Medial Unicompartmental Arthroplasty Research Articles

Is Patella Facet Arthritis a Contraindication to Unicompartmental Knee Arthroplasty: Current Concepts

Medial knee unicompartmental arthroplasty (UKA) has increased in popularity for treatment of end-stage anteromedial osteoarthritis in part secondary to its quicker recovery, improved function, and decreased risk of medical complications over total knee arthroplasty (TKA). However, despite the success of medial UKA, dilemma still exists over certain patient characteristics as to suitability for undergoing the procedure. In addition to patient age, body mass index (BMI), and the presence, or lack thereof, of an anterior cruciate ligament (ACL), one of the most contentious issues surrounding suitability for medial UKA is the preoperative status of the patellofemoral joint (PFJ). This review aims to look at the historical factors leading to the current dilemma as well as recent evidence surrounding anterior knee pain and preoperative PFJ arthritis on the survivability and outcomes of medial UKA. This article will also evaluate other PFJ factors possibly affecting the outcome of medial UKA such as lateral patellar subluxation and lateral facet grooving, future perspectives that may influence the utilization of medial UKA such as cementless implants, and the choice of mobile versus fixed bearing articulations.

Lateral meniscus with tears or with histologic calcification does not increase the risk of lateral osteoarthritis after medial unicompartmental arthroplasty.

Meniscal tears or histological meniscal calcifications (in the absence of radiological chondrocalcinosis) are frequent in osteoarthritis. Whether lateral meniscal lesions influence clinical outcomes after medial unicompartmental knee arthroplasty (UKA) is unknown. We analyzed 130 patients (130 knees) with medial unicompartmental knee arthroplasties between 2005 and 2015. These 130 knees had full articular cartilage thickness in the lateral compartment and no radiological chondrocalcinosis on preoperative radiographs. The lateral meniscus was analyzed with preoperative MRI and a biopsy of the anterior horn at the time of surgery. Synovial fluid was collected and analyzed for calcium pyrophosphate dihydrate crystal deposition (CPPD crystals). Lateral meniscal tears were untreated when detected on MRI or during surgery, with the hypothesis that these tears on the opposite compartment would remain asymptomatic in medial UKA. At average 10-year follow-up, patients were evaluated with clinical and radiographic outcome, with a focus on the risk of joint space narrowing of the lateral femorotibial compartment. CPPD crystals were present in the synovial fluid of 70 knees. Lateral meniscal tears were seen on MRI in 34 (49%) normal meniscuses of the 60 knees without CPPD crystals and in six other knees without histological meniscal calcification despite CPPD crystals. Histological calcification was present on 61 lateral meniscuses with 53 meniscal tears. The results showed no significant differences in the clinical outcomes between knees with lateral meniscal tears or lateral meniscal histological chondrocalcinosis or both lesions and those without these conditions. Additionally, radiographic progression of osteoarthritis in the opposite femorotibial compartment of the knee was not more frequent in patients with these meniscal issues. The tenyear cumulative survival rates, measured by the need for total knee arthroplasty, were 91% for knees without meniscal lesions and 92% for knees with these lesions. On this basis, treatment of meniscal tears of the lateral compartment and routine aspiration of the knee to assess for birefringent crystals in the planning of medial UKA do not appear necessary.

Presence of a Lateral Trochlear Osteophyte Predicts Medial Unicompartmental Arthroplasty Failure at Midterm Follow-up

