The Journal of Arthroplasty 30 (2015) 1990–1994
Contents lists available at ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Metaphyseal Sleeves for Revision Total Knee Arthroplasty: Good Short-Term Outcomes Kate E. Bugler, MRCS, BA(Hons) , Rohit Maheshwari, FRCS (Orth), Isaaq Ahmed, FRCS (Orth), Ivan J. Brenkel, FRCS (Orth), Philip J. Walmsley, FRCS (Orth) Victoria Hospital Kirkcaldy, Kirkaldy, Fife, Scotland KY2 5AH
a r t i c l e
i n f o
Article history: Received 2 October 2014 Accepted 7 May 2015 Keywords: knee arthroplasty replacement revision aseptic sleeves
a b s t r a c t Metaphyseal sleeve prostheses have shown promising results in the management of bone defects at revision TKA. We present a study of their use in aseptic revision TKA. Thirty-five revisions were included in 34 patients with wear or aseptic loosening indicated in 71% of cases. The majority of cases (63%) were AORI grade 2 or greater on the tibia or femur. Knee Society scores were excellent or good in 83% of patients with the same percentage having no or only mild pain. One patient suffered a sleeve-related complication with femoral condylar fractures three years postoperatively; these united with good outcomes. All radiographs were satisfactory; no patient required a further revision. We report good outcomes with the use of metaphyseal sleeves in revision TKA. © 2015 Elsevier Inc. All rights reserved.
The number of patients requiring revision total knee arthroplasty (TKA) is rapidly increasing with a 17% increase in procedures undertaken in the United Kingdom from 2011 to 2012 [1]. This is predicted to continue with an estimated 601% increase predicted between 2005 and 2030 in the United States [2]. In addition the Scottish Arthroplasty Project reports increasing numbers of primary procedures in increasingly younger patients suggesting that the revision burden will continue to rise [3]. Due to this increasing requirement, with its associated cost implications [4], investigation of the options for revision TKA has become of greater importance. Particular challenges exist in the setting of significant bone loss. Bone graft [5–8], cement and screws [9], block augments [10,11], tantalum metal cones [12–17], tumour megaprostheses [18] and custom prostheses [19] have all been used with some success. An alternative option is the use of a metaphyseal sleeve. These devices engage into the metaphysis of the distal femur or proximal tibia via a stepped design with a porous coating to promote bony ingrowth. Metaphyseal sleeves have been in widespread use for hinged knee arthroplasty for some time with good long term outcomes [20]. Further development has resulted in modifications to permit the use of metaphyseal sleeves with semi-constrained revision implants. Initial
One or more of the authors of this paper have disclosed potential or pertinent conflicts of interest, which may include receipt of payment, either direct or indirect, institutional support, or association with an entity in the biomedical field which may be perceived to have potential conflict of interest with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2015.05.015. Reprint requests: Kate Bugler, MRCS, BA(Hons), Victoria Hospital Kirkcaldy, Kirkaldy, Fife, Scotland, KY2 5AH. http://dx.doi.org/10.1016/j.arth.2015.05.015 0883-5403/© 2015 Elsevier Inc. All rights reserved.
studies looking at the outcomes of this use have been encouraging but the data remains limited [21–23]. The aims of this study were to assess the short term outcomes of the use of metaphyseal sleeves in revision TKA and the factors affecting the outcomes in order to assess their role in this challenging area of orthopaedics.
Patient and Methods This was a retrospective review of prospectively collected data on consecutive revision knee arthroplasty procedures performed at the study centre. A prospective database was compiled of all 109 patients undergoing revision TKA using a metaphyseal sleeve (DePuy, Warsaw, Indiana) from 2008 to 2013. In order to evaluate the short term outcomes this study only included those patients at least two years post revision surgery for aseptic loosening. Patients in whom revision was carried out for infection were also excluded. Of the 45 patients remaining, full follow up of at least two years was obtained in 35 revision knee arthroplasties (78%); mean length of follow up was 39 months with a range of 24 to 62 months. Of the remaining 10; one patient who had both knees revised with metaphyseal sleeves died prior to the two year follow up for either knee of unrelated causes, four other patients were followed up for less than two years before loss to follow up and four patients did not attend any follow up following their revision TKA. There were no significant differences in demographics (age, BMI, gender, ASA) or operative procedure (duration of procedure, length of stay) between those lost to follow up and those with at least two years follow up.
K.E. Bugler et al. / The Journal of Arthroplasty 30 (2015) 1990–1994 Table 1 Background Characteristics of Patients Included in the Study.
Table 4 Intraoperative AORI Grading of the Proximal Tibia.
