Modified orthopedic traction system for cervical and lower limb rehabilitation

Abstract

BACKGROUND:

Orthopedic tractions can be employed in the rehabilitation of patients suffering from problems affecting the spine, as well as the upper and lower extremities but the high costs of using tractions due to prolonged hospital stays is a major disadvantage particularly in low-income economies.

OBJECTIVE:

The objective of this study was to design and develop a two-way adjustable traction system that accommodates both cervical and lower limb rehabilitation and improves limb and neck positioning.

METHOD:

The production process involved the use of computer-aided design (CAD) as well as other manufacturing procedures like material selection, welding, and drilling. The system was tested for stability to be sure it does not fail under large loads.

RESULT:

A functional and easy-to-install two-way orthopedic traction system for both hospital and home use was developed, installed and tested. The dimensions and adjustability would ensure that it can be used for children and adults.

CONCLUSION:

This study describes a device that can be used in hospitals. When used at homes, it can reduce the cost of medical bills, and provide patients with the emotional/psychological benefits of being cared for in a familiar environment.

Keywords

Bone fractures design forces loads pulleys

1. Introduction

Orthopedic medicine is a branch of surgery dedicated to the diagnosis and treatment of illnesses, injuries, deformities and malformations of the musculoskeletal system, including bones, joints, ligaments, muscles, and tendons [1]. One of its important modalities involves the use of medical tractions. Traction is the application of a pulling force to a part of the body which is carried out through arrangement of bars, pulleys and loads and exerts a pulling force on a part or parts of the body or serves to fixate a part of the body. It is an important feature of the treatment and management of orthopedic conditions such as bone fractures, in children and adults [2, 3].

While traction has been used for years, the underlying central principle remains the same; alignment of a long bone fracture can be achieved and maintained by continuous isotonic traction at a point distal to the fracture on the extremity in line with its longitudinal axis [4]. Traction can also be applied in various clinical condition aside bone fractures including its use in the treatment of scoliosis with the aid of a traction chair. There are several advantages of using a traction; cost-effectiveness, minimal interference with fracture site, its adjustability [5] and more importantly, tractions are safe. Traction when performed intelligently under the supervision of clinical experts can be used in rehabilitating patient who suffer from conditions related to the spine, the upper and lower extremities [6]. Using the straight leg raise test as the endpoint, static traction between 30% and 60% of body weight has been reported to improve leg mobility in patients with low back pain and radicular symptoms [7].

In bones with a high proportion of cancellous bone tissues, fractures caused by pure tensile loads have been observed. Fractures generated by compressive loads, on the other hand, are evident in the vertebrae of elderly people whose bones have weakened owing to age [8]. Bending or torsional forces are the most common causes of long bone fractures. When the wear and tear induced by repeated mechanical stress exceeds the bone’s natural ability to mend itself, a fatigue fracture occurs. The two main types of bone fractures are simple and compound fractures. A simple fracture is one that causes the bone to fail but does not pierce the skin. The smallest of these fractures are often called hairline fractures. A compound fracture, on the other hand, completely breaks the bone and as such, the bone may break through the skin [9].

Fracture management can be conservative fracture management or surgical fracture management. Conservative fracture management involves closed reduction and if necessary, immobilization of the fractured bone and adjacent joint with a cast or splint. Early immobilization should be achieved as soon as feasible to prevent stiffening of the joints [10]. Surgical fracture management is implemented when a fracture cannot be treated with only conservative management but requires surgery for reduction and fixation; as in cases of open fractures and sever dislocations [11]. In fixation reduction methods, bone fragments are brought back to their original position by fixing special medical elements directly to the bone (frames, pins, screws, plates, wires and nails etc.) through surgeries [12].

Like the fractures that occur in long bones, neck pain is a very common problem in the general population and accounts for 15% of all soft tissue problems. Studies show that 26% to 71% of the adult population experience an episode of neck pain or stiffness in their lifetime [13]. Neck pain is one of the leading causes of disability worldwide, with 30%–50% of the population reporting symptoms annually [13]. There are many options that can help ease the pain on the neck. Cervical traction therapy, also known as non-surgical spinal decompression therapy, is one of the possible treatment options frequently included in rehabilitation programs [13].

Medical tractions may not be as popular as they were some decades ago [3] due to modern trends in orthopedic treatment and care [14], they are still heavily relied on for managing orthopedic conditions [15]. Skin tractions provide the pulling force which is exerted on the affected limb through the surrounding soft tissues and serves as the basis for other traction devices such as Hamilton-Russell traction and Thomas splint which are very popular for immobilizing the limbs during treatment after fracture. Previous studies have presented in detail the principles and use of skin traction [3], Hamilton-Russel traction [14] and Thomas splint [15]. Due to its contact with the patient’s skin, the ring of the Thomas’ splint is a substantial potential cause of pressure damage, as it can create both pressure and friction. Frequent ring maintenance, including inspection of the skin behind the ring, especially in the groin and at the gluteal fold, where it is difficult to view and where pressure injuries are most prone to occur, is a major drawback of the Thomas splint traction.

