T h e N o r m a l an d A b n o r m a l Equine Neonatal Musculoskeletal System David G. Levine,
DVM
KEYWORDS Musculoskeletal Ossification Synovial infection Osteomyelitis Flexural limb Angular limb KEY POINTS The first few weeks of life are critical in horses. Cuboidal bone ossification at birth can vary and should be assessed in premature and dysmature foals. Flexural limb deformities, angular limb deformity, and laxity are common in neonatal foals and should be assessed and treated early. Neonatal foals are susceptible to septic orthopedic conditions owing to immature immune system and physeal blood flow. Early recognition and treatment is key to success.
NORMAL OSSIFICATION
In the typical foal, the tarsal and carpal bones ossify in the last 2 to 3 months of gestation.1 The normal process of endochondrial ossification starts centrally within the bone and the process continues until the periphery of the bone is mature with the normal surrounding cartilage. Ossification of the cuboidal bones plays an important role in the foal, but should not be confused with total skeletal maturity.2 In the human, skeletal maturity is determined by radiographs of the axial skeleton because cuboidal bones are not a reliable index for total skeletal maturity.3,4 A skeletal ossification index has been used to standardize the evaluation of newborn foals.2 The index is based on 2 radiographic views of the carpus and tarsus, and 4 grades have been developed. Grade 1: Some of the cuboidal bones of the carpus and tarsus have no radiographic evidence of ossification (Fig. 1). Grade 2: Some radiographic evidence of ossification of all of the cuboidal bones of the carpus and tarsus (excluding the first carpal bone). The proximal physes of the third metacarpus/metatarsus were open (Fig. 2).
University of Pennsylvania, New Bolton Center, 382 W. Street Road, Kennett Square, PA 19348, USA E-mail address: [email protected] Vet Clin Equine 31 (2015) 601–613 http://dx.doi.org/10.1016/j.cveq.2015.09.003 vetequine.theclinics.com 0749-0739/15/$ – see front matter Ó 2015 Elsevier Inc. All rights reserved.
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Levine
Fig. 1. Grade 1 ossification. Some of the cuboidal bones show no evidence of ossification.
Grade 3: All of the cuboidal bones were ossified, but they were small with rounded edges. The joint spaces thus seemed to be wide in these individuals. The lateral styloid process and the malleoli were distinct. The proximal physes of the third metacarpus and metatarsus were closed (Fig. 3).
Fig. 2. Grade 2 ossification. All cuboidal bones have some evidence of ossification. There is a faint line representing the open proximal metacarpal physes.
Equine Neonatal Musculoskeletal System
Fig. 3. Grade 3 ossification. All cuboidal bones are present but have rounded edges with increased joint space and the proximal metacarpal physis is closed.
Grade 4: All of the criteria of grade 3 were met, and the cuboidal bones were shaped like the corresponding bones in the adult and the joint spaces were of expected width (Fig. 4). A common condition in immature foals is incomplete ossification of the cuboidal bones. This condition is not limited to the immature foal; dysmature foals may also display this condition. There are many reported causes for incomplete ossification of the cuboidal bones. These can include1,5,6:
Prematurity related to short gestational age (2 g/dL) and high leukocyte counts (>10,000 cells/mL; primarily neutrophils) are typical. Foals with septic synovial structures can often have leukocyte counts of greater than 50,000 cells/mL, although cell count does not seem to correspond with the severity of disease.18,19 Samples should be submitted for culture and sensitivity, often accompanied with a blood culture, to determine whether systemic sepsis is an ongoing problem. A complete physical examination looking for other sources of sepsis (lungs, gastrointestinal, umbilical) should always be performed. Radiographs should be obtained of affected joints to determine physeal and metaphyseal involvement. In early cases, these radiographs can serve as a baseline to follow-up examinations. Radiographic change often lags behind the clinical picture and bone that seems to be normal radiographically may still be affected. Treatment
Treatment should consist of aggressive local and, if indicated, systemic antimicrobial therapy. Broad-spectrum antimicrobials are commonly started until a positive culture or clinical suspicion helps to guide antimicrobial choice. Lavage of the septic structures can be done with through-and-through needle lavage or more aggressively with an arthrotomy or arthroscopy. Several studies have shown the benefit of more aggressive treatment with arthotomy/arthroscopy with improved survival and no increase in morbidity.19,20 This is owing to the removal of fibrin, inflammatory mediators, and diseased bone and synovial membrane that cannot be removed by simple needle lavage. Local implantation of antibiotic impregnated beads, intraarticular injection of antimicrobials, and regional limb perfusions can be used in addition to lavage and may improve the outcome.20 Although regional limb perfusion is an appropriate way to deliver high concentrations of antimicrobials to the distal limb, intraarticular injections still achieve higher concentrations within the joint as well as adjacent bone. Prognosis
Survival in these cases ranges from 45% to 85%.21 Athletic outcome depends on the number of joints affected, severity of infection, as well as the response to treatment. Thoroughbred foals have been shown to have a decreased likelihood to race compared with controls with only 30% of survivors becoming racehorses.22,23 Factors that decrease survival include21–23:
Duration of infection before treatment; Number of joints affected; Bone involvement; and Multisystemic disease.
