Papers by Thomas Schmalzried
Journal of Applied Biomaterials, 1993
Ultra high molecular weight polyethylene (UHMWPE) wear particles are frequently implicated in cau... more Ultra high molecular weight polyethylene (UHMWPE) wear particles are frequently implicated in causing failure of total joint arthroplasties by eliciting a foreign body reaction. The majority of these particles are subcellular and many are submicron in size. Identification of these small particles of UHMWPE by conventional histologic techniques is difficult. We have therefore investigated the utility of Oil Red 0 (ORO) stain to identify UHMWPE on histologic sections.
Pathology, Biomaterials and Clinical Practice, 2005
Journal of Applied Biomaterials, 1993
A simple, yet specific, means to identify submicron polyethylene (PE) particles in routine histol... more A simple, yet specific, means to identify submicron polyethylene (PE) particles in routine histologic sections would be practically useful. We have previously reported a very fine, diffuse, birefringence (when viewed under polarized light) in the cytoplasm of phagocytic cells from around total hip replacements (THRs) with a PE acetabular bearing and proposed that this finding was caused by multiple submicron PE particles. In order to determine the specificity of this light microscopic finding, we have analyzed a wide range of specimens ( N = 27), characterized by a foreign-body inflammatory response to both biologic and prosthetic material, that do not contain PE. In no case was there any suggestion of the diffuse cytoplasmic birefringence that is characteristic of specimens from THRs with a PE acetabular bearing surface. This study indicates that, within the range of orthopedic implant materials and designs currently in use, this diffuse birefringence is a specific finding and it represents a simple, practical, and useful method for light microscopic identification of submicron PE. 0
Journal of applied biomaterials : an official journal of the Society for Biomaterials, 1994
Differences in bearing surface conformity and wear mechanisms suggest that the polyethylene (PE) ... more Differences in bearing surface conformity and wear mechanisms suggest that the polyethylene (PE) wear debris generated by total knee replacement (TKR) prostheses should be different than that in total hip replacement prostheses (THR). To address this issue, PE wear debris and the cellular response in periprosthetic tissues from 19 failed TKRs was compared to that from 24 failed THRs using polarized light microscopy and a semiquantitative grading system. The foreign-body inflammatory reaction in the THR case was characterized by plump macrophages with a diffuse cytoplasmic birefringence when examined under polarized light, indicating the presence of multiple submicron particles of PE. The majority of PE particles were less than 1 mum in size and only a small fraction of the total were greater than 10 mum. The foreign-body inflammatory reaction in the TKR cases was characterized by giant cells with fewer macrophages. In the TKR specimens, the size range of PE particles was broader tha...
Journal of materials science. Materials in medicine, 2002
The resurgence of metal-on-metal articulating surfaces for hip arthroplasty has also heightened c... more The resurgence of metal-on-metal articulating surfaces for hip arthroplasty has also heightened concerns about the degree and magnitude of metal particle generation and the accompanying increase in circulating metal ion concentrations. In this study, we measured the concentration of chromium in serum and urine and the concentration of cobalt in serum in twenty-five patients with modern metal-on-metal surface arthroplasty of the hip in a prospective manner. The results showed that the mean post-operative chromium in serum levels were 22-fold, 23-fold and 21-fold higher at 3, 6 and 12 months post-operative, respectively, than pre-operative levels. The mean post-operative cobalt in serum levels were 8-fold, 7-fold and 6-fold higher at 3, 6 and 12 months post-operative, respectively, than pre-operative levels. The mean post-operative chromium in urine levels were 9-fold, 10-fold and 14-fold higher at 3, 6 and 12 months post-operative, respectively, than pre-operative levels. The values ...
ABSTRACT Hip arthroplasty and extended travel are each recognized as risk factors for venous thro... more ABSTRACT Hip arthroplasty and extended travel are each recognized as risk factors for venous thromboembolism (VTE). The safety of travel after hip arthroplasty is currently unknown. Patients who had traveled more than 200 miles within 6 weeks of a hip arthroplasty or hip resurfacing were identified and contacted. All patients received VTE chemoprophylaxis with enoxaparin, dalteparin, fondaparinox, or warfarin. A total of 608 patients traveled an average of 1377 miles at an average of 6.5 days after surgery. Among these patients, 462 traveled by airplane, 143 by car, and 3 by train. There were no deaths, no symptomatic pulmonary embolisms, and only 5 (0.82%) symptomatic deep venous thromboses. Nine (1.5%) patients experienced bleeding complications. With chemical VTE prophylaxis, extended travel within 6 weeks of hip arthroplasty surgery is associated with a low rate of symptomatic deep venous thrombosis, with no known pulmonary embolisms and no deaths.
