Tourniquet cuff pressure and nerve injury in knee arthroplasty in a bloodless field

Figures & data

Table 1. Demographic baseline data for all patients included (n = 18)

Case	Sex	Age	BMI	Height cm	Control/ LOP	Cuff pressure, mmHg	Bloodless field time, min	Suspected nerve change/injury
1	F	68	23	167	LOP	173	56	Suspected
2	M	53	27	185	LOP	260	81	No
4	F	46	29	172	LOP	172	63	No
5	M	67	29	180	Control	250	67	No
6	F	74	28	168	Control	240	81	No
7 ^a	F	58	29	162	LOP	217	86	Suspected
8	M	56	27	178	Control	250	72	Suspected
9	M	63	24	177	LOP	209	87	Suspected
10	M	74	22	175	Control	250	85	No
11	F	66	24	163	Control	250	65	No
12	F	69	29	164	LOP	262	122	No
13	F	68	23	158	LOP	212	88	No
15	F	64	29	168	Control	250	78	No
16	M	56	26	185	LOP	294	100	Nerve injury
17	M	68	24	183	Control	280	67	Suspected
18	F	72	26	167	LOP	210	81	No
19	M	71	24	182	Control	240	105	No
20	F	73	23	159	Control	250	83	No
Mean (SD)	8/10	65 (8)	26 (2)	172 (9)	9/9	237 (33)	81 (16)	5/1

^a DVT postoperatively, no EMG examination performed

Table 2. Results of F-wave studies in the operated leg and median of the differences between the unoperated and the operated leg on day 3 and 2 months postoperatively

	Operated leg		Differences between the unoperated and the operated leg
	Day 3 ^a	2 months ^a	Day 3 ^b	p-value ^c	2 months ^b	p-value ^c
Peroneal nerve
F-latency (ms)	48.5 (39–61)	47 (42–65)	1.5 (0–3)	0.07	0.5 (-1.5–2.5)	0.7
F-wave persistence (%)	60 (15–100)	65 (15–100)	-10 (-27.5–2.5)	0.1	0 (-10–8.5)	1.0
Tibial nerve
F-latency (ms)	50 (42–57)	50 (45–58)	0 (-1.5–1)	0.9	-1 (-2–0.5)	0.2
F-wave persistence (%)	100 (90–100)	100 (55–100)	0 (-5–0)	0.2	2.5 (0–5)	0.3

^a median (min-max)

^b Hodges–Lehmann median (95% CI)

^c p value, Wilcoxon test

Figure 1. F-wave latency (in ms) and F-wave persistence (%) in the peroneal nerve in the operated leg both at day 3 and 2 months postoperatively. Patient no. 16 had EMG-confirmed nerve injury and the highest cuff pressure of 294 mmHg.

Figure 2. F-wave latency (in ms) and F-wave persistence (%) in the tibial nerve in the operated leg both at day 3 and 2 months postoperatively. Patient no. 16 had EMG-confirmed nerve injury and the highest cuff pressure of 294 mmHg. Patient no. 12 had the longest bloodless field duration of 122 minutes.