Polymethylmethacrylate (PMMA) Augmentation Enhances the Mechanical Characteristics of Midfoot Beam Constructs in Charcot Neuroarthropathy Cadaver Model

BACKGROUND

Even with the best conservative care, patients with Charcot neuroarthropathy (CN) of the foot and ankle often ulcerate, increasing their risk of infection, amputation, and death. Surgical fixation has been associated with risk of recurrent ulceration, potentially due to poor bone quality prone to recurrent deformity and ulceration. We propose midfoot beam reconstruction with PMMA augmentation as a novel means of improving fixation.

METHODS

A protocol was developed to create characteristic CN midfoot fragmentation both visually and fluoroscopically in each of 12 matched-pair cadaveric feet. Afterward, the pairs were divided into 2 groups: (1) midfoot beam fusion surgery alone, and (2) midfoot beam fusion surgery augmented with PMMA. A solid 7.0-mm beam was placed into the medial column and a solid 5.5-mm beam was placed across the lateral column. In the PMMA group, 8 to 10 mL of PMMA was inserted into the medial column. The hindfoot of each specimen was potted and the metatarsal heads were cyclically loaded for 1800 cycles, followed by load to failure while load and displacement were continually recorded.

RESULTS

One specimen in the beam alone group failed before reaching the 1800th cycle and was not included in the failure analysis. The midfoot beam only group demonstrated greater mean displacement during cycle testing compared with the PMMA group, P < .05. The maximum force (N), stiffness (N/mm), and toughness (Nmm) were all significantly greater in the group augmented with PMMA, P < .05.

CONCLUSION

In a CN cadaveric model, PMMA augmentation significantly decreased gapping during cyclic loading and nearly doubled the load to failure compared with midfoot beams alone.

CLINICAL RELEVANCE

The results of this biomechanical study demonstrate that augmentation of midfoot beams with PMMA increases the strength and stiffness of the fusion construct. This increased mechanical toughness may help reduce the risk of nonunion and infection in patients with neuropathic midfoot collapse.

Biomechanical Comparison of Ulnar Collateral Ligament Reconstruction Between Palmaris Longus Autograft and Knee Medial Collateral Ligament Allograft

Background

Medial ulnar collateral ligament (mUCL) injury can cause significant pain and alter throwing mechanics. Common autograft options for mUCL reconstruction (UCLR) include the palmaris longus (PL) and hamstring tendons. Allograft use may reduce donor site morbidity and decrease function related to PL autografts.

Purpose

To compare varus stability and load to failure between a novel allograft for UCLR-knee medial collateral ligament (kMCL)-and a PL autograft in human donor elbow specimens.

Study Design

Controlled laboratory study.

Methods

A total of 24 fresh-frozen human elbows were dissected to expose the mUCL. Medial elbow stability was tested with the mUCL intact (native), deficient, and reconstructed utilizing the humeral single-docking technique with either a (1) kMCL allograft (n = 12) or (2) a PL autograft (n = 12). A 3-N·m valgus torque was applied to the elbow, and valgus rotation of the ulna was recorded via motion tracking cameras. The elbow was cycled through a full range of motion 5 times. After kinematic testing, specimens were loaded to failure at 70° of elbow flexion, and failure modes were recorded.

Results

The mUCL-deficient elbows demonstrated significantly greater valgus rotation compared with the intact and reconstructed elbows at every flexion angle tested (10°-120°) (P <.001). Both kMCL- and PL-reconstructed elbows exhibited significantly higher mean valgus rotation compared with the intact state between 10° and 40° of flexion (P < .01). There were no significant differences in valgus rotation at any flexion angle between the kMCL and PL graft groups. When loaded to failure, elbows reconstructed with both kMCL and PL grafts failed at similar torque values (18.6 ± 4 and 18.1 ± 3.4 N·m, respectively; P = .765).

Conclusion

Fresh-frozen and aseptically processed kMCL allografts demonstrated similar kinematic and failure properties to PL tendon autografts in UCL-reconstructed elbows, although neither graft fully restored kinematics between 10° and 40°.

Clinical Relevance

Prepared kMCL ligament allografts may provide a viable graft material when reconstructing elbow ligaments while avoiding the potential complications related to PL autografts- including donor site morbidity.

The impact of SMARTpass algorithm status on inappropriate shock rates in the UNTOUCHED Study

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Boston Scientific Corporation

Background

The current Subcutaneous ICD (S-ICD) model incorporates SMART Pass (SP) to improve sensing and discrimination capabilities to reduce inappropriate shocks (IAS). SP status is programmable but may also be disabled automatically in the setting of low amplitude signals or low heart rate in order to avoid under-sensing of VT/VF.

Objective

To evaluate SP impact on IAS, appropriate shocks (AS), complications and mortality in the UNTOUCHED S-ICD trial.

Methods

Primary prevention patients (pts, n=1111) with ejection fraction ≤35% and no pacing requirement were followed for up to 18 months. SP status during a study visit was programmed ON or OFF and status between visits was either consistently OFF, ON, or automatically disabled (DIS). The impact of SP status on pt outcomes was evaluated using Kaplan-Meier (K-M) analysis. Multivariable proportional hazard analysis identified predictors of IAS and SP disable events.

