An interesting X-ray. The patient, who is in the later part of the 8th decade of life, but otherwise walking independently at home, had a hip implant following an accident 6 years ago. Had recurrent left hip pain with multiple hospitalisations.

Pelvic X-ray of the patient with left hip pain.

Questions: What is the likely diagnosis and how should this elderly patient be managed?

[Updated 17 March 2017]

On the X-ray, it is apparent that the left acetabulum has virtually been destroyed and the implant has actually entered the pelvic space. The left femur also looks both “moth-eaten” and hypertrophic, with new bone formation around the implant (compare with the right femur).

In this case, the patient has developed chronic left prosthetic hip implant infection. There was also a sinus tract which cannot be seen from the X-ray.

Clinical management is difficult here. The standard treatment for prosthetic joint implant infections is to:

• Determine the microbiological etiology.
• Start appropriate antibiotics, which will need to be continued for a long time – usually 6 weeks and beyond.
• Replace the infected implant, usually via a 2-stage process (although some orthopaedic centres do a 1-stage replacement with good outcomes).

In this particular case however, given the destruction of the acetabulum and the chronic osteomyelitis changes of the femur, it is unlikely that a new implant can be successfully placed from a mechanistic perspective. Joint arthrodesis is another option – usually after multiple failed attempts at prosthetic joint replacement. There may not be sufficient bone for left hip fusion in this particular case, especially after the extensive debridement required to surgically clear the infected material.

The final option is chronic life-long antibiotic suppression. This is reserved for patients who are poor surgical candidates, especially if the infection is recurrent despite prolonged courses of antibiotics. This is because antibiotics alone are associated with high risk of recurrence of infection in prosthetic implant infections, after they are stopped.