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Objectives and questions: Distalization of the tibial tuberosity (dTTO) is an effective technique for treating patella alta, yet complications can be severe. This study aims to evaluate the biomechanical effects of different distal sawing techniques on tibial fracture risk, with a focus on cut orientation. Specifically, it was investigated whether an oblique distal cut provides greater stability than an orthogonal cut and whether accidental cortical notching affects stability.

Material and methods: A total of 61 porcine tibiae were tested in three biomechanical setups. In the main trial (n = 32), dTTO was performed using four sawing techniques: 1) oblique, 2) orthogonal (no notch), 3) orthogonal with 2 mm notch, 4) orthogonal with 4 mm notch (each n = 8). Specimens were embedded in Technovit 4004 and axially loaded to structural failure using an MTS Bionix 358 machine. The second trial investigated cyclic loading behavior (oblique, orthogonal, 2 mm notch; n = 17), while the third tested osteosynthesis methods (2-hole one-third tubular plate vs. two 3.5 mm lag screws; n = 12). Maximum load to failure (N) and stiffness (N/mm) were determined to assess comparability. Linear regression was used to analyze the relationship between residual distal tibial thickness and failure load. Statistical analyses were performed via t-tests and ANOVA (α = 0.05).

Results: Oblique distal cuts showed the highest failure load (784.5 N ± 118.0), with a non-significant trend toward higher stability compared to orthogonal cuts (538.8 N ± 229.5, p = 0.087). Both notched groups demonstrated significantly reduced stability (2 mm: 294.0 N ± 91.8; 4 mm: 274.6 N ± 96.5). Similar trends were seen in cyclic testing: the oblique group withstood significantly more cycles until failure (5,894 ± 2,187) than the orthogonal group (3142 ± 808; p = 0,004), while the 2 mm notch group failed after fewer cycles (1,400 ± 530, p < 0.002). No significant difference was found between plate and screw osteosynthesis regarding failure load (p = 0,802). No significant differences in stiffness were observed between groups (mean: 47–57 N/mm, p > 0.05), indicating similar baseline bone quality. Also, proximal and distal residual tibial thickness did not differ significantly between groups (p > 0.05), confirming comparable bone geometry. Regression analysis showed a moderate to strong positive association between distal tibial thickness and failure load across all groups (r = 0.55 - 0.77, all p < 0.05), indicating that thicker residual bone was associated with greater stability. The proximal tibial thickness showed no relevant correlation with failure load and was not further considered.

Discussion and conclusions: The oblique distal sawing technique provides greater biomechanical stability compared with orthogonal cuts. Cortical notching reduces stability and should be avoided. In this model, even with increased fracture risk from the distal sawing technique, the choice of osteosynthesis technique had no significant effect on failure load.