Large Femoral Head Research Articles

Metal-on-Metal Hybrid Surface Arthroplasty: Two to Six-Year Follow-up Study

Following the reintroduction of metal-on-metal articulating surfaces for total hip arthroplasty in Europe in 1988, we developed a surface arthroplasty prosthetic system using a metal-on-metal articulation. The present study describes the clinical and radiographic results of the first 400 hips treated with metal-on-metal hybrid surface arthroplasties at an average follow-up of three and a half years. Between November 1996 and November 2000, 400 metal-on-metal hybrid surface arthroplasties were performed in 355 patients. All femoral head components were cemented, but only fifty-nine of the short metaphyseal stems were cemented. The patients had an average age of forty-eight years, 73% were men, and 66% had a diagnosis of osteoarthritis. Clinical and radiographic follow-up were performed at three months postoperatively and yearly thereafter. The majority of the patients returned to a high level of activity, including sports, and 54% had activity scores of >7 on the University of California at Los Angeles activity assessment system. Kaplan-Meier survivorship curves demonstrated that the rate of survival of the components at four years was 94.4%. For patients with a surface arthroplasty risk index score of >3, the rate of survival of the components at four years was 89% compared with a rate of 97% for those with a score of </=3. The patients with a higher risk index were 4.2 times more likely to undergo revision to a total hip replacement at four years. Twelve hips (3%) had a revision to a total hip replacement. Seven of the twelve hips were revised because of loosening of the femoral component, and three were revised because of a femoral neck fracture. Substantial radiolucencies were seen around sixteen uncemented metaphyseal femoral stems. No femoral radiolucencies were observed among the hips in which the metaphyseal stem was cemented. The most important risk factors for femoral component loosening and substantial stem radiolucencies were large femoral head cysts (p = 0.029), patient height (p = 0.032), female gender (p = 0.005), and smaller component size in male patients (p = 0.005). The preliminary experience with this hybrid metal-on-metal bearing is encouraging. Optimal femoral bone preparation and component fixation are critical to improving durability. The metal-on-metal hybrid surface arthroplasty is easily revised to a standard femoral component if necessary. Therapeutic study, Level IV (case series [no, or historical, control group]). See Instructions to Authors for a complete description of levels of evidence.

Orthopaedic crossfire®—larger femoral heads: A triumph of hope over reason!: In opposition

For the past decade, large femoral heads have for the most part been avoided in total hip arthroplasty, especially in younger active patients, because of their association with increased polyethylene wear. However, it has become equally clear that large femoral heads offer a benefit in terms of hip stability and reducing postoperative dislocation. With increasing head size, there is less chance of component-on-component impingement and increased displacement for dislocation. Highly cross-linked polyethylene appears to be relatively insensitive to head size and may offer the surgeon the opportunity to use large femoral heads, especially in patients who are at high risk for dislocation. © 2003 Elsevier Inc. All rights reserved.

Orthopaedic Crossfire®—larger femoral heads: A triumph of hope over reason!: In the affirmative

The authors' wear studies of total hip arthroplasty cohorts have shown that less polyethylene wear and less deleterious effects of third body debris were found when smaller femoral head sizes were used. The authors' sliding-distance-coupled finite element model findings were corroborated by these clinical wear studies. Thus, with polyethylene on metal bearing surfaces, less wear should occur when smaller head sizes are used. Careful, precise component positioning is important to prevent dislocation. © 2003 Elsevier Inc. All rights reserved.

Arthroplasty in the treatment of subcapital hip fracture.

After reviewing recent literature on the treatment of displaced intracapsular fractures of the femoral neck (Garden types III and IV) and from personal experience, a number of conclusions can be made. Orthopedic surgeons and hospitals face the challenge of providing the treatment most beneficial to patients with intracapsular, subcapital hip fractures in the most cost-effective way. The numbers of patients will increase annually and exceed the 125,000 per year at present in the United States. Most authors agree that fractures with the least displacement and younger, more demanding patients will do well with a precise fracture reduction without delay and an accurately placed internal fixation system. However, an overall median risk for reoperation 2 years after internal fixation is 35%. A patient with a displaced intracapsular fracture will need to consider monopolar, bipolar, or THA as the treatment of choice. Monopolar and bipolar arthroplasty have a reduced survivorship compared to THA and are not as suitable for the younger, more active patient. A large femoral head implant leads to decreased motion from increased friction and an undersized head implant leads to reduced contact area with increased erosion and pain. Bipolar arthroplasties, while allowing early mobilization, may develop some of the characteristics of monopolar implants if motion is not mainly at the internal joint. The increased cost may not justify their use over monopolar arthroplasty. Should dislocation occur, monopolar implants are easier to reduce (closed) than bipolar. Ceramic heads on monopolar or bipolar arthroplasties offer reduced wear and less erosion of the acetabulum. Total hip arthroplasty provides early mobilization, long-term pain relief, and little additional morbidity at surgery. The increased rate of early dislocation may be related to surgeon skill rather than an inherent failure of the system. If the early dislocators are removed from consideration, the complication rate drops to equal that of monopolar and bipolar implants. Total hip arthroplasty also is cost effective. Total hip arthroplasty may be the only option if pre-existing arthritis, significant osteoporosis, or Paget's disease of the pelvis is present.

