Survivorship and clinical outcomes of reverse total shoulder arthroplasty in patients with large glenoid defects using the stilting technique and a baseplate with central ingrowth cage and peripheral locking screws.

BACKGROUND

Stilting is a novel technique used in reverse shoulder arthroplasty (RSA) in patients with significant glenoid bone loss. This technique utilizes peripheral locking screws placed behind an unseated portion of the baseplate to transmit forces from the baseplate to the cortical surface of the glenoid, without the need for bone grafting. The stilted screw, once locked, provides a fixed angle point of support for this unseated aspect of a baseplate. The primary advantages of this technique are reduced cost compared to a custom implant and reduced operative time compared to bone grafting.

METHODS

We conducted a retrospective, nonrandomized, comparative cohort study of 41 patients who underwent primary RSA using the stilting technique with the Exactech Equinoxe Reverse System (Gainesville, FL, USA) at a single academic center from the years 2004 to 2021. Exclusion criteria included age under 18 or over 100 and oncologic or acute fracture RSA indications. Operative data was documented, including implant records, percent baseplate seating, and operative duration. Survivorship was compared among primary stilted RSA (n = 41), bone grafted RSA (n = 42), and non-stilted/non-bone grafted RSA (n = 1032) within our institutional shoulder arthroplasty database. A radiographic examination of baseplate failure was also conducted across the study groups. Postoperative functional outcomes were compared in a matched analysis involving patients with a minimum 2-year follow-up between stilted patients and a non-stilted/non-bone grafted control group for primary RSA.

RESULTS

All stilted RSA cases utilized metal augments and demonstrated a mean baseplate seating of 61% (range 45%-75%). For stilted RSAs, survivorship was 100% and 92.6% at 2 years and 5 years, compared to 98.3% and 94.6% for non-stilted/non-bone grafted and 96.3% and 79.5% for bone grafted RSAs (P = .042). At 5 years, the baseplate-related failure rates were greater in the stilted (7.4%) and the bone-grafted (9.3%) cohorts compared with the non-stilted/non-bone grafted cohort (1.1%, P < .001). The mean time to baseplate failure was 30 months for stilted RSA. Functional outcomes for primary RSA were statistically similar between stilted and non-stilted patients, including range of motion, Constant, American Shoulder and Elbow Surgeons, Simple Shoulder Test, University of California, Los Angeles, and Shoulder Pain and Disability Index scores.

CONCLUSION

The stilted RSA cohort exhibited noninferior revision and baseplate failure rates to that of bone grafted RSA. This suggests that stilting may be a viable technique for patients undergoing primary RSA with significant glenoid deformity.