Facet-Sparing Trans-Kambin Lumbar Interbody Fusion Versus Oblique Lumbar Interbody Fusion (Anterior-to-Psoas): Effect on Disc Height, Segmental Lordosis, and Lumbar Lordosis – Retrospective Case Series
Article information
Abstract
Objective
The aim of this study was to compare the effect on disc height (DH), segmental lordosis (SL), and lumbar lordosis (LL) between trans-Kambin lumbar interbody fusion (KLIF) and oblique lumbar interbody fusion (OLIF) procedures. Facet-sparing KLIF and OLIF are techniques of spinal fusion that rely on the principle of indirect decompression. Both procedures can restore DH, SL, and LL in a minimally invasive manner. However, approach-related complications and the need to change position for screw placement are some of the disadvantages of OLIF. In contrast, KLIF can be done in a single position, overcoming the aforementioned complications.
Methods
This retrospective study included patients who had undergone KLIF and OLIF. DH, SL, and LL were measured on preoperative and postoperative x-rays using Surgimap software. DH was measured as the average of anterior and posterior DHs. Clinical evaluation was done using modified MacNab grading. Statistical analysis was conducted using the Mann-Whitney test.
Results
Fifty segments each of KLIF (41 patients) and OLIF (35 patients) were included in our study. The average percentage increase in DH in KLIF group was 58.25% versus 103.41% in OLIF group. The change in SL was 3.16° in the KLIF group and 5.36° in the OLIF group. The LL change was 2.73° in the KLIF group and 3.79° in the OLIF group. Modified MacNab grading did not show any significant difference in the outcome scores in both procedures.
Conclusion
Our study showed that both KLIF and OLIF can effectively help restore DH, SL, and LL. Furthermore, OLIF enabled significantly greater correction of SL and LL due to the lordotic cage design and effective compression maneuver of percutaneous fixation on the anterior fulcrum on the cage.
INTRODUCTION
Trans-Kambin lumbar interbody fusion (KLIF) and oblique lumbar interbody fusion (OLIF) are the techniques of spinal fusion which rely in the principle of indirect decompression. The primary consideration of any spinal fusion procedure is restoration of normal vertebral alignment and disc height (DH) along with segmental lordosis (SL) and lumbar lordosis (LL). There is an increasing recognition of the importance of restoration of these parameters for improved patient outcomes [1]. It is also a known fact that sagittal parameters are important even single- or double-level fusions for better health-related quality of life (HRQoL) scores [2,3].
OLIF utilizes the anterior retroperitoneal approach for cage placement [4]. It also requires change of position for placement of pedicle screws and there are approach-related concerns with OLIF such as psoas irritation, lumbar plexopathy and vascular injury [5]. OLIF cannot be performed when there is inadequate vascular window between the iliac vessels and psoas muscle [6]. Furthermore, an access surgeon/vascular surgeon is required for standard retroperitoneal exposure for cage insertion [7].
The aforementioned concerns of OLIF are overcome by KLIF, while retaining the advantages of indirect decompression and restoration of radiological parameters. Therefore, our study aims to compare the change in DH, SL and LL in OLIF and KLIF patients. KLIF can be by multiple techniques: (1) percutaneous technique [8], (2) full-endoscopic technique [9], (3) with the help of tubular retractor system, or (4) transfacet [10]. The details of each have been described in the methodology section of our study.
While both techniques are facet-sparing, OLIF utilizes a lateral retroperitoneal corridor to access the disc space, where KLIF utilizes the extra-foraminal trans-Kambin corridor to achieve the same. Facet excision is therefore avoided in both the techniques, which results in preservation of the posterior tension band, thus reducing the risk of adjacent segment issues.
MATERIALS AND METHODS
1. Patient Selection Criteria
Patients with lumbar spinal canal stenosis with or without foraminal stenosis and spinal instability, who had undergone OLIF and KLIF from a period of March 2023 to March 2025, and with a minimum follow-up of three months were included in the study. Patients with revision surgery, trauma, tumors and infections were excluded.
Patients were regularly followed up at 1 month, 3 months, 6 months, and 12 months postoperatively.
