Biomechanical comparison of a new staple technique with tension band wiring for transverse patella fractures

Background

The tension band wiring technique is the most common method of transverse patella fracture fixation. Since post-operative instabilities have been reported for this technique, alternative osteosynthesis solutions are of interest. We investigated the biomechanical behaviour of a new staple technique for treatment of transverse patella fractures in a cadaveric model.

Methods

Eight human cadaveric knees with femur and tibia including soft tissue were used. A transverse osteotomy of the patella was created. Each specimen was fixed consecutively with tension band wiring and two Nitinol compression staples. Testing was performed by pull on the quadriceps tendon between a 90° flexed position and full knee extension for up to 5000 cycles.

Findings

At 1000 cycles, fracture site displacements in flexion and extension were significantly smaller for the staple group at the ventral aspect of the patella as compared to the tension band wiring group. With a failure criterion of 2 mm fracture site displacement, cycles until failure were significantly smaller for the staple group.

Interpretation

This study provides evidence based on a cadaveric model that compression staples have a promising potential to treat transverse patella fractures.     

Is a helical shaped implant a superior alternative to the Dynamic Hip Screw for unstable femoral neck fractures? A biomechanical investigation

Background

The Dynamic Hip Screw is well established for the treatment of femoral neck fractures. However, cut-out occurs in 1–6% of all cases. This study compared the biomechanical performance of a helical shaped implant (DHS-Blade) to the Dynamic Hip Screw in an unstable femoral neck fracture model.

Methods

Ten pairs of human cadaveric femora were either instrumented with a DHS-Blade or a Dynamic Hip Screw. Osteotomies were created using a custom-made saw-guide. Cyclic loading was performed by introducing in vivo measured load-trajectories to the femoral head. Starting at 1500 N, the load was stepwise increased until failure of the construct. Radiographs were taken in 5000 cycles increments to identify onset of femoral head migration with respect to the implant. A survival analysis was performed on the cycles to onset of migration. A paired t-test was carried out on the displacements of the femoral head relative to the shaft as determined by optical motion tracking.

Findings

One hundred percent migrations occurred for the Dynamic Hip Screw compared to 50% for the DHS-Blade. The survival probability in terms of implant anchorage was found higher for the blade (P = 0.023). However, significant higher deformation of the repair construct was observed for the DHS-Blade (P = 0.004).

Interpretation

The study showed superior implant anchorage of the DHS-Blade compared to the DHS, which might reduce the cut-out risk. Nevertheless, the blade allowed higher deformation of the femur mainly resulting in shortening of the neck, which might be due to a systematic loss of fracture reduction.     

Trichodysplasia Spinulosa—A Rare Complication in Immunosuppressed Patients

Abstract: Immunosuppression is necessary in a large number of conditions to modify immune responses and control disease severity. It is a vital part of treatment regimes following organ and bone marrow transplants. However, the use of immunosuppressive drugs has been shown to cause infections with common and unusual pathogens. We present the case of a 5‐year‐old female heart transplant recipient. Nine months after the transplant, she developed a tender acneiform eruption on her face consisting of numerous small yellowish to pink papules and pustules. Many of the lesions had a central, firm, small spinulous excrescence or a central dell. Histopathology demonstrated abnormal maturation of the hair follicles, nucleated eosinophilic cells with trichohyalin granules. The clinical presentation and histological features were in keeping with trichodysplasia spinulosa, a rare complication in immunosuppressed subjects. Treatment trials included reduction of immunosuppression combined with topical and oral retinoids, topical acyclovir, and oral valganciclovir with limited success.     

The anesthetic efficacy of midazolam in the enflurane-anesthetized dog

This study determined the anesthetic efficacy of midazolam (MID) in terms of its ability to reduce enflurane MAC (EMAC). Control EMAC was determined by the tail-clamp method in 15 mongrel dogs. Each animal then received at least three incremental infusion rates of MID from among the following: 0.48, 2.4, 9.6, 19.2, 28.8, 48, or 151.2 micrograms.kg-1.min-1. MAC was determined during each infusion rate following a 1-h observation period, during which time MID concentration in plasma [( MID]) stabilized. [MID] was measured every 15 min beginning 45 min from the start of each new infusion rate. There was a linear relationship between MID infusion rates and the resulting [MID] (r = 0.995). In the range of [MID] from 14 to 14,118 ng/ml, there was a linear relationship between the log [MID] and the percent EMAC reduction. The slope of the line was very shallow, and the [MID] required to reduce EMAC by more than 50% exceeded the [MID] likely to be employed clinically in humans (750 ng/ml). Also, the 73 +/- 4% (mean +/- SEM) EMAC reduction produced by [MID] = 9,763 +/- 1213 ng/ml was not significantly greater than the 60 +/- 3% EMAC reduction achieved by [MID] = 1,464 +/- 293 ng/ml, a finding which suggests a ceiling effect to the anesthetic efficacy of midazolam. The authors conclude that, within the dose range of MID likely to be employed in humans, MID produced a concentration-dependent reduction of enflurane MAC in the dog. In doses above those likely to be employed clinically, a ceiling effect to the anesthetic efficacy of MID may become evident.     

