The Journal of Bone and Joint Surgery (American) 79:1416-21 (1997)
© 1997 The Journal of Bone and Joint Surgery, Inc.
Instructional Course Lecture |
Instructional Course Lectures, The American Academy of Orthopaedic Surgeons - Periprosthetic Fractures of the Acetabulum during and following Total Hip Arthroplasty*
JOHN J. CALLAGHAN, M.D. , IOWA CITY, IOWA
An Instructional Course Lecture, The American Academy of Orthopaedic Surgeons
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Introduction
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The occurrence of fractures around the femoral component of a total hip prosthesis has been well described, and the treatment options have been studied extensively. However, few reports concerning the occurrence and treatment of periprosthetic fractures of the acetabulum during and following total hip arthroplasty are available10,12,14,18. In this paper, I will review the literature concerning periprosthetic fractures of the acetabulum and outline measures to prevent and treat the problem.
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Historical Review
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In 1972, Miller described ischiopubic fractures following the insertion of a Ring component without cement in five hips and following the insertion of a McKee component with cement in four. The fractures failed to unite with non-operative treatment, and resection arthroplasty was performed in all of the hips. McElfresh and Coventry documented only one periprosthetic acetabular fracture among 5400 total hip arthroplasties performed with cement at the Mayo Clinic. Silvello et al. reported the successful treatment of a periprosthetic acetabular fracture (associated with loosening of the component) with revision of the component and bone-grafting. More recently, in a study of periprosthetic acetabular fractures following total hip arthroplasty, Peterson and Lewallen reported that long-term survival of the components was poor (eight of ten were revised) unless additional operative intervention was performed. The occurrence and recognition of periprosthetic fractures of the acetabulum, as well as those of the femur, may be on the rise, especially during the intraoperative and early postoperative periods, because of the need for so-called press-fit stability of total hip prostheses inserted without cement1,2,19.
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In Vitro Studies
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As fixation of the acetabular component without cement has become the standard construct in total hip arthroplasties, problems associated with this approach are now being recognized. In vitro studies have demonstrated minimum bone-prosthesis micromotion when screws have been used to augment fixation of acetabular components without cement1,8,19. Clinical studies have demonstrated durability of five to ten years when this form of fixation has been utilized9,15,16. However, actual and potential complications, including inadvertent perforation of vessels4,7,21, screw-fretting3, and channels13 (along screw tracks or through unfilled screw-holes) for the access of debris14,15 have been concerns. These concerns have led to the use of so-called press-fit techniques (underreaming of the acetabulum in relationship to the size of the acetabular component that is to be inserted). In vitro and in vivo studies have demonstrated stability of components inserted with this approach1,2,16. In an in vitro study of acetabular components inserted in cadaveric human bone, performed by Kim, myself, Ahn, and Brown, a fracture occurred in four of fifteen acetabula that had been underreamed by two millimeters and in four of fifteen that had been underreamed by four millimeters6. Although most fractures were peripheral, column and transverse fractures also occurred (Fig. 1). Multiple projections were required to demonstrate many of the fractures on plain radiographs (Figs. 2-A and 2-B). In addition, substantial impaction (approximately 2000 newtons) was necessary to advance the acetabular component into the underreamed acetabulum (Fig. 3). Even with large impaction blows, gaps between the dome of the prosthesis and the bone were unavoidable (Fig. 4), as demonstrated with studies involving injection of epoxy to make molds and those employing Pressensor contact film5,6,11. When screws are used to secure the acetabular implant to bone, the posterosuperior and posteroinferior regions of the acetabulum provide optimum purchase, especially when bicortical fixation is achieved (Figs. 5-A and 5-B)20.
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FIG1: Fig. 1 Patterns of acetabular fractures observed during the insertion of oversized acetabular components. They include anterior wall (A), transverse (B), inferior lip (C), and posterior wall (D) fractures.
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Fig. 2-A A peripheral rim fracture (arrow) is demonstrated on one radiograph (Fig. 2-A) but not on the other (Fig. 2-B).
