title: Distal femoral bone mineral density decreases following patellofemoral arthroplasty: 1-year follow-up study of 14 patients.
abstract: BACKGROUND
  The bone mineral density (BMD) of the distal femur decreases by 16-36% within one year after total knee arthroplasty (TKA) because of the femoral component's stress-shielding effect. The aim of this prospective study was to determine the quantitative change from the baseline BMD in the distal femur 1 year after patellofemoral arthroplasty using dual-energy X-ray absorptiometry (DXA).
  
  
  METHODS
  Between December 2007 and December 2008, 14 patients had patellofemoral arthroplasty for isolated patellofemoral osteoarthritis. Distal femoral BMD was assessed using DXA in 2 regions of interest (ROI) on the lateral view 2 weeks before and 12 months after patellofemoral arthroplasty. The contra-lateral knee was used as a control, with BMD measurements performed in identical ROIs.
  
  
  RESULTS
  The mean change from baseline BMD in the operated knees after 1 year was -0.169 g/cm2 (95% CI: -0.293 to -0.046 g/cm2) behind the anterior flange (-15%), and -0.076 g/cm2 (95% CI: -0.177 to 0.024 g/cm2) in the supracondylar area 1 cm above the prosthesis (-8%) (p = 0.01 and p = 0.13, respectively). The mean change from baseline BMD in the non-operated knees after 1 year was 0.016 g/cm2 (95% CI: -0.152 to 0.185 g/cm2) behind the anterior flange (2%), and 0.023 g/cm2 (95% CI: -0.135 to 0.180 g/cm2) in the supracondylar area 1 cm above the prosthesis (2%) (p = 0.83, and p = 0.76, respectively).
  
  
  CONCLUSIONS
  Our findings suggest that patellofemoral arthroplasty results in a statistically significant decrease in BMD behind the anterior flange.
authors.affiliation: Department of Orthopedic Surgery, Deventer Hospital, Nico Bolkesteinlaan 75, 7416 SE Deventer, The Netherlands. vanjonbergen@dz.nl
authors.forename: Hans-Peter W
authors.initials: HP
authors.lastname: van Jonbergen
authors.forename: Kenneth
authors.initials: K
authors.lastname: Koster
authors.forename: Luc
authors.initials: L
authors.lastname: Labey
authors.forename: Bernardo
authors.initials: B
authors.lastname: Innocenti
authors.forename: Albert
authors.initials: A
authors.lastname: van Kampen
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D001696:Biomechanical Phenomena / Q000502:physiology; D001862:Bone Resorption / Q000000981:diagnostic imaging / Q000209:etiology / Q000503:physiopathology*; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D005500:Follow-Up Studies; D006801:Humans; D007049:Iatrogenic Disease / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D010329:Patella / Q000601:surgery; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000209:etiology / Q000503:physiopathology*; D011446:Prospective Studies; D013314:Stress, Mechanical; D013995:Time; D013997:Time Factors; D016474:Weight-Bearing / Q000502:physiology
references.citation: J Arthroplasty. 2010 Oct;25(7):1066-71
references.pmid: 20056375
references.citation: Arch Orthop Trauma Surg. 1999;119(5-6):324-6
references.pmid: 10447632
references.citation: Calcif Tissue Int. 1998 Apr;62(4):359-61
references.pmid: 9504962
references.citation: J Bone Joint Surg Br. 2006 May;88(5):606-13
references.pmid: 16645105
references.citation: J Bone Joint Surg Br. 1997 Jan;79(1):117-22
references.pmid: 9020459
references.citation: Calcif Tissue Int. 2000 Sep;67(3):267-72
references.pmid: 10954783
references.citation: J Arthroplasty. 1995 Feb;10(1):7-11
references.pmid: 7730833
references.citation: Rev Chir Orthop Reparatrice Appar Mot. 2006 Apr;92(2):140-7
references.pmid: 16800070
references.citation: Knee. 2004 Aug;11(4):297-302
references.pmid: 15261216
references.citation: Orthop Rev. 1987 Jul;16(7):449-56
references.pmid: 3453978
references.citation: Acta Orthop Belg. 1999 Jun;65(2):154-63
references.pmid: 10427796
references.citation: J Arthroplasty. 1999 Dec;14(8):957-63
references.pmid: 10614887
references.citation: Clin Orthop Relat Res. 1989 Nov;(248):9-12
references.pmid: 2805502
references.citation: J Bone Joint Surg Am. 2006 Nov;88(11):2337-42
references.pmid: 17079388
references.citation: Int Orthop. 1995;19(6):346-51
references.pmid: 8567149
references.citation: Arch Orthop Trauma Surg. 2001 May;121(5):282-5
references.pmid: 11409560
references.citation: J Orthop Res. 1996 Sep;14(5):778-85
references.pmid: 8893772
references.citation: Acta Orthop. 2009 Feb;80(1):62-6
references.pmid: 19234887