The John Charnley Award: a study of implant failure in metal-on-metal surface arthroplasties.
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Adult↗
Biomedical subjects
Edward Ebramzadeh
Publications and source records attributed to Edward Ebramzadeh.
Evaluation of elbow flexion and linel tests for cubital tunnel syndrome in asymptomatic individuals.
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Cubital Tunnel Syndrome↗
Simulation of fretting wear at orthopaedic implant interfaces.
Osteolysis due to wear debris is a primary cause of failure of total joint replacements. Although debris produced by the joint articulating surfaces has been studied and simulated extensively, fretting wear debris, produced at nonarticulating surfaces, has not received adequate attention. We developed a three-station fretting wear simulator to reproduce in vivo motion and stresses at the interfaces of total joint replacements. The simulator is based on the beam bending theory and is capable of producing cyclic displacement from 3 to 1000 microns, under varying magnitudes of contact stresses. The simulator offers three potential advantages over previous studies: The ability to control the displacement by load, the ability to produce very small displacements, and dynamic normal loads as opposed to static. A pilot study was designed to test the functionality of the simulator, and verify that calculated displacements and loads produced the predicted differences between two commonly used porous ingrowth titanium alloy surfaces fretting against cortical bone. After 1.5 million cycles, the simulator functioned as designed, producing greater wear of bone against the rougher plasma-sprayed surface compared to the fiber-mesh surface, as predicted. A novel pin-on-disk apparatus for simulating fretting wear at orthopaedic implant interfaces due to micromotion is introduced. The test parameters measured with the fretting wear simulator were as predicted by design calculations, and were sufficient to measure differences in the height and weight of cortical bone pins rubbing against two porous ingrowth surfaces, plasma-sprayed titanium and titanium fiber mesh.
Cadaver↗
Correlation of hallux valgus surgical outcome with AOFAS forefoot score and radiological parameters.
BACKGROUND: The purpose of the study was to evaluate the effect of three different types of hallux valgus surgeries on patient function using validated questionnaires and to correlate the results with radiographic and physical examinations. This study presents the 2-year followup data of a previous prospective outcome study. METHODS: One hundred and ninety-six patients were enrolled in this study and completed a baseline AAOS Lower Limb Outcomes Data Collection Questionnaire. They completed the same form at 6, 12, and 24 months after having one of three types of hallux valgus surgeries (106 chevron osteotomies, 72 modified McBride procedures, and 18 modified Lapidus procedures). This questionnaire included the Short Form-36 Health Survey (SF-36) as well as questions relating to lower extremity function. Additionally, physicians were asked to complete preoperative and postoperative questionnaires on each patient that included radiographic and physical examination data and the type of surgery done. Completed outcome surveys and radiographic data were available on 196 patients, and physical examination scores were available to assign an AOFAS score in 111 patients at 24-month followup. A one-way comparison was done after stratifying the results for the type of surgery, preoperative hallux valgus angle and 1-2 intermetatarsal angle, postoperative hallux valgus angle and 1-2 intermetatarsal angle, and the change in the angles. RESULTS: Four of the 10 SF-36 scores (physical function, role-physical, bodily pain, and role-emotional) for the combined data improved by more than five points. For the AAOS lower extremity function scores, physical health and pain (68.5 to 81.6), satisfaction with symptoms (1.8 to 3.6), global foot and ankle (77.6 to 93.4), and shoe comfort (29.0 to 58.7) scores all increased significantly. The AOFAS score increased from 52.6 to 85.5 (p <0.001). Surprisingly, when comparing mild-to-moderate to severe deformities preoperatively and postoperatively using the absolute magnitude of the angular change in the hallux valgus or intermetatarsal angles, similar improvement was noted in AOFAS, SF-36, and AAOS lower extremity scores. The magnitude of preoperative deformity, postoperative residual deformity, and magnitude of correction also did not significantly change the amount of improvement in any of these scores. No significant differences were noted in the outcome scores among the three different surgeries. CONCLUSION: Patients who had hallux valgus surgery had significant improvements in four of their SF-36 scores, four of five of AAOS lower extremity scores, and AOFAS scores. The degree of deformity, amount of correction, or type of operation did not influence outcome.
Adolescent↗
Age-adjusted baseline data for women with hallux valgus undergoing corrective surgery.
