A Study Comparing Computerized Tomographic Progression of Bone Bridging After Subtalar Fusion Using Fully and Partially Threaded Screws

The study was designed by the principal investigator, Dr. Alastair Younger, and the St. Paul's Hospital Foot and Ankle Research Group, who will conduct the study. The study is being funded by Acumed LLC, the manufacturer of the Health Canada approved Acutrak 2® - 7.5 fully threaded screw.

The purpose of this study is to assess and compare the effectiveness of fully threaded screws versus partially threaded screws in subtalar fusion, in order to determine the effect of the thread configuration on the success of the fusion procedure.

Efficacy will be assessed primarily by computed tomography (CT) analysis of percent bone bridging across the subtalar joint at both 12 and 24 weeks post-op. Outcome scores will also be administered to compare general health and foot function between the two groups at baseline and at multiple post-op follow-up visits. Additional resource utilization (i.e. additional clinic and/or hospital admissions) will also be compared between the two groups post-op.


Eligibility Criteria:
Inclusion Criteria:

* The subject is at least 19 years of age.
* The subject is considered to be skeletally mature.
* The subject qualifies for subtalar fusion based on physical examination and/ or past medical history including isolated osteoarthritis, post-traumatic, degenerative, or rheumatoid arthritis of the ankle.
* The subject experiences severe pain in the subtalar joint that could not be cured with non-operative treatment options.
* The patient may undergo a subtalar fusion as part of a triple arthrodesis.
* The patient has a normally functioning ankle joint, a solidly fused ankle joint, or a well-functioning ankle joint replacement.
* The patient may have forefoot pathology addressed by either prior or concurrent surgery (osteotomies or fusions).
* An ankle joint replacement or ankle joint fusion may be performed during the same sitting.
* The patient consented for either an arthroscopic or open procedure.
* The subject is able to comply with all post-operative evaluations and visits.
* The subject consents to and will receive either a cancellous autograft bone graft or synthetic bone graft substitute

Exclusion Criteria:

* The subject has:

  1. Severe osteoporosis
  2. Neuromuscular impairment
  3. Prior infection in the affected joint
* The subject currently has acute infections that, in the opinion of the Investigator, may complicate healing.
* The subject has a known sensitivity or allergic reaction to the screw material.
* The subject has insufficient bone stock or bone quality to support the screws.
* The subject has a major risk factor for non-union (ex. poorly controlled diabetes or current smoker).
* The subject is undergoing a revision of a prior subtalar fusion.
* The subject has a BMI of \> 50 kg/m2.
* The subject is known to be pregnant, or plans to become pregnant during the study period
* The investigator judges the subject to be unable or unlikely to remain compliant to follow-up due to a physical or mental condition (ex. currently being treated for a psychiatric disorder, senile dementia, Alzheimer's disease, etc.).
* The subject is unable to provide informed consent.
* The subject is unable to communicate with the research team.
* The subject is unable to comply with follow-up.
* The subject has a history of substance addiction (e.g. recreational drugs, narcotics, or alcohol) within 12 months prior to screening for study entry
* The subject is a prisoner, or is known or suspected to be transient
* The subject either does not consent to or will not be receiving either a cancellous autograft bone graft or synthetic bone graft substitute
* The subject will be receiving a structural autograft or allograft (such as a femoral head graft or tri cortical iliac crest graft) to fill a defect greater than 1cm3