Relationship of Femoral Intramedullary Pins to the Sciatic Nerve and Gluteal Muscles after Retrograde and Normograde Insertion

Abstract

An anatomic analysis of retrograde and normograde intramedullary (IM) pinning of proximal, midshaft, and distal femoral fractures was performed in 28 canine cadavers. For all fracture locations, normograde pins were significantly more cranial in the middle gluteal muscle than retrograde pins (p less than 0.01). There was no significant difference between pinning techniques in craniocaudal position of the IM pin in the superficial gluteal muscle. In distal fractures, normograde pins were placed significantly more lateral than retrograde pins in the superficial gluteal muscle (p less than 0.01). One of 15 normograde pins and 9 of 13 retrograde pins were located in the medial half of the trochanteric fossa. Normograde pins were significantly more lateral in the trochanteric fossa than were retrograde pins in midshaft fractures (p less than 0.01). Normograde pins were significantly (p less than 0.01) farther from the sciatic nerve than retrograde pins when the hip was positioned at coxofemoral flexion angles of 85 degrees in midshaft and 110 degrees in distal fractures. Seven of 13 retrograde pins, but none of 15 normograde pins, contacted the sciatic nerve. Normograde pinning of the femur may be less likely to induce sciatic nerve injury, particularly in midshaft and distal fractures.

Effect of stack pins on the stiffness of interlocking nails in an unstable osteotomy model

“…Potentialc omplications relatedt ot he placementofSPs in femoral fracture repairs include pin migration ands ciatic neuropathy.NormogradedistalplacementofIM pins in the femur wasshown to be lesslikely to cause damage to the sciatic nerve ( 25). Cases of sciatic neuropathy were not experienced in the 13 cases in whichwehaveused SPs in the femur.Inordertoprevent sciatic nervei rritation,w er ecommend countersinking IM pins belowt he levelo ft he greater trochanter.…”

“…However, in the fracture situation, the normal blood supplytoalongbone via the nutrient artery is disrupted. Thei nitial blood supplyt ot he healing bone andp eriosteal callus arises not from the medullary canal,but from the surrounding soft tissues (23)(24)(25). This hasb een termed the extraosseousbloodsupplyofhealing bone (24).…”

Iatrogenic Sciatic Nerve Injury in Eighteen Dogs and Nine Cats (1997–2006)

“…The cat femur is straighter and does not have the slight degree of curvature observed in the dog femur. This may possibly affect IM pin positioning resulting in medial pin placement or excessive pin length, both of which are recognized causal factors for iatrogenic sciatic nerve damage 16 …”

Ischio-ilial Pinning for Stabilization of Coxo-femoral Luxations: An Anatomical Study

“…Ischiatic nerve dysfunction, due to its entrapment by fibrous tissue, is a wellrecognized complication following intramedullary pinning of femoral fractures (25,26). Anatomical studies have identified femoral intramedullary pinning techniques which reduce the risk of ischiatic nerve entrapment by lateralizing the pin's position in the trochanteric fossa and maximizing gluteal muscle interposition between the pin and the ischiatic nerve (27). Similarly, introducing the pin either at the medial position where the obturator, gemelli and gluteal muscles are interposed between the pin and the ischiatic nerve or at the lateral position where the pin coursed several millimeters lateral to the ischiatic nerve would decrease the potential for ischiatic nerve entrapment.…”