Predictors of Subjective Outcome After Medial Unicompartmental Knee Arthroplasty

Characterization of clinical data for patient stratification in moderate osteoarthritis with support vector machines, regulatory network models, and verification against osteoarthritis Initiative data

Knee osteoarthritis (OA) diagnosis is based on symptoms, assessed through questionnaires such as the WOMAC. However, the inconsistency of pain recording and the discrepancy between joint phenotype and symptoms highlight the need for objective biomarkers in knee OA diagnosis. To this end, we study relationships among clinical and molecular data in a cohort of women (n = 51) with Kellgren-Lawrence grade 2-3 knee OA through a Support Vector Machine (SVM) and a regulation network model. Clinical descriptors (i.e., pain catastrophism, depression, functionality, joint pain, rigidity, sensitization and synovitis) are used to classify patients. A Youden's test is performed for each classifier to determine optimal binarization thresholds for the descriptors. Thresholds are tested against patient stratification according to baseline WOMAC data from the Osteoarthritis Initiative, and the mean accuracy is 0.97. For our cohort, the data used as SVM inputs are knee OA descriptors, synovial fluid proteomic measurements (n = 25), and transcription factor activation obtained from regulatory network model stimulated with the synovial fluid measurements. The relative weights after classification reflect input importance. The performance of each classifier is evaluated through ROC-AUC analysis. The best classifier with clinical data is pain catastrophism (AUC = 0.9), highly influenced by funcionality and pain sensetization, suggesting that kinesophobia is involved in pain perception. With synovial fluid proteins used as input, leptin strongly influences every classifier, suggesting the importance of low-grade inflammation. When transcription factors are used, the mean AUC is limited to 0.608, which can be related to the pleomorphic behaviour of osteoarthritic chondrocytes. Nevertheless, funcionality has an AUC of 0.7 with a decisive importance of FOXO downregulation. Though larger and longitudinal cohorts are needed, this unique combination of SVM and regulatory network model shall help to stratify knee OA patients more objectively.

Valgus stress radiographs have a minor additional value in detecting lateral cartilage wear when selecting patients for medial partial knee replacement

INTRODUCTION

A valgus stress radiograph, in addition to the weight-bearing fixed flexion posteroanterior radiograph (e.g., Rosenberg), is deemed useful to assess lateral cartilage wear by measuring lateral joint space width (JSW) in patients with medial knee osteoarthritis. This study aimed to assess: (1) the difference in measured lateral JSW between the Rosenberg and the valgus stress radiograph, and (2) the ability of the valgus stress radiograph to detect lateral cartilage wear (indicated by joint space narrowing) in patients where the Rosenberg radiograph showed full thickness cartilage (i.e., the additional value).

MATERIALS AND METHODS

The Rosenberg and valgus stress radiographs, obtained between January 1st 2018 and December 31st 2018, of 137 patients with medial knee osteoarthritis prior to total or partial knee replacement were retrospectively collected. The lateral JSW was measured at its midpoint (midJSW) and minimum (minJSW). The differences were tested with a paired-sample t test. The valgus stress radiograph was considered to have an additional value if: (1) JSW ≥ 5 mm on the Rosenberg radiograph, (2) JSW < 5 mm on valgus stress radiograph, and (3) > 2 mm less JSW on the valgus stress than on the Rosenberg radiograph.

RESULTS

The mean differences in lateral JSW between the Rosenberg and valgus stress radiographs were 0.53 mm (SD = 1.0 mm, p < 0.001) for midJSW and 0.66 mm (SD = 1.1 mm, p < 0.001) for minJSW with both values being lower on the valgus stress radiograph. The valgus stress radiograph was of additional value in 4-6% of the patients.

CONCLUSIONS

Although the valgus stress radiograph shows more lateral JSW narrowing compared to Rosenberg radiograph, it only has an additional value in 1 out of 17-25 patients with medial osteoarthritis. We, therefore, recommend a Rosenberg radiograph as routine radiographic assessment and only use an additional valgus stress radiograph in case of discrepancy between clinical and radiological findings.

Factors predicting lower limb alignment after Oxford medial unicompartmental knee arthroplasty

This study aimed to identify the factors affecting hip-knee-ankle (HKA) angle following Oxford medial unicompartmental knee arthroplasty (MUKA). A retrospective analysis of 200 patients who underwent Oxford MUKA from June 2018 to October 2020 was conducted. Univariate and multivariate analyses were performed to investigate the impact of surgical and radiographic characteristics on the postoperative HKA angle. The mean HKA angle was 9.5 ± 4.3° before surgery and 3.6 ± 3.7° after surgery (p < 0.001). The postoperative HKA angle significantly correlated with the preoperative HKA angle, bearing size, tibial component alignment angle, and BMI (r = 0.71, p < 0.001; r =  - 0.24, p = 0.001; r = 0.21, p = 0.004; r =  - 0.18, p = 0.011). Multiple linear regression analysis revealed that the preoperative HKA angle (β = 0.68, p < 0.001), bearing size (β =  - 0.31, p < 0.001), tibial component alignment angle (β = 0.14, p = 0.003), and BMI (β =  - 0.09, p = 0.047) significantly affected the postoperative HKA angle. In conclusion, larger preoperative varus deformity, smaller bearing size, greater varus alignment of the tibial component, and lower BMI lead to greater postoperative varus alignment of the lower limb in Oxford MUKA. With this concept, surgeons can more accurately predict postoperative lower limb alignment and avoid malalignment in Oxford MUKA.

Fixed-Bearing Unicompartmental Knee Arthroplasty in Tibia Vara Knees Results in Joint Surface Malalignment and Varus Joint Line Obliquity, but Does Not Affect Functional Outcomes at Greater Than 5 Years Follow-Up

BACKGROUND

This study aimed to investigate the clinical outcomes of fixed-bearing medial unicompartmental knee arthroplasty (UKA) for tibia vara knees and the associated changes in joint space malalignment (JSM) and joint line obliquity (JLO).

METHODS

We retrospectively analyzed a consecutive group of 100 patients who underwent fixed-bearing medial UKA with a preoperative medial proximal tibia angle (MPTA) ≥86° (n = 50) and MPTA <86° (n = 50) and who had a minimum 5-year follow-up. Radiological parameters, including the hip-knee-ankle angle, MPTA, and the postoperative JSM and JLO, were measured. Functional evaluation was performed using the range of motion, visual analog scale, Knee Society Knee Score, Knee Society Function Score, and Western Ontario and McMaster Universities Osteoarthritis Index score.

RESULTS

The MPTA <86° group showed significantly higher postoperative JLO (91.8 versus 90.4°, respectively; P = .002) and JSM (6.1 versus 4.2°, respectively; P = .026) compared to the MPTA ≥86° group. Functional outcomes, including range of motion, visual analog scale, Knee Society Knee Score, Knee Society Function Score, and Western Ontario and McMaster Universities Osteoarthritis Index scores, were not significantly different between the 2 groups.

CONCLUSIONS

Fixed-bearing medial UKA is a safe and effective surgical option for patients who have tibia vara knees, as an increase in JLO and JSM postoperatively does not have a clinically relevant impact, even after a minimum 5-year follow-up.

Knees with anteromedial osteoarthritis show a substantial phenotypic variation prior and following medial unicompartmental knee arthroplasty

PURPOSE

The primary aim of this study was to evaluate the phenotypic variation using the Coronal Plane Alignment of the Knee (CPAK) classification among 1000 knees with anteromedial osteoarthritis (OA) both prior to and following medial unicompartmental knee arthroplasty (UKA). The secondary aim of this study was to investigate whether knees maintained their preoperative CPAK phenotype and to evaluate the phenotypic alterations following medial UKA.

METHODS

The CPAK classification was used to analyze 1000 knees that underwent medial UKA as treatment for anteromedial OA. Knees were categorized into nine distinct CPAK phenotypes based on their arithmetic hip-knee-ankle angle (aHKA), which estimates the pre-arthritic alignment, and joint line obliquity (JLO), both pre- and postoperatively. Phenotypic variation was analyzed by sex and age, and the phenotypic alterations following medial UKA were evaluated by phenotype.

RESULTS

Preoperatively, CPAK phenotype I had the highest prevalence (45.0%). Among males, the preoperative prevalence of CPAK phenotype I was significantly higher compared to females (53.2% vs. 35.0%, respectively; p ≤ .001), whereas females exhibited a significantly higher occurrence of CPAK phenotype V compared to males (9.8% vs. 4.4%, respectively; p ≤ .015). Following medial UKA, CPAK phenotype II had the highest prevalence (53.3%). Overall, 45.1% of knees maintained their preoperative CPAK phenotype following medial UKA, which was most frequently observed among CPAK phenotype II (67.7%) and III (65.8%).

CONCLUSION

There is a substantial variation in CPAK phenotypes among knees with anteromedial OA, as well as following treatment with medial UKA. This variability challenges the assumption of uniform characteristics among knees with an identical wear pattern associated with anteromedial OA and emphasizes the complexity and variability of this specific form of OA.

LEVEL OF EVIDENCE

III, Retrospective cohort study.

Preoperative valgus-corrected hip-knee-ankle angle and medial meniscal extrusion are useful for evaluating postoperative alignment in mobile-bearing UKA

Purpose

The purposes of the study were to analyze the correlation between preoperative variables (valgus corrected hip-knee-ankle angle (vcHKA), medial osteophyte areas of the tibia and femur, and medial meniscus extrusion (MME)) and the postoperative alignment in mobile-bearing unicompartmental knee arthroplasty (UKA).

