A differential diagnosis is developed based on results of history, signalment, and physical examination. Other tests or procedures may be necessary to define the disease once the aforementioned findings have narrowed the diagnostic possibilities. Many orthopedic diseases are predictable within certain age groups and breeds (Table 32-1). Information on the animal’s general condition includes anorexia, depression or fever, limb affected, multiple limb involvement, degree of pain or lameness, duration, intensity of onset, historical trauma, effect of exercise, time of day of greatest clinical signs, effect of rest, and changes in lameness associated with weather. Such information provides initial clues to form a differential list of potential causes. Additional questioning, physical examination, and imaging will usually provide data to make a definitive diagnosis.

TABLE 32-1

Differential Diagnoses for Lameness

OCD, Osteochondritis dissecans; UAP, ununited anconeal process; FCP, fragmented coronoid process.

^*Denotes potential differential diagnoses in cats.

Orthopedic Examination

Physical Examination

The animal’s general health should be assessed as part of the physical examination. Baseline examination includes obtaining the animal’s temperature, pulse, and respiration. The animal’s overall appearance should be noted (e.g., obesity) and thoracic auscultation and abdominal palpation performed. A general health evaluation is important before anesthetizing any animal that has orthopedic disease. Traumatized animals brought in for fracture evaluation should have thoracic radiographs and serial electrocardiograms (ECGs) performed. Evaluation of the abdominal cavity is done initially with palpation and evaluation of serum chemistry tests. Abdominocentesis (see p. 380) and radiographic or ultrasonographic evaluation of the urinary tract (see p. 757) should be performed if clinical signs suggest injury. Traumatized animals with long bone fractures frequently have concurrent soft tissue injuries (e.g., pneumothorax, traumatic myocarditis, diaphragmatic hernia, and ruptured bladder or urethra). It is crucial to diagnose and treat these injuries before the animal is anesthetized for fracture repair.

Orthopedic Examination

An orthopedic examination begins by observing the animal for signs of lameness while obtaining the history. This is necessary even if the owner has attributed the lameness to a particular limb because the correct limb may not have been identified. The animal should be observed in the examination room for obvious lameness and for more subtle signs, such as reducing the weight placed on the affected limb when standing or sitting. Other observations may include unilateral or bilateral muscle atrophy and abnormal muscle development. Dogs with bilateral hip dysplasia or chronic cruciate ligament rupture may appear underdeveloped or weak in the rear quarters and heavily muscled in the forequarters.

If the lameness has not been localized during the initial observation, the animal should be observed while walking and trotting. It may be necessary to take dogs outside to improve footing. To protect a sore limb, animals quickly shift their weight from the affected limb, making it appear that they are landing heavily on the opposite, or “good,” limb. Animals with forelimb lameness will lift their heads after the lame limb strikes the ground in an attempt to remove weight from the affected limb. A short stride occurs when the animal has a decreased range of motion in a diseased joint (e.g., hip dysplasia). External swinging, or paddling, of the affected limb(s) occurs when the animal tries to advance a limb that cannot be adequately flexed. This is often observed in dogs with severe degenerative joint disease of the elbows. Animals with bilateral lameness may not limp, but they often show more subtle signs, such as shifting their weight from limb to limb while standing, shortened stride, shaking, and bilateral muscle atrophy.

After the lame limb has been identified, the animal should be returned to the examination room. Limb palpation and a screening neurologic examination should be performed simultaneously. Optimally the first examination should be done without sedation to determine the animal’s response to pain; however, this may not be possible in aggressive animals. The examiner should develop a consistent evaluation pattern. One technique is to start at the front of the animal and work toward the rear. Also, starting at the toes of each limb and progressing proximally is useful. It is preferable to begin examining a sound limb to identify the individual’s normal response to manipulation and pressure. The initial examination should be done with the animal standing to assess muscular symmetry, joint enlargement, and proprioceptive responses. As each bone, joint, and soft tissue area is palpated, any asymmetry (between limbs), response to pain, swelling, abnormalities in range of motion, instability, and crepitation should be noted. Asymmetry should be assessed before and during individual limb palpation and may indicate tumor, abscess, atrophy, joint swelling, or greenstick fracture. Long bones should be palpated to determine if there is swelling (e.g., fracture or tumor), a response to pain while firm pressure is applied (e.g., panosteitis, fracture, or tumor), instability, or crepitation (e.g., fracture). Joints should be isolated and moved through a complete range of motion to detect crepitation, pain, or abnormalities in range of motion. Additional tests of shoulder, hip, and stifle instability should be performed if abnormalities are detected in these joints (see p. 1039 [shoulder], p. 1041 [hip], and p. 1040 [stifle]). Muscles and tendons should be palpated to determine if they are normal and intact. After the initial orthopedic examination to localize pain, the animal may be sedated to facilitate closer examination and to obtain radiographs (Tables 32-2 and 32-3).

