Impact of sufficient contact between the autograft and endplate soon after surgery to prevent nonunion at 12 months following posterior lumbar interbody fusion

OBJECTIVENonunion after posterior lumbar interbody fusion (PLIF) is associated with poor long-term outcomes in terms of health-related quality of life. Biomechanical factors in the fusion segment may influence spinal fusion rates. There are no reports on the relationship between intervertebral union and the absorption of autografts or vertebral endplates. Therefore, the purpose of this retrospective study was to evaluate the risk factors of nonunion after PLIF and identify preventive measures.METHODSThe authors analyzed 138 patients who underwent 1-level PLIF between 2016 and 2018 (75 males, 63 females; mean age 67 years; minimum follow-up period 12 months). Lumbar CT images obtained soon after the surgery and at 6 and 12 months of follow-up were examined for the mean total occupancy rate of the autograft, presence of a translucent zone between the autograft and endplate (more than 50% of vertebral diameter), cage subsidence, and screw loosening. Complete intervertebral union was defined as the presence of both upper and lower complete fusion in the center cage regions on coronal and sagittal CT slices at 12 months postoperatively. Patients were classified into either union or nonunion groups.RESULTSComplete union after PLIF was observed in 62 patients (45%), while nonunion was observed in 76 patients (55%). The mean total occupancy rate of the autograft immediately after the surgery was higher in the union group than in the nonunion group (59% vs 53%; p = 0.046). At 12 months postoperatively, the total occupancy rate of the autograft had decreased by 5.4% in the union group and by 11.9% in the nonunion group (p = 0.020). A translucent zone between the autograft and endplate immediately after the surgery was observed in 14 and 38 patients (23% and 50%) in the union and nonunion groups, respectively (p = 0.001). The nonunion group had a significantly higher proportion of cases with cage subsidence and screw loosening at 12 months postoperatively in comparison to the union group (p = 0.010 and p = 0.009, respectively).CONCLUSIONSA lower occupancy rate of the autograft and the presence of a translucent zone between the autograft and endplate immediately after the surgery were associated with nonunion at 12 months after PLIF. It may be important to achieve sufficient contact between the autograft and endplate intraoperatively for osseous union enhancement and to avoid excessive absorption of the autograft. The achievement of complete intervertebral union may decrease the incidence of cage subsidence or screw loosening.

Optimized Screw Trajectory for Lumbar Cortical Bone Trajectory Pedicle Screws Based on Clinical Outcome: Evidence Favoring the Buttress Effect Theory

Background Cortical bone trajectory (CBT) is a relatively new technique for pedicle screw insertion in the field of spine surgery. Previous studies have demonstrated the significantly better pullout and toggle characteristics the new method offers, and it appears to have certain advantages over the widely used traditional trajectory. The mechanism of the pullout and toggle characteristics still remains unknown. Purpose To report the medium- to long-term follow-up findings of patients who underwent posterior lumbar interbody fusion or posterior lumbar fusion (PLIF/PLF) at our institution and to discuss the ideal screw trajectory when using this technique. Study Design Retrospective radiologic study. Methods Fifty-five patients who underwent PLIF/PLF for lumbar spondylosis using the new technique between January 2011 and January 2016 were included. Clinical outcome was assessed using the Japanese Orthopaedic Association scores for low back pain and visual analog scale scores. Screw loosening was evaluated via the presence of a translucent zone surrounding the pedicle screw using plain X-radiography (Xp). The screw trajectory was evaluated by measuring the rostral range (RR) and the lateral range score (LRS). The RR is the angle between the line drawn along the distal end plate of the vertebra and the line drawn along the screw on the lateral view. The LRS is the score given depending on the position of the tip of the screw seen on the Xp taken in the anteroposterior (AP) view. The pedicle ring is equally divided into the medial third (zone A), central third (zone B), and the lateral third (zone C) by four vertical lines. A score of 0 to 3 points is given depending on the position of the tip of the screw: 0, outside the pedicle ring; 1, zone A; 2, zone B; and 3, zone C. Results Bone fusion was recorded in 49 patients (49/55 patients). The total number of screws with a visible translucent zone on Xp was 26 (26/242 screws). When the screws are inserted at a more acute angle in the lateral view (low RR) or when the screws are directed more medially (low LRS), the risk of developing a translucent zone around the pedicle screw increased. Conclusion With CBT, the pedicle screws are inserted from the pars interarticularis that is rich in cortical bone, strong enough to withstand the substantial forces usually encountered in the region. Our clinical data suggest that the optimal screw trajectory is one where the screw is inserted at an angle > 22.55 degrees (high RR) on the lateral view Xp and where the tip of the screw is directed toward the lateral third of the pedicle on the AP Xp. We believe the naturally occurring buttress effect that exists in the vertebra may give CBT a mechanical and anatomical advantage over the traditional screw trajectory.

