Congenital pseudarthrosis of the tibia: biological and biomechanical considerations to achieve union and prevent refracture.

Congenital pseudarthrosis of the tibia (CPT) is likely to be a primary periosteal disease and secondary bone disease. The primary goal of treatment is to obtain union, correct the diaphyseal deformity, correct any proximal fibular migration and prevent refracture. The pathobiology demonstrates increased osteoclasis by the surrounding fibrous hamartoma and reduced osteogenesis and bone morphogenic protein production by the bone. This leads to a loss of remodelling potential and gradual bowing and atrophy of the bone with eventual fracture of the tibia and or fibula. This recommends the synergistic use of bisphosphonates and bone morphogenic protein. The pathomechanics of CPT implicate the anterolateral bowing, narrow diameter of the atrophic bone ends and proximal fibular migration. These biomechanical factors can be addressed by means of straightening of the deformity, intramedullary support of both bones, stable fixation and reduction of proximal migration of the fibula. A summary of the literature on CPT shows that the mean probability of achieving primary union without refracture, by most treatments is 50% (12% to 80%). Two recent studies have shown a much higher success rate approaching 100%, by creating a cross-union between the tibia and fibula. The cross-union with intramedullary reinforcement of the bone makes refracture unlikely due to the cross-sectional area of union with its two-bar linkage. A new classification to guide such treatment is also proposed. LEVEL OF EVIDENCE: V - expert opinion.

Engineering the Structural and Electronic Phases of MoTe2 through W Substitution.

MoTe2 is an exfoliable transition metal dichalcogenide (TMD) that crystallizes in three symmetries: the semiconducting trigonal-prismatic 2H- or α-phase, the semimetallic and monoclinic 1T'- or ß-phase, and the semimetallic orthorhombic γ-structure. The 2H-phase displays a band gap of ∼1 eV making it appealing for flexible and transparent optoelectronics. The γ-phase is predicted to possess unique topological properties that might lead to topologically protected nondissipative transport channels. Recently, it was argued that it is possible to locally induce phase-transformations in TMDs, through chemical doping, local heating, or electric-field to achieve ohmic contacts or to induce useful functionalities such as electronic phase-change memory elements. The combination of semiconducting and topological elements based upon the same compound might produce a new generation of high performance, low dissipation optoelectronic elements. Here, we show that it is possible to engineer the phases of MoTe2 through W substitution by unveiling the phase-diagram of the Mo1-xWxTe2 solid solution, which displays a semiconducting to semimetallic transition as a function of x. We find that a small critical W concentration xc ∼ 8% stabilizes the γ-phase at room temperature. This suggests that crystals with x close to xc might be particularly susceptible to phase transformations induced by an external perturbation, for example, an electric field. Photoemission spectroscopy, indicates that the γ-phase possesses a Fermi surface akin to that of WTe2.

Tibial lengthening over intramedullary nails: A matched case comparison with Ilizarov tibial lengthening.

OBJECTIVES: The purpose of this study was to compare the results and complications of tibial lengthening over an intramedullary nail with treatment using the traditional Ilizarov method. METHODS: In this matched case study, 16 adult patients underwent 19 tibial lengthening over nails (LON) procedures. For the matched case group, 17 patients who underwent 19 Ilizarov tibial lengthenings were retrospectively matched to the LON group. RESULTS: The mean external fixation time for the LON group was 2.6 months and for the matched case group was 7.6 months. The mean lengthening amounts for the LON and the matched case groups were 5.2 cm and 4.9 cm, respectively. The radiographic consolidation time in the LON group was 6.6 months and in the matched case group 7.6 months. Using a clinical and radiographic outcome score that was designed for this study, the outcome was determined to be excellent in 17 and good in two patients for the LON group. The outcome was excellent in 14 and good in five patients in the matched case group. The LON group had increased blood loss and increased cost. The LON group had four deep infections; the matched case group did not have any deep infections. CONCLUSIONS: The outcomes in the LON group were comparable with the outcomes in the matched case group. The LON group had a shorter external fixation time but experienced increased blood loss, increased cost, and four cases of deep infection. The advantage of reducing external fixation treatment time may outweigh these disadvantages in patients who have a healthy soft-tissue envelope.Cite this article: J. E. Herzenberg. Tibial lengthening over intramedullary nails: A matched case comparison with Ilizarov tibial lengthening. Bone Joint Res 2016;5:1-10. doi: 10.1302/2046-3758.51.2000577.

Life- and limb-threatening infections following the use of an external fixator.

