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Biomedical subjects

D W Jackson

Publications and source records attributed to D W Jackson.

At least 37 records · Page 2Linked to original sources
PubMed1996

Lysosomal enzymuria in preeclampsia.

We hypothesize that the preeclamptic patient has proximal tubule epithelial injury, which leads to the release of lysosomal enzymes, and that the excretion of these enzymes might serve as a diagnostic or predictive marker in preeclamptic women. The study group consisted of 14 women with preeclampsia (10 severe and 4 mild, as defined by The American College of Obstetricians and Gynecologists criteria) and 28 normotensive controls with singleton pregnancies at 27 to 41 weeks. There were no significant differences between the two groups for gestational age, maternal age, or race. Maternal serum and urine specimens were prospectively obtained and analyzed for beta-glucuronidase, beta-hexosaminidase, alpha-galactosidase, beta-galactosidase, and alpha-mannosidase using fluorometric assays. Median serum and urine activities and fractional excretions of each of the five hydrolases were compared between the two study groups using the Mann-Whitney two-sample rank test. The serum enzyme activities of beta-hexosaminidase (P = 0.002), alpha-galactosidase (P = 0.0001), and alpha-mannosidase (P = 0.02) were significantly lower in preeclamptic patients than in controls. The urine enzyme activities of beta-glucuronidase (P = 0.001), alpha-galactosidase (P = 0.002), beta-galactosidase (P 0.0003), and alpha-mannosidase (P = 0.003) were significantly higher in the preeclamptic patients. The fractional enzyme excretions of all five lysosomal hydrolases were higher in preeclamptic patients than in controls with P < or = 0.0003 for each enzyme. Preeclampsia is associated with a significant decrease in serum activities of three of the five hydrolases studied, a significant increase in urine enzyme activities in four of the five hydrolases studied, and a significant increase in the fractional excretion of all five lysosomal hydrolases.

Adolescent↗
PubMed1996

Chondrocyte transplantation.

The transplantation of chondrocytes as a treatment to repair defects and degeneration in hyaline articular cartilage is being tested in numerous laboratory and clinical settings. This has included transplanting chondrocytes grown in tissue culture that were procured from non-weight-bearing areas of the affected joint to transplanting allografts with living chondrocytes in their intact cartilaginous matrix. Reported success with transplanting host and donor chondrocytes has varied and widespread application of these techniques still awaits more definitive studies. The clinician needs more evidence that the transplanted chondrocytes maintain their viability and that they synthesize the appropriate extracellular matrix. This new matrix needs to reproduce the functional, mechanical, and long-term wear properties of the native articular cartilage. Chondrocyte transplantation also merits further monitoring for possible delayed immunogenicity or for any signs of neoplastic potential. This exciting technology and its potential application to damaged and degenerated articular cartilage remains a stimulus to encourage further scientific work. Duplicating the unique and complex interrelations of the chondrocytes, matrix, and various bioactive factors is still some years away from general patient care.

Cartilage↗
PubMed1996

Biologic incorporation of allograft anterior cruciate ligament replacements.

Soft tissue allografts allow the orthopaedic surgeon to reconstruct ligaments without having to harvest additional tissue from the patient, which can eliminate donor tissue site morbidity and reduce surgical time. There is still much to be learned about the biologic aspects of the remodeling and incorporation of allografts in comparison with autografts. The interaction of cells, matrix, and biomolecules, such as growth factors, plays an important role that can potentially modulate, enhance, or impede the healing response in allografts. The authors have shown that, in the short term, allografts used in anterior cruciate ligament reconstruction are not as rapidly remodeled and incorporated into host tissue as are autografts. The long-term implications of this slower allograft incorporation in anterior cruciate ligament reconstruction are still unknown. The cells that repopulate allografts and autografts favor production of smaller diameter collagen fibrils, which in sufficient numbers can provide significant strength. Use of allografts raises other issues and potential disadvantages, including scarcity, immunogenicity, the potential for disease transmission, and cost-effectiveness in anterior cruciate ligament reconstruction.

Animals↗
PubMed1996

Failure of anterior cruciate ligament reconstruction: the biologic basis.

The replacement tissue used for anterior cruciate ligament reconstruction undergoes extensive biologic remodeling and incorporation after implantation. Successful biologic incorporation of the graft is dependent on a number of factors including graft placement, tensioning, and the nature of the tissue (allograft versus autograft). Failure of an anterior cruciate ligament reconstruction may occur on the basis of either technical, mechanical, or biological factors. Biologic factors include cellular repopulation, matrix remodeling, the ultimate small diameter collagen fibril orientation, the final cross sectional area of the graft, a favorable vascularization, and not overloading the graft during the remodeling process. The fully incorporated graft never duplicates the native anterior cruciate ligament but works as a check reign that makes the knee more functional.

