Three new and exceptional Damarchus species from Thailand (Araneae: Bemmeridae).

Damarchus pylorus sp. nov., D. lanna sp. nov. and D. dao sp. nov. are described from males and females collected in western and northern Thailand. Damarchus pylorus sp. nov. and D. lanna sp. nov. are morphologically unique within the genus by males having a para-embolic apophysis and a keel composed of coarse laminae on the lower (posterior) side of the palpal organ, and by females having sperm receptacles, composed of a strongly sclerotized base and an unsclerotized head, situated on the ventral side of a relatively long genital atrium. The distantly related D. dao sp. nov. is distinguished from all other congeners by males having a tibia I coupling spur with three megaspines. Presumed relationships of these three species and of the genus Damarchus are discussed. Information on biology and burrow structures of the new species is provided. Damarchus pylorus sp. nov. stands out by plugging the side shaft of its burrow with a soil pellet; similar plugging devices in unbranched burrows are known from other spider families.

Descriptions of four new trapdoor spider species in the subfamily Ummidiinae from Thailand (Araneae, Mygalomorphae, Halonoproctidae).

Males and females of four mygalomorph spider species (family Halonoproctidae, subfamily Ummidiinae) are newly described from Thailand, and the taxonomy of Ummidiinae is discussed. This is the first time that trapdoor spider species in this subfamily are described from Thailand. Two of these new species belong to the genus Conothele, the other two species are placed in the genus Latouchia. Conothele martensi spec. nov. was found in the north of the country (Chiang Mai Province), C. isan spec. nov. and Latouchia incerta spec. nov. were collected in northeastern Thailand (Buri Ram Province, Surin Province and Roi Et Province), and L. maculosa spec. nov. was found in the southern coastal province of Prachuap Khiri Khan.

Preface.

To process a Festschrift is an honour and a unique opportunity to show respect to someone who made important contributions over many years in a special field of scientific research. In the case of Jochen Martens the contribution is to not only in one field, but in several: harvestmen, birds, high mountains, taxonomy, systematics, evolution etc.

Single column plate plus other column lag screw fixation vs. both column plate fixation for anterior column with posterior hemitransverse acetabular fractures - a biomechanical analysis using different loading protocols.

OBJECTIVES: Open reduction and internal fixation of both columns is considered the treatment of choice for displaced anterior column with posterior hemitransverse (ACPHT) fractures in non-geriatric patients. Plate fixation of one column combined with lag screw fixation of the other column allows to decrease operative time and approach-related morbidity compared to conventional both column plating. The aim of this biomechanical study was to evaluate whether single column plate plus other column lag screw fixation confers similar stability to both column plate fixation. Physiological loads were simulated using both the single-leg stance (SLS) as well as the sit-to-stand (STS) loading protocols. METHODS: A clinically relevant ACPHT fracture model was created using fourth-generation composite hemipelves. Fractures were stabilized with three different fixation constructs: (1) anterior column plate plus posterior column screw fixation (AP+PCS), posterior column plate plus anterior column screw fixation (PP+ACS) and anterior column plate plus posterior column plate fixation (AP+PP). Specimens were loaded from 50 to 750 N with a ramp of 100 N/s. Fracture gap motion (FGM) and relative interfragmentary rotation (RIFR) between the three main fracture fragments were assessed under loads of 750 N using an optical 3D measurement system. RESULTS: STS loading generally resulted in higher mean FGM and RIFR than STS loading in the AP+PCS and AP+PP groups, while no significant differences were found in the PP+ACS group. Compared to conventional both column plate fixation (AP+PP), PP+ACS displayed significantly higher FGM and RIFR between the iliac wing and the posterior column during SLS loading. No significant differences in FGM and RIFR were identified between the AP+PCS and the AP+PP group. CONCLUSION: Overall, single column plate plus other column lag screw fixation conferred similar stability to conventional both column plate fixation. From a clinical point of view, AP+PCS appears to be the most attractive alternative to conventional AP+PP for internal fixation of ACPHT fractures.

Biomechanical comparison of fixation techniques for transverse acetabular fractures - Single-leg stance vs. sit-to-stand loading.