BACKGROUND: Functional and health-related quality-of-life data on a population of patients with hallux valgus are lacking. Similarly, the correlation of the severity of the deformity with these measures is unknown. METHODS: Two hundred and eighty-five women with an average age of forty-nine years who were scheduled for bunion surgery were enrolled in the study. The patients completed a baseline American Academy of Orthopaedic Surgeons (AAOS) foot and ankle outcomes questionnaire, which includes the Short Form-36 (SF-36) and a specific lower-extremity section on the foot and ankle. Preoperative radiographic data with regard to the hallux valgus angle and the intermetatarsal angle were stratified into groups according to the severity of the deformity (mild, moderate, or severe). The data were then stratified into age-groups consistent with those reported for the SF-36, and the results were compared with the SF-36 scores for the general population. The global foot and ankle score and the shoe comfort score were compared with general population scores that were published previously. The severity of the preoperative deformity was correlated with the baseline scores. RESULTS: General health scores were noted to be relatively stable throughout the age-groups for patients with bunions, with the older groups demonstrating better scores than the general population. Bodily pain scores were consistently worse for patients with a bunion through all age-groups compared with the general population. The average global foot and ankle score and the shoe comfort score were significantly lower (p < 0.001 for both) for the patients with a bunion than for the general population. The severity of the preoperative deformity did not correlate with any of the outcome scores. CONCLUSIONS: The bodily pain score from the SF-36 appears to be a sensitive measure of problems experienced by patients undergoing bunion surgery. Surprisingly, the severity of the deformity as measured radiographically did not correlate with any of the fifteen scores measured. These data may serve as a baseline for clinical hallux valgus studies with use of the SF-36 or the AAOS outcomes questionnaire.
Age Factors↗
Fixation strength of an all-metal acetabular component cemented into an acetabular shell: a biomechanical analysis.
When an acetabular shell is well fixed but the locking mechanism is compromised, cementing a new liner into the existing acetabular component can provide a simple revision solution. The pull-out and torsional fixation strength of cobalt chromium (CoCr) alloy acetabular components cemented into 3 sizes of titanium alloy acetabular components was tested under conditions of 0 or 2 mm cement mantle at the dome and 2 mm cement with the cemented component in 20 degrees of version with respect to the shell. The lowest mean tensile load to failure was 1500 N, and occurred with no cement at the dome of the 54 mm shell, whereas the greatest load was with 2 mm cement thickness. Smallest mean torque to failure was 43 Nm. Version angle did not substantially change failure load. Although not cyclically loaded, fixation strength of metal liners cemented into shells was comparable to that of commonly used locking mechanisms, suggesting sufficient strength for clinical application.
Acetabulum↗
Initial stability of cemented femoral stems as a function of surface finish, collar, and stem size.
BACKGROUND: The optimum surface roughness of cemented femoral stems used for total hip replacement is a subject of controversy. While rougher surfaces provide stronger cement adhesion, it has been hypothesized that polished, tapered, noncollared stems settle into the cement mantle, providing improved stability. However, the effects of surface finish on the stability of straight, cemented stems tapered only in the coronal plane are not known. METHODS: Using composite model femora, we assessed the initial stability of a straight, cemented femoral stem as a function of surface roughness, the presence or absence of a collar, stem size, and the resultant cement thickness under simulated walking and stair-climbing loads. Otherwise identical stems were manufactured with polished or rough surfaces, with or without a collar, in two different sizes. We isolated these three variables and compared their relative contributions to the motion at the stem-cement interface throughout cyclic loading. We defined three indicators of stability: per-cycle motion, rate of migration, and final migration. RESULTS: Surface roughness had a greater influence on per-cycle motions than did the presence or absence of a collar or cement thickness. Specifically, in the medial-lateral direction, per-cycle motion of polished stems was 43 micro m greater than that of rough stems (p < 0.01). None of the per-cycle motions decreased over the 77,000 load cycles. In contrast, with all stems, the rate of migration decreased over the course of cyclic loading, but the rate of migration of the polished stems was greater than that of the rough stems. Final migrations of the stems over the course of loading were generally distal, medial, and into retroversion. Compared with rough stems, polished stems had 8 to 18 micro m more axial migration (p < 0.001), 48 micro m more anterior-posterior migration (p < 0.001), and 0.4 degrees more rotational migration (p = 0.01). CONCLUSIONS: and CLINICAL RELEVANCE: The results indicated that, for cemented, straight femoral stems tapered only in the coronal plane, a rough surface offers the advantage of less per-cycle motion. These results may apply to widely used cemented stem designs based on the profile of the original Charnley femoral component, which has approximately parallel anterior and posterior aspects.
Arthroplasty, Replacement, Hip↗
Effects of dorsal flanges on fixation of a cemented total hip replacement femoral stem.
