Total joint replacement of the lumbar spine: surgical technique and procedural details

Introduction

Over the past 60 years, total joint arthroplasty has significantly advanced the surgical management of degenerative conditions of the large synovial joints. However, in the spine, neural decompression coupled with instrumented arthrodesis currently remains the surgical procedure of choice when symptoms of low back pain, radiculopathy and/or neurogenic claudication become persistently severe and there is corresponding imaging evidence of arthritic degeneration and/or stenosis across a vertebral motion segment and when reconstruction is warranted (1-3). While neural decompression provides palliative relief, the associated fusion, meant to ensure stability and maintenance of the decompression, eliminates natural motion at the operative level. This disruption in joint kinematics can have the untoward effect of accelerating adjacent segment degeneration resulting in pain and increasing the likelihood of subsequent revision surgery (4,5).

In contrast to fusion, total joint replacement (TJR) of the lumbar spine allows for neural decompression, stabilization and symptom relief, while also re-establishing balance and preserving natural spinal motion (6). The TJR procedure involves the implantation of the MOTUS device (3Spine, Inc., Chattanooga, TN, USA) which mimics the biomechanical characteristics of the three-joint complex, where the disc and facets work in harmony to provide constrained motion not only to the spinal motion segment but to the coordinated function of the entire lumbar spine (Figure 1) (7). This paper and accompanying video detail the TJR surgical procedure including joint space preparation, reconstruction and implantation of the device (8). We present this article in accordance with the SUPER reporting checklist (available at https://jss.amegroups.com/article/view/10.21037/jss-2025-aw-185/rc).

Figure 1 The MOTUS device (3Spine, Inc., Chattanooga, TN, USA).

Preoperative preparations and requirements

The TJR procedure is indicated for the biomechanical reconstruction and stabilization of a spinal motion segment following decompression at one lumbar level from L1 to S1 in skeletally mature patients. The indicated pathology of these patients includes symptomatic lumbar degeneration with or without foraminal or lateral recess spinal stenosis confirmed by radiographic imaging [computed tomography (CT), magnetic resonance imaging (MRI), X-rays], with no more than a grade 1 spondylolisthesis at the involved level. Detailed eligibility criteria are available at ClinicalTrials.gov (NCT05438719).

Step-by-step description

Background

The TJR procedure utilizes a bilateral transforaminal lumbar interbody approach to access the disc space. A complete lumbar motion segment reconstruction is achieved via central and bilateral neural decompression allowing for device implantation (see Video 1). The lateral annulus, at least the anterior half of the anterior annulus and anterior longitudinal ligament are preserved to maintain soft tissue integrity to facilitate appropriate tension and balance while maintaining stability when the disc height is restored.

Patient positioning

The patient should be positioned prone on a Jackson spine table, with the hips in neutral position, chest pads in standard position and the head centered over the hips/pelvis in neutral sagittal alignment. The endplates of the treated level will be brought into lordosis as the intraoperative osteotomy is performed and as the implants are placed. This amount of lordosis created at the target level can be regarded as “neutral lordosis” and should be approximately the normal segmental alignment as in a healthy asymptomatic individual (9). To assure proper positioning, anteroposterior (AP) and lateral fluoroscopic images should be obtained to match prone positioned lordosis to standing lordosis. Some minor adjustments of chest and hip pads may be required (Figure 2).

Figure 2 L5–S1 level before osteotomy.

The inferior endplate in the disc space must be osteotomized to become nearly parallel to the superior endplate during disc space preparation to allow the implant to rest in neutral position on insertion. The inferior endplate and pedicle are osteotomized in a wedge shape with the point of the wedge anterior and the base of the wedge posterior creating lordosis. This allows for maximal flexion (10°) and extension (8°) of the implant during sitting and standing. The device allows the patient to self-center themselves into their own most efficient posture, referred to as the “cone of economy” (10).