External fixation is widely used in orthopaedic and trauma surgery. Infections around pin or wire sites, which are usually localised, non-invasive, and are easily managed, are common. Occasionally, more serious invasive complications such as necrotising fasciitis (NF) and toxic shock syndrome (TSS) may occur. We retrospectively reviewed all patients who underwent external fixation between 1997 and 2012 in our limb lengthening and reconstruction programme. A total of eight patients (seven female and one male) with a mean age of 20 years (5 to 45) in which pin/wire track infections became limb- or life-threatening were identified. Of these, four were due to TSS and four to NF. Their management is described. A satisfactory outcome was obtained with early diagnosis and aggressive medical and surgical treatment. Clinicians caring for patients who have external fixation and in whom infection has developed should be aware of the possibility of these more serious complications. Early diagnosis and aggressive treatment are required in order to obtain a satisfactory outcome.

Rheotaxis performance increases with group size in a coupled phase model with sensory noise: The effects of noise and group size on rheotaxis.

Many fish exhibit rheotaxis, a behavior in which fish orient themselves relative to flow. Rheotaxis confers many benefits, including energetic cost savings and interception of drifting prey. Despite the fact that most species of fish school during at least some portion of their life, little is known about the importance of rheotactic behavior to schooling fish and, conversely, how the presence of nearby conspecifics affects rheotactic behavior. Understanding how rheotaxis is modified by social factors is thus of ecological importance. Here we present a mathematical model in the form of an all-to-all, coupled-oscillator framework over the non-Euclidean space of fish orientations to model group rheotactic behavior. Individuals in the model measure the orientation of their neighbors and the flow direction relative to their own orientation. These measures are corrupted by sensory noise. We study the effect of sensory noise and group size on internal (i.e., within the school) and external (i.e., with the flow) disagreement in orientation. We find that under noisy environmental conditions, increased group size improves rheotaxis. Results of this study have implications for understanding animal behavior, as well as for potential applications in bio-inspired engineering.

The effects of flow on schooling Devario aequipinnatus: school structure, startle response and information transmission.

To assess how flow affects school structure and threat detection, startle response rates of solitary and small groups of giant danio Devario aequipinnatus to visual looming stimuli were compared in flow and no-flow conditions. The instantaneous position and heading of each D. aequipinnatus was extracted from high-speed videos. Behavioural results indicate that (1) school structure is altered in flow such that D. aequipinnatus orient upstream while spanning out in a crosswise direction, (2) the probability of at least one D. aequipinnatus detecting the visual looming stimulus is higher in flow than no flow for both solitary D. aequipinnatus and groups of eight D. aequipinnatus; however, (3) the probability of three or more individuals responding is higher in no flow than in flow. These results indicate a higher probability of stimulus detection in flow but a higher probability of internal transmission of information in no flow. Finally, results were well predicted by a computational model of collective fright response that included the probability of direct detection (based on signal detection theory) and indirect detection (i.e. via interactions between group members) of threatening stimuli. This model provides a new theoretical framework for analysing the collective transfer of information among groups of fishes and other organisms.

The spatiotemporal dynamics of rheotactic behavior depends on flow speed and available sensory information.

Rheotaxis is a robust, multisensory behavior with many potential benefits for fish and other aquatic organisms. Visual (optic flow) cues appear to be sufficient for rheotaxis, but other sensory cues can clearly compensate for the loss of vision. Nevertheless, the nature of multisensory interactions and the relative contributions of different senses under varying conditions are poorly understood - largely because there is so little description of the actual behavior. Here, we examined the effects of different flow speeds and different sensory conditions on the spatiotemporal dynamics of rheotaxis. Although the overall ability of giant danio (Devario aequipinnatus) to head upstream is largely unaffected by either unimodal or bimodal deprivation of visual and/or lateral line senses, the spatiotemporal form of the behavior is altered in subtle ways. When deprived of vision, fish move further upstream, but the angular accuracy of the upstream heading is reduced. In addition, visually deprived fish exhibit left/right sweeping movements near the upstream barrier at low flow speeds. Sweeping movements are abolished when these fish are additionally deprived of lateral line information. These results indicate that fish adopt different sensorimotor strategies to compensate for the loss of one or more senses and that the nature of multisensory interactions is a complex function of flow speed.

The effect on mechanical axis deviation of femoral lengthening with an intramedullary telescopic nail.

Internal lengthening devices in the femur lengthen along the anatomical axis, potentially creating lateral shift of the mechanical axis. We aimed to determine whether femoral lengthening along the anatomical axis has an inadvertent effect on lower limb alignment. Isolated femoral lengthening using the Intramedullary Skeletal Kinetic Distractor was performed in 27 femora in 24 patients (mean age 32 years (16 to 57)). Patients who underwent simultaneous realignment procedures or concurrent tibial lengthening, or who developed mal- or nonunion, were excluded. Pre-operative and six-month post-operative radiographs were used to measure lower limb alignment. The mean lengthening achieved was 4.4 cm (1.5 to 8.0). In 26 of 27 limbs, the mechanical axis shifted laterally by a mean of 1.0 mm/cm of lengthening (0 to 3.5). In one femur that was initially in varus, a 3 mm medial shift occurred during a lengthening of 2.2 cm. In a normally aligned limb, intramedullary lengthening along the anatomical axis of the femur results in a lateral shift of the mechanical axis by approximately 1 mm for each 1 cm of lengthening.

