Reliability of modified Radiographic Union Scale for Tibial Fractures (mRUST) Scores in Ballistic Lower Extremity Trauma
Patrick Sun, Jennifer Eurich, Douglas Zhang, Gregory Schimizzi, Anthony Christiano, Mary Kate ErdmanOBJECTIVES:
To investigate the reliability of the modified Radiographic Union Scale for Tibial Fractures (mRUST) scores in ballistic lower extremity trauma and to assess the ability of 3-month post-op mRUST in predicting union status at 9-months.
METHODS:
Design: Retrospective review
Setting:
Single Level 1 Trauma Center
Patient Selection Criteria:
Patients that sustained a ballistic femoral (AO/OTA 32) or tibial shaft fracture (AO/OTA 42) aged 18 or over and were treated with intramedullary nailing between 2019 and 2023.
Outcome Measures and Comparisons:
Inter- and intra-rater reliability of mRUST score measurements between three fellowship trained orthopaedic trauma surgeons was assessed. The sensitivity and specificity of predicting nonunion at 9-months postoperatively from mRUST 3-months postoperatively was assessed. Inclusion criteria for nonunion analysis required patients to have a 3-month mRUST score as well as a determinable union status.
RESULTS:
107 ballistic femoral shaft fractures (203 radiograph sets; 100 male; mean age 31 [18-56]) and 62 ballistic tibial shaft fractures (153 radiograph sets; 51 male; mean age 33 [18-61]) were used to calculate reliability metrics. Inter-rater reliability (Intraclass Correlation Coefficient, ICC) of mRUST in ballistic femoral shaft fractures was 0.64 (95% CI[0.34,0.80]). Intra-rater reliability of mRUST in ballistic femoral shaft fractures was 0.87 (95% CI[0.85,0.89]). Inter-rater reliability of mRUST in ballistic tibial shaft fractures was 0.61 (95% CI[0.43,0.73]) and intra-rater reliability of mRUST in ballistic tibial shaft fractures was 0.81 (95% CI[0.77, 0.84]). In 28 ballistic femoral shaft fractures (24 male; mean age 31 [18-46]), an mRUST-3MO < 8 predicted nonunion in ballistic femoral shaft fractures with a sensitivity of 1.00 and specificity of 0.83. In 25 ballistic tibial shaft fractures (17 males; mean age 34 [18-61]), an mRUST-3MO < 8 predicted nonunion with a sensitivity of 0.71 and specificity of 0.94.
CONCLUSIONS:
This study suggests that the modified Radiographic Union Scale for Tibial Fractures (mRUST) scores possess a lower inter and intra rater reliability in ballistic fractures compared to blunt fractures. They may predict union at 9-months well in ballistic femoral fractures, but only moderately in ballistic tibia fractures.
LEVEL OF EVIDENCE:
Diagnostic Level III