Search PubMed⌕ Search

Biomedical subjects

L D Dorr

Publications and source records attributed to L D Dorr.

At least 73 records · Page 4Linked to original sources
PubMed1994

Long-term results of cemented total hip arthroplasty in patients 45 years old or younger. A 16-year follow-up study.

Forty-nine cemented total hip arthroplasties in patients younger than 45 years were reviewed, with an average follow-up period of 16.2 years. The results were compared with the same group previously reported at average follow-up periods of 4.5 and 9.2 years. Clinically satisfactory results were 27% at 16.2 years compared with 78% at 4.5 years and 58% at 9.2 years. The revision rate increased from 12% at 4.5 years to 33% at 9.2 years to 67% in this study. The revision rate for patients younger than 30 at the time of the index arthroplasty was 82% compared with 56% for those over 30. Impending failure was present in 81% of the 16 unrevised hips compared with 56% at 9.2 years and 29% at 4.5 years. Patients younger than 30, in Charnley category A or B, and with a diagnosis of osteonecrosis or osteoarthritis had the poorest clinical results. As in the previous two studies, the best results were obtained in category C patients who were over 30 years of age with inflammatory collagen disease. The purpose of this study is to report the long-term (average, 16.2 years) follow-up results of patients under the age of 45 who underwent cemented total hip arthroplasty at Rancho Los Amigos Medical Center between 1972 and 1978. The 4.5-year and 9.2-year results form the basis for comparison.

Adolescent↗
PubMed1994

Complications with hydroxyapatite particulate separation in total hip arthroplasty.

This study reports on the results of the implant and tissue analysis of clinically retrieved hydroxyapatite (HA)-coated implants. Five of the patients with fixed HA-coated stems had been clinically diagnosed with osteolysis. The semiquantitative histologic grading in these patients showed HA, polyethylene, and metal particles were all present (Grade 3+) in the osteolytic regions of the periprosthetic tissue. Additionally, inflammatory cells (Grade 3+) were present in these regions. Back-scattered electron (BSE) and correlated elemental analysis showed HA particulate was present in the polyethylene inserts. The HA could be distinguished from bone chips in the polyethylene based on morphology and anatomic number gray level differences. This study was limited in that no clinical results of particular HA-coated implant series were reported. Careful follow-up care in patients with coated devices is recommended.

Adult↗
PubMed1993

Metal ion concentrations in retrieved polyethylene total hip inserts and implications for artifactually high readings in tissue.

Although there are many studies which document high metal ion concentrations in clinically retrieved tissues surrounding total joint replacements, most investigations have remained cautious in their interpretation due to the artifactual influences of metal particulate. The possible contribution of polyethylene wear debris to artifactually high periprosthetic metal ion concentration readings has not been previously considered. This study documents the potential role of polyethylene particulate contamination in causing artifactually high metal concentration readings in tissues. The data showed metal ion contamination in the polyethylene was progressive at each stage of exposure to metal: from bar stock preparation, to manufacturing, to in vivo ambulation. The manufacturing and machining processes showed a statistically significant (P < or = .05) increase in metal ion concentrations in the nonarticulated acetabular inserts over bar stock. The results of this study demonstrate that periprosthetic tissue and synovial fluid metal ion concentration data must be interpreted with caution due to possible artifactual problems associated with metal ion contaminated polyethylene particulate.

Alloys↗
PubMed1993

Revision total hip arthroplasty. The use of solid allograft.

Intact solid allograft was used to augment severe bone loss in 8 acetabula and 15 femora in 22 patients who underwent revision total hip arthroplasty with noncemented implants. The average follow-up period was 4 years. The average time to radiographic union of whole acetabular allografts was 11 months. Superior migration of the allografts occurred in four patients. Varus tilt of the acetabular component within the allografts was noted in three patients. Eleven patients underwent entire proximal femoral allograft reconstruction, and four patients had femoral head allograft reconstruction. Nine patients with entire proximal femoral allografts achieved radiographic union at an average of 13 months and two failed by nonunion. Only one of the four patients with femoral head allograft reconstruction achieved union. Femoral component subsidence was noted in seven whole proximal femoral allografts (64%). Entire proximal femoral allograft reconstruction was complicated by at least one episode of postoperative dislocation in 6 of 11 procedures. The authors recommend that femoral head allografts should be used with caution to reconstruct proximal femoral deficiencies in which structural support is required for stability of the implant. Successful use of acetabular allografts requires that the majority of the allograft be contiguous to host bone and not to soft tissue. With entire proximal femoral reconstruction, the tip of the femoral component should not reside at the host-graft junction. All components should be cemented into allograft bone; and revision surgery should be performed before osteolytic destruction of bone advances to the point where allograft reconstruction is required.

Acetabulum↗
PubMed1993

Postmortem comparative analysis of titanium and hydroxyapatite porous-coated femoral implants retrieved from the same patient. A case study.

