Updates on the prevention and treatment of cervicothoracic distal junctional failure: a narrative review

Introduction

Surgical correction of cervical deformity is associated with a high rate of complications (1). However, untreated adult cervical deformity (ACD) can result in severe dysfunction such as progressive myelopathy and severe disability (2). Common complications in cervical spine surgery include dysphagia, respiratory failure, cerebrospinal fluid leak, C5 palsy, and instrumentation failure (1,3-5). Distal junctional kyphosis (DJK) and distal junctional failure (DJF) are complications with the potential for catastrophic clinical consequences given the location of deformity in the cervicothoracic spine.

DJK is characterized by kyphotic malalignment of the vertebrae one or two levels below the lowest instrumented vertebra (LIV) by >10° (6). DJF is clinical or radiographic signs of failure at the distal junction of a construct secondary to a number of causes including but not limited to pain, loss of mobility or function, screw-bone-interface weakening, screw pull-out, instrumentation breakage, pseudarthrosis, fracture, and adjacent segment disease (6).

While extensive research has been conducted on adult spinal deformity (ASD) and proximal junctional kyphosis (PJK) in the thoracolumbar spine, research on DJK and DJF in cervical deformity has been less robust. Currently, there is a paucity of literature focusing on cervicothoracic DJK and DJF treatment strategies, prevention, and clinical outcomes. With an increase in the proportion of elderly people within the population and improved ability to diagnose cervical spine pathology, the prevalence of ACD surgery continues to rise, consequently leading to a higher prevalence of DJK/DJF in surgically managed patients (7). This has led to an increased number of studies attempting to identify risk factors for DJK and DJF to aid with prevention or guide early treatment (8-11). Unfortunately, to our knowledge, no current review articles exist examining this important topic.

The aim of this article is to provide a review of clinical, radiographic, and surgical factors influencing DJK and DJF in cervical deformity surgery. Additionally, this review aims to explore current non-operative and operative strategies available to help manage DJK and DJF. We present this article in accordance with the Narrative Review reporting checklist (available at https://asj.amegroups.com/article/view/10.21037/asj-24-58/rc).

Methods

A literature search utilizing PubMed, Scopus, and Cochrane Library was performed. Key words used were “distal junctional kyphosis”, “distal junctional failure”, “cervical”, “cervicothoracic”, “surgery”, and “deformity”, and a critical review of title, abstract, and manuscript were used to select appropriate articles (Table S1). All studies were in English and from the years 1996–2024 (Table 1).

Strengths and limitations

This review utilized multiple search strategies including multiple databases searches and selected references from pertinent articles on a broad topic to provide a comprehensive review. However, this was not a systematic review process and does not have the same rigor as true systematic review. There is current a lack of data focusing on DJK and DJF, and significant inferences must be made from articles focusing generally on cervical deformity in its entirety rather than specifically DJK. The authors were not able to find any studies which evaluated treatment outcomes or strategies for DJF once it has occurred.

Epidemiology

Reported incidence of DJK following cervical fusion surgery vary widely in the literature, with rates ranging from 6.9% to 38% (4,8,9,12); 44.7% of cases of DJK occur within the first 3 months, 21.1% by 6 months, 23.7% by 12 months, and 10.5% by 24 months following surgery (13). Although, DJK is commonly defined as a sagittal Cobb angle change of greater than 10° between the LIV and the vertebra immediately 1–2 segments inferior, an angle exceeding 20° is associated with a higher incidence of symptoms and a greater likelihood of requiring reoperation (12). Radiographically, mild DJK is a cobb angle measured at 10° to 20°, whereas severe DJK is classified as a cobb angle of 20° or more (14). In a study of 131 patients, the average DJK angle (DJKa) was 9.47°±11.01°, with mild DJK occurring in 35.1% and severe DJK in 10.7% of cases (12). Approximately 20–50% of postoperative ACD patients with DJK or a mechanical failure will undergo revision surgery (15,16). Conversely, these findings also suggest that many if not most patients with DJK are able to be managed conservatively.

