Hip-knee Angle Research Articles

Visual Inspection for Lower Limb Malalignment Diagnosis Is Unreliable.

Visual inspection of the lower limb is often part of standard clinical practice during a physical examination at the outpatient clinic. This study aims to investigate how reliable visual inspections are in terms of detecting lower limb malalignments without additional tools and physical examinations. This study enrolled 50 patients. Each patient underwent a whole leg radiograph (WLR); in addition, a standardized digital photograph was taken of the lower limbs. Four persons (different experience levels) visually rated the digital photograph twice (unaware of the hip knee angle [HKA] on the WLR) and placed them in the category: severe valgus (>5°); moderate valgus (2°-5°); neutral, moderate varus (2°-5°); and severe varus (>5°). Visual ratings were compared with the measured HKA on WLRs for correlation using Spearman's rho. Linear ordinal regression models with significance when P < 0.05 were used to test whether body mass index (BMI), age, gender, and HKA were possible risk factors for incorrect visual HKA assessment. Spearman's rho between the visual assessment and measured HKA on the WLR was moderate with 0.478 (P < 0.01). Women had an increased odds ratio of 3.7 (P = 0.001) for incorrect visual assessment. Higher HKA also increased the odds ratio for erroneous visual assessment with 1.4 (P = 0.003). BMI and age did not significantly increase the odds of erroneous visual leg axis assessments in this study. Visual assessment of the lower limb alignment does not provide clinically relevant information. Lower limb malalignment diagnoses cannot be performed using only a visual inspection. Physical examination tests and radiographical assessments are advised. Diagnostic level II.

Coronal-plane leg alignment in adolescence and the effects of activity:A full leg length MRI study.

The aim of this study was to explore the association between developing coronal-plane leg alignment and activity levels during adolescence. We performed a cross-sectional cohort study with individuals from soccer club academies and an age-matched control population. Outcome measures were the hip knee angle (HKA), medial proximal tibial physeal angle (MPTPhyA), lateral distal femoral physeal angle (LDFPhyA) on full leg length magnetic reasonance imaginescans, and the physical activity questionnaire (PAQ) score. The cohort comprised 57 elite male soccer players, 34 male and 34 female controls aged 11-21 years. Mean HKA became more varus with age, with little change after 16 years or skeletal maturity. Skeletally mature elite male soccer players were significantly more varus than male controls with a HKA 2.28° less than male controls (p < 0.001). Skeletally mature male controls had a HKA 1.34°less than female controls (p < 0.001). A negative correlation existed between HKA and PAQ score (coefficient -0.24, p = 0.029). A positive correlation existed between HKA and MPTPhyA (coefficient 0.32, p = 0.008). In conclusion, high activity levels during adolescence are associated with the development of varus leg alignment. Mean HKA becomes more varus with age until skeletal maturity. The development of varus alignment may represent a physiological adaptation to load at the proximal tibial physis. Clinical Significance: A time period may exist for intervention before the development of varus leg alignment in young athletes, such as training load modification or proximal tibial morphology monitoring.

Total knee replacements using rotating hinge implants in polio patients: clinical and functional outcomes.

Little evidences are available in the literature concerning the outcomes of total knee replacement (TKR) in poliomyelitis patients with severe knee deformities or degeneration. Encouraging results have been reported concerning the use of constrained implants, i.e., rotating hinge knee prosthesis (RHK), compared to less constrained ones. The purpose of this paper is to report our experience with rotating hinge total knee replacement, using only RHK prosthesis, to determine functional results, complications, and survival of TKR in poliomyelitis patients. We performed a retrospective chart review of 14 patients with a history of knee osteoarthritis following poliomyelitis that underwent primary TKR, for a total of 15 surgical procedure (one bilateral case). Preoperative and postoperative clinical measurements have been conducted for all patients using the Knee Society Score (KSS). Hip-knee angle, recurvatum knee angle, and Insall-Salvati index were evaluated with full weight-bearing panoramic view X-ray preoperatively and postoperatively. The 2-year postoperative clinical KSS significantly improved from the preoperative scores. The average clinical KSS improved from 32,9 (range 3-48) preoperatively to 77,4 (range 60-88) postoperatively (P value < 0.005). The average functional KSS improved from 32,5 (range 10-60) preoperatively to 59,4 (range 30-95) postoperatively (P value < 0.005). TKR is a successful treatment in improving knee function and patient's quality of life. Using constrained implants, especially rotating hinge implants in polio patients with a quadriceps muscle weakness, could be a good alternative to maintain a physiological kinematics and reducing the revision rate due to knee instability.

