Radiographic interpretation of calcified stylomandibular and stylohyoid ligaments

Radiographic and

interpretation

stylohyoid

of

calcified

stylomandibular

ligaments

Gary R. Goldstein, D.D.S.,* and Veterans Administration Hospital,

Irwin W. Scopp, D.D.S.** New York, N. Y.

C

alcified stylomandibular ligaments have been known to cause pain and functional limitations that.were incorrectly diagnosed as “temporomandibular joint paindysfunction syndrome.“l These calcifications can cause pain deep in the lateral aspect of the neck and throat. Accidental fracture of calcified ligaments usually results in immediate relief of pain. “Calcifications are usually seen in patients in the fourth or fifth decade of life and may be associated with arthritic conditions.“’ It appears from observing Panorex radiography that this condition is common enough to merit further investigations. Many theories are concerned with the function of the ligaments in mandibular movement, and some insight into the ligament might shed light on some of these theories. THE LIGAMENT Gross and histologic anatomy. A ligament is a band of tissue that connects bone or supports viscera.2 The stylomandibular ligament is a type of cervical fascia which extends from the apex of the styloid process of the temporal bone to the angle of the mandible, between the masseter and the internal pterygoid muscles.:’ The stylohyoid ligament is a fibrous cord which extends from the tip of the styloid process to the lesser cornu of the hyoid bone. It can either contain some cartilage in its center, or it may be partially ossified.3 Most histology books merely say that ligaments are similar to tendons.“. ’ They are dense connective tissue with regularly arranged collagenous fibers. Interspersed within these fibers are nests of tendon cells, which are a type of fibroblast.” In general, ligaments are cord-like thickenings around the fibrous capsule of a joint. They undergo a transition to fibrocartilage as they enter the substance of the bone.’ *Senior

Resident,

Prosthodontics,

**Chief Dental Service, Professor of Periodontia and York, N. Y.

330

Veterans

Administration

Veterans Administration Hospital, Oral Medicine, New York University

Hospital,

New

York,

N. Y.

New York, N. Y.; Clinicai College of Dentistry, New

Volunle Numhrr

30 3

Radiographic

interpretation

of calcified

ligaments

331

Function and significance. The function of the ligaments or lack of it is a most controversial subject, especially as it relates to centric relation. Basically, there are two schools of thought: the Posselt8’ g school which states that centric relation is a ligamentous position and the BoucherlO school which calls centric relation a neuromuscular position. Posselt8 concluded that centric relation was a ligamentous position. Posselt and ThilanderY used local anesthesia to determine the origin of the proprioceptive stimulus to jaw position. They made injections into the muscles and found that the patients could return their mandibles to predetermined positions. Anesthetizing both joints had the same result as anesthetizing only one joint. They repeated Gothic arch tracings and found that both the centric position and the border movements could be duplicated.” Boucher’” did two experiments to test Posselt’s results. He first used curare on rats to the point where the intercostal muscles and diaphragm were relaxed, which resulted in a 30 per cent more posterior position on Gothic arch tracings.lO He then severed the ligaments on cadavers and found that they were not a determining factor in the position of the condyles, but a limiting one.ll However, one point remains unanswered; do the ligaments function or not? Burch,12 in his study on the activity of the accessory ligaments, concluded that the stylomandibular ligament tensed in severe protraction and the sphenomandibular ligament tensed in severe overclosure. Ramfjord and AshI admit that there seems to be an abundance of sensory receptors in the capsule which influence the trigeminal nerve, which will obviously influence the muscles of mastication. They admit to doubt over the ligaments being sole restrictors of lateral movement, yet they still insist that centric relation is a “ligamentous position.” Sarnat” maintains that :the accessory ligaments have no functional relationship to mandibular articulation or in movements of the mandible. He does suppose though that the temporomandibular ligament by stretching will limit this possible injurious movement since there is retrusion. METHOD Criteria. Before evaluating the stylomandibular processes, some criteria had to be set up for determining a normal styloid process and a calcification of the ligament as revealed on Panorex radiographs. Examination of skulls and dissection of cadavers indicate that a normal styloid process usually extends no further than the equivalent of one third of the way‘down the ramus of the mandible. Since the position of the styloid process in a Panorex radiograph is close to the ramus, and hence any distortion of it would also result in a similar vertical distortion of the ramus, the following criteria were set up: 1. If the area of the stylomandibular ligament was not shown or was indistinct and readings were unclear, it was placed in the category of “area not observable.” 2. If radioopacity was less than one third of the length of the mandible, it was arbitrarily assumed to be within normal range for a styloid process and considered negative (Fig. 1). 3. If the radioopacity was more than one third, but not down to the level of the

332

Goldstein

.I, l’roathet. September,

and scopp

Fig. 1. An uncalcified is less than one third

stylomandibular ligament. The radioopacity the length of the ramus of the mandible.

