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Biomedical subjects

Michael D Ries

Publications and source records attributed to Michael D Ries.

At least 37 records · Page 2Linked to original sources
PubMed2004

Zirconia femoral head fractures: a clinical and retrieval analysis.

Zirconia femoral heads provide increased fracture strength, but 343 zirconia head failures have been documented since 2000. Retrieval analysis of 6 fractured heads, 4 suspect heads, 4 control zirconia heads, and 2 failed alumina heads was performed. Zirconia failures have been isolated to heads sintered in a "tunnel" furnace introduced in 1998. The monoclinic composition at the taper surface of fractured and nonfractured heads was significantly elevated (21% to 68%) compared to that of control zirconia heads (less than 5%). Electron microscopy identified circular fracture footprints unique to the zirconia heads produced in the tunnel furnace. Cobalt chrome heads were used in the urgent revision setting due to Morse taper damage. Partial capsulectomy was performed in an effort to reduce future third body wear. Monoclinic phase transformation following implantation remains a potential mechanism of ceramic head failure. We recommend that patients with recalled zirconia heads be advised of a potential fracture risk.

Adult↗
PubMed2004

A pilot, two-year longitudinal study of the interrelationship between trabecular bone and articular cartilage in the osteoarthritic knee.

OBJECTIVE: To examine the relationship between structural changes of trabecular bone and cartilage, in patients with varying degrees of osteoarthritis (OA) over 2 years, using magnetic resonance imaging. METHODS: High-resolution, axial images were acquired for assessing trabecular bone structure, using a 3-D fast gradient-echo sequence. High-resolution, fat-suppressed, sagittal images were acquired for assessing cartilage structure, using a 3-D spoiled gradient-echo sequence. In a subset of the patients, sagittal images were acquired for measuring T(2) relaxation time, using a 2-D dual-echo spin echo sequence. RESULTS: A large variation in bone and cartilage parameters is evident among individual subjects in each group, however, group-specific means demonstrate decreasing trends (in bone and cartilage parameters) in osteoarthritic subjects (especially in mild OA subjects). The mean T(2) increased significantly (P<0.05) between the baseline and follow-up exams for all cartilage compartments except the lateral tibia. A positive relationship was established between cartilage changes and localized bone changes closest to the joint line, while a negative relationship was established between cartilage changes and global bone changes farthest from the joint line. CONCLUSION: This study quantifies the changes in bone and cartilage structural parameters over time, and demonstrates a longitudinal relationship between the morphological changes in bone and cartilage structure in patients with varying degrees of OA. Although a large variation of bone and cartilage changes is apparent among subjects, significant trends are evident in a relatively small sample size, with a short follow-up duration.

Adult↗
PubMed2004

Computer-aided quantification of focal cartilage lesions of osteoarthritic knee using MRI.

Noninvasive assessment of articular cartilage using magnetic resonance imaging (MRI) has gained popularity in the diagnosis of osteoarthritis (OA), a condition that affects 20 million Americans. Focal cartilage lesions, a defect found in roughly 19% of the OA population, currently can only be evaluated with confidence using minimally invasive arthroscopy. This article presents a computer-aided procedure using MRI to quantify focal cartilage lesions and aims to support clinical practices of diagnosis and monitoring of lesion progress. Upon a local minima search for identifying focal lesions, the proposed gradient peak method outlines lesion boundaries and then generates morphological properties, such as lesion volume and lesion area. The procedure was evaluated using simulated and in vivo data. First, a simulated lesion was created and analyzed, and the results were compared with the exact solutions. Second, an in vivo evaluation was carried out on seven human knees in which nine focal lesions were identified and quantified. Three of the subjects had follow-up analyses, at either 1 or 2 years. Finally, in an attempt to characterize local biochemical changes underlying focal lesions, MR-derived T2 values of defective cartilage within the lesion boundaries were examined and compared with the values of adjacent cartilage compartments.

Aged↗
PubMed2004

A study of the relationship between molecular biomarkers of joint degeneration and the magnetic resonance-measured characteristics of cartilage in 16 symptomatic knees.