BackgroundSpecific clinical and radiographic risk factors for medial unicompartmental knee arthroplasty (UKA) failure are incompletely understood. The purpose of this study was to perform a midterm survivorship analysis of medial UKA from a single, nondesigner surgeon. Based on observations from clinical practice, we hypothesized that the presence of a lateral trochlear osteophyte on preoperative Merchant radiographs may be predictive of medial UKA failure secondary to progressive osteoarthritis (OA). MethodsPatients who underwent a mobile-bearing medial UKA by a single surgeon with minimum 24 months of clinical follow-up from 2008 to 2019 were retrospectively identified. Radiographic parameters, including the presence of a lateral trochlear osteophyte, were measured. Kaplan-Meier survivorship analyses were performed. Cox proportional hazards models were used to evaluate variables as risk factors for UKA failure, defined as reoperation or component revision. ResultsA total of 233 UKAs were included. The mean age was 60 years, mean BMI 32 kg/m2, and 53% of patients were male. The mean follow-up duration was 5.7 years (range, 2.0-13.1 years). Using any reoperation as an endpoint, the 10-year survival was 91%. Using any component revision as an endpoint, the 10-year survival was 93%. Using revision due to progressive OA as an endpoint, the 10-year survival was 95%. The presence of a lateral trochlear osteophyte was associated with an increased risk of any reoperation (hazard ratio 3.6; 95% confidence interval 1.3-9.5) and increased risk of revision due to progressive OA (hazard ratio 9.8; 95% confidence interval 2.9-32.7). ConclusionsThe presence of a lateral trochlear osteophyte on preoperative Merchant view radiographs was associated with an increased risk of medial UKA failure.

CRPS after unicompartmental knee arthroplasty: A case report

A 59-year-old female presented with pain, warmth, erythema, and swelling over the medial aspect of her left knee that began after medial unicompartmental arthroplasty. Exam fulfilled the Budapest criteria for diagnosis of Complex Regional Pain Syndrome (CRPS) type 2. Topical compound cream and physical therapy were prescribed, and symptoms were improved at follow up visit. CRPS localized to the knee after unicompartmental arthroplasty has not been reported in the literature to date, therefore we report a case of CRPS after unicompartmental knee arthroplasty.

Radiographic Outliers, Revisions, and Functional Outcomes in Fixed-Bearing Medial Unicompartmental Arthroplasty

Background and Hypothesis:
 Unicompartmental Knee Arthroplasty (UKA) is a technically demanding procedure vulnerable to errors in component positioning. Recent studies suggest robotic-assistance improves precision of implant placement, minimizes outliers, and improves survivorship. However, we have previously demonstrated an experienced surgeon can match robotic accuracy. This study evaluated revision rates and functional outcomes of radiographic outliers in manual UKA.
 Experimental Design or Project Methods:
 A retrospective review of 222 consecutive fixed-bearing medial UKAs was conducted. Implant positioning and alignment were assessed radiographically measuring tibial coronal (TCA), femoral coronal (FCA), tibial sagittal (TSA) and femoral sagittal (FSA) angles as well as implant overhang. UCLA Activity Level and all-cause survivorship were evaluated. Student’s t-test, Chi square, and Kaplan Meier curves were used in analyses with alpha ≤ .05 designating statistical significance.
 Results:
 Using previously published alignment goals, our manual UKAs achieved the following targets: 92% for TCA, 100% for FCA, 88% for TSA, and 100% for FSA. For implant overhang, 100% met medial, anterior, and posterior targets. Our manual UKAs achieved desired alignment and overhang goals more frequently than previously published manual success. Survivorship free from aseptic revision in this study was 96% at 8.5 years. Additionally, there was no difference in UCLA Activity Level improvement comparing outliers and non-outliers (p³0.159).
 Conclusion and Potential Impact:
 Manual UKAs performed by an experienced surgeon showed improved success in achieving alignment and implant overhang goals compared to published manual UKA data and similar success compared to published robotic-assisted UKA data. We found no differences in revision rates or functional outcomes between outliers and non-outliers using previously published targets. For robotic assistance to be cost effective, it must demonstrate improved outcomes or survivorship when compared to manual UKAs. Our results contradict recently published claims that manual alignment outliers and failure rates fail to meet expectations for UKA.

