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Influence of Technique With Distally Fixed Modular Stems in Revision Total Hip Arthroplasty
The Journal of Arthroplasty Vol. 25 No. 6 2010
Influence of Technique With Distally Fixed Modular Stems in Revision Total Hip Arthroplasty Preetesh D. Patel, MD,* Alison K. Klika, MS,y Trevor G. Murray, MD,y Karim A. Elsharkawy, MD,y Viktor E. Krebs, MD,y and Wael K. Barsoum, MDy
Abstract: Distally fixed modular implants have seen a recent increase in use, to manage proximal femoral bone loss often encountered during revision total hip arthroplasty (THA). Forty-three distally fixed modular stems implanted at our institution between 1999 and 2006 were clinically and radiographically reviewed. These patients had either a minimum 2-year follow-up (average, 2.4 years; range, 2-5.6 years) or failure (ie, explant or rerevision required). Eleven stems subsided, and 4 were rerevised (n = 4), for a rate of 9.3%. All revised stems were radiographically undersized, emphasizing the importance of the technique. Although being a valuable option in revision THA, these stems are not free of complications. The high rate of subsidence encountered in our early experience shows that there is a learning curve. This complication is preventable by avoiding undersizing. Keywords: total hip arthroplasty, revision, modularity, distal fixation, subsidence, undersizing. © 2010 Elsevier Inc. All rights reserved.
Revision total hip arthroplasty (THA) remains a challenge for the orthopedic surgeon. The particular challenges in the management of bone loss, soft tissue deficiencies, and loss of tissue planes have traditionally led to higher complication rates. These complications include higher rates of infection, stem subsidence, and instability. Proximal femoral bone loss encountered during revision THA is a significant and highly variable problem. Bone loss is typically attributed to mechanical loosening, osteolysis, stress shielding, fracture, or infection. This lack of proximal bone integrity can also be the result of bone loss from difficulty in the extraction of well-fixed components or secondary to the use of various osteotomies to ensure safe implant removal. Several techniques have been used to treat this problem with varying degrees of success, including the use of long From the *Department of Orthopedic Surgery, Cleveland Clinic Florida, Weston, Florida; and yDepartment of Orthopedic Surgery, Cleveland Clinic, Cleveland, Ohio. Submitted August 8, 2008; accepted July 7, 2009. Research support was received in support of this study from Stryker Orthopedics. Dr Barsoum reported that he has received grant support and is a consultant to Stryker Orthopedics. Dr Krebs acknowledged that he has received income as a Stryker consultant. This study was approved by the institutional review board at The Cleveland Clinic Foundation (no. 07-106). All authors were involved in the data collection, the preparation of the manuscript, and agree with the content. Reprint requests: Alison K. Klika, MS, Department of Orthopedic Surgery, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44195. © 2010 Elsevier Inc. All rights reserved. 0883-5403/2506-0014$36.00/0 doi:10.1016/j.arth.2009.07.006
stem implants with cement [1], uncemented extensively coated cylindrical implants [2,3], nonmodular fluted, tapered implants [4], distally fixed (cylindrical or tapered) modular implants [5-7], allograft-prosthetic composites [8], proximal femoral arthroplasties (megaprostheses) [9], and impaction grafting [10]. Although all of these implants have varying degrees of success, modular distally tapered implants have seen a recent increase in interest and use [11]. Historically, tapered stems have shown a high incidence of success but have been associated with early subsidence. Modularity may offer the surgeon intraoperative flexibility to achieve anatomical reconstructions of leg length and offset restoration in the setting of bone and/or soft tissue deficiencies. The variety of options allows for the ability to adjust for leg length, offset, and version to maximize implant stability and hip kinematics. These potential advantages have increased the use of modularity in revision THA at our institution. In cases of the deficient and proximally compromised femur, we have instituted the use of a distally fixed modular implant to achieve initial stability in the intact bone of the femoral diaphysis. The objective of this retrospective analysis was to report on the subsidence rate, its relationship to the surgical technique, as well as the other early clinical complications of a distally fixed modular implant at our institution. We addressed the question as to whether the distally fixed modular stem is an appropriate implant in revision THA, in which substantial proximal femoral bone loss is often encountered.
926
Influence of Technique With Molecular Stems Patel et al
Materials and Methods Institutional review board approval was obtained before the initiation of the study. Between 1999 and 2006, 43 distally fixed modular stems were implanted at our institution with either a minimum 2-year follow-up or failure (ie, explant or rerevision required). The 43 cases included the T3 Modular (n = 22) and the Restoration Modular (n = 21) (Fig. 1) stems (Stryker Howmedica Osteonics, Mahwah, NJ), for which the patient demographics are described in Table 1. The T3 Modular and Restoration Modular are fluted, tapered, grit-blasted titanium stems. Both systems offer 3 distal segment lengths of varying diameters, 4 body segments, and 5 head segments. The T3 Modular was the original design used at our institution from 1999 to 2003. The surface of the T3 proximal cone body was smooth and available in only one diameter. The Restoration Modular stem was introduced in 2004 and has been used up to the present day. The proximal cone bodies of the Restoration Modular design are available with a circumferentially plasma-sprayed titanium surface with a hydroyxapatite overspray. In addition, this proximal body is available in 7 diameters with varying offsets. To our knowledge, there has been no previous report on the Stryker Howmedica Osteonics T3 and Restoration Modular stem. The preoperative diagnoses for all 43 patients receiving distally fixed modular stems included 21 (49.0%) cases of aseptic loosening, 10 (23.2%) cases of reimplantation after a periprosthetic infection, 3 (7.0%) cases of periprosthetic fractures, 2 (4.6%) cases of osteolysis, 3 (7.0%) cases of
927
Table 1. Details of the 43 Patients Age (y) Weight (lb) Height (in) Body mass index
Mean
(Range, SD)
68.4 192 66.8 30.3
(50-88, 14.0) (125-318, 48.1) (51-72, 4.2) (16.8-48.7, 7.3)
recurrent instability, 2 (4.6%) cases of component fractures, and 2 (4.6%) complex revisions—one was posttraumatic avascular necrosis with retained hardware and the other was post-open reduction internal fixation and Girdlestone resection. This was the first revision or complex primary for 13 (30.2%) patients, whereas 30 (69.7%) patients had previously undergone at least one prior revision, with an average of 2.7 ± 1.5 revision surgeries (range, 1-6). The posterior approach was used in 26 patients (60.4%), and the modified lateral (Hardinge) was used in 17 (39.5%). For 3 (7.0%) patients, a trochanteric osteotomy was used; for 2 (4.6%) patients, a transverse femoral osteotomy was used; and for 9 (21%) patients, an extended trochanteric osteotomy was used. The preoperative proximal femoral bone deficiencies were evaluated radiographically for the 39 patients with available images and classified according to the classification by Paprosky et al [12]. In this sample, 3 (7.0%) patients were classified as type II, 15 (35.0%) patients were type IIIA, 13 (30.2%) patients were type IIIB, and 8 (18.6%) patients were type IV. The 3 periprosthetic fractures were evaluated radiographically and classified according to the Vancouver classification as type B2. Serial postoperative radiographs were reviewed of the pelvis, hip, and femur in all patients for evidence of subsidence, radiolucency, and other modes of failure.
