The Journal of Arthroplasty Vol. 26 No. 8 2011
Revision Total Knee Arthroplasty Clinical Outcome Comparison With and Without the Use of Femoral Head Structural Allograft Corey J. Richards, MD, MASc, FRCSC,* Donald S. Garbuz, MD, MHSc, FRCSC,y Luke Pugh, MD,z and Bassam A. Masri, MD, FRCSCz
Abstract: The use of femoral head structural allograft (FHSA) for the management of massive bony defects during revision total knee arthroplasty (TKA) is well documented in the literature. The purpose of this study was to compare the clinical outcomes of patients undergoing revision (TKA) with FHSA to those without. All patients undergoing revision TKA between January 2000 and August 2005 were reviewed. Two cohorts were generated: a study cohort—revision TKA using FHSA (n = 24)—and control cohort—revision TKA without FHSA (n = 48). The 2 study cohorts groups were comparable. All patients completed validated outcome questionnaires. The FHSA cohort was found to have significantly better outcome scores. This study demonstrates improved clinical outcomes for patients undergoing revision TKA using a structural allograft compared with those without. Keywords: total knee arthroplasty, femoral head structural allograft, bony defects. © 2011 Elsevier Inc. All rights reserved.
The intraoperative goal of revision total knee arthroplasty (TKA) is to reconstruct bony defects to restore the anatomical joint line to ensure properly tensioned collateral ligaments, balanced flexion and extension gaps, and correct patellar height. The long-term goal is a well-fixed, stable knee joint that improves the patient's functional status and quality of life. Achieving these goals in the setting of massive femoral and/or tibial bone loss continues to be a challenge during revision TKA. The surgical management of bony defects during revision TKA depends on the size of the defect and whether or not it is contained. The Anderson Orthopaedic Research Institute (AORI) classification categorizes bony defects based on preoperative radiographs . The bony defect may be reclassified intraopera-
From the *Department of Orthopaedics Hull Hospital 116 boul. Lionel emond Gatineau, Quebec, Canada; yDivision of Lower Limb Reconstruction and Oncology Department of Orthopaedics University of British Columbia, Vancouver, Canada; and zDepartment of Orthopaedics University of British Columbia, Vancouver, Canada. Submitted May 27, 2010; accepted December 3, 2010. The Conflict of Interest statement associated with this article can be found at doi:10.1016/j.arth.2010.12.003. Reprint request: Corey J. Richards, MD, MASc, FRCSC, Department of Orthopaedics Hull Hospital 116 boul. Lionel emond Gatineau, Quebec, Canada J8Y 1W7. © 2011 Elsevier Inc. All rights reserved. 0883-5403/2608-0029$36.00/0 doi:10.1016/j.arth.2010.12.003
tively on the basis of the size of the defect and the surgical management required. Anderson Orthopaedic Research Institute type 1 defects are small and/or contained defects that can be adequately addressed with cement or morselized allograft. The use of cement to fill defects exceeding 5 mm has not been recommended . For moderately sized defects, AORI type 2, the use of metal augments or a small allograft is often required to restore the anatomical joint line. Various surgical options are reported for the management of massive bony defects, AORI type 3, including impaction grafting, bulk structural allograft, bone substituting tumour prostheses, and, more recently, porous metal cone augments. The choice of surgical treatment depends on the size and location of the defect, the patient's age, and life expectancy, as well as the surgeon's preference and experience. Structural allograft reconstruction is an attractive alternative for younger patients in whom potential bone restoration, for possible future operations, is a priority. The choice of allograft includes bulk distal femur, proximal tibia, or femoral head. The successful use of FHSA for managing bony defects during revision TKA is well documented [3,4]. Hockman and associates  recently published a study demonstrating improved survivorship for patients managed with a structural allograft during their revision TKA compared with those managed without allograft, despite worse preoperative
1300 The Journal of Arthroplasty Vol. 26 No. 8 December 2011 bony defects for the structural allograft group. To date, no study has compared the results of revision TKA with/ without structural allograft in terms of quality of life. The purposes of this study were to evaluate the clinical outcomes of patients undergoing revision TKA with AORI type 3 defects managed with a FHSA and to compare this patient population to a control cohort consisting of aseptic revision TKA patients with AORI type 1 or 2 defects where structural allograft was not used.
