Does Interlimb Knee Symmetry Exist After Unicompartmental Knee Arthroplasty?

Background

Unicompartmental knee arthroplasty (UKA) has long been a treatment option for patients with disease limited primarily to one compartment with small, correctable deformities. However, some surgeons presume that normal kinematics of a lateral compartment UKA are difficult to achieve. Furthermore, it is unclear whether UKA restores normal knee kinematics and interlimb symmetry.

Questions/purposes

We determined knee kinematics exhibited during stair ascent by patients with medial- (MED-UKA) or lateral-UKA (LAT-UKA) and if the knee kinematics of the operated and nonoperated limbs were symmetrical.

Methods

Participants were 17 individuals with MED-UKA and nine with LAT-UKA, all with nondiseased contralateral limbs. For each limb, participants walked up four stairs for five trials while a motion-capture system obtained reflective marker locations. Temporal events were determined by force platform signals. Interlimb symmetry was classified for temporal gait and knee angular kinematics by comparing observed interlimb differences with clinically meaningful differences set at 5% of stride time for temporal variables and 5° for angular variables. The minimum postoperative followup was 6 months (median, 24 months; range, 6–53 months).

Results

Neither group demonstrated clinically meaningful mean interlimb differences. However, approximately half of participants of each UKA group displayed asymmetry favoring the operative or nonoperative limb with similar frequency.

Conclusions

Many patients undergoing UKA demonstrate kinematic interlimb symmetry during stair ascent. Interlimb asymmetry may be affected by a variety of factors unrelated to the UKA.

Clinical Relevance

A MED- or LAT-UKA can potentially restore normal knee function for a demanding task of daily life.     

Improved Survival of Computer-Assisted Unicompartmental Knee Arthroplasty: 252 Cases With a Minimum Follow-Up of 5 Years

Background

Unicompartmental knee arthroplasty (UKA) is an underutilized implant for medial tibiofemoral arthritis despite proven benefits in performance and reduced complications. This is likely related to registry recorded higher revision rates compared with total knee arthroplasty. It is our feeling that better component alignment resulting from the usage of computer-assisted surgery should improve longer-term functional results and survival of UKAs.

Proximal Tibial Bone Density Is Preserved After Unicompartmental Knee Arthroplasty

Background

Bone mineral density (BMD) in the proximal tibia decreases after TKA and is believed to be a factor in implant migration and loosening. Unicompartmental knee arthroplasty (UKA) is a less invasive procedure preserving knee compartments unaffected by degeneration. Finite element studies have suggested UKA may preserve BMD and that implants of differing stiffnesses might differentially affect BMD but these notions have not been clinically confirmed.

Questions/purposes

We therefore asked whether (1) proximal tibial BMD decreases after UKA, and (2) a cemented metal tibial component with a mobile polyethylene (PE) bearing would have greater BMD loss than a cemented PE tibial component.

Methods

We prospectively followed 48 patients who underwent 50 UKAs using one of two implants: one with a cemented metal tibial baseplate and a mobile PE insert (n = 26) and one with a cemented all-PE tibial component (n = 24). In followup we assessed pain and function (Oxford Knee Score, SF-12, The Knee Society Score^©) and radiographs. BMD changes were assessed using quantitative CT osteodensitometry performed postoperatively and at 1 and 2 years after the index procedure.

Results

Mean cancellous BMD decreased 1.9% on the medial side and 1.1% on the lateral side. Mean cortical BMD was static, decreasing 0.4% on the medial side and increasing 0.5% on the lateral side. The greatest observed difference between implants for any region was 3.7%. There were no differences in pain or functional outcome scores.

Conclusions

BMD was preserved 2 years after UKA with no major differences seen between implant types.     

In vivo kinematics of a robot-assisted uni- and multi-compartmental knee arthroplasty

Background

There is great interest in providing reliable and durable treatments for one- and two-compartment arthritic degeneration of the cruciate-ligament intact knee. One approach is to resurface only the diseased compartments with discrete unicompartmental components, retaining the undamaged compartment(s). However, placing multiple small implants into the knee presents a greater surgical challenge than total knee arthroplasty, so it is not certain that the natural knee mechanics can be maintained or restored. The goal of this study was to determine whether near-normal knee kinematics can be obtained with a robot-assisted multi-compartmental knee arthroplasty.

