Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2011 Jun 22:5:17.
doi: 10.1186/1754-9493-5-17.

Failure of fixation of trochanteric femur fractures: Clinical recommendations for avoiding Z-effect and reverse Z-effect type complications

Robinson Esteves Santos Pires  1 , Egídio Oliveira Santana Jr, Leandro Emílio Nascimento Santos, Vincenzo Giordano, Daniel Balbachevsky, Fernando Baldy Dos Reis
Affiliations

Failure of fixation of trochanteric femur fractures: Clinical recommendations for avoiding Z-effect and reverse Z-effect type complications

Robinson Esteves Santos Pires et al. Patient Saf Surg. .

Abstract

Background: Z-effect and reverse Z-effect are complications that arise from the surgical treatment of pertrochanteric fractures of the femur with proximal femoral nails (PFN) comprising two interlocking head screws. Such complications are induced by the migration of screws in opposite directions, which may lead to failure of the osteosynthesis.

Findings: The paper describes three cases of pertrochanteric fractures that were treated with PFN with two interlocking screws that evolved to either Z-effect or reverse Z-effect. Literature-based explanations for this phenomenon are provided together with recommendations of how to avoid such complications.

Conclusions: Although intramedullary fixation is an established method of treatment of femoral intertrochanteric and subtrochanteric fractures, the evolution of the procedure may include complications associated with the migration of the interlocking head screws. The occurrence of Z-effect and reverse Z-effect has not been completely elucidated, but the main causes of such complications are probably fracture fixation in varus position, severe medial comminution, inappropriate entry point of the nail and poor bone quality.

PubMed Disclaimer

Figures

Figure 1
Figure 1
Case 1 - Radiographic images of the pelvis in anteroposterior view (A), and the hip joint in anteroposterior and lateral view (B), showing the subtrochanteric fracture of the right femur consolidated in varus angulation. The reduction in varus and the intense periosteal reaction caused by infection can be observed. The entry point of the nail is excessively lateral, and the interlocking screws are short and incorrectly positioned culminating in the lateral migration of the inferior screw (Z-effect).
Figure 2
Figure 2
Case 2 - Radiographic images showing the intertrochanteric fracture that was fixed with a proximal femoral nail - (A) preoperative and (B) postoperative; (C and D) the lateral migration of the superior screw and perforation of the femoral head by the inferior screw (reverse Z-effect); (E) the incorrect positioning of the interlocking screws in the lateral incidence, together with poor bone material, may have been responsible for the reverse Z-effect; (F) the removal of the material of osteosynthesis is shown together with signs of chondrolysis of the hip.
Figure 3
Figure 3
Case 3 - Radiographies of the left hip joint showing the correct consolidation of the left intertrochanteric femoral fracture (A), together with the lateral migration of the superior screw while the sliding screw remained in the original position. The removal of the superior screw is shown in (B).
See this image and copyright information in PMC

References

    1. Brunner A, Jöckel JA, Babst R. The PFNA proximal femoral nail in treatment of unstable proximal femur fractures - 3 cases of postoperative perforation of the helical blade into the hip joint. J Orthop Trauma. 2008;22:731–736. doi: 10.1097/BOT.0b013e3181893b1b. - DOI - PubMed
    1. Guimarães JAM, Guimarães ACA, Franco JS. Avaliação do emprego da haste femoral curta na fratura transtrocantérica instável do fêmur. Rev Bras Ortop. 2008;43:406–417.
    1. Tyllianakis M, Panagopoulos A, Papadopoulos A, Papasmos S, Mousafiris. Treatment of extracapsular hip fractures with the proximal femoral nail (PFN): Long term results in 45 patients. Acta Orthop Belg. 2004;70:444–454. - PubMed
    1. Rethnam U, Cordell-Smith J, Kumar TM, Simha A. Complex proximal femoral fractures in the elderly managed by reconstruction nailing - complications and outcomes: a retrospective analysis. J Trauma Manag Outcomes. 2007;1(7):1–7. - PMC - PubMed
    1. Davis TRC, Sher JL, Horsman A, Simpson M, Porter BB, Checketts RG. Intertrochanteric femoral fractures. Mechanical failure after internal fixation. J Bone Joint Surgery Br. 1990;72:26–31. - PubMed

LinkOut - more resources