Valgus high tibial osteotomy (HTO) results in changes in the frontal as well as sagittal planes. Our hypothesis suggests that patellar height increases and posterior tibial inclination decreases after closed wedge (cw) HTO, whereas patellar height decreases and tibial slope increases after open wedge (ow) HTO.

Lateral radiographs of 100 knees were assessed for patellar height (PH) using Insall-Salvati (ISI), Caton-De Champ (CDI) and Blackburne-Peel indices (BPI) as well as posterior tibial slope. Measurements were done before HTO (50 cw and 50 ow), direct postoperatively and before hardware removal.

In the cw-group all three PH indices increased direct postoperatively and at removal of the hardware with changes in CDI and BPI being significant (P < 0.05). In the ow-group all three indices showed a significant patellar height decrease direct postoperatively and at hardware removal. There were no significant changes between the two follow-up measurements (P > 0.05). Posterior tibial slope showed a significant decrease of 3.1 ± 3.4° after closed wedge HTO and a significant increase of 2.1 ± 3.6° after ow HTO direct postoperatively. In cw-HTO the correlations between frontal plane correction and PH changes were moderate (CDI: r = 0.57; BPI: r = 0.64). In ow-HTO these correlations were weak (CDI: r = 0.44; BPI: r = 0.46). According to ISI there was no correlation (cw: r = 0.11; ow: r =0.16). There was no correlation between PH changes according to CDI and slope changes.

The incidence of patella infera increases after open wedge HTO, whereas the incidence of patella alta increases after closed wedge HTO. We recommend considering the PH and tibial slope before planning for HTO or TKR after HTO, also performing cw-HTO or ow-HTO with the tuberosity left at the proximal tibia in cases of patellofemoral complaint or patella infera.