A statement of the purposes of the study. This study examined the stability of two different hexapod frames at increasing strut angles and the possible use of an additional strut to aid stability. Introduction. Hexapod frames have certain advantages over standard circular frames, however disadvantages include a rattle and instability at some strut angles. This could be particularly important when larger diameter rings are used over a shorter distance resulting in lower ring strut angles such as in the femur. Method. A standard hexapod frame was constructed with identical diameter rings for each manufacturer (Taylor Spatial, Orthosolutions). The stability of each frame was tested using a Zwick/Roell Z005 table top materials testing machine, which applied 4 cyclical loads of maximum strain 200 N. This process was performed twice. The frame configuration was then modified with increasing strut angles from 15°–70°. The Taylor Spatial Frame was retested with the addition of a seventh strut. Results. Frame stability significantly deteriorated with shorter struts. This was particularly apparent at angles less than 35 degrees. Stiffness was significantly improved with the addition of a seventh strut. This was especially important for angles less than 35 degrees where displacement was reduced by up to 2 mm. Conclusions. Ring-strut angle plays a significant factor in hexapod frame stability. Stability can be improved with the addition of a seventh strut. This may be particularly important in the paediatric community and in frame around the thigh were a larger ring may increase the strut angle

A huge commitment is required from patients and families who undergo a limb reconstruction procedure using the hexapod frame. This includes turning the struts on the frame, pin site care and intensive rehabilitation. Montpetit et al (2009) discovered that function, participation, engagement in regular activities of daily living is severely impacted during the hexapod lengthening period. Due to the long duration and burden for families, it is imperative that healthcare professionals understand the impact that the hexapod frame has on functional abilities and health related quality of life (HRQL). This project involved a retrospective review of prospectively collected data on function and HRQL during two periods of time: (1) when the hexapod frame is applied on the child's lower extremity and (2) when the lengthening phase is completed, and the hexapod frame is removed. Data from 38 children (mean age: 12 years SD 3.8) who completed lower extremity reconstruction using the hexapod frame and completed either or both the Pediatric Quality of Life Inventory 4.0 Generic Core Scale (PedsQL) and Pediatric Outcomes data Collection Instrument (PODCI) was included. Analysis included, standardized response means, the non-parametric Wilcoxon test and effect size calculation. A Wilcoxon signed rank test for those children who completed pre and post frame PODCI’;s revealed those scores were significantly greater once the hexapod frame was removed (Md=85.10, n=10) compared to during (Md=66.50, n=10) with a large effect size, r= 1.45. Similar, the PedsQL scores improved post frame removal (Md= 66.30, n=10) compared to during treatment (Md = 53.34, n=10), with a medium size effect, r= 0.62. All subtests improved once the frame was removed. This study provides essential insights into the burden of the hexapod frame for children and provides valuable information for all allied healthcare professionals targeted interventions for health domains. This study shows that children's function improves once the hexapod frame is removed. However, this study highlights the importance for all healthcare professional to address health domains for the duration of the hexapod procedure where the child scored lower e.g. sports and physical function, pain and comfort, happiness from the PODCI. The PedsQL identified lower mean scores in physical and emotional function

Aims. The timing of when to remove a circular frame is crucial; early removal results in refracture or deformity, while late removal increases the patient morbidity and delay in return to work. This study was designed to assess the effectiveness of a staged reloading protocol. We report the incidence of mechanical failure following both single-stage and two stage reloading protocols and analyze the associated risk factors. Methods. We identified consecutive patients from our departmental database. Both trauma and elective cases were included, of all ages, frame types, and pathologies who underwent circular frame treatment. Our protocol is either a single-stage or two-stage process implemented by defunctioning the frame, in order to progressively increase the weightbearing load through the bone, and promote full loading prior to frame removal. Before progression, through the process we monitor patients for any increase in pain and assess radiographs for deformity or refracture. Results. There were 244 frames (230 patients) included in the analyses, of which 90 were Ilizarov type frames and 154 were hexapods. There were 149 frames which underwent single-stage reloading and 95 frames which underwent a two-stage reloading protocol. Mechanical failure occurred after frame removal in 13 frames (5%), which suffered refracture. There were no cases of change in alignment. There was no difference between refracture patients who underwent single-stage or two-stage reloading protocols (p = 0.772). In all, 14 patients had failure prevented through identification with the reloading protocol. Conclusion. Our reloading protocol is a simple and effective way to confirm the timing of frame removal and minimize the rate of mechanical failure. Similar failure rates occurred between patients undergoing single-stage and two-stage reloading protocols. If the surgeon is confident with clinical and radiological assessment, it may be possible to progress directly to stage two and decrease frame time and patient morbidity. Cite this article: Bone Jt Open 2022;3(5):359–366

