Brian Vannozzi, Gwo-Chin Lee, and Jonathan Garino
DEFINITION
Substantial bone loss and bone defects are among the most challenging problems faced by surgeons performing revision knee arthroplasty. Tibial bone loss in failed total knee arthroplasty (TKA) is a complex and difficult problem.
Awareness and proper management of bone loss, through cement fill, metal augments, or bone grafting, are crucial for achieving stability and longevity of the newly implanted revision components.
ANATOMY
Tibial bone loss during revision TKA is common. The most common areas of deficiency involve the posterolateral and medial tibial plateau.
Smaller contained defects can often be addressed with morselized bone graft or cement alone. Larger, uncontained defects may require the use of metallic wedges or structural allografts.
PATHOGENESIS
The etiology of bone loss after TKA is multifactorial. Bone stock deficiency may result from any of the following causes:
Stress shielding of the proximal tibia and distal femur can cause clinically significant osteopenia surrounding the knee following TKA.
Osteolysis is a biologic response to wear debris following TKA that can result in bony destruction.
Aseptic implant loosening can result in pathologic micromotion at the implant–bone interface, resulting in increased wear debris and formation of a biologically active membrane.
Removal of well-fixed implants, even using proper technique, can result in some degree of bone loss, particularly from the subchondral region.5
NATURAL HISTORY
Regardless of the mechanism of bone loss, once significant bony destruction is visible on plain radiographs, it is likely that continuing progression leading to failure of the knee arthroplasty will occur.
In this spiral toward implant failure, patients may be asymptomatic initially, but pain, swelling, and instability, including hyperextension due to loss of tibial height, can be expected and are likely sequelae of the failing TKA with significant tibial bone loss.
PATIENT HISTORY AND PHYSICAL FINDINGS
Patient history and physical findings can range from completely asymptomatic to debilitating pain and instability with normal gait walking.
A full history and physical examination are essential, and should include an assessment of type, quality, location, and duration of pain. Any new, severe pain or progressive pain in a previously well-functioning implant, particularly during weight bearing, is of particular concern. The presence of start up pain is also important to elicit in the history.
Additional questions should focus on the stability of the knee. A new onset of slowly progressive symptoms “giving out” or weakness of the knee can be an indication of problems.
Local tenderness along the interface between the tibial implant and the tibia can be seen in tibial component loosening. This should be distinguished from local tenderness over the pes anserine bursa.7
Finally, as with all patients undergoing revision knee replacement, infection must be ruled out.
IMAGING AND OTHER DIAGNOSTIC STUDIES
A thorough clinical and radiographic evaluation is a prerequisite for revision TKA. The extent and location of bone loss, the quality of the remaining bone, the degree of cortical continuity, and the absence of infection must be determined.
Standing anteroposterior, lateral, and patellar radiographs usually are sufficient for assessment of tibial bone loss (FIG 1), but CT scans can be more accurate in estimating the degree of bone loss and may be helpful when there is massive bone loss or abnormal anatomy.
All patients should have the appropriate infection laboratory studies (ie, complete blood count, C-reactive protein, erythrocyte sedimentation rate) as well as an attempt at knee aspiration and synovial fluid sent for Gram stain, cell count, and culture. Serial knee aspirations with repeat laboratory studies often are performed on patients with a high index of suspicion for infection.
DIFFERENTIAL DIAGNOSIS
Bone loss in TKA may result from the following factors, singly or in combination:
Stress shielding
Osteolysis
Instability
Implant failure (malalignment)
Infection (must be evaluated and ruled out before reconstruction begins).
In addition, extremity pain in a patient with a TKA can have several possible nonsurgical diagnoses,10 including:
Referred pain from hip, thigh, or calf
Complex regional pain syndrome
Pes anserine bursitis
Patellar or hamstring tendinitis
Crystalline deposition disease (ie, gout or pseudogout)
Neurovascular problems: neuropathy, radiculopathy, spinal stenosis
FIG 1 • A,B. AP and lateral preoperative radiographs showing a failed total knee arthroplasty (TKA) with tibial component subsidence and loosening. C. AP radiograph of a revision TKA demonstrating significant tibial component loosening and severe tibial bone loss.
