Clinical outcome in total hip arthroplasty using a cemented titanium femoral prosthesis

The Journal of Arthroplasty Vol. 17 No. 5 2002

Clinical Outcome in Total Hip Arthroplasty Using a Cemented Titanium Femoral Prosthesis Harry E. Jergesen, MD,*† and Judson W. Karlen, BS†

Abstract: Between 1988 and 1993, 118 total hip arthroplasties were carried out using cemented titanium alloy stems with modular cobalt-chrome heads. At a mean follow-up of 66.2 months, the overall clinical failure rate as a result of aseptic loosening of the femoral stem was 11.5%. Most failures occurred with smaller stems, especially in heavier patients. Clinical and radiographic data suggest that failure of femoral component fixation was due to high stresses in the cement mantle associated with the increased flexibility of the smaller stems. Radiographs of successful arthroplasties in patients with larger stems showed proximal stress shielding in most. The findings in this study do not support the contention that titanium alloys provide an advantage over more rigid materials in the manufacture of cemented femoral components for total hip arthroplasty. Key words: total hip arthroplasty (THA), femoral prosthesis, titanium alloy, aseptic loosening. Copyright 2002, Elsevier Science (USA). All rights reserved.

Titanium alloys have been used widely in the manufacture of orthopaedic implants for total hip arthroplasty (THA). Attributes of titanium include its biocompatibility, low modulus of elasticity, and resistance to fatigue. Good midterm results have been reported in uncemented modular femoral stems made of titanium alloy [1]. In contrast to the good overall results in uncemented femoral stems, there are conflicting results on the clinical outcome when titanium alloys are used in the manufacture of cemented femoral stems. In 1985, Sarmiento et al [2] reported good results with cemented titanium

stems at early follow-up of 2 to 6 years. They reported a low incidence of loosening and calcar resorption. Several more recent studies have produced similar findings, with results equal to or better than those expected for cemented cobaltchrome stems in terms of clinical failure, loosening, and proximal bone loss [3–5]. In contrast to these results, other studies have shown high rates of early clinical failure, leading the authors to conclude that titanium stems should not be used in cemented THA [6,7]. Between 1988 and 1993, surgeons in our institution used a THA system that included a cemented femoral stem made of titanium alloy and a modular cobalt-chrome head. This implant was used in primary THA and in the treatment of femoral neck fractures. Several early clinical failures resulting from femoral component loosening, particularly with shorter, smaller diameter stems, prompted a retrospective review of the entire group of patients who underwent surgery with this implant. The purpose of this study is to report the prevalence of clinical and radiographic failure, to identify factors that may have contributed to failure, and to deter-

From the *Orthopaedic Surgery Section, San Francisco Veteran’s Affairs Medical Center; and †Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, California. Submitted April 23, 2001; accepted February 1, 2002. No benefits or funds were received in support of this study. Reprint requests: Harry E. Jergesen, MD, Department of Orthopaedic Surgery MU-320W, University of California San Francisco, San Francisco, CA 94143-0728. E-mail: jergesen@ orthosurg.ucsf.edu Copyright 2002, Elsevier Science (USA). All rights reserved. 0883-5403/02/1705-0006$35.00/0 doi:10.1054/arth.2002.32697

592

Cemented Titanium Stems in THA • Jergesen and Karlen

mine if the pattern of failure reflects unsuitable design characteristics of the implant.

Methods Between July 1988 and November 1993, 118 THAs in 115 patients were done at the San Francisco Veteran’s Affairs Medical Center using the KMW femoral component (KMW Hip; Kirschner Medical Corporation, Timonium, MD). Patients with ⬍2 years of clinical follow-up after surgery were excluded from review. There were 26 patients lost to follow-up, and 23 died within 2 years of their operation, leaving 69 cases for review. Most of the patients who died were elderly at the time of surgery and had undergone bipolar hemiarthroplasty for the treatment of femoral neck fractures. Although 7 attending surgeons were involved in the care of the study patients, most operations (53 of 69) were performed by 2 surgeons. The KMW femoral component is a curved modular design of titanium-aluminum-vanadium alloy with a collar, a broad lateral aspect, and a blasted matt finish. Five stem sizes were used, with size designations based on the stem length, measured in millimeters from the medial collar to the tip of the stem: 110 mm, 120 mm, 130 mm, 140 mm, and 150 mm (Fig. 1.). The relative geometry of the implant was similar in the different sizes; the diameter of the stem increased in proportion to the length. The size

Fig. 1. The 110-mm, 120-mm, and 130-mm KMW titanium femoral prostheses show progressive increases in diameter and length in implants of increasing sizes. The 140-mm and 150-mm stems are not pictured.

