Below is a narrated animation about electrical conduction of the heart and ECG anatomy. Click here to license this video and/or other cardiovascular related videos on Alila Medical Media website.
The cardiac conduction system consists of the following components:
– The sinoatrial node, or SA node, located in the right atrium near the entrance of the superior vena cava. This is the natural pacemaker of the heart. It initiates all heartbeat and determines heart rate. Electrical impulses from the SA node spread throughout both atria and stimulate them to contract.
– The atrioventricular node, or AV node, located on the other side of the right atrium, near the AV valve. The AV node serves as electrical gateway to the ventricles. It delays the passage of electrical impulses to the ventricles. This delay is to ensure that the atria have ejected all the blood into the ventricles before the ventricles contract. Fig. 1: The cardiac conduction system. Click on image to see it on Alila Medical Media website where the image is also available for licensing (together with other related images and videos).
– The AV node receives signals from the SA node and passes them onto the atrioventricular bundle, AV bundle or bundle of His.
– This bundle is then divided into right and left bundle branches which conduct the impulses toward the apex of the heart. The signals are then passed onto Purkinje fibers, turning upward and spreading throughout the ventricular myocardium.
Understanding ECG/EKG
Electrical activities of the heart can be recorded in the form of electrocardiogram, ECG or EKG. An ECG is a composite recording of all the action potentials produced by the nodes and the cells of the myocardium. Each wave or segment of the ECG corresponds to a certain event of the cardiac electrical cycle. Fig. 2: Electrical activities of the heart and relationship to ECG. Click on image to see it on Alila Medical Media website where the image is also available for licensing (together with other related images and videos).
When the atria are full of blood, the SA node fires, electrical signals spread throughout the atria and cause them to depolarize. This is represented by the P wave on the ECG. Atrial contraction , or atrial systole (SIS-toe-lee) starts about 100 mili-seconds after the P wave begins.
The P-Q segment represents the time the signals travel from the SA node to the AV node.
The QRS complex marks the firing of the AV node and represents ventricular depolarization:
– Q wave corresponds to depolarization of the interventricular septum.
– R wave is produced by depolarization of the main mass of the ventricles.
– S wave represents the last phase of ventricular depolarization at the base of the heart.
– Atrial repolarization also occurs during this time but the signal is obscured by the large QRS complex.
The S-T segment reflects the plateau in the myocardial action potential. This is when the ventricles contract and pump blood.
The T wave represents ventricular repolarization immediately before ventricular relaxation, or ventricular diastole (dy-ASS-toe-lee).
The cycle repeats itself with every heartbeat.
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Breast reconstruction surgery is a vital component of breast cancer treatment plan. Breast reconstruction surgery can be done immediately after mastectomy or in a delayed operation depending on whether post-mastectomy radiation therapy will be needed. Immediate reconstruction offers better aesthetic results if radiation is not needed. When radiation is required, delayed reconstruction is preferred to avoid possible complications.
Breast Implant
Breast implant involves insertion of a breast prosthesis made of synthetic material. A typical breast implant has a silicone shell and is filled with saline or silicone gel.
Advantages: requires short initial hospital stay, simplest of all procedures, no additional scars, no other sites on body to heal except for the breast.
Disadvantages: As a result of the body’s response to foreign material, the implant may be squeezed within scar tissues leading to distorted shape (capsular contracture), leak, rupture and infection. In fact as many as half of all women will require surgery to remove the implant later in life.
Natural Tissue Breast Reconstruction Surgery
These techniques use body’s own tissue for the new breast. A section (flap) of skin, fat, and possibly muscle is harvested from a donor site elsewhere in the body and transferred to the chest to make the new breast. Possible tissue donor sites include: lower abdomen, back, buttock and area above it, inner thigh. Lower abdomen is by far the preferred donor site as it comes with a bonus of a flatter tummy after operation.
Advantages compared to breast implants: The use of autologous tissue allows the reconstruction of a breast which looks and feels most like a normal breast. More importantly, this also solves the problem of the new breast being rejected by body’s immune system.
Disadvantages compared to breast implants: Longer initial hospital stay; additional scar on the donor site; donor site may be weaken due to loss of muscle.