Incidence of Cell-Saver contamination during cardiopulmonary bypass

During regular bacteriological surveillance of cardiac surgical equipment and patients, the Cell Saver apparatus (CSA) was prospectively evaluated to determine if it represented an additional risk for infection. Nineteen patients were studied. After each operation, the effluent from the CSA was sterilely sealed for subsequent culture. A total of 42 aerobic and 42 anaerobic cultures were made. Postoperatively all patients were evaluated daily for four days and before discharge for clinical evidence of infection. Four patients had positive CSA cultures without evidence of postoperative clinical infection. Five patients in whom postoperative infectious complications developed had negative CSA cultures. Ten patients had negative CSA cultures and no evidence of postoperative infection. We conclude that the CSA does not appear to contribute to the risk of infection in cardiac surgical patients and that it is a safe adjunct to cardiac surgery.     

Biomechanical investigation of an alternative concept to angular stable plating using conventional fixation hardware

Background  

Angle-stable locking plates have improved the surgical management of fractures. However, locking implants are costly and removal can be difficult. The aim of this in vitro study was to evaluate the biomechanical performance of a newly proposed crossed-screw concept ("Fence") utilizing conventional (non-locked) implants in comparison to conventional LC-DCP (limited contact dynamic compression plate) and LCP (locking compression plate) stabilization, in a human cadaveric diaphyseal gap model.     

Ankle joint pressure in pes cavovarus

A cavovarus foot deformity was simulated in cadaver specimens by inserting metallic wedges of 15 degrees and 30 degrees dorsally into the first tarsometatarsal joint. Sensors in the ankle joint recorded static tibiotalar pressure distribution at physiological load. The peak pressure increased significantly from neutral alignment to the 30 degrees cavus deformity, and the centre of force migrated medially. The anterior migration of the centre of force was significant for both the 15 degrees (repeated measures analysis of variance (ANOVA), p = 0.021) and the 30 degrees (repeated measures ANOVA, p = 0.007) cavus deformity. Differences in ligament laxity did not influence the peak pressure. These findings support the hypothesis that the cavovarus foot deformity causes an increase in anteromedial ankle joint pressure leading to anteromedial arthrosis in the long term, even in the absence of lateral hindfoot instability.     

Pelvic girdle reconstruction based on spinal fusion and ischial screw fixation in a case of aneurysmal bone cyst

A case of lytic lesion of the pelvis in a 23-year-old woman is presented. A biopsy led to the diagnosis aneurysmal bone cyst (ABC). Due to the histologically very aggressive growth of the tumor, a low malignant osteosarcoma could not be excluded. In an initial operation the tumour, affecting the sacrum, the iliac crest and the lower lumbar spine was resected. Temporary restabilisation of the pelvic ring was achieved by a titanium plate. The histological examination of the entire tumour confirmed the diagnosis ABC. After 6 months, the MRI showed no recurrence. The observed tilt of the spine to the operated side on the sacral base prompted a second surgical procedure: a transpedicular fixation of L5 and L4 was connected via bent titanium stems to the ischium, where the fixation was achieved by two screws. This construction allowed the correction of the base angle and yielded a stable closure of the pelvic ring. The patient has now been followed for 6 years: the bone grafts have been incorporated and, in spite of radiological signs of screw loosening in the ischium, the patient is fully rehabilitated and free of symptoms. Pedicle screws in the lower spine can be recommended for fixation of a pelvic ring discontinuity.     

Mechanism of Oleogel‐S10: A triterpene preparation for the treatment of epidermolysis bullosa

Epidermolysis bullosa (EB) is a group of rare heterogeneous, genetic disorders. Currently, there is no effective pharmacological or genetic therapy for all EB subtypes. Dry extract from birch bark and betulin upregulate some pro‐inflammatory mediators and downregulate others. The increase in pro‐inflammatory cytokines is temporary and attenuated over long‐term treatment. This inflammatory stimulus is thought to be prerequisite for a secondary anti‐inflammatory response. Dry extract from birch bark and its active marker substances have also been shown to increase the migration of primary human keratinocytes, accelerate wound closure, and promote differentiation of keratinocytes in vitro and in vivo—processes that are essential for reepithelialization and maintenance of the skin barrier. Comprehensive clinical data are available to support the use of Oleogel‐S10 in the treatment of partial thickness wounds of different etiologies, and a proof‐of‐concept Phase 2 study in patients with dystrophic EB has suggested the potential for faster reepithelialization of wounds treated with Oleogel‐S10.