The results of bilateral postmortem analysis of titanium and plasma-sprayed hydroxyapatite (HA) porous-coated femoral components of the same Anatomic Porous Replacement design retrieved from a 35-year-old female donor are reported. Analysis was conducted using backscattered electron imaging, histology, and radiographic techniques. The appositional bone index, percent bone ingrowth, and mineral content were measured for both implants. The results showed a 177% higher appositional bone index (P = .014) for the HA porous-coated Anatomic Porous Replacement component compared to the titanium Anatomic Porous Replacement component. Backscattered electron analysis showed 50% more bone in the HA porous-coated implant (P = .028). The mineral content analysis demonstrated that the bone ingrown into the HA porous-coated device was 23% less mineralized (P = .016). The data from this case study suggested that plasma-sprayed HA porous-coated implants may assist in increasing the amount of bone ingrowth and skeletal attachment in total hip arthroplasties.

Adult↗
PubMed1993

Results of noncemented revision.

The results of revision of total hip replacements with noncemented fixation are dependent on implant design, postoperative treatment, and the technique selected in relationship to the bone quality and quantity. When proximal femoral bone ingrowth fixation is desired an implant must have a double wedge design, which permits a high percentage contact between the host bone and the porous coating of the implant. Bone graft in either the femur or acetabulum should be used at a minimum. Every attempt to obtain host bone contact to porous coating should be done. When a bone graft is used to replace the proximal femur or when an acetabular bone graft covers more than 50% of the cup, the implant should be cemented into the bone graft. Bone structure affects the outcome of noncemented revisions more than the thickness of the bone. Even thin and weak femoral bone has dynamic remodeling capability. The structure influences result more according to the ability to contact the host bone to the porous coating. When this can be done, the bone will heal to the porous coating. Postoperatively, 40% of our patients are treated with a cast to protect bone grafts and weak bones that are important for stability of the implant. We believe that conservative postoperative rehabilitation for noncemented revision arthroplasty significantly improves the healing for the bone to the implant.

Bone Transplantation↗
PubMed1993

Patellar tilt and subluxation in total knee arthroplasty. Relationship to pain, fixation, and design.

Two hundred thirty-four primary total knee prostheses were evaluated with a 45 degrees merchant view to examine patellar position and fixation. Despite a standardized technique for obtaining roentgenographs, patellar position varied with leg position. Overall, 54.7% tracked centrally, 31.2% tilted, and 14.5% displaced. The incidence of these findings was the same whether the patella was domed or congruent. Neither pain scores nor fixation were affected by position. Postoperative tilt and displacement were more common in patellae that were tilted preoperatively. The incidence of postoperative tilt or displacement was not significantly different in knees in which a lateral release was performed. Patellar tilt in some patients seems inevitable despite careful technique because intraoperative tests are static and postoperative function is dynamic. This does not bode well for wear in a metal-backed patella. Tilt caused increased loading at the periphery of the component where most metal-backed prostheses have thin polyethylene.

Aged↗
PubMed1993

Functional recovery of noncemented total hip arthroplasty.

Eighteen patients with unilateral hip disease had noncemented total hip arthroplasty. Clinical follow-up data were complete to five years postsurgery. Gait analysis was done preoperatively, at three and six months, and at one and two years. Force plate data showed continued weakness of the operated hip in all patients at two years postsurgery. Preoperative dynamic electromyograms (EMGs) were abnormal in eight patients and showed two patterns. Stance loss seen in three patients was characterized by absence of activity of the gluteus medius and upper and lower gluteus maximus muscles. In five patients, continuous activity occurred in the tensor fascia lata, rectus femoris, and adductor longus muscles during the entire gait cycle. Postoperatively, all abnormal EMGs returned to normal. Four patients with a normal preoperative EMG developed abnormal EMG patterns postoperatively, demonstrating either a prolonged stance or stance loss pattern. All four of these hips have been revised. Although gait characteristics return to normal by two years postsurgery, weakness of the hip persists. This weakness jeopardizes the implant fixation interface. This study supports the prohibition of activities that cause high impact loading of total hip arthroplasties and suggests that a prolonged exercise program be employed postoperatively.

Adult↗
PubMed1992

Treatment of fractures about hip prostheses with compression plating.

Between 1984 and 1986, 10 patients who sustained a femur fracture about a hip prosthesis were treated with open reduction and internal fixation using compression plating. Nine of the 10 fractures healed in an average time of 5 months. Other than one nonunion, no significant complications were noted. Follow-up study, ranging from 13 to 44 months (average, 26 months), was obtained on all 10 patients. One had a loose femoral component, which was attributed to inadequate stem size. None of the other patients had either clinical or radiographic evidence of loosening. Based on Harris hip scores, there was no indication that plating significantly interfered with hip function. The authors believe that these results demonstrate that plating can be an effective method of treating femoral fractures about hip prostheses.

Adult↗
PubMed1992

Clinical results from the calcitite-coated press fit APR hip system.

Hydroxyapatite (HA)-coated APR Total Hip Replacement was found to be superior to a press-fit only control group in a randomized trial. This study confirms the importance of biologic fixation for durability of total hip replacement as compared with press-fit fixation only.

Adult↗
PubMed1991

Factors related to failure of structural bone grafts in acetabular reconstruction of total hip arthroplasty.

