Knee surgery basics

Since the first knee replacement surgery in 1968, there has been enormous progress in improving the surgical techniques and medical devices used to replace damaged bone and cartilage in the knee.1

Let's first review some of the basic surgical steps that almost all knee replacements have in common:

Bone preparation. During this step, the damaged cartilage surfaces at the ends of the femur (the thigh bone) and the tibia (the larger of the two lower leg bones) are removed along with a small amount of underlying bone.

Install the metal implants. During this step, carefully selected metal components are fitted to the prepared bones of both the femur and tibia.

Insert a spacer. During this step, a medical-grade, plastic spacer is attached to the lower, metal tibial component, creating a smooth surface for upper, metal femoral component to slide against as the knee moves.

All of the progress in knee replacement surgery and implant technology also means that today's informed patients face a wide array of surgery and implant choices, as well as a potentially confusing vocabulary of terms including total replacement, patient-matched instruments, partial replacement, robotic-assisted surgery, minimally invasive techniques and more. Let's explore and explain some of these:

Types of knee replacements

Total knee replacement

Total knee replacement (sometimes shortened to TKR) is a surgical procedure to replace the ends of the femur and the tibia that have been damaged by osteoarthritis or other conditions, with prosthetic devices that duplicate the motion and weight-bearing abilities of the original joint.

In Total knee replacement, the prosthesis is comprised of several parts:

Implant components

  • The tibial component includes a metal base and a plastic insert. Together these replace the top of the tibia (shin bone) and the cartilage in the knee to provide half of the new joint's bearing surface.
  • The femoral component replaces the bottom of the femur (the thigh bone). This component also replaces the groove in the natural knee where the patella or kneecap rides.
  • The patellar component replaces the surface of the knee cap, which rubs against the femur. The patella protects the joint, and the resurfaced patellar button will slide smoothly on the front of the joint. In some cases, surgeons do not resurface the patella.3

Partial knee replacement

Replacing only what is damaged

A partial knee replacement (also known as Unicompartmental, or UKR) may be recommended if arthritic damage is confined to only one area of your knee. Because a partial knee replacement doesn't extend across the entire joint, the damaged portion of the knee is replaced while the supporting ligaments vital to knee stability may be spared.

Candidates for partial knee replacement generally have osteoarthritis limited to one compartment of the knee; this group makes up roughly 35%+ of people dealing with knee pain.4,5

Partial knee replacement implant components are similar to Total Knee Replacement, but the implants replace only part of the tibial and femoral surfaces.

Knee surgery techniques and technologies

Traditional knee surgery may be enhanced with advanced techniques, tools and technologies. Since the earliest attempts at surgical knee replacement, there has a wide range of technological innovation. Medical imaging, more precise surgical tools, and the design and construction of the implants themselves have all come a long way since the first replacement surgery some 50 years ago. The intended benefit for patients is shorter recovery time, less post-surgical pain, longer lasting implants and more natural-feeling, 'knee-like' motion of the prosthesis.

Minimally invasive knee surgery

Whether you are having a total or a partial knee replacement, you may be a candidate for what's known as minimally invasive surgery. This surgical technique uses specially designed instruments that help minimize disruption of the soft tissues in the joint during your surgery, with the aim of reducing post-operative pain and speeding the recovery process. A primary cause of post-surgical pain is the swelling that occurs any time the soft tissue of the body is cut or otherwise manipulated. Minimally invasive surgery may also result in a smaller incision scar.

Robotic-assisted surgery - CORI◊ Surgical System

Some surgeons use robotic assistance as part of their knee replacement surgery. This assistance is designed to optimize the accuracy of bone preparation, implant positioning, and soft tissue balancing both in the planning stage and during the surgery itself. Robotic assistance leaves the surgeon in complete control of the operation while helping the implant to remain stable and properly aligned throughout the knee's full range of motion.

Want more detail on the CORI System? Visit our CORI pages for technical information, and references to scientific studies on its use and effectiveness.

Patient matched technology - VISIONAIRE◊ technology

Like robotic-assisted surgery, patient matched technologies such as VISIONAIRE Cutting Guides are intended to help make sure your implant is correctly sized and aligned based on your unique physical needs.

Created using your own MRI and X-ray images, VISIONAIRE Cutting Guides help to direct the surgeon's saw to assure that all bone cuts are precisely aligned. Standard cutting guides require an aligning device known as an intramedullary (IM) rod which is inserted into the core of the femur bone. VISIONAIRE Cutting Guides eliminate the need for the IM Rod and several other surgical steps. This may help reduce the potential for infection, and shorten the overall time you spend under anesthesia.

Want more detail on Visionaire technology? Visit our Visionaire pages for technical information, and references to supporting studies.

Important safety notes

Individual results of joint replacement vary. Implants are intended to relieve knee pain and improve function, but may not produce the same feel or function as your original knee. There are potential risks with knee replacement surgery such as loosening, wear and infection that may result in the need for additional surgery. Patients should not perform high impact activities such as running and jumping unless their surgeon tells them that the bone has healed and these activities are acceptable. Early device failure, breakage or loosening may occur if a surgeon's limitations on activity level are not followed.

References

  1. American Academy of Orthopaedic Surgeons website, accessed March 7, 2017: https://orthoinfo.aaos.org/topic.cfm?topic=A00389
  2. Willis-Owen, Charles, et al, Unicondylar knee arthroplasty in the UK National Health Service: An analysis of candidacy, outcome and cost efficacy, The Knee 16, 473-478, https://www.academia.edu/22765713, January 3, 2009
  3. Liddle, A.D., Pandit, H., Et al, Optimal Usage of Unicompartmental Knee Arthroplasty, The Bone & Joint Journal, https://www.bjj.boneandjoint.org.uk/content/97-B/11/1506, November 3, 2015
  4. Willis-Owen, Charles, et al, Unicondylar knee arthroplasty in the UK National Health Service: An analysis of candidacy, outcome and cost efficacy, The Knee 16, 473-478, https://www.academia.edu/22765713, January 3, 2009
  5. Liddle, A.D., Pandit, H., Et al, Optimal Usage of Unicompartmental Knee Arthroplasty, The Bone & Joint Journal, https://www.bjj.boneandjoint.org.uk/content/97-B/11/1506, November 3, 2015

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References

*Journey II BCS.

