chpt 72: Brachymet Flashcards
how does a floating toe result with a brachymet?
Short metatarsal bears no weight, and the flexor plate fails to load, the digit does not purchase the ground and becomes unstable
what are the 3 main techniques for brachymet?
- lengthening/slide osteotomy- if there is a small amount of length needed, or sagittal plane deformity, sagittal Z osteotomy can be used
(usually hard to obtain the amt of length needed) - osteotomy with insertion of bone graft
- callus distraction
what is a risk for bone graft osteotomy
(biggest concern is neurovascular compromise) - great concern when one -stage lengthening procedure is performed, all soft tissues have to be stretched and can cause vasospasm and can potentially lose digit.
when does callus start to form during callus distraction?
approximately 3 weeks callus begins to form as fine cancellous bone and laid down in columns
regenerating bone continuously matures during and after lengthening. The radiolucent growth zones becomes ablated approximately 4 weeks after distraction have started
When does corticalization take place?
aka cortex formation take place around 4 to 6 months after surgery and continues to remodel over a year or more
what is the difference between regenerate bone and fracture callus
callus distraction has organized longitudinal striations
fracture callus has more bulbous shape and lacks longitudinal striation
what are the two types of incisional approach for calluous distraction
1st: make incision over the proximal metaphysis of the affected metatarsal. this allows for execution of the osteotomy. then small stab incision may be placed over the proximal and distal pin sites.
2. one incisional approach with standard dorsal linear approach over affected metatarsal: incision begins over distal aspected of cuboid or corresponding cuneiform and distally into the affected metatarsal.
where is the best location to perform osteotomy for brachymet?
proximal metaphysis :has greater surface are for distraction. It has increased strength and stability due to larger diameter of the bone when compared to diaphysis
there is also more soft tissue in the area which increases vascularity and stability via ligamentous and muscular attachment.
proximal metaphysis is rich in cancellous bone and has increased metabolic activity compared to diaphysis
what is the pin alignment and order to placement?
The most proximal of the distal pins is placed first to ensure that it is not too close to proposed osteotomy. (should be bicortical)
the 2nd and most distal pin is then placed with continuous use of the frame as a guide
then the two proximal pins placed next: the first proximal pin is placed closest to osteotomy-this is ensure that there is adequate space maintained between the pin and the osteotomy. (4th and final pin is the most proximal pin)
place all pins prior to making osteotomy. pins should be parallel to one another
what can make pin penetration challenging on the 4th met
it often has a dorsal ridge that makes it hard to put in proper alignment
Describe osteotomy cut
transverse osteotomy through and through at the proximal metatphysis.
Also important to make osteotomy perpendicular to the long axis of the metatarsal to avoid angulation during distraction and lengthening process
when does the distraction process start? what is this time period called between surgery and prior to distraction process
7th post op day (latency period)
what is the recommended distraction for brachymet?
different recommendations:
lesser metatarsal: 5/8** mm/day
nunley rec 0.25 mm q6h= 1mm/day
Rate of distraction is key to avoiding complications: smaller, more frequent interval for distraction is recommended.
Turning rate preferred for lesser metatarsal is 1/8 mm 5x a day *****
what is the recommended amount of lengthening in compared to original length? what happens if it overlengthens
it should not exceed 40% of original length of the metatarsal. When metatarsal is lengthened greater than 40% of its preoperative length, complication such as decreased ROM and joint stiffness of MPJ, subluxation of MPJ, digital deviation and neurovascular compromise.
If overlengths, the MPJ typically dislocates.
depending on how much distraction needed, usually takes about 3-4 weeks
what is the rule of thumb for the ossification period
Latency period plus the time of distraction = estimated time for consolidation
(1:1 ratio)
