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

Pires RE, Santana EO, Santos LE, Giordano V, Balbachevsky D, Dos Reis FB - Patient Saf Surg (2011)

Bottom Line: Literature-based explanations for this phenomenon are provided together with recommendations of how to avoid such complications.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Hospital Felício Rocho, Av, do Contorno 9790, 30110-060, Belo Horizonte, MG, Brasil. robinsonesteves@ig.com.br.

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.

No MeSH data available.


Related in: MedlinePlus

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).
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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).

Mentions: A 44-year old male doctor (with no comorbidities), who had been injured in a car accident, presented subtrochanteric fracture (AO/OTA 32-B1) of the right femur and was submitted to osteosynthesis with PFN (Hexagon®, Campinas, SP, Brazil) one day after the trauma. The femur fracture was classified as level 3 on the abbreviated injury scale (AIS), whereas the injury severity score (ISS) was level 9 without any associated injuries. After 10 months, the patient evolved with varus consolidation, chronic osteomyelitis and migration of the proximal interlocking screws in different directions with the caudal screw migrating laterally (characteristic of the Z-effect). Because of the protruding inferior screw, it was necessary to remove the implant and to treat the chronic osteomyelitis. Radiographic images are presented in Figure 1.


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

Pires RE, Santana EO, Santos LE, Giordano V, Balbachevsky D, Dos Reis FB - Patient Saf Surg (2011)

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).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3142479&req=5

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).
Mentions: A 44-year old male doctor (with no comorbidities), who had been injured in a car accident, presented subtrochanteric fracture (AO/OTA 32-B1) of the right femur and was submitted to osteosynthesis with PFN (Hexagon®, Campinas, SP, Brazil) one day after the trauma. The femur fracture was classified as level 3 on the abbreviated injury scale (AIS), whereas the injury severity score (ISS) was level 9 without any associated injuries. After 10 months, the patient evolved with varus consolidation, chronic osteomyelitis and migration of the proximal interlocking screws in different directions with the caudal screw migrating laterally (characteristic of the Z-effect). Because of the protruding inferior screw, it was necessary to remove the implant and to treat the chronic osteomyelitis. Radiographic images are presented in Figure 1.

Bottom Line: Literature-based explanations for this phenomenon are provided together with recommendations of how to avoid such complications.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Hospital Felício Rocho, Av, do Contorno 9790, 30110-060, Belo Horizonte, MG, Brasil. robinsonesteves@ig.com.br.

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.

No MeSH data available.


Related in: MedlinePlus