Surgical Approaches to the Thorax: Intercostal and Median Sternotomy

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

Key Takeaways

• Intercostal thoracotomy offers rapid, unilateral hemithoracic access for focal lesions, minimizing tissue dissection but limiting exposure to one side; preservation of the intercostal neurovascular bundle is critical for pain management and chest wall function.
• Median sternotomy provides wide bilateral access to the thorax, cranial mediastinum, and heart, making it ideal for cardiac surgery or bilateral lung disease, but involves a longer incision and more extensive closure with a higher risk of sternal instability or infection.
• Thoracic wall healing by callus formation takes 4-8 weeks, requiring stable fixation and preservation of periosteal blood supply; closure techniques must restore thoracic wall integrity to prevent paradoxical chest wall motion and impaired ventilation.
• Approach selection is dictated by the target structure, need for bilateral access, and patient condition, with intercostal thoracotomy favored for unilateral lung or thoracic wall lesions and median sternotomy for cardiac, pericardial, or cranial mediastinal pathology.
• Major complications include hemorrhage from intercostal or internal thoracic vessels, pneumothorax, persistent air leak, sternal wire failure, osteomyelitis, and intercostal neuralgia, necessitating vigilant intraoperative monitoring and structured postoperative surveillance.
• Postoperative care prioritizes multimodal analgesia, oxygen supplementation, and early ambulation, with thoracostomy tube management crucial for lung re-expansion and prevention of complications like atelectasis and pneumonia.

This article details the two standard open approaches to the thoracic cavity in dogs and cats: intercostal thoracotomy and median sternotomy. It is written for practicing veterinarians who perform or assist in thoracic surgery and covers patient positioning, surgical technique, exposure limitations, and closure methods for each approach. The practical steps that follow depend on a clear understanding of thoracic wall anatomy, biomechanics of healing, and the specific indications that favour one approach over the other.

Selection of the appropriate approach is a clinical decision based on the target structure, the need for bilateral access, and the patient's body condition. Intercostal thoracotomy provides rapid, focal exposure to one hemithorax with minimal tissue dissection. Median sternotomy offers wide access to both hemithoraces, the cranial mediastinum, and the heart, at the cost of a longer incision and more extensive closure. The evidence base for specific technical recommendations in veterinary patients is limited, and much of the procedural guidance in this article reflects established surgical principles and expert consensus as summarized by specialist organizations such as the American College of Veterinary Surgeons.

At a Glance

Thoracic Wall Anatomy Relevant to Surgical Approach

The thoracic wall consists of the ribs, intercostal muscles, and parietal pleura. Each intercostal space contains an external intercostal muscle, an internal intercostal muscle, and the innermost intercostal muscle. The intercostal neurovascular bundle, comprising the intercostal artery, vein, and nerve, runs along the caudal border of each rib within the costal groove. This bundle is the principal structure at risk during intercostal thoracotomy, and its preservation determines the quality of postoperative pain control and chest wall function.

The ribs articulate dorsally with the thoracic vertebrae and ventrally with the sternum via costal cartilages. The sternum is a segmented bone composed of the manubrium, sternebrae, and xiphoid process. The internal thoracic artery and vein run parasagittally along the dorsal surface of the sternum, approximately 3 to 5 mm lateral to the midline, and are vulnerable during median sternotomy if the osteotomy deviates from the midline.

Biomechanics of Thoracic Wall Healing

The thoracic wall must provide rigid structural support for ventilation while healing. Rib fractures and sternotomy osteotomies heal by callus formation, a process that takes 4 to 8 weeks in adult dogs and cats. The strength of the healed wall depends on the stability of the initial fixation and the preservation of periosteal blood supply. Stripping the periosteum from the ribs during exposure delays healing and increases the risk of non-union. Similarly, the sternal periosteum should be preserved during sternotomy to optimize osteotomy healing.

