Improved weight bearing during gait at 6 weeks post-surgery with an angle stable locking system after distal tibial fracture.

BACKGROUND: Functional recovery after intramedullary nailing of distal tibial fractures can be monitored using ipsilateral vertical ground reaction forces (vGRF), giving insight into recovery of patients' gait symmetry. Previous work compared patient cohorts to healthy controls, but it remains unclear if these metrics can identify treatment-based differences in return to function post-surgery. RESEARCH QUESTION: Is treatment of a distal tibial fracture with intramedullary nailing with an angle stable locking system (ASLS) associated with higher ipsilateral vGRF and improved symmetry compared to conventional intramedullary nailing at an early time point? METHODS: Thirty-nine patients treated with ASLS intramedullary nailing were retrospectively compared to thirty-nine patients with conventional locking. vGRFs were collected at 1, 6, 12, 26, and 52 weeks post-surgery during standing and gait. Discrete metrics of ipsilateral vGRF (maximal force, impulse) and asymmetry were compared between treatments at each time point. Time-scale comparisons of ipsilateral vGRF and lower limb asymmetry were additionally performed for gait trials. Mann-Whitney Test or a two-way analysis of variance tested discrete comparisons; statistical non-parametric mapping tested time-scale data between treatment groups. RESULTS: During gait, ASLS-treated patients applied more load on the operated limb (17-38% stance, p = 0.015) and consequently loaded limbs more symmetrically (8-37% stance, p = 0.008) during the loading response at 6 weeks post-surgery compared to conventional IM treatment. Discrete measures of symmetry at the same time point identified treatment-based differences in maximal force (p = 0.039) and impulse (p = 0.012), with ASLS-treated patients exhibiting more symmetry. No differences were identified in gait trials at later time points nor from all standing trials. SIGNIFICANCE: During the initial loading response of gait, increased ipsilateral vGRF and improved weightbearing symmetry were identified in ASLS patients at 6 weeks post-surgery compared to conventional IM nailing. Early and objective metrics of dynamic movement are suggested to identify treatment-based differences in functional recovery.

Clinical feasibility of fracture healing assessment through continuous monitoring of implant load.

Current fracture fixation follow-up is based on subjective radiological and clinical examination. Efforts to objectify the procedure have been undertaken since decades. Assessment of implant load as an indirect predictor of callus maturity has so far failed to enter clinical routine due to limited practicability, technical obstacles and its snap-shot nature. We recently introduced the concept of continuous implant load monitoring to aid in diagnosing fracture healing progression. This study aimed at investigating the feasibility of the system in a clinical context. Ten patients treated with Taylor-Spatial-Frame external fixators following pathological tibia fractures were equipped with a Fracture Monitor device attached to a fixator-strut and were monitored until hardware removal. Two patients were excluded due to technical issues. Implant load and fracture activity was continuously and autonomously measured for 139 ± 89 days (mean ± SD). Data was wirelessly collected with consumer smartphones. Relative implant load initially rose for 34.1 ± 22.2 days and finally declined to a level of 45.0 ± 33.8% of the maximum implant load. In five patients the load dropped below 50% of the maximum load. These patients underwent hardware removal according to the clinical assessment. In three patients, whose external fixators were exchanged to internal fixation at the end of the study, implant load did not drop below the 50% margin. The continuous measurement principle allows resolving implant load progression and appears indicative for the bone healing status. Data can be acquired in a homecare setting and is believed to provide valuable information to support timely healing assessment and enable patient specific after-care.

Biomechanical evaluation of the tension band wiring principle. A comparison between two different techniques for transverse patella fracture fixation.

