- Email: [email protected]
The Wagner Cone Stem for the Management of the Challenging Femur in Primary Hip Arthroplasty
The Journal of Arthroplasty xxx (2016) 1e6
Contents lists available at ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Original article
The Wagner Cone Stem for the Management of the Challenging Femur in Primary Hip Arthroplasty Michael C. Parry, BSc (Hons), MD, FRCS *, Mihai H. Vioreanu, MCh, MD, FRCS, Donald S. Garbuz, MD, MHSc, FRCS (C), Bassam A. Masri, MD, FRCS (C), Clive P. Duncan, MD, MSc, FRCS (C) Department of Orthopaedics, University of British Columbia, Vancouver, British Columbia, Canada
a r t i c l e i n f o
a b s t r a c t
Article history: Received 19 October 2015 Received in revised form 14 January 2016 Accepted 2 February 2016 Available online XXX
Background: Splined conical stems offer design features that facilitate their use in the misshapen, dysplastic proximal femur. Methods: This study assessed the survivorship of a conical prosthesis when applied to secondary coxarthrosis because of a range of pathologies. Fifty-one prostheses were implanted in 50 patients with a mean age of 50 (range, 15-80) and a median follow-up of 34 months (range, 24-73 months). Indications for the stem included developmental (36), neuromuscular (7), post-traumatic or surgical (7), and inflammatory conditions (1). Survivorship, functional outcome (WOMAC [Western Ontaria and McMaster University Osteoarthrits Index], Oxford Hip Score, and UCLA [University of California Los Angeles]), health status (short form-12 [SF-12]), satisfaction, and osseointegration were determined. Results: Survivorship for aseptic loosening was 100% at 2 years and 98.04% for septic revision. Eight patients required reoperation, 4 for instability, and 1 each for infection, impingement, adverse reaction to metal debris, and pelvic insufficiency fracture. The mean WOMAC score was 85 (standard deviation [SD], 18), the mean Oxford Hip Score 84 (SD, 18), the mean physical SF-12 score was 48.3 (SD, 8.6), and the mean mental SF-12 was 53.7 (SD, 9.2), the mean satisfaction score was 91.5 (SD, 3.9), and the mean UCLA was 6 (SD, 1.6). All femoral components demonstrated osseointegration. Conclusion: The cone femoral prosthesis demonstrates excellent early survival and osseointegration when applied to the challenging femur. Because of these encouraging results, we recommend this prosthesis be considered for the small, abnormal femur in primary hip arthroplasty. © 2016 Elsevier Inc. All rights reserved.
Keywords: taper fluted stem complex primary arthroplasty dysplasia skeletal dysplasia survival
A number of congenital, developmental, or acquired abnormalities of hip development can lead to distorted anatomy of the proximal femur after skeletal maturity. These include developmental dysplasia, neuromuscular disorders, as well as infection, injury, or surgical intervention in early childhood, to mention just a few. The following anatomic variations may follow, alone or in combination, in these settings: undersized femoral neck or canal, excessive varus or valgus angulation, abnormal version, and limited
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.2016.02.007. * Reprint requests: Michael C. Parry, BSc (Hons), MD, FRCS, The Royal Orthopaedic Hospital, Bristol Road South, Birmingham, B31 2AP, UK. http://dx.doi.org/10.1016/j.arth.2016.02.007 0883-5403/© 2016 Elsevier Inc. All rights reserved.
horizontal offset [1,2]. If hip joint arthroplasty is later required, these deformities may prove to be challenging to manage because standard stems cannot be easily accommodated by the undersized, deformed femur. Instead the surgeon needs to consider specialized designs, modularity, or customized manufacture [3-5]. The Cone prosthesis (Zimmer-Biomet, Warsaw, IN), developed by Wagner H and Wagner M [6], was designed to address many of these issues. Meant for cementless fixation, it is a Protasul-64 titanium alloy stem with a corundum-blasted surface with a mean surface asperity height of 5 mm, a 5 taper, and 8 longitudinal flutes distributed around the circumference and length of the stem. The presence of the flutes results in high contact pressures between the stem and endosteal bone, which confers rotational stability [7-9]. The relatively high conical taper leads to taper-lock axial or vertical stability. The cylindrical design allows for “dial-in” selection of anteversion, permitting correction of torsional abnormalities affecting the proximal femur. In addition, it has a reduced
2
M.C. Parry et al. / The Journal of Arthroplasty xxx (2016) 1e6
horizontal offset to accommodate the limited offset encountered in so many of the congenital and acquired deformities encountered in this group of patients. Implantation is relatively straightforward. The medullary canal is prepared with a series of conical reamers of increasing size instead of the angular-shaped rasps and broaches used for more conventional femoral stems. These features of the implantation system and final stem have expanded the indications for the cone prosthesis to include the undersized, cylindrical femur seen in congenital dislocation and dysplastic coxarthrosis, congenital coxa vara, deformation and intramedullary bony scarring of the proximal femur resulting from previous osteotomies, fractures or growth disturbances, and congenital deformities [10-12]. It is easily adapted to deformities relating to neuromuscular disorders as well, such as cerebral palsy, poliomyelitis, and spina bifida. Many of these entities also have a reduced horizontal offsetdanother attractive feature of the stem design. Initial reports have demonstrated excellent results in both the short and medium term with the Cone prosthesis [6,13,14]. Longer term survivorship of 91.5% at a mean of 11.5 years [12] has been reported. This represents an improvement on previous studies in this difficult cohort of patients [15-17]. To date, most published outcome studies have either been from the designer center or include cases treated by one of the designer surgeons [6,9,12]. Reports of its use and outcomes in the North American centers have not been well documented. The aims of this study were to report the radiological, clinical, and patient-reported outcomes of the Wagner cone femoral prosthesis when applied to the challenging femur resulting from a breadth of underlying conditions in the largest series from a North American institution.
Materials and Methods To assess the use of the implant in the context of “the challenging femur,” inclusion to the study was restricted on the basis of preoperative diagnosis. As previously described, this included coxarthrosis secondary to dislocation and dysplasia, coxa vara, Legg-Calve-Perthes disease, skeletal dysplasia (multiple or spondyloepiphyseal types), previous hip fusion (Fig. 1), juvenile rheumatoid arthritis, and previous trauma requiring proximal femoral instrumentation.
