Femoral Stem Design Research Articles

A New Cemented Femoral Stem: A Prospective Study of the Stryker Accolade C With 2- to 5-Year Follow-Up

This prospective study evaluates the short-term results of a recently released cemented femoral stem design in primary cemented and hybrid total hip arthroplasty (THA). There were 100 all-cemented and 100 hybrid THAs in the 2-year study group. Good to excellent results were obtained in 96%. There was one reoperation for recurrent dislocation in each cohort (1%) and one single-staged reoperation for sepsis in the cemented cohort. There were 47 THA available for 5-year follow-up. Good to excellent results were maintained in 98%. One additional patient had a revision because of late recurrent dislocation. This study has demonstrated excellent early results and safety with this cemented femoral stem. The features include a dual-wedge geometry with a 0.88-μm Ra surface roughness, proximal macro-normalizations, distal anti-rotation grooves, and an optimized head-and-neck ratio approaching 4:1 using a standard 28-mm head.

Total Hip Arthroplasty with the Secur-Fit and Secur-Fit Plus Femoral Stem Design: A Brief Follow-Up Report at 5 to 10 Years

This report represents a 5- to 10-year follow-up of our initial 2- to 5-year data with this proximally hydroxyapatite-coated stem design (Secur-Fit, Stryker Orthopaedics, Mahwah, NJ). This is a retrospective review of a single surgeon's consecutive cases. A total of 105 cases were available for complete review. The average follow-up was 6.7 years (60-123 months). All stems achieved bony ingrowth. Harris hip score and Oxford hip score averaged to 91 and 17, respectively, with no differences seen between the 132° and the 127° stem designs. Leg length measurements were considered equal side-to-side differences of 7 mm or less in 87% of cases: 82% of standard- and 92% of high-offset cases ( P < .05). Four cases of osteolysis were identified and occurred only in patients with an elevated rim liner, implicating neck-liner impingement. The stem design performed exceedingly well over the course of this study. Having a high-offset option aids the surgeon in proper leg length management.

Clinical Outcome of Total Hip Arthroplasty Using the Normalized and Proportionalized Femoral Stem With a Minimum 20-Year Follow-Up

Currently, there are several femoral stem designs available for use, but few have an extended track record. We have previously reported on 10- and 15-year outcome studies of total hip arthroplasty (THA) using a cemented normalized and proportionalized femoral stem from a single surgeon series. This is a follow-up study reporting the minimum 20-year outcome of this femoral stem design. The study began with THA performed in a consecutive series of 184 patients; stem fixation was achieved using first-generation cementing techniques. The overall early complication rate was 10%. There were 23 patients (31 hips) who had been followed-up for a minimum 20-year period (average 21.3 years). Mean d'Aubigne and Postel scores improved from 5.9 to 11.3; mean Harris hip scores improved from 43.8 to 92.8. Kaplan-Meier survivorship was 93% at 20 years (95% confidence interval); there were no stem failures. The use of a cemented normalized and proportionalized femoral stem in primary THA provides satisfactory long-term clinical and radiological outcomes in patients.

Is 7206 ISO standard enough to prove the endurance of femoral components of hip prostheses?

The design of a cementless femoral stem that fractured at the neck–shoulder junction was analysed with reference to parts 4 and 8 of ISO standard 7206. The stresses in the section where fracturing occurred were calculated assuming the 2300 N loading specified in ISO 7206-8. The results show that the prosthesis met ISO standard requirements regarding fatigue behaviour. However, this feature does not occur when a load of 4000 N, corresponding to a patient with a body weight of 1000 N, is applied. It is therefore suggested that patient body weight should be taken into account when designing and choosing the appropriate stem size.

Improved Outcome in Femoral Revision Arthroplasty with Tapered Fluted Modular Titanium Stems

Many techniques have been advanced to achieve reliable femoral stem fixation in revision total hip arthroplasty. In a cross-sectional study, we compared quality of life in 220 patients with two femoral stem designs: a modular tapered and fluted titanium stem design and a cylindrical extensively coated chrome-cobalt stem with single modularity (head size and neck length alone). We matched cohorts based on age decade and gender. The minimum followup was 1 year with a median of 2 years. Subjective outcome assessment and patient satisfaction were measured using the WOMAC Osteoarthritis Index, the Oxford Hip Score, the SF-12, and the Arthroplasty Satisfaction Scale. At followup, all quality of life measures favored the tapered titanium stem. WOMAC pain, function, and overall scores all were higher in this group. The Oxford Hip Score and the Satisfaction score reflected a greater difference in outcome between the two stem designs. We presume reduced stiffness of the titanium stem, coupled with the intraoperative modularity, resulted in the improved patient outcomes observed in this study.

