The present invention relates generally to the medical field, and more particularly to apparatus and method for applying and controlling the traction force applied to limbs during orthopaedic surgery, where traction is applied between a patient's foot or leg and a restraining post located at the patient's groin. The invention teaches applying traction force with an actuator, measuring the force applied and regulating the force applied with a control circuit in order to limit the risk of injury to the patient.
In the treatment of certain medical conditions it is desirable to provide a traction force to a patient's limb or limbs. Examples include distraction of the hip for hip arthroscopy or distraction of fractures of the leg bones in order to re-align the broken bones to ensure correct healing (‘fracture reduction’). In each of these cases, tension is applied to the patient's lower limb or foot. In order to maintain the traction force, it is necessary to apply a counter-force to prevent the patient's body being pulled off the operating table.
Various means have been developed to apply this counter-traction force, including harnesses and patient positions that use the patient's weight as the counter-force, however the most common approach is to provide a cylindrical post (called a ‘perineal post’) located at the patient's groin. In this position, traction force is usually applied to both the operative and non-operative limb to prevent the patient's pelvis rotating about the perineal post.
Examples of such apparatus are described in U.S. Pat. No. 1,697,121 (Knebel), U.S. Pat. No. 2,658,507 (Neufeld) and numerous others, generally called ‘fracture tables’. Variations of fracture tables provide means to apply and adjust traction forces using screw mechanisms or suspended weights (see U.S. Pat. No. 4,802,464 (Deprez) and U.S. Pat. No. 3,088,460 (Wright)).
Although this technique for applying limb traction has been in use for more than 100 years, it still presents a risk of significant injury to the patient, primarily sciatic or pudental nerve injury. Nerve injuries, largely due to the counter forces applied to the patient's groin, are reported in the medical literature at rates between 1.7% and more than 27%, most intraoperative, but many resulting in long-term damage (Telleria et al 2012, Polyois et al 2013). The risk of nerve damage is increased with increase in the applied traction force, and to a lesser extent, the length of time that traction is applied.
Traction application devices such as screws or weights can easily be (and sometimes are) equipped with indicating scales to show the amount of traction force applied. Unfortunately, such indicating scales are usually not visible during surgery as they are under the surgical drapes or otherwise obscured, and thus do not allow the surgeon to know if the traction force has increased or decreased during surgery. Furthermore, during the course of surgery, it may be necessary to alter the position of the patient, the direction or the magnitude of the traction force applied to the patient's limb in order to provide visualization of or access to the surgical site. When such changes in the direction and magnitude of the traction force are made, traditional indicating scales do not provide adequate feedback to the surgeon, nor is it possible (particularly with screw-applied traction force) to know if applied traction has increased beyond acceptable limits while the patient is repositioned. Further, should the amount of traction force need to be increased or decreased, a non-sterile surgical assistant must be called to get under the surgical drapes to adjust the applied traction force, risking contamination of the surgical field and disruption of the surgical site.
In summary, current fracture tables depend on traction applied through the lower limb, countered by a perineal post. In the surgical setting, there is no indication of the traction force applied to the operative or non-operative limb visible to the surgeon, nor is it easily possible to increase or decrease the applied traction force during the surgical procedure. Further, there is no means provided to directly measure the length of time that traction is applied to the limbs, nor is there a means to regulate the traction force applied, nor is there any provision for providing a warning to the surgeon should the traction force exceed safe limits.
The object of the current invention is to provide means for applying a selectable traction force to the patient's operative and non-operative limbs, measuring and displaying to a surgeon the traction force applied to the limbs and using a control circuit to regulate and maintain the selected amount of traction force. Further the invention includes provision of alarms to indicate if traction has exceeded safe limits, a timer to measure the duration of traction application and advantageously, a means to alert the surgeon should application of the traction force result in an unacceptably large change in position of the patient's limb.
The features and advantages of the present invention will become apparent upon reference to the following detailed description of the preferred embodiments and to the drawings, wherein
With reference now to the drawings,
Traction application devices 16 are connected to support arms 17 which are in turn connected to the body of operating table 12 so that activating traction application device 16 will apply a force generally along the axis of the patient's leg.
