PURPOSE: Stress shielding is known to occur around rigidly fixed implants. We hypothesized that stress shielding around radial head prostheses is common but nonprogressive. In this study, we present a classification scheme to support our radiographic observations. METHODS: We reviewed charts and radiographs of 86 cases from 79 patients with radial head implants from both primary and revision surgeries between 1999 and 2009. Exclusion criteria included infection, loosening, or follow-up of less than 12 months. We classified stress shielding as: I, cortical thinning; II, partially (IIa) or circumferentially (IIb) exposed stem; and III, impending mechanical failure. RESULTS: Of 26 well-fixed stems, 17 (63%) demonstrated stress shielding: I = 2, II = 15 (IIa = 12, IIb = 3), and III = 0. We saw stress shielding with all stem types: cemented or noncemented; long or short; and straight, curved, or tapered. The only significant difference was that stems implanted into the radial shaft had less stress shielding than stems implanted into the neck or tuberosity (P = .03). The average follow-up was 33 months (range, 13-70 mo). Stress shielding was detectable by an average of 11 months (range, 1-15 mo). The pattern of bone loss was similar in 16 of 17 cases (94%), starting on the outer periosteal cortex. The 3 cases with circumferential exposure of the stem (stage IIb) averaged 2.6 mm (range, 1-4 mm) of exposed stem. Stress shielding never extended to the bicipital tuberosity, and there were no cases of impending mechanical failure. CONCLUSIONS: Stress shielding around radial head prostheses is common, regardless of stem design. However, it is typically minor, nonprogressive, and of questionable clinical consequence. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.
PURPOSE: Stress shielding is known to occur around rigidly fixed implants. We hypothesized that stress shielding around radial head prostheses is common but nonprogressive. In this study, we present a classification scheme to support our radiographic observations. METHODS: We reviewed charts and radiographs of 86 cases from 79 patients with radial head implants from both primary and revision surgeries between 1999 and 2009. Exclusion criteria included infection, loosening, or follow-up of less than 12 months. We classified stress shielding as: I, cortical thinning; II, partially (IIa) or circumferentially (IIb) exposed stem; and III, impending mechanical failure. RESULTS: Of 26 well-fixed stems, 17 (63%) demonstrated stress shielding: I = 2, II = 15 (IIa = 12, IIb = 3), and III = 0. We saw stress shielding with all stem types: cemented or noncemented; long or short; and straight, curved, or tapered. The only significant difference was that stems implanted into the radial shaft had less stress shielding than stems implanted into the neck or tuberosity (P = .03). The average follow-up was 33 months (range, 13-70 mo). Stress shielding was detectable by an average of 11 months (range, 1-15 mo). The pattern of bone loss was similar in 16 of 17 cases (94%), starting on the outer periosteal cortex. The 3 cases with circumferential exposure of the stem (stage IIb) averaged 2.6 mm (range, 1-4 mm) of exposed stem. Stress shielding never extended to the bicipital tuberosity, and there were no cases of impending mechanical failure. CONCLUSIONS: Stress shielding around radial head prostheses is common, regardless of stem design. However, it is typically minor, nonprogressive, and of questionable clinical consequence. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.
Authors: Pierre Laumonerie; Meagan E Tibbo; Panagiotis Kerezoudis; Marc Olivier Gauci; Nicolas Reina; Nicolas Bonnevialle; Pierre Mansat Journal: Int Orthop Date: 2018-07-30 Impact factor: 3.075
Authors: Pierre Laumonerie; Nicolas Reina; Claudia Gutierrez; Stephanie Delclaux; Meagan E Tibbo; Nicolas Bonnevialle; Pierre Mansat Journal: Int Orthop Date: 2017-09-21 Impact factor: 3.075
Authors: Jeremy N DiNoro; Naomi C Paxton; Jacob Skewes; Zhilian Yue; Philip M Lewis; Robert G Thompson; Stephen Beirne; Maria A Woodruff; Gordon G Wallace Journal: Polymers (Basel) Date: 2022-06-09 Impact factor: 4.967
Authors: Pierre Laumonerie; Maroun Raad; Meagan E Tibbo; Panagiotis Kerezoudis; Nicolas Bonnevialle; Pierre Mansat Journal: Shoulder Elbow Date: 2019-05-19