ABSTRACT
Objective:To investigate the biomechanical properties of cannulated screws fixation in a configuration of "axial compression and lateral buttress" in the treatment of Pauwels type Ⅱ femoral neck fractures.Methods:Ten specimens of Sawbones artificial femur were first made into models of type Ⅱ femoral neck fracture with a Pauwells angle of 50° and then randomized into 2 equal groups ( n=5). The specimens in the experimental group were subjected to fixation with cannulated screws in a configuration of "axial compression and lateral buttress" in which the axial screw was 8.5 mm in diameter and the lateral screw 6.5 mm in diameter. The specimens in the control group were subjected to conventional fixation with cannulated screws in a configuration of "inverted triangle and parallel compression" in which the 3 screws was 7.3 mm in diameter. Finally, the specimens were placed onto a biomechanical testing machine to determine the parameters of static axial stiffness, displacement under 60 to 600 N load for 5,000 cycles, ultimate load and ultimate stiffness in turn. The 2 groups were compared to find out their differences. Results:The static axial stiffness was (1,492.00 ± 87.86) N/mm, significantly higher than that in the control group [(1,200.22 ± 228.06) N/mm] ( P<0.05). There was no significant difference between the 2 groups in the cyclic load displacement [(0.44 ± 0.01) mm versus (0.57 ± 0.17) mm] ( P>0.05), but the experimental group showed a lower trend. The ultimate load and ultimate stiffness were (4,292.61 ± 804.29) N and (1,623.55 ± 180.94) N/mm in the experimental group and (4,383.64 ± 1,423.24) N and (1,433.77 ± 289.93) N/mm in the control group, showing no significant difference between the 2 groups ( P>0.05). Conclusion:In the treatment of Pauwels type Ⅱ femoral neck fractures, fixation with cannulated screws in a configuration of "axial compression and lateral buttress" may exhibit better biomechanical properties than that in a conventional configuration of "inverted triangle" .
ABSTRACT
Objective:To compare the conventional percutaneous minimally invasive plate fixation sparing pronator quadratus versus the 3-point positioning percutaneous minimally invasive palmar locking plate fixation sparing pronator quadratus for distal radial fractures.Methods:Between January 2015 and December 2017, 50 patients with distal radius fracture were treated surgically at Department of Orthopaedics, The Second Hospital of Fuzhou by percutaneous minimally invasive plate fixation sparing pronator quadratus. They were 24 males and 26 females, aged from 21 to 71 years. Conventional percutaneous minimally invasive plate fixation was conducted for 25 patients and 3-point positioning minimally invasive plate fixation for the other 25 patients. The 2 groups were compared in terms of fluoroscopic adjustments of the plate under the pronator quadratus, fracture healing time, visual analogue scale (VAS) on days 1, 3 and 7 postoperation, and wrist flexion and extension, forearm rotation and upper limb function by Disabilities of the Arm, Shoulder and Hand(DASH) scores and Gartland-Werley scores at 3 months postoperation.Results:There was no significant difference in the general data between the 2 groups, showing comparability between groups ( P>0.05). The fluoroscopic adjustments of the plate under the pronator quadratus for the conventional group (3.4±0.5) were significantly more than for the 3-point positioning group (1.1±0.3) ( P<0.05). The VAS scores on days 1, 3 and 7 postoperation for the conventional group were significantly higher than for the 3-point positioning group ( P<0.05). At 3 months postoperation, the wrist pronation was respectively 76.6°±1.9° and 82.3°±2.0°, and the Gartland-Werley scores were respectively 3.4±0.5 and 1.9±0.2 for the conventional and 3-point positioning groups, showing significant differences between the 2 groups ( P< 0.05). Conclusions:In the treatment of distal radial fractures, compared with conventional percutaneous minimally invasive plate fixation, the 3-point positioning minimally invasive plate fixation sparing pronator quadratus may minimize the damage to the pronator quadratus, be more minimally invasive, and lead to less early postoperative pain and faster functional recovery.
ABSTRACT
Objective To investigate the biomechanical properties of our self-designed 4 cannulated screws in 4 configurations for fixation of extremely unstable femoral neck fractures.Methods Twelve adult cadaveric femoral specimens were randomly divided into 4 equal groups (n =3) and made into models of extremely unstable femoral neck fracture combined with comminution (Pauwels type Ⅲ).Group A was subjected to fixation in configuration of “double axial compressions plus double stabilizations”,group B to configuration of “positive triangle parallel compression plus small angle screwing”,group C to configuration of “inverted triangle parallel compression plus small angle screwing”,and group D to configuration of “diamond pattern screwing”.Static compression tests,cyclic loading tests and limit load tests were carried out for the 4 groups on a biomechanical testing machine.Results For groups A,B C and D,the axial compression stiffness was respectively 995.29 ±34.16 N/mm,509.89 ± 138.90 N/mm,559.28 ± 111.25 N/mm and 610.18 ±232.35 N/mm,and the limit load was respectively 3,225.33 ±461.31 N,2,008.67 ±237.27 N,2,705.67 ±496.39 N and 2,395.33 ±403.71 N,showing significant differences between the 4 groups (P ＜ 0.05).For groups A,B C and D,the displacement was respectively 0.46 ± 0.10 mm,1.47 ± 0.72 mm,1.14 ±0.24 mm and 1.22 ±0.22 mm,and the limit stiffness was respectively 1,139.28 ±342.09 N/mm,843.56 ±408.91 N/mm,585.98 ± 81.60 N/mm and 729.96 ±251.37 N/mm,showing no significant differences between the 4 groups (P ＞ 0.05).Conclusions In the fixation of extremely unstable femoral neck fracture with our self-designed 4 cannulated screws,the configuration of “double axial compressions plus double stabilizations” may lead to the greatest biomechanical advantage while the configuration of “positive triangle parallel compression plus small angle screwing” may result in the poorest biomechanical properties.