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. 2025 Feb 17;37(1):8.
doi: 10.1186/s43019-025-00260-x.

Caliper verification and gap measurements of kinematic alignment total knee arthroplasty utilizing an imageless, accelerometer-based navigation system

James H Sikes  1 , Drew P Melancon  1 , Isaac J Spears  1 , Evan H Powers  1 , Spencer J Montgomery  2
Affiliations

Caliper verification and gap measurements of kinematic alignment total knee arthroplasty utilizing an imageless, accelerometer-based navigation system

James H Sikes et al. Knee Surg Relat Res. .

Abstract

Purpose: Kinematic alignment (KA) in total knee arthroplasty (TKA) aims to restore the patient's knee to the prearthritic state. The purpose of this study was to investigate the accuracy of using an implant-agnostic, imageless, accelerometer-based navigation system to perform KA TKA on the basis of caliper verification and quantification of the flexion and extension gaps.

Materials and methods: Seven cadaveric lower extremities underwent primary TKA utilizing a kinematic alignment workflow with the imageless navigation system. Accuracy of the technique was confirmed through caliper verification of bone cuts.

Results: All cuts were within 1 mm of anticipated measurements, except for the lateral tibial fragment, which averaged 1 mm (standard deviation [SD] 0.9 mm) thicker than anticipated. In extension, medial and lateral gaps were symmetric and averaged within 0.6 mm of expectation. In flexion, the medial gap averaged within 0.5 mm of expectation, while the lateral gap averaged 2.6 mm larger than the symmetric expectation, consistently producing a trapezoidal space.

Conclusions: The implementation of an accelerometer-based navigation system in KA TKA allows for highly accurate results, which was confirmed with caliper verification. This workflow produced a symmetric extension gap and a trapezoidal flexion gap with an average increased lateral flexion gap of 2.6 mm compared with the medial side.

Keywords: Caliper; Kinematic alignment; Navigation; Total knee arthroplasty; Total knee replacement.

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Conflict of interest statement

Declarations. Ethics approval and consent to participate: Formal institutional review board (IRB) approval is not required for cadaveric study. Consent for publication: Not applicable. Competing interests: The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
The OrthAlign settings demonstrate femoral flexion (degrees) and tibial slope (degrees)
Fig. 2
Fig. 2
The femur is registered, and resections are made on the basis of desired settings
Fig. 3
Fig. 3
Depth resection paddles are resting on healthy cartilage on the medial and femoral condyles when placed according to mLDFA measurement
Fig. 4
Fig. 4
The tibia is registered, and resections are made on the basis of desired settings
Fig. 5
Fig. 5
The gap measurement was obtained by inserting the paddles and turning the torque driver
Fig. 6
Fig. 6
Gap assessment was performed in extension, demonstrating a symmetric extension gap
See this image and copyright information in PMC

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