Dynaloc®

SolidFemoral Neck Fracture System

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Dynaloc® SolidFemoral Neck Fracture System

The unsolved problemThe femoral neck fracture is often referred to as the last unsolved fracture. Displacement of the fracture is one of the main complications associated with fixation of femoral neck fractures. It occurs in about 5-8% of the undisplaced fractures and up to 20-30% of the displaced fractures (Ref. 1-5).

Traditional fixation implants such as cannulated screws or sliding hip screws will often fail to hold a fracture. These implants often cannot provide enough mechanical stability to allow the fracture to heal in its reduced position.

A possible solutionThe Dynaloc Solid looks to recreate the stability of the patients original anatomy by locking three screws and a plate into one dynamic unit.

The screws cannot rotate independently from each other, this enables unparalleled stability of the femoral head. This means that the femoral head can only rotate if the bone cuts through the screws simultaneously.

Our initial results are indicating that the Dynaloc Solid reduces complications during the fracture healing process and in turn increases the quality of life for the patient.

The Dynaloc Solid Femoral Neck Fracture System is a patented product with world wide patent protection.

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The principleAfter reduction of the fracture, three cylindrical screws are inserted through a locking plate and into pre-drilled holes. Fixation of the femoral head is achieved without locking the plate to the femoral shaft, allowing the distal shaft fragment to slide on the parallel screws.

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How to prevent failure of fixation and non-unions

Rotationally stable proximal and distal fixation

ll Strong resistance to rotation Femoral neck fractures cannot heal through periosteal (external) callus formation, due to the femoral neck having no cambium layer. Femoral neck fractures heal through endosteal (internal) union but in order for this to happen effectively they require absolute stability. By locking three screws and a plate into one unit, the screws can not twist in relation to each other. The torsional resistance of the Dynaloc Solid is far superior to independent screws. (Ref. 6-8).

Torsional Test*Comparing three Synthes Cannulated Screws Ø7,3 mm against Dynaloc Solid Ø6.5 mm.

Test setupThe test was performed by testing laboratory EndoLab® Mechanical Engineering GmbH. (Ref. 9)

Torsional Feed Rate 90 °/min

1st Step 0° to 20° (Clockwise)

2nd Step 0° to 30° (Clockwise)

3rd Step 0° to 40° (Clockwise)

Axial Preload 100 N

Test Environment Dry Air

Temperature Room Temperature

First Polyurethane Foam Block Grade 15 (0.24 g/cc) Laminated with Glass-fiber Epoxy Sheet

Second Polyurethane Foam Block Grade 15 (0.24 g/cc)

Borehole Diameter 2.8 mm

Free Length 40 mm

A metal triangle cannot rotate inside a cortical bone triangle. CT-image showing the Dynaloc Solid through the femoral neck.

Synthes Cannulated Screw Ø7,3 is a trademark of Depuy & Synthes

*) Ref. Swemac internal document on file TD-0043-00

Max Torque (Nm)

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Angular stable fixationll Use of cortical bone for buttressing

When implanted correctly each screw should achieve contact with strong cortical bone in three places to provide maximum stability. The Dynaloc System does not rely on soft cancellous bone for support and thereby the risk of displacement is minimized. (Ref. 10-11)

ll Large contact area It is important to have a large contact area at the fracture site in order to stabilize the fracture. In direct contrast with the smaller traditional screws indicated for femoral neck fractures, the Dynaloc screws have a shaft diameter of 6.5mm. This will help to achieve optimum stability via the large contact area at the fracture site.

Three point contact with cortical bone provides maximum stability. The inferior screw contacts the inferior cortex of the femoral neck.

The posterior screw contacts the posterior cortex of the femoral neck. The anterior screw contacts the anterior cortex of the femoral neck.

Our findings indicate that a posterior position with cortical support for the proximal screw, compared to a central screw position with only cancellous bone support, increases the stability of femoral neck fractures.

Lindequist S, Wredmark T, Eriksson S A V, Samnegård E.

Screw Positions in femoral neck fractures: Comparison of two different screw positions in cadavers.

Acta Orthopaedica,64:1,67-70

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How to prevent failure of fixation and non-unions

Prevents posterior tiltll The posterior screw cannot slide

independently of the other screws Post-operatively, the Dynaloc implant will allow the distal fragment to slide on the parallel screws, compressing the fracture. By locking three screws and a plate together into one dynamic unit, the posterior screw cannot slide independent of the other screws. This prevents posterior tilt and shortening on the posterior side.

