Friday, September 22, 2017

Total Shoulder Arthroplasty – glenoid component failure is progressive and is associated with inferior clinical outcomes.

Radiographic and clinical comparison of pegged and keeled glenoid components using modern cementing techniques: midterm results of a prospective randomized study

These authors point out the that most frequent indication for revision total shoulder arthroplasty is loosening of the glenoid component, which has been correlated radiographically with the appearance of lucencies around the glenoid component.

They evaluated the radiographic and clinical outcomes of patients with primary osteoarthritis randomized to receive either a Tornier smooth pegged glenoid component or a Tornier keeled glenoid (see below)  at minimum 5-year follow-up. Surgeries were all performed by an individual highly experienced shoulder surgeon.

Of note is that the great majority of these cases had simple (A1) glenohumeral pathoanatomy.

Of the 50 patients (59 shoulders) initially enrolled, 10 died.

Three patients with keeled components had early failure and were revised before 5-year follow-up. In all, 20% of the keeled shoulders (6 of 30) and 7% of the pegged shoulders (2 of 29) underwent revision surgery.

Eight shoulders did not return for followup at a minimum of 5 years. 38 of 46 shoulders (30 patients) were available with minimum 5-year follow-up (82.6%) At an average of 7.9 years, all but 2 shoulders showed at least grade 2 lucency and approximately 40% of shoulders in each group showed either grade 4 or 5 lucency (see below)

Importantly, the shoulders with high radiolucency scores had worse clinical outcomes.

Comment: This report is a followup of a shorter term study (see this link) on the same initial patient cohort. The findings of the earlier paper were:

"After an average follow-up of 26 months, the rate of glenoid lucency (of at least grade 2) was significantly higher in patients with a keeled glenoid component (46%) compared to patients with a pegged glenoid component (15%).

Glenoid lucency progressed (at least 1 grade) between postoperative radiographs and follow-up radiographs in 29% of patients, including 10 patients with keeled glenoid components (42%) and 3 patients with pegged glenoid  components (14%). The rate of progression and the final grade of glenoid lucency were higher in patients with keeled glenoid components compared to patients with pegged glenoid components."

The important findings from both of these reports are that glenoid loosening is common and progressive with time. The 20% revision rate for keeled in the hands of an experienced surgeon is a concern. Furthermore, this study points out that the rate of surgical revision does not reflect the rate of glenoid failure: apparently a substantial percentage of patients with high grades of lucency and inferior clinical outcomes are reluctant to have a revision procedure.

As for the comparison of smooth non-ingrowth peg versus keeled glenoid components, this study suggests an early loosening problem with the keeled components. The pegged component used in this study does not take advantage of the fluted central peg which is now available (see below) so the results with the modern design are not reflected in this study.

It is of note that these authors conclude, “ given that biomechanical data have shown pegged glenoid superiority, with clinical and radiographic data showing improved early results, we continue to use pegged glenoid components.”

Finally, the observation that patients accept deterioration in shoulder function for an extended period of time prior to revision, suggests that monitoring function may be a more cost effective method than sequential x-rays for tracking the long term outcome of shoulder arthroplasty.

This point is made in the paper referenced below.

Patient functional self-assessment in late glenoid component failure at three to eleven years after total shoulder arthroplasty

"Failure of the glenoid component is the most common indication for late revision of a total shoulder arthroplasty (TSA). This is the first study to characterize the deterioration in patient self-assessment of shoulder function occurring with glenoid component failure at times remote from the index surgery. Of 115 total shoulders, 11 had revision by the original surgeon for isolated glenoid loosening. Simple Shoulder Test scores averaged 4.4 before TSA, rose to a mean of 11.3 after surgery, and fell to a mean of 4.6 before revision for glenoid loosening performed at a mean of 7 years after TSA. All shoulders showed a drop of at least 3 points between the peak Simple Shoulder Test score and the prerevision Simple Shoulder Test score. Periodic self-assessment of shoulder function may offer a method of screening patients for the possibility of late glenoid component failure. "

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