Surgical Approaches to the Spine: Dorsal and Ventral Exposure

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-08-11

Key Takeaways

• The dorsal midline approach is the primary surgical access for thoracolumbar and lumbosacral spinal decompression and stabilization, utilizing sternal recumbency and subperiosteal elevation of epaxial muscles from spinous processes and laminae. Major risks include iatrogenic spinal cord trauma and hemorrhage from the epidural venous plexus.
• The ventral cervical approach is indicated for ventral slot decompression and stabilization of the cervical spine, requiring dorsal recumbency and careful dissection to avoid injury to the carotid sheath, recurrent laryngeal nerve, and esophagus. Hemorrhage from vertebral venous sinuses is a significant intraoperative concern.
• Approach selection is dictated by vertebral region and lesion location; the cervical spine's mobility favors ventral access for caudal segments, while the thoracic spine's rib cage necessitates dorsal approaches. The lumbar spine's depth requires either dorsal or lateral dissection, with ventral access reserved for specific indications due to vascular risks.
• Hemorrhage control during spinal surgery is critical, with the dorsal approach risking epidural venous plexuses and the ventral approach risking vertebral venous sinuses and thyroid vessels; hemostatic agents like gelatin sponges and bone wax are essential adjuncts.
• Postoperative monitoring differs significantly between approaches, with dorsal procedures focusing on gait and proprioception, while ventral cervical procedures require vigilance for respiratory rate, swallowing function, and laryngeal paralysis.
• Common errors include inadequate exposure in dorsal approaches and off-midline dissection in ventral approaches, necessitating careful landmark identification and precise instrument control to minimize iatrogenic trauma and ensure adequate decompression.

This article provides a procedural reference for the dorsal and ventral surgical approaches most commonly used in canine and feline spinal surgery. It is written for practicing veterinarians who perform or assist in decompressive and stabilization procedures. The focus is on surgical anatomy, patient positioning, exposure technique, and the complications specific to each approach. Specific spinal diseases, such as intervertebral disc disease or vertebral fracture classification, are addressed only where they influence approach selection.

The clinical question this article answers is practical: given a lesion localized to a specific vertebral region, which exposure gives the safest and most complete access, and what anatomic hazards must be respected along the way? The reader is assumed to be comfortable with basic surgical principles, instrument handling, and postoperative care. The content bridges standard textbook anatomy and the intraoperative decisions that determine whether an exposure is adequate or inadequate.

At a Glance

Anatomic Basis of Approach Selection

The vertebral column is segmentally organized, and each region imposes distinct constraints on surgical access. The cervical spine is mobile and relatively superficial ventrally, which makes a ventral approach feasible for the caudal cervical vertebrae. The thoracic spine is stabilized by the rib cage and the long spinous processes, which favor a dorsal approach. The lumbar spine is deep to the epaxial musculature, and the lumbosacral junction sits within the pelvic canal, requiring either a dorsal midline exposure or a lateral approach depending on the target.

The spinal cord occupies a variable proportion of the vertebral canal. In the cervical region, the cord is large relative to the canal, leaving little space for manipulation. In the caudal lumbar region, the cord tapers into the cauda equina, which tolerates gentle retraction better than the cord itself. These differences determine how much working room the surgeon can expect and how aggressively the exposure must be developed.

The blood supply to the spinal cord is segmental. The dorsal approach risks injury to the dorsal spinal arteries and the epidural venous plexus, while the ventral cervical approach risks the vertebral arteries and the ventral venous sinuses. Hemorrhage from these structures is also inconvenient, it obscures the surgical field and can cause postoperative neurologic deterioration if epidural hematoma forms.

Dorsal Approach: Principles and Technique

The dorsal midline approach is the workhorse for thoracolumbar and lumbosacral surgery. It provides access to the vertebral laminae, articular processes, and spinous processes through a single incision. The approach is extensile, meaning that additional vertebrae can be exposed by extending the incision cranially or caudally without compromising the exposure.

The patient is positioned in sternal recumbency with the spine as straight as possible. The spinous processes are palpated and the incision is made directly over them. The subcutaneous fat is divided, and the thoracolumbar fascia is incised along the dorsal midline. The epaxial muscles, primarily the longissimus and multifidus, are elevated subperiosteally from the spinous processes and laminae using a periosteal elevator. Subperiosteal elevation minimizes hemorrhage and preserves the muscle attachments for closure.

