Muscle Density and Bone Quality of the Distal Lower Extremity Among Individuals with Chronic Spinal Cord Injury

Top Spinal Cord Inj Rehabil, 2015 · DOI: 10.1310/sci2104-282 · Published: January 1, 2015

Spinal Cord Injury Musculoskeletal Medicine

Simple Explanation

This study looks at the connection between muscle density and bone health in people with long-term spinal cord injuries (SCI). It's known that SCI can lead to muscle loss and changes in bone density, but this research digs deeper into how muscle quality (density) relates to bone quality in the lower legs. Using special scans, the researchers measured muscle density and bone quality in the lower legs of adults with SCI. They wanted to see if there was a link between how dense the muscles were and how strong the bones were. The study found that denser muscles were linked to better bone quality in certain areas of the lower leg. This suggests that maintaining muscle quality could be important for keeping bones healthy after a spinal cord injury.

Study Duration

Not specified

Participants

70 adults with chronic SCI (C2-T12; American Spinal Injury Association Impairment Scale [AIS] A-D; ≥2 years post injury).

Evidence Level

Level 3; Secondary data analysis from a prospective, observational cohort study

Key Findings

1
Muscle density was positively associated with trabecular vBMD, cortical thickness, and cortical vBMD.
2
Muscle CSA was most strongly associated with CtAr and PMI.
3
cLEMS was most strongly associated with TbBMD.

Research Summary

This study examined the associations between muscle density and indices of bone quality at the distal lower extremity of adults with chronic SCI. Muscle density and function were most strongly associated with TbBMD at the distal tibia in adults with chronic SCI, whereas muscle size was most strongly associated with bone size and geometry at the tibial shaft. The findings suggest that lower muscle density or fatty infiltration at the calf is linked to lower vBMD at the distal lower extremity among individuals with chronic SCI.

Practical Implications

Rehabilitation targets

Muscle size and function may represent therapeutic targets for preventing bone loss and attenuating fracture risk following SCI, in addition to being related to glucose metabolism and muscle strength.

Intervention strategies

Future research should examine the effect of therapeutic interventions (eg, electrical stimulation, vibration, resistance training) targeting muscle density, size, and function on longitudinal changes in tibial vBMD and bone microarchitecture and fracture risk after chronic SCI.

Understanding Muscle-Bone Relationships

The study contributes to a growing body of research on the muscle-bone unit theory under conditions of disuse and neurological impairment and provides data on the contributions of muscle density to bone quality indices at the tibia.

Study Limitations

1
The cohort with chronic SCI included a large proportion of individuals who were 15 years or more post injury.
2
The findings regarding muscle-bone associations may be influenced by the active or remote exposure to bisphosphonate therapy in our participants with chronic SCI.
3
The nature of the cross-sectional design limits our ability to make causal inferences from the data regarding the muscle-bone unit theory in response to SCI.

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