Closure techniques must restore the thoracic wall's ability to resist the negative intrathoracic pressure generated during inspiration. Failure of the closure leads to paradoxical chest wall motion, impaired ventilation, and prolonged recovery. The biomechanical principles that govern chest wall repair are analogous to those described for vascular and connective tissue repair in other surgical contexts, where the integrity of the primary repair determines the outcome Mechanisms of aortic aneurysm formation.

Patient Positioning and Preparation

Intercostal Thoracotomy

The patient is placed in lateral recumbency with the operated side uppermost. A rolled towel or vacuum bag is placed beneath the thorax to elevate the operative field and open the intercostal spaces. The thoracic limb on the operative side is pulled cranially and secured to expose the lateral chest wall. The entire hemithorax is clipped from the dorsal midline to the ventral midline and from the axilla to the last rib. The clipped field should extend beyond the planned incision by at least 5 cm in each direction.

Median Sternotomy

The patient is placed in dorsal recumbency with the forelimbs extended cranially and secured. The thorax is clipped from the manubrium to the xiphoid and laterally to the costochondral junctions. A midline incision is planned from the cranial aspect of the manubrium to the xiphoid process. The width of the clipped field must accommodate the sternotomy saw or osteotome and the subsequent retraction of the sternal halves.

Intercostal Thoracotomy Technique

The skin incision is made directly over the selected intercostal space. The subcutaneous tissues and cutaneous trunci muscle are divided to expose the latissimus dorsi muscle dorsally and the external abdominal oblique muscle ventrally. The latissimus dorsi is incised parallel to its fibers or elevated and retracted, taking care to preserve the thoracodorsal nerve. The scalenus and external intercostal muscles are then divided over the chosen space.

The intercostal muscles are incised in the center of the space, midway between the ribs, to avoid the neurovascular bundle along the caudal border of the cranial rib. The pleura is opened with a stab incision and extended with scissors. A Finochetto retractor is placed with the ratchet mechanism directed ventrally to avoid interference with the surgeon's hands. The ribs are spread gradually to minimize trauma to the costovertebral joints.

Closure of the intercostal space requires apposition of the ribs without compromising the neurovascular bundle. Simple interrupted sutures are placed around the cranial rib and through the intercostal muscles caudal to the caudal rib, or through predrilled holes in the ribs. The suture material should be monofilament, non-absorbable or slowly absorbable, and of sufficient calibre to resist the forces of ventilation. The muscle layers are closed in separate layers, and the skin is apposed routinely.

Median Sternotomy Technique

Median sternotomy provides access to both hemithoraces, the cranial mediastinum, the heart base, and the dorsal thoracic structures. It is the approach of choice for cardiac surgery, pericardectomy, and resection of cranial mediastinal masses. The procedure requires a sternal saw or osteotome, and the closure must restore rigid stability to the sternum to allow normal ventilation and healing.

The patient is positioned in dorsal recumbency with the forelimbs extended cranially and secured. The incision begins at the manubrium and extends caudally to the xiphoid process. The subcutaneous tissue and the sternohyoideus and sternocephalicus muscles are divided on the midline. The sternum is identified along its entire length, and the periosteum is incised with a scalpel or electrocautery.

A sternal saw with an oscillating blade is used to divide the sternum along its midline. The saw must be held perpendicular to the sternum to avoid entering the thoracic cavity obliquely. The assistant retracts the soft tissues laterally to protect the underlying vessels and lungs. The saw advances from cranial to caudal, and the surgeon monitors the depth of the cut by visualizing the saw blade through the thin cortical bone. In cats and small dogs, a heavy scissors or osteotome may be used, but the saw produces a cleaner cut with less comminution.

Once the sternum is divided, a self-retaining retractor is placed. The retractor is opened gradually to avoid tearing the pleura or avulsing the internal thoracic vessels. The thymic fat and the mediastinal pleura are divided to expose the heart and great vessels. The phrenic nerves are identified on the lateral surface of the pericardium and preserved.