Results

Percent of pts with SP always ON, always OFF, ON with DIS, and OFF then ON with no DIS were 56, 16, 15, and 13%, respectively. At least one SP DIS occurred in 177 pts, but only 13% had 2 or more, mostly due to PVCs and low EGM amplitudes. Significant multivariable predictors of SP disable events are history of atrial fibrillation (hazard ratio (HR) 2.49, odds ratio (OR) (1.49-4.16); p=.0005), only one passing vector at S-ICD screening, (HR 1.85, OR (1.10-3.10; p=.0202) and lower left ventricular ejection fraction (HR 1.05, OR (1.01-1.08); p=.0074). K-M IAS rates were highest for pts experiencing DIS (fig 1) and lowest for SP ON. While neither AS (p=0.58) nor complication (p=0.58) rates varied significantly according to SP status, mortality was lower for pts with SP ON during any duration of time (p=0.044) by univariate analysis. Further analysis is planned to better understand the relationship between SP status and mortality.

Conclusion

Patients in the UNTOUCHED trial with SMART Pass (SP) consistently ON had significantly fewer inappropriate shocks, with no impact on appropriate therapy for VT/VF. Patients with history of atrial fibrillation, lower left ventricular ejection fraction, and only one passing vector at S-ICD screening are at higher risk of SP disable events; therefore, care should be taken for these patients to assess SP status and their higher risk for inappropriate shocks.

A systematic review and meta-analysis of early goal-directed therapy for septic shock: the ARISE, ProCESS and ProMISe Investigators

PURPOSE

To determine whether early goal-directed therapy (EGDT) reduces mortality compared with other resuscitation strategies for patients presenting to the emergency department (ED) with septic shock.

METHODS

Using a search strategy of PubMed, EmBase and CENTRAL, we selected all relevant randomised clinical trials published from January 2000 to January 2015. We translated non-English papers and contacted authors as necessary. Our primary analysis generated a pooled odds ratio (OR) from a fixed-effect model. Sensitivity analyses explored the effect of including non-ED studies, adjusting for study quality, and conducting a random-effects model. Secondary outcomes included organ support and hospital and ICU length of stay.

RESULTS

From 2395 initially eligible abstracts, five randomised clinical trials (n = 4735 patients) met all criteria and generally scored high for quality except for lack of blinding. There was no effect on the primary mortality outcome (EGDT: 23.2% [495/2134] versus control: 22.4% [582/2601]; pooled OR 1.01 [95% CI 0.88-1.16], P = 0.9, with heterogeneity [I(2) = 57%; P = 0.055]). The pooled estimate of 90-day mortality from the three recent multicentre studies (n = 4063) also showed no difference [pooled OR 0.99 (95% CI 0.86-1.15), P = 0.93] with no heterogeneity (I(2) = 0.0%; P = 0.97). EGDT increased vasopressor use (OR 1.25 [95% CI 1.10-1.41]; P < 0.001) and ICU admission [OR 2.19 (95% CI 1.82-2.65); P < 0.001]. Including six non-ED randomised trials increased heterogeneity (I(2) = 71%; P < 0.001) but did not change overall results [pooled OR 0.94 (95% CI 0.82 to 1.07); P = 0.33].

CONCLUSION

EGDT is not superior to usual care for ED patients with septic shock but is associated with increased utilisation of ICU resources.

Ministry of health clinical practice guidelines: cancer screening

The Ministry of Health publishes national clinical practice guidelines to provide doctors and patients in Singapore with evidence-based guidance on managing important medical conditions. This article reproduces the introduction and executive summary (with key recommendations from the guidelines) from the Ministry of Health clinical practice guidelines on cancer screening, for the information of readers of the Singapore Medical Journal. Chapters and page numbers mentioned in the reproduced extract refer to the full text of the guidelines, which are available from the Ministry of Health website (http://www.moh.gov. sg/mohcorp/publications.aspx?id=24018). The recommendations should be used with reference to the full text of the guidelines. Following this article are multiple choice questions based on the full text of the guidelines.

After-hour home care service provided by a hospice in Singapore

A home care Hospice programme was set up to provide care to the patients with advanced diseases and their families in Singapore. After office-hour, the service is managed by a doctor on weekdays, with the assistance of a nurse during daytime on Saturdays, Sundays and public holidays. The doctor on-call made an average of 3.1 phone calls and 1.3 visits each weekday evening. Over the weekends and public holidays, there were a mean of 16.7 phone calls and 6 visits each day. More than half of the visits (50.3%) were made for certification of death. The commonest symptoms that prompted visits were dyspnoea (20%) and pain (12.2%). The busiest period during weekdays was between 6.00 pm and 11.00 pm, when our doctors did most of their visits. The workload of the hospice home care service is likely to increase and resources such as family health physicians can be explored to help to meet this increasing demand. This can be achieved through the provision of comprehensive training and easy accessibility to medical records which are kept with patients.

Molecular enhancement of porcine cardiac chronotropy

OBJECTIVE

To test the potential of gene transfer approaches to enhance cardiac chronotropy in a porcine system as a model of the human heart.

METHODS

Plasmids encoding either the human beta(2) adrenergic receptor or control constructs were injected into the right atria of native Yorkshire pig hearts. Percutaneous electrophysiological recording catheters equipped with 33 gauge circular injection needles were positioned in the mid-lateral right atrium. At the site of the earliest atrial potential the circular injection needles were rotated into the myocardium and the beta(2) adrenergic receptor (n = 6) or control plasmid constructs (n = 5) were injected.

RESULTS

Injection of the beta(2) adrenergic receptor construct significantly enhanced chronotropy compared with control injections. The average (SD) heart rate of the pigs was 108 (16) beats/min before injection. Two days after injection with control plasmids the heart rate was 127 (25) beats/min (NS compared with preinjection rates). After injection with plasmid encoding the beta(2) adrenergic receptor the heart rate increased by 50% to 163 (33) beats/min (p < 0.05 compared with preinjection and postinjection control rates).

