- Email: [email protected]
Muscular rehabilitation after orthognathic surgery
oral surgery oral medicine oral pathology Wirhsections onenclodolltics ant/dental radiology Volume 56, Number 3, Svptembe~, 1983
oral surgery Editor. ROBERT
B. SHIRA, D.D.S.
School of Dental Medicine, Tufts Universio I Kneeland Street Boston Massachusetts 02 I I I
Muscular rehabilitation after orthognathic
surgery William H. Bell, D.D.S.,* William Gon,yea, Ph.D.,** Richard A. Finn, D.D.S.,*** Kenneth A. Storum, D.D.S.,**** Craig Johnston, D.D.S.,**** and Gaylord S. Throckmorton, Ph.D.,***** Dallas, Texas
There is both a biologic and a clinical foundation for the use of therapeutic exercise afler otthognathic surgical procedures to restore normal function ‘of the jaw muscles. This can be accomplished by a systematic plan of occlusal and muscular rehabilitation after release of maxillomandibular fixation. Through the diligent application of physical therapy principles, the function of the masticatory muscles can be more efficiently rehabilitated after orthognathic surgery and maxillomandibular fixation.
R
estoration of normal function and long-term stability are the sine qua non of successful surgical procedures for the correction of dentofacial deformities. Both function and stability, however, may be compromised by inadequate or incorrect postoperaThis research was partially supported by National Institutes of Health Grant 5ROI DE0 3794-10. *Professor, Department of Surgery, Division of Oral and Ma.xillofacial Surgery, University of Texas Health Science Centelr at Dallas, Center for the Correction of Dentofacial Deformities. **Professor, Department of Cell Biology, Director of Anatomy, University of Texas Southwestern Medical School. ***Assistant Professor, Department of Cell Biology, University of Texas Southwestern Medical School, and Chief of Oral Surglery, Department of Oral Surgery, Veteran’s Administration Medical Center at Dallas. ****Resident, Department of Surgery, Division of Oral Surglery, University of Texas Southwestern Medical School, Center for Correction of Dentofacial Deformities. *****Associate Professor, Department of Cell Biology, University of Texas Southwestern Medical School.
tive muscular rehabilitation after orthognathic surgery. Muscle atrophy, denervation, alteration of fiber types, myofibrosis, decreasedmuscle mass, and morphologic alterations of the condyle are biologic consequencesof orthognathic surgery and intermaxillary fixatioP which can have profound clinical consequences.Despite the fact that decreased muscular extensibility and strength, increased muscular fatigability, hypomobility (Fig. l), and alteration of the biomechanical efficiency and length of the masticatory muscles are documented clinical consequences,6-‘othere has been published no systematic method of obviating such problems through muscular rehabilitation. Our clinical, electromyographic, fatigability, and histochemical studies of dentofacialdeformity patients before and after maxillary and mandibular osteotomies indicated the need to develop a systematic method of efficiently rehabilitating masticatory function after orthognathic surgical procedures. 229
230
Bell et al.
Oral Surg. September. 1983
Fig. 2. During muscular rehabilitation, the occlusion is controlled by the use of light full-time vertical training elastics attached to sliding surgical ball hooks (American Orthodontics, Sheboygan, Wis.) which are attached around orthodontic arch wires in the canine-first premolar interspaces. The use of such sliding surgical ball hook attachments in the interproximal spaces provides sufficient fixation points and reduces the time necessary for the orthodontist to prepare the arch wires.
Fig. 1. Mandibular hypomobility (interincisal distance = 25 mm.) in 33-year-old woman 3 years after mandibular advancement by bilateral sagittal split ramus osteotomies without muscular rehabilitation after release of maxillomandibular fixation.
We have developeda rehabilitation regimen which incorporates postoperative range-of-motion and motion-resistance exercises. A rehabilitation appliance with multiple calibrated coil springs was designed to normalize the strength and function of the masticatory musculature after orthognathic surgery. Dynamic exercisesare used in concert with the calibrated appliance. PRESURGICAL
EXAMINATION
Postoperative rehabilitation is based upon an evaluation of dynamic jaw function prior to the surgical procedure. This is predetermined for each patient on the basis of preoperative measurement of maximal interincisal opening and lateral and protrusive movements. The information is recorded systematically in chart form so that realistic postsurgical rehabilitation goals can be projected and ultimately achieved by meticulous monitoring of the patient’s progress.
Clinically, the range of motion is examined. A 50 to 55 mm. interincisal distance is the normal range for ages 10 to 70 years.‘l-l5 In the past, 40 mm. has been considered an acceptable empirical minimum. The mouth opening should have a straight and smooth gait. Lateral and protrusive movements are also examined. Lateral movements should average 10 mm. and protrusive movements, 8 to 10 rnrn.14.” Hypomobility before mandibular advancement or retraction surgery may be indicative of an internal derangement of the temporomandibular joints, necessitating treatment before or concomitant with definitive mandibular ramus surgery. Failure to provide such treatment could invite relapse, progression of the internal derangement, and ultimately additional hypomobility. Pre-existing temporomandibular joint or muscular dysfunction must be elucidated by a careful clinical and radiographic assessment. Such examinations may reveal a wide range of variability; internal derangement, degenerativejoint disease,muscle dysfunction, variations of condylar morphology and/or translation, or hypomobility are not infrequent findings. The temporomandibular joints are evaluated clinically and radiographically with respect to the patient’s ability to translate, pain on palpation, noise on function, and morphologic abnormalities.16 The joints should be examined from a lateral approach by compression of the overlying soft tissue and through the external auditory meatus. Pain
Muscular rehabilitation after orthognathic surgery
Volume 56 Number 3
231
resulting from such palpation is highly suggestive of an intracapsular problem. Joint noises, such as popping, clicking, or crepitus, should also be evaluated. Transcranial tomographic (or transpharyngeal) and open-mouth panographic radiographs are routinely taken before surgery.“, I8 In suspectedcasesof internal derangement or casesof mandibular hypomobility of TMJ dysfunction of unexplained origin, arthrotomographic or sagittal computed tomography of the temporomandibular joints can be useful in elucidating the cause and pathogenesis of soft-tissue abnormalities which are related to meniscus dysfunction.” There should be a close correlation between the clinical symptoms and arthrographic studies. Decreasedcondylar mobility is frequently associated with meniscus displacement without reduction. Such a diagnosis may be indicated when limitation of jaw opening with deviation to the affected side is clinically manifest.*O A lateral cephalometric radiograph is made before surgery for comparison with the immediate postoperative and release-of-fixation radiographs. From this information, the direction and magnitude of surgical change and relapse during fixation can be identified, analyzed, and used for timing and planning of appropriate postsurgical orthodontic treatment and muscular rehabilitation. CONTROL OF THE OCCLUSION REHABILITATION
DURING
Surgical healing of the jaws is usually complete enough for the patient to resume mandibular function within 1 to 4 weeksafter maxillary surgery alone and 5 to 8 weeks after mandibular ramus surgery or combined maxillary and mandibular osteotomies.On the day of release from maxillomandibular fixation, the fixation wires and interocclusal splint are removed and the occlusion is examined for any disparity between centric relation and centric occlusion. Light vertical training elastics are placed bilaterally between surgical ball hooks attached to upper and lower orthodontic arch wires (or hooks or arch bars) in the canine-first premolar interspaces. A single elastic is worn on both sides continuously to facilitate direct centric closure and interdigitation of the teeth (Fig. 2). The only exceptions to the use of full-time elastic therapy are the periods of time when elastics are removed so that the patient can eat, exercise the jaw muscles, and brush the teeth. Whenever the elastics are worn, the maxillary and mandibular teeth are maintained in contact with one another to avoid extrusion of teeth by intermaxillary
Fig. 3. The interincisal distanceis systematicallymonitored and recorded by the patient and the therapist.
