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Biomedical subjects

W N Scott

Publications and source records attributed to W N Scott.

At least 19 recordsLinked to original sources
PubMed2001

Knee: axial instability.

The long term results of total knee replacement are among the most successful of any orthopedic procedure; however, certain patterns of failure have been identified including varus-valgus instability and anterior-posterior instability in flexion. While trauma may cause acute ligamentous injury that results in instability, the majority of cases likely result from intraoperative decisions that result in malalignment and inadequate soft tissue balancing. Failure to restore medial-lateral soft tissue balance with symmetric flexion and extension spaces may result in postoperative instability. Techniques to achieve correct soft tissue balancing and symmetric flexion and extension gaps, as well as the management of postoperative instability, are reviewed.

Arthroplasty, Replacement, Knee↗
PubMed2001

The Insall legacy in total knee arthroplasty.

John N. Insall was a pioneer in the field of knee surgery. He was a rare individual who accomplished unparalleled levels of success as a surgeon, designer, and teacher. During the past 4 decades, he was instrumental in evolving total knee arthroplasty to its current state of excellence. Insall's impact on orthopaedics is felt by all who have come in contact with him.

History, 20th Century↗
PubMed2001

Use of recombinant human erythropoietin in two-stage total knee arthroplasty for infection.

A multicenter prospective study was conducted to determine whether epoetin alfa could be used to lower transfusion requirements after two-stage exchange arthroplasty for infection. Forty-one consecutive patients undergoing successful two-stage exchange arthroplasty for an infected total knee arthroplasty were enrolled in a prospective study. Epoetin alfa (40,000 units) was administered subcutaneously after prosthesis resection and antibiotic spacer placement. Although there was no difference in the hemoglobin levels before resection arthroplasty or on postoperative Day 3 between the study group and the control group, hemoglobin levels before reimplantation were higher in the patients who received epoetin alfa (12.4 mg/dL; range, 9.3-15.1 mg/dL) compared with the control group (11.3 mg/dL; range, 8.1-14.4 mg/dL). Average increase in hemoglobin level in the interval between stages was higher in the treatment group (3.2 mg/dL; range, -0.7-6.8 mg/dL) than the control group (1.7 mg/dL; range, -1.9-6 mg/dL). The transfusion rate decreased from 83% of patients in the control group to 34% in the study group during reimplantation. In addition, overall incidence of transfusion for either stage improved from 89% in the control group to 44% in the patients treated with epoetin alfa. Perioperative epoetin alfa statistically increased the hemoglobin levels and decreased transfusion rates for patients undergoing two-stage revision for infected total knee arthroplasty.

Arthroplasty, Replacement, Knee↗
PubMed2000

Development of laminin receptor agonists: identification of important functional residues by alanine scanning.

An antagonist of cellular adhesion and motility, acetyl-C-[S-Acm]-VIGYSGDRC-[S-Acm]-NH(2) (mEGF(33-42)), shares homology with the agonist sequence CDPGYIGSR-NH(2). It has been proposed that the latter peptide binds to the high affinity 67 kDa laminin receptor. Both peptides have equal affinities for the receptor and similar conformations have been derived for both. We have examined the importance of individual non-homologous residues with respect to receptor binding and antagonistic properties of mEGF(33-42). Alanine scanning of non-conserved residues in the N-terminal half of mEGF(33-42) caused loss of biological activity with respect to cell attachment, receptor binding and migratory response. Substitution of alanine for serine (position 6) caused loss of laminin-specific cell attachment and receptor binding activities. However, the peptide did stimulate migration suggesting that this peptide may be a non-specific stimulator of migration. In contrast, alanine substitution for the C-terminal Cys-S-Acm had no apparent effect on the attachment or receptor binding activities of the peptide but generated an agonist from the antagonist parent. Comparison of the modelled folds of the alanine containing peptides revealed the presence of significant helical content in those peptides capable of stimulating migration and suggests that a reduction in bulk in the N-terminal residues is not conducive to adopting a productive binding conformation.

Alanine↗
PubMed2000

The expression of membrane-associated 67-kDa laminin receptor (67LR) is modulated in vitro by cell-contact inhibition.

The interaction of cells with their substratum is an important determinant of cell behaviour, influencing attachment, proliferation, and motility. Such interactions are mediated by cell surface receptors which bind to attachment factors, like the glycoprotein laminin in basement membranes. We have previously shown that expression of the 67-kDa laminin receptor (67LR) is elevated in proliferating retinal microvasculature compared with mature, quiescent vessels. Here, we examined 67LR mRNA and protein expression in primary cultures of retinal microvascular endothelial cells (RMEC) and in the breast cancer cell-line T47D during stages of contact inhibition. In both cell types, the expression levels of 67LR mRNA and membrane-associated 67LR protein were significantly increased during the proliferative phases of monolayer formation. As the cells achieved contact inhibition, 67LR expression was reduced to comparatively low levels. Thus, the differential expression of 67LR between dividing and contact-inhibited cells may indicate a role for this receptor during proliferative processes.

