Nearly a quarter of screws cause damage during insertion by stripping the bone, reducing pullout strength by over 80%. Studies assessing surgically achieved tightness have predominately shown that variations between individual surgeons can lead to underpowered investigations. Further to the variables that have been previously explored, several basic aspects related to tightening screws have not been evaluated with regards to how they affect screw insertion. This study aims to identify the achieved tightness for several variables, firstly to better understand factors related to achieving optimal intraoperative screw purchase and secondly to establish improved methodologies for future studies. Two torque screwdrivers were used consecutively by two orthopaedic surgeons to insert 60 cortical, non-locking, stainless-steel screws of 3.5 mm diameter through a 3.5 mm plate, into custom-made 4 mm thick 20 PCF sheets of Sawbone, mounted on a custom-made jig. Screws were inserted to optimal tightness subjectively chosen by each surgeon. The jig was attached to a bench for vertical screw insertion, before a further 60 screws were inserted using the first torque screwdriver with the jig mounted vertically, enabling horizontal screw insertion. Following the decision to use the first screwdriver to insert the remaining screws in the vertical position for the other variables, the following test parameters were assessed with 60 screws inserted per surgeon: without gloves, double surgical gloves, single surgical gloves, non-sterile nitrile gloves and, with and then without augmented feedback (using digitally displayed real-time achieved torque). For all tests, except when augmented feedback was used, the surgeon was blinded to the insertion torque. Once the stopping torque was reached, screws were tightened until the stripping torque was found, this being used to calculate tightness (stopping/stripping torque ratio). Screws were recorded to have stripped the material if the stopping torque was greater than the stripping torque. Following tests of normality, Mann-Whitney-U comparisons were performed between and combining both surgeons for each variable, with Bonferroni corrections for multiple comparisons. There was no significant (p=0.29) difference in the achieved tightness between different torque screw drivers nor different jig positions (p=0.53). The use of any gloves led to significant (p < 0 .001) increases in achieved tightness compared to not using gloves for one surgeon but made no difference for the other (p=0.38–0.74). Using augmented feedback was found to virtually eliminate stripping. For one surgeon average tightness increased significantly (p < 0 .001) when torque values were displayed from 55 to 75%, whilst for the other, this was associated with significantly decreases (p < 0 .001), 72 to 57%, both surgeons returned to their pre-augmentation tightness when it was removed. Individual techniques make a considerable difference to the impact from some variables involved when inserting screws. However, the orientation of screws insertion and the type of screwdriver did not affect achieved screw tightness. Using visual feedback reduces rates of stripping and investigating ways to incorporate this into clinical use are recommended. Further work is underway into the effect of other variables such as bone density and cortical thickness

Purpose:. To determine the insertion of the different layers of the rotator cuff and apply it to rotator cuff tears. Anatomical insertion of the rotator cuff holds the key to a proper anatomical repair. Method:. A study of the rotator cuff insertion was done in conjunction with MSc student department Anatomy. The rotator cuff consists of a capsular and tendinous layer. They have different mechanical properties. The capsular layer inserts ± 3 mm more medially on the tuberosity and the tendinous layer more laterally. It was shown that the superficial layer extends beyond the greater tuberosity and connects the supra-spinatus tendon to the sub-scapularis tendon via the bicepital groove. This connection was called the “rotator hood”. The “rotator hood” has a mechanically advantageous insertion, is a strong structure with a compressive force on the proximal humerus. Conclusion:. 1. The rotator cuff inserts on the greater tuberosity as two separate entities. 2. The capsular layer inserts on the more medial 2–3 mm. 3. The tendinous layer is attached over a broader more lateral area giving it a mechanical advantage. 4. The tendinous layer of supra-spinatus extends beyond the tuberosity to connect to the sub-scapularis tendon providing an even greater mechanical advantage

