Screw Density is Not Associated with Outcomes of Lateral Bridge Plating of Distal Femur Fractures

OBJECTIVE: To examine whether screw density was associated with reoperation to promote union in distal femur fractures fixed with lateral bridge plating. METHODS: Design: Systematic review, meta-analysis and retrospective clinical cohort. SETTING: Tertiary referral center. PATIENT SELECTION CRITERIA: Systematic review and meta-analysis: PubMed, Embase, and Cochrane databases were systematically searched from the earliest available records of each database through May 2025. Included were observational studies and randomized controlled trials that reported the union rate following index distal femur fracture fixation with a single lateral distal femur plate and screw density of the lateral distal femur plate for groups that did and did not require a reoperation to promote union. RETROSPECTIVE CLINICAL COHORT: Adult patients who underwent lateral single-plate bridge fixation for acute distal femur fracture (OTA/AO 33A and 33C) at a single institution from January 2017 to January 2024 were reviewed. Excluded were patients with pathologic fractures, interprosthetic fractures, missing records, and <6 months of follow-up without radiographic union. OUTCOME MEASURES AND COMPARISONS: Systematic review and meta-analysis: The meta-analysis used total screw density (TSD) of the lateral distal femur plate as the effect variable on reoperation rates in the groups that either did or did not achieve union following distal femur fracture fixation. Proximal Screw Density (PSD) was not used as a main effect variable to avoid the inconsistent definitions and reporting of PSD used in the literature. RETROSPECTIVE CLINICAL COHORT: The primary outcome was reoperation to promote union. PSD (screw holes filled proximal to the fracture / screw holes proximal to the fracture) and TSD (TSD; screw holes filled / screw holes) were calculated and compared between groups that either did or did not require a reoperation to promote union. Screws in the distal metaphyseal block of the plate were excluded from all analyses. RESULTS: Meta-analysis and systematic review: The search generated 429 articles, of which 6 studies met inclusion criteria producing a patient sample of 1,272 with mean age 65.1 years (range 16-102 years) and 33% male (range 20-53%) with a mean nonunion rate of 16.5% (range 10.5%-28.8%). There was no significant association between TSD and nonunion rates (effect size = 0.05, 95% CI -0.21, 0.32). The mean TSD for patients achieving union versus those who did not was 0.60 versus 0.61, respectively (p=0.98). No study showed a significant effect of TSD on reoperation to promote union. RETROSPECTIVE COHORT: Fifty-six patients were included with a mean age of 72.2 (range 25-97) years, of which 80.4% were female. Six (10.7%) underwent reoperation to promote union. For patients requiring reoperation to promote union versus those who did not, there was no statistically significant difference in age, sex, OTA/AO classification, body mass index, past medical history, smoking history (p>0.05). Screw densities were not associated with re-operation to promote union (PSD 64.3% in those with re-operation and 55.6% in those without (p=.526), TSD (45.7% in those with re-operation and 52.0% in those without, p=.455). CONCLUSIONS: Based on both a meta-analysis and a clinical study, no association between screw density and reoperation to promote union in distal femur fractures fixed with a lateral single-plate bridging construct were found. Focus on parameters other than screw density are warranted in designing optimal bridge plate constructs. LEVEL OF EVIDENCE: A level III retrospective prognostic study.