Surgical Instrument Tip Design for Bone Torque Measurement
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Solution Overview
Problem
Existing surgical instruments for measuring mechanical resistance in porous bone require separate tools for drilling and measurement, leading to variable frictional torque due to the use of a K-wire, which can result in inaccurate bone mineral density assessments.
Innovation Solution
A single surgical instrument that drills a hole in cancellous bone and measures bone quality by using a modified tip design with cutting edges for drilling and flat surfaces for torque measurement, minimizing friction with the cortical bone and allowing for accurate resistance assessment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a separate drill bit is used to drill a hole in cortical bone, then the cortical bone can be opened, but the friction between the drill bit and cortical bone affects the torque measurement accuracy
Solution Approach 1:
The patent combines the drilling function and measurement function into a single integrated surgical instrument. The tip portion includes both cutting edges for drilling and flat surfaces for torque measurement, eliminating the need for separate drill bit and measurement device. This merging resolves the contradiction by making the instrument easier to use (single tool) while maintaining measurement accuracy through the specific geometric design of the flat surfaces that minimize friction during cortical bone penetration.
Solution Approach 2:
The tip portion is designed with different local geometries for different functions: cutting edges with specific angles for drilling through cortical bone, and flat surfaces with optimized orientation for torque measurement in cancellous bone. The flat surfaces are positioned and oriented to minimize frictional contact with cortical bone during drilling, thereby maintaining measurement precision while enabling the combined function.
2Ease of operation
If a K-wire is used as a guide wire in a cannulated probe, then the probe can be inserted, but the K-wire deforms resulting in variable contact area and high friction between the K-wire and probe inner surface
Solution Approach 1:
The patent removes the K-wire guide wire component from the measurement system. Instead of using a cannulated probe that slides over a K-wire, the invention uses a solid shaft with an integrated tip portion that performs both drilling and measurement functions. This extraction eliminates the source of variable friction (K-wire deformation) while maintaining ease of operation through the streamlined single-piece design.
3Ease of operation
If a single instrument is used to drill and measure, then the ease of use is improved, but the instrument design becomes more complex
Solution Approach 1:
The patent combines multiple functions (drilling and torque measurement) into a single integrated tip portion on a solid shaft. The tip portion includes cutting edges for drilling and flat surfaces for measurement, all in one component. This merging achieves ease of operation (single instrument for both tasks) while controlling complexity through the elegant geometric integration of functions rather than adding separate components.
Solution Approach 2:
The surgical instrument is designed as a multi-functional tool where the same shaft and tip portion perform both drilling through cortical bone and torque measurement in cancellous bone. The flat surfaces on the tip portion serve dual purposes: they are part of the cutting structure during drilling and serve as the measurement interface during torque assessment, embodying universality that reduces overall system complexity.
4Productivity
If the tip has cutting edges for drilling, then the drilling function is achieved, but the cutting edges may interfere with torque measurement
Solution Approach 1:
The tip portion is designed with distinct local geometries: sharp cutting edges oriented for efficient drilling through cortical bone, and separate flat surfaces oriented perpendicular to the shaft axis for accurate torque measurement. The flat surfaces are positioned such that during reverse rotation for measurement, they contact the cancellous bone while minimizing contact with cortical bone walls, thereby eliminating interference from the cutting edges and ensuring measurement precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables precise measurement of local mechanical resistance in cancellous bone without the bias of cortical bone friction, facilitating accurate decision-making during surgical procedures such as implantation or prosthetic placement.
Implementation Method 1
the cutting edges face the cutting direction... the cutting edge separates the bone tissue into parts with a sharp edge
Implementation Method 2
the measuring surface deforms the bone tissue until if fails... the flat surfaces face the measuring direction
Implementation Method 3
the torque sensor is coupled to the shaft (2). The torque sensor (10) is configured to measure the breakaway torque of the bone tissue when the shaft (2) is rotated in the counter-clockwise direction
Implementation Method 4
the surgical instrument further comprises a resilient means able to rotate the shaft in the second direction for crushing bone tissue
Data Source
Figure 1~2
AI summary
Surgical instrument (1) comprising a longitudinal shaft (2) with a tip portion (3), a rear portion (4) and a longitudinal axis (5) and rotatable in the clock-wise and in the counter-clockwise direction around the longitudinal axis (5), said surgical instrument (1) further comprising: A) first means (6) for drilling a hole in a bone by rotation of the shaft (2) in one of the two directions; B) second means (7) for crushing bone tissue when the shaft (2) rotates in the other of the two directions; and C) a torque sensor (10) coupled to the shaft (2). Method for measuring the local mechanical resistance of a porous body comprising the steps of: a) drilling a hole to a desired depth into a porous body by advancing and rotating the shaft (2) in a first sense of rotation, preferably clockwise so that said first means (6) are active; b) hammering the shaft (2) gently further into the porous body as far as the tip portion (3) of the shaft (2) has reached a desired measuring position; and c) performing the torque measurement by rotating the shaft (2) in the opposite second sense of rotation, preferably counter-clockwise so that said second means (7) are active.