PURPOSE: The aim of this study was to investigate the validity of the dynamic compression principle of tension band wiring in two techniques for patella fracture treatment. METHODS: Twelve human cadaveric knees with simulated transverse patella fractures were assigned to two groups for treatment with tension band wiring using either Kirschner (K-) wires or cannulated screws. Biomechanical testing was performed over three knee movement cycles between 90° flexion and 0° full extension. Pressure distribution in the fracture gap and fracture site displacement were evaluated at the 3rd cycle in 15° steps, namely 90°-75°-60°-45°-30°-15°-0° extension phase and 0°-15°-30°-45°-60°-75°-90° flexion phase. RESULTS: Mean anterior / posterior interfragmentary pressure in the groups with K-wires and cannulated screws ranged within 0.16-0.40MPa / 0.12-0.35MPa and 0.37-0.59MPa / 0.10-0.30MPa, respectively. These changes remained non-significant for both groups and loading phases (P≥0.171). Mean anterior / posterior fracture site displacement for K-wires and cannulated screws ranged within -0.01-0.53mm / 0.11-0.74mm and 0.11-0.55mm / -0.10-0.50mm, respectively. Anterior displacement remained without significant changes for both groups and loading phases (P≥0.112). However, posterior displacement underwent a significant increase in the course of knee extension for K-wires (P≤0.047), but not for cannulated screws (P≥0.202). Significantly smaller displacement at the posterior fracture site was detected in the group with cannulated screws compared to K-wires at 60° and 75° extension phase (P≤0.017), as well as at 45°, 60° and 75° flexion phase (P≤0.018). The critical value of 2mm displacement at the posterior fracture site was not reached for any specimen and fixation technique. Knee extension was accompanied by synchronous increase in quadriceps pulling force. CONCLUSIONS: Tension band wiring fulfills from a biomechanical perspective the requirements for sufficient stability of transverse patella fracture fixation. It should, however, rather be considered as a static fixation principle than a dynamic one. Tension band wiring with cannulated screws was found advantageous over Kirschner wires in terms of interfragmentary movements at the posterior fracture site.

[Titanium or steel as osteosynthesis material : Systematic literature search for clinical evidence]. / Titan oder Stahl als Osteosynthesematerial : Systematische Literaturrecherche über die klinische Evidenz.

BACKGROUND: The selection of the appropriate implant material, stainless steel or titanium, is still the decision of the surgeon and/or the affiliated institution. Additionally, remarkable international differences can be found between the different markets, which cannot really be explained. OBJECTIVE: A systematic literature search was performed to verify whether there is clinical evidence for the preference of one material over the other. MATERIAL AND METHODS: The systematic literature search was performed utilizing the internet databases PubMed, Cochrane and Web of Science. Comparative studies were included that reported on adult patients with osteosynthesis of extremities after trauma using either stainless steel or titanium implants. Information was extracted about infection rates, incidence of clinically relevant allergies, problems with implant removal and other complications. RESULTS: A total of 18 publications were identified to be eligible and 2 referenced articles were added. In summary, there is insufficient clinical evidence that the use of titanium or steel implants has a positive or negative effect on fracture healing, shows different rates of allergies, different rates of infections or mechanical failure. No supporting evidence could be identified for the difficulties with removal of titanium implants reported by surgeons. CONCLUSION: This systematic literature search did not provide any clinical evidence for material-related differences between titanium or stainless steel implants for fracture fixation. Based on the current clinical evidence both titanium and steel implants can be considered to be of equal value. The reported difficulties with implant removal are not reflected in the published literature.

Semi-rigid screws provide an auxiliary option to plate working length to control interfragmentary movement in locking plate fixation at the distal femur.

