Medullary nail

Details Medullary nail Medullary nail

1991-03-04

1993-11-23

Hafer, Robert A.

Surgery

Instruments

Orthopedic instrumentation

606 64, 606 62, A61B 1756

Patent

active

052639550

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a medullary nail having, forming a cavity, a wall having a tapering end, and having an insertion end and, disposed at intervals over its length, fixing holes which extend transversely through its wall.
It is already known that medullary nailing is used in the field of long tubular bones, following fractures, for settling the two end of the fracture in respect of each other after the fashion of an inner splint. For this, after the medullary cavity has been drilled out, the medullary nail is in most cases rammed home from the proximal end of the medullated bone and, once it is finally positioned, it is secured against axial displacement and twisting by a plurality of transverse bolts which pass through the bone cortex and fixing holes in the medullary nail. Since the periosteum which encloses the outside of the bone is not damaged to any substantial degree with this type of treatment, the nourishment which is important to the healing process is encouraged and infection obviated.
In the advanced stages of fracture healing, the locking pins on one side of the fracture gap can be removed. An axial loading now results in the released part of the bone sliding toward the still pinned bone, which thus produces an axial compression on the fracture gap, so that the newly formed bone becomes solidified.
In the past, lengthening of tubular bones or bridging of defects following shattered breakages, an inflammation of the bone or after the removal of tumours in the region of long tubular bones have been carried out by means of external fixing systems. In such cases, the bone ends are held by bone screws or wires which are passed through the skin and connected on the outside to a frame. By displacing the frame parts associated with the relevant bone ends, by means of tension bolts or wire winches, a relative movement between the bone ends is necessarily achieved, the minimal displacement distances being continuously bridged by newly forming bone tissue. Both for extension and also for segmental displacement, an osteotomy is necessary, and with segmental displacement, the segment of bone which is separated is drawn into the defective zone.
The prior art external fixing systems have an unfavourable force application point so that tilting occurs and expensive patient-impeding structures are needed and they constitute a constant risk of infection due to germs penetrating through the bone screws or the wires and they result in unattractive scars.
The problem on which the invention is based resides then in so modifying a medullary nail that while it maintains its function of serving as an inner splint and providing stability, it does at the same time permit an axial displacement of separate bone parts away from each other.
On a basis of the medullary nail of the type mentioned at the outset, this problem is resolved by an inner part, rotationally rigidly disposed in the cavity and which can be displaced longitudinally by a drive and by, provided in the region of the insertion end, a transversely continuous elongated hole either in the oppositely disposed sides of the wall forming the cavity or in the inner part and by at least one fixing hole aligned with the elongated hole, either in the inner part or in the oppositely disposed sides of the wall forming the cavity.
The drive for longitudinal displacement of the inner part into the cavity may be a mechanical, pneumatic or hydraulic or also an electric, electromagnetic or piezoelectric drive which is installed inside and/or outside the cavity. For example, in the case of a closed cavity, the inner part may take over the function of a piston adapted for longitudinal displacement in the cavity and which in a predetermined manner is subjected to pressure which produces the required displacement. By means of a pneumatic spring, a longitudinal displacement is also possible.
If the inner part is provided with an internally screwthreaded bore extending from one of its ends and if at the insertion end a rod with an external screwthread is rotatably mounted and

REFERENCES:
patent: 4227518 (1980-10-01), Aginsky
patent: 4858602 (1989-08-01), Seidel et al.
patent: 4875475 (1989-10-01), Comte et al.
patent: 5074882 (1991-12-01), Grammont et al.
International Search Report of application PCT/EP 90/01076 dated Jun. 12, 1990 (4 pgs.).
Office Action relating to the German Priority Application P 39 21 972.0, dated Jun. 3, 1990 (2 pgs.).

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