Human Latissimus Dorsi Research Articles

Ventilator induzierter Zwerchfellschaden: ein Update

There is rising evidence that ventilator-induced diaphragmatic dysfunction (VIDD) is not just an artifactual finding from animal studies, but actually occurs in humans undergoing invasive mechanical ventilation. Initial research findings in humans have demonstrated that periods of controlled invasive mechanical ventilation lasting just 18 - 69 hours can lead to a marked reduction in diaphragmatic myofibers. More recently, it has been shown that even short periods (e. g. two-hours) of controlled invasive mechanical ventilation are sufficient to initiate VIDD. The evidence available at present suggests that VIDD is most likely based on increased proteolysis of the respiratory muscles. Moreover, VIDD seems not to be part of a general muscle wasting process, as suggested by the fact that e. g. the human latissimus dorsi and the pectoralis major muscles seem not to be subjected to early muscle fiber atrophy when directly compared to the human diaphragm. Novel in vivo data have also revealed that VIDD in humans is associated with a reduction in diaphragmatic force generation after only one day of controlled invasive mechanical ventilation. This impairment was observed to progress further over the one-week investigation period. The introduction of a simple bedside ultrasound measurement of diaphragmatic function is of great importance to the clinician, as it may serve as a surrogate measure for VIDD, with high predictive value. Regarding potential therapeutic interventions against VIDD, the primary aim should be to encourage sufficient diaphragmatic use in susceptible patients so as to avoid VIDD; this approach remains in fundamental contrast to that of reducing respiratory muscle load by (invasive) mechanical ventilation.

Architectural analysis and predicted functional capability of the human latissimus dorsi muscle

The latissimus dorsi is primarily considered a muscle with actions at the shoulder, despite its widespread attachments at the spine. There is some dispute regarding the potential contribution of this muscle to lumbar spine function. The architectural design of a muscle is one of the most accurate predictors of muscle function; however, detailed architectural data on the latissimus dorsi muscle are limited. Therefore, the aim of this study was to quantify the architectural properties of the latissimus dorsi muscle and model mechanical function in light of these new data. One latissimus dorsi muscle was removed from each of 12 human cadavers, separated into regions, and micro-dissected for quantification of fascicle length, sarcomere length, and physiological cross-sectional area. From these data, sarcomere length operating ranges were modelled to determine the force-length characteristics of latissimus dorsi across the spine and shoulder ranges of motion. The physiological cross-sectional area of latissimus dorsi was 5.6±0.5 cm2 and normalized fascicle length was 26.4±1.0 cm, indicating that this muscle is designed to produce a moderate amount of force over a large range of lengths. Measured sarcomere length in the post-mortem neutral spine posture was nearly optimal at 2.69±0.06 μm. Across spine range of motion, biomechanical modelling predicted latissimus dorsi acts across both the ascending and descending limbs of the force-length curve during lateral bend, and primarily at or near the plateau region (where maximum force generation is possible) during flexion/extension and axial twist. Across shoulder range of motion, latissimus dorsi acts primarily on the plateau region and descending limbs of the force length curve during both flexion/extension and abduction/adduction. These data provide novel insights into the ability of the latissimus dorsi muscle to generate force and change length throughout the spine and shoulder ranges of motion. In addition, these findings provide an improved understanding of the spine and shoulder positions at which the force-generating capacity of this muscle can become jeopardized, and consequently how this may affect its spine-stabilizing ability.