OBJECTIVES: To biomechanically compare five different fixation techniques for transverse acetabular fractures using both the single-leg stance (SLS) and the sit-to-stand (STS) loading protocols and to directly compare fracture gap motion (FGM) and relative interfragmentary rotation (RIFR). METHODS: Transtectal transverse acetabular fractures were created on fourth-generation composite hemipelves in a reproducible manner. Five different fixation techniques were biomechanically assessed using both an SLS and STS loading protocol: anterior plate (AP) only, posterior plate (PP) only, anterior plate plus posterior column screw (AP+PCS), posterior plate plus anterior column screw (PP+ACS) and anterior plus posterior plate (AP+PP). After preconditioning, the specimens were loaded from 50 to 750 N with a ramp of 100 N/s. FGM and RIFR under loads of 750 N were measured using an optical 3D measurement system. RESULTS: In the three groups of fixation techniques addressing both columns, STS loading resulted in higher mean FGM and in RIFR than SLS loading. No construct failure was observed. In the single plate groups (AP only and PP only), STS loading resulted in failure of all specimens before reaching loads of 750 N, while no failure occurred after SLS loading. No significant differences in FGM and RIFR were found between the double plate (AP+PP) and the single plate plus column screw (AP+PCS and PP+ACS) techniques. CONCLUSION: SLS loading appeared to overestimate the strength of acetabular fracture fixation constructs and STS loading may be more appropriate to provide clinically relevant biomechanical data. Internal fixation of a single column might not provide adequate stability for transverse fractures, while strength of single plate plus column screw fixation and double plate fixation was comparable.

Arthroscopic assisted treatment of distal radius fractures and concomitant injuries.

Wrist arthroscopy is mainly used to assist fracture reduction and fixation and to diagnose and treat concomitant injuries mainly to the scapholunate (SL), lunotriquetral (LT) ligament and the triangular fibrocartilage complex (TFCC). Arthroscopy is beneficial in improving anatomical reduction of fracture steps and gaps in intra-articular distal radius fractures (DRFs). Yet, the literature that the functional outcome correlates with the use of arthroscopy, is limited. Non-surgical treatment and immobilization is recommended for Geissler grade I-III Sl-ligament injuries, while open reduction, ligament suture and/or K-wire pinning is mandatory for complete ligament tears according to Geissler grade IV. This manuscript describes the current literature and gives insight into the authors' opinions and practice.

Fluoroscopically guided acetabular posterior column screw fixation via an anterior approach.

OBJECTIVE: Safe posterior column screw fixation via an anterior approach under two-dimensional fluoroscopic control. INDICATIONS: Anterior column with posterior hemitransverse fractures (ACPHF); transverse fractures; two-column fractures and T­type fractures without relevant residual displacement of the posterior column after reduction of the anterior column and the quadrilateral plate. CONTRAINDICATION: Acetabular fractures requiring direct open reduction via a posterior approach; very narrow osseous corridor in preoperative planning; insufficient intraoperative fluoroscopic visualization of the anatomical landmarks. SURGICAL TECHNIQUE: Preoperative planning of the starting point and screw trajectory using a standard pelvic CT scan and a multiplanar reconstruction tool. Intraoperative fluoroscopically controlled identification of the starting point using the anterior-posterior (ap) view. Advancing the guidewire under fluoroscopic control using the lateral-oblique view. Lag screw fixation of the posterior column with cannulated screws. POSTOPERATIVE MANAGEMENT: Partial weight bearing as advised by the surgeon. Postoperative CT scan for the assessment of screw position and quality of reduction of the posterior column. Generally no implant removal. RESULTS: In a series of 100 pelvic CT scans, the mean posterior angle of the ideal posterior column screw trajectory was 28.0° (range 11.1-46.2°) to the coronal plane and the mean medial angle was 21.6° (range 8.0-35.0°) to the sagittal plane. The maximum screw length was 106.3 mm (range 82.1-135.0 mm). Twelve patients were included in this study: 10 ACPHF and 2 transverse fractures. The residual maximum displacement of the posterior column fracture component in the postoperative CT scan was 1.4 mm (0-4 mm). There was one intraarticular screw penetration and one perforation of the cortical bone in the transition zone between the posterior column and the sciatic tuber without neurological impairment.

