Lumbar Spondylolysis in Extension Related Sport

Introduction

In addition to the knowledge of the Spondylolsis physiopedia page, this page aims to provide readers with a background understanding of lumbar spondylolysis in extension-related sports. This page shall discuss the characteristics of the condition alongside explaining the most relevant treatment options. In detail we will discuss the different management options based on the most recent evidence, focusing on a return to sport, providing examples for Cricket, Tennis and Gymnastics.

Definition/Description

Lumbar Spondylolysis is the unilateral or bilateral defect of the pars interarticularis of the vertebral arch, which can be accompanied by vertebral displacement in the lumbar region [1]. As a result this can be characterised by the collapse or narrowing of the disc space [2]. Spondylolysis derives from the Greek words Spondylos (Vertebra) and lysis (Defect) [3]. Spondylolysis is a common cause of low back pain.

Clinically Relevant Anatomy

Small structures called vertebrae comprise the vertebral column, otherwise known as the spine. The vertebral column extends from the base of the skull to the coccyx, protecting the length of the spinal cord [2]. In human anatomy the lumbar vertebrae lie between the rib cage and top of the sacrum. Lumbar vertebrae are the largest of the vertebral column [4]. Together they form the curve of the lower back, known as lordosis. Each lumbar vertebrae is formed of a vertebral body where it is attached to by a bony ring, formed of two pedicles followed by two lamina at the posterior side of the vertebrae. This area where the pedicles and lamina meet is called the pars interarticularis. The pars interarticularis are the most feeble part of the vertebral body and is the area affected in spondylolysis [5].

Anatomy of a lumbar vertebra [6]

Epidemiology/Etiology

The incidence of lumbar spondylolysis has been estimated to be approximately 6% in the general population [7]. It is also said to be twice as prevalent in males compared to females [8]. Furthermore, the incidence of spondylolysis is very high in adolescent athletes [9] [10]. Incidence can also vary depending on country of origin; the incidence in the United States is reported to be 11.5% [11], however; the incidence of spondylolysis in the Japanese population is predicted to be around 5.9% [12].

Lumbar spondylolysis will typically begin as a stress fracture in one of the two pars interarticularis’ which make up the vertebrae. The unilateral fracture will increase loading on the contralateral side which could cause a bilateral pars interarticularis fracture, and eventually spondylolisthesis (slipping of the vertebrae) [13].

One of the main risk factors of lumbar spondylolysis is believed to be repeated hyperextension and is more commonly seen in athletes that repeatedly go into end range lumbar extension, e.g. ballet dancers, gymnasts, cricketers, tennis players etc. [10]. In particular, research has found gymnasts to be more likely to suffer a pars interarticularis fracture than sedentary individuals [14]. Research has also illustrated that extension movements with compression (commonly seen in gymnastics, cricket and tennis) implement more stress on the pars interarticularis than just compression alone [15]. Furthermore, lumbar spondylolysis is more common in adolescents due to their continued spinal growth. The pars interarticularis is said to have not achieved full bony remodelling until the age of 25, therefore anyone under this age will be at a high risk of developing lumbar spondylolysis [10].

Lumbar spondylolysis mainly concerns the L5 vertebrae which accounts for 85%-95% of all cases [7]. This is thought to be due to the facet joint positioning of the L5/S1 vertebrae. The posterior facing facet of the S1 vertebrae creates a large anterior shear upon the pars interarticularis of the L5 vertebrae which increases in individuals with excessive anterior pelvic tilt [16]. Enhanced anterior pelvic tilt is a very common movement pattern in extension related sports such as ballet, gymnastics and tennis, making individuals in these sports more susceptible to the development of spondylolysis.

A visual representation of lumbar spondylolysis [17]

Characteristics/Clinical Presentation

Spondylolysis sufferers are usually asymptomatic, with approximately 10% of affected individuals exhibiting symptoms.

Subjective assessment:

  • Insidious or gradual onset [18]
  • Low back pain primarily worsening with extension related activities [19]
  • Pain varying from a dull ache to sharp pain especially upon extension [19]
  • Muscle guarding either unilateral or bilateral [19]
  • Improves with rest [19]
  • Individuals may be excessively hypermobile [19]
  • Pain radiating to buttock [20]
  • Pain worsening with sport activity [18]

Objective assessment:

  • Tenderness and pain on palpation of spinous process of affected vertebra [19]
  • Lordotic lumbar spine [20]
  • Muscle guarding either unilateral or bilateral of erector spinae [19]
  • Weakness in gluteals and abdominals [20]
  • Pain on extension [19]
  • Positive single leg hyperextension test [20]
  • Hamstring tightness [20]

Spondylolisthesis

Spondylolisthesis is the slippage of one vertebral body on top of another. Approximately 75% of people with spondylolysis will end up developing spondylolisthesis [21]. Spondylolisthesis is graded based on the degree a vertebral body will anteriorly shift [11]. There are 6 known types of spondylolisthesis first introduced by Wiltse in 1976 [22];

  1. Degenerative: Occurs due to degenerative changes in the vertebra.
  2. Isthmic: Results from defects in the bilateral pars interarticularis
  3. Dysplastic: A congenital birth defect that occurs at level L5/S1
  4. Traumatic: Commonly seen after trauma of the pars interarticularis
  5. Pathologic: Seen in bone or connective tissue disorders such as Paget’s disease
  6. Iatrogenic: Commonly seen after the removal of large sections of the spine

Isthmic spondylolisthesis is most commonly seen in athletes primarily due to the frequency of extension and rotational related movements they carry out, particularly in the adolescent population [11].