Tumor (needs to be considered)
Vascular claudication
Thrombophlebitis or deep vein thrombosis
Fibromyalgia
NONOPERATIVE MANAGEMENT
Nonoperative management of a painful TKA with tibial bone loss is not often indicated. However, if revision is not deemed a safe option for medical, psychosocial, or other reasons, management is similar to that for a patient with endstage knee arthritis.
Treatment options are symptom based and can include activity modification, walking aids, nonsteroidal pain medications, and bracing.
SURGICAL MANAGEMENT
Various joint reconstruction techniques have been described for dealing with bone loss. The choice of reconstruction depends largely on the type of bone loss (ie, contained or uncontained) and the location and size of the defect (Table 1).
AORI, Anderson Orthopaedic Research Institute.
Cement filling
Morselized particulate bone grafting
Modular metal augments
Modular endoprostheses
Structural allograft
Impaction bone grafting12
Preoperative Planning
Bone loss around a knee implant should be assessed systematically, including both femoral condyles, both tibial plateaus, and the patellofemoral joint.
Location of the joint line is marked. Reference points include the fibular head and the epicondyles of the femur. The joint line typically sits 20 to 25 mm distal to the lateral epicondyle.1
The magnitude of bone loss has significant implications for decisions regarding the use of bone graft or prosthesis augmentation, choice of prosthesis sizing, selection of articular constraint, and need for supplemental stem fixation.2
Positioning
Revision TKA usually is performed with the patient in the supine position.
Approach
A standard medial parapatellar approach to the knee is used. The medial collateral ligament is circumferentially released from the proximal tibial metaphysis as a single sleeve.
Additional exposure often is required if metal wire mesh is need for unconstrained defects. The proximal portion of the tibia must be well exposed to ensure fixation of the wire mesh onto the bone. External rotation of the tibia and elevation of the medial sleeve often help with exposure of the cortical margins.
The patellar tendon should be protected throughout the entire procedure, and the patella should not be everted, to minimize the risk of avulsion. In cases with severe joint ankylosis, the surgeon should be prepared to convert to more extensive revision approaches if necessary to obtain visualization (eg, quadriceps snip, tibial tubercle osteotomy, or V-Y quadricepsplasty).
IMPACTION GRAFTING8
Full exposure of the knee joint is accomplished using a standard medial parapatellar arthrotomy, as described earlier.
A formal synovectomy with sharp dissection is performed for removal of polyethylene wear particles and improved exposure.
Following removal of the components, a high-speed burr is used to define bony lesions, clean multiloculated defects from cavitary defects, and decorticate sclerotic areas.
Contained Defects
Contained defects require impaction of bone directly into the defect (TECH FIG 1).
Cancellous allograft is introduced into the tibial canal.
A trial stem is inserted into the tibial canal in proper alignment, bone graft is impacted around the stem, and the stem is removed when the bone graft has filled the defect.
Uncontained Defects
Uncontained defects call for wire mesh to reproduce the cortical anatomy (TECH FIG 2).
Wire mesh is molded to estimate normal contours of the proximal tibia and is held in place with small cortical screws.
A central intramedullary guide rod with cement restrictor is inserted to allow a gap of 2 cm from the anticipated end of the final tibial stem component.
A trial tibial stem is inserted into the tibial canal in neutral alignment. The final chosen stem should be smaller to allow for a 2-mm circumferential cement mantle.
Thawed fresh-frozen morselized cancellous allograft is introduced into the tibial canal and impacted tightly around the stem using either cannulated or standard tamps and a mallet.
The trial stem is removed, leaving a restored mantle of cancellous bone.
The stemmed tibial prosthesis is cemented in standard fashion.
TECH FIG 1 • Contained tibial defect in the same patient shown in Figure 1A,B. A. Primary components have been removed, and the lesion has been found to have intact cortices. B. Cancellous allograft is introduced into the tibial canal. C,D. A trial stem is inserted into the tibial canal in proper alignment, bone graft is impacted around the stem, and when the bone graft has filled the defect, the stem is removed. E,F. Postoperative AP and lateral radiographs after completion of the tibial impaction grafting and cementing of the final components.
