Comparing Mid Lumbar Interbody Fusion (MIDLF) with Traditional Posterior Lumbar Interbody Fusion (PLIF)

Mid-lumbar interbody fusion (MIDLF) uses a novel cortical bone trajectory (CBT) screw that provides robust fixation that is less dependent on cancellous bone quality than a traditional pedicle screw. MIDLF also allows for decompression and instrumentation through a smaller central surgical window. The aim of this study is to compare MIDLF with posterior lumbar interbody fusion (PLIF) with regards to perioperative complications, operative time, blood loss, length in hospital, radiographic outcomes and post-operative patient functional scores. A retrospective review of our institutional database was performed of patients undergoing MIDLF. Matched PLIF controls were then selected from the same database for comparison. 20 MIDLF patients were identified as were 20 matched PLIF controls. Primary outcomes included perioperative clinical and radiographic measures as well as postoperative patient self-reported function. Results demonstrated no significant difference between the two groups with respect to all clinical, radiographic and patient self-reported measures

In Vitro Biomechanical Testing and Computational: Modeling in Spine

Two separate in vitro biomechanical studies were conducted on human cadaveric spines (Lumbar) to evaluate the stability following the implantation of two different spinal fixation devices interspinous fixation device (ISD) and Hybrid dynamic stabilizers. ISD was evaluated as a stand-alone and in combination with unilateral pedicle rod system. The results were compared against the gold standard, spinal fusion (bilateral pedicle rod system). The second study involving the hybrid dynamic system, evaluated the effect on adjacent levels using a hybrid testing protocol. A robotic spine testing system was used to conduct the biomechanical tests. This system has the ability to apply continuous unconstrained pure moments while dynamically optimizing the motion path to minimize off-axis loads during testing. Thus enabling precise control over the loading and boundary conditions of the test. This ensures test reliability and reproducibility. We found that in flexion-extension, the ISD can provide lumbar stability comparable to spinal fusion. However, it provides minimal rigidity in lateral bending and axial rotation when used as a stand-alone. The ISD with a unilateral pedicle rod system when compared to the spinal fusion construct were shown to provide similar levels of stability in all directions, though the spinal fusion construct showed a trend toward improved stiffness overall. The results for the dynamic stabilization system showed stability characteristics similar to a solid all metal construct. Its addition to the supra adjacent level (L3- L4) to the fusion (L4- L5) indeed protected the adjacent level from excessive motion. However, it essentially transformed a 1 level into a 2 level lumbar fusion with exponential transfer of motion to the fewer remaining discs (excessive adjacent level motion). The computational aspect of the study involved the development of a spine model (single segment). The kinematic data from these biomechanical studies (ISD study) was then used to validate a finite element model

Low Back Pain Pathogenesis and Treatment

Low back pain is a common disorder which affects the lumbar spine, and is associated with substantial morbidity for about 80% of the general population at some stages during their lives. Although low back pain usually is a self-limiting disorder that improves spontaneously over time, the etiology of low back pain is generally unknown and the diagnostic label, "non-specific low back pain", is frequently given. This book contains reviews and original articles with emphasis on pathogenesis and treatment of low back pain except for the rehabilitative aspect. Consisting of three sections, the first section of the book has a focus on pathogenesis of low back pain, while the second and third sections are on the treatment including conservative and surgical procedure, respectively

An Investigation of Subaxial Cervical Spine Trauma and Surgical Treatment through Biomechanical Simulation and Kinematic Analysis

In vitro biomechanical investigations can help to identify changes in subaxial cervical spine (C3-C7) stability following injury, and determine the efficacy of surgical treatments through controlled joint simulation experiments and kinematic analyses. However, with the large spectrum of cervical spine trauma, a large fraction of the potential injuries have not been examined biomechanically. This includes a lack of studies investigating prevalent flexion-distraction injuries. Therefore, the overall objective of this thesis was to investigate the changes in subaxial cervical spine kinematic stability with simulated flexion-distraction injuries and current surgical instrumentation approaches using both established and novel biomechanical techniques. Three in vitro experiments were performed with a custom-designed spinal loading simulator. The first evaluated sequential disruption of the posterior ligaments with and without a simulated facet fracture (n=7). In these specimens, posterior lateral mass screw fixation provided more stability than anterior cervical discectomy and fusion with plating (ACDFP). A second study examined a unilateral facet perch injury by reproducing a flexion-distraction injury mechanism with the simulator (n=9). The resulting soft tissue damage was quantified through meticulous dissection of each specimen, which identified the most commonly injured structures across all specimens as both facet capsules, ¾ of the annulus, and ½ of the ligamentum flavum. This information was used to develop and validate a standardized injury model (SIM) in new specimens (n=10). A final study examined the ACDFP surgical factor of graft size height (bony spacer replacing the intervertebral disc to promote fusion) for the SIM and two other injuries (n=7). Results were motion and injury dependent, which suggests that both these factors must be considered in the surgical decision. Two additional investigations were completed. The first examined mathematical techniques to generate a large number of accurate finite helical axes from six-DOF rigid body tracker output to describe changes in cervical spine kinematic stability. The second explored the effect of boundary conditions and PID control settings on the ability of the current simulator design to reproduce desired loading techniques. Ultimately, it is hoped that these results, and the protocols developed for future investigations, will provide valuable biomechanical evidence for standardized treatment algorithms

