Large Femoral Head Research Articles

Stresses in cement mantles of hip replacements: effect of femoral implant sizes, body mass index and bone quality

The effects of femoral prosthetic heads of diameters 22 and 28 mm were investigated on the stability of reconstructed hemi-pelves with cement mantles of thicknesses 1–4 mm and different bone qualities. Materialise medical imaging package and I-Deas finite element (FE) software were used to create accurate geometry of a hemi-pelvis from CT-scan images. Our FE results show an increase in cement mantle stresses associated with the larger femoral head. When a 22 mm femoral head is used on acetabulae of diameters 56 mm and above, the probability of survivorship can be increased by creating a cement mantle of at least 1 mm thick. However, when a 28 mm femoral head is used, a cement mantle thickness of at least 4 mm is needed. Poor bone quality resulted in an average 45% increase in the tensile stresses of the cement mantles, indicating resulting poor survivorship rate.

Hip Resurfacing Results for Osteonecrosis Are as Good as for Other Etiologies at 2 to 12 Years

A bone-conserving prosthetic solution, such as hip resurfacing arthroplasty, is desirable for patients with osteonecrosis (ON) of the femoral head because of their young age. However, many surgeons are reluctant to perform hip resurfacing for ON because of large femoral head defects. To ascertain whether this reluctance is warranted, we determined the mid- to long-term effects of ON on the survivorship, radiographic implant fixation, and disease-specific and quality-of-life scores of hip resurfacing. We compared the results of metal-on-metal resurfacing performed for ON of the hip (including large lesions) with those of resurfacing performed for other causes. The ON group had 70 patients (85 hips) and the control group 768 patients (915 hips) including all other etiologies operated on during the same period. The ON group was younger and had a greater incidence of femoral defects, a smaller component size, and a lower body mass index, three variables previously shown to reduce survivorship in hip resurfacing. We observed no difference in survivorship between the ON group and the control group even after adjusting for head size, body mass index, and defect size. Pain relief, walking, and function scores were comparable postoperatively. The activity level was lower in the ON group. Our data suggest ON is not a contraindication for resurfacing even with large femoral head defects. Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

The Dislocator, Early and Late: The Role of Large Heads

Dislocation after total hip arthroplasty (THA) is a potentially devastating complication that can be difficult to manage. Many patient and mechanical factors have been associated with an increased risk of dislocation. Conservative treatments such as abduction bracing have not proven effective at treating this difficult problem. Surgical options include the use of larger femoral heads, unconstrained tripolar femoral heads, and constrained devices. While each device has its merits, there is no one-size-fits-all solution to this problem. With the development of highly cross-linked polyethylene and its superior wear characteristics and mechanical properties, the use of larger femoral heads is now available. Twenty-six hips in 25 patients who underwent revision surgery for recurrent dislocation were treated with a femoral head =/>36 mm in diameter. The direct lateral surgical approach was used in 24 hips, and the posterior and anterior supine intermuscular approaches were used in 1 hip each. One patient died 5 years after revision surgery, and 3 patients have not returned for clinical follow-up over the past 2 years. Four hips subsequently suffered a repeat dislocation, for a dislocation rate of 17%. Two patients underwent a subsequent surgery: 1 irrigation and debridement and 1 hardware removal. There have been no other revisions to date. Mean time to follow-up is 17.2 months. While the use of large femoral heads for the treatment of dislocation is warranted, continued follow-up is necessary.