Study Compares Outcomes in Total Knee Arthroplasty Versus Medial Unicompartmental Arthroplasty

Study Compares Outcomes in Total Knee Arthroplasty Versus Medial Unicompartmental Arthroplasty

Medial bicompartmental arthroplasty patients display more normal gait and improved satisfaction, compared to matched total knee arthroplasty patients

PurposeMedial bicompartmental arthroplasty, the combination of ipsilateral medial unicompartmental and patellofemoral arthroplasty, is an alternative to total knee arthroplasty for patients with medial tibiofemoral and severe patellofemoral arthritis, when the lateral tibiofemoral compartment and anterior cruciate ligament are intact. This study reports the gait and subjective outcomes following medial bicompartmental arthroplasty.MethodsFifty-five subjects were measured on the instrumented treadmill at top walking speeds, using standard metrics of gait. Modular, single-stage, medial bicompartmental arthroplasty subjects (n = 16) were compared to age, body mass index, height- and sex-matched healthy (n = 19) and total knee arthroplasty (n = 20) subjects. Total knee arthroplasty subjects with pre-operative evidence of tricompartmental osteoarthritis or anterior cruciate ligament dysfunction were excluded. The vertical component of ground reaction force and temporospatial measurements were compared using Kruskal–Wallis, then Mann–Whitney test with Bonferroni correction (α = 0.05). Oxford Knee and EuroQoL EQ-5D scores were compared.ResultsObjectively, the medial bicompartmental arthroplasty top walking speed of 6.7 ± 0.8 km/h was 0.5 km/h (7%) slower than that of healthy controls (p = 0.2), but 1.3 km/h (24%) faster than that of total knee arthroplasty subjects (5.4 ± 0.6 km/h, p < 0.001). Medial bicompartmental arthroplasty recorded more normal maximum weight acceptance (p < 0.001) and mid-stance forces (p = 0.03) than total knee arthroplasty subjects, with 11 cm (15%) longer steps (p < 0.001) and 21 cm (14%) longer strides (p = 0.006). Subjectively, medial bicompartmental arthroplasty subjects reported Oxford Knee Scores of median 41 (interquartile range 38.8–45.5) compared to total knee arthroplasty Oxford Knee Scores of 38 (interquartile range 30.5–41, p < 0.02). Medial bicompartmental arthroplasty subjects reported EQ-5D median 0.88 (interquartile range 0.84–0.94) compared to total knee arthroplasty median 0.81 (interquartile range 0.73–0.89, p < 0.02.)ConclusionThis study finds that, in the treatment of medial tibiofemoral osteoarthritis with severe patellofemoral arthritis, medial bicompartmental arthroplasty results in nearer-normal gait and improved patient-reported outcomes compared to total knee arthroplasty.Level of evidenceIII.

Pulsatile Lavage Improves Tibial Cement Penetration and Implant Stability in Medial Unicompartmental Arthroplasty: A Cadaveric Study.

Cemented unicompartmental knee arthroplasty (UKA) shows good survivorship and function. However, implant failure, causing the need for revision, can occur. Aseptic loosening is still among the most common reasons for revision. The purpose of this study was to assess the influence of preimplantation lavage technique on tibial cement penetration depth, tibial cement volume, and load to fracture in the tibial component of mobile-bearing UKA. In 10 pairs of fresh frozen human tibiae, cemented UKA was implanted by an experienced surgeon. Tibial components were then implanted, left and right tibiae were randomly allocated to group A or B. Prior to implantation, irrigation was performed with either syringe lavage or pulsatile jet lavage in a standardized manner. Cement surface was 4170.2 mm2 (3271.6-5497.8 mm2) in the syringe lavage group, whereas the jet lavage group showed 4499.3 mm2 (3354.3-5809.1 mm2); cement volume was significantly higher as well (4143.4 mm3 (2956.6-6198.6 mm3) compared with 5936.9 mm3 (3077.5-8183.1 mm3)). Cement penetration depth was 2.5 mm (1.7-3.2 mm) for the jet lavage, and 1.8 mm (1.2-2.4 mm) for the syringe lavage. The mean fracture load was 4680 N in the jet lavage group and 3800 N in the syringe lavage group (p = 0.001). Subsidence was significantly higher for syringe lavage. This study suggests a correlation of cement penetration depth and cement volume to implant failure in the tibial component of a UKA using a cadaveric model. The type of bone lavage most likely influences these two key parameters.

