To explore the blocking effect of temporary epiphysiodesis technique with "8"-plate in the treatment of leg length discrepancy (LLD) in children.

From January 2013 to July 2020, 49 children (27 males and 22 females) with leg length discrepancy treated with "8"-plate in Pediatric Orthopedics Department of Beijing Jishuitan hospital were analyzed retrospectively. The average age at the time of surgery was 8.8±2.6 years (ranging from 3.8 to 13.1 years). The length difference between femur and tibia was measured before operation on full-length X-ray films of lower limbs, and the "8"-plate was placed on both medial and lateral sides of the distal femur and/or the proximal tibia. During the follow-up, the shape of epiphyseal plate and internal fixation change were evaluated on X-ray films of the knee joint, and the length difference before and after the operation was compared to evaluate the blocking effect. The blocking rate was compared according to the following conditions: the blocking position (femur, tibia), classification of LLD (constant or increasing), screw diameter (3.5 mm or 4.5 mm) and the age at operation (≥8 or <8 years).

49 patients were successfully operated. The follow-up time was 39.6±18.5 months (range 16-91 months) with the fixing time of 24.3±11.8 months (range 7-66 months). A total of 76 independent data of single bone were obtained. The correction range was 8.6±6.4 mm (range -8-37 mm). The correction rate was 0.35±0.31 mm/month. The correction rate of 52 femurs was 0.41±0.32 mm/month, which was significant higher than that of 24 tibias with 0.20±0.14mm/month (t=5.323, P=0.008). The correction rate of the constant group with 0.54±0.32 mm/month was obviously better than the increasing group with 0.26±0.21 mm/month (t=7.362, P=0.001). The average correction rate of 4.5 mm diameter screw group was 0.46±0.23 mm/month, which was significantly better than that of 3.5 mm diameter screw group with 0.26±0.24 mm/month (t=3.467, P=0.022). The correction rate in the group of <8 years old was 0.32±0.25 mm/month, which was not significantly different from that in the group of ≥8 years old with 0.37±0.31 mm/month (t=1.026, P=0.548).

The blocking effect of "8" -plate temporary epiphysiodesis technique in the treatment of leg length discrepancy was related to the LLD classification and blocking position. Distal femoral block was better than proximal tibia block. Block effect of patients with constant unequal distance between lower limbs was better than that of patients with increased distance. 4.5 mm diameter screw was better than 3.5mm. Because the blocking effect was slow, early treatment and a firm stick to indications was of great importance.

Child; Internal fixators; Epiphyses; Leg length discrepancy