CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Number 446, pp. 140–148 © 2006 Lippincott Williams & Wilkins Cementless Fixation in Revision Total Knee Arthroplasty Leo A. Whiteside, MD A surgical approach to revision total knee arthroplasty that includes minimal bone resection, minimal soft-tissue stripping, cementless fixation of the femoral and tibial components, and morselized allografting of defects was used and evaluated in 105 patients (110 knees) with severe bone loss. The patients were followed for 60 to 127 months postoperatively. Fixation included a tightly-fit fluted titanium stem in the femoral and tibial canals and rim contact on the peripheral rim of the tibia. One tibia loosened and one knee failed because of infection. Ligamentous stability and pain relief were consistent through the followup period. At 10 years the mean valgus laxity was 4° ± 2.5°, and the mean varus laxity was 5.2° ± 3.3°. Mean Knee Society pain score was 47 ± 2.1. Pain was mild in 28 knees, moderate in eight knees, and severe in two knees. Evidence of bone healing occurred in the bone defects that could be seen on radiographs. Increase in radiodensity always was found at postoperative intervals greater than one year. An approach to revision total knee arthroplasty that maintains bone and soft tissue about the knee establishes an effective and durable construct. and durable knee and also improve the mechanical environment in cases of later revision. These basic principles and techniques obviate high-risk, potentially destructive techniques, such as massive allografting, cemented stems, and fixed hinges that destroy additional bone and set the stage for catastrophic failure. Though massive allografts can incorporate and heal solidly to bone in the knee, the failure rate is high because of immunocompatibility, resorption, and infection.5,8,10 Techniques that use the remnants of the patients’ own bone, replace the remaining lost articular bone stock with the implants themselves, and reconstruct bone stock with demineralized or morselized allograft and bone marrow autograft offer excellent early and long-term results.11,12,15 Function and durability of this construct has been excellent and repeat revision rare using these techniques.11,12,15 Soft-tissue management in revision TKA correlates directly with exposure techniques and management of bone stock. When the soft-tissue envelope is left attached to carefully preserved bone stock of the femoral and tibial metaphyses, the spacer effect of the implants can be used to achieve stability in flexion and extension.15 Preoperative planning and templating cannot predict the size and position of the implants because the radiographs and physical examination do not provide adequate information about the condition of the ligaments and bone stock to predict ligament balance in flexion and extension. The position of the patella is one of the least reliable preoperative predictors of correct joint line position for the new implants because the patellar tendon often shrinks or elongates according to pathological conditions involved with the previous implants. We hypothesized that stability and ligament balance could be achieved and that bone reconstruction could occur without the use of linked hinges or highly constrained implants. Level of Evidence: Therapeutic study, level II (prospective study). See Guidelines for Authors for a complete description of levels of evidence. Failed total knee arthroplasty (TKA), when accompanied by major bone loss and ligament imbalance, offers one of the most difficult problems in reconstructive orthopaedic surgery. Nevertheless, a strong and reliable capsular structure remains attached to bone remnants even in the most severely damaged knees.11,12,15,16,18 Using these bone and soft-tissue structures to fix the implants and balance the knee can achieve the ultimate goal of a pain-free, stable, From the Missouri Bone and Joint Research Foundation, Missouri Bone and Joint Center, St. Louis, MO. The author certifies that he has or may receive payments or benefits from a commercial entity related to this work. The author certifies that his institution has approved the human protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research, and that informed consent was obtained. Correspondence to: Leo A. Whiteside, MD, Missouri Bone and Joint Research Foundation, 1000 Des Peres Rd., Suite 150, St. Louis, MO 63131. Phone: 314-775-0521; Fax: 314-775-0525; E-mail: email@example.com. DOI: 10.1097/01.blo.0000218724.29344.89 MATERIALS AND METHODS I reviewed prospectively collected data on a series of 110 knees (105 patients; 61 women, 44 men) requiring revision arthroplasty between January 1, 1989 and June 1, 2000. These knees were 140 Number 446 May 2006 operated on consecutively by the author and selected from a database of 202 revision TKAs (195 patients) Only knees with femoral or tibial defects classified as grade III or higher by the Engh and Ammeen method4 and treated with a tightly fit fluted diaphyseal stem and rim seating on remaining metaphyseal bone were chosen. Thirty-five knees (35 patients) had this degree of defect only in the