Aims. Manual impaction, with a mallet and introducer, remains the standard method of installing cementless acetabular cups during total hip arthroplasty (THA). This study aims to quantify the accuracy and precision of manual impaction strikes during the seating of an acetabular component. This understanding aims to help improve impaction surgical techniques and inform the development of future technologies. Methods. Posterior approach THAs were carried out on three cadavers by an expert orthopaedic surgeon. An instrumented mallet and introducer were used to insert cementless acetabular cups. The motion of the mallet, relative to the introducer, was analyzed for a total of 110 strikes split into low-, medium-, and high-effort strikes. Three parameters were extracted from these data: strike vector, strike offset, and mallet face alignment. Results. The force vector of the mallet strike, relative to the introducer axis, was misaligned by an average of 18.1°, resulting in an average wasted strike energy of 6.1%. Furthermore, the mean strike offset was 19.8 mm from the centre of the introducer axis and the mallet face, relative to the introducer strike face, was misaligned by a mean angle of 15.2° from the introducer strike face. Conclusion. The direction of the impact vector in manual impaction lacks both accuracy and precision. There is an opportunity to improve this through more advanced impaction instruments or surgical training. Cite this article: Bone Joint Res 2024;13(4):193–200

Aims. Symptomatic spinal stenosis is a very common problem, and decompression surgery has been shown to be superior to nonoperative treatment in selected patient groups. However, performing an instrumented fusion in addition to decompression may avoid revision and improve outcomes. The aim of the SpInOuT feasibility study was to establish whether a definitive randomized controlled trial (RCT) that accounted for the spectrum of pathology contributing to spinal stenosis, including pelvic incidence-lumbar lordosis (PI-LL) mismatch and mobile spondylolisthesis, could be conducted. Methods. As part of the SpInOuT-F study, a pilot randomized trial was carried out across five NHS hospitals. Patients were randomized to either spinal decompression alone or spinal decompression plus instrumented fusion. Patient-reported outcome measures were collected at baseline and three months. The intended sample size was 60 patients. Results. Of the 90 patients screened, 77 passed the initial screening criteria. A total of 27 patients had a PI-LL mismatch and 23 had a dynamic spondylolisthesis. Following secondary inclusion and exclusion criteria, 31 patients were eligible for the study. Six patients were randomized and one underwent surgery during the study period. Given the low number of patients recruited and randomized, it was not possible to assess completion rates, quality of life, imaging, or health economic outcomes as intended. Conclusion. This study provides a unique insight into the prevalence of dynamic spondylolisthesis and PI-LL mismatch in patients with symptomatic spinal stenosis, and demonstrates that there is a need for a definitive RCT which stratifies for these groups in order to inform surgical decision-making. Nonetheless a definitive study would need further refinement in design and implementation in order to be feasible. Cite this article: Bone Jt Open 2023;4(8):573–579

Objectives. The monitoring of fracture healing is a complex process. Typically, successive radiographs are performed and an emerging calcification of the fracture area is evaluated. The aim of this study was to investigate whether different bone healing patterns can be distinguished using a telemetric instrumented femoral internal plate fixator. Materials and Methods. An electronic telemetric system was developed to assess bone healing mechanically. The system consists of a telemetry module which is applied to an internal locking plate fixator, an external reader device, a sensor for measuring externally applied load and a laptop computer with processing software. By correlation between externally applied load and load measured in the implant, the elasticity of the osteosynthesis is calculated. The elasticity decreases with ongoing consolidation of a fracture or nonunion and is an appropriate parameter for the course of bone healing. At our centre, clinical application has been performed in 56 patients suffering nonunion or fracture of the femur. Results. A total of 39 cases of clinical application were reviewed for this study. In total, four different types of healing curves were observed: fast healing; slow healing; plateau followed by healing; and non-healing. Conclusion. The electronically instrumented internal fixator proved to be valuable for the assessment of bone healing in difficult healing situations. Cost-effective manufacturing is possible because the used electronic components are derived from large-scale production. The incorporation of microelectronics into orthopaedic implants will be an important innovation in future clinical care. Cite this article: B. Kienast, B. Kowald, K. Seide, M. Aljudaibi, M. Faschingbauer, C. Juergens, J. Gille. An electronically instrumented internal fixator for the assessment of bone healing. Bone Joint Res 2016;5:191–197. DOI: 10.1302/2046-3758.55.2000611

