Hugo Henríquez

Genotypic interaction between DRD4 and DAT1 loci is a high risk factor for attention-deficit/hyperactivity disorder in Chilean families.

Attention‐deficit/hyperactivity disorder, ADHD [MIM 126452], is a common, highly heritable neurobiological disorder of childhood onset, characterized by hyperactivity, impulsiveness, and/or inattentiveness. As part of an ongoing study of ADHD, we carried out a family‐based discordant sib‐pair analysis to detect possible associations between dopamine receptor D4 (DRD4) and dopamine transporter 1 (DAT1) polymorphisms and ADHD in Chilean families. Both loci individually classified as homozygotes or heterozygotes for the DRD4 7‐repeat and DAT1 10‐repeat alleles, did not exhibit genotype frequency differences between affected children and their healthy siblings (Fishers exact test P > 0.25 in both cases). However, the simultaneous presence of both DRD4 7‐repeat heterozygosity and DAT1 10 allele homozygosity were significantly higher (34.6%) in cases (26), compared with their unaffected siblings (25) (4%; Fishers exact test P = 0.0096; odds‐ratio, OR = 12.71). Increased density of dopamine transporter in ADHD brains, along with abundance of 7‐repeat D4 receptors in prefrontal cortex, which is impaired in ADHD patients, make the observed gene–gene interaction worthy of further incisive studies.

Continuous popliteal block for postoperative analgesia in total ankle arthroplasty.

Background: Total ankle arthroplasty is associated with severe postoperative pain. Development of analgesic techniques such as a block with continuous infusion at the popliteal level has been shown to result in good pain control, a decrease in the use of rescue analgesia and a low rate of complications. We reviewed our experience with this method of analgesia in patients who underwent total ankle arthroplasty. Methods: A prospective study of 30 patients undergoing total ankle arthroplasty was carried out. Twenty-two of these received and maintained a block at the popliteal level with a continuous infusion of bupivacaine, while the remaining eight received no such block. Results: The visual analog scale evaluation (VAS) showed a significant improvement in pain control in the group with the popliteal block after 6, 12, 18, and 24 hours postsurgery, with pain levels peaking and being most different between 6 and 12 hours postsurgery for the two groups. The group with the popliteal block also exhibited a significantly lower consumption of morphine and a greater degree of patient satisfaction. Conclusion: The block with continuous infusion at the popliteal fossa was a safe technique for total ankle arthroplasty postoperative analgesia, which provided good pain control, a lower requirement of opiates and a higher level of patient satisfaction. Level of Evidence: II; Prospective Comparative Study

Postoperative Range of Motion Trends Following Total Ankle Arthroplasty

Background: It is still unknown how ankle range of motion changes following total ankle arthroplasty. This study was undertaken to more accurately address patient expectations, guide postoperative rehabilitation, and improve our understanding of how ankle range of motion changes with time. Methods: 119 total ankle replacements of 3 different prosthetic designs from 1 surgeon were retrospectively examined and compared. Ankle dorsiflexion and plantar flexion ranges of motion were calculated and analyzed preoperatively and postoperatively at 6 weeks, 3 months, 6 months, and 1 year. The different ankle replacement systems were analyzed individually and together to determine whether trends were replicated. Results: No significant increase in ankle range of motion was found 6 months postoperatively (P = .75). Mean combined postoperative range of motion did not change significantly from 24.3 degrees at 1 year versus a preoperative mean of 22.7 degrees (P = .75). Mean dorsiflexion improved significantly at the 6-week postoperative stage by 5.5 degrees (P < .001), whereas plantar flexion only improved by 2.9 degrees (P = .06). Mean dorsiflexion improved from preoperative levels by 5.4 degrees (P = .001), whereas mean plantar flexion decreased by 3.7 degrees (P = .004). Conclusions: We found no notable improvement in ankle range of motion after 6 months following total ankle arthroplasty. We also found a disproportionately higher increase in dorsiflexion compared with plantar flexion following surgery and an overall reduction in mean plantar flexion range compared with preoperative values. Notwithstanding this discrepancy, total mean ankle range of motion 1 year postoperatively was similar to preoperative values. Reasons for the discrepancy between dorsiflexion and plantar flexion are unclear. Level of Evidence: Level III, retrospective comparative study.

Are locking plates better than non-locking plates for treating distal tibial fractures?

BACKGROUND Locking and non-locking plates has been used for distal tibia fracture osteosynthesis. Sufficient evidence to favor one implant over the other is lacking in the current literature. Our aim is to compare them in terms of fracture healing, alignment, functional outcome, complications. METHODS Sixty-eight patients operated on using a percutaneous plate were retrospectively reviewed. They were divided into two groups: in group 1 (28 patients) a 4.5mm narrow conventional dynamic compression plate (DCP) was used. In group 2 (40 patients) a titanium locked compression plate (LCP) was used. RESULTS Mean time to union was 16.2 and 15.4 weeks for group 1 and 2, respectively (p=0.618). 11 patients (39.3%) in group 1 and 4 patients (10%) in group 2 showed malalignment (p=0.016). AOFAS scores at follow up were 89 and 88 in groups 1 and 2, respectively. Implant removal was necessary in 9 cases (32.1%) and 4 cases (10%) in group 1 and group 2, respectively (p=0.042). Three patients (10.7%) in group 1 and three patients (7.5%) in group 2 had an infection. CONCLUSIONS Both plating systems have similar results in terms of time to union, infection, and AOFAS scores. The LCP seems superior with respect to alignment and the need for implant removal.

