Patellar height measurement in trochlear dysplasia

Abstract

A number of measurements of patellar height are in clinical use all of which reference from the tibia. The patellotrochlear index (PTI) has been proposed recently as a more accurate reflection of the functional height of the patella and described in normal knees. We compared patellar height measurements in patients with patellofemoral dysplasia. In a retrospective analysis of the MRI scans of 33 knees in 29 patients with patellofemoral dysplasia we assessed the inter- and intraobserver reliability of four patellar height measurements: the recently described PTI, Insall-Salvati (IS), Blackburne-Peel (BP) and Caton-Deschamps (CD) ratios. We also assessed the correlation between the different measurements in predicting patella alta. Three blinded observers on two separate occasions performed the measurements. There were 21 females and 8 males with a median age of 21 years (range 13-33). Statistical analysis revealed good inter-observer reliability for all measurements (0.78 for PTI, 0.78 for IS, 0.73 for BP and 0.77 for CD). Intra-observer reliability was also good (0.80, 0.83, 0.75 and 0.78, respectively). There was weak correlation between the PTI and the other ratios for patella alta. There was a strong correlation between the CD and BP ratios (0.96) and a moderate correlation between IS and CD and IS and BP ratios (0.594 and 0.539, respectively). We propose the PTI as a more clinically relevant measure than the IS, CD and BP ratios.

The lateral condyle index: a new index for assessing the length of the lateral articular trochlea as predisposing factor for patellar instability

“…In addition, we found no pathological MR signs for abnormal patella height or TT-TG distance [14,15], which would merit specific surgical considerations [12,18]. Therefore, another underlying pathomorphology other than those described by Dejour et al [2,12] must be present for proximal lateral patellar subluxation close to extension.…”

“…Documentation of the patellar height was calculated on sagittal MR images using the patellotrochlear index [14]. Compared with other measurement methods, this has been shown to be the most clinical relevant [15,16]. The measurements were assessed independently by three raters: one radiologist (IG), and one experienced (PN) and one inexperienced (PT) orthopaedic surgeon.…”

The role of magnetic resonance imaging in the evaluation of patellofemoral joint diseases

“…Normal değerin üstünde veya altında ölçümlerde patella alta (Şekil 7) veya infera (baja) tanısı konur. [13] 2. Femoral troklear oluk-patellanın ilişkisinin değerlendirilmesi: En iyi aksiyel MR görüntü-lerinde yapılır.…”

“…Manyetik rezonans görüntülemenin troklear sulkus şekil ve karakterizasyonunu değerlendirme-de konvansiyonel röntgenden daha duyarlı olduğu gösterilmiştir. [13] Troklea yapısını değerlendirmede troklear sulkus açısı, lateral inklinasyon açısı, troklear sulkus derinliği ve troklear yükseklik kullanılan ölçümlerdir. Sulkus açısı 144 dereceden daha büyük ise hipoplazi göstergesidir (Şekil 10a).…”

MRT nach Patellaluxation: Quantifizierung der Risikofaktoren und Beschreibung der Folgeschäden

“…Es sind zahlreiche Methoden zur Vermessung des Abstands der Patella zum Tibiaplateau bekannt, die jeweils spezifische Vorund Nachteile aufweisen. In der klinischen Praxis haben sich für die Auswertung an sagittalen MRT-Bildern der Insall-Salvati-Index und der Canton-Duchamps-Index etabliert, die jeweils eine robuste Reproduzierbarkeit aufweisen [32,33]. Die ursprünglich an konventionellen Seitbildern entwickelten Messtechniken sind mit hoher Übereinstimmung an sagittalen MR-Bildern anwendbar [29,34].…”