Femoral head sizes larger than 32 mm against highly cross-linked polyethylene.

The advent of highly cross-linked ultrahigh molecular weight polyethylene, which shows extremely low wear independent of head size in vitro, allows for the reevaluation of the use of femoral heads larger than 32 mm. The current authors discuss information that supports this hypothesis. The supporting information includes in vitro wear testing and in vitro anatomic studies, and prior clinical studies in which large femoral heads were used.

Stability of total hip arthroplasty in patients 75 years or older.

Increasing patient age (> 75 years) is a known risk factor for dislocation of total hip arthroplasty. This is a study of total hip arthroplasties by one surgeon in patients 75 years or older to determine the prevalence of dislocation and a review of the surgical options for prevention and treatment of instability in this population. Of 140 primary total hip arthroplasties done in patients 75 years or older who were followed up for at least 1 year, the preoperative diagnosis was osteoarthritis in 82% and the mean followup time was 4 years. The acetabular component was cementless: modular in 121 arthroplasties and cemented in 19 arthroplasties. There were five dislocations (3.5%), but only two were recurrent and the patients were treated successfully by modular component exchange. Bipolar arthroplasty has a lower rate of dislocation, but there are problems with residual pain and high rates of reoperation, wear, and osteolysis. Constrained components may be indicated in older patients with dementia, abductor insufficiency, or failure of modular exchange. Large femoral heads, to increase the range of motion before dislocation occurs, may be used with highly cross-linked acetabular liners. Modular cementless acetabular components are preferable in patients who are 75 years or older. A 28-mm or 32-mm femoral head is recommended, but larger femoral heads should be considered in patients with fractures and for the treatment of recurrent dislocation.

The computer simulation of wear behavior appearing in total hip prosthesis

Computer algorithms are proposed for the estimation of wear appearing in artificial hip joints using finite element analysis based on the modified Archard's wear law, contact features and an analogue wear process. A pin-on-disk plate experiment is reconstructed to assess the efficiency and validity of the algorithms proposed here. Through the successful verification of wear depth and volume loss of the pin-on-disk plate as well as the artificial hip joint, the current algorithms provide significant agreement with experiments, clinical measurements and numerical calculations and are shown to be both valid and feasible. Further investigation into the effect of femoral heads with various sizes suggests that the larger femoral head may induce larger wear volume but gives a smaller wear depth and that wear depth and volume loss are apparently nonlinearly related to the femoral head diameter. It is shown that the current algorithms are useful and helpful in understanding wear behavior for alternative or new designs of artificial hip joints and even for other analogous structures.

Postcranial adaptations for leaping in primates

Leaping primates are specialized for hindlimb-propelled locomotion within arboreal habitats. As a group, they include members of Galagonidae, Lemuriformes and Tarsiidae. Postcranial characters analysed here include humeral and femoral diaphyseal rigidity, articular surface areas and lengths. Data for leaper taxa are compared with corresponding data for less specialized small primates. The more generalized comparative primates include both closely related prosimians and distantly related platyrrhines (New World monkeys). In addition, the leapers are subdivided for further analysis according to body size and taxonomic association. Questions addressed concern the identification of functionally and/or phylogenetically linked traits in leaper postcrania. Results indicate that leapers as a group have relatively higher femoral diaphyseal rigidity and longer femora than do more generalized primates. These traits are also present in Pithecia pithecia, a platyrrhine leaper included for comparison. These enhanced properties probably function in resisting large hindlimb forces incurred during leaping, and in producing longer, more efficient leaps. Most of the large-bodied lemuriform leapers are further distinguished in having relatively bigger femoral heads and reduced humeral rigidity. The small-bodied leapers, galagonids and tarsiids, do not differ in either femoral head surface area or in any of the humeral properties from more generalized primates. Pithecia has a large femoral head like lemuriforms, but it is not reduced in humeral rigidity. Aspects of hip joint structure and mobility may be related to femoral head size in lemuriforms and Pithecia. Explanations regarding reduced lemuriform humeral rigidity are also explored. Differences between lemuriform primates are also present, most notably in aspects of the distal humerus. Indrids are characterized by relatively reduced trochleae, while many lemurids have relatively small capitula. These features are interpreted with regard to frequencies of suspensory behaviour and quadrupedalism.

