Aims. Guided growth has been used to treat coxa valga for cerebral palsy (CP) children. However, there has been no study on the optimal position of screw application. In this paper we have investigated the influence of screw position on the outcomes of guided growth. Methods. We retrospectively analyzed 61 hips in 32 CP children who underwent proximal femoral hemi epiphysiodesis between July 2012 and September 2017. The hips were divided into two groups according to the transphyseal position of the screw in the coronal plane: across medial quarter (Group 1) or middle quarter (Group 2) of the medial half of the physis. We compared pre- and postoperative radiographs in head-shaft angle (HSA), Reimer’s migration percentage (MP), acetabular index (AI), and femoral anteversion angle (FAVA), as well as incidences of the physis growing-off the screw within two years. Linear and Cox regression analysis were conducted to identify factors related to HSA correction and risk of the physis growing-off the screw. Results. A total of 37 hips in Group 1 and 24 hips in Group 2 were compared. Group 1 showed a more substantial decrease in the HSA (p = 0.003) and the MP (p = 0.032). Both groups had significant and similar improvements in the AI (p = 0.809) and the FAVA (p = 0.304). Group 1 presented a higher incidence of the physis growing-off the screw (p = 0.038). Results of the regression analysis indicated that the eccentricity of screw position correlated with HSA correction and increases the risk of the physis growing-off the screw. Conclusion. Guided growth is effective in improving coxa valga and excessive femoral anteversion in CP children. For younger children, despite compromised efficacy of varus correction, we recommend a more centered screw position, at least across the middle quarter of the medial physis, to avoid early revision. Cite this article: Bone Joint J 2020;102-B(9):1242–1247

Study design: A retrospective evaluation of screw position after double rod anterior spinal fusion in idiopathic scoliosis using computerised tomography (CT). Objective: To evaluate screw position and complications related to screw position after double rod anterior instrumentation in idiopathic scoliosis. Summary of Background Data: Anterior instrumentation and fusion in idiopathic scoliosis is gaining widespread use. However, no studies have been published regarding the accuracy of screw placement and screw related complications in double rod and double screw anterior spinal fusion and instrumentation in idiopathic thoracolumbar scoliosis surgery. Methods: CT examinations were performed after anterior spinal fusion and instrumentation in 17 patients with idiopathic scoliosis. The vertebral rotation at each level was measured. At each instrumented level the position of the screw and the plate relative to the spinal canal, relative to the neural foramen and relative to the aorta was measured. Complications related to screw position were registered. Results: 189 screws in 17 patients were evaluated. The average age of the patients was 31 years (range 15–53 years). Fourteen patients had a left convex thoracolumbar curve and three patients a right convex thoracolumbar curve. The mean lumbar apical rotation preoperatively was 27°. Malposition occurred in 23% of the total number of screws. Three screws were in the spinal canal (1%). This resulted in pain in the right leg. However, electromyography showed no abnormalities. On three levels there was contact between the instrumentation and the aorta. No vascular complications did occur. 113 screws (ten patients) were placed under fluoroscopic guidance and 76 screws (seven patients) were placed without use of fluoroscopy. No complications related to screw position were observed in the group in which the screws were placed under fluoroscopic guidance. Conclusions: Adequate placement of two screws in the vertebra in idiopathic scoliosis is a technically demanding procedure, which results in frequent malposition, fortunately with a low risk of neurological and vascular complications

Minimizing tip-apex distance has been shown to reduce clinical failure of sliding hip screws used to fix peritro-chanteric fractures. The purpose of this study was to determine if such a relationship exists for the position of the lag screw in the femoral head using a cephalomedullary device. Methods: Thirty intact synthetic femur specimens (Model #3406, Pacific Research Laboratories, Vashon, WA) were potted into cement blocks distally for testing on an Instron 8874 (Instron, Canton, MA). A long cephalomedullary nail (Long Gamma 3 Nail, Stryker, Mahwah, NJ) was inserted into each of the femurs. An unstable four-part fracture was created, anatomically reduced, and repaired using one of 5 lag screw placements in the femoral head:. Superior (N=6),. Inferior (N=6),. Anterior (N=6),. Posterior (N=6),. Central (N=6). Mechanical tests were repeated for axial, lateral and torsional stiffness. All specimens were radiographed in the anterioposterior and lateral planes and tip-apex (TAD) distance was calculated. A calcar referenced tip-apex distance (CalTAD) was also calculated. ANOVA was used to compare means of the five treatment groups. Linear regression analysis was used to compare axial, lateral and torsional stiffness (dependant variables) to both TAD and CalTAD (independent variables). Results: ANOVA testing proved that the mean axial (p< 0.01) and torsional stiffness (p< 0.01) between the 5 groups was significantly different, but lateral stiffness was not statistically different (p=0.494). Post hoc analysis showed that the inferior lag screw position provided significantly higher mean axial stiffness (568.14±66.9N/ mm) than superior (428.0±45.6N/mm; p< 0.01), anterior (443.2±45.4N/mm; p=0.02) and posterior (456.7±69.3N/ mm; p=0.04) lag screw positions. There was no significant difference in mean axial stiffness between inferior (568.14±66.9N/mm) and central (525.4±81.7N/mm) lag screw positions (p=0.77). Post hoc analysis revealed significantly less mean torsional stiffness for the superior lag screw position compared to other lag screw positions (p< 0.01 all 4 pairings). There were no significant correlations between TAD and axial (r=−0.33, p=0.08), lateral (r=−0.22, p=0.24) or torsional (r=0.08, p=0.69) stiffness. There were significant correlations between CalTAD and axial (r=−0.66, p< 0.01), lateral (r=−0.38, p=0.04) and torsional (r=−0.38, p=0.04) stiffness. Discussion: Our results suggest that placement of the lag screw inferiorly in the femoral head when using a cephalomedullary nail to treat an unstable peritrochanteric fracture results in the stiffest construct in axial and torsional biomechanical testing. A simple radiographic measurement, CalTAD, provides an intraoperative method of determining optimal cephalomedullary nail lag screw position to achieve greatest construct stiffness

Purpose: Minimizing tip-apex distance (TAD) has been shown to reduce clinical failure of extramedullary sliding hip screws used to fix peritrochanteric fractures. There is debate regarding the optimal position of the lag screw in the femoral head when a cephalomedullary nail is used to treat a peritrochanteric fracture. Some authors suggest the TAD should be minimized as with an extramedullary sliding hip screw, while others suggest the lag screw should be placed inferior within the femoral head. The primary goal of this study was to determine which of 5 possible lag screw positions in the femoral head provides greatest mechanical stiffness and/or load-to-failure for an unstable peritrochanteric fracture treated with a cepha-clomedullary nail. The secondary goal was to determine if there is a linear correlation between implant-femur mechanical stiffness and/or load to failure (dependent variables) with a series of five radiographic measurements (independent variables) of distance from the lag screw tip to the femoral head apex. Method: Long Gamma 3 Nails (Stryker, Mahwah, NJ) were inserted into 30 left synthetic femurs (Pacific Research Laboratories, Vashon, WA). An unstable four-part fracture was created, anatomically reduced, and repaired using one of 5 lag screw placements in the femoral head:. superior (n=6),. inferior (n=6),. anterior (n=6),. posterior (n=6),. central (n=6). All specimens were radiographed in the anterioposterior and lateral planes, and radiographic measurements including TAD and a calcar referenced tip-apex distance (CalTAD) were calculated. All specimens were tested for axial, lateral, and torsional stiffness, and then loaded-to-failure in the axial position using an Instron 8874 (Canton, MA). ANOVA was used to compare means of the five treatment groups. Linear regression analysis was used to compare stiffness and load-to-failure (dependant variables) with radiographic measurements (independent variables). A post hoc power analysis was performed. Results: The inferior lag screw position had significantly greater mean axial stiffness than superior (p< 0.01), anterior (p=0.02) and posterior (p=0.04) positions. Analysis revealed significantly less mean torsional stiffness for the superior lag screw position compared to other lag screw positions (p< 0.01 all 4 pairings). No statistical differences were noted for lateral stiffness. Superior and central lag screw positions had significantly greater mean load-to-failure than anterior (p< 0.01 and p=0.02) and posterior (p< 0.01 and p=0.05) positions. There were significant negative linear correlations between stiffness tests with CalTAD, and load-to-failure with TAD. Power was greater than 95% for axial stiffness, torsional stiffness and load-to-failure tests. Conclusion: Position of the lag screw in the femoral head affects the biomechanical properties of the implant-femur construct. Central placement of the lag screw with minimization of TAD may provide the best combination of stiffness and load-to-failure