Results
Fig. 1. The Restoration Modular stem, showing options for stem length and proximal bodies (courtesy of Stryker Orthopedics).
Of the 43 patients, 10 presented with prior periprosthetic infection. Of these 10 patients, 3 were an attempted second-time reimplantation with an average of 5.3 previous revision operations (range, 3-12). All 3 patients developed a second deep periprosthetic infection that required resection arthroplasties. Further attempts at reimplantation were not performed. Two of the remaining 7 patients with first-time reimplantations have remained free of infection as of their latest follow-up visit. Of the 43 cases reviewed, 8 required an explantation procedure due to infection (all of which were previously infected) and 1 case was rerevised due to subsidence (29 mm) before 1 year postoperatively, leaving 34 cases with an average clinical and radiographic follow-up of 2.4 years (range, 2.0-5.6 years). Thirty-two stems (74.4%) demonstrated stable ingrowth without any subsidence at last follow-up, whereas 11 (25.5%) stems subsided an average of 10 mm (range, 2.0-29 mm), yielding an overall average subsidence of 2.5 mm (range, 0.0-29 mm), including the stem that subsided before 1 year. Seven stems (16.2%)
928 The Journal of Arthroplasty Vol. 25 No. 6 September 2010 subsided an average of 4.3 mm (range, 2.0-8.0 mm) and ceased subsiding within the first year of surgery (Fig. 2). These patients were asymptomatic and showed no further subsidence at their latest follow-up. Four (9.3%) stems subsided an average of 20 mm (range, 1229 mm) and required rerevision. The difference in subsidence between these 2 groups was found to be statistically significant (P b .0001), indicating that subsidence beyond 1 cm is likely to require rerevision. Two were in Paprosky type IIIB femurs and 2 were in Paprosky type IV femurs. These 4 stems were radiographically grossly undersized (ie, ≥2-mm gap between the stem and cortex) and occurred early in our experience likely indicating a learning curve when using this component (Fig. 3). Two (4.6%) of the 43 stems subsided 5 mm each and were found to be infected and underwent explantation. Two patients had a dislocation, managed with closed reduction, and have not had recurrence at last follow-up (Table 2). One (2.3%) periprosthetic fracture occurred 18 months after the index operation secondary to a traumatic event. The stem was found to be stable at the time of fracture fixation and therefore was retained. None of the patients implanted with T3 prosthesis experienced any implant breakage—a notable result since the T3 was withdrawn from the market due to a high rate of failure at the modular junction. Longer follow-up is required to fully address the problem of implant breakage.
Discussion The use of long stem implants with cement were used initially but had high failure rates at 10 years (9%-29%) [1,13-16]. This was attributed to a decrease in shear strength at the bone-cement interface secondary to poor cement interdigitation within a smooth sclerotic endosteal surface [17], which led to the use of cementless techniques. Proximally porous-coated stems, although successful in primary THA, had largely unsatisfactory results in the revision setting [18,19]. Poor proximal bone stock compromised initial implant stability, whereas diminished vascularity threatened the potential for long-term biologic ingrowth. As a result, many surgeons today use extensively porous-coated implants that rely on distal femoral fixation. Reports on the results of porous-coated implants have been encouraging. Lawrence et al [2] reported a 6% need for repeat revision at 5 years in 174 patients. Paprosky et al [3] reported a survivorship greater than 95% at a minimum of 10 years in 170 patients. However, thigh pain and proximal stress-shielding secondary to the modulus mismatch remain a concern [20]. An alternative implant for distal fixation is a fluted tapered stem [21], which initially gained popularity in Europe in the mid to late 1980s. The prototype for these implants was the Wagner self-locking stem (Sulzer Medica, Baar, Switzerland). The fluted design allows for rotational control, whereas the taper provides axial
Fig. 2. Anteroposterior radiographs of an 87-year-old female, showing the condition of the right hip. (A) Preoperative. (B) 1 month postoperative. (C) 9 months postoperative. At the 9month follow-up, 5-mm subsidence was observed.
stability. Theoretically, a lower modulus of elasticity with this design would decrease proximal stress shielding. Several authors have reported survival rates of greater
Influence of Technique With Molecular Stems Patel et al
Fig. 3. Anteroposterior radiograph showing a grossly undersized stem (ie, ≥2-mm gap between the stem and cortex).
than 92% at 10 years [4-7], which is comparable to or slightly lower than that reported for its extensively porous-coated cylindrical counterparts. Bohm and Bischel [4] reported on 129 hips using the Wagner SL revision stem with an average follow-up of 4.8 years.
