November 22, 2021
spondylolisthesis and spondylolysis cover

spondylolysis and spondylolisthesis


There is always confusion in the medical community in regards to spondylolysis and spondylolisthesis, although it is very likely to be seen in the adolescent athlete population. Spondylolysis is an anatomical defect or fracture of the pars interarticularis of the vertebral arch. The pars interarticularis is an isthmus of bone connecting the superior and inferior facet surfaces in the spine at a given level. Spondylolysis occurs at the L5 vertebrae between 85 and 95% of the time and occurs at the L4 vertebrae 5–15% of the time [1]. The defects can occur unilaterally or bilaterally. Spondylolysis is one of the most common causes of lower back pain in adolescents, although it remains asymptomatic in the majority of patients. Spondylolysis can progress to spondylolisthesis, which is defined as anterior displacement of the vertebral body in reference to the bordering vertebral bodies.


There are five categories of spondylolisthesis classified by Wiltse et al. [24].  Type I is dysplastic and refers to a congenital dysplasia that results in the anterior and superior rounding of the S1 vertebrae. This rounding allows the L5 vertebrae to slip anteriorly on the S1 vertebrae. Type II is isthmic and is separated into Type IIA and Type IIB. Type IIA is caused by a stress fracture of the pars interarticularis (spondylolysis) that results in anterior slippage of the vertebrae. Type II B is caused by repetitive fractures and subsequent healing which results in lengthening of the pars interarticularis leading to anterior slippage of the vertebrae. Type III is degenerative and the root cause is commonly from arthritis.  Type IV is traumatic and is caused by high energy trauma to the spine. Type V is pathologic and can be caused by lytic bone tumors, osteopetrosis, or osteoporosis.

Image 1: Adopted from [28].

The Meyerding classification defines the amount of vertebral slippage on X-ray in reference to the caudal vertebrae. There are five grades of spondylolisthesis in the Meyerding classification. Grade I is less than 25 percent slippage, grade II is 26–50% slippage, grade III is 51–75% slippage, grade IV is 76–100% slippage, and grade V is over 100% slippage and is referred to as spondyloptosis [25].

Image 2.  Meyerding Classification.

There are congenital factors such as spina bifida occulta and exaggerated lumbar lordosis that may predispose individuals to pars fractures [2]. In addition to congenital factors, activity-related exposures such as sport participation may contribute to pars fractures. Participation in sports, particularly sports involving repetitive hyperextension and axial loading of the spine, predisposes young athletes to pars fractures. Common examples include baseball, gymnastics, football, tennis, and weightlifting [2,3].

Image 3.  Spondylolysis is more common in baseball, gymnastics, football, tennis, and weightlifting.

The incidence of lumbar spondylolysis in the general population is generally thought to be between 3 and 10 percent [4].  One study in 532 patients aged eight or younger presenting with general lumbar complaints, spondylolysis was shown in 4.7% of those children [4].  In another study, rates were as high as 30 % among 1025 adolescent athletes presenting to a sports medicine clinic with low back pain.  Therefore, there seems to be a significantly higher incidence and prevalence of spondylolysis among young athletes than those in the general pediatric population [5].

physical examination

The athlete or patient will typically present with insidious, atraumatic and focal low back pain that seems to worsen with activity. Pain does typically get exacerbated with lumbar extension and there is normally not any radiation into the legs. On examination, there may be increased lumbar lordosis and tightness of the hamstring muscles when compared to adolescents without spondylolysis [6]. Assessment and documentation of the following are recommended in the physical examination:
(a) Observation: posture, spinal alignment, AROM, quadrant motion, and presence of directional preference
(b)Gait: walking and running (if indicated)
(c)Palpation: lumbar muscle tenderness and tone, bony landmarks, and step-off deformity of the spine
(d)Movement analysis: provocative movements during sport, function, play, and activity (measure consistency with AROM limitations or directional preference); presence of aberrant movements
(e) Lower extremity flexibility: hamstring length and hip flexor tightness
(f) Manual muscle testing: gluteal musculature, hamstring, abdominal/trunk strength, and lumbar extensor endurance (if tolerable)
(g) Neurological evaluation: reflexes, dermatomal sensory loss, and myotomal strength loss (e.g., L5 – hip abduction, ankle dorsiflexion, and great toe extension)
(h) Motor control: ability to contract transverse abdominus and internal oblique.

