Assessment of CAOS as a training model in spinal surgery: a randomised study

The objectives of this study were (1) to quantify the benefit of computer assisted orthopaedic surgery (CAOS) pedicle screw insertion in a porcine cadaver model evaluated by dissection and computed tomography (CT); (2) to compare the effect on performance of four surgeons with no experience of CAOS, and varying experience of pedicle screw insertion; (3) to see if CT with extended windows was an acceptable method to evaluate the position of the pedicle screws in the porcine cadaver model, compared to dissection. This was a prospective, randomised, controlled and blinded porcine cadaver study. Twelve 6-month-old porcine (white skinned Landrace) lumbar spines were scanned pre-operatively by spiral CT, as required for the CAOS computer data set. Computer randomisation allocated the specimens to one of four surgeons, all new to CAOS but with different levels of experience in spinal surgery. The usual anatomical landmarks for the freehand technique were known to all four surgeons. Two pedicles at each vertebral level were randomly allocated between conventional free hand insertion and an electromagnetic image guided surgery (NAVITRAK) and 6.5 mm cancellous AO screws inserted. Post-operatively, spiral CT was blindly evaluated by an independent radiologist and the spine fellow to assess the accuracy of pedicle screw placement, by each method. The inter- and intra-observer reliability of CT was evaluated compared to dissection. The pedicle screw placement was assessed as perfect if within the pedicle along its central axis, or acceptable (within < 2 mm from perfect), and measured in millimetres from perfect thereafter. One hundred and sixty-six of 168 pedicles in 12 porcine spines were operated on. Complete data were present for 163 pedicles (81 CAOS, 82 freehand). In the CAOS group 84% of screws were deemed acceptable or perfect, compared to 75.6% with the freehand technique. Screw misplacement was significantly reduced using CAOS (P = 0.049). Seventy-nine percent of CAOS screws were ideally placed compared with 64% with a conventional freehand technique (P = 0.05). A logistic linear regression model showed that the miss placed pedicle screw rate was significantly reduced using CAOS (P = 0.047). CAOS benefited the least experienced surgeons most (the research registrars acceptable rate increased from 70 to 90% and the spine fellow from 76 to 86%). CAOS did not have a statistically significant effect on the experienced consultant spine surgeon increasing from 70 to 79% (P = 0.39). The experienced general orthopaedic surgeon did not benefit from CAOS (P = 0.5). CT compared to dissection showed an intra-observer reliability of 99.4% and inter-observer reliability of 92.6%. The conclusions of this study were as follows: (1) an increased number of pedicle screws were ideally placed using the CAOS electromagnetic guidance system compared to the conventional freehand technique; (2) junior surgeons benefited most from CAOS; (3) we believe CAOS (Navitrak) with porcine lumbar spines evaluated by post operative CT, represents a useful model for training junior surgeons in pedicle screw placement; (4) experienced spine surgeons, who have never used CAOS, may find CAOS less helpful than previously reported.

Evaluation of ER, PgR, HER-2 and Ki-67 as predictors of response to neoadjuvant anthracycline chemotherapy for operable breast cancer

Primary systemic therapy (PST) for operable breast cancer enables the identification of in vivo biological markers that predict response to treatment. A total of 118 patients with T2–4 N0–1 M0 primary breast cancer received six cycles of anthracycline-based PST. Clinical and radiological response was assessed before and after treatment using UICC criteria. A grading system to score pathological response was devised. Diagnostic biopsies and postchemotherapy surgical specimens were stained for oestrogen (ER) and progesterone (PgR) receptor, HER-2 and cell proliferation (Ki-67). Clinical, radiological and pathological response rates were 78, 72 and 38%, respectively. There was a strong correlation between ER and PgR staining (P<0.0001). Higher Ki-67 proliferation indices were associated with PgR− tumours (median 28.3%, PgR+ 22.9%; P=0.042). There was no relationship between HER-2 and other biological markers. No single pretreatment or postchemotherapy biological parameter predicted response by any modality of assessment. In all, 10 tumours changed hormone receptor classification after chemotherapy (three ER, seven PgR); HER-2 staining changed in nine cases. Median Ki-67 index was 24.9% before and 18.1% after treatment (P=0.02); the median reduction in Ki-67 index after treatment was 21.2%. Tumours displaying >75% reduction in Ki-67 after chemotherapy were more likely to achieve a pathological response (77.8 vs 26.7%, P=0.004).

