Table of Contents IS SCINTIGRAPHY STILL RELEVANT? PAGE 3 INCORPORATING MRI DIAGNOSTICS INTO YOUR PRACTICE PAGE 17 DIAGNOSIS AND MANAGEMENT OF SELECTED HINDLIMB LAMENESS ISSUES AND THOUGHTS PAGE 25 INJURIES OF THE SAGITTAL GROVE OF THE PROXIMAL PHALANX – A DIAGNOSTIC DILEMMA PAGE 34 DIAGNOSIS AND MANAGEMENT OF SUSPENSORY BRANCH DESMOPATHY IN SPORT HORSES PAGE 39 WHY IS IT IMPORTANT TO SEE SPORTS HORSES RIDDEN? PAGE 50 SACROILIAC JOINT REGION PAIN IN SPORTS HORSES: A GROWING PROBLEM? PAGE 56 HINDLIMB PROXIMAL SUSPENSORY DESMOPATHY: WHY IS IT SUCH A MANAGEMENT CHALLENGE? PAGE 62 MY HORSE WON’T BEND - CERVICAL STIFFNESS AND DYSFUNCTION PAGE 69 UNDERSTANDING BACK PAIN, THORACOLUMBAR FASCIA AND THE MIDDLE COMPARTMENT PAGE 79 BISPHOSPHONATES IN EQUINE PRACTICE PAGE 89 2 IS SCINTIGRAPHY STILL RELEVANT? Michael W. Ross, D.V.M., Diplomate, ACVS Professor of Surgery University of Pennsylvania -- Kennett Square, Pennsylvania, USA [email protected] Synopsis: In this day-and-age of standing and recumbent computed tomography and widespread use of magnetic resonance imaging, many may question the relevance of using nuclear scintigraphy as a diagnostic tool. Far from being over-the-hill the modality continues to be a workhorse for lameness diagnosis and one of the best ways of assessing current activity and relevance of bony abnormalities. I will tell you why using clinical cases. +NO, a nuclear scintigraphic examination is neither a substitute for a detailed clinical lameness examination nor for diagnostic analgesia. Scintigraphy is HUGELY IMPORTANT in evaluating racehorses with poor performance but can be frustrating in sport horses (SHs). Scintigraphy is an enormously useful tool, is cost-effective when used with reasonable expectations and with proper case selection. Scintigraphy is an important ancillary imaging modality; it should not be viewed as an "answer machine." Often clients expect a straight-forward answer to a chronic, complex, and multifaceted performance problem with a single pass of the gamma camera. Scintigraphy cannot give an answer to every lameness problem but provides useful and interesting clinical information. Negative scintigraphic examination can in itself provide a clinical direction by ruling out active bony remodeling. A dressage horse has a chronic obscure performance problem and a negative whole- body bone scan would ensure a training intensity change could be done without exacerbating an existing bony lesion. Alternatively, a negative bone scan can implicate a soft-tissue abnormality (see below). We have been through many generations of equipment, hardware, software and just recently upgraded our equipment to include a custom-made, 91 hex-photomultiplier rectangular LFOV camera, a Segami Oasis nuclear medicine workstation (custom designed to output images according to our specifications), and a modified overhead gantry with upgraded motion (can now rotate the camera on its axis).* If asked if I thought scintigraphy was still “in vogue” my answer would be a resounding, yes indeed! During this lecture and during presentation of case studies at this meeting I will share my thoughts regarding the continuing value of scintigraphy in lameness diagnosis despite advancements in other imaging modalities and why it remains the imaging modality of choice 3 for difficult lameness answers. My thoughts regarding scintigraphy can be found either in various publications or textbooks.1,2 Scintigraphy is a very sensitive modality, but lacks specificity, simply because resolution can be poor and focal areas of increased uptake can represent anything from abnormal bony remodeling to fracture. Resolution can be improved by reducing camera-to-limb distance and to some degree by upgrading imaging equipment. To improve overall accuracy multiple images should be used. For instance, to determine the position of a focal area of increased radiopharmaceutical uptake (IRU) in the fetlock joint, it is important to have lateral, dorsal (plantar), and flexed lateral images. With this information, rather than report a finding of a “hot spot in the fetlock joint,” the clinician can say, “there is a focal area of IRU involving the distal, plantarolateral aspect of MtIII” a much more accurate description of the area of abnormal bony activity. Flexed lateral images of the hock, flexed dorsal images of the carpus and solar or palmar images of the foot are important. To diagnose medial femorotibial joint disease, a caudal image of the stifle is mandatory. A minimum of 2 images should be taken when possible. For instance, after a peroneal and tibial nerve block, focal IRU is often seen in delayed images over the cranial tibial cortex. Without the caudal image showing uptake is clearly in soft-tissues, inadvertent diagnosis of a tibial