Femoral Head Size and Wear of Highly Cross-linked Polyethylene at 5 to 8 Years

Wear of highly cross-linked polyethylene is reportedly independent of head size. To confirm that observation we asked in our population whether head size related to wear with one type of electron beam highly cross-linked polyethylene. Of 146 hips implanted, we evaluated complete clinical and radiographic data for 90 patients (102 hips or 70%). The minimum followup was 5 years (mean, 5.7 years; range, 5-8 years). The head size was selected intraoperatively based on the size of the acetabular component and presumed risk of dislocation. Polyethylene wear measurements were performed in one experienced laboratory using the method of Martell et al. There was no hip with pelvic or femoral osteolysis. The median linear wear rate was 0.028 mm/year (mean, 0.04 mm/year), and the median volumetric wear rate was 25.6 mm(3)/year (mean, 80.5 mm(3)/year). Median total volumetric wear was 41.0 mm(3) (mean, 98.5 mm(3)). We found no association between femoral head size and the linear wear rate, but observed an association between larger (36- and 40-mm) head size and volumetric wear rate and total volumetric wear. Although the linear wear rate of polyethylene was not related to femoral head diameter, there was greater volumetric wear (156.6 mm(3)/year) with the 36- and 40-mm heads. Pending long-term studies of large head sizes, we advise caution in using larger femoral heads in young or active patients and in those with a low risk of dislocation. Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Hip Stability in Primary Total Hip Arthroplasty Using an Anatomically Sized Femoral Head

Dislocation after total hip arthroplasty (THA) remains a problem despite many advances in technique and prosthetic design over the 5 decades since the introduction of total joint replacement. This article reports the short-term results (1 year of follow-up) of THA in 235 patients who received a large, anatomically sized femoral head (BFH Technology; Wright Medical Technology, Inc, Arlington, Tennessee) with modular necks for hip stability. The prosthesis allows a 6-mm differential between the size of the acetabular component and femoral head size. Patients also received a Conserve monoblock acetabular cup and a Profemur femoral stem (Wright Medical Technology, Inc) implanted without cement. Postoperative clinical evaluations included measurements of Harris Hip Scores and range of motion, along with assessments of pain and function and radiological evaluations. There were no complications (deep venous thrombosis, pulmonary embolism, infection, reoperations) and no dislocations. All clinical evaluations showed statistically significant improvement (P<.001) at 1-year follow-up, and radiographic evaluation has shown no evidence of osteolysis or implant loosening. This study indicates that using a large femoral head may reduce the incidence of dislocation and may enable early return to activities postoperatively. Future evaluations of this patient group will elicit longer-term follow-up data.

Metal-on-Metal Hip Resurfacing and Total Hip Arthroplasty in the Same Patient: A Case Series Comparison

Early outcomes for metal-on-metal total hip resurfacing (MOMHR) suggest that it may have a role as a bone-sparing alternative to total hip arthroplasty (THA) in younger patients. The possible biomechanical advantages of MOMHR over THA have been extensively discussed in the published data and have been clinically examined. However, few studies have offered a direct, controlled comparison of patients' experiences after MOMHR and THA. To more accurately describe differences in patient outcomes between MOMHR and THA in comparable patients, we present a report of 8 patients who had both MOMHR and a contralateral THA. This report included a patient-completed hip comparison questionnaire that assessed hip pain, stiffness, surgical recovery, proprioception, hip strength, and overall preference. Most patients preferred MOMHR, citing reasons such as better range of motion, improved proprioception, and a faster, easier recovery. These preferences may likely be related to the biomechanical advantages of a larger femoral head. However, it is important to consider how differences in the time elapsed since the patients' index surgeries, changes in surgical technique and differences in rehabilitation affect patients' preferences. At this point, there are on-going prospective clinical trials comparing MOMHR to THA, and only after long-term reports are critically examined there may be more definitive recommendations.

The Effect of Polyethylene Thickness on the Wear of Highly Cross-Linked Acetabular Liners in a “Near-Impingement” Hip Simulator Model

Concern for stability and increased range of motion in THA has increased popularity of large femoral heads, while thin polyethylene liners have allowed acetabular component thickness to remain constant. Highly cross-linked polyethylene improves wear, but is accompanied by reduced toughness. Decreasing thickness may increase wear or cause gross fracture, especially at extremes of motion when contact between head and acetabulum nears the liner edge. We determined the effect of liner thickness on wear with large diameter heads in a near impingement model.