Philosophies of Stem Designs in Cemented Total Hip Replacement

Stem designs, which have different design features, may produce similar clinical survival curves. Alteratively, some designs that are considered to be similar in design produce different survival rates. In this paper, design aspects of cemented femoral total hip replacement stems, how they can be grouped to design philosophies, and how they may affect the failure process are discussed. In addition, explanations of unsuccessful designs are posed to learn from previous mistakes and improve understanding of design aspects that affect the longevity of cemented femoral stem designs.

The Importance of the Thickness of the Femoral Cement Mantle

The importance of mantle thickness in the long-term survival of cemented femoral components remains controversial. One complexity in evaluating mantle thickness alone is the dominating fact that so many other factors can influence the incidence of failure. Nonetheless, a cement grading system has been applied to the assessment of the intermediate and long-term follow-up series of the following cemented femoral stem designs HD-2 (Howmedica, Rutherford, NJ), CAD (Howmedica, Rutherford, NJ), Precoat (Zimmer, Warsaw, IN), Iowa (Zimmer, Warsaw, IN), Ti32 (Zimmer, Warsaw, IN), and DF80 (Zimmer, Warsaw, IN). In each series, a statistically significant increased risk of failure was found in those cases with cement mantles that were thin or deficient. While these data do not mean that all such cases fail, the data strongly support the concept of avoiding such deficiencies in the cement mantle of these stem designs.

Dependency of cement mantle thickness on femoral stem design and centralizer

Abstract: Deficient cement mantles may be detrimental with regard to long-term outcome of cemented femoral stems. We performed a cadaver study on 48 left femora with 4 different stem designs (1 anatomic, 3 straight) to study the influence of stem design, centralizer, and femur type on cement mantle thickness. A radiographic and microradiograhic analysis was done. Overall, 88% of stems were aligned within 1° of neutral in the frontal plane. In Gruen zones 1 through 7, we measured 24 thin cement mantles (<2 mm) in 19 specimens with no correlation to stem design or zone. In the sagittal plane, typical areas of thin cement mantles were identified in Gruen zones 8 and 9 (n = 39) and 12 (n = 21). The anatomic stem design carried the lowest risk (54%) of producing a thin cement mantle proximally in Gruen zones 8 and 9. The risk for straight stem designs was >90%. Straight stems without centralizer showed the highest risk of thin cement mantles in Gruen zone 12 (93%). Centralizers were efficient to prevent thin cement mantles in zone 12 but had no effect proximally. Lateral radiographs are essential to allow for adequate radiographic assessment of the cement mantle and stem alignment. There is a high risk of producing thin cement mantles in Gruen zones 8 and 9, in particular when straight stems are used. Posterior canal entry and low neck osteotomies are essential. Anatomic stems respect the anatomy, allow for more even cement mantles, minimize the risk of thin cement mantles without the use of centralizers, and may be considered in the femur with marked proximal bow.

A comparison of bone remodelling around hydroxyapatite-coated, porous-coated and grit-blasted hip replacements retrieved at post-mortem

We investigated the implant-bone interface around one design of femoral stem, proximally coated with either a plasma-sprayed porous coating (plain porous) or a hydroxyapatite porous coating (porous HA), or which had been grit-blasted (Interlok). Of 165 patients implanted with a Bimetric hip hemiarthroplasty (Biomet, Bridgend, UK) specimens were retrieved from 58 at post-mortem. We estimated ingrowth and attachment of bone to the surface of the implant in 21 of these, eight plain porous, seven porous HA and six Interlok, using image analysis and light morphometric techniques. The amount of HA coating was also quantified. There was significantly more ingrowth (p = 0.012) and attachment of bone (p &gt; 0.05) to the porous HA surface (mean bone ingrowth 29.093 ± 2.019%; mean bone attachment 37.287 ± 2.489%) than to the plain porous surface (mean bone ingrowth 21.762 ± 2.068%; mean bone attachment 18.9411 ± 1.971%). There was no significant difference in attachment between the plain porous and Interlok surfaces. Bone grew more evenly over the surface of the HA coating whereas on the porous surface, bone ingrowth and attachment occurred more on the distal and medial parts of the coated surface. No significant differences in the volume of HA were found with the passage of time. This study shows that HA coating increases the amount of ingrowth and attachment of bone and leads to a more even distribution of bone over the surface of the implant. This may have implications in reducing stress shielding and limiting osteolysis induced by wear particles.

