Mild Valgus Alignment After Lateral Unicompartmental Knee Arthroplasty Led to Lower Functional Results and Survivorship at Mean 8-Year Follow-Up

Long-Term Excellent Clinical Outcomes, High Survivorship, and Low Osteoarthritis Progression in Lateral Unicompartmental Knee Arthroplasty: A 10-Year Minimum Follow-Up

Background: The literature on the long-term outcomes of lateral unicompartmental knee arthroplasty (UKA) remains limited due to the lower prevalence of lateral osteoarthritis (OA) and the technical challenges of the procedure. This study aimed to assess the long-term clinical outcomes, implant survivorship, and OA progression in patients undergoing lateral UKA with a minimum follow-up of 10 years. Methods: This retrospective study analyzed 96 lateral UKAs from 2001 to 2013 using a cemented, fixed-bearing implant. Patients with at least 10 years of follow-up were included. Clinical outcomes were measured using range of motion (ROM), a pain visual analog scale (VAS), Knee Society Scores (KSSs), and the Forgotten Joint Score (FJS). Implant survivorship was assessed using a Kaplan-Meier analysis, while OA progression in the medial compartment was evaluated radiographically. Results: At a mean follow-up of 14.5 years, implant survivorship was 94.7%, with five revisions primarily due to OA progression. Significant improvements were observed in ROM, VAS, and KSS (p < 0.01). An increase in the Kellgren-Lawrence grade in the medial compartment was reported in 47.9% of patients. Conclusions: Lateral UKA provides excellent long-term outcomes, demonstrating high survivorship, significant functional improvement, and high patient satisfaction.

Lateral unicompartmental knee arthroplasty is an effective procedure for lateral post-meniscectomy knee osteoarthritis: a case-control study at a mean 7-year follow-up

BACKGROUND

Meniscectomy is a common knee surgery for meniscal tear, and is associated with progressive osteoarthritis (OA). There are few literatures focus on the use of lateral unicompartmental knee arthroplasty (UKA) for lateral post-meniscectomy knee osteoarthritis (PMKO). Therefore, the purpose of this study is to compare the outcomes of lateral UKA performed for lateral PMKO and primary lateral compartment knee osteoarthritis (LCKO).

METHODS

A total of 38 consecutive patients (38 knees) who received lateral UKAs for isolated lateral PMKO between September 2013 and September 2019 were retrospectively analyzed. Other thirty-eight patients (38 knees) with primary LCKO were allocated into control group by 1:1 matching according to age, gender, and body mass index. The clinical outcomes were evaluated using the American Knee Society Score, range of motion, Forgotten Joint Score, and EuroQol-5D (EQ-5D) Score. The radiographic assessments included hip-knee-ankle (HKA) angle, mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA), and posterior tibial slope angle (PTSA).

RESULTS

With a mean 7 years follow-up, there was no significant difference in functional and radiographic outcomes between groups. However, the PMKO group showed severe lateral OA (p = 0.02) preoperatively and less OA progression in the medial compartment postoperatively (p = 0.046). The preoperative mLDFA was significantly more valgus in the LCKO group (p < 0.001). No case of revision occurred in either group.

CONCLUSION

Lateral UKA is a valid procedure for lateral PMKO. The clinical and radiographic results are similar in patients underwent lateral UKA for lateral PMKO and for LCKO. Patients with lateral PMKO exhibited severe lateral OA preoperatively and less OA progression in the medial compartment compared to those with LCKO. It is crucial to prevent ascension of the lateral femoral joint-line and maintain proper valgus alignment during lateral UKA.

Unicompartmental Knee Arthroplasty: What is the optimal alignment correction to achieve success? The role of kinematic alignment

