Excessive distal migration of fiber-mesh coated femoral stems

Figures & data

Figure 1. Flow chart showing the recruitment and randomization strategy.

Figure 2. The distally tapered, extensively coated stem (VerSys Fiber Metal Taper) (left) and the straight, proximally coated stem (VerSys Fiber Metal MidCoat) (right).

Figure 3. The coordinate axes of stem rotation and translation.

Table 1. Double examination of 10 patients. The precision is presented as the mean absolute value + 2 SD (95% CI for significant movement)

	Stem migration
Translation
Medial-lateral (x)	0.12 mm
Proximal-distal (y)	0.10 mm
Anterior-posterior (z)	0.19 mm
Rotation
Anterior(+) / posterior (-) tilt	0.41°
Ante(-) / retroversion (+)	0.98°
Valgus (+) / varus (-)	0.62°

Table 2. Stem translation and rotation at 3, 12, and 24 months. Absolute values are shown as mean with 95% confidence interval

	3 months (n=49)		12 months (n=46)		24 months (n = 41)
	Mean	95% CI	Mean	95% CI	Mean	95% CI
Translation (mm)
Medial(+) / lateral (-)
FMT	0.13	-0.21 to 0.47	0.07	-0.31 to 0.44	0.12	-0.10 to 0.35
FMM	-0.04	-0.31 to 0.22	-0.26	-0.60 to 0.08	-0.08	-0.75 to 0.58
Proximal(+) / distal (-)
FMT	-2.41	-3.66 to -1.18	-2.32	-2.98 to -0.64	-2.67	-3,93 to -1.42
FMM	-1.95	-2.93 to -0.31	-1.82	-2.88 to -0.77	-1.80	-2.45 to -1.15
Anterior(+)/ posterior (-)
FMT	-0.51	-0.89 to -0.14	-0.13	-0.55 to 0.30	0.07	-0.52 to 0.67
FMM	-0.20	-0.49 to 0.10	-0.02	-0.43 to 0.39	-0.31	-1.15 to 0.52
Total migration
FMT	2.75	1.42 to 4.09	2.78	-0.59 to 6.14	3.28	0.11 to 6.67
FMM	2.20	1.24 to 3.17	2.80	1.67 to 3.93	2.73	1.48 to 3.98
Rotation (°)
Anterior(+) / posterior (-) tilt
FMT	-0.35	-0.72 to 0.02	-0.54	-1.06 to -0.02	-0.94	-1.44 to -0.44
FMM	0.23	-0.60 to 1.05	-0.49	-1.41 to 0.44	-0.62	-1.90 to -1.67
Ante(-) / retroversion (+)
FMT	-1.63	-3.89 to 0.62	0.34	-1.98 to 2.65	1.86	0.17 to 3.55
FMM	-0.56	-1.55 to 0.43	0.43	-1.45 to 2.30	1.29	-0.85 to 3.44
Valgus (+) / varus (-)
FMT	0.16	0.01 to 0.32	-0.07	-0.26 to 0.11	-0.09	-0.28 to 0.10
FMM	-0.07	-0.44 to 0.29	0.43	-0.60 to 1.45	-0.19	-0.68 to 0.30

Figure 4. Mean distal migration (in mm) of the FMM and FMT femoral components. Migration values are mean with 95% confidence interval.

Figure 5. Distal migration of an FMT stem. A. Immediately postoperatively. B. At 3 months. C. At 12 months. D. At 24 months.

Table 3. Migration and revision in different RSA studies

Stem type (references)	No. of hips	Observation time (years)	Distal migration (mm)	Revised hips during the observation time	Additional follow-up: Hips revised due to aseptic loosening
Cemented Elite Plus (Derbyshire and Porter 2007, Hauptfleisch et al. 2006)	25	3	0.3 (0.02–1.28) ^a	4%	9 years, 10%
Cemented C-stem (Sundberg et al. 2005)	33	2	1.35 (0.62) ^b	Not reported
Cemented Exeter (Alfaro-Adrian et al. 2001)	32	1	0.86 (0.11) ^c	Not reported
Cemented Lubinus SP I (Karrholm et al. 1994)	84	2	1.3–15.9 ^d	0%	7 years, 50% (subgroup revised)
Uncemented Epoch & Anatomic (Karrholm et al. 2002)	68	2	E: 0.05 (–0.16 to 1.04) ^a A: –0.02 (–0.31 to 0.31) ^a	0%
Uncemented Ribbed stem (Karrholm and Snorrason 1993)	18	2	1.06 (0.4–2.1) ^a	6% (Indication: pain)
Uncemented VerSys (Current study)	41	2	FMT: 2.67 (3.13) ^b FMM: 1.80 (1.52) ^b	4%

^a Mean and range

^b Mean and SD

^c Mean and SE

^d Range

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