Robert Schleip
July 2002
Dear Bodywork Colleagues
The Musculus Pterygoiddus Lateralis (one of the smallest
and most hidden jaw muscles) has been a focus of particular interest for many
of us. Based on the anatomy of this muscle and on some clinical experience it
had been assumed by several of us that
1)
this muscle has a direct influence on what happens inside
of the jaw joint
2)
that a skillful hand is able to palpate and manipulate
this muscle directly with intraoral work.
Both of these assumptions appear as more questionable now, according to new research data.
·
The MPL sup. inserts only in 50% of the people at the
capsule; and even when it does so, it is only with a small part of its fibers (Müller et al 1992)
·
The orientation of the anterior collagen fibers of the
discus is not in line with the direction of the MPL sup. (Müller et al
1992).
·
The MPL sup is not activated in excursive disc
movements (Mahan et al 1983, Gibbs et al 1984)..
References:
Gibbs ChH, Mahan PE, Wilkinson TM, Mauderli 1984 EMG
Activity of the superior belly of
the lateral pterygoid muscle in relation
to other jaw muscles. J Prosthet Dent 51:691-
Langendoen, J, Müller J, Jull GA 1997 The retrodiscal
tissue of the temporo-mandibular joint.
Clinical anatomy and its role in
arthropathies 2(4):191-8
Mahan PE, Wilkinson TM, Gibbs A, Mauderli A, Brannon
LS 1983 Superior and inferior
bellies of the lateral pterygoid muscle
EMG activity at basic jaw positions. J Prosthet
Dent 50:710-8
Müller J, Schmid Ch, Vogl Th, Bruckner G, Randzio J
1992 Morphologisch nachweisbare
Formen
von intraartikulären Dysfunktionen der Kiefergelenke. Dtsch Zahnärztl Z 47:416-423
2)
It seems very questionable that the MPL can
be palpated intraorally.
The following is
from the abstracts of a related study, published in the Journal of
Prosthetic Dentistry 2000
May;83(5):548-54.
Clinical
anatomy and palpability of the inferior lateral pterygoid muscle
Stratmann U, Mokrys K, Meyer U, Kleinheinz J, Joos U,
Dirksen D, Bollmann F.
STATEMENT OF PROBLEM: The intraoral palpation
technique of the inferior belly of the inferior lateral pterygoid (ILP) muscle
is a standard diagnostic examination method for temporomandibular joint
dysfunction syndrome, although different studies have revealed inconsistent
results.
PURPOSE: This study assessed the feasibility of the
ILP muscle palpation by a simulated clinical setting.
MATERIAL AND METHODS: Three dentists performed a bilateral palpation of the ILP muscle in 53
fresh and unfixed human cadavers and decided
whether the muscle was palpable or unpalpable. In a second step, it was
observed through the dissected infratemporal fossa, whether the examiner's
finger did or did not touch the ILP muscle by simulating the performed
palpation. Palpatory findings were supplemented by 1-dimensional measurements
for determination of topographic relations of the ILP muscle within the
infratemporal fossa. For statistical analysis, sensitivity, specificity, and
negative and positive predictive values of the palpation technique were
calculated. Interexaminer agreement was estimated with the kappa value.
RESULTS: In 86 of 106 dissected specimens, a
superficial fascicle of the medial pterygoid muscle was found in direct
proximity to the ILP muscle. In these cases, a residual distance of 7.8 +/- 3.2
mm remained between the ILP muscle and buccinator fascia indented by the tip of
the examiner's finger. In 10 of 20 specimens with an absent superficial
fascicle, the finger was able to reach the ILP muscle.
CONCLUSION: It is recommended that the ILP muscle palpation technique should no
longer be considered as a standard clinical procedure because it is nearly
impossible to palpate the ILP muscle anatomically and because the risk of
false-positive findings (by palpation of the medial pterygoid muscle) is high.
(Highlighting by bold face and color added by
the author).