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.

Radiographic reference values of the central knee anatomy in 8-16-year-old children.

BACKGROUND AND PURPOSE: For correction of leg-length discrepancy or angular deformity of the lower limb in skeletally immature patients temporary or permanent (hemi-)epiphysiodesis can be employed. These are reliable treatments with few complications. Recently, radiographic analysis of treatment-related alterations of the central knee anatomy gained interest among pediatric orthopedic surgeons. To date the comparison and adequate interpretation of potential changes of the central knee anatomy is limited due to the lack of defined standardized radiographic references. We aimed to establish new reference values of the central knee anatomy. PATIENTS AND METHODS: A retrospective analysis of calibrated longstanding anteroposterior radiographs of 254 skeletally immature patients with a chronological age ranging from 8 to 16 years was conducted. The following radiographic parameters were assessed: (1) femoral floor angle, (2) tibial roof angle, (3) width at femoral physis, and (4) femoral notch-intercondylar distance. RESULTS: All observed radiographic parameters were normally distributed with a mean age of 12.4 years (standard deviation [SD] 2, 95% confidence interval [CI] 12.2-12.6). Mean femoral floor angle was 142° (SD 6, CI 141.8-142.9), mean tibial roof angle was 144° (SD 5, CI 143.7-144.1), mean width at femoral physis was 73 mm (SD 6, CI 72.8-73.9), and mean femoral notch-intercondylar distance was 8 mm (SD 1, CI 7.5-7.7). The estimated intraclass correlation coefficient values were excellent for all measurements. CONCLUSION: This study provides new radiographic reference values of the central knee anatomy for children between 8 and 16 years and we suggest considering values within the range of 2 SD as the physiological range.