DEFINITION

Hallux rigidus is arthritis of the first metatarsophalangeal (MTP) joint.

The amount of arthritis can range from focal areas of cartilage injury or osteophyte formation without joint space narrowing to ankylosis with complete loss of the joint space. In one classification system proposed by Hattrup and Johnson, grade I is osteophyte formation without joint space narrowing, grade II is narrowing of the joint space, and grade III is loss of visible joint space.

 

 

ANATOMY

 

The joint consists of the articulation of the first metatarsal head with the hallux proximal phalanx and the medial and lateral sesamoids (FIG 1).

 

The flexor hallucis brevis contains the two sesamoids within its medial and lateral heads and inserts on the plantar base of the hallux proximal phalanx.

 

The flexor hallucis longus runs between the medial and lateral sesamoids and inserts on the plantar base of the hallux distal phalanx.

 

The extensor hallucis longus and the more lateral extensor hallucis brevis insert into the extensor mechanism of the great toe.

 

 

 

FIG 1 • Anatomy of the first MTP joint.

 

 

The abductor hallucis and adductor hallucis insert on the medial and lateral sesamoids, respectively, along with the plantar base of the hallux proximal phalanx.

 

PATHOGENESIS

 

Hallux rigidus may be secondary to primary osteoarthritis, systemic inflammatory arthritis, or less commonly septic arthritis.

 

It may also be posttraumatic in nature, developing after a previous intra-articular fracture or significant turf toe injury to the ligamentous structures of the first MTP joint.

 

Biomechanical factors such as a long, hypermobile, or dorsally elevated first metatarsal may lead to dorsal impingement of the proximal phalangeal base on the first metatarsal head with first MTP dorsiflexion.

 

NATURAL HISTORY

 

The extent of arthritis often progresses with time, leading to increased osteophyte formation and joint space

narrowing. This may occur with or without joint-sparing surgical intervention.

 

PATIENT HISTORY AND PHYSICAL FINDINGS

 

Patients often complain of pain and stiffness in their first MTP joint. Symptoms may be exacerbated by shoes with a restrictive toe box and by walking barefoot or in shoes with a flexible forefoot.

 

On examination, there may be a prominent first metatarsal head, a swollen first MTP joint, and tender osteophytes of the metatarsal head and phalangeal base.

 

 

First MTP joint motion may be limited and painful.

 

Dorsiflexion range of motion should also be assessed with the patient bearing weight or with dorsal translation applied to the first metatarsal head to simulate weight bearing to assess for “functional hallux rigidus.”

 

 

In mild to moderate hallux rigidus (Hattrup and Johnson grade I and II), pain is principally with maximum joint dorsiflexion or plantarflexion secondary to dorsal osteophytes causing bone impingement or soft tissue tenting, respectively.

 

With severe arthritis (Hattrup and Johnson grade III), there is usually pain throughout the entire arc of motion and a positive “grind test,” in which midrange of motion with axial compression applied to the first MTP joint is painful.

 

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

Anteroposterior (AP), lateral, oblique, and sesamoid views of the foot should be obtained to assess the extent of arthritis in the first MTP and in the adjacent first tarsometatarsal and hallux interphalangeal joints.

 

 

88

 

An assessment is also made for any concurrent hallux valgus or hallux varus deformity, osteopenia, avascular necrosis, or occult sesamoid fracture.

 

If needed, magnetic resonance imaging (MRI) and computed tomography (CT) scan can provide more, with respect to detailed information, particularly sesamoid pathology, which is important, as this procedure leaves the metatarsosesamoid joint intact.

 

DIFFERENTIAL DIAGNOSIS

Osteochondral lesion Avascular necrosis Occult fracture

 

 

NONOPERATIVE MANAGEMENT

 

Conservative treatment should always be offered before performing first MTP joint hermiarthroplasty.

 

The principal goal is to limit painful motion of the first MTP joint and pressure on prominent osteophytes. An accommodative shoe with a soft upper and a rigid forefoot rocker may be worn. A rigid turf toe plate may be placed under a removable soft insole or an orthotic with a Morton's extension may be worn. Doughnut pads may be placed over tender osteophytes.

 

Medications such as nonsteroidal anti-inflammatories, glucosamine and chondroitin sulfate, and

acetaminophen may be taken.

 

Corticosteroid and possibly hyaluronic acid injections may be performed.

 

SURGICAL MANAGEMENT

 

There are many surgical options for hallux rigidus, including cheilectomy, metatarsal osteotomy, proximal phalangeal osteotomy, distraction arthroplasty, tissue interposition arthroplasty, implant arthroplasty, and arthrodesis.

