Slipping rib syndrome, also known as floating rib syndrome or Cyriax syndrome, is a condition that clinicians often overlook or underdiagnose and patients misrecognize. Although it was first published by Davies-Colley in 1921,^[1] Cyriax described the syndrome in 1919 as a forward displacement of the inferior rib tips, causing pain in the chest or upper abdomen. Even though the lifetime prevalence of this condition is estimated to be 20%–40%,^[2] only a few individuals develop persistent or chronic pain from it and seek treatment, which may explain why the condition is so often underdiagnosed.

Only a few individuals develop persistent or chronic pain from it and seek treatment, which may explain why the condition is so often underdiagnosed.

An illustrative case treated in our pain clinic was a 37-year-old, otherwise healthy, female patient who complained of seven years of progressive, left-sided, anterolateral chest wall pain at the level of the 10th rib. The pain was insidious in onset without any provocative factors (ie, trauma). She had been referred by her primary care physician to a general surgeon three years prior to her visit to the pain clinic, who ruled out more serious causes of her pain. She underwent an “injection in her rib cage” at that time, which relieved her pain for several months. However, the pain returned and she was then referred to our pain clinic for better long-term management.

During her encounter in our pain clinic, her only complaint was sharp, progressive, anterolateral, lower chest pain, aggravated by movement and deep breathing, and not alleviated by conservative measures (eg, ice pack, acetaminophen, nonsteroidal anti-inflammatory drugs). All other systems were unremarkable. On physical exam, her vital signs were within normal limits and the exam was benign except for a left hooking maneuver that reproduced the pain. Our recommendations included a trigger point injection at the tender location, lidocaine patch, and acetaminophen, which helped to alleviate her symptoms and permitted her to resume activities of daily living.

Slipping rib syndrome typically consists of unilateral lower chest wall or upper abdominal pain, caused by a hypermobile rib (typically the 8th, 9th or 10th rib) that generates pain when sliding anteriorly and posteriorly on the superior rib. The latter results in irritation of the intercostal nerves and produces sharp, stabbing pain followed by dull aching. The pain is typically intermittent, can be acute or chronic, and can range from mild, tolerable pain to excruciating pain. Some patients may have a trigger point area of tenderness. Unlike the true ribs (1st through 7th) that attach directly by cartilaginous joints and ligaments, the false ribs (8th through 10th) are attached to each other by a cartilaginous cap in children and a fibrous band in adults (see Figure 1). Because the ribs are not held together by muscle, they are more susceptible to increased mobility and trauma and are mostly involved in slipping rib syndrome. If the loose rib impinges the intercostal nerve, it can cause excruciating pain around the chest into the back. The condition is sometimes accompanied by a clicking sensation, and patients are often able to demonstrate the popping sensation to the physician. Nausea or vomiting may accompany the pain, confusing the diagnosis.

Figure 1: Adult Ribcage. A fibrous band attaches the false rib (8th through 10th) to each other. The floating ribs (11th and 12th) are visible in Figure 1B.
Figure 1A	Figure 1B

The differential diagnosis of slipping rib syndrome is listed in Figure 2.

No definite etiology is associated with slipping rib syndrome. Overuse or rib trauma are thought to be some of the common risk factors but are not required, as in the case of the female patient presented earlier. McBeath and Keene demonstrated that the human ribs would only be able to slip on one another and cause the painful syndrome if the cartilaginous tips or fibrous attachments are disrupted.^[3]

Because the condition is often overlooked, many unnecessary diagnostic exams are performed to work up the diagnosis (eg, plain radiography, CT, MRI). The gold standard for diagnosing the condition is a simple hooking maneuver (see Figure 3), which was first described by Heinz and Zavala in 1977 and consists of having examiners slide their fingertips under the costal margin on the implicated side, then lifting anteriorly and superiorly.^[4] If the pain is reproduced, sometimes accompanied by a clicking sensation, the syndrome is diagnosed. Furthermore, to identify the location of the disease, local anesthetic can be injected at the suspected site; alleviation of the confirms the disease location.

Figure 3: Hooking Maneuver. The examiner slides his or her fingertips under the costal margin of the implicated side, then lifts anteriorly and superiorly.

Treatment depends on the severity of the associated pain or lifestyle limitations. Mild, tolerable pain can be managed by simple reassurance, temporary activity limitations, and use of icepacks or low-level pain medications (eg, nonsteroidal anti-inflammatory drugs, acetaminophen). For moderate levels of pain, intercostal nerve blocks with local anesthetic with or without systemic steroids have been shown to be very effective, including for the case described in this article. For more severe pain or failure to respond to other management, resection of the anterior rib and costal cartilage have been performed successfully. Almost every publication in which surgery was performed concluded that patients have complete resolution of pain following excision of the slipping ribs.^[5]

To summarize, slipping rib syndrome is a condition with a simple presentation and diagnostic test and treatment options. However, vigilance is required to narrow the differential diagnosis and effectively manage the condition.

References

1. Cyriax EF. On various conditions that may simulate the referred pains of visceral disease, and a consideration of these from the point of view of cause and effect. Practitioner. 1919;102:314–322.
2. Verdon F, Herzig L, Burnand B, et al. Chest pain in daily practice: occurrence, causes and management. Swiss Med Wkly. 2008;138(23–24):340–347. https://doi.org/2008/23/smw-12123
3. McBeath AA & Keene JS. The rib-tip syndrome. J Bone Joint Surg Am. 1975;57:795–797.
4. Heinz GJ & Zavala DC. Slipping rib syndrome. J Am Med Assoc. 1977;237:794–795.
5. Gould JL, Rentea RM, Poola AS, et al. The effectiveness of costal cartilage excision in children for slipping rib syndrome. J Pediatr Surg. 2016;51:2030–2032. https://doi.org/10.1016/j.jpedsurg.2016.09.032