Joint space preparation

Using an open posterior approach, the procedure initially involves thorough neural decompression including removal of the lamina and facets as well as disc excision to accomplish the neurologic decompression required to relieve the patients’ symptoms while allowing for full range of motion of the TJR. Following complete discectomy, manual preparation of the intervertebral space is accomplished with reciprocating rasps used on the vertebral endplates (Figure 3). These rasps are used to create a level surface and wedge osteotomy of the inferior endplate and the superior portion of the inferior pedicle into the posterior disc space to appropriately balance the TJR. The apex of the wedge is in the anterior disc space to create lordosis so that a rectangular implant placed in the disc space rests in the wedge-shaped osteotomy with the segment itself in lordosis. This “pedicle vertebral body osteotomy” (PVBO) can be regarded as leveling the inferior endplate in the disc space to allow the implant to be inserted horizontal as the lateral body often sweeps up on the lateral edge of the superior vertebrae and to a lesser extent the lower interbody surface. The device axis roughly follows the pedicle into the interbody space stopping just short of the annulus to allow for motion with no impingement with the annulus. Special attention should be paid to avoid resecting the annulus to avoid destabilizing the anterior longitudinal ligament/annulus complex. Unlike a fusion procedure, the aim should only be to remove the nucleus and create just enough space for the implant. Implant convergence occurs naturally along the axis of the pedicle and can be adjusted at the discretion of the surgeon. This convergence increases from cephalad to caudal requiring the surgeon to angle more lateral to medial at the lower levels. The soft tissue compressive forces and the placement in a neutral position with a wedge shaped PVBO restore lordosis (Figure 4). Thus, in a standing posture, the implant will be in a neutral position to allow the patient’s head to fall easily within the cone of economy. For patients with a high sacral slope at S1, this osteotomy can be thought of as reducing the pelvic incidence and sacral slope, which allows for restoration of sagittal plane alignment prior to implant insertion. Rasps are used to complete the parallel surface modifications for the subsequent keel cuts, allowing the device to be seated in a balanced “parallelized” position.

Figure 3 Surgical rasp used for endplate preparation for TJR. The shorter rasp is for the inferior endplate of the superior vertebrae. The longer rasp is for the superior endplate of the inferior vertebrae. TJR, total joint replacement.

Figure 4 Distractor in place and on the contralateral side a reciprocating rasp is being used to resect the superior S1 pedicle and posterior vertebral body to create a wedge-shaped osteotomy with the apex in the anterior disc space.

Length and height trials are used to determine the appropriate size of the implant. There are five different heights starting at 11 mm. There are three lengths based on anatomic studies; short, medium and long. The placement of the implant is intended to be located ~5 mm from the anterior vertebral margin to ensure that the anterior longitudinal ligament is not compromised and to plan for the correct placement of the center of rotation (COR). To allow for the coordinated fit of the superior and inferior components of the device, aligned superior and inferior keel cuts in the vertebral bodies are created manually with cutters (Figure 5). Bilateral soft tissue balancing is completed at this point in the procedure by working to restore disc height and bilateral soft tissue tension without over-stuffing the disc space. Surgeons must recognize that in the axial plane the anterior vertebral body/annulus curves posteriorly due to the shape of the vertebra, such that on a lateral X-ray the trial may appear to be “short” of the anterior body, but may still be impinging or disrupting the annulus if the leading edge of the trial is not perfectly convergent towards the midline.

Figure 5 Surgical cutters are used to create keels to anchor the implant. The shorter keel cutter is for the inferior endplate of the superior vertebra (no pedicle). The inferior keel cutter is for the superior endplate of the inferior vertebrae (includes pedicle).

