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Biomedical subjects

L D Dorr

Publications and source records attributed to L D Dorr.

At least 37 records · Page 2Linked to original sources
PubMed1998

Bilateral total hip arthroplasty comparing hydroxyapatite coating to porous-coated fixation.

Fifteen patients had bilateral hip replacement with a porous-coated hip replacement in one hip and in the contralateral hip the same design, which had adjunctive hydroxyapatite coating on the porous coating. These patients were followed for an average of 6.5 years (range, 5-7.9 years). There was no difference in the clinical Harris Hip Scores between the two hips in these patients. The radiographic measurements did show improved bone remodeling in hips with adjunctive hydroxyapatite coating as measured by proximal cancellous hypertrophy and evidence of a buttress sign. The fixation of stems with hydroxyapatite coating showed fewer radiolucent lines (P = .013). The improved bone remodeling, which we had previously reported, has been maintained in these hips at intermediate-term follow-up and the fixation of the hydroxyapatite-coated stems is also now better. The results in these patients with bilateral hips, which allows complete control of the bone type, immunology, weight, activity, and age of the patient, suggests that the use of hydroxyapatite coating does provide improved fixation and the possibility of improved durability.

Adult↗
PubMed1998

Soft tissue balance of the hip.

Release of static and dynamic contractures around the hip provides significant immediate benefits for the patient and accelerates postoperative rehabilitation. Knee pain is decreased, groin pain is eliminated, range of motion of the hip is increased, and functional leg-length difference is reduced. This article emphasizes the importance of techniques used to ensure soft tissue balance.

Arthroplasty, Replacement, Hip↗
PubMed1998

Current concepts review: symmetry versus asymmetry in the design of total knee femoral components--an unresolved controversy.

Despite the excellent success of earlier total knee replacement designs such as the Total Condylar Knee (Johnson & Johnson, Raynham, MA), which had a symmetrical femoral component, the majority of modern designs feature a more anatomic and asymmetric femoral prosthesis. A raised lateral phalange, an angled trochlear groove, or both are thought to improve patellar tracking. Laboratory studies, however, suggest that surgical technique may be the dominant factor in determining patellofemoral kinematics. Component design has not been proven to be significant. A prosthesis with asymmetric femoral components may cost more. The literature reviewed in this article finds no advantage to the use of asymmetric versus symmetrical femoral components in total knee replacement.

Arthroplasty, Replacement, Knee↗
PubMed1998

Causes of and treatment protocol for instability of total hip replacement.

Dislocation of the total hip replacement is a devastating complication, physically and mentally. It was determined whether there are radiographic or operative findings predictive of repeat dislocation and whether there are causes of dislocation that require immediate reoperation. A previously published classification of dislocations was used which evaluates (1) positional (no radiographic abnormality); (2) component malposition (femur or acetabulum), which is inadequate version or position of the acetabular or femoral component; (3) soft tissue imbalance (change in the length or displacement of the hip), which is a change in the muscle functional length of the hip; and (4) component malposition and soft tissue imbalance. Categories of treatment of dislocations were established that could be correlated to the cause of the dislocation: (1) Category I is a successful closed reduction; (2) Category II is a successful reoperation; (3) Category III is a reoperation with subsequent repeat dislocations successfully treated with closed reduction; and (4) Category IV is comprised of hips that require multiple reoperations for treatment of dislocations. The results are that any dislocation of any origin may be treated successfully with closed reduction so that this should be the first choice of treatment. To avoid multiple treatments, immediate reoperation should be performed if the hip is unstable when the patient is examined under anesthesia after the closed reduction. Hips with soft tissue imbalance and weakness of the abductor musculature, with or without component malposition, are most at risk for multiple operations. These hips may be considered for mechanical stability (constraint in the acetabular replacement) at reoperation.

Adult↗
PubMed1998

Hemispheric titanium porous coated acetabular component without screw fixation.

