Relationships between T-scores at the hip and bone mineral density at the distal femur and proximal tibia in persons with spinal cord injury.

Objective

To identify T-score values at the total hip (TH) and femoral neck (FN) that correspond to the cutoff value of <0.60 g/cm2 for heightened risk of fracture at the distal femur (DF) and proximal tibia (PT).

Design

Retrospective analysis of data in a research center's database.

Setting

Community-based individuals with spinal cord injury (SCI).

Participants

105 unique individuals with SCI. Outcome Measurements: DXA derived areal BMD (aBMD) and T-score of the DF, PT, TH, and FN.

Results

The aBMD at the DF and PT regions were predictors of T-scores at the TH (R2 = 0.63, P < 0.001 and R2 = 0.65, P < 0.001) and FN (R2 = 0.55, P < 0.001 and R2 = 0.58, P < 0.001). Using the DF and PT aBMD of 0.60 g/cm2 as a value below which fractures were more likely to occur, the predicted T-score was -3.1 and -3.5 at the TH and -2.6 and -2.9 at the FN, respectively. However, when the predicted and observed T-score values disagree outside the 95% limit of agreement, the predicted T-score values are lower than the measured T-score values, overestimating the measured values between -2.0 and -4.0 SD.

Conclusion

The DF and PT cutoff value for aBMD of 0.60 g/cm2 was a moderate predictor of T-score values at the TH and FN, with considerable inaccuracies outside the clinically acceptable limits of agreement. As such, the direct measurement of knee aBMD in persons with SCI should be performed, whenever possible, prior to prescribing weight bearing upright activities, such as robotic exoskeletal-assisted walking.