Avascular Necrosis of the Femoral Head

Avascular necrosis (AVN) or osteonecrosis of the hip is a painful, degenerative condition where blood supply to the head of the femur is interrupted. Due to the vascular interruption, the femoral head receives less and less blood and results in parts of the bone dying. This results in pain, reduced movement and arthritis.

AVN typically affects those aged between 20-50 and is usually developed secondary an underlying health issue or previous injury (5). Therefore, those who remain healthy and physically active around during this age bracket have a reduced chance of developing AVN of the femoral head (5).

Causes

AVN has a range of causes that can be classified into two major groups – traumatic and nontraumatic (5). Typically, a traumatic causation of femoral AVN is via a dislocated hip (5). Research suggests that 20% of those who dislocate their hip develop the disease.

The most noted nontraumatic causes of AVN are excessive alcohol use, chronic use of corticosteroids and/or vascular compromisation such as blood clots or artery damage that supplies blood to the femur (5).

Studies have also shown that there is a higher prevalence in males, potentially due to smoking and alcohol use, and that greater fluctuations in climate temperatures may also contribute to a non-traumatic development of AVN.

Stages of symptoms

1. Asymptomatic

AVN has a typically slow onset of symptoms and it can be relatively asymptomatic initially until the disease progresses.

2. Painful

The first symptom reported with AVN of the femoral head is pain. Clients often report a deep dull ache and/or a throbbing pain in the groin/buttock area.The pain is usually felt standing or sitting down with most find relief when lying down.

3. Limping

Progression from this deep ache is a pain that is more sudden or sharp when the injured person puts weight on or moves the affected hip. This can result in an observable limp as the individual has difficulty walking on the injured side.

Diagnosis

AVN can often mask itself as other conditions, particularly in its earlier stages (5). It is for this reason that a thorough assessment and diagnosis is undertaken by a qualified health professional. The assessment should rule out other potential causes for the client’s symptoms as should also be confirmed via imagery such as x-ray or MRI (5). MRIs are more effective at detecting osteonecrosis in the early stages – once a more advanced stage is reached then an x-ray can confirm the diagnosis (4)

Factors to look for when assessing a client include:

• Steroid exposure
• Alcohol abuse
• Age (younger > older)
• Locking, popping or painful clicking when moving the hip
• Reduced mobility of the hip
• Antalgic gait
• Double line sign on MRI (inner bright line and outer dark line)
• “Crescent sign” on MRI (indicates imminent articular collapse)

Management

Physiotherapy

Conservative management such as physiotherapy is necessary to prevent further deterioration of the affected hip(s). However, while it has been shown to delay the disease progression, physiotherapy alone cannot cure the disease – with 70-80% of clients requiring surgical treatment (4). Physiotherapy treatment aims include:

1. Weight-bear

A large aim of conservative treatment is to decrease the weight-bearing load through the head of the femur (5). This is usually done by the implementation of crutches or a walking aid of some sort.

2. Educate

It is also important for the health professional to educate the client on the prevention, removal or reduction of risk factors such as smoking, alcohol abuse, obesity and corticosteroids (4).

3. Range of motion

Once education has been addressed, physiotherapists should help the client maintain joint mobility via both passive and active exercises. This is done through hands-on mobilisation techniques in conjunction with stretching of tight musculature – however both techniques should remain within pain free ranges.

4. Strengthen

Strengthening hip musculature is another focus for the conservative management of this condition. These primarily include the gluteal muscles, quadricep muscles and core muscles. If strength is gained in these muscle groups then less pressure is placed on the hip joint itself – resulting in less pain, more movement and improved function.

5. Exercise

Exercise or physical activity that doesn’t involve putting weight through the hip joint is recommended, particularly for those that are in more advanced stages of AVN. Hydrotherapy, with its warm and buoyant properties can provide relief to the area as well as improved range of motion (movement) (2). Stationary cycling is another “non-weight bearing” exercise example that is very appropriate for this condition. Another positive of thee cardio-based exercises is the weight-loss benefits. If obesity was a factor in the development of AVN then these exercises would also aid in its rehabilitation as less weight = less pressure on the affected joint.

Example exercises

1. Squats with theraband

2. Banded glut med bridges

3. Stationary Cycling

Technique

Due to the pain involved with AVN, compensatory methods may present. Thus, Physiotherapists and/or health professionals should also take time to analyse clients’ technique when performing any exercise as incorrect motor patterns can result in accelerated degeneration of the hip joint (2).

Surgical Intervention

Due to various features of AVN, those that are diagnosed, usually result in requiring surgical input. Here are some of the most common operations for this disease.

Core decompression: surgeon removes part of the femoral head that causes a decompression and stimulates an increase in blood flow which can result in new bone formation. This technique is most effective if osteonecrosis is diagnosed early and can have clients walking pain-free in 3 months (1).

Figure 1: Core decompression

Bone transplant (graft): this is done to help strengthen the affected area of bone by debriding the dead or dying bone and replacing it with healthy bone from another body part (1)(3).

Figure 2: Fibular graft

Osteotomy: a surgical operation where a bone is shortened or lengthened to change alignment and decrease the load on the painful/necrotic bone (3)

Joint replacement: this method is undertaken when the diseased bone has collapse or when other management strategies fail. The damaged bone and cartilage is removed and replaced with prosthetic components (plastic, ceramic or metal). This technique is typically used of the bone has collapsed (late stage) and relieves pain/restores function in the majority of clients (1).

Figure 3: Total hip replacement

Post-op Physiotherapy

Generally speaking, femoral AVN clients respond well to physiotherapy following surgery (2). However, if pain persists and/or improvement is not at a rate the therapist believes it should be – then a follow-up review with the surgeon is advised (2).

Alec Lablache
POGO Physiotherapist

Featured in the Top 50 Physical Therapy Blog

References

1. American Academy of Orthopedic Surgeons. (2018). Osteonecrosis of the hip. Retrieved from https://orthoinfo.aaos.org/en/diseases–conditions/osteonecrosis-of-the-hip
2. Human Physical Therapy and Sports Medicine Centres. Avascular Necrosis of the Hip (2018). Retrieved from https://www.humpalphysicaltherapy.com/Injuries-Conditions/Hip/Hip-Issues/Avascular-Necrosis-of-the-Hip/a~5525/article.html
3. Mayo Clinic. (2019). Avascular necrosis. Retrieved from https://www.mayoclinic.org/diseases-conditions/avascular-necrosis/diagnosis-treatment/drc-20369863
4. Physiopedia. (2019). Avascular Necrosis. Retrieved from https://www.physio-pedia.com/Avascular_Necrosis
5. Shane Armfield (n.d). Avascular Necrosis of the Femoral Head. Retrieved from https://physioworks.com.au/injuries-conditions-1/avascular-necrosis-of-the-femoral-head