新型可转向医疗设备：微侵入手术的机械关节设计

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"Steerable medical devices是指一类具有可操控转向机制的医疗工具，尤其适用于微创手术。这种设备的转向机制由一个交叉配置的柔顺滚动接触元素构成，该元素形成器械的关节，并通过配置成平行四边形机构的柔性转向梁来旋转。这样的设计允许在保持高负载传输的同时，实现微型侵入性器械的精细转向。在《SteerableMechanicalJointforHighLoadTransmissioninMinimallyInvasiveInstruments》这篇论文中，作者Tin Yan Nai、Just L. Herder和Gabrielle J.M. Tuijthof等人详细探讨了这一创新技术。他们隶属于荷兰代尔夫特理工大学生物力学工程系，以及阿姆斯特丹大学医学中心的骨科研究部门。这些研究人员致力于解决微创手术中直型手术器械操纵能力有限的问题。在狭小解剖区域，如膝关节等，由于手术通道狭窄且可用入口有限，传统的直型手术器械往往难以达到病灶部位。因此，他们提出了一种新的侧向可转向的器械关节设计，该设计能够在小直径内实现。这种新型关节旨在提供更大的操作灵活性，同时保持足够的强度来传递高负载，这对于在复杂和受限的体内环境中进行精确手术至关重要。论文中对这种新型侧向可转向关节进行了详细介绍和评估。其工作原理是利用柔性材料制成的转向梁，通过平行四边形机构的变形来驱动交叉配置的柔顺滚动接触元素旋转，从而改变器械的方向。这种方式可以确保在施加力时器械的稳定性和控制性，同时减少对周围组织的损害。此外，这种设计考虑了微创手术的特殊需求，如小尺寸、高精度和低侵入性。通过这种方式，医生能够更有效地导航器械到达手术部位，提高手术的准确性和成功率，同时减少患者恢复期的不适和并发症的风险。 Steerable medical devices的核心在于其创新的转向机制，它结合了机械工程和生物力学的原理，旨在克服微创手术中的操作挑战。通过优化设计，这些设备有望在未来进一步提升医疗手术的安全性和效率。"

Steerable Mechanical Joint for High

Load Transmission in Minimally

Invasive Instruments

Tin Yan Nai

e-mail: timnai@gmail.com

Just L. Herder

e-mail: j.l.herder@tudelft.nl

Department of Biomechanical Engineering,

Faculty of Mechanical, Maritime and Materials Engineering,

Delft University of Technology,

Delft, The Netherlands

Gabrie¨lle J. M. Tuijthof

Department of Biomechanical Engineering,

Faculty of Mechanical, Maritime and Materials Engineering,

Delft University of Technology,

Delft, The Netherlands;

Orthopedic Research Center Amsterdam,

Department of Orthopedic Surgery,

Academic Medical Centre,

Amsterdam, The Netherlands

e-mail: g.j.m.tuijthof@tudelft.nl; g.j.tuijthof@amc.uva.nl

As minimally invasive operations are performed through small por-

tals, the limited manipulation capability of straight surgical instru-

ments is an issue. Access to the pathology site can be challenging,

especially in conﬁned anatomic areas with few available portals,

such as the knee joint. The goal in this paper is to present and eval-

uate a new sideways-steerable instrument joint that ﬁts within a

small diameter and enables transmission of relative high forces

(e.g., for cutting of tough tissue). Meniscectomy was selected as a

target procedure for which quantitative design criteria were formu-

lated. The steering mechanism consists of a crossed conﬁguration

of a compliant rolling-contact element that forms the instrument

joint, which is rotated by ﬂexural steering beams that are conﬁg-

ured in a parallelogram mechanism. The actuation of cutting is

performed by steel wire that runs through the center of rotation of

the instrument joint. A prototype of the concept was fabricated and

evaluated technically. The prototype demonstrated a range of

motion between 22



and 25



with a steering stiffness of 17.6

Nmm/rad (min 16.9 – max 18.2 Nmm/rad). Mechanical tests con-

ﬁrmed that the prototype can transmit an axial load of 200 N on

the tip with a maximum parasitic deﬂection of 4.4



. A new sideways

steerable mechanical instrument joint was designed to improve

sideways range of motion while enabling the cutting of strong tis-

sues in a minimally invasive procedure. Proof of principle was

achieved for the main criteria, which encourages the future devel-

opment of a complete instrument. [DOI: 10.1115/1.4004649]

Keywords: compliant mechanism, meniscectomy, steerable

mechanical joint, rolling contact

1 Introduction

As minimally invasive operations are performed through small

portals and the manipulation capability of straight surgical instru-

ments is limited, access to the pathology site can be challenging

[1]. This is especially true for body cavities with conﬁned spaces

and few available access portals [2]. An example is the human knee

joint, which is surrounded by bones, ligaments, and neurovascular

structures [3].

