Are all Cages Created Equal? Analysis of Cervical Cage Malfunctions Using FDA MAUDE Database.

STUDY DESIGN: Retrospective case series. OBJECTIVE: To characterize failure rates of cervical cages based on manufacturer and design characteristics using the nationwide database of reported malfunctions. BACKGROUND: The Food and Drug Administration (FDA) aims to ensure the safety and efficacy of cervical interbody implants postimplantation; however, intraoperative malfunctions may be overlooked. MATERIALS AND METHODS: The FDA's Manufacturer and User Facility Device Experience database was queried for reports of cervical cage device malfunctions from 2012 to 2021. Each report was categorized based on the failure type, implant design, and manufacturer. Two market analyses were performed. First, "failure-to-market share indices" were generated by dividing the number of failures per year for each implant material by its yearly US market share in cervical spine fusion. Second, "failure-to-revenue indices" were calculated by dividing the total number of failures per year for each manufacturer by their approximate yearly revenue from spinal implants in the US. Outlier analysis was performed to generate a threshold value above which failure rates were defined as greater than the normal index. RESULTS: In total, 1336 entries were identified, and 1225 met the inclusion criteria. Of these, 354 (28.9%) were cage breakages, 54 (4.4%) were cage migrations, 321 (26.2%) were instrumentation-related failures, 301 (24.6%) were assembly failures, and 195 (15.9%) were screw failures. Poly-ether-ether-ketone implants had higher failure by market share indices for both migration and breakage compared with titanium. Upon manufacturer market analysis, Seaspine, Zimmer-Biomet, K2M, and LDR exceeded the failure threshold. CONCLUSION: The most common cause of implant malfunction was breakage. Poly-ether-ether-ketone cages were more likely to break and migrate compared with titanium ones. Many of these implant failures occurred intraoperatively during instrumentation, which underscores the need for FDA evaluation of these implants and their accompanying instrumentation under the appropriate loading conditions before commercial approval.

Multiexpandable cage for minimally invasive posterior lumbar interbody fusion.

The increasing adoption of minimally invasive techniques for spine surgery in recent years has led to significant advancements in instrumentation for lumbar interbody fusion. Percutaneous pedicle screw fixation is now a mature technology, but the role of expandable cages is still evolving. The capability to deliver a multiexpandable interbody cage with a large footprint through a narrow surgical cannula represents a significant advancement in spinal surgery technology. The purpose of this report is to describe a multiexpandable lumbar interbody fusion cage, including implant characteristics, intended use, surgical technique, preclinical testing, and early clinical experience. Results to date suggest that the multiexpandable cage allows a less invasive approach to posterior/transforaminal lumbar interbody fusion surgery by minimizing iatrogenic risks associated with static or vertically expanding interbody prostheses while providing immediate vertebral height restoration, restoration of anatomic alignment, and excellent early-term clinical results.

Biomechanics of a Posterior Lumbar Motion Stabilizing Device: In Vitro Comparison to Intact and Fused Conditions.

STUDY DESIGN: Nondestructive flexibility tests were performed in vitro, comparing multiple conditions of fixation in a single group of specimens. OBJECTIVE: To compare the biomechanical behavior of the lumbar spine in the intact condition, after implanting a novel motion stabilizer, and after implanting a rigid fixator. SUMMARY OF BACKGROUND DATA: Two specific scenarios that may benefit from dynamic lumbar stabilization are single-level moderate instability, where the stabilizing tissues are relatively incompetent, and juxta-level to fusion, where the last instrumented level requires intermediate stiffness ("topping off") to prevent transfer of high stresses from the stiffer fusion construct to the intact adjacent levels. Both scenarios were evaluated in vitro. METHODS: Seven human cadaveric L2-S1 segments were tested (1) intact, (2) after moderate destabilization, (3) after 2-level hybrid posterior fixation, consisting of bilateral dynamic pedicle screws at L4 interconnected with rigid rods to standard pedicle screws at L5 and S1, (4) after 2-level rigid fixation, (5) after 1-level (L4-L5) dynamic fixation, and (6) after 1-level rigid fixation. In each condition, angular range of motion (ROM) and sagittal instantaneous axis of rotation (IAR) were assessed. RESULTS: In 1-level constructs, dynamic hardware allowed 104% of intact ROM, whereas rigid hardware allowed 49% of intact ROM. Relative to the intact, the IAR was shifted significantly farther posterior by rigid 1-level instrumentation than by dynamic 1-level instrumentation. In 2-level constructs, the dynamic level allowed significantly greater ROM than the rigid level in all directions but allowed significantly less ROM than the intact level in all directions except axial rotation. CONCLUSION: Dynamic instrumentation shifted the IAR less than rigid instrumentation, providing more favorable kinematics. This dynamic stabilizer provided 1-level ROM that was close to intact ROM during all loading modes in vitro. In the topping-off construct, the dynamic segment allowed intermediate ROM to give balanced transitional flexibility. LEVEL OF EVIDENCE: N/A.

