Circular frame fixation has become a cornerstone of non-union and deformity management since its inception in the 1950s. As a consequence of modularity and heterogenous patient and injury factors, the prediction of the mechanobiological environment within a defect is subject to wide variations in practice. Given these wide range of confounding variables, clinical and cadaveric experimentation is close to impossible and frame constructs are based upon clinician experience. The Finite Element Analysis (FEA) method provides a powerful tool to numerically analyse mechanics. This work aims to develop an FEA model of a tibial defect and predict the mechanical response within the construct. The geometry of a tibia was acquired via CT and a series of bone defects were digitally created in the tibial diaphysis. A 4-ring, 10-wire Ilizarov fixator was constructed using 180mm stainless steel rings and 1.8mm stainless steel wires tensioned to 1200N. An axial load (800N) was applied to simulate single leg stance of an 80kg patient. The magnitude of displacement was measured for defects with varying sizes (5–40mm). A numerical analysis was performed in large-strain regime using open-source FEA library (MoFEM).Introduction
Materials and Methods
Survivors of infantile meningococcal septicaemia often develop progressive skeletal deformity as a consequence of physeal damage at multiple sites, particularly in the lower limb. Distal tibial physeal arrest typically occurs with sparing of the distal fibular physis leading to a rapidly progressive varus deformity. Isolated case reports include this deformity, but to our knowledge there is no previous literature that specifically reports the development of this deformity and potential treatment options. We report our experience of 6 patients (7ankles) with this deformity, managed with corrective osteotomy using a programmable circular fixator.
Complex regional pain syndrome (type 1) (CRPS) is a chronically painful and disabling condition commonly encountered following trauma and surgery to an extremity. The condition comprises of a combination of pain, swelling, sensory impairment, joint stiffness, trophic changes, motor abnormalities and vasomotor instability. Post-traumatic CRPS is a significant clinical problem presenting to the orthopaedic surgeon and pain specialist. A clear understanding of the condition has been hampered by a lack of uniformity of diagnostic criteria ( Breuhl’s criteria use a combination of symptoms and signs from 4 distinct groups (hypersensitivity; vasomotor; swelling and sudomotor; motor and trophic). Atkins’ criteria require the finding of vasomotor instability symptoms, abnormal finger dolorimetry and abnormal finger range of movements. We have compared these different criteria on a series of 262 patients with distal radial fracture. The incidence of CRPS was similar using either criteria (Bruehl 20.61% vs. Atkins 22.52%). Using the Bruehl criteria as a gold standard, there was strong diagnostic agreement (Kappa = 0.79, sensitivity = 0.87, specificity = 0.94). The main difference between the two methods was in pain assessment. 16 patients had vasomotor instability, swelling and motor changes but 12 did not complain of hypersensitivity although the dolorimetry ratio was lowered. These cases have CRPS by the Atkins criteria but not the Bruehl. In contrast 4 of these cases had normal finger dolorimetry but abnormal forearm hypersensitivity and therefore had CRPS by the Bruehl criteria and not the Atkins. These finding show that the Bruehl and Atkins criteria are basically concordant. The differences reflect only minor variations in the assessment of pain. Agreement between researchers in the orthopaedic and pain therapy communities will allow improved understanding of the pathophysiology, possible prevention and future methods of managing CRPS.