Methods

This study enrolled 109 patients (118 knees) who underwent mobile-bearing UKA between January 1, 2019 and January 1, 2023, retrospectively. Radiographic parameters, including the HKA, hip-knee-shaft angle (HKS), and valgus-corrected femorotibial angle (vcFTA), were measured using preoperative radiographs. The vcHKA was calculated as vcFTA - HKS. The medial osteophyte areas of the tibia and femur and MME were measured using knee magnetic resonance imaging (MRI). Simple and multiple linear regression analyses, univariate and multivariate logistic regression analyses, and receiver operating characteristic (ROC) curves were performed.

Results

In total, 109 patients (118 knees) were enrolled in this study. In the multiple linear regression analysis, vcHKA (β = 0.732, 95 % confidence interval (95%CI) = 0.582 to 0.881; p < 0.001) and MME (β = 0.203, 95%CI = 0.001 to 0.405; p = 0.049) were positively correlated with postoperative HKA, and postoperative HKA was modeled according to the following equation: 45.420 + (0.732° * vcHKA) + (0.203 mm × MME). In the multivariate logistic regression analysis, vcHKA (odds ratio (OR) = 2.007, 95 % CI = 1.433 to 2.810, p < 0.001) was associated with postoperative valgus malalignment independently. In the ROC curve, vcHKA (cutoff value: 180°) was predictive of postoperative valgus malalignment, with an accuracy (95%CI) of 0.862 (0.780-0.944).

Conclusion

Overcorrection of a varus knee under valgus stress radiograph (VSR) and excessive MME on preoperative MRI increase the possibility of overcorrection of postoperative alignment in mobile-bearing UKA.

Significant correlations between postoperative outcomes and various limb and component alignment strategies in medial unicompartmental knee arthroplasty: a systematic review

PURPOSE

To investigate the correlation between postoperative limb/component alignments and clinical/functional outcomes following medial unicondylar knee arthroplasty (mUKA).

METHODS

Inclusion criteria included peer-reviewed English- or German-language publications assessing postoperative limb or implant alignment and clinical outcomes of mUKA. Methodological Index for Non-Randomized Studies (MINORS) was used to assess article quality.

RESULTS

A total of 2767 knees from 2604 patients were evaluated. Significant correlations were observed between postoperative limb/component alignments and clinical/functional outcomes after mUKA. Inferior outcomes were associated with lower placement and excessive valgus alignment of the tibia component (> 3°). A recommended external rotation of 4°-5° was identified for the tibia component, with specific cut-off values for the femoral and tibia components.

CONCLUSIONS

Optimal outcomes in mUKA were associated with a varus coronal limb alignment. The tibia implant component performed well within a specific alignment range. An exact external rotation value was recommended for the tibia component, while internal rotation correlated negatively with the femoral component.

LEVEL OF EVIDENCE

IV (level IV retrospective case series were included).

Incidence and Trends of High Tibial Osteotomy and Unicompartmental Knee Arthroplasty Over the Past Decade: A Lost Art

Background

After failed nonoperative treatment, unicompartmental osteoarthritis can be treated surgically by either unicompartmental knee arthroplasty (UKA) or high tibial osteotomy (HTO). The purpose of this retrospective study is to analyze utilization and demographic trends of UKA and HTO relative to total knee arthroplasty (TKA) over the past decade.

Methods

A retrospective review was conducted using the PearlDiver database. Patients that received a UKA or HTO were identified. Trend analyses of surgical procedure utilization were performed with the Mann-Kendall trend test. Demographic data and the rates of various comorbidities were also queried.

Results

A total of 103,465 UKAs, 2183 HTOs, and 1,413,425 TKAs, between 2010 and 2021 quarter 1, were analyzed. Trend analyses revealed that relative to TKA utilization, UKA utilization significantly increased (P < .001) while HTO utilization significantly decreased (P < .001). The compound annual growth rate of UKA utilization relative to TKA was +5.16% from 2010 to 2017 but was -10.61% from 2018 to 2021, while that of HTO relative to TKA was -9.69% from 2010 to 2021. Demographic analyses demonstrated the UKA cohort (63.1) was significantly older than the HTO cohort (46.5) (P < .001). Additionally, there were significantly more female patients who underwent UKA than HTO (P < .001).

Conclusions

The present study demonstrated that relative to TKA, UKA utilization increased from 2010 to 2017, with a subsequent decrease afterward, whereas HTO utilization decreased since 2010. Demographic differences exist between the 2 operations, with HTOs more commonly performed in younger male patients, and UKAs in older female patients.

Level of Evidence

Level III.

Robotic-assisted medial unicompartmental knee arthroplasty restores estimated pre-arthritic coronal limb alignment: A retrospective cohort study

BACKGROUND

Robotic-assisted medial unicompartmental knee arthroplasty (UKA) aims to restore pre-arthritic (constitutional) limb alignment, by re-tensioning of the medial collateral ligament (MCL). This study aimed to determine whether pre-arthritic coronal alignment was restored following robotic-assisted medial UKA in patients with medial compartment osteoarthritis.

METHOD

A retrospective study was undertaken, including 102 patients with a unilateral robotic-assisted medial UKA and a contralateral unaffected knee. Both the validated arithmetic hip-knee-ankle angle (aHKA) and alignment of the contralateral unaffected knee were used to estimate pre-arthritic alignment. The aHKA is a radiographic method to estimate the pre-arthritic mechanical hip-knee-ankle angle (mHKA). To verify restoration of pre-arthritic alignment, postoperative mHKA was compared to the aHKA. Additionally, postoperative mHKA, joint line congruence (JLCA), and knee joint line obliquity (KJLO) angles were compared between the operative and contralateral unaffected knee. Equivalence between postoperative and pre-arthritic alignment was assessed through the two-one-sided t-test (TOST), using equivalence margins of ±2.0°.

RESULTS

Postoperative mHKA was equivalent to the aHKA (mean difference -0.38°, 90% CI -0.69 to -0.07;p < .001), with 93 knees (91%) restored within 3.0° their aHKA. Postoperative mHKA, JLCA and KJLO were equivalent between the operative and contralateral unaffected knees, with mean differences of -0.65°, -0.65°, and -0.40°, respectively; all p < .001.

CONCLUSIONS

Postoperative and pre-arthritic coronal alignment were equivalent following robotic-assisted medial UKA, with 91% of knees restored within 3.0° of their pre-arthritic mechanical axis. These results demonstrate that both mechanical alignment and joint line congruence are restored by MCL re-tensioning in patients undergoing robotic-assisted medial UKA for medial compartment osteoarthritis.

Pre-operative predictive factors of residual varus on the mechanical axis after Oxford unicompartmental knee arthroplasty

Background

Residual varus after Oxford unicompartmental knee arthroplasty (UKA) happens frequently. This study aims to evaluate the pre-operative contributing factors of residual varus.

Methods

A total of 1,002 knees (880 patients, 201 patients were male, and 679 were female) underwent Oxford UKA in the Orthopedic Surgery Department of the Beijing Jishuitan Hospital from March 2018 to April 2021. The mean age of the patient was 64.7 ± 7.7 years. To assess residual varus, the full-length lower extremity is placed upright for EOS imaging, with the knee fully extended. The angle of post-operative residual varus was measured as described by Noyes et al. Of the knees studied, they were either categorized into an under-corrected group (post-operative Noyes angle >5°) or a corrected group (post-operative Noyes angle ≤5°). Age, gender, body mass index (BMI), range of motion (ROM), Clinical American Knee Society Score (Clinical AKSS), and Function American Knee Society Score (Function AKSS) were compared. The following additional parameters were measured: pre-operative Noyes angle, lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), the posterior slope of the proximal tibia angle (PPTA), joint line converge angle (JLCA), and fixed flexion deformity (FFD).

Results

There was no statistically significant difference between the two groups in regards to gender (p = 0.428), surgical leg (p = 0.937), age (p = 0.851), BMI (p = 0.064), pre-operative Clinical AKSS (p = 0.206) and Function AKSS (p = 0.100). However, pre-operative ROM statistically differed between the two groups (p < 0.001). The contributing factors of post-operative residual varus were determined to be the following parameters: pre-operative MPTA (p < 0.001, OR = 4.522, 95% CI: 2.927-6.984), pre-operative Noyes (p < 0.001, OR = 3.262, 95% CI: 1.802-5.907) and pre-operative FFD (p = 0.007, OR = 1.862, 95% CI: 1.182-2.934). The effects of pre-operative LDFA (p = 0.146), JLCA (p = 0.942), and pre-operative PPTA (p = 0.899) on the post-operative mechanical axis did not show statistical significance.

Conclusions

Patients with severe pre-operative varus, particularly varus deformity mainly from the tibial side or pre-operative FFD, are more prone to get extremity mechanical axis residual varus after UKA with Oxford.

Large Reduction in Postoperative Posterior Tibial Slope Risks Anterior Collapse of the Tibial Component in Fixed-Bearing Unicompartmental Knee Arthroplasty

Background

Although the posterior tibial slope (PTS) of the tibial component in unicompartmental knee arthroplasty is recommended to be between 3° and 7°, variations in preoperative PTS are wide. The purpose of this study was to evaluate the influence of the changes in preoperative and postoperative PTS on clinical outcomes.

Methods

One-hundred and eighty-two knees that underwent medial fixed-bearing unicompartmental knee arthroplasty were evaluated retrospectively. The mean follow-up period was 36.4 ± 13.2 months (range, 24 to 63 months). Preoperative and postoperative PTS were measured on lateral radiographs. Knees were classified in the large reduction group if the postoperative PTS was reduced by more than 5° compared with the preoperative value and in the small reduction group if not. Knee flexion angle and 2011 Knee Society Knee Scoring System were evaluated at the last follow-up of at least 2 years.

