Device for lengthening of a musculotendinous unit by direct continuous traction in the sheep

Background Retraction, atrophy and fatty infiltration are signs subsequent to chronic rotator cuff tendon tears. They are associated with an increased pennation angle and a shortening of the muscle fibers in series. These deleterious changes of the muscular architecture are not reversible with current repair techniques and are the main factors for failed rotator cuff tendon repair. Whereas fast stretching of the retracted musculotendinous unit results in proliferation of non-contractile fibrous tissue, slow stretching may lead to muscle regeneration in terms of sarcomerogenesis. To slowly stretch the retracted musculotendinous unit in a sheep model, two here described tensioning devices have been developed and mounted on the scapular spine of the sheep using an expandable threaded rod, which has been interposed between the retracted tendon end and the original insertion site at the humeral head. Traction is transmitted in line with the musculotendinous unit by sutures knotted on the expandable threaded rod. The threaded rod of the tensioner is driven within the body through a rotating axis, which enters the body on the opposite side. The tendon end, which was previously released (16 weeks prior) from its insertion site with a bone chip, was elongated with a velocity of 1 mm/day. Results After several steps of technical improvements, the tensioner proved to be capable of actively stretching the retracted and degenerated muscle back to the original length and to withstand the external forces acting on it. Conclusion This technical report describes the experimental technique for continuous elongation of the musculotendinous unit and reversion of the length of chronically shortened muscle

Recombinant prion protein induces a new transmissible prion disease in wild-type animals

Prion disease is a neurodegenerative malady, which is believed to be transmitted via a prion protein in its abnormal conformation (PrPSc). Previous studies have failed to demonstrate that prion disease could be induced in wild-type animals using recombinant prion protein (rPrP) produced in Escherichia coli. Here, we report that prion infectivity was generated in Syrian hamsters after inoculating full-length rPrP that had been converted into the cross-β-sheet amyloid form and subjected to annealing. Serial transmission gave rise to a disease phenotype with highly unique clinical and neuropathological features. Among them were the deposition of large PrPSc plaques in subpial and subependymal areas in brain and spinal cord, very minor lesioning of the hippocampus and cerebellum, and a very slow progression of disease after onset of clinical signs despite the accumulation of large amounts of PrPSc in the brain. The length of the clinical duration is more typical of human and large animal prion diseases, than those of rodents. Our studies establish that transmissible prion disease can be induced in wild-type animals by inoculation of rPrP and introduce a valuable new model of prion diseases

Malunion after midshaft clavicle fractures in adults: The current view on clavicular malunion in the literature

This is an overview of the current literature on malunion after midshaft clavicle fracture. Anatomy, trauma mechanism, classification, incidence, symptoms, prevention, and treatment options are all discussed. The conclusion is that clavicle malunion is a distinct clinical entity that can be treated successfully

Dynamization at the near cortex in locking plate osteosynthesis by means of dynamic locking screws: an experimental study of transverse tibial osteotomies in sheep

BACKGROUND: Locking plates are widely used in fracture fixation, mainly for meta-diaphyseal fractures, comminuted fractures, fractures with a critical-size bone defect, periprosthetic fractures, osteotomies, and fractures in osteoporotic bone. The aim of this animal study was to evaluate the effect on bone-healing of dynamization of locking plate constructs by means of new 5.0-mm dynamic locking screws (in the DLS group), which allow near-cortex micromotion, compared with a more rigid construct utilizing standard bicortical locking-head screws (in the LS group). Use of dynamic locking screws allows modulation of the stiffness of existing locking compression plate systems via parallel interfragmentary micromotion. METHODS: A standardized diaphyseal tibial osteotomy (90°, 3-mm fracture gap) was performed and stabilized with a six-hole large-fragment locking compression plate in twelve female sheep (six in each group). Radiographs were made postoperatively and then weekly from week three until sacrifice at nine weeks. Macroscopic, biomechanical, histologic, and radiographic assessments and microcomputed tomography were performed. RESULTS: The callus in the tested specimens in the DLS group had better biomechanical stability, with a significantly greater maximum failure moment (mean and standard deviation [SD] as a percentage of intact, 55.15 ± 20.65 compared with 26.80 ± 14.96 in the LS group; p = 0.021). The DLS group also had greater periosteal callus volume at the near cortex (mean volume and SD as a percentage of the tibial shaft volume, 36.21% ± 10.08% compared with 18.98% ± 8.61% in the LS group; p = 0.026) and in the intercortical region (mean volume and SD as a percentage of the bone volume of the tibial shaft, 3.56% ± 0.52% compared with 2.64% ± 0.98% in the LS group; p = 0.045), as shown by microcomputed tomography. The DLS group also had significantly greater torsional stiffness (mean and SD as a percentage of intact, 84.88 ± 13.51 compared with 58.89 ± 20.61 in the LS group; p = 0.027). CONCLUSIONS: Controlled micromotion and nearly homogeneous interfragmentary strain at the fracture site, together with the stable bicortical fixation achieved by the new dynamic locking screw, led to more uniform callus formation, significantly more callus formation at the near cortex, and biomechanically more competent bone-healing compared with use of rigid locking plate constructs with locking-head screws