2. Radiological and Clinical Evaluation
DH, SL, and LL were measured on preoperative and postoperative x-rays using Surgimap software (v2.3.2.1) (Figure 1). DH was measured as the average of anterior and posterior DHs. SL was measured as the angle between the inferior endplate of the cranial vertebra and superior endplate of the caudal vertebra. LL was measured as the Cobb angle between L1 and S1. Clinical evaluation was done using modified MacNab grading [11] and visual analogue scale scores for back pain and leg pain.
Pre-operative and post-operative X-rays of KLIF (A) and OLIF (B) showing the measurement of segmental lordosis (yellow lines), lumbar lordosis (green lines) and disc height (red lines) as measured on Surgimap software v2.3.2.1.
3. Statistical Analysis
Appropriate statistical analysis was done using Mann-Whitney test. A p-value of <0.05 was considered to be statistically significant. Other complications such as implant loosening, cage subsidence, end-plate fractures and pseudoarthrosis, if any, were noted.
4. Technical Note
OLIF was performed using the standard anterior retroperitoneal approach in right lateral decubitus. Self-retaining tubular retractor system was used following exposure of the disc space. Cage with bone graft substitute was inserted after adequate end-plate preparation. Six-degree lordotic polyetheretherketone cages were used in all the patients in the study to maintain standardization. The wound was closed in layers without using drain. The patient was then turned prone and posterior percutaneous pedicle screw fixation was done in prone position [12].
KLIF was done through percutaneous, tubular or full-endoscopic technique along with posterior percutaneous pedicle screw fixation in single prone position. We did not use the transfacet technique of trans-Kambin fusion. Trans-Kambin cages did not have a lordotic design.
(1) In percutaneous technique, the trans-Kambin fusion was done over flexible guidewires under image intensifier television (IITV) guidance without direct visualization of the disc space. Docking of the Jamshidi needle was done into the disc space using our novel technique under IITV guidance, followed by guidewire insertion into the disc space and adequate end-plate preparation was carried out by specially designed cannulated tools such as reamers and shavers. Static porous titanium cage with bone graft substitute was then inserted into the disc space [13].
(2) In the full-endoscopic technique, the end-plate preparation is done using transforaminal endoscope inserted into the disc space. Once adequately prepared, the cage with bone graft substitute is then inserted over a guidewire. The endoscope is re-inserted for final checks. Expandable titanium cages were used in full-endoscopic technique [14].
(3) Similarly, a tubular retractor system can be docked on the Kambin triangle and visualization is done with the help of a surgical microscope.
The most commonly used cage height in both the procedures was 10–12 mm. Direct posterior decompression was not done in any patient.
This study was approved by the Institutional Review Board of HCG Multispecialty Ethics Committee (HCG-MA/ECR/92/Inst/GJ/2013/RR-24). (Reg no. ECR/92/Inst/GJ/2013/RR-24).
RESULTS
1. Demography
A total of 76 patients were enrolled in the study, 35 patients who had undergone OLIF while 41 patients had undergone KLIF surgery. The mean age and gender distribution were statistically comparable between surgery groups. Most of the enrolled patients in both the surgery groups were females (65.71% in OLIF group and 70.73% in the KLIF group).
The proportion of patients with single level involvement were more commonly noted in both study groups (65.71% in OLIF group and 78.04% in the KLIF group). Most of the lumbar spinal stenosis had degenerative etiology in both study groups (Figure 2) (80% in OLIF group, 66% in KLIF group). We had two patients with adjacent segment disease (ASD) in the OLIF group. ASD is defined as new, symptomatic spinal pathology arising in the adjacent level to a prior fusion surgery. In our study, we have included patients with ASD in whom indirect decompression was indicated and therefore, OLIF surgery was performed.
Distribution of etiology in OLIF (Oblique Lumbar Interbody Fusion) and KLIF (Transkambin Lumbar Interbody Fusion) groups.
The most common level involved was L4–5 in both study groups. (Figure 3) Significantly greater proportion of patients in OLIF group had L3–4 involvement (30% vs 8%, p<0.05), while significantly higher number of cases in KLIF group had L5–S1 involvement (34% vs 0%, p<0.05). Most of the lumbar spinal stenosis had degenerative etiology in both study groups (80% in OLIF group, 66% in KLIF group).
