Bilateral Facet Research Articles

Does intraoperative neurophysiological monitoring have predictive value for functional recovery following spinal cord injury? A case report

To present a case report of a patient with an ASIA B spinal cord injury with partially intact baseline IONM who made a complete functional recovery postoperatively. A thirty-three year old male presented after a motor vehicle accident. Imaging studies revealed a C4-C5 bilateral facet dislocation. On presentation the patient had 4/5 strength in bilateral biceps and wrist extensors, 3/5 strength in bilateral triceps, and 0/5 strength in the finger flexors, intrinsics and all lower extremity muscles. Motor level was C7. Sensation was grossly intact to light touch throughout all extremities, intact to pinprick from C2 to T7, and absent to pinprick caudal to T7. Rectal tone and contraction were absent. After attempts at closed reduction failed the patient underwent an open reduction and posterior C4-C5 fusion. Intraoperative neurophysiologic monitoring (IONM) revealed the presence of baseline responses to the posterior tibial nerve using somatosensory evoked potentials and to the right abductor hallucis using transcranial motor evoked potentials. At the 6 weeks postoperative visit the patient had full 5/5 motor strength to all muscles except the left deltoid that was 4/5 due to a rotator cuff injury. This case illustrates a potential prognostic value of IONM. Despite lack of clinical motor function at the time of surgery, IONM was able to illicit a motor response in the right lower extremity. Further prospective studies are needed for further investigation.

Effects of the adjustive tractor in treatment of cervical dislocation

Objective To observe the clinical effects of the adjustive tractor for cervical dislocation.Methods Forty-seven patients were included between September 2007 and November 2011.There were 36 males and 11 females with age ranged from 7 to 62 (mean,35 years).The mean interval from injury to admission was 8.6 h (range,0.5-72 h).There were atlanto-occipital dislocation in 2 cases,C1.2 in 2 cases,C2.3 dislocation in 5 cases,C3.4 dislocation in 2,C4.5 in 9,C5.6 in 13,C6.7 in 14.Thirty cases were complicated by fracture.No facet locking occurred in sixteen cases.Facet locking was found in ten cases and bilateral facet locking was in 21 cases.After reduction,brace or internal fixation followed.According to American Spinal Injury Association (ASIA) spinal function impairment scale standard,there were 4 cases in level A,10 cases in level B,18 in C,10 in D,and 5 in E.According to Japanese Orthopaedic Association (JOA) spinal function rating standard,the mean JOA score was 9 (range,2-14).Results All 47 cases were reduced successfully without neuronal function aggravation.Traction power ranged from 7 to 60 kg (mean,25.6 kg),the mean time of traction was 8 min (range,3-10 min).The mean follow-up was 38 (range,6-48) months.All the patients achieved normal alignment and intervertebral height.The intervertebral body fusion was observed in all of cases,the mean fusion time was 3.3 months (range,3-6 months).One patient who experienced nonunion of vertebral arch fracture didn't receive further treatment because of absence of symptoms.At last follow-up,there were 3 cases in level A,1 in level B,4 in C,8 in D,and 31 in E according to ASIA scale.The mean JOA score was 12 (range,2-17).Conclusion The adjustive tractor is simple and safe for prompt reduction. Key words: Cervical vertebrae; Dislocations; Fractures; Traction

Cervical spine injury with bilateral facet dislocation, surgical treatment and outcome analysis: A prospective study of 19 cases

BackgroundBilateral cervical facet dislocations present with severe neurological deficits and an unstable spine. Aim of this study was to evaluate the surgical outcome in cervical spine injury with bilateral facet dislocations. MethodsThere were 19 cases of cervical bilateral facet dislocations from Jan 2010 to March 2011. The SLIC scoring was used for surgical decision. Anterior approach with decompression and fixation was done. Postoperative CT/neurological outcome assessment postoperatively/follow up visits. ResultsMean age was 38 years (range 11–60 years), (M:F 18:1). Fall from height noted in 80% (n = 15), road traffic accident in 10% (n = 2) and two were domestic violence related. High velocity injury seen in 16% (n = 3) and low velocity injury in 84% (n = 16). ASIA A noted in majority, one patient had no neurological deficit (ASIA E). C5/6 and C 6/7 were most common injured segments (80%). Disc compression noted in 58% (n = 11) patients. Mean SLIC score was 8 (range 6–9) and the mean time from injury to surgery 9 days (range 1–50 days). Mean hospital stay 28 days (range 5–100 days). Realignment and reduction of facets achieved in 84% (n = 16) patients. Improvement of ASIA impairment score by >1 score noted in 37% (7/19) patients, mortality was 37% (7/19). Preoperative neurological status was the only significant determinant of neurological outcome (p = 0.009). ConclusionBilateral facet dislocations are mostly low velocity injuries related and have poor neurological outcome. Anterior only approach with peroperative reduction of dislocated facets is recommended to stabilize the spine.