Computer navigation in total knee arthroplasty (TKA) has proven to significantly reduce the number of outliers in prosthesis positioning and to improve mechanical leg alignment. Despite these advantages the acceptance of navigation technologies is still low among orthopaedic surgeons. The time required for navigation might be a reason for the low acceptance. The aim of the study was to test whether software and instrument improvements made in an established navigation system could lead to a significant navigation acquisition time reduction. An improved and the current version of the TKA navigation software were used to perform surgery trials on a human cadaveric specimen by two experienced orthopaedic surgeons. A significant effect of the “procedure” (navigation software version) on the navigation time (p< 0.001) was found, whereas the difference between surgeons was not significant (p= 0.2). There was no significant interaction between surgeon and navigation software version (p= 0.5). The improved version led to a significant navigation acquisition time reduction of 28%. Software and instrument improvements led to a statistically significant navigation acquisition time reduction. The achieved navigation acquisition time decrease was independent from surgeon. Specific instrument and software improvements in established navigation systems may significantly decrease the surgery time segments where navigation takes place. However, the total navigation acquisition time is low in comparison to the total surgery time

Acetabular component malalignment remains the since greatest root cause for revision THA with malposition of at least ½ of all acetabular component placed using conventional methods1. The use of local anatomical landmarks has repeatedly proven to be an unreliable. The reason for this is that the position of local anatomical landmarks varies widely from one patient to another. Another alternative is to simply place acetabular components in a supine position. Unfortunately, cups placed in the supine position under fluoroscopy had the highest incidence of cup malposition in the Callanan study. This is because acetabular anteversion is critically important and pelvic tilt during surgery in the supine position is unknown, uncontrolled, and not correlated with post-operative pelvic tilt. Image-free surgical navigation can be useful for cup alignment in the absence of pelvic deformity. Image-based surgical navigation can be effective for cup alignment in the presence or absence of pelvic deformity. Unfortunately, while these technologies have been available for a decade, few surgeons employ these technologies. This is likely due to added time, complexity, and expense. Current robotic technology embodies all of these limitations in an even more extreme form. The HipSextant is a smart mechanical instrument system was developed to quickly and easily achieve accurate cup alignment. The system is image based (CT or MR) and can handle extreme asymmetry and deformity. The instrument docks on a patient-specific basis with 3 legs: one through the incision behind the posterior rim, one percutaneously on the lateral side of the ASIS, and a third percutaneously on the surface of the ilium. A direction indicator on the top of the instrument points in the desired cup orientation. Since the planning is provided, the surgeon needs to only review and adjust the plan as desired. Further the system is robust, showing greater accuracy than image-based traditional navigation. Finally, the system takes typically only 3 minutes to use, making it practical for busy practices and hospitals

Surgical navigation systems enable surgeons to carry out surgical interventions more accurately and less invasively, by tracking the surgical instruments inside human body with respect to the target anatomy. Currently, optical tracking (OPT) is the gold standard in surgical instrument tracking because of its sub-millimeter accuracy, but is constrained by direct line of sight (LOS) between camera sensors and active or passive markers. Electromagnetic tracking (EMT) is an alternative without the requirement of LOS, but subject to environmental ferromagnetic distortion. An intuitive idea is to integrate respective strengths of them to overcome respective weakness and we aim to develop a tightly-coupled method emphasising the interactive coupled sensor fusion from magnetic and optical tracking data. In order to get real-time position and orientation of surgical instruments in the surgical field, we developed a new tracking system, which is aiming to overcome the constraints of line-of-sight and paired-point interference in surgical environment. The primary contribution of this study is that the LOS and point correspondence problems can be mitigated using the initial measurements of EMT, and in turn the OPT result can provide initial value for non-linear iterative solver of EMT sensing module. We developed an integrated optical and electromagnetic tracker comprised of custom multiple infrared cameras, optical marker, field generator and sensing coils, because the current commercial optical or magnetic tracker typically consists of unchangeable lower level proprietary hardware and firmware. For the instrument-affixed markers, the relative pose between passive optical markers and magnetic coils is calibrated. The pose of magnetic sensing coils calculated by electromagnetic sensing module, can speed up the extraction of fiducial points and the point correspondences due to the reduced search space. Moreover, the magnetic tracking can compensate the missing information when the optical markers are temporarily occluded. For magnetic sensing subsystem comprised of 3-axis transmitters and 3-axis receiving coils, the objective function for nonlinear pose estimator is given by the summation of the square difference between the measured sensing data and theoretical data from the dipole model. Non-linear optimisation is computational intensive and requires initial pose estimation value. Traditionally, the initial value is calculated by equation-based algorithm, which is sensitive to noise. Instead, we get the initial value from the measurement of optical tracking subsystem. The real-time integrated tracking system was validated to have tracking errors about 0.87mm. The proposed interactive and tightly coupled sensor-fusion of magnetic-optical tracking method is efficient and applicable for both general surgeries as well as intracorporeal surgeries

