Insights Into the Pathophysiology of Cellulite: A Review.

BACKGROUND: The etiology of cellulite is unclear. Treatment of cellulite has targeted adipose tissue, dermis, and fibrous septae with varying degrees of success and durability of response. OBJECTIVE: Results from clinical trials that target different anatomical aspects of cellulite can provide insights into the underlying pathophysiology of cellulite. MATERIALS AND METHODS: A search of the PubMed database and ClinicalTrials.gov website was conducted to identify clinical trials that have investigated treatments for cellulite. RESULTS: A lack of trial protocol standardization, objective means for quantification of improvement and reported cellulite severity, and short-term follow-up, as well as variation in assessment methods have made comparisons among efficacy studies challenging. However, the lack of durable efficacy and inconsistency seen in clinical results suggest that dermal or adipose tissue changes are not the primary etiologies of cellulite. Clinical studies targeting the collagen-rich fibrous septae in cellulite dimples through mechanical, surgical, or enzymatic approaches suggest that targeting fibrous septae is the strategy most likely to provide durable improvement of skin topography and the appearance of cellulite. CONCLUSION: The etiology of cellulite has not been completely elucidated. However, there is compelling clinical evidence that fibrous septae play a central role in the pathophysiology of cellulite.

Does resistance training increase aponeurosis width? The current results and future tasks.

PURPOSE: The aponeurosis, a sheet of fibrous tissue, is the deep and superficial fascia where muscle fibers attach in pennate muscles. It is quite possible that the aponeurosis size increases in response to resistance training-induced fiber hypertrophy due to an increase in connection area. As a result, it leads to an increase in anatomical muscle cross-sectional area. However, attention has not been paid to aponeurosis area changes. This review sought to determine whether muscle hypertrophy changes aponeurosis width following short-term resistance training using an equation we modified [post/pre changes in aponeurosis width (AWpost/pre) = post/pre changes in anatomical cross-sectional area (CSApost/pre) ÷ post/pre changes in pennation angle (PApost/pre) ÷ post/pre changes in fascicle length (FLpost/pre)]. METHODS: A search using two electronic databases (PubMed and Google Scholar) was conducted. Nine studies measured CSApost/pre, PApost/pre, and FLpost/pre of the vastus lateralis muscle by ultrasound and magnetic resonance imaging. RESULTS: There was a statistically significant 2.73 [95% CI 1.11, 4.36; p = 0.009] cm2 increase in CSApost/pre along with a statistically significant 1.21° [95% CI 0.44, 1.97; p = 0.002] increase in PApost/pre and a statistically significant 0.36 cm [95% CI 0.19, 0.54; p = 0.0002] increase in FLpost/pre. These results yield an estimated 1% reduction in aponeurosis width. CONCLUSION: Our results suggest that while muscle CSA, pennation angle, and fascicle length all increase following short-term resistance training, the aponeurosis width is not altered.

The Role of Plantar Fascia Tightness in Hallux Limitus: A Biomechanical Analysis.

Restriction of greater toe dorsiflexion without degeneration of the first metatarsophalangeal joint is defined as hallux limitus. We assume that in hallux limitus the limitation of greater toe dorsiflexion takes place in the terminal stance phase because of massive tightening of the calf and plantar structures. The current study investigated the role of a tight plantar fascial structure in impairing dorsiflexion of the greater toe. For the purpose of the study, 7 lower limbs from Thiel-fixated human cadavers were evaluated. To simulate double-limb standing stance, the tibia and fibula were mounted on a materials testing machine and constantly loaded with 350N. Additionally, the tendons of the specimens were loaded using a custom-made system. The plantar fascia was fixed to a clamp and tensioned using a threaded bar. Four different tensile forces were then applied to the plantar fascia (approximately 100, 200, 300, and 350 N) and the extension of the first toe was measured. The results show a significant positive correlation between the decrease in extension of the hallux and the tension applied to the plantar fascia reaching a maximum mean decrease of 4.2° (117% compared with the untightened situation) for an applied tension of 364N.

Biomechanics of the Levator Aponeurosis.

