Previous research involving cluster analysis of Minnesota Multiphasic Personality Inventory (MMPI) profiles among persons with chronic low back pain has suggested the existence of four distinct profile clusters. The present study had two goals: (1) to replicate the previous finding independently and (2) to investigate the relationship of the profiles to the subjects' self-reported pain history and response to treatment. Subjects were 92 patients in a multimodal inpatient low back-pain treatment program. A cluster analysis of the MMPI profiles was performed and the resultant clusters were compared in terms of histories and treatment outcome. The four clusters were successfully replicated for the total sample and for males and females separately. The profiles were significantly related to subjects' pain histories, but only one outcome difference was found. It was inferred that the MMPI is of value in understanding patients' pain coping behaviors but that further research is needed to explore the utility of the MMPI in understanding their response to treatment.

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The osteoconductive capacity of fibrillar collagen-biphasic calcium phosphate composition was compared to autogenous bone in a canine spinal fusion model. All animals underwent a standard intervertebral body fusion (L2-L4) with rigid internal fixation and received either autogenous bone alone or a mixture of the ceramic and autogenous bone (3:1) as the graft material. Animals were followed for 12 months and the quality of fusion in each animal assessed by biomechanical testing and histological analysis. The fused L2-L4 segment of each dog was embedded in bone cement and mounted in a specially designed mechanical tester for testing in flexion, extension, and side bending. Overall, the mean rigidity of the fusion mass was not significantly different between the two groups [10.5 +/- 4.1 (SD) for autogenous bone vs. 11.3 +/- 1.7 for the ceramic plus autogenous bone, p greater than 0.05]. Similar findings were obtained for mean bending moment, compressive load, angular deformation, and energy absorbed for the two groups. Histological analysis was performed on transverse nondecalcified specimens. Quantitation of bone ingrowth using back-scattered electron imaging disclosed no significant differences in the amount of new bone formed at the graft site between autogenous bone and the ceramic plus autogenous bone recipients (23.4 +/- 10% vs. 25.8 +/- 8.8%) when correction for the autogenous bone volumes was performed. Light microscopic analysis of toluidine blue-stained transverse sections demonstrated new bone growth around and through the ceramic bone graft material. These results suggest that use of a collagen-biphasic calcium phosphate ceramic and autogenous bone mixture (3:1) provides a suitable osteoconductive alternative to the use of autogenous bone and results in the formation of a mechanically competent fusion mass not significantly different from that obtained with autogenous bone alone.

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