A comparative study of perioperative pain, blood loss, and hospital stay in an Indian population undergoing mini-open oblique lumbar interbody fusion versus open transforaminal lumbar interbody fusion

ABSTRACT

Background:

There are several approaches for lumbar fusion, although there is yet to be a consensus on which approach is the best. This study aimed to evaluate the intraoperative blood loss and acute postoperative pain in single-level mini-open oblique lumbar interbody fusion (OLIF) versus open transforaminal lumbar interbody fusion (TLIF) surgeries for the degenerative spine.

Methods:

Thirty-two patients were assigned by the surgeon to OLIF or TLIF groups – 16 in mini-open OLIF and 16 in open TLIF groups. The intraoperative blood loss and postoperative hemoglobin, numerical rating scale (NRS) at proposed time intervals for 24 h postoperative, and rescue analgesics used were compared among the groups. The operative duration and hospital stay in both groups were also compared.

Results:

The OLIF group showed significantly higher postoperative hemoglobin (11.5 vs. 10.5 g %, P = 0.04), lower 24-h postoperative pain scores on movement, (NRS 4 vs. 5.5, P = 0.0001), and shorter hospital stay (4.5 vs. 7 days, P = 0.003) than TLIF group. However, the surgery duration was significantly longer in OLIF than in TLIF (190 vs. 150 min, P = 0.005). Intraoperative hemodynamics, other postoperative pain scores at variable time points, and rescue analgesics given were comparable among groups (P > 0.05). Intraoperative blood loss was lower in OLIF than TLIF (275 vs. 500 mL) but was not statistically significant (P > 0.05).

Conclusion:

Mini-open OLIF has favorable perioperative outcomes compared to open TLIF. Patients have higher postoperative hemoglobin and lesser pain on movement on the first postoperative day, leading to earlier mobilization and a shorter hospital stay.

INTRODUCTION

Surgical decompression for lumbar degenerative diseases (LDD) is undertaken when all noninvasive conservative methods have failed. LDD often presents with intractable low back pain (LBP). LBP is one of the most common health ailments, with an estimated lifetime global prevalence of 60%–80%.[1] Favorable postoperative outcomes regarding better analgesia will lead to early mobilization of such patients. Better analgesia may also reduce the incidence of failed back surgery syndrome and postlaminectomy pain.[1] Less blood loss is desirable.[2]

Treatment of LDD involves lumbar interbody fusion (LIF) and is often done with canal decompression. These spinal surgeries are accompanied by excessive blood loss and postoperative pain, which is not desirable in any surgery. Anemia impedes wound healing on the one hand and requires an allogenic transfusion, which leads to transfusion-related complications on the other hand.[3] Effective acute postoperative pain management is essential for better postoperative outcomes in reducing LBP, better patient satisfaction, and reduced hospital stay.[4]

There are various approaches for LIF, although there has yet to be a consensus on which approach is the best.[5] The ideal approach would be one that would allay the preoperative malady of LBP and is associated with better perioperative outcomes. Although the open transforaminal lumbar interbody fusion (open-TLIF) is the most popular and widely practiced LIF procedure, especially in the Indian subcontinent, it is associated with significant blood loss. This is because the open-TLIF technique requires extensive muscle dissection, often with the cutting of lamina/facets, leading to intraoperative and postoperative back pain. Oblique lumbar interbody fusion (OLIF) is a novel, effective approach gaining popularity. It is a minimally invasive anterior-lateral approach for LIF procedures providing indirect neural decompression.[6] The approach is through relatively avascular planes, hence muscle sparing passing through an oblique anterolateral corridor between the psoas major muscle and the aorta/common iliac vessel on the left side. It also needs augmentation with pedicular screws which can be percutaneous minimally invasive surgery (MIS) or via the intermuscular Wiltse approach (mini-open). This procedure can also be associated with injury to the psoas and back muscles.

There is a paucity of studies comparing intraoperative blood loss and acute postoperative pain between both techniques. However, in Western literature, few studies compare the MIS-OLIF to MIS-TLIF.[7,8] MIS-TLIF is done by fewer surgeons in the Indian subcontinent. Therefore, there is a need to compare these two procedures (mini-open OLIS and open TLIF). We aimed to evaluate the perioperative outcomes of single-level mini-open-OLIF versus open-TLIF procedures.