Intra-operative Tip-Apex Distance (TAD) estimation optimises dynamic hip screw (DHS) placement during hip fracture fixation, reducing risk of cut-out. Thread-width of a standard DHS screw measures approximately 12.5 millimetres. We assessed the effect of introducing screw thread-width as an intra-operative distance reference to surgeons. The null hypothesis was that there were no differences between hip fracture fixation before and after this intervention. Primary outcome measure was TAD. Secondary outcome measures included position of the screw in the femoral head, quality of reduction, cut-out and surgeon accuracy of estimating TAD. 150 intra-operative DHS radiographs were assessed before and after introducing screw thread-width distance reference to surgeons. Mean TAD reduced from 19.37mm in the control group to 16.49mm in the prospective group (p=<0.001). The number of DHS with a TAD > 25mm reduced from 14% to 6%. Screw position on lateral radiographs was significantly improved (p=0.004). There were no significant differences in screw position on antero-posterior radiographs, quality of reduction, or rate of cut-out. Significant improvement in accuracy (p=0.05) and precision (p=0.005) of TAD estimation was demonstrated. Awareness and use of screw-thread width improves estimation and positioning of a DHS screw in the femoral head during fixation of hip fractures

Aims. Paediatric triplane fractures and adult trimalleolar ankle fractures both arise from a supination external rotation injury. By relating the experience of adult to paediatric fractures, clarification has been sought on the sequence of injury, ligament involvement, and fracture pattern of triplane fractures. This study explores the similarities between triplane and trimalleolar fractures for each stage of the Lauge-Hansen classification, with the aim of aiding reduction and fixation techniques. Methods. Imaging data of 83 paediatric patients with triplane fractures and 100 adult patients with trimalleolar fractures were collected, and their fracture morphology was compared using fracture maps. Visual fracture maps were assessed, classified, and compared with each other, to establish the progression of injury according to the Lauge-Hansen classification. Results. Four stages of injury in triplane fractures, resembling the adult supination external rotation Lauge-Hansen stages, were observed. Stage I consists of rupture of the anterior syndesmosis or small avulsion of the anterolateral tibia in trimalleolar fractures, and the avulsion of a larger Tillaux fragment in triplanes. Stage II is defined as oblique fracturing of the fibula at the level of the syndesmosis, present in all trimalleolar fractures and in 30% (25/83) of triplane fractures. Stage III is the fracturing of the posterior malleolus. In trimalleolar fractures, the different Haraguchi types can be discerned. In triplane fractures, the delineation of the posterior fragment has a wave-like shape, which is part of the characteristic Y-pattern of triplane fractures, originating from the Tillaux fragment. Stage IV represents a fracture of the medial malleolus, which is highly variable in both the trimalleolar and triplane fractures. Conclusion. The paediatric triplane and adult trimalleolar fractures share common features according to the Lauge-Hansen classification. This highlights that the adolescent injury arises from a combination of ligament traction and a growth plate in the process of closing. With this knowledge, a specific sequence of reduction and optimal screw positions are recommended. Cite this article: Bone Joint J 2024;106-B(9):1008–1014

Introduction Concentric interference screw placement has been proposed as having potentially better biological graft integration than eccentric interference screw placement during soft tissue ACL reconstruction. The purpose of this study was to determine whether a wedge shaped concentric screw was at least equivalent to an eccentric screw in stiffness, yield load, ultimate load and mode of failure. Methods Seven matched pairs of human cadaveric tendon in porcine tibia with titanium wedge shaped screws were randomly allocated to either the eccentric or concentric groups. Bone tunnels were drilled 45° to the long axis of the tibia, akin to standard ACL reconstruction. Tendon diameter was matched to tunnel diameter and a screw one millimetre larger than tunnel diameter was inserted. An Instrom machine was used to pull in the line of the tendon. Tendons were inspected after construct disassembly. Results The concentric screw configuration showed significantly higher stiffness (p< 0.0085), yield load (p< 0.0135) and ultimate load (p< 0.0075). The mode of failure in the eccentric screw position was slippage at the screw tendon interface in all cases. In the concentric group 88% of cases had a breakage in the tendon and 13% of cases had slippage at the tendon bone interface. However, it was observed during construct disassembly that there was more macroscopic damage to the tendon substance in the concentric group. Failure was mostly by tendon breakage, which reflects the strongest fixation possible with the tendon being the weakest link in the system. Conclusions Concentric interference screw fixation of soft tissue graft offers superior fixation in single pullout mode when compared to eccentric interference screw fixation

Biomechanical stability is important for fracture healing. With standard plate and screw constructs, longer plates with screws well spaced, near and far from the fracture site, are biomechanically superior. Newer locked plates have been shown to be superior to conventional plating for difficult fractures. The ideal screw configuration for fixation with locked plates has yet to be addressed. This study investigates the effects of screw position on construct stiffness as well as strain in both the plate and bone during fixation of a diaphyseal comminuted fracture using a locking plate with bicortical fixation. A composite cylinder (Sawbones) was machined to produce two models:. (a) comminuted model (4mm gap) and. (b) whole model (no gap) to simulate the remodelling phase. Five strain gauges were mounted to the bone models and one between the center holes of the locking plate. Four different configurations of screw number and position were evaluated using a twelve-hole locking plate (Smith & Nephew Perilock). Plate holes were numbered on each side of the gap from one to six. Screw configuration 654321, 621, 654 and 321 were tested in four-point bending on an MTS 858 Mini-Bionix. Force (N) and displacement (mm) as well as strain readings were recorded at 10 Hz. Plate strain in the gap model did not vary significantly for the different configurations. Construct stiffness of the 654 model (all screws far from gap) showed a 30% decrease in stiffness as compared to other screw configurations (p< 0.001). In the whole bone model, the maximal bone strain was outside the farthest screw from the center of the plate (stress shielding) and bone strain at the fracture site in 654 was significantly higher than in 621 (p< 0.001). Results showed that three screw fixation produced similar construct stiffness to a six screw construct when well spaced. Three screws placed far from the fracture gap (654) as compared to three screws evenly spaced (621) showed decreased stability in the comminuted model but resulted in increased bone strain at the fracture site in the whole bone model. All configurations produced similar plate strain

Introduction: Since the introduction of locked implants new possibilities in the treatment of proximal humeral fractures have evolved. Despite the success using locked plates recent publications report the cutting of screws through the humeral head in up to 30% of the cases. The distribution of the bone strength in the humeral head is not linear. Can polyaxial screw positioning in areas with higher bone strength reduce the “cutout” rate? Which effect has an inferomedial screw if the medial hinge is not restored?. Methods: 4 groups were formed from 31 fresh frozen proximal humeral cadavers. A polyaxial proximal humeral locking plate was used to perform the tests. A standardised unstable intraarticular fracture was created. Main Outcome measure was the load and cycle where at least one screw was cutting through the cartilage. Results: Polyaxial screw placement in areas of incresead bone strength compared to random screw placement had no effect on the cutout behaviour (p=0.7). Increased screw number (3 vs. 5) significantly increases the resistance against cutout (p< 0.04). An inferomedial screw significantly increases the resistance to develop a cutout compared to the control groups(p=0.03 and p< 0.05). Discussion: The placement of an inferomedial screw significantly increases the resistence to develop a cutout in proximal humeral fractures without a medial hinge independently of the total screw number. In addition we could also show that the number of screws in the humeral head has a significant effect on cutout resistance in a human cadaver setup

Background

Open-wedge high tibial osteotomy (OWHTO) is an operation involving proper load re-distribution in the treatment for medial uni-compartmental arthritis of the knee joint. Therefore, stable fixation is mandatory for safe healing of this additive type of osteotomy to minimize the risk of non-union and loss of correction. For stability, screws provide optimal support and anchorage of the fixator in the condylar area without risking penetration of either the articulating surface. The purpose of the study was to evaluate the screw insertion angle and orientation with an anatomical plate that is post-contoured to the surface geometry of the proximal tibia after OWHTO.

Soft tissue balancing in total knee replacement may well be the determining factor in raising the fair patient satisfaction. The development of intelligent implants allows quantification of reactive loads to applied pressures. This can be tested in dynamic mode such as heel push test at surgery, or in static mode such as when testing for varus/valgus (VV) laxity of the collateral ligaments of the knee. We postulate that a well-balanced knee will have comparable if not equal load distribution across compartments in dynamic loading. When tested for laxity, we anticipate an equal or comparable response to VV applied loads under physiologic load range of 10–50N. This study sought to analyze the relationship between the kinematic (joint motion) and kinetic (force) effects to VV testing in the 0–15 degrees range of flexion. One goal was to demonstrate that testing the knee in locked extension (Screw Home effect) is unreliable and should be abandoned in favor of the more reliable VV testing at 10–15 degrees of flexion.

This is a preliminary cadaveric study utilizing data from two hemibodies. The pelvis was fixed in a custom test rig with open or closed chain lower leg testing capability along a sliding rail with foot VV translational. Forces were applied at the malleoli with a wireless hand held dynamometer. Kinematic analysis of the hip-knee-ankle (HKA) tibiofemoral angle was derived from a commercial navigation system with mounted infrared trackers. Kinetic analysis was derived from a commercially available sensor imbedded in a tibial trial liner. Balance was optimized by conventional methods with the use of the sensor feedback until loads were roughly symmetrical and VV testing yielded symmetrical rise in opposite compartments. The VV testing was then performed with the knees locked at the femoral side in axial rotation and translational motion in any plane. Sagittal flexion was pre-set at 0, 10, and 15 degrees and progressive load was applied.