CONCLUSIONS

The present studies showed in a large animal model that local targeting of gene expression may be a feasible modality to regulate cardiac pacemaking activity. In addition, these investigations provide an experimental basis for developing future clinical gene transfer approaches to upregulate heart rate and modulate cardiac conduction.

Autosomal recessive lissencephaly with cerebellar hypoplasia is associated with human RELN mutations

Normal development of the cerebral cortex requires long-range migration of cortical neurons from proliferative regions deep in the brain. Lissencephaly ("smooth brain," from "lissos," meaning smooth, and "encephalos," meaning brain) is a severe developmental disorder in which neuronal migration is impaired, leading to a thickened cerebral cortex whose normally folded contour is simplified and smooth. Two identified lissencephaly genes do not account for all known cases, and additional lissencephaly syndromes have been described. An autosomal recessive form of lissencephaly (LCH) associated with severe abnormalities of the cerebellum, hippocampus and brainstem maps to chromosome 7q22, and is associated with two independent mutations in the human gene encoding reelin (RELN). The mutations disrupt splicing of RELN cDNA, resulting in low or undetectable amounts of reelin protein. LCH parallels the reeler mouse mutant (Reln(rl)), in which Reln mutations cause cerebellar hypoplasia, abnormal cerebral cortical neuronal migration and abnormal axonal connectivity. RELN encodes a large (388 kD) secreted protein that acts on migrating cortical neurons by binding to the very low density lipoprotein receptor (VLDLR), the apolipoprotein E receptor 2 (ApoER2; refs 9-11 ), alpha3beta1 integrin and protocadherins. Although reelin was previously thought to function exclusively in brain, some humans with RELN mutations show abnormal neuromuscular connectivity and congenital lymphoedema, suggesting previously unsuspected functions for reelin in and outside of the brain.

Concomitant boost radiation therapy for inoperable non-small-cell lung cancer: preliminary report of a prospective randomized study

PURPOSE

The radiation therapy results for patients with inoperable non-small-cell lung cancer (NSCLC) have been disappointing. Tumor dose escalation using concomitant boost technique (CBT) has been shown to improve local control in a few prospective studies. This trial was carried out to prospectively assess the radiation response and acute toxicity of CBT in comparison to the conventional treatment technique (CTT).

METHODS AND MATERIALS

Ninety-seven consecutive eligible patients were entered in this prospective clinical trial between November 1994 and February 1998. Patients were randomized to receive either CBT (43 patients) or CTT (54 patients) radiation therapy. These patients either refused chemotherapy or were judged as unsuitable for chemotherapy. Patients in the CBT group received 46.8 Gy in 26 fractions using large fields that encompassed the gross and occult disease. A concomitant boost of 18.2 Gy (0.7 Gy per fraction) was delivered to the gross disease using small fields with 1.5-cm margins. The small fields were treated concurrently with the large fields and the total dose to the tumor area was 65 Gy in 26 fractions. Patients in the CTT group received 70.8 Gy in 38 fractions. The acute toxicity between each group was compared. The response rate was analyzed and compared by treatment group, gender, age, stage, histology, initial Karnofsky performance score (KPS), severity of acute toxicity, and maximum body weight loss (MBWL) during treatment course.

RESULTS

The demographic parameters such as sex, age, and stage were evenly distributed in each treatment group. The majority of these patients had Stage IIIA and IIIB disease. Overall median treatment times were 39 days for the CBT group of patients and 62 days for the CTT group. No treatment-related mortality was found. There were 2 patients in the CTT group with acute RTOG Grade 3 lung toxicity, and no Grade 3 lung or esophageal toxicity was observed in CBT group. The response rates, assessed by radiographic images, were 69.8% and 48.1% for the CBT and CTT patients, respectively. Univariate and multivariate analysis revealed that patients in the CBT group, patients with better KPS, and patients with more severe acute toxicity had a higher response rate.

CONCLUSION

This study demonstrates that concomitant boost radiation therapy is tolerable, and produces a superior response rate than conventional radiation therapy for patients with inoperable NSCLC. The length of treatment was reduced from 38 to 26 treatment days, almost a 30% reduction.

Y2K: effects on pacemaker and implantable defibrillator programmers

All permanent pacemakers and implantable defibrillators (PPM/ICDs) will continue to function as programmed without regard to the date in the year 2000 (Y2K). All manufacturers contacted reassured us that some of these devices incorporate a day/year clock in the circuitry; however, these are not involved in sensing or delivering programmed therapy. Some manufacturers' device programmers will roll over to the year 2000 without any problems at all, whereas others may have difficulty with date and time stamping on printed reports. We tested 14 different types of PPM/ICD programmers for Y2K compliance using 8 tests. Five of the 14 models passed each test and were labeled at our institution with a green "Y2K" sticker to identify them as Y2K compatible and needing no special attention after December 31, 1999. The most common test failed was the ability to roll the date forward from December 31, 1999, with the programmer power off. Organizations should consider testing and replacing noncompliant device programmers or placing a red sticker with "Y2K" crossed out on noncompliant pieces. The red sticker alerts the advanced practice nurse or physician to the need to confirm the appropriate date and time in the programmer after startup in the year 2000 and before interrogating or programming any PPM/ICD, to avoid inappropriate date and time stamping on printed reports from that programmer.

Ectopic orbital meningioma: a case report and review

PURPOSE

To describe a well-documented case of ectopic orbital meningioma, to review the literature on the subject, and to recommend treatment.

METHODS

Neuroradiologic investigations were suggestive of orbital meningioma. The patient underwent total excision of the mass, which was subsequently examined by light microscopy and immunohistochemistry.