 

Of the many implants available, our preference is a cobaltchrome proximal phalangeal hemiarthroplasty made by BioPro (FIG 2). The material does not break down with associated extensive bone destruction such as the silicone total and hemi implants; there are good long-term results published in the literature, and the amount of bone removed is small, making salvage of a failed prosthesis less challenging. The prosthesis is also available in titanium for patients with metal sensitivity.

 

 

 

FIG 2 • BioPro first MTP hemiarthroplasty implant.

 

 

Our potential indications for performing a first MTP hemiarthroplasty are symptomatic grade II arthritis with loss of greater than 50% of the metatarsal head articular cartilage and grade III arthritis without severe involvement of the articulation between the metatarsal head and the sesamoids.

 

Preoperative Planning

 

History, physical examination, and radiographs are reviewed to confirm the appropriate indications for the procedure and determine if there are any concurrent deformities or biomechanical abnormalities that also need to be addressed.

 

The patient needs to be told that based on the intraoperative findings, a decision may be made that hemiarthroplasty is not the best option and that a simple cheilectomy, arthrodesis, or tissue interposition

arthroplasty may be preferable.

 

The equipment to perform the hemiarthroplasty and the alternatives mentioned earlier should be readily available in the operating room.

 

Positioning

 

The patient is placed in the supine position with a leg or thigh tourniquet.

 

Approach

 

A dorsomedial approach is preferable, although a medial longitudinal approach can also be used in the presence of a previous incision there.

 

Perioperative antibiotics and a regional anesthetic block are given.

 

 

89

 

 

TECHNIQUES

• Exposure

  Make a longitudinal dorsomedial incision over the first MTP joint.

  Protecting the dorsomedial sensory nerve, expose the extensor digitorum longus tendon and dorsomedial joint capsule.

  Leaving a sufficient cuff of capsular tissue for subsequent repair, make a longitudinal capsulotomy medial to the extensor digitorum longus tendon.

  Using subperiosteal dissection and preserving the collateral ligaments, expose the dorsal aspect of the proximal phalanx and the dorsal, medial, and, if prominent, lateral aspect of the metatarsal head (TECH FIG 1).

  Release any adhesions between the sesamoids and the metatarsal head.

  Inspect the joint to determine the extent of articular cartilage damage.

  If there is severe ankylosis and arthritis of the metatarsosesamoid joints, then a first MTP joint arthrodesis or tissue interposition arthroplasty is probably a better option.

  If the cartilage of the proximal phalanx and the plantar half of the metatarsal head is in good condition, then a cheilectomy with or without a metatarsal or phalangeal osteotomy is usually sufficient.

   

   

   

  TECH FIG 1 • Exposure of dorsal osteophytes after capsular incision.

• Site Preparation

   

  Using a rongeur or sagittal saw, remove osteophytes from the metatarsal head, proximal phalangeal base, and also circumferentially about the sesamoids.

   

  Remove a prominent medial eminence of the metatarsal head if it is present.

   

  Make an adequate dorsal cheilectomy of the metatarsal head.

   

  With dorsal stress applied to the metatarsal head, there should be at least 70 degrees and preferably 90 degrees of first MTP dorsiflexion relative to the axis of the first metatarsal shaft.

   

  Make an initial cut parallel to the dorsal cortex of the first metatarsal head. However, after the trial and final prostheses have been inserted, range of motion is reassessed and, usually, additional dorsal bone resection (up to 25% to 40% of the normal metatarsal head) is required. My experience with this procedure and with isolated cheilectomy is that there is a higher rate of recurrent symptoms if less than 30% of the dorsal metatarsal head is removed.

   

  Debride loose chondral flaps and drill or microfracture areas of visible subchondral bone on the remaining metatarsal head to promote fibrocartilage ingrowth.

   

  Remove the base of the proximal phalanx using a sagittal saw, with the cut perpendicular to the axis of the proximal phalanx.

   

  Take care to avoid injuring the flexor hallucis brevis insertion, which may occur with resection of too much bone (>6 mm or 20% of the total proximal phalangeal length) or overpenetration of the saw blade.

   

  The implant sizer is the same thickness as the prosthesis (2 mm) and can be used to guide the amount of bone resection.

   

  If only 2 mm of bone is removed, then the joint is usually too tight and postoperative motion is restricted.

   

  Usually, at least 3 to 4 mm of bone resection is required for adequate motion; this can be assessed by the amount of “shuck” with the trial implant inserted.

   

  Ideally, the space between the trial or final implant and the metatarsal head should distract at least 3 mm with applied force.

   

  Visualization of the plantar aspect of the joint may be easier after this cut has been made.

