Prediction method for postoperative implant subsidence

Abstract

To provide a method for quantitatively predicting a postoperative implant sinkage amount in an artificial hip joint implant insertion surgery, for preventing occurrence of postoperative complication.SOLUTION: In an artificial hip joint implant insertion surgery, there are provided: (1) a step for inputting a beating sound of broaching through a sound collecting microphone, to a computer which has a sound collecting microphone, and a software for analyzing a sound pressure of input sound, and a frequency of the input sound; (2) a step for determining a ratio (sound pressure ratio: b / a) of a whole sound pressure of the broaching sound and a sound pressure of each frequency region; (3) a step for predicting a postoperative implant sinkage amount (mm) on the basis of the sound pressure ratio of a low frequency region of 0.5-3.0 kHz, and the sound pressure ratio of a high frequency region of 8.5-9.5 kHz, using following formula, where the mathematical formula 1 is: a postoperative implant sinkage amount=α+β×(the sound pressure ratio of the low frequency region)-γ×(the sound pressure ratio of the high frequency region), in the formula,α,β and γ represent a numerical value obtained by linear regression respectively.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for predicting the amount of implant subsidence after a hip prosthesis insertion operation. [Background technology]

[0002] Surgery to insert an artificial hip joint (also known as total hip replacement, femoral head replacement, or artificial hip implant surgery) is performed as a treatment for hip joint diseases such as osteoarthritis. Approximately 100,000 artificial hip joint implant surgeries are performed annually in Japan. In this surgery, a hammer is used to insert an instrument called a broach or rasp into the femur, which determines the formation of the femur (called broaching) and the appropriate size of the artificial hip joint. The artificial hip joint is then hammered into the femur, and inserted into the femur. If the hammering is too strong, an iatrogenic fracture can occur, while if it is too weak, complications such as postoperative implant subsidence can occur. In other words, if the hammering is too strong, an iatrogenic fracture can occur, so the surgeon stops the hammering before a fracture occurs. However, if the hammering is too weak, a complication occurs in which the implant sinks into the femur several weeks after surgery (also known as postoperative stem subsidence). The validity of this hammering technique (strength and number of hits) was judged based on the subjective technical experience of the surgeon, and there was no objective method for evaluating validity. Summary of the Invention [Problem to be solved by the invention]

[0003] An object of the present invention is to provide a method for quantitatively predicting the amount of postoperative implant subsidence in artificial hip joint implant insertion surgery, and preventing the occurrence of postoperative complications. [Means for solving the problem]

[0004] Therefore, the inventors came up with the idea that analyzing the strength and frequency of the tapping sound and using both of these could predict the amount of postoperative implant subsidence, and conducted various studies.The tapping sound during broaching during surgery was recorded on a computer using a sound-collecting microphone, and the frequency and sound pressure of the tapping sound were examined in cases where postoperative implant subsidence occurred and cases where it did not, and it was found that postoperative implant subsidence occurred at sound pressures of certain frequencies, and on the other hand, at sound pressures of certain frequencies. However, this sound pressure is affected by the strength of the tap, making it impossible to perform a reproducible evaluation. Therefore, we discovered that by using a parameter (sound pressure ratio) obtained by dividing the sound intensity in each frequency range by the overall sound pressure, we could objectively evaluate the characteristics of tapping sounds that are not affected by the strength of the tap. Using this sound pressure ratio, we analyzed the differences between tapping sounds that caused postoperative implant subsidence and those that did not. We found a statistically significant difference between tapping sounds that caused postoperative implant subsidence in certain low-frequency ranges and those that did not in certain high-frequency ranges. Next, the inventors used a statistical method to perform linear regression using the sound pressure ratio between the frequency ranges where postoperative implant subsidence occurs and the frequency ranges where it does not occur, and established a prediction formula that can predict the amount of postoperative implant subsidence. Therefore, they found that if the amount of postoperative implant subsidence is calculated using this prediction formula based on tapping sounds via a computer, the amount of postoperative implant subsidence can be accurately predicted and the occurrence of postoperative complications can be prevented, and they have completed the present invention.

[0005] That is, the present invention provides the following inventions [1] to [5]. [1] In artificial hip joint implant insertion surgery, (1) A step of inputting the tapping sound during broaching via a sound collection microphone into a computer having software capable of analyzing the sound pressure and frequency of the input sound; (2) (a) calculating the ratio of the overall sound pressure of the tapping sound to (b) the sound pressure in each frequency range (sound pressure ratio: b / a); and (3) predicting the postoperative implant subsidence (mm) using the following formula based on the sound pressure ratio in the low frequency range of 0.5 to 3.0 kHz and the sound pressure ratio in the high frequency range of 8.5 to 9.5 kHz;

[0006] [Number 1] Postoperative implant subsidence amount = α + β × (sound pressure ratio in the low frequency region) - γ × (sound pressure ratio in the high frequency region) (wherein α, β, and γ represent values ​​obtained by linear regression), A method for predicting postoperative implant subsidence.

