The Journal of Arthroplasty 30 (2015) 1397–1402
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Femoral Component Revision Using a 2nd Generation Modular Femoral Implant Puneet K. Bhatia, MD a, Steven L. Barnett, MD b, Timothy P. Lovell, MD c, William J. Hozack, MD d, Arthur L. Malkani, MD a a
University of Louisville, Louisville, Kentucky Hoag Orthopaedic Institute, Irvine, California Providence Joint and Sports Center, Spokane, Washington d Rothman Institute, Philadelphia, Pennsylvania b c
a r t i c l e
i n f o
Article history: Received 1 March 2013 Accepted 13 March 2015 Keywords: revision THA modular femoral implant femoral bone loss dislocation following revision THA intraoperative fracture
a b s t r a c t The purpose of this prospective multicenter study was to evaluate results of 122 revision THAs using a 2nd generation modular femoral implant in 120 patients. Majority of cases had significant femoral bone loss. HHS improved from a pre-operative mean score of 46 to 88 points, and SF-36 scores improved from 31 to 44 points at 2- to 5-year follow-up. There were 18 cases of intraoperative fractures of which 10 were femur shaft, 7 trochanteric, and 1 acetabular. Dislocation incidence was 9% and overall survivorship at 5 years was 97%. Use of modular femoral implants provides versatility and simplification to restore stability, limb length and offset in patients undergoing femoral component revision, Additional steps need to be undertaken to minimize incidence of fracture and dislocation. © 2015 Elsevier Inc. All rights reserved.
Total hip arthroplasty is an effective procedure for advanced hip arthritis. With an increase in the number of primary total hip arthroplasties performed in the United States, the number of revisions is also on the rise. Between 1990 and 2004, the number of revision THA procedures performed in the United States increased from 26,100 to 38,600 (+48%) [1,2]. Revision hip arthroplasty can be a challenging situation, especially with significant bone loss and poor bone quality. Della Valle and Paprosky [3] developed a classification scheme and an algorithmic approach to the reconstruction of femoral deficiency in revision total hip arthroplasty. Depending upon the extent of the femoral bone loss, different surgical options are available for implant fixation including long stem cemented implants [4]; porous, extensively coated implants [5]; modular, extensively coated or fluted stems [6]; impaction grafting [7]; allograft-prosthetic composites [8] or tumor type mega prostheses [9]. Modular femoral stems are gaining popularity in revision hip surgery. Modular stems allow for independent sizing of the metaphyseal/ diaphyseal component, variable stem and neck length options including the ability to change version and offset with a modular, proximal femoral body. These options using modular femoral implants provide the ability to achieve the surgical goals with independent steps for diaphyseal and metaphyseal fixation therefore simplifying the overall procedure. Stable One or more of the authors of this paper have disclosed potential or pertinent conflicts of interest, which may include receipt of payment, either direct or indirect, institutional support, or association with an entity in the biomedical field which may be perceived to have potential conflict of interest with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2015.03.034. Reprint requests: Arthur L. Malkani, MD, 550 S. Jackson Street, Louisville, KY 40202. http://dx.doi.org/10.1016/j.arth.2015.03.034 0883-5403/© 2015 Elsevier Inc. All rights reserved.
initial distal stem fixation is a critical requirement for success of the reconstruction and a modular stem separates this step of the procedure from other aspects of the revision procedure. Other goals of the revision surgery such as offset restoration, leg length equality, and hip stability can then be obtained independent of stem fixation [10]. The purpose of this study was to evaluate the two to five year results, complications and survivorship of a 2nd generation distally fixed cementless modular femoral hip system and determine if consistent results could be obtained at multiple centers.
Materials and Methods Data for this study were obtained from a prospective, multicenter IRB-approved study evaluating the use of the Restoration¨ modular implant (Stryker Orthopaedics, Mahwah, NJ) in patients undergoing revision total hip arthroplasty (Figs. 1 and 2). There were a total of 120 patients: 118 unilateral and 2 bilateral, with 122 revision hip surgeries enrolled. There were 59 males (49%) and 61 females (51%) with a mean age of 68 years (range 31–85 years) (Table 1). Seventy five percent of cases had one prior hip surgery. The mean time to revision surgery for this study was 10.8 years from the primary or last procedure for all cases. Indications for surgery included aseptic loosening in 85 cases (71%), painful hip in 79 cases (66%), peri-prosthetic fracture in 6 cases (5%)), septic loosening in 4 cases (3%), stem fracture in 4 cases (3%) and other indications in 36 cases (30%). Infections were excluded from this study. The majority of the cases had type 2 and type 3 Paprosky
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Fig. 1. (A) and (B): Preoperative A/P x-rays of 78-year-old male with aseptic loosening of his left THA.
type femoral bone defects: 17 cases (14%) had type 1, 49 (41%) had type 2 (extensive metaphyseal bone loss with intact diaphysis), 47 (39%) had type 3 A (extensive metadiaphyseal bone loss with minimum of 4 cm of intact cortical bone in diaphysis) and 3B defects (extensive metadiaphyseal bone loss with less than 4 cm of diaphyseal cortical bone) and 5 (4%) had a type 4 defect (extensive metadiaphyseal bone loss without diaphyseal support). A posterior approach was used in 62 cases (52%), antero-lateral approach was used in 52 cases (43%) and an anterior approach was used in 6 cases (5%). Trochanteric osteotomy (transverse, slide or extended) was performed in 34 cases (28%). Cup inserts were revised in 108 cases (88%). The cone body/conical or tapered fluted stem combination was used in 88 (73%) cases (Table 2). The desired leg length correction based on the pre-operative plan was achieved in 99 cases (83%) with a mean correction of 15 mm (0–63 mm). A cable system was used in 58 cases (48%) either prophylactically, or to repair an intraoperative fracture or trochanteric osteotomy. Allografts were used in 37 (31%) and autografts were used in 11 cases (9%). The mean duration of surgery was 174 min (50–385 min) with an estimated mean blood loss of 952 ml. Patients were reviewed preoperatively for clinical and radiological assessment including the Harris Hip Score and SF-36. Preoperative planning included radiographic assessment of the failed hip arthroplasty
was performed using templates to achieve the desired leg length and offset. A posterior or antero-lateral approach was used in the majority of the cases. Trochanteric osteotomy (transverse, slide or extended) was performed when indicated. A Restoration¨ Modular Revision Hip System (Stryker Orthopaedics, Mahwah, NJ) was utilized in all cases and consists of a distal portion, a fluted, plasma or conical stem, and a proximal portion or body (Fig. 3). The distal portion is a titanium stem with three available options: titanium alloy (Ti–6Al–4 V) fluted, polished stem (immediate diaphyseal stability without in growth); circumferentially plasma-sprayed titanium stem with hydroxyapatite (HA) coating for interference fit (distal fixation with on growth); and heavily grit-blasted, fluted, conical or tapered stem (rotational stability and on growth). The geometry of the conical stem is based on the philosophy of the Wagner design in that the fluted conical stem is believed to provide initial rotational stability [11]. The conical stems are available in three lengths: a straight 155 mm, a straight or bowed 195 mm, and a bowed 235 72 mm. Each is available in 15 diameters (range, 14–28 mm) in 1 mm increments. The fluted and plasma-sprayed stems are available in five lengths: a straight 127 mm, a straight or bowed 167 mm, and a bowed 217 mm, 267 mm, and 317 mm (Fig. 4). Each is available in 16 diameters (range, 11–26 mm) in 1 mm increments.
Fig. 2. (A) and (B): A/P and lateral x-rays of revision THA with Restoration® Modular system using a cone body and a conical stem at 5-year follow-up with well-fixed implants.
