Pathophysiology

The report of trauma as a precursor to adolescent and pediatric disc herniation is varied. Sarma et al. found this was a significant factor in 57% cases, and Ozgen et al. found a positive history of trauma or intense sports activities in 83% of adolescent cases [10, 17]. Epstein et al. found 52% of teenaged children reported antecedent trauma prior to symptomatic LDH [11]. Slotkin et al. opined that pediatric disc herniations are much more likely to be the result of an acute injury rather than a degenerative condition [5]. Kumar et al. believed that gross trauma is not necessarily a contributory factor in adolescent LDH since it was only present in 8% of their patients, but repetitive microtrauma may be a predominant factor [7]. Papagelopoulos et al. reported 60% of the patients in their series had an antecedent trauma, which included sports injuries [16].

In a study on surgical treatment of adolescent intervertebral disc herniations, Grobler et al. found trauma was a significant factor in 59% of the cases [13]. In patients under 16 y/o, 61% were female, while in patients 16–20 y/o, 63% were male [13]. They suggested this occurred secondary to earlier skeletal maturity in females [13]. Cahill et al. found that 64% of adolescent LDH patients were competitive athletes [22].

In our experience, we have found younger athletes often have a traumatic prodrome to their LDH. In particular, athletic trauma due to training, such as dead lifts, squats, and power cleans, is often documented.

Ring Apophysis

Many symptoms of adolescent disc herniations are morphologically found to be fractures of the ring apophysis rather than the herniated nuclear material typically found in the adult population. It has been emphasized that recognition of these fractures is essential for appropriate treatment, preoperative planning of surgery, if indicated, and prognosis. Since this is an osseous/cartilaginous lesion, it is more readily appreciated on computed tomography (CT) scan than magnetic resonance (MRI) imaging. Epstein et al. found only one third of limbus vertebrae fractures were identified on the MRI scan, while 100% were appreciated on CT scan [23]. CT scanning is considered the optimal modality for imaging these types of fractures [24].

Bick et al. was the first to histologically evaluate the ring apophysis (RA) in detail, after Schmorl defined it [25]. Bick et al. described the RA as a region with increased amounts of traction due to the branching fibers of the long intervertebral ligament inserting into the individual vertebrae [25]. Calcification begins at approximately 6 y/o, ossification begins at 13 y/o, and fusion with the vertebral body at around 17 y/o [25]. By 18 years, fusion is complete, and at 20 y/o, the ring cannot be histologically identified [25].

The RA can separate from the caudal aspect of the cephalad vertebra or the cephalad aspect of the caudal vertebrae before skeletal maturity causing mass effect similar to, or in conjunction with, a disc herniation. The exact mechanism of the fracture is not understood, but many theories exist. In a study by Epstein et al., approximately half of the patients, mostly athletes, had a trauma as the inciting event [23]. Moreover, if there is neural compression, a radiculopathy may present.

Takata et al. described fractures of the RA and then morphologically classified them as type I, II, or III, as seen in Fig. 16.2 [26]. Type I fractures are a separation of the posterior margin or rim of the vertebra with no osseous defect [26]. It is described on CT scan to have an arcuate structure in the spinal canal. Type II fractures are an avulsion fracture of the posterior rim of the vertebral body [26]. There are cortical and cancellous bone fragments with a portion of the vertebral body that include the annulus. Type III fractures are smaller, more localized lateral chip fractures with a bone defect adjoining the fracture site [26]. Type I fractures tend to occur in younger adolescent patients, while type III are more commonly found in the skeletally mature [26]. Takata et al. looked at 29 patients, 66% were male. Of those with symptoms, 84% had a positive straight leg raise [26]. All surgical patients in the study had a good outcome [26]. Epstein et al. described a type IV fracture, where the lesion spans the entire length and breadth of the posterior vertebral margin between the end plates as seen in Fig. 16.2 [23].

Grobler et al. found that 38% of pediatric LDHs had a RAF [13]. They reported on 29 surgical patients with a RAF and found that trauma was a significant factor in 59% of cases. Moreover, 78% of these were caused by sports [13].

