A growing number of recent investigations on the human genome, gut microbiome, and proteomics suggests that the loss of mucosal barrier function, particularly in the gastrointestinal tract, may substantially affect antigen trafficking, ultimately influencing the close bidirectional interaction between the gut microbiome and the immune system. This cross-talk is highly influential in shaping the host immune system and ultimately clinical infections. The hypothesis of the current study was that a change in microbiome and/or breach in GI epithelial barrier could be partially responsible for development of periprosthetic joint infections (PJI). Multiple biomarkers of gut barrier disruption were tested in parallel in plasma samples collected as part of a prospective cohort study of patients undergoing revision arthroplasty for aseptic failures or PJI (As defined by the 2018 ICM criteria). All blood samples were collected before any antibiotic was administered. Samples were tested for Zonulin, soluble CD14 (sCD14), and lipopolysaccharide (LPS) using commercially available enzyme-linked immunosorbent assays. Statistical analysis consisted of descriptive statistics, Mann-Whitney t-test, and Kruskal-Wallis test. A total of 134 patients were consented and included in the study. 44 were classified as PJI (30 chronic and 14 acute), and 90 as aseptic failures (26 primaries and 64 aseptic revisions). Both Zonulin and sCD14, but not LPS, were found to be significantly increased in the PJI group compared to non-infected cases (p<0.001; p=0.003). Higher levels of Zonulin were found in acute infections compared to chronic PJI (p=0.005. This prospective ongoing study reveals a possible link between gut permeability and the ‘gut-immune-joint axis’ in PJI. If this association continues to be born out with larger cohort recruitment and more in-depth analysis, it would have an immense implication in managing patients with PJI. In addition to administering antimicrobials, patients with PJI and other orthopedic infections may require gastrointestinal modulators such as pro and prebiotics

Aims. Treatment of high-grade limb bone sarcoma that invades a joint requires en bloc extra-articular excision. MRI can demonstrate joint invasion but is frequently inconclusive, and its predictive value is unknown. We evaluated the diagnostic accuracy of direct and indirect radiological signs of intra-articular tumour extension and the performance characteristics of MRI findings of intra-articular tumour extension. Methods. We performed a retrospective case-control study of patients who underwent extra-articular excision for sarcoma of the knee, hip, or shoulder from 1 June 2000 to 1 November 2020. Radiologists blinded to the pathology results evaluated preoperative MRI for three direct signs of joint invasion (capsular disruption, cortical breach, cartilage invasion) and indirect signs (e.g. joint effusion, synovial thickening). The discriminatory ability of MRI to detect intra-articular tumour extension was determined by receiver operating characteristic analysis. Results. Overall, 49 patients underwent extra-articular excision. The area under the curve (AUC) ranged from 0.65 to 0.76 for direct signs of joint invasion, and was 0.83 for all three combined. In all, 26 patients had only one to two direct signs of invasion, representing an equivocal result. In these patients, the AUC was 0.63 for joint effusion and 0.85 for synovial thickening. When direct signs and synovial thickening were combined, the AUC was 0.89. Conclusion. MRI provides excellent discrimination for determining intra-articular tumour extension when multiple direct signs of invasion are present. When MRI results are equivocal, assessment of synovial thickening increases MRI’s discriminatory ability to predict intra-articular joint extension. These results should be interpreted in the context of the study’s limitations. The inclusion of only extra-articular excisions enriched the sample for true positive cases. Direct signs likely varied with tumour histology and location. A larger, prospective study of periarticular bone sarcomas with spatial correlation of histological and radiological findings is needed to validate these results before their adoption in clinical practice. Cite this article: Bone Jt Open 2024;5(10):944–952

Removal of bullets retained within joints is indicated to prevent mechanical blockade, 3rd body wear and resultant arthritis, plus lead arthropathy and systemic lead poisoning. The literature is sparse on this subject, with mostly sporadic case reports utilizing hip arthroscopy. We report on the largest series of removal of bullets from the hip joints using open surgical. We reviewed prospectively collected data of patients who presented to a single institution with civilian gunshot injuries that breached the hip joint between 01 January 2009 and 31 December 2022. We included all cases where the bullet was retained within the hip joint area. Exclusion criteria: cases where the hip joint was not breached, bullets were not retained around the hip area or cases with isolated acetabulum involvement. One hundred and eighteen (118) patients were identified. One patient was excluded as the bullet embedded in the femur neck was sustained 10 years earlier. Of the remaining 117 patients, 70 had retained bullets around the hip joint. In 44 patients we undertook bullet removal using the followingsurgical hip dislocation (n = 18), hip arthrotomy (n = 18), removal at site of fracture fixation/replacement (n = 2), posterior wall osteotomy (n = 1), direct removal without capsulotomy (tractotomy) (n = 5). In 26 patients we did not remove bullets for the following reasons: final location was extra-capsular embedded in the soft tissues (n=17), clinical decision to not remove (n=4), patients’ clinical condition did not allow for further surgery (n= 4) and patient refusal (n=1). No patients underwent hip arthroscopy. With adequate pre-operative imaging and surgical planning, safe surgical removal of retained bullets in the hip joint can be achieved without the use of hip arthroscopy; using the traditional open surgical approaches of arthrotomy, tractotomy and surgical hip dislocation