Lag screw cut-out is a serious complication of dynamic hip screw fixation in trochanteric hip fractures. Lag screw position is recognised as a crucial factor influencing the occurrence of lag screw cut-out. We propose a modification of the Tip Apex Distance (TAD) and hypothesize that it could enhance the reliability of predicting lag screw cut-out in these injuries. A retrospective study of hip fracture cases was conducted from January 2018 to July 2022. A total of 109 patients were eligible for the final analysis. The modified TAD was measured in millimetres, based on the sum of the traditional TAD in the lateral view and the net value of two distances in the anteroposterior (AP) view. The first distance is from the lag screw tip to the opposite point on the femoral head along the lag screw axis, while the second distance is from that point to the femoral head apex. The first distance is a positive value, whereas the second distance is positive if the lag screw is superior and negative if it is inferior. Receiver operating characteristic (ROC) curve analysis was used to assess the reliability of various parameters for evaluating the lag screw position within the femoral head. Factors such as reduction quality, fracture pattern according to the AO/OTA classification, TAD, Calcar-Referenced TAD, Axis Blade Angle, Parker’s ratio in the AP view, Cleveland Zone 1, and modified TAD were statistically associated with lag screw cut-out. Among the tested parameters, the novel parameter exhibited 90.1% sensitivity and 90.9% specificity for predicting lag screw cut-out at a cut-off value of 25 mm, with a p-value < 0.001. The modified TAD demonstrated the highest reliability in predicting lag screw cut-out. A value of 25 mm may potentially reduce the risk of lag screw cut-out in trochanteric hip fractures

Reverse shoulder arthroplasty (RSA) is commonly used to treat patients with rotator cuff tear arthropathy. Loosening of the glenoid component remains one of the principal modes of failure and is the main complication leading to revision. For optimal RSA implant osseointegration to occur, the micromotion between the baseplate and the bone must not exceed a threshold of 150 µm. Excess micromotion contributes to glenoid loosening. This study assessed the effects of various factors on glenoid baseplate micromotion for primary fixation of RSA. A half-fractional factorial experiment design (2k-1) was used to assess four factors: central element type (central peg or screw), central element cortical engagement according to length (13.5 or 23.5 mm), anterior-posterior (A-P) peripheral screw type (nonlocking or locking), and bone surrogate density (10 or 25 pounds per cubic foot [pcf]). This created eight unique conditions, each repeated five times for 40 total runs. Glenoid baseplates were implanted into high- or low-density Sawbones™ rigid polyurethane (PU) foam blocks and cyclically loaded at 60 degrees for 1000 cycles (500 N compressive force range) using a custom designed loading apparatus. Micromotion at the four peripheral screw positions was recorded using linear variable displacement transducers (LVDTs). Maximum micromotion was quantified as the displacement range at the implant-PU interface, averaged over the last 10 cycles of loading. Baseplates with short central elements that lacked cortical bone engagement generated 373% greater maximum micromotion at all peripheral screw positions compared to those with long central elements (p < 0.001). Central peg fixation generated 360% greater maximum micromotion than central screw fixation (p < 0.001). No significant effects were observed when varying A-P peripheral screw type or bone surrogate density. There were significant interactions between central element length and type (p < 0.001). An interaction existed between central element type and level of cortical engagement. A central screw and a long central element that engaged cortical bone reduced RSA baseplate micromotion. These findings serve to inform surgical decision-making regarding baseplate fixation elements to minimize the risk of glenoid loosening and thus, the need for revision surgery

Aims. To develop a core outcome set of measurements from postoperative radiographs that can be used to assess technical skill in performing dynamic hip screw (DHS) and hemiarthroplasty, and to validate these against Van der Vleuten’s criteria for effective assessment. Methods. A Delphi exercise was undertaken at a regional major trauma centre to identify candidate measurement items. The feasibility of taking these measurements was tested by two of the authors (HKJ, GTRP). Validity and reliability were examined using the radiographs of operations performed by orthopaedic resident participants (n = 28) of a multicentre randomized controlled educational trial (ISRCTN20431944). Trainees were divided into novice and intermediate groups, defined as having performed < ten or ≥ ten cases each for DHS and hemiarthroplasty at baseline. The procedure-based assessment (PBA) global rating score was assumed as the gold standard assessment for the purposes of concurrent validity. Intra- and inter-rater reliability testing were performed on a random subset of 25 cases. Results. In total, 327 DHS and 248 hemiarthroplasty procedures were performed by 28 postgraduate year (PGY) 3 to 5 orthopaedic trainees during the 2014 to 2015 surgical training year at nine NHS hospitals in the West Midlands, UK. Overall, 109 PBAs were completed for DHS and 80 for hemiarthroplasty. Expert consensus identified four ‘final product analysis’ (FPA) radiological parameters of technical success for DHS: tip-apex distance (TAD); lag screw position in the femoral head; flushness of the plate against the lateral femoral cortex; and eight-cortex hold of the plate screws. Three parameters were identified for hemiarthroplasty: leg length discrepancy; femoral stem alignment; and femoral offset. Face validity, content validity, and feasibility were excellent. For all measurements, performance was better in the intermediate compared with the novice group, and this was statistically significant for TAD (p < 0.001) and femoral stem alignment (p = 0.023). Concurrent validity was poor when measured against global PBA score. This may be explained by the fact that they are measuring difference facets of competence. Intra-and inter-rater reliability were excellent for TAD, moderate for lag screw position (DHS), and moderate for leg length discrepancy (hemiarthroplasty). Use of a large multicentre dataset suggests good generalizability of the results to other settings. Assessment using FPA was time- and cost-effective compared with PBA. Conclusion. Final product analysis using post-implantation radiographs to measure technical skill in hip fracture surgery is feasible, valid, reliable, and cost-effective. It can complement traditional workplace-based assessment for measuring performance in the real-world operating room . It may have particular utility in competency-based training frameworks and for assessing skill transfer from the simulated to live operating theatre. Cite this article: Bone Joint Open 2020;1-9:594–604

Variations in pelvic anatomy are a major risk factor for misplaced percutaneous sacroiliac screws used to treat unstable posterior pelvic ring injuries. A better understanding of pelvic morphology improves preoperative planning and therefore minimises the risk of malpositioned screws, neurological or vascular injuries, failed fixation or malreduction. Hence a classification system which identifies the clinically important anatomical variations of the sacrum would improve communication among pelvic surgeons and inform treatment strategy. 300 Pelvic CT scans from skeletally mature trauma patients that did not have pre-existing posterior pelvic pathology were identified. Axial and coronal transosseous corridor widths at both S1 and S2 were recorded. Additionally, the S1 lateral mass angle were also calculated. Pelvises were classified based upon the sacroiliac joint (SIJ) height using the midpoint of the anterior cortex of L5 as a reference point. Four distinct types could be identified:. Type-A – SIJ height is above the midpoint of the anterior cortex of the L5 vertebra. Type-B – SIJ height is between the midpoint and the lowest point of the anterior cortex of the L5 vertebra. Type-C – SIJ height is below the lowest point of the anterior cortex of the L5 vertebra. Type-D – a subgroup for those with a lumbosacral transitional vertebra, in particular a sacralised L5. Differences in transosseous corridor widths and lateral mass angles between classification types were assessed using two-way ANOVAs. Type-B was the most common pelvic type followed by Type-A, Type-C, and Type-D. Significant differences in the axial and coronal corridors was observed for all pelvic types at each level. Lateral mass angles increased from Types-A to C, but were smaller in Type-D. This classification system offers a guide to surgeons navigating variable pelvic anatomy and understanding how it is associated with the differences in transosseous sacral corridors. It can assist surgeons’ preoperative planning of screw position, choice of fixation or the need for technological assistance

Recently, a new generation of superior clavicle plates was developed featuring the variable-angle locking technology for enhanced screw positioning and optimized plate-to-bone fit design. On the other hand, mini-fragment plates used in dual plating mode have demonstrated promising clinical results. However, these two bone-implant constructs have not been investigated biomechanically in a human cadaveric model. Therefore, the aim of the current study was to compare the biomechanical competence of single superior plating using the new generation plate versus dual plating with low-profile mini-fragment plates. Sixteen paired human cadaveric clavicles were assigned pairwise to two groups for instrumentation with either a 2.7 mm Variable Angle Locking Compression Plate placed superiorly (Group 1), or with one 2.5 mm anterior plate combined with one 2.0 mm superior matrix mandible plate (Group 2). An unstable clavicle shaft fracture AO/OTA15.2C was simulated by means of a 5 mm osteotomy gap. All specimens were cyclically tested to failure under craniocaudal cantilever bending, superimposed with bidirectional torsion around the shaft axis and monitored via motion tracking. Initial stiffness was significantly higher in Group 2 (9.28±4.40 N/mm) compared to Group 1 (3.68±1.08 N/mm), p=0.003. The amplitudes of interfragmentary motions in terms of craniocaudal and shear displacement, fracture gap opening and torsion were significantly bigger over the course of 12500 cycles in Group 1 compared to Group 2; p≤0.038. Cycles to 2 mm shear displacement were significantly lower in Group 1 (22792±4346) compared to Group 2 (27437±1877), p=0.047. From a biomechanical perspective, low-profile 2.5/2.0 dual plates demonstrated significantly higher initial stiffness, less interfragmentary movements, and higher resistance to failure compared to 2.7 single superior variable-angle locking plates and can therefore be considered as a useful alternative for diaphyseal clavicle fracture fixation especially in unstable fracture configurations

