BIODEVICES 2013 : check!

BIODEVICES is part of BIOSTEC, the International Joint Conference on Biomedical Engineering Systems and Technologies. The purpose of the International Conference on Biomedical Electronics and Devices is to bring together researchers and practitioners from electronics and mechanical engineering, interested in studying and using models, equipments and materials inspired from biological systems and/or addressing biological requirements. Monitoring devices, instrumentation sensors and systems, biorobotics, micro-nanotechnologies and biomaterials are some of the technologies addressed at this conference.

I’m here (in Barcelona) to present my paper! The conference atmosphere is nice and the presentations are really interesting. I especially like the possibility of having some good exchanges with others researchers working in the same fields of study ūüôā

present at this conference!

just wipe that Cataract out of your eye

macchina fotoWe live in the Instagram era, when even a simple cup of coffee suddenly becomes one of the most artistic things to be photographed. After sharing your shot with all your friends on the web (so that you’ll have shown that you DO have a social life, yop!), you put back your Reflex (the best camera ever for shooting cups of coffee, we all know that) and notice that its lens is a bit misted up. Inside. So you’ll never be able to get rid of it and all your shots will look blurry. You’ll be able to post only photos of blurry coffee served in blurry cups on blurry tables. You’ll be a blurry person, forever.

Now, transpose this “blurriness” to one of your eyes. Imagine you have one eye which “works” perfectly, like HD vision, and the other one with some misted up lens inside, so that everything you see looks blurry. This is clearly a much worse problem than not being able to shoot cool photos. This problem is called Cataract and nowadays is¬†the most common cause of vision loss in people aged over 40.

human eyeHuman eye is composed of different layers. Without giving too many details, a very important component of the eye is a transparent tissue known as crystalline lens. This lens is able to change its thickness so that the eye is able to focus on objects at various distances. The changes of thickness are controlled by a suspensory ligament, called Zonule of Zinn, that connects the crystalline to the ciliary body of the eye. Their combined movements are really important for correctly focusing light onto the back of the eye (the retina) so that images appear clear and without distortion.

The crystalline lens is¬†made mainly of water and proteins and it is¬†nourished by the aqueous fluid that is present between the cornea and the crystalline lens.¬†Metabolic changes of the crystalline lens fibers over time lead to the development of¬†opacifications, mainly due to the proteins that clump together. As a consequence, the lens gets “clouded” and this clouding is actually known as Cataract. This process normally worsens the way light enters the eye and, as a result, our sight is blurry.

Cataract vs Normal

Nowadays, modern cataract surgery is one of the safest and most effective surgical procedures.¬†Over 90% of operations are successful in restoring useful vision, with a low complication rate. The operation itself is typically performed¬†using only local anesthesia and in one-day hospitals.¬†Very often, the postoperative recovery is really quick and¬†can greatly reduce the patient’s dependence on¬†eye glasses.

cataract surgeryThe most common surgical procedure for removing cataract is the so called phacoemulsification.

By using a microscope, the surgeon focuses on the lateral side of the eye and makes a small incision on the cornea.

Then, a tiny ultrasound probe is inserted into the eye in order to break the lens. The high vibration frequency (40 kHz) of the probe tip causes the emulsification of the lens material, which gets broken in very small fragments.

By accessing the eye always through the same incision, the crystalline pieces are removed through an aspiration probe.

Next, the same tool is employed again, this time to insert an artificial intraocular lens that actually replaces the crystalline. The artificial lens is usually made of plastic, silicone or acrylic compounds and is supposed to remain in place for the rest of the patient’s life. No stitch is generally necessary, just¬†a protective shield is usually placed over the eye to keep it safe in the early recovery stages.

Recently, lasers have been approved for use in cataract surgery: they improve the accuracy of the surgery, since they reduce the need for surgical blades and other hand-held tools. Moreover, they result to be more efficient than ultrasonic probes for crystalline fragmentation. Laser-assisted cataract surgery is fairly new and significantly increases cataract surgery cost. However, medical consultation is always the best way to evaluate all the possible surgical risks.

sources: one, two and three

hammers, screws and Intramedullary nails

If you study orthopaedics, you’ll know for sure that IM femoral nailthe¬†femur¬†is the¬†longest, heaviest and strongest bone in the human body.¬†One day, by chance, it happens that you see a bar like the one in the picture on the right. Well, maybe you’ll also notice two things: it is as long as your femur bone and it has more or less the same curvature. With a bit of fantasy and science fiction mood, you could even get to figure out a strange surgery where such long bars are plugged into the bones of some patients in order to strengthen their skeleton and create an army of solid soldiers.

