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T Miclau

Publications and source records attributed to T Miclau.

47 records · Page 3Linked to original sources
PubMed1996

Posterior stabilization in L5-S1 isthmic spondylolisthesis with paralaminar screw fixation: anatomical and clinical results.

Combined anterior and posterior fusion with posterior instrumentation may be indicated in the treatment of select cases of L5-S1 spondylolisthesis. The instrumentation, however, is expensive and usually bulky, occasionally requiring removal. In an effort to avoid these problems, an L5-S1 paralaminar screw technique was developed for posterior stabilization after an L5-S1 anterior interbody fusion. The technique involves the placement of cortical screws from the base of the articular process of S1 to the pedicle of L5. This study evaluates the anatomic applications and clinical results of this technique. The relationship between the screw and L5 nerve root was examined using five cadaveric specimens with olisthesis of 0, 25, 50, and 75%. This work demonstrates that the screws can only be inserted safely if an L5-S1 olisthesis of at least 25% is present. If < 25%, the screws will either impinge on or directly injure the L5 nerve root. In the clinical study, the outcomes of 20 patients who had an isthmic spondylolisthesis of 25-81% and were treated with partial reduction, L5-S1 anterior interbody fusion, and L5-S1 posterior paralaminar screw fixation were reviewed. Nineteen patients had adequate posterior stabilization to completely heal an L5-S1 anterior interbody fusion without loss of the correction. In one patient, a pseudarthrosis occurred secondary to poor surgical technique of both anterior and posterior fusions. This patient required an additional L4-S1 posterior fusion 9 months later and had a good clinical outcome. No other complications due to screw placement occurred. We conclude that this procedure can be used safely and reliably for the posterior stabilization of L5-S1 after stable anterior L5-S1 interbody fusion in residual slips of at least 25%. Prerequisites are proper patient compliance and low weight. Compared with other posterior instrumentation systems, this screw fixation is inexpensive and does not require implant removal. The disadvantages of the method are the degree of difficulty of the procedure and the limited clinical application to cases of L5-S1 spondylolisthesis with corrected residual slips of 25 to 50-60%. The procedure is technically demanding and should be limited to those surgeons who are comfortable with the method.

Adolescent↗
PubMed1996

Effect of cefazolin and vancomycin on osteoblasts in vitro.

The effect of cefazolin and vancomycin on osteoblast-like cells was studied. Cells from the MG-63 human osteosarcoma cell line were grown in antibiotic free media and exposed to concentrations of cefazolin and vancomycin at order of magnitude intervals between 0 and 10,000 microg/ml. For cefazolin, a second interval was performed between 100 and 1000 microg/ml to define toxic levels more accurately. Cell number and 3H-thymidine incorporation at 0, 24, and 72 hours were determined. The results of this study show that local levels of vancomycin of 1000 microg/ml and less have little or no effect on osteoblast replication, and concentrations of 10,000 microg/ml cause cell death. Concentrations of cefazolin of 100 microg/ml and less have little or no effect on osteoblast replication, 200 microg/ml significantly decrease cell replication, and 10,000 microg/ml cause cell death. The authors conclude that vancomycin is less toxic than is cefazolin to osteoblasts at higher concentrations and may be a better antibiotic for local administration in the treatment of similarly sensitive bacterial infections.

Anti-Bacterial Agents↗
PubMed1995

A mechanical comparison of the dynamic compression plate, limited contact-dynamic compression plate, and point contact fixator.

Cortical bone porosis associated with the dynamic compression plate (DCP) prompted the development of the limited-contact dynamic compression plate (LC-DCP) and the point-contact fixator (PC-Fix) to increase bone vascularity. However, the comparative fixation characteristics of the three designs are unknown. Transverse fractures were physiologically created in paired cadaveric sheep tibiae, which were plated before torsion testing and four-point bending to failure. The tibiae were grouped randomly and compared as follows: DCP versus LC-DCP, DCP versus PC-Fix, and LC-DCP versus PC-Fix. Mean torque to failure demonstrated no significant difference between the three plates (p < 0.33). Mean bending stiffness, gap opening, and moment to failure also demonstrated no significant difference between the three designs with p < 0.29, < 0.13, and < 0.16, respectively. The LC-DCP and PC-Fix have torsion and bending properties comparable with the DCP in the fixation of simple transverse diaphyseal fractures.

