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“Top-Out” Removal of Well-Fixed Dual-Taper Femoral Stems: Surgical Technique and Radiographic Risk Factors
The Journal of Arthroplasty xxx (2016) 1e7
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The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Original Article
“Top-Out” Removal of Well-Fixed Dual-Taper Femoral Stems: Surgical Technique and Radiographic Risk Factors Young-Min Kwon, MD, PhD *, Valentin Antoci Jr, MD, PhD, Eric Eisemon, MD, Tsung-Yuan Tsai, PhD, Yu Yan, MD, PhD, Ming Han Lincoln Liow, MD Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
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a b s t r a c t
Article history: Received 16 March 2016 Received in revised form 29 April 2016 Accepted 23 May 2016 Available online xxx
Background: Contemporary “dual-taper” modular femoral neck-stem designs have been associated with taper corrosionerelated adverse local tissue reaction (ALTR) requiring revision surgery and stem removal. Extended trochanteric osteotomy is recognized as the workhorse procedure for revision hip surgery. The aim of our study is to describe our “top-out” stem removal surgical technique and identify preoperative radiographic risk factors associated with periprosthetic fractures when using this technique. Methods: This is a single-center, single-surgeon, retrospective case series. Operative and clinic records were reviewed for patients with dual-taper modular femoral neck-stem junction who underwent revision surgery for taper tribocorrosionerelated ALTR. Results: Eighty-three patients (36 men and 47 women; mean age, 61.8 ± 10.3; body mass index, 30.2 ± 8.6) were revised using the top-out technique. Significant improvements in postoperative Harris hip score (P ¼ .004), EuroQol 5-dimension questionnaire (EQ-5D; P < .001), and EQ-5D US-adjusted scores (P < .001) were observed at 19-months follow-up. Our study reports periprosthetic fracture incidence of 14% and reoperation rate of 7%. Periprosthetic fractures were positively correlated with radiographic parameters such as overhang distance (R ¼ 0.376; P ¼ .002) and overhang ratio (R ¼ 0.312; P ¼ .01) and negatively correlated with radiographic implant medial calcar prominence (R ¼ 0.299; P ¼ .01). Conclusion: Removal of well-fixed femoral components can be challenging, and the burden of revision surgery for taper tribocorrosionerelated ALTR of these femoral stems is likely to rise. A top-out technique with systematic preoperative planning with radiographs provides a viable, alternative surgical option to remove well-fixed femoral component while preserving the femoral bony envelope. © 2016 Elsevier Inc. All rights reserved.
Keywords: top-out technique modular neck femoral stems revision total hip arthroplasty taper corrosion adverse local tissue reaction
Modularity in total hip arthroplasty (THA) allows for intraoperative optimization and restoration of patient anatomy [1]. Traditionally, modularity has existed at the head-neck junction of femoral implants. Newer dual-taper modular neck femoral THA implants have an additional modularity at the neck-stem junction. The additional modularity at the neck-stem junction has the potential to allow for easier adjustment of mechanical parameters
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.2016.05.046. * Reprint requests: Young-Min Kwon, MD, PhD, Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114. http://dx.doi.org/10.1016/j.arth.2016.05.046 0883-5403/© 2016 Elsevier Inc. All rights reserved.
including offset, version, and length, independent of femoral stem position [2]. However, the use of contemporary dual-taper modular neck femoral stems has led to mechanically assisted crevice corrosion, fretting, femoral neck fractures [3-6], elevated serum metal ion levels as well as the occurrence of adverse local tissue reaction (ALTR) [7-10]. This has led to the voluntary recall of 2 femoral stem designs from a manufacturer, with an increasing burden of revision surgery of these implants [7,11-15]. It is estimated that more than 30,000 patients have been implanted with these recalled modular neck stems. Revision surgery for dual-taper femoral stems in the setting of ALTR is a challenging endeavor that requires a systematic preoperative evaluation [16] and careful surgical planning for stem removal [17]. Removal of a well-fixed cementless femoral stem classically requires an extended trochanteric osteotomy (ETO) [18-20]. ETO has been used to extract well-fixed femoral stems in
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modular neck THA fractures [3-6]. Cooper et al [7] reported on 12 hips with ALTR secondary to taper corrosion at the modular neckstem junction who underwent revision surgery. All femoral components were well fixed and required explant. Nine hips were approached with an ETO and the 3 revisions attempted without ETO resulted in a proximal femoral fracture requiring additional surgery. ETO is an important tool in the armamentarium of the arthroplasty surgeon who performs revision hip surgery. Although widely recognized as the workhorse procedure for revision hip surgery, ETO requires extended incisions, risk of osteotomy nonunion, and protected postoperative weight bearing. In a series by Miner et al [19], the reoperation rate of ETO was 10.2%, with an average time to union of 12.8 weeks, 1.2% nonunion rate, and 10.8% nondisplaced fractures extending distally. More recent studies have also described 8.3%-23% intraoperative fracture rate when using ETO for revision THA [21]. In the case of well-fixed modular neck femoral stem revision for taper corrosioneassociated ALTR, removal of well-fixed femoral stems without an ETO provides the potential advantages, eliminating risks of delayed bony union and potentially reducing time to ambulatory rehabilitation. However, there is a paucity of literature on alternative revision THA techniques for modular neck-stem taper corrosion. The aim of our study is to (1) describe our topout stem removal surgical technique without the need for an ETO; (2) report complication rates; and (3) identify preoperative radiographic risk factors associated with periprosthetic fractures when using the top-out technique in patients with well-fixed dual-taper femoral stem THA. Materials and Methods Patients This is a retrospective, single-surgeon case series reporting on patients requiring revision surgery for modular femoral neck-stem corrosion secondary to ALTR at a tertiary referral center. Institutional review board approval was obtained. A total of 83 consecutive patients with modular neck-stem THA taper corrosion associated with ALTR underwent revision surgery from April 2013 to February 2014. Indications for revision THA included elevated cobalt and chromium serum metal ion levels in symptomatic patients with dual-taper modular neck stems with the presence of adverse tissue reaction on cross-sectional imaging. Mean time from index surgery to revision surgery was 31.3 ± 12.8 months. In 25 cases, the acetabular components were assessed to be loose intraoperatively and were revised with a highly porous tantalum acetabular cup (Trabecular Metal Modular Acetabular cup; Zimmer Inc, Warsaw, IN). In the presence of reactive tissue necrosis, the area of necrosis was extensively debrided except in the close proximity of neurovascular structures. Patients received revision titanium modular tapered femoral stems (Stryker, Mahwah, NJ) to optimize intraoperative stability in the setting of taper corrosionerelated periprosthetic tissue necrosis. All patients received ceramic on highly crosslinked polyethylene articulations. Our mean patient follow-up time was 19.3 ± 7.7 months after the revision surgery (Table 1). Preoperative and postoperative Harris hip score (HHS), EuroQol 5dimension questionnaire (EQ-5D), and University of California, Los Angeles (UCLA) activity scores were recorded (Table 2). Top-Out Femoral Stem Removal Technique Lateral decubitus patient positioning was used for all revision surgery. To allow for maximum femoral exposure, the patient is positioned toward the anterior edge of the operating table, which
Table 1 Patient Demographics. Variable Gender Male Female Age (y; mean ± SD) BMI (kg/m2; mean ± SD) Revision surgery operative duration (mo; mean ± SD) Operative duration (min; mean ± SD) Mean preoperative metal ion levels Cobalt (ug/L) Chromium (ug/L) Type of modular femoral stem implant ABG/ABGII modular anatomic reconstruction Rejuvenate total hip system Profemur Plasma Z Profemur Renaissance Type of revision implant Restoration modular system Wagner cone prosthesis Mean stem diameter (mm) Mean head size (mm)
36 (43%) 47 (57%) 61.8 ± 10.3 30.2 ± 8.6 31.3 ± 12.8 135 ± 22 4.5 ± 3.4 1.8 ± 7.6 46 (56%) 35 (42%) 1 (1%) 1 (1%) 80 (96%) 3 (4%) 16.0 ± 1.8 33 ± 5.0
SD, standard deviation; BMI, body mass index.
