One of the more common conditions seen in a podiatrist’s office is hallux limitus. In this condition, the range of motion of the first toe at the first metatarsophalangeal joint (MPJ) is limited to a number that is less than normal. A normal range of motion is generally considered to be approximately 65 degrees of dorsiflexion (motion of the toe upwards). Hallux limitus may be distinguished from hallux rigidus, using the latter of the terms to describe a condition where the toe is almost or completely fused, and little to no motion is available at the joint. Many will refer to the condition as Hallux Limitus/Rigidus, sometimes abbreviating it as HL/HR.
Hallux limitus is caused by jamming of the proximal phalanx into the first metatarsal. This may be caused by muscle imbalance, biomechanical deformity, trauma, osteoarthritis of the joint, and a number of other conditions. Regardless of the cause, hallux limitus can be very painful, and can lead to significant changes in gait.
Nonsurgical treatment of hallux limits and hallux rigidus typically involves the use of an orthotic device, often aimed at limiting the motion of the joint. This may prevent some of the pain associated with the condition. It may also be combined with modifications to the design of the shoe, range of motion exercises with physical therapy, anti-inflammatory medications, alteration of activities, and joint protective supplements such as glucosamine. However, with the failure of nonsurgical intervention, an attempt at surgical correction may become necessary.
It is quite common for the joint to be fused by a surgeon. This prevents any motion at all at the joint, with a goal of decreasing the level of pain. However, another option is to replace the joint.
The idea of replacing the first MPJ came into practice in the 1950’s as an alternative to fusing the joint. It became quite popular among foot and ankle surgeons, and has seen drastic improvement in the past 10-15 years with the advent of more sophisticated implant devices and materials.
Joint implants can be broken down into two basic categories; hemi-implants and total implants. Hemi-implants are not true joint replacements, but act more as a spacer for the joint. The spacer is usually placed into the head of the first metatarsal. This spacer allows the proximal phalanx to move more smoothly over the head of the metatarsal. By using a hemi-implant, more motion can be allowed at the level of the joint.
A total implant is placed into both sides of the joint. That is, it is inserted into both the head of the first metatarsal as well as the base of the proximal phalanx. Thus, a new joint is created at the first MPJ. A total implant may be used in cases of more severe arthritis at the joint, when neither of the articular surfaces that create the joint can be salvaged.
Both types of implants may be made of silicone or metal, or a combination of the two. Metals used in implants include titanium, stainless steel, cobalt chromium, and various alloys. Ceramic implants have also been used, but are less common.
A meta-analysis performed by Cook et al. in 2009 showed that the overall patient satisfaction in first MPJ replacement arthroplasty was approximately 85%. This study looked at 47 different clinical studies of first MPJ replacement, and the results from those surgeries. According to the research, when the follow-up time was increased, the patient satisfaction went up to over 94%. Thus, the procedure remains popular among foot and ankle surgeons.
