Surgical outcome of a patient with Bertolotti’s syndrome in whom the established Castellvi classification system failed: illustrative case

Abstract

BACKGROUND

Bertolotti’s syndrome is a condition of the lower back and/or L5 distribution leg pain caused by a lumbosacral transitional vertebra (LSTV). Diagnosing the LSTV as the cause of the symptoms and condition is essential for accurate management of this syndrome. Castellvi’s classification system is widely accepted for LSTV anatomy, but it measures only one aspect of transitional anatomy and was intended primarily to identify target-level disk herniations.

OBSERVATIONS

In this case, the Castellvi classification system failed to identify the patient (with 2 years of back and L5 pain) as having an LSTV, even though he displayed LSTV-like anatomy because both L5 transverse process heights measured less than 19 mm. He attained brief but significant relief from bilateral injections into the L5–S1 transverse/ala region and underwent a minimally invasive bilateral decompression of L5–S1 with almost complete relief of his symptoms maintained more than 6 months postoperatively.

LESSONS

Given that the patient gained significant relief from treatment of transitional anatomy that failed to be identified using Castellvi’s classification system, this case suggests that transverse process height may not be adequate or even the most clinically relevant indicator in identifying LSTV anatomy, which is a precursor to the diagnosis of Bertolotti’s syndrome.

A lumbosacral transitional vertebra (LSTV) is defined as a congenital anomaly of the lumbosacral junction, where the lowest lumbar vertebral body has proximity to or pseudoarticulates to the sacral ala with varying degrees (Fig. 1), as compared with a more normal gap between the transverse process and sacral ala of 2–3 cm. LSTVs are increasingly recognized as a prevalent anatomical variant and the most common congenital anomaly of the lumbosacral spine, ranging from 4% to 35% of the population, with an overall average incidence of 12.3%.^1,2 Bertolotti’s syndrome is a condition in which this LSTV causes sacroiliac (SI) regional pain, hip pain, groin pain, and/or L5 distribution leg pain.³ Across adults presenting with lower back pain, Bertolotti’s syndrome has a reported prevalence of 4.6% to 7%.⁴ Several etiologies, including (1) transverse process and sacral ala articulation, (2) adjacent level disc degeneration, (3) contralateral facet joint to a pseudoarticulating LSTV, and (4) extraforaminal stenosis from an enlarged transverse process, have all been proposed.⁵ Although the exact mechanism of pain generation in this syndrome is unclear, a commonly described association is the varying levels of proximity or articulation between the transverse process and the sacral ala.^6–8

FIG. 1.

Type I LSTV constitutes unilateral (IA) or bilateral (IB) enlarged transverse processes, where the width in the craniocaudal dimension measures at least 19 mm. Type II encompasses partial unilateral (IIA) or bilateral (IIB) lumbarization/sacralization, creating a diarthrodial joint between the enlarged transverse process and the sacrum. Type III LSTV shows a complete unilateral (IIIA) or bilateral (IIIB) lumbarization/sacralization fusion across the transverse process(es) and the sacrum. Type IV displays type II anatomy on one side and type III anatomy on the contralateral side.¹³

As part of conservative treatment and for diagnostic purposes, pain management clinicians can inject this pseudoarticulation with steroid or local anesthetic injection.^9,10 Surgical options of a resection or fusion procedure are commonly proposed upon failure of conservative management. Although definitive surgical recommendations are currently inconclusive, there have been reports of patients with complete resolution of their lower back pain and related symptoms 1 year postoperatively with both surgical options.^11,12 Because of this uncertainty in evaluation and treatment, clinicians can commonly overlook or mistreat Bertolotti’s syndrome when patients present with back pain. The presence of other comorbidities in the spine can also contribute to the difficulty of isolating this syndrome, often making it a diagnosis of exclusion. The accurate assessment of both LSTV anatomy and Bertolotti’s syndrome is critical to patient care because it directs recommended treatments from conservative management to surgical intervention.

Almost 40 years have passed since the inception of the Castellvi classification system for LSTVs in 1984, and more than a century has passed since Mario Bertolotti³ first described the clinical association between pain symptoms and LSTV anatomical findings.¹³ Castellvi et al.¹³ classified LSTVs into 4 types of varying levels of articulation, pseudoarticulation, and fusion across the lumbosacral region (Fig. 1).

In this report, we describe a patient who presented with the appearance of transitional lumbosacral anatomy that would not fit into the Castellvi classification system. Confirmed through significant relief from bilateral diagnostic injections into the transverse/ala junction, this patient was diagnosed with Bertolotti’s syndrome and underwent a minimally invasive reduction of the prominent S1 congenital anomaly with an excellent and durable response to treatment.