allows the operative leg to be fully flexed and adducted beyond the edge of the operating table. A standard posterolateral approach is preferred due to its extensile nature. The extent of ALTR is determined, and any necrotic tissue is removed to the extent of the safe anatomic margins, without compromising juxtaposed neurovascular structures. Four working quadrants are delineated, including the anterior and posterior flat margins around the stem, as well as the lateral along the greater trochanter and medial under the calcar (Fig. 1). The degree of trochanteric overhang is determined and any extra bone removed. A pineapple-shaped burr (Medtronic, Las Vegas, NV) is helpful by providing stepwise controlled access without splintering or torqueing the bone fragments. Any bony overgrowth or osteophytes around all 4 quadrants should be removed and cleared. Once all quadrants have been visualized and the implant-bone interface is cleared of any soft tissue, the junction is clearly visualized for removal of the modular neck and subsequent removal of the stem can be attempted. Most systems have a implant-specific removal device that slides around the modular neck and allows for disengagement of the modular neck component from stem. In the absence of such device, a pair of pliers or vice grips can be used to grab onto the neck and tamp it out with a mallet. Once removed, the extent of visible corrosion should be carefully documented. A top-out technique involves using a pencil-tipped burr (Medtronic, Las Vegas, NV) to disrupt the bone and implant interface. Cortical thickness and the proximal geometry of the implant are critical as it directs the orientation of the burr. The pencil-tipped burr is carefully introduced into the bone-implant interface paralleling the implant. To preserve maximum amount of bone in cases of eccentrically positioned implants with minimum space between Table 2 Preoperative and Postoperative Functional Outcome Scores. Functional Score
Preoperative
HHS (mean ± SD) EQ-5D (mean ± SD) EQ-5D US adjusted (mean ± SD) UCLA (mean ± SD)
69.1 53.7 66.8 5.1
± ± ± ±
19.4 29.4 19.0 2.1
Postoperative 76.9 69.8 77.6 5.4
± ± ± ±
19.3 26.3 17.8 1.9
P Value .004 <.001 <.001 .28 (n.s.)
HHS, Harris hip score; EQ-5D, EuroQol 5-dimension questionnaire; UCLA, University of California, Los Angeles; SD, standard deviation; n.s., not significant.
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Fig. 1. Four working quadrants are delineated. (A) Anterior and (P) posterior flat margins around the stem, (L) lateral along medial aspect of greater trochanter, and (M) medial under the calcar.
the cortex and material, the burr is directed toward the implant side of the implant-bone interface to remove any ongrowth. Preoperative lateral view radiographs allow identification of noncentered stems and provide information regarding the available working space for the pencil-tip burr along the anterior and posterior cortex. Once all quadrants around the proximal femoral stem-bone interfaces have been freed, a modular neck-stem extractor is used to engage the female bore of the stem taper, and the implant is gently backslapped. Manufacturers have implant-specific extraction devices. If the implant is not easily removed, further work should be carried out to clear any further ongrowth areas. Persistent attempts at forcefully backslapping the implant may result in femoral fractures. Once the stem is removed, the proximal femur, femoral canal, greater trochanter, and cortical integrity should be inspected for the presence of fracture, excessive thinning, or cortical defects. Any defects should be bypassed appropriately by a distal diaphysis engaging stem. During reimplantation of the revision femoral component, care must be used to avoid aggressive retraction of the weakened proximal femur.
posterior cortex distance to implant (E), and (3) eccentricity ratio (D/E; Fig. 6). The interobserver reliability was 0.85, 0.84, 0.79, 0.82, and 0.80 for measurements of A, B, C, D, and E, respectively. In addition, presence of osteolysis in preoperative radiographs was recorded. Postoperative films were used to evaluate fracture and subsidence.
Postoperative Regime Maintaining the integrity of the cortex and preserving the greater trochanter allow for early mobilization and ambulation. Patients can start physical therapy on their first postoperative day. Partial weight bearing is usually used to protect a revision reconstruction femoral stem and allow bone integration. There are no trochanteric precautions, and abduction orthoses are not used. Radiographic Parameters To identify potential radiographic risk factors associated with intraoperative fractures with top-out technique, preoperative anteroposterior radiographs were reviewed for the following parameters: (1) overhang distance (A), (2) distance from lateral edge of implant to lateral edge of greater trochanter (B), (3) overhang ratio (A/B), and (4) implant medial calcar prominence (C; Figs. 2-5). Lateral radiographs were reviewed for the following parameters: (1) anterior cortex distance to implant (D), (2)
Fig. 2. Overhang distancedgreater trochanteric overhang distance measured from lateral edge of implant to medial bone-implant interface (A).
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Fig. 3. Distance from lateral edge of implant to lateral edge of greater trochanter (B).
Statistical Analysis Spearman rank correlation was performed to determine the relationship between periprosthetic fracture rates and age, gender, body mass index (BMI), metal ion levels, presence of osteolysis on radiographs, index THA stem type, revision stem size, time to revision, presence of intraoperative adverse tissue necrosis, radiological parameters (A to E, A/B ratio, and D/E ratio), and patientreported outcomes (EQ-5D, HHS, and UCLA scores). Student's unpaired t test was used to compare all recorded variables between patients with and without periprosthetic fractures. All the statistical analyses were performed using SPSS version 22 software (SPSS Inc, Chicago, IL).
