Inverted-Bearing Reverse Shoulder Arthroplasty: Consequences on Scapular Notching and Clinical Results at Mid-Term Follow-Up

Background: Scapular notching following reverse shoulder arthroplasty (RSA) is caused by both biological and mechanical mechanisms. Some authors postulated that osteolysis that extends over the inferior screw is caused mainly by biological notching. Inverted-bearing RSA (IB-RSA) is characterized by a polyethylene glenosphere and a metallic humeral liner, decreasing the poly debris formation and potentially reducing high grades of notching. This study aims to report the results of IB-RSA on a consecutive series of patients at mid-term follow-up, focusing on the incidence of Sirveaux grade 3 and 4 scapular notching. Methods: A retrospective study on 78 consecutive patients who underwent primary IB-RSA between 2015−2017 was performed. At a 4 years minimum follow-up, 49 patients were evaluated clinically with Constant score (CS), Subjective shoulder value (SSV), American Shoulder and Elbow score (ASES), pain and range of motion, and with an X-ray assessing baseplate position (high, low), implant loosening, and scapular notching. Results: At a mean follow-up of 5.0 ± 0.9, all the clinical parameters improved (p < 0.05). One patient was revised for an infection and was excluded from the evaluation, two patients had an acromial fracture, and one had an axillary neuropraxia. Scapular notching was present in 13 (27%) patients (six grade 1, seven grade 2) and no cases of grade 3 and 4 were observed. Scapular nothing was significantly associated with high glenoid position (p < 0.001) and with lower CS (70 ± 15 vs. 58 ± 20; p = 0.046), SSV (81 ± 14 vs. 68 ± 20; p = 0.027), ASES (86 ± 14 vs. 70 ± 22; p = 0.031), and anterior elevation (148 ± 23 vs. 115 ± 37; p = 0.006). A 44 mm- compared to 40 mm-glenosphere was associate with better CS (63 ± 17 vs. 78 ± 11; p = 0.006), external (23 ± 17 vs. 36 ± 17; p = 0.036), and internal rotation (4.8 ± 2.7 vs. 7.8 ± 2.2; p = 0.011). Conclusions: IB-RSA is a safe and effective procedure for mid-term follow-up. Inverting biomaterials leads to a distinct kind of notching with mainly mechanical features. Scapular notching is associated with a high baseplate position and has a negative influence on range of motion and clinical outcome.

[Computerized tomography of the thorax and abdomen. Cost-effectiveness]

This work was aimed at investigating the cost-effectiveness of body CT, toward better equipment allocation in a given area. CT economics were calculated taking into account four main parameters: equipment, drugs, sanitary material and personnel. The biological cost in terms of radiation exposure was calculated on the effective dose. Quality was evaluated by comparing it with that of our standard examinations and on the basis of the diagnostic yield according to the index of radiological diagnoses by the American College of Radiology (ACR). The economic cost of chest CT was It. L. 257,240, that of abdominal CT was It. L. 365,000 and that of both regions It. L. 464,620. The effective dose was relatively high, i.e., 15.2 mSV for chest CT, 18.65 mSV in men and 27.46 mSV in women for abdominal CT and finally 27.38 mSV in men and 33.59 in women for chest-abdominal CT. The coded diagnoses were positive in approximately 60% of the cases examined consecutively; positivity was related to clinically relevant conditions in most of the cases. The economics and the biological cost of body CT exams were closely related to exam quality, whose standard was high. The high rate of positive findings and the clinical relevance of the condition make an indirect indicator of high quality and of accurate patients selection. To conclude, the allocation of CT equipment in a given area should be preceded by a careful cost-effectiveness analysis, considering optimized equipment use as related to local clinical needs.

Inverted-bearing reverse shoulder arthroplasty: long-term survivorship, complications, clinical, and radiological outcomes

BACKGROUND

Inverted-bearing reverse shoulder arthroplasty (IB-RSA) is characterized by a polyethylene glenosphere and a metallic humeral liner to minimize polyethylene wear and debris secondary to impingement between the humerus and glenoid neck. IB-RSA long-term survivorship, complication and revision rates, as well as clinical and radiographic outcomes have not been reported yet.

METHODS

This is a monocentric retrospective study on a consecutive series of 151 patients who underwent primary IB-RSA from January 2009 to September 2015 and were evaluated clinically and radiologically at the minimum 8-year follow-up. All complications and reoperations were recorded. Survivorship analysis with any revision surgery as endpoint was done using Kaplan-Meier survival curves.

RESULTS

Seventy-eight patients (follow-up rate 51.7%) were reviewed at a mean follow-up of 10.1 ± 1.9 years. At 10 years, the revision-free survival was 98.7% (95% confidence interval: 94.8-99.7). Sixteen complications (10.6%) were observed: 2 axillary nerve injuries, 2 infections, 2 glenoid loosening (which stabilized within 1 year), 2 cases of otherwise unexplained painful stiffness, 4 acromial fractures, 1 post-traumatic scapular pillar fracture, and 3 post-traumatic humeral periprosthetic fractures. Two patients were revised due to infection. No cases of late glenoid loosening and humeral loosening were observed. The revision rate was 1.3%. All the clinical scores and range of motion significantly improved at the last follow-up compared with preoperative status: final Constant score was 66.1 ± 17.4, Subjective Shoulder Value 79.1 ± 20.9, and the American Shoulder and Elbow Surgeons 82.2 ± 17.7. Scapular notching was observed in 51.4% of patients: only 1 case of grade 3 notching was observed in an early glenoid subsidence case.

CONCLUSIONS

Primary IB-RSA appears to be a safe and effective procedure and does not present specific implant-associated complications at long-term follow-up. Radiographic analysis showed that inverting the biomaterials leads to a distinct kind of notching with mainly mechanical features.