The study population comprised 51 prostheses implanted in 50 patients between July 2007 and April 2012. Thirty were females, and the median age was 50 years (range, 15-80 years). The indications for hip arthroplasty are listed in Table 1. Previous surgery had been performed in 15 hips and comprised pelvic osteotomy in 4, femoral osteotomy in 7 (Fig. 2), hip arthrodesis or attempted arthrodesis in 3, instrumentation of the proximal femur after trauma in 1, and trochanteric advancement and limb lengthening in 1. Of the 50 patients included in the study, 49 were alive at final follow-up, 1 patient having died of an unrelated condition but after completion of radiographic and patient-reported outcome. The median duration of follow-up was 34 months (range, 24-73 months). The decision to use the prosthesis was surgeon dependent but was based on preoperative templating where the proximal femoral morphology was felt to preclude a conventional, proximally flared, metaphyseal loading uncemented implant, and when the narrow diameter of the femoral medullary canal would not allow insertion of a cemented component with a satisfactory cement mantle. The implant was also chosen when correction of femoral torsion was required to accurately restore proximal femoral anatomy and hip joint mechanics and in cases where a preexisting reduced horizontal offset required a similar offset in the stem design (Fig. 3). A posterolateral approach was used in 48 hips, whereas in 3 cases of either arthrodesis takedown or failed arthrodesis, a trochanteric osteotomy was used. After dislocation of the femoral head, the femoral neck was osteotomized at a distance from the lesser trochanter determined during preoperative templating. Implantation of the acetabular component proceeded in a conventional fashion taking into consideration the altered morphology of the acetabulum and, when required, the increased risk of postoperative instability due to preoperative neuromuscular imbalance. The medullary canal was identified with a cavity probe, and the presence of obstruction identified, for example, cortical bars from previous proximal femoral instrumentation or osteotomy. A tapered conical reamer was then introduced in the long axis of the femur. Serial reaming was performed to dilate the medullary canal and was completed when significant resistance was encountered at an appropriate penetration depth as measured from the head-center mark on the reamer. Prostheses are available in a range of diameters from 13 to 24 mm with increasing horizontal offset and 2 neck-shaft angles (125 or 135 ). Trial reduction was undertaken with the appropriately sized prosthesis, the surgeon
Fig. 1. The case of a patient presenting with low back pain attributed to a previous successful right hip arthrodesis for the treatment of secondary coxarthrosis because of septic arthritis in childhood. A subsequent fracture was treated with open reduction and fixation: (A) preoperative radiograph demonstrating evidence of significant deformity of the proximal femur; (B) postoperative radiograph with evidence of integration of both femoral and acetabular components and union of the trochanteric osteotomy.
M.C. Parry et al. / The Journal of Arthroplasty xxx (2016) 1e6 Table 1 Relative Numbers of Underlying Pathologies Resulting in End-Stage Coxarthrosis Within the Study Population. Diagnosis
n (%)
Developmental dysplasia Legg-Calve-Perthes disease Neuromuscular condition (cerebral palsy, Down’s syndrome, childhood brain injury, and poliomyelitis) Childhood trauma including septic arthritis MED/SED Takedown hip arthrodesis Juvenile rheumatoid arthritis Osteopetrosis Proximal femoral focal deficiency
24 (47) 7 (13.7) 7 (13.7) 4 3 3 1 1 1
(7.8) (5.9) (5.9) (1.9) (1.9) (1.9)
MED, multiple epiphyseal dysplasia; SED, spondyloepiphyseal dysplasia.
dialing in 15 -25 of anteversion as required, to achieve a combined anteversion (cup and femur) of 40 . Definitive reduction was achieved with the appropriate stem and femoral head combination. The neck angle (125 or 135 ) was chosen during preoperative templating, and a final decision made during operation. Most femoral components were in the size range 14-19 mm with only 1 patient requiring a 13-mm component and 5 patients requiring components >19 mm. Acetabular component size ranged form 44 to 58 mm. One patient required a constrained acetabular liner at the primary procedure for stability. This was against the background of cerebral palsy with global muscle weakness and poor muscular coordination. Femoral head sizes were 28 mm (6), 32 mm (36), 36 mm (8) and 44 mm (1). Radiographic assessment of femoral components was made on 2 separate occasions, the first in the immediate postoperative period and the second a minimum of 24 months after operation. Radiographic signs of osseointegration between the femoral component and the host bone were adapted from the criteria of Engh et al [18]. The following signs of fixation were noted: (1) absence of a radiolucent line at the bone-implant interface and (2) presence of spot-welds. A search for signs of interface instability or motion was also completed: (1) appearance of progressive radiolucencies; (2) a distal pedestal sign attempting to support a subsiding stem; and (3) component subsidence or migration.
3
Assessments of health status were made at a minimum 24 months after operation and comprised an Short Form-12 (SF-12) questionnaire [19]. Hip function outcome was assessed with the Oxford Hip Score [20], and patient function outcome was assessed using the Western Ontaria and McMaster University Osteoarthrits Index (WOMAC) score [21]. Patient activity was measured with the University of California Los Angeles (UCLA) 10-point activity score [22]. Satisfaction was recorded using a self-administered questionnaire assessing satisfaction in 4 domains [23]. Statistics A D’Agostini and Pearson normality test was performed to determine distribution of data. When data were normally distributed, central tendency is described with the mean and standard deviation (SD). When data were not normally distributed, median and ranges are presented. A Wilcoxon rank sum test was used to compare patient-reported outcomes, stratified for diagnosis. Survival of the implant was defined as revision for any cause and revision for aseptic loosening and was assessed using a KaplanMeier survivorship analysis with 95% confidence intervals. Results The survivorship of the Wagner Cone femoral prosthesis at a minimum 2-year follow-up was 98.04% (Fig. 4). Survivorship of the femoral component when aseptic loosening was considered as the end point was 100% at 2 years. The survivorship of the operated hip without reoperation for any reason at 2 years was 84.31% (Fig. 5). Exchange of the stem was required in only 1 patient as part of a 2-stage approach to management of hematogenous infection at 40 months after the index procedure. Reoperation for other reasons was required in 7 patients. Four patients required revision for recurrent instability. This was managed by revising the femoral head in 2 cases, revision of the acetabular component to a constrained liner in 2 cases. In none of these cases of instability was the stem revised. One patient, initially implanted with a large diameter metal-on-metal bearing, developed a symptomatic pseudotumor necessitating revision of the acetabular component and conversion
Fig. 2. Typical case representative of the series: (A) the patient presented with symptomatic coxarthrosis secondary to poliomyelitis after previous valgising proximal femoral osteotomy; (B) subsequent recurrent instability after the primary procedure was treated by revision of the acetabular component to accommodate a focally constrained acetabular liner.
4
M.C. Parry et al. / The Journal of Arthroplasty xxx (2016) 1e6
Fig. 3. Thirty-eight-year-old female patient presenting with end-stage coxarthrosis secondary to Leg-Calve-Perthes disease with typical reduction in femoral offset, shortening and dysplasia of the proximal femur (A). The patient underwent staged bilateral total hip arthroplasty, combined with modest lengthening of each leg, using the Wagner cone prosthesis (B).