Introduction

To report our early experience and suitability over unicortical fixation system to reduce and hold the bone fragments in position during a CHAOS procedure of the femur or tibia during lower limb reconstruction surgery.

Introduction. Classical fixation using a circular frame involves two rings per segment and in many units this remains the norm whether using ilizarov or hexapod type frames. We present the results of two ring circular frame at King's College Hospital. Materials & Methods. A prospective database has been maintained of all frames applied since 2007. Radiographs from frames applied prior to July 2022 were examined. Clinic letters were then used to identify complications. Included: two ring hexapod for fracture, malunion, nonunion, arthrodesis or deformity correction in the lower limb. Excluded: patients under 16 years old, diabetic feet, Charcot joints, soft tissue contractures, arthrodiastasis, correction of the mid/forefoot, plate fixation augmentation, fixation off a third ring. Results. 518 two ring hexapods were identified. Mean age was 46 (16–89). 55% were for fracture, 18% for malunion, 11% for nonunion. Mean frame time was 7 months (2–29 months). All clinic letters from 384 patients showed 203 patients (52%) had at least one pin site infection, 27 nonunions (7%), 16 frame revisions (4%), 25 bone grafting procedures (7%), 5 cases of septic arthritis (1%), 3 periprosthetic fractures (0.8%),), 12 malunions (3%), 4 Amputations (1%). Conclusions. These results demonstrate the efficacy of a two ring hexapod for patients requiring reconstruction of the lower limb

Aims. Computer hexapod assisted orthopaedic surgery (CHAOS), is a method to achieve the intra-operative correction of long bone deformities using a hexapod external fixator before definitive internal fixation with minimally invasive stabilisation techniques. The aims of this study were to determine the reliability of this method in a consecutive case series of patients undergoing femoral deformity correction, with a minimum six-month follow-up, to assess the complications and to define the ideal group of patients for whom this treatment is appropriate. Patients and Methods. The medical records and radiographs of all patients who underwent CHAOS for femoral deformity at our institution between 2005 and 2011 were retrospectively reviewed. Records were available for all 55 consecutive procedures undertaken in 49 patients with a mean age of 35.6 years (10.9 to 75.3) at the time of surgery. Results. Patients were assessed at a mean interval of 44 months (6 to 90) following surgery. The indications were broad; the most common were vitamin D resistant rickets (n = 10), growth plate arrest (n = 6) and post-traumatic deformity (n = 20). Multi-planar correction was required in 33 cases. A single level osteotomy was performed in 43 cases. Locking plates were used to stabilise the osteotomy in 33 cases and intramedullary nails in the remainder. Complications included two nonunions, one death, one below-knee deep vein thrombosis, one deep infection and one revision procedure due to initial under-correction. There were no neurovascular injuries or incidence of compartment syndrome. Conclusion. This is the largest reported series of femoral deformity corrections using the CHAOS technique. This series demonstrates that precise intra-operative realignment is possible with a hexapod external fixator prior to definitive stabilisation with contemporary internal fixation. This combination allows reproducible correction of complex femoral deformity from a wide variety of diagnoses and age range with a low complication rate. Cite this article: Bone Joint J 2017;99-B:283–8

