A stem design change to reduce peak cement strains at the tip of cemented total hip arthroplasty

A series of 3-dimensional finite element models was created to assess different designs of the tip of the stems of cemented femoral components of total hip arthroplasty that would decrease the peak axial tensile cement strains developed near the tip. Features of stem design that would facilitate positioning the femoral component in a neutral position centered in uniform cement mantle of adequate thickness also were evaluated. These studies showed that a stem that had a narrow tip profile that would accept an externally applied polymethyl methacrylate centralizer shaped similar to a napkin ring and had a gradual transition zone to join the body of the implant achieved these objectives. Such a combination resulted in the reduction of the peak axial strains to less than half the magnitude of the peak strains around a conventional tip (830 vs 1,868 microstrain). The reduction in peak axial strains was to one third the magnitude of the strains developed adjacent to a stem with a hole drilled into the tip to accept the commonly used fin-type polymethyl methacrylate centralizer (830 vs 2,466 microstrain). These goals were achieved because a stem that is designed to accept a napkin ring-style centralizer i) has a lower bending stiffness at the tip of the implant, ii) allows room for a thicker cement mantle, and iii) avoids creating a stress riser adjacent to the edge of the drill hole. The peak cement strains adjacent to a stem of this design are well below the endurance limit of cement as long as the transition zone where the narrow tip meets the body of the implant is gradual.     

Long-term survival of a cemented titanium-aluminium-vanadium alloy straight-stem femoral component

We present a retrospective series of 170 cemented titanium straight-stem femoral components combined with two types of femoral head: cobalt-chromium (CoCr) alloy (114 heads) and alumina ceramic (50 heads). Of the study group, 55 patients (55 stems) had died and six (six stems) were lost to follow-up. At a mean of 13.1 years (3 to 15.3) 26 stems had been revised for aseptic loosening. The mean follow-up time for stable stems was 15.1 years (12.1 to 16.6). Survival of the stem at 15 years was 75.4% (95% confidence interval (CI) 67.3 to 83.5) with aseptic failure (including radiological failure) as the end-point, irrespective of the nature of the head and the quality of the cement mantle. Survival of the stem at 15 years was 79.1% (95% CI 69.8 to 88.4) and 67.1% (95% CI 51.3 to 82.9) with the CoCr alloy and ceramic heads, respectively. The quality of the cement mantle was graded as a function of stem coverage: stems with complete tip coverage (type 1) had an 84.9% (95% CI 77.6 to 92.2) survival at 15 years, compared with those with a poor tip coverage (type 2) which had a survival of only 22.4% (95% CI 2.4 to 42.4). The poor quality of the cement mantle and the implantation of an alumina head substantially lowered the survival of the stem. In our opinion, further use of the cemented titanium alloy straight-stem femoral components used in our series is undesirable.     

A preliminary report of the use of a cementless acetabular component with a cemented femoral component

A clinical and roentgenographic study was done on 52 primary total hip arthroplasties (THAs) in which all patients were treated with hip reconstruction with a combination of a cementless, porous-coated acetabular component and a cemented femoral component. The operations were performed between November 1982 and May 1984, and the patients were followed for an average of 31 months (range, 24-40 months). The average age of the patients (55 years) was younger than in many THA series. At the last follow-up assessment, 50 hips were classified as good or excellent, one as fair, and one as a poor result. No total hip component required revision. No acetabular components had migrated as judged by conventional roentgenographic examination, and only one hip had progressive radiolucencies around the acetabular component. No femoral component was rated definitely loose or probably loose, and only one was rated possibly loose. If long-term follow-up study confirms these preliminary results, the combination of a cemented femoral component with a cementless socket may prove to be of value for selected patients requiring THA.     

The survival of the cemented femoral component of a total hip replacement

A series of 1321 total hip arthroplasties including 238 primary revisions (18%) were evaluated to identify intrinsic factors of the femoral canal that might influence the success of a cemented total hip replacement. A survival analysis was used to compare the success rates of cemented femoral components. These were classified into five groups according to the condition of the medullary canal at the time of surgery: primary surgery, aseptic cemented loosening, failed noncemented hemiarthroplasty, previous septic failure, or fractured femoral prosthesis with rigid distally fixed cement. The overall survival rates of the five groups were found to be significantly different (p less than 0.01). Specifically, the success rates of recemented revisions for aseptic loosening were significantly lower than those for primary total hip replacements (p less than 0.01). No statistical difference was found between the success rates of primary surgeries and the revision success rates for septic failure or for a fractured femoral component.     