Patients Mean age at time of revision (range) (years) Gender (male) BMI (kg/m2) Mean (range) Underweight (b18.5) Normal (18.5–25) Overweight (25–30) Obese (30–40) Morbidly obese (N40) Not recorded ASA Mean I II III Side (left:right)
1991
AORI grading 72 (55–86) 57% 30.2 (20–42) 0 (0%) 4 (11%) 10 (29%) 18 (51%) 2 (6%) 1 (3%) 2.26 3 (9%) 20 (57%) 12 (34%) 46:54
For the patients included in the study demographic data was recorded including age at time of procedure, gender and body mass index (BMI) (Table 1). General health status was recorded using the American Society of Anestheologists’ (ASA) grading system. All procedures were undertaken as single stage revisions by one of two revision knee surgeons in the unit (IJB and PW). The indication for revision was defined by the lead surgeon at the time of the procedure with the majority undertaken for aseptic loosening (45%) or polyethylene wear (26%) (Table 2). Primary procedures were performed in all cases between 1987 and 2009 with the mean time from primary procedure to revision 11 years (range 2–23; standard deviation (SD) 6.5). Most patients (82%) had only undergone one procedure prior to their revision surgery but a minority (18%) had undergone two procedures. The majority of the revision knee arthroplasty was performed under spinal or epidural anaesthesia (97%) with the remaining patient requiring a general anaesthetic due to anaesthetic difficulties. All procedures were carried out with the use of a thigh tourniquet with the incision was made through the previous scar and a medial parapatellar approach. The primary prosthesis was removed with attention to keeping any bone loss to a minimum. Anderson Orthopaedic Research Institute (AORI) grading [24] was carried out intraoperatively by the lead surgeon following removal of the primary prosthesis (Tables 3 and 4). Following grading a decision was made regarding the most appropriate implant for the bone loss. Metaphyseal sleeves were used for both the femoral and tibial components in the majority of patients (69%) with a small proportion of cases requiring only a tibial (10; 28%) or femoral (1; 3%) sleeved
1 2 3
Frequency 20 (57%) 13 (37%) 2 (6%)
prosthesis (Fig. 1). Initially all implants were inserted with a stem but it became apparent that this was not necessary unless there was an uncontained defect in zone one, two or three. An additional stem was applied in 21 (60%) of the tibial prostheses and 12 (34%) of the femoral prostheses. When stems were used they were predominantly 12×75mm with the aim to provide additional stability but not metaphyseal fixation in zone three as this could cause stress shielding in zone one (Fig. 2). A range of sizes were used in all components with the majority of patients requiring size 3 femoral and tibial prostheses. Size 10 polyethylene inserts were the most commonly used. These were mobile bearing in all cases except the patient in whom a tibial sleeve was not required where a fixed bearing polyethylene was used in conjunction with a PFC Sigma prosthesis (DePuy Synthes). Where required, morselized bone graft and block augments were used with 5 cases (14%) requiring bone graft either around the tibia or femoral prosthesis and augments attached to the femoral component either distally or posteriorly. No patient required a tibial tubercle osteotomy or rectus snip. Post operatively patients were permitted to mobilise fully weight bearing immediately with the assistance of the physiotherapy team prior to discharge home with an outpatient self directed physiotherapy regime. Patients were followed up both radiographically and clinically for a minimum of two years following the procedure. All radiographs were reviewed by the senior author (IJB) to assess for signs of loosening. In addition information regarding complications, range of movement and pain was prospectively collected. Patient reported outcome questionnaires were completed by all patients including the general health related physical component (PCS) and mental component (MCS) scores of the Short Form 12 [25] (SF12), and the knee specific Oxford Knee Score [26] (OKS), with 0 as the worst score and 48 the best score, American Knee Society Score (KSS) and American Knee Society Functional Score (KSFS) [27]. A satisfaction score was also obtained on a linear scale from one to ten. Results were analysed using SPSS software version 19 (SPSS Inc., Chicago, IL, USA). Chi-squared tests were used for categorical data, unpaired t-tests for two groups of continuous data and ANOVA for
Table 2 Indication for Revision Surgery. Indication Aseptic loosening Polyethylene wear Malalignment Instability Unexplained pain
Frequency 16 (45%) 9 (26%) 6 (17%) 2 (6%) 2 (6%)
Table 3 Intraoperative AORI Grading of the Distal Femur. AORI grading
Frequency
1 2 3 Not recorded
17 (49%) 16 (46%) 0 (0%) 2 (5%)
Fig. 1. Intraoperative Photograph Showing Bone Surfaces Prepared for Insertion of Tibial and Femoral Metaphyseal Sleeves.
1992
K.E. Bugler et al. / The Journal of Arthroplasty 30 (2015) 1990–1994 Table 5 Outcomes in the 35 Patients With Follow Up of at Least Two Years (mean 39 months). Score American Knee Society Functional Score American Knee Society Score Oxford Knee Score Satisfaction SF12 (PCS) SF12 (MCS)
Mean
SD
Range
58.1 81.3 34.0 7.5 38.3 47.1
33.1 18.1 9.6 2.3 10.8 10.4
−20 to 100 32–100 5–47 2–10 20.2–55.5 27.4–64.0
three or more groups. Correlation was assessed using the Pearson correlation co-efficient. A p value of b 0.05 was considered significant. Standard deviations were calculated to show spread of data. Results Thirty-five patients were included in this study of the use of metaphyseal sleeves in revision TKA. The mean duration of procedure was 108 minutes (range 60–154 minutes, SD 22.0 minutes). There was a significant correlation between increasing duration of procedure and BMI (Pearsons; P= .04). Minimal blood loss was recorded for all procedures. The mean haemoglobin drop post operatively was 2.8 g/dl with only seven patients (20%) requiring blood transfusion. These patients had a mean haemoglobin of 13.3 g/dl pre-transfusion and a mean haemoglobin drop of 3.2 g/dl. Mean length of stay was 8 days (range 4–18). Good patient reported outcomes (PROMs) were found in all measures used (Table 5). Knee Society Scores were good or excellent in 83% of patients (20% good, 63% excellent) [4]. Satisfaction scores greater than or equal to 8 out of 10 were expressed by 63% of patients (Fig. 3). Further analysis revealed 43% of patients reported no pain at final follow up with a further 40% reporting only mild or occasional pain. There were no significant differences in the PROMs scores when compared for different AORI grades of femoral and tibial bone loss (ANOVA; P values from 0.967 to 0.072). A small number of complications were recorded (Table 6). Intraoperatively one patient sustained a tibial fracture. This was treated conservatively and the patient had good final outcomes. Post-operatively
Fig. 2. a, b and c: Failed unicompartmental knee replacement revised with a tibial metaphyseal sleeve. (A) Pre operative radiograph. (B) Immediate post operative radiograph. (C) Four years following revision showing metaphyseal loading by the sleeve.
Fig. 3. Distribution of satisfaction scores on a linear scale from 1–10.