Radiographs were available on all patients at a minimum of 2 years after operation. All femoral components displayed features of osseointegration. Three femoral components demonstrated radiolucent lines in Gruen zones 1 and 7. One femoral component demonstrated a lucent line in zone 1 only. In all cases, these radiolucencies were stable and nonprogressive. The patients were asymptomatic. No femoral components demonstrated lucencies at the diaphyseal interface.
to a ceramic-on-polyethylene bearing. A further patient developed painful abduction impingement because of prominence of the greater trochanter. This was successfully treated by trochanteric advancement without revision of components. One patient developed an acetabular periprosthetic fracture, which required revision of the acetabular component and acetabular reconstruction. The mean WOMAC global score was 85 (SD, 18) and the Oxford Hip Score (OHS) 84 (SD, 18). The mean SF-12 was 48.3 (SD, 8.6) for the physical component and 53.7 (SD, 9.2) for the mental component. The mean satisfaction score was 89.8 (SD, 24.5) with individual components scoring means of 92.2 (SD, 23.7) for pain, 88.7 (SD, 27.4) for function, 86.3 (SD, 26.8) for recreation, and 91.5 (SD, 3.9) for overall satisfaction. The mean UCLA score was 6 (SD, 1.3). Although comparison of functional outcome scores between groups, stratified for diagnosis, was limited because of the small numbers of each individual diagnosis, when diagnoses were grouped as dysplastic and nondysplastic, no significant difference was demonstrated in the global WOMAC score (P ¼ .128), the OHS (P ¼ .325), the physical component of the SF-12 (P ¼ .053), the mental component of the SF-12 (P ¼ .628), overall satisfaction (P ¼ .017), or UCLA score (P ¼ .052). When comparing individual diagnoses, no significant difference in outcome was demonstrated for any of the outcome measures for each of the diagnoses.
The management of secondary coxarthrosis with significant alteration in the proximal femoral morphology can be challenging. A number of solutions have been proposed. Our aim is to report the short-term patient-reported and radiographic outcomes when the Wagner Cone stem is chosen in this setting. The small population and the lack of a comparison group limit the study. However, this is representative of the underlying conditions for which the implant was used, which account for less than 5% of the arthroplasty burden [24]. Survivorship of the Wagner Cone femoral prosthesis when aseptic and septic loosening of the component was considered as the end point was 98.04% at a minimum of 2 years with a
Fig. 4. The survivorship curve shows the Kaplan-Meier analysis with 95% confidence intervals with the need for revision of the Wagner cone femoral prosthesis as the end point.
Fig. 5. The survivorship curve shows the Kaplan-Meier analysis with 95% confidence intervals with the need for reoperation for any cause as the end point.
Discussion
M.C. Parry et al. / The Journal of Arthroplasty xxx (2016) 1e6 Table 2 Previous Studies Demonstrating the Use of the Wagner Cone Prosthesis. Author
No. of Prostheses Included
Follow-Up (y)
Survival (%)
Wagner H and Wagner M [6] €m et al [14] Stro Schuh et al [12] Faldini et al [25] Faldini et al [26] Pavone et al [11] Pak and de Steiger [27]
97 14 94 34 35 7 17
8 5 11.5 12 12 6 4.2
100 100 100 100 100 88.7 100
survivorship of 100% when aseptic loosening of the femoral component was considered. This is comparable to other reports using the Wagner Cone femoral prosthesis for similar pathologies (Table 2). In our series, the Wagner cone prosthesis demonstrated radiological osseointegration in all cases with no evidence of subsidence. Four hips demonstrated nonprogressive radiolucent lines in zones 1 and 7 only. Kim et al [13] reported 1 case of clinically irrelevant stem subsidence and secondary stabilization in a cohort of 60 prostheses implanted for dysplastic coxarthrosis. Wagner H and Wagner M [6], in a report on the first 100 cone prostheses implanted in the designer institution, reported 2 cases of stem subsidence >2 mm. One stem stabilized after subsidence while the other continued to subside requiring revision due to infection. Strom et al [14] reported a mean stem subsidence of 0.27 mm in 13 Wagner cone prostheses. The 100% stem survival with aseptic loosening as the end point is predictive of a 95% 10-year survival in the absence of radiolucent lines 2 mm or subsidence 2 mm [28,29]. The patients included in this study were younger than those treated for primary osteoarthritis, and it is, therefore, conceivable that the increased demands placed on the prosthesis may result in a reduced survival [30-32]. However, the long-term survivorship demonstrated by others with this implant would not support this assumption [6,12,25]. The contribution of the underlying cause of the coxarthrosis on the long-term survival of the implant remains to be demonstrated. The survivorship of this design of femoral component when used in the setting of the challenging femur is encouraging and demonstrates significant improvements from the early failures demonstrated by both cemented and cementless designs [13,16,17,33-36]. This may be representative of the high degree of axial and rotational stability conferred by the conical fluted design when used in the abnormal morphology of the proximal femur [37]. Early and late complications in this series are comparable to those reported by others [12]. We identified 4 cases of instability, which were treated with revision of the acetabular component or upsizing of the femoral head. Instability in these cases may be attributable to the abnormal muscle function of the affected hip (Fig. 3). One patient underwent revision of both components for periprosthetic infection presenting at nearly 4 years after operation. One revision of the acetabular component and femoral head was required for a symptomatic adverse reaction to metal debris because of trunnion corrosion. Further complications, including painful trochanteric impingement and acetabular periprosthetic fracture, can be attributed to the underlying pathology affecting both the proximal femur and pelvis. The patient-reported outcome scores recorded here are reflective of the represented complex preoperative conditions. When compared to conventional total hip arthroplasty (THA) for primary osteoarthritis performed in the same institution, the WOMAC and
5
