Introduction

Meniscal injuries are very common cause of knee pain and resultant attendance to the orthopaedics or sports medicine clinics. The current protocol stands at clinical examination at first contact and establishing a diagnosis with clinical indicators like joint line tenderness, McMurray's, Apley's and weight-bearing test for meniscal pathology followed by MRI scan to confirm the diagnosis. Either surgical or conservative management follows this. We aim to assess clinical examination alone provide sufficient evidence for further management of meniscal injury and does a role of MRI scan exist to corroborate the findings.

The opposable thumb is one of the defining characteristics of human anatomy and is involved in most activities of daily life. Lack of optimal thumb motion results in pain, weakness, and decrease in quality of life. First carpometacarpal (CMC1) osteoarthritis (OA) is one of the most common sites of OA. Current clinical diagnosis and monitoring of CMC1 OA disease are primarily aided by X-ray radiography; however, many studies have reported discrepancies between radiographic evidence of CMC1 OA and patient-related outcomes of pain and disability. Radiographs lack soft-tissue contrast and are insufficient for the detection of early characteristics of OA such as synovitis, which play a key role in CMC OA disease progression. Magnetic resonance imaging (MRI) and two-dimensional ultrasound (2D-US) are alternative options that are excellent for imaging soft tissue pathology. However, MRI has high operating costs and long wait-times, while 2D-US is highly operator dependent and provides 2D images of 3D anatomical structures. Three-dimensional ultrasound imaging may be an option to address the clinical need for a rapid and safe point of care imaging device. The purpose of this research project is to validate the use of mechanically translated 3D-US in CMC OA patients to assess the measurement capabilities of the device in a clinically diverse population in comparison to MRI. Four CMC1-OA patients were scanned using the 3D-US device, which was attached to a Canon Aplio i700 US machine with a 14L5 linear transducer with a 10MHz operating frequency and 58mm. Complimentary MR images were acquired using a 3.0 T MRI system and LT 3D coronal photon dense cube fat suppression sequence was used. The volume of the synovium was segmented from both 3D-US and MR images by two raters and the measured volumes were compared to find volume percent differences. Paired sample t-test were used to determine any statistically significant differences between the volumetric measurements observed by the raters and in the measurements found using MRI vs. 3D-US. Interclass Correlation Coefficients were used to determine inter- and intra-rater reliability. The mean volume percent difference observed between the two raters for the 3D-US and MRI acquired synovial volumes was 1.77% and 4.76%, respectively. The smallest percent difference in volume found between raters was 0.91% and was from an MR image. A paired sample t-test demonstrated that there was no significant difference between the volumetric values observed between MRI and 3D-US. ICC values of 0.99 and 0.98 for 3D-US and MRI respectively, indicate that there was excellent inter-rater reliability between the two raters. A novel application of a 3D-US acquisition device was evaluated using a CMC OA patient population to determine its clinical feasibility and measurement capabilities in comparison to MRI. As this device is compatible with any commercially available ultrasound machine, it increases its accessibility and ease of use, while proving a method for overcoming some of the limitations associated with radiography, MRI, and 2DUS. 3DUS has the potential to provide clinicians with a tool to quantitatively measure and monitor OA progression at the patient's bedside

Recently, several preliminary reports have been issued on the application of computer assistance to bone tumour surgery. Surgical navigation systems can apply three-dimensional images such as CT and MR images to intraoperative visualization. Although CT is better at describing cortical bone status, MRI is considered the best method for defining the extent of marrow involvement for bone tumours and for planning surgical resection in bone tumour surgery. There have been a few reports on the application of MR imaging to navigation-assisted bone tumour surgery through CT–MR image fusion. However, the CT–MRI fusion technique requires additional costs and exposure of the patient to radiation from the preoperative CT, as well as additional time for image fusion. Above all, the image fusion process is a kind of registration (image to image registration) that inevitably leads to registration error. Herein we describe a new method for the direct application of MR images to navigation-assisted bone tumour surgery as an alternative to CT–MRI fusion. Six patients with an orthopaedic malignancy were employed for this method during navigation-assisted tumour resection. Resorbable pin placement and rapid 3-dimensional spoiled gradient echo sequences made the direct application of MR images to computer-assisted bone tumour surgery without CT–MR image fusion possible. A paired-point registration technique was employed for patient-image registration in all patients. It took 20 min on average to set up the navigation (range 15 to 25 minutes). The mean registration error was 0.98 mm (range 0.4 to 1.7 mm). On histologic examination, distances from tumours to resection margins were in accord with preoperative plans. Mean duration of follow-up was 25.8 months (range 18 to 32 months). No patient had a local recurrence or distant metastasis at the last follow-up. Direct patient-to-MRI registration is a very useful method for bone tumour surgery, permitting the application of MR images to intraoperative visualization without any additional costs or exposure of the patient to radiation from the preoperative CT scan