Objectives. To assess the accuracy of patient-specific instruments (PSIs) versus standard manual technique and the precision of computer-assisted planning and PSI-guided osteotomies in pelvic tumour resection. Methods. CT scans were obtained from five female cadaveric pelvises. Five osteotomies were designed using Mimics software: sacroiliac, biplanar supra-acetabular, two parallel iliopubic and ischial. For cases of the left hemipelvis, PSIs were designed to guide standard oscillating saw osteotomies and later manufactured using 3D printing. Osteotomies were performed using the standard manual technique in cases of the right hemipelvis. Post-resection CT scans were quantitatively analysed. Student’s t-test and Mann–Whitney U test were used. Results. Compared with the manual technique, PSI-guided osteotomies improved accuracy by a mean 9.6 mm (p < 0.008) in the sacroiliac osteotomies, 6.2 mm (p < 0.008) and 5.8 mm (p < 0.032) in the biplanar supra-acetabular, 3 mm (p < 0.016) in the ischial and 2.2 mm (p < 0.032) and 2.6 mm (p < 0.008) in the parallel iliopubic osteotomies, with a mean linear deviation of 4.9 mm (p < 0.001) for all osteotomies. Of the manual osteotomies, 53% (n = 16) had a linear deviation > 5 mm and 27% (n = 8) were > 10 mm. In the PSI cases, deviations were 10% (n = 3) and 0 % (n = 0), respectively. For angular deviation from pre-operative plans, we observed a mean improvement of 7.06° (p < 0.001) in pitch and 2.94° (p < 0.001) in roll, comparing PSI and the standard manual technique. Conclusion. In an experimental study, computer-assisted planning and PSIs improved accuracy in pelvic tumour resections, bringing osteotomy results closer to the parameters set in pre-operative planning, as compared with standard manual techniques. Cite this article: A. Sallent, M. Vicente, M. M. Reverté, A. Lopez, A. Rodríguez-Baeza, M. Pérez-Domínguez, R. Velez. How 3D patient-specific instruments improve accuracy of pelvic bone tumour resection in a cadaveric study. Bone Joint Res 2017;6:577–583. DOI: 10.1302/2046-3758.610.BJR-2017-0094.R1

Background. Surgeons are waiting for a hassle free, time saving, precise and accurate guide for hip arthroplasty. Industry are waiting for instruments to reduce manufacturing costs associated with washing, assembling, sterilization and transportation. Patient specific / custom made surgical guides may deliver these goals but current systems have had limited assessments. We comprehensively assessed a new guiding system for the acetabular component of hip replacement, “Bullseye”. Methods. Planning. We used either Computer Tomography (CT) (n=22) or Magnetic Resonance (MR) (n=6) imaging to plan the position of acetabular components into 28 acetabulums of cadavers (n=12) and dry bone models (n=16). 10 of the dry bone models had complex deformities (crowe 4 hip dysplasia or Paprosky 3A defects). Surgical positioning. Patient specific “Bullseye” guides were manufactured using 3D printing and standard instruments were used to ream the acetabulum, guided by Bullseye, and position cup components. Post surgery. The pelvises underwent CT scanning after implantation of acetabular cups. 3D software measured the “radiographic” (as opposed to operative or anatomic) cup inclination and version angles using the anterior pelvic plane as a reference. Achieved position was compared to the plan. Statistics. We used Bland Altman plots to quantify the strength of the agreement between the planned and achieved cup orientations in terms of fixed bias, correlation coefficient and 2 standard deviation limits of agreement. Results. Measurement of the cup position angles with 3D CT after implantation with the Bullseye hip instruments showed a median (Interquartile range) difference in degrees between planned and achieved position of 2.5 (1–6) for inclination and 8 (3–10) for version. The use of CT or MR imaging for planning produced similar results. Bland Altman plots for cup inclination and version angles respectively, showed a fixed bias of +3 and +6 degrees; in other words the guide increased the planned cup angles by consistent 3 and 7 degrees on average. The estimated bias, was 3.9 and 7 degrees respectively. The 95% (1.96 SD) limits of agreement were 7 and 10 respectively. Discussion. This robust assessment, involving the use of 3D CT, of the Bullseye hip instruments system showed good early results with 95% limits of agreement between planned and achieved cup angles of 7.3 and 10 degrees for inclination and version respectively. In other words, the Bullseye instruments can achieve better cup position than any published study of conventional techniques. Or put another way, a cup planned to be at the centre of Lewinnek's safe zone of acetabular cup position (inclination range between 30 and 50 degrees; version range between 5 and 25 degrees) would be achieved in 95% of cases. This could be improved further by adjusting for the fixed bias and choosing cases with simple bony anatomy. Conclusion. The Bullseye hip instruments have the potential to reduce the wide variation in the positioning of acetabular components during hip arthroplasty. It is now ready for a clinical evaluation