Below we discuss different techniques available for breast reconstruction surgery with lower abdomen as the donor site, in order from the oldest to the newest, with advantages and disadvantages of each as compared to each other.
TRAM flaps
Transverse Rectus Abdominus Myocutaneous flap – the first of all natural tissue reconstruction technique.
Fig. 1 : Pedicle TRAM flap breast reconstruction surgery. Click on image to see it on Alila Medical Media website where the image is also available for licensing.
The original (pedicled) TRAM flap (Fig. 1) : A section of skin and fat is cut from the lower abdomen. One of the rectus abdominis muscles (six-pack muscles) is divided in the lower abdomen. The lower end of the muscle remains attached to the skin/fat tissue. This is the flap that is now attached to the body by the upper end of the muscle at its original position. The flap is rotated together with the muscle and passed under the skin to the new location in the chest. Here it is shaped to form the new breast. The flap is supplied by the blood vessels that run inside the rectus abdominis muscle. A piece of synthetic mesh is placed in the abdomen to provide support for the abdominal wall that is now weakened due to removal of the muscle.
Advantages: Relatively simpler procedure compared to newer techniques as microsurgery expertise is not required, more surgeons are able to offer this procedure.
Disadvantages: Significant loss of muscle from the abdomen makes the abdominal wall weakened and subject to risk of hernia; attachment of the flap to the body makes it harder to be configured into desired shape.
Free TRAM Flaps
An improvement from the original TRAM flaps technique. In this procedure, a section of skin, fat and part of rectus abdominis muscle with blood vessels within it, is separated completely from the body (hence “free”) and transferred to the breast location. The blood vessels of the flap (deep inferior epigastric artery and vein) are connected to recipient vessels in the breast using microsurgery technique.
Fig. 2 : Free TRAM flap breast reconstruction surgery. Click on image to see it on Alila Medical Media website where the image is also available for licensing.
Advantages: Free flaps are easier to sculpt into desired shape; blood supply is more robust.
Disadvantages: Microsurgery expertise is required; weakened abdominal wall due to muscle loss.
A modification of the procedure called muscle-sparing (MS) free TRAM flap is designed to remove only a minimum amount of muscle.
DIEP Flaps
Deep Inferior Epigastric Perforator flaps. A significant improvement from TRAM flaps. In this procedure the blood vessels (deep inferior epigastric artery and vein) are carefully dissected from the muscle. An incision is made in the rectus abdominis muscle for dissection of blood vessels but no muscle is taken out. The flap contains skin, fat, blood vessels but no muscle. The blood vessels of the flap are then connected to recipient vessels in the breast using microsurgery technique (Fig. 3 and Fig. 5).
Fig. 3 : DIEP flap breast reconstruction surgery. Click on image to see it on Alila Medical Media website where the image is also available for licensing.
Advantages: all advantages of a free flap; no muscle taken from donor site.
Disadvantages: Microsurgery required; longer operation time; not offered by many surgeons.
SIEA Flaps
This procedure is based on a different set of blood vessels – Superficial Inferior Epigastric Artery and Vein. These vessels supply the skin and fat tissue of the abdomen and run within the fat layer. With this flap, the abdominal muscle is left untouched, and therefore this is the preferred technique whenever it’s possible. The reason why this is not widely used is because these vessels are not large enough in 90% of patients. Commonly, these superficial blood vessels are approached first during surgery. If the surgeon sees that they are big enough, a SIEA flap will be used, if not, a DIEP flap will be performed instead.
Fig. 4 : SIEA flap breast reconstruction surgery. Click on image to see it on Alila Medical Media website where the image is also available for licensing.
Advantages: all advantages of a free flap; no muscle taken from donor site; no damage to the muscle.
Disadvantages: only possible in about 10% of women; microsurgery required; not offered by many surgeons.
Fig. 5 : Comparing the flaps from different breast reconstruction surgery techniques. Click on image to see it on Alila Medical Media website where the image is also available for licensing.
The videos on this page can be downloaded upon purchase of a license on Alila Medical Media website. Click here!
