Instruments for minimally invasive surgery total knee arthroplasty
View Patent ↗An anti-backout stylus comprising a stylus and a locking stylus holder. The locking stylus holder engages the stylus at a series of discrete positions during insertion of the stylus into the holder. The locking stylus holder prevents inadvertent backing out of the stylus by preventing the stylus from being withdrawn to a previous one of the discrete positions. The locking stylus holder can preferably be selectively disengaged from the stylus to allow for selective withdrawal of the stylus. Each engagement of one of the discrete positions by the locking stylus holder preferably indicates a femoral size. The discrete positions are preferably defined by detents formed on the stylus and a stop member on the locking stylus holder. The locking stylus holder can be provided on an anterior rough cut guide, with the anterior rough cut guide preferably mountable on an intramedullary rod.
1. An anti-backout stylus instrument assembly comprising:
an anterior rough cut guide having an anterior resection slot therethrough, a locking stylus holder supported by said anterior rough cut guide, said locking stylus holder having a stylus bore for receiving a stylus, said stylus bore having a stop member disposed therein, said stop member biased to normally engage a detent of a stylus disposed in said stylus bore,
a stylus, said stylus having a substantially flat portion, a tip on a forward end, and a sloped portion between said flat portion and said tip,
a lower side of said flat portion of said stylus having a series of detents thereon, said detents configured to depress and pass over said stop member when said stylus is slid forward into said stylus bore, but to engage said stop member when said stylus is slid distally to thereby prevent inadvertent withdrawal of said stylus from said stylus bore, and each of said detents positioned to match a particular femoral size, such that each engagement of a detent by said stop member indicates a femoral size.
2. The instrument assembly of claim 1 , wherein each of said detents has an inclined forward side configured to slide over said stop member when said stylus is slid forward and a substantially flat or declined trailing side configured to abut against said stop member when said stylus is slid backward.
3. The instrument assembly of claim 2 , wherein a part of said stylus bore of said locking stylus holder is formed by a biased button, such that a user can selectively backout said stylus by depressing said biased button and simultaneously pulling said stylus distally.
4. The instrument assembly of claim 3 , wherein said biased button comprises a bore for receiving said anti-back out stylus, said stop member on a lower wall of said biased button bore, said biased button normally biased anteriorly such that said stop member normally engages said detents formed along a posterior surface of an engagement portion of said stylus.
5. The instrument assembly of claim 4 , wherein said biased button is biased by a captured spring.
6. The instrument assembly of claim 1 , wherein said anterior rough cut guide is configured to insert into a distal intramedullary paddle mounted on an intramedullary rod.
7. The instrument assembly of claim 6 , wherein said anterior rough cut guide is configured to insert into said distal intramedullary paddle via a pair of support bars depending downward from said anterior rough cut guide.
8. The instrument assembly of claim 1 , wherein each engagement of a detent by said stop member produces a sound, said sound providing indication of a femoral size.
9. The instrument assembly of claim 1 , further comprising femoral size markings on said stylus for use in visually determining a femoral size.
10. The instrument of claim 1 , further including a medial distal cut guide having a cut guide portion, said cut guide portion having a cut slot therein for use in resecting a medial distal condyle of the femur, a medial distal cut paddle supporting said medial distal cut guide, said medial distal cut paddle configured to mount on the intramedullary rod, said medial distal cut paddle and said medial distal cut guide configured to orient said medial distal cut slot substantially along an anterior-medial slope of the medial distal condyle when said medial distal cut paddle is mounted on the intramedullary rod to thereby define an anterior-medial approach for making a medial distal resection of the medial distal condyle. wherein said anterior cut guide has a curved profile, said curved profile generally tracking the anterior-medial slope of the medial distal condyle.
11. The instrument of claim 10 , including a distal medial cut guide having a stem portion, said stem portion including an offset portion,
said medial distal cut paddle including a platform, said platform having a distal medial cut guide bore configured to closely receive the stem portion of the medial distal cut guide in a sliding engagement to thereby allow for selective positioning of the cut guide portion relative to the distal end of the femur, and
said stem portion of said distal medial cut guide disposed in said distal medial cut guide bore of said platform such that said medial distal cut guide is offset proximally from said platform via said offset portion of said stem portion.
12. The instrument of claim 11 , wherein said platform has a flat profile on at least a proximal side thereof for positioning said platform against the medial distal condyle prior to resection of the medial distal condyle.
13. The instrument of claim 12 , further comprising said medial distal cut guide having one or more fixation bores on a proximal side of the cut guide portion for use in fixing the cut guide portion on the femur.
14. The instrument of claim 10 , wherein cut guide portion of said medial distal cut guide is slidingly engaged to said stem to thereby allow selective positioning of said cut slot along a range of anterior-medial approaches, and a means for selectively locking said cut guide portion on said stem.
15. The instrument of claim 10 , wherein said medial distal cut guide is universal.