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CASE REPORT
Bilateral calcaneal stress fractures in two cats M. Cantatore and D. N. Clements Hospital for Small Animals, Royal (Dick) School of Veterinary Studies, Easter Bush Veterinary Centre, Roslin, Midlothian EH25 9RG
Two cats that developed bilateral calcaneal stress fractures are reported. One cat developed lameness associated with incomplete fractures at the base of both calcanei, both of which progressed to acute, complete fractures 2 months later. The second cat presented with acute complete calcaneal fracture, with evidence of remodelling of the contralateral calcaneus, which subsequently fractured two years later. The calcaneal fractures were successfully stabilised with lateral bone plates in each case. Stress fractures were suspected because of the bilateral nature, the simple and similar configuration, the consistent location of the fractures, the absence of other signs of trauma in both cases and the suspected insidious onset of the lameness. The feline calcaneus is susceptible to stress fracture, and cats presenting with calcaneal fractures without evidence of trauma should be evaluated for concurrent skeletal pathology. Journal of Small Animal Practice (2015) 56, 417–421 DOI: 10.1111/jsap.12358 Accepted: 12 February 2015; Published online: 30 April 2015
INTRODUCTION Fractures of the calcaneus are rare in dogs and cats (Carmichael & Marshall 2012). Calcaneal fractures develop either as fatigue fractures (in canine performance athletes) or following external trauma (Gannon 1972, Ost et al. 1987, Schmökel et al. 1994, Carmichael & Marshall 2012) and have been most commonly reported in the racing greyhound but only sporadically in other non-performance athletic canine breeds and cats (Gannon 1972, Ost et al. 1987, Schmökel et al. 1994, Carmichael & Marshall 2012). Stress fractures can be classified into two main categories; fatigue fractures, caused by repeated stresses applied to a normal bone, or insufficiency fractures, caused by normal stresses applied to an abnormal bone (Daffner & Pavlov 1992). Calcaneal fractures in the racing greyhound are generally considered fatigue fractures (Gannon 1972, Ost et al. 1987). Stress fractures have been reported in cats, affecting the ribs, patellae and proximal tibia (Arnbjerg & Bindseil 1994, Hardie et al. 1998, LangleyHobbs 2009, Langley-Hobbs et al. 2009). In this report, the clinical presentation, management and outcome of two consecutive feline cases of bilateral calcaneal fractures suspected to be stress fractures are described.
CASE 1 A 4.3 kg, seven-year-old, male neutered domestic shorthair cat was presented to its primary veterinarian, with a 1-week history Journal of Small Animal Practice
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of left pelvic limb lameness that progressed to bilateral pelvic limb lameness within a few days. The cat was a house pet but had free outdoor access. Orthopaedic examination was unremarkable. No abnormalities were noted on orthogonal radiographs of the lumbar spine, pelvis and entire pelvic limbs. The cat was discharged with a course of 0.05 mg/kg meloxicam (Metacam; Boehringer Ingelheim) orally once daily for 5 days, which resulted in complete resolution of the clinical signs. Two months later, the cat was re-presented with acute onset bilateral hindlimb lameness and plantigrade stance. Routine haematology, serum biochemistry and electrolytes were within their respective reference intervals. The cat was referred as an emergency the same day for further investigation. At presentation to the Small Animal Hospital of the Royal (Dick) School of Veterinary Studies, the cat demonstrated severe bilateral pelvic limb lameness with a plantigrade stance. Bilateral swelling around both calcanei was identified. Assessment of the radiographs taken on initial presentation by the primary veterinarian (2 months before referral) revealed bilateral, partial, transverse, minimally displaced fractures at the base of each calcaneus (Fig 1A, B) and changes of the caudal endplate of the fourth and fifth lumbar vertebrae suggestive of healed vertebral fractures or spondylosis deformans. Radiography of both tarsi was repeated, which revealed progression to complete, transverse displaced fractures at the base of each calcaneus (Fig 1C, D). The radiographic changes of the fourth and fifth lumbar vertebrae (Fig 2A) were confirmed and healed fractures of the fifth and sixth ribs were also noted (Fig 2B). The calcaneal fracture sites were approached with a
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FIG 1. Mediolateral radiographs of the tarsi of Case 1, 2 months before referral (A,B) and at initial referral presentation (C,D).
A
A
B
FIG 3. Mediolateral (A) and dorsoplantar (B) radiographs of the right tarsus of Case 1 immediately after surgical stabilisation with a laterally applied plate.
B
FIG 2. The abnormal appearance of caudal endplate of fourth and fifth (arrow) lumbar vertebrae (A) and healed fractures of the fifth and sixth (arrow) ribs (B) were also identified at the referral presentation in Case 1.