Sciatica or sciatic neuralgia is a common condition in which one of the spinal nerve roots of the sciatic nerve is compressed resulting in lower back, buttock and leg pain. Sciatic nerve is a large nerve derived from 5 spinal nerve roots (L4, L5, S1, S2 and S3). It runs from the lumbar spine through the buttock down the leg and foot on the posterior side. There is one sciatic nerve on each (right and left) side of the body. Typically only one side of the body is affected.
Fig. 1 : Sciatic nerve anatomy and pain patterns of sciatica. Only one side (right leg) is illustrated for simplicity. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Symptoms
A typical sciatica pain is described as a sharp shooting pain in the lower back, down the buttock, thigh and leg on one side of the body. There may also be numbness, burning and tingling sensations. The pain can get worse with sitting, moving, sneezing, or coughing.
The patterns of pain depend on which nerve root is compressed, and follow the dermatome distribution (Fig. 1).
Causes
The most common cause of sciatica is herniated spinal disc. The spinal disc is a soft elastic cushion that sits in between the vertebrae of the spine. With age, the discs become rigid and may crack, the gel-like center of the disc may protrude out and become a herniation outside the normal boundaries of the disc. Disc herniation presses on the nerve root as it exits the spine. Fig. 2 : Anatomy of the lumbar spine, lateral view. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Fig. 3 : Normal disc and herniated disc, superior view. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Treatment
In majority of the cases the condition resolves by itself after a few weeks of rest and conservative treatment. Pain relief, nonsteroidal anti-inflammatory drugs and muscle relaxants may be prescribed. Stretching exercises and physical therapy may be recommended.
Surgery may be needed if the the pain doesn’t go away after 3 months or more of conservative treatments. The herniated disc may be removed (discectomy) or part of the bone of the vertebrae may be cut to make room for the nerve (laminotomy).
Piriformis syndrome (PS) is a neuromuscular condition where the piriformis muscle – one of the deep gluteal muscles – presses on and compresses the sciatic nerve causing pain, tingling and numbness in the buttock area, and down the path of sciatic nerve to the thigh and leg. Sciatic nerve runs under the piriformis muscle (Fig. 1) and may be irritated when the muscle is too tight or shortened due to spasms. Piriformis syndrome is to be differentiated from sciatica which shows similar symptoms but has different causes.
Fig. 1 : Piriformis syndrome. Posterior view of the pelvis showing location of piriformis muscle and sciatic nerve. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Diagnosis is difficult as it produces similar symptoms as sciatica and is commonly done by exclusion of sciaticacaused by compression of sciatic nerve roots by a herniated disc.
Fig. 2 : Sciatica caused by compression of spinal nerve roots by a herniated disc. Lateral view of the lumbar spine. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Causes and Risk factors
– Anatomical abnormality of the nerve/muscle relation. Some people are more likely to get PS than others.
– Tightness or spasm of piriformis muscle due to overuse injury. This commonly happens in sport activities that put pressure on the piriformis muscle such as bicycling, running without proper stretching, or any activity that involves repeated movements of the leg performed in sitting position.
Treatment
– Conservative treatment includes stretching exercises, massage, avoidance of causative activities.
– Physical therapy that strengthens the gluteus maximus, gluteus medius, and biceps femoris is usually recommended to reduce strain on the piriformis muscle.
– Relief of symptoms may be achieved with anti-inflammatory drugs or muscle relaxants.
Temporomandibular joint (TMJ) anatomy and function
Below is a narrated animation about TMJ anatomy, disc displacement and natural adaptation. Click here to license this video and/or other related videos on Alila Medical Media website.
The temporomandibular joint (TMJ) is the joint between the lower jawbone – the mandible – and the temporal bone of the skull (Fig. 1). The TMJ is responsible for jaw movement and is the most used joint in the body.
The TMJ is essentially the articulation between the condyle of the mandible and the mandibular fossa – a socket in the temporal bone. The unique feature of the TMJ is the articular disc – a flexible and elastic cartilage that divides the joint into two parts: a upper joint and a lower joint. . Fig. 1 : Anatomy of the TMJ with jaw closed and open. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
The disc serves as a cushion between the two bone surfaces. The disc lacks nerve endings and blood vessels in its center and therefore is insensitive to pain. Anteriorly it attaches to lateral pterygoid muscle – a muscle of mastication (chewing). Posteriorly it continues as retrodiscal tissue fully supplied with blood vessels and nerves. This is commonly the source of pain in disorders with anterior disc displacement (see below).
