Morphology of the knee after guided growth using tension-band devices: a retrospective multicenter study of 222 limbs and 285 implants.

Background and purpose: Temporary hemiepiphysiodesis by tension-band devices is commonly applied to correct angular limb deformities in children. We aimed to evaluate knee joint morphology after guided growth using these devices.

Patients and methods: In a retrospective multicenter study we analyzed standardized anteroposterior long-leg radiographs of 222 limbs (285 implants) of patients treated by temporary hemiepiphysiodesis with either eight-Plates or FlexTacks for coronal angular deformities of the knee joint between 2013 and 2019. Femoral floor angle (FFA), femoral notch-intercondylar distance (FNID), and tibial roof angle (TRA) were measured pre- and postoperatively to assess the central knee joint morphology. Statistical exploratory analyses were performed using linear mixed models, t-tests, Wilcoxon signed-rank test, and Mann-Whitney U test.

Results: 217 FlexTacks (femur 106, tibia 111) in 104 children and 68 eight-Plates (femur 61, tibia 7) in 35 children were identified. Median time period under growth guidance was 11 months (range 4-42). No statistically significant change in the FFA was detected (eight-Plate: P = 0.2; FlexTack: P = 0.3). A statistically significant difference of the FNID was found in the eight-Plate group (P = 0.02), but not in the FlexTack group (P = 0.3). While TRA increased in both groups, a statistical significance was observed only in the FlexTack group (P < 0.01).

Conclusion: We found minor but clinically irrelevant changes in knee morphology after the treatment.