The key technical error in the dorsal approach is straying lateral to the spinous processes, which enters the epaxial muscle mass and causes unnecessary bleeding. The surgeon should identify the spinous processes by palpation throughout the dissection. Once the laminae are exposed, a laminectomy can be performed using a high-speed burr or rongeurs. The extent of bone removal depends on the lesion location and the surgeon's preference for a dorsal, dorsolateral, or pediculectomy approach.

Complications of the dorsal approach include iatrogenic spinal cord trauma from instrument slippage, epidural hemorrhage, and postoperative seroma formation. The paraspinal muscles must be reapproximated in layers to prevent dead space and to preserve the stabilizing function of the epaxial musculature. The use of robotic assistance for posterior spinal approaches has been described in experimental models, with the goal of improving surgeon ergonomics and instrument control, but this technology is not yet standard in veterinary practice Robotic approaches to the posterior spine.

Ventral Approach: Principles and Technique

The ventral approach to the cervical spine is used for ventral slot decompression, interbody fusion, and stabilization procedures. The patient is placed in dorsal recumbency with the neck extended and a sandbag or rolled towel under the cervical region to elevate the surgical site. The incision is made on the ventral midline from the larynx to the manubrium, depending on the target vertebrae.

The dissection proceeds through the subcutaneous tissue and the paired sternohyoid and sternothyroid muscles, which are separated on the midline. The trachea and esophagus are retracted to one side, and the carotid sheath, containing the carotid artery, vagosympathetic trunk, and internal jugular vein, is retracted to the other. The longus colli muscles overlie the ventral aspect of the cervical vertebral bodies and must be elevated laterally to expose the intervertebral disc spaces and vertebral bodies.

The ventral slot is created by removing bone from the ventral aspect of two adjacent vertebrae and the intervening disc. The slot must be wide enough to allow visualization of the spinal cord but narrow enough to preserve vertebral stability. The vertebral venous sinuses lie within the vertebral canal and can hemorrhage profusely if violated. Hemorrhage control with bone wax, gelatin sponges, or hemostatic matrix is often necessary.

The ventral approach carries specific risks. The recurrent laryngeal nerve runs within the carotid sheath and can be injured during retraction, causing laryngeal paralysis and voice change. The esophagus is at risk if the retraction is excessive or if the dissection strays from the midline. Postoperative monitoring should include assessment of swallowing and respiratory function. The choice of interbody device, whether a cage or a bone graft, influences the biomechanical stability of the construct. Interbody cages have been shown to stabilize the motion segment in flexion and lateral bending, though their performance in extension is less robust Interbody cage devices.

Dorsal Approach: Applied Technique and Decision Points

Patient Positioning and Preparation

The patient is positioned in sternal recumbency with the spine in a neutral or slightly flexed posture. Foam troughs or sandbags stabilize the trunk, and the forelimbs are pulled caudally and secured. For cervical dorsal approaches, the head is elevated and flexed ventrally to open the dorsal interspaces. The surgical field is clipped widely, extending at least three vertebral segments cranial and caudal to the intended site. Aseptic preparation includes the dorsal midline and paraspinal musculature bilaterally. Intraoperative fluoroscopy or radiography with a sterile marker is used to confirm the correct vertebral level before incision, because palpable landmarks alone are unreliable in obese or heavily muscled patients.

Incision and Dissection Sequence

A dorsal midline skin incision is made over the spinous processes of the target region. The subcutaneous fat is divided, and the thoracolumbar fascia is incised along the midline. The epaxial musculature is elevated subperiosteally from the spinous processes and laminae using a periosteal elevator. Elevation proceeds from caudal to cranial to reduce hemorrhage from segmental vessels. Self-retaining retractors are placed to maintain exposure. The extent of lateral dissection depends on the procedure: a hemilaminectomy requires exposure of the lamina and articular processes on the affected side, while a dorsal laminectomy requires only the midline structures.

For the cervical spine, the dorsal approach follows the same principles. The nuchal ligament is identified and retracted laterally or divided if necessary. The cervical epaxial muscles are elevated from the dorsal spinous processes and laminae. The articular processes are preserved unless the procedure requires their removal.