[0007] [2] The method for predicting the amount of postoperative implant subsidence described in [1], wherein the computer used has software for performing steps (2) and (3). [3] The method for predicting the amount of postoperative implant subsidence according to [1] or [2], wherein the low frequency range of 0.5 to 3.0 kHz is a low frequency range selected from 0.5 to 1.0 kHz, 1.0 to 1.5 kHz, 1.5 to 2.0 kHz, 2.0 to 2.5 kHz, and 2.5 to 3.0 kHz. [4] The method for predicting the amount of postoperative implant subsidence according to any one of [1] to [3], wherein the high frequency range of 8.5 to 9.5 kHz is a high frequency range selected from 8.5 to 9.0 kHz and 9.0 to 9.5 kHz. [5] A method for predicting postoperative implant subsidence described in any one of [1] to [4], wherein the low frequency region of 0.5 to 3.0 kHz is a low frequency region of 2.5 to 3.0 kHz, the high frequency region of 8.5 to 9.5 kHz is a high frequency region of 9.0 to 9.5 kHz, α is 2.634, β is 3.268, and γ is 4.956. [Effects of the Invention]

[0008] According to the method of the present invention, the amount of implant subsidence after the insertion of an artificial hip joint implant can be accurately predicted, thereby preventing the occurrence of postoperative complications. [Brief explanation of the drawings]

[0009] [Figure 1]FIG. 10 is a diagram showing how a hammer is used to strike the broach or artificial hip joint, and how the broach or artificial hip joint is inserted into the femur. [Figure 2] This figure shows the complication of the implant sinking into the femur several weeks after surgery (also known as postoperative stem subsidence). [Figure 3] Step (1) was performed on 55 cases, and the graph shows the results of tabulating the cases in which postoperative implant subsidence occurred (Subsidence) and cases in which it did not occur (no Subsidence). [Figure 4] This is a graph showing the sound pressure ratio (b / a) in each frequency range and the cases in which postoperative implant subsidence occurred (Subsidence) and cases in which it did not occur (no Subsidence). DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention is a method for predicting the amount of implant subsidence after an artificial hip joint implant insertion operation, the method comprising the following steps (1) to (3): (1) inputting the tapping sound of the broaching via a sound collecting microphone into a computer having software capable of analyzing the sound pressure and frequency of the input sound; (2) (a) calculating the ratio of the overall sound pressure of the tapping sound to (b) the sound pressure in each frequency range (sound pressure ratio: b / a); and (3) predicting the postoperative implant subsidence (mm) using the following formula based on the sound pressure ratio in the low frequency range of 0.5 to 3.0 kHz and the sound pressure ratio in the high frequency range of 8.5 to 9.5 kHz;

[0011] [Number 2] Postoperative implant subsidence amount = α + β × (sound pressure ratio in the low frequency region) - γ × (sound pressure ratio in the high frequency region) (where α, β and γ represent values ​​obtained by linear regression).

[0012] Traditional hip implant insertion involves inserting an instrument called a broach or rasp into the femur by hammering it into the femur (broaching), determining the appropriate size of the prosthesis, and then hammering the prosthesis into the femur with a hammer (Figure 1). Hammering that is too strong can result in iatrogenic fractures, while hammering that is too weak can lead to complications such as postoperative implant subsidence. Because hammering that is too strong can result in iatrogenic fractures, the surgeon stops hammering before a fracture occurs. However, hammering that is too weak can result in the implant sinking into the femur several weeks after surgery (also known as postoperative stem subsidence), as shown in Figure 2. The appropriateness of this hammering technique (strength and number of hammerings) is determined based on the surgeon's subjective technical experience. Therefore, the inventors came up with the idea that analyzing the strength and frequency of the tapping sound and using both of these could predict the amount of postoperative implant subsidence, and conducted various studies.The tapping sound during broaching during surgery was recorded on a computer using a sound-collecting microphone, and the frequency and sound pressure of the tapping sound were examined in cases where postoperative implant subsidence occurred and cases where it did not.It was found that postoperative implant subsidence occurred at sound pressures of certain frequencies, and also at sound pressures of certain other frequencies (Figure 3). However, this sound pressure is affected by the strength of the tap, making it impossible to perform a reproducible evaluation. Therefore, we discovered that by using a parameter (sound pressure ratio) obtained by dividing the sound intensity in each frequency range by the overall sound pressure, we could objectively evaluate the characteristics of tapping sounds that are not affected by the strength of the tap. Using this sound pressure ratio, we analyzed the differences between tapping sounds that caused postoperative implant subsidence and those that did not. We found a statistically significant difference between tapping sounds that caused postoperative implant subsidence in certain low-frequency ranges and those that did not in certain high-frequency ranges (Figure 4). Next, the inventors established the above-mentioned prediction formula, which can predict the amount of postoperative implant subsidence, by performing linear regression using a statistical method using the sound pressure ratio between the frequency range in which postoperative implant subsidence occurs and the frequency range in which it does not occur. Therefore, they found that if the above-mentioned steps (1) to (3) are performed via a computer based on the tapping sound, the amount of postoperative implant subsidence can be accurately predicted and the occurrence of postoperative complications can be prevented.