There’s no need to invent anything like that, since we are talking about a surgery that already exists (but not for military purposes). Intramedullary nailing consists in forcing a metal nail (or rod) into the medullary cavity of a bone. Normally, IntraMedullary (IM) nails are employed to treat fractures of long bones of the body. Nowadays, this surgery¬†is regarded as the standard of treatment for both femoral and tibial shaft fractures.

Let’s focus on an IM femoral nail. What about its surgery?

First, the surgeon makes use of a¬†Reamer. Wikipedia defines it as a “metalworking tool used to create an accurate sized hole“.¬†¬†The medical version of this device is actually employed to hollow out the center of the medullary canal of the femur, by accessing it from the top (next to the pelvis bone). This doesn’t affect too much the bone solidity and is necessary when the medullary cavity is not continuous (for example, in the case of broken leg injuries).

Once the femur has been properly drilled, an intramedullary nail is tapped into place. This means that a hammer¬†is used to push the rod down into the hollow medullary cavity. In a sense, this action recreates a well-defined medullary cavity in the case of displaced or unstable fractures. Moreover, it obviously provides stabilization for the healing bone (that starts growing again in a proper “shape”).

Finally, screws are usually placed in the head of the femur to secure the nail and prevent its collapse or rotation. During the progressive return to activity, the leg of the patient will take benefit from the fact that the loads will be shared by both the healing bone and its solid metal core. This leads also to a faster rehabilitation period (which requires a first non-weight bearing stage followed by specific exercise programmes).

hammer IM nail

After the implantation, the intramedullary nail is usually left inside the bone forever. In some cases, the patient may develop some long-term complications that cause pain and general ache at the insertion site. In such cases, a second surgery might be necessary to remove the IM nail from the recovered bone. Wikipedia gives us some interesting data about long-term complications of IM nailing for the femur, that “may include persistent or permanent knee pain (present in 73.2% of patients), atrophy of the calf muscle (27.3%), atrophy of the quadriceps (27.3%), and arthritis (35.4%)“.

The following image shows the femoral fracture (A) and the IM nail inserted all along the bone (B), the relatively small scar on the patient’s leg (C) and the recovered bone (D, E).

IM nailing steps

sources: Wiki, Journal of Orthopaedic Science and About.com

Knuckle Popping is addictive

Awesome people always pop their knuckles when they are with someone who clearly state they can’t stand it. The cracking sound that our knuckles (but also our fingers themselves, and sometimes our elbows and knees) produce when we “stretch” them is somehow addictive. I thought it would be interesting to understand what makes our joints pop in this strange way and I asked God Google for that.

First of all we have to focus on Diarthrodial Joints, better known (maybe) as Synovial Joints. We have synovial joints all over our body: in our hands, wrists, arms, but also in our shoulders and knees. Wikipedia actually says that a synovial joint¬†is “the most common and most movable type of¬†joint¬†in the body of a mammal”.

As probably said in joint capsulesome previous post, in this kind of articulation two bones get in contact with each other through cartilage surfaces. A Joint Capsule acts as a connective tissue that folds the whole articulation and keeps everything at the right place, ensuring mobility and stability at the same time. This capsule is filled by Synovial Fluid, which has two main functions:

  • it continuously lubricates the articulation;
  • it is a source of nutrients for the cells that maintain the joint cartilage.

The synovial fluid contains dissolved gases, mainly oxygen (O2), nitrogen (N2) and carbon dioxide (CO2). These gases are responsible for the popping sound we are trying to explain! After this necessary introduction (yep, I’ve just spoiled the name of the murderer), let’s come back to the action of cracking our knuckles.

crack 1 crack 2In order to pop our knuckles, we can stretch or bend our fingers. In any case, the bones of each knuckle joint (which is a synovial joint) pull apart. As we can easily figure out, by doing this the knuckle joint capsule gets stretched.

knuckleThis causes the volume of the joint capsule to increase a bit (+ 15-20%). This slight change of volume is followed by a corresponding decrease of the synovial fluid pressure. As a consequence, the gases in the fluid suddenly become less soluble and they form small bubbles inside the tiny joint capsule. The process of “rapid pressure change -> formation of small cavities in the liquid -> formation of bubbles that immediately implode” is defined by fluid dynamics as cavitation.

