The kickstand rod technique for correction of coronal malalignment in patients with adult spinal deformity: a systematic review and pooled analysis of 97 cases

Vishal Kumar; Sarvdeep Singh Dhatt; Parth Bansal; Akshat Srivastava; Vishnu Baburaj; Arvind Janardhan Vatkar

doi:10.31616/asj.2023.0367

Asian Spine J > Volume 18(3); 2024 > Article

Kumar, Dhatt, Bansal, Srivastava, Baburaj, and Vatkar: The kickstand rod technique for correction of coronal malalignment in patients with adult spinal deformity: a systematic review and pooled analysis of 97 cases

Review Article

Asian Spine Journal 2024;18(3):472-482.

Online first: June 25, 2024

DOI: https://doi.org/10.31616/asj.2023.0367

The kickstand rod technique for correction of coronal malalignment in patients with adult spinal deformity: a systematic review and pooled analysis of 97 cases

Vishal Kumar^1,^*

, Sarvdeep Singh Dhatt^1,^*

, Parth Bansal¹

, Akshat Srivastava¹

, Vishnu Baburaj¹

, Arvind Janardhan Vatkar²

¹Department of Orthopaedics, Postgraduate Institute of Medical Education and Research, Chandigarh, India

²Department of Spine Surgery, Fortis Hiranandani Hospital, Vashi, India

Corresponding author: Parth Bansal, Spine Surgery, Department of Orthopaedics, PGIMER, Chandigarh, India,
Tel: +91-9878333131, Fax: +91-172-2756740, E-mail: parthbansal93@gmail.com

^* These authors contributed equally to this work as the first authors.

Received November 9, 2023 Revised February 10, 2024 Accepted February 25, 2024

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Coronal malalignment (CM) has recently gained focus as a key predictor of functional outcomes in patients with adult spinal deformity (ASD). The kickstand rod technique has been described as a novel technique for CM correction using an accessory rod on the convex side of the deformity. This review aimed to evaluate the surgical technique and outcomes of corrective surgery using this technique. The literature search was conducted on three databases (PubMed, EMBASE, and Scopus). After reviewing the search results, six studies were shortlisted for data extraction and pooled analysis. Weighted means for surgical duration, length of stay, amount of coronal correction, and sagittal parameters were calculated. The studies included in the review were published between 2018 and 2023, with a total sample size of 97 patients. The mean age of the study cohort was 61.1 years, with female preponderance. The mean operative time was 333.6 minutes. The mean correction of CM was 5.1 cm (95% confidence interval [CI], 3.6–6.6), the mean sagittal correction was 5.6 cm (95% CI, 4.1–7.1), and the mean change in lumbar lordosis was 17° (95% CI, 10.4–24.1). Preoperative coronal imbalance and mean correction achieved postoperatively were directly related with age. The reoperation rate was 13.2%. The kickstand rod technique compares favorably with conventional techniques such as asymmetric osteotomies in CM management. This technique provides an additional accessory rod that helps increase construct stiffness. Because of limited data, definitive conclusions cannot be drawn from this review; however, this technique is a valuable tool for a surgeon dealing with ASD.

Keywords: Kickstand rod; Coronal malalignment; Coronal imbalance; Adult spinal deformity; Degenerative scoliosis

Introduction

Adult spinal deformity (ASD) is a chronic, debilitating condition with a significant effect on the health-related quality of life of the affected individuals [1,2]. Pellise et al. [1] reported that individuals with ASD had lower 36-Item Short-Form Survey (SF-36) scores on self-reported questionnaires than those with other common chronic conditions. In the literature, scoliosis develops in 68% in the otherwise healthy older population [3]. If conservative treatment fails, the surgical goals in ASD include achieving sagittal and coronal alignment, adequate neural decompression, and fusion [4,5].

