1. Imaging Findings

Based on the provided MRI images (coronal, sagittal, and axial sequences), different degrees of fluid signal and thickening of the tendon sheath can be observed around the first dorsal compartment near the radial styloid (mainly including the abductor pollicis longus [APL] and the extensor pollicis brevis [EPB]), accompanied by mild edema of adjacent soft tissue. Specifically, the findings include:

• Obvious T2 high signal around the first dorsal compartment, indicating fluid exudation or edema within the tendon sheath.
• Local tendon tissue may show moderate to slightly low signal on PD or T1 sequences. Some areas exhibit thickening and blurred margins, consistent with tenosynovitis or associated tendon disorders.
• The distal radial bony structure appears acceptable, with no apparent osseous abnormalities or fracture lines; other bones around the wrist joint remain relatively intact.
• No obvious large occupying lesion or other special pathological signal in the soft tissues around the distal wrist joint.

2. Potential Diagnoses (Differential Diagnosis)

Based on the patient’s clinical presentation (pain at the radial styloid, positive Finkelstein’s test) and the imaging findings of tendon sheath inflammation and fluid, the following diagnoses should be considered:

1. De Quervain’s tenosynovitis: Chronic overuse and inflammation of the first dorsal compartment (APL and EPB), often related to repetitive hand or wrist movements.
2. Radial-sided wrist arthritis or radial-sided tendon syndrome: If tendon sheath inflammation overlaps with arthritis or other inflammatory conditions, wrist pain may present, often with changes to the articular surfaces or involvement of other tendon compartments.
3. Fracture of the radial styloid or scaphoid: These should be ruled out, though no obvious fracture lines or osseous abnormalities were observed on this patient’s X-ray and MRI.
4. Avascular necrosis of the scaphoid (Kienböck or Preiser’s disease): This would typically manifest with distinct bone signal changes on MRI. No such findings were noted in this case.

3. Final Diagnosis

Considering the patient’s age, typical clinical presentation (pain around the radial styloid, exacerbated by fist closure with ulnar deviation, positive Finkelstein’s test), and MRI evidence of increased fluid signal within the first dorsal compartment tendon sheath and signs of inflammation around the tendon, the most likely diagnosis is:

De Quervain’s tenosynovitis.

4. Treatment Plan and Rehabilitation Program

4.1 Conservative Treatment

• Immobilization and Rest: Use a thumb spica cast or brace to limit excessive thumb and wrist movements and reduce tendon sheath irritation.
• Physical Therapy: Cold or heat therapy, ultrasound, low- or medium-frequency electrical therapy to alleviate local pain and inflammation.
• Medication: Under medical supervision, use nonsteroidal anti-inflammatory drugs (NSAIDs) orally or topically to lessen pain and inflammation. If symptoms are persistent, a corticosteroid injection into the tendon sheath may be considered.

4.2 Surgical Intervention

• If there is no significant improvement after several weeks or months of conservative treatment, or if the condition is severe, surgical release of the tendon sheath may be considered.
• The operation typically involves an incision over the radial styloid to expose the fibrous synovial sheath of the first dorsal compartment, thus reducing friction and pressure on the tendon within the sheath.

4.3 Rehabilitation / Exercise Prescription Suggestions

During rehabilitation, the intensity and volume of hand and wrist activities should be gradually increased according to improvements in pain and function, adhering to the FITT-VP principles (Frequency, Intensity, Time, Type, Progression, and Individualization). Below are brief recommendations:

1. Early Stage (Acute Phase)
   • Frequency: Perform gentle thumb and wrist range-of-motion exercises 1-2 times a day.
   • Intensity: Exercise to a point of no pain or mild soreness, avoiding aggressive stretches.
   • Time: About 5-10 minutes each session, including short practice before and after heat or ultrasound therapy.
   • Type: Light wrist and thumb movements, such as gentle fist closure, wrist flexion/extension, and thumb abduction/adduction.
2. Middle Stage (Inflammation Relief and Functional Recovery)
   • Frequency: 3-4 times per week, gradually increasing as tolerated.
   • Intensity: Introduce light resistance exercises, such as using a soft grip ball or resistance bands for thumb and wrist.
   • Time: 15-20 minutes per session, progressively increasing the duration.
   • Type: Include more arc movements and functional tasks, such as gentle thumb pinch/grasp exercises and wrist circumduction.
3. Late Stage (Strengthening and Relapse Prevention)
   • Frequency: Maintain 3 times per week or more, emphasizing long-term consistency and protection.
   • Intensity: Increase resistance gradually as appropriate, focusing on coordination and flexibility training.
   • Time: 20-30 minutes per session, combined with adjustments of daily tasks to prevent re-injury.
   • Type: Incorporate fine motor training (e.g., pinching small objects, practicing writing) and wrist coordination exercises, avoiding repetitive strain.
4. Individual Adjustments: If the patient has other comorbidities (e.g., wrist arthritis, osteoporosis), exercises should be done within tolerance and under guidance of a therapist or doctor.

Throughout the rehabilitation process, attention should be paid to changes in pain and swelling. If noticeable discomfort occurs after exercising, adjust the intensity or frequency accordingly, and consult with a rehabilitation therapist or specialist.

Disclaimer: This report is based solely on the provided clinical and imaging data for preliminary reference. It does not replace an in-person consultation or the professional diagnosis and treatment advice of a medical doctor. Patients experiencing any severe discomfort should seek further medical evaluation and treatment promptly.