514975 2014
JFM16810.1177/1098612X13514975Journal of Feline Medicine and SurgeryLee et al
Case Report Journal of Feline Medicine and Surgery 2014, Vol. 16(8) 703–707 © ISFM and AAFP 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/1098612X13514975 jfms.com
Congenital thoracic lordosis and scoliosis in a cat Maris S Lee1, Jim Taylor1 and Bonnie Lefbom2
Abstract
A 10-week-old domestic shorthair kitten was referred for intermittent episodes of dyspnea, cyanosis and a suspected congenital thoracic anomaly. Physical examination showed an obvious palpable concavity in the caudal thoracic spine. Thoracic radiographs showed severe caudal thoracic lordosis from T5 to T13 with a Cobb angle of −77°, a centroid lordosis angle of −68°, a vertebral index of 6.3 and a flattened sternum. Severe loss of vital capacity was suspected and surgical correction of the thoracic deformity was to be performed in two separate stages, the first being surgical ventral distraction on the sternum to increase thoracic volume and rigid fixation with an external splint. The second stage, if required, would be surgical correction of the spinal deformity to also increase thoracic volume. The initial stage of surgery was performed and postoperative radiographs showed a vertebral index of 10.3. The kitten suffered a left sided pneumothorax in recovery and died from cardiorespiratory arrest despite immediate pleural drainage and cardiopulmonary resuscitation. Treatment recommendations that may benefit future case management are discussed. Accepted: 7 November 2013
Lordosis is defined as an abnormal ventral curvature of the spinal column.1 Congenital thoracic lordosis has been reported in human literature to be a severely debilitating and progressive disease among juveniles causing loss of vital capacity, which may eventually lead to pulmonary deficits and death.2–9 The majority of patients present for dyspnea; however, dysphagia due to esophageal compression, right ventricular hypertrophy and pulmonary artery hypertension have also been repor ted.2–9 Failure of vertebral segmentation, vertebral synostoses, severe lordosis and scolisis are common radiographic and surgical findings. Scoliosis is defined as an abnormal lateral deviation of the spinal column.1 Surgical management of severe cases in humans consists of one or a combination of the following dependent upon the time period, institution and individual patient: anterior spinal fusion, posterior spinal fusion, excision of posterior synostoses, anterior discectomy, anterior closing wedge ostectomy, multiple rib osteotomy, posterior Harrington rods with sublaminar wiring and expansion thoracotomy with expandable prosthetic ribs.2–9 Potential postoperative complications include quadriplegia, prolonged ventilatory support, cardiac arrest and death. To our knowledge, an attempt to correct a severe form of this condition in a cat has not yet been reported. Therefore, the purpose of this report is to describe the clinical course of a cat with congential thoracic lordosis,
scoliosis and a flattened sternum, and to offer recommendations for future attempts at correction. A 10-week-old intact male domestic shorthair kitten was referred for intermittent episodes of dyspnea, cyanosis and a suspected congenital thoracic anomaly. The kitten was born from a known litter, of which no other kittens were affected and there was no known trauma at birthing. The kitten was housed indoors and had been weaned from the mother 4 weeks prior to presentation. The owner had taken the kitten to the primary veterinarian twice for separate episodes of dyspnea and cyanosis, which seemed to be the sequelae of moderate activity. The first episode responded well to oxygen therapy and the kitten was discharged without further treatment. During the second episode, oxygen therapy was immediately instituted, which again resulted in rapid resolution of the clinical signs. Thoracic radiographs were obtained and showed a caudal thoracic lordosis, flattened sternum and a dorsoventrally compressed cardiac 1Veterinary
Surgical Centers, Leesburg, VA, USA Center for Advanced Veterinary Medicine, Vienna, VA, USA
2Hope
Corresponding author: Maris S Lee DVM, Veterinary Surgical Centers, 165 Fort Evans Rd NE, Leesburg, VA 20176, USA Email: [email protected]
Downloaded from jfm.sagepub.com by guest on March 13, 2015
Journal of Feline Medicine and Surgery 16(8)