Cervical and lower limb fractures are often managed with separate tractions in the hospital. This can be quite disturbing for both patient and care providers if a patient has combined fractures of both structures in terms of appliance monitoring, maintaining precautionary measures and preventing adverse effects. The modified traction system presented in this study solves the problem of developing pressure injuries associated with the Thomas splint traction as well as provides an attachment for cervical traction which does not exist in the ordinary Hamilton-Russel traction. Patients and care providers will greatly benefit from a traction appliance that could be applied to both structures simultaneously and still produce maximum therapeutic effect. Furthermore, if this appliance is properly designed and adapted, it could be used in patients’ homes, resulting in reduced hospital bills in addition to the emotional/psychological benefit of been cared for in a familiar environment. Thus, this study sets out to design and construct a modified Hamilton-Russel traction system for lower limb and cervical rehabilitation.

2. Method

2.1 Design

The computer-aided design utilized Autodesk (version 2019) to create a 2D and 3-D models of the traction system based on the anthropometric data representative of children and adults in Akure, Nigeria, where the present study was carried out. The anthropometric measures used in the present study is based on recently reported measures for children and adults from recent studies [16, 17, 18] conducted in the same city. The measures include stature, sitting height, and thigh thickness. According to the studies, children (mean age 6.99 $\pm$ 1.33 years) had mean values for stature (124.37 $\pm$ 8.43 cm), sitting height (63.54 $\pm$ 3.93 cm), thigh thickness (8.40 $\pm$ 1.62 cm) and body weight (30.33 $\pm$ 6.46 kg). Older children (mean age 12.86 $\pm$ 1.88 years) had mean values for stature (156.72 $\pm$ 12.52 cm), sitting height (73.05 $\pm$ 6.05 cm), thigh thickness (11.02 $\pm$ 2.22 cm) and body weight (48.01 $\pm$ 12.76 kg). Adult stature and thigh thickness were reported as 173.9 $\pm$ 5.2 cm and 15.3 $\pm$ 1.1 cm respectively for men and 164.1 $\pm$ 4.3 cm and 13.1 $\pm$ 2.5 for women.

2.2 Implementation

In this phase the plans from the previous phase were executed to achieve the expected results. Some factors were taken into consideration during the design and construction of this traction system, including ergonomic considerations, financial considerations, availability of materials, and functional expectations of the eventual prototype. An important element of functionality was the need to have an adjustable system that permits its use for persons of different anthropometric measures. As such, the design and size of the system were based on these measures.

To successfully implement this phase, the following steps were taken:

1.
The metal pipes (diameter, 45 mm) were cut, drilled and welded together as appropriate and based on design, in a metal workshop.
2.
The choice of galvanized metal pipes was due to strength, cost and availability.
3.
The pipes were cut according to the design dimensions.

2.3 Testing

In this phase, the orthopedic traction system was installed and tested in a rehabilitation engineering laboratory to ensure that the traction met all design considerations at minimum risk to users (both patients and clinicians). The following variables were evaluated:

1)
That the system is easy to assemble. Five (5) randomly selected, non-medics were invited to evaluate the ease of assembling the system. It took the group an average of 23.05 $\pm$ 7.7 minutes to assemble the traction.
2)
That the system accommodates both lower limb and cervical rehabilitation and can accommodate various medically approved angles for traction. Under the supervision of a medical practitioner, we had non-fracture, volunteer test subjects lie on the traction system with the various cervical and lower limb traction accessories attached. The traction was found to be long and wide enough to accommodate various angles of traction and volunteers of varied statures.
3)
That the system’s frame is rigid and can sustain the various weights without failure. We tested this by placing different loads, representative of medically approved loads per body weight of patient, on the traction at all ends. The traction system was observed to withstand these various loading conditions, indicative of the strength of assemblage.

2.4 Ethical statement

The present study was conducted in compliance with the ethical guidelines of the Federal University of Technology, Akure, Nigeria. The anthropometric data used for the design was obtained from previous studies as mentioned earlier. Also, volunteers who evaluated the prototype device signed an informed consent and were given detailed description of the purpose of the study. These evaluations involved testing the ease of assemblage of the device as well as ensuring that it accommodates various medically approved angles for traction. This phase of the study did not require an ethical approval as it did not predispose the participants to any significant risk.

3. Result

Three-dimensional (3D) and two-dimensional (2D) images of the design created using Autodesk (version 2019) are shown in Figs 1 and 2. The dimension of the traction system in the computer-aided design (CAD) are in millimeters (mm).

