Bone mineral densities of the vertebral body and intertransverse fusion mass after instrumented intertransverse process fusion.
METHODS
We used dual-energy x-ray absorptiometry to examine the bone mineral densities (BMDs) of the vertebral bodies at the fused level (the fused vertebral BMDs), at the unfused level (the unfused vertebral BMDs), and the intertransverse fusion mass (the fusion mass BMD) after instrumented intertransverse process fusion.


OBJECTIVE
We wanted to determine whether there are any relationships among the unfused vertebral BMDs, the fused vertebral BMD, and the fusion mass BMD after successful solid union.


BACKGROUND
Device-related vertebral osteoporosis is a well-known phenomenon that occurs in an early adaptive phase after instrumented spinal fusion. However, any relationships among the unfused vertebral BMDs, the fused vertebral BMD, and the fusion mass BMD in a later phase after obtaining successful spinal union are unknown.


METHODS
This study included 17 female patients, who had a solid union after instrumented intertransverse process fusion at the L4-L5 level. The average patient age at the time of this study was 54 years (range: 46-69 years). The vertebral BMDs at the fused level (L4), the vertebral BMDs at the unfused levels (L1-L3), and the fusion mass BMD were measured at a mean follow-up period of 42 months (range: 24-131 months) after surgery. The reciprocal correlations among the vertebral BMDs and the fusion mass BMD were analyzed. RESULTS.: The vertebral BMDs (g/cm) at the fused level (L4), the unfused level (L1-L3), and the fusion mass BMD were 0.84 ± 0.27, 0.72 ± 0.23, 0.56 ± 0.19, 0.58 ± 0.21, and 0.54 ± 0.16, respectively. There were significant reciprocal correlations among the vertebral BMDs at the fused and unfused level. However, the fusion mass BMD had no significant correlations with any of the vertebral BMDs.


CONCLUSIONS
The vertebral bodies at the fused level may undergo osteoporosis in a pattern similar to what naturally occurs in the vertebral bodies at the unfused level. However, the fusion mass BMD seems to be influenced by bone remodeling mechanisms that are different from those that influence the vertebral bodies.
Lee
Jun-Seok
JS
Department of Orthopedic Surgery, Dongshin General Hospital, Seoul, Korea.
Kim
Ki-Won
KW
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density / Q000502:physiology*; D005260:Female; D006801:Humans; D016268:Internal Fixators / Q000009:adverse effects* / Q000592:standards; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology; D019919:Prosthesis Implantation / Q000009:adverse effects* / Q000295:instrumentation / Q000379:methods; D011859:Radiography; D013123:Spinal Fusion / Q000009:adverse effects* / Q000295:instrumentation / Q000379:methods; D013131:Spine / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery*; D055815:Young Adult