Novel applications of osseointegration in orthopedic limb salvage surgery

Salvage Treatment for a Periprosthetic Humeral Nonunion: A Case Report

The patient, a 69-year-old female, presented one year after receiving a total elbow arthroplasty with a nonunion periprosthetic fracture of the humerus. Due to the patient's severe osteoarthritis of the ipsilateral shoulder and significant humeral deformity, a procedure linking the total elbow arthroplasty to the reverse shoulder implant via a cemented allograft-composite linkage sleeve was performed. Previous literature suggests upper extremity salvage surgery using large-scale allografts is successful in treating large tumor or infection-derived defects, though data is lacking as to whether this treatment is effective in periprosthetic fractures in patients with significant comorbidities. This patient's success in the postoperative year supports the use of allograft-composite reconstruction followed by linkage to a reverse shoulder implant as a salvage treatment for periprosthetic fractures under certain conditions, such as multiple adjacent implants, bone deformity, and severe osteoarthritis.

Reduced Cell Adhesion on LightPLAS-Coated Implant Surfaces in a Three-Dimensional Bioreactor System

Most implants used in trauma surgery are made of steel and remain inside the body only temporarily. The strong tissue interaction of such implants sometimes creates problems with their explantation. Modified implant surfaces, which decrease tissue attachment, might allow an easier removal and therefore a better outcome. Such a modification must retain the implant function, and needs to be biocompatible and cost-effective. Here, we used a novel VUV-light (Vacuum-Ultraviolett)-based coating technology (LightPLAS) to generate coated stainless-steel plates. The tested LightPLAS coating only had an average thickness of around 335 nm, making it unlikely to interfere with implant function. The coated plates showed good biocompatibility according to ISO 10993-5 and ISO 10993-12, and reduced cell adhesion after four different time points in a 2D cell culture system with osteoblast-like MG-63 cells. Furthermore, we could show decreased cell adhesion in our 3D cell culture system, which mimics the fluid flow above the implant materials as commonly present in the in vivo environment. This new method of surface coating could offer extended options to design implant surfaces for trauma surgery to reduce cell adhesion and implant ingrowth. This may allow for a faster removal time, resulting in shorter overall operation times, thereby reducing costs and complication rates and increasing patient wellbeing.

What Are the Long-term Surgical Outcomes of Compressive Endoprosthetic Osseointegration of the Femur with a Minimum 10-year Follow-up Period?

BACKGROUND

Endoprosthetic reconstruction after oncologic resection of bone tumors requires stable fixation between the prosthesis and residual host bone. Compressive osseointegration has been developed as an alternative to traditional stemmed implants to address the challenges and complications of achieving this fixation. Sufficient time has now passed from the advent of compressive implants to allow for an assessment of the intermediate-term and long-term results of this form of fixation.

QUESTIONS/PURPOSES

At a minimum follow-up of 10 years after implantation of a compressive osseointegration device for oncologic reconstruction: (1) What is the risk of periprosthetic fracture, aseptic loosening, or implant breakage resulting in revision surgery for endoprosthesis removal? (2) What is the long-term cortical response at the host-endoprosthesis interface as visualized on plain radiographs?

METHODS

A single-center, retrospective study was performed between 2002 and 2010, in which 110 patients with primary bone sarcoma of the proximal or distal femur were considered for oncologic resection and reconstruction. Patients were considered for a compressive osseointegration endoprosthesis if they were 50 years of age or younger, had not previously received femoral radiation, had no metabolic disease impairing bone healing, were not diagnosed with metastatic disease, and had life expectancy greater than six months. Of the 110 patients, 25 were treated with a compressive osseointegration implant of the proximal or distal femur, and 85 patients were treated with conventional stemmed implants or amputation because of older age, advanced disease, metabolic comorbidities, inability to tolerate a nonweightbearing postoperative period, or in the case of rotationplasty, patient preference. All patients who received this device during the period of study were considered eligible for inclusion in this review. The median (range) age was 18 years (7 to 50), and 13 of 25 patients were men. Five patients died of disease before the minimum follow-up duration of 10 years; two underwent amputation due to local recurrence and three died with the implant in situ, leaving 20 patients for complete analysis. Median follow-up was 144 months, and all 20 surviving patients had a minimum follow-up of 10 years (121 to 230 months). The primary endpoint was reoperation and implant removal for periprosthetic fracture, aseptic loosening, or mechanical breakage of any component of the compressive device in the endoprosthesis. In final analysis, death was considered a competing event to revision surgery, and cumulative incidence was reported after competing-event analysis. A secondary aim was radiographic evaluation of the host-implant interface to assess the long-term cortical response to compressive osseointegration.

RESULTS

Spindle fracture or loosening was noted in three patients, and the remaining 17 patients maintained the compression device until the final follow-up. The risk of reoperation for aseptic loosening, periprosthetic fracture, or mechanical breakage of the implant using a competing risks estimator was 12% at 10 years (95% CI 0% to 26%). These complications occurred within 29 months of the index surgery; no patients had implant loosening or mechanical breakdown after this initial period. On radiographic assessment, 14 patients demonstrated cortical hypertrophy of the bone-implant interface, six patients had maintenance of the native cortical contour, and no patients had cortical atrophy or narrowing at the implant interface.Conclusion Long-term follow-up in patients with compressive osseointegrative endoprosthetic devices demonstrated no late revisions because of periprosthetic fracture, aseptic loosening, or implant breakage in this cohort with a minimum 10-year follow-up. There was no evidence of late-onset cortical atrophy or stress shielding at the host-implant interface. This study supports the long-term stability of the interface between host bone and the endoprosthesis in compressive osseointegration devices.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

A Quantitative Approach for the Bone-implant Osseointegration Assessment Based on Ultrasonic Elastic Guided Waves

Quantitative and reliable monitoring of osseointegration will help further evaluate the integrity of the orthopaedic construct to promote novel prosthesis design and allow early mobilisation. Quantitative assessment of the degree or the lack of osseointegration is important for the clinical management with the introduction of prosthetic implants to amputees. Acousto-ultrasonic wave propagation has been used in structural health monitoring as well as human health monitoring but so far has not extended to osseointegrated implants or prostheses. This paper presents an ultrasonic guided wave approach to assess the osseointegration of a novel implant. This study explores the potential of integrating structural health monitoring concepts into a new osseointegrated implant. The aim is to demonstrate the extension of acousto-ultrasonic techniques, which have been widely reported for the structural health monitoring of engineering structures, to assess the state of osseointegration of a bone and implant. To illustrate this potential, this paper will report on the experimental findings which investigated the unification of an aluminium implant and bone-like geometry surrogate. The core of the test specimen is filled with silicone and wrapped with plasticine to simulate the highly damped cancellous bone and soft tissue, respectively. To simulate the osseointegration process, a 2-h adhesive epoxy is used to bond the surrogate implant and a bone-like structure. A series of piezoelectric elements are bonded onto the surrogate implant to serve as actuators and sensors. The actuating piezoelectric element on an extramedullary strut is excited with a 1 MHz pulse signal. The reception of the ultrasonic wave by the sensing elements located on the adjacent and furthest struts is used to assess the integration of this implant to the parent bone structure. The study shows an Osseointegration Index can be formulated by using engineering and acousto-ultrasonic methods to measure the unification of a bone and implant. This also highlights a potential quantitative evaluation technique regardless of bone-implant geometry and soft tissue damping.