femur, 42 knees (42 patients) had this degree of defect only in the tibia, and 33 knees (28 patients) had this degree of defect in the femur and the tibia. Followup was 60 to 127 months. All cases of revision TKA were operated with the same surgical technique by the author, splitting the interval between the vastus medialis and rectus femoris. All but one knee had revision with unconstrained implants. This knee was revised with hinged implants because it was operated on for failure of revision TKA and ligament balancing procedure. This knee became infected, was débrided, and ultimately was revised using unconstrained implants. Eighteen patients were lost to followup because of death unrelated to their arthroplasty. This left 92 patients (58 women and 34 men) in the study. The age range was 37–86 years (mean 73 ± 9 years). The interval between the conjoined quadriceps tendon and vastus medialis was used for exposure in all cases, and capsular stripping was minimal. Problems of difficult exposure were solved with the tibial tubercle osteotomy technique instead of stripping soft tissue from bone.13,14,17 The medullary canals were reamed to achieve tight fit at 150 to 200 mm depth. The reamers were used for alignment, accepting cutting guides that were set to resect as little bone as possible, and to align the tibial surface perpendicular to the long axis of the bone and the femur in 5° valgus to the reamer. In flexion, the surfaces of the femur were aligned parallel with the epicondylar axis. The tibial tray size was chosen by placing an assortment of trial components against the remaining upper tibial bone stock to ensure good coverage. Often the remaining tibial rim was less than 1⁄3 the original circumference, and the fibular surface supported the posterolateral edge of the tibial tray. Alignment of the knees and positioning of the implants are equally important in flexion and extension. Regardless of the implants chosen by the surgeon, the knee must be aligned correctly in the coronal plane so that the articular surface is perpendicular to the mechanical axis of the lower extremity in flexion and extension, and the tibia, patellar groove, and femoral head remain in the median sagittal plane through the full arc of flexion. Fortunately, the femoral epicondylar axis and medullary canals of the femur and tibia can be relied upon as effective alignment landmarks for the knee even after severe damage to the architecture of the knee. The medullary canal of the femur (Fig 1) and tibia (Fig 2) are the landmarks for extension, and the epicondylar axis of the femur is the landmark for flexion (Fig 3). Bone surface preparation usually was simple. Using the medullary reamer as an alignment landmark, the saw cut guide was used to resect minimal bone from the femur and tibia. This often left only a fraction of the metaphyseal rim to support axial load, but this generally was sufficient (Fig 4). Preserving as much bone as possible and leaving its ligamentous and capsular attachments intact allows the spacer effect of the implants to tension the ligaments without using additional constraint beyond a deep-dish tibial polyethylene component. Cementless Fixation in Revision TKA 141 Fig 1. Intramedullary alignment of the distal femoral and proximal tibial surface resections is shown. The reamer is aligned with the isthmus of the femoral medullary canal, and a small amount of bone is resected from the distal metaphyseal rim at a 5° valgus angle. If one side is severely deficient, the intact rim provides sufficient distal fixation if tight fit in the medullary canal is achieved. (Reprinted with permission from Whiteside LA. Bone reconstruction and ligament balancing. In: Whiteside LA, ed. Revision Total Knee Arthroplasty. Rosemont, IL: The American Academy of Orthopaedic Surgeons; 2003:1–16.) 142 Whiteside Clinical Orthopaedics and Related Research The femoral component was rotationally aligned with the epicondylar axis and finally seated on the distal femoral bone surface. The trial tibial component was inserted and ligament balancing completed by releasing abnormally tight medial or lateral ligaments until the knee had correct ligament balance in flexion and extension. The next step was to position the distal joint surface correctly. This was done with the knee in flexion as thicker tibial polyethylene spacers were added until the knee was adequately stable in flexion. Next the knee was extended. If the knee would extend fully and was stable, then the balancing procedure was finished. If the knee would not extend fully, the joint surface was moved proximally by choosing a thinner femoral Fig 2. The reamer is aligned with the isthmus of the tibial medullary canal, and a small amount of bone is resected from the proximal metaphyseal rim perpendicular to the long axis of the tibia. (Reprinted with permission from Whiteside LA. Bone reconstruction and ligament balancing. In: Whiteside LA, ed. Revision Total Knee Arthroplasty. Rosemont, IL: The American Academy of Orthopaedic Surgeons; 2003:1–16.) Whereas varus-valgus alignment was fairly simple, joint-line position required trial-and-error and empirical decision