Abstract
PurposeThe medial patellofemoral ligament (MPFLL)/lateral patellar retinaculum (LPR) ratio were assessed in knees as a means to detect patellar malalignment. We also aimed to evaluate the prevalence of the various types of trochlear dysplasia in patients with patellar malalignment.Materials and methodsAfter approval of our institutional ethics committee, we conducted a retrospective study that included 450 consecutive patients to evaluate them for the presence of patellar malalignment. Parameters investigated were the trochlear type, sulcus angle, presence of a supratrochlear spur, MPFLL, LPR, patella alta, and patella baja by means of 1.5T magnetic resonance imaging (MRI). Overall, 133 patients were excluded because of the presence of major trauma, multiple ligament injuries, bipartite patella, and/or previous knee surgery. The Dejour classification was used to assess trochlear dysplasia. Two experienced radiologists (HKY, EEE) evaluated the images. Their concordance was assessed using the kappa (κ) test.ResultsThe frequencies of patellar malalignment and trochlear dysplasia were 34.7 and 63.7 %, respectively. The frequency of trochlear dysplasia associated with patellar malalignment was 97.2 %. An MPFLL/LPR ratio of 1.033–1.041 had high sensitivity and specificity for malalignment. The researchers’ concordance was good (κ = 0.89, SE = 0.034, P < 0.001).ConclusionTrochlear dysplasia is frequently associated with patellar malalignment. An increased MPFLL/LPR ratio is useful for detecting patellar malalignment on knee MRI, which is a novel quantitative method based on ligament length.
Highlights
Patellar malalignment is defined as an abnormal position of the patella with respect to the femoral trochlear groove in any position (Grelsamer 2005)
Trochlear dysplasia is frequently associated with patellar malalignment
An increased medial patellofemoral ligament (MPFLL)/lateral patellar retinaculum (LPR) ratio is useful for detecting patellar malalignment on knee magnetic resonance imaging (MRI), which is a novel quantitative method based on ligament length
Summary
Patellar malalignment is defined as an abnormal position of the patella with respect to the femoral trochlear groove in any position (Grelsamer 2005). With lateral tracking of the patella, is held responsible for the patellofemoral pain syndrome, which is a common problem (Doucette and Goble 1992). Important predisposing factors for patellar malalignment are trochlear dysplasia, medial patellofemoral ligamentous laxity, lateral retinacular shortness, patella alta, a tibial tubercle–trochlear groove (TT-TG) distance of >20 mm, and patellar tilt (Bollier and Fulkerson 2011; Arendt and Dejour 2013; Oliveira et al 2014). The first line of treatment of patellofemoral malalignment is conservative. When it is decided that surgery is necessary, various combinations of medial patellofemoral ligament (MPFL) reconstruction, lateral release, medial capsular plication, and trochleoplasty can be used (LaPrade et al 2014). Preoperative anatomic evaluation is important for the surgical decision and selection of techniques to be used
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