Biomedical subjects

Charles A Engh

Publications and source records attributed to Charles A Engh.

At least 19 recordsLinked to original sources

PubMed2006

Radiographic signs of osseointegration in porous-coated acetabular components.

UNLABELLED: There currently is no direct method to radiographically determine osseointegration of an uncemented, porous-coated acetabular component. We defined five radiographic signs for detecting acetabular osseointegration: (1) absence of radiolucent lines; (2) presence of a superolateral buttress; (3) medial stress-shielding; (4) radial trabeculae; and (5) an inferomedial buttress. We assessed their ability to predict acetabular osseointegration by reviewing the postprimary and prerevision radiographs from a series of 119 total hip arthroplasties that had revision surgery. Each sign had a high positive predictive value for the presence of bone ingrowth (range, 92.2-96.3%). The absence of radiolucent lines, presence of superolateral buttresses, and presence of medial stress-shielding were the most sensitive signs for indicating bone ingrowth. Ninety-seven percent of the cups with three to five signs were bone ingrown, whereas 83% of the cups with one or no signs were unstable. When three or more signs were present, the positive predictive value of the radio-graphic test was 96.9%, the sensitivity was 89.6%, and the specificity was 76.9%. The five signs of acetabular osseointegration reliably predicted osseointegration, especially when used in combination. They can be used as a tool for radio-graphically assessing the status of patients with porous-coated uncemented cups. LEVEL OF EVIDENCE: Diagnostic study, Level III (Study of nonconsecutive patients; without consistently applied reference "gold" standard). See the Guidelines for Authors for a complete description of levels of evidence.

Acetabulum↗

PubMed2006

Second-generation porous-coated cementless total hip arthroplasties have high survival.

We retrospectively reviewed 157 consecutive total hip arthroplasties performed with Prodigy stems and Duraloc cups to see whether design modifications made to these components would improve their clinical performance as compared with first-generation porous-coated components. At an average of 6.7 years postoperatively, 145 hips were available for followup. The data suggested encouraging clinical and radiographic performances for these second-generation components. With only two hips (1.4%) in this population being revised, survivorship analysis was 99% 5 years postoperatively. Bone ingrowth was evident in 99% of the stems, and all cups were stable at last followup. Large osteolytic lesions were observed in three acetabula and seven femurs with all femoral lesions being confined to the proximal Gruen Zones 1 or 7. Polyethylene wear averaged 0.10 +/- 0.14 mm/year. Ninety-eight percent of patients reported satisfaction with the procedure, and 7% reported activity-limiting pain. Early followup of the Prodigy-Duraloc combination in primary cementless total hip arthroplasties showed the Prodigy stem had similarly good clinical results compared with its predecessor, the AML stem, and the Duraloc cup was superior to its first-generation predecessor, the anatomic medullary locking cup with Acetabular Cup System (ACS) liner.

Adult↗

PubMed2005

Magnetic resonance imaging in the evaluation of periprosthetic acetabular osteolysis: a cadaveric study.

Periprosthetic osteolysis is a well recognized complication of total hip arthroplasty that leads to implant failure. The ability to accurately assess and visualize the position and volume of periacetabular bone defects is paramount for clinical observation and medical treatment, as well as pre-operative planning of revision surgery. We have developed a modified magnetic resonance imaging (MRI) protocol that is useful in detection and quantification of periacetabular bone loss. The purpose of this study is to compare MRI to plain film analysis in the assessment of periacetabular bone loss using a cadaver model. MRI was 95% sensitive in the detection of lesions. Specificity was 98%, and accuracy was 96%. Lesion detection was not statistically dependent on lesion location (p=0.27). The mean absolute error in determining lesion size was 0.8+/-2.2 cm3. There was a correlation between increasing lesion size and lesion detection (p=0.02, logistic regression). The largest lesion that was missed by MRI analysis measured 2.8 cm3, and all lesions 3.0 cm3 were correctly identified, with a relative error volume measurement of 12.4+/-25.3%. This correlated to an absolute error of 1.4+/-2.4 cm3. Using conventional radiographic analysis, the overall sensitivity of lesion detection was 52%, and the specificity was 96%. Using plain film analysis, identification of true lesions depended on the location with 83% of ilial lesions, 64% of pubic lesions, 55% of ischial lesions, and 0% of posterior wall lesions correctly identified. The modified MRI technique utilized did allow for accurate visualization of simulated osteolytic lesions, and may provide a suitable noninvasive method to provide serial assessment of clinical periacetabular osteolysis without the use of ionizing radiation.

