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Biomedical subjects

D G Lewallen

Publications and source records attributed to D G Lewallen.

At least 37 records · Page 2Linked to original sources
PubMed1996

The effect of superior placement of the acetabular component on the rate of loosening after total hip arthroplasty.

A method for measurement of the true acetabular region and the approximate femoral head center as well as a classification consisting of four zones for assessment of the acetabular position of the acetabular cup were used to analyze the results of primary total hip arthroplasty with cement in 117 patients (145 hips). All patients had Crowe type-II congenital dysplasia of the hip. The mean age at the time of the arthroplasty was fifty-one years (range, fifteen to seventy-six years), and the mean duration of follow-up was fourteen years (range, two to twenty-two years). The initial position of the acetabular cup outside of the true acetabular region and outside of zone 1 (inferior and medial) was associated with an increase in the rates of loosening (p < 0.05) and revision (p < 0.04) of the femoral components. Cups that initially were more than fifteen millimeters superior to the approximate femoral head center, without lateral displacement, were associated with an increased rate of loosening (p < 0.001) and of revision (p < 0.04) of the femoral components as well as with an increased rate of loosening (p < 0.002) and of revision (p < 0.01) of the acetabular components. These findings suggest that superior positioning of the acetabular component, even without lateral displacement, leads to increased rates of loosening of the femoral and acetabular components. An attempt should be made to position the acetabular component in or near the true acetabular region.

Acetabulum↗
PubMed1996

Periprosthetic fracture of the acetabulum after total hip arthroplasty.

Eleven patients who had sustained a periprosthetic fracture of the acetabulum at a mean of 6.2 years (range, one month to thirteen years) after a total hip arthroplasty were managed at our institution between 1985 and 1991. Five patients had a fracture of the medial wall; three, a fracture of the posterior column; two, a transverse fracture; and one, a fracture of the anterior column. Six fractures were displaced by two millimeters or more. Eight fractures were caused by blunt trauma or a fall, and three occurred spontaneously. A fracture was classified as type 1 if the acetabular component was clinically and radiographically stable (eight patients) and as type 2 if the component was unstable (three patients). One patient, who had a displaced type-2 fracture of the posterior column, died of an associated intrapelvic vascular injury. The other two patients who had a type-2 fracture were managed with revision of the acetabular component without supplemental plate fixation, immediately after the diagnosis of the fracture. The eight patients who had a type-1 fracture initially were managed with limitation of weight-bearing or modification of activity; in six of these patients, the fracture united without additional treatment. The ten surviving patients were followed for a mean of sixty-two months after the fracture. Eight of these patients-including four in whom a type-1 fracture had united after non-operative treatment-had a revision of the acetabular component because of pain, loosening, or non-union by the time of the most recent follow-up. Two patients (one of whom had a type-1 fracture and the other, a type-2 fracture) had multiple revisions of the acetabular component; both had supplemental internal fixation with a plate. All ten patients ultimately had a stable, functioning prosthesis. We conclude that periprosthetic acetabular fractures are associated with a poor prognosis with regard to the survival of the acetabular component but that it is possible to achieve union and to salvage a functional prosthesis in patients who have sustained such a fracture.

Acetabulum↗
PubMed1996

Hybrid primary total hip arthroplasty: a 5- to 9-year followup study.

One hundred fifty-two hips were reviewed at a minimum of 5 years after hybrid primary total hip arthroplasty using uncemented porous coated acetabular components and cemented femoral stems to determine the intermediate term durability of this method of fixation. Five hips (3.6%) have been revised: 1 for dislocation (0.7%), 1 for cup loosening (0.7%), and 3 for femoral loosening (2.2%). Clinical results proved to be extremely reliable in this series with 78% of the patients reporting no pain and 19.7% reporting slight or occasional pain. Radiographic evidence of polyethylene wear was evident in more than 1/2 of cups, but significant osteolysis or component loosening was not commonly seen on the cup side. On the femoral side incomplete radiolucencies were present in 31%, and focal osteolysis in 12.2%, nearly always proximally in Zones 1 and 7. These intermediate term results compare favorably on the femoral side and very favorably on the acetabular side to prior reported series. These results support the continued use of this combination of fixation methods for primary arthroplasty, but polyethylene wear and its effects remain a concern regarding the long term performance of these arthroplasties.

