Document Detail

Stress shielding around radial head prostheses.
MedLine Citation:
PMID:  23021176     Owner:  NLM     Status:  In-Data-Review    
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.
Cholawish Chanlalit; Dave R Shukla; James S Fitzsimmons; Kai-Nan An; Shawn W O'Driscoll
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  The Journal of hand surgery     Volume:  37     ISSN:  1531-6564     ISO Abbreviation:  J Hand Surg Am     Publication Date:  2012 Oct 
Date Detail:
Created Date:  2012-10-01     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7609631     Medline TA:  J Hand Surg Am     Country:  United States    
Other Details:
Languages:  eng     Pagination:  2118-25     Citation Subset:  IM    
Copyright Information:
Copyright © 2012 American Society for Surgery of the Hand. All rights reserved.
Biomechanics Laboratory, Department of Orthopedic Surgery, Mayo Clinic, Rochester MN; and the Department of Orthopedics, Faculty of Medicine, HRH Princess Maha Chakri Sirindhorn Medical Center, Srinakhrinwirot University, Bangkok, Thailand.
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