Wu et al. conducted a literature review on RAF with LDH that included 366 patients and discussed the importance of preoperative planning. The surgical treatment with excision of the apophyseal fragment was somewhat different than a more typical LDH. Wu et al. concluded that the surgical outcomes in patients were equally beneficial for the posterior RAF and LDH patients, but due to the shortcomings in the literature, no definitive consensus on treatment modality could be established [27]. Wu et al. demonstrated that there was a 2.85:1 male-to-female ratio, and 7.9% of RAF occurred at vertebral levels other than L4-L5 and L5-S1 which were similar to LDH patients [27].

Epstein et al. evaluated 27 patients with a RAF with a mean age of 32 years [23]. Fifty-nine percent of patients were male [23]. Trauma, which included sports-related injuries, was related to more than half the patients [23]. Lavelle et al. found that 28% of adolescent disc herniations involve apophyseal fractures, and these have a higher rate of surgical intervention [28].

Singhal et al. evaluated CT scans of 42 patients less than 18 y/o that were evaluated for LDH [29]. Fifty-five percent of patients with a LDH had a traumatic etiology [29]. Of the 42 patients, 38% of the pediatric patients did have an associated RAF [29]. Of their LDH patients, 55% of the males and 20% of the females were found to a RAF [29]. RAF was also associated with central herniations [29].

The literature on RAF shows a clear association with LDH in the adolescent. This trend is especially notable in adolescent males likely due to their delayed skeletal maturity in comparison to females. Recognition of this lesion preoperatively and maintaining a level of suspicion intraoperatively are essential when surgical treatment on an adolescent is performed. Failure to adequately resect the lesion can lead to persistent radiculopathy. Figure 16.3 is a case example of a failure to resect a RAF . The figure shows a postcontrast MRI in a 16 y/o male demonstrating a persistent RAF that was not resected at the time of initial micro-decompressive surgery. Postoperatively, the radiculopathy persisted, and he was unable to participate in all sporting and leisure activities. The severity of symptoms also precluded him from returning to school, and home schooling was necessary. Two years postoperatively, his parents sought another opinion. Within 2 weeks after revision decompressive surgery where a RAF was removed, he had returned to school and 3 months after revision surgery, was competing in sports.

Disc Degeneration in Adolescent Athletes

Alyas et al. evaluated MRI findings in 33 asymptomatic elite adolescent tennis players with a mean age of 17.3 and found disc degeneration, desiccation, and bulging in 39% of these athletes [30]. Only 15% of those studied had a normal MRI exam of the lumbar spine [30]. Additionally, 27% had a pars lesion and 70% had early facet arthropathy [30]. Most pathology was exclusively displayed at the most caudal two motion segments [30]. This study, as with others in the spine literature, underlies the importance of correlating abnormal imaging to the patient’s symptoms. Abnormal imaging alone does not indicate a diagnosis necessitating treatment.

Gerbino et al. found degenerative disc disease (DDD) , facet degeneration, and low back pain increased in football players with their years of participation [31]. Bono discussed that while the prevalence of disc degeneration in athletes is higher than in nonathletes, it remains unclear whether it correlates with a higher rate of low back pain [32].

Sarma et al. found that 29% of skeletally immature patients with a disc herniation had a single level of disc degeneration, and 29% had multilevel disc degeneration [17]. Kumar et al. found only 16% of LDH patients had underlying degenerative changes [7].

Bartolozzi et al. looked at training and the occurrence of disc lesions with training overload in volleyball athletes. They found training regimens are a more important risk factor than player age and overall period of athletic activity [33]. Volleyball players who followed appropriate training procedures had positive MRI findings 21% of the time, and those who trained with exercises creating significant functional overload had positive findings in 62% of cases [33]. Their control group of swimmers displayed positive MRI findings in only 20% of cases [33].

Ong et al. looked at Olympic athletes with low back pain and/or sciatica. They showed 58% had an element of disc displacement, most of which were disc bulges [34]. Elite athletes have a greater prevalence and degree of disc degeneration than their age-matched controls [34]. In total radiographic disc degeneration does appear to occur at a slightly higher rate in elite athletes; however, it is unclear if these changes cause long-term pain or disability. Figures 16.4 and 16.5 demonstrate morphologic differences in the nonathletic population compared to elite athletes.