BACKGROUND: Although current designs of cemented femoral stems for total hip replacement include both those with and those without a flanged shape at the proximal end, the influence of anteroposterior dorsal flanges on the fixation of the stem is not completely understood. The purpose of this study was to assess the effects of flanges on femoral stem stability and load transfer to the femur with use of an in vitro model. METHODS: We measured femoral surface strains and three-dimensional micromotion in synthetic femora under cyclic loading with four types of stems: those with flanges and those without flanges in two sizes each. The four types of stems were otherwise identical; that is, all of them were straight, polished, and collarless. Stem-cement micromotion measurements and strain measurements were repeated with three stems of each type, whereas bone-cement micromotion measurements were made with one stem of each type. RESULTS: Flanges had a greater influence on femoral strains and micromotion than did the difference in the cement thickness resulting from the different stem sizes. Specifically, the flanged stems produced greater strains on the medial femoral surface but smaller strains on the anterior surface than did the non-flanged stems. Flanged stems achieved tighter mechanical interlock within the cement, but these stems increased bone-cement micromotion. Specifically, the motion per cycle of flanged stems within the cement mantle was smaller than that of non-flanged stems, whereas the motion per cycle of the cement mantle within the femoral canal was greater with the flanged stems than with the non-flanged stems. CONCLUSIONS: Flanges on a total hip femoral stem increase the interlock between the stem and the cement and decrease the proximal-medial stress-shielding. However, these advantages occur with increased bone-cement interface motion, which may be detrimental to the survival of the implant.
Adult↗
Cementing a liner into a stable cementless acetabular shell: the double-socket technique.
BACKGROUND: During revision hip replacement surgery, the cementless acetabular shell is often well fixed but the locking mechanism may be ineffective. Cementing a new liner into the existing acetabular shell (the double-socket technique) can provide a simple solution. The purposes of the present study were to review our initial clinical results and to define the potential limitations of this technique. METHODS: Thirty-two hips with a preexisting well-fixed acetabular socket that had been in situ for an average of 8.6 years were treated with the insertion of a new polyethylene liner (seventeen hips) or a metal liner (fifteen hips) with use of cement. The indication for this technique was a deficient locking mechanism in twenty-two hips and the unavailability of a matching liner in ten hips. Anteroposterior radiographs of all hips were analyzed by a single independent reviewer. RESULTS: The mean duration of follow-up was 5.1 years. Six hips required a reoperation after a mean of 29.7 months; the reasons for the reoperations included aseptic failure of the acetabular construct (four hips), instability (one hip), and sepsis (one hip). The University of California at Los Angeles hip scores improved significantly (p < 0.001) compared with the preoperative values; specifically, the mean score improved from 6.2 to 9.1 for pain, from 6.3 to 8.3 for walking, from 6.2 to 7.8 for function, and from 4.7 to 5.8 for activity. The prevalence of dislocation was 22%. Kaplan-Meier analysis with revision as the end point revealed a five-year survival rate of 78% (95% confidence interval, 55% to 91%). CONCLUSIONS: The double-socket technique is a good alternative to acetabular socket removal for suitable candidates who have a well-fixed cementless socket with an inner diameter that is larger than the outer diameter of the cemented liner. This technique preserves acetabular bone stock and permits conversion to alternate bearing surfaces. We believe, however, that removal of a well-fixed acetabular shell or the use of a constrained liner should be strongly considered for patients with a history of hip instability.
Acetabulum↗
Orientation of the femoral component in surface arthroplasty of the hip. A biomechanical and clinical analysis.
BACKGROUND: Although the orientation of the femoral component has been shown to influence the outcome of total hip replacement, its effect on the clinical outcome of surface arthroplasty has not been studied, to our knowledge. The purpose of this study was to examine the relationship between femoral component positioning and the outcome of a surface arthroplasty of the hip. METHODS: We reviewed the results of ninety-four hybrid metal-on-metal surface arthroplasties in patients who were forty years old or younger at the time of the operation and were followed for a minimum of two years or until the prosthesis failed. Measurements of the hip reconstruction were made on the anteroposterior pelvic radiograph. The correlation between the orientation of the femoral component and the outcome of the arthroplasty was evaluated, as were stresses within the resurfaced femoral head as a function of the orientation of the femoral component. RESULTS: The mean duration of follow-up was 4.2 years. Thirteen hips had an adverse outcome, defined as conversion to a total hip replacement, radiolucency of >1 mm in thickness adjacent to the femoral stem, or narrowing of the femoral neck of >10%. The mean femoral stem-shaft angle in the coronal plane was 138 degrees, with the hips that had an adverse outcome having a significantly lower mean angle than the rest of the cohort (133 degrees compared with 139 degrees, p = 0.03). Hips with an angle of <or=130 degrees had an increase in the relative risk of an adverse outcome by a factor of 6.1 (p < 0.004). In the entire cohort, stresses in the superior aspect of the resurfaced femoral head were substantially lower during slow walking than they were during fast walking (7.1 N/mm(2) compared with 14.2 N/mm(2)). CONCLUSIONS: Optimizing the femoral stem-shaft angle toward a valgus orientation during the preparation of the femoral head is important when a hip is being reconstructed with a surface arthroplasty because the resurfaced hip transmits the load through a narrow critical zone in the femoral head-neck region and the valgus angulation may reduce these stresses.