Adult↗
PubMed1995

Thermal response and torque resistance of five cortical half-pins under simulated insertion technique.

A model was developed that can quantitate heat generation during placement of half-pins in cortical bone. Five half-pins were tested to assess differences in insertion torque, heat generation, and micro-damage at the pin-bone interface. Thin thermocouple probes were placed 0.5 mm from the track of the pin and within the pin to measure its temperature during insertion. Scanning electron microscopy was used to view the pin-bone interface to assess the microdamage during placement. The design of the tip of the pin influenced insertion torque and heat generation. Higher heat generation was measured when a thermocouple was placed within the pin itself and less was measured when thermocouple probes were placed within bone samples 0.5 mm from the impending pin track. Furthermore, insertion torque and thermal responses were related, but there were no significant differences in microdamage to bone when different pins and drilling/tapping techniques were used. Due to the significant heat generation at the pin-bone interface, proper cooling with saline irrigation should be applied during pin insertion regardless of the design of the pin. The microdamage observed at the surface of the pin track may have significant implications with regard to loosening of pins, but such effects must be studied with in vivo models.

Animals↗
PubMed1995

Age-related hip fractures in men: clinical spectrum and short-term outcomes.

Clinical spectrum, treatment and short-term outcomes were assessed among the 131 Rochester, Minnesota, men who contracted an initial hip fracture due to moderate trauma during 1978-89. Three-fourths of falls leading to hip fracture occurred indoors with little seasonality, and 91% of fractures were in men 65 years of age or older. The ratio of cervical to intertrochanteric femur fractures was 1.4:1, and there was a tendency toward more neurological conditions among the patients with cervical fractures. Hemiarthroplasty and total hip replacement were mostly performed for cervical fractures, while internal fixation was preferred for intertrochanteric fractures. In-hospital mortality was 11.5%, and the 30-day case fatality rate was 16.0%. Age and postoperative deterioration of mental status significantly increased the risk of early death, the latter even after adjustment in a multivariate model, while comorbidity had a suggestive but not statistically significant influence on mortality. More than half the men were discharged to nursing homes, and 79% of the patients who survived at 1 year resided in nursing homes or intermediate care facilities or were attended by home care. Only 41% of survivors recovered their prefracture level of functioning and nearly 60% of patients limped and required a cane or walker. After implementation of the prospective payment system in 1984, the length of hospital stay was reduced, but there was no change in early mortality rates, in the duration of physical therapy following fracture or in attendance at nursing homes. The results of this population-based study demonstrate the strong impact of hip fractures on short-term outcomes in men.

Accidental Falls↗
PubMed1995

Survivorship of uncemented proximally porous-coated femoral components.

Three hundred seventy-five consecutive total hip arthroplasty revisions done using proximally porous-coated femoral components of 6 designs were reviewed a mean of 4.7 years after surgery. Fifty-nine hips have been rerevised for aseptic femoral loosening, and 4 for osteolysis. Moderate or severe pain was present in 23% of surviving hips, and radiographic evidence of femoral loosening was present in 38% of surviving hips at the most recent followup. At 8 years, survivorship free of revision for aseptic femoral failure (for loosening or osteolysis) was 58% (95% confidence intervals, 44.3%, 69.6%); survivorship free of aseptic femoral loosening (revision for aseptic loosening or radiographic loosening) was 20% (95% confidence intervals, 12%, 27%); and survivorship free of symptomatic femoral loosening (revision for aseptic loosening or radiographic femoral loosening with moderate or severe pain) was 45% (95% confidence intervals, 32.3%, 56%). More severe preoperative bone loss correlated with poorer survivorship free of aseptic loosening and subsidence of > or = 5 mm. Differences among the prosthetic-type groups with respect to patient's age, gender, and bone loss severity precluded direct comparison of performance for each prosthetic type; however, all the prostheses had a significant rate of rerevision and aseptic loosening. Stable long-term fixation with the proximally porous-coated femoral components used in this series was not achieved on a predictable and reproducible basis. The damaged, weakened bone often present in the proximal femur during revision probably does not provide an optimal environment for sturdy initial or long-term biologic fixation of these devices that rely on the proximal femoral bone for fixation.