Functional results of total-knee arthroplasty versus medial unicompartmental arthroplasty: two-year results of a randomised, assessor-blinded multicentre trial

ObjectiveThe primary objective of the trial was to assess the clinical effectiveness of medial unicompartmental knee arthroplasty versus total knee arthroplasty in patients with isolated medial osteoarthritis of the knee.DesignProspective,...

No differences in 10-year clinical outcomes and quality of life between patients with different mediolateral femoral component positions in fixed-bearing medial unicompartmental knee arthroplasty.

There has been a paucity of literature evaluating the role of mediolateral femoral component position (FCP) in medial unicompartmental arthroplasty (UKA). Hence, the aim of this study is to evaluate whether the mediolateral FCP in UKA will affect the 10-year clinical outcomes and quality of life of patients who underwent medial UKA. Data of 262 patients who underwent medial UKA were analyzed. All patients were assessed at 6 months, 2 years and 10 years using the Knee Society Function Score, Knee Society Knee Score, Oxford Knee Score, Short-Form 36 Physical/Mental Component Scores and postoperative satisfaction. The mediolateral FCP on postoperative radiographs was measured by independent assessors using the Picture Archiving and Communication Systems. 144 patients were distributed into group C (center), 98 into group M (medial) and 20 into group L (lateral) according to FCP, and one-way ANOVA was used to compare the functional outcomes of the three groups. No statistical differences were found between the three groups in terms of 10-year clinical outcomes, quality of life, satisfaction rates and revision rates. Differences in mediolateral FCP did not result in significant difference in 10-year postoperative clinical outcomes for patients who underwent fixed-bearing medial UKAs. Retrospective study, Level III.

St Georg Sled medial unicompartmental arthroplasty: survivorship analysis and function at 20years follow up.

The peri-operative and short-term benefits of unicompartmental knee arthroplasty (UKA) are well supported in the literature. However, there remains concern regarding the higher revision rate when compared with total knee replacement. This manuscript reports the functional outcome and survivorship of a large series of fixed bearing, medial unicompartmental replacements (St Georg Sled), with a minimum of 20years follow-up. Between 1974 and 1994, 399 patients (496 knees) underwent a medial fixed-bearing UKA. Prospective data were collected pre-operatively and at regular intervals post-operatively using the Bristol Knee Score (BKS), Oxford Knee (OKS) and Western Ontario MacMaster (WOMAC) scores. Kaplan-Meier survival analysis was used to determine survivorship, with revision or need for revision as end point, and differences assessed using Mantel-Cox log rank test. Functional knee scores improved post-operatively, but demonstrated a slight decline from 10years of follow-up onwards. Survivorship is estimated as 86% at 10years, 80% at 15years, and 78% at 20years. Sixty knees were revised, with progression of disease in another compartment the commonest reason. Eighty eight percent were revised using a primary prosthesis. For patients over the age of 65years at the time of index procedure, 93% died with a functioning prosthesis in situ. Medial UKA demonstrates good long-term function and survivorship, and represents an excellent surgical option for patients aged over 65years of age, where few patients will require a revision procedure. IV.

Lateral Unicompartmental Knee Arthroplasty in Structure of Modern Knee Replacement: Is It «Woe From Wit» or a Viable Go-To Method?

