Is Injectable Beta-Tricalcium Phosphate Effective as Gap Filler for Medial Open Wedge High Tibial Osteotomy?

We aimed to evaluate whether using novel injectable gel-type beta Tricalcium Phosphate (β-TCP) as gap filler for Medial Open Wedge High Tibial Osteotomy (MOWHTO) is effective. Consecutive 28 patients who were scheduled to undergo biplanar MOWHTO for medial compartmental osteoarthritis were prospectively enrolled. The osteotomy was fixed by an anatomical locking plate and the gap was filled with novel injectable β-TCP. The degree of bone union and maturation of β-TCP was assessed by radiographs and Computed Tomography (CT) scans at postoperative 3 and 12 months. The mechanical Femoro-Tibial Angle (mFTA) was measured and compared between pre and postoperative period. Clinical outcome was evaluated by determining International Knee Documentation Committee (IKDC), Western Ontario and McMaster Universities Arthritis Index (WOMAC) and Visual Analogue Scales (VAS) for pain scores. Twenty-five patients (89.3%) were analyzed and all cases showed bony union of osteotomy site without any complication. Serial progress of bone union was found on radiographs and the mean ratio (β-TCP/ host bone) of CT attenuation values significantly changed from postoperative 3 months (12.26) to 12 months (8.37) (P=0.012), which indicates maturation of β-TCP. The average mFTA significantly changed from preoperative (4.1° varus) to 3 months (4.8° valgus) and maintained at 12 months (4.3° valgus) (P<0.001). Significant improvements of the IKDC, WOMAC and VAS pain scores were also seen (P<0.001, P=0.002 and P=0.002 respectively). We found satisfactory bone union and clinical outcome without any complication after using injectable β-TCP as gap filler for MOWHTO.