Reliability of Tuffier's line as an anatomic landmark.

STUDY DESIGN: The level of Tuffier's line was assessed on 200 standing and 60 prone lumbar radiographs. Sex, height, weight, and body mass index (BMI) were correlated with the radiograph findings.

OBJECTIVE: To determine whether the level of Tuffier's line is associated with sex, height, weight, or BMI.

SUMMARY OF BACKGROUND DATA: Tuffier's line (intercristal line) is a commonly used landmark for identification of the L4-L5 interspace; however, multiple studies have identified that this landmark is unreliable.

METHODS: The level of Tuffier's line was assessed retrospectively on 200 standing anteroposterior lumbar radiographs and correlated with sex. Prospectively, the level of Tuffier's line was assessed on 60 prone posteroanterior lumbar radiographs and correlated with sex, height, weight, and BMI.

RESULTS: In men, the intercristal line most often intersected the L4 body or inferior endplate. In women, the intercristal line most often intersected the L5 body or superior endplate. Weight and BMI had no correlation with Tuffier's line. Subjects with a Tuffier's line through L4 were taller than those with a Tuffier's line through L5.

CONCLUSION: Tuffier's line demonstrated predictable sex-related differences: men had an intercristal line that most often intersected the L4 body or inferior endplate whereas the women's intercristal line most often intersected the L5 body or superior endplate. However, because the actual level of Tuffier's line may vary from the L4 body to the L5 body, the intercristal line is insufficient to use as the sole landmark for assessing spinal segmental level.