Presentation: Historical and Physical Features

Postthoracotomy pain syndrome (PTPS) is a neuropathic pain syndrome that occurs in the region of a previous thoracotomy incision. It is defined by the International Association for the Study of Pain as “chronic dysesthetic burning and aching pain that recurs or persists along a thoracotomy scar at least 2 months following a surgical procedure.” It is thought to be related to trauma of the intercostal nerves as a result of transection, retraction, suturing, or pressure from trocar placement. This is supported by the fact that patients often suffer from allodynia to touch, motion, and temperature variation along the same distribution as their pain. The ipsilateral arm can also undergo sensory and autonomic dysfunction in a complex regional pain syndrome–like fashion. The pain can restrict movement of the ipsilateral shoulder and cause significant disability and limitation to patients. In addition, some patients with PTPS have a significant myofascial component that is characterized by a taut muscular band near the scapula.

Demographics

PTPS is a common problem for patients who undergo thoracotomy incisions. Studies over the past several decades estimate the incidence of chronic pain following thoracotomy to be anywhere from 30% to 50%, although the incidence of severe pain is much lower, approximately 5%. Limb amputation is the only surgery that has a higher incidence of chronic postsurgical pain than thoracotomy.

The risk of developing chronic pain following surgery, in general, is increased in younger patients, female patients, and those with severe uncontrolled acute postoperative pain. Although none of the above-mentioned risk factors have been specifically linked to PTPS, it can be extrapolated that PTPS would behave similarly to other chronic postsurgical pain syndromes. Identification of specific preoperative risk factors for the development of PTPS remains an important question that requires more research. The literature evaluating the risk of chronic preoperative pain as a risk factor for the development of PTPS offers no consensus. In the past, many studies that evaluated PTPS had excluded patients with preoperative chronic pain and analgesic treatment, which limits the available data. Multiple studies found no association between preoperative pain and PTPS, whereas others have shown significant correlations between the use of preoperative analgesics and the development of PTPS. More research is needed to fully elucidate this possible risk factor.

Intraoperative Factors: Surgical Technique

There have been attempts to decrease the incidence of PTPS via differing surgical approaches. A thoracotomy incision can be performed using four different surgical techniques: anterior, axillary, posterolateral, or muscle-sparing posterolateral (avoiding division of the latissimus dorsi muscle). There have been multiple retrospective studies evaluating these different approaches; there is a lack of convincing prospective data that favors one over another. Therefore, no consensus can be drawn on the superiority of the differing thoracotomy techniques with regard to the prevention of PTPS.

Video-assisted thoracic surgery (VATS), a less invasive technique utilizing endoscopes inserted through small incisions thus avoiding the large thoracotomy incision, was expected to have a lower incidence of PTPS; however, again, the literature offers no consensus. Data from two prospective trials did not reveal a decrease in PTPS when VATS was compared with the posterolateral approach or muscle sparing posterolateral approach with classic thoracotomy incision. However, one retrospective study suggested that VATS was superior to a muscle sparing posterolateral approach for the prevention of PTPS. The high incidence of PTPS after VATS is not surprising given that the surgical technique of placing a trocar through the intercostal space and suturing the chest wounds offer opportunities to traumatize intercostal nerves and the surrounding tissue.

Several specific surgical techniques have been successful in protecting the intercostal nerve and reducing the incidence of PTPS. These strategies include harvesting of an intercostal muscle flap, dissection and preservation of the intercostal nerve, and intracostal suturing. One review supports that these intercostal nerve protection strategies seem to decrease the incidence of PTPS, and the literature supports their use.

Intraoperative Factors: Anesthetic Technique

Numerous anesthetic techniques have been attempted to minimize the development of PTPS with mixed results. The cornerstone of these techniques is the concept of preventative anesthesia. The goal of preventative anesthesia is to decrease the transmission of afferent pain signals arising from the surgical incision, thereby limiting central sensitization, which is thought to be instrumental in the development of chronic pain. A variety of neuraxial, regional, and pharmacologic techniques have been attempted with mixed results.

Thoracic epidural anesthesia (TEA) has been used for decades in thoracic surgery, and it remains the gold standard for both acute postoperative pain and prevention of PTPS. Multiple prospective randomized controlled trials have shown that TEA both decreases the incidence of PTPS and significantly improves acute postoperative pain control when compared with intravenous opioids. In addition, significant benefit both for acute postsurgical pain and prevention of PTPS was further conferred when TEA was utilized preoperatively as opposed to postoperatively. Although the benefit conferred by the timing of the TEA was called into question by another prospective randomized controlled trial, there is strong evidence supporting the use of TEA in the anesthetic management of patients undergoing thoracic surgery.

