What is the Translumbar Interbody Fusion?

Firstly there are many sites that cover this topic and they all give different methods and ways of performing the operation. Before you research you will need to find out if you are having a posterior or anterior operation. If it is posterior you need to search the words PLIF if its anterior then ALIF. I will be post more on the PILF as that is what I had performed

You will also find many varied opinions from people who say that having surgery is the worst thing you can do to those that swear by it. My consultant/surgeon gave me the opportunity to speak to one of his former patients and I found this very helpful. I also did a search on my surgeon and found that he was one of the leading surgeons for my area so I felt a lot more comfortable facing the prospect of surgery. I personally wanted to be assured 100% that I was making the right decision because there is a very long list of risks associated with this surgery and I needed to make an informed decision.

Posterior Lumbar Interbody Fusion (PLIF)

Posterior lumbar interbody fusion (PLIF) is a surgical technique for placing bone graft between adjacent vertebrae (interbody). Typically, screws and rods or other types of spinal instrumentation are used to hold the spine in position while the bone heals. Indications for this procedure may include pain and spinal instability resulting from spondylolisthesis degenerative disc disease or when a discectomy is performed to relieve nerve compression and the patient has associated mechanical low back pain.

Spinal fusion uses bone graft to promote specific vertebrae to grow or fuse together into a solid and stable construct. Instrumentation, also called internal fixation, incorporates the use of rods, screws, cages, and other types of medical hardware to provide immediate stability to the spine and facilitate fusion.

Minimal Access Spinal Technologies
Today, spinal surgery has advanced to a new level that utilizes Minimal Access Spinal Technologies (MAST). These technologies replace traditional open surgical procedures with innovative minimally invasive techniques and tools. To grasp the importance and benefits of minimally invasive spine surgery, review the following comparison:

Open Approach
A longer incision along the middle of the back is necessary. Large bands of muscle tissue are stripped from the underlying spinal elements including the spinous process, lamina, and facets. These tissues are pulled aside (retracted) during surgery to provide the surgeon a good view of the spine and room for performing the procedure. During complex spine surgeries, these surrounding tissues (paraspinous) may need to be retracted for long periods of time. Stripping the paraspinous tissues and retracting them can contribute to post-operative pain and prolong the patient's recovery.

Minimally Invasive Approach
In minimally invasive procedures, the surgical incisions are small, there is no need (or minimal need) for muscle stripping, there is less tissue retraction, and blood loss is minimized. Special surgical tools allow the surgeon to achieve the same goals and objectives as the open surgery while minimizing cutting and retracting of the paraspinous muscles. Therefore, tissue trauma (injury) and post-operative pain are reduced, hospital stays are shorter, and patients can recover more quickly.

Open PLIF Procedure
A typical PLIF procedure involves an open incision (approximately 6 inches long) in the middle of the lower back followed by stripping the paraspinous muscles away from the spine. Bone removal (laminectomy) and lumbar discectomy are performed to remove pressure from affected spinal nerve roots. When the offending disc is removed an empty space is left between the upper and lower vertebrae (interbody). This is filled with bone graft. Implants made of bone, metal, or other materials are typically inserted into the interbody space. Finally, pedicle screws are placed into the upper and lower vertebrae and connected with rods or plates.

This info was taken from the spine universe website. The following links discuss the PLIF further and is the most informative site I have come across.

http://www.spineuniverse.com/displayarticle.php/lumbar-fusion-3115.html Discusses the history of the operation

http://www.spineuniverse.com/displayarticle.php/lumbar-fusion-3116.html Discusses the advantages and Indications

http://www.spineuniverse.com/displayarticle.php/lumbar-fusion-3117.html Discusses the surgical techniques

Anterior Lumbar Interbody Fusion (ALIF)

