Predictors of serum chromium levels after stainless steel posterior spinal instrumentation for adolescent idiopathic scoliosis.
METHODS
Prospective cohort study.


OBJECTIVE
To determine the predictors of serum chromium levels after stainless steel posterior spinal instrumentation for adolescent idiopathic scoliosis.


BACKGROUND
Abnormally elevated serum chromium levels have been detected in patients with adolescent idiopathic scoliosis after stainless steel instrumentation. To date, the relationship among serum chromium levels, time of implantation, and implant characteristics (including surface area, rod length, numbers of hooks, screws, and cross connectors) has not been studied.


METHODS
Thirty patients with adolescent idiopathic scoliosis undergoing posterior instrumented spinal arthrodesis using stainless steel implants between 1998 and 2002 were prospectively studied. Serum chromium levels were measured between October 2006 and June 2007. Postoperative radiographs were used to measure rod lengths, number of hooks, screws, cross-connectors, and cables. The surface area of each component and the total surface area for each patient were calculated. Possible associations between serum chromium levels, time of implantation, and implant characteristics were investigated.


RESULTS
Implant exposure, whether expressed in the form of total metal implant surface area, rod length, or number of metal interfaces, was found to be positively associated with serum chromium levels. Specifically, chromium levels increased by a multiplicative factor of 1.0060 for every additional square centimeter of total metal implant surface area (P = 0.02). In addition, the chromium level was found to decrease by a multiplicative factor of 0.7766 for every additional year since surgery (P = 0.02).


CONCLUSIONS
After adjusting for the number of years since surgery, metal implant exposure is positively associated with elevated serum chromium levels in adolescent idiopathic scoliosis patients with stainless steel posterior spinal implants. This is the first study to identify statistically significant positive associations between specific spinal implant characteristics (other than corrosion identified by radiographs) and serum chromium levels.
Rackham
Matthew D
MD
Department of Orthopaedic Surgery, Women's and Children's Hospital, University of Adelaide, 72 King William Road, North Adelaide, SA 5006, Australia.
Cundy
Thomas P
TP
Antoniou
Georgia
G
Freeman
Brian J C
BJ
Sutherland
Leanne M
LM
Cundy
Peter J
PJ
D000293:Adolescent; D000704:Analysis of Variance; D001863:Bone Screws / Q000009:adverse effects*; D002648:Child; D002857:Chromium / Q000032:analysis / Q000097:blood*; D016208:Databases, Factual; D005260:Female; D006801:Humans; D016268:Internal Fixators / Q000009:adverse effects*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery; D008297:Male; D018579:Patient Selection; D011446:Prospective Studies; D011859:Radiography; D012600:Scoliosis / Q000097:blood / Q000000981:diagnostic imaging / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation*; D013193:Stainless Steel; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery
D002857:Chromium; D013193:Stainless Steel