Physeal-sparing ACL reconstruction provides better knee laxity restoration but similar clinical outcomes to partial transphyseal and complete transphyseal approaches in the pediatric population: a systematic review and meta-analysis.

The aim of this meta-analysis was to evaluate complete transphyseal (CTP), partial transphyseal (PTP), and physeal-sparing (PS) techniques for anterior cruciate ligament (ACL) reconstruction. A systematic literature search of the PubMed, Web of Science, Cochrane Library, and Scopus literature databases was performed on 10.05.2021. All human studies evaluating the outcomes of CTP, PTP, and PS techniques were included. The influence of the selected approach was evaluated in terms of rates of retears, return to previous level of sport competition, IKDC subjective and objective scores, Lysholm score, rate of normal Lachman and pivot-shift tests, limb length discrepancy, and hip-knee angle (HKA) deviation. Risk of bias and quality of evidence were assessed following the Downs and Black checklist. Forty-nine out of 425 retrieved studies (3260 patients) met the inclusion criteria. The results of the meta-analysis comparing CTP, PTP, and PS approaches for ACL reconstruction in the under 20-year-old population showed a significant difference in terms of differential laxity (CTP 1.98mm, PTP 1.69mm, PS 0.22mm, p < 0.001). No significant differences were seen in terms of growth malalignment, rate of normal Lachman and pivot-shift tests, and rate of normal/quasi-normal IKDC objective score. The present meta-analysis found overall similar results with the three ACL reconstruction approaches. The PS technique showed better results in terms of knee laxity than the PTP and CTP approaches, but this did not lead to a significant difference in terms of subjective and objective scores. No clear superiority of one technique over the others was found with respect to re-ruptures, growth disturbances, and axial deviations. While the argument for avoiding growth malalignment does not seem to be a crucial point, the PS technique should be the preferred approach in a young population to ensure knee laxity restoration. Level III.

Evaluation of postoperative orientation of the knee and ankle joint after open wedge high tibial osteotomy

BackgroundCases with varus knee osteoarthritis (OA) often present concomitant ankle joint deformity and poor tibial plafond inclination (TPI) in the coronal plane. Although changes to the TPI with respect to the ground after open wedge high tibial osteotomy (OWHTO) have been described, reports on the relationship between the correction angle and severity of knee joint line obliquity (KJLO) are scarce. This study aimed to examine the correlation between the correction angle after OWHTO and the change in knee and ankle inclination with respect to the floor. MethodsBetween January 2016 and December 2019, 39 knees in 39 patients (mean age, 58.3 ± 9.7 years; male, 14 knees; female, 25 knees) underwent OWHTO for varus knee OA. The mean duration of follow up was 30.1 ± 9.8 months. Radiological severity of OA was evaluated for those with Kellgren-Lawrence grade 1–3. Preoperative and 1-year postoperative radiographs were used to examine the postoperative femorotibial angle, hip-knee angle, KJLO, TPI, talar tilt (TT), position of weight bearing line of the tibial plateau width (WBL ratio; %), and the relationship between the pre-to postoperative changes in each measured value and intraoperative correction angle. The relationship between the pre-to postoperative changes in each measured value and intraoperative correction angle were evaluated. Clinical evaluations were conducted before and 2 years after OWHTO using the Knee Injury and Osteoarthritis Outcome Score (KOOS) subscale of pain. ResultsThe mean pre-to post-operative changes were 3.2 ± 2.2 for KJLO and 3.1 ± 2.5 for TPI, both demonstrating significant differences as well as significant correlations with the correction angle. The knee joint demonstrated postoperative changes in the valgus direction and none in the varus direction with respect to the floor in all cases. Furthermore, the sum of changes to the KJLO and TPI showed a positive correlation that approximates the change in the correction angle. The mean pre- and postoperative 2-year KOOS subscale of pain were 50.2 ± 10.2 and 82.3 ± 9.1. There were no correlations between preoperative TPI, pre-to postoperative change in TPI, and 2-year postoperative of KOOS subscale of pain. ConclusionFor those who underwent OWHTO for varus OA, the knee joint changed from a preoperative varus malalignment to mild valgus malalignment, and the ankle joint tended to improve from a preoperative valgus malalignment to the postoperative neutral alignment with respect to the floor. Although a positive correlation was found in which the correction angle approximates the sum of changes to the KJLO and TPI, no significant difference was found between changes in KJLO and TPI nor in the ratio between the correction angle and changes in each measured value.