Clinical protocol for the registration of individual translucent zones of frontal teeth

In contemporary dentistry, a successful restoration should not only restore the shape and function of the impaired dentition, but also contribute to the overall aesthetic appearance. In order to achieve this goal, the dental team should possess complete information about the different optical dimensions of the tooth structure. Besides the standard properties of the color, it is important to define, register and interpret the shape and position of the individual translucent zone.With the help of a device and software developed by the authors, a five step clinical protocol has been developed by the authors for individual translucent zone registration, with the help of trans-illumination. The translucent areas are then shown in a digital photograph of the teeth, analyzed and interpreted. The translucent zone is finally visualized as a ‘translucent map’, which is clearly defined, and is easily interpreted and used by the dental team.

age and growth in a temperate euryhaline notothenioid, eleginops maclovinus from the falkland islands

falkland islands' mullet (eleginops maclovinus) were aged successfully using whole sagittal otoliths from 1403 individuals. marginal increment analysis indicated that one opaque and one translucent zone were laid down annually. unvalidated daily ring counts confirmed what was thought to be the first translucent zone. the translucent zones were found to form earlier in juveniles than in adults. juveniles over winter in the creeks and inlets whereas adults are more common in deeper inshore waters where there is a one month lag in the minimum winter water-temperature. the maximum observed age was found to be 11 years. the calculated von bertalanffy growth model (lt=124.41(1−e−0.14/year(t-0.01years))) showed that e. maclovinus is a fast-growing fish, growing on average 10.2 cm/year for the first six years of its life.

Growth Zones within the Statolith Microstructure of the Deepwater Squid Moroteuthis ingens (Cephalopoda: Onychoteuthidae): Evidence for a Habitat Shift?

Within the statoliths of the onychoteuthid squid Moroteuthis ingens captured off the southeast coast and the Chatham Rise (New Zealand} between 500 and 1239 m depth, there were conspicuous zones consisting of an inner opaque and outer translucent zone; these strikingly resembled zones observed in some teleost fish otoliths. There was no relationship between the number of increments within the opaque zone among individuals of different length and age, but the width of the opaque zone was negatively related to both mantle length and age. The smallest juveniles captured in bottom trawls had a narrow translucent zone relative to the opaque zone which suggested that the translucent zone is laid down after settlement and that settlement takes place probably at or before 160 mm mantle length in this species. This study suggests that the transition observed within the statolith microstructure of M. ingens represents a habitat change from an epipelagic habitat to a demersal habitat. Evidence for the hypothesis is drawn from analogous features observed within teleost otolith microstructure and from available information on Moroteuthis and Onykia.

Age determination of harbour porpoise, Phocoena phocoena (L.), in the western North Atlantic

Age, based on analysis of dentinal growth layers, was determined in a sample of 121 harbour porpoises, Phocoena phocoena (L.), from western North Atlantic waters. One growth layer, consisting of a thick opaque zone and a relatively thin translucent zone, is deposited each year.Mean thicknesses of opaque and translucent zones in males and females were 347 μm, 114 μm, 432 μm, and 125 μm, respectively. Significant reduction in thicknesses of growth layers with age was found in both sexes, the major contribution in both cases being progressive reduction in thickness of the opaque zones. Translucent-zone thickness decreased with age in males, but significantly increased in thickness in females. Formation of the opaque zone occurs from June through February, and formation of the translucent zone from January to early September. This overlap is attributed to the protracted calving season of this population, and precludes any simple relationship between food supply and zonation, as proposed by others. Age–length relationships based on numbers of dentinal layers were calculated for males and females using regression analysis. Best fits of body length (b) against age (expressed by completed dentinal layers) (d) were obtained from the curvilinear equations: d = [b/(−1.30b + 209.35)] −1 for males, and d = [b/(−0.84b + 156.15)] −1 for females.

Age, Growth, and Maturity of Bottlenosed Dolphin (Tursiops truncatus) from Northeast Florida

It is confirmed that one growth layer consisting of one opaque and one translucent zone is laid down annually in the dentine of the teeth of bottlenosed dolphin (Tursiops truncatus), allowing absolute age determination, although the seasonal sequence of dentine deposition is not yet clear. On this basis females from northeast Florida were found to mature at about 12 years and males at 13 years, both sexes living to about 25 years of age. Females accumulated up to 14 corpora albicantia in the ovaries, indicating an accumulation rate of about one per annum. Birth occurred at 100-cm length. Males and females matured at about 245- and 235-cm length, respectively, and attained asymptotic lengths of about 270 and 250 cm.