593

of implant used in each patient was determined by templating preoperative radiographs to set the implant in neutral alignment with a minimal cement mantle thickness of 2 mm. Cobalt-chrome heads that were 26 mm, 28 mm, or 32 mm in diameter were used according to the preference of the surgeon. Although the length of the taper on each stem was fixed at 30 mm, neck lengths could be varied by choosing different heads that adjusted the final neck length between ⫺5 and ⫹15 mm. All patients with femoral neck fractures received bipolar components, and all patients undergoing THA received a cementless acetabular component consisting of a titanium alloy shell and an ultra-high molecular weight polyethylene liner (Arthropor; Joint Medical Products, Stamford, CT). All procedures were done through a posterolateral incision, and all stems were implanted with standard cementing technique using vacuum mixing, placement of a polyethylene canal plug, pulsatile lavage of the medullary canal, and cement pressurization. Weight bearing as tolerated was begun within 2 days of surgery, and patients were allowed to discontinue the use of supports by the 6th week postoperatively. Patient data were collected from computer records, paper charts, telephone contact, and follow-up visits. These data included age at surgery, height, weight, femoral stem size, neck length, head diameter, arthroplasty type, comorbid health conditions, length of clinical follow-up, and clinical status at most recent follow-up. Clinical failure was defined as impending or completed revision of the femoral component because of aseptic, nontraumatic loosening. Radiographic data were assessed using anteroposterior and lateral hip radiographs from the immediate postoperative period and from interval and most recent follow-up visits. The evaluation of the immediate postoperative radiographs included assessment of the varus-valgus stem alignment; width of the cement mantle in Gruen zones 1, 3, 5, and 7 [2]; the presence of cement defects; and grading of the cement technique. A cement grade of A, B, C, or D was given according to the criteria of Barrack et al [8]: A refers to complete filling of the canal by cement; B refers to slight radiolucency at the bone– cement interface; C refers to radiolucency of 50% to 99% of the bone– cement interface or an incomplete cement mantle; and D refers to 100% radiolucency at the bone– cement interface on any radiographic projection or failure of coverage of the tip of the stem by cement.

594 The Journal of Arthroplasty Vol. 17 No. 5 August 2002 Table 1. Patient and Prosthetic Variables That Were Evaluated and Statistically Compared in the 3 Study Groups Group 1 (n ⫽ 17)

Group 2 (n ⫽ 21)

Group 3 (n ⫽ 31)

Age (y) 68.8 70.8 70.5 Average follow-up (y) 5.6 5.6 5.4 Weight (kg) 71.6 85.6 79.8 Height (m) 1.70 1.77 1.76 Comorbid conditions 0.76 ⫾ 1.09 1.05 ⫾ 0.67 1.32 ⫾ 0.79 Neck length (mm) 33.0 ⫾ 2.9 34.2 ⫾ 4.5 38.3 ⫾ 4.2 Head diameter (mm) 28.0 ⫾ 2.8 28.0 ⫾ 2.9 28.1 ⫾ 2.9

Results Demographic Data P NS

NS ⬍.02 ⬍.03 NS ⬍.01

Patients in group 1 were significantly shorter and lighter than patients in groups 2 and 3 (Table 1). There were no significant differences in the 3 groups with respect to age, sex, follow-up interval, and number of comorbid conditions. There were no differences in prosthetic variables except for mean neck length, which was significantly longer in the large implants in group 3 than in the implants in groups 1 and 2.

NS

Abbreviation: NS, not significant.