The Effect of Soft-Tissue Restraints After Type II Odontoid Fractures in the Elderly

A biomechanical analysis of soft-tissue restraints to passive motion in odontoid fractures. To quantify the role of the C1-C2 facet joint capsules and anterior longitudinal ligaments (ALLs) in the setting of a type II odontoid fracture in the elderly. The odontoid process itself is the primary stabilizer at the C1-C2 level; however, little is known about the role of the soft-tissue structures that remain intact in the setting of an odontoid fracture after a low-energy mechanism. Ten cadaveric C0-C2 spinal segments were studied. Specimens were tested under simulated axial rotation with an applied moment of ±1 Nm and with an application of a 10 N anteriorly directed force to the body of C2 to induce sagittal translation. Optical motion data were initially collected for the intact state and after a simulated dens fracture. The specimens were then divided into 2 groups, where 1 group underwent unilateral and then bilateral C1-C2 facet capsular injuries followed by an ALL injury. The second group underwent the ALL injury before the same capsular injuries. Changes in axial range of motion and C1-C2 translation were analyzed using 2-way repeated measures analyses of variance and post hoc Student-Newman-Keuls tests (α = 0.05). In axial rotation, there was an increase in range of motion by approximately 13%, with the fracture of the dens compared with the intact state (P < 0.05). An increase was also present for each subsequent soft-tissue injury state compared with the previous (P < 0.05); however, there was no difference found between the 2 sectioning protocols. For sagittal translation testing, it was found that the odontoid fracture alone showed an increase of 3 mm of C1-C2 translation compared with intact (P < 0.05). Further soft-tissue injuries did not show an increase until the complete injury state. This study identifies that type II odontoid fractures without associated soft-tissue injury may be stable under certain loading modes.

Bilateral locked facets at lower lumbar spine without facet fracture: a case report.

Bilateral locked facets at L4-5 without facet fracture is a rarely known disease. We present a case of a 37-year-old male patient diagnosed as traumatic L4-5 bilateral facets dislocation without facet fracture. We carried out open reduction, epidural hematoma removal, posterior interbody fusion. After surgery, we attained rapid improvement of the neurologic deficits and competent stabilization.

Delayed Presentation of Cervical Facet Dislocations

To review treatment outcomes of 19 patients with delayed presentation of cervical facet dislocations. Records of 17 men and 2 women aged 21 to 63 (mean, 39) years who presented with unilateral (n=14) or bilateral (n=5) cervical facet dislocation after a delay of 7 to 21 (mean, 14) days were reviewed. The most common level of dislocation was C5-C6 (n=9), followed by C4-C5 (n=6), C3- C4 (n=2), and C6-C7 (n=2). The neurological status was graded according to the Frankel classification. One patient (with bilateral facet dislocation) had complete quadriplegia (grade A), 11 had incomplete spinal cord injury (grades C and D), and 7 had nerve root injury. Closed reduction using continuous skull traction for 2 days was attempted. In patients achieving closed reduction, only anterior discectomy and fusion was performed. Those who failed closed reduction underwent posterior partial/complete facetectomy and fixation. If there was traumatic disk prolapse, anterior decompression and fusion was then performed. The mean follow-up was 46 (range, 12- 108) months. 10 of 14 patients with unilateral facet dislocation were reduced with traction and then underwent anterior discectomy and fusion. The remaining 4 patients who failed closed reduction underwent posterior facetectomy and fixation; 3 of them had traumatic disk prolapse and thus also underwent anterior discectomy and fusion with cage and plate. Four of the 5 patients with bilateral facet dislocations failed closed reduction and underwent posterior facetectomy and lateral mass fixation, as well as anterior surgery. The remaining patient achieved reduction after traction and hence underwent only anterior discectomy and fusion. All patients achieved pain relief and sufficient neck movement for normal activities. All 7 patients with nerve root injury improved completely; 9 of the 11 patients with incomplete spinal cord injury improved by one Frankel grade, and the remaining 2 by 2 grades. The patient with complete quadriplegia showed no improvement. Preoperative traction is a safe and effective initial treatment for neglected cervical facet dislocation, as it reduces the need for extensive (anterior and posterior) surgery. If closed reduction is successful, anterior discectomy and fusion is the surgery of choice. If not, posterior facetectomy and fusion followed by anterior surgery is preferred.