Methods

Thirteen patients with 15 multi-compartmental knee arthroplasties using haptic robotic-assisted bone preparation were involved in this study. Nine subjects received a medial unicompartmental knee arthroplasty (UKA), three subjects received a medial UKA and patellofemoral (PF) arthroplasty, and three subjects received medial and lateral bi-unicondylar arthroplasty. Knee motions were recorded using video-fluoroscopy an average of 13 months (6–29 months) after surgery during stair and kneeling activities. The three-dimensional position and orientation of the implant components were determined using model-image registration techniques.

Results

Knee kinematics during maximum flexion kneeling showed femoral external rotation and posterior lateral condylar translation. All knees showed femoral external rotation and posterior condylar translation with flexion during the step activity. Knees with medial UKA and PF arthroplasty showed the most femoral external rotation and posterior translation, and knees with bicondylar UKA showed the least.

Conclusions

Knees with accurately placed uni- or bi-compartmental arthroplasty exhibited stable knee kinematics consistent with intact and functioning cruciate ligaments. The patterns of tibiofemoral motion were more similar to natural knees than commonly has been observed in knees with total knee arthroplasty. Larger series are required to confirm these as general observations, but the present results demonstrate the potential to restore or maintain closer-to-normal knee kinematics by retaining intact structures and compartments.     

Moderne unikondyläre Kniearthroplastik

Background

Unicondylar knee arthroplasty (UKA) is an established therapeutic option for advanced medial or lateral gonarthrosis.

Objectives

The cornerstones of a successful UKA, careful patient selection, preoperative planning and precise operation technique, are discussed in this overview article.

Importance

In contrast to total knee arthroplasty, UKA allows preservation of the contralateral and patellofemoral compartments as well as the cruciate ligaments and is often associated with rapid postoperative recovery, improved knee kinematics and knee function. However, UKA is technically very demanding. High revision rates have been reported in particular with widespread application, according to national joint replacement registries.

Conclusion

Successful UKA relies on meticulous patient selection, preoperative planning and surgical technique. It is justified to broaden classic UKA indications. In medial and lateral UKA three types of mechanical varus-valgus deformity can be encountered: type 1 (isolated intraarticular deformity), type 2 (pronounced deformity due to extraarticular varus deformity in medial UKA or valgus deformity in lateral UKA), type 3 (reduced deformity due to extraarticular valgus deformity in medial UKA or varus deformity in lateral UKA). We believe these deformities should be addressed accordingly with surgical technique.     

Effect of Computer Navigation on Complication Rates Following Unicompartmental Knee Arthroplasty

Background

We evaluated whether the complication and revision rates of unicompartmental knee arthroplasty (UKA) performed with intraoperative computer-based navigation differ from standard UKAs performed without intraoperative computer-based navigation.

Disease Progression After Lateral and Medial Unicondylar Knee Arthroplasty

Background

Medial unicompartmental knee arthroplasty (UKA) has been a successful option for treatment of arthritis in patients with a healthy lateral compartment. However, lateral UKA is less common and results are less consistent. The purpose of this study is to compare progression of radiographically evident osteoarthritis in unoperated compartments during 5 years after lateral and medial UKA.

Patterns of Compartment Involvement in End‐stage Knee Osteoarthritis in a Chinese Orthopedic Center: Implications for Implant Choice

Objectives

Knee osteoarthritis (OA) is a prevalent disease in the elderly, causing pain and contributing to poor quality of life. Surgical intervention, such as knee arthroplasty, can be used in those with end‐stage knee OA. Total knee arthroplasty (TKA) is one of the most common surgical procedures for end‐stage knee OA, with promising clinical outcomes. However, a large proportion of patients with isolated compartment OA can be treated with unicompartmental knee arthroplasty (UKA) instead. UKA has shown better patient‐reported functional outcomes, and lower mortality and major complication rates than TKA. The percentage of UKA in knee arthroplasty varied in different orthopedic centers, and we believed that the requirement for UKA was underestimated in many centers. A retrospective study was carried out on our Chinese patient population presenting for knee arthroplasty; it aimed to identify the proportion of patients that might be suitable for UKA.

Methods

A retrospective cross‐sectional study of 155 consecutive patients (168 knees) awaiting TKA for end‐stage primary OA was performed. The pattern and grade of OA was recorded from preoperative weight‐bearing anteroposterior and non‐weight‐bearing lateral radiographs. The medial, lateral, patellofemoral compartment was given an individual Kellgren–Lawrence grade on the radiographs, and those grade ≥3 were defined as end‐stage OA. The compartments involvement was established then. The integrity of the anterior cruciate ligament (ACL) was determined by the modified Keyes classification on lateral radiographs. The applicability for total or partial knee arthroplasty was determined according to the compartments involvement.