The jawbone (mandible) is the only bone that moves when the mouth opens. The first 20 mm (three quarters of an inch) opening involves only a rotational movement of the condyle within the socket. For the mouth to open wider, the condyle and the disc have to move out of the socket, forward and down the articular eminence, a convex bone surface located anteriorly to the socket (see Fig.1 and video below). This movement is called translation.
Click here to see an animation of normal TMJ function on Alila Medical Media website where the video is also available for licensing.
TMJ disorders
The most common disorder of the TMJ is disc displacement, and in most of the cases, the disc is dislocated anteriorly (Fig. 2, middle and lower panels). As the disc moves forwards, the retrodiscal tissue is pulled in between the two bones. This can be very painful as this tissue is fully vascular and innervated, unlike the disc. The movements made by chewing or even talking cause a chronic bruise to the tissue resulting in inflammation and pain. Fig. 2 : Anterior disc displacement, “clicking” and “locking” symptoms, see text for details. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
The forward dislocated disc is an obstacle for the condyle movement when the mouth is opening. In order to fully open the jaw, the condyle has to jump over the back end of the disc and onto its center. This produces a clicking or popping sound. Upon closing, the condyle slides back out of the disc hence another “click” or “pop”. This condition is called disc displacement with reduction. In later stage of disc dislocation, the condyle stays behind the disc all the time, unable to get back onto the disc. The clicking sound disappeared but mouth opening is limited. This is usually the most symptomatic stage – the jaw is said to be “locked” as it is unable to open wide. At this stage the condition is called disc displacement without reduction.
Click here to see an animation of TMJ disc displacement on Alila Medical Media website where the video is also available for licensing.
Fortunately, in most of the cases, the condition resolves by itself after some time. This is thanks to a process called natural adaptation of the retrodiscal tissue, which after a while becomes scar tissue and can functionally replace the disc. In fact, it becomes so similar to the disc that it is called a pseudodisc.
Below is a narrated animation about glaucoma development and types of glaucoma. Click hereto license this video and/or other eye and vision related videos on Alila Medical Media website.
Glaucoma is a group of eye diseases in which the optic nerve is damaged leading to irreversible loss of vision. In most cases, this damage is due to anincreased pressure within the eye – elevated intraocular pressure.
How glaucoma develops
The eye produces a fluid called aqueous humor which is secreted by the ciliary body into the posterior chamber, a space between the iris and the lens. It then flows through the pupil into the anterior chamber between the iris and the cornea. From here, it is drained through a sponge-like structure located at the base of the iris called the trabecular meshwork and leaves the eye. In a healthy eye, the rate of secretion balances the rate of drainage.
In people with glaucoma, this drainage canal is partially or completely blocked. Fluid builds up in the chambers and this increases pressure within the eye. The pressure drives the lens back and presses on the vitreous body which in turn compresses and damages the blood vessels and nerve fibers running at the back of the eye. These damaged fibers result in patches of vision loss and if left untreated may lead to total blindness.
Click here to see an animation of glaucoma progression on Alila Medical Media website where the video is also available for licensing. Fig. 1 : Development of glaucoma. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Open-Angle Glaucoma vs. Angle-Closure Glaucoma
These are the two main types of glaucoma. The “angle” here refers to the corner between the cornea and the iris where the trabecular meshwork is located.
Primary Open-Angle or Chronic Open-Angle Glaucoma is the most common form of glaucoma accounting for about 90% of cases. This is caused by partial blockage of the drainage canal. The angle is “open”, meaning the entrance to the drain is clear, but the flow of aqueous humor is somewhat slow. The pressure builds up gradually in the eye over a long period of time. There is no pain and visual loss appears gradually, starting from peripheral vision, and may go on unnoticed until the central vision is affected. Progression of glaucoma can be stopped with medical treatments, but part of vision that is already lost can not be restored. This is why it’s very important to detect signs of glaucoma early with regular eye exams.
