JBJS 2005 Managing Bone Loss in Acetabular Revision
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This is an enhanced PDF from The Journal of Bone and Joint Surgery The PDF of the article you requested follows this cover page. Managing Bone Loss in Acetabular Revision Scott M. Sporer, Wayne G. Paprosky and Michael O'Rourke J Bone Joint Surg Am. 2005;87:1620-1630. This information is current as of March 17, 2009 Reprints and Permissions Click here to order reprints or request permission to use material from this article, or locate the article citation on jbjs.org and click on the [Reprints and Permissions] link. Publisher Information The Journal of Bone and Joint Surgery 20 Pickering Street, Needham, MA 02492-3157 www.jbjs.org THE JOURNAL OF BONE & JOINT SURGERY · JBJS.ORG MANAGING BONE LOSS IN VOLUME 87-A · NUMBER 7 · JULY 2005 ACETABULAR REVISION Managing Bone Loss in Acetabular Revision BY SCOTT M. SPORER, MD, WAYNE G. PAPROSKY, MD, AND MICHAEL O’ROURKE, MD An Instructional Course Lecture, American Academy of Orthopaedic Surgeons Revision of cemented acetabular com- of reconstruction that achieves stability tabular components had a 14% rate of ponents is most commonly performed of the acetabular component through a revision for aseptic loosening and a because of aseptic loosening with mi- mechanical construct without the need 33% prevalence of radiographic evi- gration of the component. The most for osseointegration between the ace- dence of aseptic loosening1,2. Della Valle challenging aspect of acetabular revi- tabular shell and the host bone. Bio- et al., in a study of the experience with sion is the management of bone loss logic fixation refers to any surgical cementless acetabular revision at the compromising implant fixation and option that requires direct contact Rush University Medical Center, found stability. The severity of bone loss can with host bone and osseointegration aseptic loosening in two of 138 patients be pronounced, as a result of asymp- into the acetabular shell in order to followed for a mean of fifteen years, tomatic osteolysis and stress-shielding, provide long-term fixation. Nonbio- with revision (for any reason) reported prior to migration of cementless com- logic fixation options include cement- in nineteen of the 138 patients3. In a ponents. This bone loss is a common ing of a polyethylene cup, use of a study of the results of cementless revi- condition that is expected to become superior structural allograft and a ce- sions performed by Harris, Hallstrom more common in the future. mented polyethylene cup with or with- et al. reported a rate of aseptic loosen- The prevalence of revision hip ar- out an antiprotrusio cage, impaction ing of 11% (thirteen of 122) and a rate throplasty is 18% in the United States grafting with or without an antipro- of revision because of aseptic loosening and 8% in the Swedish registry. The in- trusio cage, and application of a total of 4% (five of 122)4. dications for acetabular revision in- acetabular allograft. Biologic fixation Reliable and durable fixation of clude symptomatic aseptic loosening, options include use of a hemispherical cementless acetabular components re- failure of fixation, infection, wear, os- uncemented cup at the anatomic hip quires intimate contact between the teolysis, and instability. Revision may center or a high hip center (>2 cm su- implant and viable bone as well as me- be indicated for an asymptomatic pa- perior to the native hip center), a jumbo chanical stability (motion of less than tient who has progressive osteolysis, cup (66 to 80 mm), an oblong cup, an 40 to 50 µm). Bone loss can compro- severe wear, or bone loss that could uncemented hemispherical cup sup- mise both of these prerequisites for suc- compromise a future reconstruction. ported by structural allograft, and a cessful use of cementless implants. The Contraindications for revision of the modular cementless implant system. amount of host bone required to pro- acetabular component include severe As the outcomes of acetabular re- vide durable fixation is not known. Al- bone loss precluding allograft fixation vision have been better with cementless though it is difficult to measure the or implant fixation, uncontrolled infec- fixation than they have been with ce- amount of bone supporting an implant, tion, or medical comorbidities that pre- ment fixation, cementless fixation has most surgeons believe that 50% to 60% clude surgery. become the preferred method for the is necessary. This value was derived majority of acetabular revisions. Tem- from the literature and is a measure of Options for Acetabular Revision pleton et al.1 and Gaffey et al.2 reported the coverage of the acetabular compo- Several options, including both non- no cases of aseptic loosening of unce- nent in the coronal plane as seen on biologic and biologic fixation, are mented Harris-Galante-I components an anteroposterior radiograph. How- available for acetabular revision. Non- used for revisions of cemented