Andre M. Jakoi

Biomechanics of Degenerative Spinal Disorders

The spine has several important functions including load transmission, permission of limited motion, and protection of the spinal cord. The vertebrae form functional spinal units, which represent the smallest segment that has characteristics of the entire spinal column. Discs and paired facet joints within each functional unit form a three-joint complex between which loads are transmitted. Surrounding the spinal motion segment are ligaments, composed of elastin and collagen, and joint capsules which restrict motion to within normal limits. Ligaments have variable strengths and act via different lever arm lengths to contribute to spinal stability. As a consequence of the longer moment arm from the spinous process to the instantaneous axis of rotation, inherently weaker ligaments (interspinous and supraspinous) are able to provide resistance to excessive flexion. Degenerative processes of the spine are a normal result of aging and occur on a spectrum. During the second decade of life, the intervertebral disc demonstrates histologic evidence of nucleus pulposus degradation caused by reduced end plate blood supply. As disc height decreases, the functional unit is capable of an increased range of axial rotation which subjects the posterior facet capsules to greater mechanical loads. A concurrent change in load transmission across the end plates and translation of the instantaneous axis of rotation further increase the degenerative processes at adjacent structures. The behavior of the functional unit is impacted by these processes and is reflected by changes in the stress-strain relationship. Back pain and other clinical symptoms may occur as a result of the biomechanical alterations of degeneration.

Reoperation Rates Following Single-Level Lumbar Discectomy.

Study Design. Retrospective analysis of national insurance billing database. Objective. To examine trends in reoperation after single-level lumbar discectomy. Summary of Background Data. Lumbar discectomy is the most commonly performed procedure for treatment of radiculopathy caused by disc herniation. Randomized clinical trials have demonstrated the advantage of discectomy over nonsurgical treatment options, allowing for a more rapid reduction in symptoms. However, population-level data regarding reoperation after single level discectomy is limited. Methods. Data were collected using the commercially available PearlDiver software for patients billed with the Current Procedural Terminology code for our index procedure, hemilaminotomy and removal of disc material, between January 2007 and September 2014. The index group was then followed for up to 4 years for recurrent lumbar surgery, including spinal fusion, laminectomy, and additional discectomy. Results. Analysis of data obtained from 13,654 patient records revealed a rate of additional lumbar surgeries after single-level discectomy of 3.95% (539/13654) within 3 months and 12.2% (766/6274) within 4 years of the index procedure. Lumbar spinal fusion was performed on 5.9% (370/6274) of patients within 4 years. Patients who received a re-exploration discectomy within 2 years of the index procedure went on to receive lumbar fusion at a rate of 38.4% (48/125) within the 4 years after the re-exploration discectomy. The average additional cost of lumbar reoperation, as measured by insurance reimbursement, was approximately

Postoperative complications in patients undergoing minimally invasive sacroiliac fusion

11,161 per-patient per year. Conclusion. We report an overall 4-year reoperation rate of 12.2% after single-level discectomy. In addition, we report a rate of progression to lumbar fusion following re-exploration discectomy of 38.4% within 4 years of reoperation. Further studies are needed regarding the best treatment algorithm in patients with reherniation or iatrogenic instability after lumbar discectomy. This study should enhance the shared decision making process by providing surgeons and patients with valuable data regarding the frequency and nature of reoperations after discectomy. Level of Evidence: 3

Complications associated with the Dynesys dynamic stabilization system: a comprehensive review of the literature

BACKGROUND CONTEXT Minimally invasive sacroiliac (SI) joint fusion has become increasingly relevant in recent years as a treatment for SI joint pathology. Previous studies have found minimally invasive SI fusion to be an effective and safe treatment option for chronic SI joint pain. However, these studies have been primarily single-center, case-based, or manufacturer-sponsored investigations, and as such their findings are limited to their sample populations. PURPOSE The aim of this study was to investigate the safety of minimally invasive SI fusion using a large nationwide sample group to more accurately identify complication rates of this increasingly popular procedure. STUDY DESIGN/SETTING This is a retrospective database study. PATIENT SAMPLE The sample includes patients within the orthopedic subset of Humana database who underwent minimally invasive SI fusion between 2007 and 2014. OUTCOME MEASURES Complications and novel lumbar and nerve pathology were the outcome measures. METHODS Patients undergoing minimally invasive SI fusion from 2007 to 2014 were identified using the Pearl Diver patient record database (Pearl Diver Technologies, West Conshohocken, PA, USA) from the nationwide private insurance provider Humana Inc. This approach provided access to records of over 18 million patients in every major geographic region of the country. Using the ICD-9 diagnosis codes (International Classification of Diseases 9th edition), data from patient records were analyzed to reveal incidence of postoperative infection, pain, osteomyelitis, joint derangement, urinary tract infection, and novel lumbar and nervous system pathology. RESULTS Four hundred sixty-nine patients (305 female; 164 male) within the Humana insurance database received minimally invasive SI fusion between 2007 and 2014. Data from these patients showed a substantial increase in the use of the procedure over this 7-year period. Among these patients, an overall complication rate of 13.2% (n=62) was seen at 90 days postoperatively and 16.4% (n=77) at 6 months. The number of patients receiving a first time diagnosis of lumbar pathology following minimally invasive SI fusion in the sample population was also analyzed. The incidence of novel lumbar pathology in this population was 3.6% (n=17) at 90 days postoperatively and 5.3% (n=25) at 6 months. Men experienced diagnoses of novel lumbar pathology at higher rates than women within both 90 days (men=6.7%; women≤3.3%) and 6 months (men=9.1%; women≤3.3%) of the procedure (p<.01). CONCLUSIONS The results of this study show that minimally invasive SI joint fusion could possibly carry higher risks of complications than previously stated. These findings are useful for physicians and patients when considering treatment for chronic SI joint pain.