929
Repeat revision of the stem was required in 6 (5%) of 129 stems due to infection (n = 3), stem subsidence (n = 2), and recurrent dislocation (n = 1). Proximal bone restoration to some degree was observed in 113 hips (88%). New bone formation at the proximal femur has been seen in other series as well [22]. One of the problems with a monolithic tapered implant has been early stem subsidence requiring a repeat revision [4,6,22,23]. Two authors reported an 8% rerevision rate secondary to early stem subsidence (2/31 cases and 4/40 cases) [6,22]. Berry [23] noted the significant subsidence rates for these stems, which he partially attributed to a “learning curve” effect when transitioning between a “fit and fill” stem to a fluted tapered stem that leads to undersizing. In addition, difficulty in establishing leg length and soft tissue tension can sometimes prevent full seating of this implant [23]. These issues have led manufacturers to design implants that allow for modularity. Modularity builds on the advantages of the Wagner design with the goal of increasing survivorship and decreasing the prevalence of stem subsidence and instability. The distal tapered stem and the proximal bodies are independently sized allowing for an intimate fit against the isthmus and proximal metaphysis, respectively. This versatility allows for precision in establishing the femoral center of rotation, neck offset, and anteversion. Multiple designs have been introduced and have shown early success, but no long-term results are currently available. Kwong et al [24] reported on the Link MP stem (Link Orthopedics, Denville, NJ) and found a survival rate of 97.2%, a dislocation rate of 2.1%, and an average stem subsidence of 2.1 mm (Table 2). In a series of 16 stems including the Link MP and ZMR stems (Zimmer, Warsaw, Ind), Sporer and Paprosky [25] reported that one stem subsided secondary to septic loosening and was rerevised for recurrent instability, whereas none of the other stems showed femoral subsidence. Murphy and Rodriguez [26] reported on 35 patients in which the Link MP stem was used. No stems demonstrated any measurable subsidence, and 34 of 35 stems developed radiographic evidence of osseointegration. Six patients (17%) were revised secondary to instability; however, the distal stem was retained with a modular exchange of the proximal body in all cases. McInnis et al [27] reported on 70 stems using the Press-Fit Modular (Sulzer Orthopedics, Baar, Switzerland) and found that 3 stems (4.3%) were rerevised due to periprosthetic fracture (n = 2) and uncontrolled subsidence (n = 1; 52 mm secondary to undersizing). Results showed a subsidence rate of 84% (59/70) and a dislocation rate of 10% (7/70). In 4 of 7, the dislocation occurred once and was treated closed without further instability. The other 3 hips required acetabular nonconstrained revision for recurrent instability with retention of the femoral stem. There are potential disadvantages associated with modular hip systems [28], including modular junction
930 The Journal of Arthroplasty Vol. 25 No. 6 September 2010 Table 2. Literature Comparison Publication
Implant
Kwong et al (2003) Link MP Sporer and Paprosky (2004) Link MP ZMR Murphy et al (2004) Link MP McInnis et al (2006) Press-Fit Modular Current study T3 Modular, Restoration Modular
No. of Revisions
Average Follow-up, y (Range)
143 5 11 35 70 43
Average Subsidence, mm
Rerevision Rate (Excluding Infection)
Dislocation Rate
3.3 (2.0-6.0) 2.0 (1.0-4.0)
2.1 NA
3/143 (2.1%) 0/16 (0.0%)
3/143 (2.1%) 1/16 (6.3%)
3.6 (2.0-NA) 3.9 (2.0-5.3) 2.4 (2.0-5.6)
NA 9.9 2.5
7/35 (20%) 3/70 (4.3%) 4/43 (9.3%)
6/35 (17%) 7/70 (10%) 2/43 (4.6)%
NA indicates not available.
fretting and fracture at or near the trunion. Stresses generated at the modular junctions may result in complications such as fretting and fracture, as evidenced by retrieval studies [29]. Sporer et al [30] reported on the disassociation of a modular femoral neck from its junction with a well-fixed stem. Fatigue fracture of the Link MP stem was recently reported, which may have been due to the absence of proximal femoral bone support [31]. Manufacturers have tried to obviate the risk of fracture with various treatments to the modular joint with shot peening, low plasticity burnishing, and using larger trunions. In addition, ingrowth/ongrowth surfaces have been added to the proximal sections of these stems in an attempt to promote proximal ingrowth, effectively reducing the stresses across the trunion. These efforts have led to a significant decrease in stem fractures. We have used these stems even in significantly compromised proximal bone. Our goal is always to try to get some intimate contact with the proximal body of the stem to relieve stress on the trunions, but in rare cases, this is not possible. The work by Bobyn et al [32] examining firstgeneration modular junctions has shown fretting to not be an area of concern for failure of those prosthetics. We have reported a rerevision rate of 9.3% due to subsidence. This was encountered in our early experience with the use of distally fixed modular stems. All patients who had subsidence were operated on between 2000 and 2004 except one patient, who underwent revision in 2006 because of infection. Our data show that subsidence is one of the biggest risks for rerevision, which may be prevented by avoiding undersizing of the stem. This demonstrates that there can be a learning curve when using these stems, and it is important that surgeons are made aware of this preventable complication. These data serve as a caution to surgeons with little experience using this stem, and our experience demonstrate a valuable lesson for future users. It is our practice now to use intraoperative radiographs when using these stems. We strongly suggest that an intraoperative radiograph be obtained with the last reamer in place. This allows the surgeon to assess canal fill and the potential need for upsizing before selecting the final implant size. Reaming can be done either manually or using power instruments. This method should be used with this stem until the
surgeon becomes comfortable appropriately sizing the prosthesis. Once this learning curve is passed, the use of intraoperative radiographs may be discontinued at the surgeon's level of comfort. It is the experience of the senior surgeons in this series that once initial stability is found with the reamer an additional 1-size to 2-size increase is usually necessary to stabilize the stem. This is easily done in the bone with thick cortices, but care must be taken in the patient with thin cortices so as not to perforate the femur. An alternative option for a patient with thin cortices is to cable the femur prophylactically with or without struts to reduce the hoop stresses and decrease the risk of intraoperative fracture. These early data draw the attention to the importance of the technique when using distally fixed modular stems. They can be a valuable option to the surgeon facing increasingly complex revision THA cases but only when used appropriately in the presence of sufficient proximal bone support (host or allograft) and with careful stem sizing. Concerns with mechanical failure and fretting are legitimate but have not been demonstrated in the current literature. Further follow-up study is needed to fully address these issues and to establish long-term durability of these implants.