Total Hip Arthroplasty Using a Large Femoral Head: The Short-Term Follow-up Results and the Early Complications

Purpose: This study evaluated the short-term follow-up results after total hip arthroplasty with using a 36 mm large femoral head. Materials and Methods: Between August 2004 and August 2007, 104 patients were treated with total hip arthroplasties using a 36 mm-Cobalt-Chrome femoral head with Longevity (Zimmer, Warsaw, IN) as the polyethylene liner. The average age at the time of the index operation was 61.4 years (range: 23 to 87 years), and the mean follow-up period was 27 months (range: 18 to 46 months). The clinical results and early complications after the operation were analyzed. Results: The Harris Hip Scores were more than ‘Good’ in all cases with an average score of 93, and the Merle d’ Aubigne and Postel scores were more than ‘Good’ in 75% of the patients. All the femoral stems that were cemented or cementless had satisfactory fixation. Dislocation developed in one case and only one time, and there were no other complications during the follow-up period Conclusion: Total hip arthroplasty with using a 36 mm large femoral head is a recommendable treatment with a low dislocation rate and high satisfaction, which comes from the lack of restriction of the postoperative hip position and movement.

Mathematical evaluation of jumping distance in total hip arthroplasty

Background and purpose The jumping distance (JD) is the degree of lateral translation of the femoral head center required before dislocation occurs. The smaller the distance, the higher the theoretical risk of dislocation. The aim of our study was to evaluate this jumping distance and its variation according to the characteristics of the implant, and also the theoretical gain in using large head diameters of above 38 mm.Methods The JD was calculated as a function of the cup ante-version and abduction angles, the head diameter, and the head offset (defined as the distance between the center of the femoral head and the cup opening plane). Head diameters of 28, 32, 36, 40, 44 and 48 mm were analyzed. The abduction angle was increased from 0° to 80° with a 10° increment. The anteversion angle was increased from 0° to 40° with a 5° increment.Results The jumping distance was found to decrease as the cup abduction angle increased (0.25 mm each 1° for 32-mm head diameter). It increased by 0.05 mm for a 1° increase in the ante-version angle. The jumping distance increased as the head diameter increased (0.4 mm each mm diameter for a 45° abduction angle). The net gain obtained by increasing the diameter, however, decreased when abduction angle increased (0.25 each mm diameter for 60° abduction). The JD decreased by 0.92 mm for each 1-mm increase in head offset, showing that head offset was the most important parameter influencing the JD.Interpretation The theoretical gain in stability obtained by using a large femoral head (above 36 mm) is negligible in cases where there is a high cup abduction angle. An increase in offset of the femoral head substantially reduces the jumping distance and it should therefore be avoided.

Hip Resurfacing for the Treatment of Developmental Dysplasia of the Hip

Total hip arthroplasty (THA) with ceramic-on-ceramic bearings and an uncemented design is considered an effective treatment of developmental dysplasia of the hip, especially for young, active patients. The new generation of hip resurfacing with large femoral heads offers more stability, better range of motion (ROM), and more bone preservation than conventional THA. Twenty-one consecutive patients (26 hips) with osteoarthritis secondary to developmental dysplasia of the hip underwent metal-on-metal hip resurfacing. Average patient age at the time of surgery was 46.5 years (range, 37-59 years). Six patients (28.6%) were men and 15 (71.4%) were women. During the same period, another 21 patients (26 hips) with developmental dysplasia of the hip secondary to osteoarthritis were treated with ceramic-on-ceramic THA. Average patient age at the time of surgery was 48.2 years (range, 38-64 years). At follow-up, no complications (eg, dislocation, infection, or symptomatic deep venous thrombosis) occurred in the 2 groups. No significant difference was noted in Harris Hip Score between the 2 groups, but the average ROM of the hip resurfacing group was significantly better than the THA group (P<.05). All patients reported significant pain relief on their operated hips, with the postoperative visual analog scale scores <2. No signs of early loosening were observed on radiographs. The short-term results of the metal-on-metal hip resurfacing have been encouraging in the treatment of developmental dysplasia of the hip, with better ROM recovery than conventional THA.

