A. Jay Khanna

Magnetic resonance imaging of the shoulder. Current techniques and spectrum of disease.

Magnetic resonance imaging is an excellent modality for imaging pathological processes of the shoulder joint. It allows high-resolution imaging of all anatomic structures, including the glenoid, the humeral head, the articular cartilage, the acromion, the muscles and tendons of the rotator cuff, the labrum, the biceps tendon, and the glenohumeral ligaments, in multiple orthogonal planes. Numerous technical options and several pulse sequences can be utilized for the performance of magnetic resonance imaging of the shoulder. The aim of this review is to update orthopaedic surgeons on the technical aspects of performing magnetic resonance imaging of the shoulder. In addition, this report will define the normal anatomy of the shoulder as demonstrated by magnetic resonance imaging and review the spectrum of disease detectable with this technique. After reviewing this article, the reader should (1) have a basic understanding of the physics, pulse sequences, and terminology of magnetic resonance imaging; (2) be able to systematically evaluate the findings of a complete magnetic resonance imaging examination of the shoulder and know the features of normal shoulder anatomy; (3) be able to identify various tissue types on T1-weighted, fat-suppressed T2-weighted, and proton-density images; and (4) be able to diagnose certain pathological processes of the shoulder on the basis of magnetic resonance imaging findings. ### Process of Image Production First, the subject is positioned in the scanner. For magnetic resonance imaging of the shoulder, the patient is supine and the arm is held at the side, as opposed to across the chest, in order to minimize transmission of respiratory motion to the shoulder. The arm is placed in slight external rotation to optimally orient the supraspinatus tendon in order to prevent confusing overlap with the infraspinatus tendon on coronal oblique images1. The external rotation also allows maximum visualization of the supraspinatus insertion2. The magnetic field of …

Pelvic Fixation In Spine Surgery: Historical Overview, Indications, Biomechanical Relevance, And Current Techniques

F usions of the lumbosacral spine continue to be a challenging area in spine surgery. The complex local anatomy, unique biomechanical forces, and poor bone quality of the sacrum are just a few of the many reasons why fusions of the lumbosacral spine have been notoriously difficult to perform. The goals of this review were (1) to familiarize the reader with the complicated anatomy of the lumbosacral region, the specific pathological entities that involve this region, and the biomechanical forces that lead to high pseudarthrosis rates; (2) to discuss the various types of lumbosacral and spinopelvic implants and their respective advantages and disadvantages; (3) to review the most common clinical indications for lumbosacral and spinopelvic fusions; and (4) to emphasize that iliac screw placement is a safe and reproducible technique for achieving stable caudad pelvic fixation that minimizes the risk of pseudarthrosis at the lumbosacral junction. T he sacrum, which functions as the keystone that unites the two hemipelves, consists of five fused vertebrae with transverse processes that merge into a thick, continuous lateral mass. Its anteroposterior diameter tapers rapidly from 47 mm at S1 to 28 mm at S2 in women and from 50 to 31 mm in men1. For the most part, the sacrum has a cancellous osseous architecture, but areas of increased bone density are present in the sacral alae and particularly in the sacral promontory2. Therefore, it is best that pedicle screws be directed toward the midline. The sacrum is connected to each hemipelvis by the sacroiliac joint, which is the largest joint in the axial skeleton. The sacroiliac joint contains a synovial membrane but has minimal motion because of the matching interdigitating contours of the sacral and iliac bones and the strong interosseous, dorsal, ventral, and accessory ligaments3. It …

Instrumentation of the osteoporotic spine: biomechanical and clinical considerations

BACKGROUND CONTEXT Osteoporosis is a major health-care problem that is increasing in magnitude with the aging population. Such patients are more prone to develop painful and debilitating spinal deformities but are difficult to treat. Currently, no definitive treatment algorithm has been established. PURPOSE To review the failure modes of instrumentation and novel surgical treatments of spinal deformities in patients with osteoporosis with the goal of improving surgical care. STUDY DESIGN/SETTING Review article. METHODS We systematically searched PubMed for articles regarding instrumentation failure modes and surgical treatments of spinal deformities in patients with osteoporosis and summarized current treatment options. RESULTS The surgical treatment options are severely limited because of the tendency for instrument failure secondary to pullout and subsidence, leading to revision procedures; multiple levels and multiple fixation points are recommended to minimize the risk. The literature supports the use of vertebroplasty in conjunction with pedicle screw-based instrumentation for treating more severe spinal deformities. Other techniques and modifications with evidence of reduced failure risk are bicortical screws, hydroxyapatite coatings, double screws, and expandable screws. Anterior approaches may provide another avenue of treatment, but only a few studies have been conducted on these implants in patients with osteoporosis. CONCLUSIONS Spinal deformities in patients with osteoporosis are difficult to treat because of their debilitating and progressive nature. Novel surgical approaches and instruments have been designed to decrease construct failures in this patient population by reducing implant pullout, subsidence, and incidence of revision surgery. The success of these techniques depends on integrating biomaterial, biologic, and biomechanical aspects with clinical considerations. Synthesizing this myriad of aspects will lead to improved treatment options for patients with osteoporosis who are suffering from spinal deformities.

