Medical Imaging Analysis Report

I. Imaging Findings

1. X-ray (anteroposterior, oblique, and magnified views of the metatarsal-phalangeal region): In the area around the first metatarsal head and the metatarsophalangeal (MTP) joint, there is a slight change in local bone density, with mild sclerosis or potential destructive signs at the margins. Soft tissue swelling is not pronounced, and the joint space remains acceptable. No obvious fracture line is detected.
2. MRI (T1, T2 FS/STIR, and contrast-enhanced sequences): In the first metatarsal head and the distal phalanx region (including the MTP joint and surrounding sesamoid bones), the following characteristic signal changes are observed:
 • T1-weighted images show areas of low signal, suggesting abnormal bone marrow structure;
 • T2 FS/STIR sequences show high signal, indicating bone marrow edema or inflammatory exudation;
 • After contrast administration, enhancement is seen in this region, suggesting increased local vascular permeability and inflammatory activity.

These imaging findings of bone destruction, bone marrow edema, and associated enhancement are highly suggestive of an infectious process (particularly osteomyelitis). No obvious large-scale soft tissue abscess or other distal complications are noted.

II. Potential Diagnoses

1. Infectious Osteomyelitis:
   Based on the patient’s history of intravenous drug use and local symptoms (pain, redness, warmth, and tenderness), imaging results showing abnormal bone marrow signals align with common radiological features of osteomyelitis. In combination with clinical findings such as fever and elevated laboratory markers (e.g., white blood cell count, CRP, ESR), along with characteristic changes seen in T1/T2 FS on MRI, infectious osteomyelitis should be highly suspected.
2. Non-infectious Bone Marrow Edema (e.g., stress-related changes, occult fracture):
   If only edema is visible on T2 FS sequences while T1 signal remains relatively normal, stress-related bone marrow edema or minor injury might be considered. However, the current images already show a decreased T1 signal, which makes infection or another severe pathology more likely.
3. Gouty Arthritis or Other Inflammatory Joint Disorders:
   The first MTP joint is a common site for gout, but X-ray findings typically show tophi or marked soft tissue swelling and erosions. In this case, there is no typical presence of gouty tophi or significant soft tissue swelling. Considering intravenous drug use, infection remains the primary consideration.
4. Avascular Necrosis (AVN):
   AVN can appear in the sesamoid bones or the metatarsal head, causing abnormal signals. However, it is more common in specific populations (e.g., those on long-term corticosteroids or with alcohol abuse). On MRI, AVN frequently shows the characteristic “double line sign,” whereas findings here are more consistent with an infectious process.

III. Final Diagnosis

Considering the patient’s history (intravenous drug use), clinical presentation (local pain, fever, etc.), laboratory results (if showing elevated white blood cells or infection markers), and imaging findings on X-ray and MRI (abnormal bone signals, low T1 signal, high T2 FS signal with heterogeneous enhancement), the most likely diagnosis is:

Infectious osteomyelitis of the first metatarsal head and related sesamoid bone region (with or without mild joint involvement).

IV. Treatment Plan and Rehabilitation

1. Treatment Strategy

• Antibiotic Therapy: Select antibiotics based on common pathogens (especially Staphylococcus aureus) and sensitivity results. A typical course lasts 4–6 weeks, extended if necessary.
• Surgical Intervention: If there is a localized abscess, a bone abscess, or significant destruction of the joint surface, surgical debridement or removal of the lesion may be considered to reduce local inflammation and promote healing.
• Supportive Treatment: Includes symptomatic management (pain relief, anti-swelling) and nutritional support to aid overall recovery.

2. Rehabilitation/Exercise Prescription (FITT-VP Principle)

After controlling the infection and inflammation, a gradual rehabilitation protocol under the guidance of a professional therapist or physician is recommended. Premature weight-bearing should be avoided to prevent reinjury.

1. Frequency: 3–5 rehabilitation sessions per week; in the early stage, 2–3 times per week might suffice, gradually increasing to 3–5 times.
2. Intensity: Initially, exercises should not cause pronounced pain or obvious swelling of the MTP joint. Slight soreness is acceptable. As the condition improves, the intensity can gradually be increased.
3. Time: Each session should last 15–30 minutes, divided into segments (e.g., rest every 5–10 minutes) to avoid fatigue.
4. Type:
    • Early Stage: Focus on non-weight-bearing or light weight-bearing exercises, such as seated ankle movements or toe-towel curls to maintain foot joint flexibility;
    • Middle Stage: Introduce mild resistance exercises for the lower limbs (e.g., using resistance bands for lateral ankle training), progressing gradually to single-leg balance work to improve coordination and stability;
    • Late Stage: Advance to light treadmill walking or slow outdoor walks, progressively restoring normal gait and daily activities.
5. Volume and Progression: As rehabilitation progresses, incrementally increase the duration and weight-bearing level of each session. For example, increase training volume by 10–20% weekly or biweekly, closely monitoring any pain or swelling.

If the patient has fragile bones or other comorbidities (e.g., poor cardiopulmonary function), exercise intensity and methods should be individually adjusted to ensure safety.

Disclaimer

This report is a reference analysis based on the available imaging and clinical information and cannot replace in-person consultation or professional medical advice. If there are any questions or changes in condition, please seek timely medical attention and follow the recommendations of a specialist.