Orthopaedic fixator

Details Orthopaedic fixator Orthopaedic fixator

1998-06-11

2001-01-23

Hirsch, Paul J. (Department: 3732)

Surgery

Instruments

Orthopedic instrumentation

C606S057000

Reexamination Certificate

active

06176860

ABSTRACT:

The present invention relates to an orthopedic fixator, more particularly, to a dynamic external fixator for osteosynthesis.
Fractures of long bone constitute about 30% of trauma-related disabilities that, in the U.S.A., affect more than 400,000 people per year, at a cost to the American economy of an order of tens of billions of dollars.
Recent evaluation of the accumulating clinical evidence clearly indicated that stabilization of all major unstable fractures by external or internal fixation within the first 24 hours in a patient sustaining multiple injuries decreases the duration of ventilatory support required, decreases mortality, decreases the time spent in intensive-care units, decreases the incidence of adult respiratory distress syndrome, reduces the incidence of multi-organ failure and late sepsis, reduces the incidence of complication related to the fractures and improves fracture outcome, and decreases the length of hospitalization and medical costs. In addition, early fixation greatly reduces fracture pain, facilitates access to the patient (essential in the case of open fractures), and simplifies nursing care. The need for forced recumbency is reduced, together with the risk of pressure sores, pulmonary infection, pulmonary embolus, etc.
External fixation is a safe and reliable method of achieving osseous stability in long bones. The advantages of external fixation are versatility, ease of application with minimum operative time and trauma (of great importance in the early stage after major trauma), and maintenance of access to any concurrent soft tissue injury. While in the past, rigidity of the fracture was considered advantageous and many of the available devices are built to eliminate all movement at the fracture site, it is now generally accepted that some movement at the fracture site is essential for good fracture healing; hence, dynamization of the fracture is desirable. However, known fixators that do allow dynamization, permit only compression, and this only on the “micromovement” scale of 0.2-0.6 mm. Thus, only stable fractures are suitable for application of present dynamic fixators. All unstable fractures have to have a static fixator until the healing of the fracture has progressed to the stage when the fracture is stable enough for dynamization. Yet it is precisely this early stage which requires the micromovements to induce sufficient healing to produce this stability.
Existing fixators described in UK Application No. GB 2,104,782 A and PCT Publication No. WO 91/11149, are designed in light of the assumption that “excessive movement will produce non-union. ” Recent experience has, however, shown the bone to be not only forgiving of “detectable” movements of several millimeters in the early stage, but that such early movements are actually desirable. The all-important callus response dying away with time, prior art fixators thus miss the optimal period for stimulating callus formation.
It is thus one of the objects oaf the present invention to provide a relatively inexpensive device that, while permitting immediate weight bearing by patients also with unstable fractures, will produce an axial compression/distraction cycle automatically controlled by the patient's own walking rhythm, a cycle that promotes the early formation of the primary callus so important for the rapid progress of the healing process.
According to the invention, the above object is achieved by providing a dynamic external fixator comprising an elongate body having an axial bore accommodating, in a first portion thereof, at least part of a first member of a universal joint and, in a second portion thereof, a linear guide means; a first arm having an end portion carrying the second member of said universal joint, said rod being provided with a plurality of apertures for the traversing therethrough of bone pins; and a second arm integral with, or fixedly attached to, a member of said guide means and provided with a plurality of apertures for the traversing therethrough of bone pins, and spring means accommodated in said axial bore of said body and bearing, on the one hand, against said first member of said universal joint and, on the other, at least indirectly, against said guide means, thereby opposing forces acting on said second arm.
The invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figures so that it may be more fully understood.
With specific reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.


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