Tibial joint line orientation has no effect on joint awareness after mechanically aligned total knee arthroplasty.

PURPOSE: Joint line orientation (JLO) plays an important role in total knee arthroplasty (TKA), but its influence on patient-reported outcomes (PROs) is unclear. The purpose of this study was to examine JLO impact as measured by the forgotten joint score (FJS-12). The hypothesis was that restoring the joint line (JL) parallel to the floor would influence joint awareness favorably, i.e., allow the patient to forget about the joint in daily living. METHODS: All computer-navigated primary TKAs using a cemented, cruciate-retaining (CR) design implanted between January 2018 and September 2019 were reviewed in this retrospective single-center analysis. Primary endpoints were: clinical [range of motion (ROM)], and patient-reported (FJS-12) and radiographical outcomes [tibia joint line angle (TJLA), hip knee axis (HKA), mechanical medial proximal tibia angle (mMPTA) as well as mechanical lateral distal femoral angle (mLDFA)]. RESULTS: Seventy-six patients (mean age: 70.3 ± 9.7 years, mean BMI: 29.7 ± 5.2 kg/m2) were included. Postoperative ROM averaged 118.7 ± 9.6°. The mean FJS-12 improved from 16.4 ± 15.3 (preoperatively) to 89.4 ± 16.9 (1-year follow-up; p < 0.001). Clinical outcomes and PROs did not correlate with JLO (p = n.s.). Cluster analysis using six measures revealed that a medially opened TJLA was associated with significantly better postoperative FJS-12. CONCLUSION: Tibial JLO was found to have no effect on PROs. Considering the JLO in the coronal plane alone probably has questionable clinical relevance. Lower limb alignment should be assessed in all three planes and correlated with the clinical outcome. LEVEL OF CLINICAL EVIDENCE: Level IV.

Osteoarthritic and non-osteoarthritic patients show comparable coronal knee joint line orientations in a cross-sectional study based on 3D reconstructed CT images.

PURPOSE: Recently introduced total knee arthroplasty (TKA) alignment strategies aim to restore the pre-arthritic alignment of an individual patient. The native alignment of a patient can only be restored with detailed knowledge about the native and osteoarthritic alignment as well as differences between them. The first aim of this study was to assess the alignment of a large series of osteoarthritic (OA) knees and investigate whether femoral and tibial joint lines vary within patients with the same overall lower limb alignment. The secondary aim was to compare the alignment of OA patients to the previously published data of non-OA patients. This information could be useful for surgeons considering implementing one of the new alignment concepts. MATERIAL: Coronal alignment parameters of 2692 knee OA patients were measured based on 3D reconstructed CT data using a validated planning software (Knee-PLAN®, Symbios, Yverdon les Bains, Switzerland). Based on these measurements, patients' coronal alignment was phenotyped according to the functional knee phenotype concept. These phenotypes represent an alignment variation of either the overall alignment, the femoral joint line orientation or the tibial joint line orientation. Each phenotype is defined by a specific mean and covers a range of ± 1.5° from this mean. Mean values and distribution among the phenotypes are presented and compared between two populations (OA patients of this study and non-OA patients of a previously published study) as well as between HKA subgroups (varus, valgus and neutral) using t tests and Chi-square tests (p < 0.05). RESULTS: Femoral and tibial joint lines varied within patients with the same overall lower limb alignment. A total of 162 functional knee phenotypes were found (119 males, 136 females and 94 mutual phenotypes). Mean values differed between the OA and non-OA population, but differences were small (< 2°) except for the overall alignment (e.g. HKA). The distribution of OA and non-OA patients among the phenotypes differed significantly, especially among the limb phenotypes. CONCLUSION: Differences between OA and non-OA knees are small regarding coronal femoral and tibial joint line orientation. Femoral and tibial joint line orientation of osteoarthritic patients can, therefore, be used to estimate their native coronal alignment and plan an individualized knee alignment. LEVEL OF CLINICAL EVIDENCE: III.

High inter- and intraindividual differences in medial and lateral posterior tibial slope are not reproduced accurately by conventional TKA alignment techniques.