METHODS

This was a prospective observational study with a study duration from November 1, 2021, to September 30, 2022. Informed consent was obtained from all participants. Patients aged 18–85 years, American Society of Anesthesiologists (ASA) grades I and II, and those suffering from LDD undergoing single-level mini-open OLIF or open TLIF were included in our study. Patients having preoperative thigh pain or hip flexion deformity, those with previous spine surgery (anterior or posterior), those undergoing multiple-level fusion, and those undergoing MIS surgery were excluded from our study. Similarly, those with preoperative hemoglobin <8 g% were also omitted from our study. The primary objective was to assess the intraoperative blood loss during the procedure. The secondary objective was to assess the postoperative pain scores at rest at various set time points in the first 24 h and pain score on movement at the 24^th h, surgical duration, and postoperative duration of hospital stays.

Anesthesia protocol

Standard institute anesthesia protocol was followed for both the surgery groups. A preanesthetic checkup was done for all patients before surgery. Multimodal analgesia protocol was followed. Buprenorphine transdermal patch (10 mg, i.e.,10 μg/h) was applied to all patients the previous night of surgery. Patients were assigned for mini-open OLIF or open TLIF after a thorough discussion between the surgeon and patient regarding the two available procedures and informed consent. All patients were administered general anesthesia with endotracheal intubation as per the institutional protocol. Intravenous (IV) fentanyl 1–2 μ g/kg was given in premedication. Induction was done with IV propofol 1.5–2.5 mg/kg and muscle relaxation with IV vecuronium 1.2 mg/kg. The patient was shifted to a lateral position for mini-open OLIF and a prone position for open TLIF. A bilateral erector spinae block was given with 20 mL bupivacaine 0.25% at the designated level on either side. Patients were given IV fentanyl in the perioperative period for analgesia, and the amount given was recorded. Injection paracetamol 1 g IV was given just after an incision was made. Target mean arterial blood pressure (MAP) was maintained between 55–65 mm Hg; if required, IV labetalol was given. This deliberate hypotension was continued until spinal instrumentation was complete. Then, blood pressure was allowed to return to the preoperative baseline level. Tranexamic acid 15 g/kg IV bolus was given intraoperatively to all patients. At the end of the surgery, local anesthetic infiltrate was given with 0.25% bupivacaine at the surgical incision site. The patient was made supine, and ondansetron 0.1 mg/kg IV was given 10 min before extubation. After adequate reversal dosage with IV neostigmine and glycopyrrolate, the patients were extubated. Postoperative paracetamol 1 g IV was given thrice daily in addition to tramadol 100 mg IV twice or thrice daily to all patients. Rescue analgesic used, if needed, was diclofenac 75 mg IV infusion. The total amount given was noted.

SURGICAL METHODS

The open TLIF surgery was done by traditional open exposure with stripping of the paravertebral muscles and screw placement. The cage (either titanium or polyetheretherketone) was placed from one side after doing a hemilaminectomy and facetectomy on the more symptomatic side. In bilateral symptoms, over-the-top decompression of the contralateral side was done.

The mini-open OLIF patients had a right lateral position, and through an approximately 5 cm skin incision, a cage was inserted, taking autograft from the adjacent iliac crest. The patient was flipped prone, and then, through the Wiltse approach (mini-open), pedicle screws were placed.[9]

Estimated blood loss

Intraoperative blood loss was assessed by adding the volume of quantified blood in suction canisters, and the volume of quantified blood calculated from the blood-soaked gauze pieces. A blood transfusion was done if blood loss exceeded the estimated allowable blood loss or if persistent hemodynamic instability was present.

Pain assessment

The pain at the surgical site was enquired and noted as per the Numerical Rating Scale (NRS). NRS “0” is the least pain, and NRS “10” is the worst.[10] They were asked to choose the intensity of pain that correlated best with a number ranging from 0 to 10. Two kinds of pain were noted – pain at rest and pain on movement in bed. The NRS was noted at immediate preoperative time (NRS preoperative), NRS (at rest) at 2, 12, and 24 h, and NRS (on movement) at 24 h.

The collected variables included intraoperative blood loss, NRS at proposed time intervals, analgesics and rescue analgesics, operative duration, and hospital stay.

Sample size calculation

We expected a difference in blood loss of 20% between the two groups – mini-open OLIF versus open TLIF based on the study by Hung et al.[11] For the power of the study to be 80% and type 1 error of 5%, the sample size was calculated to be 16 in each group using http://powerandsamplesize.com software.