611
612
Levine
SUMMARY
The first weeks of a foal’s life can be challenging. Orthopedic conditions can occur frequently and some do require emergency treatment. The key is early diagnosis and appropriate care. Prognosis for most conditions improves with early recognition and corrective treatments. It is important to know the appropriate treatment for each condition because often the incorrect treatment can lead to further complications. REFERENCES
1. McIlwraith CW. Incomplete ossification of carpal and tarsal bones in foals. Equine Vet Ed 2003;15(2):79–81. 2. Adams R, Poulos P. A skeletal ossification index for neonatal foals. Vet Radiol 1988;29:217–22. 3. Kuhns LR, Finnstrom O. New standards of ossification of the newborn. Radiology 1976;119:655–60. 4. Kuhns LR, Sherman MP, Poznanski AK. Determination of neonatal maturation on the chest radiograph. Radiology 1972;102:597–603. 5. Auer JA, Martens RJ, Morris EL. Angular limb deformities in foals. Comp Cont Educ Pract Vet 1982;4:330–9. 6. Rossdale PD, Ousey JC. Fetal programming for athletic performance in the horse: potential effects of IUGR. Equine Vet Ed 2002;14:98–112. 7. Auer J. Angular limb deformities. In: Auer JA, editor. Equine surgery. St Louis (MO): Elsevier; 2012. p. 1201–21. 8. Hunt RJ. Flexural limb deformities. In: Ross MW, Dyson SJ, editors. Diagnosis and management of lameness in the horse. St Louis (MO): Elsevier; 2003. p. 562–5. 9. Adams SB, Santschi EM. Management of flexural limb deformities in young horses. Equine Pract 1999;21:9–16. 10. Auer JA. Flexural limb deformities. In: Auer JA, editor. Equine surgery. St Louis (MO): Elsevier; 2012. p. 1150–65. 11. Adams SB, Santschi EM. Management of congenital and acquired flexural limb deformities. Proceedings AAEP 2000;46:117–25. 12. Whitehair KJ, Adams SB, Toombs JP, et al. Arthrodesis for congenital flexural deformity of the metacarpophalangeal and metatarsophalangeal joints. Vet Surg 1992;22:228–33. 13. Madison JB, Garber JL, Rice B, et al. Effect of oxytetracycline on metacarpophalangeal and distal interphalangeal joint angles in new born foals. J Am Vet Med Assoc 1994;204:240–9. 14. Trumble TN. Orthopedic disorders in neonatal foals. Vet Clin Equine 2005;21: 357–85. 15. Stoneham SJ, Digby NJ, Ricketts SW. Failure of passive transfer of colostral immunity in the foal. Vet Rec 1991;22:42–5. 16. Cohen ND. Causes of and farm management factors associated with disease and death in foals. J Am Vet Med Assoc 1994;204:1644–51. 17. Madison JB, Sommer M, Spencer PA. Relations among synovial membrane histopathologic findings, synovial fluid cytologic findings, and bacterial culture results in horses with suspected infectious arthritis. J Am Vet Med Assoc 1991; 198:1655–61. 18. Firth EC. Current concepts of infectious polyarthirtis in foals. Equine Vet J 1983; 15:5–9.
Equine Neonatal Musculoskeletal System
19. Vos NJ, Ducharme NG. Analysis of factors influencing prognosis in foals with septic arthritis. Irish Vet J 2008;61:102–6. 20. Bertone AL, Davis M, Cox HU. Arthrotomy versus arthroscopy and partial synovectomy for treatment of experimentally induced septic arthritis in horses. Am J Vet Res 1992;53:585–9. 21. Goodrich LR, Nixon AJ. Treatment options for osteomyelitis. Equine Vet Ed 2004; 16:267–80. 22. Smith LJ, Marr CM, Payne RJ. What is the likelihood that Thoroughbred foals treated for septic arthritis will race? Equine Vet J 2004;36:452–6. 23. Steel CM, Hunt AR, Adams PL, et al. Factors associated with prognosis for survival and athletic use in foals with septic arthritis. J Am Vet Med Assoc 1999; 215:973–7.
