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R J Bartlett

Publications and source records attributed to R J Bartlett.

At least 19 recordsLinked to original sources
PubMed2006

Posterior stability in fixed-bearing versus mobile-bearing total knee replacement: a radiological comparison of two implants.

INTRODUCTION: Posterior tibial translation in total knee replacement (TKR) could be one major factor for PE wear, delamination and loosening of the tibial component due to increased shear forces and component-to-bone interface stress. The aim of this study was to assess the posterior stability of two different designs of posterior cruciate ligament (PCL) substituting TKR. METHOD: In this non-randomised consecutive study 43 patients underwent TKR for primary osteoarthritis. Twenty-six patients in group FB received a deep-dished fixed-bearing Duracon TKR (Howmedica, Rutherford, NJ, USA) and 17 patients in group MB a deep-dished rotating mobile-bearing Duracon TKR. In both groups the PCL was resected. All patients had pre- and postoperative kneeling stress radiographs and were clinically evaluated with the Knee Society Score. Posterior tibial translation was measured by tracing a line along the posterior tibial cortex in relationship to the posterior edge of Blumensaat's line. RESULTS: The average follow-up was 13 months for group FB and 11 months for group MB. Both groups demonstrated a statistical significant increase of the mean posterior tibial translation on kneeling stress X-ray of 4.1 mm (group FB) (P < 0.001) and of 6.6 mm (group MB) (P < 0.001) compared to pre-operative. Group MB showed a significant higher posterior draw (P < 0.008). Clinical assessment using the Knee Society Score showed comparable short-term results. CONCLUSION: The deep-dished fixed-bearing TKR as well as the deep-dished rotating mobile-bearing TKR demonstrated significant posterior tibial translation on kneeling stress X-ray. It remains to be determined what amount of joint play is optimal for clinical function and to minimise shear forces and PE wear. Moreover the amount of posterior tibial translation was significantly higher with the mobile-bearing insert, which could be directly related to the asymmetric rotational mobility of the tibial insert. A long-term follow-up is necessary to investigate whether our findings correlate with the survival-rate of these specific implants.

Aged, 80 and over↗
PubMed2005

Assessment of posterior stability in total knee replacement by stress radiographs: prospective comparison of two different types of mobile bearing implants.

The aim of this study was to assess the posterior stability of two different designs of total knee replacement (TKR) with deep-dished mobile bearing (MB) implants using stress X-rays. In a prospective non-randomized consecutive study, 34 patients with primary osteoarthritis of the knee underwent TKR. In group A (17 knees), they received a MB insert with a Duracon prosthesis and in group B (18 knees), a Genesis prosthesis. In all cases the posterior cruciate ligament (PCL) was resected. All patients had pre- and post-operative kneeling X-rays and were clinically evaluated with the Knee Society Score. Measurements on the radiographs were taken by tracing a line along the posterior cortex of the tibia and then measuring the perpendicular distance to a point marked at the posterior corner of Blumensaat's line. The average follow up was 10.7 months for group A and 5.4 months for group B. No statistical difference could be found in terms of clinical results and pre- and post-operative kneeling X-rays between the two groups. In each group, all knees demonstrated a significant posterior tibial translation postoperatively compare to their pre-operative status (p<0.0001). There are advantages in resecting the PCL in TKR: mobile flexion gap, correction of fixed deformity, more flexibility to adjust the joint line. The use of a deep dished polyethylene (PE) insert provides stability and use of MB insert reduces PE wear whilst retaining congruity. Two designs of deep-dished MB inserts showed significant posterior tibial translation on stress X-rays. It remains to be determined what amount of laxity is optimal for clinical function and polyethylene longevity.

Aged↗
PubMed2003

Post-operative drainage after cemented, hybrid and uncemented total knee replacement.

We recorded the total and 8-hourly post-operative drainage of 100 consecutive total knee replacements (33 cemented, 35 hybrid and 32 uncemented). The cemented, hybrid and uncemented prostheses had mean total drainage of 745, 1035 and 1220 ml, respectively. The difference in drainage between cemented and both hybrid and uncemented was statistically significant (P<0.05 and P<0.001). A significantly higher percentage of drainage occurred in the first 8-h period in the hybrid and uncemented groups. Total drainage in the cemented group was lower, but occurred more slowly, with a significantly higher percentage of drainage in the 17-48-h post-operative period when compared with the uncemented group (P<0.05). Within the cemented group, posterior-stabilised implants drained significantly more than those with an AP-lipped tibial insert (P<0.05). This information has implications for planning of blood product usage and timing of drain tube removal.

Anticoagulants↗
PubMed2001

Photochemically induced formation of the "Al13" tridecameric polycation in the presence of Fe(III) and organic acids.