elastic traction. If skeletal and occlusal stability have been adequately maintained and a minimum intkrincisal opening of 20 to 25 mm. has been achieved through range-of-motion exercises within 7 to 14 days after release of maxillomandibular fixation, stabilizing arch wires can be removed by the orthodontist and appropriate arch wire changes made. As small positional changes of the teeth occur to compensatefor the positional changes of the jaw, the mandible assumes its functional position. Bony remodeling and healing of the osteotomized segments occur simultaneously as muscular adaptation takes place through muscle rehabilitation and training.*’ Although most skeletal relapse typically occurs during the period of maxillomandibular fixation,22,23 orthodontic appliances (or arch bars when orthodontic appliances are not used) are retained in place for at least 2 to 4 months following resumption of mandibular function in order to control any mild relapse tendencies. This period of time is usually required to achieve occlusal and skeletal stability.
232
Bell et al.
Oral September,
Surg. 19X3
Fig. 4. Two-handed active assisted range-of-motion exercises are facilitated by bilateral digital pressure in the canine-premolar regions.
Fig. 5. Repetitive active assisted lateral excursive movements to exercise the external pterygoid muscles.
Now, if the orthodontic goals of treatment have been met, the orthodontic appliances can be removed and appropriate retainers or positioners are placed. Muscular rehabilitation is simultaneously accomplished during this vital period of postsurgical occlusal rehabilitation.
maxillomandibular fixation, and the dates are inscribed on a tongue blade in view of the patient, who maintains a daily log of the measurements. Within 6 to 10 weeks this measurement usually progressively increases and gradually returns to, or plateaus near, the desired presurgery interincisal opening. If, for any reason, the interincisal distance ceases to increase or the projected goal is not reached, the patient is instructed to notify the therapist accordingly. During the first 10 days, the patient is seen on an average of once every 2 or 3 days, depending on the therapist’s discretion and the patient’s cooperation and progress. Thereafter, the patient is observed at least once every week. Four to 10 weeks of therapeutic exercises are generally necessary to achieve an interincisal opening comparable to the presurgical measurement. Only when physical therapy does not achieve the desired goal are the jaws forcibly dilated with the aid of a side-action mouth prop. Even when this occurs, the therapist must be vigilant for a possible internal derangement of the temporomandibular joints.
MUSCULAR
REHABILITATION
The benefits of and the rationale for the use of therapeutic exercise are explained to the patient several weeks before the surgical procedure. The exercisesare initially practiced under supervision of the therapist. Once learned, the patient practices them periodically at home. Normal hinge and translatory movements of the condyle, protrusive and lateral jaw movements, and function of the masticatory muscles are demonstrated on a skull. The onus of responsibility for maintaining the interincisal distance is shared by the patient and the therapist, both of whom monitor and record the results of therapeutic exercise (Fig. 3). The interincisal distance prior to surgery, the distance after releasefrom
Muscular
Volume 56 Number 3
rehabilitation
after orthognathic
surgery
233
Fig. 7. Dynamic exerciser comprises a handle and four variable nonfatigable coil springs which are connected to a tractable lower bite table. The use of progressively heavier coil springs allows the patient to adapt to increasing bite strengths as tolerance increases. The tractable lower bite force table allows the interincisal distance to increase gradually during muscular rehabilitation by therapeutic exercises.
Fig. 6. Motion-resistance dynamic exercise therapy is accomplised over a fuull range of mandibular motion by repetitive and intermittent jaw clenching and opening against resistance of a dyanmic exerciser. RANGE-OF-MOTION
EXERCISES
The rehabilitation regimen consists of an initial stage of range-of-motion exercises to increase the interincisal distance, followed by dynamic exercises to strengthen the muscles. The muscular rehabilitation regimen is initiated with a short “warming-up” period of exercise followed by active assisted rangeof-motion and dynamic exercises. Immediately after release of maxillomandibular fixation, very gentle assistive range-of-motion exercises are accomplished to assist with opening the mandible as wide as possible, but within pain-free limits.24 After a gentle limbering-up, the interincisal distance will normally vary between 10 and 15 mm. Such limbering-up exercises are accomplished at least four times daily for the first day or two after release of fixation. Thereafter, progressively more active range-ofmotion exercises are accomplished. For 2 to 3 minutes, two-handed active assisted range-ofmotion exercises are performed, facilitated by bilateral digital pressure (thumb and forefinger) in the
canine-premolar regions (Fig. 4). These therapeutic exercises are accomplished four times a day (morning, noon, evening, and at bedtime) within pain-free limits. For another minute, the patient performs eight to ten active assisted lateral excursions to exercise the pterygoid muscles (Fig. 5); these muscles are further exercised by repetitive protrusion of the mandible. Range-of-motion exercises are intended to increase the interincisal opening and prepare the masticatory muscles for subsequent dynamic exercises. DYNAMIC
EXERCISES
The second stage of rehabilitation, which generally commenceswithin 2 weeks after release of maxillomandibular fixation, consists of motion-resistance dynamic exercise therapy designed to increase muscle strength and reverse degenerative and atrophic muscle changes induced by surgery and immobiliza-
tion (Fig. 6). This is accomplished by repeated contractions of the elevator muscles produced by intermittent jaw clenching for 5 seconds and relaxation for another 5 seconds.These dynamic exercises are repeated over a full range of mandibular motion for a period of 3 minutes. Controlled dynamic exercisesare performed with the aid of an appliance which was designed for simplicity and versatility.*
It
consists of a handle, variable nonfatigable coil springs, and a tractable lower bite table (Fig. 7). The variable coil springs allow the patient to adapt *Walter
Lorenz Surgical Instruments, Jacksonville,
FI.
