Can Custom Bone Pegs Facilitate Effective Treatment Of Nonunions?

Author(s): 
By Devon Glazer, DPM

Nonunions can be difficult to address with any patient. Accordingly, the surgeon may benefit from any additional modalities that can prevent a recurrent nonunion after a revision. When evaluating a nonunion for surgical revision, one should critically evaluate the primary fixation. If a fixation technique has failed with the use of screws and both sides of the failed fusion have been penetrated, bone pegs can be a consideration for a secondary form of fixation.    The revised fusion will need primary fixation. My personal choice is to place the new fixation in a different manner than the one that had originally failed. When the surgeon removes the original screw fixation, there is a deficit. However, surgeons can use that deficit to their advantage as a lattice for bone growth. By placing a corticocancellous graft peg across the deficit site, the surgeon can achieve a secondary form of fixation with the benefits of rigidity and incorporation that corticocancellous grafts possess. The combination of pegs in conjunction with primary standard fixation will obviously increase stability. The increase of stability can only assist the surgeon in completing the goal of fusion.    The use of corticocancellous bone pegs has shown fusion rates of 90 percent in the hand.1 Commercial pegs may not be available and without a strong cortical wall, they could fail in the application process. The fabrication of a custom graft from a tricortical bone graft intraoperatively can actually be quite easy and completed in an efficient manner.

A Step-By-Step Guide To Surgical Technique

Presurgical planning should focus around fixation placement outside of the hardware deficits without compromising overall stability. Examples would be using a plate or staples instead of screws or placing the screws in a different manner. I also review the first surgical record to determine the length of the hardware that needs to be removed. This will optimize graft selection. Having an autograft harvested is ideal but rarely a reality. Therefore, I prescreen a few choices of allogenic tricortical iliac crest at the facility on the day of surgery.    The final look of the peg should be similar to a wedge nail with slight widening from the tip to the head. The cortical portion of the peg will have an “L” shape with cancellous bone filling in the “L” from tip to head. The short leg of the “L” will become the head of the peg. This shape gives rigidity to the peg.    In graft selection, I first look for an angle more than 90 degrees between the converging portions of the cortical wall. The rationale is if you have an angle at 90 degrees or more, you will have less fatiguing at the cortical convergence of the “L” while tamping the peg. Then I look for a straight, long arm portion of the graft. This will be the rigid portion of the peg. At this point, I roughly verify that the overall length will be as long as the fixation I am removing.    At the beginning of the case, I start soaking the graft per protocol to optimize OR time. If the alignment is good, I draw alignment lines at the failed fusion site in order to prevent loss of correction. After pulling the original hardware, one should measure hardware for width and length. Revise the site and place temporary fixation. Remove the graft from the pre-soak and place it on the Mayo stand on top of OR towels. One would do this to reduce the vibrations from the sagittal saw during the fabrication. This helps keep the graft on the stand. Immobilize the graft with a bone clamp.    The surgeon makes the first cut with a sagittal saw through all three cortical walls from side to side at slightly less than the screw width. It is best to hold the resulting graft with a Kocker clamp. Cut the graft to form the short leg and long legs of the “L,” sculpting the cancellous portion of the peg at a width slightly less than the screw and tapering it at the tip. At this point, the other portion can be a second peg or one can utilize it as a backup.    The surgeon should then curette the hardware deficit prior to applying the peg. Hold the peg longitudinally with a Kelly clamp and cautiously advance it to three-quarters of the deficit. At this time, it is usually necessary to advance the peg with a light mallet and tamp. Stabilizing the peg with a stat decreases graft fatiguing when using a mallet. The peg’s cortical head should match the patient’s cortical wall at final seating. Place final fixation and reevaluate the pegs for proper depth.

A Closer Look At Pertinent Case Studies

One 54-year-old female had a closing base wedge bunionectomy. I was consulted after several months of standard delayed union care without response. The patient underwent a revision as described above. I removed the patient’s previous hardware (screw) and replaced it with plate fixation. I applied the peg as discussed above. On plain films, the cortical portion is clearly visible and a point of secondary fixation. The patient underwent an uneventful recovery with fusion within a six-week time period.    A 53-year-old male had a Lapidus fusion for gouty joint destruction. The patient had a gouty attack several weeks after surgery and the fusion was destroyed. We removed the screw fixation and placed two pegs. We utilized Nitinol staples as the primary fixation. The patient underwent an uneventful recovery with good signs of fusion and was pain free in seven weeks.

Final Thoughts

The Glazer Bone Peg technique can act as a lattice for new bone through the cancellous bone. The stability of the cortical wall on one border of the peg adds a level of rigidity without interfering with the easily replaced cancellous tract of the peg.    The peg should never be the only fixation. Using a plate or staples will help avoid encountering a peg during fixation. If one places a compression screw, one should do it in non-perpendicular planes to the peg. Perpendicular placement of the screw to the peg will crack the longitudinal portion of the peg. Use caution with long fixation deficits. The longer the deficit, there is an increased likelihood of peg fatigue during the tamping process. In regard to OR time efficiency, I recommend doing a first time application with an assistant. The assistant can prepare the peg site and apply temporary fixation as the lead surgeon prepares the peg.    One would follow a similar postoperative course as a surgeon would utilize with any other type of revisional nonunion case. Dr. Glazer is an Associate Professor of Anatomy at Santa Ana College in Santa Ana, Calif. He is a Fellow of the Academy of Ambulatory Foot and Ankle Surgeons, and an Associate of the American College of Foot and Ankle Surgeons. Dr. Glazer is in private practice at Aloha Foot and Ankle Associates in Orange County, Calif. Dr. Burks is a Fellow of the American College of Foot and Ankle Surgeons, and is board certified in foot and ankle surgery. Dr. Burks practices in Little Rock, Ark.
 

 

References:

Reference 1.     Bohler J, Ender HG. Pseudarthrosis of the scaphoid. Orthopade. 1986 Apr;15(2):109-20.

 

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