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C A Engh

Publications and source records attributed to C A Engh.

At least 19 recordsLinked to original sources
PubMed2001

Pattern of osteolysis around two different cementless metal-backed cups: retrospective, radiographic analysis at minimum 10-year follow-up.

In this retrospective study, we analyzed the formation of osteolysis with 2 cementless cups to evaluate if surface holes in metal shells influence the radiographic pattern of osteolysis. At a minimum of 10 years' follow-up, serial radiographs of 112 hips with Arthropor cups (having multiple shell holes) and 126 hips with Anatomic Medullary Locking (AML) cups (with no holes) were reviewed. Despite differences in variables other than cup design that can affect polyethylene wear and osteolysis rates, the incidence of osteolysis between the groups was coincidentally similar (47.3%, Arthropor; 47.6%, AML). The time of onset of osteolysis (mean, 7.5 and 7.4 years) also was similar. The radiographic pattern of the osteolytic lesions, which is largely a factor of cup design, differed. The Arthropor group had significantly larger lesions in Charnley zone I and significantly more hips with retroacetabular lesions (Charnley zones I and II); however, these lesions did not compromise cup stability. Patients with AML cups had more and larger lesions in the greater trochanter.

Chi-Square Distribution↗
PubMed2001

Wear-through of a modular polyethylene liner: four case reports.

Four patients in whom the S-ROM Total Hip System Polydial polyethylene liner was used illustrate the importance of, and difficulties in, detecting polyethylene wear-through before a complete acetabular revision is necessary. The patients in these cases had full thickness polyethylene wear-through 11 or more years after total hip arthroplasties. Dorr and Livermore wear measurements from radiographs of the patients underestimated the actual wear and did not indicate wear-through. Because excessive head penetration was not evident radiographically with the S-ROM components, the cases showed the necessity of using additional measures to diagnose wear-through, particularly with these components. Repeat radiographs at a higher kilovoltage were used to better visualize the outline of the femoral head, and hip aspiration was used to diagnose metallosis. These cases also showed the importance of yearly followup evaluations, especially 10 or more years after surgery for patients with the S-ROM Polydial locking mechanism.

Adult↗
PubMed2001

Effect of radiographic quality on computer-assisted head penetration measurements.

Even the most sophisticated computer-assisted radiographic techniques of measuring femoral head penetration into the polyethylene liner depend on the quality of the radiograph being evaluated, which varies greatly in clinical settings. The authors of this study sought to determine how the accuracy and reproducibility of three commercially available computer-assisted measurement systems differed when measuring optimal radiographs (with sharply defined component edges) and suboptimal radiographs (with less well defined edges). Using three computer-assisted measurement systems, the authors measured head penetration on simulated and clinical hip radiographs. All systems calculated head penetration as the movement of the head center relative to the cup center. To define the periphery of the prosthetic head and cup, one method (System One) used the human eye and a digitizing tablet, whereas the other two methods (System Two and System Three) used digital edge detection algorithms. For simulated hip radiographs, error was calculated as the absolute value of the difference between the known amount of head penetration, determined by a coordinate measuring machine, and the amount of penetration determined by the software. Three way analysis of variance showed a significant difference in absolute error among the three measurement techniques. System One had a significantly smaller absolute error (0.11 +/- 0.06 mm) than did System Two (0.25 +/- 0.25 mm) and System Three (0.19 +/- 0.13 mm). In addition, three-way analysis of variance showed that optimal radiographs were associated with a significantly lower absolute error (0.14 +/- 0.09 mm) than were suboptimal radiographs (0.23 +/- 0.22 mm). For optimal radiographs, there was no significant difference in error among the three measurement methods; all systems were accurate and reproducible. However, for suboptimal radiographs absolute error increased and varied widely, and a significant difference among the methods existed. These data show the susceptibility of head penetration measurements to radiographic technique and underscore the importance of good quality radiographs for all analyses of head penetration.

Analysis of Variance↗
PubMed2001

Effect of femoral stiffness on bone remodeling after uncemented arthroplasty.