Anterior Cruciate Ligament↗
PubMed1996

Magnetic resonance imaging of the anterior cruciate ligament: current concepts.

MR imaging of the anterior cruciate ligament (ACL) can provide highly accurate information and is the most diagnostic current imaging procedure for suspected injuries to the ligament. It is safe, absent of ionizing radiation, non-invasive, and tolerated well by patients. There have been significant advances in technique and the ability to interpret images. One can expect sensitivities of 92% to 96% and specificities of 92% to 98%. This imaging test of the ACL can provide useful information in establishing the normal anatomy, diagnosing tears, and studying the reconstructed graft.

Anterior Cruciate Ligament↗
PubMed1995

Tibial interference screw removal following anterior cruciate ligament reconstruction.

A small number of patients developed pain and tenderness at the tibial tunnel following anterior cruciate ligament reconstruction. Twenty-three knees in 22 patients underwent removal of the tibial interference screw. Ten knees had a preoperative flexion contracture and underwent a concomitant procedure to address the loss of motion at the time of hardware removal. In the 13 knees with full extension, the interval between ligament reconstruction and screw removal averaged 16 months. Eleven of these knees also underwent arthroscopy, but no intra-articular causes of pain were identified. Roentgenographic analysis showed protrusion of the interference screw above the tibial cortex in three cases. Follow-up after hardware removal averaged 2 years. Tibial tunnel tenderness resolved in 21 of 23 knees, including those of the two patients who underwent hardware removal alone. Although it cannot be stated with certainty that tibial interferences screws may cause pain, this review suggests an association. This is an uncommon problem and it is estimated to be a factor in less than 3% of the author's anterior cruciate ligament reconstructions. More common causes of knee pain should be sought before electing to remove the tibial interference screw.

Anterior Cruciate Ligament↗
PubMed1995

Preparation of an exogenous fibrin clot.

Exogenous fibrin clot has been proposed to promote the healing of meniscal tears in areas of compromised vascularity. We present a method to reproducibly prepare a tightly wound exogenous fibrin clot using 5 to 10 mL of blood obtained by sterile venipuncture. The technique produces a clot of increased consistency and high fibrin content that is adaptable in preparation as a longer, thinner clot or a shorter, thicker clot. Clots prepared in this manner will hold suture or can be morselized for extrusion through a syringe.

Animals↗
PubMed1995

Assessment of initial fixation of endoscopic interference femoral screws with divergent and parallel placement.

Divergence of the interference screw placement used for femoral fixation during endoscopically assisted reconstruction of the anterior cruciate ligament has been described. This study is a biomechanical evaluation in 12 pairs of fresh intact bovine knees of femoral interference screws placed divergently and parallel relative to the bone block and its tunnel. One knee of each pair had the interference screw placed in a parallel fashion and the other knee had a 15 degrees divergence from the bone plug. Paired specimens were used to provide an optimal comparison of biomechanical data of the two different screw placements. No statistically significant differences were seen between the two groups when looking at ultimate load, deformation, and stiffness. Mode of failure was of more concern: in 4 of 12 divergent constructs, bone plug pullout occurred compared with only 1 of 12 in the parallel construct. The pullout strength remains high even with divergence of up to 15 degrees between the bone plug and femoral interference screws placed endoscopically.

Animals↗
PubMed1995

Comparison of pullout strength for seven- and nine-millimeter diameter interference screw size as used in anterior cruciate ligament reconstruction.

This study compares biomechanical properties of 7- and 9-mm diameter screws providing interference fixation in anterior cruciate ligament reconstruction. Sixteen pairs of fresh-frozen bovine knees were evaluated. Uniaxial load to failure was performed at a deformation rate of 30 mm/s along the mechanical axis of the ligament graft with the knees secured at 45 degrees of flexion in a custom jig. A video analyzer was used to measure ligament strain and bone-to-bone deformation. Ultimate force, deformation, and failure mode were recorded and compared. The 7-mm screws provided 98% yield strength, and 95% ultimate force compared with the 9-mm screws. The average femoral pullout strength was 1161 +/- 93 N in the 7-mm group and 1198 +/- 142 N in the 9-mm group. Failure mode was similar in both groups. Clinically, the usage of 7-mm screws may reduce iatrogenic injuries to the patellar tendon graft compared with larger screws. This study shows that the biomechanical advantages of 9-mm screws compared with 7-mm screws are minimal.

Animals↗
PubMed1994

Tibial tunnel placement in ACL reconstruction.

In reconstructing the ACL, ideal tibial tunnel placement requires an understanding of the unique anatomy of the ACL tibial footprint and its relationship to the PCL, lateral meniscus, and medial tibial part of the spine. In addition to precise placement of the tibial tunnel, its length and angulation are factors to consider. Using consistent anatomic landmarks with attention to detail, the tibial tunnel can be reproducibly placed in a manner that is not detrimental to the graft.

