Ischiopubic synchondrosis osteomyelitis: a rare presentation of a limping child presenting to a paediatric emergency department
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Background
The ischiopubic synchondrosis (IPS) is a temporary cartilaginous junction located between the inferior pubic ramus and ischium. Its closure typically begins in early childhood and is completed before puberty. It is a rare benign condition that presents with pain due to chondritis of the ischiopubic junction that occurs between the ages of 4 and 16 years. Osteomyelitis of the IPS is an uncommon infection and extremely rare and considered a diagnostic dilemma. Careful examination, wide-ranging differential diagnoses, a high clinical suspicion and appropriate investigations are essential to establish a definitive diagnosis.
IPS involves the hip and the gluteal region, causing marked limping and spontaneous tension of the adductors unrelated to trauma. IPS osteomyelitis (IPSOM) presents with similar pain described in IPS in addition to infective symptoms.
Based on our patient’s presentation, it was difficult to give a definitive diagnosis since there was no fever at initial presentation, and the pain was non-specific. Having said that, our differential diagnoses were wide enough to avoid missing life and limb-threatening conditions such as testicular torsion, atypical appendicitis, septic arthritis, osteomyelitis, slipped capital femoral epiphysis (SCFE), fractures, dislocations, myositis and tumours.
Case presentation
We present a case of a middle childhood boy, who presented to our paediatric emergency department with severe right upper thigh pain, radiating to inguinal/hip area. The pain was sharp in nature, described like a severe cramp which started 10 hours prior to presentation and progressively worsened over time. He denied any recent trauma or infective symptoms. There were no other associated complaints.
On physical examination, the patient was in severe pain in the right upper thigh. A general examination was within normal limits barring a few pertinent observations. Muscles in the posterior compartment of the right thigh appeared taut and in spasm. All range of movements in the hip was limited due to severe pain. It was also noted the patient had mild right testicular tenderness on examination which he did not complain of before, no scrotal skin changes or swelling, and a normal cremasteric reflex. Neurological examination revealed power and sensation were intact in all four limbs. Deep tendon reflexes were intact in all limbs, except for the right lower limb as reflexes cannot be assessed due to pain. It should be noted that all distal pulses were intact and capillary refill time in the toes was within normal limits.
Pelvic X-ray done which demonstrated asymmetric IPS, suggestive of right-sided osteochondritis/van Neck-Odelberg disease (VND) (figure 1).
Figure 1
Pelvic X-ray: blue arrow demonstrates an asymmetric lesion of the right ramus.
A scrotal ultrasonogram showed no evidence of testicular torsion or associated abnormalities. Abdominal ultrasonogram was also within normal limits.
Initial blood tests were within normal limits except for a mild neutrophilia of 10×109/L (normal range 1.5 and 8×109/L).
The patient was given intravenous analgesia and observed in the emergency department for approximately 8 hours. On reassessment, the patient was well, pain-free with normal vitals, hence discharged home with safety netting to return to the emergency department instructions.
After 12 hours from being discharged, the patient developed fever at home, recorded at 40℃ and returned to the emergency department. On the second visit, in addition to fever, he reported a recurrence of the same excruciating non-specific right thigh pain as described above. On this second visit, his complete blood count showed elevated white cell count (WCC) of 21×109/L (4.5–11×109/L) with a left shift as demonstrated with neutrophilia. His inflammatory markers were also elevated with a C reactive protein (CRP) of 31 mg/dL (less than 0.3 mg/dL) and procalcitonin 0.53 µg/L (
A differential diagnosis of septic arthritis or osteomyelitis was considered, and the patient was commenced on empirical broad-spectrum antibiotics (ceftriaxone and vancomycin). An ultrasound of the right hip revealed minimal effusion of the hip joint.
After consulting the paediatric orthopaedic service, pelvic MRI was performed which revealed right IPSOM associated with myositis of the right obturator externus, adductor minimis and obturator internus muscles. A small collection of fluid was seen in the right obturator externus muscle. Also demonstrated was a small focus of osteitis in the right superior pubic ramus with no drainable fluid collections (figures 2 and 3).
Figure 2
Pelvic MRI (coronal plane): blue arrow demonstrates right ischiopubic synchondrosis osteomyelitis, right obturator externus/adductor minimis/obturator internus myositis with a small fluid pocket in the right obturator externus.
Figure 3
Pelvic MRI (transverse plane): blue arrow demonstrates right ischiopubic synchondrosis osteomyelitis, right obturator externus/adductor minimis/obturator internus myositis with a small fluid pocket in the right obturator externus.
Blood culture collected on the initial visit was positive for methicillin-sensitive Staphylococcus aureus.
The patient required admission for 10 days started on intravenous antibiotics. Initially, he received a combination of ceftriaxone, vancomycin and clindamycin for 48 hours as agreed on by orthopaedics as well as paediatric infectious disease. After reviewing the blood culture result with trending down inflammatory markers, vancomycin and clindamycin were discontinued. He was discharged home to continue intravenous ceftriaxone for a total of 2 weeks in the short stay unit, followed by oral cefuroxime for another 2 weeks.
Differential diagnosis
One of the main differential diagnoses we needed to exclude as soon as possible was testicular torsion which can present with inguinal, lower abdominal pain or thigh pain rather than isolated groin pain. It was ruled out by a normal ultrasound Doppler of the testicles.