Number of levels involved in OLIF and KLIF groups.
Complete demographic and baseline details are given in Table 1.
Demographic and patient-related data
2. Radiological Outcomes
The mean change in the SL angle (Figure 4) was noted to be significantly greater in the OLIF group versus the KLIF group (5.36±2.56 vs. 3.16±2.15, p<0.05 by Mann-Whitney test).
Mean change in segmental and lumbar lordosis in OLIF and KLIF groups.
Similarly, the mean change in the LL angle was noted to be significantly greater in the OLIF group versus the KLIF group (3.79±2.64 vs. 2.73±2.16, p<0.05 by Mann-Whitney test).
The mean percentage change in the DH (Figure 5) was noted to be significantly greater in the OLIF group versus the KLIF group (103.41±88.55 vs. 58.25±49.28, p<0.05 by Mann-Whitney test).
Mean percentage change in disc height in OLIF and KLIF groups.
In the OLIF group, the change of percentage DH was noted to be significantly better in the degenerative aetiology subgroup versus the lytic subgroup (107.13±86.44 vs. 84.42±35.30, p<0.05 by Mann-Whitney test). However, in the KLIF group, the mean change in the percentage DH was noted to be significantly comparable between lytic and degenerative subgroups (61.69±49.08 in degenerative subgroup vs. 60.98±49.2 in lytic subgroup, p>0.05 by Mann-Whitney test).
3. Complications Profile
• No patient had any implant-related complications such as implant loosening, cage subsidence or endplate fractures.
• No patient required direct posterior decompression.
• No patient had any approach-related complications such as lumbar plexus injury or vascular injury in OLIF group.
• In KLIF group, 6 patients had exiting nerve root irritation, all of which resolved in 4-week time with analgesics only. There was no motor neurological deficit.
• There was no incidence of postoperative hematomas or wound healing problems.
• No patient had endplate injury or cage subsidence.
Modified MacNab grading did not show any significant difference in the outcome scores in both the procedures. Fusion was assessed in patients with a minimum follow-up period of 9 months and all patients showed Bridwell [15] grade 2 fusion at 9-months.
DISCUSSION
With increasing life-span, the number of patients requiring spinal fusion surgery are increasing [16]. The restoration of sagittal plane balance is an important goal in spinal fusion surgery [17]. Sagittal plane parameters are those related to the curvature of the spine, and are divided into SL and LL [18]. The restoration of these parameters is also linked to better long-term outcomes [19].
The KLIF and OLIF are spinal fusion procedures which aim to restore the DH, SL, and LL. Both the techniques work through the principles of indirect decompression.
OLIF utilizes the anterior retroperitoneal approach, which raises concern of vascular injury, bowel-related issues, psoas irritation and other approach-related complications [20]. It also requires a change of patient position for placement of pedicle screws. Single-position OLIF can also be done; however, it requires navigation guidance and therefore adds to the infrastructural cost as intra-operative navigation is not easily available [21]. These problems are overcome by KLIF which can be done in single prone position, with a familiar approach, while retaining the advantages of indirect decompression and restoration of sagittal balance parameters.
It was hypothesized that the prone transpsoas approach allows single position spinal fusion and aids in better lordosis restoration, as the patient position on bolsters aids in natural extension of the spine [22]. The same was also demonstrated later that prone transpsoas fusion indeed gives better lordosis correction than standard OLIF procedure [23]. Trans-Kambin fusion utilizes the same principle as we can see here, however, the restoration of radiological parameters is still significantly less as compared to standard OLIF technique in our study.
In our study, the change in DH, SL and LL in OLIF group was significant higher as compared to the KLIF group. To our best knowledge, there is no study comparing the radiological outcomes between the two procedures. Also, we could not find any study demonstrating the change in radiological parameters of KLIF.
To our best knowledge, we could not find any study in our literature review which demonstrates change in radiological parameters in KLIF as mentioned here. The change in radiological parameters in OLIF has been extensively reported.
