I. Causes of Implant Failure
A. Aseptic failure can be caused by osteolysis, loosening, implant wear, dislocation, malalignment, limb-length inequality, or a loose cemented stem.
B. For a discussion of septic failure, see chapter 105.
II. Evaluation of the Painful Total Hip Arthroplasty
A. History and physical examination
1. The history should address the indications for the index procedure and symptoms of loosening (eg, start-up thigh pain), infection (prolonged drainage, fever, night sweats), and instability (dislocation or impingement).
2. The physical examination should include an assessment of gait and range of motion and an evaluation of any limb-length inequality.
B. Imaging evaluation
1. Radiographs
a. AP pelvis and orthogonal views of the involved hip should be obtained.
b. Preimplant and immediate postoperative radiographs may provide additional information.
c. Judet views can further evaluate the columns.
d. Radiographs usually underestimate the size of osteolytic lesions.
*Keith R. Berend, MD, or the department with which he is affiliated has received research or institutional support from Biomet, holds stock or stock options in Biomet, and is a consultant for or employee of Biomet. Adolph V. Lombardi, Jr, MD, FACS, or the department with which he is affiliated has received research or institutional support and royalties from Biomet, holds stock or stock options in Biomet, and is a consultant for or employee of Biomet.
2. CT scanning can be used to define the extent of osteolytic lesions and create a three-dimensional model for preoperative planning.
C. Laboratory evaluation
1. A complete blood count with differential, erythrocyte sedimentation rate, and C-reactive protein are useful for diagnosis.
2. Consideration can be given to an aspiration if the above laboratory values are abnormal.
D. Index procedure information
1. Surgical report and implant stickers of the index procedure should be obtained.
2. This information is needed to determine the type of implant, sizes, and complications.
III. Indications for Revision
A. Femoral component revision is indicated for aseptic loosening, osteolysis, or in cases of monoblock stems with nonmodular heads, for recurrent dislocations if stability cannot be achieved or the head is damaged.
B. Acetabular component revision is indicated for loosening, osteolysis, recurrent dislocations due to malalignment, and polyethylene wear. Also, a component with a poor history should be considered for revision.
IV. Classification of Bone Defects
A. The most widely used and accepted classification system for femoral deficiency is that of the American Academy of Orthopaedic Surgeons (AAOS) Committee on the Hip. The most widely used system for classifying acetabular defects is the Paprosky system. Both systems are ideally suited for both preoperative evaluation and planning and surgical classification to be used for outcome studies.
B. Femoral defects
1. The AAOS Committee on the Hip classification system is shown in
Figure 1.
[Figure 1. AAOS Committee on the Hip femoral defect classification: I, segmental bone loss; IIA, cavitary bone loss; IIB, ectasia; III, combined segmental and cavitary defects; IV, malalignment; V, stenosis; VI, femoral discontinuity.]
[
Figure 2. Paprosky classification system for femoral defects: Type I, minimal loss of metaphyseal bone, intact diaphysis; type II, extensive loss of metaphyseal bone, intact diaphysis; type III-A, nonsupportive, severely damaged metaphysis with >4 cm intact diaphyseal bone for fixation; type III-B, similar to type III-A but with <4 cm of diaphyseal bone for fixation; and type IV, extensive metaphyseal and diaphyseal damage with a widened femoral canal.]
2. The Paprosky classification system for femoral defects is shown in Figure 2.
C. Acetabular defects
1. The AAOS Committee on the Hip classification system is also used to classify acetabular defects.
2. The Paprosky classification system for acetabular defects is shown in
Figure 3 and described in
Table 1.
V. Treatment
A. Approaches and exposure
1. Identification of previous skin incisions is indicated. The old incision should be used whenever possible.
2. An anterolateral or posterior approach can be used.
[Figure 3. Paprosky classification system for acetabular defects. A, Type I—supportive rim with no bone lysis or component migration. B through D, Type II—distorted hemisphere with intact supportive columns and <2 cm of superomedial or lateral migration. E, Type IIIA—superior migration >2 cm and severe ischial lysis with the Kohler line intact. F, Type IIIB—superior migration >2 cm and severe ischial lysis with the Kohler line broken.]
3. An extended trochanteric osteotomy can facilitate exposure and implant removal and is especially useful when removing a well-fixed implant and cement. It has a high rate of union and also provides excellent access to the fixation surface.
4. The trochanteric slide, vastus slide, and controlled perforations also can be used to facilitate exposure as well as implant and cement removal.
B. Treatment options
1. Acetabular options
a. Hemispheric porous-coated cup
i. At least 50% of acetabular bone stock must be present for use of a porous hemispheric cup.
ii. This procedure usually involves placement of a cup 1 to 2 mm larger than the last reamer used. It can be augmented with screws. Survivorship has been shown to be 97% at 15 years.
iii. A jumbo cup, 6 to 10 mm larger than the diameter of the original implant, can also be used when a larger reamer is needed to make rim contact; this technique has shown 95% survival at 5-year follow-up.
iv. Alternatively, a high hip center can be used to achieve a stable socket, but the hip center of rotation will be altered.
b. Impaction grafting uses an impacted cancellous bed into which a cup is cemented. This technique is challenging and is associated with a high risk of fracture but has shown a 97% survival at 4 years (
Table 2).
c. Structural allografts (femoral head, distal femur, proximal tibia, or acetabular graft) have usually been used in combination with hemispheric cementless cups. The purpose of the structural graft is to provide stability for the cementless cup until it ingrows into the bone. Over time, this structural graft can resorb.