Fracture of the femur, pelvis as well as dislocations, Slipped Capital Femoral Epiphysis (SCFE) and stress fractures were all excluded by pelvic and femur X-rays.
Also, an ultrasound of the abdomen was done to rule out an atypical presentation of appendicitis as well as intra-abdominal pathology that might cause referred pain to the right thigh and right inguinal area, which was within normal limits as well.
Other entities such as benign or malignant tumours and autoimmune disorders were excluded by blood work, X-ray and MRI. Also, the short history of his illness and signs and symptoms made it unlikely to be a chronic process; hence, we did not investigate for rheumatological conditions.
Treatment
Based on radiological imaging and consultations with paediatric orthopaedics and paediatric infectious diseases, the patient was commenced on systemic antibiotics. He received a combination of third generation cephalosporins (ceftriaxone), macrolides (clindamycin) and glycopeptides (vancomycin). The patient required a peripherally inserted central venous catheter line for a 2-week course of intravenous antibiotics. This was followed by an additional 2 weeks of oral third generation cephalosporins (cefuroxime). A combination of paracetamol and non-steroidal anti-inflammatory drugs was used for pain management.
Outcome and follow-up
The patient was followed up by general paediatrics, paediatric infectious diseases as well as paediatric orthopaedics outpatient clinics after discharge for a duration of 6 months. He made a full recovery with return to normal daily activities with no limitations. We followed the condition with the family up to a year from the diagnosis via telephone follow-up.
Discussion
Ischiopubic synchondrosis (IPS) was first described by Odelberg (1923) and van Neck (1924) addressing the radiographic changes of Synchrondosis Ischiopubic Syndrome (SIS) as swelling and demineralisation of the ischiopubic fusion zone and referred to this entity as ‘osteochondritis ischiopubica’.1 IPS is due to osteochondritis of the ischiopubic area, which is a rare but benign condition of children aged 4–16 years of age. Careful examination and appropriate investigations are essential to establish a definite diagnosis.2 In some patients, a slight limp and limitation in flexion and extension was observed. The side of IPS correlated with foot dominance, which probably suggests that IPS is a physiological reaction to forces exerted on the nondominant limb during physical activity.3 4 Adolescents who present with pain in the hip region accompanied by a limp must be properly evaluated for an accurate diagnosis. It is important to exclude SCFE, which is a commonly missed diagnosis.
The potential causes for these symptoms include benign or malignant tumours, infection, autoimmune disorders and stress fractures.4 5
IPS should be differentiated from IPSOM as the management plan will differ accordingly. IPS presents with hip pain and limping in the absence of fever and inflammatory markers and is confirmed by X-ray.6 On the other hand, IPSOM presents as pain mainly with rotation of the hip, sometimes involving the gluteal region, causing marked limping and spontaneous tension of the adductors not related to trauma. In addition to the pain, there is fever, elevated inflammatory markers such CRP >20 mg/dL or erythrocyte sedimentation rate (ESR) >10 mm and WCC>12×109/L. Studies have suggested a haematogenous aetiology as a leading cause for IPSOM, with S. aureus being the most common organism grown on blood culture. Regarding treatment, a duration of intravenous antibiotics between 1 and 3 weeks has been suggested to be followed by oral antibiotics. The total duration of treatment is typically between 4 and 6 weeks.5 7
Ischiopubic synchondrosis is usually treated with non-steroidal anti-inflammatory medications for 2–3 weeks and avoidance of exercise.8 In contrast, IPSOM requires antibiotics via intravenous route initially. Diagnostic procedures, including biopsies, are unnecessary when appropriate investigations are performed. Acute or subacute infections show signs of periosteal reaction on plain radiography, along with signs of localised osteoporosis. MRI of cases of IPSOM shows diffuse oedema with periosteal reactions and signs of diffuse oedema of the adjacent muscle (peripheral enhancement). Blood tests with elevated ESR and CRP levels are helpful in acute infections but may be normal or slightly elevated in subacute infections.6 9–11
Despite advances in radiographic modalities, IPS/VND is still a condition that many physicians find difficult to diagnose. An understanding of the physiological processes of IPS fusion during skeletal maturation is essential, and a standardised algorithm was developed that may contribute to avoiding unnecessary diagnostic and therapeutic measures and minimising uncertainty and anxiety among affected patients, their families and managing physicians10 (figure 4).
Figure 4
Standardised algorithm for diagnosis and treatment of VND. Adapted from Schneider et al.10 Available at: (Accessed: 12 January 2025). VND, van Neck-Odelberg disease.
Learning points
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Ischiopubic synchondrosis osteomyelitis is a rare clinical entity. Early diagnosis is often challenging, which may delay the initiation of effective treatment and increase the risk of disease progression, morbidity and complications.
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A high index of suspicion is essential, particularly in cases with atypical presentations that do not align with more common conditions. Maintaining a broad differential diagnosis can help reduce diagnostic delays.
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Accurate diagnosis requires appropriate investigations, which are typically conducted in a tertiary care centre due to the complexity of the condition.
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Optimal management necessitates a multidisciplinary team approach involving paediatric emergency, orthopaedics, paediatric infectious diseases and paediatric radiology to ensure comprehensive care and improved outcomes.
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