Biomedical applications of polymer-composite materials: a review

STUDY DESIGN: Systematic literature review. OBJECTIVE: To evaluate the safety and efficacy of vertebroplasty and kyphoplasty using the data presented in published clinical studies, with respect to patient pain relief, restoration of mobility and vertebral body height, complication rate, and incidence of new adjacent vertebral fractures. SUMMARY OF BACKGROUND DATA: Vertebroplasty and kyphoplasty have been gaining popularity for treating vertebral fractures. Current reviews provide an overview of the procedures but are not comprehensive and tend to rely heavily on personal experience. This article aimed to compile all available data and evaluate the clinical outcome of the 2 procedures. METHODS: This is a systematic review of all the available data presented in peer-reviewed published clinical trials. The methodological quality of included studies was evaluated, and data were collected targeting specific standard measurements. Where possible, a quantitative aggregation of the data was performed. RESULTS: A large proportion of subjects had some pain relief, including 87% with vertebroplasty and 92% with kyphoplasty. Vertebral height restoration was possible using kyphoplasty (average 6.6 degrees ) and for a subset of patients using vertebroplasty (average 6.6 degrees ). Cement leaks occurred for 41% and 9% of treated vertebrae for vertebroplasty and kyphoplasty, respectively. New fractures of adjacent vertebrae occurred for both procedures at rates that are higher than the general osteoporotic population but approximately equivalent to the general osteoporotic population that had a previous vertebral fracture. CONCLUSIONS: The problem with stating definitely that vertebroplasty and kyphoplasty are safe and effective procedures is the lack of comparative, blinded, randomized clinical trials. Standardized evaluative methods should be adopted.

/pdf/vertebroplasty-and-kyphoplasty-a-systematic-review-of-69-27mm39raap.pdf

Vertebroplasty and kyphoplasty: a systematic review of 69 clinical studies.

Study design A meta-analysis of the published literature was conducted specifically looking at accuracy and the postoperative methods used for the assessment of pedicle screw placement in the human spine. Objectives This study specifically aimed to identify postoperative methods used for pedicle screw placement assessment, including the most common method, and to report cumulative pedicle screw placement study statistics from synthesis of the published literature. Summary of background data Safety concerns have driven specific interests in the accuracy and precision of pedicle screw placement. A large variation in reported accuracy may exist partly due to the lack of a standardized evaluation method and/or the lack of consensus to what, or in which range, is pedicle screw placement accuracy considered satisfactory. Methods A MEDLINE search was executed covering the span from 1966 until 2006, and references from identified papers were reviewed. An extensive database was constructed for synthesis of the identified studies. Subgroups and descriptive statistics were determined based on the type of population, in vivo or cadaveric, and separated based on whether the assistance of navigation was employed. Results In total, we report on 130 studies resulting in 37,337 total pedicle screws implanted, of which 34,107 (91.3%) were identified as accurately placed for the combined in vivo and cadaveric populations. The most common assessment method identified pedicle screw violations simply as either present or absent. Overall, the median placement accuracy for the in vivo assisted navigation subgroup (95.2%) was higher than that of the subgroup without the use of navigation (90.3%). Conclusions Navigation does indeed provide a higher accuracy in the placement of pedicle screws for most of the subgroups presented. However, an exception is found at the thoracic levels for both the in vivo and cadaveric populations, where no advantage in the use of navigation was found.

Pedicle screw placement accuracy: a meta-analysis.

We sought to determine prospectively the natural history of acute, isolated, nonoperatively treated posterior cruciate ligament injuries in athletically active patients. The study population consisted of 133 patients (average age, 25.2 years at time of injury). All patients completed a subjective questionnaire each year for an average of 5.4 years (range, 2.3 to 11.4). Sixty-eight of the 133 patients returned to the clinic for long-term follow-up evaluation. Objectively, physical examination revealed no change in laxity from initial injury to follow-up. No correlation was found between radiographic joint space narrowing and grade of laxity. The mean modified Noyes knee score was 84.2 points, the mean Lysholm score was 83.4, and the mean Tegner activity score was 5.7. Patients with greater laxity did not have worse subjective scores. No correlation was found between subjective knee scores and time from injury. Regardless of the amount of laxity, half of the patients returned to the same sport at the same or higher level, one-third returned to the same sport at a lower level, and one-sixth did not return to the same sport. Results of this study suggest that athletically active patients with acute isolated posterior cruciate ligament tears treated nonoperatively achieved a level of objective and subjective knee function that was independent of the grade of laxity.

The natural history of acute, isolated, nonoperatively treated posterior cruciate ligament injuries. A prospective study.

