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Repeated Early Failure of a Newly Designed Hinged Knee System
The Journal of Arthroplasty Vol. 28 No. 2 2013
Case Report
Repeated Early Failure of a Newly Designed Hinged Knee System Joshua K.L. Lee, MSc, FRCS (Tr&Orth), Vikram Chatrath, MD, and Paul R. Kim, MD, FRCSC
Abstract: We report a case of acute and recurrent accelerated wear of the polyethylene bushings of the hinge mechanism in the Zimmer Segmental Knee System. This resulted in an unacceptable recurvatum deformity leading to multiple revision knee operations, which was unexpected in a modern design hinged knee system. A custom modification of the original design was used to prevent further recurvatum deformity. The current design of the hinge post mechanism in this system appears to be inadequate, which led to the development of a significant recurvatum deformity in our patient. Surgeons should be aware of this potential complication when considering the use of this revision knee system. Keywords: total knee arthroplasty, implant failure, polyethylene wear, revision, hinged knee system. © 2013 Elsevier Inc. All rights reserved.
Constrained prostheses have been used for performing knee arthroplasties in cases of instability [1], soft tissue imbalance [2], bone loss, or a combination of all of these [3]. This is a common situation in revision knee arthroplasty surgery. With increasing severity of the previously mentioned factors, modular segmental arthroplasty prostheses with rotating hinge articulations can be used to compensate for these significant deficiencies with reasonable outcomes [4]. Currently, third-generation modular rotating platform hinge knee systems are being used. These have been designed with improvements in the articulation of the rotating hinge mechanism, which, in earlier fixed hinge designs, was thought to contribute to premature failure [5]. The Zimmer Segmental Knee System (ZSKS) (Zimmer, Warsaw, Indiana) is a modern design salvage knee prosthesis intended to replace the distal femur, midshaft femur, proximal femur, and/or total knee in cases that require extensive resection and restoration. It is
From the Division of Orthopaedic Surgery, The Ottawa Hospital/University of Ottawa, Ottawa, Ontario, Canada. Submitted February 1, 2012; accepted April 23, 2012. The Conflict of Interest statement associated with this article can be found at http://dx.doi.org/10.1016/j.arth.2012.04.029. Reprint requests: Paul R. Kim, MD, FRCSC, Division of Orthopaedic Surgery, The Ottawa Hospital, General Campus, 501 Smyth Rd., CCW 1650, Box 502, Ottawa, Ontario, Canada K1H 8L6. © 2013 Elsevier Inc. All rights reserved. 0883-5403/2802-0038$36.00/0 http://dx.doi.org/10.1016/j.arth.2012.04.029
designed to be compatible with the NexGen Rotating Hinge Knee (RHK) System (Zimmer). We report a case of acute and recurrent accelerated wear of the polyethylene bushings of the hinge mechanism in the ZSKS resulting in an unacceptable recurvatum deformity leading to multiple revision knee operations. A literature review did not reveal any prior reports of failure of this newly designed system. The following is a description of the case and its subsequent management.