No Correlation Between Clinical Outcomes and Changes in the Tibia-Metaphyseal Angle Following Total Knee Arthroplasty: A Retrospective Study

BackgroundDespite numerous advances in the implant design and surgical technique, improvement in patient satisfaction following total knee arthroplasty (TKA) has plateaued. Various TKA alignment strategies have been introduced that impact the coronal positioning of the tibial component relative to the native joint line. This study aims to analyze if postoperative variance of the joint line from preoperative native alignment is correlated with changes in patient-reported outcomes following primary TKA. MethodsA retrospective review of an academic center’s patient population identified all primary TKAs between 2013 and 2021 with full-length, standing radiographs and patient-reported outcome measures (PROMs) data. These measures included the Knee injury and Osteoarthritis Outcome Score for Joint Replacement, Patient-Reported Outcome Measurement Information System, and Veterans RAND 12 scores. Preoperative and postoperative radiographic measurements for hip-knee angle, tibia-metaphyseal angle, tibial-axis orientation angle, and joint-line obliquity angle were recorded. Three-month, 1-year, and 2-year PROM scores were correlated with the change in degrees for each of the angles using a Spearman’s correlation. A Mann-Whitney U-test was used to compare angular changes with a change in PROM scores. ResultsOne hundred and ninety nine patients (204 knees) with a mean age of 67 years were included. Average follow-up was 23 months. Three-month, 1-year, and 2-year follow-up rates were 93%, 64%, and 34%, respectively. Improvements were seen across all PROMs regardless of an angular change. ConclusionThere were no clear correlations between PROMs and variation in joint line obliquity in the coronal plane. These data suggest that the magnitude of the variation in coronal tibial alignment from native alignment does not impact PROMs. Further study is indicated to correlate an angular change with functional measures.

Continuous motion estimation of lower limbs based on deep belief networks and random forest.

Due to the lag problem of traditional sensor acquisition data, the following movement of exoskeleton robots can affect the comfort of the wearer and even the normal movement pattern of the wearer. In order to solve the problem of lag in exoskeleton motion control, this paper designs a continuous motion estimation method for lower limbs based on the human surface electromyographic (sEMG) signal and achieves the recognition of the motion intention of the wearer through a combination of the deep belief network (DBN) and random forest (RF) algorithm. First, the motion characteristics of human lower limbs are analyzed, and the hip-knee angle and sEMG signal related to lower limb motion are collected and extracted; then, the DBN is used in the dimensionality reduction of the sEMG signal feature values; finally, the motion intention of the wearer is predicted using the RF model optimized by the genetic algorithm. The experimental results show that the root mean square error of knee and hip prediction results of the combined algorithm proposed in this article improved by 0.2573° and 0.3375°, respectively, compared to the algorithm with dimensionality reduction by principal component analysis, and the single prediction time is 0.28 ms less than that before dimensionality reduction, provided that other conditions are exactly the same.