Origen y microdiferenciación de la población del Archipiélago de Chiloé

Las etnias originarias del archipielago de Chiloe presentan caracteristicas culturales que plantean preguntas acerca de su origen como entidad genetica independiente y distinta del grupo continental. Al respecto, hemos caracterizado las frecuencias de los cuatro haplogrupos amerindios fundadores del ADN mitocondrial en cuatro poblaciones del archipielago. El componente aborigen materno de estas poblaciones fue superior al 90 %. El analisis de distancias geneticas sugiere una segregacion norte-sur en donde las poblaciones septentrionales aparecen mas relacionadas con la etnia continental Huilliche. Aun cuando el analisis de diferenciacion interpoblacional y de componentes principales muestran una singularidad en el grupo insular, esta puede ser interpretada a partir de datos geneticos, etnohistoricos y arqueologicos

Biomechanical properties of different techniques used in vitro for suturing mid-substance Achilles tendon ruptures

Background: The Dresden technique preserves the paratenon during Achilles tendon repair and may improve the plantarflexor mechanism when combined with mobilization during early rehabilitation. However, the surgical repair design for Achilles tendon ruptures can affect rates of re‐rupture or lengthening. Therefore, the aim of this study was to determine the biomechanical properties of the Krackow, Double‐Kessler, Double‐Dresden, and Triple‐Dresden techniques used for repairing mid‐substance Achilles tendon ruptures during cyclical and maximum traction. Methods: Sixty mid‐substance bovine tendons repaired after transverse rupturing were divided randomly into four groups by repair technique: Krackow, Double‐Kessler, Double‐Dresden, and Triple‐Dresden. Cyclical tractions of 4.7, 5.8, 7.9, and 11.7 mm (equivalent to 5°, 8°, 10°, and 15° of dorsal flexion, respectively) were applied to determine gapping, tensile strength, nominal suture stress, repair deformation, and specimens with clinical failure (gap > 5 mm). Maximal traction was applied to measure maximum strength and failure type (i.e. suture, knot, or tendon). Findings: The Triple‐Dresden technique resulted in decreased gapping, nominal suture stress, repair deformation, and quantity of specimens with clinical failure as compared to the other techniques. Furthermore, Triple‐Dresden tendons showed greater comparative tensile and maximum strength. During maximal traction testing, this technique presented tendon failure, whereas the Krackow, Double‐Kessler, and Double‐Dresden techniques had suture failures. Interpretation: Triple‐Dresden repair results in better cyclical and maximum traction strengths, suggesting that this technique might be more appropriate when performing early mobilization after mid‐substance Achilles tendon rupture repair. HighlightsTriple‐Dresden technique prevents gap generation during cyclical traction of Achilles tendon.Triple‐Dresden technique provides greater strength capacity after mid‐substance rupture.Triple‐Dresden technique tolerates clinical failure in Achilles tendon until 10° of dorsal flexion.Triple‐Dresden might be more appropriate when performing early mobilization after mid‐substance.

Changes in the ankle muscles co-activation pattern after 5 years following total ankle joint replacement

Background: The Hintegra® arthroplasty provides inversion‐eversion stability, permits axial rotation, ankle flexion‐extension, and improvements of the gait patterns are expected up to 12 months of rehabilitation. However, sensorimotor impairments are observed in ankle flexors/extensors muscles after rehabilitation, with potential negative effects on locomotion. Here we determined the timing and amplitude of co‐activation of the tibialis anterior and medial gastrocnemius muscles during gait by assessing non‐operated and operated legs of patients with total ankle replacement, 5 years after surgery. Methods: Twenty‐nine patients (age: 58 [5.5] years, height: 156.4 [6.5] cm, body mass: 72.9 [6.5] kg, 10 men, and 19 women) that underwent Hintegra® ankle arthroplasty were included. Inclusion criteria included 5 years prosthesis survivorship. The onset and offset of muscle activation (timing), as well as the amplitude of activation, were determined during barefoot walking at self‐selected speed by surface electromyography. The timing, percentage, and index of co‐activation between the tibialis anterior and medial gastrocnemius were quantified and compared between non‐operated and operated legs. Findings: The operated leg showed higher co‐activation index and temporal overlapping between tibialis anterior and medial gastrocnemius during gait (p < 0.001). Interpretation: The neuromuscular changes developed during the process of degeneration do not appear to be restored 5 years following arthroplasty. The insertion of an ankle implant may restore anatomy and alignment but neuromuscular adaptations to degeneration are not corrected by 5 years following joint replacement.

¿Es la técnica Dresden un diseño mecánico de elección apropiado para la reparación de roturas de tercio medio del tendón de Aquiles? Ensayo biomecánico

OBJECTIVE To compare the mechanical failure of the Dresden technique for Achilles tendon repair with the double modified Kessler technique controlled repair technique. The maximum resistance of the two repair techniques are also compared. MATERIAL AND METHODS A total of 30 Achilles tendon ruptures in bovine specimens were repaired with an Ethibond(®) suture to 4.5cm from the calcaneal insertion. Each rupture was randomly distributed into one of two surgical groups. After repair, each specimen was subjected to a maximum traction test. The mechanical failure (tendon, suture, or knot) rates (proportions) were compared using the exact Fisher test (α=.05), and the maximum resistances using the Student t test (α=.05). RESULTS There was a difference in the proportions of mechanical failures, with the most frequent being a tendon tear in the Dresden technique, and a rupture of the suture in the Kessler technique. DISCUSSION The repair using the Dresden technique performed in the open mode, compared to the Kessler technique, has a more suitable mechanical design for the repair of middle third Achilles tendon ruptures on developing a higher tensile resistance in 58.7%. However, its most common mechanical failure was a tendon tear, which due to inappropriate loads could lead to lengthening of the Achilles tendon.