PURPOSE: The purpose of this study was to describe the medial and lateral posterior tibial slope (MPTS and LPTS) on 3D-CT in a Caucasian population without osteoarthritis. It was hypothesised that standard TKA alignment techniques would not reproduce the anatomy in a high percentage of native knees. METHODS: CT scans of 301 knees [male:female = 192:109; mean age 30.1 ([Formula: see text] 6.1)] were analysed retrospectively. Tibial slope was measured medially and laterally in relation to the mechanical axis of the tibia. The proportion of MPTS and LPTS was calculated, corresponding to the "standard PTS" of 3°-7°. The proportion of knees accurately reproduced with the recommended PTS of 0°-3° for PS and 5°-7° for CR TKA were evaluated. RESULTS: Interindividual mean values of MPTS and LPTS did not differ significantly (mean (range); MPTS: 7.2° ( - 1.0°-19.0°) vs. LPTS: 7.2° ( - 2.4°-17.8°), n.s.). The mean absolute intraindividual difference was 2.9° (0.0°-10.8°). In 40.5% the intraindividual difference between MPTS and LPTS was > 3°. When the standard slope of 3°-7° medial and lateral was considered, only 15% of the knees were covered. The tibial cut for a PS TKA or a CR TKA changes the combined PTS (MPTS + LPTS) in 99.3% and 95.3% of cases, respectively. CONCLUSION: A high interindividual range of MPTS and LPTS as well as considerable intraindividual differences were shown. When implementing the recommended slope values for PS and CR prostheses, changes in native slope must be accepted. Further research is needed to evaluate the impact of altering a patient's native slope on the clinical outcome. LEVEL OF EVIDENCE: IV.

Osteoarthritic knees have a highly variable patellofemoral alignment: a systematic review.

PURPOSE: This systematic review aimed to evaluate the variability of patellofemoral (PF) alignment and trochlear morphology in osteoarthritic knees. METHODS: PF alignment of the knee was defined by the following parameters: the sulcus angle (SA), femoral trochlear depth (FTD), patellar tilt angle (PTA), lateral patellofemoral angle (LPFA), lateral femoral trochlear inclination (LFTI) and tibial tubercle-trochlear groove distance (TT-TG). The electronic databases MEDLINE and EMBASE were searched from database inception to the search date (February 19, 2019) and were screened for relevant studies. The PRISMA guidelines were followed. Articles reporting PF alignment measurements of osteoarthritic knees in patients over 40 years old were included. Data were extracted and methodological quality was assessed using a 14-item checklist. RESULTS: A total of 8 studies met the inclusion criteria. The studies reported mean values ± SD between 120° and 141.1° ± 7.7 for the SA; 5.8 mm ± 1.4 for the FTD; between - 0.1° ± 3.3 and 10.3° ± 5.7 for the PTA; between 5.8° ± 5.4 and 17° for the LPFA; between 23.2° ± 5.0 and 27.1° ± 4.4 for the LFTI; and 5.8 mm ± 5.4 for the TT-TG. CONCLUSION: PF alignment in the osteoarthritic knee is more variable than expected. This finding should encourage surgeons to consider the individual preoperative PF alignment more precisely with the aim of reducing anterior knee pain (AKP) after TKA. 3D-CT imaging might be of great value to analyse the PF alignment in an appropriate way. LEVEL OF EVIDENCE: Level III.

[When should we perform a knee or hip arthroplasty?] / Wann ist es Zeit für einen Gelenkersatz an Knie und Hüfte?

When should we perform a knee or hip arthroplasty? Abstract. Total hip (THA) and knee arthroplasties (TKA) rank among the most successful and effective orthopedic operations. They improve health-related quality of life and result in high patient satisfaction. But when is the right moment to perform an arthroplasty? A differentiated indication is decisive for a good outcome. Pain, limitations in quality of life because of osteoarthritis, radiological confirmation of osteoarthritis and inadequate response to conservative treatment should be reported. Moreover, medical history, clinical examination and radiographic findings need to be conclusive. Expectations need to be realistic and reasonable. When all of these criteria are met, the attending physician may indicate an operation. Finally, the patients' level of suffering and discomfort defines the timing of an arthroplasty.

No difference in radiolucent lines after TKA: a matched-pair analysis of the classic implant and its evolutional design.

PURPOSE: Total knee arthroplasty (TKA) designs evolve continuously to improve patient outcomes. However, incidences of radiolucent lines (RLL) in the latest TKA system have recently been reported, raising concerns. The purpose of the current study was to compare radiographic outcomes of this new TKA implant to its predecessor design. METHODS: A group of 100 patients undergoing TKA using the newer design (Attune) was matched by age and gender to 191 patients with the classic design (LCS). All patients underwent computer-navigated primary TKA by the same surgeon using the same technique. Radiographs were taken before discharge, and 2 and 12 months postoperatively. Radiographic analysis was performed independently by three assessors, using the Modern Knee Society Radiographic Evaluation System and Methodology (MKSRES). RESULTS: At 12 months postoperatively, the incidence of RLL did not statistically differ between the two implants (14%, n = 14 Attune vs. 8% n = 17 LCS, n.s.). The posterior femoral flange was most commonly affected (12%; n = 12 Attune vs. 7.9%; n = 15 LCS, n.s.) followed by the anterior flange (1%; n = 1 Attune vs. 3.1%; n = 6 LCS, n.s.). The tibial baseplate was only affected in 1% (n = 1) of the Attune and 2.6% (n = 5) of the LCS (n.s.). CONCLUSION: At 12 months follow-up we found no significant difference in RLL between the two implants. Both Attune and LCS TKA systems showed RLL predominantly at the posterior femoral flange. The reasons for the RLL remain a matter of speculation; however, shortcomings in surgical and cementing techniques seem to be more important than implant-related factors. LEVEL OF EVIDENCE: III.

