Summary

Although rare, younger patients are at higher risk of patella fracture after MPFL reconstruction.

Abstract

Purpose

Medial patellofemoral ligament reconstruction (MPFL-R) is often used to restore patellofemoral stability. The use of patellar bone tunnels and suture anchors creates a risk of postoperative patellar fractures; however, little is known about risk factors and timing of patella fractures after MPFL-R. The purpose of this study was to assess the incidence of postoperative patella fracture after MPFL-R and to determine if age and sex influence either the risk or timing of fracture.

Methods

The PearlDiver Mariner165 database was used in this study which contains insurance claims information on more than 165 million orthopaedic patients. Patients between the ages of 14 and 40 that underwent MPFL-R were identified by Current Procedural Terminology codes (CPT 27420, 27422, or 27427) and diagnosis codes associated with patellar instability. Index procedures were performed between January 1, 2010 and December 31, 2021 and only patients with active insurance coverage spanning from one year prior to and after the index surgical procedure were included. The incidence of subsequent patella fracture was then identified using CPT and diagnosis codes associated with either open or closed fracture treatment. The incidence of patella fracture was compared between sexes and age groups (< 20 y vs. >20 y) using chi square tests and Odds Ratios (OR) were calculated for any significant findings. Kaplan Meier survivorship curves were also created to assess subsequent patellar fracture after MPFL-R.

Results

A total of 29,539 patients were identified (19,950 female, 9,589 male; 17,011 < 20 y, 12,528 >20 y), with 141 having a subsequent patella fracture (0.47%). The incidence of patella fracture after MPFL-R did not differ by sex (female:0.44%, male:0.54%, p=0.26); however, patella fractures were significantly more common amongst younger patients as all 141 fractures occurred in patients < 20 years old (0.83% vs. 0.00%, OR=210.2 [95%CI: 13.1, 3577.0]). When limiting the comparison to only those < 20 years old, again we did not observe differences in the incidence of patella fracture between female and male patients (female:0.82%, male:0.86%, p=0.78). In terms of timing of fractures in the younger age group, 31.9% of fractures occurred in the first 90 days after MPFL-R with 36.9% occurring between 90 days and 1 year, and 38.3% occurring after 1 year (Figure 1).

Conclusions

The incidence of patella fracture after MPFL-R was extremely low and did not differ between males and females. However, the odds of having a patella fracture after MPFL-R was significantly higher for patients aged 20 and under than for older patients. All of the observed fractures in this nationwide database were in younger patients, and a majority of fractures occurred during the first postoperative year.