Physeal Migration During Knee-guided Growth With Tension Band Plates: Influence of Implant Position

Abstract

Objective: Physeal migration during guided growth with tension band plates (TBPs) has been poorly described. The positioning factors associated with this phenomenon and its clinical implications are unknown. Our aim is to determine the influence of implant position on the risk of physeal migration during knee-guided growth with TBP.

Methods: Retrospective study of 491 patients who underwent temporary hemi or epiphysiodesis with TBP around the knee between 2007 and 2019. We identified 29 patients who presented physeal migration during follow-up. Demographic and clinical data were collected, and the following measures were obtained from the immediate postoperative radiographs: epiphyseal screw base-physis distance/epiphyseal screw tip-physis distance, interscrew angle, epiphyseal screw-physis angle(ES-PHa)/metaphyseal screw-physis angle, plate-physis angle, epiphyseal screw-plate angle/metaphyseal screw-plate angle, and epiphyseal screw-physis length ratio. Using follow-up radiographs, the type of physeal migration of the epiphyseal screw (touch, occupy, or traverse) and the status of the physis after implant removal (unaltered, physeal bar, and skeletal maturity) were also recorded. A descriptive analysis of the cases and a case-control comparison of imaging studies were performed.

Results: The median patient age at intervention was 12.2 years (interquartile range: 11.3 to 14.1), and 76% were males. A statistically significant difference between cases and controls was obtained for epiphyseal screw base-physis distance (3.7 vs 6.3; P = 0.029), epiphyseal screw tip-physis distance (3.6 vs 7.85; P = 0.002), ES-PHa (-0.1 vs 7.45; P = 0.007), and plate-physis angle (85.45 vs 88.60; P = 0.012). In a categorical analysis, a significant difference was found for the ES-PHa categories ( P = 0.002) and for the ES-PHa/metaphyseal screw-physis angle categorical pair ( P = 0.018). In 16, 17, and 12 cases the physis was touched, occupied, or traversed, respectively, although we found no physeal alterations after plate removal.

Conclusions: In our study, physeal migration of TBP is not an uncommon phenomenon, although no physeal abnormalities were detected. Convergent placement of the epiphyseal screw with the base or tip close to the physis should be avoided as this position is associated with a higher risk of physeal migration.

Level of evidence: Level III-case-control study.