Plateau-patella angle: An option for the evaluation of patellar height in patients with patellar instability.
BACKGROUND
Patellar instability is a debilitating disease. An important factor related to recurrent dislocation is patellar height. A new method of patellar height measurement, the plateau-patella angle (PPA), was proposed in 2011. However, to date, there is no study evaluating the use of this method in patients with patellar instability. The aim of this study was to evaluate the PPA in patients with recurrent patellar dislocation.


METHODS
This was a retrospective evaluation of the radiographs of 78 knees with patellar instability. Patellar height was measured using the Insall-Salvati (I/S), Caton-Deschamps (C/D) and Blackburne-Peel (B/P) indices and the PPA. The qualitative and quantitative correlations between the various methods and between observers were calculated.


RESULTS
The PPA had a Pearson correlation of 0.76 (P<0.001) with the I/S index, 0.78 (P<0.001) with the C/D index and 0.90 (P<0.001) with the B/P index. In the qualitative correlation using the Spearman coefficient, the PPA had a correlation of 0.52 (P<0.001) with the I/S index, 0.72 (P<0.001) with the C/D index and 0.70 (P<0.001) with the B/P index. The correlations between the conventional methods were as follows: 0.57 (P<0.001) between the I/S and C/D indices; 0.61 (P<0.001) between the I/S and B/P indices; and 0.73 (P<0.001) between the C/D and B/P indices.


CONCLUSIONS
The determination of the PPA is a reproducible method that is consistent with the methods currently used to measure patellar height in patients with recurrent patellar dislocation.
Knee Surgery Division, Institute of Orthopedics and Traumatology, University o São Paulo, São Paulo, Brazil. Electronic address: bonadio@usp.br.
Marcelo Batista
MB
Bonadio
Knee Surgery Division, Institute of Orthopedics and Traumatology, University o São Paulo, São Paulo, Brazil.
Camilo Partezani
CP
Helito
Knee Surgery Division, Institute of Orthopedics and Traumatology, University o São Paulo, São Paulo, Brazil.
Julio Augusto
JA
do Prado Torres
Knee Surgery Division, Institute of Orthopedics and Traumatology, University o São Paulo, São Paulo, Brazil.
Riccardo Gomes
RG
Gobbi
Knee Surgery Division, Institute of Orthopedics and Traumatology, University o São Paulo, São Paulo, Brazil.
José Ricardo
JR
Pécora
Knee Surgery Division, Institute of Orthopedics and Traumatology, University o São Paulo, São Paulo, Brazil.
Gilberto Luis
GL
Camanho
Knee Surgery Division, Institute of Orthopedics and Traumatology, University o São Paulo, São Paulo, Brazil.
Marco Kawamura
MK
Demange
D000293:Adolescent; D000328:Adult; D001837:Body Weights and Measures; D002648:Child; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D010329:Patella / Q000000981:diagnostic imaging*; D031222:Patellar Dislocation / Q000000981:diagnostic imaging*; D012008:Recurrence; D012189:Retrospective Studies; D013977:Tibia / Q000000981:diagnostic imaging*; D055815:Young Adult
Knee; Measurement; Patellar dislocation; Patellar height; Plateau–patella angle; Radiograph