A new protocol for obtaining whole leg radiographs with excellent reproducibility

IntroductionWhole Leg Radiographs (WLR) are the gold standard for diagnosing malalignment and for pre-operative osteotomy planning. Positioning can affect the reproducibility of the measured hip knee angle (HKA), resulting in insufficient diagnostics and preoperative plans. We developed an easy-to-use WLR protocol by standardizing patient positioning and focusing on reproducibility. ObjectivesThis study aims on testing this reproducibility of the novel WLR protocol. MethodsThis study enrolled 30 patients for a test-retest analysis. Each patient underwent two bilateral WLRs on the same day using the investigated positioning protocol. Three observers measured the HKA, mechanical medial proximal tibial angle (mMPTA), mechanical lateral distal femoral angle (mLDFA), and joint line convergence angle (JLCA) on the two radiographs. Twice each, with one week between. ResultsThe intra-observer and inter-observer reliabilities were excellent, with intraclass correlation coefficients (ICCs) between 0.990 and 0.996. The ICCs between the measured HKA (0.985), mMPTA (0.922), and mLDFA (0.903) on the two separate radiographs were excellent. The ICC between the JLCA measured on the first and second WLR was moderate with 0.632. The mean absolute error between the HKA, mMPTA, mLDFA, and JLCA measurements on the first and second WLR were respectively: 0.442°, 0.783°, 0.828°, and 0.794°. ConclusionsThe investigated novel WLR positioning protocol produced excellent and reproducible HKA measurements, with clinically acceptable degrees of error. We recommend applying this easy-to-use protocol when obtaining WLRs for osteotomy planning. Physicians still need to be aware of possible rotational and fixed flexion deformities in the lower limb present on WLRs and during physical examination.

Can Hip-Knee Line Angle Distinguish the Size of Pelvic Incidence?-Development of Quick Noninvasive Assessment Tool for Pelvic Incidence Classification.

This study aimed to explore effective measurement angles for pelvic incidence (PI) classification and to develop a quick, noninvasive assessment tool for PI classification. We defined five variation types of hip–knee line (HKL) angles and tested the discrimination ability of the receiver operating characteristic (ROC) analysis using 125 photographs of upright standing posture from the right lateral side. ROC analysis revealed an applicable HKL angle defined by the line connecting the most raised part of the buttock and the central point of the knee and the midthigh line. The acceptable cut-off points for discriminating small or large PIs in terms of HKL angle were 18.5° for small PI (sensitivity, 0.91; specificity, 0.79) and 21.5° for large PI discrimination (sensitivity, 0.74; specificity, 0.72). In addition, we devised a quick noninvasive assessment tool for PI classification using the cut-offs of the HKL angle with a view to practical application. The results of intra- and inter-rater reliability ensured a substantial/moderate level of the tool (Cohen’s kappa coefficient, 0.79; Fleiss’s kappa coefficient, 0.50–0.54). These results revealed that the HKL angle can distinguish the size of the PI with a high/moderate discrimination ability. Furthermore, the tool indicated acceptable inter-/intra-rater reliability for practical applications.

Wide variation in tibial slopes and trochlear angles in the arthritic knee: a CT evaluation of 4116 pre-operative knees

As surgeons continue to grapple with persistent issues of patient dissatisfaction post-TKA, the literature has focused on the coronal plane when considering alignment strategies but has largely ignored the sagittal and axial planes. The purpose of this retrospective observational cohort study is to evaluate variability in knee anatomy and alignment beyond the coronal plane and rationalise how this relates to existing arthroplasty alignment philosophies. 4116 knee CTs from 360 Knee Systems© database of arthritic pre-operative TKA patients were evaluated. Standardised bony landmarks were used in each CT to determine the hip-knee angle, medial proximal tibial angle, lateral distal femoral angle, medial plateau posterior tibial slope, lateral plateau posterior tibial slope, trochlea angle (TA) to distal femoral angle (TA-DFA) and TA to posterior condylar angle (TA-PCA). Analysis was performed to determine the distributions of each measure across the cohort population. Both the medial and lateral PTS ranged from 5° anterior to 25° posterior. 22.6% of patients had differential PTS greater than 5°. 14.5% have greater lateral PTS (mean difference to medial PTS of 4.8° ± 5.0°), whilst 31.0% have greater medial PTS (mean difference to lateral PTS of 5.7° ± 3.2°). 14% of TA-DFAs and 5.2% of TA-PCAs vary greater than 10°. This study demonstrates a wide variation in tibial slope, differential slope between the medial and lateral tibial plateau as well as variation in the trochlear geometry. There has been an overemphasis in the literature on coronal alignment, ignoring the considerable variability present in tibial and patellofemoral morphology. Existing arthroplasty techniques are based on assumptions that may not adequately address the anatomy of morphologic outliers and could lead to dissatisfaction. III-retrospective cohort study.

