How A Sagittal Z Osteotomy Can Be Beneficial With Revisional Surgery Of The First Metatarsal
- William Fishco DPM FACFAS
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An important part of any busy podiatric surgeon’s practice is revision of failed foot surgery. Since forefoot surgery makes up the majority of procedures performed on the foot, one commonly encounters aberrations of the metatarsals from prior surgery. One of the most common conditions affecting the forefoot includes excessive shortening or sagittal plane malposition of the first metatarsal.
The sagittal Z osteotomy is a powerful and versatile osteotomy that can lengthen or shorten the metatarsal, and reposition the bone within the sagittal plane. Even a small amount of transverse plane correction, such as reducing the intermetatarsal angle, can occur by modifying the osteotomy by performing it in an oblique fashion.
The osteotomy works well when one needs approximately 5 mm of lengthening and/or with sagittal plane repositioning. I will also use the osteotomy when significant shortening of a metatarsal is necessary. I have found that shortening a metatarsal more than 3 to 5 mm with a double-V osteotomy or a Weil osteotomy causes problems with instability or plantarflexion of the capital fragment respectively. Modifications of the Weil osteotomy by removing a segment of bone can help with excessive plantarflexion. However, I find more joint stiffening occurs with the latter versus a sagittal Z, which is an extra-articular osteotomy.
As with any surgical procedure, there are some drawbacks. There is a learning curve as certain aspects can be technically challenging. Fixation for a lesser metatarsal can be tricky, especially for the central rays. The majority of the osteotomy is in cortical bone. Therefore, healing will be prolonged. In fact, on a lesser metatarsal, it may take six months or more before the osteotomy appears to be completely incorporated on X-ray although clinically, the bone is healed prior to that. Finally, a period of postoperative non-weightbearing is necessary with the sagittal Z osteotomy, unlike a distal metaphyseal osteotomy.
A Step-By-Step Guide To Surgical Technique
The technique for lengthening a first metatarsal is straightforward. Perform standard dissection over the great toe joint and extend it toward the base of the metatarsal. Retract the extensor tendon laterally. Create a midline periosteal incision to expose the bone. Then place guide pins distally and proximally in the center of the bone. Make sure the osteotomy is long enough so you can achieve two-screw fixation from medial to lateral with ample room between the screws to reduce stress risers.
I typically make the arms of the osteotomy first although I don’t think it matters when you do this. Make the proximal arm exit medially to avoid the nutrient artery and make the distal osteotomy laterally. Now cut the midline osteotomy longitudinally to connect the arms.
After completing the osteotomy, remove the guide pins and begin manipulation. Typically, I will pull the great toe and hold it for a few minutes to relax soft tissues. Once I manipulate the bone to the proper position in length, I can manipulate sagittal plane position if necessary. Typically, it is a metatarsal elevatus deformity that is undergoing correction and the head of the metatarsal will be tilted down (swiveled) slightly. It is important to maintain as much bone-to-bone contact of the dorsal and plantar cortices when doing this. Unlike a Scarf osteotomy in which troughing occurs, the entire bone is not plantarly displaced, just tilted down slightly.
Once the position is to your liking, use a bone clamp to hold the position while inserting a 0.062 K-wire where the permanent fixation will go. Certainly, the use of fluoroscopy is paramount and one should confirm that K-wire position prior to fixation. I recommend that you use two 2.7 mm fully threaded cortical screws in standard lag fashion. Partially threaded cannulated screws can work but you will never get the bite and compression as you will with bicortical screw fixation.
After placing fixation, if there has been repositioning of the metatarsal in the sagittal plane, there will be some overhang of bone on the dorsal distal cortex. One can shave this bone flush with a sagittal saw and then use the removed bone for bone graft to fill the void created by the osteotomy. You can then supplement this with the allograft of your choice.
The postoperative protocol includes a minimum of six weeks non-weightbearing followed by protected weightbearing in a fracture boot. Typically, there is return to shoes about 10 weeks after the procedure when the osteotomy is clinically healed.
In summary, the sagittal Z metatarsal osteotomy is a powerful procedure to help with aberrations in metatarsal length and poor sagittal plane position. For conditions in which larger increments of bone lengthening is necessary, then one is looking at callus distraction or large bone block grafting techniques. Don’t forget the sagittal Z osteotomy for the occasion when you need significant shortening of the metatarsal.