[0013] The steps (1) to (3) of the present invention will now be described. Step (1) is a step in which the tapping sound of broaching is input via a sound-collecting microphone to a computer having software capable of analyzing the sound pressure and frequency of the input sound. Examples of computers that can be used include PCs, tablets, and smartphones. The computer is equipped with a sound-collecting microphone and software that can analyze the sound pressure and frequency of the input sound. Software is required that can analyze the broaching impact sound input to the computer by the sound-collecting microphone by dividing it into sound pressure and frequency. This software can be any software commonly used in the field of acoustics. In step (1), the tapping sound of the broaching is input to a computer having such a configuration via a sound-collecting microphone. Here, the tapping sounds to be input are preferably about 3 to 5 times in the final stage of hammering in broaching. The artificial hip joint implants used include broaches that are actually inserted into patients. These implants are made of stainless steel or the like. The hammers used include stainless steel hammers. Since the frequency of the tapping sound varies depending on the implant and hammer, it is desirable to collect data for steps (2) and (3) described below in advance using the tapping sound of the implant and hammer that will actually be used. Step (1) was performed on 55 cases, and the graph showing the cases in which postoperative implant subsidence occurred and those in which it did not is shown in Figure 3. Figure 3 suggests that there is a tendency in the high frequency range for cases in which postoperative implant subsidence did not occur, but this is not clear.

[0014] Step (2) is a step of finding the ratio (sound pressure ratio: b / a) between (a) the overall sound pressure of the tapping sound and (b) the sound pressure in each frequency range. Since sound pressure is affected by the strength of the hit, it was not possible to perform a reproducible evaluation. Therefore, we discovered that by using a parameter (b / a: sound pressure ratio) obtained by dividing the sound pressure in each frequency range (b) by the overall sound pressure (a), it is possible to objectively evaluate the characteristics of the tapping sound without being affected by the strength of the hit. Figure 4 is a graph summarizing the sound pressure ratio (b / a) in each frequency range and the cases in which postoperative implant subsidence occurred and those in which it did not. Figure 4 shows that there is a statistically significant difference between the cases in which postoperative implant subsidence occurred in a specific low frequency range (0.5-3.0 kHz) and the cases in which postoperative implant subsidence did not occur in a specific high frequency range (8.5-9.5 kHz).

[0015] Step (3) is a step of predicting the postoperative implant subsidence (mm) using the following formula from the sound pressure ratio in the low frequency range of 0.5 to 3.0 kHz and the sound pressure ratio in the high frequency range of 8.5 to 9.5 kHz.

[0016] [Number 3] Postoperative implant subsidence amount = α + β × (sound pressure ratio in the low frequency region) - γ × (sound pressure ratio in the high frequency region) (wherein α, β, and γ represent values ​​obtained by linear regression),

[0017] The above formula was obtained by linear regression of the results of previous experiments shown in Figure 4. Here, IBM SPSS Statistics, IBM SPSS Modeler, JMP, etc. can be used as linear regression software. The sound pressure ratio in the low frequency region of 0.5 to 3.0 kHz may be the sound pressure ratio of the entire region, but it is preferable to use a sound pressure ratio in a low frequency region selected from 0.5 to 1.0 kHz, 1.0 to 1.5 kHz, 1.5 to 2.0 kHz, 2.0 to 2.5 kHz, and 2.5 to 3.0 kHz, and it is even more preferable to use a sound pressure ratio in a low frequency region selected from 2.5 to 3.0 kHz. Furthermore, as the sound pressure ratio in the high frequency range of 8.5 to 9.5 kHz, it is preferable to use a sound pressure ratio in a high frequency range selected from 8.5 to 9.0 kHz and 9.0 to 9.5 kHz, and it is more preferable to use a sound pressure ratio in a high frequency range of 9.0 to 9.5 kHz. Furthermore, it is preferable to use the sound pressure ratio in the low frequency range of 2.5 to 3.0 kHz and the sound pressure ratio in the high frequency range of 9.0 to 9.5 kHz, where α, β, and γ are preferably 2.634, 3.268, and 4.956, respectively.