Acute Paraplegia After Spinal Manipulation: A casereport

This is a case report about a 53-year-old female patient with a history of chronic back pain, suffered from complete paraplegia shortly after spinal manipulation. CT and MRI images consistently showed ossification of the ligamenta flava in conjunction with bilateral facet joints hypertrophy at the T10-11, T11-12 and L1-2 levels. Spinal cord injury with T12 paraplegia ASIA-A was thus diagnosed. Posterior laminectomy at the T10, T11, L1 and L2 levels and interbody fusion from T10 to L2 spines for fixation were performed. After rehabilitation, the patient regained some activities of daily living despite complete paraplegia. To raise public awareness, our report highlights the risk of acute paraplegia after forceful spinal manipulation. Furthermore, prompt evaluation and intervention is necessary when symptoms were worsen or neurological deficits were developed.

Posterior Epidural Migration of Sequestrated Lumbar Disc Fragments Into the Bilateral Facet Joints

Symptomatic lumbar disc herniation is common. Migration of a free disc fragment is usually found in rostral, caudal, or lateral directions. Posterior epidural migration is very rare. We report the first case with posterior epidural migration and sequestration into bilateral facet joints of a free disc fragment. A 78-year-old female presented with low back pain and right leg pain. Plain radiographs showed lumbar spondylolisthesis. Magnetic resonance imaging revealed a posterior epidural mass and intrafacet mass, which was hypointense on T1-weighted images and hyperintense on T2-weighted images. The lesion in the left L3-4 facet joint had rim enhancement, whereas the right one was not contrasted after gadolinium injection. Preoperative differential diagnosis included abscess, tumor, hematoma, or synovial cyst. An interbody cage fusion at L3-4 and L4-5 for spondylolisthesis was performed, and a hybrid technique was applied with the Dynesys flexible rod system at L3-S1 for multisegment degenerative disc disease. The lesion proved to be an epidural disc fragment with sequestration into bilateral facet joints. A free disc fragment should be considered in the differential diagnosis of posterior epidural lesions, and even in the facet joint.

Bilateral Traumatic Dislocation Without Fracture of the Lumbosacral Junction

Case report. The diagnosis and surgical management of a patient with a traumatic bilateral dislocation of the lumbosacral junction (L5-S1) without facet or pars interarticularis fracture is presented with a thorough review of the existing literature. Lumbar fracture-dislocations have been widely reported. However, only five cases of lumbosacral junction dislocation without a fracture have been previously reported. A 23-year-old patient was involved in a high-energy occupational injury and presented with complaints of back pain and inability to ambulate. Neurological assessment confirmed adequate motor strength (4+/5 bilaterally), normal perianal and lower extremity sensation, and urinary retention (postvoid residual: 1000 mL). Imaging studies revealed bilateral L5-S1 facet dislocation (bilateral jumped facets) without articulating processes or pars interarticularis fractures. Three-column ligamentous injury was confirmed on magnetic resonance imaging with complete tear of the ligamentum flavum, anterior and posterior longitudinal ligaments, interspinous and supraspinous ligaments, and avulsion of the L5 spinous process. The patient underwent bilateral facetectomies, diskectomy, laminectomies, and reduction of slippage with interbody and posterolateral transpedicular instrumented fusion. At 1-year follow-up, the patient reported mild back pain well controlled with naproxen. He continued to report good improvement in his daily function. A careful clinical examination and imaging assessment must be done for appropriate diagnosis and treatment of this rare type of injury. Reduction in the face of intact articulating processes and pars interarticularis is challenging because of acting heavy forces on the lumbosacral joint. Facetectomies, nerve root decompression, and circumferential instrumented fusion are ways to decompress the neural elements, restore alignment, and maintain segmental stability.

