Surgery – Diagnostic testing – Measuring anatomical characteristic or force applied to or...
Reexamination Certificate
2001-05-23
2002-11-12
Ganey, Steven J. (Department: 3752)
Surgery
Diagnostic testing
Measuring anatomical characteristic or force applied to or...
C600S587000, C073S789000
Reexamination Certificate
active
06478753
ABSTRACT:
The present invention relates to a tension measuring device, and particularly, but not exclusively, relates to a tension measuring device for graft fixation, for example, tendon or ligament fixation.
Due to increasing involvement of people with active sport, injuries are becoming increasingly common where tissues such as ligaments or tendons tear or detach from bone. Surgical techniques have been developed to reconstruct such soft tissues and to re-attach them to the relevant bone. Some of the most common types of such injuries are tearing of the anterior or posterior cruciate ligament (ACL or PCL). Reconstruction of such tissues generally involves replacement with a graft such as autologous or artificial tendon. An autologous tendon graft may be taken from the patients patella tendon or, alternatively, the Semi-tendinosus or Semitendinosus/Gracilis may be utilised.
A particularly important issue in these and other grafting operations is that the graft is fixed in the bone tunnel at the required and at a reproducible tension.
Therefore, in an attempt to improve the quality and consistency of arthroscopic ACL or PCL replacement, surgeons are paying more attention to the level of pre-tensioning applied to the graft prior to it being locked in place. The ultimate goal is to place the graft into the knee joint and lock it at a tension which accurately replicates the normal cruciate ligament of the patient. U.S. Pat. No. 5,713,897 describes an ACL tensioning device which maintains a required tensile stress on the distal end of a cruciate ligament graft fixed in the femoral tunnel section, and for maintaining that applied tensile stress as the ligament is mounted in or onto the tibia. However, this and other current methods of tensioning the distal end of the graft below the tibial tunnel are somewhat without justification as there is no way of measuring the tension of a normal ACL at its distal point. An applied force at this point could be said to be irrelevant, as there is no standard to compare against.
With a view to addressing the problems of the prior art mentioned above, or otherwise, it is one of the aims of at least preferred embodiments of the present invention to provide a device which, instead of applying a known tension to the distal end of the graft, measures the resultant effect that the tension applied at this point has on the graft in the joint.
According to a first aspect of the present invention, there is provided a tension measuring device suitable for measuring the tension of soft tissue attached to bone, the device comprising a body region, force applying means extending from said body and operable to apply a translational force to soft tissue attached to bone, and abutment means extending from said body and operable to abut, in use, a bone to which the soft tissue is attached, the abutment means being responsive to the application of translational movement to the force applying means to thereby measure the applied translational movement and the force applying means being responsive to the tension in the soft tissue to transfer said applied translational movement to the soft tissue below a predetermined soft-tissue tension and to extend above the said pre-determined tension to prevent further translation of the soft tissue.
Preferably, the extension of the force applying means is measured by suitable measuring means such as an associated translation scale.
Preferably, the force applying means is resiliently longitudinally deformable. Preferably, the abutment means is resiliently longitudinally deformable. Preferably, the abutment means distal end is biased, preferably, longitudinally biased, towards the bone, in use, to remain in contact therewith during the application of translational movement away from the bone. Preferably, the force applying means is under a fixed tension with respect to elongation thereof. Preferably, the fixed tension is applied by means of a tension spring which engages the force applying means to prevent elongation below a pre-determined applied force.
Preferably, the device measures the tension in the soft tissue by determining the extent of the translational movement of the soft tissue in response to the force applying means.
Advantageously, instead of applying a known force to the distal end of the soft tissue, the device measures the effect the applied force has on the soft tissue and thereby the tension in the soft tissue. Preferably, the device is used to measure the tension of the soft tissue which is attached to the bone by both the proximal and distal ends of said soft tissue.
Preferably, the force applying means and the abutment means extend outwardly in the same direction from the body region. Preferably, the force applying means and the abutment means are, preferably, spaced from each other and, preferably, substantially parallel to one another.
Preferably, the abutment means is operable to abut the anterior surface of a tibia bone, more preferably, the proximal anterior surface of the said bone. Preferably, the abutment means comprises an elongate shaft with, preferably, spike means at the distal end thereof, the spike means being operable to make a firm contact with the bone. Preferably, the abutment means comprises resilient means which urges the elongate shaft into abutment with the bone. The resilient means may be a compression spring which engages a proximal part of the abutment means to urge it into abutting contact with the bone.
The abutment means may further comprise locking means to lock the abutment means in a retracted position. The locking means may be released thereby urging the abutment means outwards towards the bone. Preferably, the abutment means comprises suitable translation measuring means, preferably, a translation scale on which the applied translational movement, typically, translation of the body region with respect to the bone may be measured. The translation scale may be located within the body region at the proximal end of the abutment means to that of the bone abutting end.
The translation scale may be analogue or digital.
Preferably, the force applying means is a pulling means which is placed, preferably, in direct contact with the soft tissue to which the translation force is to be applied. Preferably, the pulling means is adapted at its distal end to abut at least part of the rearwardly facing side of the soft tissue with respect to the body of the device. Preferably, the pulling means comprises a hooking means which is hookable around the soft tissue. Preferably, the pulling means comprises an elongate shaft which has hooking means at the distal end thereof. Preferably, the hooking means is hooked around the rear of the soft tissue and arranged to apply translational force to the soft tissue in the required direction.
Preferably, the pulling means comprises resilient means which is arranged to apply a pre-determined force to the soft tissue resulting from the translational movement applied to the tissue by the user. The resilient means may be associated with the pulling means and may be a spring, preferably a tension spring which, preferably, engages at least part of the pulling means.
Preferably, the force applying means is associated with a translation scale by which the elongation of the force applying means and thereby the tissue may be measured. The translational movement in the tissue is determined by subtracting the elongation of the force applying means from the applied translational movement. The translation scale may be located within the body region of the device. The translation scale may be analogue or digital and may measure the extent of the movement of the soft tissue under a specific force of the resilient means and this may be measured in appropriate units. Preferably, a tension spring at a pre-determined tension is used in engagement with the force applying means.
The pulling means may comprise adjustment means to adjust the resilience or pre-determined tension of the pulling means.
The device may be used to measure the tension of any soft tissue attached to any bone. Pr
Atlantech House
Ganey Steven J.
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