Strengths and limitations of International Classification of Disease Ninth Revision Clinical Modification codes in defining cervical spine surgery.

STUDY DESIGN: Retrospective study.

OBJECTIVE: To evaluate the sensitivity and specificity of International Classification of Disease Ninth Revision Clinical Modification (ICD9-CM) hospital discharge codes to define degenerative cervical spine surgery in comparison to patient operative notes in the medical record.

SUMMARY OF BACKGROUND DATA: Population-based studies of spine surgery have often relied on administrative databases as a primary information source, but little is known about the validity of using ICD9-CM codes to identify these operations.

METHODS: We performed a retrospective study comparing ICD9-CM billing codes to patient operative notes, the gold standard, for patients undergoing spine surgery in 2006 at a single academic center.

RESULTS: We identified 1090 procedures of which 265 were categorized as cervical spine surgery for degenerative indications based on the operative notes. Compared to operative notes, our ICD9-CM algorithm had high sensitivity and specificity for selecting surgery at the cervical spine level and cervical spine surgery for degenerative indications. Categorization of cases by procedure had high sensitivity and specificity for fusion and surgical approach (>95%). Categorization of cases by primary diagnosis was generally less accurate. Cervical spondylosis with myelopathy was the most sensitive primary diagnosis. Categorization of cases by procedure had high sensitivity and specificity for fusion and surgical approach (≥96%). However, diagnoses such as herniated disc and procedures such as laminectomy had low sensitivity but high specificity.

CONCLUSION: The use of our ICD9-CM algorithm to define spine surgery at the cervical spine level, and degenerative cervical spine surgery is highly accurate. Although specific diagnoses codes are mostly insensitive, an ICD9-CM algorithm can be used to study these procedures with reasonable precision.