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Decreased precision for BMD measurements in the prosthetic knee using a non-knee-specific software
Ming G Li1, Kjell G Nilsson, Bo Nivbrant
1Perth Orthopaedic Institute, the University of Western Australia, Nedlands, Western Australia. mingguo@cyllene.uwa.edu.au
Summary
Using non-knee-specific software for bone mineral density (BMD) measurements in prosthetic knees leads to high error. Hip-specific software is not recommended for knee BMD analysis due to poor precision.
Area of Science:
- Orthopedics
- Radiology
- Biomedical Engineering
Background:
- Non-knee-specific software is frequently used for bone mineral density (BMD) measurement at the knee.
- This practice is associated with increased measurement error and reduced precision.
Purpose of the Study:
- To evaluate the suitability of hip-specific software for knee BMD measurement using dual-energy X-ray absorptiometry (DXA).
- To determine the influence of knee rotational alignment and soft tissue substitutes on BMD measurement precision.
Main Methods:
- Twelve knees with total knee arthroplasty were scanned 4-6 times each in four rotational positions.
- DXA scans were performed using Plexiglas rods or rice bags as soft tissue substitutes.
- BMD was measured in the proximal tibia using orthopedic software.
Main Results:
- Precision (coefficient of variation) ranged from 5.1-9.0% with Plexiglas rods and 7.3% with rice bags.
- Poor precision was attributed to inconsistent baseline establishment and low bone density.
- Knee rotation and soft tissue substitutes did not significantly impact precision.
Conclusions:
- The use of non-knee-specific software for BMD measurement in prosthetic knees is inappropriate.
- Current software limitations hinder accurate BMD assessment in the knee joint.