704 silhouette. Cephalexin (26.7 mg/kg PO q12h) was prescribed, and the owner was instructed to limit the kitten’s activity and administer oxygen therapy as needed Upon presentation to our facility, physical examination revealed a rectal temperature of 39.1°C, a pulse of 230 beats per minute, a respiratory rate of 52 breaths per minute and a weight of 0.82 kg. Entropion was noted in both eyes, in addition to mild mucoid discharge and chemosis. A grade III/VI heart murmur was ausculted with normal pulses and no arrhythmias. All lung fields ausculted clearly; however, a mild inspiratory effort was noted at rest. There was an obvious palpable concavity at the caudal aspect of the thoracic vertebrae. The rest of the physical examination was within normal limits. There were no other orthopedic abnormalities, and no neurological deficits were present. The owner consented to a further work-up including packed cell volume/total solids (PCV/TS), blood glucose (BG), two-view thoracic radiographs, an echocardiogram and an electrocardiogram. The PCV/TS was normal at 31% and 5.9 g/dl. BG was 184 g/dl. Thoracic radiographs were obtained. The ventrodorsal view showed a very mild interstitial pattern in the caudal lung fields and significant rightward scoliosis of the caudal thoracic vertebrae without significant spinal torsion. The right lateral view showed a flattened sternum, caudal thoracic lordosis from the T5 to T13 vertebrae causing dorsoventral compression of the heart, secondary horizontal displacement of the cardiac silhouette, compression of the mainstem bronchi and severe loss of thoracic volume. Objective measurements for the flattened sternum and spinal deformity were obtained and evaluated for vertebral index, Cobb angle and centroid lordosis angle. The vertebral index is calculated as the ratio of the distance between the center of the dorsal surface of the selected vertebral body to the nearest point on the sternum and the dorsoventral diameter of the center of the same vertebral body.10 The vertebral index (Figure 1)11 was measured to be 6.3 (9 = mild).10 Centroid lordosis and Cobb angles were measured and found to be −68° and −77°, respectively. The contours of vertebraes T6, T7, T11 and T12 were identified and conture tangents made. The tangents are connected diagonally to provide a vertebral centroid point. Adjacent vertebral centroids are connected and a perpendicular line drawn. The centroid lordosis angle14 was obtained from the intersection of the perpendicular lines. The Cobb angle12 was defined as the angle between the cranial endplate of T6 and caudal endplate of T12. An electrocardiogram was performed, which showed a sinus tachycardia and normal conduction pattern. An echocardiogram was performed which showed pulmonary hypertension, mild compression, and obstruction of pulmonary venous inflow and moderate tricuspid regurgitation.
Figure 1 Right lateral view of the thorax showing caudal thoracic lordosis from T5 to T13. Measurements shown are the ventrodorsal height of the vertebral body (0.3 cm) and the distance from the ventral vertebral body to the nearest point on the sternum (1.9 cm). Vertebral index = 6.3
The severe loss of vital capacity (thoracic volume) that prevented normal pulmonary expansion and resulted in secondary functional problems with the heart was the most likely reason for the kitten’s clinical signs of episodic dyspnea and cyanosis at home, as well as increased inspiratory effort at rest. It was hypothesized that alleviation of the cardiac compression would result in improvement of the pulmonary hypertension and tricuspid regurgitation. A plan was formulated to initially attempt to increase thoracic volume by applying outward and ventral traction on the sternum as previously described for treating pectus excavatum with an external splint.13 This was intended to alleviate the kitten’s clinical signs and allow an increase in size before further surgical intervention of the spinal deformity be performed, should it be required. All potential complications were discussed with the owner, including re-expansion pulmonary edema; cardiac or pulmonary puncture with needle, with subsequent hemorrhage or pneumothorax, respectively; cardiorespiratory arrest; infection; sternebral fracture from suture pull through; and failure of the procedure to improve clinical signs. The owner consented to surgery, but the procedure was postponed until the following week owing to financial constraints. One week later the kitten was returned for surgery. The owner reported mild progression of inspiratory effort and the need for occasional oxygen therapy at home. However, no cyanosis had been observed. Recheck physical examination revealed a mild increase in the kitten’s inspiratory effort. The lungs ausculted clearly and the remainder of the examination revealed
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no changes. No changes were noted on recheck thoracic radiographs, and the results of the PCV/TS and BG were within normal limits. A 22 G intravenous (IV) catheter was placed in the right medial saphenous vein. The patient was pre-medicated with butorphanol 0.16 mg (0.2 mg/kg IV) and anesthesia was induced with diazepam 0.2 mg IV (0.25 mg/kg IV) followed by propofol to effect (6 mg/kg IV). Endotracheal intubation was performed with a #3 endotracheal tube and anesthesia was maintained with sevoflurane mixed with oxygen under intermittent positive pressure ventilation limited to 15 cm H2O. A balanced electrolyte solution was administered intravenously at 10 ml/kg/h. The kitten was placed in dorsal recumbency, and a ventral midline approach to the sternum facilitated identification of each sternebrae and suture placement. Circumsternebral sutures were placed with 2-0 polypropylene on a taper point needle passed from the left to right side, carefully ensuring that the needle point was in contact with the