The Harris-Galante uncemented femoral component in primary total hip replacement at 10 years

Eighty-eight primary femoral reconstructions in 80 patients were performed with the Harris-Galante uncemented femoral stem by 1 surgeon between March 1984 and December 1987. Seventy-seven femoral components in 72 patients were followed for an average 126 months or until femoral revisions. The average age at operation was 54 years (range, 30–70 years). Fifty-two patients were men, and 20 were women. The present article documents the incidence of femoral osteolysis and femoral revision in this series of this type of femoral component at an average of 10 years. Fifteen femoral components (15 of 77, 19%) were revised, 14 (14 of 77, 18%) for aseptic loosening, osteolysis, or fracture through osteolysis. The remaining 62 femoral components were functioning well (average Harris Hip Score 89 points), but 7 (11%) were loose, and 32 (52%) had femoral endosteal lysis. Overall, 19 (25%) were revised or loose, and 46 (46 of 77, 60%) had lysis. The high incidence of femoral lysis and aseptic loosening with this early design of uncemented femoral stem continues to increase at 10-year follow-up.

Long-term results of cemented femoral stems with roughened precoated surfaces.

Several recent articles have raised the question that rough surfaces with or without precoating may contribute to the loosening of cemented femoral stems. In this article the author collates selected reports of several different cemented femoral stem designs that have rough surfaces which have shown excellent long term results. Femoral stem loosening is generally multifactorial. It often is difficult to separate the effect of stem design or other changes from the effect of surface finish. Many rough surfaced cemented femoral stems have served well for decades. It is important to analyze all the pertinent factors in cases of early loosening.

EARLY RADIOLOGICAL OBSERVATIONS MAY PREDICT THE LONG-TERM SURVIVAL OF FEMORAL HIP PROSTHESES

We reviewed a consecutive series of 527 uninfected hip replacements in patients resident in the UK which had been implanted from 1981 to 1993. All had the same basic design of femoral prosthesis, but four fixation techniques had been used: two press-fit, one HA-coated and one cemented. Review and radiography were planned prospectively. For assessment the components were retrospectively placed into two groups: those which had failed from two years onwards by aseptic femoral loosening and those in which the femoral component had survived without revision or recommendation for revision. All available radiographs in both groups were measured to determine vertical migration and examined by two observers to agree the presence of radiolucent lines (RLLs), lytic lesions, resorption of the neck, proximal osteopenia and distal intramedullary and distal subperiosteal formation of new bone. We then related the presence or absence of these features and the rate of migration at two years to the outcome with regard to aseptic loosening and determined the predictive value of each of these variables. Migration of ≥2 mm at two years, the presence of an RLL of 2 mm occupying one-third of any one zone, and subperiosteal formation of new bone at the tip of the stem were predictors of aseptic loosening after two years. There were too few lytic lesions to assess at two years, but at five years a lytic lesion ≥2 mm also predicted failure. We discuss the use of these variables as predictors of femoral aseptic loosening for groups of hips and for individual hips. We conclude that if a group of about 50 total hip replacements, perhaps with a new design of femoral stem, were studied in this way at two years, a mean migration of &lt; 0.4 mm and an incidence of &lt; 10% of RLLs of 2 mm in any one zone would predict 95% survival at ten years. For an individual prosthesis, migration of &lt; 2 mm and the absence of an RLL of ≤2 mm at two years predict a 6% chance of revision over approximately ten years. If either 2 mm of migration or an RLL of 2 mm is present, the chances of revision rise to 27%, and if both radiological signs are present they are 50%. If at five years a lytic lesion has developed, whatever the situation at two years, there is approximately a 50% chance of failure in the following five years. Our findings suggest that replacements using a limited number of any new design of femoral prosthesis should be screened radiologically at two years before they are generally introduced. We also suggest that radiographs of individual patients at two years and perhaps at five years should be studied to help to decide whether or not the patient should remain under close review or be discharged from specialist follow-up.