SF-12 are lower in the complex femur group [38], although it should be noted that overall satisfaction after THA in this group remains high. As is the case for the OHS [39], the activity levels in such a group of patients will be best predicted by the preoperative function [40]. The patient-reported outcomes in this population are comparable to those recorded by others with this stem design, although a variety of methods have been used to record outcome [11,12,25,27,41]. A consistent feature from all these reports is that although satisfaction is high after arthroplasty, function in patients with significant preoperative limitation due to skeletal or neuromuscular conditions is not comparable to that of patients undergoing hip arthroplasty for primary osteoarthritis. In summary, the Wagner cone prosthesis has demonstrated excellent early survivorship when applied to cases of coxarthrosis where there are significant abnormalities in proximal femoral morphology. All femoral components demonstrated osseointegration with no revisions for aseptic loosening. Given the complex nature of the prearthroplasty conditions, THA using the Wagner cone demonstrates high levels of patient-reported outcomes, especially satisfaction. The prosthesis is a simple, versatile stem with wide clinical applications and has become our default stem for the small, challenging femur in all but the most challenging cases. References €ld A. Changes in the capital growth plate and the proximal femoral 1. Langenskio -Perthes disease. Clin Orthop Relat Res 1980;150:110. metaphysis in Legg-Calve 2. Noble PC, Kamaric E, Sugano N, et al. Three-dimensional shape of the dysplastic femur: implications for THR. Clin Orthop Relat Res 2003;417:27. 3. Bargar WL. Shape the implant to the patient. A rationale for the use of customfit cementless total hip implants. Clin Orthop Relat Res 1989;249:73. 4. Huo MH, Salvati EA, Lieberman JR, et al. Custom-designed femoral prostheses in total hip arthroplasty done with cement for severe dysplasia of the hip. J Bone Joint Surg Am 1993;75:1497. 5. Osagie L, Figgie M, Bostrom M. Custom total hip arthroplasty in skeletal dysplasia. Int Orthop 2011;36:527. 6. Wagner H, Wagner M. Cone prosthesis for the hip joint. Arch Orthop Trauma Surg 2000;120:88. €hm P, Bischel O. Femoral revision with the Wagner SL revision stem: eval7. Bo uation of one hundred and twenty-nine revisions followed for a mean of 4.8 years. J Bone Joint Surg Am 2001;83-A:1023. 8. Grünig R, Morscher E, Ochsner PE. Three-to 7-year results with the uncemented SL femoral revision prosthesis. Arch Orthop Trauma Surg 1997;116:187. 9. Wagner H, Wagner M. Femur revision prosthesis. Z Orthop Ihre Grenzgeb 1993;131:574. 10. Kayali C, Agus H, Ozluk S, et al. Treatment for unstable intertrochanteric fractures in elderly patients: internal fixation versus cone hemiarthroplasty. J Orthop Surg (Hong Kong) 2006;14:240. 11. Pavone V, Costarella L, Privitera V, et al. Bilateral total hip arthroplasty in subjects with multiple epiphyseal dysplasia. J Arthroplasty 2009;24:868. 12. Schuh A, Schraml A, Hohenberger G. Long-term results of the Wagner cone prosthesis. Int Orthop 2007;33:53. 13. Kim YY, Kim BJ, Ko HS, et al. Total hip reconstruction in the anatomically distorted hip. Cemented versus hybrid total hip arthroplasty. Arch Orthop Trauma Surg 1998;117:8. €m H, Mallmin H, Milbrink J, et al. The cone hip stem: a prospective study of 14. Stro 13 patients followed for 5 years with RSA. Acta Orthop Scand 2003;74:525. 15. Dickob M, Martini T. The cementless PM hip arthroplasty. Four-to-seven-year results. J Bone Joint Surg Br 1996;78:195. 16. Kawamoto K, Hasegawa Y, Iwase T, et al. Failed cementless total hip arthroplasty for osteoarthrosis due to hip dysplasia. A minimum five-year follow-up study. Bull Hosp Jt Dis 1998;57:130. 17. Nagano H, Inoue H, Usui M, et al. Long-term results of Charnley low-friction arthroplasty for coxarthrosis with congenital hip dysplasia. 15 year follow-up study. Bull Hosp Jt Dis 1997;56:197. 18. Engh CA, Massin P, Suthers KE. Roentgenographic assessment of the biologic fixation of porous-surfaced femoral components. Clin Orthop Relat Res 1990;257:107. 19. Ware JE, Kosinski M, Keller SD. A 12-item short-form health survey: construction of scales and preliminary tests of reliability and validity. Med Care 1996;34: 220. 20. Dawson J, Fitzpatrick R, Carr A, et al. Questionnaire on the perceptions of patients about total hip replacement. J Bone Joint Surg Br 1996;78:185. 21. Bellamy N, Buchanan WW, Goldsmith CH, et al. Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee. J Rheumatol 1988;15:1833.
6
M.C. Parry et al. / The Journal of Arthroplasty xxx (2016) 1e6
22. Amstutz HC, Thomas BJ, Jinnah R, et al. Treatment of primary osteoarthritis of the hip. A comparison of total joint and surface replacement arthroplasty. J Bone Joint Surg Am 1984;66:228. 23. Mahomed N, Gandhi R, Daltroy L, et al. The self-administered patient satisfaction scale for primary hip and knee arthroplasty. Arthritis 2011;2011:1. 24. On Behalf of the National Joint Registry for England WANI, editor. National Joint Registry for England and Wales. http://www.hqip.org.uk/national-jointregistry-9th-annual-report-2012/. [accessed 28.12.2013]. 25. Faldini C, Miscione MT, Chehrassan M, et al. Congenital hip dysplasia treated by total hip arthroplasty using cementless tapered stem in patients younger than 50 years old: results after 12-years follow-up. J Orthop Traumatol 2011;12:213. 26. Faldini C, Nanni M, Leonetti D, et al. Total hip arthroplasty in developmental hip dysplasia using cementless tapered stem. Results after a minimum 10-year follow-up. Hip Int 2011;21:415. 27. Pak P, de Steiger R. Cone femoral prosthesis for osteoarthritis of the hip with femoral dysplasia. J Orthop Surg (Hong Kong) 2008;16:206. 28. Freeman MA, Plante-Bordeneuve P. Early migration and late aseptic failure of proximal femoral prostheses. J Bone Joint Surg Br 1994;76:432. 29. Kobayashi A, Donnelly WJ, Scott G, et al. Early radiological observations may predict the long-term survival of femoral hip prostheses. J Bone Joint Surg Br 1997;79:583. 30. Berry DJ, Harmsen WS, Cabanela ME, et al. Twenty-five-year survivorship of two thousand consecutive primary Charnley total hip replacements. J Bone Joint Surg Am 2002;84:171. 31. Boeree NR, Bannister GC. Cemented total hip arthroplasty in patients younger than 50 years of age. Ten- to 18-year results. Clin Orthop Relat Res 1993;287:153.
32. Losina E, Bliss RL, Wright J, et al. Risk factors for revision of primary total hip arthroplasty: a systematic review. BMC Musculoskelet Disord 2012;13:251. 33. Charnley J, Feagin JA. Low-friction arthroplasty in congenital subluxation of the hip. Clin Orthop Relat Res 1973;91:98. 34. DiFazio F, Shon WY, Salvati EA, et al. Long-term results of total hip arthroplasty with a cemented custom-designed swan-neck femoral component for congenital dislocation or severe dysplasia. J Bone Joint Surg Am 2002;84:204. 35. Papachristou G, Hatzigrigoris P, Panousis K, et al. Total hip arthroplasty for developmental hip dysplasia. Int Orthop 2006;30:21. 36. Stans AA, Pagnano MW, Shaughnessy WJ, et al. Results of total hip arthroplasty for Crowe Type III developmental hip dysplasia. Clin Orthop Relat Res 1998;348:149. 37. Kendrick JB, Noble PC, Tullos HS. Distal stem design and the torsional stability of cementless femoral stems. J Arthroplasty 1995;10:463. 38. Garbuz DS, Tanzer M, Greidanus NV, et al. The John Charnley Award: metal-on-metal hip resurfacing versus large-diameter head metal-on-metal total hip arthroplasty: a randomized clinical trial. Clin Orthop Relat Res 2009;468:318. 39. Field RE. The Oxford hip scores for primary and revision hip replacement. J Bone Joint Surg Br 2005;87-B:618. 40. Williams DH, Greidanus NV, Masri BA, et al. Predictors of participation in sports after hip and knee arthroplasty. Clin Orthop Relat Res 2012;470:555. 41. Maheshwari R, Neill GO, Marsh A, et al. Total hip replacement in developmental dysplasia of the hip using Wagner cone prosthesis with small diameter metalon-metal articulation. Orthop Muscular Syst 2013;2:2161.