Risk factors

Significant research efforts have been dedicated to understanding the etiologies and risk factors for DJK, with the aim of developing effective preventive strategies (17). Recognized risk factors for DJK include osteoporosis, frailty, neuromuscular disease, poor spinal alignment, as well as specific surgical errors. Avoiding these risk factors while utilizing described surgical strategies and techniques is important in the prevention of DJK.

Frailty

Frailty and associated conditions such as anemia, diabetes, malnutrition, psychiatric disorders, and osteoporosis have all been shown to increase complication rates in cervical spine surgery (1,18,19). Studies show mixed evidence on the association of DJK with frailty status (13,20,21). A recent study suggests that frailty is a risk factor for mechanical failure following cervical fusion surgery (17,19,22). Given these recent observations and the increased complication risk associated with frail patients; it is reasonable to briefly discuss the perioperative optimization of this patient population in this article.

Several validated frailty assessment tools can be used to identify higher risk frail patients undergoing ACD surgery (23-25). Enhanced recovery after surgery protocols offers strategies to minimize the effects of frailty by maintaining physiological resilience throughout the perioperative period with prehabilitation, physical therapy, nutritional optimization, and comprehensive medical management. These protocols have been shown to reduce healthcare costs, readmissions, and complications while enhancing patient satisfaction (26,27).

Osteoporosis

Osteoporosis is characterized by an imbalance of bone metabolism homeostasis which leads to decreased bone mineral density (BMD) and has an increased fracture risk. Multiple methods exist to assess BMD, including dual-energy X-ray absorptiometry (DEXA), magnetic resonance imaging (MRI), and computed tomography (CT)-derived Hounsfield units (HUs) (28,29). Preoperative bone health evaluation in patients over 50 years old or younger patients with risk factors is an important part of planning cervical deformity correction (1,30-32).

Decreased HUs are associated with an increased risk of known causes of DJF such as mechanical failure, pseudoarthrosis, adjacent segment degeneration, fractures, and instrumentation failure (33). In a study of 109 ACD patients, HU values below 190 at the LIV were associated with higher rates of complications including DJK (11). Studies have shown that a low MRI vertebral bone quality score (VBQS), is associated with an increased risk of DJK (34). Given the widespread usage of CT and MRI in surgical planning, it is imperative the surgeon assess the BMD at vertebral levels of the potential construct endpoints when creating a surgical plan.

Initial management of osteoporosis should begin with non-medical lifestyle modifications such as, proper nutrition, avoiding toxic habits, and medical optimization (35). A bone health specialist or endocrinologist should be consulted early to ensure that there is adequate latency for non-surgical treatment strategies to take effect. Perioperative vitamin D, calcium, and anabolic agents such as teriparatide are commonly referred to as the preferred medical treatment options around spine surgery (36,37). Teriparatide is associated with better fusion rates and decreased pedicle screw loosening when compared to bisphosphonates, although bisphosphonates are commonly accepted alternatives under certain circumstances (38).

Neuromuscular disease

Dropped head syndrome (DHS), also known as camptocephalia, is a rare type of cervical deformity associated with neuromuscular disease, affecting 1% of patients with neuromuscular disorders (39). This condition can be the presentation of a severe form of DJF and is associated with severe disability and poor quality of life (40,41). Diagnosing the underlying etiology of DHS is the first step in preventing and managing this condition.

DHS has been linked to isolated neck extensor myopathy, potentially caused by cervicothoracic kyphosis leading to stretching and fatigue of the posterior cervical paraspinal musculature (42). Another proposed cause is inflammatory myositis (22,43,44). Neuromuscular conditions such as amyotrophic lateral sclerosis (ALS), myelopathy, myasthenia gravis, pathologically increased neck flexor tone, Parkinson’s disease, and polymyositis can also lead to DHS (44). Determination of DHS etiology is critical in determining the optimal treatment plan for these severely disabled patients.

Treatment of the underlying neuromuscular disease is the mainstay of preventing associated operative complications. Non-surgical management typically begins with treatment of the underlying condition, alongside orthoses and physical therapy. If these initial measures fail, glucocorticoids are often considered as the go to second-line treatment option (40,44,45). While nonoperative approaches are largely effective depending on the underlying etiology, surgical intervention remains a viable alternative in refractory cases (44,46).