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FIG3: Fig. 3 Load-deflection curves. In both of these recordings, tracings of
the individual loading cycles are deliberately offset for clarity.
a: The curve on the left shows the advancement of a cup that was
oversized by two millimeters; a 2000-newton pulse was used. The advancement
of the cup is indicated by irrecoverable deformation (that is, the open
load-deflection loop) after the unloading-curve segment. However, the curve
on the right shows that a subsequent 2000-newton pulse failed to advance
the cup farther. b: Multiple pulses of 1000 newtons failed to
advance the cup: there is no net offset between loading and unloading
curves (that is, the load-deflection loops are closed.) (Reprinted, with
permission, from: Kim, Y. S.; Callaghan, J. J.; Ahn, P. B.; and Brown, T.
D.: Fracture of the acetabulum during insertion of an oversized
hemispherical component. J. Bone and Joint Surg., 77-A: 112, Jan.
1995.)
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FIG4: Fig. 4 Graph representing the area of contact between the acetabular
prosthesis and the bone, starting from the dome and proceeding to the
periphery. A change in the geometry that enlarges the periphery (the outer
1.3 centimeters of the dual-radius component [PSL; Osteonics, Allendale,
New Jersey] provided better peripheral contact and similar polar contact
compared with those provided by the two-millimeter-oversized Harris-Galante
(H-G) spherical component (Zimmer, Warsaw, Indiana). The spherical (H-G)
component inserted after on-line reaming also provided better contact
between the dome and the bone compared with that in the other conditions.
(Reprinted, with permission, from: Kim, Y. S.; Brown, T. D.; Pedersen, D.
R.; and Callaghan, J. J.: Reamed surface topography and component seating
in press-fit cementless acetabular fixation. J. Arthroplasty, 10
[Supplement]: S17, 1995.)
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FIG5-A: Fig. 5 Schematic of the acetabular zones on the left side of a pelvis.
(Reprinted, with permission, from: Stranne, S. K.; Callaghan, J. J.; Elder,
S. H.; Glisson, R. R.; and Seaber, A. V.: Screw-augmented fixation of
acetabular components. A mechanical model to determine optimal screw
placement. J. Arthroplasty, 6: 302, 1991.)
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FIG5-B: Fig. 5-B Graphic representation of the screw pull-out data recorded in
the zones shown in Fig. 5-A. The posterosuperior quadrant provides the best
screw purchase, followed by the posteroinferior quadrant. Bicortical screw
purchase is better than unicortical purchase. (Reprinted, with permission,
from: Stranne, S. K.; Callaghan, J. J.; Elder, S. H.; Glisson, R. R.; and
Seaber, A. V.: Screw-augmented fixation of acetabular components. A
mechanical model to determine optimal screw placement. J. Arthroplasty, 6:
304, 1991.)
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Clinical Recognition and Treatment
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Intraoperative Fractures
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I recently collaborated in a multicenter study of intraoperative acetabular fractures following the insertion of components in underreamed acetabula17. Eleven of thirteen fractures occurred in women who had osteopenic bone. Evaluation of these patients led me to manage this population in the following manner.
Prevention is always better than treatment. Excessive underreaming (greater than one millimeter) is strongly discouraged, especially in patients who have osteopenic bone. In my practice, patients who have osteopenic bone are managed with so-called on-line reaming (reaming of the acetabulum to the size of the acetabular component that is to be inserted), gentle insertion of the component, and augmentation of the fixation with screws through the dome of the component. In other patients, only one millimeter of underreaming is performed. I recommend that surgeons refrain from underreaming by more than two millimeters because of the potential for acetabular fracture and for leaving gaps in the prosthesis-bone interval in the polar portion of the acetabulum.
