Short Notes in Orthopaedics

Complications arising from fixation of unstable proximal femur fracture with PFN having 2 screws . 1.Z-effect   lateral migration of caudal screw , varus collapse and perforation of femoral head by superior screw 2. Reverse Z-effect   lateral  migration of superior screw , varus collapse and femoral head cut by inferior screw Causes  varus fixation of fractures , severe medial communition , inappropriate entry point and poor bone   quality. Intaoperative Procedures to stabilize unstable IT fractures  Osteotomies and fixed with nail plate   Design (Smith -Peterson nail plate  )     e.g. 1. Dimon  -Hughston medial displacement Osteotomy            2. Sarmiento Valgus Osteotomy            3. Wayne -County lateral displacement Osteotomy No evidence are there to support these osteotomies combined with sliding hip screw fixation .

Advantages 1.Ability to fix majority of fractures 2. Short surgical time and less blood loss   for unstable Intertrochanteric fractures , (no difference compare to DHS fixation for stable IT fracture 3. smaller moment arm - to bear tensile forces and lesser calcar strain  DHS - produces 1.5 times calcar strain of a normal femur  IM < 10 percent of strain 4.Better controlled collapse as bending moment at lag screw for nail is lesser than DHS . 5. Biomechanically nail construct are more stiff so more stable than DHS for torsion and bending       stress. Disadvantages   1. Abductor injury while insertion   2. difficult revision by arthroplasty if it fails    3. anterior thigh pain due  to impingement of nail tip   4. curative mismatch of nail and femora produces iatrogenic fractures   5. stress concentration at nail tip leads to fracture   6. implants are costlier .