Lumbosacral spondylolisthesis is the forward translation of the fifth lumbar vertebra (L5) over the first sacral vertebra (S1). Bilateral L5 pars defect (spondylolysis) or repetitive stress injury is the primary etiology behind lumbosacral spondylolisthesis. The degree of a slip often correlates with the degree of symptoms.
The prevalence of spondylolysis (pars defect), in the general population, is 6%, and a third of those will subsequently develop a degree of spondylolisthesis.[1] The majority of cases are mild or asymptomatic, and only a relatively small percentage of symptomatic patients require surgical intervention.
The most commonly affected populations are children and adolescents participating in sports that require repetitive lower back hyperextension (divers, pace cricket bowlers, baseball, softball, rugby, weightlifting, sailing, table tennis, wrestlers, gymnasts, dancers, and footballers). They usually present with lower back pain exacerbated by activity.[2] Occasionally pain can radiate to both buttocks and legs, and in advanced cases, the gait pattern and walking distance may be affected. Presentation in adults is more insidious and commonly associated with long-standing degenerative changes secondary to the slip, often leading to spinal canal stenosis and radicular pain.
Management of the majority of the cases is non-operative, but patients who fail non-operative treatment and continue having disabling symptoms may require surgical treatment.[2][3]
A Wiltse-Newman classification describes different etiology of pars interarticularis failure [4]:
Depending on the degree of the forward slip, the severity of this process is graded as mild, severe, or complete slip (spondyloptosis) - described later in Myerding classification.
In the most common isthmic spondylolisthesis, which leads to an L5/S1 slip, the following stages have been identified.
The second most common types of spondylolisthesis are type I (dysplastic) and III (degenerative). Degenerative spondylolisthesis is most prevalent in the adult population, and levels affected most frequently are L4/L5 followed by L3/L4. Due to the chronicity of the instability, often associated degenerative changes in intervertebral disc and facet joints occur. They often lead to secondary hypertrophy of the ligamentum teres and subsequent spinal canal stenosis. This condition usually presents with bilateral buttock pain and neurogenic claudication (back pain eased by sitting down/leaning forward).
Estimates are that 4 to 6% of the population has a degree of lumbosacral spondylolisthesis. The majority of cases are asymptomatic.[5]
Most of the symptomatic high-grade slips occur in the pediatric/adolescent population participating in sports involving repetitive hyperextension, while adults tend to present with milder and more chronic onset of symptoms.[6]
The most commonly affected adolescent groups are female dancers or gymnasts with hyperlordosis and hyper flexibility, male football players, or weight lifters with limited motion at lumbar spine undergoing growth spurt or novice athlete vigorously training while having poor core strength.[7]
There are reports of familial association and congenital abnormalities, including spina bifida occulta, thoracic hyperkyphosis (Shauerman disease) as predisposing factors as well as general ligamentous laxity.
Several anatomical factors described below predispose to spondylolisthesis.
Two mechanisms may cause the lytic defect. The first is the pincer effect due to repeated hyperextension.[8] The inferior facet of L4 and the superior facet of S1 creates a pincer effect on the pars interarticularis, causing a failure of the L5 pars. This condition is more likely to occur in a situation where the sacral slope has a low value with a more horizontally orientated superior sacral endplate. The second mechanism is when there is an increased sacral slope and hence increased traction on the pars interarticularis.[9] The repeated traction on the pars from a downsloping lumbosacral junction results in failure and fracture of the pars interarticularis. In high-grade slips, the anterosuperior part of the sacrum becomes dome-shaped, which may be due to repeated trauma to the anterosuperior apophyseal ring of the S1 vertebrae.[10]
The spinopelvic balance and the global spinal alignment is essential in understanding the etiology, grading, and planning the treatment protocol.[11] These parameters are measured on a standing lateral radiograph. The main parameters and their definitions are as follows.
Forward translation of the vertebrae may cause a narrowing of the spinal canal at the level of the slip. This situation is rare as most of the slips are only grade I or II, but the secondary canal and foraminal stenosis can occur due to subsequent degenerative changes in facet joints, hypertrophy of ligamentum flavum, hypertrophic fibrous repair tissue of the pars defect or bulging of L5/S1 disc. In severe L5/S1 slips, the L5 nerve root is most commonly affected by being pulled forward by the superior vertebra.
Most cases of spondylolisthesis are asymptomatic.
Severe slips are uncommon, and deformity rarely progresses beyond Meyerding grade II (see Evaluation chapter).
Typical history and examination findings in symptomatic cases involve:
History:
Examination findings:
Listhetic crisis (rapid progression of symptoms). Common during a growth spurt or increased physical activities with bilateral pars failure.
