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Biomedical subjects

S D Stulberg

Publications and source records attributed to S D Stulberg.

At least 55 records · Page 3Linked to original sources
PubMed1991

Total hip replacement with cemented, uncemented, and hybrid prostheses. A comparison of clinical and radiographic results at two to four years.

One hundred and thirty-one patients who had 144 cemented or uncemented hip prostheses were followed prospectively for two to four years. A cemented or a hybrid prosthesis (consisting of a cemented femoral component and an uncemented acetabular component) was used in men older than seventy years, in women older than sixty years, and in younger patients in whom adequate initial fixation could not be obtained without cement. Uncemented, porous-surfaced implants were used in all other patients. The over-all clinical results were similar for the three groups. For the fifty-two hips that had a cemented prosthesis, the mean total Harris hip rating was 91 points and the score for pain, 42 points; for the twenty-seven hips that had a hybrid prosthesis, 90 and 43 points; and for the sixty-five hips that had an implant allowing ingrowth of bone in both the acetabulum and the femur, 95 and 43 points. Two prosthetic stems that were designed to allow ingrowth of bone had aseptic loosening; one was revised. Pain in the thigh, usually slight and not disabling, occurred at one year in 24 per cent of the patients in whom a femoral component allowing ingrowth had been used; the prevalence of pain then declined. The incidences of migration of the components and of radiolucent lines were greater in the acetabula that had a cemented component than in those that had a cup allowing ingrowth of bone.

Aged↗
PubMed1991

The arthroscopic evaluation and characteristics of severe polyethylene wear in total knee arthroplasty.

Four hundred eighty-seven porous-coated anatomic (PCA) total arthroplasties were performed by the same surgeon between January 1982 and December 1989. Forty-three patients developed an effusion, pain, or decreased range of motion after a period of pain-free function. Average time to onset of symptoms was 4.5 years. Joint fluid aspirations were sterile and revealed the presence of high-density polyethylene crystals, best seen under a polarizing microscope. Thirty-three of these patients were arthroscopically evaluated. Extensive polyethylene wear and delamination were identified. Wear was most extensive on the medial tibial plateau. Patellar polyethylene wear was also identified. Substantial femoral component abrasions were present in areas where exposure of the tibial and patellar base plates had occurred. Diffuse granulomatous synovial tissue revealed an extensive foreign-body giant-cell reaction to polyethylene particles. In all patients, temporary symptomatic relief was obtained after arthroscopy. Thirty-two patients have, subsequently, had revision surgery. Intraoperative findings and biopsies at the time of revision confirmed the arthroscopic observations. Arthroscopy allowed the accurate diagnosis of polyethylene wear, provided temporary symptomatic relief, and facilitated preoperative revision planning. Polyethylene wear in PCA total knee replacements was related to patient characteristics (larger, younger, more active patients), nonconforming femotibial articular surfaces, thin polyethylene, heat-pressed polyethylene, and nonrigid mechanical attachment of polyethylene to metal base plate. Younger, more active, larger patients with total knee arthroplasties should be observed closely for evidence of polyethylene wear.

Aged↗
PubMed1991

A new model to assess tibial fixation in knee arthroplasty. I. Histologic and roentgenographic results.

A model to assess tibial fixation in knee arthroplasty is described. Eighteen mongrel dogs were implanted with a right tibial hemiarthroplasty. Implantation was of a press-fit, smooth implant (eight dogs) or a titanium alloy beaded device (ten dogs). Animals were studied at six, 12, 18, and 24 weeks. Roentgenographic and histologic analysis was performed for all implants. All animals were ambulatory. Roentgenographically, smooth implants showed progressive radiolucencies with increasing trabecular sclerosis under the implants. These changes were less prominent under the porous implants. Histologically, fibrous interfaces were identified focally under all implants but were thicker under smooth devices. Eighteen- and 24-week specimens showed substantial ingrowth into the porous pegs but minimal ingrowth into the porous plateau. Concurrent histologic and biochemical evaluation in dogs demonstrates the possible fate of implants in knee arthroplasty in human beings. As has been observed, histologic analyses suggest that clinically satisfactory results do not constitute evidence of stabilization by bone ingrowth.

Animals↗
PubMed1991

A new model to assess tibial fixation. II. Concurrent histologic and biomechanical observations.

