- Email: [email protected]
Saturday, November 2, 2001 3:29–4:12 pm Concurrent Session 7A: Lumbar Spine—Outcomes
90S
Proceedings of the NASS 17th Annual Meeting / The Spine Journal 2 (2002) 47S–128S
Saturday, November 2, 2001 3:29–4:12 pm Concurrent Session 7A: Lumbar Spine—Outcomes 3:29 Factors influencing return to work after single-level anterior lumbar interbody fusion for degenerative disc disease Matthew F. Gornet, MD1, George Frey, MD2, Thomas A. Zdeblick, MD3, Surgical Interbody Research Group1; 1Missouri Bone and Joint Center, St. Louis, MO, USA; 2Englewood, CO, USA; 3University of Wisconsin Orthopedics, Madison, WI, USA Purpose of study: Return to work is an important measurement of treatment outcomes after spinal fusion. This large prospective, multicenter study identifies demographic and procedural factors and preoperative measures that may have influenced patients’ return to work. Methods used: This cohort includes 413 patients with single-level lumbar disc degeneration who failed at least 6 months of nonoperative treatment. Patients were on average 42.7 years old, 87.9% Caucasian, 49.0% male, 32.9% smokers, 32.9% seeking workers compensation. Two investigational groups received recombinant human bone morphogenic protein (rhBMP)-2 on a collagen sponge carrier with a tapered cylindrical cage (InFuse Bone Graft/LT-CAGE; Medtronic Sofamor Danek, Minneapolis, MN) either placed through open anterior lumbar interbody fusion (ALIF; n143) or through laproscopic ALIF approach (n134). A control group (n136) was treated with crest autograft using the same tapered metal cage through open ALIF. Data collected included preoperative work status, workers compensation status and various demographic data: age, sex, race, height, weight, marital status, education, litigation status, preoperative tobacco and alcohol use and medication use including narcotics. Additional data included Oswestry Short Form (SF)-36, back and leg pain scores, preoperative neurological score, treatment level and operative approach. In total, 26 demographic variables and preoperative measurements were considered potential covariates. Regression analyses were conducted using both 12 and 24 months as endpoints. However, to investigate variables associated with patients who return to work more quickly, the more powerful SAS procedure PHREG was used (time-to-event analysis) based on the Cox proportional hazards model. Finally, data were analyzed to look for salient information about areas of specific interest, such as workers compensation and preoperative work status. Summary of findings: Of 413 patients, 188 (45.5%) were working before surgery and 136 (32.9%) were seeking workers compensation. Of the workers compensation patients, 23.5% (32 of 136) were working preoperatively, whereas 56.3% (156 of 277) of noncompensation patients were working before surgery. At 24 months after surgery, 204 of 231 patients (63.6%) were working, including 135 of 153 patients (88.2%) who were working before surgery. Of these patients, 80.0% (20 of 25) of workers compensation patients and 86.5% (115 of 128) of noncompensation patients were working before surgery. The time-to-event analysis for “days to return to work” suggests that patients who are younger, Caucasian, working before surgery, not receiving workers compensation, with relatively higher preoperative weight, higher preoperative neurological score and having had a transperitoneal surgical approach tend to go back to work faster. The regression analysis at 24 months suggested a similar profile for return to work. Relationship between findings and existing knowledge: This is one of the largest prospective studies to collect return-to-work information after spine fusion. The analysis presents new learning regarding preoperative variables that may influence return to work. Overall significance of findings: Results demonstrate that preoperative work status is an important variable for return to work in both workers compensation and noncompensation patients. Choice of surgical procedure may increase rate of return to work, but this requires additional investigation into potential offsets in overall treatment outcomes. The profile of a spinal fusion patient developed in the days-to-return-to-work regression
analysis is interesting in particular for highlighting that working preoperatively and not receiving workers compensation are characteristics of patients who are quicker to return to work. Disclosures: Device or drug: LT-CAGE; Status: approved. Device or drug: InFuse Bone Graft; Status: investigational. Conflict of interest: No conflicts. PII: S1529-9430(02)00354-6
3:35 Demographic influences on the outcome of spinal fusion Stephen Faust, MD1, Thomas Ducker, MD2, David Hatef, MD3; 1Orthopaedic and Sports Medicine Center, Annapolis, MD, USA; 2Annapolis Neurosurgery, Annapolis, MD, USA; 3University of Maryland, College Park, MD, USA Purpose of study: To analyze the outcome of spinal fusion with respect to both surgical and nonmedical variables. Methods used: The first 82 patients treated at our institution with a combined posterior lumbar interbody fusion/bilateral lateral fusion/pedicle screw instrumentation technique were retrospectively studied. Sixty-nine (84%) of the patients were located, with results evaluated by a structured telephone interview by an investigator not involved with the surgery (DH). Results were analyzed with respect to numbers of levels operated on, presence or absence of previous surgery at these levels, success of fusion, smoking history, involvement with the workmans compensation-legal system, education level obtained