Figure 1.

3-D representation of the isometric view of the traction system.

Figure 2.

2-D representation of the side view of the traction system with dimensions.

The orthopedic traction system developed in the present study is a good option for the rehabilitation of patients suffering from problems affecting the spine and lower extremities. The parts of the system were subjected to stress analyses with various loads hanging from the pulley system. Skin traction use light loads about (2 kg–6 kg) while skeletal traction requires heavier loads (11–18 kg) because they are usually applied for longer period [19]. The test loads were large enough to mimic those used for the rehabilitation of the lower limbs and cervical vertebrae. The loads were in the range of 2 kg–16 kg for skin traction and 11–30 kg for skeletal traction.

Figure 3.

2-D illustration of the two-way traction model showing the neck and lower limb under traction.

3.1 Forces acting within the traction system

The two-way traction model in Fig. 3 shows the directions of forces acting on a person undergoing rehabilitation on the device. The figure depicts horizontal forces exerted via loads, pulleys, and ropes and pulling the cervical area and lower limb away from the body. The force is W (in Newton, N) $=$ m (kg)*g, where m is the mass and g is acceleration due to gravity [9.81 meter per square second]. This obeys the Newton’s third law of motion which says that if body A exerts a force on body B (action), then body B exerts an equal but opposite force on body A (reaction). This means for every action, there must be an equal and opposite reaction. The vertical force on the limb is a balanced suspension that permits the limb to “float” above the bed.

The ratio of the body weight and the frictional force operating in the system may be represented as:

$\displaystyle\mu=F/N$ (1)

where $\mu$ is the coefficient of friction, $F$ is the friction force, and $N$ is the normal force.

The coefficient of static friction, or the frictional force required to maintain the body at rest, between the skin and patient’s bed should be 0.5 [20].

CASE STUDY 1: Hypothetical determination of the frictional force and the traction force needed to rehabilitate a 70 kg patient with a femur fracture. If the weight of the leg is 16.7% of the total body weight [21] and the coefficient of static friction is 0.5 to keep a body at rest, then;

Applying Eq. (1), where $\mu=$ 0.5, N $=$ 11.69*9.81 $=$ 114.7 N F $=\mu$ *N F $=$ 0.5*114.7 F $=$ 57.35N

The percentage of the weight of the leg required to create the traction force can be determined. The traction force has to exceed the frictional force, in this case greater than 57.35N. If we choose forces in the range of 60N–65N, then,

The lower limit of the force yields (60/114.7*100) $=$ 52% of the weight of the leg. The upper limit of the force yields (65/114.7*100) $=$ 57% of the weight of the leg.

Therefore, to rehabilitate the lower limb, the traction force should be between 52% and 57% of the total weight of the leg.

CASE STUDY 2: Hypothetical determination of the frictional force and the traction force needed to rehabilitate a 70 kg patient with chronic neck pain. If the weight of the head is 8.26% of the total body weight [21] and the coefficient of static friction is 0.5 to keep a body at rest, then:

Applying Eq. (1), where $\mu=$ 0.5, N $=$ 5.8*9.81 $=$ 56.9 F $=\mu$ *N F $=$ 0.5*56.9 F $=$ 28.45N

The percentage of the weight of the head required to create the traction force can be determined. The traction force has to exceed the frictional force, in this case greater than 28.45N. If we choose forces in the range of 30N–35N, then,

The lower limit of the force yields (30/56.9*100) $=$ 52% of the weight of the head. The upper limit of the force yields (35/56.9*100) $=$ 62% of the weight of the head.

Therefore, to rehabilitate the neck, the traction force should be between 52% and 62% of the weight of the head.

4. Discussion

During an extensive period of healing, the limb must be supported to assist in maintaining fragment alignment, but the patient should still be able to move other parts as much as possible until union is achieved. This is why a second system of loads and pulleys called “balanced suspension” is often used. Balanced suspension permits the limb to “float” over the bed and facilitates bed pan use and changing of bed linen with minimal disturbance of the fracture. With the traction arrangements, counter traction is a consideration [12]. Counter traction, which is the resistance of the body to move in the direction of the forces exerted by a traction device, is a factor which is built into each setup by utilizing the patient’s body weight. When necessary, the counter traction of the patient’s body weight may be increased by elevation of the foot of the bed or using blanket rolls and sandbags [3].

