Is Pseudo-Patella Baja Really a Serious Complication of Total Knee Arthroplasty?

Alfredo Aguirre-Pastor; David J Ortolá; Alejandro Lizaur-Utrilla; Michele A Rosa; Fernando A Lopez-Prats

doi:10.1016/j.arth.2019.09.031

Is Pseudo-Patella Baja Really a Serious Complication of Total Knee Arthroplasty?

J Arthroplasty. 2020 Feb;35(2):557-562. doi: 10.1016/j.arth.2019.09.031. Epub 2019 Sep 23.

Authors

Alfredo Aguirre-Pastor¹, David J Ortolá², Alejandro Lizaur-Utrilla³, Michele A Rosa², Fernando A Lopez-Prats⁴

Affiliations

¹ Department of Orthopaedic Surgery, General University Hospital of Elche, Alicante, Spain.
² Department of Biomedical and Dental Sciences and Morphofunctional Imaging, School of Orthopaedics and Traumatology, Universita degli Studi di Messina, Messina, Italy.
³ Traumatology and Orthopaedia, Faculty of Medicine, Universidad Miguel Hernandez de Elche, Alicante, Spain.
⁴ Department of Orthopaedic Surgery, General University Hospital of Elche, Alicante, Spain; Traumatology and Orthopaedia, Faculty of Medicine, Universidad Miguel Hernandez de Elche, Alicante, Spain.

PMID: 31615703
DOI: 10.1016/j.arth.2019.09.031

Abstract

Background: The available evidence on pseudo-patella baja (PPB) is limited. The purpose of this study is to investigate prospectively the occurrence of PPB after primary total knee arthroplasty and its clinical consequences in a large series of patients with a minimum follow-up of 2 years. PPB was defined as a patella distally displaced in relationship to the femoral trochlea with absence of patellar tendon shortening (Grelsamer RP. J Arthroplasty 2002;17:66-69) due to elevation of the joint line.

Methods: This study is a prospective case series of 354 patients with a mean age of 71.7 (range 52-87) years. Clinical evaluation was performed by the Knee Society Scores (KSS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Short-Form 12-item (SF12), and range of motion. Patellar height was assessed by the Insall-Salvati and Blackburne-Peel ratios.

Results: The mean follow-up was 3.6 (range 2.0-6.6) years. Postoperatively, 286 (80.7%) patients had a normal patellar height, 17 (4.8%) had true patella baja (TPB), and 51 (14.4%) had PPB. There were no significant differences between the 3 groups in mean KSS-function (P = .107), range of motion (P = .408), WOMAC-pain (P = .095), WOMAC-stiffness (P = .279), or SF12-mental (P = .363). Between normal and PPB groups, there were no significant differences in mean KSS-knee (P = .903), WOMAC-function (P = .294), or SF12-physical (P = .940). However, the TPB group had significantly lower mean KSS-knee (P = .031), WOMAC-function (P = .018), and SF12-physical (P = .005) as compared with either 2 other groups.

Conclusion: PPB was a relatively common finding, but no significant differences in terms of clinical outcomes were found as compared to patients with postoperative normal patellar height. TPB was infrequent, but these patients had significantly worse clinical outcomes than those with PPB or normal patellar height.

Keywords: joint line elevation; patella baja; patella infera; pseudo-patella baja; total knee arthroplasty.

MeSH terms

Aged
Aged, 80 and over
Arthroplasty, Replacement, Knee* / adverse effects
Humans
Knee Joint / diagnostic imaging
Knee Joint / surgery
Middle Aged
Osteoarthritis, Knee* / surgery
Patella / diagnostic imaging
Patella / surgery
Prospective Studies
Range of Motion, Articular