Knee Revison

 

American Academy of Orthopaedic Surgeons Annual Meeting
Day 3 - March 17, 2000

Revision Total Knee Arthroplasty

Chritranjan S. Ranawat, MD; Mark McBride, MD; VJ Rasquinha, MD

Introduction

The success of total knee arthroplasty (TKA) in relieving pain and improving function has led to its widespread use worldwide. In addition, the increasing size of the aging population, especially in the United States, will only further test the longevity and durability of TKA. With the increasing demands placed on TKA in terms of longevity and function, the problem of failure has manifested itself as a substantial reconstructive challenge in the last decade. The most common indications for revision TKA are infection, mechanical loosening, and instability. Approximately 5% to 10% of knees undergoing TKA will require revision within 10 to 15 years. Polyethylene wear has emerged as an important cause of TKA failure (aseptic loosening and osteolysis), particularly with some designs.

The principles of revision TKA are similar to those of primary surgery. However, factors such as bone loss and infection place an enormous demand on the technical expertise of the surgeon. Success depends on obtaining a wide exposure, restoration of mechanical alignment in 3 planes, maintenance of the joint line, balance of ligaments and soft tissue, restoration of functioning quadriceps mechanism, achieving stable implant -- bone fixation (intramedullary stems), and reconstruction of substantial bone loss with metal wedges or bone graft. Although it is recognized that the results of revision TKA may not be as good as primary TKA, it behooves the surgeon to attain an understanding of the principles and the relevant skills required to provide an optimal, durable outcome.

 

Bulk Allografts

To address the difficult reconstruction issues associated with extensive femoral bone loss (type III defects), Nazarian and colleagues[1] reported their experience with the use of massive distal femoral allografts in conjunction with the constrained condylar system (CCK) prosthesis. A series of 14 knees with a mean follow-up of 3.6 years was presented. Noncemented stems were cemented to the allograft to form a composite that was then implanted into host bone in all cases. The main indications were infection (8) and aseptic loosening or osteolysis (4). Clinical success was obtained in 86% (12 knees) with a mean knee score of 83 and average range of motion (ROM) between 3║ and 96║. The average time to union was 6 months. There were 2 failures, 1 due to infection (the primary diagnosis was infection) and the other secondary to nonunion.

Discussion

The combination of infection and extensive bone loss are among the most challenging reconstructive situations in revision TKA. In our experience, the degree of bone loss that requires massive allograft is loss of one or both columns extending proximal to the femoral epicondyles. The extent of this loss is roughly 1 inch or more proximal to the normal joint line. The surgical options for this situation are hinged/custom components or bulk allograft reconstruction. The risk of reinfection with bulk allograft has been documented, especially in reconstruction following bone tumor resection, and this study reports reasonable results at short-term follow-up in this difficult setting.

Although required infrequently, bulk allograft is an important technique in a reconstructive surgeon's treatment armamentarium. The most common causes of failure with this type of reconstruction are infection, resorption, and late fracture. These risks increase with longer follow-up. These authors confirmed that healing of the allograft to host bone occurs in a high percentage of cases. We suggest that this technique should be reserved for reconstruction when bone loss is proximal to the attachments of the collateral ligaments. To address profound ligamentous instability, it is our opinion that a well designed rotating hinge device may provide a better functioning, more durable reconstruction. Longer-term data should provide further insight as to the most durable approach in these difficult cases.

Implant Selection

Bugbee and associates[2] provided a retrospective review of 139 consecutive revision TKAs using (a) primary implants, (b) modified primary implants, and (c) revision implant systems. With a mean follow-up of 7 years, they report failure rates of 26% in group (a), 11% in group (b), and 3% in group (c). Although there was a bias toward the use of revision implant systems in the more difficult revision situations, this group provided superior performance and durability when compared with the other 2 groups. The authors concluded that revision implant systems were justified in view of the improved longevity and function.

Discussion

The degree of difficulty in TKA revision is variable. However, the compromise of bone and soft-tissue structures places increasing demands on the implants. In our view, revision of the femoral or tibial components ought to have intramedullary stems when there is damage to the metaphyseal bone to supplement fixation and provide stress transfer to host bone. Modularity gives the surgeon numerous options to aid in restoration of the joint line. In addition, some amount of added constraint is beneficial in addressing the oft-encountered soft-tissue imbalance, predominantly in flexion. We agree with the authors that the appropriate reconstruction in revision TKA warrants the use of modular revision implant systems to obtain good durable function and outcome.

Articulating vs Static Spacers

Fehring and colleagues[3] presents a retrospective review of 2 consecutive series of staged treatment approaches for patients with infected TKA. There were 25 patients treated with static spacers and 30 patients treated with articulating spacers for 2-stage management of sepsis in TKA. The mean follow-up for the patients with articulating spacers was 2 years. The rates of reinfection were 12% for static spacers and 7% for articulating spacers. Patients with static spacers developed unexpected bone loss between stages. There were no significant differences in clinical outcome scores or ROM between the 2 groups. In addition, the authors report a reduced operative time during the reimplantation procedure in those with articulating spacers.