Summary Statement. Incorrect pedicle screw placement can lead to neurological complications. Practice outside the operating room on realistic bone models, with force feedback, could improve safety. Pedicle forces in cadaveric specimens are reported, to support development of a training tool for residents. Introduction. Inserting screws into the vertebral pedicles is a challenging step in spinal fusion and scoliosis surgeries. Errors in placement can lead to neurological complications and poor mechanical fixation. The more experienced the surgeon, the better the accuracy of the screw placement. A physical training system would provide orthopaedic residents with the feel of performing pedicle cannulation before operating on a patient. The proposed system consists of realistic bone models mimicking the geometry and material properties of typical patients, coupled with a force feedback probe. The purpose of the present study was to determine the forces encountered during pedicle probing to aid in the development of this training system. Methods. We performed two separate investigations. In the first study, 15 participants (9 expert surgeons, 3 fellows, 3 residents) were asked to press a standard pedicle awl three times onto a mechanical scale, blinded to the force, demonstrating what force they would apply during safe pedicle cannulation and during unsafe cortical breach. In the second study, three experienced surgeons used a standard pedicle awl fitted with a one-degree of freedom load cell to probe selected thoracolumbar vertebrae of eight cadaveric specimens to measure the forces required during pedicle cannulation and deliberate breaching, in randomised order. A total of 42 pedicles were tested. Results. Both studies had wide variations in the results, but were in general agreement. Cannulation (safe) forces averaged approximately 90 N (20 lb) whereas breach (unsafe) forces averaged approximately 135–155 N (30–35 lb). The lowest average forces in the cadaveric study were for pedicle cannulation, averaging 86 N (range, 23–125 N), which was significantly lower (p<0.001) than for anterior breach (135 N; range, 80–195 N); medial breach (149 N; range, 98–186 N) and lateral breach (157 N; range, 114–228 N). There were no significant differences among the breach forces (p>0.1). Cannulation forces were on average 59% of the breach forces (range, 19–84%) or conversely, breach forces were 70% higher than cannulation forces. Discussion. To our knowledge, axial force data have not previously been reported for pedicle cannulation and breaching. A large range of forces was measured, as is experienced clinically. Additional testing is planned with a six-degree-of-freedom load cell to determine all of the forces and moments involved in cannulation and breaching throughout the thoracolumbar spine. These results will inform the development of a realistic bone model as well as a breach prediction algorithm for a physical training system for spine surgery. The opportunity to learn and practice outside of the operating room, including learning from deliberate mistakes, should increase the confidence and comprehension of residents performing the procedure, enhance patient safety, reduce surgical time, and allow faster progression of learning inside the operating room

Introduction. The education of residents in the proper placement of pedicle screws is key to the safety of the surgery. The more experienced the surgeon, the more accurately the pedicle screws tend to be placed. A physical bone model, with properties and tactile feel similar to human bone, was developed with the intention of using the bone model to train residents in pedicle screw placement. The purpose of this study was to test whether the model improves the performance of orthopaedic residents when cannulating spinal pedicles, as judged by the number of breaches, and to gain feedback from the residents on their experiences. Materials and Methods. Six orthopaedic residents were recruited, with ethics approval. Prior to testing, the residents were given an instructional video describing the correct cannulation of a lumbar vertebra. The residents were each provided with 12 bones mounted in holders: 3 for initial skills assessment, 6 for free practice, and 3 for final skills assessment. In the pre- and post-practice sets, the 3 bone models had different properties: weak, normal and strong. The residents were asked to complete both pre and post-testing questionnaires. The number of breaches was counted in initial and final bone testing. The forces for each bone model were compared using an ANOVA; these were followed by post-hoc t-tests if significant (p<0.05). Results. All but one of the residents improved the number of breaches with practice, and the one that did not improve did not make the same breaches twice. The total number of breaches in the final testing (14) was lower than in the initial testing (31). The entry points chosen by the residents were all deemed appropriate as per the video instruction. The resident with the most experience had the least number of breaches; the resident with the least amount of experience had the most breaches. Discussion. The reduction of the number of breaches between the initial and final testing indicates that the residents did learn. Overall the response from the residents was positive; they all indicated they would like to have the simulator as part of their training; most even indicated an interest to use them outside of training hours. Almost all indicated that the bones felt more realistic than those currently available (if they were aware of them). Positively, the more surgical experience the resident had, the more their survey responses indicated a positive impression of the bones