RESULTS

The patient was diagnosed with ectopic orbital meningioma which was locally invasive. The tumor was surgically excised, and did not recur during a 42-month follow-up interval.

CONCLUSIONS

Ectopic orbital meningiomas are rare tumors that develop from ectopic arachnoid tissue. Although locally invasive, the prognosis is favorable if the tumor is completely removed.

Divalent metal derivatives of the hamster dihydroorotase domain

Dihydroorotase (DHOase, EC 3.5.2.3) is a zinc enzyme that catalyzes the reversible cyclization of N-carbamyl-L-aspartate to L-dihydroorotate in the third reaction of the de novo pathway for biosynthesis of pyrimidine nucleotides. The recombinant hamster DHOase domain from the trifunctional protein, CAD, was overexpressed in Escherichia coli and purified. The DHOase domain contained one bound zinc atom at the active site which was removed by dialysis against the chelator, pyridine-2,6-dicarboxylate, at pH 6.0. The apoenzyme was reconstituted with different divalent cations at pH 7.4. Co(II)-, Zn(II)-, Mn(II)-, and Cd(II)-substituted DHOases had enzymic activity, but replacement with Ni(2+), Cu(2+), Mg(2+), or Ca(2+) ions did not restore activity. Atomic absorption spectroscopy showed binding of one Co(II), Zn(II), Mn(II), Cd(II), Ni(II), or Cu(II) to the enzyme, while Mg(II) and Ca(II) were not bound. The maximal enzymic activities of the active, reconstituted DHOases were in the following order: Co(II) --> Zn(II) --> Mn(II) --> Cd(II). These metal substitutions had major effects upon values for V(max); effects upon the corresponding K(m) values were less pronounced. The pK(a) values of the Co(II)-, Mn(II)-, and Cd(II)-substituted enzymes derived from pH-rate profiles are similar to that of Zn(II)-DHOase, indicating that the derived pK(a) value of 6.56 obtained for Zn-DHOase is not due to ionization of an enzyme-metal aquo complex, but probably a histidine residue at the active site. The visible spectrum of Co(II)-substituted DHOase exhibits maxima at 520 and 570 nm with molar extinction coefficients of 195 and 210 M(-1) cm(-1), consistent with pentacoordination of Co(II) at the active site. The spectra at high and low pH are different, suggesting that the environment of the metal binding site is different at these pHs where the reverse and forward reactions, respectively, are favored.

Synthesis and enzymic evaluation of 4-mercapto-6-oxo-1, 4-azaphosphinane-2-carboxylic acid 4-oxide as an inhibitor of mammalian dihydroorotase

The design, synthesis, and enzymic evaluation of cis- and trans-4-mercapto-6-oxo-1,4-azaphosphinane-2-carboxylic acid 4-oxide 5 against mammalian dihydroorotase is presented. The design strategy for 5 was based on the strong affinity of phosphinothioic acids for zinc and that 5 also resembles the postulated tetrahedral transition state for the enzyme-catalyzed reaction. The synthesis of 5 utilized a novel protection/deprotection sequence upon 4-hydroxy-6-oxo-1, 4-azaphosphinane-2-carboxylic acid 4-oxide 4, followed by incorporation of alpha-phenyl benzenemethanethiol and exhaustive deprotection to afford 5 in 40% overall yield from 4. The activities of both isomers of 5 as inhibitors of mammalian dihydroorotase were marginally greater than that of the parent phosphinic acid 4, indicating a weak binding enhancement due to the phosphinothioic acid moiety.

Regulated expression of cadherin-11 in human extravillous cytotrophoblasts undergoing aggregation and fusion in response to transforming growth factor beta 1

Transforming growth factor beta 1 is believed to be a key regulator of extravillous cytotrophoblast invasion during the first trimester of pregnancy. In addition, this growth factor has been shown to regulate cellular differentiation and fusion in cultured extravillous cytotrophoblasts. To date, the cellular mechanisms by which transforming growth factor beta 1 promotes these developmental processes remain poorly understood. Recent studies indicate that the expression of the novel cadherin subtype, known as cadherin-11, is associated with the terminal differentiation and fusion of villous cytotrophoblasts isolated from the human term placenta and human myoblasts in vitro. In this study, cadherin-11 mRNA and protein expression were examined in primary cultures of human extravillous cytotrophoblasts cultured in the presence of increasing concentrations of transforming growth factor beta 1 using northern and western blot analysis, respectively. Transforming growth factor beta 1 was shown to increase cadherin-11 mRNA and protein expression in these cultured extravillous cytotrophoblasts in a dose-dependent manner. Cadherin-11 was further localized to the large cellular aggregates and multinucleated cells that formed in response to increasing concentrations of transforming growth factor beta 1 using immunocytochemistry. Collectively, these observations suggest that the morphogenetic effects of transforming growth factor beta 1 on cultured extravillous cytotrophoblasts are mediated, at least in part, by an increase in cadherin-11 expression. This study not only adds to the understanding of the cellular mechanisms by which transforming growth factor beta 1 promotes trophoblast differentiation and fusion but provides useful insight into the cell biology of the cadherins.

Hybrid pharmacologic and ablative therapy: a novel and effective approach for the management of atrial fibrillation

INTRODUCTION

Maintenance of sinus rhythm in patients with recurrent atrial fibrillation is often difficult to achieve with pharmacologic therapy. Complex catheter ablative procedures are being developed, but efficacy and safety issues remain to be clarified. We hypothesized that combined pharmacologic and simple ablative therapies in a targeted subset of patients will improve success in the treatment of atrial fibrillation.

