Osteitis pubis (OP) is a noninfectious, chronic inflammatory state of the pubic symphysis and surrounding soft tissues with multiple etiologies, all resulting in the groin or lower abdominal pain.
Osteitis pubis has an incomplete understanding of the exact cause of the condition. However, it is commonly believed to result from overuse stress injury of the pubic symphysis. The pubic symphysis is a fulcrum for muscles inserting and originating from the anterior pelvis, such as the rectus abdominis and adductor muscle complex, which are antagonistic. Repetitive use causing microtrauma or injury of anterior pelvic musculature results in muscle imbalance between the two. This imbalance disrupts the force distribution across the pubic symphysis altering the joint’s biomechanics. The altered biomechanics of the joint results in stress injury to the pubic bone and eventual cartilage degeneration. Altered hip biomechanics, such as those seen with femoroacetabular impingement (FAI), may also lead to osteitis pubis, although its relationship is less delineated. Other, less commonly cited reasons the development of osteitis pubis are rheumatologic disorders, prior urologic and gynecologic procedures, pregnancy.
To date, there has been no epidemiological study to determine the true incidence of osteitis pubis. The incidence in athletes has been reported as 0.5% to 8% with a higher incidence in distance runners and athletes in kicking sports, in particular male soccer players who account for 10% to 18% of injuries per year. However, it is commonly accepted to be of higher incidence in previously mentioned athletic activities. In one study of 189 athletes experiencing groin pain, osteitis pubis was the primary cause in 14%. In an MRI study of 97 athletes with groin pain, isolated osteitis pubis was found in 9.3% of subjects, and osteitis pubis with associated adductor microtear was found in 42.3% of patients. Classically, osteitis pubis is more common in men than women. In previous studies, it was found to be two to five times more common in men. However, as women's athletic participation has increased, this discrepancy is believed to decrease.
More recently, the relationship of FAI and athletic pubalgia has been of interest. Eight six percent of those diagnosed with osteitis pubis undergoing operative intervention had FAI on radiographs. In an MRI study of nonathletic subjects, those with FAI were 13.89 times more likely to have OP. This result is also supported by Verrall et al., who found that those with a decreased hip range of motion had a higher incidence of pubic bone stress injury than in those with a normal hip range of motion. Saito et al. demonstrated that approximately 68% of soccer players with symptomatic FAI had radiographic evidence of OP. Finally, Larson et al. demonstrated those with increasing cam hip deformity showed a statistically higher prevalence of symptoms of OP.
In regards to urological procedures resulting in osteitis pubis, in the literature review, the Marachall-Marchetti-Kranz (MMK) urethropexy has an incidence of 2.5%. Overall it occurs in less than 1% of those undergoing urologic procedures.
The pubic symphysis is a non-synovial amphiarthrodial joint with an interposed fibrocartilaginous disc separating hyaline cartilage. The joint normally has minimal motion due to the static ligamentous complex. The pubic symphysis serves as the insertion point of the rectus abdominis and origin of the adductor complex. The antagonistic nature of the rectus abdominis, which elevates the pubic symphysis while the adductors depress the joint serves as a nidus for the development of osteitis pubis. The repetitive use of the anterior pelvic musculature results in chronic tendinosis. The chronic muscle imbalance results in abnormal forces across the pubic symphysis, causing symphyseal instability, pubic bone stress reaction, and eventually degeneration of the hyaline cartilage. Another emerging theory poses that osteitis pubis develops secondary to increased compensatory motion across the joint because of limited motion elsewhere in the kinetic chain, such as in FAI. Birmingham et al. found increased rotational motion at pubic symphysis when cam-type FAI was mimicked in cadaveric pelvis specimens. Also, in intimate contact with the pubic symphysis periosteum in the inguinal ligament, which is an important suture for the inguinal canal. Urological procedures may result in injury to the inguinal ligament, or in the case of MMK procedure, sutures through the pubic bone may result in chronic irritation. Finally, osteitis pubis can result from direct trauma to the pubic symphysis.
The few histological studies regarding OP come from bone and cartilage samples taken during surgical procedures on athletes with OP. The study by Verrall et al. took samples of pubic rami from Australian rugby players with pubic bone stress injuries. The samples, surprisingly, revealed the lack of inflammatory cells or signs of osteonecrosis. The samples, however, did demonstrate woven immature bone with neovascularization, osteoblasts, and fibroblasts consistent with a bony stress response. In a second histology study, by Radic and Annear, cartilage samples obtained from 15 athletes demonstrated degenerative cartilage void of inflammatory cells. The lack of inflammatory cells in both studies contradicts the notion that OP is primarily a disease of inflammation. As noted by Hitti et al., the idea that OP is an inflammatory disease stemmed from the published study by Coventry and Mitchell in 1961. Coventry et al. found evidence of marrow fibrosis, vascular areas, and thin layers of new bone. However, their subject population was not athletes, but those who had prior pelvic surgery and infection. Thus this lends itself that OP may result from differing etiologies causing differing histology, which can be elicited from the patient history and presentation.
Patients, particularly athletes with osteitis pubis, often have concomitant pathology making the diagnosis difficult. The entire kinetic chain of the lower extremity can be involved requiring evaluation of the sacroiliac joint, hip labrum, FAI, adductors, and abdominal muscles. Pathology at any of these locations can result in osteitis pubis for the reasons mentioned earlier. Patients with OP often present with anterior and medial groin pain. Pertinent history information is athletic participation, chronicity of symptoms, and aggravating movements. If the patient is a non-athlete, surgical or procedural history should be obtained. The onset of pain is usually gradual and can be debilitating, especially to the athlete. Commonly, patients will state pain is elicited with rapid hip flexion from an extended position such as with kicking or hurdles, adductor stretching, abdominal muscle strengthening exercises, or movement from a seated to standing position.
