ZA200603205B

ZA200603205B - Intramedullary nail

Info

Publication number: ZA200603205B
Application number: ZA200603205A
Authority: ZA
Inventors: Schlienger Andre; Buettler Markus; Senn Peter
Original assignee: Synthes Ag
Priority date: 2006-04-21
Filing date: 2006-04-21
Publication date: 2007-04-25

Description

E , 1953/PCT 20.10.2003

English translation of the specification of the Internati onal Patent Application Nos.

PCT/CHO03/00683 “Iritramedullary pin” in the name of SSynthes AG Chur

Intramedullary pin

The invention conce rns an intramedullary pin, in particzular for the tibia, according to the preamble of patent claim 1.

From CH-A 674 613 a generic intramedullary pin is Eknown, that has a proximaal and a distal end po-riion, both of them angled away from the central part. The proximal end portion can have a curvature with a maxi mum radius of 220 mm.

Because by nature the tibiae is different for each patie=nt and particularly its lengtin and the size of the tibial plateau, which are interdepe=ndent, are of different size , the intramedullary p in should also have parameters which change according to the length. Thus a firm curvature radius, valid for eavery intramedullary pin of whatever length, is not optimal for the insertion, because it will require am increased force and will lead to an increased loss of reeduction.

This is where the inwention wants to provide remedy. The object of the inventiom is to produce an int ramedullary pin that takes the aratomical ratios of the tibia , relative to its length , into consideration and is optimal particularly regarding the course of the medull ary canal.

This objective is achieved according to the inventiorm with an intramedullary pir having the features of claim 1.

The advantages achieved by the invention are essentially that as a result of the intramedullary pin according to the invention a) the insertion forc e is reduced in the case of certain indications, especially im the case when the technique of not-opening drilling is used, b) due to the low ins ertion force a lesser loss of reduction is present, c) after the insertion the intramedullary pin is in the b iomedically ideal position im the medullary camal,

d) as soon as the intramedu llary pin comes against the posterior wall during the insertion, its curvature becomes effective (in the case of the state-of-the-art the intramedullary pin has to be either bent at this stage osr the loss of reduction has to be taken into accows nt).

In the case of a particular ermbodiment the distal end of tHe intramedullary pin is constructed as a straight se ction having a length of 1 =< L. This brings about several advantages, namely: a) a concurrence with the bimmechanical axis, b) the possibility of a distal fraction repair without loss of reeduction, and c) the displacement of distal bone fragments is avoided.

The length 1 of the distal end portion of the intramedul lary pin is advisedly in the range of 0.20-0.55 L, pre ferably in the range of 0.25-0.50 L.

In the case of a particular embodiment the curved secstion includes with the straight section an angle a, that is in the range of 7°-12< and preferably in the range of 8°-9°. Together wi th the distal end section andl the special curvature radius this will result in an optimum position of the intramedullary pin in the medullary canal relative to th e entry point of the intramedullary pin.

In the case of a particular embodiment the cross-sectiom, at right angle to the central axis of the intramedu llary pin, is not circular and has preferably an oval or elliptical construction. By virtue of this the intramedullary pin can be introduced deeper into the medullary ca nai until it reaches the posterior wall.

In the case of a further embodiment the intramedullary pin has a longitudinal bore (7) that is coaxial with the central axis. This makes t he introduction of the intramedullary pin possible bby a guide wire, that can also be used for the drilled out operating technique.

In the case of a further embodiment the proximal end porticon of the intramedullary pin is constructed as a straight section with a lengthm of P < L. This has advantages ass far as production technology is concerned. The length P of the proximal end portion is advisedly in the range of 1/6-1/3 L.

In the case of a further embodiment in the region of the proximal end portior at least one locki ng hole, extending transversely to th e central axis, is present.

In the case of a further embodiment in the region of the distal end portion at least one locking hoele, extending transversely to the ceratral axis, is present. By usimg a locking elememt, introduced through the locking hole, both a positional fixing in the axial direc tion, i.e. fixing against axial dislocation, and a rotational fixing, ie. fixing against torsional dislocation, is affected.

In the case of a further the curvature radius R Of the curved section is in the range of 350-1200 mm, preferably in the region of 400-1100 mm. The L/R ratmo is advisedly in th e range of 0.3-0.7, preferably in the wange of 0.4-0.6.

In the case of a further embodiment two locking moles, extending transversel y to the central axis, are present in the region of the d istal end portion. This will b-ring about several advantages: a) the possibil ity of locking in several directions, b) an angularly stable fixing of the bone fragments relative one another, ¢) a more favourable absorption of the bending meoments and axial and torsieonal loads.

In the case of a further embodiment the two lockire g holes, extending transver-sely to the central axis, include between them an angle of 45° to 90°.

In the case of a further embodiment the distal end portion has three locking holes, while the middle locking hole is at a different distance from the other two holes.

The advantage of this arrangement is that none of the axes of the three loc king holes can potentially become an axis of rotation. This results in a reduced play between the intramedullary pin and the locking ele=ments.

The i mplanting method is briefly described in the following based on a ¢ annulated intrarmedullary pin: step ‘A! establishing and holding the optim al reduction, depending on the type of fracture, step B: opening the medullary canal with trae aid of an opening instrumert, so that the entry angle and the orientation relative to the medullary can al, to suit the operating technique employed, agree, step C: introducing a guide wire up to the distal, future end position of the intramedullary pin and determi ning the length of the required intramedullary pin, step D: the intramedullary pin, pre-ass embled on the insertion h andle, is introduced into the medulla through the entry channel via the guide wire, step E: after checking the axial positior of the intramedullary pin and the reduction the intramedullary pin is locked by using the locking options.

