Spondyloarthropathy is a group of distinct inflammatory arthritis with certain genetic predisposition factors and clinical features. This group mainly includes ankylosing spondylitis reactive arthritis (including Rett syndrome) psoriatic arthritis inflammatory bowel disease Disease-associated spondyloarthropathy and undifferentiated spondyloarthropathy.   Level 5
The main pathological sites are the sacroiliac joints, the bony insertion of the fibrotic ring of the intervertebral disc, and the condyle joints of the spine. 
Ankylosing spondylitis (AS), also known as Marie-Strumpell disease or bamboo spondylosis, is an inflammatory joint disease of the axial skeleton, usually involving the sacroiliac, condyle, costovertebral, and disc joints.  AS is a chronic progressive inflammatory A disorder that causes inflammation of the joints in the spine, which can lead to severe chronic pain and discomfort. In advanced stages, inflammation can cause new bone to form in the spine, causing the spine to fuse in a fixed position, often resulting in a forward leaning posture. 
Clinically Relevant Anatomy
The spine has 24 vertebrae: 7 cervical, 12 thoracic, and 5 lumbar. The vertebrae are held together by ligaments and separated by intervertebral discs. The intervertebral disc consists of the inner nucleus pulposus and the outer annulus fibrosus fibrocartilage ring. People with spondyloarthropathy are highly prone to inflammation at the point where the tendons, ligaments, and joint capsules attach to the bone. These sites are called insertion points.  Level 5
The sacroiliac joint consists of a cartilaginous portion and a fibrous (or ligamentous) compartment, with very strong anterior and posterior sacroiliac ligaments. This makes SIJ a double joint deformity, with movement limited to slight rotation and translation. Another feature of SIJ is that Two different types of cartilage cover the two articular surfaces. While the sacral cartilage is pure hyaline, the iliac side is covered by a mixture of hyaline and fibrocartilage. Due to its fibrocartilaginous composition, the sacroiliac joint is a so-called articular attachment point.  Class 1B
Ankylosing spondylitis (the most common spondyloarthropathy) has a prevalence of 0.1% to 0.2% in the U.S. general population and is associated with the prevalence of HLA-B27. Diagnostic criteria for spondyloarthropathies were developed for research purposes, which are rarely almost Not used in clinical practice. There is no laboratory test for the diagnosis of ankylosing spondylitis, but the HLA-B27 gene has been found to be present in approximately 90% to 95% of affected Caucasian patients in Central Europe and North America  Grade 5
AS is three times more common in men than women and is most common between the ages of 20-40.  (Grade 5) Recent research suggests that AS may be equally common in women but is less diagnosed because of a milder course, fewer spinal problems, and more joint involvement Such as knees and ankles. In the United States, AS affects nearly 2 million people, or 0.1% to 0.2% of the population. It occurs more often in Caucasians and some Native Americans than in African-Americans, Asians, or other nonwhite groups.  AS is 10 to 20 times more common First-degree relatives of AS patients were more likely than the general population. The risk of AS in first-degree relatives with the HLA-B27 allele is approximately 20%. 
The most characteristic feature of spondyloarthropathy is inflammatory back pain. Another feature is enthesitis, which involves inflammation where the tendon, ligament, or joint capsule attaches to the bone.  Grade 5  Other clinical features of Grade 5 include inflammatory back pain Painful dactylitis and extra-articular manifestations such as uveitis and rash.  Grade 5 is usually in men under the age of 40 who may also have hip or hip pain and stiffness for more than 3 months.  The condition is most severe in the morning, lasts for more than 1 hour, and is described as Dull local pain, but may be intermittently severe or tremor. Pain can become severe and persistent after overtime, and may be aggravated by coughing, sneezing, and writhing. Pain may radiate into the thigh, but usually not below the knee. Hip pain is usually unilateral But may alternate left and right. 
Pain and stiffness of the paravertebral muscles are common, making the sacroiliac region and spinous processes very tender to palpation.  Bending posture can relieve back pain and paraspinal muscle spasms; thus, kyphosis is common in untreated patients. 
