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

The Journal of Spinal Cord Medicine, 2020 · DOI: 10.1080/10790268.2019.1669957 · Published: October 1, 2020

Spinal Cord Injury Musculoskeletal Medicine

Simple Explanation

This study investigates the relationship between bone density measurements at the hip and knee in people with spinal cord injury (SCI). People with SCI often experience bone loss below the level of their injury, increasing their risk of fractures. The researchers aimed to determine if hip T-scores, a common measure of bone density, could predict bone density at the distal femur (DF) and proximal tibia (PT), two knee locations vulnerable to fractures in individuals with SCI. The study found a moderate correlation but also significant inaccuracies, suggesting direct knee bone density measurements are preferable when assessing fracture risk in SCI patients before prescribing weight-bearing activities.

Study Duration

Not specified

Participants

105 unique individuals with SCI

Evidence Level

Level 3; Retrospective analysis

Key Findings

1
aBMD at the DF and PT regions were significant predictors of T-score 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).
2
Using the DF and PT aBMD of 0.60 g/cm2 to designate heightened risk of fracture, the predicted T-score was −3.1 and −3.5 at the TH and −2.6 and −2.9 at the FN.
3
when the predicted and observed T-score values are 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

Research Summary

This study aimed 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) in persons with SCI. The aBMD at the DF and PT regions were predictors of T-scores at the TH and FN. 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. 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.

Practical Implications

Clinical Assessment

Direct measurement of knee aBMD in persons with SCI should be performed whenever possible.

Rehabilitation Strategies

Assessment should occur prior to prescribing weight bearing upright activities, such as robotic exoskeletal-assisted walking.

Fracture Risk

The findings highlight the importance of accurately assessing fracture risk in SCI patients.

Study Limitations

1
Information describing the level of physical activity, smoking history, alcohol consumption, fracture history, spasticity, vitamin D concentrations, calcium intake, and medication history was not available
2
the use of DXA methodology did not permit measurement of trabecular and cortical vBMD of the hip and knee regions.
3
The absence of standardized protocols to acquire aBMD at the distal femur and proximal tibia is a major source of the variability between values reported by investigators.

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