Novel methodology for assessing cement injection behaviour in cancellous bone

Understanding the cement injection behaviour in cancellous bone and accurately predicting the cement placement within the vertebral body is extremely challenging. We propose a novel method using reproducible and pathologically representative 2D and 3D bone surrogates to help study the influence of cement properties on injection behaviour. Bespoke methodology was developed to control the injection volume and flow rate, measure the injection pressure, and allow visualization and quantitative analysis of the spreading distribution. Morphology analysis showed that the variability in the 2D and 3D bone surrogates was very low, indicating that the geometrical structure of the surrogates was constant. The overall pore size of the surrogates was very similar to that reported for human osteoporotic vertebral cancellous bone, indicating that the surrogates were pathologically representative. Injections performed into the 3D surrogates revealed that an increase in the fluid starting viscosity significantly increases the injection pressure in all surrogates, decreases the risk of leakage for osteoporosis surrogates only, decreases the mean spreading distance for multiple myeloma surrogates only and increases the sphericity causing a more uniform spreading pattern for the metastasis surrogates only. Injections performed into the 2D surrogates highlighted the influence of cement formulations and model structure on the injection behaviour and showed that (i) cements with similar composition/particle size have similar flow behaviour, (ii) cements with a high liquid-to-powder ratio cause irregular filling patterns and have a high risk of leakage, and (iii) the injection behaviour of certain cement formulations improves in the presence of lesion or fracture, suggesting the notion of pathology specific bone cements. The developed methodology provides a fast, robust tool for discerning subtle differences in bone cement formulations and allows comprehensive assessment of cement flow behaviour through controlling the surrogate morphology, controlling the injection parameters, measuring the injection pressure, and allowing the visualization and quantitative analysis of the spreading distribution. The advantage of this methodology is that it provides a clinically relevant representation of cement flow patterns and a tool for validating computational simulations

Low Back Pain (LBP)

Low back pain (LBP) is a major public health problem, being the most commonly reported musculoskeletal disorder (MSD) and the leading cause of compromised quality of life and work absenteeism. Indeed, LBP is the leading worldwide cause of years lost to disability, and its burden is growing alongside the increasing and aging population. The etiology, pathogenesis, and occupational risk factors of LBP are still not fully understood. It is crucial to give a stronger focus to reducing the consequences of LBP, as well as preventing its onset. Primary prevention at the occupational level remains important for highly exposed groups. Therefore, it is essential to identify which treatment options and workplace-based intervention strategies are effective in increasing participation at work and encouraging early return-to-work to reduce the consequences of LBP. The present Special Issue offers a unique opportunity to update many of the recent advances and perspectives of this health problem. A number of topics will be covered in order to attract high-quality research papers, including the following major areas: prevalence and epidemiological data, etiology, prevention, assessment and treatment approaches, and health promotion strategies for LBP. We have received a wide range of submissions, including research on the physical, psychosocial, environmental, and occupational perspectives, also focused on workplace interventions