Animals↗
PubMed1995

Bone toxicity of locally applied aminoglycosides.

The effect of tobramycin on osteoblasts was studied. Osteoblast-like cells from the MG-63 human osteosarcoma cell line were grown in antibiotic-free media and exposed to concentrations of tobramycin: first at order of magnitude intervals between 0 and 10,000 micrograms/ml, and then at closer intervals between 100 and 1,000 micrograms/ml to more accurately define toxic levels. Cell number and 3H-thymidine incorporation at 0, 24 and 72 h were determined. Similarly, primary cultures of rat osteoblasts were exposed to the same concentrations of tobramycin to confirm the validity of the MG-63 cell line as a model for nontransformed cells. The results of this study demonstrate that local levels of tobramycin of < or = 200 micrograms/ml have little or no effect on osteoblast replication. Concentrations of 400 micrograms/ml significantly decreased cell replication, and concentrations of 10,000 micrograms/ml caused cell death. Results obtained with primary rat osteoblast cultures were similar to those obtained from the MG-63 cultures at the tested tobramycin concentrations.

Animals↗
PubMed1993

In vitro pharmacokinetics of antibiotic release from locally implantable materials.

Local deposition of antibiotics has became increasingly popular in the management of open fractures or osteomyelitis, and several substances have been employed as the vehicle for delivery. Although the elution characteristics of some substances have been documented, a comparative study of the characteristics of the commonly used substances could establish the clinical indications for particular vehicles. Cylindrical pellets of uniform size (6 x 4 mm) were prepared from bone graft (BG), demineralized bone matrix (DBM), plaster of Paris (POP), or polymethylmethacrylate (PMMA), with 25 mg of tobramycin/g of substance in each pellet. The pellets were suspended in phosphate buffered saline, and the antibiotic concentration in the buffer was determined at various time intervals by an enzyme immunoassay. BG and DBM eluted 70 and 45% of their antibiotic load by 24 h, and negligible amounts were detected at 1 week; POP released 17% of its load by 24 h, with trace amounts detected at 3 weeks; and PMMA eluted 7% at 24 h, with trace amounts detected for as long as 14 days. These findings suggest that the optimal vehicle for local deposition of antibiotic depends on the clinical setting. BG and DBM may be best employed when brief antibiotic coverage is required (as for acute contaminated open fractures), whereas POP and PMMA may be better suited for long-term coverage (such as for established osteomyelitis).

Animals↗
PubMed1993

The effects of antibiotic-impregnated autogeneic cancellous bone graft on bone healing.

Autogeneic cancellous bone graft has been recommended as a vehicle for local antibiotic delivery. Its effect on graft incorporation, however, is unknown. The healing of defects grafted with tobramycin-impregnated cancellous bone were compared with those grafted with cancellous bone alone. Plane roentgenographs, microradiographs, bone density analyses, histologic examination, and biomechanical testing were performed on specimens throughout the course of healing. The presence of large concentrations of local tobramycin does not appear to affect the normal healing characteristics of cancellous bone graft.

Animals↗
PubMed1988

Dynamic compression plate fixation: a biomechanical comparison of unicortical vs bicortical distal screw fixation.

The use of unicortical screws instead of bicortical screws in the extreme outer holes of dynamic compression plates (DCPs) has been recommended to minimize the stress riser effect at the end of the plates. The authors examined in vitro two groups of paired canine femurs after compression plates had been applied to the anterolateral diaphyseal surface bilaterally. Group I: intact paired femurs with bicortical peripheral screws in one DCP and unicortical peripheral screws in the other; Group II: osteotomized paired femurs again comparing unicortical and bicortical peripheral DCP screws. All specimens were torsion tested to failure and the torque, stiffness, energy, rotation, and failure fracture length were calculated. Unicortical screws did not enhance the torsional strength in either group, and significantly compromised stiffness, energy, and rotation in the osteotomized group. The only apparent benefit of unicortical peripheral screws in a DCP was a shorter, less comminuted fracture upon failure.

Animals↗
PubMedDate not supplied

High pressure pulsatile lavage irrigation of intraarticular fractures: effects on fracture healing.

