Arthritis of the big toe joint can be a very disabling condition, as painful motion of this joint can hamper the ability to comfortably walk. Conservative treatment options of this joint are somewhat limited owing to the strain placed on it by the body during walking. Surgery is usually performed for treatment, and the use of joint implants is very popular. This article will review the types of joint implants available to treat big toe joint arthritis.
Arthritis of the big toe joint, also called the 1st metatarsal phalangeal joint, is very common, and is the most common place of symptomatic arthritis in the foot. The big toe joint is comprised of the roundish head of the first metatarsal, and the concave base part of the proximal phalanx, the first bone of two in the big toe itself. Arthritis occurs when the cartilage that covers the ends of the above two bones erodes away, resulting in a loss of the normal smooth motion of the joint. Bone grinds on bone, and the tissue in and around the joint becomes inflamed. Large spurs on top of and around the joint form, and can limit motion even further. The destruction in the big toe joint usually begins as a result of long term wear and tear on the cartilage due to a first metatarsal that is formed either too long, too short, or too elevated. Bunions can also result in arthritis where the big toe is angled too far toward the second toe, and the 1st metatarsal sticks out too far in the other direction. Trauma, particularly prior fractures that involved the joint or one of its bones, can eventually result in joint destruction and arthritis. There are also a number of other diseases that result in more significant (and some cases unsalvageable) joint destruction, including psoriasis, body-wide immune system-related arthritic conditions, bone infections, loss of blood supply to the bone, and nerve disease associated with certain conditions.
Nonsurgical treatment of big toe joint arthritis can have limited help compared with arthritis in larger joints like the knees and hips. These can include stiff shoes and inserts to limit the motion of the joint, as well as anti-inflammatory medications and injections. These measures rarely provide lasting relief.
Surgical treatment of big toe joint arthritis involves procedures that either preserve the joint, replace the joint, or destroy the joint all together. Joint preserving procedures are used in mild cases of arthritis, or in those who have high functional demands (like competing athletes) or cannot undergo a joint implant or destruction procedure due to poor health or bone density. These procedures involve removal of bone spurs and loose bone particles, and possibly a correction of any abnormal 1st metatarsal position. Joint destruction, which amounts to a removal of all cartilage and fusing the joint so it does not move at all (eliminating the pain), is done when arthritis is severe, and also in more moderate cases depending on the philosophy of the surgeon. Some surgeons prefer to use this option in all painful arthritic cases, others prefer implants to artificially restore motion.
Since the scope of this article is joint implants, the discussion will be centered on this option. Joint implants for the big toe joint have been around for well over fifty years. Joint implants can replace both sides of the joint, or only one side, leaving the other side's cartilage intact. A variety of materials have been used to make these implants, including silicone, metal of various alloys, and ceramics. Some implants have withstood the test of time, and others have faded into obscurity due to design issues or implant failures.
One of the first implant designs, and one that is still in use today by some surgeons, is essentially a hinge with stems that run into the 1st metatarsal and proximal phalanx, respectively. This implant is made of a firm silicone gel, that is stiff enough to withstand the forces acting on the big toe, and flexible enough to allow for a bending motion at the hinge. This implant has been used for nearly forty years, and has a fairly decent success rate. The nature of the silicone gel material can lead to complications, including silicone degeneration and depositing of particles in the surrounding soft tissue, as well as stem fracturing and implant slippage if not tightly seated in the bone due to stem hole widening.
Perhaps the most popular implant design today is historically the earliest implant. This implant design has been in use since the 1950's, and has proven itself durable, effective, and generally complication free when properly installed. This implant design replaces the 'cup' of the proximal phalanx part of the joint, and consists of a concave plate attached to a stem that is impacted into the bone. This implant fits in tightly, and has a thin profile so that not a lot of anatomic bone has to be removed in order to fit it into the joint. The original design is still in use, and many companies have implants that are very similar in shape and function. This implant, while it replaces the only one side of the joint, is very effective at restoring joint motion without pain, even if the other side of the joint has a large amount of cartilage loss as well. Complications can include extended joint swelling follow the surgery for awhile, as well as implant slippage out of position or toe bone fracturing in a very low number of cases. This author has personally used this design for years with good success.
A more recent design developed in the last decade provides a surface replacement for the metatarsal side of the joint. Anatomically, this is the side that wears down the most, and so theoretically this is the most optimal part of the joint to replace. Unfortunately, this bone is much more difficult to design a partial implant for given it's size, shape, and role within the joint's motion. A recent design has overcome these challenges, and has success in resurfacing the metatarsal portion of the joint to resolve the arthritis pain and degeneration. This type of implant essentially consists of a round 'head' portion that replaces much, but not all, of the end of the 1st metatarsal. It is secured to the end of the bone via a stem that is either screwed or impacted into the canal of the bone. The base part of the proximal phalanx will then move over this implant, with the end result being better motion and reduced pain. Like implants in the other bone, this design can cause bone fracturing, and if improperly placed (or if the bone quality is not ideal), the stem can move in the bone canal, leading to implant surface motion.
A final design in implants for big toe joint arthritis has been the one most technically challenged, and historically least successful and consistent in design. These implants have two pieces that replace both sides of the joint respectively. Essentially, there is a cup component for the proximal phalanx and a 'ball' component for the 1st metatarsal. These designs require the removal of a lot of bone in order for them to fit in properly, and historically have had a higher failure rate that the one-sided implants. This joint takes on a great amount of force during walking, and the presence of metal in the bones at this joint increases the stress on the respective bones. When the metal is present on both sides of the joint,a higher rate of bone stress can develop, as well as a higher rate of implant fracture and bone fracture. Design improvements persist even now, and there are many surgeons who prefer to use implants with two sides rather than one-side despite this history, usually given their own success with using the two-sided design. While this author does not prefer the use of total joint implants in the big toe joint, contemporary designs are still very much a legitimate and effective way to improve joint motion and reduce pain, especially in the case of severe erosion of both sides of the joint surface.
Joint implants for big toe joint arthritis is a valuable option for relieving pain and improving foot function. There are some patients who should not use these implants, no matter what the design. These include very heavy and obese people and people with poor bone density or who heavily smoke and have decreased bone density as a result of nicotine on blood flow to the bone. They also include diabetics or others with significant nerve disease, as decreased sensation can lead to excessive foot joint pressures and eventual destruction. People with big toe joint implants also need to keep in mind that motion is rarely ever 100% improved, and most of the time squatting over one's toes is not comfortable due to some restriction of motion that the presence of an artificial joint creates. However, in the big picture, these implants are more reliable, more durable, and are less likely to become infected than larger implants like those in the hips and knees, and they rarely ever have to be removed or replaced.
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