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Correlation found between diameter of cement keyholes for THR and strength
Investigators noted that increasing depth of the holes did not increase the strength of acetabular fixation.
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British researchers found that increasing the diameter, not the depth of cement keyholes increased their strength for acetabular fixation in total hip replacement.
“The belief that increasing diameter of these keyholes led to increasing strength was validated, but depth had no benefit and did not confirm a significant increase in strength,” Arijit Ghosh, MBBS, MA (Cantab), MRCS, MSc (Orth Eng), registrar at East Midlands Healthcare Workforce Deanery at the University of Leicester, said during his presentation at the British Orthopaedic Association Congress.
Optimal dimensions of cement keyholes
The standard size of keyholes for maximum strength is unknown, Ghosh said, and surgeons have their own preferences regarding the size of these holes. Therefore, Ghosh and colleagues conducted a load to failure experiment on keyholes as well as a finite element analysis to discover the optimal depth and diameter for cement keyholes.
The researchers tested 16 keyholes drilled into four blocks with diameters increasing from 2.5 mm to 6 mm at the end of each block. Additionally, depth increased from 2.5 mm to 6 mm, with the smallest keyhole measuring 2.5 mm by 2.5 mm.
Increasing force for failure
The investigators noted that from block one to block four, there was an increase in the force needed for failure with the increase in diameter. When going down the block, rather than up, they found however that increasing diameter did not confer any increase in strength to the keyhole.
“The diameter provided increasing strength, the depth did not,” Ghosh.
A finite element analysis confirmed the researchers’ theory, according to Ghosh, with increased stresses found at the base of each keyhole.
“The length of the keyhole should not matter in the failure,” Ghosh said. “We understand that these are preliminary findings, and we are doing further studies with increasing further numbers and also increasing all the numbers of actual keyholes themselves to see if that makes any difference.” – by Renee Blisard Buddle
- Reference:
- Ghosh A. Paper #21. Presented at: British Orthopaedic Association Congress; Sept. 11-14, 2012; Manchester.
- For more information:
- Arijit Ghosh, MBBS, MA (Cantab), MRCS, MSc (Orth Eng), can be reached at Orthopaedic Offices, Leicester Royal Infirmary, Leicester LE1 5WW United Kingdom; email: arijitkg@hotmail.com.
Disclosure: Ghosh has no relevant financial disclosures.