Blotting, Southern↗
PubMed2000

Measurement of brake response time after right anterior cruciate ligament reconstruction.

OBJECTIVE: Recommendations on safe driving after anterior cruciate ligament (ACL) reconstruction have been largely intuitive. We studied brake response time in patients who participated in outpatient rehabilitation after right ACL reconstruction. DESIGN: Prospective, repeated measures design comparing 14 patients post-ACL reconstruction with 21 subjects with normal knees. INTERVENTIONS AND MAIN OUTCOME MEASURES: The following measures were assessed every 2 weeks for 10 weeks: brake response time, 6-meter walk time, knee range of motion, pain, and joint effusion. Statistical testing used analysis of covariance with repeated measures. Significant variables were analyzed separately and post hoc tests conducted using the least squares differences method. Both groups were compared with published norms from the American Automobile Association. RESULTS: No significant gender differences across main effects were detected. Brake response times for men improved significantly after week 6 (p < .05) and week 10 (p < .01). Brake response times for women in the ACL treatment group matched controls at 6 weeks. Six-meter walk times for control subjects were faster than those for the ACL group preoperatively (2.6 sec vs 5.5 sec), but equalized by week 6. CONCLUSIONS: After right ACL reconstruction, brake reaction times of rehabilitated men and women matched those of established controls after 4 to 6 weeks. Measuring brake response times during rehabilitation may ensure that individual patients return to driving in a safe and timely manner.

Adult↗
PubMed2000

Measurement of brake response time after right anterior cruciate ligament reconstruction.

Recommendations on safe driving after anterior cruciate ligament (ACL) reconstruction have been largely intuitive. This study evaluated 12 male patients who underwent ACL reconstruction with subsequent outpatient rehabilitation and compared them with 10 subjects who had no knee dysfunction. The following clinical measures were assessed every 2 weeks for 10 weeks: brake response time (BRT), 6-meter walk time (6MWT), knee range of motion (ROM), pain (visual analog scale), and joint effusion. Statistical testing was completed using analysis of covariance with repeated measures. The results from treatment group were compared with norms from the AAA Traffic Safety and Engineering Department. BRT showed significant differences over 10 weeks (P =.043) in the study group. There were no significant differences between the study and control group based on condition (ACL reconstruction v control) (P =.586). Pain and effusion were found to have no significant interaction effect on BRT. The treatment group's BRT increased from the 25th percentile (AAA normals) to the 87th percentile after 10 weeks of rehabilitation. Although treatment group BRT was equal to AAA normal population BRT at week 4, the large improvement from week 2 to week 4 meant that learning effects could not be ruled out until week 6. Significant differences were found for 6MWT between week 2 and all other weeks (P <.0001). The results suggest brake reaction time matches control times at 4 to 6 weeks. Thus, BRT might be used to establish return to driving criteria (in part) after ACL reconstruction if other driving impediments do not exist.

Adult↗
PubMed2000

Long-term results of total knee arthroplasty after the use of soft tissue expanders.

The success of total knee arthroplasty can be jeopardized by poor wound healing. In the current study, the results of knee arthroplasty after soft tissue expansion were reviewed retrospectively in 27 patients (29 knees) at risk for problematic healing. The incidence of wound complications was recorded for all patients after the expansion procedure and the arthroplasty. A Knee Society score also was calculated at the latest evaluation. Minor wound complications occurred after 21% (six of 29) of the tissue expansion procedures and after 18% (five of 28) of the subsequent arthroplasties. One major wound complication occurred during tissue expansion necessitating abandonment of the planned arthroplasty. No major wound complications occurred in those patients who underwent knee arthroplasty. At an average followup of 34.4 months, the average Knee Society score was 83.7 points. The results of the current study show that the technique of soft tissue expansion before total knee arthroplasty in patients at high risk for wound healing problems can successfully prevent catastrophic wound complications after the arthroplasty procedure and can avoid the need for disfiguring soft tissue reconstructions.

Adult↗
PubMed1999

Debridement arthroscopy. 10-year followup.