To prevent patient 10 from being pulled along the surface of operating table 12 upon application of the traction force, perineal post 18 is mounted to operating table 12 and is located in the patient's groin. Perineal post 18 provides a portion of the counter force to the force applied to the patient's legs by traction application devices 16, thereby preventing the movement of patient 10's body in the direction of the applied traction force. Additional counter force is provided by the friction between the body of patient 10 and table 12. The combination of perineal post 18 and the friction force allow significantly large tension forces to be created in the lower limbs of patient 10.
It should be noted that traction could be applied to patient 10's lower limbs in other orientations using a substantially similar apparatus. For example, patient 10 could be positioned in a prone position, or in a lateral position while allowing and traction to be applied to the lower limbs in a similar manner. Further, although the current embodiment uses a boot-like apparatus to apply traction force through the feet, it is known in the art to insert a pin crosswise through the bones of the lower limb and connect this pin to traction application devices 16 to apply traction force directly to the bones of patient 10. Such variations in technique do not substantially change the function or intent of the present invention.
Returning now to the configuration of
Mechanical connector 28 is designed to fit the accessory connector provided as part of the support arms 17 of operating table 12. Advantageously, connecter 28 can be removed and replaced with different forms of mechanical connector 28 such that traction application devices 16 can be attached to a wide range of different operating tables 12.
Similarly, mechanical connector 20 duplicates the mechanical connector provided as part of support arm 17 of operating table 12, such that patient applied part 14, which may be provided with operating table 12, can be easily connected to traction application device 16.
Once mechanically connected as shown in
Processor 36 is a conventional computer that includes a microprocessor containing a software program for receiving signals from load cells 26, position sensors 22 and touch screen display 38, and sending signals to linear actuator 24, touch screen display 38 and alarm 40. Processor 36 also incorporates amplifiers to properly condition the signals from load cells 26 and position sensor 22, and to provide the control current required to activate linear actuator 24.
Touch screen display 38 receives display information from processor 36 so as to provide a graphical display as hereinafter described, and sends touch information back to processor 36 in response to a user touching the various control areas of touch screen display 38 as hereinafter described.
Alarm 40 is a loudspeaker capable of reproducing audio signals produced by processor 36 and is used to produce audible alarms in the event of certain conditions being determined by the software program running on the microprocessor incorporated in processor 36.
In typical use, a traction application system in accordance with the invention is used as hereinafter described. Patient 10 is positioned on operating table 12, usually in a supine position. Perineal post 18 is located between the legs of patient 10 to provide counter-traction force. Support arms 17 of operating table 12 are deployed more or less along the intended axis of each leg of patient 10. Two traction application devices 16 are typically used. Each traction application device is connected to processor 36 via connection cables 30, 32 and 34. Once connected, the software running on the microprocessor within processor 36 detects the connection of the traction application devices 16 and sends a signal to linear actuator 24, causing it to fully extend. This step ensures that the maximum range of motion is available for applying traction.
Once linear actuator 24 is fully extended, each traction application device 16 is attached to connector 28 of support arm 17. In turn, patient applied part 14 is attached to traction application device 16 using connector 20. Finally the foot of patient 10 is attached to patient applied part 14 using straps 15.
Once both legs and both traction application devices 16 are connected to support arms 17, support arms 17 are extended and locked in place so that the legs of patient 10 are suspended. This will apply a small amount of traction to the legs of patient 10 due to their weight. This traction force is applied through load cell 26, hence load cell 26 is able to measure the traction force and send a force signal representing the traction force to processor 36 via connection cable 30. Processor 36 uses this force signal to calculate the traction force in standard units (either pounds force or newtons), and displays this on touch screen 38. The force signal is proportional to the force applied to the patient through the patient applied part 14.
Now that patient 10 is properly positioned, the user may use the controls on touch screen 38 to safely apply traction. As a first step, the user uses controls 40 and 42 to increase or decrease the maximum allowed traction force permitted during the current surgical procedure. Should the traction force measured by load cell 26 ever exceed this limit, processor 36 will cause alarm 40 to activate, warning the user.
Next the user sets the maximum traction application time to be allowed during the surgical procedure. The maximum time is set using touch screen controls 44 and 46. Should traction be applied for longer than this time, processor 36 will cause alarm 40 to activate, warning the user.