sternebrae at all times. To help minimize the risk of cardiac and pulmonary puncture, sutures were placed around the second sternebrae first and progressed caudally to the xiphoid. This allowed for ventral traction on the sternum during suture passage around the remainder of the sternebrae in effort to avoid cardiac puncture. Once all circumsternebral sutures were placed, the site was lavaged and the subcutaneous and skin layers were closed routinely. A fiberglass splint was pre-molded to the ventral aspect of the thorax, allowing 1–2 cm of free space between the sternum and splint for ventral traction while ensuring smooth contact around the lateral aspect of the ventral thoracic wall. The splint was padded around the margin with cotton cast padding and central holes were predrilled for passage of the circumsternbral sutures. The splint was applied to the ventral aspect of the thorax and the sutures were passed through the drill holes and tied cranially to caudally while applying gentle ventral traction on each suture. The kitten was then transported to radiology for postoperative thoracic radiographs. An increased respiratory rate and effort was noted immediately following postoperative radiographs, which was quickly followed by cardiorespiratory arrest. Review of the thoracic radiographs showed ventral distraction of the sternum with a vertebral index of 10.3 (Figure 2); however, a left-sided pneumothorax was present. A left sided thoracocentesis was performed and 10 ml of air was removed from the thorax. CPR was performed for 15 mins without success. The left side of the thorax was aspirated twice more during CPR. However, no further free air was removed. The owner consented to a necropsy. The thoracic splint was removed and the thorax was explored by a median sternotomy approach. There was no trauma evident to any intrathoracic structure. No abnormal soft
Figure 2 Postoperative right lateral view of the thorax showing a pneumothorax, pulmonary atelectasis and the cardiac silhouette elevated from the sternum. Vertebral index = 10.3
tissue attachments were present, and the heart and lungs were freely moveable in relation to the sternum and ventral spine. The caudal thoracic spine appeared severely lordotic with osteophytosis present along the ventral aspect. The lordotic portion of the spine was subjectively evaluated for flexibility. Direct digital pressure on the ventral aspect of the lordotic portion of the spine resulted in no movement. A dorsal approach to the affected area of the thoracic spine was performed and manual retraction of the dorsal spinous processes failed to result in correction of the lordosis. No histopathology was performed. This case report describes an attempt to improve loss of vital capacity in a 0.8 kg kitten secondary to severe caudal thoracic lordosis and a flattened sternum. Cardiovascular defects were also documented that were likely to be secondary to dorsoventral compression of the heart. We are unaware of any published reports describing attempted surgical correction of this specific condition in a kitten. During preoperative planning and discussion, we felt that thoracic volume could be increased in one of three ways: reduction and stabilization of the spinal deformity, reduction and stabilization of the sternum, or both. Given the lack of neurological deficits, despite a significant spinal deformity, we felt that increasing thoracic volume was a priority over vertebral alignment. In addition, the bone density at 10 weeks of age is poor, and any manipulation and fixation of the vertebral column performed that early would likely result in fixation failure. Therefore, the least invasive way to increase vital capacity in this patient was by ventral distraction of the sternum to a more appropriate anatomic position thereby increasing thoracic volume as measured by the vertebral index. Unfortunately, there are no objective guidelines for the amount of sternal distraction that can be applied
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Journal of Feline Medicine and Surgery 16(8)
706 without increasing the risk of complications. We reduced the sternum in a single phase approach in this kitten. In retrospect, staged reduction may have led to fewer complications and an improved outcome. Alternatively, the sternum could have been reduced in lateral recumbency under fluoroscopic guidance allowing precise distraction based on the vertebral index. Measurement of the Cobb and centroid lordosis angles was an attempt to objectively document changes in spinal curvature. To our knowledge, there have not yet been studies defining normal values in canine and feline subjects. A left-sided pneumothorax was diagnosed postoperatively in this kitten, and may have been the cause of cardiorespiratory arrest. No trauma was noted to any intrathoracic structure on necropsy. Free air may have been introduced into the thoracic cavity through the same holes created by suture passage around the sternebrae. Alternative considerations include puncture of the lung during placement of circumsternabral sutures, despite precautions taken and the lack of evidence of apparent