Biomechanical Comparison of Anterior, Posterior, and Circumferential Fixation After One-Level Anterior Cervical Corpectomy in the Human Cadaveric Spine

In vitro biomechanical study of cadaveric cervical spine. To compare the rigidity of the cervical spine after anterior, posterior, and circumferential fixation after 1-level corpectomy, and evaluate the effects of the integrity of the facet capsules and posterior ligaments (PL). Anterior cervical corpectomy is commonly used for decompression of the spinal canal in the treatment of different pathologic conditions. The effect of the integrity of the facet capsules and PLs on the biomechanical stability provided by anterior, posterior, or circumferential fixation following 1-level corpectomy has not been investigated. Nine cadaveric cervical spines were potted rostrally at C2, and caudally at T1-T2, and were tested in 6 directions with pure moment application, in 5 conditions: In the intact spine, after a C5 corpectomy and anterior fixation, after anterior fixation and disruption of the C4-C5 and C5-C6 facet capsules and PL, after circumferential fixation, and after posterior fixation alone without anterior cage. Angular motion of C4 relative to C6 was measured. Despite C5 corpectomy, anterior grafting and plate fixation was more rigid than the intact spine with all loads in flexion, at loads of 0.5 Nm and 1.0 Nm in right axial rotation and right lateral bending, and at all loads in left lateral bending. Posterior ligamentous disruption increased motion in the coronal and axial planes, but not in the sagittal plane. Circumferential instrumentation resulted in a significant reduction in motion of the spine compared with anterior instrumentation in both the coronal and axial planes but not in the sagittal plane. Posterior fixation without anterior cage failed to limit cervical spine motion in the sagittal plane, but was restrictive in axial rotation and lateral bending when compared with circumferential fixation. After C5 corpectomy, with intact PLs and facet capsules, anterior instrumentation is sufficient for spinal stabilization as the resultant construct is more rigid than the intact state. In the presence of C5 corpectomy with PL and bilateral facet capsule disruption, anterior plus posterior instrumentation is more rigid than anterior instrumentation alone in the axial and coronal planes and more rigid than posterior instrumentation without anterior cage in the sagittal plane.

Case Example: Lumbar Spine Injury, Treated with Spinal Injections

Abstract This Case Example illustrates common questions associated with the use of the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Fifth Edition, including the selection of appropriate methodology and the issue of whether spinal injections are considered to be ratable events. A 32-year-old male worker in California sustained a work-related low back injury and was examined by a chiropractic Qualified Medical Examiner (QME). The patient was referred for magnetic resonance imaging, which showed multiple lumbar disk protrusions and an L4-5 annular fissure. An epidural steroid injection at L5-S1 was of limited benefit, but bilateral L4-5 and L5-S1 facet injections, followed by chiropractic care, precluded any need for medial branch blocks or a facet rhizotomy. On presentation to the QME, the individual reported experiencing low back pain 10% of the time; this was rated 3/10 and was localized around the lumbar and lumbosacral region and was exacerbated with prolonged sitting or playing sports. The evaluator provided a rating of the lumbar spine using the range of motion (ROM) method, but the AMA Guides, Fifth Edition, states that the Diagnosis-related estimate (DRE) must be used because the impairment is due to an injury. The article demonstrates in detail how the DRE method would be applied in this case. The performance of epidural and facet injections does not constitute a ratable surgical event because these are not intradiscal injections intended to produce permanent anatomic changes in the disk.

Decompression via posterior-anterior approach and anterior fixation in treatment of fracturedislocation of the lower cervical spine with bilateral facet joints dislocation