Revision total hip arthroplasty with cemented femoral component

We reviewed retrospectively the results of 28 hips (25 patients) after revision of the femoral component with use of a cemented stem, because of aseptic loosening. The mean duration of follow-up was 4.43 years (range 2–12 years). Over the course of the study period, repeat revision was done in 4 hips after an average of 4.45 years. Three hips had a repeat revision of the femoral component because of aseptic loosening and one for a deep infection. The rate of loosening of the femoral component was 32.4% (9 hips) at an average of 5.22 years. The 5-year survival rate was 76.9% with mechanical failure as end point; and 90% with re-revision of femoral component because of aseptic loosening as end point. The cement mantle was the principal factor, which was significantly associated with a better survival rate of femur fixation (P < 0.05). No correlation was noted between quality of bone loss at the time of revision, bone graft or the use of long stems, and the survival rate of femoral component. By improving the cementing technique and in selected patients, the use of cemented femoral stem could be a good alternative for aseptic loosening THA.     

Total hip arthroplasty cemented femoral component distal stem centralizer: Effect on stem centralization and cement mantle

The effectiveness, benefits, and potential risks of employing a total hip arthroplasty cemented femoral component distal centralizer were evaluated. First postoperative (6-week) radiographs of 100 primary hybrid total hip arthroplastics in consecutive groups of 50 patients without and 50 patients with a femoeral stem distal centralizer were retrospectively reviewed. Femoral stems with a distal centralizer were more centralized within the femoral canal (center of stem tip to center of intramedullary canal: mean, 1.1 mm with a centralizer, 3.2 mm without; P < .0001) and more neutrally aligned (mean, 0.7° valgus with a centralizer, 1.3° valgus without; P < .01). Femoral stems with a distal centralizer were less likely to have a cement mantle with suboptimal thickness, that is, less than 2 mm at the medial distal femoral stem (3 of 50 stems with a centralizer, 22 of 50 stems without; chi-square, P < .0001). There were no complications, adverse effects on the cement mantle, radiographic evidence of loosening, or implant failures associated with the use of a distal centralizer, with a minimum follow-up period of 2 years.     

Factors affecting socket fixation after cemented revision

Summary. Factors influencing the radiographic outcome of revised cemented sockets have been investigated in 360 cases; 70 with radiological signs of failure were analysed. The acetabular bone stock at revision and preparation of the acetabular floor were the two factors which had a significant influence on the outcome. The thickness of the cement mantle around the socket also had an influence. Young patients were at a higher risk of failure. The use of a flanged socket and an acetabular cement pressuriser appeared to improve the radiographic result, but this was not statistically significant.

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Résumé. Nous étudions les facteurs influen*ant l’évolution radiologique des cupules cimentées après changement. Dans cette étude, 360 cupules cimentées dont 70 présentant un descellement radiologique ont eu à une analyse statistique. Le capital osseux de l’acétabulum et la préparation du fond du cotyle lors du changement de la prothèse se sont révélés être les deux facteurs ayant une influence hautement significative (p = 0.0001) sur l’évolution de ces cupules. Nous avons aussi constaté que l’épaisseur du manteau de ciment autour de la cupule influence le pronostic. En outre, les patients jeunes présentent un risque élevé de descellement radiologique. L’utilisation du pressurisateur à ciment et des cupules avec rebord tend à améliorer l’évolution radiologique, mais de fa*on non significative statistiquement.

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Accepted: 12 July 1996     

Total hip arthroplasty with a cementless acetabular component and a cemented femoral component in the treatment of Chinese patients with femoral head necrosis

The purpose of this study was to evaluate midterm clinical and radiographic outcomes associated with hybrid total hip arthroplasty in a consecutive series of 86 Chinese patients (93 hips) with osteonecrosis of the femoral head, which revealed that the mean Harris hip score increased from 39 +/- 6.0 points before operation to 90.4 +/- 4.6 points at the latest follow-up. There was pelvic osteolysis in one hip (1%), which required revision, and some small focal areas of femoral osteolysis in 12 hips (13%) were observed. The mean linear wear rate was 0.143 +/- 0.05 mm/y (0.02-0.45 mm/y). No loosening of the components was observed radiographically. The survival rate of the acetabular and femoral components for revision was 98% (95% confidence interval, 0.96-1.0) and 100% (95% confidence interval, 0.95-1.0). Hybrid total hip arthroplasty in patients with osteonecrosis of the femoral head had a satisfactory clinical and radiographic outcome at a minimum 5 years of follow-up. Because polyethylene wear and osteolysis cannot be avoided, the long-term effect should be further studied.     

