• PURPOSE
    • To test that patellar height decreases (patellar baja) after opening wedge high tibial osteotomy (HTO) and increases (patellar alta) after closing wedge HTO. In addition, this meta-analysis evaluated whether the method of measuring patellar height affected the change in patellar height after opening and closing HTO.
  • METHODS
    • Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, all studies comparing pre- and postoperative patellar height using various indices, including the Insall-Salvati index (ISI), Blackburne-Peel index, and Caton Deschamps index, in patients who underwent opening or closing wedge HTO were included. The main outcome of this meta-analysis, mean change in patellar height from before to after surgery, was analyzed with a random effects model. Publication bias was evaluated using funnel plots and Egger's test.
  • RESULTS
    • Twenty-three studies were included in the meta-analysis. Pooled data, including subgroups of the 3 measurement methods, showed that patellar height decreased 7% after opening wedge HTO (95% confidence interval [CI]: 0.05 to 0.10; P < .001), except when patellar height was assessed by ISI (95% CI: -0.02 to 0.06; P = .34), but that there was no change in patellar height after closing HTO (95% CI: -0.01 to 0.04; P = .29).
  • CONCLUSIONS
    • The patellar height decreased after opening wedge HTO, except when assessed by ISI. In contrast, patellar height was unchanged after closing wedge HTO, regardless of the measurement method.
  • LEVEL OF EVIDENCE
    • Level II, meta-analysis of Level I and II studies.