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Updated: Jan 10 2024

Proximal Tibiofibular Joint Ganglion Cysts

Images
https://upload.orthobullets.com/topic/423108/images/1e1188a7-b5f5-4a65-af6e-efc77c60c417_ptfj_cyst_xr.jpg
https://upload.orthobullets.com/topic/423108/images/2b646eb7-5178-45a6-ba74-708994feb9cd_t1_ptfj_cyst.jpg
https://upload.orthobullets.com/topic/423108/images/22131aca-de99-4d0e-9bca-167eabbda2da_t2_ptfj_cyst.jpg
  • Summary
    • Proximal tibiofibular joint ganglion cyst is a rare, mucin-filled synovial cyst. They typically are seen in adults and present with lateral knee pain, fullness, and neurological symptoms due to compression of the common peroneal nerve. 
    • Diagnosis is often initially made based on typical MRI findings and is confirmed histologically.  
    • Nonoperative treatment is indicated for asymptomatic lesions. Operative treatment is indicated for persistent symptoms or associated neurological deficits. 
  • Epidemiology
    • Incidence
      • <1% of patients undergoing MRI for knee pain
    • Demographics
      • age range: 20-76 years old
      • median age: 67 years old
      • male (90%)
    • Location
      • more commonly found in right leg (~70%)
      • extraneural (80%) > intraneural (20%)
  • Etiology
    • Pathophysiology
      • mechanism of injury 
        • repetitive microtrauma   
        • degenerative
      • pathoanatomy
        • mucin-filled synovial cell lined sac without a true epithelial lining
      • cell biology
        • walls contain sheets of collagen fibers
        • mucinous material is highly viscous due to high concentration of hyaluronic acid and mucopolysaccharides
    • Associated conditions
      • osteoarthritis 
  • Anatomy
    • Osteology
      • fibular head sits in groove behind lateral tibial ridge
        • limits anterior fibular movement with knee flexion
    • Arthrology
      • proximal tibiofibular joint 
        • articulation of the lateral tibial plateau of the tibia and fibular head
    • Ligament
      • PTFJ capsule stabilizers 
        • anterior and posterior tibiofibular ligaments
        • lateral collateral ligament 
        • popliteus
        • biceps femoris tendons 
    • Muscles
      • long head of biceps femoris
        • insertion 
          • posterior to short head on fibular head
        • innervation
          • tibial nerve
      • short head of biceps femoris
        • insertion
          • anterior to long head on fibular head
        • innervation 
          • common peroneal nerve
    • Blood Supply
      • anterior tibial artery
        • passes just distal to PTFJ
    • Nervous System
      • common peroneal nerve 
        • courses laterally around the fibular neck
        • two branches 
          • superficial peroneal nerve  
          • deep peroneal nerve 
    • Biomechanics
      • PTFJ
        • anterolateral and posteromedial sliding movement of PTFJ
          • reduces torsional forces from the ankle
          • disperses axial load while standing
  • Classification
    • Location of tumor
      • intraneural
        •  within epineurium
      • extraneural 
        • outside of epineurium 
  • Presentation
    • Symptoms 
      • usually asymptomatic 
      • if symptomatic 
        • pain
        • palpable mass
        • fullness
        • paresthesias
    • Physical exam
      • inspection
        • mass near lateral aspect of knee
      • palpation
        • freely mobile, circumscribed palpable mass
      • neurological exam 
        •  foot drop due to common peroneal nerve compression  
  • Imaging
    • Radiographs
      • recommended views
        • AP and lateral of knee and tibia
      • findings
        • typically unremarkable
        • may see sclerotic lesions on lateral aspect of proximal tibia
    • MRI
      • indications
        • persistent symptoms 
        • neurological deficits
      • findings
        • well-circumscribed cystic homogenous structure
        • low signal on T1  
        • high signal on T2 
    • Ultrasound
      • indications
        • unable to undergo an MRI
      • findings
        • fluid filled cyst with thin wall
  • Studies
    • Labs
      • typically unremarkable
    • Invasive studies
      • Histology
        • gross anatomy
          • cystic structure with thin wall
          • gelatinous material
        • microscopic analysis 
          • absence of true epithelial lining
          • no nuclear atypia or mitotic activity
      • EMG and NCS
        • adjunct to MRI to determine the extent of sensory and motor dysfunction
  • Differential
    • Differential diagnosis  
      • Aneurysmal bone cyst
      • Chondroblastoma
      • Giant-cell tumor
      • Juxta-articular myxomas
      • Lumbar disc herniation 
      • Pigmented villonodular synovitis 
      • Solid nerve tumors
  • Diagnosis
    • Diagnostic criteria 
      • MRI is diagnostic tool of choice if typical features and enhancement patterns are present
      • Histological analysis can be used to confirm diagnosis   
  • Treatment 
    • Nonoperative
      • observation, NSAIDS, aspiration
        • indications
          • asymptomatic
          • initial management for symptomatic lesions
      • technique 
        • observation
        • NSAIDs
        • aspiration
          • some studies show aspiration is ineffective due to risk of recurrance
      • outcomes
        • may spontaneously resolve but high risk of recurrence
    • Operative
      • surgical decompression and marginal excision 
        • indications
          • failed nonoperative treatment 
          • progressive neurologic symptoms 
        • outcomes
          • generally good outcomes with lower rates of recurrence (8-25%)
      • proximal tibiofibular joint arthrodesis (PTFJ fusion) 
        • indications
          • cyst recurrence after the first resection
        • techniques
          • 6.5mm partially threaded cancellous screw
        • outcomes
          • lowest rate of recurrence (<5%) 
  • Techniques
    • Nonoperative 
      • technique
        • symptomatic treatment
        • aspiration to decompress
      • complications
        • high rate of recurrence with aspiration alone (80%)
    • Decompression and Marginal Excision 
      • technique 
        • hockey-stick lateral approach 
        • dissect cyst from common peroneal nerve and perform neurolysis 
        • excise stalk from joint 
        • additional options
          • proximal tibiofibular joint arthrodesis
          • fibular head resection
      • complications
        • recurrence (8-25%)
        • neuropraxia
        • perineural fibrosis
    • PTFJ arthrodesis 
      • indications 
        • failed nonoperative management 
        • recurrent cyst
      • technique
        • hockey stick lateral approach
        • removal of PTFJ cartilage
        • arthrodesis with 6.5mm partially threaded cancellous screw 
      • complications
        • recurrence (<5%)
  • Complications
    • Peroneal nerve dysfunction
      • indicence 
        • up to 50%
      • risk factors
        • intraneural cyst
      • treatment
        • surgical decompression
          • consider tendon transfer if complete nerve palsy  
    • Recurrence
      • incidence
        • 5-80%
      • risk factors
        • treatment with aspiration only (80% recurrence)
      • treatment 
        • observation 
          • asymptomatic 
        • arthrodesis 
          • symptomatic  
    • Hardware irritation
      • risk factor
        • arthrodesis
      • treatment 
        • hardware removal 
  • Prognosis
    • Natural history of disease / Prognosis without treatment
      • may resolve but higher likelihood of recurrence 
    • Prognostic variable
      • negative
        • prolonged duration of neurologic symptoms
    • Survival with treatment
      • good outcomes with low rate of recurrence 
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