Mallet finger - A modified technique using the finger nail as a fixation point for the temporary immobilization of the distal interphalangeal joint - A biomechanical study.

BACKGROUND: The aim of the current biomechanical study was to investigate a newly developed surgical technique for mallet fingers. The new method is based on the Ishiguro method which requires a K-wire through the distal interphalangeal joint for temporary fixation. The new technique avoids the joint trans fixation using a specially designed finger nail holder. This method was compared to the established Ishiguro's technique. METHODS: For biomechanical testing, 32 paired, fresh-frozen human fingers (Digit II-V) of 4 donors (ages 60 to 71 years) were used. The paired fingers were assigned to either the new method or Ishiguro's technique. The biomechanical testing consisted of a cyclic cantilever bending (2000 cycles, 1-7N) followed by a load to failure test. The groups were evaluated for plastic deformation, stiffness, change in stiffness during cyclic loading, subluxation and failure load by analysing force-deflect data and fluoroscopic images. FINDINGS: The nail fixation group showed significantly higher failure loads and stiffness than the trans fixation group. The values of plastic deformation were significantly lower in the nail fixation group. No differences were found in the change of stiffness. No subluxation was found in both groups. INTERPRETATION: In the current biomechanical study, nail fixation performed at least as good as Ishiguro's trans fixation technique. The results and ease of implementation indicate that the newly developed nail fixation technique might be a useful treatment method in daily clinical practice without the need of temporary joint trans-fixation avoiding possible associated problems. To establish this method, clinical trials will be necessary.

Risk factors for nonunion after intramedullary nailing of subtrochanteric femoral fractures.

INTRODUCTION: Nonunion is a common complication after intramedullary nailing of subtrochanteric femoral fractures. A more detailed knowledge, particularly of avoidable risk factors for subtrochanteric fracture nonunion, is thus desired to develop strategies for reducing nonunion rates. The aim of the present study therefore was to analyse a wide range of parameters as potential risk factors for nonunion after intramedullary nailing of subtrochanteric fractures. MATERIALS AND METHODS: Seventy-four patients who sustained a subtrochanteric fracture and were treated by femoral intramedullary nailing at a single level 1 trauma centre within a 6-year period were included in this study. A total of 15 patient-related, fracture-related, surgery-related, mechanical and biological parameters were analysed as potential risk factors for nonunion. Furthermore, the accuracy of each of these parameters to predict nonunion was calculated. RESULTS: Nonunion occurred in 17 of 74 patients (23.0%). Of the 15 potential risk factors analysed, only 3 were found to have a significant effect on the nonunion rate (p < 0.05): postoperative varus malalignment, postoperative lack of medial cortical support and autodynamisation of the nail within the first 12 weeks post-surgery. Accuracy of each of these 3 parameters to predict nonunion was > 0.70. Furthermore, the nonunion rate significantly increased with the number of risk factors (no risk factor: 2.9%, one risk factor: 23.8%, two risk factors: 52.9%, and three risk factors: 100% [Chi-square test, p = 0.001)]. CONCLUSIONS: Our study indicates that intraoperative correction of varus malalignment and restoration of the medial cortical support are the most critical factors to prevent nonunion after intramedullary nailing of subtrochanteric femoral fractures. In addition, autodynamisation of the nail within the first 3 months post-surgery is a strong predictor for failure and should result in revision surgery.

Three new Prothemenops species (Araneae: Idiopidae) from central Thailand.

Prothemenops irineae sp. n., P. khirikhan sp. n. and P. phanthurat sp. n. are described from males and females collected in the Thai provinces of Prachuap Khiri Khan and Phetchaburi. The diagnosis of the genus Prothemenops is emended to include these three species and others to be described later. Notes on variation of morphological characters, biology and phenology are given.

On two Liphistius species (Araneae: Liphistiidae) from Laos.

Two mesothelid trapdoor spider species, Liphistius isan Schwendinger, 1998 and L. laoticus sp. n., are reported from southern Laos, east of the Mekong River. Liphistius isan was previously known only from the type locality in northeastern Thailand, and it is here also reported from a second Thai locality. Liphistius laoticus sp. n. is newly described from males and females. The two species belong to distinct lineages and they both have their closest relatives in northeastern Thailand. Information on biology and relationships of these two species is given.