- Email: [email protected]
A bone cutting device for rotational acetabular osteotomy (RAO) with a curved oscillating saw
International Congress Series 1268 (2004) 632 – 637
www.ics-elsevier.com
A bone cutting device for rotational acetabular osteotomy (RAO) with a curved oscillating saw I. Sakuma a,*, K. Mukaiyama a, I. Iordachita a, K. Matsumiya b, E. Kobayashi a, H. Yano c a
Institute of Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, 7-3-1, Hongo, Bunkyo, Tokyo 113-8656, Japan b Department of Precision Engineering, Graduate School of Engineering, The University of Tokyo, Japan c Fuji Hot spring Hospital, Japan
Abstract. The purpose of the present study is to develop a bone cutting device that can generate a spherical bone cutting surface for rotational acetabular osteotomy (RAO) with minimal invasiveness under image-guided operation. We developed a prototype of a device, and conducted its initial evaluation. It uses a curved small oscillating saw to cut acetabular with spherical surface. The width of the saw as wide as 2.4 mm to maintain mechanical strength. The length of the saw was 31.1 mm. Its oscillating stroke was 7 mm. This oscillating saw was connected with a reciprocating attachment with steel ribbon like structure. This connecting steel ribbon was supported by curved slit to keep its radius of 50 mm. We evaluated the device by cutting a model bone made of solid rigid polyurethane foam with density of 0.20 g/cm3. We could generate a spherical surface by properly positioning and manipulating the device with oscillation of the saw set at 2500 – 3000 cycles per minutes (42 – 50 Hz). The developed device was also evaluated by cutting the porcine pelvis. The length and depth of the cut portion was 20 and 5 mm. We could successfully cut the porcine pelvis including cartilage, cortical bone, and cancellous tissue. D 2004 Published by Elsevier B.V. Keywords: Rotational acetabular osteotomy; Curved saw oscillating saw; Image-guided surgery; Minimally invasive surgery
1. Introduction Rotational acetabular osteotomy (RAO) is surgical procedure to treat osteoarthritis. Osteotomy of a patient’s acetabulum and adjustment of its position are conducted to reduce the excessive stress in the hip joint [1 –3]. Spherical cutting surface is required in RAO since resected acetabulum must be rotated for position adjustment while keeping the surrounding cartilage as shown in Fig. 1 The surgeon must conduct osteotomy in narrow space to preserve muscle and nerve fiber surrounding the hip joint. * Corresponding author. Tel.: +81-3-5841-7481; fax: +81-3-5841-6481. E-mail address: [email protected] (I. Sakuma). 0531-5131/ D 2004 Published by Elsevier B.V. doi:10.1016/j.ics.2004.03.293
I. Sakuma et al. / International Congress Series 1268 (2004) 632–637
633
Fig. 1. Rotational acetabular osteotomy (RAO).
Surgeons usually use a curved chisel cut bone. However, there are following device related problems:
Impulsive force is applied at the end of the chisel to form the curved surface at the other end of the chisel. However, the transmitted force is not always appropriate to generate the required spherical surface of the bone. Large incision is required to make operation field. Impulsive force applied to the chisel makes its manual positioning inaccurate. Bone cutting must be conducted at the end of the chisel that cannot be seen from the surgeon’s eyes. It is important not to injure important anatomical structure such as nerve fibers and arteries near the operation field of rotational acetabular osteotomy. Thus the image-guided operation is effective to conduct RAO. The purpose of the present study is to develop a bone cutting device that can generate the spherical bone cutting surface for RAO with minimal invasiveness under image-guided operation. In this report, we will present the design of a prototype of a device and its initial evaluation results. We developed a surgical device for cutting bone with spherical surface using a small oscillating saw. Phantom study and animal experiment were performed to evaluate the device. 2. Design of the bone cutting device for RAO 2.1. Design of minimally invasive procedure for RAO In order to conduct minimally invasive RAO, we designed the following surgical procedure: (1) A curved surgical bone saw is inserted through the insertion point that is set near the iliac spine. (2) Muscles are separated from pelvis to create operation field between muscle and pelvis. The device is inserted into the space between the retracted muscle and pelvis. (3) A curved bone saw with oscillating bone saw attached at its end is inserted. The shape of the tool is designed as circular arc with the same radius with the required radius of spherical bone cutting surface. The lateral side of the curved surgical tool functions as a bone saw.
