All-polyethylene vs. metal-backed tibial component in total knee arthroplasty—a randomized RSA study comparing early fixation of horizontally and completely cemented tibial components: Part 2. Completely cemented components: MB not superior to AP components

Figures & data

Table 1.  Patient profile with APCC (all-polyethylene completely cemented components) vs. MBCC (metal-backed completely cemented components) after randomization. MBCC/RSA denotes patient profile in group included in RSA after exclusions, see Table 2

	APCC	MBCC	MBCC/RSA
No. of knees	20	20	16
Excluded from RSA	1	4	–
Women; men	16; 4	18; 2	15; 1
Age, median years	73	70	69
range	55–78	51–82	52–82
Weight, median kg	79	78	77
range	58–92	55–110	56–110
Deformity > 10°	1	0	0

Table 2.  Patients in the MBCC group who were excluded from RSA. Patients are presented with their case letters in the series

Reason for exclusion	MBCC (n = 20)
	Postop	3 m	12 m	24 m
<3 visible markers	1	2	1	3
cases	a	a,g	a	a,c,g
Missing examination	1	2	1	3
cases	b	b,d	b	b,d,h
Condition value too high	1	1	1	1
cases	e	e	e	e
ME above accepted level	1	1	1	1
cases	f	f	f	f
Remaining for examination	16	14	16	12

Excluded cases (n = 4): a,b,e,f

MBCC/RSA study group: n = 20 – 4 = 16

Figure 1. All-polyethylene (left) and metal-backed (right) tibial components of the AGC prosthesis. Both have non-modular, identical articulating surface and similar geometry.

Figure 2. Standard anterior postoperative radiographs of the a) all-polyethylene completely, cemented (APCC), and b) metal-backed, completely cemented (MBCC) tibial components.

Table 3.  HSS score (maximum 100 points). Values are median (range)

Group	n	HSS preoperatively	HSS 2 years postoperatively
APCC	19	59(37–83)	90 (70–100)
MBCC	20	62 (38–79)	94 (75–99)
MBCC/RSA	16	64 (38–75)	93 (75–99)

For abbreviations, see Table 1.

Table 4.  HKA (in degrees) for the separate groups. The figures denote the number of individuals within each HKA intervel

HKA °	180 ± 2	180 ± 4	180 ± 6	180 ± >6
APCC	9	4	5	1 (188)
MBCC	14	4	2	0
MBCC/RSA	11	4	1	0

For abbreviations, see Table 1.

Table 5.  Absolute rotations degrees and translations mm. median with range in parenthesis

	3 months		12 months		24 months
	APCC	MBCC/RSA	APCC	MBCC/RSA	APCC	MBCC/RSA
Anterior-posterior tilt	0.22	0.17	0.42	0.27	0.33	0.28
range	0.05–0.8	0.03–0.65	0.01–1.24	0.02–0.79	0.03–1.13	0.01–1.54
Inward-outward rotation	0.09	0.14	0.12	0.16	0.16	0.46
range	0.01–2.8	0.03–1.35	0.01–2.89	0.03–1.25	0.0–3.0	0.04–0.97
Varus-valgus tilt	0.12	0.12	0.24	0.24	0.26	0.26
range	0.02–1.02	0.01–0.55	0.01–0.71	0.07–0.65	0.01–1.25	0.06–1.06
Maximum subsidence^a	–0.09	0.01	–0.16	–0.06	–0.21	–0.05
range	–0.86–0.08	–0.4–0.56	–0.78–0.11	–0.57–0.36	–0.72–0.07	–0.40–0.45
Maximum lift-off^b	0.06	0.21	0.09	0.2	0.1	0.24
range	–0.10–0.53	–0.06–0.56	–0.14–0.68	–0.09–0.62	–0.08–0.79	–0.02–1.12

^aNegative values denote distal axial migration.

^bRange of maximum lift–off always denotes positive maximal lift–off.