lesions on post-mortem examination. The intraoperative placement of a thoracostomy tube would have allowed pleural drainage and may have prevented cardiorespiratory arrest. The placement of a thoracostomy tube should be considered in future cases with such severe deformities. Manual reduction of the spinal column was attempted via direct pressure applied to the ventral aspect of the thoracic vertebrae and by dorsal traction applied to the rib heads during the necropsy of our case. The spinal deformity was determined to be uncorrectable with distraction alone. It is possible that the addition of multiple releasing rib osteotomies, excision of any synostoses and/or anterior discectomy would have allowed for improved vertebral mobility and distraction/reduction. Severe thoracic lordosis with loss of vital capacity is well documented in the human literature, with multiple case reports describing both successful and unsuccessful outcomes using varying methods of correction.2–9 Postoperative complications reported in the human literature include death, tetraparesis, prolonged ventilatory support, construct failure and infection. Prior to surgery, we hypothesized that the loss of thoracic vital capacity and cardiac compression caused by the spinal defect and flattened sternum were the likely sources of clinical signs in this patient. The vertebral index preoperatively was 6.3 (moderate-to-severe) compared to 10.3 (mild-to-normal) postoperatively, which is a significant improvement in thoracic volume. Had the kitten lived through the initial surgery and significant improvement or resolution of clinical signs obtained, correction of the spinal deformity may not have been necessary. Should correction be required at an early age, ventral spinal fusion may allow sufficient dorsal vertebral growth and self correction. Owing to fatality, we were
unable to prove our hypothesis that alleviation of the pulmonary hypertension and tricuspid regurgitation would have improved following appropriate sternal reduction. However, a successful case of resolution of right ventricular outflow obstruction with external splinting in a 7-week-old Shih Tzu has been documented.14
Conclusions This case report reviews a rare congenital spinal deformity in veterinary medicine. Should the need to improve thoracic volume in future cases arise, in a case such as this we feel that ventral distraction on the sternebrae may be sufficient to palliate clinical signs and allow further growth. Based on the gross findings at necropsy, simple dorsal distraction on the spinal column resulted in minimal deformity correction. Correction of similar spinal deformities may be better served by either ventral spinal fusion allowing continued dorsal growth and selfcorrection or multiple releasing rib osteotomies and/or anterior discectomy and synostosis excision. Correction in human medicine with multiple rib osteotomies creates a flail chest, which may require prolonged ventilatory support, and owners should be so informed. Corrective spinal surgery in a small patient may be feasible, but has not yet been reported, and obvious significant limitations exist owing to patient size and the literature currently available in veterinary medicine. Owners must be informed that until more evidencebased outcomes are available, accurate preoperative patient evaluation is imperative and potential complications are significant, thereby also making euthanasia an acceptable option in severe cases that do not show a favorable response to sternal distraction. Funding The authors received no specific grant from any funding agency in the public, commercial or not-for-profit sectors for the preparation of this case report.
Conflict of interest The authors do not have any potential conflicts of interest to declare.
References 1 Blood DC and Studdert VP. Baillière’s comprehensive veterinary dictionary. London: WB Saunders, 1988. 2 Gogus A, Talu U and Hamzaoglu A. One-stage surgical correction of congenital thoracic lordosis – report of 2 cases. Acta Orthop Scand 2001; 72: 413–418. 3 Campbell RM. Spine deformities in rare congenital syndromes. Spine 2009; 34: 1815–1827. 4 Emans JB, Caubet JF, Ordonez CL, et al. The treatment of spine and chest wall deformities with fused ribs by expansion thoracostomy and insertion of vertical expandable prosthetic titanium rib. Spine 2005; 30 Suppl: S58–S68. 5 Winter RB, Moe JH and Bradford DS. Congenital thoracic lordosis. J Bone Joint Surg Am 1978; 60: 806–810.
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6 Bradford DS, Blatt JM and Rasp FL. Surgical management of severe thoracic lordosis. A new technique to restore normal kyphosis. Spine 1983; 8: 420–428. 7 Winter RB. Thoracic lordoscoliosis in neurofibromatosis: treatment by a Harrington rod with sublaminar wiring. Report of two cases. J Bone Joint Surg Am 1984; 66: 1102–1106. 8 Winter RB, Lovell WW and Moe JH. Excessive thoracic lordosis and loss of pulmonary function in patients with idiopathic scoliosis. J Bone Joint Surg Am 1975; 57: 972–977. 9 Winter RB and Leonard AS. Surgical correction of congenital thoracic lordosis. J Ped Ortho 1990; 10: 805–808.