References 1. Pellicci PM, Wilson Jr PD, Sledge CB, et al. Long-term results of revision total hip replacement. A follow-up report. J Bone Joint Surg Am 1985;67:513. 2. Lawrence JM, Engh CA, Macalino GE. Revision total hip arthroplasty. Long-term results without cement. Orthop Clin North Am 1993;24:635. 3. Paprosky WG, Greidanus NV, Antoniou J. Minimum 10-year-results of extensively porous-coated stems in revision hip arthroplasty. Clin Orthop Relat Res 1999; 230. 4. Bohm P, Bischel O. Femoral revision with the Wagner SL revision stem: evaluation of one hundred and twenty-nine revisions followed for a mean of 4.8 years. J Bone Joint Surg Am 2001;83-A:1023. 5. Bircher HP, Riede U, Luem M, et al. The value of the Wagner SL revision prosthesis for bridging large femoral defects. Orthopade 2001;30:294. 6. Grunig R, Morscher E, Ochsner PE. Three- to 7-year results with the uncemented SL femoral revision prosthesis. Arch Orthop Trauma Surg 1997;116:187.
Influence of Technique With Molecular Stems Patel et al 7. Rinaldi E, Marenghi P, Vaienti E. The Wagner prosthesis for femoral reconstruction by transfemoral approach. Chir Organi Mov 1994;79:353. 8. Chandler H, Clark J, Murphy S, et al. Reconstruction of major segmental loss of the proximal femur in revision total hip arthroplasty. Clin Orthop Relat Res 1994;67. 9. Malkani AL, Sim FH, Chao EY. Custom-made segmental femoral replacement prosthesis in revision total hip arthroplasty. Orthop Clin North Am 1993;24:727. 10. Knight JL, Helming C. Collarless polished tapered impaction grafting of the femur during revision total hip arthroplasty: pitfalls of the surgical technique and follow-up in 31 cases. J Arthroplasty 2000;15:159. 11. Yates PJ, Burston BJ, Whitley E, et al. Collarless polished tapered stem: clinical and radiological results at a minimum of ten years' follow-up. J Bone Joint Surg Br 2008;90:16. 12. Paprosky WG, Lawrence WJ, Cameron H. Femoral defect classification: clinical application. Orthop Rev 1990(Suppl 19);9. 13. Callaghan JJ, Salvati EA, Pellicci PM, et al. Results of revision for mechanical failure after cemented total hip replacement, 1979 to 1982. A two to five-year follow-up. J Bone Joint Surg Am 1985;67:1074. 14. Mulroy WF, Harris WH. Revision total hip arthroplasty with use of so-called second-generation cementing techniques for aseptic loosening of the femoral component. A fifteenyear-average follow-up study. J Bone Joint Surg Am 1996; 78:325. 15. Kershaw CJ, Atkins RM, Dodd CA, et al. Revision total hip arthroplasty for aseptic failure. A review of 276 cases. J Bone Joint Surg Br 1991;73:564. 16. Estok II DM, Harris WH. Long-term results of cemented femoral revision surgery using second-generation techniques. An average 11.7-year follow-up evaluation. Clin Orthop Relat Res 1994;190. 17. Dohmae Y, Bechtold JE, Sherman RE, et al. Reduction in cement-bone interface shear strength between primary and revision arthroplasty. Clin Orthop Relat Res 1988;214. 18. Berry DJ, Harmsen WS, Ilstrup D, et al. Survivorship of uncemented proximally porous-coated femoral components. Clin Orthop Relat Res 1995;168.
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19. Mulliken BD, Rorabeck CH, Bourne RB. Uncemented revision total hip arthroplasty: a 4-to-6-year review. Clin Orthop Relat Res 1996;156. 20. Engh Jr CA, Young AM, Engh Sr CA, et al. Clinical consequences of stress shielding after porous-coated total hip arthroplasty. Clin Orthop Relat Res 2003;157. 21. Wagner H. Revision prosthesis for the hip joint in severe bone loss. Orthopade 1987;16:295. 22. Kolstad K, Adalberth G, Mallmin H, et al. The Wagner revision stem for severe osteolysis. 31 hips followed for 1.55 years. Acta Orthop Scand 1996;67:541. 23. Berry DJ. Femoral revision: distal fixation with fluted, tapered grit-blasted stems. J Arthroplasty 2002;17(4 Suppl 1):142. 24. Kwong LM, Miller AJ, Lubinus P. A modular distal fixation option for proximal bone loss in revision total hip arthroplasty: a 2- to 6-year follow-up study. J Arthroplasty 2003;18(3 Suppl 1):94. 25. Sporer SM, Paprosky WG. Femoral fixation in the face of considerable bone loss: the use of modular stems. Clin Orthop Relat Res 2004;227. 26. Murphy SB, Rodriguez J. Revision total hip arthroplasty with proximal bone loss. J Arthroplasty 2004;19(4 Suppl 1): 115. 27. McInnis DP, Horne G, Devane PA. Femoral revision with a fluted, tapered, modular stem seventy patients followed for a mean of 3.9 years. J Arthroplasty 2006;21:372. 28. Helm CS, Greenwald AS. The rationale and performance of modularity in total hip arthroplasty. Orthopedics 2005;28(9 Suppl):s1113. 29. Goldberg JR, Gilbert JL, Jacobs JJ, et al. A multicenter retrieval study of the taper interfaces of modular hip prostheses. Clin Orthop Relat Res 2002;149. 30. Sporer SM, DellaValle C, Jacobs J, et al. A case of disassociation of a modular femoral neck trunion after total hip arthroplasty. J Arthroplasty 2006;21:918. 31. Buttaro MA, Mayor MB, Van Citters D, et al. Fatigue fracture of a proximally modular, distally tapered fluted implant with diaphyseal fixation. J Arthroplasty 2007;22: 780. 32. Bobyn JD, Tanzer M, Krygier JJ, et al. Concerns with modularity in total hip arthroplasty. Clin Orthop Relat Res 1994;27.
