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Biomedical subjects

Lawrence D Dorr

Publications and source records attributed to Lawrence D Dorr.

At least 19 recordsLinked to original sources
PubMed2007

Psychologic reasons for patients preferring minimally invasive total hip arthroplasty.

Success of an orthopaedic operation depends on patients achieving their primary goal(s) and having satisfaction with the outcome. The enthusiasm of patients for minimally invasive total hip arthroplasty seems related to satisfaction with the operation. We hypothesized patients' attitude toward a small incision would increase their confidence and satisfaction with the operation but the importance of the incision would dissipate after patients realized their goals of pain relief and functional recovery. One hundred sixty-five patients responded to a 14-question patient-perception questionnaire preoperatively and 6 weeks postoperatively and a followup survey at 6 months to 1 year postoperatively. One hundred nine patients had small incisions (mean, 9.6 cm) and 56 had long incisions (mean, 17.9 cm). Preoperatively patients expected small-incision surgery would positively influence their primary goals and satisfaction; at 6 weeks postoperative they believed more strongly that this was true. By 6 months to 1 year, the importance of the incision diminished because 100% of patients met their primary goals. Forty percent of patients with a long incision were not satisfied and the reasons given were related to the process of reincorporating their injured hip into their whole-body image. We confirmed our first hypothesis that a small incision influences a patient's satisfaction postoperatively; we could not confirm our second hypothesis that incision length did not matter after attaining primary goals.

Arthroplasty, Replacement, Hip↗
PubMed2006

Painful metal-on-metal total hip arthroplasty.

Two patients were evaluated for the possibility of hypersensitivity to a Metasul articulation (Centerpulse, Austin, Tex) coupled with total hip arthroplasty. Serum was tested with a lymphocyte proliferation assay, and the capsular tissues from the hip were examined for perivascular lymphocytes. The diagnosis of hypersensitivity to Metasul could not be confirmed in these patients, and ultimately, the painful hip arthroplasties were felt to be caused by a combination of musculoskeletal problems.

Arthroplasty, Replacement, Hip↗
PubMed2006

Bone graft for tibial defects in total knee arthroplasty. 1986.

Twenty-four knees with bone grafts for tibial defects at the time of either primary or revision total knee arthroplasty were followed for three to six years. With 22 of 24 bone grafts, union and revascularization were seen and no clinical collapse was present. In two, nonunion occurred, accompanied by collapse in one. Failure was attributed to varus alignment of the leg in one (a medial condylar graft) and to insufficient preparation of the bony bed in the second (bleeding bone was not exposed). Evidence for incorporation of the grafts was obtained by tomogram, bone scan, and bone biopsy. Incorporation was present by six months, but the time to complete remodeling was not determined. A bone graft is recommended for tibial defect involving 50% or more of the bony support of either tibial plateau. A bone graft is indicated whenever a cement column under the prosthesis would measure more than 5 mm in height.

Arthritis, Rheumatoid↗
PubMed2006

Precision and limitation of measuring two-dimensional wear on clinical radiographs.

The precision of measuring polyethylene penetration in total hip arthroplasties has been studied using phantom models and retrieved cups, but not on radiographs obtained in vivo. We used Hip Analysis Suite Hip32 computer software to measure two-dimensional penetration in two groups of anteroposterior pelvic radiographs taken in vivo. We determined the measurement error for precision, the effect of position change on precision, and compared direct and indirect measurements. The influences on precision with respect to followup time were measured using a separate group of radiographs. Precision was 0.89 to 1.16 mm and decreased as more variables were added. The direction of wear was toward the contact surface of the cup in greater than 50% of patients with more than 5 years followup. Negative wear severely affected precision in 40% to 50% of patients. Individual penetration measurements were unreliable when total penetration was low (< 1.1 mm). The two-dimensional computer technique has limitations when measuring such low wear. Measurement errors were caused by slight radio-graphic distortions of the femoral head and acetabular component and by blurred edges on some clinical radiographs.

Adult↗
PubMed2006

Multimodal analgesia without routine parenteral narcotics for total hip arthroplasty.