Aim: The assessment of shoulder mobility is essential for clinical follow-up of shoulder treatment. Only a few high sophisticated instruments for objective measurements of shoulder mobility are available. The interobserver dependency of conventional goniometer measurements is high. In the 1990s an isokinetic measuring system of BIODEX Inc. was introduced, which is a very complex but valid instrument. Since 2008 a new user-friendly system (DynaPort ShoulderTest-System) is available. Aim of this study is the validation of this measuring instrument with the BIODEX-System. Methods: The DynaPort ShoulderTest-System is a small, light-weighted three-dimensional gyroscope that is fixed on the distal upper patient arm, recording abduction, fiexion and rotation. For direct comparison we fixed the DynaPort on the lever arm of the BIODEX-system. The accuracy of measurement was determined at different positions, angles and distances from the center of rotation as well as different motion speeds in the radius between 0° – 180° in steps of 20°. All measurements were repeated ten times and observed with a digital water level. As satisfactory accuracy we defined a difference between both systems below 5°. The statistical analysis was performed with a linear regression model. Results: The evaluation showed very high accuracy of measurements. The maximum average deviation was 0,5°. Below 60° the DynaPort was underestimating comparing the BIODEX system, whereas in higher positions higher data was measured. At higher angles the differences between both got higher. The distance to the center of rotation as well as the position of the Dyna-Port on the lever arm and different motion speeds infiuenced the results. The highest significant matches were measured at highest distance from the center of rotation (1,8° vs. 3,1°, p < 0,05) and a highest motion speed (2,1° at 60°/s, vs. 3,1° at 30°/s, p < 0,05). Conclusion: In summary the results showed a high correlation and good reproducibility of measurements. All deviations were inside the tolerance interval of 5 °. These laboratory trials are promising for the validation of this system in shoulder patients. The challenge for both systems will be the changing of the center of rotation in the shoulder joint at elevations higher than 90°

Introduction: We studied prospectively two groups of patients treated operatively for acute achilles tendon rupture admitted in our institution in order to compare post operative morbidity, usage of hospital resources and immobilisation regimen involving immediate weight-bearing with traditional non-weight-bearing. The aim was to assess the benefit of instrument guided surgical method, which reduces hospitalisation cost, post operative wound care cost and reduce requirement of post-operative analgesics together with improved rehabilitation and return to normal activity for young patients [age below 45] with a rupture of the Achilles tendon. Material and methods: 34 patients had repair of the tendon with an open method as an inpatient under instruction of the admitting consultant. Second group of 25 patients had repair as limited open technique with an Achillon instrument and immediate weight bearing. Result: Opiates or opiate-based analgesia were used in the open repair group and in the minimally invasive group, patients reported no pain with paracetamol or ibuprofen. Two cases of severe wound infection leading to dehiscence requiring further surgery and 5 cases of minor surgical site infection leading to delayed wound healing were reported as wound complications in the open group. All the patients in the mini invasive group reported their satisfaction with wound healing and minimal scar at the incision site. Based on self-reports, the time taken to return to normal walking was median of 11 weeks in the achillon treatment group and 17 weeks for the open group. There was also an earlier return to normal stair climbing, with a median of 13 weeks [9–21 weeks] in the achillon treatment group and 19 weeks [13–27 weeks] for the opens technique. Conclusion: This study has shown that mini invasive repair with Achillon instrument may allow us to perform surgery with less bed usage, less consumption of post operative analgesics and other associated indirect cost to the healthcare provider. It also allows faster rehabilitation. It provides further evidence that minimally invasive repair with early weight bearing rehabilitation has advantages over traditional open repair with delayed mobilisation for patients who have undergone surgery for ruptured Achilles tendon. The practical advantages for patients in early weight-bearing mobilisation were earlier return to normal walking and stair climbing than their open group counterparts. We would, therefore, advocate the use of minimally invasive procedure with early weight-bearing mobilisation for the rehabilitation of all patients with acute ruptures of the Achilles tendon