634
I. Sakuma et al. / International Congress Series 1268 (2004) 632–637
Fig. 2. Minimally invasive procedure for RAO with a curved saw: (A) approach from anterior side; (B) approach from dorsal side.
(4) The three-dimensional motion of the curved saw is controlled by an electromechanical (robotic) system to generate the spherical bone cutting surface of acetabulum. Fig. 2 shows the position and approach of curved saw to pelvis. The left panel shows the approach from anterior side, and the right panel shows the approach from dorsal side. 2.2. Design of curved saw [4 – 6] To realize the above-mentioned surgical procedure, we designed a curved surgical bone cutting device with an oscillating saw. Although the removed bone should be as small as possible, we designed the width of the saw as wide as 2.4 mm while maintaining its mechanical strength. The length of the saw was 31.1 mm. Its oscillating stroke was 7 mm. Fig. 3A shows structure of the saw at the tip of the curved holder. Fig. 3B shows its picture of the tip of the curved saw. Fig. 4A shows the entire assembly of the curved saw module. Pitch, height, and rake angle of saw blade was 0.8 mm, 1.5 mm, and 10j, respectively. This oscillating saw was connected with a reciprocating attachment (L140 A, Zimmer) with steel ribbon like structure. This connecting steel ribbon was supported by curved slit to keep its radius of 50 mm. Height of the supporting slit structure was 18 mm. The reciprocating attachment transforms the rotational motion of an AC
Fig. 3. Structure of curved saw. (A) Structure of the curved saw’s tip. (B) Tip of the curved saw.
I. Sakuma et al. / International Congress Series 1268 (2004) 632–637
635
Fig. 4. Curved saw assembly and curved bone cutting saw attached to the motor drive system. (A) Curved saw assembly. (B) Overview of the device.
speed controlled motor to transversal reciprocating motion driving the oscillating saw. The rotation of the motor is transmitted with a flexible shaft to separate sterilizable parts and the unsterilizable AC motor. Fig. 4B shows an overview of the device. 3. Results 3.1. Evaluation using bone models The developed device was evaluated by cutting bone model. As a bone model, we used solid rigid polyurethane foam (Pacific Research Laboratories, Washington, USA; density: 0.20 g/cm3). The developed surgical bone cutting device was positioned manually. The oscillation of the saw was set at 2500– 3000 cycles per minutes (42 – 50 Hz). The bone model was cut with good efficiency. The cut specimen is shown in Fig. 5 The width of the resected portion was 3.0 –3.6 mm though the width of the saw blade was 2.4 mm. Vibration of the saw and three-dimensional motion of the saw was considered as a cause of increased width of resected portion. We could generate the spherical surface by properly positioning and manipulating the device. 3.2. Evaluation using porcine pelvis The developed device was evaluated by cutting the porcine pelvis. The oscillation of the saw was set at 2500 –3000 cycles per minutes (42 – 50 Hz). The animal’s muscles were
Fig. 5. Cut specimen of polyurethane foam model bone.
636
I. Sakuma et al. / International Congress Series 1268 (2004) 632–637
Fig. 6. Photograph of cut porcine pelvis and its location.
