Etiology of Adult-onset Stress Fracture in the Lumbar Spine

Abstract

Study Design: 

This study was a case series.

Objective: 

The purpose of this paper was to present a case series of fresh stress fractures (spondylolysis) in the lumbar spines of adult athletes.

Summary of Background Data: 

Lumbar spondylolysis is a stress fracture of the pars interarticularis, which is generally considered a disease of children or adolescence. There is only 1 case series written in English reporting on adult-onset fresh spondylolysis.

Methods: 

Eleven patients aged 20–27 years are included in this case series. A retrospective analysis was made of events that may cause stress fracture such as traumatic episodes or sports activities, spinal level, radiologic findings, stage of spondylolysis, treatment, and prognosis.

Results: 

Among the 11 patients, two had bilateral early-stage spondylolysis, 7 had unilateral early-stage spondylolysis and 2 had unilateral progressive-stage spondylolysis. Three occurred subsequent to a preexisting terminal-stage spondylolysis in the contralateral side, 1 occurred subsequent to a terminal-stage spondylolysis at the adjacent spinal level, and 1 occurred subsequent to a terminal-stage spondylolysis at a distant level. Thirteen pedicles adjacent to the pars interarticularis in the 11 patients showed bone marrow edema-like signal on magnetic resonance imaging. Six spondylolyses were found at L5, 2 each at L3 and L4, and 1 spondylolysis at L2. The 11 patients were divided into 4 groups according to suspected pathogenic mechanism: preexistent spondylolysis in the contralateral side, alteration of the athletic event, apparent traumatic episode, and others. Conservative treatment was prescribed for return to sports in all cases. Although 1 patient retired because of persistent low back pain, the remaining 10 patients returned to competition.

Conclusions: 

Although lumbar spondylolysis is generally recognized to occur in childhood or adolescence, fresh lumbar spondylolysis should be included in the differential diagnosis of adult low back pain when patients are high-level athletes. Conservative treatment should be attempted for adult patients.

Lumbar spondylolysis is a stress fracture of the pars interarticularis in the lumbar spine, which is well known for having a congenital predisposition for, and is a frequent cause of, low back pain (LBP) in teenagers and young adults, especially in adolescents involved in sporting activities.^1–3 Individuals engaging in specific athletic activities that involve repetitive trunk movements, such as weight lifting, wrestling, gymnastics, football, diving, throwing, and rowing, appear more likely to develop symptomatic LBP associated with lumbar spondylolysis.⁴

There is a general agreement that athletic movements requiring repetitive lumbar extension and rotation carry a risk for spondylolysis, especially in the immature spine. Indeed, a much higher incidence of spondylolysis has been reported among professional soccer and baseball players.^5,6 Sakai et al⁷ reported an incidence of lumbar spondylolysis of 5.9% among the general adult Japanese population and that all cases of spondylolysis were in the terminal stage [ie, no fresh (early-stage or progressive-stage) lumbar spondylolysis]. It would appear then that fresh lumbar spondylolysis rarely occurs in adults, and there are few reports in the English literature about it.

In this case series, we describe the clinical characteristics of 11 high-level adult athletes who presented with fresh lumbar spondylolysis.

METHODS

Eleven patients (2 women, 9 men; age range, 20–27 y) with fresh lumbar spondylolysis were examined in this study. Events that may cause lumbar spondylolysis including sports activities and trauma, spinal level of the spondylolysis, radiologic findings, stage of spondylolysis, treatment, and prognosis were investigated. Stage of spondylolysis was evaluated on computed tomography (CT) and magnetic resonance imaging (MRI) scans and defined as follows: a hairline fracture is visible in the early stage, it progresses into a gap in the progressive stage, and the terminal-stage defect manifests as pseudoarthrosis.⁸ Skeletal age of the vertebrae was evaluated from plain x-ray films.⁹

RESULTS

The 11 patients consisted of 3 professional baseball players, 2 professional soccer players, and 6 intercollegiate athletes (4 track-and-field athletes, 1 baseball player, and 1 gymnast) (Table 1). The patients could be divided into 4 groups based on suspected pathogenic mechanism: preexistent spondylolysis in the contralateral side, alteration of the athletic event, apparent traumatic episode, and other (Table 2).

