A novel evaluation system to monitor bone formation and β-tricalcium phosphate resorption in opening wedge high tibial osteotomy.
OBJECTIVE
The aim of this study was to establish an evaluation system to monitor bone formation and beta-tricalcium phosphate (TCP) resorption in opening high tibial osteotomy (HTO).


METHODS
From 2003 to 2005, opening HTO was performed in 36 patients using a Puddu plate and β-TCP blocks with 60 and 75 % porosity. Thirty-one patients were used for evaluation. All patients underwent CT examination at 2 weeks and 6 years. The CT image data were divided into three areas, and CT values of each area were analysed using the imaging software, Osirix.


RESULTS
CT image analysis at 2 weeks showed that the mean CT-attenuation values (in Hounsfield units) of the implanted area with β-TCP of 60 % porosity, the implanted area with β-TCP of 75 % porosity, and cancellous bone were, 1,694.0 ± 94.2, 1,010.9 ± 81.1, and 178.0 ± 45.1, respectively. Six years after surgery, these values were 574.1 ± 273.5, 168.8 ± 75.1, and 174.9 ± 69.3, respectively.


CONCLUSIONS
β-TCP with 75 % porosity was completely resorbed and replaced by bone. β-TCP with 60 % porosity was resorbed, but approximately 1/3 still remained even 6 years after surgery. The imaging software, Osirix, enabled scanning of the whole area to measure CT values. This system is the first to quantitatively evaluate β-TCP resorption and bone formation in opening HTO.


METHODS
Laboratory studies.
Department of Orthopaedic Surgery, NHO Utsunomiya National Hospital, 2160 Shimo-Okamoto, Utsunomiya, Tochigi, 329-1193, Japan, tanakat@e-utunomiya.hosp.go.jp.
T
T
Tanaka
Y
Y
Kumagae
M
M
Chazono
S
S
Kitasato
A
A
Kakuta
K
K
Marumo
D000368:Aged; D001672:Biocompatible Materials; D001860:Bone Plates; D002130:Calcium Phosphates; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000503:physiopathology / Q000601:surgery*; D010012:Osteogenesis / Q000502:physiology*; D010027:Osteotomy / Q000379:methods*; D016062:Porosity; D013977:Tibia / Q000000981:diagnostic imaging / Q000378:metabolism / Q000503:physiopathology* / Q000601:surgery*; D014057:Tomography, X-Ray Computed
D001672:Biocompatible Materials; D002130:Calcium Phosphates; C485817:beta-tricalcium phosphate