Survival of medial versus lateral unicompartmental knee arthroplasty: A meta-analysis

Lateral unicompartmental knee arthroplasty: is really a good option?

INTRODUCTION

Lateral unicompartmental knee arthroplasties (LUKA) account for only < 1% of all knee arthroplasties and for only 5-10% of all unicompartmental knee replacements. This means that there is less published literature on these procedures and that the surgeon's experience with them is smaller than with medial UKA. The aim of this study was to analyze the survival and the clinical-functional outcomes of LUKA according to the type of bearing surface (all-polyethylene versus metal-backed) used.

MATERIALS AND METHODS

This was a retrospective study including 42 LUKAs operated between 2009 and 2021. Two fixed polyethylene-bearing models were used: the all-polyethylene ACCURIS knee (38%) and the metal-backed Triathlon PKR system (62%). Demographic parameters, knee range of motion (ROM), tibiofemoral alignment, implant survival (as estimated with the Kaplan-Meier curve), and clinical-functional outcomes (as measured with the Knee Society Score) were analyzed.

RESULTS

Average patient age was 65.5 (range, 36-87) years and mean follow-up was 8.2 (range, 2.1-12.8) years. Thirty LUKAs (71.4%) were implanted in women. The main reason for performing a LUKA was osteoarthritis (88.1%). No patient developed post-surgical complications or had to be re-operated. Overall LUKA survival was 100% at 1-year and 5-year's follow-up. Knee Society Score, knee ROM and tibiofemoral alignment all improved significantly post-surgery (p < 0.001). The clinical Knee Society Score increased from 46.5 ± 14.5 pre-surgery to 93.5 ± 10.3 post-surgery, the functional Knee Society Score increased from 48.1 ± 13.5 pre-surgery to 94.6 ± 9.3 post-surgery, maximum flexion increased from 108.5 ± 8.7 degrees pre-surgery to 121 ± 8.9 degrees post-surgery and tibiofemoral alignment was corrected from 13.1 ± 1.74 degrees pre-surgery to 5.7 ± 0.8 degrees post-surgery. There were no statistically significant clinical-functional improvement or knee ROM differences between groups (p < 0.05, respectively).

CONCLUSION

LUKA is a valid and definitive option for patients with lateral tibiofemoral osteoarthritis, with a survival rate of > 95% at 5-years follow-up. Clinical-functional outcomes are the same, irrespective of the tibial component used.

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.

Change in patellar height in medial and lateral unicompartmental knee arthroplasty: a clinical trial

INTRODUCTION

Evidence on patellar height changes following unicompartmental knee arthroplasty (UKA) is lacking. Therefore, this study compared the patella height in patients who underwent medial versus lateral UKA. Moreover, a subgroup analysis was conducted to investigate whether sex, age, and BMI of the patients exert an influence on the postoperative patellar height.

METHODS

Radiographs and hospital records of patients undergoing UKA were prospectively collected. Surgeries were performed by one author with long experience in UKA in a highly standardised fashion. The implants were fixed-bearing medial PPK (Zimmer Biomet, Warsaw, Indiana, USA) and fixed-bearing lateral ZUK (Lima Corporate, Udine, Italy). The patellar height was measured using the Insall-Salvati and Caton-Deschamps indices.

RESULTS

A total of 203 patients were included: 119 patients were included in the medial and 84 in the lateral UKA. The mean age of the patients was 68.9 ± 6.7 years, and the mean BMI was 28.1 ± 4.1 kg/m2. 54% (110 of 203 patients) were women. On admission, between-group comparability was found in age, BMI, sex, and length of the follow-up. No between-group and within-group difference was detected pre- and post-operatively in the Insall-Salvati and Caton-Deschamps indices in patients who have undergone medial versus lateral UKA. Concerning the subgroup analyses, no between-group and within-group difference was detected pre- and post-operatively in all comparisons according to sex, age, and BMI.

CONCLUSION

No difference was found in patella height in patients who have undergone medial compared to lateral UKA. Furthermore, there was no evidence of an association between patient characteristics (sex, age, BMI) and patella height between medial and lateral 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.

Short term outcomes following robotic arm-assisted lateral unicompartmental knee arthroplasty

Introduction

Robotic-arm assisted medial unicompartmental knee arthroplasty (RA-UKA) is associated with improved accuracy of implant positioning and excellent early functional outcomes. However, there is paucity of evidence regarding outcomes following RA-UKA for isolated lateral compartment osteoarthritis. The purpose of this study was to assess the short-term clinical and patient reported outcomes of lateral compartment UKA, utilising robotic-arm assistance.

