Biomechanical comparison of the pullout properties of external skeletal fixation pins in the tibiae of intact and ovariectomised ewes.

The pin-bone interface is the least stable component of the external skeletal fixator. Concerns exist regarding the ability to obtain adequate implant purchase in poor quality bone. Consequently, reduced bone quality has been viewed as a contra-indication for the use of external skeletal fixators. The aim of this study was to investigate the holding power of two different fixator pin designs in bone from entire and ovariectomised sheep. Thirty-two aged ewes were divided into two groups. Group 1 were controls, and Group 2 were ovariectomised (OVX). The ewes were sacrificed 12 months post-ovariectomy and five pairs of tibiae were harvested from each group. The holding power of cortical and cancellous fixator pins was assessed at five standardised locations on each tibia. An increase in mean cortical thickness was noted in the OVX group. The holding power of cancellous fixator pins was superior to that of cortical pins, irrespective of whether or not ovariectomy had been performed. Cancellous pins had an increased holding power in post ovariectomy bone compared to control bone. Cortical pin performance was not affected by ovariectomy. There was a lack of correlation between the incidence of insertional fractures of the far cortex and implant holding power. The results raise questions over the effectiveness of ovariectomy in establishing osteopaenic bone suitable for assessing implant performance, hence further investigations are warranted.

Congenital oesophageal hiatal hernia in a pug.

Congenital sliding, oesophageal or type I hiatal hernia was diagnosed in a five-month-old pug puppy presented for evaluation of dyspnoea post feeding. The diagnosis was confirmed using plain film radiography. Surgical reduction of the hernia followed by plication of the oesophageal hiatus, oesophagopexy and left flank gastropexy permitted restoration of normal function. At 12 months of age, the dog was asymptomatic. This article describes the diagnosis and treatment of a congenital type 1 oesophageal hiatal herniation with unusual clinical presentation.

Variable content of double minute chromosomes is not correlated with degree of phenotype instability in methotrexate-resistant human cell lines.

Several variants resistant to 1.8 x 10(-4) M DL-methotrexate (MTX) have been isolated from the human cell lines HeLa BU25 and VA2-B by exposing them to progressively increasing concentrations of the drug. A striking variability of phenotype and chromosome constitution was observed among the different variants. All resistant cell lines exhibited a greatly increased dihydrofolic acid reductase (DHFR) activity and DHFR content; however, the DHFR activity levels varied considerably among the variants, ranging between about 35 and 275 times the parental level. In the absence of selective pressure, the increased DHFR activity was unstable, and in all cell lines but one was completely lost over a period ranging in different variants between 25 and 200 days. The MTX-resistant cells lines showed anomalies in their chromosome constitution, which involved the occurrence of a duplicated set of chromosomes in most cells of some of the variants and the presence of double minute chromosomes in all cell lines. An analysis of the correlation of loss of double minute chromosomes and loss of DHFR activity in the absence of MTX has given results consistent with the idea that the double-minute chromosomes contain amplified DHFR genes. However, the most significant finding is that, in contrast to what has been reported in the mouse system, the recognizable double-minute chromosomes varied greatly in number in different variants without any relationship to either the level of DHFR activity or the degree of instability of MTX resistance in the absence of selective pressure. These and other observations point to the occurrence in the human MTX-resistant variants of another set of DHFR genes, representing a varied proportion of the total, which is associated with the regular chromosomes, and which may be unstable in the absence of selective pressure.

Stifle joint luxation in the dog and cat: the use of temporary intraoperative transarticular pinning to facilitate joint reconstruction.

Multiple ligament injuries of the canine and feline stifle joint which result in luxation are uncommon. Two cats and one dog, that had sustained such a joint injury were surgically treated. A rupture of the cranial and caudal cruciate ligaments, and at least one collateral ligament was observed in all of the three animals. Prosthetic reconstruction was used, as previously described, in combination with a novel technique of intraoperative placement of a temporary trans-articular pin (TTP) to maintain intra-operative anatomical reduction. TTP placement facilitated maintenance of joint alignment during surgical reconstruction and aided appropriate tensioning of the prosthetic sutures, preventing collapse of femorotibial joint compartments. The TTP was removed prior to closure of the joint allowing immediate post-operative joint mobilisation. Based on assessment by their owners, all the animals made a complete recovery. TTP was considered a relatively simple and effective adjunctive aid for surgical treatment of traumatic luxation of the stifle joint.

A modified tibial compression test for the detection of meniscal injury in dogs.

OBJECTIVE: To assess diagnostic efficacy of a modified tibial compression test in predicting medial meniscal injury in dogs with cranial cruciate ligament failure. METHODS: Dogs admitted for surgical stabilisation of stifles with cranial cruciate ligament failure were examined by five preoperative physical tests to assess medial meniscal injury. Results of each physical test were compared with findings at arthrotomy and used to calculate sensitivities, specificities, positive and negative predictive values. RESULTS: None of the physical tests were accurate in reflecting meniscal integrity for dogs with cranial cruciate failure. Out of the five tests, the modified tibial compression test exhibited the highest concordance and sensitivity for the detection of medial meniscal tears. A palpable click during the modified tibial compression test had a sensitivity and specificity up to 63 and 77%, respectively, for the detection of medial meniscal lesions. Concordance values were up to 40% for the modified tibial compression test, followed by the range of motion test (up to 25%), while all other physical tests had concordance values below 10%. CLINICAL SIGNIFICANCE: Physical tests are highly available, affordable and can be easily performed, but their efficacy in diagnosing medical meniscal injury is low. Meniscal clicks associated with meniscal tears were more frequently elicited during the modified tibial compression test when compared with other traditional tests.