We used quantitative magnetic resonance (MR) imaging to determine if relationships exist between proposed molecular biomarkers for degenerative joint disease (DJD) and structural characteristics of articular cartilage. Subjects were eight male and eight female volunteers diagnosed with osteoarthritis. Magnetic resonance images of the symptomatic knee were taken and blood samples were drawn. Concentrations of serum cartilage oligomeric matrix protein (COMP) and cleaved collagen neoepitope were compared to cartilage volume and cartilage T2, respectively, in four compartments of the tibiofemoral joint. A significant, negative correlation was found between serum COMP and medial tibia volume in the male subject group (rho=-.738, P=.037). A significant, positive correlation (rho=.881, P=.0039) was found between serum COMP and lateral femur volume in the female subject group. In both groups, positive correlations were found between serum C2C and cartilage T2, which were significant in two compartments of the male group (rho=.714, P=.047; rho=.738, P=.037) and similarly strong, but not statistically significant (rho=.750, P=.052), in one compartment of the female group. We identify strong and biologically relevant correlations between two proposed molecular biomarkers for DJD and MR measures of symptomatic knees of a small number of arthritic patients. Our findings support the hypothesis that cartilage molecular biomarkers reflect the molecular processes of cartilage degeneration and loss.

Adult↗
PubMed2004

Extended medial gastrocnemius rotational flap for treatment of chronic knee extensor mechanism deficiency in patients with and without total knee arthroplasty.

Nine patients with chronic extensor mechanism disruption were treated with an extended medial gastrocnemius rotational flap reconstruction of the extensor mechanism. Seven patients previously had total knee arthroplasty and two patients had chronic infection of nonreplaced, native knees. Four patients previously had failed Achilles' tendon allograft reconstruction after total knee arthroplasty and two were complicated by infection. Infected arthroplasty patients had a staged procedure with placement of an antibiotic spacer after debridement and extended medial gastrocnemius rotational flap, followed by total knee arthroplasty replant 8 weeks later. The four infected arthroplasty patients had medical comorbidities that included a patient with HIV and hemophilia, and two with diabetes mellitus. Another patient with rheumatoid arthritis was severely malnourished as a result of dumping syndrome. Of the four patients treated by this two-stage procedure, one died in the early postoperative period from chronic medical issues after the second stage and another patient elected to have above-knee amputation after the first stage because of severe reflex sympathetic dystrophy. The final group of seven patients was studied at a mean followup of 21 months (range, 7-31 months), the average extensor lag was 13.5 degrees (range, 0-50 degrees ), and the average range of motion was 2 degrees to 93 degrees . The two patients with nonreplaced, native knees had extensor lags of 30 degrees and 10 degrees . All patients were able to regain sufficient extensor mechanism strength to return to independent ambulation, and all infections resolved after treatment. Two patients were able to ascend stairs foot over foot without support. In addition to the patient who had amputation, the other complication involved a wound breakdown that required a free flap at 13 months in a patient who had a failed Achilles' tendon allograft reconstruction after takedown of a knee fusion. Medial gastrocnemius flap reconstruction can provide successful salvage of a failed extensor mechanism allograft or an alternative to allograft reconstruction in patients with poor soft tissue coverage, previous infection, or a compromised immune system.

Achilles Tendon↗
PubMed2004

Fatigue crack propagation resistance of highly crosslinked polyethylene.

A higher degree of cross-linking has been shown to improve wear properties of ultra-high molecular weight polyethylene in laboratory studies. However, cross-linking can also affect the mechanical properties of ultra-high molecular weight polyethylene. Fatigue crack propagation resistance was determined for electron beam cross-linked ultra-high molecular weight polyethylene and compared with gamma irradiation cross-linked and noncross-linked polyethylene fatigue specimens. Crosslinking was done with different dosages of irradiation followed by melting. For one irradiation dose (50 kGy) extrusion and molding processes were compared. A fracture mechanics approach was used to determine how the degree of cross-linking affects resistance to crack propagation in ultra-high molecular weight polyethylene. Fatigue crack propagation resistance was reduced in proportion to the irradiation dose. The type of irradiation (gamma or electron beam) or manufacturing method (extrusion or molding) did not affect fatigue crack propagation resistance. The reduced fatigue strength of highly cross-linked ultra-high molecular weight polyethylene could lead to mechanical failure in conditions that are associated with cyclic local tensile stresses.

