Articles
Fracture threshold in the femur and tibia of people with spinal cord injury as determined by peripheral quantitative computed tomography

https://doi.org/10.1016/j.apmr.2004.09.006Get rights and content

Abstract

Eser P, Frotzler A, Zehnder Y, Denoth J. Fracture threshold in the femur and tibia of people with spinal cord injury as determined by peripheral quantitative computed tomography.

Objective

To determine bone traits of the femur and tibia with peripheral quantitative computed tomography (pQCT) that best distinguish between spinal cord injury (SCI) subjects with and without fractures.

Design

Cross-sectional study.

Setting

In- and outpatient paraplegic center in Switzerland.

Participants

Ninety-nine motor complete SCI subjects (duration of paralysis, 2mo–49y), 21 of whom had sustained fractures of the femur or tibia.

Interventions

Not applicable.

Main outcome measures

Subjects with SCI were questioned about the occurrence, location, and approximate date of fractures to their lower extremities. Trabecular and cortical bone mineral density (BMD), as well as bone geometric properties of distal epiphyses and midshafts of the femur and tibia, were measured by pQCT.

Results

Trabecular BMD of the femur and tibia distal epiphyses was found to distinguish best subjects with fractures from those without. Fractures occurred in subjects with trabecular BMD of less than 114mg/cm3 and less than 72mg/cm3 for the femoral and tibial distal epiphysis, respectively (corresponding to 46% and 29% of mean values of an able-bodied reference group). Approximately 50% of the subjects with chronic SCI (defined as time postinjury >5y for femur data and >7y for tibia data) had trabecular BMD values above the fracture threshold in the femur and about one third above the fracture threshold in the tibia.

Conclusions

By using pQCT, it may be possible to identify subjects with SCI who are at risk of sustaining fractures of the femur and tibia through minor trauma.

Section snippets

Participants

Subjects were recruited from among ambulatory patients seen at the Swiss Paraplegic Centre, Nottwil, and in-house patients participating in the 4-month study. Inclusion criteria were motor complete para- and tetraplegia (American Spinal Injury Association grades A and B) as a result of trauma and a minimum age of 18 years. Exclusion criteria were menopausal or postmenopausal status for women and medical conditions other than paralysis known to influence bone mineral metabolism. Patients meeting

Participants

There were 103 subjects in the study. Data from 99 subjects were included in the analysis; 4 subjects had to be excluded because of movement artifacts in the pQCT measurements caused by muscle spasms. Subject characteristics are shown in table 1.

In the 99 subjects, 99 tibia and 97 femur measurements were completed. Two femur measurements could not be completed because of difficulties in placing the limb in the gantry. Furthermore, of a total of 194 femur scans, 21 had to be excluded because of

Discussion

We found trabecular BMD of the epiphyses is the most sensitive parameter to differentiate between SCI patients at high or low risk of a fracture of the paralyzed lower extremities. Trabecular BMD is the parameter experiencing the most extensive loss: in the distal femur 54% was lost within the first 5 years after the SCI, and in the distal tibia 73% was lost within the first 7 years after injury.20 Thereafter, a new steady state was reached that showed the same intersubject variation as the

Conclusions

In this study, we have shown that volumetric trabecular BMD of the epiphyses of the lower extremities is the most sensitive bone parameter in determining a fracture threshold. Trabecular BMD can only be determined by QCT or pQCT. With DXA, the trabecular bone compartment cannot be separated from the thin cortical shell on the bone’s perimeter. Furthermore, areal BMD as measured by DXA is dependent on the exact positioning of the limb on bone size, and on the distribution and composition of soft

Acknowledgments

We gratefully acknowledge the help of Peter Wüseke from Stratec Medical, Pforzheim, Germany, for the programming of special software for some of our analyses. Hans Schiessl and Johannes Willnecker provided many helpful comments to the manuscript. The supportive collaboration of the Radiology Department of the Swiss Paraplegic Centre was invaluable.

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  • Cited by (0)

    Supported by the Swiss Paraplegic Foundation.

    No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit on the author(s) or on any organization with which the author(s) is/are associated.

    1

    Eser is currently affiliated with the Centre of Physical Activity and Nutrition Research, School of Health Sciences, Deakin University, Melbourne, Australia.

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