Contents lists available at ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Original article
The Wagner Cone Stem for the Management of the Challenging Femur in Primary Hip Arthroplasty Michael C. Parry, BSc (Hons), MD, FRCS *, Mihai H. Vioreanu, MCh, MD, FRCS, Donald S. Garbuz, MD, MHSc, FRCS (C), Bassam A. Masri, MD, FRCS (C), Clive P. Duncan, MD, MSc, FRCS (C) Department of Orthopaedics, University of British Columbia, Vancouver, British Columbia, Canada
a r t i c l e i n f o
a b s t r a c t
Article history: Received 19 October 2015 Received in revised form 14 January 2016 Accepted 2 February 2016 Available online XXX
Background: Splined conical stems offer design features that facilitate their use in the misshapen, dysplastic proximal femur. Methods: This study assessed the survivorship of a conical prosthesis when applied to secondary coxarthrosis because of a range of pathologies. Fifty-one prostheses were implanted in 50 patients with a mean age of 50 (range, 15-80) and a median follow-up of 34 months (range, 24-73 months). Indications for the stem included developmental (36), neuromuscular (7), post-traumatic or surgical (7), and inflammatory conditions (1). Survivorship, functional outcome (WOMAC [Western Ontaria and McMaster University Osteoarthrits Index], Oxford Hip Score, and UCLA [University of California Los Angeles]), health status (short form-12 [SF-12]), satisfaction, and osseointegration were determined. Results: Survivorship for aseptic loosening was 100% at 2 years and 98.04% for septic revision. Eight patients required reoperation, 4 for instability, and 1 each for infection, impingement, adverse reaction to metal debris, and pelvic insufficiency fracture. The mean WOMAC score was 85 (standard deviation [SD], 18), the mean Oxford Hip Score 84 (SD, 18), the mean physical SF-12 score was 48.3 (SD, 8.6), and the mean mental SF-12 was 53.7 (SD, 9.2), the mean satisfaction score was 91.5 (SD, 3.9), and the mean UCLA was 6 (SD, 1.6). All femoral components demonstrated osseointegration. Conclusion: The cone femoral prosthesis demonstrates excellent early survival and osseointegration when applied to the challenging femur. Because of these encouraging results, we recommend this prosthesis be considered for the small, abnormal femur in primary hip arthroplasty. © 2016 Elsevier Inc. All rights reserved.
Keywords: taper fluted stem complex primary arthroplasty dysplasia skeletal dysplasia survival
A number of congenital, developmental, or acquired abnormalities of hip development can lead to distorted anatomy of the proximal femur after skeletal maturity. These include developmental dysplasia, neuromuscular disorders, as well as infection, injury, or surgical intervention in early childhood, to mention just a few. The following anatomic variations may follow, alone or in combination, in these settings: undersized femoral neck or canal, excessive varus or valgus angulation, abnormal version, and limited
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.2016.02.007. * Reprint requests: Michael C. Parry, BSc (Hons), MD, FRCS, The Royal Orthopaedic Hospital, Bristol Road South, Birmingham, B31 2AP, UK. http://dx.doi.org/10.1016/j.arth.2016.02.007 0883-5403/© 2016 Elsevier Inc. All rights reserved.
horizontal offset [1,2]. If hip joint arthroplasty is later required, these deformities may prove to be challenging to manage because standard stems cannot be easily accommodated by the undersized, deformed femur. Instead the surgeon needs to consider specialized designs, modularity, or customized manufacture [3-5]. The Cone prosthesis (Zimmer-Biomet, Warsaw, IN), developed by Wagner H and Wagner M [6], was designed to address many of these issues. Meant for cementless fixation, it is a Protasul-64 titanium alloy stem with a corundum-blasted surface with a mean surface asperity height of 5 mm, a 5 taper, and 8 longitudinal flutes distributed around the circumference and length of the stem. The presence of the flutes results in high contact pressures between the stem and endosteal bone, which confers rotational stability [7-9]. The relatively high conical taper leads to taper-lock axial or vertical stability. The cylindrical design allows for “dial-in” selection of anteversion, permitting correction of torsional abnormalities affecting the proximal femur. In addition, it has a reduced
2
M.C. Parry et al. / The Journal of Arthroplasty xxx (2016) 1e6
horizontal offset to accommodate the limited offset encountered in so many of the congenital and acquired deformities encountered in this group of patients. Implantation is relatively straightforward. The medullary canal is prepared with a series of conical reamers of increasing size instead of the angular-shaped rasps and broaches used for more conventional femoral stems. These features of the implantation system and final stem have expanded the indications for the cone prosthesis to include the undersized, cylindrical femur seen in congenital dislocation and dysplastic coxarthrosis, congenital coxa vara, deformation and intramedullary bony scarring of the proximal femur resulting from previous osteotomies, fractures or growth disturbances, and congenital deformities [10-12]. It is easily adapted to deformities relating to neuromuscular disorders as well, such as cerebral palsy, poliomyelitis, and spina bifida. Many of these entities also have a reduced horizontal offsetdanother attractive feature of the stem design. Initial reports have demonstrated excellent results in both the short and medium term with the Cone prosthesis [6,13,14]. Longer term survivorship of 91.5% at a mean of 11.5 years [12] has been reported. This represents an improvement on previous studies in this difficult cohort of patients [15-17]. To date, most published outcome studies have either been from the designer center or include cases treated by one of the designer surgeons [6,9,12]. Reports of its use and outcomes in the North American centers have not been well documented. The aims of this study were to report the radiological, clinical, and patient-reported outcomes of the Wagner cone femoral prosthesis when applied to the challenging femur resulting from a breadth of underlying conditions in the largest series from a North American institution.
Materials and Methods To assess the use of the implant in the context of “the challenging femur,” inclusion to the study was restricted on the basis of preoperative diagnosis. As previously described, this included coxarthrosis secondary to dislocation and dysplasia, coxa vara, Legg-Calve-Perthes disease, skeletal dysplasia (multiple or spondyloepiphyseal types), previous hip fusion (Fig. 1), juvenile rheumatoid arthritis, and previous trauma requiring proximal femoral instrumentation.