K.E. Bugler et al. / The Journal of Arthroplasty 30 (2015) 1990–1994 Table 6 Complications of use of Metaphyseal Sleeves. Complications
Frequency
Intraoperative Proximal tibial fracture
1
Early post-operative Myocardial infarction Superficial wound infection Wound dehiscence
1 1 1
Late post-operative Varus instability Late femoral condyle fracture Patellofemoral symptoms
1 1 3
one patient suffered a myocardial infarction but went on to a successful recovery. Two other patients had wound problems one remaining in hospital for 13 days due to prolonged wound leakage and the other with a dehiscence of their wound requiring plastic surgical intervention in the form of a split skin graft. At final review one patient with a previous femoral shaft malunion was found to have instability with laxity on varus stressing, following extensive discussion with the patient regarding the possibility of revision to a hinged TKA they are currently considering their options. Finally one patient sustained femoral condylar fractures three years post-operatively. These were treated conservatively and at most recent follow up the patient was asymptomatic and happy with their outcome. There were no cases of end of stem pain. In addition three patients reported patellofemoral symptoms postoperatively. These necessitated patellofemoral arthroplasty five and ten months post operatively in two patients with the other patient currently awaiting surgery. One of these patients developed a deep infection following their patellofemoral arthroplasty, having previously not had any evidence of infection, eventually requiring an above knee amputation 30 months following surgery. The other patient was much improved following surgery. Subsequent to the finding of a high rate of patellofemoral symptoms patella resurfacing is now a routine part of the operative protocol in all patients. Objective clinical outcomes found that all but six patients achieved full extension (83%), mean flexion was 100 degrees ranging from 70 to 130 degrees. Radiographic outcomes were also encouraging with no evidence of osteolysis around or loosening of either the femoral or tibial prostheses. Finally, to date no patient has required a further revision TKA. Discussion Revision knee arthroplasty can have a significant impact on patients’ quality of life resulting in improvements in PROMs [28]. The increasing requirement for revision arthroplasty has resulted in significant innovation with a range of methods available to counter the bone loss that is often a problem at time of surgery. Metaphyseal sleeves have been used for revision TKA with the hinged S-ROM Noiles knee system (DePuy Synthes) with good results reported [20,29]. Little has been published on their use with semiconstrained implants for revision TKA [21–23], indeed only one study has considered the use of metaphyseal sleeves for both the femur and tibia as we have done here. We have used metaphyseal sleeves in a large number of patients since 2008. This study of the use of metaphyseal sleeves in 35 patients with a minimum of two year shows good results in well selected patients. The cohort of patients included in this study were comparable to those included in other studies of revision arthroplasty. In line with most patients undergoing revision TKA the majority of patients were overweight or obese (mean BMI 30.2) with other significant health problems (mean ASA 2.26) [30]. The majority of patients in this cohort
1993
underwent revision due to aseptic loosening or polyethylene wear (71%) which is comparable to other studies [30,31] allowing comparison to other techniques of revision arthroplasty. We have excluded revision TKA undertaken for infection as these patients have previously been shown to have different patient reported outcomes pre and post operatively to those undergoing revision procedures for aseptic causes [32,33]. Although this is a relatively new development of the technique, we did not find a significant learning curve when used by experienced knee arthroplasty surgeons with a mean duration of procedure of only 111 minutes. The only learning curve was in the resurfacing of the patellofemoral joint. Initially this was not undertaken routinely, but there were a number of patients who complained of anterior knee pain, possibly due to the high box on the TC3 femoral component, and as a result patients now all routinely undergo patellofemoral resurfacing. There were no patients in whom the metaphyseal sleeve was found to be unsuitable at operation. This contrasts with the use of block augments which have been found to be unsuitable without the addition of bone graft in up to 48% of patients at time of surgery [11]. We have found good patient reported outcomes in this cohort in all outcome scores used; OKS, KSS, KSFS, SF12 and overall satisfaction. This agrees with previous work by Agarwal et al who reported similar postoperative OKS in their retrospective study of 102 knees that underwent revision TKA with the use of metaphyseal sleeves [21]. Two studies have also reported equally positive post-operative KSS and KSFS in their retrospective reviews of their use of metaphyseal sleeves in the tibial component of revision TKAs [22,23]. There were a small number of complications in this cohort. Complications following primary TKA have been found to be significantly higher in morbidly obese patients [34]. This may also be the case in revision surgery as it is interesting to note that the two patients with BMIs over 40 (morbidly obese) both suffered complications post operatively and there was a significant correlation between duration of operation and BMI. The patient that suffered fractures of the femoral condyles was a patient with a previous Kinemax Plus knee prosthesis who had developed a significant polyethylene reaction, this has been reported in a cohort of patients previously and is thought to be due to a manufacturing defect [35]. These have previously shown a predeliction for the femoral condyles and may have caused significant weakness of the condyles. Following fracture he was treated in a hinged knee brace and went on to good final outcomes. Agarwal et al [21] report two cases of early loosening with no definitive evidence of infection in patients in whom the metaphyseal sleeves were used without a stem. As a result they advocate the use of stems in all patients routinely. In our study almost half of the tibial and femoral metaphyseal sleeves (40% and 66%, respectively) were implanted without the use of a stem. None of these knees have shown evidence of early loosening but further follow up will be required to identify later changes. In addition the use of a stem has been reported to result in end of stem pain in some patients with a tibial metaphyseal sleeve [22,23], we have not found any cases of this in this study. In view of our good outcomes, we no longer routinely use a stem attachment utilising the additional stability only in cases where an uncontained defect in zone two or three required additional zone three fixation. We will continue to follow up these patients to identify any evidence of late loosening. We found no evidence of loosening of the prostheses in any patient. This compares with other methods of revision TKA which have shown evidence of loosening in some patients requiring further surgery. Tantalum metal cones have shown rates of loosening of around 6% [13]. This may be due to the cement required to connect the implant to the metal cone resulting in a potential region of instability. Whilst the use of bone graft has shown promising radiographic results the use of bone graft is limited by host factors including previously irradiated bone, immunosuppression and metabolic bone disease [6] as well as
1994
K.E. Bugler et al. / The Journal of Arthroplasty 30 (2015) 1990–1994
the risk of transmission of infection [5]. In addition the positive radiographic findings of custom prostheses [19] and tumour megaprostheses [18] are limited by the significant cost of these implants resulting in a limited application of these to the increasing population requiring revision TKA. A limitation of this study is the lack of pre-operative PROMs scores. However, the patients included in this study are similar to those included in other studies and we report similarly positive post-operative results. Although the follow up in this study is only short term a number of authors have shown patient reported outcomes continue to improve for one year after revision TKA followed by a plateau period [36,37]. This would suggest that all of our patients with a follow up of at least two years should have reached this steady state in patient reported outcomes. Whilst longer term outcome studies of the use of metaphyseal sleeves for revision TKA are evidently needed in order to sufficiently assess their longevity this study does show that good patient reported outcomes can be achieved in the short term. In conclusion this is the first prospective cohort study of patients undergoing revision TKA using metaphyseal sleeves. We have found good outcomes, objectively, functionally and radiographically, in appropriately selected patients. Further long term follow up is required to identify the optimum role of metaphyseal sleeves in revision knee arthroplasty. References 1. National Joint Registry for England, Wales and Northern Ireland. 10th Annual Report 2013; 2013. 2. Kurtz S, Ong K, Lau E, et al. Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030. J Bone Joint Surg Am 2007; 89(4):780. 3. Scottish Arthroplasty Project. Annual Report 2012; 2012. 4. Kurtz SM, Ong KL, Schmier J, et al. Future clinical and economic impact of revision total hip and knee arthroplasty. J Bone Joint Surg Am 2007;89(Suppl 3):144. 5. Clatworthy MG, Ballance J, Brick GW, et al. The use of structural allograft for uncontained defects in revision total knee arthroplasty. A minimum five-year review. J Bone Joint Surg Am 2001;83-A(3):404. 6. Engh GA, Ammeen DJ. Use of structural allograft in revision total knee arthroplasty in knees with severe tibial bone loss. J Bone Joint Surg 2007;89(12):2640. 7. Lotke PA, Carolan GF, Puri N. Impaction grafting for bone defects in revision total knee arthroplasty. Clin Orthop Relat Res 2006;446:99. 8. Lyall HS, Sanghrajka A, Scott G. Severe tibial bone loss in revision total knee replacement managed with structural femoral head allograft: a prospective case series from the Royal London Hospital. Knee 2009;16(5):326. 9. Ritter MA, Keating EM, Faris PM. Screw and cement fixation of large defects in total knee arthroplasty. A sequel. J Arthroplasty 1993;8(1):63. 10. Patel JV, Masonis JL, Guerin J, et al. The fate of augments to treat type-2 bone defects in revision knee arthroplasty. J Bone Joint Surg (Br) 2004;86(2):195. 11. Hockman DE, Ammeen D, Engh GA. Augments and allografts in revision total knee arthroplasty: usage and outcome using one modular revision prosthesis. J Arthroplasty 2005;20(1):35.
