Rick B. Delamarter

Spinal fusion in the United States: analysis of trends from 1998 to 2008.

Study Design. Epidemiological study using national administrative data. Objective. To provide a complete analysis of national trends in spinal fusion from 1998 to 2008 and compare with trends in laminectomy, hip replacement, knee arthroplasty, percutaneous transluminal coronary angioplasty, and coronary artery bypass graft. Summary of Background Data. Previous studies have reported a rapid increase in volume of spinal fusions in the United States prior to 2001, but limited reports exist beyond this point, analyzing all spinal fusion procedures collectively. Methods. Data were obtained from the Healthcare Cost and Utilization Project Nationwide Inpatient Sample for the years 1998 to 2008. Discharges were identified using International Classification of Diseases, Ninth Revision, Clinical Modification procedure codes for the following procedures: spinal fusion, laminectomy, hip replacement, knee arthroplasty, percutaneous transluminal coronary angioplasty, and coronary artery bypass graft. Population-based utilization rates were calculated from the US census data. Results. Between 1998 and 2008, the annual number of spinal fusion discharges increased 2.4-fold (137%) from 174,223 to 413,171 (P < 0.001). In contrast, during the same time period, laminectomy, hip replacement, knee arthroplasty, and percutaneous coronary angioplasty yielded relative increases of only 11.3%, 49.1%, 126.8%, and 38.8% in discharges, while coronary artery bypass graft experienced a decrease of 40.1%. Between 1998 and 2008, mean age for spinal fusion increased from 48.8 to 54.2 years (P < 0.001), in-hospital mortality rate decreased from 0.29% to 0.25% (P < 0.01), and mean total hospital charges associated with spinal fusion increased 3.3-fold (P < 0.001). The national bill for spinal fusion increased 7.9-fold (P < 0.001). Conclusion. Frequency, utilization, and hospital charges of spinal fusion have increased at a higher rate than other notable inpatient procedures, as seen in this study from 1998 to 2008. In addition, patient demographics and hospital characteristics changed significantly; in particular, whereas the average age for spinal fusion increased, the in-hospital mortality rate decreased.

Results of the prospective, randomized, controlled multicenter Food and Drug Administration investigational device exemption study of the ProDisc-C total disc replacement versus anterior discectomy and fusion for the treatment of 1-level symptomatic cervical disc disease.

BACKGROUND CONTEXT Cervical total disc replacement (TDR) is intended to address radicular pain and preserve functional motion between two vertebral bodies in patients with symptomatic cervical disc disease (SCDD). PURPOSE The purpose of this trial is to compare the safety and efficacy of cervical TDR, ProDisc-C (Synthes Spine Company, L.P., West Chester, PA), to anterior cervical discectomy and fusion (ACDF) surgery for the treatment of one-level SCDD between C3 and C7. STUDY DESIGN/SETTING The study was conducted at 13 sites. A noninferiority design with a 1:1 randomization was used. PATIENT SAMPLE Two hundred nine patients were randomized and treated (106 ACDF; 103 ProDisc-C). OUTCOME MEASURES Visual analog scale (VAS) pain and intensity (neck and arm), VAS satisfaction, neck disability index (NDI), neurological exam, device success, adverse event occurrence, and short form-36 (SF-36) standardized questionnaires. METHODS A prospective, randomized, controlled clinical trial was performed. Patients were enrolled and treated in accordance with the US Food and Drug Administration (FDA)-approved protocol. Patients were assessed pre- and postoperatively at six weeks, 3, 6, 12, 18, and 24 months. RESULTS Demographics were similar between the two patient groups (ProDisc-C: 42.1+/-8.4 years, 44.7% males; Fusion: 43.5 +/- 7.1 years, 46.2% males). The most commonly treated level was C5-C6 (ProDisc-C: 56.3%; Fusion=57.5%). NDI and SF-36 scores were significantly less compared with presurgery scores at all follow-up visits for both the treatment groups (p<.0001). VAS neck pain intensity and frequency as well as VAS arm pain intensity and frequency were statistically lower at all follow-up timepoints compared with preoperative levels (p<.0001) but were not different between treatments. Neurologic success (improvement or maintenance) was achieved at 24 months in 90.9% of ProDisc-C and 88.0% of Fusion patients (p=.638). Results show that at 24 months postoperatively, 84.4% of ProDisc-C patients achieved a more than or equal to 4 degrees of motion or maintained motion relative to preoperative baseline at the operated level. There was a statistically significant difference in the number of secondary surgeries with 8.5% of Fusion patients needing a re-operation, revision, or supplemental fixation within the 24 month postoperative period compared with 1.8% of ProDisc-C patients (p=.033). At 24 months, there was a statistically significant difference in medication usage with 89.9% of ProDisc-C patients not on strong narcotics or muscle relaxants, compared with 81.5% of Fusion patients. CONCLUSIONS The results of this clinical trial demonstrate that ProDisc-C is a safe and effective surgical treatment for patients with disabling cervical radiculopathy because of single-level disease. By all primary and secondary measures evaluated, clinical outcomes after ProDisc-C implantation were either equivalent or superior to those same clinical outcomes after Fusion.

