Post-operative outcomes associated with posterolateral tibial plateau impaction fractures in the setting of primary ACL tear
Authors: DePhillipo Nicholas , Dornan Grant , Aman Zachary , Kennedy Mitchell , LaPrade Robert , Bernholt David 
Published: July 2020

Objectives: The primary objective was to assess the effect of impaction fractures of the posterolateral tibial plateau on patient reported post-operative outcomes following primary ACL surgery. Methods: Patients with available MRI images who underwent surgery for primary ACL tears by a single surgeon between April 2010 and September 2017 were identified. A prospectively and consecutively enrolled clinical outcomes database was queried for all patients within this cohort who had 2-year or greater post-operative patient reported outcomes available. Patient reported outcomes included the 12-item Short Form Health Survery (SF-12) Physical Composite Scale (PCS) and Mental Health Composite Scale (MCS), the Western Ontario and McMaster University Osteoarthritis Index (WOMAC), International Knee Documentation Committee Questionnaire (IKDC), Lysholm Knee Questionnaire, Tegner Activity Scale and patient satisfaction. For patients without existing 2-year outcomes, additional inclusion criteria included English-speaking and current age greater than or equal to 18. Patients meeting these criteria were sent electronic surveys to collect patient reported outcomes. MRI images were reviewed for all patients with denotation of displaced posterolateral tibial impaction fractures. Posterolateral tibial impactions were classified based on morphology using the following classification: (Type I) posterior cortical buckle not involving the articular surface, (Type II) posterior impaction fracture involving the articular surface [(with subtype based on (A) tibial plateau depth bone loss <10% and (B) bone loss >10%)], and (III) displaced osteochondral fragment [(with subtypes for (A) shear or (B) depressed fragment)]. All tibial impaction fractures were measured to determine amount of tibial plateau bone loss in the sagittal plane. Pre-operative and 2-year or greater post-operative patient reported outcome scales were compared based on posterolateral tibial impaction fracture classification using Kruskal-Wallis non-parametric ANOVA with Nemenyi post-hoc test. Pearson’s correlations were used to assess for correlations between post-operative patient reported outcomes and amount of tibial plateau sagittal plane bone loss present. Results: There were 638 knees identified with primary ACL tears who underwent surgery between April 2010 and September 2017. Thirty-nine patients met exclusion criteria, leaving 599 total patients. Of these, 2-year outcomes were available for 416 patients for a 69.4% follow-up rate at a mean time of 158 weeks (range: 90-422). There were statistically significant improvements in all PROs from pre-op to 2-year post-op (p < 0.001). Kruskal-Wallis non-parametric ANOVA showed no difference in all PROs based upon posterolateral impaction fracture classification type, except for Tegner Activity Scale which showed difference in outcomes based on impaction fracture type (p < .002) (Table 1). Specifically, diminished post-operative activity level was observed in patients with type 2B, type 3A, and type 3B fractures. Pearson correlation testing showed weak but statistically significant correlations between tibial plateau impaction fracture sagittal bone loss amount and SF-12 PCS (PCC: -0.156, p = 0.023), WOMAC Total Score (PCC: 0.159, p = 0.02), Lysholm (PCC: -0.203, p = .003), and Tegner Activity Scale (PCC: -0.151, p = 0.032). Independent T-testing showed no difference in any patient reported outcome scores at 2-year follow-up when all posterolateral tibial impaction fractures were grouped together compared to those without impaction fracture. Conclusion: Displaced posterolateral tibial plateau impaction fractures occurring in the setting of ACL tear are associated with diminished 2-year post-operative outcomes after ACL reconstruction. When classified based on fracture morphology, posterolateral tibial plateau impaction fracture types 2B, 3A, and 3B are associated with decreased post-operative activity level as assessed by Tegner Activity Scale. When comparing patients with posterolateral impaction fractures, greater amounts sagittal plane tibial plateau bone loss at the posterior rim showed weak but significant correlations with worse scores on SF-12 PCS, WOMAC, Lysholm, and Tegner patient reported outcome measures. [Figure: see text]