RADIOSTEREOMETRIC ANALYSIS (RSA) OF THREE-DIMENSIONAL MICROMOTION IN A FRACTURE MODEL OF FEMUR

Due to its popularity of intramedullary nails (IMN) high success rate, newer design (titanium) IMN system have been introduced to replace stainless steel system. However the stability provided by the titanium IMN may not be adequate, there by influencing the union rate. We aimed to compare the results of both IMN systems via prospective clinical study and biomechanical testing using RSA. Biomechanical study This study was done in an experimental set-up which consisted of a physically simulated femoral shaft fractures models fixed with a stainless steel (Russell Taylor) or Titanium (Trigen) IM nailing system. Two common fracture configurations with stimulated weight bearing conditions were used and the axis of fragment movements recorded. Clinical study The data on two groups of patients were collected as part of a prospective cohort study. Details of the implant, such as size of nail, cross screw lengths, screw thickness, etc. was collected. Patients were followed up for a minimum of 4 months and details of clinical complications recorded Biomechanical study The degree of translation movement in comminuted fracture, using titanium IMN system, was 6 times more compared to stainless steel IMN system. Clinical study The results show that there is a 5.7% of non union and 14% hardware problems with titanium based IMN system when compared to 2.2% non union in the stainless steel IMN system. Titanium based IM nailing system have a potential to inherent mechanical instability when used to treat comminuted fractures. This may explain some of the clinically observed delayed or non-union of femoral fractures.