TABLE 1: Data of the 11 Adult Patients With Fresh Lumbar Spondylolysis

TABLE 2: Classification From the Features of Possible Pathogenic Mechanisms

Skeletal age of the vertebrae in all patients was in the epiphyseal stage. Six spondylolyses were found at L5, 2 each at L4 and L3 and 1 spondylolysis at L2. Two of the 11 patients had bilateral early-stage spondylolysis, 7 had unilateral early-stage spondylolysis, and 2 had unilateral progressive-stage spondylolysis (Table 1). Three cases of spondylolysis (1 unilateral early-stage and 2 unilateral progressive-stage) were subsequent to preexisting terminal-stage spondylolysis in the contralateral side, 1 case was subsequent to preexisting bilateral terminal-stage spondylolysis at an adjacent spinal level, and 1 cases was subsequent to preexisting unilateral spondylolysis at a distant level. Thirteen pedicles adjacent to the pars interarticularis in the 11 patients had bone marrow edema-like signal on MRI. Except for terminal-stage spondylolyses that had been diagnosed in childhood (6 spondylolyses in 5 patients), all spondylolyses had high signal change (HSC) on short T1 inversion recovery (STIR)-MRI in this study. Conservative treatment consisting of bracing, rest and rehabilitation was prescribed for return to sport in all cases. Although only 1 female professional football player retired because of LBP, the remaining 10 patients returned to competition.

REPRESENTATIVE CASES

Patient 2 in Group 1: Preexistent Spondylolysis in the Contralateral Side

A 25-year-old male professional baseball player (catcher) felt mild LBP on practicing. On initial presentation, CT showed a terminal-stage lumbar spondylolysis in the left L5 pars, which had been diagnosed in childhood (Fig. 1).

FIGURE 1: Computed tomography scans of patient 2 at initial presentation show L5 terminal-stage spondylolysis of the left side (clear arrow). A, Sagittal view through right L5 pedicle. B, Axial view through right pedicle. C, Sagittal view through left L5 pedicle.

A few days later, he felt severe LBP after swinging a bat, and CT revealed a progressive-stage lumbar spondylolysis on the contralateral lamina (Fig. 2). Thus, the progressive-stage spondylolysis was thought to occur subsequent to the preexisting contralateral spondylolysis (group 1 in Table 2). He returned to competition after conservative management.

FIGURE 2: Computed tomography scans taken of patient 2 a few days later show L5 progressive-stage spondylolysis of the right side (white arrow). A, Sagittal view through right L5 pedicle. B, Axial view through L5 pedicle. C, Sagittal view through left L5 pedicle.

Patient 4 in Group 2: Alteration of the Athletic Event

A 22-year-old female professional soccer player suffered severe LBP after her training program was altered (group 2 in Table 2). CT showed bilateral early-stage lumbar spondylolysis at L3. STIR-MRI showed HSC in the bilateral pedicle adjacent to the pars interarticularis, which indicated a fresh stress fracture. Although she returned to play soccer after pain management, the LBP was too persistent to play professionally and she retired to undergo conservative treatment to achieve bony healing (Fig. 3).

FIGURE 3: Computed tomography scans and STIR-MRI of patient 4 show L3 bilateral early-stage spondylolysis (white arrow). A, Sagittal view through right L3 pedicle. B, STIR-MRI axial view through L3 pedicle shows high signal change in the bilateral pedicle adjacent to the pars interarticularis (clear arrow). C, Sagittal view through left L3 pedicle. STIR-MRI indicates short T1 inversion recovery-magnetic resonance imaging.

Patient 6 in Group 2: Alteration of the Athletic Event

A 21-year-old professional baseball player (left-handed pitcher) presented with LBP after changing his pitching form (group 2 in Table 2). CT scans and STIR-MRI showed early-stage unilateral spondylolysis (HSC in STIR-MRI) at L2 and terminal-stage ipsilateral spondylolysis at L5 both on the right side (Fig. 4). After conservative management, he is playing professionally again.

FIGURE 4: Patient 6. A, STIR-MRI shows high signal change in the right L2 pedicle (white arrow). B, Computed tomography scan shows early-stage spondylolysis at L2 on the right side (white arrow) and terminal-stage spondylolysis at L5 on the same side (clear arrow). C, CT scan axial view through L2 pedicle. STIR-MRI indicates short T1 inversion recovery-magnetic resonance imaging.