The current study examined the relationships among femoral stiffness, implant stiffness, and bone remodeling in 40 femurs retrieved at autopsy from 20 patients with unilateral uncemented hip replacements. The purpose of the study was to determine if the magnitude of periprosthetic bone loss after arthroplasty was correlated with, and could be predicted from, stem and femoral stiffness terms. For analysis, the contralateral normal femur was used as a control to represent the unremodeled condition of the in vivo implanted femur. Bone loss attributable to remodeling was quantified by video-densitometric analysis. Stiffness terms were calculated as the product of the elastic modulus and geometric properties digitized from cross-sectional slab radiographs. Femoral stiffness calculations accounted for variations in modulus attributable to patient differences in bone mineral density and geometric properties attributable to differences in the shape of individual femurs. Similarly, calculations of implant stiffness accounted for variations in implant shape. Results showed axial bone stiffness was the variable most strongly correlated with bone loss. Individual stem stiffness terms were not significantly correlated with bone loss. Multiple linear regression analysis, using stem-to-bone stiffness ratios as independent variables, accounted for 46% of the variance in bone loss data. In the regression analysis, the axial stem-to-bone stiffness ratio was the strongest correlate with bone loss. Although these results show the influence of mechanical stiffness factors on bone remodeling, other factors (hormonal status, drugs, disease, activity level) could represent the variance in bone loss data not accounted for in the study.

Aged↗
PubMed2001

Surgical treatment of pelvic osteolysis.

Sixty-eight well-fixed acetabular cups with osteolysis in the pelvis and polyethylene wear were identified from a series of 124 reoperations for failed cementless sockets. The well-fixed sockets requiring reoperation were subdivided based on whether the liner was exchanged and lytic lesion grafted (Type I case) or the socket was removed and a complete revision was done (Type II case). In 40 patients (Type I cases), the polyethylene liner was exchanged and the osteolytic lesions were debrided. Allograft bone chips were packed into the lytic defect in 29 patients. In the remaining 11 patients, the lesions were debrided but not grafted. At final followup, all of the acetabular components were radiographically stable. No new osteolytic lesions were identified. Approximately 1/3 of the lesions had resolved completely regardless of whether they were grafted. The remaining 2/3 had decreased in size. In 28 patients (Type II cases), the socket was revised. Both strategies were successful in arresting the process of osteolysis during the course of this study (mean, 3.5 years). However, removal of well-fixed sockets was associated with significantly more bone loss.

Adult↗
PubMed2001

Long-term results using the anatomic medullary locking hip prosthesis.

Since the introduction of cementless total hip arthroplasty in the early 1980s, concern has shifted from component loosening toward polyethylene wear and osteolysis. The current review of 223 consecutive unselected Anatomic Medullary Locking femoral and acetabular components extends the followup on a series of patients previously reported on at 5 and 10 years. The purposes are to describe the reasons for revisions and to assess the onset and size of osteolytic lesions, with the hypothesis that osteolysis represents an important cause of loosening. The population included 204 patients (211 hips) with mean followup of 13.9 years (range, 2-18 years). Among them, 122 patients (129 hips) had a minimum 15-year followup. Minimum 2-year radiographs with a mean radiographic followup of 12.2 years (range, 2-18 years) were available for 204 hips (197 patients). Of the entire study group, 39 hips (38 patients) had 44 component revisions, increasing the number of revisions by 24 since this series was reported previously. Twenty-six patients (27 hips) had their first revision surgery more than 10 years after the primary surgery. The most common reason for revision of original components was wear or osteolysis occurring in 22 of the 39 hips (21 of 38 patients). The overall loosening rate was 3.4% (seven of 204) for femoral components and 5.4% (11 of 204) for acetabular components. Twenty-four percent of hips (48 of 204) had evidence of femoral or pelvic osteolytic lesions larger than 1.5 cm2. Femoral osteolysis was not associated with any case of femoral loosening, whereas seven of the 11 loose acetabular components were associated with pelvic lesions larger than 1.5 cm2.

Adolescent↗
PubMed2001

Total hip arthroplasty using porous-coated femoral components in patients with rheumatoid arthritis.

We studied the results of total hip arthroplasty (THA) using AML porous-coated femoral components at a mean follow-up of 11 years in a non-selected, consecutive series of patients with rheumatoid arthritis. We reviewed 64 patients with 82 primary THAs using these components. There were seven men (8 hips) and 57 women (74 hips) with a mean age of 55.1 years (24 to 80) at the time of surgery. Nine patients (11 hips) died before the two-year follow-up. Of the remaining 71 hips, only one stem was revised for aseptic loosening. Survivorship for the stems was 98.1% (95% confidence interval (CI) 94.5 to 100.0) at ten years, using a life-table analysis, with revision for any reason as an endpoint. Of the 70 unrevised stems, 66 (94%) had bony ingrowth, while four (6%) were radiologically loose at the most recent follow-up (mean 11.4 years). Our study shows the excellent long-term results which can be achieved with porous-coated femoral components in patients with rheumatoid arthritis.

Adult↗
PubMed2001

Modular component exchange for treatment of recurrent dislocation of a total hip replacement in selected patients.