Closure of the median sternotomy requires reapproximation of the two sternal halves. Multiple techniques are described, including wire cerclage, suture loops, and locking plates. The most common method uses orthopedic wire passed around or through the sternebrae. The wire is placed in a figure-of-eight or simple loop pattern, and the ends are twisted to tighten. The sternum must be reduced anatomically, and the wires are tightened sequentially from cranial to caudal to distribute tension evenly.

The choice of closure material depends on patient size and bone quality. Stainless steel wire is standard in dogs and cats. In osteoporotic or very young patients, wire can cut through the bone, and a plate or suture technique may be preferable. The periosteum and the overlying muscles are closed in separate layers to cover the wire knots and reduce the risk of implant irritation.

Approach Selection by Target Structure

The choice between intercostal thoracotomy and median sternotomy depends on the target organ, the need for bilateral access, and the surgeon's experience. The following table summarizes the selection criteria for common intrathoracic procedures.

The intercostal approach is faster to perform and causes less postoperative pain than sternotomy in most patients. However, it provides access to only one hemithorax, and the exposure is limited by the width of the intercostal space. Median sternotomy is more versatile but requires more time for closure and carries a higher risk of implant failure if the sternum does not heal.

Patient status changes the decision. A patient with a confirmed unilateral lesion and no evidence of contralateral disease is best served by an intercostal approach. A patient with a cranial mediastinal mass that may invade both hemithoraces requires sternotomy. The availability of a sternal saw and the surgeon's comfort with sternal closure also influence the choice. In an emergency, such as a penetrating thoracic wound, the intercostal approach is often faster and can be extended as needed.

Intraoperative Monitoring and Complications

Continuous monitoring is required during any thoracic surgical approach. The monitoring parameters and their clinical significance are summarized below.

The most common intraoperative complication is hemorrhage from the internal thoracic vessels or the intercostal vessels. These vessels lie close to the sternum and the caudal border of each rib, and they are easily damaged during the approach or closure. Hemorrhage from the internal thoracic artery can be brisk and may require ligation of the vessel. The surgeon must be prepared to control bleeding quickly, as blood loss is poorly tolerated in patients with compromised cardiac or pulmonary function.

Arrhythmias are common during manipulation of the heart and great vessels. Ventricular premature complexes may occur when the pericardium is incised or the heart is retracted. The anesthetist should be informed, and the surgeon should minimize direct cardiac manipulation. Lidocaine or other antiarrhythmic agents may be required, and the current formulary should be consulted for dosing.

Pneumothorax is an expected consequence of any open thoracic approach, and the chest is closed with a thoracostomy tube in place. The tube is connected to a closed suction system or a one-way valve to evacuate air and fluid during the postoperative period. The tube is removed when the volume of air or fluid is minimal and the lung has re-expanded.

Postoperative Care and Monitoring

The immediate postoperative period is critical for patients recovering from thoracic surgery. Pain management is a priority, as inadequate analgesia impairs ventilation and increases the risk of atelectasis and pneumonia. A multimodal approach using opioids, non-steroidal anti-inflammatory drugs, and local anesthetic techniques is recommended. The specific drugs and doses should be selected from the current formulary and adjusted to the individual patient.

Oxygen supplementation is provided for the first 12 to 24 hours after surgery. The patient is monitored for respiratory rate and effort, mucous membrane color, and pulse oximetry. A rising respiratory rate with increased effort may indicate pain, pneumothorax, or pulmonary edema. The thoracostomy tube is checked regularly for patency and the volume of air or fluid evacuated is recorded.

The patient is kept in sternal or lateral recumbency and turned every 2 to 4 hours to prevent dependent lung atelectasis. Early ambulation is encouraged once the patient is stable. The thoracostomy tube is removed when the lung has fully expanded and the drainage is minimal, typically within 24 to 48 hours.