Anterior Cruciate Ligament↗
PubMed1993

Altered urinary excretion of lysosomal hydrolases in pregnancy.

Creatinine concentrations and the activities of five lysosomal hydrolases were measured in the serum and urine of 14 healthy nonpregnant control women and 19 healthy pregnant women. Fractional enzyme excretion (FEE) values for beta-glucuronidase, beta-hexosaminidase, alpha-galactosidase, beta-galactosidase, and alpha-mannosidase were calculated and compared between the two groups of subjects. Fractional enzyme excretion was calculated as the ratio of enzyme clearance to creatinine clearance. The FEE values for beta-galactosidase and alpha-mannosidase between the nonpregnant and pregnant populations were not statistically different; however, relative to the nonpregnant control group, the median FEE values for beta-glucuronidase (P < 0.03), beta-hexosaminidase (P < 0.06), and alpha-galactosidase (P < 0.02) were decreased approximately 1.5-, 1.8-, and 2.7-fold, respectively, in the pregnant population. The median urinary beta-galactosidase activity for the pregnant population, when expressed on the basis of creatinine, was twofold higher than that of the control group (P < 0.0005). These data indicate that with pregnancy there are marked changes in the urinary excretion of selected lysosomal enzymes, particularly alpha-galactosidase and beta-glucuronidase. When the molecular weights of these five hydrolases were compared between kidney homogenate and control urine, a correlation of 0.96 was observed, while the correlation between control serum and control urine was 0.69. This suggests that the FEE value differences between the pregnant and control groups are most likely due to changes in tubule cell metabolism, either decreased secretion or increased reabsorption. These biochemical changes may provide a means of assessing changes in renal function during pregnancy.

Adolescent↗
PubMed1993

Radiographic analysis of femoral interference screw placement during ACL reconstruction: endoscopic versus open technique.

Fifty patients with anterior cruciate ligament reconstruction using a bone-patellar tendon-bone autograft performed by two techniques were evaluated roentgenographically to compare the position of the femoral interference screws. Group I consisted of 25 patients in whom the screw was placed using a distal lateral femoral incision (the two-incision technique). Group II patients underwent arthroscopically assisted intraarticular placement of the screw. These patients were then evaluated with anterior-posterior (AP) and lateral roentgenograms. We observed that the AP and lateral screw angles were significantly different with the two techniques. In addition, the endoscopic placement of the femoral screw had an associated divergence of the screw relative to the bone plug in nine of 25 patients compared with zero of 25 in the open group. In conclusion, radiographic differences do exist between femoral interference screws placed for fixation of an ACL graft using the open approach and those placed endoscopically. Although the clinical significance of these differences is not known, we raise the question of greater divergence in femoral interference screw placement with the newer intraarticular femoral interference screw placement techniques.

Anterior Cruciate Ligament↗
PubMed1993

Arthroscopic assisted PCL reconstruction: a technical note on potential neurovascular injury related to drill bit configuration.

Neurovascular injury is a potential complication during arthroscopic assisted or open posterior cruciate ligament (PCL) reconstruction. The anatomical configuration of the posterior tibia and the square configuration of the end of commonly used drill bits require special attention. One portion of the drill bit may cut out of the tibia < or = 20 mm distal to the exit point of the guide wire. The sharp square edges of these drill bits have a greater potential to traumatize adjacent soft tissue and to increase the risk of neurovascular damage. This risk may be decreased by using a tapered drill bit, an oscillating drill, and careful elevation and retraction of the overlying soft tissue.

Adult↗
PubMed1993

Endoscopic ACL reconstruction: a technical note on tunnel length for interference fixation.

The total length of bone-patella tendon-bone autografts can vary significantly between individuals. Grafts that are "too long" may protrude from the tibial tunnel site, precluding interference screw fixation. A simple calculation can be used to estimate the length of the tibial tunnel required to accommodate the graft. An intraoperative final check can be made with a calibrated drill. This distance should accommodate the total graft length. If necessary, minor adjustments that include trimming the bone plugs or deepening the femoral osseous tunnel can be made to prevent graft protrusion.

Anterior Cruciate Ligament↗
PubMed1993

Endoscopic ACL reconstruction.

The endoscopic technique offers the advantage of one incision and a femoral osseous tunnel trajectory that is more in line with the collagen fibers of the graft. Technically, it is more demanding to reproducibly obtain the interference fixation than using the two-incision technique. There is a tendency for screw and graft divergence in the femoral tunnel. The exact clinical significance of this screw and bone plug divergence has yet to be clarified. Surgeons must assess their ability to obtain the best results for the patient. There is a definite learning curve for the endoscopic technique. We believe that, with further advances in instrumentation, fixation, and alternative grafts, it will eventually be the approach of preference for ACL reconstructions.

Anterior Cruciate Ligament↗