Clinical Significance of β-Tricalcium Phosphate and Polyphosphate for Mastoid Cavity Obliteration during Middle Ear Surgery: Human and Animal Study

OBJECTIVES Mastoid obliteration is used to obliterate the mastoid cavity following a mastoidectomy or to prevent the formation of a retraction pocket. This study evaluated the effectiveness of β-tricalcium phosphate and polyphosphate (β-TPP) for mastoid obliteration in middle ear surgeries in prospective human and animal studies. METHODS Twenty patients with chronic otitis media underwent mastoid obliteration using β-TPP after a intact canal wall mastoidectomy or simple mastoidectomy. The clinical data were prospectively evaluated including: the diagnosis, temporal bone computed tomography (TBCT), otoscopic findings, pure tone audiogram, and complications. In the animal experiment, β-TPP was applied into the right bulla in five rats, and the opposite bulla was used as the control in the non-obliterated state. The skulls of five other rats were drilled out and the holes were obliterated with β-TPP. TBCT were obtained at 3, 6, and 9 months after the obliteration and histologic analysis was done at 3 and 9 months after surgery. RESULTS In the human study, fourteen TBCTs were obtained at 12 months after the surgery. All demonstrated no bone resorption in the obliterated mastoids. Among the 15 cases displaying retracted tympanic membranes preoperatively, 11 showed no retraction, 2 showed retraction postoperatively, 1 was lost to follow-up and 1 was a case of postoperative wound infection. Among 20 cases, one case developed a postoperative infection that necessitated a second operation. Sixteen underwent ossiculoplasty; hearing improvements were obtained in 15 cases and 1 case showed decreased hearing. In the animal study, new bone formation without significant bone resorption in the radiologic and histologic findings were noted in both the skull and bulla groups. CONCLUSION Although β-TPP is a foreign material having the possibility of infection, mastoid obliteration with it can be a treatment option in middle ear surgeries to prevent retraction pockets or the recurrence of diseases.