Introduction. Aneurysmal bone cysts commonly found in lower limbs are locally aggressive masses that can lead to bony erosion, instability and fractures. This has major implications in the lower limbs especially in paediatric patients, with potential growth disturbance and deformity. In this case series we describe radical aneurysmal bone cyst resection and lower limb reconstruction using cable transport and syndesmosis preservation. Materials & Methods. Case 1 - A 12-year-old boy presented with a two-week history of atraumatic right ankle pain. An X-ray demonstrated a distal tibia metaphyseal cyst confirmed on biopsy as an aneurysmal bone cyst. The cyst expanded on interval X-rays from 5.5cm to 8.5cm in 9 weeks. A wide-margin en-bloc resection was performed leaving a 13.8cm tibial defect. A cable transport hexapod frame and a proximal tibial osteotomy was performed, with syndesmosis screw fixation. The transport phase lasted 11 months. While in frame, the boy sustained a distal femur fracture from a fall. The femur and the docking site were plated at the same sitting and frame removed. At one-year post-frame removal he is pain-free, with full ankle dorsiflexion but plantarflexion limited to 25 degrees. He has begun graduated return to sport. Results. Case 2 - A 12-year-old girl was referred with a three-month history of lateral left ankle swelling. X-ray demonstrated an aneurysmal bone cyst in the distal fibula metaphysis. The cyst grew from 4.2 × 2.3cm to 5.2 × 3.32cm in 2 months. A distal fibula resection (6.2cm) with syndesmosis fixation and hexapod cable transport frame were undertaken. The frame was in situ for 13 weeks and during this time she required an additional osteotomy for premature consolidation and had one pin site infection. After 13 weeks a second syndesmosis screw was placed, frame removed, and a cast applied. 3 months later she had fibular plating, BMAC and autologous iliac crest bone graft for slow union. At 3 years post-operative she has no evidence of recurrence, is pain-free and has no functional limitation. Conclusions. We describe two cases of ankle syndesmosis preservation using cable transport for juxta-articular aneurysmal bone cysts. This allows wide resection to prevent recurrence while also preserving primary ankle stability and leg length in children. Both children had a minor complication, but both had an excellent final outcome. Cable bone transport and prophylactic syndesmosis stabilization allows treatment of challenging juxta-articular aneurysmal bone cysts about the ankle. These techniques are especially useful in large bone defects

Introduction. Deformations of forearm with different degree of expression and functional restrictions of upper limb in children with hereditary multiple exostosis are formed in almost 80% of the cases. The question of indications for the selection and conduct of surgical procedure remains controversial, existing treatment methods and post-operative recovery methods for children need to be improved. Materials and Methods. The long-term outcomes of surgical treatment of 112 patients diagnosed with “Hereditary Multiple Exostosis” (HME) aged from 2 till 17 years old were researched. Evaluation of surgical treatment results was carried out in accordance with complaints, functional condition of the forearm, radiographs (taking into account reference lines and angles). Depending on the variant of deformation, the following surgical operations were performed: resection of bone-cartilage exostoses (in 20.5%); correction of forearm deformation with external fixator (in 79.5). In 14 cases, for a more accurate correction of deformity a hexapod frame was used. Results. Differentiated approach provided “good” anatomical and functional results in 55.6%; “satisfactory” results in 40.2%; “unsatisfactory” results in 4.2%. Postoperative complications in the form of non-union, pseudoarthrosis, delayed consolidation or neurological disorders were in 6.2%. Conclusions. The choice of surgical treatment is determined by the variant and severity of deformation. This approach allows to improve cosmetic and functional condition of forearm and adjacent joints. The use of hexapod allows to increase accuracy of correction of physiological axis of forearm bones