A tibial hemiarthroplasty model was designed to allow concurrent histologic and biomechanical analysis of the tibial implant-bone interface. In this study, micromotion was visually observed at the implant-bone interface of cemented and uncemented implants. Six dogs had staged bilateral implantation. Biomechanical analysis of three- and 12-month specimens was correlated with histologic analysis of the same specimen. Load transmission involved compression of trabecular bone and fibrous tissue at the interface. Failure of the interface occurred through cyclic fatigue and microfracture of trabeculae. Micromotion was seen at all interfaces, porous or smooth, cemented or uncemented. Displacement was greatest under an eccentrically loaded plateau. Micromotion at ingrown and cemented interfaces was because of trabecular compression. Uncemented smooth devices and uncemented porous devices with fibrous fixation of the plateau appeared unstable. The cemented implants and a single uncemented implant studied at 12 months showed no interface micromovement. The absence of micromovement in the uncemented implant was associated with subsidence and with ingrowth of 30% into the porous peg and porous plateau.

Animals↗
PubMed1990

Prerandomization: an alternative to classic randomization. The effects on recruitment in a controlled trial of arthroscopy for osteoarthrosis of the knee.

Possibly the greatest threat to the success of a randomized clinical trial is the inability to recruit an adequate number of subjects. Concern that the randomized clinical trial will adversely affect the physician-patient relationship is the most common reason for physicians' reluctance to enroll patients in such trials. We report a modification of a prerandomized design, first described by Zelen, which was implemented in a randomized clinical trial of arthroscopy for patients who had osteoarthrosis of the knee. The method was associated with a sixfold increase in the rate of accrual of patients as compared with the use of a classic randomization trial. We propose the design as a potential solution to the problem of recruitment of subjects, particularly for clinical studies.

Arthroscopy↗
PubMed1989

Rigidity of initial fixation with uncemented tibial knee implants.

This study quantifies the in vitro motion occurring between bone and cemented and noncemented tibial components. Liquid metal strain gauges were used to measure the motion between the tibial component and bone at four locations in eight cadaver tibia at near-point cyclic loads ranging from 10 to 2,000 N. Two types of motion were observed: inducible displacement, which is reversible, followed the oscillating load and occurred in both cemented and uncemented tests, and liftoff or separation of the component and bone, which occurred only for the noncemented cases and remained even after removal of the load. For both motion types, noncemented tests exhibited significant (P less than .05) and dramatic increased interface motion compared to the cemented cases for all load types. The results suggest that the magnitudes of implant-bone interface separation at loads in the low physiologic range for noncemented implants can be sufficiently large to inhibit bony ingrowth into a prosthesis with an average pore size of 300 microns.

Adult↗
PubMed1989

The rationale, design characteristics, and preliminary results of a primary custom total hip prosthesis.

Seventy-three primary custom-made uncemented hip implants have been inserted since July 1987. The initial clinical results are equivalent to those of conventionally made components, but there has been less residual and recurrent thigh pain with the custom devices. The custom implants have achieved 20% greater canal fill with much less variation than conventionally made devices. Custom components have been particularly useful in patients with significant anatomic deformity and associated arthritis.

Bone Cements↗
PubMed1989

Classification and management of acetabular abnormalities in total hip arthroplasty.

Total hip arthroplasty, for both primary and revision operations, frequently involves bony abnormalities of the acetabulum. No standard nomenclature currently exists for the definition of acetabular deficiencies. A classification system is presented to assist in the preoperative evaluation and to provide a treatment protocol for these defects.

Acetabulum↗
PubMed1988

Arthropathy and surgery in congenital factor VII deficiency.

A 35-year-old woman with severe (less than 1 percent) factor VII deficiency had recurrent hemarthroses involving the left knee, leading to deformity, pain, and virtually complete loss of function. It was elected to perform a total knee replacement. In preparation for surgery, the patient received heat-treated prothrombin complex concentrate containing 870 units of factor VII per vial. A dose of 50 U/kg raised the factor VII level to 115 percent. At surgery, dense adhesions were found within the joint, the articular cartilage was overgrown with pannus extending out to the lateral patella, and there was extensive deformity of the femoral condyle and tibial plateau. The joint was excised and replaced by a cemented Microloc prosthesis. Postoperatively, factor VII levels were maintained above 10 percent by six-hourly infusions of concentrate. Beginning on Day 4, single daily infusions of 25 U/kg were given prior to physical therapy. No bleeding occurred, and the patient was ambulating at the time of discharge 20 days postoperatively. This experience indicates that despite its short half-life (less than four hours), factor VII levels sufficient to prevent bleeding can be maintained in factor VII-deficient patients undergoing major operative procedures.