Two-Year Evaluation of the X-STOP Interspinous Spacer in Different Primary Patient Populations With Neurogenic Intermittent Claudication Because of Lumbar Spinal Stenosis.

STUDY DESIGN: Multicenter, prospective single-arm study in patients diagnosed with neurogenic intermittent claudication because of lumbar spinal stenosis. OBJECTIVE: To collect data from 2 different primary patient populations, new participants meeting entry criteria [Continued Access Program (CAP)], or subjects who had been randomly assigned to nonsurgical management in the pivotal Investigational Device Exemption study and failed to respond upon study completion [Crossover Study (COS)]. SUMMARY OF BACKGROUND DATA: The X-STOP interspinous spacer is a minimally invasive treatment option for neurogenic intermittent claudication shown to improve pain, physical functioning, and/or overall quality of life. METHODS: Fifty-five subjects were enrolled, 42 in CAP and 13 in COS. Zurich Claudication Questionnaire (ZCQ) success rates were obtained based on the number of subjects achieving a threshold level of success. Mean SF-36 domain scores were compared with baseline using repeated measures analysis of variance. RESULTS: Eighty percent of subjects completed the study. At 2 years, 26/43 subjects (60.5%) achieved clinically significant improvement in the Symptom Severity domain, 25/43 (58.1%) achieved clinically significant improvement in the Physical Function domain, and 31/44 (70.5%) achieved clinically significant improvement in the Patient Satisfaction domain of the ZCQ. Statistically significant improvement in mean scores was obtained in all physical domains of the SF-36 (with the exception of General Health) at 24 months. Mean improvement in ZCQ and SF-36 scores was not as pronounced in the COS cohort compared with the CAP cohort. The most frequently reported device-related or treatment-related adverse event was stenosis pain reported by 3 subjects. CONCLUSIONS: Overall data are consistent with the randomized pivotal Investigational Device Exemption trial. On the basis of the COS cohort which was subject to several additional years of failed conservative treatment, overall success rates do not improve as greatly in patients with long-standing lumbar spinal stenosis symptoms.

Scoliosis and interspinous decompression with the X-STOP: prospective minimum 1-year outcomes in lumbar spinal stenosis.

BACKGROUND CONTEXT: The X-STOP interspinous decompression device, as a treatment for neurogenic intermittent claudication (NIC) because of lumbar spinal stenosis (LSS), has been shown to be superior to nonoperative control treatment. Current Food and Drug Administration labeling limits X-STOP use to NIC patients with a maximum of 25° concomitant lumbar scoliosis. This value was arrived at arbitrarily by the device developers and is untested. PURPOSE: To determine X-STOP utility for NIC in patients with concomitant lumbar scoliosis. STUDY DESIGN: A prospective, single institution, clinical outcome study comparing patients with scoliosis with patients without scoliosis who underwent X-STOP interspinous decompression for NIC because of LSS. PATIENT SAMPLE: A cohort of 179 consecutive patients, 63 with scoliosis (Cobb angle 11° or more) and 116 without scoliosis, with symptoms attributable to NIC treated between January 2006 and May 2007, were included in the study. OUTCOME MEASURES: All patients completed self-reported preoperative and minimum 1-year postoperative outcome forms. Functional measures included Oswestry Disability Index (ODI), visual analog scale (VAS) pain score, and maximum walking and standing times in minutes. Three questions measured patient satisfaction: How satisfied were you with the procedure (very satisfied, somewhat satisfied, somewhat dissatisfied, or very dissatisfied); Would you have the procedure again? (yes or no); Would you recommend the procedure to a friend? (yes or no). METHODS: Before analysis, the 179 consecutive X-STOP patients were divided into three groups: Group 1 (controls without scoliosis, n=116); Group 2 (low scoliosis: 11-25°, n=41), and Group 3 (high scoliosis: 26° or more, n=22). The three groups were not statistically different for any preoperative functional scores. Groups were analyzed for pre- to postoperative functional change and level of satisfaction. Segmental scoliosis at the treated level was also analyzed. RESULTS: Fifty-six percent of Group 1 and Group 2 patients, but only 18% of Group 3 patients, achieved the success criterion of an ODI improvement of 15 or more points (Group 3 the outlier, p=.004). The satisfaction rate was Group 1, 76%; Group 2, 78%; Group 3, 59% (Group 3 the outlier, p=.0001). On average, all three groups improved for each outcome: Group 1 (ODI 17.3, VAS 2.0, standing time 39 minutes, and walking time 43 minutes), Group 2 (ODI 20.0, VAS 1.9, standing time 65 minutes, and walking time 64 minutes), Group 3 (ODI 7.2, VAS 0.9, standing time 18 minutes, and walking time 16 minutes). There was no statistical relationship between any outcome and segmental scoliosis. CONCLUSIONS: The outcome success rate for the X-STOP procedure to treat NIC is lower in patients with overall lumbar scoliosis more than 25° but is unaltered by segmental scoliosis at the affected level. Although patients and surgeons must be aware that the presence of more than 25° of scoliosis portends less favorable results with X-STOP implantation for NIC because of LSS, success in these patients is not precluded, and selection of treatment must be put into the context of individual patient risk and other treatment options.

