Christian Knop

Late results of thoracolumbar fractures after posterior instrumentation and transpedicular bone grafting

Study Design. A retrospective clinical study was performed. Objective. To study clinical and radiologic late results after posterior stabilization of thoracolumbar fractures with internal fixator and interbody fusion via transpedicular bone grafting. Summary of Background Data. The posterior approach, using an internal fixator, is a standard procedure for stabilizing the injured thoracolumbar spine. Transpedicular bone grafting was invented by Daniaux in 1986 for achieving an interbody fusion. Pedicle screw fixation with additional transpedicular fusion has remained controversial because of inconsistent reports and a lack of late results. Methods. Between January 1989 and July 1992, 76 patients with thoracolumbar fractures were operatively treated, and after a mean of more than 3 years, 56 of 62 patients (90%) still alive who had their implants removed were examined. Results. According to the Magerl classification, 33 patients sustained Type A, 13 Type B, and 10 Type C fractures. Three patients with incomplete paraplegia returned to normal. In one case of complete paraplegia, no change occurred. The mean operative time was 3 hours. In this study, two complications (3.6%) were observed: one iatrogenic vertebral arch fracture without consequences and one deep infection. Compared with the preoperative status, follow-up examinations demonstrated permanent physical and social sequelae: The percentage of individuals able to do physical labor was reduced by half (22 to 11 patients), whereas the share of unemployed or retired patients doubled (4 to 8 patients). At the time of follow-up examination, only 21 of 42 patients continued in sports. The assessment of reported problems and functional outcome with the Hannover spine score reflected a significant difference between the status before injury (96.6/100 points) and at the time of follow-up evaluation (71.4/100 points) (P < 0.001). The radiographic assessment in the lateral plane (Cobb technique) demonstrated a significant (P < 0.001) mean restoration from an initial angle of −15.6° (kyphosis) to +0.4°(lordosis). Serial postoperative radiographicfollow-up assessment showed progressive loss of correction. At follow-up examination, a mean difference from the postoperative angle of 10.1° was found (P < 0.001). Compared with the preoperative deformity, a mean improvement of 6.1° (average, −9.7°) at follow-up examination was noted. The addition of transpedicular cancellous bone grafting did not decrease the loss of correction. Computed tomography scans after implant removal were performed in nine cases: Only three of nine patients showed evidence of intervertebral fusion. No correlation could be found between the Magerl classification and radiographic outcome. However, the preoperative wedge angle of the vertebral body correlated significantly with the postoperative loss of reduction. Conclusions. Because of the disappointing results from this study, the authors cannot recommend the additional transpedicular cancellous bone grafting as an interbody fusion technique after posterior stabilization in cases of complete or incomplete burst injury to the vertebral body.

Evaluation of the mobility of adjacent segments after posterior thoracolumbar fixation: a biomechanical study

Abstract. An investigation was conducted into the effects of double-level T12–L2 posterior fixation on the mobility of neighboring unfused segments. The segmental mobility of adjacent segments above and below the fixation in ten cadaveric human thoracolumbar spine specimens was measured before and after fixation by biomechanical testing in flexion, extension, right lateral bending, and right rotation, and the data were compared. In flexion and extension, mobility of the segment above the double-level T12–L2 posterior fixation was significantly increased (P<0.05). In the adjacent segment below the fixation, there was no significant increased mobility after fixation for each moment applied. There is evidence that the adjacent segment above a double-level T12–L2 posterior fixation becomes more mobile, and this may lead to an accelerated degeneration in the facet joints due to increased stress at this point. This could be responsible for symptoms like low back pain after spinal surgery.

Complications in surgical treatment of thoracolumbar injuries.

Abstract. The range of surgical methods for operative treatment of thoracolumbar injuries, with their different ways of approach, grafts and techniques, remains wide. The authors present sources of error and specific complications based on their own experience and on the results of a multicenter study of the Spine Study Group of the German Trauma Association (DGU). A systematic overview of possible mistakes and complications is first presented in anatomical order. A detailed analysis is then presented of the complications reported in a multicenter study, carried out prospectively between 1994 and 1996, on 682 patients operated for acute traumatic injuries of the thoracolumbar spine. In 101 cases (15%) at least one complication occurred intra- or postoperatively. In 41 patients (6%) a revision was performed, and in 60 patients (9%) complications without operative revision were observed. These complications were analysed according to the chosen method of initial treatment.

