Intra-Articular Influence of PETS Technique Treating Limb Length Discrepancy for Both Femur and Tibia

Volcano deformity is an intra-articular deformity discovered after the wide use of the tension band plate (TBP) all over the world. Controversy on whether this is a pervasive effect that applies to all TBP treatments or just a sporadic event is still under debate. In contrast, percutaneous epiphysiodesis using transphyseal screws (PETS) has been under the radar for producing intra-articular influence. This study aimed to evaluate the potential for such central deformity.

Fifty-three patients who received percutaneous epiphysiodesis using transphyseal screws (PETS) from January 2017 to March 2024 to both the distal femur and proximal tibia at our institution were reviewed. Forty-two patients with a minimum 1-year follow-up with a minimum 1-year implant retention period were included in the study. For the quantitative analysis, 2 sets of radiographs were selected. The first set consisted of the immediate postoperative X-rays, while the second set comprised the latest follow-up radiographs meeting the defined inclusion criteria. Radiologic parameters for assessment of central deformity for our study were intercondylar distance, intercondylar notch depth (femur), and intercondylar eminence height (tibia). In addition, preoperative scanogram and final scanogram at the last follow-up were used to assess alignment.

The operated limb demonstrated a significant decrease in intercondylar distance between initial and final radiographs (mean change: -1.92±1.46 mm, P <0.001), while the nonoperated limb showed no statistically significant change ( P =0.094). Furthermore, notable differences were observed in other parameters of the operated limb. Intercondylar notch depth decreased by -1.47±1.45 mm ( P <0.001), and intercondylar eminence height increased by 0.85±0.92 mm ( P <0.001). In contrast, measurements on the nonoperated limb remained consistent, mirroring the findings for intercondylar distance.

Intra-articular deformity may result from PETS for both the femur and the tibia. The clinical importance of these findings is yet to be determined. Further research is needed to better understand the nature of this change.

Level IV.