Muscle anatomy's hidden dangers: How varied structures jeopardize surgery

A systematic analysis of the chewing muscles' anatomy has revealed a link between individual structural variability and the risk of postoperative complications, as well as the development of obstructive sleep apnea and aspiration pneumonia. The study suggests that high anatomical diversity makes standard surgical protocols insufficient for ensuring patient safety.

Analysis Method and Data Sources

The researchers conducted a meta-analysis of 469 scientific publications focused on the structure and function of the masticatory apparatus published over the last 10 years. Following the removal of duplicates, 68 papers were selected for detailed review.

To identify patterns between microscopic muscle structure and clinical manifestations, the authors compared data from anatomical autopsies with live scanning results, including MRI, CT, and ultrasound. The research focused on three muscles that lower the mandible: the mylohyoid, geniohyoid, and the anterior belly of the digastric muscle, which together facilitate swallowing, speech, and chewing.

Surgical Risks in Mandibular Procedures

The data indicate that anatomical uniformity is rare. In 57% of cases, interfascial gaps were found in the mylohyoid muscle, while 23% exhibited hernial protrusions of the sublingual salivary gland. These structural anomalies provide pathways for hematomas to spread rapidly from the surgical site into the submandibular space.

The study also identified a significant risk of chin numbness during surgery. Findings show that in 43-50% of individuals, the mylohyoid nerve contains sensory fibers in addition to motor fibers. This implies that postoperative numbness in nearly half of patients results from their specific anatomy rather than surgical error.

Links to Sleep Apnea and Pneumonia

Researchers found a direct association between the tone of the geniohyoid muscle and the patency of the airways. A decrease in this muscle's tone allows the tongue to block the pharynx, contributing to obstructive sleep apnea.

The effectiveness of surgical muscle tensioning to widen airways depends on the point of attachment to the hyoid bone; if the attachment is shifted toward the edge, standard plastic surgery may be ineffective.

For elderly patients, the cross-sectional area of this muscle serves as a critical marker. An ultrasound measurement below 0.32 sq cm indicates sarcopenia—age-related loss of muscle mass. This prevents the hyoid bone from rising sufficiently during swallowing, increasing the risk of food or saliva entering the respiratory tract and causing aspiration pneumonia.

Muscle Fiber Specialization

Analysis of the digastric muscle revealed additional bundles in 40% of people. These structures can compress the facial artery—leading to ischemia of the submandibular salivary gland—or create facial asymmetry that may be mistaken for a tumor.

The authors also noted functional fiber separation within single muscles. In the area attached to the jaw, "fast" fibers predominate (70%), providing sudden force for biting food. Closer to the hyoid bone, "endurance" fibers dominate for swallowing functions. This distinction allows for more precise rehabilitation exercises after strokes or during dysphagia treatment.

Interpretive Boundaries and Practical Application

Because the work is based on a retrospective analysis of existing data rather than new controlled experiments, the results serve to refine tactics for oral surgeons and somnologists rather than establish a new universal treatment standard. Further clinical trials with larger patient groups are required to validate the ultrasound marker for sarcopenia. The study was published in the journal "Clinical Stomatology" (Klinicheskaya Stomatologiya).

Source: This article was adapted from an original Russian-language publication by Pravda.Ru.