Higher risk of adjacent segment degeneration after floating fusions: long-term outcome after low lumbar spine fusions.

Study Design We report the long-term outcome after mono-segmental and bisegmental fusions at the lumbar L4-S1 region of the spine. Objective Long-term clinical and radiologic outcome measures were used to determine a lumbar fusions contribution to degenerative changes in adjacent motion segments (ASD). Summary of Background Data The role of low lumbar spinal fusions and their long-term contribution to accelerated degenerative changes in the adjacent motion segments continues to be a subject of controversy. Patients and Methods We followed-up 102 patients with an average age of 54 (22 to 78) years and a follow-up time of 14 (3 to 22) years. Results Overall results in patients were good, the Oswestry-Disability Index (ODI) showed an average of 26% (0% to 70%) at follow-up, the Visual Analog Scale rose from 2.7 (postoperative) and 2.9 (12 wk follow-up) to 3.6 (latest follow-up) points, respectively. Patient satisfaction with their health-related situation at follow-up was 69% (15% to 100%). Patients who underwent fusions of the segment L5/S1 showed a significant (P<0.05) lower risk for ASD than patients with fusions L4/5 (20% vs. 46%). Compared with L4/5 fusions, bisegmental L4-S1 fusions showed a similar trend (P=0.06) with a lower risk for ASD (24%). Objective and subjective clinical results showed no differences between these groups. Patients suffering from ASD showed significant (P<0.05) reduced sacral inclination and lumbar lordosis angles and also significant (P<0.05) higher ODI values compared with non-ASD patients. Conclusions We conclude that floating fusions of single low lumbar segments are more likely to result in ASD and are negatively influenced by sagittal plane abnormalities.

Influence of screw positioning in a new anterior spine fixator on implant loosening in osteoporotic vertebrae.

Study Design. A biomechanical study was designed to assess implant cut-out of three different angular stable anterior spinal implants. Subsidence of the implant relative to the vertebral body was measured during an in vitro cyclic loading test. Objectives. The objective of the study was to evaluate two prototypes (Synthes) of a new anterior spine fixator with different screw angulations in comparison to the established MACSTL® Twin Screw Concept (Aesculap). The influence of factors like load-bearing cross-sectional area, screw angulation and bone mineral density upon implant stability should be investigated. Summary of Background Data. Epidemiologic data predict a growing demand for appropriate anterior spinal fixation devices especially in patients with inferior structural and mechanical bone properties. Although different concepts for anterior spinal instrumentation systems have been tried out, implant stability is still a problem. Methods. Three angular stable, anterior spinal implants were tested using 24 human lumbar osteoporotic vertebrae (L1-L5; age 84 (73–92)): MASC TL system (Aesculap); prototype 1 (MP1) with 18° and prototype 2 (MP2) with 40° screw angulation (both Synthes). All implants consisted of two screws with different outer screw diameters: 7-mm polyaxial screw with 6.5-mm stabilization screw (MASC TL), two 5-mm locking-head screws each (MP1 and MP2). Bone mineral density (BMD) and vertebral body width of the three specimen groups were evenly distributed. The specimens were loaded in craniocaudal direction (1Hz) for 1000 cycles each at three consecutive load steps; 10–100 N, 10–200 N and 10–400 N. During cyclic loading subsidence of the implant relative to the vertebral body was measured in the unloaded condition. Cycle number at failure (defined as a subsidence of 2 mm) was determined for each specimen. A survival analysis (Cox Regression) was performed to detect differences between implant groups at a probability level of 95%. Results. High correlations were found between BMD and number of cycles until failure (MP1; r = 0.905, P = 0.013; MP2: r = 0.640, P = 0.121; MACS TL: r = 0.904, P = 0.013) and between load bearing cross sectional area and number of cycles until failure (MP1: r = 0.849, P = 0.032;MP2: r = 0.692, P = 0.085; MACS TL: r = 0.902, P = 0.014). Both Prototypes survived significantly longer than the MACS TL implant (MP1: P = 0.012, MP2: P = 0.014). The survival behaviour of MP1 and MP2 was not significantly different (P = 0.354). Conclusions. Implant stability within each implant group was influenced by BMD and load bearing cross-sectional area. The angulation of the two screws did not have a significant influence on cut-out. As conclusion from this study, promising approaches for further implant development are: 1) increase of load-bearing cross-sectional area (e.g., larger outer diameter of the anchorage device), 2) screw positioning in areas of higher BMD (e.g., opposite cortex, proximity to pedicles or the endplates).