Magnetic resonance imaging of soft-tissue tumors : Determinate and indeterminate lesions

The evaluation of patients with soft-tissue masses must be done in a systematic fashion to prevent management errors. Although most soft-tissue masses (approximately 99%) are benign, an error in the management of a soft-tissue sarcoma can lead to limb loss or adversely affect survival1. Before magnetic resonance imaging became easily available, physicians relied on the patients history, physical examination, conventional radiographs, and computed tomography scans for decision-making. These modalities often were insufficient for establishing a definitive diagnosis. The patients history alone cannot provide enough information for a diagnosis and, in fact, may be misleading. For example, lesions identified after a traumatic episode are not necessarily traumatic in origin; only half of soft-tissue sarcomas are painful at presentation2, and the growth rate may not assist in the diagnosis (slow-growing lesions can be malignant or benign). Similarly, although a patient may present with systemic symptoms, the lack of systemic symptoms does not exclude malignancy. Physical examination may provide some clues that may suggest malignancy, but none are pathognomonic. Conventional radiography and computed tomography are not specific enough in differentiating benign and malignant soft-tissue masses. If one relies solely on these modalities, biopsy often is necessary for diagnosis and management. Biopsy is associated with several hazards, including neurovascular injury, hematoma formation, and delayed wound-healing. The use of magnetic resonance imaging to identify soft-tissue lesions has markedly altered the treatment algorithm for a number of lesions3,4. In contrast to conventional radiography and computed tomography, magnetic resonance imaging provides clear advantages in terms of diagnosis: the spatial resolution of the images is excellent; the images can be reconstructed in multiple planes; lesions can be identified more readily, and the lesions signal characteristics can help to narrow the differential diagnosis; areas of hemorrhage, cysts, and vascular structures are …

Cervical stenosis secondary to rhizomelic chondrodysplasia punctata

Rhizomelic chondrodysplasia punctata (RCDP) is a rare peroxisomal disorder leading to multiple developmental malformations, including skeletal deformity. Specifically, involvement of the vertebral bodies has been described. Presented here is a case of a two-year-old female child with RCDP leading to advanced cervical stenosis as detected on magnetic resonance imaging (MRI) studies of the cervical spine. The practicing clinician should be aware of the possibility of cervical stenosis secondary to RCDP and its impact on the management of the patient with this rare disease process.

Soft-tissue imaging with C-arm cone-beam CT using statistical reconstruction.

The potential for statistical image reconstruction methods such as penalized-likelihood (PL) to improve C-arm cone-beam CT (CBCT) soft-tissue visualization for intraoperative imaging over conventional filtered backprojection (FBP) is assessed in this work by making a fair comparison in relation to soft-tissue performance. A prototype mobile C-arm was used to scan anthropomorphic head and abdomen phantoms as well as a cadaveric torso at doses substantially lower than typical values in diagnostic CT, and the effects of dose reduction via tube current reduction and sparse sampling were also compared. Matched spatial resolution between PL and FBP was determined by the edge spread function of low-contrast (∼ 40-80 HU) spheres in the phantoms, which were representative of soft-tissue imaging tasks. PL using the non-quadratic Huber penalty was found to substantially reduce noise relative to FBP, especially at lower spatial resolution where PL provides a contrast-to-noise ratio increase up to 1.4-2.2 × over FBP at 50% dose reduction across all objects. Comparison of sampling strategies indicates that soft-tissue imaging benefits from fully sampled acquisitions at dose above ∼ 1.7 mGy and benefits from 50% sparsity at dose below ∼ 1.0 mGy. Therefore, an appropriate sampling strategy along with the improved low-contrast visualization offered by statistical reconstruction demonstrates the potential for extending intraoperative C-arm CBCT to applications in soft-tissue interventions in neurosurgery as well as thoracic and abdominal surgeries by overcoming conventional tradeoffs in noise, spatial resolution, and dose.

The Effect of Fear of Movement Beliefs on Pain and Disability After Surgery for Lumbar and Cervical Degenerative Conditions

Study Design. Prospective cohort study. Objective. To examine differences between preoperative and postoperative fear of movement and investigate the relationship between fear of movement and pain, disability and physical health after spinal surgery for degenerative conditions. Summary of Background Data. Consistent evidence supports the relationship between fear of movement and higher levels of pain and disability in various chronic pain populations. Fear of movement among patients undergoing spinal surgery for chronic pain has received little attention in the literature. Methods. Participants were 141 patients treated with surgery for lumbar and cervical degenerative conditions. Assessments were conducted before surgery and 6 weeks and 3 months after hospitalization. Fear of movement was measured with the Tampa Scale for Kinesiophobia and outcomes were measured with the Brief Pain Inventory, Oswestry or Neck Disability Index, and 12-Item Short Form Health Survey (SF-12). Results. Follow-up rates were 91% and 87% for 6 weeks and 3 months, respectively. Fear of movement beliefs improved after surgery, but 49% of patients continued to have high fear of movement at 6-week follow-up and 39% at 3-month follow-up. Patients with higher levels of fear of movement had poorer postoperative outcomes. Multilevel linear regression analyses found that postoperative fear of movement was independently associated with postoperative pain intensity, pain interference, disability, and physical health (P < 0.001), after controlling for depression, age, sex, education, race, comorbidities, type and area of surgery, prior surgeries, and baseline outcome score. Preoperative fear of movement was not predictive of poorer surgical outcomes. Conclusion. Results demonstrate that postoperative but not preoperative fear of movement beliefs explain unique and significant variance in postoperative pain, disability, and physical health. Clinicians interested in improving surgical outcomes should address postoperative fear of movement along with other traditional clinical and medical risk factors. Recommendations include postoperative screening for high fear of movement beliefs and incorporating cognitive-behavioral techniques into postoperative rehabilitation for at-risk surgical spine patients.

