Ingy Hanna MD, Presenter: Nothing to Disclose

Javier Beltran MD, Abstract Co-Author: Nothing to Disclose

The characteristic findings of lateral patellar dislocation on MRI have been well documented in the literature for many years. One of the most common injuries associated with lateral patellar dislocation is tear of the medial patello-femoral ligament (MPFL). Our objective is to assess the association of specific MPFL tears with other injuries during lateral patellar dislocation.

This study reviews 42 patients, ages 11-42, with lateral patellar dislocation on MRI. The images were evaluated by fellowship trained musculoskeletal radiologists for the presence and location of MPFL tear, other ligamentous tears, chondral and osteochondral injury, bone contusions, tendinous strain, and muscle injury. Demographic data, including age, sex, knee affected and activity being performed when injury took place were retrieved from the chart. Fisher’s exact tests were performed to compare group differences in percent outcome.

To be included patients had to be diagnosed as having lateral patellar dislocation on MRI.  Forty two patients, including 29 males and 13 females with a mean age of 19.4 years (range, 11-42 years), were included. MRI demonstrated MPFL tear at an isolated patellar insertion in 31% of patients (n=13) and an isolated femoral insertion in 57% of patients (n= 24). One patient had MPFL injury at more than one site. Patients with an isolated patellar MPFL tear were more likely to have a lateral femoral condyle (LFC) chondral injury (36% vs 7 %, p= .047) as well as medial meniscal injury (29% vs 0 %, p=.009) . Patients with an isolated femoral MPFL tear were found to have vastus medialis oblique (VMO) injury (68% vs 24%, p= .011).

The association between specific MPFL insertion tears and meniscal, LFC chondral and VMO injury has not been described in the literature. Patients with MPFL tear at the patellar insertion are more likely to have LFC chondral and medial meniscal injury. Patients with MPFL tear at the femoral insertion are more likely to have VMO affliction. Identification of MPFL tear should increase the interpreting radiologists sensitivity to associated injuries.

Lateral patellar dislocation is a common injury amongst active young adults. The identification of associated injuries may potentially alter treatment and rehabilitation options for the patient.

Hanna, I, Beltran, J, Lateral Patellar Dislocation: Medial Patello-Femoral Ligament Tears and Their Associated Injuries.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12029318.html