• Implant Sizing and Insertion

   

  Available BioPro implant diameters are 17 mm (small), 18.5 mm (medium/small), 20 mm (medium), 21.5 mm (medium/large), and 23 mm (large); these implants are either porous coated or nonporous coated.

   

  With the toe plantarflexed 90 degrees to improve exposure, use the sizer guide to determine the largest size implant that does not extend beyond the margins of the proximal phalangeal cut.

   

  With respect to orientation, the prosthesis is slightly wider in the mediolateral dimension than the dorsal-plantar dimension.

   

  There is a hole in the center of the sizer that is drilled to accommodate the stem of the trial prosthesis.

   

  90

   

  Insert the trial stem and evaluate the extent of phalangeal base coverage and joint range of motion and stability. If, as noted earlier, there is insufficient joint distraction or dorsiflexion, more bone can be removed from the phalangeal base or dorsal metatarsal head, respectively.

   

  Once you are satisfied with the implant size and bone cuts, center the chisel with its longer end in the mediolateral dimension on the trial hole and use it to create a channel for the stem of the final prosthesis.

   

   

   

  TECH FIG 2 • A. Cheilectomy has been performed and implant inserted. B. Postoperative lateral radiograph showing component in place.

   

  Impact the prosthesis into position.

  It should be flush with the phalangeal base and should not extend beyond its margins (TECH FIG 2A). Joint motion should be smooth with dorsiflexion and there should be at least 3 mm of shuck, as noted earlier.

  Use AP and lateral fluoroscopy or plain radiographs to confirm acceptable prosthesis position (TECH FIG 2B).

  If the patient is not allergic, place bone wax on the cut dorsal surface of the metatarsal head and irrigate the joint.

• Wound Closure

Close the joint capsule with absorbable suture.

If a large dorsal and medial eminence has been resected, then sometimes the capsule needs to be imbricated or partially removed. However, take care not to make the closure too tight, which may restrict postoperative motion.

Close the subcutaneous tissue and skin in layers and apply a sterile compressive dressing.

 

PEARLS AND PITFALLS

Failure to recognize and address concurrent deformity or potential causative biomechanical abnormalities may lead to progressive arthritis of the remaining metatarsal head and sesamoids, component loosening, and postoperative pain and stiffness.

An adequate cheilectomy must be performed, particularly if there is residual elevation of the metatarsal head or hypermobility of the first tarsometatarsal joint. If not, there is more likely to be recurrent dorsal osteophyte formation and decreased postoperative range of motion.

Sufficient bone must be removed from the proximal phalangeal base to decompress the joint without damaging the flexor hallucis brevis insertion.

The stem of the prosthesis needs to press-fit tightly and be centered within the proximal phalangeal canal. An attempt to remove more dorsal than plantar phalangeal bone to “increase relative toe dorsiflexion” or protect the flexor hallucis brevis insertion risks having the tip of the stem abut or penetrate the plantar cortex and may lead to poorer results.

 

 

POSTOPERATIVE CARE

 

Postoperatively, the patient may be weight bearing as tolerated in an orthopaedic or regular shoe.

 

Aggressive early first MTP joint range-of-motion and strengthening exercises should be initiated within the first few days after surgery.

 

Sutures are removed at 10 to 15 days postoperatively.

OUTCOMES

The developer of the prosthesis reported his results for 279 procedures with follow-up of 8 months to 33 years as 93.1% excellent, 2.2% good, and 4.7% unsatisfactory results.9

 

 

Twelve of the 13 unsatisfactory results underwent revision, including prosthesis removal.

 

91

 

A subsequent update on 468 procedures with follow-up of 2 months to 38 years noted no additional

revisions and one case of radiographic loosening.3

 

In another study, seven patients (nine feet) underwent a BioPro resurfacing endoprosthesis and at 1-year follow-up noted an average increase on a modified American Orthopaedic Foot and Ankle Society hallux metatarsophalangeal-interphalangeal 100-point scale from 51.1 to 77.8, an average increase in first MTP joint dorsiflexion range of motion from 11.9 to 17.9 degrees, and no change in first MTP join

plantarflexion range of motion.6

 

In a different study, 23 patients completed 1-year followup after BioPro hemiarthroplasty with an average American College of Foot and Ankle Surgeons (ACFAS) score increase from 41.2 to 80, average first MTP joint dorsiflexion increase from 12.6 to 50 degrees, and an average first MTP joint plantarflexion

increase from 8 to 17.5 degrees.4

 

Another study evaluated 32 procedures in 28 patients with an average follow-up of 33 months.8

 

Foot Function Index pain, disability, and activity scores improved; 82% of patients were completely satisfied and 11% were satisfied with reservations.

 

There were three cases of radiographic loosening or subsidence.