A novel technique of intra-spinous process injection of PMMA to augment the strength of an inter-spinous process device such as the X STOP.

STUDY DESIGN: Biomechanical. OBJECTIVE: To determine if cement injection into the spinous process will improve compression strength. SUMMARY OF BACKGROUND DATA: The X STOP (St. Francis Medical Technologies) has been shown to be a safe and effective means for decompressing 1- or 2-level lumbar spinal stenosis (LSS). The X STOP is indicated for LSS patients with osteoporosis, but contraindicated for patients with severe osteoporosis. In an attempt to address these LSS patients with demonstrably weaker bone, a technique to strengthen the spinous process with polymethylmethacrylate (PMMA) injection is presented. METHODS: Nine pairs of adjacent fresh frozen cadaveric lumbar vertebrae were DEXA scanned before testing. They were randomly assigned to the PMMA group and a control group. Nine of the specimens were injected with PMMA. Each spinous process was then compressed between 2 X STOPs. The testing model was designed to simulate the loading of a 2-level X STOP placement. The mean load to failure and stiffness values of the treated and untreated groups were calculated. The specimens were inspected carefully for PMMA infiltration and extrusion. RESULTS: The mean bone mineral density (BMD) values of the control and PMMA treatment groups were 0.99 +/- 0.13 g/cm and 0.98 +/- 0.10 g/cm, respectively; P > 0.616. The mean volume of cement injected was 2.2 +/- 0.3 cc. The mean failure load values of the control and PMMA treatment groups were 1250 +/- 627 N and 2386 +/- 1034 N, respectively; P < 0.001. The mean stiffness values of the control and PMMA treatment groups were 296 +/- 139 N/mm and 381 +/- 131 N/mm, respectively; P > 0.059. Most specimens had flow of the cement into the laminae and some into the facet and pedicle. No PMMA was found within the spinal canal. CONCLUSION: This first reported technique of posterior element vertebroplasty may increase the indications and success for patients with decreased BMD who seek an interspinous implant such as the X STOP. A possible role may exist in increasing the effectiveness of such devices. However, clinical trials have yet been performed. These results demonstrate that PMMA injection in the spinous processes is effective in increasing resistance to compressive forces in an X STOP model.

Quality of life of lumbar stenosis-treated patients in whom the X STOP interspinous device was implanted.

