15-Year Follow-Up of Mobile Bearing Medial Unicompartmental Knee Arthroplasty

Wear patterns of compartments in varus knee osteoarthritis among an asian population: A cross-sectional study with radiographic and intraoperative analysis

PURPOSE

Osteoarthritis (OA) of the knee significantly impairs mobility and quality of life. Knee arthroplasties have dramatically improved patient outcomes, allowing individuals to regain independence. Unicompartmental knee arthroplasty (UKA) is a surgical option for patients with isolated single-compartment disease, offering the benefits of reduced surgical time and minimized surgical risks. However, the appropriateness of UKA is often underestimated. Therefore, this study aims to determine the proportion of patients with varus knee OA who are suitable candidates for UKA.

METHODS

A prospective cross-sectional study was conducted on 207 knees undergoing knee arthroplasty surgery for varus knee OA. Pre-operative radiographs were graded using both the Kellgren-Lawrence (KL) and modified Keyes classifications. Intra-operatively, the knees were inspected, and photographs of the tibial cut were reviewed by a neutral observer. The appropriateness of UKA was determined based on these evaluations.

RESULTS

The lateral compartment was not involved in 169 (81.6%) knees. Only six (2.9%) knees had a KL grade 4 involvement of the lateral compartment. After excluding patients with isolated medial compartment OA, no radiographic evidence of lateral and patellofemoral involvement, and a grade 1 on the modified Keyes classification, we found that 79 (38.2%) patients were suitable candidates for a medial UKA. Intraoperatively, 84 (40.6%) patients had a functional ACL with no observable wear in the lateral and patellofemoral joint (PFJ) compartments.

CONCLUSION

In patients with varus knee OA, a significant proportion have wear patterns suitable for management with a UKA. Identifying these patients requires targeted examinations and specific radiographic views.

Varus/valgus angle of the femoral component relative to the tibial component increases risk of bearing dislocation in medial mobile bearing unicompartmental knee arthroplasty

BACKGROUND

In medial mobile-bearing unicompartmental knee arthroplasty (MB-UKA), the position of the bearing does not correspond to the planned position which will increasing the risk of bearing dislocation. This study aimed to explore the relationship between the malposition of the femoral and tibial components and the phenomenon of bearing deviation using postoperative radiological measurements.

METHODS

One hundred twenty patients who underwent mobile-bearing uni-compartmental knee arthroplasty (MB-UKA) at our hospital between January and August 2023 were enrolled in this retrospective study. Standard anteroposterior radiographs were obtained postoperatively using C-arm fluoroscopy. A 3D-2D image matching method was used to measure the femoral component varus/valgus angle and internal/external rotation (IR/ER) relative to the tibial component. The bearing position parameters were measured. Patients were divided into varus/valgus and IR/ER groups according to the femoral component varus/valgus and IR/ER angles. The bearing position parameters of each group were compared separately.

RESULTS

There were 57 patients in the varus group, 63 in the valgus group, 59 in the IR group, and 61 in the ER group. The distance between the bearing lateral edge and the lateral wall of the tibial component (W-BED) was significantly lower in the varus group than the valgus group (1.9 [0-6.4] vs. 2.8 [0.3-7.7] mm; P < 0.001). No differences were detected in any bearing position parameters. The varus/valgus angle of the femoral component showed a significant negative correlation with the W-BED. The IR/ER angle of the femoral component showed no significant correlation with any of the positional parameters.

CONCLUSIONS

Implantation of femoral component with varus/valgus angle relative to tibial component can cause the bearing to deviate from the planned position. If the varus/valgus angle exceeds 8° it can cause the bearing to hit or away from the lateral wall of the tibial component, resulting in an increased risk of dislocation of the bearing.

Unicompartmental knee arthroplasty for lateral compartment knee osteoarthritis: a credible surgical approach and short-term clinical outcomes

PURPOSE

We aimed to investigate the technical advantages and clinical outcomes of lateral unicompartmental knee arthroplasty (LUKA) through the medial parapatellar approach.

METHODS

From August 2022 to June 2024, 104 patients who underwent LUKA via the medial parapatellar approach were enrolled. The operation time, hospital stays, surgical complications and follow-up period were collected. Pre- and postoperative Range of movement (ROM), Oxford knee score (OKS) and Hospital for special surgery knee score (HSS) were recorded and further investigated by paired-samples t-test analysis.

RESULTS

Primary demographic data of the retrospective case series collected include gender (30 males and 74 females), age (63.1 ± 8.37 years, range 49-84 years), operation time (86 ± 17 min, range 52-135 min), hospital stays (4.0 ± 1.1 days, range 3-8 days) and follow-up period (9.9 ± 5.7 months, range 1-23 months). There was a significant improvement in ROM (P < 0.001), OKS (P < 0.001) and HSS (P < 0.001) compared to preoperative values. Patient satisfaction at 1-month postoperative follow-up was up to 95%. The incidence of deep venous thrombosis was 16.3%. There was no incidence of postoperative infection.

CONCLUSION

The medial parapatellar approach is a understandable, easy to master and credible surgical approach for LUKA, showing a striking improvement in clinical outcomes without adverse events in the short-term follow-up.

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.

Unicompartmental knee arthroplasty in obese patients, poorer survivorship at 15 years

Introduction

The preclusion of obese patients from unicompartmental knee arthroplasty (UKA) has increasingly been challenged. This study aimed to evaluate the impact of Body Mass Index (BMI) on UKA at 15-year follow-up.

Materials and methods

169 unilateral UKA patients from 2003 to 2007 were followed-up prospectively for at least 15 years. 70 patients were left for analysis after accounting for patient demise, revision surgery and loss to follow-up. 48 of these patients (69%) were in the Control group (BMI <30 kg/m2) and 22 (31%) were in the Obese group (BMI ≥30 kg/m2). Patients were assessed before and after operation using the Knee Society Function Score (KSFS), Knee Society Knee Score (KSKS), Oxford Knee Score (OKS), and Physical (PCS) and Mental (MCS) component of the Short Form 12. Survivorship analysis was also performed.