Acetabulum↗

PubMed2005

Sensitivity and specificity of plain radiographs for detection of medial-wall perforation secondary to osteolysis.

Medial-wall perforation secondary to pelvic osteolysis impacts planning of acetabular revision surgery and may result in pelvic fracture. We compared commonly used radiographic signs for detecting medial-wall perforation (ballooning or discontinuity of Kohler's line or the iliopubic line) to findings from computed tomography (CT) in 27 cementless total hip arthroplasty patients with pelvic osteolysis. Used alone, none of the radiographic signs examined were reliable for detecting medial-wall perforation. When assessed together, however, the development of a discontinuity of Kohler's line, the iliopubic line, or both on anteroposterior pelvic radiographs was a reliable indicator for the presence of medial-wall perforation. Thus, the authors recommend a CT scan to evaluate the integrity of the medial wall when a discontinuity of Kohler's line or the iliopubic line has occurred and a revision surgery is planned.

Female↗

PubMed2005

The relationship between shelf life and in vivo wear for polyethylene acetabular liners.

Abstract: Although laboratory studies have correlated shelf life for gamma-irradiated-in-air polyethylene with material degradation, it is unknown whether this clinically affects wear. Therefore, we examined the relationship between shelf life and clinical wear for 152 gamma-irradiated-in-air acetabular liners. True wear rates were calculated from computer-assisted head penetration analyses of serial radiographs. Follow-up averaged 6.6 years. Shelf life averaged 11.8 months with 96% of liners having shelf lives of less than 3 years. Data analysis revealed no correlation between shelf life and true wear rates (r2 = 0.002; P = .60). This study provides useful information for surgeons concerned about shelf life as a potential cause of high wear in previously implanted components. For conventional liners in inventory less than 3 years, we found no evidence of increased wear in vivo.

Acetabulum↗

PubMed2005

The effect of total hip arthroplasty cup design on polyethylene wear rate.

Using 743 total hip arthroplasties that included 6 hemispheric porous-coated cup designs, this study used a multiple linear regression to identify those factors that influenced polyethylene wear rates. Wear rates for each hip were based on serial head penetration measurement made with computer-assisted techniques. Implant factors associated with an increased wear rate included terminal sterilization with a non-cross-linking chemical surface treatment, a 4-mm lateralized liner, a cobalt-chrome femoral head, and a longer shelf life for liners gamma-irradiated in air. After accounting for these implant characteristics and patient factors, wear rates among the 6 cup designs were not significantly different (P = .89). Although polyethylene wear is frequently characterized for specific implant designs, this study demonstrated that there are several common factors that influence polyethylene wear rates.

Acetabulum↗

PubMed2005

Comparison of CT, MRI, and radiographs in assessing pelvic osteolysis: a cadaveric study.

In this study, we compared the accuracy of radiography, computed tomography, and magnetic resonance imaging in assessing periacetabular osteolytic lesions. Using a previously published cadaver model, we created 87 lesions in pelves implanted with total hip replacement components. The sensitivity for detecting lesions was 51.7% for radiography, 74.7% for computed tomography, and 95.4% for magnetic resonance imaging. For all three techniques, sensitivity increased as lesion size increased. Magnetic resonance imaging emerged as the most effective tool for detecting small periacetabular osteolytic lesions (< or = 3 cm). For lesions larger than 3 cm, which are of more concern clinically, computed tomography and magnetic resonance imaging were effective in identifying lesions with detection rates greater than 80%. For radiography and computed tomography, lesion detection was dependent on lesion location, whereas magnetic resonance imaging had consistently good sensitivity in all lesion locations. Although the mean volumetric errors for computed tomography and magnetic resonance imaging (0.3 cm and 0.8 cm) were small compared with mean lesion volume (6.1 cm), computed tomography was more accurate than magnetic resonance imaging at measuring lesion volume, with a lower mean absolute error. This study verifies the problems associated with radiographic detection of osteolysis while showing the effectiveness of computed tomography and magnetic resonance imaging in determining the presence of lesions and assessing their three-dimensional volume.

Arthrography↗

PubMed2005

Characteristics of pelvic osteolysis on computed tomography after total hip arthroplasty.

