Osteonecrosis of the Knee

There are three different types of osteonecrosis of the knee. There is Spontaneous Osteonecrosis of the Knee, Post Arthroscopic Osteonecrosis of the knee, and Secondary Osteonecrosis of the knee. Osteonecrosis is further classified by severity using Ficat Stages of Knee Osteonecrosis. In Stage I, the x-ray appears normal. Stage II, Sclerosis of the condyle is present. In Stage III, the crescent sign is found as well as a subchondral fracture. Stage IV, there is a collapse of subchondral bone.

ficatSpontaneous Osteonecrosis of the Knee typically occurs in females older than 55. Usually one joint and one compartment is affected (medial femoral compartment). No etiology is known. Symptoms typically consist of a sudden onset of severe pain with decreased range of motion as well as swelling in the knee. X-rays will probably appear to be normal. An MRI is helpful, the provider may find a crescent shaped lesion. This conditionspontaneous can cause arthritis. If severe knee pain is present in a middle aged or elderly female patient, and the x-ray is negative, the provider should order an MRI to rule out osteonecrosis of the knee. Treatment consists of protected weightbearing as well as therapy and NSAIDs. An arthroplasty may be required when conservative treatment fails. A unicompartmental knee arthroplasty will be performed for small lesions. A total knee arthroplasty will be completed for large lesions or collapse.

Post Arthroscopy Osteonecrosis of the Knee most commonly occurs in middle aged secondarywomen after a knee arthroplasty. Secondary Osteonecrosis of the knee is common in women under 55 years of age and has associated risk factors. This condition involves more than one compartment or the metaphysis of the knee. Secondary Osteonecrosis occurs bilaterally in 80% of cases and multifocal lesions may be seen. There is a cause for Secondary Osteonecrosis of the knee, which is why it can be bilateral, multiple, and everywhere. Risk factors include:

  • Alcohol use
  • Sickle cell disease
  • Steroid usedissecans
  • Trauma
  • HIV medications
  • Gaucher Disease

 

These patients should be screened for other joint involvement. The lesion is a subcondylar insufficiency fracture and the patient will have severe pain with weight bearing either standing or sitting. An x-ray may show a wedge-shaped lesion and MRI is the better study. A differential diagnosis is Osteochondral Dissecans, which is located in the lateral aspect of the medial femoral condyle in younger patients. Other differentials include: Occult trauma, bone bruise and overuse, as well as transient osteoporosis which is found more in middle-aged men and usually in the hip rather than the knee. Treatment consists of NSAIDs, a decrease in activity and weightbearing, and physical therapy. A scope surgery may be necessary to remove loose fragments or core decompression for lesions not extending to the joint. An Osteocondylar allograft may be performed for large, painful lesions in younger patients. A total knee replacement may be done for larger lesions, for collapse, or if multiple compartments are involved. Conservative treatment is not as successful with secondary avascular necrosis. Without surgery, secondary AVN will advance to osteoarthritis. Bisphosphonates have no effect on knee osteonecrosis.

Lesions of the Shoulder—Hill-Sachs Lesion

hillsachs

The Hill-Sachs lesions is a dent in the posterior aspect of the humeral head, which occurs during an anterior shoulder dislocation. The humeral head impacts against the front of the glenoid cavity of the scapula. A Hill-Sachs lesion is usually associated with a Bankart lesion. A Bankart lesion is the most common lesion of anterior shoulder instability following dislocation. It involves an avulsion of the anterior inferior labrum. The Hill-Sachs lesion can range from a small to large indentation and the size of the lesion can affect the treatment given to the patient. The larger the Hill-Sachs lesion, the more likely that the shoulder will be unstable and the more likely to

bankart lesiondislocate again (recurrent dislocations). The larger the Hill-Sachs lesion is, the more likely that the glenoid labrum and joint capsule have a significant tear.

Treatment for a small sized Hill-Sachs lesion of less than 20% can usually be treated nonoperatively. A medium sized Hill-Sachs lesion—a defect greater than 25%– may require an arthroscopic or open remplissage procedure (may be performed in combination with Bankart repair). The defect is “filled in” with the posterior capsule and rotator cuff. Larger sized Hill-Sachs lesions are rare. Lesions greater than 40% are usually filled with bone or metal.

lesion

Q-Angle of the Knee

A well-functioning knee joint is important for mobility. The knee must be able to support the weight of the body during activities such as walking or running.

What is a Q-angle? knee anatomy

The Q Angle, or quadriceps angle, is the angle between the quadriceps tendon and the patellar tendon. An increased Q-angle is a risk factor for patellar subluxation.

How do you measure the Q-angle?

First, you will need to find the patella and its border. Then, you will need to find the center of the patella. You will then need to find the tibial tubercle and draw a line from the ASIS to the center of the patella and a second line from the tibial tubercle through the center of the patella.

normal qThe Q-angle is formed in the frontal plane by the two line segments. It is the angle formed by a line drawn from the Anterior Superior Iliac Spine (ASIS) to the center of the patella. A second line is drawn from the center of the patella to the tibial tubercle. The angle formed by the two lines is called the Q-angle. The normal Q-angle is variable. In males, the angle is usually 14° and 17° in females. A wider pelvis and an increased Q-angle in females is linked to knee pain, patellofemoral pain, and ACL injury. The alignment of the patellofemoral joint is effected by the patellar tendon length and the Q-angle. It is best to measure the Q-angle with the knee in extension as well as flexion.increased q

A larger Q-angle plus a strong quadriceps contraction can dislocate the patella. The Q-angle is increased by:

  • Genu valgum
  • External tibial torsion
  • Femoral anteversion
  • Lateral positioned tibial tuberosity
  • Tight lateral retinaculum

A CT scan study of the patellofemoral articulation is found to be very helpful.

Sternal Fractures

sternum fracture

Fractures of the sternum (breastbone), are fractures to the bone located in the center of the chest. These injuries usually occur due to a significant blunt trauma to the chest. There are two types of sternal fractures, direct and indirect.

A direct fracture occurs due to a direct blow to the anterior chest wall, resulting in posterior displacement of the distal sternal segment. An indirect fracture is a hyperflexion injury to the sternum, causing posterior displacement of the proximal sternal segment. When indirect sternal fractures occur, it is important for the physician to also observe for a vertebral fracture. A CT scan is useful to assess patients with sternal fractures and associated spinal fractures.

 

indirect
Indirect Fracture

 

 

direct
Direct Fracture

 

 

 

 

 

 

 

A direct fracture occurs due to a direct blow to the anterior chest wall, resulting in posterior displacement of the distal sternal segment. An indirect fracture is a hyperflexion injury to the sternum, causing posterior displacement of the proximal sternal segment. When indirect sternal fractures occur, it is important for the physician to also observe for a vertebral fracture. A CT scan is useful to assess patients with sternal fractures and associated spinal fractures.

CT scan