Sunday, December 11, 2011

Revision for failed total shoulder arthroplasty because of glenoid loosening

As we've discussed in previous posts, glenoid component wear and loosening is one of the commonest causes of failure of total shoulder arthroplasty. While some surgeons recommend complex approaches to revision surgery, including glenoid bone grafting and special components, our approach is different.

Let me explain the reasons that we avoid bone grafting and avoid replacing the glenoid component:

(1) When a glenoid component has loosened, the bone beneath it is in the process of active resorption. While we clean out all the reactive tissue, we can't be sure that we've arrested this process and would not want to put a new component on deteriorating bone.

(2) When a glenoid component has loosened, there is a major structural defect, making the fixation of new glenoid component less secure that what was available at the original total shoulder replacement. Thus, it is logical to assume that the rate of failure for a reinsertion will be greater than that for primary total shoulder arthroplasty. We try to avoid building a house on an unstable foundation.

(3) When a glenoid component has loosened, the diagnosis of infection cannot be excluded at the time of surgery. Cultures for the most common organism found in this circumstance, P Acnes, are not final until several weeks after surgery. We avoid putting a new glenoid component or devitalized bone graft into a surgical field that may be contaminated.

(4) Revision to an uncemented humeral hemiarthroplasty with smoothing of the residual glenoid bone after thorough removal of all reactive tissue and scar offers the patient the opportunity for a permanent single stage revision on one hand while maintaing the option for a simple re-revision if that should become necessary down the line on the other hand. Furthermore, articulation of the soft glenoid bone with the metal humeral head gives the bone a chance to stabilize and mature with time, so that in the uncommon circumstance that glenoid reinsertion becomes desirable, this procedure can be performed with a more stable bony foundation and after any concern about infection has been resolved.

One of our first cases was a superior court judge known to be very tough on drunken drivers. He had a total shoulder that worked well for several years, but, perhaps related to his enjoying digging for geoducks, his glenoid component became loose. Over fifteen years ago we removed his loose glenoid, did no grafting or reimplantation. He continues to bang the gavel and to clam.

Here is a more recent case. A 50 year old coach from California came to see us because of bilateral painful total shoulders. It is obvious from the x-rays below that both of his glenoid components have failed. His SST scores were 5/12 on each side.

Three years ago we revised the left side. We withheld antibiotics until cultures could be obtained. There was a substantial amount of reactive tissue throughout the shoulder and abundant scar in the humeroscapular motion interface. The rotator cuff was intact. The glenoid component was loose. The humeral component was well fixed but proud superiorly. There was a substantial amount of osteolysis of the humerus and glenoid. Abundant samples of fluid and scar tissue were harvested from the area around the humerus. Some of this appeared to be chronic inflammatory, and some of the other elements appeared to be acute inflammatory reactions. These were sent for frozen section as well as for permanent sections, and finally specimens were sent for culture.

Both the humeral and glenoid components were removed; all reactive tissue was removed; the residual glenoid bone was smoothed with a 56 +2 "ream and run" reamer. A new humeral component was inserted using a press-fit with antibiotic-impregnated (vancomycin) allograft. Antibiotics were administered and continued for 6 weeks.

Two weeks after surgery, his cultures grew out P. Acnes.

Three months later we performed a revision of the right side. On this side there was no evidence of inflammation. The glenoid component and humeral head were removed. An extensive debridement was carried out. The humeral head was replaced with the appropriate eccentric inferior prosthesis after the glenoid bone was smoothed. No glenoid bone grafting was performed. Cultures were negative at one month.

His current x-rays (below) show healed, stable glenoid bone surfaces and secure humeral fixation. While both humeral heads are medialized, this has not been associated with loss of function: currently he answers "yes" to all 12 of the SST questions.

Here's another example of the many cases we've treated this way. This time it is an active lady, again from California with painful total shoulder replacements on each side.

Her preoperative films are shown here with loose glenoid compnents on the right and left sides. SST scores were 4/12 on the left and 5/12 on the right.

She had revisions on each side consisting of glenoid component removal, thorough removal of all reactive tissue, no bone grafting or reinsertion of glenoid components, and humeral head exchange.

Two years after her revision surgeries, she's regained the comfort and function in both shoulders with 10/12 SST scores on both sides. Here are her most recent films

We find this is a safe, straightforward approach to the relatively common problem of glenoid component failure.


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