Fig. 4. Overhang ratio (A/B).
operating room for trochanteric stabilization with plates and cerclage wires. The remaining 6 patients with nondisplaced trochanteric fractures (5 greater trochanter, 1 lesser trochanter) recognized on postoperative radiographs were treated conservatively (Fig. 8). Two patients with periprosthetic infection underwent staged revisions. One patient with suspected acetabular component loosening was managed conservatively as the radiolucency around the acetabular implant remained stable during serial radiographs. There were significant improvements in postoperative HHS (P ¼ .004), EQ-5D (P < .001), and EQ-5D US-adjusted scores (P < .001). Postoperative UCLA scores were not significantly different (P ¼ .28; Table 2). Radiographic Parameters Associated With Periprosthetic Fracture
Results Complication Rate There was an overall complication rate of 21% with periprosthetic fracture incidence of 14% and a reoperation rate of 7%. A total of 12 periprosthetic fractures (10 greater trochanter, 2 lesser trochanter), 3 cases of recurrent dislocation, 2 cases of periprosthetic infection, and 1 case of acetabular component loosening were observed in our study. Six patients had intraoperative greater trochanteric fractures and were treated with trochanteric stabilization plates and cables (Fig. 7). Five of 6 patients had a greater trochanteric fracture that was identified intraoperatively which required trochanteric stabilization surgery during the surgery. One patient was observed to have a displaced greater trochanteric fracture 2 weeks postoperatively and was taken back to the
Periprosthetic fractures were positively correlated with overhang distance (A) (R ¼ 0.376; P ¼ .002) and positively correlated with overhang ratio (A/B) (R ¼ 0.312; P ¼ .01), suggesting a greater degree of trochanteric overhang resulted in higher risk of periprosthetic fracture. Periprosthetic fractures were also negatively correlated with implant medial calcar prominence (R ¼ 0.299; P ¼ .01), suggesting a greater implant medial calcar prominence resulted in reduced periprosthetic fracture risk, likely due to the relative easy access to the neck-stem modular junction during implant removal. Size of the revision stem was also positively correlated with overhang distance (A) (R ¼ 0.315; P ¼ .02) and the distance from lateral edge of implant to lateral edge of greater trochanter (B) (R ¼ 0.29; P ¼ .03), suggesting that increased burring and bone removal were required for patients with increased trochanteric overhang. Male gender was positively correlated with
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(R ¼ 0.128), stem size (R ¼ 0.16), and postoperative EQ-5D (R ¼ 0.05), HHS (R ¼ 0.14), and UCLA (R ¼ 0.14). Of the 12 periprosthetic fractures, 6 occurred in Rejuvenate stems and 6 occurred in ABG/ABGII stems, indicating no association with implant type. Nine of the fractures occurred during the first 40 operations, with 3 occurring in subsequent 43 cases. Discussion
Fig. 5. Implant medial calcar prominence (C).
the distance from lateral edge of implant to lateral edge of greater trochanter (B) (R ¼ 0.321; P ¼ .01), anterior cortex distance to implant (D) (R ¼ 0.266; P ¼ .04), and posterior cortex distance to implant (E) (R ¼ 0.356; P ¼ .004). This finding suggests that men were found to have larger bones, resulting in a positive correlation with our measurements of B, D, and E. There was no correlation between the incidence of periprosthetic fractures and age (R ¼ 0.06), gender (R ¼ 0.08), BMI (R ¼ 0.22), preoperative Co (R ¼ 0.176), Cr (R ¼ 0.08) metal ion levels, presence of osteolysis (R ¼ 0.10), type of index THA stem
Fig. 6. Anterior cortex distance to implant (D), posterior cortex distance to implant (E), and eccentricity ratio (D/E).
We report a top-out technique without the use of ETO in revision hip surgery for removal of well-fixed modular neck-stem THA in patients with taper corrosion associated with ALTR. Several studies have described taper corrosion and ALTR in modular neck femoral stems; however, there has been no detailed description of the surgical technique employed during revision surgery [11-14]. Walsh et al [15] reported usage of ETO in 43.7% of cases, with others removed using a simple osteotome technique, burr, or stacked pin technique. Barlow et al [22] used their surgical technique with the use of a Midas Rex burr. However, as the aim of the study was to examine metal ion trends after revision, no detailed description of the surgical technique employed during revision surgery was provided. Our study demonstrated periprosthetic fracture incidence of 14% and a reoperation rate of 7%. This is comparable to published complication rates for ETO [19,23,24]. Drexler et al [23] show 1 intraoperative fracture extension distally after an ETO and an overall 15% complication postoperatively after revision of 34 stems. The original description of an ETO by Younger et al [18] had no reports of complications related to the osteotomy in a review of 20 patients. In contrast, Miner et al [19], in a review of 192 revision hips with ETO, report a reoperation rate of 10.2% with an overall complication rate of 24%. In contrast, our top-out technique avoided bony union complications related to the ETO technique. Interestingly, a reduction of periprosthetic fractures over time in our cohort was observed, with most (75%) of the periprosthetic fractures occurring during the first 40 cases of using this technique. This indicates that a learning curve is associated with this technique. We have identified radiographic risk factors associated with the fractures in our series. Although periprosthetic fracture complication rate was not correlated with age (R ¼ 0.04), gender (R ¼ 0.05), BMI (R ¼ 0.09), stem size (R ¼ 0.06) or implant type, femoral trochanteric overhang ratio (A/B), implant medial calcar prominence (C), and the eccentricity ratio (D/E) are important preoperative factors to consider before considering this technique. A larger overhang ratio (A/B) was positively correlated with periprosthetic fracture rate. Iatrogenic creation of large metaphyseal defects by over-burring is a common pitfall of this technique. Greater trochanteric fractures can be caused by high torque forces from burring or excessive cortex thinning during attempts to bypass the implant shoulder. To avoid this, any trochanteric overhang should be carefully eliminated to allow a collinear direction of burr placement with the lateral border of the stem. In addition, the risk of greater trochanteric fractures may be minimized by measuring the length of the lateral implant shoulder and matching it with the depth of the burring. An implant with medial calcar subsidence (C) may also result in limited medial calcar working space during burring, and care should be taken to minimize medial cortical breech. These findings correspond with the positive correlation observed between the size of the revision stem and overhang distance (A) (R ¼ 0.315; P ¼ .02) and distance from lateral edge of implant to lateral edge of greater trochanter (B) (R ¼ 0.321; P ¼ .01), which suggest that greater trochanteric overhang would require additional burring and clearance, resulting in a larger revision stem. Although the eccentricity ratio (D/E) was not correlated with periprosthetic fractures, in our experience,
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Fig. 7. Intraoperative periprosthetic greater trochanteric fracture (white arrow visible on intraoperative radiograph) treated with trochanteric stabilization plate and cerclage wires. White arrow indicates displaced greater trochanteric fracture.
eccentric alignment is associated with higher degree of iatrogenic burreassociated cortical penetration, fractures, and bone defects, and surgeons using this technique should be mindful regarding the femoral stem's position in sagittal plane with the femoral shaft. A top-out technique provides the surgeon an option to proceed with ETO with minimum additional risk if an attempt with top-out technique becomes prolonged or unsafe due to anatomy, stem design, or other technical considerations. The use of an ETO instead of the top-out technique should be considered in patients at high risk for periprosthetic fractures with increased overhang ratio (A/B) and increased implant subsidence (C). Preoperative planning with anteroposterior and lateral view radiographs is important in identification of trochanteric overhang and noncentered stems, providing information regarding the available working space for
the pencil-tip burr around the greater trochanter as well as anterior and posterior cortex. Risk areas including acute angle changes in stem geometry and close adherence of the implant stem with cortex can be highlighted. Although implant removal with shorter operative time has been reported for ETO [18,25,26], longer incisions are required for exposure of the ETO and the revision stem has to bypass the fracture site, often requiring longer and bowed stems. In addition, the osteotomy requires reduction and fixation as well as postoperative protection to allow for bone healing. Alternative techniques to the ETO [27,28] can be added to the repertoire of a revision surgeon as ETO may not be necessary in all cases. Our study should be interpreted in light of its potential limitations. Firstly, this is a single-surgeon and single-institution study and retrospective in nature. There is no ETO control group to
Fig. 8. Nondisplaced lesser and greater trochanteric fractures on postoperative radiograph managed non-operatively (white arrow indicates nondisplaced fractures).