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plantaro-lateral incision (Piermattei & Johnson 2004). The fractures were reduced and stabilised with laterally applied 7-hole 2.0 mm dynamic compression plates (DCP) (Synthes Vet) spanning the intertarsal and tarsometatarsal joints (Fig 3). Debridement of the articular cartilage of the intertarsal and tarsometatarsal joint spaces was not performed. Postoperative radiographs confirmed adequate fracture reduction and implant placement. Modified Robert-Jones bandages were placed to support both distal pelvic limbs for 48 hours. The cat recovered uneventfully from surgery and anaesthesia. Postoperative analgesia was provided with the administration of 0.02 mg/kg buprenorphine (Vetergesic Injection, Reckitt Benckiser Healthcare LTD), intravenously (IV) three times daily for 3 days, and 0.05 mg/kg meloxicam (Metacam; Boehringer Ingelheim), orally once daily. The cat was discharged 4 days after surgery with a course of 0.05 mg/kg meloxicam (orally once daily for 2 weeks) and
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instructions for strict cage rest for 8 weeks. Re-evaluation 8 weeks postoperatively revealed mild bilateral residual lameness. Radiographic evaluation revealed complete healing of the calcaneal fractures and bony ankylosis of the intertarsal and tarsometatarsal joints. No residual lameness was reported by the owner at telephone follow-up 21 months after surgery. CASE 2 A 4.1 kg, five-year-old, female neutered domestic shorthair cat was referred for the treatment of a right calcaneal fracture. The cat was a house pet but had free outdoor access. No traumatic episode had been witnessed and no obvious sign of external trauma was present, although the cat was reported to be in the owner’s garden at the time of the injury. At presentation, a non-weight bearing right hindlimb lameness was observed. Radiographs of the right tarsus revealed a complete, transverse, displaced fracture of the calcaneal body with remodelling of the plantar cortex (Fig 4A). Radiography of the left tarsus revealed an incomplete fissure of the plantar calcaneus with remodelling of the plantar cortex (Fig 4B). Routine haematology, serum biochemistry and electrolytes were unremarkable. The fracture was approached with a plantaro-lateral incision (Piermattei & Johnson 2004). The fracture was reduced and stabilised with a laterally applied 7-hole 1.5/2.0 mm veterinary cuttable plate (VCP) (Synthes Vet) and 2.0 mm cortical screws spanning the intertarsal and tarsometatarsal joints. Debridement of the articular cartilage of the intertarsal and tarsometatarsal joint spaces was not performed. Postoperative radiographs confirmed adequate fracture reduction and implant placement. The cat was discharged 2 days after surgery with analgesia and instructions for activity restriction as described for Case 1. Reevaluation 8 weeks postoperatively revealed mild residual lameness. Radiography revealed progressive but incomplete healing of the calcaneal fracture. Instructions were given for indoor confinement for a further 4 weeks, after which the owner reported a complete resolution of the cat’s lameness. Two and a half years later the cat was re-referred with a 2-week history of left pelvic limb lameness. Radiography revealed a A
complete transverse displaced fracture of the left calcaneus with sclerosis of each fracture end (Fig 4C). Orthogonal radiographic projections of the right tarsus revealed complete intertarsal and tarsometatarsal bony fusion, talocrural osteoarthritis and complete healing of the right calcaneal fracture. A plantaro-lateral approach to the calcaneus (Piermattei & Johnson 2004) permitted fracture reduction and stabilisation with a laterally applied 7-hole 1.5/2.0 mm VCP plate with 2.0 mm screws. Debridement of the articular cartilage of the intertarsal and tarsometatarsal joint spaces was not performed. Postoperative radiographs confirmed appropriate fracture reduction and implant placement. A modified RobertJones dressing was applied for 48 hours postoperatively. The cat recovered uneventfully from surgery and anaesthesia. Postoperative analgesia involved administration of 0.02 mg/kg buprenorphine (IV three times daily for 5 days) and 0.05 mg/ kg meloxicam (orally once daily for 10 days). The cat was discharged with instructions for strict cage rest for 8 weeks. Reevaluation 9 weeks postoperatively identified moderate weight bearing lameness of the left pelvic limb. Radiography revealed progressive, but incomplete, healing of the left calcaneal fracture. Indoor confinement for a further 8 weeks was advised and no residual lameness was reported by the owner at telephone followup 16 months later.
DISCUSSION To the authors’ knowledge, bilateral calcaneal fractures have not been previously reported in cats. It is hypothesised that the aetiology of the fractures in these two cases was stress. Even if a traumatic aetiology cannot be ruled out as the cause of the fractures, trauma was unlikely for several reasons; the bilateral nature of the injuries, the simple and nearly identical configuration of the fractures, their consistent location, the absence of other signs of trauma such as external wounds or bruising, the suspected insidious onset of the lameness in Case 1 and the calcaneal remodelling preceding the development of a complete fracture by two years in Case 2.
