# Clinical Cases: Musculoskeletal Imaging

## Case 1: Colles Fracture (Distal Radius Fracture)

### Patient Demographics
- **Age:** 68 years
- **Sex:** Female

### Chief Complaint
Right wrist pain and deformity after fall

### Presenting Symptoms
The patient fell onto her outstretched right hand while walking her dog when she tripped on an uneven sidewalk. She experienced immediate severe pain in her right wrist and noticed obvious deformity. She has a history of osteoporosis diagnosed 5 years ago but admits she stopped taking her bisphosphonate medication 2 years ago due to concerns about side effects.

### Physical Exam Findings
- **Vital Signs:** BP 148/84 mmHg, HR 92 bpm, Temp 36.6C
- **Right Wrist:**
  - Obvious "dinner fork" deformity with dorsal angulation
  - Significant swelling over the distal radius
  - Point tenderness over the dorsal distal radius
  - Limited range of motion due to pain
  - Intact skin, no open wound
- **Neurovascular:** Radial pulse intact, capillary refill <2 seconds, sensation intact in median, ulnar, and radial nerve distributions
- **Hand Function:** Able to flex and extend fingers, pain with wrist movement

### Imaging Findings and Interpretation
**Wrist Radiographs (PA and Lateral):**

**Posteroanterior (PA) View:**
- Transverse fracture through the distal radius metaphysis, approximately 2.5 cm proximal to the radiocarpal joint
- Radial shortening of 4 mm (compared to ulna)
- Loss of normal radial inclination (normally 22-23 degrees)
- Associated ulnar styloid avulsion fracture
- Radiocarpal joint congruent

**Lateral View:**
- **Dorsal displacement:** Distal fragment displaced dorsally
- **Dorsal angulation:** Loss of normal volar tilt; dorsal angulation of 25 degrees (normal volar tilt 11-12 degrees)
- **Apex volar angulation:** The apex of the fracture angle points volarly
- No volar cortical comminution visible
- Carpal alignment maintained

**Fracture Classification:**
- **Colles Fracture Pattern:** Extra-articular distal radius fracture with dorsal angulation, dorsal displacement, and radial shortening
- **AO/OTA Classification:** 23-A2.2 (extra-articular, metaphyseal, simple with dorsal displacement)
- **Frykman Classification:** Type I (extra-articular radius, no ulnar styloid involvement) - though ulnar styloid IS involved, making this Type II

**Soft Tissue Assessment:**
- Dorsal soft tissue swelling
- No evidence of compartment syndrome clinically
- Fat pad displaced but no suggestion of additional carpal fracture

### Diagnosis
Colles fracture (extra-articular distal radius fracture with dorsal angulation) with associated ulnar styloid fracture, likely pathologic through osteoporotic bone (fragility fracture)

### Management
1. **Immediate:**
   - Closed reduction under hematoma block anesthesia
   - Post-reduction goals: Restore radial inclination >15 degrees, volar tilt 0-15 degrees, radial length within 2-3mm of ulna

2. **Post-Reduction Imaging:**
   - Repeat radiographs show improved alignment
   - Radial inclination: 18 degrees (acceptable)
   - Volar tilt: 5 degrees (acceptable)
   - Radial length: Within 2 mm of ulna

3. **Immobilization:**
   - Sugar tong splint initially for swelling
   - Conversion to short arm cast at 1 week follow-up
   - Total immobilization: 6 weeks

4. **Follow-up Imaging:**
   - Weekly radiographs for first 3 weeks to monitor for displacement
   - Final radiographs at 6 weeks before cast removal

5. **Osteoporosis Management:**
   - Referral to endocrinology/osteoporosis specialist
   - DEXA scan to reassess bone mineral density
   - Restart osteoporosis treatment (discussion of bisphosphonate vs. denosumab)
   - Calcium and Vitamin D supplementation
   - Fall risk assessment and prevention

### Radiological Image

![Colles Fracture X-ray](case_01_image.jpg)

**Image Description:** Lateral radiograph of the wrist demonstrating a classic Colles fracture with dorsal angulation and dorsal displacement of the distal radius fragment. The normal volar tilt is lost, creating the characteristic "dinner fork" deformity seen clinically.

**Source:** Wikimedia Commons - "Colles fracture"
**URL:** https://commons.wikimedia.org/wiki/File:Colles_fracture.JPG
**License:** Creative Commons Attribution 3.0 Unported

---

## Case 2: Anterior Cruciate Ligament (ACL) Tear

### Patient Demographics
- **Age:** 24 years
- **Sex:** Female

### Chief Complaint
Left knee pain and instability after basketball injury

### Presenting Symptoms
The patient was playing recreational basketball when she landed awkwardly after a jump shot. She felt a "pop" in her left knee and experienced immediate pain and swelling. She was unable to continue playing and had difficulty bearing weight. She describes her knee as feeling "unstable" and "like it might give out." She iced the knee and took ibuprofen but presents the following day due to persistent symptoms.