retracted under general anesthesia and after application of muscle relaxant. A six-axis force-torque sensor was attached at the holding portion of the device to measure the required force to position the device during the bone cutting process. The device was inserted into the space between the muscle and the pelvis. The length and depth of the cut portion was 20 mm and 5 mm. We could successfully cut the porcine pelvis including cartilage, cortical bone, and cancellous tissue. The required force to hold the device was less than 4.5 kgf (44.1 N). This data will be utilized in designing the robotic manipulator to position the device under image-guided procedure (Fig. 6). 4. Conclusion We have proposed new minimally invasive image-guided surgical procedures for rotational acetabular osteotomy (RAO). The curved oscillating saw is inserted through an inlet port and is operated in the space between retracted muscle and pelvis. We designed a prototype of the curved oscillating bone cutting device for RAO that can generate a spherical cut surface of the bone. The feasibility of the device was confirmed both in bone model cutting experiments and an animal experiment. It could cut the bone efficiently and could generate spherical surfaces. We will apply the device to a robotic positioning system under image-guided environment to develop a minimally invasive and safer surgical system for rotational acetabular osteotomy (RAO). Acknowledgements This research is partly supported by Grant in Aid from The Organization for Pharmaceutical Safety and Research (OPDR/kiko) MF-15. References [1] M. Nozawa, et al., Rotational acetabular osteotomy foracetabular dysplasia, J. Bone Jt. Surg., Br. 84-B (2002) 59 – 65. [2] H. Kanai, et al., Rotational acetabular osteotomy for the treatment of dysplastic hips with end-stage osteoarthrosis—a biological alternative to total hip arthroplasty? Arch. Orthop. Trauma Surg. 119 (2002) 376 – 379.
I. Sakuma et al. / International Congress Series 1268 (2004) 632–637
637
[3] Y. Yasunaga, et al., Rotational acetabular osteotomy for advanced osteoarthrosis secondary to dysplasia of the hip. Results at 6 – 11 years postoperatively, Arch. Orthop. Trauma Surg. 119 (1999) 253 – 257. [4] T.W. Ark, et al., A technique for quantifying the performance of oscillating bone saw blades, J. Long-Term Eff. Med. Implants 7 (1977) 255 – 270. [5] T.W. Ark, et al., Durability of oscillating bone saw blades, J. Long-Term Eff. Med. Implants 7 (1977) 271 – 278. [6] T.W. Ark, et al., Innovations in oscillating bone saw blades, J. Long-Term Eff. Med. Implants 7 (1977) 279 – 286.
www.ics-elsevier.com
A bone cutting device for rotational acetabular osteotomy (RAO) with a curved oscillating saw I. Sakuma a,*, K. Mukaiyama a, I. Iordachita a, K. Matsumiya b, E. Kobayashi a, H. Yano c a
Institute of Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, 7-3-1, Hongo, Bunkyo, Tokyo 113-8656, Japan b Department of Precision Engineering, Graduate School of Engineering, The University of Tokyo, Japan c Fuji Hot spring Hospital, Japan
Abstract. The purpose of the present study is to develop a bone cutting device that can generate a spherical bone cutting surface for rotational acetabular osteotomy (RAO) with minimal invasiveness under image-guided operation. We developed a prototype of a device, and conducted its initial evaluation. It uses a curved small oscillating saw to cut acetabular with spherical surface. The width of the saw as wide as 2.4 mm to maintain mechanical strength. The length of the saw was 31.1 mm. Its oscillating stroke was 7 mm. This oscillating saw was connected with a reciprocating attachment with steel ribbon like structure. This connecting steel ribbon was supported by curved slit to keep its radius of 50 mm. We evaluated the device by cutting a model bone made of solid rigid polyurethane foam with density of 0.20 g/cm3. We could generate a spherical surface by properly positioning and manipulating the device with oscillation of the saw set at 2500 – 3000 cycles per minutes (42 – 50 Hz). The developed device was also evaluated by cutting the porcine pelvis. The length and depth of the cut portion was 20 and 5 mm. We could successfully cut the porcine pelvis including cartilage, cortical bone, and cancellous tissue. D 2004 Published by Elsevier B.V. Keywords: Rotational acetabular osteotomy; Curved saw oscillating saw; Image-guided surgery; Minimally invasive surgery
1. Introduction Rotational acetabular osteotomy (RAO) is surgical procedure to treat osteoarthritis. Osteotomy of a patient’s acetabulum and adjustment of its position are conducted to reduce the excessive stress in the hip joint [1 –3]. Spherical cutting surface is required in RAO since resected acetabulum must be rotated for position adjustment while keeping the surrounding cartilage as shown in Fig. 1 The surgeon must conduct osteotomy in narrow space to preserve muscle and nerve fiber surrounding the hip joint. * Corresponding author. Tel.: +81-3-5841-7481; fax: +81-3-5841-6481. E-mail address: [email protected] (I. Sakuma). 0531-5131/ D 2004 Published by Elsevier B.V. doi:10.1016/j.ics.2004.03.293
I. Sakuma et al. / International Congress Series 1268 (2004) 632–637
633
Fig. 1. Rotational acetabular osteotomy (RAO).
