The goal of this clinical trial is to compare two surgical approaches for treating symptomatic subtalar arthritis in patients who have failed conservative treatment. The main questions it aims to answer are:

What is the fusion rate for each surgical technique? Which technique achieves bony union faster with fewer complications?

Researchers will compare arthroscopic subtalar arthrodesis (ASTA) using a combined three-to-four portal approach to open in situ subtalar arthrodesis (ISTA) to see if one technique results in superior fusion rates, faster healing, and better functional outcomes.

Participants will:

Undergo one of two surgical procedures (either ASTA or ISTA) Attend follow-up visits at 6 weeks, 3 months, 6 months, and 12 months after surgery Have X-rays taken to assess fusion and bone healing Complete pain and function questionnaires at each visit

Background and Rationale:

Subtalar arthritis is a debilitating condition frequently resulting from intra-articular calcaneal fractures, leading to progressive cartilage degeneration, hindfoot pain, and functional impairment. When conservative management fails, subtalar arthrodesis (fusion) is the established gold standard surgical treatment. Open in situ subtalar arthrodesis (ISTA) via the sinus tarsi approach has a long history of success with reported fusion rates of 85-95%. However, arthroscopic subtalar arthrodesis (ASTA) has gained popularity due to proposed advantages including preservation of blood supply, reduced soft tissue trauma, and lower wound complication rates. High-quality prospective comparative data between these two techniques remain limited.

Study Design:

Single-center, prospective, randomized controlled trial at Kasr Al-Ainy Hospitals, Cairo University. Forty patients with symptomatic subtalar arthritis are randomized 1:1 to ASTA (n=20) or ISTA (n=20) using computer-generated sequences with allocation concealment via sequentially numbered sealed opaque envelopes. Due to the nature of surgical interventions, blinding of patients and surgeons is not feasible; however, outcome assessment is performed by a blinded independent assessor.

Surgical Interventions:

Arthroscopic Subtalar Arthrodesis (ASTA): Performed under spinal anesthesia in the prone position. A combined three-to-four portal arthroscopic technique is used, including anterolateral (sinus tarsi), posterolateral, and posteromedial portals for complete visualization of the subtalar joint. Complete synovectomy and cartilage debridement until healthy bleeding subchondral bone is exposed.. Subchondral drilling creates microfractures to enhance vascular ingrowth. Fixation is achieved with two percutaneously inserted 6.5-7.3 mm cannulated screws under fluoroscopic guidance.

Open In Situ Subtalar Arthrodesis (ISTA): Performed under spinal anesthesia with the patient supine via a 4-5 cm oblique sinus tarsi approach. All residual articular cartilage is removed to bleeding cancellous bone. The subchondral plate is perforated to enhance fusion. Fixation is achieved with two percutaneously inserted cannulated screws under fluoroscopic guidance.

Postoperative Protocol:

Standardized rehabilitation: non-weight-bearing in a short-leg removable cast boot for 6 weeks, followed by progressive weight-bearing once radiographic union is confirmed. Formal physiotherapy begins after transition to full weight-bearing.

Outcome Evaluation:

Patients are assessed at 2 weeks, 6 weeks, 3 months, 6 months, and 12 months postoperatively. Primary outcomes are radiographic fusion rate and time to radiographic union (defined as trabecular bridging across the posterior facet on plain radiographs or CT). Secondary outcomes include pain (VAS), functional status (Modified AOFAS), quality of life (SF-12), operative time, blood loss, and complication rates. Subgroup analyses by age, sex, BMI, smoking status, and arthritis etiology are performed.

Statistical Analysis:

Sample size (40 patients) calculated for expected fusion rates of 100% (ASTA) vs 95% (ISTA) with non-inferiority margin of 0.15, 80% power, and two-tailed alpha 0.05. Analysis includes t-tests, chi-square tests, Kaplan-Meier survival analysis, and multivariable regression. Significance set at p < 0.05.

Ethics:

Study approved by Research Ethics Committee, Faculty of Medicine, Cairo University (13 February 2024). All patients provide written informed consent. Conducted in accordance with the Declaration of Helsinki (2013), ICMJE, and CONSORT guidelines.

Inclusion Criteria:

• Clinically and radiographically confirmed symptomatic subtalar arthritis (post-traumatic, primary osteoarthritis, inflammatory or cured post-infective arthritis, symptomatic talocalcaneal coalition, or isolated subtalar arthrosis secondary to pes planovalgus deformity)
• Failure of an adequate trial of non-operative treatment for a minimum of six months
• Skeletal maturity: patients aged 18 years or older
• Ability and willingness to provide written informed consent and to comply fully with the scheduled postoperative follow-up protocol

Exclusion Criteria:

• Primary subtalar arthrodesis performed for an acute, displaced intra-articular calcaneal fracture
• Arthrodesis planned in conjunction with other simultaneous ipsilateral hindfoot procedures
• Patients with open physes (skeletal immaturity)
• Indication for a distraction-type arthrodesis requiring structural bone graft
• History of previous or current active infection at the planned operative site
• Previous failed attempt at subtalar arthrodesis
• Presence of significant peripheral vascular disease or other major medical comorbidities precluding safe surgical intervention

Due to the inherent nature of the surgical interventions, blinding of the patients and the primary surgeon was not feasible. However, the assessor responsible for collecting postoperative outcome scores was kept blinded to group assignment to minimize detection bias.