Enthesitis (inflammation of the attachment of tendons, ligaments, and bone capsules) may cause axial bone pain or stiffness and limited mobility.  Dactylitis (inflammation of the entire finger), often called “sausage finger,” also occurs in spondyloarthropathies and is Presumed to be caused by inflammation of the joints and tendon sheaths  Grade 5. Because AS is a systemic disease, intermittent low-grade fever, fatigue, or weight loss may occur. 
In advanced stages, the spine may fuse and lose normal lordosis, with increased thoracic kyphosis, painful limitation of cervical joint motion and loss of spinal flexibility in all planes of motion. Less than 2 cm reduction in chest wall excursion may be An indicator of AS because chest wall excursion is an indicator of decreased axial skeletal mobility. 
Anterior uveitis is the most common extra-articular finding, occurring in 25% to 30% of patients. Uveitis is usually acutely unilateral and recurrent. Eye pain, red eyes, blurred vision, photophobia, and increased tearing are all signs of development. Cardiac manifestations include the aorta and Dilated mitral valve root with regurgitation and conduction defects. Patients with long-term disease may develop fibrosis in the upper lobes of the lungs.  Level 5
Most Common differential diagnosis
- Rheumatoid arthritis
- Reiter’s syndrome
- Inflammatory bowel disease : Ulcerative colitis and Crohn’s disease
- Psoriatic spondylitis 
- Scheuermann’s disease/|Scheuermann’s kyphosis 
- Paget disease  Grade 5
Differential diagnosis between ankylosing spondylitis and thoracic spinal stenosis
Ankylosing spondylitis History of thoracic spinal stenosis Morning stiffness Intermittent soreness Predominantly male Sharp pain Bilateral sacroiliac joint pain May refer to the back of the thigh Pain May refer to walking with legs Limited active movement May be normal Passive Movement limitation May be normal Obstructed isometric movement is normal Normal Special tests None Van Gelderen’s bicycle test May be positive Stooping test may be positive Reflexes are normal May be affected with prolonged standing Sensory deficits None Usually temporary diagnostic imaging Plain radiographs are computed diagnostically Tomography is diagnostic
In the early stages of ankylosing spondylitis, changes in the sacroiliac joints are similar to changes in rheumatoid arthritis, but the changes are almost always bilateral and symmetrical. This fact distinguishes ankylosing spondylitis from psoriasis Reiter syndrome and Infect. Changes in the sacroiliac joint occur throughout the joint, but primarily on the iliac side.
AS can be diagnosed by modified New York criteria, and patients must have radiographic evidence of sacroiliitis and one of the following: (1) limited motion of the lumbar spine in the sagittal and frontal planes (2) limited thoracic expansion (typically < 2.5 cm) (3) back to history Pain included onset at 3 months. 
- X-rays. Radiographic findings of symmetric bilateral sacroiliitis include blurred joint margins, extraarticular sclerotic erosions, and narrowing of the joint space. The lumbar and thoracic vertebrae form a “bamboo spine” image on the upper back as bony tissue bridges the vertebral bodies and posterior arches Radiography
- Computed tomography (CT). A CT scan combines X-ray views taken from many different angles into cross-sectional images of internal structures. CT scans provide more detail and more radiation exposure than regular X-rays. 
- Magnetic resonance imaging (MRI). Intra-articular inflammation, early cartilage changes and underlying bone marrow edema and osteitis can be seen using an MRI technique called short tau inversion recovery (STIR). MRI scans using radio waves and strong magnetic fields can better visualize soft tissues such as cartilage. 
- lab testing. There are currently no laboratory tests for the diagnosis of ankylosing spondylitis, but the HLA-B27 gene has been found to be present in approximately 90% to 95% of affected Caucasian patients in Central Europe and North America  Grade 5. Presence of HLA-B27 antigen is a useful adjunct to diagnosis But it cannot be diagnosed alone. 
Affirmative answers to four out of five of the following questions may help identify AS:
- Did back pain start before age 40?