234
Bell et al.
to increasing bite strengths as tolerance improves. The bite force initially selectedfor oral rehabilitation will be a relatively low percentage of postoperative maximum isometric bite capacity. The low bite force was selected for three reasons. First, postoperative skeletal stability could be compromised following orthognathic surgery if too high a resistance were selected. For example, after correction of vertical maxillary deficiency by Le Fort I osteotomy and interpositional bone grafting,25 excessive loading of the graft could accelerate graft resorption and induce vertical relapse. Second, maximum bite forces could produce pain in the teeth, jaw muscles, or temporomandibular joint. Third, as shown by Manns and Spreng,26bite force is maintained at the lower levels by the recruitment of new motor units as fatigue sets in, thus involving a large proportion of the muscle in rehabilitation without compromising stability at the early stages of rehabilitation. The therapist can adjust the biting force by progressive use of the coil springs, each of which has a different tension which requires increased bite force during muscular contraction to move the lower bite table against the upper bite table. With gradually increasing strength of the adductor muscles and improved tolerance, the therapist progressively increasesthe biting resistance by selecting a spring with more tension that requires greater biting strength. (Approximate range of the four coil springs is 0 to 20 kg.) The variable coil springs allow the patient to adapt to increasing bite strengths as tolerance increases. A low force (coil A = range of 0 to 3 kg.) is initially selected. The tractable lower bite table allows the interincisal distance to increase as rehabilitation progressesduring therapeutic exercises. The bite table consists of two flat bite planes joined at a centroid whose axis is located just distal to the third molar. The tractable lower table simulates hinge-type mandibular movement. If there is a tendency to unload the maxillary anterior teeth, additional rubber padding may be placed on the maxillary bite table to increase contact between the incisor teeth and the bite table. DISCUSSION
Our experience with the use of the musclerehabilitation principles described in this article has been very positive. With certain modifications, the same principles have been applied successfully in oral and maxillofacial surgery to facilitate rehabilitation after TMJ, ankylosis, and reconstructive surgery and maxillofacial trauma. Becauseof the wide range of individual variability of tolerance, the rehabilitation regimen must be flexible. Not all patients undergoing orthognathic surgery with sub-
Oral September.
Surg. 19X3
sequent maxillomandibular fixation require the same degree of rehabilitation.6 Maxillary surgery patients rehabilitate rapidly, with a return to near the preoperative interincisal distance. Rehabilitation after intraoral vertical ramus osteotomiesfor correction of absolute mandibular excess has also been relatively problem-free. On the other hand, certain mandibular ramus surgery patients require lengtheir periods of rehabilitation which may be more problematic and frequently end with smaller interincisal openings than they had before surgery. Rehabilitation after sagittal split ramus osteotomies to advance the mandible has been most problematic, and such patients are significantly more difficult to rehabilitate. Increasing or decreasing the length of a muscle may have a dramatic effect on rehabilitation after immobilization. Muscles immobilized in a shortened position demonstrate a significant decreasein lengthtension properties and extensibility compared to immobilization in a lengthened position.27-29 Therefore, patients requiring superior repositioning of the maxilla and concomitant shortening of the masseteric sling for correction of vertical maxillary excess may require a more extensive rehabilitation regimen. All therapeutic procedures designed for rehabilitation after orthognathic surgery should be accomplished within painless limits. Facial pain will not only inhibit further rehabilitation30 but it will also create unnecessaryanxiety. Some discomfort is to be expected during muscular rehabilitation. Mild pain in the adductor musclescontiguous to ramus osteotomy sites, tooth sensitivity due to recent orthodontic adjustments, and transient temporomandibular joint pain are not uncommon. Such pain is usually mild and transient, however, and is tolerated by most patients. Becauseof the wide range of patient tolerance, the rehabilitation regimen must be flexible and the therapist should carefully and systematically monitor the results of treatment. Hypomobility after a reasonable period of rehabilitation may be the consequenceof intra- or extracapsular factors.lh Internal derangement of the TMJ and excessivesoft-tissue contracture are common causes. If and when the anteriorly displaced meniscus is not successfully “captured” by the short-term use of an orthodontic splint, arthroplasty may be necessary to treat the internal derangement. Restriction of opening secondary to scar contracture, injury to the tendinous attachments of the temporalis muscles, inadequate muscular rehabilitation due to poor patient compliance, muscle atrophy, and myofibrosis can indicate the need for prolonged range-of-motion exercisesto normalize the soft tissue and the interin-
Volume
56
Number
Muscular rehabilitation after orthognathic surgery
cisal distance. Occasionally, it may be necessary.to employ secondary soft-tissue procedures to release the scar contracture. Long-term hypomobility caused by myofibrotic contracture can be treated only by muscle detachment and reattachment, followed by systematic muscular rehabilitation. In such cases, however, it is probably impossible to achieve normal mobility and muscular function. The therapist must accept an interincisal distance of 30 to 35 mm. and realistically project such limits to the patient prior to orthognathic surgery. Specialthanks to our secretary, Ms. Carole Gardner, for the countless hours she devoted to preparation of this manuscript. REFERENCES I. Boyd, S. B., Gonyea,
2.
3.
4.
5.
6. 7.
8.
