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PRODUCED BY AND FOR MEMBERS OF THE DEPARTMENT OF SURGERY February 2013 | Archived Issues

Spine Center Starts Year with New Trial, Publications

The surgeons, specialists and researchers at the Cedars-Sinai Spine Center have started the year with a new trial and several recent publications.

Study on Electric Current Stimulation in Disc Repair

One of the holy grails of spine tissue engineering is intervertebral disc tissue injury repair. After several injection trials of growth factors or stem cells, Hyun Bae, MD, will head up new study on electric current stimulation (Biomet study) to repair small cracks in the disc and possibly regenerate it. This treatment is not invasive; it looks similar to the electrical bone stimulator).

Surgeons and medical specialists at the Spine Center will soon begin enrollment in this a multicenter trial approved by the Food and Drug Administration. To find out more information or refer patients, please contact Linda Kanim or Annie Sharabidze at (310) 248-7326 or the Spine Center at (310) 248-7300. (Investigators: Hyun W. Bae, MD (PI), Rick Delamarter, MD, Michael A. Kropf, MD, Timothy Davis, MD, Theodore Goldstein, MD, Howard Rosner, MD, Resa Oshiro, MD, Patrick Rhoten, MD, Roy Nini, MD, Avrom Gart, MD)

Study of Disc Replacement vs. ACDF

Cedars Sinai Spine Center surgeons Rick B. Delamarter, MD, Michael A. Kropf, MD, and Hyun W. Bae, MD, are conducting long-term follow-up of cervical spine patients who participated in a multicenter clinical trial (US-RCT IDE) study of artificial disc replacement versus anterior cervical discectomy and fusion (ACDF). The five-year, most recent results from this study were published in February 2013 in the journal Spine.

This trial includes patients' self-reported outcomes after ProDisc-C compared to ACDF through five years after surgery and demonstrates that the ProDisc-C continues to be a safe and effective surgical treatment for patients with disabling single-level cervical radiculopathy that is refractory to conservative treatment. This study provides level I data with baseline patient characteristics well balanced between the experimental and comparison treatment group and the excellent follow-up rates for ProDisc-C and ACDF (98 percent and 96 percent at two years, and 73 percent and 64 percent at five years).

For all patients, there was a statistically and clinically significant improvement at two and five years compared with pre-operative values (baseline). At five years, ProDisc-C patients had statistically significantly less neck pain intensity and frequency. All patients were satisfied (VAS satisfaction 10 cm) at five years, with ProDisc-C 86.56 and ACDF 82.74. There were no reports of device failures or implant migration with ProDisc-C. The ProDisc-C patients maintained motion at their index level.

At five years, the ProDisc-C patients had a statistically significantly lower rate of reoperation compared with ACDF patients (2.9 percent vs. 11.3 percent). At five years after surgery, ProDisc-C total disc replacement is a safe and effective treatment of single-level symptomatic cervical disc disease. Clinical outcomes were comparable with ACDF. ProDisc-C patients maintained motion at the index level and had significantly less neck pain intensity and frequency as well as a lower probability of secondary surgery. (Zigler JE, Delamarter RB, Murrey D, Spivak J, Janssen M: ProDisc-C and Anterior Cervical Discectomy and Fusion as Surgical Treatment for Single-Level Cervical Symptomatic Degenerative Disc Disease: Five-Year Results of a Food and Drug Administration Study. Spine (Phila Pa 1976). 2013 Feb 1;38(3):203-9. doi: 10.1097/BRS.0b013e318278eb38.; Delamarter RB , Zigler JE: Five-year reoperation rates, cervical total disc replacement versus fusion, results of a prospective randomized clinical trial Spine 2013)

Evaluation of Disc Replacement Devices

Another ongoing, multicenter FDA-approved RCT study at the Spine Center is evaluating two total disc replacement devices, Freedom Disc (Axiomed) versus ProDisc-L (Synthes-DePuy), for patients who were treated for degenerative disc disease of the lumbar spine. Michael Kropf, Alexander Rasouli, Hyun Bae and Rick Delamarter have completed enrollment, surgeries and two-year follow-up on these patients.

Self-assessments of VAS back pain, VAS leg pain and ODI were significantly improved from preoperative levels over the follow-up period to 24 months (p<0.0001) for patients treated using either device (ADR-F and ADR-P). There was slightly greater earlier reduction in back pain, as measured by the VAS back pain scale, for patients treated with ADR-F compared to ADR-P (six weeks: 2.6 vs. 4.2, p< 0.03; three months: 2.3 vs 4.0; six months: 1.5 vs. 3.7). Similarly, there was 40 percent to 60 percent improvement in ODI scores for ADR-F-treated patients and 38 percent to 60 percent improvement reported by ADR-P-treated patients.

Improvements (preoperative to follow-up) were significant and maintained to 24 months (all comparisons p<0.0001 for both ADR-F and ADR-P); ADR-F patients reported statistically significantly less disability than ADR-P patients at six months (p<0.001). Motion was observed at the disc replacement level.

Follow-up out to five years has just started for these patients, and this longer-term follow-up will reveal if viscoelastic core motion characteristic of the ADR-F device will translate to decreased adjacent segment degeneration.