Hemilaminectomy Technique

A high-speed burr is used to create a trough in the lamina at the junction of the lamina and the articular process. The burr is directed parallel to the spinal cord, and the inner cortical bone is thinned until the ligamentum flavum is visible. Kerrison rongeurs complete the removal of the remaining bone. The ligamentum flavum is then incised and removed to expose the spinal cord and nerve roots. Hemorrhage from epidural vessels is controlled with bipolar electrocautery, gelatin sponges, or cottonoid patties. The exposure should extend cranially and caudally until the affected disc space or lesion is fully visualized.

Dorsal Laminectomy Technique

A dorsal laminectomy removes the spinous process and dorsal lamina over the affected segment. The burr is used to thin the lamina on both sides of the midline, and the bone plate is lifted away. This approach provides bilateral exposure but sacrifices the dorsal stabilizing structures. It is used primarily for dorsal or dorsolateral spinal cord compression. The surgeon must recognize that the articular processes are preserved when possible to maintain stability.

Closure and Drainage

The epaxial musculature is reapposed with absorbable suture in a simple continuous pattern. The thoracolumbar fascia is closed separately. Subcutaneous tissue and skin are closed routinely. A closed suction drain is placed when dead space is substantial or when hemorrhage is ongoing. Postoperative radiographs confirm implant position when stabilization was performed.

Ventral Approach: Applied Technique and Decision Points

Positioning for the Ventral Cervical Approach

The patient is placed in dorsal recumbency with the forelimbs pulled caudally and secured. The neck is extended with a rolled towel or sandbag beneath the cervical region. The ventral midline is clipped from the mandibular symphysis to the manubrium. The trachea and esophagus are identified by palpation. A midline incision is made from the larynx to the thoracic inlet for lesions of C2 to C7. For lesions at C6 to T1, the incision extends to the manubrium, and a partial median sternotomy may be required for caudal exposure.

Dissection Sequence for Ventral Slot

The paired sternohyoid and sternothyroid muscles are separated on the midline. The trachea is retracted to one side, and the carotid sheath is retracted to the opposite side. The esophagus lies dorsal and lateral to the trachea and must be identified and protected. The longus colli muscles are elevated subperiosteally from the ventral aspect of the vertebral bodies. The intervertebral disc spaces are identified by the transverse processes and by the slight elevation of the annulus. A spinal needle or hypodermic needle is placed in the target disc space, and a lateral radiograph confirms the level.

The ventral slot is created with a high-speed burr centered over the affected disc space. The slot extends laterally to the medial edges of the longus colli muscles and craniocaudally to include the dorsal annulus and the ventral floor of the vertebral canal. The burr is directed perpendicular to the floor of the canal. The dorsal cortical bone and the dorsal longitudinal ligament are removed with fine curettes or Kerrison rongeurs. The spinal cord and nerve roots are visualized, and the herniated disc material is removed with fine instruments.

Complications of the Ventral Approach

The ventral approach carries specific risks. The recurrent laryngeal nerve lies within the carotid sheath and can be injured by excessive retraction, causing laryngeal paralysis. The sympathetic trunk is dorsal to the carotid sheath and may be damaged, producing Horner syndrome. The esophagus is vulnerable to inadvertent penetration, particularly when the dissection is carried too far laterally. The vertebral arteries lie within the transverse foramina and are at risk if the slot is extended too far laterally. The surgeon must monitor for hemorrhage from the venous sinuses within the vertebral canal, which can be controlled with hemostatic agents and gentle pressure.

Ventral Approach to the Lumbar Spine

The ventral approach to the lumbar spine is used for disc fenestration, biopsy, or vertebral stabilization. The patient is positioned in dorsal recumbency. A ventral midline celiotomy is performed, and the retroperitoneal space is entered. The aorta, vena cava, and ureters are identified and retracted. The psoas muscles are elevated from the ventrolateral aspect of the vertebral bodies. The disc spaces are identified by palpation and confirmed with imaging. This approach provides excellent access to the ventral annulus but carries risks of vascular injury, ureteral damage, and postoperative ileus. The approach is less commonly used than the dorsal or lateral routes because of these risks.