Results

Thirty-three knees were classified in the large reduction group, and 149 knees were classified in the small reduction group. The preoperative and postoperative PTS of large and small reduction groups were 10.9 ± 2.2, 3.6 ± 2.4 degrees and 7.7 ± 2.7, 7.1 ± 2.4 degrees, respectively. Flexion angle and 2011 Knee Society Knee Scoring System were not significantly different between the groups. However, the incidence of anterior collapse of the tibial component in the large group was significantly higher than that in the other group (P < .001).

Conclusions

Large reduction in the postoperative PTS may be associated with anterior tibial collapse, and therefore this study shows one potential benefit for matching native slope.

Predictors of a forgotten joint after medial fixed-bearing unicompartmental knee arthroplasty

BACKGROUND

A forgotten joint is considered the ultimate goal of joint replacement. We aim to explore the predictive factors of a forgotten joint after fixed-bearing unicompartmental knee arthroplasty (UKA).

METHODS

This retrospective cohort study used prospectively collected data from 302 cases of medial-compartment UKA with a minimum of 2-year follow-up. The primary outcome was the achievement of a forgotten joint after UKA, according to the Forgotten Joint Score (FJS-12) at the last follow-up. Patients with FJS-12 > 84 were considered to have forgotten UKA. Univariate and multivariate logistic regression analyses were conducted with preoperative patient characteristics and surgery-related factors as potential predictors.

RESULTS

Of patients, 94 (31.1%) achieved a forgotten joint post-surgery. Multivariate logistic regression analysis revealed that preoperative hip-knee-ankle angle (HKAA), anatomic lateral distal femoral angle (aLDFA), and postoperative HKAA and HKAA changes were independent predictors of a forgotten joint. The probability of achieving a forgotten joint increased by 29% (OR = 1.29, 95% CI: 1.12-1.51) with a 1° increase in aLDFA. Preoperative HKAA, postoperative HKAA, HKAA changes (ΔHKAA), and outcomes exhibited a non-linear relationship. The probability of achieving a forgotten joint was the highest with preoperative HKAA > 172.0°, postoperative HKAA of 176.0-178.5°, and ΔHKAA < 5.5°.

CONCLUSION

To achieve the forgotten joint state, the ideal HKAA range after medial fixed-bearing UKA is 176.0-178.5° and ΔHKAA should be <5.5°. Patients with smaller preoperative aLDFA and HKAA have a lower probability of achieving a forgotten joint after UKA.

Pre-Arthritic/Kinematic Alignment in Fixed-Bearing Medial Unicompartmental Knee Arthroplasty Results in Return to Activity at Mean 10-Year Follow-up

BACKGROUND

The optimal alignment strategy in unicompartmental knee arthroplasty (UKA) is debated. Recent studies have suggested that kinematic alignment may lead to improved biomechanics and outcomes. The aim of the present study was to determine if pre-arthritic/kinematic alignment of knees would result in sustained long-term restoration of function, without conversion to total knee arthroplasty (TKA), following non-robotically assisted, fixed-bearing medial UKA.

METHODS

A total of 236 UKAs were performed from 2000 to 2015. Of these, a total of 150 medial UKAs met the inclusion criteria and were included in the study. There were 76 UKAs performed in female patients. The mean age was 65 ± 10 years and the mean body mass index was 28.6 ± 5 kg/m2. Patients with ≥15° of varus alignment preoperatively were excluded. Varus deformity was evaluated with use of the hip-knee-ankle angle (HKAA). Pre-arthritic/kinematic alignment was estimated with use of an arithmetic HKAA (aHKA, calculated as the medial proximal tibial angle minus the lateral distal femoral angle). We defined pre-arthritic/kinematic alignment as a postoperative HKAA within 3° of the aHKA. The primary outcome measures were the Knee Injury and Osteoarthritis Outcome Score (KOOS) Activities of Daily Living and Sport subscales, including the percentage of patients who met the patient acceptable symptom state (PASS) for these measures. Failure was defined as conversion to TKA.

RESULTS

The mean follow-up was 10 years (range, 4 to 20 years), with a mean survival time estimate of 18.3 years (95% confidence interval [CI], 17.8 to 18.8). The rate of conversion to TKA was 3% (5 of 150 UKAs). Postoperatively, 127 (85%) of 150 knees were pre-arthritic/kinematically aligned, and 23 knees (15%) were not. Patients with compared to those without pre-arthritic/kinematically aligned knees had significantly longer mean survival (18.6 years; 95% CI, 18.2 to 19) compared with 15.4 years; 95% CI, 13.4 to 17.5, respectively; p = 0.008) and higher KOOS Activities of Daily Living (92 compared with 74; p < 0.001) and Sport subscale scores (74 compared with 36; p < 0.001). A greater proportion of knees in the pre-arthritic/kinematically aligned cohort met the PASS for the KOOS Activities of Daily Living (85%, 106 of 125 knees) and Sport subscales (109 of 125, 87%) compared with the non-pre-arthritic/kinematically aligned cohort (28% and 57%, respectively; p < 0.01).

CONCLUSIONS

Pre-arthritic/kinematically aligned knees in this non-robotically assisted fixed-bearing medial UKA cohort had superior outcomes, including the KOOS Activities of Daily Living and Sport subscales and achievement of the PASS for these measures, compared with non-pre-arthritic/kinematically aligned at an average of 10 years after UKA. Knees that fell within 3° of a simple aHKA measurement on a 3-foot (1-m)-long standing radiograph had greater longevity and return to activities.

LEVEL OF EVIDENCE

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

Difference between medial and lateral tibia plateau in the coronal plane: importance of preoperative evaluation for medial unicompartmental knee arthroplasty

Background

Setting bone cutting levels for different joint line orientations of the medial and lateral tibia plateaus in individual patients is not clear. We aimed to evaluate the difference between joint line orientation of the medial and lateral tibia plateaus relative to the horizontal line of mechanical axis of tibia as tibial plateau difference (TPD) for an optimal tibial bone cut in medial unicompartmental knee arthroplasty (UKA) and determine which factors could influence TPD. We aimed to investigate the effect of preoperative TPD on polyethylene liner size in medial UKA.

Methods

TPD in the coronal plane were measured in 181 female patients (181 knees). To determine the morphology of proximal tibia according to the severity of osteoarthritis, the patients were classified into three groups based on diagnosis and treatment: 80 who underwent robot-assisted medial UKA, 45 who underwent total knee arthroplasty (TKA), and 56 with early-stage osteoarthritis (OA) who had conservative management. Also, we divided the medial UKA group into two groups according to TPD (greater than or less than 5 mm) and compared polyethylene liner sizes.

Results

No significant difference was observed in TPD (p = 0.662), difference between the medial and lateral femoral condyle levels (p = 0.54), medial proximal tibial angle (p = 0.169), or posterior tibial slope (p = 0.466) among the three groups. Increased TPD was significantly associated with increased mechanical femorotibial angle(mFTA) (p < 0.01). The medial UKA group was divided into two groups according to TPD greater or less than 5 mm. Thicker polyethylene liners were used for groups with TPD greater than 5 mm (8.5 ± 0.7 mm versus 8.2 ± 0.3 mm, p = 0.01). Additionally, the proportion of patients using the thinnest polyethylene (8 mm) in each TPD group (greater or less than 5 mm) was higher in patients with TPD less than 5 mm (82.4% versus 58.7%, p = 0.038).

Conclusions

Preoperative measurement of TPD is important to help surgeons predict the most appropriate bone cutting level in the coronal plane in primary medial UKA. Tibial bone resection would be likely to be thicker than needed in patients with increased TPD in medial UKA.

Makoplasty medial unicondylar knee replacement: Correction or postoperative angle matters?

INTRODUCTION

Various considerations prevail around optimal postoperative varus deformity, correction angle and physiological constitutional varus deformity. The goal of our present study was to understand correlation between these parameters and their influence over Western Ontario McMaster University Osteoarthritis Index scale (WOMAC).

MATERIALS AND METHODS

Consecutive robotic-arm-assisted medial onlay fixed bearing unicompartmental knee arthroplasty (UKA) in 143 knees studied. WOMAC score was recorded preoperatively and at specific intervals after surgery for consecutive 2 years.

RESULTS

Mean preoperative and postoperative varus deformities were 10.2° and 4.8°, respectively, and mean correction angle was 5.4°. The preoperative varus and correction angles were found well correlated (r = 0.815). The amount of improvement in the WOMAC total score was not influenced by the postoperative varus angle.

CONCLUSION

The correction angle has a stronger correlation with preoperative varus deformity, and postoperative varus deformity does not imply favourable clinical outcomes.

Robotic-assisted knee arthroplasty: an evolution in progress. A concise review of the available systems and the data supporting them

INTRODUCTION

A review of the data supporting robotic systems currently available is presented focussing on precision and reproducibility, radiological outcomes, clinical outcomes, and survivorship.

MATERIALS AND METHODS

Scientific literature published on robotic systems for knee arthroplasty was reviewed using the reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Inclusion criteria were any study involving robotic-assisted UKA or TKA that reported precision of implant positioning or functional outcomes or range of motion or survivorship, including cadaveric or dry bone studies with a minimum of 6-month follow-up.

RESULTS

Thirty-nine studies were identified for robotic-assisted unicompartmental knee arthroplasty, and 24 studies for robotic-assisted total knee arthroplasty. Those that reported on radiological outcomes or cadaver studies consistently demonstrated improved precision with the use of robotic systems irrespective of the system. PROMS and survival data demonstrated equivalent short-term results. However, many studies reported outcomes inconsistently and few had long-term clinical follow-up or survivorship data.

