Abstract
Background
The goal of patellofemoral arthroplasty (PFA) is to replace damaged cartilage, and to correct underlying deformities, to reduce pain and prevent maltracking. We aimed to determine how PFA modifies patellar height, tilt, and tibial tuberosity to trochlear groove (TT-TG) distance. The hypothesis was that PFA would correct trochlear dysplasia or extensor mechanism malalignment.
Methods
The authors prospectively studied a series of 16 patients (13 women and 3 men) aged 64.9 ± 16.3 years (range, 41 to 86) that received PFA. All knees were assessed pre-operatively and six months post-operatively using frontal, lateral, and ‘skyline’ x-rays, and CT scans to calculate patellar tilt, patellar height and tibial tuberosity–trochlear groove (TT-TG) distance.
Results
The inter-observer agreement was excellent for all parameters. (ICC > 0.95). Pre-operatively, the median patellar tilt without quadriceps contraction (QC) was 17.5° (range, 5.3°–33.4°) and with QC was 19.8° (range, 0°–52.0°). The median Caton- Deschamps Index (CDI) was 0.91 (range, 0.80–1.22) and TT-TG distance was 14.5mm (range, 4.0–22.0). Post-operatively, the median patellar tilt without QC was 0.3° (range, −15.3°–9.5°) and with QC was 6.1° (range, −11.5°–13.3°). The median CDI was 1.11 (range, 0.81–1.20) and TT-TG distance was 10.1mm (range, 1.8–13.8mm).
Conclusion
The present study demonstrates that, beyond replacing arthritic cartilage, trochlear-cutting PFA improves patellofemoral congruence by correcting trochlear dysplasia and standardizing radiological measurements as patellar tilt and TT-TG. The association of lateral patellar facetectomy diminishes local effects of OA and improves patellar tracking by reducing the patellar tilt.
