The relationships between the temporomandibular joint disc and related masticatory muscles in humans

A study of the relationships of the temporomandibular joint disc and the lateral pterygoid, temporalis, and masseter muscles during the human fetal period and in the adult was conducted. The superior head of the lateral pterygoid muscle was seen to insert into the anteromedial two thirds of the temporomandibular joint disc. The fibers of the posterior one third of the temporalis muscle and fibers of the deep bundle of the masseter muscle were attached on the anterolateral one third of the disc. The attachment of these muscles to the disc was through the anterior extension of the disc, also known as the premeniscal or prediscal lamina. The possible functional role of these muscle attachments is discussed.     

Reticular afferents from vestibular nuclei

The purpose of the present study is to observe the electromyogram (EGM) manifestations of the lateral pterygoid muscle (LPM) in monkey during mouth opening and closing movements. The lateral pterygoid muscle of five healthy monkeys (macaques) was exposed by operation under general anesthsia and the electropolar needles were placed into the superior and inferior head of LPM respectively. The EMG manifestations of the superior and inferior head of LPM were recorded by O.T.E. Biomedica EMG Recorder during the natural condition and the movements of opening and closing mouth after complete recovery from anesthesia. It has been found that the two heads acted synergistically only in opening movement and no activity was noted in closing movement. This finding disagrees with the previous viewpoint that the function of the superior and inferior head of LPM is independent.     

Cytologic diagnosis of anal intraepithelial neoplasia using smears and cytyc thin-preps

Because of inconsistencies in the literature regarding popliteus and its relation to the lateral meniscus, it was decided to investigate the influence on the behavior of the lateral meniscus of contraction of the popliteus muscle via arthroscopy. A series of 50 knees from 44 patients who underwent elective arthroscopic surgery were examined. During arthroscopy, popliteus was stimulated to contract using surface electrodes. Any resultant meniscal retraction was observed and recorded. Thirty-one knees showed such retraction, and no retraction was observed in the remaining 19 knees. The clinical implications of this study are limited, but the results may support a number of proposed theories. It may be concluded that in a population exhibiting normal, intact lateral menisci, popliteus variably acts as a retractor of the lateral meniscus.     

Influence of the Esmarch splint on chewing and tongue muscle activity during sleep

To clarify the functional mechanism of the Esmarch device in the treatment of sleep apnea, its effect on muscle activity during sleep was studied electromyographically with and without the appliance at the inferior head of the lateral pterygoid muscle, the genioglossal muscle, and the masseter muscle in 15 patients with sleep apnea syndrome. During the obstructive apnea the muscles showed significantly lower amplitudes than before the apnea. No significant decrease in the amplitude was observed during the central apnea, but, after the obstructive and central apnea, significantly higher amplitudes were seen than beforehand. The amplitudes rose after the placement of the appliance, and the amplitudes of the genioglossal and lateral pterygoid muscles during obstructive apnea increased significantly after the insertion of the appliance. The results suggest that the device can activate the masticatory and tongue muscle activity and indicate that the muscles activated with the appliance can prevent obstruction in the oropharynx. The Esmarch device not only helps avoid obstruction by mandibular protraction, but also affects function by activating the muscles.     

The hypomobile temporomandibular joint

The hypomobile (restricted) temporomandibular joint (TMJ) is usually caused by a restricted joint capsule or by an anteriorly displaced disk. Here, painful unilateral hypomobility (19 mm jaw opening), with normal disk position, caused by voluntary immobilization after a dental procedure, was the presenting symptom. Management included inflammation control, TMJ manipulation (mobilization), and lateral pterygoid muscle relaxation. Inflammation and pain were alleviated by nonsteroidal anti-inflammatory drugs (NSAIDs) and local TMJ ice massage. TMJ mobilization was performed at every visit, to tear joint capsule adhesions and to realign collagen fibers. Exercise consisted mainly of resistive opening (the patient resists an upward force applied to the chin), with the jaw maintained at full opening. This produced lateral pterygoid muscle relaxation at full length, aiding in the restoration of a pain-free 44 mm opening.     

The development and morphofunctional characteristics of the human lateral pterygoid muscle

Peculiarities of the development of superior and inferior heads of lateral pterygoid muscle (LPM) as well as their micro- and ultramicroscopic structure were studied as related to the temporomandibular joint elements in human fetuses and newborns. As a result, heterogeneity and asynchronism of the development of myogenic elements of certain LPM heads were demonstrated. The process of muscle fibres differentiation in LPM superior head leads to more mature structural organization and runs faster than in the inferior head. By the moment of birth average section area of superior head muscle fibres is significantly higher than the inferior head similar parameter.     