The technique of femoral insertion was judged to be technically satisfactory or unsatisfactory according to the criteria of Dorr et al [9]. According to these criteria, cement technique for the femoral component is deemed satisfactory if all of the following criteria are met: absence of varus stem positioning, an intact cement mantle, a minimum of 3 mm of cement in the proximal medial third and distal lateral third of the mantle, and presence of cement at least 1 cm distal to the tip of the stem. On the interval and most recent follow-up radiographs, evidence of progressive lucent intervals and proximal remodeling as a result of stress shielding was recorded. The severity of proximal stress shielding was assessed by the criteria of Engh et al [10]. Significant stress shielding was defined as bone atrophy assessed as second degree or greater; second-degree stress shielding is defined by rounding off of the proximal medial femoral neck in combination with loss of density in the subjacent proximal medial cortex. Radiographic failure was defined as evidence of either implant debonding with stem migration or progressive bone– cement radiolucencies on anteroposterior or lateral hip radiographs. For the purpose of statistical analysis, hips with the 110-mm and 120-mm implants were combined to form a small implant group (group 1), hips with the 130-mm stems formed the medium implant group (group 2), and hips with the 140-mm and 150-mm stems formed the large implant group (group 3). Categorical variables were evaluated with chi-square and Fisher exact tests. Continuous variables were examined using Student t-test. Implant survival was evaluated using the KaplanMeier method.

Analysis of Initial Radiographs Of 69 patients in the study group, 60 had adequate preoperative and postoperative radiographs available for review. Initial radiographs showed that 10 stems were aligned in varus, 8 in valgus, and 42 in neutral. According to the Harris criteria, the cement mantle was graded as A in 20 hips, B in 14, C in 22, and D in 4. According to the Dorr criteria, femoral component insertion technique was judged to be satisfactory in 33 hips and unsatisfactory in 27. There was no significant difference in the distribution of hips with the various cement mantle grades between the 3 groups. Clinical Outcome At an average follow-up of 66.2 months (range, 24 –119 months), 11.5% (8 of 69) of the femoral stems in the study group failed because of aseptic loosening and required revision THA. Most clinical failures occurred after an interval of 4 years from the time of surgery (Fig. 2). Clinical failure was not distributed evenly across the stem size groups (Fig. 3). Of the 8 failures, 5 were in group 1, and 3 were in group 2; no failures occurred in group 3. Of the

Fig. 2. Kaplan-Meier survival curves for implants in the 3 size groups. Failure is defined as revision THA because of symptomatic aseptic loosening.

Cemented Titanium Stems in THA • Jergesen and Karlen

595

stems (44.4%) and small stems (37.5%); however, these differences did not reach statistical significance. Findings at Revision Surgery

Fig. 3. Histogram shows distribution of failures among patient groups.

patients in group 1, who received the smaller 110-mm and 120-mm stems, 29.4% (5 of 17) experienced painful femoral loosening. These failures were significantly more prevalent compared with group 3, in which the larger 140-mm and 150-mm stems were used (P⬍.004). There was a trend toward a higher prevalence of failure in group 2 containing the patients with medium stems (14.3% [3 of 21]) compared with group 3, but this did not reach significance (P⬍.06). There was no significant difference between the prevalence of failures in group 1 (smaller stems) and group 2 (P⬍.23). Within group 1, the patients who experienced clinical failure were heavier (P⬍.02) and taller (P⬍.04) than those who did not (Table 2). In the 8 patients with clinical failures, there was a trend toward an association with initial varus positioning of the stem (P⬍.13). Independent variables that had no statistical effect on outcome included patient age, sex, body mass index, number of comorbid conditions, initial cement grade and technique, cement mantle thickness, head diameter, and neck length. Radiographic Findings In failed THAs, the pattern of radiographic deterioration was uniform and typically included evidence of implant debonding in the proximal lateral cement mantle with occasional debonding medially, fractures within the cement mantle, osteolysis, and implant migration (Fig. 4). In addition to the 8 clinical failures, 6.7% of the patients with follow-up radiographs (4 of 60) showed evidence of progressive loosening and met the criteria for radiographic failure. The most recent follow-up radiographs from clinically successful THAs from each group were assessed to document proximal stress shielding. There was a trend for femora with the larger stems to show higher grades of stress shielding (76.9%) compared with femora implanted with medium

At the time of revision surgery, all implants were found to be grossly loose within the cement mantle. In most cases, there was fragmentation of cement with localized areas of separation of cement at the bone– cement interface. The stem of removed prosthesis typically showed localized burnishing (Fig. 5), but in no case was there gross evidence of crevice corrosion or metallosis.