Influence of Technique With Distally Fixed Modular Stems in Revision Total Hip Arthroplasty Preetesh D. Patel, MD,* Alison K. Klika, MS,y Trevor G. Murray, MD,y Karim A. Elsharkawy, MD,y Viktor E. Krebs, MD,y and Wael K. Barsoum, MDy
Abstract: Distally fixed modular implants have seen a recent increase in use, to manage proximal femoral bone loss often encountered during revision total hip arthroplasty (THA). Forty-three distally fixed modular stems implanted at our institution between 1999 and 2006 were clinically and radiographically reviewed. These patients had either a minimum 2-year follow-up (average, 2.4 years; range, 2-5.6 years) or failure (ie, explant or rerevision required). Eleven stems subsided, and 4 were rerevised (n = 4), for a rate of 9.3%. All revised stems were radiographically undersized, emphasizing the importance of the technique. Although being a valuable option in revision THA, these stems are not free of complications. The high rate of subsidence encountered in our early experience shows that there is a learning curve. This complication is preventable by avoiding undersizing. Keywords: total hip arthroplasty, revision, modularity, distal fixation, subsidence, undersizing. © 2010 Elsevier Inc. All rights reserved.
Revision total hip arthroplasty (THA) remains a challenge for the orthopedic surgeon. The particular challenges in the management of bone loss, soft tissue deficiencies, and loss of tissue planes have traditionally led to higher complication rates. These complications include higher rates of infection, stem subsidence, and instability. Proximal femoral bone loss encountered during revision THA is a significant and highly variable problem. Bone loss is typically attributed to mechanical loosening, osteolysis, stress shielding, fracture, or infection. This lack of proximal bone integrity can also be the result of bone loss from difficulty in the extraction of well-fixed components or secondary to the use of various osteotomies to ensure safe implant removal. Several techniques have been used to treat this problem with varying degrees of success, including the use of long From the *Department of Orthopedic Surgery, Cleveland Clinic Florida, Weston, Florida; and yDepartment of Orthopedic Surgery, Cleveland Clinic, Cleveland, Ohio. Submitted August 8, 2008; accepted July 7, 2009. Research support was received in support of this study from Stryker Orthopedics. Dr Barsoum reported that he has received grant support and is a consultant to Stryker Orthopedics. Dr Krebs acknowledged that he has received income as a Stryker consultant. This study was approved by the institutional review board at The Cleveland Clinic Foundation (no. 07-106). All authors were involved in the data collection, the preparation of the manuscript, and agree with the content. Reprint requests: Alison K. Klika, MS, Department of Orthopedic Surgery, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44195. © 2010 Elsevier Inc. All rights reserved. 0883-5403/2506-0014$36.00/0 doi:10.1016/j.arth.2009.07.006
stem implants with cement [1], uncemented extensively coated cylindrical implants [2,3], nonmodular fluted, tapered implants [4], distally fixed (cylindrical or tapered) modular implants [5-7], allograft-prosthetic composites [8], proximal femoral arthroplasties (megaprostheses) [9], and impaction grafting [10]. Although all of these implants have varying degrees of success, modular distally tapered implants have seen a recent increase in interest and use [11]. Historically, tapered stems have shown a high incidence of success but have been associated with early subsidence. Modularity may offer the surgeon intraoperative flexibility to achieve anatomical reconstructions of leg length and offset restoration in the setting of bone and/or soft tissue deficiencies. The variety of options allows for the ability to adjust for leg length, offset, and version to maximize implant stability and hip kinematics. These potential advantages have increased the use of modularity in revision THA at our institution. In cases of the deficient and proximally compromised femur, we have instituted the use of a distally fixed modular implant to achieve initial stability in the intact bone of the femoral diaphysis. The objective of this retrospective analysis was to report on the subsidence rate, its relationship to the surgical technique, as well as the other early clinical complications of a distally fixed modular implant at our institution. We addressed the question as to whether the distally fixed modular stem is an appropriate implant in revision THA, in which substantial proximal femoral bone loss is often encountered.
926
Influence of Technique With Molecular Stems Patel et al
Materials and Methods Institutional review board approval was obtained before the initiation of the study. Between 1999 and 2006, 43 distally fixed modular stems were implanted at our institution with either a minimum 2-year follow-up or failure (ie, explant or rerevision required). The 43 cases included the T3 Modular (n = 22) and the Restoration Modular (n = 21) (Fig. 1) stems (Stryker Howmedica Osteonics, Mahwah, NJ), for which the patient demographics are described in Table 1. The T3 Modular and Restoration Modular are fluted, tapered, grit-blasted titanium stems. Both systems offer 3 distal segment lengths of varying diameters, 4 body segments, and 5 head segments. The T3 Modular was the original design used at our institution from 1999 to 2003. The surface of the T3 proximal cone body was smooth and available in only one diameter. The Restoration Modular stem was introduced in 2004 and has been used up to the present day. The proximal cone bodies of the Restoration Modular design are available with a circumferentially plasma-sprayed titanium surface with a hydroyxapatite overspray. In addition, this proximal body is available in 7 diameters with varying offsets. To our knowledge, there has been no previous report on the Stryker Howmedica Osteonics T3 and Restoration Modular stem. The preoperative diagnoses for all 43 patients receiving distally fixed modular stems included 21 (49.0%) cases of aseptic loosening, 10 (23.2%) cases of reimplantation after a periprosthetic infection, 3 (7.0%) cases of periprosthetic fractures, 2 (4.6%) cases of osteolysis, 3 (7.0%) cases of
927
Table 1. Details of the 43 Patients Age (y) Weight (lb) Height (in) Body mass index
Mean
(Range, SD)
68.4 192 66.8 30.3
(50-88, 14.0) (125-318, 48.1) (51-72, 4.2) (16.8-48.7, 7.3)
recurrent instability, 2 (4.6%) cases of component fractures, and 2 (4.6%) complex revisions—one was posttraumatic avascular necrosis with retained hardware and the other was post-open reduction internal fixation and Girdlestone resection. This was the first revision or complex primary for 13 (30.2%) patients, whereas 30 (69.7%) patients had previously undergone at least one prior revision, with an average of 2.7 ± 1.5 revision surgeries (range, 1-6). The posterior approach was used in 26 patients (60.4%), and the modified lateral (Hardinge) was used in 17 (39.5%). For 3 (7.0%) patients, a trochanteric osteotomy was used; for 2 (4.6%) patients, a transverse femoral osteotomy was used; and for 9 (21%) patients, an extended trochanteric osteotomy was used. The preoperative proximal femoral bone deficiencies were evaluated radiographically for the 39 patients with available images and classified according to the classification by Paprosky et al [12]. In this sample, 3 (7.0%) patients were classified as type II, 15 (35.0%) patients were type IIIA, 13 (30.2%) patients were type IIIB, and 8 (18.6%) patients were type IV. The 3 periprosthetic fractures were evaluated radiographically and classified according to the Vancouver classification as type B2. Serial postoperative radiographs were reviewed of the pelvis, hip, and femur in all patients for evidence of subsidence, radiolucency, and other modes of failure.
