Intrinsic Causes- coming from inside of the hip joint:
– Loosening
– Infection
– Instability
– Impingement
– Metal Sensitivity
Extrinsic Causes- coming from outside of the hip joint:
– Trochanteric Pain Syndrome
– Insufficiency Fractures
– Spinal Pathology
– Post-Surgical Pain Syndrome
– Other causes known to refer pain to the hip
Intrinsic Causes
Loosening
In some cases, the cup and or stem of the replacement may become loose, requiring revision surgery of the hip replacement. Loosening of the implants can occur shortly after surgery or even years later.
Prosthetic Joint Infection
Unfortunately, any surgery runs the risk of infection. For total hip replacements, this ranges from a superficial infection of the incision (cellulitis) or a deep infection around the implant, known as prosthetic joint infection. However, the incidence of this deep infection is relatively low, less than 1%.
Instability
Instability of the hip joint may also be caused by improper fitting or placement of the prosthetic implants. However, not following through with post-operative guidelines (in posterior hip replacements) can put you at risk for instability or dislocation.
Impingement
Impingement of your hip replacement can occur due to improper implant sizing or soft tissue irritation. Implants that are sized too large can cause your tendons to become overstretched and irritated. Conversely, implants that are sized too small can cause your tendons to be under-tensioned and lead to dislocation. Impingement can cause pain of the groin, front of your hip, and even into your thigh or buttock.
Metal Sensitivity
Unexplained pain after a hip replacement can sometimes be from a reaction to the replacement components. Metal-on-metal components are a discontinued hip replacement that many surgeons thought would last longer. Unfortunately, these hip replacements have had early failures and need to be revised.
Extrinsic Causes
Extrinsic causes of a painful total hip arthroplasty happen outside of the hip joint and are not directly related to the implant itself. As you may have realized already, all of the intrinsic reasons revolve around the implants.
Extrinsic causes of pain after a total hip arthroplasty can often be treated with more conservative measures.
Lateral Femoral Cutaneous Nerve
During the anterior approach to a hip replacement, the lateral femoral cutaneous nerve travels near the incision. The nerve can be stretched or cut during surgery. Injury to the nerve can cause numbness to the thigh region. Sometimes the damage can create a neuroma, which can become painful.
Trochanteric Pain Syndrome
Your trochanter is a bony prominence of your hip bone, the most prominent portion of bone that you can feel on the outside of your hip. Many tendons and bursa reside near this trochanter.
Insufficiency fractures
Insufficiency fractures are small fractures or stress fractures without a known mechanism or known trauma to an area. These fractures come on due to a change in weight-bearing status and activity level that is too much for the new implant’s bone.
Spinal Pathology
Degeneration of the spine can also mimic pain at the hip. Nerves that travel down to the hip may be impinged or inflamed, resulting in pain and dysfunction. Even the sacroiliac joint (SI joint) can refer pain to the hip if it is not moving or functioning optimally.