Slipping rib syndrome (SRS) may not be as rare a diagnosis as previously believed; instead, it may be more underrecognized (1). SRS presents as a unilateral more often than bilateral shooting, stabbing, or aching pain at the anterior lower rib margin (2). Pain is often associated with activities involving the upper extremities but also can arise from coughing, laughing, twisting, or side bending (3). The pain is typically insidious onset but can be the result of trauma (2). The pain can affect all ages, with a higher incidence in females of child-bearing age (2).
The primary mechanism of SRS is a defect of the costochondral cartilage, particularly the interchondral ligaments of the anterior false ribs 8 to 10. Weakness of the cartilage can result from hypermobility, disruption of the fibrous articulation, or congenital/developmental deformities (4). The insufficient cartilage causes the laxity of the affected rib and subsequent slippage above and below the adjacent superior rib (1,3,5). Slippage may produce a clicking or popping sensation. The proximity of the lower rib to the superior rib causes intercostal nerve irritation, soft tissue impingement, and pain (3).
Hypermobility may be affected by hormones that increase joint laxity. Joint laxity, in combination with increased range of motion required by athletes, places female athletes at the highest risk of SRS (2,4,6). In a recent case, a 16-year-old gymnast with Ehlers-Danlos syndrome was identified with SRS (7). Athletes are at a greater risk secondary to their repetitive movement patterns (e.g., swimming and running) and also because of the demand for greater range of motion with sports, like gymnastics (2,4).
Recent studies suggest that genetic predisposition, age, and depression can act as predictors for SRS (5). Mean age of diagnosed patients is around 19 years and typically younger than 40 years (2). As ultrasound studies for SRS increase, congenital rib defects are being identified. With experience, we may be able to identify congenital or developmental conditions associated with SRS (4,5). Depression or other psychiatric diagnoses also have been linked to patients with SRS (2,5). Patients have been described as hysterical, neurotic, or depressed (6). These labels are given possibly out of the frustration by both the patient and the practitioner when there is a lack of a reason for the pain. Delineation of the relationship between the diseases is not clear, but secondary to chronic pain experienced with SRS, depression, and other behavioral changes may follow (5). There is the possibility that once a diagnosis has been reached and treatment provided, the psychiatric symptoms will abate.
Review of the literature reveals a presence of the diagnosis, but difficulty still lies in the identification and treatment. The hooking maneuver, performed by placing finger tips under the costal margin and pulling the rib cartilage upward, displacing the rib anteriorly and superiorly, remains the best physical examination finding. However, the most pressing discovery in the last 4 years has been the development of a protocol to diagnose SRS with dynamic ultrasound (4). With ultrasound, the pathology has become better understood, and there is better confirmation of diagnosis prior to surgery. The painful hooking maneuver may be replaced by a combination of more gentle palpation and ultrasound.
There are innovative treatments for pain relief that are less invasive, like osteopathic manipulative treatment (OMT), stretching, botulinum toxin injections, and prolotherapy (2,4,5,8,9). Lastly, surgical excision still appears to be beneficial, but research is revealing more reports of reoccurring pain following surgery. As the number of patients identified with SRS increases, there is hope that with better visualization under ultrasound and more experience with the condition, surgical techniques can be improved to decrease recurrence of pain following surgery.
Diagnosis: Diagnostic Ultrasound
Early literature revealed a low prevalence of SRS in patient populations (2,10,11). Foley et al. (2) diagnosed 54 patients between the years of 1999 and 2015 at a high-volume sports medicine and orthopedic clinic in a city. Bonasso et al. (10) reported 32 patients from 2001 to 2016, and Gould et al. (11) reported 30 patients who received surgical care from 2006 to 2015. Retrospective reviews are susceptible to bias that previous practitioners were not as familiar with the diagnosis. These early reviews reported an average of 2.1 to 3.4 cases a year. A more recent study of patients at a facility familiar with identifying and treating SRS recorded 46 patients in 1 year, March 2017 to April 2018 (4). These findings may indicate that SRS is not as unlikely a diagnosis as previously believed and may be more underdiagnosed.
Patients with SRS present with longstanding histories of pain (2,5,11,12). Many patients have undergone prior imaging studies and failed treatments. Static imaging studies that expose the patient to unnecessary radiation include radiographs and computed tomography (CT); these are not usually helpful in the diagnosis of SRS (2,8). Patients diagnosed with SRS have undergone surgery, including laparoscopic cholecystectomy, for internal organs (11). This difficulty in diagnosis may stem from the nerve supply for the anterior rib cage. Pain may seem intraabdominal secondary to the innervation of the intercostal nerves and visceral sympathetics converging at the same spinal cord level as the slipping rib (6). In a recent case report, a patient experienced 3 years of recurrent abdominal pain. She underwent an esophagogastroduodenoscopy twice with negative results on both occasions. She was evaluated by multiple imaging modalities including CT, magnetic resonance imaging, and radiographs; all failed to identify an underlying abnormality. The one imaging study to return positive was a dynamic ultrasound. The patient's hooking maneuver also was positive (12).