Central core disease: clinical, pathological, and genetic features

Central core disease (CCD) is a dominantly inherited congenital myopathy allelic to malignant hyperthermia (MH) caused by mutations in the RYR1 gene on chromosome 19q13.1. Eleven individuals with RYR1 mutations are described. Four index cases showed features consistent with a congenital myopathy (hypotonia, delayed motor milestones, and skeletal abnormalities including congenital hip dislocation and scoliosis). All four cases and subsequently seven other family members were found to possess novel mutations in the RYR1 gene. The degree of disability varied from one clinically normal individual, to another who had never achieved independent ambulation (the only patient with a de novo mutation). Four cases showed a mild reduction in vital capacity, repeated nocturnal polysomnography showed hypoxaemia in one case. A variety of muscle biopsy features were found; central cores were absent in the youngest case, and the biopsy specimens from two others were more suggestive of mini-core myopathy. In all cases missense mutations in exons 101, 102, and 103 of the RYR1 gene on were found. Future laboratory diagnosis of suspected cases and family members will be less invasive and more accurate with DNA analysis. Clinicians, especially paediatricians and orthopaedic surgeons, should be aware of this disorder because of the potential risk of MH.

The spectrum of pathology in central core disease

Central core disease is a congenital myopathy with muscle weakness defined pathologically by the presence of extensive areas in muscle fibres that are devoid of oxidative enzyme activity. The gene responsible has been shown to be the ryanodine receptor 1 on chromosome 19q13 and mutations have now been identified in several patients. Some cases with the morphological defect remain molecularly undefined, particularly those studied before molecular studies were available. We have studied three families with congenital onset, each with a dominantly inherited mutation in a C-terminal exon of the ryanodine receptor 1. They illustrate the spectrum of pathology that can be observed in patients with the myopathic features of central core disease. We show that extensive fibrosis and fat may be present, type 1 fibre uniformity may occur in the absence of cores; cores may be central or peripheral, single or multiple; and that an appearance of multiple focal minicores might cause a diagnostic pathological dilemma. In addition, we show the value of immunocytochemistry in identifying cores, in particular the use of antibodies to desmin and gamma-filamin.

A study of the mechanical stability of scoliosis constructs using variable numbers of sublaminar wires

Sublaminar wiring with posterior instrumentation is one of the methods used when long fusions involving 10-12 thoracolumbar levels are required. Classically, wires are used at every consecutive level to make the construct as rigid as possible, although complications like dural tears, cerebrospinal fluid leak, and neurological deficit have been reported during their passage. We compared the mechanical stability under torsional strain of five specimens of each of three construct designs, by static and fatigue testing, using an electro-servo-hydraulic testing machine. In construct A, a contoured Hartshill rectangle was used from T2 to L2, with sublaminar wires passed at every level. In construct B, the Hartshill rectangle was wired to the spine at every alternate level. In construct C, every alternate level was wired except at the proximal end, where two consecutive levels were wired. Industrially fabricated spine models were used to prepare these constructs. The intervertebral motion within the construct was measured using the Fastrak magnetic field sensor device. On static testing, no statistically significant difference was found in the rotational displacement of the three construct designs. On fatigue testing, all samples of construct B consistently failed, with breakage of the wire at the most proximal level on the left side. But on adding additional wires to the next level (construct C), all five samples withstood fatigue testing at 300 N load to three million cycles. We conclude that wiring alternate levels instead of every level does not compromise the stability of the construct, provided that the most proximal two levels are consecutively wired. This practice would minimise the risk of dural tears and cord damage during wire passage and reduce surgical time, not to mention the economic benefits.

Shared care in gastroenterology: GPs' views of open access to out-patient follow-up for patients with inflammatory bowel disease

OBJECTIVE

The aim of this study was to ascertain GPs' views about open access to out-patient follow-up for patients with inflammatory bowel disease (IBD).