Adolescent↗
Preservation of bone mineral density of the proximal femur following hemisurface arthroplasty.
Bone mineral density of the proximal femur was measured in six patients who underwent hemisurface replacement for osteonecrosis of the femoral head. Bone mineral density values in operated and contralateral nonoperated hips were compared. In four patients who had sequential examinations, bone mineral density was compared over time. Average patient age was 34.6 years, average follow-up was 9.1 years, and mean follow-up of bone mineral density measurements was 6.6 years. Average bone mineral density variation was 0.0048 to -0.0264 g/cm2 per year in all five regions in nonoperated hips and -0.012 to -0.0300 g/cm2 in operated hips. These results support bone conservation and preservation with hemiresurfacing arthroplasty in young patients with osteonecrosis of the femoral head.
Adolescent↗
Measurement of polyethylene wear in total hip arthroplasty--accuracy versus ease of use.
The aim of this study was to compare the accuracy of four different methods for measuring wear using an apparatus that simulates known amounts of three dimensional wear. Wear was measured using the manual methods reported by Charnley, Livermore, Dorr and Wan and the computerized method reported by Devane. Only the method reported by Devane measured the three-dimensional (superior and anterior) wear with a reasonable accuracy, with a mean measurement error of 0.21 mm. With superior wear alone, Charnley's method underestimated the extent of wear by 16.6%, with a mean error of 0.35 mm; Livermore's method estimated wear to within 9.5%, with a mean error of 0.16 mm; Devane's method estimated wear to within 9.5%, with a mean error of 0.15 mm; and Dorr's method underestimated wear by 25.4%, with a mean error of 0.56 mm. Dorr's method was modified as a result of the experimental tests. The clinical application of the new method showed comparable data to that using the Devane method. In conclusion, this new method can be used to estimate the average wear in groups of patients accurately.
Equipment Failure Analysis↗
Long-term radiographic changes in cemented total hip arthroplasty with six designs of femoral components.
Measurements were made from annual follow-up radiographs, obtained over 27.6 years, of 860 cemented total hip arthroplasties implanted by one surgeon. Femoral components were made of stainless steel or titanium alloy, were non-modular, and were all fixed with cement, and acetabular cups were all-polyethylene and were fixed with cement. Radiographic outcome was correlated with the shape and material of the femoral component. Specifically, throughout the follow-up, stems made of titanium alloy were at greater risk of developing bone-cement radiolucent lines than those made of stainless steel, the difference ranging from approximately 10-50 percent at 2-10 years of follow-up. Similarly, titanium alloy stems were at greater risk of developing endosteal scalloping, indicating osteolytic lesions. Among the stainless steel Charnley cobra and straight-narrow Charnley stems, none developed cement fracture, only one became radiographically loose and one developed endosteal scalloping. The differences in the risk of developing radiolucent lines, cement fracture and progressive loosening among these stems were correlated with the relative rigidity of the femoral stems, and were generally consistent with the predictions made heretofore using finite element models, although differences in stem surface finish and femoral ball size and material could have also influenced the results.
Aged↗
Accuracy of measurement of polyethylene wear with use of radiographs of total hip replacements.
