title: Hydroxyapatite-coated collars reduce radiolucent line progression in cemented distal femoral bone tumor implants.
abstract: BACKGROUND
  Aseptic loosening of massive bone tumor implants is a major cause of prosthesis failure. Evidence suggests that an osteointegrated hydroxyapatite (HA)-coated collar would reduce the incidence of aseptic loosening around the cemented intramedullary stem in distal femoral bone tumor prostheses. Because these implants often are used in young patients with a tumor, such treatment might extend the longevity of tumor implants. Questions/purposes We asked whether (1) HA-coated collars were more likely to osteointegrate; (2) HA collars were associated with fewer progressive radiolucent lines around the stem-cement interface; and (3) HA-coated collars were associated with less bone loss at the bone-shoulder implant junction?
  
  
  METHODS
  Twenty-two patients were pair-matched to one of two groups--either (1) implants with a HA-coated ingrowth collar (HA Collar Group); or (2) implants without an ingrowth collar (Noncollar Group). Age, sex, and length of followup were similar in both groups. HA-coated collars were developed and used at our institution from 1992 to address the high failure rate attributable to aseptic loosening in patients with massive bone tumor implants. Before this, smooth titanium shafts were used routinely adjacent to bone at the transection site. The minimum followup was 2 years (mean, 7 years; range, 2-12 years). Radiographs obtained throughout the followup period were analyzed and osteointegration at the shaft of the implant quantified. Radiolucent line progression around the cemented stem was semi-quantitatively assessed and cortical bone loss at the bone-shoulder implant junction was measured during the followup period.
  
  
  RESULTS
  Comparison of the most recent radiographs showed nine of 11 patients had osteointegrated HA collars, whereas only one patient in the Noncollar Group had osteointegration (p > 0.001). The radiolucent line score quantified around the cemented stem was lower in the HA Collar Group when compared with the Noncollar Group (p = 0.001). Results showed an increase in cortical bone loss at the bone-shoulder implant junction in the Noncollar Group when compared with the HA Collar Group (p < 0.001).
  
  
  CONCLUSIONS
  Osteointegration at the implant collar resulted in fewer radiolucent lines adjacent to the intramedullary cemented stem and decreased cortical bone loss immediately adjacent to the transection site. These results suggest that the HA collar may help reduce the risk of aseptic loosening in patients with this type of implant, but longer followup and a larger prospective comparison series are necessary to prove this more definitively.
authors: John Scales Centre for Biomedical Engineering, Institute of Orthopaedics and Musculoskeletal Science, Division of Surgery and Interventional Science, University College London, London, UK, m.coathup@ucl.ac.uk.
authors: Melanie J
authors: MJ
authors: Coathup
authors: Anish
authors: A
authors: Sanghrajka
authors: William J
authors: WJ
authors: Aston
authors: Panagiotis D
authors: PD
authors: Gikas
authors: Robin C
authors: RC
authors: Pollock
authors: Stephen R
authors: SR
authors: Cannon
authors: John A
authors: JA
authors: Skinner
authors: Timothy W R
authors: TW
authors: Briggs
authors: Gordon W
authors: GW
authors: Blunn
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001859:Bone Neoplasms / Q000601:surgery*; D002813:Chondrosarcoma / Q000601:surgery*; D020099:Coated Materials, Biocompatible; D017886:Durapatite; D005260:Female; D005266:Femoral Neoplasms / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016348:Osseointegration; D012516:Osteosarcoma / Q000601:surgery*; D019736:Prostheses and Implants; D011475:Prosthesis Failure
chemical_list: D020099:Coated Materials, Biocompatible; D017886:Durapatite
references: J Arthroplasty. 1997 Oct;12(7):741-50
references: 9355003
references: Clin Orthop Relat Res. 2001 Jul;(388):167-77
references: 11451116
references: Clin Orthop Relat Res. 2005 Sep;438:71-9
references: 16131872
references: Tissue Eng. 2006 Jun;12(6):1617-26
references: 16846357
references: Clin Orthop Relat Res. 2006 Sep;450:164-71
references: 16691142
references: Int Orthop. 2006 Dec;30(6):452-7
references: 16967279
references: J Bone Joint Surg Br. 2007 Aug;89(8):1084-7
references: 17785750
references: J Bone Joint Surg Br. 2007 Dec;89(12):1632-7
references: 18057365
references: Clin Orthop Relat Res. 2000 Mar;(372):223-30
references: 10738431
references: Bone Joint J. 2014 Feb;96-B(2):263-9
references: 24493195
references: J Bone Joint Surg Am. 2003 Dec;85-A(12):2365-70
references: 14668506
references: J Bone Joint Surg Am. 2004 May;86-A(5):948-55
references: 15118037
references: J Bone Joint Surg Am. 1979 Sep;61(6A):887-92
references: 479235
references: Clin Orthop Relat Res. 1983 Jun;(176):108-14
references: 6573988
references: Clin Orthop Relat Res. 1986 Mar;(204):266-85
references: 3956014
references: J Bone Joint Surg Am. 1986 Dec;68(9):1331-7
references: 3465732
references: Chir Organi Mov. 1990;75(1 Suppl):171-3
references: 2249522
references: J Orthop Res. 1991 Nov;9(6):809-19
references: 1919843
references: Clin Orthop Relat Res. 1992 Mar;(276):91-101
references: 1537180
references: J Bone Joint Surg Am. 1993 Jul;75(7):976-87
references: 8335673
references: J Bone Joint Surg Br. 1996 Jan;78(1):5-13
references: 8898118
references: J Biomech. 1997 Mar;30(3):225-34
references: 9119821
references: J Bone Joint Surg Am. 2008 Jun;90(6):1265-71
references: 18519320
references: J Bone Joint Surg Br. 2008 Aug;90(8):1084-9
references: 18669968
references: Clin Orthop Relat Res. 2009 Nov;467(11):2792-9
references: 19513799
references: J Surg Oncol. 2010 Feb 1;101(2):166-9
references: 19924724
references: Clin Orthop Relat Res. 2011 May;469(5):1470-8
references: 20878288
references: J Biomed Mater Res A. 2013 Aug;101(8):2210-8
references: 23281219
references: J Bone Joint Surg Am. 2013 Sep 4;95(17):1569-75
references: 24005197
references: Clin Orthop Relat Res. 2005 Sep;438:51-9
references: 16131869