Frequently Asked Questions (FAQ)

Answers to the most frequent questions are listed below. Questions are grouped in tabs by category.


The overall failure rate for the non-displaced fractures was 4,6% and for the displaced fractures 13,1%. Excluding the inadequately reduced fractures the failure rate of the displaced femoral neck fractures further reduced to 9,8%. These results are favourable when compared to the literature with failure rates of 35% and up to 48% for the displaced fractures and 9% to 11% for the undisplaced fractures.

In gap healing a fracture gap, with a width smaller than 1mm, is filled with blood vessels ad loose connective tissue. After about two weeks vascular supply is established osteoblasts deposit lamellar bone in the fracture gap perpendicular to the fracture ends. Cutting cones cross the area formed by new osteons within the gap and those at fracture ends and, according Wolff’s law, new bone is remodelled along lines of load. In the context of the bone healing of femoral neck fractures it is of clinical importance that contact healing or gap healing only occurs with anatomic alignment and full bony contact of the fracture ends.

In contact healing cutting cones are formed at ends of osteons nearest the fracture. Osteoclasts line the spearhead of the cutting cone for bone resorption. Osteoblasts line the rear of the cutting cone for bone formation. Resorption and formation occur simultaneously at 50-80 um/day. Osteonal remodelling occurs across locations of cortical contact of fracture ends. Therefore anatomic reduction with 3600 cortical bone contact is mandatory for primary bone healing by contact healing.

Primary osteonal reconstruction requires absolute stability with an interfragmentary strain of less then 2%. Contact healing or gap healing only occurs with anatomic alignment of the fracture ends with a maximum width of the gap of maximal 1mm. Another anatomical factor compromising the fracture healing is the intra-articular position of the fracture where the synovial fluid prevents blood clot formation thereby eliminating a factor contributing to bone healing.

As the femoral neck lacks a periosteal layer, the fracture cannot heal by external callus formation but can only heal by primary osteonal reconstruction. This primary bone healing can only take place by contact healing which needs an anatomical reduction and absolute stability with an interfragmentary strain less than 2%. This absolute stability means angle and rotational stability combined by dynamisation providing the necessary bone contact.

The vascularisation of the femoral head after an intracapsular fracture is dependant on the remaining vascularisation and on the revascularisation of the femoral head after fixation. To spare the remaining vascularisation th fractures should be gently reduced anatomically. Revascularisation of the femoral head is very much dependable on the stability of the osteosynthesis.

The possible underlying causes of the high failure rate are twofold: the specific type of bone healing of the intracapsular fracture and the specific vascularisation of the femoral head.

The main complications are: avascular necrosis, non-union and implant failure.

Because literature shows an overall re-intervention rate of over 35% after fixation of the femoral neck fracture, either by SHS devices or by multiple screw/pins fixation.

Increasing volume of the implant in the femoral head will compromise the (re) vascularisation of the head of femur and increase the incidence of avascular necrosis.
The volume of the DHS in the femoral head is 1975 mm3, while the volume of the DLBP is reduced to 920 mm3. Compared to the DHS, the cross section of the DLBP is reduced from 133 to 31 mm2. Also there exists a marked difference in the diameter of the pre-drilling in the femoral head; this is 9mm for the DHS and 5 mm for the DLBP. Because of the minimal cross section and volume of the implant in the femoral head, the DLBP is minimal invasive where it should be minimal invasive: that is the femoral head.

The GANNET does not have a so called compression screw basically because it is a dynamic implant. As soon as the patient is off the extension table dynamic compression of the fracture will take place (and simultaneously a compression screw will loose its function).

– To preserve the remaining blood supply.
– To provide the stability necessary for revascularisation.
– To provide the stability necessary for primary osteonal reconstruction.

– Rotational stability
– Angular stability
– Dynamic compression
– Impaction locking
– Minimal invasive
– Cannulated technique
– Simple instrumentation

The GANNET is made up of:

– GANNET nail with two side wings and two compaction anchors in the tip of the nail
– Barrelled side plate (similar to the SHS)
– Two cortical screws

The GANNET offers both angular and rotational stability, screws and pins provide neither. Both in terms of volume and cross section, the GANNET is also less invasive in the femoral head. While the screws and pins are all placed in the periphery of the femoral head, the GANNET fixes the head with a just a single implant in the rotational neutral centre of the femoral head.

The main differences are the stability and the invasiveness of the implant. Loading test showed the rotational stability of the GANNET to be 300% compared to the SHS. Also the GANNET is minimal invasive in the femoral head. The volume of the GANNET is less than 50% of the SHS and the cross section even less than 25% combined with a axial load bearing surface of 150% compared to the SHS. Another important difference is the fact that, unlike the introduction of sliding hip screw devices, no torque force at all is exerted on the femoral head on insertion the DLBP, avoiding secondary displacement.