9
10
II
12 I3
235
3
W. J., Finn, R., Woodard, C., and Bell, W. H.: Masseter Muscle Adaptation Following Surgical Correction of Vertical Maxillary Excess, J. Oral Maxillofac. Surg. (In press.) Finn, R. A., Throckmorton, G. S., Gonyea, W. J., Barker, D. R.. and Bell, W. H.: Neuromuscular Aspects of Vertical Maxillary Dysplasias. In Bell, W. H., et al.: Surgical Correction of Dentofacial Deformities, Philadelphia, 1980, W. B. Saunders Company, vol. II, pp. 1712-1731. Warner, M. R., Boyd, S. B., Gonyea, W. J., Woodard, C. E., and Bell, W. H.: Histochemical Study of the Masseter Muscle in Patients With Vertical Maxillary Deficiency, J. Oral Maxillofac. Surg. (In press, 1983). Goldspink, G., Tabary, C., Tabary, J. C., Tardieu, C., and Tardieu. G.: The Effect of Denervation on the Adaptation 01 Sarcomere Number and Muscle Extensibility to the Functional Length of the Muscle, J. Physiol. 236: 733-742. 1974. Glineburg, R. W., Laskin, D. M., and Blaustein, D. I.: The Effects of Immobilization on the Primate Temporomandibular Joint, J. Oral Maxillofac. Surg. 40: 3-8, 1982. Storum. K. A., and Bell, W. H.: Hypomobility After Maxillary and Mandibular Osteotomies (In preparation.) Finn, R. A., Throckmorton, G. S., Bell, W. H., and Legan, H. L.: Biomechanicai Considerations in the Surgical Correction of Mandibular Deficiency, J. Oral Surg. 38: 257-264, 1980. Throckmorton, G. S., Finn, R. A., and Bell, W. H.: Biomechanics of Ditferences in Lower Facial Height, Am. J. Orthod. 77: 410-420. 1980. Astrand, P.: Chewing EHiciency Before and After Surgical Correction of Developmental Deformities of the Jaws, Swed. Dent. J. 67: 136-146, 1974. Edlund, J., Hansson, T., Peterson, A., and Willmar, K.: Sagittal Splitting of the Mandibular Ramus, Stand. J. Plast. Reconstr. Surg. 13: 437-443, 1978. Landtwing, K.: Evaluation of the Normal Range of Vertical Mandibular Opening in Children and Adolescents With Special Reference to Age and Stature, J. Maxillofac. Surg. 6: 157-162, 1978. Agerberg, G.: Maximal Mandibular Movements in Young Men and Women, Swed. Dent. J. 67: 81-100, 1974. Agerberg, G., and Osterberg, T.: Maximal Mandibular Movements and Symptoms of Mandibular Dysfunction in 70-Year-Old Men and Women, Swed. Dent. J. 67: 147-164, 1974.
14. Ingervall, B., Ridell, A., and Thilander, B.: Changes in Activity of the Temporal, Masseter and Lip Muscles After Surgical Correction of Mandibular Prognathism. Int. J. Oral Sura. 8: 290-300. 1979. 15. Ringquist, M.: Isometric Bite Force and Its Relation to Dimensions of the Facial Skeleton, Acta Odontol. Stand. 42: 31-35, 1973. 16. Bell, W. E.: Clinical Management of Temporomandibular Disorders, Chicago, 1982, Year Book Medical Publishers, Inc., pp. 177-188. 17. Stanson, A. W., and Baker, H. L.: Routine Tomography of the Tempormandibular Joint, Radiol. Clin. North Am. 14: 105-127, 1976. Radiography for Arthritis 18. Toiler, P. A.: The Transpharyngeal of the Mandibular Condyle, Br. J. Oral Surg. 7: 47, 1969. 19. Katzberg, R. W., Dolwick, M. F., Helms, C. A., Hopens, T., Bales, D. J., and Coggs, G. C.: Arthrotomography of the Temporomandibular Joint, Am. J. Radiol. 134: 995-1003, 1980. 20. Dolwick, M. F., Katzberg, R. W., Helms, C. A., and Bales, D. J.: Arthrotomographic Evaluation of the Temporomandibular Joint, J. Oral Surg. 37: 793-799, 1979. R. V.: Mandibular Excess. In Bell, W. H., Proffit, 21. Walker, W. R.. and White, R. P.: Surgical Correction of Dentofacial Deformities. Philadelphia, 1980. W.B. Saunders Company, Vol. II, p. 955. D. R., and Ware, W. H.: Surgical-Orthodontic 22. Poulton, Treatment of Severe Mandibular Retrusion, Am. J. Orthod. 59: 244. 1971. 23. McNeill, R. W., Hooley, J. R., and Sundberg, R. J.: Skeletal Relapse During Intermaxillary Fixation, J. Oral Surg. 31: 212-227, 1973. B. H., and Eriksson, M. B. E.: Endorphins and 24. Sjolund, Analgesia Produced by Peripheral Conditioning Stimulation. In Bonica, J. J., Liebeskind, J. C., and Albe-Fessard, D. G. (editors): Advances in Pain Research and Therapy, New York, 1979, Raven Press. vol. 3, pp. 587-592. of the Short Face Syndrome-Vertical 25. Bell, W. H.: Correction Maxillary Deficiency: A Preliminary Report, J. Oral Surg. 35: 110-120, 1977. and Frequency 26. Manns, A., and Spreng. M.: EMG Amplitude at Different Muscular Elongations Under Constant Masticatory Force or EMG Activity, Acta Physiol. Lat. Am. 27: 259-271, 1977. P. E., and Goldspink, G.: The Effect of Immobili27. Williams, zation on the Longitudinal Growth of Striated Muscle Fibers. II. Immobilization. J. Ant. 118: 531-541. 1974. J. C., Tabary, C.. Tardieu, C., Tardieu, G., and 28. Tabary, Goldspink, G.: Physiological and Structural Changes in the Cat’s Soleus Muscle due to Immobilization at Different Lengths by Plaster Casts, J. Physiol. 224: 231-244, 1972. D.: Skeletal Muscle Regeneration, Muscle Nerve 4: 29. Allbrook, 234-245, 1981. of Physical Medicine and Rehabil30. Kruaen. F. H.: Handbook Philadelphia, 1965, W.B. Saunders Company, itation. p. 279.