Results
Fig. 1. The Restoration Modular stem, showing options for stem length and proximal bodies (courtesy of Stryker Orthopedics).
Of the 43 patients, 10 presented with prior periprosthetic infection. Of these 10 patients, 3 were an attempted second-time reimplantation with an average of 5.3 previous revision operations (range, 3-12). All 3 patients developed a second deep periprosthetic infection that required resection arthroplasties. Further attempts at reimplantation were not performed. Two of the remaining 7 patients with first-time reimplantations have remained free of infection as of their latest follow-up visit. Of the 43 cases reviewed, 8 required an explantation procedure due to infection (all of which were previously infected) and 1 case was rerevised due to subsidence (29 mm) before 1 year postoperatively, leaving 34 cases with an average clinical and radiographic follow-up of 2.4 years (range, 2.0-5.6 years). Thirty-two stems (74.4%) demonstrated stable ingrowth without any subsidence at last follow-up, whereas 11 (25.5%) stems subsided an average of 10 mm (range, 2.0-29 mm), yielding an overall average subsidence of 2.5 mm (range, 0.0-29 mm), including the stem that subsided before 1 year. Seven stems (16.2%)
928 The Journal of Arthroplasty Vol. 25 No. 6 September 2010 subsided an average of 4.3 mm (range, 2.0-8.0 mm) and ceased subsiding within the first year of surgery (Fig. 2). These patients were asymptomatic and showed no further subsidence at their latest follow-up. Four (9.3%) stems subsided an average of 20 mm (range, 1229 mm) and required rerevision. The difference in subsidence between these 2 groups was found to be statistically significant (P b .0001), indicating that subsidence beyond 1 cm is likely to require rerevision. Two were in Paprosky type IIIB femurs and 2 were in Paprosky type IV femurs. These 4 stems were radiographically grossly undersized (ie, ≥2-mm gap between the stem and cortex) and occurred early in our experience likely indicating a learning curve when using this component (Fig. 3). Two (4.6%) of the 43 stems subsided 5 mm each and were found to be infected and underwent explantation. Two patients had a dislocation, managed with closed reduction, and have not had recurrence at last follow-up (Table 2). One (2.3%) periprosthetic fracture occurred 18 months after the index operation secondary to a traumatic event. The stem was found to be stable at the time of fracture fixation and therefore was retained. None of the patients implanted with T3 prosthesis experienced any implant breakage—a notable result since the T3 was withdrawn from the market due to a high rate of failure at the modular junction. Longer follow-up is required to fully address the problem of implant breakage.
Discussion The use of long stem implants with cement were used initially but had high failure rates at 10 years (9%-29%) [1,13-16]. This was attributed to a decrease in shear strength at the bone-cement interface secondary to poor cement interdigitation within a smooth sclerotic endosteal surface [17], which led to the use of cementless techniques. Proximally porous-coated stems, although successful in primary THA, had largely unsatisfactory results in the revision setting [18,19]. Poor proximal bone stock compromised initial implant stability, whereas diminished vascularity threatened the potential for long-term biologic ingrowth. As a result, many surgeons today use extensively porous-coated implants that rely on distal femoral fixation. Reports on the results of porous-coated implants have been encouraging. Lawrence et al [2] reported a 6% need for repeat revision at 5 years in 174 patients. Paprosky et al [3] reported a survivorship greater than 95% at a minimum of 10 years in 170 patients. However, thigh pain and proximal stress-shielding secondary to the modulus mismatch remain a concern [20]. An alternative implant for distal fixation is a fluted tapered stem [21], which initially gained popularity in Europe in the mid to late 1980s. The prototype for these implants was the Wagner self-locking stem (Sulzer Medica, Baar, Switzerland). The fluted design allows for rotational control, whereas the taper provides axial
Fig. 2. Anteroposterior radiographs of an 87-year-old female, showing the condition of the right hip. (A) Preoperative. (B) 1 month postoperative. (C) 9 months postoperative. At the 9month follow-up, 5-mm subsidence was observed.
stability. Theoretically, a lower modulus of elasticity with this design would decrease proximal stress shielding. Several authors have reported survival rates of greater
Influence of Technique With Molecular Stems Patel et al
Fig. 3. Anteroposterior radiograph showing a grossly undersized stem (ie, ≥2-mm gap between the stem and cortex).
than 92% at 10 years [4-7], which is comparable to or slightly lower than that reported for its extensively porous-coated cylindrical counterparts. Bohm and Bischel [4] reported on 129 hips using the Wagner SL revision stem with an average follow-up of 4.8 years.