Purpose. To develop a low complexity highly-automated multimodal approach to segment vertebral structure and quantify mixed osteolytic/osteoblastic metastases in the rat spine using a combination of CT and MR imaging. We hypothesize that semi-automated multimodal analysis applied to 3D CT and MRI reconstructions will yield accurate and repeatable quantification of whole vertebrae affected by mixed metastases. Method. Mixed spinal metastases were developed via intra-cardiac injection of canine Ace-1 luciferase transfected prostate cancer cells in a 3 week old rnu/rnu rat. Two sequential MR images of the L1-L3 vertebral motion segments were acquired using a 1H quadrature customized birdcage coil at 60 m isotropic voxel size followed by CT imaging at a 14m isotropic voxel size. The first MR image was T1 weighted to highlight the trabecular structure to ensure accurate registration with the CT image. The second MR image was T2 weighted to optimize differentiation between bone marrow and osteolytic tumour tissue. Samples were then processed for undecalcified histology and stained with Goldners Trichrome to identify mineralized bone and unmineralized new bone formation. All images were resampled to 34.9 m and manually aligned to a global axis. This was followed by an affine registration using a Quasi Newton optimizer and a Normalized Mutual Information metric to ensure accurate registration. The whole individual vertebrae and their trabecular centrums were then segmented from the CT images using an extended version of a previously developed atlas based registration algorithm. An intensity-based thresholding method was used to segment the regions corresponding to osteoblastic tumor predominantly attached to the outside of the cortical shell. The whole vertebral segmentation from the CT was warped around the T2 weighted MR to define the bone boundaries. An intensity-based thresholding approach was then applied to the T2 weighted MR segment the osteolytic tumor. Results. The customized MR coil acquired good quality images of both the bone and soft tissue structures in the spine. The CT based automated segmentation of the whole vertebrae and the trabecular centrums yielded high volumetric concurrency (∼90%) when compared to manually refined segmentations. Automated thresholding was even more robust in segmenting the individual trabecular networks and osteolytic tumours. The automation of the osteoblastic tumor segmentation was more challenging yielding concurrencies of ∼80% when compared to manually refined segmentations. Conclusion. We successfully combined CT and μMR imaging to accurately segment mixed metastatic lesions within rat vertebrae using a highly-automated algorithm. These segmentations could readily be used for quantitative evaluation of new and existing treatments aimed at skeletal metastases or to generate finite element models to evaluate biomechanical behaviour or fracture risk

Introduction. Patient specific instrumentation (PSI) generates customized guides from an MRI- or CT-based preoperative plan for use in total knee arthroplasty (TKA). PSI software executes the preoperative planning process. Several manufacturers have developed proprietary PSI software for preoperative planning. It is possible that each proprietary software has a unique preoperative planning process, which may lead to variation in preoperative plans among manufactures and thus variation in the overall PSI technology. The purpose of this study was to determine whether different PSI software generate similar preoperative plans when applied to a single implant system and given identical MR images. Methods. In this prospective comparative study, we evaluated PSI preoperative plans generated by Materialise software and Zimmer Patient Specific Instruments software for 37 consecutive knees. All plans utilized the Zimmer Persona™ CR implant system and were approved by a single experienced surgeon blinded to the other software-generated preoperative plan. For each knee, the MRI reconstructions for both software programs were evaluated to qualitatively determine differences in bony landmark identification. The software-generated preoperative plans were assessed to determine differences in preoperative alignment, component sizes, and resection depth. PSI planned bone resection was compared to actual bone resection to assess the accuracy of intraoperative execution. Results. Materialise and Zimmer PSI software displayed differences in identification of bony landmarks in the femur and tibia. Zimmer software determined preoperative alignment to be 0.5° more varus (p=0.008) compared to Materialise software. Discordance in femoral component size prediction occurred in 37.8% of cases (p<0.001) with 11 cases differing by one size and 3 cases differing by two sizes. Tibial component size prediction was 32.4% discordant (p<0.001) with 12 cases differing by 1 size. In cases in which both software planned identical femoral component sizes, Zimmer software planned significantly more bone resection compared to Materialise in the medial posterior femur (1.5 mm, p<0.001) and lateral posterior femur (1.4 mm, p<0.001). Discussion. The present study suggests that there is notable variation in the PSI preoperative planning process of generating a preoperative plan from MR images. We found clinically significant differences with regard to bony landmark identification, component size selection, and predicted bone resection in the posterior femur between preoperative plans generated by two PSI software programs using identical MR images and a single implant system. Surgeons should be prepared to intraoperatively deviate from PSI selected size by 1 size. They should be aware that the inherent magnitude of error for PSI bone resection with regard to both planning and execution is within 2–3 mm. Users of PSI should acknowledge the variation in the preoperative planning process when using PSI software from different manufacturers. Manufacturers should continue to improve three-dimensional MRI reconstruction, bony landmark identification, preoperative alignment assessment, component size selection, and algorithms for bone resection in order to improve PSI preoperative planning process

