UNICOMPARTMENTAL KNEE ARTHROPLASTY VS. HIGH/PROXIMAL TIBIAL OSTEOTOMY
The practitioner could use unicompartmental knee arthroplasty or tibial osteotomy for the treatment of knee osteoarthritis.

Rationale

This statement was downgraded due to the quality of evidence in support of UKA. There is limited high quality evidence to support the use of UKA versus HTO in early, unicompartmental OA. All included literature examined these procedures for the treatment of medial unicompartmental knee osteoarthritis. One high quality study (Stukenborg-Colsman 2001) of patients with predominantly medial compartment osteoarthritis demonstrated equivalent postoperative complication rates, implant survivorship, and knee society scores among UKA versus HTO recipients. Such equivalence in postoperative adverse event rates was supported by four additional low quality studies (Watanabe 2021, Rodkey 2021, Tuncay 2015, Petersen 2016) which found similar rates of total revision, infection, deep venous thrombosis, hematoma formation, implant loosening (but not aseptic loosening), mechanical symptoms and arthritis progression. Conversely, one moderate quality study (Shaofei 2017) and four low quality studies (Petersen 2016, Ziqi 2020, Kim 2019, Jeon 2017) reported superior early pain, physical function, and/or quality of life metrics with UKA compared to HTO.

Overall, there is considerable overlap in indications for UKA and HTO, based on patient’s age range, levels of activity demands/expectations, and clinical presentation of unicompartmental osteoarthritis. Furthermore, TKA represents the revision option for both treatments and yields satisfactory functional outcomes and survivorship. A recent meta-analysis (Cao 2018) reported that UKA patients have lower revision rates, mitigated minor and major complications, and less postoperative pain compared to their HTO counterparts. However, such results are ascertained from the compilation and pooled analysis of relatively low-quality evidence. In contrast, HTO patients attain a greater range of motion; nevertheless, this advantage may not be of clinical significance given the satisfactory ROM attained using UKA. Both modalities offer a similar postoperative knee function score, walking velocity, and mid-term revision rates. It is critical to highlight those outcomes and survivorship of both surgical modalities are heavily modified by surgeon experience and technique, in addition to implant design for UKA. Advances such as robotic UKA may offer a venue for further improvement in survivorship.

Benefits/ Harms of Implementation

Performing UKA in an appropriately selected population affords the advantages of lower revision rates, mitigated minor and major complications, and less postoperative pain compared to their HTO counterparts. However, such advantages are contingent upon surgeon experience and implant design; thereby rendering the potential for failure (i.e., higher revision and lower mid-to long term survivorship) among less experienced substantially higher. Nevertheless, the introduction of robotic UKA may mitigate, in part, the inter-surgeon variability.

Cost Effectiveness / Resource Utilization

Owing to the lower costs and near-comparability of outcomes, HTO affords higher cost-effectiveness compared to UKA especially in 50 to 60-year-old patient with medial unicompartmental knee osteoarthritis (Kamaruzaman 2017). Specifically, Markov model using a probabilistic willingness-to-pay (WTP) threshold sensitivity analysis demonstrated that a $50,000 per QALY, HTO was cost effective in 57% of the time compared to 19% in UKA. At a WTP threshold of $100,000/QALY, HTO was cost-effective 43% of time versus 26% for UKA. HTO and UKA are associated with 14.62, and 14.63, estimated discounted QALYs, respectively. Conversely, discounted total direct medical costs were $20,436 for HTO versus $24,637 for UKA (in 2012 U.S.D). The incremental cost-effectiveness ratio (ICER) was $420,100 per QALY for unicompartmental knee arthroplasty.

Acceptability and Feasibility

Overall, UKA has fair acceptability and feasibility among surgeons and patients. AJRR data indicates diminishing rates reaching 2.7% of all primary knee arthroplasties reported to AJRR for 2017. However, such rates rebounded with numbers increasing to 4.2% in 2020 (American Joint Replacement Registry 2020 Annual Report).

Future Research

Further research into long-term cost-effectiveness using both surgical modalities is required, especially in delineating indications and patient selection. Such investigational venues should account for costs and outcomes of conversion TKA after each modality; specifically, the incidence of infection, early failure, and patient reported outcomes after the conversion surgery. This is critical given that TKA is the final common pathway after either procedure which may be considered less invasive “temporizing measures” in a substantial subset of the young osteoarthritis patient population until TKA is eventually performed. Further research is also warranted into the comparative utilization rates of each procedure over the last decade and their respective projected volumes.