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Lumbar Segmental Instability - Current Concepts

Asst Professor of Orthopaedics
Medical College Calicut

Addresses for Correspondence

Asst Professor of Orthopaedics
Medical College Calicut

J.Orthopaedics 2005;2(1)e1



The diagnosis and the management of lumbar segmental instability(LSI) is one of the difficult problems for orthopaedics surgeons all over the world. The primary concern  of LSI is radicular pain and pain due to instability. The intervertebral disc is the most stabilizing structure of the spine. The reduction in the disc height results in narrowing of the size of the intervetebral foramen and results in root compression.The transverse diameter of the foramen is only 7mm and the size of the L4 root is 6mm so there is a critical area through which the root escapes. This can be addressed to a certain extent by foraminotomy but total correction of the fundamental pathologic processes is possible only by maintaining the disc height. The purpose of this review article is understand the current concept regarding the diagnosis and management of lumbar segmental instability along with the review of Authorís own experience


Hicks GE etal concluded that they agree with previous studies suggesting that segmental mobility testing is not reliable. The prone instability test, generalized Ligamentous laxity scale, and aberrant motion with trunk ROM demonstrated higher levels of reliability.(1)

Diedrich etal inferred in their study that normal sagittal alignment after single-level lumbar fusion can be achieved with rectangular and 4 degrees -wedged cages(2)

Oísullivan PBetal made the final conclusion in their study   that individuals with a clinical diagnosis of lumbar segmental instability demonstrate an inability to reposition the lumbar spine accurately into a neutral spinal posture while seated. This finding provides evidence of a deficiency in lumbar proprioceptive awareness among this population.(3)

OíSullivan etal inferred that, Lumbar segmental instability is considered to represent a significant sub-group within the chronic low back pain population. The clinical diagnosis of this chronic low back pain condition is based on the report of pain and the observation of movement dysfunction within the neutral zone and the associated finding of excessive intervertebral motion at the symptomatic level.(4)

Krismer M etal concluded that Several authors have tried to define segmental lumbar instability. Their definitions are, increased antero-posterior translation, pathologic coupled motion, increased neutral zone, pathologic instantaneous center of rotation describe some mechanic findings occurring in the aging spine. However, there is no evidence that they help to differentiate the pathologic entity of segmental lumbar instability from the normal aging process. The most important structure to maintain lumbar stability is the intervertebral disc. In the third and fourth decade, more than 50 percent of specimen show peripheral tears of the anulus. It was shown in animal experiments that these tears develop to radial tears, which are accompanied by nuclear volume loss and decreased height. The facets degenerate one or two decades later. Corresponding with the loss of discal function, they increasingly contribute to spinal stability It is recommended to base the decision of lumbar fusion on a painful degenerated disc, and additional findings promising a good result.(5)

 KaigleAM etal inferred that, Segmental instability in the lumbar spine is associated with abnormal intervertebral motion. The majority of biomechanical studies have examined the in vitro effects of transecting individual stabilizing structures (i.e., intervertebral disc, facet joints, and ligaments), and have not simultaneously considered the effects of active musculature on spinal kinematics, which exist in the in vivo environment. Also, few studies have evaluated the kinematic behavior in the neutral region, for example, the transition phase between flexion and extension. Because of the direct attachment to the vertebrae, both passive and active strain from the musculature influence the spinal kinematics in normal or destabilized motion segments. Although increasing the range of motion, stimulation of the musculature surrounding the injured motion segment has a stabilizing effect by reducing abrupt kinematic behavior, particularly in the neutral region where the muscles are under reduced tension. A facetectomy produces a paradoxical kinematic behavior, which enhances the unstable condition of the motion segment. Surgical and rehabilitative treatments for patients with segmental instability need to consider the physiologic influences of the spinal musculature.  (6)

Murata M etal made the following findings that they analyzed disc space height, angular displacement, tilting movement, and horizontal displacement in 109 patients with low back pain and/or sciatica, on plain radiographs of the lumbar spine. These parameters were compared with the grade of disc degeneration as evaluated by magnetic resonance imaging with the aim of studying lumbar segmental instability. Disc space height decreased in proportion to the grade of disc degeneration. Angular displacement was significantly less with severe disc degeneration, accompanied by a tendency to stabilization of the motion segment. Tilting movement and horizontal displacement did not correlate with the grade of disc degeneration. Lumbar segmental instability was recognized at all levels even in individuals who appeared to be normal or to have mild disc degeneration. The incidence of lumbar segmental instability at the L3-4 level was significantly higher in patients with normal discs or mild disc degeneration. At the L4-5 and L5-S levels it did not differ between different grades of disc degeneration.(7)