BACKGROUND: Exchange of modular components is a treatment option for the correction of recurrent dislocation of a total hip replacement. In this study, we reviewed our experience with this technique in order to define patient selection criteria and to report the outcome of treatment. METHODS: Of 2935 hips treated with primary porous-coated total hip arthroplasty, fourteen (in fourteen patients) that met certain preoperative and intraoperative criteria were treated with modular component exchange because of recurrent hip instability. The primary arthroplasties in these fourteen patients had been performed through a posterior approach. At the revisions, we removed any sources of osseous or soft-tissue impingement that contributed to dislocation. Acceptable stability at the completion of component exchange was defined as stability in maximum flexion, in full extension with external rotation, and in at least 45 degrees of internal rotation with the hip in 90 degrees of flexion and maximum adduction. RESULTS: One patient was lost to follow-up. At a mean of 5.8 years (range, 2.8 to 11.8 years) after the revision, ten of the remaining thirteen patients had not had a dislocation. Of the three patients in whom the hip dislocated after the modular component exchange, only one had recurrent dislocation; thus, recurrent dislocation was eliminated in twelve of thirteen patients. CONCLUSIONS: In selected cases, modular component exchange for the treatment of recurrent hip dislocation has a success rate comparable with that of more extensive operations. This method should be considered because it avoids the morbidity associated with revision of well-fixed components. However, to ensure the appropriateness of this surgical option, each patient must be thoroughly evaluated to identify all factors that contribute to instability and adequate intraoperative stability must be achieved.

Adult↗
PubMed2001

A clinically practical method of manually assessing polyethylene liner thickness.

BACKGROUND: Most orthopaedists do not have access to contemporary computer-assisted radiographic techniques and therefore must use manual radiographic methods to assess polyethylene wear. The accuracy of most manual methods, however, has not been verified on clinical radiographs. In this study, we used manufacturer-developed wear templates to measure polyethylene wear and compared that technique with two other commonly used manual radiographic methods. Our purpose was to compare the accuracy of these techniques and thus determine their usefulness in assessing polyethylene wear in individual patients. METHODS: We analyzed seventeen polyethylene liners that were retrieved during revision operations after a mean of 12.0 years in situ. With use of digital calipers, we directly measured the true minimum polyethylene thickness of the explanted liner. We then measured the polyethylene thickness on anteroposterior pelvic radiographs that had been made before the revision. Three different manual techniques were used to evaluate the radiographs: the Dorr method, the Livermore method, and the newly described wear-template method. The minimum polyethylene thickness that was calculated with use of each of these methods was compared with the thickness as determined by direct measurement of the explanted liner. RESULTS: The mean error for the Dorr method (1.54 +/- 1.21 mm) was significantly greater than that for both the Livermore method (0.07 +/- 0.62 mm) and the wear-template method (-0.04 +/- 0.28 mm) (p < 0.01). The mean error for the Dorr method was significantly greater than zero (p < 0.01), indicating that this method consistently overestimated the true measurement. In contrast, the mean errors for the Livermore and wear-template methods were not significantly different from zero (p = 0.64 and 0.58, respectively), indicating that these methods did not consistently underestimate or overestimate the true measurement. However, the large standard deviations for all three methods suggest that the ranges in error are wide. The limits of agreement for the Livermore technique ranged from a 1.17-mm underestimation to a 1.31-mm overestimation of the true thickness of the polyethylene; those of the wear-template technique were smaller, ranging from a 0.60-mm underestimation to a 0.52-mm overestimation. CONCLUSION: The practicing orthopaedist needs an accurate and efficient method for determining the polyethylene thickness of modular acetabular components. We found that the template method best met this requirement because it involved a simple procedure: placing the template over the radiograph and measuring the distance between the femoral head and the inner surface of the metal shell. The other methods were less accurate, required additional information from the manufacturer, were more time-consuming, and were not as easy to demonstrate to the patient.

Acetabulum↗
PubMed2001

The relationship between lysis and loosening in failed anatomic medullary locking components.

Lysis does not cause loosening of extensively porous-coated, apparently well-fixed femoral components. We attribute this in large part to the fact that the area of strongest bone ingrowth is in the femoral diaphysis remote from the joint space. In contrast, for the acetabular component, osteolysis can be the sole or a contributing factor to loosening. We attribute this difference to the fact that the bone-implant interface of the acetabular component is much closer to the joint space and more readily accessible to osteolytic damage. In the future, with improved bearing surfaces, lysis may occur less frequently. Whether lysis is diminished as a result of these new designs, the authors contend that without adequate initial fixation, loosening will still occur. Because of our observations concerning osteolysis and loosening, we are more cautious in revising patients for osteolyis and do not revise when osteolysis first becomes apparent. Rather, we closely monitor osteolysis in these patients. For us, the question of when to operate for osteolysis remains unanswered.