The use of 3D imaging methodologies in orthopaedics has allowed the introduction of new technologies, such as the design of patient-specific implants or surgical instrumentation. This has introduced the need for high accuracy, in addition to a correct diagnosis. Until recently, little was known about the accuracy of MR imaging to reconstruct 3D models of the skeletal anatomy. This study was conducted to quantify the accuracy of MRI-based segmentation of the knee joint. Nine knees of unfixed human cadavers were used to compare the accuracy of MR imaging to an optical scan. MR images of the specimens were obtained with a 1.5T clinical MRI scanner (GE Signa HDxt), using a slice thickness of 2 mm and a pixel size of 0.39 mm × 0.39 mm. Manual segmentation of the images was done using Mimics® (Materialise NV, Leuven, Belgium). The specimens were cleaned using an acetone treatment to remove soft-tissue but to keep the cartilage intact. The cleaned bones were optically scanned using a white-light optical scanner (ATOS II by GOM mbH, Braunschweig, Germany) having a resolution of 1.2 million pixels per measuring volume, yielding an accuracy of 0.02 mm. The optical scan of each bone reflects the actual dimensions of the bone and is considered as a ground truth measurement. First, a registration of the optical scan and the MRI-based 3D reconstruction was performed. Then, the optical scan was compared to the 3D model of the bone by calculating the distance of the vertices of the optical scan to the reconstructed 3D object. Comparison of the 3D reconstruction using MRI images and the optical scans resulted in an average absolute error of 0.67 mm (± 0.52 mm standard deviation) for segmentation of the cartilage surface, with an RMS value of circa twice the pixel size. Segmenting the bone surface resulted in an average absolute error of 0.42 mm (± 0.38 mm standard deviation) and an RMS error of 1.5 times the pixel size. This accuracy is higher than reported previously by White, who compared MRI and CT imaging by looking at the positioning of landmarks on 3D printed models of the segmented images using a calliper [White, 2008]. They reported an average accuracy of 2.15 mm (± 2.44 mm) on bone using MRI images. In comparison, Rathnayaka compared both CT- and MRI-based 3D models to measurements of the real bone using a mechanical contact scanner [Rathnayaka, 2012]. They listed an accuracy of 0.23 mm for MRI segmentation using five ovine limbs. This study is one of the first to report on the segmentation accuracy of MRI technology on knee cartilage, using human specimens and a clinical scanning protocol. The results found for both bone and cartilage segmentation demonstrate the feasibility of accurate 3D reconstructions of the knee using MRI technology

INTRODUCTION. Over the last twenty years, image-guided interventions have been greatly expanded by the advances in medical imaging and computing power. A key step for any image-guided intervention is to find the image-to-patient transformation matrix, which is the transformation matrix between the preoperative 3D model of patient anatomy and the real position of the patient in the operating room. In this work, we propose a robust registration algorithm to match ultrasound (US) images with preoperative Magnetic Resonance (MR) images of the Humerus. MATERIALS AND METHODS. The fusion of preoperative MR images with intra-operative US images is performed through an NDI Spectra® Polaris system and a L12-5L60N TELEMED® ultrasound transducer. The use of an ultrasound probe requires a calibration procedure in order to determine the transformation between an US image pixel and its position according to a global reference system. After the calibration step, the patient anatomy is scanned with US probe. US images are segmented in real time in order to extract the desired bone contour. The use of an optical measurement system together with trackers and the previously-computed calibration matrix makes it possible to assign a world coordinate position to any pixel of the 2D US image. As a result, the set of US pixels extracted from the images results in a cloud of 3D points which will be registered with the 3D Humerus model reconstructed from MR images. The proposed registration method is composed of two steps. The first step consists of US 3D points cloud alignment with the 3D bone model. Then, the second step performs the widely-known Iterative Closest Point (ICP) algorithm. In order to perform this, we define the coordinate system of both the 3D Humerus model and the US points cloud. The frame directions correspond to the directions of the principal axes of inertia calculated from the matrices of inertia of both the preoperative 3D model and the US data obtained intra-operatively. Then, we compute the rotation matrix to estimate the transformation between the two coordinate systems previously calculated. Finally the translation is determined by evaluating the distance between the mass centres of the two 3D surfaces. RESULTS. In order to evaluate the performance of this registration method in terms of precision and accuracy, we performed the US/MRI fusion on 8 patients. The evaluation criterion used for the validation step was the fiducial registration error (FRE) estimation based on 8 anatomic fiducials detected on the Humerus of the patient. The mean, standard deviation, minimum and maximum values of the 8 Fiducial Registration Errors were 4.34, 2.20, 2.81 and 9.48 mm, respectively. DISCUSSIONS. In this work, we propose a robust registration method of MR and US data. Thanks to the optical system, this fusion will allow us for example to guide and assist surgeons in the positioning of the radiofrequency probe for bone tumor ablation. In addition to the fact that it is completely automatic, the proposed image-to-patient registration method is minimally invasive