The Forgotten Joint Score-12 as a valuable patient-reported outcome measure for patients after first-time patellar dislocation.

BACKGROUND: The aim of this study is to assess joint awareness after first-time patellar dislocation using the Forgotten Joint Score-12 (FJS-12) and to compare performance of this measurement tool to acknowledged patient-reported outcome scores. METHODS: A retrospective analysis of patients with confirmed first-time patellar dislocation was performed. Patients were assessed with the FJS-12, the Kujala and the WOMAC scores. Reference values for the FJS-12 were obtained from a matched healthy control group with no history of previous knee joint pathology. We calculated Cronbach's alpha, assessed the ceiling effect for all scores, and calculated the Spearman correlation coefficient between them RESULTS: Fifty-six patients (mean follow-up 8.2 years, range 1.6-14.1) with a mean age of 26.4 years were analysed. Compared with the age- and gender-matched control group, the patellar dislocation group showed significantly lower (worse) mean FJS-12 scores (88 vs. 71, P < 0.001). Inter-score correlation between the FJS-12 and the Kujala was high (r = 0.74) and significant (P < 0.001), as well as between FJS-12 and WOMAC (r = 0.81, P < 0.001). Cronbach's alpha of the FJS-12 was 0.92 (95% confidence interval 0.90-0.94). The FJS-12 showed less ceiling effect (16%) compared with the Kujala score (23%) and the WOMAC score (32%). CONCLUSIONS: The concept of joint awareness has been successfully applied to a patient population after patellar dislocation. The FJS-12 showed less ceiling effect compared with the Kujala and the WOMAC scores, suggesting the score was able to capture subtle knee problems in patients after patellar dislocation.

Healthy knees have a highly variable patellofemoral alignment: a systematic review.

PURPOSE: There is still lack of knowledge regarding the variability of patellofemoral alignment in healthy, non-osteoarthritic knees, without patellofemoral instability. Therefore, a systematic review of the existing literature was performed to evaluate the variability of patellofemoral alignment. METHODS: Patellofemoral alignment of the knee was defined by the following parameters: sulcus angle (SA), femoral trochlear depth (FTD), patellar tilt angle (PTA), lateral patellofemoral angle (LPFA), lateral femoral trochlear inclination (LFTI) and tibial tubercle-trochlear groove distance (TT-TG). The electronic databases MEDLINE and EMBASE were searched from database inception to search date (January 11, 2019) and screened for relevant studies. The PRISMA guidelines were followed. Articles reporting PF alignment measurements of healthy knees in patients between 15 years and 47 years were included. RESULTS: A total of 15 studies met the inclusion criteria. The studies reported mean values and standard deviations for the SA between 118.7° ± 7 and 168°; for the FTD between 3.4 mm ± 1.1 and 7.1 mm ± 1.8; for the PTA between 0.7° ± 4.99 and 17.05° ± 4.3; for the LPFA between 6.26° ± 4.1 and 11.1° ± 4.0; for the LFTI between 16.3° ± 2.8 and 22.1° ± 1.9; and for the TT-TG between 9.8 mm ± 4.6 and 17.3 mm ± 5.3. CONCLUSION: Patellofemoral alignment in the healthy knee is extremely variable. A more precise knowledge of the complex relationship between the patella and the trochlea may help to better diagnose PF disorders and eventually help in selecting the correct therapy. Furthermore, standardised imaging protocols and measurement techniques for patellofemoral parameters are needed. LEVEL OF EVIDENCE: III.

Correction to: Healthy knees have a highly variable patellofemoral alignment: a systematic review.

Authors would like to add the below acknowledgement statement to the original article.

Functional knee phenotypes: a novel classification for phenotyping the coronal lower limb alignment based on the native alignment in young non-osteoarthritic patients.