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Table 1 Demographic Information. Frequency Number of cases/patients Unilateral Bilateral Men/Women (n) Mean age, years (range) Mean height, inches (range) Mean weight, pounds (range) Diagnosis (% of cases) Osteoarthritis Rheumatoid arthritis Posttraumatic arthritis Avascular necrosis Others Previous surgeries (% of cases) 1 2 3 N3 Mean time to revision, years (range) [evaluation date to previous implant date]
122/120 118/118 2/2 59/61 67.82 (31–85) 66.32 (56.0–80.0) 174.60 (100.0–295.0) 62 (50.8%) 7 (5.7%) 10 (8.2%) 13 (10.7%) 30 (24.6%) 92 (75.4%) 20 (16.4%) 5 (4.1%) 5 (4.1%) 10.76 (0.02–32.24)
Table 2 Surgical Details. Frequency (% of cases) Number of cases/patients Reason for revision Pain Aseptic loosening Septic loosening Femoral fracture Stem fracture Other Bone defect classification Type 1 Type 2 Type 3A Type 3B Type 4 Unspecified Mean surgical time, min (range) Mean blood loss, ml (range) Approach Anterior Posterior Lateral Transtrochanteric osteotomy Yes No Stem/Body combination Broached body/fluted stem Broached body/plasma stem Calcar body/plasma stem Cone body/conical stem Cone body/plasma stem Other Cabling used Yes—Dall Miles Yes—Other No Bone graft used Yes—allograft Yes—autograft No Leg length correction attempted Yes No Mean leg length correction, mm (range) Attempted Achieved
122/120 79 (65.3%) 85 (70.8%) 4 (3.3%) 6 (5%) 4 (3.3%) 36 (30%) 17 (14.2%) 49 (40.8%) 35 (29.2%) 12 (10%) 5 (4.2%) 2 (1.6%) 174.3 (50.0–385.0) 952.1 (20.0–6000.0) 6 (5%) 62 (51.7%) 52 (43.3%) 34 (28.3%) 86 (71.7%) 1 (0.8%) 6 (5%) 5 (4.2%) 88 (73.3%) 18 (15%) 2 (1.7%)
Fig. 3. Image of Restoration Modular implant with varying cone body sizes and conical, tapered, fluted stems with various diameters.
The proximal portion or body is made of a titanium–aluminum vanadium alloy (Ti–6Al–4 V) and is circumferentially plasma sprayed with commercially pure titanium and sprayed over again with hydroxyapatite (PureFix™ HA; Stryker Orthopaedics). It has a regular cylindrical form for the cone type and a flange with cobalt–chrome (CoCr) brushings to allow proper abductor reattachment added to the cylindrical form in the calcar type. Both body types have a 132¡ neck angle and are available in seven body diameters (range, 19–31 mm) with 2 mm increments. The cone type body has four vertical offsets (+ 0 mm, + 10 mm, + 20 mm, and + 30 mm) providing a vertical size of 70 mm, 80 mm, 90 mm, and 100 mm, respectively; the calcar type has three vertical offsets (+10 mm, +20 mm, and +30 mm) providing a vertical size of 80 mm, 90 mm, and 100 mm, respectively. Both body types have a V40TM (Stryker Orthopaedics) trunnion to accept CoCr 22-mm, 26-mm, 28-mm, 32-mm, 36-mm, 40-mm or 44-mm heads or alumina ceramic 28-mm, 32-mm, or 36-mm heads. Lateral offset is achieved through head-neck increments of − 4 mm, + 0 mm, +4 mm, +8 mm, or +12 mm [12]. Other proximal body types included the milled body and broached body. Both the milled and broached bodies are used when there is adequate proximal bone available and are designed to provide maximum stability with proximal fit and fill. The MT3 body is no longer offered by the manufacturer. Surgical Technique
56 (46.7%) 2 (1.7%) 62 (51.6%) 37 (30.8%) 11 (9.2%) 72 (60%) 99 (82.5%) 19 (15.8%) 16.1 (0.3–63.0) 15.1 (0.3–63.0)
Depending upon the quality of the host bone, either a porous-coated, plasma sprayed cylindrical, or tapered, grit blasted, fluted stem can be utilized when distal fixation is required. The polished fluted stem provides rotational stability but lacks the ability for on growth. The choice of implant is determined by the surgeon based on the extent of bone loss and the quality of the available host bone. The surgical technique consisted of removal of the prior implant along with any debris in the medullary canal such as methylmethacrylate. The medullary canal of the femur can be reamed with flexible reamers to remove debris and sclerotic bone. Rigid reamers either conical or cylindrical are then
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Fig. 4. Image of commonly used Restoration Modular (Stryker, Mahwah, NJ) proximal body (broached, calcar, milled, conical, MT3 no longer offered) and stem options (polished fluted, tapered fluted, grit blasted, and cylindrical plasma sprayed) utilized for fixation during femoral component revision.
utilized to obtain cortical contact. Under reaming of 0.5–1 mm was performed with plasma sprayed cylindrical stems while line-to-line reaming was undertaken with fluted, tapered stems. If there was any risk of femoral cortical fracture due to osteolysis or bone defects then prophylactic cables or strut graft would be applied prior to the reaming process. In cases of extended trochanteric osteotomies, a prophylactic cable was applied distal to the osteotomy to prevent migration of any fracture line. The length of the desired femoral stem is based on the pre-operative plan. Once the rigid reamers obtained cortical contact at the appropriate length, the modular femoral stem was then inserted. The proximal femoral canal was then reamed to achieve some cortical contact and a trial reduction undertaken. In most cases a cone type of proximal body was utilized since it is inserted with a reaming process which can minimize fracture risk as opposed to a broaching technique. The modular proximal femoral bodies comes in 4 different heights (standard, + 10 mm, +20 mm, +30 mm) and several diameters which helps achieve the desired leg length and offset regardless of the stem diameter. The implant combination of a cone body with a tapered, fluted, conical stem (Wagner type) was the most commonly used combinations. Cables were utilized for fixation of strut grafts, repair of trochanteric osteotomies, or fixation of intraoperative fractures. Patients were followed at six weeks, three months, one year, two years, and at five years post-surgery. Standard pelvis AP and lateral radiographs of the affected hip were taken at follow-up visits for evaluation. Radiographic implant stability was assessed at all visits. Radiographic assessment of femoral component employed seven zones (1–7) in the AP view and 7 zones (8–14) in the lateral view [13]. Radiolucency in at least 50% of a zone and measuring at least 1 mm in width was considered as radiolucency present. Failure was defined as radiolucent lines 3 2 mm around the entire stem in either the AP or lateral view. Stem migration was defined as a measurable change in the position of the femoral component in a varus or valgus position, and reported as progressive if movement of at least 5 mm was observed on two serial films. Stem subsidence was calculated between the initial immediate postoperative radiograph and the most recent follow-up radiograph with progressive subsidence defined as settling in of the femoral implant of at least 3 mm on two serial films [14]. Implant failure was defined as reoperation of the femoral component for any cause. Standard questionnaires were completed at each visit to calculate the Harris Hip Score [15] and SF-36 [16].
