Vertebral Osteomyelitis and Discitis

Nathan Wanderman

Ilyas S. Aleem

Ahmad Nassr

Vertebral osteomyelitis and discitis constitute almost 97% of all spine infections.¹ Untreated, these infections carry a mortality rate as high as 25% and predispose individuals to significant pain, deformity, and neurologic deterioration.² Treatment can significantly reduce the morbidity and mortality rate and may include antibiotic therapy with or without bracing, or a combination of medical and surgical management.², ³, ⁴ The goals of treatment are to appropriately identify the offending pathogen, eliminate or suppress the infection, obtain spinal stability, and mitigate progressive neurologic impairment.²

While computer tomography-guided needle biopsy and blood cultures, antibiotics, immobilization, and nutritional optimization are the mainstays of diagnosis and treatment,² surgery is sometimes indicated in specific circumstances. Current indications for surgery include obtaining an open biopsy when closed needle biopsy has failed to reveal an organism, progressive neurologic deficit, spinal deformity or instability, intractable pain, or failed medical management.⁵

The open surgical approach to vertebral osteomyelitis and discitis in the thoracolumbar spine has traditionally involved an anterior or posterior approach with or without fusion and instrumentation. The approach is guided by the location of the pathology, vascular anatomy, previous abdominal approaches, and other patient factors. An open anterior approach has been the most commonly used, often with decompression and fusion with cages or autogenous strut grafts.⁶ A posterior decompression alone has historically resulted in poorer outcomes due to limited exposure and difficulties placing the anterior bone graft,³,⁷ but may be indicated for medically unstable patients with secondary posterior thoracolumbar epidural abscesses who are unable to medically tolerate an anterior approach.⁸ Use of fusion with or without instrumentation remains controversial, as some authors argue that placement of graft into an infected bed could interfere with treatment, while others contend that a single-stage debridement and reconstruction is superior to subjecting individuals to a two-stage procedure.⁹,¹⁰ Thus, while carrying a theoretically increased risk of facilitating chronic infection, a combined anterior decompression and fusion with posterior stabilization has the advantage of facilitating early mobilization.¹¹

With comorbidities such as diabetes, immunosuppression, renal failure, recent systemic infection, smoking, malnutrition, and intravenous (IV) drug abuse being common in spinal infections, open surgical treatment can be challenging.¹² This has recently given rise to an increase in the use of minimally invasive surgical (MIS) approaches. The general indications for MIS approaches in the treatment of vertebral osteomyelitis or discitis largely overlap with traditional surgical intervention.¹³

MIS TECHNIQUES

Transthoracic, retroperitoneal, transforaminal lumbar interbody fusion (TLIF), and percutaneous pedicle screw fixation techniques can be used for treatment of thoracolumbar vertebral osteomyelitis or discitis.

Transthoracic Thoracoscopic

The transthoracic thoracoscopic approach is the primary minimally invasive technique for treating vertebral osteomyelitis in the thoracic spine, and can be extended to L2 by endoscopic splitting
of the diaphragm. Huang et al.¹⁴ first reported using an anterolateral thoracoscopic approach for corpectomy and fusion with autograft in 10 patients with thoracic spinal tuberculosis.

This technique was further developed by Muckley et al.,¹⁵ who published a case series describing a thoracoscopic fusion with instrumentation in three patients with pyogenic vertebral osteomyelitis. The transthoracic thoracoscopic MIS technique is as follows:¹⁴, ¹⁵, ¹⁶

Along with routine imaging, preoperative workup should include dedicated lung/chest imaging to evaluate for potential pleural fluid, fibrinous membranes, or adhesions in the pleural space. Preoperative cross-sectional imaging should also include careful assessment of the patient’s vascular anatomy.
Induction of general endotracheal anesthesia and intubation using a double-lumen endobrachial tube to achieve single-lung ventilation for maximal surgical exposure
The patient is positioned in the lateral decubitus position on a radiolucent table and secured with a four-point system to the sacrum, public bone, scapula, and sternum. An axillary roll is placed under the axilla and bony prominences are appropriately padded. The patient is draped for posterior-lateral thoracotomy to permit conversion to an open procedure if the need arises.
C-arm fluoroscopy is used to ensure that the patient and the spine are perpendicular to the operating table.
A left-sided approach is preferred for access to the thoracolumbar junction (T11-L2) and a right-sided approach for the middle to upper thoracic spine (T3-T10).
Precise marking of trocar insertion sites on the thoracic wall is made under C-arm fluoroscopy. The authors disagree about the location of the main working channel. Huang et al. advocate placement along the anterior axillary line and in the intercostal space two levels above the lesion, with secondary channels along the posterior axillary line at the two intercostal levels below. Muckley et al. advocate for placement of the main channel directly over the lesion on lateral fluoroscopy.
The upside lung is selectively collapsed.
After an appropriate incision is made and carried through subcutaneous tissue, a 11-mm trochar is used to introduce a 0¹⁴ or 30¹⁵ degree 10 mm thoracoscope and visualize the lesion.
Two incisions 2.5 to 3.5 cm in length are made for the manipulating channels. The channel to be used for tissue removal is protected using a flexible thoracoport.
Monopolar electrocautery and a Yankauer suction tube are used to longitudinally divide the mediastinal pleura overlying the lesion.
Tissue samples are obtained and should be sent for gram stain, cell count with differential, and microbiology culture (typical and atypical) to include fungi, tuberculosis, aerobes, and anaerobes, as well as special stains for more unusual organisms if suspected.
Intercostal arteries and veins around the lesion are ligated with hemoclips and divided, allowing for careful debridement of the lesion.
If using instrumentation, Muckley et al. advocate placing polyaxial screws for anterior plating prior to vertebral body resection to serve as orienting landmarks.
A partial corpectomy of involved vertebral bodies is performed using pituitary rongeurs and elongated curettes. A thorough decompression is performed down to the epidural space. The ipsilateral pedicle can be resected to facilitate debridement.
Fusion is achieved by inserting a well-fitting bone graft into the defect. Tricortical iliac autograft is preferred, though other options are reasonable depending upon the virulence of the organism.¹⁴
Alternatively, a titanium cage filled with autologous bone graft mixed with antibiotics is inserted. Fixation is achieved by connecting rods or a plate to the preinserted polyaxial screws.¹⁵ A titanium cage is preferred over stainless steel, as it has been shown to provide greater resistance to biofilm formation.¹⁷
A 32 or 24 French chest tube is inserted through one incision.
Muscle layers are closed with absorbable sutures, and the skin is closed with a 3-0 nylon suture.

In the Huang et al. series, 1 of 10 patients experienced lung atelectasis due to prolonged air leak, and three other patients had an air leak without significant complication. No intraoperative complications were reported, but one conversion to open was required due to a severe
pleural adhesion. Postoperative protocol included an average of 5 days of chest tube placement for drainage, and average hospital stay (including rehabilitation) was 21 days. Pleural adhesions developed in four patients. In the Muckley et al. series, 1 of 3 patients required revision anterior instrumentation along with posterior fusion due to infection recurrence and kyphotic progression 3 weeks postoperatively. In both series, the surgical goal was structural stability without a recurrence of infection.

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