The concept of controlled and uncontrolled fragment is of importance. A controlled fragment is the one that the surgeon can move into its natural position and the uncontrolled fragment is the part of the bone, which the surgeon cannot move. When considering the lower limb fractures, the proximal fragment tends to remain flexed and abducted no matter how great the traction is [12]. The key is to move the controlled distal fragment into the line of uncontrolled proximal fragment. This reduction can be achieved by applying counter forces against muscle traction, which is called traction reduction [22]. The opposing force to the muscle traction can be applied in three ways; traction with a splint, traction using gravity and traction using a pulley arrangement [11]. The system in the present study is designed to facilitate this type of traction reduction. The horizontal forces acting on the lower limb and cervical region are in two directions; one is applied by the weights pulling the limb and neck towards the direction of the weights and is known as the traction force. The other is applied by the weight of the body opposing the pull of the weights, W, in a direction opposite the direction of the weights; this is achieved by elevating the head and lower limb and is known as a counter traction. The balance between traction and counter-traction is what allows for successful traction during rehabilitation. Until the lower limb heals, the patient should be able to move other parts of the body as much as possible.

Traction pulls are opposed by friction forces. For traction forces to effectively rehabilitate both cervical and lower limb regions, traction force must exceed friction force [23]. There is a mathematical relationship between body weight and the amount of friction force from the treatment surface; this is called the “coefficient of static friction”. The hypothetical cases show how the weight of the patient is needed to determine the weights to be used in the traction system for effective rehabilitation of the cervical and lower limb regions. In the cervical spine, traction forces have to be between 52% and 62% of the weight of the head in order to overcome the friction force between the body of the patient and the surface of the bed. In the lower limb, traction forces have to be between 52% and 57% of the weight of the leg in order to overcome the friction force between the body of the patient and the surface of the bed.

The overall cost of developing the traction system in the present study sums up to around NGN 49,500.00 (equivalent to about $99.50). This is the cost of purchasing the galvanized pipes (7/8” and $\raise 2.15pt\hbox{$\scriptstyle 1$}\kern-1.0pt/\kern-1.5pt\lower 1.075pt\hbox% {$\scriptstyle 2$}$ ” pipes), pulleys, clamps (for the joints), traction load as well as the traction accessories that are attached directly to the patient. This amount is comparatively less than the cost of purchasing a cervical and a lower limb traction in the market as at today. An over-the-door cervical traction (the Neck Stretcher Cervical) which requires the patient to stand/sit on a spot during the treatment time costs around $31.99 on Amazon, and $38.99 on Ebay [24, 25]. Another design (the Fisher traction) that can permit the patient in a lying position cost $99.99 on Amazon. Neither Amazon nor Ebay had a lower limb traction system listed in store at the time of writing this manuscript. A combine cost a cervical and lower limb traction of the Hamilton-Russel type will surely exceed the cost of developing the model in the study. This is a major significance of the design especially for low-income countries.

The Hamilton-Russel does not present with associated problems of pressure in the groin area. When applied properly with adequate nursing care can yield excellent result. The present study has therefore modified the Hamilton-Russel traction to incorporate cervical traction. A mobile bed with attachments that can support a traction frame for lower extremity traction is included in the system. The frame is secured to the bed and designed with the largest available bars and clamps to hold the patient’s injured limb as well as his or her body weight during transfers. It can also fit through entrances and elevators, allowing for cross-hospital transportation [26].

5. Conclusion

The objective of the study was to make an adjustable and easy-to-use traction system. The galvanized clamps make it relatively easy to assemble and to maintain rigidity; the entire traction system was designed to provide adjustable height. The bed used to mount the traction frame is a typical examination couch. This design attaches the traction frame to the examination bed through four points of contact for better weight distribution. Because a cervical traction and a lower limb traction device have been combined into one, it is expected that complete commercialization of this invention would minimize the cost of buying them separately. Patients for whom an orthopedic traction have been prescribed, can also request that the system be placed in their homes, giving them the emotional/psychological advantage of been cared for in a familiar setting. This traction device can be used for both skin and skeletal traction, bare weight variations used in orthopedics and can also be adjusted to various angles as desired by the clinician. In the future, an investigation into clinical outcome and effectiveness of the newly developed traction system on the cervical vertebrae and the lower limb will be conducted.

Footnotes

Conflict of interest

None to disclose.

Funding

The study did not receive any financial support from funding organizations.

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Modified orthopedic traction system for cervical and lower limb rehabilitation

Abstract

BACKGROUND:

OBJECTIVE:

METHOD:

RESULT:

CONCLUSION:

Keywords

1. Introduction

2. Method

2.1 Design

2.2 Implementation

1. The metal pipes (diameter, 45 mm) were cut, drilled and welded together as appropriate and based on design, in a metal workshop. 2. The choice of galvanized metal pipes was due to strength, cost and availability. 3. The pipes were cut according to the design dimensions. 2.3 Testing

3. Result

5. Conclusion

Footnotes

Conflict of interest

Funding

References

1.
The metal pipes (diameter, 45 mm) were cut, drilled and welded together as appropriate and based on design, in a metal workshop.
2.
The choice of galvanized metal pipes was due to strength, cost and availability.
3.
The pipes were cut according to the design dimensions.

2.3 Testing