Fig. 2. A partially the ramus

calcified ligament. of the mandible (arrow).

Fig. 3. A completely mandible. Figs. 4-5.

The

calcified

radioopacity

The

ligament. of

the

radioopac-ity The

ligament

is more

radioopacity seems

of the styloid than

extends

to he turning

pr~rcese

one third near

to thr

away

from

Dent 1973

larroz

the, iensti~ anqlr the

of

:I’ t11v

mandible

(arrow).

Fig. 6. The radioopacity of the ligament has unusual size and length. Fig. 7. A typical appearing radioopacity of a ligament (arrow 1. Fig. 8. A lateral radiograph of a skull of the patient in Fig:. 7 showing (arrow). Fig. 9. An anteroposterior to the mandible (nrrow).

radiograph This view

the length

of the oparit:

of the patient in Fig. 7 showing the radioopacity clearly demonstrates that it is a stylohyoid ligament.

medial

Radiographic Table I. Panoramic ligament

radiographs

interpretation

examined

Area .4rea

not observable

Both sides observable Negative One ii& partial

One Both Both ()ne

side complete side? partial sides complete side partial&one

side complete

T(rtal One side Neqtive

calcified

ligaments

333

of the stylomandibular

NO.

Total

310

310

60 28 6 32 7 4 137

137

observable 61 36 6

Partial Cflmplc;c Total At least

for calcification

of

103

103

one side calcified

Past the angle of the mandible

4

‘rota1

4 554

angle of the mandible, it was placed in the “partially calcified” group (Fig. 2). 4. If the radioopacity was touching or at the level of the angle of the mandible, it was placed in the “completely calcified” group (Fig. 3). Admittedly, there were arbitrary parameters, but the impression was that they \vould
Professor and Chairman

of the Department

<)f Xnatomy

of NYL’

334

Goldstein

and Scopp

Calcified stylohyoid ligaments are well documented in the medical and dental literature.“! I50 ” Unfortunately, these ligaments seem to have no function in determining centric relation or mandibular movement, and hence our findings shed no light on the theories previously discussed. This article then merely serves to identify a common Panorex landmark. CONCLUSION

ICadioopacities distal calcified stylomandibular ments.

to the angle of the mandible, previously ligaments, have been shown to be calcified

thought to be stylohyoid liga-

References 1. Fay, J. T., and Schow, S. R.: Bilateral Stylomandibular Ligament Calcification, Oral Surg. 27: 759, 1969. 2. Dorland’s Illustrated Medical Dictionary, ed. 24, Philadelphia, 1961, W. B. Saunders Company. 3. Goss, C. M., editor: Gray’s Anatomy, ed. 27, Philadelphia, 1965, Lea & Febiger, Publishers, pp. 335-337. 4. Bailey’s 1967, The Williams & Wilkins Company. Textbookof Histology, ed. 15, Baltimore, 5. Bloom, W., and Fawcett, D.: A Textbook of Histology, Philadelphia, 1968, W. B. Saunders Company, pp. 157-158. S.: Atlas of Histology, Philadelphia, 1965, J. B. 6. Piliero, S., Jacobs, M., and Wischnitzer, Lippincott Company, p. 32. 7. Ham, A.: Histology, ed. 3, Philadelphia, 1957, J. B. Lippincott Company, pp. 330-333. 8. Posselt, U.: Studies on the Mobility of the Human Mandible, Acta Odontol. Stand. 10 (Suppl.) : 19-160, 1952. 9. Posselt, U., and Thilander, B.: Influence of the Innervation of the Temporomandibular, Joint Capsule on Mandibular Border Movements, Acta Odontol. Stand. 23: 601-613, 1965. of Temporomandibular Joints. J. 10. Boucher, I,. J.: Observations in Arthrodial Types PROSTHET. DENT. 10: 1086-1091, 1960. of Mandibular Condyles, J. 11. Boucher, L. J.: Limiting Factors in Posterior Movements PROSTIIET. DENT. 11: 23-25, 1961. 12. Burch, J. G.: Activity of the Accessory Ligaments of the Temporomandibular Jointz J. PROSTHET.DENT. 24:621-628, 1970. ed. 2, Philadelphia, 1971, W. R. Saunders Com13. Ramfjord, S., and Ash, M.: Occlusion, pany, p. 16. 14. Sarnat, B. : The Temporomandibular Joint, Springfield, 1964, Charles C Thomas, Pub lisher, pp. 28-58. 15. Lavine, M. H., Stoopack, J. C., and Jerrold, T. L.: Calcification of the Stylohyoid Ligament, Oral Surg. 25: 55-58, 1968. 16. Freedman, G. L., and Hooley, J. R.: Ossified Stylohyoid Ligament, Oral Surg. 25: 190191, 1968. DENTAL NAVAL

GREAT

DEPARTMENT ADCOM N.T.C. ~AKES,ILL. 60088