Statistics

Demographics were analyzed using descriptive statistics using the SPSS version 21 (IBM Corp., Armonk, NY, USA). The data being a nonparametric study, the quantitative data were presented as median ± interquartile range (IQR). The quantitative data were analyzed using Mann–Whitney’s U-test where applicable. P < 0.05 was considered statistically significant. Qualitative data, such as age and ASA Physical Status Classification System (ASA classification), were analyzed using the Chi-square test.

RESULTS

The demographic parameters – age, gender, body mass index, and ASA Classification – were comparable in both groups [P > 0.05; Table 1]. The intraoperative fentanyl was comparable in both groups [P > 0.05; Table 2]. The intraoperative hemodynamics were stable in both groups [Table 2]. The median MAP was 90 (85.75–94.25) and 92 (90–97) in OLIF and TLIF groups, respectively, which had no significant difference (P = 0.174). However, the heart rate (HR) was significantly higher in OLIF compared to the TLIF group (83 [78.5–84] vs. 77 [70–83], P = 0.026), although not clinically significant. Intraoperative crystalloids were comparable (P > 0.05). No packed red blood cell or colloid was given in the OLIF group, while one packed red blood cells (PRBC) and two PRBCs were transfused intraoperatively and postoperatively, respectively, in the TLIF group. One colloid was given postoperatively in the TLIF group.

Table 1.

Demographic variables

Type of surgery 1. OLIF, 2. TLIF	OLIF (n=16)		TLIF (n=16)		P @
	Median	IQR	Median	IQR
Age	43	38–59.25	53.5	42–61.25	0.162
Gender (female/male)	9/7		6/10		0.288
BMI	22	20.025–22.9	22	21.05–22.9	0.516
ASA I/II	9/7		8/8		0.723

P ≥0.05 is not significant. IQR: Interquartile range, BMI: Body mass index, ASA: American Society of Anesthesiologists, TLIF: Transforaminal lumbar interbody fusion, OLIF: Oblique lumbar interbody fusion

Table 2.

Intraoperative variables

Type of surgery 1. OLIF, 2. TLIF	OLIF		TLIF		P @
	Median	IQR	Median	IQR
Intraoperative fentanyl (µg)	100	100–100	100	100–118.75	0.097
Intraoperative diclofenac	0	0–0	0	0–75	0.546
Mean BP intraoperative	90	85.75–94.25	92	90–97	0.174
Mean HR intraoperative	83	78.5–84	77	70–83	0.026*
Intraoperative crystalloid	1500	1225–1575	1500	1500–2150	0.088
Preoperative NRS	6.5	6–7	6.5	6–7	0.872
Duration of surgery (min)	190	180–210	150	122.5–183.75	0.005*

*P≤ 0.05 is significant. IQR: Interquartile range, HR: Heart rate, NRS: Numerical Rating Scale, BP: Blood pressure, OLIF: Oblique lumbar interbody fusion, TLIF: Transforaminal lumbar interbody fusion

Preoperative hemoglobin was comparable in both groups (P > 0.05). The median (IQR) intraoperative blood loss in the OLIF group was 275 mL (200–375), which was less than in the open TLIF group, 500 mL [350–600; Table 3]. However, the difference was not statistically significant. However, the postoperative hemoglobin was significantly higher in the OLIF group than in the TLIF group (11.5 [11.1–12.1] vs. 10.5 [9.8–11.3], [P = 0.04; Figure 1]).

Table 3.

Hemoglobin and blood loss variables

Type of surgery 1. OLIF, 2. TLIF	OLIF (n=16)		TLIF (n=16)		P @
	Median	IQR	Median	IQR
Intraoperative blood loss (mL)	275	200–375	500	350–600	0
Preoperative hemoglobin	12.65	11.675–13	12.65	11.525–13.4	0.94
Postoperative hemoglobin	11.4	11.1–12.175	10.5	9.825–11.3	0.04*

*P≤ 0.05 is significant. OLIF: Oblique lumbar interbody fusion, TLIF: Transforaminal lumbar interbody fusion, IQR: Interquartile range

Figure 1.

Graph showing the comparison of postoperative hemoglobin in oblique lumbar interbody fusion (OLIF) and transforaminal lumbar interbody fusion (TLIF) groups (11.5 g % vs. 10.5 g %, P = 0.04) and 24^th-h postoperative numerical rating scale (NRS) on movement in the OLIF and TLIF groups (4 vs. 5.5. P =0001)

The preoperative NRS was also comparable among both groups [P > 0.05; Table 2]. Moreover, the postoperative NRS at rest values at 2, 12, and 24 h was comparable in both groups (P > 0.05). The median (IQR) NRS on movement at 24 h was significantly less in the mini-open OLIF group – 4 (4–4.75) than in the open TLIF group – 5.5 (5–6), [P = 0.0001; Figure 1]. The postoperative tramadol and rescue analgesics diclofenac (P > 0.05) were comparable, as shown in Table 4.

