Commentary by Bernard F. Morrey, MD*,
Mayo Clinic, Rochester, MN
Carefully performed studies of long-term results of total elbow arthroplasty are of great value, particularly when they demonstrate various aspects of prosthetic design. This report on the Kudo type-3 prosthesis provides results with the longest duration of follow-up of this design in the literature. Additionally, the patients in this series were operated on by surgeons other than the inventor of the prosthesis.
The most interesting aspect of this study is that it questions the need for soft-tissue stabilization, with use of this particular design, at least as it relates to preservation or resection of the collateral ligaments. The absence of postoperative dislocations among the patients in this series is distinctly uncommon and is particularly impressive since these procedures were done by four surgeons, obviously with somewhat varying surgical expertise, experience, and technique. That an unconstrained total elbow prosthesis proves stable, independent of collateral ligament repair, is not only unexpected but challenges one to search for an explanation. Since the author did not provide an explanation for the stability achieved, even in the absence of collateral ligament repair, we can only speculate on the reason for this result.
If collateral ligament repair is not necessary, might one anticipate improved motion in extension since this arc of motion is sometimes limited by contracted collateral ligaments? Although those patients who had collateral ligament repair did have less extension, both groups (i.e., the one with collateral ligament repair [group I] and the one without [group II]) had flexion contractures greater than those usually reported after total elbow arthroplasty. The other observations of interest in the group of patients who had collateral ligament repair are a higher prevalence of radiolucent lines and a lower revision-free survival rate. These observations are not readily attributable only to the presence or absence of collateral ligaments. One is therefore inclined to question whether differences in surgical technique among the surgeons may have accounted for some of the differences in outcome that the authors attribute to the presence or absence of collateral repair. The overall survival rate of 90% of the prostheses at sixteen years is impressive and justifies the perception that the success of this implant in these particular investigators' hands rivals that of hip joint replacement.
In spite of these positive features, the degree of residual flexion contracture in this series is greater than that seen in other long-term follow-up studies of total elbow replacement and may be a necessary concomitant of enhanced stability. Further, some concern may be expressed with regard to the high prevalence of radiolucency. That there were so few revisions for gross loosening is encouraging, but the high prevalence of radiolucent lines is a concern and merits further monitoring since it may indicate future failure. With this documentation of such a stellar performance of the so-called type-3 design, one might also question why there have been subsequent type-4 and type-5 designs. These latest innovations involve the surface of the humeral component and apparently represent attempts to address the issue of the high rate of radiolucency.
Finally, although this study had institutional review board approval, the operations were performed between twelve and eighteen years ago, and this is not a prospective, controlled study but rather a retrospective review with no real controls. Outcomes were determined by a retrospective review of patients' charts. Nevertheless, many intriguing questions are raised by this carefully conducted study, and it represents a significant contribution to the orthopaedic literature.
*The author did not receive grants or outside funding in support of his research or preparation of this manuscript. He did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the author is affiliated or associated.