Percutaneous Transphyseal Screw Hemiepiphysiodesis (PETS) for Tibia Vara in Blount's Disease.

BACKGROUND

Blount's disease is a progressive developmental disorder causing pathologic genu varum due to growth disturbances in the medial proximal tibial physis. Guided growth is a primary treatment, but established methods like staples and 8-plates have limitations, including hardware failure and unpredictable correction. This study evaluates an alternative technique of hemiepiphysiodesis using percutaneous transphyseal screws (PETS) for treating juvenile and adolescent Blount's disease.

METHODS

This prospective case series included 61 patients (80 knees) aged 4 to 12 years treated for Blount's disease at a single institution. All patients underwent lateral proximal tibial hemiepiphysiodesis with a single, fully threaded cannulated screw. The primary outcome was the change in Mechanical Axis Deviation (MAD). Secondary outcomes included changes in the Medial Proximal Tibial Angle (MPTA), rate of correction, functional outcomes measured by the Böstman knee score, and complications.

RESULTS

The mean preoperative MAD was 44 mm. It improved to a mean of 0.7 mm at implant removal, representing a mean correction of 43 mm ( P <0.001). The mean rate of correction was 3.7 mm per month. The mean MPTA improved from 77 to 86 degrees. The mean postoperative Böstman score was 29, indicating excellent functional recovery. Complications were minimal, with a reoperation rate of 9.8% and a rebound deformity rate of 3.3%. No cases of overcorrection, hardware failure, or deep infection were observed.

CONCLUSIONS

PETS is a safe, effective, and rapid method for correcting tibia vara in juvenile and adolescent Blount's disease. It provides predictable alignment correction with a low complication profile, representing a strong alternative to other guided growth techniques.

LEVEL OF EVIDENCE: Level IV.