The Meyerding scale is the grading system used in spondylolisthesis. It categorises the degree of vertebral slippage [23];

The Meyerding grading scale for lumbar spondylolisthesis [24]

Differential Diagnosis

For a list of differential diagnoses, please see the Spondylolysis page.

Diagnosis Procedures

One-Legged Hyperextension Test

The one-legged hyperextension manoeuvre is an orthopaedic test used to assist in the diagnosis of spondylolysis. Although one of the very few diagnostic tests used by clinicians, fairly recent research has found it to have reduced value in the diagnosis of spondylolysis [25]. The test is performed as follows;

  • The patient stands facing away from the physiotherapist (or associated medical professional) [26]
  • The patient then balances on one leg, bending the elevated knee to 90° and leans backwards slightly [26]
  • A positive test will reproduce pain, either unilaterally or bilaterally; unilateral lesions will reproduce pain when performed on the ipsilateral leg [26]

The patient will repeat this on both legs to compare differences [26]

One-legged hyperextension test

Diagnostic Imaging

Single Photon Emission Computerised Tomography (SPECT)/ Computerised Tomography (CT) Scanning

SPECT and CT scans are two separate types of scan regularly used in conjunction with one another to produce a merged image, used to identify a bony lesion. SPECT scanning is a nuclear imaging method that involves a radioactive tracer tracked by a special gamma camera which allows for the reconstruction of three-dimensional images. CT images are created as a patient lies on a bed which moves into a ring-shaped X-ray machine. A camera which rotates 360 degrees around the patient then produces the CT image.

The method of using SPECT with CT scanning has been shown to be of more value than using SPECT alone [27]. Many papers suggest this method to be the gold standard in spondylolysis diagnosis, particularly in athletes [28]. SPECT/CT scans also have a high sensitivity in determining pars interarticularis fractures when compared to alternative imaging methods [29].

Magnetic Resonance Imaging (MRI)

MRI’s are used to provide detailed images using the body’s magnetic properties. It does this by using the body’s hydrogen nuclei, and when put under a strong magnetic field such as an MRI scanner the hydrogen protons axes line up to form a detailed image [30]. This image can then be used to look for any pars articularis fractures seen in spondylolysis.

MRI scanning has proved useful in the detection of pars interarticularis fractures, with a high sensitivity rate [31]. Furthermore, the lack of ionising radiation when taking MRI scans makes it a desirable modality in the diagnosis of spondylolysis [32].

X-Rays

The radiographic imaging of a pars interarticularis lesion is essential in the diagnosis of symptomatic spondylolysis [33], however X-rays have limited sensitivity when compared to SPECT/CT scans [5]. X-ray imaging uses electromagnetic waves to create pictures of the inside of a patient's’ body. Different bodily tissues absorb varying amounts of radiation. This causes the X-ray image to appear different shades of black and white. X-rays can be taken in AP, PA, lateral or oblique planes. Oblique planes provide the best angle to spot pars interarticularis defects [5]. In lumbar spondylolysis, the appearance of a dog like structure can be seen on a plain radiograph when there is a pars interarticularis fracture. This is referred to as the ‘scotty dog’ sign which is seen in oblique planes only [34].

Oblique X-ray view showing the 'Scotty dog' sign [35]
X-ray of pars interarticularis fracture in lumbar spine [36]

Outcome Measures

  • Numeric pain rating scale (NPRS): This is a scale that measures pain intensity, patients are asked to score their pain 3 times over 24 hours and the score takes the average of these 3 values [37].
  • Roland Morris disability questionnaire (RMDQ): This is a questionnaire which consists of sentences that people have used to describe their feelings during episodes of back pain. As the list is read out, if patients recognise a specific sentence that they feel they fit into, they must tick the boxes they see fit and a score is created in accordance with the number of boxes ticked. The questionnaire makes it possible to track changes over time [38].
  • Oswestry disability index (ODI): This is used to evaluate how back pain affects people in their daily life activities. Six categories are available for each question ranging from 0 (no limitation) to 6 (most limitation), the score is then calculated by adding the ten questions together and dividing by 2. This score represents the total effect as a percentage [39].
  • Pain self-efficacy questionnaire (PSEQ): This is a questionnaire which rates the confidence of a patient performing activities despite pain. It rates confidence on a scale from 0 (no confidence) to 6 (completely confident). All scores are then added up and a score ranging between 0-60 is generated. The closer to 60 the score is the stronger belief of self efficacy the patient has [40].
  • The patient-specific functional scale (PSFS): This is a questionnaire which asks patients to identify up to three activities that they have difficulty with or are unable to perform due to their back pain. Each item is given a score from 0 (unable) to 10 (able), and the total score is assessed by the sum of activity scores/number of activities [41].

