patella fracture
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A patella fracture is a
break Break or Breaks or The Break may refer to: Time off from duties * Recess (break), time in which a group of people is temporarily dismissed from its duties * Break (work), time off during a shift/recess ** Coffee break, a short mid-morning res ...
of the
kneecap The patella, also known as the kneecap, is a flat, rounded triangular bone which articulates with the femur (thigh bone) and covers and protects the anterior articular surface of the knee joint. The patella is found in many tetrapods, such as m ...
. Symptoms include pain, swelling, and bruising to the front of the knee. A person may also be unable to walk. Complications may include injury to the
tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...
,
femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...
, or knee ligaments. It typically results from a hard blow to the front of the
knee In humans and other primates, the knee joins the thigh with the leg and consists of two joints: one between the femur and tibia (tibiofemoral joint), and one between the femur and patella (patellofemoral joint). It is the largest joint in the hu ...
or falling on the knee. Occasionally it may occur from a strong contraction of the thigh muscles. Diagnosis is based on symptoms and confirmed with
X-rays An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 Picometre, picometers to 10 Nanometre, nanometers, corresponding to frequency, ...
. In children an
MRI Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves ...
may be required. Treatment may be with or without surgery, depending on the type of fracture. Undisplaced fracture can usually be treated by
cast Cast may refer to: Music * Cast (band), an English alternative rock band * Cast (Mexican band), a progressive Mexican rock band * The Cast, a Scottish musical duo: Mairi Campbell and Dave Francis * ''Cast'', a 2012 album by Trespassers William * ...
ing. Even some displaced fractures can be treated with casting as long as a person can straighten their leg without help. Typically the leg is immobilized in a straight position for the first three weeks and then increasing degrees of bending are allowed. Other types of fractures generally require surgery. Patella fractures make up about 1% of all broken bones. Males are affected more often than females. Those of middle age are most often affected. Outcomes with treatment are generally good.


Signs and symptoms

Also known as a broken kneecap, a patella fracture usually follows a history of trauma and commonly presents with swelling, pain, bruising and inability to both bend and straighten the knee. The pain is worse when trying to stand and the person may be unable to walk. The pain can also be aggravated by prolonged periods of sitting. A painful defect may be felt in the knee and there may be blood in the joint.


Complications

Complications may include injury to the
tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...
,
femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...
, or knee ligaments. In the longer term, the knee may not regain full movement, pain may persist and there is an increased likelihood of
osteoarthritis Osteoarthritis (OA) is a type of degenerative joint disease that results from breakdown of joint cartilage and underlying bone which affects 1 in 7 adults in the United States. It is believed to be the fourth leading cause of disability in the w ...
of the knee. If there is an associated open wound as in an open fracture, complications also include risk of infection, inability of the broken bones to reunite and
osteonecrosis Avascular necrosis (AVN), also called osteonecrosis or bone infarction, is death of bone tissue due to interruption of the blood supply. Early on, there may be no symptoms. Gradually joint pain may develop which may limit the ability to move. Co ...
.


Diagnosis

Diagnosis is based on symptoms and confirmed with
X-rays An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 Picometre, picometers to 10 Nanometre, nanometers, corresponding to frequency, ...
. In children an
MRI Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves ...
may be required.


Differential diagnosis

Some people have a normal bipartite patella or two-part patella which can appear as a fracture. The fragment is usually seen in the top outer corner of the patella and can be distinguished from a fracture by being present in both knees.


Types

The patella can break in various ways depending on the way it is injured, and into two or more pieces. Types include transverse, with one fracture line and is the most common type, marginal, osteochondral and the rare vertical type, or stellate, where a direct compression force gives rise to a comminuted pattern. Patella fractures can be further classified as displaced, where the broken ends of bone do not line up correctly and separate by more than 2mm, or undisplaced and stable where pieces of bone remain in contact with each other. If fragments of patella bone stick out from the skin it is known as an open patella fracture, and closed if the overlying skin is intact. File:Patellaquerfraktur seitlich.jpg, Transverse fracture of patella File:ZP+B fraktura patelly (39).jpg, Comminuted fracture of patella File:Patellafraktur laengs.jpg, Osteochondral fracture of patella File:Patella fracture.JPG, Vertical patella fracture


Treatment

Treatment may be with or without surgery, depending on the type of fracture and whether the overlying skin is intact or broken.