A secure bone/cement interface at the bone cement junction is an important requirement for the long-term success in the cemented hip arthroplasty. Cementing techniques have evolved and now involve pressurisation of the acetabulum and femur. It can be difficult to get a complete rim seal and hence adequate pressurisation due to the unique anatomy of the acetabulum and the contyloid notch. Several acetabular pressurisers are commercially available. We have developed an instrument for controlled and reproducible cement pressurisation in the acetabulum before socket insertion. It is a T-bar incorporating a central plunger, which protrudes from an outer sleeve when force is applied. The protrusion of the central plunger and hence the amount of force applied can be limited by a stop-sleeve. A laboratory saw bone model was designed to assess this system and compare it with two existing pressurisers. A polypropylene model of the acetabulum was used. Included in the model were two 1.3mm diameter capillary outlets, one at its pole and one at a point close to its rim opposite the cotyloid notch. Water was free to flow through the capillaries at a pressure of 13.5” WG to represent blood flow. 5 test per pressuriser were performed. CMW 1 Gentamicin bone cement was mixed as per manufacturers instruction in a Vacuum Mix system. The cement was then pressurised using one of three systems; the Depuy T handle pressuriser, the Exeter pressuriser and our new instrument. The cement mantle produced with the Depuy T-handle and the Exeter pressuriser was thicker at the pole than the rim and the cement intrusion was not consistent nor reproducible. The new pressurizer produced a cement mantle equal at the pole and the rim to within 1mm. A reproducible cement mantle compatible to the shape of the socket and with cement intrusion of 5mm (+/− 1mm) could be achieved. We recommend the use of this pressuriser

Our prospective observational study of patients treated for Thoracolumbar Adolescent Idiopathic Scoliosis (AIS) by anterior instrumentation aimed at investigating the correlation between the radiographic outcome and the recently-developed scoliosis research society self-reported outcomes instrument (SRS-22) which has been validated as a tool for self-assessment in scoliosis patients. Previous patient based questionnaires demonstrated poor correlation with the radiological parameters. Materials and Methods. Pre-operative, post-operative and two years follow-up radiographs of 30 patients were assessed. Thirteen radiographic parameters including Cobb angles and balance were recorded. The percentage improvements for each were noted. The SRS-22 questionnaire was completed by all patients at final follow-up. Correlation was sought between each radiographic parameter, total SRS score and each of the five domains by quantifying Pearson's Correlation Coefficient (r). Results. Percentage improvement in primary Cobb angle (r = 0.052), secondary Cobb angle (r = 0.165), apical vertebra translation of the primary curve (r = -0.353), thoracic kyphosis (r = 0.043) and lumbar lordosis (r = 0.147) showed little or no correlation with the SRS-22 total score and its five individual domains. Significant inverse correlation was found between the upper instrumented vertebra angle and at follow-up and SRS-22 (r = -0.516). The same was true for Sagittal plumb line shift at final follow up (r = -0.447). Conclusion. SRS-22 is a validated tool for the self-assessment of health status in spinal deformity patients; however, it does not seem to correlate with most of the radiographic parameters commonly used by clinicians to assess patient outcome with the exception of upper instrumented vertebra angle and sagittal plumb line which do correlate significantly with the SRS-22 outcomes instrument. A comprehensive system of assessing the success of surgery both from the patient and clinicians perspective is required in the spinal deformity patient

A 51 years old female who experienced difficulty in gait ambulation due to secondary osteoarthritis of knee showed knee instability caused by paralysis associated with poliomyelitis and scoliosis. At the first medical examination, right knee range of motion was 0° to 90°, and spino malleolar distance (SMD) showed 72cm for the right leg, 78cm for the left leg, and the bilateral comparison of SMD indicated the leg length discrepancy of 6cm. The patient has a history of surgeries with an anterior – posterior instrument for the treatment of scoliosis, and with Langenskiöld method for the paralyzed right knee at the age of seventeen. The patient also experienced varus degeneration at the age of twenty seven, which was surgically treated with high tibial osteotomy. In this case, a reoperation of her right knee was performed due to the reoccurrence of the knee pain. Preoperative planning was performed using Patient-matched instrument (Signature; Biomet) which was created based on computed tomography data. Each part of osteotomy followed the resection guide by Signature, and a total knee arthroplasty was carried out using the Rotating Hinge Knee System (Zimmer, warsaw. Inc). Two week after the operation, the patient showed the ability to walk without any assistance, and has been in a good condition

