Biomechanical Comparison of Anatomic Humeral Head Resurfacing and Hemiarthroplasty in Functional Glenohumeral Positions

Long Beach Orthopaedic Surgical and Medical Group, 1040 Elm Avenue, Suite 100, Long Beach, CA 90813, USA.
The Journal of Bone and Joint Surgery (Impact Factor: 4.31). 01/2012; 94(1):68-76. DOI: 10.2106/JBJS.I.00171
Source: PubMed

ABSTRACT Resurfacing of the humeral head has gained interest as an alternative to traditional hemiarthroplasty because it preserves bone stock and respects the native geometry of the glenohumeral articulation. The purpose of this study was to compare the biomechanics of the intact glenohumeral joint with those following humeral head resurfacing and following hemiarthroplasty.
Seven fresh-frozen cadaveric shoulders were tested with the rotator cuff, pectoralis major, and latissimus dorsi musculature loaded with 20 N and the deltoid muscle loaded with 40 N in a custom shoulder testing system. Each specimen was tested in 20°, 40°, 60°, and 80° of vertical abduction. The articular surfaces of the humeral head and the glenoid were digitized to calculate the positions of the geometric center and apex of the humeral head relative to the geometric center of the glenoid at each testing position. The contact area and contact pressures were also measured with use of a Tekscan pressure sensor.
The geometric center of the humeral head shifted by a mean (and standard error) of 2.2 ± 0.3 mm following humeral resurfacing and 4.7 ± 0.3 mm following hemiarthroplasty (p < 0.0002). The apex of the humeral head was shifted superiorly at all abduction angles following hemiarthroplasty (p < 0.03). Both humeral resurfacing and hemiarthroplasty decreased the glenohumeral contact area and increased the peak pressure.
Resurfacing more closely restored the geometric center of the humeral head than hemiarthroplasty did, with less eccentric loading of the glenoid.
Compared with hemiarthroplasty, humeral resurfacing may limit eccentric glenoid wear and permit better function because the glenohumeral joint biomechanics and the moment arms of the rotator cuff and the deltoid muscle are restored more closely to those of the intact condition.

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    ABSTRACT: Purpose The aim of this study was to conduct a randomised, clinical trial comparing stemmed hemiarthroplasty and resurfacing hemiarthroplasty in the treatment of glenohumeral osteoarthritis. Methods A total of 40 shoulders (35 patients) were randomised to stemmed hemiarthroplasty or resurfacing hemiarthroplasty and evaluated three and 12 months postoperatively using the Constant-Murley score (CMS) and Western Ontario Osteoarthritis of the Shoulder (WOOS) index. Results There were no statistically significant differences in age, gender or pre-operative scores except for WOOS at baseline. Two patients were lost to follow-up. Significant improvements in CMS and WOOS were observed at one year after both arthroplasty designs. At one year, the mean CMS was 48.9 (range 6-80) after resurfacing hemiarthroplasty and 59.1 (range 0-88) after stemmed hemiarthroplasty {mean difference 10.2 [95 % confidence interval (CI) −3.3 to 23.6], P = 0.14}. The mean WOOS was 59.2 (range 5.2-100.0) and 79.4 (range 12.8-98.6), respectively [mean difference 20.2 (95 % CI 3.4-36.9), P = 0.02]. No major complications occurred and there were no revisions. Conclusions The effects of resurfacing hemiarthroplasty tended to be inferior to those of stemmed hemiarthroplasty. It is unclear whether this reflects a real difference in effect or baseline differences due to the limited number of randomised patients. We suggest there is a need for a larger, more definitive trial.
    International Orthopaedics 08/2014; 39(2). DOI:10.1007/s00264-014-2505-9 · 2.02 Impact Factor
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    ABSTRACT: Introduction Resurfacing shoulder arthroplasty is proposed in primary osteoarthritis of the shoulder. The present study compared resurfacing versus 3rd generation stemmed hemiarthroplasty in terms of survival, functional results and implant positioning effects. Materials and methods Seventy eight patients underwent arthroplasty for primary osteoarthritis of the shoulder: 41 by resurfacing and 37 by stemmed hemiarthroplasty. The two populations were comparable on all baseline variables. Minimum follow-up was 2 years. The principal assessment criterion was survivorship with surgical revision as end-point. Secondary criteria were functional results on Constant, quick-DASH, Neer and SSV scores, and implant positioning effects assessed on radiology. Results At a mean 44 months’ follow-up (range, 24–118 months), there were no significant differences in functional scores. Radiologic analysis found greater varus positioning and lateral offset of the humeral head in resurfacing compared with stemmed hemiarthroplasty (128° vs 138°, P < 0.01; 6.5 ± 2 vs 4.6 ± 1.6 mm, P < 0.01). Survivorship without revision was significantly poorer in resurfacing, with 4 revision procedures for glenoid wear (9.8%), versus none in hemiarthroplasty (P = 0.02). There was no correlation between humeral head size, positioning or lateral offset and revision. Conclusion Revision-free survival was significantly lower in resurfacing than in hemiarthroplasty. Greater humeral head size may increase lateral offset, accelerating glenoid wear. Down-sizing the humeral head in resurfacing procedures might limit these complications. Level of evidence Level III; case-control study.
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