Soft tissue damage after minimally invasive THA

Figures & data

Figure 1. Schematic representation of the muscle damage measurements relative to the midsubstance cross-sectional surface area (MCSA). A relatively large damaged area at the origo (α1) may yield the same percentage of damaged MCSA (α) as a relatively small area at the musculotendinous insertion (α2).

Figure 2. Color segmentation of a cross-sectional slice of a damaged gluteus medius muscle. Panel A is an image of the color-stained slice. Panel B shows the same slice after color segmentation.

Table 1. Percentage of gluteus medius muscle damage in 5 hips during each approach

Hip	Lateral transgluteal	MIS anterior	MIS anterolateral	MIS 2-incision	MIS posterior
1	6	35	27	29	22
2	22	0	14	24	0
3	16	0	6	40	18
4	32	0	23	26	0
5	40	0	18	14	22
Median	22	0	18	26	18

Table 2. Comparison of the amount (%) of MCSA muscle damage between the lateral transgluteal approach and the 4 MIS approaches. Values are median (range)

Muscle	Lateral transgluteal	MIS anterior	MIS anterolateral	MIS 2-incision	MIS posterior	p-value (K-W test)
M. gluteus medius	22 (6–40)	0 (0–35)	18 (6–27)	26 (14–40)	18 (0–22)	0.1
M. gluteus maximus	1 (0–3)	0 (0–0)	0 (0–0)	0 (0–5)	2 (0–5)	0.1
M. gluteus minimus	48 (0–100)	31 (0–54)	27 (0–46)	12 (0–21)	24 (0–45)	0.5
M. quadratus	0 (0–0)	0 (0–20)	0 (0–0)	0 (0–0)	70 (13–100)	< 0.01
M. rectus femoris	0 (0–0)	0 (0–24)	0 (0–0)	0 (0–0)	0 (0–0)	0.8
M. tensor fascia latae	0 (0–26)	35 (16–100)	0 (0–0)	44 (7–49)	0 (0–0)	0.01

Table 3. The frequency of released external rotators and transected nerves for each of the 5 approaches

	Lateral transgluteal	MIS anterior	MIS anterolateral	MIS 2-incision	MIS posterior
	(n)	(n)	(n)	(n)	(n)
Muscle release
M. piriformis	1	0	0	0	3
M. gemellus superior	1	1	0	0	5
M. gemellus inferior	1	1	0	2	5
M. obturator internus	1	1	0	0	5
Transected nerves
Gluteus superior nerve	1	0	3	0	0
Lateral femoral cutaneous nerve	0	1	0	1	0
Sciatic nerve	0	0	0	0	0

Figure 3. The course of the lateral femoral cutaneous nerve (yellow dotted line) is shown in relation to the interval between the sartorius muscle and TFL muscle in the MIS anterior and the MIS 2-incision approaches.