Introduction and Objective. The aim of this study was to evaluate whether CT-based pre-operative planning, integrated with intra-operative navigation could improve glenoid baseplate fixation and positioning by increasing screw length, reducing number of screws required to obtain fixation and increasing the use of augmented baseplate to gain the desired positioning. Reverse total shoulder arthroplasty (RSA) successfully restores shoulder function in different conditions. Glenoid baseplate fixation and positioning seem to be the most important factors influencing RSA survival. When scapular anatomy is distorted (primitive or secondary), optimal baseplate positioning and secure screw purchase can be challenging. Materials and Methods. Twenty patients who underwent navigated RSA (oct 2018 and feb 2019) were compared retrospectively with twenty patients operated on with a conventional technique. All the procedures were performed by the same surgeon, using the same implant in cases of eccentric osteoarthritis or complete cuff tear. Exclusion criteria were: other diagnosis as proximal humeral fractures, post-traumatic OA previously treated operatively with hardware retention, revision shoulder arthroplasty. Results. The NAV procedure required mean 11 (range 7–16) minutes more to performed than the conventional procedure. Mean screw length was significantly longer in the navigation group (35.5+4.4 mm vs 29.9+3.6 mm; p . .001). Significant higher rate of optimal fixation using 2 screws only (17 vs 3 cases, p . .019) and higher rate of augmented baseplate usage (13 vs 4 cases, p . .009) was also present in the navigation group. Signficant difference there is all in function outcomes, DASH score is 15.7 vs 29.4 and constant scale 78.1 vs 69.8. Conclusions. The glenoid component positioning in RSA is crucial to prevent failure, loosening and biomechanical mismatch, coverage by the baseplate of the glenoid surface, version, inclination and offset are all essential for implant survival. This study showed how useful 3D CT-based planning helps in identifying the best position of the metaglena and the usefulness of receiving directly in the operation theater real-time feedback on the change in position. This study shows promising results, suggesting that improved baseplate and screw positioning and fixation is possible when computer-assisted implantation is used in RSA comparing to a conventional procedure

Summary Statement. In this study, excellent positioning of custom-made glenoid components was achieved using patient-specific guides. Achieving the preoperatively planned orientation of the component improved significantly and more screws were located inside the scapular bone compared to implantations without such guide. Introduction. Today's techniques for total or reverse shoulder arthroplasty are limited when dealing with severe glenoid defects. The available procedures, for instance the use of bone allografts in combination with available standard implants, are technically difficult and tend to give uncertain outcomes (Hill et al. 2001; Elhassan et al. 2008; Sears et al. 2012). A durable fixation between bone and implant with optimal fit and implant positioning needs to be achieved. Custom-made defect-filling glenoid components are a new treatment option for severe glenoid defects. Despite that the patient-specific implants are uniquely designed to fit the patient's bone, it can be difficult to achieve the preoperatively planned position of the component, resulting in less optimal screw fixation. We hypothesised that the use of a patient-specific guide would improve implant and screw positioning. The aim of this study was to evaluate the added value of a newly developed patient-specific guide for implant and screw positioning, by comparing glenoid implantations with and without such guide. Patients & Methods. Large glenoid defects, representative for the defects encountered in clinical practice, were created in ten cadaveric shoulders. A CT scan of each cadaver was taken to evaluate the defects and to generate three-dimensional models of the scapular bones. Based on these models, custom glenoid components were designed. Furthermore, a newly developed custom guide was designed for five randomly selected shoulders. New CT scans were taken after implantation to generate 3D models of the bone and the implanted component and screws. This enabled to compare the experimentally achieved and preoperatively planned reconstruction. The location and orientation of the glenoid component and screw positioning were determined and differences with the optimal preoperative planning were calculated. Results. An excellent component positioning (difference in location: 1.4±0, 7mm; difference in orientation: 2, 5±1, 2°) was achieved when using the guide compared to implantations without guidance (respectively 1, 7±0, 5mm; 5, 1±2, 3°). The guide improved component orientation significantly (P<0.1). After using the guide, all screws were positioned inside the scapular bone whereas 25% of the screws placed without guidance were positioned outside the scapular bone. Discussion/Conclusion. In this study, excellent positioning of custom-made glenoid components was achieved using patient-specific guides. Achieving the preoperatively planned orientation of the component improved significantly and more screws were located inside the scapular bone compared to implantations without such guide

Introduction:- We reviewed 69 patients with subcapital fracture neck of femur treated with two hole plate DHS and parallel de-rotation screw into the cranial part of the femoral head between January 2000 to January 2005. Methods:- Patients were selected for fixation by having Garden 1 to 4 fractures, being younger, more active and mobile. Reduction was classified as “good” when residual angulation in the lateral projection was less than 15 degrees, no varus angulation and good alignment in the calcar area. Screw position was considered “good” when there was less than 10 degrees deviation in the direction of screws, screw threads not bridging the fracture site, screw tips less than 5mm from subchondral bone and no signs of intra-articular penetration. The fracture was considered healed when bridging of trabecular bone was present. Patients were reviewed until they were pain free at rest or on walking and had radiological healing of fracture. Results:- 13 had Garden 3 & 4, 46 had Garden 1 & 2 and 10 had impacted fractures. Sixty eight patients had operation within 24 hours in the next available trauma list. Average age at operation was 70 years (range 21– 89) and hospitals stay 13 days (range 2–52). Good reduction was achieved in 61 patients, 54 of these had good screw position, 8 patients (11%) had combination of poor reduction and poor screw position; five of them had loss of fixation within 6 to 12 weeks postoperatively, one each had segmental collapse and avascular necrosis between 12 to 24 months of operation. Conclusion:- Their was no re-displacement, non-union, avascular necrosis or segmental collapse when fractures were well reduced and had good screw position. Two hole plate DHS and a parallel de-rotation screw has high rate of fracture union. We recommend its use for treatment of subcapital femoral neck fractures

Study Design: A radiographic study using disarticulated cadaver thoracic vertebrae. Objective: To determine the accuracy of orthogonal X-rays in detecting thoracic pedicle screw position by different groups of observers. Summary of Background Data: Pedicle screws are increasingly being used for internal fixation of the thoracic spine. Surgeons and radiologists are often required to make decisions on the pedicle screw position by plain antero-posterior (AP) and lateral radiographs. Materials and Methods: 23 disarticulated fresh adult thoracic vertebrae were used in this study. Pedicle screws were inserted completely within the pedicle; or deliberately violating the lateral or medial cortex of the pedicle. AP and lateral radiographs of each vertebrae were assessed by 2 spine surgeons, 2 spine trainees, and 2 musculoskeletal radiologists in a sequence of AP alone, and AP + lateral views. They were supposed to cataogorize the pedicular screw as ‘out laterally’/‘inside the pedicle’/‘out medially’ or ‘unsure’. Their assessments were compared to the actual position of the screws determined by the axial views. Results: For each screw position, trend was found towards slightly better accuracy with availability of AP & lateral views in combination. From either AP alone or AP + lateral views, significantly higher accuracy was found in detecting screws “out laterally” than “inside pedicle” (p< 0.01), or “out medially”(p< 0.05), respectively. Nearly 30% of screws that were deliberately placed through the medial pedicle wall were not correctly identified. In addition, surgeons have highest accuracy from either AP alone, or AP + lateral views, followed by the spine trainees and radiologists. Radiologists provided more “unsure” answers than surgeons or trainees. Conclusions: Screws that perforated the lateral cortex were the easiest, and those that were wholly within the pedicle were the most difficult to identify correctly. The use of plain radiographs to detect thoracic pedicle screws placed through the critical medial cortex is unreliable. The positions of thoracic pedicle screws appear to be more accurately detected by AP + lateral, however, the major contribution was from AP views. Surgeon experience continues to be vitally important in the safe placement of thoracic pedicle screws. Key points:. Screws that perforated the lateral cortex were the easiest, and those that were wholly within the pedicle were the most difficult to identify correctly. The use of plain radiographs to detect thoracic pedicle screws placed through the critical medial cortex is unreliable. AP + lateral views provides higher accuracy in determining the screw position, while, the major contribution comes from AP views. Surgeon experience, in the use of tactile skills and anatomical knowledge continue to be vitally important in the safe placement of thoracic pedicle screws