613
DVM
KEYWORDS Musculoskeletal Ossification Synovial infection Osteomyelitis Flexural limb Angular limb KEY POINTS The first few weeks of life are critical in horses. Cuboidal bone ossification at birth can vary and should be assessed in premature and dysmature foals. Flexural limb deformities, angular limb deformity, and laxity are common in neonatal foals and should be assessed and treated early. Neonatal foals are susceptible to septic orthopedic conditions owing to immature immune system and physeal blood flow. Early recognition and treatment is key to success.
NORMAL OSSIFICATION
In the typical foal, the tarsal and carpal bones ossify in the last 2 to 3 months of gestation.1 The normal process of endochondrial ossification starts centrally within the bone and the process continues until the periphery of the bone is mature with the normal surrounding cartilage. Ossification of the cuboidal bones plays an important role in the foal, but should not be confused with total skeletal maturity.2 In the human, skeletal maturity is determined by radiographs of the axial skeleton because cuboidal bones are not a reliable index for total skeletal maturity.3,4 A skeletal ossification index has been used to standardize the evaluation of newborn foals.2 The index is based on 2 radiographic views of the carpus and tarsus, and 4 grades have been developed. Grade 1: Some of the cuboidal bones of the carpus and tarsus have no radiographic evidence of ossification (Fig. 1). Grade 2: Some radiographic evidence of ossification of all of the cuboidal bones of the carpus and tarsus (excluding the first carpal bone). The proximal physes of the third metacarpus/metatarsus were open (Fig. 2).
University of Pennsylvania, New Bolton Center, 382 W. Street Road, Kennett Square, PA 19348, USA E-mail address: [email protected] Vet Clin Equine 31 (2015) 601–613 http://dx.doi.org/10.1016/j.cveq.2015.09.003 vetequine.theclinics.com 0749-0739/15/$ – see front matter Ó 2015 Elsevier Inc. All rights reserved.
602
Levine
Fig. 1. Grade 1 ossification. Some of the cuboidal bones show no evidence of ossification.
Grade 3: All of the cuboidal bones were ossified, but they were small with rounded edges. The joint spaces thus seemed to be wide in these individuals. The lateral styloid process and the malleoli were distinct. The proximal physes of the third metacarpus and metatarsus were closed (Fig. 3).
Fig. 2. Grade 2 ossification. All cuboidal bones have some evidence of ossification. There is a faint line representing the open proximal metacarpal physes.
Equine Neonatal Musculoskeletal System
Fig. 3. Grade 3 ossification. All cuboidal bones are present but have rounded edges with increased joint space and the proximal metacarpal physis is closed.
Grade 4: All of the criteria of grade 3 were met, and the cuboidal bones were shaped like the corresponding bones in the adult and the joint spaces were of expected width (Fig. 4). A common condition in immature foals is incomplete ossification of the cuboidal bones. This condition is not limited to the immature foal; dysmature foals may also display this condition. There are many reported causes for incomplete ossification of the cuboidal bones. These can include1,5,6:
Prematurity related to short gestational age (2 g/dL) and high leukocyte counts (>10,000 cells/mL; primarily neutrophils) are typical. Foals with septic synovial structures can often have leukocyte counts of greater than 50,000 cells/mL, although cell count does not seem to correspond with the severity of disease.18,19 Samples should be submitted for culture and sensitivity, often accompanied with a blood culture, to determine whether systemic sepsis is an ongoing problem. A complete physical examination looking for other sources of sepsis (lungs, gastrointestinal, umbilical) should always be performed. Radiographs should be obtained of affected joints to determine physeal and metaphyseal involvement. In early cases, these radiographs can serve as a baseline to follow-up examinations. Radiographic change often lags behind the clinical picture and bone that seems to be normal radiographically may still be affected. Treatment
Treatment should consist of aggressive local and, if indicated, systemic antimicrobial therapy. Broad-spectrum antimicrobials are commonly started until a positive culture or clinical suspicion helps to guide antimicrobial choice. Lavage of the septic structures can be done with through-and-through needle lavage or more aggressively with an arthrotomy or arthroscopy. Several studies have shown the benefit of more aggressive treatment with arthotomy/arthroscopy with improved survival and no increase in morbidity.19,20 This is owing to the removal of fibrin, inflammatory mediators, and diseased bone and synovial membrane that cannot be removed by simple needle lavage. Local implantation of antibiotic impregnated beads, intraarticular injection of antimicrobials, and regional limb perfusions can be used in addition to lavage and may improve the outcome.20 Although regional limb perfusion is an appropriate way to deliver high concentrations of antimicrobials to the distal limb, intraarticular injections still achieve higher concentrations within the joint as well as adjacent bone. Prognosis
Survival in these cases ranges from 45% to 85%.21 Athletic outcome depends on the number of joints affected, severity of infection, as well as the response to treatment. Thoroughbred foals have been shown to have a decreased likelihood to race compared with controls with only 30% of survivors becoming racehorses.22,23 Factors that decrease survival include21–23:
Duration of infection before treatment; Number of joints affected; Bone involvement; and Multisystemic disease.
