Design of an affordable, modular implant device for soft tissue tension assessment and range of motion tracking during total hip arthroplasty

<p>Inexperienced surgeons undertaking hip arthroplasties are twice as likely to experience errors than their experienced colleagues, leading to dislocations, pain and discomfort for the patients. To address this issue, a new 3DOF force measurement system was developed and integrated in multiple new prototypes able to measure forces and movements intraoperatively in 3D. The prototypes were evaluated in three cadaver trials, with the goal of providing surgeons objective data to help determine the optimal implant fit and configuration. The devices comprise deformable polymer material that provide strain-based displacements measured with electromagnetic-based sensors and inertial measurement unit (IMU) for motion data. Device results show an accuracy of approx. 2 N and a sensitivity of approx. 1 N. Cadaver results indicated that soft tissue forces on the hip joint peak in the order of ~100 N and trend with positions of the leg during range of motion (ROM) tests, although force patterns differ between each cadaver. We propose that by monitoring forces and force patterns, in combination with standardised ROM tests, anomalies could be detected and corrected during surgery.</p>

The Wagner Modular (S2) Prosthesis for Proximal Femur Bone Loss ; Prospective Study of 19 Cases

Background: Wagner proximal femur prosthesis is the versatile modular implant. Study Design: Prospective study Setting: Department of Orthopaedic Surgery Dow University of Health Sciences / Civil Hospital Karachi, from January 2013 to December 2019. Methodology: Total 19 patients of both genders with proximal femur bone loss due to tumor, implant failure for proximal femur fixation, comminuted intertrochanteric fracture, and failed arthroplasty included in the study. After taking written informed consent, detailed demographics including age, gender, indication of wagner prosthesis, and wagner stem type were recorded. Among all the patients 11 patients received total hip replacement and 8 patients received bipolar. Complications associated with procedure were recorded. Outcomes were assessed by Merle D Aubgine scale. Results: Total 19 patients were included in the study who were operated with wagner prosthesis for proximal femur bone deficit problems. 7 (37%) patients were male and 12 (67%) were female , between age of 16 to 70. 13 (68%) patient have proximal femur problem on right side and 6(32%) patient on left side .10 Patient have proximal femur fixation problems and 9 with proximal femur tumor. Modular wagner prosthesis used in all patients . Per-operative one (5%) patient have perforation of cortex and One (5%)patient posterior hip dislocation on next day . Two (11%) patient had per-operative fracture . Maximum follow-up is from 6.3 years to minimum 6 months. One patient with metastasis died within four weeks of surgery. Outcome measured with modified Merle D Aubgine scale showed no excellent , good in 15(79%) , fair 3 (16%), poor 1(5%). Conclusion: Wagner proximal femur modular implant is a versatile implant for proximal femur fixation failure and after proximal femur resection in tumor patients. It is modular with variable options to make stable hip joint. It is cheap as comparative to proximal femur replacement implant for tumor. Keywords: Implant failure, Proximal femur, Tumor, Wagner implant.

Surgical Technique and Outcome of Custom Joint-Sparing Endoprosthesis as a Reconstructive Modality in Juxta-Articular Bone Sarcoma

Background. Joint-sparing limb salvage surgery (JSLSS) is an advancement in the techniques and concepts of limb salvage surgery, which makes it possible to save not only the limb affected by malignancy but also the adjacent joint and the epiphyseal plate. In the growing child, this procedure is technically demanding due to the availability of small length of bone for implant purchase. Reconstruction options can be biological reconstruction or endoprosthesis; however, the outcome of endoprosthetic reconstruction after joint-sparing resection is not well described in the literature. Purposes. (1) To determine the prosthesis survival rates when using customized Joint-Sparing Endoprosthesis (JSE) after juxta-articular resection of bone tumors, (2) to investigate the rates of local recurrence, (3) to evaluate the need for revision surgery, and (4) to compare the outcome of customized JSE with that of joint-sacrificing techniques. Methods. In our study, joint sparing is defined as any procedure where a custom-made JSE is used in lieu of sacrificing the adjacent joint whenever the length of the remaining bone segment is not enough to accommodate the stem of a modular implant. Twenty-eight patients received JSE, and 31 joints were spared. Their age ranged from 4 to 55 years with a median age of 13 years. Twenty-one patients received surgery for primary reconstruction and 7 patients for revision of failed bone allograft or modular implant. Twenty-four joints are spared in the lower limbs and 7 in the upper limbs. Osteosarcoma was the most common pathological diagnosis (n = 13). Flat surface HA-coated custom JSE was used to spare 15 joints, and short-stemmed custom JSE was used to spare 16 joints. The length of the remaining bone epiphysis for JSE anchorage from the knee and ankle joints was 25–75 mm, median = 45 mm, and the length of the cortical bone remaining for the proximal femur and distal humerus was 5–70 mm, median = 10 mm. Results. Operative time was 2.5 to 4 hours (avg. 3 hr.) The bone resection surface fitted the prosthesis surface with <2 mm difference. Histological examination of all resected specimens shows clear bone resection margins; 2 patients had positive soft tissue margins. At mean follow-up period of 3 years (6 months–10 years), 6 patients developed local and systemic recurrences, three of them had a pathological fracture at the time of diagnosis (P=0.139), and 4 showed a poor response to chemotherapy (P=0.014); all recurrences occurred in the soft tissue. Implant survival at 5 years was 86.15%, and MSTS score was 90% (83–96%). Conclusions. Whenever this kind of implant is affordable and can be utilized, particularly in younger age groups, JSE may be a good reconstruction option to avoid the use of expandable implants and to avoid the potentially higher revision and complication rates associated with biological reconstruction, as well as the complications of conventional joint-sacrificing implant, mainly dislocations and polyethylene wear and tear.

