Figure 1. Dissected hyoplatysmal ligament. A, A clamp is placed on the hyoid bone. B, A probe demonstrates the ligament from the surrounding soft tissue.
Figure 2. Pictoral representation of the anatomical location of hyoplatysmal ligament.
Figure 3. Histology of the hyoplatysmal ligament. A, Ligament insertion at hyoid bone, which then extends up and to the right in the image. B, Ligament insertion under polarized light. Note the highly organized collagen structure of ligament. C, Ligament coursing through the platysma to merge with subcutaneous fascial layer. D, Trichrome stain highlighting collagen in bluish-green and the muscle in red. Note the band of ligament coursing through the muscle.
Brandt MG, Hassa A, Roth K, Wehrli B, Moore CC. The Hyoplatysmal LigamentCharacterization and Biomechanical Properties. Arch Facial Plast Surg. 2012;14(5):369-371. doi:10.1001/archfacial.2011.1502
Author Affiliations: Division of Facial Plastic and Reconstructive Surgery, Department of Otolaryngology–Head and Neck Surgery, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada (Dr Brandt); and Division of Plastic Surgery, Department of Surgery (Dr Hassa), Division of Facial Plastic and Reconstructive Surgery, Department of Otolaryngology–Head and Neck Surgery (Drs Roth and Moore), and Department of Pathology (Dr Wehrli), Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario.
Although many factors contribute to the aging neck, the platysma plays a critical role. Contiguous with the superficial musculoaponeurotic system (SMAS) of the face, the platysma acts as a corset—maintaining the position of the neck viscera, submandibular glands, and the overlying skin.1 Similar to facial rejuvenation procedures that elevate the skin from the SMAS, techniques to rejuvenate the aging neck typically involve the elevation of skin from the underlying platysma.1- 3 In the process of performing cervical rejuvenation procedures, it has been noted by the senior author (C.C.M.) that a fibrous connection exists within the neck that may contribute to the maintenance of the cervical mental angle. It extends from the hyoid bone to the platysma muscle and the overlying skin. We define this fibrous connection as the hyoplatysmal ligament and sought to anatomically characterize this ligament and define its biomechanical properties.
This investigation proceeded concurrently with an investigation of the 4 “true” osteocutaneous ligaments of the face.4 As such, only those methods specific to this investigation are reviewed.
Dissections were performed of 5 fresh frozen cadaver heads in a systematic fashion by the senior author (C.C.M.). A subplatysmal flap was elevated to the hyoid bone. The larynx was retracted inferiorly to expose the hyoid. The suprahyoid and infrahyoid muscular attachments were carefully identified and dissected away. Once the hyoid was free of its muscular attachments, a fibrous ligament (hyoplatysmal ligament) was evident originating from the superior aspect of the body of the hyoid bone just medial to the fascial sling of the digastric tendon. This fibrous ligament extended to the platysma and its overlying dermis.
The length, width, and thickness of the hyoplatysmal ligament were measured. For uniformity, ligament width and thickness were assessed at the midpoint of the ligament—the region which was most likely to rupture under biomechanical testing.
The biomechanical properties of the hyoplatysmal ligament were measured in a standardized fashion using an Instron 8501 Servohydraulic Mechanical Testing Apparatus (Canton, Massachusetts). Because the hyoplatysmal ligament could not be tested in situ, the hyoid bone was split at its midpoint. The bone was then secured to the Instron device via a clamp. To allow fixation of the ligament to the Instron, a braided, nonabsorbable suture (3.0 Merseline; Ethicon Inc) was woven in a repeating figure eight pattern at the insertion of the ligament into the retinacula cutis and tied securely. This suture was then tightly secured to a crossbar attachment on the Instron device.
Ligament length from bony origin to skin insertion and the width and thickness were measured with dial calipers at a preload of 0.5 to 2.0 Newtons. Testing was performed with uniaxial tension perpendicular to the bone surface at a displacement rate of 2 mm per minute until failure. Force and deformation data were recorded at 20 Hz and stored for subsequent analysis.
Dissected hyoplatysmal ligaments were submitted for independent histologic examination by a board-certified pathologist (B.W) who was blinded to the specimens and asked to comment on their structure relative to other osteocutaneous ligaments.4 Permanent paraffin-impregnated sections were obtained and stained with hematoxylin-eosin as well as trichrome stain.
The force vs deformation data were graphed, and the following measures were obtained: force to initial failure, force to ultimate ligament rupture, stiffness, and percentage elongation, with the assumptions of each variable previously defined.4 All statistical comparisons were made by an independent statistician blinded to the goals of this investigation using Tukey-Kramer multiple comparisons tests with statistical significance defined as P < .01 (GraphPad InStat software, version 3.05).