Approach Selection by Region and Lesion

Equipment and Consumable Selection

The choice of burr and rongeur influences the safety and efficiency of the approach. A 3 to 4 mm round burr is suitable for most ventral slots and hemilaminectomies. A smaller 1 to 2 mm burr is used for fine work near the spinal cord. The surgeon should have a selection of Kerrison rongeurs from 1 to 3 mm, fine curettes, and nerve hooks. Bipolar electrocautery is preferred over monopolar near neural structures. Hemostatic agents such as gelatin sponges, oxidized cellulose, and bone wax are essential. For stabilization procedures, the surgeon must have the appropriate implants available, including screws, plates, and polymethylmethacrylate. Interbody cage devices have been described for fusion in human patients, and similar principles apply to veterinary patients when ventral interbody stabilization is planned interbody cage devices in spinal fusion. The choice of implant material affects fusion outcomes, with titanium cages showing improved osteointegration compared with other materials interbody fusion approaches and implant materials.

Monitoring and Documentation

Intraoperative monitoring includes assessment of hemorrhage, heart rate, and blood pressure. Significant blood loss is replaced with crystalloids and colloids as indicated. The surgeon monitors for changes in spinal cord evoked potentials when available, although this is not standard in most veterinary practices. Postoperative neurologic assessment is performed at extubation and at regular intervals. The patient is evaluated for voluntary motor function, deep pain perception, and urinary bladder function. Deterioration in neurologic status after surgery warrants immediate re-evaluation, including advanced imaging.

Documentation includes a detailed operative report describing the approach, the findings, the decompression or stabilization performed, and any complications. Intraoperative photographs are useful for teaching and for medicolegal records. Postoperative radiographs are obtained to document implant position and alignment. The patient's neurologic status is recorded using a standardized grading system, and the owner is provided with written discharge instructions that include activity restriction, wound care, and signs of complications.

Complications and Failure Modes

Early recognition of complications begins with the surgeon's awareness of what can go wrong before it happens. Hemorrhage from the vertebral venous sinuses during dorsal laminectomy is the most common intraoperative complication. The sinus lies within the vertebral canal floor and is easily torn when rongeurs or burrs penetrate too deeply. Detection is immediate: bright venous bleeding obscures the surgical field. The correct response is direct pressure with gelatin sponge or cottonoid, not blind clamping. Blind clamping risks iatrogenic spinal cord trauma.

Neurologic deterioration after surgery is the most feared complication. It can result from direct cord contusion during burring, excessive retraction, or postoperative hematoma or seroma formation. Detection requires serial neurologic examinations in the recovery period. A patient that was ambulatory before surgery and is nonambulatory after recovery warrants immediate reassessment. If deterioration is progressive, advanced imaging or surgical re-exploration may be indicated.

Implant failure occurs most often with ventral stabilization procedures. Screw loosening, plate migration, and graft or cage subsidence are recognized failure modes. In human lumbar interbody fusion, titanium cages produce improved osteointegration and fusion rates but also increase subsidence risk compared with other materials, as described in a review of interbody fusion approaches. In the canine cervical spine, similar biomechanical principles apply. Serial radiographs at 4, 8, and 12 weeks postoperatively detect early loosening. Radiolucent lines around screws, change in implant position, or loss of disc space height indicate failure.

Infection is uncommon but serious. Fever, incisional swelling, and wound discharge are the presenting signs. Deep infection involving the vertebral body or implant requires aggressive debridement and culture-guided antimicrobial therapy. The American College of Veterinary Surgeons provides specialist summaries of expected postoperative management and complication recognition for spinal procedures.

Common Errors and Corrective Actions

The most frequent error in dorsal approaches is inadequate exposure. A surgeon who cannot see the full extent of the lesion cannot decompress it completely. The corrective action is to extend the incision and elevate more muscle before attempting laminectomy. The second most common error is excessive burr depth. The surgeon should check depth frequently with a probe or dental mirror and remember that the ventral floor of the vertebral canal is only a few millimeters below the dorsal lamina in small dogs.

In ventral approaches, the most common error is off-midline dissection. This places the carotid sheath, esophagus, and recurrent laryngeal nerve at risk. The corrective action is to palpate the trachea and carotid pulse continuously and to identify the sternothyroid and sternocephalicus muscles as midline landmarks. Another error is failure to identify the ventral spinous process of the vertebra before burring. The ventral slot should be centered on this process.