Introduction

Spinal fusion for the management of lumbar degenerative disc disease has been available for several decades. The results of this procedure remain under constant scrutiny and progressive development. Anterior lumbar fusion was initially introduced in the early 1920s. Fibula and iliac struts, femoral rings and dowel, as well as synthetic metallic devices have been applied as fixation implements to aid in lumbar interbody fusion. Approaches to the spine have experienced similar evolutionary changes. Prior to the 1950s most anterior lumbar approaches were extensive transperitoneal exposures (i.e. through the membrane lining the walls of the abdominal and pelvic cavities). In 1957, Southwick and Robinson introduced the retroperitoneal approach (i.e., behind the peritoneum). Transperitoneal exposures (i.e., through the peritoneum) require incision of both the anterior and posterior peritoneum. In contrast, retroperitoneal expoures maintain the integrity of the peritoneum and approach the spinal column laterally behind the bowel and peritoneal contents. This has the advantage of less post-operative bowel problems. Additional changes in technique have seen the advent of minimally invasive approaches, including endoscopic and laparoscopic methods. Minimally invasive approaches are generally directed at one or two-level disease processes. Anterior lumbar interbody fusion (ALIF) may be useful in the treatment of unyielding low-back pain. The cause of this pain is often difficult to diagnose. Broad categories of pathology that may be associated with persistent low-back pain include degenerative disc disease spondylolysis, spondylolisthesis or iatrogenic segmental instability.

ALIF should only be considered following the patient's unsuccessful completion of an organizednonoperative rehabilitation program. Aids to diagnosis in the case of a patient with mechanicallow-back pain expand upon a thorough history and physical examination. Radiographic studies;plain films, bone scan (SPECT), CT scan, MRI and discography, all play a role in patient evaluation. Frequently more than one of these diagnostic studies is needed for an accurate diagnosis. ALIF may be utilized as an isolated procedure or in conjunction with posterior spinal fusion. The method with which ALIF is accomplished depends largely on the surgeon's preference and experience. Minimally invasive techniques - open or laparoscopic - require greater intraoperative attention to detail and preoperative surgical planning.

Indications for ALIF Degenerative Disc Disease

The suspected lumbar level requires confirmation as a pain generator by diagnostic testing. Multilevel disease, i.e., greater than two levels of the spine, is less predictable and therefore rarely indicated for ALIF. We have found that single-level disease in a psychologically stable patient, responds well to ALIF.

Spondylolysis and Spondylolisthesis

The vast majority of patients with spondylolysis or spondylolisthesis do not require surgery. Patients with spondylolysis or spondylolisthesis (grade I) may be effectively treated with ALIF as an isolated procedure. Present data is inconclusive regarding the effectiveness of isolated ALIF in grade II spondylolisthesis. Furthermore, biomechanical data related to the degree of vertebral translation concomitant with grade III or greater spondylolisthesis implies that isolated ALIF may be associated with a high pseudoarthrosis rate (failure of fusion). Therefore, in grade III or greater spondylolisthesis, a posterior fusion in addition to ALIF is strongly recommended. ALIF as the only procedure (i.e. without a posterior operation), is not recommended in a spondylolesthesis above grade I.

Iatrogenic Segmental Instability

Hypermobility of a lumbar-motion segment requires rigid fixation to improve fusion rate. Limited sagittal translation may be addressed by isolated ALIF. As inferred above, high degrees of translation are difficult to stabilize; therefore circumferential fusion is often required.

Surgical Technique

While the technique is both skilled and complex, it can be explained in three basic phases:

1) Pre-operative Templating Before the surgery, the surgeon will refer to various MRI and CAT scans of the patient to determine what size implant(s) the patient will need. The implant(s) are used to help promote fusion of two vertebra in the spine.

2) Preparing the Disc Space After the patient is positioned on the OR table and carefully prepared for the surgery, the surgeon begins the procedure. Some of the disc and anaulus is carefully removed, thus preparing the disc space for insertion of the implant(s).

3) Implants Inserted After correct preparation of the disc space a dowel or other implant will be inserted, to promote fusion of the two adjacent vertebra.

Lumbar Facet Joint Injection

What is a Lumbar Facet Injection?

A facet injection will place a numbing fluid into the joint whilst a steroid medicine will also be added. This is normally a time released cortisone which will help to reduce any inflammation. The numbing medicine first used can provide immediate relief as it did in my case.

The Procedure

The patients are placed on the X-ray table on their stomach in such a way that the physician can best visualize these joints in the back using x-ray guidance. The skin on the low back is scrubbed using 2 types of sterile scrub (soap). Next, the physician numbs a small area of skin with numbing medicine. This medicine stings for several seconds. After the numbing medicine has been given time to be effective, the physician directs a very small needle, using x-ray guidance into the joint. A small amount of contrast (dye) is injected to insure proper needle position inside the joint space. Then, a small mixture of numbing medicine (anesthetic) and anti-inflammatory (cortisone/steroid) is injected. One or several joints may be injected depending on location of the patients usual pain.

