Surgery – Instruments – Orthopedic instrumentation
Patent
1993-09-16
1995-08-01
Pellegrino, Stephen C.
Surgery
Instruments
Orthopedic instrumentation
606 54, A61B 1760
Patent
active
054376661
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to an external fixation device for osteosynthesis, in particular for the treatment of distal radius fractures.
BACKGROUND OF THE INVENTION
Distal radius fractures are among the most common encountered fractures in emergency departments of hospitals. Usually they are referred to as Colles or Pouteau fractures. The frequency of report is about 10% of all fractures. The most common cause of this fracture are a fall on the outstretched hand, a fall from height and motorvehicle accidents. The classic method of treatment is closed reduction of the fracture and plaster cast support. However, plaster cast is only sufficient for fractures with no or little displacement and/or comminution. Other treatment possibilities include open reduction and plate osteosynthesis, functional bracing and external fixation. External fixation is mainly applied in comminuted, intra-articular and/or unstable fractures. The management of distal radius fractures by means of external fixation is based on the principle of ligamentotaxis. This means that when a force is applied across a joint (e.g. the wrist) by distraction, the capsule and ligaments of the joint are placed under tension and thus tend to maintain the reduction of the adjacent bone fragments.
The conventional external fixation devices consist of a rigid frame built up from two proximal pins (e.g. Kirschher wires) in the radius and two distal pins in the second and/or third metacarpal, connected by one or more cross bars. Since this configuration of the frame crosses the wrist joint, no movement of this joint is possible in presence of the external fixator. This can result in severe complications like post-traumatic joint arthrosis, reflex sympathetic dystrophy (Sudeck's dystrophy) and osteoporosis, leading to impairment of wrist function and further morbidity.
From EP-A1 0 458 486 RICHARDSON a bone fixator frame is known which allows relative rotation of the bone segments in two axes. Similar single axis frames have been used for the fixation of radius fractures. These known fixators do not allow for physiological range of movement and require less than optimal surgical approach.
SUMMARY OF THE INVENTION
In accordance with the invention an external fixation device is provided which will enable e.g. motion of the wrist joint about all three axes, while keeping the center of rotation at one point during treatment of the fracture and thus preventing the above mentioned complications.
The device comprises a first and a second longitudinal bar as carrier for fixation means to the bone, a three-dimensional shell attached to the extremity of said first bar and a gliding element attached to the extremity of said second bar, whereby said shell and said gliding element are movably arranged to each other in such a way that the free ends of said first and second bars are extending in opposite directions.
The three-dimensional shell may have an ellipsoid or any other suitable three-dimensional shape but preferably has the shape of a spherical zone.
The gliding element needs at least three gliding points on each side of the shell, preferably it consist of a first disk gliding on one side of the shell and a second disk gliding on the opposite side of the shell, the first and second disks being connected through a central hole in the center of the shell. Most preferably the first and second disks are provided with an annular gliding area for contacting the shell.
The two disks of the gliding element can either be fixed exchangeably or permanently to each other. Preferably the first and second disks are connected by means of screw threads allowing releasable relative positioning of said disks to said shell.
In another aspect the invention comprises a third longitudinal bar releasably fixed and running parallel to said first and second longitudinal bars, which is to be used only temporarily to immobilize the fixator and the joint.
While a number of metals can be used to construct the external fixation device according to the invention, alu
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Goslings Carel
Tepic Slobodan
Pellegrino Stephen C.
Synthes (U.S.A.)
Tucker Guy
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