Introduction. Several hexapod external fixator devices are used in the treatment of bone fracture and deformity corrections. One characteristic of all of them is the requirement for manual adjustment of the fixator struts. The purpose of this study was to introduce a novel robotic system that executes automatic adjustment of the struts. Materials and Methods. Ten patients were treated for various bone deformities using a hexapod external fixator with Auto Strut system, which implemented automatic adjustment of the fixator struts. Patients arrived at the clinic for follow during the correction period until the removal of the hardware. During each visit, the progress of the correction was assessed (clinically and radiographically) and reading of the strut scale numbers was performed. Results. All patients completed the treatment plan during the follow up period achieving all planned correction goals. Healing of the bone ranged between approximately one to seven months. Duration of distraction ranged between 10 and 90 days. The distraction index ranged between 8 and 15 days/cm. The length of distraction varied between 1 and 6 cm. The planned corrections were fully attained in all patients who completed the treatment (n=10). No device related adverse events were reported. One patient was not available for registration of struts length, one patient switched to manual struts due to personal preference.48 struts of eight patients were recorded, 94% of the final strut number readings presented a displacement of 0–1 mm, three struts (6%) had 2–3 mm displacement due to inter-observer reading errors. indicating high precision of the automatic adjustment. Conclusions. This study presents preliminary result, showing that Auto Strut can successfully replace the manual strut adjustment providing important advantages that benefit the patient, the caregiver and the surgeon

Introduction. Charcot neuroarthropathy is a limb threatening condition and the optimal surgical strategy for limb salvage in gross foot deformity remains unclear. We present our experience of using fine wire frames to correct severe midfoot deformity, followed by internal beaming to maintain the correction. Materials and Methods. Nine patients underwent this treatment between 2020–2023. Initial deformity correction by Ilizarov or hexapod butt frame was followed by internal beaming with a mean follow up of 11 months. A retrospective analysis of radiographs and electronic records was performed. Meary's angle, calcaneal pitch, cuboid height, hindfoot midfoot angle and AP Meary's angle were compared throughout treatment. Complications, length of stay and the number of operations are also described. Results. Mean age was 53 years (range:40–59). Mean frame duration was 3.3 months before conversion to beaming. Prior frame-assisted deformity correction resulted in consistently improved radiological parameters. Varying degrees of subsequent collapse were universal, but 5 patients still regained mobility and a stable, plantargrade, ulcer-free foot. Complications were common, including hardware migration (N=6,66%), breakage (N=2,22%), loosening (N=3,33%), infection (N=4,44%), 1 amputation and an unscheduled reoperation rate of 55%. Mean cumulative length of stay was 42 days. Conclusions. Aggressive deformity correction and internal fixation for Charcot arthropathy requires strategic and individualised care plans. Complications are expected for each patient. Patients must understand this is a limb salvage scenario. This management strategy is resource heavy and requires timely interventions at each stage with a well-structured MDT delivering care. The departmental learning points are to be discussed

Introduction. The accuracy of hexapod circular external fixator deformity correction is contingent on the precision of radiographic analysis during the planning stage. The aim of this study was to compare the SMART TSF (Smith and Nephew, Memphis, Tennessee) in-suite radiographic analysis methods with the traditional manual deformity analysis methods in terms of accuracy of correction. Materials and Methods. Sawbones models were used to simulate two commonly encountered clinical scenarios. Traditional manual radiographic analysis and digital SMART TSF analysis methods were used to correct the simulated deformities. Results. The final outcomes of all six analysis methods across both simulated scenarios were satisfactory. Any differences in residual deformity between the analysis methods are unlikely to be clinically relevant. All three SMART TSF digital analyses were faster to complete than manual radiographic analyses. Conclusions. With experience and a good understanding of the software, manual radiographic analysis can be extremely accurate and remains the gold standard for deformity analysis. In-suite SMART TSF radiographic analysis is fast and accurate to within clinically relevant parameters. Surgeons can with confidence trust the SMART TSF software to provide analysis and corrections that are clinically acceptable