The physical exam can be difficult in OP as it does overlap with athletic pubalgia or sports hernia. However, according to Lynch et al., the two can be differentiated with pain elicited by direct palpation over the pubic symphysis with OP. Another exam maneuver, the spring test, where direct pressure is applied just lateral to the pubic symphysis on the ramus, evokes pain. Verrall et al. proposed three provocation tests: single adductor, squeeze, and bilateral adductor tests. If tests were positive, they highly correlated with pubic bone marrow edema on MRI. Patients may also exhibit a waddling gait due to pain and a sensation of tightness in the adductor muscles.
Due to OP’s common association with FAI, the hip joint must be evaluated. Patients with limited flexion, extension, internal, and external rotation of the hip should undergo evaluation. Patients presenting with either sacroiliac pathology or with FAI may have pain with the FABER test, which is flexion, abduction, and external rotation of the hip.
Both radiographs and MRI aid in the diagnosis of osteitis pubis. In the early stage, plain radiographs might appear normal. In chronic OP, the pubic symphysis demonstrates lytic changes, sclerosis, and widening. Dynamic instability of the pubic symphysis can be observed on the flamingo view. The flamingo view is obtained by double- and single-legged stance positions bilaterally on a pelvic anterior-posterior radiograph. Greater than 2 mm of subluxation is considered a positive finding for symphyseal instability.
MRI has become the imaging modality of choice. In the acute setting, MRI demonstrates subchondral bone edema, typically with bilateral involvement. In chronic cases, MRI findings are similar to plain radiographs demonstrating periosteal reaction, bone resorption, the irregular contour of the articular surface, osteophytes, and subchondral cyst formation. MRI has a high sensitivity for distinguishing between chronic and acute cases (Krishnamoorthy et al.). Pubic symphyseal bone marrow edema can commonly be found in asymptomatic patients as well. A linear subchondral T2 signal paralleling the pubis has to found in more symptomatic patients.
In patients diagnosed with cam-type FAI with symptoms greater than 3 months, Akgun et al. demonstrated a 45.56% prevalence of osteitis pubis on MRI findings compared to 5.86% in control subjects. Philips et al. also support this result. Those with FAI had a prevalence of OP at 43.48% in and only 12.8% in the control group. However, Krishnamoorthy et al. found a low prevalence (2.3%) of symphyseal changes on MRI in patients with FAI. However, when the subjects were matched for age and BMI, the findings of symphyseal changes did have clinical significance. Findings on MRI also correlate with clinical outcomes in those suffering from OP. Patients with edema in both the pubic bone and surrounding musculature had a much lower percentage of complete recovery. Whereas those who had edema confined to just the bone had a much higher percentage chance of complete recovery at 18 months. Finally, MRI is usual for diagnosing concomitant injuries that can contribute to OP, such as adductor tears, FAI, rectus femoris tears, labral tears. Patients with FAI treated with hip arthroscopy who also had symphyseal changes, such as bone marrow edema, on MRI had inferior surgical outcomes when compared to those who do not have such changes.
The management of OP includes both conservative and surgical options. The first option remains conservative treatment. Conservative management includes rest, NSAIDs, and a progressive course of physical therapy. There is no standard conservative treatment protocol resulting in a variety of outcomes. The conservative treatment of OP can be protracted. It may take some athletes six months or more to return to the preinjury level, but more commonly, most return by 3 months. Albeit protracted, conservative management remains the mainstay of treatment. Only approximately 5% to 10% of athletes require surgical treatment.
Steroid injections have been demonstrated as a useful adjunctive therapy. However, their role remains controversial. Two case series have demonstrated successful treatment with prolotherapy. Even though none of the injection studies were experimental in design, all reported positive outcomes. However, the areas injected, the amount injected, time to return to play, number of injections, and persistent symptoms were highly variable.
If conservative management does fail, surgical intervention may be required. The timeframe of when to consider conservative treatment as a failure ranges and no set time table has been established. Commonly at a minimum of six months of conservative treatment is attempted before surgical options are discussed. Surgical options include curettage of symphyseal fibrocartilage, symphyseal fusion, wedge resection of the symphysis with or without arthrodesis, and an array of procedures to reinforce or repair abdominal or pelvic floor musculature. Williams et al. performed arthrodesis with a compression plate and bone graft in seven rugby players. All were able to return to sport and were symptom-free at a 52 month follow up. More recently, endoscopic techniques have been successfully demonstrated in case reports. Surgical indications are not well defined as some surgeons consider OP an isolated condition, while others attribute it to a constellation of other entities. In addition, there have been no significant differences between surgical outcomes between the differing procedures. Athletes are able to return to unrestricted activity at approximately 6 months.
Those with symptomatic FAI and OP may see relief of OP when FAI is treated, supporting the notion that OP is a result of altered joint motion elsewhere in the pelvis. Thirty-nine percent of patients diagnosed with both conditions had complete resolution of OP when FAI treated alone. Results from Saito et al. also support this finding where arthroscopic surgery for FAI alone resulted in a high rate of return to sports and resolution of bone marrow edema among soccer players.
The prognosis of those with OP is very good. Those treated conservatively return to sports in approximately 3 months with a low chance of recurrence. Only 5% to 10% of patients with OP require surgery. Surgical outcomes are also very favorable, with an overwhelming return to sport at approximately 3 to 4 months.
Surgical treatment of OP can result in:
Patients, especially athletes with osteitis pubis, benefit from a team approach involving orthopedic surgeons, coaches, physical therapists, and athletic trainers. Conservative treatment should be attempted first and results in successful treatment in a majority of cases. Orthopedic surgeons and physical therapists should be mindful of concomitant pathology and treat them accordingly.
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