Arthroplasty in the Management of Acute Femoral Neck Fractures in the Elderly

Femoral neck fractures are among the most common orthopaedic injuries that afflict the elderly population with over 250,000 occurring annually in North America. They are associated with a significant increase in mortality and loss of functionality, and annual cost estimates in the United States for hip fractures range from $9.8 billion to $15 billion. Treatment options include reduction and internal fixation, hemiarthroplasty, and total hip arthroplasty. Used primarily for younger patients or non-displaced fractures, internal fixation allows for preservation of the femoral head, less invasive surgery, and less perioperative morbidity, although nonunion, osteonecrosis, and implant failure may occur. For displaced femoral neck fractures, acute arthroplasty has been demonstrated to have better outcomes and to be less costly overall due to lower rates of implant failure and reoperation. Hemiarthroplasty permits more rapid return to weightbearing and earlier functional rehabilitation when compared to internal fixation and provides good stability and pain relief in the elderly. Complications include dislocation, acetabular wear, implant loosening, and periprosthetic fracture. Total hip arthroplasty addresses antecedent hip arthritis and eliminates the risk of acetabular wear associated with hemiarthroplasty, although concerns about risk of dislocation have historically limited its use. Refinements in technique including use of larger femoral heads and routine capsular repair have alleviated these concerns to some degree. Current research supports use of total hip arthroplasty for displaced femoral neck fracture in younger, active patients demonstrating improved pain relief and mobility.

Autologous Chondrocyte Implantation in the Hip: Case Report and Technique

The treatment of symptomatic, full-thickness articular lesions in the hip in young patients provides a challenge to orthopedic surgeons. The advent of hip arthroscopy has improved the diagnostic as well as some therapeutic capabilities surrounding certain hip pathologies. With the advancements in diagnostic ability, more symptomatic chondral defects are being recognized in the hips of young patients. The optimal surgical treatment for these patients has not been clearly defined, and there is little in the literature about biological repair for hip chondral defects. The current options include open and arthroscopic debridements and microfracture, redirectional osteotomies, autologous and allogenic osteochondral grafting, biological resurfacing with periosteum or autologous chondrocyte implantation, and prosthetic resurfacing arthroplasties. This article presents a clinical case and describes the surgical technique of autologous chondrocyte implantation for a large femoral head chondral defect (10 cm 2 ) in a young patient who had progression of disease after prior autologous osteochondral mosaicplasty.

Use of Larger Femoral Heads in Revision Total Hip Arthroplasty: Will This Solve Dislocation?

Increasing the femoral head diameter to treat recurrent dislocation in primary total hip arthroplasty may lower the postrevision incidence of dislocation. The lateral jump distance or lateral translation for several femoral head diameters were mathematically modeled as a function of varying acetabular abduction angles.

Instability After Total Hip Arthroplasty: Treatment with Large Femoral Heads vs Constrained Liners

One of the most common complications after total hip arthroplasty is instability. This study reviewed the recent literature concerning the indications, contraindications, and results of recent studies using both constrained liners and large femoral heads to treat instability after total hip arthroplasty. We also report on the results of a series of 41 patients (52 hips) considered being at high risk for dislocation who were treated with large-diameter metal-on-metal bearings and who were compared with a matched group of hips treated with standard-size metal-on-polyethylene bearings. The large-diameter femoral head group had no dislocations at a minimum follow-up of 24 months, whereas the standard-size group had 2 dislocations. We support the use of large femoral heads to treat instability in a wide variety of patients because of the increased stability, decreased wear of modern metal-on-metal designs, increased range of motion, and variety of revision options.

Results of hip resurfacing for developmental dysplasia of the hip of Crowe type I and II