Results

Medial compartment involvement was found in 154 (91.7%) knees, while the involvement of the lateral compartment and patellofemoral joint was found in 54 (32.1%) and 57 (33.9%) knees, respectively. Eighty‐one (48.2%) of the knees showed medial compartment OA with or without patellofemoral joint involvement, and modified Keyes classification grade 1, indicating an intact ACL, and, hence, potential suitability for medial UKA. Isolated lateral OA indicating possible suitability for lateral UKA was identified in 11 knees (6.5%). No patients showed isolated patellofemoral joint OA. The other 76 (45.2%) knees could be treated by TKA.

Conclusions

The medial compartment was the most commonly affected in our Chinese patients indicated for knee arthroplasty. More than half of the patients in this group could be treated by either medial or lateral UKA.

     

Die mediale monokondyläre Kniegelenkprothese

Background

Unicondylar knee replacement (UKA) is a viable alternative to high tibial osteotomy (HTO) and total knee replacement in the treatment of medial osteoarthritis of the knee. With the correct indication, the results of UKA and HTO are comparable.

Results

In comparison with the results of total knee replacements, UKA leads to faster rehabilitation, superior postoperative range of motion, and higher postoperative activity levels. Despite the excellent long-term results, the survival rate is inferior to the results of total knee replacement. The major causes for failure are progression of osteoarthritis in the lateral and patellofemoral joint as well as the loosening of the tibial component.

Conclusion

The conversion to total knee replacement can mostly be performed without problems. However, the expected results are inferior to primary total knee replacement and the reported revision rates are higher.     

Midterm-Adjusted Survival Comparing the Best Performing Unicompartmental and Total Knee Arthroplasties in a Registry

Background

Recent literature suggests that the difference in revision risk between unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) can be influenced by surgeon volume and other confounders. We hypothesized that implant selection might decrease the relative risk of revision in an adjusted model.

Does an Unloader Brace Reduce Knee Loading in Normally Aligned Knees?

Background

Unloading knee braces often are used after tibiofemoral articular cartilage repair. However, the experimental basis for their use in patients with normal tibiofemoral alignment such as those undergoing cartilage repair is lacking.

Questions/purposes

The purpose of this study was to investigate the effect of varus and valgus adjustments to one commercially available unloader knee brace on tibiofemoral joint loading and knee muscle activation in populations with normal knee alignment.

Methods

The gait of 20 healthy participants (mean age 28.3 years; body mass index 22.9 kg/m²) was analyzed with varus and valgus knee brace conditions and without a brace. Spatiotemporal variables were calculated as were knee adduction moments and muscle activation during stance. A directed cocontraction ratio was also calculated to investigate the relative change in the activation of muscles with medial (versus lateral) moment arms about the knee. Group differences were investigated using analysis of variance. The numbers available would have provided 85% power to detect a 0.05 increase or decrease in the knee adduction moment (Nm/kg*m) in the braced condition compared with the no brace condition.

Results

With the numbers available, there were no differences between the braced and nonbraced conditions in kinetic or muscle activity parameters. Both varus (directed cocontraction ratio 0.29, SD 0.21, effect size 0.95, p = 0.315) and valgus (directed cocontraction ratio 0.28, SD 0.24, effect size 0.93, p = 0.315) bracing conditions increased the relative activation of muscles with lateral moment arms compared with no brace (directed cocontraction ratio 0.49, SD 0.21).

Conclusions

Results revealed inconsistencies in knee kinetics and muscle activation strategies after varus and valgus bracing conditions. Although in this pilot study the results were not statistically significant, the magnitudes of the observed effect sizes were moderate to large and represent suitable pilot data for future work. Varus bracing increased knee adduction moments as expected; however, they produced a more laterally directed muscular activation profile. Valgus bracing produced a more laterally directed muscular activation profile; however, it increased knee adduction moments.

Clinical Relevance

When evaluating changes in knee kinetics and muscle activation together, this study demonstrated conflicting outcomes and questions the efficacy for the use of unloader bracing for people with normally aligned knees such as those after articular cartilage repair.     

Reduziert ein erh?hter tibialer Slope den Abrieb bei unikondyl?ren Schlittenprothesen?

