Review Question - QID 219464

A variety of implants are available for the treatment of intertrochanteric femur fractures, including cephalomedulary nails with both helical blade (Illustration A1) or screw fixation (Illustration AA). Helical blade constructs are at a much higher risk of experiencing the "cut through" phenomenon, defined as postoperative central perforation of the head by the blade without subsequent collapse (Answer 5).

Intertrochanteric fractures are common injuries, defined as extracapsular fractures of the proximal femur at the level of the greater and lesser trochanter. These injuries are commonly seen following ground-level falls in elderly patients. These fractures account for 50% of all hip fractures, and approximately 150,000 occur per year in the United States. These injuries occur 2-8x more frequently in elderly female patients when compared to elderly male patients. Risk factors for intertrochanteric fractures include a history of a proximal humerus fracture, osteoporosis, advancing age, increased medical comorbidities, and increased dependency with completion of activities of daily living (ADLs).

These fractures almost always represent fractures of necessity, as nonoperative treatment is associated with a one-year mortality rate of nearly 85%. Historically, many of these fractures were treated with sliding hip screw (SHS) devices. The American Academy of Orthopaedic Surgeons (AAOS) has issued a strong recommendation for using either a SHS or a cephalomedullary nail (CMN) device, and many surgeons and centers exclusively utilize this fixation construct. Concerning CMN design, both helical blade and lag screw implants have been developed. While lag screws represent the gold standard and have a proven track record, there is a concern for both femoral head rotation during insertion and removal of cancellous bone during reaming. Helical blade constructs have the theoretical benefit of compacting cancellous bone around the blade during insertion, with biomechanical studies demonstrating that these implants may confer greater resistance to screw "cut-out," defined as postoperative intracranial perforation with subsequent varus collapse when compared to lag screw constructs. Helical blades, however, are at a markedly increased risk of screw "cut through", defined as central perforation without collapse (Illustration B).

Frei et al. performed a study to investigate the "cut through" phenomenon following the utilization of helical blade constructs in the treatment of peritrochanteric femur fractures. Their study followed 112 patients for a minimum of 12 months. Overall, 7 patients experienced "cut through". The authors note that "cut through", defined as postoperative central perforation of the helical blade into the hip joint without subsequent displacement or collapse, is a failure mode unique to helical blade constructs, and should be differentiated from "cut-out", defined as anterocranial screw perforation with varus collapse, as is seen following the utilization of lag screw constructs.

Kim et al. performed a systematic review and meta-analysis to investigate hardware failure rates following CMN fixation of hip fractures. Overall, 12 studies reporting on 2,331 patients were included in the analysis. The authors found that fixation failure, especially "cut through," was far more common following helical blade fixation when compared to lag screw fixation. "Cut-out" rates did not differ between the two constructs. The authors concluded that surgeons should heed caution when selecting a blade-type CMN to treat hip fractures.

Figure A is an AP radiograph of the hip demonstrating an intertrochanteric hip fracture. Illustration A depicts two CMNs, one with a helical blade (A) and one with a lag screw (B). Illustration B demonstrates an intraoperative (A) and postoperative (B) radiograph showing the "cut through" phenomenon, with central perforation and no collapse.

Incorrect Answers:
Answers 1-2: screw "cut-out" is defined as anterocranial perforation of the femoral head by the screw/blade, with subsequent varus collapse. Helical blade constructs are not at an increased risk of "cut-out" when compared to lag screw constructs.
Answers 3-4: blade "cut through" is defined as central perforation without collapse.