Postcranial adaptations for leaping in primates

AbstractLeaping primates are specialized for hindlimb‐propelled locomotion within arboreal habitats. As a group, they include members of Galagonidae, Lemuriformes and Tarsiidae. Postcranial characters analysed here include humeral and femoral diaphyseal rigidity, articular surface areas and lengths. Data for leaper taxa are compared with corresponding data for less specialized small primates. The more generalized comparative primates include both closely related prosimians and distantly related platyrrhines (New World monkeys). In addition, the leapers are subdivided for further analysis according to body size and taxonomic association. Questions addressed concern the identification of functionally and/or phylogenetically linked traits in leaper postcrania. Results indicate that leapers as a group have relatively higher femoral diaphyseal rigidity and longer femora than do more generalized primates. These traits are also present in Pithecia pithecia, a platyrrhine leaper included for comparison. These enhanced properties probably function in resisting large hindlimb forces incurred during leaping, and in producing longer, more efficient leaps. Most of the large‐bodied lemuriform leapers are further distinguished in having relatively bigger femoral heads and reduced humeral rigidity. The small‐bodied leapers, galagonids and tarsiids, do not differ in either femoral head surface area or in any of the humeral properties from more generalized primates. Pithecia has a large femoral head like lemuriforms, but it is not reduced in humeral rigidity. Aspects of hip joint structure and mobility may be related to femoral head size in lemuriforms and Pithecia. Explanations regarding reduced lemuriform humeral rigidity are also explored. Differences between lemuriform primates are also present, most notably in aspects of the distal humerus. Indrids are characterized by relatively reduced trochleae, while many lemurids have relatively small capitula. These features are interpreted with regard to frequencies of suspensory behaviour and quadrupedalism.

Femoral neck length and hip fracture risk.

To determine whether there are differences in femoral skeletal geometry in fracture-prone subjects when size, positioning diagnosis, and age are controlled, we compared femoral measurements made from the uninvolved hip on 119 plane anteroposterior pelvis radiographs of women without fracture to those of the contralateral hip in a group of 43 female patients with hip fractures (neck, 23; intertrochanteric, 20). The hip was imaged in a standardized position of rotation and adduction. Race, age, and musculoskeletal diagnosis were known. Subjects were grouped by diagnosis of the opposite hip condition (rheumatoid arthritis, osteoarthritis, and normal) and compared. Measurements were also analyzed as ratios to head diameter (HD), neck diameter (ND), and pelvic width. Femoral neck length (NL) was measured from skeletal preparations and imaged in controlled positions of abduction and external rotation. No differences were found between the neck and intertrochanteric fracture groups. The differences between the fracture group and the controls were a thinner femoral cortex (measured at a point one head radius below the lesser trochanter) a larger femoral head, and a larger femoral ND in the fracture group (p < 0.025). The difference in cortical thickness was still significant when scaled by size, but the ratio of HD to ND was equivalent in fractures and controls. No difference in femoral NL could be demonstrated. The experimental measurements showed that apparent NL is significantly position sensitive and this may explain previously reported differences in fracture-prone groups.

