18-year-old woman complaining of shoulder pain.
CT and MR of the shoulder were performed. CT revealed a cortical-based intraarticular low-attenuation lesion (black arrow in Fig. 1, 2) compatible with the nidus of an osteoid osteoma with some internal foci of osteoid mineralization. There was also mild reactive cortical thickening of the humeral metaphysial cortex. MR of the shoulder again showed the intraarticular lesion with low signal intensity on proton density sequences (Fig. 3, 4) and high signal intensity on fluid-sensitive sequences (Fig. 5, 6) with millimetric internal foci of low signal intensity due to mineralization (which is better seen on CT). There was also reactive bone marrow oedema and small joint effusion.
Osteoid osteoma is a benign bone tumour that frequently occurs in the second decade of life and is more frequent in men than in women (2:1). Classically, patients complain of pain that is worse at night and relieves with salicylates. [1]
They may be located in the cortex of the bone or more rarely in the medulla or beneath the periosteum (subperiosteal). [1] Osteoid osteomas are more common in the diaphysis or metaphysis of the femur, tibia, humerus and at the posterior elements of the spine. [1] Less frequently they occur within a joint, where clinical manifestations tend to be atypical and mimic other intraarticular processes. [1-5]
The lesion is usually composed of a nidus of bone at various stages of maturity. On plain films and CT it appears as small (less than 2 cm) round and well-defined radiolucent focus demonstrating a variable amount of central mineralization, surrounded by reactive sclerosis and cortical thickening. [1, 2] On MR the nidus shows low signal intensity on T1WI and variable signal intensity on T2WI depending on the amount of mineralization. [6, 7] MR sometimes fails to show a small nidus because its signal intensity is often similar to that of the cortical bone. Enhancement of the nidus may be seen on both CT and MR after intravenous contrast administration. [1, 8]
In intraarticular osteoid osteomas reactive cortical thickening is often minimal or absent, such as seen in our case. In this setting MR may be particularly useful for the diagnosis as it shows oedema of the bone marrow around the nidus and joint effusion. [1]
Some authors have reported spontaneous regression of osteoid osteomas and that NSAIDs accelerate this process. [9] Due to the intraarticular location of the osteoid osteoma our patient was conservatively treated with NSAIDs and remained free of pain 5 months after treatment initiation. Therapeutic alternatives to medical management include surgical resection and curettage. Recently, minimally invasive procedures such as imaging-guided drill excision and radiofrequency ablation (RFA) has become increasingly used in recent years. Other minimally invasive techniques include cryoablation, arthroscopic excision, ethanol injection, and interstitial laser photocoagulation. [9]
Intraarticular osteoid osteoma
From the provided shoulder CT and MRI images, the following can be observed:
1. A small, clearly defined low-density or relatively low-signal lesion in the humeral head (presenting on CT as a round or oval translucent area with a diameter less than 2 cm, resembling a “nidus”), with mild surrounding sclerotic changes or reactive bone formation. However, because the lesion is intra-articular, the reactive sclerosis is relatively limited.
2. On MRI T1-weighted images, the lesion appears to have low signal intensity, and on T2-weighted images, the signal may be heterogeneous or relatively high. The specific signal intensity may be related to the degree of calcification within the lesion. Bone marrow edema and a small amount of joint effusion can be seen around the lesion.
3. The lesion is localized, with no apparent sign of further bone destruction extending outward. Soft tissue involvement appears minimal, and the overall structure of the joint surface is still intact.
Considering the patient’s age (18-year-old female), clinical symptoms (night pain relieved by NSAIDs), and imaging features (a characteristic nidus < 2 cm, bone marrow edema, and a small amount of joint effusion on MRI), the most likely diagnosis is: Osteoid Osteoma.
If further confirmation is needed, image-guided biopsy or pathological examination can be considered. However, in most cases, the typical clinical and imaging presentations are sufficient for diagnosis.
Treatment Strategy:
1. Conservative Treatment: For patients whose symptoms can be effectively controlled by NSAIDs, such as in this case, conservative treatment can be attempted first, closely monitoring the lesion size and pain relief.
2. Minimally Invasive Interventional Therapy: If symptoms are significant, unresponsive to conservative treatment, or if the patient desires, minimally invasive options include CT-guided radiofrequency ablation (RFA), curettage, laser photocoagulation, or cryoablation.
3. Surgical Resection: For lesions in difficult locations or with serious complications, open surgery or arthroscopic resection may be performed.
Rehabilitation / Exercise Prescription (FITT-VP Principle):
1. Frequency: It is recommended to perform low- to moderate-intensity shoulder and upper limb exercises 3-5 times per week.
2. Intensity: Begin with low-intensity exercises (such as bodyweight or light resistance training). Once pain relief is evident, gradually increase resistance or load.
3. Time: 20-30 minutes per session, with adjustments based on pain and fatigue levels.
4. Type:
- Range of Motion Exercises: Such as shoulder circumduction (within anatomical limits), forward raises, lateral raises, either passively or actively.
- Strength Training: Using light resistance bands or small dumbbells, focusing on strengthening the rotator cuff muscles, deltoid, and related muscular groups.
- Joint Stability Training: For example, core stability exercises or using appropriate positioning and support to train shoulder proprioception and stability.
5. Volume: Determined by weekly frequency and duration per session. In the initial phase, prioritize pain control and gradual recovery of the range of motion.
6. Progression: As the patient’s pain subsides and joint mobility improves, gradually increase exercise intensity, frequency, or resistance, avoiding excessive increments that could exacerbate shoulder pain.
Throughout the rehabilitation process, if marked swelling, severe pain, or other discomfort in the joint occurs, stop exercising and seek medical evaluation. For patients with osteoid osteoma, regular follow-up imaging and pain assessment are necessary to ensure treatment safety and efficacy.
Disclaimer:
This report is for reference only based on the provided information and does not replace an in-person consultation or professional medical advice. If you have any questions, please consult an orthopedic or relevant specialist.
Intraarticular osteoid osteoma