Introduction. Computer hexapod assisted orthopaedic surgery (CHAOS) has previously been shown to provide a predictable and safe method for correcting multiplanar femoral deformity. We report the outcomes of tibial deformity correction using CHAOS, as well as a new cohort of femoral CHAOS procedures. Materials and Methods. Retrospective review of medical records and radiographs for patients who underwent CHAOS for lower limb deformity at our tertiary centre between 2012–2020. Results. There were 70 consecutive cases from 56 patients with no loss to follow-up. Mean age was 40 years (17 to 77); 59% male. There were 48 femoral and 22 tibial procedures. Method of fixation was intramedullary nailing in 47 cases and locking plates in 23. Multiplanar correction was required in 43 cases. The largest correction of rotation was 40 degrees, and angulation was 28 degrees. Mean mechanical axis deviation reduction per procedure was 17.2 mm, maximum 89 mm. Deformity correction was mechanically satisfactory in all patients bar one who was under-corrected, requiring revision. Complications from femoral surgery included one under-correction, two cases of non-union, and one pulmonary embolism. Complications from tibial surgery were one locking plate fatigue failure, one compartment syndrome, one pseudoaneurysm of the anterior tibial artery requiring stenting, and one transient neurapraxia of the common peroneal nerve. There were no deaths. Conclusions. CHAOS can be used for reliable correction of complex deformities of both the femur and tibia. The risk profile appears to differ between femoral and tibial surgeries

Introduction. Methoxyflurane can cause hepatotoxicity and nephrotoxicity at anaesthetic doses but has excellent analgesic properties and no nephrotoxic effects in patients without preexisting disease. Approved for use in the UK and Ireland in 2015, it is currently being used in emergency departments for analgesia during fracture reduction. During the Covid emergency, with theatre access severely restricted and many patients unwilling to use inhaled Nitrous oxide, Penthrox had the potential to provide adequate pain relief to aid frame removals and minor procedures in the clinic. Materials and Methods. Patients presenting to the Limb Reconstruction Unit Elective clinic and requiring frame removal or minor procedures were included in the study. Patients with renal, cardiac or hepatic disease, history of sensitivity to fluorinated anaesthetic agents and those on any nephrotoxic or enzyme inducing drugs were excluded. Verbal consent was obtained, the risks and benefits explained and the procedure was done in a side room in the clinic. Besides patient and procedure details, the Visual Analog Score and Richmond Agitation Scale was noted and patient's satisfaction documented. The results were presented as numbers, means and averages. Results. A total of 39 patients were included in the study of which 17 had Ilizarov frames removed, 10 had Hexapod Removals, 9 had heel rings removed and 3 others had an ex fix removed. Eleven patients required/ requested extra pain relief in the form of oral analgesia. All patients were satisfied or very satisfied with the experience. One patient had a wire jam during removal and required a GA for removal. Conclusions. Patient satisfaction was very high (>95%) with good results and allowed frame removals and minor procedures to be done in the clinic during the Covid pandemic. It also cut expenses and has potential for regular future use

Background:. Recurrent or late presenting Tibia Vara is a complex clinical problem. In addition to the multiplanar deformity the disorder is often accompanied by obesity. Simple re-alignment osteotomy with acute correction is effective early in the disease. Its use in recurrent or severe deformities is limited by geometric constraints (mechanical axis translation), difficult fixation and the risk of compartment syndrome. Gradual correction with external fixation devices is a well-accepted technique in these cases. It has been shown to obtain accurate correction and provides stable fixation. This allows early weight bearing which facilitate consolidation and rehabilitation. Hexapod fixators are technically less demanding than standard Ilizarov techniques. The TLHex is a relatively new hexapod fixator available in South Africa. Frame pre-assembly allows easier mounting on a limb with complex deformity. The software allows for non-orthogonal mounting, which simplifies frame-mounting assessment. Double telescoping struts allow greater strut excursion and the outside mounting of struts on the ring increases mounting options for fixation elements. This is the first report on its use in Blount's disease. Purpose:. Evaluation of the result of gradual correction with the TLHex external fixator in Blount's disease in terms accuracy of correction, union and complications. Illustration of key hardware and software features. Methods:. A retrospective chart and X-ray review of 7 patients (9 legs) treated by gradual correction with the TLHex external fixator was performed. The degree of correction of varus and procurvatum was assessed on pre-operative and post-correction X-rays. Internal rotation deformity correction was assessed clinically. Complications such as neurovascular compromise, minor and major pin tract infection and hardware complications were documented. The pre-operative planning, surgical technique and post-operative treatment protocol is reviewed. Results:. Mean varus was corrected from 21° (17° to 45°) to 1°(−2° to 4°). Mean procurvatum was corrected from 8° (0° to 25°) to 0° (0° to 8°). Internal rotation was corrected to between 5° to 10° of external rotation in all patients. The mean time in the frame was 112 days. Three patients needed one additional program to correct residual deformity (one over-corrected coronal aligment, one under-corrected saggital alignment and one rotational over-correction). Three patients required oral antibiotics for minor pin tract infection. One patient required intravenous antibiotics and wire removal for major pin tract infection. One patient required frame adjustment after correction for soft tissue impingement. One strut loosened after consolidation prior to frame removal. Conclusion:. Gradual correction of Tibia Vara with the TLHex external fixator is a safe and effective treatment method

