28-mm Femoral Head Research Articles

Comparison of Steady State Femoral Head Penetration Rates Between Two Highly Cross-Linked Polyethylenes in Total Hip Arthroplasty

Given that the manufacture of highly cross-linked polyethylene (HXLPE) is not standardized, the behavior of these materials may vary. Our study compares minimum 5-year steady state femoral head penetration rates using the Martell method, in 2 HXPLEs produced by different manufacturers. Patients received a primary hip arthroplasty using an uncemented acetabular component with an HXLPE liner and a 28-mm femoral head. Forty-seven patients in group A received an HXLPE liner (Reflection XLPE, Smith and Nephew Inc, Memphis, Tenn), and 36 patients in group B received a different HXLPE liner (Longevity, Zimmer Inc, Warsaw, Ind). Average follow-up was 6.42 years in group A and 7.64 years in group B. The steady state head penetration rates were not significantly ( P > .05) different between the HXPLE groups over the midterm with 0.026 mm/y and 0.025 mm/y in groups A and B, respectively.

Protrusio of a Ceramic Femoral Head Through the Acetabular Metallic Shell, Extensive Metallosis and ‘Bubble Sign’

A 24-year-old patient with a history of juvenile rheumatoid arthritis underwent a primary cementless left total hip arthroplasty (THA). The original THA consisted of an Optifix 54 cup with a 3-mm thick polyethylene liner, an Optifix size 4 stem (Smith & Nephew Richards, Memphis, Tennessee) and a Biolox aluminum 32-mm femoral head. Fourteen years later, radiographs demonstrated extensive wear of the polyethylene liner resulting in direct articulation and abrasion wear of the ceramic femoral head on the cup and a bubble sign. This article presents a case of a catastrophic failure of a ceramic/polyethylene bearing with destruction of the polyethylene liner and the metallic shell and protrusio of the nonfractured ceramic head through the metallic shell. To our knowledge this is the first description of extensive metallosis and subsequent radiograph bubble sign not presenting as a result of wear of a metal-on-metal articulation. At the time of revision surgery-Hydrocel TNT Monoblock 58 cup (Zimmer, Warsaw, Indiana), Wagner 265/14 stem (Zimmer), and a Co/Cr 28-mm head-copious metallic debris was seen both macroscopically and histologically, with the ceramic head protruding behind the metallic shell. Multiple factors may have been responsible for this failure including a thin polyethylene shell, a suboptimal locking mechanism, gamma in air sterilization for polyethylene, multiple screw-holes that reduce the contact surface between shell and polyethylene, the rough surface on the inside of the shell and non-articular wear at the metal polyethylene interface within the acetabular component and the high demands of this active young patient.

Metal Ion Levels in the Blood of Patients After Hip Resurfacing: A Comparison Between Twenty-eight and Thirty-six-Millimeter-Head Metal-on-Metal Prostheses

Metal ion toxicity, metal hypersensitivity, and metal carcinogenicity are causes for concern for patients with metal-on-metal hip replacements. Thus, understanding the biological fate of metal ions, and consequently their long-term systemic effects, is of great interest to patients and surgeons alike. Inductively coupled plasma mass spectrometry was used to measure the levels of cobalt, chromium, and molybdenum ions in the blood of control patients (preoperative control pre-resurfacing patients), patients with a metal-on-polyethylene total hip prosthesis, patients with a metal-on-metal total hip prosthesis with either a 28 or 36-mm femoral head, and patients with a hip resurfacing prosthesis. Since cobalt and chromium ions have the potential to induce oxidative stress through irreversible biochemical damage to macromolecules, the levels of ions were correlated to the concentration of three oxidative stress markers in the plasma of these patients. The median cobalt level was significantly lower (p < 0.001) in the 36-mm metal-on-metal total hip arthroplasty group (1.8 parts per billion [1.8 microg/L]) compared with the 28-mm metal-on-metal total hip arthroplasty group (2.5 parts per billion [2.5 microg/L]) and the hip resurfacing group (2.3 parts per billion [2.3 microg/L]) at six months postoperatively. The median chromium level was also significantly lower (p < 0.01) in the 36-mm metal-on-metal total hip arthroplasty group (0.25 parts per billion [0.25 microg/L]) compared with the 28-mm metal-on-metal total hip arthroplasty group (0.35 parts per billion [0.35 microg/L]) and the hip resurfacing group (0.50 parts per billion [0.50 microg/L]) at six months postoperatively. However, neither the median cobalt levels nor the median chromium levels were significantly different among the three metal-on-metal groups at one year. The median levels of molybdenum were not significantly different among the three groups at either six months or one year. In addition, there was no significant difference in the plasma concentration of oxidative stress markers in patients with metal-on-metal bearings compared with that in control patients. The blood metal ion levels in the hip resurfacing group were similar to those in the 28 and 36-mm-head metal-on-metal total hip arthroplasty groups. This study suggests that the increased metal ion levels had no effect on oxidative stress markers in the blood of these patients.