Surgeons usually use a curved chisel cut bone. However, there are following device related problems:
Impulsive force is applied at the end of the chisel to form the curved surface at the other end of the chisel. However, the transmitted force is not always appropriate to generate the required spherical surface of the bone. Large incision is required to make operation field. Impulsive force applied to the chisel makes its manual positioning inaccurate. Bone cutting must be conducted at the end of the chisel that cannot be seen from the surgeon’s eyes. It is important not to injure important anatomical structure such as nerve fibers and arteries near the operation field of rotational acetabular osteotomy. Thus the image-guided operation is effective to conduct RAO. The purpose of the present study is to develop a bone cutting device that can generate the spherical bone cutting surface for RAO with minimal invasiveness under image-guided operation. In this report, we will present the design of a prototype of a device and its initial evaluation results. We developed a surgical device for cutting bone with spherical surface using a small oscillating saw. Phantom study and animal experiment were performed to evaluate the device. 2. Design of the bone cutting device for RAO 2.1. Design of minimally invasive procedure for RAO In order to conduct minimally invasive RAO, we designed the following surgical procedure: (1) A curved surgical bone saw is inserted through the insertion point that is set near the iliac spine. (2) Muscles are separated from pelvis to create operation field between muscle and pelvis. The device is inserted into the space between the retracted muscle and pelvis. (3) A curved bone saw with oscillating bone saw attached at its end is inserted. The shape of the tool is designed as circular arc with the same radius with the required radius of spherical bone cutting surface. The lateral side of the curved surgical tool functions as a bone saw.
634
I. Sakuma et al. / International Congress Series 1268 (2004) 632–637
Fig. 2. Minimally invasive procedure for RAO with a curved saw: (A) approach from anterior side; (B) approach from dorsal side.
(4) The three-dimensional motion of the curved saw is controlled by an electromechanical (robotic) system to generate the spherical bone cutting surface of acetabulum. Fig. 2 shows the position and approach of curved saw to pelvis. The left panel shows the approach from anterior side, and the right panel shows the approach from dorsal side. 2.2. Design of curved saw [4 – 6] To realize the above-mentioned surgical procedure, we designed a curved surgical bone cutting device with an oscillating saw. Although the removed bone should be as small as possible, we designed the width of the saw as wide as 2.4 mm while maintaining its mechanical strength. The length of the saw was 31.1 mm. Its oscillating stroke was 7 mm. Fig. 3A shows structure of the saw at the tip of the curved holder. Fig. 3B shows its picture of the tip of the curved saw. Fig. 4A shows the entire assembly of the curved saw module. Pitch, height, and rake angle of saw blade was 0.8 mm, 1.5 mm, and 10j, respectively. This oscillating saw was connected with a reciprocating attachment (L140 A, Zimmer) with steel ribbon like structure. This connecting steel ribbon was supported by curved slit to keep its radius of 50 mm. Height of the supporting slit structure was 18 mm. The reciprocating attachment transforms the rotational motion of an AC
Fig. 3. Structure of curved saw. (A) Structure of the curved saw’s tip. (B) Tip of the curved saw.
