Background: Lateral locked plating remains an important treatment strategy for distal femoral fractures but has been associated with nonunion rates ranging from 6% to 20%. The objective of this study was to identify factors associated with nonunion following lateral locked plating of distal femoral fractures with use of a Bayesian analysis. Methods: All consecutive patients ≥18 years of age who were treated with lateral locked plating for a distal femoral fracture at 2 Level-I trauma centers between 2006 and 2024 and who had ≥3 months of follow-up were included. Multivariable Bayesian logistic regression analysis was performed to identify factors associated with nonunion, which was defined as a reoperation to promote healing, and the results are reported as odds ratios (ORs) with 95% credible intervals (CrIs). Probabilities of >95% were considered very strong evidence of an association with nonunion, and probabilities of 90% to 95% were considered strong evidence. Results: A total of 560 patients (median age, 68 years; 29% male; 90% White; 97% non-Hispanic; 41% with distal periprosthetic fractures) were included. Fifty-four patients (9.6%) underwent reoperation to promote healing. There was very strong evidence that multifragmentary comminution of the metaphysis (versus simple fracture: OR, 2.60; 95% CrI, 0.91 to 8.06), medial cortical comminution of >0 to 25 mm (versus 0 mm: OR, 3.11; 95% CrI, 1.35 to 7.48), and varus (lateral distal femoral angle [LDFA] of ≥84°: OR, 3.04; 95% CrI, 1.46 to 6.51) or valgus (LDFA of ≤78°: OR, 2.42; 95% CrI, 0.96 to 5.99) malalignment increased the odds of nonunion. A screw density of ≤0.60 proximal to the working length reduced the odds of nonunion (versus ≥0.81: OR, 0.40; 95% CrI, 0.16 to 0.95), although the size and certainty of this effect varied in the sensitivity analysis that utilized alternative thresholds. There was strong evidence that obesity increased the odds of nonunion (OR, 1.64; 95% CrI, 0.86 to 3.13) and that intact wedge fractures reduced the odds of nonunion (versus simple fracture: OR, 0.35; 95% CrI, 0.05 to 1.74). Conclusions: One in 10 patients developed nonunion and underwent reoperation to promote healing. Surgeons should restore coronal plane alignment and may consider augmenting fixation in the presence of multifragmentary comminution. Constructs in which all screw holes proximal to the working length are filled should be avoided, although the optimal configuration remains unclear and depends on other construct characteristics influencing biomechanics. Overall, the small to moderate effect sizes highlight the multifactorial etiology of nonunion following lateral locked plating of distal femoral fractures. Level of Evidence: Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

OBJECTIVES: To determine the rate of and risk factors for reoperation to promote fracture union of periprosthetic distal femur fractures treated with lateral locked plating. METHODS: Design: Retrospective cohort study. Setting: Two level 1 trauma centers. Patient Selection Criteria: Adult patients undergoing operative treatment for a periprosthetic distal femur fracture (AO/OTA 33A or 33C) between 2006 and 2023 with a minimum follow-up of 3 months. Outcome Measures and Comparisons: Reoperation to promote fracture union compared across patient, fracture, and treatment characteristics. RESULTS: Two hundred and eighteen patients [mean age 72 years (range: 52–84), 77% women] were included. There were 133 (61%) Su type 2 fractures, 10 (4.6%) open injuries, and 118 (54%) fractures with multifragmentary comminution of the metaphysis. Twenty (9.2%) patients required reoperation to promote fracture union, including 15 (6.9%) patients who presented with nonunion with implant failure. In multivariable logistic regression analysis, body mass index [5-point increase; OR: 1.37 (95% CI, 1.00–1.86), P = 0.047], multifragmentary metaphyseal comminution [OR: 5.17 (95% CI, 1.47–18.3), P = 0.011], and varus malalignment [OR: 5.88 (95% CI, 1.29–26.8), P = 0.023] were associated with increased odds of reoperation for nonunion, whereas the use of titanium plates was protective [OR: 0.21 (95% CI, 0.07–0.63), P = 0.005]. CONCLUSIONS: In this study of 218 patients undergoing lateral locked plating for a periprosthetic distal femur fracture, 9 out of 10 patients did not undergo reoperation to promote fracture union. Factors associated with reoperation included increased body mass index, the presence of multifragmentary metaphyseal comminution, and varus malalignment with a lateral distal femoral angle of ≥84 degrees. The use of titanium plates was associated with decreased odds of reoperation although this finding should be interpreted in the context of varying plate designs and configurations. These results may help delineate indications for the selection of specific fixation constructs when treating periprosthetic distal femur fractures. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

OBJECTIVES: To report on adverse events during magnetic resonance imaging (MRI) on patients with external fixators. METHODS: Design: Retrospective case series. Setting: Two Level 1 Trauma Centers. Patient Selection Criteria: Patients with external fixators on the appendicular skeleton or pelvis undergoing MRI between January 2005 and September 2023. Outcome Measures and Comparisons: Adverse events, defined as any undesirable event associated with the external fixator being inside or outside the MRI bore during imaging, including: (subjective) heating, displacement or pullout of external fixator, or early MRI termination for any reason. RESULTS: Ninety-seven patients with 110 external fixators had at least one MRI with an external fixator inside or outside of the MRI bore. The median age was 51 years (IQR: 39 – 63) and 56 (58%) were male. The most common external fixator locations were the ankle (24%), knee (21%), femur (21%), and pelvis (19%). The median duration of an MRI was 40 minutes (IQR: 26 – 58), 86% were performed using 1.5 Tesla MRI, and 14% were performed using 3.0 Tesla MRI. Ninety-five percent of MRI were performed for the cervical spine/head. Two MRI scans (1.6%), one of the shoulder and one of the head and cervical spine, with the external fixator outside of the bore were terminated early due to patient discomfort. There were no documented events of displacement or pullout of the external fixator. CONCLUSIONS: These findings suggest that MRI of the (cervical) spine and head can be safely obtained in patients with external fixators on the appendicular skeleton or pelvis. Given the low numbers of MRIs performed with the external fixator inside the bore, further studies are necessitated to determine the safety of this procedure. The results from this study can aid orthopaedic surgeons, radiologists, and other stakeholders in developing local institutional guidelines on MRI scanning with external fixators in situ. LEVEL OF EVIDENCE: Prognostic Level lV. See Instructions for Authors for a complete description of levels of evidence.