Background. Results of numerous contemporary studies indicate that medial and lateral unicompartmental knee arthroplasty (UKA) are almost equally effective both in clinical and functional aspects with no statistically significant difference in most cases. Furthermore, both operations tend to reach the effectiveness of total knee arthroplasty (TKA), despite the common opinion that any UKA is a more complex and skill challenging surgery with a less predictable outcome. The purpose — to asses if UKA in the patients with end-stage lateral unicompartmental osteoarthritis is an effective surgical intervention that may allow obtaining good and excellent medium-term functional results, that are comparable to the results of the medial unicompartmental arthroplasty, and to see if there are any benefits in comparison to the total knee arthroplasty (TKA). Materials and Methods. 140 middle-aged and elderly adults with end-stage osteoarthritis underwent knee arthroplasty at Vreden National Medical Research Center of Traumatology and Cheboksary Federal Center of Traumatology, Orthopedics and Arthroplasty. Group I (lateral UKA) (the main ) consisted of 15 patients with knee arthritis and type I Krakow valgus knee deformity, who underwent the lateral UKA with a fixed all-polyethylene tibial component. Group II (medial UKA) included 58 patients with end-stage medial unicompartmental osteoarthritis, who underwent the medial UKA using an endoprosthesis of a similar design. Group III (TKA) was represented by 67 patients with gonarthrosis accompanied by type II Krackow valgus knee deformity, who underwent the total knee arthroplasty with cruciate retaining (CR) prosthesis. The comparison between the groups was carried out regarding the achieved range of motion, functional result (using Oxford Knee Score and Forgotten Joint Score), as well as the rate of different types of complications. Results. During the study, two main objectives were set. The first was to compare the outcomes of the lateral and medial UKA. It was revealed that the lateral UKA allowed the patients to obtain good function of the operated knee, with the best results among the compared groups on the Forgotten Joint Score. The second objective was to compare the results of the lateral UKA and TKA in the patients with type II Krackow knee valgus deformity. Here, our study revealed that the group of UKA (group I) compared to the TKA had better results according to Forgotten Joint Score (71.5±5.3 vs 65.2±7; p = 0.9) and had a slightly lower range of motion according to Oxford Knee Score (34.6±2.3 versus 35.9±2.2; p = 0.7). It is worth noting that in both cases the difference was not statistically significant. Conclusion. Despite the fact that the lateral UKA made it possible to achieve a good functional outcome, the integral score was the same as in the groups with the medial UKA and the total knee arthroplasty. The older patients were more satisfied with the results of the partial arthroplasty than with the results of the total.

Patient satisfaction after total knee replacement—still a challenge

textabstractDuring a validation process of the Swedish Knee Arthroplasty Register (SKAR), living registered patients were sent a questionnaire to ask if they had been reoperated on. This gave an opportunity to pose a simple four-point question with respect to patient satisfaction which 95% of patients answered. We analyzed the answers of patients operated on between 1981 and 1995 and found that only 8% of the patients were dissatisfied regarding their knee arthroplasty 2–17 years postoperatively. The satisfaction rate was constant, regardless of when the operation had been performed during the 15-year period. The proportion of satisfied patients was affected by the preoperative diagnosis, patients operated on for a long-standing disease more often being satisfied than those with a short disease-duration. There was no difference in proportions of satisfied patients, whether they had primarily been operated on with a total knee arthroplasty (TKA) or a medial unicompartmental arthroplasty (UKA). For TKAs performed with primary patellar resurfacing, there was a higher ratio of satisfied patients than for TKAs not resurfaced, but this increased ratio diminished with time passed since the primary operation. Unrevised knees had a higher proportion of satisfied patients than knees that had been subject to revision, and among patients revised for medial UKA, the proportion of satisfied patients was higher than among patients revised for TKA. We conclude that satisfaction after knee arthroplasty is stable and long-lasting in unrevised cases and that even after revision most patients are satisfied.