TABLE 32-2

Sedation for Palpation and Radiographs of Dogs *

IV, Intravenous; SC, subcutaneous; IM, intramuscular.

^*Animals receiving sedatives should be carefully monitored. Parameters including (but not limited to) respiratory rate, heart rate, and pulse oximetry should be monitored regularly. Blood pressure should be checked when blood pressure changes are anticipated. Temperature should be monitored if the animal is sedated for longer than 30 minutes.

^†Acepromazine (0.05 mg/kg IM or SC; maximum of 2 mg) may be used alone for radiographs and palpation; however, it provides minimal restraint.

Protocols courtesy Dr. Stuart Clark-Price.

TABLE 32-3

Sedation for Palpation and Radiographs of Cats *

IV, Intravenous; SC, subcutaneous; IM, intramuscular.

^†Acepromazine (0.05 mg/kg IM or SC; maximum of 2 mg) may be used alone for radiographs and palpation; however, it provides minimal restraint.

Protocols courtesy Dr. Stuart Clark-Price.

Perform the tibial compression test to detect cranial tibial thrust. Detect forward motion of the tibia by placing the index finger along the patella and the tibial tuberosity. With the leg in a standing position, flex the hock to tense the gastrocnemius muscle (Fig. 32-8). This compresses the femur and tibia together, causing the tibia to move forward in a cranial cruciate-deficient stifle. The presence and amount of drawer motion depend on the animal’s age, size, state of relaxation, and the duration and type of cruciate pathology. There is minimal drawer motion in normal dogs and cats, although very young puppies may have a “lax” stifle. Sedation or general anesthesia increases the likelihood of a positive drawer sign in dogs with cranial cruciate rupture. Minimal drawer motion may be noted with chronic cruciate pathology (especially in large dogs) because periarticular fibrosis restricts stifle motion. Minimal or partial drawer motion may also occur with incomplete tears or stretching of the cranial cruciate ligament. Drawer motion is also evident with a torn caudal cruciate ligament. To identify caudal drawer motion, start with the stifle in a neutral position. Most caudal ligament ruptures are not discovered until exploration because they are mistaken for cranial ligament injuries.

FIG 32-8 Flexing the hock while the limb is in a standing position will tense the gastrocnemius muscle and force the proximal tibia forward if the cranial cruciate ligament is ruptured.

Meniscus

Feel for a click or pop as the stifle is extended and flexed displacing the injured caudal horn of the medial meniscus. In most cases, meniscal tears are identified during exploratory arthrotomy or arthroscopic examination. Occasionally, a click or pop may be felt as the stifle is flexed and extended.

Femur

Palpate the femur for instability (fracture), swelling (fracture, tumor), and pain response to deep bone palpation (panosteitis). Take care to isolate bone from muscle during deep palpation.

Hip

Extend and flex the hip while a hand is placed over the greater trochanter to detect crepitation. The femur should extend caudally to a position almost parallel to the pelvis without inducing pain in a normal hip. The stifle should approach the ilium with full flexion. Degenerative joint disease limits the range of motion and may induce pain.

Hip luxation

To detect luxation of the hip, use the position of the greater trochanter in relationship to the tuber ischium as a landmark. In the standing animal, compare the distance from the greater trochanter with the tuber ischium bilaterally. A unilateral increase in the distance indicates hip luxation. Animals with acute hip luxations are not weight bearing and may have swelling over the greater trochanter. Externally rotate the femur while placing the thumb in the space between the greater trochanter; the thumb should become displaced (Fig. 32-9, A and B). With hip luxation, the trochanter rolls over the thumb (Fig. 32-9, C and D).

FIG 32-9 A and B, To examine for hip luxation, place the thumb in the space caudal to the greater trochanter and externally rotate the femur. If the coxofemoral joint is intact, the greater trochanter will displace the thumb. C and D, If the coxofemoral joint is luxated, the greater trochanter will roll over the thumb.

Hip laxity

With the animal in lateral recumbency, perform the Ortolani maneuver to detect hip laxity associated with hip dysplasia. Place one hand over the dorsal pelvis. Grasp the stifle with the other hand, and orient the femur parallel with the table surface. Simultaneously adduct and push the stifle toward the pelvis. Maintain the pressure and abduct the stifle. As the femoral head returns to the acetabulum, use the hand stabilizing the pelvis to detect a click (Fig. 32-10). The Ortolani maneuver can also be performed with the animal in dorsal recumbency, with the stifles held parallel to each other and perpendicular to the table. Apply downward pressure on the stifle to subluxate the hip. Maintain pressure and abduct the stifle. With both procedures, a click is noted as the femoral head returns to the acetabulum in a subluxated hip (Fig. 32-11). The angle of subluxation is the point at which the hip subluxates, and the angle of reduction is the point at which the femoral head returns to the acetabulum. Evaluation of hip laxity is best done with the dog sedated or anesthetized.