Unicompartmental knee arthroplasty (UKA) is in many ways the ultimate kinematic operation, as the express aim is to resurface the diseased side of the joint and restore pre-arthritic alignment and balance while maintaining integrity of both cruciate ligaments. An increasing body of knowledge relates the outcomes of UKA to pre-arthritic anatomy rather than an arbitrarily defined neutral. The Coronal Plane Alignment of the Knee (CPAK) classification provides a validated technique for calculating pre-arthritic limb alignment (the arithmetic hip-knee-ankle angle (aHKA)) and joint line obliquity (JLO) and will enable a greater understanding of the interactions between pre-arthritic anatomy, choice of prosthetic position and outcomes. When pre-arthritic alignment is not taken into consideration a post-operative limb alignment of mild to moderate varus for medial UKA and moderate valgus for lateral UKA appears to produce the best outcomes. When pre-arthritic anatomy is taken into account, superior results have been reported with restoration of pre-arthritic limb alignment and joint line obliquity. Restriction boundaries have yet to be clearly defined for tibial component coronal and hip-knee-ankle (HKA) angles when applying this new paradigm, but existing evidence would suggest a 6° varus limit for the tibial coronal angle may be a reasonable starting point. Lateral UKA has inherent differences in terms of tibial component positioning and ligament balance targets. Mobile bearing UKA demands a three-dimensional understanding of the effect of implant position on bearing stability. Modification of technique is necessary to produce anatomic tibia component angles with equipment designed for mechanical alignment. Robotic technology allows accurate understanding of pre-arthritic anatomy, precise reproduction of patient specific virtual planning, equally precise manipulation of soft tissue balance, and future research using these platforms is likely to further clarify in terms of ideal patient-specific component and limb alignment targets.

Perfect indications and how to avoid complications in lateral unicompartmental knee arthroplasty

Lateral unicompartmental knee arthroplasty (LUKA) is a favorable alternative to distal femoral osteotomy and total knee arthroplasty in patients with isolated lateral compartment knee osteoarthritis; however, it only accounts for less than 1 ​% of the total number of knee replacements documented in national joint registries. The anatomy and biomechanics of the lateral knee compartment differ from the medial side, with a greater intrinsic laxity of the lateral collateral ligament complex compared with medial structures. Indications and surgical techniques must be tailored to each unicompartmental replacement to optimize outcomes and mitigate complications. This article will discuss the clinical indications, preoperative evaluation and workup, surgical technique, and outcomes for LUKA.

Lateral UKA can be a safe solution in a young patients' population: a 10-year follow-up report

BACKGROUND

This study aimed to assess the long-term survivorship and functional outcomes of fixed-bearing lateral unicompartmental knee arthroplasty (UKA) in a young patients' population with osteoarthritis limited to the lateral compartment.

METHODS

The study included a cohort of consecutive patients who underwent lateral UKA between January 2008 and December 2014 at a single high-volume surgical center. The surgical procedures were performed by experienced surgeons using a lateral parapatellar approach and fixed-bearing implants. Patient follow-up included a retrospective re-evaluation, clinical assessments, patient-reported outcome measures (PROMs), and X-ray analysis.

RESULTS

A total of 40 lateral UKAs were analyzed, with 19 performed on the left and 21 on the right knee. The mean age of the patients at the time of surgery was 57.6 years, and the mean BMI was 24.8. At the final follow-up, 80% of patients achieved excellent outcomes (OKS > 41), and 20% had good outcomes (OKS: 34-41). No patients exhibited fair or poor outcomes. The mean FJS at the final follow-up was 82.8. The mean WOMAC was 10.5. Kaplan-Meier survival analysis revealed a survivorship rate of 93.1% at 10 years, considering revision for any reason as endpoint.

CONCLUSIONS

Lateral UKA proved to be an effective treatment option for osteoarthritis affecting the lateral compartment of the knee. The study demonstrated a high survivorship rate and favorable functional outcomes at a mean follow-up of 132.7 months. These findings highlight the potential benefits of fixed-bearing lateral UKA in selected patients with lateral compartment knee pathology.

Robotic-arm-assisted lateral unicompartmental knee arthroplasty leads to high implant survival and patient satisfaction at mean 10-year follow-up

BACKGROUND

There is a lack of literature reporting on long-term outcomes following robotic-arm-assisted lateral unicompartmental knee arthroplasty (UKA). This study assessed the long-term survivorship, patient-reported satisfaction and pain scores following robotic-arm-assisted lateral UKA for lateral compartment osteoarthritis (OA).

METHODS

A single surgeon's database was reviewed to identify all patients who underwent robotic-arm-assisted lateral UKA with a cemented, fixed-bearing prosthesis prior to May 2015. Patients were contacted to determine implant survivorship, satisfaction and pain. Kaplan-Meier models were applied to analyse survival.

RESULTS

A total of 77 knees (70 patients) with a mean follow-up of 10.2 ± 1.5 years (range: 8.1-13.3) were included. Five knees were revised, corresponding to a 10-year survivorship of 96.1% and estimated survival time of 12.7 ± 0.3 years (95% confidence interval: 12.2-13.2) with all-cause revision as the endpoint. Unexplained pain (40.0%) and progression of OA (40.0%) in contralateral compartments were the most reported reasons for revision. Among patients without revision, 94.4% were either satisfied or very satisfied with their lateral UKA and the average pain score was 1.1.

