Learning curve of total ankle replacement from the lateral approach

Table 1 Concomitant procedures performed during total ankle replacement

Procedure	Early phase (cases 1-33)	Late phase (cases 34-65)	Total (n)	Percentage of total (n = 65)
Modified Broström/ATFL repair	6	11	17	26.2
ATFL + DL repair	0	1	1	1.5
Subtalar distraction arthrodesis	1	0	1	1.5
Double/triple arthrodesis (hindfoot)	1	0	1	1.5
Medial displacement calcaneal osteotomy + ATFL repair	0	1	1	1.5
Percutaneous Achilles tendon lengthening (Hoke)	0	4	4	6.2
Deltoid ligament release	1	0	1	1.5
Medial (anteromedial) gutter debridement	6	4	10	15.4
Removal of previous fixation (fibular plate/screws)	1	3	4	6.2
Internal fixation of intraoperative medial malleolar fracture	0	1	1	1.5
Total number of concomitant procedures	16/33 (48.5%)	26/32 (81.3%)	42	64.6

ATFL: Anterotalofibular ligament; DL: Deltoid ligament.

Table 2 Baseline demographic and clinical characteristics of the study cohort

Variable	Category	Number of patients (n = 65)	Percentage
Operated leg	Left	36	55.4
	Right	29	44.6
Cause	Post-traumatic	35	53.8
	Chronic osteoarthritis	27	41.5
	Rheumatoid arthritis	3	4.6
BMI (kg/m2)	mean ± SD (range)	29.4 ± 4.0 (20.8-35.6)
	≥ 25 (overweight + obese)	51/59	86.4
	≥ 30 (obese)	27/59	45.8
Diabetes mellitus/prediabetes	Diabetes mellitus (insulin)	2	3.1
	Diabetes mellitus (oral therapy)	1	1.5
	Prediabetes	1	1.5
	No	61	93.9
Smoking status	Occasional smoker	7	10.8
	Former smoker	5	7.7
	Never smoker	53	81.5

BMI: Body mass index; SD: Standard deviation.

Table 3 European Foot and Ankle Society score results and changes

Cause of total ankle replacement procedure	Score before procedure	SD (before)	Score after procedure	SD (after)	Difference before and after surgery (P value)
Post-traumatic	4.42	4.00	17.35	2.46	12.93 (< 0.001)
Chronic osteoarthritis	2.27	3.04	14.23	5.83	11.96 (< 0.001)
Rheumatoid arthritis	7.67	3.79	20.33	2.08	12.66 (0.100)

SD: Standard deviation.

Table 4 Manchester-Oxford Foot Questionnaire score results and changes

Cause of total ankle replacement procedure	Score before procedure	SD (before)	Score after procedure	SD (after)	Difference before and after surgery (P value)
Post-traumatic	77.23	15.42	25.31	19.15	51.92 (< 0.001)
Chronic osteoarthritis	79.58	12.41	35.38	31.02	44.20 (< 0.001)
Rheumatoid arthritis	71.33	10.97	9.00	1.73	62.33 (0.077)
Total	78.02	13.78	21.57	25.76	58.50 (< 0.001)

SD: Standard deviation.

Table 5 Functional outcomes and quartile-based learning-curve analysis (n = 65)

Parameter	Pre-operative (mean ± SD)	Post-operative (mean ± SD)	Δ (mean ± SD)	Median	Range
EFAS score	3.6 ± 2.9	17.2 ± 3.1	+ 13.0 ± 4.6	14	-2 to 20
MOXFQ score	82.5 ± 10.7	21.3 ± 22.3	+ 58.5 ± 21.8	64	-6 to 86

EFAS: European Foot and Ankle Society; MOXFQ: Manchester-Oxford Foot Questionnaire; SD: Standard deviation.

Table 6 Quartile-based analysis (chronological segmentation)

Quartile (case order)	n	mean ΔEFAS ± SD	mean ΔMOXFQ ± SD	Interpretation
Q1 (cases 1-16)	16	14.6 ± 2.5	63.8 ± 20.8	Stable early improvement
Q2 (cases 17-32)	16	12.7 ± 5.3	60.9 ± 24.7	Slight variability, consistent trend
Q3 (cases 33-48)	16	13.5 ± 5.2	57.1 ± 25.9	Plateau maintained
Q4 (cases 49-65)	17	13.8 ± 5.5	62.7 ± 18.2	Sustained functional gain

Kruskal-Wallis: P = 0.42 (European Foot and Ankle Society); P = 0.47 (Manchester-Oxford Foot Questionnaire). Spearman’s ρ = 0.09 for Δ European Foot and Ankle Society (P = 0.56); ρ = 0.12 for Δ Manchester-Oxford Foot Questionnaire (P = 0.43). EFAS: European Foot and Ankle Society; MOXFQ: Manchester-Oxford Foot Questionnaire; SD: Standard deviation.

Table 7 Mean operative time by consecutive case groups

Case range	Mean operative time (minute)	SD (minute)
1-10	175.5	25.8
11-20	158.5	39.7
21-30	136.0	22.4
31-40	122.5	16.8
41-50	118.1	19.5
75-85	109.6	22.4

SD: Standard deviation.

Table 8 Distribution of reoperations and conservatively managed complications across learning-curve phases

Type of complication/reoperation	Early phase (cases 1-30)	Late phase (cases 31-60)
Operative (reoperations)
Infection-related procedures (washout, liner exchange, explant/spacer, sinus/peroneal tendon revisions)	5	1
Lateral malleolus stabilization/nonunion revision	3	0
Tarsal tunnel release	1	2
Total talus replacement	1	0
Medial/Lateral recess release ± syndesmosis screw removal/ATFL repair	8	6
Hardware removal (isolated)	1	1
Calcaneal osteotomy (MDCO)	0	1
Total operative procedures (patients)	19 (13)	10 (7)
Conservatively managed complications
Superficial infection (occasional smoker)	1	0
Lateral malleolus fixation instability (treated nonoperatively)	1	0
Syndesmotic screw loosening/destabilization	2	1
Equinus contracture (treated with physiotherapy)	1	0
Intraoperative medial malleolar fracture without fixation	1	0
Intraoperative medial malleolar fracture with screw fixation with delayed union	0	1
Total conservative complications (patients)	6 (6)	2 (2)

ATFL: Anterotalofibular ligament; MDCO: Medializing displacement calcaneal osteotomy.