Finite element analysis of optimization on placement of medial fixed-bearing unicompartmental knee arthroplasty

Objective To investigate the influence of displacement of femoral and tibial components on the biomechanics of femoral or tibial bone in coronal view. Methods A series of CT and MRI of the left knee joint of a Han male volunteer was taken and a three-dimensional finite element model of the healthy knee joint was established. The femoral component and the tibial component were designed with varus 6°, varus 3°, 0°, valgus 3°, and valgus 6°, and were combined into 25 three-dimensional finite element model (FEM) of medial unicompartmental knee arthroplasty. A 1 000 N load was applied along the femoral mechanical axis. The von Mises cloud stress distribution was observed. Moreover, the lateral compartment load ratio, the high contact stress of cancellous bone and medial cortical bone below the tibial component, the upper surface of the polyethylene liner, and the femoral cartilage in the lateral compartment was measured. The statistically significant indicators compared with the neutral position (0° varus or valgus of the tibia and the femoral prosthesis, and 5° posterior slope of tibia prosthesis) were identified by scatter plots to find the dense and sparse areas of point items. The optimal position of the femoral component and the tibial component was determined by the number of items with statistical significance in the sparse area. Results When the femoral component was placed at 0° position, there was no significant difference in the high contact stress of cancellous bone below the tibial component in the five groups. When the femoral component was placed at 0° position, the tibial component was 6° varus or 6° valgus and the stress was increased by 9.21±3.38 MPa and 9.08±4.13 MPa (P<0.05), respectively. With the changes of femoral and tibial components from 6° varus to 6° valgus, the high contact stress of the medial cortical bone below the tibia was gradually decreased (P<0.05). When the femoral component was placed at 0°, the tibial component changes from 6° varus to 6° valgus without significant difference in the high contact stress on the upper surface of each group of polyethylene gasket. Compared with the neutral position group, the high contact stress of the 6° varus or 6° valgus group were increased by 2.88±2.53 MPa and 3.47±2.86 MPa, respective ly (P<0.05). The lateral compartment load ratio and the high contact stress of lateral compartment femoral cartilage was gradually decreased (P<0.05), when the femoral and tibial components changed from 6° varus to 6° valgus. The number (2.8%, 1/36) of indicators in the sparse area (the combination of all combinations of femur or tibia from 3° varus to 3° valgus) was less than that (57.8%, 37/64) in the dense area (set of all combinations except sparse area), and the difference was significant (χ2=29.61, P<0.001). Conclusion It is suggested that the position of the femoral component and the tibial component in fixed medial unicompartmental arthroplasty should not exceed 3° varus or valgus in patients with standard lower limb alignment. Key words: Osteoarthritis, knee; Arthroplasty, replacement, knee; Prosthesis fitting; Finite element analysis

Medial UKA tends to increase patellar height, whereas open-wedge HTO tends to decrease patellar height

Background: There is no consensus on the most appropriate method to assess patellar height following medial unicompartmental arthroplasty (UKA) or open-wedge high tibial osteotomy (HTO). The purpose of this study was to evaluate the difference between pre- and post-operative patellar height in patients receiving UKA or HTO using three indices of patellar height. Methods: The authors retrospectively analysed pre- and post-operative radiographs of 44 patients that received medial UKA (n=21) or open-wedge HTO (n=23). Pre- and post-operative radiographs were standardised between patients, including anterior-posterior, and lateral in 30° flexion images. Postoperative radiographs were obtained at 6 weeks. Patellar height was assessed according to the Insall-Salvati index, Blackburne-Peel index, and Caton-Deschamps index. Results: Patients that received UKA (67.4±5.8 years) were significantly older than patients that received HTO (51.3±9.0 years, p<0.001). Preoperative patellar height was similar between patients that received UKA or HTO according to all three indices. Postoperative patellar height was similar among the two groups according to the Insall-Salvati index, but was significantly greater following UKA according to the Blackburne-Peel index (0.95±0.13 vs. 0.75±0.24, p=0.003) and Caton-Deschamps index (1.09±0.17 vs. 0.93±0.26, p=0.019). According to all three indices, UKA tended to increase patellar height, whereas HTO tended to decrease patellar height. The differences between pre- and post-operative patellar heights were however not significant, except for the Caton-Deschamps index following UKA (p=0.043). Conclusion: According to all three indices, medial UKA tended to increase patellar height, whereas open-wedge HTO tended to decrease patellar height.