METHODS AND RESULTS

We identified 13 patients (mean age 61.5 +/- 16.2 years) with atrial fibrillation who converted to electrocardiographic atrial flutter during antiarrhythmic drug treatment. Surface ECG suggested "typical" atrial flutter in 11 patients and "atypical" atrial flutter in 2. Intracardiac mapping and entrainment studies revealed 9 patients had counterclockwise isthmus-dependent atrial flutter, and the remaining 4 had complex activation patterns, suggesting the presence of multiple wavefronts. All 9 patients with typical atrial flutter underwent successful ablation. None of the 4 patients with complex activation patterns had successful ablation. Patients were followed for recurrences of atrial arrhythmias via clinic visits, record review, and interviews. In patients who underwent successful ablation and continued on antiarrhythmic drugs, 88.9% remain in sinus rhythm after a mean follow-up of 14.3 +/- 6.9 months (range 1 to 28).

CONCLUSION

In patients who experience conversion of atrial fibrillation to atrial flutter during antiarrhythmic drug treatment, ablation and continuation of pharmacologic therapy is a safe and effective means of achieving and maintaining sinus rhythm.

Combined-modality therapy for squamous carcinoma of the buccal mucosa: treatment results and prognostic factors

BACKGROUND

Reports on locoregional control and survival of squamous cell carcinoma of buccal mucosa are scarce in literature. In this study, a single institutions's experience of combined surgery and postoperative radiotherapy (RT) for buccal mucosal malignancy with favorable results was analyzed and presented. The prognostic factors on locoregional control were also discussed.

METHODS

From January 1988 to July 1994, 57 patients with squamous cell carcinoma of buccal mucosa treated by surgery and RT were reviewed. The distributions according to American Joint Committee on Cancer (AJCC) staging were: stage II, 6; stage III, 21; and stage IV, 30 patients. Total dose of RT at the buccal area ranged from 45 Gy to 68.4 Gy, median 61.2 Gy. Tumor-related factors (AJCC stage, T stage, histologic grading, pathologic tumor invasion to skin of cheek, adjacent bony structures, and regional lymph nodes) and treatment-related factors (surgical margin, radiation dose, and the time interval between operation and RT) were analyzed to determine their influence on locoregional control.

RESULTS

Three-year actuarial locoregional control rate, overall survival rate, and disease-specific survival rates were 64%, 55%, and 62%, respectively. Ten of these 22 patients (45%) with recurrent tumors were reoperated, but only 2 patients were successfully salvaged. Positive surgical margin and tumor invasion to skin of cheek were significantly poor prognostic factors on locoregional control by univariate analysis. In multivariate analysis, tumor invasion to skin of cheek was the only prognostic factor (p = .0014).

CONCLUSIONS

Locoregional failure was the major cause of death for squamous buccal mucosa cancers managed with surgery and RT. Few recurrences could be detected early and successfully salvaged. Skin of cheek involvement is an important prognostic factor for buccal mucosa cancers.

The biological effectiveness of intermittent irradiation as a function of overall treatment time: development of correction factors for linac-based stereotactic radiotherapy

PURPOSE

Continuous irradiation of relatively short duration as administered in gamma-ray stereotactic radiosurgery (SRS) is biologically not equivalent to the more protracted intermittent exposures during accelerator-based radiosurgery with multiple arcs. Accelerator-based SRS and fractionated stereotactic radiotherapy (SRT) is currently performed with a high degree of variability in equipment and techniques resulting in highly variable treatment delivery times. The present work is designed to quantify the effects of radiation delivery times on biological effectiveness. For this, the intermittent radiation delivery schemes, typical for linac-based SRS/SRT, have been simulated in vitro to derive biological correction factors.

METHODS AND MATERIALS

The experiments were carried out using U-87MG human glioma cells in suspension at 37 degrees C irradiated with 6 MV X-rays to clinically relevant doses ranging from 6 to 18 Gy, delivered over total irradiation times from 16 min to 3 h. The resulting cell survival data was used to calculate dose correction factors to compensate for wide variations in dose delivery times.

RESULTS

At each total dose level, cell survival increased with increasing total irradiation time. The increase in survival was more pronounced at higher dose levels. At a total dose of 12 Gy, cell survival increased by a factor of 4.7 when irradiation time was increased from 16 to 112 min. Dose correction factors were calculated to allow biologically equivalent irradiations over the range of exposure times. Cells irradiated with corrected total doses of 11.5 Gy delivered incrementally in 16 min up to 13.3 Gy in 112 min were found to exhibit the same survival within the experimental limits of accuracy.

CONCLUSIONS

For a given total dose, variations in dose delivery time typical of SRS/SRT techniques will result in significant changes in cell survival. In the dose range studied, an isoeffect dose correction factor of 2 to 3 cGy/min was shown to compensate for the change in delivery time for U-87 MG human gloma cells in vitro.

Electron/photon matched field technique for treatment of orbital disease

PURPOSE

A number of approaches have been described in the literature for irradiation of malignant and benign diseases of the orbit. Techniques described to date do not deliver a homogeneous dose to the orbital contents while sparing the cornea and lens of excessive dose. This is a result of the geometry encountered in this region and the fact that the target volume, which includes the periorbital and retroorbital tissues but excludes the cornea, anterior chamber, and lens, cannot be readily accommodated by photon beams alone. To improve the dose distribution for these treatments, we have developed a technique that combines a low-energy electron field carefully matched with modified photon fields to achieve acceptable dose coverage and uniformity.