Repetitive manual handling caused 31% of all work related musculoskeletal disorders in 2015, with the back being the site of injury 38% of the time. Despite its high resilience, studies have shown that intervertebral discs can be damaged during repetitive loading at physiological motions, causing cumulative damage and disc herniation. To understand the mechanism of disc injury resulting from repetitive lifting, it is important to measure disc deformations/strains accompanied by MRI imaging to identify disc tissue damage. Therefore, the aim of this study was to examine associations between the magnitude of 3D internal strains, tissue damage and macroscopic evidence of disc injury after simulated repetitive lifting on normal human lumbar discs. Sixteen cadaver lumbar functional spinal units (FSUs) were subjected to pre-test MRI. Eight FSUs (control) underwent 20,000 cycles or until failure (5 mm displacement) of loading under compression (1.7 MPa – to simulate lifting a 20 kg weight) + flexion (13°) + right axial rotation (2°) using a novel Hexapod Robot. The remaining eight FSUs (experimental) had a grid of tantalum wires inserted, and stereoradiographs were taken to track internal disc displacements at increasing cyclic intervals. Maximum shear strains (MSS) were calculated from the displacements using radiostereometric analysis at cycle 1 and 20,000 cycles (or failure). Post-test MRI was conducted to determine the extent of tissue damage and associated with regions of highest MSS. A repeated measures ANOVA was performed on MSS with a within–subjects factor of cycle number (cycle 1 and failure cycle) and a between subjects-factor of disc region and failure type (p < 0 .05). Pfirrmann grading revealed mostly normal discs [I (N=2), II (N=13), and III (N=1)]. No significant difference in MSS between control and experimental groups was found for number of cycles to failure (p=0.279). Pre and post-test MRI analysis revealed that 13 specimens were injured after repetitive lifting with either an endplate failure (N=9) or disc bulge (N=4), and two specimens did not fail. Failure strain was significantly greater than cycle 1 in all regions except posterior, left/right posterolateral (p>0.109). Largest MSS at failure was seen in the anterior (60%), and left/right posterolateral regions (64% and 70%, respectively). MSS at failure for the endplate failure group was significantly larger than the no injury group in all regions except right lateral and nucleus (p>0.707). Disc bulge group MSS was significantly larger than the no injury group in the anterior, right anterolateral, and left/right posterolateral regions (p < 0 .027). Simulated repetitive lifting led to largest shear strains in the anterior, left and right posterolateral regions that corresponded to annular tears or annular protrusion. The no injury group shear strain was less than 50% in all regions, indicating there may be a threshold that could be associated with tissue damage linked with injuries such as disc bulge and endplate failure. There was no evidence of disc herniation in normal discs, agreeing with current clinical knowledge. These results may be indicative of the effects of repetitive manual handling on normal discs of younger patients