The charnley versus the spectron hip prosthesis: Radiographic evaluation of a randomized, prospective study of 2 different hip implants

A total of 410 hips were randomized to treatment with either a Charnley (206 hips) or a Spectron (204 hips) total hip arthroplasty. The patients were operated on by a standardized procedure using a contemporary cementing technique and were followed after 1, 3, 5 to 6, and 10 years. The postoperative radiographs showed a significantly increased rate of malalignment and consequently low grade of cement mantle quality of the Charnley stem compared to the Spectron. No differences concerning cement mantle quality or positioning were found between the Charnley ogee cup and the metal-backed Spectron. Evaluation of the follow-up radiographs revealed 10 loose Charnley stems and 1 loose Spectron stem and 4 loose Charnley ogee cups and 23 loose Spectron metal-backed cups. The differences of revision rate for the femoral and acetabular components of the 2 prostheses were significant ( P = .03, Charnley femoral component more frequent; P = .03, Spectron acetabular component more frequent). The radiographic evaluation strengthened this disparity. Poor wear characteristics of the metal-backed Spectron cup are perhaps the main reason for the highly significant difference in mechanical failure rate between the 2 cups. We therefore propose that metal-backing of cemented cups should be avoided, at least when combined with larger femoral heads. The difficulty in positioning the Charnley stem with an adequate cement mantle, especially in the absence of trochanteric osteotomy, might explain the inferior Charnley stem longevity in this study.

Combined survivorship and multivariate analyses of revisions in 799 hip prostheses. A 10- to 20-year review of mechanical loosening

From 1970 to 1980 cemented metal-on-plastic total hip replacement was performed on 799 hips with primary osteoarthritis using one surgical technique. At the 10- to 20-year follow-up there had been 97 revisions for mechanical loosening. Univariate survivorship analysis showed that an increased risk of revision was associated with male gender, young age at primary THR, the Brunswik and Lubinus snap-fit prostheses with large femoral heads (as compared with the Charnley prosthesis), and varying experience of the surgeon. Multivariate statistical analysis showed a three-fold increased risk of revision for men (p < 0.0001), an increase in relative risk of 1.8 per 10 years younger at surgery (p < 0.0001), a fivefold increase in risk for the Brunswik prosthesis (p < 0.0001) and a twofold increase for the Lubinus prosthesis (p = 0.0067). Inexperience of the surgeon, however, was not validated as a risk factor. The study shows that the true risk factors for revision can be identified accurately by combining univariate survivorship and multivariate statistical analyses.

Radiographic demarcation of the acetabular bone-cement interface: The effect of femoral head size

Between 1983 and 1988, 182 total hip arthroplastics were inserted using modern cement techniques including metal-backed acetabular components. Femoral head size was 32 mm in 84, 22 mm in 98. Radiographic analysis revealed three-zone demarcation of acetabular bone-cement interface in 56% of the 32 mm group as compared to 5% of the 22 mm group at 19 and 24 months mean follow-up period, respectively. When a subgroup of women under 60 years of age was created to control variables, the high-grade demarcation rates were 67% and 18%, respectively. Although Charnley hip scores remain similar between the two groups, these results emphasize the adverse effects of large femoral head prostheses on cement-bone interface and underline the need for alternative methods of fixation

Hindlimb articular surface allometry in hominoidea and Macaca, with comparisons to diaphyseal scaling

The scaling of hindlimb articular surface dimensions with body mass is investigated in Pan, Gorilla, Pongo, Macaca fascicularis, and, for the femoral head, two population samples of recent Homo sapiens sapiens. Articular dimensions scale very strongly with body mass within pongids at close to isometry. Body mass can be estimated relatively precisely given the appropriate reference group, with femoral head dimensions giving the best estimates. Several deviations from general scaling trends are also present and have functional implications. Positive allometry of the medial femoral condyle, and thus condyle asymmetry, is shown to be related to degree of varus (bowleggedness) of the knee, most marked in gorillas and declining in the smaller pongids and macaques. Macaques show somewhat smaller hindlimb articulations for their body mass, while modern humans have large femoral heads relative to body mass. Relative to diaphyseal cross-sectional dimensions (Ruff, 1987), orangutans and modern humans have large articulations and macaques small articulations. These proportional differences are explained in terms of differences between species in joint excursion, mode of locomotion, and activity level. Orangutans load their hind limbs less than other pongids due to more pronounced forelimb suspensory behavior and thus have less robust diaphyses, but maintain relatively large articulations to allow greater joint excursion, particularly hip abduction. Relatively smaller hindlimb articulations in macaques may be linked to reduced joint mobility relative to pongids. Modern humans, due to their bipedality, load the lower limb more than quadrupedal primates and thus have relatively large joints, but shaft dimensions remain smaller than expected, possibly at least partly because of lower activity levels. Within recent humans, femoral head dimensions are highly positively allometric. Because of this, femoral head size in two relatively complete early hominids (AL 288-1 and KNM-WT 15000) is approximately at or above what would be predicted for hominids of their respective body masses.