Kalebo P etal  inferred that  the translatory movements in the patients were composed of a predominant anterior displacement in the compression view and a smaller posterior movement in the traction view. Analysis of sagittal rotation, ie, angulatory movements in the L5-S1 segment, resulted in no significant difference between the two groups. Compression-traction radiography may detect pathologic translatory movements, indicative of lumbar segmental instability.(8)

Harris BM etal concluded that the anterior lumbar interbody fusion, posterior lumbar interbody fusion, and combined anterior-posterior spinal procedures are gaining wide acceptance for the treatment of selected patients with segmental spinal instability and spondylolisthesis with associated degenerative changes.(9)

Iguchi T etal made the final coclusion in their study that anterior lumbar interbody fusion, posterior lumbar interbody fusion, and combined anterior-posterior spinal procedures are gaining wide acceptance for the treatment of selected patients with segmental spinal instability and spondylolisthesis with associated degenerative changes. Each fusion technique may have different effects on the overall flexibility of the lumbar spine. The unilateral TLIF procedure with adjunctive pedicular fixation is one variation of an interbody fusion technique that requires less bony and soft tissue dissection and minimizes nerve root manipulation compared with other interbody fusion methods.

The presence of patients with excessive angulation and translation in younger age groups suggests they have a hypermobile segment with least degenerated discs. Different predominant patterns of these radiologic factors may reveal the probable aging process of the instability.(10)

Sciffman etal concludedthat bilateral implantation of low-profile cages in this patient population led to satisfactory outcomes. Subsidence and changes in lordosis were minimal. Fusion rates were good, especially for one-level cases. Patient satisfaction was relatively high, considering the population consisted of 96% worker's compensation cases. With proper surgical technique, bilateral low-profile cages can be used effectively to treat patients with degenerative disc disease.(11)

 La RosaG etal made the inference that the  findings support the view that an interbody fusion confers superior mechanical strength to the spinal construct; when posterolateral fusion is the sole intervention, progressive loss of the extreme correction can be expected. Such mechanical insufficiency, however, did not influence clinical outcome.(12)

Patwardhan AG etal concluded that insertion of an anterior lumbar interbody fusion cage has been shown to reduce motion in a human spine segment in all loading directions except extension. The "stand-alone" cages depend on compressive preload produced by anular pretensioning and muscle forces for initial stabilization. However, the effect that the in vivo compressive preload generated during activities of daily living has on the construct is not fully understood. This study tested the hypothesis that the ability of the cages to reduce the segmental motions in flexion and extension is significantly affected by the magnitude of the externally applied compressive preload.   In contrast to the observed extension instability under anular tension preload only, the two-cage construct exerted a stabilizing effect on the motion segment (a reduction in segmental motion) in flexion as well as extension under externally applied compressive preloads of physiologic magnitudes. The external compressive preload significantly affected the stabilization provided by the cages. The cages provided substantially more stabilization, both in flexion and in extension, at larger preloads than at smaller preloads. Clinical Relevance: The study suggests that the segment treated with an anterior lumbar interbody fusion cage is relatively less stable under conditions of low external compressive preload. The magnitude of preload required to achieve stabilization with stand-alone cages may be only partially achieved by anular pretensioning. Since the magnitude of the preload across the disc space due to muscle activity can vary with activities of daily living, supplemental stabilization of the cage construct may provide a more predictably stable environment for lumbar spine fusion.(13)

OdaI etal inferred that  it remains undetermined what types of spinal instability require interbody support in posterior lumbar reconstruction.  For spinal instability with preserved anterior load sharing, pedicle screw fixation alone is biomechanically adequate, and interbody cages should not be used because they further increase segmental motion at the adjacent segment. However, Posterior stabilization alone  provides insufficient stability and high implant strain in case of damaged anterior column. In such cases, additional interbody cages significantly increase construct stiffness and decrease hardware strain. However, they increase ROM at the adjacent segment as well.(14)