Reprint requests lo. Dr. William H. Bell Department of Surgery Division of Oral and Maxillofacial Surgery University of Texas Health Science Center at Dallas Center for Correction of Dentofacial Deformities 5323 Harry Hines Blvd. Dallas, Texas 75235
oral surgery Editor. ROBERT
B. SHIRA, D.D.S.
School of Dental Medicine, Tufts Universio I Kneeland Street Boston Massachusetts 02 I I I
Muscular rehabilitation after orthognathic
surgery William H. Bell, D.D.S.,* William Gon,yea, Ph.D.,** Richard A. Finn, D.D.S.,*** Kenneth A. Storum, D.D.S.,**** Craig Johnston, D.D.S.,**** and Gaylord S. Throckmorton, Ph.D.,***** Dallas, Texas
There is both a biologic and a clinical foundation for the use of therapeutic exercise afler otthognathic surgical procedures to restore normal function ‘of the jaw muscles. This can be accomplished by a systematic plan of occlusal and muscular rehabilitation after release of maxillomandibular fixation. Through the diligent application of physical therapy principles, the function of the masticatory muscles can be more efficiently rehabilitated after orthognathic surgery and maxillomandibular fixation.
R
estoration of normal function and long-term stability are the sine qua non of successful surgical procedures for the correction of dentofacial deformities. Both function and stability, however, may be compromised by inadequate or incorrect postoperaThis research was partially supported by National Institutes of Health Grant 5ROI DE0 3794-10. *Professor, Department of Surgery, Division of Oral and Ma.xillofacial Surgery, University of Texas Health Science Centelr at Dallas, Center for the Correction of Dentofacial Deformities. **Professor, Department of Cell Biology, Director of Anatomy, University of Texas Southwestern Medical School. ***Assistant Professor, Department of Cell Biology, University of Texas Southwestern Medical School, and Chief of Oral Surglery, Department of Oral Surgery, Veteran’s Administration Medical Center at Dallas. ****Resident, Department of Surgery, Division of Oral Surglery, University of Texas Southwestern Medical School, Center for Correction of Dentofacial Deformities. *****Associate Professor, Department of Cell Biology, University of Texas Southwestern Medical School.
tive muscular rehabilitation after orthognathic surgery. Muscle atrophy, denervation, alteration of fiber types, myofibrosis, decreasedmuscle mass, and morphologic alterations of the condyle are biologic consequencesof orthognathic surgery and intermaxillary fixatioP which can have profound clinical consequences.Despite the fact that decreased muscular extensibility and strength, increased muscular fatigability, hypomobility (Fig. l), and alteration of the biomechanical efficiency and length of the masticatory muscles are documented clinical consequences,6-‘othere has been published no systematic method of obviating such problems through muscular rehabilitation. Our clinical, electromyographic, fatigability, and histochemical studies of dentofacialdeformity patients before and after maxillary and mandibular osteotomies indicated the need to develop a systematic method of efficiently rehabilitating masticatory function after orthognathic surgical procedures. 229
230
Bell et al.
Oral Surg. September. 1983
Fig. 2. During muscular rehabilitation, the occlusion is controlled by the use of light full-time vertical training elastics attached to sliding surgical ball hooks (American Orthodontics, Sheboygan, Wis.) which are attached around orthodontic arch wires in the canine-first premolar interspaces. The use of such sliding surgical ball hook attachments in the interproximal spaces provides sufficient fixation points and reduces the time necessary for the orthodontist to prepare the arch wires.
Fig. 1. Mandibular hypomobility (interincisal distance = 25 mm.) in 33-year-old woman 3 years after mandibular advancement by bilateral sagittal split ramus osteotomies without muscular rehabilitation after release of maxillomandibular fixation.
We have developeda rehabilitation regimen which incorporates postoperative range-of-motion and motion-resistance exercises. A rehabilitation appliance with multiple calibrated coil springs was designed to normalize the strength and function of the masticatory musculature after orthognathic surgery. Dynamic exercisesare used in concert with the calibrated appliance. PRESURGICAL
EXAMINATION
Postoperative rehabilitation is based upon an evaluation of dynamic jaw function prior to the surgical procedure. This is predetermined for each patient on the basis of preoperative measurement of maximal interincisal opening and lateral and protrusive movements. The information is recorded systematically in chart form so that realistic postsurgical rehabilitation goals can be projected and ultimately achieved by meticulous monitoring of the patient’s progress.
Clinically, the range of motion is examined. A 50 to 55 mm. interincisal distance is the normal range for ages 10 to 70 years.‘l-l5 In the past, 40 mm. has been considered an acceptable empirical minimum. The mouth opening should have a straight and smooth gait. Lateral and protrusive movements are also examined. Lateral movements should average 10 mm. and protrusive movements, 8 to 10 rnrn.14.” Hypomobility before mandibular advancement or retraction surgery may be indicative of an internal derangement of the temporomandibular joints, necessitating treatment before or concomitant with definitive mandibular ramus surgery. Failure to provide such treatment could invite relapse, progression of the internal derangement, and ultimately additional hypomobility. Pre-existing temporomandibular joint or muscular dysfunction must be elucidated by a careful clinical and radiographic assessment. Such examinations may reveal a wide range of variability; internal derangement, degenerativejoint disease,muscle dysfunction, variations of condylar morphology and/or translation, or hypomobility are not infrequent findings. The temporomandibular joints are evaluated clinically and radiographically with respect to the patient’s ability to translate, pain on palpation, noise on function, and morphologic abnormalities.16 The joints should be examined from a lateral approach by compression of the overlying soft tissue and through the external auditory meatus. Pain
Muscular rehabilitation after orthognathic surgery
Volume 56 Number 3
231
resulting from such palpation is highly suggestive of an intracapsular problem. Joint noises, such as popping, clicking, or crepitus, should also be evaluated. Transcranial tomographic (or transpharyngeal) and open-mouth panographic radiographs are routinely taken before surgery.“, I8 In suspectedcasesof internal derangement or casesof mandibular hypomobility of TMJ dysfunction of unexplained origin, arthrotomographic or sagittal computed tomography of the temporomandibular joints can be useful in elucidating the cause and pathogenesis of soft-tissue abnormalities which are related to meniscus dysfunction.” There should be a close correlation between the clinical symptoms and arthrographic studies. Decreasedcondylar mobility is frequently associated with meniscus displacement without reduction. Such a diagnosis may be indicated when limitation of jaw opening with deviation to the affected side is clinically manifest.*O A lateral cephalometric radiograph is made before surgery for comparison with the immediate postoperative and release-of-fixation radiographs. From this information, the direction and magnitude of surgical change and relapse during fixation can be identified, analyzed, and used for timing and planning of appropriate postsurgical orthodontic treatment and muscular rehabilitation. CONTROL OF THE OCCLUSION REHABILITATION
DURING
Surgical healing of the jaws is usually complete enough for the patient to resume mandibular function within 1 to 4 weeksafter maxillary surgery alone and 5 to 8 weeks after mandibular ramus surgery or combined maxillary and mandibular osteotomies.On the day of release from maxillomandibular fixation, the fixation wires and interocclusal splint are removed and the occlusion is examined for any disparity between centric relation and centric occlusion. Light vertical training elastics are placed bilaterally between surgical ball hooks attached to upper and lower orthodontic arch wires (or hooks or arch bars) in the canine-first premolar interspaces. A single elastic is worn on both sides continuously to facilitate direct centric closure and interdigitation of the teeth (Fig. 2). The only exceptions to the use of full-time elastic therapy are the periods of time when elastics are removed so that the patient can eat, exercise the jaw muscles, and brush the teeth. Whenever the elastics are worn, the maxillary and mandibular teeth are maintained in contact with one another to avoid extrusion of teeth by intermaxillary
Fig. 3. The interincisal distanceis systematicallymonitored and recorded by the patient and the therapist.
