Hallux Rigidus

Etiology

Normally, the first MTP joint carries approximately 119% of body weight during gait with each step.[5] This could be aggravated by certain foot structures and biomechanical imbalances, leading to the exacerbation of degenerative arthritis.  

Multiple theories have been proposed to explain the cause of hallux rigidus. Coughlin found a strong association between a history of trauma and unilateral involvement of first MTP arthritis.[1] In contrast, bilateral cases have been reported to be most commonly associated with family history and the female gender.[5] 

Additional documented etiologies include a flat or chevron-shaped joint, increased hallux interphalangeal angle, longer proximal phalanx, first metatarsal length, and first ray hypermobility.[6][7][8] Metatarsus adductus, equinus deformity, hallux valgus, and footwear are other proposed etiologies with no supportive evidence. 

Systemic metabolic and inflammatory conditions such as gout, rheumatoid arthritis, and seronegative arthropathies may also contribute to early degeneration of the joint and should be considered.[1] 

Epidemiology

Hallux rigidus is the second most common condition affecting the first MTP joint, after hallux valgus. It affects 25% of patients who are older than 50 and present with foot disorders and is as high as 73% in a population with end-stage ankle arthritis.[9] 

Females are twice as likely as men to have hallux rigidus.[5] The condition can occur in adolescence but is uncommon. The condition is associated with osteochondritic lesions when present in the adolescent patient.[10]

In 2021, a cross-sectional study from Japan revealed that knee osteoarthritis, gout attacks, and hallux abducto valgus deformities are strongly correlated to the degeneration of the first metatarsophalangeal joint. In addition, the frequency of knee osteoarthritis was significantly associated with hallux rigidus.[11]

Pathophysiology

Most cases of hallux rigidus are idiopathic. However, multiple authors have noted an association with the development of arthritis changes through both traumatic and iatrogenic causes.[1] The underlying cause is likely multifactorial. Bilateral involvement is more common and is associated with family history and the female gender. Up to two-thirds of patients have a family history of hallux valgus. Achilles contracture, shoe wear, and an elevated metatarsal head also appear to contribute to developing the first MTP joint arthritis.[5]

Histopathology

Although a history of trauma is not always present, similar histological features are noticeable under the microscope. Common characteristics include a cleavage lesion in the articular cartilage with detached subchondral bone at the center of the metatarsal head. The forced extension and axial compression of the dorsal aspect of the proximal phalanx on the convex metatarsal head can produce an osteochondral defect, whether caused by a traumatic event or repetitive microtrauma. Osteochondral lesions are usually located at the center of the metatarsal head, followed by a horseshoe-shaped collar of bone, responsible for the limitation in joint dorsiflexion.[12]

History and Physical

Presentation

• Presenting symptoms include pain, altered gait, and increased bulk of joints, leading to difficulty with shoe wear.
• The compression of the dorsal medial cutaneous nerve may lead to numbness along the medial border of the great toe.

Physical Exam

• As with all foot examinations, neurovascular status should be confirmed. A positive Tinel sign might be present when the medial dorsal cutaneous nerve impinges on the medial aspect of the hallux. 
• The first MTP joint is often swollen and tender and may have palpable dorsal osteophytes. There is a decrease in passive and active range of motion (ROM), most commonly in dorsiflexion. The pain usually occurs at terminal ROM with milder diseases. Pain during midrange motion may indicate a more severe arthritic condition due to more global articular wear to the metatarsal head. The production of pain with forced dorsiflexion and the grind test suggest pathology.[13] 
• A pronated foot may be noted accompanied by pes planus, but studies have shown no strong association between hallux rigidus and a pronated foot. In contrast, patients with supinated feet have significantly lower odds of suffering from hallux rigidus.[14]  
• Dermatologic manifestations could include redness and skin irritation overlying the dorsal osteophyte of the 1st MTP joint, which is likely secondary to shoe gear.

Evaluation

Radiographic Evaluation

• Weight-bearing plain radiographs in anteroposterior, lateral, and oblique views are indicated (see Image. Mild Hallux Rigidus). The main flaw of plain radiographs is that they do not reveal the site or size of cartilage loss.[13] MRI and CT scans are not required for diagnosis or treatment planning of the disease. An oblique radiograph best determines the extent of joint space narrowing.[5]

Classification

• Coughlin and Shurnas modified Hattrup and Johnson's grading in 2003, offering clinical and radiographic findings of the disease. The Coughlin and Shurnas Clinical Radiographic System for Grading Hallux Rigidus is the most comprehensive grading accepted today.[4] The characteristics of each grade are as follows:

Grade 0

• Dorsiflexion: 40 to 60° or 10% to 20% loss compared to the normal side.
• Radiographic findings: normal
• Clinical Findings: No pain. Stiffness and loss of motion are present on physical examination.

