Analysis of callus pattern of tibia lengthening in achondroplasia and a novel method of regeneration assessment using pixel values.
OBJECTIVE
To relate morphology of new bone formation to outcome after tibial lengthening performed in patients with achondroplasia.


METHODS
A retrospective analysis of 60 tibial segments in 30 achondroplasia patients was performed. There were 22 female patients and eight male patients, with a mean age of 9.8 years. New bone formation was classified by shape, homogeneity and density. Pixel values in relation to original bone were measured using a picture-archiving communication system (PACS). Clinical outcome was described by the external fixator and maturation indices.


RESULTS
Mean lengthening was 9.2 cm (range 3-12.7 cm). The mean external fixator index was 23.4 (range 15.1-50). The mean maturation index was 12.3 days/cm (range 6-40 days/cm). Homogeneous pathways were associated with the best clinical results (fixator index 20.4, maturation index 10.8), followed by heterogeneous pathway (external fixator index 26.5, maturation index 16.8) and radiolucent pathway (fixator index 31.2, maturation index 21.4). Both cylindrical (external fixator index 25.2, maturation index 14.5) and concave (external fixator index 26.6, maturation index 16.3) callus shapes were favourable. Mineralization of new bone became equal to that of normal bone within 16 weeks (mean) for homogeneous pathway, 12 weeks for heterogeneous pathway and 32 weeks for lucent pathway.


CONCLUSIONS
The type of new bone formation seen on radiographs is related to clinical outcome, with homogeneous pathways being the most favourable ones.
Rare Diseases Institute, Department of Orthopedic Surgery, Korea University Guro Hospital, 80 Guro-Dong, Guro-Gu, Seoul, 152-703, Korea.
Suryaudai
S
Singh
Hae-Ryong
HR
Song
K P
KP
Venkatesh
Hitesh N
HN
Modi
Man Sik
MS
Park
Ki-Mo
KM
Jang
Seung J
SJ
Kim
D000130:Achondroplasia / Q000000981:diagnostic imaging* / Q000601:surgery*; D000293:Adolescent; D001852:Bone Lengthening; D001861:Bone Regeneration; D002146:Bony Callus / Q000000981:diagnostic imaging*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013977:Tibia / Q000000981:diagnostic imaging* / Q000601:surgery*; D016896:Treatment Outcome; D055815:Young Adult