Lumbar Spondylolysis In Extension Related Sport

This section will aim to identify the extension related movements of specific sports, exhibiting literature and using visual aids to understand why athletes involved in these types of sports are at a higher risk of developing spondylolysis. Please see examples from cricket, gymnastics and tennis.

Lumbar Spondylolysis In Cricket

A 2019 literature review looking into the incidence of pars interarticularis defects in sporting athletes found that cricket players had the second highest incidence of pars interarticularis abnormalities (31.97%) when compared with other sports, with the majority occurring in the lumbar spine [42].

In cricket, a bowler will throw the ball at least six times to complete an over and will typically be bowling for up to 50 overs throughout a 4 day test match, which involves repeated hyperextension and rotational movements of the lumbar spine. Specifically, fast bowling has been identified as a main risk factor for pars interarticularis fractures due to the increased force applied onto the pars interarticularis [43]. A randomised control study used MRI scans to conclude that professional fast bowlers in cricket had twice the prevalence of pars interarticularis abnormalities (81%) when compared to control subjects (36%) [44]. Moreover, a study has found that 33% of fast bowlers had at least one pars interarticularis defect, which primarily occurred at level L5 on the non-dominant arm side [45]. Hyperextension and rotation of the lumbar spine during the bowling action will predominantly occur during the front foot contact phase [46].

The action of a fast bowl in cricket [47]

Previous research has also focused on the asymmetry of the quadratus lumborum muscle in cricketers. The main role of the quadratus lumborum is to extend, side flex and stabilise the lumbar spine, however; it can also aid in breathing. A study involving English and Welsh professional cricketers found that bowlers with a quadratus lumborum asymmetry >25% have a 58% probability of developing a pars interarticularis defect compared to a 4% probability in those who had an asymmetry of <5% [48].

Lumbar Spondylolysis In Gymnastics

Gymnastics is a sport that combines dance, speed, the agility of ornamental jumps and the flexibility of ballet [49]. Spinal injuries are accountable for 17.2% of all injuries within Olympic gymnastics, with spondylolysis accounting for a large portion of this percentage although varying between level of participation and gender [49]. In the non elite adolescent female population studies have shown a prevalence of 34.4% [50], whereas in the competitive elite population, larger studies have shown that the prevalence is slightly lower, being 16% including both male and female athletes [49]. Spondylolysis accounts for 47% of all lumbar pain among gymnasts [49].

Gymnastics utilizes many unique and diverse positions while traveling at high velocities to perform stunts such as somersaults and dismounts, putting large amount of forces through the axial spine. Along with these large forces, athletes are put into positions such as hyperextension which puts a great amount of pressure on the posterior aspects of the lumbar vertebra, e.g. when performing a flip or when trying to maintain a specific pose. Athletes are also forced into hyperextension when vaulting and landing, applying excessive stress on the vertebra [49].

[51]A gymnast in lumbar hyperextension

Lumbar Spondylolysis In Tennis

A 2019 literature review found that the occurrence of spondylolysis is greater in the elite athletic population in comparison to the non-athletic population. It was found that elite tennis players have an occurence of 40% in contrast to the 1.1% of the non-athletic population [42]. Meanwhilst a retrospective cohort study displayed a 12.9% risk of developing a stress fracture during a two year period for elite tennis players with a 16% incidence in the pars interarticularis [52] .

In the youth, another study of young tennis players found that 80% of reported spondylolysis cases were at L5, 12% at L4, 3% at L3, and 1% at L2. Meanwhile the remainder were formed of bilateral L5, and unilateral L4 & L3 spondylolysis cases. Amongst the young tennis players the mean age of reported spondylolysis cases was 14.8 years of age [53]. Further support was found in a 2014 study that performed MRI’s on 98 asymptomatic junior elite tennis players (51 male, 47 female) with a mean age of 18 years old and found 305 of players had pars defects with 93% occurring at the L5 level [54]. This research indicates that a vast majority of lumbar spondylolysis cases occur at the L5 level in the lumbar spine.

Tennis is a largely one sided sport, with common fast movements of flexion and extension of the trunk in the sagittal and frontal planes in addition to the rotational movements. Competitive adult tennis players spend several years training to reach professional status, which involves repetitive and strenuous training  during the developmental stage of the body going into adulthood. As a result it leaves them at an increased risk of developing overuse injuries such as spondylolysis. In tennis, the specific actions that cause overloading of the posterior arch of the vertebrae are hyperextension when serving and the combined movement of extension with rotation when returning with the forehand. These movements are used to generate power to strike the ball. Whilst performing a tennis serve, the lumbar spine experiences lateral flexion forces 8 times greater than those faced during running [55].

During serving, a player will perform mainly extension of their spine which causes compression of the lumbar spine, however, dependent on the serve other forces can factor in to apply torsion to the lumbar region. For example when performing a topspin serve, lumbar extension is combined with rotation and lateral flexion which puts a greater amount of torsion through the lumbar spine. The coupled movement of lumbar extension, rotation and lateral flexion, combined with the ground reaction force from rear leg drive in the serve, puts up to 10 times body weight through the lower trunk. This has been suggested as a potential mechanism for abdominal tissue strain and low back injuries in adolescent players.