Bisphosphonate's and Intermittent Parathyroid Hormone's Effect on Human Spinal Fusion: A Systematic Review of the Literature

The Dynesys dynamic stabilization system is an alternative to rigid instrumentation and fusion for the treatment of lumbar degenerative disease. Although many outcomes studies have shown good results, currently lacking is a comprehensive report on complications associated with this system, especially in terms of how it compares with reported complication rates of fusion. For the present study, the authors reviewed the literature to find all studies involving the Dynesys dynamic stabilization system that reported complications or adverse events. Twenty-one studies were included for a total of 1166 patients with a mean age of 55.5 years (range 39-71 years) and a mean follow-up period of 33.7 months (range 12.0-81.6 months). Analysis of these studies demonstrated a surgical-site infection rate of 4.3%, pedicle screw loosening rate of 11.7%, pedicle screw fracture rate of 1.6%, and adjacent-segment disease (ASD) rate of 7.0%. Of studies reporting revision surgeries, 11.3% of patients underwent a reoperation. Of patients who developed ASD, 40.6% underwent a reoperation for treatment. The Dynesys dynamic stabilization system appears to have a fairly similar complication-rate profile compared with published literature on lumbar fusion, and is associated with a slightly lower incidence of ASD.

Semitendinosus Graft for Interspinous Ligament Reinforcement in Adult Spinal Deformity.

There has been a conscious effort to address osteoporosis in the aging population. As bisphosphonate and intermittent parathyroid hormone (PTH) therapy become more widely prescribed to treat osteoporosis, it is important to understand their effects on other physiologic processes, particularly the impact on spinal fusion. Despite early animal model studies and more recent clinical studies, the impact of these medications on spinal fusion is not fully understood. Previous animal studies suggest that bisphosphonate therapy resulted in inhibition of fusion mass with impeded maturity and an unknown effect on biomechanical strength. Prior animal studies demonstrate an improved fusion rate and fusion mass microstructure with the use of intermittent PTH. The purpose of this study was to determine if bisphosphonates and intermittent PTH treatment have impact on human spinal fusion. A systematic review of the literature published between 1980 and 2015 was conducted using major electronic databases. Studies reporting outcomes of human subjects undergoing 1, 2, or 3-level spinal fusion while receiving bisphosphonates and/or intermittent PTH treatment were included. The results of relevant human studies were analyzed for consensus on the effects of these medications in regards to spinal fusion. There were nine human studies evaluating the impact of these medications on spinal fusion. Improved fusion rates were noted in patients receiving bisphosphonates compared to control groups, and greater fusion rates in patients receiving PTH compared to control groups. Prior studies involving animal models found an improved fusion rate and fusion mass microstructure with the use of intermittent PTH. No significant complications were demonstrated in any study included in the analysis. Bisphosphonate use in humans may not be a deterrent to spinal fusion. Intermittent parathyroid use has shown early promise to increase fusion mass in both animal and human studies but further studies are needed to support routine use.

S-1 and S-2-alar-iliac screw fixation via intraoperative navigation.

Proximal junctional kyphosis is an increasingly recognized complication following long-segment posterior spinal fusion for adult spinal deformity. The authors describe a novel technique for interspinous ligament reinforcement at the proximal adjacent levels using a cadaveric semitendinosus tendon graft secured with an Ethibond No. 2 double filament (Ethicon, Somerville, New Jersey) via the Krackow suture weave. A retrospective review identified 4 patients who had received this graft. No proximal junctional kyphosis was seen at a mean short-term follow-up of 5.5 months. Interspinous ligament reinforcement at the proximal adjacent level with a cadaveric semitendinosus tendon graft is a feasible strategy for preventing proximal junctional kyphosis. [Orthopedics. 2017; 40(1):e206-e210.].