Recently, the new generation of metal-on-metal total hip resurfacing arthroplasty is well known for preserving the proximal femoral bone stock, minimizing the risk of postoperative dislocation using large femoral heads, and expecting low wear of metal-on-metal articulation for longer prosthesis survival. It also has the advantage in biomechanical loading in the proximal femur. The osteoarthritis secondary to developmental dysplasia of the hip (DDH) has been the most common reason for total hip arthroplasty. Most of the patients are young and active, who require improved range of motion of the hip besides relief of the pain, even expect to resume the ability to run and jump after the joint arthroplasty, thus to be allowed an active lifestyle. The objective of the current study was to evaluate the early outcome of resurfacing arthroplasty for the mild DDH cases (Crowe type I and II). Between September 2005 and May 2007, twenty-one consecutive patients (twenty-six hips) with the diagnosis of osteoarthritis secondary to DDH underwent metal-on-metal resurfacing arthroplasty. The average age at the time of surgery was 46.5 years (range, 37-59 years). Six patients (28.6%) were male and fifteen (71.4%) were female. Clinical and radiographic results were observed. The follow-up was performed at 6 weeks, 3, 6, 9 months and then yearly. All patients were followed for a mean of 18 months (9-29 months). During the follow-up period no complications, such as dislocation of hip joints, infection or femoral neck fracture occurred. The clinical outcomes, as rated with the Harris hip score, improved significantly compared with the preoperative ratings. The mean postoperative Harris hip score was 90.7, compared to 35.5 preoperatively. The radiographic analysis showed that all prostheses were fixed with no radiolucencies. All of the patients who had equal limb lengths preoperatively had equal lengths postoperatively. Of the nine patients with preoperative limb-length discrepancy of 0.8 to 1.2 cm, all regained equal limb length postoperatively. In addition the pain was nearly completely relieved, the range of motion was remarkably improved and no restriction was needed after operation regarding early exercise. The new generation of metal-on-metal resurfacing arthroplasty may be a reasonable option for DDH of the Crowe types I and II.

Selective breeding as a tool to probe skeletal response to high voluntary locomotor activity in mice.

We present a novel mouse-model for the study of skeletal structure and evolution, based on selective breeding for high levels of voluntary wheel running. Whereas traditional models (originally inbred strains, more recently knockouts and transgenics) rely on the study of mutant or laboratory-manipulated phenotypes, we have studied changes in skeletal morphometrics resulting from many generations of artificial selection for high activity in the form of wheel running, in which mice engage voluntarily. Mice from the four replicate High Runner (HR) lines run nearly three times as many revolutions during days 5 and 6 of a 6-day exposure to wheels (1.12 m circumference). We have found significant changes in skeletal dimensions of the hind limbs, including decreased directional asymmetry, larger femoral heads, and wider distal femora. The latter two have been hypothesized as evolutionary adaptations for long-distance locomotion in hominids. Exercise-training studies involving experimental groups with and without access to wheels have shown increased diameters of both femora and tibiafibulae, and suggest genetic effects on trainability (genotype-by-environment interactions). Reanalysis of previously published data on bone masses of hind limbs revealed novel patterns of change in bone mass associated with access to wheels for 2 months. Without access to wheels, HR mice have significantly heavier tibiafibulae and foot bones, whereas with chronic access to wheels, a significant increase in foot bone mass that was linearly related to increases in daily wheel running was observed. Mice exhibiting a recently discovered small-muscle phenotype ("mini-muscle," [MM] caused by a Mendelian recessive gene), in which the mass of the triceps surae muscle complex is ∼50% lower than in normal individuals, have significantly longer and thinner bones in the hind limb. We present new data for the ontogenetic development of muscle mass in Control, HR, and MM phenotypes in mice of 1-7 weeks postnatal age. Statistical comparisons reveal highly significant differences both in triceps surae mass and mass-corrected triceps surae mass between normal and MM mice at all but the postnatal age of 1 week. Based on previously observed differences in distributions of myosin isoforms in adult MM mice, we hypothesize that a reduction of myosin heavy-chain type-IIb isoforms with accounts for our observed ontogenetic changes in muscle mass.

