Thomas H. Hohl

Condylar position following mandibular advancement: Its relationship to relapse

Forty-one patients who elected to receive a bilateral sagittal osteotomy to advance the mandible were examined clinically and radiographically to assess condylar position preoperatively and at three specific times postoperatively. Parameters designed to measure changes in condylar and distal fragment position were located on tracings and digitized for statistical analysis. Changes in distal fragment position included advancement and clockwise rotation during the surgical interval and significant posterior relapse with continued clockwise rotation during the period of maxillomandibular fixation. A small amount of counterclockwise rotation associated with interocclusal splint removal was seen following fixation release. No significant condylar movement was seen during the surgical interval. During the period of maxillomandibular fixation, both condyles exhibited a significant superior movement, and the left condyle also moved posteriorly. No changes in condylar position were noted following release of fixation. The clinical significance of these condylar movements is not clear. Despite minimal changes, 18 patients, six of whom had had no preoperative symptoms and one of whom had exhibited reciprocal clicking, complained of temporomandibular joint pain or noise postoperatively. This suggests that maintenance of condylar position during surgery may not prevent temporomandibular joint dysfunction. In addition, the observed 37% relapse in surgical advancement in the absence of significant condylar distraction implies the interaction of other factors in the relapse process.

Psychologic changes in orthognathic surgery patients: a 24-month follow up.

This report describes the final, two-year follow up in a longitudinal study of 74 patients who underwent orthognathic surgery for developmental deformities. Data for all six measurement periods were available for 46 patients. Complaints of functional problems decreased significantly from before surgery to 24 months after, although 49% of the patients continued to report lip paresthesia. The incidence of postsurgical problems had no effect on the satisfaction expressed with surgical outcomes, which remained high throughout the postoperative course. Self-esteem appeared to rise in anticipation of surgery, only to decline significantly at nine months after surgery, to rise again by 24 months (but not as high as before surgery). In some components, self-esteem remained significantly lower after surgery than before. Body image also showed a decline at nine months, although overall body image and profile image 20-26 months after surgery were significantly more positive than before surgery. These results point to the importance of continued contact with orthognathic surgery patients by surgeons and orthodontists for at least two years after surgery, particular attention being paid to the intermediate stages (six to 12 months) after surgery. This period of psychologic upheaval appears to be related to the patients desire to complete postsurgical orthodontics.

Osseointegrated titanium implants for maxillofacial protraction in monkeys

Titanium implants were placed surgically into the maxillary, zygomatic, frontal, and occipital bones of four pigtail monkeys. After a 4-month healing period, the implants were exposed and abutments were placed. Extraoral traction appliances were then attached to the abutments. The cranial implants were used to support the framework of the traction appliance; those in the facial bones were used to attach springs that delivered a protraction force. The application of force varied among animals. In animal A, the force was applied to the maxilla. In animal B, the force was applied to the zygomatic bones. Animals C and D had force applied to both the maxillary and zygomatic bones. A tensile force of 600 gm per side was maintained until approximately 8 mm of maxillary anterior displacement had occurred. This amount of movement required 12 weeks of force application in animals A and B, and 18 weeks in animals C and D. Cephalometric and dry skull analyses showed that the amount of skeletal protraction was significant. The findings also demonstrated that it was possible to control the direction of maxillary protraction. The facial implants remained immobile throughout the experiment.

Predicting psychologic responses to orthognathic surgery

A longitudinal study was conducted of the psychologic characteristics of 74 persons undergoing orthognathic surgery. The effects of neuroticism, locus of control, and expectations upon postsurgical outcomes were examined. The majority of patients scored in the normal range of most personality variables. The findings suggest a generally intact ego and accurate self-concept among orthognathic surgery patients. Expectations of pain and parasthesia were the best predictors of postsurgical outcomes, while neuroticism and locus of control scores predicted some outcomes in the early postoperative stages. The results indicate the importance of preparing orthognathic surgery patients against unrealistic expectations before surgery is undertaken, and of counseling certain patients during the early postoperative period.

Macrogenia: A study of treatment results, with surgical recommendations

Abstract A review of the literature pertaining to the development and treatment of macrogenia is presented. No study of treatment results could be found in order to judge the efficiency of the various proposed surgical approaches. In view of this, we have made a retrospective study of treatment results in eleven patients followed for at least 12 months and up to 50 months postoperatively. We propose a classification of macrogenia that is based upon an exact description of the existing esthetic and anatomic deformity. Recommendations for treatment are made on the basis of this classification, the treatment results from the present study, and preliminary results from alternative treatment methods.