Wound complications are uncommon but include seroma formation, infection, and dehiscence. The incision is inspected daily for swelling, discharge, or erythema. Sternal osteomyelitis is a rare but serious complication of median sternotomy, and it presents with fever, lethargy, and incisional pain. Treatment requires surgical debridement and long-term antibiotic therapy.

The evidence base for many aspects of thoracic surgical technique in veterinary patients is limited, and much of the current practice is extrapolated from human surgery or experimental models. For example, the biomechanics of sternal closure have been studied in human cadavers, but comparable veterinary data are sparse. The American College of Veterinary Surgeons animal health resources provide practical summaries of expected outcomes and postoperative management for common thoracic procedures. The MSD Veterinary Manual offers species-specific guidance on perioperative care and complication management. The surgeon should be aware that individual patient factors, including age, body condition, and concurrent disease, may alter the expected course of recovery.

Complications and Failure Modes

Intercostal thoracotomy and median sternotomy share a set of recognized complications that the surgeon must actively monitor for during and after the procedure. Early detection depends on disciplined intraoperative assessment and structured postoperative surveillance.

Hemorrhage most commonly arises from the internal thoracic vessels during median sternotomy or from intercostal vessels during rib retraction. Persistent bleeding from the sternal marrow cavity can occur after osteotomy. Detection relies on serial measurement of arterial pressure, heart rate, and packed cell volume, combined with direct inspection of the thoracic cavity before closure. A sudden drop in blood pressure with a rising heart rate in the recovery period should prompt immediate thoracic imaging or exploration.

Pneumothorax and persistent air leak follow pulmonary parenchymal trauma or incomplete pleural closure. Continuous chest drainage with a sealed collection system allows quantification of air leakage. A leak that fails to diminish over 24 to 48 hours suggests a significant parenchymal defect or bronchial injury requiring reoperation.

Postoperative respiratory compromise may reflect pain, pneumothorax, pleural effusion, or diaphragmatic dysfunction. Serial assessment of respiratory rate, effort, and pulse oximetry, together with thoracic auscultation and ultrasound, distinguishes these causes. Intercostal nerve blockade or systemic analgesia should be optimized before attributing tachypnoea to pulmonary pathology alone.

Sternal instability or non-union occurs when wire fixation fails, particularly in large or obese dogs. Palpable crepitus or step deformity at the sternotomy site within the first postoperative weeks indicates fixation failure. Radiographic evaluation confirms the diagnosis, and revision fixation is indicated if instability compromises respiration or causes significant pain.

Infection of the median sternotomy wound is a serious complication that can extend to osteomyelitis and mediastinitis. Fever, wound discharge, and leukocytosis warrant immediate wound sampling and imaging. Early debridement with appropriate antimicrobial therapy, guided by culture and susceptibility testing, is the central element of management.

Intercostal neuralgia is a recognized sequela of intercostal thoracotomy, caused by compression or entrapment of the intercostal nerve during rib retraction. Clinical signs include persistent thoracic wall pain, resentment of palpation, and reluctance to move. Prevention centers on careful retractor placement and meticulous closure that avoids nerve entrapment.

Common Errors and Corrective Action

Less experienced surgeons frequently make errors that are predictable and correctable.

Incorrect intercostal space selection leads to poor exposure of the target structure. The surgeon should confirm the intended space by counting ribs from the first rib or from the xiphoid before incision. If exposure proves inadequate, extending the incision or converting to a different approach is preferable to struggling with limited access.

Excessive rib retraction causes rib fracture, nerve injury, and prolonged postoperative pain. The retractor should be opened gradually, with pauses to allow tissue creep. If the exposure remains insufficient, the incision should be extended dorsally or ventrally instead of forcing further retraction.

Injury to the internal thoracic artery during sternotomy occurs when the osteotomy deviates from the midline. The surgeon should verify that the saw or osteotome remains centerd on the sternal keel. Hemorrhage from this vessel requires immediate ligation or vascular clip application.