The Dynaloc Solid has the ability to compress the fracture, maintain length and prevent posterior tilt.

Compression Maintaining length

Pre-operative posterior tilt in femoral neck fractures is influencing the rate of reoperation. (Ref. 12)

14/25 (0.6) of patients with posterior tilt of ≥ 20° were reoperated, as compared to 12/88 (0.1) of patients with tilt of < 20° (p < 0.001). A posterior tilt of ≥ 20° was the only significant predictor of reoperation.

Palm H, Gosvig K, Krasheninnikoff M, Jacobsen S, Gebuhr P.

A new measurement for posterior tilt predicts reoperation in undisplaced femoral neck fractures: 113 consecutive

patients treated by internal fixation and followed for 1 year. Acta Orthop. 2009 Jun;80(3):303-7.

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Parallel placement of the screws ensures continuous compression at the fracture site (Ref. 13).

Allows early mobilisationll Strong stable fixation with continuous compression

at the fracture site will allow most patients to be mobilized during their first postoperative day and to be discharged early.

Maintains contact with bonell Precise parallel placement

Precise parallel placement allows for fracture dynamization thus ensuring continuous contact with bone, even during resorption. This reduces the risk of implant breakage and cut-out of the femoral head.

Convergence has been reported to increase the incidence of non-union. Therefore, placement of parallel peripheral pins, is considered ideal

Bray TJ, Smith-Hoefer E, Hooper A, Timmerman L.

The displaced femoral neck fracture. Internal fixation versus bipolar endoprosthesis. Results of a prospective, randomized comparison. Clin Orthop Relat Res. 1988 May;(230):127-40.

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How to prevent failure of fixation and non-unions

Optimal holding power in the femoral headAdequate fixation in the femoral head is crucial for successful fixation of femoral neck fractures. The Dynaloc Solid Screw has been designed to overcome the strength-reduction in the cancellous bone caused by osteoporosis. Strength of fixation is dependent upon both implant and bone properties (Ref. 14-15).

The screw has nine unique features increasing the holding power in the femoral head:

1. A conical core allows an increase of the total area of the thread and compresses the bone in radial direction.

2. A gradually decreasing distance between the threads compresses the bone in axial direction.

3. A consistent outer diameter over the whole length of the thread increases the total area.

4. A blunt tip minimizes the risk of femoral head penetration.

5. A self-cutting edge does not reduce the holding power like traditional cutting flutes.

6. A proximal thread having the same outer diameter as the shank does not need reverse cutting.

7. A distal locking thread allows the screw to lock in the plate. This transforms the three screws into a single load-sharing implant and increases the holding power in the femoral head.

8. A screw locked in a plate cannot rotate forward or backwards, which will reduce the risk of femoral head penetration or loosening.

9. Having the same tread diameter as the shank diameter will create a perfect round hole through the lateral cortex, minimizing the risk of subtrochanteric fractures.

Impaction bone-grafting increases the holding power of cancellous screws in the femoral head.

Lenzner A, Kaur I, Haviko T, Sõgel V, Gapejevo J, Ereline J, Pääsuke M.

Impaction bone-grafting increases the holding power of cacellous screws in the femoral head. Acta Orthop Scand 1999;70(1):25-28

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Push-in and Pull-out Test*Standard specification and test methods for metallic medical bone screws. Performed by testing laboratory EndoLab® Mechanical Engineering GmbH. (Ref. 16)

Push-in test setupType of PUR foam Grade 10

Test block thickness 40 mm

Push-in rate 5 mm/min

Insertion depth / drilling depth 30 mm for proximal screws (stepdrill) 20 mm for distal screw

Pilot hole diameter (stepdrill) 6.7 mm

Grip span 105 mm

Pull-out test setupType of PUR foam grade 10

Test block thickness 40 mm

Pull-out rate 5 mm/min

Insertion depth / drilling depth 30 mm for proximal screws (stepdrill) 20 mm for distal screw

Pilot hole diameter (stepdrill) 6.7 mm

Grip span 105 mm

Synthes Cannulated Screw Ø7,3 is a trademark of Depuy & Synthes

*) Ref Swemac internal document on file TD-0041-00

Push in (Newton)

Pull out (Newton)

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Reduces the risk of femoral head necrosis

Preserves the blood supplyll Avoiding the area of lateral epiphyseal arteries

By placing the proximal Screws of the Dynaloc Solid just above the central axis of the femoral neck, the area where the lateral epiphyseal arteries enters the femoral head, will be avoided.

ll Prevents femoral head rotation There are always two drills or screws that remain in the femoral head during insertion. This is designed to prevent rotation of the femoral head during the surgery. Post-operatively, the Dynaloc Solid provides a torsional resistance that is much higher than two or three independent screws. This will prevent the epiphyseal arteries from rupturing and thereby minimizing the consequent danger of avascular necrosis. (Ref. 9)

A screw is inserted through a drilled hole and atraumatically advanced into the femoral head.