I. Sakuma et al. / International Congress Series 1268 (2004) 632–637
635
Fig. 4. Curved saw assembly and curved bone cutting saw attached to the motor drive system. (A) Curved saw assembly. (B) Overview of the device.
speed controlled motor to transversal reciprocating motion driving the oscillating saw. The rotation of the motor is transmitted with a flexible shaft to separate sterilizable parts and the unsterilizable AC motor. Fig. 4B shows an overview of the device. 3. Results 3.1. Evaluation using bone models The developed device was evaluated by cutting bone model. As a bone model, we used solid rigid polyurethane foam (Pacific Research Laboratories, Washington, USA; density: 0.20 g/cm3). The developed surgical bone cutting device was positioned manually. The oscillation of the saw was set at 2500– 3000 cycles per minutes (42 – 50 Hz). The bone model was cut with good efficiency. The cut specimen is shown in Fig. 5 The width of the resected portion was 3.0 –3.6 mm though the width of the saw blade was 2.4 mm. Vibration of the saw and three-dimensional motion of the saw was considered as a cause of increased width of resected portion. We could generate the spherical surface by properly positioning and manipulating the device. 3.2. Evaluation using porcine pelvis The developed device was evaluated by cutting the porcine pelvis. The oscillation of the saw was set at 2500 –3000 cycles per minutes (42 – 50 Hz). The animal’s muscles were
Fig. 5. Cut specimen of polyurethane foam model bone.
636
I. Sakuma et al. / International Congress Series 1268 (2004) 632–637
Fig. 6. Photograph of cut porcine pelvis and its location.
retracted under general anesthesia and after application of muscle relaxant. A six-axis force-torque sensor was attached at the holding portion of the device to measure the required force to position the device during the bone cutting process. The device was inserted into the space between the muscle and the pelvis. The length and depth of the cut portion was 20 mm and 5 mm. We could successfully cut the porcine pelvis including cartilage, cortical bone, and cancellous tissue. The required force to hold the device was less than 4.5 kgf (44.1 N). This data will be utilized in designing the robotic manipulator to position the device under image-guided procedure (Fig. 6). 4. Conclusion We have proposed new minimally invasive image-guided surgical procedures for rotational acetabular osteotomy (RAO). The curved oscillating saw is inserted through an inlet port and is operated in the space between retracted muscle and pelvis. We designed a prototype of the curved oscillating bone cutting device for RAO that can generate a spherical cut surface of the bone. The feasibility of the device was confirmed both in bone model cutting experiments and an animal experiment. It could cut the bone efficiently and could generate spherical surfaces. We will apply the device to a robotic positioning system under image-guided environment to develop a minimally invasive and safer surgical system for rotational acetabular osteotomy (RAO). Acknowledgements This research is partly supported by Grant in Aid from The Organization for Pharmaceutical Safety and Research (OPDR/kiko) MF-15. References [1] M. Nozawa, et al., Rotational acetabular osteotomy foracetabular dysplasia, J. Bone Jt. Surg., Br. 84-B (2002) 59 – 65. [2] H. Kanai, et al., Rotational acetabular osteotomy for the treatment of dysplastic hips with end-stage osteoarthrosis—a biological alternative to total hip arthroplasty? Arch. Orthop. Trauma Surg. 119 (2002) 376 – 379.
I. Sakuma et al. / International Congress Series 1268 (2004) 632–637
637
[3] Y. Yasunaga, et al., Rotational acetabular osteotomy for advanced osteoarthrosis secondary to dysplasia of the hip. Results at 6 – 11 years postoperatively, Arch. Orthop. Trauma Surg. 119 (1999) 253 – 257. [4] T.W. Ark, et al., A technique for quantifying the performance of oscillating bone saw blades, J. Long-Term Eff. Med. Implants 7 (1977) 255 – 270. [5] T.W. Ark, et al., Durability of oscillating bone saw blades, J. Long-Term Eff. Med. Implants 7 (1977) 271 – 278. [6] T.W. Ark, et al., Innovations in oscillating bone saw blades, J. Long-Term Eff. Med. Implants 7 (1977) 279 – 286.