Knee biomechanics after total knee arthroplasty (TKA) has received more attention in recent years. One critical biomechanical aspect involved in the workflow of present TKA strategies is the intraoperative optimisation of ligament balancing. Ligament balancing is usually performed with passive flexion-extension in unloaded situations. Medial and lateral ligaments strains after TKA differ in loaded flexion compared to unloaded passive flexion making the passive unloaded ligament balancing for TKA questionable. To address this problem, the development of detailed and specific knowledge on the biomechanical behaviour of loaded knee structures is essential. Stress MRI techniques were introduced in previous studies to evaluate loaded joint kinematics. Previous studies captured the knee movement either in atypical loading supine positions, or in upright positions with help of inclined supporting backrests being insufficient for movement capture under full body weight-bearing conditions. In this work, we proposed a combined MR imaging approach for measurement and assessment of knee kinematics under full body weight-bearing in single legged stance as a first step towards the understanding of complex biomechanical aspects of bony structures and soft tissue envelope. The proposed method is based on registration of high resolution static MRI data (supine acquisition) with low resolution data, quasi-static upright-MRI data (loaded flexion positions) and was applied for the measurement of tibio-femoral kinematics in 10 healthy volunteers. The high resolution MRI data were acquired using a 1.5T Philips-Intera system, while the quasi-static MRI data (full bodyweight-bearing) was obtained with a 0.6T Fonar-Upright™ system. Contours of femur, tibia, and patella from both MRI techniques were extracted using expert manual segmentation. Anatomical surface models were then obtained for the high resolution static data. The upright-MRI acquisition consisted of Multi-2D, quasi-static sagittal scans each including 4 slices for each flexion angle. Starting with full knee extension, the subjects were asked to increase the flexion in 4–5 steps to reach the maximum flexion angle possible under space and force limitations. Knees were softly padded for stabilisation in lateral-medial direction only in order to reduce motion artifacts. During the upright acquisition the subjects were asked to transfer their bodyweight onto the leg being imaged and maintain the predefined flexion position in single legged stance. The acquisition at every flexion angle was obtained near the scanner's isocenter and takes ∼39 seconds. The anatomical surface models of the static data were each registered to their corresponding contours from the weight-bearing scans using an iterative closest point (ICP) based approach. A reference registration step was carried out to register the surface models to the full extension loaded position. The registered surfaces from this step were then considered as initial conditions for next ICP registration step. This procedure was similarly repeated to ensure successful registrations between subsequent flexion acquisitions. The tibio-femoral kinematics was calculated using the joint coordinate system (JCS). The combined MR imaging approach allows the non-invasive measurement of kinematics in single legged stance and under physiological full weight-bearing conditions. We believe that this method can provide valuable insights for TKA for the validation of patient-specific biomechanical models

Knee biomechanics after total knee arthroplasty (TKA) has received more attention in recent years. One critical biomechanical aspect involved in the workflow of present TKA strategies is the intraoperative optimisation of ligament balancing. Ligament balancing is usually performed with passive flexion-extension in unloaded situations. Medial and lateral ligaments strains after TKA differ in loaded flexion compared to unloaded passive flexion making the passive unloaded ligament balancing for TKA questionable. To address this problem, the development of detailed and specific knowledge on the biomechanical behavior of loaded knee structures is essential. Stress MRI techniques were introduced in previous studies to evaluate loaded joint kinematics. Previous studies captured the knee movement either in atypical loading supine positions, or in upright positions with help of inclined supporting backrests being insufficient for movement capture under full body weight-bearing conditions. In this work, we proposed a combined MR imaging approach for measurement and assessment of knee kinematics under full body weight-bearing in single legged stance as a first step towards the understanding of complex biomechanical aspects of bony structures and soft tissue envelope. The proposed method is based on registration of high resolution static MRI data (supine acquisition) with low resolution data, quasi-static upright-MRI data (loaded flexion positions) and was applied for the measurement of tibio-femoral kinematics in 10 healthy volunteers. The high resolution MRI data were acquired using a 1.5T Philips-Intera system, while the quasi-static MRI data (full bodyweight-bearing) was obtained with a 0.6T Fonar-Upright™ system. Contours of femur, tibia, and patella from both MRI techniques were extracted using expert manual segmentation. Anatomical surface models were then obtained for the high resolution static data. The upright-MRI acquisition consisted of Multi-2D, quasi-static sagittal scans each including 4 slices for each flexion angle. Starting with full knee extension, the subjects were asked to increase the flexion in 4–5 steps to reach the maximum flexion angle possible under space and force limitations. Knees were softly padded for stabilisation in lateral-medial direction only in order to reduce motion artifacts. During the upright acquisition the subjects were asked to transfer their bodyweight onto the leg being imaged and maintain the predefined flexion position in single legged stance. The acquisition at every flexion angle was obtained near the scanner's isocenter and takes ∼39 seconds. The anatomical surface models of the static data were each registered to their corresponding contours from the weight-bearing scans using an iterative closest point (ICP) based approach. A reference registration step was carried out to register the surface models to the full extension loaded position. The registered surfaces from this step were then considered as initial conditions for next ICP registration step. This procedure was similarly repeated to ensure successful registrations between subsequent flexion acquisitions. The tibio-femoral kinematics was calculated using the joint coordinate system (JCS). The combined MR imaging approach allows the non-invasive measurement of kinematics in single legged stance and under physiological full weight-bearing conditions. We believe that this method can provide valuable insights for TKA for the validation of patient-specific biomechanical models