Objective To evaluate the surgical strategy of decompression via posterior-anterior approach and anterior fixation in treatment fracture-dislocation of the lower cervical spine with bilateral facet joints dislocation. Methods This study retrospectively reviewed 37 cases of lower cervical spine fracture with bilateral joints dislocation. There were 21 males and 16 females with an average age of 42 years （19-58）. Distraction-flexion stage 3（DFS 3） were found in 24 cases and DFS 4 in 13 cases. All the cases were diagnosed by X-ray, CT and MRI and confirmed during the surgery. Decompression via posterior-anterior approach and anterior fixation had been adapted as the surgical strategy. The NASCIS and IMSOP standard were applied to definite the level of cervical spinal cord injury. The ASIA grading was used for evaluation the spinal cord function and the recovery rate. The X-ray and CT were used to observe reduction and bone fusion. Results The mean operative time was （4.5：±0.5） h, and the mean amount of blood loss was 360 ml （200-500 ml）. All the incision healed. The two segments fixation was used in 23 cases, 3 segments fixation in 13 cases, and 4 segments fixation in 1 case. The mean follow-up period was 32 months （16-45 months）.Postoperative X-ray and CT showed that bone fusion was achieved in all patients within 4-8 months, without graft displacement, or failure of implants. Spinal cord function did not aggravate, and sensory recovery ranged from 7 to 20 levels （averaged, 12.7）. The ASIA grade were improved with an average of one grade. Conclusion To treat fracture-dislocation of the lower cervical spine with bilateral facet joints dislocation, the posterlor-anterior approach and anterior fixation/fusion was benefit to preservation the cervical spinal cord function and reconstruction biomechanical stability of the cervical spine. Key words: Spinal fractures; Dislocations; Decompression, surgical; Fracture fixation

Spinal Facet Joint Biomechanics and Mechanotransduction in Normal, Injury and Degenerative Conditions

The facet joint is a crucial anatomic region of the spine owing to its biomechanical role in facilitating articulation of the vertebrae of the spinal column. It is a diarthrodial joint with opposing articular cartilage surfaces that provide a low friction environment and a ligamentous capsule that encloses the joint space. Together with the disc, the bilateral facet joints transfer loads and guide and constrain motions in the spine due to their geometry and mechanical function. Although a great deal of research has focused on defining the biomechanics of the spine and the form and function of the disc, the facet joint has only recently become the focus of experimental, computational and clinical studies. This mechanical behavior ensures the normal health and function of the spine during physiologic loading but can also lead to its dysfunction when the tissues of the facet joint are altered either by injury, degeneration or as a result of surgical modification of the spine. The anatomical, biomechanical and physiological characteristics of the facet joints in the cervical and lumbar spines have become the focus of increased attention recently with the advent of surgical procedures of the spine, such as disc repair and replacement, which may impact facet responses. Accordingly, this review summarizes the relevant anatomy and biomechanics of the facet joint and the individual tissues that comprise it. In order to better understand the physiological implications of tissue loading in all conditions, a review of mechanotransduction pathways in the cartilage, ligament and bone is also presented ranging from the tissue-level scale to cellular modifications. With this context, experimental studies are summarized as they relate to the most common modifications that alter the biomechanics and health of the spine-injury and degeneration. In addition, many computational and finite element models have been developed that enable more-detailed and specific investigations of the facet joint and its tissues than are provided by experimental approaches and also that expand their utility for the field of biomechanics. These are also reviewed to provide a more complete summary of the current knowledge of facet joint mechanics. Overall, the goal of this review is to present a comprehensive review of the breadth and depth of knowledge regarding the mechanical and adaptive responses of the facet joint and its tissues across a variety of relevant size scales.

Metabotropic Glutamate Receptor-5 and Protein Kinase C-Epsilon Increase in Dorsal Root Ganglion Neurons and Spinal Glial Activation in an Adolescent Rat Model of Painful Neck Injury

There is growing evidence that neck pain is common in adolescence and is a risk factor for the development of chronic neck pain in adulthood. The cervical facet joint and its capsular ligament is a common source of pain in the neck in adults, but its role in adolescent pain remains unknown. The aim of this study was to define the biomechanics, behavioral sensitivity, and indicators of neuronal and glial activation in an adolescent model of mechanical facet joint injury. A bilateral C6-C7 facet joint distraction was imposed in an adolescent rat and biomechanical metrics were measured during injury. Following injury, forepaw mechanical hyperalgesia was measured, and protein kinase C-epsilon (PKCɛ) and metabotropic glutamate receptor-5 (mGluR5) expression in the dorsal root ganglion and markers of spinal glial activation were assessed. Joint distraction induced significant mechanical hyperalgesia during the 7 days post-injury (p < 0.001). Painful injury significantly increased PKCɛ expression in small- and medium-diameter neurons compared to sham (p < 0.05) and naïve tissue (p < 0.001). Similarly, mGluR5 expression was significantly elevated in small-diameter neurons after injury (p < 0.05). Spinal astrocytic activation after injury was also elevated over sham (p < 0.035) and naïve (p < 0.0001) levels; microglial activation was only greater than naïve levels (p < 0.006). Mean strains in the facet capsule during injury were 32.8 ± 12.9%, which were consistent with the strains associated with comparable degrees of hypersensitivity in the adult rat. These results suggest that adolescents may have a lower tissue tolerance to induce pain and associated nociceptive response than do adults.