CONCLUSIONS

This review adds to the body of evidence supporting improved precision and reproducibility with robotic assistance in knee arthroplasty. Despite intensive funding of research into robotic knee systems, there remains considerable heterogeneity in exposure and outcome analysis and few quality long-term studies demonstrating translation to better clinical outcomes and implant survivorship.

Prior high tibial osteotomy is not a contraindication for medial unicompartmental knee arthroplasty

PURPOSE

To report on the outcome and complications of minimal invasive medial unicondylar knee arthroplasty (UKA) after failed prior high tibial osteotomy (HTO) as treatment for medial osteoarthritis in the knee. The hypothesis was that good results can be achieved, if no excessive postoperative valgus alignment and abnormal proximal tibial geometry is present.

METHODS

All medial UKAs after failed prior HTO (n = 30), performed between 2010 and 2018 were retrospectively reviewed. The patients were followed for revision surgery and survival of the UKA (defined as revision to TKA). Clinical examination using the Knee Society Score (KSS), Oxford Knee Score (OKS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), as well as radiological examination was performed. Radiographs were studied and the influence of the demographic factors and the radiographic measurements on the survival and the clinical outcome was analysed.

RESULTS

After a follow-up of 4.3 ± 2.6 years (2.1-9.9) 27 UKAs were available. The survival rate was 93.0%. Two UKAs were revised to TKA (excessive valgus alignment and tibial loosening with femoropatellar degeneration). Two further patients had revision surgery (hematoma and lateral meniscus tear). Follow-up clinical and radiological examination was performed in 21 cases: KSS 82.9 ± 10.1 (54.0-100.0), KSS (function) 93.3 ± 9.7 (70.0-100.0); OKS 42.7 ± 6.0 (25.0-48.0); WOMAC 7.9 ± 15.6 (0.0-67.1). No significant influence of demographic factors or radiological measurements on the clinical outcome was present.

CONCLUSION

Prior HTO is not a contraindication for medial UKA, because good-to-excellent results can be achieved in selected patients with medial osteoarthritis and previous HTO, treated with medial UKA, in a midterm follow-up. Excessive mechanical valgus axis should be avoided; therefore, patient selection and accurate evaluation of medial laxity, preoperative mechanical axis, joint line convergence and proximal tibial geometry are important.

LEVEL OF EVIDENCE

III.

Radiographic Comparison of the Mechanical Axis Including Calcaneus to the Conventional Mechanical Axis in Medial Unicompartmental Knee Arthroplasty

Since a hindfoot alignment is not included in the conventional mechanical axis (hip-ankle [HA] line), a mechanical axis including the calcaneus (hip-calcaneus [HC] line) has recently attracted attention as an alternative weight-bearing line. However, there are few reports on unicompartmental knee arthroplasty (UKA) regarding the HC line. Therefore, this study aimed to compare postoperative alignments after UKA between the HA line and the HC line. Postoperatively, HC radiographs were taken in 88 consecutive patients who underwent medial UKA. The hip-knee-ankle (HKA) and hip-knee-calcaneus (HKC) angles were compared in the same patient. Regarding tibial inclination, the conventional tibial component-ankle (TCA) angle was compared with reference to the HC line (tibial component-calcaneus [TCC] angle). The mean postoperative HKA and HKC angles were 2.8 ± 2.7 and 2.0 ± 2.5 degree, respectively. The mean postoperative TCA and TCC angles were 87.7 ± 2.1 and 88.5 ± 2.1 degree, respectively. There were significant differences between the two groups in both lower limb alignment and tibial component angle. The present study indicated that the HKC and the TCC angles significantly decreased the varus alignment by approximately 1 degree compared with the HKA and TCA angles. Neutral in the HA line corresponds to valgus in reference to the HC line, which may result in overcorrection. Surgeons should consider evaluating the HC line in place of the HA line, which may affect preoperative planning and postoperative outcome during UKA. This is a Level II, diagnostic study.

Minimally Invasive Inlay Prosthesis Unicompartmental Knee Arthroplasty for the Treatment of Unicompartmental Osteoarthritis: A Prospective Observational Cohort Study with Minimum 2-Year Outcomes and up to 14-Year Survival

There are limited medium-term outcome data available for the Repicci II device in unicompartmental knee arthroplasty (UKA). The purpose of this study was to report the medium-term (minimum 2 years) patient-reported outcomes and long-term (up to 14 years) procedure survival in a consecutive series of patients undergoing an inlay prosthesis UKA (Repicci II) at an independent orthopaedic clinic. Patients presenting with medially localized unicompartmental knee osteoarthritis and meeting the criteria appropriate for UKA were recruited to a clinical patient registry at the time of presentation. A cemented unicompartmental prosthesis (Repicci II) was implanted using minimally invasive techniques with rapid postoperative mobilization. Patients were asked to complete patient-reported outcomes preoperatively and annually postoperatively. A procedure list was cross-matched with the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR), and an analysis of procedure survival was performed with comparison to the national data for UKA. Data from a cohort of 661 primary medial compartment UKA procedures performed in 551 patients over a 15-year period were extracted from the clinical patient registry. Significant improvements were maintained in general health, disease symptoms, pain, and function at an average follow-up of 9 years compared with preoperative data. Threshold analysis revealed that >65% of patients exceeded Patient Acceptable Symptom State at the latest follow-up, with >80% within or exceeding age-matched norms for general health. Cumulative revision rate was significantly lower than that reported for UKA in the AOANJRR at up to 13 years follow-up. This series represents a lower cumulative revision rate than previously reported, with >65% of patients reporting satisfactory functional outcomes at an average of 9 years from surgery. Surgical options for treating unicompartmental knee osteoarthritis could include UKA as a viable alternative; however, clear definitions of procedure success and its overall cost-benefit ratio in the context of ongoing management of knee osteoarthritis remain to be elucidated.

[Focal femoral resurfacing and unicompartmental knee replacement : Between osteotomy and total knee replacement]

Unicompartmental knee arthroplasty, especially for both femorotibial compartments of the knee, is an established partly joint-saving treatment option for osteoarthritis of the knee if the disease is limited to one compartment. Even smaller implants or resurfacing of the patellofemoral joint have been shown-in smaller patient collectives-to have the potential to yield good clinical results.

The effect of component alignment on clinical outcomes in fixed bearing unicompartmental knee arthroplasty

BACKGROUND

The aim of this study is to report component alignment in a series of ZUK fixed bearing unicompartmental knee arthroplasty (UKA) implants and compare this to clinical outcomes.

METHODS

The radiographs, Knee Society Scores (KSS) and knee flexion of 223 medial UKAs were evaluated. The following alignment parameters were assessed; coronal and sagittalfemoral component angle (c-FCA and s-FCA), coronal and sagittal tibia component angle (c-TCA and s-TCA)and the coronal tibiofemoralangle (c-TFA). Each alignment parameter was grouped at consecutive 2.5° intervals, mean KSS and knee flexion was then compared between the interval groups.

RESULTS

96.4% of femoral components were between 7.5° of varus and valgus and 95.1% between 7.5° extension and 5° flexion. 89.6% of tibial components were between 7.5° of varus and 2.5° valgus and 97.3% between 2.5° and 15° flexion. There was no significant difference between the KSS or knee flexion between any of the incremental groups of component alignment. Mean c-TFA was 0.2 ± 3.0°, 92.4% were between -5° (varus) and 5° (valgus). KSS were significantly greater for two of the increments with slightly more varus. Linear regression analysis showed there was very weak correlation (R² = 0.1933) between c-TFA and c-TCA.

CONCLUSIONS

The results of this study show that fixed bearing UKA components are forgiving to accommodate some variation in tibial and femoral component position without effecting clinical outcome scores or knee flexion. Limb alignment matters more than component position and knees with slight varus tibiofemoral alignment have better clinical scores than those with valgus.

Evidence-based surgical technique for medial unicompartmental knee arthroplasty

Unicompartmental knee arthroplasty (UKA) is a successful treatment modality in selected patients having advanced, single-compartment osteoarthritis of the knee. The bone and ligament preservation leading to shorter recovery periods, better functional outcomes, lower perioperative complication rates, and easier revision, if needed, are proposed as some of the advantages of UKA over total knee arthroplasty (TKA). Despite several advantages, UKA is reported to have higher failure rates as compared to TKA. The prosthesis failure of UKA is directly correlated to intraoperative technique-related factors like malpositioning of components and the inability to replicate the target-limb alignment as per preoperative planning. An evidence-based surgical technique for UKA may help surgeons to avoid the intraoperative technique-related errors. The purpose of this paper is to describe a stepwise surgical technique for the fixed-bearing medial UKA.

Low femoral component prominence negatively influences early revision rate in robotic unicompartmental knee arthroplasty

PURPOSE

The revision rate of unicompartmental knee arthroplasty (UKA) is higher than in total knee arthroplasty (TKA), and implant positioning may play a role. In combination with a pre-operative CT, robotic UKA may provide the ability to position the implants more precisely. The aim of this study was to investigate the influence of component prominence relative to the native joint surface on early outcomes and revisions. The hypothesis was that aiming for restoration of joint space to 0.5-1.5 mm will improve outcomes.

METHODS

Retrospective analysis of prospectively collected data of 94 patients undergoing robotic-assisted UKA (Mako, Stryker) was performed. The 'prominence' of the implant surface relative to the native bony surface in sagittal plane, hip-knee-ankle (HKA) correction in coronal plane was documented intraoperatively. The mean achieved gap between two components under valgus stress captured in at least 5 different flexion angles was calculated. These were then analysed for impact on early revision rate and outcomes, stratified by gender.

