Title : Distalising tibial tubercle osteotomy for patellofemoral instability: A systematic review
Abstract:
Background: Distalising Tibial Tubercle Osteotomy (TTO) is used to treat patella alta in Patello Femoral Instability (PFI) to restore early patellotrochlear contact. Nevertheless, indications, planning techniques and correction targets are not well standardised. Unlike prior reviews focusing solely on outcomes, this study uniquely analyses planning strategies and correction targets to propose a structured framework.
Methods: PubMed, Embase and Cochrane Library were searched up to April 2026 using full search strings with Boolean operators (Appendix A) to identify studies that reported distalising TTO for PFI with radiographic indices or clinical outcomes. Two independent reviewers assessed eligibility with inter-reviewer agreement calculated (kapp= 0.85), and conflicts resolved by consensus. The quality of methods was evaluated based on MINORS. Bias was integrated analytically by comparing outcomes in high vs low quality studies. Synthesis was descriptive according to SWiM guidelines with subgroup analyses comparing empirical vs target-based vs formula-based planning.
Findings: Seventeen studies (1,534 patients; 1,642 knees) were eligible. The mean MINORS score was 10.2/16 (SD 1.7), indicating moderate quality. Studies with MINORS≥12 (higher quality) reported more consistent outcomes. The Caton-Deschamps Index (CDI) thresholds for patella alta ranged between >1.2 and >1.4. Planning strategies were formula-based calculation, target-based reverse planning and empirical intraoperative judgement, empirical being the dominant despite its poor reproducibility.The magnitude of distalisation ranged 5–20 mm (pooled mean 12.2 ± 4.5 mm). No dose–response relationship was identified between CDI and millimetric correction. Postoperative CDI clustered at 0.9–1.2, although 30% of knees had persistent alta and 17% had patella baja. Functional outcomes improved consistently (Kujala: 52→89; Lysholm: 50→83; IKDC: 50→85; all p<0.001). Redislocation rates were 3–8% at two years. Complication rates were 5–20% and reoperation 14–21%, mostly for hardware removal.
Conclusion: Distalising TTO improves functional performance and reduces instability in PFI with patella alta, though significant heterogeneity in indications, planning and execution prevents standardised practice. Empirical intraoperative judgement remains dominant despite lack of reproducibility—this likely contributes directly to overcorrection and undercorrection rates. Based on current evidence, surgeons should avoid relying solely on intraoperative judgement and instead aim for CDI 1.0–1.1 using preoperative planning. This review proposes a structured planning framework (Figure 1) to guide surgical decision-making.