Adult↗
PubMed1988

Failure mechanisms of metal-backed patellar components.

A specific type of failure of a metal-backed patella occurred, consisting of a separation of the polyethylene from the metal backing. This dissociation is followed by wearing of the metal backing against the femoral component. This produces clinical signs and symptoms that usually require revision. This failure occurred in 16 knees of 14 patients. Average time to failure was 14 months. Failure was associated with patellar implant design, surgical technique, patient characteristics, and femoral component design. The plastic of the metal-backed patellae was thin at the periphery. The metal plate did not extend to the edge of the plastic and acted like a sharp edge that cut the thin plastic. The plastic dome was not bonded to the plate and became separated from the plate once the plastic tore. The plate became deformed. Failure was more likely with a subluxated, tilted, or excessively thick patella or flexed femoral component. The typical patient was a large, active male who had achieved more than 115 degrees of flexion. A prominent edge on the lateral intercondylar ridge of the femoral component resulted in a concentrated load being applied to the plastic dome and favored rapid wear of the patella. Until a greater understanding of patello-femoral loading is acquired, caution in the use of metal-backed patellae is recommended.

Aged↗
PubMed1986

Ambulatory containment treatment in Perthes' disease.

The results of four different ambulatory methods used in the treatment of 248 patients with Perthes' disease were compared in five different hospitals. In each hospital the patient population was selected for the era of treatment policy. Seventy-two patients were treated with crutches alone, 58 with a Scottish Rite orthosis, 48 with a Newington abduction orthosis (a bilateral long-leg brace holding the hips in abduction and internal rotation), and 70 with proximal femoral osteotomy. The end results of treatment were rated according to head sphericity using the MOSE method. Prognostic indicators were recorded, including age of onset of disease, Catterall type, and femoral subluxation. Patients with partial-head involvement under eight years of age at disease onset with minimal lateral subluxation (less than 1.5 lateral subluxation ratios) and no proximal subluxation fared equally well with crutch walking or any of the three ambulatory-containment treatments studied. With greater degrees of subluxation, all three containment groups were superior to crutch walking and all were equally effective. In partial-head involvement, patients between eight and 12 years of age, with or without lateral or proximal subluxation, all three ambulatory containment methods were superior to crutch walking. Femoral osteotomy and the Newington abduction orthosis were equally effective. Only five Scottish Rite patients were in this age group, too small a number to compare with the other treatment methods. Patients with partial-head involvement over 12 years of age at disease onset had poor results. For patients with total-head involvement under eight years of age at disease onset, femoral osteotomy was correlated with a lesser degree of femoral head flattening than either brace or crutch treatment. In whole-head involvement patients over eight years old at disease onset, all three ambulatory containment methods were equally effective and superior to crutch walking; however, there were few crutch walking and Newington abduction arthrosis patients in this age group.

Adolescent↗
PubMed1984

The role of fluid hydrostatic pressure in bone-implant interface load transfer.

Permeability of the soft tissue-bone system surrounding artificial joints fixed in cancellous bone was measured in four adult dogs after implants had been in place 2 months. Fluid was forced through a cavity formed by removal of the implant, the cavity was capped with a stopper to allow for pressure generation. Surface permeability of the 2-month-old implant cavity was 45 times less than the permeability of freshly drilled holes in cancellous bone. A mathematical model of a rigid implant resting on a biphasic solid-fluid layer showed the fluid carried 90% of the load when the implant cavity permeability was assumed, but only 27% when the freshly drilled permeability was used. The results suggest caution in interpreting finite-element models with bonded interfaces and suggest a possible role of the fluid in biological response at the interface.

Animals↗
PubMed1983

Acetabular dysplasia in the adult.

Twenty adults (32 hips) with acetabular dysplasia were followed up for an average of 22 years to determine the natural history of the disorder. Initially, all hips had a center-edge (CE) angle of Wiberg of 20 degrees or less and an essentially intact Shenton's line with no roentgenographic evidence of osteoarthritis. Average patient age initially was 43 years (range, 27-57 years) and at final follow-up examination, 65 years. Various parameters of hip integrity were measured, including the CE angle of Wiberg, acetabular angle of Sharp, percentage of the femoral head covered by the acetabulum, acetabular depth, and inclination of the lateral lip of the acetabulum. None of these indicators proved a reliable prognostic aid for predicting the rate at which the osteoarthritis process supervened in any one case.

Adult↗