BACKGROUND: Extent and orientation of interfragmentary movement (IFM) are crucially affecting course and quality of fracture healing. The effect of different configurations for implant fixation on successful fracture healing remain unclear. We hypothesize that screw type and configuration of locking plate fixation profoundly influences stiffness and IFM for a given load in a distal femur fracture model. METHODS: Simple analytical models are presented to elucidate the influence of fixation configuration on construct stiffness. Models were refined with a consistent single-patient-data-set to create finite-element femur models. Locking plate fixation of a distal femoral 10mm-osteotomy (comminution model) was fitted with rigid locking screws (rLS) or semi-rigid locking screws (sLS). Systematic variations of screw placements in the proximal fragment were tested. IFM was quantitatively assessed and compared for different screw placements and screw types. RESULTS: Different screw allocations significantly affect IFM in a locking plate construct. LS placement of the first screw proximal to the fracture (plate working length, PWL) has a significant effect on axial IFM (p < 0.001). Replacing rLS with sLS caused an increase (p < 0.001) of IFM under the plate (cis-cortex) between +8.4% and +28.1% for the tested configurations but remained constant medially (<1.1%, trans-cortex). Resultant shear movements markedly increased at fracture level (p < 0.001) to the extent that plate working length increased. The ratio of shear/axial IFM was found to enhance for longer PWL. sLS versus rLS lead to significantly smaller ratios of shear/axial IFM at the cis-cortex for PWL of ≥ 62 mm (p ≤ 0.003). CONCLUSION: Mechanical frame conditions can be significantly influenced by type and placement of the screws in locking plate osteosynthesis of the distal femur. By varying plate working length stiffness and IFM are modulated. Moderate axial and concomitantly low shear IFM could not be achieved through changes in screw placement alone. In the present transverse osteotomy model, ratio of shear/axial IFM with simultaneous moderate axial IFM is optimized by the use of appropriate plate working length of about 42-62 mm. Fixation with sLS demonstrated significantly more axial IFM underneath the plate and may further contribute to compensation of asymmetric straining.

Callus massage after distraction osteogenesis using the concept of lengthening then dynamic plating.

Correction of complex deformities is a challenging procedure. Long-term wearing of a fixator after correction and lengthening are inconvenient and has a high rate of complication. The goals of the surgical treatment in the presented case were: (1) correction of the deformity and lengthening of the left leg by the Taylor spatial frame (TSF, Smith and Nephew, Marl, Germany); (2) reduction in the time the patient wears the TSF by changing the fixation system to a plate (lengthening then plating-LTP) and using a locking compression plate in conjunction with the 5.0 dynamic locking screws in order to accelerate bone healing.

Evaluation of the effectiveness of the angular stable locking system in patients with distal tibial fractures treated with intramedullary nailing: a multicenter randomized controlled trial.

BACKGROUND: Angular stable locking of intramedullary nails has been shown to enhance fixation stability of tibial fractures in biomechanical and animal studies. The aim of our study was to assess whether use of the angular stable locking system or conventional locking resulted in earlier full weight-bearing with minimum pain for patients with a distal tibial fracture treated with an intramedullary nail. METHODS: A prospective multicenter, randomized, patient-blinded trial was conducted with adults who had a distal tibial fracture. Patients' fractures were managed with an intramedullary nail locked with either an angular stable locking system or conventional locking screws. Outcomes were evaluated at six weeks, twelve weeks, six months, and one year after surgery. Time to full weight-bearing with minimum pain was calculated with use of daily entries from patient diaries. Secondary outcomes included pain at the fracture site under load, quality of life, gait analysis, mobility, radiographic findings, and adverse events. RESULTS: One hundred and forty-two patients were randomly allocated to two treatment groups: seventy-five to the group receiving intramedullary nailing with the angular stable locking system and sixty-seven to the group receiving conventional intramedullary nailing. No clinically important differences were found for either the primary or secondary outcome parameters between the groups during the entire follow-up period. CONCLUSIONS: Use of an angular stable locking system with intramedullary nailing did not improve the outcome compared with conventional locking screws in the treatment of distal tibial fractures.

DLS 5.0--the biomechanical effects of dynamic locking screws.

INTRODUCTION: Indirect reduction of dia-/metaphyseal fractures with minimally invasive implant application bridges the fracture zone in order to protect the soft-tissue and blood supply. The goal of this fixation strategy is to allow stable motion at the fracture site to achieve indirect bone healing with callus formation. However, concerns have arisen that the high axial stiffness and eccentric position of locked plating constructs may suppress interfragmentary motion and callus formation, particularly under the plate. The reason for this is an asymmetric fracture movement. The biological need for sufficient callus formation and secondary bone healing is three-dimensional micro movement in the fracture zone. The DLS was designed to allow for increased fracture site motion. The purpose of the current study was to determine the biomechanical effect of the DLS_5.0. METHODS: Twelve surrogate bone models were used for analyzing the characteristics of the DLS_5.0. The axial stiffness and the interfragmentary motion of locked plating constructs with DLS were compared to conventional constructs with Locking Head Screws (LS_5.0). A quasi-static axial load of 0 to 2.5 kN was applied. Relative motion was measured. RESULTS: The dynamic system showed a biphasic axial stiffness distribution and provided a significant reduction of the initial axial stiffness of 74.4%. Additionally, the interfragmentary motion at the near cortex increased significantly from 0.033 mm to 0.210 mm (at 200N). CONCLUSIONS: The DLS may ultimately be an improvement over the angular stable plate osteosynthesis. The advantages of the angular stability are not only preserved but even supplemented by a dynamic element which leads to homogenous fracture movement and to a potentially uniform callus distribution.