- Did the discomfort begin slowly
- Has the discomfort lasted 3 months
- Was morning stiffness a problem
- Did the discomfort improve with exercise
Specificity = 0.82 Sensitivity = 0.23LR, 4 out of 5 positive responses = 1.3
Chronic low back pain (LBP) is the cardinal symptom of ankylosing spondylitis (AS) and undifferentiated axial spondyloarthritis (SpA), sometimes many years before the development of radiographic sacroiliitis.  Level 4
An increased risk of bone loss and vertebral fractures has also been noted in patients with ankylosing spondylitis (AS).  Level 3B
In summary, the diagnostic procedure for ankylosing spondylitis includes:
- Imaging tests such as X-ray and CT scans
- HLA B27 gene presence (genetical factor)
- Blood samples with focus on CRP levels
- BASDAI BASMI and BASFI  Level 1B
Modified Health Assessment Questionnaire (MHAQ) Bath Ankylosing Spondylitis Disease Activity Index (BASDAI)  Grade 1 BASQoL  Grade 1 Duration of morning stiffness and morning stiffness were assessed using a visual analog scale at the “0-10 cm” level duration in minute.  Level 1B Self-reported joint tenderness: This is done on a joint chart with the name of the joint written next to it as a guide and the patient is asked to tick the box that matches the painful joint  Level 1B Self-reported soft tissue tenderness (enthesitis): this is in Skeletal models are made and the patient is asked to highlight where he feels pain.  Level 1B
A physical examination of the spine involves the cervical, thoracic and lumbar regions. Cervical involvement tends to occur late. The curvature of the neck can be measured by the distance from the occiput to the wall. The patient is standing with the back and heels against the wall, the distance between the back and heels Measure the head and the wall. Video occiput-to-wall test The thoracic spine can be tested by expanding the chest. It is measured in women in the fourth intercostal space and just below the breasts. The patient should be asked to exert maximum inhalation and exhalation and the difference in chest cavity Extend to measure. Chest expansion less than 5 cm is suspicious and < 2.5 cm is abnormal and increases the likelihood of AS unless there are other causes such as emphysema. Exacerbated normal thoracic kyphosis of the dorsal spine. Costovertebral costotransverse processes and The wrist joints should be palpated to detect inflammation causing palpitation pain. The lumbar spine can be tested with Schober’s test. This is performed by making a mark between the posterior superior iliac spines at the spinous process of the 5th lumbar vertebra. The second token is 10 cm above the first, ask the patient to bend forward and straighten the knee. The distance between the two markers increases from 10 to at least 15 cm in normal individuals, but only to 13 or less in the case of AS.  Level 5
According to Braun et al.  (evidence level 5, 2010), the general principles for the management of patients with AS are:
- Multidisciplinary treatment coordinated by a rheumatologist is required.
- The main goal is to maximize long-term health-related quality of life. Therefore, it is important to control symptoms and inflammation, prevent progressive structural damage, and maintain/normalize function and social participation.
- Treatment should aim at the best care and require a shared decision between the patient and the rheumatologist.
- A combination of non-drug and pharmacological treatment modalities is needed.
1. General treatment
Treatment of patients with AS should be individualized based on:
- Current manifestations of the disease (extra-articular symptoms and signs of peripheral axial entheses).
- Levels of current symptoms Prognostic indicators and clinical findings.
- General clinical status (sex-age comorbidity psychosocial factors concomitant medication).
2. Disease monitoring
Condition monitoring of patients with AS should include:
- Patient history (eg, questionnaires)
- Laboratory tests
- Clinical parameters
- Frequency of monitoring should vary from individual to individual, depending on: Symptom treatment course and severity
3. Non-pharmacological treatment
- Patient education and regular exercise are the cornerstones of nonpharmacologic management of AS patients.
- Home exercise works. However, physical therapy with supervised exercise on land or water on an individual or group basis should be preferred, as these are more effective than home exercises.
- Self-help groups and patient associations may be useful.
4. Extra-articular manifestations and complications
- Psoriatic uveitis and IBD are some common extra-articular manifestations. They should be managed in collaboration with their respective experts.
- Rheumatologists should be aware of the increased risk of cardiovascular disease and osteoporosis in patients with AS.
5. Non-steroidal anti-inflammatory drugs
- NSAIDs, including coxibs, are recommended as first-line drug therapy for AS patients with pain and stiffness.
- For patients with persistently active symptomatic disease, continuous NSAID therapy is preferred.
6. Pain medications: contraindicated and/or poorly tolerated after failure of previously recommended therapy. 7. Anti-TNF Therapy
- According to ASAS recommendations, anti-TNF therapy should be given to patients with persistently high disease activity despite conventional treatment.
- Switching to another TNF blocker may be beneficial, especially in unresponsive patients.
