Foot & Ankle

Arthroplasty

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Options for MTPJ arthroplasty include silastic implants, all-metal implants and synthetic cartilage implants.

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Metallic implants attempted to replicate total hip and total knee designs in the first MTP joint. There are some reports of moderate patient satisfaction and pain improvement, however, these implants have been associated with early and high failure rates due to osteolysis and subsidence.

Pulavarti reported a revision rate of 5.5% and implant subsidence rate of 33% at average 3.9-year follow-up in a prospective study of 32 patients.

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Gibson and Thomson reported on 63 patients in an RCT comparing arthrodesis to arthroplasty and found that 49% of patients had radiographic loosening at one year with a 15% revision rate at two years in arthroplasty group.

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Ceramic implants have been reported to have similarly poor results. Nagy et al. reported 68% implant survival at 9 years for 31 second-generation ceramic implants in a retrospective study. Dawson-Bowling reported a 26% re-operation rate at 8 years with 52% of implant loosening in a retrospective study of 32 cases.

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Hemi-arthroplasty involves a metallic implant of either the proximal phalanx or the metatarsal head. Townley et al. reported on a retrospective series of 279 patients with 8-months to 33-year follow-up of a metal hemiarthroplasty of the proximal phalanx and found good to excellent results in 95% of patients. However, other studies could not replicate these results and reported poor outcomes.

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Konkel et al. reported subsidence and radiolucencies in all ten patients retrospectively reviewed at 37 to 105 months after a proximal phalanx hemi-arthroplasty.

Raikin et al. retrospectively reviewed 21 metatarsal head hemiarthroplasties at average 6.6-year follow-up and found a revision rate of 24% with decreased satisfaction, AOFAS scores and higher VAS pain scores compared with a cohort of 27 arthrodesis patients.

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Gheorghiu et al. observed a marked decrease in patient satisfaction and ROM in patients undergoing hemiarthroplasty compared to arthrodesis with a mean follow up of 4 years. In contrast another study by Voskuiji et al. reported better satisfaction rates in patients undergoing hemiarthroplasty.

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The reported complications include loosening, change in angulation, subsidence, stiffness and ongoing pain. These reports of higher complication rates, unpredictable long-term results and poor survival have lead to their cautious use among surgeons. In addition, failure of arthroplasty is difficult to manage due to significant bone loss.

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Silastic implants have a better outlook but in selected patients. An ideal patient is over 55 years of age with relatively lower physical demands and neutral alignment of the big toe. In a suitably selected patient these implants have been shown to provide good clinical and functional results with longer survival rates.

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For silastic implants, Clough et al. reported satisfactory functional outcomes and high patient satisfaction in 83 patients (108 feet) with mean age of 55 years at the time of surgery and a mean follow up of 8.3 years with the use of double-stem implants. These results provide a more-encouraging account compared to the available reports of metallic implants in terms of symptomatic and functional improvements and fewer complications.

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A systematic review included all 28 studies published on silastic implants and included 2354 feet in 1884 patients (1968 to 2003). The review included 8 studies with first generation single stem implants and 20 studies with 2nd generation double stem implants and showed an overall failure rate of 5.3% (11% single vs 3.6% double stem) at a mean follow up of 85 months. There was a mean improvement of 76% in pain and 84% patient satisfaction. Radiological changes were reported in 14.7% cases.

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Interpositional Arthroplasty

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It is a joint sparing option that aims to maintain joint motion in patients with severe hallux rigidus. Keller resection arthroplasty was one of the initial procedures in this regard that involves resection of up to 50% of the base of the proximal phalanx. However, the procedure may potentially destabilize the first MTP joint leading to transfer metatarsalgia, excessive shortening of the toe, cock-up deformity, clawing of the IP joint, and high rates of revision. It has therefore been proposed to reserve the Keller resection in patients with severe hallux rigidus who are over the age of 70, and functionally have low physical demands.

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Schneider et al. reported a 90% stable first MTP joint in 78 patients (87 toes) who underwent Keller resection with 23 years of follow-up, 5% revision rate, 23% (19 toes) patients with a cock-up deformity, however, only one patient required revision.

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In view of the potential complications of Keller’s resection, multiple modifications have been developed, including a limited resection, addition of a cheilectomy, and a placement of a spacer (joint capsule, extensor hallucis brevis, tendon autograft, tendon allograft, synthetic matrix) with an aim to preserve the bone stock, maintain or increase joint motion, stability and length.

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Aynardi et al. retrospectively reviewed 133 patients who underwent interpositional arthroplasty with either autograft or synthetic soft tissue with 90% patients reporting good to excellent outcomes at a mean follow-up of 62.2 months, an overall failure rate of 3.8%, an infection rate of 1.5% and transfer metatarsalgia in 23% patients.

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Schenk et al. compared the outcomes of Keller’s resection and interpositonal arthroplasty. They did not find any significant difference between the clinical and radiological outcomes of the two procedures in a short-term follow-up study of 1.26 years.

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Mackey et al. compared interpositional arthroplasty with arthrodesis and reported equivalent clinical outcomes. However, interpositional arthroplasty reported an additional benefit of motion preserving motion and a more physiologic pattern of plantar pressure during gait cycle.

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Berlet et al. described the use of a regenerative tissue matrix (RTM) as an allograft interpositional spacer for the treating advanced hallux rigidus. It is a biologically engineered allograft consisting of collagen and extracellular protein matrices. In their early report, 9 patients underwent the procedure with no failure at 10 month follow-up. At 5-year follow-up, none of the patients had subsequent fusion or additional procedures performed and all were satisfied with the procedure.

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In a multicentre prospective randomised trial of 202 patients a 8-mm to 10-mm synthetic cartilage implant (Cartiva) placed in the first MT head and compared with a first MTP arthrodesis at two-year follow-up.

Baumhauer et al. reported equivalent reduction in VAS pain scores and improvement in FAAM sports functional scores with the synthetic implant and first MTP arthrodesis. Synthetic cartilage patients had an average of 4° of improvement in dorsiflexion and a revision rate of 9.2% to arthrodesis.

While longer survivorship analysis is planned, this implant offers encouraging results. Additionally, because the implant removes only 8 to10 mm of bone surrounding the metatarsal head, revision to arthrodesis is less challenging with minimal loss of length of the first metatarsal.​

Summary

Conservative treatment for hallux rigidus is the first line and may provide symptomatic benefit in about 50% for an interim period.

Surgical treatment is indicated once the conservative measures fail and is individualised for each patient depending on their physical demands and expectations.

For mild to moderate degenerated changes cheilectomy (+/- Cartiva) provides consistent results but are interim procedures.

For severe cases, fusion remains the ‘gold standard’ and provides consistent results to improve pain and function. 

Arthroplasty (Silastic) has a reasonable role in selected patients and provides good results.

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