Characteristics of Osteochondral Fractures Caused by Patellar Dislocation

Mikko Uimonen; Ville Ponkilainen; Juha Paloneva; Ville M Mattila; Heikki Nurmi; Jussi P Repo

doi:10.1177/2325967120974649

Characteristics of Osteochondral Fractures Caused by Patellar Dislocation

Orthop J Sports Med. 2021 Jan 26;9(1):2325967120974649. doi: 10.1177/2325967120974649. eCollection 2021 Jan.

Authors

Mikko Uimonen¹, Ville Ponkilainen¹, Juha Paloneva^{1

2}, Ville M Mattila^{3

4

5}, Heikki Nurmi¹, Jussi P Repo¹

Affiliations

¹ Department of Surgery, Central Finland Hospital, Jyväskylä, Finland.
² University of Eastern Finland, Kuopio, Finland.
³ Department of Orthopaedics and Traumatology, Tampere University Hospital, Tampere, Finland.
⁴ COXA Hospital for Joint Replacement, Tampere, Finland.
⁵ Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland.

Abstract

Background: Literature describing the anatomic characteristics of osteochondral fractures (OCFs) in the knee joint after patellar dislocation is scarce.

Purpose: To describe the patterns of OCFs in the knee joint after acute or recurrent patellar dislocation in a sample of patients from 2 orthopaedic trauma centers.

Study design: Case series; Level of evidence, 4.

Methods: In this multicenter study, all patients who had International Classification of Diseases, 10th Revision, diagnostic codes S83.0 and M22.0 between 2012 and 2018 were screened. Of the 2181 patients with clinically diagnosed patellar dislocation, 1189 had undergone magnetic resonance imaging (MRI). Patients with diagnosed patellar dislocation and osteochondral fragment verified on MRI scans were included. Demographic and clinical data were collected from electronic patient records. OCF location and size were assessed from MRI scans. Results were further compared in subgroups by sex, skeletal maturity, and primary versus recurrent patellar dislocation.

Results: An OCF was detected in 134 patients with injured knees, all of whom were included in the final analysis. It occurred in the patella in 63% of patients, in the lateral femoral condyle in 34%, and in both locations in 3%. The median OCF size was 146 mm² (interquartile range, 105-262 mm²). There was no statistically significant difference in OCF size between patellar and lateral femoral condyle fractures. Patellar OCFs were more frequent in female than male patients (P = .009) and were larger after primary than recurrent dislocation (P = .040).

Conclusion: OCFs were mainly located in the medial facet of the patella and in the lateral femoral condyle, with these locations accounting for approximately two-thirds and one-third of all OCFs, respectively. Proportion of patellar OCF was higher in female than in male. Patellar OCFs may be larger after primary than recurrent dislocation.

Keywords: knee trauma; magnetic resonance imaging; osteochondral fracture; patellar dislocation.