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Correlation of bony ingrowth to the distribution of stress and strain parameters surrounding a porous‐coated implant
Author(s) -
Qin YiXian,
McLeod Kenneth J.,
Guilak Farshid,
Rubin Clinton T.,
Chiang FuPen
Publication year - 1996
Publication title -
journal of orthopaedic research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.041
H-Index - 155
eISSN - 1554-527X
pISSN - 0736-0266
DOI - 10.1002/jor.1100140604
Subject(s) - materials science , implant , strain gauge , shear stress , finite element method , stress–strain curve , orthotropic material , composite material , biomedical engineering , strain (injury) , shear (geology) , stress (linguistics) , anatomy , structural engineering , surgery , medicine , linguistics , philosophy , deformation (meteorology) , engineering
The ability of shear strains to inhibit bony ingrowth was investigated by use of a transcortical porouscoated cylindrical plug implant in a functionally isolated turkey ulna model in which the mechanical loading environment could be accurately controlled and rigorously defined. The distribution of ingrowth at the bone‐implant interface was quantified following 8 weeks of in vivo loading consisting of 100 seconds per day of a 20 Hz sinusoidal stimulus sufficient to cause a local peak strain of approximately 100 microstrain in the cortex at the bone‐implant interface in four turkeys. A nonuniform but repeatable pattern of bony ingrowth, from 33 ± 6 to 72 ± 6% (mean ± SE), was observed. The mechanical environment in the vicinity of the bone‐implant interface was calculated using a three‐dimensional elastic orthotropic finite element model. The general stress‐strain state of the bone as predicted by the finite element model was validated in two additional turkeys using four three‐element rosette strain gauges, while high resolution moiré interferometry was used to determine the mechanical state of the region immediately adjacent to the implant itself. Shear strains and stresses were evaluated at the interface and correlated to the pattern of bony ingrowth circumscribing the implant interface. Linear regressions between ingrowth and both shear strain and shear stress were negative, with the values of R = −0.75 and R = −0.78 (p < 0.001), respectively, indicating significant inhibition of ingrowth where shear components were maximal. These results suggest that the minimization of shear stress and strain components is a major determinant in achieving successful ingrowth of bone into a prosthesis.