making. The process began with the surgeon choosing the largest size femoral component that would fit reasonably on the medial and lateral rims of the distal femur (Fig 5). Once the size was determined, the trial femoral implant was inserted (along with its stem) so that the anterior flange was flush with the anterior cortex of the femur. In some cases, the anterior bow of the femur pushed the femoral component anteriorly and prevented seating of the flange when the stem fit tightly in the medullary canal. In these cases, an offset stem was necessary to achieve this correct position. Ten knees (10 patients) required femoral stems with posterior offset of the femoral component, and one tibia required a stem with medial offset of the component. Femoral build-up modules were chosen to place the joint surface approximately equidistant from epicondylar attachment of the ligaments in flexion and extension (Fig 6). Fig 3. The epicondylar axis of the femur is the most reliable landmark for alignment of the revision knee in flexion. A perpendicular to this line passes through the hip, so resection of the femoral surface parallel to this line will place the joint surface in correct varus-valgus alignment in flexion. Number 446 May 2006 Cementless Fixation in Revision TKA 143 Fig 4. Soft-tissue envelope is shown attached to the epicondylar areas of the femur and spreading across the tibial metaphysis. Though the posterior capsule can stabilize the knee in extension, only the epicondylar soft-tissue structures can stabilize the knee in flexion. (Reprinted with permission from Whiteside LA. Bone reconstruction and ligament balancing. In: Whiteside LA, ed. Revision Total Knee Arthroplasty. Rosemont, IL: The American Academy of Orthopaedic Surgeons; 2003:1–16.) augment module or by resecting more distal bone. If the knee hyperextended, the articular surface was moved distally with a thicker distal femoral augmentation module. Femoral position was adjusted until balance was appropriate in flexion and extension. If the ligaments had been left attached to the epicondylar surfaces of the femur and metaphyseal flare of the tibia, the joint surface remained equidistant from the epicondyles in flexion and extension and stable through the full arc of flexion. Fixation of the implants depended on a semi-rigid stem, tightly fixed into the diaphysis. A smooth stem with distal flutes provides excellent fixation without stress-relieving the periarticular bone. A slot in the distal 1⁄4 of the stem provides enough Fig 5. Anterior view of the knee in flexion with trial revision components in place. The femoral component covers the mediolateral dimension of the distal femoral surface fully with minimal overhang. Despite major deficiency of bone in the proximal tibia, the tibial trial component is stabilized adequately with rim support and stem fixation. The joint is stabilized in flexion with as thick a tibial polyethylene trial component as is necessary to achieve stability. (Reprinted with permission from Whiteside LA. Bone reconstruction and ligament balancing. In: Whiteside LA, ed. Revision Total Knee Arthroplasty. Rosemont, IL: The American Academy of Orthopaedic Surgeons; 2003:1–16.) 144 Whiteside Clinical Orthopaedics and Related Research Fig 6. Lateral view of a revision femoral component using a posterior-offset module for the femoral stem. The anterior femoral flange lies in line with the anterior femoral cortex, and the diaphyseal stem engages the femoral isthmus. The component size has been chosen to restore posterior offset and to cover the medial-to-lateral extent of the distal femoral surfaces. The distal and posterior surfaces are placed approximately equidistant from the epicondylar ligament attachments (arrows A and B). Posterior offset (arrow C) has been reestablished to ensure maximum flexion without impingement. (Reprinted with permission from Whiteside LA. Bone reconstruction and ligament balancing. In: Whiteside LA, ed. Revision Total Knee Arthroplasty. Rosemont, IL: The American Academy of Orthopaedic Surgeons; 2003:1–16.) flexibility to allow safe insertion with minimal risk of fracture, and also to allow bending and torsional stresses to be borne by the diaphyseal bone. This fixation technique converts large peripheral defects to cavitary defects that can be filled with morselized cancellous bone or demineralized bone, and covered over with the soft-tissue envelope (Fig 7). Identifying the ligaments that were excessively tight was done with a formula that could be applied to all knees. Anterior ligaments tighten in flexion and posterior ligaments tighten in extension.7,9,15,18 Ligaments that attach near the epicondyles of the femur are effective in flexion and extension. Structures that bypass the distal femur entirely (iliotibial band, semimembranosus, pes anserinus) are effective as varus-valgus stabilizers only in extension.15 The Advantim (Wright Medical Technology, Arlington, TN) and Profix (Smith & Nephew Inc, Memphis, TN) total knee systems were used. In each system the femoral component was cobalt-chromium and the tibial component was a titanium tray, both with sintered-bead porous