Purpose. Current methods for inserting a press fit hemispherical metal-backed acetabular component within the acetabula are uncontrolled, relying on the surgeon to generate the necessary forces required for sufficient introduction. While previous studies have recorded impact forces of 2–3 kN necessary to seat an acetabular cup using visual observation[1], some researchers have observed users imparting as high as 8.9 kN of force[2]. The aim of this study is to quantify the forces required to generate optimal implant primary stability, as well as compare force delivery methods. Method. The experiments were carried out using prepared bone substitute. A high frequency force sensor was rigidly mounted under the substitute to measure impact force and duration. An acetabular cup was inserted using successive reproducible impacts of varying magnitude (2.5 kg falling 17, 34, 43, 51, 68, or 85 mm). Impacts were repeated until the cup was no longer advancing. Each test recorded the number of impacts, maximum impact force, impact duration, and extraction force of the cup after insertion. The results were then compared against manual insertion (tapping) and high frequency vibratory insertion (50–500 Hz). Results. As shown in figure 1, an exponential relationship was found between the maximum impact force and cup extraction force (R. 2. = 0.97), with a mean impact force of 4200 N at full insertion. By contrast, manual insertion resulted in maximum impacts 30% greater on average, with no discernible increase in extraction force. High frequency vibratory insertion resulted in a linear relationship (R. 2. = 0.86) with a maximum extraction force of 335 N. Conclusion. Manual insertion has been shown to result in excessive force being used. This may result in additional stress to the acetabula, although additional study is needed to determine the clinical relevance. High frequency vibratory insertion has shown promise of reducing the impact forces required, with ongoing study of the effect at higher impact forces

Background:. During the past two decades the medial Patellofemoral ligament has come to the fore as the essential lesion of acute patella dislocation and its reconstruction in cases of chronic instability seems logical. The femoral insertion of the medial Patellofemoral ligament (MPFL) is key to the isometry or desired anisometry of the reconstruction. Radiographic landmarks for the femoral insertion has been described in literature most notably by Schottle et al. AJSM 2007. We examined the consistency of these landmarks of the femoral insertion of the MPFL. Methods:. 24 unpaired knees of cadavaric specimen were dissected for the origin of the MPFL. A radiographic marker was then placed in the centre of the femoral attachment of the MPFL and a direct lateral X-ray obtained of the distal femur. The sweet spot was defined according to the landmarks described by Schottle et al and deviation from the sweet spot was measured. Results:. The average distance from the centre of the described radiological centre of the MPFL was 5.4 mm. In six cases the ligament insertion was 5.6 mm distal to the ideal radiological centre. We did not find the origin of the MPFL to be a consistent radiological landmark due to a wide insertion of the ligament on the femur with a variable anisometric centre. We recommend dynamically testing the insertion site of the MPFL around a guide wire inserted into the femur instead of relying solely on the radiological position

Introduction. Aseptic acetabular component failure rates have been reported to be similar or even slightly higher than femoral component failure. Obtaining proper initial stability by press fitting the cementless acetabular cup into an undersized cavity is crucial to allow for secondary osseous integration. However, finding the insertion endpoint that corresponds to an optimal initial stability is challenging. This in vitro study presents an alternative method that allows tracking the insertion progress of acetabular implants in a non-destructive, real-time manner. Materials and Methods. A simplified acetabular bone model was used for a series of insertion experiments. The bone model consisted of polyurethane solid foam blocks (Sawbones #1522-04 and #1522-05) into which a hemispherical cavity and cylindrical wall, representing the acetabular rim, were machined using a computer numerically controlled (CNC) milling machine (Haas Automation Inc., Oxnard, CA, USA). Fig. 1 depicts the bone model and setup used. A total of 10 insertions were carried out, 5 on a low density block, 5 on a high density block. The acetabular cups were press fitted into the bone models by succeeding hammer hits. The acceleration of the implant-insertor combination was measured using 2 shock accelerometers mounted on the insertor during the insertion process (PCB 350C03, PCB Depew, NY, USA). The force applied to the implant-insertor combination was also measured. 15 hammer hits were applied per insertion experiment. Two features were extracted from the acceleration time signal; total signal energy (E) and signal length (LS). Two features and one correlation measure were extracted from the acceleration frequency spectra; the relative signal power in the low frequency band (PL, from 500–2500Hz) and the signal power in the high frequency band (P Hf, from 4000–4800 Hz). The changes in the low frequency spectra (P Lf, from 500–2500 Hz) between two steps were tracked by calculating the Frequency Response Assurance Criterion (FRAC). Force features similar to the ones proposed by Mathieu et al., 2013 were obtained from the force time data. The convergence behavior of the features was tracked as insertion progressed. Results. Differences were noted visually between the acceleration data recorded at the beginning of insertion and towards the end, both in the time domain (fig. 2A) as well as in the frequency domain (fig. 2B). These differences were also captured by the proposed features. Fig. 3 shows a typical representation of how the time (A), frequency (B) and force (C) features evolved during insertion. Based on a simple convergence criterion, the insertion endpoint could be determined. Conclusions. The convergence behavior, and the insertion endpoint thus identified, of the force-based and acceleration based features correlated well. The different features capture the changes in damping and stiffness of the implant-bone system that are occurring as the insertion progresses and combining them improves the robustness of the endpoint detection method. For any figures or tables, please contact the authors directly