The most well known special clinical test is the single-leg hyperextension test. However the test has not been shown to be particularly sensitive or specific for spondylolysis [7,8]. Therefore, imaging is necessary when a clinician wishes to confidently determine if a spondylolytic lesion is present in an adolescent athlete with low back pain.

Progression of spondylolisthesis after the age of 20 years is much less common compared to progression during childhood and adolescence. This is likely due to ossification of the growth plate. McPhee et al. followed 51 patients under the age of 30 with spondylolisthesis and evaluated the progression of slippage. The incidence of progression in the entire study population was 24%. It was found that the rate of progression was highest in adolescents with 38% of the adolescents progressing [9].


Radiographs often serve as the primary imaging modality for the evaluation of low back pain. Although radiographs can readily identify a vertebral slip, pars fractures alone are often difficult to identify [10]. In addition, bone marrow edema cannot be assessed on radiography, negating the ability to identify early-stage disease [11], as well as separate an active spondylolysis from an inactive chronic nonunion.  Evaluation of the pars interarticularis is suboptimal on routine views of the lumbar spine and additional views are needed.  These added views include a 45 lateral oblique projection, frontal projection with 30 cranial angulation, and 40 lateral oblique projection with 30 cranial angulation [11].  The 45 lateral oblique angle is theoretically transverse to the pars interarticularis, which produces the classic Scottie dog appearance that has been described in the literature, where the pars interarticularis represents the neck of the dog (Image 4) [12].  

Image 4: MRI T2 image showing the classic “Scottie Dog” appearance on the lateral oblique view.  A fracture through the neck or collar is shown here. Adopted from [28].

Advanced imaging modalities can be more sensitive than plain film x-rays in the diagnosis of spondylolysis. In comparing MRI with CT, where CT is used as the gold standard for evaluation, the sensitivity of MRI was 83% [12]. Two studies have compared CT to single-proton emission CT (SPECT) as the gold standard; they demonstrate the sensitivity of CT is 85% [13-14]. Lastly, comparing MRI to SPECT, where SPECT was the control gold standard, the sensitivity of MRI is 80% [15].  The most up-to-date systematic review of 10 major pediatric imaging studies conditionally recommends the following: MRI as the initial advanced imaging option after plain films with CT scans recommended in equivocal situations.  MRI remains a better diagnostic tool for the early detection of pars injury than CT; however, CT is superior for longitudinal follow-up [16,17].


There are few large clinical trials focused on the treatment of spondylolysis which makes it difficult to determine a proper treatment algorithm for conservative and surgical treatment. Young patients with spondylolysis generally receive conservative management as their initial treatment. In this population, ample evidence exists to support the development of core-strengthening exercises, specifically activating and isolating the transverse abdominis (TA), internal oblique (IO), and multifidi to structurally stabilize the lumbar segments [18]. These deep abdominal muscles (TA and IO) and lumbar multifidus are particularly relevant in the management of patients with low back pain and/or lumbar instability because of their impact on increasing intra-abdominal pressure as well as their co contraction resulting in tension placed on the thoracolumbar fascia and lumbar vertebrae, thereby increasing lumbar stiffness [22]. Recommendations related to the parameters of PT intervention after spondylolysis diagnosis (i.e., stage of recovery to initiate, frequency, and duration) vary significantly, resulting in a lack of standardization of postinjury rehabilitation programs. The timing of therapy initiation discussed in the literature spans from early within the diagnostic process to waiting until complete fracture healing.  [18]. 

