Anatomical basis for the clinical application of the arterial supply of musculus pectoralis major.

The pattern of arterial supply to the various parts (clavicular, sternocostal and aponeurotic) of the pectoralis major muscle was studied in 7 cadaver dissections and 10 angiograms by injecting a radio-opaque substance. Three main arteries supplied the muscle, i.e. the pectoral branch of the thoracoacromial trunk (TAT-PB), the lateral thoracic artery and the perorating branch of the internal thoracic artery, supported by other branches of the TAT and the superior thoracic artery. It is observed that the TAT-PB, a chief vascular pedicle, anastomoses freely with other arteries and supplies most parts of the muscle. The present study is mainly focussed on the exclusion of the chief vascular pedicle of muscle to eliminate the confusion of previous studies and prevent the unnecessary hindrance and complications of the muscle flap.     

Standard bipolar surface EMG estimations mischaracterize pectoralis major activity in commonly performed tasks

The pectoralis major assists in several shoulder movements, such as humeral vertical and horizontal adduction, flexion, extension, and internal rotation. Despite its involvement in numerous functional activities, its role in typical shoulder function is ambiguous. Due to this, its purpose in arm movement is largely diminished. However, mounting evidence associates pectoralis major injuries to long-term debilitating arm disability. Therefore, a more deliberate investigation of its role in typical shoulder function is paramount. The purpose of this paper is to outline the current limitations in the acquisition and characterization of pectoralis major activation using standard bipolar surface electromyography. Macroscopic level analyses are used to investigate pectoralis major activation in eight tasks at low (15–25% of maximal voluntary effort (MVE) and moderate (50% MVE) efforts in healthy males. Virtually derived bipolar EMG amplitudes are quantified for the clavicular and the upper sternocostal regions based on the common locations used to acquire EMG signals from classic EMG. HD-sEMG amplitudes from three pectoralis major regions (i.e. clavicular, upper, and lower sternocostal) were compared to virtually derived bipolar EMG amplitudes (i.e. clavicular and upper sternocostal) to determine if current EMG methods misestimate pectoralis major activity. Current findings indicate that classic EMG recordings mischaracterize pectoralis major activation in several tasks and effort levels, highlighting the importance of acquiring signals from multiple pectoralis major regions.     

The segmental pectoralis major muscle flap: a function-preserving procedure

A function-sparing pectoralis major muscle flap is presented. The flap is a medially based segmental transfer of a single intercostal portion of the pectoralis major muscle supplied by a single perforating branch of the internal thoracic artery. The segmental terminal nerve distribution of the medial and lateral pectoral nerves permits preservation of the remainder of the muscle in situ. Six cases of this procedure are presented with five successful outcomes. The single exception was in the loss of the distal tip when used to cover an irradiated carotid sheath to the base of the skull.     

Quantifying differences in the material properties of the fiber regions of the pectoralis major using ultrasound shear wave elastography

The sternocostal and clavicular regions of the pectoralis major are independently harvested to provide shoulder stability, but surgical decision making does not consider the biomechanical consequences that disinsertion of one fiber region over the other has on shoulder function. Differences in material properties between the fiber regions could influence which tissue is more optimal for surgical harvesting. The current study utilized ultrasound shear wave elastography (SWE) to investigate whether the in vivo material properties differ between the fiber regions. Shear wave velocities (SWVs) were collected from the sternocostal and clavicular fiber regions of the pectoralis major from ten healthy young male participants. Participants produced isometric shoulder torques of varying magnitudes (passive, 15%, and 30% MVC) and directions (horizontal and vertical adduction). Four shoulder positions encompassing different vertical abduction and external rotation angles were examined. One-way ANOVAs tested the hypotheses that differences in SWVs during rest existed between the fiber regions as a function of shoulder position, and differences in SWVs during contraction existed as a function of shoulder position and torque direction. In all shoulder positions, the clavicular region exhibited greater SWVs during rest than the sternocostal region (P < 0.001). In shoulder positions that did not include external rotation, the clavicular region exhibited greater SWVs during contraction when producing horizontal adduction torques (P < 0.001), while the sternocostal region exhibited greater SWVs during contraction when producing vertical adduction torques at 30% MVC (P < 0.01). Our results suggest that each fiber region of the pectoralis major provides unique contributions to passive and active shoulder function.     