A computer-assisted surgical system and method are described herein. The computer-assisted surgical system comprises a computer including three-dimensional models of anatomical structures and a user interface including a position sensing system to register in real-time the relative positions of the anatomical structures of interest and of a surgical tool. Interactions between the tool and the anatomical structure are displayed on a monitor using the three-dimensional models. Multi-view display, transparency display and use of cutting planes allow the surgeon to visualize the interaction between the tool and the anatomical structures any time during the surgical procedure. The system can also predict the constraint on anatomical structures before surgery.

Interactive computer-assisted surgical system and method thereof

Overall, vertebroplasty has a low complication rate. Nevertheless, severe complications can occur. The majority of these are related to cement extrusion. The rate of cement leakage is often obtained by X-ray, with only a single leak registration per vertebra. Detection rate of leaks in comparison with CT and inter-observer reliability for X-ray is, in large parts, unknown. We conducted this study to determine the value of fluoroscopy and X-ray used to detect cement leakage as compared to CT scans. Intraoperative findings in lateral fluoroscopy by the surgeon, and postoperative findings in X-rays by two orthopaedic surgeons, were compared with CT scans for the same study group. Multiple cement leakage was considered, and agreement rate was determined. The detection rate for leaks was 34% for lateral X-ray and 48% for lateral and AP view. Additional AP views only enhanced the detection of leaks in the segmental veins. The agreement rate between fluoroscopy/X-ray and CT scans ranged between 66% and 74%, while inter-observer reliability showed only fair agreement. The rate of cement leaks in vertebroplasty is high if multiple leaks are considered in CT scans. Detection rates using X-rays are low and complicated by only fair inter-observer agreement. Leaks in the basivertebral veins are frequently misinterpreted and can lead to severe complications. Therefore, CT scans should be obtained to calculate the exact leakage rate and to assess persistent or new pain occurring postoperatively.

/pdf/cement-leakage-during-vertebroplasty-an-underestimated-18s3qjzr7a.pdf

Cement leakage during vertebroplasty: an underestimated problem?

Study Design. Prospective clinical study with postoperative radiologic control of pedicle screw placement in the cervical spine. Objectives. To evaluate whether cervical pedicle screws can be placed safely in a conventional technique when using cannulated screws and separate stab incisions. Also, to evaluate if accuracy and safety of pedicle screw placement can be improved using a computer-assisted surgery (CAS) system (VectorVision®; BrainLAB AG, Heimstetten, Germany). Summary of Background Data. Pedicle screws are rarely used in the cervical spine compared to the use in lumbar and thoracic spine. The main reason is probably the potential risk of iatrogenic damage to the spinal cord, nerve roots, or vertebral artery caused by screw misplacement as well as the more demanding technique of pedicle screw placement in the cervical spine. Methods. A total of 52 consecutive patients with posterior cervical or cervicothoracic instrumentations using pedicle screws were evaluated prospectively. For the first 20 patients, 93 pedicle screws were implanted using the conventional technique with the image intensifier in the lateral view, and for the next 32 patients (167 screws), a CAS system was additionally used. For registration of the vertebra, surface-matching algorithms were used. For evaluation of screw placement, postoperative computerized tomography with multiplanar reconstructions in the screw axis was performed for each screw. Results. No implant-related complications were observed. No neurologic or vascular complications were found related to pedicle screws. The rate of pedicle perforations was 8.6% (8 screws) in the conventional group and 3.0% (5 screws) in the CAS group, and in all cases, less than 2-mm displacement. None of the screws with pedicle perforation had to be revised as a result of nonsufficient biomechanical stability or compression of neural/vascular structures. Conclusions. Transpedicular screws in the cervical spine and cervicothoracic junction can be applied safely and with high accuracy in a conventional technique. Cannulated screws and the use of separate stab incisions from C3–C6 with a trocar system allow for reduced screw misplacement rates. The CAS system leads to significantly reduced screw misplacement rates. Therefore, because of the potential risk of injury to the vertebral artery and neural elements, the use of a CAS system seems to be beneficial, especially for pedicle instrumentation C3–C6.

Cervical pedicle screws: conventional versus computer-assisted placement of cannulated screws.