- There is no evidence to support the use of biologics other than TNF inhibitors in AS.
- Total hip arthroplasty should be considered in patients with intractable pain or disability, and radiographic evidence of age-independent structural damage.
- Corrective spinal osteotomy may be considered in patients with severe disabling deformities.
- Patients with AS and acute vertebral fractures should consult a spinal surgeon.
9. Change in disease course: If there is a significant change in disease course, causes other than inflammation (eg, spinal fracture) should be considered and appropriate evaluations, including imaging studies, should be performed.
Physical Therapy Management
Rehabilitation should be patient-centered. It should also enable patients to achieve independent social integration and improve quality of life. The goals of AS physical therapy and rehabilitation are to:
- Reduce discomfort and pain;
- Maintain or improve endurance and muscle strength;
- Maintain or improve mobility and balance;
- maintain or improve physical health and social participation;
- Prevents abnormal curvature of the spine and deformities of the spine and joints.  Level 5
A multimodal physical therapy program that includes aerobic stretching education and lung exercises combined with conventional medical management has been shown to produce greater improvements in spinal mobility and chest expansion than medical care alone.  The evidence shows that Aerobic training improves walking distance and aerobic capacity in patients with AS. However, aerobic training did not provide additional benefits in terms of functional capacity, exercise capacity, disease activity, quality of life, and lipid levels compared with stretching alone (Jennings et al. 2015). Evidence also suggests that passive stretching during physical therapy results in a significant increase in hip range of motion (ROM) in all directions except flexion. Patients who performed stretching exercises maintained this increase in ROM Periodic  Level 1B. Because the severity of AS varies from person to person, there is no specific exercise program that shows the greatest improvement. Several studies have shown that a multimodal exercise program of 50 minutes three times a week shows significant improvement after 3 months Chest wall offset Chin-to-chest distance occiput-to-wall distance and modified Schober flexion test. 
However, according to Ozgocmen et al.  (Grade 5) Some key recommendations can be formulated for patients with AS:
- Once AS is diagnosed, physical therapy and rehabilitation should begin immediately.
- Physical therapy should be planned, initiated and monitored appropriately based on the patient’s needs, expectations and clinical condition.
- Physiotherapy should be administered as an inpatient or outpatient program for all patients, regardless of disease stage, and general rules and contraindications should be observed.
- Regular exercise throughout life is the mainstay of treatment. A combination of inpatient spa exercise therapy and group physical therapy is recommended for maximum benefit, group physical therapy is also preferred over home exercise  Grade 5  Grade 5
- As previously mentioned, we recommend a traditional physical therapy program that includes stretches, flexibility and breathing exercises as well as pool and land exercises with accompanying recreational activities.
- Physiotherapy modalities should be used as complementary therapies based on their experience with other musculoskeletal disorders  Level 5
Exercise training program Some recommended exercises for patients with AS (Masiero et al 2011)  Grade 1B:
- Respiratory exercises (10min)
2 Series of 10 repetitions each:
1. Chest expansion
2. Deep breathing
3. Thoracic breathless
4. Expiratory breathless
5. Diaphragmatic Breathing Exercises and Abdominal Control
6. Shoulder girdle muscle exercise (i.e. shoulder raising combined with breathing)
- Exercises to mobilize the vertebrae and extremities (15 minutes)
2 series of 10 repetitions per mobilization. Lying and/or sitting and/or standing and/or walking on all fours or without pain. Spine exercises can also be combined with breathing exercises (i.e. deep breathing or breath-holding on exhalation)
1. Cervical side: lateral flexion and rotation (left and right) stretching
2. Thoracic and lumbar side: lateral flexion, extension and rotation
3. Shoulder and upper limb side: abdomen/adduction flexion elevation and rotation
4. Coxofemoral knee and ankle side: abdominal/adduction rotation and flexion and extension
- Balance and Proprioception Exercises (10 minutes)
2 sets of 10 reps: standing and walking
- Postural Exercises and Stretching and Strengthening of the Spine and Limb Muscles (15 minutes)
2 reps, each averaging about 30/40 seconds for the stretch. All exercises can be performed lying and sitting or on all fours or standing, active and passive movements are painless
1. Stretching exercises for the posterior chain of the spine (thoracolumbar spine and all erector spinae, etc.) and the anterior chain of the spine (upper abdomen, lower abdomen, etc.)
