Musculoskeletal Disorders
Injuries
2
NSC 834 – Advanced Pathophysiology
Mary DeLetter, PhD, RN
Associate Professor
Dept. of Baccalaureate and Graduate Nursing
Eastern Kentucky University
Musculoskeletal Disorders: Injuries
1 / This is Dr. Mary DeLetter. This presentation will focus on Injuries to the Musculoskeletal System.2 / If you are not familiar with basic bone and soft tissue anatomy and physiology, you may want to review Figures 41-3 and 41-4 in your textbook.
3 / There are three different types of bone cells that will be discussed as part of this section on the musculoskeletal system.
Osteoclasts are large cells that dissolve bone. They are produced in the bone marrow and are related to white blood cells.
Osteoblasts are multifunctional cells that form new bone. These are also produced in the bone marrow, and are similar to structural cells of other body systems. Osteoblasts help produce new bone from bone collagen and other proteins. Osteoblasts also help regulate calcium and other mineral deposition in bones.
When the osteoblasts have finished filling in a bone cavity, the cells change form, becoming flat and lining the surface of the bone. The old osteoblasts are called Lining Cells, and regulate passage of calcium into and out of the bone. Finally, the osteoblasts respond to hormone stimulation by making special proteins that activate the osteoclasts to break down bone.
Osteocytes are the cells inside the bones. They originate as osteoblasts, but become osteocytes as the new bone is formed. The osteocytes get surrounded by new bone as osteoblasts are activated to a bone repair site.
4 / I will start by talking about skeletal injuries. A fracture is any break in the continuity of the bone. There are several different ways of classifying fractures, so be sure to look at the picture in your textbook to understand the different types of fractures. Classification of fractures, explained with more detail over the next few slides, includes a determination of whether fractures are
· Open or closed,
· Complete or incomplete,
· Displaced or in normal alignment,
· The number of bone fragments, and
· The orientation of the fracture.
5 / Closed fractures, formerly called simple fractures, do not penetrate the skin, while open fractures, formerly called compound fractures, are those which do penetrate the skin.
6 / The Gustilo and Anderson Open Fracture Classification System is a scale which was developed primarily by military health care system, based on the need to prioritize the care of wounded military personnel. You may see open fractures classified using this system which helps describe the condition of the injury and direct the initial management and follow-up surgical intervention.
7 / A complete fracture means that the bone has broken all the way through and is in two or more pieces; an incomplete or greenstick fracture indicates that the bone is damaged, but still in one piece.
8 / In a displaced fracture, the two ends of the bone are separated from one another, whereas a non-displaced fracture indicates that bone remains in normal alignment.
9 / A comminuted fracture is one in which the bone has been shattered into more than two fragments.
10 / The orientation of the fracture line is also relevant:
· Linear fractures run parallel to the long axis of the bone
· Oblique fractures are slanted to the long axis of the bone
· Transverse fractures occur straight across the bone, and
· Spiral fractures circle around the bone.
11 / When a bone is fractured, several components of the bone structure are disrupted, including the periosteum, where the blood vessels and nerves are located, the bone cortex, which is the hard outer layer, the bone marrow, and the surrounding soft tissue.
Bleeding can occur from all damaged ends of the bone as well as the surrounding soft tissue. As a result, hematoma can form in the medullary bone canal, between the fractured bone ends, and underneath the periosteum. As you will see in a few slides, this hematoma formation is the first stage of bone repair.
12 / Next, there is bone tissue necrosis next to the fracture. This produces an inflammatory response, accompanied by vasodilation, leakage of plasma and leukocytes into the surrounding bone and soft tissue, and an infiltration of inflammatory leukocytes and mast cells.
During the initial 48-hours following a bone injury, there is increased blood flow to the entire bone, followed by activation of the bone-forming osteoblasts in the periosteum, endosteum, and bone marrow.
13 / Bone Repair begins within 48 hours of the initial injury.
· The first stage is the hematoma formation in the various bone areas: the periosteum, medullary canal, and fractured bone ends.
· Next, granulation tissue begins to form under the periosteum, forming the first phase of a callus.
· Third, the osteoblasts activated in the procallus form a membranous boney substance called the callus.
· The osteoblasts continue to rebuild bone, replacing the callus with new lamellar or trabecular bone, the spongy bone which surrounds the bone marrow.
· Finally, the bone remodeling begins.
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14 / Bone remodeling occurs when the Periosteal and endosteal bone surfaces are rebuilt, or remodeled, to the same size and shape of the bone before the injury occurred. There are three phases of remodeling:
· In the activation phase, there is apoptosis, or cell death of the osteocytes.
· In the second phase, called , resorption, dead osteocytes, or dead bone is broken down by the osteoclasts. During this process, there is a transfer of minerals such as calcium from the formerly healthy bone to the bloodstream.
· Finally, the osteoblasts form new bone to replace the injured and dead bone. This process of remodeling and healing takes approximately 6-8 weeks.
15 / A strain is a stretch, tear or rupture of a tendon that connects the muscle to an adjacent bone. It can be caused by an injury or can be spontaneous, especially following extended corticosteroid use or systemic conditions which cause joint inflammation, such as rheumatoid arthritis or systemic lupus erythematosus.
Strains are most common in tendons of frequently used joints, bones or muscles – the hands and feet, knee, upper arm, thigh, or heel.
16 / A sprain is a stretch, tear or ruptures of ligaments that connects bone to adjacent bone. Again, the most common are small but frequently used and vulnerable joints, such as the wrists, ankles, elbows, or knees.