Introduction. Since 1989, we have been developing lateral flare stem. The concept of lateral flare stem is to deliver proximal part big enough to fill the proximal cavity that most of the cement stems can fill and most of the cementless stems cannot. Also having distal part polished, much less distal load transfer occurs than cement stem. Thus, we can expect high proximal load transfer to prevent stress shielding. To deliver lateral flare stem, straight insertion path cannot be available, as proximal lateral part to fill inside the greater throchanter collides to the greater trochanter. So 3-Dimension insertion path was calculated to deliver that part through the narrow made by neck osteotomy. The first generation of the lateral flare stem was custom made. The second generation was designed as an off-the-shelf stem from what we have learned by the experience of custom stems. With the third generation, the stem was shortened to achieve more proximal load transfer. Direct Anterior Approach (DAA) developed by Judet is one of less invasive hip approach. With a stem with straight insertion path, the extended line of proximal femoral axis should come out of the skin. To achieve this position, proximal end of the femur has to be fully pulled up. (Fig.1) Some of the cases would be able to be lifted up but some have difficulty. Using lateral flare stem with curved 3 dimensional insertion path, even the axis extension does not come out of the skin, it would be expected to be inserted. In the present study, 3D insertion path of the lateral flare short stem for DAA was analyzed. Materials and methods. Preoperative CAT scan data were transferred to STL data by Mimics®. The procedures after that were done by Magics®. First, neck osteotomy was done, externally rotated, and mild extension that doesn't make the axis come out of the skin was added. Then insertion path was verified keeping the stem attached medial sidewall of the canal (Fig. 2). In actual case, skin translation and pelvis rotation was assessed by 3D scanner. (Fig. 3). Results. Three D scanner revealed that the pelvis rotation is less than detective limit, and the upper skin incision where the stem passes remains almost the same place by dropping the leg. Lateral flare short stem could be inserted without lifting the femur out of the skin. So it was expected that lateral flare short stem has high applicability for DAA. Discussion. We can expect less invasive THA with DAA. However, once we have problem during surgery such as hard insertion or fracture and so forth, it is very hard to recover from those difficulties, because with supine position we cannot access posterior side of the leg. By easier insertion, less stress for bone and other tissues, we can reduce the risks. Even cases with easier femoral lift up, pulling femur less can reduce those risks

Introduction. Each year, a large number of total hip arthroplasties (THA) are performed, of which 60 % use cementless fixation. The initial fixation is one of the most important factors for a long lasting fixation [Gheduzzi 2007]. The point of optimal initial fixation, the endpoint of insertion, is not easy to achieve, as the margin between optimal fixation and a femoral fracture is small. Femoral fractures are caused by peak stresses induced during broaching or by the hammer blows when the implant is excessively press-fitted in the femur. In order to reduce the peak stresses during broaching, IMT Integral Medizintechnik (Luzern, Switzerland) designed the Woodpecker, a pneumatic broach that generates impulses at a frequency of 70 Hz. This study explores the feasibility of using the Woodpecker for implant insertion by measuring both the strain in the cortical bone and the vibrational response. An in vitro study is presented. Material and Methods. A Profemur Gladiator modular stem (MicroPort Orthopedics Inc. Arlington, TN, USA) and two artificial femora (composite bone 4th generation #3403, Sawbones Europe AB, Malmö, Sweden) were used. One artificial femur was instrumented with three rectangular strain gauge rosettes (Micro-Measurements, Raleigh, NC, USA). The rosettes were placed medially, posteriorly and anteriorly proximally on the cortical bone. Five paired implant insertions were repeated on both artificial bones, alternating between standard hammering and Woodpecker insertions. During the insertion processes the vibrational response was measured at the implant and Woodpecker side (fig. 1) using two shock accelerometers (PCB Piezotronics, Depew, NY, USA). Frequency spectra were derived from the vibrational responses. The endpoint of insertion was defined as the point when the static strain stopped increasing during the insertion. Results. Peak stress values calculated out of the strain measurement during the insertion showed to be significantly (p < 0.05) lower at two locations using the Woodpecker compared to the hammer blows at the same level of static strain. However, the final static strain at the endpoint of insertion was approximately a factor two lower using the Woodpecker compared to the hammer. During the last hammer insertion a fracture occurred, which was clearly visible in the frequency spectra. Figure 2 shows the sudden change between the spectra of the hit prior and after the fracture. Discussion/Conclusion. Peak stresses showed to be lower using the Woodpecker compared to hammer insertion, which is a promising result concerning fracture prevention. However it needs to be taken into account that it was not possible to reach the same level of static strain using the Woodpecker as with the hammer insertion. It is expected that the Woodpecker in its actual design is not able to reach a similar level of press-fit as hammer blows. Using vibrational data showed to be promising for fracture detection, as fractures are not always visible due to the soft tissue. For figures, please contact authors directly

