Collum screw – to parallel or not

Two bridges
Bridging the knowledge gap in how to operate femoral neck fractures. The image is CC by Nick Mealey.

One of the first surgeries young orthopaedic surgeons learn is the femoral neck fracture fixation with collum screws. A common theme is how to position the screws and as a young surgeon one often believe that everything depends on the screw position, especially if they’re parallel or not. It was therefore quite fun and liberating to read Nyholm et al’s study with the subtitle: “Minimal Effect of Implant Position on Risk of Reoperation”

They reviewed an impressive 1,200 surgeries with a failure rate of 13%. The median time to re-operation was 3 months and factors that increased the risk were (in falling order):

  • Screw penetration (RR ≈ 3.0)
  • Displaced fracture (RR ≈ 2.3)
  • Failure to reduce (RR ≈ 1.9)
  • Angle ≤125° (RR ≈ 1.9)
  • Female gender (RR ≈ 1.6)
  • ASA 3-4 (RR ≈ 1.6)

Interestingly the angle of ≤125° is surprisingly little discussed in rounds. It is difficult to position implants at >125° as the distance for the screws becomes greater and any deviation of initial angle has a greater impact in the screw caput position. Other factors that did not have any impact were, how parallel the screws are, calcar distance, posterior distance, tip-caput distance, number of screws (2 or 3). These are though frequently a topic during x-ray rounds.

Summary

The fractures severity matters most unless the screw positioning is fatal with the only exception for the screw inclination that should be >125°. Also, no difference can be seen between 2 and 3 screws.

A. M. Nyholm, H. Palm, H. Sandholdt, A. Troelsen, and K. Gromov, “Osteosynthesis with Parallel Implants in the Treatment of Femoral Neck Fractures: Minimal Effect of Implant Position on Risk of Reoperation,” The Journal of Bone and Joint Surgery, vol. 100, no. 19, pp. 1682–1690, Oct. 2018.

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