The fate of augments to treat type-2 bone defects in revision knee arthroplasty

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1 Knee The fate of augments to treat type-2 bone defects in revision knee arthroplasty J. V. Patel, J. L. Masonis, J. Guerin, R. B. Bourne, C. H. Rorabeck From the University of Western Ontario, London, Canada We report the five- to-ten year results of Anderson Orthopaedic Research Institute type-2 bone defects treated with modular metal augments in revision knee surgery. A total of 12 revision knee arthroplasties in patients with type-2 defects treated with augments and stems were prospectively studied. Seven patients (seven knees) had incomplete follow-up and 15 patients (16 knees) died with the arthroplasty in situ. The mean follow-up of the 79 remaining knees was 7 ± 2 years (5 to 11). The presence of nonprogressive radiolucent lines around the augment in 14% of knees was not associated with poorer knee scores, the range of movement, survival of the component or the type of insert which was used (p >.5). The survival of the components was 92 ±.3% at 11 years (95% CI, 1.3 to 11.2). We recommend the use of modular augmentation devices to treat type-2 defects in revision knee surgery. J. V. Patel, BM, FRCS (Tr and Orth), Consultant Orthopaedic Surgeon J. L. Masonis, MD, Attending Orthopaedic Surgeon J. Guerin, BMath, Research Director R. B. Bourne, MD, FRCS C, Professor of Orthopaedic Surgery C. H. Rorabeck, MD, FRCS C, Professor of Orthopaedic Surgery Division of Orthopaedics, London Health Sciences Center, University of Western Ontario, 339 Windermere Road, London, Ontario N6A 5A5, Canada. Correspondence should be sent to Mr J. V. Patel at the Department of Orthopaedics, The Middlesex Hospital, Mortimer Street, London W1T 3AA, UK. 24 British Editorial Society of Bone and Joint Surgery doi:1.132/31-62x.86b $2. J Bone Joint Surg [Br] 24;86-B: Received 22 May 22; Accepted after revision 15 May 23 The reported outcomes after cemented revision total knee replacement (TKR) have been satisfactory, but most studies have involved small numbers of patients with short follow-up. 1-9 Classification systems have been developed to described the severity of the bony defects which may be encountered and provide a basis for comparison between alternative forms of treatment. There are, however, few reports of revision knee arthroplasty which use these classifications. Bony defects may be treated by using metal augmentation devices. Some complications including fretting, radiolucent lines and poor fixation after using these devices have been described in a few studies with short followup To date, the mid-term results have not been reported. Our aim was to report the five- to ten-year results on the specific use of metal augmentation devices with knee revision implants for Anderson Orthopaedic Research Institute (AORI) type-2 bone defects (Table I). 17 Patients and Methods Between 1991 and 1996, 135 revision TKR procedures were described by the surgeon undertaking the operation as having AORI type-2 bone defects (Fig. 1). 17 Bulk allograft or impaction grafting and cement were used in 33 knees. The remaining 98 patients (12 knees) were revised using stemmed components with Table I. The Anderson Orthopaedic Research Institute classification of bony defects Pre-operative radiological or Defect type intra-operative findings 1 Intact and full metaphyseal bone and flare Femur or No component subsidence or osteolysis tibia 2 Damaged metaphysis, shortened metaphyseal flare Femur Component subsidence/osteolysis distal to epicondyles Tibia Component subsidence/osteolysis up to or below tip of fibula head 3 Deficient metaphyseal segment Femur Component subsidence/osteolysis at or beyond level of epicondyles Tibia Component subsidence/osteolysis at or beyond level of tubercle augmentation devices to treat bony defects. There were 44 men and 54 women with a mean age of 69 ± 9 years (41 to 87). There were 53 right and 49 left knees. The mean Body Mass Index of the patients at operation was 3 ± 6 kg/m 2 (17 to 42). The underlying pathology was primary osteoarthritis for 88 knees, rheumatoid arthritis for ten and posttraumatic osteoarthritis for four. Revision was for wear and osteolysis in 28 knees, for sepsis in 26, for aseptic loosening in 21, for patellofemoral complications in 12 (two for unstable patellae and ten for worn polyethylene components), for instability in 11, for periprosthetic fracture in two and for pain of VOL. 86-B, No. 2, MARCH

