CT-based 3D planning-supported stem-free screw-cement augmentation versus 2D radiograph-planned short-stem reconstruction for AORI type I-II medial tibial defects in TKA: a two-year retrospective study.

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Abstract

Medial tibial defects in varus knee osteoarthritis (KOA) challenge alignment and tibial support in primary total knee arthroplasty (TKA). A stem-free metaphyseal screw-cement strategy supported by computed tomography (CT)-based three-dimensional (3D) planning, with artificial intelligence (AI)-assisted segmentation used for model generation in the planning software, may be a bone-preserving alternative to conventional two-dimensional (2D) radiograph planning with short tibial stems. This study compared early tibial alignment and clinical outcomes between two reconstructive pathways in Anderson Orthopaedic Research Institute (AORI) type I-II medial tibial defects. In this single-centre retrospective cohort, 97 patients with varus KOA and AORI type I-II medial tibial defects undergoing TKA were managed using either a CT-based 3D planning-supported stem-free screw-cement pathway (n = 38) or a 2D radiograph-planned short-stem pathway (n = 59). Given non-randomised pathway allocation, analyses assessed associations. The primary outcome was the absolute deviation of the mechanical medial proximal tibial angle (mMPTA) from 90° at 4-8 weeks. Secondary outcomes included achievement of mMPTA within 90° ± 3°, intraoperative visible blood loss, pain and function measured by the visual analogue scale (VAS), Knee Society Score (KSS), and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) at 3 and 24 months, and complications. Between-pathway comparisons used standard univariable tests, findings were interpreted as associative given non-randomised allocation. Baseline characteristics were comparable between pathways (all P > 0.05). Postoperative tibial alignment did not differ, with comparable absolute deviation of mMPTA from 90° and similar rates within 90° ± 3°. Operative time was similar, but visible blood loss was lower in the CT-3D screw-cement pathway than in the 2D short-stem pathway (262.7 ± 75.3 vs 381.9 ± 71.3 mL, P < 0.001). At 3 months, the CT-3D screw-cement pathway showed lower VAS and better KSS/WOMAC, whereas outcomes were comparable at 24 months. No deep infection, radiographic loosening, periprosthetic fracture, or revision was observed within 24 months. The CT-3D screw-cement pathway was associated with tibial alignment and 24-month function comparable to the 2D short-stem pathway, with lower blood loss and better early recovery. Fixation-related inferences are limited to early radiographic stability.

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