12. Howard JL, Kudera J, Lewallen DG, et al. Early results of the use of tantalum femoral cones for revision total knee arthroplasty. J Bone Joint Surg 2011;93(5):478. 13. Lachiewicz PF, Bolognesi MP, Henderson RA, et al. Can tantalum cones provide fixation in complex revision knee arthroplasty? Clin Orthop Relat Res 2012; 470(1):199. 14. Long WJ, Scuderi GR. Porous tantalum cones for large metaphyseal tibial defects in revision total knee arthroplasty: a minimum 2-year follow-up. J Arthroplasty 2009; 24(7):1086. 15. Meneghini RM, Lewallen DG, Hanssen AD. Use of porous tantalum metaphyseal cones for severe tibial bone loss during revision total knee replacement. J Bone Joint Surg 2008;90(1):78. 16. Rao BM, Kamal TT, Vafaye J, et al. Tantalum cones for major osteolysis in revision knee replacement. Bone Joint J 2013;95-B(8):1069. 17. Schmitz H-CR, Klauser W, Citak M, et al. Three-year follow up utilizing tantal cones in revision total knee arthroplasty. J Arthroplasty 2013;28(9):1556. 18. Höll S, Schlomberg A, Gosheger G, et al. Distal femur and proximal tibia replacement with megaprosthesis in revision knee arthroplasty: a limb-saving procedure. Knee Surg Sports Traumatol Arthrosc 2012;20(12):2513. 19. Macmull S, Bartlett W, Miles J, et al. Custom-made hinged spacers in revision knee surgery for patients with infection, bone loss and instability. Knee 2010;17(6):403. 20. Jones RE, Barrack RL, Skedros J. Modular, mobile-bearing hinge total knee arthroplasty. Clin Orthop Relat Res 2001;392:306. 21. Agarwal S, Azam A, Morgan-Jones R. Metal metaphyseal sleeves in revision total knee replacement. Bone Joint J 2013;95-B(12):1640. 22. Alexander GE, Bernasek TL, Crank RL, et al. Cementless metaphyseal sleeves used for large tibial defects in revision total knee arthroplasty. J Arthroplasty 2013; 28(4):604. 23. Barnett SL, Mayer RR, Gondusky JS, et al. Use of Stepped Porous Titanium Metaphyseal Sleeves for Tibial Defects in Revision Total Knee Arthroplasty: Short Term Results. J Arthroplasty 2014;29(6):1219. 24. Engh GA, Ammeen DJ. Bone loss with revision total knee arthroplasty: defect classification and alternatives for reconstruction. Instr Course Lect 1999;48:167. 25. Ware J, Kosinski M, Keller SD. A 12-Item Short-Form Health Survey: construction of scales and preliminary tests of reliability and validity. Med Care 1996;34(3):220. 26. Dawson J, Fitzpatrick R, Murray D, et al. Questionnaire on the perceptions of patients about total knee replacement. J Bone Joint Surg (Br) 1998;80(1):63. 27. Insall JN, Dorr LD, Scott RD, et al. Rationale of the Knee Society clinical rating system. Clin Orthop Relat Res 1989;248:13. 28. Kasmire KE, Rasouli MR, Mortazavi SMJ, et al. Predictors of functional outcome after revision total knee arthroplasty following aseptic failure. Knee 2014;21(1):264. 29. Jones RE, Skedros JG, Chan AJ, et al. Total knee arthroplasty using the S-ROM mobilebearing hinge prosthesis. J Arthroplasty 2001;16(3):279. 30. Dalury DF, Pomeroy DL, Gorab RS, et al. Why are total knee arthroplasties being revised? J Arthroplasty 2013;28(8 Suppl.):120. 31. Bozic KJ, Kurtz SM, Lau E, et al. The Epidemiology of Revision Total Knee Arthroplasty in the United States. Clin Orthop Relat Res 2009;468(1):45. 32. Barrack RL, Engh G, Rorabeck C, et al. Patient satisfaction and outcome after septic versus aseptic revision total knee arthroplasty. J Arthroplasty 2000;15(8):990. 33. Deehan DJ, Murray JD, Birdsall PD, et al. Quality of life after knee revision arthroplasty. Acta Orthop 2006;77(5):761. 34. Amin AK, Clayton RAE, Patton JT, et al. Total knee replacement in morbidly obese patients. Results of a prospective, matched study. J Bone Joint Surg (Br) 2006; 88(10):1321. 35. Reay E, Wu J, Holland J, et al. Premature failure of Kinemax Plus total knee replacements. J Bone Joint Surg (Br) 2009;91(5):604. 36. Malviya A, Bettinson K, Kurtz SM, et al. When do patient-reported assessments peak after revision knee arthroplasty? Clin Orthop Relat Res 2012;470(6):1728. 37. Ghomrawi HMK, Kane RL, Eberly LE, et al. Patterns of functional improvement after revision knee arthroplasty. J Bone Joint Surg 2009;91(12):2838.