Our results are comparable with other studies as mentioned in Table 2. Kepler et al. [24], in their study of 29 patients showed a 3.7° increase in SL in their study. Another study of 43 patients by Sharma et al. [25] showed a 2.8° increase in SL and 0.5° in LL. A study of 80 patients by Shiga et al. [26] showed a 3.8° increase in SL. Champagne et al. [27] showed a 4.4° increase in SL, 4.8° increase in LL and 84.6% increase in DH in their study of 38 patients. In a study of 147 patients by Sembrano et al. [28], a 3.2° increase in SL and 2.5° in LL was noted. Mahatthanatrakul et al. [29] in their study of 46 patients demonstrated a 3.0° increase in SL, 6.5° increase in LL and 56% increase in DH. A study of 21 patients by Hung et al. [30] showed a 3.65° increase in SL and 115% increase in DH. Li et al. noted a 3.4° increase in SL, 3.2° increase in LL and 50.5% increase in DH in their study of 120 patients.
Comparison of radiological parameters
Our study shows a 5.3° increase in SL, 3.7° increase in LL et al. [31] and 103% increase in DH in OLIF group. In the KLIF group, there was a 3.1° increase in SL, 2.7° increase in LL and 58% increase in DH.
OLIF and KLIF both work in the principle of indirect decompression by ligamentotaxis. Due to the oblique approach of cage insertion in both the techniques, cages with more length and height can be inserted into the disc space, which aid in restoration of DH and sagittal balance parameters.
The increase in the parameters is however higher in the OLIF group, which can be attributed to a few reasons. OLIF cage has a lordotic design. The cage insertion in OLIF is through the anterior half of the disc leading to improved jacking up of the disc space. Furthermore, the anterior position also allows for a long lever arm (Figure 6) when compression is applied after placement of percutaneous pedicle screws and rods.
Diagrammatic representation of mechanism of OLIF and KLIF in restoration of segmental lordosis. In OLIF, the lordotic cage design (red lines) and more anterior placement of the cage provide a longer lever arm (green line) when compression is applied (blue arrows). In KLIF, the lever arm is short and the cage occupies a more posterior location in the disc space therefore restriction compression up to a certain extent (yellow arrows).
There is statistically significant difference in the restoration of SL in KLIF and OLIF groups. Therefore, it is imperative that each technique is used accurately in a patient to avoid PI-LL (pelvic incidence minus LL) mismatch and subsequent cascade of spinopelvic imbalance. If not employed adequately, there will be inadequate restoration of sagittal parameters leading to poor health-related HRQoL scores and suboptimal patient outcomes. In order to overcome this, we have devised our own flow-chart for patient selection for these techniques.
1. Author’s Preference
Figure 7 shows a rough flow-chart of our patient selection for OLIF or KLIF.
Depicts flow chart for patient selection for OLIF or KLIF.
If a patient is eligible for indirect decompression, we check the magnetic resonance imaging scan for vascular window.
• If a vascular window is absent, KLIF is the procedure of choice.
• If a vascular window is present, an extension film of the patient is procured to see the PI-LL mismatch.
• If PI-LL <15°, KLIF is performed.
• However, the PI-LL >15° or there is gross sagittal imbalance, OLIF is the procedure of choice.
• Furthermore, we have limited KLIF to 1–2 levels.
• If more than 2-level fusion is required, OLIF is preferred.
2. Study Limitations
• It is a retrospective study of a small sample size.
• Other radiological parameters such as changes in spinal canal cross-sectional area, foraminal cross-sectional area and ligamentum flavum thickness have not been compared.
• Long-term follow-up is required for assessment of fusion, cage subsidence, adjacent segment degeneration/disease.
CONCLUSION
Our study showed that both OLIF and KLIF procedures can effectively help restore DH, SL, and LL. However, the change in DH is significantly more in OLIF as compared to KLIF due to anterior placement of the cage. Furthermore, there is significantly higher correction of SL and LL in OLIF due to lordotic cage designs and effective compression maneuver of percutaneous fixation due to the more anterior fulcrum of the anteriorly positioned cage. Despite the differences, the clinical outcomes of KLIF and OLIF are comparable and did not show any statistical difference.
Notes
Conflicts of interest
The authors have nothing to disclose.
Funding/Support
This study received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.