CT and MRI scans are complementary preoperative imaging investigations for planning complex musculoskeletal bone tumours resection and reconstruction. Conventionally, tumour surgeons analyse two-dimensional (2-D) imaging information, mentally integrate and formulate a three-dimensional (3-D) surgical plan. Difficulties are anticipated with increase in case complexity and distorted surgical anatomy. Incorporating computer technology to aid in this surgical planning and executing the intended resection may improve precision. Although computer-assisted surgery has been widely used in cranial biopsies and tumour resection, only small case series using CT-based navigation are recently reported in the field of musculoskeletal tumor surgery. We investigated the results of CT/MRI image fusion for Computer Assisted Tumor Surgery (CATS) with the help of a navigation system. We studied 21 patients with 22 musculoskeletal tumours who underwent CATS from March 2006 to July 2009. A commercially available CT-based spine navigation system (Stryker Navigation; CT spine) was used. Of the 22 patients, 10 were males, 11 were females, and the mean age was 32 years at the time of surgery (range, 6–80 years). Five tumours were located in the pelvis, seven sacrum, eight femurs, and two tibia. The primary diagnosis was primary bone tumours in 16 (3 benign, 13 sarcoma) and metastatic carcinoma in four. The minimum follow-up was 17 months (average, 35.5 months; range, 17–52 months). Preoperative CT and MRI scan of each patient were performed. Axial CT slices of 0.0625mm or 1.25mm thickness and various sequences of MR images in Digital Imaging and Communications in Medicine (DICOM) format were obtained. CT and MR images for 22 cases were fused using the navigation software. All the reconstructed 2-D and 3-D images were used for preoperative surgical planning. The plane of tumour resection was defined and marked using multiple virtual screws sited along the margin of the planned resection. We also integrated the computer-aided design (CAD) data of custom-made prostheses in the final navigation resection planning for eight cases. All tumour resections could be carried out as planned under navigation guidance. Navigation software enabled surgeons to examine all fused image datasets (CT/MRI scans) together in two spatial and three spatial dimensions. It allowed easier understanding of the exact anatomical tumor location and relationship with surrounding structures. Intraoperatively, image guidance with the help of fusion images, provided precise visual orientation, easy identification of tumor extent, neural structures and intended resection planes in all cases. The mean time for preoperative navigation planning was 1.85 hours (1 to 3.8). The mean time for intraoperative navigation procedures was 29.6 minutes (13 to 60). The time increased with case complexity but lessened with practice. The mean registration error was 0.47mm (0.31 to 0.8). The virtual preoperative images matched well with the patients' operative anatomy. A postoperative superficial wound infection developed in one patient with sacral chordoma that resolved with antibiotic whereas a wound infection in another with sacral osteosarcoma required surgical debridement and antibiotic. After a mean follow-up of 35.5 months (17–52 months), five patients died of distant metastases. Three out of four patients with local recurrence had tumors at sacral region. Three of them were soft tissue tumour recurrence. The mean functional MSTS score in patients with limb salvage surgery was 28.3 (23 to 30). All patients (except one) with limb sparing surgery and prosthetic reconstruction could walk without aids. Multimodal image fusion yields hybrid images that combine the key characteristics of each image technique. Back conversion of custom prosthesis in CAD to DICOM format allowed fusion with navigation resection planning and prosthesis reconstruction in musculoskeletal tumours. CATS with image fusion offers advanced preoperative 3-D surgical planning and supports surgeons with precise intraoperative visualisation and identification of intended resection for pelvic, sacral tumors. It enables surgeons to reliably perform joint sparing intercalated tumor resection and accurately fit CAD custom-made prostheses for the resulting skeletal defect

High tibial osteotomy (HTO) is a common surgical procedure for treatment of patients with varus mal-alignment. The success rate of the procedure is strongly dependent on the quality of the correction. Thus, an accurate pre-planning is essential to ensure that the precise amount of alignment is achieved postoperatively. The purpose of this study was to simulate the HTO in a patient with varus deformity in order to explore the interactions between the wedge angle, the mechanical axis, and the knee joint configuration. A finite element model of the knee joint of a patient with varus deformity was developed. The geometry was obtained using the whole limb CT scans the knee MR images. The bones were assumed as rigid bodies, the articular cartilage and the meniscus as elastic solids, and the ligaments as nonlinear springs. A 600N force was applied at the femoral head in the line of the mechanical axis and the resulting knee configuration was studied. The HTO was simulated assuming insertion of wedges with different angles beneath the tibial plate and applying the resulting alteration of the loading axis to the model. The results indicated that the actual change of the mechanical axes was always smaller than what predicted by a geometric pre-planning approach that does not consider the post-operative change of the knee joint configuration. It was suggested that subject-specific models are needed to simulate the HTO in patients before surgery and determine the appropriate wedge angle that locates the mechanical axis in the middle of the knee

An 83-year-old woman presented with acute weakness in her right hand and wrist extensors and swelling in the proximal right forearm. Nerve conduction studies confirmed compression of posterior introsseous nerve at the level of proximal forearm. MR imaging demonstrated the characteristics of lipoma which extended on the atero-lateral aspect of the right radius neck. The lesion was parosteal lipoma of the proximal radius causing paralysis of the posterior interosseous nerve without sensory deficit. In this case report, posterior inretosseous nerve palsy due to compression of a parostel lipoma was recovered after excision of the lipoma followed by intensive rehabilitation for six month. Surgical excision should be promptly performed to ensure optimal recovery from the nerve paralysis