Luk KD etal stated that the lateral radiographs of patients in flexion and extension are widely used to obtain quantitative and qualitative data on lumbar spondylolisthesis. Changes in lumbar disc height and segmental translation in a group of patients with spondylolisthesis have been demonstrated with the addition of traction and compression. Erect flexion and prone traction radiographs represent the extremes of subluxation and reduction of the olisthesis, respectively, and the change in olisthesis seen between these extremes is correlated with the change in disc area and the intervertebral slip angle. Vertical laxity of the affected functional spinal unit resulting from disc degeneration produces laxity in the ligaments and disc anulus, allowing olisthetic motion. Restoration of disc height in turn restores tension to the soft tissues around the disc and results in a spontaneous reduction of the subluxation. Restoration and maintenance of disc height with a spacer or interbody fusion therefore is recommended as a goal in the treatment of spondylolisthesis. When spondylolytic spondylolisthesis involves a posterior column deficiency, additional reconstruction of this column with posterior instrumentation is recommended. Application of the traction radiographic technique in planning for spondylolisthesis reduction is discussed along with the technique of stabilization(15)

Tay BB etal  concluded that the lumbar interbody arthrodesis is a surgical technique that results in fusion of the anterior column of the spine. The indications for this procedure have evolved over time, and current indications include spinal deformity, segmental instability, and discogenic low back pain. Arthrodesis in the interbody space can be accomplished through anterior or posterior approaches to the spine, and these techniques are discussed.(16).

Pitkanen MT etal inferred that the sliding instability is strongly associated with various plain radiographic findings. In mechanical back pain, functional flexion-extension radiographs should be limited to situations when symptoms are not explained by findings of plain radiographs and/or when they are likely to alter therapy.(17)

LeeSW etal concluded that the  spine instability, a clinical condition that is common but difficult to diagnose, has been suggested to involve a characteristic change in the relation between vertebrae during motion. Assessment of lumbar instability using functional radiographs is controversial. Information regarding dynamic spine kinematics in vivo is limited. The results from this study showed that the newly developed technique is reliable. It may have potential value for evaluating spine instability in clinical practice.(18)

Laohacharoensombat W etal made the following findings that the Interspinous bursa is common in the older population. It has been associated with degenerative lumbar diseases, aging and anatomical distance between the spinous process. However, no detailed exploration of the segmental instability as a cause of bursal formation has been done.angular mobility is a possible cause of interspinous bursa. On the contrary, the presence of insterspinous bursa may be evidence of segmental hypermobility.(19)

Togawa D etal concluded that the use of interbody fusion cages is gaining rapid acceptance, but there is little histologic documentation of the nature of tissue within successful human interbody fusion cages.  Autogenous bone graft was incorporated in these radiographically successful human intervertebral body fusion cages. A few debris particles were observed, but there was no histologic evidence of particle-induced(20)

Fujiwara A etal inferred that the degenerative processes in the disc and facet joints affect the stability of the motion segment. The exact relations among disc degeneration, facet joint osteoarthritis, and the kinematics of the motion segment are not well defined in the literature. Abnormal tilting movement on flexion and anteroposterior translatory instability both had negative associations with facet joint osteoarthritis. However, anterior translatory instability was positively associated with disc degeneration and facet joint osteoarthritis. Rotatory instability in the sagittal plane and posterior translatory instability were not associated with disc degeneration and facet joint osteoarthritis.(21)

.Tsantriozs A etal cocluded that the cages were introduced to overcome the limitations of conventional allografts. Radiodense cage materials impede radiographic assessment of the fusion, however, and may cause stress shielding of the graft.  The biomechanical data did not suggest any implant construct to behave superiorly either as a stand-alone or with supplemental posterior fixation. The PLIF Allograph Spacer is biomechanically equivalent to titanium cages but is devoid of the deficiencies associated with other cage technologies. Therefore, the PLIF Allograft Spacer is a valid alternative to conventional cages.(22)

Axelsson P etal inferred that as evidenced by the resulting olisthetic deformity and supported by the outcome from prior investigations, spondylolysis is assumed to induce spinal segmental instability/hypermobility.  The spondylolytic defect in pars interarticularis does not cause permanent instability/hypermobility detectable in the adult patient with low back pain and low-grade olisthesis(23).

