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Standardized Sagittal Alignment Targets Fail to Restore Native Medial and Lateral Posterior Tibial Slope in Primary
Richard Hwang1, Fernando Quevedo-Gonzalez2, Carmelo Burgio3
1Department of Orthopedics, The Permanente Medical Group, Fremont, California.
Background:
Prior studies report high variability of the posterior tibial slope (PTS) in patients undergoing total knee arthroplasty (TKA). However, these studies are often performed using radiographs and do not differentiate between the medial and lateral PTS. The purpose of this study was to report the medial and lateral PTS using computed tomography (CT) on patients undergoing primary TKA.
Methods:
Retrospective analysis was performed on 591 consecutive patients undergoing a robotic-assisted TKA from May 2023 to November 2024. Preoperative CT scans were obtained as part of the standard CT-based planning workflow and used to measure the medial and lateral PTS relative to the tibial mechanical axis.
Results:
The mean medial PTS was 6.9° (range, -5.9 to 25.8), while the mean lateral PTS was 9.3° (range, -3.4 to 24.6; P < 0.01). The medial PTS was greater for women (mean 7.5°, range, -3.9 to 25.8) than for men (mean 6.4°, range, -5.9 to 21.1; P < 0.01). The lateral PTS was 9.1° (range, -3.4 to 24.6) for women and 9.6° (range, -0.4 to 23.7) for men (P = 0.09). There were 45% of patients who had a medial PTS of greater than 3° from the mean, while there were 40% of patients who had a lateral PTS of greater than 3° from the mean. Using a standardized sagittal alignment target of 3° of PTS would result in greater than 4° deviation from the native medial and lateral PTS in 51 and 71% of patients, respectively.
Conclusion:
Patients undergoing primary TKA demonstrate high variability in medial and lateral PTS as measured on preoperative CT. The use of standardized sagittal alignment targets in TKA will alter the medial and lateral PTS in a large proportion of patients. Additional studies are needed to determine the optimal target for PTS in patients undergoing primary TKA.
