Objectives

External fixators are the traditional fixation method of choice for contaminated open fractures. However, patient acceptance is low due to the high profile and therefore physical burden of the constructs. An externalised locking compression plate is a low profile alternative. However, the biomechanical differences have not been assessed. The objective of this study was to evaluate the axial and torsional stiffness of the externalised titanium locking compression plate (ET-LCP), the externalised stainless steel locking compression plate (ESS-LCP) and the unilateral external fixator (UEF).

Proximal humeral shaft fractures are commonly treated with long straight plates or intramedullary nails. Helical plates might overcome the downsides of these techniques as they are able to avoid the radial nerve distally. The aim of this study was to investigate in an artificial bone model: (1) the biomechanical competence of different plate designs and (2) to compare them against the alternative treatment option of intramedullary nails. Twenty-four artificial humeri were assigned in 4 groups and instrumented as follows: group1 (straight 10-hole-PHILOS), group2 (MULTILOCK-nail), group3 (45°-helical-PHILOS) and group4 (90°-helical-PHILOS). An unstable proximal humeral shaft fracture was simulated. Specimens were tested under quasi-static loading in axial compression, internal/external rotation and bending in 4 directions monitored by optical motion tracking. Axial displacement (mm) was significantly lower in group2 (0.1±0.1) compared to all other groups (1: 3.7±0.6; 3: 3.8±0.8; 4: 3.5±0.4), p<0.001. Varus stiffness in group2 (0.8±0.1) was significantly higher compared to groups1+3, p≤0.013 (1: 0.7±0.1; 3: 0.7±0.1; 4: 0.8±0.1). Varus bending (°) was significantly lower in group2 compared to all other groups (p<0.001) and group4 to group1, p=0.022. Flexion stiffness in group1 was significantly higher compared to groups2+4 (p≤0,03) and group4 to group1, p≤0,029 (1: 0.8±0.1; 2: 0.7±0.1; 3: 0.7±0.1; 4: 0.6±0.1). Flexion bending (°) in group4 was higher compared to all other groups (p≤0.024) and lower in group2 compared to groups1+4, p≤0.024. Torsional stiffness remained non significantly different, p≥0.086. Torsional deformation in group2 was significantly higher compared to all other groups, p≤0.017. Shear displacement remained non significantly different, p≥0.112. From a biomechanical perspective, helical plating with 45° and 90° may be considered as a valid alternative fixation technique to standard straight plating of proximal third humeral fractures. Intramedullary nails demonstrated higher axial and bending stiffness as well as lower fracture gap movements during axial loading compared to all plate designs. However, despite similar torsional stiffness they were associated with higher torsional movements during internal/external rotation as compared to all investigated plate designs

Abstract. Objective. To compare the periprosthetic fracture mechanics between a collared and collarless fully coated cementless femoral stem in a composite femur. Methods. Two groups of six composite femurs (‘Osteoporotic femur’, SawBones, WA USA) were implanted with either a collared (collared group) or collarless (collarless group) cementless femoral stem which was otherwise identical by a single experienced surgeon. Periprosthetic fractures of the femur were simulated using a previously published technique. High speed video recording was used to identify fracture mechanism. Fracture torque and angular displacement were measured and rotational work and system stiffness were estimated for each trial. Results were compared between collared and collarless group and the comparison was evaluated against previously published work using fresh frozen femurs and the same protocol. Results. In composite femur testing median fracture torque (IQR) was greater with a collared versus collarless implant (48.41 [42.60 to 50.27] Nm versus 45.12 [39.13 to 48.09] Nm, p= 0.4). Median rotational displacement (IQR) was less with a collared versus collarless implant (0.29 [0.27 to 0.31] radians versus 0.33 [0.32 to 0.34] radians, p= 0.07). Estimated rotary work was similar between groups (5.76 [4.92 to 6.64] J versus 5.21 [4.25 to 6.04] J, p= 0.4). Torsional stiffness was greater with a collared versus collarless implant (158.36 [152.61, 163.54] Nm per radian versus 138.79 [122.53, 140.59] Nm per radian, p= 0.5). Collarless stems were seen to move independently of the femur and fracture patterns originated at the calcar. Conclusions. Testing with composite femurs using an established protocol produced similar results to previously published studies using human femurs, but the difference between collared and collarless stems was smaller. The internal homogenous foam material in composite femurs does not accurately represent the heterogeneous cancellous bone which supports a femoral stem in vivo and may lead to overestimation of implant stability. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

