Better Stability for Proximal Humeral Hemiarthroplasty
Better Stability for Proximal Humeral Hemiarthroplasty
Abstract & Commentary
Synopsis: A biomechanical study of tuberosity reattachment in hemiarthroplasty after 4-part humeral head fractures found that cerclage wiring provided optimal stability.
Source: Frankle MA, et al. Stability of tuberosity attachment in proximal humeral hemiarthroplasty. J Shoulder Elbow Surg. 2002;11(5):413-420.
Hemiarthroplasty is an established treatment for 4-part proximal humerus fractures, especially with significant displacement or poor-quality bone. This study evaluates 5 different techniques for tuberosity attachment in an attempt to analyze interfragmentary stability.
In the control group, the tuberosities were attached to the humeral shaft with nylon strap ties, and the rotator interval was closed. The second group added the attachment of the tuberosities to each other. The third group added attachment to the anterior fin. The fourth, fifth, and sixth groups included the addition of a circumferential cerclage to the previous 3. A robotic arm was used to test the reconstruction at 10°/s from 0° to 60°. Three cycles were performed for each reconstruction and interfragmentary displacements were measured at 15°, 30°, and 50° of external rotation. Using analysis of variance, Frankle and associates did not determine a difference within the cerclage or noncerclage groups. Therefore, the similar groups were combined and compared to the control and to each other for statistical analysis.
This study demonstrated that cerclage containing repairs had significantly lower displacements and strains (P < 0.05) than those without cerclages. Incorporation of the anterior fin did not enhance fixation when cerclage was used. The noncerclage groups allowed 45° of external rotation before reaching 100% strain, whereas the cerclage-containing groups allowed an additional 15° (total of 60° ER). Strain at the fracture site measured 200% at only 50° ER without the use of cerclage.
Comment by COL Patrick St. Pierre, MD
This is a well-done biomechanical study of tuberosity fixation in the treatment of a 4-part proximal humerus fracture by hemiarthroplasty. Frankle et al were recognized for their efforts by winning the Neer Award for 2001. They quite nicely tried to control as many factors in their experimental design as possible while testing the one question of whether cerclage fixation of the tuberosities brings increased fixation strength. Although it appears that the original design was to test several reconstruction techniques, they were able to combine similar designs and increase the power of their study.
Frankle et al recognized several limitations to their study. First, they acknowledged that they created perfect fracture lines with a saw, allowing for anatomic reduction of the fragments. Second, they only tested in rotation, while in the postoperative setting there would be forward flexion and abduction forces. Third, they only tested one prosthesis design, and variable designs may decrease the effect of cerclage fixation. Because these limitations affected both test groups equally, they do not invalidate their conclusions.
One major concern about the study design was that they used as the control a method that did not attach the tuberosities to each other. This would not be standard practice and may have had an effect on the statistical analysis. However, based on the information provided, Frankle et al demonstrate enough difference between the 2 combined groups to make their conclusions valid.
They should be commended on their study and their critical evaluation of tuberosity fixation in hemiarthroplasty. This is a preliminary study to what should be a more extensive evaluation of this technique using different prostheses and additional motion planes. However, even with just this study, surgeons should consider the use of cerclage when performing this operation in order to maximize fixation strength.
Dr. Pierre is Assistant Professor, Uniformed Services University, Orthopaedic Co-Director, Primary Care Sports Medicine Fellowship, DeWitt Army Community Hospital, Belvoir, VA.
Synopsis: A biomechanical study of tuberosity reattachment in hemiarthroplasty after 4-part humeral head fractures found that cerclage wiring provided optimal stability.Subscribe Now for Access
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