Kurd et al. retrospectively reviewed the medical records of 436 juvenile and adolescent patients with symptomatic spondylolysis confirmed by SPECT or CT [19]. All patients were treated nonoperatively with a prescription for a thoracolumbar orthosis and discontinuation of sporting activity for three months followed by a structured PT program. At the final clinical follow-up, 95% of patients in the study achieved excellent results with the remaining individuals reporting good results and occasional use of NSAIDs. All patients returned to their preinjury level of activity, and zero patients required surgery. In 2010, Watkins and Watkins reported their 25-year experience caring for athletes with spine-related, sports injuries, utilizing a “trunk-stabilizing program.” During that period, only two athletes required operative intervention for spondylolysis [2].  

Arima et al. evaluated the use of low-intensity pulsed ultrasound (LIPUS) versus conventional conservative treatment in patients with the progressive stage of spondylolysis [29]. The experimental group consisted of 9 adolescent patients that received a combination of LIPUS for 20 min every day in addition to conventional conservative treatment. The control group consisted of 10 adolescent patients who received only conventional conservative treatment. The experimental group treated with LIPUS achieved a union rate of 66.7% with a mean treatment time of 3.8 months. In the control group treated with conventional conservative treatment, a union rate of 10% was achieved with a treatment time of 3.8 months. Busse et al. performed a meta analysis of 3 trials with a total of 158 fractures of various bones that utilized LIPUS and found an average increase in healing time of 64 days between the LIPUS and control groups [30]. Larger studies are needed, but low-intensity pulsed ultrasound shows promise in early studies. 

Conflicting recommendations exist relating to the use of external bracing in the setting of spondylolysis, including timing of bracing after diagnosis. However, specific to the diagnosis of spondylolysis, there is good evidence for conservative management, including the restriction of activity/sport combined with PT and implementation of external bracing only if symptoms persist [2,23]. In a retrospective study of 121 adolescents who underwent external bracing after initial diagnosis, Selhorst et al. identified several factors that failed to show a statistically significant, long-term effect on prognosis. These factors included bracing, type of injury (unilateral, bilateral, and spondylolisthesis), duration of symptoms, and previous episodes of low back pain (LBP) [23].  Therefore, bracing is debatable in this population.

In the small percentage of young patients who fail conservative treatments, direct surgical repair of the spondylolysis has been shown to be highly effective. Reports on direct surgical repair of spondylolysis focus on patients younger than 30 years of age with recommended age cutoffs for improved surgical outcomes stated as 20 or 25 years [20,21]. Criteria that should be met for direct repair of the pars include as follows: (1) healthy appearance and preserved height of the intervertebral disk on MRI and (2) no demonstration of significant motion between vertebral bodies on dynamic radiographs [21].

Patients with grade I or II spondylolisthesis that have no accompanying impairments of daily living activities can be managed conservatively. In patients with grade III, IV, or V spondylolisthesis, the decision to treat surgically is still very controversial [26]. Lundinine et al. compared quality of life measurements in patients with grades III, IV, or V spondylolisthesis that were managed conservatively against those that were managed surgically [27]. They concluded that surgical management of a symptomatic patient achieves a similar quality of life to those patients that had minimal symptoms and were managed conservatively. They found that patients who had delayed surgical treatment did not have worse outcomes [27].


In summary, stress injuries and fractures to the lumbar pars interarticularis are common sports-related injuries among young athletes. It is much more common in adolescent athletes and occurs at the L5 level the vast majority of the time.  It is more common in sports that require repetitive extension activities such as baseball, gymnastics, football, tennis, and weightlifting.  After diagnosis, an individualized PT rehabilitation program including education, activity modification, and a progressive course of specific exercise will lead to symptom resolution and return to athletic participation in the vast majority of young athletes. Surgery for direct pars repair is rarely necessary; however, it has high success rates when required in refractory patients. 


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