Table 4.

Pain scores and postoperative variables

Type of surgery 1. OLIF, 2. TLIF	OLIF		TLIF		P @
	Median	IQR	Median	IQR
NRS (rest) at 2 h	5	4–5	5	4–5	0.81
NRS (rest) at 12 h	5	4–5	4	4–5	0.341
NRS (rest) at 24 h	3.5	3–4	4	3–4.75	0.323
NRS (movement) at 24 h	4	4–4.75	5.5	5–6	0.0001*
Postoperative diclofenac	75	0–150	150	0–150	0.947
Postoperative tramadol	100	25–200	100	100–175	0.593
Duration of postoperative hospital stay (days)	4.5	3–6.75	7	6–11	0.003*

*P≤ 0.05 is significant. OLIF: Oblique lumbar interbody fusion, TLIF: Transforaminal lumbar interbody fusion, IQR: Interquartile range, NRS: Numerical Rating Scale

The duration of surgery was significantly longer in the mini-open OLIF group, 190 min, (180–210) than in the open TLIF group, 150 min (122.5–183.75) [P = 0.005; Table 1]. The postoperative hospital duration of stay was significantly shorter in mini-open OLIF, 4.5 days, (3–6.75) than in open TLIF, 7 days (6–11, P = 0.003), as shown in Table 4.

DISCUSSION

Mini-open OLIF is a relatively new technique with satisfactory perioperative outcomes. Since it is a muscle-sparing approach, we expect less pain and blood loss. To our knowledge, mini-open OLIF has not been compared to open-TLIF concerning perioperative blood loss outcomes and pain scores, especially in Indian patients. Although blood loss has been compared in a few studies, these are mainly MIS-OLIF versus MIS-TLIF. This prospective study aimed to analyze the perioperative pain scores and blood loss, primarily in Indian patients.

Although the postoperative hemoglobin was significantly higher in the OLIF group than in the TLIF group, it may not be clinically significant given the marginal difference in hemoglobin among the groups. However, it is notable that no additional PRBC or colloid was infused in the patients of the OLIF group, while in the TLIF group, one intraoperatively and two postoperatively were transfused with PRBC. One patient in the TLIF group also needed a colloid infusion postoperatively. This may reflect greater chances of surgical oozing in the TLIF group.

Open TLIF has a higher tendency for bleeding than mini-open OLIF. However, this difference was not statistically significant. In a prospective study by Zhu et al., the authors found lesser estimated blood loss in the MIS OLIF (percutaneous screws) group compared to the MIS-TLIF group. However, their result was significant (123.1 vs. 232.0 mL, P < 0.001).[7] Abbasi and Abbasi, in yet another study, similarly found that blood loss is reduced by over 80% in OLIF compared to TLIF (mean: 355 mL).[12] The intraoperative blood loss was lesser in OLIF patients compared to TLIF in a retrospective study by Chandra et al. (112.5 mL in OLIF and 144.6 mL in TLIF)[13] and Yang et al.[8] The insignificant difference in our study can be explained by the fact that the pedicle screws in OLIF were inserted by the mini-open Wiltse approach, which would cause more blood loss than percutaneous screws, as seen in other OLIF studies. The blood loss for the cage insertion (OLIF) and posterior screw placement were not separately recorded in our cases.

The intraoperative hemodynamics were stable in both groups [Table 2]. The median MAP was 90 (85.75–94.25) and 92 (90–97) in the OLIF and TLIF groups, respectively, with no significant difference (P = 0.174). However, the HR was significantly higher in the OLIF group compared to the TLIF group (83 [78.5–84] vs. 77 [70–83], P = 0.026). This difference can be attributed to the position changes, first lateral and then prone position done intraoperatively in the OLIF group, as adequate analgesia had been given. To our knowledge, this aspect has yet to be analyzed in any previous study.

