No abstract

This concept has potential to improve the biologic fixation of porous reconstructive implants.

Background Bony fixation of cementless orthopaedic implants is not always achieved, particularly in challenging scenarios such as revision surgery, trauma, and tumor reconstruction. An adjunct therapy for improving porous implant fixation could improve the reliability and durability of these reconstructive procedures. Questions/purposes In this study, we asked whether there is a positive and dose-dependent effect of the local release of the bisphosphonate alendronate from (1) alendronate/ hydroxyapatite (HA) porous-coated titanium implants compared with bare metal porous controls; and (2) alendronate/HA on porous-coated titanium implants compared with HA-coated porous controls with respect to extent of bone ingrowth, bone apposition, and periimplant bone formation in a canine model? Methods Three-dimensional printed porous-coated cylindrical implants coated with three different doses (0.02, 0.06, and 0.18 mg/cm 2 ) of alendronate were inserted bilaterally in the intramedullary canal of the proximal femora of 15 adult mongrel dogs (age range, 3-9 years; mean, 5 years) weighing between 36 kg and 60 kg (mean, 43 kg). In each dog, an implant coated with HA and one of three different doses of alendronate was inserted on one side while the contralateral femur had a bare metal porous control implant and an identical control implant with a coating of HA. The dose effect of locally released alendronate on the extent of bone ingrowth, bone apposition, and periimplant bone was assessed by backscattered electron microscopy of three pairs of crosssections taken from each implant at 12 weeks after surgery. A linear mixed model was used to perform the statistical analyses to account for the correlation in the data resulting from the multiple measures performed on each dog. Results Compared with paired bare metal controls, periimplant bone increased by 92% (p = 0.007), and 114% (p\ 0.001) in the femora with the alendronate implants with a dose of 0.06 mg/cm 2 , or 0.18 mg/cm 2 , respectively. At a dose of 0.02 mg/cm 2 , there was no difference (46% change; p = 0.184, with the numbers available). The comparison of the alendronate-dosed implants with their HA-coated controls showed that the intermediate dose of 0.06 mg/cm 2 alendronate had the greatest effect on net bone formation. Bone apposition was enhanced with the 0.06-mg/cm 2 alendronate femoral implants (82%; p = 0.008), although there was no change in bone ingrowth Two of the authors certify that they (JDB, MT), or a member of their immediate families, has or may receive payments or benefits, during the study period, an amount of USD 10,000 to USD 100,000 from Pipeline Biotechnology (Cedar Knolls, NJ, USA). (37% change; p = 0.902, with the numbers available). When compared with the HA-coated control implants, the greatest effect of the alendronate-dosed implants was the increased amount of periimplant bone at the intermediate dose of 0.06-mg/cm 2 (108%, p = 0.009). There was no effect of the low (0.02-mg/cm 2 ) and high (0.18-mg/cm 2 ) alendronate-dosed implants (...

In the Materials and Methods section of the published study by Bobyn and colleagues, the abbreviation for HA is incorrectly defined. The corrected version should read: All implants were plasma spray-coated with a thin (10-15 lm) layer of hydroxyapatite (HA; 98% purity, 99% density, 64% crystallinity, calcium: phosphate ratio of 1.67) such that only the outermost porous structure was HA-coated, leaving the innermost pores uncoated.The editors apologize for the error.The online version of the original article can be found under