Total Hip Arthroplasty: Techniques and Results

R. Stephen J. Burnett, MD, FRCSC, Dipl ABOS

Total hip arthroplasty: Techniques and results

Younger, more active patients are now candidates for total hip replacement with the advent of improved implant fixation and new low-wearing bearing surfaces.

ABSTRACT: Primary total hip arthro- exposure. The most commonly uti- he current long-term suc- plasty has become one of the most lized bearing surface for both hip cess of total hip replacement successful surgical procedures over replacement and hip resurfacing in (THR) surgery has led to the the past 50 years and is currently Canada is a metal (cobalt-chrome) Tobservation by Coventry1 performed worldwide with similar femoral head combined with a that “total hip replacement, indeed, techniques and excellent results. second-generation cross-linked poly- might be the orthopaedic operation of Despite variations in technique and ethylene, combined with cementless the century.” The indications for THR implant selection, medium and long- implant fixation. Alternative bear- have expanded to such an extent that term outcome studies have demon- ings such as ceramic-on-ceramic this surgery is no longer performed strated over 90% implant survival at and metal-on-metal may be consid- only in the elderly or in those with de - 15 to 20 years. Previous problems ered for hip replacement in younger bilitating hip pain, arthritis, and severe with implant fixation have now been patients. Although it has not been functional restrictions. Rather, THR is reduced, and the focus has shifted determined which surface will prove now performed in younger and higher- to the selection of improved bearing best for younger patients in the long- demand patients, with expectations, surfaces to limit wear, hip replace- term, there is no question about the quality-of-life measures, and inten- ment options for younger patients, benefits of total hip arthroplasty. tions to return to prior activity levels and improved surgical and anesthet- With current techniques, the results that challenge surgical techniques and ic techniques. Current surgical ap - are favorable, and patient satisfaction, implant design technology. The ad- proaches to the hip rely most often pain relief, and long-term implant vantages of THR generally outweigh on direct lateral or posterolateral survival are excellent. the disadvantages (Table ), and attention is now focused on improved fixation of the implants, reduction in the rates of failure, and development of bearing surfaces to reduce long-term wear and improve implant longevity.

Surgical exposure Several surgical exposures are utilized for THR. The two most common

Dr Burnett is a consultant orthopaedic surgeon in the Division of Orthopaedic Sur- gery, Adult Reconstructive Surgery of the Hip and Knee, Vancouver Island Health– South Island.

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Table. Advantages and disadvantages of total hip replacement.

Advantages • Predictable immediate pain relief and return to function. • Predictable long-term implant survival. • Low risks and few complications for healthy patients. • Contemporary bearing surfaces that may reduce long-term wear. • Multiple indications (osteoarthritis, inflammatory arthritis, osteonecrosis, posttraumatic hip conditions). • Bone preservation options (hip resurfacing, tapered femoral stems).

Disadvantages • Prosthetic joint replacement limitations. • Activity limitations (nonimpact only). • Bearing surface wear in younger active patients. Figure 1. Common surgical exposures. (A) Anterolateral incision. This incision is centred • Revision surgery complications (three to longitudinally over the greater trochanter and permits an abductor-splitting approach. (B) five times higher than for primary THR). Posterolateral incision. This approach is similar distally to the anterolateral, curving from the • Major complications (infrequent). tip of the greater trochanter slightly posteriorly, entering the hip posterior to the abductor musculature.