the follow-up period, eight were lost to follow-up, three had removal of the femoral implant and eleven withdrew from the study for various reasons, leaving 91 revisions in 89 patients with a 2–5 year follow up, average 3.7 years. Harris Hip Scores improved from a preoperative mean score of 46 to 88 points at five-year follow-up with more than 86% of cases reported with fair, good, or excellent scores. The SF-36 score showed improvement from a mean preoperative score of 31 to 44 points at five-year follow-up. Radiographic assessment at follow-up intervals showed absence of radiolucency in zones 1–7 in the AP view for 90% of cases at one-year and more than 84% of cases at five-year follow-up. There was absence of radiolucency in zones 8–14 in the lateral view in 89% of cases at one-year and more than 92% of cases at five-year follow-up. Stem migration was observed in four cases within the first postoperative year, which was progressive in three cases. One of the three cases with progressive stem migration underwent a femoral stem revision for a postoperative femoral fracture. The other two cases had no significant clinical findings and were asymptomatic at latest follow up. There were 26 patients with subsidence measured by the independent radiographic reviewer. Fifteen of these cases were first observed within 3 months postoperatively without further subsidence. The distance of the stem subsidence was stratified into 3 groups: 1) less than 2 mm, 2) 2–4 mm, and 3) 5 mm or greater. Of these 15 there were 6 in group 1, 5 in group 2 and 4 in group 3. Those that subsided at 1–2 years included two in group 1 and 3 in group 2. None of these cases had further progression. Of the 26 patients that subsided, 22 had a conical stem and 4 had a plasma stem. There were a total of 11 dislocations (9%) in this study group. There were a total of 229 adverse events reported for all cases over the five-year follow-up period (Table 3). There were nine revisions in eight cases of which three involved the femoral stem and body: two required revision of the femoral stem and one required revision of the femoral head and body only. The remaining six revisions in five cases involved only acetabular components and/or femoral heads. There were 14 reoperations reported for other reasons: six incidences of debridement for superficial wound infection/hematoma, three debridements in a case of deep infection, two cases for ORIF of periprosthetic fractures, and three cases of later removal of trochanteric hardware. There were 18 intraoperative fractures that went on to union. Overall, there was 97% survivability of the Restoration¨ Modular revision hip implant in the above study at five-year follow-up.
Results
Discussion
Of the initial 120 revision cases, one death occurred immediately postoperatively. There were a total of seven deaths over the course of
Proximal femoral deficiency at the time of revision THA can be a challenging situation and in most cases requires distal femoral fixation
P.K. Bhatia et al. / The Journal of Arthroplasty 30 (2015) 1397–1402 Table 3 Adverse Events. Related to Device
Related to surgery
Patient related
Total
Subsidence of femoral component Loosening of femoral component Loosening of acetabular component Dislocation Subluxation Dissociation of modular junction Intra-op femoral fracture/crack Intra-op trochanteric fracture/crack Intra-op acetabular fracture Deep joint infection Superficial wound infection Wound hematoma/wound related/other Post-op femoral fracture Post-op trochanteric fracture Trochanteric non-union Bursitis Thrombophlebitis Cardiovascular Bronchopulmonary Genitourinary Gastrointestinal Neurological Others 229
2 1 3 10 2 1 10 7 1 2 4 9 2 2 1 12 1 24 5 11 6 8 104
for predictable outcomes [17]. The results of revision THA using cement have a high failure rate primarily due to poor bone–cement interdigitation due to a smooth sclerotic femoral surface.[14,18,19]. The incidence of failure after revision total hip arthroplasty without cement is somewhat better with a failure of 2% to 7% at three to six years postoperatively [20–24]. Immediate stability is mandatory for uncemented revision components. Since there is no proportional relationship between the metaphyseal and diaphyseal geometry in the proximal portion of the femur, as often is the case in revision surgery, fit and fill are often difficult to achieve in practice. Due to the osteolytic defects there is invariably a metaphyseal/ diaphyseal mismatch at the proximal femur. Various options are available to manage the mismatch in the proximal femoral geometry encountered at the time of revision [3,5,6,10,25]. The use of modular femoral implants is an option and provides intraoperative versatility to correct leg length discrepancy, restoration of offset and stability independent of distal fixation. Proximally coated monobloc stems for femoral component revision have demonstrated relatively higher failure rates as compared to modular stems. Mulliken et al [26] reported a 24% mechanical failure rate with 10% of cases undergoing revision at four to six years of follow-up. Malkani et al [27] reported a 28.7% revision rate in 69 patients at mid-term follow-up. Woolson and Delaney [28] reported a 20% revision rate and a 45% mechanical failure rate in their study of 28 hips. Although there has been success in revision hip arthroplasty using extensively coated monolithic stems, intraoperative challenges with metaphyseal and diaphyseal mismatch and complications were still reported [29,30]. There are several studies demonstrating success of modular femoral implants in revision surgeries [10,25,31,32]. Offset and leg length restoration are important goals of the revision procedure and likely play a large role in the functional outcome of the procedure [33]. The low mechanical failure rate experienced with the modular stems in these studies can be the result of the ability of the surgeon to obtain independent distal fixation from the other aspects of the revision procedure such as version, offset, and leg length. Garbuz et al [34] showed improved outcomes with modular fluted and tapered titanium stems compared to cylindrical extensively coated cobalt chrome stems with single modularity. Koster et al [22] showed a 96% survival rate with aseptic loosening as an end point over an average of 10 years for a modular uncemented revision stem. Christie et al [35] noted about a 99% survival rate from revision with a modular femoral stem. Our study showed a
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97% survival rate with only one incidence of aseptic stem loosening requiring revision. In this case, the stem had subsided greater than 5 mm. Although we had other patients subside. They were not symptomatic or had subsided into a stable position. Two other cases of stem revisions were for a periprosthetic fracture and for dissociation at the modular junction. The survival rate in our series is comparable to other studies of similar and even non-modular extensively porous coated implants. There were 18 cases of intraoperative fractures (15%) out of which 10 were of the femur shaft, 7 trochanteric and 1 acetabular. Studies in the literature have also reported high intraoperative fracture rates in femoral component revision. Mulliken et al [26] reported a 40% intraoperative fracture rate. Christie et al [35] reported a 22.5% intraoperative fracture rate. We were able to reduce our intraoperative fracture incidence by using prophylactic cables especially when an extended trochanteric osteotomy was utilized. In an attempt to obtain rigid distal fixation, significant hoop stresses are applied; and on compromised bone, this can lead to fracture. Twelve of the fractures (67%) occurred during the initial 10 cases contributed by each of the individual surgeons implying a learning curve with the use of this modular femoral system. The incidence of fracture diminished with the use of prophylactic cables prior to the reaming process and insertion of the implant. Dislocation is a common complication following revision total hip arthroplasty. The incidence of dislocation has been reported in the literature from 4% to 25% following revision hip arthroplasty due to several factors. In this current series, the rate of dislocation was 9% which may be comparable with other studies such as Restrepo et al [10] with a 3% dislocation rate, Park et al [12] with a 5%, Ovesen et al [31] with a 6%, and Rodriguez et al [32] with a 10% dislocation rate. Dislocation can be minimized with modular proximal bodies given the ability to alter offset and version. The offset can change through modification of cone body diameter and height in combination with neck length. Although an attempt was made to restore offset a direct liner radiographic measurement was not part of the radiographic study protocol and therefore hard data to compare