The study population comprised 51 prostheses implanted in 50 patients between July 2007 and April 2012. Thirty were females, and the median age was 50 years (range, 15-80 years). The indications for hip arthroplasty are listed in Table 1. Previous surgery had been performed in 15 hips and comprised pelvic osteotomy in 4, femoral osteotomy in 7 (Fig. 2), hip arthrodesis or attempted arthrodesis in 3, instrumentation of the proximal femur after trauma in 1, and trochanteric advancement and limb lengthening in 1. Of the 50 patients included in the study, 49 were alive at final follow-up, 1 patient having died of an unrelated condition but after completion of radiographic and patient-reported outcome. The median duration of follow-up was 34 months (range, 24-73 months). The decision to use the prosthesis was surgeon dependent but was based on preoperative templating where the proximal femoral morphology was felt to preclude a conventional, proximally flared, metaphyseal loading uncemented implant, and when the narrow diameter of the femoral medullary canal would not allow insertion of a cemented component with a satisfactory cement mantle. The implant was also chosen when correction of femoral torsion was required to accurately restore proximal femoral anatomy and hip joint mechanics and in cases where a preexisting reduced horizontal offset required a similar offset in the stem design (Fig. 3). A posterolateral approach was used in 48 hips, whereas in 3 cases of either arthrodesis takedown or failed arthrodesis, a trochanteric osteotomy was used. After dislocation of the femoral head, the femoral neck was osteotomized at a distance from the lesser trochanter determined during preoperative templating. Implantation of the acetabular component proceeded in a conventional fashion taking into consideration the altered morphology of the acetabulum and, when required, the increased risk of postoperative instability due to preoperative neuromuscular imbalance. The medullary canal was identified with a cavity probe, and the presence of obstruction identified, for example, cortical bars from previous proximal femoral instrumentation or osteotomy. A tapered conical reamer was then introduced in the long axis of the femur. Serial reaming was performed to dilate the medullary canal and was completed when significant resistance was encountered at an appropriate penetration depth as measured from the head-center mark on the reamer. Prostheses are available in a range of diameters from 13 to 24 mm with increasing horizontal offset and 2 neck-shaft angles (125 or 135 ). Trial reduction was undertaken with the appropriately sized prosthesis, the surgeon
Fig. 1. The case of a patient presenting with low back pain attributed to a previous successful right hip arthrodesis for the treatment of secondary coxarthrosis because of septic arthritis in childhood. A subsequent fracture was treated with open reduction and fixation: (A) preoperative radiograph demonstrating evidence of significant deformity of the proximal femur; (B) postoperative radiograph with evidence of integration of both femoral and acetabular components and union of the trochanteric osteotomy.
M.C. Parry et al. / The Journal of Arthroplasty xxx (2016) 1e6 Table 1 Relative Numbers of Underlying Pathologies Resulting in End-Stage Coxarthrosis Within the Study Population. Diagnosis
n (%)
Developmental dysplasia Legg-Calve-Perthes disease Neuromuscular condition (cerebral palsy, Down’s syndrome, childhood brain injury, and poliomyelitis) Childhood trauma including septic arthritis MED/SED Takedown hip arthrodesis Juvenile rheumatoid arthritis Osteopetrosis Proximal femoral focal deficiency
24 (47) 7 (13.7) 7 (13.7) 4 3 3 1 1 1
(7.8) (5.9) (5.9) (1.9) (1.9) (1.9)
MED, multiple epiphyseal dysplasia; SED, spondyloepiphyseal dysplasia.
dialing in 15 -25 of anteversion as required, to achieve a combined anteversion (cup and femur) of 40 . Definitive reduction was achieved with the appropriate stem and femoral head combination. The neck angle (125 or 135 ) was chosen during preoperative templating, and a final decision made during operation. Most femoral components were in the size range 14-19 mm with only 1 patient requiring a 13-mm component and 5 patients requiring components >19 mm. Acetabular component size ranged form 44 to 58 mm. One patient required a constrained acetabular liner at the primary procedure for stability. This was against the background of cerebral palsy with global muscle weakness and poor muscular coordination. Femoral head sizes were 28 mm (6), 32 mm (36), 36 mm (8) and 44 mm (1). Radiographic assessment of femoral components was made on 2 separate occasions, the first in the immediate postoperative period and the second a minimum of 24 months after operation. Radiographic signs of osseointegration between the femoral component and the host bone were adapted from the criteria of Engh et al [18]. The following signs of fixation were noted: (1) absence of a radiolucent line at the bone-implant interface and (2) presence of spot-welds. A search for signs of interface instability or motion was also completed: (1) appearance of progressive radiolucencies; (2) a distal pedestal sign attempting to support a subsiding stem; and (3) component subsidence or migration.
3
Assessments of health status were made at a minimum 24 months after operation and comprised an Short Form-12 (SF-12) questionnaire [19]. Hip function outcome was assessed with the Oxford Hip Score [20], and patient function outcome was assessed using the Western Ontaria and McMaster University Osteoarthrits Index (WOMAC) score [21]. Patient activity was measured with the University of California Los Angeles (UCLA) 10-point activity score [22]. Satisfaction was recorded using a self-administered questionnaire assessing satisfaction in 4 domains [23]. Statistics A D’Agostini and Pearson normality test was performed to determine distribution of data. When data were normally distributed, central tendency is described with the mean and standard deviation (SD). When data were not normally distributed, median and ranges are presented. A Wilcoxon rank sum test was used to compare patient-reported outcomes, stratified for diagnosis. Survival of the implant was defined as revision for any cause and revision for aseptic loosening and was assessed using a KaplanMeier survivorship analysis with 95% confidence intervals. Results The survivorship of the Wagner Cone femoral prosthesis at a minimum 2-year follow-up was 98.04% (Fig. 4). Survivorship of the femoral component when aseptic loosening was considered as the end point was 100% at 2 years. The survivorship of the operated hip without reoperation for any reason at 2 years was 84.31% (Fig. 5). Exchange of the stem was required in only 1 patient as part of a 2-stage approach to management of hematogenous infection at 40 months after the index procedure. Reoperation for other reasons was required in 7 patients. Four patients required revision for recurrent instability. This was managed by revising the femoral head in 2 cases, revision of the acetabular component to a constrained liner in 2 cases. In none of these cases of instability was the stem revised. One patient, initially implanted with a large diameter metal-on-metal bearing, developed a symptomatic pseudotumor necessitating revision of the acetabular component and conversion
Fig. 2. Typical case representative of the series: (A) the patient presented with symptomatic coxarthrosis secondary to poliomyelitis after previous valgising proximal femoral osteotomy; (B) subsequent recurrent instability after the primary procedure was treated by revision of the acetabular component to accommodate a focally constrained acetabular liner.
4
M.C. Parry et al. / The Journal of Arthroplasty xxx (2016) 1e6
Fig. 3. Thirty-eight-year-old female patient presenting with end-stage coxarthrosis secondary to Leg-Calve-Perthes disease with typical reduction in femoral offset, shortening and dysplasia of the proximal femur (A). The patient underwent staged bilateral total hip arthroplasty, combined with modest lengthening of each leg, using the Wagner cone prosthesis (B).