Coronal malalignment (CM), or coronal imbalance, which clinically manifests as a truncal shift, is a significant lateral displacement of the C7 plumb line (C7PL) from the central sacral vertical line (CSVL) [6]. It is evaluated on a posteroanterior standing radiograph. Because of the lack of compensatory mechanisms compared with sagittal imbalance, it can cause severe impairment including gait disturbances and difficulty sitting in nonambulatory individuals [7]. In patients with rigid deformities and generally lower bone mineral density, corrective surgery can be challenging, and correction is difficult to attain and maintain [8]. In the literature, various techniques have been described for the correction of coronal plane deformities. Asymmetrical osteotomies are the most commonly described procedure but are associated with several complications such as dural tears, pseudoarthrosis, and implant failure because these are mostly performed in revision cases [9–12]. Extreme lateral interbody fusion via a minimally invasive transpsoas approach was also described for coronal plane correction [13]. In addition, the use of accessory rods has been described for CM correction [14,15]. Makhni et al. [14] described the use of an accessory kickstand rod on the convex side of the deformity, which is proximally anchored in the thoracic spine via a domino connector and distally to the pelvis with the placement of an iliac or sacral–alar–iliac (S2AI) screw. In the tie–rod technique, the accessory rod is placed on the convex side of the deformity [15].

The kickstand rod technique has various theoretical advantages compared with other techniques, which include shorter operative time, less invasiveness, additional stability with the accessory rod, and low complication rates. This review focuses on the currently available data of this novel technique, including surgical outcomes and safety.

Methods

Search methodology

PRISMA guidelines for systematic reviews were followed [16], and a comprehensive search was conducted on PubMed, Embase, and Scopus databases on September 9, 2023. The keywords used in the search strategy were “kickstand” and “rod” with reference to the title, abstract, and keywords. A secondary search from the reference lists of published original studies and previous reviews was performed for more relevant studies. Our search strategy was as follows: PubMed, kickstand [Title/Abstract] AND rod [Title/Abstract]; Embase, kickstand:ti,ab,kw AND rod:ti,ab,k; Scopus, TITLE-ABS-KEY (kickstand AND rod).

Inclusion and exclusion criteria

Non-English studies, conference abstracts, cadaveric studies, and animal trials were excluded. Studies that reported the use of the kickstand rod technique in ASD management and had a minimum of five study participants were included in the review and analysis. Articles on surgical techniques, case reports, review articles, and papers that did not separately report the outcomes of patients who underwent the kickstand rod procedure were excluded.

Data collection

Two reviewers independently screened all search results. Conflicts, if any, were resolved with input from the other authors before reaching a consensus. Collected data were entered on a structured format. Table 1 summarizes the study design, sample size, outcomes reported, and follow-up. Table 2 is a detailed representation of the outcomes and variables reported by the studies. Standard variables were identified and segregated for further analysis. Variables that were reported by at least three studies were considered for statistical testing.

Statistical analysis

Statistical analysis was conducted with OpenMeta Analyst ver. 10.2 (Brown University, Providence, RI, USA; http://www.cebm.brown.edu/openmeta/), and a p-value of <0.05 was considered statistically significant. Means were weighted for the sample size, and DerSimonian–Laird inverse-variance weighted pooled analysis was performed using a random-effects model to calculate the mean difference and confidence intervals (CIs). Forest plots were generated for a visual summary. The I² test assessed statistical heterogeneity. Meta-regression and subgroup analysis were performed wherever possible to determine the cause of heterogeneity.

Risk of bias assessment

The methodological index for nonrandomized studies was used to assess the risk of bias in the included studies [17]. Based on whether they are comparative or noncomparative, studies were scored out of 24 or 16 points, respectively.

Results

Search and screening results

The initial search across databases retrieved 63 studies, out of which duplicates were removed, and the remaining 21 studies were assessed for suitability based on the inclusion and exclusion criteria. After reading their titles and abstracts, these articles were further shortlisted to 10 based on the study design, and the research question and outcomes were reported. The full texts of these 10 articles were then read to assess for eligibility. Of these, six studies were included in the review, and data were extracted for pooled analysis [18–23] (Fig. 1).