Inserting screws into the vertebral pedicles is a challenging step in spinal fusion and scoliosis surgeries. Errors in placement can lead to neurological complications. The more experienced the surgeon, the better the accuracy of the screw placement. A physical training system would provide residents with the feel of performing pedicle cannulation before operating on a patient. The proposed system consists of realistic bone models mimicking the geometry and material properties of typical patients, coupled with a force feedback probe. The purpose of the present study was to determine the forces encountered during pedicle probing to aid in the development of this training system. We performed two separate investigations: [1] 15 participants (9 expert surgeons, 3 fellows and 3 residents) were asked to press a standard pedicle awl three times onto a mechanical scale, blinded to the force, demonstrating what force they would apply during safe pedicle cannulation and during unsafe cortical breach; [2] three experienced surgeons used a standard pedicle awl fitted with a one-degree of freedom load cell to probe selected thoracolumbar vertebrae of eight cadaveric specimens to measure the forces required during pedicle cannulation and deliberate breaching. A total of 42 pedicles were tested. Both studies had wide variations in the results, but were in general agreement. Cannulation (safe) forces averaged approximately 90 N (20 lb) whereas breach (unsafe) forces averaged approximately 135–155 N (30–35 lb). The lowest average forces in the cadaveric study were for pedicle cannulation, averaging 86 N (range, 23–125 N), significantly lower (p<0.001) than for anterior breach (135 N; range, 80–195 N); medial breach (149 N; range, 98–186 N) and lateral breach (157 N; range, 114–228 N). There were no significant differences between the breach forces (p>0.1). Cannulation forces were on average 59% of the breach forces (range, 19–84%) or conversely, breach forces were 70% higher than cannulation forces. To our knowledge, these axial force data are the first available for pedicle cannulation and breaching. A large range of forces was measured, as is experienced clinically. Additional testing is planned with a six-degree-of-freedom load cell to determine all of the forces and moments involved in cannulation and breaching, throughout the thoracolumbar spine. These results will inform the development of a realistic bone model as well as a breach prediction algorithm for a physical training system for spine surgery

To evaluate the clinical accuracy of computer-assisted fluoroscopy for the placement of percutaneous lumbosacral (LS) pedicle screws. A prospective computed tomographic (CT) analysis was performed in forty consecutive patients. Three independent observers were utilised. Postoperative CT scans of one hundred and fifty-nine titanium pedicle screws (n = 6(L3); thirty-eight(L4); sixty-five(l5) and fifty(S1)) were reviewed. All screws were percutaneously placed using the two-dimensional FluoroNavTM system. The relative position of the screw to the pedicle was graded as follows: I-completely in; II – < 2mm breach; III - = 2–4mm breach; IV – > 4mm breach. The direction of the breach was further classified as well as its trajectory. Correlation between observers was near perfect. The three observers rated 74.2%, 78.6%, and 78.0% of screws were completely contained within the pedicle. The data from the observer with the most significant pedicle breaches is as follows: thirty-five (22%) pedicle breaches (grade II -n=30; III - n=4; IV - n=1/n= 11 medial; n=19 lateral; 5 superior). Only one clinically significant breach occurred medially (grade III) at L5. This required screw revision (performed with a minimal access technique) with complete resolution of acute post-op L5 radiculopathy. The in-vivo percutaneous pedicle breach rate in this study was higher than that reported for similar open navigational techniques. The majority (85.7%) of breaches were minor (< 2mm) and over half (54.3%) were lateral with no potential for clinical squealae. This high lateral breach rate is due to a modified lateral starting point required for the percutaneous technique. However, there is concern that this technique resulted in one clinically significant medial breach and highlights the increased risk associated with percutatneous pedicle screw placement. The findings of this study suggest that improved screw placement accuracy for minimal access instrumented fusions is required

To quantify bone-nail fit in response to varying nail placements by entry point translation in straight antegrade humeral nailing using three-dimensional (3D) computational analysis. CT scans of ten cadaveric humeri were processed in 3D Slicer to obtain 3D models of the cortical and cancellous bone. The bone was divided into individual slices each consisting of 2% humeral length (L) with the centroid of each slice determined. To represent straight antegrade humeral nail, a rod consisting of two cylinders with diameters of 9.5mm and 8.5mm and length of 0.22L mm and 0.44L mm respectively joined at one end was modelled. The humeral head apex (surgical entry point) was translated by 1mm in both anterior-posterior and medio-lateral directions to generate eight entry points. Total nail protrusion surface area, maximum nail protrusion distance into cortical shell and top, middle, bottom deviation between nail and intramedullary cavity centre were investigated. Statistical analysis between the apex and translated entry points was conducted using paired t-test. A posterior-lateral translation was considered as the optimal entry point with minimum protrusion in comparison to the anterior-medial translation experiencing twice the level of protrusion. Statistically significant differences in cortical protrusion were found in anterior-medial and posterior-lateral directions producing increased and decreased level of protrusion respectively compared to the apex. The bottom anterior-posterior deviation distance appeared to be a key predictor of cortical breach with the distal nail being more susceptible. Furthermore, nails with anterior translation generated higher anterior-posterior deviation (>4mm) compared to posterior translation (<3mm). Aside from slight posterolateral translation of the entry point from the apex, inclusion of a distal posterior-lateral bend into current straight nail design could improve nail fitting within the curved humeral bone, potentially improving distal working length within the flat and narrow medullary canal of the distal humeral shaft