We found that light-induced Fe(III) reduction associated with the oxidation of a simple hydroxy-carboxylic acid (lactate) caused the formation of the AlO4Al12(OH)24(H2O)12 polycation ("Al13"). Initial conditions were a lactate:Al:Fe ratio of 1:0.76:0.11 in a partially neutralized solution. Base was added rapidly and no Al13 was detected in samples kept in the dark. With exposure to light, Fe(III) reduction was rapid and Fe(II) reached a maximum within 1 day. After the maximum, steady-state Fe(II) declined from 54% to 43% over eight days. During this same time period, the lactate concentration fell to 2% of the original, pH rose from 4.05 to 4.46, and the Al13 detectable by 27Al NMR increased to 2.3 mmol l(-1) (51% of the total solution Al). The formation of Al13 is attributed to the pH rise resulting from the removal of the organic acid buffer. Similar photo-induced chemical changes occur in natural waters and may promote the formation of Al13, conditions permitting.

Aluminum↗
PubMed2000

Light-induced disappearance of nitrite in the presence of iron (III).

Understanding of rapid disappearance of nitrite in natural waters and its impact on nitrogen natural cycling has remained limited. We found that NO2- disappeared rapidly in pH 3.2 aqueous Fe(III) solutions both in sunlight and in 356 nm light. Quantum yields of the NO2- loss at 356 nm were 0.049-0.14 for initial levels of 10-80 microns NO2- and 200 microns Fe(III). The NO2- loss (at 356 nm) followed apparent first-order kinetics. The rate constants were 1.3 x 10(-3) (40 microns NO2-) and 4.1 x 10(-4) s-1 (80 microns NO2-) for 100 microns Fe(III), and 2.3 x 10(-3) (40 microns NO2-) and 7.5 x 10(-4) s-1 (80 microns NO2(-1)) for 200 microns Fe(III) (t1/2 = 8.7, 27.9, 5.1, and 15.3 min, respectively). The rate constants were directly proportional to [Fe(III)]0 and inversely proportional to [NO2-]0. Agreement between the rate constants obtained experimentally and those calculated mechanistically supports the hypothesis that NO2- was oxidized to NO2 by .OH radicals from photolysis of FeOH2+ complexes, and at high [NO2-]0 (e.g., 80 microns) relative to [Fe(III)]0, hydrolysis of NO2 or N2O4 to form NO3- and NO2- could be significant. This study showed that light and Fe(III)-induced oxidation of NO2- (rate = approximately 10(-1)-10(-2) microns s-1) was more rapid than its direct photolysis (rate = approximately 10(-4) microns s-1), and the photolysis could be a significant source of .OH radicals only in cases where the Fe(III) level is much lower than the NO2- level ([Fe(III)]/[NO2-] < 1/80). This study suggests that the light and Fe(III)-induced oxidation of NO2- would be one potential important pathway responsible for the rapid transformation of NO2- in acidic surface waters, especially those affected by acid-mine drainage or volcanic activities. This study also may be of interest for modeling certain acidic atmospheric water environments.

Hydrogen-Ion Concentration↗
PubMed2000

In vivo targeted repair of a point mutation in the canine dystrophin gene by a chimeric RNA/DNA oligonucleotide.

In the canine model of Duchenne muscular dystrophy in golden retrievers (GRMD), a point mutation within the splice acceptor site of intron 6 leads to deletion of exon 7 from the dystrophin mRNA, and the consequent frameshift causes early termination of translation. We have designed a DNA and RNA chimeric oligonucleotide to induce host cell mismatch repair mechanisms and correct the chromosomal mutation to wild type. Direct skeletal muscle injection of the chimeric oligonucleotide into the cranial tibialis compartment of a six-week-old affected male dog, and subsequent analysis of biopsy and necropsy samples, demonstrated in vivo repair of the GRMD mutation that was sustained for 48 weeks. Reverse transcription-polymerase chain reaction (RT-PCR) analysis of exons 5-10 demonstrated increasing levels of exon 7 inclusion with time. An isolated exon 7-specific dystrophin antibody confirmed synthesis of normal-sized dystrophin product and positive localization to the sarcolemma. Chromosomal repair in muscle tissue was confirmed by restriction fragment length polymorphism (RFLP)-PCR and sequencing the PCR product. This work provides evidence for the long-term repair of a specific dystrophin point mutation in muscle of a live animal using a chimeric oligonucleotide.

Animals↗
PubMed1999

Tunnel widening in anterior cruciate ligament reconstruction: a prospective evaluation of hamstring and patella tendon grafts.