Tsantriozs A etal  concluded that the  differences between cages in flexion/extension and lateral bending NZ are attributed to the severity of geometrical cage-endplate surface mismatch. Stand-alone cage constructs reduced ROM effectively, but the residual ROM present indicates the presence of micromotion at the cage-endplate interface.(24)

Lu WW etal inferred that  In the management of lumbar spinal stenosis, wide decompressive laminectomy with partial or total facetectomy has been the standard procedure for multilevel nerve decompression. Main complications with these procedures have been instability and chronic pain syndrome. Multilevel fenestration with undermining enlargement of the spinal canal has been selected for multilevel nerve decompression in recent years. However, the biomechanical effects of multilevel fenestration and discectomy have been controversial and difficult to validate. This study investigated the in vitro biomechanical effects of multilevel fenestrations and discectomies on motion behavior of the whole lumbar spine CONCLUSIONS: The results demonstrate that multilevel fenestrations and discectomies affect lumbar spinal stability in flexion, but have no effect on the stability of the lumbar spine in lateral bending or axial rotation.(25)

Kotilainen etal made tha findings that, comfirming earlier observations, the findings of their study support the concept that patients with postoperative lumbar instability have a poor prognosis. Further studies are needed to define the optimal treatment for this problematic patient group.(26)

Shono etal concluded that recently, many adverse effects have been reported in fusion augmented with rigid instrumentation. Only few reports are available regarding biomechanical effects of stability provided by spinal instrumentation and its effects on residual adjacent motion segments in the lumbar-lumbosacral spine.  However, segmental displacement at the site of simulated instability becomes more obvious. Application of segmental instrumentation changes the motion pattern of the residual intact motion segments, and the changes in the motion pattern become more distinct as the fixation range becomes more extensive and as the rigidity of the construct increases.(27)

Tekeoglu etal concluded that the gravitational traction is performed by suspending the patient in a hanging, upright position for an extended period of time. In spite of disagreement among authors about the effect of lumbar traction, recent innovations have enabled the distraction of vertebrae Gravitational traction had a very apparent effect on intervertebral space and was found to be an effective method to distract lumbar vertebrae. Discomfort experienced by the patient during suspension may be overcome by making biomedical changes to the suspension corset.(28)

The authorís preferred method is that maintenance of the disc space is the most important factor in treating the LSI.(29).


Lumbar segmental instability is one of the difficult problems to spine surgeons all over the world. The standard clinical tests including prone instability test and stress radiography will help in a long way to make a clinical diagnosis. Identification of the individual problem which results in a particular symptom and addressing each one of them individually will give symptomatic relief and patient satisfaction. Posterior instrumentation and fusion alone may not always result in biomechanical stability. Combined anterior and posterior fusion will stabilize the spine in a clinically useful manner