stress fracture could be made (of course, tibial stress fracture involving the cranial cortex is unusual). Two images also allow a determination of cortical or medullary IRU in long bones, and differentiation of stress fractures from enostosis-like lesions (a.k.a. bone islands). Focal IRU is more important than diffuse IRU, regardless of intensity. Bone IRU early in the flow or pool phases usually indicates active periosteal proliferation, seen in stress fractures, cortical trauma, or osteomyelitis. Most false negative scans result from problems with limb or camera positioning, body part-to-camera distance, shielding by overlying soft-tissues or bone, background (bladder) and physeal activity. Careful interpretation of caudal images of the stifle helps diagnose osseous cyst-like lesions. Authentic negatives are useful in horses in which an increase in exercise is planned, but care must be taken in racehorses. Negative delayed-phase supports pain is likely originating from soft tissues. In horses with hindlimb lameness, negative scan findings often lead me to suspect the stifle because delayed images lack sensitivity. Findings in horses with chronic proximal suspensory desmitis (PSD) also are often negative. Remember it is called a bone scan for a reason; sensitivity for soft tissue injury, chronic problems such as PSD is poor. DO NOT expect the bone scan to be positive in a horse with PSD. Case selection - racehorses are ideal since they undergo high-impact exercise and are prone to stress- related cortical or subchondral trauma. Older SHs, particularly Warmbloods are much less than ideal. Low-impact exercise coupled with advanced age decrease the possibility of an answer. Scintigraphic examination may provide disappointing information regarding chronic osteoarthritis, particularly of the fetlock joint. In racehorses IRU of the palmar/plantar aspect of the fetlock joint (Mc/MtIII most common) is often pronounced, whereas in sport horses focal, mild IRU, most often seen associated 4 with the dorsomedial aspect of the joint can be subtle and is often under-appreciated or interpreted incorrectly. It is sometimes difficult to find correlation between scintigraphic and radiological changes in the distal hock joint. In SHs, scintigraphic examination is useful with pain associated with the foot, fetlock, proximal metacarpus/metatarsus, stifle, and the back. But, two important factors determining the usefulness of the bone scan include, the horse is clinically lame at the time of the scan and lameness has been localized. Scintigraphy provides a "functional evaluation" of osteoblastic activity (modeling) at the time of the scan. If a horse with chronic lameness is rested for several months before evaluation, the chances of seeing IRU are greatly diminished. In a known area of clinical lameness, diagnostic accuracy can be increased, since a differentiation can be made between soft-tissue and bony problems, and radiographs can be more carefully evaluated considering scintigraphic findings. Scintigraphy is least likely to yield a diagnosis in SHs with nebulous histories of gait abnormalities and poor performance and with problems that can be perceived only by the rider. These horses usually are not lame, may have equivocal or negative manipulative test results, and may be difficult individuals with which to work. Diagnostic analgesia may be difficult to perform or interpret but selective analgesic techniques may improve the feel of the horse. Blocking one limb in a horse suspected of having bilateral nearly symmetric pain may produce obvious contralateral signs. Scintigraphic examination has been used as part of a comprehensive purchase examination, but results must be carefully interpreted and clinical relevance established. Although unusual, this adjunct imaging procedure usually is requested in high-profile, expensive, upper-level sport horses and results can often be confusing. Finding an upper-level horse of any type without any scintigraphic changes would be unusual, mirroring radiological findings in these horses. Scintigraphy was useful in establishing clinical relevance of mineralization of the cartilages of the foot and when present, intense IRU was associated with radiological changes that could be differentiated (wider and more irregular) from unimportant areas of mineralization or separate centers of ossification.3-5 A possible benefit to clinicians performing examinations before purchase was proposed.3 5 Focal or diffuse areas of IRU are found in the thoracolumbar dorsal spinous processes and may account for clinical signs of back pain, poor performance, or gait restriction but occur only in horses that are ridden. A wide spectrum of scintigraphic and radiological changes in the thoracolumbar spine in horses without