Device implantation

After PVBO, keel cuts, soft tissue tensioning, and size trialing, two implants are inserted bilaterally along the axis of the pedicles. The goal is to place the implants such that the midpoint of the articulating ball is approximately 40% ventral to the posterior vertebral body cortex. This placement is consistent with the physiologic COR (Figure 6). Initial fixation is achieved by both the implant keels impacted in bone and through the placement of a retention screw into the caudal portion of the implant. The screw is placed through a safety guide obliquely and through the pedicle from superior to inferior into the vertebral body. This dual ball design replaces the stabilizing function of the resected facet joints by providing a check-rein to excessive flexion and extension as well as resistance to shear/listhesis. Although the implant is non-compressive, it is placed into the disc space and substitutes for the function of the bilateral facet joints and resected disc.

Figure 6 Final implant placement showing the rectangular implant resting on posterior superior S1 with the L5–S1 segment in lordosis. The wedge-shaped pedicle vertebral body osteotomy of S1 allows the rectangular implant to rest in the disc space while maintaining segmental lordosis.

Postoperative considerations and tasks

Closure and pain control techniques are at the discretion of the surgeon. Postoperative enhanced recovery after surgery (ERAS) protocols are helpful. An intrathecal agent such as fentanyl or duramorph combined with a myofascial plane block using long acting bupivacaine is one option. A second option is using long acting bupivacaine to complete an erector spinae plane (ESP) block at L3 or L4. Mobilization and discharge of patients can occur on the same day as surgery. Postoperative drains are rarely required, but can be used at the discretion the surgeon. Before discharge, the patient should be able to urinate, and be safely ambulating, followed by a standard period of post-surgical observation.

During the initial 3 months, mild controlled activities can be initiated such as supportive stretching (seated or lying supine) and, during the first month, this should only include minimal bending, lifting, and twisting. After the first month, patients can be allowed to initially bend and twist gently while avoiding complex motions such as lifting and twisting forcefully until their strength improves. Supported stretching should be continued through the first 3 months as patients slowly increase their strength and range of motion. Formal physical therapy can then be initiated. At the discretion of the therapist, patients should attend sessions 2–4 times/week with therapy focusing on gentle stretching, isometric core strengthening and lumbar range of motion maneuvers. These are standard suggestions but should be modified and adapted as the physician deems appropriate for individual differences among patients.

Tips and pearls

Meticulous hemostasis with gelfoam/thrombin should be maintained throughout the decompression and device implantation procedure. To minimize bleeding preemptive control of facet and epidural veins should be identified and cauterized to the extent possible. In the severely-degenerated lumbar spine, neural decompression should be extensive and complete. In some patients Kambin’s triangle is small because of a low exiting nerve root. In this case, it is critical to remove the entirety of the lamina to avoid nerve impingement with the implant during flexion and extension. If there is significant crowding of this area, then a partial pediculectomy of the caudal aspect of the pedicle above can be considered to create more working space. This allows the exiting nerve root to “drift” more cranially creating more space in this area so impingement does not occur. As the levels move caudal the surgeon should recognize that the angle of the pedicle inclines more medially. With particular attention to L5/S1, it is possible for the surgeon to inadvertently disrupt the anterior longitudinal ligament if the inclination for the sacrum and the trajectory of the keel cuts is not carefully understood. A CT/MRI should be reviewed preoperatively to avoid malposition. Advance intraoperative, three-dimensional (3D) imaging with navigational assisted surgery can be considered and may play a large role in the future.

If the endplate is inadvertently violated due to underlying osteopenic bone, conversion to fusion should be performed. The lateral bony edge of the disc space can converge, so the rasp can be utilized to level the endplate surfaces so the device is implanted with good balance and symmetry. When working near the annulus, care should be taken not to inadvertently violate the anterior longitudinal ligament. Intra-operative fluoroscopy is utilized during endplate/disc space preparation and implantation to assure good positioning.