The fixation of the cemented femoral component. Effects of stem stiffness, cement thickness and roughness of the cement-bone surface

After cemented total hip arthroplasty (THA) there may be failure at either the cement-stem or the cement-bone interface. This results from the occurrence of abnormally high shear and compressive stresses within the cement and excessive relative micromovement. We therefore evaluated micromovement and stress at the cement-bone and cement-stem interfaces for a titanium and a chromium-cobalt stem. The behaviour of both implants was similar and no substantial differences were found in the size and distribution of micromovement on either interface with respect to the stiffness of the stem. Micromovement was minimal with a cement mantle 3 to 4 mm thick but then increased with greater thickness of the cement. Abnormally high micromovement occurred when the cement was thinner than 2 mm and the stem was made of titanium. The relative decrease in surface roughness augmented slipping but decreased debonding at the cement-bone interface. Shear stress at this site did not vary significantly for the different coefficients of cement-bone friction while compressive and hoop stresses within the cement increased slightly.     

The timing of femoral component insertion in cemented hip arthroplasty

The time to insertion of the femoral component into a cemented medullary cavity during total hip arthroplasty was reviewed. A survey of current practice among a group of surgeons was undertaken, and reproducible model of femoral cement penetration was developed. Under standard conditions, this showed maximum penetration of Vacu-Mix Plus CMW1 gentamicin cement (DePuy, Leeds, UK) at 3 minutes.     

A prospective study of a titanium femoral component for cemented total hip arthroplasty

The authors studied the clinical and radiographic results of a modern titanium-alloy femoral stem with a cobalt-chrome-alloy head for use in cemented total hip arthroplasty. One hundred sixteen hips (102 patients) were operated on using modern cement techniques and prospectively followed using the Hospital for Special Surgery hip rating system and standard radiographic criteria. At a mean follow-up period of 4.8 years (range, 2–8 years), 69 hips were rated excellent, 38 good, 4 fair, and 5 poor. A total of 13 femoral components (11%) were radiographically loose according to the criteria of Harris. In 11 of these loose femoral components, debonding or separation at the cement-prosthesis interface, was the initial cause of failure, with bone-cement interface erosions occurring later in five hips. Revision of a loose femoral component has been performed in three hips and is pending in two other hips (4.3%). Significant calcar resorption was seen in only 17 hips (14.6%), and serial measurements of distal femoral cortical widths showed no distal cortical hypertrophy except in one femur. The incidence of loosening with this cemented titanium-alloy femoral component (with a cobalt-chrome-alloy head) is much higher than published reports of similar cobalt-chrome-alloy stems. The authors have abandoned the use of titaniumalloy femoral components for cemented total hip arthroplasty.     

Total dislodgement of the femoral component following cemented total knee arthroplasty: a case report

Total dislodgement of the components, which is the most severe form of loosening, has hitherto been unreported following total knee arthroplasty. An eighty-four-year-old woman presented with complaints of pain and sensation of insecurity of her right knee after cemented total knee arthroplasty. On physical examination, a clunk was elicited during movements of the knee; however, radiographs appeared normal except for a separated fragment of the medial femoral condyle. Further examination with varus and valgus stress tests under fluoroscopic control showed dislodgement of the femoral component, which was only apparent on stress radiographs. She underwent revision cemented total knee arthroplasty and her complaints disappeared completely within a follow-up period of three years. This case illustrates the need for stress radiographs when standard radiographs are normal in the face of a high suspicion of loosening.     