Management of pelvic ring injuries

Jan Lindahl: MANAGEMENT OF PELVIC RING INJURIES Unstable pelvic ring injuries are relatively rare injuries, but they constitute a major cause of death and disability in high-energy polytrauma patients Massive hemorrhage is the leading cause of potentially preventable death following a blunt pelvic trauma. The overall aim of surgical treatment for unstable pelvic ring injuries is to restore the pelvic anatomy and perform neural decompression, thus allowing normal function with a low rate of complications. This doctoral thesis was initiated to investigate the outcomes of acute and definitive management strategies for unstable pelvic ring injuries. The first study investigated the radiological and functional results of treating type B and C pelvic injuries with an anterior external fixation frame. The second study focused on identifying factors for early predictions of mortality-related outcome and prognosis in patients with pelvic fracture-related arterial bleeding that were treated with transcatheter angiographic embolization (TAE). The third study investigated the outcomes of type C pelvic fractures treated with standardized reduction and internal fixation methods. The fourth study evaluated outcomes and identified prognostic factors for operatively-treated, H-shaped sacral fractures with spinopelvic dissociation. Study I showed that an anterior external fixator failed to achieve and properly maintain reduction in 75% of type B open book injuries and in nearly all (95%) type C pelvic ring injuries. Therefore, an external frame is not a suitable method of treatment for the most unstable pelvic ring injuries as a definitive treatment. The current clinical applications of anterior pelvic external fixators comprise the resuscitation phase, initial fracture stabilization phase, and sometimes, in complex injuries (type C), the definitive phase for fixation of the anterior part of the pelvic ring, in conjunction with posterior internal fixation. Study II of pelvic fracture related arterial bleedings showed that the worst prognosis was related to exsanguinating bleeding from the main trunk of the internal or external iliac artery (large pelvic arteries) or from multiple branches of the internal or external iliac vasculature (high vessel size score). Definitive control of arterial bleeding was achieved with TAE in all patients. In massive hemorrhage with several bleeding arteries uni- or bilaterally, it is reasonable to use non-selective embolization by promptly occluding the main trunk of the internal iliac artery, either uni- or bilaterally. Study III of operatively treated type C pelvic fractures revealed that, internal fixation of injuries in the posterior and anterior pelvic ring provided excellent or good radiological results in 90% of cases. Additionally, because a reduction with displacement less than or equal to 5 mm was more often associated with a good functional outcome, that should be the goal of operative management. However, the prognosis is also often dependent on associated injuries, particularly a permanent lumbosacral plexus injury. The results favoured internal fixation of all the injured elements of the pelvis for improved stability and a more accurate anatomical result in the entire pelvic ring. The H-shaped sacral fracture with spinopelvic dissociation is a rare injury pattern. Study IV revealed that lumbopelvic fixation was a reliable treatment method. The study also showed that neurological recovery and clinical outcome were associated with the degree of initial translational displacement of the transverse sacral fracture component. Permanent neurological deficits were more frequent and the clinical outcome was worst in completely displaced transverse sacral fractures. An accurate operative reduction of all sacral fracture components was associated with better neurological recovery and clinical outcome. We conclude, that with appropriate treatment of unstable pelvic ring injuries, and associated injuries in other organs, it is possible to achieve better survival rates and functional results, and to reduce long-term disability.Jan Lindahl: LANTIORENKAAN MURTUMIEN HOITO (MANAGEMENT OF PELVIC RING INJURIES) Lantiorenkaan murtumat ovat suhteellisen harvinaisia vammoja käsittäen 1% kaikista sairaalahoitoa vaativista murtumista Suomessa. Epätukevat lantiorenkaan murtumat syntyvät yleensä suuren vammaenergian seurauksena ja niihin liittyy usein muiden kehonosien vammoja. Massiivinen verenvuoto on merkittävin ja usein estettävissä oleva kuolinsyy tylpällä vammamekanismilla syntyneissä lantiorenkaan vammoissa. Mikäli akuuttivaiheen hoito ei ole tehokasta, massiivinen verenvuoto johtaa sydämen ja verenkierron pettämiseen