METHODS

Semi-structured interviews and a postal survey were carried out in general practices in West Glamorgan UK, each with at least one IBD patient taking part in a randomized trial of open access versus routine follow-up, which has been reported elsewhere. A total of 112 GPs from 53 general practices who referred the 180 study patients to specialist gastroenterological care in Neath or Swansea were included in the study. Main outcome measures were GPs' experience of the trial; preferences between methods of out-patient follow-up; and their views about enhancing open access follow-up.

RESULTS

Sixty-nine GPs from 40 practices took part in the practice-specific data collection and 91 returned 156 patient-specific questionnaires. They expressed a strong preference for open access follow-up, for both specific patients (108/156 patients) and IBD patients in general (47/69 GPs). Preference for extending open access follow-up to other chronic conditions was not so strong (21/69 GPs). A substantial number of GPs considered their experience of the trial limited (30/69), and few GPs were aware of the shared care guideline distributed before the trial started (8/69). Few GPs encountered any problems in the management of the study patients (9/69) and <50% of the GPs used a Cumulative Encounter Form (29/69) developed for the study. Most GPs were supportive of giving patients written guidelines (56/69) and establishing a gastroenterological (GI) nurse practitioner (45/69).

CONCLUSIONS

Open access follow-up of patients with IBD is supported by GPs. The approach would probably be improved by the distribution of written information to patients, the establishment of a GI nurse practitioner and an integrated approach between the nurse, hospital specialist, GP and patient.

Temperature and pH studies of short tandem repeat systems using capillary electrophoresis at elevated pH

The DNA secondary structure can affect the migration time and precision of DNA separations in the physical gels used in capillary electrophoresis (CE). To counteract these effects, DNA typing is performed using elevated temperatures (60 degrees C) and high concentrations (7 M) of urea. These conditions affect the precision and lifetime of the analysis. To better understand the effects of these conditions on the reproducibility of DNA migration, we examined the effects of temperature and pH on short tandem repeat (STR) analysis using the PE/ABI 310 Genetic Analyzer. Separations were performed using the Profiler + multiplex system, a set of coamplified STRs with a 4-base repeat motif, labeled at the 5'-end using fluorescent dyes. The analytical separations were obtained using a commercial buffer at pH 8 and an experimental buffer consisting of 3% hydroxyethylcellulose at pH settings ranging from 8-12. Multichannel laser-induced fluorescence detection was used. Temperatures were examined from 30-70 degrees C. The results demonstrate the fact that highly efficient separations can be carried out at alkaline pH. In addition, improvements in temperature stability were seen when compared to results at lower pH. However, high concentrations of urea were found to be necessary to achieve optimal resolution.

Mechanism-based inactivation of a yeast methylamine oxidase mutant: implications for the functional role of the consensus sequence surrounding topaquinone

The copper-containing yeast methylamine oxidase E406N mutant has an altered consensus sequence surrounding the topaquinone cofactor (residue 405). The mutation has no effect on the final yield of the active-site topaquinone cofactor during biogenesis but causes the enzyme to be inactivated by substrate methylamine [Cai, D., and Klinman, J. P. (1994) Biochemistry 33, 7674-7653]. In this study we show that the inactivation leads to the formation of a covalent adduct, which has a UV/vis spectrum very similar to that of a product Schiff base, an intermediate of topaquinone-catalyzed amine oxidation reactions. The kinetic isotope effects on the second-order rate constant for the inactivation and catalytic turnover are identical, indicating that the two processes share a common intermediate that follows C_H bond cleavage. Resonance Raman spectroscopy provides direct evidence for the accumulation of a neutral product Schiff base species. Removal of excess methylamine leads to recovery of both activity and the native absorption spectrum for E406N, indicating that the cofactor in the inactivated enzyme is chemically competent for hydrolysis. The rate of the reactivation is slow, however; the shortest half-life of the inhibited E406N at 25 degrees C is 5.9 min at pH 6.15. pH effect experiments show that the inactivation and reactivation steps are controlled by a single ionizable group with a pKa of 6.9-7.1; under basic conditions, when this residue is deprotonated, the inactivation is the fastest and the half-life of the inhibited enzyme is the longest. On the basis of the available crystal structures of copper amine oxidases, we propose that a histidine residue in the dimer interface is responsible for the observed ionization. In the wild-type enzyme this histidine is kept protonated by virtue of Glu at position 406. Unlike methylamine, the larger substrates ethylamine and benzylamine give normal turnover with E406N. Disruption of structure at the subunit interface in E406N may allow a rotation of the relatively small topa-product Schiff base complex (formed from methylamine) away from the active-site base to a conformation that is incompetent toward hydrolysis.