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compare functional outcomes or complication rates in patients who have undergone revision THA for ALTR-associated taper corrosion. However, the use of ETO in extracting well-fixed femoral stems in modular neck THA with ALTR secondary to taper corrosion at the modular neck-stem junction has been previously reported. Secondly, there was lack of a statistically significant correlation between the eccentricity ratio (D/E) and periprosthetic fractures. This may also be due to the variation in radiographic rotation. In conclusion, removal of well-fixed femoral dual-taper components remains a surgical challenge, and the burden of revision surgery for taper corrosionerelated ALTR of these femoral stems is likely to rise. A top-out technique with systematic preoperative planning with radiographs adds to the armamentarium of a revision surgeon as a viable, alternative option to ETO for the safe removal of well-fixed femoral component while preserving the femoral bony envelope. References 1. Bobyn JD, Tanzer M, Krygier JJ, et al. Concerns with modularity in total hip arthroplasty. Clin Orthop Relat Res 1994;(298):27. 2. Duwelius PJ, Hartzband MA, Burkhart R, et al. Clinical results of a modular neck hip system: hitting the “bull's-eye” more accurately. Am J Orthop (Belle Mead NJ) 2010;39(10 Suppl):2. 3. Hernandez A, Gargallo-Margarit A, Barro V, et al. Fracture of the modular neck in total hip arthroplasty. Case Rep Orthop 2015;2015:591509. 4. Ellman MB, Levine BR. Fracture of the modular femoral neck component in total hip arthroplasty. J Arthroplasty 2013;28(1):196.e1. 5. Skendzel JG, Blaha JD, Urquhart AG. Total hip arthroplasty modular neck failure. J Arthroplasty 2011;26(2):338.e1. 6. Messana J, Adelani M, Goodman SB. Case report: pseudotumor associated with corrosion of a femoral component with a modular neck and a ceramic-onpolyethylene bearing. J Long Term Eff Med Implants 2014;24(1):1. 7. Cooper HJ, Urban RM, Wixson RL, et al. Adverse local tissue reaction arising from corrosion at the femoral neck-body junction in a dual-taper stem with a cobalt-chromium modular neck. J Bone Joint Surg Am 2013;95(10):865. 8. Kop AM, Keogh C, Swarts E. Proximal component modularity in THAeat what cost? An implant retrieval study. Clin Orthop Relat Res 2012;470(7):1885. 9. Kop AM, Swarts E. Corrosion of a hip stem with a modular neck taper junction: a retrieval study of 16 cases. J Arthroplasty 2009;24(7):1019. 10. Walsh CP, Hubbard JC, Nessler JP, et al. MRI findings associated with recalled modular femoral neck Rejuvenate and ABG implants. J Arthroplasty 2015;30(11):2021.
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11. Ghanem E, Ward DM, Robbins CE, et al. Corrosion and adverse local tissue reaction in one type of modular neck stem. J Arthroplasty 2015;30(10): 1787. 12. Restrepo C, Ross D, Restrepo S, et al. Adverse clinical outcomes in a primary modular neck/stem system. J Arthroplasty 2014;29(9 Suppl):173. 13. Molloy DO, Munir S, Jack CM, et al. Fretting and corrosion in modular-neck total hip arthroplasty femoral stems. J Bone Joint Surg Am 2014;96(6):488. 14. Meftah M, Haleem AM, Burn MB, et al. Early corrosion-related failure of the rejuvenate modular total hip replacement. J Bone Joint Surg Am 2014;96(6):481. 15. Walsh CP, Hubbard JC, Nessler JP, et al. Revision of recalled modular neck Rejuvenate and ABG femoral implants. J Arthroplasty 2015;30(5):822. 16. Kwon YM, Fehring TK, Lombardi AV, et al. Risk stratification algorithm for management of patients with dual modular taper total hip arthroplasty: consensus statement of the American Association of Hip and Knee Surgeons, the American Academy of Orthopaedic Surgeons and the Hip Society. J Arthroplasty 2014;29(11):2060. 17. Dimitriou D, Liow MH, Tsai TY, et al. Early outcomes of revision surgery for taper corrosion of dual taper total hip arthroplasty in 187 patients. J Arthroplasty 2016;31(7):1549. 18. Younger TI, Bradford MS, Magnus RE, et al. Extended proximal femoral osteotomy. A new technique for femoral revision arthroplasty. J Arthroplasty 1995;10(3):329. 19. Miner TM, Momberger NG, Chong D, et al. The extended trochanteric osteotomy in revision hip arthroplasty: a critical review of 166 cases at mean 3-year, 9-month follow-up. J Arthroplasty 2001;16(8 Suppl 1):188. 20. Paprosky WG, Weeden SH, Bowling Jr JW. Component removal in revision total hip arthroplasty. Clin Orthop Relat Res 2001;(393):181. 21. Levine BR, Della Valle CJ, Hamming M, et al. Use of the extended trochanteric osteotomy in treating prosthetic hip infection. J Arthroplasty 2009;24(1):49. 22. Barlow BT, Assini J, Boles J, et al. Short-term metal ion trends following removal of recalled modular neck femoral stems. J Arthroplasty 2015;30(7):1191. 23. Drexler M, Dwyer T, Chakravertty R, et al. The outcome of modified extended trochanteric osteotomy in revision THA for Vancouver B2/B3 periprosthetic fractures of the femur. J Arthroplasty 2014;29(8):1598. 24. Lakstein D, Kosashvili Y, Backstein D, et al. The long modified extended sliding trochanteric osteotomy. Int Orthop 2011;35(1):13. 25. Pemmaraju GM, Killampalli VV. Extended proximal femoral osteotomy: technical tip. Eur J Orthop Surg Traumatol 2015;25(6):1111. 26. Chen WM, McAuley JP, Engh Jr CA, et al. Extended slide trochanteric osteotomy for revision total hip arthroplasty. J Bone Joint Surg Am 2000;82(9):1215. 27. Kim YM, Lim ST, Yoo JJ, et al. Removal of a well-fixed cementless femoral stem using a microsagittal saw. J Arthroplasty 2003;18(4):511. 28. Jack CM, Molloy DO, Esposito C, et al. Limited slot femorotomy for removal of proximally coated cementless stems. A 10-year follow-up of an unreported surgical technique. J Arthroplasty 2013;28(6):1000.