Results

Obese patients went through UKA at an earlier age than the non-obese patients (54.7 ± 4.7 years compared to 59.9 ± 7.8 years, p = 0.005). At 2, 10, and 15-year follow-up, both groups achieved clinically significant improvements in outcomes. There was no significant association found between obesity and outcome using multiple linear regression. While propensity matching found PCS improvement at 2 years to be greater in obese patients, no significant association between obesity and 15-year outcome was found. All 13 patients who required revision, underwent total knee arthroplasty (TKA). The overall 15-year survivorship was 74.2% within the obese group and 92.4% within the control group.

Conclusion

Compared to non-obese patients, obese patients had poorer 15-year survivorship with greater odds of requiring revision surgery. However, assuming implant survival, obese patients can expect a non-inferior outcome relative to their non-obese counterparts in all patient reported outcome measures 15 years after surgery.

Catastrophic Femoral Component Failure of a Unicompartmental Knee Arthroplasty

We report a case of previously undescribed medial unicompartmental knee arthroplasty failure due to femoral component implant fracture. The patient experienced sudden pain and locking while ambulating 8 years postoperatively. Radiographs revealed catastrophic femoral component failure with a transverse break through the metal. The patient underwent revision to total knee arthroplasty. At 1-year follow-up, the patient had no pain and a range of motion of 130 degrees. Particular attention should be paid to obtaining adequate femoral component posterior flange fixation during unicompartmental knee arthroplasty. Patient education regarding maintaining a healthy weight is crucial to preventing this complication.

Image-based robotic-arm assisted unicompartmental knee arthroplasty provides high survival and good-to-excellent clinical outcomes at minimum 10 years follow-up

PURPOSE

The purpose of the present study was to determine the incidence of revision and report on clinical outcomes at a minimum of 10 years follow-up in patients who had received a medial unicompartmental knee arthroplasty (UKA) with an three-dimensional image-based robotic system.

METHODS

A total of 239 patients (247 knees), who underwent medial robotic-arm assisted (RA)-UKA at a single center between April 2011 and June 2013, were assessed. The mean age at surgery was 67.0 years (SD 8.4). Post-operatively, patients were administered the Forgotten Joint Score-12 (FJS-12) and asked about their satisfaction (from 1 to 5). Post-operative complications were recorded. Failure mechanisms, revisions and reoperations were collected. Kaplan-Meier survival curves were calculated, considering revision as the event of interest.

RESULTS

A total of 188 patients (196 knees) were assessed at a mean follow-up of 11.1 years (SD 0.5, range 10.0-11.9), resulting in a 79.4% follow-up rate. Seven RA-UKA underwent revision, resulting in a survivorship rate of 96.4% (CI 94.6%-99.2%). Causes of revision included aseptic loosening (2 cases), infection (1 case), post-traumatic (1 case), and unexplained pain (3 cases). The mean FJS-12 and satisfaction were 82.2 (SD 23.9) and 4.4 (SD 0.9), respectively. Majority of cases (174/196, 88.8%) attained the Patient Acceptable Symptoms State (PASS, FJS-12 > 40.63). Male subjects had a higher probability of attaining a "forgotten joint" (p < 0.001) and high satisfaction (equal to 5, p < 0.05), when compared to females.

CONCLUSIONS

Three-dimensional image-based RA-UKA demonstrated high implant survivorship and good-to-excellent clinical outcomes at minimum 10 years follow-up. Pain of unknown origin represented the most common reason for RA-UKA revision.

LEVEL OF EVIDENCE

III.

A decreased tibial tuberosity-trochlear groove distance is associated with lateral patellofemoral joint degeneration after implantation of medial fixed-bearing unicompartmental knee arthroplasty - a minimum five year follow-up

PURPOSE

The influence of lateral patellofemoral osteoarthritis (PFOA) in medial unicompartmental knee arthroplasty (UKA) is controversial. Our aim was to identify radiographic factors that may lead to progressive PFOA after implantation of a fixed-bearing medial UKA and their impact on patient-reported outcomes (PROMs).

METHODS

A retrospective consecutive cohort of patients undergoing medial UKA with a minimum follow-up of 60 months between September 2011 and January 2017 was identified. All UKAs had a fixed-bearing design with cemented femoral and tibial components. PROMs included documentation of the Oxford Knee Score (OKS). The following radiographic parameters were evaluated on conventional radiographs and computer tomography (CT) scans: patella tilt angle, patella congruence angle, Caton-Deschamps index, medial and lateral patellofemoral degeneration (Kellgren-Lawrence Classification (KL)), mechanical anteroposterior axis, femoral torsion, tibial tuberosity to trochlear groove distance (TTTG), anteroposterior translation of the femoral component. A hierarchical multiple regression analysis and partial Pearson correlation analysis (SPSS) were used to evaluate for predictors of progression of lateral PFOA.

RESULTS

Forty-nine knees allowed PFOA assessment and had an average follow-up of 62 months (range 60-108). Twenty-three patients did not exhibit any progression of lateral PFOA. Twenty-two progressed with 1 stage, whereas four had progressed 2 stages according to the KL classification. TTTG negatively correlated with progressive lateral PFOA (r =  - 0.436, p = 0.01). Progression of lateral PFOA did not correlate with OKS at last follow-up (p = 0.613).

CONCLUSION

A decreased TTGT correlated with radiographic progression of lateral PFOA after medial fixed-bearing cemented UKA. PFOA however did not influence PROMs at a minimum of five years postoperatively.