One hundred fifteen hips in 108 patients with primary total hip arthroplasty using the anatomic porous replacement hemispheric acetabular component implanted without adjunctive screw fixation had a mean postoperative followup time of 6 years (range, 5-7.4 years). Clinical evaluation was performed using the Harris hip score and patient self assessment using a modified Short Form-36 questionnaire. Radiographs were measured for radiolucent lines, polyethylene wear, osteolysis, migration, and fractures. No acetabular metal shell had been revised for loosening or was radiographically loose with or without migration (more than 3 mm) at final followup. Reoperation was done in nine (8%) hips because of polyethylene insert wear or disassembly. No fracture of the acetabular bone occurred at the time of surgery or was observed on radiograph. Fixation of the metal shell was stable, with progressive radiolucent lines observed at final followup in 2% of the hips. Osteolysis was recorded in one patient with two acetabular components. The fixation of noncemented hemispheric porous coated acetabular components is more related to the technique of acetabular bone preparation and press fit implantation than to whether additional screws or peg fixation are used. Fixation of this acetabular component without screws at an average of 6 years after surgery is reproducible and predictable in primary hip arthroplasty. The design of modular polyethylene inserts has been improved and should reduce the wear rate of reoperations of the polyethylene insert.

Acetabulum↗
PubMed1997

Medialization of the patella in total knee arthroplasty.

Patellar complications of total knee arthroplasty remain the most common cause of pain and reoperation. Laboratory studies have suggested that medialization of the patella will improve tracking of the patella on the trochlea of the femoral component. The purpose of this study was to determine if clinical medialization of the patellar component on the patellar bone would improve tracking of the patella as demonstrated radiographically. Sixty-two knees were randomized so that 31 knees had a centrally placed patellar component and 31 had the patellar component placed on the medial two thirds of the patellar bone. There was no difference between the two groups with respect to either clinical or radiographic results in the first year after surgery. There was no improvement compared with previous reports in the incidence of tilt and displacement. The one improvement was a reduction in the incidence of lateral release. Thus, consequences of lateral release such as postoperative morbidity, avascular necrosis of the patella, and stress fracture of the patella can be avoided. It is recommended that the patellar component be placed on the medial two thirds of the patella to reduce the occurrence of lateral release. Tracking of the patella during surgery can be assessed using a single suture placed at the superior pole of the patella, and this technique in combination with the no-thumbs test provides an additional means of evaluation for patellar tracking.

Adult↗
PubMed1997

Cementless revision of total hip arthroplasty using the anatomic porous replacement revision prosthesis.

This study reports the results of revision total hip arthroplasty with the Anatomic Porous Replacement Revision Hip System (Intermedics Orthopedics, Austin, TX) to investigate the value of cementless fixation. Sixty-six hips in 65 patients were followed for a mean of 4.7 years in patients with a mean age of 56 years. Thirty-six patients were categorized as Charnley class A, 16 as class B, and 13 as class C. Forty (61%) of the femurs were classified before surgery as having loss of bone distal to the intertrochanteric line. Thirty-two (48%) of the femurs required augmentation with demineralized strut cortical allografts, 5 (8%) required bulk femoral allografts, and 12 hips (18%) required acetabular allografts. Overall, 4 stems (6%) and 2 acetabular components (4%) required further revision surgery. The reason for further revision in 1 stem and both acetabular components was allograft failure. Fifty-six (85%) hips had excellent or good Harris hip scores. Ninety percent of hips had no or slight pain, and 90% allowed patients to walk with no or slight limp. Those hips that had hydroxyapatite coating added to the porous coating had statistically improved Harris hip scores for both pain and limp. Stable fixation was present in 95% of stems. Demineralized strut grafts healed in 30 of 32 hips. Thirty-nine of 44 noncemented revision sockets had no radiolucent lines and there were no loose components. Cementless fixation was effective for these hips.

Acetabulum↗
PubMed1997

Functional results in total hip replacement in patients 65 years and older.

