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General Orthopaedics

TIBIAL COMPONENT ROTATION DURING THE UNICOMPARTMENTAL KNEE ARTHROPLASTY: IS THE ANTERIOR SUPERIOR ILIAC SPINE APPROPRIATE GUIDANCE FOR DETERMINATION OF THE TIBIAL COMPONENT ROTATION?

The International Society for Technology in Arthroplasty (ISTA), 29th Annual Congress, October 2016. PART 2.



Abstract

Purpose

We aimed to investigate whether the anterior superior iliac spine could provide consistent rotational landmark of the tibial component during mobile-bearing medial unicompartmental knee arthroplasty (UKA) using computed tomography (CT).

Methods

During sagittal tibial resection, we utilized the ASIS as a rotational landmark. In 47 knees that underwent postoperative CT scans after medial UKA, the tibial component position was assessed by drawing a line tangential to the lateral wall of the tibial component. Rotation of the tibial component was measured using two reference lines: a line perpendicular to the posterior cortical rim of the tibia (angle α) and Akagi's line (angle β). Instant bearing position and posterior cruciate ligament fossa involvement were also evaluated. External rotation of the tibial component relative to each reference line and external rotation of the bearing relative to the lateral wall of the tibial component were considered positive values.

Results

The mean angle α and β were 8.0 ± 6.1° (range, −4.0 – 24.3) and 8.7 ± 4.8° (range, 1.9 – 25.2), respectively. The mean instant bearing position was 4.3 ± 28.6° (range, −52.9 – 179.7). One bearing showed complete 180° rotation at 2 weeks postoperatively. Fourteen knees (29.8%) showed posterior cruciate ligament fossa involvement of the tibial resection margin.

Conclusions

Due to the wide variation in, and inherent difficulty in identification of, the ASIS during the operation, it is not recommended for guidance of sagittal tibial resection during mobile-bearing medial UKA.

Level of Evidence: Level IV


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