Distribution of bony defects for the 98 patients (12 knees) who underwent revision knee surgery with modular metal augments Femur (number) Tibia (number) Defect Medial Lateral Medial Lateral

2 196 J. V. PATEL, J. L. MASONIS, J. GUERIN, R. B. BOURNE, C. H. RORABECK Fig. 1a Fig. 1b Drawings showing a) unicondylar femoral damage (AORI 2A) and an intact tibia (AORI 1), and b) deficient femoral condyle (AORI 3), and bicondylar damage to tibial metaphysis (AORI 2B). Table II. Distribution of bony defects for the 98 patients (12 knees) who underwent revision knee surgery with modular metal augments Femur (number) Tibia (number) Defect Medial Lateral Medial Lateral Unicondylar AORI 2 A Bicondylar AORI 2 B 56 9 unknown origin in two. There were 99 revisions of a primary TKR and three revisions of a unicondylar prosthesis. The distribution of bony defects encountered is shown in Table II. We revised 68 knees using the Co-ordinate knee system DePuy, Warsaw, Indiana) and 34 using the Genesis I system (Smith & Nephew, Memphis, Tennessee). The Co-ordinate system has a 6 to 1 mm thick cobaltchrome femoral component, depending on size, which accepts 4 and 8 mm thick cobalt-chrome distal and posterior augments which are cemented in place. The augments have a 1 mm polymethylmethacrylate (PPMA) spacer to reduce fretting. The cobalt-chrome tibial trays may have non-modular 5, 1 or 15 wedges or 5 or 1 half wedges. Both femoral and tibial components accept canal filling fluted stems of between 95 and 14 mm in length. The Genesis I system has modular titanium 4 and 8 mm thick posterior and distal femoral wedges which are cemented onto the 11.5 mm thick cobalt-chrome femoral component (including conversion module). Titanium modular tibial wedges are available in thicknesses of 5 and 1 mm and are cemented on to the titanium tibial component. Femoral stems are available in lengths of 1, 15 and 2 mm and tibial stems are available in lengths of 4 and 9 mm. All operations were under the direction of one of the two senior authors (CHR or RBB). The site and size of the augments was recorded, as was the length of stem. All stems were cemented using a hybrid technique with cement being applied to the prepared condylar surfaces and to the metaphyseal segment of the stem only. Antibiotic-loaded cement was used in all operations (Simplex, Howmedica, East Rutherford, New Jersey). The thickness and distribution of the 176 femoral augments which were used is shown in Table III. Distal femoral augments were most commonly used. For the tibia medially, 5 wedges were used in four knees, 1 wedges in six knees and 1 mm stepped hemi-wedges in seven knees. Laterally, a 5 wedge was used in one knee. A thickened tibial tray was used to make up defects both medially and laterally in two knees. The lengths of stems used in association with an augment are shown in Figure 2. Of the 12 knees, 32 were treated with a varus-valgus constrained polyethylene insert, and 7 with a posterior stabilised insert. Patients were evaluated clinically using Knee Society Scores. 18,19 Standing anteroposterior and lateral radiographs of the knee were taken six weeks after operation and annually thereafter. The presence of radiolucent lines and osteolysis around the augment was recorded. Data were analysed in two groups. First the clinical outcome was identified with survivorship being calculated using the Kaplan-Meier method. 2 The indications for re-revision were recorded. Secondly, those knees with THE JOURNAL OF BONE AND JOINT SURGERY

3 THE FATE OF AUGMENTS TO TREAT TYPE-2 BONE DEFECTS IN REVISION KNEE ARTHROPLASTY 197 Table III. The thickness and distribution of 151 femoral augment devices used in 79 knees and the association with radiolucent lines Distal Posterior Mean thickness ± SD Cases (%) in mm (range) Mean thickness ± SD Cases (%) in mm (range) Medial 36 (24) 5.4 ± 1.8 (4 to 8) 31 (21) 5.2 ± 2 (4 to 8) Lateral 46 (3) 5.2 ± 1.8 (4 to 8) 38 (25) 4.8 ± 2 (4 to 8) Radiolucent lines 2 (2) 9 (13) % used Cumulative survival Femur Tibia 9 to to 15 2 Stem length (mm) Fig. 2 The lengths of the stems used with the augments in 98 patients with type- 2 bony defects who underwent revision TKR Years Fig. 3 Following revision TKR for type-2 bony defects, re-revision for any reason was 92 ±.3% at 11 years (95% CI; 1.3 to 11.2). radiolucent lines were compared with those without in order to identify any association with the grade of bony defect, a predilection for distal or posterior femoral augments, the revision knee system used, the level of constraint used and the clinical outcome. Results At the time of follow-up 15 patients (16 knees) had died