Post Procedure

Immediately after the procedure, the patient will get up and be asked to ambulate try to imitate something that would normally bring about their usual pain. Patients are then asked to report the percentage of pain relief

The leg(s) may feel weak or numb for a few hours. This is fairly uncommon, but does occasionally happen. The patient may be referred to a chiropractor or physical therapist immediately after the injection(s) while the numbing medicine is still working for manipulation or massage.

Risks

Although these are pretty infrequent this was all I could find when I researched it. Nerve damage, bruising at the site, infection at the injection site.

My Opinion

This worked really well for me and gave me 2 - 3 months of very little pain. I even went surfing after this and thought everything was fixed. What I did not take into account was that for some people this is just a temporary fix and for others it can be a permanent fix. After the 2-3 months I was back where I started and it felt more pain full probably because without the pain I had been a little more than previously. The procedure is not really painful and minimal discomfort.

Lumbar Discography (Discogram)

Firstly before I go into detail about this it must be said that if you research the Internet you will find many varied responses from specialists regarding this procedure and most class this procedure as a controversial one. This is taken from one website;

• The protagonists of discography believe the information gleaned from this examination is unobtainable any other way.


• The procedure’s antagonists feel the responses evoked from disc pressurization are not useful in evaluating back pain patients.
  

What is a Discogram?

A discogram is a study in which radioopaque dye is injected into the disk space. This is both an anatomical study as well as a functional study. It looks at the anatomy of the disk space, and can show when dye leaks through rents in the annulus fibrosis. But just as or even more important, it is a functional test. When the physician injects dye into the disk space, the patient reports, on a scale from 1 to 10, how much pain has been produced. If the pressure injection of dye into the disk space reproduces the patients usual low back pain, then surgical fusion of the disk space may have some benefit in improving the pain. As far as the low back team knows, it is the only test in which we hope a patient has significant pain, because that means the disk is likely a cause of the pain, and surgical fusion may help. This is usually a method of last resort, after all else has failed.

The Procedure

This is the procedure that I underwent and may be somewhat different for you but will give the basic outlines.

Firstly I will tell you the procedure is very uncomfortable and painful. I was laid on my side with my lumbar region exposed. I was given a sedative but you are very much aware of what is happening. An X ray machine was used so that the correct disk space can be obtained and the radiopaque dye can be injected into the disk space. This will create pain and indicate whether the disk is the problem and if surgery will help. Unfortunately in my case it did not create anymore pain. I also had 24 hours bed rest after this procedure which is the normal aftercare.

The picture below shows the needle entering the disc space

The Risks

As with any procedure there are risks but the main risk here is infection of the disk and the injection area and possible bruising of the injection site. As it replicates the pain obviously there may be some aggravated sides like the ones you experience with your normal daily pain.

My Opinion

This did not work for me at all and I found it very uncomfortable. If you can get away without having this done go for that option. Before even contemplating this all I would say is exhaust the other options first.

The MRI Scan

As taken from the BUPA fact sheet

MRI scan
This factsheet is for people who are considering having an MRI scan or for people who would like information about MRI scans.
A magnetic resonance imaging (MRI) scan is a special technique that uses magnets and radiowaves to produce two and three-dimensional pictures of the inside of the body. These images can help your doctor to make a diagnosis about a number of conditions.

About MRI
The magnetic field produced by an MRI scanner allows radio receivers (placed close to the body) to detect tiny signals from inside the body. A computer turns these tiny signals into two or three-dimensional pictures.
MRI may be used to make images of many parts of the body. Different types of tissue show up in different shades of grey on a computer-generated image. Abnormalities can be seen as darker or lighter areas in some tissues.
Depending on the part of the body being examined, having an MRI scan may involve being enclosed in a fairly narrow space. If you are worried about this aspect of the scan you should speak to your doctor in advance. Having an MRI scan does not hurt. It does not use X-rays and you are not exposed to radiation.

