Saturday, October 22, 2016

Humeral and glenoid component loosening - aseptic or culture positive? What can we learn?

Here are the films of the right shoulder of a man in his late 60s with glenohumeral arthritis

 and a posteriorly biconcave glenoid.

He had a total shoulder with mono block chrome-cobalt humeral component and a Hylamer glenoid.

He did very well after surgery, returning to gym workouts and a wide range of outdoor physical activities. His x-ray at three monte after surgery is shown below.

One year after surgery, he was still doing well. His X-ray at that time is shown below.

Seven years after surgery, his shoulder was becoming somewhat painful, but not so much that he wanted anything done. His x-rays at that time show glenoid component wear and humeral subsidence.

Thirteen years after his surgery, his symptoms were worsening as were the x-ray findings. He elected to give it a bit more time.

 Three months later the symptoms and x-ray changes (see below)

led to a revision surgery. Preoperative blood tests were normal.

At surgery the joint fluid was cloudy, but gram stains showed no neutrophils.

The humeral and glenoid components were loose and there was a thick humeral membrane. Frozen sections showed "Humeral membrane, right shoulder, excision: - Synovial tissue with extensive fibrosis and marked foreign body giant cell reaction with associated polarizable foreign material. - No neutrophils identified." 

The retrieved glenoid component showed substantial wear.

 Based on these findings, we considered the diagnosis of detritic synovitis (see this link).

He had a single stage revision to a hemiarthroplasty using Vancoymycin allograft for humeral fixation.

As a precaution we placed the patient on oral antibiotics (Augmentin) until the culture results were finalized.

In a week after surgery, the culture results came back as shown below

Note that the preoperative culture of his unprepared skin was strongly positive for Propionibacterium.
The humeral and glenoid explants and the membrane deep to the glenoid component were also strongly positive for Propionibacterium, while the humeral membrane specimens and joint fluid were unimpressive.
These findings emphasize that Propionibacterium is not uniformly distributed throughout the shoulder. Had the cultures been limited to the humeral membrane and joint fluid, the presence of Propionibacterium may have been overlooked.

With these culture results he was converted to the red protocol (see this link) of IV Ceftriaxone and Rifampin. 

Clinically, he is doing well with 140 degrees of assisted elevation and minimal shoulder discomfort.

Comment: This case is an excellent example of the complexities of the evaluation and management of a shoulder with delayed loosening of the total shoulder components. It is not possible to know if the Propionibacterium recovered from this shoulder were introduced from the patient's skin at the index surgery 13 years prior to the revision or if they arrived in the shoulder subsequently.

We have so much left to learn.