Purpose: The purpose of this clinical trial was to investigate the accuracy of a novel method for computer-assisted distal radius osteotomy, in which computer-generated patient-specific plastic guides were used for intra-operative guidance. Our hypothesis was that these guides combine the accuracy and precision of computer-assisted techniques with the ease of use of mechanical guides. Method: In a consecutive series of 9 patients we tested the accuracy of the proposed method. Prior to surgery, CT scans were obtained of both radii and ulnae in neutral rotation. Three-dimensional virtual models for both the affected and unaffected radius and ulna were created. The models of the unaffected radius and ulna were reflected to serve as a template for the correction. Custom-made software was used to plan the correction. The locations of the distal and proximal drill holes for the plate were saved and the locations of the distal holes before the osteotomy were determined. The design of a patient-specific instrument guide was calculated, into which a mirror image of intra-operative accessible bone structure of the distal radius was integrated. This allowed for unique positioning of the guide intra-operatively. For each planned drill location a guidance hole was incorporated into the guide. A plastic model of the guide was created using a rapid prototyping machine. Intra-operatively, a conventional incision was made and the guide was positioned on the distal end of the radius. The surgeon drilled the holes for the plate screws into the intact radius. The guide was removed and the surgeon performed the osteotomy using the conventional technique and shaved the bone from the distal radius fragment to accommodate the plate. Using the pre-drilled holes the plate was affixed to the distal radius fragment. The distal fragment was reduced until the proximal screw holes in the plate aligned with the pilot holes in the bone. To analyze the accuracy of the intra-operative procedure we compared the post-operative alignment of the radius with the planned alignment. A lateral and an A/P digitally reconstructed radiograph (DRR) of the plan were calculated. These DRRs were used to evaluate the radial inclination, the volar tilt and the ulnar variance of the planned alignment. Post-operative lateral and A/P X-Rays were used to determine the same three post-operative radiographic indices. The post-operative values were compared with the planned values. Results: We found an average deviation for the radial inclination of 0.5°(StDev 1.8), for the volar tilt of 0.7°(StDev 2.3), and for the ulnar variance of 0.8mm (StDev 1.9). Conclusion: These results show that the computer-generated instrument guides accurately achieved the planned alignment. The guides were easy to integrate into the surgical workflow and eliminated the need for intra-operative fluoroscopy for guidance of the procedure

A large number of total hip arthroplasties (THA) are performed each year, of which 60 % use cementless femoral fixation. This means that the implant is press-fitted in the bone by hammer blows. The initial fixation is one of the most important factors for a long lasting fixation [Gheduzzi 2007]. It is not easy to obtain the point of optimal initial fixation, because excessively press-fitting the implant by the hammer blows can cause peak stresses resulting in femoral fracture. In order to reduce these peak stresses during reaming, IMT Integral Medizintechnik (Luzern, Switzerland) designed the Woodpecker, a pneumatic reaming device using a vibrating tool. This study explores the feasibility of using this Woodpecker for implant insertion and detection of optimal fixation by analyzing the vibrational response of the implant and Woodpecker. The press-fit of the implant is quantified by measuring the strain in the cortical bone surrounding the implant. An in vitro study is presented. Two replica femur models (Sawbones Europe AB, Malmo Sweden) were used in this study. One of the femur models was instrumented with three rectangular strain gauge rosettes (Micro-Measurements, Raleigh, USA). The rosettes were placed medially, posteriorly and anteriorly on the proximal femur. Five paired implant insertions were performed on both bone models, alternating between standard hammer blow insertions and using the Woodpecker. The vibrational response was measured during the insertion process, at the implant and Woodpecker side using two shock accelerometers (PCB Piezotronics, Depew, NY, USA). The endpoint of insertion was defined as the point when the static strain stopped increasing. Significant trends were observed in the bandpower feature that was calculated from the vibrational spectrum at the implant side during the Woodpecker insertion. The bandpower is defined as the percentage power of the spectrum in the band 0–1000 Hz. Peak stress values calculated from 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. A decreasing trend was observed in the bandpower feature, followed by a stagnation. This point of stagnation was correlated with the stagnation of the periprosthetic stress in the bone measured by the strain gages. The behavior of this bandpower feature shows the possibility of using vibrational measurements during insertion to assess the endpoint of insertion. 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. This could mean that either extra hammer blows or a more powerful pneumatic device could be needed for proper implant insertion

