Similar effect of stem geometry on radiological changes with 2 types of cemented straight stem

Figures & data

Figure 1. The Virtec (VSS) straight stem and the Müller (MSS) straight stem (lateral version).

Table 1. Demographics

	Müller straight stem (MSS)	Virtec straight stem (VSS)
Number of hips	356	355
Sex (male/female)	202/154	217/138
Mean age at surgery (SD)	69 (10)	69 (11)

Table 2. Diagnosis at operation

	Müller straight stem (MSS) (n = 356 hips)	Virtec straight stem (VSS) (n = 355 hips)
Osteoarthritis	269	257
Rheumatoid arthritis	5	4
Femoral neck fracture	17	19
Dysplasia	44	49
Other	21	26

Table 3. Acetabular components

	Müller straight stem (MSS) (n = 356 hips)	Virtec straight stem (VSS) (n = 355 hips)
SL cup	271	272
SL cup with Metasul PE	26	33
ARR ring (Müller)	51	45
AP cage (Burch-Schneider)	2	1
Polyethylene cemented	6	4

Figure 2. Survival status at latest follow-up with the 399 included radiographic examinations for osteolysis analysis and the excluded radiographic examinations due to missing data or follow-up time that was too short.

Table 8. Risk of revision and osteolysis in THA patients with the Virtec straight stem (VSS) or the Müller straight stem (MSS)

Risk analysis	MSS		VSS		HR (95% CI)	p-value
	events	%	events	%
	Any revision	(n = 356)		(n = 355)
any exchange	32	9.0	22	6.2	0.7 (0.4–1.2)	0.2
Stem revision
aseptic	15	4.2	9	2.5	0.6 (0.3–1.3)	0.2
any cause	24	6.7	16	4.5	0.7 (0.3–1.2)	0.2
worst case	33	9.3	26	7.3	0.8 (0.5–1.3)	0.3
Osteolysis	(n = 196)		(n = 203)
any	40	20	28	14	0.7 (0.4–1.1)	0.1
G1	10	5	4	2	0.4 (0.1–1.3)	0.1
G2	23	12	12	6	0.5 (0.3–1.0)	0.06
G3	15	8	7	3	0.5 (0.2–1.1)	0.09
G4	7	4	4	2	0.6 (0.2–2.0)	0.4
G5	18	9	10	5	0.5 (0.3–1.2)	0.1
G6	26	13	15	7	0.6 (0.3–1.1)	0.07
G7	23	12	11	5	0.5 (0.2–1.0)	0.04

Table 4. Revisions (74 hips)

Revised components	Müller straight stem (MSS) (n = 44 hips)			Virtec straight stem (VSS) (n = 30 hips)
	n	%	Time to revision	n	%	Time to revision
	Both components	13	3.7	4.4 (0.8–16.3)	9	2.5	4.2 (1.7–11.1)
Stem	11	3.1	7.1 (1.9–14.2)	7	2.0	6.0 (1.0–12.0)
Cup	7	2.0	3.5 (1.5–7.8)	3	0.8	8.0 (3.7–10.6)
Only inlay	1	0.3	3.3	3	0.8	0.5 (0.3–0.7)
Reoperation^a	12	3.4	3.2 (0.3–11.4)	8	2.3	4.6 (0.1–13.3)

a without component exchange

Table 5. Stem revisions for different reasons (40 hips)

Revised components	Müller straight stem (MSS) (n = 24 hips)			Virtec straight stem (VSS) (n = 16 hips)
	n	%	Time to revision	n	%	Time to revision
	Aseptic loosening	15	4.1	7.2 (1.3–16.3)	9	2.5	6.3 (1.0–12.0)
stem	11	2.2	6.8 (4.2–12.1)	6	1.4	6.5 (3.8–12.0)
both components	4	0.6	2.6 (1.3–4.0)	3	0.6	2.9 (2.8–3.0)
Infection	8	2.2	3.7 (0.8–9.9)	5	1.4	3.7 (1.7–9.4)
Periprosthetic fracture	1	0.3	2.4	1	0.3	8.1
Malposition	0	–	–	1	0.3	2.5

Figure 3. Kaplan-Meier survival curve with component revision for any reason as endpoint.

Figure 4. Kaplan-Meier survival curve with revision for aseptic loosening of the stem as endpoint.