P = 0.002), and work loss (P = 0.01) over the 4-year study. Compared with controls not having undergone discography, there was no significant difference in back pain, function, work loss, doctors visits for back pain, or medication intake in any group. A subset in the injection group with somatization disorder had a higher LBP visual analog score compared with somatization disorder controls at 1 year,but this was not significant at 4 years after testing. Conclusions. Painful disc injections are poor independent predictors of subsequent LBP episodes in subjects initially without active lower back complaints. Anular disruption is a weak predictor of future LBP problems. Psychological distress and preexisting chronic pain processes are stronger predictors of LBP outcomes.

Vertebroplasty versus kyphoplasty: biomechanical behavior under repetitive loading conditions.

Study Design. Ex vivo biomechanical study using osteoporotic cadaveric fractured vertebral bodies. Objective. To investigate the behavior of fractured osteoporotic vertebral bodies treated with either vertebroplasty or kyphoplasty under repetitive loading conditions. Summary of Background Data. Vertebroplasty and kyphoplasty are newer alternatives for the treatment of osteoporotic vertebral fractures. Loading conditions that can lead to fractures treated with these methods will likely be encountered subsequently; as such, it is important to understand differences in the biomechanical behavior of the resultant constructs. Methods. There were 7 pairs of osteoporotic T8 and T10 vertebral bodies cyclically loaded to produce a vertebral compression fracture. Of each pair, one was assigned to the kyphoplasty group and the other to the vertebroplasty group. After treatment, specimens were cyclically loaded to 100,000 cycles, between 20% and 70% of the predicted failure load. Results. Height was restored with kyphoplasty, but the vertebral bodies showed significant height loss during cyclic loading. Vertebroplasty specimens had higher compression stiffness and smaller height reduction. Conclusions. Under repetitive loading conditions, fractured vertebral bodies treated with kyphoplasty were initially taller, but because of a progressive loss of height during loading, the resulting constructs were shorter after 100,000 cycles than those treated with vertebroplasty.

Discography ☆ ☆☆: a review

BACKGROUND CONTEXT Discography is used today as the basis of the diagnosis of discogenic back and neck pain. As such, it plays a pivotal role in the formulation of treatment plans for patients complaining of chronic axial spine pain. PURPOSE A brief history of discography is described here, followed by a discussion of the current uses of discography, the technique involved, and recent studies questioning its validity. STUDY DESIGN/SETTING A selective review of discography articles from peer-reviewed literature from 1967 to 2000 is provided. We included articles analyzing the validity of discography as well as those concerning its proper use, technique, and complications. METHODS Articles relevant to the subject of discography were systematically reviewed for recommendations regarding technique, the interpretation of results, and conclusions regarding its validity. RESULTS The specificity of discography is dramatically affected by the characteristics of the patient examined. In a patient with chronic pain states and psychiatric risk factors, the specificity was determined to be at most 20%. In healthy patients with no chronic pain states and a normal psychiatric profile, the specificity was found to be at most 90%. The ability of a patient to determine reliably the concordance of pain provoked during discography is poor. We could find no data addressing the sensitivity of the study. CONCLUSIONS Clinicians who use discography to determine treatment pathways for their patients need to critically examine the validity of the test. Recent studies examining the specificity of discography have led us to proceed much more cautiously in interpreting the results of discography.

Does minor trauma cause serious low back illness

Study Design. Prospective, 5-year, cohort study of working subjects. Objectives. To assess whether the occurrence of common minor trauma events affects the risk of developing serious low back pain (LBP) and LBP disability in subjects with and without degenerative changes to the lumbar spine. Summary of Background Data. Although some theories suggest that minor traumatic events in combination with preexisting degenerative changes commonly cause significant structural injury to spinal segments and serious LBP illness, no prospective data exist on the relationship of minor trauma, detailed structural changes, and outcome measures of serious LBP episodes and occupational disability. Methods. Two hundred subjects without clinical LBP problems were recruited, and underwent baseline clinical and imaging studies. Every 6 months, subjects completed a scripted, algorithm-based interview assessing interval back pain episodes, severity, medical treatment, occupational disability, and the subjects perceived relation of this LBP episode to any preceding event. If a serious LBP episode clinically required a new magnetic resonance examination, the follow-up imaging was obtained and compared to baseline for interval changes. Results. There was no association of minor trauma to adverse LBP events. For each 6-month study interval, the risk of developing a serious LBP episode was 2.1% unassociated with minor trauma and 2.4% following minor trauma (P = 0.59). Neither the frequency of minor trauma events nor the reported severity of the event correlated with adverse outcomes. Subjects with advanced structural findings were not more likely to become symptomatic with minor trauma events than with spontaneously evolving LBP episodes. Follow-up magnetic resonance imaging evaluating new serious LBP illness rarely revealed new clinically significant findings. Age and sex-adjusted prediction models, including abnormal psychometric testing, smoking, and compensation issues, accurately identified 80% of serious LBP events and 93% of LBP disability events. Conclusions. In this study cohort, minor trauma does not appear to increase the risk of serious LBP episodes or disability. The vast majority of incident-adverse LBP events may be predicted not by structural findings or minor trauma but by a small set of demographic and behavioral variables.