elastic traction. If skeletal and occlusal stability have been adequately maintained and a minimum intkrincisal opening of 20 to 25 mm. has been achieved through range-of-motion exercises within 7 to 14 days after release of maxillomandibular fixation, stabilizing arch wires can be removed by the orthodontist and appropriate arch wire changes made. As small positional changes of the teeth occur to compensatefor the positional changes of the jaw, the mandible assumes its functional position. Bony remodeling and healing of the osteotomized segments occur simultaneously as muscular adaptation takes place through muscle rehabilitation and training.*’ Although most skeletal relapse typically occurs during the period of maxillomandibular fixation,22,23 orthodontic appliances (or arch bars when orthodontic appliances are not used) are retained in place for at least 2 to 4 months following resumption of mandibular function in order to control any mild relapse tendencies. This period of time is usually required to achieve occlusal and skeletal stability.
232
Bell et al.
Oral September,
Surg. 19X3
Fig. 4. Two-handed active assisted range-of-motion exercises are facilitated by bilateral digital pressure in the canine-premolar regions.
Fig. 5. Repetitive active assisted lateral excursive movements to exercise the external pterygoid muscles.
Now, if the orthodontic goals of treatment have been met, the orthodontic appliances can be removed and appropriate retainers or positioners are placed. Muscular rehabilitation is simultaneously accomplished during this vital period of postsurgical occlusal rehabilitation.
maxillomandibular fixation, and the dates are inscribed on a tongue blade in view of the patient, who maintains a daily log of the measurements. Within 6 to 10 weeks this measurement usually progressively increases and gradually returns to, or plateaus near, the desired presurgery interincisal opening. If, for any reason, the interincisal distance ceases to increase or the projected goal is not reached, the patient is instructed to notify the therapist accordingly. During the first 10 days, the patient is seen on an average of once every 2 or 3 days, depending on the therapist’s discretion and the patient’s cooperation and progress. Thereafter, the patient is observed at least once every week. Four to 10 weeks of therapeutic exercises are generally necessary to achieve an interincisal opening comparable to the presurgical measurement. Only when physical therapy does not achieve the desired goal are the jaws forcibly dilated with the aid of a side-action mouth prop. Even when this occurs, the therapist must be vigilant for a possible internal derangement of the temporomandibular joints.
MUSCULAR
REHABILITATION
The benefits of and the rationale for the use of therapeutic exercise are explained to the patient several weeks before the surgical procedure. The exercisesare initially practiced under supervision of the therapist. Once learned, the patient practices them periodically at home. Normal hinge and translatory movements of the condyle, protrusive and lateral jaw movements, and function of the masticatory muscles are demonstrated on a skull. The onus of responsibility for maintaining the interincisal distance is shared by the patient and the therapist, both of whom monitor and record the results of therapeutic exercise (Fig. 3). The interincisal distance prior to surgery, the distance after releasefrom
Muscular
Volume 56 Number 3
rehabilitation
after orthognathic
surgery
233
Fig. 7. Dynamic exerciser comprises a handle and four variable nonfatigable coil springs which are connected to a tractable lower bite table. The use of progressively heavier coil springs allows the patient to adapt to increasing bite strengths as tolerance increases. The tractable lower bite force table allows the interincisal distance to increase gradually during muscular rehabilitation by therapeutic exercises.
Fig. 6. Motion-resistance dynamic exercise therapy is accomplised over a fuull range of mandibular motion by repetitive and intermittent jaw clenching and opening against resistance of a dyanmic exerciser. RANGE-OF-MOTION
EXERCISES
The rehabilitation regimen consists of an initial stage of range-of-motion exercises to increase the interincisal distance, followed by dynamic exercises to strengthen the muscles. The muscular rehabilitation regimen is initiated with a short “warming-up” period of exercise followed by active assisted rangeof-motion and dynamic exercises. Immediately after release of maxillomandibular fixation, very gentle assistive range-of-motion exercises are accomplished to assist with opening the mandible as wide as possible, but within pain-free limits.24 After a gentle limbering-up, the interincisal distance will normally vary between 10 and 15 mm. Such limbering-up exercises are accomplished at least four times daily for the first day or two after release of fixation. Thereafter, progressively more active range-ofmotion exercises are accomplished. For 2 to 3 minutes, two-handed active assisted range-ofmotion exercises are performed, facilitated by bilateral digital pressure (thumb and forefinger) in the
canine-premolar regions (Fig. 4). These therapeutic exercises are accomplished four times a day (morning, noon, evening, and at bedtime) within pain-free limits. For another minute, the patient performs eight to ten active assisted lateral excursions to exercise the pterygoid muscles (Fig. 5); these muscles are further exercised by repetitive protrusion of the mandible. Range-of-motion exercises are intended to increase the interincisal opening and prepare the masticatory muscles for subsequent dynamic exercises. DYNAMIC
EXERCISES
The second stage of rehabilitation, which generally commenceswithin 2 weeks after release of maxillomandibular fixation, consists of motion-resistance dynamic exercise therapy designed to increase muscle strength and reverse degenerative and atrophic muscle changes induced by surgery and immobiliza-
tion (Fig. 6). This is accomplished by repeated contractions of the elevator muscles produced by intermittent jaw clenching for 5 seconds and relaxation for another 5 seconds.These dynamic exercises are repeated over a full range of mandibular motion for a period of 3 minutes. Controlled dynamic exercisesare performed with the aid of an appliance which was designed for simplicity and versatility.*
It
consists of a handle, variable nonfatigable coil springs, and a tractable lower bite table (Fig. 7). The variable coil springs allow the patient to adapt *Walter
Lorenz Surgical Instruments, Jacksonville,
FI.