When performing a tennis stroke, the stance of a player can also have an effect on the forces which go through the lower back. An open forehand stance where the trunk is facing the net can lead to increased incidence of spondylolysis in the lower back. This is a result of rapid anteversion (medial hip rotation) and lumbar hyperextension during a stroke [53]. The more open the stance, the more likely the lumbar pars interarticularis is being loaded on all levels rather than other parts of the body such as the knee or thoracic levels of the spine.

Biomechanics of a tennis serve [56] [57] [58]
Different stances in tennis [59]

Management of Lumbar Spondylolysis

Conservative Management

When treating spondylolysis following diagnosis, there are several options available to a patient, the main one being conservative treatment. Conservative management has been shown to have good functional outcomes, with a functional capacity of 82-84% for cessation of sports with or without bracing. Conservative management which consists of bracing and sports modification or cessation followed by physiotherapy has been shown excellent return to sport rates for athletes at any level including pre-injury level, with a mean time period of 4.6 months. When conservative treatment fails it is usually managed with surgical treatment with a return to sports rate of 6.8 months [60].

Cessation from sport consists of complete rest from sport for around 4 weeks but this can in fact go up to 8 weeks. During this time bracing can be considered as a complementary treatment technique and patients can start increasing their activity levels, with particular emphasis placed on avoidance of pain eliciting manoeuvres, particularly hyperextension [61]. Existing literature shows that management that includes bracing, activity modification and cessation from sport may be the best initial therapy [62]. Athletic activities may be gradually resumed as pain subsides.

The main purpose of bracing is to limit spinal mobilisation and stress on the pars interarticularis. Though non-operatively it is proven that patients improve clinically regardless of bracing [61]. Bracing can come in two common forms; Thoracolumbosacral orthoses (TLSO's) and lumbosacral orthoses (LSO's), both of which are available in flexible and rigid variations. TLSO's help brace from the thoracic down to the sacral region whilst LSOs brace just the lumbar and sacral regions, whilst the rigidity of the brace allows a difference in the freedom of movement. It is believed that bracing should be progressively discontinued once the patient is asymptomatic regardless radiographic bony union [62].

TLSO (left) and LSO (right) braces [63]

Complementary Treatments

The following well-tolerated treatments can be used throughout rehabilitation to help reduce pain symptoms [10];

  • Thermotherapy
  • NSAIDS
  • Epidural Steroid Injections
  • Massage
  • Osteopathic/chiropractic manipulation
  • Cognitive Behavioural Therapy (CBT)

Surgical Management

Surgery is commonly used as an alternative management route to conservative management if there is no progress after at least 6 months. For surgical management there are 2 main types of procedures, namely the Buck and Scott procedures. The Buck procedure is designed specifically to repair a defect in the pars interarticularis, utilising a 3.5-mm lag screw fixation technique passing through the pars interarticularis to compress the defect. The technique involves bone grafts to fill the pars defect followed by screws inserted into the superior articular processes bilaterally. These screws are altered such that they accommodate a hook, which hangs over the lamina, which is later secured by a lock nut. The Buck procedure is the predominant operative method with the Scott procedure as well as modifications of this procedure used less often [61].

Buck procedure [64]

The Scott technique involves a wire passing through the transverse processes of the vertebrae which is tightened around the spinous processes to supplement autologous bone graft repair by providing compression and stabilization of the bony defect [61]. Postoperative rehabilitative care would then include protection of the surgical site until wound closure (bracing is typically surgeon dependent) and analgesia. Physiotherapy and re-education on proper biomechanics with an emphasis on posture and sleeping positioning are also given once the surgical wound is healed. An integral part of the postoperative rehabilitative care of athletes is a graded return to sports protocol consisting of education on proper biomechanics followed by the gradual progression to sport specific activities as tolerated [10].

Scott technique [65]

Physiotherapy Management

Physiotherapy management focuses on reducing pain levels as well as optimising physical function through the use of specific stabilization, strengthening and range of motion exercises. More recently, pilates and Transcutaneous Electrical Nerve Stimulation (TENS) have been introduced for the management of chronic lower back pain conditions, including spondylolysis [66], however; there is little to no research illustrating the effectiveness of TENS [67]. The main goal of physiotherapy management is to promote normal movement patterns which are pain free.

Initially, a period of rest is needed to settle down symptoms and promote additional blood flow in order to speed up pars interarticularis healing [68]. This is usually followed by months of physiotherapy training, incorporating a ‘return to play’ stage towards the end of rehabilitation.

Overview of rehabilitation guidelines for spondylolysis [69]

During rehabilitation, introducing exercises which focus on improving pelvic control and stability of the core muscles is important [70].

