H. Kärcher

Assessment of Bone Resorption After Secondary Alveolar Bone Grafting Using Three-Dimensional Computed Tomography: A Three-Year Study

Objective: Secondary bone grafting plays an important role in the dental rehabilitation of patients with clefts of the lip, alveolus, and palate. A major complication of this surgical technique is resorption of the grafted bone transplant. Conventional two-dimensional radiographs are often inconclusive and do not demonstrate the true deficit. The main objective of this study was to evaluate the amount and exact location of bone loss on the basis of three-dimensional models over a period of 3 years. Design: Twenty-four patients with unilateral cleft palate were included in this prospective study. Axial computed tomography scans of all patients were taken immediately preoperatively, and 1, 2, and 3 years postoperatively. Volumetric analysis was performed on three-dimensional models of the cleft defects and the bone bridges using three-dimensional computed tomography. Interventions: All patients were treated by secondary alveolar bone grafting prior to eruption of the permanent canine. Results: Extensive bone resorption was found in the bucco-palatal dimension of the alveolar portion of the transplant. The success rate of secondary bone grafting was high in cases of rapid orthodontic gap closures. The mean bone loss in the first year after surgery was 49.5%. The transplants remained almost constant in the following 2 years. Conclusions: Radiographic scales based on orthopantomography only evaluate the vertical dimension of the transplants. This study, however, showed that bone resorption in the transversal dimension is clearly underestimated with conventional two-dimensional radiographs.

Three-dimensional evaluation of secondary alveolar bone grafting using a 3D- navigation system based on computed tomography: a two-year follow-up.

Secondary bone grafting is widely used in the closure of oronasal fistulas and reconstruction of maxillary defects. It often fails from lack of physiological stress or inadequate covering of the transplanted bone with surrounding tissue. The aim of this study was to assess the exact bone volume after secondary alveolar bone grafting over a period of two years using a navigation system based on computed tomography (CT). We examined 20 patients with complete unilateral cleft lip and palate (UCLP) who had been treated by secondary bone grafting during late mixed dentition. CT scans of the upper jaw were taken immediately preoperatively, and 1 and 2 years postoperatively. The cleft defects and the bony bridges were marked on the monitor. The software of the navigation system created three-dimensional models showing the amount and site of bone resorption. The mean bone loss after one and two years was 51% and 52%, respectively. There was a significant correlation between the size of the cleft and the success of the alveolar bone grafting (p=0.01). When the teeth adjacent to the cleft were missing the amount of bone lost was 95% after the first year. There was also significant bone loss in the buccopalatine direction. Three-dimensional reconstruction of the bony bridges with a navigation system accurately shows the amount of bone within the cleft site. This method is definitely superior to conventional two-dimensional orthopantomography.

Intraoperative control of resection margins in advanced head and neck cancer using a 3D-navigation system based on PET/CT image fusion

Local recurrent of disease in advanced carcinomas of the head and neck is strongly correlated with the presence of positive or close resection margins after operative treatment. The purpose of this study is to present a new method of assessing resection margins intraoperatively using image-guided surgery based on positron emission tomography/computed tomography (PET/CT) image fusion. In 6 patients who underwent surgical treatment of head and neck stage for T4a-T4b carcinomas PET/CT image fusion was done on the workstation of a 3D-navigation system. Intraoperative image-guided navigation of the defect following surgical ablation of the tumour was performed in every patient. Intraoperative navigation of the ablative defect showed an unsafe resection margin in 4 patients. In three of these patients additional image-guided resection allowed local control of the tumour to be achieved. In one patient additional resection was not possible due to skull base invasion. The histopathological exam of the four tumour specimens confirmed positive or close resection margins. The current results suggest that intraoperative control of the surgical margins using a 3D-navigation system based on PET/CT image fusion can be a useful tool to assess and improve local control in advanced cancer of the head and neck.

Surgical treatment of synovial chondromatosis of the temporomandibular joint with erosion of the skull base: a case report and review of the literature.

Synovial chondromatosis (SC) is a rare metaplastic disease of the larger joints. It is rarely observed in smaller joints, especially in the temporomandibular joint (TMJ). This disease is considered to be metaplastic and shows no malignant tendencies, but can become locally aggressive, erode the cranial base, and even spread intracranially. To date, nine cases of spread into the intracranial space have been reported in the literature; however, the disease remained extradural in all cases. The authors present a review of the literature and report the case of a 70-year-old man with SC of the right TMJ that had eroded the cranial base, reaching the dura mater; a large intracranial mass was not present. The disease was considered to be stage 3 according to Milgrams classification. The patient was treated surgically, the tumour mass was removed, reconstruction of the cranial base was performed using titanium mesh, and the joint was reconstructed with a temporal muscle interposition flap. Diagnostic images and intraoperative photographs are also presented.

Trans-tragal incision for improved exposure of diacapitular and condylar neck fractures

The authors present a modification of the preauricular approach that improves the exposure of the condyle whilst reducing diacapitular and condylar neck fractures. The incision is a combination of the hockey-stick and endaural incisions. Its inferior part runs within the ear on the posterior face of the tragus; the tragal cartilage is transected together with the retrotragal skin and included in the anterior skin flap. Between May 2009 and December 2010, 16 patients with diacapitular or condylar neck fractures were treated with this approach. All patients showed good occlusion postoperatively and satisfactory aesthetic results. No infection or cartilage necrosis was observed in this series. This approach improves the exposure of the condylar head during the reduction of diacapitular and condylar neck fractures, ensuring easier internal fixation and good cosmetic results.