The preoperative NRS and NRS at rest values at 2 h, 12 h, and 24 h postoperative were comparable in both groups (P > 0.05). However, the NRS at 24 h postoperatively on movement was significantly lesser in the OLIF group (4 [4–4.75]) than in the TLIF group (5.5 [5–6], P = 0.0001). Clinically, this might be of little significance as the median values of NRS in both groups are moderate (4 in the OLIF group and 5.5 in the TLIF group). The postoperative rescue analgesic, diclofenac, used in two cases was comparable with both groups in our study [Table 4]. The lower NRS in the OLIF group can be projected as the lower requirement of analgesics in this group. This is akin to Chandra et al., who, in their retrospective analysis, found that the mean duration of the analgesia requirement after OLIF is only 3 months compared to a longer 5 months after minimally invasive TLIF (P < 0.05).[13] They also found that the time to return to regular work is better in OLIF (2.04 months) than in TLIF (4 months; P < 0.05). Yang et al. analyzed retrospectively that the 1-week postoperative pain course and disability index of patients in the OLIF group were lower than those in the TLIF group.[8] They showed that OLIF treatment reduced patients’ pain to a greater extent and was more conducive to the recovery of patients. This is in contrast to Koike et al., who found in their retrospective analysis that there were no differences in the preoperative and postoperative Visual Analog Scale score change between the two groups (OLIF and TLIF).[14] However, Koike et al. found that the effectiveness rate in the psychological domain of a back pain evaluation questionnaire was significantly higher in group OLIF than in group TLIF (47.1% vs. 14.6%, P < 0.05).[14]

The duration of OLIF surgery was slightly prolonged (190 min [180–210]) than TLIF surgery (150 min [122.5–183.75]) and was statistically significant. This is similar to the retrospective analysis by Chandra et al., who found that the duration of surgery in MIS-OLIF was 4.41 h and higher than 3.16 h in MIS-TLIF.[13] However, some studies show OLIF duration to be shorter than TLIF surgery. Abbasi et al. found that the mean surgery time was 69 min in OLIF compared to 135 min in TLIF in a single-level lumbar degenerative disease, twice as fast as open TLIF.[12] Zhu et al. also found the surgery duration to be shorter in MIS-OLIF compared to MIS-TLIF (110.5 vs. 183.8 min, P < 0.001).[7] The relatively more extended time in our mini-open OLIF procedure can be explained by the fact that in OLIF, mini-open posterior screws require a change of position intraoperatively along with a separate procedure, unlike the percutaneous (MIS) method of screw placement used by others, which can be placed in the same position and hence the faster time.

The postoperative hospital stay was lesser in mini-open OLIF (4.5 [3–6.75]) than in open TLIF (7 [6–11]). One case of TLIF had a postoperative stay of 22 days due to a surgical site infection. The shorter hospital stay in OLIF could be due to lower morbidity (facet/bone and muscle sparing) and a larger anterior cage that allows earlier mobility and lesser postoperative pain. The earlier mobilization of the patient itself has several beneficial implications. This is per a previous study by Zhu et al. who found a shorter length of hospital stay (5.5 vs. 6.7 days, P < 0.001) and even lower serum creatine kinase (CK; 1 day postoperatively) (376.0 vs. 541.8 IU/L, P < 0.01) in OLIF than that of the MI-TLIF group.[7]

We acknowledge a few limitations of our study. The blood loss and postoperative analgesia results would have been more defined if the surgical procedure had been entirely minimally invasive. We did only a short-term evaluation of our patients, and functional outcomes were not a part of our study. A longer follow-up, including functional quality of life, can give a better picture of patients undergoing lumbar fusion.

CONCLUSION

Mini-open OLIF had better perioperative outcomes than open TLIF analyzed in this study. We found better postoperative pain relief on mobilization on the day after surgery and higher postoperative hemoglobin profile in mini-open OLIF compared to open TLIF. Although these two might not have a clinically relevant difference among the groups, patients had shorter hospital stays in mini-open OLIF than open TLIF. Therefore, we conclude that more widespread proficiency in surgical skill development for OLIF is needed, especially in the Indian subcontinent.

Research quality and ethics statement

This study was approved by the Institutional Review Board/Ethics Committee at AIIMS Bhubaneswar (Approval #: T/IM-NF/Anesth/21/73; Approval date: November 24, 2021). The study was prospectively registered with the Clinical Trials Registry-India (Registration #: CTRI/2022/02/039982; Registration date: February 3, 2022). The authors followed the applicable EQUATOR Network (http://www.equator-network.org/) guidelines, specifically the STROBE guidelines, during the conduct of this research project.

Financial support and sponsorship

This study was funded by AIIMS Bhubaneswar (no grants).

Conflicts of interest

There are no conflicts of interest.