Functional Outcome After Nonoperative Management of Tibial Plateau Fractures in Skeletally Mature Patients: What Sizes of Gaps and Stepoffs Can be Accepted?
Authors: Vaartjes Thijs P. , Assink Nick , Nijveldt Robert J. , van Helden Svenhjalmar H. , Bosma Eelke , El Moumni Mostafa , Duis Kaj ten , Hogervorst Mike , Doornberg Job N. , de Vries Jean-Paul P. M. , Hoekstra Harm , IJpma Frank F. A. 
Published: May 2022

Abstract

Background
Gap and stepoff measurements provide information about fracture displacement and are used for clinical decision-making when choosing either operative or nonoperative management of tibial plateau fractures. However, there is no consensus about the maximum size of gaps and stepoffs on CT images and their relation to functional outcome in skeletally mature patients with tibial plateau fractures who were treated without surgery. Because this is important for patient counseling regarding treatment and prognosis, it is critical to identify the limits of gaps and stepoffs that are well tolerated.

Questions/purposes
(1) In patients treated nonoperatively for tibial plateau fractures, what is the association between initial fracture displacement, as measured by gaps and stepoffs at the articular surface on a CT image, and functional outcome? (2) What is the survivorship of the native joint, free from conversion to a total knee prosthesis, among patients with tibial plateau fractures who were treated without surgery?

Methods
A multicenter cross-sectional study was performed in all patients who were treated nonoperatively for a tibial plateau fracture between 2003 and 2018 in four trauma centers. All patients had a diagnostic CT scan, and a gap and/or stepoff more than 2 mm was an indication for recommending surgery. Some patients with gaps and/or stepoffs exceeding 2 mm might not have had surgery based on shared decision-making. Between 2003 and 2018, 530 patients were treated nonoperatively for tibial plateau fractures, of which 45 had died at follow-up, 30 were younger than 18 years at the time of injury, and 10 had isolated tibial eminence avulsions, leaving 445 patients for follow-up analysis. All patients were asked to complete the validated Knee Injury and Osteoarthritis Outcome Score (KOOS) questionnaire consisting of five subscales: symptoms, pain, activities of daily living (ADL), function in sports and recreation, and knee-related quality of life (QOL). The score for each subscale ranged from 0 to 100, with higher scores indicating better function. A total of 46% (203 of 445) of patients participated at a mean follow-up of 6 ± 3 years since injury. All knee radiographs and CT images were reassessed, fractures were classified, and gap and stepoff measurements were taken. Nonresponders did not differ much from responders in terms of age (53 ± 16 years versus 54 ± 20 years; p = 0.89), gender (70% [142 of 203] women versus 59% [142 of 242] women; p = 0.01), fracture classifications (Schatzker types and three-column concept), gaps (2.1 ± 1.3 mm versus 1.7 ± 1.6 mm; p = 0.02), and stepoffs (2.1 ± 2.2 mm versus 1.9 ± 1.7 mm; p = 0.13). In our study population, the mean gap was 2.1 ± 1.3 mm and stepoff was 2.1 ± 2.2 mm. The participating patients divided into groups with increasing fracture displacement based on gap and/or stepoff (< 2 mm, 2 to 4 mm, or > 4 mm), as measured on CT images. ANOVA was used to assess whether an increase in the initial fracture displacement was associated with poorer functional outcome. We estimated the survivorship of the knee free from conversion to total knee prosthesis at a mean follow-up of 5 years using a Kaplan-Meier survivorship estimator.

Results
KOOS scores in patients with a less than 2 mm, 2 to 4 mm, or greater than 4 mm gap did not differ (symptoms: 83 versus 83 versus 82; p = 0.98, pain: 85 versus 83 versus 86; p = 0.69, ADL: 87 versus 84 versus 89; p = 0.44, sport: 65 versus 64 versus 66; p = 0.95, QOL: 70 versus 71 versus 74; p = 0.85). The KOOS scores in patients with a less than 2 mm, 2 to 4 mm, or greater than 4 mm stepoff did not differ (symptoms: 84 versus 83 versus 77; p = 0.32, pain: 85 versus 85 versus 81; p = 0.66, ADL: 86 versus 87 versus 82; p = 0.54, sport: 65 versus 68 versus 56; p = 0.43, QOL: 71 versus 73 versus 61; p = 0.19). Survivorship of the knee free from conversion to total knee prosthesis at mean follow-up of 5 years was 97% (95% CI 94% to 99%).

Conclusion
Patients with minimally displaced tibial plateau fractures who opt for nonoperative fracture treatment should be told that fracture gaps or stepoffs up to 4 mm, as measured on CT images, could result in good functional outcome. Therefore, the arbitrary 2-mm limit of gaps and stepoffs for tibial plateau fractures could be revisited. The survivorship of the native knee free from conversion to a total knee prosthesis was high. Large prospective cohort studies with high response rates are needed to learn more about the relationship between the degree of fracture displacement and functional recovery after tibial plateau fractures.

Level of Evidence
Level III, prognostic study.