Spinal alignment

Understanding cervical alignment has become increasingly critical for treating ACD and preventing DJK. Radiographic assessment of the cervical spine often reveals significant variability, even in asymptomatic individuals. Ames et al. demonstrated that changes in cervical lordosis (CL), sagittal vertical axis (SVA), and thoracic kyphosis associated with aging are not necessarily symptomatic (47). Radiographic alignment parameters include T1 slope (T1s), T1s minus CL (T1s-CL), McGregor’s slope, neck tilt, cervical sagittal vertical alignment (cSVA), and thoracic inlet angle, where a small thoracic inlet angle correlates with reduced T1s and CL (Figure 1) (48). Evaluating radiographic alignment has become a critical component of DJK risk assessment.

Figure 1 Cervical alignment parameters. C2, C7, and T1 slopes are measured by lines drawn parallel to the horizontal axis and a line connecting the slope of the superior endplate of the vertebral body (A). cSVA is measured by measuring the distance between the posterior border of C7 and the midpoint of the C2 vertebral body (B). The C2–C7 angle is measured with an angle drawn between the angles of the posterior borders of C2 and C7 (C). Adapted from Chai Z, Yang X, Lu H, et al. Relationship between C2 slope with sagittal parameters and clinical function of degenerative cervical kyphosis. J Orthop Surg Res 2023;18:514. doi: 10.1186/s13018-023-04011-0. cSVA, cervical sagittal vertical alignment.

Preoperative films should include standing or erect cervical spine plain films for detailed cervicothoracic spinal alignment review. Excessive T1s and poor preoperative cSVA have been identified as risk factors for DJK (8,49). It is plausible that these increased values represent a subset of patients with a delayed presentation that is more resistant to surgical correction. Identifying these higher risk radiographs is an important component preoperative planning and risk assessment.

Recently, intraoperative measurements, such as C2-LIV tilt, have been identified which can help predict DJK (10,12). C2-LIV measures alignment within the fusion construct and evaluates the angle between C2 and the LIV with a line paralleling the posterior border of the LIV. Identifying patients with an increased C2-LIV intraoperatively can guide decision making (Figure 2). Further studies may be helpful in identifying other intraoperative radiographic alignment risk factors for DJK that can potentially serve as real assessments for the chosen cervicothoracic deformity correction strategy.

Figure 2 Here is an example of two patients who presented with cervical kyphotic deformities with pre-operative C2-LIV angles of 40° (A) and 17° (B). The first patient underwent a back-front-back correction with complete correction of their C2-LIV (C) whereas the second patient underwent a posterior-only based surgery with improved but residual C2-LIV of 9° (D). Additionally, the first patient (C) had a re-distribution of their CLDI to 85% which represents a favorable re-distribution whereas the second patient (D) had a re-distribution of their CLDI to 24%, which is a less favorable distribution. CLDI, cervical lordosis distribution index; LIV, lowest instrumented vertebra.

Postoperative radiographic analysis may be able to assist surgeons in recognizing which patients are at risk for DJK. Patients requiring revision surgery for DJK exhibited larger offsets from age-adjusted alignment goals, with significant associations between poor postoperative alignment and mechanical failure (15). Scoring indexes and cervical scores such as the cervical lordosis distribution index (CLDI) have been published attempting to predict cervical surgery outcomes including DJK by assessing postoperative radiographic alignments to identify patients at risk for DJK and other complications (8,16,50). Specifically, the CLDI evaluates the cranial lordosis as a portion of the entire C2-T2 lordosis to predict outcomes (Table 2) (50). Analysis of these key parameters in the postoperative environment is a useful strategy for surgeons to identify and follow closely patients at greater risk of DJK following surgery. Although further studies are required, these alignment parameters may be useful for creating effective alignment goals in the preoperative planning and intraoperative execution phases as well.