surfaces. Seating these implants on the rim of the femoral and tibial metaphyses resulted in cavi- tary defects that often consisted of more than 2⁄3 the volume of the metaphyseal bone. The defects were filled with a combination of morselized cancellous allograft, medullary reamings from the patient’s own femur and tibia, and bone marrow aspirate from the medullary canals. In most cases (105 knees in 102 patients) a deep-dish or conforming-plus tibial surface was needed to achieve posterior stability of the tibial surface in flexion and extension, but none of the knees required a stabilized condylar design (i.e. a large tibial post captured rigidly by a femoral housing). One was salvaged with a hinge prosthesis. Even in cases with severe femoral and tibial metaphyseal bone destruction including the femoral epicondylar and tibiofibular joint, stability could be achieved with the spacer effect of the implants without clinically noticeable leg lengthening. Postoperatively, the patients were started on partial weightbearing, advancing as tolerated to full weightbearing in 6 to 12 weeks. All patients could bear full weight by 8 weeks postoperatively. Clinical evaluations and radiographic assessment of the knees was done by the author or his surgical assistant at 1 month, 3 Number 446 May 2006 Cementless Fixation in Revision TKA 145 evidence of migration, but specific measurement of position relative to bone landmarks was not done for this study. RESULTS Fig 7. Tibial component positioned on carefully preserved bone stock. This technique maintains attachment of the softtissue sleeve to bone and places the implants near the ideal position for stability in flexion and extension. (Reprinted with permission from Whiteside LA. Bone reconstruction and ligament balancing. In: Whiteside LA, ed. Revision Total Knee Arthroplasty. Rosemont, IL: The American Academy of Orthopaedic Surgeons; 2003:1–16.) months, 1 year, then at 3-year intervals. Varus and valgus laxity was assessed manually in full extension and estimated in degrees. Anterior and posterior laxity was assessed manually at 90° flexion and estimated in millimeters. The Knee Society scoring system was used to grade each knee.6 The radiographs were evaluated for radiolucent lines at all interfaces, and the width of each radiolucent line was measured with a ruler and recorded. The grafted areas were evaluated for signs of increasing radiodensity over a period of two or more office visits, suggesting healing of the defect. The ends of the stems were evaluated for radiolucent lines, pedestal formation, diaphyseal bone hypertrophy, and migration. The radiographs were inspected for gross Knee stability and ligament balance were achieved with the revision surgical technique described. Varus and valgus and anteroposterior stability did not change appreciably during the followup period. At 5 years after surgery, mean valgus laxity was 3° ± 2.8° and mean varus laxity was 4.8° ± 2.3°. The values at 10 years were a mean valgus laxity of 4° ± 2.5° and a mean varus laxity of 5.2° ± 3.3°. The conforming tibial articular surface was effective in maintaining anteroposterior (AP) stability. Anterior laxity at 5 years postoperative was 7.2° ± 3.1°, and at 10 years was 6.6° ± 4.1°. None of the knees has symptomatic posterior laxity or rotational instability. The bone grafting technique used in conjunction with the implants provided a substrate for bone reconstitution. Healing in grafted areas was difficult to assess radiographically, but when the defects could be imaged in profile, apparent increase in radiodensity always was found at postoperative intervals greater than 1 year. This radiographic finding was present in 31 tibias (31 patients) and 28 femurs (28 patients) (Figs 8, 9). One knee developed infection after hinge arthroplasty and was revised in two stages to a non-linked cementless implant. One tibial component was revised for loosening. Mean Knee Society pain score was 47 ± 2.1 (out of 50). Twenty-eight knees (28 patients) had mild pain, eight knees (eight patients) had moderate pain, and two knees (two patients) had severe pain postoperatively. None of the components except for the case of tibial component loosening has had radiographically apparent migration, progressive radiolucent lines, or pedestal formation around the stem. DISCUSSION Durable fixation of the femoral and tibial components is of paramount importance in revision TKA. No revision knee is effective in the long term if fixation fails, and improving bone stock to enhance the odds of success in cases of late failure should be one of the main goals of revision TKA. This paper reports that a revision technique that uses bone preservation, ligament balancing, bone grafting, and osteointegration techniques to achieve stability postoperatively was effective in restoring patient knee function. Using techniques that do not consume additional bone stock to achieve fixation is attractive, especially in view of the substantial revision rate reported for revision TKA.10 Attempting to support massive implants on cement that is supported by poor bone stock is mechanically unsound and 146 Whiteside Fig 