The two Drills will prevent rotation during the insertion of the inferior screw.

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Preserves bone integrityll Reduced bone disruption

If too much bone trabeculae is removed, the interaction between bone and implant may be impaired. To achieve a good fixation, it is vital to have sufficient bone trabeculae in the femoral head. By using only three Ø6.5 mm Solid Screws with a conical core, there is no need to pre-drill the femoral head more than the diameter of the core. The cancellous bone within the femoral head is preserved.

ll Enters the lateral femoral cortex at a point opposite the lesser trochanter Reducing the risk of subtrochanteric hip fractures.

Minimal invasive surgeryll Small incision

The complete procedure is carried out through a 30-40 mm skin incision.

ll Short procedure Simple instrumentation and a reproducible procedure allows fixation to be achieved within an adequate time frame.

ll Easy extraction The procedure for screw removal is quick and straightforward. The risk of the screw being trapped in the bone is reduced as the screw surface is smooth. The screw has been treated with anodization type II which prevents bone ongrowth. The whole length of the screw is in one diameter which in turn enables easy screw removal.

Three Ø6.5 mm screws destroy 21% less bone area than three Ø7.3 mm cannulated screws.

The screws can be removed without further disruption to bone.

Three Ø7.3 mm cannulated screws = 125.6 mm2

(Shank 4.5-4.8 mm)

Three Ø6.5 mm screws = 99.5 mm2

π × r 2 =Total area of destroyed bone

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1. Lu Yao GL, 1994, Kelletr RB, Littenberg B, Wennberg JE. Meta-analysis Yao. J Bone Joint Surgery Am. 1994; 76: 1525.

2. Bhandari M, Devereaux PJ, Swiontkowski MF et al. Meta-analysis Bhandari. J Bone Joint Surg Am. 2003;85-A:1673-1681.

3. Rogmark C, Johnell O. Meta-analysis Rogmark. Acta Orthopaedica 2006; 77 (3): 359–367.

4. Parker MJ, Stockton G, Gurusamy K. Cochrane review. The Cochrane Library 2006, Issue 2.

5. Heetveld MJ, Raaijmakers ELFB, van Eck-Smit BL, van Walsum ADP, Luitse JSK. Meta-analysis Heetveld: J Bone Joint Surgery Br. 2005; 87: 367-73.)

6. Jönsson A (MD, PhD), Mellgren M (M.Sc.), Theodorsson J (M.Sc.). Analysis of Dynaloc System for femoral neck fractures. The fracture gap modeled by a very elastic material.

12702.02.06-TR-01, XDIN® Develop and Deliver. (Data on file)

7. Jönsson A (MD, PhD), Mellgren M (M.Sc.), Theodorsson J (M.Sc.). Torsional rigidity of Dynaloc System for femoral neck fractures. 12702.02.04-TR-01, XDIN® Develop and Deliver.

(Data on file)

8. Brattjerd J-E (MD). Torsional Analysis of Femoral Neck Fracture Fixation: The Role of Implant Design and Configuration in a

synthetic bone model. (Data on file)

9. Loferer M. Torsional test. EndoLab® Mechanical Engineering GmbH – Test Report No.: 728.150417.120.450

10. Jönsson A (MD, PhD), Lannergård A. Biomechanical test – Pinloc; standing case. (Data on file)

11. Lenzner A, Kaur I, Haviko T, Sõgel V, Gapejevo J, Ereline J, Pääsuke M. Impaction bone-grafting increases the holding power of cacellous screws in the femoral head. Acta Orthop Scand

1999;70(1):25-28

12. Palm H, Gosvig K, Krasheninnikoff M, Jacobsen S, Gebuhr P. A new measurement for posterior tilt predicts reoperation in

undisplaced femoral neck fractures: 113 consecutive patients

treated by internal fixation and followed for 1 year. Acta Orthop.