If a fracture is recognized at the time of the operation and the fracture is non-displaced and the component is stable, the component is further stabilized by as many posterosuperior and posteroinferior bicortical screws as possible (usually two, three, or four). Only toe-touch weight-bearing is allowed for eight to twelve weeks. If a displaced intraoperative fracture is found, the component is removed and cancellous-bone screws are used to fix the displaced fragment. If the posterior column is involved, a buttress plate is utilized. On-line reaming is performed, and the component is gently positioned in the reconstructed acetabulum. The fixation of the component to the acetabulum is then augmented with screws through the dome of the implant. Only toe-touch weight-bearing is allowed for twelve weeks. If a non-displaced or minimally displaced intraoperative fracture is recognized during the initial hospitalization and adequate supplemental screw fixation was utilized at the time of the operation, a spica cast or a brace is used for six to eight weeks with toe-touch weight-bearing. If an intraoperative fracture is recognized later than the immediate postoperative period (Figs. 6-A, 6-B, 6-C and 6-D) and the component-bone construct appears secure, the treatment consists of toe-touch weight-bearing with crutches for twelve to sixteen weeks. If a displaced fracture with loosening of the component occurs or is recognized late, the fracture should be fixed and the fixation of the component should be augmented with screws. If a patient has pain in the groin in the early period after the insertion of an acetabular component without cement, radiographs in multiple projections (including Judet or fluoroscopic spot radiographs) should be made to rule out an unrecognized fracture. If the fracture is displaced and adequate fixation was utilized, twelve weeks of toe-touch weight-bearing is considered. If fixation is inadequate, I consider application of a spica cast, to be worn for eight weeks, or a reoperation to augment the fixation with screws.
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FIG6-A: Figs. 6-A through 6-D: A woman in whom an acetabular component was inserted without cement, with one millimeter of underreaming and screw augmentation, in osteopenic bone.
Fig. 6-A: Preoperative radiograph showing an insufficiency fracture (arrows) of the pubic ramus. The osteopenia is evident on the basis of this finding.
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FIG6-C: Fig. 6-C: At six weeks, the radiograph demonstrated a displaced healing periprosthetic fracture (arrow) and a displaced acetabular component.
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FIG6-D: Fig. 6-D: At one year, the radiograph demonstrated no more change in the position of the acetabular component.
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Postoperative Fractures
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Peterson and Lewallen recently classified periprosthetic acetabular fractures into two types: type 1 indicates that the acetabular component is clinically and radiographically stable, and type 2 indicates that the acetabular component is unstable. Most (nine) of the eleven fractures in their study occurred around a cemented component. The eight type-1 fractures were treated non-operatively with toe-touch weight-bearing with or without immobilization of the hip with a brace or a spica cast. Although six of these fractures healed, four of the six were associated with eventual loosening of the acetabular component that necessitated revision. I continue to treat acetabular fractures associated with a radiographically stable component non-operatively, but I explain to the patient that the component may later have to be revised after the fracture has healed. When acute pain in the groin occurs following a total hip replacement, the diagnosis of a periprosthetic acetabular fracture should be considered, as should an insufficiency fracture of the pubic ramus. (I am regularly consulted after a workup for infection, done for acute pain that developed months or years [typically] after a total hip arthroplasty, was found to be negative. Some of these patients are found to have evidence of an insufficiency fracture of the pubic ramus on plain radiographs.)
Type-2 fractures associated with loosening of the acetabular component should be treated with operative intervention. In the study by Peterson and Lewallen, one patient was initially seen with an acute injury and migration, into the pelvis, of an acetabular component that had been fixed with screws and without cement. The patient died from vascular injury. Vascular continuity should be assessed in these patients, and preoperative vascular studies are appropriate when the component has migrated into the pelvis. If the fracture involves only the medial wall, and the anterior and posterior walls and columns are intact, a large acetabular component with bone-grafting of the medial wall and augmentation of the fixation with screws may provide adequate fixation without cement, especially if at least one centimeter of the peripheral rim is intact. Patients are allowed only toe-touch weight-bearing for three to four months. Elderly patients can be managed with a protrusio ring or cage with medial morselized allograft and fixation of the acetabular component with cement.
In patients who have a transverse acetabular fracture or a posterior-column fracture, fixation of the posterior column with a plate, filling of the fracture site with morselized bone graft, and insertion of the component without cement and with screws through the dome usually provide secure fixation. In elderly patients who have discontinuity of the posterior wall or column, or both, I use an acetabular reconstruction cage to secure the superior aspect of the hemipelvis to the ischium, morselized graft at the fracture site, and cementing of the acetabular component.