Using post-operative CT analysis the clinical accuracy of computer-assisted fluoroscopy for the placement of thoracic (n=69) and lumbosacral (n=271) pedicle screws was assessed. All screws were placed using the Fluoro-Nav™ system (Medtronic Sofamor Danek, Memphis, TN, USA). Screw position was completely intrapedicular in 86.5%. There were no clinically significant screw misplacements. Pedicle breaches with a potential for neurological injury (> 2 mm; medial) was 0.6%. The overall pedicle screw misplacement rate in this study is less than or comparable to reported misplacement rates using other techniques. The use of computer-assisted fluoroscopy may improve the safety of pedicle screw placement. The purpose of this prospective study is to evaluate the clinical accuracy of computer-assisted fluoroscopy for the placement of thoracic (T) and lumbosacral (LS) pedicle screws. The overall thoracic and lumbar pedicle screw misplacement rate in this study is less than or comparable to reported misplacement rates using other techniques. The use of computer-assisted fluoroscopy may improve the safety of pedicle screw placement. Postoperative computed tomographs (CT) of three hundred and forty pedicle screws were independently reviewed. All screws were placed using the Fluoro-Nav™ system (Medtronic Sofamor Danek, Memphis, TN, USA). The relative position of the screw to the pedicle was assessed and graded as follows – A- completely in; B – < 2mm breach; C – 2–4mm breach; D – > 4–6mm breach. If an osseous breach occurred, the direction of the breach was further classified. Overall screw position was graded A in 86.5% (294/340) of screws (91.1 % (24/271) -lumbosacral and 68.1.0% (47/69)-thoracic). Forty-six pedicle breaches occurred (24 medial; 22 lateral). Thirty-five percent (16/46) of breaches were unavoidable secondary to a pedicle screw that was larger than the size of pedicle (thoracic-13). Pedicle breaches were Grade B in 11.8%, Grade C in 1.5% and Grade D in 0.3% of screws. There were no clinically significant screw misplacements. Pedicle breaches with a potential for neurological (> 2 mm; medial) or vascular injury was 0.6% and 0% respectively. FluoroNav™ appears to be a safe and practical adjunct for the placement of thoracic and lumbosacral pedicle screws. Funding: Medtronic-Sofamor Danek – research support

To determine whether neurophysiological electrical pedicle testing (EPT) is a useful aid in the detection of malpostioned pedicle screw tracts. EPT data from 246 screws in 32 spinal operations on 32 patients over a 5 year period (2009–2014) were recorded and analysed. In addition to physical palpation, a ball-tipped electrode delivered stimuli and the output was recorded by evoked electromyogram (EMG). When breach threshold values were recorded, the surgeon rechecked the tract for breaches and responded appropriately. In addition, standard motor evoked potential (MEP) and sensory evoked potential(SEP) spinal cord monitoring was performed. There were 24(9.8%) pedicle breaches by tract testing and 8(3.3%) by screw testing. In 11 instances in 7 patients where the tract testing showed a breach, the tract was redirected and subsequent screw testing showed adequate integrity of the pedicle. The total time for tract and screw testing was 25 seconds. There were no associated changes in MEP or SEP monitoring with any of the recorded pedicle breaches and none of the patients had any post-operative neurological deficit. EPT for the pedicle screw and tract is a safe, simple, practical and reliable technique which improves the accuracy of screw placement. Further studies would be required to confirm (and possibly revise) the threshold levels and to demonstrate whether EPT reduces the risk of misplaced screws or post-operative neurological deficit