Discussion

Two-stage reimplantation protocols are considered the gold standard for ablation of infection in TKA. However, this treatment protocol has increased morbidity when compared with less effective single-stage revision. The advantages of 2-stage revision include adequate delivery of antibiotics (both locally and systemically), opportunity for second debridement, and higher success rates. In a study of 64 infected TKAs treated with a 2-stage protocol, Goldman and colleagues[4] reported good clinical results at a mean of 7.5 years. The 10-year predicted survival rate was 77%. Hirakawa and associates[5] evaluated 66 infected TKAs treated with 2-stage reimplantation. At a mean follow-up of 5 years, the reimplantation was successful in 80% with low virulence organisms and decreased to 66% with high virulence organisms (MRSA).

The benefits of articulating spacers include reasonably good function with preservation of host bone and the soft-tissue envelope, greatly facilitating second-stage reimplantation. The current study supports the use of articulating spacers instead of static spacers, as there was no statistical difference in the rate of success (there was a trend toward higher success rates with the articulating spacer), but significant advantages were noted. Hofmann and colleagues[6] evaluated 26 patients with infected TKA utilizing an articulating spacer combined with partial weight-bearing and limited knee ROM between the 2 stages. They reported no recurrence of infection, ROM of 5║ to 106║,and a mean knee score of 87 at an average follow-up of 30 months.

The experience at our center with articulating knee spacers during the 2-stage treatment of sepsis in TKA is in agreement with that of Hofmann and colleagues.[6]Use of spacers should lead to improved function and quality of life for the patient during the interval between the 2 stages, minimal unexpected bone loss, and improved soft tissue envelope that facilitates exposure at reimplantation.

Restoration of the Joint Line

This retrospective review by Lyons and associates[7] of 100 revision TKAs in 93 patients (mean follow-up of 5.5 years) with a single-revision knee system evaluated the correlation between joint line restoration and various functional outcomes. The joint line was assessed relative to a transverse line drawn through the adductor tubercle. The authors used a highly constrained conforming design of revision prosthesis. They report a significant correlation between a greater than 3 mm deviation from the normal joint and a compromise of the dependent variables (pain score, HSS knee score, and ROM). The functional outcomes following accurate reproduction of the joint line were not affected by factors such as age, gender, mechanism of failure, infection, or length of follow-up.

Discussion

The accurate reproduction of anatomic geometry following primary or revision TKA has a direct bearing on functional outcomes. Specifically, in revision TKA, bone loss and destruction of landmarks make restoration of the joint line more challenging. To optimize knee kinematics, proper alignment in 3 planes with restoration of the joint line is critical. In our opinion, the conforming constrained knee designs are more sensitive to small variations in joint line than are posterior stabilized knee designs (TC3). This is due to the fact that with the posterior cruciate-substituting revision design, the extended post-cam mechanism, compensates for flexion laxity.

In our experience, utilization of the interepicondylar axis as an intraoperative reference is effective. Placing the reconstructed joint line 1 inch distal to this line results in near anatomic restoration in cases with loss of typical landmarks. In addition, the proper relationship of the patellar component to the trochlear groove is equally important in obtaining appropriate tracking and adequate knee flexion. We agree with the authors that restoration of the joint line is important if one is to achieve a well-functioning, durable revision TKA.

References

  1. Nazarian DG, Buechel F, Booth Jr. RE. Use of massive structural allograft for extensive distal femoral defects in revision knee arthroplasty. In: Program and abstracts of the 67th annual meeting of the American Academy of Orthopaedic Surgeons; March 15-19, 2000; Orlando, Fla. Paper No. 253.
  2. Bugbee WD, Engh GA, Ameen D. Does implant selection affect outcome of revision knee arthroplasty? In: Program and abstracts of the 67th annual meeting of the American Academy of Orthopaedic Surgeons; March 15-19, 2000; Orlando, Fla. Paper No. 256.
  3. Fehring TK, Mason JB. A comparison of articulating versus static spacers in revision total knee arthroplasty. In: Program and abstracts of the 67th annual meeting of the American Academy of Orthopaedic Surgeons; March 15-19, 2000; Orlando, Fla. Paper No. 257.
  4. Goldman RT, Scuderi GR, et al. Two-stage reimplantation for infected total knee replacement. Clin Orthop. 1996;331:118-124.
  5. Hirakawa K, Stulberg BN, et al. Results of two-stage reimplantation for infected total knee arthroplasty. J Arthroplasty. 1998;13:22-28.
  6. Hofmann AA, Kane KR, Tkach TK, Plaster RL, Camargo MP. Treatment of infected total knee arthroplasty using an articulating spacer. Clin Orthop. 1995;321:45-54.
  7. Lyons ST, Hofmann AA, Camargo M, Moen C, Feign M. Restoration of the line based on the distal femur in revision total knee arthroplasty. In: Program and abstracts of the 67th annual meeting of the American Academy of Orthopaedic Surgeons; March 15-19, 2000; Orlando, Fla. Paper No. 258.

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