Arthroplasty, Replacement, Hip↗
PubMed2001

Patient self-testing of prothrombin time after hip arthroplasty.

We determined whether total hip arthroplasty (THA) patients could test their own prothrombin time reliably over 6 weeks of anticoagulation prophylaxis with a portable device that measures prothrombin time and whether self-testing would improve or maintain the quality of care at a lower cost than our standard procedure. Forty-six THA patients participated in the study and were compared with a matched group managed with our standard protocol using a home health-care nurse. Seven patients (15%) could not be trained to obtain the blood sample, and others required multiple finger sticks to obtain valid results. However, the results from the 29 patients completing the study showed high reliability when compared with results obtained through standard protocol. Self-testing saved about $260 per patient over the cost of venipuncture. Patient self-testing of prothrombin time using the device in this study is reliable and cost-effective for monitoring the anticoagulation status after THA in a select group of elderly patients.

Adult↗
PubMed2000

Migration of polyethylene wear debris in one type of uncemented femoral component with circumferential porous coating: an autopsy study of 5 femurs.

This autopsy study analyzed the migration of polyethylene wear debris adjacent to uncemented femoral components with circumferential porous coating. Five femoral specimens retrieved at autopsy from 3 patients were investigated. Two stems were 40% porous coated, 2 were 80% porous coated, and 1 was 100% porous coated. The implants' time in situ ranged from 53 to 132 months (average, 94.8 months). All patients were followed clinically and radiographically until death. Radiographically, 3 of the stems were bone ingrown with proximal bone loss, 1 stem was mainly fibrous encapsulated, and 1 stem was completely fibrous encapsulated. Histologic examination of bone adjacent to the middle and distal sections of the femoral implant revealed no polyethylene wear debris or granulation tissue in any of the specimens. In 2 bone-ingrown cases, a small number of polyethylene particles and small areas of granulation tissue were present at the proximal level. This granulation tissue, however, did not cause major osteolysis. The findings in this study imply that circumferential porous coating of cementless femoral components could prevent distal migration of polyethylene wear debris along the bone-implant interface in both bone-ingrown and fibrous-encapsulated femoral implants.

Aged↗
PubMed2000

Influence of porous coating level on proximal femoral remodeling. A postmortem analysis.

This study used femurs retrieved at autopsy to compare the extent and location of bone remodeling between four patients implanted with proximally porous coated femoral prostheses and a matched group of four patients implanted with extensively porous coated femoral prostheses. The femoral components studied were large, cementless, straight, cobalt chrome stems and were identical except for the amount of porous coating. The contralateral normal femur of each patient also was retrieved, implanted with an identical prosthesis, and used as a control for bone mineral content. Dual energy x-ray absorptiometric analysis showed marked loss of bone mineral content in both groups of patients. The extensively coated group had less bone loss on average (18.4%) than did the proximally coated group (38.6%). There was no relationship between the extent of coating and the location of bone mineral loss; specifically, proximal coating did not protect against loss of bone mineral content proximally or distally in the femur. Videodensitometric analysis of cross sections of periprosthetic bone also showed that the extensively coated group tended to have less decrease in bone density than did the proximally coated group (14.3% versus 28.4%). Although one cannot presume that all proximally fixed stem designs would produce results similar to those presented here, these findings show that decreasing the extent of porous coating alone does not necessarily reduce proximal femoral bone loss.

Absorptiometry, Photon↗
PubMed2000

Comparison of in vivo wear between polyethylene liners articulating with ceramic and cobalt-chrome femoral heads.

At yearly intervals we compared the radiological wear characteristics of 81 alumina ceramic femoral heads with a well-matched group of 43 cobalt-chrome femoral heads. Using a computer-assisted measurement system we assessed two-dimensional penetration of the head into the polyethylene liner. We used linear regression analysis of temporal data of the penetration of the head to calculate the true rates of polyethylene wear for both groups. At a mean of seven years the true rate of wear of the ceramic group was slightly greater (0.09 mm/year, SD 0.07) than that of the cobalt-chrome group (0.07 mm/year, SD 0.04). Despite the numerous theoretical advantages of ceramic over cobalt-chrome femoral heads, the wear performance in vivo of these components was similar.

Aged↗
PubMed2000

Acetabular revision with use of a bilobed component inserted without cement in patients who have acetabular bone-stock deficiency.