Predictors of survival after surgical treatment of spinal metastasis.

BACKGROUND:Surgery for spinal metastasis is a palliative treatment aimed at improving patient quality of life by alleviating pain and reversing or delaying neurologic dysfunction, but with a mean survival time of less than 1 year and significant complication rates, appropriate patient selection is crucial. OBJECTIVE:To identify the most significant prognostic variables of survival after surgery for spinal metastasis. METHODS:Chart review was performed on 200 surgically treated spinal metastasis patients at Stanford Hospital between 1999 and 2009. Survival analysis was performed and variables entered into a Cox proportional hazards model to determine their significance. RESULTS:Median overall survival was 8.0 months, with a 30-day mortality rate of 3.0% and a 30-day complication rate of 34.0%. A Cox proportional hazards model showed radiosensitivity of the tumor (hazard ratio: 2.557, P < .001), preoperative ambulatory status (hazard ratio: 2.355, P = .0001), and Charlson Comorbidity Index (hazard ratio: 2.955, P < .01) to be significant predictors of survival. Breast cancer had the best prognosis (median survival, 27.1 months), whereas gastrointestinal tumors had the worst (median survival, 2.66 months). CONCLUSION:We identified the Charlson Comorbidity Index score as one of the strongest predictors of survival after surgery for spinal metastasis. We confirmed previous findings that radiosensitivity of the tumor and ambulatory status are significant predictors of survival.

Bacteriologic culture of excised intervertebral disc from immunocompetent patients undergoing single level primary lumbar microdiscectomy.

Study Design A consecutive case series from a single center of patients undergoing primary microdiscectomy for lumbar herniated nucleus pulposus (HNP) who received microbiologic laboratory culture of excised disc material. Objective To determine the prevalence of positive bacterial cultures in the disc material of immunocompetent patients without diabetes mellitus or other immune compromise. Summary of Background Data The intradiscal space is a physiologically tenuous environment in terms of oxygen tension, pH, and vascularity. This space may be susceptible to indolent infections with an unknown effect on the pathogenesis of HNP. Methods This case series included 52 patients with radiculopathy and magnetic resonance imaging positive for HNP who elected for lumbar microdiscectomy after failure of conservative management. All patients received primary surgery at a single spinal level in the absence of diabetes mellitus, systemic steroid use, chemotherapy, other immune compromise, or prior lumbar surgery. Excised disc material was sent for routine bacterial culture. No special culture techniques were used to improve the yield of positive cultures. Results Cultures were positive in 10 patients (19.2%). Propionibacterium acnes was the sole organism isolated in 7 (13.5%), with Peptostreptococcus and Staphylococcus species accounting for the remainder. There were 24 women (46.2%) and 28 men (53.8%) with a mean age of 43.9 years (SE 1.8). Duration of symptoms was greater than 12 weeks in 35 patients (67.3%). Onset of symptoms was insidious in 22 patients (42.3%), sudden in 16 (30.8%), and the history was unclear in the remainder. Prior epidural steroid injection was received by 17 patients (32.7%), and 11 patients had a history of smoking (21.2%). None of these variables was significantly different in patients with positive and negative cultures (P >0.05). Conclusions P. acnes was isolated by routine laboratory culture of excised disc material in 13.5% of immunocompetent patients undergoing primary single level discectomy for radiculopathy with lumbar HNP; other organisms were isolated in 6% of patients. Level of Evidence Diagnostic level of evidence III.