Myosin Isoforms and Contractile Properties of Single Fibers of Human Latissimus Dorsi Muscle

The aim of our study was to investigate fiber type distribution and contractile characteristics of Latissimus Dorsi muscle (LDM). Samples were collected from 18 young healthy subjects (9 males and 9 females) through percutaneous fine needle muscle biopsy. The results showed a predominance of fast myosin heavy chain isoforms (MyHC) with 42% of MyHC 2A and 25% of MyHC 2X, while MyHC 1 represented only 33%. The unbalance toward fast isoforms was even greater in males (71%) than in females (64%). Fiber type distribution partially reflected MyHC isoform distribution with 28% type 1/slow fibers and 5% hybrid 1/2A fibers, while fast fibers were divided into 30% type 2A, 31% type A/X, 4% type X, and 2% type 1/2X. Type 1/slow fibers were not only less abundant but also smaller in cross-sectional area than fast fibers. During maximal isometric contraction, type 1/slow fibers developed force and tension significantly lower than the two major groups of fast fibers. In conclusion, the predominance of fast fibers and their greater size and strength compared to slow fibers reveal that LDM is a muscle specialized mainly in phasic and powerful activity. Importantly, such specialization is more pronounced in males than in females.

The nutrition of active muscle flaps

In the last 25 years, techniques utilising muscle flaps to perform mechanical work have become part of the reconstructive surgeon's repertoire. In this paper, these techniques and the particular physiological challenges faced by active flaps are discussed and a sub-classification of muscle flaps into passive and active is proposed. A series of experiments are described that were designed to compare local pO(2) and gaseous perfusion, at multiple sites in pedicled tibialis anterior muscle flaps and controls, using specially developed dual amperometric microelectrodes, in an in vivo rabbit model. No significant difference in perfusion was found comparing flaps and controls until the flap's vascular pedicles were divided and ligated, and then flap perfusion fell to zero. Flap and control oxygenation varied significantly only during mobilisation and again, after pedicle division and ligation (F[13,55] = 12.3; P < 0.001)]. This absence of functional ischaemia as a consequence of mobilisation in the model used suggests the practice of delaying electrical conditioning of muscle flaps in dynamic cardiomyoplasty and neoanal sphincteroplasty might be unnecessary if these data are reproduced in human latissimus dorsi muscle. The relevance of these findings to free flap oxygen consumption and to the delay phenomenon is discussed.

Differences in intramuscular vascular connections of human and dog latissimus dorsi muscles

Background. Distal ischemia and necrosis of the dog latissimus dorsi muscle flap used in experimental cardiomyoplasty have been reported. However, little information on the intramuscular vascular anatomy of the dog latissimus dorsi is available. It is unclear whether there are any anatomic factors relating to the muscle flap ischemia and necrosis, and whether the dog latissimus dorsi is a suitable experimental model. Methods. To study the intramuscular vascular territories in the dog latissimus dorsi muscle, and to compare the intramuscular vasculature of the dog with that of the human, 5 fresh dog cadavers and 7 fresh human cadavers were injected with a mixture of lead oxide, gelatin, and water (200 mL/kg) through the carotid artery. Both the dog and the human latissimus dorsi muscles and neurovascular pedicles were dissected and radiographed. The intramuscular vascular anatomy of the latissimus dorsi muscles was compared. Results. Radiographs demonstrate clearly that the pattern of latissimus dorsi intramuscular anastomoses between branches of the thoracodorsal artery and the perforators of posterior intercostal arteries in the proximal half of the muscle are different between the dog and the human. In the dog muscle, vascular connections between the thoracodorsal artery and the posterior intercostal arteries are formed by reduced-caliber choke arteries, whereas four to six true anastomoses without a change in caliber between them are found in the human muscle. The portion of the latissimus dorsi muscle supplied by the dominant thoracodorsal vascular territory was 25.9% ± 0.3% in the dog and 23.9% ± 0.5% in the human. For further comparison, an extended vascular territory in the latissimus dorsi muscle was demonstrated, including both the thoracodorsal territory and the posterior intercostal territories. The area of the extended vascular territory was 52% ± 0.5% of the total muscle. Conclusions. The dog latissimus dorsi model may not be a perfect predictor of the behavior of the human latissimus dorsi muscle flap in cardiomyoplasty.