It is common belief that consolidated intramedullary nailed trochanteric femur fractures can result in secondary midshaft or supracondylar fractures, involving the distal screws, when short or long nails are used, respectively. In addition, limited data exists in the literature to indicate when short or long nails should be selected for treatment. The aim of this biomechanical cadaveric study was to investigate short versus long Trochanteric Femoral Nail Advanced (TFNA) fixation in terms of construct stability and generation of secondary fracture pattern following trochanteric fracture consolidation. Eight intact human cadaveric femur pairs were assigned to 2 groups of 8 specimens each for nailing using either short or long TFNA with blade as head element. Each specimen was first biomechanically preloaded at 1 Hz over 2000 cycles in superimposed synchronous axial compression to 1800 N and internal rotation to 11.5 Nm. Following, internal rotation to failure was applied over an arc of 90° within 1 second under 700 N axial load. Torsional stiffness, torque at failure, angle at failure and energy at failure were evaluated. Fracture patterns were analyzed. Outcomes in the groups with short and long nails were 9.7±2.4 Nm/° and 10.2±2.9 Nm/° for torsional stiffness, 119.8±37.2 Nm and 128.5±46.7 Nm for torque at failure, 13.5±3.5° and 13.4±2.6° for angle at failure, and 887.5±416.9 Nm° and 928.3±461.0 Nm° for energy at failure, respectively, with no significant differences between them, P≥0.167. Fractures through the distal locking screw occurred in 5 and 6 femora instrumented with short and long nails, respectively. Fractures through the lateral entry site of the head element were detected in 3 specimens within each group. For short nails, fractures through the distal shaft region, not interfacing with the implant, were detected in 3 specimens. From biomechanical perspective, the risk of secondary peri-implant fracture after intramedullary nailed trochanteric fracture consolidation is similar when using short or long TFNA. Moreover, for both nail versions the fracture pattern does not unexceptionally involve the distal locking screw

Purpose: Little has been written about the size of bone defect that could be restored with one-stage lengthening over a reamed intramedullary nail. The aim of this study was to investigate the mechanical properties of the callus created at gaps of various sizes in sheep tibiae treated with reamed intramedullary nailing. Material-Methods: Sixteen adult female sheep were divided into four main groups: a simple osteotomy group (group I) and three segmental defect groups (1, 2, and 3 cm gap; groups I to III). One intact left tibia from each group was also used as the non-osteotomized intact-control group (group V). In all cases the osteotomy was fixed with an interlocked Universal Humeral Nail after 7 mm reaming. The osteotomized site was closed in layers including the periosteum without additional bone grafting and the limb was protected with long soft cast for 5 weeks postoperatively. Healing of the osteotomies was evaluated after 16 weeks by biomechanical testing. The examined parameters were torsional stiffness, shear stress and angle of torsion at the time of fracture. Results: Samples with a simple osteotomy or 1 cm gap were fractured distally to the callus zone, whereas samples with 2 and 3 cm gaps were fractured at the callus zone or at distal metaphysis. The regenerate bone obvious in the x-rays in the group of 1 cm and 2 cm gap had considerable mechanical properties. Torsional stiffness in these two groups was nearly similar and its value was about 60% of the stiffness of the simple osteotomy group. A gradually decreased stiffness was observed as the osteotomy gap increased. There was a decrease in maximum shear stress from simple osteotomy to osteotomy with a fracture gap of 3 cm. No significant differences were found among the angles of torsion at fracture for the various osteotomies or the intact bone. Our results showed that the group of 1 cm gap had the 65% of the shear stress at failure of the simple osteotomy group. Conclusion: We believe that there is evidence indicating that intramedullary nailing would be a reasonable option when one-stage lengthening of a long bone of 1 or 2 cm is contemplated