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The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Original Article
“Top-Out” Removal of Well-Fixed Dual-Taper Femoral Stems: Surgical Technique and Radiographic Risk Factors Young-Min Kwon, MD, PhD *, Valentin Antoci Jr, MD, PhD, Eric Eisemon, MD, Tsung-Yuan Tsai, PhD, Yu Yan, MD, PhD, Ming Han Lincoln Liow, MD Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
a r t i c l e i n f o
a b s t r a c t
Article history: Received 16 March 2016 Received in revised form 29 April 2016 Accepted 23 May 2016 Available online xxx
Background: Contemporary “dual-taper” modular femoral neck-stem designs have been associated with taper corrosionerelated adverse local tissue reaction (ALTR) requiring revision surgery and stem removal. Extended trochanteric osteotomy is recognized as the workhorse procedure for revision hip surgery. The aim of our study is to describe our “top-out” stem removal surgical technique and identify preoperative radiographic risk factors associated with periprosthetic fractures when using this technique. Methods: This is a single-center, single-surgeon, retrospective case series. Operative and clinic records were reviewed for patients with dual-taper modular femoral neck-stem junction who underwent revision surgery for taper tribocorrosionerelated ALTR. Results: Eighty-three patients (36 men and 47 women; mean age, 61.8 ± 10.3; body mass index, 30.2 ± 8.6) were revised using the top-out technique. Significant improvements in postoperative Harris hip score (P ¼ .004), EuroQol 5-dimension questionnaire (EQ-5D; P < .001), and EQ-5D US-adjusted scores (P < .001) were observed at 19-months follow-up. Our study reports periprosthetic fracture incidence of 14% and reoperation rate of 7%. Periprosthetic fractures were positively correlated with radiographic parameters such as overhang distance (R ¼ 0.376; P ¼ .002) and overhang ratio (R ¼ 0.312; P ¼ .01) and negatively correlated with radiographic implant medial calcar prominence (R ¼ 0.299; P ¼ .01). Conclusion: Removal of well-fixed femoral components can be challenging, and the burden of revision surgery for taper tribocorrosionerelated ALTR of these femoral stems is likely to rise. A top-out technique with systematic preoperative planning with radiographs provides a viable, alternative surgical option to remove well-fixed femoral component while preserving the femoral bony envelope. © 2016 Elsevier Inc. All rights reserved.
Keywords: top-out technique modular neck femoral stems revision total hip arthroplasty taper corrosion adverse local tissue reaction
Modularity in total hip arthroplasty (THA) allows for intraoperative optimization and restoration of patient anatomy [1]. Traditionally, modularity has existed at the head-neck junction of femoral implants. Newer dual-taper modular neck femoral THA implants have an additional modularity at the neck-stem junction. The additional modularity at the neck-stem junction has the potential to allow for easier adjustment of mechanical parameters
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.2016.05.046. * Reprint requests: Young-Min Kwon, MD, PhD, Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114. http://dx.doi.org/10.1016/j.arth.2016.05.046 0883-5403/© 2016 Elsevier Inc. All rights reserved.
including offset, version, and length, independent of femoral stem position [2]. However, the use of contemporary dual-taper modular neck femoral stems has led to mechanically assisted crevice corrosion, fretting, femoral neck fractures [3-6], elevated serum metal ion levels as well as the occurrence of adverse local tissue reaction (ALTR) [7-10]. This has led to the voluntary recall of 2 femoral stem designs from a manufacturer, with an increasing burden of revision surgery of these implants [7,11-15]. It is estimated that more than 30,000 patients have been implanted with these recalled modular neck stems. Revision surgery for dual-taper femoral stems in the setting of ALTR is a challenging endeavor that requires a systematic preoperative evaluation [16] and careful surgical planning for stem removal [17]. Removal of a well-fixed cementless femoral stem classically requires an extended trochanteric osteotomy (ETO) [18-20]. ETO has been used to extract well-fixed femoral stems in
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modular neck THA fractures [3-6]. Cooper et al [7] reported on 12 hips with ALTR secondary to taper corrosion at the modular neckstem junction who underwent revision surgery. All femoral components were well fixed and required explant. Nine hips were approached with an ETO and the 3 revisions attempted without ETO resulted in a proximal femoral fracture requiring additional surgery. ETO is an important tool in the armamentarium of the arthroplasty surgeon who performs revision hip surgery. Although widely recognized as the workhorse procedure for revision hip surgery, ETO requires extended incisions, risk of osteotomy nonunion, and protected postoperative weight bearing. In a series by Miner et al [19], the reoperation rate of ETO was 10.2%, with an average time to union of 12.8 weeks, 1.2% nonunion rate, and 10.8% nondisplaced fractures extending distally. More recent studies have also described 8.3%-23% intraoperative fracture rate when using ETO for revision THA [21]. In the case of well-fixed modular neck femoral stem revision for taper corrosioneassociated ALTR, removal of well-fixed femoral stems without an ETO provides the potential advantages, eliminating risks of delayed bony union and potentially reducing time to ambulatory rehabilitation. However, there is a paucity of literature on alternative revision THA techniques for modular neck-stem taper corrosion. The aim of our study is to (1) describe our topout stem removal surgical technique without the need for an ETO; (2) report complication rates; and (3) identify preoperative radiographic risk factors associated with periprosthetic fractures when using the top-out technique in patients with well-fixed dual-taper femoral stem THA. Materials and Methods Patients This is a retrospective, single-surgeon case series reporting on patients requiring revision surgery for modular femoral neck-stem corrosion secondary to ALTR at a tertiary referral center. Institutional review board approval was obtained. A total of 83 consecutive patients with modular neck-stem THA taper corrosion associated with ALTR underwent revision surgery from April 2013 to February 2014. Indications for revision THA included elevated cobalt and chromium serum metal ion levels in symptomatic patients with dual-taper modular neck stems with the presence of adverse tissue reaction on cross-sectional imaging. Mean time from index surgery to revision surgery was 31.3 ± 12.8 months. In 25 cases, the acetabular components were assessed to be loose intraoperatively and were revised with a highly porous tantalum acetabular cup (Trabecular Metal Modular Acetabular cup; Zimmer Inc, Warsaw, IN). In the presence of reactive tissue necrosis, the area of necrosis was extensively debrided except in the close proximity of neurovascular structures. Patients received revision titanium modular tapered femoral stems (Stryker, Mahwah, NJ) to optimize intraoperative stability in the setting of taper corrosionerelated periprosthetic tissue necrosis. All patients received ceramic on highly crosslinked polyethylene articulations. Our mean patient follow-up time was 19.3 ± 7.7 months after the revision surgery (Table 1). Preoperative and postoperative Harris hip score (HHS), EuroQol 5dimension questionnaire (EQ-5D), and University of California, Los Angeles (UCLA) activity scores were recorded (Table 2). Top-Out Femoral Stem Removal Technique Lateral decubitus patient positioning was used for all revision surgery. To allow for maximum femoral exposure, the patient is positioned toward the anterior edge of the operating table, which
Table 1 Patient Demographics. Variable Gender Male Female Age (y; mean ± SD) BMI (kg/m2; mean ± SD) Revision surgery operative duration (mo; mean ± SD) Operative duration (min; mean ± SD) Mean preoperative metal ion levels Cobalt (ug/L) Chromium (ug/L) Type of modular femoral stem implant ABG/ABGII modular anatomic reconstruction Rejuvenate total hip system Profemur Plasma Z Profemur Renaissance Type of revision implant Restoration modular system Wagner cone prosthesis Mean stem diameter (mm) Mean head size (mm)
36 (43%) 47 (57%) 61.8 ± 10.3 30.2 ± 8.6 31.3 ± 12.8 135 ± 22 4.5 ± 3.4 1.8 ± 7.6 46 (56%) 35 (42%) 1 (1%) 1 (1%) 80 (96%) 3 (4%) 16.0 ± 1.8 33 ± 5.0
SD, standard deviation; BMI, body mass index.