Kinematic alignment in total knee arthroplasty.

The objective of kinematic alignment in total knee arthroplasty is to implant the prosthesis according to the individual joint line, leg axis and ligament tension. Knee osteoarthritis with failure of nonsurgical treatment according to current guidelines. Severe deformity or instability requiring aconstrained knee prosthesis. Necessity of intramedullary stems. Medial parapatellar approach to the knee. Resection of the cruciate ligaments, the meniscus and the osteophytes. Femur-first technique with distal resection of the femur, the intramedullary guide is only used for the extension/flexion positioning of the femoral component. The positioning in varus-valgus is orientated according to the native joint line after correction of chondral wear. The distal resection should be equal to the thickness of the prosthesis considering the chondral wear (up to 2 mm) and the thickness of the saw blade (1 mm). The rotation of the femoral component is set according to the posterior condylar axis under consideration of chondral wear. The amount of resected dorsal bone should correspond to the thickness of the dorsal condyles of the prosthesis. The alignment of the tibia is parallel to the individual joint line. This enables reconstruction of the individual physiological slope, rotation and the varus-valgus axis. Extension and flexion gap are controlled. Asymmetries between the lateral and medial joint space are corrected through avarus or valgus recut of the tibia as long as the surgical planning has not been achieved. The hip-knee angle is controlled; however, the aim in kinematic alignment is to reconstruct the individual axes and ligament tensions and not astraight leg axis. Persisting asymmetries in ligament tension are adjusted by classical soft tissue balancing techniques. Differences between the extension and flexion spaces are corrected by adapting the tibial slope. Release of the ligaments is usually not necessary; sometimes astripping of the dorsal capsule is performed. After the trial implantation, the original prosthesis is implanted. Functional rehabilitation with weight bearing as tolerated. Randomized studies showed abetter function in the Knee Society Score and abetter range of motion with kinematically aligned prostheses compared to mechanical alignment. Available meta-analyses also showed better results for kinematically aligned knees. The first mid-term results of this new technique with afollow-up of 10years show asurvival rate of 97.5% of the prosthesis.

Change of tibial tuberosity-trochlear groove (TT-TG) distance during total knee arthroplasty had no influence on clinical outcome and anterior knee pain

PurposeThe main purpose of this study was to determine whether there is a correlation between the change of tibial tuberosity-trochlear groove (TT-TG) distance and clinical outcomes after total knee arthroplasty (TKA).MethodsA total of 52 knees undergoing TKA due to primary osteoarthritis were included in this retrospective study. All patients had pre- and postoperative CT scans. TT-TG distance was measured by two independent observers and the following alignment parameters were measured: hip-knee ankle angle (HKA), femoral mechanical angle (FMA), tibial mechanical angle (TMA), and posterior condylar angle (PCA). Clinical outcome was assessed using Knee Society Score (KSS) pre- and post-operatively and at a minimum of 12-month follow-up. Evidence of AKP was noted from follow-up reports. Pre- and postoperative scores were compared using a paired Student t-test. Pearson correlations were calculated to assess the influence of TT-TG on clinical outcome and of alignment parameters on the change in TT-TG. TT-TG between patients with and without AKP was compared using unpaired Student’s t-test (p < 0.05).ResultsNeither the absolute postoperative TT-TG nor the amount of change in TT-TG correlated with the post-operative KSS or the change in KSS. Post-operative TT-TG and change in TT-TG did not differ significantly between patients with and patients without AKP. Only the change in FMA showed a correlation with the change in TT-TG (p = 0.01, r = 0.36).ConclusionDespite a missing correlation between outcomes and TT-TG distance in this study, excessive TT-TG distance should be avoided. Furthermore, surgeons need to be aware that changes in femoral joint line orientation might affect TT-TG distance.