2. Stretching exercises for the anterior girdle chain (psoas major, hamstrings, etc.) and posterior pelvic girdle chain
3. Stretching of the front and rear muscles of the lower limbs
- Endurance training (10 min)
Step by step walking treadmill cycling or swimming according to the patient’s functional capacity (low speed without resistance).
- Postural education is also a very important component for patients to maintain an upright posture. 
- For most patients, water therapy can provide an excellent alternative to the principles of low-impact stretching and rotation. 
- Pain education is also a very important benefit for patients (Masiero et al., 2011).  Level 1B
Exercises to avoid include high-impact and flexion exercises. Excessive exercise can be harmful and may exacerbate the inflammatory process. 
Manual Therapy Some advocate the efficacy and use of gentle, non-thrusting manual therapy for the spine. Eight weeks of self- and manual mobilization improve chest expansion posture and spinal mobility in patients with ankylosing spondylitis. Physical therapy interventions initially consisted of Warm up the soft tissues of the back muscles (vibration via a vibrator) and gentle mobility exercises. This is followed by active angle and passive movement exercises in the physiological orientation of the joints in the three directions of the spine and chest wall Movements (flexion/extension, lateral flexion and rotation) and different starting positions (supine and seated). Passive mobility exercises include general angular movements and specific translational movements. Tight muscles are stretched Use the contraction-relaxation method. Soft tissue therapy (manual massage) to the neck, followed by relaxation exercises in a standing position, followed by rest on the treatment table for a few minutes 
Dagfinrud H. Hagen K. B. & Kvien T. K. (2008). Physiotherapy interventions for ankylosing spondylitis. Cochrane Library.
Chang W. D. Tsou Y. A. & Lee C. L. (2016). Comparison of specific exercises and physical therapy for the treatment of patients with ankylosing spondylitis: a meta-analysis of randomized controlled trials. International Journal of Clinical and Experimental Medicine 9(9) 17028-17039.
Liang H. Zhang H. Ji H. & Wang C. (2015). Effect of home exercise intervention on health-related quality of life in patients with ankylosing spondylitis: a meta-analysis. Clinical Rheumatology 34(10) 1737-1744.
O’Dwyer T. O’Shea F. & Wilson F. (2014). Exercise therapy for spondyloarthritis: a systematic review. Rheumatology International 34(7) 887-902.
Martins N. A. Furtado G. E. Campos M. J. Ferreira J. P. Leitão J. C. & Filaire E. (2014). Exercise and ankylosing spondylitis and the New York Modification criteria: a systematic review and meta-analysis of controlled trials. Acta Reumatológica Portugalsa 39(4).
Nghiem F. T. & Donohue J. P. (2008). Rehabilitation of ankylosing spondylitis. Current Opinion in Rheumatology 20(2) 203-207.
Fernandez-de-Las-Penas C. Alonso-Blanco C. Eagle-Maturana A. M. Elizabeth-of-the-Key-Corner A. Molero-Sanchez A. & Miangolarra-Page J. C. (2006). Exercise and Ankylosing Spondylitis—Which Exercises Are Right? critical comment. Critical ReviewsTM in Physical and Rehabilitation Reviews Medicine 18(1).
Stasinopoulos D. Papadopoulos K. Lamnisos D. & Stergioulas A. (2016). LLLT is used to treat patients with ankylosing spondylitis. Lasers in Medicine 31(3) 459-469.
Karamanlioğlu D. Ş. Aktas I. Ozkan F. U. Kaysin M. & Girgin N. (2016). Efficacy of ultrasound therapy combined with exercise therapy in patients with ankylosing spondylitis: a double-blind randomized placebo-controlled trial. Rheumatology International 36(5) 653-661.
Jennings F. Oliveira H. A. de Souza M. C. da Graça Cruz V. & Natour J. (2015). Effects of aerobic training in patients with ankylosing spondylitis. Journal of Rheumatology 42(12) 2347-2353.
Niedermann K. Sidelnikov E. Muggli C. et al. (2013) Effects of cardiovascular training on physical performance and perceived disease activity in patients with ankylosing spondylitis. Arthritis Care and Research 65(11) 1844-1852.