Purpose. External rotation of the femoral component is one factor that favors a satisfactory clinical result. New technologies have been developed to precisely implant the components of a total knee arthroplasty, including computer-assisted surgery (CAS) and patient-specific instruments (PSIs). The aim of this study was to compare the precision of CAS and PSIs when determining the orientation of the femoral component. Methods. A total of 65 patients operated on in 2008 with CAS had pre- and post-operative computed tomography (CT) in which the posterior condylar angle (PCA) was measured. The same pre- and post-operative measurements were performed for 27 patients operated on in 2010 with the assistance of PSI. For both populations, the antero-posterior femoral cuts were directed to implant the femoral component 3° of external rotation from the pre-operative posterior condylar line (PCL). Results. The pre-operative parameters for both groups were identical. The post-operative PCA was not significantly different between the CAS and PSI groups, but the pre- to post-operative difference in PCA for the PSI group indicated a diminution of 2 ± 2° compared to no change in the CAS group. A total of 28% of the patients operated on with CAS had their femoral component more internally rotated after the surgery compared to the pre-operative measurements. Conclusion. Both PSI and CAS achieve the same objective of externally rotate the femoral component in the transversal plan, even if CAS, some femoral components still remains less rotated than the plan

Clinical management of patellofemoral (PF) instability is a challenge, particularly considering the wide range of contributing variables that must be taken into consideration when determining optimal treatment. An important outcome measure to consider in this patient population is disease-specific quality of life (QOL). The purpose of this study was to factor analyse and reduce the total number of items in the Banff Patellar Instability Instrument (BPII). Subsequent to the factor analysis, the new, item-reduced BPII 2.0 was tested for validity, reliability and responsiveness. Disease-specific QOL was measured in patients with a confirmed diagnosis of PF instability (n = 223) at the initial consultation with the original BPII. Data from these BPII scores was used to employ a principal component analysis (PCA) to factor analyse and reduce the total number of items in the original BPII, to create the new BPII 2.0. The BPII 2.0 underwent content validation (Cronbach's Alpha, patient interviews and reading-level); construct validation (ANOVA comparing the initial consultation, 6, 12 and 24 month post-operative, Eta squared); convergent validation (Pearson r correlation to the original BPII); responsiveness testing (Eta squared, anchor-based distribution testing); and reliability testing (intra-class correlation coefficient (ICC) 2,k). The original BPII was successfully reduced from 32 to 23 items. The new BPII 2.0 demonstrated excellent Cronbach's Alpha values: initial consult = 0.91; 6-months = 0.96; 12-months = 0.97; and 24-months post-operative = 0.76. Grade-level reading assessment for all items in the BPII 2.0 was below grade twelve. The ANOVA determined the BPII 2.0 was able to discriminate between the initial consultation, 6, 12 and 24 months post-operative assessments, with significant differences between each time-point (p < 0.05). Eta squared was 0.40, demonstrating a medium to large effect size. Convergent validity was established with the BPII 2.0 significantly correlated to the original BPII (initial consult = 0.82, 6-month = 0.90, 12-month = 0.90, and 24-month = 0.94). Anchor-based responsiveness was established with a significant correlation between the 7-point scale of patient-perceived improvement and 24-month post-operative BPII 2.0 scores. Strong reliability was established with an ICC (2,k) = .97. The BPII has undergone a critical step in its psychometric and clinimetric evolution: structural validation. With the work completed in this study, the BPII and BPII 2.0 have completed assessment of seven of the nine Consensus-based Standards for the selection of health Measurement INstruments (COSMIN) properties including: 1) Internal consistency; 2) Reliability; 3) Standard error of measurement; 4) Content validation; 5) Structural validity; 6) Criterion validity; and, 7) Responsiveness testing. Completion of these assessments and the introduction of a structurally valid and shorter questionnaire, the BPII 2.0, provides a definitive level of credibility to this disease-specific outcome measure