Meuwly et al. (1) used ultrasound to corroborate clinical findings consistent with SRS. High-resolution sonographic longitudinal views of the thoracic wall in a patient with SRS revealed the movement of the ribs. Initially, there is an overlapping movement of the lower rib above the upper rib (1). Both ribs then move downward together as the rectus continues to contract over the ribs. Suddenly, the lower rib slips under, deep to the superior rib with shearing stress (1). The Valsalva maneuver was used to elicit the movement under ultrasound. The Valsalva maneuver was utilized again in 2016 in a study with ultrasound evaluation for SRS to provoke the slipping motion (3).
In recent literature, the Valsalva maneuver was found to be less reliable when compared with a “crunch maneuver” and a “rib push” maneuver to simulate a slipping rib (4). Images of the ribs were obtained in the parasagittal plane, and cine clips were recorded of the bilateral ribs at rest and during dynamic movement. The crunch was performed by asking the patient to raise up only their head, contracting their abdominal muscles at the same time. The rib push resembled the hooking maneuver. The practitioner used graded pressure in a deep and upward motion to displace the inferior rib deep to the superior rib while scanning. Lastly, the scan was performed during any movement that the patient reported would elicit their slipping rib. The crunch, push, and other dynamic maneuvers were performed at each individual rib level as the practitioner scanned medially along the course of each rib, paying close attention to the movement at the rib tips (4).
When compared with clinical examination using the hooking maneuver or surgical confirmation of slipping rib, the dynamic ultrasound protocol correctly detected SRS 89% of the time (4). The protocol also found no evidence of SRS 100% of the time. The rib push maneuver, closely resembling the hooking maneuver, had the highest sensitivity at 87% followed by the crunch (54%), and the least sensitive was the Valsalva (13%) (4). These results seem to support the use of the hooking maneuver as an effective tool to not only elicit the pain but also to reproduce the slipping during evaluation by ultrasound.
Ultrasound has identified abnormal congenital and developmental rib pathology during scans for patients with slipping rib. Developmental anomalies are reported most often in children and young adults (3). The most common defects are sternal and costal variations (3). The conditions encountered in the anterior chest wall include aplasia, hypoplasia, fused ribs or cartilages, increased angularity of the costal cartilage or rib, rib clefts, supernumerary costal cartilages and spiked ends of ribs (3). There is room for further research into the prevalence of abnormal rib pathology in patients with pain.
Van Tassel et al. (4) identified the presence of fused cartilage levels immediately above the symptomatic level. Cartilaginous bars or bridges were found to form between ribs, and ultrasound identified abnormal rib morphology, including hooked or dysmorphic rib tips (4). Congenital rib defects were reportedly common but often were unnoticed due to the lack of symptomatology (5). A congenital defect, like a bifid anterior rib end, was likely to cause symptoms of clicking and slipping (5). How common these congenital or developmental findings are in the cases of SRS are unknown, but they may place the patient at an increased risk of pain (4).
In their study, Van Tassel et al. (4) discussed the ability to identify echogenicity of the intercostal soft tissues surrounding a symptomatic slipped rib. Increased echogenicity likely represents sonographic sequelae of inflammation, edema, and possible fibrosis within the intercostal muscle and fat (4). Asymptomatic levels lacked the hyperechoic inflammatory changes noted at symptomatic levels. Ribs with fused cartilage levels and inflammation, in conjunction with dynamic mobility of the ribs during the crunch or push provocative maneuver, were most consistent with the diagnosis of SRS. This study also suggested that regions that have abnormal morphology yet lack hyperechoic inflammatory changes are at-risk for developing SRS (4).
Although ultrasound has proven to be a robust tool for evaluation and diagnosis of SRS, the hooking maneuver is still utilized as an effective physical examination finding (4,5,12). McMahon (6) suggested that by palpating carefully along the lower cartilages, practitioners can identify disconnected cartilages and their associated movement. Point tenderness can be elicited by following the contour of the costal margin. Practitioners look for curling of the cartilage beneath or superior to the overlying rib (6). In one study, pain from SRS was reproduced with gentle direct pressure of the cartilage itself (11). Although this is very similar to the hooking maneuver, there is the absence of pulling upward. This technique, in experienced hands, may identify the slipping rib with less pain caused to the patient. Pressure also can be applied laterally to the ribs, reproducing the pain at the anterior location. Often, the patient can provoke the movement at the rib themselves with Valsalva or crunch-like motions that allow the practitioner to palpate, hear, or even see the slipping (11). Despite progress in this area of study, the hooking maneuver is not yet replaced by these techniques or by ultrasound and remains the gold standard for diagnosis.