pre and post operative offset was not available. But in theory, based on the design of the modular proximal body, the surgeon has the ability to modify offset intraoperatively, based on the desired goals. Despite the many options available to restore offset and leg length, the dislocation incidence could be further reduced and additional work is necessary to identify factors that play a role. Pierson et al [36] reported on a series of fractures at the modular body stem junction of modular implants. Two other recent reports on modular revision stems [31,32] experienced a 1% stem fracture rate. In this current design 2nd generation modular femoral implant, the biomechanical properties of the morse taper junction have been significantly improved with the use of nitride impregnation, burnishing and shot peening at the morse taper to significantly add further strength [37]. The proximal metaphyseal body is porous coated which promotes ongrowth with proximal loading, potentially minimizing proximal stress shielding as well as decreasing the stresses placed on the morse taper junction [38]. There have been no fractures of the femoral stem in our series, but there has been one case of dissociation at the modular body stem junction where the body was not completely seated on the stem taper requiring revision. There are several limitations to our study. This was a prospective multicenter study with different surgeons bringing their own surgical technique, experience, and perspective. The excellent survivorship despite the learning curve demonstrates the versatility of the modular revision hip system utilized at the various multiple centers. Patients were not randomized, and the our results are short-to midterm. The true benefit of modular femoral stems in revision total hip arthroplasty is the ability to provide independent diaphyseal and metaphyseal fixation which simplifies and separates the surgical goals in achieving distal stability and restoring leg length, version and offset. The versatility of this modular femoral implant is exemplified by the fact that multiple surgeons with their own prior surgical experience were able to effectively
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achieve good clinical results in a host of patients with varying degrees of bone loss undergoing revision THA. The current challenges and further studies that are required need to minimize complications such as fracture and dislocation. Based on our studies we feel that a 2nd generation modular femoral implant provides at least equivalent results to those of extensively coated monolithic stems but with greater versatility and simplicity. References 1. Kurtz S, Mowat F, Ong K, et al. Prevalence of primary and revision total hip and knee arthroplasty in the United States from 1990 through 2002. J Bone Joint Surg Am 2005; 87:1487. 2. Kurtz S, Mowat F, Ong K, et al. Primary and revision arthroplasty surgery caseloads in the United States from 1990–2004. J Arthroplasty 2009;24(2):195. 3. Della Valle CJ, Paprosky WG. Classification and an algorithmic approach to the reconstruction of femoral deficiency in revision total hip arthroplasty. J Bone Joint Surg Am 2003;85-A(Suppl. 4):1. 4. Gramkow J, Jensen TH, Varmarken JE, et al. Long-term results after cemented revision of the femoral component in total hip arthroplasty. J Arthroplasty 2001;16(6):777. 5. Engh Jr CA, Ellis TJ, Koralewicz LM, et al. Extensively porous-coated femoral revision for severe femoral bone loss: minimum 10-year follow-up. J Arthroplasty 2002;17(8):955. 6. Sporer SM, Paprosky WG. Femoral fixation in the face of considerable bone loss: the use of modular stems. Clin Orthop Relat Res 2004;429:227. 7. Hostner J, Hultmark P, Karrholm J, et al. Impaction technique and graft treatment in revisions of the femoral component: laboratory studies and clinical validation. J Arthroplasty 2001;16(1):76. 8. Blackley HR, Davis AM, Hutchison CR, et al. Proximal femoral allograft for reconstruction of bone stock in revision arthroplasty of the hip. A nine to fifteen-year follow-up. J Bone Joint Surg Am 2001;83-A(3):346. 9. Malkani AL, Settecerri JJ, Sim FH, et al. Long-term results of proximal femoral replacement for non-neoplastic disorders. J Bone Joint Surg (Br) 1995;77(3):351. 10. Restrepo C, Mashadi M, Parvizi J, et al. Modular femoral stems for revision total hip arthroplasty. Clin Orthop Relat Res 2011;469:476. 11. Berry DJ. Treatment of Vancouver B3 periprosthetic femur fractures with a fluted tapered stem. Clin Orthop Relat Res 2003;417:224. 12. Park YS, Moon YW, Lim SJ. Revision total hip arthroplasty using a fluted and tapered modular distal fixation stem with and without extended trochanteric osteotomy. J Arthroplasty 2007;22:993. 13. Engh CA, Massin P, Suthers KE. Roentgenographic assessment of the biologic fixation of porous-surfaced femoral components. Clin Orthop Relat Res 1990;257:107. 14. 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. 15. Harris WH. Traumatic arthritis of the hip after dislocation and acetabular fractures: treatment by mold arthroplasty. An end-result study using a new method of result evaluation. J Bone Join Surg Am 1969;51:737. 16. Ware Jr JE, Sherbourne CD. The MOS 36-item short-form health survey (SF-36). I. conceptual framework and item selection. Med Care 1992;30:473.
17. Sporer SM, Paprosky WG. Revision total hip arthroplasty: the limits of fully coated items. Clin Orthop Relat Res 2003;417:203. 18. Estok 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;299:190 [296]. 19. Meding JB, Ritter MA, Keating EM, et al. Impaction bone grafting before insertion of femoral stem with cement in revision total hip arthroplasty: a minimum two-year follow up study. J Bone Joint Surg Am 1997;79:1834. 20. Gustilo R, Pasternak H. Revision total hip arthroplasty with titanium ingrowth prosthesis and bone grafting for the failed cemented femoral segment loosening. Clin Orthop 1988;235:111. 21. Hungerford DS, Jones LC. The rationale of cementless revision of cemented arthroplasty failures. Clin Orthop 1988;235:12. 22. Koster G, Walde TA, Willert HG. Five- to 10-year results using a noncemented modular revision stem without bone grafting. J Arthroplasty 2008;23(7):964. 23. Krishnamurthy AB, MacDonald SJ, Paprosky WG. 5- to-13-year follow up study on cementless femoral components in revision surgery. J Arthroplasty 1997;12:839. 24. Moreland JR, Bernstein ML. Femoral revision hip arthroplasty with uncemented porous310 coated stems. Clin Orthop Relat Res 1995;319:141. 25. Myung-Sin Park, Lee Ju-Hong. A distal fluted, proximal modular femoral prosthesis in revision hip arthroplasty. J Arthroplasty 2010;25(6):932. 26. Mulliken BD, Rorabeck CH, Bourne RB. Uncemented revision total hip arthroplasty: a 4314 to-6-year review. Clin Orthop Relat Res 1996;325:156. 27. Malkani AL, Lewallen DG, Cabanela ME, et al. Femoral component revision using an uncemented, proximally coated, long-stem prosthesis. J Arthroplasty 1996;11(4):411. 28. Woolson ST, Delaney TJ. Failure of a proximally porous-coated femoral prosthesis in revision total hip arthroplasty. J Arthroplasty 1995(10 Suppl.):S22. 29. Crawford CH, Malkani A, Incavo SJ, et al. Femoral component revision using an extensively hydroxyapatite-coated stem. J Arthroplasty 2004;19(1):8. 30. Weeden SH, Paprosky WG. Minimal 11-yr follow-up of extensively porous coated stems in femoral revision total hip arthroplasty. J Arthroplasty 2002;17(4 Suppl. 1):134. 31. Ovesen O, Emmeluth C, Hofbauer C, et al. Revision total hip arthroplasty using a modular tapered stem with distal fixation good short-term results in 125 revisions. J Arthroplasty 2010;25:348. 32. Rodriguez JA, Fada R, Murphy SB, et al. Two-year to five-year follow-up of femoral defects in femoral revision treated with the link MP modular stem. J Arthroplasty 2009; 24:751. 33. Lecerf G, Fessy MH, Philippot R, et al. Femoral offset: anatomical concept, definition, assessment, implications for preoperative templating and hip arthroplasty. Orthop Traumatol Surg Res 2009;95:210. 34. Garbuz DS, Toms A, Masri BA, et al. Improved outcome in femoral revision arthroplasty with tapered fluted modular titanium stems. Clin Orthop Relat Res 2006;453:199. 35. Christie MJ, DeBoer DK, Tingstad EM, et al. Clinical experience with a modular non cemented femoral component in revision total hip arthroplasty: 4- to 7-year results. J Arthroplasty 2000;15(7):840. 36. Pierson JL, Crowninshield RD, Earles DR. Fatigue fracture of a modular revision femoral component: a report of forty cases. Presented at the Annual Meeting. February, 2005; Am Acad Orthop Surg, Washington, DC; 2005. 37. Shot Peening Applications. Metal Improvement Company, Inc.; 2003[Eighth edition]. 38. Hnat WP, Conway JS, Malkani AL, et al. The effect of modular tapered fluted stems on proximal stress shielding in the human femur. J Arthroplasty 2009;24(6):957.