234
Bell et al.
to increasing bite strengths as tolerance improves. The bite force initially selectedfor oral rehabilitation will be a relatively low percentage of postoperative maximum isometric bite capacity. The low bite force was selected for three reasons. First, postoperative skeletal stability could be compromised following orthognathic surgery if too high a resistance were selected. For example, after correction of vertical maxillary deficiency by Le Fort I osteotomy and interpositional bone grafting,25 excessive loading of the graft could accelerate graft resorption and induce vertical relapse. Second, maximum bite forces could produce pain in the teeth, jaw muscles, or temporomandibular joint. Third, as shown by Manns and Spreng,26bite force is maintained at the lower levels by the recruitment of new motor units as fatigue sets in, thus involving a large proportion of the muscle in rehabilitation without compromising stability at the early stages of rehabilitation. The therapist can adjust the biting force by progressive use of the coil springs, each of which has a different tension which requires increased bite force during muscular contraction to move the lower bite table against the upper bite table. With gradually increasing strength of the adductor muscles and improved tolerance, the therapist progressively increasesthe biting resistance by selecting a spring with more tension that requires greater biting strength. (Approximate range of the four coil springs is 0 to 20 kg.) The variable coil springs allow the patient to adapt to increasing bite strengths as tolerance increases. A low force (coil A = range of 0 to 3 kg.) is initially selected. The tractable lower bite table allows the interincisal distance to increase as rehabilitation progressesduring therapeutic exercises. The bite table consists of two flat bite planes joined at a centroid whose axis is located just distal to the third molar. The tractable lower table simulates hinge-type mandibular movement. If there is a tendency to unload the maxillary anterior teeth, additional rubber padding may be placed on the maxillary bite table to increase contact between the incisor teeth and the bite table. DISCUSSION
Our experience with the use of the musclerehabilitation principles described in this article has been very positive. With certain modifications, the same principles have been applied successfully in oral and maxillofacial surgery to facilitate rehabilitation after TMJ, ankylosis, and reconstructive surgery and maxillofacial trauma. Becauseof the wide range of individual variability of tolerance, the rehabilitation regimen must be flexible. Not all patients undergoing orthognathic surgery with sub-
Oral September.
Surg. 19X3
sequent maxillomandibular fixation require the same degree of rehabilitation.6 Maxillary surgery patients rehabilitate rapidly, with a return to near the preoperative interincisal distance. Rehabilitation after intraoral vertical ramus osteotomiesfor correction of absolute mandibular excess has also been relatively problem-free. On the other hand, certain mandibular ramus surgery patients require lengtheir periods of rehabilitation which may be more problematic and frequently end with smaller interincisal openings than they had before surgery. Rehabilitation after sagittal split ramus osteotomies to advance the mandible has been most problematic, and such patients are significantly more difficult to rehabilitate. Increasing or decreasing the length of a muscle may have a dramatic effect on rehabilitation after immobilization. Muscles immobilized in a shortened position demonstrate a significant decreasein lengthtension properties and extensibility compared to immobilization in a lengthened position.27-29 Therefore, patients requiring superior repositioning of the maxilla and concomitant shortening of the masseteric sling for correction of vertical maxillary excess may require a more extensive rehabilitation regimen. All therapeutic procedures designed for rehabilitation after orthognathic surgery should be accomplished within painless limits. Facial pain will not only inhibit further rehabilitation30 but it will also create unnecessaryanxiety. Some discomfort is to be expected during muscular rehabilitation. Mild pain in the adductor musclescontiguous to ramus osteotomy sites, tooth sensitivity due to recent orthodontic adjustments, and transient temporomandibular joint pain are not uncommon. Such pain is usually mild and transient, however, and is tolerated by most patients. Becauseof the wide range of patient tolerance, the rehabilitation regimen must be flexible and the therapist should carefully and systematically monitor the results of treatment. Hypomobility after a reasonable period of rehabilitation may be the consequenceof intra- or extracapsular factors.lh Internal derangement of the TMJ and excessivesoft-tissue contracture are common causes. If and when the anteriorly displaced meniscus is not successfully “captured” by the short-term use of an orthodontic splint, arthroplasty may be necessary to treat the internal derangement. Restriction of opening secondary to scar contracture, injury to the tendinous attachments of the temporalis muscles, inadequate muscular rehabilitation due to poor patient compliance, muscle atrophy, and myofibrosis can indicate the need for prolonged range-of-motion exercisesto normalize the soft tissue and the interin-
Volume
56
Number
Muscular rehabilitation after orthognathic surgery
cisal distance. Occasionally, it may be necessary.to employ secondary soft-tissue procedures to release the scar contracture. Long-term hypomobility caused by myofibrotic contracture can be treated only by muscle detachment and reattachment, followed by systematic muscular rehabilitation. In such cases, however, it is probably impossible to achieve normal mobility and muscular function. The therapist must accept an interincisal distance of 30 to 35 mm. and realistically project such limits to the patient prior to orthognathic surgery. Specialthanks to our secretary, Ms. Carole Gardner, for the countless hours she devoted to preparation of this manuscript. REFERENCES I. Boyd, S. B., Gonyea,
2.
3.
4.
5.
6. 7.
8.