allows the operative leg to be fully flexed and adducted beyond the edge of the operating table. A standard posterolateral approach is preferred due to its extensile nature. The extent of ALTR is determined, and any necrotic tissue is removed to the extent of the safe anatomic margins, without compromising juxtaposed neurovascular structures. Four working quadrants are delineated, including the anterior and posterior flat margins around the stem, as well as the lateral along the greater trochanter and medial under the calcar (Fig. 1). The degree of trochanteric overhang is determined and any extra bone removed. A pineapple-shaped burr (Medtronic, Las Vegas, NV) is helpful by providing stepwise controlled access without splintering or torqueing the bone fragments. Any bony overgrowth or osteophytes around all 4 quadrants should be removed and cleared. Once all quadrants have been visualized and the implant-bone interface is cleared of any soft tissue, the junction is clearly visualized for removal of the modular neck and subsequent removal of the stem can be attempted. Most systems have a implant-specific removal device that slides around the modular neck and allows for disengagement of the modular neck component from stem. In the absence of such device, a pair of pliers or vice grips can be used to grab onto the neck and tamp it out with a mallet. Once removed, the extent of visible corrosion should be carefully documented. A top-out technique involves using a pencil-tipped burr (Medtronic, Las Vegas, NV) to disrupt the bone and implant interface. Cortical thickness and the proximal geometry of the implant are critical as it directs the orientation of the burr. The pencil-tipped burr is carefully introduced into the bone-implant interface paralleling the implant. To preserve maximum amount of bone in cases of eccentrically positioned implants with minimum space between Table 2 Preoperative and Postoperative Functional Outcome Scores. Functional Score
Preoperative
HHS (mean ± SD) EQ-5D (mean ± SD) EQ-5D US adjusted (mean ± SD) UCLA (mean ± SD)
69.1 53.7 66.8 5.1
± ± ± ±
19.4 29.4 19.0 2.1
Postoperative 76.9 69.8 77.6 5.4
± ± ± ±
19.3 26.3 17.8 1.9
P Value .004 <.001 <.001 .28 (n.s.)
HHS, Harris hip score; EQ-5D, EuroQol 5-dimension questionnaire; UCLA, University of California, Los Angeles; SD, standard deviation; n.s., not significant.
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Fig. 1. Four working quadrants are delineated. (A) Anterior and (P) posterior flat margins around the stem, (L) lateral along medial aspect of greater trochanter, and (M) medial under the calcar.
the cortex and material, the burr is directed toward the implant side of the implant-bone interface to remove any ongrowth. Preoperative lateral view radiographs allow identification of noncentered stems and provide information regarding the available working space for the pencil-tip burr along the anterior and posterior cortex. Once all quadrants around the proximal femoral stem-bone interfaces have been freed, a modular neck-stem extractor is used to engage the female bore of the stem taper, and the implant is gently backslapped. Manufacturers have implant-specific extraction devices. If the implant is not easily removed, further work should be carried out to clear any further ongrowth areas. Persistent attempts at forcefully backslapping the implant may result in femoral fractures. Once the stem is removed, the proximal femur, femoral canal, greater trochanter, and cortical integrity should be inspected for the presence of fracture, excessive thinning, or cortical defects. Any defects should be bypassed appropriately by a distal diaphysis engaging stem. During reimplantation of the revision femoral component, care must be used to avoid aggressive retraction of the weakened proximal femur.
posterior cortex distance to implant (E), and (3) eccentricity ratio (D/E; Fig. 6). The interobserver reliability was 0.85, 0.84, 0.79, 0.82, and 0.80 for measurements of A, B, C, D, and E, respectively. In addition, presence of osteolysis in preoperative radiographs was recorded. Postoperative films were used to evaluate fracture and subsidence.
Postoperative Regime Maintaining the integrity of the cortex and preserving the greater trochanter allow for early mobilization and ambulation. Patients can start physical therapy on their first postoperative day. Partial weight bearing is usually used to protect a revision reconstruction femoral stem and allow bone integration. There are no trochanteric precautions, and abduction orthoses are not used. Radiographic Parameters To identify potential radiographic risk factors associated with intraoperative fractures with top-out technique, preoperative anteroposterior radiographs were reviewed for the following parameters: (1) overhang distance (A), (2) distance from lateral edge of implant to lateral edge of greater trochanter (B), (3) overhang ratio (A/B), and (4) implant medial calcar prominence (C; Figs. 2-5). Lateral radiographs were reviewed for the following parameters: (1) anterior cortex distance to implant (D), (2)
Fig. 2. Overhang distancedgreater trochanteric overhang distance measured from lateral edge of implant to medial bone-implant interface (A).
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Fig. 3. Distance from lateral edge of implant to lateral edge of greater trochanter (B).
Statistical Analysis Spearman rank correlation was performed to determine the relationship between periprosthetic fracture rates and age, gender, body mass index (BMI), metal ion levels, presence of osteolysis on radiographs, index THA stem type, revision stem size, time to revision, presence of intraoperative adverse tissue necrosis, radiological parameters (A to E, A/B ratio, and D/E ratio), and patientreported outcomes (EQ-5D, HHS, and UCLA scores). Student's unpaired t test was used to compare all recorded variables between patients with and without periprosthetic fractures. All the statistical analyses were performed using SPSS version 22 software (SPSS Inc, Chicago, IL).
