The Head, The Base, or Both |
by Jay Lieberman, DPM |
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Jay Lieberman, DPM
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Patients with functional hallux limitus, Grade III, who do not respond to conservative care, will need a joint implant, a joint fusion, or a resurfacing prosthesis. While fusion works very well, many patients are reluctant to be non-weight bearing or immobilized for extended periods. If a female patient undergoes a fusion procedure, the toe is maintained in a slightly elevated position to afford the patient the ability to wear a shoe with a heel. Many patients are not comfortable with the idea of losing joint function and having a toe that does not purchase the ground.
The low profile hemi implants for the base of the proximal phalanx have been very much in vogue for the past ten years. They are an excellent alternative to joint fusion or total joint replacement. Hemis are simple to insert and heal rapidly. The surgeon also has the option of performing a cheilectomy with or without a decompression osteotomy on the first metatarsal.
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See the degenerated cartilage and spurring on the head of the first metatarsal |
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Subchondral drilling of the first metatarsal head and freeing the adhesed sesamoids can be used to augment the procedure and enhance the results. In the event that the implant fails, it can easily be removed and a fusion can be performed or the patient can be left with a Keller type arthroplasty of the first MPJ.
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The cutting jig makes a precise oblique osteotomy |
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The longitudinal axis of the handle should be parallel to the long axis of the second metatarsal. Jig fixation is preferred |
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Quite often, however, the surgeon comes to realize that the degeneration effects predominantly the articular cartilage of the first metatarsal and NOT the base of the proximal phalanx. Will a hemi-implant of the phalangeal base suffice here? Previously the alternatives were limited to a metallic or silastic total joint replacement.
Enter the resurfacing prosthesis of the first metatarsal. Although we are in the early stages of knowing what this device is capable of, it seems to be very promising and may ultimately replace the total joint implants. These were first demonstrated to me two years ago. A lathe type device would remove a circular area from the articular cartilage and this would allow for fit of the endoprosthesis. I was concerned that the seams would offset in the long term, creating a step down in the joint surface, causing pain on ROM.
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Wright's resurfacing prosthesis system involves removing the entire articular cartilage and there are no seams.
The Wright Medical resurfacing prosthesis has a head that is angled from plantar distal to dorsal proximal. It incorporates the benefits of a Waterman osteotomy, a cheilectomy, and a decompression osteotomy. The sesamoids will remain functional, leaving the patient with better propulsion during gait.
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The broach squares off the drill hole for press fit of the implant stem. |
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It is particularly applicable in the patient who has a square shape first metatarsal head with apex. These patients tend to demonstrate extreme wear of the central component of the articular cartilage of both the first metatarsal and base of the proximal phalanx. Most patients with Hallux Limitus have a rectus forefoot. The patient in this case had a mild IM angle and therefore the stem is angled medially and NOT directly down the medullary canal. Higher IM angles than this one probably should be corrected if the surgeon intends to use an endoprosthesis.
Case Two (overview):
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