Purpose
To arthroscopically describe patellar position based on lateralization, tilt, and
engagement, and compare measurements in normal, medial patellofemoral complex-(MPFC)
deficient, and MPFC-reconstructed knees.
Methods
In 10 cadaveric knees, arthroscopic patellar position was assessed by performing digital
measurements on arthroscopic images obtained through a standard anterolateral portal.
Lateralization was measured as millimeters overhang of the patella past the lateral
edge of the lateral femoral condyle, viewing from the lateral gutter. Patellar tilt
was calculated as the difference in medial and lateral distances from the patella
to the trochlea, viewing from the sunrise view. Patellotrochlear distance was measured
as the anteroposterior distance between the central trochlear groove and patella on
the sunrise view. Measurements were obtained at 10° intervals of knee flexion from
0° to 90°, in intact knees (group 1), after arthroscopically transecting the MPFC
fibers (group 2), and after MPFC reconstruction (group 3). Optimal cutoff values were
identified to distinguish between intact versus MPFC-deficient states.
Results
When compared to group 1, group 2 demonstrated increased patellar lateralization by
22.5% at 0°-40° knee flexion (P = .006), which corrected to baseline in group 3 (P = .006). Patellar tilt measurements demonstrated no differences between groups. Patellotrochlear
distance increased by 21.0% after MPFC transection (P = .031) at 0°-40° knee flexion, with correction to baseline after MPFC reconstruction
(P = .031). More than 7 mm of lateral overhang at 20°-30° flexion and >6 mm of patellotrochlear
distance at 10°-20° flexion were found to indicate MPFC deficiency.
Conclusions
Utilizing standardized arthroscopic views, we identified significant increases in
patellar lateralization and patellotrochlear distance in early knee flexion angles
after MPFC transection, and these changes normalized after MPFC reconstruction.
Clinical Relevance
Arthroscopic assessments of patellar position may be useful in evaluating patellofemoral
stability during patellar stabilization surgery.
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Article info
Publication history
Published online: July 09, 2021
Accepted:
June 29,
2021
Received:
February 17,
2021
Footnotes
The authors report the following potential conflicts of interest or sources of funding: B.L. and G.W. report nonfinancial research support from Arthrex, Inc., during the conduct of the study. Full ICMJE author disclosure forms are available for this article online, as supplementary material.
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© 2021 by the Arthroscopy Association of North America