Students often err by using excessive force with rongeurs instead of allowing the instrument to cut. This crushes bone and can transmit force to the spinal cord. The corrective action is to use sharp instruments and to take small bites. A third error is premature closure without checking for adequate hemostasis. The surgeon should irrigate, observe for 2 to 3 minutes, and confirm that bleeding has stopped before closure.

Troubleshooting Table

Evidence Limitations and Expert Disagreement

The evidence base for spinal surgical approaches in veterinary patients is largely extrapolated from human literature and small case series. Controlled comparative studies in dogs and cats are limited. Expert opinion differs on several points. The choice between dorsal laminectomy and hemilaminectomy for thoracolumbar disc disease remains debated. Some surgeons prefer hemilaminectomy for its reduced muscle trauma, while others favor dorsal laminectomy for its wider exposure. Both approaches have advocates and neither has been proven superior in a prospective veterinary trial.

The role of interbody cages in veterinary cervical fusion is similarly contested. Human literature describes cages as a useful fusion technique with high rates of clinical and radiographic success. However, the canine cervical spine differs in size, biomechanics, and loading. Some veterinary surgeons use cages routinely, while others report equivalent results with autogenous bone grafts. The evidence does not currently resolve this disagreement.

Smoking is a well-established risk factor for failed fusion in human patients. The veterinary analogue is unclear. No comparable large study exists for dogs or cats. Some surgeons recommend delaying elective fusion in patients with active infection or poor body condition, but this guidance is based on clinical judgment instead of controlled data. Regenerative treatment strategies, including growth factors and cell-based therapies, remain experimental in veterinary spinal surgery. Their role in clinical practice is not yet defined.

Referral and Escalation Criteria

Referral to a board-certified veterinary surgeon is appropriate when the surgeon lacks experience with the specific approach, when the lesion is extensive or recurrent, or when the patient has comorbidities that complicate anesthesia. Specialist consultation is also warranted when intraoperative findings differ from preoperative imaging. The American College of Veterinary Surgeons maintains resources for locating specialists and understanding expected outcomes.

Laboratory involvement is indicated when infection is suspected, when histopathology is needed for a mass lesion, or when preoperative coagulation testing reveals abnormalities. Regulatory reporting is rarely required for spinal surgery complications. However, if an implant fails and the manufacturer is involved, reporting to the manufacturer and to the appropriate regulatory body may be required. The American Veterinary Medical Association provides practice resources on professional obligations and adverse event reporting. International standards for animal health and welfare may apply in research or production settings, as described in the World Organization for Animal Health terrestrial code.

Frequently Asked Questions

How do I decide between referral and performing the approach in general practice?

Referral is indicated when the lesion location is uncertain, advanced imaging is unavailable, or the surgeon lacks recent experience with the specific approach. Cervical ventral slot procedures carry substantial risk to the carotid sheath, esophagus, and recurrent laryngeal nerve, and a misdirected slot can cause catastrophic spinal cord injury. For dorsal thoracolumbar hemilaminectomy, referral is appropriate when the surgeon cannot reliably identify the correct vertebral segment or when the patient requires concurrent stabilization beyond simple decompression. The American College of Veterinary Surgeons publishes specialist summaries of surgical conditions and expected outcomes that can guide the referral conversation. If the patient is deteriorating neurologically and referral is not immediately available, decompression may be justified, but the owner must understand the elevated risk profile.

What do I do when the ideal equipment is unavailable?

A standard surgical kit can accomplish most dorsal approaches. A high-speed burr is strongly preferred for laminectomy, but a Kerrison rongeur and bone curette can complete a hemilaminectomy if used carefully. The slot width will be less precise, and the risk of iatrogenic trauma increases. For ventral slot, an oscillating saw or burr is effectively mandatory, attempting this approach with rongeurs alone invites vertebral artery or spinal cord injury. If no burr is available, do not attempt a ventral slot. Consider a dorsal cervical approach instead, or refer. Interbody cage devices are not required for routine decompression, and their use in veterinary patients remains limited compared with human practice, where they are a popular fusion technique with high reported success rates Zdeblick and Phillips, institutional publication. Graft harvest from the ilium or rib remains a viable alternative.