ja potilaan kuolemaan. Tämän väitöskirjatutkimuksen tarkoituksena oli selvittää: 1) ulkoisen tukilaitteen soveltuvuus B- ja C-tyypin lantiorenkaan murtumien lopulliseksi hoitomuodoksi, 2) hengenvaarallisten, runsaasti vuotavien lantionmurtumien alkuvaiheen vuodon tukkimista embolisaation (TAE) avulla ja samalla kartoittaa riskitekijöitä, jotka ennustavat huonoa lopputulosta ja potilaan kuolemaa vaikeimmin vammautuneiden lantionmurtumapotilaiden kohdalla, 3) C-tyypin murtumien kohdalla standardoidun leikkaushoidon ja sisäisen kiinnitysmenetelmän luotettavuutta ja hoidon pitkäaikaistulokset ja 4) ristiluun vaikeimpien ns. H-tyypin murtumien leikkaushoidon luotettavuutta sekä saavutetun asennonkorjauksen, murtumakiinnityksen ja hermorakenteiden vapautuksen pitkäaikaistulokset sekä toipumisennusteeseen vaikuttavat tekijät. Ensimmäisen osajulkaisun tulokset osoittivat, että lantiorenkaan etuosaan kiinnitettävä ulkoinen kiinnityslaite (externi fiksaatiolaite) ei ollut luotettava, eikä sillä voitu taata asianmukaista murtuman paikalleen asettamista ja hyvää lopputulosta vaikeimmissa B- ja C-tyypin murtumissa. Toinen osajulkaisu osoitti, että vuotavien lantionmurtumien kohdalla huonoin ennuste liittyi lantiovammoihin, joissa valtimoiden varjoainekuvauksessa (angiografiassa) todettiin lantion päävaltimon (arteria iliaca interna tai externa) repeämä tai useampia samanaikaisia pienempien valtimosuonten repeämiä. Embolisaatio osoittautui luotettavaksi hoitomenetelmäksi ja kaikki valtimoperäiset vuodot pystyttiin tukkimaan. Kriittisessä vuototilanteessa, jossa angiografiassa todetaan useita vuotokohtia lantion valtimoissa, tulee embolisaatio suorittaa ei-selektiivisesti siten, että lantion aluetta suonittava päävaltimo (arteria iliaca interna) tukitaan välittömästi. Näin vuoto saadaan nopeammin hallintaan ja potilaan selviytymisennuste paranee. C-tyypin lantionmurtumien sisäinen kiinnitysmenetelmä, lantiorenkaan kiinnitys edestä levyin sekä takaa ruuvein tai levyin, osoittautui luotettavaksi (kolmas osajulkaisu). Saavutettu asento säilyi seurannassa erinomaisena tai hyvänä 90%:ssa tapauksista. Leikkauksessa saavutettu murtuman hyvä asento korreloi hyvään neurologiseen toipumiseen ja toiminnalliseen tulokseen. Epäanatominen tulos siten, että murtuman lopullinen siirtymä oli yli 5 mm, ennusti huonompaa toiminnallista lopputulosta. Merkittävin toimintakykyä rajoittava tekijä aiheutui lantion alueen hermopunosvauriosta. Tulokset tukevat käsitystä, jonka mukaan C-tyypin vammoissa tulee korjata ja kiinnittää kaikki murtumat lantiorenkaan etu- ja takaosassa, jolloin saavutetaan parempi anatominen tulos ja samalla parempi lantiorenkaan kokonaistukevuus. Ristiluun H-tyypin murtuma, johon liittyy selkärangan ja lantiorenkaan irtoama toisistaan, on harvinainen lantion takaosan alueen vammakokonaisuus. Neljännessä osajulkaisussa käytetty lannerangan ja lantion välinen kiinnitysmenetelmä (lumbopelvinen kiinnitys) osoittautui luotettavaksi. Lantiohermopunoksen (alaraajojen osittainen halvaus) ja ristiluuhermojen vammat (ns. kauda equina syndrooma) ovat tähän vammatyyppiin liittyen yleisiä. Hermovaurion korjaantuminen ja kokonaistoipumisen ennuste oli riippuvainen ristiluun poikittaisen murtuman siirtymän asteesta. Hermovaurio oli vaikeampiasteinen ja toipumistulos huonompi, mikäli siirtymä ensimmäisessä kuvauksessa oli yli ristiluun paksuuden, kun tuloksia verrattiin siihen potilasryhmään, jolla siirtymä oli osittainen. Hyvä leikkauksessa saavutettu asento kaikissa ristiluun murtumalinjoissa oli yhteydessä parempaan toipumisennusteeseen. Systemaattisella tutkimisella sekä määrätietoisella ja vaikuttavalla hoidolla voidaan vähentää lantiorenkaan murtumiin liittyvää kuolleisuutta, sairastavuutta ja pysyvää vammautumista

Progenitor cells in auricular cartilage demonstrate promising cartilage regenerative potential in 3D hydrogel culture

The reconstruction of auricular deformities is a very challenging surgical procedure that could benefit from a tissue engineering approach. Nevertheless, a major obstacle is presented by the acquisition of sufficient amounts of autologous cells to create a cartilage construct the size of the human ear. Extensively expanded chondrocytes are unable to retain their phenotype, while bone marrow-derived mesenchymal stromal cells (MSC) show endochondral terminal differentiation by formation of a calcified matrix. The identification of tissue-specific progenitor cells in auricular cartilage, which can be expanded to high numbers without loss of cartilage phenotype, has great prospects for cartilage regeneration of larger constructs. This study investigates the largely unexplored potential of auricular progenitor cells for cartilage tissue engineering in 3D hydrogels