Methods

This was a retrospective study of prospectively collected data of 21 consecutive patients who underwent lateral RA-UKA. The study included 9 (42.9%) males and 12 (57.1%) females with a mean age of 63.4 ± 9.2 years. The Oxford Knee Score (OKS) was measured pre-operatively and at 1-year post-operatively, while range of motion (ROM) and complications were also recorded.

Results

There was significant improvement of OKS at 1 year's follow up compared with the baseline score (21.8 ± 5.6 vs. 45.2 ± 2.8 respectively; p < 0.001). There was also an improvement in pre-operative ROM when compared to ROM at 1 year's follow up (123.5° ± 8° vs. 131.5° ± 6.3° respectively; p < 0.001). None of the study patients underwent revision surgery within 1 year's follow-up.

Conclusion

In our study, lateral RA-UKA resulted in significant improvements in clinical and patient reported outcomes with low complications rates. Further long-term comparative studies are needed to assess the utility of lateral RA-UKA vs. conventional UKA.

Survival of lateral unicompartmental knee arthroplasty at short-, mid-, and long-term follow-up: a systematic review and meta-analysis

BACKGROUND

The infrequency of lateral unicompartmental knee arthroplasty (UKA) has led to a lack of understanding of its survival. This study aimed to systematically evaluate the survivorship results of lateral UKA at different follow-ups based on available literature.

METHODS

Five databases were searched for eligible studies. Pooled survivorships with 95% confidence intervals (CIs) at 3, 5, 10, 15, and 20 years after lateral UKA were estimated using a random-effect model. Subgroup and sensitivity analyses were performed.

RESULTS

A total of 26 studies involving 5470 lateral UKAs were included. Survivorships of lateral UKA at 3-, 5-, 10-, 15-, and 20-year follow-ups were 96% (95% CI: 95-98%, I2 : 77.5%), 94% (95% CI: 93-96%, I2 : 70.8%), 88% (95% CI: 84-91%, I2 : 70.8%), 85% (95% CI: 79-91%, I2 : 70.8%), and 78% (95% CI: 71-85%, I2 : 54.2%), respectively. Subgroup analyses found that bearing type, the number of surgeons, and year of publication might be associated with implant survival outcomes.

CONCLUSION

Lateral UKA is an effective procedure with excellent survivorships at short-, mid-, and long-term follow-ups. Results suggest a single-surgeon lateral UKA using fixed-bearing. Additional well-designed studies are needed to elucidate the current findings.

Lateral unicompartmental knee arthroplasty (UKA) showed a lower risk of failure compared to medial unicompartmental knee arthroplasty in the Register of Prosthetic Orthopedic Implants (RIPO)

INTRODUCTION

The present study aimed to investigate differences in survivorship between medial and lateral unicompartmental knee arthroplasty (UKA) by analyzing the data of an Italian regional registry. The hypothesis was that, according to recent literature, lateral implants have comparable survivorship with regard to the medial implants.

MATERIALS AND METHODS

The Register of Orthopaedic Prosthetic Implants (RIPO) of Emilia-Romagna (Italy) database was searched for all UKAs between July 1, 2000, and December 31, 2019. For both cohorts, subject demographics and reasons for revision were presented as a percentage of the total cohort. Kaplan-Meier survivorship analysis was performed using revision of any component as the endpoint and survival times of unrevised UKAs taken as the last observation date (December 31, 2019, or date of death).

RESULTS

Patients living outside the region and symmetrical implants (which do not allow the compartment operated to be traced) were excluded. 5571 UKAs implanted on 5172 patients (5215 medial UKAs and 356 lateral UKAs) were included in the study. The survivorship analysis revealed 13 failures out of 356 lateral UKAs (3.7%) at a mean follow-up of 6.3 years and 495 failures out of 5215 medial UKAs (9.5%) at a mean follow-up of 6.7 years. The medial UKAs had a significantly higher risk of failure, with a Hazard Ratio of 2.6 (CI 95% 1.6-4.8; p < 0.001), adjusted for age, gender, weight, and mobility of the insert. Both the groups revealed a good survival rate, with 95.2% of lateral implants and 87.5% of medial implants still in situ at 10 years of follow-up.

CONCLUSIONS

Lateral UKA is a safe procedure showing longer survivorship than medial UKAs (95.2% and 87.5% at 10 years, respectively) in the present study.

LEVEL OF EVIDENCE

Level 3, therapeutic study.