### Physical Exam Findings
- **Vital Signs:** Within normal limits
- **Left Knee:**
  - Moderate effusion with loss of normal knee contour
  - Tenderness along the medial and lateral joint lines
  - Limited range of motion (20-90 degrees) due to pain and swelling
  - **Lachman Test:** Positive with soft endpoint (Grade 2, 5-10mm translation)
  - **Anterior Drawer Test:** Positive
  - **Pivot Shift Test:** Unable to perform due to guarding
  - **McMurray Test:** Equivocal due to pain
  - No varus/valgus laxity at 0 or 30 degrees of flexion
- **Neurovascular:** Intact distally

### Imaging Findings and Interpretation
**Knee Radiographs (AP, Lateral, Sunrise):**
- **Lipohemarthrosis:** Fat-fluid level visible on cross-table lateral view, indicating intra-articular fracture (likely Segond fracture or osteochondral injury)
- **Segond Fracture:** Small avulsion fracture of the lateral tibial plateau at the site of the lateral capsular ligament attachment - pathognomonic for ACL injury
- No other acute fractures
- Joint space maintained

**MRI Knee without Contrast:**

**ACL Findings:**
- **Complete ACL tear:** Discontinuity of ACL fibers with abnormal course
- **Edema:** T2 hyperintense signal within the residual ligament stump
- **Location:** Mid-substance tear (most common)
- **"Empty notch sign":** Absence of normal ACL in the intercondylar notch

**Associated Findings:**
- **Bone Contusions (Kissing contusions):**
  - Lateral femoral condyle: Sulcus deepening and bone marrow edema (pivot shift mechanism)
  - Posterolateral tibial plateau: Bone marrow edema
  - This "kissing contusion" pattern is characteristic of ACL injury
- **Segond Fracture:** Small avulsion at anterolateral tibial plateau confirmed
- **Medial Meniscus:** Intact, no tear
- **Lateral Meniscus:** Posterior horn shows increased signal not reaching articular surface (Grade 2 signal, no tear)
- **MCL:** Intact
- **PCL:** Intact

**O'Donoghue Triad Assessment:**
Classic "unhappy triad" (ACL + MCL + medial meniscus) NOT present. This is an isolated ACL tear with bone contusions.

### Diagnosis
Complete ACL tear, mid-substance, with characteristic bone contusion pattern and Segond fracture

### Management
1. **Acute Phase:**
   - RICE (Rest, Ice, Compression, Elevation)
   - Hinged knee brace locked in extension
   - Crutches, partial weight-bearing as tolerated
   - NSAIDs for pain and inflammation

2. **Prehabilitation:**
   - Physical therapy focusing on:
     - Quadriceps strengthening
     - Range of motion restoration
     - Reduction of swelling
   - Goal: Restore full extension and reduce swelling before surgery

3. **Surgical Planning:**
   - ACL reconstruction recommended given:
     - Young, active patient
     - Desire to return to pivoting sports
     - Symptomatic instability
   - Graft options discussed: Bone-patellar tendon-bone autograft vs. hamstring autograft
   - Surgery scheduled for 4-6 weeks post-injury (after "prehab")

4. **Post-operative Rehabilitation:**
   - Standardized ACL reconstruction protocol
   - Return to sports at 9-12 months if criteria met

### Radiological Image

![ACL Tear MRI](case_02_image.jpg)

**Image Description:** Sagittal T2-weighted MRI of the knee demonstrating a complete ACL tear. The normal taut band of the ACL is absent, with only edematous, discontinuous fibers visible. Associated bone marrow edema (bone contusions) is seen in the lateral femoral condyle and posterolateral tibial plateau.

**Source:** Radiopaedia - Educational image of ACL tear
**URL:** https://radiopaedia.org/articles/anterior-cruciate-ligament-tear
**License:** Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported

---

## Case 3: Osteosarcoma

### Patient Demographics
- **Age:** 16 years
- **Sex:** Male

### Chief Complaint
Progressive left knee pain for 3 months

### Presenting Symptoms
The patient reports gradual onset of left knee pain that began approximately 3 months ago. Initially, he attributed it to a minor injury during soccer practice. The pain has progressively worsened and is now present at rest and at night, disturbing his sleep. He has noticed swelling above his left knee. He denies fevers, weight loss, or other joint involvement. No history of prior malignancy or radiation exposure.

