Research Summary Research topic: Comparing outcomes in patients receiving either posterior cruciate ligament retaining or posterior substituting total knee replacement designs
Research results: Determination of which total knee replacement design— posterior cruciate ligament retaining or posterior substituting— has superior functioning in patients’ activities of daily living.
Patient care application of results: Better information for decision-making in total knee Arthroplasty to give improved joint sensorimotor function, especially proprioception and kinematics.
Simplified patient care application: Patients receive total knee replacements that allow them the best movement and function possible.
What Type of Knee replacement is best?
OREF-funded study compares posterior cruciate ligament retaining and posterior-substituting designs
Osteoarthritis is one of the most prevalent health conditions worldwide. It causes severe chronic pain, loss of mobility and loss of function among an estimated 27 million adults in the United States1, and as the population ages, the economic burden of this condition is expected to significantly increase to almost 67 million adults by 20302. Estimated total annual costs of osteoarthritis are as high as $89 billion, with almost 15 percent of expenses due to job-related osteoarthritis.
Moreover, osteoarthritis worsens with age. One of the most prevalent forms attacks the knees; among those 55 and older, osteoarthritis of the knee is three times more prevalent than hip osteoarthritis3.
The rising need for TKA
For many patients, conservative interventions for treatment of knee osteoarthritis no longer work, and the disease progresses, leaving total knee arthroplasty (TKA) as their only option for treatment. The AAOS estimates that 600,000 knee replacements are performed each year. The demand for this surgery is likely to rise by 673 percent to 3.4 million surgeries by 20304.
The question then becomes: Which type of total knee arthroplasty (TKA) is “best”—posterior-cruciate ligament retaining or posterior substituting? With funding from the Orthopaedic Research and Education Foundation (OREF), Jason E. Lang, MD, associate professor of Orthopaedic Surgery at Wake Forest University Health Sciences in Winston-Salem, North Carolina, studies this question.
Which TKA is best?
Since the first TKA was done in 1968, there have been many improvements in surgical techniques, implant designs, ligament balancing and fixation principles. Many mid- and long-term studies have shown good outcomes and long term durability of the prostheses, with most patients regaining mobility and health-related improved quality of life5. Yet, although walking velocity and other gait parameters are improved after TKA, patients continue to have a slower gait speed than control subjects6.
Proponents of the posterior-cruciate ligament retaining (CR) design believe that preservation of the posterior cruciate ligament maintains normal joint sensorimotor function, especially proprioception and kinematics7. Other advantages include bone preservation and prevention of anterior femoral translation on the tibia. However, the surgical technique for the CR implant design is more difficult because it requires precise ligament balancing to recreate natural joint motion. In addition to being less complex, some studies have shown that the posterior substituting designs result in greater knee range of motion and stable component interface8.
The results of previous studies comparing outcomes in patients receiving either posterior cruciate ligament retaining or posterior substituting total knee replacement designs have been equivocal, and the question remains unresolved as to whether there is any advantage of one design over the other. Dr. Lang and his research team are evaluating the differences in proprioception and gait between patients receiving the two types of total knee prostheses to determine whether proprioception plays a role in patient outcomes following TKA.
Dr. Lang hypothesized that the posterior cruciate ligament retaining design maintains proprioception to a greater degree than the posterior substituting design. Further, the study proposed that the use of the cruciate retaining TKA design will facilitate earlier functional outcomes in gait and balance when compared with posterior substituting TKA.
Dr. Lang explained, “Based on pain scores and on fluoroscopic data, there is literature that supports both designs. With this study, we wanted to learn whether one design is superior to the other in terms of “real-world” functionality. We did this by recruiting patients to come in for a gait analysis before surgery and then again at six months and a year after their operation.”
Members of Dr. Lang’s research team, Judy Foxworth, PT, PhD, OCS, and Christopher Wendt, MS, coordinate the motion analysis studies through a partnership between the Department of Orthopaedic Surgery at Wake Forest University Health Sciences and the Human Performance and Biodynamics Laboratory at Winston-Salem State University. Patients recruited for the study were randomized to receive either a cruciate retaining or a posterior stabilized TKA design.
At each study time point, Dr. Foxworth and her research team placed motion markers along both of the patients’ lower extremities. As patients performed common daily activities, such as stepping over small obstacles, walking up and down varying degrees of inclines and declines and climbing up and down stairs, their movements were recorded by motion-capture cameras. Dr. Lang and Dr. Foxworth then analyzed the data to determine how the arthritic state varied from the post-surgical state and how it varied between the two TKA designs.
Dr. Lang said that he has had little trouble recruiting patients for this study. “We coordinated it with other pre-surgical visits to make it convenient for the patient, and, after I explained that they would be doing this to help advance orthopaedics for other patients, they were usually receptive and happy to participate.”
Opportunities for advancing orthopaedics
Dr. Lang said he had difficulty finding resources to fund this research until he received the OREF grant. “The grant has been extraordinarily important. It allowed the pieces to fall together and the wheels to turn. It was truly the key to moving this forward.”
Dr. Lang said that OREF also gave him the opportunity to be a mentor. “I’m fortunate to have an opportunity through OREF to involve and mentor resident physicians. The (AAOS/OREF/Orthopaedic Research Society) Clinician Scholar Career Development Program for residents and early-on graduates is tailored to those in their first three years.”
Dr. Lang also pointed out that supporting OREF gives orthopaedic surgeons who don’t conduct research of their own a way to still be involved in advancing the specialty. “In such cases,” Dr. Lang said, “supporting OREF gives others the opportunity to ask questions and get some answers. That’s their way of contributing to the community of orthopaedic surgeons.”
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4. Jordan JM, Helmick CG, Renner JB, et al. Prevalence of knee symptoms and radiographic and symptomatic knee osteoarthritis in African Americans and Caucasians: the Johnston County Osteoarthritis Project. J Rheumatol. Jan 2007;34(1):172-180.
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6. Diduch DR, Insall JN, Scott WN, Scuderi GR, Font-Rodriguez D. Total Knee Replacement in Young, Active Patients. Long-Term Follow-up and Functional Outcome. J Bone Joint Surg Am. April 1, 1997 1997;79(4):575-582.
7. Roberts VI, Esler CNA, Harper WM. A 15-year follow-up study of 4606 primary total knee replacements. J Bone Joint Surg Br. November 1, 2007 2007;89-B(11):1452-1456.
8. Attar FG, Khaw F-M, Kirk LMG, Gregg PJ. Survivorship Analysis at 15 Years of Cemented Press-Fit Condylar Total Knee Arthroplasty. The Journal of Arthroplasty. 2008;23(3):344-349.