Adult↗
PubMed1995

Acetabular reconstruction using bipolar endoprosthesis and bone grafting in patients with severe bone deficiency.

Eighty-one patients who had hip reconstruction with bone grafting and bipolar endoprosthesis for severe acetabular deficiency were reviewed retrospectively at 3 to 8 years postoperatively. Failed total hip arthroplasty was the most common indication for operation. Bone grafts were fixed bone blocks, morselized cancellous bone, and wafer-type grafts used singly or in combination. The average Harris hip rating score was 49.9 points preoperatively, 81.4 points at 1 year, and 70.8 points at latest followup examination. The 35 unsuccessful procedures included 25 reoperations for implant removal (resection arthroplasty or revision) and 10 cases pending revision. At latest followup examination, 54.7% of patients considered themselves improved and 62.7% had no or mild pain. Eighty-five percent of cases had radiographic evidence of component migration that was superior and medial in direction. Overall probability of implant survival was 96% at 1 year, but only 47% at 6.5 years postoperatively. Because of the high failure rate, this procedure has a limited role in hip reconstruction, but may be a reasonable part of a staged reconstruction for patients with massive bone loss or in certain revision cases where instability is a concern.

Acetabulum↗
PubMed1995

Heterotopic ossification following total hip arthroplasty.

Although heterotopic ossification following total hip arthroplasty is frequently observed radiographically, it fortunately is much less commonly of clinical importance. There are, however, a group of patients that develop significant heterotopic bone formation, which can be symptomatic and, in some cases, can require repeat surgery. Careful surgical technique seems indicated in all patients undergoing total hip arthroplasty to try to reduce the incidence of this problem. Patients who are recognized to be at risk should be treated with prophylaxis. These include patients with active ankylosing spondylitis, skeletal hyperostosis, and prior heterotopic bone formation. Both low-dose radiation and nonsteroidal anti-inflammatories have been shown to be effective. The choice between these two modalities depends on the patient's individual circumstances, the availability of radiotherapy support (including custom shielding for ingrowth components), and the presence of areas of bone grafting and any osteotomies or fractures. Nonsteroidal anti-inflammatories, particularly Indomethacin, are a very acceptable form of prophylaxis and may be preferred in certain patients, including young women of childbearing age. Radiation is preferred in those patients with known GI intolerance to these medications or with a prior history of peptic ulcer disease. Excision of heterotopic bone, if symptomatic, should not be performed before 6 to 12 months and then only once it is clear that the process is mature. Bone scans can be helpful in assessing the maturity of heterotopic bone and can guide the timing of excision. Prophylaxis should be carried out in all patients following excision of heterotopic bone.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1994

Lack of evidence for gender bias in the utilization of total hip arthroplasty among Olmsted County, Minnesota residents with osteoarthritis.

OBJECTIVE: To evaluate whether women have more advanced osteoarthritis (OA) than men prior to total hip arthroplasty (THA). METHODS: Preoperative clinical and radiographic severity of hip OA was determined among Olmsted County, Minnesota residents who underwent THA. The time from first radiographic changes and first symptoms to THA was compared between genders. RESULTS: Fifty men and 80 women underwent their first THA between 1985 and 1990. Men had higher disease activity levels preoperatively; however, 16 other clinical severity variables and 2 summary measures of OA severity were similar for both genders. Men had radiographically more advanced hip OA preoperatively. The time from first symptom of hip OA to THA was similar for both genders, while the time from first radiographic change to THA was significantly longer for men. CONCLUSION: These results fail to support the hypothesis that hip OA prior to THA is more severe among women compared with men.

Bias↗
PubMed1994

Low intensity ultrasound treatment increases strength in a rat femoral fracture model.