1 Hicks GE, Fritz JM, Delitto A, Mishock J. Interrater reliability of clinical examination measures for identification of lumbar segmental instability. Arch Phys Med Rehabil. 2003 Dec;84(12):1858-64.
2 Diedrich O, Luring C, Pennekamp PH, Perlick L,  Wallny T, Kraft CN. [Effect of posterior lumbar interbody fusion on the lumbar sagittal spinal profile] Z Orthop Ihre Grenzgeb. 2003 Jul-Aug;141(4):425-32.
3 O'Sullivan PB, Burnett A, Floyd AN, Gadsdon K, Logiudice J, Miller D, Quirke H. Lumbar repositioning deficit in a specific low back pain population Spine. 2003 May 15;28(10):1074-9.
4 O'Sullivan PB. Lumbar segmental 'instability': clinical presentation and specific stabilizing exercise management. Man Ther. 2000 Feb;5(1):2-12.
5 Krismer M, Haid C, Ogon M, Behensky H, Wimmer C. [Biomechanics of lumbar instability] Orthopade. 1997 Jun;26(6):516-20.
 6 Kaigle AM, Holm SH, Hansson TH. Experimental instability in the lumbar spine Spine. 1995 Feb 15;20(4):421-30.
7 Murata M, Morio Y, Kuranobu K. Lumbar disc degeneration and segmental instability: a comparison of magnetic resonance images and plain radiographs of patients with low back pain. Arch Orthop Trauma Surg. 1994;113(6):297-301.
8 Kalebo P, Kadziolka R, Sward L. Compression-traction radiography of lumbar segmental instability. Spine. 1990 May;15(5):351-5.
9 Harris BM, Hilibrand AS, Savas PE, Pellegrino A, Vaccaro AR, Siegler S, Albert TJ. Transforaminal lumbar interbody fusion: the effect of various instrumentation techniques on the flexibility of the lumbar spine. Spine. 2004 Feb 15;29(4):E65-70.
10 Iguchi T, Kanemura A, Kasahara K, Kurihara A, Doita M, Yoshiya S. Age distribution of three radiologic factors for lumbar instability: probable aging process of the instability with disc degeneration. Spine. 2003 Dec 1;28(23):2628-33.
11 Schiffman M, Brau SA, Henderson R, Gimmestad G. Bilateral implantation of low-profile interbody fusion cages: subsidence, lordosis, and fusion analysis. Spine J. 2003 Sep-Oct;3(5):377-87.
12 La Rosa G, Conti A, Cacciola F, Cardali S, La Torre D, Gambadauro NM, Tomasello F. Pedicle screw fixation for isthmic spondylolisthesis: does posterior lumbar interbody fusion improve outcome over posterolateral fusion? J Neurosurg Spine. 2003 Sep;99(2):143-50.
13 Patwardhan AG, Carandang G, Ghanayem AJ, Havey RM, Cunningham B, Voronov LI, Phillips FM. Compressive preload improves the stability of anterior lumbar interbody fusion cage constructs. J Bone Joint Surg Am. 2003 Sep;85-A(9):1749-56.
14 Oda I, Abumi K, Yu BS, Sudo H, Minami A. Types of spinal instability that require interbody support in posterior lumbar reconstruction: an in vitro biomechanical investigation. Spine. 2003 Jul 15;28(14):1573-80.
15 Luk KD, Chow DH, Holmes A. Vertical instability in spondylolisthesis: a traction radiographic assessment technique and the principle of management. Spine. 2003 Apr 15;28(8):819-27
16 Tay BB, Berven S. Indications, techniques, and complications of lumbar interbody fusion. Semin Neurol. 2002 Jun;22(2):221-30.
17 Pitkanen MT, Manninen HI, Lindgren KA, Sihvonen TA, Airaksinen O, Soimakallio S. Segmental lumbar spine instability at flexion-extension radiography can be predicted by conventional radiography. Clin Radiol. 2002 Jul;57(7):632-9.
18 Lee SW, Wong KW, Chan MK, Yeung HM, Chiu JL, Leong JC. Development and validation of a new technique for assessing lumbar spine motion. Spine. 2002 Apr 15;27(8):E215-20.
19Laohacharoensombat W, Sirikulchayanonta V, Meejan P, Wajanavisit W. Interspinous bursa and spinal instability J Med Assoc Thai. 2001 Oct;84 Suppl 2:S520-7.
20 Togawa D, Bauer TW, Brantigan JW, Lowery GL. Bone graft incorporation in radiographically successful human intervertebral body fusion cages. Spine. 2001 Dec 15;26(24):2744-50.
21 Fujiwara A, Tamai K, An HS, Kurihashi T, Lim TH, Yoshida H, Saotome K. The relationship between disc degeneration, facet joint osteoarthritis, and stability of the degenerative lumbar spine J Spinal Disord. 2000 Oct;13(5):444-50.
22 Tsantrizos A, Baramki HG, Zeidman S, Steffen T. Segmental stability and compressive strength of posterior lumbar interbody fusion implants. Spine. 2000 Aug 1;25(15):1899-907.
23 Axelsson P, Johnsson R, Stromqvist B. Is there increased intervertebral mobility in isthmic adult spondylolisthesis? A matched comparative study using roentgen stereophotogrammetry. Spine. 2000 Jul 1;25(13):1701-3.
24 Tsantrizos A, Andreou A, Aebi M, Steffen T Biomechanical stability of five stand-alone anterior lumbar interbody fusion constructs Eur Spine J. 2000 Feb;9(1):14-22.
25 Lu WW, Luk KD, Ruan DK, Fei ZQ, Leong JC. Stability of the whole lumbar spine after multilevel fenestration and discectomy. Spine. 1999 Jul 1;24(13):1277-82.
26 Kotilainen E. Long-term outcome of patients suffering from clinical instability after microsurgical treatment of lumbar disc herniation. Acta Neurochir (Wien). 1998;140(2):120-5.
27 Shono Y, Kaneda K, Abumi K, McAfee PC, Cunningham BW. Stability of posterior spinal instrumentation and its effects on adjacent motion segments in the lumbosacral spine. Spine. 1998 Jul 15;23(14):1550-8.
28 Tekeoglu I, Adak B, Bozkurt M, Gurbuzoglu N. Distraction of lumbar vertebrae in gravitational traction. Spine. 1998 May 1;23(9):1061-3; 1064.
29 DrPGopinathan DrAnwarMH Dr Yassir Hussain Physiologic distraction of the intervetebral space a better way of treating lumbar segmental instability JCOA 2004 vol2 No4  62 -66

 This is a peer reviewed paper 

Please cite as :
gopinath P:Lumbar Segmental Instability Current Concepts
J.Orthopaedics 2005;2(1)e1






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