Lateral patellar luxation in dogs: a retrospective study of 65 dogs.

OBJECTIVE: To report the signalment and clinical features of dogs with non-traumatic lateral patellar luxation and to report the complications and outcomes following surgery. METHODS: A multicentre retrospective study was performed. Medical records were reviewed and the signalment, clinical features, and treatment of dogs presenting with lateral patellar luxation were recorded. In dogs treated surgically, the outcome and complications were investigated. RESULTS: Sixty-five dogs (95 stifles) were included; 39 were male and median age at presentation was 10 months. Breeds were classified as small (n = 6), medium (n = 23), large (n = 27), and giant (n = 9). Lateral patellar luxation was classified as grade I (n = 14), II (n = 41), III (n = 29), and IV (n = 11). Conformational abnormalities were noted in 34 stifles; genu valgum was the most common (n = 28). Higher-grade luxation was associated with a younger age at presentation (p = 0.032) and genu valgum (p = 0.01). Surgery was performed on 58 stifles, 22 of which sustained one or more complications; 16 complications were managed conservatively, four with implant removal and six with revision surgery. Surgeon-assessed outcome was good or excellent in 47 of the 51 dogs available for review. CONCLUSIONS: Non-traumatic lateral patellar luxation is a disease of predominantly medium and large breed dogs. It has several similar clinical features and can be surgically treated in a similar manner to medial patellar luxation with similar types of complications and outcomes expected.

Effect of signalment on the presentation of canine patients suffering from cranial cruciate ligament disease.

OBJECTIVE: To determine the effect of signalment on the incidence and presentation of patients suffering from cranial cruciate ligament disease. METHODS: Data relating to 426 dogs (44 breeds) that met specific selection criteria were obtained from the hospital archive (2002 to 2008). Cases were followed up for 2 years. RESULTS: The breeds most commonly presented with cranial cruciate ligament disease were Labrador retriever (16%), Rottweiler (15%), golden retriever (12%) and boxer (9%). Rottweilers were significantly more likely (69%; P=0·05) to develop and present with (50%; P=0·03) bilateral cranial cruciate ligament disease. Rottweilers presenting with cranial cruciate ligament disease were significantly younger (median 977 days; P<0·0001) than other breeds; golden retrievers being significantly older at presentation (median 1994 days; P=0·004). Neither sex nor neutered status significantly affected the incidence of developing (P=0·77 and P=0·30, respectively) or presenting with (P=0·62 and P=0·35, respectively) bilateral cranial cruciate ligament disease. Entire dogs were significantly younger than neutered dogs at presentation (P=0·0004). Entire female dogs presented significantly younger than neutered females (P=0·0002), entire males (P=0·01) and neutered males (P=0·0001). CLINICAL SIGNIFICANCE: Breed affects the incidence of developing and presenting with bilateral cranial cruciate ligament disease. Breed and sex both affect the age that patients present with cranial cruciate ligament disease.

Photosensitivity and heat resistance conferred by BrdU incorporation upon a thymidine kinase-deficient mouse cell line with persistent mitochondrial enzyme activity.

The selective incorporation of 5-bromodeoxyuridine (BrdU) into mitochondrial DNA (mit-DNA) in the LM(TK-) ClID cell line, a thymidine kinase-deficient derivative of L fibroblasts with persistent mitochondrial enzyme activity, has been utilized to specifically damage mit-DNA by 'visible' light irradiation. ('Visible light' indicates the source of light used, although the components most active photochemically on BrdU-substituted DNA are in the near-visible range, 300-340 nm.) (Szybalski & Opara-Kubinski, 1965). LM(TK-) Cl ID cells, which had been grown in the presence of 30 mug/ml BrdU, were irradiated with 'visible' light. Analysis of the pre-existing mit-DNA in these cells, which had been long-term labelled with [5-3H]deoxycytidine, showed a progressive decrease, with increasing duration of irradiation, in the proportion of the closed-circular form and an increase in that of the open-circular form of mit-DNA, with the subsequent appearance of fragments of this DNA. Furthermore, there was a decrease during irradiation in the total amount of mit-DNA, which became about 35% of the non-irradiated control after 65 h irradiation. On the other hand, irradiation with 'visible' light failed to cause any quantitative or qualitative change, with respect to the non-irradiated control, in mit-DNA from cells grown in the absence of BrdU and long-term labelled with [Me-3h]thymidine. An analysis of the incorporation of [5-3H]deoxycytidine into mit-DNA of BrdU-grown cells, during a 3-h exposure of the cells to the precursor following irradiation, showed a fairly rapid decline of mit-DNA labelling; this became about 50% of the non-irradiated control after 12 h irradiation, decreasing to about 25% in the next 48 h. By contrast, no effect of irradiation was observed on the subsequent pulse-labelling of mit-DNA with [Me-3H]thymidine in cells grown in the absence of BrdU. Furthermore, no change in the size of the extracted nuclear DNA was found in irradiated BrdU-grown cells. The progressive and selective damage and destruction of mit-DNA during irradiation with 'visible' light of Cl ID cells correlate fairly well with the kinetics of loss of cell viability occurring under the same conditions, as described in the accompanying paper, strongly suggesting a link between the two phenomena.