The purpose of this study is to quantify the distribution of bone density in the scapulae of patients undergoing reverse shoulder arthroplasty (RSA) to guide optimal screw placement. To achieve this aim, we compared bone density in regions around the glenoid that are targeted for screw placement, as well as bone density variations medial to lateral within the glenoid. Specimen included twelve scapula in 12 patients with a mean age of 74 years (standard deviation = 9.2 years). Each scapula underwent a computed tomography (CT) scan with a Lightspeed+ XCR 16-Slice CT scanner (General Electric, Milwaukee, USA). Three-dimensional (three-D) surface mesh models and masks of the scapulae containing three-D voxel locations along with the relative Hounsfield Units (HU) were created. Regions of interest (ROI) were selected based on their potential glenoid baseplate screw positioning in RSA surgery. These included the base of coracoid inferior and lateral to the suprascapular notch, an anterior and posterior portion of the scapular spine, and an anterosuperior and inferior portion of the lateral border. Five additional regions resembling a clock face, on the glenoid articular surface were then selected to analyze medial to lateral variations in bone density including twelve, three, six, and nine-o'clock positions as well as a central region. Analysis of Variance (ANOVA) tests were used to examine statistical differences in bone density between each region of interest (p < 0 .05). For the regional evaluation, the coracoid lateral to the suprascapular notch was significantly less dense than the inferior portion of the lateral border (mean difference = 85.6 HU, p=0.03), anterosuperior portion of the lateral border (mean difference = 82.7 HU, p=0.04), posterior spine (mean difference = 97.6 HU, p=0.007), and anterior spine (mean difference = 99.3 HU, p=0.006). For the medial to lateral evaluation, preliminary findings indicate a “U” pattern with the densest regions of bone in the glenoid most medially and most laterally with a region of less dense bone in-between. The results from this study utilizing clinical patient CT scans, showed similar results to those found in our previous cadaveric study where the coracoid region was significantly less dense than regions around the lateral scapular border and scapular spine. We also have found for medial to lateral bone density, a “U” distribution with the densest regions of bone most medially and most laterally in the glenoid, with a region of less dense bone between most medial and most lateral. Clinical applications for our results include a carefully planned trajectory when placing screws in the scapula, potentially avoiding the base of coracoid. Additionally, surgeons may choose variable screw lengths depending on the region of bone and its variation of density medial to lateral, and that screws that pass beyond the most lateral (subchondral) bone, will only achieve further purchase if they enter the denser bone more medially. We suspect that if surgeons strategically aim screw placement for the regions of higher bone density, they may be able to decrease micromotion in baseplate fixation and increase the longevity of RSA

The outcome following arthroscopic anterior cruciate (ACL) reconstruction is dependant on a combination of surgical and non-surgical factors. Technical error is the commonest cause for graft failure, with poor tunnel placement accounting for over 80% of those errors. A routine audit of femoral and tibial tunnel positions following single bundle hamstring arthroscopic ACL reconstruction identified apparent inconsistent positioning of the tibial tunnel in the sagittal plane. Intra-operative fluoroscopy was therefore introduced (when available) to verify tibial guide wire position prior to tunnel reaming. This paper reports a comparison of tibial interference screw position measured on post-operative radiographs with known tunnel position as shown on intra-operative fluoroscopic images in 20 patients undergoing routine primary ACL reconstruction between January and June 2009. Surgery took a mean of 5 minutes longer when intra-operative fluoroscopy was used. In 3/20 patients, fluoroscopy led to re-positioning of the tibial guide wire prior to tunnel reaming. The mean tibial tunnel position as indicated by the tunnel reamer was 41 +/− 2.7 % of the total plateau depth (range 37% to 47%). The mean position projected from the tibial screw on post operative radiographs was 46 +/− 9.2% (range 38% to 76%). A paired t-test showed a significant difference (p = 0.022) between true tunnel position and tibial screw position. 6/20 patients had post operative screw positions that were > 5% more posterior than the known position of the tibial tunnel. The position of the tunnel should be measured at its mid-point where this is evident. On most early radiographic images, the margins of the tunnel are not clear and therefore a line projected from the centre of the screw is used. This audit demonstrates the potential inaccuracy associated with this

Summary. Optimum position of pedicle screws can be determined preoperatively by CT based planning. We conducted a comparative study in order to analyse manually determined pedicle screw plans and those that were obtained automatically by a computer software and found an agreement in plans between both methods, yet an increase in fastening strengths was observed for automatically obtained plans. Hypothesys. Automatic planning of pedicle screw positions and sizing is not inferior to manual planning. Design. Prospective comparative study. Introduction. Preoperative planning in spinal deformity surgery starts by a proper selection of implant anchors throughout the instrumented spine, where pedicle screws provide the optimum choice for bone fixation. In the case of severe spinal deformities, dysplastic pedicles can limit screw usage, and therefore studying the anatomy of vertebrae from preoperative images can aid in achieving the safest screw position through optimal fastening strength. The purpose of this study is to compare manually and automatically obtained preoperative pedicle screw plans. Materials and Methods. CT scans of 17 deformed thoracic spines were studied by two experienced spine deformity surgeons, who placed 316 pedicle screws in 3D using a software positioning tool by aiming for the safest trajectory that permitted the largest possible screw sizes. The resulting manually obtained screw sizes, trajectory angles, entry points and normalised fastening strengths were compared to those obtained automatically by a dedicated computer software that, basing on vertebral anatomy and bone density in 3D, determined optimal screw sizes and trajectories. Results. Statistically significant differences were observed between manually and automatically obtained plans for screw sizes (p < 0.05) and trajectory angles (p < 0.001). However, for automatically obtained plans, screws were not smaller in diameter (p < 0.05) or shorter in length (p < 0.001), while screw normalised fastening strengths were higher (p < 0.001). Conclusions. In comparison to manual planning, automatically obtained plans did not result in smaller screw diameters or shorter screw lengths, which is in agreement with the definition of the pull-out strength, but in different screw trajectory angles, which is reflected by higher normalised fastening strengths. Captions. Fig. 1. Visual comparison among automatically obtained (green colour) and manually defined pedicle screw placement plans by two experienced spine surgeons (red and blue colour) for three different patients with adolescent idiopathic scoliosis, shown from top to bottom in a three-dimensional view, left sagittal, right sagittal and coronal view. Fig. 2. Histograms of differences between observers and (left column), between observer and automated method (middle column), and between observer and automated method (right column), shown from top to bottom for differences in pedicle screw pedicle screw diameter, sagittal inclination, and normalised fastening strength. For figures/tables, please contact authors directly.

Introduction Thoracic pedicle screws are increasingly being used for internal fixation. Surgeons and radiologists are often required to make decisions about the position of the screws in relation to the pedicle based on AP and lateral plain radiographs alone. We ventured to assess the value of orthogonal radiographs in determining the position of thoracic pedicle screws in 23 cadaveric thoracic vertebrae. Methods Disarticulated cadaveric thoracic vertebrae were used in this study. Pedicle screws were inserted in three positions: 1) within the pedicle, deliberately violating the 2) lateral cortex of the pedicle and 3) medial cortex of the pedicle. AP (antero-posterior) & lateral radiographs were obtained and presented to 6 readers (4 surgeons & 2 radiologists) in booklets consisting of AP views alone, lateral views alone and both AP & lateral views together in a sequential manner. The readers were asked to indicate the position of the screws and the results of the evaluation were compared to the actual position (axial views). Results On AP views alone, the accuracy in detecting screws placed out of the pedicle laterally and medially were 93% and 76% respectively, while the accuracy for screws placed inside the pedicle was 85% . On LATERAL views alone, the accuracy for the same screw positions were 69%, 58% and 64% respectively. When AP + LATERAL views were considered together, the accuracy for the same screw positions were 93%, 80% and 87% respectively. Comparing the three groups, it was observed that screw positions were read more accurately in AP + LATERAL views (87%) compared to AP views alone (85%), or LATERAL views alone (64%). The sensitivity of correctly identifying screws placement is highest in AP + LATERAL (90%) views with a specificity of 94%. The specificity of detecting screws placed inside the pedicle is highest in AP (94%). The positive predictive value (PPV) of radiographs in general (AP +LATERAL) in detecting screws placed inside the pedicle, out of the pedicle laterally and medially were 73%, 92% and 86% respectively. The negative predictive value (NPV) of radiographs in general for the same screw locations were 90%, 96% and 76% respectively. On AP and AP + LATERAL views respectively, 25% and 23% of screws placed inside the pedicle were read as medially ‘out’. 10% of screws placed medially ‘out’ were read as ‘in’ on both AP and AP + LATERAL views. Inter-observer difference was substantial. In general, surgeons appeared to have consistently higher accuracy, sensitivity, specificity, PPV and NPV values compared to radiologists and fellows in determining screw position. Discussion The positions of the screws appear to be most accurately detected when both AP and lateral x-rays are provided compared to AP or lateral alone. Screws that perforated the lateral cortex were the easiest and those that were medially out were the most difficult to identify. Screws passed inside the pedicle may create an unnecessary apprehension that they may be medial and screws passed medially may give a false sense of security that the screw is inside the pedicle. Radiographs are just one component in ensuring accurate pedicle screw placement and surgeon’s experience, in the use of tactile skills and anatomical knowledge continue to be vitally important in the safe placement of thoracic pedicle screws

