Magnesium calcium alloys are promising candidates for an application as biodegradable osteosynthesis implants [1,2]. As the success of most internal fracture fixation techniques relies on safe anchorage of bone screws, there is necessity to investigate the holding power of biodegradable magnesium calcium alloy screws. Therefore, the aim of the present study was to compare the holding power of magnesium calcium alloy screws and commonly used surgical steel screws, as a control, by pull-out testing.

Magnesium calcium alloy screws with 0.8wt% calcium (MgCa0.8) and conventional surgical steel screws (S316L) of identical geometries (major diameter 4mm, core diameter 3mm, thread pitch 1mm) were implanted into both tibiae of 40 rabbits. The screws were placed into the lateral tibial cortex just proximal of the fibula insertion and tightened with a manual torque gauge (15cNm). For intended pull-out tests a 1.5mm thick silicone washer served as spacer between bone and screw head. Six animals with MgCa0.8 and four animals with S316L were followed up for 2, 4, 6 and 8 weeks, respectively. Thereafter the rabbits were sacrificed. Both tibiae were explanted, adherent soft tissue and new bone was carefully dissected around the screw head. Pull-out tests were carried out with an MTS 858 MiniBionix at a rate of 0.1mm/sec until failure of the screw or the bone. For each trial the maximum pull-out force [N] was determined. Statistical analysis was performed (ANOVA, Student's t-test).

Both implant materials were tolerated well. Radiographically, new bone was detected at the implantation site of MgCa0.8 and S316L, which was carefully removed to perform pull-out trials. Furthermore, periimplant accumulations of gas were radiographically detected in MgCa0.8. The pull-out force of MgCa0.8 and S316L did not significantly differ (p = 0.121) after two weeks. From 6 weeks on the pull-out force of MgCa0.8 decreased resulting in significantly lower pull-out values after 8 weeks. Contrary, S316L pull-out force increased throughout the follow up. Thus, S316L showed significantly higher pull-out values than MgCa0.8 after 4, 6 and 8 weeks (p<0.001).

MgCa0.8 showed good biocompatibility and pull-out values comparable to S316L in the first weeks of implantation. Thus, its application as biodegradable osteosynthesis implant is conceivable. Further studies are necessary to investigate whether the reduced holding power of MgCa0.8 is sufficient for secure fracture fixation. In addition, not only solitary screws, but also screw-plate-combinations should be examined over a longer time period.

Objectives

We aimed to further evaluate the biomechanical characteristics of two locking screws versus three standard bicortical screws in synthetic models of normal and osteoporotic bone.

Introduction

Pedicle screw pullout or loosening is increased in the osteoporotic spine. Recent studies showed a significant increase of pullout forces especially for PMMA-augmentation. With application of conventional viscosity PMMA the risk of cement extravasation is associated. This risk can be reduced by using radiofrequency-responsive, ultrahigh viscosity bone cement.

Background

In a systematic review of 1125 distal tibia fractures treated with an intramedullary nail, the reported incidence of malalignment was 14%. The purpose of our study is to assess whether the addition of blocking screws during intramedullary nailing of a distal tibia fracture improved radiological outcomes. As a secondary outcome, the time to radiographic union was compared to see if a more rigid bone-implant construct had an effect on healing.

Background

Tightrope fixation has been suggested as an alternative to screw stabilisation for distal tibiofibular joint diastasis that provides stability but avoids the problems of rigid screws across the joint. Recent case series (of 6 and 16 patients) have however, reported soft tissue problems and infections in 19–33% of patients. This study aims to review treatment and complications of distal tibiofibular diastasis fixation in our unit with the use of Tightrope or diastasis screws.

Introduction

Femoral neck fractures are a large clinical and economical problem. One of the most common fixation options for femoral neck fractures are multiple cancellous screws. A previous clinical study has shown the lack of washers to be the single largest predictor of fixation failure in the treatment of femoral neck fractures with cancellous screws. This finding was somewhat surprising as washers do not prevent the screws from backing out and do not provide any increase resistance to varus collapse. Therefore a follow-up biomechanical study was designed to test this observation. The purpose was to evaluate the maximal insertional torque of screws in osteoporotic bone with and without washers. We hypothesized that the lateral cortex of an osteoporotic proximal femur does not provide sufficient counter resistance for the screw heads to obtain maximum torque upon screw insertion in the femoral head and that the use of washers would increase screw purchase by providing a larger rigid surface area and subsequent higher counter resistance thereby allowing a higher maximal screw insertion torque.

