Pedro Augusto Pontin

Epidemiologic study of ankle fractures in a tertiary hospital

OBJECTIVES: To evaluate the epidemiology of ankle fractures surgically treated at the Instituto de Ortopedia e Traumatologia do Hospital das Clínicas da Universidade de São Paulo. METHODS: Medical records of patients admitted with foot and ankle fractures between 2006 and 2011 were revised. Seventy three ankle fractures that underwent surgical treatment were identified. The parameters analyzed included age, gender, injured side, AO and Gustilo & Anderson classification, associated injuries, exposure, need to urgent treatment, time to definitive treatment and early post-operative complications. Study design: retrospective epidemiological study. RESULTS: Male gender was predominant among subjects and the mean age was 27.5 years old. Thirty nine fractures resulted from traffic accidents and type B fracture according to AO classification was the most common. Twenty one were open fractures and 22 patients had associated injuries. The average time to definitive treatment was 6.5 days. Early post-operative complications were found in 21.3% of patients. CONCLUSIONS: Ankle fractures treated in a tertiary hospital of a large city in Brazil affect young people victims of high-energy accidents and present significant rates of associated injuries and post-operative complications. Level of Evidence IV, Cases Series.

Novel animal model for Achilles tendinopathy: Controlled experimental study of serial injections of collagenase in rabbits

Our goal was to develop a novel technique for inducing Achilles tendinopathy in animal models which more accurately represents the progressive histological and biomechanical characteristic of chronic Achilles tendinopathy in humans. In this animal research study, forty-five rabbits were randomly assigned to three groups and given bilateral Achilles injections. Low dose (LD group) (n = 18) underwent a novel technique with three low-dose (0.1mg) injections of collagenase that were separated by two weeks, the high dose group (HD) (n = 18) underwent traditional single high-dose (0.3mg) injections, and the third group were controls (n = 9). Six rabbits were sacrificed from each experimental group (LD and HD) at 10, 12 and 16 weeks. Control animals were sacrificed after 16 weeks. Histological and biomechanical properties were then compared in all three groups. At 10 weeks, Bonar score and tendon cross sectional area was highest in HD group, with impaired biomechanical properties compared to LD group. At 12 weeks, Bonar score was higher in LD group, with similar biomechanical findings when compared to HD group. After 16 weeks, Bonar score was significantly increased for both LD group (11,8±2,28) and HD group (5,6±2,51), when compared to controls (2±0,76). LD group showed more pronounced histological and biomechanical findings, including cross sectional area of the tendon, Young’s modulus, yield stress and ultimate tensile strength. In conclusion, Achilles tendinopathy in animal models that were induced by serial injections of low-dose collagenase showed more pronounced histological and biomechanical findings after 16 weeks than traditional techniques, mimicking better the progressive and chronic characteristic of the tendinopathy in humans.

Polymorphisms of Alpha and Beta Estrogen Receptors in Post-Menopausal Women with Posterior Tibial Tendon Dysfunction

Category: Basic Sciences/Biologics Introduction/Purpose: Posterior tibial tendon dysfunction (PTTD), the most common cause of flatfoot deformity in adults, is more frequent in the female gender with peak incidence in the sixth decade of life. Multiple risk factors - intrinsic and extrinsic - and associated systemic conditions have been described in the literature. Genetic predisposition secondary to hyperexpression of genes related to hormonal metabolism, particularly the estrogens, may play a role in the pathogenesis of this disease acting in association with behavioral and endogenous risk factors. Methods: 202 female patients over the age of 40 were included in the study (N = 202). They were then divided into 2 different groups (n = 101): cases and controls. We defined as cases postmenopausal women with symptomatic PTTD, diagnosed by clinical and MRI examinations. Females with similar epidemiology, but clinically asymptomatic and with normal MRI evaluation for the posterior tibial tendon were defined as controls. Oral mucosa epithelial cells were collected from the patients and genomic DNA was extracted from the samples. The SNPs for the ER1 (XbaI and PvuII) and ER2 (AluI) genes were assessed by PCR-RFLP. Results: Patients with SNP Xbal genotype xx had 2.38 higher estimated risk (p = 0,029) in developing PTTD, when compared to patients with the other genotypes. No associations were found for the SNP PvuII and AluI. Conclusion: The present study demonstrates that patients with the Xbal single nucleotide polymorphism of estrogen receptor 1 gene have higher risk of developing posterior tibial tendon dysfunction.

