Costotransversectomy Approach to the Thoracic Spine

The costotransversectomy approach provides posterolateral extrapleural access to the thoracic vertebral body and disc space through resection of the transverse process and proximal rib. It is the classic route for thoracic disc herniation, vertebral body biopsy, debridement of infection or tumour, and limited anterolateral decompression. The approach is performed through a paramedian or gently curved incision, staying strictly extrapleural while protecting the intercostal neurovascular bundle and the exiting nerve root. The spinal cord remains medial and must never be retracted. This approach is distinct from the transthoracic (which enters the pleural cavity) and the lateral extracavitary (which splits the paraspinal muscles more laterally and provides a more anterior trajectory).

Primary Indications:

• Thoracic disc herniation (soft or calcified) causing myelopathy or radiculopathy
• Vertebral body biopsy for suspected tumour or infection
• Debridement of pyogenic spondylodiscitis or tuberculous spondylitis with paravertebral abscess
• Limited anterolateral decompression for anterior cord compression (metastasis, burst fracture)
• Drainage of paraspinal or epidural abscess when posterior approach insufficient
• Excision of rib head or costovertebral joint pathology

Why This Approach is Chosen: The costotransversectomy provides direct posterolateral extrapleural access to the lateral vertebral body and disc without entering the pleural cavity. It avoids the morbidity of a thoracotomy while giving better access to the anterior column than a pure posterior approach. The approach is particularly useful when the pathology is lateral or anterolateral and the surgeon wishes to avoid the lung, great vessels, and sympathetic chain that are encountered in a transthoracic route.

Contraindications:

• Pathology requiring extensive anterior column reconstruction (consider transthoracic or combined)
• Severe pulmonary disease precluding even brief single-lung ventilation if pleural breach occurs
• Previous ipsilateral thoracotomy or pleurodesis making extrapleural plane obliteration likely
• Midline anterior pathology best addressed by sternotomy or transthoracic route
• Inability to tolerate prone or lateral positioning (rare)

Alternative Approaches:

• Transthoracic approach: Transpleural, excellent anterior access, higher morbidity, requires chest drain routinely
• Lateral extracavitary approach: More lateral muscle-splitting trajectory, better anterior visualization, more extensive
• Transpedicular approach: Purely posterior, limited anterior access, useful for biopsy only
• Laminectomy alone: Insufficient for anterior pathology, risks cord manipulation
• Combined anterior-posterior: For circumferential tumours or severe deformity

Bony Anatomy: The thoracic spine has twelve vertebrae. Each rib articulates with the vertebral body at two points (costovertebral and costotransverse joints) except the first, eleventh and twelfth ribs. The transverse process is short and projects posterolaterally. The rib head lies immediately anterior to the transverse process and articulates with the vertebral body and disc. Resection of the transverse process and proximal rib removes the bony obstacles to the lateral vertebral body.

Muscular Layers: The approach passes through:

• Trapezius (upper thoracic) or latissimus dorsi / paraspinal muscles (lower thoracic)
• Erector spinae (longissimus and iliocostalis)
• The plane between the erector spinae and the rib/transverse process is developed

Neurovascular Anatomy:

• Intercostal neurovascular bundle: Runs in the subcostal groove on the inferior border of each rib (vein-artery-nerve from superior to inferior). The bundle must be identified before rib resection.
• Exiting nerve root: Emerges from the neural foramen just below the pedicle. Can be sacrificed unilaterally at thoracic levels with minimal deficit.
• Segmental radicular arteries: Contribute to the anterior spinal artery. The artery of Adamkiewicz (great radicular artery) usually enters on the left between T9 and T12 - protect if possible.
• Sympathetic chain: Lies on the anterolateral vertebral body - usually not seen in this approach but at risk with deeper dissection.

Pleura: The parietal pleura lines the inner surface of the rib cage. It is loosely attached to the vertebral bodies and can be gently dissected away. The pleural reflection is more posterior at the costovertebral junction, making extrapleural access possible.

Deep Internervous Plane: There is no true internervous plane in the classical sense. The approach is intermuscular between the erector spinae (dorsal rami of spinal nerves) medially and the intercostal muscles / external oblique (ventral rami via intercostal nerves) laterally. The plane is developed by elevating the paraspinal muscles from the ribs and transverse processes.

Superficial Dissection: The skin and subcutaneous tissue are incised. The trapezius (upper) or latissimus (lower) is divided in line with the skin incision or retracted. The erector spinae is elevated subperiosteally from the rib and transverse process. No motor nerves are divided.

Structures at Risk in Each Layer:

Position: Prone or Lateral Decubitus

Pre-positioning Checklist:

• Confirm correct spinal level with preoperative imaging and skin marking
• Anaesthetic assessment for prone positioning (cardiovascular stability, neck mobility)
• Padding for all pressure points (face, chest, pelvis, knees, ankles)
• Arms positioned with shoulders abducted less than 90 degrees
• Radiolucent table or Jackson table for fluoroscopy
• C-arm or O-arm available and tested for anteroposterior and lateral views
• Neuromonitoring (MEP/SSEP) if available and indicated

Positioning Details:

• Prone position on radiolucent table with chest rolls or Wilson frame
• Head in neutral position on padded headrest or Mayfield pins
• Slight reverse Trendelenburg to reduce venous bleeding
• Knees flexed to relax hamstrings and reduce lumbar lordosis if lower thoracic
• Lateral decubitus (affected side up) is an alternative that allows conversion to thoracotomy if needed