Does Implant Design Influence Failure Rate of Lateral Unicompartmental Knee Arthroplasty? A Meta-Analysis

BACKGROUND

Lateral unicompartmental knee arthroplasty (UKA) is a viable solution for isolated lateral compartment arthritis. Several prosthetic designs are available such as fixed-bearing metal-backed (FB M-B), fixed-bearing all-polyethylene (FB A-P), and mobile-bearing metal-backed (MB M-B) implants. The purpose of this meta-analysis is to compare failure rates of different prosthetic designs.

METHODS

Preferred Reporting Items for Systematic Reviews and Meta-Analyses systematic review was conducted using 4 databases (MEDLINE, EMBASE, Cochrane, and PubMed) to identify all studies that investigate outcomes of lateral UKA. Twenty-one studies met the inclusion criteria, and failure rates were compared by implant type and follow-up time separately in order to assess potential confounding factors. Two separate analyses have been performed among different implant designs (FB M-B vs FB A-P vs MB M-B) and different follow-ups (<5 years, between 5 and 10 years, >10 years).

RESULTS

The failure rate of FB M-B lateral UKA was significantly lower compared to other lateral UKA designs present in the market (0.8% vs 8.6% and 7.1% for FB M-B, FB A-P, and MB M-B, respectively). No significative difference among groups has been detected when comparing all implants with regard to follow-up time.

CONCLUSION

Considering actual evidence, for a surgeon approaching lateral UKA, the FB M-B design is preferable, given the lower failure rates and subsequently a longer implant survivorship.

Cemented Lateral Unicompartmental Knee Replacement: A retrospective single centre independent series

Background

Unicompartmental knee replacement (UKR) has functional and economic benefits when compared with total knee replacement, however it is technically demanding and may be associated with higher failure rates. The primary aim of this independent series study was to evaluate the survival of lateral UKRs implanted in our institution and their clinical outcomes. The secondary outcome was to compare the results of mobile and fixed-bearing prostheses.

Methods

This is a retrospective series study of 183 cemented lateral UKRs implanted in 170 patients, for advanced isolated lateral compartment arthritis, under the care of two senior surgeons. Fixed or mobile-bearing prostheses were used according to the surgeon's preference. Kaplan Meier analysis was used to evaluate prosthesis survival with the endpoint being revision for any reason. A subgroup analysis of survival was also done for each bearing type. Functional outcomes were evaluated using the Oxford knee score (OKS) at final follow-up.

Results

This series included 103 Fixed-bearing and 80 mobile-bearing prostheses. Median follow-up was 6.9 years. 9 knees required revision. The commonest reason for revision was progression of arthritis to the medial compartment. Dislocation was the commonest cause of revision in the mobile-bearing group. Survival at 10 years was 91.9% with no significant difference ( p = 0.083) between bearing types (fixed-bearing 93.8% and mobile-bearing 90.6%). The OKS were comparable in both groups, the mean OKS was 44/48.

Conclusion

Good survival and functional outcomes can be achieved using cemented lateral UKRs with both bearing types. There was a trend towards superior outcomes in the fixed-bearing group.

Lateral unicompartmental knee arthroplasty: A review

Isolated lateral compartment osteoarthritis of the knee is a rare condition affecting approximately 1% of the population, which is ten times less common than osteoarthritis affecting only the medial compartment. Unicompartmental knee arthroplasty (UKA) has many potential advantages over total knee arthroplasty. The benefits of UKA include a smaller incision, preservation of more native tissue (including cruciate ligaments and bone), decreased blood loss, and better overall proprioception. When UKA was first introduced in the 1970s, the outcomes of medial UKA (MUKA) were poor, but the few cases of lateral UKA (LUKA) showed promise. Since that time, there has been a relative paucity of literature focused specifically on LUKA given it is a rare procedure. Refinements in patient selection criteria, implant design, and surgical technique have been made leading to increased popularity. A review of the recent literature reveals that LUKA is associated with excellent long-term clinical outcomes and implant survivorship when performed in properly selected patients. Implant design options include fixed vs mobile bearing as well as metal backed vs all polyethylene tibial component, with improved outcomes noted with fixed bearing designs. Three reasons cited for revision (i.e., fracture of the femoral component, fracture of the tibial component, and valgus malalignment) had been reported in past literature but not recently. Presently, while rare, the most common cause of failure and need for revision are osteoarthritis progression and aseptic loosening. Despite the need for an occasional revision procedure, the survivorship of LUKA is comparable to MUKA, although it should be noted that outcomes of MUKA have been notably varied. Continued pursuit of improved techniques and implant designs will continue to show LUKA to be an excellent procedure for appropriately indicated patients.