Bilateral closed femoral shaft fractures were made in 22 male Long-Evans rats. In 16 animals, ultrasound was applied to one limb for 15 minutes daily 10 times within the first 14 postoperative days. The treated limbs received a 200 microseconds burst of 1.5 or 0.5 MHz sine waves repeated at 1.0 kHz at a spatial average and temporal average intensity of 30 mW/cm2. The contralateral limb of each animal served as a nontreated control. Six remaining animals with fractures and six additional animals without fractures received sham ultrasound treatment to control for the effects of anesthesia and handling. Fracture repair was evaluated on postoperative day 21 by radiography, mechanical testing in torsion, and histology. Five of 16 ultrasound-treated fractures showed obliteration of the fracture gap on radiographs, whereas none of the 28 controls did. The average maximum torque of fractures treated with either signal was 22% greater than that of the contralateral controls (p < 0.05). The stiffness of treated fractures was greater than that of control fractures, but the difference was significant only in animals treated with the 1.5 MHz signal (p < 0.02). Sham treatment did not affect repair in the control group. These results indicate that low-intensity pulsed ultrasound at either 0.5 or 1.5 MHz can accelerate fracture repair at 21 days in this highly controlled model.

Animals↗
PubMed1994

Pull-out strength of screws from polymethylmethacrylate cement.

We aimed to determine the optimal method of inserting a screw into polymethylmethacrylate (PMMA) cement to enhance fixation. We performed six groups of ten axial pull-out tests with two sizes of screw (3.5 and 4.5 mm AO cortical) and three methods of insertion. Screws were placed into 'fluid' PMMA, into 'solid' PMMA by drilling and tapping, or into 'curing' PMMA with quarter-revolution turns every 30 seconds until the PMMA had hardened. After full hardening, we measured the maximum load to failure for each screw-PMMA construct. We found no significant difference in the pull-out strengths between screw sizes or between screws placed in fluid or solid PMMA. Screws placed in curing PMMA were significantly weaker: the relative strengths of solid, fluid and curing groups were 100%, 97% and 71%, respectively. We recommend the use of either solid or fluid insertion according to the circumstances and the preference of the surgeon.

Biomechanical Phenomena↗
PubMed1994

Long-term follow-up of forearm bone diaphyseal plating.

A retrospective review of 175 patients treated with forearm bone plating for acute diaphyseal fractures, nonunions, and malunions was undertaken to identify problems related to plate removal as opposed to plate retention. One hundred thirteen patients retained their forearm plates, of which five patients experienced complications related to the plate, including infection, bone failure, plate failure, and loosening. Patients retaining forearm bone plates reported minimal discomfort or functional limitation. Sixty-two patients had plate removal at an average of 19 months after insertion. Ten patients suffered major complication, including seven refractures through screw holes, osteotomy, or original fracture sites. Fractures occurred at an average of six months after plate removal. The difference in complication rates between patients treated with plate removal and patients retaining plates was statistically significant.

Acute Disease↗
PubMed1993

Trends in the utilization of primary total hip arthroplasty, 1969 through 1990: a population-based study in Olmsted County, Minnesota.

Using the unique data resources of the Rochester Epidemiology Project, we identified the residents of Olmsted County, Minnesota, who underwent total hip arthroplasty (THA) between 1969, when this technique was introduced, and 1990. During this period, 735 residents underwent 859 primary THAs. An initial dramatic upsurge in utilization of THA soon after its introduction was followed by a lower rate of increase, to an age- and sex-adjusted rate of 59.9 per 100,000 person-years in 1987 through 1990. In Olmsted County, the procedure was used more often in women than in men, but men underwent THA at a younger age than did women. THAs were performed for various conditions of the hip, but the increased utilization during the last decade of the study was mainly attributable to its application in primary degenerative hip disease among patients (male more often than female) from a wider age range; utilization of THA for hip fractures decreased during the study period. Most THAs were of the cemented variety (86.1%); however, the rate of use of noncemented THAs, first performed in 1984, is increasing. The overall upward trend in Olmsted County was consistent with European data but less than the rate of increase observed for the United States as a whole between 1983 and 1987. Olmsted County utilization rates, if projected nationally, suggest a need for more than 139,000 primary THAs each year at an annual direct cost of more than $2.7 billion. An urgent need exists for detailed examination of national utilization patterns and clarification of the role of cementless implants and of THA for hip fractures.

Adult↗
PubMed1993

Biomechanics of pin and screw fixation of femoral neck fractures.

