17-year-old male, known case of Acute Lymphoblastic leukaemia (ALL) on high dose steroids since one year, came with complaints of right elbow joint pain and restriction of movements since 3 months. MRI right elbow with screening of left elbow was done.
MRI revealed irregular areas of altered signal intensity involving the distal humeral epiphysis of right elbow, showing a T1/T2 hyperintense center with a serpiginous rim of STIR hyperintensity followed by a STIR hypointense rim. Similar morphology changes were seen in left humerus too in limited screening sequences.
The articular surface of capitellum is irregular and shows focal subchondral collapse. Thinning of articular cartilage of corresponding radial and capitellar articular surfaces is seen with formation of marginal osteophytes, indicating secondary osteoarthritis.
Background
Osteonecrosis (ON) is a generic term for death of bone constituents secondary to ischemia. The term‘ avascular necrosis’ is often used to describe epiphyseal or subarticular bone involvement, while ‘bone infarction’ is often used for metadiaphyseal sites[2].
Commonest sites include head of femur and humerus, knee, femoral/tibial metadiaphysis, and carpals and tarsals like scaphoid, lunate, and talus [1].
Pathophysiology and clinical features
Similar to other organs of the body, ON occurs as a result of reduction of complete loss of blood supply to the bone. It is a common condition with most important etiological factors including trauma, chronic corticosteroid therapy, alcoholism, and smoking or sometimes may be idiopathic [1].
Ischemia leads to loss of bone cell metabolic activity and interruption of cell enzymes. This is followed by attempts to repair the area of ON by means of increased reactive vascularity and marrow reaction with increased inflammatory fibrovascular infiltration. Subsequently, secondary osteoarthritis and fragmentation of articular cartilage sets in [1].
Avascular necrosis (AVN) is asymptomatic in early stages. It gradually progresses to joint pain (at first, only on weight-bearing over the joint) and eventually leads to constant pain and discomfort. Pain may be severe if there is involvement of bone and surrounding joint surface collapse. Disabling osteoarthritis may develop in the affected joint. The period of time between the first symptoms and loss of joint function may range from several months to more than a year.
Untreated elbow osteonecrosis can often lead to elbow collapse, with decrease in range on motion [7].
Avascular necrosis is a rare but serious complication in patients who are being treated for ALL, and is usually related to use of corticosteroids.
Imaging Features
MRI is considered as the most sensitive modality and can detect early changes of the disease. On T1W images, a crescentic/band-like (epiphyseal) or serpigineous (meta- diaphyseal) low signal intensity is most often seen. A “double-line sign” on T2W images is considered diagnostic, which is seen as an inner high signal with outer low signal intensity area. The high signal intensity denotes the presence of a hydrated or cellular marrow area, while meaning of the low-signal-intensity component indicates the reactive interface or the peripheral fibrosis or sclerosis[3].
One key feature is the preserved fat signal (T1W) within the ON, representing the dead and mummified fat.
It has been documented that the band-like pattern is the initial finding of the necroticlesion and later the developing bone marrow oedema is considered a marker for potential progression and collapse of the bone[4].
Multi-detector CT helps in accurate assessment of sclerosis, osteophytes, joint space narrowing and subchondral or cancellous bone fracture and collapse [5]. It is a good modality for evaluation of extent of disease and calcifications.
Bone scintigraphy is also quite sensitive and used when multiple sites/joints are affected, for example, sickle cell disease.
Panner's disease is one such condition affecting the elbow joints, particularly capitellum. Although, it typically occurs in children (5-10 years of age) with open growth plates (unlike our case with mature skeleton).
Outcome
Early stages can be managed conservatively. In most cases, however, surgery is the treatment of choice. Core decompression, bone grafting, osteotomy and joint replacement in advanced cases are the usual modalities. The prognosis improves with early diagnosis and initiation of treatment.
Osteonecrosis of the adult elbow can lead to end-stage arthritis, in contrast to the pediatric population. [6]
Being an atypical site and bilateral involvement, with features of osteoarthritis already set in, our patient was managed conservatively and started on bisphosphonate therapy.
Take-Home Message / Teaching Points
The distal humeral epiphysis is a rare site for the development of avascular necrosis. However, it should be considered in the differential diagnosis in the presence of significant risk factors (such as leukaemia in our case) and characteristic imaging findings (particularly serpigineous margins and the presence of interspersed areas of preserved fatty marrow within the signal abnormality).
Avascular necrosis of bilateral distal humeral epiphyses
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Based on the patient’s imaging studies (including X-ray and MRI of the right and left elbows), the following observations were made:
Considering the patient’s history (17 years old, acute lymphoblastic leukemia, long-term corticosteroid use) and the imaging characteristics described above, the potential diagnoses include:
Given the patient’s age, extensive corticosteroid use, bilateral elbow involvement, and the MRI findings of a “band-like low signal” and “double line sign,” the most likely diagnosis is:
Bilateral Avascular Necrosis of the Distal Humerus.
Since the patient is at an early to mid-stage of bone necrosis without marked collapse, the following treatment and rehabilitation strategies can be considered:
Pay close attention to any worsening pain or elbow instability during training. If severe discomfort occurs, discontinue the exercises and seek medical advice promptly.
This report is prepared as a reference based on the available imaging data and medical history. It does not replace in-person clinical diagnosis or the recommendations of a qualified physician. If you have any doubts or if symptoms worsen, it is advised to seek medical attention and undergo further relevant examinations.
Avascular necrosis of bilateral distal humeral epiphyses