Meniscal position on routine MR imaging of the knee

OBJECTIVE: To determine the prevalence of meniscal protrusion (i.e. location of the outer edge of a meniscus beyond the tibial articular surface), and to determine its relationship with internal derangement, joint effusion, and degenerative arthropathy. DESIGN AND PATIENTS: Sagittal and coronal MR images of 111 abnormal and 46 normal knees were evaluated for the presence of meniscal protrusion. We set 25% as the minimum amount of displacement considered abnormal because this was the smallest amount of displacement we could confidently discern. Presence of meniscal tear, anterior cruciate ligament (ACL) injury, joint effusion, or osteophytosis was also recorded. RESULTS AND CONCLUSION: Normal examinations demonstrated protrusion of the medial meniscus in 6.5% of sagittal images and 15% of coronal images, and of the lateral meniscus in 2% and 13%, respectively. Fisher's exact test demonstrated a statistically significant difference between the normal and abnormal groups for the medial meniscus on both sagittal (P < 0.0001) and coronal (P = 0.01) images, but not for the lateral meniscus in either plane (P > 0.2). A protruding medial meniscus was associated with effusion and osteophytosis (P < 0.05) but not with meniscal or ACL tear (P > 0.1). Posterior protrusion of the lateral meniscus was only associated with ACL injury (P < 0.0001); protruding anterior horns and bodies of lateral menisci were not associated with any of the four abnormalities. It is concluded that the medial meniscus may occasionally protrude more than 25% of its width, but protrusion is more often due to effusion and osteophytes. Protrusion of the posterior horn of the lateral meniscus is associated with ACL insufficiency, while protrusion of the body and anterior horn of the lateral meniscus is a normal variant.     

Relationship of the meniscofemoral ligaments of the knee to lateral meniscus tears: magnetic resonance imaging evaluation

This study sought to determine if the presence or absence of meniscofemoral ligaments exerts an influence on the prevalence of tears of the lateral meniscus. We reviewed the sagittal and coronal magnetic resonance images of 173 knees for lateral meniscus tears and the presence of the meniscofemoral ligaments. One or both meniscofemoral ligaments were present in 142 of 173 knees (82%). Fifty-four knees had lateral meniscus tears, 27 of which involved the posterior horn. Thirty-three percent of knees with meniscofemoral ligaments had a lateral meniscus tear, and 23% of knees without meniscofemoral ligaments had a lateral meniscus tear (no significant difference). We found no association between the presence of the meniscofemoral ligaments and tears of the lateral meniscus. Our study questions the importance of preserving or reconstructing these ligaments in instances of meniscal transplantation.     

Tendinous insertion of semimembranosus muscle into the lateral meniscus

Forty-two cadaver knees were used for morphologic and MRI observations of the tendinous distal expansions of the semimembranosus m. and the posterior capsular structures of the knee. A tendinous branch of the semimembranosus m. inserting into the posterior horn of the lateral meniscus was found in 43.2% of the knees dissected, besides five already known insertional branches; capsular, direct, anterior and inferior, as well as the oblique popliteal ligament. The tendon had three morphologic types; thin, broad and round. All three types moved the lateral meniscus posteriorly when pulled on. Thus, the semimembranosus m. may also have a protective function for the lateral meniscus as well as the already well established function of protecting the medial meniscus in knee flexion. When a semimembranosus tendon attachment to the posterior horn of the lateral meniscus is present, its normal insertion is difficult to differentiate from a lateral meniscus tear in MRI and this may cause misdiagnosis.     

The role of the lateral pterygoid muscles in TMJ disorders during static conditions

Intramuscular EMG of the lateral pterygoid muscles (LPM), surface EMG of the temporalis and masseter muscles and force measurements of the temporomandibular joint (TMJ) were synchronously used to investigate the biomechanical role of the two heads of the LPM in relation to internal derangement (ID) of the TMJ. EMG and kinetic analysis of five static conditions (resting, protraction, opening, molar and incisor clenching) and three maximum isometric masticatory forces (opening, molar and incisor clenching) were done to compare forces and muscular activity between TMJ ID and control subjects. The analysis of variance results of the integrated linear envelope (LE) EMG showed no significant differences between the two groups for the masseter and temporalis muscles. Therefore, there is no apparent reason to believe that these muscles are hyperactive in TMJ ID. The integrated LE EMG of the SLP was significantly lower in the TMJ group during molar clenching (104 microV + 60.0 over 159 microV + 68.8 for a p = .020). The superior head of the lateral pterygoid muscle (SLP) seemed to have lost its diskal stabilizing function. The integrated LE EMG signals of the ILP were significantly higher in the TMJ ID group during rest, resisted protraction and incisor clenching (p = .029, p = .046, p = .031 respectively). The ILP muscle has probably adapted to control the inner joint instability while continuing its own actions. The ILP muscle seemed to have lost its functional specificity. The results of the isometric forces showed that TMJ ID subjects exhibited significantly lower molar bite forces (297.1N over 419N, p = .042) confirming that they have less muscle strength and tissue tolerance than subjects with healthy masticatory muscle systems. A neuromuscular adaptation could be occurring in the TMJ ID masticatory system affecting muscular actions and forces.     