An injury that completely separates the tendon or ligament from the adjacent bony structure is called an avulsion.
17 / Many people think of strains and sprains as being less serious than bone fractures, but in reality, the pathophysiology is important, and attention to the healing process should be just as long as a fracture.
Initially, the inflammatory process allows exudation to rush into the soft tissue at the injury site. In this early process, granulation tissue grows inward from the soft tissue toward the bone.
Within 4-5 days of the injury, collagen growth begins. Initially, this is a disorganized growth, but becomes organized as the healing continues.
The healing tendon separates from the inflamed soft tissue, but is still weak.
Similar to all tissue healing, about 4 – 6 weeks is required for full soft tissue repair.
18 / A subluxation is the loss of contact between tow bony surfaces. As shown in the next slide, the articulation of two bones in a joint is broken, causing temporary separation of the bones.
A dislocation is a temporary displacement of the bone from its normal position in the joint. It creates a disruption in soft tissue surrounding the joint. Dislocations are not usually serious unless they are not corrected. A prolonged untreated dislocation increases the risk of avascular necrosis from a lack of blood supply to the joint surfaces.
19 / Here you can see the simple artist’s illustration of normal, subluxed, and dislocated joints. Subluxations and dislocations can occur from congenital or traumatic causes. Congenital issues include muscular imbalances from neuromuscular diseases or weaknesses, disarticulation of the joints from joint disorders such as rheumatoid arthritis, or joint instability from any musculoskeletal disorder.
Trauma is also a common cause of subluxations or dislocations, especially from sports or athletic-related injuries.
The most common sites for subluxations and dislocations include shoulders, elbows, wrists, fingers, hips, or knees.
20 / Tendinopathies generally develop from repeated stress or trauma to the tendon or articulating joint. Three common conditions include:
· Tendinosis – a chronic degradation of collagen fibers in the tendon. This cellular level destruction often results in acute or chronic tendon injury.
· Tendinitis is an acute or chronic inflammation of the tendon, and can occur from either metabolic diseases such as inflammatory arthritis or injury.
· Paratenonitis is an inflammation of the paratenon, the outer layer or covering of the tendon. This is particularly common when a tendon rubs excessively over a bony protuberance. The Achilles tendon is a common site of this injury, since it does not pass through a synovial sheath, but is only covered by the paratenon.
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21 / The pathophysiology of a tendinopathy starts with the accumulation of fluid during the inflammatory process. The tendons and enclosing sheaths, such as the paratenons and the synovial swell. The sheaths thicken, limiting tendon mobility and causing pain. Microtears of the tendons and surrounding structures cause bleeding, producing further edema and exacerbating the pain.
22 / Bursitis is an inflammation of the bursa, or the fluid-filled sacs lined by a synovial membrane that keep two surfaces from rubbing together. Bursitis most commonly results from overuse of chronic pressure on the bursa of a particular joint. Once inflamed, the bursal sac fills becomes engorged with exudative fluid and swells to a noticeable fluid sac under the skin. The inflammation can spread to adjacent tissue, causing pain, but s usually temporary, lasting anywhere from a few days to a few weeks.
23 / Snyovitis is an inflammation of a synovial membrane, usually painful, particularly on motion, and characterized by fluctuating swelling, due to exudative engorgement which is reabsorbed when inflammation resolves. It is usually temporary, resolving as the inflammation decreases.
24 / Muscle strains most often result from sports or athletic injuries. When the muscle is stretched beyond its capacity, local muscle damage results. Patients who do not stop the injurious activity will repeatedly strain or injure their muscle, producing chronic muscle strain.
25 / Rhabdomyolysis, also called myoglobinuria, is a condition of severe muscle trauma with muscle cell loss. As muscle cells are damaged, they release myoglobin, an intracellular muscle protein, which enters the blood stream. The myoglobin is not filtered by the renal tubules, so is secreted in the urine.
The pathophysiology of rhabdomyolysis comes from the excessive pressure increase within the muscle compartment. The muscle suffers a compromise in the microvascular network, resulting in muscle cell death.
Two outcomes of severe muscle cell loss are compartment syndrome and crush syndrome, explained in more detail on the next slide.
26 / A crush injury occurs when a body part, particularly a large muscle, is subjected to a high degree of force or pressure, usually after being squeezed between two heavy objects and the affected area is immobile for an extended period of time. Like many discoveries in health care, crush syndrome resulting from crush injuries was first recognized by military health personnel caring for military or civilian patients who experienced compression trauma.
More recently, it has been recognized that crush injuries can also occur in muscles subjected to toxic substances such as snake venoms, toxic gases, or excessive drug or alcohol use.
The inflexible muscle fasciae does not allow outward swelling when blood begins to collect in the injured tissue. As a result, the muscle becomes more and more engorged with blood, the pressure within the muscle compartment increases, eventually damaging the muscle, vessels, and nerves. The outcome of a crush injury is an initial Compartment Syndrome which can progress to Crush Syndrome.
Compartment Syndrome produces tissue damage, muscle infarction, and irreversible muscle death. When the muscle cells die, the patient is at great risk for Crush Syndrome.
Crush syndrome is a localized crush injury with systemic manifestations caused by the myoglobin release following the traumatic rhabdomyolysis. It was first identified during WWII, when crush injuries were initially thought to be minimal. However, as the muscle infracted, the myoglobin and other toxins leaking into the body produced hypotension, renal failure, and cardiac arrhythmias.
Long-term consequences of patients who survive Crush Syndrome include the loss of extremities and renal and cardiac compromise.
27 / This concludes the presentation on Injuries to the Musculoskeletal System.