10 Fossum TW, Hedlund CS, Johnson AL, et al. Small animal surgery. 3rd ed. Philadelphia: Mosby, 2007. 11 Fossum TW, Hedlund CS, Hulse DA, et al. Small animal surgery. 2nd ed. Philadelphia: Mosby, 2002. 12 Chen YL. Vertebral centroid measurement of lumbar lordosis compared with the Cobb technique. Spine 1999; 24: 1786–1790. 13 Fossum TW, Boudrieau RJ, Hobson HP, et al. Surgical correction of pectus excavatum using external splintage in two dogs and a cat. J Am Vet Med Assoc 1989; 195: 91–97. 14 Gifford AT and Flanders JA. External splinting for treatment of pectus excavatum in a dog with right ventricular outflow obstruction. J Vet Cardiol 2010; 12: 53–57.
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JFM16810.1177/1098612X13514975Journal of Feline Medicine and SurgeryLee et al
Case Report Journal of Feline Medicine and Surgery 2014, Vol. 16(8) 703–707 © ISFM and AAFP 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/1098612X13514975 jfms.com
Congenital thoracic lordosis and scoliosis in a cat Maris S Lee1, Jim Taylor1 and Bonnie Lefbom2
Abstract
A 10-week-old domestic shorthair kitten was referred for intermittent episodes of dyspnea, cyanosis and a suspected congenital thoracic anomaly. Physical examination showed an obvious palpable concavity in the caudal thoracic spine. Thoracic radiographs showed severe caudal thoracic lordosis from T5 to T13 with a Cobb angle of −77°, a centroid lordosis angle of −68°, a vertebral index of 6.3 and a flattened sternum. Severe loss of vital capacity was suspected and surgical correction of the thoracic deformity was to be performed in two separate stages, the first being surgical ventral distraction on the sternum to increase thoracic volume and rigid fixation with an external splint. The second stage, if required, would be surgical correction of the spinal deformity to also increase thoracic volume. The initial stage of surgery was performed and postoperative radiographs showed a vertebral index of 10.3. The kitten suffered a left sided pneumothorax in recovery and died from cardiorespiratory arrest despite immediate pleural drainage and cardiopulmonary resuscitation. Treatment recommendations that may benefit future case management are discussed. Accepted: 7 November 2013
Lordosis is defined as an abnormal ventral curvature of the spinal column.1 Congenital thoracic lordosis has been reported in human literature to be a severely debilitating and progressive disease among juveniles causing loss of vital capacity, which may eventually lead to pulmonary deficits and death.2–9 The majority of patients present for dyspnea; however, dysphagia due to esophageal compression, right ventricular hypertrophy and pulmonary artery hypertension have also been repor ted.2–9 Failure of vertebral segmentation, vertebral synostoses, severe lordosis and scolisis are common radiographic and surgical findings. Scoliosis is defined as an abnormal lateral deviation of the spinal column.1 Surgical management of severe cases in humans consists of one or a combination of the following dependent upon the time period, institution and individual patient: anterior spinal fusion, posterior spinal fusion, excision of posterior synostoses, anterior discectomy, anterior closing wedge ostectomy, multiple rib osteotomy, posterior Harrington rods with sublaminar wiring and expansion thoracotomy with expandable prosthetic ribs.2–9 Potential postoperative complications include quadriplegia, prolonged ventilatory support, cardiac arrest and death. To our knowledge, an attempt to correct a severe form of this condition in a cat has not yet been reported. Therefore, the purpose of this report is to describe the clinical course of a cat with congential thoracic lordosis,
