Shrey Kumar Thawait MD, Presenter: Nothing to Disclose

Majid Chalian MD, Abstract Co-Author: Nothing to Disclose

Vibhor Wadhwa, Abstract Co-Author: Nothing to Disclose

John A. Carrino MD, MPH, Abstract Co-Author: Research Grant, Siemens AG Research Grant, Carestream Health, Inc Research Consultant, General Electric Company

John Eng MD, Abstract Co-Author: Nothing to Disclose

Avneesh Chhabra MD, Abstract Co-Author: Research Grant, Siemens AG Research Consultant, Siemens AG Research Grant, Integra LifeSciences Holdings Corporation Research Grant, General Electric Company

The association of patellar instability, dislocation and retinacular tears, including medial patellofemoral ligament injury is well established in the literature. However, there is no information on how the patellar instability/malalignment affects the thickness of the medial patellar retinaculum (MPR) and lateral patellar retinaculum (LPR) on MR imaging (MRI). The purpose of this study was to determine the association of thickness of the MPR and LPR at multiple levels with patellar malalignment measures.

Institutional review board approval was obtained for this HIPAA compliant study. MRI scans of knees were reviewed. The maximal thickness of MPR and LPR was measured at the femoral attachment, the mid portion and at the patellar attachment. Anatomical parameters of patellar instability, such as Patellar Tendon-Patellar Length (PTPL) ratio using the Insall-Salvati method and Tibial Tubercle-Trochlear Groove (TTTG) distance were measured using the Schoettle and coworkers' method. Paired t-test was used to compare variables. P value of <0.05 was considered statistically significant.

37 knee MRIs were evaluated (24 women, 13 men, age range 13-75 years, mean age ± SD of 38±18 years, right knee 13, and left knee 24). Using a cut-off of ≥15mm for TTTG distance, the case group consisted of 12 patients while the control group comprised of 25 patients. The mean thickness ± SD (mm) of MPR in case and control group was 0.11±0.04 and 0.16±0.04 at the patellar attachment; 0.10±0.02 and 0.15±0.04 at mid portion; and 0.09±0.03 and 0.12±0.04 at the femoral attachment respectively. The mean thickness ± SD (mm) of LPR in case and control group was 0.24±0.3 and 0.12±0.04 at the femoral attachment, respectively. These differences were statistically significant. No significant differences in thickness of MPR and LPR were found in the cases and controls based on PTPL ratio.

Statistically significant diffuse attenuation (thinning) of the MPR, and focal thickening of the LPR at femoral attachment is seen with patellar malalignment, likely related to abnormal stresses and chronic remodeling.

Retinacular thickness should be reported in knee MRIs performed for patellar instability, as they may have implications for future tears/pre-operative planning.

Thawait, S, Chalian, M, Wadhwa, V, Carrino, J, Eng, J, Chhabra, A, Is There an Association between the Thickness of Medial and Lateral Patellar Retinacula and Patellar Malalignment Measures?.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12043680.html