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Sciatic Nerve

   

 - Anatomy:
    - arises from lumbrosacral plexus: L4, L5, S1, S2, S3;
    - nerve emerges from pelvis below piriformis & enters thigh between ischial tuberosity & greater trochanter;
    - in 10% of patients, the sciatic nerve is separated in greater sciatic foramen by all or part of the piriformis;
    - sciatic nerve is accompanied by PFCN & by inferior gluteal artery and its special branch to nerve;
    - nerve enters thigh beneath lower border of maximus;
    - descends near middle of thigh, lying on adductor magnus muscle & being crossed obliquely by long head of biceps femoris ;
    - nerve usually separates in upper part of popliteal space;

- Tibal Nerve  Branch:
    - from anterion branches of LS plexus: L4, L5, S1, S2, S3;
    - 2 branches from tibial division: below quadratus femoris:
         - upper branch passes to long head of  biceps femoris  & upper portion of semitendinosus;
         - lower branch: innervates lower portion of  semitendinosus  & semimembranous  & ischiocondylar portion of adductor magnus ;

- Common Peroneal Nerve:
    - from posterior branches: L4, L5, S1, S2;
    - nerve to short head of biceps femoris arises from lateral side of sciatic nerve (common peroneal portion) in middle of thigh & enters 
            superficial surface of the muscle;

- Sciatic Nerve in THR: 
    - protection of sciatic nerve in THR
    -
nerve injuries from THR
    - in THR the sciatic nerve may be injured by excessive tension when extremity has been lengthened significantly, especially in pts w/ DDH ;
    - sciatic nerve is at risk during leg lengthening;
    - peroneal division is most often affected;
    - w/ sciatic nerve injury following THR, keep pts leg flexed over side of bed; 
    - if injury was due to traction, the nerve may recover in the relaxed position;

- Sciatic Nerver Injury from Kocher Langenbock Approach;
    - sciatic nerve palsy from Kocher Langenbock Approach;
    - can be prevented by intraop monitoring of amount of tension applied by assistants retracting the nerve;
    - early treatment consists of AFO
    - sciatic nerve recovery may occur over a 3 yr period;
    - tendon transfers are usually not performed unitl 3 yr post op


- References:
  Sciatic nerve palsy after total hip arthroplasty: treatment by modular neck shortening.

  Nerve palsy associated  with total hip replacement. Risk factors and prognosis.

  Contributory factors and etiology of sciatic nerve palsy in total hip arthroplasty.

  Somatosensory-evoked potential monitored during total hip arthroplasty.

  Treatment of sciatic denervation disuse osteoporosis in the rat tibia with capacitively coupled electrical stimulation. Dose response and duty cycle.

  Sciatic paralysis. A complication of bleeding following hip surgery.

  Spontaneous gluteal artery  rupture resulting in compartment syndrome and sciatic neuropathy. Report of a case in Ehlers-Danlos syndrome.

  Paralytic drop foot and gluteal fibrosis after intramuscular injections.

  Extrapelvic compression of the sciatic nerve. An unusual cause of pain about the hip: report of five cases.  
                                                                
  Sciatic Nerve Resection. Is That Truly an Indication for Amputation?  

  Sciatic Nerve Release Following Fracture or Reconstructive Surgery of the Acetabulum