SLR - May 2020 - Victoria E. Teti

Silastic First Metatarsophalangeal Joint Arthroplasty for the Treatment of End-Stage Hallux Rigidus

Reference: Clough TM, Ring J. Silastic First Metatarsophalangeal Joint Arthroplasty for the Treatment of End-Stage Hallux Rigidus. Bone Joint J. 2020 Feb;102-B(2):220-226

Scientific Literature Review

Reviewed By: Victoria E. Teti, DPM
Residency Program: NewYork Presbyterian/Queens – Queens, NY

Podiatric Relevance: Hallux rigidus is a common diagnosis encountered in an outpatient setting. Certain patients opt for joint arthroplasty instead of arthrodesis to preserve joint motion. Silastic joint implants are rarely used and remain controversial due to a high rate of complications seen in initial studies in the 1980s. This article aimed to evaluate functional outcomes of patients who underwent first MPJ arthroplasty with a double-stemmed silastic implant. 

Methods: This was a retrospective review on 108 implants in 76 patients with minimum follow-up of two years. Outcome measures included implant survivorship, patient reported outcomes (MOXFQ, EQ-5D-5L, VAS scores, level of satisfaction), complications, radiographs, and cost. 

-Implant survivorship was 97.2 percent. 
-Mean MOXFQ score improved from 78.8 to 11. Mean EQ-5D-5L score improved from 0.63 to 0.81. Mean VAS score improved from 7 to 1.3. Mean ROM was 26.3 degrees. Overall satisfaction rate was 91 percent.
-Complications: One patient developed deep infection requiring revision surgery one month postoperatively; they eventually went on to arthrodesis with bone graft supplementation. Two stem breakages occurred at 10.4 and 13.3 years respectively; ultimately, undergoing revision surgery to another silastic implant. Complication rates were 23.1 percent and most were considered minor.
-Radiographs: cyst formation in 21 patients (21.4 percent), although none were symptomatic or progressive.
-Cost: £265 (~$308)

Conclusions: The authors found that the double-stemmed first MPJ implant provided a reliable treatment option for end stage hallux rigidus. Implant survivorship and overall satisfaction level was quite high with a low rate of complications at a mean follow-up of 5.3 years. The group did not find complications of synovitis, osteolysis and migration as seen in the earlier studies performed in the 1980s (mostly seen in single stemmed hemi-implants. The study ultimately concludes that this implant should be considered as a treatment option for patients with end stage hallux rigidus.

Limitations of this study include the retrospective nature of this study with no available data on preoperative range of motion and only radiographs performed postoperatively (no advanced imaging). Mean follow-up in this study was 5.3 years, which is relatively short for a study assessing survivorship of implants. Notably, this implant was not recommended to be used in those with valgus deformity as the silastic implant acts as a hinged dynamic spacer and has no ability to correct deformity. No comparison groups were noted in this study For future research, patients can be randomly divided into several treatment groups to compare outcomes. For example: silastic implant, one or two other implants currently in use for joint replacement, and an arthrodesis group. Outcome data can be compared for these groups to determine if the silastic implant is indeed superior to other available implants. Though I would like to see more long term studies with this implant, results from this study and those preceding it are promising. I would consider it for patients with severe hallux rigidus with no valgus deformity who are interested in avoiding an arthrodesis procedure to retain first MPJ motion. 

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