Two-Piece Interlocking Implant for Lesser Digit Fusions: A Case Series Sabina Malhotra, DPM1 & Paul Cooper, MD2

1Resident Physician, MedStar Washington Hospital Center; 2Attending Physician, MedStar Georgetown University Hospital

Abstract Methods & Results Analysis & Discussion

Implant

This is a two-piece stainless steel interlocking implant. The ratchet design allows for retained compression or complete disengagement if repositioning of the implant is warranted. 10° of plantarflexion have been incorporated into the middle phalanx implant to allow for a natural anatomical design.

Sabina Malhotra, DPM MedStar Washington Hospital Center Division of Podiatric Surgery 110 Irving Street, NW Washington, DC 20010 (202) 877-7000 sabinamalhotra@gmail.com

Thirty patients were involved in this study. Each patient was diagnosed with lesser digital contractures (one or more) via clinical and radiographic workup. Intraoperatively, a standard proximal interphalangeal joint arthroplasty was performed on the affected digit(s). The PIPJ was prepped and fused utilizing a 2-piece interlocking metal implant. Implant positioning was verified both clinically and under intraoperative fluoroscopy.

All patients were non-weightbearing in a surgical shoe for the first 2 weeks postoperatively, and were then progressed to partial weight bearing to the heel in an ortho wedge shoe for 6 weeks. A retrospective chart and radiographic review was performed. Patients were initially seen at two-week follow-up intervals with a total of 12 months. No soft tissue or osseous complications were encountered. As confirmed with serial radiographs, the 2-piece interlocking metal implant maintained stable anatomic alignment with no incidence of shifting or breakage. All patients were able to fully return to preoperative weight bearing and activity status.

Surgical implants used in the correction of lesser digital contractures are constantly evolving. Recent literature has shown that there are still many difficulties with finding an irremovable implant that is both easy to insert and consistently reliable. By using a 2-piece interlocking implant, the surgeon is able to insert one piece at a time at the PIPJ. There are no time stresses as the implant is stored and applied at room temperature, and repositioning is made simple with the inherent implant design. To our knowledge, this is the first case series presentation with long-term follow-up of said implant. Based on our clinical findings, we hypothesize that a 2-piece interlocking metal implant provides increased surgical precision, stable internal fixation, and is a viable tool for long-term lesser digit fusion.

Fusion of the proximal interphalangeal joints of lesser digits is a viable treatment option for rigid, symptomatic contractures. There are a variety of fusion methods, with irremovable and implantable hardware quickly becoming the preference for both surgeons and patients. However, most implants used in recent years have had several associated hardships. For example, the need for hot/cold storage, difficulty with intraoperative placement, inability to readjust the implant once placed, and postoperative shifting and/or breaking of the implant. This study evaluates a new 2-piece interlocking metal implant for achieving fusion of the proximal interphalangeal joints of lesser digits.

Contact

Proximal Phalanx Implant Middle Phalanx Implant Impacted Hammertoe Implant

Intra-operative steps showing piece by piece

implant insertion and final engagement

(bottom right). Photos courtesy of Richard Jay, DPM.

Patient C at 1, 3, & 6 mos. Increased IPJ callous formation and good alignment of implant noted.

Patient D at 1, 2, & 10 mos. post-op. Full return to pre-op activity levels noted.

Patient A pre-op (lateral). Patient A post-op (lateral). Note reduction in digital contracture.

Patient A pre-op (dorsoplantar). Patient A post-op (dorsoplantar).

Patient B at 12 mos. Note fusion of PIPJ with implant intact.