CONCLUSION

Robotic-arm-assisted lateral UKA led to high implant survivorship and patient satisfaction, and low pain scores at long-term follow-up. Progression of OA in contralateral compartments and unexplained pain were the most frequent reasons for revision. These findings support the continued use of robotic-arm-assisted lateral UKA for lateral compartment OA; however, its clinical value over conventional techniques remains to be established in prospective comparative studies.

LEVEL OF EVIDENCE

Therapeutic Level IV.

Long-term functional success and robust implant survival in lateral unicompartmental knee arthroplasty: A case series with a mean follow-up of twenty two and a half years

PURPOSE

Lateral unicompartmental knee arthroplasty (UKA) is an accepted treatment option in cases of end-stage lateral osteoarthritis. While lateral UKA has many proposed advantages compared to total knee arthroplasty, its technical challenges and relatively small number of cases make this an uncommon procedure. The aim of this study was to report the survivorship and functional outcomes beyond 20 years of follow-up of isolated UKA.

METHODS

Between January 1988 and October 2003, 54 lateral UKAs were performed in a single center. The fitted prosthesis was a fixed plate and cemented polyethylene (PE). All patients had isolated lateral tibiofemoral osteoarthritis, including five open meniscectomies, three arthroscopies, and three open reductions of lateral tibial plateau fractures. Patients with a minimum of 20 years of follow-up were included in the final analysis.

RESULTS

Of the 54 UKA, 22 died before reaching the minimum follow-up period and four were lost to follow-up. Twenty-eight were included in the final analysis. Among them, 21 patients remained alive and an additional seven were deceased after 20 years. The mean age at the last follow-up was 84.8 ± 11.9 years with a mean follow-up duration of 22.5 ± 2.1 years. Of the 28 knees, eight underwent revision surgery (5 for the progression of osteoarthritis; 2 for aseptic loosening; 1 for PE wear). Kaplan-Meier survival analysis revealed a survival rate at 20 and 25 years of 72.3% (CI 59.1; 88.6). The average time to revision was 14.9 ± 4.9 years. At the last follow-up, the mean function Knee Society Score (KSS) was 41.5 ± 32.9 and the mean objective KSS score was 79.4 ± 9.7. In the unrevised population, 94.7% of patients (n = 18) reported being satisfied or very satisfied with the surgery.

CONCLUSION

Lateral UKA remains a viable treatment option for patients with isolated lateral tibiofemoral osteoarthritis, providing satisfactory 20-year implant survivorship and high patient satisfaction.

Lateral Unicompartmental Knee Arthroplasty for Osteoarthritis Secondary to Lateral Meniscectomy: High Functional Results and Survivorship and Low Osteoarthritis Progression at a Mean 10 Years of Follow-up

BACKGROUND

Meniscectomy, whether partial or total, is a common knee surgery, but it considerably increases the risk of knee osteoarthritis (OA). Lateral meniscectomy has more severe consequences than medial meniscectomy, leading to faster OA progression and worse clinical outcomes. Unicompartmental knee arthroplasty (UKA) is a suitable treatment option for lateral OA and has demonstrated better outcomes than total knee arthroplasty (TKA). The aims of this study were to evaluate the clinical and functional results, OA progression in the medial compartment, and implant survivorship following lateral UKA in patients with OA secondary to lateral meniscectomy and to compare these outcomes with those of patients who underwent lateral UKA for primary lateral OA.

METHODS

Between 2001 and 2017, 214 lateral UKAs were performed. Of these, 42 were performed for OA secondary to lateral meniscectomy. The control group was composed of patients who underwent lateral UKA for primary lateral OA and was formed through a 1:1 case-control matching process based on sex, age, body mass index, and operation date. The outcomes that were studied included range of motion, Knee Society Score, University of California Los Angeles (UCLA) Activity Score, Tegner Activity Scale, Forgotten Joint Score, visual analog scale for pain, OA progression in the medial compartment, and implant survivorship.

RESULTS

At a mean follow-up of 10.2 years, both groups demonstrated significant improvements (p < 0.01) after lateral UKA in all clinical and functional scores except the UCLA Activity Score and Tegner Activity Scale. No significant differences in clinical and functional scores were found between the groups. However, patients with OA secondary to meniscectomy exhibited significantly less OA progression in the medial compartment (p = 0.035) and higher 10-year implant survival (97.6% versus 83.3%).