Closed-angle or Acute angle-closure glaucoma (AACG) is less common. This type of glaucoma is caused by a sudden and complete blockage of aqueous humor drainage. The pressure within the eye rises rapidly and may lead to total vision loss quickly. This is a medical emergency and requires immediate attention. Symptoms to watch out for: sudden severe pain inside and around the eye, redness, blurry vision, seeing halos around a light, some people may also feel headache, nausea.
Certain anatomical features of the eye make it easier for AACG to happen. These include: narrow drainage angle, shallow anterior chamber, thin and droopy iris, lens sitting too much forward. These features are often inherited and so AACG incidents are likely to run in the family.
Fig. 2 : Open angle vs closed angle glaucoma. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Typically, this is what happens in AACG : the pupil is dilated (e.g. when looking in the dark) and the lens is stick to the back of the iris. This prevents the aqueous humor from flowing through the pupil into the anterior chamber (primary block). As the fluid accumulates in the posterior chamber it presses on the iris causing it to bulge outward and block the drainage angle (secondary block).
Other types of Glaucoma
Normal pressure glaucoma – Some people can get glaucoma (vision loss due to damaged optic nerve) without elevated intraocular pressure. This may be due to poor blood supply (e.g. damaged blood vessels in diseases such as diabetes) to the nerve fibers.
Secondary glaucoma – glaucoma develops as a result of trauma after eye injuries.
Congenital glaucoma – glaucoma that is present at birth.
Treatments
Progression of glaucoma can be halted or slowed down with medical treatments, but part of vision that is already lost can not be recovered. This is why it’s very important to detect signs of glaucoma early with regular eye exams.
– Laser treatments : Laser is used to burn part of the trabecular meshwork to improve fluid flow – laser trabeculoplasty. It can also be used to remove part of the ciliary body to reduce fluid secretion. For acute glaucoma, small holes can be made in the iris to relieve the primary block – laser iridotomy.
– Eye surgeries: a procedure called trabeculectomy is used to create a channel – an alternative route – for aqueous fluid drainage. For acute glaucoma a procedure called iridectomy may be performed to drill a hole in the iris. Canaloplastyis a newer, less invasive surgical procedure performed for treatment of open angle glaucoma. This procedure involves enlargement of the eye’s natural drainage canal.
In people with AACG, laser and surgical treatments may be performed for the other, still healthy eye as well to prevent future development of glaucoma.
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Reverse Total Shoulder Replacement or Delta Shoulder Replacement is a modification of total shoulder replacement procedure. The conventional procedure has a metal ball on the humerus (replacing the natural humeral head) and a plastic component on the glenoid. The reverse procedure has the reverse positions of the prostheses : the metal ball is now fixed on the glenoid socket and the plastic cup is fixed in place of the humeral head (Fig. 1). This configuration is indicated for people with rotator cuff arthropathy. Fig. 1: Configuration of conventional versus reverse total shoulder replacement. Note the location of the metal head and plastic component in each case. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Why a conventional total shoulder will not work with rotator cuff arthropathy?
Rotator cuff arthropathy or cuff tear arthropathy (CTA) is shoulder arthritis in a setting of rotator cuff tears. Rotator cuff muscles hold the ball and the socket together and prevent the humeral head from moving out of the socket when the deltoid muscle raises the arm. In people with torn rotator cuff, the head of the humerus moves upwards out of the socket resulting in shoulder instability. Conventional total shoulder preserving the natural configuration of the shoulder joint will encounter the same problem (Fig. 2, left panel).
Fig. 2: Conventional versus reverse total shoulder replacement with torn rotator cuff. The upward force displaces the humeral head in conventional configuration but stabilizes the joint in reverse configuration. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Why a reverse total shoulder would work?
In reverse total shoulder procedure, the arthritic humeral head is replaced with a plastic cup and the metal ball is fixed onto the glenoid surface. With this configuration, the contraction of the deltoid will move the arm up and compress the socket to the ball at the same time (Fig. 2, right panel). The ball and the socket will fit more snugly together providing stability.
The videos on this page can be downloaded upon purchase of a license on Alila Medical Media website. Click here!
Shoulder arthritis refers to loss of cartilage on the surface of the ball (humeral head) and the socket (glenoid) of the shoulder glenohumeral joint. The two bones rub against each other and produce pain, stiffness and difficulty moving an arm.