Pedicle screw (PS) insertion has been critised for its risk of serious injury to neurovascular structures. Although computed tomography (CT)-based navigation has been developed to avoid such complications, perforation remains an issue, even with the aid of additional guidance. We clarify screw perforation rate and direction in 359 consecutive patients treated using CT-based PS insertion and present important considerations for more accurate screw placement. The medical records of 359 consecutive patients who underwent PS insertion involving C2-L5 using a CT-based navigation system were reviewed. Postoperative CT images were analysed to evaluate the accuracy of screw placement. We investigated both rate and direction of screw perforation according to vertebral level. Of the 3413 PS that were inserted, 3.0% (104/3413) were judged as Grade 3 (more than 4mm) perforations. Allover perforation rates by vertebral level were shown in Table 1. The rate of these perforations was 5.0% for C2, 7.8% for C3–5, 3.9% for C6–7, 3.4% for T1–4, 3.5% for T5–8, 1.4% for T9–12, and 1.7% for L1–5. We also analysed the odds ratio (OR) for screw perforation in vertebrae accounting for the effects of age and disease. Multivariate analysis identified that PS insertions at C3–5 (OR 4.9, 95% CI 2.2–10.9; p<0.001) were significantly associated with Grade 3 screw perforation as compared with that of L1–5. Even with CT-based navigation, careful insertion of PS is needed in the middle cervical spine because of a significantly higher perforation rate as compared with the lumbar region. For figures and tables, please contact authors directly

Introduction:. One method of femoral head preservation following avascular necrosis (AVN) is core decompression and Tantalum Rod insertion. There is, however, a published failure rate of up to 32% at 4 years. The purpose of the present study was to document the clinical and radiological outcome following Total Hip Arthroplasty (THA) subsequent to failed Tantalum Rod insertion. Methods:. Twenty-five failed Tantalum Rod insertions subsequently requiring THA were identified from a prospectively updated database. Seventeen patients met minimum 2 year clinical and radiographic follow-up criteria. St. Michael's Hip (SMH) scores were compared to a matched cohort of patients with THA for AVN without prior Tantalum Rod insertion. Postoperative radiographs were reviewed assessing component alignment, linear wear (Dorr & Wan) and presence of tantalum residue within the joint space. Results:. Nine females and eight males underwent removal of a Tantalum Rod with subsequent THA between May 2005 and March 2010. The mean time between Tantalum Rod insertion and conversion to THA was 23 months (range 6–48) with a mean follow-up of 3.5 years (range 2–5). At each follow-up interval the mean SMH scores were comparable between the two groups (p = 0.445). Femoral stem alignment (p = 0.428) and acetabular cup inclination (p = 0.723) were comparable between groups. Articular tantalum residue was identified in 12 of 17 articulations (7 mild, 3 moderate, 2 severe). Linear wear rates were comparable between the tantalum group (0.07 mm/yr, range 0.01–0.40) and controls (0.07 mm/yr, range 0.02–0.21, p = 0.951). There was no evidence of catastrophic wear. Conclusion:. Tantalum rod conversion to THA in the young adult patient with AVN reveals no early catastrophic sequelae. In the short term, Tantalum Rod insertion does not demonstrate a deleterious effect on subsequent total joint replacement surgery. There is, however, a high rate of retained tantalum debris within the effective joint space with the procedure and thus there is an unknown risk of accelerated articular wear necessitating longer term study