Introduction

Unicompartmental knee arthroplasty (UKA) has become a standard procedure with good clinical outcome in patients with isolated medial osteoarthritis of the knee. However, the survival rates of UKA are still inferior compared to that of total knee arthroplasty. Aseptic loosening and wear are responsible for more than 50% of revisions. Therefore, this study evaluated the influence of the tibial slope on the wear rate in a medial UKA.

Materials and methods

The wear rate of a medial mobile-bearing UKA (Univation? Aesculap, Tuttlingen, Deutschland) was evaluated according to the ISO 14243-1:2002(E) norm with a customized four-station servo-hydraulic knee wear simulator (EndoLab, Thansau, Germany). In the first group, the prostheses was medially implanted with 0° slope (n?=?3) and in the second group the prostheses was medially implanted with 8° slope (n?=?3). The lateral side was kept constant with 0° in both groups. For each implant, a total of 5.0 million cycles was performed and after every 0.5 million cycles the gravimetric wear rate was determined.

Results

The wear rate in the 0° slope group was 3.46?±?0.59?mg/million cycles and therefore significantly higher than in the 8° slope group with 0.99?±?0.42?mg/million cycles (p?Discussion An increase in the tibial slope leads to a reduced wear rate in a mobile-bearing UKA. Therefore, at least for this mobile-bearing UKA a higher tibial slope seems favorable to reduce the wear. However, before an optimal position of the tibial slope can be recommended, further investigations are required to evaluate the influence of the tibial slope on other factors, such as the ligament tension or the strain on the lateral compartment.     

In vivo pre- and postoperative three-dimensional knee kinematics in unicompartmental knee arthroplasty

Background

Pre- and postoperative knee kinematics in unicompartmental knee arthroplasty (UKA) can be theoretically related to clinical outcome and longevity after UKA with regard to ligament function and the degree of arthritic changes. However, the preoperative knee kinematics of patients indicated for UKA remain to be elucidated, and it is also unclear whether the preoperative kinematics can be maintained by the UKA procedure. The objective of this study was to examine the in vivo pre- and postoperative three-dimensional knee kinematics in UKA while referencing the normal knee kinematics reported in our previous study.

Methods

We analyzed the knee kinematics in 17 knees (14 patients) undergoing UKA via a three-dimensional to two-dimensional registration technique employing femoral condylar translation and femoral axial rotation. The pre- and postoperative knee kinematics during squat motion were evaluated in the same subjects, employing consistent evaluation parameters.

Results

On average, both pre- and postoperative knee kinematics in the range 10–100° of knee flexion demonstrated near-consistent femoral external rotation and anterior translation of the medial condyle and posterior translation of the lateral condyle. However, the mean femoral external rotation angle and the posterior translation of the lateral condyle postoperatively were significantly smaller than the values observed preoperatively.

Discussion

Although the patterns of preoperative knee motion were similar to those seen in normal knees, the magnitude of this motion varied widely between patients, so it was not necessarily representative of normal knees. These variations may be due to the varying degrees of arthritic changes caused by osteoarthritis. Although the patterns of knee kinematics were largely maintained by the UKA procedure, the causes of the significant reductions in the magnitude of motion upon performing the UKA procedure should be investigated in subsequent studies with a larger number of patients.     

Feasibility and safety of performing outpatient unicompartmental knee arthroplasty

Purpose

Unicompartmental knee arthroplasty (UKA) has a faster short-term recovery than total knee arthroplasty (TKA). The purpose of this study was to determine the feasibility and safety of performing outpatient UKAs in a consecutive group of patients presenting with unicompartmental knee osteoarthritis.

Methods

A total of 105 consecutive patients underwent unicompartmental arthroplasty before noon with the intention of being discharged as an outpatient. All patients followed an established rapid recovery pathway to facilitate a same-day discharge. Post-operative complications and hospital readmissions were retrospectively recorded for all patients at one week and at three months after surgery.

Results

All of the 105 patients (100 %) indicated for outpatient UKA could be discharged home on the same day of surgery. No patients required readmission within the first week post-operatively, while one patient required readmission between week one and week 12. The single patient who required readmission developed a post-operative infection requiring irrigation/debridement with polyethylene liner exchange and intravenous antibiotics.

Conclusion

Using an established, multidisciplinary, rapid recovery protocol, outpatient UKA is safe and feasible in the vast majority of patients.     

Differences in Patient-Reported Outcomes Between Unicompartmental and Total Knee Arthroplasties: A Propensity Score-Matched Analysis

Background

The purpose of this study was to compare the patient-reported outcomes regarding joint awareness, function, and satisfaction after unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA).