Knee Implants CNC Machining for Medical Industry

Innovative technologies for knee implants include CNC milling on all axes for the femur pieces of knee implants. It involves the creation of complex three-dimensional condyles that emulate the anatomical three-dimensional contours along the knee's anterior-posterior and medial-lateral axes and the three-dimensional contours of the knee with varying curvatures. For femoral trochlear grooves, CNC milling creates patellar tracking surfaces. Peg holes, screw holes, and cement pockets in the tibial baseplates are drilled and located with positional accuracy of ±0.1 millimeters. The undersurfaces of the tibial baseplates are milled to a surface flatness of 0.020 millimeters for uniform load distribution and specified radius contours are milled onto the condylar surfaces to match the contours of the polyethylene insert. CNC techniques that include wire EDM are used for grinding and polishing of articulating surfaces. Konstrukta and Zebrak describe the surfaces as achieving Ra of 0.02 microns on cobalt and 0.01 microns on oxidized zirconium surfaces. Porous coatings are made using plasma spray and sintered bead techniques. 50 to 400 micron base plates are created for bone ingrowth. Texturing surfaces with thread milling and tread blasting are used for interlocking features. Modular junctions and screw holes receive thread milling, while laser marking, and screw holes receive thread milling and oxidation of zirconium. The surface holds stable ceramic layers and textured surfaces create a mechanical lock. The condylar surfaces and articulated Z and articulated Z surfaces of the knee implants created by Z fail to meet ISO standards for thickness and surface quality.

We routinely achieve tolerances as tight as ± 0.0002 inches on critical implant features which include: femoral condyle radii within ± 0.050 millimeters for contact mechanics with polyethylene inserts that maintain designed conformity to prevent edge loading and accelerated wear, accurate tibial baseplate flatness within 0.020 millimeters for uniform cement penetration or bone contact to mitigate uneven load distribution, proper post and cam geometry in posterior stabilized designs within ± 0.1 millimeters for kinematic function designed to provide rollback and prevent anterior-posterior instability, controlled peg and keel dimensions designed for tibial fixation within ± 0.1 millimeters for proper fit in prepared bone, accurate screw hole locations within ± 0.2 millimeters for supplemental fixation and modular component attachment, proper rotational alignment features within ± 1 degree designed to allow component positioning relative to anatomical landmarks, uniform component thickness within ± 0.05 millimeters to maintain designed joint line and flexion-extension gaps, controlled surface finish on articulating surfaces with Ra below 0.02 microns to minimize polyethylene wear, and accurate overall component dimensions within ± 0.2 millimeters for size consistency and surgical planning to allow implants achieve biomechanical stability with proper ligament balancing through flexion-extension range, approximating normal rollback and screw-home mechanism for knee kinematics, 120 degrees flexion for stair climbing and deep knee bends, polyethylene wear rates below 0.1 millimeters per year, and implant clinical performance with survival rates exceeding 95 percent at 10 years and 90 percent at 15 years in properly aligned and balanced total knee arthroplasty.

Yes. We offer flexible manufacturing capabilities including:
Rapid prototyping for design validation
Low-volume production for specialized applications
High-volume production with consistent quality control
Full structural and dimensional verification at every stage

Yes, all components are constructed utilizing ISO 13485 certified comprehensive quality management systems for the manufacturing of medical devices and for knee implants, confirming full adherence to FDA regulations for Class III medical devices, compliance with European Medical Device Regulation (MDR), fulfillment of biocompatibility testing per ISO 10993 for materials including cytotoxicity, sensitization, and long-term implantation studies, mechanical testing for wear performance per ISO 14243, ISO 14879 for tibial component fatigue and subsidence resistance, and ISO 14243 for mechanical testing, dimensional verification testing design and anatomical specifications, comprehensive traceability from raw material heat lot to the final sterile finished packaged product, enabling post market surveillance and investigation of adverse events, compliance with FDA Quality System Regulation and Good Manufacturing Practices for consistent quality and patient safety on devices that are already implanted on over a million patients all over the world annually.

We provide comprehensive finishing solutions tailored to aerospace requirements:
Anodizing (Type II and Type III)
Passivation for corrosion resistance
Precision polishing for aerodynamic surfaces
Custom protective coatings and thermal barriers

The lead time for knee implants depends on the design's complexity and the governing regulations. For the established design standard knee implant components, implant machining could take about 15 to 20 business days inclusive of surface finishing, quality assurance, and packing for sterilization. On the other hand, custom patient-specific implants and cutting guides could take about 3 to 4 weeks starting from the approval of the imaging to completed devices that are packaged for sterilization. For prototype runs needed for preclinical testing and for submission of implants for regulation, they could be completed in 10 to 14 days, although this depends on the available materials and the required surface finishing. Also, for high-volume production orders, we are able to minimize cycle time. For each of these orders we provide a production schedule during the quoting process and include all the time for material certifications.

The efficiency of CNC machining contributes to knee implants performance in multiple ways. Reproducing the effective geometry of the femoral condyle within ±0.050 facillitates the contact mechanics with polyethylene inserts positional conformity engineered to maintain contact stresses below 20 MPa to prevent accelerated wear and delamination. The flatness tolerance of the tibial baseplate affects the load distribution at the bone or cement interface. Poor load distribution causes subsidence and component migration which occurs in 2 to 5 percent of the implants poorly designed or manufactured. Articulating surfaces that are controlled to have an Ra of less than 0.02 microns have an elevated surface finish which friction and polyethylene wear particulates generation are produced thus extending the bearing life to over 15 years. Linear wear rates below 0.1 millimeters suggests effective wear. Correct post and cam geometry in posterior stabilized designs enables femoral rollback during flexion, which improves the flexion range to 125 plus degrees and prevents anterior-posterior instability. Accurate peg and keel dimensions in tibial implants reduces component loosening. Specifically designed screw holes are used in patients with osteoporosis for augmenting fixation and stem stabilization.
Achieving nearly perfect femoral and tibial rotations and avoiding patellofemoral complications associated with malrotation hinge on rotational alignment features and assistive technology in component positioning. Limiting variation with respect to component thickness consistently achieves the position of the designed joint line within 4mm of the anatomical location, protecting the function of the collateral ligaments and the patellofemoral joint. Optimized porous coating with 100 to 400 micron pores promotes bone ingrowth achieving biological fixation with interface strength exceeding 20 MPa enabling cementless fixation in younger patients. Tried and tested design, as well as the use of biocompatible materials, permit incorporation with no adverse tissue reactions, guaranteeing permanent implantation. Predictability with regard to the surgical technique in the assembly of limb segments is achievable with balanced flexion-extension gaps. This is the result of the quality of design and wavering standards of construction, as well as incorporation of features that remove fatigue from the assembly and use of materials.
When properly designed and manufactured, fatigue strength allows for more than 10 million cycles at ISO 14879 physiological stresses. This, together with precision machined knee implants, establishes the clinical groundwork for successful outcomes, including relief of pain, where the Knee Society Scores increase from 40 pre-operatively to more than 85 post-operatively, functional restoration where patients reclaimed their daily activities of walking, stair climbing, and some recreational activities, and restoration of function with implant survival rates over 95 percent at 10 years and 90 percent at 15 years for modern total knee prostheses with optimal alignment. Complication rates are low with infections below 1 percent, postoperative instability below 2 percent, and aseptic loosening below 0.5 percent per year. Cross-linked polyethylene showed minimal wear with a volumetric loss of less than 100 cubic millimeters over 10 years. Properly selected patients with good preoperative motion can achieve more than 120 degrees of flexion and range of motion. Patient satisfaction exceeds 80 percent alongside restoration of pain-free mobility and functional activities, work, and recreation for a 15 to 30 year post-operative lifetime to improve the quality of life for patients with severe knee arthritis or knee injuries.