Early radiological observations may predict the long-term survival of femoral hip prostheses.

We reviewed a consecutive series of 527 uninfected hip replacements in patients resident in the UK which had been implanted from 1981 to 1993. All had the same basic design of femoral prosthesis, but four fixation techniques had been used: two press-fit, one HA-coated and one cemented. Review and radiography were planned prospectively. For assessment the components were retrospectively placed into two groups: those which had failed from two years onwards by aseptic femoral loosening and those in which the femoral component had survived without revision or recommendation for revision. All available radiographs in both groups were measured to determine vertical migration and examined by two observers to agree the presence of radiolucent lines (RLLs), lytic lesions, resorption of the neck, proximal osteopenia and distal intramedullary and distal subperiosteal formation of new bone. We then related the presence or absence of these features and the rate of migration at two years to the outcome with regard to aseptic loosening and determined the predictive value of each of these variables. Migration of > or = 2 mm at two years, the presence of an RLL of 2 mm occupying one-third of any one zone, and subperiosteal formation of new bone at the tip of the stem were predictors of aseptic loosening after two years. There were too few lytic lesions to assess at two years, but at five years a lytic lesion > or = 2 mm also predicted failure. We discuss the use of these variables as predictors of femoral aseptic loosening for groups of hips and for individual hips. We conclude that if a group of about 50 total hip replacements, perhaps with a new design of femoral stem, were studied in this way at two years, a mean migration of < 0.4 mm and an incidence of < 10% of RLLs of 2 mm in any one zone would predict 95% survival at ten years. For an individual prosthesis, migration of < 2 mm and the absence of an RLL of < or = 2 mm at two years predict a 6% chance of revision over approximately ten years. If either 2 mm of migration or an RLL of 2 mm is present, the chances of revision rise to 27%, and if both radiological signs are present they are 50%. If at five years a lytic lesion has developed, whatever the situation at two years, there is approximately a 50% chance of failure in the following five years. Our findings suggest that replacements using a limited number of any new design of femoral prosthesis should be screened radiologically at two years before they are generally introduced. We also suggest that radiographs of individual patients at two years and perhaps at five years should be studied to help to decide whether or not the patient should remain under close review or be discharged from specialist follow-up.

Total hip arthroplasty

Total hip arthroplasty continues to be an extremely successful procedure, with ever-widening indications and regular improvement in technique, materials, and design. In the past year several studies were published evaluating the results of both cemented and cementless total hip arthroplasty at mid- to long-term follow-up. In addition, careful analysis of basic laboratory studies including finite-element analyses have added to our understanding of materials and design. Specific findings in the past year included poor results with cemented hips in younger patients at long-term follow-up of greater than 16 years. A lower incidence of loosening has been found for cobalt chrome-cemented components compared with titanium-cemented components. No difference was found in the results of metal-backed versus non-metal backed cemented acetabular components, and an increasing incidence of loosening was shown for cemented acetabular components with time. The newer cementless hip arthroplasties showed evidence of learning curve, particularly with regard to innovative design such as acetabular screw rings, whereas porous-coated hemispherical cups appeared to do well. Thigh pain continues to be a problem with cementless designs, and the controversy of titanium versus cobalt chrome for cementless femoral stem designs continues at full tilt.

Normalized and proportionalized cemented femoral stem designs: A 10-year clinical study

Two hundred fifteen cemented total hip arthroplasties were performed in 184 patients using normalized and proportionalized femoral stems. Normalization or stepped tapering of the stem minimizes development of tensile hoop stresses by altering force transmission from the femoral stem to the cement mantle. The proportionality of the stem was based on an anatomic study that resulted in the development of a series of prostheses achieving a more complete femoral canal fill. Patients were followed clinically and radiographically from 8 to 12 years or until revision. Average hip scores (d'Aubigne and Postel) improved for pain (3.0–5.9), function (2.9–5.5), and motion (3.3–5.5). Radiographic results demonstrated a 4% incidence of loosening, a 16% incidence of cortical hypertrophy, and no femoral stem fractures. Revision rate was 3%. These results support use of this device.