CONCLUSIONS

Lateral UKA is an effective treatment option for OA secondary to lateral meniscectomy, providing excellent functional outcomes and survivorship. Patients with post-meniscectomy OA exhibited less OA progression in the medial compartment than patients with primary OA and, consequently, had better 10-year implant survivorship.

LEVEL OF EVIDENCE

Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Robotic-assisted unicompartmental knee arthroplasty improves functional outcomes, complications, and revisions

Aims

Robotic-assisted unicompartmental knee arthroplasty (R-UKA) has been proposed as an approach to improve the results of the conventional manual UKA (C-UKA). The aim of this meta-analysis was to analyze the studies comparing R-UKA and C-UKA in terms of clinical outcomes, radiological results, operating time, complications, and revisions.

Methods

The literature search was conducted on three databases (PubMed, Cochrane, and Web of Science) on 20 February 2024 according to the guidelines for Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). Inclusion criteria were comparative studies, written in the English language, with no time limitations, on the comparison of R-UKA and C-UKA. The quality of each article was assessed using the Downs and Black Checklist for Measuring Quality.

Results

Among the 3,669 articles retrieved, 21 studies on 19 series of patients were included. A total of 3,074 patients (59.5% female and 40.5% male; mean age 65.2 years (SD 3.9); mean BMI 27.4 kg/m2 (SD 2.2)) were analyzed. R-UKA obtained a superior Knee Society Score improvement compared to C-UKA (mean difference (MD) 4.9; p < 0.001) and better Forgotten Joint Score postoperative values (MD 5.5; p = 0.032). The analysis of radiological outcomes did not find a statistically significant difference between the two approaches. R-UKA showed longer operating time (MD 15.6; p < 0.001), but reduced complication and revision rates compared to C-UKA (5.2% vs 10.1% and 4.1% vs 7.2%, respectively).

Conclusion

This meta-analysis showed that the robotic approach for UKA provided a significant improvement in functional outcomes compared to the conventional manual technique. R-UKA showed similar radiological results and longer operating time, but reduced complication and revision rates compared to C-UKA. Overall, R-UKA seems to provide relevant benefits over C-UKA in the management of patients undergoing UKA.

Trends in unicompartmental knee arthroplasty among 138 international experienced arthroplasty knee surgeons

Purpose

Unicompartmental knee arthroplasty (UKA) is an established option for treating isolated unicompartmental knee osteoarthritis (OA), but controversies still exist about patient selection, indications, perioperative management and alignment goals. This survey was designed to understand the current trends of experienced arthroplasty knee surgeons performing UKA.

Methods

An online questionnaire was created with SurveyMonkey® to assess global tendencies in the utilization of UKA. A link to the survey was shared with all ESSKA (European Society for Sports Traumatology, Knee Surgery and Arthroscopy) members. The questionnaire consisted of free and multiple-choice questions and was divided into four sections: demographic information, the surgical activity of the respondents, indications for surgery and postoperative alignment goals.

Results

A total of 138 ESSKA members from 34 different countries completed the survey. A total of 81 % of the responders performed fewer than 50 UKAs per year; 53 % of UKAs represented less than 20 % of their knee replacements; 71 % used mainly or only fixed-bearing implants; 81 % performed UKA in a shorter time compared to TKA; and 61 % and 72 % were interested in custom-made UKA and robotics, respectively. Thirty-six percent considered a minimum postoperative alignment of 0° for medial UKA, and 32 % considered 10° as the maximum valgus deformity for lateral UKA. Fifty-five percent had no minimum age cut-off, 47 % had no BMI cut-off, and 57 % believed TKA was better than UKA in knees with concomitant high-grade patellofemoral OA. Approximately 50 % of the surgeons desired a coronal alignment that was the same as the predegeneration alignment.

Conclusion

A high level of agreement was reached regarding the following: preference for fixed-bearing UKAs, lower surgical time for UKA compared to TKA, interest in custom-made and robotic UKAs, no age and weight cut-off, TKA preferred in the presence of patellofemoral OA, and a final alignment goal of the predegenerative state both for medial and lateral. There was no agreement regarding length of stay, rehabilitation protocol, preoperative varus and valgus cut-off values, and treatment in cases of absence of anterior cruciate ligament or previous osteotomy.