Methods for managing pain after a total hip replacement have changed substantially in the past 5 years. We documented the outcome of patients treated with a multimodal pain program designed to avoid parenteral narcotics. Avoidance of parenteral narcotics can essentially eliminate the complications of respiratory depression, ileus, and narcotic-induced hypotension. It can minimize nausea and vomiting which cause dissatisfaction with an operation. Twenty-one of 140 patients (15%) needed parenteral narcotics postoperatively with only nine patients (6.4%) using parenteral narcotics after the day of surgery. Mean pain scores were below 3 of 10 on all postoperative days. There were no patients with respiratory depression or ileus, and four (2.9%) with urinary retention. Nausea occurred with 35 patients (25%) in the recovery room and in 28 patients (20%) thereafter. Emesis occurred in five patients (3.6%) with two incidences in the recovery room. One hundred and thirty-eight patients (98.6%) were discharged home at a mean of 2.7 seven days postoperatively with 98 (70%) on a single assistive device. The multimodal pain management program, which avoided parenteral narcotics, was effective in providing pain relief, nearly eliminating emesis, and eliminating the severe complications of respiratory depression, urinary tract infection and ileus, as well as accelerating function.

Adult↗
PubMed2005

Constrained acetabular liners: mechanisms of failure.

Although constrained acetabular liners have been successfully used for the treatment of recurrent hip instability, their usage has led to a growing number of associated complications. Twenty-seven patients (29 hips) who experienced failure of the constrained acetabular construct were retrospectively reviewed to define mechanisms of failure. Of these patients, 8 had a recurrent failure of another constrained liner. The 4 modes of failure were failure of fixation to the pelvis, liner dissociation, biomaterial failure, and femoral head dislocation. As constrained liners are highly subject to mechanical overload, the risk of failure can be minimized by reducing prosthetic impingement and avoiding technical errors.

Acetabulum↗
PubMed2005

Periprosthetic femoral fractures associated with contralateral hip disease.

Femoral osteolysis associated with contralateral hip degenerative changes is a risk factor for ipsilateral periprosthetic femoral fracture. We report 5 comminuted proximal shaft fractures around loose femoral implants occurring in patients with both symptomatic femoral lysis and a painful hip on the other side. Our evolving strategy involves timely revision surgery once this pattern is recognized. Once fracture has occurred, emergent revision requires extensive medical evaluation, availability of long-stem revision implants, and appropriate instrumentation and allografts for fracture fixation.

Adult↗
PubMed2005

Total hip arthroplasty with the APR stem and cup follow-up of a previous report.

The 2- to 5-year results of the APR-II total hip arthroplasty system (APR-II, Zimmer, Warsaw, Ind) were previously reported for 107 consecutive total hip arthroplasties performed between January 1994 and January 1995. The purpose of this study was to report the 10-year survival data in this same cohort of patients. Seventy-two (73%) of the 99 hips originally studied met the inclusion criteria for this report. None of the femoral or acetabular components had radiographic or clinical loosening. Three hips had had revision surgery for the acetabulum with 2 for recurrent dislocation and 1 for liner disassociation. All femoral components were retained. The 10-year Kaplan-Meier survivorship analysis, with failure defined as mechanical loosening, was 100% for both the cup and stem. These hip replacements have not shown any postoperative deterioration of clinical result, fixation, or wear up to 10 years.

Adult↗
PubMed2005

Operative and patient care techniques for posterior mini-incision total hip arthroplasty.

UNLABELLED: Technical and patient care improvements have occurred with the posterior mini-incision total hip arthroplasty. We hypothesized that these changes would provide better results for patients. The clinical and radiographic results of 100 total hip arthroplasties done with the posterior mini incision between January 2004 and October 2004 were compared with 100 mini-incision total hip arthroplasties done between December 2001 and September 2002. There were no differences in diagnosis, age, and body mass index of the patients in each group. Component positions were not compromised in either group. There were improvements in the 2004 group with decreased hospital stay, reduction of postoperative pain and opioid analgesic use, reduced use of assistive devices, and earlier muscle recovery. In the 2004 group there were no complications of infection, dislocation, or sciatic palsy. The posterior mini-incision operation has shown improved results with experience and changes in technique and patient care treatment. LEVEL OF EVIDENCE: Therapeutic study, Level IV (case series). See the Guidelines for Authors for a complete description of levels of evidence.

Aged↗
PubMed2005

Clinical performance of a Durasul highly cross-linked polyethylene acetabular liner for total hip arthroplasty at five years.

