Larger-diameter trunnions and bolt-reinforced taper junctions are associated with less tribocorrosion in reverse total shoulder arthroplasty.

BACKGROUND: Morse taper junction tribocorrosion is recognized as an important failure mode in total hip arthroplasty. Although taper junctions are used in almost all shoulder arthroplasty systems currently available in the United States, with large variation in design, limited literature has described comparable analyses of taper damage in these implants. In this study, taper junction damage in retrieved reverse total shoulder arthroplasty (RTSA) implants was assessed and analyzed. METHODS: Fifty-seven retrieved RTSAs with paired baseplate and glenosphere components with Morse taper junctions were identified via database query; 19 of these also included paired humeral stems and trays or spacers with taper junctions. Components were graded for standard damage modes and for fretting and corrosion with a modified Goldberg-Cusick classification system. Medical records and preoperative radiographs were reviewed. Comparative analyses were performed assessing the impact of various implant, radiographic, and patient factors on taper damage. RESULTS: Standard damage modes were commonly found at the evaluated trunnion junctions, with scratching and edge deformation damage on 76% and 46% of all components, respectively. Fretting and corrosion damage was also common, observed on 86% and 72% of baseplates, respectively, and 23% and 40% of glenospheres, respectively. Baseplates showed greater moderate to severe (grade ≥ 3) fretting (43%) and corrosion (27%) damage than matched glenospheres (fretting, 9%; corrosion, 13%). Humeral stems showed moderate to severe fretting and corrosion on 28% and 30% of implants, respectively; matched humeral trays or spacers showed both less fretting (14%) and less corrosion (17%). On subgroup analysis, large-tapered implants had significantly lower summed fretting and corrosion grades than small-tapered implants (P < .001 for both) on glenospheres; paired baseplate corrosion grades were also significantly lower (P = .031) on large-tapered implants. Factorial analysis showed that bolt reinforcement of the taper junction was also associated with less fretting and corrosion damage on both baseplates and glenospheres. Summed fretting and corrosion grades on glenospheres with trunnions (male) were significantly greater than on glenospheres with bores (female) (P < .001 for both). CONCLUSIONS: Damage to the taper junction is commonly found in retrieved RTSAs and can occur after only months of being implanted. In this study, tribocorrosion predominantly occurred on the taper surface of the baseplate (vs. glenosphere) and on the humeral stem (vs. tray or spacer), which may relate to the flexural rigidity difference between the titanium and cobalt-chrome components. Bolt reinforcement and the use of large-diameter trunnions led to less tribocorrosion of the taper junction. The findings of this study provide evidence for the improved design of RTSA prostheses to decrease tribocorrosion.

National disparities in access to physical therapy after rotator cuff repair between patients with Medicaid vs. private health insurance.

BACKGROUND: Arthroscopic rotator cuff repair is an effective treatment for patients with symptomatic rotator cuff tears. Ensuring timely and appropriate postoperative access to physical therapy (PT) is paramount to the achievement of optimal patient outcomes. Extended immobility due to a lack of formal rehabilitation can lead to decreased range of motion, continued pain, and potential reoperation for stiffness. The purpose of this study is to evaluate national disparities in access to PT services after rotator cuff repair between patients with private vs. Medicaid insurance. This study will further evaluate differences in access to PT services between states that have previously undergone Medicaid expansion as compared with those states which have not. METHODS: The American Physical Therapy Association Website was used to identify 10 physical therapy practices from the capital city in every state. Each physical therapy practice was contacted using a mock-patient script for a patient with Medicaid insurance or private (Blue Cross Blue Shield) insurance. To maintain anonymity, calls were made by two separate investigators. Univariate analysis included independent sample t-test for differences between the study groups for continuous variables. Chi square or Fisher's exact test assessed differences in discrete variables between the study groups. RESULTS: Contact was made with 465 of 510 (91.2%) physical therapy practices. Overall, 52.7% accepted Medicaid insurance, while 94.9% accepted private insurance (P < .001). Medicaid insurance was more likely to be accepted in a Medicaid expansion state than a nonexpansion state (56.1% vs. 46.3%, P = .05). Private insurance was also more likely to be accepted in a Medicaid expansion state than a nonexpansion state (96.7% vs. 91.3%, P = .01). The time to first appointment varied more in Medicaid expansion states (private range: 0-43 days, Medicaid range: 0-72 days) than in nonexpansion states (private range: 0-11 days, medicaid range: 0-10 days). CONCLUSION: Significantly fewer PT practices accepted Medicaid insurance nationally compared with private insurance, which suggests that patients with Medicaid insurance have greater difficulty accessing PT after rotator cuff repair in the United States compared with patients with private insurance. While Medicaid insurance was more likely to be accepted in a Medicaid expansion state, this finding was only borderline significant, which indicates that patients in Medicaid expansion states are still having difficulty accessing PT, despite efforts to expand government insurance coverage to improve access to care. Orthopedic surgeons should counsel their patients with Medicaid insurance to seek out PT as early as possible in the postoperative period to avoid delays in rehabilitation.