Correlation found between diameter of cement keyholes for THA and strength

However, investigators noted that increasing depth of the holes did not increase strength of fixation.

Issue: February 2013

MANCHESTER — British researchers found increasing the diameter, not 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 found, 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 the East Midlands Healthcare Workforce Deanery at the University of Leicester, said during his presentation at the British Orthopaedic Association Congress.

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 systems analysis to discover the optimal depth and diameter for cement keyholes.

Arijit Ghosh

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.

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 system analysis confirmed the researcher’s 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 informatrion:

Arijit Ghosh, MBBS, MA (Cantab), MRCS, MSc (Orth Eng), can be reached at Orthopaedic offices, Leicester Royal Infirmary, Leicester LE1 5WW UK; email: arijitkg@hotmail.com.
Disclosure: Ghosh has no relevant financial disclosures.