Sunday, May 15, 2016

The loose glenoid component - a challenge

Aman in his 60s had a history of multiple prior procedures on the left shoulder including multiple arthroscopic subacromial decompressions, hemiarthroplasty, repair of subscapularis failure, leading to a total shoulder arthroplasty in 2006 - the shoulder was never really comfortable after that. Because of increasing pain requiring narcotic medication he presented in 2015 with no systemic signs of infection. He  had maintained good range of motion and his main complaint is pain, which is worse with overhead movement but also present with rest and at night. He had crepitus with movement particularly reaching overhead. He had no fever, chills, or wound drainge. He had had a previous workup for infection including a bone scan which was negative.

On his AP view one can see the superior placement of the humeral head relative to both the humeral tuberosity (see this prior post) and the glenoid.

Aseptic loosening of the glenoid was suspected; he desired an exploration of the shoulder. The joint fluid was clear and there was no gross evidence of infection. The subscapularis was scarred. The rotator cuff was intact. The humeral component was solidly fixed in the humerus. The head was proud superiorly. The glenoid component was grossly loose and was removed. The stem was tightly fixed and could not be removed without humeral osteotomy; because of the absence of apparent infection, it was left in place. The head was replaced  with one that was inferiorly eccentric to better align with the tuberosity and glenoid. 

He was placed on the yellow protocol (see this link). His culture results were:

Collar membrane:

 Glenoid membrane:
 Glenoid explant:
 Joint fluid:

With these culture results he was converted to the red protocol (see this link).
While on antibiotics his shoulder was comfortable and functional.

Six months after revision, the shoulder appeared stable.

However, after discontinuance of his antibiotics, the symptoms recurred, including pain in the humerus were the stem had been retained. Note the slots in the distal prosthesis and the tight fit of the stem in the diaphysis.

The patient desired another revision with stem removal to manage the potential for residual bacteria in a biofilm on the retained component.

The humeral body was extremely well fixed with substantial bone growth into the slots. An extensive humeral osteotomy was required. The shoulder showed no obvious evidence of infection. Vigorous debridement and irrigation was followed by a bodice repair (see this link) after a long stem prosthesis had been inserted. 

The patient is currently on the red protocol with the plan for lifetime antibiotics.

Comment: This case shows the challenges of decision making in the management of an apparently aseptic case of glenoid loosening.

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