title: Impaction grafted bone chip size effect on initial stability in an acetabular model: Mechanical evaluation.
abstract: BACKGROUND
  Acetabular bone defect reconstruction is an increasing problem for surgeons with patients undergoing complex primary or revision total hip replacement surgery. Impaction bone grafting is one technique that has favourable long-term clinical outcome results for patients who undergo this reconstruction method for acetabular bone defects. Creating initial mechanical stability of the impaction bone graft in this technique is known to be the key factor in achieving a favourable implant survival rate. Different sizes of bone chips were used in this technique to investigate if the size of bone chips used affected initial mechanical stability of a reconstructed acetabulum.
  
  
  METHODS
  Twenty acetabular models were created in total. Five control models were created with a cemented cup in a normal acetabulum. Then five models in three different groups of bone chip size were constructed. The three groups had an acetabular protrusion defect reconstructed using either; 2-4 mm(3), 10 mm(3) or 20 mm(3) bone chip size for impaction grafting reconstruction. The models underwent compression loading up to 9500 N and displacement within the acetabular model was measured indicating the initial mechanical stability.
  
  
  RESULTS
  This study reveals that, although not statistically significant, the largest (20 mm(3)) bone chip size grafted models have an inferior maximum stiffness compared to the medium (10 mm(3)) bone chip size.
  
  
  CONCLUSIONS
  Our study suggests that 10 mm(3) size of bone chips provide better initial mechanical stability compared to smaller or larger bone chips. We dismissed the previously held opinion that the biggest practically possible graft is best for acetabular bone graft impaction.
authors.affiliation: Department of Trauma & Orthopaedics, Leeds General Infirmary, Leeds LS1 3EX, UK.
authors.forename: Colin
authors.initials: C
authors.lastname: Holton
authors.affiliation: Department of Trauma & Orthopaedics, Leeds General Infirmary, Leeds LS1 3EX, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Bobak
authors.affiliation: Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Ruth
authors.initials: R
authors.lastname: Wilcox
authors.affiliation: Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, UK ; School of Mechanical Engineering, Xian Jiaotong University, Shanghai 200240, China.
authors.forename: Zhongmin
authors.initials: Z
authors.lastname: Jin
keywords: Acetabular model; Bone chip size; Impaction bone graft