Fig. 4. Overhang ratio (A/B).
operating room for trochanteric stabilization with plates and cerclage wires. The remaining 6 patients with nondisplaced trochanteric fractures (5 greater trochanter, 1 lesser trochanter) recognized on postoperative radiographs were treated conservatively (Fig. 8). Two patients with periprosthetic infection underwent staged revisions. One patient with suspected acetabular component loosening was managed conservatively as the radiolucency around the acetabular implant remained stable during serial radiographs. There were significant improvements in postoperative HHS (P ¼ .004), EQ-5D (P < .001), and EQ-5D US-adjusted scores (P < .001). Postoperative UCLA scores were not significantly different (P ¼ .28; Table 2). Radiographic Parameters Associated With Periprosthetic Fracture
Results Complication Rate There was an overall complication rate of 21% with periprosthetic fracture incidence of 14% and a reoperation rate of 7%. A total of 12 periprosthetic fractures (10 greater trochanter, 2 lesser trochanter), 3 cases of recurrent dislocation, 2 cases of periprosthetic infection, and 1 case of acetabular component loosening were observed in our study. Six patients had intraoperative greater trochanteric fractures and were treated with trochanteric stabilization plates and cables (Fig. 7). Five of 6 patients had a greater trochanteric fracture that was identified intraoperatively which required trochanteric stabilization surgery during the surgery. One patient was observed to have a displaced greater trochanteric fracture 2 weeks postoperatively and was taken back to the
Periprosthetic fractures were positively correlated with overhang distance (A) (R ¼ 0.376; P ¼ .002) and positively correlated with overhang ratio (A/B) (R ¼ 0.312; P ¼ .01), suggesting a greater degree of trochanteric overhang resulted in higher risk of periprosthetic fracture. Periprosthetic fractures were also negatively correlated with implant medial calcar prominence (R ¼ 0.299; P ¼ .01), suggesting a greater implant medial calcar prominence resulted in reduced periprosthetic fracture risk, likely due to the relative easy access to the neck-stem modular junction during implant removal. Size of the revision stem was also positively correlated with overhang distance (A) (R ¼ 0.315; P ¼ .02) and the distance from lateral edge of implant to lateral edge of greater trochanter (B) (R ¼ 0.29; P ¼ .03), suggesting that increased burring and bone removal were required for patients with increased trochanteric overhang. Male gender was positively correlated with
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(R ¼ 0.128), stem size (R ¼ 0.16), and postoperative EQ-5D (R ¼ 0.05), HHS (R ¼ 0.14), and UCLA (R ¼ 0.14). Of the 12 periprosthetic fractures, 6 occurred in Rejuvenate stems and 6 occurred in ABG/ABGII stems, indicating no association with implant type. Nine of the fractures occurred during the first 40 operations, with 3 occurring in subsequent 43 cases. Discussion
Fig. 5. Implant medial calcar prominence (C).
the distance from lateral edge of implant to lateral edge of greater trochanter (B) (R ¼ 0.321; P ¼ .01), anterior cortex distance to implant (D) (R ¼ 0.266; P ¼ .04), and posterior cortex distance to implant (E) (R ¼ 0.356; P ¼ .004). This finding suggests that men were found to have larger bones, resulting in a positive correlation with our measurements of B, D, and E. There was no correlation between the incidence of periprosthetic fractures and age (R ¼ 0.06), gender (R ¼ 0.08), BMI (R ¼ 0.22), preoperative Co (R ¼ 0.176), Cr (R ¼ 0.08) metal ion levels, presence of osteolysis (R ¼ 0.10), type of index THA stem
Fig. 6. Anterior cortex distance to implant (D), posterior cortex distance to implant (E), and eccentricity ratio (D/E).
We report a top-out technique without the use of ETO in revision hip surgery for removal of well-fixed modular neck-stem THA in patients with taper corrosion associated with ALTR. Several studies have described taper corrosion and ALTR in modular neck femoral stems; however, there has been no detailed description of the surgical technique employed during revision surgery [11-14]. Walsh et al [15] reported usage of ETO in 43.7% of cases, with others removed using a simple osteotome technique, burr, or stacked pin technique. Barlow et al [22] used their surgical technique with the use of a Midas Rex burr. However, as the aim of the study was to examine metal ion trends after revision, no detailed description of the surgical technique employed during revision surgery was provided. Our study demonstrated periprosthetic fracture incidence of 14% and a reoperation rate of 7%. This is comparable to published complication rates for ETO [19,23,24]. Drexler et al [23] show 1 intraoperative fracture extension distally after an ETO and an overall 15% complication postoperatively after revision of 34 stems. The original description of an ETO by Younger et al [18] had no reports of complications related to the osteotomy in a review of 20 patients. In contrast, Miner et al [19], in a review of 192 revision hips with ETO, report a reoperation rate of 10.2% with an overall complication rate of 24%. In contrast, our top-out technique avoided bony union complications related to the ETO technique. Interestingly, a reduction of periprosthetic fractures over time in our cohort was observed, with most (75%) of the periprosthetic fractures occurring during the first 40 cases of using this technique. This indicates that a learning curve is associated with this technique. We have identified radiographic risk factors associated with the fractures in our series. Although periprosthetic fracture complication rate was not correlated with age (R ¼ 0.04), gender (R ¼ 0.05), BMI (R ¼ 0.09), stem size (R ¼ 0.06) or implant type, femoral trochanteric overhang ratio (A/B), implant medial calcar prominence (C), and the eccentricity ratio (D/E) are important preoperative factors to consider before considering this technique. A larger overhang ratio (A/B) was positively correlated with periprosthetic fracture rate. Iatrogenic creation of large metaphyseal defects by over-burring is a common pitfall of this technique. Greater trochanteric fractures can be caused by high torque forces from burring or excessive cortex thinning during attempts to bypass the implant shoulder. To avoid this, any trochanteric overhang should be carefully eliminated to allow a collinear direction of burr placement with the lateral border of the stem. In addition, the risk of greater trochanteric fractures may be minimized by measuring the length of the lateral implant shoulder and matching it with the depth of the burring. An implant with medial calcar subsidence (C) may also result in limited medial calcar working space during burring, and care should be taken to minimize medial cortical breech. These findings correspond with the positive correlation observed between the size of the revision stem and overhang distance (A) (R ¼ 0.315; P ¼ .02) and distance from lateral edge of implant to lateral edge of greater trochanter (B) (R ¼ 0.321; P ¼ .01), which suggest that greater trochanteric overhang would require additional burring and clearance, resulting in a larger revision stem. Although the eccentricity ratio (D/E) was not correlated with periprosthetic fractures, in our experience,
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Fig. 7. Intraoperative periprosthetic greater trochanteric fracture (white arrow visible on intraoperative radiograph) treated with trochanteric stabilization plate and cerclage wires. White arrow indicates displaced greater trochanteric fracture.
eccentric alignment is associated with higher degree of iatrogenic burreassociated cortical penetration, fractures, and bone defects, and surgeons using this technique should be mindful regarding the femoral stem's position in sagittal plane with the femoral shaft. A top-out technique provides the surgeon an option to proceed with ETO with minimum additional risk if an attempt with top-out technique becomes prolonged or unsafe due to anatomy, stem design, or other technical considerations. The use of an ETO instead of the top-out technique should be considered in patients at high risk for periprosthetic fractures with increased overhang ratio (A/B) and increased implant subsidence (C). Preoperative planning with anteroposterior and lateral view radiographs is important in identification of trochanteric overhang and noncentered stems, providing information regarding the available working space for
the pencil-tip burr around the greater trochanter as well as anterior and posterior cortex. Risk areas including acute angle changes in stem geometry and close adherence of the implant stem with cortex can be highlighted. Although implant removal with shorter operative time has been reported for ETO [18,25,26], longer incisions are required for exposure of the ETO and the revision stem has to bypass the fracture site, often requiring longer and bowed stems. In addition, the osteotomy requires reduction and fixation as well as postoperative protection to allow for bone healing. Alternative techniques to the ETO [27,28] can be added to the repertoire of a revision surgeon as ETO may not be necessary in all cases. Our study should be interpreted in light of its potential limitations. Firstly, this is a single-surgeon and single-institution study and retrospective in nature. There is no ETO control group to
Fig. 8. Nondisplaced lesser and greater trochanteric fractures on postoperative radiograph managed non-operatively (white arrow indicates nondisplaced fractures).