Surgical errors

The Semispinalis cervicis is a key muscle in the posterior cervical musculature and originates from T3–4 and inserts onto the spinous process of C2–5. The Semispinalis capitis is another key muscle in the posterior cervicothoracic musculature and extends from T7 to insert at the base of the skull. Degradation of these muscles is a recognized risk factor for DJK (51). Furthermore, a randomized controlled trial demonstrated that preserving the C2 spinous process musculature during laminoplasty reduced the progression of cSVA and loss of lordosis two years postoperatively (52). Although laminoplasty is a motion preserving surgery, this study demonstrates the ability of intact posterior cervicothoracic musculature to prevent kyphotic deformity.

Few studies have identified additional surgical technique-related risk factors for DJK. Partial facet joint resection, combined surgical approaches, Smith-Petersen osteotomies, and tumor resections have all been associated with higher DJK rates (8,13,16). These findings suggest that more complex surgeries may inherently carry greater risk, potentially reflecting selection bias. Further biomechanical and clinical research is needed to better understand these associations.

Potential risk factors

Although there are many recognized risk factors associated with DJK, others certainly exist yet have likely not been recognized. Age, psychiatric ailments, socioeconomic status, instrumentation selection, and surgeon experience are all likely to play a role in cervical deformity outcomes. However, given the complexity of this condition, others surely exist and future research is warranted to explore and detail risk factors.

DJK prevention strategies

Soft tissue management

Ligamentous and musculature attachments at C2, C3, and C7 have been shown to have a disproportionate impact on spinal kinematics in biomechanical studies (53). Avoiding excessive lateral exposure can help potentially preserve musculature innervation and blood flow in the thoracolumbar spine, although this has not been studied in the cervical spine (54). Dissection in these regions of the cervicothoracic spine should consider preserving neck extensor musculature attachments at the upper and lower vertebra levels if involving C2, C3, and C7 (52). If musculature structures are disrupted intraoperatively, there is evidence that posterior cervical fusion with instrumentation can be preventative against DJK (55).

Intraoperative alignment goals

Adequate intra-operative imaging can be difficult due to cumbersome large equipment and patients positioned supine or prone. However, judging intra-operative cervical spine realignment is mandatory. A C2-LIV tilt of below 36.8 mm was associated with decreased rates of DJK (10). While imperfect, C2-LIV tilt has been found to be 66% sensitive and 56% specific for mild DJK, and 16.7% sensitive with 90.3% specificity for severe DJK (10,12). Using C2-LIV intraoperatively can assist the surgeon checking with adequate radiographic correction and serve as an important checkpoint.

LIV selection

The impact of crossing the cervicothoracic junction remains controversial. Advocates of crossing the cervicothoracic junction propose greater deformity correction and lower rates of pseudoarthrosis, hardware failure, and DJK (56-58). Contrarily, others have suggested less blood loss, shorter operative times, and shorter length of hospital stays if stopping in the cervical spine, and found comparable risks of adjacent segment disease between caudal endpoints in the cervical and thoracic spine (59). The in vivo literature discrepancies likely represent significant differences in patient populations, surgeon techniques, and clinical scenarios.

One study identified the highest DJK incidence with constructs ending at T10 (72.7%) and T11-L2 (50%) compared to those ending at C6/C7 (25%), T1/T2 (10.3%), and T3 (17%) (60). This biomechanical study found that although adjacent segment motion is comparable between LIV at C7 and T1, overall cervicothoracic motion in flexion-extension was decreased in constructs crossing the cervicothoracic junction, which may explain the increased rates of DJK seen in longer constructs (61). While it is generally recommended to avoid terminating a construct in a kyphotic region or adjacent to subjacent deformities, selecting a LIV remains a nuanced decision dependent on the patient’s clinical status, cervicothoracic pathology, and surgeon experience (62).

Technical tips and tricks

Some advocate for adopting PJK prevention techniques from ASD surgery to prevent DJK in ACD patients (63). Biomechanical studies looking to reduce rates of PJK in ASD and adjacent segment disease have suggested surgical cables or tape could prevent excessive strain through a more gradual transition and help compensate for damage to posterior ligamentous structures (64). Many of the described techniques utilize windows created through the adjacent lamina to connect the adjacent segments to the fusion construct. These techniques appear to require pretension to be effective biomechanically at decreasing adjacent segment stress. This clinical study shows it may be possible to reduce rates of PJK after utilizing these techniques, although further research is warranted at this time for use in ACD to prevent DJK (65).

