Direct and indirect loading of the Ilizarov external fixator: the effect on the interfragmentary movements and compressive loads

The amount of weight bearing and the force transmission to the frame have an important influence on the results of treatment with an Ilizarov external fixator. The frame provides beneficial interfragmentary movements and compressive loads at the fracture site through elastic wires. Mobilisation can be achieved by applying a weight-bearing platform at the distal end of the fixator. The effect on the interfragmentary movements and the compressive loads in indirect and direct loading were analysed in this study using a composite tibia bone model. Displacement transducers were attached to measure the interfragmentary movements and to detect relative movements of the bone fragments and movements between the rings. The compressive loads in the osteotomy were measured with loading cells in the defect zone. The weight-bearing platform had a substantial effect on the biomechanical behaviour of the frame. It led to an indirect force transmission through the fixator with respect to the osteotomy, resulting in lower compressive loads, lower interfragmentary movements and higher mechanical stress on the frame

The influence of a weight-bearing platform on the mechanical behavior of two Ilizarov ring fixators: tensioned wires vs. half-pins

<p>Abstract</p> <p>Background</p> <p>A weight-bearing platform applied at the distal end of an Ilizarov external frame allows patients with hindfoot transfixations, foot deformities or plantar skin lesions to bear weight. This leads to an indirect loading of the fracture or osteotomy site. However, the effect on the fracture/osteotomy site's motion or compressive loads is unknown. The aim of this study was to analyze the mechanical effects of a weight-bearing platform on the traditional all-wire, four-ring frame in comparison to a two-ring frame consisting of half-pins.</p> <p>Methods</p> <p>Two frame configurations, with either anatomically positioned wires or half-pins, were analyzed with and without a weight-bearing platform applied underneath the distal ring. Composite tibiae with a mid-diaphyseal osteotomy of 3.5 mm were used in all the experiments. An axial load was applied with the use of a universal test machine (UTS^®). Interfragmentary movements, the relative movements of bone fragments and movements between rings were recorded using displacement transducers. Compressive loads at the osteotomy site were recorded with loading cells.</p> <p>Results</p> <p>Indirect loading with a weight-bearing platform altered the force transmission through the osteotomy. Indirect loading of the tibiae decreased the extent of the axial micro-motion by 50% under the applied weight load when compared to direct weight loading (p < 0.05). The half pin frame was 25% stiffer than the wire frame under both direct and indirect loading of the tibiae (p < 0.05). Compressive loads under indirect loading were reduced by 67% in the wire frame and by 57% in the half-pin frames compared to direct loading of the bones (p < 0.05). While axial loading in the wire frames resulted in plain axial movements at the site of the osteotomy, it was coupled with translational movements and angular displacements in the half pin mountings. This effect was more apparent in the case of indirect loading.</p> <p>Conclusions</p> <p>A weight-bearing platform has substantial influence on the biomechanical performance of an Ilizarov external fixator. Half-pins induce greater stiffness to the Ilizarov external fixator and allow the usage of only one ring per bone segment, but shear stresses at the osteotomy under axial loading should be considered. The results allow an estimation of the size and direction of interfragmentary movements based on the extent of weight bearing.</p

“Revision of subtrochanteric femoral nonunions after intramedullary nailing with dynamic condylar screw”

Abstract Background Nonunions of the subtrochanteric region of the femur after previous intramedullary nailing can be difficult to address. Implant failure and bone defects around the implant significantly complicate the therapy, and complex surgical procedures with implant removal, extensive debridement of the nonunion site, bone grafting and reosteosynthesis usually become necessary. The purpose of this study was to evaluate the records of a series of patients with subtrochanteric femoral nonunions who were treated with dynamic condylar screws (DCS) regarding their healing rate, subsequent revision surgeries and implant-related complications. Methods We conducted a retrospective chart review of patients with aseptic femoral subtrochanteric nonunions after failed intramedullary nailing. Nonunion treatment consisted of nail removal, debridement of the nonunion, and restoration of the neck shaft angle (CCD), followed by DCS plating. Supplemental bone grafting was performed in all atrophic nonunions. All patients were followed for at least six months after DCS plating. Results Between 2002 and 2017, we identified 40 patients with a mean age of 65.4 years (range 34–91 years) who met the inclusion criteria. At a mean follow-up period of 26.3 months (range 6–173), 37 of the 40 (92.5%) nonunions healed successfully (secondary procedures included). The mean healing time of the 37 patients was 11.63 months (± 12.4 months). A total of 13 of the 40 (32.5%) patients needed a secondary revision surgery; one patient had a persistent nonunion, nine patients had persistent nonunions leading to hardware failure, two patients had deep infections requiring revision surgery, and one patient had a peri-implant fracture due to low-energy trauma four days after the index surgery. Conclusions The results indicate that revision surgery of subtrochanteric femoral nonunions after intramedullary nailing with dynamic condylar screws is a reliable treatment option overall. However, secondary revision surgery may be indicated before final healing of the nonunion