611
612
Levine
SUMMARY
The first weeks of a foal’s life can be challenging. Orthopedic conditions can occur frequently and some do require emergency treatment. The key is early diagnosis and appropriate care. Prognosis for most conditions improves with early recognition and corrective treatments. It is important to know the appropriate treatment for each condition because often the incorrect treatment can lead to further complications. REFERENCES
1. McIlwraith CW. Incomplete ossification of carpal and tarsal bones in foals. Equine Vet Ed 2003;15(2):79–81. 2. Adams R, Poulos P. A skeletal ossification index for neonatal foals. Vet Radiol 1988;29:217–22. 3. Kuhns LR, Finnstrom O. New standards of ossification of the newborn. Radiology 1976;119:655–60. 4. Kuhns LR, Sherman MP, Poznanski AK. Determination of neonatal maturation on the chest radiograph. Radiology 1972;102:597–603. 5. Auer JA, Martens RJ, Morris EL. Angular limb deformities in foals. Comp Cont Educ Pract Vet 1982;4:330–9. 6. Rossdale PD, Ousey JC. Fetal programming for athletic performance in the horse: potential effects of IUGR. Equine Vet Ed 2002;14:98–112. 7. Auer J. Angular limb deformities. In: Auer JA, editor. Equine surgery. St Louis (MO): Elsevier; 2012. p. 1201–21. 8. Hunt RJ. Flexural limb deformities. In: Ross MW, Dyson SJ, editors. Diagnosis and management of lameness in the horse. St Louis (MO): Elsevier; 2003. p. 562–5. 9. Adams SB, Santschi EM. Management of flexural limb deformities in young horses. Equine Pract 1999;21:9–16. 10. Auer JA. Flexural limb deformities. In: Auer JA, editor. Equine surgery. St Louis (MO): Elsevier; 2012. p. 1150–65. 11. Adams SB, Santschi EM. Management of congenital and acquired flexural limb deformities. Proceedings AAEP 2000;46:117–25. 12. Whitehair KJ, Adams SB, Toombs JP, et al. Arthrodesis for congenital flexural deformity of the metacarpophalangeal and metatarsophalangeal joints. Vet Surg 1992;22:228–33. 13. Madison JB, Garber JL, Rice B, et al. Effect of oxytetracycline on metacarpophalangeal and distal interphalangeal joint angles in new born foals. J Am Vet Med Assoc 1994;204:240–9. 14. Trumble TN. Orthopedic disorders in neonatal foals. Vet Clin Equine 2005;21: 357–85. 15. Stoneham SJ, Digby NJ, Ricketts SW. Failure of passive transfer of colostral immunity in the foal. Vet Rec 1991;22:42–5. 16. Cohen ND. Causes of and farm management factors associated with disease and death in foals. J Am Vet Med Assoc 1994;204:1644–51. 17. Madison JB, Sommer M, Spencer PA. Relations among synovial membrane histopathologic findings, synovial fluid cytologic findings, and bacterial culture results in horses with suspected infectious arthritis. J Am Vet Med Assoc 1991; 198:1655–61. 18. Firth EC. Current concepts of infectious polyarthirtis in foals. Equine Vet J 1983; 15:5–9.
Equine Neonatal Musculoskeletal System
19. Vos NJ, Ducharme NG. Analysis of factors influencing prognosis in foals with septic arthritis. Irish Vet J 2008;61:102–6. 20. Bertone AL, Davis M, Cox HU. Arthrotomy versus arthroscopy and partial synovectomy for treatment of experimentally induced septic arthritis in horses. Am J Vet Res 1992;53:585–9. 21. Goodrich LR, Nixon AJ. Treatment options for osteomyelitis. Equine Vet Ed 2004; 16:267–80. 22. Smith LJ, Marr CM, Payne RJ. What is the likelihood that Thoroughbred foals treated for septic arthritis will race? Equine Vet J 2004;36:452–6. 23. Steel CM, Hunt AR, Adams PL, et al. Factors associated with prognosis for survival and athletic use in foals with septic arthritis. J Am Vet Med Assoc 1999; 215:973–7.
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