The treatment of osteoarthritis of the knee is a difficult problem. In the senior author's opinion, nonaggressive arthroscopic debridement of the knee is an effective procedure to relieve pain and restore function in patients with osteoarthritis of the knee. A subjective telephone interview of patients done 10 or more years after arthroscopic debridement evaluated the long term results of this treatment in patients with osteoarthritis of the knee. The patients all were candidates for total knee replacement who selected arthroscopy as a temporizing procedure. Of the 191 knees in patients undergoing arthroscopic debridement, 77 patients (91 knees) were contacted for followup. Sixty-seven percent of the 91 knees did not have total knee arthroplasty at an average of 13.2 years followup. The Tegner activity score averaged 3.5 and patient satisfaction averaged 8.6 on a 0 to 10 scale. Twenty-one patients (30 knees) or (33%) had total knee arthroplasty at an average of 6.7 years. Seven of these had total knee arthroplasty within 2 years of arthroscopic debridement. Six of these seven knees had Outerbridge Grade 4 articular cartilage changes and clinically significant meniscus tears. Seven of the 19 knees (37%) with Outerbridge Grade 4 changes in 80% of one knee compartment did not require total knee arthroplasty after greater than 10 year followup. The difficulties in long term followup in this patient population is evident, yet the number of patients who had a functional lifestyle after arthroscopic debridement was notable.

Aged↗
PubMed1999

Blood management in two-stage revision knee arthroplasty for deep prosthetic infection.

Treatment of infected total knee arthroplasty requires aggressive management to treat the infection and restore joint function. For patients with infected knee arthroplasties, a two-stage procedure is used that involves resection of the joint and placement of an antibiotic impregnated cement spacer followed by implantation of a new prosthetic 6 weeks later. Patients undergoing the two-stage procedure typically endure high allogeneic blood transfusion rates (82% to 88%) and progressive anemia because the two surgeries are spaced closely and because the infection precludes the use of alternatives to allogeneic blood. Records were reviewed of 75 patients who underwent two-stage total knee arthroplasty to characterize perioperative hemoglobin levels and blood transfusion needs in this patient group. Although transfusions were administered only when warranted by clinical symptoms and were not based on predetermined hematologic values, 62 (82%) patients received a mean of 2.3 units of blood at first-stage surgery, and 60 (80%) patients received a mean of 2.1 units of blood at the second stage. Overall, only 12% of patients did not have allogeneic blood transfusion. At the first stage before resection, mean hemoglobin concentration was 11.6 g/dL and reached a mean nadir of 8.6 g/dL 3 days after surgery. At the second stage before reimplantation, hemoglobin concentration averaged 11.1 g/dL and reached a mean nadir of 8.2 g/dL 3 days after surgery. After the first stage, allogeneic blood transfusion failed to improve postoperative hemoglobin levels enough to prevent transfusions associated with the second-stage. Patients undergoing two-stage total knee arthroplasty have anemia, and a substantial proportion of these patients require allogeneic blood transfusion at both stages. Thus, novel blood management practices are required to improve hemoglobin levels and reduce allogeneic transfusion rates in this patient population.

Aged↗
PubMed1998

The effect of pretwisting the ACL autograft on knee laxity.

This study was undertaken to determine whether pretwisting the bone-patellar tendon-bone autograft during primary anterior cruciate ligament (ACL) reconstruction had any effect on knee laxity. Patients were assigned to have twisted or nontwisted autografts based on the date of ACL reconstruction. The control group was comprised of 60 patients without graft twist, and the twist group was comprised of 60 patients who had 90 degrees of external twist applied to the graft prior to tibial fixation to reproduce the anatomic external twist of the native ACL. The average patient age was 28.8 years for the control group and 28.3 years for the twist group. Males accounted for 68% of the control patients and 73% of the twist patients. Meniscal tears were present in 45% of control and 52% of twist patients. Reconstructions were performed using an endoscopic, single-incision technique with interference screw fixation in the femur. Follow-up examination with KT-2000 arthrometry was performed when patients were within 10% of strength of the uninjured leg by isokinetic testing. KT-2000 testing at 30 lb revealed a mean side-to-side difference for reconstructed versus noninvolved knees of 1.06 for control patients and 1.08 for twist patients. The difference between the two groups was not statistically significant. All but three control and two twist patients had a Lachman and an anterior drawer examination graded as 0 to 1+. This difference also was not statistically significant. There were no clinical failures in either group. Furthermore, there was no statistically significant difference between groups clinically or by arthrometry when comparing tibial fixation with an interference fit screw versus suture fixation to a unicortical post. These results indicate that pretwisting the patellar tendon autograft in ACL reconstruction has no significant short-term effect on knee laxity as determined by instrumented testing or clinical examination.

Adult↗