Simulation is an effective adjunct to the traditional surgical curriculum, though access to these technologies is often limited and costly. The objectives of this work were to develop a freely accessible virtual pedicle screw simulator and to improve the clinical authenticity of the simulator through integration of low-cost motion tracking. The open-source medical imaging and visualisation software, 3D Slicer, was used as the development platform for the virtual simulation. 3D Slicer contains many features for quickly rendering and transforming 3D models of the bony spine anatomy from patient-specific CT scans. A step-wise pedicle screw insertion workflow module was developed which emulated typical pre-operative planning steps. This included taking anatomic measurements, identifying insertion landmarks, and choosing appropriate screw sizes. Monitoring of the surgeon's simulated tool was assessed with a low-cost motion tracking sensor in real-time. This allowed for the surgeon's physical motions to be tracked as they defined the virtual screw's insertion point and trajectory on the rendered anatomy. Screw insertion was evaluated based on bone density contact and cortical breaches. Initial surgeon feedback of the virtual simulator with integrated motion tracking was positive, with no noticeable lag and high accuracy between the real-world and virtual environments. The software yields high fidelity 3D visualisation of the complex geometry and the tracking enabled coordination of motion to small changes in both translational and angular positioning. Future work will evaluate the benefit of this simulation platform with use over the course of resident spine rotations to improve planning and surgical competency

Introduction. During broach preparation and implant insertion of the proximal femur the surgeon may be able to use audible pitch changes to judge broaching adequacy and implant position. The aim of this study was to analyse the sound produced and explain the sound spectra using acoustic physics. Methods. A highly sensitive microphone was used to digitally record the sound made during femoral preparation and definitive implant insertion in 9 patients undergoing total hip arthroplasty. The sound data was analysed using a fast Fournier transformation spectrum analyser. The highest 4 peak spectral amplitudes of the first broach, the last strike of the final broach and the definitive implant were recorded. The sound spectra produced by striking the implant introducer in isolation were analysed in a similar manner. Results. Analysis of the sound spectra identified the appearance of a low frequency peak (mean 892Hz) during final broaching that was not present when using the first broach. This occurred in 6 of the 9 cases and correlated with a decrease in audible pitch heard by the surgeon. The spectra from the implant insertion also showed a low frequency peak (mean 709Hz). The implant introducer when struck in isolation produced a series of peaks that correlated closely to the predicted 3. rd. resonant mode frequencies for a metal object of the same dimensions. Discussion. Creating an envelope of compacted cancellous bone within the proximal femur causes the sound produced by the final broach to decrease in pitch. We postulate that this is due to vibration energy causing the femoral bone to resonate, and create longitudinal standing waves in the medullary canal. The additional spectral peaks are caused by transitional resonance vibrations from the implant and broach introducer construct

Introduction. Open wedge high tibial osteotomy (OWHTO) is an operation by the proper load re-distribution in the treatment for medial uni-compartmental arthritis of the knee joint. However, for the proper load re-distribution, stable fixation is mandatory. For the stable fixation, plate should be contoured to the bony surface and screws should be inserted from the central area of the medial side to the hinge area of the lateral side in the proximal fragment because most failures occur at the relatively lesser supported lateral hinge area. Therefore, the purpose of this study was to evaluate the screw insertion angle and orientation that is inserted to the direction of the lateral hinge with an anatomical plate that is post-contoured with a surface geometry of the proximal tibia after the OWHTO. The hypothesis of this study was that the position and orientation would be different according to the correction degree (median value 10 mm) and surgical technique (uni-planar vs bi-planar). Materials and Methods. Thirty-one uni-planar and thirty-eight bi-planar osteotomies were evaluated. Postoperative CT data obtained after OWHTO were used for the 3D reconstruction of the proximal tibia. Anterior dimension (L1) and posterior dimension (L2) of the proximal tibia were measured in sagittal plane from tibial spine. Screw insertion points using four holes were even distributed using L1 and L2 value. As screw insertion angle was set from four holes to lateral hinge of the ‘Safe Zone’. Those four angles were measured in the axial and coronal plane. These were compared according to the correction degree and surgical technique. Results. Anterior AP dimension ‘L1'and posterior AP dimension ‘L2'were measured 24.0 ± 3.7 mm, 22.6 ± 3.1 mm. Angulations of screw from respectively screw hole to lateral hinge were measured 11.3 ± 1.7°, 3.5 ± 1.3°, 3.1 ± 1.5°, and 9.5 ± 1.1° in the axial plane and 81.5 ± 6.0°, 101.5 ± 2.6°, 90.8 ± 3.7°, and 99.2 ± 2.8° in coronal plane, respectively. None of the comparisons were statistically different, regardless of the correction degree and operative technique (Table1). Conclusions. Range of screw angulation showed regular pattern according to the site of the screw hole and it was not different, regardless of the correction degree and operative technique. This study provided range of the screw angulation by the anatomical surface modeling. Future study would give additional benefit for the optimal screw angle and stability such as finite element analysis or other methods