Vertebral body replacement with Synex in combined posteroanterior surgery for treatment of thoracolumbar injuries

ZusammenfassungOperationszielReposition und Stabilisierung von instabilen Wirbelsäulenverletzungen mit dauerhafter Wiederherstellung der physiologischen Krümmungsverhältnisse, Stabilität und Tragfähigkeit der Wirbelsäule.IndikationenInstabile Verletzungen und Läsionen der Wirbelsäule von T4 bis L5 mit verminderter Tragfähigkeit der ventralen Säule durch—Wirbelkörperfraktur und Bandscheibenverletzung,—posttraumatische Fehlstellungen,—pathologische Frakturen,—Tumoren.Eingeschränkte Indikationen:—Jüngere Patienten mit monosegmentaler Verletzung.—Patienten mit ausgeprägter Osteoporose.KontraindikationenSchwerwiegende kardiopulmonale Begleitverletzung oder Vorerkrankung als Kontraindikation für den ventralen Eingriff.OperationstechnikKombinierte dorsoventrale Operation mit1. dorsaler Reposition und Stabilisierung mit einem Fixateur interne sowie interlaminärer Fusion des verletzten Wirbelsäulenabschnitts mit autogener Spongiosa;2. thorakoskopischem Wirbelkörper(teil)ersatz zur tragfesten Abstützung der vorderen Säule mit einem distrahierbaren Wirbelkörperersatzimplantat aus Titan (Synex®) und zusätzliche interkorporelle Fusion mit autogener Spongiosa und/oder β-Tricalciumphosphat.WeiterbehandlungFunktionelle Behandlung und Mobilisation ohne äußere Ruhigstellung.Ergebnisse41 der ersten 50 Patienten, die mit Synex® behandelt wurden, konnten durchschnittlich 19,5 Monate (14–31 Monate) postoperativ nachuntersucht werden. Es handelte sich um 36 frische Frakturen, acht posttraumatische Fehlstellungen, drei Tumoren, zwei veraltete Frakturen und eine Spondylodiszitis. Das Durchschnittsalter der 29 Männer und 21 Frauen betrug 43 Jahre (20–77 Jahre). Synex® wurde bei 30 Patienten bisegmental und bei 20 monosegmental eingesetzt.Bis auf einen Fall wurde weder ein Einsinken noch eine Dislokation des Implantats beobachtet.Zur Nachuntersuchung waren 18/33 der vor der Erstoperation berufstätigen Patienten wieder im alten Beruf tätig, und 32/41 Patienten hatten die vorherigen Freizeitaktivitäten wieder aufgenommen.32/41 Patienten waren zur Nachuntersuchung beschwerdefrei oder gaben gelegentliche Rückenschmerzen an.8/41 Patienten gaben deutliche Rückenbeschwerden an, ein Patient klagte nach Aufrichtung einer posttraumatischen Fehlstellung über starke Beschwerden.Vor dem Unfall erreichten die Patienten mit frischer Verletzung im VAS-Wirbelsäulen-Score (0–100 Punkte, visuelle Analogskala, 19 Items) ein durchschnittliches Ergebnis von 83,1 ± 20,2 (21–100). Zur Nachuntersuchung betrug der Score im Mittel 63,8 ± 19,5 (25–99). Der durchschnittliche Scoreverlust lag bei 19,3 ± 22,3.Die röntgenologische Reposition/Aufrichtung bei Patienten mit frischer Verletzung oder posttraumatischer Fehlstellung betrug durchschnittlich 18,6° ± 10° und der Korrekturverlust (Rekyphosierung) 2,1° ± 2,9°.AbstractObjectiveReduction and stabilization of unstable spinal injuries with reconstruction of the anterior column resulting in a permanent restitution of the physiologic spinal alignment, stability and load-bearing capacity.IndicationsUnstable injuries and lesions of the spine from T4 to L5 resulting in a reduced load-bearing capacity of the anterior spinal column caused by—vertebral fractures and injury of the intervertebral disks,—posttraumatic kyphotic deformities,—pathologic fractures,—tumors.Relative indications:—younger patients with monosegmental injuries;—patients with severe osteoporosis.ContraindicationsConcomitant serious thoracic injuries or preexisting cardiopulmonary disease precludinganterior intervention.Surgical TechniqueCombined posteroanterior treatment with(1) posterior reduction and stabilization with an internal fixator and interlaminar fusion with autogenous bone grafts;(2) thoracoscopic anterior approach with reconstruction of the anterior column with a distractible titanium implant for vertebral body replacement (Synex®), interbody fusion with autogenous bone grafts and/or β-tricalciumphosphate.Results50 consecutive patients (29 men, 21 women) with an average age of 43 years (20–77 years) were treated with Synex®. The most frequent indication was acute injury (n = 36). A bisegmental reconstruction was performed in 30 patients, a monosegmental in 20. Mean follow-up 19.5 months (14–31 months) in 41 patients.18/33 patients returned to their previous occupation, and 32/41 resumed their recreational activities.At follow-up, 32/41 were free of symptoms or complained of only occasional pain, eight reported marked pain and one severe pain.A VAS spine score (0–100 points, visual analog scale, 19 items) was used for assessment; the preoperative score amounted to 83.1 ± 20.2 (21–100), the postoperative score to 63.8 ± 19.5 (25–99). The mean decrease in VAS spine score was 19.3 ± 22.3.The average degree of correction measured radiologically for patients with fresh injuries or posttraumatic malalignment was 18.6° ± 10° and the loss of correction 2.1° ± 2.9°. No implant-related complications were observed.