Rotator cuff muscles lose responsiveness to anabolic steroids after tendon tear and musculotendinous retraction: an experimental study in sheep

BACKGROUND: Long-standing rotator cuff tendon tearing is associated with retraction, loss of work capacity, irreversible fatty infiltration, and atrophy of the rotator cuff muscles. Although continuous musculotendinous relengthening can experimentally restore muscular architecture, restoration of atrophy and fatty infiltration is hitherto impossible. HYPOTHESIS: Continuous relengthening with pharmacological stimulation of muscle growth using an anabolic steroid or insulin-like growth factor (IGF) can reverse atrophy and fatty infiltration as well as improve the work capacity of chronically retracted rotator cuff muscles in sheep. STUDY DESIGN: Controlled laboratory study. METHODS: Sixteen weeks after tenotomy of the infraspinatus (ISP) tendon, atrophy and fatty infiltration had developed in the retracted ISP muscle. The musculotendinous unit was continuously relengthened in 14 sheep during 6 weeks: Four sheep were treated without pharmacological stimulation, 4 with intramuscular administration of an anabolic steroid, and 6 with IGF before final repair and rehabilitation (12 weeks). Changes were documented by intraoperative measurements of muscle work capacity, histology, and computed tomography/magnetic resonance imaging. RESULTS: Musculotendinous relengthening by continuous traction resulted in gains of length ranging from 0.7 cm in the IGF group to 1.3 cm in the control group. Fatty infiltration progressed in all groups, and the muscle's cross-sectional area ranged from 71% to 74% of the contralateral side at sacrifice and did not show any differences between groups in weight, volume, histological composition, or work capability of the muscle. The contralateral muscles in the anabolic steroid group, however, showed significantly higher (mean ± standard deviation) muscle work capacity of 10 ± 0.9 N·m than the contralateral muscles of the control group (6.8 ± 2.4 N·m) (P < .05). This was accompanied by an increased mean muscle fiber area as well as by an unusual gain in the animals' weight after injection of the anabolic steroid. CONCLUSION: Subcutaneous continuous relengthening of a chronically retracted musculotendinous unit is feasible and advances the retracted musculotendinous junction toward its original position. This does not change the muscle work capacity. Whereas anabolic steroids have been shown to be effective in preventing classic degenerative muscle changes after tendon tears, neither an anabolic steroid nor IGF contributes to regeneration of the muscle once degenerative changes are established. CLINICAL RELEVANCE: The findings demonstrate that muscle cells lose reactiveness to an anabolic steroid and IGF once retraction has led to fatty infiltration and atrophy of the muscle. Retraction of the muscle after tendon tears must be avoided by early repair, particularly in an athlete, as no regeneration can be achieved by mechanical or pharmacological means at this time

Osseointegration and biocompatibility of different metal implants--a comparative experimental investigation in sheep