scoliosis and a flattened sternum, and to offer recommendations for future attempts at correction. A 10-week-old intact male domestic shorthair kitten was referred for intermittent episodes of dyspnea, cyanosis and a suspected congenital thoracic anomaly. The kitten was born from a known litter, of which no other kittens were affected and there was no known trauma at birthing. The kitten was housed indoors and had been weaned from the mother 4 weeks prior to presentation. The owner had taken the kitten to the primary veterinarian twice for separate episodes of dyspnea and cyanosis, which seemed to be the sequelae of moderate activity. The first episode responded well to oxygen therapy and the kitten was discharged without further treatment. During the second episode, oxygen therapy was immediately instituted, which again resulted in rapid resolution of the clinical signs. Thoracic radiographs were obtained and showed a caudal thoracic lordosis, flattened sternum and a dorsoventrally compressed cardiac 1Veterinary
Surgical Centers, Leesburg, VA, USA Center for Advanced Veterinary Medicine, Vienna, VA, USA
2Hope
Corresponding author: Maris S Lee DVM, Veterinary Surgical Centers, 165 Fort Evans Rd NE, Leesburg, VA 20176, USA Email: [email protected]
Downloaded from jfm.sagepub.com by guest on March 13, 2015
Journal of Feline Medicine and Surgery 16(8)
704 silhouette. Cephalexin (26.7 mg/kg PO q12h) was prescribed, and the owner was instructed to limit the kitten’s activity and administer oxygen therapy as needed Upon presentation to our facility, physical examination revealed a rectal temperature of 39.1°C, a pulse of 230 beats per minute, a respiratory rate of 52 breaths per minute and a weight of 0.82 kg. Entropion was noted in both eyes, in addition to mild mucoid discharge and chemosis. A grade III/VI heart murmur was ausculted with normal pulses and no arrhythmias. All lung fields ausculted clearly; however, a mild inspiratory effort was noted at rest. There was an obvious palpable concavity at the caudal aspect of the thoracic vertebrae. The rest of the physical examination was within normal limits. There were no other orthopedic abnormalities, and no neurological deficits were present. The owner consented to a further work-up including packed cell volume/total solids (PCV/TS), blood glucose (BG), two-view thoracic radiographs, an echocardiogram and an electrocardiogram. The PCV/TS was normal at 31% and 5.9 g/dl. BG was 184 g/dl. Thoracic radiographs were obtained. The ventrodorsal view showed a very mild interstitial pattern in the caudal lung fields and significant rightward scoliosis of the caudal thoracic vertebrae without significant spinal torsion. The right lateral view showed a flattened sternum, caudal thoracic lordosis from the T5 to T13 vertebrae causing dorsoventral compression of the heart, secondary horizontal displacement of the cardiac silhouette, compression of the mainstem bronchi and severe loss of thoracic volume. Objective measurements for the flattened sternum and spinal deformity were obtained and evaluated for vertebral index, Cobb angle and centroid lordosis angle. The vertebral index is calculated as the ratio of the distance between the center of the dorsal surface of the selected vertebral body to the nearest point on the sternum and the dorsoventral diameter of the center of the same vertebral body.10 The vertebral index (Figure 1)11 was measured to be 6.3 (9 = mild).10 Centroid lordosis and Cobb angles were measured and found to be −68° and −77°, respectively. The contours of vertebraes T6, T7, T11 and T12 were identified and conture tangents made. The tangents are connected diagonally to provide a vertebral centroid point. Adjacent vertebral centroids are connected and a perpendicular line drawn. The centroid lordosis angle14 was obtained from the intersection of the perpendicular lines. The Cobb angle12 was defined as the angle between the cranial endplate of T6 and caudal endplate of T12. An electrocardiogram was performed, which showed a sinus tachycardia and normal conduction pattern. An echocardiogram was performed which showed pulmonary hypertension, mild compression, and obstruction of pulmonary venous inflow and moderate tricuspid regurgitation.