Introduction. Subject-specific finite element models (FEMs) allow for a variety of biomechanical conditions to be tested in a highly repeatable manner. Accuracy of FEMs is improved by mapping density using quantitative computed tomography (QCT) and choosing a constitutive relationship relating density and mechanical properties of bone. Although QCT-derived FEMs have become common practice in contemporary computational studies of whole bones, many density-modulus relationships used at the whole bone level were derived using mechanical loading of small trabecular or cortical bone cores. These cores were mechanically loaded to derive an apparent modulus, which is related to each core's mean apparent or ash density. This study used these relationships and either elemental or nodal material mapping strategies to elucidate optimal methods for scapular QCT-FEMs. Methods. Six cadaveric scapulae (3 male; 3 female; mean age: 68±10 years) were loaded within a micro-CT in a custom CT-compatible hexapod robot Pre- and post-loaded scans were acquired (spatial resolution = 33.5 µm) and DVC was used to quantify experimental full-field displacements (BoneDVC, Insigneo) (Figure 1).. Experimental reaction forces applied to the scapulae were measured using a 6-DOF load cell. FEMs were derived from corresponding QCT scans of each cadaver bone. These models were mapped with one of fifteen density-modulus relationships and elemental or nodal material mapping strategies. DVC-derived BCs were imposed on the QCT-FEMs using local displacement measurements obtained from the DVC algorithm. Comparisons between the empirical and computational models were performed using resultant reaction loads and full-field displacements (Figure 2). Results and Discussion. Reaction forces predicted by the QCT-FEMs showed large percentage error variations across all specimens and density-modulus relationships with elemental material mapping. The percentage errors were as large as 899%, but as low as 3=57% for the different specimens. Similarly, when using a nodal material mapping strategy, percentage errors were as large as 965%, but as low as 4=59% for the different specimens (Figure 3). For all specimens, minimal variation only occurred in the slope between the QCT-FEM and DVC displacements in the x and y directions for either elemental or nodal material mapping strategies. Slopes ranged from 0.86 to 1.06. This held true for 3 specimens in the z direction; however, for the remaining 3 specimens more pronounced variations occurred between the QCT-FEM and DVC displacements, dependent on density-modulus relationship. The r. 2. values were consistently between 0.82 and 1.00 for both material mapping strategies and density-modulus relationships for all three Cartesian components of displacement and all specimens. Conclusions. The results suggest that QCT-FEMs using DVC derived boundary conditions can replicate experimental loading of cadaveric specimens. It was also shown that only slight variations exist when either elemental or nodal material mapping strategies are adopted. Given the recent advancements provided by DVC-derived BCs, this study provides a basis for a common methodology that can be implemented in future studies comparing similar outcomes in all anatomic locations. Expanding the current sample size has the potential to determine if a single density-modulus relationship can exist or if specimen or anatomic location-specific relationships should be utilized. For any figures or tables, please contact the authors directly

We would like to present this service evaluation of Taylor Spatial Frame use within a busy limb reconstruction unit. We present a cohort of 60 patients representing a year of work from January 2011 to January 2012 with a breakdown of coding data. Included are details of operative episodes, length of stay, outpatient follow up including software programming episodes, strut changes and general frame care from our specialist nurses. We have produced a comparison of cost to HRG coding tarifs with an audit of coding errors and cost implications of these corrections. Also included is a breakdown of comparison data from patients undergoing frame assisted deformity correction and internal fixation, Computer Hexapod Assisted Orthopaedic Surgery. Exact and careful coding of these procedures is required considering their relatively high cost