BACKGROUND: Highly cross-linked polyethylene is currently the most common articulation surface used for total hip arthroplasty. The hypothesis of the present study was that the Durasul highly cross-linked polyethylene acetabular liner would have less wear at five years than would a conventional polyethylene liner used in association with the same total hip replacement system. METHODS: Forty-three consecutive patients (fifty hips) underwent total hip replacement with an uncemented titanium porous-coated metal cup and a Durasul liner that was mated with a 28-mm cobalt-chromium femoral head. Thirty-one patients (thirty-seven hips) were followed for at least five years. Thirty-five other patients (thirty-seven hips) underwent total hip arthroplasty with the same system but with a conventional polyethylene liner, and these patients also were followed for five years. Clinical assessment was performed with use of the Harris hip score and a patient self-assessment examination. Radiographic analysis included measurements of acetabular component position, fixation, and osteolysis. Femoral head penetration of the Durasul liners was compared with that of the conventional liners. RESULTS: The clinical results as determined on the basis of Harris hip scores and patient self-assessment examinations did not differ between the Durasul group and the control group. The mean bedding-in penetration was 0.054 +/- 0.07 mm for the Durasul group and 0.059 +/- 0.154 mm for the control group. The subsequent penetration, with elimination of the bedding-in wear, resulted in a linear wear rate of 0.029 +/- 0.02 mm per year for the Durasul group, compared with 0.065 +/- 0.03 mm per year for the control group (p < 0.005). The annual penetration at one and five years was 0.074 mm and 0.011 mm, respectively, for the Durasul group, compared with 0.151 mm and 0.04 mm, respectively, for the control group. CONCLUSIONS: While the qualitative wear pattern of the highly cross-linked polyethylene liner was the same as that of the conventional polyethylene liner, the annual linear wear rate was 45% of that seen with the conventional polyethylene liner. Therefore, we believe that these early data support the continued use of this highly cross-linked polyethylene liner for total hip arthroplasty.

Adult↗
PubMed2005

Metal-on-metal: articulations for the new millennium.

Implants with metal-on-metal articulations (Metasul, Sulzer Medica, Winterthur, Switzerland [now Zimmer, Warsaw, IN]) have been used in nearly 300,000 total hip replacements. In three different clinical studies, clinical success has been demonstrated using this implant as measured by Harris hip scores, patient self-assessment, and assessment of mechanical complications. Of a study group of 924 patients who received this implant, the only reported complications were mechanical, incldding two cup loosenings (0.2%) and 36 dislocations (4.0%). In a randomized study, clinical resultsfor the group that received implants with metal-on-metal articulation were comparable to those of the ceramic-on-polyethylene (control) group. Reports assessing retrieved implants with metal-on-metal articulation demonstrate low annual linear wear rates and no consequences of elevated cobalt ion levels at follow-up from 4 years to 26 years. In light of these data, the continued ise of metal-on-metal articulations is recommended for any patient who does not have compromised renal function.

Arthroplasty, Replacement, Hip↗
PubMed2005

Development of imageless computer navigation for acetabular component position in total hip replacement.

The purpose of this study was to develop an imageless (without preoperative computerized tomography (CT) scans or intraoperative fluoroscopy) computer navigation system for total hip replacement. One-hundred and ninety-five hips were operated with imageless computer navigation. Eighty-five hips were operated prior to obtaining precise results, with precision refined in the subsequent 110 hips. Computer accuracy for cup-adjusted anteversion was achieved in 100% of the final 40 hips, and for adjusted inclination in 96.6%. The factors necessary for accurate measurements are mechanical stability of the tools with the light-emitting diodes, adjusted computer anteversion and inclination for the tilt of the pelvis (tilt in the AP plane), and check-and-balance techniques for confirmation of measurements of tilt, anteversion and inclination.

Acetabulum↗
PubMed2004

Fixation and osteolysis with Metasul metal-on-metal articulation.

The purpose of this study was to report the prevalence of osteolysis and loss of fixation using Metasul metal-on-metal articulation couples. Ninety-two patients with 96 hips with Metasul articulation couples were followed for 5 to 11 years. By patient self-assessment, 89 (93%) patients scored themselves as good or excellent. The occurrence of osteolysis and the grading of fixation were obtained from plain radiographs. The clinical evaluation for these patients was performed by patient self-assessment. With the use of plain radiographs, there was no osteolysis observed in these 96 hips other than calcar resorption (6 hips [6.3%]). All components were fixed, except for 1 loose cup that was revised, and this level of fixation allowed a fair evaluation for osteolysis around well-functioning implants.

Adult↗