Rotational profile of the lower extremity in achondroplasia: computed tomographic examination of 25 patients.
OBJECTIVE
To evaluate lower-extremity rotational abnormalities in subjects with achondroplasia using computed tomography (CT) scans.


METHODS
CT scans were performed in 25 subjects with achondroplasia (13 skeletally immature, mean age 8.7 years; 12 skeletally mature, mean age 17.6 years). In a total of 50 bilateral limbs, CT images were used to measure the angles of acetabular anteversion, femoral anteversion, and tibial external torsion. Measurement was performed by three examiners and then repeated by one examiner. Inter- and intraobserver agreements were analyzed, and results were compared with previously reported normal values.


RESULTS
Mean values for skeletally immature and skeletally mature subjects were 13.6+/-7.5 degrees and 21.5+/-6.4 degrees respectively for acetabular anteversion, 27.1+/-20.8 degrees and 30.5+/-20.1 degrees for femoral torsion, and 21.6+/-10.6 degrees and 22.5+/-10.8 degrees for tibial torsion. Intra- and interobserver agreements were good to excellent. Acetabular anteversion and femoral anteversion in skeletally mature subjects were greater than normal values in previous studies. Both skeletally immature and mature subjects with achondroplasia had decreased tibial torsion compared to normal skeletally immature and mature subjects.


CONCLUSIONS
Lower-extremity rotational abnormalities in subjects with achondroplasia include decreased tibial external torsion in both skeletally immature and mature subjects, as well as increased femoral and acetabular anteversion in skeletally mature subjects.
Song
Hae-Ryong
HR
Department of Orthopaedic Surgery, Rare Diseases Institute, Korea University Guro Hospital, Seoul, South Korea.
Choonia
Abi-Turab
AT
Hong
Suk Joo
SJ
Lee
Seok-Hyun
SH
Suh
Seung-Woo
SW
Cha
In Ho
IH
Park
Jong-Tae
JT
D000130:Achondroplasia / Q000000981:diagnostic imaging* / Q000503:physiopathology; D000293:Adolescent; D000328:Adult; D002648:Child; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D016059:Range of Motion, Articular; D012399:Rotation; D013977:Tibia / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed