Hans-Jörg Oestern, Otmar Trentz and Selman Uranues (eds.)European Manual of MedicineGeneral Trauma Care and Related Aspects2014Trauma Surgery II10.1007/978-3-540-88124-7_15

15. Muscle Injuries

Kuno Weise¹

(1)

Medizinisches Begutachtungsinstitut, em. o. Prof. Eberhard Karls Universität Tübingen, Forchenweg 7, 72076 Tübingen, Germany

Kuno Weise

Email: info@prof-weise.de

Abstract

The weight-bearing and locomotor system of the human body is basically composed of the skeletal muscles and of the systems that transfer the power of the muscles (i.e., the tendons and aponeuroses) in the torso, spine, and extremities. The construction and shape of the individual muscles and their position in relation to the joints determine their function.

15.1 Basics

The weight-bearing and locomotor system of the human body is basically composed of the skeletal muscles and of the systems that transfer the power of the muscles (i.e., the tendons and aponeuroses) in the torso, spine, and extremities. The construction and shape of individual muscles and their position in relation to the joints determine their function.

15.1.1 Anatomy

The microstructure of a muscle, with its individual mixture of different types of fiber, has a substantial effect on its physiological properties. While to a great extent the muscles can be trained, tendons and their origins in the skeleton cannot be strengthened in the same way, which explains their tendency toward ruptures and strain injuries. The copious blood supply to the musculature is the reason for its excellent capacity for regeneration, although increasingly severe damage to muscle fibers means that full recovery is no longer possible. In such cases fibrous scar tissue develops in the region of the rupture.

15.1.2 Physiology and Pathophysiology

Muscle injuries can be subdivided according to their severity and thus their capacity for complete regeneration, or for a type of partial healing with scar formation, as follows:

Sore muscles – microinjuries of the white, fast-twitch muscle fibers caused by overstrain. The tearing of parts of the muscle fibril accompanied by edema and the secretion of pain-inducing agents in the extracellular space are responsible for the symptoms. By reducing the intensity of the strain using stretching and mild dynamic-concentric contractions, complete recovery from sore muscle can be achieved.
Muscle stretching/overstretching – the limit of the elasticity and stability of the muscle fibers is reached; complete recovery can generally be obtained. The distinction between overstretched and pulled muscle involving scarring and partial recovery is blurred.
Pulled muscle or muscle strain – distinguished by the tearing of individual contractile elements. A complete return to the patient’s former condition is impossible after this, the most frequent muscle injury. It is always repaired with scar tissue. Again, the distinction between muscle fiber rupture is blurred.
Tearing of muscle fibers – defined as a more extensive lesion resulting from exceeding the limits of elasticity and stability of the muscle fiber bundles. It always results, to a greater or lesser degree, in partial repair with scar tissue.

From a pathophysiological point of view, sore muscles, pulled muscles, and the tearing of muscle fibers are considered to be similar lesions differing in severity.

Myorrhexis or rupture of a muscle – can give the impression of a partial or complete gap in the continuity of a muscle and represents a further increase in severity in injuries to the skeletal musculature. Depending on the extent of the lesion in relation to the total cross-section of the muscle belly, surgical treatment may be indicated under certain circumstances. There is always some degree of partial repair regardless of the treatment strategy.
Myocele or muscle herniation – always results from blunt trauma, causing a rent in the fascia. As the muscle contracts, herniation occurs, causing much pain. Surgical closure of the rent in the fascia yields good results if the suturing is resilient.
Myositis ossificans – also caused by blunt trauma, where the blunt injury to the musculature leads to metaplasia of cells from the hematoma, resulting in the formation of osteoblasts. These are responsible for dystopic ossification.
Rupture of a muscle at its origin – can be partial or complete and, as a rule, is easy to diagnose. It is particularly frequent in young people and can manifest as bony lesions that are detectable on radiographs (e.g., rupture of the rectus femoris muscle at the pelvis) [1].

15.1.3 Specific Causes of Muscle Injuries

The causes of muscle injuries and damage range from acute or chronic overstrain, uncoordinated movement causing sudden changes in tension of the contractile elements, increased resistance or tension in the antagonistic muscles, to blunt trauma. The predisposing factors for muscle injuries or damage are as follows:

Insufficient warm up/stretching before sport activities
Inadequate blood supply to the musculature (cold)
Inadequate training
Poor technique, bad equipment
Generalized disease

The disparity between the condition of the muscle and the demands made of it is the cause of indirect lesions. The individual forms and severity of muscle injuries are considered by most experts to be different manifestations of similar pathogeneses and mechanisms. Given the blurred distinctions between diverse muscle injuries, damage is considered to be either reversible (sore muscles, stretching, and overstretching) or irreversible (tearing of muscle fibers, rupture of a muscle). Pulled muscle involving a greater degree of pathologically and anatomically detectable overstretching, extending to rupture of individual contractile elements with subsequent scar tissue, represents the boundary between the two groups. In contrast, direct muscle trauma is a result of local damaging forces and involves a risk of compartment syndrome or myositis ossificans.

Most muscle injuries occur during rapid acceleration or takeoff during poorly coordinated sequences of movements and under unfavorable general conditions in the context of sport activity (e.g., track and field, ball and racket sports, and martial arts). Most direct lesions of the skeletal musculature occur in contact sports such as football or martial arts.

In accordance with the injury hypothesis, sore muscles are considered to be partial damage to the muscle fibrils in the sense of overstrain, accompanied by local edema, and are completely reversible [2].

15.1.4 Basic Principles of the Clinical Examination

The principle symptom in the diagnosis of muscle injuries is pain. The pain ranges from an unpleasant dragging pain on stretching the muscles, to the generally less severe pain accompanying a pulled muscle, and finally to the sudden burst of debilitating pain that occur when a muscle or muscle fiber is torn. In contrast, ruptures are generally less painful. The intensity of the pain is an indicator of the extent of the injury in the muscle. After documenting patient history, local inspection and palpation are the foundations of clinical diagnosis. Swelling, hematoma, changes in muscle relief, painful antalgic postures, and loss of function as well as a palpable gap in the continuity of the muscle belly (dimpling) are typical characteristics of acute muscle injury. Local pressure and indirect muscle tension pain are further diagnostic parameters.

15.1.5 Diagnosis by Imaging Procedures

The use of ultrasound to visualise the nature, localization, and extent of muscle injury plays an essential part in diagnosis as well as in the choice of therapeutic procedure. The size of the gap in muscle continuity, visualized in this way, as well as that of the accompanying hematoma, influence the choice of further procedures. In unclear cases, an additional magnetic resonance imaging (MRI) scan can provide detailed information about the extent of injury. Radiographs, particularly of the adjacent joints, are sometimes indicated; they are obtained if myositis ossificans is suspected.

If compartment syndrome is suspected, measurement of the pressure in the compartment is indicated in addition to clinical diagnosis on the basis of pain and swelling and shiny skin.

Laboratory tests to determine muscle-specific enzymes are indicated only in the case of massive, extensive, muscle contusions in the context of high-speed or crush injuries. What is known as crush syndrome, with its life-threatening secondary phenomena (crush kidney), may be a consequence of these types of traumatic events. Electrodiagnostic testing such as electromyography is indicated only if there is accompanying nerve injury.

15.1.6 Organ-Specific Imaging

Apart from the ultrasound procedure described above as the standard procedure, no further imaging procedures are necessary except MRI, which is sometimes required, and radiography, which is ordered to exclude bone injuries.

15.2 Special Muscle Injuries and Damage to the Upper Extremity

Deltoid muscle
Biceps brachii muscle
Triceps brachii muscle
Compartment syndrome in the forearm

Muscle injuries in the region of the upper extremity generally give the impression of a strain or tear in the fiber, and less frequently of a partial rupture in the belly of the muscle. A compartment syndrome in the lower arm develops because of increased pressure in the fascial compartments as a result of edema and compression of the arterioles or venules. In general, injuries to the musculature of the upper extremity are rare. In contrast, acute lesions or damage induced by degeneration to their tendinous origins occur more frequently. Compartment syndromes in the forearm are concomitant phenomena of more severe, local, blunt force trauma. While indirect damage tends to occur in the context of sport activity (e.g., gymnastics, throwing sports, boxing), direct muscle traumas are observed predominantly in the context of industrial or road traffic accidents (e.g., trapping the forearm in a machine).

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