Contents lists available at ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Metaphyseal Sleeves for Revision Total Knee Arthroplasty: Good Short-Term Outcomes Kate E. Bugler, MRCS, BA(Hons) , Rohit Maheshwari, FRCS (Orth), Isaaq Ahmed, FRCS (Orth), Ivan J. Brenkel, FRCS (Orth), Philip J. Walmsley, FRCS (Orth) Victoria Hospital Kirkcaldy, Kirkaldy, Fife, Scotland KY2 5AH
a r t i c l e
i n f o
Article history: Received 2 October 2014 Accepted 7 May 2015 Keywords: knee arthroplasty replacement revision aseptic sleeves
a b s t r a c t Metaphyseal sleeve prostheses have shown promising results in the management of bone defects at revision TKA. We present a study of their use in aseptic revision TKA. Thirty-five revisions were included in 34 patients with wear or aseptic loosening indicated in 71% of cases. The majority of cases (63%) were AORI grade 2 or greater on the tibia or femur. Knee Society scores were excellent or good in 83% of patients with the same percentage having no or only mild pain. One patient suffered a sleeve-related complication with femoral condylar fractures three years postoperatively; these united with good outcomes. All radiographs were satisfactory; no patient required a further revision. We report good outcomes with the use of metaphyseal sleeves in revision TKA. © 2015 Elsevier Inc. All rights reserved.
The number of patients requiring revision total knee arthroplasty (TKA) is rapidly increasing with a 17% increase in procedures undertaken in the United Kingdom from 2011 to 2012 [1]. This is predicted to continue with an estimated 601% increase predicted between 2005 and 2030 in the United States [2]. In addition the Scottish Arthroplasty Project reports increasing numbers of primary procedures in increasingly younger patients suggesting that the revision burden will continue to rise [3]. Due to this increasing requirement, with its associated cost implications [4], investigation of the options for revision TKA has become of greater importance. Particular challenges exist in the setting of significant bone loss. Bone graft [5–8], cement and screws [9], block augments [10,11], tantalum metal cones [12–17], tumour megaprostheses [18] and custom prostheses [19] have all been used with some success. An alternative option is the use of a metaphyseal sleeve. These devices engage into the metaphysis of the distal femur or proximal tibia via a stepped design with a porous coating to promote bony ingrowth. Metaphyseal sleeves have been in widespread use for hinged knee arthroplasty for some time with good long term outcomes [20]. Further development has resulted in modifications to permit the use of metaphyseal sleeves with semi-constrained revision implants. Initial
One or more of the authors of this paper have disclosed potential or pertinent conflicts of interest, which may include receipt of payment, either direct or indirect, institutional support, or association with an entity in the biomedical field which may be perceived to have potential conflict of interest with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2015.05.015. Reprint requests: Kate Bugler, MRCS, BA(Hons), Victoria Hospital Kirkcaldy, Kirkaldy, Fife, Scotland, KY2 5AH. http://dx.doi.org/10.1016/j.arth.2015.05.015 0883-5403/© 2015 Elsevier Inc. All rights reserved.
studies looking at the outcomes of this use have been encouraging but the data remains limited [21–23]. The aims of this study were to assess the short term outcomes of the use of metaphyseal sleeves in revision TKA and the factors affecting the outcomes in order to assess their role in this challenging area of orthopaedics.
Patient and Methods This was a retrospective review of prospectively collected data on consecutive revision knee arthroplasty procedures performed at the study centre. A prospective database was compiled of all 109 patients undergoing revision TKA using a metaphyseal sleeve (DePuy, Warsaw, Indiana) from 2008 to 2013. In order to evaluate the short term outcomes this study only included those patients at least two years post revision surgery for aseptic loosening. Patients in whom revision was carried out for infection were also excluded. Of the 45 patients remaining, full follow up of at least two years was obtained in 35 revision knee arthroplasties (78%); mean length of follow up was 39 months with a range of 24 to 62 months. Of the remaining 10; one patient who had both knees revised with metaphyseal sleeves died prior to the two year follow up for either knee of unrelated causes, four other patients were followed up for less than two years before loss to follow up and four patients did not attend any follow up following their revision TKA. There were no significant differences in demographics (age, BMI, gender, ASA) or operative procedure (duration of procedure, length of stay) between those lost to follow up and those with at least two years follow up.
K.E. Bugler et al. / The Journal of Arthroplasty 30 (2015) 1990–1994 Table 1 Background Characteristics of Patients Included in the Study.
Table 4 Intraoperative AORI Grading of the Proximal Tibia.
