Clin Orthop Surg.  2012 Sep;4(3):193-199. 10.4055/cios.2012.4.3.193.

Three Dimensional CT-based Virtual Patellar Resection in Female Patients Undergoing Total Knee Replacement: A Comparison between Tendon and Subchondral Method

• Park DY
• Ji HM
• Kwak KS
• Nair SG
• Won YY

• KMID: 1392981
• DOI: http://doi.org/10.4055/cios.2012.4.3.193

Abstract

BACKGROUND
Due to its small size, variable shape, and lack of distinct anatomical landmarks, osteoarthritic knees make a precise patellar resection extremely difficult.
METHODS
We performed virtual patellar resection with digital software using three dimensional computed tomography scans of knees from 49 patients who underwent primary total knee replacement at our hospital. We compared 2 commonly used resection methods, the tendon method (TM) and the subchondral method, to determine an ideal resection plane with respect to the symmetry and thickness of the patellar remnant.
RESULTS
The TM gave a thicker resected patella, and a less oval cut surface shape, which gives better coverage for a domed prosthesis. Both methods, however, gave a symmetric resection both superior-inferiorly, as well as mediolaterally.
CONCLUSIONS
Although TM appears statistically better with respect to the thickness and cut surface shape, only further intraoperative studies with long-term clinical follow-up may provide us with the most appropriate patellar resection method.

Keyword

Three dimensional computed tomography; Patellar resurfacing

MeSH Terms

Aged
Aged, 80 and over
Arthroplasty, Replacement, Knee/*methods
Female
Humans
Imaging, Three-Dimensional/*methods
Middle Aged
Patella/*anatomy & histology/*surgery
Surgery, Computer-Assisted/*methods
Tomography, X-Ray Computed/*methods

Figure

• 

  Fig. 1 Reconstruction of three-dimensional (3D) computed tomography images of the knee using specialized computer software. Note the corresponding coronal, sagittal and axial views (2D images) together with the 3D knee image.

• 

  Fig. 2 Thickness of the patella on the three-dimensional image is shown by the white arrow.

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  Fig. 3 Subchondral method showing the plane of resection (white dotted line) in the two-dimensional (2D) axial (A) and 3D sagittal (B) images, and the cut surface in the 2D coronal image (C) showing the cut surface width (W) and height (H) (black line).

• 

  Fig. 4 Anatomic landmarks chosen (white arrows) for resection at the fat fascia-tendon junctions, for the tendon method of resection. Posterior limits of the quadriceps tendon medially (A) and laterally (B) and one at the posterior limit (C) of patellar tendon inferiorly, where the Hounsfield units changed from fat (negative) to fascia-tendon (positive), just outside the bone. These 3 points defined the plane of resection for the tendon method.

• 

  Fig. 5 A-B measurement of the medial (white arrow) and lateral thickness (dotted arrow) for mediolateral symmetry (A) and superior (white arrow) and inferior thickness (dotted arrow) for superoinferior symmetry (B).

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  Fig. 6 A schematic representation of the resection planes with the 2 methods. The subchondral method gives a resection surface almost parallel with the anterior surface (green oval), while the tendon method gives a more oblique resection plane (red oval), shown here slightly exaggerated (red arrows). This demonstrates why the cut surface height is more with tendon method (Ht) than with the subchondral method (Hs).

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