STUDY DESIGN: Six different techniques for atlantoaxial fixation were biomechanically compared in vitro by nondestructive testing. OBJECTIVE: To evaluate the immediate three-dimensional stability of a new atlas claw combined with transarticular screws and alternative techniques for transarticular screw fixation in comparison with established techniques. SUMMARY OF BACKGROUND DATA: Posterior transarticular screw fixation in combination with wire-bone graft constructs is frequently used for C1-C2 fixation. Sublaminar wire passage carries the potential risk of neurologic complication. Transarticular screw fixation is technically demanding and, for anatomic reasons, not always feasible. METHODS: Six human cervical specimens were loaded nondestructively with pure moments, and unconstrained motion at C1-C2 was measured. The six specimens were instrumented with each of the following fixation techniques: Gallie fixation, transarticular screws and Gallie fixation, transarticular screws, transarticular screws and a new atlas claw, isthmic screws in the axis and the atlas claw, and lateral mass screws in the atlas and isthmic screws in the axis connected with rods. RESULTS: The transarticular screws restricted lateral bending and axial rotation best. The three-point fixations (transarticular + Gallie and transarticular + claw) additionally restricted flexion-extension, with lowest values for transarticular screws and the atlas claw. The alternative techniques were not as stable as the three-point fixations, but more stable than the Gallie fixation. CONCLUSIONS: Biomechanically, the three-point fixation with transarticular screws and the atlas claw provides a rigid internal fixation that is not dependent on bone graft and sublaminar wiring. In cases wherein transarticular screws are not feasible, the isthmic screws and claw or the lateral mass screws and isthmic screws are biomechanical alternatives with less immediate stability.

Posterior atlantoaxial fixation: biomechanical in vitro comparison of six different techniques.

Transarticular C1/2 screws are widely used in posterior cervical spine instrumentation. The use of pedicle screws in the cervical spine remains uncommon. Due to superior biomechanical stability compared to lateral mass screws, pedicle screws can be used, especially for patients with poor bone quality or defects in the anterior column. Nevertheless there are potential risks of iatrogenic damage to the spinal cord, nerve roots or the vertebral artery associated with both posterior cervical spine instrumentation techniques. Therefore, the aim of this study was to evaluate whether C1/2 transarticular screws as well as transpedicular screws in C3 and C4 can be applied safely and with high accuracy using a computer-assisted surgery (CAS) system. We used 13 human cadaver C0-C5 spine segments. We installed 1.4-mm Kirschner wires transarticular in C1/2, using a specially designed guide, and drilled 2.5-mm pedicle holes in C3 and C4 with the assistance of the CAS system. Hole positions were evaluated by palpation, CT and dissection. Forty-eight (92%) of the 52 drilled pedicles were correctly positioned after palpation, imaging and dissection. The vertebral artery was not injured in any specimen. All of the 26 C1/2 Kirschner wires were placed properly after imaging and dissection evaluations. No injury to vascular or bony structures was observed. C1/2 transarticular screws as well as transpedicular screws in the cervical spine can be applied safely and with high accuracy using a CAS system in vitro. Therefore, this technique may be used in a clinical setting, as it offers improved accuracy and reduced radiation dose for the patient and the medical staff. Nevertheless, users should take note of known sources of possible faults causing inaccuracies in order to prevent iatrogenic damage. Small pedicles, with a diameter of less than 4.0 mm, may not be suitable for pedicle screws.

/pdf/computer-assisted-surgery-in-posterior-instrumentation-of-2m349h3lq8.pdf

Computer-assisted surgery in posterior instrumentation of the cervical spine: an in-vitro feasibility study

We reviewed 53 of 58 patients who had primary repairs of posterior cruciate ligament injuries between 1981 and 1988. Sixteen patients had isolated posterior cruciate ligament ruptures, 16 had complex injuries with capsular and collateral ligament involvement, and 21 had additional anterior cruciate ligament ruptures. Forty-six patients were treated by transosseous multiple-loop sutures and seven with bony avulsions by screw osteosynthesis. The mean follow-up time was 7.5 years (range, 3 to 12). All patients were examined subjectively (questionnaire) and objectively (clinical examination, KT-1000 arthrometer, functional testing, radiographs, and Cybex II isokinetic strength analysis). The results were graded according to the International Knee Documentation Committee evaluation form and the Lysholm score. The average Lysholm score was 82.4 (range, 40 to 100). Thirty-eight patients returned to their preinjury activities at the same intensity level. The patients' subjective assessments were normal or nearly normal in 35 patients. The posterior drawer test was negative or 1+ in 46 patients. Cybex isokinetic strength analysis revealed a decrease in quadriceps muscle strength of the involved limb by 10.5% (P < 0.01). Our data suggest that primary repair of posterior cruciate ligament ruptures provides good results after 8 years in approximately two thirds of the patients. Distal ligamentous ruptures, lack of athletic activity, and temporary olecranization correlated with poor results. Bony avulsions, midsubstance or proximal ruptures, and athletic activity correlated with good results.

Primary Repair for Posterior Cruciate Ligament Injuries An Eight-Year Followup of Fifty-three Patients

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