Example of exercises include:

Static stretches

  • Static hamstring stretch
Static hamstring stretch exercise
  • Static hip flexor stretch
Static hip flexor stretch exercise
Core stabilisation
  • Transverse abdominis activation:

Early stage exercise

Early stage transverse abdominis activation exercise

Later stage exercise

Late stage transverse abdominis activation exercise
  • Rectus abdominis training

Early stage exercise   

     

Later stage exercise

  • Pelvic tilt control

Early stage exercise

Later stage exercise

Biopsychosocial Considerations

An athlete experiencing an injury in sport can have detrimental effects on their psychological state, particularly with chronic injuries. A lot of athletes will experience the fear of being released by their clubs, especially at an elite level where they have a lot of financial responsibility. This, on top of the frustration of not playing can have adverse effects in which a physiotherapist will try and combat.

The biopsychosocial model was developed by George Engel in 1977 and is widely recognised as one of the main models used in psychology, medicine and health care today [71]. It is mainly used in long term chronic pain conditions such as spondylolysis. The model takes into consideration the patient’s biological, psychological and social factors during treatment. A physiotherapist may use this holistic approach to aim to address the mental challenges an athlete faces. A lot of this is through re-education and motivation. Previous research has shown that psychological factors can influence the rehabilitation process of an athlete and can prolong the return to play [72] [73]. Therefore, a physiotherapist obtaining as much information from the patient as possible during initial assessment is important.

The Biopsychosocial model [74]

Return To Play

The time frame taken to return to play varies on the severity of the spondylolysis and how long the individual has had it. This means the return to play time period can last from 2-8 months. Different sports have specific areas to target with regard to rehabilitation, please see below for some considerations [75];

Tennis
At the later stage of the return to play period areas of main focus are:
  • Equipment modifications (lighter racket, etc.)
  • Technique monitoring by coach
  • Movement monitoring (to ensure correct movement is being executed)
  • Video analysis comparing old footage to new footage
  • Once returned to sport monitor external load including serve count and training loads
  • Sport specific activities
Cricket
At the later stage of the return to play period areas of main focus are:
  • Video analysis of bowling technique
  • Sport specific activities
  • Monitoring symptoms
  • Maintaining core stability and strength
Gymnastics
At the later stage of the return to play period areas of main focus are:
  • Monitoring technique
  • Monitoring load on spine
  • Sport specific activities
  • Maintaining core stability and strength
  • Monitoring symptoms

Clinical Bottom-line

Athletes that participate in extension related sports are more predisposed to developing Spondylolysis due to the high amount of hyperextension and rotational movements. There is no gold standard for treatment but conservative/non-operative management should be the first line of action, with the primary aim of allowing the internal structures to heal. Moreover, treatment with or without bracing has little effect on outcomes during rehabilitation but can help manage the condition. Surgical treatment is commonly seen as a last resort to help rehabilitation if ineffective after 6 months of conservative treatment.

