1. Imaging Findings

The patient is a 35-year-old female presenting with swelling, redness, and pain in the big toe. She has a history of multiple surgeries in the same area due to ingrown toenails.

• Plain Radiograph (X-ray): Shows a relatively obvious lucent area at the distal phalanx of the first toe, displaying a lytic lesion with clearly defined margins and no notable periosteal reaction.
• MRI: The lesion appears as low to intermediate signal on T1-weighted images and high to intermediate signal on T2-weighted images. An expansile change is observed within the lesion, with evident peripheral enhancement but no obvious internal enhancement, suggesting the blood supply mainly arises from the peripheral capsule.
• Diffusion Weighted Imaging (DWI): Specific regions show restricted diffusion, indicating the likely presence of high-density keratinous material or cholesterol within the lesion.

In summary, the lesion presents cystic or cyst-like features with localized expansile destruction.

2. Potential Diagnoses

Based on the imaging findings and clinical history, the following diagnoses should be considered:

• Dermoid/Epidermoid Cyst (Intraosseous Epidermal Cyst): Often occurs after repeated surgeries or trauma in which local skin/epidermal cells are embedded into the bone. MRI typically shows restricted diffusion and peripheral enhancement, aligning with the history and imaging characteristics of this case.
• Osteomyelitis: Clinically associated with redness, swelling, heat, pain, as well as elevated white blood cell count or inflammatory markers. However, in this case, laboratory tests (white blood cell count and PCR) are largely normal, making this diagnosis less likely.
• Aneurysmal Bone Cyst (ABC): Can show expansile lytic lesions. On MRI, internal septations or fluid-fluid levels are often visible, and restricted diffusion is usually not prominent.
• Giant Cell Tumor (GCT): Commonly found in individuals aged 20–40 and often located at the epiphysis of long bones. MRI of GCT typically shows more central enhancement rather than peripheral, and the pathology also does not match this case.
• Enchondroma: Frequently shows calcification within the cartilaginous matrix (visible as calcific foci on X-ray or CT). In this case, no significant calcification is seen, and the MRI pattern does not match a typical enchondroma.

3. Final Diagnosis

Considering the patient’s history of multiple local surgeries, imaging findings (lytic lesion, peripheral enhancement, restricted diffusion), and postoperative pathological results, the most likely diagnosis is:

Intraosseous Epidermal Cyst.

This diagnosis correlates well with repeated local surgical procedures leading to the displacement of skin or epidermal cells.

4. Treatment Plan and Rehabilitation Program

4.1 Treatment Strategy

• Surgical Treatment: For a confirmed intraosseous epidermal cyst, the usual approach is complete excision or curettage of the cyst wall with thorough removal of the cyst contents. If necessary, bone grafting or local filling may be performed for repair.
• Medical Treatment: In the event of suspected infection, antibiotics can be administered based on culture and sensitivity testing. If no infection is present, prophylactic antibiotics are generally not required.
• Postoperative Care: Care should be taken to prevent further trauma or local compression at the surgical site, and regular imaging follow-up is recommended to rule out recurrence.

4.2 Rehabilitation and Exercise Prescription

The principle of postoperative rehabilitation is to restore foot function progressively, avoiding excessive load during bone healing and soft tissue recovery. An individualized approach should be adopted. The following is a brief guideline according to the FITT-VP principles (Frequency, Intensity, Time, Type, Progression, and Volume):

• F (Frequency): During the first two weeks, low-intensity ambulation can be done 1–2 times per day, avoiding prolonged standing. As pain and swelling improve, gradually increase the duration of each session.
• I (Intensity): Begin primarily with non-weight-bearing or partial weight-bearing exercises (e.g., short-distance walking on flat ground, gentle toe flexion and extension). As pain and swelling significantly subside, transition to normal gait training.
• T (Time): Start with 5–10 minutes per session, increasing to 15–20 minutes as tolerated. In the intermediate stage, once bone healing is confirmed to be progressing well, further extension of exercise time is permissible.
• T (Type): Focus on low-impact activities such as swimming or cycling (seated stationary bike during rehabilitation) to reduce forefoot impact. Incorporate foot muscle strengthening, such as toe-grip exercises and plantarflexion/dorsiflexion exercises.
• V (Volume): Adjust the total daily exercise volume according to progress, generally keeping it within 30 minutes per day, divided into multiple sessions, as long as pain and swelling are manageable.
• P (Progression): Conduct an evaluation every 2–3 weeks. If recovery is favorable, gradually increase exercise duration and intensity. If significant pain or discomfort occurs, progression should be paused or slowed.

Throughout rehabilitation, closely monitor the foot for swelling, pain, and skin condition. If any worsening or other concerning symptoms occur, seek re-evaluation or adjust the rehabilitation plan promptly.

Disclaimer

This report provides a reference analysis based on the available information and does not replace an in-person clinical consultation or professional medical advice. If there are any questions or changes in your condition, please seek prompt medical attention or consult a specialist for further evaluation and treatment.