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Biomedical subjects

M B Coventry

Publications and source records attributed to M B Coventry.

At least 19 recordsLinked to original sources
PubMed1992

Lessons learned in 30 years of total hip arthroplasty.

Lessons learned in 30 years of total hip arthroplasty (THA) include the following: Know and understand the evolution of hip arthroplasty. Selection of the prosthesis must be carefully made from sound clinical and scientific data. Before embarking on a prosthesis program, establish an immediate and a prospective protocol for the operation during the neosurgical period and for an indefinite long-term follow-up period. Establish a data bank for easy and complete retrieval of all pertinent material. Be familiar with the basic biomechanical principles of load and stress about the hip. Learn to use polymethylmethacrylate properly. The author's studies, and others, have shown that with newer, improved methods, results are excellent. Do not accept biologic (ingrowth) fixation as the ultimate aim in THA. Many problems are emerging with biologic fixation. Be wary of the complications in THA that relate to technique as well as design and even patient selection. Loosening, infection, continued pain, ion absorption, stress shielding, possible malignancy, and foreign body reaction are all complications that must be addressed. A surgeon should never lose the ability to review his or her own experience with unbiased, objective scrutiny.

Clinical Protocols↗
PubMed1990

Normal axial alignment of the lower extremity and load-bearing distribution at the knee.

Based on a series of 120 normal subjects of different gender and age, the geometry of the knee joint was analyzed using a full-length weight-bearing roentgenogram of the lower extremity. A special computer program based on the theory of a rigid body spring model was applied to calculate the important anatomic and biomechanical factors of the knee joint. The tibiofemoral mechanical angle was 1.2 degrees varus. Hence, it is difficult to rationalize the 3 degree varus placement of the tibial component in total knee arthroplasty suggested by some authors. The distal femoral anatomic valgus (measured from the lower one-half of the femur) was 4.2 degrees in reference to its mechanical axis. This angle became 4.9 degrees when the full-length femoral anatomic axis was used. When simulating a one-legged weight-bearing stance by shifting the upper-body gravity closer to the knee joint, 75% of the knee joint load passed through the medial tibial plateau. The knee joint-line obliquity was more varus in male subjects. The female subjects had a higher peak joint pressure and a greater patello-tibial Q angle. Age had little effect on the factors relating to axial alignment of the lower extremity and load transmission through the knee joint.

Adult↗
PubMed1989

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)

Activities of Daily Living↗
PubMed1989

Wedge resection of the symphysis pubis for the treatment of osteitis pubis.

Ten patients had a wedge resection of the symphysis pubis for the treatment of symptoms of osteitis pubis that had been recalcitrant to non-operative treatment for at least six months. Preoperatively, the average duration of symptoms was thirty-two months. The symptoms included a waddling gait and crepitus, pain, and tenderness over the symphysis pubis. The early radiographic signs of the disease were rarefaction of the adjacent pubic bones and widening of the symphysis pubis. Later signs included sclerosis and narrowing of the symphyseal joint space. Pathological examination of the resected joint revealed chronic inflammatory reaction in all patients. At an average of fourteen months postoperatively, all of the patients had marked improvement and were fully active. However, at an average of ninety-two months postoperatively, three of the ten patients were not satisfied with the result. One patient needed bilateral sacro-iliac arthrodesis for pain that was caused by instability.

Adult↗
PubMed1988

Proximal tibial osteotomy.

The indications for proximal tibial osteotomy are disabling osteoarthritis that must be mostly unicompartmental, minimal bone loss, and good stability. In the 60s we saw the development of osteotomy and in the 70s we saw the development of total knee replacement. These days we're seeing the two operations being put in proper perspective. At the moment we do about 100 upper tibial osteotomies a year and close to 800 knee replacements, either unicompartmental or bicompartmental. We have had 30 years of experience with proximal tibial osteotomy, and we know it relieves pain while preserving bone stock and not involving any intra-articular foreign bodies. Only time and long-term follow-up will tell us whether our 1 to 8 ratio should change in the future.