Introduction. Total shoulder replacement is a successful treatment for gleno-humeral osteoarthritis. However, components loosening and painful prostheses, related to components wrong positioning, are still a problem for those patients who underwent this kind of surgery. CT-based intraoperative navigation system is a suitable option to improve accuracy and precision of the implants as previously described in literature for others district. Method. Eleven reverse shoulder prostheses were performed at Modena Polyclinic from October 2018 to April 2019 using GPS CT-based intraoperative navigation system (Exactech, Gainsville, Florida). In the preoperative planning, Walch classification was used to assess glenoid type. The choice of inclination of the glenoid component, the screw length, as well as the inclination of the reamer was study and recorded using specific software using the CT scan of shoulder of each patient (Fig.1, Fig.2). Intraoperative and perioperative complications were recorded. Three patients were male, eight were female. Mean age was 72 years old (range 58=84). Three glenoid were type B2, six cases were B1, two case were type C1. Results. In all cases treated by reverse shoulder prostheses we had obtain good functional results at preliminary follow up. Eight degree posterior augment was used in seven case. Planned version was 0° in eight case, an anti-version of 3° was planned in the other three cases. Final reaming was as preoperatively planned in all cases except one. Mean surgical time was 71 minutes (range 51–82). One case of coracoid rupture has been reported. In all cases the system worked in proper manner without failures, no case of infection was reported. Discussion. It is well known as the more accurate placement of the glenoid led to enhanced long-term survivorship of the implant and decrease complication rates in RSTA. Our first experience with GPS navigation system has been satisfied. Good components’ positioning has been reached in all cases, without deviation from the preoperative planning. Pre-operative preparation using software has been always respected except in one case in which we decided to ream 1mm less to avoid excessive bone loss. In 3 case we decide to increase glenoid anti-version to allow a good cage containment in the scapula. No failure of the system has been recorded, with a little increase in the surgical time respect to traditional surgeries performed in our institute. The first case performed reported coracoid fracture, probably due to lack of experience in coracoid tracker positioning. It is very important to set the surgical theatre and the position of the patient in order to make the coracoid tracker visible for the computer. Screw positioning and length is decisively improved with GPS system compared with traditional implant. The most important advantage is to avoid the malposition of the glenoid component, solving problems like loosening or restriction in shoulder range of motion. We believe that a final cross check between preoperative planning and final control of the prostheses implanted, should be used in the future, but by now the GPS navigation system is a useful way to improve our surgery, especially in difficult cases. For any figures or tables, please contact the authors directly

A prospective cohort outcome evaluation of unstable thoracic spine fractures treated with posterior pedicle screw fixation. The purpose of this study was to determine the accuracy of placement and safety of pedicle screws in open reduction of unstable thoracic spine fractures. The surgeries were performed by one of five fellowship trained spinal surgeons. CT scans were formed on twenty-three patients totaling two hundred screws using 3mm cuts. Three independent reviewers assessed and categorized the screw position as within the pedicle or as a violation of the pedicle wall. 98% of the screws were accurate and we recommend the use of pedicle screws in thoracic fractures . A prospective cohort outcome evaluation of unstable thoracic spine fractures treated with posterior pedicle screw fixation. This study is to determine the accuracy of placement, safety of pedicle screws in open reduction of unstable thoracic spine fracture. Surgery was performed by one of five fellowship trained spine surgeons. CT scans were performed on twenty-three patients using 3mm cuts in both sagittal and transverse planes. Pedicle screw position was assessed by three independent reviewers. Screw position was categorized as within the wall of the pedicle or in violation of the wall. Further sub-classification of pedicle wall violation reviewed the direction and distance of perforation. Independent perioperative and postoperative surveillance for complications was done. Twenty-three unstable thoracic spine fractures treated with two hundred posterior pedicle screws were analyzed. The pedicle screws spanned from T1-T12 with the majority of screws in the mid-thoracic region. Of the two hundred thoracic pedicle screws placed, 70% were fully contained within the pedicle wall. The remaining screws were deemed “out” with cortical perforation (30%). Of these, 20% were lateral perforations, 5% were medial perforations and 5% were anterolateral perforations. No superior, inferior, or anteromedial perforations were found. There was no regional area variation in incidence of perforations. 10% of all perforations were directly related to pedicle diameter to screw diameter mismatch. There were no adverse neurological, vascular, or visceral injuries detected intraoperatively or postoperatively. Surgical management of unstable thoracic spine fractures with posterior pedicle screw fixation is safe. 98% of screws had satisfactory accuracy. Although very minor misplacement of pedicle screws occurred, there were no complications and we recommend the use of pedicle screws in thoracic fractures

Purpose of study:. Reverse shoulder arthroplasty is effective in the management of symptomatic arthritic shoulders with a non-reconstructable rotator cuff. Optimal orientation and initial fixation of the glenoid component is correlated with improved outcomes. This may be difficult to achieve with distorted glenoid morphology. The authors present a previously undescribed system for accurate, consistent and reliable screw placement for fixation of the glenoid component with the desired version during reverse shoulder arthroplasty. Description of methods:. The pre-operative CT scan images are used to construct a scapula model (Medical Image Processing software, CustomMed Orthopaedics)allowing the surgeon to determine the optimal position for screw placement based on available bone stock. A custom drill guide is made from polyamide, which is sterilized in an autoclave and fitted to the glenoid intra-operatively prior to reaming. The system minimizes the likelihood of malposition of glenoid components and is compatible with all arthroplasty systems. Summary of results:. The technique has been performed on 5 patients after informed consent. Post-operative CT images demonstrate intended component version and screw position in all cases. Patients are being recruited for a multicenter prospective trial. Conclusion:. The authors present a new technique for achieving optimal screw position in fixation of glenoid components. A prospective trial is underway which aims to prove through post-operative imaging that intended glenoid version and screw placement was achieved and show improved long term results

Introduction. IM (Intra Medullary) nail fixation is the standard treatment for diaphyseal femur fractures and also for certain types of proximal and distal femur fractures. Despite the advances in the tribology for the same, cases of failed IM nail fixation continue to be encountered routinely in clinical practice. Common causes are poor alignment or reduction, insufficient fixation and eventual implant fatigue and failure. This study was devised to study such patients presenting to our practice and develop a predictive model for eventual failure. Materials and Methods. 57 patients who presented with failure of IM nail fixation (± infection) between Jan 2011 – Jun 2020 were included in the study and hospital records and imaging reviewed. Those fixed with any other kinds of metalwork were excluded. Classification for failure of IM nails – Type 1: Failure with loss of contact of lag screw threads in the head due to backing out and then rotational instability, Type 2A: Failure of the nail at the nail and lag screw junction, Type 2B: Failure of the screws at the nail lag screw junction, Type 3: Loosening at the distal locking sites with or without infection. X-rays reviewed and causes/site of failure noted. Results. Total patients - 57. Demography - Average age - 58.9 years, 22 Males and 35 females. Eleven patients were noted to have an infection at the fracture site that needed oral or IV antibiotics.16 patients - at least 1 cerclage wire for fracture reduction and fixation + IM Nail. Subtrochanteric fractures (42/57) were the most common to fail. In those fractures with postero-medial comminution, locking of the lag screw in position thus preventing backout can prevent failure. In type 2 failures, preventing varus fixation by early open reduction and temporary fixation with plates and screws can achieve improved results. Those with type 3 failures with periosteal reaction should be considered to be infected until proven otherwise. Conclusions. This classification for failure of IM nails in the femur can be used as a predictive model for failures and allow early recognition and intervention to tackle them

During the last decade or more, the anchors used for instrumentation in scoliosis surgery are predominantly transpedicular screws, according to Suk. The long term radiographical feature of screw fixation after scoliosis surgery is not previously studied. A consecutive series of 81 cases with AIS operated on with an all screw construct has been studied by means of low dose CT postoperatively and at 2 years postoperatively. There were 67 females and 14 males, with a mean age of 18.3 ± 3 years. In 26 / 81 (32 %) there were signs of loosing of one or more screws, at a maximum 3 screws. We observed loosened screws in the upper thoracic region in 16 cases, in the thoracolumbar 6 and in lumbar area in 4. Mean pre-op Cobb angle was 56 in cases of loosening and 53 of intact screw fixation (n.s.), the correction rate was 69% in loosened vs 70% among intact screws (n.s.). In males there were signs of loosening in 8/14 (57%) and in females 18/67 (27%). Among cases with loosening, 14% had suboptimal screw positioning postoperatively, in intact cases it was observed in 11% (n.s.). In the whole group there were signs of suboptimal screw positioning 12%. Clinically, 1 case had a loosened L4 screw replaced; and at all 21/26 had no complaints and 5/26 reported minor pain or discomfort. 1/26 had a minor proximal junctional kyphosis about 10°, in 3/26 there was a pull-out of some few mms. With plain radiography loosening could be observed in 11/26 cases; 5 were in the lumbar region. In a consecutive series of 81 adolescents with idiopathic scoliosis who had underwent scoliosis surgery according to Suk, one third showed, 2 years after the intervention, some minor screw loosening, assessed by low dose CT. One patient had one lumbar screw replaced and only 5 patients reported minor discomfort. Males were more prone to develop screw loosening

Aims

The aim of this study was to assess the accuracy of pedicle screw placement, as well as intraoperative factors, radiation exposure, and complication rates in adult patients with degenerative disorders of the thoracic and lumbar spines who have undergone robotic-navigated spinal surgery using a contemporary system.