An In Vivo Model for Intraoperative Assessment of Impingement and Dislocation in Total Hip Arthroplasty

We have developed an intraoperative model to quantify total hip arthroplasty impingement and dislocation mechanics using fluoroscopy and shape-matching techniques. Two patient groups were investigated: group 1 consisted of 12 hips using 28- or 32-mm femoral heads and an anterolateral surgical approach, and group 2 consisted of 17 hips using 22- or 26-mm femoral heads and a posterolateral surgical approach. During intraoperative hip stability testing consisting of extension and external rotation motions, group 1 was more unstable, and prosthetic impingement was the major reason for dislocation. With flexion and internal rotation motions, group 2 was more unstable, and superior-lateral impingement or soft tissue traction was the major reason for dislocation. Intraoperative quantitative assessment of hip mechanics provides a safe and clinically relevant method to characterize potential complications and evolve techniques to prevent them.

Effect of Femoral Head Size and Abductors on Dislocation after Revision THA

Dislocation is a common complication after revision total hip arthroplasty, particularly if the abductor mechanism is deficient. Use of a large femoral head may reduce the incidence of dislocation. However, it is not clear if the large femoral head is effective in controlling dislocation when the abductor mechanism is deficient. We separated 230 patients who underwent revision total hip arthroplasty into four groups: Group 1 (159 patients) had an intact abductor mechanism and a 28-mm femoral head, Group 2 (20 patients) had an absent abductor mechanism (trochanteric nonunion or complete segmental proximal femoral bone loss) and a 28-mm femoral head, Group 3 (42 patients) had an intact abductor mechanism and a 36-mm femoral head, and Group 4 (nine patients) had an absent abductor mechanism and a 36-mm femoral head. The minimum followup was 6 months (mean, 27 months; range, 6 months to 7 years). A 36-mm head was associated with a lower dislocation rate after revision total hip arthroplasty than a 28-mm head with an intact abductor mechanism; the rate of dislocation was 12.7% for Group 1, 40.0% for Group 2, 0% for Group 3, and 33.3% for Group 4. However, the use of a large-diameter head does not reduce the rate of dislocation if the abductor mechanism is absent.

Alumina-Debris-Induced Osteolysis in Contemporary Alumina-on-Alumina Total Hip Arthroplasty

Aceramic-on-ceramic bearing coupling, because of its qualities of reduced friction and wear, is an attractive alternative bearing surface in total hip arthroplasty. The use of such bearing couplings is likely to reduce problems related to polyethylene wear debris1-6. Osteolysis has only rarely been reported in association with ceramic-on-ceramic bearing couplings, and reports are generally limited to cases involving early generation ceramic bearings or loosened prostheses7,8. Recently, several cases of osteolysis have been reported after total hip arthroplasty with use of a contemporary alumina bearing, but these reports only described the femoral scalloping seen on radiographs and did not present any histological evidence that ceramic particles were the causative factor9. We present the case of a patient who had formation of a large amount of osteolysis about both the acetabulum and the proximal part of the femur, induced by ceramic wear particles from a well-functioning contemporary alumina-on-alumina total hip prosthesis. The patient was informed that data concerning the case would be submitted for publication, and she consented. A sixty-three-year-old woman underwent bilateral total hip arthroplasty in June 1998 for the treatment of corticosteroid-induced osteonecrosis. The arthroplasties included the use of cementless implants (PLASMACUP SC-BiCONTACT; Aesculap, Tuttlingen, Germany) that incorporated 28-mm alumina femoral heads and alumina acetabular inserts (BIOLOX forte; CeramTec, Plochingen, Germany). The PLASMACUP had a roughened titanium plasma-sprayed exterior and a machined interior that accepted an alumina insert with a self-locking press-fit taper. The BiCONTACT stem was a tapered, rectangular, titanium-alloy implant, the proximal one-third of which was surface-treated with titanium plasma spray. The alumina head was secured to the stem by means of a tapered cone. After surgery, the patient did not present for regular follow-up visits and did not revisit our clinic until June 2006. At the time …