Methods This study was approved by the ethics board of our university and our hospital. A cross-sectional, cohort comparison of 2 groups of patients undergoing revision TKA was completed. All patients who had undergone revision TKA between January 2000 and August 2005 (minimum 2-year follow-up) were selected for review from the patient database. Two cohorts were generated from this patient population. The study cohort consisted of patients who underwent revision TKA using FHSA for the management of an AORI type 3 defect involving either the distal femur, proximal tibia, or both. Patients found to have had an AORI type 1 or 2 defect during revision TKA were included in the control cohort. Exclusion criteria for the control cohort included infection, inadequate follow-up (less than 2 years), isolated polyethylene liner exchange, and AORI type 3 defect treated with a bulk structural allograft other than a femoral head or with a bone substituting tumour prosthesis. Patients were enrolled in each arm of the study from the practices of our group of subspecialized reconstructive orthopedic surgeons working at a large university center. Twenty-five eligible patients were identified for the FHSA study cohort. Of these, 1 patient was deceased, leaving 24 patients available for quality of life outcome evaluation. Forty-eight patients were eligible for the control cohort. The mean follow-up in the FHSA group was 48 months (range, 24-98 months) compared with 38 months (range, 24-63 months) for the control cohort. The mean age (72.8 years in the FHSA cohort vs 69.3 years in control cohort [P = .16]), sex (male to female ratio of 11:13 for the FHSA cohort and 23:25 for the control cohort), body mass index (29.2 kg/m2 for the FHSA cohort vs 29.7 kg/m2 for the control cohort [P = .73]), and comorbidity characterized by Charnley class (15/24 [62.5%] type C for the FHSA cohort vs 26/48 [54.2%] type C for the control group [P = .65]), were similar in the 2 groups. Aseptic loosening was the predominant diagnosis for both cohorts (Table 1). Bone defects were assessed intraoperatively using the AORI classification . The FHSA cohort consisted of only type 3 segmental bone defects, whereas the control cohort consisting of mostly type 2 defects (Table 2). Both the femur and tibia were revised for 21 (88%) of 24
Table 1. Preoperative Diagnosis Preoperative Diagnosis Aseptic loosening Polyethylene wear/failure Implant fracture Patellar failure and osteolysis Instability Arthrofibrosis
FHSA Cohort (n = 24) 19 2 0 0 2 1
Control Cohort (n = 48) 31 2 3 1 10 1
patients in the FHSA cohort vs 37 (77%) of 48 patients in the control cohort. The remaining patients underwent either isolated femoral revisions (2/24 patients [8%] for the FHSA cohort vs 8/48 patients [17%] for the control cohort) or an isolated tibial revision (1/24 patient [4%] for the FHSA cohort vs 3/48 patients [6%] for the control cohort). Stemmed components were used for all revisions in both groups, with the majority being pressfit stems, 21 (87.5%) of 24 press-fit stems for the FHSA group vs 42 (87.5%) of 48 press-fit stems for the control groups. Additional metal augmentation was used for 22 (92%) of 24 patients in the FHSA cohort compared with 36 (75%) of 48 patients in the control cohort. Massive bony defects were managed with a single FHSA for 19 of 24 patients and 2 femoral heads for 5 of 24 patients in FHSA cohort (Table 3). The management of bony defects using bone cement was reserved only for those defects that measured less than 5 mm for both the FHSA and control cohorts. Five validated quality of life outcome scores were used for patient assessment: the Oxford Hip Score , the Western Ontario MacMasters Universities Osteoarthritis Index (WOMAC) Osteoarthritis Index , the Short Form 12 (SF-12) , the Hip and Knee Arthroplasty Satisfaction questionnaire , and the University of California, Los Angeles (UCLA) activity score. There was no significant difference in preoperative baseline scores, available for 16 (67%) of 24 patients in the FHSA cohort and 25 (52%) of 48 patients in the control cohort, for each of the 5 outcome tools completed. Quality of life outcome questionnaires were mailed annually to patients, with informed consent obtained with the initial request for follow-up quality of life information. Patients who failed to complete routine follow-up were sent a repeat questionnaire or contacted by a telephone. The quality of life mean scores were analyzed with a paired t test of means. The χ 2 test was used for testing significance of proportions, such as Charnley classification and preoperative diagnosis. Technique for Structural Allograft Revision TKA Preoperative Planning A thorough evaluation of preoperative radiographs is vital to ensuring that the appropriate instruments, implants, and allograft bone are available at the time of the procedure. Standard anteroposterior (AP), lateral,
Revision Total Knee Arthroplasty Richards et al Table 2. Classification of Preoperative Femoral and/or Tibial Defects AORI Classification 1 2: 2: 2: 3: 3: 3: 3:
FHSA Cohort (n = 24)
Tibia Femur Femur and tibia Cavitary, tibia Cavitary, femur Segmental, tibia Segmental, femur
0 0 0 0 1 5 12 6
Control Cohort (n = 48) 12 3 27 6 0 0 0 0
