Roentgenographic and mechanical performance of centrifuged cement in a simulated total hip arthroplasty model.

Roentgenographic analysis showed that centrifugation significantly reduced the gross and regional porosity of the cement compared with hand-mixed controls in a simulated total hip arthroplasty model. Static failure test of the prosthetic system demonstrated that the centrifuged cement had significantly greater strength than the hand-mixed cement. Under low-cycle fatigue tests of the same composite models, there was a trend for the centrifuged cement to be stronger than the hand-mixed specimens, although statistically it was not significant. Thus, centrifugation can reduce porosity and significantly improve the static strength of cement in a simulated in vitro total hip replacement model. When cement is used, any possible improvement in the physical properties of bone cement should be considered.

The effect of centrifugation on the mechanical properties of cement. An in vitro total hip-arthroplasty model.

An in vitro total hip-arthroplasty model was evaluated to determine if centrifugation of bone cement results in greater static strength and low-cycle fatigue strength than hand-mixing. The static-failure test of the stem, cement, and simulated bone composite demonstrated that the centrifuged cement had significantly greater static strength than the hand-mixed cement. However, under low-cycle fatigue tests on the same composite models, the centrifuged and hand-mixed specimens were not significantly different.

Charnley total hip arthroplasty with cement. Fifteen-year results.

The results of the first 333 Charnley total hip arthroplasties that were performed with cement at the Mayo Clinic were reviewed a minimum of fifteen years postoperatively. Data were available for 166 of 170 hips of patients who were still alive. One hundred and thirty patients died, and thirty-seven hips were revised. At the time of this study, 80 per cent of the living patients had no pain, and 152 of the 160 hips remained much better than before the operation. Kaplan-Meier analysis of probable loosening of one or both components, on the basis of roentgenographic evidence, demonstrated a probability of loosening of 3 per cent incidence at one year after operation, 13 per cent at five years, 19 per cent at ten years, and 32 per cent at fifteen years. The probability of failure (that is, revision or symptomatic loosening) was 0.9 per cent at one year, 4.1 per cent at five years, 8.9 per cent at ten years, and 12.7 per cent at fifteen years. We did not identify a dramatic increase in the incidence of loosening or failure at any of the follow-up periods (one, five, ten, or fifteen years). With the Mayo Clinic clinical and roentgenographic system for scoring the hips, we found that ninety-seven hips had a good or excellent result; fifteen, a fair result; and thirteen, a poor result. (The scoring could not be completed for forty-one hips). The functional results deteriorated slightly over time.(ABSTRACT TRUNCATED AT 250 WORDS)

Cemented total hip arthroplasty with contemporary techniques. A five-year minimum follow-up study.

A retrospective clinical and roentgenographic review was performed on 251 consecutive cemented total hip arthroplasties (THA) performed from 1978 to 1980 that had been followed a minimum of five years (range, five to seven years). All arthroplasties involved the use of a Harris Design II femoral stem, an intramedullary plug, a cement gun, and pulsatile lavage of both the acetabulum and the femoral canal. At the final follow-up examination, 98% of the patients had excellent results. The average Harris hip score was 47 points preoperative and 97 points postoperative. There were three definitely loose femoral stems, one probably loose, and two possibly loose. There was one loose acetabular component, no revisions or operations were performed. When comparing this series with a similar study, there were statistically improved results in all parameters. Results from this study of cemented THAs using contemporary techniques and prosthetic stem design represent the standard for comparison when evaluating alternative THA systems.

Vertebral fractures without neurological deficit. A long-term follow-up study.

Twenty-five patients, who did not have osteoporosis and who were between the ages of seventeen and sixty years, were treated for one or more stable compression fractures of a vertebra with compaction of less than 50 per cent and without an associated neurological deficit. The patients were followed for a minimum of nine years. Associated vertebral fractures (12 per cent) were identified during the first three months after the injury, but no deformity progressed after three months. Radiographic changes of degenerative disc disease were evident in eight patients, but the changes did not correlate with symptoms or with level of activity. With one exception, all patients functioned as well as uninjured subjects of comparable age. Patients who have a compression fracture of a vertebra should have serial radiographs made for at least three months to ensure that all fractured vertebrae are identified and to document any progression of deformity.