Grade 1

• Dorsiflexion: 30 to 40° or 20% to 50% loss compared to the normal side 
• Radiographic findings: Dorsal osteophyte is the main finding. Minimal joint space narrowing, periarticular sclerosis, and flattening of the metatarsal head are present.
• Clinical findings: Mild pain and stiffness, pain at extremes of dorsiflexion or plantar flexion on examination. 

Grade 2

• Dorsiflexion: 10 to 30° or 50% to 75% loss compared to the normal side
• Radiographic findings: Dorsal, lateral, and possibly medial osteophytes give a flattened appearance to the metatarsal head. No more than one-fourth of the dorsal joint space is involved on the lateral radiograph. Mild to moderate joint space narrowing and sclerosis are present. The sesamoids are not usually affected. 
• Clinical findings: Moderate to severe pain and stiffness that may be constant; pain occurs just before maximum dorsiflexion and maximum plantarflexion on examination

Grade 3

• Dorsiflexion: 10° or less or 75% to 100% loss compared with the normal side. There is a notable loss of metatarsophalangeal plantarflexion as well. 
• Radiographic findings: Same as grade 2 but with substantial narrowing, possibly periarticular cystic changes, more than one-fourth of the dorsal joint space involved on the lateral radiograph. The sesamoids are enlarged, cystic, or irregular.
• Clinical findings: Nearly constant pain and substantial stiffness are present at extremes of the range of motion but not at mid-range.

Grade 4

• Dorsiflexion: Same as grade 3
• Radiographic findings: same as grade 3
• Clinical findings: Same criteria as grade 3, but there is definite pain at mid-range of passive motion.[15]

Treatment / Management

Nonoperative

Up to 55% of patients with hallux rigidus have adequate pain relief without surgical intervention.[16] NSAIDs can help reduce swelling and joint pain. Intraarticular steroid injections can provide temporary relief but have not shown long-term benefits. Dexamethasone phosphate should be preferred over triamcinolone due to chondrotoxic effects when intraarticular injections are utilized.[17] Activity modifications such as avoiding running, jumping, and stairs can make a difference in pain and discomfort. This may not be desirable for all patients.

Other conservative treatments include shoe modifications and orthotics, which aim to modify the biomechanics of the first MTP joint, reduce motion, limit irritation from the dorsal osteophytes, and reduce the mechanical stresses on the joint. Carbon fiber or spring steel are common materials used in prefabricated devices or are combined with custom orthotics to limit motion.[16] Morton's extension, made of a firm or rigid orthotic material that extends under the great toe, can help reduce dorsiflexion. Navicular pads have been used to alter the loading patterns of the joint. Rocker bottom soles can help diminish painful dorsiflexion during the gait cycle. Shoes with a high-toe box can take the pressure off prominent osteophytes. However, many of these modifications are not well tolerated by patients.[18]

Operative

Cheilectomy: This procedure has a good outcome for grade 1 and 2 hallux rigidus, with up to 97% of patients reporting excellent results and 92% having pain relief and function improvement in a 10-year follow-up period. However, less satisfactory results are seen with higher stages of hallux rigidus, where conversion to arthrodesis is 25% to 56%.[19] This procedure uses a dorsal approach. The capsule is opened, followed by a complete synovectomy. Approximately 30% of the dorsal aspect of the metatarsal head is removed. Removal of more than 40% can lead to a painful overload of the remaining articular surface or dorsal subluxation of the phalanx. If present, lateral osteophytes are removed as well. The dorsal bone is removed until 60 to 70° of dorsiflexion at the MTP joint is achieved. The average increase in dorsiflexion is approximately 25°. The main benefit is the relief of dorsal impingement, the primary source of pain.[20]