Now that force and time limits have been set, the user may now select the traction force to be applied to each limb. For the left limb, controls 50 and 54 are used to increase or decrease the desired amount of traction, while controls 52 and 56 are used to increase or decrease the traction applied to the right leg. Increasing the selected traction causes processor 36 to send a signal to linear actuator 24, which causes actuator 24 to retract, increasing the traction force applied to the leg of patient 10. Similarly, decreasing the selected traction causes actuator 24 to extend, reducing the traction force. Simultaneously, position sensor 22 sends a signal to processor 36 via cable 32 representative of how far linear actuator 24 is extended, that is, the position of the actuator. Using the traction force measured by load cell 26 (i.e., the force signal from the load cell), and the position measured by position sensor 22, processor 36 implements a feedback control system to regulate the traction force to be close to the desired force as set by the user. The processor 36 thus responds to the force signal from load cell 26 by generating an actuating signal that regulates the linear actuator to maintain the force applied to the patient selected part 14 at the pre-set level.
As soon as the user presses one of controls 50 or 52 to request an increase in traction force, processor 36 starts a timer, begins updating the Traction Time 48 displayed on touch screen 38, and begins checking that this time has not exceeded the maximum traction time previously set. Should the traction time exceed the time limit set with controls 44 and 46, processor 36 will cause touch screen 38 to display a warning message in alerts display 64 and will simultaneously cause alarm 40 to sound until either the traction force is reduced or control 46 is used to increase the time alarm limit.
If at any time while traction is applied, load cell 26 detects a traction force in excess of that set by controls 40 and 42, processor 36 will display a warning message in display in alerts display 64 and will simultaneously cause alarm 40 to sound until either the traction force measured by load cell 26 is reduced below the currently set level, or control 42 is used to increase the force alarm limit above the force being measured.
To further reduce the risk of injury to patient 10, the software program running on processor 36 monitors the signal from position sensor 22 and the signal from load cell 26 to ensure that traction application apparatus 16 is operating properly. Should position sensor 22 indicate that linear actuator 24 has reached its maximum or minimum extension, processor 36 will cause touch screen 38 to display a warning message in alerts display 64 and will simultaneously cause alarm 40 to sound. Similarly, should load cell 26 indicate that the traction force is significantly lower than the traction force set with controls 50, 52, 54 or 56, processor 36 will cause touch screen 38 to display a warning message in alerts display 64 and will simultaneously cause alarm 40 to sound.
During normal operation, processor 36 will cause linear actuator 24 to extend or retract by a small but predetermined amount in order to regulate the traction force as measured by load cell 26—the limits of the predetermined amount of extension or retraction being stored within processor 36. While monitoring the signal from position sensor 22, should processor 36 detect a change in position much greater than this expected small but predetermined amount, processor 36 will cause linear actuator 24 to stop moving, will cause touch screen 38 to display a warning message in alerts display 64 and will simultaneously cause alarm 40 to sound. In this way, possible injury to patient 10 due to sudden excursions of linear actuator 24 are prevented.
The current invention provides for an additional operating mode offering additional safety for patient 10. It is known that the amount of traction force required to achieve a specific clinical result, for example distraction of the hip joint for hip arthroscopy surgery, will vary over time. Usually a higher level of traction force is initially required to achieve a desired amount of distraction, but the force required decreases over time as the tissues resisting the traction force relax. In this situation, it is advantageous to allow the traction force applied to decrease as long as the amount of distraction is maintained. In this alternate mode of operation according to the invention, the user will use controls 50 and 52 to initially set a traction force that attains the degree of distraction required. Once the clinically required level of distraction is attained, the user would then use an additional control 100 (shown in
Many other variations to the apparatus described herein may be constructed without departing from the scope and spirit of the present invention. For example, although the preferred embodiment uses wired connections between processor 36 and traction application apparatus 16, traction apparatus 16 could be equipped with a battery power supply, a local microprocessor and a wireless connection to processor 36; additional controls could be added to touch screen 38 such as an alarm silence control to temporarily mute alarm 40; or an additional display element on touch screen 38 could show the current amount of extension of linear actuator 24. As another example of an equivalent alternative structure, the special arrangement of the load cell 26, linear actuator 24 and patient applied part 14 shown in
While the present invention has been described in terms of a preferred embodiment, it will be appreciated by one of ordinary skill that the spirit and scope of the invention is not limited to those embodiments, but extend to the various modifications and equivalents as defined in the appended claims.