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Common complications in canine spinal surgery

What does the evidence say about the prevalence of complications associated with spinal surgery in dogs?

Complications are broadly defined as outcomes that differ from the norm and can be described as general, specific and technical. Common general complications following spinal surgery are gastrointestinal complications and urinary tract infections. Specific complications of spinal surgery include: haematomas, surgical site infections, nerve root injury, dural tears and progressive myelomalacia. Technical complications are generally secondary to implant placement, dislocation of the implant or instrument-related. 

In a large prospective study on morbidity and mortality of major adult spinal surgery (Street et al., 2012), 87 percent of patients had at least one documented complication: 

  • Prolonged hospitalisation: 39 percent 
  • Post-operative complications: 73.5 percent 
  • Surgical complications: 10.5 percent 
  • Death: 1.5 percent

Gastrointestinal effects

In a study by Dowdle and colleagues (Dowdle et al., 2003), endoscopy was used to determine the prevalence of subclinical gastroduodenal ulceration in 30 Dachshunds undergoing decompressive surgery for acute intervertebral disc prolapse. An overall prevalence of 76 percent was calculated. Ulcerogenic medication administered prior to admission did not appear to influence the prevalence. 

Urinary tract infection 

Urinary tract infection (UTI) is a common complication in dogs with acute intervertebral disc extrusion (IVDE). The prevalence for development of UTI in 25 dogs treated surgically has been evaluated. In one study (Olby et al., 2010), presence of UTI over the three-month period was correlated to potential risk factors. Ten dogs (38 percent) developed 12 UTIs over the three-month period, with the majority occurring between the first and sixth week. Sixty percent of the UTIs were occult; haematuria in the absence of pyuria or UTI was a common finding in the perioperative period. Sex, breed and ambulatory status influenced the risk of developing a UTI. Females, Dachshunds and paraplegic dogs were at higher risk. 

Surgical site infection

The surgical site infection (SSI) rate in dogs undergoing hemilaminectomies or laminectomies for thoracolumbar disc herniation or lumbosacral disease, without use of perioperative antibiotics, has been retrospectively evaluated during a two-year period (Dyall and Schmökel, 2018). All incisional complications within 30 days were recorded and divided into superficial, deep (Figure 1) or organ/ space infections. This research study included 154 consecutive hemilaminectomy and laminectomy procedures. One superficial wound infection was recorded and treated with antimicrobials. Overall, the SSI rate was 0.6 percent, while the expected SSI rate in clean operative wounds in dogs and cats is 2.0 to 4.8 percent. The SSI rate in human spinal surgery is 0.7 to 4.3 percent.

FIGURE 1a
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FIGURE 1b
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FIGURE 1 (A,B and C) Dorsal, right parasagittal and transverse T2-weighted images of a subfascial seroma formation and deep infection of the surgical site after hemilaminectomy

Myelomalacia 

Progressive myelomalacia (PMM; Figures 2 and 3) is a catastrophic disease associated with acute IVDE. The onset and progression of clinical signs of PMM has been examined retrospectively in 51 dogs, 18 with histopathologically confirmed PMM and 33 presumptively diagnosed based on clinical signs (Olby et al., 2017). Five dogs had two sites of disc extrusion, giving 56 extrusions in total. Data on nature and progression of signs were extracted. Twenty-four of 51 dogs were Dachshunds. T12–T13 was the most common site of disc extrusion (12 of 56), and 18 mid-to-caudal lumbar discs (between L3 and L6) were affected. 

Onset of PMM signs ranged from present at first evaluation (17/51) to five days after presentation, with 25 of 51 cases developing signs within 48 hours. Progression of signs from onset of PMM to euthanasia or death, excluding seven cases euthanised at presentation, ranged from 1 to 13 days, with 23 being euthanised within three days. Nonspecific systemic signs were documented in 30 of 51 dogs.

FIGURE 2a
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FIGURE 2b
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FIGURE 2 (A, B and C) Dorsal, sagittal and transverse T2- weighted images of an L3-L4 acute disc extrusion in a Dachshund that developed late onset progressive myelomalacia (PMM) after mini-hemilaminectomy

The majority of dogs developing myelomalacia do so within two days of presentation, with euthanasia commonly occurring within another three days. The onset can be delayed up to five days after presentation, with progression to euthanasia taking as long as two weeks. Mid-tocaudal lumbar discs might be associated with an increased risk of PMM.

FIGURE 3a
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FIGURE 3b
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FIGURE 3d
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FIGURE 3e
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FIGURE 3 (A, B, C, D and E) Dorsal, sagittal, dorsal STIR and transverse T2-weighted images of a Jack Russell Terrier with L3-L4 acute disc extrusion and acute onset progressive myelomalacia (PMM). Note the extensive intramedullary hyperintensity in the spinal segment cranial and caudal to the site of the disc extrusion

Neurological deterioration 

Early post-operative neurological deterioration is a wellknown complication following dorsal cervical laminectomies and hemilaminectomies in dogs. Medical records of 100 dogs that had undergone a cervical dorsal laminectomy or hemilaminectomy were assessed retrospectively in one study to evaluate potential risk factors (Taylor-Brown et al., 2015). Multiple variables were evaluated and the outcome measures were neurological status immediately following surgery and duration of hospitalisation. 

Diagnoses included osseous associated cervical spondylomyelopathy (OACSM), and acute intervertebral disc extrusion in 72 percent of the dogs. Overall, 54 percent were neurologically worse 48 hours post-operatively. Statistical analysis identified four factors significantly related to early post-operative neurological outcome. Diagnoses of OACSM or meningioma were considered the strongest variables to predict early deterioration, followed by higher neurological grade before surgery and longer surgery time. 

This information can aid in the management of expectations of clinical colleagues and owners with dogs undergoing spinal surgical procedures. The use of prophylactic anti-ulcer medication in spinal surgery patients is suggested. Dogs with thoracolumbar IVDE should be routinely monitored for UTI with urine culture regardless of urinalysis results. The low incidence of SSI suggested reconsideration of routine perioperative antibiotic prophylaxis in dogs undergoing laminectomy procedures.

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