PURPOSE: The currently used system to classify the lower limb alignment (neutral, varus, valgus) does not consider the orientation of the joint line or its relationship to the overall lower limb alignment. Similarly, current total knee arthroplasty (TKA) alignment concepts do not sufficiently consider the variability of the native coronal alignment. Therefore, the purpose of this study was (1) to introduce a new classification system for the lower limb alignment, based on phenotypes, and (2) to compare the alignment targets of different TKA alignment concepts with the native alignment of non-osteoarthritic patients. METHODS: Two recent articles phenotyped the lower limb, the femur and tibia of 308 non-osteoarthritic knees of 160 patients [male to female ratio = 102:58, mean age ± standard deviation 30 ± 7 years (16-44 years)]. The present study introduces functional knee phenotypes, which are a combination of all previously introduced phenotypes. The functional knee phenotypes therefore enable an evaluation of all parameters in relation to each other and thus a comprehensive analysis of the coronal alignment. The existing functional knee phenotypes in the female and male population were investigated. In addition, how many non-osteoarthritic knees had an alignment within the range of current TKA alignment targets (mechanical, anatomical and restricted kinematic alignment) was investigated. Therefore, it was defined which functional knee phenotypes represented a target of the TKA alignment concepts and which percentage of the population had such a phenotype. RESULTS: Out of 125 possible functional knee phenotypes, 43 were found (35 male, 26 and 18 mutual). The most common functional knee phenotype in males was NEUHKA0° + NEUFMA0° + NEUTMA0° (19%), followed by VARHKA3° + NEUFMA0° + VARTMA0° (8.2%). The most common functional knee phenotype in females was NEUHKA0° + NEUFMA0° + NEUTMA0° (17.7%), closely followed by NEUHKA0° + NEUFMA0° + VALTMA0° (16.6%). The functional knee phenotype representing a mechanical alignment target was found in 5.6% of the males and 3.6% of the females. The phenotype representing an anatomical alignment target was found in 18% of the males and 17% in females. Five of the nine phenotypes representing a restricted kinematic alignment target were found in this population (male 5, female 4, mutual 4). They represented 31.3% of all males and 45.1% of all females. CONCLUSION: A more individualized approach to TKA alignment is needed. The functional knee phenotypes enable a simple, but detailed assessment of a patient's individual anatomy and thereby could be a helpful tool to individualize the approach to TKA. LEVEL OF CLINICAL EVIDENCE: III, retrospective cohort study.

Phenotyping of hip-knee-ankle angle in young non-osteoarthritic knees provides better understanding of native alignment variability.

PURPOSE: There is a lack of knowledge about the native coronal knee alignment in 3D. The currently used classification system (neutral, valgus and varus) oversimplifies the coronal knee alignment. The purpose of this study was therefore (1) to investigate the coronal knee alignment in non-osteoarthritic knees using 3D-reconstructed CT images and (2) to introduce a classification system for the overall knee alignment based on phenotypes. METHODS: The hospital registry was searched for patients younger than 45 years and older than 16, who received a CT according to the Imperial Knee Protocol. Patients with prosthesis, osteoarthritis, fractures or injury of the collateral ligaments were excluded. Finally, 308 non-osteoarthritic knees of 160 patients remained (102 males and 58 females, mean age ± standard deviation (SD) 30 ± 7 years). The overall lower limb alignment was defined as the hip-knee-ankle angle (HKA), which is formed by lines connecting the centers of the femoral head, the knee and the talus. The angle was measured using a commercially planning software (KneePLAN 3D, Symbios, Yverdon les Bains, Switzerland). Descriptive statistics, such as means, ranges, and measures of variance (e.g., standard deviations) are presented. Based on these results, the currently used classification system was evaluated and a new system, based on phenotypes, was introduced. These phenotypes consist of a phenotype-specific mean value (a HKA value) and cover a range of ± 1.5° from this mean (e.g., 183° ± 1.5°). The mean values represent 3° increments of the angle starting from the overall mean value (mean HKA = 180°; 3° increments = 183° and 177°, 186° and 174°). The distribution of these limb phenotypes was assessed. RESULTS: The overall mean HKA was 179.7° ± 2.9° varus and values ranged from 172.6° varus to 187.1° valgus. The mean HKA values for male and female were 179.2° ± 2.8° and 180.5° ± 2.8°, respectively, which implied a significant gender difference (r2 = 0.23). The most common limb phenotype in males was NEUHKA0° (36.4%), followed by VARHKA3° (29.2%) and VALHKA3° (23.1%). The most common limb phenotype in females was NEUHKA0° (36.4%), followed by VALHKA3° (22.1%) and VARHKA3° (15.0%). CONCLUSION: The measurements using 3D-reconstructed CT images confirmed the great variability of the overall lower limb alignment in non-osteoarthritic knees. However, the currently used classification system (neutral, varus, valgus) oversimplifies the coronal alignment and therefore the introduced classification system, based on limb phenotypes, should be used. This will help to better understand individual coronal knee alignment. LEVEL OF EVIDENCE: Level III, retrospective cohort study.