exposures (Figure 1 ) are the anterolat- to traction injury to anterior branch- approach include: eral2 and the posterolateral approaches of the superior gluteal nerve dur- • Perhaps a slightly higher risk of dis- es to the hip.3 Patients may also be ing surgery). Often the limp is re - location, although with experience offer ed one of the newer techniques of ported as being asymptomatic, but this is minimized. surgical exposure referred to as muscle- frequently it is a Trendelenburg gait. • The need for careful attention to sparing or minimally invasive. The • An increase in the formation of het- component orientation in order to decision of which surgical exposure erotopic bone within the abductor insert the implants in proper antev- to use will depend upon surgeon expe- muscles and anteriorly over the cap- ersion. rience and preference, patient body sule and greater trochanter. In Canada between 2008 and 2009, habitus (i.e., obesity), patient anatom- • A greater incidence of trochanteric the direct lateral approach (60%) and ical factors, the location and type of complications (intraoperative frac- posterolateral approach (36%) com- prior surgical incisions over the hip, ture, postoperative fracture, or es - bined for over 95% of all surgical and implant selection. The most im - cape of the greater trochanter), and exposures.4 When minimally inva- portant factor to consider is surgeon trochanteric pain (often incorrectly sive surgery for THR is performed, it experience and preference. attributed to a diagnosis of tro- is most commonly performed using The anterolateral exposure is an chanteric bursitis), most likely due one of these two approaches. Other abductor-splitting approach requiring to failure of the ab ductors to heal minimally invasive surgical approach removal and repair of the anterior 30% following the repair. options include the two-incision ap- to 40% of the gluteus medius and min- • A tendency for the surgeon to insert proach,5,6 the anterolateral (Watson- imus. This approach may also be uti- the femoral component angled from Jones) approach, and the direct ant e- lized for revision THR surgery. Many anterior to posterior within the fem- rior (Hueter) approach.7 Often these surgeons select this approach based oral canal (i.e., nonanatomic femoral surgical approaches require the sur- upon the potential for a reduced dislo- component placement). geon to change to a different OR cation rate. Disadvantages of the an- With the popularity of less inva- setup6 (i.e., one with a specialized terolateral approach include: sive surgery, the posterolateral expo- table, retractors, and lights, and access • An increase in limp due to splitting sure has again gained prominence. to intraoperative X-ray) and to use an of the abductor muscle (also likely due Disadvantages of the posterolateral implant he or she may be less familiar

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with in order to make the procedure articulating aspects of the implant). used composite for cementless acetab- feasible. While there may be a few When describing fixation methods, ular components is titanium alloy, short-term advantages to minimally we are referring to the femoral and which is favorable for bone ingrowth. invasive surgery, the early and mid- acetabular components. Typically, a modular bearing surface term results have been associated with (the liner) is inserted into the inner significantly increased risks and sur- Acetabular component aspect of the acetabular component, gical complications,5 which have not implant fixation and locks into place via a mechanism been seen in THR prior to the popu- The use of cemented acetabular com- contained within the acetabular com- larity of these techniques. Thus, the ponents has declined in recent years in ponent. The acetabular component enthusiasm for minimally invasive North America, although cemented may accept bearing surfaces, including surgery has declined recently in favor components are still used occasional- liners made of polyethylene, ceramic, of surgery performed safely through ly in older and lower-demand patients. or metal, to complete the acetabular smaller incisions, and with the goal of When compared with cementless im - component composition (Figure 2 ). achieving an ideal implant orientation plants, cemented acetabular compo- This modular bearing surface may be and longevity. Computer-assisted nents have been associated with in - exchanged in the future if wear or surgery (CAS) for total hip replace- creased rates of loosening at 10 to 20 other less common indications make ment has gained popularity and is per- years, especially in patients younger this necessary, leaving the intact formed in many centres. The advan- than 50,8 when compared to cement- osseo-integrated acetabular compo- tages and results of CAS have been less implants. Cementless acetabular nent in place. The long-term results of difficult to assess, and there does not fixation was introduced to solve the cementless titanium acetabular fixa- appear to be any significant advantage problem of loosening with cemented tion have been favorable. At a mini- to CAS at this time. The one area of acetabular cups. The most commonly mum of 20 years, the implant survival potential advantage is that CAS may be useful in identifying “outlier” acetabular component position/angu- lation and leg length and hip offset intraoperatively, which might help in select situations, especially for surgeons with less experience perform- ing THR and surgeons combining CAS with minimally invasive surgery. The main disadvantage is increased OR time and increased cost. Overall, A B CAS has not been shown to be cost- effective to date.