TECH FIG 2 • Uncontained tibial defect in the same patient shown in Figure 1C. A. Intraoperative photograph showing a wire mesh cage contoured to reestablish approximate proximal tibial anatomy and held in place with small cortical screws. B. The trial tibial stem is inserted in proper alignment, and bone graft is impacted surrounding the stem. (The trial used is larger than the actual stem to allow for several millimeters of cement mantle.) C.The trial tibial stem is removed. D,E. Cement is introduced in the impaction grafting site, the real component is inserted, and excess cement is removed. F.Intraoperative photograph showing the final components. G,H.Postoperative AP and lateral radiographs show reconstruction of the tibial plateau with wire mesh and impaction grafting.
STRUCTURAL FEMORAL HEAD ALLOGRAFT 2
Preoperatively, estimate the size of the defect and order appropriate-sized femoral head allografts.
Thaw the allograft material in warm saline for 15 to 20 minutes and mount in a grip device.
Preparation of the allograft requires the use of a male and female acetabular reamer system (DePuy, Warsaw, IN).
Female-type acetabular reamers are used to remove retained cartilage and bone (TECH FIG 3A).
Flush the structural allograft with saline to remove marrow elements.
The tibial defect is denuded of all nonviable tissue.
If sclerotic bone is encountered, the reamer may wander. In these cases, a high-speed burr may be used to remove sclerotic bone.
A male-type reamer no larger than prepared allograft is used to prepare host bone (TECH FIG 3B). The host bone is reamed to expose healthy, bleeding cancellous bone, including removal of all fibrous tissue and cement.
The allograft is placed into the defect and provisionally secured with K-wires or Steinmann pins. These should be placed so that they do not interfere with the stemmed prosthesis insertion (TECH FIG 3C,D).
Revision cutting guides are used to trim allograft for component implantation. Tibial component preparation should follow standard revision principles.
The K-wires are replaced with partially threaded 4.0-or 4.5-mm cancellous screws, and the tibial component is press-fit or cemented in the standard fashion (TECH FIG 3E–G).
TECH FIG 3 • Femoral head allografting. A. The femoral head allograft is secured into a grip device and a female-type cheese grate reamer is used to denude the allograft of cartilage and subchondral bone. B. A male-type reamer of appropriate size is used to create a socket for the allograft. C,D. The allograft is impacted into place and secured with K-wires. E. The allograft is cut to the appropriate height and fixed with cancellous bone screws. F,G. Final AP and lateral radiographs of the medial tibial plateau reconstruction with femoral head allograft secured with screw fixation. (From Hanssen A. Managing severe bone loss in revision knee arthroplasty. In: Lotke PA, Lonner JH, eds. Knee Arthroplasty, 2nd ed. Philadelphia: Lippincott Williams & Wilkins, 2003:321–344.)
POSTOPERATIVE CARE
Unless a tibial tubercle osteotomy is performed, standard postoperative care, including use of continuous passive motion machine, weight bearing as tolerated, and status with physical therapy is indicated.
However, the priority should be wound healing and incorporation of the graft. Therefore, the aggressiveness of the postoperative course depends on the type of reconstruction and the security of component or graft fixation.
OUTCOMES
Lotke et al12 recently reported prospectively on 48 consecutive patients treated with impaction allograft for substantial bone loss in revision TKA. They found no mechanical failures, and all radiographs showed incorporation and remodeling of the bone graft. They also found an improvement in Knee Society score from 52.3 to 80.3. Six complications (14%) were reported, including two infections and two periprosthetic fractures.
COMPLICATIONS
Bone graft resorption
Graft collapse
Infection
Patellar clunk
Instability
Joint line elevation
Stiffness
Periprosthetic fracture
REFERENCES
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3. Engh GA. Structural femoral head allografting with revision TKA. Orthopaedics 2004:27:999–1000.
4. Engh GA, Ammeen DJ. Bone loss with revision total knee arthroplasty: defect classification and alternative for reconstruction. Instr Course Lect 1999;48:167–175.
5. Engh GA, Parks NL. The management of bone defects in revision total knee arthroplasty. Instr Course Lect 1997;46:227–236.
6. Hanssen AD. Managing severe bone loss in revision total knee arthroplasty. In: Lotke PA, Lonner JH, eds. Knee Arthroplasty: Master Techniques in Orthopaedic Surgery. New York: Lippincott Williams & Wilkins, 2003:321–344.
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8. Lonner JH, Lotke PA, Kim J, et al. Impaction grafting and wire mesh for uncontained defects in revision knee arthroplasty. Clin Orthop Relat Res 2002;404:145–151.
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