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Original Research |
1 All authors: Department of Radiology, Cappagh National Orthopaedic Hospital, Finglas, Dublin 11, Ireland.
Received January 11, 2006;
accepted after revision July 31, 2006.
Address correspondence to P. M. Cunningham.
Abstract
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MATERIALS AND METHODS. One hundred consecutive soccer players with debilitating groin pain were referred for MRI. One hundred asymptomatic age- and sex-matched elite athletes were included as control subjects. The "secondary cleft" sign was used to indicate an adductor microtear at the symphyseal enthesis. Osteitis pubis was recorded if paraarticular bone edema was identified along the symphyseal margins but was remote from the adductor attachment. Images were reviewed independently by two radiologists who were blinded to the side of symptoms. Statistical analysis was performed using the chi-square test.
RESULTS. Of 100 patients, groin pain was directly attributed to inflammation at the symphysis pubis or its muscular attachments in 97 (isolated adductor microtears, n = 47; isolated osteitis pubis, n = 9; both, n = 41). An "accessory cleft," reflecting an adductor enthetic microtear, was identified in 88 of these patients (p < 0.001); it correlated with the side of symptoms in all cases. Bone edema was identified in 91 of 100 patients: 49 had focal edema at the attachment site of the adductor tendons accompanying an adductor microtear, two patients had focal edema without an adductor tear, and 40 patients had diffuse edema in the pubic bones secondary to osteitis pubis. There was no evidence of either adductor dysfunction or symphyseal inflammation in the control subjects (p < 0.001).
CONCLUSION. In soccer players with pubalgia, adductor dysfunction is a more frequent MRI finding than osteitis pubis. The findings of this study suggest that both entities are mechanically related and that osteitis pubis and adductor dysfunction frequently coexist but, because adductor dysfunction is commonly identified in the absence of osteitis, that adductor dysfunction most likely precedes the development of osteitis pubis in soccer players. The presence of edema on fat-suppressed images of the symphysis is a strong predictor of abnormality at this site in soccer players when compared with age- and sex-matched control subjects.
Keywords: MRI • musculoskeletal imaging • pelvic imaging • sports medicine • trauma
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In clinical practice, the term "athletic pubalgia" is used to describe exertional pubic or groin pain [7], and although many causes of pubalgia are described ranging from a labral tear of the hip, sacroiliitis, and lower lumbar disk disease to pelvic soft-tissue derangement in females, most authors conclude that adductor dysfunction, osteitis pubis, and prehernia complex (also termed "sportsman's hernia," "conjoint tendon tear," "external oblique tear," and "rectus abdominis sheath tears") are the most common causes [8-11]. Whether these entities are mechanically related is currently unclear. The purposes of this study were to determine the prevalence of adductor dysfunction and of osteitis pubis in soccer players presenting with pubalgia and, on the basis of these observations, to determine whether one of the ailments appears to precede or predispose the development of the other.
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There were 95 males and five females in the cohort, with a mean age of 27 years (range, 17-38 years). In these patients, groin pain had been present for a mean of 3 months before referral for imaging. No difference in the pattern of presentation was noted in the amateur compared with the professional soccer players, and both groups participated in soccer at an advanced level.
Control Subjects
One hundred athletes (mean age, 23 years; range, 18-28 years) without
symptoms referable to the symphysis pubis who were referred for MRI of the
pelvis were included in the study as control subjects. This group included 50
volunteers with no symptoms (rowers), 37 with unexplained hip pain (soccer
players), and 13 with suspected sacroiliac dysfunction (soccer players).
Methods
The study and control group patients were imaged on a 1.5-T scanner
(Intera, Philips Medical Systems) with a quadrature body coil. For each
examination, the groin was imaged in the coronal plane using a turbo spin-echo
T1-weighted sequence (TR/TE, 620/20; echo-train length, 6; low-high mapping; 2
excitations; 15-cm field of view) and using a turbo STIR sequence
(TR/effective TE, 2,000/20; inversion time, 160 milliseconds; echo-train
length, 14; linear mapping; 2 excitations; 15-cm field of view) and in the
axial plane using a turbo spin-echo T2-weighted sequence (2,000/80; echo-train
length, 14; linear mapping; 2 excitations; 15-cm field of view).
Image Interpretation
For the study, the "secondary cleft" sign was used as an
indicator of an adductor microtear at the symphyseal enthesis. This sign
describes an abnormal inferior extension of the cleft in symphyseal
fibrocartilage created by a microtear at the attachment of the conjoint
gracilis that extends from adductor longus tendon to the inferior pubis
[12].
For this study, osteitis pubis was recorded as present if paraarticular bone edema, either uni- or bilateral, was identified remote from the adductor attachment. Although supportive, additional features of osteitis pubis including paraarticular fatty marrow change, articular surface irregularity and stepoff, and inflammation in paraarticular soft tissues were not required for the diagnosis. This definition of osteitis pubis markedly increased the sensitivity of MRI to subtle osteitis pubis. Bone edema localized to the inferior pubis adjacent to the adductor attachment was attributed to the distraction-traction effect from the adductor tendon attachment rather than to osteitis pubis, as described by other authors [13-15].