Incomplete pleural closure after intercostal thoracotomy predisposes to pneumothorax and subcutaneous emphysema. The pleural layer should be incorporated in the closure or separately apposed. A temporary thoracostomy tube allows evacuation of residual air before complete closure.

Failure to manage pain adequately is a common error that compromises respiratory function and recovery. A multimodal analgesic plan, including regional techniques, should be initiated before surgery and continued into the postoperative period. The MSD Veterinary Manual provides species-specific guidance on analgesic selection and monitoring.

Troubleshooting Guide

Limitations of Evidence and Areas of Expert Disagreement

The evidence base for thoracic surgical approaches in dogs and cats relies heavily on expert opinion, retrospective case series, and extrapolation from human and experimental animal literature. Prospective randomised comparisons of intercostal thoracotomy versus median sternotomy in clinical veterinary patients are lacking. Consequently, opinions differ on the preferred approach for specific intrathoracic procedures, with some surgeons favouring sternotomy for its versatility and others preferring intercostal thoracotomy for its reduced soft tissue dissection.

The optimal method of sternal closure remains debated. Wire cerclage is standard, but alternatives such as locking plates and suture-based systems have advocates. Comparative biomechanical data are limited, and clinical outcome studies are needed to resolve this question.

Postoperative analgesic protocols vary widely between institutions. The relative contribution of intercostal nerve blockade, epidural analgesia, and systemic opioids to recovery quality is not fully defined. The American College of Veterinary Surgeons publishes specialist summaries that reflect current consensus, but individual practitioners should adapt protocols to their caseload and resources.

Referral and Escalation Criteria

Thoracic surgery carries inherent risks, and the general practitioner must recognize when referral is appropriate. Cases involving complex intrathoracic pathology, such as large mediastinal masses, cardiac or great vessel surgery, or recurrent pleural effusion of unknown cause, are best managed by a board-certified surgeon. The American Veterinary Medical Association provides guidance on professional standards and referral expectations.

Intraoperative findings that exceed the surgeon's experience, such as unexpected adhesions, tumor invasion into vital structures, or uncontrollable hemorrhage, warrant immediate consultation with a specialist. If a specialist is not available, stabilization followed by transfer should be arranged.

Laboratory involvement is indicated when coagulopathy is suspected preoperatively or when postoperative complications suggest a systemic process. Platelet count, coagulation times, and blood gas analysis should be performed before surgery in any patient with unexplained bruising, petechiation, or a history of bleeding.

Regulatory reporting obligations vary by jurisdiction. In most regions, unexpected deaths under anesthesia or suspected anesthetic-related mortality do not require mandatory reporting, but practitioners should be aware of local requirements. The World Organization for Animal Health sets international standards for animal health and welfare that may inform practice expectations, particularly for notifiable diseases discovered incidentally during thoracic exploration.

Frequently Asked Questions

How do I decide between intercostal thoracotomy and median sternotomy when both could provide adequate exposure?

Choose the approach that gives the most direct access to the target structure with the least tissue disruption. Intercostal thoracotomy suits unilateral lung lobectomy, thoracic duct ligation, and procedures on the lateral heart base. Median sternotomy provides bilateral access and is preferred for cranial mediastinal masses, pericardectomy, and procedures requiring cardiopulmonary bypass. Consider the need for concurrent abdominal exploration, as sternotomy extends easily through a caudal midline incision. If the lesion is peripheral and unilateral, an intercostal approach preserves sternal integrity and reduces postoperative discomfort. The American College of Veterinary Surgeons clinical resources describe expected outcomes for both approaches across common thoracic procedures.

What should I do when a rib spreader or oscillating saw is unavailable?

