2023 ISAKOS Biennial Congress ePoster
Intra-Articular Femorotibial Rotation is Associated with Tibial Tubercle-Trochlear Groove Distance
Nicolas Pascual-Leone, BA, Philadelphia, PA UNITED STATES
Amirhossein Jahandar, MS, New York, NY UNITED STATES
Ryann Davie, MD, New York, NY UNITED STATES
Joshua T Bram, MD, New York, NY UNITED STATES
Danielle E Chipman, BS, New York, NY UNITED STATES
Carl W Imhauser, PhD, New York, NY UNITED STATES
Daniel W. Green, MD, MS, New York, NY UNITED STATES
Hospital for Special Surgery, New York, NY, UNITED STATES
FDA Status Not Applicable
Summary
TT-TG distance may depend on the internal/external (IE) rotation of the tibia in relation to the femur, which is typically not controlled for. TT-TG was highly dependent on knee joint IE rotation changing by 0.52mm for every degree of knee joint IE rotation. Physicians should pay close attention to knee joint IE rotation when measuring TT-TG in their patients.
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Abstract
Objectives: A tibial tubercle-trochlear groove (TT-TG) distance of 20 mm is typically used when determining whether tibial tubercle anteromedialization (AMZ) is needed for patellar instability. TT-TG distance, however, may depend on the internal/external (IE) rotation of the tibia in relation to the femur, which is typically not controlled for. Without knowledge of the variability in an individual’s TT-TG influenced by femorotibial rotation, the use of a specific TT-TG distance during pre-operative planning for patellar instability may lead to incorrect decisions on the use of tibial tubercle AMZ. We hypothesized that knee joint IE rotation is related to the TT-TG distance.
Methods
A total of 8 independent human cadaveric knee specimens (age: 32±6; 4 males, 4 females) were utilized. A robotic manipulator (ZX165U, Kawasaki Robotics, Wixom, MI, USA) instrumented with a universal force/moment sensor was used to determine knee joint internal/external (IE) rotation under applied moments of ±5Nm at full extension. Two independent reviewers selected the trochlear groove and tibial tuberosity points on CT images of each specimen to define TT-TG (ICC=0.969). To determine the influence of knee joint IE rotation on TT-TG, 3D models generated from CT scans were registered to tibiofemoral kinematics. Subsequently, linear regression was performed to determine the relationship between knee joint IE rotation and TT-TG. Regression coefficient and standard error of measurement (a=0.05), and coefficient of determination (r2) were reported.
Results
Knee joint IE rotation averaged 23.0 ± 4.2°. TT-TG changed by 12.1 ± 2.8 mm over this range. For every degree of knee joint IE rotation, TT-TG changed by 0.52 ± 0.07 mm (p<0.001 and r2>0.987). At neutral rotation, the TT-TG averaged 14.21 ± 5.0 mm.
Conclusion
TT-TG was highly dependent on knee joint IE rotation changing by 0.52 mm for every degree of knee joint IE rotation. Thus, an offset in IE rotation of 10° would lead to a change in TT-TG of 5.2 mm, enough to alter surgical decision making for or against tibial tubercle AMZ. Physicians should pay close attention to knee joint IE rotation when measuring TT-TG in their patients, specifically in patients found to have a TT-TG near 20 mm, a key indication for surgical treatment of patellar instability.