The extended pectoralis major myocutaneous flap: uses and indications

The vascular territory of the pectoralis major muscle and overlying skin was studied by selective intraarterial dye injections in fresh cadavers. The area of skin overlying the anterior chest and abdominal wall beyond the limits of the pectoralis major muscle that can be elevated as an extended myocutaneous flap was determined. The cadaver injections were evaluated to determine the size and shape of the skin island used to reconstruct defects of the head, neck, and upper trunk with an extended skin paddle off the pectoralis major muscle. Pectoralis muscle flaps with variously shaped skin paddles, some extending beyond the limits of the muscle, were used in 27 patients to cover large soft-tissue defects of the upper thorax, face, and floor of the mouth and as a skin tube to reconstruct the cervical esophagus. The size of the skin paddle ranged from 5 x 7 cm to 26 x 16 cm. All flaps survived completely, and there were no major donor-site complications.     

Arterial and venous anatomical features of the pectoralis minor muscle flap pedicle

The pectoralis minor muscle has been used as an innervated, vascularized, free-muscle graft in the field of facial reanimation for 20 years. Throughout this period, several centers have demonstrated consistent success with functional muscle transfer; however, opinions regarding the arterial pedicle of the flap have varied. The lateral thoracic and thoracoacromial arteries have been proposed as the predominant arterial sources. It has been the experience of our unit that a vessel (not described in anatomy textbooks) arising directly from the axillary artery and entering the muscle from its dorsal surface provides the dominant supply to the flap and is capable of sustaining it for free-tissue transfer. The vascular pedicle encountered was recorded and photographed in 97 consecutive cases in which the pectoralis minor muscle flap was raised. The findings demonstrated that the dominant supply to the muscle was from a single artery in 77 percent of cases and took the form of an artery arising directly from the axillary vessel in 72 percent of cases. More than one major arterial source was noted in the remainder of the cases. The venous outflow was usually through single or multiple veins running directly from the muscle into the axillary vein.     

Non-uniform excitation of pectoralis major induced by changes in bench press inclination leads to uneven variations in the cross-sectional area measured by panoramic ultrasonography

This study combined surface electromyography with panoramic ultrasound imaging to investigate whether non-uniform excitation could lead to acute localized variations in cross-sectional area and muscle thickness of the clavicular and sternocostal heads of pectoralis major (PM). Bipolar surface electromyograms (EMGs) were acquired from both PM heads, while 13 men performed four sets of the flat and 45° inclined bench press exercises. Before and immediately after exercise, panoramic ultrasound images were collected transversely to the fibers. Normalized root mean square (RMS) amplitude and variations in the cross-sectional area and muscle thickness were calculated separately for each PM head. For all sets of the inclined bench press, the normalized RMS amplitude was greater for the clavicular head than the sternocostal head (P < 0.001), and the opposite was observed during the flat bench press (P < 0.001). Similarly, while greater increases in cross-sectional area were observed in the clavicular than in the sternocostal head after the inclined bench press (P < 0.001), greater increases were quantified in the sternocostal than in the clavicular head after the flat bench press exercise (P = 0.046). Therefore, our results suggest that the PM regional excitation induced by changes in bench press inclination leads to acute, uneven responses of muscle architecture following the exercise.     

The functional pectoralis major musculocutaneous island flap in head and neck reconstruction

We describe our experience with the true island pectoralis major musculocutaneous flap in patients with high-volume defects for whom free-tissue transfer is unsuitable. Our operative technique is presented. We have modified the method of making a true island of the pectoralis major musculocutaneous flap on a muscle-free pedicle as first described by Wei et al. in 1984. This maintains maximal donor-site muscle function and facilitates closure of the donor-site defect. We present our results in 24 patients, in whom the flap has proved to be robust and reliable. The flap's advantages in terms of increased pedicle length, wider arc of rotation, decreased pedicle bulk, and improved cosmesis of the reconstruction are discussed.     

Neuromuscular organization and regional EMG activity of the pectoralis in the pigeon

In order to improve our understanding of the neuromuscular control of the most massive avian flight muscle, we studied the innervation pattern of the pigeon pectoralis. Nine primary branches from the rostral trunk and nine to ten branches from the caudal trunk of the pectoral nerve were identified by microdissection in ten pigeons. The region of muscle that each branch innervates was delineated by nerve stimulation studies (ten pigeons) and six regions were confirmed by glycogen depletion (ten pigeons). In pigeons, branches from the rostral nerve innervate the anterior 3/5 of the sternobrachialis (SB) head of the pectoralis and branches from the caudal trunk innervate the posterior 1/2 of the SB and all of the throacobrachials (TB). In the SB, individual branches of the rostral pectoral nerve innervate wedge-shaped muscle regions (each approximately 1.3 cm wide), collectively forming a fan shaped arrangement along the sternal carina. Adjacent muscle regions partially overlap at their boundaries. Within the thoracobrachialis (TB) head of the pectrolis, muscle regions are wider. There is a region in mid-SB-where the innervation territories of the rostral and caudal nerves oferlap. Electromyographic (EMG) activity patterns were recorded within ten of the identified muscle regions during take-off, level flapping flight, and landing. Onset of EMG activity and EMG intensity within various muscle regions exhibits significant differences both within a wingbeat cycle and among different modes of flight. The innervation pattern of the pectoralis presents the anatomical substrate for neuromuscular compartmentalization and differential EMG activity within the pectoralis may reflect sensory-motor partitioning. The extent to which the neuromuscular compartmentalization of the pectoralis corresponds to its ability to produce an array of force vectors to the wing awaits further more detailed biomechanical studies. © 1993 Wiley-Liss, Inc.     