Study characteristics

All six studies had a retrospective design, with two studies [21,22] having a comparative group. The minimum mean follow-up was 21 weeks (range, 2–72 weeks) in the study by Buell et al. [19], and the longest follow-up was 2.5 years (range, 2–5 years) years in the study by Puvanesarajah et al. [23].

Patient characteristics

From the six studies, 97 patients were included in the review. The overall mean age of the study cohort was 61.1 years (95% CI, 54.4–67.9) (Fig. 2), which ranged from a mean age of 54 years (range, 20–73 years) [23] to 72.2±1.9 years [20]. Five studies reported sex distribution in the study cohort; of these, 18 of the 76 individuals (23.7%) were male [18–20,22,23].

Surgical techniques

The kickstand rod technique was first described by Makhni et al. [14]. Surgery is usually performed from an all-posterior approach. After the standard insertion of pedicle screws, decompressions, and osteotomies for sagittal balance correction, the kickstand rod is placed on the convex side of the coronal plane deformity. The kickstand rod is anchored between an iliac/S2AI screw placed distally and a domino connector at the thoracolumbar junction. While the contralateral rod secures the sagittal correction, the ipsilateral rod is loosened to allow for CM correction by the distraction of the kickstand rod. Buell et al. [19] preferred using three iliac screws for pelvic fixation, with the third iliac screw as the distal fixation point for the kickstand rod. They emphasized the importance of locking down the L4–S1 lordosis correction before starting the kickstand procedure. Many authors have highlighted the addition of a fourth rod on the side contralateral to the convexity after the kickstand maneuver [18,20,22].

Operative time

Three studies reported the duration of surgery, a mean operating time of 333.6 minutes (95% CI, 309.9–357.4) [19–21] (Fig. 3).

Length of stay

Three studies reported the length of stay, and the mean duration was 9.6 days (95% CI, 7.8–11.4) (Fig. 4).

Coronal malalignment

CM was measured by the distance between the C7PL and the CSVL. The mean preoperative CM was 6.9 cm (95% CI, 5.4–8.4) (Fig. 5A), and the heterogeneity for this estimate was high (p<0.001, I²=80.5%). Meta-regression for all estimated means was performed based on age and sex. Age was found to be a significant factor, with older individuals having higher initial CM (p=0.005) (Fig. 5B).

The mean estimate of the change in CM was 5.1 cm (95% CI, 3.6–6.6), showing moderate heterogeneity (p=0.001, I²=74.5%) (Fig. 5C). Similar to preoperative CM, increasing age significantly correlated (p=0.004) with the extent of change in CM (Fig. 5D).

Sagittal parameters

Sagittal imbalance was estimated as the distance between the C7PL and the posterior endplate of the S1 vertebra on a standing lateral radiograph and was reported by five studies [18–21,23]. The mean preoperative sagittal imbalance was measured at 8.3 cm (95% CI, 6.5–10.2), and the heterogeneity for this estimate was moderate (p=0.115, I2=46.1%) (Fig. 6A). Higher mean age was a significant factor for increased sagittal imbalance on meta-regression (Fig. 6B). The mean change in the C7–sagittal vertical axis was 5.6 cm (95% CI, 4.1–7.1) (Fig. 6C).

Lumbar lordosis

The mean preoperative lumbar lordosis was 32.1° (95% CI, 29.1–35.0) (Fig. 7A). The mean change in lordosis was 17° (95% CI, 10.4–24.1) (Fig. 7B); this estimate had a moderate heterogeneity (p=0.012, I²=68.9%). With increasing age, a significantly lower change (p=0.043) in lumbar lordosis was noted postoperatively (Fig. 7C).

Complications

The estimated mean for revision surgical procedure/reoperation was 13.2% (95% CI, 3.8–22.5) (Fig. 8). Reasons for surgical revisions included wound complications, proximal junctional kyphosis, rod fractures, and pseudoarthrosis.

Risk of bias

The risk of bias in the included studies was moderate (Table 3). This was attributed to the retrospective design of the studies and the small sample size because of the technique is relatively new.