Phenotyping the knee in young non-osteoarthritic knees shows a wide distribution of femoral and tibial coronal alignment.

PURPOSE: There is a lack of knowledge about the joint line orientation of the femur and tibia in non-osteoarthritic knees. The primary purpose of the present study was to evaluate the orientation of the joint lines in native non-osteoarthritic knees using 3D-reconstructed CT scans. The secondary purpose was to identify knee phenotypes to combine the information of the femoral and tibial alignment. METHODS: A total of 308 non-osteoarthritic knees of 160 patients (male to female ratio = 102:58, mean age ± standard deviation 30 ± 7 years (16-44 years) were retrospectively included from our registry. All patients received CT of the knee according to the Imperial Knee Protocol. The orientation of the femoral and tibial joint line was measured in relation to their mechanical axis (femoral mechanical angle, FMA, and tibial mechanical angle, TMA) using a commercially planning software (KneePLAN 3D, Symbios, Yverdon les Bains, Switzerland). The values of FMA and TMA were compared between males and females. Descriptive statistics, such as means, ranges, and measures of variance (e.g. standard deviations), were presented. Based on these results, phenotypes were introduced for the femur and tibia. These phenotypes, based on FMA and TMA values, consist of a mean value and cover a range of ± 1.5° from this mean (3° increments). The distribution of femoral and tibial phenotypes, and their combinations (knee phenotypes) were calculated for the total group and for both genders. RESULTS: The overall mean FMA ± standard deviation (SD) was 93.4° ± 2.0° and values ranged from 87.9° varus to 100° valgus. The overall mean TMA ± SD was 87.2° ± 2.4° with a range of 81.3° varus to 94.6° valgus. FMA and TMA showed significant gender differences (p < 0.01). Females showed more valgus alignment than males. The most common femoral phenotype was neutral in both genders. The most common tibial phenotype was neutral in the male knees (62.8%) and valgus (41.6%) in the female knees. In males, the most frequent combination (knee phenotype) was a neutral phenotype in the femur and a neutral phenotype in the tibia (25.6%). In females, it was a neutral femoral phenotype and a valgus tibial phenotype (28.3%). CONCLUSION: 3D-reconstructed CT scans confirmed the great variability of the joint line orientation in non-osteoarthritic knees. The introduced femoral and tibial phenotypes enable the evaluation of the femoral and tibial alignment together (knee phenotypes). The variability of knee phenotypes found in this young non-osteoarthritic population clearly shows the need for a more individualized approach in TKA. LEVEL OF EVIDENCE: III.

Highly variable coronal tibial and femoral alignment in osteoarthritic knees: a systematic review.

PURPOSE: There is a lack of knowledge about coronal alignment variability in osteoarthritic knees. Therefore, the purpose of this article was to systematically review the literature and collect data about the lower limb alignment including hip-knee-ankle angle (HKA), femoral mechanical angle (FMA), tibial mechanical angle (TMA) and the joint line convergence angle (JLCA) in osteoarthritic knees. METHODS: A systematic review was performed using the electronic databases MEDLINE (PubMed), EMBASE and Google Scholar. The following keywords were used: (morphology OR geometr* OR anatomy OR alignment OR phenotypes), (coronal OR neutral OR varus OR valgus), (knee OR lower limb OR femur OR tibia) and (osteoarthritis OR arthritis). Out of 110 full-text articles retrieved, 15 studies were included. Demographic information included author's names, year of publication, imaging modality, sample size and patient demographics (i.e. sex, age, etc.). Descriptive statistics, such as means, ranges, and measures of variance [e.g. standard deviations, 95% confidence intervals (CI)] for all angles (HKA, FMA, TMA, JLCA) are presented. RESULTS: Thirteen studies reported mean overall HKA angles ranging from 163.5° ± 2.3° to 179.9° ± 4.8°. The mean HKA angles in females were between 164.1° ± 7.2° and 178.8° ± 4.8°, and in males between 163.4° ± 5.5° and 177.4° ± 3.9°. The lowest and highest reported HKA angles were - 27.7° and + 22.0°, respectively. Seven studies reported mean FMA angles. Mean values ranged from 92.7° ± 2.7° valgus to 88.6° ± 2° varus. The reported mean FMAs for male were 87.9° ± 0.5° to 90.7° ± 3° and for female 89.91° ± 2.8° to 92.9° ± 3.1°. Six studies reported mean TMA values. TMA ranged from 81.7° ± 3.9° varus to 87.7° ± 4.1° varus. Only three studies reported mean JLCA angles, which ranged from - 4.3° to - 6.4° ± 3.8°. CONCLUSION: Osteoarthritic knees showed a huge variation in overall coronal limb alignment as well as in femoral and tibial coronal alignment. Current total knee arthroplasty (TKA) alignment philosophies and preoperative planning do not sufficiently consider these variation, which might be one reason for unhappy knees after TKA. LEVEL OF EVIDENCE: IV, systematic review.