UNLABELLED: We investigated the characteristics of pelvic osteolysis using computed tomography to assess osteolytic patterns associated with five acetabular cup designs. Additionally, we examined the relationship between polyethylene wear and volume of pelvic osteolysis. We measured defect volume on the computed tomography images of 126 hips at a mean of 10.9 years after arthroplasty. Defects were classified as osteolysis if there was: (1) a well-defined sclerotic border, (2) no radiographic evidence that the defect existed before hip arthroplasty, and (3) a clear communication between the defect and the joint space. We identified 225 bone defects in 116 hips. Of these, 184 defects in 101 hips fulfilled our criteria for osteolysis. We found that lesion size and the location of the communication pathways depended on the cup design. Osteolysis occurred primarily through central holes, and occurred only around the rim if there were no holes in the cup. The lesions that communicated only through central holes and those with multiple communications tended to be larger than rim-related lesions. There was a moderate correlation between volumetric polyethylene wear and osteolysis volume. Communication pathways between lesions and the joint space are valuable for diagnosing osteolysis on computed tomography. Lesion volume, location, and type of communication pathway to the joint are influenced by cup design. LEVEL OF EVIDENCE: Therapeutic study, Level IV-1 (retrospective case series). See the Guidelines for Authors for a complete description of levels of evidence.

Acetabulum↗

PubMed2005

Computed tomography in the assessment of periacetabular osteolysis.

BACKGROUND: Computed tomography recently has been proposed as an accurate method for diagnosing periacetabular osteolytic lesions. Several investigators have attempted to validate the accuracy of this technique, but they employed cadaveric and animal models, which cannot replicate the adaptive changes that occur over time in vivo. This study was performed to determine the accuracy of computed tomography in identifying and measuring periacetabular osteolytic lesions in hemipelves retrieved at autopsies of individuals with a previously well-functioning total hip prosthesis. METHODS: We evaluated nine hemipelves, retrieved at autopsy, that contained a cementless porous-coated acetabular component. The fresh specimens were examined with conventional radiographs and computed tomography and then were embedded and sectioned into 1.5-mm slices for evaluation with slab radiographs. Anteroposterior and iliac oblique plain radiographs as well as axial, coronal, and sagittal computed tomography scans were reviewed to determine the presence and location of any periacetabular osteolytic lesions. These results were then compared with those identified on the slab radiographs. Lesion volume was calculated from computed tomography scans with use of post-processing software. RESULTS: A total of twenty-three periacetabular osteolytic lesions were identified on the slab radiographs of the nine hemipelves. The plain radiographs identified twelve (52%) of the twenty-three lesions, and the computed tomography scans identified twenty (87%) of the twenty-three lesions. Three medial wall perforations were identified on the computed tomography scans but were not detected on the plain radiographs. Computed tomography was accurate in measuring the volume of the osteolytic lesions (r(2) = 0.997) but tended to overestimate the volumes measured on the slab radiographs. Periacetabular osteolytic lesions appeared on the computed tomography scans and slab radiographs as areas devoid of trabecular bone that were delineated by a sclerotic border and communicated with the joint space. CONCLUSIONS: In this autopsy model, computed tomography was an accurate method for detecting the location and measuring the volume of periacetabular osteolytic lesions.

Acetabulum↗

PubMed2005

Diagnostic features of pelvic osteolysis on computed tomography: the importance of communication pathways.

BACKGROUND: Progressive periacetabular osteolysis following total hip arthroplasty may require revision surgery. The purpose of this study was to use computed tomography scans of hemipelves retrieved at autopsy from patients who had had a total hip arthroplasty, to define the radiographic characteristics that differentiate clinically important osteolytic lesions from osteoarthritic bone cysts. METHODS: We analyzed forty-four hemipelves that had been retrieved at autopsy at a mean of eight years after a total hip arthroplasty with an uncemented acetabular component. Computed tomography images were analyzed to identify the location, volume, and presence of cortical erosion and/or communication pathways with the joint space for all periacetabular bone defects. Lesions that were not present on preoperative or immediate postoperative plain radiographs were defined as new lesions. These new lesions were compared with those that were present on preoperative or immediate postoperative plain radiographs, which were defined as preexisting lesions. RESULTS: Forty-six lesions were identified on computed tomography, and sixteen of them were preexisting lesions. The mean volume of the preexisting lesions was 1.5 +/- 1.5 cm(3), which was significantly smaller than the mean volume of 5.6 +/- 11.4 cm(3) of the thirty new lesions (p = 0.034). Twenty-eight of the thirty new lesions had a clear communication pathway with the joint space, while thirteen of the sixteen preexisting lesions demonstrated no communication pathway. New lesions were significantly more likely to communicate with the joint space than were preexisting lesions (p < 0.001). Cortical erosion was seen in sixteen of the thirty new lesions; none of the sixteen preexisting lesions exhibited cortical erosion (p < 0.001). CONCLUSIONS: The most important difference between osteolytic lesions and preexisting bone defects was the presence of a communication pathway to the joint space. Lesions that did not have an identifiable communication to the joint space were smaller and were not associated with cortical erosion. Lesions with communication to the joint through multiple pathways or through a central dome hole were larger and more likely to be associated with cortical erosion.