Biomechanical Phenomena↗
PubMed1988

Ten-year evaluation of geometric total knee arthroplasty.

One hundred ninety-three geometric total knee arthroplasties (TKA) were performed between 1972 and 1975 in 129 patients (66 women, 63 men; mean age, 69 years) with osteoarthritis. Of these, 102 knees were followed for a mean of 11 years. Eighty-three percent of the patients had mild or no pain. The revision rate was 20%, and the surgical complication rate was 12%. By actuarial analysis, the probability of retaining a geometric prosthesis at 10 years was 78%. With revision or moderate to severe pain as the end point, the predicted implant survival was 69% at 10 years. Lucent lines greater than 1 mm were present in 38% of the knees and progressed in 34%; they were more frequent in knees with greater than or equal to 3 degrees of varus axial alignment (p less than 0.05) or greater than or equal to 4 degrees of varus placement of the tibial component (p less than 0.05). The geometric prosthesis has provided a functional result in 69% of knees at 10 years, despite being the first two-part component knee replacement retaining the cruciate ligaments and using early surgical instrumentation and implant design.

Aged↗
PubMed1988

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.

Adult↗
PubMed1987

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.

Acetabulum↗
PubMed1987

Proximal tibial varus osteotomy for osteoarthritis of the lateral compartment of the knee.

From 1960 through 1979, a closing-wedge varus osteotomy of the proximal part of the tibia was performed in thirty-one knees (twenty-eight patients) for painful osteoarthritis of the lateral compartment of the knee that was associated with a valgus deformity. The patients were followed for two to seventeen years (average, 9.4 years). Twenty-four knees (77 per cent) had either no pain or only occasional mild pain at the last evaluation. Six knees had moderate pain and one, severe pain. Six knees required a subsequent total knee arthroplasty at an average of 9.8 years after the osteotomy. No patient had an infection or non-union. Osteotomy of the proximal part of the tibia is a reasonable method of treating unicompartmental degenerative arthritis in a knee with a valgus deformity. Although some patients with as much as 20 degrees of anatomical valgus deformity obtained a good result in this series, osteotomy in the supracondylar region of the femur is probably preferable if the valgus angulation exceeds 12 degrees or if the tilt of the tibial articular surface that will result from the surgery will exceed 10 degrees. Correction beyond the normal 5 to 7 degrees of valgus angulation to zero degree of anatomical tibiofemoral alignment is recommended to prevent recurrence of the valgus deformity and to decrease the load on the lateral tibiofemoral compartment.

Adult↗
PubMed1985

Late dislocations in patients with Charnley total hip arthroplasty.

I analyzed the cases of thirty-two patients in whom a Charnley total hip arthroplasty had dislocated for the first time between five and ten years postoperatively. I evaluated the possible factors that caused the late dislocations. Most of the factors were similar to those that were also present in a control group of patients who had had an arthroplasty that had not dislocated and in a group in which dislocation had occurred at variable times postoperatively. Two significant factors did emerge. First, the patients with late dislocation had a greater range of motion, especially in flexion, than those in the two control groups. Second, the acetabular component showed radiographic evidence of loosening in more of the patients in the group with late dislocation than in either of the control groups. I postulated, but did not prove, that stretching of the pseudocapsule of the hip over time and extremes of motion may lessen soft-tissue constraints and allow for late dislocation.

Adult↗
PubMed1979

Arthrodesis of the knee following failed total knee arthroplasty.

In forty-five patients, who had an arthrodesis because of failed total knee arthroplasty, the cause was infection in forty, instability in two, failure of the prosthesis in two, and loosening in one. The arthrodesis succeeded in twenty-nine (81%) of thirty-six patients who had had a minimally or partially constrained arthroplasty and in five (56%) of nine who had had a hinge-type prosthesis inserted. The reasons for failure were severe bone loss, persistent sepsis, and loss of bone apposition after manipulation. The technique of arthrodesis did not seem to influence the final result. External fixation most commonly had to be used because of the infections and the device was kept in place for an average of ten weeks, after which immobilization in a cast was used until the arthrodesis healed.

Adult↗