Native non-osteoarthritic knees have a highly variable coronal alignment: a systematic review.

PURPOSE: Coronal alignment of the knee is defined by the hip-knee-ankle angle (HKA), the femoral mechanical angle (FMA), the tibial mechanical angle (TMA), and the joint line convergence angle (JLCA). To date, there is still a lack of knowledge about the variability of native coronal knee alignment. The purpose of this paper is to present a systematic review of the current literature about the variability of coronal knee alignment (HKA, FMA, TMA, and JLCA) in non-osteoarthritic knees. METHODS: The electronic databases MEDLINE, EMBASE, and Google Scholar were searched from database inception to search date (November 1, 2018) and screened for relevant studies. The PRISMA guidelines were followed. Inclusion criteria were studies that reported the coronal alignment of the native, non-osteoarthritic knee. RESULTS: A total of 15 studies met the inclusion criteria. Thirteen studies performed the measurements on weight-bearing long-leg standing radiographs (LLR), one study used MRI, and one study used the EOS imaging system. The mean HKA ranged from 176.7° ± 2.8° (male) to 180.7° (female). The mean FMA ranged from 92.08° ± 1.78° (female) to 97.2° ± 2.7° (female). The mean TMA ranged from 84.6° ± 2.5° (female) to 89.6° (female). The mean JLCA ranged from - 0.47° ± 0.98° (male) to - 1.9° ± 1.4° (female). CONCLUSION: This systematic review provides a detailed overview about the variability of the coronal knee alignment in non-osteoarthritic knees. The broad variability of all coronal alignment parameters highlights the necessity for a more anatomic and individualized approach in knee arthroplasty. It also offers the fundament to understand the changes in osteoarthritic knees. LEVEL OF CLINICAL EVIDENCE: Systematic review, Level IV.

No difference in joint awareness after TKA: a matched-pair analysis of a classic implant and its evolutional design.

PURPOSE: Total knee arthroplasty (TKA) designs continuously evolve with the aim of improving patient outcomes. The purpose of the current study was to compare clinical and patient-reported outcome (PRO) results of a new TKA implant to its predecessor. The hypothesis of this study was that joint awareness and range of motion (ROM) of the newer design would be better than the classic design. METHODS: One hundred patients undergoing TKA using the newer design (Attune®) were matched by age and gender to 200 patients with the classic design (LCS®). All patients underwent computer-navigated (Vector Vision, Brain-Lab, Germany) primary TKA by the same surgeon using the same technique. Data (FJS-12, WOMAC and ROM) were collected preoperatively and at 12 months follow-up at our implant registry. RESULTS: Compared to preoperative scores, FJS-12, WOMAC and ROM improved significantly at 12 months follow-up. In the Attune group, mean FJS-12 and WOMAC at follow-up were 67.6 (SD 27.8) and 14.8 (SD 14.9) respectively, compared to 70.8 (SD 33.8) and 15 (SD 17.9) in the LCS group. Mean postoperative ROM was similar in both groups (Attune 120°, range 90°-140°, SD 10.4 and LCS 120°, range 85°-140°, SD 10.3). CONCLUSION: The newer TKA and the predecessor design achieved comparable joint awareness, WOMAC scores and ROM at 1-year follow-up. The benefits expected of the newer design could not be observed in early clinical and PROs. The clinical relevance of this study is that it questions the importance of implant design as the single most important factor for patient outcomes. LEVEL OF EVIDENCE: III.

Normative Values for the Forgotten Joint Score-12 for the US General Population.