Case Report A 72-year-old man with a body mass index of 36 kg/m 2 underwent a total knee arthroplasty (Zimmer Miller-Galante Knee Systems Zimmer) in 1997. The patient's medical history was significant for hypertension and diabetes controlled by oral hypoglycemics. This knee was revised in 2002 to a Zimmer LCCK (Zimmer) prosthesis due to aseptic loosening secondary to polyethylene wear. The intraoperative findings demonstrated significant osteolysis of the tibia and femur secondary to polyethylene wear due to oxidative degradation of the polyethylene. The patient recovered uneventfully with a postoperative range of motion from 0 to 90°. The patient sustained a fall in 2006 and had a type III Lewis-Rorabeck distal femoral periprosthetic fracture; there was a normal distal neurological function and infection markers were normal. He underwent revision knee arthroplasty with open reduction and internal
375.e17
375.e18 The Journal of Arthroplasty Vol. 28 No. 2 February 2013 fixation of the lateral condyle. A quadriceps turndown was used to improve exposure. A significant femoral cavitary defect along with varus-valgus instability was noted intraoperatively. With these considerations, a NexGen RHK Zimmer knee was implanted. Two months later, the patient developed a quadriceps tendon rupture, which was repaired. The result of the workup at that time was negative for infection. The patient recovered with a range of motion from 5° to 90°. The patient was then seen for regular follow-up visits. In 2007, the patient underwent a total knee arthroplasty on the right side, which was functioning well at the last follow-up. Four years after his last revision knee surgery, the patient presented with aseptic loosening of the femoral component along with significant distal femoral bone loss; again, the result of the workup for infection was negative. In February 2011, the patient underwent a revision knee arthroplasty with the ZSKS. This system is compatible with the RHK tibial component. Massive femoral cavitary defects were noted, along with severe ligamentous insufficiency necessitating the use of a distal femoral replacement arthroplasty. Intraoperatively, the RHK tibial component was confirmed to be well fixed and in good position and was, therefore, left in situ. The ZSKS (size C distal femoral component with 30-mm extension, 12 × 100-mm stem, 35-mm trabecular metal (TM) sleeve, and 12-mm polyethylene insert) was implanted without complication. Postoperatively, the patient was mobilized as per standard protocol. Six weeks later, the patient presented to the clinic with complaints of “knee buckling.” On examination, the patient's knee went into painless recurvatum of 20° on ambulation and 10° with elevation of the foot in a supine position (Fig. 1). Knee flexion was 100°. This system uses a unique bushing design that includes a mechanism for blocking hyperextension, rather than a separate “bumper” as seen in traditional rotating hinge designs. We postulated that the bushing had failed prematurely, and the patient was scheduled for revision knee surgery. Zimmer representatives and the system design engineer were present during the revision (June 2011). Intraoperatively, it was noted that the plastic bushing that prevents hyperextension had undergone severe deformation around the hinge. The polyethylene blocking piece had deformed both along the circular contact area with the axle and anteriorly where it was supposed to prevent recurvatum (Fig. 2). Because the tibial and femoral components remained well fixed and in good position, it was elected to insert a new set of polyethylene bushings, axle, and tibial insert, assuming the prior one had failed because of a potential polyethylene imperfection. Intraoperatively, this corrected the recurvatum deformity, and the knee was closed as per standard protocol. After surgery, we were informed by Zimmer that this similar issue had happened in 2 other cases that they were aware of.
Fig. 1. Lateral and anteroposterior x-rays of the ZSKS showing significant recurvatum deformity.
Two weeks later, the patient presented again with an onset of a recurvatum deformity of 15° similar to the previous occasion. There was no history of trauma, and radiographs did not reveal any mechanical issues with the prosthesis. Considering the recurrent and accelerated failure of the polyethylene blocking piece, it was decided to custom design a modification to the femoral implant to avoid full revision of his well-fixed components. The ZSKS allows for isolated exchange of the distal femoral component without having to revise the existing cemented stem construct. The custom-made piece was designed in consultation with the engineers of the ZSKS (Fig. 3). It was decided to fashion a positive “stop” in the system. This was done by adding a polyethylene button into a recess inside the box of the femoral component and adding a cobalt-chrome–raised bumper on the hinge post, which would contact the polyethylene button in full extension and, therefore, provide a mechanical block to hyperextension. In addition, the polyethylene bushings around the axle were also thickened to provide improved tolerances here. The other surgical option would have been to revise the whole implant to another salvage knee
Repeated Early Failure of a Newly Designed Hinged Knee System Lee et al
375.e19
Fig. 2. (A) Intraoperative photograph of the knee in extension. Red circle demonstrates metal post engaging the roof of the notch where the poly insert is being deformed. (B) Retrieved poly insert and hinge showing deformation of poly (red circles). Unimplanted poly inserts are shown for comparison.
system. This would have involved removal of the wellfixed tibial and femoral stems, leaving us with little residual bone stock and further limiting future reconstructive options.