Development and manufacturing of a custom made implant regarding the new European Medical Device Regulation

New technologies are great opportunities for personalized medicine. Custom made implants can be very helpful for patients with severe bone defects or in case of bone tumor. Through the European Union it is regulated how many possibilities and restrictions all medical devices have. Because of critical vulnerabilities a new European Medical Device Regulation (MDR) was published in May 2017 and it will enter into force in May 2020. For the manufacturers of customized products it will change the documentation of the manufacturing and tracking of serious incidents. Patients with a pelvis defect of Paprosky IIb and higher can benefit from a custom made pelvis implant, because all planning steps according to biomechanic and bone contact to the implant can be designed and proofed during a reconstruction process. With regular modular implant systems, it probably can be a trial and error procedure during the surgery according to biomechanic and a stable position of the implant. Based on the 3D-Reconstruction of CT-Scans of a patient with a Paprosky 2b pelvis defect, a personalized acetabulum implant was designed. To maintain as much bone as possible, the implant was shaped to the remaining pelvic bone stock. Additive manufacturing gives the opportunity to produce custom made single items even in a quality that ful-fills the requirements of the MDR. Modern Selective Laser Melting (SLM) and Electron Beam melting (EBM) Systems are able to produce Titanium or CoCr parts in the ISO standards for Implants (ISO 5832 ff). In this study the process chain, starting from the reconstruction, to the design and the production of a custom made acetabulum cup was run through on an exemplary CTData of one patient. With this example, it was shown that it is possible, to establish a process, that is able to address surgical needs for patients that benefit from those techniques.

Numerical Analysis on the Influence of Taper Junction Corrosion Profile With Emphasis on Ti-Alloy Modular Hip Arthroplasty

Modular designs give orthopaedic surgeons a greater flexibility to custom fit the implant to the patients bone while performing total hip arthroplasty. Titanium alloy (Ti6Al4V (ASTM F-136)) is typically used for modular hip implant stems. This highly corrosion resistant alloy forms passive surface oxide films spontaneously. However, with modular designs, micro-motion may occur at the taper junctions during mechanical loading. Crevices between the taper junctions may allow the body fluids to enter and remain stagnant. These conditions make the modular tapers susceptible to fatigue and mechanically assisted crevice corrosion. The in vivo degradation of metal alloy implants compromises the structural integrity. The influence of stress corrosion induced pits of a titanium-alloy modular implant in cement-less total hip arthroplasty was numerically investigated. The effect of pit geometry parameters — cylindrical, conical, and hemispherical dimple are compared and discussed in terms of taper performance.

Irrigation and Debridement for Periprosthetic Hip Infection: Does Timing Play a Role?

Periprosthetic joint infection (PJI) is a devastating complication of total joint arthroplasty (TJA). The rate of PJIs in total hip arthroplasty (THA) procedures varies from 0.3 to 2.9%. Irrigation and debridement (I&D) with modular implant exchange is often performed to treat PJIs. Early management of infection is cited to offer a higher success rate. The goal of this study was to examine the outcomes of early I&D for THA PJIs. We reviewed 38 patients diagnosed with a PJI between 2009 and 2014 who went on to have I&D with modular implant exchange. Patients were separated into three cohorts based on time from index procedure (≤4, 4–8, and ≥8 weeks), and were subsequently linked to treatment success and failure. Success was defined as the eradication of infection and resolution of presenting symptoms. All patients who required additional procedures due to infection were considered failures. Twenty-eight patients (73.7%) were successfully treated while 10 patients (26.3%) required further surgical interventions for persistent infection. Overall, average time between THA and I&D was 44.4 days. Successful I&Ds on average occurred within 41.9 days of the index procedure; while unsuccessful I&Ds were performed 51.6 days after index THA. Additionally, our study demonstrated that obese patients were more likely to fail debridement, antibiotics, irrigation, and retention of the prosthesis (DAIR) procedures (p = 0.006). While our results demonstrate that the average time to I&D with a modular exchange was shorter for those who had a successful outcome, the difference was not significant (p = 0.37).