Conservative

Undisplaced fractures can usually be treated by
cast Cast may refer to: Music * Cast (band), an English alternative rock band * Cast (Mexican band), a progressive Mexican rock band * The Cast, a Scottish musical duo: Mairi Campbell and Dave Francis * ''Cast'', a 2012 album by Trespassers William * ...
ing. Even some displaced fractures can be treated with casting as long as the person can straighten their leg without help, thus confirming that the quadriceps mechanism of the leg is intact. In this case the leg is immobilized in a straight position for the first three weeks and then increasing degrees of bending are allowed as healing occurs.


Surgery

Most patella fractures are transverse or comminuted, hence the quadriceps mechanism is disrupted and they are treated by a combination of wires in a tension band construct. This unites the fractured bones, reconstructing the straightening mechanism of the leg. If the patella is broken in several places, that is comminuted, then traditionally a patellectomy (removal of the whole patella) is performed in order to reconstruct the extensor mechanism and prevent the onset of an extension lag at the knee joint, resulting in instability. Some surgeons however would rather opt for
internal fixation Internal fixation is an operation in orthopedics that involves the surgical implementation of implants for the purpose of repairing a bone, a concept that dates to the mid-nineteenth century and was made applicable for routine treatment in the m ...
. A partial patellectomy is removal of only a portion of the patella, and may be carried out if at least 60% of the patella can be maintained. Open fractures of the patella require emergency treatment with irrigation, debridement and fixation.


Rehabilitation

Irrespective of surgical or non-surgical resolution to the fracture, a
physical therapist Physical therapy (PT), also known as physiotherapy, is one of the allied health professions. It is provided by physical therapists who promote, maintain, or restore health through physical examination, diagnosis, management, prognosis, patient ...
can advise on progressive weight-bearing exercises and help with strengthening muscles of the leg, improving range of motion of the knee and in reducing stiffness.


Prognosis

Outcomes with treatment are generally good, unless there is involvement of the articular surface or the quadriceps mechanism. There is an increased risk of developing
osteoarthritis Osteoarthritis (OA) is a type of degenerative joint disease that results from breakdown of joint cartilage and underlying bone which affects 1 in 7 adults in the United States. It is believed to be the fourth leading cause of disability in the w ...
in people who have broken their patella. There is limited evidence supporting the different surgical interventions for treating fractures of the patella in adults. There is also no evidence of trials that could evaluate the effects of surgical treatment compared with the conservative treatment or other different types of conservative interventions.


Epidemiology

Patella fractures make up about 1% of all broken bones. Males are affected more often than females. Those of middle age are most often affected. 6% to 9% of patellar fractures are of the open type. An ageing population and global increase in the number of TKAs has led to an increasing number of periprosthetic fractures of which a patella fracture is one type.


History

Prior to the 19th century most patella fractures were treated non-surgically with extension splinting, frequently resulting in poorly joined fragments of bone and long-term pain and disability. Incomplete understanding of the importance of the patella led to the trend of removing the whole patella, also resulting in pain, disability and dissatisfaction. The first open reduction and internal fixation for a patella fracture was performed in 1877 by Scottish surgeon Sir Hector Cameron. Several techniques followed and materials used included metal loops, pins, kangaroo tendons and screws. Significant advances in surgery occurred in the 1950s with the development of banding after Herbert A. Haxton and others demonstrated that the patella was not just to protect the knee but important for straightening the leg. Subsequently, the three surgical treatments for displaced patella fractures became tension banding, partial patellectomy and total patellectomy, the decision of which to use tailored to the individual.


References


External links

{{Fractures Bone fractures Knee injuries Patella Wikipedia medicine articles ready to translate