Custom-made 3D-printed cup-cage implants for complex acetabular revisions: evaluation of pre-planned versus achieved positioning and 1-year migration data in 10 patients

Figures & data

Table 1. Patient demographics. Values are number unless otherwise specified

Variable
No. of patients	10
Mean age (range)	64 (36–87)
Sex (M:F)	5:5
Mean BMI (range)	26 (19–34)
Paprosky III-A	10
Right:left	7:3
First-time vs. repeat revisions	3:7

Figure 1. Bone quality assessed by the software; red color reveals a poor and green shows excellent bone quality. (a): Assessment of bone quality as described by Gelaude. (b): Defect analysis quantifies in percentages and colors bone loss in the different regions of the acetabulum on which the Paprosky classification is based. Red color reveals an inferior and green shows excellent bone quality while yellow is acceptable. The output data consists of a ratio and a graph, which allow the direct comparison between specimens. The amount of original acetabular bone that is missing is defined as a ratio. The remaining bone stock in the radial direction is presented by the graph (c).

Figure 2. Custom made impalnt, planned screw positions and implant position based on CT scan. CT was taken prior to surgery. The radiograph shows the postoperative result. The position of the implant after surgery was compared with the preoperative planning using the pre- and postoperative CT scans.

Table 2. Median difference between planned versus postoperative plus migration values from direct postoperative to 1-year follow-up

Factor	Deviation from planned cup position			First year migration			Repeatability limit ^a
	median	IQR	range	median	IQR	range	Postop.	1 year
Inclination (°)	3.6	1.0 to 5.4	–11 to 11	0.04	–0.06 to 0.09	–0.22 to 0.98	0.48	0.51
Anteversion (°)	–2.8	–7.5 to 1.2	–12 to 5.7	–0.13	–0.23 to –0.06	–0.41 to 0.05	2.1	1.0
Rotation (°)	–1.2	–3.3 to 0.0	–7.4 to 14	0.05	–0.07 to 0.36	–0.46 to 1.4	0.97	0.99
Translation of COR (mm)
AP plane (anterior +)	–0.5	–2.9 to 0.7	–7.0 to 3.4	–0.08	–0.18 to –0.04	–0.48 to 0.43	0.28	0.25
ML plane (medial +)	–0.6	–1.8 to –0.1	–3.6 to 2.2	0.14	–0.08 to 0.22	–0.35 to 0.51	0.63	0.34
SI plane (superior +)	1.1	–1.6 to 2.8	–9.7 to 8.9	0.06	–0.02 to 0.35	–0.15 to 0.61	0.44	0.26

Values are presented as signed, thus indicating the direction of the migration except for rotation where signed values are positive for clockwise rotation after signed values for left hips are shifted.

^a Repeatability limit: the value less than or equal to which the absolute difference between two tests results obtained under repeatability conditions may be expected to have a probability of 95%.

IQR: interquartile range.

Table 3. The presented values are the average of the 2 repeated measurements (M1, M2) and show the difference between planned and postop position as well as the change in position postoperatively to 1 year follow-up. At the bottom rows, the median signed values show the direction of migration, whereas the unsigned median values show the amplitude of the migration

	Inclination (°)					Anteversion (°)
Case	Planned	Postop.	1 year	Δ planned to postop.	Δ postop. to 1 year	Planned	Postop.	1 year	Δ planned to postop.	Δ postop.to 1 year
1	40	43.66	43.67	3.66	0.02	20	21.39	21.29	1.39	–0.11
2	40	43.60	43.66	3.60	0.06	20	25.69	25.74	5.69	0.05
3	40	51.20	51.16	11.20	–0.04	20	12.34	11.99	–7.66	–0.35
4	40	45.50	45.76	5.50	0.25	20	20.61	20.56	0.61	–0.05
5	40	45.27	45.36	5.27	0.09	20	11.98	11.84	–8.03	–0.14
6	40	41.04	40.97	1.04	–0.06	20	16.89	16.82	–3.12	–0.07
7	40	39.76	40.74	–0.24	0.98	20	7.90	7.88	–12.10	–0.02
8	40	40.99	40.92	0.98	–0.07	20	17.48	17.07	–2.53	–0.41
9	40	47.32	47.10	7.32	–0.23	20	12.95	12.70	–7.05	–0.25
10	40	29.32	29.38	–10.69	0.07	20	22.68	22.52	2.68	–0.16
Signed median				3.63	0.04				–2.82	–0.12
Unsigned median				4.46	0.07				4.40	0.12

In the bottom rows, the median signed values show the direction of deviation/migration, whereas the unsigned median values show the amplitude of deviation/migration.

Δ: difference.