Patients Mean age at time of revision (range) (years) Gender (male) BMI (kg/m2) Mean (range) Underweight (b18.5) Normal (18.5–25) Overweight (25–30) Obese (30–40) Morbidly obese (N40) Not recorded ASA Mean I II III Side (left:right)
1991
AORI grading 72 (55–86) 57% 30.2 (20–42) 0 (0%) 4 (11%) 10 (29%) 18 (51%) 2 (6%) 1 (3%) 2.26 3 (9%) 20 (57%) 12 (34%) 46:54
For the patients included in the study demographic data was recorded including age at time of procedure, gender and body mass index (BMI) (Table 1). General health status was recorded using the American Society of Anestheologists’ (ASA) grading system. All procedures were undertaken as single stage revisions by one of two revision knee surgeons in the unit (IJB and PW). The indication for revision was defined by the lead surgeon at the time of the procedure with the majority undertaken for aseptic loosening (45%) or polyethylene wear (26%) (Table 2). Primary procedures were performed in all cases between 1987 and 2009 with the mean time from primary procedure to revision 11 years (range 2–23; standard deviation (SD) 6.5). Most patients (82%) had only undergone one procedure prior to their revision surgery but a minority (18%) had undergone two procedures. The majority of the revision knee arthroplasty was performed under spinal or epidural anaesthesia (97%) with the remaining patient requiring a general anaesthetic due to anaesthetic difficulties. All procedures were carried out with the use of a thigh tourniquet with the incision was made through the previous scar and a medial parapatellar approach. The primary prosthesis was removed with attention to keeping any bone loss to a minimum. Anderson Orthopaedic Research Institute (AORI) grading [24] was carried out intraoperatively by the lead surgeon following removal of the primary prosthesis (Tables 3 and 4). Following grading a decision was made regarding the most appropriate implant for the bone loss. Metaphyseal sleeves were used for both the femoral and tibial components in the majority of patients (69%) with a small proportion of cases requiring only a tibial (10; 28%) or femoral (1; 3%) sleeved
1 2 3
Frequency 20 (57%) 13 (37%) 2 (6%)
prosthesis (Fig. 1). Initially all implants were inserted with a stem but it became apparent that this was not necessary unless there was an uncontained defect in zone one, two or three. An additional stem was applied in 21 (60%) of the tibial prostheses and 12 (34%) of the femoral prostheses. When stems were used they were predominantly 12×75mm with the aim to provide additional stability but not metaphyseal fixation in zone three as this could cause stress shielding in zone one (Fig. 2). A range of sizes were used in all components with the majority of patients requiring size 3 femoral and tibial prostheses. Size 10 polyethylene inserts were the most commonly used. These were mobile bearing in all cases except the patient in whom a tibial sleeve was not required where a fixed bearing polyethylene was used in conjunction with a PFC Sigma prosthesis (DePuy Synthes). Where required, morselized bone graft and block augments were used with 5 cases (14%) requiring bone graft either around the tibia or femoral prosthesis and augments attached to the femoral component either distally or posteriorly. No patient required a tibial tubercle osteotomy or rectus snip. Post operatively patients were permitted to mobilise fully weight bearing immediately with the assistance of the physiotherapy team prior to discharge home with an outpatient self directed physiotherapy regime. Patients were followed up both radiographically and clinically for a minimum of two years following the procedure. All radiographs were reviewed by the senior author (IJB) to assess for signs of loosening. In addition information regarding complications, range of movement and pain was prospectively collected. Patient reported outcome questionnaires were completed by all patients including the general health related physical component (PCS) and mental component (MCS) scores of the Short Form 12 [25] (SF12), and the knee specific Oxford Knee Score [26] (OKS), with 0 as the worst score and 48 the best score, American Knee Society Score (KSS) and American Knee Society Functional Score (KSFS) [27]. A satisfaction score was also obtained on a linear scale from one to ten. Results were analysed using SPSS software version 19 (SPSS Inc., Chicago, IL, USA). Chi-squared tests were used for categorical data, unpaired t-tests for two groups of continuous data and ANOVA for
Table 2 Indication for Revision Surgery. Indication Aseptic loosening Polyethylene wear Malalignment Instability Unexplained pain
Frequency 16 (45%) 9 (26%) 6 (17%) 2 (6%) 2 (6%)
Table 3 Intraoperative AORI Grading of the Distal Femur. AORI grading
Frequency
1 2 3 Not recorded
17 (49%) 16 (46%) 0 (0%) 2 (5%)
Fig. 1. Intraoperative Photograph Showing Bone Surfaces Prepared for Insertion of Tibial and Femoral Metaphyseal Sleeves.
1992
K.E. Bugler et al. / The Journal of Arthroplasty 30 (2015) 1990–1994 Table 5 Outcomes in the 35 Patients With Follow Up of at Least Two Years (mean 39 months). Score American Knee Society Functional Score American Knee Society Score Oxford Knee Score Satisfaction SF12 (PCS) SF12 (MCS)
Mean
SD
Range
58.1 81.3 34.0 7.5 38.3 47.1
33.1 18.1 9.6 2.3 10.8 10.4
−20 to 100 32–100 5–47 2–10 20.2–55.5 27.4–64.0
three or more groups. Correlation was assessed using the Pearson correlation co-efficient. A p value of b 0.05 was considered significant. Standard deviations were calculated to show spread of data. Results Thirty-five patients were included in this study of the use of metaphyseal sleeves in revision TKA. The mean duration of procedure was 108 minutes (range 60–154 minutes, SD 22.0 minutes). There was a significant correlation between increasing duration of procedure and BMI (Pearsons; P= .04). Minimal blood loss was recorded for all procedures. The mean haemoglobin drop post operatively was 2.8 g/dl with only seven patients (20%) requiring blood transfusion. These patients had a mean haemoglobin of 13.3 g/dl pre-transfusion and a mean haemoglobin drop of 3.2 g/dl. Mean length of stay was 8 days (range 4–18). Good patient reported outcomes (PROMs) were found in all measures used (Table 5). Knee Society Scores were good or excellent in 83% of patients (20% good, 63% excellent) [4]. Satisfaction scores greater than or equal to 8 out of 10 were expressed by 63% of patients (Fig. 3). Further analysis revealed 43% of patients reported no pain at final follow up with a further 40% reporting only mild or occasional pain. There were no significant differences in the PROMs scores when compared for different AORI grades of femoral and tibial bone loss (ANOVA; P values from 0.967 to 0.072). A small number of complications were recorded (Table 6). Intraoperatively one patient sustained a tibial fracture. This was treated conservatively and the patient had good final outcomes. Post-operatively
Fig. 2. a, b and c: Failed unicompartmental knee replacement revised with a tibial metaphyseal sleeve. (A) Pre operative radiograph. (B) Immediate post operative radiograph. (C) Four years following revision showing metaphyseal loading by the sleeve.
Fig. 3. Distribution of satisfaction scores on a linear scale from 1–10.
