Device for external fixation of bone fragments

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BACKGROUND OF THE INVENTION

This invention relates to a device for the reduction of bone fractures of the type having pins intended to be inserted in groups into the portions of bone to be mutually fixed or realigned, the pins being connected by sliding universal articulated couplings to at least one rigid tie-rod.

External fixation devices are illustrated and described, for example, in catalogue No. HJ 1012 E published in April, 1977, by Ets Jaquet Freres, Geneva, Switzerland, entitled "Osteotaxis.RTM.".

SUMMARY OF THE INVENTION

It is an object of this invention to provide a device of this type which is more simply constructed, easier to handle, and lighter in weight.

A further object of this invention is to provide such a device which ensures a more stable connection between the pins (so-called Steinmann pins) and the bone fragments to be realigned.

To this end, in the device according to the present invention, the improvement comprises a plurality of sliding universal articulated couplings, each including a T-shaped member having two arms exhibiting respective longitudinal slots, clamping means cooperating with associated nut-and-bolt assemblies disposed in each of the slots for adjustably clamping and unclamping end portions of the pins to the arms of the T-shaped member, a spherical adapter sleeve split by staggered slots and slidingly mounted on the tie-rod, a coupling locking clamp comprising a ring portion having a spherical-shaped inner clamping surface embracing and fitted to the adapter sleeve and two straight end portions to which clamp lugs having respective screw holes are integrally affixed, and a further nut-and-bolt assembly traversing the clamp lugs through the screw holes for securing the coupling locking clamp to the upright of the T-shaped member and, when tightened, for simultaneously preventing both swivelling of the coupling locking clamp and the T-shaped member about the center of the spherical adapter sleeve and sliding of the adapter sleeve, together with the coupling locking clamp and the T-shaped member, along the tie-rod.

In a preferred embodiment of the invention, one side of the upright of the T-shaped member includes a recess fitted for receiving one of the clamp lugs. In addition, the tie-rod or tie-rods may be tubular.

BRIEF DESCRIPTION OF THE DRAWINGS

This preferred embodiment of the invention will now be described in detail with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a device according to the present invention for the reduction of fractures, and

FIG. 2 is a side elevation view in partial section taken along the line II-II of FIG. 1 of one of the sliding unviersal articulated couplings utilized in the device.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The overall construction of the device illustrated in FIG. 1 is similar to that of the device shown on the cover of the above-mentioned catalogue. In both cases, it is one of a plurality of possible mountings which can be produced with a greater or lesser number of the various elements, as will be evident from the other illustrations in the catalogue.

Resiliently flexible pins 1 (Steinmann pins), intended for insertion in the bone portions K1, K2 to be mutually fixed or realigned, are connected to rigid tie-rods 2 by sliding universal articulated couplings 3. In order to achieve high bending resistance combined with light weight, tie-rods 2 take the form of stainless-steel tubes.

Each coupling 3(FIG. 2) is made up of a T-shaped block 4, nut-and-bolt assemblies 5 & 6, clamping members 7, an adapter sleeve 8, a coupling locking clamp 9, and a nut-and-bolt assembly 10 & 11.

T-shaped block 4 has elongated slots 12 in its arms for the passage of bolts 5, which, together with nuts 6 and clamping members 7, make it possible to clamp pins 1 to block 4; a continuously-variable mutual adjustment can be carried out in two orthogonal directions prior to such clamping. Adapter sleeve 8 is split by staggered slots for increasing its radial elasticity, is spherical in shape, and is slidingly fitted on the smooth surface of tie-rod 2. Coupling locking clamp 9 comprises an open ring portion 9a embracing adapter sleeve 8 with a spherical-shaped inner surface fitted thereto, and two end portions to which clamp lugs 9b having holes for bolt 10 are integrally affixed; bolt 10 also passes through the upright of T-shaped block 4, which has a lateral recess fitted for receiving one of the two clamp lugs 9b, so that coupling locking clamp 9 is secured on block 4 against rotation about bolt 10. By tightening nut 11, ring portion 9a is pressed against adapter sleeve 8, and the latter in turn against tie-rod 2, so that tie-rod 2 is firmly coupled to block 4. Beforehand, however, any desired adjustments may be made about the center of spherical adapter sleeve 8 and along tie-rod 2 in the course of reducing the fracture. thus neutralization, compression, or distraction of the bone fragments may easily be effected and fixation secured. By means of the sliding displacement of clamping members 7 on the arms of block 4 prior to tightening of nuts 6, two important effects can be achieved:

(1) If so desired, the relaxed, straight Steinmann pins 1 can be subjected to bending stress, as shown in FIG. 1, whereby they are prevented from unintentionally slipping in the holes drilled in bone portions K1, K2.

(2) After the associated clamping members 7 on the respective blocks 4 have been tightened, the pins 1 situated in each of the bone fragments K1 and K2 are no longer parallel, and together with blocks 4 and clamping members 7, they form a kind of stiff truss structure; the two truss structures rigidly interconnected by the two tie-rods 2 hold bone portions K1 and K2 immovably fast to one another when they are subjected to axial stress, e.g., by the weight of the patient. Hence, the patient can be put "back on his feet" quite soon after a fracture of the femur or tibia has been reduced, even when a comminuted fracture is involved.

While specific embodiments of the present invention have been shown and described in the specification and drawings to illustrate and explain the present invention, it should be understood that the present invention is not limited to these specific embodiments, but contemplates other embodiments falling within the scope of the following claims.

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