Kinematic rotating-hinge total knee arthroplasty.

The first fifty kinematic rotating-hinge total knee arthroplasties that were done at the Mayo Clinic were reviewed. The indication for use of this prosthesis was either ligamentous instability or loss of bone, or both. At a mean length of follow-up of fifty months (range, twenty-nine to seventy-nine months), the clinical results of thirty-eight knees in thirty-six patients were evaluated. Fifteen of the thirty-eight knees had had a primary arthroplasty and twenty-three had had a revision arthroplasty using the kinematic rotating-hinge prosthesis. Using the knee-rating score of The Hospital for Special Surgery, there were fourteen excellent, twelve good, five fair, and five poor results. For two knees there was inadequate information to calculate a knee-rating score. Lucent lines that were more than one millimeter in width were seen with 25 per cent of the femoral and 50 per cent of the tibial components. Progression of lucent lines was observed in thirteen knees, and five knees showed probable radiographic loosening. The high incidence of complications was distressing, with a 16 per cent rate of sepsis, a 22 per cent rate of patellar instability, and a 6 per cent rate of breakage of the implant. In our opinion, this implant should be used only in knees in which there is functional absence of a collateral ligament that cannot be managed by soft-tissue reconstruction.

Fixed-head and bipolar hip endoprostheses. A retrospective clinical and roentgenographic study.

A retrospective review of 1,001 hip hemiarthroplasties was performed. The prosthetic designs were grouped into fixed-head types (682 cases) and bipolar types (319 cases) for comparison. The main indications for operation were femoral neck fracture and avascular necrosis of the femoral head. Clinical and roentgenographic data for different follow-up periods were compared between prosthetic types, using multivariate analysis. Roentgenographic loosening of the femoral component was noted in 25.4% of cases but was significantly higher (P less than .05) in the bipolar groups for a follow-up period less than 2 years, regardless of the method of fixation. The acetabular erosion rate was significantly higher (P less than .05) in the fixed head group, but this finding was related to length of follow-up period, bone porosity, and prosthesis/acetabulum fit. The reoperation rate, including revision to total hip arthroplasty, was higher in the fixed-head group (12.5%) than the bipolar group (7.2%). Based on Kaplan-Meier survivorship analysis, 13.7% of the bipolar and 22.9% of the fixed-head hip endoprostheses are expected to be reoperated 8 years after initial implantation. Cement fixation of the femoral component led to a higher prosthesis survival rate, regardless of type. Both prosthetic types are useful in hip surgery, but the bipolar type appears to be indicated in younger and more active patients, whereas the fixed-head design is more suitable for older patients with femoral neck fractures.

Functional evaluation of total knee replacement.

The assessment of patients following prosthetic knee replacement suffers from a lack of objective criteria. An automated method of laboratory assessment that permits the objective evaluation of knee joint function is described. Nine biomechanical parameters were statistically selected, weighted, and combined to develop a Performance Index (Ip). One hundred ninety-two patients (274 diseased knees) were studied prior to total knee replacement surgery, with 107 patients (138 knees) returning for a 1-year postoperative study. Preoperative rheumatoid knees were found to have significantly poorer function than those involved with degenerative disease. Overall, the patients experienced a marked improvement 1 year post-total knee replacement (TKR), with their functional scores approaching the lower limits of normal. Prostheses were assessed according to generic classes as well as specific design types. The newer generation devices were found to produce better functional results. In the patients receiving Anametric and Total Condylar total knee devices, a patellar resurfacing component was found to produce improved knee function in comparison with patients receiving the same prosthesis but without patellar resurfacing.

Normative data of knee joint motion and ground reaction forces in adult level walking.

A normative data base of temporal distance factors, knee joint motion and ground reaction force patterns for 148 adults during level walking is reported. The data were studied using parametric and non-parametric (Fourier series) representations to facilitate statistical analyses. Key parameters were divided according to age and sex. Individual force and motion curves of each normal subject were averaged to establish the 'typical' patterns. All typical patterns were combined to construct the 'general' patterns. The essential number and most significant Fourier coefficients were determined. It was found that the sex-related variation is more significant than the age-related variation in adult gait. This data base can serve as a common reference for comparison.

Rates of total hip arthroplasty; a population-based study.