Figure 1: http://www.physio-pedia.com/images/f/fe/Spondy_1.png Table 1: Source 22 (Kataria et al., 2004) Figure 2: http://www.physio-pedia. com/images/b/b0/Spondy4.jpg Figure 3: http://www.physio-pedia.com/images/c/c5/Spine-t_ankylosing_spondylitis.jpg video occiput-to-wall test: https://www.youtube.com/watch?v=rOR70O_zTdA
Clinical Bottom Line
Spondyloarthropathies are a group of multisystem inflammatory disorders affecting various joints, including the peripheral articular and periarticular structures of the spine. They are associated with extra-articular manifestations such as fever. Most were HLA B27 positive (serological test) and Rheumatoid factor (RF) negative. There are 4 main seronegative spondyloarthropathies:
- Ankylosing spondylitis (AS): the archetype, more men than women
- Reiter’s Syndrome
- Psoriatic Arthritis
- Arthritis of Inflammatory Bowel Disease
Sacroiliitis is a common manifestation of all these diseases. Although triggering infection and immune mechanisms are thought to underlie most spondyloarthropathies, their pathogenesis remains unclear. A physical examination of the spine involves the cervical, thoracic and lumbar regions. this The doctor may ask the patient to bend the back in different ways to check the bust, and may also press on different parts of the pelvis to look for pain points. Suspicion of doctors influencing different diagnostic procedures such as x-ray imaging HLA B27 presence of CRP levels blood sample. The treatment of AS can be divided into:
- Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)
- Anti – TNF therapy
Physical therapy is the best-known non-surgical treatment for AS to improve flexibility and strength. Surgery is only recommended for patients with chronic cases Most cases can be treated without surgery.
- ↑ Jump up to:1.0 1.1 1.2 1.3 1.4 1.5 1.6 Goodman C, Snyder T. Differential Diagnosis for Physical Therapists: Screening for Referral. St. Louis, MO: Saunders Elsevier: 2007. 539
- ↑ Jump up to:2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 2.18 2.19 2.20 2.21 2.22 2.23 2.24 2.25 Kataria R.K. et al., Spondyloarthropathies. Am Fam Physician, 2004, 69 (12):2853-2860 Level of Evidence 5
- ↑ Jump up to:3.0 3.1 Benjamin M. and McGonagle D., The anatomical basis for disease localization in seronegative spondyloarthropathy at entheses and related sites. J. Anat., 2001. Level of Evidence 5
- ↑ Jump up to:4.0 4.1 4.2 4.3 Hermann K.G.A., Bollow M., Magnetic Resonance Imaging of Sacroiliitis in Patients with Spondyloarthritis: Correlation with Anatomy and Histology. Fortschr Röntgenstr, 2014, 186:3, 230-237 Level of Evidence 1B
- ↑ Jump up to:5.0 5.1 5.2 5.3 5.4 5.5 Beers MH, et. al. eds. The Merck Manual of Diagnosis and Therapy. 18th ed. Whitehouse Station, NJ: Merck Research Laboratories; 2006.
- ↑ Jump up to:6.0 6.1 Sieper J., et al. Ankylosing spondylitis: an overview. Ann Rheum Dis 2002;61, 8-18. Level of Evidence 5
- ↑ Jump up to:7.0 7.1 7.2 7.3 7.4 7.5 Jarvik, J. G., & Deyo, R. A. (2002). Diagnostic evaluation of low back pain with emphasis on imaging. Annals of internal medicine, 137(7), 586-597. Level of Evidence 3B
- ↑ Beers MH, ed. The Merck Manual of Diagnosis and Therapy, 18th edition. Whitehouse Station, NJ: Merck and CO; 2006
- ↑ Jump up to:9.0 9.1 9.2 9.3 9.4 El Miedany Y. Towards a multidimensional patient reported outcome measures assessment: Development and validation of a questionnaire for patients with ankylosing spondylitis/spondyloarthritis. Elsevier, 2010, Volume 77, Issue 6 Level of Evidence 1B
- ↑ Braun, J. von, Van Den Berg, R., Baraliakos, X., et al. 2010 update of the ASAS/EULAR recommendations for the management of ankylosing spondylitis. Annals of the rheumatic diseases, 2011, vol. 70, no 6, p. 896-904. Level of Evidence 5