Discussion

Our literature search revealed only six case series that reported the outcomes of surgery for ASD in which a kickstand rod was used as a corrective technique. In our analysis, this technique was associated with a revision rate of 13.2% and a mean coronal correction of 5.1 cm (95% CI, 3.6–6.6). The authors of the studies included in our review [18–23] used the approach described by Makhni et al. [14] while incorporating some of their modifications and reported satisfactory outcomes in their respective study cohorts.

Although previous studies and treatment focused on the correction of sagittal imbalance in patients with ASD, recent evidence suggests that CM correction is an important predictor of the functional outcomes of these individuals [5–7,24,25]. Patients with ASD require global correction of deformity, which necessitates biplanar correction that is difficult to achieve [26,27]. Addressing the coronal curve can be a challenging endeavor, with techniques such as asymmetric osteotomies being technically demanding and having longer surgical times and increased risk of intraoperative and postoperative complications [9,10].

The kickstand rod technique is a recently described technique for CM correction [14,28], which involves the use of an accessory rod on the convex side of the deformity. It is named after the lever on the side of bicycles/motorcycles that keeps them propped up when not in use [18]. In biomechanical studies, accessory rods help maintain correction and limit the range of motion across the instrumented spinal segment [29,30]. The kickstand rod provides a theoretical additional advantage of correction of the scoliotic curve in patients with ASD, along with the less invasiveness of the procedure and additional biomechanical support in long posterior constructs [31] (Fig. 9).

Satisfactory CM correction was achieved in all six studies. Makhni et al. [18] reported that at 1.4 years of follow-up, their study cohort had an average of 21 mm of CI in comparison with 63 mm in the preoperative period. Buell et al. [19] emphasized the importance of maintaining lumbar lordosis while performing the kickstand procedure and noted that sagittal correction was also well maintained in their patients; this finding was echoed by other studies [21–23]. Alternative techniques such as asymmetrical osteotomies have variable results, with Lenke et al. [32] reporting postoperative neurological deficits in up to 22% of the patients. On meta-regression, increasing age was associated with an increase in preoperative CM and extent of coronal correction because older patients with chronic diseases would have a greater magnitude of curves and therefore undergo more correction intraoperatively.

In our analysis, the causes of reoperations included wound complications, proximal junctional kyphosis, and prominent screws. None of the 97 patients underwent a second surgery for implant- or kickstand rod-related failure that required revision. Five studies reported no cases of rod fractures, screw fractures, or kickstand rod-related failure [18–22]. Puvanesarajah et al. [23] reported two cases of S2AI screw fractures (one ipsilateral and one contralateral) and one case of kickstand iliac screw shank fracture; however, none of these cases required revision. Overall, surgeon comfort with the technique, postoperative maintenance of correction, and implant-related failure rates were satisfactory by the authors.

Four of the included studies evaluated functional outcomes based on leg and back pain scores, Oswestry Disability Index (ODI) scores, and SF-36 functional outcome scores [19–21,23]. Because of the lack of consistency in reporting of back and leg pain across studies, the data could not be pooled and analyzed; however, all authors reported statistically significant improvement in back and leg pain. Disability based on the ODI score also showed improvement in all reported cohorts. In a comparison of the kickstand and non-kickstand groups, Mundis et al. [21] reported no significant difference in functional outcomes between the groups; however, this was attributed to the small sample size.

This study has several limitations. The kickstand rod technique is a novel technique described in literature within the last 5 years; thus, data and long-term outcomes of this technique are still lacking. All studies included in our analysis were retrospective, with a moderate risk of bias, limiting our ability to draw definite conclusions. Despite these limitations, we believe that our review provides valuable insights into the effectiveness of this technique in addressing CM.

Conclusions

This review provides insight into the surgical technique and the outcomes associated with the kickstand rod technique described for CM correction in ASD. This technique provides a less invasive alternative to conventional techniques such as osteotomies and interbody fusion in CM management. Its advantages include the addition of accessory rods that provide more support to the stability of the posterior construct and low reported implant-related complication rates. Although further prospective studies would be valuable to confirm our findings, this valuable technique must be included in a surgeon’s armamentarium when treating ASD.