B
C
FIG 4. Mediolateral radiographs of the tarsi of Case 2 at initial presentation (A, B), and two and a half years later (C). Remodelling of the plantar cortex of the left calcaneus, two years before fracture, is arrowed. Journal of Small Animal Practice
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Stress fractures in the pelvic limbs of cats have previously been reported to affect the patella and the proximal tibia (Arnbjerg & Bindseil 1994, Langley-Hobbs 2009, Langley-Hobbs et al. 2009), and the presented cases share some similarities with these previous reports. In particular, the transverse configuration (Langley-Hobbs 2009, Langley-Hobbs et al. 2009), as observed in the fractures herein, suggests that tension is the primary force involved in their genesis, as would be expected at this location, and is consistent with a low energy injury (Langley-Hobbs 2009, Langley-Hobbs et al. 2009, Cross 2012). The bilateral nature of the injuries as described in this report was also noted in more than 50% of cats with stress patellar fractures (Langley-Hobbs 2013). The fractured edges of both calcanei in Case 1 and of the left calcaneus in Case 2 were sclerotic at the time of presentation, suggesting pre-existing pathology and chronicity. Repetitive mechanical stimulus results in additional bone deposition and increased bone density and is a radiographic feature of stress fractures (Goodship et al. 1979, Langley-Hobbs 2009, LangleyHobbs et al. 2009). Bone sclerosis has been commonly observed in the fractured and contralateral unfractured patella and proximal tibia in the case series of feline patella and tibial stress fractures (Langley-Hobbs 2009, Langley-Hobbs et al. 2009). Concurrent incidental fractures have been frequently observed in cats with patellar fractures and stress fractures of the proximal tibia (Langley-Hobbs 2009, Langley-Hobbs et al. 2009) and were suspected in Case 1. They could not be ruled out in Case 2 as the remaining skeleton was not evaluated. One case with stress patellar fracture was reported to have a concurrent calcaneal fracture, although the configuration was not described (Langley-Hobbs 2009). It has been hypothesised that multiple stress fractures in cats are the result of insufficiency rather than fatigue and that they may result from a mild form of osteogenesis imperfecta (Langley-Hobbs 2009, Langley-Hobbs et al. 2009, Langley-Hobbs 2013). Calcaneal stress fractures are a frequently unrecognised source of heel pain in humans and they are the second most common stress fracture in the foot (Aldridge 2004, Tu & Bytomski 2011, Imerci et al. 2012). Calcaneal stress fractures can be bilateral and can occur in both juvenile and adult populations, but they are more common among active people such as athletes, sports enthusiasts and military personnel (Tu & Bytomski 2011, Imerci et al. 2012), which suggests that they are likely to arise as a result of bone fatigue. Similarly, calcaneal fractures in the racing greyhound are generally considered fatigue fractures (Gannon 1972, Ost et al. 1987). In cats, the Achilles tendon/calcaneus mechanism is an anatomical area subject to significant tensile forces during jumping, which may make it susceptible to fatigue. In a previous report of Achilles tendon injuries in cats, 11 out of 14 (78.6%) of the tendinosseus avulsions were atraumatic in nature and repetitive mechanical stress has been implicated in the aetiopathogenesis of these injuries (Cervi et al. 2010). The same mechanism might have been responsible for the development of the stress fractures described in the current report. The fractures in both cases were repaired using laterally applied bone plate. Both DCP and VCP plates have been previously reported as successful for partial tarsal arthrodesis in 420
cats (Dyce et al. 1998, Muir & Norris 1999, Théoret & Moens 2007), and the choice of implant does not appear to affect the surgical outcome. Even though the articular cartilage was not debrided, progressive intertarsal and tarsometatarsal bony ankylosis was noted. The intertarsal and tarsometatarsal articulations are low motion joints and their fusion is of no obvious functional consequence. Partial tarsal arthrodeses are generally associated with a good to excellent outcome because the talocrural joint, where most of the tarsal joint movement occurs, is preserved (Penwick & Clark 1988, Dyce et al. 1998, Muir & Norris 1999, Fettig et al. 2002, Théoret & Moens 2007). Other surgical options could have been considered including pin and tension band wire or a plate applied on the plantar surface (Voss et al. 2009). In conclusion, bilateral non-traumatic fractures of the calcaneus in cats can be successfully treated with laterally applied plates. These cases share similarities with previous reports of stress