Clinical and sonographic meniscus diagnosis

Clinical examination still plays an important role in diagnosing meniscal tears. The types of sensitive nerves in the knee joint are responsible for nonspecific pain, which is often correlated with too little specificity in meniscal tests. Ultrasound examination of meniscal structures of the knee joint has been debated extensively in recent years. Criticism of this noninvasive technique was due to small patient groups, improper technical and inaccurate manual standards. Since 1988 ultrasound of the tibial meniscus has become a standard technique in our Department of Orthopaedic Surgery with defined criteria of the intersecting plane and evaluation of ultrasound images. A prospective follow-up study during 6/1988 and 5/1993 including 1186 ultrasound examinations before arthroscopy, was performed. The sensitivity for ultrasound of the lateral meniscus was 58% and for the medial meniscus 83%. Specificity with 98% for the lateral and 90% for the medial meniscus was good. Sonographic detection of meniscal tears depends on the shape and location of meniscal tears. This has been shown by experimental studies in cadavers. A follow-up study including 113 knee joints was performed to prove the value of clinical and ultrasound examination in relation to arthroscopy. The sensitivity of sonography for medial meniscus was 81% and 40% for the lateral meniscus. Although the sensitivity of the clinical examination was 81% (medial) and 47% (lateral), the low specificity of 70% for meniscus tears indicated that it was because of false-positive clinical evaluation of meniscal disorders. In young patients with reflectory muscle spasm and those with acute trauma of the knee joint, clinical examination of the meniscal structures showed poor results. In these cases, too, ultrasound examination showed advantages. Ultrasound of the knee joint meniscus is noninvasive, reproducible and low cost. In cases of uncertain clinical results, ultrasound offers a good opportunity to visualize meniscal disorders.     

Influence of the status of the contralateral carotid artery on the outcome of carotid surgery

This is a preliminary report of four cases of meniscal displaced tears: two bucket handle medial meniscus tears, one complex tear in the avascular zone or lateral meniscus, and one longitudinal full-thickness tear on the lateral meniscus. These tears were treated by applying hi-frequency current stimulation to the tissues and obtaining total meniscal visual healing on a second arthroscopic view after 6 weeks.     

Patterns of meniscal tears associated with anterior cruciate ligament lesions in athletes

In this study, 400 clinically anterior cruciate ligament (ACL) deficient knees were arthroscoped and studied prospectively in the period January 1986 to April 1992. An ACL tear was always confirmed, and 41 per cent of these patients did not have an associated meniscal tear. In 30.25 per cent the lateral meniscus was torn; in 21.25 per cent the ACL tear was associated with a medial meniscus tear, and in the remaining 7 per cent both menisci were torn. The most frequently associated meniscal injury was the bucket handle tear of the medial meniscus (9 per cent), followed by the posterior horn tear of the lateral meniscus, which showed the same frequency as the ragged (or degenerated) tear of the lateral meniscus (6 per cent). The horizontal tear of the posterior part of the lateral meniscus showed a prevalence of 4.3 per cent. This picture is probably dependent on a secondary referral nature of the centre surveyed, in which the average time between injury and arthroscopy was 23.3 months.     

Conservation of the 168 divIB gene in Bacillus subtilis W23 and B. licheniformis, and evidence for homology to ftsQ of Escherichia coli

Recent reports indicate that combined anterior cruciate ligament/medial collateral ligament (ACL/MCL) knee injuries are usually associated with a lateral meniscus tear. In our center, snow skiing is the athletic activity most frequently associated with this double-ligament injury complex. A sports-specific analysis was undertaken to evaluate the hypothesis that the snow skiing ligament injury is different from similar injuries caused by other athletic activities. Of a total of 64 acute arthroscopically confirmed tears of both the MCL and ACL, 23 were caused by snow skiing and 41 by nonskiing activities. There were fewer lateral meniscus tears in skiers (43%) when compared with the nonskiers (88%). Skiers also had fewer medial meniscus tears (13%) than did nonskiers (37%). No medial meniscus tears occurred in the absence of a lateral meniscus tear. Although 78% of the skiers were women, only 12% of the nonskiers were women. Skiers were older (average age 35 years) than the nonskiers (average age 28 years). The right knee was injured almost twice as frequently as the left. These data suggest that the double (ACL/MCL) ligament injury in skiers might be distinctly different from that in nonskiers.     