and 3-ft standing radiographs of the affected knee are required. The degree of bone loss is best seen on the lateral radiograph for the distal femur and with orthogonal views for the proximal tibia. If significant bone loss is suspected, stemmed revision components and possibly allograft bone should be made available. Maintaining a high index of suspicion for bone loss is important given that preoperative radiographs often underestimate the amount of bony destruction. Because massive bone loss can lead to ligamentous insufficiency, constrained condylar or hinged prostheses should also be available, but are rarely used. Because of the tertiary and quaternary nature of our practices, allograft and the necessary instruments are available for every revision knee arthroplasty. For this reason, we do not obtain routine computed tomographic scans to evaluate bone loss preoperatively. The final decision regarding the need for allograft is made at the time of operation. Surgical Exposure Our preferred surgical technique for revision TKA using FHSA is as follows. Following a midline incision and medial parapatellar arthrotomy, an extensive synovectomy is performed. Careful attention is paid to resection of scar tissues in the medial and lateral gutters. A complete release of patellofemoral adhesions is undertaken by releasing all scar tissue anterior to the origin of the lateral collateral ligament. All scar superficial to the lateral collateral ligament is also released to allow the patella to be safely retracted laterally. No attempt is made to evert the patella. This accomplished by initially subluxing the patella laterally
and inserting a narrow Holman retractor around the lateral femoral condyle. Using scissors, the scarred lateral patellofemoral ligament is released, allowing the patella to relax and to fall inferiorly. Subsequently, scar tissue between the patellar tendon and the anterior tibia is resected to allow the patellar tendon to be safely retracted. Scar tissue at the lateral edge of the tibia is then released up to the midcoronal plane. This allows an adequate release that protects the patellar tendon and allows safe exposure of the knee. This extensive release allows adequate visualization of both femur and tibia while avoiding the need for additional surgical techniques, which may weaken the extensor mechanism (rectus snip, quadriceps turndown, tibial tubercle osteotomy). If there is lateral subluxation or tilting of the patella on the preoperative radiographs, a lateral retinacular release is performed as well. Defining the Defect The full extent of the bony defects can only truly be appreciated with intraoperative assessment, at which time, the final decision to use a structural allograft is made (Fig. 1). The FHSA requires adequate host bone support to ensure stability of the implant and eventual union of the allograft-host bone junction. This is readily achieved if the defect is contained. For segmental defects, sufficient host bone contact on at least 3 of 4 sides is necessary to ensure stability. Following adequate exposure, the implants are removed, minimizing iatrogenic bone loss. All residual bone cement is carefully removed, and any underlying fibrous membrane is gently debrided exposing the host bone. The medullary canals of the femur and the tibia are then accessed using a sharp-tipped drill. The canal is then sequentially reamed in preparation for a stem extension. At this stage, an assessment of the femur and tibia is made to determine whether a FHSA is required. If
Table 3. Management of Bone Defects Management of Bone Defects Morsellized allograft A single FHSA 2 FHSA No metal augments Isolated metal femoral augments Isolated metal tibial augments Metal femoral and tibial augments
FHSA Cohort (n = 24) 0 19 5 2 14 1 7
Control Cohort (n = 48) 2 – – 14 27 2 5
Fig. 1. Anderson Orthopaedic Research Institute type 3 tibial defect.
1302 The Journal of Arthroplasty Vol. 26 No. 8 December 2011 an FHSA is needed, it is inserted at this stage of the operation before proceeding with the preparation of the bony surfaces for the tibial and femoral components. Insertion/Fixation of the Femoral Head Structural Allograft Before fixing the FHSA to host bone, the defect and allograft must be prepared. An appropriately sized acetabular reamer is used to prepare the defect, avoiding iatrogenic weakening of the host bone support. This is typically 38 to 42 mm in diameter. A female reamer (Allogrip set, Depuy, Warsaw, Ind) 1 mm larger than the acetabular reamer is used to prepare the FHSA, which is held in the allogrip bone holder (Depuy). The FHSA is inserted in a press-fit fashion and then temporarily fixed with 2 Kirschner wires, which have to be strategically directed away from the path of the tibia component keel or the cutting guides of the femur and anterior femoral flange. On the tibial side, the K-wires are inserted to the posterior cortex and not beyond, and on the femoral side, the K-wires are advanced in a retrograde manner as to bury the tip of the wire within the allograft so that it does not interfere with the saw blade when the distal femoral cut is being made. On the femoral side, the FHSA is then further prepared by making a preliminary distal femoral cut about 3 cm distal to the medial epicondyle or 2.5 cm distal to the lateral epicondyle. This distance is obtained from the AP radiograph of the contralateral normal knee, when available. In addition, a preliminary notch cut through the allograft is made to allow the insertion of the intramedullary revision TKA cutting guides. On the tibial side, after the tibial cut is made, a high speed burr with a pencil tip is then used to create the keel cut instead of a standard keel chisel. The use of a standard keel chisel will apply so much force that the allograft fixation will be disrupted. The standard revision instruments can then be used to make the remaining femoral cuts. Residual defects, particularly posteriorly because of the curvature of the femoral head,
Fig. 3. Postoperative AP (A) and lateral (B) radiographs— patient managed with femoral and tibial metal augments, FHSA of the tibia, and stemmed components.
can then be addressed with standard metal augments or morselized allograft. The components are cemented in place, ensuring correct rotation, using a press-fit stem extension. The temporary Kirschner wires are removed as soon as the implants are cemented (Figs. 2 and 3).