A biomechanical study on proximal plate fixation techniques in periprosthetic femur fractures.

INTRODUCTION: Proximal plate fixation is a crucial factor in osteosynthesis of periprosthetic femur fractures. Stability and strength of different fixation concepts for proximal plate fixation were compared. MATERIALS AND METHODS: Twelve fresh frozen, bone mineral density matched human femora, instrumented with cemented hip endoprosthesis were osteotomized simulating a Vancouver B1 fracture. Specimens were instrumented with locking compression plates, fixed proximally with either locking attachment plate (LAP), monocortical screws, cerclage plus monocortical screws (1cerclage) or cerclages only (4cerclages). Cyclic testing was performed with monotonically increasing load until failure. Relative movements at the proximal plate-femur interface were registered by motion tracking. RESULTS: The LAP construct exhibited a significantly longer cumulative survival (failure criterion 1mm separation at the proximal plate fixation) compared to the monocortical (p=0.048) and 4cerclages constructs (p=0.012) but not to 1cerclage constructs. CONCLUSION: Bicortical screw anchorage improves proximal plate fixation in periprosthetic fractures. The cerclage-screw combination is a valuable alternative especially in osteoporotic bone.

Mechanical behavior of fixation components for periprosthetic fracture surgery.

BACKGROUND: Reliable periprosthetic fracture treatment needs detailed knowledge on the mechanical behavior of the fixation components used. The holding capacity of three conventional fixation components for periprosthetic fracture treatment was systematically investigated under different loading directions. METHODS: Locking compression plates were fixed to a 7 cm long part of diaphyseal fresh frozen human femur with either a single 1.7 mm cerclage cable, a 5.0mm monocortical or a bicortical locking screw (n=5 per group). Constructs were loaded in lateral, torsional and axial direction with respect to the bone axis in a load-to-failure test. Corresponding stress distribution around the screw holes was analyzed by finite element modeling. FINDINGS: Both screw fixations revealed significantly higher stiffness and ultimate strength in axial compression and torsion compared to the cerclage (all P<0.01). Ultimate strength in lateral loading and torsion was significantly higher for bicortical screws (mean 3968 N SD 657; mean 28.8 Nm SD 5.9) compared to monocortical screws (mean 2748 N SD 585; mean 14.4 Nm SD 5.7 Nm) and cerclages (mean 3001N SD 252; mean 3.2 Nm SD 2.0) (P≤0.04). Stress distribution around the screw hole varied according to the screw type and load direction. INTERPRETATION: Fixation components may be combined according to their individual advantages to achieve an optimal periprosthetic fracture fixation.

Fatigue performance of angle-stable tibial nail interlocking screws.

PURPOSE: Tibial nail interlocking screw failure often occurs during delayed fracture consolidation or at early weight bearing of nailed unstable fractures, in general when high implant stress could not be reduced by other means. Is there a biomechanical improvement in long-term performance of angle stable locking screws compared to conventional locking screws for distal locking of intramedullary tibial nails? METHODS: Surrogate bones of human tibiae were cut in the distal third and distal locking of the 10 mm intramedullary tibial nail was performed with either two angle stable locking screws or two conventional locking screws in the mediolateral plane. Six specimens per group were mechanically tested under quasi-static and cyclic axial loading with constantly increasing force. RESULTS: Angle stable locking screw constructs exhibited significantly higher stiffness values (7,809 N/mm ± 647, mean ± SD) than conventional locking screw constructs (6,614 N/mm ± 859, p = 0.025). Angle stable locking screw constructs provided a longer fatigue life, expressed in a significantly higher number of cycles to failure (187,200 ± 18,100) compared to conventional locking screw constructs (128,700 ± 7,000, p = 0.004). CONCLUSION: Fatigue performance of locking screws can be ameliorated by the use of angle stable locking screws, being especially important if the nail acts as load carrier and an improved stability during fracture healing is needed.