Prediction of clinical outcome of THR from migration measurements on standard radiographs. A study of cemented Charnley and Stanmore femoral stems

We report the theoretical basis of a method to measure axial migration of femoral components of total hip replacements (THR). The use of the top of the greater trochanter and a lateral point on the collar of the stem, allowing for variations of up to 10 degrees rotation of the femur in any direction between successive radiographs, gave a maximum error of 0.37 mm. At a more realistic 5 degrees rotational variation, the error was only 0.13 mm. These data were confirmed in an experimental study using digitisation of points and special software. We also showed that the centre of the femoral head, the stem tip, and the lesser trochanter provided less accurate landmarks. In a second study we digitised a series of radiographs of 51 Charnley and 57 Stanmore THRs; the mean migration rates were found to be identical. We then studied 46 successful stems with a minimum follow-up of eight years and 46 stems which had failed by aseptic loosening at different times. At two years, the successful stems had migrated by a mean of 1.45 +/- 0.68 mm, but the failed cases had a mean migration of 4.32 +/- 2.58 mm (p < 0.0001). Of the successful cases 76% had migrated less than 2 mm, while in the failed group 84% had migrated more than 2 mm. For any particular case migration of more than 2.6 mm at two years had only a 5% chance of continuing success and would therefore merit special follow-up. Only 24% of the eventually successful stems showed migration at the stem-cement interface, but this had happened in every failed stem. We conclude that it would be possible to evaluate a new cemented design of femoral stem over a two-year period by the use of our method and to compare its performance against the reported known standard of the Charnley and Stanmore designs.

A MISSING LINK IN THE EVOLUTION OF THR: "DISCOVERY" OF THE LATERAL FEMUR

Using cadaveric studies and mathematical models that include consideration of the iliotibial band (ITB) as a "tension band," the authors have demonstrated that compression loading occurs throughout the entire lateral femoral cortex from the apophyseal line of the greater trochanter to the lateral femoral epicondyle at the knee. This model suggests that the magnitude of this load on the medial and lateral cortices is proportional to the medial displacement of these cortices from the ITB. The authors have further demonstrated that the "tension band" model is more consistent with actual bone morphology and function than existing models and is a strong argument for the incorporation of design concepts such as lateral extensions into total hip arthroplasty femoral components. Such extensions would permit use of lateral femoral cortical bone as an additional base of prosthesis support, distributing loads over a greater area of the proximal femur. This model, therefore, would theoretically reduce the areas of stress concentration in diaphyseal bone and stress shielding of the proximal femur, both of which appear to be deficiencies of present femoral stem designs.

Radiological Analysis of the Proximal Femoral Geometry in Korean Adults and the Design of the Cementless Femoral Stem

Radiological Analysis of the Proximal Femoral Geometry in Korean Adults and the Design of the Cementless Femoral Stem

Femoral Cement Pressurization during Total Hip Arthroplasty The Role of Different Femoral Stems with Reference to Stem Size and Shape

Aseptic loosening is the most common cause of femoral component failure following total hip arthroplasty (THA). Improvements have been made in cementing technique, but little attention has been directed toward the effect of different femoral components on bone cement pressurization. The effect of three different femoral stem sizes in one femoral canal and of eight different femoral stem designs on bone cement extrusion pressures was investigated on autopsy specimens. In a given femur significant increases in bone cement pressurization were achieved about the distal two-thirds of the femoral component in progressing from a small to a medium to a large stem. Similarly, femoral stems with rounded, rectangular cross sections generated greater bone cement pressurization about the distal two-thirds of the stems than stems trapezoidal and diamond-shaped in cross section due to their increased stem volume. The results of this study favor the use of the largest femoral component stem, preferably one with a rounded, rectangular cross section, that will fit comfortably in a given femoral canal and still allow a surrounding cement envelope such that bone cement pressurization will be enhanced with implant introduction.

日本人大腿骨に適合する人工骨頭ステムに関する研究

日本人大腿骨に適合する人工骨頭ステムに関する研究