A new CT scan method for measuring the tibial tubercle trochlear groove distance in patellar instability.
Patellar malalignment leading to objective or potential patella instability can be caused by tibial tuberosity lateralisation. This can be treated with a tuberosity medialisation. CT scan measurements are needed to assess the tibial tubercle trochlear groove distance. When using the previously described methods to determine this distance it can be difficult to determine the anatomical structures on the maximum intensity projection images, and this can lead to measurement error. This study was designed to compare the reliability of a new computer based CT measurement to the previously described method to determine the tibial tubercle trochlear groove distance. For each method, four observers measured each of 50 knees twice. The inter- and intra-observer variability for the conventional method and a new method were determined. Using the conventional method, the number of knees for which the difference between the aggregate mean of all eight measurements and the mean of duplicate measurements per observer greater than 2 mm varied among the observers between 7 and 24 for the 50 knees, while this variation between four and seven for the same 50 knees using the new method. The limits of reproducibility based on measurements from the four different observers improved by 25%, indicating that the measurement error is considerably smaller with the new method. We advise using this more accurate method to improve the selection of patients for a tuberosity medialisation.
Koëter
Sander
S
Department of Orthopaedic Surgery, Sint Maartenskliniek Nijmegen, Nijmegen, The Netherlands.
Horstmann
Wieger G
WG
Wagenaar
Frank-Christiaan B M
FC
Huysse
Wouter
W
Wymenga
Ate B
AB
Anderson
Patricia G
PG
D015331:Cohort Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007593:Joint Instability / Q000000981:diagnostic imaging*; D007719:Knee Joint / Q000000981:diagnostic imaging*; D015588:Observer Variation; D015203:Reproducibility of Results; D013977:Tibia / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*