Hyoplatysmal ligaments were consistently observed to originate from the body of the hyoid bone, medial to lesser cornu and in proximity but medial to the stylohyoid ligament origin (Figure 1 and Figure 2). The medial margin of the ligament was 4 to 7.5 mm from the midline of the hyoid (mean [SE], 5.41 [0.42] mm). The length of the ligament ranged from 8 to 17 mm (11.0 [1.31] mm), width from 3 to 5 mm (4.6 [0.25] mm), and thickness from 0.5 to 1.5 mm (1.0 [0.1] mm). In all instances, the ligament was fibrous, with variable amounts of fatty tissue surrounding but not infiltrating the structure. There were no statistically significant differences found between the right and left ligaments of each cadaver. In addition, there were no statistically significant relationships between the ligament dimensions and the ages or sexes of the cadavers.
Histologic examination using trichrome stain confirmed all specimens as osteocutaneous ligaments. A true bony origin and subcutaneous insertion were histologically identified (Figure 3). In addition, the fibrous hyoplatysmal connection demonstrated histologic consistency with other true osteocutaneous facial ligaments.4
All of the ligaments tested ruptured in midsubstance, with no failure of suture or clamp attachment. The mean (SE) force to initial failure for the hyoplatysmal ligament was 4.63 (1.44) Newtons. The mean force to ultimate failure was 4.76 (1.17) Newtons. Hyoplatysmal ligament stiffness (resistance to a constant elongating force) was found to be 0.83 (0.26) Newtons/mm. The percentage of elongation for the hyoplatysmal ligaments were found to be 66% (6.6 mm).
The hyoplatysmal ligament spans from the superior aspect of the body of the hyoid bone just medial to the fascial sling of the digastric tendon and inserting within the dermis of the neck (Figure 2) Its dimensions and biomechanical properties have been empirically defined. Although little variability was observed in the surgical dissection of this ligament, true confirmation of its attachments and structure have been further endorsed through independent histologic analysis.
Hyoplatysmal ligament biomechanical properties demonstrated a generally weak ligament compared with other facial osteocutaneous ligaments.4 This ligament seemed to be the weakest of all true cervicofacial ligaments with initial and ultimate failures at 4.63 and 4.76 Newtons, respectively. Predictably, the hypoplastysmal ligament also demonstrated minimal stiffness and resistance to mechanical failure.
A combination of advantageous skeletal structure and dynamic muscular action assists in retaining a youthful cervical appearance. Although not empirically evaluated, this muscular action also seems to be load bearing because individuals with stronger platysma muscles traditionally demonstrate less soft-tissue descent compared with those individuals with weaker platysma muscles. In light of the complex load structure of the cervical region, it is not unreasonable that the hyoplatysmal ligament is quite weak. Correspondingly and given the little resistance to failure and minimal stiffness of the hyoplatysmal ligament, it is easily surgically transected.
Curiously, variations in age and sex were not appreciated within our sample. One would anticipate that more youthful ligaments, and perhaps male ligaments would demonstrate greater strength. Does the stronger male platysma perhaps obviate the need for a strong hyoplatysmal ligament? Only through further investigation with a substantially larger sample size could this question be answered and a more precise biomechanical assessment take place. A larger sample size could also ensure the accuracy of ligament dimensions that appeared to be quite uniform in this sample.
In conclusion, to our knowledge this is the first investigation to document the presence of a true osteocutaneous ligament of the neck. Although further investigation is required to better define its dimensions and biomechanical properties, the presence of the hyoplatysmal ligament suggests an additional variable in the factors contributing to an acute cervicomental angle.
Correspondence: Dr Moore, Division of Facial Plastic and Reconstructive Surgery, Department of Otolaryngology–Head and Neck Surgery, Schulich School of Medicine and Dentistry, University of Western Ontario, London, 268 Grosvenor St, London, ON N6A 4V2, Canada (firstname.lastname@example.org).
Author Contributions: Dr Brandt had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: Brandt, Hassa, Roth, and Moore. Acquisition of data: Hassa, Roth, and Moore. Analysis and interpretation of data: Brandt, Hassa, Roth, Wehrli, and Moore. Drafting of the manuscript: Brandt, Hassa, Wehrli, and Moore. Critical revision of the manuscript for important intellectual content: Brandt, Roth, Wehrli, and Moore. Statistical analysis: Brandt, Hassa, and Moore. Obtained funding: Moore. Administrative, technical, and material support: Brandt, Roth, Wehrli, and Moore. Study supervision: Moore.
Financial Disclosure: None reported.
Additional Contributions: We wish to extend our sincere appreciation to Lauren Thomson for her anatomic drawing (Figure 2).