Meniscal cyst in the posterior intercondylar space found by magnetic resonance imaging

We report a rare case of meniscal cyst from the posterior horn of the lateral meniscus, extending in the posterior intercondylar space of the right knee of a 15-year-old boy, in whom magnetic resonance imaging was very useful for evaluation. A cyst in this location has not been reported previously. The cyst was removed surgically, while preserving the lateral meniscus. A good result was obtained, and no recurrence has been seen in 12 months.     

Heparin immobilized on proteins usable for arterial prosthesis coating: growth inhibition of smooth-muscle cells

Fifty-one patients with meniscal repair using the outside-in technique were reassessed with second-look arthroscopic procedures (N = 15), arthrographic examination (N = 41), magnetic resonance imaging (N = 36), or a combination of these techniques. Forty-one medial and 10 lateral menisci were repaired. The average clinical follow-up was 15 months (range, 3 to 80). Forty-five of 51 patients had tears that were located in or extended into the posterior horn of the medial or lateral meniscus. Complete healing occurred in 23 menisci (45%), partial healing was observed in 16 (15 medial, 1 lateral) (32%), and no healing occurred in 12 (24%). Remarkably, in all 15 patients who had tears extending from the posterior to the middle third of the medial meniscus that were partially healed, it was always the posterior third that had not fully healed. This finding is statistically significant. In addition, the middle third of these menisci had not fully healed in five patients. No healing occurred in the two patients with tears in the posterior third of the medial meniscus. Poor healing with the outside-in technique was observed in patients with tears into the posterior horn of the medial meniscus. For tears in the middle and anterior portion of the medial meniscus, as well as all lateral meniscus tears, the outside-in technique is our current method of choice.     

A practical approach for lateral meniscectomy

A variant surgical approach to the lateral meniscus is described in an effort to overcome the difficulties encountered in the region of the anterior horn of this meniscus. The knee is braced in 90 degrees of flexion and the incision is made from the lower lateral side of the patella, extending down and back for 4-5 cm.     

Periosteal migration in the growing mandible: an animal model

Migration of mandibular periosteum and attached musculature was tracked along the inferior border of the ramus in growing and nongrowing guinea pigs (Cavia porcellus) over a 6-week period. Particulate metallic growth-tracing implants were placed through the bony mandible and adjacent musculature at two anteroposterior locations and two bony reference markers were placed anteriorly. Quantification from weekly radiographs of growing animals showed marked posterior migration of the periosteum, whereas in nongrowing animals there was negligible periosteum movement. Significantly greater migration occurred in posterior (6.37 +/- 0.76 mm) implants relative to the anterior implants (3.45 +/- 0.86 mm, p < 0.001). The neutral zone, where little periosteal migration occurs, was calculated to be approximately at the anteroposterior center of the molar tooth row. Analysis of the orientation of the medial pterygoid muscle relative to the mandible showed that muscle fibers on average become more horizontal. Thus, the study found differential anteroposterior migration of the mandibular periosteum in growing animals and correlative changes in orientation of the medial pterygoid muscle.     

Arthroscopic treatment of cysts of the lateral meniscus

We have treated 69 patients with 72 cystic lateral menisci by arthroscopic surgery. Meniscal tears were observed in all cases, and 69 of these had a horizontal cleavage component. Three types of tear were identified and may be progressive. Treatment was by arthroscopic resection of the meniscal tear, and decompression of the cyst through the substance of the meniscus. After a mean follow-up of 34 months the results were good or excellent in 64 knees (89%) and there were few complications. We recommend this technique as the treatment of choice for cysts of the lateral meniscus.     

Arthroscopic partial resection of the discoid meniscus in children

Thirteen children with 14 lateral discoid menisci were reviewed at an average follow-up of 2.7 years. Their average age at the time of the operation was 12.8 years. Most of the children had vague and intermittent painful symptoms, and the classical "clunk" was demonstrable in nine of the 13 patients in clinical examinations. Thirteen children underwent arthroscopic partial meniscectomy for symptomatic discoid lateral meniscus, by performing partial resection. This procedure, modifying the discoid lateral meniscus to the normal semilunar shape, was indicated only when the capsular attachment was intact. The results were excellent both clinically and radiologically. Furthermore, rehabilitation time was considerably shorter than the time required after open procedures. Arthroscopic discoid meniscus surgery performed by experienced and skilled hands gives better results. According to the literature and our experiences, it is better to perform open techniques in patients with stiff knees. Additionally, it is technically feasible to use small joint instruments in the pediatric age group.