Incidence of subsequent vertebral fracture after kyphoplasty.

Study Design. A retrospective review of charts and radiographs of all consecutive patients who underwent kyphoplasty at the authors’ center from the initial procedure in September 2000 to the end of the collection period in July 2002. Summary of Background Data. The best available natural history data would suggest that after experiencing an osteoporotic vertebral compression fracture, patients have a 19% incidence of subsequent fracture in the following year when no surgical intervention is performed. When kyphoplasty is performed, there are conflicting data regarding the incidence of subsequent fracture, ranging anywhere from 3 to 29%. These fractures occur at adjacent levels between 30 and 90% of the time, with no clear explanation for the wide variation in the results of three different studies. There are biomechanical data to suggest that injection of cement does increase the stiffness of the treated vertebra and that this increases strain on adjacent vertebrae, especially in forward bending. Methods. A database was created containing patient age, gender, height, weight, medication history, comorbidities, fracture levels, and pain level before and after surgery. Subsequent fractures were confirmed with radiographs and MRI. Statistical analysis was performed. Results. Thirty-eight patients (10 men and 28 women) were treated for 47 levels initially. L1 and L2 were the most common level of fracture managed initially. The gender, smoking and medication history, location of fracture, and number of fracture levels of the patients did not correlate with the risk of subsequent fracture. Over the follow-up period (average, 8 months), 10 patients sustained 17 subsequent fractures. Eight patients sustained fractures in the first 2 months after the index procedure, all with at least one fracture at an adjacent level. Of the 17 subsequent fractures, there were nine at the adjacent-above levels, four at adjacent-below levels, and four at remote levels. The remote fractures occurred at significantly greater time intervals after the index procedure (P < 0.001). Conclusion. This study demonstrated a higher rate of subsequent fracture after kyphoplasty compared with natural history data for untreated fractures. Most of these occurred at an adjacent level within 2 months of the index procedure. After this 2-month period, there were only occasional subsequent fractures, which occurred at remote levels. This confirms biomechanical studies showing that cement augmentation places additional stress on adjacent levels. Patients with an increase in back pain after kyphoplasty should be evaluated carefully for subsequent adjacent fractures, especially during the first 2 months after the index procedure.

Results of the prospective, randomized, multicenter Food and Drug Administration investigational device exemption study of the ProDisc-L total disc replacement versus circumferential fusion for the treatment of 1-level degenerative disc disease.

