Copyright © 2006 by The Journal of Bone and Joint Surgery, Inc.
Commentary & Perspective
Commentary & Perspective by
John J. Callaghan, MD*,
Department of Orthopaedics, University of Iowa, Iowa City, Iowa
"Intraoperative Fractures of the Acetabulum During Primary Total Hip Arthroplasty," by Haidukewych et al., addresses an uncommon but clinically relevant complication that can occur during total hip arthroplasty. The authors attempt to answer several questions:
What is the prevalence of acetabular fracture during the
total hip procedure when cemented and cementless acetabular components are
utilized; Is the use of certain acetabular component
designs more likely to cause the complication; and finally, What is the outcome
following the intraoperative recognition and treatment of intraoperative
fractures?
The authors' institution has a robust total hip replacement
database and registry, which allows them to determine the number of arthroplasties
in which a complication has been recorded and to determine the prevalence of
that complication. The authors report an overall low prevalence of
intraoperative acetabular fractures, and, notably, they report no such
fractures in association with cemented fixation of the acetabulum. Most
surgeons who perform large numbers of total hip replacements have recognized
that this complication became recognized only after the introduction of cementless
acetabular fixation. In fact, even in the infancy of the use of cementless
acetabular components, fracture was not reported and probably did not occur
because line-to-line reaming was used in the early and mid 1980s for acetabular
preparation. It was not until the
technique of underreaming with press-fit fixation of components became popular
that this complication was recognized and reported. In addition, when the
technique of underreaming was initially implemented, some surgeons were recommending
that 3 or 4 mm of underreaming might be optimal1. Fortunately, this
practice was abandoned by most surgeons when cadaveric studies demonstrated
fractures with as little as 2 mm of underreaming and when clinical presentation
of acetabular fractures became recognized2,3.
The importance of the present paper is that the time interval that was
evaluated began in 1990, a time when the so-called learning curve for this
technique and cementless fixation had already passed. Hence, the reported fracture
rate of 0.4% is for procedures in which contemporary techniques (i.e., 2 mm or
less of underreaming) are used. Also, as noted by the authors, this is probably
an underestimation of the prevalence because it does not include fractures
recognized on the postoperative radiograph or in the early postoperative
course. I have personally seen both of these scenarios in my practice on rare
occasions. Hence, surgeons should be aware that this problem can and does
occasionally occur with the techniques and designs that we use today.
The authors did find that the use of certain acetabular
component designs was associated with a larger prevalence of this complication.
This problem was more prevalent with use of elliptical monolithic components. Elliptical
components were designed to potentially provide better initial fixation of the
acetabular component. If a component provides better fixation by design, it
also must produce greater stresses in the bone to which it is being press fit,
and hence the bone is more susceptible to fracture. Surgeons should be aware
that the use of elliptical components has been associated with a greater risk
of intraoperative acetabular fracture, especially when the components are monolithic.
Whatever component a surgeon uses, he or she should try to use it regularly. The
"feel" of each component design on insertion is different due to geometry,
fixation surface, and thickness of the metal. If the goal is to bottom out the
component, which I believe it is, relatively large impactions are needed to
seat the component. The quandary for the surgeon, however, is to impact the cup
"not too hard but not too soft," and thus, to determine that feel, the surgeon
needs to use that type of component regularly. I also believe having holes in a
modular shell takes some, but not all, of the guesswork out of whether the
component has bottomed out.
The third point that the authors address is the intermediate-term
results of total hip arthroplasty and acetabular fixation after an
intraoperative fracture does occur, is recognized, and
when treatment is modified. When the authors recognized the problem, they used
a component with supplemented screw fixation, added bone graft to the fracture
site, and treated the patients with partial weight-bearing for six weeks
postoperatively, which resulted in all fractures healing and all components
appearing to be bone ingrown on radiographs. Hence it is important at the time
of surgery to be able to evaluate the acetabulum for fracture, especially when
vigorous impaction is needed to seat a particular component. I agree with the authors that, with small
incisions, the surgeon may fail to recognize the fracture. I am also concerned about the aggressive
rehabilitation protocols that have been initiated by some surgeons who perform
hip replacements through small incisions, as unrecognized nondisplaced
fractures have been reported to displace postoperatively4.
In conclusion, although the authors may be underreporting
the problem and although they do not address fractures initially recognized
postoperatively, they have provided important information on the prevalence of
intraoperative acetabular fracture, the designs that pose greatest risk, and the
likely outcome after recognition and treatment of the problem.
*The author did not receive grants or outside funding in
support of his research for or preparation of this manuscript. The author
received payments or other benefits or a commitment or agreement to provide
such benefits from a commercial entity (DePuy). In addition, a commercial
entity (DePuy) paid or directed, or agreed to pay or direct, benefits to a
research fund, foundation, educational institution, or other charitable or
nonprofit organization with which the authors are affiliated or associated.
References
1. Schmalzried TP, Wessinger SJ, Hill GE, Harris WH. The Harris-Galante porous acetabular component press-fit without screw fixation: five-year radiographic analysis of primary cases. J Arthroplasty. 1994;9:235-42.
2. Kim YS, Callaghan JJ, Ahn PB, Brown TD. Fracture of the acetabulum during insertion of an oversized hemispherical component. J Bone Joint Surg Am. 1995;77:111-7.
3. MacKenzie JR, Callaghan JJ, Pedersen DR, Brown TD. Areas of contact and extent of gaps with implantation of oversized acetabular components in total hip arthroplasty. Clin Orthop Relat Res. 1994;298:127-36.
4. Fehring TK, Mason JB. Catastrophic complications of minimally invasive hip surgery. A series of three cases. J Bone Joint Surg Am. 2005;87:711-14.
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