The Use of a Sustained Dynamic Compression Intramedullary Nail for Subtalar Arthrodesis

This proposal is a collaborative effort between MedShape and the University of California, Davis Medical Center. This is a prospective investigation to assess the clinical outcomes of patients with a subtalar arthrodesis with the Sustained Dynamic Compression Intramedullary Nail (DynaNail Mini). The study plan is to enroll 60 patients.

Patients with end-stage talocalcaneal (subtalar) joint arthritis from any etiology will be asked to enroll in the study. After informed consent, the patients will be asked to complete the following patient reported outcomes questionnaires as part of the Surgical Outcomes System (SOS) Global Registry: Visual Analog Scale (VAS) for pain, Veterans RAND 12 Item Health Survey for function, Foot Function Index - Revised for function and pain, the Foot and Ankle Ability Measure (FAAM) for function, and the American Orthopaedic Foot and Ankle Society (AOFAS) scales for pain, function, and alignment. After informed consent, they will then be scheduled for surgery in a routine fashion.

The following surgical procedure is standard of care. The surgical procedure will involve subtalar (talocalcaneal) joint preparation through a lateral approach. The use of supplemental bone graft is at the discretion of the treating surgeon but must be documented. The MedShape DynaNail Mini will then be inserted according to the manufacturer's technique. The patient will be placed in a short leg splint and kept non-weight bearing. The patient will be discharged from the hospital when medically ready.

The patient will return to clinic for visits at the following intervals after surgery: 6 (+/- 1) weeks, 14 (+/- 1) weeks, 6 months (+/- 2 weeks), and 12 months (+/- 2 weeks). At each of these time points, the same SOS patient specific outcome questionnaires will be administered. 3-view X-rays will be taken at each of these visits to assess the amount of travel of the Mini compressive element. At 15 (+/- 1) weeks post-op, a CT scan will be obtained to assess healing. Additionally, a radiographic and clinical follow-up form will be filled out at each of the following follow-up visits: 6 weeks, 14 weeks, 6 months, and 1 year.

Patients will be identified in the clinic by an attending orthopaedic foot and ankle surgeon or his physician assistant based on clinical exam and radiographic findings. Inclusion criteria include anyone over age 18 who has end-stage subtalar arthritis and has failed nonoperative management. Typically, these patients have multiple medical comorbidities and therefore the exclusion criteria will be patients who are not healthy enough to undergo surgery. Additional exclusion criteria include non-English speakers, and patients that are blind, illiterate, or are prisoners. Additionally, pregnant women will be excluded. Patients of all racial, religious, and cultural backgrounds will be included in this study.

• Subtalar (Talocalcaneal) arthrodesis (Procedure): Subtalar (Talocalcaneal) arthrodesis with a novel sustained dynamic compression intramedullary nail
• DynaNail Mini (Device): Utilization of a novel sustained dynamic compression pseudoelastic intramedullary nail

Primary outcomes

• Fusion [From surgery up to one year post-surgery]: Joint Fusion, as measured by radiograph and CT scan

Secondary outcomes

• Pain - VAS [Pre-Operative up to one year post-surgery]: Pain Visual Analog Scale (VAS) - Rates the intensity of pain from 0 - 10 with 10 being the worst pain possible.
• Veterans RAND 12 Item Health Survey (VR-12) [Pre-Operative up to one year post-surgery]: The Veterans RAND 12 Item Health Survey (VR-12, formerly called the Veterans SF-12) was Version Date 01.27.2020 3 developed from the Veterans RAND 36 (VR-36, formerly called the Veterans SF-36), which was modified from the original Medical Outcomes Survey (MOS) SF-36. The VR-12 measures Physical functioning (PF), social functioning (SF), role limitation due to physical problems (RP), role limitation due to emotional problems (RE), mental health (MH), energy and vitality (VT), bodily pain (BP) and general perception of health (GH). Standard based scoring (sometimes called norm based scoring) is used to calculate the physical component summary (PCS) and mental component summary (MCS) for both measures. The PCS and MCS are standardized using a t-score transformation and normed to a US population at a score of 50 and a standard deviation of 10.
• Foot Function Index - Revised (FFI-R) [Pre-Operative up to one year post-surgery]: Measures the impact of foot pathology on function in terms of pain, disability, and activity restriction. The score is a percentage. The higher the score, the greater the disability.
• Foot and Ankle Ability Measure (FAAM) [Pre-Operative up to one year post-surgery]: Measures activities of daily living and sports. The final score is a percentage. The higher final score represents a higher level of physical function.
• American Orthopaedic Foot and Ankle Society Scales (AOFAS) [Pre-Operative up to one year post-surgery]: Clinician-based outcome that measures foot/ankle pain, function, and alignment. The lower the score, the greater the disability. The maximum score is 100.

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* End-stage talocalcaneal (subtalar) joint arthritis from any etiology will be eligible to enroll in the study
* Meets indications for subtalar arthrodesis to receive the DynaNail Mini implant
* Able to understand the requirements of the study, provide a written consent, and willing to comply with the study protocol
* 18 years of age or older

Exclusion Criteria:

* Investigator determines that the subject is unlikely to comply with the requirements of the study
* Non-English speaker
* Blind
* Illiterate
* Prisoner
* Pregnant women

• Kreulen C, Lian E, Giza E. Technique for Use of Trabecular Metal Spacers in Tibiotalocalcaneal Arthrodesis With Large Bony Defects. Foot Ankle Int. 2017 Jan;38(1):96-106. doi: 10.1177/1071100716681743. Epub 2016 Dec 7. PMID 27920334

• Christopher Kreulen, MD, MS, Principal investigator, University of California, Davis