Hallux limitus/rigidus is defined as a degenerative arthrosis of the first metatarsophalangeal joint (MTPJ) which is characterized by a decrease in the MTPJ range of motion and an eventual lack of motion.1 Treatment for this condition is a frequently discussed topic at podiatric conferences. When it comes to the stages of osteoarthritis in the MTPJ, one may consider performing joint preservation or joint destructive procedures. Joint preservation procedures include cheilectomy procedures, soft tissue correction and distal/proximal osteotomies as indicated for osseous correction. With more advanced stage osteoarthritic changes, you would consider a joint destructive procedure such as a Keller arthroplasty, a joint replacement or an arthrodesis. One should consider structural variables such as soft tissue contractures, hallux deviation, metatarsus primus elevatus, the metatarsal parabola and the quality of the bone density. External influencing factors will include the patient’s shoe type, work environment, precipitating pain and his or her recreational activities. Understanding The Importance Of Appropriate Patient Selection In regard to the implant arthroplasty, we usually reserve this as an end-stage procedure in non-salvageable joint disease with the MTPJ. Keep in mind that the patient’s activity alone may play a roll in selecting an implant arthroplasty over a joint fusion.2 Granted, one must weigh the merits of using a hemi-toe implant versus a total joint implant, which may be a single stemmed component or a two-component articulated joint replacement. I have found that metallic hemi-implants offer significant benefits over silastic devices. These benefits include the absence of plastic deformation; fatigue fracture due to stress loading over time; and microfragmentation and medullary shearing at the bone interface. There is no shortening of the first metatarsal so you are able to preserve the weightbearing distribution. I prefer to perform a hemi-toe implant arthroplasty with the LPT Titanium Hemi-Toe Implant (Wright Medical). This procedure is beneficial for the patient who has an advanced stage arthritic first MTPJ with a lack of joint space, provided that you have the ability to restore the contour of the first metatarsal head. Also be aware that dorsal and marginal spurs can form at the first metatarsal head and restrict range of motion. You can resect these spurs without performing a partial arthroplasty. For the best long-term results, these patients should have the following criteria: • good bone stock to allow for proper seating of the implant; • normal alignment of the first metatarsal in the transverse and sagittal plane; • normal to short first metatarsal; • a non-arthritic metatarsal sesamoid complex; and • the absence of a metabolic arthritis process.2 Keep in mind that any structural malalignments of the first metatarsal that are not addressed may lead to complications and abnormal stresses on the implant. This can increase the incidence of implant failure over time. Implant failure may also be precipitated by abnormal pronation that induces a functional hallux limitus. Step-By-Step Insights On Performing The Hemi-Toe Implant Arthroplasty To begin this procedure, you would start with a standard dorsal medial incisional approach. This not only facilitates joint exposure but allows you to preserve the joint capsule, which facilitates remodeling of the first metatarsal head including the resection of lateral and dorsal bone spurs. It is essential to release and mobilize the medial, lateral and plantar fibrous adhesions for intraoperative joint mobilization. Doing so enables you to use the instrumentation for placing the implant. I find the McGlamry elevator invaluable in performing the soft tissue release and minimizing the amount of soft tissue dissection and trauma to that area. A good release will increase the first metatarsophalangeal joint space and allow for better exposure for soft tissue reflection at the base of the phalanx as you prepare for bone resection. Proceed to perform a 5-mm to 10-mm resection at the base of the proximal phalanx when you release the capsular attachments. Exercise care in the area under the phalanx base so you can prevent a possible release of the flexor brevis tendon. I perform conservative but adequate resection that maintains hallux length and minimizes damage to the flexor tendon. You can resect additional bone later when using the reamer to remodel the contour of the base to match the implant after broaching the canal. I find that using a 2.7-mm drill instead of the pointed broach helps create a pilot hole in the center of the bone since the sclerotic base is difficult to penetrate. The triangular shape of the stemmed broach enables you to correctly orient the right and left side appropriate implant. Bear in mind that you will need to use a mallet to seat the device. While the 2.7-mm drill requires less force in driving the broach into place in a sclerotic base, you still need to have resistance and a firm grip on the great toe in order to prevent excessive tension on the capsule structures. At this point, you can place the trial implant with the impactor and subsequently reevaluate the patient’s range of motion. If you find the implant to be tight in the joint space, you can resect additional bone with a sagittal saw or the shallow reamer. You must follow this with the stem broach in order to facilitate full seating of the implant. Now you can place the LPT Hemi-Toe Implant. The implant will have one perforated hole at the dorsal surface and one at the plantar surface. This allows for right and left great toe placement where the flexor tendon can be reinforced or reattached at your preference. I have found that this is not a common part of the procedure I perform, given the low profile size of the implant. I also prefer not to handle the implant any more than necessary in order to minimize intraoperative complications or the occasional mistake that requires a new implant. What You Should Consider In The Post-Op Evaluation Proceed to close the soft tissue and reevaluate the patient’s range of motion and joint stiffness along with his or her skin. Occasionally, I may evaluate the trial implant with capsule closure to ensure appropriate range of motion prior to implanting the permanent implant. Pre-op and post-op implant placement should demonstrate corrected hallux position and preserved toe length. As in any procedure, there may be potential complications. These include: • a lack of hallux purchase; • fracture of the metatarsal head or base of the proximal phalanx; • loosening of the prosthesis; • osteolysis or osteoproliferation around the implant system; • blockage of the hallucal sesamoid position; • unmasking of preexisting sesamoid pathology; • recurrence of the deformity; and • painful/limited MTPJ range of motion. Final Words Although silastic implant arthroplasty has been performed for nearly 40 years, the metallic implant devices present a new era for use in the arthritic joint. Appropriate patient selection is essential and the procedure can be successful when the first metatarsal head has a restorable contour and a corrected intermetatarsal angle with no unaddressed biomechanical abnormalities. The thinner anatomic articulate design of the implant allows for a smaller resection of the proximal phalanx base and preserves the flexor hallucis brevis tendon. Dr. Cusumano is a Fellow of the American College of Foot and Ankle Surgeons. He currently practices in Englewood, Fairlawn and Riverdale, N.J., and serves as a team physician/podiatrist for the athletic teams at Fairleigh Dickinson and Montclair State Universities. Editor’s Note: For a related article, see “Titanium Hemi-Implant: A Vital New Solution For MTPJ Pain?” in the January 2001 issue of Podiatry Today or check out the archives at www.podiatrytoday.com .
References 1. Marcinko DE: Medical and Surgical Therapeutics of the Foot and Ankle, pp 423-465, Williams & Wilkins, Baltimore, 1992. 2. Gerbert J, Chang T: Clinical Experience with Two-Component First metatarsal Phalangeal Joint Implants. Implantable Biomaterials 12(3)403-413, 1995.