PURPOSE: To investigate biomechanical properties of the levator aponeurosis. METHODS: Patients undergoing external levator resection for primary or revision correction of acquired ptosis were analyzed as primary and revision groups. Immediately postoperatively, the resected segments of the levator aponeurosis were stressed by adding sequential masses to the tissue. Specimen length was recorded at each stress level. Stress-strain diagrams were used to summarize how the tissue elongated in response to the external forces, because these diagrams correct for differences in specimen size. Representative specimens were analyzed histologically. RESULTS: Twenty-two specimens from 14 patients in the primary group and 10 specimens from 7 patients in the revision group met inclusion criteria. In the primary group, the mean age was 66 years; 8 patients were women. In the revision group, the mean age was 69 years; 6 patients were women. Levator aponeurosis specimens in both the primary and revision group demonstrated proportional increases in length with increasing stress, demonstrating that the levator aponeurosis is extensile. Given the same amount of stress, the levator aponeurosis from primary specimens elongated more than revision specimens. Histologically, revision specimens exhibited increased collagen and haphazard, tangled elastin fibers. CONCLUSIONS: The levator aponeurosis obtained during surgical correction of acquired ptosis elongates in response to nominal external forces. This biomechanical property is important because the length of the aponeurosis may vary intraoperatively if variable forces are applied to the eyelid. This property might be related to connective tissue architecture and, specifically, fibrosis. Surgeons performing levator aponeurosis resection should be mindful to maintain a consistent amount of force on the levator aponeurosis when performing the resection to maximize intercase consistency.

Stuck in gear: age-related loss of variable gearing in skeletal muscle.

Skeletal muscles power a broad diversity of animal movements, despite only being able to produce high forces over a limited range of velocities. Pennate muscles use a range of gear ratios, the ratio of muscle shortening velocity to fiber shortening velocity, to partially circumvent these force-velocity constraints. Muscles operate with a high gear ratio at low forces; fibers rotate to greater angles of pennation, enhancing velocity but compromising force. At higher forces, muscles operate with a lower gear ratio; fibers rotate little so limiting muscle shortening velocity, but helping to preserve force. This ability to shift gears is thought to be due to the interplay of contractile force and connective tissue constraints. In order to test this hypothesis, gear ratios were determined in the medial gastrocnemius muscles of both healthy young rats, and old rats where the interaction between contractile and connective tissue properties was assumed to be disrupted. Muscle fiber and aponeurosis stiffness increased with age (P<0.05) from 19.1±5.0 kPa and 188.5±24.2 MPa, respectively, in young rats to 39.1±4.2 kPa and 328.0±48.3 MPa in old rats, indicating a mechanical change in the interaction between contractile and connective tissues. Gear ratio decreased with increasing force in young (P<0.001) but not old (P=0.72) muscles, indicating that variable gearing is lost in old muscle. These findings support the hypothesis that variable gearing results from the interaction between contractile and connective tissues and suggest novel explanations for the decline in muscle performance with age.

Unilateral ectopic insertion of the pectoralis minor: Clinical and functional significance.

During routine dissection of a 70-year-old female, we observed a unilateral ectopic insertion of the left pectoralis minor muscle. The tendon was cord-like and passed through a tendon sheath superior to the coracoid process to insert on the greater tubercle of the humerus. Additionally, an aponeurosis extended from the distal aspect of the muscle's tendon and passed medially to insert near the base of the coracoid process. This is the first report of an additional aponeurosis extending from the tendon of the pectoralis minor and attaching to the coracoid process. We also observed that the pectoralis minor tendon caused an unusually smooth deep indentation on the superior aspect of the coracoid process; considering its insertion on the humerus, we hypothesize that the muscle acted as an abductor of the shoulder along with the supraspinatus. The medial extension of an aponeurotic tendon from the pectoralis minor tendon near its insertion, to the base of the coracoid process further suggests that the muscle provided stability to the glenohumeral joint while acting as an abductor. Pectoralis minor variations have been described since 1897; however, few studies have demonstrated functional or clinical significance. The redundancy of the actions of this muscle along with its long tendon suggests a potential source for autograft.