Operative treatment for cervical fracture and dislocation with blunt unilateral vertebral artery injury

Objective To investigate risks and clinical effects of operative treatment for cervical vertebral fracture and dislocation associated with unilateral vertebral artery injury. Methods This group consisted of 76 cases of closed cervical spine trauma combined with unilateral vertebral artery injury (23 cases of bilateral facet dislocation, 28 unilateral facet dislocation and 25 fracture). All patients underwent prospective examination of cervical spine MRI and vertebral artery two-dimensional time-of-flight (2D TOF) magnetic resonance angiography (MRA), and anterior cervical decompression. The healthy vertebral artery paths were evaluated before the surgery, and were protected during the surgery according to the anatomical signs. Results There were no acute or chronic clinical damage symptoms in 76 cases after surgery. No neural damage symptoms were observed in patients with normal neural functions. The neural functions of incomplete paralyzed patients were improved in different grades. Conclusion Reliable anterior operation can produce good results for cervical fracture and dislocation with unilateral vertebral artery injury. Detecting the course of uninjured vertebral artery before operation and locating the anatomical site during operation are effective to avoid damaging vertebral artery of uninjured side.

Morphological traits in sacra associated with complete and partial lumbarization of first sacral segment

Background context Transitional states of vertebrae at the lumbosacral junction are associated with low back pain. Lumbarization may present as partial (incomplete separation of S1–S2 bodies and their neural arches) or complete separation of the S1 from the S2 segment in a sacrum. Separation of S1 entails alteration of the anatomy at the lumbosacral junction that affects load bearing at the region. Purposes To 1) identify characteristic structural features in sacra associated with lumbarization of the S1 sacral element; 2) compare linear dimensions and surface areas in such sacra with that of the normal samples; 3) calculate relative contributions of different dimensions in the variant sacral corpuses by working out indices; and 4) analyze load bearing at these sacra in light of their altered morphology. Study design Three hundred thirty-two dried human sacra were measured for specific dimensions and surface areas. They were screened for partial or complete lumbarization of the S1 segment. Outcome measures All parameters and indices of the lumbarized specimen were compared with those in the normal sacra. Methods Seven linear dimensions and five surface areas were measured in 332 sacra. Nine indices were formulated from them. Sacra with partial or complete lumbarization of S1 were analyzed for all the parameters and evaluated for their morphological variations and traits. Results A total of 3.9% of sacra presented lumbarization, seven (2.1%) with partial and six (1.8%) with complete separation of the S1. Sacrum with partial lumbarization presented parameters similar to the normal variety. Auricular surfaces in these sacra were situated lower than normal with negligible contribution from the S1 segments. Parameters in sacral samples showing complete separation of S1 (with remaining S2-S5 segments) were smaller than normal dimensions except for some. These “baseline” (S2–S5) sacra transmitted load to the sacroiliac joints via the S2 and S3 elements. Four of six of these samples demonstrated unilateral or bilateral accessory facets between the transverse elements of the free S1 segment and the ala of the remaining sacrum (formed by S2). Significant load passed through the accessory articulations that abutted near the sacroiliac joints. A good number of these sacra showed highly attenuated laminae and at times presented incomplete fusion at the spines (spina bifida). Conclusions Lumbarization involved distinct anatomical alterations at the S1–S2 junctions. Partially lumbarized samples showed 1) gap (mean 1.43 mm) between S1 and S2 bodies; 2) incomplete separation between S1 and S2 neural arch elements with the S1 arches resembling lumbar laminae; 3) well-developed “baseline” (S2–S5) segments; and 4) “low-down” (positioned at S2–S3) auricular surfaces. Complete separation of S1 involved 1) smaller overall dimensions with diminished facet depth, sacral height, and facet area at S1; 2) auricular surface areas comparable to the normal and greater than those found in the partially lumbarized specimen; 3) large “baseline” (S2–S5) sacra with “high-up” auricular surfaces (positioned at S2–S3); 4) occasional S1–S2 accessory articulations; and 5) small zygapophyseal joints and attenuated sacral laminae with high sacral hiatuses associated at times, with “spina bifida.”