  1. Hall, et al. Unicompartmental knee arthroplasty (alias uni-knee): an overview with nursing implications. Orthopaedic Nursing. 2004;23(3):163-171. Accessed April 25, 2019.
    • Based on pre-surgical pain levels in UKA patients.
  2. Mayman DJ, Patel AR, Carroll KM. Hospital related clinical and economic outcomes of a bicruciate knee system in total knee arthroplasty patients. Poster presented at: ISPOR Symposium; May 19-23, 2018; Baltimore, Maryland, USA.
  3. Nodzo SR, Carroll KM, Mayman DJ. The Bicruciate Substituting Knee Design and Initial Experience. Techniques in Orthopaedics. 2018;33(1):37-41
    • Compared to non-JOURNEY II knees; Based on BCS evidence
  4. 1Short-term Range of Motion is Increased after TKA with an asymmetric bicruciatestabilized implant.AcceptedPoster Presentation, AAOS 2018 New Orleans. Kaitlin M. Carroll, Peter K. Sculco, Brian CMichaels,RichardL. Murphy, Seth A, Jerabek, David J. Mayman
  5. 2J Orthop. 2017 Jan 7;14(1):201- 206. doi: 10.1016/j.jor.2016.12.005. eCollection 2017. Bi-cruciate substituting total knee arthroplasty improved medio-lateral instability in mid-flexion range
  6.  In Vivo Kinematic Comparison of a Bicruciate Stabilized Total Knee Arthroplasty and the Normal Knee Using Fluoroscopy Trevor F. Grieco, MS a, *, Adrija Sharma, PhD a, Garett M. Dessinger, BS a, Harold E. Cates, MD b, Richard D. Komistek, PhD. The Journal of Arthroplasty, September 2017
  7. Testing concluded at 45 million cycles, ISO 14242-1 and 14243-3 define test completion at 5 million cycles. The results of laboratory wear simulation testing have not been proven to predict actual joint durability and performance in people. A reduction in wear alone may not result in improved joint durability and performance because other factors, such as bone structure, can affect joint durability and performance and cause medical conditions that may result in the need for additional surgery. These other factors were not studied as part of the testing.
  8. Iriuchishima T, Ryu K. Bicruciate substituting total knee arthroplasty improves stair climbing ability when compared with cruciate-retain or posterior stabilizing total knee arthroplasty. Indian J Orthop. 2019. doi:10.4103/ortho.IJOrtho_392_18.
  9. Smith JR, Picard F, Lonner J, et al. The accuracy of a robotically-controlled freehand sculpting tool for unicondylar knee arthroplasty. Congress of the International Society of Biomechanics. August 4-9, 2013. Natal, Brazil.
  10. Zardiackas, Lyle D., Kraay, Matthew J., Freese, Howard L, editors. Titanium, Niobium, Zirconium, and Tantalum for Medical and Surgical Applications ASTM special technical publication; 1471. Ann Arbor, MI: ASTM, Dec. 2005

Additional claim statements and support regarding Smith+Nephew implants and Robotics-assisted surgery