Study of the Use of Spinal Fusion

Rajaee SS, Bae HW, Kanim LEA, Delamarter RB. Spinal fusion in the United States: analysis of trends from 1998 to 2008. Spine (Phila Pa 1976). 2012;37:67-76. To better understand the frequency of revision spinal fusion and primary spinal fusions performed annually in the U.S. our research group Rajaee, SS; Kanim, LEA; and Bae, H, performed an analysis and presented "The National Burden of Revision Spinal Fusion: A Focus on Patient Characteristics and Complications." The study related that the national trend in revision spinal fusion is increasing along with the frequency of fusion surgery, while adjusting for increases in the U.S. population.

This study presented a comparison of co-morbidities, inpatient complications and surgical factors in revision spinal fusion compared to primary fusion using a nationwide inpatient sample (NIS). It presented a retrospective comparative cohort analysis design for revision surgery versus primary spinal fusion from 2002 to 2009. Refusions represented 5.1 percent of the total number of annual fusions performed; the figure was 5.3 percent in 2002). From 2002 to 2009, primary fusions increased at a higher rate than refusions (56.4 percent vs 51.0 percent) (p<0.05). Length of stay and hospital charges were higher for refusion discharges (4.2 days vs. 3.8 days , p<0.0001; $91,909 vs. $87,161, p<0.0001).

In 2009, rhBMP-2 (Infuse) was used more in refusion cases than in primary cases (39.7 percent vs. 27.6 percent), while interbody devices were used less in refusion cases (41.7 percent vs. 56.4 percent) (p<0.05). In the multiple variable logistic regression model for all spinal fusions, depression (odds ratio, 1.53; p <0.0001), psychotic disorders (odds ratio, 1.49; p <0.0001), deficiency anemias (odds ratio, 1.35; p <0.0001) and smoking (odds ratio, 1.10; p < 0.01), occurred more frequently in revision spinal fusion discharges, adjusting for other variables.

In regard to complications, dural tears (odds ratio, 1.41; p<0.0001), surgical site infections (odds ratio, 3.40; p<0.0001) and wound dehiscence (odds ratio, 2.30; p<0.05) were more commonly reported in refusion discharges, adjusting for other variables. The most common primary diagnosis was ICD9 996.49 (mechanical complication of internal orthopedic device, implant and graft) for cervical, thoracic and lumbar refusion.

In summary, the study found that the national refusion rate has increased at a lower rate than primary fusions from 2002 to 2009. Length of stay and hospital charges were higher for refusions, while inpatient mortality was less. Co-morbidities of depression, psychotic disorders, tobacco use and deficiency anemias were more common in spinal refusion discharges compared to primary fusion discharges. Trans. Orthopaedics Research Society. 2013; 1654.

Work presented in January 2013 in the Orthopaedic Research Society (ORS 2013) included:

  • Bedi H (spine fellow at the Spine Center), Goomer R, Kanim LEA, Delamarter RB, Bae HW: "Novel Growth-Factor Loaded Controlled-Release Scaffolds Induce Dose-Dependent L4-L5 Spinal Fusion." Trans. Orthopaedic Research Society. 2013;38:1652
  • Melodie Metzger, PhD (Biomechanics-Spine Center), LEA Kanim, Li Zhao, PhD, Samuel T Robinson, Zorica Buser, PhD, Rick Delamarter, MD: "The Relationship Between Serum Vitamin D levels, Successful Fusion, and Fusion Strength: A Quantitative Analysis." Trans. Orthopaedics Research Society. 2013;0852
  • Buser, Z; Thang, C; Safai, Y; Kanim, L; Zhao, L; Delamarter, RB: Stem cell injection suppresses apoptosis in rat spinal cord injury model Trans. Orthopaedics Research Society. 2013; 0796

Projects ongoing by Spine Center research team:

  • Melodie Metzger, PhD, LEA Kanim, Li Zhao, PhD, Samuel T Robinson, Zorica Buser, PhD, Rick Delamarter, MD. "The Relationship Between Serum Vitamin D levels, Successful Fusion, and Fusion Strength: A Quantitative Analysis"
  • Samuel T Robinson, Rick B Delamarter, MD, Mark T Svet, Melodie F Metzger, PhD. "Does Sacral Geometry Affect Biomechanical Bahavior and Facet Forces after Total Disc Replacement at the Lumbosacral Junction?"
  • Samuel T Robinson, Mark T Svet, Melodie F Metzger, PhD. "Four-Point Bending in Flexion as a Method for Quantitatively Assessing Spinal Fusions."
  • Mark T Svet, Samuel T Robinson, Rick B Delamarter, MD, FL Acosta, DG Drazin, MD, Melodie F Metzger, PhD. "Biomechanical Analysis of the Effect of Different Instrumentation Techniques on Adjacent Level Stability After Long Segment Instrumentation of the Thoracic Spine."
  • Zorica Buser, PhD, Li Zhao, PhD, Yalda Safai, Linda E A Kanim, Rick B. Delamarter, MD, Alexander Rasouli, MD: "Inflammatory response after spinal cord injury in rats is modified by Enbrel."
  • Zorica Buser, PhD, Christopher Buser, PhD, Rick B. Delamarter, MD. "Differentiation of adipose stem cell constructs for intervertebral disc regeneration."
  • Hyun W. Bae, MD, assisted the team of Dmitriy Sheyn, PhD, Wafa Tawackoli, PhD, Deuk Soo Jun, MD, Young Do Koh, PhD, Xiaoyu Da, Susan Su, PhD, Zulma Gazit, PhD, Gadi Pelled, PhD, DMD, and Dan Gazit, PhD, DMD, for "Systemic treatment for multiple lumbar bone defects using combined human MSCs and PTH therapy."