Introduction. The French paradox regarding cemented femoral components has not been resolved, so we compared the mechanical behavior of a French stem, the CMK stem (Biomet, Warsaw, IN, USA), with a collarless, polished, tapered stem (CPT, Zimmer, Warsaw, IN, USA) using an original biomechanical instrument. Materials and Methods. Two size-3 CPT stems and two size-302 CMK stems stems were fixed with bone cement into a composite femur soaked in vegetable oil to simulate wet condition. The composite femur was attached to a biomechanical testing instrument after stem implantation, and a 1-Hz dynamic sine wave load (3000 N) was applied to the stems for a total of 1 million cycles. An 8-hour unload period was set after every 16 hours of load. Femur temperature was maintained at 37°C during testing. The femoral canal was prepared for the CPT stems by standard rasping; for the CMK stems, however, the French method was used, in which cancellous bone was removed with a reamer. One CMK stem (CMK-1) was inserted into a femur without collar contact (>2 mm above the calcar), and the other (CMK-2) was inserted into a femur with collar contact. Stem subsidence was measured at the stem shoulder. Compressive force and horizontal cement movement were measured via rods set at the cement–bone interface on the medial, lateral, anterior, and posterior sides of the proximal and distal portions of the composite femurs. Results. Subsidence was as follows: 0.521 mm and 0.629 mm for the CPT stems, 0.46 mm for CMK-1, and 0.36 mm for CMK-2. Compressive force at the cement–bone interface was at the maximum level at the proximomedial portion of all stems. These forces increased gradually until the one-millionth loading. Maximum compressive forces were 183 N and 107 N for the CPT stems, 180 N for CMK-1, and 215 N for CMK-2. There was a strong positive correlation between stem subsidence and compressive force in all stems. Radial cement creep at the proximomedial portion was 90 μ for one of the CPT stems, 184 μ for CMK-1, and −636 μ for CMK-2. Discussion. We previously reported our findings of a positive correlation between stem subsidence and compressive force in CPT stems. In the current study, CMK stems also subsided even when there was stem collar contact with bone. Subsidence was less in CMK stems than in CPT stems, but the values were close. In addition, compressive force and radial cement creep in CMK stems were also similar to or greater than in CPT stems. Conclusion. The two different concept stems demonstrated similar behavior in relation to bone cement, a finding that may present a solution to the French paradox

To determine the factors that influences the clinical outcomes in surgical correction of thoracic AIS. There are conflicting data regarding the effects of back shape and radiologic parameters on the self-reported outcomes of surgery in AIS. Prospective, cohort study; mean follow-up 29 months (range 9-88). 30 patients (5 males);. Rib hump 17 ° corrected to 7 °. Thoracic Cobb 66 ° corrected to 25 ° (63%). Lumbar Cobb 42 ° corrected to 17°. Thoracic apical vertebral translation (AVT) 48mm corrected to 18mm. Lumbar AVT 34mm corrected to 19mm. Thoracic kyphosis 29° preoperatively 23° postoperatively. Lumbo-sacral lordosis 57° preoperatively 49° postoperatively. Modified SRS Outcomes Instrument (MSRSI) filled out pre-operatively and at final follow up. Primary= rib hump, radiological (frontal Cobb correction, lumbar & thoracic AVT, sagittal profile), Modified SRS Outcomes Instrument (MSRSI) domain scores. The magnitude of the rib hump had a significant association with pain:. Rib hump vs. MSRSI pain r= -0.55 p<0.000. Similar correlations existed between rib hump and self-image (r=-0.64, p<0.0000), thoracic Cobb angle with pain (r=-0.48 p<0.0001) and self-image (r= -0.57, P<0.0000). The postoperative thoracic Cobb angle, and percentage thoracic Cobb correction had significant correlations with self-image (r=-0.55 p=0.003 & r=0.54 p0.004 respectively). The size of the rib hump has a significant impact on pain & self-image. These domains are also significantly influenced by the residual thoracic Cobb angle and overall scoliosis correction

Background: To assess whether modern instrumentation systems are biomechanically strong enough to allow instrumented fusion to pelvis on the concavity of the major curve only and if this confers a significant advantage with respect to complications rates and disadvantages with respect to correction achieved and fusion rates. Methods: A retrospective review from the notes and radiographs of blood loss, operation time, complication rates, degree of correction and fusion rates. Comparisons drawn with neuromuscular curves of similar aetiology treated by same surgeon using more traditional two rod fusion techniques. Subjects were high risk children with progressive neuromuscular scoliosis of varying aetiology requiring stabilisation. (7 cases to date) We compared operation times, blood loss, complication rates, degree of correction and fusion rates with standard segmental fusion techniques in a similar cohort of children. Basic statistical analysis only required to compare the two groups (Analysis of Variance (ANOV A) and Chi squared tests). Results: Mean operation times, blood loss and complication rates of this small cohort were lower than the control group. No implant failure to date with longest follow-up now approaching two years. Conclusion: We hope to open a debate as to whether there is a place for this more limited fusion technique in an effort to minimise the complication rates in these highly challenging children