Timothy A Burkhart1, Mehrdad Khadem2, Thomas J Wood3, Cynthia E Dunning2, Ryan Degen4, Brent A Lanting5. 1. Lawson Health Science Institute, Canada; Department of Mechanical and Materials Engineering, Western University, 1151 Richmond Rd, London, ON N6A 3K7, Canada. Electronic address: tburkhar@uwo.ca. 2. Department of Mechanical and Materials Engineering, Western University, 1151 Richmond Rd, London, ON N6A 3K7, Canada. 3. Department of Surgery, London Health Sciences Centre, 339 Windermere Road, London, ON N6A 5A5, Canada. 4. Fowler Kennedy Sports Medicine Clinic, Canada; Department of Surgery, Western University, 1151 Richmond Rd, London, ON N6A 3K7, Canada. 5. London Health Sciences Centre, Canada; Department of Surgery, 1151 Richmond Rd, London, ON N6A 3K7, Canada.
Abstract
BACKGROUND: Total hip arthroplasty complications are associated with mechanical loosening of the acetabular component, which may be attributed to the type of fixation used (press fit, trans-cortical screws, cancellous screws). Therefore, the purpose of this study was to compare trans-cortical and cancellous screws to press fit for fixation of the acetabular shell. METHODS: Five cadaveric pelvis specimens were hemisected (N = 10) at the sacroiliac joint. Each hemi-pelvis was initially tested with a press fit cup followed by the left and right pairs being randomized to either a cancellous or trans-cortical screw condition. Each fixation was tested by applying a load to a rod inserted into the centre of the acetabular cup at 0.5 mm/s, until failure occurred. The failure force, failure moment, and the rotation angle of the cup at failure were calculated. FINDINGS: The cups fixated with a trans-cortical screw failed at a significantly greater mean [SD] force (1046.20 [386.52] N). The trans-cortical screws also significantly increased the angle of failure 46.29 (16.90) ° compared to the press-fit cups (6.73 [4.59] °). Finally, there was a significant increase in the failure moment, such that, the trans-cortical condition failed at a mean (SD) moment of 53.75 (16.24) Nm compared to 9.59 (1.85) Nm and 32.15 (18.16) Nm for the press fit and cancellous (p = 0.044) conditions, respectively. INTERPRETATION: The acetabular shells that were fixated with trans-cortical screws provide greater stability compared to the press-fit cups or cancellous screws.
BACKGROUND: Total hip arthroplasty complications are associated with mechanical loosening of the acetabular component, which may be attributed to the type of fixation used (press fit, trans-cortical screws, cancellous screws). Therefore, the purpose of this study was to compare trans-cortical and cancellous screws to press fit for fixation of the acetabular shell. METHODS: Five cadaveric pelvis specimens were hemisected (N = 10) at the sacroiliac joint. Each hemi-pelvis was initially tested with a press fit cup followed by the left and right pairs being randomized to either a cancellous or trans-cortical screw condition. Each fixation was tested by applying a load to a rod inserted into the centre of the acetabular cup at 0.5 mm/s, until failure occurred. The failure force, failure moment, and the rotation angle of the cup at failure were calculated. FINDINGS: The cups fixated with a trans-cortical screw failed at a significantly greater mean [SD] force (1046.20 [386.52] N). The trans-cortical screws also significantly increased the angle of failure 46.29 (16.90) ° compared to the press-fit cups (6.73 [4.59] °). Finally, there was a significant increase in the failure moment, such that, the trans-cortical condition failed at a mean (SD) moment of 53.75 (16.24) Nm compared to 9.59 (1.85) Nm and 32.15 (18.16) Nm for the press fit and cancellous (p = 0.044) conditions, respectively. INTERPRETATION: The acetabular shells that were fixated with trans-cortical screws provide greater stability compared to the press-fit cups or cancellous screws.