 

In a retrospective comparison study, 21 BioPro hemiarthroplasties and 27 first MTP arthrodeses were evaluated at mean final follow-up of 79.4 and 30 months, respectively. Five (24%) of the hemiarthroplasties failed, 1 of them was revised, and 4 were converted to an arthrodesis. Eight of the feet in which the hemiprosthesis had survived had evidence of plantar cutout of the prosthetic stem on the final follow-up radiographs. The satisfaction ratings in the hemiarthroplasty group were good or excellent

for 12 feet, fair for 2, and poor or failure for 7, with a mean pain score of 2.4 out of 10.5

 

Seventy-nine BioPro first MTP hemiarthroplasties were performed in 76 patients with mean of 2.91-year follow-up with 34 of the procedures also involving flexor hallucis longus transfer to the proximal phalanx. Forty were done in first MTP joints with minimal adaptive arthritic changes and 10 in joints with ankylosis. The mean postoperative ACFAS score was 94, 42 (53%) had freedom from pain, and 45 (57%) had satisfaction or a high level of satisfaction with the outcome. There were eight complications: two patients with severe pain with one requiring implant removal, one sesamoiditis, one extensor hallucis longus

contracture, one hallux subluxation, one hallux dislocation, and two misaligned implants.7

 

Twenty-two elective BioPro first MTP hemiarthroplasties were performed on 20 patients with grade III hallux rigidus with follow-up examination at 1 year and questionnaire at 2 years. There was improvement in average range of motion of 15 degrees from 33 to 48 degrees, visual analogue scale pain score from

4.7 to approximately 1.0, and AOFAS forefoot score from 61 to 86. Painless ambulation occurred after 6 weeks. At 1 year, there was no radiographic loosening or subsidence of any implants. Three patients had postoperative stiffness requiring manipulation under anesthesia and two patients underwent conversion

to arthrodesis for pain attributed to sesamoid arthritis.2

 

In the 16 procedures in 15 patients that we performed (average follow-up of 49 months), there was a 92% satisfaction rate and an 83% incidence of no or mild occasional pain for index procedures and a 50% satisfaction rate and 25% incidence of no or mild occasional pain for patients having had a previous

failed first MTP joint cheilectomy or tissue interposition arthroplasty.1

 

There were three revision procedures—one implant removal for postoperative infection and two

revision cheilectomies for recurrent osteophytes, possibly secondary to inadequate initial cheilectomy.

 

 

COMPLICATIONS

Infection Nerve injury

Component loosening

Recurrent pain and loss of motion

 

 

REFERENCES

1. Aronow MS, Leger R, Sullivan RJ. The results of first MTP joint hemiarthroplasty in grade 3 hallux rigidus. Presented at the American Orthopaedic Foot and Ankle Society 22nd Annual Summer Meeting, La Jolla, CA, July 15, 2006.

    

    

2. Giza E, Sullivan M, Ocel D, et al. First metatarsophalangeal hemiarthroplasty for hallux rigidus. Int Orthop 2010;34(8):1193-1198.

    

    

3. Goez JC, Townley CO, Taranow WS. An update on the metallic hemiarthroplasty resurfacing prosthesis for the hallux. Presented at the 56th Annual Meeting and Scientific Seminar of the American College of Foot and Ankle Surgeons, Orlando, FL, February 1998.

    

    

4. Kissel CG, Husain ZS, Wooley PH, et al. A prospective investigation of the BioPro hemi-arthroplasty for the first metatarsophalangeal joint. J Foot Ankle Surg 2008;47(6):505-509.

    

    

5. Raikin SM, Ahmad J, Pour AE, et al. Comparison of arthrodesis and metallic hemiarthroplasty of the hallux metatarsophalangeal joint. J Bone Joint Surg Am 2007;89(9):1979-1985.

    

    

6. Roukis TS, Townley CO. BIOPRO resurfacing endoprosthesis versus periarticular osteotomy for hallux rigidus: short-term follow-up and analysis. J Foot Ankle Surg 2003;42(6):350-358.

    

    

7. Salonga CC, Novicki DC, Pressman MM, et al. A retrospective cohort study of the BioPro hemiarthroplasty prosthesis. J Foot Ankle Surg 2010;49(4):331-339.

    

    

8. Taranow WS, Moutsatson MJ, Cooper JM. Contemporary approaches to stage II and III hallux rigidus: the role of metallic hemiarthroplasty of the proximal phalanx. Foot Ankle Clin 2005;10:713-728.

    

    

9. Townley CO, Taranow WS. A metallic hemiarthroplasty resurfacing prosthesis for the hallux metatarsophalangeal joint. Foot Ankle Int 1994;15:575-580.