Why Locking Plates Will Make Your Surgical Life Easier
- Patrick DeHeer DPM FACFAS
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I was having a conversation with my orthopedic surgeon friend, James Friedlander, MD, and he made a comment that really caught my attention. He said locking plates were the most significant advancement in orthopedic surgery in the last 25 years.
Are you using locking plates? If not, is it because you do not understand the concepts or applications of these devices? Hopefully, this blog will provide you with something that will make your surgical life easier and more predictable.
Locking plates in the most basic terms combine the best features of rigid internal fixation and external fixation. There are many uses for locking plates, regardless of whether you do forefoot surgery or all types of foot and ankle surgery. Once you understand the concepts and principles, you will see the advantages locking plates have to offer.
The primary goal of locking plates is to increase the functional performance of the plate, screw and bone connection in order to improve healing (especially in poor quality bone). Traditional plating has two modes of failure, namely toggle between the screw/plate interface and instability, which results when the patient load is greater than the bone/plate frictional force. With locking plates, instability results only when the patient load is greater than the compressive strength of the bone. This is a significant difference.
Locked plating does not depend on screw purchase in bone. It relies on rigid, fixed, right angle stability by locking the screw into the plate. Unicortical fixation in locking plates provides fixation similar to conventional bicortical fixation. By locking the screws into the plate, locking plates do not compress the periosteum and bone is not pre-stressed. With traditional plating, the surgeon can use a well-contoured plate to help reduce a fracture and the plate then maintains the reduction as compression occurs between plate and bone.
Plate contour is not critical for fixation and locking screws will not reduce the fracture. The surgeon should first reduce the fracture or fusion site, and then fixate the site. These are the biomechanical features that differentiate locking plates from standard plates.
This rigid, fixed, right angle fixation is similar to that provided by external fixation. One can accomplish compression by having a compression hole or combination hole that possesses both a locking portion and compression portion with a bicortical compression screw. After achieving compression, adding more rigid, fixed, right angle fixation with multiple locking screws further reinforces the construct. Using locked plating with a compression screw adds stability to the construct. This is all internal fixation in comparison to an external fixator, and avoids the potential complications associated with this type of external fixation.
A Step-By-Step Guide To Using Locking Plates
So when do I use locking plates? The most common procedure I use locking plates for is first metatarsophalangeal joint (MPJ) arthrodesis. I use a 4.0 cortical compression screw from the medial aspect of the base of the proximal phalanx to the lateral aspect of the first metatarsal head. I then reinforce the fixation with a 2.4 mm locking plate with five or six holes.
I fill the first hole, the more proximal of the distal two holes, with a locking screw. I place the next screw in the proximal aspect behind the sesamoids and use a compression screw in the rear portion of the combination hole. This screw must be bicortical. I fill the remaining screw holes with locking screws except the hole over the fusion site. If the distal aspect of the plate is too far off the bone, one can bring it down to contour better to the proximal phalanx by using cortical screw the purchases both cortices.
A locking screw will not bend the plate down to the bone. Some models of locking plates for this procedure are already pre-bent in dorsiflexion and abduction. This can be especially helpful in revision cases of failed implant arthroplasty (of course I think all of them fail at some point in time).
Other uses for locking plates include tarsometatarsal arthrodesis, metatarsal fractures, tarsal arthrodesis, revision surgery and for intra-operative failed fixation (I use a 2.0 locking plate when I have intra-operative fixation failure on a Weil osteotomy).
Locking plates provide the foot and ankle surgeon with a great deal of versatility and reliability. If you have not used them, meet with a representative of companies that carry them. If you play with locking plates on some saw bones and get familiar with them, you will come to appreciate their use.