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- Sandén, B., et al.
(författare)
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The significance of radiolucent zones surrounding pedicle screws : definition of screw loosening in spinal instrumentation
- 2004
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Ingår i: Journal of Bone and Joint Surgery. - 0301-620X .- 2044-5377. ; 86 B:3, s. 457-461
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Tidskriftsartikel (refereegranskat)abstract
- We examined the radiographs from a prospective clinical study of fixation by pedicle screws and those from an experimental study in a sheep model. In the clinical study, instruments were removed from 21 patients after implantation for 11 to 16 months and the extraction torques of the screws were recorded. A structured protocol was used for the radiological examinations. In the experimental study, loaded pedicle screw instrumentations were implanted in the sheep for six or 12 weeks. After radiological examination the pull-out resistance and the histological characteristics were studied. In the clinical study, all screws with radiolucent zones had a significantly reduced mean extraction torque compared with screws without radiolucent zones (16 +/- 10 Ncm v 403 +/- 220 Ncm; p < 0.0001). In the experimental study the mean maximum pull-out resistance for the screws with radiolucent zones was significantly lower than for those with no radiolucency (243 +/- 156 N v2214 +/- 578 N; p = 0.0006) and the mean bone-to-screw contact was reduced for screws with zones compared with those without zones (8 +/- 9% v 55 +/- 29%; p = 0.0002). Our findings showed that all screws with radiolucent zones had low extraction torques or low pull-out resistance. A radiolucent zone is a good indicator of loosening of a pedicle screw.
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- Henriques, Thomas, et al.
(författare)
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In vitro biomechanical evaluation of four fixation techniques for distractive-flexion injury stage 3 of the cervical spine
- 2015
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Ingår i: Upsala Journal of Medical Sciences. - : Uppsala Medical Society. - 0300-9734 .- 2000-1967. ; 120:3, s. 198-206
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Tidskriftsartikel (refereegranskat)abstract
- Purpose. Anterior plate fixation has been reported to provide satisfactory results in cervical spine distractive flexion (DF) injuries stages 1 and 2, but will result in a substantial failure rate in more unstable stage 3 and above. The aim of this investigation was to determine the biomechanical properties of different fixation techniques in a DF-3 injury model where all structures responsible for the posterior tension band mechanism are torn. Methods. The multidirectional three-dimensional stiffness of the subaxial cervical spine was measured in eight cadaveric specimens with a simulated DF-3 injury at C5-C6, stabilized with four different fixation techniques: anterior plate alone, anterior plate combined with posterior wire, transarticular facet screws, and a pedicle screw-rod construct, respectively. Results. The anterior plate alone did not improve stability compared to the intact spine condition, thus allowing considerable range of motion around all three cardinal axes (p > 0.05). The anterior plate combined with posterior wire technique improved flexion-extension stiffness (p = 0.023), but not in axial rotation and lateral bending. When the anterior plate was combined with transarticular facet screws or with a pedicle screws-rod instrumentation, the stability improved in flexion-extension, lateral bending, and in axial rotation (p < 0.05). Conclusions. These findings imply that the use of anterior fixation alone is insufficient for fixation of the highly unstable DF-3 injury. In these situations, the use of anterior fixation combined with a competent posterior tension band reconstruction (e.g. transarticular screws or a posterior pedicle screws-rod device) improves segmental stability.
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- Stridh, Sara, et al.
(författare)
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Angiotensin converting enzyme inhibition blocks interstitial hyaluronan dissipation in the neonatal rat kidney via hyaluronan synthase 2 and hyaluronidase 1.
- 2011
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Ingår i: Matrix biology : journal of the International Society for Matrix Biology. - : Elsevier BV. - 1569-1802 .- 0945-053X. ; 30:1, s. 62-9
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Tidskriftsartikel (refereegranskat)abstract
- A functional renin-angiotensin system (RAS) is required for normal kidney development. Neonatal inhibition of the RAS in rats results in long-term pathological renal phenotype and causes hyaluronan (HA), which is involved in morphogenesis and inflammation, to accumulate. To elucidate the mechanisms, intrarenal HA content was followed during neonatal completion of nephrogenesis with or without angiotensin converting enzyme inhibition (ACEI) together with mRNA expression of hyaluronan synthases (HAS), hyaluronidases (Hyal), urinary hyaluronidase activity and cortical lymphatic vessels, which facilitate the drainage of HA from the tissue. In 6-8days old control rats cortical HA content was high and reduced by 93% on days 10-21, reaching adult low levels. Medullary HA content was high on days 6-8 and then reduced by 85% to 12-fold above cortical levels at day 21. In neonatally ACEI-treated rats the reduction in HA was abolished. Temporal expression of HAS2 corresponded with the reduction in HA content in the normal kidney. In ACEI-treated animals cortical HAS2 remained twice the expression of controls. Medullary Hyal1 increased in controls but decreased in ACEI-treated animals. Urine hyaluronidase activity decreased with time in control animals while in ACEI-treated animals it was initially 50% lower and did not change over time. Cells expressing the lymphatic endothelial mucoprotein podoplanin in ACEI-treated animals were increased 18-fold compared to controls suggesting compensation. In conclusion, the high renal HA content is rapidly reduced due to reduced HAS2 and increased Hyal1 mRNA expressions. Normal angiotensin II function is crucial for inducing these changes. Due to the extreme water-attracting and pro-inflammatory properties of HA, accumulation in the neonatally ACEI-treated kidneys may partly explain the pathological renal phenotype of the adult kidney, which include reduced urinary concentration ability and tubulointerstitial inflammation.
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- Söderlund, Anne, et al.
(författare)
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Acute whiplash-associated disorders (WAD) : the effects of early mobilization and prognostic factors in long-term symptomatology.
- 2000
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Ingår i: Clinical Rehabilitation. - : SAGE Publications. - 0269-2155 .- 1477-0873. ; 14:5, s. 457-467
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To compare two different home exercise programmes for patients with acute whiplash-associated disorders (WAD). A further aim was to describe the initial prognostic variables related to self-reported pain at six months follow-up. DESIGN: A randomized treatment study with a follow-up period of six months. SETTINGS: The study was undertaken in an orthopaedic clinic at a university hospital. SUBJECTS: A total of 59 symptomatic (neck pain, stiffness, etc.) patients with acute whiplash injury. INTERVENTIONS: Patients were randomized to a regular treatment group (RT group) and an additional-exercise treatment group (AT group). MAIN OUTCOME MEASURES: Pain Disability Index (PDI), Self-Efficacy Scale (SES), Coping Strategies Questionnaire (CSQ), neck range of motion (ROM), head posture, kinaesthetic sensibility, visual analogue scale (VAS). RESULTS: Patients given an additional exercise did not improve more than patients with regular treatment. Only one CSQ item, 'Ability to decrease pain', showed a significant difference between the groups in its pattern of change over time: the AT group had a significant increase between three and six months whilst values in the RT group decreased. Nonsymptomatic patients at six months follow-up were characterized by initially better self-efficacy, lower disability and significantly different patterns in the use of 'behavioural coping strategies' when compared with symptomatic patients. The nonsymptomatic patients also reported more frequent training than symptomatic patients, i.e. they complied better with the treatment regime. CONCLUSION: This home exercise programme, including training of neck and shoulder ROM, relaxation and general advice seems to be sufficient treatment for acute WAD patients when used on a daily basis. Additionally, patients reporting low self-efficacy and high disability levels may profit from more attention initially, as these psychological factors are significant predictors of pain at long-term follow-up.
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