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Miscellaneous Musculoskeletal Conditions  1155


               Traumatic wounds  that involve a bony surface  or   resonance imaging (MRI) and scintigraphy are the
             chronic synovial sepsis are most likely to result in osteo­  modalities of choice for suspected cases of human osteo­
  VetBooks.ir  matory or infective process of the cortex and marrow   earlier diagnosis in horses.  Ultrasonography also can
                                                                 myelitis and septic arthritis and may also provide for an
             myelitis or osteitis. Osteomyelitis refers to the inflam­
                                                                                        20
                                                                 be effective in helping to diagnose osteomyelitis by
             components of bone.  If only cortical bone is infected,
                               17
                                  17
             it is classified as osteitis.  Penetrating wound tracts that   imaging fluid pockets in and around the infected bone. 41
             lead to bone should be treated aggressively. The presence
             of osteomyelitis/osteitis is significantly associated with   Treatment
             nonsurvival in cases with synovial sepsis (Figure 12.20). 57, 61
             Radiography is commonly used to diagnose osteomyeli­  Acute wounds involving synovial structures, includ­
             tis/osteitis, but unfortunately, 30–50% of bone deminer­  ing joints, bursae, and tendon sheaths, often directly
             alization must occur before it can be observed on plain   introduce bacteria and other contaminants into the syn­
             radiographs. This may require 14–21 days, resulting in   ovial space. The clinician’s primary concern is removing
             very low sensitivity and a delayed diagnosis. magnetic   the bacteria from the space before infection can become
                                                                 established. Early recognition and treatment of a syno­
                                                                 vial penetrating wound are imperative to reduce the risk
                                                                 of developing septic arthritis. One study reported that
                                                                 horses treated within 24 hours had a lower risk of devel­
                                                                 oping septic arthritis compared with those treated after
                                                                 24 hours.  Wereszka et al.  found that horses with sep­
                                                                         16
                                                                                       58
                                                                 tic tenosynovitis were significantly more likely to sur­
                                                                 vive if treated during the first day after clinical signs of
                                                                 synovial infection were observed than horses that did
                                                                 not receive treatment within 10 days after clinical signs
                                                                 of infection appeared. However, more recent publica­
                                                                 tions reported that the duration of time until treatment
                                                                 may not affect survival 33,57  or the ability to return to
                                                                                57
                                                                 athletic function.  Logically, it would still be advised
                                                                 that the quicker or earlier these cases are treated, the
                                                                 better the success (Figure 12.21).
                                                                   Any wound that communicates with a synovial  structure
                                                                 or bone should be considered contaminated.  Therefore,
                                                                 early treatment with antimicrobials may help decrease the
                                                                 progression to synovial sepsis and/or osteomyelitis/osteitis.
                                                                 Antimicrobials can be administered parenterally, region­
                                                                 ally, locally, or a combination of all. Additional therapies
                                                                 for preventing infection in a synovial cavity include some
                                                                 form of synovial lavage, drainage or endoscopic explora­
                                                                 tion, and wound debridement with or without closure.
                                                                 Small wounds with minimal contamination can be man­
                                                                 aged conservatively, but the clinical response should be
                                                                 monitored closely, and any deterioration should be met
                                                                 with more aggressive treatment.
                                                                   Systemic antibiotics can be initiated for any infected
                                                                 wound, regardless of the structures, to provide a broad
                                                                 spectrum of activity against common microbes. These
                                                                 antibiotics are maintained until sensitivity of the cul­
             Figure 12.19.  This traumatic wound was associated with an   tured organism is obtained or concerns about sepsis
             open comminuted fracture of the fourth metatarsus. Wound   have diminished. Most commonly, a combination of
             debridement and lavage are important to prevent osteomyelitis in   penicillin (22,000 IU/kg every 6 hours IV, every 12 hours
             these horses. Source: Courtesy of Dr. Gary Baxter.

             Table 12.2.  Synovial fluid parameters used to aid diagnosis of synovial sepsis.


              Fluid analysis parameter           Normal joint              Traumatic synovitis       Septic synovitis

              Total protein (g/L)                18 ± 3                    20–40                     >40
                                                 Less than 20
              Total nucleated cell count (× 10 /L)  <1.0                   <10.0                     >30.0
                                   9
                                                 <3.5 (tendon sheath)
              Neutrophils (%)                    <10                       <10                       >80
   1184   1185   1186   1187   1188   1189   1190   1191   1192   1193   1194