Aims

Proper preoperative planning benefits fracture reduction, fixation, and stability in tibial plateau fracture surgery. We developed and clinically implemented a novel workflow for 3D surgical planning including patient-specific drilling guides in tibial plateau fracture surgery.

Aims

Total hip arthroplasty (THA) is considered the preferred treatment for displaced proximal femoral neck fractures. However, in many countries this option is economically unviable. To improve outcomes in financially disadvantaged populations, we studied the technique of concomitant valgus hip osteotomy and operative fixation (VOOF). This prospective serial study compares two treatment groups: VOOF versus operative fixation alone with cannulated compression screws (CCSs).

To date, the fixation of proximal humeral fractures with angular stable locking plates is still insufficient with mechanical failure rates of 18% to 35%. The PHILOS plate (DePuy Synthes, Switzerland) is one of the most used implants. However, this plate has not been demonstrated to be optimal; the closely symmetric plate design and the largely heterogeneous bone mineral density (BMD) distribution of the humeral head suggest that the primary implant stability may be improved by optimizing the screw orientations. Finite element (FE) analysis allows testing of various implant configurations repeatedly to find the optimal design. The aim of this study was to evaluate whether computational optimization of the orientation of the PHILOS plate locking screws using a validated FE methodology can improve the predicted primary implant stability. The FE models of nineteen low-density (humeral head BMD range: 73.5 – 139.5 mg/cm3) left proximal humeri of 10 male and 9 female elderly donors (mean ± SD age: 83 ± 8.8 years) were created from high-resolution peripheral computer tomography images (XtremeCT, Scanco Medical, Switzerland), using a previously developed and validated computational osteosynthesis framework. To simulate an unstable mal-reduced 3-part fracture (AO/OTA 11-B3.2), the samples were virtually osteotomized and fixed with the PHILOS plate, using six proximal screws (rows A, B and E) according to the surgical guide. Three physiological loading modes with forces taken from musculoskeletal models (AnyBody, AnyBody Technology A/S, Denmark) were applied. The FE analyses were performed with Abaqus/Standard (Simulia, USA). The average principal compressive strain was evaluated in cylindrical bone regions around the screw tips; since this parameter was shown to be correlated with the experimental number of cycles to screw cut-out failure (R2 = 0.90). In a parametric analysis, the orientation of each of the six proximal screws was varied by steps of 5 in a 5×5 grid, while keeping the screw head positions constant. Unfeasible configurations were discarded. 5280 simulations were performed by repeating the procedure for each sample and loading case. The best screw configuration was defined as the one achieving the largest overall reduction in peri-screw bone strain in comparison with the PHILOS plate. With the final optimized configuration, the angle of each screw could be improved, exhibiting significantly smaller average bone strain around the screw tips (range of reduction: 0.4% – 38.3%, mean ± SD: 18.49% ± 9.56%). The used simulation approach may help to improve the fixation of complex proximal humerus fractures, especially for the target populations of patients at high risk of failure

The extended lateral approach offers a safe surgical approach in the fixation of calcaneal fractures. Lateral plating of the calcaneum could put structures on the medial side at risk. The aim was to identify structures at risk on the medial side of the calcaneum from wires, drills or screws passed from lateral to medial. Ten embalmed cadaveric feet were dissected. A standard extended lateral approach was performed. The DePuy perimeter plate was first applied and 2mm K-wires were drilled through each of the holes. The medial side was now examined to determine the structures at risk through each hole. The process was repeated with the Stryker plate. The calcaneum was divided into 6 zones, by two vertical lines, from the margins of the posterior facet and a transverse line along the axis of the bone through the highest point of the peroneal tubercle. The DePuy and the Stryker plates have 12 screw positions, 5 of which are common. With both systems, screw positions in zone 1 risk injury to the medial plantar nerve and zone 3 the lateral plantar nerve. A screw through zone 2 compromises the medial plantar in both. Screws through zone 4 risk the lateral plantar nerve with the DePuy plate. Screws through zone 5 of the DePuy plate risk the medial calcaneal nerve. Zone 5 of the Stryker plate and Zone 6 of both are safe. There is significant risk to medial structures from laterally placed wires, drills or screws. Subtalar screws have the highest risk and have to be carefully measured and placed. The Stryker plating system is relatively safer than the DePuy perimeter plate with three safe zones out of six

Aims

Proximal femur fractures treatment can involve anterograde nailing with a single or double cephalic screw. An undesirable failure for this fixation is screw cut-out. In a single-screw nail, a tip-apex distance (TAD) greater than 25 mm has been associated with an increased risk of cut-out. The aim of the study was to examine the role of TAD as a risk factor in a cephalic double-screw nail.

In orthopaedic spine surgery pedicle screw systems are used for stabilisation of the spine after injuries or disorders. With an percutaneous operation method surgeons are faced with huge challenges compared to an open surgery, but it's less traumatic and the patient benefits with a faster rehabilitation and less traumatic injuries. The screw positions and the required rod dimensions for the stabilising connection between the screws are hard to define without an open view on the operating field. Because of these facts a new smart device based system for rod shape determination was invented. Therefore, an application was developed, which integrates a localiser module to get the position data of the pedicle screws, with help of rigid bodies placed on top of the pedicle screws down-tubes. An algorithm was developed to choose the best fitting rod to connect the pedicle screws with help of calculating the rod length and the rod radius. The system was tested in a test scenario where four pedicle screws were drilled into a wooden plate. The positions of the screws were adjusted to fit a curved and a straight rod. In the test scenario the application chose always the rod correctly

Aims

To evaluate if, for orthopaedic trainees, additional cadaveric simulation training or standard training alone yields superior radiological and clinical outcomes in patients undergoing dynamic hip screw (DHS) fixation or hemiarthroplasty for hip fracture.

Aims

The aim of this study was to examine the implant accuracy of custom-made partial pelvis replacements (PPRs) in revision total hip arthroplasty (rTHA). Custom-made implants offer an option to achieve a reconstruction in cases with severe acetabular bone loss. By analyzing implant deviation in CT and radiograph imaging and correlating early clinical complications, we aimed to optimize the usage of custom-made implants.

Over the past four decades, internal fixation has continued to gain popularity as a method for treating fractures because of significant improvements in both implant design and materials. This biomechanical study compares the compressive forces generated by a conventional 4.5 AO/ASIF cortical screw lag screw with a differential pitch cortical compression screw in a simulated fracture model using whole bone composite femur. The differential pitch screw investigated in this study generates 82% of the compression generated by a conventional 4.5mm AO/ASIF cortical screw. Proving compression in diaphyseal fractures is achievable using a differential pitch screw. Sufficient compression is generated to allow osteosynthesis using a plate to be preformed independent of the lag screw positioning. It is thus advantageous over the traditional compromise that arises when exposure to the fracture site is limited, of either incorporating the lag screw into the plate of choosing a non-optimal plate or screw position. It is proposed as an adjunct to the internal fixation of long bone fractures and not a single fixation device

Purpose of study: A single dynamic hip screw is the recommended method of fixation for slipped upper femoral epiphysis (SUFE). Current practice favours placement of the screw in the centre of the femoral head on both anteroposterior and lateral planes. This study investigated screw placement in the femoral head for SUFE and the prevalence of AVN, chondrolysis, late slippage, and time to physeal closure. Method: Clinical notes and radiographs of 38 consecutive patients (61 hips), who underwent single screw fixation for SUFE, were evaluated retrospectively with a minimum follow up of 24 months (24–56). Two way ANOVA and post hoc tests were performed to analyse the correlation between the different variables and the outcome, at a 5% significance level. Results: There were 16 acute slips, 18 chronic slips and 10 acute on chronic slips. 17 slips were treated prophylactically. Mild slip was noted in 39 hips, moderate in 4 and severe in 1 hip. A central-central position was only achieved in 50% of cases. No significant difference between the time to physeal closure and the screw position was found. No late slippage, AVN or chondrolysis occurred in this series. Conclusions: Our results demonstrate that positions of the screw, other than in the centre of the femoral head, provide adequate stability. There is no correlation between screw position and the time to physeal closure, the risk of avascular necrosis or chondrolysis. We recommend that positions other than the “optimal central-central position” be accepted if not initially achieved, especially for mild SUFE. The potential hazards from several attempts to achieve the optimum position outweigh the benefits

The February 2023 Spine Roundup³⁶⁰ looks at: S2AI screws: At what cost?; Just how good is spinal deformity surgery?; Is 80 years of age too late in the day for spine surgery?; Factors affecting the accuracy of pedicle screw placement in robot-assisted surgery; Factors causing delay in discharge in patients eligible for ambulatory lumbar fusion surgery; Anterior cervical discectomy or fusion and selective laminoplasty for cervical spondylotic myelopathy; Surgery for cervical radiculopathy: what is the complication burden?; Hypercholesterolemia and neck pain; Return to work after surgery for cervical radiculopathy: a nationwide registry-based observational study.