Implant fixation: Cemented or cementless? Both cemented and cementless fixation are currently utilized in THR surgery, although there has been a trend C D in North America toward cementless implants over the past 10 years. Total Figure 2. Cementless titanium acetabular hip replacement implants typically component. (A) The porous outer surface permits bone ingrowth and the cluster holes consist of the acetabular component allow for adjunctive screw fixation. (B) The (which is fitted into the patient’s polished inner surface with circumferential native acetabular pelvic bone with or locking mechanism accommodates a modular acetabular bearing surface. The without cement), the femoral compo- modular acetabular liners available for this nent (inserted down the femoral component include: (C) Cross-linked canal), and the bearing surfaces (the polyethylene. (D) Ceramic. (E) Metal. E

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tion to promote osseo-integration. All uncemented femoral stem designs rely on metaphyseal fixation, metaphyseal-diaphyseal junction fixation, diaphyseal fixation, or a combination of the three. The tapered titanium alloy cementless stem (Figure 4 ) has grown in popularity17 and is becoming commonly used worldwide. Achieving a press-fit via a single or dual taper - ed wedge with subsequent proximal osseo-integration of bone has proven successful in multiple long-term stud- ies18 of tapered titanium stems, with over 95% survival at 10 to 20 years. In summary, while cemented fem - oral stem fixation remains the gold standard in long-term studies, it is highly dependent on cementing technique and implant design. Cemented acetabular fixation is rarely utilized in North America. Cementless fixation A B on both the femoral and acetabular sides is performed most commonly Figure 3. Cemented femoral component. (A) Spectron EF component (Smith & Nephew, and relies on an immediate press-fit Memphis, TN). (B) Postoperative radiograph showing cemented femoral stem combined with a of the implant followed by osseo- cementless acetabular component, cross-linked polyethylene modular liner, and cobalt- chrome modular femoral head. integration into host bone. Hip resurfacing for titanium hemispherical cups has In addition to cement technique, there Total hip resurfacing, also known as recently been reported at over 95%.9 are two implant designs: the cemented surface replacement arthroplasty or However, wear-related complications tapered polished collarless stem (Ex - hip resurfacing (HR), has gained in of the polyethylene liner inside and on eter, Stryker Orthopaedics, Mahwah popularity partly because of two the backside (and of the associated NJ) and the Spectron EF stem (Smith metal-on-metal HR implants approv - modular locking mechanism) occur in & Nephew Orthopaedics, Memphis ed by the FDA within the past 9 years. approximately 20% of patients by 20 TN) (Figure 3 ) which have incor po- HR has been performed for 15 years years, a problem that has become the rated differing design characteristics, in both North America and Europe focus of research in THR surgery. yet which have both proven very with favorable results.19,20 It is per- successful in the long-term clinical formed using a cemented metal fem- Femoral component trials.15,16 Early failures of cemented oral component shaped to the patient’s implant fixation stems implanted with older cementing native femoral head and a cementless Cemented femoral component fixa- technique included loosening, stem acetabular component with a polished tion has achieved excellent long-term fracture, and localized areas of bone inner cobalt-chrome metal surface results in multiple studies at 17 to 30 destruction (osteolysis) from cement (Figure 5 ). The two surfaces join to years10-14 and continues to be the gold wear debris. Cementless implants were create a metal-on-metal bearing standard against which the more pop- developed to solve these problems. surface that has low-wear properties. ular cementless femoral fixation must Today, cementless femoral compo- Relative indications for HR surgery21 be measured. Contemporary cement- nents are produced in various designs include younger age, active occu- ing techniques were refined in the and shapes, and with different metal- pational and lifestyle requirements, 1970s and require attention to detail. lic compositions and surface prepara- favorable bone anatomy and quality

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A B

Figure 4. Cementless femoral component. (A) Dual 3-degree tapered titanium component. The proximal portion of the stem has porous coating for bone ingrowth, while the middle of the stem is roughened by grit-blasting for bone ongrowth. (B) Postoperative radiograph showing a cementless tapered stem, cementless titanium acetabular component with screw fixation, and modular metal-on-metal bearing surface.

A B

Figure 5. Hip resurfacing. (A) Metal-on-metal bearing surface. (B) Postoperative radiograph showing left hip resurfacing.

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A B

Figure 6. Hip resurfacing in case of proximal femoral deformity. (A) Preoperative radiograph used to investigate left hip pain. This patient had previously undergone an intertrochanteric osteotomy. The residual femoral canal deformity seen on the radiograph means that an osteotomy would be required to perform a THR with a femoral component stem. (B) Postoperative radiograph showing left hip resurfacing performed to avoid the femoral osteotomy.