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Femoral Component Revision Using a 2nd Generation Modular Femoral Implant Puneet K. Bhatia, MD a, Steven L. Barnett, MD b, Timothy P. Lovell, MD c, William J. Hozack, MD d, Arthur L. Malkani, MD a a
University of Louisville, Louisville, Kentucky Hoag Orthopaedic Institute, Irvine, California Providence Joint and Sports Center, Spokane, Washington d Rothman Institute, Philadelphia, Pennsylvania b c
a r t i c l e
i n f o
Article history: Received 1 March 2013 Accepted 13 March 2015 Keywords: revision THA modular femoral implant femoral bone loss dislocation following revision THA intraoperative fracture
a b s t r a c t The purpose of this prospective multicenter study was to evaluate results of 122 revision THAs using a 2nd generation modular femoral implant in 120 patients. Majority of cases had significant femoral bone loss. HHS improved from a pre-operative mean score of 46 to 88 points, and SF-36 scores improved from 31 to 44 points at 2- to 5-year follow-up. There were 18 cases of intraoperative fractures of which 10 were femur shaft, 7 trochanteric, and 1 acetabular. Dislocation incidence was 9% and overall survivorship at 5 years was 97%. Use of modular femoral implants provides versatility and simplification to restore stability, limb length and offset in patients undergoing femoral component revision, Additional steps need to be undertaken to minimize incidence of fracture and dislocation. © 2015 Elsevier Inc. All rights reserved.
Total hip arthroplasty is an effective procedure for advanced hip arthritis. With an increase in the number of primary total hip arthroplasties performed in the United States, the number of revisions is also on the rise. Between 1990 and 2004, the number of revision THA procedures performed in the United States increased from 26,100 to 38,600 (+48%) [1,2]. Revision hip arthroplasty can be a challenging situation, especially with significant bone loss and poor bone quality. Della Valle and Paprosky [3] developed a classification scheme and an algorithmic approach to the reconstruction of femoral deficiency in revision total hip arthroplasty. Depending upon the extent of the femoral bone loss, different surgical options are available for implant fixation including long stem cemented implants [4]; porous, extensively coated implants [5]; modular, extensively coated or fluted stems [6]; impaction grafting [7]; allograft-prosthetic composites [8] or tumor type mega prostheses [9]. Modular femoral stems are gaining popularity in revision hip surgery. Modular stems allow for independent sizing of the metaphyseal/ diaphyseal component, variable stem and neck length options including the ability to change version and offset with a modular, proximal femoral body. These options using modular femoral implants provide the ability to achieve the surgical goals with independent steps for diaphyseal and metaphyseal fixation therefore simplifying the overall procedure. Stable One or more of the authors of this paper have disclosed potential or pertinent conflicts of interest, which may include receipt of payment, either direct or indirect, institutional support, or association with an entity in the biomedical field which may be perceived to have potential conflict of interest with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2015.03.034. Reprint requests: Arthur L. Malkani, MD, 550 S. Jackson Street, Louisville, KY 40202. http://dx.doi.org/10.1016/j.arth.2015.03.034 0883-5403/© 2015 Elsevier Inc. All rights reserved.
initial distal stem fixation is a critical requirement for success of the reconstruction and a modular stem separates this step of the procedure from other aspects of the revision procedure. Other goals of the revision surgery such as offset restoration, leg length equality, and hip stability can then be obtained independent of stem fixation [10]. The purpose of this study was to evaluate the two to five year results, complications and survivorship of a 2nd generation distally fixed cementless modular femoral hip system and determine if consistent results could be obtained at multiple centers.
Materials and Methods Data for this study were obtained from a prospective, multicenter IRB-approved study evaluating the use of the Restoration¨ modular implant (Stryker Orthopaedics, Mahwah, NJ) in patients undergoing revision total hip arthroplasty (Figs. 1 and 2). There were a total of 120 patients: 118 unilateral and 2 bilateral, with 122 revision hip surgeries enrolled. There were 59 males (49%) and 61 females (51%) with a mean age of 68 years (range 31–85 years) (Table 1). Seventy five percent of cases had one prior hip surgery. The mean time to revision surgery for this study was 10.8 years from the primary or last procedure for all cases. Indications for surgery included aseptic loosening in 85 cases (71%), painful hip in 79 cases (66%), peri-prosthetic fracture in 6 cases (5%)), septic loosening in 4 cases (3%), stem fracture in 4 cases (3%) and other indications in 36 cases (30%). Infections were excluded from this study. The majority of the cases had type 2 and type 3 Paprosky
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Fig. 1. (A) and (B): Preoperative A/P x-rays of 78-year-old male with aseptic loosening of his left THA.
type femoral bone defects: 17 cases (14%) had type 1, 49 (41%) had type 2 (extensive metaphyseal bone loss with intact diaphysis), 47 (39%) had type 3 A (extensive metadiaphyseal bone loss with minimum of 4 cm of intact cortical bone in diaphysis) and 3B defects (extensive metadiaphyseal bone loss with less than 4 cm of diaphyseal cortical bone) and 5 (4%) had a type 4 defect (extensive metadiaphyseal bone loss without diaphyseal support). A posterior approach was used in 62 cases (52%), antero-lateral approach was used in 52 cases (43%) and an anterior approach was used in 6 cases (5%). Trochanteric osteotomy (transverse, slide or extended) was performed in 34 cases (28%). Cup inserts were revised in 108 cases (88%). The cone body/conical or tapered fluted stem combination was used in 88 (73%) cases (Table 2). The desired leg length correction based on the pre-operative plan was achieved in 99 cases (83%) with a mean correction of 15 mm (0–63 mm). A cable system was used in 58 cases (48%) either prophylactically, or to repair an intraoperative fracture or trochanteric osteotomy. Allografts were used in 37 (31%) and autografts were used in 11 cases (9%). The mean duration of surgery was 174 min (50–385 min) with an estimated mean blood loss of 952 ml. Patients were reviewed preoperatively for clinical and radiological assessment including the Harris Hip Score and SF-36. Preoperative planning included radiographic assessment of the failed hip arthroplasty
was performed using templates to achieve the desired leg length and offset. A posterior or antero-lateral approach was used in the majority of the cases. Trochanteric osteotomy (transverse, slide or extended) was performed when indicated. A Restoration¨ Modular Revision Hip System (Stryker Orthopaedics, Mahwah, NJ) was utilized in all cases and consists of a distal portion, a fluted, plasma or conical stem, and a proximal portion or body (Fig. 3). The distal portion is a titanium stem with three available options: titanium alloy (Ti–6Al–4 V) fluted, polished stem (immediate diaphyseal stability without in growth); circumferentially plasma-sprayed titanium stem with hydroxyapatite (HA) coating for interference fit (distal fixation with on growth); and heavily grit-blasted, fluted, conical or tapered stem (rotational stability and on growth). The geometry of the conical stem is based on the philosophy of the Wagner design in that the fluted conical stem is believed to provide initial rotational stability [11]. The conical stems are available in three lengths: a straight 155 mm, a straight or bowed 195 mm, and a bowed 235 72 mm. Each is available in 15 diameters (range, 14–28 mm) in 1 mm increments. The fluted and plasma-sprayed stems are available in five lengths: a straight 127 mm, a straight or bowed 167 mm, and a bowed 217 mm, 267 mm, and 317 mm (Fig. 4). Each is available in 16 diameters (range, 11–26 mm) in 1 mm increments.
Fig. 2. (A) and (B): A/P and lateral x-rays of revision THA with Restoration® Modular system using a cone body and a conical stem at 5-year follow-up with well-fixed implants.