Figure 1 Right lateral view of the thorax showing caudal thoracic lordosis from T5 to T13. Measurements shown are the ventrodorsal height of the vertebral body (0.3 cm) and the distance from the ventral vertebral body to the nearest point on the sternum (1.9 cm). Vertebral index = 6.3
The severe loss of vital capacity (thoracic volume) that prevented normal pulmonary expansion and resulted in secondary functional problems with the heart was the most likely reason for the kitten’s clinical signs of episodic dyspnea and cyanosis at home, as well as increased inspiratory effort at rest. It was hypothesized that alleviation of the cardiac compression would result in improvement of the pulmonary hypertension and tricuspid regurgitation. A plan was formulated to initially attempt to increase thoracic volume by applying outward and ventral traction on the sternum as previously described for treating pectus excavatum with an external splint.13 This was intended to alleviate the kitten’s clinical signs and allow an increase in size before further surgical intervention of the spinal deformity be performed, should it be required. All potential complications were discussed with the owner, including re-expansion pulmonary edema; cardiac or pulmonary puncture with needle, with subsequent hemorrhage or pneumothorax, respectively; cardiorespiratory arrest; infection; sternebral fracture from suture pull through; and failure of the procedure to improve clinical signs. The owner consented to surgery, but the procedure was postponed until the following week owing to financial constraints. One week later the kitten was returned for surgery. The owner reported mild progression of inspiratory effort and the need for occasional oxygen therapy at home. However, no cyanosis had been observed. Recheck physical examination revealed a mild increase in the kitten’s inspiratory effort. The lungs ausculted clearly and the remainder of the examination revealed
Downloaded from jfm.sagepub.com by guest on March 13, 2015
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no changes. No changes were noted on recheck thoracic radiographs, and the results of the PCV/TS and BG were within normal limits. A 22 G intravenous (IV) catheter was placed in the right medial saphenous vein. The patient was pre-medicated with butorphanol 0.16 mg (0.2 mg/kg IV) and anesthesia was induced with diazepam 0.2 mg IV (0.25 mg/kg IV) followed by propofol to effect (6 mg/kg IV). Endotracheal intubation was performed with a #3 endotracheal tube and anesthesia was maintained with sevoflurane mixed with oxygen under intermittent positive pressure ventilation limited to 15 cm H2O. A balanced electrolyte solution was administered intravenously at 10 ml/kg/h. The kitten was placed in dorsal recumbency, and a ventral midline approach to the sternum facilitated identification of each sternebrae and suture placement. Circumsternebral sutures were placed with 2-0 polypropylene on a taper point needle passed from the left to right side, carefully ensuring that the needle point was in contact with the sternebrae at all times. To help minimize the risk of cardiac and pulmonary puncture, sutures were placed around the second sternebrae first and progressed caudally to the xiphoid. This allowed for ventral traction on the sternum during suture passage around the remainder of the sternebrae in effort to avoid cardiac puncture. Once all circumsternebral sutures were placed, the site was lavaged and the subcutaneous and skin layers were closed routinely. A fiberglass splint was pre-molded to the ventral aspect of the thorax, allowing 1–2 cm of free space between the sternum and splint for ventral traction while ensuring smooth contact around the lateral aspect of the ventral thoracic wall. The splint was padded around the margin with cotton cast padding and central holes were predrilled for passage of the circumsternbral sutures. The splint was applied to the ventral aspect of the thorax and the sutures were passed through the drill holes and tied cranially to caudally while applying gentle ventral traction on each suture. The kitten was then transported to radiology for postoperative thoracic radiographs. An increased respiratory rate and effort was noted immediately following postoperative radiographs, which was quickly followed by cardiorespiratory arrest. Review of the thoracic radiographs showed ventral distraction of the sternum with a vertebral index of 10.3 (Figure 2); however, a left-sided pneumothorax was present. A left sided thoracocentesis was performed and 10 ml of air was removed from the thorax. CPR was performed for 15 mins without success. The left side of the thorax was aspirated twice more during CPR. However, no further free air was removed. The owner consented to a necropsy. The thoracic splint was removed and the thorax was explored by a median sternotomy approach. There was no trauma evident to any intrathoracic structure. No abnormal soft
Figure 2 Postoperative right lateral view of the thorax showing a pneumothorax, pulmonary atelectasis and the cardiac silhouette elevated from the sternum. Vertebral index = 10.3