Illustrative Case

History

A 16-year-old male presented with ongoing right greater than left bilateral lower back, hip, and buttock pain for 2 years preoperatively. On the basis of the visual analog scale (VAS) pain scale, he rated his overall pain as 9 out of 10. He was very active and involved in sports but stopped because performing athletic activity worsened his pain. He reported that he experienced buttock pain when lying down and waking up. He denied any sciatica or radiation into other regions. Previously, the patient had failed numerous accounts of conservative management since the start of his pain, including rest, physical therapy, chiropractor manipulation, and epidural steroid injections.

Imaging Studies

Given his symptoms, both lumbar spine computed tomography (CT) and spine magnetic resonance imaging (MRI) were performed for diagnostic purposes (Figs. 2 and 3). The patient’s MRI revealed mild disc bulging at L3–4, L4–5, and L5–S1 with no significant foraminal or central stenosis, disk herniations, synovial cysts, fractures, spondylolisthesis, or other intraspinal or extraspinal pathology. With an average spinal canal of 17.5 mm, there was no congenital lumbar stenosis and no significant spinous process impingement observed. On an axial view, compression on the extraforaminal L5 nerve root was challenging to visualize due to the large slice thickness between fields of view on the patient’s preoperative MRI. Therefore, L5 nerve root decompression was visualized intraoperatively during bone resection (Fig. 2).

FIG. 2.

Pretreatment midsagittal lumbar T2-weighted MRI without contrast showing a normal 17.5-mm spinal canal at L2 and no significant congenital spinal stenosis or other diagnosis in the lumbar region.

FIG. 3.

Pretreatment lumbar CT with coronal reconstruction. A: Coronal cut showing both sides, displaying proximity between the L5 transverse processes and sacral ala. B: Bone window from coronal reconstruction of the same CT scan, exhibiting a right transverse process width of 14.4 mm. C: Bone window from coronal reconstruction of the same CT scan, exhibiting a left transverse process width of 14.6 mm.

His CT scans displayed 5 lumbar vertebrae. The scan and its various reconstructions revealed no other fractures, spondylolisthesis, spondylosis, or significant degeneration. There was proximity observed between the L5 transverse process and sacral ala bilaterally (Fig. 3A). Using both sagittal and coronal reconstructions, the transverse process to ala distance reached a nadir of a 6.65-mm gap on the right and an 8.81-mm gap on the left, with no observed contact with the iliac crest.

Also, using coronal reconstruction of the same CT scan of the lumbar spine, the largest vertical measurements of the transverse processes were both less than 19 mm, with a left L5 transverse process height measuring 14.6 mm and a right-side height of 14.4 mm (Fig. 3B and C). This was not identified as an LSTV by the Castellvi classification system.

Injections

Failing extensive conservative management (including other injections that failed to provide any meaningful benefit), the patient underwent bilateral injections (dexamethasone and bupivacaine) into the region between the L5 transverse process and sacral ala, at the point of closest proximity of the transverse process and ala on both sides, under fluoroscopic control. The patient reportedly had more than 85% pain relief immediately, which lasted 24 hours before his pain returned. The patient was diagnosed as having Bertolotti’s syndrome, and after reviewing surgical and nonsurgical options, he opted to receive a minimally invasive bilateral L5–S1 Bertolotti’s decompression procedure.

Surgical Intervention

Under general anesthesia, and with the use of neuromonitoring, including somatosensory evoked potentials and free-running electromyography potentials, the patient was positioned prone on the Jackson table (Mizuhosi). He underwent, via bilateral Wiltse-type approaches using the METRx tubular system (Medtronic), minimally invasive shaving of the inferior portion of the superior projection of the abnormal ala laterally, using microsurgical dissection techniques.¹⁴ The intertransverse membrane was taken down until the L5 nerve root exiting was visualized. This was done similarly on the contralateral right side. An Iso-C C-arm spin was generated, producing an intraoperative CT scan, confirming adequate bone resection. The L5 nerve root was now completely free of compression. Any fibrous bands, ventral periosteum, and adhesions between the transverse process of L5 and the sacral ala were removed bilaterally. This left a wide gap (more than 10 mm on each side, as measured intraoperatively) with no fibrous or bone osseous impingement. Bone wax was gently placed on the exposed surfaces of the ala, followed by a thin layer of commercially prepared fibrin glue (VISTASEAL, Ethicon) sprayed on the surface of the transverse processes and ala for hemostasis and to prevent bone regrowth. The patient was awakened from anesthesia without complications, tolerated the procedure well, and was discharged from the hospital the same day.

