# Clinical Cases: Pediatric Musculoskeletal Disorders ## Case 1: Septic Arthritis of the Hip ### Patient Demographics - **Age:** 3-year-old male - **Sex:** Male ### Chief Complaint "He won't walk and cries when we try to move his leg." ### History of Present Illness A 3-year-old boy is brought to the emergency department because he refuses to walk since this morning. Yesterday evening, his parents noticed he was limping and seemed fussy. Overnight, he developed fever to 39.5C. Today he will not bear weight on his right leg and cries out when anyone tries to move his hip. He has no history of trauma. He had an upper respiratory infection one week ago that resolved without treatment. He has been previously healthy with no prior hospitalizations. ### Physical Examination - **Vital Signs:** Temperature 39.2C, HR 132 bpm, RR 24/min, BP 90/60 mmHg - **General:** Ill-appearing, irritable child lying with right hip flexed, abducted, and externally rotated - **HEENT:** Normal - **Cardiovascular:** Tachycardic, regular rhythm, no murmurs - **Respiratory:** Clear to auscultation - **Abdomen:** Soft, non-tender - **Musculoskeletal:** Right hip held in flexion, abduction, and external rotation; severe pain with any passive range of motion of right hip; minimal pain with knee or ankle examination; no erythema or warmth over hip (deep joint) - **Neurologic:** Unable to assess gait; moves all extremities when not touching right leg ### Laboratory Findings - **WBC:** 18,500/uL with 82% neutrophils (elevated) - **ESR:** 65 mm/hr (elevated) - **CRP:** 8.5 mg/dL (elevated) - **Blood culture:** Pending - **Hip ultrasound:** Right hip effusion present - **Hip arthrocentesis:** Turbid yellow fluid; WBC 85,000/uL with 92% neutrophils; Gram stain shows gram-positive cocci in clusters ### Diagnosis **Septic arthritis of the right hip (Staphylococcus aureus)** ### Clinical Reasoning This child meets all four Kocher criteria for septic arthritis: fever >38.5C, non-weight-bearing, ESR >40 mm/hr, and WBC >12,000/uL. With all four criteria positive, the probability of septic arthritis exceeds 99%. The hip is held in the position of maximum capsular volume (flexion, abduction, external rotation) to minimize intra-articular pressure. Hip ultrasound confirms effusion, and arthrocentesis reveals purulent fluid with high WBC count and gram-positive cocci. The hip joint is a surgical emergency because increased intra-articular pressure can compromise blood supply to the femoral head, leading to avascular necrosis. ### Management 1. **Emergent surgical drainage:** Open arthrotomy or arthroscopic drainage of the hip joint (hip requires operative drainage unlike some other joints) 2. **Intravenous antibiotics:** Nafcillin or cefazolin for MSSA; add vancomycin if MRSA suspected or in high-prevalence areas 3. **Blood and synovial fluid cultures:** Guide antibiotic adjustment once sensitivities available 4. **IV antibiotics duration:** Minimum 3-4 weeks total; transition to oral when clinically improved and CRP trending down 5. **Monitoring:** Serial CRP to monitor treatment response (should decline within 3-5 days) 6. **Physical therapy:** Early mobilization once acute infection controlled ### Clinical Image ![Child with septic hip in position of comfort](case_01_image.jpg) **Image Description:** A child with septic arthritis of the hip demonstrating the characteristic position of comfort with the hip flexed, abducted, and externally rotated to maximize joint capsule volume and minimize intra-articular pressure. **Source:** Radiopaedia **URL:** https://radiopaedia.org/cases/septic-arthritis-hip-paediatric **License:** CC BY-NC-SA 3.0 --- ## Case 2: Slipped Capital Femoral Epiphysis ### Patient Demographics - **Age:** 13-year-old male - **Sex:** Male ### Chief Complaint "My knee hurts and I've been limping for about a month." ### History of Present Illness A 13-year-old obese boy presents with a one-month history of progressive right knee pain and limping. The pain is dull, located in the anterior thigh and knee, and worsens with activity. He denies any specific injury. He has not had fever, swelling, or night pain. His mother notes that he seems to walk with his foot turned outward. He plays basketball recreationally but has had to stop due to the pain. His past medical history is notable for obesity (BMI 32 kg/m2, >99th percentile). ### Physical Examination - **Vital Signs:** Temperature 36.8C, HR 82 bpm, BP 118/74 mmHg - **General:** Obese adolescent male, appears comfortable at rest - **Height:** 165 cm (75th percentile) - **Weight:** 87 kg (>99th percentile) - **BMI:** 32 kg/m2 (>99th percentile) - **Gait:** Antalgic gait with right leg externally rotated - **Right hip:** Limited internal rotation (10 degrees vs 40 degrees on left); obligate external rotation with hip flexion; no tenderness over hip - **Right knee:** No effusion, full range of motion, no tenderness - **Left hip and knee:** Normal examination ### Imaging Findings - **AP pelvis radiograph:** Subtle widening of the right proximal femoral physis - **Frog-leg lateral radiograph:** Posterior displacement of the right femoral epiphysis relative to the metaphysis; Klein's line (line along superior femoral neck) does not intersect the epiphysis on the affected side; "ice cream falling off the cone" appearance ### Diagnosis **Slipped capital femoral epiphysis (SCFE), right hip, stable** ### Clinical Reasoning This obese adolescent male presents with the classic SCFE profile: insidious onset hip/thigh/knee pain, limp, and limited internal rotation with obligate external rotation during hip flexion. The referral of hip pain to the knee is common and may delay diagnosis if hip examination is not performed. His ability to bear weight classifies this as a "stable" SCFE, which has a much lower risk of avascular necrosis than unstable SCFE. The frog-leg lateral radiograph demonstrates the pathognomonic posterior slippage of the epiphysis. Risk factors include obesity (mechanical stress on the physis), male sex, and the adolescent growth spurt. ### Management 1. **Non-weight-bearing:** Immediately; use crutches or wheelchair until surgery 2. **Urgent orthopedic surgery:** In situ screw fixation within 24-48 hours to prevent further slippage 3. **NO REDUCTION ATTEMPTS:** Attempting to reduce the slip increases avascular necrosis risk 4. **Contralateral hip:** Evaluate carefully; prophylactic pinning considered in high-risk patients (young age, obesity, endocrine disorders) 5. **Endocrine evaluation:** Consider thyroid function tests if atypical presentation (younger age, bilateral, not obese) 6. **Long-term follow-up:** Monitor for AVN, chondrolysis, and early osteoarthritis ### Clinical Image ![Frog-leg lateral radiograph showing SCFE](case_02_image.jpg) **Image Description:** Frog-leg lateral radiograph of the pelvis demonstrating slipped capital femoral epiphysis with posterior displacement of the femoral epiphysis relative to the metaphysis, described as "ice cream falling off the cone." **Source:** Radiopaedia **URL:** https://radiopaedia.org/cases/slipped-capital-femoral-epiphysis-1 **License:** CC BY-NC-SA 3.0 --- ## Case 3: Developmental Dysplasia of the Hip ### Patient Demographics - **Age:** 6-week-old female - **Sex:** Female ### Chief Complaint Newborn screening examination reveals hip abnormality. ### History of Present Illness A 6-week-old female infant is referred to orthopedics after her pediatrician noted an abnormal hip examination at the 1-month well-child visit. The infant was born at 39 weeks via cesarean delivery due to frank breech presentation. Birth weight was 3.2 kg. She is the first-born child. The parents report no concerns; the baby is feeding well and meeting developmental milestones. Family history reveals that the mother was treated for "hip problems" as an infant. ### Physical Examination - **Vital Signs:** Weight 4.1 kg (50th percentile), Length 54 cm (50th percentile) - **General:** Alert, active infant in no distress - **Hips - Right:** - Ortolani maneuver: Negative (no clunk with abduction) - Barlow maneuver: Negative (hip stable with adduction) - Abduction: Symmetric with left - **Hips - Left:** - Ortolani maneuver: Positive - palpable clunk felt as femoral head reduces into acetabulum with hip abduction - Barlow maneuver: Positive - hip subluxes posteriorly with gentle posterior pressure during adduction - Abduction: Mildly limited compared to right - **Extremities:** Equal leg lengths, symmetric thigh folds - **Neurologic:** Normal tone, symmetric reflexes ### Imaging Findings - **Hip ultrasound (Graf method):** - Right hip: Alpha angle 65 degrees (normal >60), beta angle 52 degrees - normal, mature hip - Left hip: Alpha angle 48 degrees (abnormal <60), beta angle 72 degrees - Graf Type IIc, indicating dysplasia with poor acetabular coverage; dynamic instability present ### Diagnosis **Developmental dysplasia of the hip (DDH), left hip** ### Clinical Reasoning This infant has multiple risk factors for DDH: female sex (4:1 female predominance), breech presentation (highest risk factor), first-born status, and positive family history. The positive Ortolani maneuver (reduction clunk) indicates that the hip is dislocated at rest but can be reduced with abduction. The positive Barlow maneuver indicates the hip is unstable and can be dislocated. Hip ultrasound is the appropriate imaging modality before 4-6 months of age (before femoral head ossification) and confirms dysplasia with poor acetabular coverage. Early diagnosis is critical because treatment at this age has excellent outcomes. ### Management 1. **Pavlik harness:** Immediate fitting; maintains hips in flexion (100-110 degrees) and abduction (50-70 degrees) to promote acetabular development 2. **Wearing schedule:** Full-time wear (23 hours/day) for 6-12 weeks until hip is stable 3. **Follow-up:** Weekly ultrasound and clinical examination for first 2-3 weeks to confirm reduction and monitor progress 4. **If Pavlik fails:** Closed reduction under anesthesia with spica casting (typically if diagnosed after 6 months or harness unsuccessful) 5. **Prognosis:** Excellent if treated before 6 months; >95% achieve normal hip development 6. **Screen siblings:** Especially female siblings of affected children ### Clinical Image ![Infant in Pavlik harness for DDH treatment](case_03_image.jpg) **Image Description:** Infant wearing a Pavlik harness, which maintains the hips in flexion and abduction to allow proper acetabular development in developmental dysplasia of the hip. **Source:** Wikimedia Commons **URL:** https://commons.wikimedia.org/wiki/File:Pavlik_harness.jpg **License:** CC BY-SA 4.0