Role of Rotation in Total Ankle Replacement.
BACKGROUND
The importance of total ankle replacement (TAR) implant orientation in the axial plane is poorly understood with major variation in surgical technique of implants on the market. Our aim was to better understand the axial rotational profile of patients undergoing TAR.


METHODS
In 157 standardized computed tomography (CT) scans of patients with end-stage ankle arthritis planning to undergo primary TAR surgery, we measured the relationship between the knee posterior condylar axis, the tibial tuberosity, the transmalleolar axis (TMA), and the tibiotalar angle. The foot position was measured in relation to the TMA with the foot plantigrade. The variation between the medial gutter line and the line bisecting both gutters was assessed.


RESULTS
The mean external tibial torsion was 34.5 ± 10.3 degrees (11.8-62 degrees). When plantigrade, the mean foot position relative to the TMA was 21 ± 10.6 degrees (0.7-38.4 degrees) internally rotated. As external tibial torsion increased, the foot position became more internally rotated relative to the TMA (Pearson correlation, 0.6; P < .0001). As the tibiotalar angle became more valgus, the foot became more externally rotated relative to the TMA (Pearson correlation, -0.4; P < .01). The mean difference between the medial gutter line and a line bisecting both gutters was 4.9 ± 2.8 degrees (1.7-9.4 degrees). More than 51% of patients had a difference greater than 5 degrees. The mean angle between the medial gutter line and a line perpendicular to the TMA was 7.5 ± 2.6 degrees (2.8-13.7 degrees).


CONCLUSION
There was a large variation in rotational profile of patients undergoing TAR, particularly between the medial gutter line and the TMA. Surgeon designers and implant manufacturers should develop consistent methods to guide surgeons toward judging the appropriate axial rotation of their implant on an individual basis. We recommend careful clinical assessment and preoperative CT scans to enable the correct rotation to be determined.


LEVEL OF EVIDENCE
Level IIc, outcomes research.
['Najefi|Ali-Asgar|AA|https://orcid.org/0000-0002-2871-6735', 'Ghani|Yaser|Y|', 'Goldberg|Andy|A|']
D000328:Adult D000368:Aged D000369:Aged, 80 and over D058737:Arthroplasty, Replacement, Ankle D005260:Female D006801:Humans D021621:Imaging, Three-Dimensional D008297:Male D008875:Middle Aged D010003:Osteoarthritis D012189:Retrospective Studies D012399:Rotation D013628:Talus D013977:Tibia D014057:Tomography, X-Ray Computed D014102:Torsion Abnormality
arthritis gutter alignment biomechanics deformity impingement loosening