Objectives. Delayed gadolinium enhanced MRI of cartilage (dGEMRIC) is a novel MRI-based technique with intravenous contrast agent that allows an objective quantification of biochemical cartilage properties. It enables a ‘monitoring' of the loss of cartilage glycosaminoglycan content which ultimately leads to osteoarthritis. Data regarding the longitudinal change of cartilage property after joint preserving hip surgery is sparse. We asked (1) if and how the dGEMRIC-index changes in patients undergoing open/arthroscopic treatment of femoroacetabular impingement (FAI) one year postoperatively compared to a control group of patients with non-operative treatment; (2) and if a change correlates with the clinical short term outcome. Methods. IRB-approved prospective comparative longitudinal study of two groups involving a total of 61 hips in 55 symptomatic patients with FAI. The ‘operative' group consisted of patients that underwent open/arthroscopic treatment of their pathomorphology. The ‘non-operative' group consisted of conservatively treated patients. Groups were comparable for preoperative radiographic arthritis (Tönnis score), preoperative HOOS- and WOMAC-scores and baseline dGEMRIC indices. All patients eligible for evaluation had preoperative radiographs and dGEMRIC scans at baseline and repeated dGEMRIC scans using the same scanner and protocol. (1) dGEMRIC indices of femoral and acetabular cartilage were assessed separately on the initial and follow-up dGEMRIC scans. Radial images were reformatted from a 3D T1 map for measurements. Regions of interest were placed manually peripherally and centrally within the cartilage based on anatomical landmarks at the 12 ‘hour' position of the clcok-face with the help of radial high-resolution PD-weighted MR images. (2) Patient-reported outcome was evaluated at baseline and at 1 year follow-up: Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Hip disability and Osteoarthritis Outcome Score (HOOS). Statistical analysis included Student's t-Tests, Mann-Whitney U-tests and Wilcoxon signed-rank tests (p<0.05). Results. On the acetabular side, the dGEMRIC index decreased significantly (p<0.05) in 17/20 (85%) zones respectively in 21/24 (88%) of femoral zones in the operated group [Fig. 1]. In the non-operative group, no acetabular zone and 2/24 (8%) femoral zones presented with a significant drop [Fig. 2]. After one year the WOMAC and the HOOS scores significantly improved (58±42 to 33±42; p= 0.007 respectively 63±16 to 74±18; p= 0.028) for the operative group, while there was no change (55±45 to 48±50; p= 0.825 respectively 63±14 to 66±19; p= 0.816) for the non-operative group. Discussion. Interestingly joint-preserving surgery for FAI led to a decline in biochemical cartilage properties on MRI at a one year follow-up despite the significant improvement of patient outcome. This short-term phenomenon was described after periacetabular osteotomy for correction of hip dysplasia in literature with a normalization of the dGEMRIC values at 2 years

Introduction:. Pigmented Villonodular Synovitis (PVNS) is a rare inflammatory disorder of the synovium, bursa and tendon sheath. The objective of this study was to evaluate the long-term outcomes and morbidity associated with operative management of PVNS of the hand. Methods:. Histological databases were retrospectively interrogated. All patients between 2003–2008 with confirmed PVNS of the hand were included in the study. Results:. 15 patients were identified with PVNS of the hand. 10/15 (67%) patients had growths over the digits and 4/15 (26%) involved the thumb with two of these involving the IPJ. 6/10 (60%) of cases with digital involvement arose from a joint (4 PIPJ & 2 MCPJ). Nodular growth was the most common cause for referral. Average length of symptoms prior to presentation was 2.4 years (6 months–5 years). 6/15(40%) of cases had pre-operative MR scans with 100% radiological and histological correlation. Marginal excision was the operative intervention of choice. There was no evidence of bony destruction in any cases. 4/15(26.7%) patients developed a temporary neurapraxia. 4/15 (26.7%) had recurrence at 5 years of which 3/10 had amputations p=0.008. One amputation was due to digital artery injury, two due to recurrence. All patients reported stiffness post-operatively. No functional deficit was recorded. Conclusions:. MR imaging is useful in radiological confirmation of PVNS and is both sensitive and specific making routine biopsy unnecessary. PVNS joint destruction appears rare in such patients although excision carries a high morbidity and risk of recurrence. Those with recurrence are significantly more likely to undergo amputation

Introduction. Recently ventral plating implants made of carbon/PEEK composite material have been developed with apparently superior material properties in terms of implant fatigue and imaging suitability. In this study we assessed the outcome of the first clinical application of this new implant. Methods. Retrospective, single-center case series of 16 consecutive patients between 2011 and 2013 undergoing ventral stabilization surgery with a new carbon plating system (see figure 1). We collected data in terms of safety of the procedure (screw positioning, blood loss, operation time), quality and reliability of the implant (revisions, dislocations, screw loosening, fusion, adjacent segment degeneration), clinical outcome and biological tolerance (cervical pain / discomfort, dysphagia). Results. All patients were available for clinical and radiological follow up. Mean surgery time was 128 minutes, in 11 cases one in 5 cases 2 segments were treated. The clinical findings and patient's satisfaction were good in 14 and fair in two cases. All patients who completed the 6 months control had a radiographically confirmed interbody fusion; no implant loosening or failure and no infections were observed. (see figure 2). There was one implant related complication (dysphagia due to malpositioning of the plate which was removed 4 days after implant insertion) and one complication related to the approach (Horner's syndrome). Conclusion. In this retrospective study of 16 patients we found that the use of a carbon-composite plating system lead to results comparable to the “gold standard” metal plates in terms of safety / clinical outcome and reliability of the implant. There was one revision due to dysphagia. The MR imaging of the patients who have been operated with the carbon/PEEK system showed superior quality with reduced artifacts and improved diagnostical properties, especially when evaluating the neurogical structures. (see figure 3). The overall clinical outcome and patient acceptance of the implant was good. The radiologic findings on follow up of 2, 6 and 12 months have shown a high fatigue strength with no signs of implant failure in terms of dislocation, loosening or breakage. Therefore we conclude that the use of the carbon/PEEK plating system is suitable for ventral stabilization in trauma and degenerative disease

