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Comparison of cutout resistance of dynamic condylar screw and proximal femoral nail in reverse oblique trochanteric fractures: A biomechanical study.

Cheema GS, Rastogi A, Singh V, Goel SC, Mishra D, Arora S - Indian J Orthop (2012)

Bottom Line: The bending moment of the PFN group was approximately 50% less than that of the DCS group (P<0.0001).The PFN group resisted more number of cycles than the DCS group (P=0.03) and showed lesser number of component failures as compared with the DCS group (P=0.003).The PFN is biomechanically superior to DCS for the fixation of reverse oblique trochanteric fractures of femur.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, Maulana Azad Medical College and Associated Lok Nayak Hospital, New Delhi, India.

ABSTRACT

Background: Reverse oblique trochanteric fracture of femur is a distinct fracture pattern. 95° Dynamic condylar screw (DCS) and proximal femoral nail (PFN) are currently the most commonly used implants for its fixation. This study aims to biomechanically compare the cutout resistance as well as modes of failure of DCS and PFN in reverse oblique trochanteric fractures.

Materials and methods: Sixteen freshly harvested cadaveric proximal femoral specimens were randomly assigned to three mean bone mineral density matched groups, eight of which were implanted with 95° DCS and the other eight with PFN. The constructs were made unstable to resemble a reverse oblique trochanteric fracture by removing a standard size posteromedial wedge. These constructs were subjected to computer controlled cyclic compressive loading with 200 kg at a frequency of 1 cycle/second (1 Hz) and end points of both the groups were analyzed.

Results: The bending moment of the PFN group was approximately 50% less than that of the DCS group (P<0.0001). The PFN group resisted more number of cycles than the DCS group (P=0.03) and showed lesser number of component failures as compared with the DCS group (P=0.003).

Conclusions: The PFN is biomechanically superior to DCS for the fixation of reverse oblique trochanteric fractures of femur.

No MeSH data available.


Related in: MedlinePlus

X-rays of cadaveric femoral specimen (a) with unstable reverse oblique trochanteric fracture with posteromedial defect implanted with 95° dynamic hip screw and it was subjected to cyclical compression load. (b) It failed after 1962cycles. Plate bending of 10°, and screw bending of 1° were observed at the end of cyclical loading
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Figure 4: X-rays of cadaveric femoral specimen (a) with unstable reverse oblique trochanteric fracture with posteromedial defect implanted with 95° dynamic hip screw and it was subjected to cyclical compression load. (b) It failed after 1962cycles. Plate bending of 10°, and screw bending of 1° were observed at the end of cyclical loading

Mentions: In the PFN group, there were four failures (three macroscopic and one microscopic). All the failures were present in screw component [Figure 1], and no failures were noticed in nail component. There was no failure in group C (BMD>1.0 g/cm2). One specimen from group A (BMD<0.5 g/cm2) failed at 10,000 cycles and this was the earliest failure seen in PFN constructs. Five out of eight constructs completed 50,000 cycles successfully without any gross failure [Figure 2]. No failure of any implant was seen in the initial 10,000 cycles. In the DCS group, we noticed plate barrel angle deformation [Figure 3] in 5 constructs, screw bending [Figures 3 and 4] in 6 constructs, and plate bending [Figures 3 and 4] in 7 constructs (18 component failures out of total 24 components). Only one specimen with BMD>1.0 g/cm2 (group C) remained stable. Five out of eight specimens failed within the initial 5000 cycles. Only two specimens completed 50,000 cycles successfully, out of which one showed microscopic deformation. Only six components actually remained stable at the end-point. Thus, there were 4 component failures (out of total 16 components) in the PFN group and 18 component failures (out of total 24 components) in the DCS group. The difference in component failures in both the groups was found to be statistically significant (P=0.003).


Comparison of cutout resistance of dynamic condylar screw and proximal femoral nail in reverse oblique trochanteric fractures: A biomechanical study.

Cheema GS, Rastogi A, Singh V, Goel SC, Mishra D, Arora S - Indian J Orthop (2012)

X-rays of cadaveric femoral specimen (a) with unstable reverse oblique trochanteric fracture with posteromedial defect implanted with 95° dynamic hip screw and it was subjected to cyclical compression load. (b) It failed after 1962cycles. Plate bending of 10°, and screw bending of 1° were observed at the end of cyclical loading
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3377134&req=5

Figure 4: X-rays of cadaveric femoral specimen (a) with unstable reverse oblique trochanteric fracture with posteromedial defect implanted with 95° dynamic hip screw and it was subjected to cyclical compression load. (b) It failed after 1962cycles. Plate bending of 10°, and screw bending of 1° were observed at the end of cyclical loading
Mentions: In the PFN group, there were four failures (three macroscopic and one microscopic). All the failures were present in screw component [Figure 1], and no failures were noticed in nail component. There was no failure in group C (BMD>1.0 g/cm2). One specimen from group A (BMD<0.5 g/cm2) failed at 10,000 cycles and this was the earliest failure seen in PFN constructs. Five out of eight constructs completed 50,000 cycles successfully without any gross failure [Figure 2]. No failure of any implant was seen in the initial 10,000 cycles. In the DCS group, we noticed plate barrel angle deformation [Figure 3] in 5 constructs, screw bending [Figures 3 and 4] in 6 constructs, and plate bending [Figures 3 and 4] in 7 constructs (18 component failures out of total 24 components). Only one specimen with BMD>1.0 g/cm2 (group C) remained stable. Five out of eight specimens failed within the initial 5000 cycles. Only two specimens completed 50,000 cycles successfully, out of which one showed microscopic deformation. Only six components actually remained stable at the end-point. Thus, there were 4 component failures (out of total 16 components) in the PFN group and 18 component failures (out of total 24 components) in the DCS group. The difference in component failures in both the groups was found to be statistically significant (P=0.003).

Bottom Line: The bending moment of the PFN group was approximately 50% less than that of the DCS group (P<0.0001).The PFN group resisted more number of cycles than the DCS group (P=0.03) and showed lesser number of component failures as compared with the DCS group (P=0.003).The PFN is biomechanically superior to DCS for the fixation of reverse oblique trochanteric fractures of femur.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, Maulana Azad Medical College and Associated Lok Nayak Hospital, New Delhi, India.

ABSTRACT

Background: Reverse oblique trochanteric fracture of femur is a distinct fracture pattern. 95° Dynamic condylar screw (DCS) and proximal femoral nail (PFN) are currently the most commonly used implants for its fixation. This study aims to biomechanically compare the cutout resistance as well as modes of failure of DCS and PFN in reverse oblique trochanteric fractures.

Materials and methods: Sixteen freshly harvested cadaveric proximal femoral specimens were randomly assigned to three mean bone mineral density matched groups, eight of which were implanted with 95° DCS and the other eight with PFN. The constructs were made unstable to resemble a reverse oblique trochanteric fracture by removing a standard size posteromedial wedge. These constructs were subjected to computer controlled cyclic compressive loading with 200 kg at a frequency of 1 cycle/second (1 Hz) and end points of both the groups were analyzed.

Results: The bending moment of the PFN group was approximately 50% less than that of the DCS group (P<0.0001). The PFN group resisted more number of cycles than the DCS group (P=0.03) and showed lesser number of component failures as compared with the DCS group (P=0.003).

Conclusions: The PFN is biomechanically superior to DCS for the fixation of reverse oblique trochanteric fractures of femur.

No MeSH data available.


Related in: MedlinePlus