A Guide To First MPJ Head Resurfacing

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By Bora Rhim, DPM

     Hallux rigidus of the first metatarsophalangeal joint (MPJ) is the most common form of osteoarthritis of the foot.1 Hallux rigidus is defined as a progressive arthritic process of the first MPJ that causes pain, stiffness and enlargement of the joint.1

     There are numerous surgical procedures to help address the pain and stiffness of this joint. These procedures include cheilectomy, osteotomies, resection arthroplasty, interpositional arthroplasty, hemiarthroplasty, total joint arthroplasty and arthrodesis.

     Although cheilectomy and osteotomies are considered first line surgical treatments for early stages of hallux rigidus, these procedures are not recommended for more advanced stages.2 Transfer metatarsalgia, postoperative deformities and loss of push-off strength are commonly associated with resection arthroplasty, and are recommended only for elderly and sedentary patients.3

     Recently, interpositional arthroplasties have gained some popularity but long-term follow-up studies are lacking.4 Metallic hemiarthroplasties that resurface the proximal phalangeal base of hallux have shown promise but researchers have found the clinical and functional results to be significantly inferior to those obtained with arthrodesis of the first MPJ.5 Total joint arthroplasties have been associated with loosening and malalignment, leading to subsequent revisional surgeries.

     Currently, the gold standard treatment for advanced hallux rigidus is arthrodesis of the first MPJ. Postoperatively, however, these patients have experienced limitations in shoe wear, complications of malunion or nonunion, or require permanent activity modifications. Accordingly, the first MPJ arthrodesis is less attractive for many active individuals.6 An alternative procedure that relieves pain and maintains motion without affecting strength or stability of the hallux is necessary.

Is There An Alternative Treatment For Active Patients?

The HemiCAP System (Arthrosurface) first debuted in 2002 and this implant was indicated for use in the shoulder, hip and knee with positive clinical outcomes.7 This implant resurfaces the damaged articular surface and restores the patient’s joint geometry with minimal bone resection.

     Three years later, this device received approval for resurfacing of the metatarsal head in hallux rigidus. The implant is composed of a cobalt chromium alloy for the articular portion and attaches to a titanium alloy taper fixation post via a Morse taper. In advanced stages of hallux rigidus, in which there is denuded or damaged cartilage on the head of the metatarsal, this metallic implant resurfaces the metatarsal head with minimal bone resection and without altering the sesamoid articulation. The advantage of this implant is that it does not interfere with the normal balance of the flexor-extensor tendons, plantar plate or adductor-abductor mechanisms.

Emphasizing Proper Patient Selection

One should only consider HemiCAP implantation for a patient who has advanced stages of the hallux rigidus, displays symptoms of pain all through range of motion at the joint, has dorsal pain of the first MPJ with increased activities, or has difficulty with walking barefoot or in soft sole shoes. Before physicians consider utilizing the implant, the patients must have previously failed conservative treatments including nonsteroidal anti-inflammatory medications, physical therapy, activity alteration, orthotic therapy and shoe wear modifications.

     The ideal patient for this procedure is one who demonstrates the aforementioned signs and symptoms, but expects to remain active after the surgical procedure and maintain motion at the first MPJ. Surgeons can also consider this procedure for patients who previously failed cheilectomy of the first MPJ with adequate soft tissue coverage.

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