The implosion of such small bubbles is thought to be the origin of the cracking sound that we hear while popping our knuckles. It normally takes 20-30 minutes¬†for the gas to properly redissolve into the synovial fluid and reestablish the initial conditions. This means that after more or less half an hour of silence we’ll be able to start having fun again ūüôā

Many people seem to be frightened by the idea that excessive knuckle popping may lead to unpleasant consequences, such as arthritis or sudden death (…). Luckily, a few studies confirm that apparently there is no correlation between knuckle cracking and osteoarthritis in the finger joints.¬†i love itAnother study, however, showed that pathological addiction to knuckle popping may affect the joint capsule soft tissue (higher risk of damages and wear) and worsen hand¬†grip strength conditions.¬†On the positive side, there’s evidence of slightly¬†increased mobility in¬†joints¬†right after popping (mainly thanks to muscle relaxation induced by this action).

In conclusion, we can crack our knuckles¬†whenever we want, but we’d better do it in moderation.

sources: this website, this other one and wikipedia 

Mallet Finger: don’t try this at home

There are a few everyday life experiences that everybody is destined to go through every now and then. Like correctly plugging a USB device only at the third attempt (despite there are only two possibilities), or directly setting the alarm clock half an hour earlier because we know we’re used to putting it off at least four times, or having Mallet Finger.

Mallet Finger is probably one of the most painful and annoying injuries of all time. Technically, it¬†is an injury of the¬†extensor digitorum tendon of the fingers¬†at the¬†distal interphalangeal joint¬†(DIP). In more simple terms, it is the typical injury that occurs when we play basketball and the ball suddenly hits our extended finger. Besides the immediate sensation of pain, within a few minutes our finger will start swelling and we won’t be able to¬†straighten it for a while. We then leave the court with an awesome facial expression (it really hurts, you all know…), but do we know what happened inside our finger?

mallet finger The distal interphalangeal joint (DIP) hinge jointof the hand is nothing more than a hinge joint between the two last phalanges of the finger. This kind of joint only admits one degree of freedom, which is the rotation about the joint axis. As a result, our phalanges are allowed to make flexion and extension movements. Thus, the DIP is the last joint of the finger. A sudden high force acting at the tip of the finger (the ball we were trying to catch) strongly solicits the thin DIP extensor tendon. In case of rupture, or tearing, of this tendon from the bone, the finger usually gets painful, swollen, and bruised. Occasionally, blood can collect beneath the nail. In the worst case, the force of the blow may even pull away a piece of bone along with the tendon. mallet finger bruised The loss of extensor tendon continuity might lead to severe consequences and must be carefully treated. In a first moment, ice should be immediately applied and the hand should be elevated above the level of the heart. Medical attention should be sought within a week after injury. Most mallet finger injuries can be treated without surgery. fingertip splintsNormally, X-rays are necessary in order to look for potential bone fractures or joint misalignment. The presence of blood beneath the nail and nail detachment may be a sign of nail bed laceration or open (compound) fracture. A splint can be applied to hold the fingertip straight (in extension) until it heals (8 weeks full-time, 3-4 further weeks less frequently). With this treatment plan, the finger usually regains an acceptable function and appearance. Despite that, it is not guaranteed that the patient will be able to regain full fingertip extension.

If nonsurgical treatment fails, after mallet finger surgeryconsultation with an orthopaedic surgeon the patient may consider to resort to surgical repair. In case of very severe deformity or inability to properly use the injured finger, surgery is done to repair the fracture using pins, pins and wire, or even small screws. Surgical treatment of the damaged tendon can include tightening the stretched tendon tissue, using tendon grafts, or even fusing the joint straight.