Discussion The long-term survival of cemented protheses in THA is related directly to the magnitude and the distribution of stresses within the prosthesis, cement mantle, and surrounding bone [11]. Numerous factors combine to determine these various stresses: the material properties of the prosthesis, cement, and bone; the shape of the implant; the interfaces between the implant and the cement and between the cement and the bone; the thickness of the cement mantle; and the surgical technique of

Table 2. Demographic, Prosthetic, and Radiographic Variables Evaluated in the Failed and Successful Hips Group 1

Group 2

Revised Unrevised Revised Unrevised (n ⫽ 5) (n ⫽ 12) (n ⫽ 3) (n ⫽ 18) Clinical data Age (y) Sex (% male) Weight (kg) Height (m) BMI Comorbid conditions Prosthetic data Neck length (mm) Head diameter (mm) Radiographic data Stem alignment (% varus) Harris grade (% A or B) Dorr grade (% satisfactory)

66.9 100 84.0* 1.77* 26.7

67.7 83 69.6* 1.70* 24.3

67.4 100 92.0 1.84 27.2

69.6 94 86.9 1.76 28.3

0.4

0.9

1.0

1.1

34.0

33.0

36.7

34.0

28.4

28.0

28.0

28.0

50⫹

10⫹

33

14

50

60

67

64

50

60

33

64

Abbreviation: BMI, body mass index. *Significant Pⱕ.05. ⫹ Trend, P⬍.13.

596 The Journal of Arthroplasty Vol. 17 No. 5 August 2002

Fig. 4. Radiographs of a 66-year-old man immediately postoperatively (A) and 48 months later (B). There is proximal implant– cement debonding, subsidence, cement fracture, and endosteal osteolysis.

insertion [11–14]. In the early 1980s, mechanical loosening and failure of the cement mantle in patients who had undergone THA with cobalt-chrome stems led some investigators to explore the possibility that the cause might lie in excessive stiffness of the stems [15–17]. It was hypothesized that a reduction in the rigidity of the stem might yield mechanical properties that would resemble more closely those of the surrounding cement mantle and bone. This resemblance in turn would reduce stresses in the distal cement mantle and simultaneously allow more physiologic loading within the proximal femur [17]. Although it was recognized that the use of implants made of a lower modulus material, such as titanium alloy, might increase the stresses within the proximal cement mantle [11], these increases were judged to be within the predicted failure levels for polymethyl methacrylate cement [17]. Using finite element modeling, some investigators predicted that the use of a collar in lower modulus implants would improve load transmission to the calcar further [15]. To date, clinical studies have failed to show conclusively whether the use of cemented titanium stems accomplishes the dual goals of reducing proximal femoral stress shielding and achieving longterm clinical efficacy. In 1985, Sarmiento and Gruen [2] reported their experience with a rela-

Fig. 5. Burnishing of the type seen on the surface of this stem was seen in all titanium femoral components retrieved at the time of revision THA.

Cemented Titanium Stems in THA • Jergesen and Karlen

tively slender monolithic titanium alloy stem 114 mm in length of curved and straight designs. With a relatively short follow-up (average, 52 months; range, 24 – 80 months), they concluded that stress shielding was minimized and that the clinical success rate was similar to that found with stems of similar design made of stiffer materials, such as stainless steel or cobalt-chrome. Nonetheless, radiolucencies at the stem– cement interface were observed in 11.1% of hips and at the cement– bone interface in 47.1%. Stem– cement loosening was more common with the curved stem design. Cement fracture was observed in 1.5% of hips, and 4.3% were thought to have progressive loosening. The clinical outcome in patients with this implant was not reviewed in detail, but it was noted that of 321 hips, only 3 underwent revision because of painful loosening. In 1989, Robinson et al [6] reviewed their results with a monolithic titanium stem of a different design and recorded a much different outcome. With a mean follow-up of only 37.1 months (range, 9 – 60 months), 23.4% of 57 hips showed femoral stem subsidence, 78.7% had bone– cement lucencies, and 4.3% (2 cases) required revision because of loosening. In both of the revisions, burnishing of the titanium femoral head was observed. Other investigators reported burnishing of titanium heads, resulting in the generation of unacceptable amounts of polyethylene wear debris [4,18]. Robinson et al [6] attributed their poor results, however, primarily to loosening at the bone– cement interface caused by bone necrosis from overaggressive reaming and high cement temperatures. In 1994, Tompkins et al [7] reported clinical and radiographic findings in patients who received a cemented titanium alloy stem equipped with a modular cobalt-chrome head. With a mean follow-up period of 57.6 months (range, 24 –96 months), these authors recorded excellent or good clinical results in 92% of hips, femoral component loosening in 11%, and a revision rate of 4.3%. Stem– cement debonding was noted in 11 of 126 cases (8.7%), and in 5 of these, cystic cortical erosion of the femur was observed. These authors hypothesized that loosening arose from failure of the proximal cement mantle, possibly exacerbated by the lack of vacuum mixing or centrifugation of the cement before insertion. In each of these last 2 studies, failure was more common in stems with increased offset. In 1996, Willert et al [19] described an unusual mode of failure in 28 revision THAs that were carried out because of pain in patients who had received cemented titanium alloy femoral compo-