BACKGROUND: Although a number of methods are used to estimate polyethylene liner wear from radiographs of total hip replacements, there is no consensus with regard to the accuracy of these methods. The purpose of this study was to compare the accuracy of several such measurement methods with use of both laboratory radiographs and routine clinical radiographs. METHODS: A phantom apparatus was designed to simulate random values of three-dimensional wear, with varying degrees of cup abduction and anteversion, and to obtain anteroposterior and cross-table lateral radiographs with each value. Wear was measured with use of the Charnley duoradiographic method, the Livermore method, and the method described by Dorr and Wan, as well as with use of PolyWare and Hip32 software packages, both with and without three-dimensional measurements. Clinical wear was measured from conventional radiographs made prior to revision surgery in fourteen patients and was compared with wear measured directly from the retrieved liners with use of a coordinate measuring machine. RESULTS: With laboratory radiographs, median errors were 0.1 mm with the Livermore method and both computerized methods, 0.23 mm with the Charnley method, and 1.7 mm with the method of Dorr and Wan. Maximum errors were between 0.6 mm (Livermore) and 4.3 mm (Dorr and Wan). In contrast, with use of clinical radiographs, median errors ranged between 0.2 mm (Hip32) and 0.6 mm (Dorr and Wan). Maximum errors ranged between 1.8 mm (Dorr and Wan) and 2.5 mm (Livermore). CONCLUSIONS: With laboratory radiographs, computerized methods of polyethylene wear measurement offered distinctly greater accuracy than did manual methods; however, with clinical radiographs, they offered only slightly better accuracy. Although the increased accuracy of computerized methods may be necessary in research settings, manual methods provided sufficient accuracy for routine clinical assessment of wear.
Arthroplasty, Replacement, Hip↗
Incidence of inpatient surgeries in children and young adults with childhood orthopaedic diagnoses.
The incidence of orthopaedic surgery for young people with childhood onset of orthopaedic disabilities is not well documented. This study tabulated that incidence in the past two decades in California. Trauma, tumors, and hand surgery were not included in the study. Common pediatric orthopaedic diagnoses by ICD-9 code requiring CPT orthopaedic surgical procedures were tabulated in three years: 1983, 1990, and 1999. The most common procedures in each of these years studied were, in order of incidence, scoliosis, congenital hip problems, slipped femoral capital epiphyses, and clubfeet. The incidence of surgery for scoliosis and slipped femoral capital epiphyses increased over the past two decades. These data should be helpful in planning for future inpatient services for orthopaedically handicapped children.
Adolescent↗
Surgical repair of distal biceps tendon ruptures: a biomechanical comparison of two techniques.
BACKGROUND: Rupture of the distal biceps brachii tendon has most commonly been repaired by anatomic reattachment of the tendon to the radial tuberosity by a single- or two-incision approach. Researchers have studied suture anchor attachment through a single incision, but the tendon-suture interface and bone quality have not previously been analyzed. HYPOTHESIS: Suture anchor repair results in stiffness and tensile strength equal to that of bone-tunnel repair for biceps tendon rupture. STUDY DESIGN: Controlled laboratory study. METHODS: Twelve matched pairs of fresh-frozen cadaveric elbow specimens were used. Suture anchor and bone-tunnel tendon repairs were performed in a randomized fashion. Each specimen was loaded to tensile failure. Load-displacement graphs were generated to calculate repair stiffness, yield strength, and ultimate strength. Computed tomography bone density measurements and additional statistical analyses were then performed after grouping the specimens by mode of failure. RESULTS: The bone-tunnel repair was found to be significantly stiffer in all cases and to have significantly greater tensile strength than the suture anchor repair in the younger, nonosteoporotic elbows. CONCLUSIONS: Suture anchor repairs were not as stiff or strong as bone-tunnel repairs. CLINICAL RELEVANCE: Biceps tendon surgery using the traditional two-incision technique yields a stronger and stiffer repair in the typical patient with this injury.
Adult↗
Delayed treatment of type 3 supracondylar humerus fractures in children.
A retrospective review of 158 type 3 supracondylar humerus fractures was undertaken to determine whether any correlation exists between an increased time from injury to surgery and four unfavorable results: a longer operative time, an increase in hospital stay, an increase in the need to open the fracture, or an increase in unsatisfactory outcomes. The average age of the patients was 5.0 years. Five children had nerve injury on initial examination, and no arm was poorly perfused. The average time from injury to evaluation in the emergency department was 9.8 hours and the average time from the emergency department to surgery was 11.5 hours. The average total time from injury to surgical treatment was 21.3 hours. The patients were in the hospital between 1 to 6 days. The average operative time was 53 minutes. Thirty patients had unsatisfactory results, defined as a pin infection, more than 15 degrees loss of motion in any plane, loss of normal carrying angle, neuropraxia, or retained hardware. There was no correlation between an increase in time to surgical intervention and longer operative time or need to open the fracture site, nor was there an indication that the delay to surgical treatment resulted in a longer hospital stay or an increase in unsatisfactory results.
Arm↗