Copyright © 2008 by The Journal of Bone and Joint Surgery, Inc.
Commentary & Perspective
Commentary & Perspective by
T. Bradley Edwards, MD*,
Fondren Orthopedic Group, Houston, Texas
Posted October 2008
With information
from the Mayo Clinic database, Taunton and colleagues present a very
interesting and useful investigation into their use of a specific design of
metal-backed, bone-ingrowth glenoid component employed in unconstrained total
shoulder arthroplasty at their institution over a five-year period. Although
retrospective in design, this study provides very useful information to any
surgeon performing total shoulder arthroplasty. Their publication of the
overall disappointing results with this type of glenoid component, although not
glamorous to report, will help other surgeons and implant designers to avoid
the same types of complications observed by the authors. This manuscript also serves
as a reminder that the encouraging early results of a particular procedure or
implant do not necessarily translate into long-term success.
Although the study
was retrospective, all data were collected in a prospective manner, thus
minimizing this methodological weakness. To my knowledge, this is the largest
peer-reviewed series to report the results of an unconstrained metal-backed,
bone-ingrowth glenoid component. Dr. Cofield, who has a wealth of experience in
performing shoulder arthroplasty, performed all of the operations. The inclusion
criteria selected patients who would seemingly be optimal for implantation of a
metal-backed, bone-ingrowth glenoid component (large glenoid size and good bone
quality). The average follow-up of greater than nine years further serves to
strengthen the authors' conclusions. The minor deviations in surgical technique
(surgical approach, glenoid bone-grafting) reported would not, in my view, affect
the results.
There were two very
important results of the study. First and foremost, the type of metal-backed,
bone-ingrowth glenoid component utilized in this study has an unacceptably high
failure rate at middle to long-term follow-up. Kaplan-Meier survival estimates
show a failure rate of 21% when defined by an end point of revision, and 48%
when defined by a combined revision and radiographic failure end point at ten
years. Interestingly, the radiographic problems observed with the glenoid
component were associated with humeral component problems via polyethylene wear
debris in over one-fourth of the shoulders. Secondly, the promising early
clinical and radiographic findings observed and previously reported by the
authors after implantation of this type of glenoid component deteriorated with
time. This deterioration was presumably caused by progressive polyethylene
wear.
The search for the
ideal glenoid component continues. The high frequency of occurrence of radiolucent
lines around both pegged and keeled all-polyethylene cemented glenoid
components led to the development of metal-backed, bone-ingrowth glenoid
components1. Although the early results by the Mayo Clinic group and
others showed promise, longer term follow-up has shown unacceptably high
failure rates with these types of components2. These high failure
rates occurred despite the selection of only patients with good glenoid bone as
recipients of this type of component. The main problem encountered with these
components has been polyethylene wear. A thin piece of polyethylene placed
between a metallic humeral head component and a metal glenoid component base is
susceptible to accelerated wear. It seems that this wear becomes apparent approximately
three years after implantation and advances thereafter, ultimately leading to
component failure in many patients3.
The need for a
different type of glenoid component still exists, particularly in the revision
setting. The substantial glenoid bone loss often observed in the revision
situation frequently requires bone-graft reconstruction of the glenoid. Bone-graft
reconstruction of the glenoid combined with placement of an unconstrained
glenoid component as a single-stage procedure has been fraught with
complications, leading us to the use of a two-stage reconstruction4.
Obviously, a two-stage reconstruction represents a hardship for the patient; thus,
a single-stage glenoid revision remains desirable. Metal-backed, bone-ingrowth
glenoid components have been used in this indication with only limited success.
In fact, the authors list glenoid bone loss requiring reconstruction as their
only indication for use of the implant presented in this study. The quest for a
satisfactory unconstrained glenoid revision component continues.
I congratulate Dr.
Cofield and the shoulder service at the Mayo Clinic for their work in this
study. This paper presents important information to those performing shoulder
arthroplasty and will help others avoid the same complications and
unsatisfactory results presented by the authors. Research and development on
new glenoid components, both all-polyethylene and metal-backed, is ongoing and
is being performed by surgeons as well as industry. This paper will undoubtedly
serve and caution these innovators in their pursuit of advanced glenoid
components.
*The author did not receive any outside funding or grants in support of their research for or preparation of this work. He or a member of his immediate family received, in any one year, payments or other benefits in excess of $10,000 or a commitment or agreement to provide such benefits from a commercial entity (Tornier, Inc.). Also, a commercial entity (Tornier, Inc.) paid or directed in any one year, or agreed to pay or direct, benefits in excess of $10,000 to a research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the author, or a member of his immediate family, is affiliated or associated.
References
1. Gartsman GM, Elkousy HA, Warnock KM, Edwards TB, O'Connor DP. Radiographic comparison of pegged and keeled glenoid components. J Shoulder Elbow Surg. 2005;14:252-7.
2. Boileau P, Avidor C, Krishnan SG, Walch G, Kempf JF, Molé D. Cemented polyethylene versus uncemented metal-backed glenoid components in total shoulder arthroplasty: a prospective, double-blind, randomized study. J Shoulder Elbow Surg. 2002;11:351-9.
3. Boileau P, Avidor C, Walch G. Prothèse totale d'épaule avec un implant glenoïdien métallique non scellé: etude prospective de 354 implants suivis à plus de 2 ans. In: Walch G, Boileau P, and Molé D, editors. 2000 Prosthèses d'épaule. . . recul de 2 à 10 ans. Paris: Sauramps Medical; 2001. p 489-505.
4. Neyton L, Walch G, Nové-Josserand L, Edwards TB. Glenoid corticocancellous bone grafting after glenoid component removal in the treatment of glenoid loosening. J Shoulder Elbow Surg. 2006;15:173-9.
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