Measurement of condylar loading forces by instrumented prosthesis in the baboon

Mathematical models have been developed to predict hypothetical forces acting on the mandibular condyles during mastication, but no direct measurements of condylar forces in vivo have been reported. This preliminary study presents the technical development of an instrumented prosthesis which was implanted in the mandibular ramus of a baboon, and some preliminary data collected while measuring with this prosthesis the condylar forces exerted during simulated mastication under general anaesthesia. Simulated mastication was induced by stimulating the motor tracts of the trigeminal nerve bilaterally, and the forces in response to increasing amperage were recorded. The pathogenesis of TMJ degeneration may be more fully understood by directly measuring the direction and magnitude of forces acting on the condyles during function. In addition, the future development of a total TMJ replacement for traumatized, deranged, or degeneratively impaired joints, must be accomplished with reliably engineered prostheses based upon direct force measurements.

Masticatory muscle transposition in primates: Effects on craniofacial growth

The effects of early transposition of the masticatory muscles on the craniofacial growth and development of infant primates are documented with the aid of serial cephalometry, EMGs, and dry-skull preparations. The bilateral posterior transposition of the insertion of the masseter and temporalis muscles was followed by a significant superior and anterior rotation of the midfacial growth pattern as well as by marked skeletal morphological changes. The study documents the ability to change skeletal craniofacial growth patterns by altering muscle attachments.

Experimentally induced ankylosis and facial asymmetry in the macaque monkey

Six Macaca nemestrina were used for induction of ankylosis by different methods. One TMJ capsule was either (a) mechanically damaged, (b) injected with sodium morrhuate, or (c) injected with a strain of Staphylococcus aureus. The other capsule served as a control. Facial asymmetry of varying degrees was evident from dry-skull preparations and histologically. Sodium morrhuate caused the least degree of alteration; mechanical damage, the most. The effects of Staph. aureus injection into the TMJ seemed to depend upon the length of time elapsed since injection. In one animal there was no change at autopsy after two injections several weeks apart, once on each side; in the other, the capsule injected initially showed no change at autopsy, whereas that injected several weeks prior to autopsy was considerably altered. Induction of ankylosis was achieved with varying degrees of success, causing differing degrees of facial asymmetry.

The effects of early Le Fort I osteotomies on craniofacial growth of juvenileMacaca nemestrina monkeys

Le Fort I osteotomies were performed on three juvenile Macaca nemestrina monkeys with midface deficiencies from prior extraoral traction. The maxillas of these monkeys were moved anteriorly an amount necessary to achieve about 8 mm. of horizontal overjet. Interosseous wires were used to stabilize the segments; the animals were not placed in intermaxillary fixation. Craniofacial growth in the three experimental monkeys and in three control monkeys was monitored for 2 years with serial cephalometric radiographs. Compared to the controls, the maxillas of the experimental animals demonstrated less anterior growth, and this was manifested clinically in anterior dental cross-bite relationships. Histologic examination of the circummaxillary sutural complex revealed normal morphology. It is concluded, therefore, that early Le Fort I osteotomies significantly affect subsequent maxillary growth in monkeys and that this effect probably is due to formation of scar tissue.

Recreational and social activities of orthognathic surgery patients.

The present study examined changes in recreational and social activities after orthognathic surgery. Because this is often an expectation of patients seeking surgery, it was hypothesized that activity levels would increase gradually after surgery, particularly for patients who become more extroverted and for unmarried patients. Information on the frequencies of recreational and social activities, and the persons with whom these activities were performed, were obtained from 53 patients in a self-administered questionnaire administered at least 2 days before surgery and again 3 weeks, 4 months, and 9 months after surgery. In addition, patients were assessed on introversion-extroversion before and after surgery. The results indicated that (1) for both married and single patients, recreational and social activities dropped immediately after surgery and gradually increased to a level similar to that prior to surgery at nine months after surgery; (2) contrary to expectations, the single patients over age 15 did not increase their recreational and social activities with friends of the opposite sex after surgery; and (3) the degree of change in introversion-extroversion after surgery was not associated with the degree of change in recreational and social activities performed with others. Implications for postsurgical adjustment of orthognathic patients and recommendations for future research are discussed.