Do clinical results of arthroscopic subtalar arthrodesis correlate with CT fusion ratio?

Background: CT analysis of arthroscopic subtalar arthrodesis rarely finds complete fusion. The aim of the present study was to determine, at 12 months' follow-up of arthroscopic subtalar arthrodesis: (1) CT fusion ratio, (2) functional results, and (3) the correlation between the two.

Hypothesis: Incomplete fusion ratio does not impair the result of arthrodesis.

Materials And Methods: A continuous series of 22 arthroscopic subtalar arthrodeses was assessed at 12 months' follow-up. The procedure used a posterior approach without bone graft, with stabilization by 2 compression screws. Clinical assessment comprised of a numerical analog pain scale (NAS, AOFAS and SF12) scores. Satisfaction was assessed on an NAS and on Odom's criteria. CT analysis at 12 months determined the posterior subtalar joint fusion ratio.

Results: At follow-up, 2 patients showed non-union (9.1%). Among the 20 patients with fusion (91%), fusion was complete (>67°) in 16 (72.7%) and partial (34-66%) in 4 (18.2%). Mean fusion ratio at 12 months was 77.7%±14.8 (range, 36-98%). Functional gains (Δ) were: Δ pain NAS 4.8±2 (range, 1-10) and Δ AOFAS score 31.1±14 (range, 10-59). Mean satisfaction score was 8±2.5 (range, 3-10). There were no significant correlations between fusion ratio and any clinical or satisfaction scores.

Conclusion: Although clinical gain was systematic, functional and satisfaction scores were independent of whether subtalar fusion ratio was partial or complete.

Level Of Evidence: IV, retrospective study.