without having had further surgery to their knee. The mean age of these patients was 68 ± 12 years (6 to 82) and the mean follow-up was 4 ± 2 years (1 to 7). Four patients (4 knees) were lost to follow-up and three (3 knees) refused or could not attend for review. There remained 79 TKRs (76 patients) with complete clinical and radiographic follow-up at a mean of 7 ± 2 years (5 to 11). The mean age of these patients at the time of surgery was 68 ± 9 years (41 to 84). Clinical analysis. The mean pre-operative knee score of the 79 TKRs had improved from 87 ± 34 (2 to 165) to 137 ± 36 (8 to 199) at final follow-up. The mean pre-operative range of movement was 9 ± 22 (3 to 125), which improved to 1 ± 2 (3 to 13). Six knees were re-revised, three for aseptic loosening of the tibial tray 1.3, 1.6 and seven years after surgery, respectively. One knee was re-revised the year after surgery for coronal instability associated with a posterior stabilised insert. Deep infection requiring two-stage re-revision occurred in two knees, in one the infection was recurrent. In none of these knees were there radiolucent lines or loosening of the augment. Survival calculated by the Kaplan- Meier method (Fig. 3) was 92 ±.3% at 11 years (95% CI, 1.3 to 11.2). Radiographic analysis. Radiolucent lines were seen around 11 of the 79 knees (15.6%) where a femoral augment was used. Radiolucent lines could only be seen on the lateral radiograph and whether they occurred medially or laterally could not be reliably established. Non-progressive radiolucent lines were seen in three of the 2 knees (15%) where a tibial augment was used. For both femoral and tibial augments, radiolucent lines developed at a mean of 2.7 years (1 to 5) after surgery. None were progressive or associated with clinical failure. Pearson chi-squared tests did not demonstrate a significant predilection for radiolucencies to occur around the augments in 2A or 2B defects (p =.59), distal or posterior femoral augments (p =.75), Genesis or Co-ordinate knee systems (p =.36), or with the use of either a posterior stabilised or varus-valgus constrained polyethylene insert (p =.36). Mann-Whitney U testing of data failed to demonstrate poorer knee scores with radiolucencies around an augment (p =.28). Discussion Wedged tibial polyethylene augments were originally used by Jeffery et al. 15 Currently metal augments are available in VOL. 86-B, No. 2, MARCH 24

4 198 J. V. PATEL, J. L. MASONIS, J. GUERIN, R. B. BOURNE, C. H. RORABECK Table IV. The results of nine previous studies of cemented revision knee arthroplasty using stemmed components Author Number of patients Diagnosis (% aseptic) Bone defect treatment Constrained inserts (%) Follow-up (years) Bertin et al Cemented Goldberg et al Bone graft Rotating hinge (14) 5 9 Elia and Lotke Cement and graft Friedman et al Cement and graft Not reported Murray et al Not reported Hartford et al Not reported CCK* (1) 5 81 Haas et al Augments CCK (25) Takahashi and Augments 2 97 Gustilo 8 Bugbee et al (27 AORI type 2) Augments Not reported 5 94 * constrained condylar knee Component survival (%) wedges and blocks for femoral and tibial defects, which are about 1 cm thick. A number of advantages make augmentation devices used in revision knee arthroplasty appropriate for the management of bony defects. These devices allow for versatile intra-operative customisation. Asymmetric defects which may be encountered in the tibia and femur, do not require further resection of bone in order to produce a symmetrical bed to seat the prosthesis, thus preserving bone stock. Minimising the amount of tibial resection optimises the strength of the cancellous bone, which is available to support the component, as the strength of the tibial cancellous bone is inversely proportional to its distance from the joint line. 21 Additionally, the conical shape of the proximal tibia causes relatively undersized tibial components to be used if the defects are not reconstructed. This may cause a mismatch between the size of the femoral and tibial components in some revision knee arthroplasty systems. For the femur, minimal resection of bone and reconstruction of defects with augments aids restoration of the joint kine, knee joint kinematics, correct rotation of the component and soft tissue balancing. 