Introduction. An equal knee joint height during flexion and extension is of critical importance in optimizing soft-tissue balancing following total knee arthroplasty (TKA). However, there is a paucity of data regarding the in-vivo knee joint height behavior. This study evaluated in-vivo heights and anterior-posterior (AP) translations of the medial and lateral femoral condyles before and after a cruciate-retaining (CR)-TKA using two flexion axes: surgical transepicondylar axis (sTEA) and geometric center axis (GCA). Methods. Eleven patient with advanced medial knee osteoarthritis (age: 51–73 years) who scheduled for a CR TKA and 9 knees from 8 healthy subjects (age: 23–49 years) were recruited. 3D models of the tibia and femur were created from their MR images. Dual fluoroscopic images of each knee were acquired during a weight-bearing single leg lunge. The OA knee was imaged again one year after surgery using the fluoroscopy during the same weight-bearing single leg lunge. The in vivo positions of the knee along the flexion path were determined using a 2D/3D matching technique. The GCA and sTEA were determined based on existing methods. Besides the anterior-posterior translation, the femoral condyle heights were determined using the distances from the medial and lateral epicondyle centers on the sTEA and GCA to the tibial plateau surface in coronal plane (Fig. 1). The paired t-test was applied to compare the medial and lateral condyle motion within each group (Healthy, OA, and CR-TKA). Two-way ANOVA followed post hoc Newman–Keuls test was adopted to detect significant differences among the groups. p<0.05 was considered significant. Results. The results demonstrated that following TKA, the medial and lateral femoral condyle heights were not equal at mid-flexion (15° to 45°, medial condyle lower then lateral by 2.4mm at least, p<0.01), although the knees were well-balanced at 0° and 90° (Fig. 2). While the femoral condyle heights increased from the pre-operative values (>2mm increase on average, p<0.05), they were similar to the intact knees except that the medial sTEA was lower than the intact medial condyle between 0 and 90°. At deep flexion (>90°), both condyles were significantly higher (>2mm, p <0.01) than the healthy knees. Anterior femoral translation of the TKA knee was more pronounce at mid-flexion (Fig. 3), whereas limited posterior translation was found at deep flexion. Conclusion. Femoral condyle heights and AP translations of the CR TKA knees were significantly different from the healthy knees during the weight bearing flexion activity when measured using both the sTEA and GCA, especially at mid-flexion (15° to 45°) and deep flexion (>90°). These results suggest that a well-balanced knee intra-operatively might not necessarily result in mid-flexion and deep flexion balance during functional weight-bearing motion, implying mid-flexion instability and deep flexion tightness of the knee. The data could be useful for improvement of future prostheses designs and surgical techniques in treatment of patients with end-stage medial knee OA

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

Introduction. Advancements in knee surgery require a profound understanding of knee mechanics. However, there are seemingly contradicting reports regarding certain aspects of normal knee function, such as the location of the pivot of internal-external rotation in the transverse plane. Among others, it has been suggested to be located close to the knee center or in the medial compartment. We hypothesized that this apparent contradiction is a result of different studied knee motions and that it can be explained by the underlying envelopes of motion. The study objective was to characterize normal knee behavior in-vitro with an emphasis on pivot location. Methods. Thirty-four cadaveric human knee specimens (Age: 61±8 years, BMI: 25±7) underwent CT and MR imaging and load controlled in-vitro testing using an industrial robot (KUKA, Augsburg, Germany). The robot simulated passive knee flexion and assessed the envelopes of motion through anterior-posterior (AP, ±100 N), medial-lateral (ML, ±100 N) and internal-external (IE, ±6 Nm) laxity testing at five flexion angles. Kinematics were expressed by the femoral flexion facet centers (FFC). The pivot location was determined for IE laxity testing and passive flexion by computing the center of transverse femoral rotation in a least squares sense. Groups were compared by one-way ANOVA (α = 0.05). Results are stated as average ± standard deviation. Results. During IE laxity testing the pivot was located centrally, exhibiting a small medial offset from the tibia center (Fig. 1). The medial offsets were 4.1±3.0 mm, 3.6±1.9 mm, 4.4±1.9 mm, 5.3±2.0 mm, and 5.4±2.2 mm at 0°, 30°, 60°, 90° and 120° of flexion. In contrast, the passive flexion pivot location was close to the medial plateau border (Fig 2.). Its medial offset from the center amounted to 36.0±11.7 mm and was significantly larger than any offset detected during IE rotation at a given flexion angle (p « 0.001). The resulting envelopes of motion corresponded to these findings (Fig. 3). The average AP laxities of the medial and lateral FFCs were 14.9±2.9 mm and 17.1±3.0 mm whereas laxity at the knee center was only 6.0±2.8 mm. The average IE laxity was 37.8±6.1°. Over the arc of flexion, the envelope centers shifted posteriorly by −0.3±3.1 mm, 14.5±3.9 mm and 10.3±2.9 mm for the medial FFC, lateral FFC and the knee center respectively. Discussion and Conclusion. Our results confirm that the pivot location can vary and is influenced by the type of knee motion. Furthermore, fundamental characteristics of knee biomechanics such as AP stability, IE laxity as well as femoral rollback and external rotation with flexion help explain what could be construed as contradictions in the literature. AP stability and rollback are controlled centrally by the cruciate ligaments. A central pivot during IE laxity testing is a direct consequence of the central AP stabilization. However, a medial pivot during passive flexion results from the superposition of the rollback guided by the cruciates and external rotation with flexion. This current study provides a comprehensive evaluation of the intact knee that when examined as a whole begins to explain contradictory data in the literature and provides a broader picture of passive knee kinematics