Three hundred eighty-one total hip arthroplasties were performed on residents of Olmsted County, Minnesota, during the period from 1969 to 1980, for a rate (adjusted for sex and age) of 44.6 per 100,000 person-years. Rates rose with age, were higher for women than men, and were higher among urban than rural residents of the county. If we assume that the Olmsted County experience is medically optimal and apply it to the 1980 United States population, we calculate a national requirement of over 100,000 total hip arthroplasties per year, well above the current actual figure. If this calculated number of total hip arthroplasties were actually performed each year, over 1.4 million hospital days would be required, and direct medical costs would probably exceed $1 billion annually.

Salvage of painful total ankle arthroplasty.

Revision of painful total ankle arthroplasties with reinsertion of a prosthetic device has been unsatisfactory. After removal of the prosthetic components, generally, the remaining bony stock is insufficient to allow adequate fixation with methylmethacrylate. Revision with arthrodesis by the modified Chuinard compression technique has been successful. Ankle arthrodesis is the only available surgical alternative to prosthetic ankle arthroplasty. Consequently, should a total ankle arthroplasty fail, a reliable salvage procedure is available that leaves the patient with minor, if any, additional functional impairment compared to that with an ankle arthrodesis done initially.

Ten-year follow-up study of total hip replacement.

Of the first 300 consecutive patients who had a Charnley total hip replacement at the Mayo Clinic during the years 1960 to 1970, 207 (231 hips) were re-evaluated ten years postoperative by questionnaire and roentgenograms. Forty-three of these were also evaluated by personal examination. Roentgenographic loosening of the acetabular component was determined using the criterion of a complete radiolucent line more than one millimeter in width at the bone-cement interface or any migration or tilting of the component. For the femoral component, the criterion for loosening was a radiolucent line more than one millimeter wide at either the bone-cement or the cement-prosthesis interface, or any change in the position of the component. As previously reported, the incidence of loose components at five years was 6.5 per cent for the acetabular component and 24 per cent for the femoral component. At ten years the incidence of loosening had increased to 11.3 per cent for the acetabular component and 29.9 per cent for the femoral component. Therefore, between five and ten years postoperatively the rate of femoral loosening decreased, while the rate of acetabular loosening remained about the same. The overall-revision rate for loosening of total hip components increased from 3 per cent at five years to 7.4 per cent at ten years. Acetabular wear was not a significant problem. Resorption of the medial femoral cortex near the calcar was generally non-progressive and was not significantly related to loosening. two modes of loosening are suggested, the more common being cracking of the cement mantle due to circumferential (hoop) stresses within the cement. This series probably represents a so-called worst-case experience, since changes in design and materials as well as the improvements in surgical technique that have evolved over the past decade should provide significantly better long-term fixation.

Total ankle arthroplasty: four years' experience.

A review of 102 total ankle arthroplasties performed during a four-year period revealed that complications occurred in 41%. 22% with impingement of various types 6.9% with loosening and 2.9% with deep sepsis. The best results were obtained in patients with rheumatoid arthritis and those with posttraumatic osteoarthritis who were older than 60 years of age. Total ankle arthroplasty currently should not be considered in patients with posttraumatic osteoarthritis who are younger than 60 years old. Arthrodesis remains the only acceptable method of treatment in these individuals. Total ankle arthroplasty seems indicated in patients who have significant ankle joint disability secondary to rheumatoid arthritis and in elderly patients with disabling posttraumatic degeneration whose physical demands are limited.

Management of hip fractures by total hip arthroplasty.

One hundred and twelve patients ranging in age from 40 to 89 with acute intracapsular fractures of the hip were treated between the years 1970 to 1978 by total hip arthroplasty; 63% were subcapital, 27.6% were midcervical, and 8.9% were basilar; 53.5% were classified as Garden's Stage IV, 34.8% as Stage III and 11.6% as Stage II. A significant number of patients had associated medical conditions that made them poor risks for a possible second-stage operation. Moreover, 16 patients were considered for total hip arthroplasty because of associated hip disease. Of 85 patients evaluated after one year, 81.2% had no pain. Most patients maintained their previous levels of activity, but 13 were more active than before injury; 33 were worse. The decrease in activity was generally due to deterioration in associated medical conditions. Our experience indicates that total hip arthroplasty is best reserved for the previously active elderly patient with a displaced subcapital fracture who meets the criteria for prosthetic replacement.