References

  1. Lumbar Spondylolysis. (2012). Contemporary Spine Surgery, 13(7), p.8.
  2. 2.0 2.1 Umesh P., M. and Umraniya, Y. (2018). Morphological Study of Pedicle of Dry Human Lumbar Vertebrae and its Clinical Significance. Indian Journal of Anatomy, 7(3), pp.342-345.
  3. Standaert, C. (2000). Spondylolysis: a critical review. British Journal of Sports Medicine, 34(6), pp.415-422.
  4. Gray's Anatomy: Anatomy of the Human Body. Basic Human Anatomy. (1967). Annals of Internal Medicine, 66(2), p.462.
  5. 5.0 5.1 5.2 Standaert, C. (2000). Spondylolysis: a critical review. British Journal of Sports Medicine, 34(6), pp.415-422.
  6. STUDYBLUE. (2017). cervical vertebrae - Anatomy Osteology 1 with Me at Medical University of Warsaw - StudyBlue. [online] Available at: https://www.studyblue.com/notes/note/n/cervical-vertebrae/deck/20457914 [Accessed 27 May 2019].
  7. 7.0 7.1 Peng, B. (2016). Natural History of Lumbar Spondylolysis-Advances and Concerns. International Journal of Orthopaedics, 3(4), pp.591-594.
  8. Pilloud, M. and Canzonieri, C. (2012). The Occurrence and Possible Aetiology of Spondylolysis in a Pre-contact California Population. International Journal of Osteoarchaeology, 24(5), pp.602-613.
  9. Selhorst, M., Fischer, A. and MacDonald, J. (2017). Prevalence of Spondylolysis in Symptomatic Adolescent Athletes. Clinical Journal of Sport Medicine, p.1.
  10. 10.0 10.1 10.2 10.3 10.4 McCleary, M. and Congeni, J. (2007). Current Concepts in the Diagnosis and Treatment of Spondylolysis in Young Athletes. Current Sports Medicine Reports, 6(1), pp.62-66.
  11. 11.0 11.1 11.2 Kalichman, L., Kim, D., Li, L., Guermazi, A., Berkin, V. and Hunter, D. (2009). Spondylolysis and Spondylolisthesis. Spine, 34(2), pp.199-205.
  12. Sakai, T., Sairyo, K., Suzue, N., Kosaka, H. and Yasui, N. (2010). Incidence and etiology of lumbar spondylolysis: review of the literature. Journal of Orthopaedic Science, 15(3), pp.281-288.
  13. Sairyo, K., Katoh, S., Sasa, T., Yasui, N., Goel, V., Vadapalli, S., Masuda, A., Biyani, A. and Ebraheim, N. (2005). Athletes with Unilateral Spondylolysis are at Risk of Stress Fracture at the Contralateral Pedicle and Pars Interarticularis: A Clinical and Biomechanical Study. The American Journal of Sports Medicine, 33(4), pp.583-590.
  14. Jackson, D., Wiltse, L. and Cirincione, R. (1976). Spondylolysis in the Female Gymnast. Clinical Orthopaedics and Related Research, &NA;(117), pp.68???73.
  15. Chosa, E., Totoribe, K. and Tajima, N. (2004). A biomechanical study of lumbar spondylolysis based on a three-dimensional finite element method. Journal of Orthopaedic Research, 22(1), pp.158-163.
  16. Palestro, C. (2007). Nuclear Medicine and the Musculoskeletal System. Seminars in Musculoskeletal Radiology, 11(4), pp.279-279.
  17. Hospital, M. (2019). Spondylolysis and Spondylolisthesis of the Lumbar Spine, Children's Orthopaedics, Mass General - Massachusetts General Hospital, Boston, MA. [online] Massgeneral.org. Available at: https://www.massgeneral.org/ortho-childrens/conditions-treatments/spondylolysis.aspx [Accessed 27 May 2019].
  18. 18.0 18.1 McDonald BT, Lucas JA. Spondylolysis. [Updated 2019 Apr 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK513333/
  19. 19.0 19.1 19.2 19.3 19.4 19.5 19.6 19.7 Lawrence, K., Elser, T. and Stromberg, R. (2016). Lumbar spondylolysis in the adolescent athlete. Physical Therapy in Sport, 20, pp.56-60.
  20. 20.0 20.1 20.2 20.3 20.4 Grazina, R., Andrade, R., Santos, F., Marinhas, J., Pereira, R., Bastos, R. and Espregueira-Mendes, J. (2019). Return to play after conservative and surgical treatment in athletes with spondylolysis: A systematic review. Physical Therapy in Sport, 37, pp.34-43.
  21. Coates, C., McMurtry, C., Lingley-Pottie, P. and McGrath, P. (2010). The Prevalence of Painful Incidents among Young Recreational Gymnasts. Pain Research and Management, 15(3), pp.179-184.
  22. Wiltse, L. L., Newman, P., & Macnab, I. (1976). Classification of Spondyloisis and Spondylolisthesis. Clinical orthopaedics and related research, 117, 23–29.
  23. Meyerding, H. W. (1932). Spondylolisthesis. Surg Gynecol Obstet, 54, 371–377.
  24. Slideshare.net. (2015). Spondylolisthesis ms. [online] Available at: https://www.slideshare.net/DrMohitSharma3/spondylolisthesis-ms [Accessed 27 May 2019].
  25. Alqarni, A., Schneiders, A., Cook, C. and Hendrick, P. (2015). Clinical tests to diagnose lumbar spondylolysis and spondylolisthesis: A systematic review. Physical Therapy in Sport, 16(3), pp.268-275.
  26. 26.0 26.1 26.2 26.3 Masci, L., Pike, J., Malara, F., Phillips, B., Bennell, K., Brukner, P., Standaert, C. and Micheli, L. (2006). Use of the one-legged hyperextension test and magnetic resonance imaging in the diagnosis of active spondylolysis. British Journal of Sports Medicine, 40(11), pp.940-946.
