RESUMO
BACKGROUND: Precontoured quadrilateral surface buttress (PQSB) plates have grown in popularity for acetabular fracture fixation. However, our experience has pushed us to hypothesize that their use as sole means of fixation may cause fracture malreduction. A biomechanical model was created to investigate this theory. METHODS: A transverse acetabular fracture was created and reduced anatomically in 18 synthetic hemipelvises. The reduced hemipelvises were fixated using 3 different techniques. Group A fixation included anterior and posterior column screws plus a suprapectineal pelvic reconstruction plate; group B models were fixed using a PQSB plate only; and group C models were fixed with an anterior column screw and a PQSB plate. Acetabular tracking points were placed before final fixation and used to quantify any postfixation displacement. One-way analysis of variance and Tukey HSD testing were used to determine the significant difference (P < 0.05). RESULTS: Models in group B had significant fracture displacement after final fixation when compared with group A and group C models. The average amount of displacement at the anterior column and within the acetabulum was 1.37 mm (95% CI, 1.08-1.65) in group B constructs compared with 0.32 mm (95% CI, 0.22-0.42) and 0.26 mm (95% CI, 0.15-0.38) in groups A and C constructs, respectively. There were no significant differences in displacement after final fixation between group A and group C models. CONCLUSIONS: PQSB plates for acetabular fractures cause malreduction when applied in isolation in this biomechanical model. If a PQSB plate is chosen for fixation, we suggest the use of a columnar lag screw at minimum to hold reduction before plate application.
Assuntos
Fixação Interna de Fraturas , Fraturas Ósseas , Acetábulo/diagnóstico por imagem , Acetábulo/cirurgia , Fenômenos Biomecânicos , Placas Ósseas , Parafusos Ósseos , Fraturas Ósseas/cirurgia , HumanosRESUMO
OBJECTIVE: To compare the stability of 3 fixation strategies for a transverse acetabular fracture: a reconstruction plate with anterior and posterior column screws (group A); an infrapectineal precontoured quadrilateral surface buttress (iPQSB) plate alone (group B); and an anterior column lag-screw and iPQSB plate (group C). METHODS: A transverse acetabular fracture was created in 18 synthetic hemipelvises. Six were fixed by each of the 3 methods described. Specimens underwent cyclic axial compressive loading to 1700N for 42,000 cycles while anterior and posterior column displacements were measured, followed 4800N for 50 cycles. Displacement and stiffness data were analyzed with analysis of variance and Tukey HSD. A Cox proportional hazards regression model was used to determine survival rate. P values < 0.05 were considered significant. RESULTS: Group C had significantly less posterior column displacement (0.16 ± 0.06 mm) compared with group B (0.38 ± 0.37 mm, P < 0.0001) and group A (0.38 ± 0.37 mm, P < 0.0001). In addition, group A had significantly more anterior column displacement (0.28 ± 0.11 mm) than group B (0.22 ± 0.14 mm, P = 0.0310) and group C (0.18 ± 0.09 mm, P = 0.0001). Group C was 10.5% stiffer than group A (P = 0.0037). Group B had a 7.27x greater rate of failure than group C (95% confidence interval, 1.6-33.2). DISCUSSION AND CONCLUSION: Under anatomical loading, iPQSB plates with anterior column lag-screw fixation demonstrate increased stability in a synthetic bone transverse acetabular fracture model. Based on our data, we support additional evaluation of early weight-bearing after transverse acetabular fracture fixation in patients with healthy bone when an anterior column screw-iPQSB plate construct is used.
Assuntos
Acetábulo/lesões , Acetábulo/cirurgia , Placas Ósseas , Parafusos Ósseos , Fixação Interna de Fraturas/instrumentação , Fixação Interna de Fraturas/métodos , Fraturas Ósseas/cirurgia , Fenômenos Biomecânicos , Desenho de Equipamento , Humanos , Modelos AnatômicosRESUMO
Introduction: Cue reactivity (CR) research has reliably demonstrated robust cue-induced responding among smokers exposed to common proximal smoking cues (eg, cigarettes, lighter). More recent work demonstrates that distal stimuli, most notably the actual environments in which smoking previously occurred, can also gain associative control over craving. In the real world, proximal cues always occur within an environment; thus, a more informative test of how cues affect smokers might be to present these two cue types simultaneously. Methods: Using a combined-cue counterbalanced CR paradigm, the present study tested the impact of proximal (smoking and neutral) + personal environment (smoking and nonsmoking places) pictorial cues, on smokers' subjective and behavioral CR; as well as the extent to which cue-induced craving predicts immediate subsequent smoking in a within-subjects design. Results: As anticipated, the dual smoking cue combination (ProxS + EnvS) led to the greatest cue-induced craving relative to the other three cue combinations (ProxS + EnvN, ProxN + EnvS, and ProxN ± EnvN), ps < .004. Dual smoking cues also led to significantly shorter post-trial latencies to smoke, ps < .01. Overall CR difference score (post-trial craving minus baseline craving) was predictive of subsequent immediate smoking indexed by: post-trial latency to smoke [B = -2.69, SE = 9.02; t(143) = -2.98, p = .003]; total puff volume [B = 2.99, SE = 1.13; t(143) = 2.65, p = .009]; and total number of puffs [B = .053, SE = .027; t(143) = 1.95, p = .05]. Conclusions: The implications of these findings for better understanding the impact of cues on smoking behavior and cessation are discussed. Implications: This novel cue reactivity study examined smokers' reactivity to combined proximal and distal smoking cues. Exposure to a combination of two smoking cues (proximal and environment) led to the greatest increases in cue-induced craving and smoking behavior compared to all other cue combinations. Further, the overall magnitude of cue-induced craving was found to significantly predict immediate subsequent smoking. This work provides new insight on how exposure to various cues and cue combinations directly affect smokers' craving and actual smoking behavior, as well as the relationship between those two indices of reactivity.