Adult Degenerative Scoliosis with Spinal Stenosis Treated with Stand-Alone Cage via an Extreme Lateral Transpsoas Approach; a Case Report and Literature Review.

We report the case of a 73-year-old female with severe degenerative scoliosis and back and leg pain that was successfully treated with stand- alone cages via an extreme lateral transpsoas approach. This patient had declined open surgery and instrumentation due to her advanced age concerns about potential side effects.

Introduction

Adult degenerative scoliosis is prevalent in 68% of the asymptomatic population, who are over 60 (1). In symptomatic patients who failed non-operative treatment, surgery is usually performed via open decompression and fusion procedures using posterior instrumentation with or without interbody fusion. Since the introduction of minimally invasive access to the spine, surgical treatment options for this pathology are becoming more versatile (2-4).

Surgical decompression alone, which would be the least invasive traditional surgical option, is frequently prohibitive due to a high risk of worsening of the spinal deformity (5, 6). Non-instrumented decompression with posterolateral fusion is associated with a risk of non-union and deterioration of the scoliosis. Finally, surgeons can consider decompression with instrumentation and posterolateral fusion (7-13). However in the elderly patient with multiple comorbidities there are significant preoperative risks related to high blood loss, long hospital stays, and instrumentation failure (7, 14, 15). On the other hand, potential advantages of minimally invasive spine surgery include less blood loss and tissue injuries, shorter hospital stay, less narcotic use, smaller scars and earlier return to normal activities (3, 16).

Ozgur et al. have described the lateral transpsoas approach for lumbar discectomy and interbody fusion. Recently this technique has been successfully implemented for patients with adult degenerative scoliosis (17-21). The anterior discectomy and fusion using an interbody spacer leads to indirect decompression of the neuroforamina and the spinal canal. This procedure is usually performed in conjunction with posterior instrumentation and fusion, sometimes also with additional direct decompression (22). We did not plan to address the spinal deformity by this procedure.

Surgeons have used this technique without posterior instrumentation. However, to our knowledge this has not been reported in the peer-reviewed literature. We report the case of a 73-year-old female with degenerative scoliosis and back and leg pain that was successfully treated with stand-alone cages via an extreme lateral transpsoas approach. This patient had declined open surgery and instrumentation due to her advanced age and concerns about potential side effects.

Case Report

A 73-year-old woman consented to have her medical records published. She presented with low back pain, bilateral radiculopathy, and neurogenic claudication as well as with osteopenia of her lumbar spine, which was treated with bisphosphonates. On a self-reported scale her back pain was scored 7 out of 10, accompanied by bilateral leg pain scored 8 and 9 out of 10. Nonsurgical treatment including physical therapy and three epidural steroid injections could not relieve her clinical symptoms over a period of 14 months. Magnetic resonance imaging (MRI) showed scoliosis with left-sided convexity at L1-2 and right-sided convexity at L4. Lumbar spinal canal stenosis with severe neural foraminal narrowing was present at levels L2-L3, L3-L4, L4-L5 [Figure 1].

Figure 1.

Pre operative anteroposterior X-Ray (A) and sagittal T2-wighted MRI scan (B, C).

Operative Technique and Results

The patient was placed in a true lateral decubitus position guided by intraoperative fluoroscopy. A small incision was made on the right side and access to the L2 to L5 disc spaces was obtained using tubular dilators (Nuvasive, CA) as described by Ozgur et al. (17). The abdominal muscle was divided bluntly, followed by a gentle finger dissection into the retroperitoneal space. A series of tubular dilators was inserted to gain access to the L4 and L5 area. Safe docking of the spreaders onto the intervertebral disc space was performed under continuous intraoperative EMG control (electromyography) (Neurovision®, NuVasive, California). We performed an extensive discectomy and with extensive release of the contralateral annulus and ligaments. A 22 x 50 x 10 mm cage was inserted, filled with Actifuse® bone graft substitute (Actifuse Synthetic Bone Graft, Apatech, Ltd.). The same procedure was performed for L3-L4 and L2-L3, through the same skin incision but through different fascial incisions. At the end of the procedure abdominal fascia, subcutaneous and skin tissues were closed separately. There were no complications during the procedure; the blood loss was minimal.

The patient was discharged home on post-operative day one and was treated with a brace for six weeks after surgery. The patient had mild right thigh numbness and pain, which improved gradually. Within 4 weeks after the operation, her VAS (Visual Analogue Scale) back pain and VAS leg pain completely resolved from a pre-operative value of 8-9, to a scale of 0 out of 10. The patient was last seen 36 months postoperatively, with continued complete resolution of her symptoms. Imaging studies at 36 months revealed stable implants, minimal subsidence and most likely evidence of fusion [Figures 2; 3].