K.E. Bugler et al. / The Journal of Arthroplasty 30 (2015) 1990–1994 Table 6 Complications of use of Metaphyseal Sleeves. Complications
Frequency
Intraoperative Proximal tibial fracture
1
Early post-operative Myocardial infarction Superficial wound infection Wound dehiscence
1 1 1
Late post-operative Varus instability Late femoral condyle fracture Patellofemoral symptoms
1 1 3
one patient suffered a myocardial infarction but went on to a successful recovery. Two other patients had wound problems one remaining in hospital for 13 days due to prolonged wound leakage and the other with a dehiscence of their wound requiring plastic surgical intervention in the form of a split skin graft. At final review one patient with a previous femoral shaft malunion was found to have instability with laxity on varus stressing, following extensive discussion with the patient regarding the possibility of revision to a hinged TKA they are currently considering their options. Finally one patient sustained femoral condylar fractures three years post-operatively. These were treated conservatively and at most recent follow up the patient was asymptomatic and happy with their outcome. There were no cases of end of stem pain. In addition three patients reported patellofemoral symptoms postoperatively. These necessitated patellofemoral arthroplasty five and ten months post operatively in two patients with the other patient currently awaiting surgery. One of these patients developed a deep infection following their patellofemoral arthroplasty, having previously not had any evidence of infection, eventually requiring an above knee amputation 30 months following surgery. The other patient was much improved following surgery. Subsequent to the finding of a high rate of patellofemoral symptoms patella resurfacing is now a routine part of the operative protocol in all patients. Objective clinical outcomes found that all but six patients achieved full extension (83%), mean flexion was 100 degrees ranging from 70 to 130 degrees. Radiographic outcomes were also encouraging with no evidence of osteolysis around or loosening of either the femoral or tibial prostheses. Finally, to date no patient has required a further revision TKA. Discussion Revision knee arthroplasty can have a significant impact on patients’ quality of life resulting in improvements in PROMs [28]. The increasing requirement for revision arthroplasty has resulted in significant innovation with a range of methods available to counter the bone loss that is often a problem at time of surgery. Metaphyseal sleeves have been used for revision TKA with the hinged S-ROM Noiles knee system (DePuy Synthes) with good results reported [20,29]. Little has been published on their use with semiconstrained implants for revision TKA [21–23], indeed only one study has considered the use of metaphyseal sleeves for both the femur and tibia as we have done here. We have used metaphyseal sleeves in a large number of patients since 2008. This study of the use of metaphyseal sleeves in 35 patients with a minimum of two year shows good results in well selected patients. The cohort of patients included in this study were comparable to those included in other studies of revision arthroplasty. In line with most patients undergoing revision TKA the majority of patients were overweight or obese (mean BMI 30.2) with other significant health problems (mean ASA 2.26) [30]. The majority of patients in this cohort
1993
underwent revision due to aseptic loosening or polyethylene wear (71%) which is comparable to other studies [30,31] allowing comparison to other techniques of revision arthroplasty. We have excluded revision TKA undertaken for infection as these patients have previously been shown to have different patient reported outcomes pre and post operatively to those undergoing revision procedures for aseptic causes [32,33]. Although this is a relatively new development of the technique, we did not find a significant learning curve when used by experienced knee arthroplasty surgeons with a mean duration of procedure of only 111 minutes. The only learning curve was in the resurfacing of the patellofemoral joint. Initially this was not undertaken routinely, but there were a number of patients who complained of anterior knee pain, possibly due to the high box on the TC3 femoral component, and as a result patients now all routinely undergo patellofemoral resurfacing. There were no patients in whom the metaphyseal sleeve was found to be unsuitable at operation. This contrasts with the use of block augments which have been found to be unsuitable without the addition of bone graft in up to 48% of patients at time of surgery [11]. We have found good patient reported outcomes in this cohort in all outcome scores used; OKS, KSS, KSFS, SF12 and overall satisfaction. This agrees with previous work by Agarwal et al who reported similar postoperative OKS in their retrospective study of 102 knees that underwent revision TKA with the use of metaphyseal sleeves [21]. Two studies have also reported equally positive post-operative KSS and KSFS in their retrospective reviews of their use of metaphyseal sleeves in the tibial component of revision TKAs [22,23]. There were a small number of complications in this cohort. Complications following primary TKA have been found to be significantly higher in morbidly obese patients [34]. This may also be the case in revision surgery as it is interesting to note that the two patients with BMIs over 40 (morbidly obese) both suffered complications post operatively and there was a significant correlation between duration of operation and BMI. The patient that suffered fractures of the femoral condyles was a patient with a previous Kinemax Plus knee prosthesis who had developed a significant polyethylene reaction, this has been reported in a cohort of patients previously and is thought to be due to a manufacturing defect [35]. These have previously shown a predeliction for the femoral condyles and may have caused significant weakness of the condyles. Following fracture he was treated in a hinged knee brace and went on to good final outcomes. Agarwal et al [21] report two cases of early loosening with no definitive evidence of infection in patients in whom the metaphyseal sleeves were used without a stem. As a result they advocate the use of stems in all patients routinely. In our study almost half of the tibial and femoral metaphyseal sleeves (40% and 66%, respectively) were implanted without the use of a stem. None of these knees have shown evidence of early loosening but further follow up will be required to identify later changes. In addition the use of a stem has been reported to result in end of stem pain in some patients with a tibial metaphyseal sleeve [22,23], we have not found any cases of this in this study. In view of our good outcomes, we no longer routinely use a stem attachment utilising the additional stability only in cases where an uncontained defect in zone two or three required additional zone three fixation. We will continue to follow up these patients to identify any evidence of late loosening. We found no evidence of loosening of the prostheses in any patient. This compares with other methods of revision TKA which have shown evidence of loosening in some patients requiring further surgery. Tantalum metal cones have shown rates of loosening of around 6% [13]. This may be due to the cement required to connect the implant to the metal cone resulting in a potential region of instability. Whilst the use of bone graft has shown promising radiographic results the use of bone graft is limited by host factors including previously irradiated bone, immunosuppression and metabolic bone disease [6] as well as
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the risk of transmission of infection [5]. In addition the positive radiographic findings of custom prostheses [19] and tumour megaprostheses [18] are limited by the significant cost of these implants resulting in a limited application of these to the increasing population requiring revision TKA. A limitation of this study is the lack of pre-operative PROMs scores. However, the patients included in this study are similar to those included in other studies and we report similarly positive post-operative results. Although the follow up in this study is only short term a number of authors have shown patient reported outcomes continue to improve for one year after revision TKA followed by a plateau period [36,37]. This would suggest that all of our patients with a follow up of at least two years should have reached this steady state in patient reported outcomes. Whilst longer term outcome studies of the use of metaphyseal sleeves for revision TKA are evidently needed in order to sufficiently assess their longevity this study does show that good patient reported outcomes can be achieved in the short term. In conclusion this is the first prospective cohort study of patients undergoing revision TKA using metaphyseal sleeves. We have found good outcomes, objectively, functionally and radiographically, in appropriately selected patients. Further long term follow up is required to identify the optimum role of metaphyseal sleeves in revision knee arthroplasty. References 1. National Joint Registry for England, Wales and Northern Ireland. 10th Annual Report 2013; 2013. 2. Kurtz S, Ong K, Lau E, et al. Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030. J Bone Joint Surg Am 2007; 89(4):780. 3. Scottish Arthroplasty Project. Annual Report 2012; 2012. 4. Kurtz SM, Ong KL, Schmier J, et al. Future clinical and economic impact of revision total hip and knee arthroplasty. J Bone Joint Surg Am 2007;89(Suppl 3):144. 5. Clatworthy MG, Ballance J, Brick GW, et al. The use of structural allograft for uncontained defects in revision total knee arthroplasty. A minimum five-year review. J Bone Joint Surg Am 2001;83-A(3):404. 6. Engh GA, Ammeen DJ. Use of structural allograft in revision total knee arthroplasty in knees with severe tibial bone loss. J Bone Joint Surg 2007;89(12):2640. 7. Lotke PA, Carolan GF, Puri N. Impaction grafting for bone defects in revision total knee arthroplasty. Clin Orthop Relat Res 2006;446:99. 8. Lyall HS, Sanghrajka A, Scott G. Severe tibial bone loss in revision total knee replacement managed with structural femoral head allograft: a prospective case series from the Royal London Hospital. Knee 2009;16(5):326. 9. Ritter MA, Keating EM, Faris PM. Screw and cement fixation of large defects in total knee arthroplasty. A sequel. J Arthroplasty 1993;8(1):63. 10. Patel JV, Masonis JL, Guerin J, et al. The fate of augments to treat type-2 bone defects in revision knee arthroplasty. J Bone Joint Surg (Br) 2004;86(2):195. 11. Hockman DE, Ammeen D, Engh GA. Augments and allografts in revision total knee arthroplasty: usage and outcome using one modular revision prosthesis. J Arthroplasty 2005;20(1):35.
