Clinical History
A 12-year-old female patient arrived, presenting with left hip joint pain and limping. She communicated that she had an active weekend and suffered a fall while playing sport.
Imaging Findings
The patient was evaluated with a radiograph of the pelvis (see Image 1). Image 1 shows normal left hip joint space with acetabular linear lucency. The x-ray is suggestive of an occult fracture.
It was decided that further evaluation was needed, therefore a day later we conducted a CT scan of the pelvis (Image 2). The CT scan showed an asymmetric left hip with axial narrowing of the left hip joint space and unfused acetabular apophysis.
The patient was referred to an orthopaedist who saw her two weeks later. After the consultation, she had an MRI to look for the cause of the persistent pain and limitation of movement.
Image 3 shows that the MRI revealed a wedge-shaped (25 x 18 x 14 mm) T1 hypointense. Image 4 shows a T2/STIR hyperintense area in the mid-region of the left femoral head, and Image 5 reveals mild thinning of the articular cartilage, narrowing of the joint space, and moderate joint effusion.
The results of the MRI also revealed that the acetabulum appeared normal, and the femoral head contour, alignment, and growth plate were within normal limits.
The decision was made to manage the patient conservatively with analgesics and rest.
Discussion
Progressive articular cartilage loss in the femoral head and acetabulum is referred to as chondrolysis of the hip.
Chondrolysis of the hip is a condition that can progress to severe joint space narrowing and restricted joint movements.
The first case of hip chondrolysis was reported by Waldenstrom [1] In 1930, and the condition occurs in children and adults [2].
Research reveals that many paediatric conditions can lead to chondrolysis of the hip. Conditions such as slipped capital femoral epiphysis, Perthe’s disease, trauma, long-term immobilisation, infective/inflammatory joint diseases, and malignancies have all been connected to chondrolysis of the hip. However, it’s important to note, that when no cause for chondrolysis is identified it is labelled as idiopathic [3].
Idiopathic chondrolysis of the hip (ICH) is commonly seen in adolescents and young children, particularly females, in the age group of 9-12 years. ICH is also most commonly unilateral, often involving the right joint. Patients present with a painful hip that is sometimes associated with restricted movements, and often there is no identifiable cause.
When it comes to diagnosis, initial radiographs of the hip are usually normal. This is why MRI is the imaging modality of choice for diagnosis. The other benefit of MRIs is that they also rule out certain identifiable causes.
When examining an MRI look out for wedge-shaped marrow oedema (T1-hypointensity, T2-hyperintensity) in the middle of the femoral head in the early stage [4]. Fluid-sensitive sequences with fat suppression like STIR can make it more conspicuous. Signs of the progressive disease manifest as articular cartilage loss, joint space reduction, and acetabular changes. The final stages are secondary osteoarthritis and spontaneous fusion of the joint.
The recommendation is to use a CT as a problem-solving tool in doubtful advanced cases.
The staging method includes [5]
- Stage 0: Normal imaging
- Stage 1: Variable reduction in the hip joint space. Wedge-shaped focal area of marrow oedema located in the middle third of the femoral head in coronal images and synovial hypertrophy and joint effusion (this is characteristic and the earliest finding in an MRI).
- Stage 2: Marrow oedema in the superomedial aspect of the acetabulum along the triradiate cartilage. This is in addition to the above findings. There may also be protrusio acetabuli.
- Stage 3: Enlargement of the marrow oedema seen in the proximal femoral epiphysis, femoral head collapse, widely involved acetabulum, osteoporotic and degenerative changes (fibrous ankylosis), and femoral head overgrowing on the neck (“buttress” sign).
The natural course of the disease is reversible with conservative management. The management plan should focus on alleviating pain by encouraging rest and avoiding weight bearing. If ICH is initially neglected it can progress to severe joint deformation where the patient can end up with spontaneous ankylosis. If ICH reaches this stage then surgical management [6] is warranted.
It is prudent to know the various stages of ICH on imaging so that early diagnosis and appropriate treatment can limit permanent joint deformities.
Differential Diagnosis List
- Subchondral fracture/ Marrow contusion
- Idiopathic chondrolysis of the left hip joint
- Avascular necrosis
- Infection/Tumor
Final Diagnosis
Idiopathic chondrolysis of the left hip joint.
Learning Points
- X-rays alone are insufficient in trauma cases.
- Negative findings warrant further imaging in conjunction with the clinical picture. Beyond fractures, there are soft structures – such as cartilage, ligament, tendon and synovium.
- Specialist referral and advanced imaging, such as MRI, are adequate problem-solving tools for accurate diagnosis and appropriate management.
References
[1] Waldenström H (1930) On necrosis of the joint cartilage by epiphyseolysis capitis femoris. Acta Chir Scand 67:936-46
[2] Wada Y, Higuchi F, Inoue A (1995) Adult idiopathic chondrolysis of the hip report of 2 cases. Kurume Med J 42:121-8 (PMID: 7564163)
[3] Sparks LT, Dall G (1982) Idiopathic chondrolysis of the hip joint in adolescents: Case reports. S Afr Med J 63:883-6 (PMID: 7079920)
[4] Laor T (2009) Idiopathic chondrolysis of the hip in children: Early MRI findings. AJR Am J Roentgenol 192:526-31 (PMID: 19155420)
[5] C Amarnath, Priya Muthaiyan, T Helen Mary, Shilpa Mohanan, and K Gopinathan (2018) Idiopathic chondrolysis of hip in children: New proposal and implication for radiological staging. Indian J Radiol Imaging Apr-Jun; 28(2): 205–213 (PMID: 30050245)
[6] Korula RJ, Jebaraj I, David KS (2005) Idiopathic chondrolysis of the hip: medium-to long-term results. ANZ J Surg 75:750–753 (PMID: 16173986)