(without cystic change, defects, or dys- results should be interpreted with These advantages, however, can plasia), normal weight, and male sex. caution.22,23 all be obtained from conventional Hip resurfacing may also be used ad - Hip resurfacing surgery is perform- THR with the use of a metal-on-metal junct when there is proximal femoral ed with similar exposures to those bearing surface, particularly if a large deformity that would otherwise re - used in conventional THR. Contrary femoral head is used. quire an osteotomy to perform a THR to popular belief, hip resurfacing is Surgeons who disfavor hip resur- (Figure 6 ). Contraindications include not a minimally invasive procedure. facing do so for several reasons: impaired renal function (or the poten- Rather, it often requires a larger inci- • Bone preservation may not neces- tial for impairment with a diagnosis sion and surgical exposure, with addi- sarily occur, with occasionally more such as diabetes) with an inability to tional soft tissue capsular releases that bone being removed on the acetab- process serum metal ions, older age, are not typically performed in THR— ular side to achieve a deepened sock- osteoporosis or osteopenia, unfavor- thus HR is often more invasive, not et with a press-fit and no option for able femoral head geometry, clinical less. Despite this, recovery following screw fixation. metal sensitivity history (usually a hip resurfacing is similar to conven- • The risk of notching the femoral neck nickel sensitivity), a leg-length discrep- tional THR, likely due to generally and subsequent femoral neck fracture ancy greater than 1 cm, and women of younger patient age. The proposed (risk 0.8%–1.5%)24,25 ().Figure 7 childbearing age. The primary con- advantages (which remain controver- • Elevated levels of serum and urine cern regarding HR in younger women sial) of HR surgery include: cobalt, chromium, molybdenum, and is how the increased ion levels of • Bone preservation on the femoral side. selenium ions that remain elevated cobalt and chromium normally asso- • Ease of future revision surgery on lifelong. ciated with a metal-on-metal bearings the femoral side. • The risk of lymphocyte-mediated could effect fetal development, as • Large-head bearing surface with a metal sensitivity reactions and/or these ions do cross the placenta. Two reduced dislocation rate. the development of pseudotumors, recent studies suggest that although • Use of a metal-on-metal low-wear recently highlighted in research at these ions cross the placenta, a modu- bearing surface. UBC and McGill University.26 latory effect occurs, decreasing their • Patient findings that HR feels more • It is a technically more demanding concentration in the fetus. Still, such normal than THR. surgical procedure for the surgeon

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would be cross-linked at an appropri- ate level of radiation, and then remelt- ed to remove these free radicals and thus reduce the oxidation process. Currently, all of the THR implant manufacturers produce either a first- generation or second-generation XLPE. When combined with a polished cobalt-chrome head of multiple sizes, these new XLPEs have shown prom- ise in reducing in vivo and simulator wear measurements significantly29 compared with traditional UHMWPE. The increase in wear resistance is, however, associated with a decrease in fatigue strength and toughness. The use of XLPE liners requires meti cu- lous positioning of the acetabular component to avoid vertical place- Figure 7. Radiograph showing a femoral neck fracture that occurred at 4 months following ment of the implant, which reports a left hip resurfacing procedure. have associated with an increased risk of fracture at the rim of the polyethylene liner (Figure 8 ). The use of XLPE and team, with a steep learning research. The bearing surface is where has allowed the introduction of larger curve27 and potentially increased the movement of the two bearings femoral heads, which increase the sta- risks and complications when com- occurs and which provides the range bility of the hip with their greater dia - pared with conventional THR. of motion and articulation of the pros- meter and increased “jump distance.” While HR is an option to consider thetic ball and socket joint. Within the When XLPE is used, wear rates of the in younger and more active patients, it last 10 years, the use of traditional polyethylene have not been shown to requires careful preoperative assess- ultrahigh molecular weight polyethyl- be worse with larger femoral heads. ment and a discussion with the patient ene (UHMWPE) acetabular liners has This is in contrast to older UHMWPE, about all of the issues, including the declined with the development of new which demonstrates higher volumet- risk of increased metal ion levels and kinds of polyethylene. ric polyethylene wear as the size of metal sensitivity reactions, and the the femoral head is increased. low risk of psuedotumor.28 In addi- Highly cross-linked tion, impact activities are not encour- polyethylenes Alternative bearing surfaces aged after HR, and the restrictions and To reduce wear rates and particulate Other bearing surfaces have been precautions following surgery are debris, highly cross-linked polyethyl- developed and utilized in THR in an similar to those for THR. Overall, the ene (XLPE) has been used in total attempt to reduce the wear-related short-term results of HR (up to 5 hip arthroplasty for 8 years. The man- polyethylene complications. Polyeth- years) have been worse than for THR, ufacturing process for these materials ylene wear and debris formation result and therefore hip resurfacing should cross-links the molecules and im- in hip joint synovitis, joint instability, be used with caution. THR remains proves wear characteristics but slight- osteolysis, and, potentially, prosthesis the gold standard. ly reduces the strength of the polyeth- loosening. Alternative bearing surfaces ylene. Free radicals may be generated such as metal-on-metal, ceramic-on- Bearing surfaces in the process, potentially allowing ceramic, ceramic-on-XLPE, oxinium With current implant fixation meth- for oxidative changes in the polyeth- (oxidized zirconium), and even the ods demonstrating excellent long- ylene, unless these changes are appro- new XLPEs themselves have been term results, the bearing surface priately managed in the manufactur- developed in an attempt to reduce in THR is now the focus of much ing process. Thus, the ideal XLPE wear and improve implant survival in