Introduction

Short-segment posterior instrumentation for spine fractures is threatened by unacceptable failure rates. Two important design objectives of pedicle screws, bending and pullout strength, may conflict with each other.

Introduction

Locking nail have considerably improved the treatment of long weight bearing bones. However, distal locking needs experience and may expose to radiations. Many methods have been proposed to facilitate distal locking and improve safety. Recently, an external distal targeting device adapted to the ancillary of the Long Gamma Nail has been proposed. We report our experience with this device through a comparative series of distal lockings. Aim of this work was to assess feasibility and advantages brought about with this targeting device when considering time or dose of irradiation.

Background

Systematic reviews disagree, but some recent studies have shown better function and less pain after operation with bipolar hemiarthroplasty compared to fixation by two screws in elderly patients operated for displaced femoral neck fractures. There is still uncertainty regarding the mortality associated with both procedures.

Introduction. Conventional screws achieve sufficient insertion torque in healthy bone. In poor bone screw stripping can occur prior to sufficient torque generation. It was hypothesized that a screw with a larger major/minor diameter ratio would provide improved purchase in poor bone as compared to conventional screws. We evaluated the mechanical characteristics of such a screw using multiple poor bone quality models. Methods. Testing groups included: conventional screws, osteopenia screws used in bail-out manner (ie, larger major/minor diameter screws inserted into a hole stripped by a conventional screw), and osteopenia screws used in a preemptive manner (ie, no screw stripping occurrence). Stripping Torque: Screws were inserted through standard straight plates into a low density block of foam with a predrilled hole. Stripping torque was defined as maximum insertion torque reached by the screw before the screw began to spin freely in the foam. Pullout. Pullout tests were conducted on screws inserted into the same test media. Axial pull-out testing was then conducted by applying a tensile load to the screws. Compression. Screws were inserted through standard straight plates by hand while the amount of compression achieved between plate and bone was measured using a pressure sensor. The same foam test media was utilized in addition to osteoporotic fresh-frozen femoral diaphyseal cadaver (bone mineral density<0.60 g/cm2). The screws were tightened across a range of possible insertion torques with pressure measurements taken at multiple intervals. Results. The osteopenia bone screws showed a 67% increase in torque before stripping occurred (p<0.01) when compared to the conventional screw. The osteopenia screw used in a bail-out manner showed a 57% increase in stripping torque (p<0.01) and a 76% increase in pullout strength (p<0.01) when compared to the conventional screw. Additionally, the bail-out screw showed a minimal decrease in both stripping torque (6%, p = 0.45) and pullout strength (11%, p<0.01) when compared to the osteopenia screw tested in preemptive manner. There was a linear relationship between applied torque and compressive force generation for both osteopenia and conventional screws. The osteopenia screws were able to gain greater compression against bone across a range of insertion values as compared to conventional bone screws. Discussion. The osteopenia screw achieved superior stripping torque, pullout strength, and compressive forces when compared to conventional screws in simulated poor quality bone and osteoporotic cadaver bone. When used as a bail-out screw, it also achieved superior stripping torque and pullout strength. The results of this study indicate that a screw of larger major/minor diameter ratio could be an effective bail-out option for screw stripping associated with osteopenic fracture fixation

Aims

The aim of this study was to compare the functional and radiological outcomes and the complication rate after nail and plate fixation of unstable fractures of the ankle in elderly patients.

Aims

Proper preoperative planning benefits fracture reduction, fixation, and stability in tibial plateau fracture surgery. We developed and clinically implemented a novel workflow for 3D surgical planning including patient-specific drilling guides in tibial plateau fracture surgery.