Following the history and examination, the best screening tool is an AP and lateral weight-bearing X-ray of the lumbar spine.[15] Lumbosacral spondylolisthesis can be best assessed mainly on the lateral view, but occasional coronal deformity should not be missed. In cases where clinical examination indicates an abnormal sagittal balance of the spinal column, a whole spine lateral standing X-ray is indicated. In the majority of cases, an isthmic defect will be detected on radiographs but in doubtful cases. An MRI scan is recommended. Oblique X-rays of the lumbosacral junction, Computerised Tomography (CT) scan, SPECT scans may also identify the defect but involve ionic radiation.
MRI scans are more sensitive in identifying pars lesions.MRI can also identify stress reactions that occur even before a fracture line develops.[16] In dysplastic cases, dome-shaped or significantly inclined sacrum can present as well as trapezoid-shaped L5 and dysplastic facets of S1. Neoplasms and infections are an extremely rare primary cause of spondylolisthesis but should merit consideration as a differential diagnosis in patients with constitutional symptoms. To assess dynamic instability, flexion and extension views should be obtained. Either 4 mm of translation or 10 degrees of angulation of motion compared to the adjacent motion segment are diagnostic for spondylolisthesis.
Grading of the forward slip is classified by Meyerding classification:
Pelvic incidence (PI) has a direct correlation to Meyerding grade.[12]
The Spinal Deformity Study Group has created a new classification that guides treatment. This scale takes into account the spinopelvic parameters and the overall spinal alignment.[17]
MRI (T-2 weighted sequence is best to assess spinal canal stenosis, foraminal stenosis, and nerve root impingement, as well as the morphology of lumbar and sacral vertebrae which presence correlated with history and examination findings, will dictate the surgical management). The most commonly affected nerve root is L5.
The majority of the cases can be treated non-operatively by:
Non-operative management of acute cases among sportspersons was successful in 95% of patients, and only 5% required surgical intervention. Among those treated non operatively, 82% returned to their previous level of play.[19] Approximately one-third of patients with spondylolisthesis experience a disease progression over time. Operative treatment is reserved for those with intractable pain or neurological symptoms, including claudication or radiculopathy.[23]
Surgical intervention has shown >80% success in appropriately selected patients, with a low incidence of complications. Surgical techniques include the following:
Operative options should be considered only if non-operative options fail or symptoms are significant. The reduction of the slip is controversial as in approximately 20% of cases, it causes L5 nerve root injury. Nevertheless, some evidence suggests better functional and cosmetic outcomes for patients who underwent reduction and instrumented fusion.[32] Foraminal decompression may also be necessary. Interbody fusion with the maintenance of intervertebral space improves the foraminal height, helps restore lumbar lordosis, and avoids fusion to L4 in high-grade slips. Each case requires an individual approach, and factors like the degree of spondylolisthesis, predominant neurological symptoms, and patients comorbidities should be taken into consideration.[33] Minimally invasive surgical techniques are gaining in popularity.[34]
Despite the estimate of up to 6% of the population suffering from spondylolisthesis, the majority of them are asymptomatic. Only a small percentage of symptomatic cases will require surgical treatment.
Worst prognosis in cases of:
Complication rate increases with age, increased intraoperative blood loss, longer operative time, the number of levels fused.
Sports coaches and personal trainers working with children and adolescents especially those practicing gymnastics, football or weight lifting, should be aware of the symptoms of spondylosis and spondylolisthesis. They should be able to identify cases when pain does not improve after rest and basic stretching and strengthening exercises. These sportspersons need to be referred for specialist evaluation to diagnose and treat. This is particularly important as braces that prevent extension and activity reduction have shown excellent results.
Affected patients should be educated about the importance of activity modifications and physiotherapy and engage with core muscle strengthening and flexion exercises for symptomatic treatment.
They should receive reassurance that most of the symptoms are transient. But at the same time, especially those with a high risk of slip progression should be followed up by a specialist Orthopedic surgeon and educated about symptoms and signs of slip progression and potentially serious complications like cauda equina syndrome.
Pars interarticularis defects were common in sportsperson involved in increased activity. Hyperextension of the spine during the sport was a risk factor. In cricket fast bowlers extended and laterally flexed their spine, before throwing the ball to increase the speed of delivery. This repetitive movement increased the likelihood of developing a pars defect. In a recent review pars interarticularis defects were more common in the following sports, diving (35.38%), cricket (31.97%), baseball/softball (26.91%), rugby (22.22%), weightlifting (19.49%), sailing (17.18%), table tennis (15.63%), and wrestling (14.74%).[19] The suspicion that young adolescent sportspersons could develop spondylolysis is crucial in early diagnosis and prevention of progression. Bracing and activity restriction has shown excellent results with a good return to the same level of play.
A high level of suspicion within sports coaches, general practitioners, and parents is needed to recognize patients with symptoms of spondylolisthesis.
Groups at risk like adolescent gymnasts, football players, and weight lifters should undergo health screening checks at regular intervals, and those with a history of lower back pain associated with activities undergo further evaluation and examination with those with suggestive signs and symptoms undergoing radiological investigations.
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