RESULTS

Median HKA correction was 3.5° (range 0°-9.5°). Median femoral prominence was 1.5 mm (range - 0.6 to 4 mm) and median tibial prominence was 4.3 mm (2-7 mm). The median achieved gap was 1.0 mm (- 1.2 to 2.8 mm). There was no difference in achieved correction between men and women (p = n.s.) but men had a higher achieved combined prominence than women (p < 0.001). PROMs did not correlate with the average gap (p = n.s.) nor with combined prominence (p = n.s.). Two patients underwent an early revision. Lower femoral prominence was a significant predictor of revision (p = 0.045; OR = 0.21; 95% CI 0.000-0.918).

CONCLUSION

Female patients need less component prominence to achieve the same average gap balance through a range of motion, without correlation with patient's height. Intraoperatively low femoral prominence could be a reason for early revision.

LEVEL OF EVIDENCE

IV.

Unicompartmental knee arthroplasty, an enigma, and the ten enigmas of medial UKA

Unicompartmental knee arthroplasty (UKA) is a bone- and ligament-sparing alternative to total knee arthroplasty in the patients with end-stage single-compartment degeneration of the knee. Despite being a successful procedure, the multiple advantages of UKA do not correlate with its usage, most likely due to the concerns regarding prosthesis survivability, patient selection, ideal bearing design, and judicious use of advanced technology among many others. Therefore, the purpose of this study is to review and summarize the debated literature and discuss the controversies as “Ten Enigmas of UKA.”

Should patients aged 75 years or older undergo medial unicompartmental knee arthroplasty? A propensity score-matched study

INTRODUCTION

With increasing life expectancies worldwide, more elderly patients with isolated medial compartment osteoarthritis may become suitable UKA candidates. However, there is a paucity of literature comparing outcomes between older patients (≥ 75 years) and younger patients undergoing UKA. The aim of this study was to determine if there were differences in functional and HRQoL measures between older patients (≥ 75 years) and younger controls (< 75 years) undergoing primary UKA.

MATERIALS AND METHODS

Prospectively collected registry data of 1041 patients who underwent primary, cemented, fixed-bearing medial UKA at a single institution from 2002-2013 were reviewed. Propensity scores generated using logistic regression was used to match older patients (≥ 75 years, n = 94) to controls (< 75 years, n = 188) in a 1:2 ratio. Knee Society Scores, Oxford Knee Score, Short Form-36, satisfaction/expectation scores, proportion of patients attaining OKS/SF-36 PCS MCID and survivorship were analysed.

RESULTS

Patients ≥ 75 years had significantly lower KSFS (67.1 ± 17.9 vs 79.4 ± 18.2, p < 0.001) and SF-36 PCS (47.3 ± 10.1 vs 50.4 ± 9.1, p = 0.01) as compared to the control group. In addition, a significantly lower proportion of patients ≥ 75 years attained MCID for SF-36 PCS when compared to the controls (50.0% vs 63.8%, p = 0.04). Survival rates at mean 8.3 ± 3.0 years were 98.9% (95% CI, 96.7-100) in the older group versus 92.8% (95% CI, 86.8-98.8) in the younger group (p = 0.31).

CONCLUSIONS

Our findings highlight the need to counsel older patients regarding potentially reduced improvements in functional outcomes, despite advantages of lower revision. However, UKA in older patients continues to be a viable option for isolated medial compartment osteoarthritis LEVEL OF EVIDENCE: Level III Propensity score matched study.

Varus kinematics at knee flexion affect clinical outcomes of unicompartmental knee arthroplasty: Intraoperative navigation-based kinematics evaluation

Background

The aim of the study was to investigate the effects of navigation-based varus or axial rotational alignment through knee flexion on patient reported outcomes or the maximum flexion angle of unicompartmental knee arthroplasty (UKA).

Methods

Data were retrospectively collected from 46 knees that underwent UKA for medial unicompartmental knee osteoarthritis. An image-free knee navigation system was used in all cases, and intraoperative varus and axial rotational alignment at every knee flexion angle were recorded before and after implantation. All patients completed the Knee injury and Osteoarthritis Outcome Score (KOOS) at final follow-up. By varus or valgus at 0° knee flexion, the knees were subdivided into two groups (varus at 0° group, varus above the median value; neutral at 0° group, varus equal to or below the median value). By varus or valgus at 90° knee flexion, patients were similarly subdivided into two groups (varus at 90° group; neutral at 90° group). The maximum knee flexion angle was measured 3 months after surgery.

Results

There were no differences in the KOOS between the neutral at 0° group and the varus at 0° group. However, the KOOS activity score (79 ± 17 vs 69 ± 16, p = 0.02) and the KOOS total score (72 ± 17 vs 65 ± 15, p = 0.03) of the neutral at 90° group were better than those of the varus at 90° group. The alignment and the maximum knee flexion angle 3 months after surgery were not correlated.

Conclusion

Varus at 0° knee flexion and axial rotational alignment did not affect the clinical outcomes of UKA. Patient reported outcomes was better for the neutral knees with less varus at 90° knee flexion than for varus knees.

The Impact of Coronal Alignment on Revision in Medial Fixed-Bearing Unicompartmental Knee Arthroplasty

BACKGROUND

To better define the optimal alignment target for medial fixed-bearing unicompartmental knee arthroplasty (UKA), this study compares the postoperative mechanical alignment of well-functioning UKAs against 2 groups of failed UKAs, including revisions for progression of lateral compartment osteoarthritis ("Progression") and revisions for aseptic loosening or subsidence ("Loosening").

METHODS

From our prospective institutional database of 3351 medial fixed-bearing UKAs performed since 2000, we identified 37 UKAs revised for Progression and 61 UKAs revised for Loosening. Each of these revision cohorts was matched based on age at surgery, gender, body mass index, and postoperative range of motion with unrevised UKAs that had at least 10 years of follow-up and a Knee Society Score of 70 or greater without subtracting points for alignment ("Success" groups). Postoperative alignment was quantified by the hip-knee-ankle (HKA) angle measured on long-leg alignment radiographs.

RESULTS

The mean HKA angle at 4-month follow-up for the Progression group was 0.3° ± 3.6° of valgus compared to 4.4° ± 2.6° of varus for the matched Success group (P < 0.001). For the Loosening group, the mean HKA angle was 6.1° ± 3.1° of varus versus 4.0° ± 2.7° of varus for the matched Success group (P < 0.001).

CONCLUSIONS

Patients with well-functioning UKAs at 10 years exhibited mild varus mechanical alignment of approximately 4°, whereas patients revised for progression of osteoarthritis averaged more valgus and those revised for loosening or subsidence averaged more varus. The optimal mechanical alignment for medial fixed-bearing UKA survival with contemporary polyethylene is likely slight varus.

A systematic review of robotic-assisted unicompartmental knee arthroplasty: prosthesis design and type should be reported

AIMS

Robotic-assisted unicompartmental knee arthroplasty (UKA) promises accurate implant placement with the potential of improved survival and functional outcomes. The aim of this study was to present the current evidence for robotic-assisted UKA and describe the outcome in terms of implant positioning, range of movement (ROM), function and survival, and the types of robot and implants that are currently used.

MATERIALS AND METHODS

A search of PubMed and Medline was performed in October 2018 in line with the Preferred Reporting Items for Systematic Review and Meta-Analysis statement. Search terms included "robotic", "knee", and "surgery". The criteria for inclusion was any study describing the use of robotic UKA and reporting implant positioning, ROM, function, and survival for clinical, cadaveric, or dry bone studies.

RESULTS

A total of 528 articles were initially identified from the databases and reference lists. Following full text screening, 38 studies that satisfied the inclusion criteria were included. In all, 20 studies reported on implant positioning, 18 on functional outcomes, 16 on survivorship, and six on ROM. The Mako (Stryker, Mahwah, New Jersey) robot was used in 32 studies (84%), the BlueBelt Navio (Blue Belt Technologies, Plymouth, Minnesota) in three (8%), the Sculptor RGA (Stanmore Implants, Borehamwood United Kingdom) in two (5%), and the Acrobot (The Acrobot Co. Ltd., London, United Kingdom) in one study (3%). The most commonly used implant was the Restoris MCK (Stryker). Nine studies (24%) did not report the implant that was used. The pooled survivorship at six years follow-up was 96%. However, when assessing survival according to implant design, survivorship of an inlay (all-polyethylene) tibial implant was 89%, whereas that of an onlay (metal-backed) implant was 97% at six years (odds ratio 3.66, 95% confidence interval 20.7 to 6.46, p < 0.001).

CONCLUSION

There is little description of the choice of implant when reporting robotic-assisted UKA, which is essential when assessing survivorship, in the literature. Implant positioning with robotic-assisted UKA is more accurate and more reproducible than that performed manually and may offer better functional outcomes, but whether this translates into improved implant survival in the mid- to longer-term remains to be seen. Cite this article: Bone Joint J 2019;101-B:838-847.

The trends in robotic-assisted knee arthroplasty: A statewide database study

Objective

Recent technological advancements have led to the utilization of robotic-assisted knee arthroplasty (raKA) in the operating room.

Methods

All patients who underwent knee arthroplasty from 2009 to 2013 in NYS SPARCS were reviewed. raKAs and non-raKAs were compared for utilization and institutional trends.

Results

Robotic-assistance increased by 500%. 80% of raKAs were performed in teaching hospitals. The trend increase was greater in teaching hospitals. Blood transfusion rates differed between raKA and non-raKA (6.6% vs. 10.9%, p < 0.001).