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Table 1 Demographic Information. Frequency Number of cases/patients Unilateral Bilateral Men/Women (n) Mean age, years (range) Mean height, inches (range) Mean weight, pounds (range) Diagnosis (% of cases) Osteoarthritis Rheumatoid arthritis Posttraumatic arthritis Avascular necrosis Others Previous surgeries (% of cases) 1 2 3 N3 Mean time to revision, years (range) [evaluation date to previous implant date]
122/120 118/118 2/2 59/61 67.82 (31–85) 66.32 (56.0–80.0) 174.60 (100.0–295.0) 62 (50.8%) 7 (5.7%) 10 (8.2%) 13 (10.7%) 30 (24.6%) 92 (75.4%) 20 (16.4%) 5 (4.1%) 5 (4.1%) 10.76 (0.02–32.24)
Table 2 Surgical Details. Frequency (% of cases) Number of cases/patients Reason for revision Pain Aseptic loosening Septic loosening Femoral fracture Stem fracture Other Bone defect classification Type 1 Type 2 Type 3A Type 3B Type 4 Unspecified Mean surgical time, min (range) Mean blood loss, ml (range) Approach Anterior Posterior Lateral Transtrochanteric osteotomy Yes No Stem/Body combination Broached body/fluted stem Broached body/plasma stem Calcar body/plasma stem Cone body/conical stem Cone body/plasma stem Other Cabling used Yes—Dall Miles Yes—Other No Bone graft used Yes—allograft Yes—autograft No Leg length correction attempted Yes No Mean leg length correction, mm (range) Attempted Achieved
122/120 79 (65.3%) 85 (70.8%) 4 (3.3%) 6 (5%) 4 (3.3%) 36 (30%) 17 (14.2%) 49 (40.8%) 35 (29.2%) 12 (10%) 5 (4.2%) 2 (1.6%) 174.3 (50.0–385.0) 952.1 (20.0–6000.0) 6 (5%) 62 (51.7%) 52 (43.3%) 34 (28.3%) 86 (71.7%) 1 (0.8%) 6 (5%) 5 (4.2%) 88 (73.3%) 18 (15%) 2 (1.7%)
Fig. 3. Image of Restoration Modular implant with varying cone body sizes and conical, tapered, fluted stems with various diameters.
The proximal portion or body is made of a titanium–aluminum vanadium alloy (Ti–6Al–4 V) and is circumferentially plasma sprayed with commercially pure titanium and sprayed over again with hydroxyapatite (PureFix™ HA; Stryker Orthopaedics). It has a regular cylindrical form for the cone type and a flange with cobalt–chrome (CoCr) brushings to allow proper abductor reattachment added to the cylindrical form in the calcar type. Both body types have a 132¡ neck angle and are available in seven body diameters (range, 19–31 mm) with 2 mm increments. The cone type body has four vertical offsets (+ 0 mm, + 10 mm, + 20 mm, and + 30 mm) providing a vertical size of 70 mm, 80 mm, 90 mm, and 100 mm, respectively; the calcar type has three vertical offsets (+10 mm, +20 mm, and +30 mm) providing a vertical size of 80 mm, 90 mm, and 100 mm, respectively. Both body types have a V40TM (Stryker Orthopaedics) trunnion to accept CoCr 22-mm, 26-mm, 28-mm, 32-mm, 36-mm, 40-mm or 44-mm heads or alumina ceramic 28-mm, 32-mm, or 36-mm heads. Lateral offset is achieved through head-neck increments of − 4 mm, + 0 mm, +4 mm, +8 mm, or +12 mm [12]. Other proximal body types included the milled body and broached body. Both the milled and broached bodies are used when there is adequate proximal bone available and are designed to provide maximum stability with proximal fit and fill. The MT3 body is no longer offered by the manufacturer. Surgical Technique
56 (46.7%) 2 (1.7%) 62 (51.6%) 37 (30.8%) 11 (9.2%) 72 (60%) 99 (82.5%) 19 (15.8%) 16.1 (0.3–63.0) 15.1 (0.3–63.0)
Depending upon the quality of the host bone, either a porous-coated, plasma sprayed cylindrical, or tapered, grit blasted, fluted stem can be utilized when distal fixation is required. The polished fluted stem provides rotational stability but lacks the ability for on growth. The choice of implant is determined by the surgeon based on the extent of bone loss and the quality of the available host bone. The surgical technique consisted of removal of the prior implant along with any debris in the medullary canal such as methylmethacrylate. The medullary canal of the femur can be reamed with flexible reamers to remove debris and sclerotic bone. Rigid reamers either conical or cylindrical are then
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Fig. 4. Image of commonly used Restoration Modular (Stryker, Mahwah, NJ) proximal body (broached, calcar, milled, conical, MT3 no longer offered) and stem options (polished fluted, tapered fluted, grit blasted, and cylindrical plasma sprayed) utilized for fixation during femoral component revision.
utilized to obtain cortical contact. Under reaming of 0.5–1 mm was performed with plasma sprayed cylindrical stems while line-to-line reaming was undertaken with fluted, tapered stems. If there was any risk of femoral cortical fracture due to osteolysis or bone defects then prophylactic cables or strut graft would be applied prior to the reaming process. In cases of extended trochanteric osteotomies, a prophylactic cable was applied distal to the osteotomy to prevent migration of any fracture line. The length of the desired femoral stem is based on the pre-operative plan. Once the rigid reamers obtained cortical contact at the appropriate length, the modular femoral stem was then inserted. The proximal femoral canal was then reamed to achieve some cortical contact and a trial reduction undertaken. In most cases a cone type of proximal body was utilized since it is inserted with a reaming process which can minimize fracture risk as opposed to a broaching technique. The modular proximal femoral bodies comes in 4 different heights (standard, + 10 mm, +20 mm, +30 mm) and several diameters which helps achieve the desired leg length and offset regardless of the stem diameter. The implant combination of a cone body with a tapered, fluted, conical stem (Wagner type) was the most commonly used combinations. Cables were utilized for fixation of strut grafts, repair of trochanteric osteotomies, or fixation of intraoperative fractures. Patients were followed at six weeks, three months, one year, two years, and at five years post-surgery. Standard pelvis AP and lateral radiographs of the affected hip were taken at follow-up visits for evaluation. Radiographic implant stability was assessed at all visits. Radiographic assessment of femoral component employed seven zones (1–7) in the AP view and 7 zones (8–14) in the lateral view [13]. Radiolucency in at least 50% of a zone and measuring at least 1 mm in width was considered as radiolucency present. Failure was defined as radiolucent lines 3 2 mm around the entire stem in either the AP or lateral view. Stem migration was defined as a measurable change in the position of the femoral component in a varus or valgus position, and reported as progressive if movement of at least 5 mm was observed on two serial films. Stem subsidence was calculated between the initial immediate postoperative radiograph and the most recent follow-up radiograph with progressive subsidence defined as settling in of the femoral implant of at least 3 mm on two serial films [14]. Implant failure was defined as reoperation of the femoral component for any cause. Standard questionnaires were completed at each visit to calculate the Harris Hip Score [15] and SF-36 [16].
