Two Cases of Maxillary Malpositioning Following Maxillary and Mandibular Orthognathic Surgery Using CT-guided Virtual Surgical Planning
Orthognathic Surgery is one of the most common major procedures performed by Oral and Maxillofacial Surgeons. Much has been written about the inherent inaccuracies of traditional treatment planning using model surgery mounted via facebow transfers (1). Recent advances in technology, such as CT-guided surgery (aka “virtual surgical planning”), have permitted more accurate positioning of the maxilla and mandible in reference to the skull base (2). While this technology has greatly improved the predictability of skeletal movements, it is not infallible, and the practitioner must remain vigilant during orthognathic cases to ensure proper placement of the skeletal components for optimal results. We present two cases, which were planned with CT-guidance using prefabricated surgical splints, that were complicated by malposition of the patient’s maxilla, and subsequently, the mandible.
Materials and Methods:
Retrospective chart review was performed of all two-jaw orthognathic surgery cases done using CT-guided virtual planning technology with digitally fabricated surgical occlusal splints from 1/2012 to 3/2014. For the two cases requiring intra-op or post-op correction of significant jaw malpositioning, careful evaluation was performed to deduce factors involved in case error.
Results:
During the greater than 2 year time period, 2 of 29 cases performed using virtual surgical planning required either significant intraoperative repositioning and replating, or postoperative day #1 return to the operating room for revision.
Case 1: 17 year old male who underwent Lefort 1 osteotomy, left sagittal split mandibular osteotomy and right inverted L osteotomy with anterior iliac crest bone grafting. After completion of maxillary and mandibular components of surgery, but prior to closure and extubation, the surgical team noted that the maxilla was significantly canted downward on the left side. Plating was removed and the maxilla was carefully repositioned and re-plated. As the maxilla was used as reference for mandibular positioning, this also required repositioning and fixation. Improper positioning was attributed to incomplete maxillary lateral wall removal for left sided impaction to correct the preoperative cant further complicated by insufficient compensation for the cant in the intermediate occlusal splint.
Case 2: 17 year old male who underwent Lefort 1 osteotomy and bilateral sagittal split mandibular osteotomies. Upon post-op evaluation of the patient on post-operative day #0, it was noted that the patient’s maxillary midline was approximately 7mm to the left of his facial midline. The patient was returned to the OR on POD #1 for revision surgery. Upon review, malpositioning was attributed to slight lateral dislocation of the left mandibular condyle during seating for maxillary plating. This was further complicated by inadequate re-evaluation the completion of the case.
Conclusion:
Accuracy in maxillo-mandibular positioning in orthognathic surgery has greatly improved in recent years with the advent of CT-guided virtual planning. However, there are still areas in which oversights in pre-op planning and intraoperative errors can lead to undesirable results. In situations like our first case, one should ensure that the pre-operative virtual surgery with plans for adequate bone removal to correct a cant is translated to the actual surgery. For both cases, reliance on occlusal splints without use of internal or external markers may not be sufficient. Also, continued technological advances, such as orthognathic positioning systems may further increase accuracy of surgery. And finally, multiple complete intraoperative reevaluations are critical to prevent malpositioning errors from leaving the operating room.
References:
(1) Ellis E, et.al. Accuracy of face-bow transfer: effect on surgical prediction and postsurgical result.JOMS, 50 (1992), pp.562-567
(2) Hsu SS, et.al. Accuracy of computer-aided surgical simulation protocol for orthognathic surgery: a prospective multicenter study. JOMS. 71(2013), pp.128-142