Conclusion

raKA utilization increased in NYS, moreso within teaching hospitals. raKA transfusion rates were lower but higher in teaching hospitals, potentially related to learning curve.

Functional Outcome and Revision Rate Are Independent of Limb Alignment Following Oxford Medial Unicompartmental Knee Replacement

BACKGROUND

There is controversy about optimal limb alignment following knee replacement. An aim of using Oxford medial unicompartmental knee replacement (UKR) implants is to accurately restore normal ligament tension in the knee, thereby restoring normal kinematics. This return to normal tension typically results in a return to prearthritic alignment, which is frequently varus. The aim of this study was to investigate the relationship between postoperative limb alignment and postoperative patient-reported outcome and implant revision rate.

METHODS

We used a consecutive cohort of 891 knees with cemented Oxford medial UKR implants with a mean 10-year follow-up and recorded alignment. We grouped knees according to postoperative mechanical alignment as marked varus (estimated at 10°), mild varus (estimated at 5°), neutral, and valgus. The mean Oxford Knee Score (OKS) was calculated at 5 and 10 years postoperatively. Revision risk was assessed by survival analysis and component-time incidence rates.

RESULTS

Postoperatively, 67 (8%) of the 891 knees were in marked varus; 308 (35%), in mild varus; 508 (57%), in neutral; and 8 (1%), in valgus. The valgus group (8 knees) was too small for further analysis. The mean OKS (and standard deviation [SD]) at 10 years postoperatively was 41.7 ± 7 for marked varus, 40.5 ± 8 for mild varus, and 39.4 ± 9 for neutral alignment (p = 0.28). At 10 years, 92%, 85%, and 76% achieved a good or excellent OKS outcome, respectively (p = 0.02). Twelve-year survival rates were 93.3% for marked varus, 93.2% for mild varus, and 93.6% for neutral alignment, respectively (p = 0.53). Revision incidence rates per 100 component-years were 0.49 (95% confidence interval [CI], 0.2 to 1.5), 0.36 (95% CI, 0.2 to 0.7), and 0.54 (95% CI, 0.4 to 0.8), respectively, and were not significantly different (p = 0.53).

CONCLUSIONS

Marked postoperative varus mechanical alignment of an estimated 10° was present in 8%, and mild varus of about 5° was present in 35%. Increasing varus alignment was associated with an increasing percentage of good or excellent OKS outcomes, but otherwise there were no significant differences between alignment groups in patient-reported outcome or revision rate. These data support the standard operative technique for the Oxford UKR, which aims to restore ligament tension and therefore prearthritic alignment rather than neutral mechanical alignment.

LEVEL OF EVIDENCE

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

Predictors of return to desired activity 12 months following unicompartmental and total knee arthroplasty

Background and purpose - 1 in 5 patients are dissatisfied following unicompartmental or total knee arthroplasty (UKA or TKA). This may be partly explained by failing to return to desired activity post-arthroplasty. To facilitate return to desired activity, a greater understanding of predictors of return to desired activity in UKA and TKA patients is needed. We compared rates of return to desired activity 12 months following UKA vs. TKA, and identified and compared predictors of return to desired activity 12 months following UKA vs. TKA. Patients and methods - Patients were prospectively recruited from 2 hospitals prior to undergoing UKA or primary TKA. Patients reported preoperatively the activity/activities that were limited due to their knee that they wished to return to after arthroplasty. At 12-months postoperatively, patients reported whether they had returned to these activities ('return to desired activity'). Preoperative predictors evaluated were age, sex, BMI, education, comorbidities, pain expectations, Oxford Knee Score (OKS), UCLA Activity Score, and EQ-5D. Generalized linear models assessed the relationship between potential predictors and return-to-desired-activity. Results - The response rate of all patients eligible for 12-month follow-up was 74%. TKA patients (n = 575) were older (mean (SD) 70 (9) vs. 67 (10)) with a greater BMI (31 (6) vs. 30 (5)) than patients undergoing UKA (n = 420). 75% of UKA and 59% of TKA patients returned to desired activity. TKA patients had a greater risk of non-return to desired activity than patients undergoing UKA (risk ratio (95% CI) 1.5 (1.2-1.8)). Predictors of non-return to desired activity following UKA were worse OKS (0.96 (0.93-0.99)), higher BMI (1.04 (1.01-1.08)), and worse expectations (1.9 (1.2-2.8)). Predictors of non-return to desired activity following TKA were worse EQ-5D (0.53 (0.33-0.85)) and worse OKS (0.98 (0.96-1.0)). Interpretation - UKA patients were more likely to return to desired activity than TKA patients. Predictors of return to desired activity differed following UKA and TKA. Optimizing selection of arthroplasty procedure based on patient characteristics and targeting predictors of poor outcome may facilitate return to desired activity with potential to enhance postoperative satisfaction.

Redislocation after Bearing Exchange for the Treatment of Mobile Bearing Dislocation in Medial Unicompartmental Knee Arthroplasty

Purpose

This study was conducted to investigate the outcomes of bearing exchange for the treatment of mobile bearing dislocation in medial unicompartmental knee arthroplasty (UKA).

Materials and Methods

We retrospectively reviewed 18 patients (15 females and 3 males, mean age of 65 years) treated with bearing exchange following mobile bearing dislocation in medial UKA. The occurrence of bearing redislocation, the Oxford Knee Score, and radiographic changes at the last follow-up were investigated.

Results

Bearing redislocation after bearing exchange occurred in 9 of 18 patients (50%). Of these 9 patients, 7 underwent conversion to total knee arthroplasty after bearing redislocation. The 9 patients without bearing redislocation showed good to excellent clinical outcomes at a mean follow-up of 55 months after bearing exchange. The non-redislocation group had a higher percentage of posterior dislocation of the bearing than the redislocation group (55.5% vs. 22.2%, p=0.040). Univariate logistic regression analysis showed no significant risk factors for bearing redislocation.

Conclusions

This study showed a high rate of bearing redislocation after isolated, mobile bearing exchange for bearing dislocation following medial UKA. Therefore, bearing exchange as a sole treatment should be carefully considered in selected patients with correctable causes of bearing dislocation.

Robotic-Assisted Unicompartmental Knee Arthroplasty: State-of-the Art and Review of the Literature

BACKGROUND

Unicompartmental knee arthroplasty is a successful treatment for unicompartmental knee osteoarthritis that has lower complication rates, faster recovery, and a more natural feeling knee compared to total knee arthroplasty. However, long-term survival has been a persistent concern. As more surgeon-controlled variables have been linked to survival, interest in robotic-assisted surgery has continued to grow.

METHODS

A review and synthesis of the literature on the subject of robotic-assisted unicompartmental knee arthroplasty was performed.

RESULTS

We present the driving factors behind the development of robotic-assisted techniques in unicompartmental knee arthroplasty and the current state-of-the art. The ability of surgeons to achieve intraoperative targets with robotic assistance and the outcomes of robotic-assisted surgery are also described.

CONCLUSION

Robotic-assisted surgery has become increasingly popular in unicompartmental knee arthroplasty, as it allows surgeons to more accurately and reproducibly plan and achieve operative targets during surgery. Cost remains a concern, and it remains to be seen whether robotic-assisted surgery will improve long-term survivorship after unicompartmental knee arthroplasty.

Effects of Lower Limb Alignment and Tibial Component Inclination on the Biomechanics of Lateral Compartment in Unicompartmental Knee Arthroplasty

Background:

Lateral compartmental osteoarthritis (LCOA), a major complication after medial mobile-bearing unicompartmental knee arthroplasty (UKA), is highly associated with the increased stress of the lateral compartment. This study aimed to analyze the effects on the stress and load distribution of the lateral compartment induced by lower limb alignment and coronal inclination of the tibial component in UKA through a finite element analysis.

Methods:

Eight three-dimensional models were constructed based on a validated model for analyzing the biomechanical effects of implantation parameters on the lateral compartment after medial Oxford UKA: postoperative lower limb alignment of 3° valgus, neutral and 3° varus, and the inclination of tibial components placed in 4°, 2° valgus, square, and 2° and 4° varus. The contact stress of femoral and tibial cartilage and load distribution were calculated for all models.

Results:

In the 3° valgus lower limb alignment model, the contact stress of femoral (3.38 MPa) and tibial (3.50 MPa) cartilage as well as load percentage (45.78%) was highest compared to any other model, and was increased by 36.75%, 47.70%, and 27.63%, respectively when compared to 3° varus. In the condition of a neutral position, the outcome was comparable for the different tibial tray inclination models. The inclination did not greatly affect the lateral compartmental stress and load distribution.

Conclusions:

This study suggested that slightly varus (undercorrection) lower limb alignment might be a way to prevent LCOA in medial mobile-bearing UKA. However, the inclination (4° varus to 4° valgus) of the tibial component in the coronal plane would not be a risk factor for LCOA in neutral position.

Unicompartmental knee arthroplasty: Current indications, technical issues and results

An age younger than 60 years, a body weight of 180 lb (82 kg) or more, performing heavy work, having chondrocalcinosis and having exposed bone in the patellofemoral (PF) joint are not contraindications for unicompartmental knee arthroplasty (UKA).Severe wear of the lateral facet of the PF joint with bone loss and grooving is a contraindication for UKA.Medial UKA should only be performed in cases of severe osteoarthritis (OA) as shown in pre-operative X-rays, with medial bone-on-bone contact and a medial/lateral ratio of < 20%.The post-operative results of UKA are generally good. Medium-term and long-term studies have reported acceptable results at 10 years, with implant survival greater than 95% for UKAs performed for medial OA or osteonecrosis and for lateral UKA, especially when fixed-bearing implants are used.When all implant-related re-operations are considered, the 10-year survival rate is 94%, and the 15-year survival rate is 91%.Aseptic loosening is the principal failure mechanism in the first few years in mobile-bearing implants, whereas OA progression causes most failures in later years in fixed-bearing implants.The overall complication rate and the comprehensive re-operation rate are comparable in both mobile bearings and fixed bearings.The survival likelihood of the all-polyethylene UKA implant is similar to that of metal-backed modular designs for UKA.Notable cost savings of approximately 50% can be achieved with an outpatient UKA surgery protocol. Outpatient surgery for UKA is efficacious and safe, with satisfactory clinical results thus far. Cite this article: EFORT Open Rev 2018;3:363-373. DOI: 10.1302/2058-5241.3.170048.