Conservative Treatment Innovations: OMT, Stretching, Botulinum Toxin Injections, and Prolotherapy
Previous literature cites treatment with education on the pathophysiology of SRS and with reassurance of the benign nature of the disease as effective (13). Initial therapy can include rest from the inciting activity, ice, topical analgesics like diclofenac gel or Lidoderm patches, and nonsteroidal antiinflammatories (2,6). More-invasive techniques such as physical therapy, acupuncture, and chiropractic treatment also may play a role in treatment; however, these were found less effective (2). Ultrasound-guided anesthetic and steroid rib blocks have been found effective in diagnosis and treatment, but their relief is usually short-lived (2,6). Repeat injections are a form of treatment. OMT also has been found helpful in the treatment of SRS (2,14,15).
The goals of OMT are to decrease pain, improve lymphatic and circulatory function, and calm autonomic or viscerosomatic responses (14). Treatment choice depends on the pain control of the patient and the physicians comfort with the technique. Direct techniques may be too painful unless a nerve block has been placed to reduce pain (14,15). Myofascial release, direct or indirect, treats somatic dysfunction of the connective tissues and is preferred in the treatment of musculoskeletal chest pain (14). Facilitated positional release can treat hypertonic muscles and soft tissue (14). A convincing case report of three cases of SRS described muscle energy as an effective treatment for SRS (15). Each patient received an ultrasound-guided intercostal nerve block 7 cm lateral from spinous processes using 3 mL of 0.25% bupivacaine via a 22-gauge, 50-mm laser-etched block needle. OMT replaced the affected ribs into a neutral position 30 min after the intercostal nerve block (15). Recent studies have reported some patients who describe temporary relief by stretching the affected side or placing pressure on the area (4,5). Direct reduction of the offending rib segment might be the most immediate form of relief in conjunction with indirect release of surrounding soft tissues.
A case of botulinum toxin injection for the treatment of SRS was reported in a 50-year-old woman in Italy (8). She, like many SRS patients, underwent negative studies and experienced several years of pain before an ultrasound revealed costal hypermobility and overlapping ribs with Valsalva. Under electromyographic guidance, a team injected the posterior muscles surrounding the painful rib with incobotulinumtoxin A. The first treatment resulted in 1 month of pain relief. Subsequent treatments injected the muscle transversus abdomini, abdominal external oblique muscle, recto abdomini, and quadratus lumborum close to their rib insertion. Ten months after these four treatments, the patient did not have any further episodes of pain (8).
Tietze syndrome, a rare condition, typically only affects one costosternal joint, usually the second or the third rib (16,17). Tietze also may affect the sternoclavicular joint (18). The syndrome is defined as nonpurulent arthropathy associated with tenderness, pain, and swelling (18). The edema can present similarly to SRS. Tietze syndrome is more common in younger patients, those younger than 40 years (17). Tietze syndrome, a clinically individual disease process, can be confused with SRS and/or costochondritis, which are not accompanied by costosternal swelling. The similarities and differences of these three etiologies of rib pain are represented in the Table (2,17,18).
Costochondritis, Tietze and SRS comparison Summarya
||More than 1 in 90% of patients
||Ribs 2 to 5
||Repetitive physical activity provokes pain, rarely at rest
||Seronegative arthropathies, anginal pain
||Analgesics, heat, ice, manual therapy, rarely steroid injections
||1 site in 70% of patients
||Ribs 2 and 3 are the most common
||New vigorous physical activity, excessive coughing, chest impact, etc
||Rheumatoid arthritis, pyogenic arthritis
||Self-limiting, analgesics, nonsteroidal antiinflammatory drugs, rarely steroid injections
||<40 (mean, 19.1)
||1 to 3 sites
||Rib 10 > than rib 9 and 8
||Insidious, associated with increased upper extremity/torso use, sports related
||No joint swelling, soft tissue swelling is possible as is chest wall deformity
||Reassurance, topical analgesics, OMT, surgical resection, diclofenac gel, frequently anesthetic and steroid injections
Adapted from Proloux et al. and Rokicki et al. (2,16,17
Prolotherapy is an injection-based medical therapy used for chronic musculoskeletal pain (9). A proliferate, such as dextrose and/or lidocaine, is injected into the painful area to cause local irritation and superior tissue healing during prolotherapy. Prolotherapy has been applied to patients with Tietze syndrome and been compared with conservative therapy using analgesics (9). Treatment with prolotherapy provided faster recovery and significantly reduced clinical findings recorded by a visual analogue score when compared with analgesics (9). The similarities of Tietze syndrome to SRS leads to the following question: could prolotherapy be a good option for slipping rib patients? Other conservative treatment options could be beneficial, but the literature is lacking in the effectiveness of physical therapy and platelet-rich-plasma injections for the treatment of SRS.