fractures affecting the patella and tibia in cats. Calcaneal fractures should be considered as a differential diagnosis for chronic plantigrade stance or insidious lameness localised to the hock. It is recommended that cats with unilateral calcaneal fractures be monitored for the presence of contralateral calcaneal pathology and bone pathology elsewhere in the musculoskeletal system. Conflict of interest None of the authors of this article has a financial or personal relationship with other people or organisations that could inappropriately influence or bias the content of the paper. References Aldridge, T. (2004) Diagnosing heel pain in adults. American Family Physician 70, 332-338 Arnbjerg, J. & Bindseil, E. (1994) Patella fracture in cats. Feline Practice 22, 31-35 Carmichael, S. & Marshall, W. (2012) Tarsus and metatarsus. In: Veterinary Surgery Small Animal. Eds K. M. Tobias and S. A. Johnston. Elsevier Saunders, St. Louis, MO, USA. pp 1014-1028 Cervi, M., Brebner, N. & Liptak, J. (2010) Short- and long-term outcomes of primary achilles tendon repair in cats: 21 cases. Veterinary and Comparative Orthopaedics and Traumatology 23, 348-353 Cross, A. R. (2012) Fracture biology and biomechanics. In: Veterinary Surgery Small Animal. Eds K. M. Tobias and S. A. Johnston. Elsevier Saunders, St. Louis, MO, USA. pp 565-571 Daffner, R. H. and Pavlov, H. (1992) Stress fractures: current concepts. American Journal of Roentgenology 159, 245-252 Dyce, J., Whitelock, R. G., Robinson, K. V., et al. (1998) Arthrodesis of the tarsometatarsal joint using a laterally applied plate in 10 dogs. Journal of Small Animal Practice 39, 19-22 Fettig, A. A., McCarthy, R. J. & Kowaleski, M. P. (2002) Intertarsal and tarsometatarsal arthrodesis using 2.0/2.7-mm or 2.7/3.5-mm hybrid dynamic compression plates. Journal of the American Animal Hospital Association 38, 364-369 Gannon, J. R. (1972) Stress fractures in the greyhound. Australian Veterinary Journal 48, 244-250 Goodship, A. E., Lanyon, L. E. & McFie, H. (1979) Functional adaptation of bone to increased stress. Journal of Bone and Joint Surgery 61, 539-546 Hardie, E. M., Ramirez, O., Clary, E. M. et al. (1998) Abnormalities of the thoracic bellows: stress fractures of the ribs and hiatal hernia. Journal of Veterinary Internal Medicine 12, 279-287 Imerci, A., Incesu, M., Bozoglan, M., et al. (2012) Bilateral calcaneal stress fractures: a case report. Ortopedia Traumatologia Rehabilitacja 14, 477-481 Langley-Hobbs, S. J. (2009) Survey of 52 fractures of the patella in 34 cats. Veterinary Record 164, 80-86 Langley-Hobbs, S. J., Ball, S. & McKee, W. M. (2009) Transverse stress fractures of the proximal tibia in 10 cats with non-union patellar fractures. Veterinary Record 164, 425-430 Langley-Hobbs, S. J. (2013) Patellar fractures in cats. Veterinary Record 172, 83-84 Muir, P. & Norris, J. L. (1999) Tarsometatarsal subluxation in dogs: partial arthrodesis by plate fixation. Journal of the American Animal Hospital Association 35, 155-162
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Ost, P. C., Dee, J. F., Dee, L. G., et al. (1987) Fractures of the calcaneus in racing greyhounds. Veterinary Surgery 16, 53-59 Penwick, R. C. & Clark, D. M. (1988) A simple technique for tarsometatarsal arthrodesis in small animals. Journal of the American Animal Hospital Association 24, 183-188 Piermattei, D. L. & Johnson, K. A. (2004) Approach to the lateral bones of the tarsus. In: An Atlas of Surgical Approaches to the Bones and Joints of the Dog and Cat. 4th edn. Eds D. L. Piermattei and K. A. Johnson. Saunders, Philadelphia, PA, USA, pp 386-387 Schmökel, H. G., Hartmeier, G. E., Kaser-Hotz, B. et al. (1994) Tarsal injuries in the cat: a retrospective study of 21 cases. Journal of Small Animal Practice 35, 156-162
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Théoret, M. C. & Moens, N. M. M. (2007) The use of veterinary cuttable plates for carpal and tarsal arthrodesis in small dogs and cats. Canadian Veterinary Journal 48, 165-168 Tu, P. & Bytomski, J. R. (2011) Diagnosis of heel pain. American Family Physician 84, 909-916 Voss, K., Langley Hobbs, S. J. & Montavon, P. M. (2009) Tarsal joint. In: Feline orthopedic surgery and musculoskeletal disease Eds P. M. Montavon, K. Voss, and S. J. Langley-Hobbs. Saunders Elsevier, Philadelphia, PA, USA. pp 507-525 Weber, J. M., Vidt, L. G., Gehl, R. S., et al. (2005) Calcaneal stress fractures. Clinics in Podiatric Medicine and Surgery 22, 45-54
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CASE REPORT
Bilateral calcaneal stress fractures in two cats M. Cantatore and D. N. Clements Hospital for Small Animals, Royal (Dick) School of Veterinary Studies, Easter Bush Veterinary Centre, Roslin, Midlothian EH25 9RG