Angular Stable Anterior Plating Following Thoracolumbar Corpectomy Reveals Superior Segmental Stability Compared to Conventional Polyaxial Plate Fixation

Study Design. Biomechanical in vitro testing of primary and secondary stability in 12 human thoracolumbar spinal specimens using a spine simulator. Objective. In a corpectomy model anterior plate systems were investigated for their ability to restore spinal stability particularly focusing on the influence of angular stability, bone mineral density (BMD) and failure mode. Summary of Background Data. The concept of isolated anterior column reconstruction following thoracolumbar fractures using newly developed minimally invasive spine surgical techniques has attracted major clinical interest. In analogy to angular stable plate systems in long bone fixation the application of locking plates to the spine is aimed to limit loss of reduction and to improve stability. Methods. Twelve human spinal specimens (Th11-L3) were tested in a 6-degree-of-freedom spine simulator under pure moments of 7.5 Nm to investigate primary and secondary stiffness of 2 different anterior reconstruction options: (1) Synex II cage and MACS TL polyaxial anterior plating system, (2) Synex II cage and ArcoFix angular stable anterior plating system. An increasing 4-step cyclic loading model was included. Results. The angular stable plate system showed superior stability compared to the nonangular system in axial rotation and lateral bending. Flexion/extension loading demonstrated no difference between the systems in range of motion. A positive correlation between BMD and the number of load cycles until failure for the nonangular stable system (R2 = 0.90) was found. Different failure modes were investigated for the plating systems. The MACS system showed loosening at the connection between screw and plate inducing tilting under flexural load and final failure. The ArcoFix system revealed increased stability under cyclic loading and failed by parallel sintering to the endplate. Conclusion. Anterior angular stable fixation showed higher primary and secondary stability following thoracolumbar corpectomy. In specimens with lower BMD the use of angular stable systems substantially increased stability. Angular stable systems, however, differ in the way of construct failure.

Der Wirbelkörperersatz mit Synex® bei kombinierter dorsoventraler Behandlung thorakolumbaler Verletzungen