and gender. Both univariate and multivariate stratifications were carried out. Summary of findings: Overall, 64% of patients were improved and satisfied. While the number of involved levels and the presence of previous surgery (the “surgical factors”) had effects on the results, the magnitude of these effects was overall much less than that of tobacco use, involvement with the workers compensation/legal system, educational level obtained and even gender (nonmedical factors). Only one patient failed to fuse, so pseudarthrosis was not a significant variable in the results. Patients with multilevel pathology did worse than those with single-level pathology (43.5% improved vs. 74%), as did patients with previous surgery at the same level (57% revision patients improved vs. 71% of primary patients, although among nonsmokers the results for primary and revision surgery were much closer, with 83% of primary patients and 73% of revision patients improved). Male patients had better results than female in all categories. Eighty-four percent of men but only 53% of women improved. No male but 19% of females felt themselves to be worsened by surgery. Even among college graduates (the best group), 100% of men and only 81% of women improved. Tobacco use, involvement with workers compensation or litigation and educational level below a college degree all had major negative effects on the outcome of surgery. The negative effects were additive, so that the worst results were obtained in smokers who were involved with workers compensation/litigation (only 14% improved) and smokers undergoing revision surgery (only 11% improved). Relationship between findings and existing knowledge: Previous studies have shown poorer results among patients who smoke or who are involved in the workers compensation/legal system. This study confirms those results and furthermore shows that smoking does not require pseudarthrosis to exert its negative effect. Furthermore, our study shows that gender and the level of education attained have important effects on the results of spinal fusion and that these effects are additive. The study also shows that the extent of pathology and a history of previous surgery on the same spinal segment have significant effects on outcome. Overall significance of findings: In our patients, demographic factors unrelated to anatomical or surgical considerations had important and even dominant influences on the outcome of spinal surgery. This suggests that some groups of patients may not benefit from even the most technically successful surgery. Disclosures: Device or drug: pedicle screws. Status: approved. Device of drug: sculptured interbody allografts. Status: approved. Conflict of interest: Stephen Faust, speaker’s bureau; Stephen Faust, other support; Thomas Ducker, speaker’s bureau; Thomas Ducker, grant from synthespine for outcomes research.
Proceedings of the NASS 17th Annual Meeting / The Spine Journal 2 (2002) 47S–128S
Saturday, November 2, 2001 3:29–4:12 pm Concurrent Session 7A: Lumbar Spine—Outcomes 3:29 Factors influencing return to work after single-level anterior lumbar interbody fusion for degenerative disc disease Matthew F. Gornet, MD1, George Frey, MD2, Thomas A. Zdeblick, MD3, Surgical Interbody Research Group1; 1Missouri Bone and Joint Center, St. Louis, MO, USA; 2Englewood, CO, USA; 3University of Wisconsin Orthopedics, Madison, WI, USA Purpose of study: Return to work is an important measurement of treatment outcomes after spinal fusion. This large prospective, multicenter study identifies demographic and procedural factors and preoperative measures that may have influenced patients’ return to work. Methods used: This cohort includes 413 patients with single-level lumbar disc degeneration who failed at least 6 months of nonoperative treatment. Patients were on average 42.7 years old, 87.9% Caucasian, 49.0% male, 32.9% smokers, 32.9% seeking workers compensation. Two investigational groups received recombinant human bone morphogenic protein (rhBMP)-2 on a collagen sponge carrier with a tapered cylindrical cage (InFuse Bone Graft/LT-CAGE; Medtronic Sofamor Danek, Minneapolis, MN) either placed through open anterior lumbar interbody fusion (ALIF; n143) or through laproscopic ALIF approach (n134). A control group (n136) was treated with crest autograft using the same tapered metal cage through open ALIF. Data collected included preoperative work status, workers compensation status and various demographic data: age, sex, race, height, weight, marital status, education, litigation status, preoperative tobacco and alcohol use and medication use including narcotics. Additional data included Oswestry Short Form (SF)-36, back and leg pain scores, preoperative neurological score, treatment level and operative approach. In total, 26 demographic variables and preoperative measurements were considered potential covariates. Regression analyses were conducted using both 12 and 24 months as endpoints. However, to investigate variables associated with patients who return to work more quickly, the more powerful SAS procedure PHREG was used (time-to-event analysis) based on the Cox proportional hazards model. Finally, data were analyzed to look for salient information about areas of specific interest, such as workers compensation and preoperative work status. Summary of findings: Of 413 patients, 188 (45.5%) were working before surgery and 136 (32.9%) were seeking workers compensation. Of the workers compensation patients, 23.5% (32 of 136) were working preoperatively, whereas 56.3% (156 of 277) of noncompensation patients were working before surgery. At 24 