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Figure 8. Fractured rim of a cross-linked polyethylene liner. The acetabular component was Figure 9. A ceramic-on-ceramic modular placed in a vertical orientation, leading to a fatigue fracture at the superior aspect of the bearing surface. polyethylene liner.

younger and more active patients. is attractive to younger patients, espe- sounds from the hip) occurs more fre- Currently in Canada, the most com- cially females of childbearing age. quently than originally reported, and monly utilized bearing surface is a Although ceramics can fracture be- is experienced by 10% to 17% of cobalt-chrome head combined with cause of their brittle composition, the patients with a ceramic-on-ceramic cross-linked polyethylene (59%), rate of fracture is very low (0.5%)31 in bearing surface.32,33 The causes and while other alternative bearings such most studies. Newer ceramic compos- implications of squeaking have yet to as metal-on-metal (11% ; includes HR ites of alumina (Biolox Delta Ceram- be determined, but are likely to be use) and ceramics (13%) are used less ic, CeramTec AG, Lauf, Germany) multifactorial: acetabular modular frequently, and usually in younger have demonstrated increased strength implant design-specific factors, com- patients.4 and fracture resistance, and offer ponent orientation and malposition, Ceramics. Alumina ceramics were increased neck-length options intra- instability, and femoral component introduced in the 1970s. They have a operatively (Figure 9 ). Ceramic-on- design have all been implicated. The very low coefficient of friction and ceramic bearing surfaces have been use of ceramic-on-ceramic bearings demonstrate the lowest wear rates of associated with squeaking that is audi- offers many advantages in terms of any implant bearing surface.30 They ble to the patient and others. Initially wear reduction, especially for young are scratch resistant and may be com- believed to occur rarely (~1%) in and active patients. Nonetheless, pa- bined as a modular ceramic acetabular ceramic-on-ceramic THR, recent stud- tients considering ceramic-on-ceramic liner with a ceramic head. There is no ies have shown that noise (squeaking, bearings should be informed of this potential for metal ion release, which grinding, rubbing, or other audible phenomenon, and the surgeon and