We report a prospective series evaluating the incidence and degree of tunnel widening in a well-matched series of patients receiving a hamstring or patella tendon graft for anterior cruciate ligament (ACL) deficiency. We correlated tunnel widening with clinical factors, knee scores, KT-1000 and isokinetic muscle strength to determine the clinical significance of this finding. Seventy-three patients at least 12 months post-ACL reconstruction were evaluated. Thirty-eight patients had received a doubled semitendinous and gracilis graft and 35 a bone-patella tendon-bone graft. All patients underwent a similar endoscopic procedure and accelerated postoperative rehabilitation. Tunnel widening was determined using standardized anteroposterior (AP) and lateral X-rays adjusted for magnification. A limited series of MRIs was performed to validate these measurements. There was a significant difference in the degree of tunnel widening between the two groups. The mean increase in femoral tunnel area in the hamstring group was 100.4% compared with a decrease of 25% in the patella tendon group (P = < 0.0001). In the tibial tunnel the mean increase in the hamstring group was 73.9% compared with a decrease of 2.1% in the patella tendon group (P = < 0.0001). The MRIs validated the plain film measurements. Tunnel widening did not correlate with the clinical findings, knee scores, KT-1000 or isokinetic muscle strength. Tunnel widening is marked in the hamstring group. Tunnel widening does not correlate with instability or a poor clinical outcome in the short term. The long-term implications of this finding are still to be determined.

Adult↗
PubMed1998

A comparison of T2 and gadolinium enhanced MRI with CT myelography in cervical radiculopathy.

Two MRI strategies which have been reported to be effective in assessing cervical exit foramina, were prospectively compared with CT myelography in 20 patients with cervical radiculopathy. The first strategy utilized 3D T2* images, the second gadolinium enhanced 2D T1 images. Gadolinium (dimeglumine gadopentetate, Schering Ltd) enhanced images did not confer any benefit in the investigation of this condition, probably due to enhancement of herniated disc material and osteophytes adjacent to the neurocentral joint. Three-dimensional (3D) T2* white cerebrospinal fluid images had an accuracy approaching 90% for the diagnosis of foraminal encroachment, compared with a gold standard. MRI including a 3D T2* sequence is thus an acceptable primary investigation for cervical radiculopathy, but when the findings are incompatible with clinical symptomatology, CT myelography is still indicated.

Adult↗
PubMed1997

The insulin gene is transcribed in the human thymus and transcription levels correlated with allelic variation at the INS VNTR-IDDM2 susceptibility locus for type 1 diabetes.

Type 1, or insulin-dependent diabetes mellitus (IDDM) is an autoimmune disease associated with loss of tolerance to several pancreatic islet cell molecules, including insulin, glutamic acid decarboxylase (GAD), ICA69 and the tyrosine phosphatase IA-2 (refs 1-3). Among several predisposing loci, IDDM2 maps to the insulin gene (INS) VNTR (variable number of tandem repeats) minisatellite on chromosome 11p15 (refs 4-9). Allelic variation at this VNTR locus correlates with steady-state levels of INS mRNA in pancreas and transfected rodent cell lines, but it is difficult to reconcile the association of lower INS mRNA levels in the pancreas with class III VNTRs that are dominantly protective from IDDM. We show that during fetal development and childhood, mRNAs for insulin and other islet cell autoantigens (GAD, ICA69, IA-2) are expressed at low levels in the human thymus. Critically, we also detect proinsulin and insulin protein. VNTR alleles correlate with differential INS mRNA expression in the thymus where, in contrast to the pancreas, protective class III VNTRs are associated with higher steady-state levels of INS mRNA expression. This finding provides a plausible explanation for the dominant protective effect of class III VNTRs, and suggests that diabetes susceptibility and resistance associated with IDDM2 may derive from the VNTR influence on INS transcription in the thymus. Higher levels of (pro)insulin in the thymus may promote negative selection (deletion) of insulin-specific T-lymphocytes which play a critical role in the pathogenesis of type-1 diabetes.

Aging↗
PubMed1997

Intradiploic meningocoele in a 16-year-old girl.

Osteolytic lesions of the skull have many causes, but magnetic resonance imaging may immediately distinguish cerebrospinal fluid intradiploic lakes from other causes. A case of a 16-year-old girl with such a lesion in relation to the sagittal sinus is presented and its aetiology is discussed.

Adolescent↗
PubMed1996

Two-dimensional MRI at 1.5 and 0.5 T versus CT myelography in the diagnosis of cervical radiculopathy.

A prospective comparison was made of standard two-dimensional MRI sequences, at both high and midfield strength, with CT myelography in 23 patients with cervical spondylosis. MRI is adequate for assessment of cord compression, where high field strength is superior to midfield strength. MRI using 4-mm sections is inadequate for presurgical assessment of root compression. It remains to be proven whether thin-section white-CSF volume sequences or gadolinium-enhanced volume studies can replace CT myelography.

Adult↗