Radiographs were available on all patients at a minimum of 2 years after operation. All femoral components displayed features of osseointegration. Three femoral components demonstrated radiolucent lines in Gruen zones 1 and 7. One femoral component demonstrated a lucent line in zone 1 only. In all cases, these radiolucencies were stable and nonprogressive. The patients were asymptomatic. No femoral components demonstrated lucencies at the diaphyseal interface.
to a ceramic-on-polyethylene bearing. A further patient developed painful abduction impingement because of prominence of the greater trochanter. This was successfully treated by trochanteric advancement without revision of components. One patient developed an acetabular periprosthetic fracture, which required revision of the acetabular component and acetabular reconstruction. The mean WOMAC global score was 85 (SD, 18) and the Oxford Hip Score (OHS) 84 (SD, 18). The mean SF-12 was 48.3 (SD, 8.6) for the physical component and 53.7 (SD, 9.2) for the mental component. The mean satisfaction score was 89.8 (SD, 24.5) with individual components scoring means of 92.2 (SD, 23.7) for pain, 88.7 (SD, 27.4) for function, 86.3 (SD, 26.8) for recreation, and 91.5 (SD, 3.9) for overall satisfaction. The mean UCLA score was 6 (SD, 1.3). Although comparison of functional outcome scores between groups, stratified for diagnosis, was limited because of the small numbers of each individual diagnosis, when diagnoses were grouped as dysplastic and nondysplastic, no significant difference was demonstrated in the global WOMAC score (P ¼ .128), the OHS (P ¼ .325), the physical component of the SF-12 (P ¼ .053), the mental component of the SF-12 (P ¼ .628), overall satisfaction (P ¼ .017), or UCLA score (P ¼ .052). When comparing individual diagnoses, no significant difference in outcome was demonstrated for any of the outcome measures for each of the diagnoses.
The management of secondary coxarthrosis with significant alteration in the proximal femoral morphology can be challenging. A number of solutions have been proposed. Our aim is to report the short-term patient-reported and radiographic outcomes when the Wagner Cone stem is chosen in this setting. The small population and the lack of a comparison group limit the study. However, this is representative of the underlying conditions for which the implant was used, which account for less than 5% of the arthroplasty burden [24]. Survivorship of the Wagner Cone femoral prosthesis when aseptic and septic loosening of the component was considered as the end point was 98.04% at a minimum of 2 years with a
Fig. 4. The survivorship curve shows the Kaplan-Meier analysis with 95% confidence intervals with the need for revision of the Wagner cone femoral prosthesis as the end point.
Fig. 5. The survivorship curve shows the Kaplan-Meier analysis with 95% confidence intervals with the need for reoperation for any cause as the end point.
Discussion
M.C. Parry et al. / The Journal of Arthroplasty xxx (2016) 1e6 Table 2 Previous Studies Demonstrating the Use of the Wagner Cone Prosthesis. Author
No. of Prostheses Included
Follow-Up (y)
Survival (%)
Wagner H and Wagner M [6] €m et al [14] Stro Schuh et al [12] Faldini et al [25] Faldini et al [26] Pavone et al [11] Pak and de Steiger [27]
97 14 94 34 35 7 17
8 5 11.5 12 12 6 4.2
100 100 100 100 100 88.7 100
survivorship of 100% when aseptic loosening of the femoral component was considered. This is comparable to other reports using the Wagner Cone femoral prosthesis for similar pathologies (Table 2). In our series, the Wagner cone prosthesis demonstrated radiological osseointegration in all cases with no evidence of subsidence. Four hips demonstrated nonprogressive radiolucent lines in zones 1 and 7 only. Kim et al [13] reported 1 case of clinically irrelevant stem subsidence and secondary stabilization in a cohort of 60 prostheses implanted for dysplastic coxarthrosis. Wagner H and Wagner M [6], in a report on the first 100 cone prostheses implanted in the designer institution, reported 2 cases of stem subsidence >2 mm. One stem stabilized after subsidence while the other continued to subside requiring revision due to infection. Strom et al [14] reported a mean stem subsidence of 0.27 mm in 13 Wagner cone prostheses. The 100% stem survival with aseptic loosening as the end point is predictive of a 95% 10-year survival in the absence of radiolucent lines 2 mm or subsidence 2 mm [28,29]. The patients included in this study were younger than those treated for primary osteoarthritis, and it is, therefore, conceivable that the increased demands placed on the prosthesis may result in a reduced survival [30-32]. However, the long-term survivorship demonstrated by others with this implant would not support this assumption [6,12,25]. The contribution of the underlying cause of the coxarthrosis on the long-term survival of the implant remains to be demonstrated. The survivorship of this design of femoral component when used in the setting of the challenging femur is encouraging and demonstrates significant improvements from the early failures demonstrated by both cemented and cementless designs [13,16,17,33-36]. This may be representative of the high degree of axial and rotational stability conferred by the conical fluted design when used in the abnormal morphology of the proximal femur [37]. Early and late complications in this series are comparable to those reported by others [12]. We identified 4 cases of instability, which were treated with revision of the acetabular component or upsizing of the femoral head. Instability in these cases may be attributable to the abnormal muscle function of the affected hip (Fig. 3). One patient underwent revision of both components for periprosthetic infection presenting at nearly 4 years after operation. One revision of the acetabular component and femoral head was required for a symptomatic adverse reaction to metal debris because of trunnion corrosion. Further complications, including painful trochanteric impingement and acetabular periprosthetic fracture, can be attributed to the underlying pathology affecting both the proximal femur and pelvis. The patient-reported outcome scores recorded here are reflective of the represented complex preoperative conditions. When compared to conventional total hip arthroplasty (THA) for primary osteoarthritis performed in the same institution, the WOMAC and
5