  27. Trout, A., Sharp, S., Anton, C., Gelfand, M. and Mehlman, C. (2015). Spondylolysis and Beyond: Value of SPECT/CT in Evaluation of Low Back Pain in Children and Young Adults. RadioGraphics, 35(3), pp.819-834.
  28. Standaert, C. and Herring, S. (2007). Expert Opinion and Controversies in Sports and Musculoskeletal Medicine: The Diagnosis and Treatment of Spondylolysis in Adolescent Athletes. Archives of Physical Medicine and Rehabilitation, 88(4), pp.537-540.
  29. Roy, S., Shaw, P. and Beattie, T. (2015). Low back pain in the paediatric athlete. European Journal of Emergency Medicine, 22(5), pp.348-354.
  30. Chai, B. and Cho, C. (2013). Cervical spine mass imaging: MRI or CT. The Spine Journal, 13(6), pp.713-714.
  31. Rush, J., Astur, N., Scott, S., Kelly, D., Sawyer, J. and Warner, W. (2014). The Use of Magnetic Resonance Imaging in the Evaluation of Spondylolysis. Journal of Pediatric Orthopaedics, p.1.
  32. Harvey, C., Richenberg, J., Saifuddin, A. and Wolman, R. (1998). Pictorial review: The radiological investigation of lumbar spondylolysis. Clinical Radiology, 53(10), pp.723-728.
  33. Jarvik, J. and Deyo, R. (2002). Diagnostic Evaluation of Low Back Pain with Emphasis on Imaging. Annals of Internal Medicine, 137(7), p.586.
  34. Syrmou, E., Tsitsopoulous, P. and Marinopoulos, D. (2007). Spondylolysis. Orthopaedic Nursing, 26(2), pp.112-113.
  35. Gaillard, F. (2015). Scotty dog (diagram) | Radiology Case | Radiopaedia.org. [online] Radiopaedia.org. Available at: https://radiopaedia.org/cases/scotty-dog-diagram [Accessed 27 May 2019].
  36. Gentili.net. (2017). Scotty Dog Sign. [online] Available at: http://www.gentili.net/signs/20.htm [Accessed 27 May 2019].
  37. Childs, J., Piva, S. and Fritz, J. (2005). Responsiveness of the Numeric Pain Rating Scale in Patients with Low Back Pain. Spine, 30(11), pp.1331-1334.
  38. Chapman, J., Norvell, D., Hermsmeyer, J., Bransford, R., DeVine, J., McGirt, M. and Lee, M. (2011). Evaluating Common Outcomes for Measuring Treatment Success for Chronic Low Back Pain. Spine, 36, pp.S54-S68.
  39. Chiarotto, A., Maxwell, L., Terwee, C., Wells, G., Tugwell, P. and Ostelo, R. (2016). Roland-Morris Disability Questionnaire and Oswestry Disability Index: Which Has Better Measurement Properties for Measuring Physical Functioning in Nonspecific Low Back Pain? Systematic Review and Meta-Analysis. Physical Therapy, 96(10), pp.1620-1637.
  40. Nicholas, M. (2007). The pain self-efficacy questionnaire: Taking pain into account. European Journal of Pain, 11(2), pp.153-163.
  41. Stratford, P. (1995). Assessing Disability and Change on Individual Patients: A Report of a Patient Specific Measure. Physiotherapy Canada, 47(4), pp.258-263.
  42. 42.0 42.1 Tawfik, S., Phan, K., Mobbs, R. and Rao, P. (2019). The Incidence of Pars Interarticularis Defects in Athletes. Global Spine Journal, p.219256821882369.
  43. Annear, P., Chakera, T., Foster, D. and Hardcastle, P. (1992). PARS INTERARTICULARIS STRESS AND DISC DEGENERATION IN CRICKET'S POTENT STRIKE FORCE: THE FAST BOWLER. ANZ Journal of Surgery, 62(10), pp.768-773.
  44. Ranson, C., Kerslake, R., Burnett, A., Batt, M. and Abdi, S. (2005). Magnetic resonance imaging of the lumbar spine in asymptomatic professional fast bowlers in cricket. The Journal of Bone and Joint Surgery. British volume, 87-B(8), pp.1111-1116.
  45. Crewe, H., Elliott, B., Couanis, G., Campbell, A. and Alderson, J. (2012). The lumbar spine of the young cricket fast bowler: An MRI study. Journal of Science and Medicine in Sport, 15(3), pp.190-194.
  46. Ranson, C. A., Burnett, A. F., King, M., Patel, N., & O’Sullivan, P. B. (2008). The relationship between bowling action classification and three-dimensional lower trunk motion in fast bowlers in cricket. Journal of sports sciences, 26(3), 267–276.
  47. Ranson, C. A., Burnett, A. F., King, M., Patel, N., & O’Sullivan, P. B. (2008). The relationship between bowling action classification and three-dimensional lower trunk motion in fast bowlers in cricket. Journal of sports sciences, 26(3), 267–276
  48. Ranson, C., Burnett, A., OʼSullivan, P., Batt, M. and Kerslake, R. (2008). The Lumbar Paraspinal Muscle Morphometry of Fast Bowlers in Cricket. Clinical Journal of Sport Medicine, 18(1), pp.31-37.
  49. 49.0 49.1 49.2 49.3 49.4 Mohriak, R., Vargas Silva, P., Trandafilov, M., Martins, D., Wajchenberg, M., Cohen, M. and Puertas, E. (2010). SPONDYLOLYSIS AND SPONDYLOLISTHESIS IN YOUNG GYMNASTS. Revista Brasileira de Ortopedia (English Edition), 45(1), pp.79-83.
  50. Selhorst, M., Fischer, A. and MacDonald, J. (2017). Prevalence of Spondylolysis in Symptomatic Adolescent Athletes. Clinical Journal of Sport Medicine, p.1.
  51. Medium. (2019). Lumbar Spine Stress Fractures — Spondyolysis. [online] Available at: https://medium.com/@TheTennisPhysio/the-sporting-lumbar-spondylolysis-75ed41ed27e [Accessed 27 May 2019].