Aims. We compared the accuracy, operating time and radiation exposure of the introduction of iliosacral screws using O-arm/Stealth Navigation and standard fluoroscopy. Materials and Methods. Iliosacral screws were introduced percutaneously into the first sacral body (S1) of ten human cadavers, four men and six women. The mean age was 77 years (58 to 85). Screws were introduced using a standard technique into the left side of S1 using C-Arm fluoroscopy and then into the right side using O-Arm/Stealth Navigation. The radiation was measured on the surgeon by dosimeters placed under a lead thyroid shield and apron, on a finger, a hat and on the cadavers. Results. There were no neuroforaminal breaches in either group. The set-up time for the O-Arm was significantly longer than for the C-Arm, while total time for placement of the screws was significantly shorter for the O-Arm than for the C-Arm (p = 0.001). The mean absorbed radiation dose during fluoroscopy was 1063 mRad (432.5 mRad to 4150 mRad). No radiation was detected on the surgeon during fluoroscopy, or when he left the room during the use of the O-Arm. The mean radiation detected on the cadavers was significantly higher in the O-Arm group (2710 mRem standard deviation (. sd. ) 1922) than during fluoroscopy (11.9 mRem . sd 14.8). (p < 0.01). Conclusion. O-Arm/Stealth Navigation allows for faster percutaneous placement of iliosacral screws in a radiation-free environment for surgeons, albeit with the same accuracy and significantly more radiation exposure to cadavers, when compared with standard fluoroscopy. Take home message: Placement of iliosacral screws with O-Arm/Stealth Navigation can be performed safely and effectively. Cite this article: Bone Joint J 2016;98-B:696–702

Aims

To determine if patient ethnicity among patients with a hip fracture influences the type of fracture, surgical care, and outcome.

Percutaneous stabilisation of tibial fractures by locking plates has become an accepted form of osteosynthesis. A potential disadvantage of this technique is the risk of damage to the neurovascular bundles in the anterior and peroneal compartments. Our aim in this anatomical study was to examine the relationship of the deep peroneal nerve to a percutaneously-inserted Less Invasive Stabilisation System tibial plate in the lower limbs of 18 cadavers. Screws were inserted through stab incisions. The neurovascular bundle was dissected to reveal its relationship to the plate and screws. In all cases, the deep peroneal nerve was in direct contact with the plate between the 11th and the 13th holes. In ten specimens the nerve crossed superficial to the plate, in six it was interposed between the plate and the bone and in the remaining two specimens it coursed at the edge of the plate. Percutaneous insertion of plates with more than ten holes is not recommended because of the risk of injury to the neurovascular structures. When longer plates are required we suggest distal exposure so that the neurovascular bundle may be displayed and protected

Introduction. A new triggered electromyography test for detection of stimulus diffusion to intercostal muscles of the contralateral side during thoracic pedicle screw placement was evaluated. Experimental research was carried out in order to determine if, using this test, neural contact at different aspects of the spinal cord and nerve roots could be discriminated. Methods. Nine industrial pigs (60–75 kg) had 108 pedicle screws placed bilaterally in the thoracic spine (T8–T13). Neural structures were stimulated under direct vision at different anatomic locations from T9 to T12. Recording electrodes were placed over the right and left intercostal muscles. Increasing intensity of the stimulus was applied until muscle response was detected at the contralateral side (diffusion phenomenon). After this first experiment, the thoracic spine was instrumented. Screws were placed in the pedicle in two different positions, the anatomic intrapedicular location and with purposeful contact with the neural elements. Results. Response thresholds to direct stimulation of nerve root at different points were significantly lower than those obtained by stimulation of the dorsal aspect of the spinal cord (0.44±0.22 mA vs 1.38±0.71 mA). However, a 24-fold stimulation intensity (6.50±0.29 mA) was necessary to obtain diffusion of the EMG response to the opposite left side if the right nerve root was stimulated. Only a 2-fold increment (3.17±0.93 mA) was able to elicit diffusion of EMG responses to the contralateral side when stimulation was applied to the dorsal aspect of the spinal cord. Contralateral EMG responses after high increases of stimulation thresholds indicated nerve root contact. Diffusion phenomenon after low threshold increments reflected medullar contact. Electromyography recordings after triggered stimulation of the screws showed that only screws in contact with the spinal cord had significantly lower responses (2.72±1.48 mA). Conclusion. Stimulus-triggered EMG could only discriminate screws with violation of the medial pedicle wall if they were contact with neural tissues. Recording EMG-potentials at the contralateral paraspinal muscles (stimulus diffusion phenomenon) proved to be a reliable method to discriminate which of the neural structures was at risk