597

nents. In most of these cases, in which modular cobalt-chrome or ceramic heads were used, the predominant finding at revision was spindle-shaped thickening of the femoral shaft and crevice corrosion of the stem surface. These authors also noted debonding at the implant– cement interface proximally, especially with stems of smaller sizes. In our study, the principal finding was the high rate of loosening in cases in which small stems were used. Possible explanations for femoral component loosening include deficiencies in operative technique, patient-associated factors, characteristics of implant design, or a combination of these. The operative technique that was used in the present study incorporated maneuvers to align the implant properly and to provide a minimal cement mantle thickness of 2 mm, to maximize fixation at the bone interface through cement pressurization, and to reduce inclusions in the cement by vacuum mixing. These measures have been shown to enhance the long-term fixation of cemented femoral stems [8,20– 22]. Although ideal technique was not achieved in all cases, no significant differences in prosthetic alignment, quality of cementation, or cement mantle thickness were found in the hips that performed well clinically and those that failed. In the group of patients with small-diameter stems, there was a trend toward varus stem positioning in the group of patients with a poor clinical outcome. The assessment of patient characteristics that might have led to a disproportionate increase in loading of the failed hips revealed no differences in the distribution of either causative diagnoses or comorbid health conditions in patients with the failed and successful hips. An important finding was, however, that patients with small stems that failed were significantly heavier and taller than patients with similar stems who had a successful clinical result. The skewed distribution of failures, the radiographic abnormalities in failed cases, and the observations at revision THA all support the notion that the primary explanation for failure lies in the inadequate stiffness of the smaller implants. The stiffness, or flexural rigidity, of an implant is a function of the material properties of the alloy of which it is composed and its cross-sectional geometry. The findings in the present study suggest that the flexural rigidity of the smaller diameter titanium stems was inadequate for some patients, resulting in high cement stresses and early cement failure. Despite the fact that their average weight was greater, patients who received the largest diameter, more rigid stems had no clinical failures. The highest rate of failure was observed in the stems that were the shortest and had the smallest diameter. Patients

598 The Journal of Arthroplasty Vol. 17 No. 5 August 2002 with failed small stems were significantly heavier than were patients with similar stems who did well clinically. In addition, there was a trend toward varus positioning in failed hips. It is reasonable to assume that loading forces on the hip were greatest in the heavier patients, perhaps exacerbated by varus positioning in some cases, and that these factors exacerbated the high cement stresses present with the smaller diameter, more flexible stems. Loss of femoral component fixation because of high cement stresses is suggested strongly by the pattern of the radiographic findings in the failed hips. Debonding of the stem from the cement laterally was seen early, followed subsequently by cement fracture and osteolysis proximally and distally. Early debonding at the stem– cement interface has been implicated by some authors as the earliest event in loss of femoral stem fixation [12]. Findings at revision THA suggest that osteolytic lesions may have resulted from particulate debris generated by abrasion between the matt surface of the implant and the cement at the disrupted implant– cement interface. In none of our revision cases was there evidence that metallosis or crevice corrosion played a role in failure of stem fixation. The radiographic finding of stress shielding in most of the femora of patients with the clinically successful, larger diameter titanium stems indicates that titanium stems with greater flexural rigidity behave in a manner similar to that of cobalt-chrome stems. With smaller diameter titanium stems, the failure rate was unacceptably high because of excessive implant flexibility and high associated cement stresses, a problem that was exacerbated when these components were implanted in heavier patients. In the larger diameter titanium alloy stems, the flexural rigidity of the implant seemed sufficient to protect the cement mantle from high stresses and failure but too great to protect the proximal femur from stress shielding. The findings in the present study do not support the contention that titanium alloy provides an advantage over more rigid materials when used in the manufacture of cemented femoral components. In particular, cemented titanium stems with insufficient flexural rigidity are predisposed to an unacceptably high rate of aseptic loosening in the short term.