EPIDEMIOLOGICAL STUDY ON LISFRANC INJURIES

ABSTRACT Objective: To analyze the characteristics of patients with Lisfranc injuries and their associated fractures. Methods: This is a retrospective analysis on 42 patients with Lisfranc injuries hospitalized at Instituto de Ortopedia e Traumatologia do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, between 2006 and 2010. Parameters on patient profile, risk factors, fracture characteristics, data on treatment and acute complications were analyzed. Results: Analysis of 42 cases showed that in our sample, men were more affected than women, with a ratio of 4.25:1. The most frequent trauma mechanism was car accident, followed by motorcycle accident. The most frequent type of injury was isolated lesion type B of Quenu and Kuss classification, representing 50% of cases. The most common fracture on the sample was the second metatarsal bone, with 16 cases, followed by cuboid bone fracture. Among the 42 cases, 17% had exposed fractures and 33 patients presented other associated fractures. The mean time elapsed between the trauma and definitive treatment was 6.7 days, while the mean length of hospital stay was 13.8 days. Six patients presented acute postoperative complications. Conclusion: Lisfranc injuries are more common in men undergoing automobile trauma. The prevalence of associated fractures is a frequent finding and the hospital stay may be longstanding.Level of Evidence IV, Case Series.

Tendinopathy Induced by Serial Low-Dose Collagenase Injections A Novel Experimental Animal Model in the Achilles Tendon of Rabbits

Category: Basic Sciences/Biologics Introduction/Purpose: Numerous studies, as evident in literature, have attempted to develop an induced Achilles tendinopathy animal model. The most common models include collagenase injections and mechanical overload of the tendon, but both are controversial. The mechanical overload model creates a chronically induced tendinopathy and is time intensive. In addition, once the stimulus is removed the tissue changes often heal. The collagenase injection model is quicker, rarely evolve to healing but frequently results in an early acute tendon reaction. The primary objective of this study is to compare biomechanical and histological findings between two collagenase induced Achilles tendinopathy protocols. The hypothesis is that consecutive low-dose collagenase injections will result in progressive and long-lasting tendinopathy findings as compared to the traditional single high-dose injection. Methods: In this IRB approved study, the population was composed of forty-eight (n=48) New Zealand breed rabbits. Forty-two (n=42) rabbits were randomly divided into two groups (n=21). The first group, which served as the control, had both Achilles tendons injected by a single dose (0.3 mg) of A1 collagenase (Sigma-Aldrich©), as described in literature. The second experimental group had three low-dose injections (0.10 mg) with 2 weeks between each injection. Another six animals (n=6) were also randomized into two groups (n=3) receiving one-dose versus 3 injections of saline solution with 2 weeks between each injection. The animals were euthanized after 10, 12 and 16 weeks. Histological and biomechanic analysis of the Achilles tendons were carried out using a dynamic mechanical testing machine (Electropuls®, model E10000, Instron®). Mechanical strength and histological scores of tendinopathy (Bonar scoring system) were compared among the groups at each time-point. Results: After 16 weeks, all biomechanical and histological parameters analysed showed consistent differences between the groups (p < 0.05), with more pronounced and long-lasting tendinopathy findings in the Achilles tendon of the experimental group (serial collagenase injections), when compared to the control groups (single collagenase dose and single/multiple saline injections). The mean Bonar sum-score of tendons after 16 weeks in the experimental group was greater than the mean histologic score of control tendons (8.53 ± 1.52 versus 1.1 ± 0.83 in saline group and 5.2 ± 1.12 in single dose group). No statistically significant differences were found between the different collagenase injection groups at weeks 10 and 12. Conclusion: The protocol of three consecutive low-dose collagenase injections has shown biomechanical and histological findings compatible with progressive and long-lasting tendinopathy as compared to single high-dose injection. This protocol represents a feasible and effective animal model of induced Achilles tendinopathy.