tissue attachments were present, and the heart and lungs were freely moveable in relation to the sternum and ventral spine. The caudal thoracic spine appeared severely lordotic with osteophytosis present along the ventral aspect. The lordotic portion of the spine was subjectively evaluated for flexibility. Direct digital pressure on the ventral aspect of the lordotic portion of the spine resulted in no movement. A dorsal approach to the affected area of the thoracic spine was performed and manual retraction of the dorsal spinous processes failed to result in correction of the lordosis. No histopathology was performed. This case report describes an attempt to improve loss of vital capacity in a 0.8 kg kitten secondary to severe caudal thoracic lordosis and a flattened sternum. Cardiovascular defects were also documented that were likely to be secondary to dorsoventral compression of the heart. We are unaware of any published reports describing attempted surgical correction of this specific condition in a kitten. During preoperative planning and discussion, we felt that thoracic volume could be increased in one of three ways: reduction and stabilization of the spinal deformity, reduction and stabilization of the sternum, or both. Given the lack of neurological deficits, despite a significant spinal deformity, we felt that increasing thoracic volume was a priority over vertebral alignment. In addition, the bone density at 10 weeks of age is poor, and any manipulation and fixation of the vertebral column performed that early would likely result in fixation failure. Therefore, the least invasive way to increase vital capacity in this patient was by ventral distraction of the sternum to a more appropriate anatomic position thereby increasing thoracic volume as measured by the vertebral index. Unfortunately, there are no objective guidelines for the amount of sternal distraction that can be applied
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Journal of Feline Medicine and Surgery 16(8)
706 without increasing the risk of complications. We reduced the sternum in a single phase approach in this kitten. In retrospect, staged reduction may have led to fewer complications and an improved outcome. Alternatively, the sternum could have been reduced in lateral recumbency under fluoroscopic guidance allowing precise distraction based on the vertebral index. Measurement of the Cobb and centroid lordosis angles was an attempt to objectively document changes in spinal curvature. To our knowledge, there have not yet been studies defining normal values in canine and feline subjects. A left-sided pneumothorax was diagnosed postoperatively in this kitten, and may have been the cause of cardiorespiratory arrest. No trauma was noted to any intrathoracic structure on necropsy. Free air may have been introduced into the thoracic cavity through the same holes created by suture passage around the sternebrae. Alternative considerations include puncture of the lung during placement of circumsternabral sutures, despite precautions taken and the lack of evidence of apparent lesions on post-mortem examination. The intraoperative placement of a thoracostomy tube would have allowed pleural drainage and may have prevented cardiorespiratory arrest. The placement of a thoracostomy tube should be considered in future cases with such severe deformities. Manual reduction of the spinal column was attempted via direct pressure applied to the ventral aspect of the thoracic vertebrae and by dorsal traction applied to the rib heads during the necropsy of our case. The spinal deformity was determined to be uncorrectable with distraction alone. It is possible that the addition of multiple releasing rib osteotomies, excision of any synostoses and/or anterior discectomy would have allowed for improved vertebral mobility and distraction/reduction. Severe thoracic lordosis with loss of vital capacity is well documented in the human literature, with multiple case reports describing both successful and unsuccessful outcomes using varying methods of correction.2–9 Postoperative complications reported in the human literature include death, tetraparesis, prolonged ventilatory support, construct failure and infection. Prior to surgery, we hypothesized that the loss of thoracic vital capacity and cardiac compression caused by the spinal defect and flattened sternum were the likely sources of clinical signs in this patient. The vertebral index preoperatively was 6.3 (moderate-to-severe) compared to 10.3 (mild-to-normal) postoperatively, which is a significant improvement in thoracic volume. Had the kitten lived through the initial surgery and significant improvement or resolution of clinical signs obtained, correction of the spinal deformity may not have been necessary. Should correction be required at an early age, ventral spinal fusion may allow sufficient dorsal vertebral growth and self correction. Owing to fatality, we were
unable to prove our hypothesis that alleviation of the pulmonary hypertension and tricuspid regurgitation would have improved following appropriate sternal reduction. However, a successful case of resolution of right ventricular outflow obstruction with external splinting in a 7-week-old Shih Tzu has been documented.14
Conclusions This case report reviews a rare congenital spinal deformity in veterinary medicine. Should the need to improve thoracic volume in future cases arise, in a case such as this we feel that ventral distraction on the sternebrae may be sufficient to palliate clinical signs and allow further growth. Based on the gross findings at necropsy, simple dorsal distraction on the spinal column resulted in minimal deformity correction. Correction of similar spinal deformities may be better served by either ventral spinal fusion allowing continued dorsal growth and selfcorrection or multiple releasing rib osteotomies and/or anterior discectomy and synostosis excision. Correction in human medicine with multiple rib osteotomies creates a flail chest, which may require prolonged ventilatory support, and owners should be so informed. Corrective spinal surgery in a small patient may be feasible, but has not yet been reported, and obvious significant limitations exist owing to patient size and the literature currently available in veterinary medicine. Owners must be informed that until more evidencebased outcomes are available, accurate preoperative patient evaluation is imperative and potential complications are significant, thereby also making euthanasia an acceptable option in severe cases that do not show a favorable response to sternal distraction. Funding The authors received no specific grant from any funding agency in the public, commercial or not-for-profit sectors for the preparation of this case report.
Conflict of interest The authors do not have any potential conflicts of interest to declare.
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