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Discussion
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Periprosthetic fractures of the acetabulum are uncommon when acetabular components are fixed with cement, but they may be more common in association with fixation without cement. Techniques for insertion of acetabular components without cement, along with the potential for long-term factors such as medial-wall stress-shielding and pelvic osteolysis, may contribute to the potential increase in the prevalence of fractures in association with acetabular fixation without cement. Limiting the amount of underreaming of the acetabulum for the insertion of a press-fit component may prevent an intraoperative fracture. If a stable intraoperative fracture is recognized, supplemental fixation with bicortical screws and a prolonged period of toe-touch weight-bearing may be adequate treatment. Stable postoperative fractures may heal with non-operative treatment, but the component may still have to be revised. Unstable intraoperative or postoperative fractures must be fixed securely, and the component must be fixed securely to bone. This may necessitate fixation of the fracture with a plate and supplemental screw fixation of the acetabular component when cement has not been used. When cement is used, a reconstructive acetabular cage may be needed.
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Footnotes
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*Printed with permission of The American Academy of Orthopaedic Surgeons. This article will appear in Instructional Course Lectures, Volume 47, The American Academy of Orthopaedic Surgeons, Rosemont, Illinois, March 1998.
 No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Funds were received in total or partial support of the research or clinical study presented in this article. The funding sources were DePuy and Zimmer.
Department of Orthopaedics, The University of Iowa College of Medicine, Iowa City, Iowa 52242. E-mail address for Dr. Callaghan: john-callaghan@uiowa.edu.
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References
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- Kim, Y. S.; Brown, T. D.; Pedersen, D. R.; and Callaghan, J. J.: Reamed surface topography and component seating in press-fit cementless acetabular fixation. J. Arthroplasty, 10 (Supplement): 14-S21, 1995.
- Kim, Y. S.; Callaghan, J. J.; Ahn, P. B.; and Brown, T. D.: Fracture of the acetabulum during insertion of an oversized hemispherical component. J. Bone and Joint Surg., 77-A: 111-117, Jan. 1995.[Abstract/Free Full Text]
- Kirkpatrick, J. S.; Callaghan, J. J.; Vandemark, R. M.; and Goldner, R. D.: The relationship of the intrapelvic vasculature to the acetabulum. Implications in screw-fixation acetabular components. Clin. Orthop., 258: 183-190, 1990.
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- McElfresh, E. C., and Coventry, M. B.: Femoral and pelvic fractures after total hip arthroplasty. J. Bone and Joint Surg., 56-A: 483-492, April 1974.[Abstract/Free Full Text]
- MacKenzie, J. R.; Callaghan, J. J.; Pedersen, D. R.; and Brown, T. D.: Areas of contact and extent of gaps with implantation of oversized acetabular components in total hip arthroplasty. Clin. Orthop., 298: 127-136, 1994.
- Miller, A. J.: Late fracture of the acetabulum after total hip replacement. J. Bone and Joint Surg., 54-B(4): 600-606, 1972.
- Peters, P. C., Jr.; Engh, G. A.; Dwyer, K. A.; and Vinh, T. N.: Osteolysis after total knee arthroplasty without cement. J. Bone and Joint Surg., 74-A: 864-876, July 1992.[Abstract/Free Full Text]
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- Schmalzried, T. P., and Harris, W. H.: The Harris-Galante porous-coated acetabular component with screw fixation. Radiographic analysis of eighty-three primary hip replacements at a minimum of five years. J. Bone and Joint Surg., 74-A: 1130-1139, Sept. 1992.[Abstract/Free Full Text]
- Schmalzried, T. P.; Wessinger, S. J.; Hill, G. E.; and Harris, W. H.: The Harris-Galante porous acetabular component press-fit without screw fixation. Five-year radiographic analysis of primary cases. J. Arthroplasty, 9: 235-242, 1994.[Medline]
- Sharkey, P., Hozack, W., Callaghan, J., Kim, Y., Berry, D., and Hanssen, A.: Personal communication, June 1997.
- Silvello, L.; Scarponi, R.; Lucia, G.; and Guazzetti, R.: Traumatic loosening of a prosthetic acetabular cup in a young patient. Italian J. Orthop. and Traumat., 11: 237-239, 1985.[Medline]
- Stiehl, J. B.; MacMillan, E.; and Skrade, D. A.: Mechanical stability of porous-coated acetabular components in total hip arthroplasty. J. Arthroplasty, 6: 295-300, 1991.[Medline]
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Introduction
Historical Review