Journal of Knee Surgery, 2008
The rotational constraint characteristics of 4 commercially available posterior-stabilized implan... more The rotational constraint characteristics of 4 commercially available posterior-stabilized implants (Triathlon, NexGen, PFC, and Genesis II) were determined. The torques required to achieve up to +/-20 degrees of internal and external rotation were quantified at hyperextension, 0 degree, 15 degrees, 60 degrees, and 90 degrees of flexion. The effect of lubrication was tested by comparing the torque values generated in dry and serum environments. Results indicated that substantially higher torques were generated in the dry environment, compared with the serum environment. In extension, the principal design features influencing the torques were interaction of the box and post, as well as the insert anterior lip. In higher flexion angles, the amount of rollback, coupled with the posterior lip geometry, most heavily influenced the generation of torque. Comparison of the 4 designs showed that the Triathlon generated the least torques to +/-10 degrees of rotation, whereas the PFC and Genesis II were the most constrained.
Clinical orthopaedics and related research, 2005
Short-term failures of total hip resurfacing have been related to specific characteristics of the... more Short-term failures of total hip resurfacing have been related to specific characteristics of the proximal femur. A radiographic arthritic hip grading scale was used to assess four characteristics of the proximal femur: bone density, shape, biomechanics, and focal bone defects. Hips with no unfavorable characteristics were Grade A, hips with one unfavorable characteristic were Grade B, hips with two unfavorable characteristics were Grade C, hips with three unfavorable characteristics were Grade D, and hips with four unfavorable characteristics were Grade F. One hundred forty-seven consecutive hips were treated with metal-on-metal resurfacing by a single surgeon. There were no femoral neck fractures. Of the 91 hips eligible for a minimum 2 year followup, 90% were Grades A or B, 10% were Grade C, and none were Grades D or F. With a minimum 2-year followup, arthritic hip grading was associated with preoperative Harris hip score, occurrence of mild to moderate postoperative pain, preope...
Archives of Orthopaedic and Trauma Surgery, 2005
Crosslinked polyethylene (PE) was developed to reduce volumetric wear in prosthetic joints. Hip s... more Crosslinked polyethylene (PE) was developed to reduce volumetric wear in prosthetic joints. Hip simulator studies have shown promising results but there is as yet limited clinical data. We identified three patients with bilateral total hip replacements who received a crosslinked PE liner (Marathon TM , DePuy, Warsaw, IN, USA) on one side and a conventional PE insert (Enduron TM , DePuy) on the contralateral side. As an assessment of in vivo PE wear, linear head penetration was measured on standardized radiographs using a validated computer-assisted technique. In all the three cases, a marked reduction of more than 70% in volumetric wear was found in association with Marathon crosslinked PE. These case reports support the efficacy of this type of crosslinked PE in a selected group that allows direct comparison of the two different materials without the influence of patient-related factors such as activity, gender, weight, or others.
Clinical Orthopaedics and Related Research, 2003
Twenty retrieved Scorpio posterior-stabilized implants were available for analysis. The mean impl... more Twenty retrieved Scorpio posterior-stabilized implants were available for analysis. The mean implantation time was 22 months (range, 2 days-42 months). Favorable types and amounts of surface damage were seen on the tibiofemoral and backsides of these modular PE liners that had been packaged in an inert environment and then sterilized by gamma irradiation. Delamination represented only 0.1% of the total surface damage. Off-axis loading (varus malalignment) was associated with tibial component loosening but there was no evidence of peripheral damage of PE caused by edge loading. With this open-box design, hyperextension marks on the anterior aspect of the posterior-stabilized post from femoral component impingement occurred in 11 of 20 cases and was related to sagittal component positioning: excess tibial slope or increased tibial slope combined with a flexed femoral component. Unique coarse abrasions occurred in 16 of 20 cases and were the result of cement extrusion into the open box, especially with varus malalignment. These observations provide guidance for optimizing the surgical technique and the design of posterior-stabilized total knee components.