Illustration showing an MRI scanner

Why have an MRI scan?
An MRI scan can help a doctor make a diagnosis and has many uses including:
orthopaedic examinations screening and assessing cardiac conditions brain imaging to find the cause of a stroke, for example detecting suspected abnormalities in the body such as abscesses, abnormal blood vessels and tumours pinpointing the exact site of tumours before radiotherapy

Who can have an MRI scan?
Not everyone can have an MRI scan. The magnetic fields and radiowaves can seriously affect implants of metal in the body. This includes anyone who has: a heart pacemaker a cochlear implant (an internal hearing aid) metal heart implants such as prosthetic metal valves
metal surgical implants such as surgical clips or pins or rods in bones surgical implants to stop bleeding in the brain had pieces of metal removed from their eyes (due to welding or metalwork for example)

Can pregnant women have an MRI scan?
An MRI is not usually performed on pregnant women unless there is an urgent medical reason for the scan. This is because the long-term effects of strong magnetic fields on a developing baby are not yet known.

What are the alternatives?
Generally speaking, MRI provides a more detailed soft tissue image than other scans, such as a CT scan.
In some cases, depending on individual factors such as your symptoms and the specific condition being investigated, there may be alternatives to having an MRI scan. These include:
an ordinary X-ray a CT (computerised tomography) scan - for more information please see the separate BUPA factsheet, CT scan ultrasound a nuclear medicine scan which uses radioactive tracers to create images

What happens before the scan?
An MRI scan is usually performed in a hospital. In many cases no preparation is required.
Before the MRI scan you will usually talk to your radiologist or radiographer about the scan and you may be asked to sign a consent form. This confirms that you understand the risks, benefits and possible alternatives to the procedure and have given your permission for it to go ahead. You may also be asked to fill out a questionnaire which will ensure that it is safe for you to have the scan.
Some types of metal can interfere with the scan, so you will be asked to remove metal objects such as coins, keys, and jewellery. It is best to wear clothing that does not have metal zips, buttons or other metal parts such as underwired bras. Relatives or friends who wish to accompany a patient in the MRI room must also follow these guidelines.

The scan
An MRI scan is performed as a day case, which means that you can have the scan and go home the same day. An MRI scan is painless so the procedure does not usually require an anaesthetic. However it can be uncomfortable lying still for this length of time, particularly if you have a painful condition, so you may be offered a sedative which will relax you.
Small children may also be offered a sedative and sometimes a general anaesthetic.
The scan itself can take from 15 minutes to an hour to perform, depending on the specific examination, but you should allow at least two hours for the whole appointment.
You will lie on a table which will be moved inside a large "tube", which generates the magnetic field. You may need to enter the tube head-first or feet-first depending on the part of your body that is being scanned. Generally the part of your body to be examined will be placed in the middle of the tube. The tube is open ended so you will not be enclosed at any time.
A radiographer operates the scanner from behind a window, and will be able to see and hear you throughout the procedure. You may be given a call button to hold during the scan which you can press to get the radiographer's attention at any time.
It can take several minutes for each picture to be taken, and it's important to lie very still and breathe quietly during the process. The machine will make quite a loud knocking or buzzing sound so it may help to wear earplugs. In some units, music is played to help you relax. When the scan is complete, the table will be moved back out from the scanner.

What to expect afterwards
Once the examination is over, most people can resume their normal activities immediately. However, if you have had a sedative, you will need to arrange for someone to drive you home and then stay with you for the first 24 hours.
The pictures taken by the MRI scanner will be interpreted by a radiologist, who will send the results to your doctor or specialist.

Deciding whether to have an MRI scan
An MRI scan is a commonly performed and safe procedure. For most people, the potential benefit is greater than the disadvantages. However, in order to make a well-informed decision and give your consent, you need to be aware of the possible side-effects and the risk of complications.
Side-effects are the unwanted but mostly temporary effects of a successful procedure. The MRI scan itself does not usually have any physical side-effects. However, if a contrast medium is used, you may experience a temporary flushing when you are given the injection. This usually passes within seconds. People who have metal fillings in their teeth may also feel a tingling during the scan.
Complications are unexpected problems that can occur during or after the procedure. Most people are not affected. Complications that may arise from an MRI scan are related to the contrast medium, and include an allergic reaction to the dye. Different people may have different reactions to the dye - let the radiographer know if you feel uncomfortable or are short of breath during the scan. Allergic reactions happen only occasionally and can be treated immediately with appropriate medicines.