The role of TEA has been called into question by a growing body of literature that supports the use of paravertebral blocks in lieu of TEA. Paravertebral blocks offer similar levels of analgesia for thoracotomy incisions; however, paravertebral blocks avoid the hypotension that is commonly caused by neuraxial anesthesia. In addition, paravertebral blocks have a lower incidence of common side effects following TEA, including urinary retention, nausea, and vomiting. Finally, paravertebral blocks avoid instrumenting the neuraxis, which avoids the uncommon but catastrophic neurologic complications that can be caused by thoracic epidural placement. There is some evidence supporting the use of paravertebral blocks for the prevention of chronic neuropathic pain following breast surgery. However, the use of paravertebral blocks to prevent PTPS has not been studied and requires more research.

Intercostal nerve blocks and cryoanalgesia have also been studied with disappointing results. Intercostal nerve blocks show no benefit in the prevention of PTPS and were only shown to offer improved pain control during vital capacity breaths in the immediate postoperative period. When compared with TEA, cryoanalgesia was actually shown to increase the incidence of allodynia and moderate to severe chronic pain that interferes with daily life following thoracotomy.

Ketamine has been studied in relation to PTPS both intravenously and as an epidural adjuvant. The randomized placebo-controlled clinical trial studied the effect of a 1-mg/kg bolus of ketamine before the start of surgery, followed by an infusion of 1 mg/kg/h throughout the surgery, with a 1-mg/kg infusion over 24 h postoperatively. Although the ketamine group had improved pain control in the immediate postoperative period, there was no decrease in the development of PTPS. The addition of ketamine to TEA was also studied at a low dose of 1.2 mg/h and was shown to offer no benefit for the prevention of PTPS.

The effects of cyclooxygenase-2 inhibitors and acetaminophen have also been studied in postthoracotomy patients. Both drugs have been shown to improve pain control during the first 48 h after surgery when combined with TEA. Neither drug has been studied for the prevention of PTPS and could be a target for future research.

Diagnostic Criteria

A diagnosis of PTPS can be made when a patient, in whom recurrent cancer and other anatomic causes of pain have been ruled out, complains of a “chronic burning and aching pain that recurs or persists along a thoracotomy scar within 2 months following a surgical procedure.”

Differential Diagnosis

There are several other causes of chronic pain in the region of a thoracotomy scar that must be ruled out before the diagnosis of PTPS can be made. These include tumor recurrence, traumatic neuroma, thoracic disc herniation, postherpetic neuralgia, and traumatic intercostal neuralgia. Tumor recurrence is the most critical diagnosis to rule out and can be difficult to distinguish given the similar nature and localization of the pain. Tumor recurrence should be suspected and investigated whenever a neuropathic PTPS-like picture occurs and the pain is recurrent after a pain-free period. However, this history does not rule out PTPS. Traumatic intercostal neuroma pain is sometimes described as burning or stabbing and is often associated with a positive Tinel sign on examination, with paresthesias in the region of the patient’s chronic pain elicited by percussion of the affected intercostal nerve. Thoracic disc herniation can cause either unilateral or bilateral pain, can be worsened by spine flexion, and can be investigated via imaging of the spine. With an acute herpes zoster infection that incidentally occurs in the region of a previous thoracotomy scar, the pain will typically be followed several days later by the characteristic dermatomal rash. Postherpetic neuralgia in the region of a previous thoracotomy scar can be distinguished by history of shingles over the same area; however, if the thoracotomy was done for malignancy, then tumor recurrence should be ruled out. Traumatic intercostal neuralgia can be distinguished by a history of trauma causing rib or vertebral fracture in the affected area temporally related to development of the pain, although it can also be due to surgical damage.

Diagnostic Testing

There is no specific test to diagnose PTPS, as it is a clinical diagnosis. MRI may be used to rule out a thoracic disc herniation or vertebral fracture. If suspected, ultrasound imaging can be used to evaluate for an intercostal neuroma. It is absolutely critical to rule out tumor recurrence, as the symptoms of chronic neuropathic pain and time course of tumor recurrence is easily mistaken for PTPS. Thus before a diagnosis of PTPS can be made, patients should be referred to their oncologist to obtain either chest CT or PET/CT scans to confirm that their pain is not due to tumor recurrence.

Rehabilitation and Physical Medicine Options and Discussion of Function

There are no specific rehabilitation and physical medicine treatments for PTPS that have been reported in the literature. There are data supporting the use of transcutaneous electric nerve stimulation (TENS) to control acute postthoracotomy pain; however, there are no data in the literature for or against using TENS for postthoracotomy pain after 2 months. Given the significant benefit of TENS in the acute postoperative period it would be a reasonable target for future study for the treatment of PTPS. Other physical medicine techniques such as scar massage, desensitization techniques, biofeedback, relaxation techniques, and thoracic mobility have not been studied in the treatment of PTPS. Given the low incidence of adverse effects from physical medicine techniques, their use would be reasonable and could be a target for future research.