title: Quantifying postoperative bone loss in children.
abstract: BACKGROUND
  Postoperative bone density loss is an accepted phenomenon that has not been objectively quantified. The extent of this bone loss is documented using preoperative and postoperative dual energy x-ray absorptiometry scans to demonstrate the magnitude of the problem and to underline the need for prevention and treatment.
  
  
  METHODS
  Children undergoing lower extremity surgery who required a minimum of 4 weeks of either non-weight bearing or cast immobilization postoperatively were recruited to undergo preoperative and postoperative dual energy x-ray absorptiometry scans of lumbar spine and both distal femora. Percent change in bone mineral density (BMD) as well as Z-scores in preoperative and postoperative scans were compared, as were operated and nonoperated limbs, using paired t tests.
  
  
  RESULTS
  Fifteen of 18 subjects completed the second scan. Children lost up to 34% BMD in the cancellous region of the operated leg (average, 16.5%), up to 28% in transitional bone (average, 11.5%), and up to 16% (average, 4.8%) in the cortical region (P < 0.05). The Z-scores fell 1.0 SD for cancellous, 0.75 transitional, and 0.45 cortical.
  
  
  CONCLUSIONS
  That children can lose up to 34% of BMD in 4 to 6 weeks is sobering. A 1 SD drop in T score, in adults, can infer a 2-fold increase in fracture risk. This may be insignificant in a healthy child with good BMD, but to a chronically ill child, a doubling of fracture risk may lead to insufficiency fracture. Avoiding the problem and proactive treatment are the goals.
  
  
  METHODS
  Level I, prospective diagnostic study.
authors: University of New Mexico Health Sciences Center, 1127 University Blvd NE, Albuquerque, NM 87102, USA. ESzalay@salud.unm.edu
authors: Elizabeth A
authors: EA
authors: Szalay
authors: Debra
authors: D
authors: Harriman
authors: Brittany
authors: B
authors: Eastlund
authors: Deana
authors: D
authors: Mercer
mesh_terms: D000293:Adolescent; D015519:Bone Density; D001851:Bone Diseases, Metabolic / Q000453:epidemiology*; D002111:Calcaneus / Q000601:surgery; D002547:Cerebral Palsy / Q000601:surgery; D002648:Child; D002675:Child, Preschool; D005260:Female; D005269:Femur / Q000601:surgery*; D006617:Hip Dislocation / Q000601:surgery; D006801:Humans; D008297:Male; D010027:Osteotomy; D011183:Postoperative Complications / Q000453:epidemiology*; D011446:Prospective Studies