Total Hip Arthroplasty in the Severely Narrowed Femoral Canal by a Fibular Strut Using Knee Arthroscopic Tools: A Case Report and Technical Note.

A 58-year-old-male patient presented with worsening pain and restricted movements of his right hip after undergoing multiple procedures for treatment of an inter-trochanteric fracture. Secondary arthrosis and an incorporated intramedullary fibular cortical bone graft which caused severe narrowing of the medullary canal were observed by imaging. Total hip arthroplasty (THA) using knee arthroscopic tools was performed for preparation of the severely narrowed femoral canal. A satisfactory clinical outcome was achieved and stable components were observed on radiographs at the 11-year follow-up. The technique described here may be considered when attempting to perform a conversion THA for preparation of a severely narrowed femoral canal using a fibular strut in order to minimize morbidity and prevent structural destabilization.

Tibial tray rotation and posterior slope increase risk for outliers in coronal alignment.

AIMS: The extensive variation in axial rotation of tibial components can lead to coronal plane malalignment. We analyzed the change in coronal alignment induced by tray malrotation. METHODS: We constructed a computer model of knee arthroplasty and used a virtual cutting guide to cut the tibia at 90° to the coronal plane. The virtual guide was rotated axially (15° medial to 15° lateral) and with posterior slopes (0° to 7°). To assess the effect of axial malrotation, we measured the coronal plane alignment of a tibial tray that was axially rotated (25° internal to 15° external), as viewed on a standard anteroposterior (AP) radiograph. RESULTS: Axial rotation of the cutting guide induced a varus-valgus malalignment up to 1.8° (for 15° of axial rotation combined with 7° of posterior slope). Axial malrotation of tibial tray induced a substantially higher risk of coronal plane malalignment ranging from 1.9° valgus with 15° external rotation, to over 3° varus with 25° of internal rotation. Coronal alignment of the tibial cut changed by 0.07° per degree of axial rotation and 0.22° per degree of posterior slope (linear regression, R2 > 0.99). CONCLUSION: While the effect of axial malalignment has been studied, the impact on coronal alignment is not known. Our results indicate that the direction of the cutting guide and malalignment in axial rotation alter coronal plane alignment and can increase the incidence of outliers. Cite this article: Bone Joint J 2020;102-B(6 Supple A):43-48.