Gluteal muscle fatty atrophy is not associated with elevated blood metal ions or pseudotumors in patients with a unilateral metal-on-metal hip replacement

Figures & data

Figure 1. Flow chart of patient selection.

Figure 3. Box plot showing median WB Cr levels, interquartile range (boxes), and 95% CIs (whiskers) with outliers (circles), presented according to grade of g. medius atrophy.

Table 1. Clinical and radiological details of the patients

Age	Mean (SD)	58 (11)
	< 50 years	44 (17%)
	≥ 50 years	219 (83%)
	Sex	M	126 (48%)
F		137 (52%)
Diagnosis		Osteoarthritis (OA)	163 (62%)
	Other	100 (38%)
	Femoral diameter	Median (range), mm	49 (41–59)
Whole-blood Co	Median (range), ppb	4.8 (0.5–192)
	< 5 ppb	134 (51%)
	≥ 5 ppb	129 (49%)
	Whole-blood Cr	Median (range), ppb	2.1 (0.4–115)
< 5 ppb		217 (83%)
≥ 5 ppb		46 (17%)
MRI follow-up		Mean (SD), years	4.0 (1.3)
	< 3.3 years	87 (33%)
	≥ 3.3 years	176 (67%)
	Pseudotumor (PT) category	No PT	194 (74%)
Cystic		35 (13%)
Mixed- or solid-type		34 (13%)

Table 2. Prevalence (%) of fatty atrophy in each of the gluteal muscles

		No. of hips	Prevalence
Gluteus minimus atrophy	None	157	60
	Mild	74	28
	Moderate	24	9.1
	Severe	8	3.0
	Gluteus medius atrophy	None	149	57
Mild		88	33
Moderate		20	7.6
Severe		6	2.2
Gluteus maximus atrophy		None	226	86
	Mild	31	12
	Moderate	6	2.2
	Severe	–	–

Figure 4. Distribution of grade of atrophy according to different pseudotumor (PT) findings.

Figure 5. Venn diagrams showing the overlapping of findings of interest in patients with moderate-to-severe g. minimus atrophy (left panel) and with moderate-to-severe g. medius atrophy (right panel). Patients with moderate-to-severe g. maximus atrophy are not shown because of the very low prevalence.