SF-12 are lower in the complex femur group [38], although it should be noted that overall satisfaction after THA in this group remains high. As is the case for the OHS [39], the activity levels in such a group of patients will be best predicted by the preoperative function [40]. The patient-reported outcomes in this population are comparable to those recorded by others with this stem design, although a variety of methods have been used to record outcome [11,12,25,27,41]. A consistent feature from all these reports is that although satisfaction is high after arthroplasty, function in patients with significant preoperative limitation due to skeletal or neuromuscular conditions is not comparable to that of patients undergoing hip arthroplasty for primary osteoarthritis. In summary, the Wagner cone prosthesis has demonstrated excellent early survivorship when applied to cases of coxarthrosis where there are significant abnormalities in proximal femoral morphology. All femoral components demonstrated osseointegration with no revisions for aseptic loosening. Given the complex nature of the prearthroplasty conditions, THA using the Wagner cone demonstrates high levels of patient-reported outcomes, especially satisfaction. The prosthesis is a simple, versatile stem with wide clinical applications and has become our default stem for the small, challenging femur in all but the most challenging cases. References €ld A. Changes in the capital growth plate and the proximal femoral 1. Langenskio -Perthes disease. Clin Orthop Relat Res 1980;150:110. metaphysis in Legg-Calve 2. Noble PC, Kamaric E, Sugano N, et al. Three-dimensional shape of the dysplastic femur: implications for THR. Clin Orthop Relat Res 2003;417:27. 3. Bargar WL. Shape the implant to the patient. A rationale for the use of customfit cementless total hip implants. Clin Orthop Relat Res 1989;249:73. 4. Huo MH, Salvati EA, Lieberman JR, et al. Custom-designed femoral prostheses in total hip arthroplasty done with cement for severe dysplasia of the hip. J Bone Joint Surg Am 1993;75:1497. 5. Osagie L, Figgie M, Bostrom M. Custom total hip arthroplasty in skeletal dysplasia. Int Orthop 2011;36:527. 6. Wagner H, Wagner M. Cone prosthesis for the hip joint. Arch Orthop Trauma Surg 2000;120:88. €hm P, Bischel O. Femoral revision with the Wagner SL revision stem: eval7. Bo uation of one hundred and twenty-nine revisions followed for a mean of 4.8 years. J Bone Joint Surg Am 2001;83-A:1023. 8. Grünig R, Morscher E, Ochsner PE. Three-to 7-year results with the uncemented SL femoral revision prosthesis. Arch Orthop Trauma Surg 1997;116:187. 9. Wagner H, Wagner M. Femur revision prosthesis. Z Orthop Ihre Grenzgeb 1993;131:574. 10. Kayali C, Agus H, Ozluk S, et al. Treatment for unstable intertrochanteric fractures in elderly patients: internal fixation versus cone hemiarthroplasty. J Orthop Surg (Hong Kong) 2006;14:240. 11. Pavone V, Costarella L, Privitera V, et al. Bilateral total hip arthroplasty in subjects with multiple epiphyseal dysplasia. J Arthroplasty 2009;24:868. 12. Schuh A, Schraml A, Hohenberger G. Long-term results of the Wagner cone prosthesis. Int Orthop 2007;33:53. 13. Kim YY, Kim BJ, Ko HS, et al. Total hip reconstruction in the anatomically distorted hip. Cemented versus hybrid total hip arthroplasty. Arch Orthop Trauma Surg 1998;117:8. €m H, Mallmin H, Milbrink J, et al. The cone hip stem: a prospective study of 14. Stro 13 patients followed for 5 years with RSA. Acta Orthop Scand 2003;74:525. 15. Dickob M, Martini T. The cementless PM hip arthroplasty. Four-to-seven-year results. J Bone Joint Surg Br 1996;78:195. 16. Kawamoto K, Hasegawa Y, Iwase T, et al. Failed cementless total hip arthroplasty for osteoarthrosis due to hip dysplasia. A minimum five-year follow-up study. Bull Hosp Jt Dis 1998;57:130. 17. Nagano H, Inoue H, Usui M, et al. Long-term results of Charnley low-friction arthroplasty for coxarthrosis with congenital hip dysplasia. 15 year follow-up study. Bull Hosp Jt Dis 1997;56:197. 18. Engh CA, Massin P, Suthers KE. Roentgenographic assessment of the biologic fixation of porous-surfaced femoral components. Clin Orthop Relat Res 1990;257:107. 19. Ware JE, Kosinski M, Keller SD. A 12-item short-form health survey: construction of scales and preliminary tests of reliability and validity. Med Care 1996;34: 220. 20. Dawson J, Fitzpatrick R, Carr A, et al. Questionnaire on the perceptions of patients about total hip replacement. J Bone Joint Surg Br 1996;78:185. 21. Bellamy N, Buchanan WW, Goldsmith CH, et al. Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee. J Rheumatol 1988;15:1833.
6
M.C. Parry et al. / The Journal of Arthroplasty xxx (2016) 1e6
22. Amstutz HC, Thomas BJ, Jinnah R, et al. Treatment of primary osteoarthritis of the hip. A comparison of total joint and surface replacement arthroplasty. J Bone Joint Surg Am 1984;66:228. 23. Mahomed N, Gandhi R, Daltroy L, et al. The self-administered patient satisfaction scale for primary hip and knee arthroplasty. Arthritis 2011;2011:1. 24. On Behalf of the National Joint Registry for England WANI, editor. National Joint Registry for England and Wales. http://www.hqip.org.uk/national-jointregistry-9th-annual-report-2012/. [accessed 28.12.2013]. 25. Faldini C, Miscione MT, Chehrassan M, et al. Congenital hip dysplasia treated by total hip arthroplasty using cementless tapered stem in patients younger than 50 years old: results after 12-years follow-up. J Orthop Traumatol 2011;12:213. 26. Faldini C, Nanni M, Leonetti D, et al. Total hip arthroplasty in developmental hip dysplasia using cementless tapered stem. Results after a minimum 10-year follow-up. Hip Int 2011;21:415. 27. Pak P, de Steiger R. Cone femoral prosthesis for osteoarthritis of the hip with femoral dysplasia. J Orthop Surg (Hong Kong) 2008;16:206. 28. Freeman MA, Plante-Bordeneuve P. Early migration and late aseptic failure of proximal femoral prostheses. J Bone Joint Surg Br 1994;76:432. 29. Kobayashi A, Donnelly WJ, Scott G, et al. Early radiological observations may predict the long-term survival of femoral hip prostheses. J Bone Joint Surg Br 1997;79:583. 30. Berry DJ, Harmsen WS, Cabanela ME, et al. Twenty-five-year survivorship of two thousand consecutive primary Charnley total hip replacements. J Bone Joint Surg Am 2002;84:171. 31. Boeree NR, Bannister GC. Cemented total hip arthroplasty in patients younger than 50 years of age. Ten- to 18-year results. Clin Orthop Relat Res 1993;287:153.
32. Losina E, Bliss RL, Wright J, et al. Risk factors for revision of primary total hip arthroplasty: a systematic review. BMC Musculoskelet Disord 2012;13:251. 33. Charnley J, Feagin JA. Low-friction arthroplasty in congenital subluxation of the hip. Clin Orthop Relat Res 1973;91:98. 34. DiFazio F, Shon WY, Salvati EA, et al. Long-term results of total hip arthroplasty with a cemented custom-designed swan-neck femoral component for congenital dislocation or severe dysplasia. J Bone Joint Surg Am 2002;84:204. 35. Papachristou G, Hatzigrigoris P, Panousis K, et al. Total hip arthroplasty for developmental hip dysplasia. Int Orthop 2006;30:21. 36. Stans AA, Pagnano MW, Shaughnessy WJ, et al. Results of total hip arthroplasty for Crowe Type III developmental hip dysplasia. Clin Orthop Relat Res 1998;348:149. 37. Kendrick JB, Noble PC, Tullos HS. Distal stem design and the torsional stability of cementless femoral stems. J Arthroplasty 1995;10:463. 38. Garbuz DS, Tanzer M, Greidanus NV, et al. The John Charnley Award: metal-on-metal hip resurfacing versus large-diameter head metal-on-metal total hip arthroplasty: a randomized clinical trial. Clin Orthop Relat Res 2009;468:318. 39. Field RE. The Oxford hip scores for primary and revision hip replacement. J Bone Joint Surg Br 2005;87-B:618. 40. Williams DH, Greidanus NV, Masri BA, et al. Predictors of participation in sports after hip and knee arthroplasty. Clin Orthop Relat Res 2012;470:555. 41. Maheshwari R, Neill GO, Marsh A, et al. Total hip replacement in developmental dysplasia of the hip using Wagner cone prosthesis with small diameter metalon-metal articulation. Orthop Muscular Syst 2013;2:2161.