METHODS AND MATERIALS

An anterior electron field and a lateral photon field setup is used to encompass the target volume. Modification of these fields permits accurate matching as well as conformation of the dose distribution to the orbit. A flat-surfaced wax compensator assures uniform electron penetration across the field, and a sunken lead alloy eye block prevents excessive dose to the central structures of the anterior segment. The anterior edge of the photon field is modified by broadening the penumbra using a form of pseudodynamic collimation. Direct measurements using film and ion chamber dosimetry were used to study the characteristics of the fall-off region of the electron field and the penumbra of the photon fields. From the data collected, the technique for accurate field matching and dose uniformity was generated.

RESULTS

The isodose curves produced with this treatment technique demonstrate homogeneous dose coverage of the orbit, including the paralenticular region, and sufficient dose sparing of the anterior segment. The posterior lens accumulates less than 40% of the prescribed dose, and the lateral aspect of the lens receives less than 30%. A dose variation in the match region of +/-12% is confronted when an unmodified photon field edge is matched with the fall-off of the electron field at the 50% isodose lines. By modifying the penumbra, the dose variation is reduced to +/-2%. Treatment setup accuracy is essential.

CONCLUSIONS

The electron/photon matched field technique offers a uniform isodose distribution for treatment of the orbit that has not been previously achieved. With this technique a homogeneous dose can be delivered to the entire orbit while avoiding a significant dose to the anterior segment and minimizing the risk of morbidity.

Deformation-induced hierarchical flows and drag forces in bone canaliculi and matrix microporosity

Existing theories for interstitial flows in bone have only examined the contributions from different flow systems separately, such as the flows through the microporosity, the canaliculi, and the Haversian canals. An overall model encompassing the hierarchical microstructure is important to our understanding of the actual physics of flows in bone. The flow-induced drag forces and streaming electrical potentials could interact with the osteocytes to effect biological responses. A finite element model was developed to study the contributions from various hierarchical flow channels in bone. Cortical bone is modelled as a fully hydrated biphasic poroelastic material with a superposing network of one-dimensional channels radiating from the Haversian canals representing the canaliculi. Interfacial cross-flows between these one-dimensional channels and the neighbouring poroelastic matrix are driven by the pressure differences between the matrix and the channel. The model was subjected to stress fields simulating uniform compression and pure bending. The effects of the interfacial permeability and the solid content within the channels on the drag forces in the channels were assessed. Abrupt changes in these drag forces occurred as the channel solidity approached that of the microporosity. The results were quite sensitive to the interfacial permeability, i.e. the interconnectivity between the canalicular system and the matrix microporosity. This biomechanical model should be useful to the study of mechanotransduction in bone.

A retrospective quality of life analysis using the Lung Cancer Symptom Scale in patients treated with palliative radiotherapy for advanced nonsmall cell lung cancer

PURPOSE

To measure symptom palliation in patients treated with radiation therapy for advanced nonsmall cell lung cancer (NSCLC).

METHODS AND MATERIALS

Five hundred thirty patients with NSCLC were treated at the Medical College of Virginia between 1988 and 1993. Sixty-three patients with the least favorable prognostic features received palliative radiation to 30 Gy in 10 or 12 fractions for symptoms related to the presence of intrathoracic tumor. The observer portion of the Lung Cancer Symptom Scale (LCSS) was employed in a retrospective chart review, scoring measures of appetite, fatigue, cough, dyspnea, hemoptysis, and pain.

RESULTS

In 54 evaluable patients, median survival was 4 months and was independent of age, stage, performance status, or histology. Ninety-six percent of the patients had at least one LCSS symptom at presentation. Fatigue was unaffected by therapy. Improvements in appetite (p = 0.68) and pain (p = 0.61) were not statistically significant. There was, however, a statistically significant reduction in cough (p = 0.01), hemoptysis (p = 0.001), and dyspnea (p = 0.0003). Self-limiting acute side effects included transient esophagitis in 37% of patients, though no severe toxicities were noted.

CONCLUSIONS

These results suggest symptomatic benefit from radiotherapy even in those NSCLC patients with advanced disease and a limited life expectancy. Treatment should be given to patients whose symptoms are most amenable to palliation. A site-specific quality of life instrument such as the LCSS should be included within any future clinical trial of NSCLC management so that symptom control may be scored as a treatment outcome in addition to disease-free survival.

Activation and repolarization patterns are governed by different structural characteristics of ventricular myocardium: experimental study with voltage-sensitive dyes and numerical simulations

INTRODUCTION

Substantial progress has been made in our understanding of transmural activation across ventricular muscle through studies of excitation patterns and potential distributions. In contrast, repolarization sequences are poorly understood because of experimental difficulties in mapping action potential durations (APDs) using extracellular electrodes.

METHODS AND RESULTS

Langendorff-perfused guinea pig hearts and isolated coronary-perfused left ventricular sheet preparations were stained with the voltage-sensitive dye RH-421 and optical APs were recorded with a photodiode array. Epicardial maps were constructed using a triangulation method applied to matrices of activation and repolarization times determined from (dF/dt)max and (d2F/dt2)max' respectively. Numerical simulations were carried out based on: (1) a modified Luo-Rudy model; (2) the three-dimensional architecture of ventricular fibers; and (3) the intrinsic spatial distribution of APDs. In ventricular sheets, epicardial stimulation elicited elliptical activation patterns with the major axis aligned with the longitudinal axis of epicardial fibers. When the pacing electrode was progressively inserted from epicardium to endocardium, the major axes rotated gradually, clockwise by 45 degrees, and the eccentricity decreased from 2 to 1.14. Repolarization showed a relatively uniform pattern, independent of pacing site, beginning at the apex and spreading to the base.