OBJECT: This study was conducted to compare the quality of life (QOL) in patients with neurogenic intermittent claudication (NIC) secondary to lumbar spinal stenosis (LSS). Using the 36-Item Short Form (SF-36) questionnaire, the authors compared the results obtained in patients treated with the X STOP Interspinous Process Decompression (IPD) System with those obtained in patients who underwent nonoperative therapies. METHODS: Patients with LSS were enrolled in a prospective 2-year multicenter study and randomized either to the X STOP or nonoperative group. The SF-36 survey was used to assess the QOL before treatment and at 6 weeks, 6 months, 1 year, and 2 years posttreatment. An analysis of variance was used to compare individual pre- and posttreatment mean SF-36 domain scores between the two groups and within each treatment group. At all posttreatment time points, the authors observed the following: (1) mean domain scores in X STOP-treated patients were significantly greater than those in patients treated nonoperatively, with the exception of the mean General Health (GH), Role Emotional, and Mental Component Summary scores at 2 years; and (2) mean posttreatment domain scores documented in X STOP-treated patients were significantly greater than mean pretreatment scores, with the exception of mean GH scores at 6, 12, and 24 months. CONCLUSIONS: The results of this study demonstrate that the X STOP device is significantly more effective than nonoperative therapy in improving the QOL in patients with LSS. The results are comparable with those reported in other studies involving traditional decompressive techniques for LSS and suggest that the X STOP implant can provide an effective treatment compared with nonoperative and conventional surgical therapies.

Interspinous process decompression with the X-STOP device for lumbar spinal stenosis: a 4-year follow-up study.

X-STOP is the first interspinous process decompression device that was shown to be superior to nonoperative therapy in patients with neurogenic intermittent claudication secondary to spinal stenosis in the multicenter randomized study at 1 and 2 years. We present 4-year follow-up data on the X-STOP patients. Patient records were screened to identify potentially eligible subjects who underwent X-STOP implantation as part of the FDA clinical trial. The inclusion criteria for the trial were age of at least 50 years, leg, buttock, or groin pain with or without back pain relieved during flexion, being able to walk at least 50 feet and sit for at least 50 minutes. The exclusion criteria were fixed motor deficit, cauda equina syndrome, previous lumbar surgery or spondylolisthesis greater than grade I at the affected level. Eighteen X-STOP subjects participated in the study. The average follow-up was 51 months and the average age was 67 years. Twelve patients had the X-STOP implanted at either L3-4 or L4-5 levels. Six patients had the X-STOP implanted at both L3-4 and L4-5 levels. Six patients had a grade I spondylolisthesis. The mean preoperative Oswestry score was 45. The mean postoperative Oswestry score was 15. The mean improvement score was 29. Using a 15-point improvement from baseline Oswestry Disability Index score as a success criterion, 14 out of 18 patients (78%) had successful outcomes. Our results have demonstrated that the success rate in the X-STOP interspinous process decompression group was 78% at an average of 4.2 years postoperatively and are consistent with 2-year results reported by Zucherman et al previously and those reported by Lee et al. Our results suggest that intermediate-term outcomes of X-STOP surgery are stable over time as measured by the Oswestry Disability Index.

Insertion loads of the X STOP interspinous process distraction system designed to treat neurogenic intermittent claudication.

An interspinous process implant has been developed to treat patients suffering from neurogenic intermittent claudication secondary to lumbar spinal stenosis. As most patients who suffer from spinal stenosis are over the age of 50 and may have weaker bones, it is imperative to know how bone mineral density (BMD) correlates with lateral spinous process strength. The study was undertaken to characterize the lateral failure loads of the spinous process, correlate the failure loads to BMD, and compare the failure loads to the loads required to insert an interspinous process implant. Spinous process lateral failure loads were assessed, correlated to BMD, and compared to the loads required to insert an interspinous process implant. Mean spinous process failure loads were significantly greater than the lateral insertion load of the interspinous process implant. There was a significant relationship between the BMD and spinous process failure load. The technique used to insert the interspinous implant poses little risk to spinous process failure. There is ample margin of safety between the insertion loads and spinous process failure loads. The significant relationship between BMD and spinous process failure load suggests that patients with lower BMD must be approached with more caution during the implant insertion procedure.

Measurement of in vivo lumbar intervertebral disc pressure during spinal manipulation: a feasibility study.

This paper presents the first reported measurements of lumbar intervertebral disc pressure in vivo during spinal manipulation. A pressure transducer was inserted into the nucleus pulposus of one normal-appearing lumbar disc in an asymptomatic adult volunteer. Pressures were recorded during several body positions and maneuvers, then during spinal manipulation, and lastly during a repetition of the preintervention body positions. Baseline pressures in the prone and side-lying positions measured 110 kPa and 150 kPa, respectively. During the manipulation, pressure rose to a peak of 890 kPa over 250 ms. Immediately following, pressures in the prone and side-lying positions measured 150 kPa and 165 kPa, respectively. These data do not support the hypotheses that manipulation can reduce a herniation by decreasing intradiscal pressure, or cause a herniation by raising pressure to failure levels. Further work may lead to a better understanding of this treatment method.

