Acetabular cortical and cancellous bone density and radiolucent lines after cemented total hip arthroplasty: a prospective study using computed tomography and plain radiography.
BACKGROUND
The aim of this prospective study was to evaluate load-transfer mechanisms and stress patterns of periacetabular cortical and cancellous bone after cemented total hip arthroplasty (THA) in vivo using computed tomography (CT) assisted osteodensitometry. In addition we analyzed the efficacy of CT in detecting radiolucent lines around the acetabular component compared to plain radiography.


METHODS
Twenty-two cemented acetabular cups were investigated using conventional sequential axial CT scans (Ø 8 days and 26 months post-OP) and plain radiography (Ø 5 days and 40 months post-OP). CT assisted osteodensitometry was used to determine cancellous and cortical bone bone density (BD). Radiolucent lines were evaluated using both CT and plain radiography.


RESULTS
Significant BD loss at the time of follow-up was only detectable ventral to the cup (cortical bone: -16%, P = 0.001; cancellous bone: -31%, P = 0.001). The BD changes dorsal and cranial to the cup were not significant. Postoperatively no radiolucent lines were observed in the cement-bone interface by CT, while on plain radiography acetabular lucent lines were seen in 12 out of 22 cases.


CONCLUSIONS
CT-osteodensitometry has the technical ability to discriminate between cortical and cancellous bone structures with respect to strain-adapted remodeling: sufficient cancellous and cortical bone stock remained dorsal and cranial to the cup indicative of a balanced load transfer to these regions. CT-osteodensitometry has the potential to become an effective instrument for quality control in THA and the method of choice for in vivo determination of periprosthetic BD. In contrast, plain radiography is more suitable for the early detection of radiolucent lines compared to axial CT scans.
Mueller
Lutz Arne
LA
Department of Orthopaedic Surgery, Friedrich-Alexander-University of Erlangen-Nuremberg, Am Waldkrankenhaus St Marien, Rathsberger Str 57, 91054, Erlangen, Germany. ltzmll@aol.com
Nowak
Tobias Eckhard
TE
Mueller
Lars Peter
LP
Schmidt
Rainer
R
Ehrmann
Cornelia
C
Pitto
Rocco Paolo
RP
Pfander
David
D
Forst
Raimund
R
Eichinger
Stefan
S
D000077:Acetabulum / Q000000981:diagnostic imaging*; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip; D001843:Bone Cements / Q000627:therapeutic use; D015519:Bone Density; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D015207:Osteoarthritis, Hip / Q000601:surgery; D011446:Prospective Studies; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
D001843:Bone Cements