Dislocation Rate After Conversion from Hip Hemiarthroplasty to Total Hip Arthroplasty

Revision hip arthroplasty is associated with a dislocation rate that is three to five times greater than the rate following primary hip replacement. Conversion of a hip hemiarthroplasty to a total hip replacement is a revision arthroplasty, but it differs from revisions of total hip arthroplasties because a native acetabulum is replaced and the subsequent prosthetic femoral head is smaller. It was our purpose to determine whether the risk of dislocation following conversion surgery is the same as or greater than that following revision total hip replacement. From 1994 to 2005, eighty-nine hemiarthroplasties were converted to a total hip arthroplasty in seventy-seven patients, and the results were compared with those of 115 first-time revision total hip replacements following a primary total hip replacement in 111 patients. A retrospective chart review was performed, and radiographic measurements were obtained. The patient demographics were similar between the two groups. The percentages of patients who had undergone revision of only the acetabular component as compared with both components as well as the percentages of those who had received a modular femoral stem as compared with a nonmodular stem were also similar between the two groups. Postoperatively, the femoral head size and the positioning of the acetabular component were similar between the two groups. The acetabular components were significantly larger (p < 0.001) in the group in which a total hip arthroplasty had been revised because they required additional acetabular reaming for placement of a new component. There were significantly more dislocations after the conversion procedures (22%) than after the revisions of the total hip arthroplasties (10%) (p < 0.018). Within both groups, the size of the acetabular component, the intraoperative range of motion, and the positioning of the acetabular component were similar between the hips that dislocated and those that did not. However, smaller femoral head components were at greater risk for dislocation after conversion surgery than after revision of a total hip arthroplasty. A substantial reduction of the size of the prosthetic femoral head is unique to conversion arthroplasty and appears to play a role in instability after the revision surgery. While the smallest heads dislocated in the conversion group, a larger femoral head did not ensure stability. The increased dislocation risk with conversion surgery requires emphasis on soft-tissue balance and avoidance of excessive downsizing of the femoral head in an attempt to maximize hip stability.

Large Femoral Heads Can Help Reduce Risk of Dislocation in Total Hip Arthroplasty

Dislocation after total hip arthroplasty (THA) remains a significant clinical concern. The purpose of this prospective, nonrandomized multicentered study is to compare dislocation risk after THA using a single acetabular system and various femoral head sizes.

How do alternative bearing surfaces influence wear behavior?

Metal, ceramic, and polyethylene liners represent contemporary bearing choices for total joint replacement. Each has limitations in terms of design, sensitivity to manufacturing, and surgical placement. With polyethylene, larger femoral heads represent a design restriction and a potential wear issue. One side benefit is that polyethylene does not click, squeak, or create stripe wear. The attraction of hard-on-hard bearings (metal-on-metal, ceramic-on-ceramic) is that their typically ultra-low wear alleviates concerns with large femoral head designs. However, hard-on-hard bearings produce stripe wear due to the effects of the rigid liner edge. Slight subluxation (microseparation) during swing phase of gait can result in stripe wear on the ball and liner rim. In addition, high levels of implant wear with vertically placed cups can be anticipated. Currently, only alumina-on-alumina bearings can claim virtually no biologic risk. Thus, the role of laboratory studies is to isolate relevant aspects of performance by cup design and to predict the risk-benefit ratios in patients requiring total hip replacement.

Effect of femoral head size on polyethylene wear and synovitis after total hip arthroplasty: A sonographic and radiographic study of 39 patients

Background and purpose The role of synovitis and high fluid pressure in the loosening process after total hip arthroplasty has gained increasing attention. We investigated the correlation between head size, polyethylene wear, and capsular distention.Patients and methods We analyzed 39 unrevised, radiographically stable hips that had been operated with 28 or 32 mm femoral heads 10 years earlier because of osteoarthritis. We evaluated radiographic signs of loosening, linear and volumetric polyethylene wear, body mass index, activity level, and age. Sonographic examination was performed to measure capsular distance i.e. the distance between the prosthetic femoral neck and the anterior capsule.Results Linear wear was 0.09 mm/year and 0.18 mm/year in the 28 mm and 32 mm groups, respectively (p < 0.001). The volumetric wear was 51 mm3/year and 136 mm3/year (p < 0.001) and the capsular distance was 13 mm and 17 mm, respectively (p < 0.001). There was a correlation between linear wear (r = 0.54), volumetric wear (r = 0.62), and capsular distance (p < 0.001).Interpretation Wear was greater for the larger femoral head and was correlated to capsular distension.