22 Moreover, unlike bone grafts, cemented augments do not require healing to the sclerotic bed. In vitro evidence exists for greater loading of the tibia and a more stable construct with cemented metal wedges rather than cement alone when reconstructing uncontained tibial defects Despite the widespread availability and perceived advantages, there are concerns regarding the use of augments in current revision knee arthroplasty systems. Fretting of modular implants has been reported at the morse taper interfaces of femoral components and could conceivably occur between the augment and the femoral or tibial interface Disassociation of modular components in revision knee arthroplasty has also been reported. 26 The shear strength of a cemented modular tibial metal augment, retrieved after 6.5 years in vivo, was 77% of that of a newly cemented augment. 27 Wedge-shaped augments have been shown, in vitro, to be less stable than stepped and rectangular augments. 1 Non-progressive radiolucent lines have been observed between 27% and 46% of augmented tibial components. 13,16,27 Pagnano et al 13 described 28 primary TKRs with a mean follow-up of 5.6 years. There were no revisions associated with the augments, but 13 knees (46%) had radiolucent lines. Brand et al 16 similarly reported radiolucent lines in 27% of knees in which tibial augments were used on 17 primary and five revision TKRs with a mean follow-up of 37 months. In our series, radiolucent lines were found around 15% of tibial augments. The stability of the component is, undoubtedly, partly determined by the use of stems. 12,28,29 The extensive use of stems and the method of their fixation in this series may, in part, explain the reduced incidence of radiolucent lines and satisfactory results. The use of femoral augments has, to date, been poorly reported, as has the use of augments in revision TKR where the surface area of contact between cement and prosthesis is reduced and bone quality poor. 3 Radiolucent lines were observed in 2% of distal femoral augments and 13% of posterior augments (Table III). It is probable that the complex shape of the stemmed femoral component with augments obscures the full extent of radiolucent lines observed as does variations in the angle of radiographic projection. Once radiolucent lines were observed around the femoral augment, they were consistently detected on subsequent radiographs. Their presence did not correlate with the severity of the bony defect, manufacture of prosthesis, the amount of constraint used at the articulation, the Knee Score at follow-up or the requirement for further revision surgery. It is difficult to compare the results of revision TKR without a universally accepted classification system for bony defects, particularly as there are few mid-term follow-up reports of revision TKR. Elia and Lotke 3 described 1% failures in 4 revision TKRs with defects of 1 cm depth at a mean follow-up of 41 months. Bony defects were filled with cement and/or bone graft, and stems were used in all knees. The results of cemented revision TKR using stemmed components are summarised in Table IV. Our results with Kaplan-Meier survival of 92 ±.3% at 11 years, suggest satisfactory mid-term survival and compare favourably with previous reports of fewer patients and shorter followup using stemmed cemented revision TKRs. 1-9 THE JOURNAL OF BONE AND JOINT SURGERY

5 THE FATE OF AUGMENTS TO TREAT TYPE-2 BONE DEFECTS IN REVISION KNEE ARTHROPLASTY 199 We have found the AORI classification to be helpful and simple to use. It does not, however, distinguish between contained and uncontained defects, nor are central cavitary defects accounted for. Contained defects could, alternatively, be treated with non-structural bone graft or cement. Of the 28 tibial defects, only 2 were treated with augmented components. This reflects the common practice of making up for tibial defects by using a thicker polyethylene insert. Our analysis did not control for variables known to affect the results of revision TKR, such as the cause of prosthetic failure and ligament insufficiency. Our aim was to present the results of a single method of reconstruction for a specific type of bony defect. In the absence of comparative trials, we hope that these results will enable alternative methods of reconstruction to be evaluated. In conclusion, we support the use of modular augmentation devices to treat type-2 defects in revision knee surgery. We have observed 92% survival at 11 years in the treatment of these defects with metal augments, with no clinically significant complications and conclude that theoretical concerns of fretting and loosening are unfounded based on fiveto ten-year clinical data. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. References 1. Bertin KC, Freeman MA, Samuelson KM, Ratcliffe SS, Todd RC. Stemmed revision arthroplasty for aseptic loosening of total knee replacement. J Bone Joint Surg [Br] 1985;67-B: Goldberg VM, Figgie MP, Figgie HE, Sobel M. The results of revisional total knee arthroplasty. Clin Orthop 1988;226: Elia EA, Lotke PA. Results of revision total knee arthroplasty associated with significant bone loss. Clin Orthop 1991;271: Friedman RJ, Hirst P, Poss R, Kelley K, Sledge CB. Results of revision total knee arthroplasty performed for aseptic loosening. Clin Orthop 199;255: Murray PB, Rand JA, Hanssen AD. Cemented long-stem revision total knee arthroplasty. Clin Orthop 1994;39: Hartford JM, Goodman SB, Schurman DJ, Knoblick G. Complex primary and revision total knee arthroplasty using the condylar constrained prosthesis: an average 5-year follow-up. Arthroplasty 1998;13: Haas SB, Insall JN, Montgomery W 3rd, Windsor RE. Revision total knee arthroplasty with use of modular components with stems inserted without cement. J Bone Joint Surg [Am] 1995;77-A: Takahashi Y, Gustilo RB. Nonconstrained implants in revision total knee arthroplasty. Clin Orthop 1994;39: Bugbee WD, Ammeen DJ, Engh GA. Does implant selection affect outcome of revision knee arthroplasty? J Arthoplasty 21;16: Chen F, Krackow KA. Management of tibial defects in total knee arthroplasty: a biomechanical study. Clin Orthop 1994;35: Fehring TK, Peindl RD, Humble RS, Harrow ME, Frick SL. Modular tibial augmentations in total knee arthroplasty. Clin Orthop 1996;327: Brooks PJ, Walker PS, Scott RD. Tibial component fixation in deficient tibial bone stock. Clin Orthop 1984;184: Pagnano MW, Trousdale RT, Rand JA. Tibial wedge augmentation for bone deficiency in total knee arthroplasty: a follow-up study. Clin Orthop 1995;321: Rand JA. Bone deficiency in total knee arthroplasty: use of metal wedge augmentation. Clin Orthop 1991;271: Jeffery RS, Orton MA, Denham RA. Wedged tibial components for total knee arthroplasty. J Arthroplasty 1994;9: Brand MG, Daley RJ, Ewald FC, Scott RD. Tibial tray augmentation with modular metal wedges for tibial bone stock deficiency. Clin Orthop 1989;248: Engh GA. Bone defect classification. In: Engh GA, Rorabeck CH, eds. Revision total knee arthroplasty. Baltimore: Williams and Wilkins, 1997: Ewald FC. The Knee Society total knee arthroplasty roentgenographic evaluation system. Clin Orthop 1989;248: Insall JN, Dorr LD, Scott RD, Scott WN. Rationale of the Knee Society clinical rating system. Clin Orthop 1989;248: Kaplan EJ, Meier P. Nonparametric estimation from incomplete observations. J Am Stat Assoc 1959;53: Harada Y, Wevers HW, Cooke TD. Distribution of bone strength in the proximal tibia. J Arthroplasty 1988;3: Partington PF, Sawhney J, Rorabeck CH, Barrack RL, Moore J. Joint line restoration after revision total knee arthroplasty. Clin Orthop 1999;367: Collier JP, Surprenant VA, Jensen RE, Mayor MB, Surprenant HP. Corrosion between the components of modular femoral hip prostheses. J Bone Joint Surg [Br] 1992;74-B: Urban RM, Jacobs JJ, Gilbert JL, Galante JO. Migration of corrosion products from modular hip prostheses: particule microanalysis and histopathological findings. J Bone Joint Surg [Am] 1994;76-A: Rand JA. Modular augments in revision total knee arthroplasty. Orthop Clin North Am 1998;29: Lim LA, Trousdale RT, Berry DJ, Hanssen AD. Failure of the stem-condyle junction of a modular femoral stem in revision total knee arthroplasty: a report of five cases. J Arthroplasty 21;16: Rand JA. Augmentation of a total knee arthroplasty with a modular metal wedge: a case report. J Bone Joint Surg [Am] 1995;77-A: Bourne RB, Finlay JB. The influence of tibial component intramedullary stems and implant-cortex contact on the strain distribution of the proximal tibia following total knee arthroplasty. Clin Orthop 1986;28: Albrektsson BEJ, Ryd L, Carlsson LV et al. The effect of a stem on the tibial component of knee arthroplasty: a roentgen stereophotogrammetric study of uncemented tibial components in the Freeman-Samuelson knee arthroplasty. J Bone Joint Surg [Br] 199;72-B: Rand JA, Sculco TP, Miric A, Klein JDS, MacCauley W. The use of prosthetic augments is the optimal way to correct for bone defects during total knee replacement. In: Laskin RS, ed. Controversies in total knee replacement. Oxford University Press, 21: VOL. 86-B, No. 2, MARCH 24

Bilateral total knee arthroplasty: One mobile-bearing and one fixed-bearing

Journal of Orthopaedic Surgery 2001, 9(1): 45 50 Bilateral total knee arthroplasty: One mobile-bearing and one fixed-bearing KY Chiu, TP Ng, WM Tang and P Lam Department of Orthopaedic Surgery, The University