Mechanical failure of the Intramedullary Skeletal Kinetic Distractor in limb lengthening.

Between October 2001 and September 2009 we lengthened 242 lower-limb segments in 180 patients using the Intramedullary Skeletal Kinetic Distractor (ISKD). Mechanical failure was defined either as breakage of the ISKD or failure of the internal mechanism to activate. Retrieved nails which failed mechanically were examined by the manufacturer for defects. In all, 15 ISKDs in 12 patients (13 limbs) failed mechanically representing an overall failure rate of 6.2%, with fracture of the device occurring in ten of the 15 failures. Two nails in one patient failed to lengthen and had to be replaced. The manufacturer detected an error in the assembly of the nail, which prompted a wide recall. One nail jammed after being forcefully inserted, and two nails failed to lengthen fully. Lengthening was achieved in all 12 patients, although three required a second operation to exchange a defective nail for a new, functioning device. The ISKD is a complex mechanical device which lengthens by the oscillation of two telescopic sections connected by a threaded rod. The junction between these sections is surrounded by a keyring collar. This keyring collar is the weakest part of the device.

[Knee para-articular focal dome osteotomy]. / Die kniegelenknahe Focal-dome-Osteotomie.

Focal dome osteotomy (FDO) is a cylindrically shaped osteotomy, with corresponding bone cuts rotating around the central axis of the deformity. Thus, complete correction can be achieved without secondary translation. FDO provides high adjustability of the bone ends, optimal bone contact, and high primary stability. As with straight cut closing, neutral, and opening-wedge osteotomies, FDO allows closing, neutral, and opening corrections. Opening FDO allows preservation of bone contact, whereas closing FDO does not require removal of bone stock. The osteotomy can be modified to tighten the medial collateral ligament. A FDO below the tuberosity does not compromise patellofemoral function and reduces the risk of intra-articular fractures. Sufficient bone stock of the proximal tibial or distal femoral fragment allows intramedullary stabilization. FDO is of high value in the treatment of sagittal plane and frontal plane corrections of the knee even in severe deformities.

A model for susceptibility artefacts from respiration in functional echo-planar magnetic resonance imaging.

Respiration causes variations in the signals acquired during magnetic resonance imaging (MRI) and therefore is a significant source of noise in functional brain imaging. A primary component of respiratory noise may arise from variations of bulk susceptibility or air volume in the chest. Here we investigate the nature of the image artefacts that can be caused by such changes. We develop a simple model which attempts to mimic the effects of variations in susceptibility and volume during respiration. Theoretical calculations, computer simulations and imaging experiments with this model show that small variations in susceptibility within the thorax from alterations in the paramagnetism of cavity gas may lead to a shift of the image on the order of 0.1 pixels as well as a shading of the intensity by +/-1%. These effects are observed to be predominant in the phase-encoding direction. They may lead to the production of spurious activations in functional MRI and are likely to be of more importance at higher field strengths.

Multiplier method for predicting limb-length discrepancy.

BACKGROUND: In patients with a congenital or developmental limb-length discrepancy, the short limb grows at a rate proportional to that of the normal, long limb. This is the basis of predicting limb-length discrepancy with existing methods, which are complicated and require multiple data points. The purpose of our study was to derive a simple arithmetic formula that can easily and accurately predict limb-length discrepancy at skeletal maturity. METHODS: Using available databases, we divided the femoral and tibial lengths at skeletal maturity by the femoral and tibial lengths at each age for each percentile group. The resultant number was called the multiplier. Using the multiplier, we derived formulae to predict the limb-length discrepancy and the amount of growth remaining. We verified the accuracy of these formulae by evaluating two groups of patients with congenital shortening who were managed with epiphysiodesis or limb-lengthening. We also calculated and compared the multipliers for other databases according to radiographic, clinical, and anthropological lower-limb measurements. RESULTS: The multipliers for the femur and tibia were equivalent in all percentile groups, varying only by age and gender. Because congenital limb-length discrepancy increases at a rate proportional to growth, the discrepancy at maturity can be calculated as the current discrepancy times the multiplier for the current age and the gender. This calculation can be performed with use of a single measurement of limb-length discrepancy. For progressive developmental (noncongenital) discrepancies, the discrepancy at skeletal maturity can be calculated as the current discrepancy plus the growth inhibition times the amount of growth remaining. The timing of the epiphysiodesis can also be calculated with the multiplier. The predictions made with use of the multiplier method correlated well with those made with use of the Moseley method as well as with the actual limb-length discrepancy in both the limb-lengthening and epiphysiodesis groups. The multipliers derived from the radiographic, clinical, and anthropological measurements of femora and tibiae were all similar to each other despite differences in race, ethnicity, and generation. CONCLUSIONS: The multiplier method allows for a quick calculation of the predicted limb-length discrepancy at skeletal maturity, without the need to plot graphs, and is based on as few as one or two measurements. This method is independent of percentile groups and is the same for the prediction of femoral, tibial, and total-limb lengths. The multiplier values are also independent of generation, height, socioeconomic class, ethnicity, and race. We verified the accuracy of this method clinically by evaluating patients who had been managed with limb-lengthening or epiphysiodesis. The method was also comparable with or more accurate than the Moseley method of limb-length prediction.

