CHAPTER SYNOPSIS:

Hallux rigidus is a painful and disabling condition. Hallux metatarsophalangeal joint unipolar arthroplasty is a surgical treatment option for this condition. The history, indications, surgical technique, and outcomes of unipolar arthroplasty are reviewed.

IMPORTANT POINTS:

• 1
  

  Indications: painful joint arthrosis with loss of motion that has been refractory to conservative treatment modalities.

  
  
• 2
  

  Contraindications: advanced osteoporosis, osteomyelitis or joint sepsis, peripheral neuropathy, inadequate soft tissue coverage, and compromised circulatory status.

  
  
• 3
  

  Success of surgery depends on proper patient selection and careful surgical technique.

CLINICAL/SURGICAL PEARLS:

• 1
  

  The first metatarsophalangeal joint capsule is incised longitudinally.

  
  
• 2
  

  Marginal osteophytes are removed from the dorsal, lateral, and medial aspects of the metatarsal head.

  
  
• 3
  

  The soft tissues are subperiosteally released. Care is taken not to release the flexor hallucis brevis from its phalangeal insertion.

  
  
• 4
  

  The articular surface of the metatarsal head or proximal phalanx is resected, removing only the amount of bone necessary to accommodate the implant.

  
  
• 5
  

  Choose appropriate implant size.

  
  
• 6
  

  The joint is assessed for tension and motion. A normal range of concentric, unimpinged motion should be demonstrated following insertion of the final implant.

  
  
• 7
  

  A dorsal longitudinal or dorsomedial incision is used.

CLINICAl/SURGICAL PITFALLS:

• 1
  

  Adequately remove marginal osteophytes from the dorsal, lateral, and medial aspects of the metatarsal head.

  
  
• 2
  

  Take care not to release the flexor hallucis brevis from its phalangeal insertion.

  
  
• 3
  

  Remove only the amount of bone necessary to accommodate the implant.

  
  
• 4
  

  Choose appropriate implant size. Do not overstuff the joint.

  
  
• 5
  

  Carefully assess for joint tension and motion. A normal range of concentric, unimpinged motion should be demonstrated following insertion of the final implant.

VIDEO AVAILABLE:

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HISTORY/INTRODUCTION/SCOPE OF THE PROBLEM

Hallux rigidus, or osteoarthritis of the first metatarsophalangeal (MTP) joint, was first described by Davies-Colley in 1887. Hallux rigidus is a painful condition characterized by gradual onset of pain and restricted motion, especially dorsiflexion, as well as proliferative periarticular bone formation. One in 40 patients older than 50 years develop hallux rigidus. The pain and limited motion associated with arthrosis of the hallux metatarsophalangeal joint result in diminished propulsion of the foot, transfer lesser metatarsalgia, and gait alterations.

A system of CLINICAl and radiographic classification of hallux rigidus has been published by Coughlin et al. Advanced hallux rigidus is characterized by significant pain, significant stiffness and restriction of motion, and advanced arthritic change on radiographs.

If the pain of hallux rigidus becomes disabling and a patient has failed conservative therapy, then surgical intervention may be considered. Surgical treatment can be categorized as joint preserving (cheilectomy, osteotomy) for milder cases and joint sacrificing (resection arthroplasty, interpositional arthroplasty, implant arthroplasty, and arthrodesis) for more advanced disease. First MTP joint replacement arthroplasty was developed in an attempt to both relieve pain and preserve function.

In the early 1950s, implants were first designed and used for the surgical treatment of disease of the hallux MTP joint. Over the years, various implants composed of different materials have been manufactured to replace the base of the proximal phalanx, the distal articular surface of the first metatarsal, or both.

Single-stemmed and double-stemmed silastic implant arthroplasty were initially popularized. Silastic implants have been associated with many complications including late failure due to wear, osteolysis, reactive synovitis, foreign body immune response, and fracture and displacement of components. Although titanium grommets had been developed to improve implant durability, few orthopedic foot and ankle surgeons currently use these implants. Silastic implants do not appear to possess the structural durability to withstand the stresses generated by the repetitive motion associated with ambulatory activity.

Due to the limitations of Silastic implant arthroplasty, metallic hemiarthroplasty (unipolar) and metallic total joint arthroplasty (bipolar) prostheses have also been developed. Various implants composed of different materials have been manufactured to replace the base of the proximal phalanx, head of the first metatarsal, or both surfaces. Although long-term results of metallic implant hemiarthroplasty have been promising, some authors continue to consider prosthetic replacement of the first MTP joint as investigational.

Some metallic hemiarthroplasty (unipolar) design options for replacement of the base of the proximal phalanx include the Biopro (Biopro Inc., Port Huron, MI), Wright LPT (Wright Medical Technology Inc., Arlington, TN), and Futura (Nexa Orthopedics Inc., San Diego, CA) prostheses.

The Biopro hemiarthroplasty (Biopro Inc., Port Huron, MI) ( Fig. 38-1 ) design has been in CLINICAl use since 1952. It possesses a low-profile phalangeal resurfacing design, which allows minimal bone resection and facilitates preservation of the short flexors. The implant is composed of cobalt chrome alloy material. It is available in four sizes. Both porous-coated and non–porous-coated implants area available.

Biopro hemiarthroplasty implant.

(Used with permission from Biopro Inc., Port Huron, MI.)

A metallic hemiarthroplasty design for replacement of the head of the first metatarsal, the HemiCAP (Arthrosurface, Franklin, MA), has been available since 2005. The HemiCAP implant ( Fig. 38-2 ) is composed of two parts—an articular cap made from a cobalt chrome alloy and a central fixation component made of titanium. The components are connected together via a Morse taper. The component is available in 12-mm- and 15-mm-diameter sizes, and each diameter comes in a variety of incremental offset sizes that correspond to the dorsal-plantar and medial-lateral radii of curvatures at the implant site.

HemiCAP hemiarthroplasty implant.

(Used with permission from Arthrosurface, Franklin, MA.)

INDICATIONS/CONTRAINDICATIONS

Implant arthroplasty of the first MTP joint is indicated for the treatment of painful joint arthrosis with loss of motion that has been refractory to conservative treatment modalities. The etiology of the symptoms may include moderate to severe hallux rigidus, hallux valgus with degenerative changes, and posttraumatic arthritis. Implant arthroplasty may also be considered in cases of failure of cheilectomy or interpositional arthroplasty. Brage and Ball indicated that prosthetic replacement of the first MTP joint should be reserved for lower-demand patients.

Relative contraindications for implant arthroplasty of the first MTP joint include severe hallux valgus deformity and inflammatory arthritis, such as rheumatoid arthritis.

DiFelice and O’Malley recommended metallic implant hemiarthroplasty in the moderate- to low-demand patient with hallux rigidus or hallux valgus involving only one side of the joint. With intermetatarsal angle of greater than 15 degrees, the authors recommended proximal corrective osteotomy. The authors did not recommend hemiarthroplasty in the rheumatoid population.

Contraindications for implant arthroplasty of the first MTP joint include advanced osteoporosis, osteomyelitis or joint sepsis, peripheral neuropathy, inadequate soft tissue coverage, and compromised circulatory status.