Structural bone grafts in acetabular reconstruction of total hip arthroplasty have come into more common usage with the increasing number of revision arthroplasties. The authors present the outcome of 40 bone grafts with follow-up periods of 2-8 years. Primary and revision arthroplasties with both cemented and noncemented fixation are included. Factors that had a statistically significant relationship to failure of the bone graft included fit and fixation of bone graft to host, fit and fixation of prosthesis to host, union of bone graft to host, and the presence or absence of the confluence of the anterior and posterior columns of the acetabulum. Other findings of interest were a higher failure rate of multiple grafts as compared to a single graft and freeze-dried femoral heads. Migration of the socket of more than 3 mm is statistically related to failure of the socket.

Acetabulum↗
PubMed1991

Arthritis and athletics.

The number of people participating in athletics does not equal the number of people with arthritis. There are no data to support the concern that athletic participation will make the onset of arthritic joints more likely. What is clear is that injuries that occur with athletics can increase the incidence of arthritis. If a patient does develop arthritis secondary to athletics, the treatment is not different than that offered for a spontaneously occurring arthritic joint. If an operation is necessary, the best operation depends a good deal on the goals of the patient. Continued athletic participation may be reasonable as long as the athletic activity is not vigorous and does not involve running and jumping or contact. The recommended athletic activities for patients with arthritis and for those having operations for arthritis are swimming, hiking, bicycling, walking, and golfing. The operations recommended for arthritic patients under the age of 30 should be biologic operations such as fusion or osteotomy. In patients aged 30 to 45, the operation should be correlated to lifestyle and desired level of activity. A biologic operation is better for highly active patients. When patients reach the age of 45 or are older, total joint replacement usually is preferable because of the improved clinical functional results and the decreased stress on surrounding joints with arthroplasty. If patients are older than 60 years, total joint replacement is the operation of choice and usually will include a cemented prosthesis. Some surgeons at this time do prefer cementless total-joint replacement for all patients regardless of age. Patients who have arthritis can have a satisfying athletic and exercise routine if they simply apply common sense to the manner in which they conduct their activities.

Adult↗
PubMed1991

Investigation of early surface delamination observed in retrieved heat-pressed tibial inserts.

The objective was to examine possible reasons for delamination observed in tibial inserts of the porous-coated anatomic (PCA) knee replacement. To date, 33 PCA inserts have been forwarded to the authors' labs. Of these 33, 52% showed severe delamination within four years of implantation. Visual, structural, and mechanical analyses were conducted and data compared on the heat-pressed PCA type and the common machined inserts. Twenty inserts of the two different types were examined. Visual data using polarized light microscopy showed the presence of a surface layer separated from the middle region of the heat-pressed inserts by a line of demarcation 250-580 microns beneath the articulating surface. This anomaly was not observed in machined inserts. Structural analysis showed the new heat-pressed inserts had increased crystallinity in the surface layer when compared to new machined inserts. The retrieved heat-pressed inserts showed increased crystallinity in the surface and middle regions. There was a slight increase in surface crystallinity in the retrieved machined inserts. Microhardness data showed that there was an increased hardness associated with the crystallinity seen on the heat-pressed inserts. Orthopedic surgeons should be aware of early delamination and surface failure in heat-pressed inserts.

Hardness↗
PubMed1991

Clinical comparison of all-polyethylene and metal-backed tibial components in total knee arthroplasty.

Based primarily on in vitro biomechanical studies, most total knee arthroplasty (TKA) manufacturers have abandoned the all-polyethylene tibial component (APT) in favor of the metal-backed tibial component (MBT). There is little clinical evidence to support this decision. A retrospective review of cemented TKA using the total condylar prosthesis was performed. One hundred eighteen patients with 131 TKAs were evaluated. Sixty-two of these knee prostheses had tibial components made entirely of polyethylene while 69 had the MBT. There were 13 cases of bilateral TKA in which the APT was used for one knee and the MBT for the other. All patients were examined by the authors for an average follow-up period of six years. Hospital for Special Surgery knee scores and a comprehensive roentgenographic evaluation were obtained. No significant difference was noted between the patients with APT and those with MBT, raising serious doubt on the need for the MBT in patients being treated with primary, cemented TKA.

Adult↗
PubMed1990

Revision surgery for stiff total knee arthroplasty.

Thirteen stiff total knee arthroplasties were studied in 12 patients who did not have a stiff knee prior to the index arthroplasty. The reasons for replacement were osteoarthritis in seven knees, post-traumatic arthritis in two, and inflammatory collagen disease in four. Four knees were revised for fixed flexion deformity and nine for poor arc of motion. The cause of stiffness in eight knees was malpositioned components. Following postoperative revision for stiffness, three knees received excellent ratings, two received good ratings, four received fair ratings, and four received poor ratings. Satisfaction was achieved in 11 of 12 patients because of pain relief. Improved motion was achieved in patients with primary osteoarthritis and patients with malposition of components. Poor motion occurred in those with patella baja and inflammatory collagen disease. A V-Y patella turndown helped prevent patella ligament complications.

Adult↗