Shoulder pain after a fall.
The patient was admitted to the Accident & Emergency department with complaints of pain in his arm after a fall. Plain radiographs of the left shoulder and humerus were performed.
Plain films of the left shoulder and humerus showed a well-defined radiolucent lesion with cortical thinning and a thin sclerotic margin with a short zone of transition. A pathological fracture was seen along the lateral margin of the cyst. These findings are in keeping with a simple bone cyst with a pathological fracture.
Unicameral bone cysts/solitary bone cysts are fluid-filled cysts in the bone, lined by compressed fibrous tissue. They are probably the only true primary cysts of bone. They are solitary, unilocular or rarely multilocular, and usually occur the long bones of a growing child, especially the upper part of the humerus (50-60% of caes) or the upper part of the femur (25-30%). Other bones are rarely affected. They occur between the ages of 5 and 15. In older children and young adults, they tend to occur in the flat bones (pelvis/jaw/skull or the calcaneus).
The cysts are considered benign. They do not metastasise beyond the bone and tend to heal spontaneously. The pathogenesis of the lesion is believed to be due to blocked venous drainage in the bone leading to oedema and ultimately cyst formation. The cyst develops just below the epiphyseal plate and above the diaphysis and eventually can grow to fill the bone. Cortical bone is resorbed by the cyst. The cavity is lined with connective tissue and is filled with serous fluid. The overlying bone is thin, and the functional width of the bone is reduced, causing the bone to fracture easily at the site of the cyst. The cysts usually present after a trivial trauma and occasionally are incidental findings.
Radiologically, a centrally located radiolucent lesion with cortical thinning and mild osseous expansion is noted. They have a thin sclerotic margin with a short zone of transition, with the long axis parallel to the bone. They start as a metaphyseal lesion and move to the diaphysis and may even reach the junction of the middle and distal thirds by which time they usually heal. There is no periosteal reaction in the absence of fracture. Pathological fracture is common and is associated with a vertical fragment within the cyst, which is seen in the dependant portion of the lesion and moves with gravity indicating the presence of fluid and possibly benignity. This is often called the "fallen fragment sign". Plain films are adequate for the diagnosis and other imaging methods are rarely required. CT can evaluate the extent of the lesion and MR imaging confirms the fluid content. Differential diagnosis is rarely difficult, with fibrous dysplasia, Brodie's abscess, aneurysmal bone cysts, and brown tumours sometimes giving similar appearances.
Fractures are the most common complication with no significant displacement of the fracture fragments. Complete healing is seen following conservative management. Refracture and deformity is uncommon. Cementoma can occur in 10-15% of cases and is common in cysts occurring in the proximal femur. Malignant transformation is rare.
Treatment is aimed primarily at preventing recurrent fractures. Bone grafting/curettage is performed in a few cases, where the fluid is aspirated and the lining tissue is completely curetted. The remaining cavity is then packed with donor bone tissue (allograft), bone chips taken from another bone (autograft) or other materials. Steriod (methylprednisone) injection is used in a few cases to heal the cavity.
Simple (unicameral) bone cyst
Based on the provided shoulder X-ray, an obvious radiolucent area (low-density region) can be seen in the proximal humerus (below the shoulder joint). This radiolucent area has relatively clear margins and appears as a unilocular change. The surrounding cortex is thinned but remains continuous. The lesion is mainly confined to the proximal humeral medullary cavity, with no significant periosteal reaction or soft tissue swelling observed. Given the history of a fall and the thin cortex in children, there may be a mild fracture visible at the lesion site. In some cases, a “fallen fragment sign” may be present, whereby a small fragment of bone is visible floating within the cystic lesion and can move with changes in body position, suggesting the lesion contains fluid.
Taking into account the patient’s age (11 years) and the X-ray findings, the following diagnoses or differential diagnoses are considered:
This is most common in children and adolescents aged 5 to 15 years, typically occurring in the proximal humerus or proximal femur. The classic presentation is a localized radiolucent area with a thin cortex, which can fracture with minimal trauma. If a floating fragment of bone is observed, known as the “fallen fragment sign,” it is highly specific for this diagnosis.
This can also present with cystic changes and bone expansion, but it often appears multiloculated and is frequently associated with a marked periosteal reaction. It predominantly occurs in adolescents aged 10 to 20 years.
This usually shows a “ground glass” appearance of the bone with relatively irregular lesion margins and possible cortical expansion.
Typically, there are signs of inflammation or infection, such as periosteal reaction or evident soft tissue swelling. The patient may also have fever, local redness, or swelling.
Considering the patient’s age (11 years), clinical presentation (shoulder pain after a fall), and the X-ray showing a localized lytic lesion, thinning of the cortex, and a possible “fallen fragment sign,” the most likely diagnosis is Unicameral Bone Cyst (UBC).
Treatment Strategy:
1) Conservative Treatment: For cases without significant pathological fracture displacement or smaller lesions, observation and regular follow-up may be sufficient. If there is a minor fracture with good alignment, immobilization (e.g., casting or bracing) can be used until the fracture heals spontaneously.
2) Medication: In certain cases, intralesional injection of corticosteroids (e.g., methylprednisolone) can facilitate cyst healing.
3) Surgical Intervention: If the lesion is large or there is a persistent or recurrent risk of fracture, curettage of the lesion and bone grafting (either autograft or allograft) may be considered. Internal fixation can be used as needed to enhance stability.
Rehabilitation and Exercise Prescription (FITT-VP Principle Example):
1) Early Rehabilitation (Initial Fracture Healing Phase):
- Frequency: 3–4 times per week.
- Intensity: Limited to a level that does not cause significant pain; can include gentle passive shoulder movements and mild shoulder muscle strength exercises (e.g., finger wall-climbing, pendulum exercises).
- Time: 10–15 minutes per session, gradually increasing to 30 minutes.
- Type: Mainly light joint movement and bodyweight muscle exercises for the affected limb, avoiding weight-bearing activities.
- Progression: Increase the range and number of movements gradually as the fracture heals, avoiding excessive stretching or lifting heavy objects.
2) Mid Rehabilitation (Late Fracture Healing Phase):
- Frequency: 3–5 times per week.
- Intensity: Gradually increase range-of-motion exercises and introduce mild resistance training (e.g., with resistance bands).
- Time: 20–30 minutes per session.
- Type: Shoulder joint active movement and resistance band exercises to strengthen muscles; increase arm movement range, including abduction and elevation, but maintain controlled movements.
- Progression: Adjust resistance and training volume gradually based on the patient’s tolerance, closely monitoring for shoulder pain or fatigue.
3) Late Rehabilitation (Functional Recovery Phase):
- Frequency: 3–5 times per week.
- Intensity: Progressively approach normal activity levels by gradually increasing strength and coordination exercises.
- Time: 30 minutes or more per session.
- Type: Under professional guidance, carry out flexibility and strength training for the shoulder, such as using light dumbbells or other equipment; combine with whole-body aerobic exercises (e.g., jogging, swimming).
- Progression: Progress gradually according to bone healing and shoulder functionality while avoiding repeated high-impact activities or trauma.
Throughout the rehabilitation process, closely monitor changes in shoulder pain, swelling, or limited movement. If there is any significant worsening or new discomfort, seek medical advice promptly.
Disclaimer:
This report is a reference analysis based on the available information and does not replace an in-person consultation or the advice of a professional doctor. If you have any questions or if your condition changes, please seek medical attention or consult a qualified healthcare professional.
Simple (unicameral) bone cyst