Midterm Survivorship and Patient Satisfaction of Robotic-Arm-Assisted Medial Unicompartmental Knee Arthroplasty: A Multicenter Study

BACKGROUND

Studies have showed improved accuracy of lower leg alignment, precise component position, and soft-tissue balance with robotic-assisted unicompartmental knee arthroplasty (UKA). No studies, however, have assessed the effect on midterm survivorship. Therefore, the purpose of this prospective, multicenter study was to determine midtem survivorship, modes of failure, and satisfaction of robotic-assisted medial UKA.

METHODS

A total of 473 consecutive patients (528 knees) underwent robotic-arm-assisted medial UKA surgery at 4 separate institutions between March 2009 and December 2011. All patients received a fixed-bearing, metal-backed onlay tibial component. Each patient was contacted at minimum 5-year follow-up and asked a series of questions to determine survival and satisfaction. Kaplan-Meier method was used to determine survivorship.

RESULTS

Data were collected for 384 patients (432 knees) with a mean follow-up of 5.7 years (5.0-7.7). The follow-up rate was 81.2%. In total, 13 revisions were performed, of which 11 knees were converted to total knee arthroplasty and in 2 cases 1 UKA component was revised, resulting in 97% survivorship. The mean time to revision was 2.27 years. The most common failure mode was aseptic loosening (7/13). Fourteen reoperations were reported. Of all unrevised patients, 91% was either very satisfied or satisfied with their knee function.

CONCLUSION

Robotic-arm-assisted medial UKA showed high survivorship and satisfaction at midterm follow-up in this prospective, multicenter study. However, in spite of the robotic technique, early fixation failure remains the primary cause for revision with cemented implants. Comparative studies are necessary to confirm these findings and compare to conventional implanted UKA and total knee arthroplasty.

Larger range of motion and increased return to activity, but higher revision rates following unicompartmental versus total knee arthroplasty in patients under 65: a systematic review

PURPOSE

Due to the lack of comparative studies, a systematic review was conducted to determine revision rates of unicompartmental and total knee arthroplasty (UKA and TKA), and compare functional outcomes, range of motion and activity scores in patients less than 65 years of age.

METHODS

A literature search was performed using PubMed, Embase, and Cochrane systems since 2000. 27 UKA and 33 TKA studies were identified and included. Annual revision rate (ARR), functional outcomes, and return to activity were assessed for both types of arthroplasty using independent t tests.

RESULTS

Four level I studies, 12 level II, 16 level III, and 29 level IV were included, which reported on outcomes in 2224 UKAs and 4737 TKAs. UKA studies reported 183 revisions, yielding an ARR of 1.00 and extrapolated 10-year survivorship of 90.0%. TKA studies reported 324 TKA revisions, resulting in an ARR of 0.53 and extrapolated 10-year survivorship of 94.7%. Functional outcomes scores following UKA and TKA were equivalent, however, following UKA larger ROM (125° versus 114°, p = 0.004) and higher UCLA scores were observed compared to TKA (6.9 versus 6.0, n.s.).

CONCLUSION

These results show that good-to-excellent outcomes can be achieved following UKA and TKA in patients less than 65 years of age. A higher ARR was noted following UKA compared to TKA. However, improved functional outcomes, ROM and return to activity were found after UKA than TKA in this young population. Comparative studies are needed to confirm these findings and assess factors contributing to failure at the younger patient population. Outcomes of UKA and TKA in patients younger than 65 years are both satisfying, and therefore, both procedures are not contraindicated at younger age. UKA has several important advantages over TKA in this young and frequently more active population.

LEVEL OF EVIDENCE

IV.

Predicting the Feasibility of Correcting Mechanical Axis in Large Varus Deformities With Unicompartmental Knee Arthroplasty

BACKGROUND

Due to disappointing historical outcomes of unicompartmental knee arthroplasty (UKA), Kozinn and Scott proposed strict selection criteria, including preoperative varus alignment of ≤15°, to improve the outcomes of UKA. No studies to date, however, have assessed the feasibility of correcting large preoperative varus deformities with UKA surgery. The study goals were therefore to (1) assess to what extent patients with large varus deformities could be corrected and (2) determine radiographic parameters to predict sufficient correction.

METHODS

In 200 consecutive robotic-arm assisted medial UKA patients with large preoperative varus deformities (≥7°), the mechanical axis angle (MAA) and joint line convergence angle (JLCA) were measured on hip-knee-ankle radiographs. It was assessed what number of patients were corrected to optimal (≤4°) and acceptable (5°-7°) alignment, and whether the feasibility of this correction could be predicted using an estimated MAA (eMAA, preoperative MAA-JLCA) using regression analyses.

RESULTS

Mean preoperative MAA was 10° of varus (range, 7°-18°), JLCA was 5° (1°-12°), postoperative MAA was 4° of varus (-3° to 8°), and correction was 6° (1°-14°). Postoperative optimal alignment was achieved in 62% and acceptable alignment in 36%. The eMAA was a significant predictor for optimal postoperative alignment, when corrected for age and gender (P < .001).

CONCLUSION

Patients with large preoperative varus deformities (7°-18°) could be considered candidates for medial UKA, as 98% was corrected to optimal or acceptable alignment, although cautious approach is needed in deformities >15°. Furthermore, it was noted that the feasibility of achieving optimal alignment could be predicted using the preoperative MAA, JLCA, and age.

Predictors of Midterm Outcomes after Medial Unicompartmental Knee Arthroplasty in Asians

Background

This study was designed to evaluate predictors of good outcomes following medial unicompartmental knee arthroplasty (UKA) in Asian patients.

Methods

Registry data of patients who underwent primary unilateral medial UKA from 2006 to 2011 were collected. Outcomes studied were the Oxford Knee Score (OKS) and the Physical Component Score (PCS) of the Short Form 36 (SF-36) questionnaire. These outcome scores were collected prospectively, pre- and postoperatively up to 5 years. Good outcome was defined as an overall improvement in score greater than or equal to the minimal clinically important difference (MCID). The MCID for the OKS was 5 while the MCID for the PCS was 10. Regression analysis was used to identify predictors of good outcomes following medial UKA.

Results

Primary medial UKA was performed in 1,075 patients. Higher (poorer) preoperative OKS (odds ratio [OR], 1.27; p < 0.001), lower (poorer) preoperative PCS (OR, 1.08; p < 0.001), lower (poorer) preoperative Knee Society Knee Score (KSKS; OR, 1.02; p < 0.001) and higher (better) preoperative SF-36 Mental Component Score (MCS; OR, 1.02; p < 0.001) were significant predictors of good outcomes.

Conclusions

Patients with poorer OKS, PCS and KSKS and better SF-36 MCS preoperatively tended to achieve good outcomes by the MCID criterion at 5 years following the index surgery.

Regional Femoral and Tibial Radiolucency in Cemented Unicompartmental Knee Arthroplasty and the Relationship to Functional Outcomes

BACKGROUND

Femoral and tibial radiolucent lines (RLL) after unicompartmental knee arthroplasty (UKA) can be categorized in physiological and pathological radiolucencies. Although physiological tibial radiolucency is assessed extensively in literature, studies reporting femoral radiolucency are lacking. Therefore, a retrospective study was performed to assess physiological femoral RLL and its relationship to short-term functional outcomes.

METHODS

A total of 352 patients were included who underwent robotic-assisted medial UKA surgery and received a fixed-bearing metal-backed cemented medial UKA. Radiographic follow-up consisted of standard anteroposterior and lateral radiographs. Functional outcomes, using the Western Ontario and McMaster Universities Arthritis Index questionnaire, of patients with RLL were compared with a matched cohort, based on gender, age, and body mass index.

RESULTS

In this cohort, 101 patients (28.8%) had physiological regional radiolucency around the femoral (10.3%) and/or tibial (25.3%) components, of which 6.8% concerned both components. Tibial RLL were more frequently seen compared with femoral RLL (P < .001). Our data suggest that the time of onset of femoral radiolucency develops later (1.36 years) than tibial radiolucency (1.00 years, P = .02). No difference in short-term functional outcomes was found between the RLL group and the matched cohort group without radiolucency.

CONCLUSION

This study acknowledges that tibial and femoral physiological radiolucencies may develop after cemented medial UKA. Furthermore, this was the first study showing that physiological femoral RLL occur later than tibial RLL. Prospective studies with longer follow-up and larger numbers are necessary to compare radiolucency in different UKA designs and the relationship to outcomes.

Optimization of sagittal and coronal planes with robotic-assisted unicompartmental knee arthroplasty

BACKGROUND

One of the anatomic goals of total knee arthroplasty (TKA) is optimizing in the coronal and sagittal plane. Accurate alignments of both planes have been correlated to functional outcome and range of motion. There is a paucity of evidence on the accuracy of unicompartmental knee arthroplasty (UKA) in balancing biplanar knee alignment - specifically sagittal plane alignment. Because robotic assisted UKA has an advantage of more accurately manipulating sagittal plane for optimal alignment and kinematics based on pre-operative and intraoperative CT planning we assessed the accuracy.