Case-Control Studies↗
PubMed2004

Wear and surface cracking in early retrieved highly cross-linked polyethylene acetabular liners.

BACKGROUND: A higher degree of cross-linking has been shown to improve the tribological properties of ultra-high molecular weight polyethylene in laboratory studies; however, its effect on in vivo behavior has not been well established. We investigated in vivo wear mechanisms in retrieved highly cross-linked polyethylene acetabular liners in order to determine if early in vivo wear behavior is accurately predicted by hip-simulator studies. METHODS: A total of twenty-four liners (twenty-one explanted and one unimplanted highly cross-linked liners and two explanted ethylene-oxide-sterilized non-cross-linked liners) were examined for this study. The average age of the patients was 59.9 years, and the average time in vivo was 10.1 months. Articular surface damage on the front and back sides of the liners was assessed with an optical scoring system. Surface quadrants were assigned a grade from 0 to 3 according to the observed wear mechanisms and the percentage of surface affected. The micromechanisms of liner damage were evaluated with use of scanning electron microscopy. RESULTS: The average front and back-side explant damage scores were 11 (range, 2 to 26.5) and 6.7 (range, 3.7 to 13.3), respectively. There was consistent evidence of early surface deformation and cracking. All explants exhibited some form of surface change, including surface cracking, abrasion, pitting, or scratching. The original machining marks on the liner surface were observed to be either unaltered, drastically distorted, or absent. CONCLUSIONS: Highly cross-linked ultra-high molecular weight polyethylene acetabular liners that were retrieved at an average of ten months after implantation exhibited signs of surface damage that had not been predicted by in vitro hip-simulator studies. These devices had not failed clinically as a result of wear. The discrepancy between in vitro and in vivo wear surfaces may be due to variability in terms of in vivo lubrication and cyclic loading or may represent early surface damage mechanisms that are not well demonstrated by long-term simulator studies.

Acetabulum↗
PubMed2003

Structural degradation of acrylic bone cements due to in vivo and simulated aging.

Acrylic bone cement is the primary load-bearing material used for the attachment of orthopedic devices to adjoining bone. Degradation of acrylic-based cements in vivo results in a loss of structural integrity of the bone-cement-prosthesis interface and limits the longevity of cemented orthopedic implants. The purpose of this study is to investigate the effect of in vivo aging on the structure of the acrylic bone cement and to develop an in vitro artificial aging protocol that mimics the observed degradation. Three sets of retrievals are examined in this study: Palacos brand cement retrieved from hip replacements, and Simplex brand cement retrieved from both hip and knee replacement surgeries. In vitro aging is performed using oxidative and acidic environments on three acrylic-based cements: Palacos, Simplex, and CORE. Gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FTIR) are used to examine the evolution of molecular weight and chemical species within the acrylic cements due to both in vivo and simulated aging. GPC analysis indicates that molecular weight is degraded in the hip retrievals but not in the knee retrievals. Artificial aging in an oxidative environment best reproduces this degradation mechanism. FTIR analysis indicates that there exists a chemical evolution within the cement due to in vivo and in vitro aging. These findings are consistent with scission-based degradation schemes in the cement. Based on the results of this study, a pathway for structural degradation of acrylic bone cement is proposed. The findings from this investigation have broad applicability to acrylic-based cements and may provide guidance for the development of new bone cements that resist degradation in the body.

Acrylates↗
PubMed2003

Effect of cementless bowed stem distal surface contour and coronal slot on femoral bone strains and torsional stability.

Six pairs of unembalmed cadaver femurs were instrumented with strain gauges and prepared with flexible reamers for insertion of long bowed cementless femoral stems. A fully porous-coated cobalt chrome stem was inserted into each left femur, and a distally fluted, slotted, stem of the same implant geometry and implant material was inserted into each right femur. Bone strains were measured during stem insertion and torsional stability tested after the stems were fully seated. Distal strains were significantly higher (p < 0.05) for the fully porous compared to the distally fluted, slotted stem. Three fractures occurred in femurs with fully porous-coated stems. There was no difference in torsional stability between the two stem geometries. Our data demonstrate that a long bowed cementless stem with a distal coronal slot and flutes is associated with decreased bone strains and fracture risk during stem insertion compared to a fully porous-coated stem.

