Knee hemarthrosis aspiration and its effect on compartment pressures in tibial plateau fractures.

OBJECTIVES: To determine the effect knee hemarthrosis aspiration had on compartment pressures of the leg in patients with tibial plateau fractures. METHODS: Design: Prospective Pre-post interventional study. Setting: Single Level I Trauma Center. Patient Selection Criteria: Included were non-obtunded patients with tibial plateau fractures (OTA/AO 41B/41C) who were undergoing spanning external fixation, with or without compartment syndrome from December 2023 to December 2024. Outcome Measures and Comparisons: Intra-compartmental pressure in the anterior, lateral, superficial and deep posterior compartments of the leg pre and post knee hemarthrosis aspiration, volume of knee hemarthrosis aspiration, and diastolic blood pressure were obtained. Intra compartmental pressures and diastolic blood pressure were compared pre and post hemarthrosis aspiration. Also, correlation between volume of aspirate and magnitude of pressure change was measured and need for four compartment fasciotomies for compartment syndrome was evaluated. RESULTS: 20 patients were enrolled: 13 males and 7 females with an average age of 48 years, ranging from 18-68 years. The average aspiration volume was 42 mL (range 5-120mL). Across all compartments in the leg, the average pre-aspiration pressure was 36 mmHg and post-aspiration pressure was 29 mmHg (p<0.0025). Individual compartment pressure changes ranged from 0-25mmHg (p < 0.005) which represented up to approximately 20% decrease in compartment pressures. There was no correlation between aspiration volume and pressure decrease found with this range of aspirate volumes (Pearson correlation coefficient approaching 0 for each compartment). Five patients underwent four compartment fasciotomy for compartment syndrome after aspiration, and no fasciotomies were required in the 15 legs that did not undergo release at the time of index surgery. CONCLUSIONS: Aspiration of the knee hemarthrosis associated with tibial plateau fractures produced a drop in compartment pressures in the leg (average magnitude range 4-7 mmHg). The clinical significance of this change is yet to be fully understood. The study showed at least a portion of the increased pressure in the compartments of the leg following tibial plateau fractures may be attributed to direct increases of pressure in the knee capsule due to hemarthrosis formation from fracture bleeding that may be relieved from aspiration. Time of effect and effect of continuous drains are further avenues of study to be evaluated. LEVEL OF EVIDENCE: Level II