How To Salvage A Failed First MPJ Implant
A challenging problem for any podiatric surgeon is surgically managing cases in which a silicone elastomer implant in the first metatarsophalangeal joint (MPJ) has failed. When patients initially present with this problem, they will complain of pain, deformity or both at either the first or lesser metatarsophalangeal joints.
The cause of the pain or deformity can be multifactorial. The possible causes may include: chronic synovitis and swelling around the implant; chronic skin fistulas; implant breakage or fragmentation; severe periarticular bony subsidence and erosion; or biomechanical disruption of first ray stability and resultant lesser metatarsophalangeal joint overload.
The use of silicone implants in the first MPJ was described initially in 1972 when the implant was a single-stemmed hemiprosthesis designed to replace the resected base of the proximal phalanx.1 Results of this hemi-implant proved unsatisfactory. Consequently, a flexible, double-stemmed, hinged prosthesis was developed.2 Advocates of these implants cited such benefits as restoration of hallux length, good joint mobility, restoration of nearly normal joint biomechanics, adequate correction of hallux valgus and a shorter recovery period.1-8
Other clinical studies were less supportive as researchers reported high complication rates and poor functional outcomes, particularly for the hemi-implants.9-12 In one study, 36 percent of patients who received a single-stem implant were dissatisfied with the results of the operation.13 Researchers have also reported distal amputation after implant insertion.14 More recent data suggest these implants have poor rates of survival in weightbearing joints and in younger patients and that over time, these devices have high rates of mechanical failure with resultant metatarsalgia.11-13,16-19
Weighing The Possible Salvage Options
Despite the failure associated with use of first metatarsophalangeal joint silicone prostheses, there is a paucity of literature on how to salvage these failures. Salvage can be particularly difficult in younger, active patients. Options include implant removal and synovectomy; implant removal with reinsertion of an alternate implant; or bone block distraction arthrodesis.
For older, more sedentary people with low physical demands, implant removal with synovectomy is an option. However, both the surgeon and the patient must remember that this option does not provide a functional forefoot even for patients who are only minimally active. When considering this implant removal procedure, one must counsel patients on the strong possibility of lesser metatarsal overload symptoms and postoperative need for orthoses.
In a study of 11 failed silicone first MPJ implants, 10 patients received a mean 4.9 years of follow-up and seven patients had excellent clinical results.9 The authors observed a general clinical trend toward toe extension and used pressure studies to show increased load on the lateral forefoot.9 Other authors also observed postoperative lesser metatarsalgia in active patients who had received resectional arthroplasty.20,21