Iliopsoas Abscess Infection

psoas anatomy

The iliacus and the psoas are the main hip flexors supplied by the femoral nerve which lies between the two muscles. The obturator nerve is medial to the psoas. The psoas arises from the transverse process of the lateral aspect of the vertebral bodies between the 12th thoracic vertebrae and the 5th lumbar vertebrae. The psoas runs downward across the pelvic brim and then passes deep to the ilioinguinal ligament bursawhere it then forms a tendon past the hip joint capsule which inserts into the lesser trochanter of the femur. The iliacus arises from the upper two-thirds of the iliac fossa and joins the psoas to insert in the same tendon as the posas muscle. Both muscles are in the extraperitoneal space, or referred to as the iliopsoas compartment. The iliopsoas tendon is separated from the hip joint capsule by the iliopsoas bursa.

What causes an abscess of the iliopsoas muscle?

A primary abscess is caused by a hematogenous spread of the infection. The infection starts in the muscle itself. In a secondary abscess, the infection spreads from another area to the psoas muscle. For example, the infection may travel from the spine when it is infected by tuberculosis (Pott’s disease). This historically is the cause of this abscess. It can also spread from the SI joint, kidneys, or bowels. The iliopsoas abscess may initially present with sign and symptoms in the buttock, hip, or thigh. Such signs and symptoms may be obscure, nonspecific, and misleading.

staphaurusStaph aureus is the cause of iliopsoas abscesses in 88% of primary types. Polymicrobial infections are usually the cause in the secondary types. CT scans are usually the CTENLARGEDdiagnostic modality of choice.

 

An abscess of the iliopsoas muscle is a diagnostic dilemma with a difficult diagnosis that is often delayed. The patient may be lying supine with the hip flexed and refuses to move, resisting any attempt for examination. With psoas involvement, the hip appears to be flexed, with limited and painful range of motion. This diverts attention away from the abdomen or pelvic source of the abscess. The patient may have a low grade fever and cannot straighten the leg. A high index of suspicion and performing the Psoas sign is necessary for diagnosis.

Psoas Sign

The patient is positioned on their side and the hip is extended to see if there is pain present in the iliopsoas region. The psoas sign is used in diagnosis of appendicitis but is also helpful in diagnosing a psoas abscess.

psoas sign

The iliopsoas abscess manifests itself as pain in the abdomen, flank, or groin area, as well as pain in the lower back. Flexion posture of the hip is also commonly noted. These abscesses are rare and present with vague clinical features.

Treatment

treatment

Percutaneous drainage is done if the abscess is simple, small, and single. Otherwise, an open drainage is the procedure of choice. When performing an open drainage of the abscess, a splitting incision is made along the iliac crest for easy access to the iliacus, psoas, and SI joint. Other incisions may be needed such as the anterior approach in the front of the hip or the posterior approach. Other sites for drainage depend on the location and extension of the abscess.

Risk factors for developing an iliopsoas abscess:

  • Diabetes
  • Immunosuppression
  • Trauma
  • Renal failure
  • IV drug abuse
  • Older individuals and AIDS patients

 

 

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Bursae around the Hip

bursaeThere are multiple bursae located around the hip joint. These bursae are present where friction normally occurs between the muscles, tendons, and bones. A bursa is a thin sack containing minimal fluid which lubricates the tissue to decrease friction.

There are three different types of bursae located around the hip area:

  1. The Greater Trochanter group of bursa
  2. Iliopsoas bursa
  3. Ischial bursa

Three main bursae surround the greater trochanter of the femur:

Greater Trochanter Group of Bursa

  1. Subgluteus medius bursa: smaller bursa between the gluteus medius muscle and greater trochanter groupthe greater trochanter, just medial to the trochanteric bursa.
  2. Trochanteric Bursa: located just superficial to the greater trochanter and the attachments of the gluteal muscles. If the trochanteric bursa becomes irritated and inflamed, this can lead to trochanteric bursitis.
  3. Subgluteus Minimus Bursa: lies beneath the gluteus minimus tendon at the anterosuperior edge of the greater trochanter.

Some people believe that there are over twenty bursas around the greater trochanter of the femur. Needling of the bursa in different directions may be helpful when the physician injects steroids into the bursa. Trochanteric bursitis is often associated with iliotibial band syndrome.

ITBSSSSSThe iliopsoas bursa lies between the iliopsoas muscle at the front of the hip joint and the underlying bone. The bursa may become irritated and inflamed due to friction from the iliopsoas muscle where it crosses the hip joint.

iliop bursaThe Ischial bursa is also called “weaver’s bottom” or “tailor’s seat”. This bursa prevents friction between the gluteus maximus and the ischial tuberosity. The bursa is located on the posterior side of the ischium. Bursitis of the ischial bursa may be caused by prolonged sitting on a hard surface, which aggravates the bursa. The patient will complain of tenderness and pain in the buttock area during sitting.ischial bursae

 

Osteonecrosis of the Hip

Osteonecrosis or Avascular Necrosis of the hip is death of a segment of bone in the femoral head due to disruption of the blood supply. The etiology of this condition is not fully understood. There are several risk factors associated with osteonecrosis of the hip. The condition occurs bilaterally in about 80% of patients. It is important for the physician to check both hips, even if one is asymptomatic. An early diagnosis is important because during the early stages of osteonecrosis, a femoral head preserving procedure can be done. In the late stages of osteonecrosis, the femoral head collapses and cannot be saved. The femoral head may need to be replaced. Obtain AP and Frog Leg Lateral views of the hip. The Frog Leg Lateral view will show the crescent sign.

