Optimizing Mechanical Alignment With Modular Stems in Revision TKA
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Published on: February 27, 2018
Andrew N Fleischman1, Ibrahim Azboy1, Camilo Restrepo1
1The Rothman Institute at Thomas Jefferson University, Philadelphia, Pennsylvania.
Background:
Although mechanical alignment is critical for optimal function and long-term implant durability, the role of modular stems in achieving ideal alignment is unclear.
Methods:
We identified 319 revision total knee arthroplasty from 2003-2013, for which stem length, stem diameter, and stem fixation method were recorded prospectively. Three-dimensional canal-filling ratio, the product of canal-filling ratio at the stem tip in both the anteroposterior and lateral planes, and alignment were measured radiographically.
Results:
Ideal alignment of the femur was considered to be 95° in the anteroposterior (AP) plane and from 1° of extension to 4° of flexion in the lateral plane, and ideal tibial alignment was considered to be 90° in the AP plane. Even after accounting for difference in stem size and canal-fill, ideal AP alignment was more reliably achieved with press-fit stems.
Conclusion:
Furthermore, increased engagement of the diaphysis and its anatomical axis with canal-filling stems facilitates accurate alignment.