To identify the incidence of a cortical breech on the initial presentation X-rays of patients with distal femoral GCTs, and whether this lead to a higher rate of local recurrence of tumour, a prospective database is kept of all patients seen in the unit. Initial presentation X-rays on 54 patients with distal femroal GCTs were reviewed. The size of the tumour was estimated by measuring the largest dimensions of the tumour (depth, breadth & height). The volume of the distal femur was estimated using the same X-ray and computer programme. The X-rays were then carefully studied for evidence of a cortical breach. The records were also checked for evidence of subsequent locally recurrent disease and subsequent surgery. X-rays were reviewed on 54 patients (29 male, 25 female), range of 18–72 years. All patients had a biopsy-proven GCT of the distal femur, X-rays (prior to biopsy) were reviewed. 34 (63%) patients with a cortical breech on X-ray. The mean tumour volume: distal femoral volumes (TV:DFV) was statistically greater between those patients with a cortical breach and those without, using ANOVA (p< 0.0001). There were 13 patients with local recurrent disease but no statistical difference in subsequent local recurrence rates between the two patient groups. There was also no statistical differences between the number of operations for those who presented with a cortical breach or without. There was no evidence that more radical surgery was required if a patient presented with a cortical breach. The risk of cortical breech in patients with GCTs of the distal femur is dependant upon the tumour volume to distal femur volume ratio. If the ratio is above 54% then present with a cortical breech on X-ray is likely (95% confidence interval).There is no evidence those patients with a cortical breach have a higher rate of local recurrence, an increased number of operations or more radical surgery. Conclusion: The risk of cortical breech in patients with GCTs of the distal femur is dependent upon the tumour volume to distal femur volume ratio

Spinal procedures relying on percutaneous pedicle cannulation (PPC) are becoming increasingly common. The accuracy of PPC using currently available two-dimensional intraoperative imaging such as conventional C-arm fluoroscopy (CF) or computer-assisted fluoroscopy (2D_Nav) has not been evaluated. Following PPC of cadaveric spines (T4-S1) using CF and 2D_Nav, by a novice and clinical expert, the number and degree of pedicle breaches was assessed by CT. Accuracy using CF or 2D_Nav was equivalent and comparable to published reports for open pedicle cannulation. However, clinical expertise was the significant determinant of improved accuracy rather than technological factors. To assess the accuracy of percutaneous pedicle cannulation(PPC) using currently available two-dimensional intraoperative imaging (C-arm fluoroscopy (CF) or computer-assisted fluoroscopy (2D_Nav)) for two levels of clinical expertise. Accuracy using CF or 2D_Nav was equivalent and comparable to published reports for open pedicle cannulation. Main determinant of PPC accuracy is clinical experience, rather than technological factors. Current technology cannot replace the need for rigorous training required to gain skill in percutaneous pedicle procedures. Using an eleven-gauge bone biopsy needle, sixty randomized pedicles(two cadavers, T4–S1) were cannulated using CF or 2D-Nav by a staff spine surgeon or a third year orthopaedic resident. Pedicles for each vertebra were paired as internal controls for technique. After insertion of the biopsy needle, a 1.5mm aluminum tube was inserted through the needle as a marker. Using fine cut CT scans the position of each tube was assessed using a predefined grading system based on tube location relative to pedicle, direction of breech, trajectory, and position in vertebral body. Minimum score was three(ideal) and maximum was fourteen(gross misplacement). There were significantly (p< 0.05) more pedicle breaches for the resident (four CF, four 2D-Nav) compared to staff (one 2D-Nav). All breaches were thoracic with no statistical difference between number of breaches using CF and 2D-Nav for either skill group. Grade of breaches for CF (8.8) and 2D-Nav (9.4) were statistically similar. Main sources of error included poor image quality, image misinterpretation and biopsy needle flexibility causing navigational maltracking

Background: Misplaced pedicle screws are associated with significant complications during posterior spinal instrumentation. Purpose: The purpose of this study is to evaluate the efficacy of triggered electromyographic stimulation in predicting the appropriate placement of pedicle screws. Study Design: Prospective clinical trial. Patient Sample: Fifteen consecutive patients (3 males; 12 females). Outcome Measures: Not applicable. Materials and Methods: All patients underwent posterior thoracolumbar spine fusion. Surgery was performed for spondylolisthesis, spinal stenosis, degenerative scoliosis and fractures. All patients received continuous electromyographic monitoring during surgery. During insertion of pedicle screws the integrity of the medial pedicle cortex was tested by stimulating each screw head with a monopolar pedicle probe stimulator and recording the compound muscle action potentials. A threshold of 7 mA and below was considered indicative of pedicle breach. Intraoperative screw placement was verified with the use of image intensifier. Finally, all patients following surgery underwent plain radiographs and CT scan of the operated region to evaluate the position of the pedicle screws. Results: One hundred and fourteen pedicle screws were inserted from T7 to S1 in all patients. There were no myogenic responses at the threshold tested. No screw had to be repositioned intraoperatively. There were no new neurologic deficits recorded following surgery. Review of the radiographs and CT scans obtained following surgery revealed no medial pedicle cortex breach. There were two screws that violated the lateral pedicle cortex, without any subsequent complications for the patients. Conclusions: Our study suggests that the absence of myogenic responses following stimulation at a threshold of 7 mA and below during pedicle screw placement, is a strong indicator that no medial pedicle cortex breach has occurred