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sources: mainly this website and this website, and then Google Images

the Ankle Joint: some hints

The ankle is the region where the foot and the leg meet. The ankle joint is actually composed by three smaller joints:

  1. the ankle joint proper, commonly called ankle mortise joint (but also talocrural joint).  It is a synovial hinge joint that connects the distal ends of both the tibia and the fibula in the lower limb with the proximal end of the talus.
  2. the subtalar joint, that occurs at the meeting point of the talus and the calcaneus.
  3. the inferior tibiofibular joint, between the fibula and the tibia. More precisely, it is formed by the rough, convex surface of the medial side of the distal end of the fibula, and a (corresponding) rough concave surface on the lateral side of the tibia.

ankle joint and its three sub-joints

The boney architecture of the ankle consists of three bones: the¬†tibia, the¬†fibula¬†(in the leg)¬†and the¬†talus¬†(in the foot).¬†The talus is also called the¬†ankle bone since it’s the most important bone in the ankle articulation.¬†In normal health conditions, the articulation between the tibia and the talus (ankle mortise joint) bears the greatest part of body weight: it is the region where ankle efforts are mostly concentrated.

The medial malleolus is a boney processmalleoli extending distally off the medial tibia. There is also a lateral malleolus, generated by a distal-most aspect of the fibula. Together, the two malleoli, along with their supporting ligaments, stabilize the talus underneath the tibia.

The ankle joint is bound by the strong deltoid ligament (it is attached at the medial malleolus of the tibia and supports the medial side of the whole joint) and three lateral ligaments: the anterior and posterior talofibular ligaments (they support the lateral side of the joint, from the lateral malleolus to the dorsal and ventral ends of the talus) and the calcaneofibular ligament (it is attached at the lateral malleolus and to the lateral surface of the calcaneus).

ankle ligaments

Achille's tendonThe calcaneus is also attached to the Achille’s tendon¬†(also known as the¬†calcaneal tendon¬†or the¬†tendo calcaneus), that is a tendonous extension of gastrocnemius¬†and¬†soleus¬†muscles of the leg. It attaches the heel to the¬†posterior¬†leg.

Concerning the joint motion, the ankle joint theoretically admits 1 degree of freedom: movements of plantar flexion and dorsiflexion.

ankle motions

In addition to these, the geometry of the different bones that form the articulation permits other more limited movements, such as foot eversion and inversion.

sources: Wikipedia and this website

the Hip Joint: some hints

The¬†femur head¬†(Latin:¬†caput femoris)¬†hip joint bonesis the highest part¬†of the thigh bone (femur).¬†It has a roughly semispherical shape, with a short ‚Äúneck of the femur‚ÄĚ angling the head anteriorly, medially and superiorly to fit into the acetabulum of the pelvis bone.

The acetabulum, also called socket, is the cavity in the pelvis which “hosts” the femur head. It is¬†formed by three innominate bones: the ilium, the ischium and the pubis.

The femur head’s surface is smooth and normally coated with¬†cartilage. It¬†is supported by the neck of the femur and¬†gives attachment to one single intracapsular ligament,¬†the “ligament of head of femur” (ligamentum teres, on the top of the femur head in the figure on the left). head of femur and its ligamentIt may be not¬†that important as a ligament (it is only stretched when the hip is dislocated, and may then prevent further displacement) but can often be vitally important as a conduit of a small artery to the head of the femur. This small artery¬†is not present in everyone but can become the only blood supply to the bone in the head of the femur when the neck of the femur is fractured or disrupted by injury in childhood.

The femur head together with the acetabulum form the hip flexion-extensionHip Joint. The hip joint has three degrees of freedom, since it can move in three different planes:

  1. sagittal plane: flexion/extension of the leg.
    With just this movement, approximately 3 to 3¬Ĺ times the body weight acts on the hip joint. An example of this motion is shown by the figure on the right.
  2. hip adduction-abductionfrontal plane: abduction/adduction of the leg. Regardless of the direction, the respective supporting leg is then subject to approximately 3 times the body weight. This kind of motion is represented by the figure on the left.
  3. transverse plane: external/internal femur rotationrotation of the femur with respect to the pelvis bone. This motion, typical when crossing  legs, makes the femur head rotate in several directions. An example is shown by the figure on the right.

The head of the femur is attached to the femur shaft by a thin neck region that is often prone to fracture in the elderly, which is mainly due to the degenerative effects of osteoporosis. If there is a fracture of the neck of the femur, the blood supply through the ligament becomes crucial. In orthopedic surgery, the Total Hip Arthroplasty surgery consists in removing the femur head and the acetabulum and replacing them with a total prosthesis.