Less Invasive Surgical Correction of Adult Degenerative Scoliosis, Part I

Adult scoliosis is a condition with increasing prevalence and medical and socioeconomic importance. Surgery is fraught with a significant complication rate in an elderly multimorbid patient population. To assess technical feasibility and radiographic results of image-guided less invasive correction of adult degenerative scoliosis. Thirty individuals (age, 64-88 years) with progressive deformity (coronal Cobb angles > 25 degrees and < 85 degrees), intractable back pain, radiculopathy, or neurogenic claudication were treated by less invasive decompression and fusion (unilateral transforaminal interbody cage instrumentation and bilateral facet fusions) with recombinant human bone morphogenetic protein-2, spanning 3 to 8 segments (average, 6 segments), using biplanar fluoroscopy or intraoperative computed tomography (iCT)-based navigation. Accuracy of screw placement, curve correction, and fusion rate were evaluated during a mean follow-up of 19.6 months. With 415 screws implanted, misplacement (grade II or greater) was not observed, and no implants required revision. Spinal iCT with automated registration required 17.5 +/- 8.5 minutes (single registration for all segments); monosegmental bilateral screw insertion required 6.8 +/- 3.4 minutes. Mean sagittal (coronal) Cobb angle correction was 44.8 +/- 10.7 degrees (31.7 +/- 13.7 degrees). Mean lumbar lordosis increased from 8.8 +/- 8.9 degrees to -36 +/- 6.9 degrees, and sagittal balance was reduced from 31.6 +/- 15.2 to 8 +/- 8.4 mm. Solid fusion was confirmed in 90% of instrumented segments at 16 months. Average radiation dose to the surgeon was 0.025 mSv for single-level transforaminal lumbar interbody fusion with fluoroscopic guidance vs 0 mSv with iCT navigation. Instrumented correction of adult deformity was significantly facilitated by iCT navigation, eliminating radiation exposure to the surgeon. Intraoperative biplanar CT scout views including pelvis and shoulders allow comprehensive assessment of multiplanar deformity correction. Fusion rates obtained with less invasive access equal those of conventional open technique.

Association of rudimentary sacral zygapophyseal facets and accessory and ligamentous articulations: Implications for load transmission at the L5‐S1 junction

Weight transmitted from the fifth lumbar vertebrae to the sacrum is distributed as three separate components between (a) the vertebral bodies anteriorly, (b) the transverse elements intermediately, and (c) the lumbosacral facet joints, posteriorly. The posterior components of the fifth lumbar vertebra share greater proportion of load in comparison with the posterior elements of the upper lumbar vertebral levels. This study focuses on rudimentary lumbosacral facet articulations and their possible effects on load sharing at this region. Twenty sacra bearing rudimentary articulations were collected for analysis. Sixteen of these sacra presented unilateral rudimentary facets, and the remaining four had facets that were bilaterally rudimentary. Thirteen of the sacra with unilateral rudimentary facets showed an accessory articulating area on the upper surface of the ala on the same side as the rudimentary zygapophyseal facet. The remaining three sacra (out of the 16) showed evidence of strong ligamentous attachments between the L5 and S1 transverse elements on the sides of the rudimentary facets. All the sacra with bilateral rudimentary facets demonstrated bilateral accessory L5-S1 articulations. These observations indicated that load transmission at lumbosacral junctions bearing a rudimentary facet joint is not normal and that their associations with strong L5-S1 lumbosacral ligamentous attachments or accessory articulations at the transverse elements serve a compensatory mechanism for load sharing.