Biomechanical Phenomena↗
PubMed2003

Combined vertical and horizontal cable fixation of an extended trochanteric osteotomy site.

BACKGROUND: The use of an extended trochanteric osteotomy facilitates exposure and aids in the removal of a well-fixed femoral implant and cement during revision total hip arthroplasty. Occasionally, nonunion, fracture, and trochanteric migration have been reported following osteotomy. We evaluated the rate of healing of the osteotomy site and of implant stability when fixation was accomplished with use of vertical trochanteric and horizontal metaphyseal cable fixation (combined cable fixation). METHODS: The clinical and radiographic results of revision total hip arthroplasty with use of an extended trochanteric osteotomy followed by implantation of a distally porous-coated component and combined cable fixation of the osteotomy site in forty-two consecutive patients (forty-three hips) were reviewed. Intraoperative fracture at the osteotomy site occurred in five hips (12%). RESULTS: All osteotomy sites healed by six months, with an average time to union of fifteen weeks. One implant subsided 5 mm in a patient in whom a fracture had occurred at the time of the osteotomy. No trochanteric migration occurred. Two patients required a reoperation: one because of instability, and another because of recurrent infection. CONCLUSIONS: The extended trochanteric osteotomy facilitates revision of a well-fixed femoral component. Despite occasional intraoperative fracture at the osteotomy site, combined vertical trochanteric and horizontal metaphyseal cable fixation resulted in an excellent rate of healing and implant stability.

Adult↗
PubMed2003

Complications in primary total hip arthroplasty: avoidance and management: wear.

Many factors, including polyethylene processing, sterilization method, counterface material, femoral head size, femoral offset, acetabular component position, implant design, and patient activity level, affect the rate of wear in total hip arthroplasty. For patients with life expectancy that exceeds the longevity of the conventional implant materials, an alternative bearing surface (highly cross-linked polyethylene, metal-on-metal, or ceramic-on-ceramic) may be considered. Although laboratory wear tests with these materials are very favorable, clinical outcomes have not been clearly established. When osteolysis does develop in response to particulate debris, the location and progression of the lesions may be quite variable. Asymptomatic stable lesions can be followed clinically and radiographically while symptomatic or enlarging lesions or those that may compromise the integrity of the periprosthetic bone stock require surgery. If acetabular component revision is necessary and an adequate rim of host bone is maintained to support a revision acetabular component, defects can be filled with particulate bone graft. Large segmental defects generally require structural allografts. If the acetabular shell is well fixed in good position and the osteolytic defects are accessible, treatment with curettage and bone grafting of the lesions with liner revision is appropriate to avoid use of a structural allograft. Proximal femoral defects around a well-fixed stem can be managed in a similar manner with curettage and bone grafting. Distal lesions associated with risk of periprosthetic femur fracture or implant loosening require stem revision. Osteoclastic resportion of bone in response to particulate debris can be impaired with use of some drugs such as alendronate. However, the safety and efficacy of alendronate in the clinical management of osteolysis associated with total hip arthroplasty has not been established.

Arthroplasty, Replacement, Hip↗
PubMed2002

Retrieved glenoid components: a classification system for surface damage analysis.

There have been many reports describing modes of damage in retrieved total hip and total knee arthroplasty components. The most common mechanism in total hip arthroplasties has been shown to be surface wear. Fatigue failure shown as pitting and delamination are observed more often in total knee components. There has been no previous analysis of retrieved polyethylene glenoid components. This study evaluated the wear mechanisms contributing to failure of total shoulder glenoid components. Polyethylene glenoid components from 10 consecutive total shoulder arthroplasties have been retrieved and analyzed. Wear mechanisms were analyzed under low-power magnification, and a classification system was designed for total shoulder arthroplasties. This classification system is an adaptation of previous models of hip and knee surface damage. The severity of each damage mode was graded in 4 separate quadrants. The most prevalent damage modes were abrasion, pitting, and delamination. These data show a combination of abrasive wear and fatigue in retrieved total shoulder specimens. Surface wear and subsurface fatigue failure mechanisms both contribute to glenoid implant failure.

Aged↗