Adult↗

PubMed2005

Conventional ultra-high molecular weight polyethylene: a gold standard of sorts.

Data from a series of four recent studies showed that conventional polyethylene liners sterilized by gamma irradiation in air and coupled with second-generation acetabular components outperformed first-generation components with consistent average wear behavior below 0.1 mm/yr. It was found that liners sterilized by gamma irradiation in air outperformed liners sterilized by gas plasma, indicating that cross-linking induced by gamma irradiation sterilization, even if the component is radiated in an oxygen environment, is essential for keeping wear rates low. No negative clinical effects were found on wear for conventional polyethylene sterilized by gamma irradiation in air with a shelf life up to 3 years (r2 = 0.04, P = 0.60). Finally, 16-year temporal wear patterns for gamma irradiation in air sterilized components demonstrated no significant changes in wear rates over time, indicating that gamma irradiation sterilized liners with short shelf lives will not likely experience late increases in wear because of continued in vivo oxidation of the polyethylene. From these studies it was determined that standardized radiographic methods, optimal radiographs, serial measurements, and minimum 4-year follow-up are essential for reliable wear data. More specifically, it was concluded that a conventional ultra-high molecular weight polyethylene liner gamma irradiation sterilized in air with a shelf life less than 3 years, coupled with a second-generation cup, performs well in vivo and is unlikely to experience late increases in wear. Because no comparable in vivo data will be available for new cross-linked polyethylene materials for several years, conventional gamma irradiated polyethylene can be considered the industry's current gold standard for wear performance comparisons.

Hip Prosthesis↗

PubMed2004

Surgical management of polyethylene wear and pelvic osteolysis with modular uncemented acetabular components.

Osteolysis, usually associated with polyethylene wear, has become one of the most prevalent complications associated with total hip arthroplasty inserted without cement. Management of osteolysis is challenging because the disorder tends to develop silently and surgical intervention can result in complications. In addition, long-term outcomes are unknown. We discuss the current knowledge and data available on polyethylene wear and pelvic osteolysis with modular uncemented acetabular components. We also outline an algorithm for evaluation and treatment of patients. In general, we see patients with well-fixed components every 2 years, and we base follow-up visits after 6 years on predicted polyethylene wear rates and the presence or absence of pelvic osteolysis.

Arthroplasty, Replacement, Hip↗

PubMed2004

Long-term porous-coated cup survivorship using spikes, screws, and press-fitting for initial fixation.

This study examined the long-term outcome of a single institution's experience with 4,289 primary total hip arthroplasties using hemispheric porous-coated cups. Initial fixation was achieved with spikes (255 AML TriSpike cups), by press-fitting with rim screws (427 Arthropor cups) or by press-fitting the component (83 Harris-Galante, 391 ACS Triloc+, 2,537 Duraloc, and 596 Pinnacle cups). Among 203 revised hips, only 18 cups were found to be loose at the time of revision. Using revision for any reason as an end point, 15-year survivorship was 82.9% +/- 5.6% (95% confidence interval) for spiked components, 71.6% +/- 8.5% for press-fit cups with adjunctive rim screws, and 72.0% +/- 12.6% for press-fit components (P<.001, log rank). Using revision for aseptic loosening as an end point, 15-year survivorship was 94.7% +/- 3.4% for spiked cups, 98.4% +/- 1.9% for press-fit cups with screws and 100% +/- 0.1% for press-fit cups. Despite an increasing incidence of polyethylene wear-related revisions, porous-coated acetabular components have demonstrated excellent long-term fixation.

Acetabulum↗

PubMed2004

Total hip arthroplasty in patients 50 years and younger.

Because the young patient with a total hip arthroplasty is presumed to place increased demands on a reconstruction for a longer period than the average patient with a hip replacement, long-term results are expected to be inferior. To determine the efficacy of total hip replacements in this population, the current authors reviewed the long-term results of patients who were 50 years and younger who had cementless total hip arthroplasties at their institution, and reviewed the literature on total hip arthroplasty in younger patients. The results from the study population and the literature were encouraging. At the author's institute, during the past 20 years, 561 hip replacements were done on 488 patients in this age group, using extensively porous-coated cobalt-chromium stems matched with beaded, press-fit acetabular components of cobalt-chrome or titanium. Using the Kaplan-Meier technique, the survival rates for femoral and acetabular components, using any revision as an end point, were 89% at 10-year followup and 60% at 15-year followup. A subset of the authors' patients who were 40 years and younger (256 hips, 223 patients) had slightly inferior results, with 85% 10-year survivorship and 54% 15-year survivorship, using any revision as an end point. A comprehensive literature review also showed that long-term success can be achieved with cemented or cementless total hip arthroplasties in young patients. Because some reconstructions exhibited inferior results in younger patients, the authors recommend that surgeons be much more critical of the components used in these patients and allow long-term data to guide their decisions.