Abdominal part artery of axillary artery: proposed term for the artery supplying the abdominal part of the musculus pectoralis major.

In 1976, the authors reported that the abdominal part artery (Pab) supplying the abdominal part of the pectoralis major muscle usually originates from the axillary artery (Ax). The findings in the present study show that the type of origin of this artery most frequently encountered is type 2-a (44.0%) in which the Pab, as an independent branch (type a), branches out of the second part of the Ax (type 2). The second and third most frequently encountered types are type 2-b (17.0%), where the Pab has a common trunk with the thoracoacromial artery, and type 2-c (10.0%), where it has a common trunk with the lateral thoracic artery. By classification according to the supplying areas, 67% was type I-B, supplying the lower part of the pectoralis minor muscle and the abdominal part of the muscle. In 5%, the branch as type I-A courses down to the sternocostal part. In most cases (types A and B in 91%), this artery originates from the Ax proximal to the ansa mediana of the brachial plexus; however, in 4% providing the superficial brachial artery, the Pab branches out from the superficial brachial artery. Based on those findings, the authors would propose that the artery be named the arteria partis abdominalis or Pab.     

Applied anatomy of the anterolateral femoral flap

A study of the source of the blood supply to the anterolateral femoral flap was carried out on 42 lower limbs of adult cadavers (among them 35 cadavers with injection of red latex and 1 with india ink into the arteries and 6 vascular cast specimens), and the surface locations of the vascular pedicle were detected on 50 healthy adults. It was found that the descending branch of the lateral circumflex femoral vessel was an ideal axial vessel. There are constant perforating branches of the myocutaneous artery or cutaneous branches from the intermuscular space to the anterolateral femoral skin. The area extends about 12 x 30 cm. Within the flap, the anterior branch of the anterolateral cutaneous nerve of the high is located. This flap has been widely used for free transplantation in China since 1983 with satisfactory results.     

The pectoralis minor vascularized muscle graft for the treatment of unilateral facial palsy

A series of 10 pectoralis minor vascularized muscle transfers to reanimate the face in unilateral facial palsy are presented. The procedure is carried out in two stages. The first stage constitutes a nerve graft from the functional contralateral facial nerve to the preauricular region of the paralyzed side. Six months later, the pectoralis minor is transferred to the denervated side of the face with restoration of its neurovascular pedicle. The muscle is well suited to its new position with respect to length and bulk, as well as its fanlike shape. The diameter of its vascular pedicle is comparable with the facial vessels. The results demonstrate function in 8 of the 10 grafts, the two failures relating to early vascular thrombosis rather than an inability to reinnervate the muscle grafts.     

The medial sural artery perforator free flap.

The medial sural artery supplies the medial gastrocnemius muscle and sends perforating branches to the skin. The possible use of these musculocutaneous perforators as the source of a perforator-based free flap was investigated in cadavers. Ten legs were dissected, and the topography of significant perforating musculocutaneous vessels on both the medial and the lateral gastrocnemius muscles was recorded. A mean of 2.2 perforators (range, 1 to 4) was noted over the medial gastrocnemius muscle, whereas in only 20 percent of the specimens was a perforator of moderate size noted over the lateral gastrocnemius muscle. The perforating vessels from the medial sural artery clustered about 9 to 18 cm from the popliteal crease. When two perforators were present (the most frequent case), the perforators were located at a mean of 11.8 cm (range, 8.5 to 15 cm) and 17 cm (range, 15 to 19 cm) from the popliteal crease. A series of six successful clinical cases is reported, including five free flaps and one pedicled flap for ipsilateral lower-leg and foot reconstruction. The dissection is somewhat tedious, but the vascular pedicle can be considerably long and of suitable caliber. Donor-site morbidity was minimal because the muscle was not included in the flap. Although the present series is short, it seems that the medial sural artery perforator flap can be a useful flap for free and pedicled transfer in lower-limb reconstruction.     