METHODS

We reviewed the clinical and radiographic information of 94 robotic assisted UKA surgeries for balancing of sagittal and coronal knee anatomy using radiographic parameters, such as posterior condylar offset ratio (PCOR), posterior tibial slope (PTS), femoral-tibial angle, and joint line.

RESULTS

In the sagittal plane, we found no significant difference between pre and postoperative PCOR values. As planned, PTS was significantly lower after UKA compared to the native knee (4.91° vs 2.28°; p<0.0001). In the coronal plane, there was no significant difference in the joint line however pre and post-operative mechanical axis were significantly different (5.43°±2.58 of varus vs. 2.76°±2.14 of varus; p<0.0001).

CONCLUSION

This study attempts to quantify sagittal and coronal plane alignment after robotic assisted UKA. More attention should be paid to the role of sagittal plane alignment after UKA. We believe modifying posterior tibial slope, while maintaining PCOR is fundamental in achieving native kinematics and optimizing range of motion in the sagittal plane. This may be best-accomplished using robotic techniques for UKA.

Outcomes of cementless unicompartmental and total knee arthroplasty: A systematic review

BACKGROUND

Aseptic loosening is a common failure mode in cemented unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA). This led to the development of cementless designs but the historical outcomes were poor. Recent developments in cementless designs have improved outcomes, but the current status is unknown. Therefore, a systematic review was performed to assess recent outcomes of cementless knee arthroplasty.

METHODS

A search was performed using PubMed, Embase and Cochrane systems and national registries for studies reporting outcomes since 2005. Fifty-two cohort studies and four registries reported survivorship, failure modes or functional outcomes of cementless UKA and TKA.

RESULTS

Nine level I studies, six level II studies, three level III studies, 34 level IV studies and four registries were included. Three hundred eighteen failures in 10,309 cementless TKA procedures and 62 failures in 2218 cementless UKA procedures resulted in extrapolated five-year, 10-year and 15-year survivorship of cementless TKAs of 97.7%, 95.4% and 93.0%, respectively, and cementless UKA of 96.4%, 92.9% and 89.3%, respectively. Aseptic loosening was more common in cementless TKA (25%) when compared to UKA (13%). Functional outcomes of cementless TKA and UKA were excellent with 84.3% and 84.5% of the maximum possible scores, respectively.

CONCLUSIONS

This systematic review showed that good to excellent extrapolated survivorship and functional outcomes are seen following modern cementless UKA and TKA, with a low incidence of aseptic loosening following cementless UKA.

LEVEL OF EVIDENCE

Level IV.

Survivorship and patient satisfaction of robotic-assisted medial unicompartmental knee arthroplasty at a minimum two-year follow-up

BACKGROUND

Successful clinical outcomes following unicompartmental knee arthroplasty (UKA) depend on lower limb alignment, soft tissue balance and component positioning, which can be difficult to control using manual instrumentation. Although robotic-assisted surgery more reliably controls these surgical factors, studies assessing outcomes of robotic-assisted UKA are lacking. Therefore, a prospective multicenter study was performed to assess outcomes of robotic-assisted UKA.

METHODS

A total of 1007 consecutive patients (1135 knees) underwent robotic-assisted medial UKA surgery from six surgeons at separate institutions between March 2009 and December 2011. All patients received a fixed-bearing metal-backed onlay implant as tibial component. Each patient was contacted at minimum two-year follow-up and asked a series of five questions to determine survivorship and patient satisfaction. Worst-case scenario analysis was performed whereby all patients were considered as revision when they declined participation in the study.

RESULTS

Data was collected for 797 patients (909 knees) with average follow-up of 29.6months (range: 22-52months). At 2.5-years of follow-up, 11 knees were reported as revised, which resulted in a survivorship of 98.8%. Thirty-five patients declined participation in the study yielding a worst-case survivorship of 96.0%. Of all patients without revision, 92% was either very satisfied or satisfied with their knee function.

CONCLUSION

In this multicenter study, robotic-assisted UKA was found to have high survivorship and satisfaction rate at short-term follow-up. Prospective comparison studies with longer follow-up are necessary in order to compare survivorship and satisfaction rates of robotic-assisted UKA to conventional UKA and total knee arthroplasty.

The Role of Patient Characteristics on the Choice of Unicompartmental versus Total Knee Arthroplasty in Patients With Medial Osteoarthritis

BACKGROUND

Medial unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) are both viable treatment options for medial osteoarthritis (OA). However, it remains unclear when to choose for which arthroplasty treatment. Goals of this study were therefore to (1) compare outcomes after both treatments and (2) assess which treatment has superior outcomes in different patient subgroups.

METHODS

In this retrospective cohort study, 166 patients received the RESTORIS MCK Medial UKA and 63 patients the Vanguard TKA and were radiographically matched on isolated medial OA. Western Ontario and McMaster Universities Arthritis Index scores were collected preoperatively and postoperatively (mean: 3.0 years, range: 2.0-5.0 years).

RESULTS

Preoperatively, no differences were observed, but medial UKA patients reported better functional outcomes than TKA (89.7 ± 13.6 vs 81.2 ± 18.0, P = .001) at follow-up.Better functional outcomes were noted after medial UKA in patients younger than age 70 years (89.5 ± 14.2 vs 78.6 ± 20.0, P = .001), with body mass index below 30 (90.3 ± 11.4 vs 83.6 ± 14.9, P = .005), with body mass index above 30 (88.3 ± 17.5 vs 78.8 ± 21.0, P = .034) and in females (90.6 ± 11.0 vs 78.1 ± 19.4, P = .001) when compared with TKA. No differences were found in males and older patients between both arthroplasties.

CONCLUSION

Superior functional outcomes were noted after medial UKA over TKA in patients presenting with medial OA with these prostheses. Subgroup analyses suggest that medial UKA is the preferred treatment in younger patients and females while no differences were noted in older patients and males after medial UKA and TKA. This might help the orthopedic surgeon in individualizing arthroplasty treatment for patients with medial OA.

Annual revision rates of partial versus total knee arthroplasty: A comparative meta-analysis

BACKGROUND

Utilization of unicompartmental knee arthroplasty (UKA) and patellofemoral arthroplasty (PFA) as alternatives to total knee arthroplasty (TKA) for unicompartmental knee osteoarthritis (OA) has increased. However, no single resource consolidates survivorship data between TKA and partial resurfacing options for each variant of unicompartmental OA. This meta-analysis compared survivorship between TKA and medial UKA (MUKA), lateral UKA (LUKA) and PFA using annual revision rate as a standardized metric.

METHODS

A systematic literature search was performed for studies quantifying TKA, MUKA, LUKA and/or PFA implant survivorship. Studies were classified by evidence level and assessed for bias using the MINORS and PEDro instruments. Annual revision rates were calculated for each arthroplasty procedure as percentages/observed component-year, based on a Poisson-normal model with random effects using the R-statistical software package.

RESULTS

One hundred and twenty-four studies (113 cohort and 11 registry-based studies) met inclusion/exclusion criteria, providing data for 374,934 arthroplasties and 14,991 revisions. The overall evidence level was low, with 96.7% of studies classified as level III-IV. Annual revision rates were lowest for TKA (0.49%, CI 0.41 to 0.58), followed by MUKA (1.07%, CI 0.87 to 1.31), LUKA (1.13%, CI 0.69 to 1.83) and PFA (1.75%, CI 1.19 to 2.57). No difference was detected between revision rates for MUKA and LUKA (p=0.222).

CONCLUSIONS

Revisions of MUKA, LUKA and PFA occur at an annual rate of 2.18, 2.31 and 3.57-fold that of TKA, respectively. These estimates may be used to inform clinical decision-making, guide patient expectations and evaluate the cost-effectiveness of total versus partial knee replacement in the setting of unicompartmental OA.

Good short- to medium-term results after osteochondral autograft transplantation (OAT) in middle-aged patients with focal, non-traumatic osteochondral lesions of the knee

BACKGROUND

Osteochondral autograft transplantation (OAT) offers the opportunity to repair cartilaginous defects by restoring hyaline cartilage anatomy. Encouraging results have been reported in patients suffering from acute knee trauma or osteochondritis dissecans. Patients with focal chronic, non-traumatic osteochondral (FCNO) lesions of the knee, however, have rarely been the subject of investigation. Some authors even consider higher age as contraindications to OAT.

OBJECTIVES

To assess the short- to medium-term outcomes of OAT in middle-aged patients with FCNO lesions of the knee and to identify predictors of clinical outcome.

HYPOTHESIS

Filling FCNO defects with autologous osteochondral grafts should restore the congruency of the middle-aged knee joint and thereby reduce pain and loss of function on the one hand, and increase quality of life on the other hand.

METHODS

One hundred and twelve patients (48.01±1.12yrs) with FCNO of the knee were assessed before OAT and 26.2±0.24 months after surgery. Clinical outcome was measured by WOMAC Index and the Visual Analogue Scale (VAS) for pain.

RESULTS

Pain (pre-OAT VAS vs. post-OAT VAS: 7.14±0.19 vs. 3.74±0.26, P<0.001) was reduced and quality of life (pre-OAT WOMAC vs. post-OAT WOMAC: 134.88±5.84 vs. 65.92±5.34, P<0.001) improved. Retropatellar defects were associated with poor outcome, while overall surface and number of cylinders were not.

DISCUSSION

Middle-aged patients with FCNO of the knee also profit from OAT at a short follow-up.

LEVEL OF EVIDENCE

IV. Mono-centric, prospective clinical series.