Distal cortical notching significantly decreases tibial stability following tibial tubercle osteotomy: An in vitro porcine biomechanical study.

Abstract

Distalizing tibial tubercle osteotomy (dTTO) is an effective treatment for patella alta, yet complications can be severe. This study evaluates the biomechanical effects of distal cut orientation on tibial fracture risk. It was hypothesised that orthogonal cutting and cortical notching reduce tibial stability. A total of 61 porcine tibiae were tested in three setups. Four distal cut orientations were compared in a load-to-failure analysis (<i>n</i> = 32): oblique (Obl), orthogonal without notch (Orth), orthogonal 2-mm notch (Orth2), orthogonal 4-mm notch (Orth4) (each <i>n</i> = 8). Cyclic loading was evaluated in Obl, Orth and Orth2 (<i>n</i> = 17), followed by comparison of plate versus (2-hole one-third tubular plate) 3.5-mm screw fixation in Orth2 specimens (<i>n</i> = 12). Specimens were embedded in PMMA and axially loaded (MTS Bionix 358). Load-to-failure, stiffness and cycles until failure were recorded. Residual tibial thickness was measured. Linear regression analysed the relationship between residual thickness and failure load. Statistical analysis included <i>t</i>-tests and ANOVA (<i>α</i> = 0.05). Obl showed the highest failure load (784.5 N ± 118.3), although the difference compared to Orth (538.8 N ± 229.5, <i>p</i> = 0.087) did not reach statistical significance. Notching significantly reduced load-to-failure (2-mm: 294.0 N ± 91.8; 4 mm: 274.6 N ± 96.5). In cyclic testing, Obl withstood most cycles until failure (5894 ± 2187) compared to Orth (3142 ± 808; <i>p</i> = 0.004), while Orth2 failed sooner (1400 ± 530, all <i>p</i> < 0.005). Osteosynthesis techniques did not affect failure load (<i>p</i> = 0.802). Stiffness and residual tibial thickness were comparable. Distal tibial thickness was associated with failure load in all groups (all <i>p</i> < 0.05). In this porcine model, cortical notching significantly reduced tibial stability and should be avoided during TTO. Oblique distal cuts demonstrated greater resistance to cyclic loading, while no significant difference was observed in static load-to-failure. Osteosynthesis technique did not affect load-to-failure. NA, cadaveric biomechanical study.