Introduction: Non-invasive prediction of load bearing capacity during consolidation of distraction osteogenesis and fracture healing would represent a significant advance in the treatment of patients by defining the appropriate point of time for the removal of the fixator externe. Thereby the risk of refracture, malunion and infection could be reduced. Several methods have been proposed in the past to predict the load bearing capacity: dual-energy x-ray absorptiometry (DEXA), stiffness measurements, quantitative computed tomography, quantitative radiography and ultrasound. In this ex-vivo study stiffness- and DEXA-measurements were compared regarding their suitability to predict the load bearing capacity of bone regenerate. In addition this study analysed how compressive, bending and torsional stiffness as suitable tools were related to the torsional load bearing capacity using a common set of bone regenerate samples of 26 sheep treated with distraction osteogenesis. Material and Methods: After osteotomy the sheep tibiae were stabilized using an external half-ring Ilizarov fixator. Followed by a 4-day latency period the tibiae were distracted at a rate of 1.25 mm per day in two increments for 20 days. On the 74th day the sheep were sacrificed and tibiae were harvested. The ends of the specimens were embedded in PMMA for further biomechanical testing. Therefore, the specimens were mounted to a sequence of special costume made jigs for compressive testing, 4-point bending and torsional testing in a material testing machine. Stiffness was calculated by regression of the linear part of the load-displacement curves. The maximum torsional moment of the specimens was determined in a final experiment. In addition the bone mineral density (BMD) of the distracted bone tissue was measured using DEXA. The correlation between the maximum torsional moment and the various types of stiffness respectively BMD was analysed to gain information about the suitability predicting the load bearing capacity. Results: Torsional stiffness exhibits the highest correlation with the maximum torsional moment (r2 = 0.77) followed by bending (ap (r2 = 0.70); ml (r2 = 0.66)) and compressive stiffness (r2 = 0.60). The correlation for BMD with the maximum torsional moment was smallest (r2 = 0.39). Discussion: This ex-vivo study revealed that the stiffness measurements seem to be a helpful tool to predict the load bearing capacity of bone regenerate. The results of this study showed stiffness measurements as a more suitable mean to determine the load bearing capacity. Within the various types of stiffness measurements torsional stiffness measurements perform slightly better than bending and compressive stiffness measurements. Nevertheless, further studies are necessary to support the results of this study since the specimens failed applying torsional stress

Introduction Non-invasive prediction of load bearing capacity is an important issue in the advanced clinical treatment of distraction osteogenesis in order to define the appropriate point of time for the removal of the external fixateur. Therefore, non-invasive stiffness measurements were recommended as a promising tool due to the high correlation between strength and various kinds of stiffness: Torsional, bending and compressive. However, previous experiments only analysed the relationship between a single type of stiffness. This approach neglects the multi-dimensional characteristics of bone loading in compression, bending and torsion. This study investigates how compressive, bending (ap and ml) and torsional stiffness are related to the torsional load bearing capacity of healing callus tissue using a common set of bone regenerate samples of sheep treated with distraction osteogenesis. In addition, this study compares the evolution of the various kinds of stiffness. This study provides insight into how the various stiffness modes are suited to predict the load bearing capacity by in-vivo stiffness measurement. Material and Methods Mid-diaphyseal osteotomies were performed in 26 right tibiae of mature, female domestic sheep. Tibiae were then stabilized using an external half-ring Ilizarov fixator. After a 4-day latency period the tibiae were distracted at a rate of 1.25 mm per day in two increments for 20 days. As a result of a parallel study, the callus was treated with different combinations of growth factors and carrier material resulting in four treatment groups plus a contralateral control group. The sheep were sacrificed and the tibiae were harvested on the 74th day. The ends of the tibiae were embedded in PMMA and mounted to a sequence of special custom made jigs for compressive testing, 4-point-bending and torsion in a material testing machine. Stiffness was calculated by regression of the initial linear part of the load-displacement curves. In a final experiment, the specimens were loaded in torsion until failure to record the ultimate torsional moment. Results Torsional stiffness exhibits the highest correlation with the ultimate torsional moment (r2 = 0.77), while the ones for compressive (r2 = 0.60) and bending (ap (r2 = 0.70); ml (r2 = 0.66)) are only slightly lower. Discussion This ex-vivo study in sheep shows that torsional, bending (ap and ml) and compressive stiffness measurements are all suitable means to predict the load bearing capacity of healing callus tissue. Our results show that torsional stiffness measurements perform slightly better than compressive and bending stiffness measurements. However, further studies are necessary to underline the superior performance of torsional stiffness measurements, since the sheep-tibiae were failed by applying torsional stress