On subsequent revision surgery, the intraoperative findings were similar to the previous surgery. Again, severe deformation of the plastic bushing around the hinged area was noted. The knee could be placed into
Fig. 3. (A) Intraoperative photograph of the knee in flexion. Red circle highlights a custom-designed bumper and corresponding poly button in the roof of the notch to prevent recurvatum. (B) Custom-designed hinge with a raised bumper (red circles).
375.e20 The Journal of Arthroplasty Vol. 28 No. 2 February 2013 recurvatum of around 10° to 15°. We disengaged the existing hinge and the distal femoral component from the stem. The remainder of the fixation appeared solid. The custom distal femoral component was impacted onto the existing femoral stem trunnion in appropriate rotation. The new polyethylene tibial insert, along with the custom tibial post, was implanted along with the new bushings, axle, and locking bolt. The range of motion was checked, and the recurvatum deformity was resolved. The patient was last seen at 5 months postoperatively. The range of motion was from 0 to 100°, with no recurrence of the recurvatum deformity.
Discussion The current generation of hinge knee systems has shown good midterm results, providing good mediolateral, torsional, and axial stability [6,7]. The hinged systems used with salvage prostheses have become an important tool for surgeons in both tumor and nontumor settings. Nontumor settings include cases of severe loss of bone stock and ligamentous constraint of the knee leading to instability and deformity [4]. The ZSKS is a relatively new knee revision system with a purported advantage over other segmental revision systems in that it uses a porous tantalum collar to obtain osseointegration, which has been shown to be effective in complex revision surgery [8,9]. Previous authors [10] have reported problems with early dislocation with other rotating hinge designs, but recurrent recurvatum has not been noted. No prior publications related to the use of the ZSKS were found in our literature search. Traditionally, rotating hinge designs have a metal post that is attached to the femoral component through the use of a metal axle and polyethylene bushings. A separate polyethylene bumper is inserted in the anterior aspect of the tibial component, thus preventing hyperextension with a positive stop. Zimmer uses a unique system that uses a “one-piece” post that eliminates the need for a bumper. Instead, the polyethylene insert abuts a groove in the hinge post, which stops any further extension. The same segmental hinge post is used with both the Segmental Distal Femoral component and the NexGen RHK Distal Femoral Component; however, the polyethylene inserts are different. We found 2 particular problems with the hinge mechanism that led to the rapid recurvatum deformity. The first issue relates to the toggle between the hinge post and polyethylene box, which may lead to elongation of the holes on the poly box and, thus, hyperextension. The second issue is that the hinge mechanism relies on a relatively thin polyethylene surface to stop hyperextension. This surface became sandwiched between the metal post and the metallic roof of the femoral
notch and underwent rapid early deformation in our case. We feel that the design of this polyethylene insert is not robust enough to resist the forces across it, resulting in the deformation and subsequent hyperextension deformity. Recently, there have been 2 case reports of failure of the hinge post of a Depuy S-ROM Noiles rotating hinge system due to fatigue failure [11,12]. This was thought to occur secondary to a cantilever effect because of laxity of the joint and a large tibial insert size. There could be a similar effect in our case, but the construct failed at the weaker polyethylene insert rather than the metal post. The ZSKS received clearance from the US Food and Drug Administration in July 2007. Although this prosthesis has been in use for a few years, we are concerned about the current design of this implant. Zimmer has reported to us that there have been 2 prior issues with this implant device. We are not aware of the total number of implanted ZSKS knees worldwide but feel that the failure mechanism in this case is significant enough to warrant a word of caution regarding its continued use. In our case it led to early and repeated recuvatum deformity within weeks of implantation. The custom modification will hopefully prevent this issue from recurring, but longer follow-up is necessary to determine this. We felt that this modification was preferable to complete revision knee surgery in this patient. We feel that the current design of this hinge prosthesis may predispose it to failure via the mechanism described, and surgeons should be aware of this potential complication when considering the use of this system.
