Orthopedic screw and method

A system for repairing a tissue injury in a patient, the system comprising:

• a screw having:
• a root having a proximal end and a distal section having a narrowing cross section toward a distal end;
• a thread atop the root along at least a portion thereof between the proximal end and the distal end, the thread having a helical pitch having a substantially constant value along a leading section extending proximal of the distal end and having a variable value along a trailing section extending proximal of the leading section, wherein the helical pitch decreases along the trailing section to the proximal end of the root, the thread further having:
• a leading face facing the distal end, the leading face making a first angle with a helical axis having a directionality pointing from the proximal to the distal end, the first angle decreasing from a first oblique angle adjacent the distal end to a second oblique angle adjacent the proximal end, the second oblique angle smaller than the first oblique angle;
• and
• a trailing face facing the proximal end, the trailing face making a second angle with the helical axis, the second angle decreasing from a first acute angle adjacent the distal end to a second acute angle adjacent the proximal end, the second acute angle smaller than the first acute angle;
• and
• an axial bore at least partially therethrough generally along a helical axis proceeding from the proximal end and into the root, the bore having a noncircular cross-sectional shape;
• and
• an elongated driving device having:
• a distal end having means for mating with the bore;
• a proximal end having means for being rotationally driven;
• and
• a noncircular cross-sectional shape along a distal section adjacent the distal end, the distal section dimensioned for entry into the bore and to permit relative axial sliding and rotational coupling movement therebetween.

A method for affixing two pieces of tissue of a patient together, the method comprising the steps of:

• moving a needle axially into a bore of a screw, the needle adapted to drive the screw, the screw having:
• a root having a proximal end and a distal section having a narrowing cross section toward a distal end;
• and
• a thread atop the root along at least a portion thereof between the proximal end and the distal end, the thread having a helical pitch having a substantially constant value along a leading section extending proximal of the distal end and having a variable value along a trailing section extending proximal of the leading section, wherein the helical pitch decreases along the trailing section to the proximal end of the root, the thread further having:
• a leading face facing the distal end, the leading face making a first angle with a helical axis having a directionality pointing from the proximal to the distal end, the first angle decreasing from a first oblique angle adjacent the distal end to a second oblique angle adjacent the proximal end, the second oblique angle smaller than the first oblique angle;
• and
• a trailing face facing the proximal end, the trailing face making a second angle with the helical axis, the second angle decreasing from a first acute angle adjacent the distal end to a second acute angle adjacent the proximal end, the second acute angle smaller than the first acute angle;
• manipulating the distal end of the screw to a position generally normal to a face of a first piece of tissue adjacent a separation between the first and a second piece of tissue;
• piercing the first piece of tissue with a tip of the needle;
• and
• driving the screw between the tissue pieces in a screwing motion by rotating the needle and hence the screw, the proximal decrease in the helical pitch serving to bring two pieces of tissue into apposition as the screw is advanced.

A method for repairing osteochondritis dissecans comprising the steps of:

• moving a needle axially into a bore of a screw, the needle adapted to drive the screw, the screw having:
• a root having a proximal end and a distal section having a narrowing cross section toward a distal end;
• a head extending proximal of the root proximal end;
• and
• a thread atop the root along at least a portion thereof between the root proximal end and the root distal end, the thread having a helical pitch having a substantially constant value along a leading section extending proximal of the distal end and having a variable value along a trailing section extending proximal of the leading section, wherein the helical pitch decreases along the trailing section to the root proximal end, the thread further having:
• a leading face facing the distal end, the leading face making a first angle with a helical axis having a directionality pointing from the proximal to the distal end, the first angle decreasing from a first oblique angle adjacent the distal end to a second oblique angle adjacent the proximal end, the second oblique angle smaller than the first oblique angle;
• and
• a trailing face facing the proximal end, the trailing face making a second angle with the helical axis, the second angle decreasing from a first acute angle adjacent the distal end to a second acute angle adjacent the proximal end, the second acute angle smaller than the first acute angle;
• manipulating the distal end of the screw to a position adjacent a face of a piece of cartilage that has separated from an adjacent piece of bone;
• piercing the cartilage with a tip of the needle;
• and
• driving the screw through the cartilage and into the bone in a screwing motion by rotating the needle and hence the screw, the proximal decrease in the helical pitch serving to bring the cartilage and the bone into apposition as the screw is advanced, until the screw head is positioned atop the cartilage.