To reduce the risk of instrumentation failure, screw location and trajectory are important considerations for maximizing screw purchase area and pullout strength. At C2, common screw types include pedicle and pars screw with the choice primarily determined by the path of the vertebral artery, which should be carefully evaluated preoperatively (66). From C3–6, lateral mass screws are frequently chosen. The Riew technique, which involves a slightly medial and caudal starting point from the center of the lateral mass and a relatively more lateral and cranial trajectory, maximizes screw purchase while minimizing the risk of vertebral artery injury (67). The C7 lateral mass is relatively smaller compared to its cranial counterparts, for this reason, pedicle screws at C7 provide significantly more pullout strength and are often preferred (68-70). Extension of the construct to the upper thoracic spine at T1 or T2, when compared to C7, can further improve screw purchase due to the increased pedicle size and length (71). Lower in the thoracic spine, trajectories that are straight and forward or mediolateral and caudocranial, such as the cortical bone trajectory, have been shown to provide superior pullout strength compared to the anatomic pedicle screw trajectories (72,73).

Operating on osteoporotic bone presents significant technical challenges and requires specialized strategies to mitigate the risk of instrumentation failure. The primary goal is to optimize the bone-implant interface to ensure stable fixation. We now have improved biologic methods to achieve solid arthrodesis, including demineralized bone matrix, bone morphogenic proteins, and more recently the consideration of stem cells (although this has not been validated in the literature). These adjuncts have aided our ability to achieve fusion within a construct even in cases of osteoporosis. With the knowledge that pseudarthroses can increase the risk of DJK and DJF, utilizing biologics has the ability to improve fusion rates and likely decrease the rates of DJK and DJF (1). Mechanically, several techniques can be employed to enhance the integrity of spinal constructs in osteoporotic patients. Undertapping, using larger-diameter screws, and altering screw trajectories, can all enhance pullout strength (72). Cement augmentation, either before screw placement or through fenestrated screws, may also improve fixation (74). Combining anterior to posterior fixation methods may increase load sharing, and construct lengths with at least 3 fixation points above and below the deformity apex is optimal (72). Despite these strategies, further advancements are needed to achieve outcomes in osteoporotic patients equal to those in patients with normal bone density. Continued research into novel techniques and materials will be essential to address the unique challenges of osteoporotic bone and improve surgical success rates.

Navigation, robotics, and virtual reality techniques in cervical spine surgery are newer technologies being developed currently. Navigation and robotics have the potential to increase screw placement accuracy with less dissection improving both fixation and minimizing soft tissue disruption (75,76). Although given the new implementation of this technology limiting robust data, virtual reality may similarly able to aid in accurate percutaneous screw fixation (77). In the future, these techniques may be beneficial for maximizing bone-implant interface and preserving neck extensor musculature in attempt to maximize DJK prevention.

Radiographic deformity evaluation

The cervical spine serves to maintain horizontal gaze and the head centered over the pelvis and transition to the kyphotic thoracic spine distally. The human spine is sigmoid shaped with a primary endpoint of maintaining neutral sagittal and coronal balance and these compensatory changes can lead to increased lumbar lordosis (LL) to match an increased pelvic incidence (78,79). Alternatively, the cervical curvature may not be lordotic in fact, with asymptomatic cervical kyphosis being observed in a frequent number of patients with relative thoracic hypokyphosis (78,79). These global spinal alignment relationships highlight the necessity of standing scoliosis plain films during cervical pathology evaluation (47).

Cervical spine pathology is not isolated from the rest of the axial skeleton. Global alignment should be assessed for loss of LL and focal deformities in the thoracolumbar spine (80). In some cases, cervical “deformity” may be reciprocal changes to thoracolumbar deformity. In these scenarios, correction of the thoracolumbar spine can reverse the compensatory cervical sagittal malignment, and correction of the cervical spine would lead to further global malalignment (81). T1s acts a base for the cervical spine, affects cervical curvature, and is critical to determining the location of a deformity (82,83). An increased T1s above 30° suggests a thoracolumbar component of deformity, which will need to be addressed intraoperatively. A C2 tilt above 20° with an elevated T1s is seen in combined deformities (Table 3). A low T1s with high C2 tilt suggests an isolated cervical deformity.