FIG 32-10 To examine the hip for laxity with the animal positioned in lateral recumbency, place one hand over the back and grasp the stifle with the opposite hand. Hold the femur parallel to the table or in adduction and subluxate the femoral head by pushing the stifle toward the pelvis. While maintaining pressure, abduct the limb. As the femoral head returns to the acetabulum, you will feel a click.

FIG 32-11 To examine the hip for laxity with the animal positioned in dorsal recumbency, place the hands over the stifles. Hold the femurs parallel to each other and perpendicular to the table. Subluxate the femoral head by pushing the stifle toward the pelvis. While maintaining pressure, abduct the limb. As the femoral head returns to the acetabulum, you will feel a click.

Pelvis

Examine the pelvic region for evidence of fracture, including asymmetry, instability, swelling, crepitation, bruising, and pain. To detect instability, manipulate the tuber ischia and wings of the ilium. Radiographic evaluation is superior to physical manipulation for identifying fractures. Perform a rectal examination, checking for pelvic canal stenosis, pelvic fractures, and prostate enlargement.

Rule Out Neurologic Disease

Because neurologic disorders may mimic orthopedic diseases or may occur concurrently, every orthopedic examination should include several neurologic examination maneuvers performed to screen for neurologic disease. If evidence of neurologic disease is discovered, a complete neurologic examination is indicated (see Chapter 38). Evaluate conscious proprioception in all four limbs by gently supporting the animal and individually turning each paw until the dorsal surface of the paw contacts the ground. Normal animals return the paw to the correct position almost immediately. Loss of conscious proprioception usually indicates neurologic disease; however, animals with fractured limbs may be reluctant to move the limb and therefore may appear to have conscious proprioception deficits. Flex and extend the neck and bend it laterally in both directions. Apply direct pressure on the lateral processes of the sixth cervical vertebra. Animals may exhibit a forelimb lameness associated with cervical nerve root pain (root signature sign), and it is important to rule out cervical disease or nerve root tumors. Apply direct pressure on the thoracolumbar spine while supporting the abdomen. A painful response, exhibited by vocalization, flinching, or tightening the abdominal musculature may indicate thoracolumbar spinal disease. Apply direct pressure on the ventral lumbar musculature to isolate lumbosacral pain (Fig. 32-12).

FIG 32-12 To isolate lumbosacral pain, apply direct pressure to the ventral lumbar musculature.

It is important to differentiate lumbosacral and hip pain because many older dogs with radiographic signs of hip dysplasia have concurrent lumbosacral pain, which may cause lameness and reluctance to rise and move. Pressure on the dorsal lumbosacral area also pressures the hip, making it difficult to differentiate the source of the pain. Likewise, hip extension also pulls on the iliopsoas muscles, again making it difficult to pinpoint the source of the pain. Apply pressure to digits of the affected limb to elicit a response to superficial and deep pain. Peripheral nerve damage may result concurrently with fractures of the middle to distal humerus (radial nerve) or sacrum (sciatic nerve). No response may indicate peripheral nerve damage.

Additional Diagnostic Techniques

A differential diagnosis is developed based on results of history, signalment, and physical examination. Definitive diagnoses may require additional diagnostic tools including imaging, hematology, serum biochemistry, cytology, or electrodiagnostics. Radiography is generally the initial imaging modality employed to arrive at a definitive diagnosis; however computed tomography, magnetic resonance imaging, ultrasonography, and scintigraphy may be indicated for diagnosis and/or improved visualization of some problems (Table 32-4). Joint taps are useful for differentiating degenerative and inflammatory disease (see p. 1217). Fine needle aspirates or biopsies are essential for diagnosing neoplastic disease (see p. 1398).

TABLE 32-4

Imaging Modalities for Orthopedic Problems

1, Imaging modality used for primary evaluation; 2, imaging modality used for additional evaluation.

Preoperative Management

Perioperative management of surgical patients is discussed in detail in Chapter 4. Orthopedic patients may be brought in for elective surgery (e.g., cranial cruciate ligament injury, hip dysplasia, and osteochondritis dissecans), or nonelective surgery (e.g., bone fractures and joint luxations). When animals are brought in for elective surgery, there is ample time to perform an appropriate preoperative diagnostic evaluation. Younger patients (less than 5 to 7 years old) should have selected screening laboratory tests, including packed-cell volume (PCV), and serum total solids. Urinalysis, fecal analysis, and heartworm tests may be indicated, depending on the history and the animal’s geographic location. The need for further laboratory evaluation should be based on signalment, physical examination, and results of initial screening tests.