BACKGROUND: In the present study, 4 different metallic implant materials, either partly coated or polished, were tested for their osseointegration and biocompatibility in a pelvic implantation model in sheep. METHODS: Materials to be evaluated were: Cobalt-Chrome (CC), Cobalt-Chrome/Titanium coating (CCTC), Cobalt-Chrome/Zirconium/Titanium coating (CCZTC), Pure Titanium Standard (PTST), Steel, TAN Standard (TANST) and TAN new finish (TANNEW). Surgery was performed on 7 sheep, with 18 implants per sheep, for a total of 63 implants. After 8 weeks, the specimens were harvested and evaluated macroscopically, radiologically, biomechanically (removal torque), histomorphometrically and histologically. RESULTS: Cobalt-Chrome screws showed significantly (p = 0.031) lower removal torque values than pure titanium screws and also a tendency towards lower values compared to the other materials, except for steel. Steel screws showed no significant differences, in comparison to cobalt-chrome and TANST, however also a trend towards lower torque values than the remaining materials. The results of the fluorescence sections agreed with those of the biomechanical test. Histomorphometrically, there were no significant differences of bone area between the groups. The BIC (bone-to-implant-contact), used for the assessment of the osseointegration, was significantly lower for cobalt-chrome, compared to steel (p = 0.001). Steel again showed a lower ratio (p = 0.0001) compared to the other materials. CONCLUSION: This study demonstrated that cobalt-chrome and steel show less osseointegration than the other metals and metal-alloys. However, osseointegration of cobalt-chrome was improved by zirconium and/or titanium based coatings (CCTC, TANST, TAN, TANNEW) being similar as pure titanium in their osseointegrative behavior

The dynamisation of locking plate osteosynthesis by means of dynamic locking screws (DLS)-An experimental study in sheep

In this in vivo study a new generation of locking screws was tested. The design of the dynamic locking screw (DLS) enables the dynamisation of the cortex underneath the plate (cis-cortex) and, therefore, allows almost parallel interfragmentary closure of the fracture gap. A 45° angle osteotomy was performed unilaterally on the tibia of 37 sheep. Groups of 12 sheep were formed and in each group a different osteotomy gap (0, 1 and 3mm) was fixed using a locking compression plate (LCP) in combination with the DLS. The healing process was monitored radiographically every 3 weeks for 6, respectively 12 weeks. After this time the sheep were sacrificed, the bones harvested and the implants removed. The isolated bones were evaluated in the micro-computed tomography unit, tested biomechanically and evaluated histologically. The best results of interfragmentary movement (IFM) were shown in the 0mm configuration. The bones of this group demonstrated histomorphometrically the most distinct callus formation on the cis-cortex and the highest torsional stiffness relative to the untreated limb at 12 weeks after surgery. This animal study showed that IFM stimulated the synthesis of new bone matrix, especially underneath the plate and thus, could solve a current limitation in normal human bone healing. The DLS will be a valuable addition to the locking screw technology and improve fracture healing

The influence of different osteosynthesis configurations with locking compression plates (LCP) on stability and fracture healing after an oblique 45° angle osteotomy

BACKGROUND:Locking compression plates are used in various configurations with lack of detailed information on consequent bone healing. STUDY DESIGN:In this in vivo study in sheep 5 different applications of locking compression plate (LCP) were tested using a 45° oblique osteotomy simulating simple fracture pattern. 60 Swiss Alpine sheep where assigned to 5 different groups with 12 sheep each (Group 1: interfragmentary lag screw and an LCP fixed with standard cortex screws as neutralisation plate; Group 2: interfragmentary lag screw and LCP with locking head screws; Group 3: compression plate technique (hybrid construct); Group 4: internal fixator without fracture gap; Group 5: internal fixator with 3mm gap at the osteotomy site). One half of each group (6 sheep) was monitored for 6weeks, and the other half (6 sheep) where followed for 12weeks. METHODS:X-rays at 3, 6, 9 and 12weeks were performed to monitor the healing process. After sacrifice operated tibiae were tested biomechanically for nondestructive torsion and compared to the tibia of the healthy opposite side. After testing specimens were processed for microradiography, histology, histomorphometry and assessment of calcium deposition by fluorescence microscopy. RESULTS:In all groups bone healing occurred without complications. Stiffness in biomechanical testing showed a tendency for higher values in G2 but results were not statistically significant. Values for G5 were significantly lower after 6weeks, but after 12weeks values had improved to comparable results. For all groups, except G3, stiffness values improved between 6 and 12weeks. Histomorphometrical data demonstrate endosteal callus to be more marked in G2 at 6weeks. DISCUSSION AND CONCLUSION:All five configurations resulted in undisturbed bone healing and are considered safe for clinical application