8A–B. (A) Postoperative lateral view of a knee at one month after surgery. The line indicates the distal extent of the patient’s own anterior femoral bone stock. The material under the femoral flange is morselized cancellous allograft and demineralized alllograft bone. The posterior surfaces of the femoral component are seated against the remaining portion of the femoral diaphysis. (B) Postoperative lateral radiograph of the same case at two years after surgery. The bone graft has consolidated. (Reproduced with permission from Whiteside LA. Cementless revision total knee arthroplasty. In Callaghan JJ, Rosenberg AG, Rubash HE, Simonian PT, Wickiewicz TL, eds. The Adult Knee. Philadelphia, PA: Lippincott Williams & Wilkins; 2003:1465–1472.) fails at an unacceptably high rate.10 Avoiding deeply penetrated cement and extensive periosteal stripping offers advantages in bone and soft-tissue preservation and in revision cases for infection after revision TKA. This paper reports only the results gathered from a series of patients revised without the use of cement, so direct comparisons with series that use cement fixation in revision cannot be made. The potential disadvantages of this technique are tibial stem pain, which occurs frequently Clinical Orthopaedics and Related Research when a long stem is used,2 and loss of diaphyseal bone stock if failure or migration occurs. Revision TKA requires correct alignment and ligament balance in flexion and extension. Nothing less will produce a good knee. Long-term success depends on stability achieved by secure attachments of ligament to bone. Attempting to stabilize the knee with a constrained condylar type implant or linked hinge instead of ligament tension will result in an increasing failure rate as time passes. Rarely, massive avulsion of collateral and capsular ligament structures precludes balancing of the ligaments with the spacer effect of the implants. Although none of these cases are included in the present series, collateral ligament reattachment and imbrication techniques are an important part of the surgical armamentarium for ligament management in revision TKA. Following the basic principles of bone reconstruction, alignment, and ligament balancing procedures produces a durable and effective joint. Success with this effort rests with preserving the remaining bone stock with its capsular and ligamentous attachments intact. The tibial tubercle osteotomy has been instrumental in allowing the surgeon to achieve a stable joint supported by viable bone that is capable of healing, filling in defects, and osseointegrating with the implants. Even in cases of multiple revision previously stabilized with hinge arthroplasty, the soft-tissue envelope can be tensioned to regain stability using rotationally unconstrained implants.1 Severely damaged bone and soft tissue, when left in continuity and loaded appropriately, can function well and regenerate bone and ligamentous support for the knee so the failure rate will be low. The stem is the key to success in fixation of implants with rim deficiency. When the stem is tightly fit in the medullary canal, axillary load-bearing is sufficient even with a fraction of the original circumference of the rim. Adding rim support did not result in additional stability in an in vitro study of the biomechanics of fixation.3 The results of the cementless technique described appear to be superior to those of similar series of cemented revision TKA. Failure rates of 19.2% when bulk allograft was used and 42.9% when massive implants were used to replace missing bone stock with an overall survivorship of 79.4% at 8 years was reported by Hockman et al.5 Sierra et al reported mechanical failure rates of 11% at 5 years, 26% at 10 years, and 31% at 15 years10; over the past three decades no improvement in survival occurred despite continued efforts to improve design and fixation using cemented implants. Another advantage of the osseointegration technique described in this report is improvement of bone stock and soft-tissue integrity. If failure does occur, the bone and soft tissues of the knee may be improved, and aid in reconstruction. Number 446 May 2006 Cementless Fixation in Revision TKA 147 Fig 9A–B. (A) Anteroposterior radiograph of the tibia of the same case at one month after surgery. The long stem engages the diaphysis of the tibia, and the distal slot is closed. Fresh graft is visible in the tibiofibular joint. The medial edge of the tibia and upper surfaces of the fibular head support the tibial component until healing is complete. (B) Anteroposterior radiograph of the tibia of the same case at two years after surgery. The slot in the stem is still closed, and the tibiofibular joint appears to be solidly healed. (Reproduced with permission from Whiteside LA. Cementless revision total knee arthroplasty. In Callaghan JJ, Rosenberg AG, Rubash HE, Simonian PT, Wickiewicz TL eds. The Adult Knee. Philadelphia, Pa: Lippincott Williams & Wilkins; 2003:1465– 1472.) Acknowledgments The author thanks William C. Andrea, MA, CMI, for preparation of the illustrations, and Diane J. 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