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Repeat revision of the stem was required in 6 (5%) of 129 stems due to infection (n = 3), stem subsidence (n = 2), and recurrent dislocation (n = 1). Proximal bone restoration to some degree was observed in 113 hips (88%). New bone formation at the proximal femur has been seen in other series as well [22]. One of the problems with a monolithic tapered implant has been early stem subsidence requiring a repeat revision [4,6,22,23]. Two authors reported an 8% rerevision rate secondary to early stem subsidence (2/31 cases and 4/40 cases) [6,22]. Berry [23] noted the significant subsidence rates for these stems, which he partially attributed to a “learning curve” effect when transitioning between a “fit and fill” stem to a fluted tapered stem that leads to undersizing. In addition, difficulty in establishing leg length and soft tissue tension can sometimes prevent full seating of this implant [23]. These issues have led manufacturers to design implants that allow for modularity. Modularity builds on the advantages of the Wagner design with the goal of increasing survivorship and decreasing the prevalence of stem subsidence and instability. The distal tapered stem and the proximal bodies are independently sized allowing for an intimate fit against the isthmus and proximal metaphysis, respectively. This versatility allows for precision in establishing the femoral center of rotation, neck offset, and anteversion. Multiple designs have been introduced and have shown early success, but no long-term results are currently available. Kwong et al [24] reported on the Link MP stem (Link Orthopedics, Denville, NJ) and found a survival rate of 97.2%, a dislocation rate of 2.1%, and an average stem subsidence of 2.1 mm (Table 2). In a series of 16 stems including the Link MP and ZMR stems (Zimmer, Warsaw, Ind), Sporer and Paprosky [25] reported that one stem subsided secondary to septic loosening and was rerevised for recurrent instability, whereas none of the other stems showed femoral subsidence. Murphy and Rodriguez [26] reported on 35 patients in which the Link MP stem was used. No stems demonstrated any measurable subsidence, and 34 of 35 stems developed radiographic evidence of osseointegration. Six patients (17%) were revised secondary to instability; however, the distal stem was retained with a modular exchange of the proximal body in all cases. McInnis et al [27] reported on 70 stems using the Press-Fit Modular (Sulzer Orthopedics, Baar, Switzerland) and found that 3 stems (4.3%) were rerevised due to periprosthetic fracture (n = 2) and uncontrolled subsidence (n = 1; 52 mm secondary to undersizing). Results showed a subsidence rate of 84% (59/70) and a dislocation rate of 10% (7/70). In 4 of 7, the dislocation occurred once and was treated closed without further instability. The other 3 hips required acetabular nonconstrained revision for recurrent instability with retention of the femoral stem. There are potential disadvantages associated with modular hip systems [28], including modular junction
930 The Journal of Arthroplasty Vol. 25 No. 6 September 2010 Table 2. Literature Comparison Publication
Implant
Kwong et al (2003) Link MP Sporer and Paprosky (2004) Link MP ZMR Murphy et al (2004) Link MP McInnis et al (2006) Press-Fit Modular Current study T3 Modular, Restoration Modular
No. of Revisions
Average Follow-up, y (Range)
143 5 11 35 70 43
Average Subsidence, mm
Rerevision Rate (Excluding Infection)
Dislocation Rate
3.3 (2.0-6.0) 2.0 (1.0-4.0)
2.1 NA
3/143 (2.1%) 0/16 (0.0%)
3/143 (2.1%) 1/16 (6.3%)
3.6 (2.0-NA) 3.9 (2.0-5.3) 2.4 (2.0-5.6)
NA 9.9 2.5
7/35 (20%) 3/70 (4.3%) 4/43 (9.3%)
6/35 (17%) 7/70 (10%) 2/43 (4.6)%
NA indicates not available.
fretting and fracture at or near the trunion. Stresses generated at the modular junctions may result in complications such as fretting and fracture, as evidenced by retrieval studies [29]. Sporer et al [30] reported on the disassociation of a modular femoral neck from its junction with a well-fixed stem. Fatigue fracture of the Link MP stem was recently reported, which may have been due to the absence of proximal femoral bone support [31]. Manufacturers have tried to obviate the risk of fracture with various treatments to the modular joint with shot peening, low plasticity burnishing, and using larger trunions. In addition, ingrowth/ongrowth surfaces have been added to the proximal sections of these stems in an attempt to promote proximal ingrowth, effectively reducing the stresses across the trunion. These efforts have led to a significant decrease in stem fractures. We have used these stems even in significantly compromised proximal bone. Our goal is always to try to get some intimate contact with the proximal body of the stem to relieve stress on the trunions, but in rare cases, this is not possible. The work by Bobyn et al [32] examining firstgeneration modular junctions has shown fretting to not be an area of concern for failure of those prosthetics. We have reported a rerevision rate of 9.3% due to subsidence. This was encountered in our early experience with the use of distally fixed modular stems. All patients who had subsidence were operated on between 2000 and 2004 except one patient, who underwent revision in 2006 because of infection. Our data show that subsidence is one of the biggest risks for rerevision, which may be prevented by avoiding undersizing of the stem. This demonstrates that there can be a learning curve when using these stems, and it is important that surgeons are made aware of this preventable complication. These data serve as a caution to surgeons with little experience using this stem, and our experience demonstrate a valuable lesson for future users. It is our practice now to use intraoperative radiographs when using these stems. We strongly suggest that an intraoperative radiograph be obtained with the last reamer in place. This allows the surgeon to assess canal fill and the potential need for upsizing before selecting the final implant size. Reaming can be done either manually or using power instruments. This method should be used with this stem until the
surgeon becomes comfortable appropriately sizing the prosthesis. Once this learning curve is passed, the use of intraoperative radiographs may be discontinued at the surgeon's level of comfort. It is the experience of the senior surgeons in this series that once initial stability is found with the reamer an additional 1-size to 2-size increase is usually necessary to stabilize the stem. This is easily done in the bone with thick cortices, but care must be taken in the patient with thin cortices so as not to perforate the femur. An alternative option for a patient with thin cortices is to cable the femur prophylactically with or without struts to reduce the hoop stresses and decrease the risk of intraoperative fracture. These early data draw the attention to the importance of the technique when using distally fixed modular stems. They can be a valuable option to the surgeon facing increasingly complex revision THA cases but only when used appropriately in the presence of sufficient proximal bone support (host or allograft) and with careful stem sizing. Concerns with mechanical failure and fretting are legitimate but have not been demonstrated in the current literature. Further follow-up study is needed to fully address these issues and to establish long-term durability of these implants.