How does the approach differ in cats versus dogs?

Feline vertebrae are smaller and more delicate, and the spinal canal occupies a larger proportion of the vertebral canal. Burr control must be more conservative, and the authors recommend starting the laminectomy slightly more dorsal to avoid entering the canal prematurely. Feline ventral slot procedures are technically more demanding because the transverse processes are smaller and the carotid sheath lies closer to the midline. Hemorrhage from the ventral venous sinuses is comparatively more significant in cats due to lower blood volume. Recovery from anesthesia should account for the cat's higher metabolic rate and tendency toward hypothermia. Postoperative analgesia requirements differ, with cats requiring careful dose adjustment of opioids and NSAIDs. The MSD Veterinary Manual provides species-specific guidance on perioperative drug selection and monitoring.

What documentation is required during and after spinal surgery?

The operative record must include the exact vertebral segment approached, the side of the lesion, the type of laminectomy performed, and the method used to confirm segment identification, such as counting from T1 or palpating the wings of the atlas. Note the burr size, the depth of bone removal, and any dural contact or cerebrospinal fluid leakage. Record the estimated blood loss and any intraoperative complications, including hemorrhage, hypotension, or arrhythmia. Postoperative records should document neurologic status at extubation, at 12 hours, and at 24 hours, with specific grading of ambulation, proprioception, and pain perception. Photographs or video of the approach can be valuable for client communication and for review if complications arise. The AVMA practice resources offer guidance on medical record standards and client communication expectations.

How should I explain the procedure and risks to the owner?

Use a labeled diagram of the spine and describe the lesion as a compressive mass that must be removed through a surgical window in the bone. Explain that the approach itself carries risk to the spinal cord, and that neurologic recovery depends on the severity and duration of the preoperative injury. Give a realistic range of outcomes: full recovery, partial recovery with residual gait deficits, or no improvement. Discuss the possibility of recurrence, especially if the underlying disease is progressive. Mention that postoperative physiotherapy and nursing care are as important as the surgery itself. The ACVS animal health resources provide client-facing summaries that can supplement your explanation. Be honest about your own experience with the specific approach and offer referral if you have any doubt about your ability to complete the procedure safely.

What are the financial and resource considerations for spinal surgery?

Spinal surgery requires advanced imaging, typically CT or MRI, to localize the lesion before surgery. These imaging costs are substantial and are incurred before any surgical fee. The surgical procedure itself requires a high-speed burr, specialized retractors, and possibly implants, all of which add to the cost. Postoperative care may include intensive nursing, physiotherapy, and prolonged hospitalization. Owners should receive a written estimate that separates imaging, surgery, hospitalization, and contingency funds for complications. If the owner cannot afford the full workup, a myelogram may be a lower-cost alternative to MRI, but it carries additional risk and provides less anatomic detail. Discuss the option of referral to a specialty center, as costs may be comparable or lower than attempting the procedure in general practice with rented equipment. The WOAH terrestrial animal health standards do not address companion animal surgery costs, but they do emphasize the importance of perioperative welfare standards that apply across species.

Related Clinical & Scientific Guides

• Perioperative Antibiotic Prophylaxis: Timing and Selection
• Surgical Approaches to the Femur and Stifle
• Fracture Healing Assessment: Radiographic and Clinical Evaluation

References and Further Reading

• Interbody cage devices.. 2003.
• Interbody Fusions in the Lumbar Spine: A Review.. 2020.
• Regenerative treatment strategies in spinal surgery.. 2008.
• Robotic approaches to the posterior spine.. 2009.
• The Effect of Smoking on Spinal Fusion.. 2017.
• In vivo experimental study of anterior cervical fusion using bioactive polyetheretherketone in a canine model.. 2017.
• American College of Veterinary Surgeons Animal Health Resources. American College of Veterinary Surgeons.
• MSD Veterinary Manual, Professional Edition. MSD Veterinary Manual.
• American Veterinary Medical Association Practice Resources. American Veterinary Medical Association.

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This article is educational professional reference material for veterinary audiences. It is not a substitute for veterinary diagnosis, individual clinical judgment, current product labeling, or applicable regulatory requirements.