Total hip arthroplasty in patients 65 years and older has been very durable in long term results. Eighty-nine hips in 79 patients were observed for 5 to 9 years to determine the importance of advancing age and deterioration of activity levels to durability of total hip replacement. The age of patients was 65 years or older at the time of surgery. A classification of function was used that graded activity level. During the average 6.24 years of postoperative followup, 22% of the patients died, 38% had medical problems that reduced their functional level, and 10% reduced their function because of their hip surgery. Hip related deterioration occurred only in those patients with a cementless stem. There was decreasing measured wear with increasing age; otherwise, neither age nor activity change in this study was related to loss of fixation of components, osteolysis, or bone remodeling. Increasing age and decreasing activity in patients 65 years and older does not seem to be the primary reason for durability of total hip arthroplasty in these patients. In this age group, the durability of hip replacement is related mostly to the quality of fixation.

Aged↗
PubMed1997

Postmortem analysis of bone growth into porous-coated acetabular components.

Microradiography, backscattered electron microscopy, and histological analysis were used to conduct a quantitative postmortem study of seven consecutively retrieved anatomical porous replacement acetabular components that had been inserted during total hip arthroplasties. Screws had been used for the initial fixation of six components. The microradiographic analysis of all seven components showed that an average (and standard deviation) of 84 +/- 9 per cent (range, 72 to 93 per cent) of the porous coating was in direct apposition to the periprosthetic bone. The backscattered electron images demonstrated that an average of 12 +/- 6 per cent (range, 4 to 21 per cent) of the space available in the porous coating was occupied by ingrown bone. The amount of bone ingrowth was not significantly different among the three zones delineated by DeLee and Charnley. Uniformity of bone growth into the porous coating suggests that the preferential loading that occurs in the superior region did not differentially affect the bone ingrowth. The present study showed that consistent bone growth into anatomical porous replacement acetabular components can be achieved.

Acetabulum↗
PubMed1997

Failure mechanisms of anatomic porous replacement I cementless total hip replacement.

The APR-I Hip System was designed for metaphyseal bone attachment by proximal patch porous coating and the acetabular component was a hemisphere fixed with screws. The results of 100 consecutive primary total hip arthroplasties performed with the APR-I were studied in patients still alive after an average of 6.7 years. The selection of hips for implantation of this hip system was limited to those patients in whom a satisfactory intraoperative fit could be obtained. This resulted in a distribution of patients such that 75% were younger than age 65 years and only 15% had osteoporotic bone. The revision rate was 16% with a mechanical failure rate of 11%. Seventy percent of hips had progressive loss of fixation. loss of femoral component fixation was correlated with younger patient age, higher patient activity level, metaphyseal fill of less than 90%, and increased polyethylene wear and osteolysis. Eighty-nine percent of hips maintained femoral neck contact with the porous coated collar. The acetabular component was well fixed in 97% of hips. The failure rate of the APR-I stem is unacceptably high and this stem is no longer used by the authors.

Adult↗
PubMed1997

Infected total knee arthroplasty. Two-stage reimplantation with a gastrocnemius rotational flap.

This study reviews a consecutive series of 21 patients undergoing two-stage reimplantation total knee arthroplasty for late chronic infection. All 21 patients had late chronic infections, and 20 of 21 patients were compromised hosts. Seven different organisms were isolated at the time of prosthetic resection. Staphylococcus coagulase negative species was the most frequently isolated organism. At the time of reimplantation, a medial gastrocnemius rotational flap was rotated over the proximal tibia and knee for wound closure. The average explantation time was 25 weeks (range, 7-76 weeks), and no methylmethacrylate spacers were used. At an average 17-month followup (range, 5.1-33.1 months) all reimplanted total knee replacements remained in place with one patient having recurrent infection. At reimplantation, 11 patients had positive bacterial cultures from tissue specimens. Sixteen of the 33 (40%) positive cultures were from specimens taken from the medullary canal. At followup, the average Knee Society Score was 77.4 (range, 40-100). The lack of a methylmethacrylate spacer and a long explantation time were considered important factors in diminishing functional performance and determining the need for a gastrocnemius flap. A medial gastrocnemius rotational flap should be considered at the time of reimplantation total knee arthroplasty if the soft tissue envelope about the knee is compromised and cannot be closed without undue tension.

Adult↗