Cheilectomy may also be performed by a medial approach. Care is necessary to identify and protect the sensory nerve branches on the medial aspect of the toe. The medial approach allows for the inspection of the metatarsal sesamoid complex, which is not accessible by a dorsal approach. Occasionally, marginal osteophytes or adhesions may be present, requiring removal. Care is necessary to repair the medial capsule at closure to prevent hallux valgus. A minimally invasive approach can also be performed. Minimally Invasive Dorsal Cheilectomies (MIDC) have shown promising clinical outcomes.[21] However, Glenn and colleagues emphasized the importance of combining the procedure with arthroscopy due to bone debris, synovitis, loose bodies, and large cartilage flaps left within the joint.[22] Cheilectomies have a survival rate of 70% in an approximately 7-year period.[19](B2)

Moberg procedure: This procedure is a dorsal closing wedge osteotomy of the proximal phalanx. It can be used during cheilectomy if it fails to achieve adequate dorsiflexion.[23]

Arthrodesis: This procedure is the gold standard for treating more severe (grade 3 to 4) hallux rigidus.[24] Successful clinical outcomes are based on the correct positioning of the fusion (see Images. Hallux Rigidus Plate & Hallux Rigidus Screws). The recommended positioning of the hallux relative to the floor is between 10 and 15° of dorsiflexion and 10 to 15° of valgus.[20](A1)

Keller resection arthroplasty: This surgery involves the removal of the base of the proximal phalanx. It is indicated in low-demand patients older than 70.[25](B2)

First MTP implant arthroplasty: Silicone implants were the first hemi implants created in the 1960s. Since then, they have been through many modifications, including dracon jackets to aid fibrous tissue ingrowth and metal grommets to prevent detritic synovitis.[26] Newer studies have shown promising results of the double-stemmed hinge silicone implant following modifications, with pain relief in 95% of patients in up to 9 years of follow-up.[27][28](B2)

Total joint implants are controversial. Generally not recommended in young or active persons due to the risk of implant loosening, subsidence, plantar subluxation, and component malalignment.[20] Results have shown to be less superior to arthrodesis regarding clinical outcomes, reduction in pain, complications, and revisions.[25](B2)

Polyvinyl alcohol hydrogel hemiarthroplasty received FDA approval for implantation in July 2016 in the United States. It has similar material properties to human articular cartilage regarding water content, tensile strength, and compressive modulus. Early data showed similar outcomes to arthrodesis; newer studies concluded that the frequency of conflict of interest by authors weakens the strength of evidence of previous studies, and more studies with long-term data are necessary.[29]

Interposition arthroplasty: This technique includes a modification of the Keller arthroplasty with the addition of an autogenous, allogeneic, or synthetic matrix spacer. Emmons and colleagues systematically reviewed 20 studies that utilized this technique with different materials. Out of 539 feet in a mean follow-up of 4.5 years, 90% of patients reported statistically significant improvement, and only 3.8% proceeded to further surgery.[30](A1)

Differential Diagnosis

Differentiating hallux rigidus from other causes of first metatarsophalangeal joint pain, which includes bunions, gout, hallux valgus, infection, and turf toe, is crucial. Restriction in dorsiflexion and the presence of dorsal osteophytes can lead to the diagnosis of hallux rigidus. Turf toe would present more acutely after traumatic injury. While hallux rigidus can have a swollen and painful great toe, laboratory evaluation can differentiate it from other diseases such as septic first MTP joint or gout.

Prognosis

Nonoperative treatment should be the first attempted intervention, as it has been shown to have good outcomes. Grady and colleagues reviewed 772 patients with either operative or nonoperative management; 55% percent of all patients had treatment success with conservative care alone.[16] As per operative treatment, first metatarsophalangeal joint arthrodesis remains the gold standard for end-stage hallux rigidus, with a success rate of approximately 90%.[31]

Complications

Cheilectomy does not prevent disease progression. Conversion rates to arthrodesis have ranged from 7% to 9% within 10 years. If the procedure fails, it does not compromise further revision surgery.[20] A systematic review by Stevens et al demonstrated a nonunion or delayed union rate of about 6.6% associated with arthrodesis. The study also showed that about 20% of patients had asymptomatic nonunion that did not require treatment. Other complications may include hardware removal, joint stiffness, and metatarsalgia. Complications associated with Keller resection arthroplasty include hallux cock-up deformity, toe-off weakness, and transfer metatarsalgia. Arthroplasty-related complications include failure of arthroplasty. It has correlated with implant-related complications of 26%, with the majority due to prosthetic loosening, causing instability and pain while walking.[25]