12. Howard JL, Kudera J, Lewallen DG, et al. Early results of the use of tantalum femoral cones for revision total knee arthroplasty. J Bone Joint Surg 2011;93(5):478. 13. Lachiewicz PF, Bolognesi MP, Henderson RA, et al. Can tantalum cones provide fixation in complex revision knee arthroplasty? Clin Orthop Relat Res 2012; 470(1):199. 14. Long WJ, Scuderi GR. Porous tantalum cones for large metaphyseal tibial defects in revision total knee arthroplasty: a minimum 2-year follow-up. J Arthroplasty 2009; 24(7):1086. 15. Meneghini RM, Lewallen DG, Hanssen AD. Use of porous tantalum metaphyseal cones for severe tibial bone loss during revision total knee replacement. J Bone Joint Surg 2008;90(1):78. 16. Rao BM, Kamal TT, Vafaye J, et al. Tantalum cones for major osteolysis in revision knee replacement. Bone Joint J 2013;95-B(8):1069. 17. Schmitz H-CR, Klauser W, Citak M, et al. Three-year follow up utilizing tantal cones in revision total knee arthroplasty. J Arthroplasty 2013;28(9):1556. 18. Höll S, Schlomberg A, Gosheger G, et al. Distal femur and proximal tibia replacement with megaprosthesis in revision knee arthroplasty: a limb-saving procedure. Knee Surg Sports Traumatol Arthrosc 2012;20(12):2513. 19. Macmull S, Bartlett W, Miles J, et al. Custom-made hinged spacers in revision knee surgery for patients with infection, bone loss and instability. Knee 2010;17(6):403. 20. Jones RE, Barrack RL, Skedros J. Modular, mobile-bearing hinge total knee arthroplasty. Clin Orthop Relat Res 2001;392:306. 21. Agarwal S, Azam A, Morgan-Jones R. Metal metaphyseal sleeves in revision total knee replacement. Bone Joint J 2013;95-B(12):1640. 22. Alexander GE, Bernasek TL, Crank RL, et al. Cementless metaphyseal sleeves used for large tibial defects in revision total knee arthroplasty. J Arthroplasty 2013; 28(4):604. 23. Barnett SL, Mayer RR, Gondusky JS, et al. Use of Stepped Porous Titanium Metaphyseal Sleeves for Tibial Defects in Revision Total Knee Arthroplasty: Short Term Results. J Arthroplasty 2014;29(6):1219. 24. Engh GA, Ammeen DJ. Bone loss with revision total knee arthroplasty: defect classification and alternatives for reconstruction. Instr Course Lect 1999;48:167. 25. Ware J, Kosinski M, Keller SD. A 12-Item Short-Form Health Survey: construction of scales and preliminary tests of reliability and validity. Med Care 1996;34(3):220. 26. Dawson J, Fitzpatrick R, Murray D, et al. Questionnaire on the perceptions of patients about total knee replacement. J Bone Joint Surg (Br) 1998;80(1):63. 27. Insall JN, Dorr LD, Scott RD, et al. Rationale of the Knee Society clinical rating system. Clin Orthop Relat Res 1989;248:13. 28. Kasmire KE, Rasouli MR, Mortazavi SMJ, et al. Predictors of functional outcome after revision total knee arthroplasty following aseptic failure. Knee 2014;21(1):264. 29. Jones RE, Skedros JG, Chan AJ, et al. Total knee arthroplasty using the S-ROM mobilebearing hinge prosthesis. J Arthroplasty 2001;16(3):279. 30. Dalury DF, Pomeroy DL, Gorab RS, et al. Why are total knee arthroplasties being revised? J Arthroplasty 2013;28(8 Suppl.):120. 31. Bozic KJ, Kurtz SM, Lau E, et al. The Epidemiology of Revision Total Knee Arthroplasty in the United States. Clin Orthop Relat Res 2009;468(1):45. 32. Barrack RL, Engh G, Rorabeck C, et al. Patient satisfaction and outcome after septic versus aseptic revision total knee arthroplasty. J Arthroplasty 2000;15(8):990. 33. Deehan DJ, Murray JD, Birdsall PD, et al. Quality of life after knee revision arthroplasty. Acta Orthop 2006;77(5):761. 34. Amin AK, Clayton RAE, Patton JT, et al. Total knee replacement in morbidly obese patients. Results of a prospective, matched study. J Bone Joint Surg (Br) 2006; 88(10):1321. 35. Reay E, Wu J, Holland J, et al. Premature failure of Kinemax Plus total knee replacements. J Bone Joint Surg (Br) 2009;91(5):604. 36. Malviya A, Bettinson K, Kurtz SM, et al. When do patient-reported assessments peak after revision knee arthroplasty? Clin Orthop Relat Res 2012;470(6):1728. 37. Ghomrawi HMK, Kane RL, Eberly LE, et al. Patterns of functional improvement after revision knee arthroplasty. J Bone Joint Surg 2009;91(12):2838.