  52. Maquirriain, J. (2006). The incidence and distribution of stress fractures in elite tennis players * Commentary. British Journal of Sports Medicine, 40(5), pp.454-459.
  53. 53.0 53.1 Ruiz-Cotorro, A. (2006). Spondylolysis in young tennis players. British Journal of Sports Medicine, 40(5), pp.441-446.
  54. Rajeswaran, G., Turner, M., Gissane, C. and Healy, J. (2014). MRI findings in the lumbar spines of asymptomatic elite junior tennis players. Skeletal Radiology, 43(7), pp.925-932.
  55. CAMPBELL, A., STRAKER, L., O’SULLIVAN, P., ELLIOTT, B. and REID, M. (2013). Lumbar Loading in the Elite Adolescent Tennis Serve. Medicine & Science in Sports & Exercise, 45(8), pp.1562-1568.
  56. Upcouture.com. (2013). Compression vs. Non-compression Posture Shirts. [online] Available at: http://upcouture.com/en/blog//compression-vs-non-compression-posture-shirts [Accessed 27 May 2019].
  57. Feel Tennis. (2013). The Key To Improving Your Top Spin Tennis Serve Technique | Feel Tennis. [online] Available at: https://www.feeltennis.net/improve-topspin-tennis-serve-technique/ [Accessed 27 May 2019].
  58. Codecogs.com. (2013). Torsion - Materials - Engineering Reference with Worked Examples. [online] Available at: https://www.codecogs.com/library/engineering/materials/torsion.php [Accessed 27 May 2019].
  59. Codecogs.com. (2013). Torsion - Materials - Engineering Reference with Worked Examples. [online] Available at: https://www.codecogs.com/library/engineering/materials/torsion.php [Accessed 27 May 2019].
  60. Grazina, R., Andrade, R., Santos, F., Marinhas, J., Pereira, R., Bastos, R. and Espregueira-Mendes, J. (2019). Return to play after conservative and surgical treatment in athletes with spondylolysis: A systematic review. Physical Therapy in Sport, 37, pp.34-43.
  61. 61.0 61.1 61.2 61.3 Panteliadis, P., Nagra, N., Edwards, K., Behrbalk, E. and Boszczyk, B. (2016). Athletic Population with Spondylolysis: Review of Outcomes following Surgical Repair or Conservative Management. Global Spine Journal, 6(6), pp.615-625.
  62. 62.0 62.1 Bouras, T. and Korovessis, P. (2014). Management of spondylolysis and low-grade spondylolisthesis in fine athletes. A comprehensive review. European Journal of Orthopaedic Surgery & Traumatology, 25(S1), pp.167-175.
  63. Panteliadis, P., Nagra, N., Edwards, K., Behrbalk, E. and Boszczyk, B. (2016). Athletic Population with Spondylolysis: Review of Outcomes following Surgical Repair or Conservative Management. Global Spine Journal, 6(6), pp.615-625.
  64. Panteliadis, P., Nagra, N., Edwards, K., Behrbalk, E. and Boszczyk, B. (2016). Athletic Population with Spondylolysis: Review of Outcomes following Surgical Repair or Conservative Management. Global Spine Journal, 6(6), pp.615-625.
  65. Panteliadis, P., Nagra, N., Edwards, K., Behrbalk, E. and Boszczyk, B. (2016). Athletic Population with Spondylolysis: Review of Outcomes following Surgical Repair or Conservative Management. Global Spine Journal, 6(6), pp.615-625.
  66. Miyamoto, G., Costa, L. and Cabral, C. (2013). Efficacy of the Pilates method for pain and disability in patients with chronic nonspecific low back pain: a systematic review with meta-analysis. Brazilian Journal of Physical Therapy, 17(6), pp.517-532.
  67. van Tulder, M., Koes, B. and Malmivaara, A. (2005). Outcome of non-invasive treatment modalities on back pain: an evidence-based review. European Spine Journal, 15(S1), pp.S64-S81.
  68. Leone A, Cianfoni A, Cerase A, Magarelli N, Bonomo L. Lumbar spondylolysis: a review. Skeletal radiology. 2011 Jun 1;40(6):683-700.
  69. Uwhealth.org. (2010). [online] Available at: https://www.uwhealth.org/files/uwhealth/docs/sportsmed/Spondy_Rehab_Guide.pdf [Accessed 27 May 2019].
  70. Garet, M., Reiman, M., Mathers, J. and Sylvain, J. (2013). Nonoperative Treatment in Lumbar Spondylolysis and Spondylolisthesis. Sports Health: A Multidisciplinary Approach, 5(3), pp.225-232.
  71. Engel, George L. (8 April 1977). "The need for a new medical model: a challenge for biomedicine". Science. 196(4286): 129–36. doi:10.1126/science.847460. PMID 847460.
  72. Ivarsson, A., Tranaeus, U., Johnson, U. and Stenling, A. (2017). Negative psychological responses of injury and rehabilitation adherence effects on return to play in competitive athletes: a systematic review and meta-analysis. Open Access Journal of Sports Medicine, Volume 8, pp.27-32.
  73. Putukian, M. (2015). The psychological response to injury in student athletes: a narrative review with a focus on mental health. British Journal of Sports Medicine, 50(3), pp.145-148.
  74. PPSS Cumbria. (2016). Glossary of Key Terms | PPSS Cumbria. [online] Available at: https://ppss.cumbria.nhs.uk/patients/patient-resources/what-to-expect-from-our-service/glossary-of-key-terms [Accessed 27 May 2019].
  75. Medium. (2017). Lumbar Spine Stress Fractures — Spondyolysis. [online] Available at: https://medium.com/@TheTennisPhysio/the-sporting-lumbar-spondylolysis-75ed41ed27e [Accessed 26 May 2019].