Morphometric analysis and identification of characteristic features in sacra bearing accessory articulations with L5 vertebrae

Background context Occurrence of transitional vertebrae at the lumbosacral junction, especially accessory lumbosacral articulations (partial sacralization of the L5 vertebrae), is not uncommon. These transitional states are frequently associated with low back pain situations requiring surgical intervention. Purpose The study aimed to investigate the presence of distinct morphological features and structural peculiarities associated with these sacra. The features related to sacra bearing L5-S1 transitions might be significantly different from those of the normal sacra. This study tries to understand whether accessory L5-S1 articulations demonstrate altered mechanisms of load transfer as a result of structural changes at the L5–S1 junction. Study design Morphometric measurements of several linear dimensions and articular areas were obtained from 332 sacra. Thirty sacra demonstrated unilateral accessory facets on their ala. Twelve sacra showed bilateral accessory lumbosacral articulations. Indices were calculated based on the linear dimensions and on the surface areas of the bones to detect proportional contributions of the dimensions and surface areas to the overall structure of all the sacra. Outcome measures All the parameters obtained from the transitional sacra were compared with the same parameters worked out on 290 normal sacra. All parameters in the sacra bearing accessory articulations were statistically compared with parameters in the normal sacra. Method Seven linear dimensions and five surface areas were measured in 290 normal sacra. Thirty sacra bearing unilateral accessory articular facets and 12 sacra with bilateral accessory facets on their alae were measured for the same linear parameters and surface areas. Nine indices were calculated from these measurements in both the normal and transitional sacra and statistically verified. Results Analysis of the results indicated that sacra bearing accessory articulations, in comparison to the normal, carried their auricular surfaces at a higher level; possessed load bearing features mainly confined to the two upper sacral segments; showed lesser distances between the facet joints; showed smaller distance of the coronal plane of the facet joints from the posterior aspect of the S1 vertebral body; exhibited smaller and more coronally oriented facet joint surfaces; and exhibited smaller body width and height. The auricular surface area and superior surface of the body of S1 in these “transitional” sacra were similar in comparison to normal sacra. Linear dimensions in sacra with bilateral accessory articulations were smaller than the ones having unilateral accessory L5-S1 articulations. Conclusions Lumbosacral accessory articulations constituted the bulk of transitional variations at the junction. Accessory articulations were unilateral (9%) and bilateral (3%) with a total of 12% of all studied samples (n=332) demonstrating this type L5–S1 transition. Sacra with lumbosacral pseudoarticulations were associated with different anatomical features in contrast to normal sacra. Analysis of these structural differences with the normal variants may possibly help in understanding the biomechanical properties at these transitional sites. Evaluation of the relative proportions of dimensions within these bones may help plan surgical interventions or probably predict the pattern of abnormal weight bearing in these sacra.

Analysis of the Relationship Between Facet Joint Angle Orientation and Lumbar Spine Canal Diameter With Respect to the Kinematics of the Lumbar Spinal Unit

Retrospective cross-sectional study. This study aimed to elucidate the relationship among facet orientation, kinematics of a spinal unit, and change in lumbar spine canal diameter by using kinetic magnetic resonance imaging. Some studies have suggested an association between increased sagittally oriented facet angles and degenerative lumbar spondylolisthesis. However, no study has specifically addressed the association of facet orientation with the kinematics of a spinal unit and change in canal diameter. Kinetic magnetic resonance imagings were performed with patients in flexion, neutral, and extension positions. Study subjects were classified into 6 groups-AA, BB, CC, AB (BA), BC (CB), and AC (CA)-on the basis of bilateral facet angles (A, narrow; B, normal; and C, wide) and disc and facet joint degeneration. A magnetic resonance imaging analyzer was used for anatomic measurements and for calculating changes in canal diameters and disc bulging as well as the lumbar spine kinematics. Osseous canal diameters were significantly smaller in the group AA than in the group BB, whereas they were significantly larger in the group CC than in the group BB. Canal diameter at the disc level was significantly smaller in the group AA than in the group BB in all 3 positions, whereas it was significantly larger in the group CC than in the group BB. Translational motion was significantly more in the group AA than in the group BB, whereas it was significantly lesser in the group CC than in the group BB. We demonstrated the relationship among facet orientation, osseous canal diameter, kinematics of a spinal unit, and change in lumbar spine canal diameter. Patients with sagittally oriented facets had narrow osseous canals with mobility, whereas those with coronally oriented facets had stable and wider osseous canals. This finding is helpful in understanding the mechanism underlying lumbar spinal canal stenosis and degenerative spondylolisthesis.