Study Design. A prospective, randomized, multicenter, Food and Drug Administration-regulated Investigational Device Exemption clinical trial. Objective. To evaluate the safety and effectiveness of the ProDisc®-L (Synthes Spine, West Chester, PA) lumbar total disc replacement compared to circumferential spinal fusion for the treatment of discogenic pain at 1 vertebral level between L3 and S1. Summary of Background Data. As part of the Investigational Device Exemption clinical trial, favorable single center results of lumbar total disc replacement with the ProDisc®-L have been reported previously. Methods. Two hundred eighty-six (286) patients were treated on protocol. Patients were evaluated before and after surgery, at 6 weeks, 3, 6, 12, 18, and 24 months. Evaluation at each visit included patient self-assessments, physical and neurologic examinations, and radiographic evaluation. Results. Safety of ProDisc®-L implantation was demonstrated with 0% major complications. At 24 months, 91.8% of investigational and 84.5% of control patients reported improvement in the Oswestry Low Back Pain Disability Questionnaire (Oswestry Disability Index [ODI]) from preoperative levels, and 77.2% of investigational and 64.8% of control patients met the ≥15% Oswestry Disability Index improvement criteria. Overall neurologic success in the investigational group was superior to the control group (91.2% investigational and 81.4% control; P = 0.0341). At 6 weeks and 3 months follow-up time points, the ProDisc®-L patients recorded SF-36 Health Survey scores significantly higher than the control group (P = 0.018, P = 0.0036, respectively). The visual analog scale pain assessment showed statistically significant improvement from preoperative levels regardless of treatment (P < 0.0001). Visual analog scale patient satisfaction at 24 months showed a statistically significant difference favoring investigational patients over the control group (P = 0.015). Radiographic range of motion was maintained within a normal functional range in 93.7% of investigational patients and averaged 7.7°. Conclusions. ProDisc®-L has been found to be safe and efficacious. In properly chosen patients, ProDisc®-L has been shown to be superior to circumferential fusion by multiple clinical criteria.

Increased fusion rates with cervical plating for three-level anterior cervical discectomy and fusion.

Study Design. A retrospective review of all patients surgically treated by a single surgeon with a three-level anterior cervical discectomy and fusion with and without anterior plate fixation. Objectives. To compare the clinical and radiographic success of anterior three-level discectomy and fusion performed with and without anterior cervical plate fixation. Summary of Background Data. Previous studies of multilevel cervical discectomies and fusions have shown fusion rates to decrease as the number of surgical levels increases. Anterior cervical plate stabilization can provide more stability and may increase fusion rates for multilevel fusions. Methods. Over a 7-year period, 59 patients were treated surgically with a three-level anterior cervical discectomy and fusion by the senior author. Forty patients had cervical plates, whereas 19 had fusions with no plates. These patients were observed for an average of 3.2 years. Clinical and radiographic follow-up data were obtained. Results. Of the 59 patients, 14 had a pseudarthrosis (7 in each group). The pseudarthrosis rates were 18% (7 of 40) for patients with plating and 37% (7 of 19) for patients with no plating. Although the nonunion rate for unplated fusions was double that of plated fusions, this difference was not statistically significant. There was no statistically significant correlation between pseudarthrosis and gender, age, level of surgery, history of tobacco use, or previous anterior surgery. The fusion rates were improved with the use of a cervical plate. Inferior clinical results were demonstrated in patients with a pseudarthrosis, regardless of the use of a cervical plate. Conclusions. The addition of plate fixation for three-level anterior cervical discectomy and fusion is a safe procedure and does not result in higher complication rates. In this study, the pseudarthrosis rate was lower for patients with a cervical plate. However, this difference was not statistically significant. Patients treated with cervical plating had overall better results when compared with those of patients treated without cervical plates. Although the use of cervical plates decreased the pseudarthrosis rate, a three-level procedure is still associated with a high nonunion rate, and other strategies to increase fusion rates should be explored.