Impaction femoral allografting at revision hip arthroplasty: uncemented versus cemented technique using a Freeman femoral component

We report the long-term results of revision total hip replacement using femoral impaction allografting with both uncemented and cemented Freeman femoral components. A standard design of component was used in both groups, with additional proximal hydroxyapatite coating in the uncemented group. A total of 33 hips in 30 patients received an uncemented component and 31 hips in 30 patients a cemented component. The mean follow-up was 9.8 years (2 to 17) in the uncemented group and 6.2 years (1 to 11) in the cemented group. Revision procedures (for all causes) were required in?four patients (four?hips) in the uncemented group and in five patients (five hips) in the cemented group. Harris hip scores improved significantly in both groups and were maintained independently of the extent of any migration of the femoral component within the graft or graft-cement mantle.     

骨水泥型人工股骨头置换术中严重骨水泥反应的临床分析

目的探讨骨水泥型人工股骨头置换术中骨水泥反应发生的原因及预防。方法回顾调查2000年1月至2011年3月,本组行骨水泥型人工股骨头置换术189例（190髋）,男72例,女117例,平均年龄77．7岁。对术中出现骨水泥反应的患者术前年龄、身体状况、症状、体征等进行总结评价,对术前准备、术中术后处理及预防进行探讨。结果189例（190髋）患者中严重骨水泥反应7例,发生率为3．70％;其中死亡2例,死亡率为1．06％。7例患者中低粘度骨水泥组1例,高粘度骨水泥组6例;股骨颈骨折2例,股骨粗隆间骨折5例。均为85岁以上高龄患者,有骨质疏松和内科相关疾病。结论高龄、股骨近端骨折、骨质疏松、髓腔内高压和多科相关疾病是骨水泥反应的高危因素;使用低粘度骨水泥和注意其使用方法可以降低严重骨水泥反应的发生率。     

Factors affecting flexural strength in cement within cement revisions

Cement within cement revisions provide substantial benefits for conventional revision yet remains uncommon possibly because of the perceived weakness of the cement-cement interface. This study investigated the flexural strength of beams composed of 2 different cements, exploring the factors of pore size, fracture location, viscosity, and the surface roughness of the interface. We found no significant difference when comparing combinations of different cements (P = .30), varying pore sizes (P = .13), or surface roughness (P = .39). Differences in fracture locations and viscosity combinations approached statistical significance (P = .08 and .05, respectively). Our findings suggest strong bonding between cements at the interface, with other factors being more important causes of weakness. Thus, we recommend that the strength of the cement-cement interface should not be a factor when considering such revisions.     

Long-term results after cemented revision of the femoral component in total hip arthroplasty

The need for revision total hip arthroplasty has been increasing. The early results have been poor, and different revision techniques have been introduced. We report our results of 84 consecutive cemented first-time revisions of femoral components performed from 1981 through 1988 using a long-stem revision component. The average time to follow-up was 11.4 years (range, 7.9-15.0 years). Patients with 47 revisions had died; 2 of these had been rerevised. Two additional patients were lost to follow-up for other reasons. Of the living patients, 12 had been rerevised, leaving 23 patients (23 hips) for complete follow-up evaluation, including clinical and radiographic assessment. Of 23 patients, 15 reported no pain, 4 had only slight pain, and 4 had more severe pain. In 4 cases, there were definite radiographic signs of loosening of the femoral component. Kaplan-Meier survivorship analysis showed an overall 10-year survival of the femoral component of 77.9%. Using rerevision because of aseptic loosening or definite radiographic loosening as endpoint, the 10-year survival was 80.7%. Simple recementation is well indicated in elderly patients with only minor bone loss.     

Risk factors for recurrent aseptic loosening of the femoral component after cemented revision

A series of 160 consecutive cemented first revisions, performed from 1977 through 1988 for aseptic loosening of a primary cemented femoral component, were studied using survivorship methods with the purpose of identifying risk factors for recurrent loosening of the femoral component. Risk of recurrent loosening depended on the length of the revision stem, with a significantly increased risk of loosening if the tip of the primary stem was overbridged by the revision stem with less than one width of the femoral shaft. Risk of recurrent loosening was also related to the extension of a cement mantle, exceeding more than 2 mm, around the revision stem measured on postrevision anteroposterior radiographs. Furthermore, low age and neutral position of the revision stem were identified as risk factors for recurrent loosening of the cemented revision femoral component. An improved fixation of the cemented revision femoral component for revisions performed after, 1982 could be related to the use of longer revision stems and improved cementation.