Biomechanical gait evaluation of pre and postoperative total knee replacement patients.

Gait analysis based on the triaxial electrogoniometric method was carried out on a large group of normals and total knee replacement patients before and after surgery. Analysis of the objective gait variables was performed to compare the pre and postoperative results with that of the normals. Eight most significant gait variables were identified and from which two functional indices were calculated to provide an overall assessment of the reconstructive procedure based on disease type, side of involvement, and prosthetic design. It was found that total knee replacement provides significant functional improvement. Such improvement was more pronounced in certain patients, but its dependence on prosthetic type remained less conclusive. The results also suggested that there is a critical timing for surgery to obtain its maximum benefit. Knee function after joint replacement is a time-related phenomenon and, therefore, the patients must be followed beyond one-year postoperatively to provide more accurate assessment.

Limb fractures in a defined population. I. Frequency and distribution.

This population-based study revealed that 2,519 limb fractures occurring during a 3-year period produced an age-adjusted incidence rate for all limb fractures of 1,596 per 100,000 person-years. Fractures of the upper limb had a bimodal age distribution and were commoner than those of the lower limb, which had a J-shaped age distribution. The most frequent anatomic site was the lower end of the radius and ulna. Limb fractures occurred as solitary events in 93% of cases; only 4% were classified as open and more than half of the total were closed and undisplaced. Fractures were distributed evenly throughout all time periods of the day. The commonest place of fracture occurrence was the home, and the most important direct cause was falls, particularly in females. A wide range of sports activities were a major source of fractures, particularly in younger males. Underlying bone pathology was uncommon, other contributory causes being more important, particularly in the elderly. The increased ratio of metaphyseal to diaphyseal fractures with age indicated a relative loss of cancellous bone in the elderly, but no evidence was found to suggest that elderly women had reduced resistance of bone to impact forces in comparison with elderly men.

Limb fractures in a defined population. II. Orthopedic treatment and utilization of health care.

This study describes the orthopedic treatment and utilization of health care obtained by 2,333 patients in the population of Rochester, Minnesota, who suffered 2,519 limb fractures during the period 1969 through 1971. Overall, 24% of fracture occurrences required patient hospitalization, the remainder involving care on an ambulatory basis only. The mean number of physician visits was 4.5 per fracture, with the visits occurring during an interval of 103 days from the time of first evaluation. Fifteen percent of limb fractures were subject to at least one surgical operative procedure as part of their orthopedic treatment. The frequency of operative treatment increased markedly with patient age. Seventeen percent of patients with limb fractures received physiotherapy or occupational therapy or both, 4% were ambulatory patients, and the remainder were hospital inpatients. Fractures of the head and neck of the femur constituted only about 7% of fractures in the series, yet utilized an inordinate proportion of health care resources. Hip fractures were responsible for 27% of the hospital admissions, 52% of all bed days utilized, and 56% of the physiotherapy sessions.

Total joint arthroplasty. The ankle.

When conservative measures fail to relieve significant disability due to ankle joint disease, the only surgical method of treatment has been arthrodesis. Because of less than ideal results and other long-term problems with ankle arthrodesis, and after numerous investigation to characterize the ankle mechanically, we developed a prosthetic ankle joint replacement. The Mayo total ankle replacement is a metal-on-polyethylene, congruent, constrained prosthesis. Analysis of 94 patients (102 ankle prostheses) revealed good clinical results in patients with rheumatoid arthritis and in older persons with posttraumatic degenerative disease. Younger, more active patients in the latter category had more disappointing results. Further design development is under way to improve range-of-motion characteristics, decrease constraint forces, and improve bone fixation of the prosthetic components.

Total joint arthroplasty. The role of biomechanics.

The role of biomechanics is intricately involved in total joint replacement from its inception to its clinical use. By integrating knowledge of joint function and material properties, the artificial joint is designed and tested. After clinical use, the joint function is again studied and failure modes are defined. Biomechanics is the single most important discipline that can be employed to study the cause of failure in order to improve design and technique. This will increase the reliability of, and decrease the incidence of failure associated with, total joint replacement.