Acute bone changes after lower limb amputation resulting from traumatic injury
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Bone health is critical for lower limb amputees, affecting their ability to use a prosthesis and their risk of osteoporosis. We found large losses in hip bone mineral density (BMD) and in amputated bone strength in the first year of prosthesis use, suggesting a need for load bearing interventions early post-amputation.
Large deficits in hip areal BMD (aBMD) and residual limb volumetric BMD (vBMD) occur after lower limb amputation; however, the time course of these bone quality changes is unknown. The purpose of this study was to quantify changes in the amputated bone that occur during the early stages post-amputation.
Eight traumatic unilateral amputees (23–53 years) were enrolled prior to surgery. Changes in total body, hip, and spine aBMD (dual-energy X-ray absorptiometry); in vBMD, stress-strain index (SSI), and muscle cross-sectional area (MCSA) (peripheral QCT); and in bone turnover markers were assessed after amputation prior to prosthesis fitting (pre-ambulatory) and at 6 and 12 months walking with prosthesis.
Hip aBMD of the amputated limb decreased 11–15%, which persisted through 12 months. The amputated bone had decreases (p < 0.01) in BMC (−26%), vBMD (−21%), and SSI (−25%) from pre-ambulatory to 6 months on a prosthesis, which was maintained between 6 and 12 months. There was a decrease (p < 0.05) in the proportion of bone >650 mg/cm3 (58 to 43% of total area) or >480 mg/cm3 (65% to 53%), suggesting an increase in cortical porosity after amputation. Bone alkaline phosphatase and sclerostin were elevated (p < 0.05) at pre-ambulatory and then decreased towards baseline. Bone resorption markers were highest at surgery and pre-ambulatory and then progressively decreased (p < 0.05).
Rapid and substantial losses in bone content and strength occur early after amputation and are not regained by 12 months of becoming ambulatory. Early post-amputation may be the most critical window for preventing bone loss.
KeywordsBone density Bone geometry Bone remodeling Prosthesis Trauma
This study was supported by a Department of Defense US Army Medical Research and Materiel Command Grant Award Number W81XWH-09-1-0641.
Compliance with ethical standards
This study was approved by the University of Oklahoma Health Sciences Center Institutional Review Board, and patients gave written informed consent prior to participation.
Conflict of interest
Debra Bemben, Vanessa Sherk, and Michael Bemben declare they have no conflict of interest.
William Ertl received speaker fees from Acelity/KCI, not related to this work.
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