PATELLA INFERA FOLLOWING HIGH TIBIAL OSTEOTOMY: MEDIAL OPENING VS. LATERAL CLOSING WEDGE

Abstract

A radiographic review of sixty-nine lateral closing wedge high tibial osteotomies and forty-two medial opening wedge osteotomies was conducted. Patellar height and tibial slope were measured. The Blackburne-Peel (BP) and Insall-Salvati (IS) ratios were used to measure patellar height. Our results show that 18.8% and 47.6% of the lateral closing wedge group had patella-infera (PI) according the the BP and IS ratios respectively. No opening-wedge cases demonstrated patella infera with either ratio. Tibial slope was found to be significantly more neutral in the closing wedge group versus the opening wedge (−2.2° vs. −7.28° respectively).

Patients undergoing HTO typically require a definitive arthroplasty procedure at an average of six years post-HTO. Total knee arthroplasty can be complicated by the presence of PI which compromises exposure and increases the risk of patellar tendon avulsion leading to suboptimal results. The current study compares the incidence of PI between lateral closing and medial opening wedge HTO’s.

Conversion of opening wedge HTO to TKA should have less technical challenge and improved outcomes as compared to lateral closing wedge HTO conversions. This is attributable to the absence of PI.

Of the closing wedge group, 18.8% and 47.6% were found to have PI according to the BP and IS ratios respectively. Of the opening wedge group there were no cases of PI found with either ratio. Tibial slope was found to be significantly more neutral in the closing wedge compared to the opening wedge group (−2.2° vs. −7.28° respectively).

The study cohorts were abstracted from surgeon records. Sixty-nine closing wedge and forty-two opening wedge HTO’s were identified. Lateral 30° flexion x-rays were measured for patellar height and tibial slope. Both the Blackburne-Peel (BP) and Insall-Salvati (IS) patellar height measurements were used.

From this data we can conclude that in our study population the incidence of PI in the opening wedge group was 0% thus negating the potential deleterious effects of PI at the time of knee arthroplasty.