References 1. Pietsch M, Hofmann S. From tibiofemoral instability to dislocation in total knee arthroplasty. Orthopade 2007; 36:917. 2. Ayers DC, Dennis DA, Johanson NA, et al. Common complications of total knee arthroplasty. J Bone Joint Surg Am 1997;79A:278. 3. Gudnason A, Milbrink J, Hailer NP. Implant survival and outcome after rotating-hinge total knee revision arthroplasty: a minimum 6-year follow-up. Arch Orthop Trauma Surg 2011;131:1601. 4. Berend KR, Lombardi Jr AV. Distal femoral replacement in nontumor cases with severe bone loss and instability. Clin Orthop Relat Res 2009;467:485. 5. Jones RS. Mobile bearings in revision total knee arthroplasty. Instr Course Lect 2005;54:225. 6. Jones RE, Skedros JG, Chan AJ, et al. Total knee arthroplasty using the S-ROM mobile-bearing hinge prosthesis. J Arthroplasty 2001;16:279. 7. Barrack RL, Lyons TR, Ingraham RQ, et al. The use of a modular rotating hinge component in salvage revision total knee arthroplasty. J Arthroplasty 2000;15:858. 8. Flecher X, Paprosky W, Grillo JC, et al. Do tantalum components provide adequate primary fixation in all
Repeated Early Failure of a Newly Designed Hinged Knee System Lee et al acetabular revisions? Orthop Traumatol Surg Res 2010;96: 235. 9. Lachiewicz PF, Bolognesi MP, Henderson RA, et al. Can tantalum cones provide fixation in complex revision knee arthroplasty? Clin Orthop Relat Res 2012;470:199. 10. Wang CJ, Wang HE. Early catastrophic failure of rotating hinge total knee prosthesis. J Arthroplasty 2000;15:387.
375.e21
11. Schwarzkopf R, Chaudhry S, Kummer FJ, et al. Failure of the tibial insert in a rotating hinge total knee arthroplasty. J Arthroplasty 2010;26:977. 12. Springorum HR, Luring C, Beckmann J, et al. Fatigue fracture of the hinge pin in a semi-constrained total knee arthroplasty: a case report. Knee Surg Sports Traumatol Arthrosc 2010;18:1366.
Case Report
Repeated Early Failure of a Newly Designed Hinged Knee System Joshua K.L. Lee, MSc, FRCS (Tr&Orth), Vikram Chatrath, MD, and Paul R. Kim, MD, FRCSC
Abstract: We report a case of acute and recurrent accelerated wear of the polyethylene bushings of the hinge mechanism in the Zimmer Segmental Knee System. This resulted in an unacceptable recurvatum deformity leading to multiple revision knee operations, which was unexpected in a modern design hinged knee system. A custom modification of the original design was used to prevent further recurvatum deformity. The current design of the hinge post mechanism in this system appears to be inadequate, which led to the development of a significant recurvatum deformity in our patient. Surgeons should be aware of this potential complication when considering the use of this revision knee system. Keywords: total knee arthroplasty, implant failure, polyethylene wear, revision, hinged knee system. © 2013 Elsevier Inc. All rights reserved.
Constrained prostheses have been used for performing knee arthroplasties in cases of instability [1], soft tissue imbalance [2], bone loss, or a combination of all of these [3]. This is a common situation in revision knee arthroplasty surgery. With increasing severity of the previously mentioned factors, modular segmental arthroplasty prostheses with rotating hinge articulations can be used to compensate for these significant deficiencies with reasonable outcomes [4]. Currently, third-generation modular rotating platform hinge knee systems are being used. These have been designed with improvements in the articulation of the rotating hinge mechanism, which, in earlier fixed hinge designs, was thought to contribute to premature failure [5]. The Zimmer Segmental Knee System (ZSKS) (Zimmer, Warsaw, Indiana) is a modern design salvage knee prosthesis intended to replace the distal femur, midshaft femur, proximal femur, and/or total knee in cases that require extensive resection and restoration. It is
From the Division of Orthopaedic Surgery, The Ottawa Hospital/University of Ottawa, Ottawa, Ontario, Canada. Submitted February 1, 2012; accepted April 23, 2012. The Conflict of Interest statement associated with this article can be found at http://dx.doi.org/10.1016/j.arth.2012.04.029. Reprint requests: Paul R. Kim, MD, FRCSC, Division of Orthopaedic Surgery, The Ottawa Hospital, General Campus, 501 Smyth Rd., CCW 1650, Box 502, Ottawa, Ontario, Canada K1H 8L6. © 2013 Elsevier Inc. All rights reserved. 0883-5403/2802-0038$36.00/0 http://dx.doi.org/10.1016/j.arth.2012.04.029
designed to be compatible with the NexGen Rotating Hinge Knee (RHK) System (Zimmer). We report a case of acute and recurrent accelerated wear of the polyethylene bushings of the hinge mechanism in the ZSKS resulting in an unacceptable recurvatum deformity leading to multiple revision knee operations. A literature review did not reveal any prior reports of failure of this newly designed system. The following is a description of the case and its subsequent management.