Extended approach to the vascular pedicle of the gracilis muscle flap: anatomical and clinical study

Dissection of the proximal gracilis vascular pedicle proceeds in a dark tunnel-like space deep to the adductor longus. With the application of a previously described technique for an extended approach to the lateral arm free flap, the authors describe a novel technique that improves observation and thus facilitates dissection of the proximal gracilis vascular pedicle. A retrospective review of data for 18 consecutive patients who underwent gracilis muscle free flap harvesting with this modified technique between March of 1999 and October of 2001 was conducted, to assess flap viability and patient outcomes. A cadaveric dissection was also performed, to study the anatomical features of the region in depth and to test the proposed flap modification. After the standard incision has been made, the dominant pedicle is exposed on the medial aspect of the gracilis muscle, running in a fascial cleft between the adductor longus and the adductor magnus. Intramuscular branches to the adductor longus are divided. A space is bluntly created anterior and lateral to the adductor longus by separating the fibrous connections to the surrounding adductor and sartorius muscles on both sides of the vascular pedicle. The gracilis muscle is then divided and passed deep to the adductor longus, into this space. With this new position, the final dissection of the pedicle can easily be performed. The confluence of the venae comitantes is frequently encountered, providing a larger-caliber single vein for microvascular anastomosis. The ages of the patients ranged from 9 to 70 years. The majority (14 of 18 patients) had traumatic wounds. The free flap survival rate was 100 percent. One minor complication of a seroma at the donor site was observed. One major complication of venous thrombosis was detected on postoperative day 3, with complete flap salvage. No other complications were noted. This technique is safe and permits direct approach to and excellent observation of the proximal aspect of the gracilis pedicle, without the need for headlights or deep retractors. An additional benefit is the frequent finding of a single larger vein from the merging of the venae comitantes close to the deep femoral vessels.     

The lower trapezius musculocutaneous flap from pedicled to free flap: anatomical basis and clinical applications based on the dorsal scapular artery

The pedicled lower trapezius musculocutaneous flap is a standard flap in head and neck reconstruction. A review of the literature showed that there is no uniform nomenclature for the branches of the subclavian artery and the vessels supplying the trapezius muscle and that the different opinions on the vessels supplying this flap lead to confusion and technical problems when this flap is harvested. This article attempts to clarify the anatomical nomenclature, to describe exactly how the flap is planned and harvested, and to discuss the clinical relevance of this flap as an island or free flap. The authors dissected both sides of the neck in 124 cadavers to examine the variations of the subclavian artery and its branches, the vessel diameter at different levels, the course of the pedicle, the arc of rotation, and the variation of the segmental intercostal branches to the lower part of the trapezius muscle. Clinically, the flap was used in five cases as an island skin and island muscle flap and once as a free flap. The anatomical findings and clinical applications proved that there is a constant and dependable blood supply through the dorsal scapular artery (synonym for the deep branch of the transverse cervical artery in the case of a common trunk with the superficial cervical artery) as the main vessel. Harvesting an island flap or a free flap is technically demanding but possible. Planning the skin island far distally permitted a very long pedicle and wide arc of rotation. The lower part of the trapezius muscle alone could be classified as a type V muscle according to Mathes and Nahai because of its potential use as a turnover flap supplied by segmental intercostal perforators. The lower trapezius flap is a thin and pliable musculocutaneous flap with a very long constant pedicle and minor donor-site morbidity, permitting safe flap elevation and the possibility of free-tissue transfer.     

Two new cutaneous free flaps: the medial and lateral thigh flaps

Two new cutaneous free-flap donor areas are described on the medial and lateral sides of the thigh. The medial thigh flap is supplied by an unnamed artery from the superficial femoral artery and is drained by the accompanying venae comitantes. Its nerve supply is from the medial femoral cutaneous nerve. The lateral thigh flap has its vascular pedicle from the third perforating artery of the profunda femoral artery and its accompanying vein. The lateral femoral cutaneous nerve provides sensation over the area. These flaps provide a large surface area of both skin and subcutaneous tissue without the usual bulk of subcutaneous fat and muscle. Their desirable features include long vascular pedicles with large vessel diameters and potential of being neurovascular flaps with specific sensory nerve supply and predictable anatomy. The principal disadvantage is that the donor site may leave a slight contour defect with primary closure or require grafting when a large flap is taken. We predict that these flaps will become important donor sites for reconstructive problems requiring resurfacing of cutaneous defects in various anatomic areas.