Biomechanical effects of rocker shoes on plantar aponeurosis strain in patients with plantar fasciitis and healthy controls.

Plantar fasciitis is a frequently occurring overuse injury of the foot. Shoes with a stiff rocker profile are a commonly prescribed treatment modality used to alleviate complaints associated with plantar fasciitis. In rocker shoes the apex position was moved proximally as compared to normal shoes, limiting the progression of the ground reaction forces (GRF) and peak plantarflexion moments during gait. A stiff sole minimizes dorsiflexion of the toes. The aim of this study was to investigate whether the biomechanical effects of rocker shoes lead to minimization of plantar aponeurosis (PA) strain during gait in patients with plantar fasciitis and in healthy young adults. 8 patients with plantar fasciitis (1 male, 7 females; mean age 55.0 ± 8.4 years) and 8 healthy young adults (8 females; mean age 24.1 ± 1.6 years) participated in the study. Each participant walked for 1 minute on an instrumented treadmill while wearing consecutively in random order shoes with a normal apex position (61.2 ± 2.8% apex) with flexible insole (FN), normal apex position with stiff insole (SN), proximal apex position (56.1 ± 2.6% apex) with flexible insole (FR) and proximal apex position with stiff insole (SR). Marker position data of the foot and lower leg and GRF were recorded. An OpenSim foot model was used to compute the change in PA length based on changes in foot segment positions during gait. The changes in PA length due to increases in Achilles tendon forces were computed based on previous data of a cadaver study. PA strain computed from both methods was not statistically different between shoe conditions. Peak Achilles tendon force, peak first metatarsophalangeal (MTP1) joint angle and peak plantarflexion moment were significantly lower when walking with the rocker shoe with a proximal apex position and a stiff insole for all subjects (p<.05). Changes in Achilles tendon forces during gait accounted for 65 ± 2% of the total PA strain. Rocker shoes with a stiff insole reduce peak dorsiflexion angles of the toes and plantar flexion moments, but not PA strain because the effects of a proximal apex position and stiff insole do not occur at the same time, but independently affect PA strain at 80-90% and 90-100% of the stance phase. Rocker shoes with an apex position of ~56% are insufficient to significantly reduce peak PA strain values in patients with plantar fasciitis and healthy young adults.

Investigation of the passive mechanical properties of spine muscles following disruption of the thoracolumbar fascia and erector spinae aponeurosis, as well as facet injury in a rat.

BACKGROUND CONTEXT: Muscle tissue is known to remodel in response to changes to its mechanical environment. Alterations in passive mechanical properties of muscles can influence spine stiffness and stability. PURPOSE: This study aimed to determine whether passive muscle elastic moduli and passive muscle stresses increased 28 days following mechanical disruption of the thoracolumbar fascia and erector spinae aponeurosis, and injury induced by facet joint compression. STUDY DESIGN: Male Sprague Dawley rats were randomly assigned to three groups (Incision n=8; Injury n=8; and Control n=6). METHODS: The thoracolumbar fascia and erector spinae aponeurosis were incised in the Incision and Injury groups to expose the left L5-L6 facet joint. In the Injury group, this facet was additionally compressed for three minutes to induce facet injury and cartilage degeneration. Twenty-eight days after surgery, rats were sacrificed and muscle samples were harvested from lumbar and thoracic erector spinae and multifidus for mechanical testing. RESULTS: Histologic staining revealed mild cartilage degeneration and boney remodeling in the Injury group. However, the hypotheses that either (1) disruption of the thoracolumbar fascia and erector spinae aponeurosis (Incision group) or (2) the addition of facet compression (Injury group) would increase the passive elastic modulus and stress of surrounding muscles were rejected. There was no effect of surgery (Incision or Injury) on the passive elastic modulus (p=.6597). Passive muscle stresses were also not different at any sarcomere length between surgical groups (p>.7043). CONCLUSION: Disruption of the thoracolumbar fascia and erector spinae aponeurosis and mild facet damage do not lead to measurable changes in passive muscle mechanical properties within 28 days. These findings contribute to our understanding of how spine muscles are affected by injury and fundamental aspects of the initial stages of spine surgery.