References 1. Pellicci PM, Wilson Jr PD, Sledge CB, et al. Long-term results of revision total hip replacement. A follow-up report. J Bone Joint Surg Am 1985;67:513. 2. Lawrence JM, Engh CA, Macalino GE. Revision total hip arthroplasty. Long-term results without cement. Orthop Clin North Am 1993;24:635. 3. Paprosky WG, Greidanus NV, Antoniou J. Minimum 10-year-results of extensively porous-coated stems in revision hip arthroplasty. Clin Orthop Relat Res 1999; 230. 4. Bohm P, Bischel O. Femoral revision with the Wagner SL revision stem: evaluation of one hundred and twenty-nine revisions followed for a mean of 4.8 years. J Bone Joint Surg Am 2001;83-A:1023. 5. Bircher HP, Riede U, Luem M, et al. The value of the Wagner SL revision prosthesis for bridging large femoral defects. Orthopade 2001;30:294. 6. Grunig R, Morscher E, Ochsner PE. Three- to 7-year results with the uncemented SL femoral revision prosthesis. Arch Orthop Trauma Surg 1997;116:187.
Influence of Technique With Molecular Stems Patel et al 7. Rinaldi E, Marenghi P, Vaienti E. The Wagner prosthesis for femoral reconstruction by transfemoral approach. Chir Organi Mov 1994;79:353. 8. Chandler H, Clark J, Murphy S, et al. Reconstruction of major segmental loss of the proximal femur in revision total hip arthroplasty. Clin Orthop Relat Res 1994;67. 9. Malkani AL, Sim FH, Chao EY. Custom-made segmental femoral replacement prosthesis in revision total hip arthroplasty. Orthop Clin North Am 1993;24:727. 10. Knight JL, Helming C. Collarless polished tapered impaction grafting of the femur during revision total hip arthroplasty: pitfalls of the surgical technique and follow-up in 31 cases. J Arthroplasty 2000;15:159. 11. Yates PJ, Burston BJ, Whitley E, et al. Collarless polished tapered stem: clinical and radiological results at a minimum of ten years' follow-up. J Bone Joint Surg Br 2008;90:16. 12. Paprosky WG, Lawrence WJ, Cameron H. Femoral defect classification: clinical application. Orthop Rev 1990(Suppl 19);9. 13. Callaghan JJ, Salvati EA, Pellicci PM, et al. Results of revision for mechanical failure after cemented total hip replacement, 1979 to 1982. A two to five-year follow-up. J Bone Joint Surg Am 1985;67:1074. 14. Mulroy WF, Harris WH. Revision total hip arthroplasty with use of so-called second-generation cementing techniques for aseptic loosening of the femoral component. A fifteenyear-average follow-up study. J Bone Joint Surg Am 1996; 78:325. 15. Kershaw CJ, Atkins RM, Dodd CA, et al. Revision total hip arthroplasty for aseptic failure. A review of 276 cases. J Bone Joint Surg Br 1991;73:564. 16. Estok II DM, Harris WH. Long-term results of cemented femoral revision surgery using second-generation techniques. An average 11.7-year follow-up evaluation. Clin Orthop Relat Res 1994;190. 17. Dohmae Y, Bechtold JE, Sherman RE, et al. Reduction in cement-bone interface shear strength between primary and revision arthroplasty. Clin Orthop Relat Res 1988;214. 18. Berry DJ, Harmsen WS, Ilstrup D, et al. Survivorship of uncemented proximally porous-coated femoral components. Clin Orthop Relat Res 1995;168.
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19. Mulliken BD, Rorabeck CH, Bourne RB. Uncemented revision total hip arthroplasty: a 4-to-6-year review. Clin Orthop Relat Res 1996;156. 20. Engh Jr CA, Young AM, Engh Sr CA, et al. Clinical consequences of stress shielding after porous-coated total hip arthroplasty. Clin Orthop Relat Res 2003;157. 21. Wagner H. Revision prosthesis for the hip joint in severe bone loss. Orthopade 1987;16:295. 22. Kolstad K, Adalberth G, Mallmin H, et al. The Wagner revision stem for severe osteolysis. 31 hips followed for 1.55 years. Acta Orthop Scand 1996;67:541. 23. Berry DJ. Femoral revision: distal fixation with fluted, tapered grit-blasted stems. J Arthroplasty 2002;17(4 Suppl 1):142. 24. Kwong LM, Miller AJ, Lubinus P. A modular distal fixation option for proximal bone loss in revision total hip arthroplasty: a 2- to 6-year follow-up study. J Arthroplasty 2003;18(3 Suppl 1):94. 25. Sporer SM, Paprosky WG. Femoral fixation in the face of considerable bone loss: the use of modular stems. Clin Orthop Relat Res 2004;227. 26. Murphy SB, Rodriguez J. Revision total hip arthroplasty with proximal bone loss. J Arthroplasty 2004;19(4 Suppl 1): 115. 27. McInnis DP, Horne G, Devane PA. Femoral revision with a fluted, tapered, modular stem seventy patients followed for a mean of 3.9 years. J Arthroplasty 2006;21:372. 28. Helm CS, Greenwald AS. The rationale and performance of modularity in total hip arthroplasty. Orthopedics 2005;28(9 Suppl):s1113. 29. Goldberg JR, Gilbert JL, Jacobs JJ, et al. A multicenter retrieval study of the taper interfaces of modular hip prostheses. Clin Orthop Relat Res 2002;149. 30. Sporer SM, DellaValle C, Jacobs J, et al. A case of disassociation of a modular femoral neck trunion after total hip arthroplasty. J Arthroplasty 2006;21:918. 31. Buttaro MA, Mayor MB, Van Citters D, et al. Fatigue fracture of a proximally modular, distally tapered fluted implant with diaphyseal fixation. J Arthroplasty 2007;22: 780. 32. Bobyn JD, Tanzer M, Krygier JJ, et al. Concerns with modularity in total hip arthroplasty. Clin Orthop Relat Res 1994;27.