The invention and developments of the in vention are explained in detail in the follow ing based on the partly schematic illustrations of an embodiment.

They show in:

Fig.1 — a longitudinal section through the intr-amedullary pin, and

Fig.2 — a section along line 1l-1l of Fig.1.

The intramedullary pin 1, illustrated in Figs. 1 and 2, is intended to be use=d on the tibia. Ft has a proximal end portion 2, a distal end portion 3 intended for the introduction into the medulla and a central axis 6. The proximal end portion 2 is provided with a threaded bore 11 to accept a conventional assistance. The overall length L of the intramedullary pin 1 is 255 mm. Furthermeore, the intramedullary pin has a curved section 4- with the length of G = 1275 mm, having a curvature radius R of 380 mm. “Thus the L/R ratio is 0.67. After the intramedullary pin 1 has been implanted, thes curvature of the intramedullaary pin in the plane of the drawing corresponds to thes anatomical medio-lateral plane, i.e.

after the implartation the intramedullary pir 1 is bent in the ante=ro-posterior direction.

The distal end p-ortion 3 is a straight section 5 with the length of 1 = 127.5 mm. 5 The curved sect ion 4 includes an angle a = 8° with the straight section 5.

The intramedullary pin further has a passing through longitudinal bore 7, that is coaxial with the «central axis 6.

The proximal en d portion 2 is constructed as a straight section 8 with a length of

P=75mm,sothatP=03L.

In the region of the proximal end portion 2 of the intramedullary pin 1 there are two locking holes 9 extending transversely to the central axis 6, while ne of them is constructed ass a slot, so that to enable to carry out a compression.

In the region of khe distal end portion 3 there are three locking holes (10,12, 10) extending transv ersely to the central axis 6, w~hich are provided in different radial directions and imclude an angle of 90° with One another. At the sanme time the middie locking hole 12 is at a different distance to the other two locking holes 10.

Claims

CC ¢ 1953/PCT

14.7.2004 6 . ’ English translation of thes amendments according t.o PCT Article 19 of the International Patent Application No. PCT/CH03/00683 ‘Intramedullary pin” in the name of Synthes AG Chur Patent claims

1. An intramedullary pin in particular for the tibia, with & proximal end portion, a distal end portion intended for the introduction into &he medulla and a central axis , that A) has a total length of £_in the range of 200-500 mr, and B) a curved section with the length of G < L, characterised in that C) the curved section with the length of G has a curvature radius R in the range of 300-1300 mm, D) the L/R ratio is in the range of 0.2-0.8, and E) the distal end portion is constructed as a straight section with the length of 1 <L.

2. An intramedullary pin according to claim 1, characte rised in that the length I is in the range of 0.20-0 .55 L.

3. An intramedullary pin according to claim 2, characte rised in that the length 1 is in the range of 0.25-0 .50 L.

4. An intramedullary pin according to claim 2 or 3, char—acterised in that the tangents at the two end points of the curved section include an angle a in the range of 7°-12°, preferably 8°-10°.

5. An intramedullary pin according to any one of claimss 1 to 4, characterised in that the cross-section, a t right angle to the central axis, is not circular and has preferably an oval or elli ptical construction.

6. An intramedullary pin according to any one of claimss 1 to 5, characterised in that it has a longitudinal bore that is coaxial with the central axis. AMENDED SHEET

L}

7. An intramedullary pin according to any one of claims 1 to 6, characterised in that the proximal end portion is constructed as a straight s ection with the length of P< L.

8. An intramedullary pi n substantially as described with reference to the accompanying drawings. AMENDED SHEET

X ¢

8. An intramedullary pin (1) according to claim 7, characterised i n that the length P of t he proximal end portion (2) is in t he range of 1/6-1/3 L.

9. An in tramedullary pin (1) according to any one of claims 1 to 8, characterised in thaat in the region of the proximal ened portion (2) at least onez locking hole (9) is prexsent that extends transversely to the central axis (6).

10. An imtramedullary pin (1) according tc any one of claims 1 to 9, characterised in that in the region of the distal end portion (3) at least one locking hole (10) is present that extends transversely t o the central axis (6).

11. An intramedullary pin (1) accord ing to any one of claims 1 to 10, cha racterised in that the curvature raadius R of the curved se=ction (4) is in the range of 350-1200 mm, preferably in the region of 400-1100 mm.

12. An intramedullary pin (1) according to any one of claims 1 to 11, cha racterised in that the L/R ratio is in the range of 0.3-0.°~7, preferably 0.4-

0.6

13. An intramedullary pin (1) according to any one of claims 1 to 12, chawracterised in that in the region «of the distal end portiom (3) two locking holes (10) are present extending trarsversely to the central =xis (6).

14. An intramedullary pin (1) according to claim 13, character-ised in that both lock<ing holes (10), extending transversely to the central axis (6), include bet-ween them an angle of 45°-90°.

15. An. intramedullary pin (1) according to any one of «claims 1 to 14, characterised in that the distal end portion (3) has three locking holes (10, 12, 10), while the middle locking hole (1 2) is at a different distarce from the other two holes (10).