Going beyond the recognition of cervical deformity, distal deformity, and combined deformity, it is vital to recognize global alignment in the overall consideration of spinal realignment. From the early days of Dubousset recognizing the “cone of economy” where the head should be aligned above the pelvis for optimal energy expenditure, more recent literature has focused on radiographic measurements, such as the center of the acoustic auditory meatus being aligned over the hip joint and the posterior cranial vertical line, which is a plumb line drawn from the posterior aspect of the occiput and can help classify regional deformities in a more global perspective (84).

Cervical deformity may also be rigid or flexible and distinguishable by their response to gravity, neck flexion, and extension (49). Rigid neck deformities can be visualized by comparing upright cervical plain films in neutral, flexion, and extension alignment to supine plain films, advanced imaging of the patient lying supine such as lateral scout CT or MRI images. Some cases may be visualized in clinic with the patient lying flat and the head remaining elevated off the exam table despite neck musculature being relaxed. Rigidity can clue the clinician into underlying pathology and treatment choice. With Koller et al. describing four categories of rigid cervical deformity, types A–D, based upon cervicothoracic alignment and global balance or imbalance (49). Notably, health related quality of life scores and DJK rates between these groups are similar (85).

Treatment strategies

Nonoperative strategies

While uncommon, DJK/DJF is a serious complication among ACD patients who have undergone surgical correction. Thus, deformity surgeons should be prepared to treat this challenging patient population. Management of DJK and DJF begins with a comprehensive evaluation of the patient, focusing on symptoms and functional status rather than solely on radiographic findings. A detailed history assessing clinical progression, medical comorbidities, psychosocial factors, and frailty is essential. Mild deformities may cause neck pain or neurological symptoms, while severe deformities can present with significant functional loss without pain. Management choice will be determined based upon clinical, radiographic, patient specific factors, and surgeon preferences.

Nonoperative treatment addressing underlying etiologies with the potential addition of supplemental hard or soft collar use, steroid injections, medications, sterno-occipital mandibular immobilization (SOMI), or physical therapy may be appropriate in certain cases of severe cervical deformity such as from neuromuscular disease (40,86). One study found 22% of patients with DHS were able to be managed conservatively with soft collar, neck strengthening exercises, and medical or immune modulating agents had a greater than 70% success rate (86). However, these were not postsurgical patients and it unclear the effectiveness of these treatments in a postoperative setting. If clinically appropriate, nonoperative treatment should be considered for mild cases given the morbidity of revision surgery.

Surgical deformity correction

Revision cervical deformity surgeries can be technically challenging operations. While there is no concrete data regarding DJK rates specific to different types of deformity, residual deformity increases DJK rates and thus the specific nature of the deformity must be considered to adequately realign the spine and decrease rates of DJK (1). Therefore, once the decision for surgery has been made, a DJF deformity analysis and a precise surgical plan is imperative. Multiple classification systems for cervicothoracic deformity exist to assist with surgical planning (49,87-89). Kim et al.’s classification system classifies cervicothoracic deformities into four types using dynamic plain films and provides associated treatment strategies (Table 4) (89). While surgeons can achieve ideal post-operative radiographs and thereby improve sagittal plane deformity, the ultimate goal of spine surgery is to improve patient outcomes, such as pain scores and outcome measures. Multiple studies have demonstrated improved pain and outcome scores with improved radiographic alignment, but this must be the ultimate goal of all spine surgeries (1).

Type 1 deformities are driven by T1s-CL mismatch. Surgery should address neurological deficits at the site of compression, horizontal gaze, T1s-CL mismatch, and realign any focal kyphosis present (89). When using interbody cages, it is essential to select those with a large footprint that promote lordotic alignment. These flat-neck deformity patients often are treated with posterior or combined approaches, and roughly half of patient’s constructs end caudally at T1–4.

