Arthroscopic ankle fusion only has a limited advantage over the open operation if osseous operation type is the same: a retrospective comparative study

Table 4 Outcomes of AOFAS score

	Between-group difference (all patients)			Difference detailed into subgroup (osseous operation type: not same)			Difference detailed into subgroup (osseous operation type: same)			Internal difference of OAF group (osseous operation type: not same)
	AAF	OAF	P	AAF	COO	P	AAF	SOO	P	COO	SOO	P
Mean of AOFAS score
Within 2 weeks before surgery	36.2 ± 13.5 (n = 17)	32.5 ± 11.8 (n = 26)	0.347	36.2 ± 13.5 (n = 17)	30.7 ± 12.8 (n = 15)	0.253	36.2 ± 13.5 (n = 17)	34.8 ± 10.5 (n = 11)	0.780	30.7 ± 12.8 (n = 15)	34.8 ± 10.5 (n = 11)	0.395
Post-op 3 months	63.1 ± 3.3 (n = 17)	59.6 ± 4.7 (n = 26)	0.013	63.1 ± 3.3 (n = 17)	57.9 ± 4.7 (n = 15)	0.001	63.1 ± 3.3 (n = 17)	61.9 ± 3.9 (n = 11)	0.412	57.9 ± 4.7 (n = 15)	61.9 ± 3.9 (n = 11)	0.031
Post-op 6 months	70.5 ± 5.7 (n = 15)	66.7 ± 5.1 (n = 25)	0.034	70.5 ± 5.7 (n = 15)	64.9 ± 3.8 (n = 15)	0.004	70.5 ± 5.7 (n = 15)	69.4 ± 5.7 (n = 10)	0.633	64.9 ± 3.8 (n = 15)	69.4 ± 5.7 (n = 10)	0.027
Post-op 1 year	76.2 ± 3.9 (n = 16)	73.0 ± 7.1 (n = 23)	0.160	76.2 ± 3.9 (n = 16)	72.1 ± 6.2 (n = 14)	0.037	76.2 ± 3.9 (n = 16)	74.3 ± 8.1 (n = 9)	0.439	72.1 ± 6.2 (n = 14)	74.3 ± 8.1 (n = 9)	0.467
Final (at least 1 year post-op)	77.7 ± 3.8 (n = 17)	75.8 ± 4.5 (n = 26)	0.148	77.7 ± 3.8 (n = 17)	75.4 ± 3.7 (n = 15)	0.090	77.7 ± 3.8 (n = 17)	76.3 ± 5.6 (n = 11)	0.423	75.4 ± 3.7 (n = 15)	76.3 ± 5.6 (n = 11)	0.632

AAF arthroscopic ankle fusion group, OAF open ankle fusion group (demographic composition: OAF = COO + SOO), COO complex osseous operation, SOO simple osseous operation, Post-op postoperative, AOFAS score the American Orthopedic Foot and Ankle Society score. P P values: α = 0.05 (Independent-samples t test)

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