Radiostereometric Analysis Comparison of Wear of Highly Cross-Linked Polyethylene Against 36- vs 28-mm Femoral Heads

This study used radiostereometric analysis (RSA) to compare the femoral head penetration of 28- vs 36-mm-diameter femoral heads into highly cross-linked polyethylene in 2 groups of total hip arthroplasty patients. Thirty patients were enrolled in this RSA study using highly cross-linked polyethylene (Longevity, Zimmer Inc, Warsaw, Idaho) against either 28- or 36-mm-diameter cobalt chrome femoral heads. At 3-year follow-up, there was no significant difference in the total average femoral head penetration, including both creep and wear, using 3 methods of RSA measurement between the 2 groups. Importantly, after bedding-in, there was no further significant increase in the amount of femoral head penetration (ie, wear) with either head size between years 1 and 3. There were no radiographic signs of lysis or radiolucencies at a minimum 3-year follow-up.

Unconstrained Tripolar Hip Implants

Tripolar implants were developed to treat unstable total hip arthroplasties. However, there is limited confirmation that they achieve this purpose despite their increasing use. Because they have a larger effective head size, these implants are expected to increase range of motion to impingement and improve stability in situations at risk for impingement compared with conventional implants. We assessed the range of motion to impingement using a tripolar implant mounted to an automated hip simulator using 22.2-mm and 28-mm femoral head sizes. The 22 and 28-mm tripolar implants provided increases of 30.5 degrees in flexion, 15.4 degrees in adduction, and 22.4 degrees in external rotation compared with the conventional 22.2-mm femoral head diameter implant. At the critical position of 90 degrees hip flexion, there was an increase of 45.2 degrees in internal rotation. At 0 degrees and 30 degrees external rotation, extension increases were 18.8 degrees and 7.8 degrees, respectively. Bony impingement was the limiting factor. Tripolar implants increased the arc of motion before impingement in positions at risk for dislocation and are expected to provide greater stability.

Clinical and radiographic results and wear performance in different generations of a cementless porous-coated acetabular cup

We compared clinical results and wear performance in two different generations of a cementless porous-coated cup, analysing the long-term results of 83 uncemented Harris-Galante I cups (32-mm femoral head) and 93 uncemented Harris-Galante II cups (28-mm femoral head). All polyethylene liners were gamma irradiated in air. Polyethylene linear wear was estimated using a software package. The minimum follow-up was 10 years. Nine Harris-Galante I cups and two Harris-Galante II cups were revised due to aseptic loosening or polyethylene problems. The mean femoral head penetration at 6 weeks after surgery was 0.15 +/- 0.05 mm for the Harris-Galante I cups and 0.12 +/- 0.03 for the Harris-Galante II cups (p < 0.001);but mean wear was 0.13 +/- 0.23 mm per year for the Harris-Galante I cups and 0.11 +/- 0.10 for the Harris-Galante II cups (p = 0.740). Most of the metallic shells in both groups showed stable fixation. The so-called second-generation cups had lower initial polyethylene wear that resulted in less polyethylene wear at the latest the follow-up, but the overall wear rate was similar in both groups despite the different femoral head sizes and the improved locking mechanism.

Polyethylene Sterilization and Production Affects Wear in Total Hip Arthroplasties

Production and package sterilization techniques for the polyethylene used in acetabular components for total hip arthroplasties are known to affect wear. We considered three combinations of techniques: sterilization by radiation in inert gas with isostatically molded polyethylene, in inert gas and ram-extruded polyethylene, and in air with extruded polyethylene. The intent of this study was to confirm that molded polyethylene and polyethylene radiated in inert environments reduce wear rates in vivo, to determine the combination of methods with the least wear, and to determine how much variance in wear is attributable to these methods. We reviewed 150 consecutive total hip arthroplasties done in 133 patients using 28-mm cobalt-chrome femoral heads and polyethylene-lined, titanium, ring-locked acetabular components. The least wear occurred in gamma inert-molded polyethylene components. The mean volumetric wear rates were 52.12 mm3/year for gamma inert-molded, 62.32 mm3/year for gamma inert-extruded, and 66.09 mm3/year for gamma air-extruded polyethylene components. Relative risk assessment found gamma air-extruded and gamma inert-extruded polyethylene components to wear 16% and 11% more than gamma inert-molded polyethylene components, respectively. Gender, body mass index, and age accounted for the greatest amount of the explained variance in volumetric wear (57.5%, 21.6%, and 14.4, respectively), followed by angle of wear (3.4%), and sterilization and production technique (3.2%).