months after surgery, 204 of 231 patients (63.6%) were working, including 135 of 153 patients (88.2%) who were working before surgery. Of these patients, 80.0% (20 of 25) of workers compensation patients and 86.5% (115 of 128) of noncompensation patients were working before surgery. The time-to-event analysis for “days to return to work” suggests that patients who are younger, Caucasian, working before surgery, not receiving workers compensation, with relatively higher preoperative weight, higher preoperative neurological score and having had a transperitoneal surgical approach tend to go back to work faster. The regression analysis at 24 months suggested a similar profile for return to work. Relationship between findings and existing knowledge: This is one of the largest prospective studies to collect return-to-work information after spine fusion. The analysis presents new learning regarding preoperative variables that may influence return to work. Overall significance of findings: Results demonstrate that preoperative work status is an important variable for return to work in both workers compensation and noncompensation patients. Choice of surgical procedure may increase rate of return to work, but this requires additional investigation into potential offsets in overall treatment outcomes. The profile of a spinal fusion patient developed in the days-to-return-to-work regression
analysis is interesting in particular for highlighting that working preoperatively and not receiving workers compensation are characteristics of patients who are quicker to return to work. Disclosures: Device or drug: LT-CAGE; Status: approved. Device or drug: InFuse Bone Graft; Status: investigational. Conflict of interest: No conflicts. PII: S1529-9430(02)00354-6
3:35 Demographic influences on the outcome of spinal fusion Stephen Faust, MD1, Thomas Ducker, MD2, David Hatef, MD3; 1Orthopaedic and Sports Medicine Center, Annapolis, MD, USA; 2Annapolis Neurosurgery, Annapolis, MD, USA; 3University of Maryland, College Park, MD, USA Purpose of study: To analyze the outcome of spinal fusion with respect to both surgical and nonmedical variables. Methods used: The first 82 patients treated at our institution with a combined posterior lumbar interbody fusion/bilateral lateral fusion/pedicle screw instrumentation technique were retrospectively studied. Sixty-nine (84%) of the patients were located, with results evaluated by a structured telephone interview by an investigator not involved with the surgery (DH). Results were analyzed with respect to numbers of levels operated on, presence or absence of previous surgery at these levels, success of fusion, smoking history, involvement with the workmans compensation-legal system, education level obtained and gender. Both univariate and multivariate stratifications were carried out. Summary of findings: Overall, 64% of patients were improved and satisfied. While the number of involved levels and the presence of previous surgery (the “surgical factors”) had effects on the results, the magnitude of these effects was overall much less than that of tobacco use, involvement with the workers compensation/legal system, educational level obtained and even gender (nonmedical factors). Only one patient failed to fuse, so pseudarthrosis was not a significant variable in the results. Patients with multilevel pathology did worse than those with single-level pathology (43.5% improved vs. 74%), as did patients with previous surgery at the same level (57% revision patients improved vs. 71% of primary patients, although among nonsmokers the results for primary and revision surgery were much closer, with 83% of primary patients and 73% of revision patients improved). Male patients had better results than female in all categories. Eighty-four percent of men but only 53% of women improved. No male but 19% of females felt themselves to be worsened by surgery. Even among college graduates (the best group), 100% of men and only 81% of women improved. Tobacco use, involvement with workers compensation or litigation and educational level below a college degree all had major negative effects on the outcome of surgery. The negative effects were additive, so that the worst results were obtained in smokers who were involved with workers compensation/litigation (only 14% improved) and smokers undergoing revision surgery (only 11% improved). Relationship between findings and existing knowledge: Previous studies have shown poorer results among patients who smoke or who are involved in the workers compensation/legal system. This study confirms those results and furthermore shows that smoking does not require pseudarthrosis to exert its negative effect. Furthermore, our study shows that gender and the level of education attained have important effects on the results of spinal fusion and that these effects are additive. The study also shows that the extent of pathology and a history of previous surgery on the same spinal segment have significant effects on outcome. Overall significance of findings: In our patients, demographic factors unrelated to anatomical or surgical considerations had important and even dominant influences on the outcome of spinal surgery. This suggests that some groups of patients may not benefit from even the most technically successful surgery. Disclosures: Device or drug: pedicle screws. Status: approved. Device of drug: sculptured interbody allografts. Status: approved. Conflict of interest: Stephen Faust, speaker’s bureau; Stephen Faust, other support; Thomas Ducker, speaker’s bureau; Thomas Ducker, grant from synthespine for outcomes research.