|
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 3º and 96º. 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 5º to 106º,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
- 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.
- 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.
- 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.
- Goldman RT, Scuderi GR,
et al. Two-stage reimplantation for infected total knee replacement. Clin
Orthop. 1996;331:118-124.
- Hirakawa K, Stulberg BN,
et al. Results of two-stage reimplantation for infected total knee
arthroplasty. J Arthroplasty. 1998;13:22-28.
- 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.
- 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.
[ Back ] [ Up ]
|