Case Report A 72-year-old man with a body mass index of 36 kg/m 2 underwent a total knee arthroplasty (Zimmer Miller-Galante Knee Systems Zimmer) in 1997. The patient's medical history was significant for hypertension and diabetes controlled by oral hypoglycemics. This knee was revised in 2002 to a Zimmer LCCK (Zimmer) prosthesis due to aseptic loosening secondary to polyethylene wear. The intraoperative findings demonstrated significant osteolysis of the tibia and femur secondary to polyethylene wear due to oxidative degradation of the polyethylene. The patient recovered uneventfully with a postoperative range of motion from 0 to 90°. The patient sustained a fall in 2006 and had a type III Lewis-Rorabeck distal femoral periprosthetic fracture; there was a normal distal neurological function and infection markers were normal. He underwent revision knee arthroplasty with open reduction and internal
375.e17
375.e18 The Journal of Arthroplasty Vol. 28 No. 2 February 2013 fixation of the lateral condyle. A quadriceps turndown was used to improve exposure. A significant femoral cavitary defect along with varus-valgus instability was noted intraoperatively. With these considerations, a NexGen RHK Zimmer knee was implanted. Two months later, the patient developed a quadriceps tendon rupture, which was repaired. The result of the workup at that time was negative for infection. The patient recovered with a range of motion from 5° to 90°. The patient was then seen for regular follow-up visits. In 2007, the patient underwent a total knee arthroplasty on the right side, which was functioning well at the last follow-up. Four years after his last revision knee surgery, the patient presented with aseptic loosening of the femoral component along with significant distal femoral bone loss; again, the result of the workup for infection was negative. In February 2011, the patient underwent a revision knee arthroplasty with the ZSKS. This system is compatible with the RHK tibial component. Massive femoral cavitary defects were noted, along with severe ligamentous insufficiency necessitating the use of a distal femoral replacement arthroplasty. Intraoperatively, the RHK tibial component was confirmed to be well fixed and in good position and was, therefore, left in situ. The ZSKS (size C distal femoral component with 30-mm extension, 12 × 100-mm stem, 35-mm trabecular metal (TM) sleeve, and 12-mm polyethylene insert) was implanted without complication. Postoperatively, the patient was mobilized as per standard protocol. Six weeks later, the patient presented to the clinic with complaints of “knee buckling.” On examination, the patient's knee went into painless recurvatum of 20° on ambulation and 10° with elevation of the foot in a supine position (Fig. 1). Knee flexion was 100°. This system uses a unique bushing design that includes a mechanism for blocking hyperextension, rather than a separate “bumper” as seen in traditional rotating hinge designs. We postulated that the bushing had failed prematurely, and the patient was scheduled for revision knee surgery. Zimmer representatives and the system design engineer were present during the revision (June 2011). Intraoperatively, it was noted that the plastic bushing that prevents hyperextension had undergone severe deformation around the hinge. The polyethylene blocking piece had deformed both along the circular contact area with the axle and anteriorly where it was supposed to prevent recurvatum (Fig. 2). Because the tibial and femoral components remained well fixed and in good position, it was elected to insert a new set of polyethylene bushings, axle, and tibial insert, assuming the prior one had failed because of a potential polyethylene imperfection. Intraoperatively, this corrected the recurvatum deformity, and the knee was closed as per standard protocol. After surgery, we were informed by Zimmer that this similar issue had happened in 2 other cases that they were aware of.