An MRI is the imaging of choice, especially when the patient has persistent hip pain, the radiographs are negative, and the diagnosis of osteonecrosis is suspected.

osteonoThe Ficat Classification is a commonly used system to stage osteonecrosis of the hip. Stage I classifications will have a normal appearing x-ray and an MRI will detect the lesion; changes in the marrow. Stage II classifications are identified by sclerosis and cyst formation. Characteristics of the Stage III classifications are a subchondral fracture and the appearance of a crescent sign and flattening of the femoral head. Stage IV classifications will show advanced lesions with arthritis, osteophyte formation, and a loss of the joint space.

stages

Treatment

For early stages of osteonecrosis of the hip, initial trial of nonsurgical treatment is usually done. Surgery may be needed if nonsurgical methods are not successful. Nonoperative treatment typically consists of bisphosphonates.

femoral head collapsedThese drugs may be used before the femoral head collapses and are still in the experimental stages. In regards to traditional surgical treatment, when the lesion is small a head preserving procedure can be done. For stages I & II, a core decompression is used. The surgeon can make a single large hole or multiple small holes in the femoral head. It decompresses the head and stimulates a healing response. The lesion is done anteriorly and superiorly.

bonegraft222If the surgeon chooses to perform a core decompression with bone graft, they will debride the necrotic area and insert the bone graft into the open space. Vascularized Fibular Grafts are done in younger patients. Complications include: donor site pain and leg dysfunction as well as tibial stress fractures on the side the graft was taken. Stages III and IV will require a total hip arthroplasty (cementless cup and stem) or total hip resurfacing; however, resurfacing is not commonly used. A total hip replacement is considered to be the traditional procedure for advanced stages of osteonecrosis of the hip. Total hip resurfacing is considered to be controversial because the patient will need adequate bone stock to support the femoral component. The result is not as good when compared with a patient with osteoarthritis.totalhip

 

Osteonecrosis of the Hip

Osteonecrosis or avascular necrosis of the hip is death of a segment of bone in the femoral head due to disruption of the blood supply. The etiology of this condition is not fully understood. There are several risk factors associated with osteonecrosis of the hip.

osteohip1.png

The condition is bilateral in about 80% of the patients. Check the other hip even if it is asymptomatic.

Early diagnosis is important. In early stages of osteonecrosis, a femoral head preserving procedure may be done.  In late stages of osteonecrosis, the femoral head collapses and cannot be saved. The femoral head may need to be replaced.

Obtain AP frog leg lateral views of the hip. The frog leg lateral view will show the crescent sign. MRI is the study of choice especially when the patient has persistent hip pain, radiographs are negative and the diagnosis of osteonecrosis is suspected.

osteohip4.png

The Ficat classification is a commonly used system to stage osteonecrosis of the hip.

  • Stage I: normal appearing X-ray. MRI will detect the lesion (changes in the marrow).
  • Stage II: sclerosis and cyst formation
  • Stage III: subchondral fracture. Crescent sign and flattening of the femoral head.

Stage IV: advanced lesions with arthritis, osteophyte formation and loss of the joint space.

osteohip5.png

Treatment

For early stages of osteonecrosis of the hip, initial trial of non surgical treatment is usually done. Surgery may be needed if non surgical methods are not successful.

Non-operative treatment includes:

  • Bisphosphonates: may also be used before the femoral head collapses. Still experimental.

Traditional surgical treatment: when the lesion is small, a head preserving procedure can be done.

  • Core decompression for stages I and II: can make a single large hole or multiple holes in the femoral head. It decompresses the head and stimulates a healing response. The lesion is anteriorly and superiorly.
  • Core decompression with bone graft: debride the necrotic area and place the bone graft. Some lace this much bone graft.
  • Traditional fibular graft: is done in younger patients.

osteohip7.png

Complications:

  • Donor site pain and leg dysfunction
  • Tibial stress fracture form side the graft is taken.
  • Total hip arthroplasty (cementless cup and stem) or total hip resurfacing. Resurfacing is not commonly used.

osteohip8.png

  • Total hip replacement (predictable): is considered to be the traditional procedure for advanced stages of osteonecrosis of the hip.
  • Total hip resurfacing (controversial): need adequate bone stock to support the femoral component. The result is not as good when compared with a patient with osteoarthritis (older group).