Background. Resection of sacral chordoma remains challenging because complex anatomy and important nerves in the sacrum make it difficult to achieve wide surgical margins. Computer-assisted navigation has shown promise in aiding in optimal preoperative planning and in providing accurate and precise tumour resection during surgery. Purpose. To evaluate the benefit of using computer-assisted navigation in precise resection of sacral chordoma. Methods. From 2007 to 2012, we performed sacral chordoma resections with computer-assisted navigation in 19 consecutive patients, of which 15 were primary and 4 were recurrent. There were 11 male and 8 female patients with a mean age of 53.5 years (range, 36–81 years). Eighteen lesions had their upper extent above S3 and the remaining one was below S3. Reconstructed three-dimensional images were used to plan the bone resection before operation. Five patients were treated with CT-based navigation system. 14 cases got ISO-C scanned during operation and CT and MR images were fused using the navigation software. Results. The mean intra-operative blood loss was 2821 mL and the mean operating time was 300 minutes. The mean deviation of registration during operation was 1.5 mm. Wide margins and marginal margins proved by specimen evaluation were achieved in 3 patients and 14 patients, respectively. Two patients received extensive curettage followed by post-operative radiation. With mean 25.1 (range, 7–60) months of follow-up, the overall local recurrence rate was 10.5% (2/19). No recurrence was observed in 15 primary patients treated with wide or marginal margins. A second local recurrence occurred in 2 out of 4 recurrent patients. One was treated with extensive curettage and the other with marginal margin resection. Conclusion. Computer-assisted navigation allows precise execution of intended tumour resection and therefore may improve the local control of sacral chordoma. Comparative clinical studies with long-term follow-up are necessary to confirm this benefit

Introduction. The goal of tibial tray placement in total knee arthroplasty (TKA) is to maximize tibial surface coverage while maintaining proper rotation. Maximizing tibial surface coverage without component overhang reduces the risk of tibial subsidence. Proper tibial rotation avoids excess risk of patellar maltracking, knee instability, inappropriate tibial loading, and ligament imbalance. Different tibial tray designs offer varying potential in optimizing the relationship between tibial surface coverage and rotation. Patient specific instrumentation (PSI) generates customized guides from an MRI- or CT-based preoperative plan for use in TKA. The purpose of the present study was to utilize MRI information, obtained as part of the PSI planning process, to determine, for anatomic, symmetric, and asymmetric tibial tray designs, (1) which tibial tray design achieves maximum coverage, (2) the impact of maximizing coverage on rotation, and (3) the impact of establishing neutral rotation on coverage. Methods. In this prospective comparative study, MR images for 100 consecutive patients were uploaded into Materialise™ PSI software that was used to evaluate characteristics of tibial component placement. Tibial component rotation and surface coverage was analyzed using the preoperative planning software. Anatomic (Persona™), symmetric (NexGen™), and asymmetric (Natural-Knee II™) designs from a single manufacturer (Zimmer™) were evaluated to assess the relationship of tibial coverage and tibial rotation. Tibial surface coverage, defined as the proportion of tibial surface area covered by a given implant, was measured using Adobe Photoshop™ software (Figure 1). Rotation was calculated with respect to the tibial AP axis, which was defined as the line connecting the medial third of the tibial tuberosity and the PCL insertion. Results. When tibial surface coverage was maximized, the anatomic tray compared to the symmetric/asymmetric trays showed significantly higher surface coverage (82.1% vs 80.4/80.1%; p<0.01), significantly less deviation from the AP axis (0.3° vs 3.0/2.4°; p<0.01), and a significantly higher proportion of cases within 5° of the AP axis (97% vs 73/77%). When constraining rotation to the AP axis, the anatomic tray showed significantly higher surface coverage compared to the symmetric/asymmetric trays (80.8% vs 76.3/75.8%; p<0.01). No significant differences were found between symmetric and asymmetric trays. Discussion. We found that the anatomic tibial tray resulted in significantly higher tibial coverage with significantly less deviation from the AP axis compared to the symmetric and asymmetric trays. When rotation was constrained to the AP axis, the anatomic tray resulted in significantly higher tibial coverage than the symmetric and asymmetric trays. Tibial rotation is recognized as an important factor in the success of a total knee replacement. Maximizing coverage with the least compromise in rotation is the goal for tibial tray design. In this study, the anatomic tibia seemed to optimize the relationship between tibial surface coverage and rotation. This study additionally illustrates the way by which advanced preoperative planning tools (ie. MRI/computer reconstructions) allow us to obtain valuable information with regard to implant design