ZusammenfassungOperationszielReposition und Stabilisierung von instabilen Wirbelsäulenverletzungen mit dauerhafter Wiederherstellung der physiologischen Krümmungsverhältnisse, Stabilität und Tragfähigkeit der Wirbelsäule.IndikationenInstabile Verletzungen und Läsionen der Wirbelsäule von T4 bis L5 mit verminderter Tragfähigkeit der ventralen Säule durch—Wirbelkörperfraktur und Bandscheibenverletzung,—posttraumatische Fehlstellungen,—pathologische Frakturen,—Tumoren.Eingeschränkte Indikationen:—Jüngere Patienten mit monosegmentaler Verletzung.—Patienten mit ausgeprägter Osteoporose.KontraindikationenSchwerwiegende kardiopulmonale Begleitverletzung oder Vorerkrankung als Kontraindikation für den ventralen Eingriff.OperationstechnikKombinierte dorsoventrale Operation mit1. dorsaler Reposition und Stabilisierung mit einem Fixateur interne sowie interlaminärer Fusion des verletzten Wirbelsäulenabschnitts mit autogener Spongiosa;2. thorakoskopischem Wirbelkörper(teil)ersatz zur tragfesten Abstützung der vorderen Säule mit einem distrahierbaren Wirbelkörperersatzimplantat aus Titan (Synex®) und zusätzliche interkorporelle Fusion mit autogener Spongiosa und/oder β-Tricalciumphosphat.WeiterbehandlungFunktionelle Behandlung und Mobilisation ohne äußere Ruhigstellung.Ergebnisse41 der ersten 50 Patienten, die mit Synex® behandelt wurden, konnten durchschnittlich 19,5 Monate (14–31 Monate) postoperativ nachuntersucht werden. Es handelte sich um 36 frische Frakturen, acht posttraumatische Fehlstellungen, drei Tumoren, zwei veraltete Frakturen und eine Spondylodiszitis. Das Durchschnittsalter der 29 Männer und 21 Frauen betrug 43 Jahre (20–77 Jahre). Synex® wurde bei 30 Patienten bisegmental und bei 20 monosegmental eingesetzt.Bis auf einen Fall wurde weder ein Einsinken noch eine Dislokation des Implantats beobachtet.Zur Nachuntersuchung waren 18/33 der vor der Erstoperation berufstätigen Patienten wieder im alten Beruf tätig, und 32/41 Patienten hatten die vorherigen Freizeitaktivitäten wieder aufgenommen.32/41 Patienten waren zur Nachuntersuchung beschwerdefrei oder gaben gelegentliche Rückenschmerzen an.8/41 Patienten gaben deutliche Rückenbeschwerden an, ein Patient klagte nach Aufrichtung einer posttraumatischen Fehlstellung über starke Beschwerden.Vor dem Unfall erreichten die Patienten mit frischer Verletzung im VAS-Wirbelsäulen-Score (0–100 Punkte, visuelle Analogskala, 19 Items) ein durchschnittliches Ergebnis von 83,1 ± 20,2 (21–100). Zur Nachuntersuchung betrug der Score im Mittel 63,8 ± 19,5 (25–99). Der durchschnittliche Scoreverlust lag bei 19,3 ± 22,3.Die röntgenologische Reposition/Aufrichtung bei Patienten mit frischer Verletzung oder posttraumatischer Fehlstellung betrug durchschnittlich 18,6° ± 10° und der Korrekturverlust (Rekyphosierung) 2,1° ± 2,9°.AbstractObjectiveReduction and stabilization of unstable spinal injuries with reconstruction of the anterior column resulting in a permanent restitution of the physiologic spinal alignment, stability and load-bearing capacity.IndicationsUnstable injuries and lesions of the spine from T4 to L5 resulting in a reduced load-bearing capacity of the anterior spinal column caused by—vertebral fractures and injury of the intervertebral disks,—posttraumatic kyphotic deformities,—pathologic fractures,—tumors.Relative indications:—younger patients with monosegmental injuries;—patients with severe osteoporosis.ContraindicationsConcomitant serious thoracic injuries or preexisting cardiopulmonary disease precludinganterior intervention.Surgical TechniqueCombined posteroanterior treatment with(1) posterior reduction and stabilization with an internal fixator and interlaminar fusion with autogenous bone grafts;(2) thoracoscopic anterior approach with reconstruction of the anterior column with a distractible titanium implant for vertebral body replacement (Synex®), interbody fusion with autogenous bone grafts and/or β-tricalciumphosphate.Results50 consecutive patients (29 men, 21 women) with an average age of 43 years (20–77 years) were treated with Synex®. The most frequent indication was acute injury (n = 36). A bisegmental reconstruction was performed in 30 patients, a monosegmental in 20. Mean follow-up 19.5 months (14–31 months) in 41 patients.18/33 patients returned to their previous occupation, and 32/41 resumed their recreational activities.At follow-up, 32/41 were free of symptoms or complained of only occasional pain, eight reported marked pain and one severe pain.A VAS spine score (0–100 points, visual analog scale, 19 items) was used for assessment; the preoperative score amounted to 83.1 ± 20.2 (21–100), the postoperative score to 63.8 ± 19.5 (25–99). The mean decrease in VAS spine score was 19.3 ± 22.3.The average degree of correction measured radiologically for patients with fresh injuries or posttraumatic malalignment was 18.6° ± 10° and the loss of correction 2.1° ± 2.9°. No implant-related complications were observed.