  • Implants that are built to last
  • LEGION◊CR Knee with VERILAST◊ technology was lab-tested for 45 million cycles (estimating 30 years of wear performance) and showed 81% less wear than similar 5-million cycle cobalt chrome implant.
    • Learn More
      • ISO 14243-3
      • VERILAST knee wear testing and results apply only to the VERILAST LEGION CR Primary Knee System only. Extended lab-testing for other VERILAST knee systems have not been performed. The results of laboratory wear simulation testing have not been proven to predict actual joint durability and performance in people. A reduction in wear alone may not result in improved joint durability and performance because other factors, such as bone structure, can affect joint durability and performance and cause medical conditions that may result in the need for additional surgery. These other factors were not studied as part of the testing.
  • Smith+Nephew implants may offer a more normal feeling knee
    • Based on JOURNEY◊ II BCS knee implant
    • Learn More
      • Verstaete MA, Van Onsem S, Zambianchi F, et al. Multi-centre evaluation of knee kinematics during different activities for anatomic total knee design. Poster presented at: 2nd World Arthroplasty Congress; 19-21 April, 2018; Rome, Italy.
      • Sharma A, Dessinger G, Cates H, Komistesk R. In vivo kinematic comparison for subjects having a bi-cruciate substituting TKA vs the normal knee. Poster presented at: 2nd World Arthroplasty Congress; 19-21 April, 2018; Rome, Italy.
      • Kosse NM, Heesterbeek PJC, Defoort KC, Wymenga AB, van Hellemondt GG. Improved maximal flexion after minor adaptations in implant design bicruciate-substituted total knee arthroplasty. Poster presented at 19th Congress of the European Federation of National Associations of Orthopaedics and Traumatology (EFORT); May 30 – June 1 2018; Barcelona, Spain.
  • 89% of patients were able to take the stairs again after surgery.
    • Based on JOURNEY◊ II BCS knee implant patients
      • Iriuchishima T and Ryu K. Bicruciate substituting total knee arthroplasty improves stair climbing ability when compared with cruciate-retain or posterior stabilizing total knee arthroplasty. Indian J Orthop. 2019. DOI:10.4103/ortho.IJOrtho_392_18
  • A robotics-assisted knee replacement with Smith+Nephew implants may get you back in the game six months sooner than traditional knee replacement surgery
    • Based on UKA patients
      • Canetti R, Batailler C, Bankhead C, Neyret P, Servien E, Lustig S. Faster return to sport after robotic-assisted lateral unicompartmental knee arthroplasty: a comparative study. Arch Orthop Trauma Surg. 2018;138(12):1765-1771
  • Over 90% of patients who had a Smith+Nephew knee replacement surgery returned to work within 6 months.
      • Harris AI, Luo TD, Lang JE, Kopjar B. Short-term safety and effectiveness of a second-generation motion-guided total knee system. Arthroplast Today. 2018;4:240–243. 1
  • Robotics-assisted surgery with Smith+Nephew implants may lead to a faster rehabilitation and shorter recovery time than traditional knee surgery when following your doctor’s recovery plan and physical therapy recommendations.
    • Claim 19 & 20 (PCS REC.015)
  • Due to its improved accuracy, Smith+Nephew robotics-assisted UKA has lower revision rates* compared to conventional techniques
    • Shown in clinical studies with follow-up of up to 5.5 years
      • Batailler C, White N, Ranaldi FM, Neyret P, Servien E, Lustig S. Improved implant position and lower revision rate with robotic-assisted unicompartmental knee arthroplasty. Knee Surg Sports Traumatol Arthrosc. 2019;27(4):1232-1240.
      • Battenberg AK, Netravali NA, Lonner JH. A novel handheld robotic-assisted system for unicompartmental knee arthroplasty: surgical technique and early survivorship. J Robot Surg. 2019;14(1):55-60.
      • Gregori A. 5 Yr Experience Semi Active Robotic Partial Knee Replacement: The Financial Impact. Poster presented at: SICOT;October, 2018; Montreal, Canada.
  • A study has shown Smith+Nephew robotic technology has demonstrated faster return to sport (4.2 vs 10.5 months) when compared to conventional techniques*
        • *n= 28 (n=11 robotic procedures), p<0.01
          • Canetti R, Batailler C, Bankhead C, Neyret P, Servien E, Lustig S. Faster return to sport after robotic-assisted lateral unicompartmental knee arthroplasty: a comparative study. Arch Orthop Trauma Surg. 2018;138(12):1765-1771
  • Robotics-assisted surgery with Smith+Nephew implants may help patient get discharged sooner
    • Study of UKA patients
      • Sephton BM, et al. EKS Arthroplasty Conference. May 2-3, 2019; Valencia, Spain.
      • Shearman AD, et al. EKS Arthroplasty Conference. May 2-3, 2019; Valencia, Spain.
  • Robotics-assisted surgery with Smith+Nephew implants may provide patients with a smoother recovery
    • Based on JOURNEY II family of implants
      • Mayman DJ, Patel AR, Carroll KM. Hospital Related Clinical and Economic Outcomes of a Bicruciate Knee System in Total Knee Arthroplasty Patients. Poster presented at: ISPOR Symposium; May 19-23, 2018; Baltimore, Maryland, USA.
  • Robotics-assisted surgery with Smith+Nephew implants may help patients regain function faster
      • Shearman AD, et al. EKS Arthroplasty Conference. May 2-3, 2019; Valencia, Spain.

Additional statements and support regarding Knee Replacement

  • More than 90% of people who have knee replacement surgery experience dramatic relief in knee pain and are better able to perform common activities.
    • Based on pre-surgical pain levels
      • American Academy of Orthopaedic Surgeon website, http://orthoinfo.aaos.org/topic.cfm
  • The majority of patients experience profound improvements in their physical activity after having knee replacement surgery.
    • Based on pre-surgical activity levels
      • Brandes M, et. al., “Changes in physical activity and health-related quality of life during the first year after total knee arthroplasty.” Clin Orthop Relat Res. 1991 Dec;(273):151-6. https://www.ncbi.nlm.nih.gov/pubmed/20981812 Accessed Wednesday, April 17, 2019