title: Bone Mineral Density Measurements Around Osseointegrated Implants: A Precision Study and Validation of Scan Protocol for Transfemoral Amputees.
abstract: Visual evaluation of bone changes around an osseointegration (OI) implant in femoral amputees examined on plain radiographs shows that periprosthetic bone resorption takes place during the first years after OI surgery, but the bone mineral density (BMD) change has not been previously quantified by dual-energy X-ray absorptiometry (DXA). Precision is vital when monitoring BMD changes around implants, and thus the aim of this study was to evaluate the precision and feasibility of a scan protocol for BMD measurements in proximity of OI implants. The proximal part of 2 human cadaveric femoral bones (specimens A and B) with OI implants were mounted in a positioning jig and DXA scans were repeated 5 times in increments of 5° from neutral (0°) to 20° flexion and rotation. BMD changes as a result of change in leg position were evaluated. Repeated patient examinations (n = 20) were conducted in a clinical setting and the precision error was calculated for each of 7 periprosthetic custom-made regions of interest (ROIs). The precision of cadaveric BMD measurements in neutral position was <3.3%. Even 5° flexion or rotation in femur position caused significant changes in average BMD (p <0.04). Depending on ROI, the percentage of coefficient of variation (%CV) and average BMD was <6% at 10° flexion and rotation. At 20° flexion, %CV increased up to 12.7% and average BMD increased up to 9.9%. The clinical short-term precision root mean square standard deviation ranged from 0.031 g/cm2to 0.047 g/cm2and %CV ranged from 3.12% to 6.57% depending on ROI. Simulated hip flexion or rotation of the femur affected periprosthetic BMD measurements around OI implants in cadaveric femoral bones, which stresses the importance of a reproducible set-up during DXA scans to reduce measurement errors caused by variation in leg position. Adherence to the scan protocol with a relaxed position of the residual limb resulted in an acceptable short-term precision below 6.6%.
authors.affiliation: Orthopaedic Research Unit, University Hospital of Aarhus, Aarhus, Denmark; Department of Clinical Medicine, Aarhus University, Denmark. Electronic address: rlha@clin.au.dk.
authors.forename: Rehne Lessmann
authors.initials: RL
authors.lastname: Hansen
authors.affiliation: Department of Clinical Medicine, Aarhus University, Denmark; Department of Endocrinology and Internal Medicine, University Hospital of Aarhus, Aarhus, Denmark.
authors.forename: Bente Lomholt
authors.initials: BL
authors.lastname: Langdahl
authors.affiliation: Department of Orthopaedic Surgery, University Hospital of Aarhus, Aarhus, Denmark.
authors.forename: Peter Holmberg
authors.initials: PH
authors.lastname: Jørgensen
authors.affiliation: Department of Orthopaedic Surgery, University Hospital of Aarhus, Aarhus, Denmark.
authors.forename: Klaus Kjær
authors.initials: KK
authors.lastname: Petersen
authors.affiliation: Orthopaedic Research Unit, University Hospital of Aarhus, Aarhus, Denmark; Department of Clinical Medicine, Aarhus University, Denmark; Department of Orthopaedic Surgery, University Hospital of Aarhus, Aarhus, Denmark.
authors.forename: Kjeld
authors.initials: K
authors.lastname: Søballe
authors.affiliation: Orthopaedic Research Unit, University Hospital of Aarhus, Aarhus, Denmark; Department of Clinical Medicine, Aarhus University, Denmark.
authors.forename: Maiken
authors.initials: M
authors.lastname: Stilling
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000671:Amputation, Surgical / Q000534:rehabilitation*; D015519:Bone Density / Q000502:physiology*; D000077280:Bone-Anchored Prosthesis; D002102:Cadaver; D002985:Clinical Protocols; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016348:Osseointegration / Q000502:physiology*; D056888:Patient Positioning
keywords: Bone mineral density; osseointegrated implant; precision; transfemoral amputation