the follow-up period, eight were lost to follow-up, three had removal of the femoral implant and eleven withdrew from the study for various reasons, leaving 91 revisions in 89 patients with a 2–5 year follow up, average 3.7 years. Harris Hip Scores improved from a preoperative mean score of 46 to 88 points at five-year follow-up with more than 86% of cases reported with fair, good, or excellent scores. The SF-36 score showed improvement from a mean preoperative score of 31 to 44 points at five-year follow-up. Radiographic assessment at follow-up intervals showed absence of radiolucency in zones 1–7 in the AP view for 90% of cases at one-year and more than 84% of cases at five-year follow-up. There was absence of radiolucency in zones 8–14 in the lateral view in 89% of cases at one-year and more than 92% of cases at five-year follow-up. Stem migration was observed in four cases within the first postoperative year, which was progressive in three cases. One of the three cases with progressive stem migration underwent a femoral stem revision for a postoperative femoral fracture. The other two cases had no significant clinical findings and were asymptomatic at latest follow up. There were 26 patients with subsidence measured by the independent radiographic reviewer. Fifteen of these cases were first observed within 3 months postoperatively without further subsidence. The distance of the stem subsidence was stratified into 3 groups: 1) less than 2 mm, 2) 2–4 mm, and 3) 5 mm or greater. Of these 15 there were 6 in group 1, 5 in group 2 and 4 in group 3. Those that subsided at 1–2 years included two in group 1 and 3 in group 2. None of these cases had further progression. Of the 26 patients that subsided, 22 had a conical stem and 4 had a plasma stem. There were a total of 11 dislocations (9%) in this study group. There were a total of 229 adverse events reported for all cases over the five-year follow-up period (Table 3). There were nine revisions in eight cases of which three involved the femoral stem and body: two required revision of the femoral stem and one required revision of the femoral head and body only. The remaining six revisions in five cases involved only acetabular components and/or femoral heads. There were 14 reoperations reported for other reasons: six incidences of debridement for superficial wound infection/hematoma, three debridements in a case of deep infection, two cases for ORIF of periprosthetic fractures, and three cases of later removal of trochanteric hardware. There were 18 intraoperative fractures that went on to union. Overall, there was 97% survivability of the Restoration¨ Modular revision hip implant in the above study at five-year follow-up.
Results
Discussion
Of the initial 120 revision cases, one death occurred immediately postoperatively. There were a total of seven deaths over the course of
Proximal femoral deficiency at the time of revision THA can be a challenging situation and in most cases requires distal femoral fixation
P.K. Bhatia et al. / The Journal of Arthroplasty 30 (2015) 1397–1402 Table 3 Adverse Events. Related to Device
Related to surgery
Patient related
Total
Subsidence of femoral component Loosening of femoral component Loosening of acetabular component Dislocation Subluxation Dissociation of modular junction Intra-op femoral fracture/crack Intra-op trochanteric fracture/crack Intra-op acetabular fracture Deep joint infection Superficial wound infection Wound hematoma/wound related/other Post-op femoral fracture Post-op trochanteric fracture Trochanteric non-union Bursitis Thrombophlebitis Cardiovascular Bronchopulmonary Genitourinary Gastrointestinal Neurological Others 229
2 1 3 10 2 1 10 7 1 2 4 9 2 2 1 12 1 24 5 11 6 8 104
for predictable outcomes [17]. The results of revision THA using cement have a high failure rate primarily due to poor bone–cement interdigitation due to a smooth sclerotic femoral surface.[14,18,19]. The incidence of failure after revision total hip arthroplasty without cement is somewhat better with a failure of 2% to 7% at three to six years postoperatively [20–24]. Immediate stability is mandatory for uncemented revision components. Since there is no proportional relationship between the metaphyseal and diaphyseal geometry in the proximal portion of the femur, as often is the case in revision surgery, fit and fill are often difficult to achieve in practice. Due to the osteolytic defects there is invariably a metaphyseal/ diaphyseal mismatch at the proximal femur. Various options are available to manage the mismatch in the proximal femoral geometry encountered at the time of revision [3,5,6,10,25]. The use of modular femoral implants is an option and provides intraoperative versatility to correct leg length discrepancy, restoration of offset and stability independent of distal fixation. Proximally coated monobloc stems for femoral component revision have demonstrated relatively higher failure rates as compared to modular stems. Mulliken et al [26] reported a 24% mechanical failure rate with 10% of cases undergoing revision at four to six years of follow-up. Malkani et al [27] reported a 28.7% revision rate in 69 patients at mid-term follow-up. Woolson and Delaney [28] reported a 20% revision rate and a 45% mechanical failure rate in their study of 28 hips. Although there has been success in revision hip arthroplasty using extensively coated monolithic stems, intraoperative challenges with metaphyseal and diaphyseal mismatch and complications were still reported [29,30]. There are several studies demonstrating success of modular femoral implants in revision surgeries [10,25,31,32]. Offset and leg length restoration are important goals of the revision procedure and likely play a large role in the functional outcome of the procedure [33]. The low mechanical failure rate experienced with the modular stems in these studies can be the result of the ability of the surgeon to obtain independent distal fixation from the other aspects of the revision procedure such as version, offset, and leg length. Garbuz et al [34] showed improved outcomes with modular fluted and tapered titanium stems compared to cylindrical extensively coated cobalt chrome stems with single modularity. Koster et al [22] showed a 96% survival rate with aseptic loosening as an end point over an average of 10 years for a modular uncemented revision stem. Christie et al [35] noted about a 99% survival rate from revision with a modular femoral stem. Our study showed a
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97% survival rate with only one incidence of aseptic stem loosening requiring revision. In this case, the stem had subsided greater than 5 mm. Although we had other patients subside. They were not symptomatic or had subsided into a stable position. Two other cases of stem revisions were for a periprosthetic fracture and for dissociation at the modular junction. The survival rate in our series is comparable to other studies of similar and even non-modular extensively porous coated implants. There were 18 cases of intraoperative fractures (15%) out of which 10 were of the femur shaft, 7 trochanteric and 1 acetabular. Studies in the literature have also reported high intraoperative fracture rates in femoral component revision. Mulliken et al [26] reported a 40% intraoperative fracture rate. Christie et al [35] reported a 22.5% intraoperative fracture rate. We were able to reduce our intraoperative fracture incidence by using prophylactic cables especially when an extended trochanteric osteotomy was utilized. In an attempt to obtain rigid distal fixation, significant hoop stresses are applied; and on compromised bone, this can lead to fracture. Twelve of the fractures (67%) occurred during the initial 10 cases contributed by each of the individual surgeons implying a learning curve with the use of this modular femoral system. The incidence of fracture diminished with the use of prophylactic cables prior to the reaming process and insertion of the implant. Dislocation is a common complication following revision total hip arthroplasty. The incidence of dislocation has been reported in the literature from 4% to 25% following revision hip arthroplasty due to several factors. In this current series, the rate of dislocation was 9% which may be comparable with other studies such as Restrepo et al [10] with a 3% dislocation rate, Park et al [12] with a 5%, Ovesen et al [31] with a 6%, and Rodriguez et al [32] with a 10% dislocation rate. Dislocation can be minimized with modular proximal bodies given the ability to alter offset and version. The offset can change through modification of cone body diameter and height in combination with neck length. Although an attempt was made to restore offset a direct liner radiographic measurement was not part of the radiographic study protocol and therefore hard data to compare