Pathophysiology of spinal cord injury. Recovery after immediate and delayed decompression

We evaluated the effect of the timing of decompression of the spinal cord after compression of 50 per cent of the diameter of the spinal cord at the fourth lumbar level in thirty purebred dogs. The dogs were divided into five groups of six dogs each on the basis of the duration of the compression. Decompression was performed immediately (Group I), one hour (Group II), six hours (Group III), twenty-four hours (Group IV), or one week (Group V) after the compression. Monitoring of somatosensory evoked potentials, daily neurological examinations, and histological and electron microscopic studies at the time of the autopsy were performed for all of the dogs. Initially, all of the dogs were paraplegic after the compression of the spinal cord. The dogs that had immediate decompression or decompression after one hour of compression recovered the ability to walk (grades 4 and 5, according to Tarlovs system) as well as control of the bowel and bladder, and the somatosensory evoked potentials improved an average of 85 and 72 per cent, respectively. However, when compression lasted six hours or more, there was no neurological recovery and there was progressive necrosis of the spinal cord. Somatosensory evoked potentials improved 29 per cent in Group III, 26 per cent in Group IV, and 10 per cent in Group V. The percentage of recovery of the somatosensory evoked potentials by six weeks after the decompression was significantly related to the duration of the compression (p < 0.0008).

Effective doses of recombinant human bone morphogenetic protein-2 in experimental spinal fusion.

Study Design Nineteen dogs underwent L4‐L5 intertransverse process fusions with either 58 μg, 115 μg, 230 μg, 460 μg, or 920 μg of recombinant human bone morphogenetic protein‐2 carried by a polylactic acid polymer. A previous study (12 dogs) compared 2300 μg of recombinant human bone morphogenetic protein‐2, autogenous iliac bone, and carrier alone in this model. All fusions subsequently were compared. Objectives To characterize the dose‐response relationship of recombinant human bone morphogenetic protein‐2 in a spinal fusion model. Summary of Background Data Recombinant osteoinductive morphogens, such as recombinant human bone morphogenetic protein‐2, are effective in vertebrate diaphyseal defect and spinal fusion models. It is hypothesized that the quality of spinal fusion produced with recombinant human bone morphogenetic protein‐2, above a threshold dose, does not change with increasing amounts of inductive protein. Methods After decortication of the posterior elements, the designated implants were placed along the intertransverse process space bilaterally. The fusion sites were evaluated after 3 months by computed tomography imaging, high‐resolution radiography, manual testing, mechanical testing, and histologic analysis. Results As in the study using 2300 μg of recombinant human bone morphogenetic protein‐2, implantation of 58–920 μg of recombinant human bone morphogenetic protein‐2 successfully resulted in intertransverse process fusion in the dog by 3 months. This had not occurred in animals containing autograft or carrier alone. The cross‐sectional area of the fusion mass and mechanical stiffness of the L4‐L5 intersegment were not dose‐dependent. Histologic findings varied but were not related to rhBMP‐2 dose. Inflammatory reaction to the composite implant was proportional inversely to the volume of the fusion mass. Conclusions No mechanical, radiographic, or histologic differences in the quality of intertransverse process fusion resulted from a 40‐fold variation in dose of recombinant human bone morphogenetic protein‐2.

ProDisc artificial total lumbar disc replacement: introduction and early results from the United States clinical trial.

Study Design. Multicenter prospective randomized study of artificial disc replacement (ProDisc) versus circumferential fusion (standard of care) for one- and two-level degenerative disc disease. This is an interim analysis on patients seen at the Spine Institute Saint John’s Health Center, Santa Monica, California. Objectives. To evaluate early pain and functional outcomes of patients treated with disc replacement or fusion and to assess the capacity of this intervertebral disc replacement for preserving motion in the lumbar spine. Summary of Background Data. Disc replacement is intended to reduce pain via removal of the diseased disc while restoring physiologic motion and height at the affected level. The long-term physiologic advantage of disc replacement to fusion is that preservation of motion may prevent additional degeneration at adjacent levels. Methods. Patients meeting inclusion criteria were consented for study. Randomization was performed using a 2 to 1 ratio of disc replacement procedure to a fusion procedure. Patients rated their pain on the Visual Analogue Scale and completed the Oswestry Disability Index questionnaire. Radiographs were taken. Assessments were made before surgery and after surgery at 6 weeks, 3 months, 6 months, and 1 year (ongoing). Changes from preoperative pain, disability, or motion were separately evaluated as a function of treatment using repeated measures mixed design analysis of variance. Results. This analysis includes data up to 6 months from the first 53 randomized patients. There were 35 patients who underwent disc replacements, and 18 patients had fusion procedures. Disc replacement patients had a significant reduction in pain and disability at earlier evaluations. By 6 months, the relative improvement on both the Visual Analogue Scale and Oswestry (both, P < 0.05) were similar for disc replacement and fusion patients. Greater motion was found at L4–L5 for disc replacement patients (P < 0.05) than fusion patients. A similar trend was noted at L5–S1 (P was not significant). Conclusions. Disc replacement patients reported significantly less pain (Visual Analogue Scale) and disability (Oswestry) in the early period following surgery compared to fusion patients. This difference disappeared by 6 months. When compared to fusion, the disc replacement allowed preservation of motion at L4–L5 with a similar trend at L5–S1.