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compare functional outcomes or complication rates in patients who have undergone revision THA for ALTR-associated taper corrosion. However, the use of ETO in extracting well-fixed femoral stems in modular neck THA with ALTR secondary to taper corrosion at the modular neck-stem junction has been previously reported. Secondly, there was lack of a statistically significant correlation between the eccentricity ratio (D/E) and periprosthetic fractures. This may also be due to the variation in radiographic rotation. In conclusion, removal of well-fixed femoral dual-taper components remains a surgical challenge, and the burden of revision surgery for taper corrosionerelated ALTR of these femoral stems is likely to rise. A top-out technique with systematic preoperative planning with radiographs adds to the armamentarium of a revision surgeon as a viable, alternative option to ETO for the safe removal of well-fixed femoral component while preserving the femoral bony envelope. References 1. Bobyn JD, Tanzer M, Krygier JJ, et al. Concerns with modularity in total hip arthroplasty. Clin Orthop Relat Res 1994;(298):27. 2. Duwelius PJ, Hartzband MA, Burkhart R, et al. Clinical results of a modular neck hip system: hitting the “bull's-eye” more accurately. Am J Orthop (Belle Mead NJ) 2010;39(10 Suppl):2. 3. Hernandez A, Gargallo-Margarit A, Barro V, et al. Fracture of the modular neck in total hip arthroplasty. Case Rep Orthop 2015;2015:591509. 4. Ellman MB, Levine BR. Fracture of the modular femoral neck component in total hip arthroplasty. J Arthroplasty 2013;28(1):196.e1. 5. Skendzel JG, Blaha JD, Urquhart AG. Total hip arthroplasty modular neck failure. J Arthroplasty 2011;26(2):338.e1. 6. Messana J, Adelani M, Goodman SB. Case report: pseudotumor associated with corrosion of a femoral component with a modular neck and a ceramic-onpolyethylene bearing. J Long Term Eff Med Implants 2014;24(1):1. 7. Cooper HJ, Urban RM, Wixson RL, et al. Adverse local tissue reaction arising from corrosion at the femoral neck-body junction in a dual-taper stem with a cobalt-chromium modular neck. J Bone Joint Surg Am 2013;95(10):865. 8. Kop AM, Keogh C, Swarts E. Proximal component modularity in THAeat what cost? An implant retrieval study. Clin Orthop Relat Res 2012;470(7):1885. 9. Kop AM, Swarts E. Corrosion of a hip stem with a modular neck taper junction: a retrieval study of 16 cases. J Arthroplasty 2009;24(7):1019. 10. Walsh CP, Hubbard JC, Nessler JP, et al. MRI findings associated with recalled modular femoral neck Rejuvenate and ABG implants. J Arthroplasty 2015;30(11):2021.
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11. Ghanem E, Ward DM, Robbins CE, et al. Corrosion and adverse local tissue reaction in one type of modular neck stem. J Arthroplasty 2015;30(10): 1787. 12. Restrepo C, Ross D, Restrepo S, et al. Adverse clinical outcomes in a primary modular neck/stem system. J Arthroplasty 2014;29(9 Suppl):173. 13. Molloy DO, Munir S, Jack CM, et al. Fretting and corrosion in modular-neck total hip arthroplasty femoral stems. J Bone Joint Surg Am 2014;96(6):488. 14. Meftah M, Haleem AM, Burn MB, et al. Early corrosion-related failure of the rejuvenate modular total hip replacement. J Bone Joint Surg Am 2014;96(6):481. 15. Walsh CP, Hubbard JC, Nessler JP, et al. Revision of recalled modular neck Rejuvenate and ABG femoral implants. J Arthroplasty 2015;30(5):822. 16. Kwon YM, Fehring TK, Lombardi AV, et al. Risk stratification algorithm for management of patients with dual modular taper total hip arthroplasty: consensus statement of the American Association of Hip and Knee Surgeons, the American Academy of Orthopaedic Surgeons and the Hip Society. J Arthroplasty 2014;29(11):2060. 17. Dimitriou D, Liow MH, Tsai TY, et al. Early outcomes of revision surgery for taper corrosion of dual taper total hip arthroplasty in 187 patients. J Arthroplasty 2016;31(7):1549. 18. Younger TI, Bradford MS, Magnus RE, et al. Extended proximal femoral osteotomy. A new technique for femoral revision arthroplasty. J Arthroplasty 1995;10(3):329. 19. Miner TM, Momberger NG, Chong D, et al. The extended trochanteric osteotomy in revision hip arthroplasty: a critical review of 166 cases at mean 3-year, 9-month follow-up. J Arthroplasty 2001;16(8 Suppl 1):188. 20. Paprosky WG, Weeden SH, Bowling Jr JW. Component removal in revision total hip arthroplasty. Clin Orthop Relat Res 2001;(393):181. 21. Levine BR, Della Valle CJ, Hamming M, et al. Use of the extended trochanteric osteotomy in treating prosthetic hip infection. J Arthroplasty 2009;24(1):49. 22. Barlow BT, Assini J, Boles J, et al. Short-term metal ion trends following removal of recalled modular neck femoral stems. J Arthroplasty 2015;30(7):1191. 23. Drexler M, Dwyer T, Chakravertty R, et al. The outcome of modified extended trochanteric osteotomy in revision THA for Vancouver B2/B3 periprosthetic fractures of the femur. J Arthroplasty 2014;29(8):1598. 24. Lakstein D, Kosashvili Y, Backstein D, et al. The long modified extended sliding trochanteric osteotomy. Int Orthop 2011;35(1):13. 25. Pemmaraju GM, Killampalli VV. Extended proximal femoral osteotomy: technical tip. Eur J Orthop Surg Traumatol 2015;25(6):1111. 26. Chen WM, McAuley JP, Engh Jr CA, et al. Extended slide trochanteric osteotomy for revision total hip arthroplasty. J Bone Joint Surg Am 2000;82(9):1215. 27. Kim YM, Lim ST, Yoo JJ, et al. Removal of a well-fixed cementless femoral stem using a microsagittal saw. J Arthroplasty 2003;18(4):511. 28. Jack CM, Molloy DO, Esposito C, et al. Limited slot femorotomy for removal of proximally coated cementless stems. A 10-year follow-up of an unreported surgical technique. J Arthroplasty 2013;28(6):1000.