[0018] In steps (2) and (3), it is preferable to input data obtained by performing steps (2) and (3) using the same hammer and implant into the computer to be used in advance.

[0019] As will be shown in the Examples below, if the postoperative implant subsidence amount obtained by the method of the present invention is 3 mm or less, it can be accurately predicted that the actual postoperative implant subsidence amount will also be 3 mm or less, and the occurrence of postoperative complications can be prevented. [Example]

[0020] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0021] Example 1 A preliminary test of artificial hip joint implant insertion into the femur was conducted using an artificial hip joint implant and a Stryker Accord 2 hammer. The microphone picked up the sounds of three to five taps during the final stage of broaching. Step (1) was performed on 55 cases, and the graph showing the cases in which postoperative implant subsidence occurred and those in which it did not is shown in Figure 3. Figure 3 suggests that there is a tendency in the high frequency range for cases in which postoperative implant subsidence did not occur, but this is not clear.

[0022] Figure 4 is a graph summarizing the sound pressure ratio (b / a) in each frequency range and the cases in which postoperative implant subsidence occurred and those in which it did not (step (2)). Figure 4 shows, with statistical significance, that postoperative implant subsidence occurs in a specific low frequency range (0.5-3.0 Hz), but does not occur in a specific high frequency range (8.5-9.5 Hz).

[0023] Linear regression was performed using IBM SPSS Statistics using the sound pressure ratio in the low frequency range of 2.5 to 3.0 kHz and the sound pressure ratio in the high frequency range of 9.0 to 9.5 kHz in the data in Figure 4. As a result, the following regression equation was obtained.

[0024] [Number 4] Postoperative implant subsidence amount = 2.634 + 3.268 × (sound pressure ratio in the low frequency region) - 4.956 × (sound pressure ratio in the high frequency region) (R 2 =0.361)

[0025] Using this data, when the cutoff values ​​for postoperative implant subsidence were set at 3 mm and 5 mm (i.e., whether the implant would sink by 3 mm or more after surgery, or whether it would sink by 5 mm or more), the high prediction accuracy shown in Table 1 was achieved.

[0026] [Table 1]

Claims

1. In hip joint implant insertion surgery, (1) A step in which a computer having a sound collection microphone and software capable of analyzing the sound pressure and frequency of input sound collects the tapping sound of broaching via the sound collection microphone; (2) the computer calculates a ratio (sound pressure ratio: b / a) between (a) the overall sound pressure of the beating sound and (b) the sound pressure in each frequency range; and (3) a step in which the computer predicts the postoperative implant subsidence (mm) from the sound pressure ratio in the low frequency region of 0.5 to 3.0 kHz and the sound pressure ratio in the high frequency region of 8.5 to 9.5 kHz using the following formula: [Equation 1] Postoperative implant subsidence amount = α + β × (sound pressure ratio in the low frequency region) - γ × (sound pressure ratio in the high frequency region) (wherein α, β, and γ represent values ​​obtained by linear regression). A method for predicting postoperative implant subsidence.

2. 2. The method for predicting postoperative implant subsidence according to claim 1, wherein the low frequency range of 0.5 to 3.0 kHz is a low frequency range selected from 0.5 to 1.0 kHz, 1.0 to 1.5 kHz, 1.5 to 2.0 kHz, 2.0 to 2.5 kHz, and 2.5 to 3.0 kHz.

3. 3. The method for predicting postoperative implant subsidence according to claim 1, wherein the high frequency range of 8.5 to 9.5 kHz is a high frequency range selected from 8.5 to 9.0 kHz and 9.0 to 9.5 kHz.

4. The method for predicting postoperative implant subsidence according to any one of claims 1 to 3, wherein the low frequency region of 0.5 to 3.0 kHz is a low frequency region of 2.5 to 3.0 kHz, the high frequency region of 8.5 to 9.5 kHz is a high frequency region of 9.0 to 9.5 kHz, α is 2.634, β is 3.268, and γ is 4.956.

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