Classification of combined partial knee arthroplasty.

AimsThere has been a recent resurgence in interest in combined partial knee arthroplasty (PKA) as an alternative to total knee arthroplasty (TKA). The varied terminology used to describe these procedures leads to confusion and ambiguity in communication between surgeons, allied health professionals, and patients. A standardized classification system is required for patient safety, accurate clinical record-keeping, clear communication, correct coding for appropriate remuneration, and joint registry data collection.Materials and MethodsAn advanced PubMed search was conducted, using medical subject headings (MeSH) to identify terms and abbreviations used to describe knee arthroplasty procedures. The search related to TKA, unicompartmental (UKA), patellofemoral (PFA), and combined PKA procedures. Surveys were conducted of orthopaedic surgeons, trainees, and biomechanical engineers, who were asked which of the descriptive terms and abbreviations identified from the literature search they found most intuitive and appropriate to describe each procedure. The results were used to determine a popular consensus.ResultsSurvey participants preferred “bi-unicondylar arthroplasty” (Bi-UKA) to describe ipsilateral medial and lateral unicompartmental arthroplasty; “medial bi-compartmental arthroplasty” (BCA-M) to describe ipsilateral medial unicompartmental arthroplasty with patellofemoral arthroplasty; “lateral bi-compartmental arthroplasty” (BCA-L) to describe ipsilateral lateral unicompartmental arthroplasty with patellofemoral arthroplasty; and tri-compartmental arthroplasty (TCA) to describe ipsilateral patellofemoral and medial and lateral unicompartmental arthroplasties. “Combined partial knee arthroplasty” (CPKA) was the favoured umbrella term.ConclusionWe recommend bi-unicondylar arthroplasty (Bi-UKA), medial bicompartmental arthroplasty (BCA-M), lateral bicompartmental arthroplasty (BCA-L), and tricompartmental arthroplasty (TCA) as the preferred terms to classify CPKA procedures.Cite this article: Bone Joint J 2019;101-B:922–928.

Medial Unicompartmental Arthroplasty of the Knee.

Indications for medial unicompartmental knee arthroplasty (UKA) have expanded over the past two decades. Proposed advantages include faster recovery, improved kinematics, and better functional outcomes compared with total knee arthroplasty (TKA) in age-matched control subjects. A focused preoperative examination and imaging is essential to identify appropriate surgical candidates. No difference has been demonstrated between fixed- and mobile-bearing implants for implant survivorship or patient-reported outcomes. The most common reasons for conversion to a TKA are aseptic loosening and progression of osteoarthritis. Ten-year survival for UKA in cohort studies has shown to be >90% with outcomes after conversion to TKA being similar to outcomes for revision TKA. Registries have consistently shown lower implant survival for UKA compared with that for TKA, which is likely secondary to use of several different implants by surgeons of varying levels of experience. UKA has the potential to be a cost-effective alternative to TKA in certain patient populations when performed at high-volume centers with advanced surgical techniques.

Comparison of medial and lateral posterior femoral condyle articular cartilage wear patterns

