To fuse or not to fuse – that is the bunionectomy

Adjacent segment pathology following bunionectomy procedures

Foot and ankle surgeons use a number of fusion techniques to treat forefoot pathology.  Fusion of the great toe joint is commonly used to treat acquired hallux valgus (bunion).  The Lapidus procedure (fusion of the metatarsal cuneiform joint) has also become popular as a method of bunionectomy over the past decade.  Surgeons who use these fusion procedures would argue that they feel more comfortable with structural surgical procedures in that they have more control over the outcome of the surgery and a more lasting result. 

Bunionectomy procedures that use balancing (non-fusion) rather than structural techniques are more common procedures.   Balancing procedures would include the Austin bunionectomy or Mitchell bunionectomy.  Balancing procedures, like the Austin or Mitchell, rely on ‘on the table’ results that appear good at the conclusion of the procedure.  But what you see on the operating table changes dramatically when the patient begins to walk.  Every surgeon who performs bunionectomy procedures has seen a beautiful outcome at the time of surgery change dramatically for the worse within months post-op.  That’s why many surgeons rely on the permanence of structural bunionectomy procedures.

Complications of fusion procedures of the forefoot

Fusion procedures, regardless of the location in the body, may result in a post-operative problem called adjacent segment pathology.  Adjacent segment pathology is the term used to describe the stress effects on joints adjacent to fusion sites.   The definition of adjacent segment pathology, to a great degree, focuses on spine surgery and the effects on cervical and lumbar joints adjacent to fusion sites.  Fusion of a joint limits the range of motion of the joint, altering normal range of motion and increasing load to adjacent joints.   The incidence of adjacent segment pathology post lumbar fusion ranges from 5% to 100%.(1)

Adjacent segment pathology can be broken down into two subcategories; adjacent segment degeneration and adjacent segment disease.  Hilibrand and Robbins described these two subcategories referring to adjacent segment degeneration as merely a radiographic finding with no clinical symptoms while adjacent segment disease represents a symptomatic adjacent joint with radiographic findings. (2)

Lee and Choi in their article Adjacent Segment Pathology After Lumbar Fusion, describe a number of factors that they consider to be contributing factors to adjacent segment pathology in spine sugary. (3)  Those factors include;

Pre-existing variables

• Age
• Adjacent segment disc degeneration
• Tropism of adjacent segments
• Gender
• Osteoporosis
• Physical activity

Surgery related variables

• Number of segments fused
• Adjacent segment damage during surgery
• Fusion methods
• Alignment

If we fuse a portion of the forefoot, what is the effect on adjacent segments?  In the case of the great toe joint fusion, I think the effects are minimal.  Surgeons intentionally fuse the great toe in a position that is dorsiflexed, or elevated.  By fusing the great toe in a dorsiflexed position, the forefoot will rock over the joint with no significant limitation in range of motion.  Granted, the foot may be a bit less propulsive in running, but in walking, there is minimal adjacent segment loading post great to fusion.

The Lapidus procedure may be a different story.  As mentioned earlier, the Lapidus procedure is a bunionectomy that corrects the bunion deformity by means of fusing the metatarsal cuneiform joint.  Load applied to the forefoot, post-Lapidus procedure, is no longer accommodated by the metatarsal-cuneiform joint but in now carried by the cuneiform-navicular joint.  I’ve yet to see studies in the literature that discuss the impact of medial column fusion on the remaining midtarsal joints. 

It stands to reason that the criteria defined by Lee and Choi would hold constant with the Lapidus procedure.  The result adjacent segment disease post-Lapidus procedure would be an increase in the onset and severity of midfoot osteoarthritis.

Jeff  

Jeffrey A. Oster, DPM 

Medical Advisor
Myfootshop.com  

1. Park P, Garton HJ, Gala VC, Hoff JT, McGillicuddy JE. Adjacent segment disease after lumbar or lumbosacral fusion: review of the literature. Spine (Phila Pa 1976) 2004;29:1938–1944. 
2. Hilibrand AS, Robbins M. Adjacent segment degeneration and adjacent segment disease: the consequences of spinal fusion? Spine J. 2004;4(6 Suppl):190S–194S.
3. Lee JC, Choi S. Adjacent segment pathology after lumbar fusion.  Asian Spine J. 2015 Oct; 9(5): 807–817.

Updated 12/24/2019

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