Risk Factors for Postoperative Venous Thromboembolic Events in Patients Undergoing Lumbar Spine Surgery

Adult deformity patients often require fixation to the sacrum and pelvis for construct stability and improved fusion rates. Although certain sacropelvic fixation techniques can be challenging, the availability of intraoperative navigation has made many of these techniques more feasible. In this video case presentation, the authors demonstrate the techniques of S-1 bicortical screw and S-2-alar-iliac screw fixation under intraoperative navigation in a 67-year-old female. This instrumentation placement was part of an overall T-10-pelvis construct for the correction of adult spinal deformity. The video can be found here: https://youtu.be/3HZo-80jQr8 .

The use of a novel perfusion-based cadaveric simulation model with cerebrospinal fluid reconstitution comparing dural repair techniques: a pilot study

Study Design: Retrospective, database study. Objectives: The aim of this study was to investigate incidence and risk factors associated with venous thromboembolic events (VTEs) after lumbar spine surgery. Methods: Patients who underwent lumbar surgery between 2007 and 2014 were identified using the Humana within PearlDiver database. ICD-9 (International Classification of Diseases Ninth Revision) diagnosis codes were used to search for the incidence of VTEs among surgery types, patient demographics and comorbidities. Complications including DVT and PE were queried each day from the day of surgery to postoperative day 7 and for periods 0 to 1 week, 0 to 1 month, 0 to 2 months, and 0 to 3 months postoperatively. Results: A total of 64 892 patients within the Humana insurance database received lumbar surgery between 2007 and 2014. Overall VTE rate was 0.9% at 1 week, 1.8% at 1 month, and 2.6% at 3 months postoperatively. Among patients that developed a VTE within 1 week postoperatively, 45.3% had a VTE on the day of surgery. Patients with 1 or more identified risk factors had a VTE incidence of 2.73%, compared with 0.95% for patients without risk factors (P < .001). Risk factors associated with the highest VTE incidence and odds ratios (ORs) were primary coagulation disorder (10.01%, OR 4.33), extremity paralysis (7.49%, OR 2.96), central venous line (6.70%, OR 2.87), and varicose veins (6.51%, OR 2.58). Conclusions: This study identified several patient comorbidities that were independent predictors of postoperative VTE occurrence after lumbar surgery. Clinical VTE risk assessment may improve with increased focus toward patient comorbidities rather than surgery type or patient demographics.

Bone Grafting and Spinal Fusion Options

BACKGROUND CONTEXT Watertight dural repair is crucial for both incidental durotomy and closure after intradural surgery. PURPOSE The study aimed to describe a perfusion-based cadaveric simulation model with cerebrospinal fluid (CSF) reconstitution and to compare spine dural repair techniques. STUDY DESIGN/SETTING The study is set in a fresh tissue dissection laboratory. SAMPLE SIZE The sample includes eight fresh human cadavers. OUTCOME MEASURES A watertight closure was achieved when pressurized saline up to 40 mm Hg did not cause further CSF leakage beyond the suture lines. METHODS Fresh human cadaveric specimens underwent cannulation of the intradural cervical spine for intrathecal reconstitution of the CSF system. The cervicothoracic dura was then exposed from C7-T12 via laminectomy. The entire dura was then opened in six cadavers (ALLSPINE) and closed with 6-0 Prolene (n=3) or 4-0 Nurolon (n=3), and pressurized with saline via a perfusion system to 60 mm Hg to check for leakage. In two cadavers (INCISION), six separate 2-cm incisions were made and closed with either 6-0 Prolene or 4-0 Nurolon, and then pressurized. A hydrogel sealant was then added and the closure was pressurized again to check for further leakage. RESULTS Spinal laminectomy with repair of intentional durotomy was successfully performed in eight cadavers. The operative microscope was used in all cases, and the model provided a realistic experience of spinal durotomy repair. For ALLSPINE cadavers (mean: 240 mm dura/cadaver repaired), the mean pressure threshold for CSF leakage was observed at 66.7 (±2.9) mm Hg in the 6-0 Prolene group and at 43.3 (±14.4) mm Hg in the 4-0 Nurolon group (p>.05). For INCISION cadavers, the mean pressure threshold for CSF leakage without hydrogel sealant was significantly higher in 6-0 Prolene group than in the 4-0 Nurolon group (6-0 Prolene: 80.0±4.5 mm Hg vs. 4-0 Nurolon: 32.5±2.7 mm Hg; p<.01). The mean pressure threshold for CSF leakage with the hydrogel sealants was not significantly different (6-0 Prolene: 100.0±0.0 mm Hg vs. 4-0 Nurolon: 70.0±33.1 mm Hg). The use of a hydrogel sealant significantly increased the pressure thresholds for possible CSF leakage in both the 6-0 Prolene group (p=.01) and the 4-0 Nurolon group (p<.01) when compared with mean pressures without the hydrogel sealant. CONCLUSIONS We described the feasibility of using a novel cadaveric model for both the study and training of watertight dural closure techniques. 6-0 Prolene was observed to be superior to 4-0 Nurolon for watertight dural closure without a hydrogel sealant. The use of a hydrogel sealant significantly improved watertight dural closures for both 6-0 Prolene and 4-0 Nurolon groups in the cadaveric model.