Follow-Up

Postoperatively, his right greater than left lower back, hip, and buttock pain improved significantly in a progressive manner over the course of 7 months. According to the VAS pain scale, the patient endorsed almost no pain after surgery, with an occasional 1 out of 10 pain, compared with 9 out of 10 preoperatively. He stated that he is “doing great, 100%” during his 7-month follow-up and returned to normal activity and sports exercise, including running, squatting, and core movements.

A radiograph of the lumbar spine postoperatively at the 6-month mark displayed good decompression of the transverse process sacral ala junction bilaterally with no signs of neuropathic or vascular impingement (Fig. 4).

FIG. 4.

Comparison of the preoperative and 6-month postoperative radiographs of the pelvis, anteroposterior views. A: Preoperative pelvic radiograph displaying osteophyte growth in the superior aspect of the sacral ala, causing impingement across the lumbosacral gap. B: Six-month postoperative pelvic radiograph, with red arrows showing successful bilateral resection of the osteophyte growth of the sacral ala, decompressing the previously compromised L5–S1 transverse ala junction.

Discussion

Observations

Accurately identifying both the presence and type of LSTV guides appropriate conservative and surgical management of Bertolotti’s syndrome, emphasizing the importance of a universal and clinically accurate classification system. To establish an effective treatment plan, it is crucial to use a diagnostic classification that is appropriate for identifying the clinical correlation between LSTV anatomy and patient presentation.

In our case, there was evidence of bilateral L5 nerve root compression from the type 1 anomaly during surgery, resulting from lumbarization of the L5 transverse process and sacralization of the sacral ala. The L5 nerve root impingement was subsequently visualized, and complete decompression was achieved. Although nerve decompression and bone-on-bone resection contributed to a relief of symptoms, determining an accurate pain generator for this condition should be assessed in a larger population.

This patient presented with an atypical case of an “osteophyte-like” congenital process on the superior edge of his S1 anatomy. This enlarged sacral ala allowed a closer gap across the lumbosacral junction, compensating for a smaller transverse process bilaterally with a height of less than 19 mm (Fig. 3A). However, given his left and right transverse ala heights of 14.6 and 14.4 mm, respectively, the Castellvi classification of a height greater 19 mm would fail to label the patient as type 1B, let alone give any LSTV identification (Fig. 3B and C). The current Castellvi classification using the transverse process height was unable to capture this patient’s anatomy. Clearly, the presence of transitional anatomy involves more than just the transverse process, but the Castellvi classification system does not incorporate this finding.

The novel aspect of this case is the patient’s significant relief of pain (to both injections and surgical treatment) despite the anatomical inconsistency with the Castellvi classification. Considering the failed conservative management, radiographic imaging, and significant diagnostic injection relief, the diagnosis of Bertolotti’s syndrome for this patient can be confirmed. In addition, he had a favorable outcome with alleviation of his bilateral back, hip, and buttock pain through a bilateral minimally invasive reduction of his anomaly at S1.

Thus, this is an example of variants within transitional anatomy where the transverse ala height holds minor clinical significance, suggesting that a modification of the Castellvi classification may be needed to include this anatomical presentation. Given that impingement across the transverse/ala junction is a proposed etiology of Bertolotti’s syndrome, including the proximity between the transverse processes of the lowest vertebral body and sacral ala, should be considered.

Lessons

In this case, using only dysplastic transverse process height, as in the Castellvi classification system, is not useful in identifying LSTV anatomy or as a sensitive diagnostic tool for Bertolotti’s syndrome. To our knowledge, although this is the first case in the literature where the most prominent aspect of the transitional anatomy was at the sacral ala as opposed to an enlarged transverse process, this patient is not unique in this finding. Given the patient’s almost complete relief with a bilateral decompression procedure designed for treatment of Bertolotti’s syndrome, a modification of the current Castellvi classification for type 1 LSTVs may be indicated. This includes measuring the gap between the transverse process and sacral ala to accurately assess this patient population. Because this patient is not unique in terms of the radiographic and clinical presentation, additional research should be done to validate classification systems for patients with LSTVs to better treat those with Bertolotti’s syndrome.

Disclosures

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author Contributions

Conception and design: AL Jenkins III, Chung. Acquisition of data: all authors. Analysis and interpretation of data: all authors. Drafting the article: all authors. Critically revising the article: AL Jenkins III, Chung, S Jenkins. Reviewed submitted version of manuscript: AL Jenkins III, Chung, Harvie, O’Donnell. Approved the final version of the manuscript on behalf of all authors: AL Jenkins III. Statistical analysis: AL Jenkins III, O’Donnell. Administrative/technical/material support: AL Jenkins III. Study supervision: AL Jenkins III.