[Table 1. Paprosky Classification of Acetabular Bone Deficiencies]
d. Antiprotrusio cages can address large bony defects but rely on mechanical fixation. Cages are recommended when there is no posterior wall present or there is significant loss of superior bone. Pelvic discontinuity has been treated with either cages alone or cages and posterior column plate fixation with variable success. When using a cage, an all-polyethylene cup is generally cemented into the cage.
e. Bilobed and nonhemispheric cementless implants seek to replace bone deficits with metal. Results in the past have been mediocre, with aseptic loosening as a common failure mode. The emergence of new porous metals as a material for special devices and augments seems promising, however (
Figure 4).
f. Custom implants are created from a model generated from a CT scan. A recent series has shown 90% survival at 4.5 years.
g. Bipolar implants are associated with a high rate of failure.
h. Polyethylene wear and osteolysis can be addressed with a socket revision or liner change. Bone grafting at the osteolytic lesion is usually recommended. If the locking mechanism is intact, the liner can be replaced. If the locking mechanism has failed or better polyethylene is available, a new liner can be cemented into a well-fixed socket. Liner exchange has been associated with a high dislocation rate using the posterior approach. Component position should be assessed prior to a liner exchange.
i. Use of constrained liners is indicated only when the acetabular component is in an acceptable position.
2. Femoral options (defect types classified by Paprosky system)
[Table 2. Grafting Patterns and Methods of Fixation by Acetabular Defect and Subtypes]
[Figure 4. A, AP radiograph showing failed total hip arthroplasty secondary to polyethylene wear, acetabular component migration, femoral osteolysis. B, Postoperative AP radiograph showing reconstruction with a porous tantalum cup, porous titanium augment, and primary cementless stem. C, Preoperative AP radiograph showing large acetabular defect following radical debridement and history of pelvic open reduction internal fixation. D, Postoperative AP radiograph after reconstruction with porous tantalum cup and augments.]
a. Primary total hip arthroplasty components can be used with a type I defect; a cemented or cementless stem can be used.
b. Extensively porous-coated stems are suited for type II defects. "Scratch fit" in the range of 4 to 5 cm is required. These devices can be used for type IIIA (shorter version) or type IIIB (longer version) defects. Several authors have reported 10-year survival rates of 95% for type II and III defects.
c. Modular tapered stems can be used for type III and some type IV defects. This type of stem has shown survival rates higher than 98% at 7 years for type II and III defects.
d. Monoblock or modular calcar revision stems (
Figure 5) can be used for most types of femoral revisions, including types I, II, and III. Survivorship using these calcar-loading devices is 100% at 3 years.
e. Impaction grafting technique using particulate graft and a cemented stem has been successfully used in type II and III defects. In cases with extensive cortical bone loss, a longer stem can be used to limit femoral fracture.
f. Allograft prosthetic composites (APCs) (
Figure 6) can be used for type IV defects. The implant is cemented directly into the allograft. APCs have had a success rate of 77% at an average of 11 years; however, 25% had an allograft-associated complication.
[Figure 5. AP radiograph showing a modular calcar revision stem with a metal-on-metal articulation.]
[Figure 6. AP radiograph showing APC.]
g. Modular oncology components, implants designed to address massive bone loss such as that resulting from resection of tumors, are being used with increased frequency in type IV deficits (
Figure 7).
h. Cemented stems have shown poor long-term results, with the exception of type I defects. High rates of aseptic and mechanical failure have been seen.
i. Indications for cemented revision include preserved cancellous bone in the proximal femur. The results are improved if a longer cemented stem is used.
ii. Other, more rare indications would be cement-in-cement, or so-called "tap-in, tapout" technique with a polished, smooth cemented stem.
3. Surgical pearls
a. A liner exchange can be considered with a modular, well-positioned cup with a record of good survivorship. Dislocation remains a risk.
b. A loose cemented cup should be revised to a cementless cup.
[Figure 7. AP radiograph showing massive bone loss addressed with an oncology-type salvage device.]
c. A new polyethylene liner can be cemented into a well-positioned and well-fixed socket.
d. A well-fixed cementless cup can be removed with curved osteotomes and size-specific removal tools. This facilitates revision of cups that do not have a satisfactory position.
VI. Complications
A. Stress shielding—Occurs more often with cobalt chrome stems achieving diaphyseal fixation than proximally loaded stems. Resorption of structural allografts in the pelvis may also occur secondary to stress shielding.
B. Dislocation—May occur with the retention of a well-fixed but malaligned component.
C. Other complications
1. Compared with primary hip arthroplasty, revision hip surgery is known to have higher rates of mortality, hospital readmission, dislocation, and infection.
2. The cost of revision hip arthroplasty is also higher than for the primary procedure.
Top Testing Facts
1. Radiographs of osteolytic lesions usually underestimate the size of the lesion.
2. An extended trochanteric osteotomy can be used to remove a well-fixed implant and cement.
3. Presence of at least 50% of acetabular bone stock is necessary for use of a porous hemispherical cup.
4. Femoral impaction grafting is associated with a high risk of fracture, which can be reduced by using a longer stem.
5. When using an APC, the implant is cemented directly into the allograft.
6. A liner exchange can be considered with a modular, well-positioned cup with a record of good survivorship.
7. Polyethylene liner exchange is associated with an increased risk of dislocation.
8. A loose cemented cup should be revised to a cementless cup. The amount of bone loss will determine the type of reconstruction that can be performed.
9. A new polyethylene liner can be cemented into a well-positioned and well-fixed metal socket if there are problems with the locking mechanism.
10. A well-fixed cementless cup can be removed with curved osteotomes and size-specific removal tools.
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