pre and post operative offset was not available. But in theory, based on the design of the modular proximal body, the surgeon has the ability to modify offset intraoperatively, based on the desired goals. Despite the many options available to restore offset and leg length, the dislocation incidence could be further reduced and additional work is necessary to identify factors that play a role. Pierson et al [36] reported on a series of fractures at the modular body stem junction of modular implants. Two other recent reports on modular revision stems [31,32] experienced a 1% stem fracture rate. In this current design 2nd generation modular femoral implant, the biomechanical properties of the morse taper junction have been significantly improved with the use of nitride impregnation, burnishing and shot peening at the morse taper to significantly add further strength [37]. The proximal metaphyseal body is porous coated which promotes ongrowth with proximal loading, potentially minimizing proximal stress shielding as well as decreasing the stresses placed on the morse taper junction [38]. There have been no fractures of the femoral stem in our series, but there has been one case of dissociation at the modular body stem junction where the body was not completely seated on the stem taper requiring revision. There are several limitations to our study. This was a prospective multicenter study with different surgeons bringing their own surgical technique, experience, and perspective. The excellent survivorship despite the learning curve demonstrates the versatility of the modular revision hip system utilized at the various multiple centers. Patients were not randomized, and the our results are short-to midterm. The true benefit of modular femoral stems in revision total hip arthroplasty is the ability to provide independent diaphyseal and metaphyseal fixation which simplifies and separates the surgical goals in achieving distal stability and restoring leg length, version and offset. The versatility of this modular femoral implant is exemplified by the fact that multiple surgeons with their own prior surgical experience were able to effectively
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achieve good clinical results in a host of patients with varying degrees of bone loss undergoing revision THA. The current challenges and further studies that are required need to minimize complications such as fracture and dislocation. Based on our studies we feel that a 2nd generation modular femoral implant provides at least equivalent results to those of extensively coated monolithic stems but with greater versatility and simplicity. References 1. Kurtz S, Mowat F, Ong K, et al. Prevalence of primary and revision total hip and knee arthroplasty in the United States from 1990 through 2002. J Bone Joint Surg Am 2005; 87:1487. 2. Kurtz S, Mowat F, Ong K, et al. Primary and revision arthroplasty surgery caseloads in the United States from 1990–2004. J Arthroplasty 2009;24(2):195. 3. Della Valle CJ, Paprosky WG. Classification and an algorithmic approach to the reconstruction of femoral deficiency in revision total hip arthroplasty. J Bone Joint Surg Am 2003;85-A(Suppl. 4):1. 4. Gramkow J, Jensen TH, Varmarken JE, et al. Long-term results after cemented revision of the femoral component in total hip arthroplasty. J Arthroplasty 2001;16(6):777. 5. Engh Jr CA, Ellis TJ, Koralewicz LM, et al. Extensively porous-coated femoral revision for severe femoral bone loss: minimum 10-year follow-up. J Arthroplasty 2002;17(8):955. 6. Sporer SM, Paprosky WG. Femoral fixation in the face of considerable bone loss: the use of modular stems. Clin Orthop Relat Res 2004;429:227. 7. Hostner J, Hultmark P, Karrholm J, et al. Impaction technique and graft treatment in revisions of the femoral component: laboratory studies and clinical validation. J Arthroplasty 2001;16(1):76. 8. Blackley HR, Davis AM, Hutchison CR, et al. Proximal femoral allograft for reconstruction of bone stock in revision arthroplasty of the hip. A nine to fifteen-year follow-up. J Bone Joint Surg Am 2001;83-A(3):346. 9. Malkani AL, Settecerri JJ, Sim FH, et al. Long-term results of proximal femoral replacement for non-neoplastic disorders. J Bone Joint Surg (Br) 1995;77(3):351. 10. Restrepo C, Mashadi M, Parvizi J, et al. Modular femoral stems for revision total hip arthroplasty. Clin Orthop Relat Res 2011;469:476. 11. Berry DJ. Treatment of Vancouver B3 periprosthetic femur fractures with a fluted tapered stem. Clin Orthop Relat Res 2003;417:224. 12. Park YS, Moon YW, Lim SJ. Revision total hip arthroplasty using a fluted and tapered modular distal fixation stem with and without extended trochanteric osteotomy. J Arthroplasty 2007;22:993. 13. Engh CA, Massin P, Suthers KE. Roentgenographic assessment of the biologic fixation of porous-surfaced femoral components. Clin Orthop Relat Res 1990;257:107. 14. 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. 15. Harris WH. Traumatic arthritis of the hip after dislocation and acetabular fractures: treatment by mold arthroplasty. An end-result study using a new method of result evaluation. J Bone Join Surg Am 1969;51:737. 16. Ware Jr JE, Sherbourne CD. The MOS 36-item short-form health survey (SF-36). I. conceptual framework and item selection. Med Care 1992;30:473.
17. Sporer SM, Paprosky WG. Revision total hip arthroplasty: the limits of fully coated items. Clin Orthop Relat Res 2003;417:203. 18. Estok 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;299:190 [296]. 19. Meding JB, Ritter MA, Keating EM, et al. Impaction bone grafting before insertion of femoral stem with cement in revision total hip arthroplasty: a minimum two-year follow up study. J Bone Joint Surg Am 1997;79:1834. 20. Gustilo R, Pasternak H. Revision total hip arthroplasty with titanium ingrowth prosthesis and bone grafting for the failed cemented femoral segment loosening. Clin Orthop 1988;235:111. 21. Hungerford DS, Jones LC. The rationale of cementless revision of cemented arthroplasty failures. Clin Orthop 1988;235:12. 22. Koster G, Walde TA, Willert HG. Five- to 10-year results using a noncemented modular revision stem without bone grafting. J Arthroplasty 2008;23(7):964. 23. Krishnamurthy AB, MacDonald SJ, Paprosky WG. 5- to-13-year follow up study on cementless femoral components in revision surgery. J Arthroplasty 1997;12:839. 24. Moreland JR, Bernstein ML. Femoral revision hip arthroplasty with uncemented porous310 coated stems. Clin Orthop Relat Res 1995;319:141. 25. Myung-Sin Park, Lee Ju-Hong. A distal fluted, proximal modular femoral prosthesis in revision hip arthroplasty. J Arthroplasty 2010;25(6):932. 26. Mulliken BD, Rorabeck CH, Bourne RB. Uncemented revision total hip arthroplasty: a 4314 to-6-year review. Clin Orthop Relat Res 1996;325:156. 27. Malkani AL, Lewallen DG, Cabanela ME, et al. Femoral component revision using an uncemented, proximally coated, long-stem prosthesis. J Arthroplasty 1996;11(4):411. 28. Woolson ST, Delaney TJ. Failure of a proximally porous-coated femoral prosthesis in revision total hip arthroplasty. J Arthroplasty 1995(10 Suppl.):S22. 29. Crawford CH, Malkani A, Incavo SJ, et al. Femoral component revision using an extensively hydroxyapatite-coated stem. J Arthroplasty 2004;19(1):8. 30. Weeden SH, Paprosky WG. Minimal 11-yr follow-up of extensively porous coated stems in femoral revision total hip arthroplasty. J Arthroplasty 2002;17(4 Suppl. 1):134. 31. Ovesen O, Emmeluth C, Hofbauer C, et al. Revision total hip arthroplasty using a modular tapered stem with distal fixation good short-term results in 125 revisions. J Arthroplasty 2010;25:348. 32. Rodriguez JA, Fada R, Murphy SB, et al. Two-year to five-year follow-up of femoral defects in femoral revision treated with the link MP modular stem. J Arthroplasty 2009; 24:751. 33. Lecerf G, Fessy MH, Philippot R, et al. Femoral offset: anatomical concept, definition, assessment, implications for preoperative templating and hip arthroplasty. Orthop Traumatol Surg Res 2009;95:210. 34. Garbuz DS, Toms A, Masri BA, et al. Improved outcome in femoral revision arthroplasty with tapered fluted modular titanium stems. Clin Orthop Relat Res 2006;453:199. 35. Christie MJ, DeBoer DK, Tingstad EM, et al. Clinical experience with a modular non cemented femoral component in revision total hip arthroplasty: 4- to 7-year results. J Arthroplasty 2000;15(7):840. 36. Pierson JL, Crowninshield RD, Earles DR. Fatigue fracture of a modular revision femoral component: a report of forty cases. Presented at the Annual Meeting. February, 2005; Am Acad Orthop Surg, Washington, DC; 2005. 37. Shot Peening Applications. Metal Improvement Company, Inc.; 2003[Eighth edition]. 38. Hnat WP, Conway JS, Malkani AL, et al. The effect of modular tapered fluted stems on proximal stress shielding in the human femur. J Arthroplasty 2009;24(6):957.