All images were reviewed independently by two fellowship-trained musculoskeletal radiologists who were blinded to the side of symptoms; discrepancies were resolved by consensus. The images were reviewed on printed film, with 20 images on each sheet.
In each case, the reviewers assessed the images for the presence or absence of an adductor microtear, uni- or bilateral, and the presence or absence of osteitis pubis. The integrity of the symphyseal articular surfaces, the presence or absence of symphyseal fibrocartilage herniation, and the presence and distribution of bone edema were noted. Finally, the width of the pubic symphysis joint space, measured on the axial scans at the midpoint of the symphyseal joint space, was recorded.
Statistical Analysis
Statistical analysis was performed using the chisquare test.
Ethics Committee Approval
Approval for retrospective analysis of imaging data was obtained for this
study from the hospital ethics committee.
Gold Standard
Symphyseal contrast injection was used to confirm the presence or absence
of a secondary cleft due to an adductor microtear; its presence was correlated
with the side of symptoms
[16]. Symptom relief by
subsequent injection of bupivacaine and steroids to the cleft confirmed that
symptoms were referable to the presence of the cleft
[16].
No contrast injections to the symphysis pubis were performed in the control subjects.
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Of 97 patients, isolated adductor microtears in the absence of osteitis pubis were identified in 47 patients (48.4%), isolated osteitis pubis was identified in nine patients (9.3%), and osteitis pubis and accompanied adductor microtear in 41 patients (42.3%) (Figs. 1A, 1B, 2A, 2B, 3A and 3B).
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Bone edema was identified in 91 of the 100 patients who underwent imaging. Forty-nine (53.8%) of 91 patients had focal edema in the pubic tubercle at the site of the adductor microtear. Two patients had a focal abnormality in the bone, without evidence of an adductor microtear, that was thought to be the result of early abnormal traction effect before the development of an avulsion microtear. The remaining 40 patients had diffuse edema in the pubic bones, either uni- or bilaterally, that was considered to be secondary to osteitis pubis.
An articular surface irregularity at the pubic symphysis was seen in 50 patients in conjunction with stepoff at the joint in seven patients (Fig. 4).
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Control Subjects
The images and records of the control subjects who did not have clinical
symptoms or signs of groin pain were also reviewed. None of these patients
showed evidence of bone edema at the symphysis pubis. This is a statistically
significant difference when compared with the study group (
2 =
188.34, p < 0.001). None of the control subjects was found to have
an accessory cleft secondary to adductor dysfunction, which is another
statistically significant difference when compared with the study group
(2 = 188.34, p < 0.001).
A symphyseal articular surface irregularity with paraarticular fatty marrow
change was identified in 27 of the control subjects without evidence of active
inflammation, which was defined by the presence of either soft-tissue or bone
edema. In 73 of the 100 control subjects, herniation of the fibrocartilaginous
disk posteriorly and superiorly from the symphyseal articulation was noted.
There was no statistically significant difference between the study group and
control group with regard to fibrocartilaginous disk herniation (82% vs 73%,
respectively; 2 = 2.32, p = 0.20).
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The articular surfaces of the symphysis pubis are covered by hyaline articular cartilage on either side and are the margins of a central fibrocartilaginous disk that primarily functions to dissipate impaction forces. In adults, a physiologic fluid-filled cleft develops in the fibrocartilage. Anteriorly, the fibrocartilaginous disk and symphyseal joint are supported by an aponeurosis created by the tendons of the anterior abdominal wall, particularly rectus abdominis muscles, and, to a lesser extent, by the aponeurosis created by the gracilis and adductor longus tendons. The gracilis and adductor longus tendons merge from both the right and left legs to provide support anteriorly and, to a greater extent, inferiorly where they merge with the arcuate ligament [12] (Fig. 5A, 5B, 5C). Superiorly, the fibrocartilage and symphyseal joint are supported by the superior pubic ligament [12], but in the absence of supporting musculature superiorly and posteriorly, repeated impaction forces lead to gradual herniation of the fibrocartilaginous disk superiorly and posteriorly, as was identified in 82 of the 100 symptomatic patients in the study group. The same finding was identified in 73 of the control subjects without groin pain, which suggests that herniation of the fibrocartilaginous disk is an asymptomatic mechanical phenomenon. In this study, fibrocartilage herniation was associated with narrowing of the joint space in most cases and with parasymphysial osteophytes in a minority of cases. Whether fibrocartilage herniation precedes or predisposes an individual to developing osteitis pubis is unclear.
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Although groin pain may be secondary to many entities remote from the symphysis, including hip and sacroiliac derangement, in most cases, exertional groin pain or pubalgia results from injury to the symphysis pubis and its supporting structures. Although this study focused on adductor dysfunction and osteitis pubis, in many cases, pubalgia is attributed to sportsman's hernia. This entity is one in which inguinal ligament laxity leads to widening and tearing of support structures of the internal ring. Although this single abnormality has been popularized as sportsman's hernia, confusion has given rise to a number of descriptive terms for the same entity including prehernia complex, conjoint tendon tear, external oblique tear, and rectus abdominis sheath tear [24-27]. In this study, sportsman's hernia was excluded in each of the study subjects on the basis of clinical examination before referral for MRI. Although herniography has been used and can show internal ring laxity [28] and although, more recently, Albers et al. [9] have shown the utility of MRI in revealing both muscular signal changes and myofascial bulging in affected patients, clinical examination is still considered to be the gold standard for this diagnosis [15].
