Are 6 to 12-Week Radiographic Union Scores Associated with Healing Following Lateral Locked Plating of Distal Femur Fractures?

OBJECTIVES: To determine whether 6-12 week modified Radiographic Union Score for Tibial fractures (mRUST) scores following lateral locked plating (LLP) of distal femur fractures were associated with nonunion versus healing.

METHODS: Design: Retrospective case-control study.

SETTING: Two Level 1 Trauma Centers.

PATIENT SELECTION CRITERIA: Included were adult patients with distal femur fractures (OTA/AO 33A/C) treated with LLP between 2006-2024 and with available postoperative radiographs between 6-12 weeks. Nonunion cases were defined as patients undergoing reoperation for nonunion after 12 weeks and were randomly matched 1:2 to controls, defined as those not undergoing reoperation for nonunion and with documented healing or an mRUST score of ≥12 at final follow-up.Outcome Measures and Comparisons: Total mRUST (scale:4-16) and combined medial and posterior (scale:2-8) mRUST scores were compared between nonunion cases and controls. Associations of mRUST scores with nonunion versus healing were estimated using logistic regression with adjustment for sampling distribution and time from surgery to mRUST assessment.

RESULTS: Thirty distal femur nonunion cases and 60 controls were included (median ages 58 and 63 years; with 70% and 67% females, respectively). The median total mRUST score was 6 (IQR 6-7) for nonunion cases and 10 (IQR 8-11) for controls (p<0.001). Each 1-point increase in mRUST score was associated with a 57% reduction in odds of nonunion (OR: 0.43, 95%CI: 0.24-0.66; AUC 0.91). For the combined medial and posterior cortex scores, each 1-point increase was associated with a 70% reduction in odds of nonunion (OR: 0.30, 95%CI: 0.12-0.61; AUC 0.84).

CONCLUSIONS: mRUST scores between 6-12 weeks demonstrated strong association with nonunion versus healing following LLP of distal femur fractures. This was consistent in analysis limited to medial and posterior cortices, although wide confidence intervals suggest imprecision in the effect estimate. Early mRUST assessment may serve as a helpful adjunct to support clinical decision-making and patient counseling following LLP of distal femur fractures.