References 1. Head WC, Bauk DJ, Emerson RH Jr: Titanium as the material of choice for cementless femoral components in total hip arthroplasty. Clin Orthop 311:85, 1995

2. Sarmiento A, Gruen TA: Radiographic analysis of a low-modulus titanium-alloy femoral total hip component. J Bone Joint Surg Am 67:48, 1985 3. Edidin AA, Merritt PO, Hack BH, Manley MT: A ported proximally-cemented stem for total hip arthroplasty. J Bone Joint Surg Br 80:869, 1998 4. McKellop HA, Sarmiento A, Schwinn CP, Ebramzadeh E: In vivo wear of titanium-alloy hip prostheses. J Bone Joint Surg Am 72:512, 1990 5. Wan Z, Dorr LD, Woodsome T, et al: Effect of stem stiffness and bone stiffness on bone remodeling in cemented total hip replacement. J Arthroplasty 14: 149, 1999 6. Robinson RP, Lovell TP, Green TM, Bailey GA: Early femoral component loosening in DF-80 total hip arthroplasty. J Arthroplasty 4:55, 1989 7. Tompkins GS, Lachiewicz PF, DeMasi R: A prospective study of a titanium femoral component for cemented total hip arthroplasty. J Arthroplasty 9:623, 1994 8. Barrack RL, Mulroy RD Jr, Harris WH: Improved cementing techniques and femoral component loosening in young patients with hip arthroplasty. J Bone Joint Surg Br 74:385, 1992 9. Dorr LD, Takei GK, Conaty JP: Total hip arthroplasties in patients less than forty-five years old. J Bone Joint Surg Am 65:474, 1983 10. Engh CA, Bobyn JD, Glassman AH: Porous-coated hip replacement. J Bone Joint Surg Br 69:45, 1987 11. Crowninshield RD, Brand RA, Johnston RC, Milroy JC: An analysis of femoral component stem design in total hip arthroplasty. J Bone Joint Surg Am 62:68, 1980 12. Jasty M, Maloney WJ, Bragdon CR, et al: The initiation of failure in cemented femoral components of hip arthroplasties. J Bone Joint Surg Br 73:551, 1991 13. Mohler CG, Callaghan JJ, Collis DK, Johnston RC: Early loosening of the femoral component at the cement-prosthesis interface after total hip replacement. J Bone Joint Surg Am 77:1315, 1995 14. Ramaniraka NA, Rakotomanana LR, Leyvraz PF: The fixation of the cemented femoral component. J Bone Joint Surg Br 82:297, 2000 15. Lewis JL, Askew MJ, Wixson RL, et al: The influence of prosthetic stem stiffness and of a calcar collar on stresses in the proximal end of the femur with a cemented femoral component. J Bone Joint Surg Am 66:280, 1984 16. Manley M, Stern L, Gurtowski J: Performance characteristics of total hip femoral components as a function of prosthesis modulus. Bull Hosp Joint Dis Orthop Inst 43:130, 1983 17. Miles AW, Dall DM: An experimental study of femoral cement stress in total hip replacement—influence of structural stiffness of the femoral stem. Eng Med 14:133, 1985 18. Lombardi AV Jr, Mallory TH, Vaughn BK, Drouillard P: Aseptic loosening in total hip arthroplasty sec-

Cemented Titanium Stems in THA • Jergesen and Karlen ondary to osteolysis induced by wear debris from titanium-alloy modular femoral heads. J Bone Joint Surg Am 71:1337, 1989 19. Willert HG, Broback LG, Buchhorn GH, et al: Crevice corrosion of cemented titanium alloy stems in total hip replacements. Clin Orthop 333:51, 1996 20. Bourne RB, Rorabeck CH, Sketek M, et al: The Harris Design-2 total hip replacement fixed with so-called

599

second generation cementing techniques. J Bone Joint Surg Am 80:1775, 1998 21. Harris WH, McCarthy JC, O’Neill DA: Femoral component loosening using contemporary techniques of femoral component fixation. J Bone Joint Surg Am 64:1063, 1982 22. Smith SW, Estok DM, Harris WH: Total hip arthroplasty with use of second-generation cementing techniques. J Bone Joint Surg Am 80:1632, 1998