Adolescent↗

PubMed2004

Distal ingrowth components.

The literature documents that distal ingrowth fixation provides a reproducible, durable option that can be used in many femoral revision situations. In this review, we describe our use of cylindrical, extensively porous-coated stems to achieve distal fixation. The procedure involves choosing 5 cm to 7 cm of diaphyseal bone and reaming it cylindrically for a porous-coated femoral stem. Surgical implantation is uncomplicated because the femoral diaphysis aligns the component and imparts a reproducible press-fit sensation during impaction. The complications are well documented and can be avoided with adequate exposure, intraoperative radiographs, and surgical experience. Survivorship data based on femoral revisions done at our institution with extensively porous-coated stems show overall excellent results although a relatively poorer outcome is associated with patients whose prerevision cortical damage involves bone more than 10 cm below the lesser trochanter.

Arthroplasty, Replacement, Hip↗

PubMed2004

Database production and maintenance.

The advent of computers and electronic databases have revolutionized the way that clinical research is done. If study inclusion criteria are saved in the database, creating a study population can be accomplished by constructing an electronic query. Prospectively-entered outcome data related to a particular patient population then can be accessed and exported to a statistical software application for analysis. The senior author has more than 2 decades of experience with computer-based clinical outcome databases. In the context of his personal experience, this review offers some insights related to database design and maintenance.

Arthroplasty, Replacement, Hip↗

PubMed2004

Computed tomography to assess pelvic lysis after total hip replacement.

To assess the accuracy of a computer-assisted computed tomography image analysis program in determining the location and volume of periacetabular osteolysis, we designed an osteolysis model by implanting bilateral total hip replacements in human pelvic cadavers and creating osteolytic lesions of varying sizes. The volumes of 48 defects were measured physically, and axial computed tomography scans were obtained. The computed tomography images were processed with streak artifact reduction and segmentation algorithms. The location and volume of lesions were determined from these images. Eighty-one percent (39 lesions) were identified correctly from the computed tomography scans. Detection was location-dependent. More lesions were detected in the ilium (100%) and at the rim (89%) than in the ischium (78%) or the pubis (50%). Computed tomography overestimated lesion volume by a mean of 0.5 +/- 2.3 cm. The volumetric error was unrelated to lesion location but was dependent on lesion size. As lesion size increased above 10 cm, the mean percentage error decreased to 1.8%. Computed tomography image analysis can be used more accurately than plain radiographs to investigate the effectiveness of treatment and the natural history of pelvic osteolysis.

Arthroplasty, Replacement, Hip↗

PubMed2004

The pros and cons of polyethylene sterilization with gamma irradiation.

This retrospective study evaluated the implant, patient and surgical factors associated with polyethylene wear for one type of porous-coated hemispheric total hip arthroplasty cup. Radiographic wear measurements among 567 Duraloc cups (512 patients) revealed that liners sterilized by gamma-irradiation wore 0.085 mm/year less than those that were sterilized by gas-plasma, a noncross-linking chemical surface treatment. The substantially decreased wear rate associated with gamma-irradiation was attributed to sterilization-induced polyethylene cross-linking. Shelf-aging adversely affected liners that were gamma irradiated in air. On average, highly crystalline Hylamer liners showed a 0.064 mm/year increase in wear rates for each year of shelf storage after terminal sterilization with gamma-irradiation in air. Among conventional Enduron liners, the effect of shelf aging after gamma-irradiation in air was more modest, increasing wear rates by 0.014 mm/year for each year of shelf storage. Because Hylamer's wear performance degraded at about five times the rate of Enduron's, the improved wear resistance associated with gamma-irradiation in air would be lost after 1.3 years of shelf aging for Hylamer compared with 6.1 years for Enduron. For every additional year of age at the time of surgery, the wear rate decreased by 0.003 mm/year. Increased body mass index, a preoperative diagnosis of inflammatory arthritis, and a ceramic femoral head also were associated with decreased wear rates.

Aged↗