Does the advantage of transcutaneous oximetry measurements in diabetic foot ulcer apply equally to free flap reconstruction?

Table 1 Demographic characteristics of patients with diabetic foot ulcer with and without free flap

	Total (n = 47)	Free flap (n = 17)	DFU (n = 30)	P value
Sex
Male	31 (65.96)	10 (58.82)	21 (70.00)	0.437
Female	16 (34.04)	7 (41.18)	9 (30.00)
Age	61.36 ± 2.04	54.76 ± 3.62	65.10 ± 2.21	0.013
Smoking history
Non-smoker	23 (48.94)	11 (64.71)	12 (40.00)	0.104
Smoker	24 (51.06)	6 (35.29)	18 (60.00)
HbA1c	7.00 (6.00-9.10)	6.20 (5.60-9.00)	7.25 (6.10-9.20)	0.084
HTN
None	17 (36.17)	9 (52.94)	8 (26.67)	0.072
HTN	30 (63.83)	8 (47.06)	22 (73.33)
Nephropathy
None	34 (72.34)	15 (88.24)	19 (63.33)	0.094
Nephropathy	13 (27.66)	2 (11.76)	11 (36.67)
Angiosome
ATA	26 (55.32)	7 (41.18)	19 (63.33)	0.138
PTA	21 (44.68)	10 (58.82)	11 (36.67)
TcpO2	13.00 (6.00-22.00)	12.01 (8.01-15.01)	14.50 (6.00-22.00)	0.812
ABI
Affected side	1.02 ± 0.03	1.14 ± 0.03	0.95 ± 0.05	0.002
Unaffected side	1.06 ± 0.03	1.13 ± 0.02	1.03 ± 0.04	0.024
Creatinine	1.07 (0.72-3.12)	0.74 (0.63-0.86)	1.98 (0.95-6.27)	0.001
Hb	11.10 ± 0.25	11.83 ± 0.31	10.68 ± 0.33	0.024
Duration of DM (yr)	10.00 (5.50-15.00)	3.00 (1.00-10.00)	13.50 (10.00-20.00)	< 0.001
Duration of HTN (yr)	10.50 (10.00-20.00)	11.00 (2.00-20.00)	10.00 (10.00-20.00)	0.666
CRP	11.24 (4.21-35.70)	3.50 (1.70-10.57)	27.78 (8.20-73.71)	< 0.001
BMI	23.96 ± 0.71	23.84 ± 1.28	24.03 ± 0.87	0.896

ABI: Ankle-brachial index; ATA: Anterior tibial artery; BMI: Body mass index; CRP: C-reactive protein; DFU: Diabetic foot ulcer; DM: Diabetes mellitus; Hb: Haemoglobin; HbA1c: Glycosylated haemoglobin A; HTN: Hypertension; TcpO₂: Transcutaneous oxygen pressure; PTA: Posterior tibial artery.

Table 2 Comparison of transcutaneous oxygen pressure values based on postoperative day in the group that received free flap

Value	Perforator	Distal	P value
POD 1	8.64 ± 10.72	8.27 ± 11.62	> 0.099
POD 5	18.64 ± 14.43	19.36 ± 16.11	> 0.99
POD 10	14.00 ± 16.35	16.73 ± 15.51	> 0.99
POD 15	13.82 ± 13.41	16.18 ± 13.40	> 0.99
POD 20	17.82 ± 18.21	31.00 ± 26.81	0.972
POD 30	45.86 ± 33.20	47.14 ± 23.13	> 0.99
POD 60	30.43 ± 21.95	35.57 ± 26.48	> 0.99
POD 90	18.71 ± 5.35	18.71 ± 17.37	> 0.99
POD 180	15.43 ± 11.10	19.57 ± 22.23	> 0.99
POD 360	12.86 ± 7.78	16.43 ± 13.78	> 0.99

POD: Postoperative day.

Table 3 Advantages and disadvantages of devices that determine blood flow status in diabetic foot ulcer

	Advantages	Limitations
Assessment of disease severity
ABI (normal range 1.1-1.3)	Widely used, easy to measure	Unreliable in patients with severe PAD, DFU[26]
TBI (normal range 1.0-1.1)	Compensating for ABI limitations, easy to repeat measurement	Decreased accuracy at severe vessel calcification, limitation of diagnostic threshold[27]
Continuous wave Doppler	High accuracy in PAD diagnosis[28]	Decreased accuracy in DFU[28]
Pulse volume recording	Used in PAD diagnosis	Unable to determine exact location, many other variables[29]
Assessment of morphological distribution
Duplex ultrasound	Noninvasive	Complemented by more detailed image required
Angiography	Detailed images can be provided, fast	Vulnerable to artifacts, risk for contrast nephropathy
Assessment of regional tissue perfusion
TcpO2 (normal range 40-70 mmHg)	More sensitive than ABI	DFU, autonomic neuropathy, low accuracy for severe vascular calcification[12]
Skin perfusion pressure	Useful when ABI, TBI are not possible	Requires special equipment and further validation[30]
Fluorescence angiography	Low toxicity compared with angiography, good discriminatory ability[31]	Expensive, requires special equipment
Laser Doppler	Evaluate blood flux rather than blood flow	Vulnerable to motion artifacts and temperature changes, inter-operator variation
Hyperspectral imaging	Useful for determining the effect of DFU treatment	Lack of research on interpretation of results[32]
Molecular imaging
PET and SPECT	High resolution	Expensive, requires special equipment
Contrast-enhanced ultrasound	Excellent for PAD discrimination[33]	Low accuracy for DFU[33]
Multi-modal MRI	Semi-quantitative evaluations based on relative patient conditions are possible	Take long time, no evidence of effectiveness for DFU

ABI: Ankle-brachial index; DFU: Diabetic foot ulcer; MRI: Magnetic resonance imaging; PAD: Peripheral artery disease; PET: Positron emission tomography; SPECT: Single-photon emission computed tomography; TcpO₂: Transcutaneous oxygen pressure; TBI: Toe brachial index.