Type 2 patients frequently have focal kyphosis in the cervical spine causing their deformity which can be treated via anterior, posterior, or combined approaches to realign their deformities (89). The focal kyphotic patients are often treated with multilevel anterior cervical discectomy and fusions (ACDFs) spanning from C3–4 to C7 using anterior approaches. During ACDF, placing pins divergently into kyphotic segments before distraction can help create lordosis. Posterior instrumentation from C2 to T1-4 is typical in combined or posterior only approaches.

Type 3 suggests cervicothoracic deformity, with surgical intervention often using posterior approaches with 3 column osteotomies (3COs) to correct this group’s steep T1s (89). Techniques to address the deformed alignment include upper thoracic pedicle subtraction osteotomy or multiple cervicothoracic posterior column osteotomies. Constructs are often extended distally to achieve alignment and stability, with fusion terminating at a biomechanically stable vertebra without subjacent instability. Cervicothoracic deformity constructs must address a significant thoracic kyphosis and often span from C2 or C3 to the thoracolumbar junction or T5–9. Proximal extension to C2, C1, or the occiput may improve outcomes when crossing the cervicothoracic junction or in cases requiring longer constructs (90).

Type 4 patients are rarer and exhibit coronal malalignment. These patients frequently require a posterior or combined approach spanning from C2 to the upper thoracic spine to correct their deformity (89).

Additionally, cervical spine rigidity may alter treatment strategies when correcting DJF deformities. While flexible deformities usually do not require osteotomies, except where previously discussed, rigid deformities frequently need osteotomies. Typically, posteriorly rigid deformities are corrected with posterior osteotomies and anteriorly rigid cervical deformities are realigned using anterior osteotomy techniques with anteroposterior correction (91). Deformities that are rigid anteriorly and posteriorly often require Schwab grade III or greater osteotomies (92).

Surgical treatment of DHS is determined by the underlying cause of the skeletal deformity. Surgical strategies include anterior, posterior, and combined approaches to correct the deformity with anterior musculature release in cases of excessive anterior musculature tone (40). Cavagnaro et al. observed that over 75% of DHS surgeries used C2 or the occiput as the cranial fixation point, with 87% crossing the cervicothoracic junction (46). Constructs terminating above T1 were associated with a significantly higher failure rate (71%) compared to those extending to T1 or lower (13%) (46).

Surgeons must be technically equipped to adjust their surgical plan with any new intraoperative findings. Failed instrumentation, particularly at the screw-bone interface, may require replacement with or without augmentation or construct extension. Compression deformities should be corrected to ensure proper alignment, and displaced fractures should be stabilized or removed and augmented as needed. Distal ligamentous disruptions may necessitate fusion extension or reinforcement. The complex nature of revision surgery for DJF requires a combination of techniques and strategies to achieve acceptable outcomes.

Conclusions

DJK and DJF remain significant challenges in ACD surgery. While recent studies have identified numerous preoperative, intraoperative, and postoperative variables that can guide surgical planning, managing DJF once it occurs remains complex. Currently, there is limited literature addressing operative treatment strategies or outcomes following revision surgery for DJF. Future research should focus on developing evidence-based guidelines for treatment, enhancing surgical techniques, and improving long-term outcomes. By addressing these gaps, clinicians can better prevent and manage these complications, ultimately improving patient care.

Acknowledgments

None.

Footnote

Provenance and Peer Review: This article was commissioned by Guest Editors (Mark J. Lambrechts and Munish C. Gupta) for the series “Adult Spinal Deformity: Principles, Approaches, and Advances” published in AME Surgical Journal. The article has undergone external peer review.

Reporting Checklist: The authors have completed the Narrative Review reporting checklist. Available at https://asj.amegroups.com/article/view/10.21037/asj-24-58/rc

Peer Review File: Available at https://asj.amegroups.com/article/view/10.21037/asj-24-58/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://asj.amegroups.com/article/view/10.21037/asj-24-58/coif). The series “Adult Spinal Deformity: Principles, Approaches, and Advances” was commissioned by the editorial office without any funding or sponsorship. B.A.K. has received consulting fees from Surgistep, Kuros Bioscience, and Johnson & Johnson. He has also received payment for legal expert witness services. The authors have no other conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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