Acknowledgments

We would like to thank Mr Dharamjit Singh (Senior Artist, PGIMER. Chandigarh, India) for his valuable contribution with the schematic representation for this review article.

Notes

Conflict of Interest

No potential conflict of interest relevant to this article was reported.

Author Contributions

VK helped conceptualize the study, edited the drafts, and gave final approval. SSD helped conceptualize the study, edited the drafts, and gave final approval. PB helped to perform the literature search, conducted the statistical analysis, and wrote the first draft of the article. AS helped perform the literature search and wrote the first draft of the article. VB helped with the draft review and the statistical analysis. AJV helped conceptualize the review, performed the literature search, and edited the drafts.

Fig. 1

Literature search strategy.

Fig. 2

Mean estimate for age. CI, confidence interval.

Fig. 3

Mean estimate for operative time. CI, confidence interval.

Fig. 4

Mean estimate for length of stay. CI, confidence interval.

Fig. 5

(A) Mean estimate of preoperative coronal malalignment. (B) Meta-regression of preoperative coronal malalignment on the basis of age. (C) Mean estimate of change in coronal malalignment. (D) Meta-regression of change in coronal malalignment on the basis of age. CI, confidence interval.

Fig. 6

(A) Mean estimate of preoperative sagittal imbalance. (B) Meta-regression of preoperative sagittal imbalance on the basis of age. (C) Mean estimate of change in sagittal imbalance. CI, confidence interval.

Fig. 7

(A) Mean estimate of preoperative lumbar lordosis. (B) Mean estimate of change in lumbar lordosis. (C) Meta-regression of change in lumbar lordosis on the basis of age. CI, confidence interval.

Fig. 8

Mean estimate of complication rate. CI, confidence interval; Ev/Trt, events/treated.

Fig. 9

(A) Schematic representation of kickstand rod technique–preoperative (Credit–Mr Dharamjit Singh). (B) Schematic representation of kickstand rod technique–postoperative (Credit–Mr Dharamjit Singh).

Table 1

Summary of included studies (2018–2023)

Author/year	Type of study	No. of patients	Follow-up (wk)	Outcomes evaluated
Makhni et al. [18] (2020)	Retrospective case series	24	73	Preop and postop coronal imbalance, C7–sacral alignment (C7–sagittal vertical axis), and lumbar lordosis, complications
Buell et al. [19] (2020)	Retrospective case series	19	21 (2–72)	Surgical details, complications, preop and postop coronal and sagittal parameters, Numerical Rating Scale or back and leg pain
Proietti et al. [20] (2021)	Retrospective case series	6	60.8±10.8	Estimated blood loss, operative time, length of stay, rod fracture rate, preop and postop sagittal parameters, coronal parameters, clinical outcomes
Mundis et al. [21] (2022)	Retrospective case control study	21	Min 52	Surgical details, operative duration, length of stay, preop and postop sagittal parameters, coronal parameters, clinical outcomes, complication rates
Hofler et al. [22] (2022)	Retrospective case series	7	52.5 (22.1–81.2)	Preop and postop coronal and sagittal parameters, adverse events
Puvanesarajah et al. [23] (2023)	Retrospective case series	20	130 (104–260)	Surgical variables, patient reported outcomes, postoperative complications, radiological parameters

Values are presented as number, mean (range), or mean±standard deviation.

Preop, preoperative; Postop, postoperative.