BACKGROUND: The Forgotten Joint Score-12 (FJS-12) is a patient-reported outcome questionnaire of joint awareness in patients with hip and knee pathologies. To improve interpretability of values derived from this measure, we collected normative values for the US general population. METHODS: A sample of 2000 participants, representative of US general population, was sought via an online panel. Quota sampling was used to obtain age-specific and sex-specific groups of 200 participants each. The FJS-12 is a 12-item questionnaire assessing the ability to forget the hip or knee joint during activities of daily living. To match US national census data from 2010, raking was used for determining data weights. RESULTS: Normative data for the FJS-12 could be established based on a data set from 2017 respondents (50.1% men; mean age, 54.0 years; 66.3% white/Caucasian). Median FJS-12 scores in the total sample were 75.0 points for knees and 87.5 points for hips. In the age-specific and sex-specific groups, the lowest median score for knees was 54.2 points (men aged 18-39 years) and the highest median was 97.0 (men aged above 70 years). Similarly, median scores for hips were lowest in men aged 18-39 years (60.9 points) and highest in men aged above 70 years (100 points). CONCLUSION: Normative values have been established for the FJS-12 for hips and knees in US general population. Age-specific and sex-specific differences require relying on normative values from the respective groups when interpreting FJS-12 data.

Due to great variability fixed HKS angle for alignment of the distal cut leads to a significant error in coronal TKA orientation.

PURPOSE: For coronal alignment in total knee arthroplasty (TKA) most surgeons use the patient's individual hip-knee shaft (HKS) angle (angle between the anatomical axis and the mechanical axis of the femur). The major problem of the sole use of HKS angle is that the individual patient's distal femoral asymmetry is not considered. The purpose of this study was to determine the variability of the HKS angle, the mechanical femoral angle (FMA) and to evaluate whether or not one of the two angles is more important for TKA alignment strategy. It was the hypothesis that HKS and FMA are not directly related to each other and hence HKS should not be considered as guide for coronal alignment. METHODS: Prospectively collected CT data of 1480 consecutive patients who underwent 3D reconstructed CT scans before TKA was used for this retrospective registry study [882 women and 598 men, mean age ± standard deviation 71 ± 9 years (34-99 years)]. The CT protocol was modified according to the Imperial Knee Protocol, which is a lowdose CT protocol that includes high-resolution 0.75-mm slices of the knee and 3-mm slices of the hip and ankle joints. All measurements were done using Symbios® 3D knee preoperative planning's software (Symbios, Yverdon les Bains, Switzerland). The HKS, FMA and hip-knee-ankle (HKA) angles were measured. Angles measured were displayed as mean, standard deviation (SD) and range. In addition, the angles were shown as percentages after categorization. The HKS was categorized between 3° and 9° in 1° increments. The FMA was categorized between 83.5° and 98.5° in 3° increments. The HKA was categorized between 12.5° varus 5.5° valgus in 3° increments. Pearson correlations were used to investigate correlation of HKS and FMA (p < 0.05). RESULTS: The HKS angle was not constant at 7° but averaged 6°, and ranged from 2.5° to 9°. The FMA angle was on average 93° but varied more than 20°, ranging from 75° (varus) to 104° (valgus). The mean HKA ± SD was - 3.4° ± 5.7° (range - 23.0° to 15.0°). The mean HKSSD was 5.6° ± 0.9° (range 2.5°-8.8°). The mean FMASD was 92.6° ± 2.8° (range 75.2°-103.5°). The Pearson correlations of all measured angles are presented in Table 1. HKS significantly correlated negatively with HKA and FMA (p < 0.001). FMA and HKA were strongly correlated with each other (p < 0.0001). Considering the HKS angle as a constant angle can induce a deviation of up to 5° with respect to an orthogonal distal femoral cutting objective. The great variability of the FMA angle implies that the FMA seems more relevant than the HKS angle to define the strategy of realignment of the lower limb. However, then patient specific instrumentation has to be used to precisely transfer the planning to the surgical technique. Having the aim of a more personalized TKA alignment in mind the individual constitutional knee phenotype should be taken into account.

Vitamin C demand is increased after total knee arthroplasty: a double-blind placebo-controlled-randomized study.

PURPOSE: This study was designed to determine whether perioperative supplementation of vitamin C (VC) improves range of motion (ROM) and reduces the risk of arthrofibrosis (AF) following total knee arthroplasty (TKA). METHODS: Ninety-five patients undergoing TKA were randomized to either oral VC (1000 mg daily) or placebo for 50 days (48 VC group, 47 placebo group). The effect of VC supplementation was tested on ROM, AF, WOMAC, FJS-12, and VC plasma concentrations (VCc). VCc were analyzed in both patient groups before surgery, 4 and 7 days after surgery. RESULTS: ROM at 1 year was not different between study groups. The prevalence of AF was 5 of 48 (10.4%) in the VC group compared to 11 of 47 (23.4%) in the placebo group (p = 0.09). VCc decreased post-operatively in the placebo group (49-12 µmol/l on day 7, p < 0.001), but not in the VC group (53-57 µmol/l). Patients with a perioperative drop of VCc ≥ 30 µmol/l developed significantly more AF at 1 year compared to patients with a VCc drop of < 30 µmol/l (p = 0.007). CONCLUSIONS: TKA results in VC depletion. Perioperative VC supplementation prevents VCc drop in most patients undergoing TKA and may lower the incidence of AF. The clinical relevance of this study is that VC supplementation seems to be a cheap and safe adjunct to improve functional outcome after TKA. LEVEL OF EVIDENCE: I. TRIAL REGISTRY: The study was registered at the ISRCTN registry with study ID ISRCTN40250576.

