W. Bradford Williams

Histomorphometric analysis of the porcine mandibular distraction wound.

PURPOSE To analyze the sequence of histomorphometric changes in the regenerate during distraction osteogenesis (DO) of the minipig mandible. MATERIALS AND METHODS A total of 16 minipigs underwent unilateral mandibular DO using a protocol of 0-day latency and a 1-mm/day rate for 12 days, and 24 days of fixation. The mandibles were harvested at mid-DO, end-DO, mid-fixation, and end-fixation. An additional 2 minipigs underwent acute lengthening, and 1 sham control was included. Serial gross examinations and plain radiographs were performed before paraffin embedding. The sections were stained with hematoxylin-eosin or hematoxylin/alcian blue/sirius red stain. Histomorphometric analysis was performed to determine the percentage of surface area (PSA) occupied by hematoma, fibrous tissue, cartilage, and bone. RESULTS All 19 minipigs survived the operation, and 17 survived the observation period; 2 were killed because of infection (mid-DO, n = 1 and end-fixation, n = 1). No device failures occurred. Of the 17 specimens, 4 were at mid-DO, 4 at end-DO, 4 at mid-fixation, and 2 at end-fixation; 2 were in the acute lengthening group, and 1 was the sham control. Hematoma was present only at mid-DO (16.61 +/- 8.07 PSA) and end-DO (1.17 +/- 2.33 PSA). Fibrous tissue decreased from mid-DO (53.12 +/- 8.59 PSA) to end-fixation (25.00 +/- 0.83 PSA). Cartilage was present in end-DO (1.72 +/- 2.71 PSA), mid-fixation (5.82 +/- 6.64 PSA), and acute lengthening (1.43 +/- 0.95 PSA). Bone increased from mid-DO (25.18 +/- 0.99 PSA) to end-fixation (64.89 +/- 0.79 PSA) and occurred earlier in the superior and middle thirds of the wounds. Periosteal bone formation predominated over endosteal bone formation early in distraction. CONCLUSION The results of the present study indicate that bone formation in this model consists of both intramembranous and endochondral components, with intramembranous osteogenesis predominating. Bone formation occurred earlier in the superior/middle portions of the wound, possibly owing to osteoinductive properties of developing tooth buds and the inferior alveolar nerve, respectively.

Role of computed tomographic angiography in treatment of patients with temporomandibular joint ankylosis.

PURPOSE To evaluate the use of preoperative computed tomographic angiography (CTA) and selective embolization as an ancillary tool for the treatment of patients with temporomandibular joint (TMJ) ankylosis. MATERIALS AND METHODS The present study was a case series of subjects with bilateral TMJ ankylosis who had undergone preoperative CTA and surgical release with immediate reconstruction. The indications for CTA were either an intimate association between the vessels and the ankylotic mass on the facial computed tomography (CT) scan or a history of multiple previous TMJ operations. In cases in which intimate anatomic association was present between the branches of the maxillary artery and the ankylotic masses, preoperative selective embolization was performed. All subjects underwent a standard approach to ankylosis release with immediate reconstruction and were followed up for up to 6 months postoperatively. The demographic and operative variables were recorded for each subject. RESULTS Five subjects (mean age, 36.4 years; 3 females) with bilateral TMJ ankylosis underwent release and had undergone preoperative CTA for vascular assessment. Three subjects underwent preoperative embolization. The total operating time ranged from 5.9 to 10.3 hours. The intraoperative blood loss ranged from 150 to 3,750 mL. One patient who had undergone unilateral embolization required an intraoperative transfusion because of bleeding on the nonembolized side. No adverse cardiac, renal, or neurologic events developed secondary to the blood loss. In all 5 subjects, the preoperative maximal incisor opening was less than 15 mm, increased to more than 35 mm intraoperatively, and was 30 mm or more at 6 months or longer of follow-up. CONCLUSIONS In select cases, CTA can be a useful adjunct in the treatment of patients with TMJ ankylosis.

Serial histologic and immunohistochemical changes in anterior digastric myocytes in response to distraction osteogenesis.

PURPOSE To document histologic and immunohistochemical changes in the anterior digastric muscle during distraction osteogenesis (DO). MATERIALS AND METHODS Nineteen Yucatan minipigs with mixed dentition were used for these experiments. Group A (n = 16) underwent unilateral mandibular distraction at a rate of 1 mm/day (no latency) for 12 days. Animals were killed at mid-DO (n = 5), end-DO (n = 5), mid-fixation (n = 4), and end-fixation (n = 2). Group B (n = 2) underwent acute 12-mm advancement, and group C (n = 1) dissection and osteotomy. Animals from groups B and C were killed at the end-DO time point. Digastric muscles from treatment and contralateral sides of all animals were harvested and embedded in paraffin. Specimens were stained with hematoxylin/eosin or immunohistochemically for proliferating cell nuclear antigen (PCNA; total cell proliferation), paired Box-7 gene protein (Pax7; satellite cells), or myogenic differentiation 1 protein (MyoD; differentiating myoblasts). Descriptive and bivariate statistics were computed to compare groups (P ≤ .05 statistically significant). RESULTS All animals survived the operation and observation period; there were no device failures. Two animals (1 at mid-DO, 1 at mid-fixation) were eliminated from the study because of postoperative infection. There was minimal digastric inflammation, fibrosis, and muscle fiber size variability during active DO. Immunohistochemical analysis showed statistically significant increases in PCNA (cellular proliferation), Pax7 (satellite cells), and MyoD (differentiating myoblasts) positive nuclei in digastrics at mid-DO and end-DO. CONCLUSIONS Results of this study indicate that there are minimal pathologic changes but significant increases in PCNA, Pax7, and MyoD positive nuclei during active distraction. This supports the hypothesis that the digastric muscle response to DO consists of proliferation and hypertrophy.

Management of a difficult airway with direct ventilation through nasal airway without facemask.

Mask ventilation is a key component of airway management for oral surgeons and anesthesia care providers. Clinicians often encounter a difficult airway in which adequate mask ventilation may be difficult or impossible. Difficult mask ventilation has been described as the inability for an experienced anesthesiologist to provide adequate face mask ventilation because of one or more of the following problems: inadequate mask seal, excessive gas leak, or excessive resistance to the ingress or egress of gas. 1 Although the exact pathogenesis of the difficult airway is not clearly defined, the presence of upper airway obstruction has been demonstrated to be the key contributor. Risk factors for difficult mask ventilation and upper airway obstruction correlate well and include increased age, obesity, and history of snoring or sleep apnea. 2,3 Relaxation of the upper airway musculature during sleep or anesthesia also contributes to upper airway obstruction and difficult mask ventilation. 1,3,4 The loss of upper airway muscle tone combined with the gravitational pull on the tongue and soft palate have been shown to result in airway collapse. 3-6 It is therefore logical to assume that creation of a patent upper airway would improve mask ventilation. This principle has been demonstrated in a recent study comparing oro-nasal mask ventilation and nasal mask ventilation, 7 as well as in this report. Report of a Case