Symptoms

While a significant portion of adolescent athletes experience episodic low back pain, only a small percentage have disc herniations, leading the diagnosis to often be delayed or misdiagnosed. The inability of children or adolescents to fully articulate their symptoms further compounds the issue of diagnosis. The initial differential diagnosis often includes strains, sprains, stress fractures, spondylolisthesis, DDD, Scheuermann’s disease, scoliosis, discitis, tumors, or other neoplastic lesions. These processes may all mimic LDH. It is also important to rule out an extraspinal pathology.

In the skeletally immature patient, there is a trend toward more back pain and fewer radicular complaints, although this varies between studies. Grobler et al. looked at the surgical treatment of adolescent intervertebral disc herniations and determined that back pain was a major chief complaint in all cases surgically treated [13] where sciatica was the primary symptom in only 55% of the cases [13].

In a series published by Kumar et al., all patients with LDH presented with low back pain and 68% had radiculopathy [7]. Nerve tension signs vary and significant motor deficits are not common. In a study by Ozgen et al., 88% of patients presented with low back pain, 41% of patients had a positive straight leg raise, 35% presented with radiating sciatica, 47% of patients had scoliosis, and the median duration of symptoms from the onset to time of presentation was 7.7 months [10]. Papagelopoulos et al. found a 6.4-month period between the onset of symptoms and initial surgery, and all of the patients presented with sciatica [16].

Borgesen et al. found that lumbar pain and sciatica were both present in 96% of patients less than 20 y/o [9]. Motor and sensory findings were far less common in this study. Scoliosis was present in 52% of cases [9]. In contrast to other studies, Borgesen et al. opined trauma as an unlikely etiology in adolescent lumbar disc herniation and found this in only 16% of those in their series [9]. This is the same as their adult control group; hence they concluded that disc degeneration is the primary cause, while trauma is only a precipitating factor [9]. A good or excellent surgical outcome was found in 98% of patients [9].

Grobler et al. found restricted forward flexion was found in 76% of patients, and all patients had a positive straight leg raise and 3.8 months of conservative treatment prior to surgery [13].

Pinto et al. demonstrated that scoliosis was one of the presenting findings secondary to an antalgic position, and this resolved with successful removal of the inciting disc herniation [35]. Cahill et al. reported a reactive scoliosis was present in 18% of the 87 patients [22]. In a study by Sarma et al., 31% of adolescents with a LDH had scoliosis upon presentation [17]. Zhu et al. evaluated 26 patients whose scoliotic posture was the initial symptom in adolescents with LDH and found a pattern of a short lumbosacral curve accompanied with a long thoracic or thoracolumbar curve toward the opposite side [36]. Fifty-eight percent of these that had low back pain, and only 69% had a positive straight leg raise exam finding [36]. There were 88.5% that had a trunk shift greater than 2 cm toward the side opposite of the disc herniation and had poor coronal plane balance [36]. All patients had a straight sagittal profile, and all had marked improvement in the curve after excision of the offending disc herniation [36].

Ozgen et al. evaluated 17 adolescent patients who required surgery for LDH [10]. Fifty-nine percent of the patients were male [10]. Eighty-two percent of patients were involved trauma or intense sports activities [10]. Eighty-eight percent of the patients had low back pain as the most common complaint [10]. The straight leg raise test was only positive in 41% of patients [10]. All of the cases were at the L4-L5 and L5-S1 vertebral levels [10].

As seen above, most studies show that adolescent LDH differ from adult presentation with a preponderance of back pain compared to leg symptoms . In addition, a possible reactive scoliosis should trigger the clinician that a disc pathology may be present.

Treatment

Conservative treatment options vary, including nonsteroidal anti-inflammatory drugs (NSAID), other medications as indicated, physical therapy, interventional pain management with blocks, activity modification, orthosis, and observation of the natural history of disc resorption. However, the natural history of disc regression may not be the same in adolescents and children as in adults. Many of the older case studies recommend nonoperative treatment with prolonged initial bed rest, traction, activity limitations, and a body cast [3, 21]. Early imaging with an MRI is sometimes prudent and is mandatory for any neurologic findings, systemic issues, or atypical findings.

Prior to surgical intervention, MRI is the study of choice, allowing for visualization of edema, compressive neural lesions, tumors, stenosis, disc degeneration and associated changes, pars fractures/stress reactions (edema), etc. CT scanning can be helpful for preoperative evaluation of pars lesions, RAF, and facet pathology.