compo- ever, the support of an implant is geo- biologic fixation refers to any method nents, whereas cemented revision ace- metrically more complex than can be THE JOURNAL OF BONE & JOINT SURGERY · JBJS.ORG MANAGING BONE LOSS IN VOLUME 87-A · NUMBER 7 · JULY 2005 ACETABULAR REVISION determined on a two-dimensional ra- to the classification is determining the involvement of the posterior column. diograph alone. The location of the ability of the remaining host bone to The amount of superior migration is remaining supportive bone probably provide initial stability to a hemispheri- measured as the distance in millimeters has a more important role in provid- cal cementless acetabular component (adjusted for magnification) relative to ing durable fixation than does the until ingrowth occurs. Intraoperative the superior obturator line. quantity of bone. Finally, the percent- decisions are based on the findings Ischial osteolysis indicates bone age of bone necessary to support the when trial components are used. The loss from the inferior aspect of the pos- implant probably decreases as the im- amount of rim that remains deter- terior column, including the posterior plant size increases because of the in- mines the stability of the trial implant wall. The amount of ischial osteolysis creased surface area. and is one of the variables that identifies is quantified by measuring the distance the type of acetabular defect. A Type-I from the most inferior extent of the Inherent Stability defect has an undistorted rim; a Type-II lytic area to the superior obturator line. Although there are reports of the suc- defect, a distorted but intact rim with Teardrop osteolysis indicates cessful use of uncemented cups in revi- adequate remaining bone to support a bone loss from the inferior and medial sion surgery without the achievement hemispherical cementless implant; and aspect of the acetabulum, including the of an initial press-fit1,3, we believe that it a Type-III defect, a non-supportive rim. inferior aspect of the anterior column, is necessary to achieve inherent stabil- the lateral aspect of the pubis, and the ity of the implant. Trial components are Radiographic Correlation medial wall. Moderate osteolysis in- used to accomplish this goal and to as- Preoperative findings on the anteropos- cludes partial destruction of the struc- sess the remaining bone stock properly. terior radiograph of the pelvis are used ture with maintenance of the medial A trial implant can have full inherent to predict the type of defect and allow limb of the teardrop. Severe involve- stability, partial inherent stability, or no the surgeon to plan for the acetabular ment means complete obliteration of inherent stability. A trial component reconstruction accordingly. The four the teardrop. with full inherent stability will not be criteria that are important to assess on Medial migration of the com- displaced by pushing on its rim or by the preoperative radiograph include: ponent relative to the Kohler line trial reduction. A trial component with (1) superior migration of the hip center, represents a deficiency of the anterior partial inherent stability will maintain (2) ischial osteolysis, (3) teardrop os- column. The Kohler line is defined as its position while the inserter is re- teolysis, and (4) position of the implant a line connecting the most lateral aspect moved, but it will be displaced by load- relative to the Kohler line. of the pelvic brim and the most lateral ing of its rim and by trial reduction. Superior migration of the hip aspect of the obturator foramen on an Finally, when a trial component has no center represents bone loss in the ace- anteroposterior radiograph of the pelvis. inherent stability, support by host bone tabular dome involving the anterior and The medial aspect of the implant is lat- is inadequate to maintain placement of posterior columns. Superior and medial eral to the Kohler line with Grade-1 the component in the desired location migration indicates a greater involve- migration and medial to the line with once the inserter is removed. ment of the anterior column. Superior Grade-3 migration. With Grade 2, there and lateral migration indicates a greater is migration to the Kohler line or slight Classification and Decision-Making AAOS Classification The AAOS (American Academy of Or- thopaedic Surgeons) classification of Fig. 1 bone defects, described by D’Antonio Type-I acetabular defect. Note et al.5,6, identifies the pattern and loca- that the rim remains supportive tion of bone loss but does not quantify and will provide full stability for a the defect. The bone loss is classified as hemispherical component. contained, segmental, combined con- tained and segmental, pelvic disconti- nuity, and ankylosis. This is the most commonly used classification in the literature. Paprosky Classification The classification system that we use is based on the severity of bone loss and the ability to obtain cementless fixation for a given bone loss pattern7.