• Tibial division
    • motor
      •  semitendinous 
      •  semimembranous 
      •  long head biceps femoris 
      • topic gastrocnemius 
      • topic popliteus 
      •  plantaris 
      •  soleus 
      •  tibialis posterior 
      •  flexor digitorum longus 
      •  flexor hallucis longus 
    • sensory innervation
      • none
  • Peroneal division 
    • motor
      •  abductor hallucis 
      •  flexor digitorum brevis 
      •  flexor hallucis brevis 
      •  foot lumbricals 
      •  quadratus plantae 
      •  flexor digiti minimi 
      •  adductor hallucis 
      •  foot interossei
      •  abductor digiti minimi 
    • sensory 
      • articular branch to knee joint
      • sural nerve branch
        • runs distal with the small saphenous vein
        • anastomoses with a branch from the peroneal nerve
        • continues distal on lateral aspect of the Achilles tendon
        • terminates as the lateral dorsal cutaneous nerve of the foot
  • common peroneal nerve
    • motor
      •  short head of biceps femoris
    • deep peroneal nerve 
      • motor 
        • leg
          •  tibialis anterior  
          •  extensor digitorum longus  
          •  peroneus tertius  
          •  extensor hallucis longus   
        • foot
          • extensor digitorum brevis (lateral terminal branch)
          • extensor hallucis brevis  (lateral terminal branch)
      • sensory  
        • articular branch to the ankle joint    
        • medial terminal branch: 1st dorsal webspace
    • superficial peroneal nerve 
      • motor 
        • lateral compartment of leg
          •  peroneus longus 
          •  peroneus brevis   
      • sensory  
        • majority of skin on the dorsum of foot, excluding webspace between hallux and second digit (deep peroneal nerve)    
        • anterolateral distal 1/3 of leg
  • The sciatic nerve originates from lumbosacral plexus L4-S3 
    • tibial division
      • orginates from anterior preaxial branches of L4,L5,S1,S2,S3
    • peroneal division
      • originates from from postaxial branches of L4,L5,S1,S2
  • Exits sciatic notch 
    • runs anterior or deep to piriformis
    • runs posterior or superficial to short external rotators (superior gemellus, inferior gemellus, obturator internus)  
  • Posterior leg
    • It then runs down the posterior leg where it breaks into its three main divisions at the level of the mid thigh
  • Terminal branches
    •  common peroneal nerve
    •  tibial nerve
Injury & Clinical Conditions
  • Iatrogenic Injury
    • methods to prevent injury
      • routine visual identification not advised in primary THA
      • palpation recommended
      • visual identification is recommended in revision THA
      • hip extension, knee flexion decreases tension on nerve

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Questions (1)

(OBQ11.108) During total hip arthroplasty (THA) via a posterior approach, where is the sciatic nerve most likely to be found? Review Topic


Superficial to the piriformis and superficial to the short external rotators




Superficial to the piriformis and deep to the short external rotators




Deep to the piriformis and deep to the short external rotators




Deep to the piriformis and superficial to the short external rotators




Splits the piriformis and is superficial to the short external rotators



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During the posterior approach to the hip, the most predictable course of the sciatic nerve is deep to the piriformis and superficial to the short external rotators exiting above the superior gemellus. As such, most recommend identification of the sciatic nerve by palpation in primary THA. In revision THA, many advocate identification of the sciatic nerve by both palpation and direct visualization.

The most common anatomic variant in the relationship of the short external rotators and the sciatic nerve is with the sciatic nerve traveling between the capsule and the short external rotators exiting below the superior gemellus.

Smoll reviewed the anatomy of the gluteal region and sciatic nerve anomalies in a meta-analysis and review of over 6000 cadavers. They concluded that the anomalies were present in about 16.8% of cadavers. They recommended a heightened awareness of the anomalies in hip surgery. The most common variants are found in Illustration D which were also supported by an earlier Beaton et al study.

Illustrations A,B and C depict the anatomy of the gluteal region including the anatomic relationship of the sciatic nerve to the short external rotators.


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