Objectives

We investigated the effects on fracture healing of two up-regulators of inducible nitric oxide synthase (iNOS) in a rat model of an open femoral osteotomy: tadalafil, a phosphodiesterase inhibitor, and the recently reported nutraceutical, COMB-4 (consisting of L-citrulline, Paullinia cupana, ginger and muira puama), given orally for either 14 or 42 days.

We used a canine intercalary bone defect model to determine the effects of recombinant human osteogenic protein 1 (rhOP-1) on allograft incorporation. The allograft was treated with an implant made up of rhOP-1 and type I collagen or with type I collagen alone.

Radiographic analysis showed an increased volume of periosteal callus in both test groups compared with the control group at weeks 4, 6, 8 and 10. Mechanical testing after 12 weeks revealed increased maximal torque and stiffness in the rhOP-1 treated groups compared with the control group.

These results indicate a benefit from the use of an rhOP-1 implant in the healing of bone allografts. The effect was independent of the position of the implant. There may be a beneficial clinical application for this treatment.

We investigated a new intramedullary locking nail that allows the distal interlocking screws to be locked to the nail. We compared fixation using this new implant with fixation using either a conventional nail or a locking plate in a laboratory simulation of an osteoporotic fracture of the distal femur. A total of 15 human cadaver femora were used to simulate an AO 33-A3 fracture pattern. Paired specimens compared fixation using either a locking or non-locking retrograde nail, and using either a locking retrograde nail or a locking plate. The constructs underwent cyclical loading to simulate single-leg stance up to 125 000 cycles. Axial and torsional stiffness and displacement, cycles to failure and modes of failure were recorded for each specimen. When compared with locking plate constructs, locking nail constructs had significantly longer mean fatigue life (75 800 cycles (sd 33 900) vs 12 800 cycles (sd 6100); p = 0.007) and mean axial stiffness (220 N/mm (sd 80) vs 70 N/mm (sd 18); p = 0.005), but lower mean torsional stiffness (2.5 Nm/° (sd 0.9) vs 5.1 Nm/° (sd 1.5); p = 0.008). In addition, in the nail group the mode of failure was either cut-out of the distal screws or breakage of nails, and in the locking plate group breakage of the plate was always the mode of failure. Locking nail constructs had significantly longer mean fatigue life than non-locking nail constructs (78 900 cycles (sd 25 600) vs 52 400 cycles (sd 22 500); p = 0.04).

The new locking retrograde femoral nail showed better stiffness and fatigue life than locking plates, and superior fatigue life to non-locking nails, which may be advantageous in elderly patients.

Cite this article: Bone Joint J 2014;96-B:114–21.

Objectives

The use of two implants to manage concomitant ipsilateral femoral shaft and proximal femoral fractures has been indicated, but no studies address the relationship of dynamic hip screw (DHS) side plate screws and the intramedullary nail where failure might occur after union. This study compares different implant configurations in order to investigate bridging the gap between the distal DHS and tip of the intramedullary nail.