BackgroundWhile degenerative changes to the articular cartilage of the anterior and distal portions of the femoral condyles have been well studied in the literature, the changes that occur on the posterior femoral condyle are not as clear. The purpose of this study was to assess the difference in articular cartilage thickness between the medial and lateral posterior femoral condyles in knees undergoing unicompartmental knee arthroplasty. MethodsA retrospective review of prospectively gathered data on 107 consecutive patients undergoing unicompartmental knee arthroplasty performed by a single surgeon was performed. The remaining articular cartilage thickness after resection of the posterior femoral condyle was measured and simple analysis conducted to compare cartilage thickness between medial and lateral posterior femoral condyles. ResultsNinety-two medial unicompartmental arthroplasties and 15 lateral unicompartmental arthroplasties were performed during the 16 month study period. The majority of lateral UKA patients were female and had lower BMI than medial UKA patients. The articular cartilage thickness on the medial posterior femoral condyle was 3 mm ± 1 mm (mean ± standard deviation) and 1 mm ± 1 mm on the lateral side (p-value <0.001). ConclusionsThere is a significant difference in articular cartilage thickness between the medial and lateral posterior femoral condyles in patients undergoing unicompartmental knee arthroplasty. This coincides with a potentially inherently different pattern of articular cartilage degeneration between the medial and lateral compartments of the knee and has implications on implant designs and resurfacing techniques about the knee.

How does the inclination of the tibial component matter? A three-dimensional finite element analysis of medial mobile-bearing unicompartmental arthroplasty

BackgroundMedial unicompartmental knee arthroplasty (UKA) using Oxford mobile-bearing prosthesis is performed in the treatment of medial compartmental arthritis of the knee. However, little is known about the stress distributions for mobile-bearing UKA on the medial tibial plateau. MethodsIn this study, the stresses on the coronal plane were calculated in a three-dimensional model of the proximal tibia. The features of the stress distribution were investigated when the tibial tray was placed in 15°, 10°, six degrees, and three degrees varus, neutral (0°), and in three degrees, six degrees, 10°, and 15° valgus on the coronal plane of the medial plateau. ResultsThe peak von Mises stress was found on the cortex below the medial plateau while the stresses of cortical bone increased gradually as the inclination of the tibial tray was changed from varus to valgus. The amount of peak stress was almost the same as that in the normal knee model when the tibial tray was placed in six degrees valgus and consistently lower in varus inclination than in the normal knee model. Conversely, the peak stress of soft bone was found at the bottom of the slot. ConclusionsThis study demonstrates that the inclination of the tibial component affects stress distribution in the proximal tibia after UKA. Slight varus inclination of the mobile-bearing tibial component is acceptable as it lowers the peak stress on the medial cortex. Additionally, placing the tibial tray in slight varus avoids a rise in stress between the tip of the keel and the medial tibial cortex.

Medial Mobile-Bearing Unicompartmental Knee Arthroplasty in Young Patients Aged Less Than or Equal to 50 Years

BackgroundContemporary research has shown medial mobile-bearing unicompartmental knee arthroplasty to be an effective treatment in patients younger than 60 years; however, only one other study has specifically investigated unicompartmental arthroplasty outcomes in patients 50 years or younger. The purpose of this study was to determine the clinical outcomes and survivorship of medial mobile-bearing unicompartmental arthroplasty in this younger patient population. MethodsA retrospective review of patients undergoing primary unicompartmental knee arthroplasty using the Oxford partial knee from 2003 to 2014 in a single practice database was performed. Patients were included in the study if they were 50 years of age or younger with a primary diagnosis of anteromedial osteoarthritis and minimum clinical follow-up of 2 years. Patient clinical outcomes, function, and need for revision surgery were assessed. ResultsThe study included 340 knees. Average patient age was 46.5 years, and the mean follow-up was 6.1 years. Patients demonstrated significant improvements (P < .05) in range of motion (114.5 v 116.9), University of California Los Angeles activity score (4.4 vs 5.6), Knee Society clinical (37.3 vs 86.5) and functional scores (58.8 v 79.8). Overall, 20 patients required reoperation, and the predicted survival rate was 96% at 6 years and 86% at 10 years. Aseptic loosening occurred in 7 patients at an average of 5.6 years postoperatively, while 4 patients required conversion to total knee arthroplasty because of arthritic progression at a mean time of 6.6 years. There were no revision procedures required due to polyethylene liner wear or breakage. ConclusionMedial mobile-bearing unicompartmental arthroplasty should be considered as a treatment option in patients younger than 50 years of age suffering from anteromedial osteoarthritis of the knee.