Normally, the two involved prosthetical components are:

  1. the Acetabular Cup, a shell that fits the pelvistotal hip prosthesis components bone to replace the acetabulum. It is usually attached to the bone by using friction or cement. Additional fixation can be achieved by means of screws.
  2. the Femoral Component, that is a stem with attached prosthetic femoral neck and head (a ball that fits the Acetabular Cup). Femoral bone is removed and the femur is shaped to accept the femoral stem.

The figure below shows the difference between a healthy hip (on the left) and a prosthetic hip (on the right).

hip before and after

sources: Wikipedia, this website and this other website

the Knee Bursae: some hints

The bursae of the knee can be defined in a very simple way: they are fluid sacs, or synovial pockets. This second definition comes from the sinovial fluid that fills them.

Synovial fluid is¬†made of hyaluronic acid and lubricin, proteinases and collagenases. Its main functions are¬†reducing friction by lubricating the joint, absorbing shocks and properly “feeding” joint cartilage. In the case of the knee, the Knee Capsule encloses the Knee Cavity which is filled with synovial fluid.¬†Knee Bursae surround and sometimes communicate with the Knee Cavity, as we can see in the picture.

Usually Knee Bursae are thin-walled and represent the weak point of the joint. At the same time, their presence is really important since they enlarge the joint space. They can be grouped according to:

  • their characterization as¬†communicating¬†and¬†non-communicating¬†bursae. A communicating bursa is when a bursa is located adjacent to a joint, thus having the synovial membrane in communication with the joint itself.
  • their location (frontal, lateral, medial).

In pathological conditions, such as excessive local friction, infection, arthritides or direct trauma, fluid and debris collect within the bursa or fluid extends into the bursa from the adjacent joint. As a consequence, the walls of the bursa thicken as the bursal inflammation becomes longstanding. The term bursitis refers to pathological enlargement of the bursa. Clinically, bursitis mimics several peripheral joint and muscle abnormalities.

   

<–prepatellar bursitis

¬† ¬† ¬† ¬† ¬† elbow bursitis–>

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sources: Wikipedia and this website

accepted for publication

Title:

Towards a Dynamic Tibial Component for Postoperative Fine-tuning Adjustment of Knee Ligament Imbalance

Authors:

Andrea Collo, Shaban Almouahed, Chafiaa Hamitouche, Philippe Poignet, Eric Stindel

Accepted for Publication at:

BIODEVICES 2013 Р6th International Conference on Biomedical Electronics and Devices (conference official website)

Patellar Reflex

definition _

Patellar Reflex, also called knee-jerk, is a stretch reflex associated with quadriceps femoris muscle stretching.

how it works _

The stretch is created by a blow upon the patellar tendon (positioned just below the Patella). This blow, usually performed with a specific tendon hammer, activates the muscle spindle in the quadriceps femoris muscle.

Muscle spindle is a particular type of sensory receptor, normally embedded in muscle fibers, able to¬†detect changes in the length of the muscle itself. Once “activated” by the external blow, this receptor sends a signal to the spinal cord. Instead of involving higher nervous centres (it would take too long), at the level of the spinal cord an alpha-motor neuron is immediately activated.

The alpha-motor neuron conducts an efferent impulse directly back to the quadriceps femoris muscle, leading to its contraction. At the same time, an inhibitory interneuron¬†relaxes the hamstring muscle,¬†which is the quadricep’s antagonistic muscle.

The result of such coordinated contraction-relaxation, causes the “kick movement” of the leg. In normal health conditions, the leg extends once and then comes back to rest.¬†It only takes about 50 milliseconds between the tap and the start of the leg kick.

why it is useful _

Patellar Reflex is a proprioceptive reflex which helps keeping posture and balance. The fact that everything “happens” at the level of the spinal cord, without involving higher nervous centres, allows for instance to keep balance without effort (actually, one does not have to focus on keeping an upright position). Energies are saved for more complex activities.¬†Moreover,¬†Patellar Reflex helps avoiding strong muscle contractions which could tear the tendon.

clinical interest _

As said, there is no interneuron in the pathway leading to contraction of the quadriceps muscle. Patellar Reflex can be used, for example, to check the conditions of the connections between the spinal cord and the muscles.

The absence or decrease of the Patellar Reflex is known as¬†Westphal’s sign. On the other hand, multiple oscillation of the leg following the blow may be a symptom of¬†cerebellar diseases.

source: contents taken from Wikipedia’s page