Figure 2.

Coronal CT Scan 36 months postoperatively demonstrating bony fusion at L2/L3 (A) and at L3/L5 (B).

Figure 3.

Sagittal CT scans pre-op (A), immediate post-op (B), 10 months after surgery (C), 26 months after surgery (D), and 36 months after surgery (E).

It is important to note that although in Figure 3, optimal fusion is not evident simultaneously at different levels on the final imaging, comprehensive review of the CT-Scan revealed fusion at all 3 different levels. This is because the presented case was a deformity case undergoing a multi-level interbody fusion; thus, fusion could not be discernible on a single cut at all levels.

A summary of radiographic measurements from pre- and postoperative CT and MRI scans is given in Table 1. Postoperative imaging studies showed improvement of disc height and central spinal and foraminal stenosis [Figure 3]. Pre- and postoperative MRI scans were used to compare the spinal stenosis at the surgical levels. The area of the spinal canal was determined using “SurgimapSpine” (Menaris, Mexico City Area, Mexico) software and increased 34% after surgery. Coronal and sagittal Cobb angles did not change significantly after surgery and remained stable over the course of 10 months [Figure 4]. The coronal Cobb angle increased to 16 degrees at last follow-up, although the patient remained asymptomatic. As for functional outcome, the Oswerstry Disability Index (ODI) was 48 pre-operatively, which decreased to 2, four weeks after surgery. The patient was able to return to her original level of activity and remained fully functional and pain-free 36 months after the index surgery.

Table 1.

Summary of the pre-op, post-op, 10 months follow-up, 26 months follow-up, and 36 months follow-up of changes in coronal cobb angle, sagittal lordosis, foraminal heights and disc heights

		Pre-op CT scan	Post-op CT scan	10 months follow-up CT scan	26 months follow-up CT-scan	36 months follow-up CT-scan
Coronal cobb angle (L2-L5) in °		8.3°	7.8°	7.8°	14.3°	14.4°
Sagittal Lordosis(L2-L5) in °		33.2°	32.7°	38.8°	37.2°	40.2°
Foraminal heights in mms
	L2/L3 Rt	7.55	15.58	11.32	10.82	10.37
	L2/L3 Lt	13.69	18.68	14.53	14.46	13.70
	L3/L4 Rt	12.58	15.94	15.06	14.50	13.98
	L3/L4 Lt	6.73	10.05	7.64	7.03	6.91
	L4/L5 Rt	15.39	17.26	15.22	15.12	15.06
	L4/L5 Lt	12.51	15.12	13.32	13.26	13.16
Disc heights (3 point averages) in mms
	L2/L3	4.84	7.67	7.35	6.63	6.03
	L3/L4	3.63	6.26	4.64	4.64	4.25
	L4/L5	4.45	8.68	7.16	7.08	6.37

Figure 4.

Radiographic parameters change over time.

Discussion

Currently there is scarce data on extreme lateral interbody fusion for the treatment of degenerative scoliosis and no data exists on stand-alone procedures for this pathology. Pimenta et al. has introduced the technique, which was popularized by Ozgur et al., for the treatment of degenerative disc disease (17, 23). Subsequently, its feasibility was also investigated for the treatment of degenerative scoliosis in the lumbar spine. To our knowledge, there are five studies that have described their experience of XLIF for degenerative scoliosis of the lumbar spine as seen in Table 2 (22, 24-27). In the first series of 12 patients, Anand et al. have reported on their initial results of combined minimally invasive surgery including lateral interbody fusion and instrumentation (24). After a short follow-up time of 75 days, they reported early pain reduction, although 25% had transient thigh dysesthesia or quadriceps weakness. In a subsequent study, Anand et al. described the results of 28 patients with a mean follow up of 22 months (22). Significant improvement in the VAS pain (57%) was found and all patients maintained correction of their deformity with solid fusion in all patients on plain radiographs. Wang et al. reported on 23 patients who underwent a similar technique as described by Pimenta et al. (23, 27). Although the operated time was considerably longer than all other studies, no increase in intraoperative complications was noted. Transient thigh symptoms were similar to the average of all other studies (30.4% vs. 43%). Significant pain improvement (54.1%) was shown after a mean follow up of 12 months and CT imaging confirmed fusion of all interbody levels. Dakwar et al. reported on 25 patients with symptomatic degenerative scoliosis in the lumbar spine with an average of 11 months follow up (25). Patients had significant VAS pain improvement (70.4%). At a minimum of 6 months, 20 out of the 25 patients showed solid fusion on the CT scan or flexion/extension radiographs. In another study, Tormenti et al. reported on eight patients, who underwent XLIF with posterior fusion (26). A high rate of transient thigh para- or dysesthesia was found in 6 out of the 8 patients (75%). Two patients experienced motor radiculopathy, in one patient it was resolved, but persisted in the other one for three months postoperatively. Significant improvements were seen on the VAS score and Cobb angle.