After the implants are placed, the surgeon should visualize and/or palpate the medial wall of the pedicle bilaterally to ensure there is no breach of the screw. The surface of the endplates must be completely clear of disc material and endplate cartilage to ensure good ingrowth and to avoid listhesis after completion of the procedure. The annulus should be protected to the extent possible to provide stability to the motion segment. If the anterior longitudinal ligament is suspected to be torn/incompetent, then conversion to fusion is recommended. Distraction to open a partially collapsed but mobile disc space should be done by sequentially utilizing the distractors while being cautious not to penetrate the endplates. When distracting a very collapsed level, one should start the osteotomy early in the distraction sequence to avoid rupture of the anterior longitudinal ligament which would result in the need to convert to fusion.

Discussion

TJR of the lumbar spine represents a revolutionary approach to the surgical management of severe lumbar spine degeneration (6,8,11-16). Currently, the requisite surgical option for this patient population remains decompression often coupled with instrumented fusion. In a manner similar to the preferred treatment of advanced degeneration of the large synovial joints, such as the hip and knee, the TJR procedure with the MOTUS device completely replaces the entire spinal three-joint complex with an implant that restores and preserves natural flexion/extension motion (17).

Following neural decompression, the spinal segment is prepared for the joint replacement by resection of the facets and removal of the intra-annular disc. The procedure involves complete laminectomies and thought should be given to impingement that could occur in the presence of flexion and extension much like we consider cervical foraminal decompression if arthroplasty is considered.

To date, any time an extensive posterior lumbar decompression is necessary, instrumented fusion is usually added. The TJR procedure allows for a similarly thorough decompression, coupled with a motion-preserving reconstruction with the potential of stabilizing the operative segment. However, most of the biomechanical advantage of this implant is limited to flexion/extension as opposed to other degrees of freedom.

Other surgical methods of motion preservation, such as disc arthroplasty and facet replacement, have narrower patient profiles due to treating isolated disc or facet degeneration. However, emerging evidence suggests a strong biomechanical interdependence between intervertebral disc degeneration and osteoarthritic deterioration of the facet joints (18). As such, a more holistic surgical approach may be required to address the growing population of individuals with symptomatic spinal degeneration across the entire three-joint complex. It is still to be determined how each of these treatment modalities will be precisely indicated as we transition from fusion to physiologic motion. The clinical indications and associated treatment algorithms will likely expand over time as techniques and outcomes continue to improve.

Conclusions

Lumbar TJR combines decompression with motion preservation in a single procedure, potentially offering an alternative to fusion in selected patients. The advantage of utilizing a standard posterior operative approach with TJR is that it allows for direct decompression of the neural elements prior to implant placement.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the SUPER reporting checklist. Available at https://jss.amegroups.com/article/view/10.21037/jss-2025-aw-185/rc

Peer Review File: Available at https://jss.amegroups.com/article/view/10.21037/jss-2025-aw-185/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jss.amegroups.com/article/view/10.21037/jss-2025-aw-185/coif). All authors report that this work was supported by 3Spine, Inc. (Chattanooga, TN, USA). J.E.B. received consulting fees for medical writing from 3Spine. S.C.H. and S.D.H. are patent holders in 3Spine. S.C.H., J.A.S. and S.D.H. are stockholders in 3Spine. M.J. is an employee of 3Spine. 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. The radiographic images were obtained from a participant enrolled in an IDE trial (ClinicalTrials.gov Identifier: NCT05438719). The original study had received IRB approval and informed consent. The images used in this study were de-identified and are reproduced with permission, no additional ethical approval was required.

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/.