9
10
II
12 I3
235
3
W. J., Finn, R., Woodard, C., and Bell, W. H.: Masseter Muscle Adaptation Following Surgical Correction of Vertical Maxillary Excess, J. Oral Maxillofac. Surg. (In press.) Finn, R. A., Throckmorton, G. S., Gonyea, W. J., Barker, D. R.. and Bell, W. H.: Neuromuscular Aspects of Vertical Maxillary Dysplasias. In Bell, W. H., et al.: Surgical Correction of Dentofacial Deformities, Philadelphia, 1980, W. B. Saunders Company, vol. II, pp. 1712-1731. Warner, M. R., Boyd, S. B., Gonyea, W. J., Woodard, C. E., and Bell, W. H.: Histochemical Study of the Masseter Muscle in Patients With Vertical Maxillary Deficiency, J. Oral Maxillofac. Surg. (In press, 1983). Goldspink, G., Tabary, C., Tabary, J. C., Tardieu, C., and Tardieu. G.: The Effect of Denervation on the Adaptation 01 Sarcomere Number and Muscle Extensibility to the Functional Length of the Muscle, J. Physiol. 236: 733-742. 1974. Glineburg, R. W., Laskin, D. M., and Blaustein, D. I.: The Effects of Immobilization on the Primate Temporomandibular Joint, J. Oral Maxillofac. Surg. 40: 3-8, 1982. Storum. K. A., and Bell, W. H.: Hypomobility After Maxillary and Mandibular Osteotomies (In preparation.) Finn, R. A., Throckmorton, G. S., Bell, W. H., and Legan, H. L.: Biomechanicai Considerations in the Surgical Correction of Mandibular Deficiency, J. Oral Surg. 38: 257-264, 1980. Throckmorton, G. S., Finn, R. A., and Bell, W. H.: Biomechanics of Ditferences in Lower Facial Height, Am. J. Orthod. 77: 410-420. 1980. Astrand, P.: Chewing EHiciency Before and After Surgical Correction of Developmental Deformities of the Jaws, Swed. Dent. J. 67: 136-146, 1974. Edlund, J., Hansson, T., Peterson, A., and Willmar, K.: Sagittal Splitting of the Mandibular Ramus, Stand. J. Plast. Reconstr. Surg. 13: 437-443, 1978. Landtwing, K.: Evaluation of the Normal Range of Vertical Mandibular Opening in Children and Adolescents With Special Reference to Age and Stature, J. Maxillofac. Surg. 6: 157-162, 1978. Agerberg, G.: Maximal Mandibular Movements in Young Men and Women, Swed. Dent. J. 67: 81-100, 1974. Agerberg, G., and Osterberg, T.: Maximal Mandibular Movements and Symptoms of Mandibular Dysfunction in 70-Year-Old Men and Women, Swed. Dent. J. 67: 147-164, 1974.
14. Ingervall, B., Ridell, A., and Thilander, B.: Changes in Activity of the Temporal, Masseter and Lip Muscles After Surgical Correction of Mandibular Prognathism. Int. J. Oral Sura. 8: 290-300. 1979. 15. Ringquist, M.: Isometric Bite Force and Its Relation to Dimensions of the Facial Skeleton, Acta Odontol. Stand. 42: 31-35, 1973. 16. Bell, W. E.: Clinical Management of Temporomandibular Disorders, Chicago, 1982, Year Book Medical Publishers, Inc., pp. 177-188. 17. Stanson, A. W., and Baker, H. L.: Routine Tomography of the Tempormandibular Joint, Radiol. Clin. North Am. 14: 105-127, 1976. Radiography for Arthritis 18. Toiler, P. A.: The Transpharyngeal of the Mandibular Condyle, Br. J. Oral Surg. 7: 47, 1969. 19. Katzberg, R. W., Dolwick, M. F., Helms, C. A., Hopens, T., Bales, D. J., and Coggs, G. C.: Arthrotomography of the Temporomandibular Joint, Am. J. Radiol. 134: 995-1003, 1980. 20. Dolwick, M. F., Katzberg, R. W., Helms, C. A., and Bales, D. J.: Arthrotomographic Evaluation of the Temporomandibular Joint, J. Oral Surg. 37: 793-799, 1979. R. V.: Mandibular Excess. In Bell, W. H., Proffit, 21. Walker, W. R.. and White, R. P.: Surgical Correction of Dentofacial Deformities. Philadelphia, 1980. W.B. Saunders Company, Vol. II, p. 955. D. R., and Ware, W. H.: Surgical-Orthodontic 22. Poulton, Treatment of Severe Mandibular Retrusion, Am. J. Orthod. 59: 244. 1971. 23. McNeill, R. W., Hooley, J. R., and Sundberg, R. J.: Skeletal Relapse During Intermaxillary Fixation, J. Oral Surg. 31: 212-227, 1973. B. H., and Eriksson, M. B. E.: Endorphins and 24. Sjolund, Analgesia Produced by Peripheral Conditioning Stimulation. In Bonica, J. J., Liebeskind, J. C., and Albe-Fessard, D. G. (editors): Advances in Pain Research and Therapy, New York, 1979, Raven Press. vol. 3, pp. 587-592. of the Short Face Syndrome-Vertical 25. Bell, W. H.: Correction Maxillary Deficiency: A Preliminary Report, J. Oral Surg. 35: 110-120, 1977. and Frequency 26. Manns, A., and Spreng. M.: EMG Amplitude at Different Muscular Elongations Under Constant Masticatory Force or EMG Activity, Acta Physiol. Lat. Am. 27: 259-271, 1977. P. E., and Goldspink, G.: The Effect of Immobili27. Williams, zation on the Longitudinal Growth of Striated Muscle Fibers. II. Immobilization. J. Ant. 118: 531-541. 1974. J. C., Tabary, C.. Tardieu, C., Tardieu, G., and 28. Tabary, Goldspink, G.: Physiological and Structural Changes in the Cat’s Soleus Muscle due to Immobilization at Different Lengths by Plaster Casts, J. Physiol. 224: 231-244, 1972. D.: Skeletal Muscle Regeneration, Muscle Nerve 4: 29. Allbrook, 234-245, 1981. of Physical Medicine and Rehabil30. Kruaen. F. H.: Handbook Philadelphia, 1965, W.B. Saunders Company, itation. p. 279.
Reprint requests lo. Dr. William H. Bell Department of Surgery Division of Oral and Maxillofacial Surgery University of Texas Health Science Center at Dallas Center for Correction of Dentofacial Deformities 5323 Harry Hines Blvd. Dallas, Texas 75235