Types and Causes of Shoulder arthritis
Osteoarthritis (OA) – also called degenerative joint disease (DJD), is the “wear and tear” condition of the joint commonly due to old age. OA is characterized by loss of cartilage, bone spurs (osteophytes) and no major inflammation (Fig. 1). Fig. 1: Osteoarthritis of the main shoulder joint. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Rheumatoid arthritis (RA) – Inflammation of the synovium – the membrane that encloses the joint and contains lubricant fluid. Inflammation brings in the cells of the immune system whose inflammatory chemicals damage and destroy the joint. It’s not clear how RA starts but genetic predisposition together with infection of the joint are likely to be among the causes.
Rotator cuff arthropathy or cuff tear arthropathy (CTA) – Shoulder arthritis as a result and in a setting of rotator cuff tears. Rotator cuff muscles hold the ball and the socket together and prevent the humeral head from moving out of the socket when the person raises an arm. In people with torn rotator cuff, the head of the humerus moves upwards and rub onto the acromion. This causes damages to the covering cartilage and eventually arthritis. Combination of cuff tear and arthritis is a devastating condition that seriously compromises function of the shoulder.
Post-traumatic arthritis – arthritis that develops after physical injury to the joint.
Chondrolysis – sudden loss of cartilage that happens occasionally after a shoulder surgery, commonly seen in association with infusion of local anesthetics into the joint for pain management.
Treatments
Non-surgical treatments include shoulder exercises and anti-inflammatory medications.
Surgical treatments include a variety of procedures :
1. Total shoulder replacement surgery : the arthritic humeral head is replaced with a metal ball on a stem that fits inside the humerus, the socket is replaced with a plastic component made of high density polyethylene.
Fig. 2: Total shoulder replacement procedure. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
2. Ream and Run Arthroplasty – a modification of total shoulder procedure above. The metal ball replaces the humeral head but the socket is simply shaped, smoothed to fit the ball and left to heal. No plastic component used. With time, the body grows a cartilage layer on top of the socket. This procedure is recommended for younger and more active individuals.
3.Reverse total shoulder or Delta total shoulder replacement – This is indicated for people with rotator cuff arthropathy (see types of shoulder arthritis above). This procedure reverses the positions of the prostheses : the metal ball is now fixed on the socket and the plastic component is fixed in place of the humeral head. This topic is covered in the next article about reverse total shoulder replacement. > See all Orthopedic topics
Femoral acetabular impingement (FAI) is a condition of hip joint where the bones are abnormally shaped, they pinch each other on the covering cartilages when the joint is in motion and cause damages.
The hip joint is a ball-and-socket joint (Fig. 1). The femoral head (the ball) fits into the acetabulum (the socket). The femoral head is covered with articular cartilage, the acetabulum has a ring of cartilage around its rim called the labrum. In FAI, there are abnormal bone growths (spurs) on the ball or the socket or both (Fig. 2). The ball can no longer move smoothly inside the socket. They rub onto each other and pinch on the covering cartilages causing damages.
Fig. 1 : Anatomy of the hip joint.Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Types of FAI
Pincer – Bone spurs on the acetabulum, commonly on the upper edge (Fig. 2 ). This situation is also described as over-coverage of the socket over the ball.
Cam – Bones spurs on the femoral head and neck making the neck less prominent and the head not completely round.
Combined – both cam and pincer are present, this is a very common situation. Fig. 2 : Types of FAI. Bones spurs are colored in red. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
What damages can it make?
Impingement results in cartilage breakdown on the femoral head and labral tears on the rim of the acetabulum. FAI is also the cause of premature hip osteoarthritis in young adults.
Causes and risk factors
The bone spurs are the result of abnormal bone growth during childhood development. The reasons why this happens are unclear.
FAI is more common in young athletes, dancers who practice a larger range of motions of the hip, and in active individuals.
Symptoms
Some of the symptoms may include:
– Pain at the groin area or inner hip is more common although the pain may be felt at the side of the hip.
– Pain after sitting for a long period of time.
– Stabbing pain when sitting down or standing up.
Treatment
Treatments range from lifestyle changes, physical therapies to surgeries.
Lifestyle changes usually involve being less active. Physical therapy helps to increase hip strength but stretching should be avoided.