Two cats that developed bilateral calcaneal stress fractures are reported. One cat developed lameness associated with incomplete fractures at the base of both calcanei, both of which progressed to acute, complete fractures 2 months later. The second cat presented with acute complete calcaneal fracture, with evidence of remodelling of the contralateral calcaneus, which subsequently fractured two years later. The calcaneal fractures were successfully stabilised with lateral bone plates in each case. Stress fractures were suspected because of the bilateral nature, the simple and similar configuration, the consistent location of the fractures, the absence of other signs of trauma in both cases and the suspected insidious onset of the lameness. The feline calcaneus is susceptible to stress fracture, and cats presenting with calcaneal fractures without evidence of trauma should be evaluated for concurrent skeletal pathology. Journal of Small Animal Practice (2015) 56, 417–421 DOI: 10.1111/jsap.12358 Accepted: 12 February 2015; Published online: 30 April 2015
INTRODUCTION Fractures of the calcaneus are rare in dogs and cats (Carmichael & Marshall 2012). Calcaneal fractures develop either as fatigue fractures (in canine performance athletes) or following external trauma (Gannon 1972, Ost et al. 1987, Schmökel et al. 1994, Carmichael & Marshall 2012) and have been most commonly reported in the racing greyhound but only sporadically in other non-performance athletic canine breeds and cats (Gannon 1972, Ost et al. 1987, Schmökel et al. 1994, Carmichael & Marshall 2012). Stress fractures can be classified into two main categories; fatigue fractures, caused by repeated stresses applied to a normal bone, or insufficiency fractures, caused by normal stresses applied to an abnormal bone (Daffner & Pavlov 1992). Calcaneal fractures in the racing greyhound are generally considered fatigue fractures (Gannon 1972, Ost et al. 1987). Stress fractures have been reported in cats, affecting the ribs, patellae and proximal tibia (Arnbjerg & Bindseil 1994, Hardie et al. 1998, LangleyHobbs 2009, Langley-Hobbs et al. 2009). In this report, the clinical presentation, management and outcome of two consecutive feline cases of bilateral calcaneal fractures suspected to be stress fractures are described.
CASE 1 A 4.3 kg, seven-year-old, male neutered domestic shorthair cat was presented to its primary veterinarian, with a 1-week history Journal of Small Animal Practice
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of left pelvic limb lameness that progressed to bilateral pelvic limb lameness within a few days. The cat was a house pet but had free outdoor access. Orthopaedic examination was unremarkable. No abnormalities were noted on orthogonal radiographs of the lumbar spine, pelvis and entire pelvic limbs. The cat was discharged with a course of 0.05 mg/kg meloxicam (Metacam; Boehringer Ingelheim) orally once daily for 5 days, which resulted in complete resolution of the clinical signs. Two months later, the cat was re-presented with acute onset bilateral hindlimb lameness and plantigrade stance. Routine haematology, serum biochemistry and electrolytes were within their respective reference intervals. The cat was referred as an emergency the same day for further investigation. At presentation to the Small Animal Hospital of the Royal (Dick) School of Veterinary Studies, the cat demonstrated severe bilateral pelvic limb lameness with a plantigrade stance. Bilateral swelling around both calcanei was identified. Assessment of the radiographs taken on initial presentation by the primary veterinarian (2 months before referral) revealed bilateral, partial, transverse, minimally displaced fractures at the base of each calcaneus (Fig 1A, B) and changes of the caudal endplate of the fourth and fifth lumbar vertebrae suggestive of healed vertebral fractures or spondylosis deformans. Radiography of both tarsi was repeated, which revealed progression to complete, transverse displaced fractures at the base of each calcaneus (Fig 1C, D). The radiographic changes of the fourth and fifth lumbar vertebrae (Fig 2A) were confirmed and healed fractures of the fifth and sixth ribs were also noted (Fig 2B). The calcaneal fracture sites were approached with a
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FIG 1. Mediolateral radiographs of the tarsi of Case 1, 2 months before referral (A,B) and at initial referral presentation (C,D).
A
A
B
FIG 3. Mediolateral (A) and dorsoplantar (B) radiographs of the right tarsus of Case 1 immediately after surgical stabilisation with a laterally applied plate.
B
FIG 2. The abnormal appearance of caudal endplate of fourth and fifth (arrow) lumbar vertebrae (A) and healed fractures of the fifth and sixth (arrow) ribs (B) were also identified at the referral presentation in Case 1.