BACKGROUND: Massive deficiency of acetabular bone stock is a challenging problem in the increasing number of patients who need a revision of a failed hip arthroplasty. The bilobed cup has been presented as one alternative reconstruction technique for hips with extensive acetabular bone loss. The purpose of this study was to assess the results with use of a bilobed acetabular component inserted without cement for revision reconstruction in hips with acetabular bone deficiency in order to clarify the indications for its use and to identify the factors that influence the clinical and radiographic outcome. METHODS: Forty-one hips in thirty-eight patients had an acetabular revision with a bilobed acetabular component inserted without cement between December 1991 and December 1995. These hips were a subset of the 414 hips treated with an acetabular revision during the same period of time. One patient was lost to follow-up, and one died during the study period. Two patients who could not return for radiographic evaluation completed questionnaires. The remaining thirty-four patients (thirty-seven hips) were evaluated radiographically and clinically and were followed for an average of forty-one months (range, twenty-four to sixty-six months). RESULTS: Radiographic analysis demonstrated an improvement in the average vertical displacement of the hip center. At the time of the latest follow-up examination, 76 percent (twenty-eight) of the thirty-seven cups were stable, 8 percent (three) were probably unstable with a change in the screw position but no definite migration of the cup, and 16 percent (six) were unstable. Eight of the nine loose or probably loose components were in patients who had more than two centimeters of superior migration of the component and disruption of Kohler's line on preoperative radiographs. Additionally, implants were more likely to become unstable (demonstrating more than 4 degrees of change in the abduction angle or more than four millimeters of radiographic migration) when the inferior aspect of the component did not extend to or distal to the interteardrop line, which indicated that the component was undersized. CONCLUSIONS: On the basis of our early rate of probable or definite loosening of 24 percent (nine of thirty-seven cups) and the technical difficulties involved, we do not recommend the routine use of this component. We believe that this device is indicated when a patient has an oblong-shaped acetabular defect and the surgeon wants to correct an elevated hip center. However, the medial wall of the acetabulum (Kohler's line) should be intact if the failed component has migrated more than two centimeters. An alternative reconstruction technique, such as use of a structural allograft with or without an acetabular cage, is also an option in this situation.

Acetabulum↗
PubMed2000

Characterization of long-term femoral-head-penetration rates. Association with and prediction of osteolysis.

BACKGROUND: We examined the relationship between long-term femoral-head-penetration patterns and osteolysis in a ten-year follow-up study of a well controlled patient population. The purposes of this study were to characterize the linearity of long-term head-penetration patterns over time, to describe the relationship between ten-year true wear rates and osteolysis, and to determine whether the occurrence of osteolysis at ten years could be predicted by penetration data obtained prior to five years. METHODS: Temporal femoral-head-penetration patterns were examined at a minimum of ten years after forty-eight primary total hip arthroplasties. The arthroplasties were performed with the use of an Arthropor acetabular cup (Joint Medical Products) and a thirty-two-millimeter-diameter cobalt-chromium femoral head (DePuy). Using a computer-assisted radiographic technique, we evaluated two-dimensional head penetration on serial annual radiographs. Linear regression analysis modeled penetration-versus-time data as a line for each patient. The slope of the regression line indicated the true wear rate for each patient. In a subgroup of thirty-four hips for which three annual radiographs had been made less than five years after the arthroplasty, we compared early head-penetration patterns with the later occurrence of osteolysis. RESULTS: For all forty-eight hips, the true wear rate averaged 0.18 millimeter per year (range, 0.01 to 0.44 millimeter per year) and temporal head-penetration patterns tended to be linear (mean r2 = 0.91 +/- 0.16). Osteolysis at ten years was strongly associated with increasing true wear rates (p < 0.001). Osteolysis did not develop in any of the nine hips with a true wear rate of less than 0.1 millimeter per year. However, osteolysis developed in nine (43 percent) of twenty-one hips with a rate between 0.1 and less than 0.2 millimeter per year, in eight of ten hips with a rate between 0.2 and 0.3 millimeter per year, and in all eight hips with a rate of greater than 0.3 millimeter per year. Evaluation of early true wear rates as a predictor of late osteolysis showed a similar relationship. CONCLUSIONS: This study demonstrates that true wear rates tend to be constant and that increased true wear is significantly associated with osteolysis at ten years after the operation. A similar relationship was also found at the early follow-up interval, indicating that early true wear rates (determined from serial radiographs) might enable orthopaedists to predict if patients are at risk for the development of osteolysis. CLINICAL RELEVANCE: On the basis of these findings, we use temporal femoral-head-penetration data in our practice to evaluate polyethylene inserts in asymptomatic patients, to estimate the time to component wear-through, and to adjust the frequency of follow-up evaluations for monitoring the development of osteolytic lesions in at-risk patients.

Adult↗