Introduction: Arthroscopic ankle arthrodesis is an effective treatment for end-stage arthritis. A screw that has any thread across the fusion site can not offer any compression and may be postulated to lower the rate of fusion. Similarly, maximal screw thread in the target bone would optimise fixation. This retrospective study calculates the ideal characteristics of a screw used for ankle arthrodesis, and assesses the correlation between the lack of compression and non-union. Method: Fifty-one consecutive patients(102 screws) who have had arthroscopic ankle fusions were studied. Either AO(n=38) or ACE(n=64) screws were used. We calculated the screw-thread distance that crossed the talotibial(TT) or the subtalar(ST) joints on digitised images, and recorded the outcomes of the fusions. Result: Of the 38 AO screws, only one (2.6%) had threads across the TT joint(thread-length into the joint = 1.2mm). None of the ST joints had been breached. Of the 64 ACE screws, 8(12.5%) had threads across the TT joint, representing 7(21.9%) of all posterior screws and 1(3%) of all anterior screws in the study. The mean length of screw-threads into the TT joint was 2.1mm(range 0.53 to 4.06 mm). The ST joints were breached by 4(6.25%) screws(all posterior). The mean length of protrusion was 1.8mm(range 0.28 to 3.89mm). No screw thread crossed both TT and ST joints simultaneously. No non-unions were recorded in either group. Discussion: In our study the use of ACE screws for arthroscopic arthrodesis increases the risk of screw-threads breaching either the TT or ST joints when compared to the use of AO screws. Conclusion: We conclude a thread length of 19–20mm would optimise fixation/compression. However no clinical correlation was demonstrated between reduced compression and non-union in this study

The anterior approach for total hip arthroplasty (THA) has been associated with a faster earlier functional recovery and has gained increasing utilization for primary THA exposure. However, some studies have suggested a higher risk of femoral complications, as well as difficulty with femoral exposure. Techniques of soft tissue releases have been described to offer better femoral exposure, and to help mitigate complications like femoral fracture or breach of the canal with broaching. However, appropriate titrated soft release remains important to decrease potential risk of dislocation. Here we present a suggested technique and hierarchy of soft tissue releases to adequately expose the femur. In addition, we discuss adjunctive table and patient position maneuvers for femoral exposure, as well as more extensile and revision techniques if necessary. For any figures or tables, please contact authors directly

Primary internal fixation of uncomplicated scaphoid fractures is growing in popularity due to its advantages over conventional cast fixation. Performing the procedure percutaneously reduces the risk of infection and soft tissue damage, but can be tricky because of the small size and complex three-dimensional (3D) shape of this bone. Computer-assisted navigation has been an invaluable tool in other pin insertion procedures. This in-vitro study aimed to evaluate two different rendering techniques for our navigation interface: (i) 3D volume rendering of the CBCT image to show digitally-reconstructed radiographs of the anatomy, and (ii) volume-slicing, analogous to CT-images. As the shape of the scaphoid is highly variable, a plastic model of the wrist was constructed in order to provide consistency that would not be possible in a cadaver-based study. The plastic model featured a removable scaphoid such that a new one was replaced between trials. Three surgeons each performed eight trials using each of the two navigated techniques (yielding a total of 48 trials for analysis). Central placement of scaphoid fixation has been linked with mechanical stability and improved clinical outcomes, thus the surgical goal was to place a K-wire to maximise both depth from the surface and length of the drill path. The wire was drilled through the scaphoid, from distal to proximal, allowing for post-trial analysis of the drill path. A ceiling-mounted OptoTrak Certus camera (Northern Digital Inc., Canada) and a floor-mounted isocentric 3D CBCT C-arm (Innova 4100, GE Healthcare, France) permitted a registration transformation between the tracking and imaging systems to be computed preoperatively, before each trial, using a custom calibration device. Optical local coordinate reference bodies were attached to the wrist model and a custom drill guide for tracking with the Certus camera. During each trial, a 3D spin image of the wrist model was acquired, and rendered according to the technique under study. For 3D volume rendering, the spin image was rendered as a digitally-reconstructed radiograph (DRR) that could be rotated in three dimensions. In the planning phase, the surgeon positioned a desired drill path on the images. Anterior-posterior and lateral views of the 3D volume rendering were used for navigation during the drilling phase. The real-time orientation of the drill guide was shown relative to these images and the plan on an overhead. For volume-sliced (VS) navigation, the spin image was volume-rendered and sliced along the principal planes (axial, coronal, sagittal) for planning. A slider interface allowed the surgeon to scroll through the slices in each of the planes, as if they were looking at individual CT slices. Once the desired drill path was positioned, the volume-sliced views were reconfigured to show slices along the oblique planes of the planned path for navigation. Following all trials, model scaphoids with wire intact were imaged using CT with a slice thickness of 0.625 mm. The CT series were segmented and used to construct 3D digital models of the wire and drilled scaphoid. Algorithms were developed to determine the minimum distance from the centerline of the wire and the scaphoid surface, and to compute the length of the drill path. Screw breach should be avoided as it disrupts the articular surface and may lead to a sequela of cartilage deterioration and osteoarthritic changes. The shortest distance measure was extrapolated to assess whether a standard fixation screw (Accutrak Mini, 1.78 mm radius) would have breached the scaphoid surface. There were three screw breaches noted in the 3D DRR trials, while only one occurred using volume-slicing. The minimum distance from the centerline of the wire to the scaphoid surface can also be thought of as a “safe zone” for screw breach. Although no difference in the mean distance (μ) was noted between groups (μ. DRR. = 2.3 mm, μ. VS. = 2.2 mm), the standard deviation (σ) was significantly higher for the DRR trials (σ. DRR. = 0.50 mm, σ. VS. = 0.37 mm, p < 0.1), suggesting a higher reliability of central placement using VS for navigation. In contrast, the length of the drill paths were significantly longer for the DRR trials (μ = 28.7 mm, σ = 0.66 mm) than for VS-navigation (μ = 28.3 mm, σ = 0.62 mm) at p < 0.1. The surgical goal was to pick a path that maximised both the length of the path, as well as the minimum distance from the scaphoid surface. Algorithms were developed to find the paths that would maximise: (i) the length and (ii) the distance from the surface of the model scaphoid used in this study. The maximum possible length was 29.8mm (with a minimum distance of 2.2mm from the scaphoid surface), and the maximum distance was 3.3mm (with a length of 27.5mm). Therefore, the set of optimal drill paths had length > 27.5 mm, and distance > 2.8 mm. Of the DRR-navigated trials, 11 were below the minimum optimal depth, and only one trial was below the optimal length; 13 of the 24 trials (54%) were of both optimal length and depth. Of the VS-navigated trials, nine were below the minimal optimal distance, and four were below the minimum optimal length; 11 out of 24 trials (46%) were within both the optimal length and depth. From this comparative study, we conclude that VS-navigation was superior in locating a central location for the fixation wire, while DRRs were superior in maximising the depth of the drill path. Thus, we propose a hybrid interface, incorporating both volume-slicing and DRRs, in order to maximise the effectiveness of navigation for percutaneous scaphoid pinning