Clinical Orthopaedics and Related Research, 2002
In this literature review, 30 reports provided outcome data on 37 direct exchange arthroplasties,... more In this literature review, 30 reports provided outcome data on 37 direct exchange arthroplasties, 530 open debridements, and 23 arthroscopic debridements. The average followup was approximately 4 years, but the range was broad (range, 0.02-14 years). Infection was controlled in 33 of the 37 infected total knee arthroplasties (89.2%) treated by direct exchange arthroplasty, in only 173 of the 530 infected total knee arthroplasties (32.6%) treated by open debridement and retention of the prosthetic components, and in 12 of the 23 infected total knee arthroplasties (52.2%) treated by arthroscopic debridement. There was wide variability in associated antibiotic therapy. Factors associated with successful direct exchange included infections by gram-positive organisms, absence of sinus formation, use of antibiotic-impregnated bone cement for the new prosthesis, and 12 weeks of antibiotic therapy. Direct exchange arthroplasty failed in four of 37 knees; two were in patients with rheumatoid arthritis who were taking corticosteroids. Factors associated with successful debridements included those done within 4 months of the index procedure, or in patients with less than 4 weeks of symptoms, antibiotic sensitive gram-positive organisms, well-fixed components with no radiologic evidence of osteitis, and in young healthy patients. Factors associated with the failed debridements included postoperative drainage for more than 2 weeks, sinus tracts present at the time of the debridement, a hinged prosthesis, and an immunocompromised host. Direct exchange can be successful with a sensitive organism in a healthy host with prolonged antibiotic therapy. Debridement can be successful in early infections in a healthy host.
Journal of Arthroplasty, 1995
A prospective study of the relation between nerve palsy and the surgical approach used for total ... more A prospective study of the relation between nerve palsy and the surgical approach used for total hip arthroplasty was performed on 1,000 consecutive patients. A postoperative neuropathy was diagnosed in eight patients for an overall prevalence of 0.8%. The overall prevalence of nerve palsy with the posterior approach was 0.6% and 1.0% with the lateral transtrochanteric approach. In both primary
Journal of Arthroplasty, 2004
Journal of Orthopaedic Research, 2000
The weight of patients has not been demonstrated to have a consistent effect on the rate of polye... more The weight of patients has not been demonstrated to have a consistent effect on the rate of polyethylene wear in clinical studies of total joint replacement. For this reason, we analyzed the relationship between quantitative activity, measured with a pedometer, and body mass index, a measure of obesity. Data were acquired for 209 individuals, 22-82 years of age; all were independent community walkers. One hundred and fifty-one had a well functioning total hip or knee replacement. Analysis of variance was used to evaluate the relationship between activity and body mass index, with adjustments for confounding variables. The 58 individuals with no total joint prosthesis averaged 7,781 steps per day, which was higher (p < 0.01) than those with a total hip (5,869 steps per day) or knee (4,597 steps per day) replacement. The subjects with no total joint prosthesis were, however, younger than the patients with a prosthesis (p < 0.01), and the body mass index of the patients with a total knee replacement was higher than that of the patients with a hip replacement and that of the subjects with no prosthesis (p < 0.01). After adjustment for differences in age, gender, and Charnley class, a higher body mass index (greater obesity) was associated with lower activity (p = 0.05). With regard to the rate of polyethylene wear, decreased ambulatory activity may counterbalance increased weight, which could, at least in part, explain why weight has not had a consistent effect on polyethylene wear in clinical studies. Wear is a function of use, not time. The effect of obesity on activity should be considered in radiographic studies of wear and other outcome assessments of total joint replacements.
Journal of Orthopaedic Research, 2007
The resurgence of metal-metal bearings has renewed interest in hip resurfacing, but a paucity of ... more The resurgence of metal-metal bearings has renewed interest in hip resurfacing, but a paucity of information exists regarding femoral cementing technique. We developed a laboratory model in which 72 open-cell foam specimens were used to simulate bone. Analyses of two cement viscosities, two foam porosities, and six cementing techniques were performed: manual cement application only, manual application and filling of one quarter of the component with cement, filling of half of the component, manual application and half component filling, full component filling, and manual application and full component filling. For manual application, cement was pressurized into the foam by rolling the finger tips. For component filling, a defined quantity of cement was poured into the component before pressing it onto the foam. Specimens were cut into quarters, and cement penetration was quantified in seven areas: top, chamfer, wall, interior area, and proximal, medial, and distal stem. The manual technique showed a 3-mm thick, even cement penetration of the outer fixation surface (top = 26 +/- 0 mm(2), chamfer = 14.9 +/- 0.2 mm(2), wall = 55.6 +/- 5.2 mm(2)). None of the other techniques showed a significantly higher penetration in these areas. Large differences were found between all techniques at the medial stem (27.7 +/- 17.5 mm(2), p < 0.001) and the interior area (128.5 +/- 69.6 mm(2), p = 0.013). An increasing degree of penetration occurred from manual cement application to manual application and full component filling. Sixteen specimens showed incomplete seating, which occurred with all techniques except the manual technique. The manual technique consistently gave an approximately 3-mm thick even cement penetration over the outer fixation area. Pouring any cement into the shell resulted in variable degrees of deeper penetration and a risk of incomplete seating, which have been associated with bone necrosis and early fracture.