Blackburne-Peel ratio predicts patients' outcomes after total knee arthroplasty.

PURPOSE: Alterations in patellar height and posterior tibial slope (PTS) are frequently measured radiographic parameters associated with postoperative impairments after total knee arthroplasty (TKA). Few studies correlate the clinical outcome of TKA with the radiological indices. Both the modified Insall-Salvati ratio (mISR) and the Blackburne-Peel ratio (BPR) were hypothesised to correlate with the clinical outcome after TKA. METHODS: A total of 282 computer navigated primary LCS®-TKAs, implanted in our institution from 2008 to 2012, were included. Data (ROM, FJS-12, WOMAC, and revision surgery) were collected independently and prospectively. Patellar height (mISR, BPR), joint-line position, and PTS were measured on pre- and postoperative radiographs. Bivariate and multiple regression analyses were performed. RESULTS: Mean mISR (1.5-1.4) and BPR (0.8-0.6) decreased from preoperatively to 1 year follow-up. Mean joint-line shift in a cranial direction was 2 mm after TKA implantation. Analysis of dichotomous variables (presence of PB and PPB or not) only showed significantly lower flexion in patients with PPB (p < 0.001). However, multiple regression revealed that BPR was a significant positive independent predictor for FJS-12 (p = 0.016) and flexion (p < 0.001) at 1 year follow-up. Postoperative PTS (p < 0.01) and initial patella height (p < 0.001) were both predictive for BPR at follow-up, while the joint-line height was not. CONCLUSIONS: The BPR is a useful and reliable radiographic parameter to predict patient outcomes 1 year after primary navigated TKA. Lowering the BPR should be avoided, as this may lead to significant restrictions in terms of ROM and PROMs. LEVEL OF EVIDENCE: Level 3.

Highly variable tibial tubercle-trochlear groove distance (TT-TG) in osteoarthritic knees should be considered when performing TKA.

PURPOSE: The tibial tubercle-trochlear groove distance (TT-TG) is an established measurement to assist diagnosis and treatment of patellofemoral instability. However, little is known about the distribution of TT-TG in osteoarthritic knees. The purpose of the current study is to investigate the TT-TG in a large cohort of osteoarthritic knees and to analyse, in particular, the association of knee alignment and TT-TG. METHODS: Data from 962 consecutive patients [455 male, 507 female; mean age ± SD 70.8 ± 9.3 (37-96)] who had undergone 3D-CT and preoperative knee planning with validated commercial 3D planning software before total knee arthroplasty (TKA) were collected prospectively. The TT-TG, coronal hip knee ankle angle (HKA), femoral anteversion (AVF), external tibial torsion (ETT), and femorotibial rotation (Rot FT) were analysed. Pearson correlations were performed to assess correlations between TT-TG, mechanical axis, and rotational parameters (p < 0.05). RESULTS: HKA showed a strong correlation with TT-TG (r = 0.488; p < 0.001) with 98 (67.1%) and 45 (30.8%) of valgus knees having respective abnormal and pathological TT-TG values. There were no significant correlations between parameters of rotational alignment (AVF, ETT, Rot FT) and TT-TG. Mean TT-TG was 12.9 ± 5.6 mm, ranging from 0.0 to 33.7 mm. 325 (33.8%) of all patients had abnormal (> 15 mm) and 101 (10.5%) had pathological (> 20 mm) values. A varus alignment was present in 716 (74.4%) of the cases (HKA < - 1.5°), a neutral alignment in 100 (10.4%), and a valgus alignment in 146 (15.2%) (HKA > 1.5°). CONCLUSION: A wide variation of TT-TG values in osteoarthritic knees was shown by our results. There was a relevant influence of coronal limb alignment on the TT-TG-the more valgus the higher and more pathological the TT-TG. With the aim of having a more personalised TKA, the individual TT-TG should be taken into account to improve the outcome. LEVEL OF CLINICAL EVIDENCE: III. Retrospective cohort study.