ISAKOS: 2023 Congress in Boston, MA USA

2023 ISAKOS Biennial Congress ePoster

 

Implant Size and Outcome Differences of Knees in Same Patient for Simultaneous vs Staged Bilateral TKA

Alexander P. Sah, MD, Fremont, CA UNITED STATES
Sah Orthopaedic Associates, Fremont, CA, UNITED STATES

FDA Status Cleared

Summary

Surgeons should be aware of this occurrence of size differences to avoid improperly sizing the second knee based only on its contralateral counterpart.

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Abstract

Introduction

The importance of anatomic variation in knee replacement prosthesis selection has gained popularity, encouraging more prosthesis size options for proposed customization and personalization. Size differences can also occur between knees of the same individual. The purpose of this study is to evaluate the frequency of anatomic variation between knees within the same patient and to determine whether outcomes differ depending on the component size.

Methods

From 2008-2017, 530 patients underwent staged or simultaneous bilateral knee replacements by a single surgeon. Of the 1060 procedures, there were 400 simultaneous TKAs and 660 staged procedures. Patients had an average of 70 at time of the first surgery, and BMI of 30. Patients were evaluated for perioperative complications and by clinical outcomes. Radiographs were evaluated for implant positioning and appropriateness of size.

Results

Component sizes differed within the same patient in 36.2% (384/1060). Femoral sizes differed in 50 patients (4.7%), the tibia 55 (5.2%), the patella 46 (4.3%), and liner 233 (22.0%). In 12 patients, the femur and tibia simultaneously differed in size from one knee to the other. The liner size differed simultaneously with 14 patients with differing femurs, and was thicker in 13 knees with larger tibial components, and thicker in 9 with smaller tibial components. Tibial size did not seem dependent on depth of tibial resection as the tibial insert thickness did not correlate with smaller tibial sizes (p=0.47).

Discussion

Liner thickness most frequently varies between knees, but femoral, tibial, and patellar component sizes can also differ with some regularity. Surgeons should be aware of this occurrence of size differences to avoid improperly sizing the second knee based only on its contralateral counterpart. The variability in prosthesis size is appropriate anatomically and leads to comparable outcomes compared to the contralateral knee.

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