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Distal Femoral Shaft Fractures

- 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;
    - 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;
    - femoral traction pin is inserted anteriorly just proximal to the adductor tubercle, and is placed from the inframedial to 
            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:
    - IM nails for supracondylar fractures:
    - 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

- References:

 Nails or plates for fracture of the distal femur?

  Fatigue fracture of the interlocking nail in the treatment of fractures of the distal part of the femoral shaft.

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