### Physical Exam Findings
- **Vital Signs:** Within normal limits
- **Left Knee/Distal Thigh:**
  - Firm, fixed mass palpable in the distal anterior thigh/suprapatellar region
  - Overlying warmth and prominent superficial veins
  - Tenderness to palpation over the mass
  - Mild knee effusion
  - Knee range of motion mildly limited by pain
  - No erythema or skin breakdown
- **Lymph Nodes:** No palpable inguinal lymphadenopathy
- **Systemic:** No hepatosplenomegaly, no other masses

### Imaging Findings and Interpretation
**Knee Radiographs (AP and Lateral):**

**Aggressive Features:**
- **Location:** Distal femoral metaphysis - classic location for osteosarcoma
- **Bone Destruction:** Mixed lytic and scite pattern with permeative margins
- **Periosteal Reaction:**
  - Aggressive "sunburst" pattern (spiculated periosteal new bone radiating perpendicular to cortex)
  - Codman triangle (elevated periosteum at lesion margin)
- **Tumor Matrix:** Cloud-like osteoid matrix production within the tumor (tumor bone)
- **Soft Tissue Mass:** Extension beyond the cortex with soft tissue component
- **Cortical Destruction:** Disruption of the lateral femoral cortex
- **No Pathologic Fracture:** Cortex thinned but no complete fracture

**Zone of Transition:** Wide and poorly defined - aggressive feature

**MRI Left Femur (Staging):**
- **Tumor Extent:**
  - Intramedullary tumor length: 12 cm
  - Involvement of distal femoral metaphysis and extends into diaphysis
  - Epiphysis: Tumor approaches but does not cross the growth plate
- **Soft Tissue Component:** 6 x 5 x 8 cm heterogeneous mass with areas of necrosis and hemorrhage
- **Neurovascular Structures:** Popliteal vessels displaced but not encased; appears resectable
- **Skip Lesions:** None identified in the femur
- **Joint Involvement:** No definite invasion of knee joint

**CT Chest (Metastatic Workup):**
- Multiple small bilateral pulmonary nodules (largest 8mm)
- Consistent with pulmonary metastases
- No mediastinal lymphadenopathy

**Bone Scan/PET-CT:**
- Intense uptake in distal left femur primary
- Multiple pulmonary metastases with FDG avidity
- No other skeletal lesions

### Diagnosis
Osteosarcoma of the distal femur with pulmonary metastases (Stage IVB); confirmed on biopsy: High-grade conventional osteosarcoma

### Management
1. **Multidisciplinary Tumor Board:**
   - Pediatric oncology, orthopedic oncology, thoracic surgery, radiology, pathology

2. **Biopsy:**
   - Image-guided core biopsy performed with tract planning for future resection inclusion
   - Histology: High-grade conventional osteosarcoma with osteoid production

3. **Neoadjuvant Chemotherapy:**
   - MAP regimen (Methotrexate, Doxorubicin/Adriamycin, Cisplatin)
   - 10-12 weeks prior to surgery
   - Monitor response with MRI

4. **Surgical Resection:**
   - Limb salvage surgery with wide resection and endoprosthetic reconstruction
   - Pathology: 85% tumor necrosis (good response to chemotherapy)
   - Margins negative

5. **Metastasectomy:**
   - Thoracoscopic resection of pulmonary metastases

6. **Adjuvant Chemotherapy:**
   - Continue MAP regimen post-operatively

7. **Surveillance:**
   - Chest CT every 3 months for 2 years, then every 6 months
   - Local MRI every 3-6 months
   - Functional assessment and prosthesis evaluation

### Radiological Image

![Osteosarcoma X-ray](case_03_image.jpg)

**Image Description:** Radiograph of the distal femur demonstrating osteosarcoma with characteristic aggressive features including the "sunburst" periosteal reaction (spiculated new bone radiating perpendicular to the cortex), Codman triangle (elevated periosteum at the tumor margin), tumor matrix ossification, and soft tissue mass extending beyond the destroyed cortex.

**Source:** Wikimedia Commons - "Osteosarcoma radiograph"
**URL:** https://commons.wikimedia.org/wiki/File:Osteosarcoma_-_high_mag.jpg
**License:** Creative Commons Attribution-Share Alike 3.0 Unported

---

## Learning Points

1. **Colles Fracture Characteristics:** The classic distal radius fracture pattern with dorsal displacement, dorsal angulation, and radial shortening. Post-reduction radiographs should demonstrate restored radial inclination (>15 degrees), volar tilt (0-15 degrees), and radial length. Fragility fractures warrant osteoporosis evaluation.

2. **ACL Tear Imaging:** MRI is the gold standard for diagnosing ACL tears. Associated findings include "kissing contusions" of the lateral femoral condyle and posterolateral tibial plateau, Segond fracture (pathognomonic), and lipohemarthrosis on radiographs.

3. **Aggressive vs. Benign Bone Lesion Features:**
   - **Aggressive:** Wide zone of transition, permeative destruction, aggressive periosteal reaction (sunburst, Codman triangle), soft tissue mass
   - **Benign:** Narrow zone of transition, sclerotic margins, solid periosteal reaction, no soft tissue mass

4. **Osteosarcoma Imaging Approach:** Radiographs identify the lesion and suggest aggressiveness. MRI determines local extent and surgical planning. CT chest evaluates for pulmonary metastases. Bone scan or PET-CT screens for skeletal metastases and skip lesions.