This year marks the 9th year of clinical usage with the Unity Knee in total knee arthroplasty. The implant design prioritizes medial stability throughout the entire range of motion to achieve a stable and high functioning total knee replacement. An outline of this clinical experience and key outcomes are summarised below:
ODEP rating
Unity Knee currently holds three ODEP ratings depending on the TKR construct1:
•Unity Knee CR with domed patella: ODEP 5A
•Unity Knee CR without patella: ODEP 3A
•Unity Knee PS with offset domed patella: ODEP 3A*
UK NJR and Beyond Compliance
In the latest national joint registry annual report2, Unity was highlighted as the total knee replacement brand with the lowest reported cumulative revision rate of 1.17% (0.55-2.48) at 5 years.
Unity Knee was the first total knee replacement to go through the Beyond Compliance program, which is a UK initiative to closely monitor the market introduction of new products. Results from this program have been recently published and concluded that 96% of the Unity Knee patients were satisfied after 2 years follow-up and experienced a significant improvement in PROMs3.
Short term follow up
Studies on the short-term results of Unity CR5 and PS6 cover 1 and 2 years follow-up, respectively.
Implantation of the Unity CR demonstrated significant functional improvements over all subscores specifically the symptom, pain, and ADL with twice the pre-operative value, while the average improvement in sport and quality of life subscore showed even greater improvement with scores three times the pre-operative value. The Unity PS also achieved an excellent Kaplan-Meier survivorship of 98.9% at 2 years.
Knee instrumentation and surgical efficiency
A study by Slick et al7 explored the procedural steps required to prepare the bone using 17 different TKR brands of instrumentation. Importantly, Unity PS was identified as one of the brands which required the fewest steps among PS systems within the US market. Surgical efficiency is at the core of the Unity Knee design.
Unity Knee kinematics and patient satisfaction
Dr Van Onsem studied the relationship between patient satisfaction and knee kinematics after TKA.
Three activities were assessed, including non-weight bearing flexion-extension (FE), squatting (SQ) and rise from a chair (CH). At 6 months post-op, the patients were grouped into a satisfied or dissatisfied cluster and the kinematic profiles were analysed. Unity Knee was among other knee replacements that were implanted in the patients as part of this study.
The main finding was that significant differences were observed between the kinematic profiles of satisfied versus dissatisfied patients during the weight-bearing activities. Medially, the satisfied patients were statistically more stable in early and mid-flexion. Laterally, the satisfied patients demonstrated statistically greater posterior motion in deep flexion. All Unity Knee patients were within the satisfied cluster4.
References:
1. Latest ODEP ratings can be found at www.odep.org.uk
2. NJR 17th Annual Report 2020, Table 3.K7 (a) KM estimates of cumulative revision (95% CI) by total knee replacement brands. Blue italics signify that fewer than 250 cases remained at risk at these time points.
3. Patel NG, Napier RJ, Phillips JRA, Toms AD. The first knee prosthesis to go through beyond compliance: A new standard for the safe introduction of orthopaedic implants. Surgeon. 2020 Dec;18(6):e27-e32. doi:
10.1016/j.surge.2020.06.005. Epub 2020 Jul 14. PMID: 32675025.
4. Van Onsem S, Knee Kinematics Determine Patient Satisfaction After TKA, The objective substrates of patient satisfaction after total knee arthroplasty, Chapter 3, 2018, Ghent University.
5. Pourmoghaddam A, Dettmer M, Malanka S, Kreuzer S. Comparison of Functional Outcomes of Total Knee Arthroplasty Using two Different Single Radius Implants. Reconstructive Review. 2016 Mar, Vol 6 (1):43-48.
6. Paszicsnyek T. Early Experience with a Modern Generation Knee System: Average 2 Year’s Follow-up. Reconstructive Review. 2015 Dec, Vol 5 (4):23-28.
7. Slick S, Charles M. Davis III, Elfar J, Nikkel L. Process Mapping Total Knee
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