A New Approach For Correcting Hammertoe Deformities

By Gerald W. Paul, DPM

The advantages of lesser proximal interphalangeal joint arthrodesis in hammertoe surgery are numerous and well known. Arthrodesis is indicated in patients who have compromised intrinsic muscle function and are lacking both digital and metatarsophalangeal joint stability. Indeed, digital arthrodesis has always been an excellent procedure to consider if you fear reoccurrence of the hammertoe deformity due to biomechanical factors.
Through the years, surgeons have employed several methods and devices to facilitate fusion across the lesser proximal interphalangeal joints (PIPJ) for stable hammertoe correction. This has ranged from the end to end anastomosis to the popular peg-in-hole arthrodesis of the proximal and middle phalanx. Fixation has included K-wire fixation (both buried and external), Reese screws, 26-gauge wire and absorbable fixation. I’ve also found that the Stayfuse implant (Zimmer/Pioneer Surgical) provides an excellent and simple method for approaching PIPJ arthrodesis for hammertoe correction in replacement of K-wire fixation.

How Does It Work?
The StayFuse implant is a two component (male/female) threaded system made of titanium. The threaded proximal (female) portion is the larger of the two and is fit to the medullary canal of the proximal phalanx after resection of the distal portion. You would fit the distal threaded (male) portion to the medullary canal of the middle phalanx after you’ve resected the base. The distal component has an elongated fluted stem with a thread profile at the end for its patented snap connection to the proximal phalangeal portion. Furthermore, there is a unique “Hex-Lock” design at the junction of the two components that prevents rotation of the bones.
The two components have an array of sizes and diameters that you can use, depending upon the size of the phalanges. The different sized components are also color-coded so they’re easy to identify. The remainder of the instruments include: a universal driver handle that accepts a wide array of piloting; driver bits which you’ll need during the drilling/insertion portion of the surgery; an optional transfer template that helps to ensure good alignment of the piloting holes across the fusion site; probes; and a power attachment bit for the option of using power equipment.

Initial Step-By-Step Tips
The surgical procedure using the StayFuse implant is really based on a simple three-step approach: pre-drill, insert and snap together. Prior to the procedure, you should use preoperative X-rays and the Zimmer/ Pioneer Surgical OR template to determine the correct size of the implant components. The actual procedure itself is similar to performing an arthroplasty procedure of the proximal interphalangeal joint.
Dissect carefully through the soft tissue structures, transect the extensor digitorum longus tendon and reflect it both proximally and distally. This allows for easy exposure of the base of the middle phalanx and the head of the proximal phalanx. Using a saw, resect these two structures perpendicular to the long axis of the bones. This creates two parallel planes perpendicular to the central canal of the associated bones. Then drill the holes into the middle and distal phalanx with the correct size drills.
At this point, you should reconfirm toe length and alignment before proceeding. Then take the corresponding “prox” and “mid” components of the implant (as they are actually labeled in the set) and carefully screw them into their corresponding phalanx. The “hex” or hexagonal base of each component of the StayFuse implant should be flush with the bone. Snap together the “male” and “female” portions of the implant in a parallel fashion with moderate pressure while holding the toe in reduced position.
You should examine the apposition of the arthrodesis site and probe it if necessary to confirm good alignment and approximation. You can use fluoroscopy to confirm implant position and reduction of the arthrodesis site. Irrigation, soft tissue and skin closure are the same as in an arthroplasty procedure.

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