The results of this study suggest that isolated adductor dysfunction with a microtear at its attachment is a more frequent cause of pubalgia in soccer players than isolated osteitis pubis. Indeed, our findings show that when osteitis pubis does occur, it is usually in association with a microtear at the pubic attachment of the adductor longus. Although somewhat speculative, the described patterns of disease at the symphysis suggest that an adductor microtear is frequently a primary event, followed by the development of osteitis presumably secondary to the induced muscular instability, laxity, and secondary impaction of surfaces at the symphysis. Similarly, sportsman's hernia or laxity and inflammation at the internal ring orifice, the third recognized cause of groin pain, may develop as a result of attempts to compensate for imbalance at the symphysis incurred by an adductor microtear. The fact that groin pain is frequently due to soft-tissue derangement, an adductor microtear, or a sportsman's hernia accounts for normal findings on radiographs and bone scans that are traditionally seen in these patients and further increases the requirement for MRI in this population.
It is worth noting that, similar to the findings of an MRI study of Australian-rules football players, bone edema and inflammation at the symphysis were present in only the symptomatic study group; thus, when those findings are absent, an imager should have a high level of confidence in excluding disease. Similarly, we found that the cleft created by a microtear at the adductor enthesis was also present in only the symptomatic group, as was shown in another study [29].
Why a microtear at the adductor attachment occurs so frequently in soccer players is unclear. Although it is possible that overuse of the adductor longus muscle with associated increased contractility and power in the muscle belly cannot be accommodated by the small enthetic adductor attachment, it is likely that a microtear is the consequence of tendon stretching and applied traction to the enthesis due to twisting and turning [12, 14] or, more likely, is secondary to both. The initial tear appears to occur at the tendon attachment to the inferior border of the symphyseal fibrocartilage and to extend gradually to the true bone enthesis. The extension of the physiologic cleft within the fibrocartilage created by such a tear allows interposition of fluid between the tendon and pubic bone and appears to restrict healing. Repeated activity leads to progression of the tear, inflammation, pain, and imbalance at the symphysis and subsequently to osteitis pubis. This cycle can be dramatically halted by autotenotomy where superimposed macrotrauma leads to complete detachment of the adductor longus tendon from bone with resolution of symptoms within weeks. In most, the detached tendon ultimately lengthens but heals with extensive scar formation preserving some function but limiting the imposed traction effect.
Management of groin injuries requires rest regardless of the cause. Sportsman's hernia diagnosed on the basis of clinical discomfort elicited by scrotal digital invagination [11, 25] was excluded in all the patients in this study. When confirmed by clinical findings, laxity of the internal ring is treated surgically by suture repair termed "Gilmore groin repair." Whether such a procedure facilitates recovery of osteitis pubis is unclear; the symptoms improve in many either due to renewed groin stability or as a result of enforced rest after surgery [30-33]. Gilmore's groin repair—that is, tightening the internal ring—has no impact on the adductor attachment. When an adductor microtear is identified, symptom resolution may follow guided steroid injection to the symphyseal cleft, which communicates to the site of the tear [16]. Physiotherapy, focusing on the development of core stability, has been shown to reduce symptom recurrence [34]. In refractory cases, mimicking the effects of autotenotomy, surgical tenotomy is undertaken, with division of the adductor tendon from the pubic attachment. After undergoing postprocedural physiotherapy, individuals generally return to participating in sports within 3 months of the procedure [35].
There are a number of limitations to this study. First, the control population in this study included a mixed group of athletes, rowers and soccer players, in contrast to the study population who were all soccer players. Although this difference is a potential limitation, no difference in the imaging appearances at the symphysis were recorded between the two sporting groups. Second, although previous authors have advocated and shown the utility of gadolinium enhancement in characterizing groin ailments [13], gadolinium administration was considered unnecessary in this study because the secondary cleft sign was used as a marker of adductor dysfunction [12]. Finally, we acknowledge that one cannot make a true prediction about the pathogenesis of groin pain, as was attempted in this study, without conducting a longitudinal study. Therefore, we acknowledge that assumptions based on a single observation in time drawn from data in this study, although indicating a possible trend, are somewhat speculative.
In summary, MRI more frequently shows an adductor microtear as a cause of groin pain in soccer players than osteitis pubis. MRI reliably allows differentiation of these two entities and should therefore be performed in all patients with pubalgia to allow accurate diagnosis. The identification of a secondary cleft sign or bone edema at the symphysis should increase the index of suspicion that groin pain symptoms relate to an injury at the symphysis pubis. Although speculative, the results of this study suggest that in soccer players adductor dysfunction and microtear often precede the development of osteitis pubis.
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