Regenerate augmentation with bone marrow concentrate after traumatic bone loss

Distraction osteogenesis after post-traumatic segmental bone loss of the tibia is a complex and time-consuming procedure that is often complicated due to prolonged consolidation or complete insufficiency of the regenerate. The aim of this feasibility study was to investigate the potential of bone marrow aspiration concentrate (BMAC) for percutaneous regenerate augmentation to accelerate bony consolidation of the regenerate. Eight patients (age 22-64) with an average posttraumatic bone defect of 82.4 mm and concomitant risk factors (nicotine abuse, soft-tissue defects, obesity and/or circulatory disorders) were treated with a modified Ilizarov external frame using an intramedullary cable transportation system. At the end of the distraction phase, each patient was treated with a percutaneously injection of autologous BMAC into the centre of the regenerate. The concentration factor was analysed using flow cytometry. The mean follow up after frame removal was 10 (4-15) months. With a mean healing index (HI) of 36.9 d/cm, bony consolidation of the regenerate was achieved in all eight cases. The mean concentration factor of the bone marrow aspirate was 4.6 (SD 1.23). No further operations concerning the regenerate were needed and no adverse effects were observed with the BMAC procedure. This procedure can be used for augmentation of the regenerate in cases of segmental bone transport. Further studies with a larger number of patients and control groups are needed to evaluate a possible higher success rate and accelerating effects on regenerate healing

Does the Implementation of the PRO-IMPLANT Foundation Treatment Algorithm Improve the Outcome of Chronic Periprosthetic Knee Infections? Mid-Term Results of a Prospective Study.

BACKGROUND: Several treatment options for chronic periprosthetic joint infections have been published in the current literature, with an on-going discussion to determine effective management algorithms. OBJECTIVES: To compare outcomes of the two-stage exchange procedure in revision TKA prior to and after implementation of the PRO-IMPLANT Foundation treatment algorithm. The primary endpoints were defined as (i) revisions during the interval time, (ii) duration of the interval time and (iii) successful PJI eradication. MATERIAL AND METHODS: Between 02/2013 and 09/2016, 122 patients were included in a single-centre cohort analysis. 55 patients were treated according to the previously used algorithm (K1) and 67 according to the PRO-IMPLANT Foundation algorithm (K2). A minimum follow-up period of 3 years was set as the inclusion criterion. Successful eradication of infection was defined in accordance with the consensus criteria by Diaz-Ledezma et al. RESULTS: Successful eradication was achieved in 42 (67%) patients in K1 and 47 (85.5%) in K2 (p ≤ 0.005). The mean interval time was 88 days (range 51 - 353) in K1 and 52 days (range 42 - 126) in K2 (p ≤ 0.005). In K1, a mean of 0.8 (range 0 - 6) revisions were necessary during the interval period compared with 0.5 (range 0 - 4) in K2 (p = 0.066). CONCLUSION: Implementation of the PRO-IMPLANT treatment algorithm led to significant improvement in the outcome of periprosthetic joint infections. During mid-term follow-up, infection eradication was highly successful, with decreases in the interval time as well as the number of revisions

Accuracy of radiographic measurement techniques for the Taylor spatial frame mounting parameters

Aim!#!The correction accuracy of the Taylor Spatial Frame (TSF) fixator depends considerably on the precise determination of the mounting parameters (MP). Incorrect parameters result in secondary deformities that require subsequent corrections. Different techniques have been described to improve the precision of MP measurement, although exact calculation is reportedly impossible radiologically. The aim of this study was to investigate the accuracy of intraoperative and postoperative radiographic measurement methods compared to direct MP measurement from TSF bone mounting.!##!Methods!#!A tibial Sawbone® model was established with different origins and reference ring positions. First, reference MPs for each origin were measured directly on the frame and bone using a calibrated, digital vernier calliper. In total 150 MPs measured with three different radiographic measurement techniques were compared to the reference MPs: digital radiographic measurements were performed using soft-copy PACS images without (method A) and with (method B) calibration and calibrated image intensifier images (method C).!##!Results!#!MPs measured from a non-calibrated X-ray image (method A) showed the highest variance compared to the reference MPs. A greater distance between the origin and the reference ring corresponded to less accurate MP measurements with method A. However, the MPs measured from calibrated X-ray images (method B) and calibrated image intensifier images (method C) were intercomparable (p = 0.226) and showed only minor differences compared to the reference values but significant differences to method A (p &amp;lt; 0,001).!##!Conclusion!#!The results demonstrate that MPs can be accurately measured with radiographic techniques when using calibration markers and a software calibration tool, thus minimizing the source of error and improving the quality of correction

Necrotizing fasciitis and the midterm outcomes after survival

Background and Aims: Radical surgical intervention is necessary to save patients’ lives in cases of necrotizing fasciitis. This leads to persistent disabilities and most likely to a deteriorated quality of life. The purpose of this study was to evaluate the midterm outcomes after survival of necrotizing fasciitis. Materials and Methods: A retrospective analysis of 69 patients, treated for necrotizing fasciitis between 2003 and 2012. The patients were identified using the International Classification of Diseases (10th Revision) code M 72.6. Of the 50 survivors, 22 patients completed the Short Form 36 and Short Musculoskeletal Function Assessment questionnaires as a postal survey. The follow-up averaged 59 months (range: 6–128 months). Results: The average age at the time of necrotizing fasciitis was 60.0 years. The body mass index average was 29.7. The patients had a significantly decreased physical component summary score of 33.3 compared to a normative group (p < 0.001) (Short Form 36). They further showed a significantly decreased dysfunction and bother indices (Short Musculoskeletal Function Assessment) (p < 0.001). An increased age (⩾70 years) was associated with an inferior role emotional (p = 0.048) and physical functioning (p = 0.011) as well as social functioning (p = 0.038) (Short Form 36). The majority of patients (16, 72.7%) complained of pain at the final follow-up and 50% of patients required an assistive device on a regular basis. Conclusion: Patients who survived necrotizing fasciitis suffer from functional impairment and changed body appearance. Assistive devices or pain medication are often required, and the patients present with significantly decreased physical, social, and emotional functioning at the midterm follow-up. The patient’s age is a critical factor regarding functional or mental outcome parameters. Further research on the post-hospital course and long-term multidisciplinary care is required to improve the outcomes of these patients