2015 ISAKOS Biennial Congress ePoster #1619
Evaluation of Lateral Meniscal Position With Weight Bearing: Ultrasonography to Measure Extrusion with Intact, Torn, and Repaired Posterior Root Attachments
Joshua D. Nelson, MD, PharmD, Shawnee, KS UNITED STATES
Grant Rowland, MD, Kansas City, KS UNITED STATES
Terrance McIff, PhD, Kansas City, KS UNITED STATES
Damon Mar, BS, Kansas City, KS UNITED STATES
Gary Hinson, MD, Kansas City, KS UNITED STATES
University of Kansas Medical Center, Kansas City, Kansas, USA
FDA Status Not Applicable
Summary: Ultrasound evaluation of meniscal root tears and repairs is better imaged through ultrasound in the weight bearing position, to determine functionality and position.
Meniscal extrusion is associated with increased contact pressure and decreased contact area in the ipsilateral joint space. The altered stress pattern can contribute to the advancement of knee osteoarthritis.2 The purpose of this study was to measure the relative position of the lateral meniscus within the knee under physiologic loads to determine the integrity of the posterior root. A novel technique was used to measure meniscal position with a portable ultrasound machine under physiologic loads. Our hypotheses were that (1) a significant increase in the amount of lateral meniscal extrusion would be exhibited with 50% and 100% posterior root tears compared to intact menisci, (2) imaging under loaded conditions would yield significantly larger extrusion measurements compared to unloaded state, and (3) meniscal position and extrusion following posterior root repair would correlate with the intact state.
Materials & Methods: Ten unmatched, fresh-frozen cadaver legs were utilized (mean age, 68.5 years; range, 24-94 years). A mechanical load frame (MLF) was used to apply a static, physiologic (70 kg) axial load through the knees. A portable, hand-held ultrasound was utilized for image capturing of the lateral meniscus in association with (1) an intact posterior root attachment, (2) a 50% cut posterior root, (3) a 100% cut posterior root, and (4) repaired posterior root attachment. Images were obtained on each knee while in an unloaded condition, and again while loaded with 70 kg for each of the above injury levels, and again following repair. Lateral meniscal extrusion was defined as the distance from the outer rim edge of the meniscus to the lateral-most edge of the tibial plateau.
Significant differences in extrusion were noted between the intact and 50% cut groups (p=0.028), between the intact and 100% cut groups (p<0.001), and between the 50% cut and 100% cut data groups (p=0.016) all in the loaded position. No significant difference was found in extrusion between intact state and repaired posterior root in the axially-loaded position (p=0.174). A two-factor ANOVA with replication revealed both load (p=0.003) and injury level (p=0.005) to have significant effects on the mean extrusion of the lateral meniscus.
Using a cadaver model, we demonstrated that sectioning of the lateral meniscus posterior root will produce significantly increased lateral extrusion of the meniscus under weight bearing at physiologic loads. Unlike MRI evaluation, weight bearing ultrasound images produce a functional assessment of meniscus integrity. After trans-tibial root repair, lateral meniscus position was shown to be similar to the intact state, under physiologic loading. In addition, this dynamic weight-bearing ultrasound technique may be a better functional assessment of meniscus integrity than traditional non-weight bearing MRI. Further clinical studies are needed to discern indications and technique to best address this often under-appreciated clinical presentation.