Results Quality of Life Outcome Scores Despite more severe preoperative bony defects, all measured outcome scores, except for the UCLA activity score and the SF-12 mental component, were significantly higher for the FHSA group in comparison with the control cohort (Table 4). All 4 components of the WOMAC score, function (P = .011), stiffness (P = .002), pain (P = .001), and global (P = .004) were significantly higher for the FHSA cohort. The Oxford score (P = .001) and all 4 components of the satisfaction score, pain (P b .001), function (P b .001), recreation (P b .001), and overall (P = .001) were also significantly higher for the FHSA cohort compared with the control group. There Table 4. Quality of Life Outcome Scores Quality of Life Measure WOMAC function WOMAC stiffness WOMAC pain WOMAC global Oxford score SF-12 physical component SF-12 mental component Satisfaction pain Satisfaction function Satisfaction recreation Satisfaction overall UCLA activity score
Fig. 2. Preoperative AP (A) and lateral (B) radiographs of a study patient with a large tibial defect.
FHSA Cohort (n = 24)
Control Cohort (n = 48)
76 77 85 79 80 40 52 93 94 86 93 4.9
61 61 66 62 63 33 48 68 66 55 71 4.0
.011 .002 .001 .004 .001 .027 .337 b.001 b.001 b.001 .001 .052
Oxford Hip score and WOMAC scores are normalized to a range of 0 to 100, with 0 being worst and 100 being best.
Revision Total Knee Arthroplasty Richards et al
was a trend toward a higher score on the UCLA activity score, but this was not statistically significant (P = .052). Given that most structural allograft patients were treated by a single surgeon, a subanalysis was completed on the control group to determine if the treating surgeon was a predictor of outcome. The analysis revealed that there was no significant difference between the 3 surgeons for all of the outcome scores for the control cohort (P values ranging from .605 to .996).
Discussion Most published literature on the use of structural allograft for the management of massive bony defects during revision TKA includes reports of patient cohorts in which a variety of allograft options were used [3,4,10-12]. Studies focused on the use of either bulk distal femur or proximal tibia have reported successful outcomes ranging from 77% to 100% [13-18]. Engh et al  and Engh and Ammeen  have reported successful outcomes for 87% to 91% of patients treated with structural allograft where femoral head allograft was used for the majority of cases. Hockman and associates  reported on a comparison of 2 patient cohorts, one managed with structural allograft and one managed with metal augments. This study found a significant improvement in survivorship for the structural allograft group (19.2% failure for the structural allograft group vs 42.9% failure for the metal augments group) despite the presence of more severe preoperative bony defects. Limitations of this study include lack of complete preoperative scores for both the study group (only 67%) and control group (only 52%). There was no significant difference between the preoperative scores that were available for the 2 groups. In addition, there was no selection bias for patients who did not have preoperative scores, given that whether a patient completed the preoperative score was a random event. An additional limitation is the difference in the severity of the preoperative bony defects for the FHSA and control cohorts. A randomized control study comparing the outcomes of treating AORI type 3 defects with either FHSA or metal augments would effectively eliminate this bias as well as other potential confounders. This study demonstrates significantly improved clinical outcomes for the patients undergoing revision TKA using an FHSA compared with those without. Although the aim of our study was not to focus on survivorship, the improved outcome is in keeping with a potential for longer survivorship as shown by Hockman et al . As postulated by Hockman and associates, these improved results are possibly due to better interdigitation of cement in the trabecular microstructure of the allograft bone. It is conceivable that even in type II defects, the bone quality is not of good enough quality to allow for adequate cemented fixation, and the use of a femoral
head allograft provides for normal cancellous bone for better cement fixation. Our current algorithm is to use femoral head allograft whenever the bone quality is not deemed sufficient for cemented fixation, even when the bone quantity on the surface appears adequate. If the cancellous bone is capable of accepting cement, no allograft is required. However, if the bone is sclerotic with large cavitary defects from cement removal, it is best to sacrifice that bone and replace it with a femoral head allograft. To date, we have not had any failure of any of the cases revised with FHSAs in this series. The use of porous metal cone augments for management of large metaphyseal defects is a relatively new technique that offers an alternative to FHSA. Although it provides the potential advantage of good fixation to bone (between the trabecular metal and host bone) and good fixation between the revision component and the porous metal augment, it lacks the advantage of providing increased bone stock for young patients who may need additional surgeries in the future.
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