The GANNET consists of a 2-hole standard 135° barreled side-plate combined with a cannulated locking blade. The barreled 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.

The implant is named after the seabird gannet (Morus bassanus, D: Jan-van-gent, F: Fou de Bassan, G: Basstölpel). Like the gannet seabird the GANNET implant is fast, streamlined, targeted and able to fold her wings in pursuit.

Removal of the GANNET is straightforward and even easier than removal of an SHS. First the impaction anchors are retracted by turning the internal set screw counter clockwise until the stop is reached. By retracting the anchors the ingrown bone is simply squeezed out of the anchors. After removal of the cortical crews the GANNET nail together with the side plate is tapped out by means of the extractor.

Removal of the hardware is indicated when complications necessitate re-intervention surgery. After uncomplicated fracture healing, removal of the GANNET may be indicated by local complaints caused by the implant.

No, the GANNET does not have a so called compression screw basically because it is a dynamic implant. As soon as the patient is off the extension table dynamic compression of the fracture will take place (and simultaneously a compression screw will loose its function).

The impaction anchors are deployed after insertion of the GANNET nail in the femoral head by turning the internal set screw clockwise until the stop is reached.

No, the fracture will not be distracted or disimpacted by tapping in the GANNET, because the diameter of the cannulated drill relative to the outer core diameter of the GANNET nail is selected as such that no distraction of the fracture can occur even in high density bone. This is also confirmed by laboratorium push-in tests using high density saw bone.

The GANNET nail together with the mounted side plate is assembled on the introducer and inserted over the guide pin as an on-step-procedure. The GANNET nail is inserted in the femoral head by gentle tapping with a mallet.

Yes, the GANNET is pre-drilled by a cannulated stepped drill. Herewith the femoral head is pre-drilled minimal invasively to a diameter of just 5 mm. The pre-drilling is advanced to a level of 5-10 mm subchondrally.

As the GANNET is an angle and rotational stable implant and does not need additional “anti-rotational screws, the guide pin should be positioned in the rotational neutral position in the very centre of the femoral head.

The approach is straight lateral by means of a 5-8 cm incision similar to the SHS technique. The vastus lateralis muscle is split at its posterior border.

The fracture GENTLY reduced on the extension table by GENTLE traction and endorotation under image intensifying. Undue traction and over reduction will hamper the remaining vascularisation of the femoral head.

Because in this position remaining vascular supply of the femoral head after a fracture is best preserved and the revascularisation of the head of femur is best facilitated.
Furthermore primary bone healing of a femoral neck fracture only occurs with anatomic alignment of the fracture ends with a maximum width of the gap of maximal 1mm.
No osteosynthesis will survive an inadequate reduction of a femoral neck fracture.

No osteosynthesis will survive a poor reduction of the femoral head! The fracture should be reduced anatomically. Do NOT aim for reduction in valgus to improve the stability; it will reduce the vascularisation of the femoral head.

Similar to the SHS procedure the patient is positioned supine on the fracture table with the affected leg extended and endorotated.

The GANNET can be used for the fixation of undisplaced (Garden 1 and 2) and displaced (garden 3 and 4) femoral neck fractures of any Pauwels classification.

The GANNET is contraindicated in patients not able to mobilize by partial weight bearing, in patient with poor bone quality, in patient with ipsilateral symptomatic osteoarthritis of the hip in patients with local soft tissue problems.

The GANNET is indicated for the operative fixation of femoral neck fractures in the biological younger patients less then about 75 years able to walk without walking aids.

The femoral neck fractures only heals by primary osteonal reconstruction. When the femoral neck fracture is anatomically reduced and adequately impacted while the cancellous and cortical bone surfaces interlock and have sufficient stability, primary bone healing can proceed at sites where the fracture surfaces make direct contact. Therefore in the osteosynthesis of femoral neck fractures it is imperative to perform an anatomical reduction of the fracture combined with a stable fixation of the femoral head in combination with controlled dynamic impaction of the fracture surfaces.

– Preserve the remaining vascularization of the femoral head.
– Providing the necessary stability for revascularization.
– Providing the necessary stability for the primary fracture healing.

Removal of the hardware is indicated when complications necessitate re-intervention surgery. After uncomplicated fracture healing, removal of the GANNET may be indicated by local complaints caused by the implant.

The patient is seen at the outpatient clinic at 6 weeks, 3, 6 and 12 months. This includes A.P. and lateral X-rays of the affected hip.

The postoperative after treatment is functional. The first 6 weeks the patient I allowed to mobilize with walking aids and partial weight bearing according to pain. If the control X-ray after 6 weeks does not reveal complications, full weight bearing is started.

Frequently Asked Questions (professionals)

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Publications

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 fracturesEuropean 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 youngerThe Bone & Joint Journal, VOL. 100-B, No. 4, April 2018