My Opinion of the MRI
I have now had 3 MRI scans and have found no problems with these at all. They are straight forward and over in the space of 15mins. For the Lumbar region you do not need to stop eating before it and you don,t have any injections. It is a simple case of get changed into a gown,lie on a table that moves into the enclosed area listen to a few bangs and you are back out and off home.

Keeping Fit / Active with back pain

This was so important to me as I have always trained and been very active with Martial Arts,weight training,Surfing so I needed to keep active.I found various things helped me keep active even at times kept me sane!

I found my specialist was quite helpful I would suggest what I could do and he would agree yes or no. You really need to speak to your specialist or health care professional to find what is right for you but I believe keeping active helps in the long run even helps after the operation.

Budokon
This is a form of martial arts/yoga type of training. You can buy a DVD http://www.budokon.com/store.php?selected=dvds&dvdselect=4#desc
(I bought mine off E-bay as it was cheaper) and you can do it in your own home. The martial arts side of it helps to build inner core strength and the yoga/stretching side of it helped greatly. I did not find this that stressful on the back but the kicks may make your back ache if you are not used to them.

Light weight training
I kept this light and the reps high and stayed away from heavy multi compound movements like the squat,deadlift. If you are into keeping fit and train either at home or in a gym this is another site I have found invaluable for putting routines together to suit my back pain. You can pick and choose your exercise and watch it being performed http://www.exrx.net/Lists/Directory.html I would recommend keeping away from exercises like lower back rows and bent over rows.

Keeping Active
As strange as it seems but even things we take for granted like walking can be a mission once you have a back injury I found this hard as my left leg is weaker than my right since the injury and sciatica would kick in,however I found walking a lot slower or cycling would not aggravate it. I would stay away from rowing machines as I found this increased the pain greatly. The bottom line is some form of exercise will help keep you fit release those happy endorphins which are said to improve our moods and to have an analgesic effect. No excuse not to exercise!

Non operative treatments

After the initial injury I underwent various forms of treatment before my MRI scan. You must remember that these are just my thoughts on the treatments and really have no medical basis to them at all.

Physio
I personally found this did very little but aggravate my condition further. For some people I have spoken to this has helped greatly. For me and being as active as I was before the injury it did very little. I did pursue this with hope that it would help release what was thought a trapped nerve. Any sort of movement will help and all I can say is if you are offered physio it is well worth giving it a go as it may work for you and then you won,t need to read this any further! I pursued this once a week for 3 months before giving it up.

Traction
Traction treatments can use a mechanical device consisting of a systems of weights, cables, and pulleys in an attempt to reduce pressure on the disks and the joints between the vertebrae. It was thought that such traction as well as stretching muscles and connective tissues of the back might have a beneficial effect.
I tried this and was placed on a split table and secured in a pelvic harness. I had four sessions of this and all it managed to do was pull my neck and give me unbelievable back pain almost to the point where it was near on impossible to walk the next day. If do you a search on the Internet you will find that this is a very old form of back treatment but one that is very open ended about the results and none of them seem to be conclusive about whether it actually helps or not. Personally it did not work for me and nor world I try it again

Manipulation
This is an ancient art of correcting the back and allows the chiropractioner to arrange and sort out the biomechanical and structural derangement of the spine which can affect the nervous system. This did nothing for me as doing weights and power lifting for years it was found that the lumbar muscles were spasming against the pain and allowed very little movement and maniuplation of the spine. It is worth trying this though and even though it was not possible for me it is something I believe can work.

Acupuncture
In traditional Chinese acupuncture, needles are inserted into specific areas of the body. The needles are then rotated to produce a mildly irritating stimulus. Evidence that acupuncture is effective for treating patients with chronic low back pain is not dependable. Acupuncture has not been sufficiently studied in patients with acute low back pain to permit a conclusion. Acupuncture was found to have risks of complications, including bacterial and viral infections, bleeding, and nerve injury.
I had 6 sessions of acupuncture and I was very skeptical of the results but found it did help greatly. The first 4 sessions really improved my mobility but the last 2 did not do so much and I found I bled a lot after the needles were removed. Again something I have spoken to many people about and they have had success with it. I would recommended giving it a go and maybe for people that do not like needles they could give acupressure a try? This is where the same points are used on the body but the pressure is applied by the hands.