Background:. Tibia Vara (Blount's disease) is characterized by a growth disturbance of the posteromedial proximal tibial physis. This results in the typically complex tibial deformity of varus, procurvatum and internal tibial torsion. Knee instability is due to medial tibial joint depression and lateral ligament complex attenuation. Femoral angular and rotational deformity are associated features. Obesity often complicates management. Langenskiöld observed six stages of the disorder on X-ray (stage 6 not occurring before 9 years) and obtained good results with proximal tibial realignment osteotomy if performed before the age of 8 years. Our experience is very different. Purpose:. To evaluate our experience with treatment of a consecutive cohort of patients with early onset Blount's disease in terms of clinical findings, recurrence rate and factors associated with recurrence and treatment methods and indications. Methods:. A retrospective chart and imaging review was completed of 100 extremities (58 patients) treated surgically for early onset Blount's disease. Follow-up ranged between 1 and 7 years. Results:. These children all presented with a history of onset of deformity between the ages of 1 and 3 years. Their age at first treatment varied between 2 and 10 years. Langenskiöld stage V and VI occurred in younger patients than originally described. The recurrence rate of extremities treated with simple osteotomy was 42% (25/58). Factors associated with recurrence include age >4 (p<0.001), obesity (p=0.007), instability (p=0.003), severity of deformity (femoro-tibial angle) (p<0.001), medial physeal slope (p<0.001) and advanced Langenskiöld stage (p<0.001). Surgical treatment included the use of growth retardation alone, dome realignment osteotomy with and without growth retardation, oblique proximal tibial (Rab) osteotomy, 3-in-1 procedure (medial elevation, tibial osteotomy and lateral epiphyseodesis) and gradual correction with hexapod fixators was used in some recurrent cases. In addition we describe a new surgical technique which obtains acute deformity correction at the level of the growth plate. Conclusion:. We propose that the disease follows a more aggressive course in the black population of Kwa-Zulu Natal, South Africa. The management is often complex and recurrence is not uncommon

Introduction. The Taylor Spatial Frame (TSF) is an hexapod external ring fixation system that can move with six degrees of freedom to correct complex limb deformities. The lengths of the struts between the rings are independently adjusted to correct the deformity. The struts form an acute and obtuse “ring-strut” angle with the ring with the sum of these angles totalling 180°. In the course of a correction schedule a strut may need to be exchanged for one of longer or shorter length. The manufacturer's instructions direct that a temporary seventh strut can be placed in any orientation to ensure stability during the exchange. We have noted several episodes of temporary frame instability during this procedure resulting in discomfort. The aim of this study was to investigate which temporary strut positions gave maximal stability. Methods. A TSF frame was constructed in a neutral alignment with a neutral strut height of 130mm. Strut 1 (red) was identified for exchange. There were 169 theoretical placement options for the temporary strut that were sequentially tested. Fast-FX™ struts were used. Strut 1 was released and the shortening that occurred was recorded using the strut length gauge. Shortening of over 10mm was considered grossly unstable. Results. There were 21 stable configurations and 11 unstable configurations. There were 68 mechanically impossible positions. The most important factors for frame stability were the avoidance of temporary strut crossing the strut being exchanged, and matching acute/obtuse “ring-strut” angle orientation of the temporary strut. Conclusions. This study identifies a positioning rule that ensures maximum stability of a neutral frame during strut changes. It further identifies grossly unstable positions that may result in pain during a change

Introduction. Patients undergoing limb reconstruction with the Taylor Spatial Frame (TSF) often perceive that their frame is loose due to the rattle they hear when mobilising. Our aim was to determine how much and where this movement is in the various frame/bone constructs currently on the market. Method. Using standard tibial saw bones three frames (TSF, Ilizarov and Hexapod) were made in an identical fashion. Constructs were cyclically loaded 4 times to 200 N in tension and compression using the Instron MTS. This was repeated three times. A seventh strut was also placed in the TSF construct and the tests repeated. Bones were then removed and the tests repeated for the frames alone. Results. Movement was noted between the frame and bone in all the frames in compression (average 1.5mm) and tension (average 4.5mm). Frames alone in compression moved between 0.5mm (Ilizarov) and 1.2mm (hexapod). The rattle was audible and was apparent on the TSF more than the other devices. On measuring separate components of the TSF, the ring height measured 7.9mm compared to a screw gap of 8.05mm. The locking clasp mechanism of the strut moved 0.1mm, thus allowing 0.45mm movement between compression/extension. Conclusion. This rattle is due to the combination of movement seen between the ring and screw fixation, the clasp mechanism and the universal joint. A seventh strut reduces this rattle by splinting the frame in compression or tension. All frames show movement between the frame and the bone. The stiffest bone/frame construct in tension/compression is the TSF followed by the Ilizarov and Hexapod frames. Further work is needed to determine what effect this movement has on fracture healing