Open wedge high tibial osteotomy: cause of patellar descent

Abstract

This was a retrospective review of the nine open wedge high tibial osteotomy (HTO) done in a regional hospital in Hong Kong from 2006 to 2008. The mechanical hip-knee-ankle angle improved from average 169.5°(164°-175°) to average 183.9° (179°-187°). Patellar descent was noted in all patients postoperatively, with Blackburne-Peel (BP) index significantly changing from 0.78 (0.64-0.93) to 0.59 (0.38-0.78) (p < 0.05). This change was strongly correlated with the size of anterior bone graft (r = -0.766; p = 0.016). The patellar tendon length as measured by Insall-Salvati index was not changed (pre-operative: 1.02 (0.88-1.25), final: 1.09 (0.8-1.22) (p = 0.683)), inferring that scarring contracture of patellar tendon was not related to patellar descent.

Figure 1

i) Preoperative planning. A: femoral head center; AB: Fujisawa line; C: ankle center; D: Pivot point. Tibial shaft tracing distal to DC1 rotated laterally until point C lying on line AB, DC1 intersected medial tibial cortex to form point B1. C1B1 was the size of posteromedial bone graft. ii) Postoperative radiograph. Line AC intersected the knee joint at 30% lateral to knee center.