the GANNET implant
The DLBP (Gannet) consists of a 2-hole standard 135° barreled side-plate combined with a low volume cannulated locking blade. The side plate provides angular stability combined with dynamic axial compression of the fracture. Two side wings at the tip of the blade provide rotational stable fixation of the locking blade in the head of femur. The expandable impaction anchors lock the blade in the femoral head and prevent perforation and backing out of the implant and furthermore augments the rotational stability.
After gentle anatomical reduction of the fracture and a 5-7 cm lateral approach a 3.0 mm guide wire is placed centrally in the femoral. After length measuring cannulated reaming is performed up to 5 mm subchondrally in the femoral head. Then the locking blade together with a two-hole side plate is mounted on the introducer. The complete implant is introduced over the guide wire and gently tapped in while the mounted side plate functions as a rotational guide. After the side plate is seated along the lateral cortex, the introducer is released and the locking blade further tapped in the femoral head up to 5mm subchondrally. Next the side plate is fixed to the proximal femur with two self-tapping cortical screws. By turning the setscrew in the shaft of the locking blade in clockwise direction, the impaction anchors are expanded by which the blade is locked within the femoral head. On removal, turning the setscrew anti clockwise retracts the impaction anchors. After removal of the cortical screws the locking blade together with the side plate is tapped out by means of an extractor mounted on the locking blade. The patients are mobilised postoperatively by protected weight bearing according to pain.
Notes on the surgical technique
Aimed is for an anatomical reduction and not for a valgus reduction to prevent vascular damage by kinking of the lateral retinacular vessels. The guide wire is placed centrally in the femoral head because this is the rotational neutral point and in this position the risk of avascular necrosis is further reduced. Unlike the introduction of sliding hip screw devices, no torque force at all is exerted on the femoral head. Rotational stability is provided by the side-winged tip of the locking blade and is further improved by the two impaction anchors. Neither per-operative anti rotational pin, nor an extra anti rotational screw is necessary. Also, no pre-tapping for the locking blade is needed. The inner diameter of the pre-drilling in the femoral head relative to the outer diameter of the shaft of the locking blade is as such that no disimpaction of the fracture will occur, hereby avoiding strain on the remaining intact capsular vessels, when inserting the implant in the femoral head. The cutting time is reduced by inserting the mounted blade and plate as a one step procedure. The barrelled side plate provides angular stability combined with dynamic axial compression of the fracture. The impaction anchors lock the blade in the femoral head and prevent perforation and backing out of the implant. Furthermore, dynamic testing showed augmented rotational stability by the impaction anchors. The holding power of the expanded anchors is improved by impaction of the cancellous bone. On removal, the impaction anchors are retracted by turning the setscrew anti clockwise. After removal of the cortical screws the locking blade together with the side plate is tapped out by means of an extractor mounted on the locking blade.
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|W.H. Roerdink, A.M.M. Aalsma, G. Nijenbanning, A.D.P. van Walsum. The dynamic locking blade plate, a new implant for intracapsular hip fractures: Biomechanical comparison with the sliding hip screw and Twin Hook. Injury, Int Care Injured 40 (2009) 283-287|
|W.H. Roerdink, A.M.M. Aalsma, G. Nijenbanning, A.D.P. van Walsum. Initial promising results of the dynamic locking blade plate, a new implant for the fixation of intracapsular hip fractures: results of a pilot study. Arch Orthop Trauma Surg DOI 10.1007/s00402-010-1195-z. Published online: 21 October 2010|
|W.H. Roerdink. The Dynamic Locking Blade Plate; innovation in the treatment of femoral neck fractures. Thesis. ISBN: 978-94-6108-152-0 17 May 2011|
|A. D. P. van Walsum , J. Vroemen, H. M. J. Janzing, T. Winkelhorst, J. Kalsbeek, W. H. Roerdink. Low failure rate by means of DLBP fixation of undisplaced femoral neck fractures. European Journal of Trauma and Emergency Surgery, DOI 10.1007/s00068-016-0659-4, March 2016|
|J.H. Kalsbeek, A.D.P. van Walsum, J.P.A.M. Vroemen, H.M.J. Janzing, J.T.Winkelhorst, B.P. Bertelink, W.H.Roerdink. Displaced femoral neck fractures in patients 60 years of age or younger. The Bone & Joint Journal, VOL. 100-B, No. 4, April 2018|