Introduction Intertrochanteric fractures are common and represent a major source of morbidity and mortality. As with all orthopaedic implants a DHS can fail. One of the most important predictors of failure has been shown to be the Tip-Apex Distance (TAD). An audit was carried to assess the following:. What was our rate of cut out and implant failure?. Where we achieving an acceptable screw position and TAD?. Was there any difference between TAD and grade of surgeon?. Methods An audit of the case notes and x-rays of 54 consecutive patients with hip fractures, treated with DHS, within a twelve-month period were reviewed. Demographic data, grade of surgeon, fracture stability, DHS position, mortality and implant failure were assessed. Findings Our rate of failure was 2 out of 54 patients, 3.7%. Both of the patients that failed had a TAD of greater than 20mm, and none of the patients with a TAD below 20mm required further surgery. There was no statistical correlation between TAD and grade of operating surgeon. Recommendations It is paramount importance to ensure that the basic principles of DHS position are well taught to surgical trainees in order to reduce the risk of failure. Following DHS fixation, patients should be followed up for a minimum of 3 months until evidence of radiographic union is evident. DHS failure rates and screw positions should be constantly audited to ensure that failure rates are minimised

Aims

Our objective was describing an algorithm to identify and prevent vascular injury in patients with intrapelvic components.

Background. Hip fractures cause significant morbidity and mortality, affecting 70,000 people in the UK each year. The dynamic hip screw (DHS) is used for the osteosynthesis of extracapsular neck of femur fractures, a procedure that requires complex psychomotor skills to achieve optimal lag screw positioning. The tip-apex distance (TAD) is a measure of the position of the lag screw from the apex of the femoral head, and is the most comprehensive predictor of cut-out (failure of the DHS construct). To develop these skills, trainees need exposure to the procedure, however with the European Working Time Directive, this is becoming harder to achieve. Simulation can be used as an adjunct to theatre learning, however it is limited. FluoroSim is a digital fluoroscopy simulator that can be used in conjunction with workshop bones to simulate the first step of the DHS procedure (guide-wire insertion) using image guidance. This study assessed the construct validity of FluoroSim. The null hypothesis stated that there would be no difference in the objective metrics recorded from FluoroSim between users with different exposure to the DHS procedure. Methods. This multicentre study recruited twenty-six orthopaedic doctors. They were categorised into three groups based on the number of DHS procedures they had completed as the primary surgeon (novice <10, intermediate 10≤x<40 and experienced ≥40). Twenty-six participants completed a single DHS guide-wire attempt into a workshop bone using FluoroSim. The TAD, procedural time, number of radiographs, number of guide-wire retires and cut-out rate (COR) were recorded for each attempt. Results. A significant construct effect was seen for TAD and COR between novice and other users (p < 0.05). The intermediate and experienced users were not significantly different for these metrics. For all other metrics, experienced users had the highest score, contrary to expectation. Conclusion. FluoroSim was able to separate novice users from other cohorts for the two clinically significant outcome metrics. We can therefore partially reject the null hypothesis as construct validity was present for TAD and COR. We have demonstrated that FluoroSim has the potential to be a useful adjunct when learning the psychomotor skills needed for the DHS procedure away from theatre

Pedicle screw fixation is a technically demanding procedure with potential difficulties and reoperation rates are currently on the order of 11%. The most common intraoperative practice for position assessment of pedicle screws is biplanar fluoroscopic imaging that is limited to two- dimensions and is associated to low accuracies. We have previously introduced a full-dimensional position assessment framework based on registering intraoperative X-rays to preoperative volumetric images with sufficient accuracies. However, the framework requires a semi-manual process of pedicle screw segmentation and the intraoperative X-rays have to be taken from defined positions in space in order to avoid pedicle screws' head occlusion. This motivated us to develop advancements to the system to achieve higher levels of automation in the hope of higher clinical feasibility. In this study, we developed an automatic segmentation and X-ray adequacy assessment protocol. An artificial neural network was trained on a dataset that included a number of digitally reconstructed radiographs representing pedicle screw projections from different points of view. This model was able to segment the projection of any pedicle screw given an X-ray as its input with accuracy of 93% of the pixels. Once the pedicle screw was segmented, a number of descriptive geometric features were extracted from the isolated blob. These segmented images were manually labels as ‘adequate’ or ‘not adequate’ depending on the visibility of the screw axis. The extracted features along with their corresponding labels were used to train a decision tree model that could classify each X-ray based on its adequacy with accuracies on the order of 95%. In conclusion, we presented here a robust, fast and automated pedicle screw segmentation process, combined with an accurate and automatic algorithm for classifying views of pedicle screws as adequate or not. These tools represent a useful step towards full automation of our pedicle screw positioning assessment system

Pedicle screws allow for biomechanically secure fixation of the spine. However if they are misplaced they may effect the strength of the fixation, damage nerve roots or compromise the spinal cord. For these reasons image guidance systems have been developed to help with the accuracy of screw placement. The accuracy of pedicle screw placement outside the lumbar spine is not well published. To determine the accuracy of pedicle screw placement using CT scanning post operatively. Cortex perforations were graded in 2mm steps. Prospective observational study. Plain x-rays are inaccurate for determining screw placement and therefore high definition CT scanning was used. The screw positioning on the post-operative CT scans was independently determined by a research registrar who was not present at the time of surgery. Screw position and clinical sequelae of any malposition. Thirty patients (13 F:17 M) with segmental instability. Twelve were for metastatic disease, seven for trauma, seven for spondylolisthesis, three for atlanto-axial instability and one for a vertebral haemangioma. All patients were operated on by the senior author. One hundred and seventy six pedicle screws were inserted in the thirty patients over the 20 month study period. Six screws violated the lateral cortex of the pedicle but none perforated the medial cortex. There were no adverse neurological sequelae. The findings from this study will serve as a good comparison with future studies on pedicle screw placement, which may claim to improve accuracy and safety by the use of image guidance systems, electrical impedance or malleable endoscopes

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

Aims

The aim of this study was to compare outcomes of guided growth and varus osteotomy in treating Kalamchi type II avascular necrosis (AVN) after open reduction and Pemberton acetabuloplasty for developmental dysplasia of the hip (DDH).

Aims

Ilium is the most common site of pelvic Ewing’s sarcoma (ES). Resection of the ilium and iliosacral joint causes pelvic disruption. However, the outcomes of resection and reconstruction are not well described. In this study, we report patients’ outcomes after resection of the ilium and iliosacral ES and reconstruction with a tibial strut allograft.

Purpose: The purpose of this work was to compare the precision and reliability of screw fixation using two different guiding systems. The first system was based on computed tomography (CT) imaging and the second on digitalized fluoroscopic imaging. Material and methods: Between 1998 and 2000, 88 patients underwent spinal fixation for diverse disease states (idiopathic scoliosis in 43, and fracture, spondylolisthesis or instability in 45). Pedicular screws (n = 223) were inserted in levels T4 to S1. The passive CT navigation system was used for 73 patients (177 pedicular screws) and the fluoroscopic navigation system for 15 (46 pedicular screws). An independent observer identified the position of the pedicular screws on the postoperative CT. Results: Among the 73 patients who underwent a CT-guided procedure (177 pedicular screws) the rate of incorrect screw position was 6.2% (11/117) with = 2 mm penetration of the cortical. Among the 15 patients who underwent a fluoroscopy-guided procedure (46 pedicular screws), the rate of incorrect screw position was 17% (8/46) again with = 2 mm penetration of the cortical. For scoliosis patients, the rate of erroneous screw insertion was 6% for CT navigation and 28% for fluoroscopic navigation. For fractures and degenerative instability, the rates were 6% and 11% respectively. Discussion: The passive nature of the two navigation systems used do not induce any peroperative constraint on the surgeon. With the CT system, landmarks have to be collected peroperatively on the posterior arch of the operated vertebra, a step that is not needed for the fluoroscopic system. The two techniques appear to be reliable for insertion of pedicular screws. We did not have any neurological disorders in this series. It can be recalled that the conventional method produces a 15 to 40% rate of erroneous insertion. The CT system provides better results for all types of diseases; the improvement is about 6%. Conclusion: With CT-navigation, a large portion of the per-operative radiographs are no longer necessary. Operative time is slightly longer than for the classical procedure due to the collection of the 3D information, particularly important for scoliosis. With the fluoroscopy system, no special preoperative imaging is required. Two or three peroperative radiographs are sufficient, limiting irradiation during insertion of the pedicular screws. The fluoroscopic system does not however provide 3D images