A feasibility study of computer-assisted bone graft implantation for tissue-engineered replacement of the human ankle joint

Figures & data

Figure 1. Preoperative planning of the talar defect and creation of a 3D graft model.

Figure 2. Tibial and talar grafts manufactured from bovine cancellous bone according to preoperative planning data.

Figure 3. Pair-point matching with anatomical landmarks in situ and on the CAS monitor (green and red dots mark deviation).

Figure 4. Computer-assisted debridement of the defect using a blade chisel.

Figure 5. Human cadaver ankle joint after implantation of the tibial and talar graft.

Figure 6. Postoperative CT scans (axial, coronar and sagittal) after graft implantation (pair-point matching with anatomical landmarks).

Table I.  Accuracy of graft implantation after registration by pair-point matching with anatomical landmarks.

	Axial		Coronar		Sagittal
Tibia 1	Step (mm)	Gap (mm)	Step (mm)	Gap (mm)	Step (mm)	Gap (mm)
Medial	–	0.0–1.0	–	0.0–1.1	–	–
Lateral	–	0.0–1.5	–	0.0	–	–
Posterior	–	0.0–1.0	–	–	–	0.0–2.3
Anterior	0.0	–	–	–	–	0.0
Cranial	–	–	–	1.1–1.9	–	0.0
Joint surface	–	–	0.0–1.6	–	0.0–2.3	–
	Axial		Coronar		Sagittal
Talus 1*	Step (mm)	Gap (mm)	Step (mm)	Gap (mm)	Step (mm)	Gap (mm)
Medial	–	0.0–0.7	–	0.0–0.8	–	–
Lateral	–	0.0	–	0.0	–	–
Posterior	–	4.7–7.3	–	–	–	5.6–8.0
Anterior	0.0–3.0	–	–	–	–	0.0–3.0
Caudal	–	–	–	0.0	–	0.0
Joint surface	–	–	0.0	–	0.0	–
	Axial		Coronar		Sagittal
Tibia 2*	Step (mm)	Gap (mm)	Step (mm)	Gap (mm)	Step (mm)	Gap (mm)
Medial	–	0.0–1.0	–	0.0–1.2	–	–
Lateral	–	0.0–1.1	–	0.0–0.5	–	–
Posterior	–	0.0–0.2	–	–	–	0.0
Anterior	0.0	–	–	–	–	0.0
Cranial	–	–	–	0.0	–	0.0
Joint surface	–	–	0.0–2.3	–	0.0–2.0	–
	Axial		Coronar		Sagittal
Talus 2	Step (mm)	Gap (mm)	Step (mm)	Gap (mm)	Step (mm)	Gap (mm)
Medial	–	0.0	–	0.0	–	–
Lateral	–	0.0	–	0.0	–	–
Posterior	–	0.8–1.7	–	–	–	0.0–1.5
Anterior	0.0	–	–	–	–	0.0
Caudal	–	–	–	0.0–4.0	–	0.0–3.9
Joint surface	–	–	0.0	–	0.0	–

(–: measurement not applicable; * failure of macroscopic implant fit - graft was held in place by Kirschner wire).

Table II.  Accuracy of graft implantation after registration by pair-point matching with artificial landmarks.

	Axial		Coronar		Sagittal
Tibia 3	Step (mm)	Gap (mm)	Step (mm)	Gap (mm)	Step (mm)	Gap (mm)
Medial	–	0.0	–	0.0	–	–
Lateral	–	0.0	–	0.0	–	–
Posterior	–	0.0	–	–	–	0.0
Anterior	0.0–4.5	–	–	–	–	0.0
Cranial	–	–	–	0.0	–	0.0
Joint surface	–	–	0.0–0.6	–	0.0–1.4	–
	Axial		Coronar		Sagittal
Talus 3	Step (mm)	Gap (mm)	Step (mm)	Gap (mm)	Step (mm)	Gap (mm)
Medial	–	0.5–1.0	–	0.3–1.3	–	–
Lateral	–	0.5–0.6	–	0.8–0.9	–	–
Posterior	–	0.0–1.8	–	–	–	0.0–0.6
Anterior	0.0	–	–	–	–	0.0
Caudal	–	–	–	0.0	–	0.0
Joint surface	–	–	0.0–1.5	–	0.0	–
	Axial		Coronar		Sagittal
Tibia 4	Step (mm)	Gap (mm)	Step (mm)	Gap (mm)	Step (mm)	Gap (mm)
Medial	–	0.7–2.0	–	0.0–1.4	–	–
Lateral	–	0.0–0.7	–	0.0–0.9	–	–
Posterior	–	1.0–3.8	–	–	–	0.7–3.9
Anterior	0.0	–	–	–	–(infrac.)	0.0
Cranial	–	–	–	1.2–2.0	–	1.0–2.6
Joint surface	–	–	0.0–0.1	–	0.0–0.1	–
	Axial		Coronar		Sagittal
Talus 4	Step (mm)	Gap (mm)	Step (mm)	Gap (mm)	Step (mm)	Gap (mm)
Medial	–	0.0	–	0.0	–	–
Lateral	–	0.0–1.0	–	0.0	–	–
Posterior	–	0.0–1.3	–	–	–	0.0–1.1
Anterior	0.0	–	–	–	–	0.0–0.1
Caudal	–	–	–	0.0–1.5	–	0.0–2.1
Joint surface	–	–	0.0–0.2	–	0.0–0.2	–

(–: measurement not applicable; infrac.: cortical infraction at the implantation site).

Figure 7. Two-dimensional surface scanning within a region of interest and derivation of the arthroplasty score.