Free bone flap reconstruction in retrosigmoid approach for microvascular decompression: a comparative cohort study

Titanium plates and screws are common material used for rigid bone flap fixation after retrosigmoid craniotomy such as microvascular decompression (MVD). We conducted this study to evaluate outcomes of the free bone flap cranioplasty without fixation in MVD and compared its postoperative complication rate with routine methods. We retrospectively reviewed all patients who underwent MVD at our institution from May 2017 to August 2022. Patients were divided into two groups according to whether the bone flap was fixed or not. Follow-ups periods spanned 6-28 months after the operation. Of 189 patients who underwent MVDs via retrosigmoid approach, 79 cases (42%) had their bone flaps replaced without titanium fixation after craniotomies (< 3 cm x 3 cm). Compared to fixed bone flap group, free bone flap group had shorter operative time (105.56 ± 15.87 min vs. 113.72 ± 17.80 min, P = 0.001), less in-patient costs (¥23059.66 ± 4488.54 vs. ¥27714.82 ± 2705.74, P < 0.001), and less proportion of postoperative headache and incisional pain (43.0% vs. 60.9%, P = 0.015). One case of incisional cerebrospinal fluid leak happened in free bone flap group while one case of incisional infection happened in fixed bone flap group. No statistical difference in bone flap displacement, duration of postoperative hospital stays or complication rate was found between the two groups. Nineteen patients in free bone flap group received long-term CT follow-up and all were proved to have good skull union. This study proves that free bone flap cranioplasty in MVD without titanium plate fixation can shorten the operation time and reduce hospitalization expenditure without increasing complication rates.