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plantaro-lateral incision (Piermattei & Johnson 2004). The fractures were reduced and stabilised with laterally applied 7-hole 2.0 mm dynamic compression plates (DCP) (Synthes Vet) spanning the intertarsal and tarsometatarsal joints (Fig 3). Debridement of the articular cartilage of the intertarsal and tarsometatarsal joint spaces was not performed. Postoperative radiographs confirmed adequate fracture reduction and implant placement. Modified Robert-Jones bandages were placed to support both distal pelvic limbs for 48 hours. The cat recovered uneventfully from surgery and anaesthesia. Postoperative analgesia was provided with the administration of 0.02 mg/kg buprenorphine (Vetergesic Injection, Reckitt Benckiser Healthcare LTD), intravenously (IV) three times daily for 3 days, and 0.05 mg/kg meloxicam (Metacam; Boehringer Ingelheim), orally once daily. The cat was discharged 4 days after surgery with a course of 0.05 mg/kg meloxicam (orally once daily for 2 weeks) and
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instructions for strict cage rest for 8 weeks. Re-evaluation 8 weeks postoperatively revealed mild bilateral residual lameness. Radiographic evaluation revealed complete healing of the calcaneal fractures and bony ankylosis of the intertarsal and tarsometatarsal joints. No residual lameness was reported by the owner at telephone follow-up 21 months after surgery. CASE 2 A 4.1 kg, five-year-old, female neutered domestic shorthair cat was referred for the treatment of a right calcaneal fracture. The cat was a house pet but had free outdoor access. No traumatic episode had been witnessed and no obvious sign of external trauma was present, although the cat was reported to be in the owner’s garden at the time of the injury. At presentation, a non-weight bearing right hindlimb lameness was observed. Radiographs of the right tarsus revealed a complete, transverse, displaced fracture of the calcaneal body with remodelling of the plantar cortex (Fig 4A). Radiography of the left tarsus revealed an incomplete fissure of the plantar calcaneus with remodelling of the plantar cortex (Fig 4B). Routine haematology, serum biochemistry and electrolytes were unremarkable. The fracture was approached with a plantaro-lateral incision (Piermattei & Johnson 2004). The fracture was reduced and stabilised with a laterally applied 7-hole 1.5/2.0 mm veterinary cuttable plate (VCP) (Synthes Vet) and 2.0 mm cortical screws spanning the intertarsal and tarsometatarsal joints. Debridement of the articular cartilage of the intertarsal and tarsometatarsal joint spaces was not performed. Postoperative radiographs confirmed adequate fracture reduction and implant placement. The cat was discharged 2 days after surgery with analgesia and instructions for activity restriction as described for Case 1. Reevaluation 8 weeks postoperatively revealed mild residual lameness. Radiography revealed progressive but incomplete healing of the calcaneal fracture. Instructions were given for indoor confinement for a further 4 weeks, after which the owner reported a complete resolution of the cat’s lameness. Two and a half years later the cat was re-referred with a 2-week history of left pelvic limb lameness. Radiography revealed a A
complete transverse displaced fracture of the left calcaneus with sclerosis of each fracture end (Fig 4C). Orthogonal radiographic projections of the right tarsus revealed complete intertarsal and tarsometatarsal bony fusion, talocrural osteoarthritis and complete healing of the right calcaneal fracture. A plantaro-lateral approach to the calcaneus (Piermattei & Johnson 2004) permitted fracture reduction and stabilisation with a laterally applied 7-hole 1.5/2.0 mm VCP plate with 2.0 mm screws. Debridement of the articular cartilage of the intertarsal and tarsometatarsal joint spaces was not performed. Postoperative radiographs confirmed appropriate fracture reduction and implant placement. A modified RobertJones dressing was applied for 48 hours postoperatively. The cat recovered uneventfully from surgery and anaesthesia. Postoperative analgesia involved administration of 0.02 mg/kg buprenorphine (IV three times daily for 5 days) and 0.05 mg/ kg meloxicam (orally once daily for 10 days). The cat was discharged with instructions for strict cage rest for 8 weeks. Reevaluation 9 weeks postoperatively identified moderate weight bearing lameness of the left pelvic limb. Radiography revealed progressive, but incomplete, healing of the left calcaneal fracture. Indoor confinement for a further 8 weeks was advised and no residual lameness was reported by the owner at telephone followup 16 months later.
DISCUSSION To the authors’ knowledge, bilateral calcaneal fractures have not been previously reported in cats. It is hypothesised that the aetiology of the fractures in these two cases was stress. Even if a traumatic aetiology cannot be ruled out as the cause of the fractures, trauma was unlikely for several reasons; the bilateral nature of the injuries, the simple and nearly identical configuration of the fractures, their consistent location, the absence of other signs of trauma such as external wounds or bruising, the suspected insidious onset of the lameness in Case 1 and the calcaneal remodelling preceding the development of a complete fracture by two years in Case 2.