A multicenter, prospective, randomized trial evaluating the X STOP interspinous process decompression system for the treatment of neurogenic intermittent claudication: two-year follow-up results.

STUDY DESIGN: A randomized, controlled, prospective multicenter trial comparing the outcomes of neurogenic intermittent claudication (NIC) patients treated with the interspinous process decompression system (X STOP) with patients treated nonoperatively. OBJECTIVE: To determine the safety and efficacy of the X STOP interspinous implant. SUMMARY OF BACKGROUND DATA: Patients suffering from NIC secondary to lumbar spinal stenosis have been limited to a choice between nonoperative therapies and decompressive surgical procedures, with or without fusion. The X STOP was developed to provide an alternative therapeutic treatment. METHODS.: 191 patients were treated, 100 in the X STOP group and 91 in the control group. The primary outcomes measure was the Zurich Claudication Questionnaire, a patient-completed, validated instrument for NIC. RESULTS: At every follow-up visit, X STOP patients had significantly better outcomes in each domain of the Zurich Claudication Questionnaire. At 2 years, the X STOP patients improved by 45.4% over the mean baseline Symptom Severity score compared with 7.4% in the control group; the mean improvement in the Physical Function domain was 44.3% in the X STOP group and -0.4% in the control group. In the X STOP group, 73.1% patients were satisfied with their treatment compared with 35.9% of control patients. CONCLUSIONS: The X STOP provides a conservative yet effective treatment for patients suffering from lumbar spinal stenosis. In the continuum of treatment options, the X STOP offers an attractive alternative to both conservative care and decompressive surgery.

The use of an interspinous implant in conjunction with a graded facetectomy procedure.

STUDY DESIGN: The range of motion (ROM) of lumbar cadaver spines was measured during flexion, extension, axial rotation, and lateral bending following graded facetectomies and implantation of an X STOP interspinous spacer implant. OBJECTIVE: The study was performed undertaken to understand better the influence of the interspinous spacer implant on the kinematics of the lumbar spine following graded facetectomies. SUMMARY OF THE BACKGROUND DATA: Lateral lumbar spinal stenosis is often treated with a unilateral or bilateral facetectomy procedure. Previous biomechanical research has shown that a facetectomy may increase the ROM during flexion and axial rotation. METHODS: Seven cadaver spines (L2-L5) were tested in flexion, extension, axial rotation, and lateral bending, and the individual ROM of each motion segment was measured. Specimens were tested intact and following 3 graded facetectomies (i.e., unilateral medial facetectomy [UMF], unilateral total facetectomy [UTF], and bilateral total facetectomy [BTF]), with and without the X STOP. RESULTS: A BTF caused a significant increase in ROM during flexion and axial rotation but not extension and lateral bending. The UMF and UTF did not affect the ROM during any of the 4 motions. The interspinous implant: (1) significantly decreased the flexion ROM for the intact, UMF, UTF, and BTF treatments; (2) significantly decreased the extension ROM for the intact, UMF, and BTF treatments but not the UTF (P < 0.13); (3) had no significant effect on the axial rotation ROM; and (4) significantly increased the lateral bending ROM for the UMF, UTF, and BTF treatments. CONCLUSIONS: The results suggest that the implant may be used in conjunction with a UMF or UTF. However, the X STOP should not be used in conjunction with BTF.

The effects of an interspinous implant on the kinematics of the instrumented and adjacent levels in the lumbar spine.

STUDY DESIGN: Measurement of the kinematics of the lumbar spine after insertion of an interspinous spacer in vitro. OBJECTIVES: To understand the kinematics of the instrumented and adjacent levels due to the insertion of this interspinous implant. SUMMARY OF BACKGROUND DATA: An interspinous spacer (X Stop, SFMT, Concord, California) has been developed to treat neurogenic intermittent claudication by placing the stenotic segment in slight flexion and preventing extension. This restriction of motion by the interspinous implant may affect the kinematics of levels adjacent to the instrumented level. METHODS: Seven lumbar spines (L2-L5) were tested in flexion-extension, lateral bending, and axial rotation. Images were taken during each test to determine the kinematics of each motion segment. The interspinous implant was placed at the L3-L4 level, and the test protocol was repeated. RESULTS: The flexion-extension range of motion was significantly reduced at the instrumented level. Axial rotation and lateral bending ranges of motion were not affected at the instrumented level. The range of motion in flexion-extension, axial rotation, and lateral bending at the adjacent segments was not significantly affected by the implant. CONCLUSIONS: The implant does not significantly alter the kinematics of the motion segments adjacent to the instrumented level.