Accuracy of Pedicle Screw Placement in Thoracic Spine Fractures

Background and Purpose:Transpedicular instrumentation in the thoracic spine is technically difficult because of small pedicle diameters. There are not many studies assessing in vivo accuracy, complications, and the revision rate of transpedicular screws in the thoracic spine. In this retrospective study 278 thoracic pedicle screws of 43 patients were assessed using a scoring system and postoperative computed tomography (CT) scans.Patients and Methods:43 consecutive patients with traumatic thoracic spine fractures underwent posterior transpedicular reduction and fixation. The universal spine system was used for placement of 278 pedicle screws under fluoroscopic control. Fractures were classified according to the Magerl classification by plain radiographs and CT scans. Evaluation of pedicle screw placement was assessed by a scoring system from grade I to grade III. Revision rate of pedicle screws as well as pre- and postoperative neurologic status were analyzed.Results:In the thoracic spine, vertebral body T7 was mainly fractured followed by T6 and T5. In 37 (86.0%) of 43 patients type C fractures and in three patients each type A and B fractures were determined, respectively. Of all 278 pedicle screws, 78.1% were inserted in pedicles T4–T9. The rate of optimally placed grade I screws was 84.5%. Grade II screws were scored in 6.8% and grade III screws in 8.6%. The revision rate of all pedicle screws was 5.0%, whereas 64.3% of these were grade III. None of the patients suffered neurologic or vascular structure compromise postoperatively.Conclusion:Although most pedicle screws were placed in pedicles of the middle thoracic spine where the pedicle width is smallest, most screws were optimally placed with grade I. The revision rate of pedicle screws was acceptable and associated with the grade of pedicle screw placement.

Accuracy of Pedicle Screw Placement in Thoracic Spine Fractures: Part I: Inter- and Intraobserver Reliability of the Scoring System

Background and Purpose:Accuracy of pedicle screw placement is essential for stabilization of spinal fractures and their outcome. A scoring system was developed to facilitate determination of pedicle screw placement and decision of pedicle screw revision. The aim of this study is to evaluate the inter- and intraobserver reliability of the presented scoring system in a multicenter study.Material and Methods:Postoperative computed tomography (CT) scans of 30 thoracic pedicle screws were reviewed by 50 observers in 14 hospitals experienced in spinal trauma. Pedicle screws of the universal spine system were used for dorsal stabilization of traumatic thoracic spine fractures (T1–T10). Placement of pedicle screws was scored from grade I to grade III. A compact disk was sent to each hospital including a detailed description of the scoring system. The score of each pedicle screw, its need for revision with or without postoperatively coexisting neurology of the patient had to be marked on a record. The investigation of the intraobserver reliability followed with a 2-month interval using the same set of postoperative CT scans but in another sequence. Statistics: Cohen’s κ-test.Results:Inter- and intraobserver reliability was substantial with a mean κ-coefficient of 0.70 (confidence interval 0.66–0.73; p < 0.0005) and 0.71 (confidence interval 0.68–0.75; p < 0.0005), respectively. Mean interobserver agreement for each grade of pedicle screws was 74.9%, and 73.7% for the intraobserver agreement. Revision of pedicle screws was suggested for grade III screws with or without appearance of neurologic symptoms, whereas revision was additionally recommended for grade IIb screws when neurologic deterioration occurred postoperatively.Conclusion:The inter- and intraobserver reliability of the presented scoring system was substantial. The scoring system is an appropriate tool for determination of accuracy of pedicle screw placement. The scoring system may be helpful in terms of a better comparability of different studies and the decision on pedicle screw revision.