Dislodgement of the femoral component of a total hip arthroplasty presenting through the buttock

The end result of nonsurgical management of the infected loose femoral component of a total hip arthroplasty is presented. This is the expulsion from the body of the foreign material.

Effects of age on beta adrenergic subtype activation of adenylyl cyclase in brown adipose tissue

Thermogenesis in brown adipose tissue (BAT) is believed to be mediated mainly by beta3 adrenergic receptors. We previously demonstrated that the specific beta3 adrenergic agonist CGP-12177 increases whole body oxygen consumption and BAT GDP binding to a greater extent in young than in senescent rats. In contrast, the forskolin-induced increases were maintained with age, suggesting that early events in beta3 adrenergic signal transduction are impaired with age. To investigate whether beta1 or beta3 adrenergic function is decreased with age, we assessed beta1 and beta3 adrenergic receptor mRNA levels and the ability of beta1 and beta3 adrenergic receptors to activate adenylyl cyclase in BAT membranes from 4- and 24-month-old F-344 rats. Both beta1 and beta3 adrenergic receptor mRNA levels decreased by 50% with age. Adenylyl cyclase stimulated by the nonspecific agonist, isoproterenol, and by the specific beta3 agonist, BRL 37344, also declined by 50% with age, whereas glucagon stimulation decreased by more than 70%. The isoproterenol-stimulated adenylyl cyclase activation curves were resolved by two-site regression analysis to determine the contribution of beta1 and beta3 adrenergic receptors. The Vmax for both beta1 and beta3 adrenergic receptors decreased by 50% with age. However, stimulation of adenylyl cyclase by NaF and forskolin was also diminished by the same amount as beta adrenergic stimulation, suggesting that the activation with age may be limited by the amount of adenylyl cyclase catalytic unit rather than by receptor number. These data suggest both beta1 and beta3 adrenergic receptors and adenylyl cyclase catalytic units are deficient with age in rodent BAT.

Development of a degradable composite for orthopaedic use: mechanical evaluation of an hydroxyapatite-polyhydroxybutyrate composite material

This study evaluates the mechanical properties of a composite material comprising polyhydroxybutyrate with hydroxyapatite added in proportions varying from 0 to 50%. Among the three methods of production, injection moulding was found to result in the most satisfactory mechanical properties. The tensile and compressive strength and the modulus of elasticity of composite produced in this way fell within the range for fresh human bone from different anatomical sites. With the additional advantages of biocompatibility, biodegradability and the potential for piezoelectric stimulation of new local bone formation, it was concluded that the injection-moulded composite material has considerable potential for use in orthopaedic surgery, both as a material to construct certain orthopaedic implants and as an alternative to corticocancellous bone graft.

The selection of wires for sublaminar fixation

The authors report a comparative biomechanical study of the suitability of four types of stainless steel wire for sublaminar fixation. Tensile and fatigue tests were performed on wires in the configuration used at surgery. They conclude that annealed 18-gauge (1.2 mm) wire should be used at each end of a scoliosis fusion, at the upper end of a lumbar fusion, and throughout for thoracolumbar fractures. Cold-worked 20-gauge (0.87 mm) wire may be used in all other situations, but the use of annealed 20-gauge wire should be restricted to the cervical spine. The authors emphasize the importance of achieving the correct balance between wire stiffness and flexibility, of care in the handling of wires, and of proper technique in achieving secure fixation.