Introduction. Successful designs of total hip replacement need to be robust to surgery-related variability. Until recently, only simple parametric studies have explored the influence of surgical variability [1]. This study presents a systematic method for quantifying the effect of variability in positioning on the primary stability of femoral stems using finite element (FE) models. Methods. Patient specific finite element models were generated of two femurs, one male and one female. An automated algorithm positioned and sized a Corail stem (DePuy Synthes, Warsaw) into each of the femurs to achieve maximum fill of the medullary canal without breaching into the cortical bone boundaries.. Peak joint contact and muscle forces associated with level gait were applied[2] and scaled to the body mass of each subject, whilst the distal femur was rigidly constrained. The space prone to surgical variation was defined by the “gap” between the stem and the inner boundary of the cortical bone. The anterior/posterior and the varus/valgus alignment of the stem within this “gap” was controlled by varying the location of the points defining the shaft axis. The points were taken at 20% and 80% of the stem length (Figure 1). The anteversion angle as well as the vertical and the medial position of the stem were controlled by changing the location of the head centre within the femoral head radius. The location of these points was varied using Latin Hypercube sampling to generate 200 models per femur, each with a unique stem position. The risk of failure was evaluated based on stem micromotion, equivalent strains, and percentage of the bone-prosthesis contact area experiencing more than 7000 µstrains [3]. Results. The range of positions covered in this study adhered to the anatomy of the subjects (Table 1) and none of the stem positions breached into the cortical bone of the femur. The 90th percentile peri-prosthetic strains were between 1770 – 4792 µstrains for the male subject, and 2710 – 11260µstrains for the female subject. The 90th percentile micromotion was between (15.6 – 47) µm for the male subject, and (42.4 – 102.4) µm for the female subject. The percentage of the contact area experiencing more than 7000 µstrains was between (0% – 0.33%) for the male subject, and (0% – 12%) for the female subject. Discussion. A systematic method for studying the effect of surgical-related variation on primary stability was presented its applicability demonstrated on two femurs. The study found that variation in stem position may result in large variation (up to 1.5 times the baseline position) in strains and micromotions. The magnitude Up to three times the magnitudes for the ideal stem position. This method can be applied to larger samples to understand the influence of different alignment parameters on the primary stability of femoral stems