A Finochetto retractor can be substituted with handheld right-angle retractors, though exposure will be limited and assistant fatigue becomes a factor. For sternotomy without an oscillating saw, use a Lebsche knife with a mallet or heavy scissors designed for sternal division. These instruments require deliberate, controlled strikes to avoid plunging into underlying mediastinal structures. Alternatively, a Gigli wire saw passed beneath the sternum works but is slower and carries higher risk of soft tissue trauma. If the planned procedure demands wide, stable exposure and only limited instrumentation is available, reconsider whether the procedure should proceed at your facility. Referral may be the safer option when equipment limitations compromise exposure or increase operative time.

How does the approach differ in cats compared with dogs?

Feline thoracic walls are thinner and more pliable, so intercostal thoracotomy requires less force for rib retraction and the intercostal space is easier to identify. The cranial mediastinum is proportionally larger in cats, and thymic or mediastinal masses may obscure vascular structures, making sternotomy more forgiving for cranial procedures. Feline ribs fracture more readily during retraction, particularly in older animals, so open the retractor slowly and monitor for crepitus. Closure follows the same principles, but smaller gauge suture and finer needles reduce trauma to thin tissues. The MSD Veterinary Manual professional edition provides species-specific guidance on thoracic anatomy and surgical considerations that apply to approach selection.

What documentation should I maintain in the medical record for a thoracic surgical approach?

Record the approach used, the intercostal space or sternotomy extent, and the reason for that choice. Note any difficulty encountered during exposure, such as pleural adhesions, lung herniation through the incision, or rib fracture. Document the method of rib approximation or sternal reattachment, suture material and pattern, and whether a thoracostomy tube was placed. Include intraoperative findings that influenced the approach, such as unexpected masses or adhesions requiring extension of the incision. Postoperative notes should track thoracic drain output, respiratory rate and effort, and analgesic requirements. The AVMA professional practice resources offer guidance on medical record standards that apply to surgical documentation.

How do I explain the need for a thoracic surgical approach to a client who is anxious about recovery?

Describe the procedure in functional terms: the chest is opened to reach the diseased organ, and the incision is closed in layers to restore normal breathing mechanics. Explain that the approach is chosen to give the surgeon the best view of the problem while minimizing trauma to the chest wall. Mention that a chest tube may remain in place for a day or two to remove air and fluid, and that pain is managed with a combination of local blocks and systemic analgesics. Be honest about the risks, including bleeding, infection, and prolonged healing, but frame these in the context of the underlying disease. The American College of Veterinary Surgeons outcome summaries provide language that helps owners understand expected recovery trajectories.

When should I stop and refer instead of proceed with an unfamiliar thoracic approach?

Refer when the target structure cannot be confidently identified from the chosen approach, when the procedure requires equipment you do not have, or when the patient is unstable and your facility lacks the monitoring capability to manage intraoperative complications. If you have not performed the approach recently and no experienced colleague is available, referral is appropriate. Thoracic reoperation through a previous incision carries higher risk of adhesions and bleeding, so a first attempt should be made under optimal conditions. The WOAH terrestrial animal health standards emphasize that professional judgment about procedural competence is part of responsible surgical practice. A planned referral is safer than an intraoperative rescue.

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

• Mechanisms of aortic aneurysm formation: translating preclinical studies into clinical therapies.. 2014.
• Transparent equine collagen biomatrix as dural repair. A prospective clinical study.. 2009.
• Open thoracic surgical implantation of cardiac pacemakers in rats.. 2023.
• Implementation of a Cross-specialty Training Program in Basic Laparoscopy.. 2015.
• Natural orifice transesophageal mediastinoscopy and thoracoscopy.. 2008.
• A porcine model for evaluating the management of noncompressible torso hemorrhage.. 2011.
• 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.

Related Articles

• Surgical Approaches to the Thorax: Principles and Techniques
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• Surgical Approaches to the Urogenital System
• Surgical Approaches to the Carpus and Tarsus
• Surgical Approaches to the Femur and Stifle

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.