Surgical treatment of macroglossia caused by systemic primary amyloidosis

Amyloidosis is a heterogeneous group of disorders caused by the extracellular deposition of a fibrillar protein called amyloid. Amyloid involvement of the tongue is almost universally secondary to systemic disease. The clinical manifestations result from the progressive extracellular deposition of amyloid within the suprahyoid muscles. In the late stages, the progressive enlargement of the tongue causes hypo- and oropharyngeal blockage, with obstruction of the upper airways. Conservative excision is a satisfactory treatment for local amyloid masses; the role of surgery in systemic forms is controversial. The authors present a case of systemic primary amyloidosis of the tongue treated surgically by a partial glossectomy via a pull-through approach and discuss the indications and rationale for surgical intervention.

Three dimensional comparative measurement of polyurethane milled skull models based on CT and MRI data sets.

OBJECTIVE Due to the increase in the number and complexity of surgical procedures, available to craniomaxillofacial surgeons, allied to the rapid progress of technological developments, the use and production of 3D models has become important, especially for planning complex cases. The radiation exposure of additional CT based examinations is always subject to debate, so the feasibility of producing 3D models for surgical planning based on MRI imaging has been raised. MATERIAL AND METHODS 12 male and 3 female patients (n=15) between 47 and 84 years of age (mean age=65) were selected in a prospective study. Both magnetic resonance and computed tomography data sets of the facial bones were collected. Two milled models per patient were prepared: one based on the MRI scan and one based on the CT scan. The milled models were compared in a coordinative surveying procedure within 7 representative distances using a tentative measurement method. RESULTS Difference values between CT and MRI based models ranged from 0.1mm to 5.9 mm. On average MRI based models were smaller by 0.381 mm (SD 1.176 mm) than those on CT based. The accuracy of models based on MRI data was similar to those based on CT data. MRI based three dimensional milled models provide precise structure accuracy.

Primary osteomyelitis of the mandibular condyle—a rare case

Osteomyelitis is an inflammatory process involving cortical and cancellous bone. In the maxillofacial region, the mandible is the most frequently affected bone. In the vast majority, a bacterial focus can be identified as the origin of the disease. Chronic progress of the disease may lead to destruction of mandibular bony structures, resulting in mild or severe loss of function if no adequate treatment is applied. In some cases, the etiology of osteomyelitis remains unclear. Review of literature revealed two cases of necrosis of the mandibular condyle caused by primary osteomyelitis. We report a case of primary osteomyelitis of the mandibular condyle in a 51-year-old woman. Radiography revealed an almost complete destruction of the right mandibular condyle, resulting in malocclusion. The patient was treated with long-term antibiotics. No surgical intervention had been performed. After remission of the symptoms, the malocclusion had been corrected prosthetically. After a 4-year follow up period, the occlusion is stabile and there are no signs of progression of the disease.

The use of a 3D navigation system in the treatment of mandibular angle fractures by minimally invasive insertion of Herbert screws for osteosynthesis

Objective: We present a phantom study evaluating the use of a three-dimensional navigation system in the treatment of mandibular angle fractures with traction screw osteosynthesis. The insertion of the so-called “Herbert bone screw” was tested on phantom models of the mandible. Materials and Methods: A total of ten synthetic models of the lower jaw were prepared with navigational markers. After inducing artificial fractures in the mandibular angle region, axial CT scans of the models with 1.5-mm slice thickness were performed. The CT data was then transferred to the workstation of the navigation system (STN-Zeiss Navigation System, Aalen, Germany). The access to the fracture and the drilling depth were planned preoperatively on the computer monitor using the software. After calibration of the drill wire, the cannulated traction screws were inserted under three-dimensionally directed computer navigation. Results: The inferior alveolar nerve of the model was spared in all ten cases. Cortical perforation occurred twice in the ascending lower jaw branch, but secure anchorage of the screw was still possible in every case. Conclusion: The navigation system is a helpful visualization tool that can prevent damage to the inferior alveolar nerve and enable secure anchoring of the traction screw centrally in the cortical bone without causing perforation. This computer guided insertion method enables stable fixation of the fracture via minimally invasive surgery. Positioning of a traction screw with additional tools belonging to the screw system (drill wire) is demonstrated.

Prefabricated Iliac Crest Transplant

PURPOSE Our aim was to augment the extremely atrophic mandibular alveolar crest with a pedicled transplant as the best option for a satisfactory preprosthetic outcome. MATERIALS AND METHODS After computed tomography of the mandible, a model was milled for 6 patients. The iliac crest transplant with its vascular pedicle was harvested and, after preliminary preparation, fixed to the model. The transplant was then placed in the axilla. After 3 months, the graft was removed and fixed to the mandible. RESULTS The prefabricated transplant fit exactly in all 6 patients. The length of the pedicle and coverage with the newly developed alveolar mucous membrane were satisfactory. The grafts allowed prosthetic reconstruction with good functional outcomes. No bone loss was observed during 7 years of follow-up. Additionally, indocyanine green angiography showed good perfusion in 4 patients after 6 months. CONCLUSIONS The results suggest that carefully prefabricated pedicled transplants can augment an atrophied mandibular alveolar crest.