Femoral head diameter affects the revision rate in total hip arthroplasty: An analysis of 1,720 hip replacements with 9–21 years of follow-up

Background In a previous study concerning 1,660 ScanHip THAs that were followed for up to 12 years, the cumulative revision rate was not found to be dependent on whether a 22-mm or a 32-mm head size had been used. We have re-examined these patients to see whether a longer follow-up time (9–21 years) would disclose an effect of head size on the revision rate.Patients and methods We analyzed the cumulative revision rate for 1,720 Scan Hip arthroplasties with either 22-mm or 32-mm femoral heads. The patients were followed for 9–21 years.Results Arthroplasties with 32-mm head had 2.8-times higher cumulative revision rate than those with a 22-mm head. Older age reduced the risk of revision while male sex increased the risk.Interpretation We found that head size affects revision risk, but that even in a reasonably large material a long follow-up time is required to disclose the effects of head size—and thus wear—on survival.

The 22-mm vs the 32-mm Femoral Head in Cemented Primary Hip Arthroplasty: Long-term Clinical and Radiological Follow-up Study

A retrospective clinical and radiological analysis was performed on 117 patients (138 hips) with a mean age of 75 years and a mean follow-up of 11 years. The prostheses used were 2 similar monoblock femoral components with 22- and 32-mm head sizes; their effects on the wear of the high-density polyethylene cup were studied. Wear of component was determined by evaluating the standardized initial and follow-up radiographs. The mean rate of linear wear was higher in the 22-mm femoral head, whereas the volumetric wear was higher in the 32-mm femoral head. In both groups, volumetric wear was significantly correlated with cup lysis. Increasing body weight in both groups was associated with more volumetric wear. The radiological evidence of prosthetic loosening did not correlate well with clinical evaluation of the hip.

Clinical Performance of a Durasul Highly Cross-Linked Polyethylene Acetabular Liner for Total Hip Arthroplasty at Five Years

Highly cross-linked polyethylene is currently the most common articulation surface used for total hip arthroplasty. The hypothesis of the present study was that the Durasul highly cross-linked polyethylene acetabular liner would have less wear at five years than would a conventional polyethylene liner used in association with the same total hip replacement system. Forty-three consecutive patients (fifty hips) underwent total hip replacement with an uncemented titanium porous-coated metal cup and a Durasul liner that was mated with a 28-mm cobalt-chromium femoral head. Thirty-one patients (thirty-seven hips) were followed for at least five years. Thirty-five other patients (thirty-seven hips) underwent total hip arthroplasty with the same system but with a conventional polyethylene liner, and these patients also were followed for five years. Clinical assessment was performed with use of the Harris hip score and a patient self-assessment examination. Radiographic analysis included measurements of acetabular component position, fixation, and osteolysis. Femoral head penetration of the Durasul liners was compared with that of the conventional liners. The clinical results as determined on the basis of Harris hip scores and patient self-assessment examinations did not differ between the Durasul group and the control group. The mean bedding-in penetration was 0.054 +/- 0.07 mm for the Durasul group and 0.059 +/- 0.154 mm for the control group. The subsequent penetration, with elimination of the bedding-in wear, resulted in a linear wear rate of 0.029 +/- 0.02 mm per year for the Durasul group, compared with 0.065 +/- 0.03 mm per year for the control group (p < 0.005). The annual penetration at one and five years was 0.074 mm and 0.011 mm, respectively, for the Durasul group, compared with 0.151 mm and 0.04 mm, respectively, for the control group. While the qualitative wear pattern of the highly cross-linked polyethylene liner was the same as that of the conventional polyethylene liner, the annual linear wear rate was 45% of that seen with the conventional polyethylene liner. Therefore, we believe that these early data support the continued use of this highly cross-linked polyethylene liner for total hip arthroplasty.

