title: Acute bone changes after lower limb amputation resulting from traumatic injury.
abstract: 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.
authors.affiliation: Bone Density Research Laboratory, Department of Health and Exercise Science, University of Oklahoma, 1401 Asp Avenue, Norman, OK, 73019, USA. dbemben@ou.edu.
authors.forename: D A
authors.initials: DA
authors.lastname: Bemben
authors.affiliation: Department of Medicine, Division of Endocrinology, Metabolism and Diabetes, University of Colorado at Denver Anschutz Medical Campus, Aurora, CO, 80045, USA.
authors.forename: V D
authors.initials: VD
authors.lastname: Sherk
authors.affiliation: Department of Orthopedic Surgery, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA.
authors.forename: W J J
authors.initials: WJJ
authors.lastname: Ertl
authors.affiliation: Bone Density Research Laboratory, Department of Health and Exercise Science, University of Oklahoma, 1401 Asp Avenue, Norman, OK, 73019, USA.
authors.forename: M G
authors.initials: MG
authors.lastname: Bemben
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000671:Amputation, Surgical / Q000009:adverse effects*; D001186:Artificial Limbs; D015519:Bone Density / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D035002:Lower Extremity / Q000293:injuries* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000209:etiology* / Q000503:physiopathology; D016062:Porosity; D011184:Postoperative Period; D014057:Tomography, X-Ray Computed; D055815:Young Adult
keywords: Bone density; Bone geometry; Bone remodeling; Prosthesis; Trauma