According to the experience of the senior author , in well over 60 adolescent discectomies, we have found that the herniated material is frequently contained and far more tenuous than in their adult counterparts. All of the studies that were reviewed agree with this premise and found fewer extrusions and more contained disc material as seen in Fig. 16.6. Generally, it is felt that these highly elastic disc herniations respond poorly to conservative treatment [5, 6, 22]. The pathophysiology of LDH and hence healing occurs because an inflammatory response is elicited by the body secondary to the nucleus pulposus extruding from the annulus. This inflammatory cascade over time allows the body to absorb the extruded disc material. In adolescents, the contained disc protrusion is unable to elicit the same inflammatory response. Despite this, other authors have found that only a minority of patients, around 10%, required surgery [21].

When treated surgically, the tenuous disc material often necessitates the use of reverse currets and tamps to impact the compressive lesion, sometimes including RAF’s into the disc space. The material may then be resected with a pituitary from the disc space. Also, Kerrisons, osteotomes, drills, or other instruments can be used to extract the offending lesion and provide satisfactory neural decompression. Identification of the pars interarticularis is necessary, and preservation of this structure is necessary to prevent iatrogenic instability. Consequently, this procedure may be more technically demanding than an adult microdiscectomy.

We have found that a number of patients have an osseous-cartilaginous end plate fracture, and the surgeon must be prepared to address this. While not all authors advocate removal of the bony fragment in a RAF, removal of the bony fragment is indicated for decompression when it creates neural impingement. Successful outcomes depend on the neural decompression and require meticulous microsurgical techniques. Because of this, the surgeon must have a level of awareness for the RAF pathology.

We have found, in our experience , approximately 65% of athletes, 21 y/o or younger, are able to return to sports at the collegiate or high school level. However, for each patient after the convalescence of surgery, because of their age, returning to sport would have been at a higher level (i.e., junior varsity to varsity or high school to college level), and some chose not to participate; hence, the actual return to play is still not fully understood. For example, only 6.9% of high school football players go on to play at the NCAA level and far less at the Division I level (see Table 16.1).

Table 16.1

Estimated probability of competing in college athletics

	High school participants	NCAA participants	Overall % HS to NCAA	% HS to NCAA Division I	% HS to NCAA Division II	% HS to NCAA Division III
Men
Baseball	491,790	34,980	7.1	2.1	2.2	2.8
Basketball	550,305	18,712	3.4	1.0	1.0	1.4
Cross country	266,271	14,350	5.4	1.8	1.4	2.2
Football	1,057,382	73,063	6.9	2.7	1.8	2.4
Golf	141,466	8,527	6.0	2.1	1.7	2.2
Ice hockey	35,210	4,199	11.9	4.8	0.6	6.5
Lacrosse	111,842	13,899	12.4	2.9	2.3	7.1
Soccer	450,234	24,986	5.5	1.3	1.5	2.7
Swimming	138,364	9,691	7.0	2.7	1.1	3.1
Tennis	158,171	7,957	5.0	1.6	1.1	2.3
Track and field	600,136	28,595	4.8	1.8	1.2	1.7
Volleyball	57,209	2,007	3.5	0.7	0.7	2.0
Water polo	21,286	1,013	4.8	2.7	0.7	1.3
Wrestling	244,804	7,175	2.9	1.0	0.8	1.1
Women
Basketball	430,368	16,532	3.8	1.2	1.1	1.5
Cross country	226,039	15,966	7.1	2.6	1.8	2.7
Field hockey	60,549	6,066	10.0	3.0	1.3	5.7
Golf	75,605	5,372	7.1	2.9	2.1	2.2
Ice hockey	9,599	2,355	24.5	8.8	1.2	14.5
Lacrosse	93,473	11,752	12.6	3.7	2.7	6.2
Soccer	388,339	27,638	7.1	2.4	1.9	2.8
Softball	367,405	19,999	5.4	1.7	1.6	2.1
Swimming	170,797	12,684	7.4	3.3	1.2	2.9
Tennis	187,519	8,736	4.7	1.5	1.1	2.1
Track and field	494,477	29,907	6.0	2.7	1.5	1.8
Volleyball	444,779	17,387	3.9	1.2	1.1	1.6
Water polo	20,826	1,159	5.6	3.4	0.9	1.3

Reprinted with permission of the National Collegiate Athletic Association. http://​www.​ncaa.​org/​about/​resources/​research

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