To investigate the effectiveness of avulsion fracture of tibial insertion of posterior cruciate ligament using the safe postero-medial approach through analyzing the clinical and radiographic outcomes. We treated 14 cases of acute PCL tibial avulsion fracture with “safe postero-medial approach”. The PCL and avulsion bony fragment was fixed with 1 cannuated screw and washer. The patients were assessed clinically and radiographically at 3 months, 6 months, and 12 months. Clinical examination for each visit included assessment of the knee range of motion, using goniometer and the posterior drawer test. The patients were evaluated according to the Lysholm and Tegner rating scales. Patients were followed-up for 12 to 16 months. X-ray showed that satisfactory reducdtion and bony healing was achieved in all cases. There was no neurovascular complication. All patients had negative posterior drawer tests. Excellent outcomes were reported by all patients with the Lysholm score system. And there was no signicant difference between the Tegner scores before injury and last follow-up. Surgical treatment of acute tibial avulsion fracture of the PCL with this approach can restore the stability and fuction of the joint safely in most patients without neurovascular complication. Therefore “safe postero-medial approach” may be suitable for the treatment of isolated tibial avulsion fracture of the PCL

Purpose. To evaluate Radiological changes in the lumbosacral spine after insertion of Wallis Ligament for Foraminal Stenosis. Methods and Results. Thirty two Levels in Twenty Six patients were followed up with standardised radiographs after insertion of Wallis Ligaments for Foraminal Stenosis. Wallis ligaments as a top-off or those with prolapsed discs were not included. The Radiological parameters compared were Anterior and Posterior Disc height, Foraminal height and width, The inter-vertebral angle (IVA), Lumbar lordosis and Scoliosis if any. The presence of slips and their progression post-op was noted, as was bony lysis if any. There were ten males with thirteen levels and sixteen females with nineteen levels in the study. Eighteen levels (56.25%) were L4/L5, ten (31.25%) were L5/S1 and 4 (12.5%)were L3/L4. The average age in the series was 59.6 years (Range 37 – 89 yrs). Average follow up was 9.5 months (Range 2 to 36). The Average increase in Anterior disc height was 1.89 mm (+/−1.39), the posterior disc height increased by an average 1.09 mm (+/−1.14). Foraminal height increased by an average 3.85 mm (+/− 2.72), while foraminal width increased by 2.14 mm (+/− 1.38). The IVA increased in 16 and reduced in 15 patients, with no change in 1. Lumbar Lordosis increased in 23 patients, with an average value of 2.3°. No patient exhibited progression in scoliosis and no lysis could be identified. There were three Grade I slips pre-op; none progressed. Conclusion. Foraminal dimensions and Disc height were consistently improved after Wallis insertion. Changes in IVA and Lumbar lordosis were however variable. A longer follow up is suggested to look for sustained improvement and the presence of lysis. Ethics approval- None, Audit/service standard in trust. Interest statement - None

We prospectively studied the use of intercostal EMG monitoring as an indicator of the accuracy of the placement of pedicle screws in the thoracic spine. We investigated 95 thoracic pedicles in 17 patients. Before insertion of the screw, the surgeon recorded his assessment of the integrity of the pedicle track. We then stimulated the track using a K-wire pedicle probe connected to a constant current stimulator. A compound muscle action potential (CMAP) was recorded from the appropriate intercostal or abdominal muscles. Postoperative CT was performed to establish the position of the screw. The stimulus intensity required to evoke a muscle response was correlated with the position of the screw on the CT scan. There were eight unrecognised breaches of the pedicle. Using 7.0 mA as a threshold, the sensitivity of EMG was 0.50 in detecting a breached pedicle and the specificity was 0.83. Thoracic pedicle screws were accurately placed in more than 90% of patients. EMG monitoring did not significantly improve the reliability of placement of the screw

