Review Question - QID 220007

Total Shoulder Arthroplasty QID: 220007 (SBQ24SE.68)

QID 220007 (Type "220007" in App Search)

A 55-year-old active female undergoes the procedure shown in Figure A after years of shoulder pain with overhead activities. She returns four years later after rupturing her subscapularis during a tennis tournament and is revised to the construct shown in Figure B. The surgeon dictates in her operative report that she retained the patient's platform stem and successfully removed her cemented polyethylene glenoid component with minimal bone loss, replacing it with a 32mm glenosphere. The surgeon's decision to retain the patient's platform stem has which of the following consequences?

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Increased risk of stem malalignment

54/833

Increased proximal metaphyseal stress shielding

77/833

Increased risk of infection with Cutibacterium acnes

14/833

Lower patient-reported outcome measures

10/833

Lower overall operative time

81%

673/833

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The patient has undergone conversion of her anatomic total shoulder arthroplasty (TSA) to a reverse total shoulder arthroplasty (RTSA) with a convertible platform stem, allowing for retention of the stem and placement of a modular shell component and polyethylene, which reduces the overall operative time and complexity of the revision.

Revision shoulder arthroplasty can be exceedingly complex and can pose unique intraoperative challenges that include bone loss on both the humeral and glenoid sides. Platform stems were designed to allow for modular conversion from failed TSA to RTSA without the need to remove the humeral stem. The proposed benefits of this implant design feature include reduced operative time, decreased blood loss, preservation of humeral bone stock, and possible cost reduction.

Groh et al. reviewed the results of revision from hemiarthroplasty to total shoulder arthroplasty utilizing modular component systems. The authors identified 15 patients who underwent revision from hemiarthroplasty (HA) to total shoulder arthroplasty (TSA) from 1995 to 2007 and found that revision HA to TSA was significantly associated with pain relief (P < .01) as well as improvement in forward elevation from a mean of 91 to 141 degrees. They concluded that the data from this study suggest that modular revision of painful HA for glenoid arthrosis to TSA is a reliable procedure with good improvements in pain, range of motion, and function.

Crosby et al. reviewed the role of convertible platform stems in the conversion to reverse total shoulder arthroplasty with and without humeral stem retention. The authors retrospectively reviewed 102 consecutive shoulders undergoing revision arthroplasty, 29 of which had retention of a convertible-platform humeral component. They found that patients with retention had significantly shorter operative time, lower estimated blood loss, lower rate of intraoperative complications, and slightly better postoperative range of motion.

Figure A is an AP radiograph of the shoulder showing a well-fixed, uncomplicated TSA. Figure B is an AP radiograph of the shoulder showing conversion to a RTSA.

Incorrect Answers:
Answer 1: Shorter stems, which are becoming more common, have been associated with an increased risk of stem malalignment (typically varus) due to metaphyseal-diaphyseal mismatch.
Answer 2: Though larger diameter stems with greater filling ratios are associated with increased proximal stress shielding, this is not a specific risk factor associated with retaining a convertible platform stem.
Answer 3: There is nothing to suggest that primary convertible stem retention increases the patient's risk for infection above and beyond the baseline increased risk for infection after revision surgery.
Answer 4: There is no data to support lower patient-reported outcome measures after the use of a convertible implant in the setting of revision shoulder replacement