Energy metabolism of fibre types within fascicles of human muscles

In human latissimus dorsi muscle a preponderance of type 2b fibres in the first fascicle layer and of type 1 fibres in the second layer was found. NADH-dehydrogenase (NADH) and alpha-glycerophosphate dehydrogenase (GPDH) which were measured histophotometrically in type 1, 2a, and 2b fibres showed either extreme or only partial overlapping regarding the activity of metabolic enzymes. In different fascicle layers the average activity of both enzymes did not differ significantly among the fibres of the same type, neither did the NADH and GPDH activity of type 2a and 2b.

Role of xanthine oxidase in reperfusion injury of ischemic skeletal muscles in the pig and human.

We investigated whether xanthine oxidase (XO) is a major source of oxygen-derived free radicals (oxy-radicals) in the pig and human skeletal muscles. It was observed that xanthine dehydrogenase and XO activities in nonischemic pig latissimus dorsi (LD) and gracilis muscles and human LD and rectus abdominis (RA) muscles were < 0.5 mU/g wet wt. The pig LD muscle hypoxanthine content increased significantly from 0.33 +/- 0.02 to 2.33 +/- 0.44 mumol/g dry wt after 5 h of warm ischemia, but the muscle uric acid content remained unchanged up to 2 h of reperfusion. Similarly, the hypoxanthine content in the human LD and RA muscles increased from 0.33 +/- 0.03 to 0.84 +/- 0.23 mumol/g dry wt after 2.0-3.5 h of warm ischemia, and the muscle uric acid content remained unchanged at the end of 15-90 min of reperfusion. Furthermore, 5 days of allopurinol treatment (25 mg/kg iv twice daily) starting 2 days before ischemia or 3 days of oxypurinol treatment (25 mg/kg iv twice daily) starting 15 min before reperfusion did not attenuate the extent of skeletal muscle necrosis in pig LD muscles subjected to 5 h of ischemia and 48 h of reperfusion. However, deferoxamine treatment (250 mg/kg iv twice daily) starting before or after ischemia, as described above, significantly reduced the extent of pig LD muscle necrosis. Finally, at 2 and 48 h of reperfusion significantly higher muscle neutrophil contents were seen in ischemic than in nonischemic control pig LD muscles. Neutrophil depletion with mechlorethamine (0.75 mg/kg iv) significantly reduced the extent of necrosis in pig LD muscles. These observations indicate that XO is not a major source of oxy-radicals in ischemia/reperfusion injury in the pig gracilis and LD muscles and human RA and LD muscles.

Anatomical rationale for use of the latissimus dorsi flap during the cardiomyoplasty operation.

The cardiomyoplasty procedure involves the use of a transformed skeletal muscle to augment cardiac pump function or to substitute for the heart after parietal resection. This study of the intramuscular vascularization of latissimus dorsi was carried out in order to establish the relationship between the dominant thoracodorsal blood supply and the distal supply issued from the intercostal and lumbar arteries. This data is mandatory for the safe manipulation of the muscle flap during cardiomyoplasty. Thirty human latissimus dorsi flaps were carefully studied. We confirmed anatomically as well as angiographically previous macroscopic anatomical reports, as well as the constancy of the neurovascular pedicle. Three principal branching patterns were observed for the thoracodorsal artery. The thoracodorsal artery divides into three main tributaries in 20/30 (67%), and into two tributaries in 10/30 (33%) of the flaps observed. When three tributaries were observed, one of them was a small recurrent artery for the proximal third of the latissimus dorsi (14/20, 70%). Thus the distal vascularization is actually dependent on three principals in 6/30 (20%) and two principals in 24/30 (80%). From these two or three principals emerge several subsequent longitudinal branches (5 to 9) that have a straight course until their distal anastomoses with segmental arterial pedicles issued from intercostal and lumbar arteries. The latter ligation can thus occur without ischemic damage to the medial and distal aspect of the flap. This study emphasizes that, due to macroscopic anatomic features and systematic intramuscular vascular distribution, the latissimus dorsi is probably the most suitable muscle for the purpose of cardiomyoplasty.