Patient 7 in Group 3: Apparent Traumatic Episode

A 20-year-old male long jumper with no history of LBP suffered severe LBP on landing. He was diagnosed with bilateral L4 spondylolysis. This one-time injury led to a fracture in the pars interarticularis (group 3 in Table 2). After conservative treatment with a trunk brace, he returned to competition.

Patient 11 in Group 4: Other

A 23-year-old male professional baseball player (left-handed pitcher) presented with LBP on practicing at a training camp. He had undertaken more pitching exercise than usual (group 4 in Table 2). CT showed early-stage unilateral left L5 spondylolysis, and STIR-MRI showed HSC in the left pedicle. He has returned to professional-level competition (Fig. 5).

FIGURE 5: Patient 11. A, Computed tomography scan axial view shows early-stage unilateral spondylolysis at L5 on the left side (white arrow). B, Computed tomography scan sagittal view through left L5 pedicle shows early-stage lumbar spondylolysis (white arrow). C, STIR-MRI shows high signal change in the left pedicle (clear arrow). STIR-MRI indicates short T1 inversion recovery-magnetic resonance imaging.

DISCUSSION

All 11 patients with adult-onset fresh lumbar spondylolysis presented in this paper were high-level athletes and included 5 professional players. Generally, lumbar spondylolysis has been regarded as a disease of childhood or adolescence, which was supported by Sakai et al⁷ finding no fresh spondylolysis among 2000 CT scans examined for the adult general population. Sutton et al¹⁰ did, however, publish a recent case series describing 8 intercollegiate athletes with acute lumbar spondylolysis. Conservative treatment failed in 5 of the patients and 1 patient was lost to follow-up. In their report, they used only CT scans to evaluate the spondylolysis. It is generally accepted that MRI is essential to make early diagnosis of fresh or acute lumbar spondylolysis correctly.^11,12 Therefore, the present study is the first to report MRI findings confirming a finding of fresh lumbar spondylolysis in adults.

To obtain bony union or healing, patients must refrain from all sports activities and wear a trunk brace for at least 3 months.^11,13 For high-level athletes including professional sports players, to return to their competitive level as soon as possible is paramount. Therefore, conservative treatment to achieve bony union requiring 3 months of rest is not always necessary for them. Conservative treatment consisting of bracing, rest and rehabilitation should be prescribed to maintain a pain-free condition. In fact, we were able to manage all of our patients conservatively, with all but 1 (90.9%) returning to competition.

There were 3 cases of spondylolysis (1 unilateral early-stage and 2 unilateral progressive-stage) that were subsequent to preexisting terminal-stage spondylolysis on the contralateral side, 1 case of spondylolysis subsequent to preexisting bilateral terminal-stage spondylolysis at an adjacent spinal level, and 1 case at a distant spinal level. Sairyo et al¹⁴ reported biomechanical results showing that unilateral spondylolysis could lead to stress fracture or sclerosis on the contralateral side because of increased stress in the region, and the highest increase in stress of the pedicle was 12.6-fold greater than that of the intact case. Regarding multilevel spondylolysis, biomechanical study found it was not associated with biomechanical stress because of preexistent spondylolysis at the adjacent spinal level and suggested it may occur because of genetic reasons.¹⁵

In the general population, 90% of lumbar spondylolysis is found at L5.⁷ In the present cases, 54.5% was found at L5, 18.2% at L4, 18.2% at L3, and 9.1% at L2. Sutton et al¹⁰ also reported a high rate of lumbar spondylolysis in intercollegiate athletes at mid-lumbar level. Although the pathomechanism is still unclear, there may be a relationship with certain athletic movements.

All 11 patients with adult-onset lumbar spondylolysis presented in this report were high-level athletes, who were not considered to belong to the general population. To maintain performance as a high-level athlete requires tremendous exercise, which can result in lumbar spondylolysis. Further, preexisting unilateral spondylolysis can lead to stress fracture on the contralateral side. Furthermore, alteration of stress concentration on the lumbar spine following the introduction of a new training method or new form can lead to fresh spondylolysis even in the mature spine.

In conclusion, lumbar spondylolysis has been regarded as a disease of childhood or adolescence in the general population. However, we should recognize the possibility that fresh lumbar spondylolysis can occur in high-level adult athletes. Regarding management, nonoperative treatment should be attempted initially, and it is preferable to alleviate pain for professional adult athletes as quickly as possible, not to achieve bony union.