Clinical and radiological results of hydroxyapatite-coated acetabular cups.

We prospectively studied a consecutive series of 60 primary total hip arthroplasties in 52 patients. All patients had a hydroxyapatite-coated hemispherical acetabular cup (OCTOFIT). Mean patient age was 52.5 (34-73) years. In 38 hips, a 28-mm and in 22 hips a 32-mm diameter cobalt-chrome femoral head was used. We could follow 53 hips for a mean of 81 (28-125) months. Four cups were revised because of osteolysis, and in another six cups, slight osteolysis without migration was seen. The average annual linear wear rate was 0.05 mm (+/-0.05) for 28-mm heads and 0.16 mm (+/-0.09) for 32-mm heads (p<0.0001). Survivorship analysis predicted a survival rate of 86+/-6.7% at 10 years.

Relationship between polyethylene wear and osteolysis in hips with a second-generation porous-coated cementless cup after seven years of follow-up.

The development of osteolysis, a commonly reported complication after total hip arthroplasty without cement, is perceived to be related to the amount of polyethylene particles generated from the bearing surfaces. Although the literature has suggested that the prevalence of osteolysis increases with increasing rates of polyethylene wear, this relationship has never been quantified. The goals of this study were to quantify the relationship between the prevalence of osteolysis and both linear and volumetric wear and to evaluate the risk of osteolysis as a function of wear in a currently used, porous-coated cup design. Polyethylene wear and osteolysis were examined in fifty-six hips with a Duraloc-100 acetabular cup articulating with a 28-mm femoral head. Penetration of the prosthetic head into the polyethylene liner was measured, with use of a validated computer-assisted technique, from anteroposterior pelvic radiographs of each patient. From these measurements, linear and volumetric wear rates were calculated. Each patient's series of radiographs was examined independently for the presence of osteolysis. A logistic regression analysis was performed to determine the risk of osteolysis associated with a given change in linear or volumetric wear rate. Osteolysis was found in twenty-three of the fifty-six hips. The hips with osteolysis had significantly higher linear (p < 0.001) and volumetric (p = 0.003) wear rates than the hips without osteolysis. Logistic regression revealed that every 0.1-mm/yr increase in the linear wear rate increased the likelihood of the development of osteolysis by a factor of four. Each 40-mm (3) /yr increase in volumetric wear raised the risk of osteolysis by about three times. To our knowledge, this study represents the first time that the relationship between polyethylene wear, as determined by both linear wear and volumetric wear, and the prevalence of osteolysis has been quantified. The use of the linear wear rate as a predictor of osteolysis can be a valuable tool in assessing the longevity of a particular implant. The results of our analysis provide quantitative support to the observation that a wear rate of 0.2 mm/yr seems to represent a "critical threshold" for the development of osteolysis. Close radiographic monitoring with the determination of linear wear rates to assess the risk of osteolysis is recommended for all patients after total hip arthroplasty.

Total hip arthroplasty with use of the cementless Zweymüller Alloclassic system. A ten to thirteen-year follow-up study.

The Zweymüller Alloclassic total hip arthroplasty system is widely used, although few intermediate-term studies have been published. The purpose of the present study was to evaluate the clinical and radiographic results of this system after ten years. One hundred and twenty-four consecutive primary total hip arthroplasties were performed with the Zweymüller Alloclassic cementless system at our institution between February 1988 and March 1991, and 104 hips (ninety-four patients) were retrospectively reviewed after a minimum duration of follow-up of ten years. The mean age of the patients at the time of the arthroplasty was 62.3 years (range, twenty-five to seventy-seven years). The mean duration of follow-up was 11.3 years. Standard radiographs were made for all patients immediately after the operation, at six and twelve months, and annually thereafter for at least ten years. Cox multivariate regression analysis was performed to assess the influence of various factors on survival of the implant. The cumulative probability of not having a revision of any prosthetic component for any reason was 94.1% (95% confidence interval, 91.9% to 96.3%) at twelve years in the best-case scenario and 85.3% (95% confidence interval, 82.1% to 88.5%) at twelve years in the worst-case scenario for the entire series of 124 hips. Among the 104 hips in the follow-up study, three acetabular components and no stems were revised. Two hips had level-4 pain according to the system of Merle D'Aubigné and Postel. Seven acetabular components (7%) were loose at twelve years, and all stems had radiographic evidence of stable fixation. Acetabular cup loosening was related to a vertical cup angle (p = 0.0008, Student t test), acetabular wear of > or =1 mm (p = 0.001, Fisher exact test), and a 32-mm femoral head (p = 0.001, Fisher exact test). Although femoral osteolysis was seen in eighteen hips (17%) at twelve years, all osteolytic cavities were proximal and focal. The Zweymüller Alloclassic prosthesis, particularly its femoral stem, demonstrated good results and durable fixation at a minimum of ten years of follow-up.