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patient should discuss avoiding cer - metal-on-metal bearing surfaces gen- References amic implants associated with a high- erally are associated with elevated 1. Coventry MB. Foreword. In: Amstutz HC er incidence of squeaking. There are metal ion levels,37 no long-term effects (ed). Hip arthroplasty. New York: Churchill no long-term clinical results to date are known. Preoperatively, patients Livingstone; 1991. for the newer ceramic composites. must be informed that the low risk of 2. Mulliken BD, Rorabeck CH, Bourne RB, Oxinium. Oxidized zirconium (Smith metal sensitivity and lymphocyte- et al. A modified direct lateral approach in & Nephew, Memphis, TN) has been mediated reaction is similar to that for total hip arthroplasty: A comprehensive developed for femoral head compo- hip resurfacing. Recently, inflamma- review. J Arthroplasty 1998;13:737-747. nents and has the wear-resistance of tory granulomatous pseudotumors, 3. Kwon MS, Kuskowski M, Mulhall KJ, et ceramic without the brittle fracture which are necrotic cystic soft tissue al. Does surgical approach affect total hip risk. Compared with the limited cera - tumors, have been seen following arthroplasty dislocation rates? Clin mic ball neck lengths available, oxini- large-head metal-on-metal hip replace- Orthop Relat Res 2006;447:34-38. um allows for increased length op- ment with one or more implant de - 4. Canadian Institute for Health Informa- tions intraoperatively. No long-term signs, and have been seen less often tion. Hip and knee replacements in Cana- clinical studies of this material have following HR. For this reason, metal- da—Canadian Joint Replacement Reg- been published yet, and it is only avail- on-metal bearing surfaces should be istry (CJRR) 2008–2009 annual report. able from one manufacturer. used with caution in THR, patients http://secure.cihi.ca/cihiweb/dispPage.js Metal-on-metal. Metal-on-metal bear- should be followed closely at yearly p?cw_page=PG_1519_E&cw_topic=15 ing surfaces have been used widely intervals, and patients should be coun- 19&cw_rel=AR_30_E (accessed 14 Sep- since the 1960s.34-36 Poor metallurgy, seled about the possibility of metal- tember 2010). poor design (equatorial head edge bear- related complications that will lead to 5. Bal BS, Haltom D, Aleto T, et al. Early ing), and poor fixation led to early fail- poor outcome if they occur, even after complications of primary total hip re- ures of many hip replacements using revision surgery. placement performed with a two-incision metal bearings. However, a subset of minimally invasive technique. Surgical these were found to have a suitable Conclusions technique. J Bone Joint Surg Am 2006; central-head bearing and minimal wear Total hip arthroplasty has become the 88:(suppl):221-233. when compared with hip replace- treatment of choice for hip-related dis- 6. Berger RA, Duwelius PJ. The two-inci- ments using UHMWPE. This finding orders leading to arthritis in the adult sion minimally invasive total hip arthro- led to a resurgence of interest in metal- population. With improvements in plasty: Technique and results. Orthop on-metal surface bearings, and an long-term clinical results, implant fix- Clin North Am 2004;35:163-172. attempt to create a bearing surface ation, and new low-wear bearing sur- 7. Seng BE, Berend KR, Ajluni AF, et al. with similar metallurgy and design to faces, THR surgery is now being per- Anterior-supine minimally invasive total that found in the subset with long-term formed in younger and more active hip arthroplasty: Defining the learning survival. Metal bearing surfaces dem- patients. Using current implant design curve. Orthop Clin North Am 2009; onstrate very low wear rates—some- and techniques, the implant survival 40:343-350. where between rates for ceramic-on- at 20 years is favorable, with over 90% 8. Barrack RL, Mulroy RD Jr, Harris WH. ceramic and metal-on-XLPE—and implant survival in multiple studies. Improved cementing techniques and much less wear than for conventional However, with younger and more femoral component loosening in young UHWMPE. Metal bearings support active patients undergoing total hip patients with hip arthroplasty. A 12-year the use of a larger femoral head size, replacement, the challenge will be the radiographic review. J Bone Joint Surg Br which demonstrates better fluid-film bearing surface selection. It remains 1992;74:385-389. lubrication, and lower metal ion lev- to be determined which bearing sur- 9. Della Valle CJ, Mesko NW, Quigley L, et els than found with smaller head com- faces will provide the lowest wear al. Primary total hip arthroplasty with a binations, making metal-on-metal rates and the fewest wear-related com- porous-coated acetabular component. A ideally suited for hip resurfacing. plications in the long term. concise follow-up, at a minimum of twen- Metal is not brittle like ceramic, mak- ty years, of previous reports. J Bone Joint ing it attractive for younger patients. Competing interests Surg Am 2009;91:1130-1135. Larger head sizes are also associated None declared. 10. Ling RS, Charity J, Lee AJ, et al. The long- with improved joint stability and a term results of the original Exeter pol- reduced risk of dislocation. While ished cemented femoral component: A

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