Knee joint morphology following growth arrest through temporary epiphysiodesis: No evidence of intra-articular deformity – A retrospective study of 81 patients

Background Temporary epiphysiodesis (tED) around the knee is a well-established treatment approach for leg length discrepancies (LLD) in skeletally immature patients. Moreover, it may be conducted bilaterally to reduce height in tall stature. However, secondary changes in the bony morphology of the tibial plateau after tED have been reported. This study thus aimed to evaluate secondary alterations in knee joint morphology following tED around the knee. Methods Radiographs of 81 skeletally immature patients aged 7–15 years were retrospectively analysed. 10/81 patients underwent bilateral tED with RigidTacks™ (RT) to reduce growth in tall stature, whereas 71/81 patients (35 with eight-Plates™ (EP), 36 with RT) received unilateral treatment for LLD. To assess changes in knee joint morphology, following radiographic parameters were evaluated: femoral floor angle (FFA), tibial roof angle (TRA), width at femoral physis (WFP), and femoral notch-intercondylar distance (FNID). Furthermore, mechanical axis deviation (MAD), mechanical lateral distal femoral angle, medial proximal tibial angle, and joint line convergence angle were measured to analyse coronal alignment. All parameters were assessed prior to implantation, prior to device removal, and at last follow-up. Results Mean treatment duration was 2.7 years (standard deviation (SD) 1.1). Statistically relevant changes were observed in WFP (p = 0.025), FNID (p = 0.008), and MAD (p = 0.002) after tED using EP, and in FNID (p = 0.043) using RT. Compared with reference values for untreated healthy children, these relevant changes remained within one SD. Mean absolute MAD change using EP was 3.9 mm (SD 7.1) compared to 1.9 mm (SD 8.8) using RT. Secondary coronal malalignment with need for revision surgery was found in 11/81 patients (4/35 with EP, 7/46 with RT). Conclusions Statistically relevant changes in bony morphology after tED were only observed in the distal femur. However, there was no evidence of intra-articular knee deformities. All measured femoral and tibial parameters remained within physiological margins and were considered clinically inconsequential. Nevertheless, there was a considerable number of patients with secondary coronal malalignment among both implant groups, necessitating further elucidation.