MRI of Incidental Osteochondral Lesions of the Anterior Femoral Condyle: Are they caused by Repetitive Patellar Impaction?

Research Article

Austin J Radiol. 2016; 3(4): 1056.

MRI of Incidental Osteochondral Lesions of the Anterior Femoral Condyle: Are they caused by Repetitive Patellar Impaction?

Nasim Hemmati, Ravi Shergill and Hema N Choudur*

Department of Radiology, McMaster University, Canada

*Corresponding author: Gokhan Ozkan, Adnan Menderes University, Faculty of Dentistry, Department of Oral and Maxillofacial Radiology, Aydin, Turkey

Received: August 22, 2016; Accepted: September 28, 2016; Published: October 03, 2016

Abstract

Objective: Osteochondral lesions of the anterior femoral condyle are frequent incidental findings. However, little is known about these lesions.

The purpose of this investigation was to determine the location, prevalence and pattern of these lesions.

Materials and Methods: 322 consecutive knee MRIís were retrospectively reviewed on PACS by a fellowship trained musculoskeletal radiologist for presence, location, and grade of the osteochondral lesions in anterior femoral condyle. Other data included suprapatellar or infrapatellar fat pad edema, patellar or patellar tendon lateralization.

Results: 13% of cases demonstrated osteochondral lesions in the anterior femoral condyle. All 44 positive cases demonstrated lesions at the level of inferior margin of the patella (57%) or within 1 cm below the level of the patella (43%). In 29% of cases, the lesions were located in the trochlear groove, 38% in medial aspect of the lateral femoral condyle and 32% in the lateral aspect of the medial femoral condyle. 40% of cases showed suprapatellar fat pad edema, 11% infrapatellar fat pad edema, 22% lateralization of patella or patellar tendon.

Conclusion: Incidental finding of osteochondral lesions in the anterior femoral condyle had a prevalence of 13% in our study. All of the lesions were located at or within 1 cm below the level of the inferior margin of the patella. Based on the location of the lesions, we propose that the mechanism of injury is from repetitive chronic impaction of the inferior margin of patella against the femur during hyperextension or hyperflexion of the knee.

Keywords: Osteochondral lesions; Anterior femoral condyle; Knee MRI; Anterior knee; Patellofemoral joint

Introduction

Osteochondral lesions of the anterior femoral condyle are frequently observed incidental findings on MRI of knees referred for various clinical scenarios. However, there are no specific descriptions of such lesions in the English literature, to the best of our knowledge. The purpose of this investigation was to determine the patterns of the osteochondral lesions in the anterior femoral condyle, including their location, grade and percentage occurrence in our sample. Based on this information, the probable mechanism causing these lesions was proposed.

Materials and Methods

Institutional review board approval was obtained before the initiation of this investigation. Consecutive patients who had undergone MR Imaging of the knees in 2008 and 2009 were identified and their images were reviewed on the PACS. The study group included 322 knee MRI images from 311 patients aged 16 or above. The patients were imaged on a Siemens 1.5 Tesla magnet. The sagittal PD Fat Saturated (FS) and T2 fat sat and axial PD FS sequences were reviewed (Sagittal PD FS: TR: 2710- 3110, TE: 13-14 ST: 3-4/ Sagittal T2: TR: 2900- 3000 TE: 74-78 ST: 3-4/Axial PD FS: TR: 1,800, TE: 29- 31 ST: 4). The sagittal PD and T2 fat saturated images were used to grade the lesions and determine the level of the lesion with respect to inferior margin of the patella. The axial PD FS images were reviewed to localize the lesion in the anterior femoral condyles and the trochlea.

The images were reviewed on the PACS system by a fellowship trained musculoskeletal radiologist with more than 10 years of experience. The presence, location, and grade of the osteochondral lesions in anterior femoral condyle were categorized. Those cases that were found positive for anterior osteochondral lesions were also evaluated for other MR features that reflect patellar impingement against the anterior femoral condyle. These features included suprapatellar or infrapatellar fat pad edema, patellar or patellar tendon lateralization. This methodology was used to propose the mechanism causing the anterior osteochondral lesions.

The location of a lesion was categorized into [1] medial femoral condyle [2] lateral femoral condyle, or [3] within the trochlear groove. The lesions in the medial or lateral femoral condyle were further subcategorized into the medial or lateral aspect of either medial or lateral aspects of the anterior femoral condyle.

The level of a lesion was categorized as: at the level of the inferior margin of the patella, below the inferior margin of the patella, or above the inferior margin of the patella as shown in Figure 1.