Howse II cemented titanium metal-backed acetabular cups: poor 10-year results in 107 hips.

We report a retrospective clinical and radiographic review of 107 consecutive primary total hip replacements, using the cemented Howse II prosthesis. The review concentrates on the long-term performance of the acetabular cup, which was designed with a cylindrical titanium metal backing and a polyethylene liner. In all the hips in the series, this cup was used with a modular titanium straight femoral stem and a 32-mm diameter titanium head. At a mean follow-up of 9.8 (7-11) years, 28 hips had already been revised and 10 others were recognized as clinical or radiographic failures. The indication for revision in 26 of the hips was aseptic loosening and the mean time to revision was 7.2 (3.7-10.9) years This metal-backed cup has only 42% survival at 10 years, which seems to be related to certain of its design features. These include an inadequate thickness of polyethylene sterilized by gamma irradiation in air, a lack of mechanical bonding between the liner and its metal shell, and the high wear rate from the use of a 32-mm titanium femoral head.

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.

Independent contribution of elevated-rim acetabular liner and femoral head size to the stability of total hip implants

The use of an elevated-rim acetabular liner in total hip arthroplasty is widely accepted. We sought to determine quantitatively the amount of additional stability provided by the elevated-rim liner compared with the standard nonelevated liner. The stability of the hip with a 32-mm femoral head was compared with the standard 28-mm head. Our results show that a 15° elevated-rim acetabular liner placed in the posterior quadrant increased hip stability by an additional 8.9° of internal rotation. Similarly the 32-mm head provided 8.1° of additional internal rotation. The increases were statistically significant (P<.0001). We did not encounter increased anterior dislocation intraoperatively. The findings of this study indicate that the 32-mm head may contribute to hip stability in primary total hip arthroplasty, and in instances in which a posterior approach is used, an elevated-rim liner placed in the posterior quadrant may contribute independently to hip stability.

Hip prosthesis of antibiotic-loaded acrylic cement for the treatment of infections following total hip arthroplasty.

Infection continues to be one of the most feared complications of total hip arthroplasty. Despite many advances over the past three decades, this infrequent complication continues to undermine an otherwise highly predictable and successful procedure. The prosthesis of antibiotic-loaded acrylic cement (PROSTALAC; DePuy, Warsaw, Indiana) is a temporary hip-replacement articulated spacer intended for patients who need a two-stage exchange arthroplasty for the treatment of a confirmed or suspected infection at the site of a total hip replacement. This device has received approval from the United States Food and Drug Administration as a humanitarian use device. (This humanitarian device has been authorized by federal law as a short-term total hip replacement [THR] in patients who need a two-stage procedure to treat a confirmed infection of their THR and where vancomycin and tobramycin are the most appropriate antibiotics for treatment of the infection based on the susceptibility pattern of the infecting microorganism[s]. The effectiveness of this device for this use has not been determined.) The early experience with 135 patients who were treated with the PROSTALAC implant is reported. Initial experience has also been reported in previous publications 1-2. The PROSTALAC system ( Fig. 1 ) is a temporary total hip replacement prosthesis that is used as a first-stage exchange articulated spacer and provides for local delivery of antibiotics at the infection site. It comprises a short or long-stem cobalt-chrome-alloy core femoral implant; a one-piece, ultra-high molecular weight polyethylene, snap-fit acetabular component; a standard 32-mm cobalt-chrome modular femoral head; and a polymethylmethacrylate stem centralizer. Polymethylmethacrylate bone cement and the antibiotic in powder form are the remaining components of the system. Fig. 1: The PROSTALAC system (A) consists of a snap-fit, all-polyethylene cemented acetabular component with a metal endoskeleton, femoral head, and centralizer that are inserted into a mold (B) that is …