Novel Digital Arthrometer - An Overview

Introduction:

With an increase in knee injuries in individuals involved in sports and athletics. Treatment and rehabilitation after a ligament injury in the knee become crucial due to the long-term adverse effects of knee injuries. Various clinical examinations assess knee ligament laxity after damage to the knee's ligaments. Various arthrometers with improved diagnostic accuracy are developed to evaluate knee laxity and determine the patient's proper treatment plan. This article discusses the new novel digital arthrometer and its indication in detail.

What Is the Indication for a Digital Arthrometer?

Common sports injuries always involve the knee. Significantly people who indulge in contact sports are often affected by anterior cruciate ligament injury. It is the most common traumatic injury, with an incidence of 1 in 3500 people per year in the United States alone. The anterior cruciate ligament belongs to the four major ligaments connecting the shin and thigh bones. The normal function of the anterior cruciate ligament is to prevent the excessive anterior displacement of the shin bone (tibia) and to prevent knee collapses in relation to the thigh bone. The anterior cruciate ligament provides stability as the knee moves from extension to flexion.

Anterior cruciate ligament injury often results in long-term effects such as

• Muscle atrophy.

• Lower extremity dysfunction.

• Feeling unstable, resulting in low levels of physical activity.

• Early occurrence of knee osteoarthritis.

• Risk of meniscus injury.

• Knee instability.

Therefore, the physician must determine the knee ligamentous laxity for proper treatment strategies and post-operative recovery. During the investigations of an anterior cruciate ligament injury, the clinician performs various physical examination maneuvers to assess the integrity of the anterior cruciate ligament (ACL). These tests were limited concerning the examiner's experience and the patient's cooperation. Later various instruments were developed to quantify knee laxity after ACL injury. This novel digital arthrometer was developed with improved diagnostic accuracy following the biomechanical characteristics of the anterior translation of the tibia after ACL injury to quantify knee laxity. Further, measuring the knee laxity with a digital arthrometer was necessary to prevent the risk of ACL reconstruction failure.

What Are the Advantages of the Digital Arthrometer?

• It is used to quantify and measure both the Lachman and anterior drawer tests.

• The digital arthrometer is lightweight.

• Excellent reliability.

• More accurate than formerly used devices in quantifying knee laxity.

• Non-invasive equipment.

• Inexpensive.

• Portable and easy to handle the equipment.

• Comprise a high-precision digital meter.

• It comes with accessories to facilitate its usage.

• It does not require the process of documenting the measurements of the device.

• Simplified operation by avoiding radiation exposure.

What Are the Components of a Digital Arthrometer?

The digital arthrometer device is very similar to the telos arthrometer device in appearance (a device that uses a radiographic image for measurement).

• The device contains a main frame of stainless steel, fixing brackets that could be reinforced with the legs, and a thruster for applying load.

• The main frame holds the display screen and the displacement sensors. In the display screen, the first line denotes the instantaneous load in N (Newton), and the second line in the display screen denotes the instantaneous distance in mm (Millimeter).

• At the bottom of the data acquisition interface have three columns of measured load values, corresponding displacement, and side-to-side differences (SSD).

What Were the Formerly Used Methods to Measure Knee Laxity?

• Lachman Test: The Lachmann test is one of the clinical examination techniques performed in investigating the anterior cruciate ligament injury to assess the anterior translation of the shin bone. In this technique, the patient is supine with the injured knee bent at 20 to 30 degrees and slightly externally rotated. The examiner grasps the thigh bone firmly using one hand and the other hand to hold the proximal surface of the shinbone. By keeping the thigh stable, the examiner pulls the leg forward. Anterior translation of the shinbone greater than the normal range when compared to an uninjured leg and a lack of a firm endpoint denotes a positive test. But the test is influenced by the examiner's experience and the patient’s cooperation and it does not provide any quantitative measurements.

• KT-1000 Arthrometer: This instrument was developed in the early 1980s and was one of the most commonly used devices to measure knee laxity, with a specificity of 95 percent and a sensitivity of 92 percent. However, after repeated measurements, the device shows low reproducibility and inadequate reliability and the data collected has to be written manually.

• Telos Device: This instrument is a mobile device used in conjunction with X-rays. This device measures the anterior tibial translation of patients with ACL injury by determining the measurements from the X-rays with a sensitivity of 86 percent and specificity of 89.2 percent with the knees flexed at 30 degrees and a threshold value of three millimeters. However, the primary drawback of this device is the exposure to radiation which is avoided in digital arthrometers.

What Happens During the Examination With a Digital Arthrometer?

• During the examination with a digital arthrometer, the patient is asked to lie on the examination table and the knees are bent at 20 to 30 degrees stimulating the Lachman test position.

• With the help of the fixing brackets, the components are fixed. Anteriorly, they are set over the kneecap (patella) to limit femoral movements, and the other component is placed distal to the tibia.

• The thruster at the end of the mainframe is set to a constant speed of 3 N/s (newton per second).

• The thruster applies a pushing force to the posterior aspect of the leg. The displacement was recorded in the digital meter until the force reached the set value.

• A study by Bercovy showed that the minimum load required to determine the accurate diagnosis was 180 N.

• The examiner repeated the procedure three times, and the measurements were recorded and calculated.

Conclusion:

One of the most common injuries nowadays is the anterior cruciate ligament injury. Untreated ACL injury can lead to serious long-term effects such as knee osteoarthritis. Therefore, it becomes necessary to assess a patient with an ACL tear properly. Various methods have been used for a long time to evaluate knee laxity in patients with ACL injuries. Multiple instruments are developed to accurately quantify knee laxity for a proper treatment plan and rehabilitation. The novel digital arthrometer is more accurate than the formerly used instrument KT1000 with much more reliability.