The last decade has seen a rise in the use of the gamma nail for managing inter-trochanteric and subtrochanteric hip fractures. Patients with multiple co-morbidities are under high anaesthetic risk of mortality and are usually not suitable for general or regional anaesthesia. However, there can be a strong case for fixing these fractures despite these risks. Apart from aiming to return patients to their pre-morbid mobility, other advantages include pain relief and reducing the complications of being bed bound (e.g. pressure ulcers, psychosocial factors). While operative use of local anaesthesia and sedation has been documented for insertion of extra-medullary femoral implants such as the sliding hip screw, currently no literature is present for the insertion of the gamma nail. We studied intra-operative and post-operative outcomes of three patients aged between 64 and 83 with right inter-trochanteric hip fractures and American Society of Anesthesiologists (ASA) scores of 4 or more. Consent for each case was obtained after discussion with the patient and family, or conducted with the patient's best interests in mind. All patients received a short unlocked gamma nail, and were operated on within 24 hours of admission. Each patient underwent local injections of Bupivacaine or Lignocaine or both, with Epinephrine, and with one patient receiving nerve block of the fascia iliaca. Each patient received a combination of sedatives under the discretion of the anaesthetist including Midazolam, Ketamine, Propofol, Fentanyl, and/or Haloperidol. Operating time ranged from 30–90 minutes. Patients were managed post-operatively with analgesia based on the WHO pain ladder and physiotherapy. Our results showed no intra-operative complications in any of the cases. All patients noted improvement in their pain and comfort post-operatively without complications of the operation site. Two patients achieved their pre-morbid level of mobility after undergoing physiotherapy and were subsequently discharged from the orthopaedic team. One patient with ongoing pre-operative medical complications died 5 days after the operation. This study provides a glimpse into the use of local anaesthetic and sedation on high operative risk patients, and this may be a viable alternative to extra-medullary implants or non-operation. Further research is needed to quantify the risks and benefits of operating within this patient group

To introduce a new robot-assisted surgical system for spinal posterior fixation which called TiRobot, based on intraoperative three-dimensional images. TiRobot has three components: the planning and navigation system, optical tracking system and robotic arm system. By combining navigation and robot techniques, TiRobot can guide the screw trajectories for orthopedic surgeries.

In this randomised controlled study approved by the Ethics Committee, 40 patients were involved and all has been fully informed and sign the informed consent. 17 patients were treated by free-hand fluoroscopy-guided surgery, and 23 patients were treated by robot-assisted spinal surgery.

A total of 190 pedicle screws were implanted. The overall operation times were not different for both groups. None of the screws necessitated re-surgery for revised placement. In the robot-assisted group, assessment of pedicle screw accuracy showed that 102 of 102 screws (100%) were safely placed (<2 mm, category A+B). And mean deviation in entry point was 1.70 +/− 0.83mm, mean deviation in end point was 1.84 +/− 1.04mm. In the conventional freehand group, assessment of pedicle screw accuracy showed that 87 of 88 (98.9%) were safely placed (<2 mm, category A+B), 1 screw fall in category C, mean deviation in entry point was 3.73 +/− 2.28mm, mean deviation in end point was 4.11 +/− 2.31mm.

This randomised controlled study verified that robot-assisted pedicle screw placement with real-time navigation is a more accuracy and safer method, and also revealed great clinical potential of robot-assisted surgery in the future.

Pertrochanteric femoral fractures are common and intramedullary nailing with a proximal femoral nail (PFNA®) is an accepted method for the surgical treatment. Accurate guide wire and subsequent hardware placement in the femoral neck is believed to be essential in order to avoid mechanical failure. Malpositioned implants may lead to rotational or angular malalignment or “cut out” in the femoral neck. Hip and knee arthritis might be a potential long-term consequence. The conventional technique might require multiple guidewire passes, and relies heavily on fluoroscopy. A computer-assisted surgical planning and navigation system based on 2D-fluoroscopy was developed in-house as an intraoperative guidance system for navigated guide wire placement in the femoral neck and head. To support the image acquisition process, the surgeon is supported by a so-called “zero-dose C-arm navigation” module. This tool enables a virtual radiation-free preview of the X-ray images of the femoral neck and head. The aim of this study was to compare PFNA® insertion using this system to conventional implantation technique. We hypothesised that guide wire and subsequent implant placement using our software decreases radiation exposure to the minimum of two images and reduces the number of drilling attempts. Furthermore, accuracy of implant placement in comparison to the conventional method might be improved and operation time shortened. We used 24 identical intact left femoral Sawbones® to simulate reduced pertrochanteric femoral fractures. First, we performed placement of the PFNA® into 12 Sawbones using the conventional fluoroscopic technique (group 1). Secondly, we performed placement of the PFNA® into 12 Sawbones guided by the computer-assisted surgical planning software (group 2). In each group, we first performed open and secondly minimal-invasive intramedullary nailing in six sawbones each. For minimal-invasive guide wire placement, a surgical drape imitated soft tissue coverage. Conventional and navigated technique used a C-arm fluoroscope (Siemens IsoC 3D®, Erlangen, Germany) in conventional 2D mode. Guidewire and subsequent blade placement in the femoral neck was evaluated. We documented: 1: the number of fluoroscopic images; 2: the total number of drilling attempts; 3: implant placement accuracy (3.1. Tip apex distance (TAD); 3.2. visible penetrations of the femoral neck and head; 3.3. blade-corticalis bone distance in the anteroposterior and lateral plane) and the 4: operation time. The number of fluoroscopic single shots taken to achieve an acceptable PFNA®-blade position was reduced significantly with computer-assistance by 71.5% (p<0.001) in the open and by 72,4% (p<0.001) in the minimally invasive technique. In each operation two X-rays for final documentation were taken. The average number of drilling attempts for the computer-guided system was significantly (p<0.05) less than that of the conventional technique in the minimally invasive procedure. The average number of drilling attempts showed no difference between the computer-assisted and conventional techniques in the open procedure. Accuracy of implant placement showed no difference between the computer-assisted and the conventional group. Computer assistance significantly increased the mean operation time for fixation of pertrochanteric femoral fractures with a PFNA® by 79.8% (p<0.001) in the open technique and by 54.4% (p<0.001) in the minimally invasive technique. Use of our computer-guided system for fixation of pertrochanteric femoral fractures by a PFNA® decreases the number of fluoroscopic single shots and of suboptimal guide wire passes while maintaining blade placement accuracy that is equivalent to the conventional technique. Computer-assisted surgery with our system increases the operation time and has just been tested in non-fractured sawbones. Although these results are promising, additional studies including fractured sawbones and cadaver models with extension of the navigation process to all steps of PFNA® introduction and with the goal of reducing the operation time are indispensable before integration of this navigation system into the clinical workflow

