Randomized Prospective Clinical Trial on Use of Resorbable Screws in Fixating Bilateral Sagittal Split Osteotomies for Mandibular Advancement
The use of metal rigid fixation in maxillofacial surgery is now standard in trauma of the maxillofacial skeleton, orthognathic surgery as well as craniofacial surgery.1 Resorbable fixation material is an attractive option for those patients undergoing orthognathic surgery. Besides the obvious benefit of not having permanent implants, it decreases the possible need for surgical implant removal that will be an additional cost and risk to the patient.2
The purpose of this randomized prospective clinical trial is to compare resorbable screw fixation to titanium screw fixation in orthognathic surgical procedures. In particular, efficacy of resorbable screws will be tested in bilateral mandibular sagittal split osteotomies (BSSO), which are performed for correction of retrognathic mandible.
Materials and Methods:
A total of 101 patients with mandibular retrognathia who needed mandibular advancement were enrolled in this prospective randomized clinical trial. Patients were randomly assigned to one of two groups with different fixation systems. Patients in Group 1 (n = 51) received titanium screws (Stryker) and patients in Group 2 (n = 50) received resorbable screws (Inion CPS). Outcome measures were clinical evidence of relapse, incidence of infection/inflammation, need for post-operative elastic rubber band use, changes in pre- and post-operative maximal incisal opening and need for additional procedures.
Method of Data Analysis:
To compare differences between dichotomous variables, the Chi-square or the Fisher’s exact test was used. To test continuous variables, the unpaired t-test was used. A p-value of <0.05 was considered statistically significant.
Results of Investigation:
In Group 1, the mean age was 33.4+/-14.3 (years). In Group 2, the mean age was 31.2+/-14.2 (years). A mandibular midline osteotomy was done in conjunction with BSSO in 37 cases in Group 1 (72.5%) and 39 cases (78%) in Group 2. The average length of follow-up was 8.06+/-9.24 (month) in Group 1 and 10.53+/-7.33 (month) in Group 2 (p = 0.1400). There were 2 cases of relapse (3.9%) in Group 1 and no case of relapse (0%) in Group 2 (p = 0.4950). There were 7 cases of infection/inflammation (13.7%) in Group 1 and 8 cases of infection/inflammation (16%) in Group 2 (p = 0.7862). Elastic rubber band was used in 21 cases (41.2%) in Group 1 and 48 cases (96%) in Group 2 (p = <0.0001). The pre- and post-operative maximal incisal opening difference was -1.86+/-7.51 (mm) in Group 1 and -0.31+/-6.80 (mm) in Group 2 (p = 0.2883). In Group 1, 2 cases (3.9%) required a second procedure for screw removal and there was no case (0%) that needed a second procedure in Group 2 (p = 0.4950).
Conclusion:
Resorbable screws can be used effectively for fixation of BSSO for mandibular advancement. There was a statistically significant difference in post-operative elastic rubber band use, although there was no case of relapse after the completion of treatment in patients who received resorbable screws. This finding may be related to a higher incidence of rotation around positional screws in the resorbable group secondary to the mechanical “looseness” resulting from the requirement to tap the bone. This was treated effectively with an increased elastic rubber band use during the initial stages of bone healing.