Fig. 1. Lateral and anteroposterior x-rays of the ZSKS showing significant recurvatum deformity.
Two weeks later, the patient presented again with an onset of a recurvatum deformity of 15° similar to the previous occasion. There was no history of trauma, and radiographs did not reveal any mechanical issues with the prosthesis. Considering the recurrent and accelerated failure of the polyethylene blocking piece, it was decided to custom design a modification to the femoral implant to avoid full revision of his well-fixed components. The ZSKS allows for isolated exchange of the distal femoral component without having to revise the existing cemented stem construct. The custom-made piece was designed in consultation with the engineers of the ZSKS (Fig. 3). It was decided to fashion a positive “stop” in the system. This was done by adding a polyethylene button into a recess inside the box of the femoral component and adding a cobalt-chrome–raised bumper on the hinge post, which would contact the polyethylene button in full extension and, therefore, provide a mechanical block to hyperextension. In addition, the polyethylene bushings around the axle were also thickened to provide improved tolerances here. The other surgical option would have been to revise the whole implant to another salvage knee
Repeated Early Failure of a Newly Designed Hinged Knee System Lee et al
375.e19
Fig. 2. (A) Intraoperative photograph of the knee in extension. Red circle demonstrates metal post engaging the roof of the notch where the poly insert is being deformed. (B) Retrieved poly insert and hinge showing deformation of poly (red circles). Unimplanted poly inserts are shown for comparison.
system. This would have involved removal of the wellfixed tibial and femoral stems, leaving us with little residual bone stock and further limiting future reconstructive options.
On subsequent revision surgery, the intraoperative findings were similar to the previous surgery. Again, severe deformation of the plastic bushing around the hinged area was noted. The knee could be placed into
Fig. 3. (A) Intraoperative photograph of the knee in flexion. Red circle highlights a custom-designed bumper and corresponding poly button in the roof of the notch to prevent recurvatum. (B) Custom-designed hinge with a raised bumper (red circles).
375.e20 The Journal of Arthroplasty Vol. 28 No. 2 February 2013 recurvatum of around 10° to 15°. We disengaged the existing hinge and the distal femoral component from the stem. The remainder of the fixation appeared solid. The custom distal femoral component was impacted onto the existing femoral stem trunnion in appropriate rotation. The new polyethylene tibial insert, along with the custom tibial post, was implanted along with the new bushings, axle, and locking bolt. The range of motion was checked, and the recurvatum deformity was resolved. The patient was last seen at 5 months postoperatively. The range of motion was from 0 to 100°, with no recurrence of the recurvatum deformity.