Arthroscopic surgeries are commonly performed to remove damaged tissues, repair the labrum and stimulate cartilage growth by microfractures. Removal of abnormal bony structures are also recommended to prevent future damages to the joint.
The videos on this page can be downloaded upon purchase of a license on Alila Medical Media website. Click here!
The number of cells in a tissue is determined by the balance between cell division and cell death. Uncontrollable cell division leads to formation of abnormal growths called tumors. Tumors can be benign or malignant. Benign tumors are slow-growing and constrained by surrounding connective tissue so they do not spread to other organs. They can still be harmful or even kill by pressing on nearby nerves, brain tissue or blood vessels. Examples of benign tumor include pituitary tumors which may press on optic nerves and cause loss of vision. Cancers are malignant tumors – tumors that can spread beyond of the limit of original organ where it comes from and to other organs of the body.
How cancer starts
Cancer starts from a damage in the DNA of a cell. This DNA damage is called mutation. Mutations happen when the cell duplicates its DNA prior to cell division and makes mistakes. These damages are usually detected and repaired before the cell can divide but sometimes, some of them may be ignored and transferred to daughter cells.
If the mutation is located in one of many genes that control the cell cycle, it may affect the regulation of cell cycle in the cell carrying it, and make the cell divide faster than it supposed to. Usually, one mutation is not enough to cause cancer, but as it makes the cell cycle control less reliable, many more DNA damages/mutations would go unnoticed. Cancer is usually the result of accumulation of many mutations of genes involved in cell cycle control and DNA repair. This commonly happens over a long period of time, over many rounds of cell divisions, and this explains why cancers are more common in older people.
Fig. 1 Cancer cells reproduce to from tumor.Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Some people are said to be predisposed to cancer. This is because they are born with a mutation that makes them more likely to develop a certain type of cancer. This mutation alone is not enough to cause cancer but it starts the process of making cells cancerous. The person carrying it is one step further down the road towards developing a cancer than others who do not have the mutation.
Genes that are mutated in cancer
Three main classes of genes that are found mutated in cancers:
Proto-oncogenes – when mutated become oncogenes. Most cells do not divide until a growth factor binds to a receptor on its surface and instruct it to do so. Growth factor binding activates a cascade of events preparing the cell for division. Proto-oncogenes encode for normal growth factors and growth factor receptors. Oncogenes encode for abnormal versions of these. These malfunctional growth factors and receptors instruct the cells to divide non-stop causing cancer. A well known example of oncogene is ras, which encodes for a mutated growth factor receptor.
Tumor suppressors (TS) genes – these encode for cell cycle inhibitors, a class of molecules that prevent the progression of the cell cycle. Many of these arrest the cell cycle in G1 phase by binding to and inactivating cyclin-CDK complexes. A famous TS gene is p53, which is found mutated in majority of cancers including colon, brain, breast, lung cancers and leukemia.
DNA repair genes –these encode for enzymes that repair damage in DNA before the cell can divide. Mutations in these genes lead to accumulation of mutations that eventually make the cell cancerous.
How cancer spreads
Cancer cells do not stick together like normal cells, they move and invade nearby tissues, organs, this is local spread. They may also spread to further away organs by means of blood and lymph circulation, this is systemic spread. Metastasis is the spreading of cancers to non-adjacent organs. Cancer cells from the original tumor (primary cancer) can break out and maybe taken up by a blood or a lymph vessel for a ride throughout the body. They can then squeeze out from the vessels into other tissues and start a new tumor growth in the new location which will become secondary cancer.
Fig. 2 : Cancer cells squeeze through the wall of blood and lymph capillary. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Where do cancers usually spread and why?
While travelling in the bloodstream, cancer cell usually stops at the first place where the vessel getting so narrow that it gets stuck. As blood flow from most organs goes to the capillaries of the lungs, this is where cancers spread the most. Lungs are indeed the most common site of secondary cancers.
Fig. 3 : Primary cancer from the pancreas metastases to the lungs through the bloodstream. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Likewise, while travelling in the lymphatic system, cancer cells commonly get stuck in nearest lymph nodes, where the vessels get narrower. This is the reason why surgeons usually remove nearby lymph nodes when removing tumors.