Introduction. Orthopaedic departments are increasingly put under pressure to improve services, cut waiting lists, increase efficiency and save money. It is in the interests of patients and NHS organisations to ensure that operating theatre resources are used to best effect to ensure they are cost effective, support the achievement of waiting time targets and contribute to a more positive patient experience. Patients in the UK are expected to have undergone surgery once decided within 18 weeks. A good system of planning and scheduling in theatre enables more work, however is largely delegated to non-clinical managerial and administrative staff. After numerous cancellations of elective cases due to incomplete pre-operative work-up, unavailable equipment and patient DNAs, we decided to introduce a surgeon-led scheduling system. Intervention. The surgeon-led scheduling diary involved surgeons offering patients a date for surgery in clinic. This allowed for appropriate organisation of theatre lists and surgical equipment, and pre-operative assessment. Results. Prior to surgeon-led scheduling, there were a high number of patient DNAs (11%) and cancellations (15%), and 18-week target breaches (16%). Theatre utilisation was found to be 76%, with a booking efficiency of 80%. With surgeon-led scheduling, the number of cancellations reduced significantly (7%) although theatre utilisation remained similar (75%). Booking efficiency was reported to be 97%. There was a shorter waiting time by approximately 3 weeks and only 3% of patients breached their 18-week target. Patients, theatre staff and surgeons were also surveyed. 100% of patients were satisfied with a date being offered in clinic, with 80% feeling less inclined to change or cancel the date of surgery. 100% of theatre staff were satisfied with the system, with improved communication and time to allocate surgical resources. 90% of surgical trainees reported improved satisfaction due to the mixed case-load and increased time for training. Conclusion. In hospitals, optimising utilisation of operating theatres is essential both for patient care, efficiency and economy. We believe a surgeon led scheduling diary improves the patient experience in addition to surgical team satisfaction and morale

Introduction. Pedicle screw fixation commonly uses a manual probe technique for preparation and insertion of the screw. However, the accuracy of obtaining a centrally located path using the probe is often dependent on the experience of the surgeon and may lead to increased complications. Fluoroscopy and navigation assistance improves accuracy but may expose the patient and surgeon to excessive radiation. DSG measures electrical conductivity at the tip and provides the surgeon with real-time audio and visual feedback based on differences in tissue density between cortical and cancellous bone and soft tissue. The authors investigated the effectiveness of DSG for training residents on safe placement of pedicle screws. Methods. 15 male cadaveric thoracolumbar spine specimens were fresh-frozen at the time of expiration. Residents were assigned 3 specimens each and randomised by pedicle side and order of technique for pedicle screw placement (free-hand versus DSG). Fluoroscopy and other navigation assistance were not used for pedicle preparation. All specimens were imaged using CT following insertion of all pedicle screws. The accuracy was assessed by a senior radiologist and graded as within (≤ 2mm breach) or outside (> 2mm breach) the pedicle. Results. 15 specimens were dissected in standard fashion to expose the thoracolumbar spine (T7-L5). 5 residents were randomised and assigned 3 specimens each to prepare bilateral pedicles from T8 to L5 (60 pedicles per resident) using either PediGuard or free-hand technique. A total of 249 pedicle screws were placed. Post-procedure CT scans demonstrated 214 (85.9%) screws within the pedicle. Breach rate for the DSG group was 8.2% and 19.7% for the non-DSG group, with an overall reduction of 58% (p=0.025). Conclusion. The use of Dynamic Surgical Guidance decreased the pedicle screw placement learning curve in residents, while improving breach rate by 58%. This study demonstrates that DSG has the potential for resident education and refinement in operative technique

To describe a modification of the existing technique for C2 translaminar screw fixation that can be used for salvage in difficult cases. Bilateral crossing C2 laminar screws have recently become popular as an alternative technique for C2 fixation. This technique is particularly useful in patients with anomalous anatomy, as a salvage technique where other modes of fixation have failed or as a primary procedure. However, reported disadvantages of this technique include breach of the dorsal lamina and spinal canal, early hardware failure and difficulty in bone graft placement due to the position of the polyaxial screw heads. To address some of these issues, a modified technique is described. In this technique, the upper part of the spinous process of C2 is removed and the entry point of the screw is in the base of this removed spinous process. From October 2008 to March 2009, 6 patients underwent insertion of unilateral translaminar screws using our technique. The indications were: basilar invagination(three cases), C1/C2 fracture (two cases), tumour (one case). Age varied from 22 to 81 years (mean 48 years). All patients had post-operative x-ray and CT scan to assess position of the screws. Mean follow-up was 6 months. The screw position was satisfactory in all patients. There were no intraoperative or early postoperative complications. Our modification enables placement of bone graft on the C2 lamina and is also less likely to cause inadvertent cortical breach. Because of these advantages, it is especially suitable for patients with advanced rheumatoid arthritis with destruction of the lateral masses of C2 or as part of a hybrid construct in patients with unilateral high riding vertebral artery. This technique is not suitable for bilateral translaminar screw placement