At Bispebjerg University Hospital in Denmark, an Optimized Hip Fracture Program, (OHP) is the standard of care for all hip fracture patients. Part of OHP is pain treatment with a femoral nerve catheter placed at the emergency room, dosed 4 times a day with Bupivacain until 4 days after surgery, combined with systemic analgesics as needed. In 2008, a database and a bio bank were created at the ward including all hip fracture patients to make a better description of the population and as a tool for further optimisation of the OHP. One of the aims was to identify possible subgroups having specific complications, which could lead to a differentiation of the OHP by markers known at the time of admission. In this analysis, we will focus on postoperative pain that inhibits mobilization by fracture type and type of surgery. Methods. A consecutive cohort of 898 hip fracture patients hospitalized within two years from September 2008 to July 2010 was used for this study. Patients coming from nursing homes were excluded from the study, since nearly all are discharged 1 or 2 days after surgery to rehabilitation. If the exact type of fracture was not known, or if the patient was admitted for rehabilitation after surgery at another hospital, the patient was also excluded. 508 patients were thus included in the study. Mean age 80.0 years (SD:23.7), 72.1% women and 27.9% men. Mobilization inhibited by postoperative pain as documented in the patient files was registered in the database. Overall mobilization was inhibited by pain in 26.7% of the 508 patients included. The following fracture types were studied: Femoral neck Garden 1–2, Femoral neck Garden 3–4, Pertrochanteric Evans 1–2, Pertrochanteric Evans 3–5, Basocervical and Subtrochanteric. Results. Mobilization inhibited by pain was not significantly associated with type of surgery:. Cannulated Hip Screws 16/80 (20.0%), sliding hip screw 23/94 (24.5%), Intramedullary Nail 63/186 (33.9%), partial hip replacement 33/144 (22.9%), total hip replacement 1/5 (20.0%). P = 0.09 chi square. On the other hand mobilization inhibited by pain was significantly associated with fracture type:. Femoral neck Garden 1–2: 13/64 (20.3%), Femoral neck Garden 3–4: 38/172 (22.1%), Pertrochanteric Evans 1–2: 18/69 (26.1%), Pertrochanteric Evans 3–5: 46/149 (30.9%), Basocervical: 6/28 (21.4%), Subtrochanteric 15/27(55.6%). P = 0.009 chi square. Conclusion. The fracture types Pertrochanteric Evans 3–5 and Subtrochanteric had the biggest inhibition of mobilization caused by pain. No significant association between type of surgery and inhibition of mobilization caused by pain was found

Aims

This study evaluated variation in the surgical treatment of stable (A1) and unstable (A2) trochanteric hip fractures among an international group of orthopaedic surgeons, and determined the influence of patient, fracture, and surgeon characteristics on choice of implant (intramedullary nailing (IMN) versus sliding hip screw (SHS)).

Aims

A pragmatic multicentre randomised controlled trial (PROFHER) was conducted in United Kingdom National Health Service (NHS) hospitals to evaluate the clinical effectiveness and cost effectiveness of surgery compared with non-surgical treatment for displaced fractures of the proximal humerus involving the surgical neck in adults.

Unstable bicondylar tibial plateau fractures are rare and there is little guidance in the literature as to the best form of treatment. We examined the short- to medium-term outcome of this injury in a consecutive series of patients presenting to two trauma centres. Between December 2005 and May 2010, a total of 55 fractures in 54 patients were treated by fixation, 34 with peri-articular locking plates and 21 with limited access direct internal fixation in combination with circular external fixation using a Taylor Spatial Frame (TSF). At a minimum of one year post-operatively, patient-reported outcome measures including the WOMAC index and SF-36 scores showed functional deficits, although there was no significant difference between the two forms of treatment. Despite low outcome scores, patients were generally satisfied with the outcome. We achieved good clinical and radiological outcomes, with low rates of complication. In total, only three patients (5%) had collapse of the joint of > 4 mm, and metaphysis to diaphysis angulation of greater than 5º, and five patients (9%) with displacement of > 4 mm. All patients in our study went on to achieve full union.

This study highlights the serious nature of this injury and generally poor patient-reported outcome measures following surgery, despite treatment by experienced surgeons using modern surgical techniques. Our findings suggest that treatment of complex bicondylar tibial plateau fractures with either a locking plate or a TSF gives similar clinical and radiological outcomes.

Cite this article: Bone Joint J 2014;96-B:956–62.