- See:
-
Femoral and Tibial Traction Pins:
-
Supracondylar Femoral Fractures:
- Discussion:
- failure of the nail to fill the canal of either the proximal or distal fragment,
may lead to postoperative instability;
- distal fractures within 10 cm of the joint line often can be treated
successfully with standard IM nailing;
- Traction Pins:
- when treating distal fractures, the knee must be flexed and a distal
femoral traction pin must be inserted;
- the flexed knee position releaxes the posterior knee capsule and the
gastrocnemius muscle, thereby avoiding a hyperextension deformity
at the fracture, which can prevent fracture
reduction;
- the femoral traction pin is inserted anteriorly just proximal to the
adductor tubercle, and is placed from the inframedial to the
superolateral side to pull the fracture out of valgus angulation;
- because the distal femoral traction pin needs to be placed very
distal and anterior, consider the use of fluoroscopy to avoid
penetration into the knee joint;
- note: in the lateral position, the weight of the leg produces a
valgus angulation at the fracture site;
- if the deformity is not corrected during the insertion of the nail,
the nail will be driven into the medial femoral condyle, and a
valgus deformity will result;
- finite element analysis of interlocking nails, have revealed that if a
frx is located w/in 5 cm of this hole, stresses are generated
in the nail above its endurance limit;
- Reduction:
- frx of distal third of the shaft pose a special
reduction problem;
- in supine position, the distal fragment angulates posteroirly and
must be supported with a crutch;
- in lateral position, the dstal fragment sags into valgus angulation;
- Reaming:
- faster union may be achieved in distal femoral shaft fractures which have
been reamed vs. those that have not been reamed;
- in these frxs, reaming allows insertion of a larger nail, which allows
more rigid fixation between the implant and the bone;
- IM Nail Technical Considerations:
- tend to sag into a valgus position;
- distal purchase of the nail is critical for stability;
- major loading of this region of femur, along w/ inadequacy of endosteal
purchase on distal frag, results also in a higher non union rate w/
interlocking nails than is seen in midshaft fractures;
- thus, the cancellous bone is not reamed;
- distal third frx especially require minimal 1.0 to 1.5 mm overreaming of
proximal fragment to accomodate the variable degree of anterior femoral
bow that might be present;
- nail is driven thru old epiphyseal scar to level of intercondylar
notch, hence an appropriately sized nail is extremely important;
- after nail has been driven a few mm across frx, traction may be decr
sufficiently to allow impaction of frx as nail is driven distally;
- frx angulation is also possible intraoperatively if the nail is driven
eccentrically out of alignment w/ longitudinal axis of the canal;
- w/ distal fractures the nail may be driven into the medial or lateral
condyles resulting in either a valgus or varus deformity;
- if full correction of this problem is not achieved before guide pin
insertion, the nail may be driven into the medial femoral condyle,
resulting in a valgus deformity;
- guide pin should be aimed directly at intercondylar notch on
AP view
of femur before
reaming and nailing of distal fragment;
-
reaming of distal fragment down to anticipated distal tip of nail is
unnecessary and may comprimise the purchase of nail on cancellous
bone of the distal third of the shaft;
- Length of Nail:
- distal end of medullary nail should be at superior pole of patella in
isthmal level fractures &, for more distal fractures, just proximal
(approx 3 cm) to the intercondylar notch;
- make allowance for the slight overdistraction at the fracture site;
- to prevent problems w/ protrussion into gluteal muscles, it should
not extend above the greater trochanter;
- in some cases further impaction occassionally occurs when severly
comminuted fractures are later dynamized;
- this should be considered to prevent later nail migration into the
knee or nail protrussion out of the proximal femur;
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Fatigue fracture of the interlocking nail in the treatment of fractures
of the distal part of the femoral shaft.