2009 Jun;80(3):303-7.

13. Bray TJ, Smith-Hoefer E, Hooper A, Timmerman L. The displaced femoral neck fracture. Internal fixation versus

bipolar endoprosthesis. Results of a prospective, randomized

comparison. Clin Orthop Relat Res. 1988 May;(230):127-40.

14. Benterud JG, Husby T, Graadahl O, Alho A. Implant holding power of the femoral head. A cadaver study of fracture screws.

Acta Orthop Scand. 1992 Feb;63(1):47-9.

15. Lindequist S, Wredmark T, Eriksson S A V, Samnegård E. Screw Positions in femoral neck fractures: Comparison of two different

screw positions in cadavers. Acta Orthopaedica,64:1,67-70

16. Loferer M. Push-in and Pull-out, ASTM F543 - 13e Standard Specification and Test Methods for Metallic Medical Bone

Screws. EndoLab® Mechanical Engineering GmbH – Test Report

No.: 728.150616.120.466-rev. 0

References

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Implants Bone Screw | length 70 mm 150-0070S

Bone Screw | length 72.5 mm 150-0072S

Bone Screw | length 75 mm 150-0075S

Bone Screw | length 77.5 mm 150-0077S

Bone Screw | length 80 mm 150-0080S

Bone Screw | length 82.5 mm 150-0082S

Bone Screw | length 85 mm 150-0085S

Bone Screw | length 87.5 mm 150-0087S

Bone Screw | length 90 mm 150-0090S

Bone Screw | length 92.5 mm 150-0092S

Bone Screw | length 95 mm 150-0095S

Bone Screw | length 97.5 mm 150-0097S

Bone Screw | length 100 mm 150-0100S

Bone Screw | length 102.5 mm 150-0102S

Bone Screw | length 105 mm 150-0105S

Bone Screw | length 107.5 mm 150-0107S

Bone Screw | length 110 mm 150-0110S

Bone Screw | length 112.5 mm 150-0112S

Bone Screw | length 115 mm 150-0115S

Bone Screw | length 117.5 mm 150-0117S

Bone Screw | length 120 mm 150-0120S

Bone Screw | length 122.5 mm 150-0122S

Bone Screw | length 125 mm 150-0125S

Bone Screw | length 127.5 mm 150-0127S

Bone Screw | length 130 mm 150-0130S

Bone Screw | length 132.5 mm 150-0132S

Bone Screw | length 135 mm 150-0135S

Bone Screw | length 137.5 mm 150-0137S

Bone Screw | length 140 mm 150-0140S

Product information

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Plate | 120° | 6 mm 62-2106S

Plate | 120° | 8 mm 62-2108S

Plate | 120° | 10 mm 62-2110S

Plate | 120° | 12 mm (optional) 62-2112S

Instruments

Guide Wire | Ø3.2 mm | Length 300 mm 72-2004

Drill Sleeve | Ø6.7 mm 62-3010

Solid Step Drill | Ø6.7 mm 150-3013

Cannulated Step Drill | Ø6.7 mm 150-3016

Screwdriver Hex | 6,0 mm 150-3022

Screw Holder 150-3068

Drill Sleeve | Ø6.7 mm with handle 62-3038

Drill Adapter | Quick-Lock 62-3094

Parallel Guide for Solid Drill | 6 mm 62-3072

Parallel Guide for Solid Drill | 8 mm 62-3074

Parallel Guide for Solid Drill | 10 mm 62-3076

Parallel Guide for Solid Drill | 12 mm (optional) 62-3078

Nonomiya Guide | Ø3.2 mm (optional) 200.00.320

Plate Pusher / Drill Sleeve Hex 62-3086

Plate Fit Guide Wire Sleeve 120° 62-3098

Hansson Pinloc/Dynaloc Solid positioning template 120° 62-3102

Tray 150-1000

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IFUFor the latest version of this Instruction For Use. Please visit: http://download.swemac.com/Dynaloc-Femoral-Neck-Fracture-System

Manufacturer: Swemac Innovation AB 0413 Cobolgatan 1 • SE-583 35 Linköping • Sweden Phone +46 13 37 40 30 • Fax +46 13 14 00 26 E-mail info@swemac.com • www.swemac.com

P150-28-1-20180913 Print date: 2018-09-13

Dynaloc Solid

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