Magnetic Resonance Imaging of Cartilage in the Athlete: Current Techniques and Spectrum of Disease

In the athletic population, reproducible imaging of cartilage damage is vital for treatment considerations. With appropriate pulse sequencing, magnetic resonance imaging has been shown to be an accurate noninvasive method for the evaluation of articular cartilage injuries and for evaluating postoperative changes following chondral repair. In addition, magnetic resonance imaging does not utilize ionizing radiation, has direct multiplanar capabilities, and allows high-resolution imaging of soft-tissue structures. The purposes of the present review are to update orthopaedic surgeons on the applications and techniques for magnetic resonance imaging of cartilage in the athletic population, to define the normal magnetic resonance imaging characteristics of articular cartilage, to illustrate the spectrum of articular cartilage lesions that are detectable with magnetic resonance imaging, and to review normal and abnormal magnetic resonance imaging findings following cartilage repair. After reviewing this article, the reader should (1) have a basic understanding of pulse sequences and terminology for cartilage-sensitive magnetic resonance imaging, including proton-density-weighted high-resolution fast-spin-echo sequences; (2) be able to identify normal and abnormal articular cartilage in the hip, knee, elbow, shoulder, and ankle; and (3) be able to identify normal and abnormal findings on postoperative magnetic resonance images after chondral repair techniques. An understanding of the structure of articular cartilage is crucial in order to understand the magnetic resonance imaging appearance of normal and abnormal cartilage morphology and is also the basis for the development of new imaging techniques. Articular cartilage is a viscoelastic material composed of chondrocytes (approximately 1%) embedded in an organized extracellular matrix composed primarily of water (65% to 80%), collagen, and proteoglycan. The predominant collagen is type II (95%), although smaller amounts of other collagen types (types IV, VI, IX, X, and XI) have been identified1. Collagen provides the structural framework and tensile strength of articular cartilage. Chondroitin and keratin sulfates …

Toe-walking attributable to venous malformation of the calf muscle.

Soft tissue venous malformations of muscles may produce musculoskeletal deformities caused by contracture of the involved muscle. When the venous malformation involves the flexor muscles of the leg, equinus deformity and toe-walking may occur. Three patients with unilateral toe-walking secondary to venous malformation of the calf muscle, showing the classic presentation of this unusual condition, are presented. Several methods of treating the deformity and the underlying venous malformation are discussed, and the current literature on intramuscular venous malformations, including their natural history, diagnoses, treatment options, and outcomes, is reviewed. Based on our experience and review of the literature, percutaneous sclerotherapy may be a viable option for treatment of venous malformations of the calf musculature that result in a toe-walking deformity.

Magnetic Resonance Imaging of Spine Tumors: Classification, Differential Diagnosis, and Spectrum of Disease

Magnetic resonance imaging is an excellent modality for imaging pathologic processes involving the spine1-3. It permits high-resolution imaging of not only the osseous structures but also the soft-tissue structures in multiple orthogonal planes through the use of varying pulse sequences that allow for characterization of the different tissues in and around the spine. The purposes of this report are to (1) describe the specialized pulse sequences and imaging techniques available for evaluation of the spine, (2) describe the defining characteristics of the three compartments into which spinal tumors can be classified, (3) define the differential diagnoses for tumors identified in each of these three compartments, and (4) provide a basic knowledge of the tumors that are commonly encountered in the spine. Figs. 1-A through 1-D Figs. 1-A through 1-D Magnetic resonance images of a normal lumbar spine: sagittal T1-weighted (Fig. 1-A), axial T1-weighted (Fig. 1-B), sagittal T2-weighted (Fig. 1-C), and axial T2-weighted (Fig. 1-D). ### Process of Image Production First, the patient is placed in the scanner. The magnetic field of the scanner (most frequently 1.5 T) aligns all protons within the patient along the longitudinal axis of the scanner. An electromagnetic pulse is sent into the scanner and causes reorientation of the protons (usually 90° to the external field). The pulse is turned off, and the protons are allowed to relax. As the protons relax, they emit a radiofrequency signal that is then detected by an antenna in the scanner. The signal is processed with use of an algorithm4 (Fourier Transformation), and software programs are used to create the images in multiple orthogonal planes. ### Definitions T1 indicates the amount of time required for 63% of the protons to return to their preexcited state and is a measure of the longitudinal relaxation of the protons. T2 indicates the amount of time that is needed for …