Femoral components used in total hip arthroplasty (THA) rely on good initial fixation determined by implant design, femoral morphology, and surgical technique. A higher rate of varus alignment may be of specific concern with short stem implants. Varus placement in uncemented femoral components has been proven not to be detrimental to clinical function; though long-term bone remodeling secondary to varus placement remains unknown. The goal of this study was to compare the clinical and radiographic outcomes in patients who underwent THA with one of two uncemented short stem metaphyseal engaging implants at minimum two-year follow-up.

A review of 105 patients (average age 65 years; BMI 29 kg/m²) who underwent a total of 109 primary THAs using the ABG II short stem femoral implant (Stryker, Mahwah, NJ), and 160 hips in 149 patients (average age 70 years; BMI 28 kg/m²) who underwent primary THA using the Citation stem (Stryker, Mahwah, NJ). The same surgeon (SDS) performed all surgeries through a less invasive posterolateral approach. Pre-operative and post-operative Harris Hips Scores (HHS) and WOMAC scores were collected. Digital radiograph analysis was performed including measuring the stem alignment relative to the femoral shaft. A stem placed with greater than 5 degrees of varus was considered to be in varus.

There was no significant difference in demographics (age, gender or BMI) or pre-operative HHS and WOMAC scores between the two groups. Follow-up HHS was 90 (range 63–100) and 94 (range 70–100) for the ABG II and Citation groups, respectively. Follow-up WOMAC scores were 10 (range 0–24) and 6 (range 0–43) for the ABG II and Citation groups, respectively. There was no statistically significant difference in any of the scores between the two groups (p>0.05).

When looking at AP radiographs for postoperative intramedullary alignment, none of the ABG II implants were placed in varus (>5°), while a small number (4.9%) of Citation implants were implanted in varus alignment. No significant difference was observed in the alignment between the two groups (p>0.05). Average post-op alignment with the ABG was 1.10° (range −4.7–4.9°) and 0.88° (range −4.5–8.9°) with the Citation.

The clinical results associated with the use of these stems in patients of all ages and bone types have been identical to those achieved by uncemented stems of standard length. Both implants in this study had excellent clinical and functional results in primary THA after a minimum 24-month follow up. In addition, postoperative radiographic analysis demonstrated that these stems can be reliably and reproducibly placed in neutral alignment despite their short length. The lateral flare on the Citation implant led to a greater number of implants in varus alignment, potentially affecting offset and leg-length, yet the relative increased incidence compared to the ABG II was not significant. Further research is needed in designing implants that optimize proximal femoral contact while maintaining alignment and overall hip kinematics.

Background

Reverse Geometry shoulder replacement requires fixation of a base plate (called a metaglene) to the glenoid to which a convex glenosphere is attached. Most systems use screws to achieve this fixation. The suprascapular nerve passes close to the glenoid and is known to be at risk of injury when devices and sutures are inserted into the glenoid. We investigate the risk posed to the suprascapular nerve by placement of metaglene fixation screws.