Table 2

Summary of demographics, coronal and sagittal parameters, complications, and miscellaneous findings reported

Author/year	No.	Age (yr)	M:F	Coronal malalignment (cm)		Sagittal imbalance (cm)		Lumbar lordosis (°)		Complications	Miscellaneous

				Preop	Postop	Preop	Postop	Preop	Postop
Makhni et al. [18] (2020)	24	55 (14–73)	6:18	6.3 (1.8–13.7)	2.1 (−1.2 to 8.3)	7.3 (−1.1 to 26.9)	3.0 (−7.3 to 9.8)	34 (−10 to 70)	47 (24–68)	- Wound dehiscence (n=1) - Revision (PJK) (n=1) - CSF leak (n=1)	-

Buell et al. [19] (2020)	19	67±6.5	4:15	7.9±5.7	0.9±1.3	10.9±7.8	3.7±4.1	26.7±15.3	54.5±9.2	- Reoperation (n=3) - Wound complication (n=3) - Neurological deficit (n=2)	- Estimated blood loss: 3±1.6 L - Mean operative time: 5.7±1.2 hr - Length of stay: 10.4±7.5 day - Back NRS score: 7.2±2.0 (preop) to 4.2±2.6 (postop) - Leg NRS score: 5.9±2.7 (preop) to 1.7±2.9 (postop)

Proietti et al. [20] (2021)	6	72.2±1.9	2:4	16.3±6.4	3.2±2.6	9.2±5.9	2.9±2.3	31.5±6.1	49.9±7.4	- Wound complication (n=1)	- Estimated blood loss: 458.3±56.3 mL - Mean operative time: 327.6±72.1 min - Length of stay: 9.7±3.9 day - VAS Back score: 7.9±2.1 (preop) to 3.8±2.7 (postop) - VAS Leg score: 4.8±3.4 (preop) to 3.6±2.1 (postop) - ODI score: 49±10 (preop) to 28±8 (postop) - SF-36 score: 31.1±7.2 (preop) to 47.1±6.7 (postop)

Mundis et al. [21] (2022)	21	58±8.9	-	7.6±4.2	1.8±1.8	10.2±8.3	2.0±4.4	34±20	53±13	- Surgical revision (n=2)	- Mean operative time: 322±102 min - Length of stay: 9±6.4 day - Change in ODI: 20±14 - Change in SF-36 Physical Function: 9.1±12.7 - Change in SF-36 Mental Health: 6.2±6.9

Hofler et al. [22] (2022)	7	58.6 (29–76)	3:4	4.3 (0.8–9.7)	1.8 (0.6–5.7)	-	-	-	-	- Wound infection (n=1) - Reoperation (n=2)	-

Puvanesarajah et al. [23] (2023)	20	54 (20–73)	3:17	5.7 (3.0–11.3)	1.6 (0.2–4.5)	6.2 (0–19.3)	1.5 (−2.8 to 6.2)	35.8 (1.0–62.4)	43.7 (29.7–69.1)	- Reoperation (n=6)	- ODI score: 43 (2–76) (preop) to 27 (0–68) (postop)

Values are presented as number, mean (range), or mean±standard deviation.

M, male; F, female; Preop, preoperative; Postop, postoperative; PJK, proximal junctional kyphosis; CSF, cerebrospinal fluid; NRS, Numerical Rating Scale; VAS, Visual Analog Scale; ODI, Oswestry Disability Index; SF-36, 36-Item Short-Form Survey.

Table 3

Risk of bias

Author/year	Clearly stated aim	Inclusion of consecutive patients	Prospective collection of data	Endpoints appropriate to the aim of the study	Unbiased assessment of the study endpoint	Follow-up period appropriate to the aim of the study	Loss to follow-up less than 5%	Prospective calculation of the study size	An adequate control group	Contemporary groups	Baseline equivalence of groups	Adequate statistical analysis	Global score
Makhni et al. [18] (2020)	2	2	1	2	1	2	2	0	-	-	-	-	12
Buell et al. [19] (2020)	2	2	1	2	1	1	2	0	-	-	-	-	11
Proietti et al. [20] (2021)	2	1	1	2	1	2	1	0	-	-	-	-	10
Mundis et al. [21] (2022)	2	1	1	2	1	2	1	1	1	2	2	1	17
Hofler et al. [22] (2022)	2	1	1	2	1	2	2	0	1	2	1	1	16
Puvanesarajah et al. [23] (2023)	2	2	1	2	1	2	2	0	-	-	-	-	12

NA, not applicable in non-comparative studies.

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