B
C
FIG 4. Mediolateral radiographs of the tarsi of Case 2 at initial presentation (A, B), and two and a half years later (C). Remodelling of the plantar cortex of the left calcaneus, two years before fracture, is arrowed. Journal of Small Animal Practice
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M. Cantatore & D. N. Clements
Stress fractures in the pelvic limbs of cats have previously been reported to affect the patella and the proximal tibia (Arnbjerg & Bindseil 1994, Langley-Hobbs 2009, Langley-Hobbs et al. 2009), and the presented cases share some similarities with these previous reports. In particular, the transverse configuration (Langley-Hobbs 2009, Langley-Hobbs et al. 2009), as observed in the fractures herein, suggests that tension is the primary force involved in their genesis, as would be expected at this location, and is consistent with a low energy injury (Langley-Hobbs 2009, Langley-Hobbs et al. 2009, Cross 2012). The bilateral nature of the injuries as described in this report was also noted in more than 50% of cats with stress patellar fractures (Langley-Hobbs 2013). The fractured edges of both calcanei in Case 1 and of the left calcaneus in Case 2 were sclerotic at the time of presentation, suggesting pre-existing pathology and chronicity. Repetitive mechanical stimulus results in additional bone deposition and increased bone density and is a radiographic feature of stress fractures (Goodship et al. 1979, Langley-Hobbs 2009, LangleyHobbs et al. 2009). Bone sclerosis has been commonly observed in the fractured and contralateral unfractured patella and proximal tibia in the case series of feline patella and tibial stress fractures (Langley-Hobbs 2009, Langley-Hobbs et al. 2009). Concurrent incidental fractures have been frequently observed in cats with patellar fractures and stress fractures of the proximal tibia (Langley-Hobbs 2009, Langley-Hobbs et al. 2009) and were suspected in Case 1. They could not be ruled out in Case 2 as the remaining skeleton was not evaluated. One case with stress patellar fracture was reported to have a concurrent calcaneal fracture, although the configuration was not described (Langley-Hobbs 2009). It has been hypothesised that multiple stress fractures in cats are the result of insufficiency rather than fatigue and that they may result from a mild form of osteogenesis imperfecta (Langley-Hobbs 2009, Langley-Hobbs et al. 2009, Langley-Hobbs 2013). Calcaneal stress fractures are a frequently unrecognised source of heel pain in humans and they are the second most common stress fracture in the foot (Aldridge 2004, Tu & Bytomski 2011, Imerci et al. 2012). Calcaneal stress fractures can be bilateral and can occur in both juvenile and adult populations, but they are more common among active people such as athletes, sports enthusiasts and military personnel (Tu & Bytomski 2011, Imerci et al. 2012), which suggests that they are likely to arise as a result of bone fatigue. Similarly, calcaneal fractures in the racing greyhound are generally considered fatigue fractures (Gannon 1972, Ost et al. 1987). In cats, the Achilles tendon/calcaneus mechanism is an anatomical area subject to significant tensile forces during jumping, which may make it susceptible to fatigue. In a previous report of Achilles tendon injuries in cats, 11 out of 14 (78.6%) of the tendinosseus avulsions were atraumatic in nature and repetitive mechanical stress has been implicated in the aetiopathogenesis of these injuries (Cervi et al. 2010). The same mechanism might have been responsible for the development of the stress fractures described in the current report. The fractures in both cases were repaired using laterally applied bone plate. Both DCP and VCP plates have been previously reported as successful for partial tarsal arthrodesis in 420
cats (Dyce et al. 1998, Muir & Norris 1999, Théoret & Moens 2007), and the choice of implant does not appear to affect the surgical outcome. Even though the articular cartilage was not debrided, progressive intertarsal and tarsometatarsal bony ankylosis was noted. The intertarsal and tarsometatarsal articulations are low motion joints and their fusion is of no obvious functional consequence. Partial tarsal arthrodeses are generally associated with a good to excellent outcome because the talocrural joint, where most of the tarsal joint movement occurs, is preserved (Penwick & Clark 1988, Dyce et al. 1998, Muir & Norris 1999, Fettig et al. 2002, Théoret & Moens 2007). Other surgical options could have been considered including pin and tension band wire or a plate applied on the plantar surface (Voss et al. 2009). In conclusion, bilateral non-traumatic