OBJECTIVES: To evaluate the effects of pulsatile lavage and bulb syringe irrigation on fracture healing in vivo. DESIGN: Randomized prospective trial in an animal model. SETTING: Medical school orthopaedic department. SUBJECTS: Thirty New Zealand white rabbits. INTERVENTION: The control group (C) underwent osteotomy of the medial femoral condyle, stabilization, and closure. The bulb syringe and pulsatile lavage groups underwent the same procedure as group C, with the addition of irrigation with one liter of normal saline via a bulb syringe (B) or a pulsatile lavage system (P). Animals were administered two fluorescent bone stains: xylenol orange at the time of operation, and calcein green one week postoperatively. Animals were euthanized two weeks postoperatively and femurs were retrieved for histological analysis. MAIN OUTCOME MEASURES: Union was determined by examination of microradiographs under light microscopy. The viability of bone along the fracture site was determined by evaluation of xylenol orange and calcein green staining under fluorescent microscopy. The density of new bone formed in the osteotomy site was assessed by computerized digitization of standardized regions of the proximal and distal osteotomy. RESULTS: Xylenol orange bands were present a mean of 66 +/- 8 percent (mean +/- standard error of the mean), 65 +/- 6 percent, and 44 +/- 5 percent of the distance along the osteotomy in groups C, B, and P, respectively (p < 0.001). Calcein green bands were present throughout the osteotomy site in all specimens. Calcified new bone was present in 62 +/- 4 percent, 58 +/- 7 percent, and 41 +/- 9 percent of the area measured in groups C, B, and P, respectively (p = 0.07). Twenty percent of the osteotomies in groups C and B did not unite, compared with 30 percent in group P (p > 0.5). CONCLUSIONS: Pulsatile lavage irrigation of fresh intraarticular fractures in rabbits has a detrimental effect on early new bone formation; this effect, however, is no longer apparent two weeks following irrigation. While this study evaluated the effects of pulsatile lavage irrigation in noncontaminated fractures without extensive soft tissue injury, the detrimental effects observed on early new bone formation may translate to an increased risk of nonunion in the setting of a contaminated open fracture with extensive soft tissue injury. Based on the results of this investigation, the selective use of pulsatile lavage irrigation appears warranted. In the absence of gross wound contamination, irrigation with a bulb syringe appears less likely to impair fracture healing than does pulsatile lavage irrigation. Expansion of the model used in this study to include bacterial contamination and soft tissue crushing may further elucidate the effects of pulsatile lavage irrigation on fracture healing.

Animals↗
PubMedDate not supplied

Necrotizing soft-tissue infections.

Necrotizing fasciitis is a rare and often fatal soft-tissue infection involving the superficial fascial layers of the extremities, abdomen, or perineum. Necrotizing fasciitis typically begins with trauma; however, the inciting event may be as seemingly innocuous as a simple contusion, minor burn, or insect bite. Differentiating necrotizing infections from common soft-tissue infections, such as cellulitis and impetigo, is both challenging and critically important. A high degree of suspicion may be the most important aid in early diagnosis. Prompt diagnosis is imperative because necrotizing infections typically spread rapidly and can result in multiple-organ failure, adult respiratory distress syndrome, and death. Although group A Streptococcus is the most common bacterial isolate, a polymicrobial infection with a variety of Gram-positive, Gram-negative, aerobic, and anaerobic bacteria is more common. Orthopaedic surgeons are often the first physicians to evaluate patients with such infections and therefore need to be familiar with this potentially devastating disease and its management. Prompt diagnosis, immediate administration of broad-spectrum antibiotic coverage, and emergent aggressive surgical debridement of all compromised tissues are critical to reduce the morbidity and mortality of these rapidly progressing infections.

Adolescent↗
PubMedDate not supplied

A defect-in-continuity in the canine femur: and in-vivo experimental model for the study of bone graft incorporation.

The in-vivo study of bone graft incorporation has traditionally used a segmental diaphyseal bone defect. This model reliably produces a nonunion, but is complicated by graft instability and altered limb loading stresses. The authors discuss the advantages of a defect-in-continuity canine femur model which produces a more consistent union with fewer mechanical complications despite the absence of fixation. This proposed model permits analysis of radiographic, histologic and biomechanical data which are more applicable to the usual clinical setting in which bone graft is required.

Animals↗