Underneath the cerclage: an ex vivo study on the cerclage-bone interface mechanics.

INTRODUCTION: Cerclages regain interest due to a rising number of periprosthetic fractures. The contact distribution at the circumferential cerclage-bone interface is still unknown. Local interface pressure depends on the amount of contact area. Cortical damage at the interface would provoke cerclage loosening. Therefore, the contact area, the bone pressure along the interface and the cortical resistance underneath loaded cerclages were determined in an ex vivo model. MATERIALS AND METHODS: Human diaphyseal femoral bone was used with differing cross-sectional geometry. Bone contact points of fixed 1.5 mm wire and 1.7 mm cable cerclages were identified from axial radiographs. Pressure distribution at the cerclage-bone interface was recorded with a pressure-measuring film using a distraction setup with two cortical half shells. Bone shells with installed cerclages were separated with up to 400 N force and were subsequently analyzed histologically to detect cortical damage. RESULTS: Both cerclage types exhibited a point contact fixation with non-loaded spanned zones in-between. Cables cover larger contact areas. Both cerclages exhibited an inhomogeneous interface pressure distribution depending on the bone surface geometry. Histology revealed intact cortical bone without cortical affection after loading of both cerclage types. CONCLUSION: Point contact fixation of the cerclages installs non-loaded, spanned zones where the periosteum is not compressed, rendering a strangulation of the blood supply unlikely. Cortical bone withstands static concentric pressure produced by the cerclage. Cortical groove formation is attributed to instability under functional load and not to weakness of the cortex itself.

Use of the less invasive stabilization system (LISS) in patients with distal femoral (AO33) fractures: a prospective multicenter study.

INTRODUCTION: The Less Invasive Stabilization System (LISS) is an internal fixator that can be inserted percutaneously by means of a minimally invasive surgical approach. This paper presents the use of this system exclusively in patients with AO33 distal femoral fractures, a group in which fracture management is often complicated by multiple trauma and soft-tissue damage. MATERIALS AND METHODS: A series of 62 patients (mean age 52 years) with 66 AO33A or C fractures received the LISS implant and were followed prospectively for 12 months. Assessments included the radiographic evaluation of implant placement and healing, measurement of valgus/varus and sagittal joint malalignment, and the assessment of weight-bearing capacity and range of motion. RESULTS: The mean duration of surgery was 85 min (range 40-135 min) for 33A fractures and 149 min (range 50-300 min) for 33C fractures. Postoperative radiographic assessments showed that the LISS implant was positioned correctly in 59 cases (89%). Assessment of valgus/varus alignment showed correct axial alignment in 49 cases (74%), a deviation of 5-10 degrees in 13 cases, and a 10-20 degrees deviation in 1 case. Correct sagittal alignment was observed in 56 cases (85%), 5-10 degrees malalignment in 5 cases, and 10-20 degrees in 2 cases. During the course of the 1-year follow-up, 8 patients (9 fractures) died; 2 other patients were not available for follow-up. Complete fracture healing was achieved in 85% of the followed-up patients. Forty-eight patients were capable of full weight-bearing. After fracture healing, maximum flexion of the injured limb was on average 80% of the range of the uninjured limb. An extension deficit of more than 5 degrees was measured in 3 cases. Of the 62 patients, 14 underwent further operations during the course of follow-up. Of these, 6 required bone grafting and 3 refixation of the implant due to implant loosening. Deep infections requiring several debridements occurred in 2 patients. No complications relating solely to the implant were observed. CONCLUSION: The LISS showed good overall results in the treatment of these difficult fractures. It is a good alternative to conventional extramedullary and intramedullary stabilizing techniques, especially in more complex fracture situations.