CONCLUSION

In experiments and simulations, the helical rotation of epicardial excitation isochrones caused by pacing at increasing depth in the myocardium correlated with the helical three-dimensional architecture of ventricular fibers. In contrast, repolarization was independent of the activation sequence and was mainly guided by spatial differences in APDs between apex and base.

Radiation alone for carcinoma of the vagina: variation in response related to the location of the primary tumor

BACKGROUND

A retrospective study of 40 patients with histologically confirmed carcinoma of the vagina is reported. The patients were treated by radiation alone (a combination of external beam therapy and implants) between October 1969 and September 1991 at the Medical College of Virginia Hospital in Richmond.

METHODS

Thirty-three patients (82%) had squamous cell carcinoma, 2 patients (7%) had adenocarcinoma, and 2 patients (5%) had poorly differentiated cancers (1 melanoma and 1 leiomyosarcoma). The patients were staged according to the International Federation of Gynecology and Obstetrics (FIGO) staging system; there were 13 patients (33%) in Stage 1, 21 (52%) in Stage II, 4 (10%) in Stage III, and 2 (5%) in Stage IV. Thirty-six patients (90%) were treated with external beam therapy and some combination of implant: cylinder, ovoid, or interstitial implants with iodine-125 or iridium-192 (afterloading). Only 4 patients (10%) received treatment by implant only.

RESULTS

Based on their response, two groups of patients were identified. Group I had 23 patients with tumors predominantly located in the proximal half of the vagina; there were 8 patients in Stage I, 11 in Stage II, 3 in Stage III, and 1 in Stage IV. Of these, three patients failed: one each in Stages III and IV and one Stage II patient was salvaged by surgery. Three patients died due to unrelated causes but with local control. The 5-year actuarial survival in this group was 81%. Group II had 17 patients with tumors located in the mid to distal half of the vagina; there were 5 patients in Stage I, 10 in Stage II, and 2 in Stage IV. Ten patients failed. Eight patients in Stage II had persistent disease, were lost to follow-up, and are presumed dead. Two patients with Stage IV disease also had inadequate local control. The overall actuarial survival in the distal group was 41%, which was significantly worse than the proximal group (81%), at a P value of 0.05.

CONCLUSIONS

This study discusses the curability of carcinoma of the vagina based on its anatomic location when predominantly similar treatment techniques and radiation doses were applied to either the proximal or the distal part of the vagina, those with cancer in the proximal half had better survival (81%) than those whose cancer was in the distal half (41%).

Comparison of dose homogeneity effects due to electron equilibrium loss in lung for 6 MV and 18 MV photons

PURPOSE

Loss of electronic equilibrium within and adjacent to low density materials can result in a dose reduction along the central axis and near the beam edge for megavoltage photon beams. In this context, Radiation Therapy Oncology Group (RTOG) protocol #91-05 recommends the use of photon beams of energy 12 MV or less for nonsmall cell lung cancer therapy. This work presents data to support the use of higher energy photons for some clinical lung field setups.

METHODS AND MATERIALS

Beam profiles were obtained from films inserted into homogeneous (polystyrene) and heterogeneous (polystyrene and lung-equivalent material) phantoms and irradiated in both single-field and parallel-opposed setups with 6 and 18 MV photon beams. Depth-dose curves were obtained with a parallel-plate ion chamber in the heterogeneous phantom to determine the range of field sizes over which the dose reduction at the lung/polystyrene interface becomes clinically significant.

RESULTS

Opposed field profiles show less degradation in the penumbra (50-90% width) at the lung/polystyrene interface than single-field profiles. The difference between 6 and 18 MV penumbra widths at the interface also reduced when an opposed field is added. The central axis dose reduction at the interface was negligible for single fields of a width of 8 cm or more.

CONCLUSION

Our results show that for opposed fields, the difference in penumbra degradation of the 6 and 18 MV photon beams is clinically insignificant compared to daily setup errors and patient motion. The central axis dose reduction is also shown to be small. Our data support the use of higher energy beams to obtain lower peripheral dose maxima in small clinical geometries.

The tumor volume and clonogen number relationship: tumor control predictions based upon tumor volume estimates derived from computed tomography

PURPOSE

While tumor volume is an important parameter predicting clinical outcome, its relationship to clonogen number remains uncertain. This uncertainty is related to many factors, among them treatment response heterogeneity, which obscures the influence of patients and treatment-related parameters. In this study, we analyze the effect of tumor volume on local and regional recurrence in a setting tightly controlled for dose, treatment time, and patient selection. The hypothesis that changes in clonogen number scale directly with changes in tumor volume is tested.

METHODS AND MATERIALS

Using digital reconstruction of diagnostic computed tomography (CT) scans, primary and total tumor volumes were estimated in 51 cases of advanced squamous cell carcinoma of the head and neck. All patients were managed with a concomitant boost accelerated superfractionated schedule to a median dose of 70.2 Gy. Clinical data were fitted to a mixture model to relate tumor volume parameters to control probability where volume and clonogen number were related by the relationship m = a.Vb, where m is initial clonogen number, a is a proportionality constant, V is tumor volume, and b is the volume exponent.

RESULTS

Tumor volume estimates for primary tumor ranged from 3-196 cm3 and for total tumor volume 5-196 cm3. Actuarial local-regional control is 63%. The estimated volume exponent b is 0.85 (95%, confidence interval (c.i.): 0.40-1.29) for primary tumor volume and 1.1 (95%, c.i.: 0.33-1.85) for total tumor volume.

