Posted by Dr. Ed on 5/15/07 07:40
The first MTP joint is designed to allow propulsion via a set of actions related to normal dorsiflexion of the joint. A joint that does not move is not a natural nor physiologic state of affairs.
It is important to review the grading system for hallux rigidus (painful arthritic first MTP joint with restricted motion).
Stage 1: Early degenerative changes. May be treated via orthotics, shoe modifications (distal rocker sole), possibly physical therapy.
Stage 2: Moderate degenerative changes. May be treated via orthotics but orthotic therapy must proceed cautiously as the goal of orthotics is to increase range of motion of the joint which can only be attempted if degenerative changes are not too advanced and if there is sufficient range of motion to work with. Distal rocker soles added to shoes cna be very helpful. Surgical treatment may include the cheilectomy coupled with osteochondral drilling used to attempt to stimulate new fibrocartilage ingrowth to replace osteochondral defects (divots in the cartilage).
Stage 3: Advanced degenerative changes with significantly restricted range of motion. Orthotics are contraindicated. Cheilectomies may be attempted but often fail at this stage. The reason for cheilectomy failure is that that procedure allows increased range of motion at a joint in which that new motion is likely to be painful. Two surgical options may be considered. (1)A plantarflexory osteotomy of the first metatarsal head (repositions the cartilage to a more functionally advantageous position) coupled with osteochondral drilling. (2) Plantarflexory osteotomy coupled with a hemi-implant. A hemi-implant is an implant, often metallic (cobalt-chrome or titanium) which serves to resurface only the phalangeal (big toe) side of the joint.
Stage 4: 'End stage' hallux rigidus. Minimal motion is left at the joint and minimal cartilage remains. This may be adapted conservatively to a shoe with a moderate distal rocker sole, possibly with a carbon fiber plate. Surgically, the joint may be fused or a total joint implant. The total implants that are two piece, that is, are designed as a two piece ball and socket have poor longevity. The total implants that are designed as a hinge function very well, and offer a relatively rapid recovery and restoration of function. We are now on the third generation of such implants with advanced biomaterials and design such that the longevity of such implants is not known. I have yet to see one fail and be replaced by a fusion. I use the Primus flexible big toe implant by Futura Biomedical (recently purchased by another company http://www.nexaortho.com/futura/primus.php
I have had runners return to training within two months after use of this implant. It allows ambulation with a surgical shoe within 48 hours and return to a running shoe within about 3 weeks. Should the implant 'break' it is not a large procedure to remove it and replace it with another one since the original placement can be achieved without a significant amount of bone removal. Dr. Bruce Lawrence, the designer of the implant and its predecessors had placed the first generation of such hinged implants about 30 years ago and still has some of those patients in his practice. He noted that despite the fracture of the hinge of the implant over the decades, the two ends of the implant still allowed pain free range of motion. He offered such patients replacement of the implant but most refused stating that they had little or no pain and adequate function.
There are biomechanical reasons why patients get hallux rigidus. The surgeon must be more than a surgeon but must have a good understanding of podiatric biomechanics in order to assess how a given procedure will affect gait and the mechanics of walking. Additionally, each set of procedures can be modified or custom tailored to suit the biomechanical function of a particular patient. The failure rate tends to go up when a 'cookie cutter' approach to many of such procedures is used as opposed to a flexible approach in which the surgeon/biomechanist adjusts technique to suit the individual patients
requirements.
Dr. Ed
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