References

1. Antony A, Stevenson J, Trimble T, et al. Perspective: A Proposed Diagnostic and Treatment Algorithm for Management of Lumbar Spinal Stenosis: An Integrated Team Approach. Pain Physician 2022;25:E1467-74.
2. Sharif S, Shaikh Y, Bajamal AH, et al. Fusion Surgery for Lumbar Spinal Stenosis: WFNS Spine Committee Recommendations. World Neurosurg X 2020;7:100077. [Crossref] [PubMed]
3. Resnick DK, Watters WC 3rd, Mummaneni PV, et al. Guideline update for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 10: lumbar fusion for stenosis without spondylolisthesis. J Neurosurg Spine 2014;21:62-6. [Crossref] [PubMed]
4. Eck JC, Humphreys SC, Hodges SD. Adjacent-segment degeneration after lumbar fusion: a review of clinical, biomechanical, and radiologic studies. Am J Orthop (Belle Mead NJ) 1999;28:336-40.
5. Austevoll IM, Ebbs E. Fusion Is Not a Safeguard to Prevent Revision Surgery in Lumbar Spinal Stenosis. JAMA Netw Open 2022;5:e2223812. [Crossref] [PubMed]
6. Humphreys SC, J, Nel L, Block JE, et al. Technical Note on the Role of Kambin's Triangle in the Evolution of Total Joint Replacement of the Lumbar Spine. Int J Spine Surg 2024;18:336-42. [Crossref] [PubMed]
7. Patwardhan AG, Sielatycki JA, Havey RM, et al. Loading of the lumbar spine during transition from standing to sitting: effect of fusion versus motion preservation at L4-L5 and L5-S1. Spine J 2021;21:708-19. [Crossref] [PubMed]
8. Nel LJ, Humphreys SC, Sielatycki JA, et al. Total joint replacement of the lumbar spine: report of the first two cases with 16 years of follow-up. J Spine Surg 2024;10:583-9. [Crossref] [PubMed]
9. Bernhardt M, Bridwell KH. Segmental analysis of the sagittal plane alignment of the normal thoracic and lumbar spines and thoracolumbar junction. Spine (Phila Pa 1976) 1989;14:717-21. [Crossref] [PubMed]
10. Hasegawa K, Dubousset JF. Cone of Economy with the Chain of Balance-Historical Perspective and Proof of Concept. Spine Surg Relat Res 2022;6:337-49. [Crossref] [PubMed]
11. Humphreys SC, Hodges SD, Sielatycki JA, et al. Are We Finally Ready for Total Joint Replacement of the Spine? An Extension of Charnley's Vision. Int J Spine Surg 2024;18:24-31. [Crossref] [PubMed]
12. Alex Sielatycki J, Devin CJ, Pennings J, et al. A novel lumbar total joint replacement may be an improvement over fusion for degenerative lumbar conditions: a comparative analysis of patient-reported outcomes at one year. Spine J 2021;21:829-40. [Crossref] [PubMed]
13. Sivaganesan A, Koscielski M, Kabani AS, et al. 24-month patient-reported outcomes for a novel lumbar total joint replacement. N Am Spine Soc J 2025;23:100747. [Crossref] [PubMed]
14. Nunley PD, Sielatycki JA, Humphreys SC, et al. Total Joint Replacement of the Lumbar Spine: 12-Month Pain and Functional Outcomes From an Investigational Device Exemption Clinical Trial. Int J Spine Surg 2025;19:S59-66. [Crossref] [PubMed]
15. Kurtz SM, Rundell SA, Spece H, et al. Sensitivity of Lumbar Total Joint Replacement Contact Stresses Under Misalignment Conditions-Finite Element Analysis of a Spine Wear Simulator. Bioengineering (Basel) 2025;12:229. [Crossref] [PubMed]
16. Rundell SA, Kurtz SM, Spece H, et al. Sensitivity of Lumbar Total Joint Replacement to Axial and Coronal Plane Misalignment Using Computational Modeling. Int J Spine Surg 2025;19:635-44. [Crossref] [PubMed]
17. Goldstein JA, Nunley PD, Sivaganesan A, et al. Total Joint Replacement of the Lumbar Spine: The Future of Motion Preservation. Int J Spine Surg 2025;19:S45-8. [Crossref] [PubMed]
18. Fine N, Lively S, Séguin CA, et al. Intervertebral disc degeneration and osteoarthritis: a common molecular disease spectrum. Nat Rev Rheumatol 2023;19:136-52. [Crossref] [PubMed]