Alternative Positioning:

• Lateral decubitus allows access to both costotransversectomy and transthoracic routes without repositioning
• Some surgeons prefer lateral for tumours requiring possible chest wall resection

Key Bony Landmarks:

• Spinous processes: Palpable in midline; T7 spinous process is at the level of the inferior angle of scapula
• Paraspinal gutter: Depression lateral to spinous processes
• Ribs: Count from the twelfth rib upwards or from the first rib (difficult)
• Scapula: Inferior angle marks T7; superior angle marks T3

Key Soft Tissue Landmarks:

• Trapezius: Upper thoracic, inserts on spinous processes
• Latissimus dorsi: Lower thoracic, inserts on thoracolumbar fascia
• Erector spinae: Bulge lateral to spinous processes

Incision Planning:

• Paramedian incision: 8-12 cm, 4-5 cm lateral to midline, centred over the rib two levels above the target vertebra
• J-shaped or curved incision: Allows better access to the costovertebral junction
• The incision is placed over the rib that articulates with the superior aspect of the target disc space
• Confirm level with fluoroscopy before making the skin incision

Consequence of Injury:

• Spinal cord injury: Permanent paraplegia, bowel/bladder dysfunction, sexual dysfunction
• Intercostal artery ligation at multiple levels: Anterior spinal artery syndrome
• Pleural injury: Pneumothorax, haemothorax, pleural effusion, empyema
• Nerve root sacrifice: Unilateral thoracic radiculopathy (usually tolerable)
• Sympathetic injury: Horner syndrome (ptosis, miosis, anhidrosis)

Proximal Extension: The incision can be extended proximally along the paraspinal gutter. Additional ribs and transverse processes can be resected for multilevel pathology. The scapula may need to be mobilized for upper thoracic levels (T1-T4).

Distal Extension: Extend the incision distally for lower thoracic or thoracolumbar pathology. The approach can reach the L1-L2 disc if the twelfth rib is resected, although the lumbar plexus and psoas become relevant below T12.

Bilateral Staged Approach: For circumferential tumours or severe deformity, a contralateral costotransversectomy can be performed at a second stage. This avoids the morbidity of a single-stage bilateral procedure while achieving circumferential decompression.

Combination with Posterior Stabilization: Costotransversectomy is frequently combined with pedicle screw instrumentation placed through a separate midline incision or extended paramedian exposure. The stabilization can be performed before or after the decompression depending on stability.

Conversion to Thoracotomy: If the extrapleural plane is obliterated or more anterior access is required, the approach can be converted to a formal thoracotomy by entering the pleural cavity. This requires chest drain insertion and post-operative respiratory support.

Intra-operative Complications:

Post-operative Complications:

Immediate Post-operative:

• Neurovascular assessment documenting lower limb motor and sensory function
• Chest radiograph to exclude pneumothorax or haemothorax
• Pain control with multimodal analgesia (avoid excessive opioids that depress respiration)
• Incentive spirometry and chest physiotherapy to prevent atelectasis
• DVT prophylaxis with LMWH or mechanical devices

Respiratory Management:

• Monitor oxygen saturation and respiratory effort
• Chest drain (if inserted) remains until output less than 100 mL/24 h and no air leak
• Early mobilization as tolerated to prevent pulmonary complications

Weight Bearing and Activity:

• No restrictions on weight bearing unless stabilization performed
• Log-roll for bed mobility if posterior instrumentation placed
• Gradual return to normal activities over 4-6 weeks

Follow-up Schedule:

• 2 weeks: Wound check, suture/staple removal, chest radiograph if drain was used
• 6 weeks: Clinical review, radiographs if instrumentation placed
• 3 months: CT or MRI to assess decompression if indicated
• 6-12 months: Final clinical and radiographic review

Costotransversectomy is used worldwide for thoracic disc herniation, spinal tumours, and infection when posterolateral extrapleural access is required. The approach is described in all major spine surgery textbooks and is a standard component of neurosurgical and orthopaedic spine fellowship training.

Side-by-side principles (where guidance converges): AO Spine and the North American Spine Society emphasize that thoracic disc herniations causing myelopathy should be approached from the side of the pathology using an extrapleural route when possible, avoiding cord manipulation. NICE (UK) and the Spine Society of Australia recommend costotransversectomy or lateral extracavitary approaches for lateral and anterolateral thoracic disc disease, reserving transthoracic routes for midline calcified discs requiring extensive anterior reconstruction.

Registry and population evidence: Thoracic disc herniation requiring surgery is rare (approximately 1 per 1,000,000 per year). Surgical series consistently report neurological improvement in 80-95 percent of patients with myelopathy when the cord is decompressed without manipulation. Pleural injury rates of 5-15 percent are reported across large series, with the majority managed successfully with chest drainage.

Global practice variation: In high-resource centres, intraoperative neuromonitoring (MEP/SSEP) is routine for myelopathic patients. In resource-limited settings, the same anatomical principles apply and the approach is performed without neuromonitoring with equivalent safety when meticulous technique is used. Chest drain availability and post-operative chest radiography remain essential everywhere.

Consent (globally applicable): Discuss pleural injury requiring chest drain (5-15 percent), neurological deterioration (1-3 percent), wrong-level surgery (never event), wound infection (2-5 percent), chronic radicular pain (10-20 percent), and the possibility of staged posterior stabilization if anterior column reconstruction is required.