Journal of Biomedical Materials Research, 1995
Journal of Biomedical Materials Research, 1994
... Pat Campbell,lz~* Sophia Ma: Thomas S~hmalzried?~ and Harlan C. Amstutz' 'The Bioma... more ... Pat Campbell,lz~* Sophia Ma: Thomas S~hmalzried?~ and Harlan C. Amstutz' 'The Biomaterials Group, Department of Handicap Research, Universit o Gothenburg, Sweden; 2Joint Replacement Institute of Orthopaedic Hospital ... 28, 523-526 (1994) 0 1994 John Wiley & Sons, Inc ...
Journal of Biomedical Materials Research, 1997
Periprosthetic tissue was obtained at revision surgery from 10 posterior cruciate retaining total... more Periprosthetic tissue was obtained at revision surgery from 10 posterior cruciate retaining total knee replacement cases (five different manufacturers). The tissues were hydrolyzed and polyethylene particles were isolated from each case. Individual particles were analyzed by scanning electron microscopy combined with computerized image analysis. For comparison, periprosthetic tissues from 10 total hip replacement cases (six different manufacturers) were processed and analyzed simultaneously with identical methods. The morphologies of the isolated polyethylene particles from total knee specimens were distinctly different. There was more variety of size, shape, and texture in the total knee particles. Submicron granules were less prevalent than in hip specimens. Larger flake-shaped particles, some measuring several microns in length and width, were commonly seen in knee specimens but not hip specimens. The overall average area of particles from the total knees (1.2 microns2) was twice that of total hips (0.61 micron2) (p = 0.049). The average perimeter (p = 0.026) and length (p = 0.026) of total knee particles was also greater than the total hip particles. The proportion of the smallest polyethylene particles (those averaging 0.2 micron2) in the total knee specimens was significantly less than that in total hip specimens (p < 0.0001). Although the large flake-shaped particles were visually striking, it is important to note that the majority of the wear particles from the total knee cases were also submicron. These differences in wear particle morphology and size are due to differences in the wear mechanisms of total knees and total hips. Size is only one parameter in wear particle bioreactivity. Other factors include particle shape, surface area, and possibly size/shape variability, as well as surface chemistry and particle concentration. Polyethylene wear particles are not unidimensional; they have complex and variable shapes. The combination of morphologic description and quantitative image analysis used in this study defines several differences in polyethylene wear particles from different sources.
The Journal of Arthroplasty, 2002
The effect of total knee arthroplasty design on extensor mechanism function was evaluated prospec... more The effect of total knee arthroplasty design on extensor mechanism function was evaluated prospectively in a consecutive, single-surgeon series. Group 1 knees (n = 83) were implanted with a prosthesis that has a multiradius femoral component, and group 2 knees (n = 101) were implanted with a femoral prosthesis that has a single flexion-extension axis. Group 2 knees gained flexion more rapidly: At 6 weeks, the average flexion for was 94.5 degrees for group 1 and 107.1 degrees for group 2 (P<.001). Significantly more patients with group 2 knees were able to arise from a 16-inch (low) chair without using their arms starting at 6 weeks, and a difference was maintained through 2 years (90% vs 73%; P=.003). Patients with group 2 knees had significantly less anterior knee pain when rising from a seated position starting at 6 weeks, and a difference was maintained through 2 years (1% vs 22%; P=.001).
The Journal of Arthroplasty, 2002
A two-dimensional accelerometer worn on the ankle (step activity monitor [SAM]; Prosthetic Resear... more A two-dimensional accelerometer worn on the ankle (step activity monitor [SAM]; Prosthetic Research Study, Seattle, WA) has been proved to be highly accurate for assessing walking activity. The walking activity of 33 patients with well-functioning total hip arthroplasties was measured continuously during daily life, simultaneously with a pedometer and a SAM. The SAM recorded an average of 1.9 million cycles/y. The pedometer under-recorded an average of 34% cycles per day compared with the SAM (P=.0007), but the 2 measures were highly correlated (r=0.66; P=.001). No difference was seen in the number of gait cycles per day between men and women. The previously reported difference in average walking activity between men and women is due to greater under-recording of the pedometer in women, especially those with a body mass index > or =27. The pedometer is more reliable in quantifying the walking activity of men, less obese women, and patients with >1 million gait cycles/y.
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Papers by Thomas Schmalzried