Table 2.

Summary of studies reported on XLIF for scoliosis

Author	Procedure	Indication	Anterior levels	Levels	Internal fixation	No. of posterior levels	Total n	Mean follow-up	VAS decrease	Total complications	Transient thigh problems
Anand et al.2	XLIF, DLIF, AxiaLIF	Scoliosis	2-6	T12-S1	BP	2-8	12	75d	32.4%	0%	25%
Anand et al.3	XLIF, DLIF, AxiaLIF	Scoliosis	1-6	T12-S1	BP	3-8	28	22.4mo	57%	21.4%	60.1%
Dakwar et al. 11	XLIF	Scoliosis	1-6	T10-L5	LP	2-7	25	11mo	70.4%	24%	12%
Tormenti et al34	XLIF, TLIF, PLF	Scoliosis	2-5	L1-L5	BP	6-12	8	10.5mo	60.2%	150%	75%
Wang et al.35	X, DLIF	Scoliosis	1-5	T12-L5	BP		23	12mo	54.1%	30.4%	30.4%

In this report, we described a patient in whom we performed an extreme lateral transpsoas approach for stand-alone cage placement to treat leg and back pain due to adult degenerative lumbar scoliosis. Presently, direct posterior decompression and instrumented fusion, with or without interbody fusion is the mainstay in operative treatment for degenerative lumbar scoliosis. However, because of significant co-morbidities in these patients and the risks associated with surgery, operative treatment is frequently avoided. Surgery is associated with long operative times, high blood loss and prolonged hospitalization. Complication rates with this type of surgery can be > 50% (7, 11, 13, 28). In a recent study Cho, et al. reported a complication rate of 68% including blood loss, ileus, urinary tract infection, transient delirium, superficial infection, and neurologic deficits (8).

The extreme lateral transpsoas approach was first described by Pimenta et al. in 2001 as a novel approach to the lumbar spine with some studies suggesting promising outcomes in adult scoliosis (18-20, 23). However, there are also risks associated with it such as graft subsidence, especially in osteoporosis and lateral thigh dysesthesia due to damage or irritation of the interpsoas nerve fibers or psoas edema and infection (29).

The concept of indirect decompression has been well described in the past, mainly in ALIF surgery (30, 31). In our case it also resulted in an increase of the spinal canal at the operated levels. The indirect decompression of the lumbar central and foraminal stenosis was the most likely reason for the patient’s relieve of symptoms.

Concerns with stand-alone procedures are compromised fusion rates and possible subsidence of the vertebrae. Therefore, an interbody cage is frequently backed up with anterior or posterior instrumentation to avoid cage displacement and micromotion at the cage-bone interface that may impair bone growth and eventually provoke endplate failure with subsidence and nonunion. Lateral fixation was not an option in the present case due to the number of levels involved and potential injury to the psoas muscle. Due to our promising previous experience, we decided to proceed with a stand-alone procedure without further instrumentation but with post-operative bracing.

Stand-alone interbody cages allow significantly less range of motion than normal anatomy during all loading modes except axial rotation (32). The standard cage for lateral transpsoas procedures is 18 mm. Steffen et al. have shown that a wider footprint, supported in the periphery of the endplate, is more effective in providing segmental stability, and has a higher axial strength to resist implant subsidence compared to a narrower implant (33). Therefore, we and others (Dr. Luiz Pimenta, personal communication) recommend that a rim-to-rim alignment of 22 mm cages be used in stand-alone procedures to ensure initial stability and avoidance of subsidence (34). Oxland et al. have shown that posterior instrumentation does not enhance stability and interface strength under axial compression (35). Blumenthal et al. reviewed a series of 190 patients in whom cages were used anteriorly as stand-alone devices with a minimum 2-year follow up to determine the revision rate (36). The incidence of reoperation to include supplemental posterior fixation was only 1.1%.

Although it has been shown that supplementation of posterior fixation diminishes residual segmental mobility and preserves lumbar lordosis, the optimal construct and the cage-bone interface mechanics have yet to be determined.