Patients older than 5 to 7 years with orthopedic disease must be assessed more carefully than younger patients. Just as the physiologic properties of the musculoskeletal system decline with age, other organ systems also deteriorate. Thorough physical examination remains the foundation of preoperative evaluation and should be supplemented with a complete blood count, chemistry profile, and urinalysis. Special diagnostic tests (e.g., coagulation profile) may be indicated, depending on the history, signalment, and physical findings.

Trauma patients should have a thorough and complete physical evaluation. Serial examinations are important because serious or potentially lethal problems may not become evident for several hours or days after the injury. Although organ dysfunction may be evident (or suspected) on initial physical examination, repeated examinations may be necessary to define the severity of injury. Animals that have received an external blow severe enough to disrupt musculoskeletal integrity (e.g., fracture and luxation) often have concurrent external or internal organ system injury. Cardiovascular, pulmonary, urinary, and neurologic systems are most frequently injured. If abnormalities are found, a differential diagnosis and diagnostic plan for each problem should be developed and additional diagnostic tests completed. For example, cardiac arrhythmias and femoral pulse abnormalities may be found in patients with traumatic myocarditis, necessitating thoracic radiographs and an ECG to assess treatment options and anesthetic risk. Auscultation may detect pulmonary injury (e.g., lung contusion and pneumothorax), but physical changes may be subtle and missed on physical examination. Because one third or more of fracture patients have some degree of pulmonary injury, preoperative evaluation should include thoracic radiographs. A minimum database should include a complete blood count, serum biochemistry profile, and urinalysis. Additional laboratory tests (e.g., coagulation profile, electrolytes [if not part of the biochemical profile], and acid-base balance) may be required to assess differential diagnoses developed on physical examination. Abnormal values should be assessed in light of physical findings, and the need for additional or serial tests should be determined. Serial tests are useful to validate abnormal findings and monitor patient progress. Delaying surgical intervention until abnormal organ function returns to normal is optimal; however, it is often not feasible. Some abnormalities may necessitate that surgical repair of the orthopedic disease be delayed (e.g., uroabdomen), whereas others may alter the prognosis such that repairing the orthopedic condition is not justified (e.g., vertebral fracture with loss of deep pain sensation).

Pain Management and Anesthesia

Orthopedic patients benefit from perioperative analgesics (Table 32-5). The projected level of postoperative discomfort and the duration of discomfort should be assessed to determine the choice of preoperative analgesic. Most orthopedic surgeries are considered moderately to severely painful. Although there is much debate concerning preemptive analgesia, especially in the human medical literature, there are several principles that must be followed in order for preemptive analgesia to be successful. First, the depth of analgesia must be sufficient to block pain receptors during surgery. Second, nociceptive receptors from the entire field must be blocked. And last, analgesia must be continued in the postoperative period (see Chapter 12).

TABLE 32-5

Anesthetic Considerations in the Stable Patient Undergoing Fracture Repair

HCT, Hematocrit; TP, total protein; Cr, creatinine; HR, heart rate; EBL, estimated blood loss; SpO₂, oxygen saturation via a pulse oximeter; CRI, constant rate infusion; PRN, as needed; OTM, oral transmucosal.

^*Monitor for hyperthermia in cats.

^†Buprenorphine is a better analgesic than morphine in cats.

^‡Black box warning added by the FDA in October 2010 identified cases of renal failure and death in cats with repeated uses of meloxicam. Meloxicam is approved for single use only in cats in the United States.

Anesthetic protocols should be chosen based on signalment, physical examination findings, and laboratory analysis. Patients treated for elective orthopedic problems (e.g., cruciate reconstruction) and who have no preoperative findings suggestive of major organ dysfunction can be managed using a variety of anesthetic techniques (see Table 32-5). Patients with cardiovascular compromise or trauma should be anesthetized with care (Table 32-6). When appropriate, balanced anesthetic protocols that include analgesic agents supplemented with epidural analgesia are recommended to decrease intraoperative pain response and reduce the amount of anesthetic needed (Tables 32-7 and 32-8). Epidural anesthesia (with lidocaine, bupivacaine, or ropivacaine) in combination with general anesthesia provides profound relaxation by temporarily paralyzing rear limb muscles, easing fracture reduction of the pelvis, femur, and tibia (see Chapter 12). The duration of action depends on the drug used, ranging from 1 to 6 hours. Fentanyl, morphine or buprenorphine can be added to the epidural injection, providing postoperative pain relief for up to 24 hours. Additionally, opioids may be used alone in the epidural space when relaxation of muscles is not warranted but postoperative analgesia is desired. A brachial plexus block using local anesthetics will provide additional analgesia and muscle relaxation in patients undergoing surgery of the forelimb.

TABLE 32-6