Surgical Techniques and Recurrent Pain
Surgical procedures can vary slightly depending on the institution. When conservative treatments have failed, the majority of publications in which surgery was performed concluded that many patients have complete resolution of pain following excision (6,10,11). Previous descriptions of surgical resection involve resecting the cartilages and leaving the perichondrium intact, similar to a Ravitch procedure. The Ravitch technique allows the intercostal neurovascular bundle to remain intact and the cartilages to regrow. In SRS, regrowth of the cartilage may not be ideal. McMahon (6) has reported that it is possible to excise the entire hypermobile cartilage with the perichondrium to the costochondral junction, leaving the rib and the neurovascular bundle intact. McMahon has been studying bridging the mobile ribs with an absorbable plate for stabilization, and a publication of her results were published at the same time as the production of this article.
In comparison, SRS diagnosed in the Netherlands was treated with surgical resection of part of the 10th rib (18). The anterior side of the 10th rib was resected over approximately 10 cm, which ceased the slipping. The above technique may be preferred if the rib is hypermobile. No complications occurred postoperatively, and after 2 months, the patient remained pain-free (18).
In a recent clinical study of surgical outcomes in patients with SRS, 52% underwent surgery as part of their treatment (4). Improvement was reported in 58%, but 17% experienced continued pain. Continued pain was described as “similar or identical to the initial presenting symptoms” (4). Two patients had recurrent slipping of ribs at the same level or adjacent level. The remaining patients reported postsurgical scarring or inflammatory changes attributing to the ongoing pain. Twenty-five percent (6) were lost to follow-up. The study included no ultrasound findings that could identify those who would experience recurrent pain versus those with improvement (4). Recurrent pain after surgery, both at the same surgical site and at sites ipsilateral and contralateral to the surgery, is likely underreported (6).
Gould et al. (11) described a similar surgical technique, starting at the point of maximum tenderness and dissecting down to the perichondrium. Similar to McMahon et al. (6), Gould et al. (11) excised the cartilage lateral to the boney rib edge with no effort to preserve the perichondrium. The procedure differed in that Gould et al. (11) allowed the perichondrium to remain medially as the cartilage thins out. Recurrence was a concern, which led to leaving the perichondrium intact medially where the cartilages overlapped. With the above technique, 30 initial excisions resulted in eight (26%) patients who required reoperation. Four reoperations were for reoccurrence at the same level, and four were for procedures at different ipsilateral or contralateral sites. Despite the reoccurrence rate, of the 18 patients included in follow up, 13 reported complete cure, and two reported improvement of their pain.
In another study, a gymnast had recurrence of pain after her initial surgery. The 16-year-old girl presented with a rib click and a palpable dislocation of the left sixth costal cartilage. The single mobile sixth costal cartilage was excised. Six months later, the patient underwent a modified Ravitch procedure to remove bilateral costal cartilages 7 to 10. The patient reported continued pain bilaterally at follow up. Her pain was reported to be better than before surgery; however, at 18 months postsurgery, the patient still reported pain and planned to undergo a modified Ravitch at another institution (7).
As surgical techniques may vary slightly from institution to institution, better communication about techniques may lead to better outcomes. Future research on what specific techniques produce the best results with the least amount of reoccurrence may benefit this unique patient population. Current literature also is lacking on a consensus for how many levels should be resected above and below the point of maximal tenderness.
The actual prevalence of SRS is unknown; however, as recognition improves, the reported prevalence may increase (4). The physical exam test, the hooking maneuver, appears to be supported as the most accurate recreation of slipping motion observed under ultrasound when compared with the similar “push” maneuver (4). Modifications to the hooking maneuver have been suggested, but it currently remains the most universally used physical examination test (5,6). With advances in the utilization of ultrasound, practitioners are learning more about the morphology of the ribs, the adjacent cartilages, and the surrounding soft tissue. There are very few alternatives to surgical resection for resolution of SRS pain. In the author's professional opinion, OMT is a prime area for further research. There is evidence that nonoperative treatments including botulinum toxin, prolotherapy, and other injectables also may provide pain relief (8,9). Surgical techniques are successful at treating SRS, but secondary to reoccurrence risk, there may be better techniques being developed.
The author declares no conflict of interest and does not have any financial disclosures.
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