CONCLUSION

This study quantifies the adverse influence of tumor volume on local-regional disease control in advanced head and neck cancer. The derived volume exponent approximates to one, the theoretical expectation if the growth fraction is roughly constant and clonogen number increases linearly with volume. Finally, these results suggest that radiobiological parameters are more reliably estimated from clinical data with narrowly defined strata.

Combined chemoradiotherapy for locally advanced squamous cell carcinoma of the bulbomembranous urethra: a case report

Patients with locally advanced squamous cell carcinoma of the bulbomembranous urethra fare poorly whether they undergo surgery or primary radiotherapy. Combined chemoradiotherapy has been used with encouraging results in the treatment of squamous cell carcinoma of the anal canal and esophagus, and limited reports suggest that this management may show promise in the control of squamous cell carcinoma of the urethra. We report good results in a man with locally advanced squamous cell carcinoma of the bulbomembranous urethra who underwent concomitant radiotherapy, mitomycin C and 5-fluorouracil. We encourage the use of this regimen in patients with urethral squamous cell carcinoma as well as the reporting of results.

Optical mapping of repolarization and refractoriness from intact hearts

BACKGROUND

Heterogeneities of repolarization (R) across the myocardium have been invoked to explain most reentrant arrhythmias. The measurement of refractory periods (RPs) has been widely used to assess R, but conventional electrode and extrastimulus mapping techniques have not provided reliable maps of RPs.

METHODS AND RESULTS

Guinea pig hearts were stained with a voltage-sensitive dye to measure fluorescence (F) action potentials (APs) from 124 sites with a photodiode array. AP duration (APD) was defined as the time between depolarization (dF/dt)max and R time points (ie, the time when AP returns to baseline or some percent thereof). However, R time points are difficult to determine because AP downstrokes are often encumbered by drifting baselines and motion artifacts, which make this definition ambiguous. In optical and microelectrode recordings, the second derivative of AP downstrokes is shown to contain an easily detected, unique local maximum. The correlation between the position of this maximum (d2F/dt2)max and R has been tested during altered AP characteristics induced by changes in cycle length, ischemia, and hypoxia. Under these various modifications of the AP, the time points of (d2F/dt2)max fell at 97.0 +/- 2.1% of recovery to baseline. Extrastimulus techniques applied to (1) isolated myocytes, (2) intact hearts, and (3) mathematical simulations indicated that (d2V/dt2)max coincided with the effective RPs of APs. The coincidence of RPs and (d2V/dt2)max was valid within 5 milliseconds, for resting potentials of -75 to -90 mV and extrastimuli three times threshold voltage.

CONCLUSIONS

Thus, optical APs and (d2F/dt2)max can be used to map activation, R, and RPs with AP recordings from a single heartbeat.

Stomal seeding by percutaneous endoscopic gastrostomy in patients with head and neck cancer

Presented is the first known case of squamous cell carcinoma that developed at the site of a "pull" type percutaneous endoscopic gastrostomy stoma. The patient had advanced squamous cell carcinoma of the pharynx when the percutaneous endoscopic gastrostomy tube was placed. This article should serve as a warning of this potential complication. Alternate techniques and other precautionary methods are described.

Postoperative radiotherapy in head and neck carcinoma with extracapsular lymph node extension and/or positive resection margins: a comparative study

In head and neck carcinoma, the finding of extracapsular lymph node extension and/or positive resection margins portends poor locoregional control and survival. The effectiveness of postoperative radiotherapy in these patients has been controversial due to insufficient studies comparing resected patients with those also receiving radiation. Between 1982 and 1988, 441 radical head and neck resections were performed at the Medical College of Virginia. Pathologic review of these cases identified 125 with extracapsular lymph node extension and/or positive resection margins. Of these, 43 had extracapsular lymph node extension only, 24 had both positive resection margins and extracapsular lymph node extension, and 58 demonstrated positive resection margins only. Surgery alone was performed in 71 of these patients while 54 cases received surgery and postoperative radiotherapy, (combined modality treatment) CMT. Radiotherapy doses ranged from 50 to 70 Gy. The surgery alone and combined modality treatment groups were comparable with respect to the distribution of positive resection margins and extracapsular lymph node extension. Slightly more CMT patients had clinical T4 disease compared with the surgery alone group (22% vs 14%). Slightly fewer combined modality treatment patients had clinical N0 necks than the surgery alone group (20% vs 29%). Multivariate analysis was performed with the variables T, N stages, radiotherapy, margin status, primary tumor sites, microscopic and macroscopic extracapsular lymph node extension, number of positive lymph nodes, number of nodes with extracapsular lymph node extension. Locoregional control was maintained at 5 years in 59% of the combined modality treatment group and 31% of the surgery alone group (p.0001). Subgroup analysis likewise reveals significant differences favoring the combined modality treatment group for positive resection margins only (49% vs 41%; p = .04), extracapsular lymph node extension only (66% vs 31%; p = .03) and extracapsular lymph node extension+positive resection margins (68% vs 0%; p = .001). Adjusted survival also shows a significant benefit of combined modality treatment vs surgery alone for the entire group (72% vs 41%; p = .001). Multivariate analysis revealed that the use of radiotherapy is a strongly favorable variable for local control and adjusted survival. Macroscopic extracapsular lymph node penetration and positive resection margins are unfavorable independent variables for local control. T-stage is the only variable predicting local control in the combined modality group. Extracapsular extension remains an important negative prognostic variable for survival in both treatment groups. In conclusion, this study demonstrates a locoregional control and survival benefit for postoperative radiotherapy in patients with the high risk pathologic findings of extracapsular lymph node extension and positive resection margins.