fractures of the calcaneus in cats can be successfully treated with laterally applied plates. These cases share similarities with previous reports of stress fractures affecting the patella and tibia in cats. Calcaneal fractures should be considered as a differential diagnosis for chronic plantigrade stance or insidious lameness localised to the hock. It is recommended that cats with unilateral calcaneal fractures be monitored for the presence of contralateral calcaneal pathology and bone pathology elsewhere in the musculoskeletal system. Conflict of interest None of the authors of this article has a financial or personal relationship with other people or organisations that could inappropriately influence or bias the content of the paper. References Aldridge, T. (2004) Diagnosing heel pain in adults. American Family Physician 70, 332-338 Arnbjerg, J. & Bindseil, E. (1994) Patella fracture in cats. Feline Practice 22, 31-35 Carmichael, S. & Marshall, W. (2012) Tarsus and metatarsus. In: Veterinary Surgery Small Animal. Eds K. M. Tobias and S. A. Johnston. Elsevier Saunders, St. Louis, MO, USA. pp 1014-1028 Cervi, M., Brebner, N. & Liptak, J. (2010) Short- and long-term outcomes of primary achilles tendon repair in cats: 21 cases. Veterinary and Comparative Orthopaedics and Traumatology 23, 348-353 Cross, A. R. (2012) Fracture biology and biomechanics. In: Veterinary Surgery Small Animal. Eds K. M. Tobias and S. A. Johnston. Elsevier Saunders, St. Louis, MO, USA. pp 565-571 Daffner, R. H. and Pavlov, H. (1992) Stress fractures: current concepts. American Journal of Roentgenology 159, 245-252 Dyce, J., Whitelock, R. G., Robinson, K. V., et al. (1998) Arthrodesis of the tarsometatarsal joint using a laterally applied plate in 10 dogs. Journal of Small Animal Practice 39, 19-22 Fettig, A. A., McCarthy, R. J. & Kowaleski, M. P. (2002) Intertarsal and tarsometatarsal arthrodesis using 2.0/2.7-mm or 2.7/3.5-mm hybrid dynamic compression plates. Journal of the American Animal Hospital Association 38, 364-369 Gannon, J. R. (1972) Stress fractures in the greyhound. Australian Veterinary Journal 48, 244-250 Goodship, A. E., Lanyon, L. E. & McFie, H. (1979) Functional adaptation of bone to increased stress. Journal of Bone and Joint Surgery 61, 539-546 Hardie, E. M., Ramirez, O., Clary, E. M. et al. (1998) Abnormalities of the thoracic bellows: stress fractures of the ribs and hiatal hernia. Journal of Veterinary Internal Medicine 12, 279-287 Imerci, A., Incesu, M., Bozoglan, M., et al. (2012) Bilateral calcaneal stress fractures: a case report. Ortopedia Traumatologia Rehabilitacja 14, 477-481 Langley-Hobbs, S. J. (2009) Survey of 52 fractures of the patella in 34 cats. Veterinary Record 164, 80-86 Langley-Hobbs, S. J., Ball, S. & McKee, W. M. (2009) Transverse stress fractures of the proximal tibia in 10 cats with non-union patellar fractures. Veterinary Record 164, 425-430 Langley-Hobbs, S. J. (2013) Patellar fractures in cats. Veterinary Record 172, 83-84 Muir, P. & Norris, J. L. (1999) Tarsometatarsal subluxation in dogs: partial arthrodesis by plate fixation. Journal of the American Animal Hospital Association 35, 155-162
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Ost, P. C., Dee, J. F., Dee, L. G., et al. (1987) Fractures of the calcaneus in racing greyhounds. Veterinary Surgery 16, 53-59 Penwick, R. C. & Clark, D. M. (1988) A simple technique for tarsometatarsal arthrodesis in small animals. Journal of the American Animal Hospital Association 24, 183-188 Piermattei, D. L. & Johnson, K. A. (2004) Approach to the lateral bones of the tarsus. In: An Atlas of Surgical Approaches to the Bones and Joints of the Dog and Cat. 4th edn. Eds D. L. Piermattei and K. A. Johnson. Saunders, Philadelphia, PA, USA, pp 386-387 Schmökel, H. G., Hartmeier, G. E., Kaser-Hotz, B. et al. (1994) Tarsal injuries in the cat: a retrospective study of 21 cases. Journal of Small Animal Practice 35, 156-162
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Théoret, M. C. & Moens, N. M. M. (2007) The use of veterinary cuttable plates for carpal and tarsal arthrodesis in small dogs and cats. Canadian Veterinary Journal 48, 165-168 Tu, P. & Bytomski, J. R. (2011) Diagnosis of heel pain. American Family Physician 84, 909-916 Voss, K., Langley Hobbs, S. J. & Montavon, P. M. (2009) Tarsal joint. In: Feline orthopedic surgery and musculoskeletal disease Eds P. M. Montavon, K. Voss, and S. J. Langley-Hobbs. Saunders Elsevier, Philadelphia, PA, USA. pp 507-525 Weber, J. M., Vidt, L. G., Gehl, R. S., et al. (2005) Calcaneal stress fractures. Clinics in Podiatric Medicine and Surgery 22, 45-54
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