To increase the manoeuvrability of minimally invasive surgical

instruments, different concepts of steerable mechanisms have been

presented to enhance instrument manipulation capability (e.g., Refs.

[1,4–8]). Often the focus is on achieving maximum range of motion,

multiple degrees of freedom, or miniaturisation, which is well suited

for the intended application. However, it is doubtful whether apply-

ing these concepts is feasible for manipulating or cutting of tough

tissue, such as a torn meniscus located in the knee joint [9].

Therefore, the goal is to present and to evaluate a sideways

steerable mechanical joint that ﬁts within a small diameter and is

able to withstand relatively high force transmission.

2 Design Requirements

Formulation of quantitative design requirements was performed

by choosing one minimally invasive procedure for which applica-

tion would be beneﬁcial: meniscectomy. Meniscectomy is per-

formed around 1.7  10

times a year worldwide [10] and consists

of surgical removal of a meniscal lesion to create a stable rim

[11]. Design requirements are summarized in Table 1. The maxi-

mum cutting force (F

) was calculated to be approximately 190 N,

using the maximum shear stress for punching meniscal tissue

(10.2 N/mm

)[12] and the circumferential cutting area of a con-

ventional cutter (19 mm

). F

acts as compressive force on the

proposed steerable mechanical joint. The required range of motion

(RM

tip

) was estimated to be 55



to 55



relative to the instrument

shaft in the meniscal plane [2]. For comfortable steering, a low

steering stiffness (K) is preferred. The main geometric criteria are

a maximum outer shaft diameter (d

shaft

) to ﬁt the access portal,

and a minimum shaft length (L

shaft

) to easily feed the whole

instrument in the knee joint [2] (Table 1).

To guarantee robust function when handling the instrument,

two critical situations can be identiﬁed. First, during insertion of

the instrument in an access portal, the tip should remain in line

with the shaft to minimize the risk of damaging healthy tissue.

This requires minimal deﬂection of the tip under axial (F

exaxial

)

and transverse (F

extrans

) loads (Table 1). Secondly, during tissue

cutting a maximum parasitic deﬂection (u

)of5



is allowed [2].

3 Conceptual Design

The steerable mechanical instrument joint function was divided

into steering and cutting, with steering split into hinging of me-

chanical parts and actuating them.

Traditional mechanisms using gears, pulleys, or linkages [1,13]

and actuation by hydraulics [14] or pneumatics pose a challenge

for the intended design, because possibilities for miniaturization

are limited. Compliant mechanisms in which the deﬂection of des-

ignated ﬂexible members transmits force, motion, and energy

[15], do not have these drawbacks. As a result, fewer parts are

required, leaving more construction space, reduced backlash, and

wear. However, application of compliant mechanisms for surgical

instruments was primarily performed for grasping soft tissues

[8,16–19], and design synthesis when dealing with large deﬂec-

tions, interconnected deformations, and three-dimensional struc-

tures pose problems [19].

To avoid complex three-dimensional structures, the cutting

mechanism was placed distally at the instrument tip and the

steering mechanism proximally behind the cutting m echanism.

This strategy allows superposition of two-dimensional solutions

to achieve synthesis.

Many compliant hinges only allow small displacements to

remain within the elastic deformation zone and to prevent buckling

Corresponding author.

Manuscript received December 16, 2010; ﬁnal manuscript received June 21,

2011; published online September 30, 2011. Assoc. Editor: Vijay Goel.

Journal of Medical Devices SEPTEMBER 2011, Vol. 5 / 034503-1Copyright

2011 by ASME

Downloaded 24 Nov 2011 to 155.69.4.4. Redistribution subject to ASME license or copyright; see http://www.asme.org/terms/Terms_Use.cfm

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