The effect of cervical plating on single-level anterior cervical discectomy and fusion.

The use of anterior plates for single-level cervical fusions is controversial. Previous studies that evaluated single and multiple-level fusions have shown increased and decreased fusion rates when cervical plates are used. The purpose of this study was to compare the clinical and radiographic success of single-level discectomy performed with and without anterior cervical plate fixation. During a 6-year period, 80 patients were surgically treated with a single-level anterior cervical discectomy. Forty-four patients had cervical plates, whereas 36 had fusions without plates (average follow-up, 2.3 years). The pseudarthrosis rates were 4.5% (2 of 44) for patients with plating and 8.3% (3 of 36) without plating. This difference was not significant (p = 0.653). There was no correlation of pseudarthrosis with sex, age, level of surgery, history of tobacco use, or the presence of previous anterior surgery. The amount of graft collapse for patients with plating was 0.75 mm compared with 1.5 mm for those without a plate (p = 0.026). The amount of kyphotic deformity of the fused segment was 1.2 degrees with plating compared with 1.9 degrees for patients without plating (p = 0.079). Ninety-one percent of the patients with plating had good or excellent results compared with 88% in the group without cervical plates, based on Odoms criteria. The addition of plate fixation for single-level anterior cervical discectomy and fusion is safe and not associated with a significant increase in complication rates. The pseudarthrosis rates are not significantly different when a cervical plate is used.

Experimental spinal fusion with recombinant human bone morphogenetic protein-2 without decortication of osseous elements

Study Design. L4-L5 intertransverse process fusions were produced with 58 μg, 230 μg, or 920 μg of recombinant human bone morphogenetic protein-2 in 20 dogs. Eleven had traditional decortication of posterior elements before insertion of the implant. Nine were left undecorticated. All animals were evaluated 3 months after surgery. Objectives. To determine whether decortication is a prerequisite for successful fusion in the presence of osteoinductive proteins such as bone morphogenetic protein-2. Summary of Background Data. Recombinant osteoinductive proteins can induce de novo bone in ectopic soft-tissue sites in the absence of bone marrow elements. Traditional methods for achieving spinal fusion rely on exposure of bone marrow through decortication to facilitate osteogenesis. It is hypothesized that the presence of an implanted osteoinductive protein obviates the need for exposure and release of host inductive factors. Methods. Recombinant human bone morphogenetic protein-2-induced intertransverse process fusions were performed with and without decortication. Fusion sites were evaluated by computed tomography imaging, high-resolution radiography, manual testing, mechanical testing, and histologic analysis. Results. One hundred percent of decorticated spines and 89% of undecorticated spines were clinically fused by 3 months. Ninety-one percent of decorticated spines and 78% of undecorticated specimens exhibited bilateral transverse process osseous bridging. The only spines that failed to achieve solid bilateral arthrodesis were in the lowest dose group. With the higher two doses, there was histologic evidence of osseous continuity between the fusion mass and undecorticated transverse processes. Conclusions. There were no statistical differences in clinical and radiographic fusion rates between decorticated and undecorticated sites. With higher doses of recombinant human bone morphogenetic protein-2, there was little histologic distinction between fusions in decorticated versus undecorticated spines.