The adaptation of perimuscular connective tissue during distraction osteogenesis.

It is not known whether the decreased range of motion observed during distraction osteogenesis results from the lack of adaptation of muscle or from fibrosis in the perimysium. The adaptation of the perimysium in the tibialis anterior muscle in skeletally immature rabbits using two distraction regimens (0.7 and 1.4 mm/day with 15% lengthening) was characterized. The resulting data indicate that during distraction osteogenesis, the muscle adapts by reorganization of its connective tissue. At a lengthening rate of 1.4 mm/day, there is perimysial fibrosis without major cellular pathologic abnormalities in the muscle fibers. The increase in perimysial thickness is characterized by an increase of collagen Type I. In addition, collagen Type I is deposited around the endomysium. The increase in total collagen and its cross-linking are dependent on the lengthening rate. The faster lengthening rate also leads to a significant decreased passive plantar flexion. Supplemental growth of the tibia was not observed, and a lack of adaptation in the muscle (based on resting length) was not seen. Together, the data suggest that decreased range of motion during distraction osteogenesis may be a function of the adaptation of the perimysium rather than of the muscle fibers.

Growth patterns after lengthening of congenitally short lower limbs in young children.

The purpose of this study was to assess growth patterns after lengthening of the congenitally short femur or tibia in children younger than 6 years. Twenty such children underwent 28 bone segment lengthenings (13 femora and 15 tibiae) by distraction osteogenesis. Our results show that femoral lengthening in children younger than 6 years does not lead to growth inhibition, whereas isolated femoral lengthening may be associated with growth stimulation. Isolated tibial lengthening in children younger than 6 years does not lead to growth inhibition, whereas simultaneous femoral and tibial lengthening or two tibial lengthenings in close succession can lead to tibial growth inhibition.

Ilizarov bone transport treatment for tibial defects.

OBJECTIVES: To evaluate the results and complications of Ilizarov bone transport in the treatment of tibial bone defects. DESIGN: Retrospectively reviewed consecutive series. METHODS: Nineteen patients with tibial bone defects were treated by the Ilizarov bone transport method. The mean bone defect was ten centimeters, and there were eight soft-tissue defects. The mean external fixation time was sixteen months. Ten patients required debridement of the bone ends and/or bone grafting of the docking site at the end of transport. RESULTS: Union was achieved in all cases. One refracture of the docking site required retreatment with the Ilizarov apparatus to achieve union. There was one residual leg length discrepancy greater than 2.5 centimeters and two angular deformities greater than 5 degrees. There were no recurrent or residual infections. Seven of the eight soft-tissue defects were closed by soft-tissue transport; the eighth required a free-vascularized flap. The bone results were graded as fifteen excellent, three good, and one fair. The functional results were graded as twelve excellent, six good, and one poor. There were twenty-two minor complications, sixteen major complications without residual sequelae, and three major complications with residual sequelae. To treat the bone defect and the complications, a mean of 2.9 operations per patient was required. CONCLUSIONS: Our results compare favorably with those for other methods of bone grafting as well as with those from other published accounts of the Ilizarov method, especially considering the large defect size in this series. The main disadvantage of the Ilizarov method is the lengthy external fixation time.

[Principles of deformity correction around the knee]. / Prinzipien der kniegelenknahen Deformitätenkorrektur.

Lower limb frontal and sagittal plane alignment and joint orientation have significant consequences for function and wear on the hip, knee and ankle. There is a normal range for the orientation of these joints relative to the mechanical and anatomic axis of the femur and/or tibia. We can use the normal joint orientation to accurately plan realignment of a deformed femur or tibia. In the frontal plane we use both anatomic and mechanical axis lines for planning. In the sagittal plane, the mechanical axis has less relevance and, therefore, only the anatomic axis is used for planning.