The effects of an interspinous implant on intervertebral disc pressures.

STUDY DESIGN: Measurement of intradiscal pressure was performed after placement of an interspinous implant in a cadaver model. OBJECTIVE: To understand the likelihood of accelerated adjacent-level disc degeneration as a result of the implant. SUMMARY OF BACKGROUND DATA: An interspinous implant has been developed to treat lumbar neurogenic claudication secondary to spinal stenosis that places the stenotic segment in slight flexion and prevents extension. Previous biomechanical studies demonstrated that fusing one level may significantly increase the intradiscal pressures at adjacent levels. Moreover, clinical studies have reported an increased incidence of adjacent-level degeneration after lumbar spinal fusion. METHODS: Eight cadaver lumbar specimens (L2-L5) were loaded in flexion, neutral, and extension. A pressure transducer measured intradiscal pressure and annular stresses during each of the three positions at each of the three disc levels. An appropriately sized implant was placed at L3-L4, and the pressure measurements were repeated. RESULTS: The pressures at the adjacent discs were not significantly affected by the interspinous implant insertion. There was a significant decrease in intradiscal pressure at the L3-L4 disc in the posterior annulus and nucleus in the neutral and extended positions. CONCLUSIONS: The implant does not significantly change the intradiscal pressures at the adjacent levels, yet it significantly unloads the intervertebral disc at the instrumented level in the neutral and extended positions. On the basis of the current findings, it does not appear that the implant causes accelerated disc degeneration at the adjacent levels.

Gadopentetate dimeglumine as an intradiscal contrast agent.

STUDY DESIGN: Magnetic resonance discography using gadolinium as an intradiscal contrast agent was investigated in a prospective study. OBJECTIVE: To evaluate the utility of magnetic resonance discography using gadolinium as an intradiscal contrast agent, as compared with the current standard of computed tomographic discography using intradiscal iodinated contrast agent. SUMMARY OF BACKGROUND DATA: Magnetic resonance arthrography with gadolinium has been used to evaluate shoulder, elbow, wrist, hip, knee, and other joints. Gadolinium has not been used as an intradiscal contrast agent. The authors' preliminary results using gadolinium as an intradiscal contrast agent for magnetic resonance discography were reported previously. They report the results of their completed study. METHODS: For this study, 42 disc levels were studied in 13 patients. Water-soluble iodinated contrast and gadopentetate dimeglumine were injected at each disc level. After discography, anteroposterior and lateral radiographs, computed tomography scans, and T1-weighted magnetic resonance imaging were performed. Six physicians interpreted the results from each disc level in a blinded fashion. Interscan and interobserver interpretation variability was determined for magnetic resonance discography and computed tomographic discography using the Pearson correlation-coefficient (r) test. RESULTS: Interscan variability was highly correlated between computed tomographic discography and magnetic resonance discography when used to determine disc normality (r = 0.87), general degeneration (r = 0.87), anular fissure (r = 0.89), disc herniation (r = 0.92), and contrast leakage (r = 0.77). Interscan variability was assessed by the Pearson test, and all values of r for all the readers were noted to be statistically significant at P values less than 0.01. Interobserver variability was significantly correlated among the four more experienced readers (neuroradiologists and spine surgeons), but not among the spine fellows. Interobserver variability was also significantly correlated by computed tomographic (CT) and magnetic resonance imaging (MRI) discography for disc normality (CT r = 0.60; MRI r = 0.56), general degeneration (CT r = 0.76; MRI r = 0.71), anular fissure (CT r = 0.79; MRI r = 0.84), and disc herniation (CT r = 0.63; MRI r = 0.64). The readings for contrast leakage did not reach statistical significance for computed tomographic or magnetic resonance discography. CONCLUSIONS: The high interscan and interobserver correlation rates obtained for magnetic resonance discography using gadolinium, as compared with the standard computed tomographic discography technique, indicate that magnetic resonance discography may be an acceptable substitute for the imaging of disc pathology. Magnetic resonance discography with gadolinium can be recommended for patients allergic to iodinated contrast agents and for patients who wish to limit their radiation exposure.