Drugs&Painkillers
You,ll find that you will be offered these in abundance, just remember they all have side effects. I do not really like taking pain killers but at times the pain is so bad that you need to. I found that after 12 months of taking painkillers I developed a stomach ulcer which was put down to the painkillers. Maybe I have a weak stomach or my body just does not like them but I have found Ibuprofen gels (Like Ralgex/Deep Heat) work well.

Hot&Cold Treatments
Cold treatments did nothing for me apart from make my back stiff however the heat pads and hot baths were the only time I actually felt right and the warmth really does help loosen the muscles and back up. Even now after the operation I found a hot bath really helps

What is Degenerative disc disease? (DDD)

Degenerative disc disease (DDD) is part of the natural process of growing older. Unfortunately, as we age, our intervertebral disc lose their flexibility, elasticity, and shock absorbing characteristics. The ligaments that surround the disc called the annulus fibrosis, become brittle and they are more easily torn. At the same time, the soft gel-like center of the disc, called the nucleus pulposus, starts to dry out and shrink. It is also worth noting that DDD can be caused by simply lifting which can cause microscopic tears and allows the discs in the spine to dry out.

The combination of damage to the intervertebral discs, the development of bone spurs, and a gradual thickening of the ligaments that support the spine can all contribute to degenerative arthritis of the lumbar spine.

Degenerative disc disease is as certain as death and taxes, and to a certain degree this process happens to everyone. However, not everyone who has degenerative changes in their lumbar spine has pain. Many people who have "normal" backs have MRIs that show disc herniations, degenerative changes, and narrowed spinal canals. Every patient is different, and it is important to realize that not everyone develops symptoms as a result of degenerative disc disease.

When degenerative disc disease becomes painful or symptomatic, it can cause several different symptoms, including back pain, leg pain, and weakness that are due to compression of the nerve roots. These symptoms are caused by the fact that worn out discs are a source of pain because they do not function as well as they once did, and as they shrink, the space available for the nerve roots also shrinks.

As the discs between the intervertebral bodies start to wear out, the entire lumbar spine becomes less flexible. As a result, people complain of back pain and stiffness, especially towards the end of the day.

Symptoms

The most common symptom of degenerative disc disease is back pain. When DDD causes compression of the nerve roots, the pain often radiates down the legs or into the feet, and may be associated with numbness and tingling. In severe cases of lumbar DDD, where there is evidence of nerve root compression, individuals may experience symptoms of sciatica and back pain, and sometimes even lower extremity weakness. Degenerative disc disease can lead to a chronic debilitating condition and can have a serious negative impact on a person's quality of life. When pain from degenerative disc disease is severe, traditional nonoperative treatment is often ineffective.

My Symptoms

These ranged from the classic pain in the back and down the left leg to sciatica. I also had a lot of numbness in the left leg and an occasional cold water feeling running down the back of my legs. I also experienced severe numbness in the groin and down both legs with the loss of feeling in the right leg in the later stages of my injury before the operation.

A bit about the blog and why I,m writing it

The main reason for creating the site was to give an opinion on the procedure of Translumbar Interbody Fusion (TLIF) after being told this was the surgery I required in Dec 2007. Before consenting to the operation I wanted to know the facts but found there was very little information on the Internet and most of it was medical based. What I wanted to read was other peoples opinions,how they found the recovery,the issues with the limitations whilst recovering from the operation.

Before the injury I was an active 32 year old who enjoyed martial arts, weight training, surfing and generally keeping active. Never had back pain in my life yet January 2006 whilst trying to move something I stood up and lost all feeling in my legs and was unable to walk.

What unveiled after that was 6 weeks off work and endless appointments with my Doctor and over those 22 months I did everything I could to prevent the operation. I underwent extensive physio, traction, acupuncture, chiropractioner, lumbar faucet injections, discography.

I was told I had degenerative disease of the L5 disk and despite the acute pain I proceeded to try and live a normal life and continued to do light weight training as long gone are the days were specialists encourage you to lie in bed all day!

At the point of writing this I,m 3 weeks out of my operation and recovery is well on the road. It has not been all easy but like any operation remaining positive afterwards is a must.

During the course of adding posts to the blog I,ll describe the different treatments I had. Maybe some will contain links to information I sourced or just my own opinions of it.

I hope the blog will be of some use and just give you another view of someone who has undergone the operation and giving an honest account of it all.