Using an in vitro cadaveric femoral neck osteotomy model and a paired experimental design, we compared fixation stiffness and yield load for three- and four-pin configurations for both Knowles pins and Asnis screws and for three Asnis screws versus an AO-ASIF sliding hip screw. Repeat measure analyses of variance indicated a significant increase in stiffness (p < 0.05) with the use of three versus four pins; the yield load did not depend significantly on the number of pins. Fixation was significantly stiffer (p < 0.01) and stronger (p = 0.02) for Knowles pins if the osteotomy was oblique rather than transverse to the femoral neck; the opposite was found for Asnis screws. Femoral fixed with hip screws were significantly stiffer (p < 0.01) than the contralateral side fixed with three Asnis screws. No significant difference in yield load was observed, however. Clinically, it appears from these findings that the use of three Asnis screws or three Knowles pins provides modest increases (averaging 4%) in fixation stiffness with no degradation in strength when compared with four screws or pins. Parallel placement of Asnis screws also provides advantages over nonparallel Knowles pins by allowing controlled impaction of the femoral head. While three Asnis screws provide fixation stiffness approximately 40% less than that found with a sliding hip screw, there is no compromise in fixation strength.

Aged↗
PubMed1993

Utilization of upper limb joint replacements during 1972-90: the Mayo Clinic experience.

Increasing application of expensive medical technologies, including joint replacement, is of concern in the current economic climate. Successful upper limb joint replacements (ULJRs) are being performed, but few detailed data about their utilization are available. To explore the resource implications of such surgery, the utilization of total shoulder replacement (TSR), total elbow replacement (TER) and total wrist replacement (TWR) were examined from the time these procedures first became available at the Mayo Clinic up to 1990. The age- and sex-adjusted utilization rate for TSR among Olmsted County, Minnesota, residents was 1.8 per 100,000 person-years (p-y), 0.8 per 100,000 p-y for TER and 1.1 per 100,000 p-y for TWR. Overall utilization of primary ULJR among Olmsted County residents during the 19-year study period was 3.8 per 100,000 p-y. The commonest indication for TSR was osteoarthritis (46 per cent) and for TER and TWR was rheumatoid arthritis (50 and 81 per cent respectively). There was no consistent trend in the utilization of these procedures among Olmsted County residents, but the number of referral patients receiving a ULJR at the Mayo Clinic increased steadily during the study period. The Mayo Clinic experience suggests an increasing demand for ULJR, particularly TSR and TER. With continued advances in, and diffusion of, the technology this demand may increase further.

Adult↗
PubMed1993

Urban vs rural increase in hip fracture incidence. Age and sex of 901 cases 1980-89 in Olmsted County, U.S.A.

To determine if hip fracture incidence rates are greater in urban than in rural areas of the United States, as they appear to be in Scandinavia, we undertook a study in Olmsted County, Minnesota. During the decade 1980-89, the age- and sex-adjusted incidence of proximal femur fractures among urban residents of the central city of Rochester was 36 percent greater than among residents of the rural remainder of Olmsted County. The difference was almost entirely accounted for by an excess of fractures due to moderate trauma in elderly urban women. These first detailed results from the United States confirm earlier observations from Scandinavia that hip fracture rates are lower in rural areas.

Adolescent↗
PubMed1992

Cemented versus noncemented total hip arthroplasty--embolism, hemodynamics, and intrapulmonary shunting.

Bone cement implantation syndrome is characterized by hypotension, hypoxemia, cardiac arrhythmias, cardiac arrest, or any combination of these complications. It may result from venous embolization that occurs in conjunction with intramedullary hypertension in the femur during insertion of the prosthesis in patients undergoing cemented total hip arthroplasty (THA). Intramedullary hypertension does not occur in patients undergoing noncemented THA. In this study, we sought to compare embolization between patients undergoing cemented and noncemented THA and to determine whether this state resulted in cardiorespiratory deterioration. In this prospective investigation of 35 patients undergoing elective THA, we used transesophageal echocardiography and invasive hemodynamic monitoring, and in 12 of them, we monitored distribution of pulmonary ventilation and perfusion intraoperatively. Embolization was significantly greater after insertion of the prosthesis in patients undergoing cemented than in those undergoing noncemented THA. Cemented THA was also associated with decreased cardiac output and increased pulmonary artery pressure and pulmonary vascular resistance. Increases in ventilation-perfusion mismatching, however, could not be demonstrated 30 minutes after insertion of the femoral prosthesis. Intraoperative monitoring for embolism may help physicians assess patients in whom cardiorespiratory function deteriorates during THA.

Aged↗