Discussion The current generation of hinge knee systems has shown good midterm results, providing good mediolateral, torsional, and axial stability [6,7]. The hinged systems used with salvage prostheses have become an important tool for surgeons in both tumor and nontumor settings. Nontumor settings include cases of severe loss of bone stock and ligamentous constraint of the knee leading to instability and deformity [4]. The ZSKS is a relatively new knee revision system with a purported advantage over other segmental revision systems in that it uses a porous tantalum collar to obtain osseointegration, which has been shown to be effective in complex revision surgery [8,9]. Previous authors [10] have reported problems with early dislocation with other rotating hinge designs, but recurrent recurvatum has not been noted. No prior publications related to the use of the ZSKS were found in our literature search. Traditionally, rotating hinge designs have a metal post that is attached to the femoral component through the use of a metal axle and polyethylene bushings. A separate polyethylene bumper is inserted in the anterior aspect of the tibial component, thus preventing hyperextension with a positive stop. Zimmer uses a unique system that uses a “one-piece” post that eliminates the need for a bumper. Instead, the polyethylene insert abuts a groove in the hinge post, which stops any further extension. The same segmental hinge post is used with both the Segmental Distal Femoral component and the NexGen RHK Distal Femoral Component; however, the polyethylene inserts are different. We found 2 particular problems with the hinge mechanism that led to the rapid recurvatum deformity. The first issue relates to the toggle between the hinge post and polyethylene box, which may lead to elongation of the holes on the poly box and, thus, hyperextension. The second issue is that the hinge mechanism relies on a relatively thin polyethylene surface to stop hyperextension. This surface became sandwiched between the metal post and the metallic roof of the femoral
notch and underwent rapid early deformation in our case. We feel that the design of this polyethylene insert is not robust enough to resist the forces across it, resulting in the deformation and subsequent hyperextension deformity. Recently, there have been 2 case reports of failure of the hinge post of a Depuy S-ROM Noiles rotating hinge system due to fatigue failure [11,12]. This was thought to occur secondary to a cantilever effect because of laxity of the joint and a large tibial insert size. There could be a similar effect in our case, but the construct failed at the weaker polyethylene insert rather than the metal post. The ZSKS received clearance from the US Food and Drug Administration in July 2007. Although this prosthesis has been in use for a few years, we are concerned about the current design of this implant. Zimmer has reported to us that there have been 2 prior issues with this implant device. We are not aware of the total number of implanted ZSKS knees worldwide but feel that the failure mechanism in this case is significant enough to warrant a word of caution regarding its continued use. In our case it led to early and repeated recuvatum deformity within weeks of implantation. The custom modification will hopefully prevent this issue from recurring, but longer follow-up is necessary to determine this. We felt that this modification was preferable to complete revision knee surgery in this patient. We feel that the current design of this hinge prosthesis may predispose it to failure via the mechanism described, and surgeons should be aware of this potential complication when considering the use of this system.
References 1. Pietsch M, Hofmann S. From tibiofemoral instability to dislocation in total knee arthroplasty. Orthopade 2007; 36:917. 2. Ayers DC, Dennis DA, Johanson NA, et al. Common complications of total knee arthroplasty. J Bone Joint Surg Am 1997;79A:278. 3. Gudnason A, Milbrink J, Hailer NP. Implant survival and outcome after rotating-hinge total knee revision arthroplasty: a minimum 6-year follow-up. Arch Orthop Trauma Surg 2011;131:1601. 4. Berend KR, Lombardi Jr AV. Distal femoral replacement in nontumor cases with severe bone loss and instability. Clin Orthop Relat Res 2009;467:485. 5. Jones RS. Mobile bearings in revision total knee arthroplasty. Instr Course Lect 2005;54:225. 6. Jones RE, Skedros JG, Chan AJ, et al. Total knee arthroplasty using the S-ROM mobile-bearing hinge prosthesis. J Arthroplasty 2001;16:279. 7. Barrack RL, Lyons TR, Ingraham RQ, et al. The use of a modular rotating hinge component in salvage revision total knee arthroplasty. J Arthroplasty 2000;15:858. 8. Flecher X, Paprosky W, Grillo JC, et al. Do tantalum components provide adequate primary fixation in all
Repeated Early Failure of a Newly Designed Hinged Knee System Lee et al acetabular revisions? Orthop Traumatol Surg Res 2010;96: 235. 9. Lachiewicz PF, Bolognesi MP, Henderson RA, et al. Can tantalum cones provide fixation in complex revision knee arthroplasty? Clin Orthop Relat Res 2012;470:199. 10. Wang CJ, Wang HE. Early catastrophic failure of rotating hinge total knee prosthesis. J Arthroplasty 2000;15:387.
375.e21
11. Schwarzkopf R, Chaudhry S, Kummer FJ, et al. Failure of the tibial insert in a rotating hinge total knee arthroplasty. J Arthroplasty 2010;26:977. 12. Springorum HR, Luring C, Beckmann J, et al. Fatigue fracture of the hinge pin in a semi-constrained total knee arthroplasty: a case report. Knee Surg Sports Traumatol Arthrosc 2010;18:1366.