Early experience using patient-specific instrumentation in opening wedge high tibial osteotomy

Patient-specific instruments (PSI) have been designed to improve the accuracy of performing opening-wedge high-tibial osteotomies (OW-HTO). This study aims to evaluate the lower limb alignment, by comparing pre-operative desired correction to post-operative achieved correction, the difference in surgical time and number of radiological exposures in OW-HTO using patient-specific instruments (PSI) versus conventional osteotomies and the specific and non-specific complications that occurred. We performed a single-centre, retrospective, observational study, including 25 consecutive patients undergoing OW-HTO using PSI, from January 2019 to October 2020. Pre-operatively, the mean hip-knee angle (HKA) was 167°, the mean tibial slope was 7.9° and the mean medial proximal tibial angle (MPTA) was 82.5°. Post-operatively, the mean HKA was 182.2° (180.1-184.7°), the tibial slope was 6.5° (4.2-12.9°) and the MPTA was 92.8° (90.6-93°). In both coronal and sagittal plane, all knees were within 2° from the planned value. The mean tourniquet time, by which the surgical time was measured, was 40 minutesand the average number of intra-operative fluoroscopic images was 10 (range: 7-14), significantly less than when using conventional techniques. The use of PSI in OW-HTO allows accurate achievement of the desired correction, while shortening the OR time. The number of radiological exposures is also decreased, in comparison with the conventional osteotomies.

Three-Dimensional-Printed Guiding Template for Unicompartmental Knee Arthroplasty.

Background For unicompartmental knee arthroplasty (UKA), accurate alignment of the limb is crucial. This study is aimed at investigating the efficacy and safety of a three-dimensional printed patient-customized guiding template (3DGT) for UKA. Methods A total of 22 patients receiving UKA were randomly divided into the 3DGT-UKA group (n = 11) and traditional UKA group (T-UKA group; n = 11). In the 3DGT-UKA group, the line and angle of osteotomy were decided on a 3D image of the limb reconstructed from imaging data; a guiding template was then designed and printed out. The patients in the T-UKA group underwent conventional UKA. Prosthesis size, operation time, postoperative drainage, hip–knee angle (HKA), pain, and Hospital for Special Surgery (HSS) scores were recorded at day 1, week 1, month 1, and month 3 after surgery. Results There was no significant difference in the size of prostheses between the preoperatively designed and actually used in the 3DGT-UKA group (p > 0.05). HKA was comparable in 3DGT-UKA and T-UKA patients. Operation time was shorter (53.6 ± 6.4 minutes vs. 75.8 ± 7.1 minutes) and wound drainage was less (93.2 ± 3.9 mL vs. 85.2 ± 3.0 mL) in 3DGT-UKA than in T-UKA (p < 0.05). Hospital stay was shorter in the 3DGT-UKA group. The 3DGT-UKA group had a lower VAS score on day 1, week 1, and month 1 and a higher HSS score on week 1 and month 1 after surgery. No varus/valgus deformity or prosthesis loosening was observed in either group at the final follow-up. Conclusion The 3D-printed patient-customized guiding template may help decrease operation time, decrease blood loss, and improve short-term clinical outcomes in patients undergoing UKA surgery.

CLINICAL AND RADIOLOGICAL RESULTS OF TOTAL KNEE REPLACEMENT USING PATIENT-SPECIFIC POSITIONING GUIDES WITH AT LEAST 5 YEARS OF FOLLOW-UP

Objective: Patient-specific positioning guides have been designed to improve precision in total knee arthroplasty. The aim of this study is to evaluate the medium-term clinical and radiological outcomes with magnetic resonance imaging-based patient-specific positioning guides. Material and methods: We retrospectively reviewed patients from two centers treated with total knee arthroplasty performed with patient-specific positioning guides. We enrolled patients operated on between January 2011 and December 2013, with a minimum follow-up of 5 years. Preoperative and postoperative hip knee angle (HKA) and position of each component in the coronal plane were assessed. Overall malalignment was defined as an outlier of more than [Formula: see text] from the neutral mechanical axis and specific malalignment as when any component showed more than [Formula: see text] of deviation. Clinical outcomes were evaluated using the Hospital for Special Surgery (HSS) knee Score. Results: This study included 68 patients with a mean age of 72 years. The mean postoperative alignment (HKA) was [Formula: see text] and 26.5% of patients showed coronal malalignment [Formula: see text]. Regarding femoral components, 19.1% showed specific malalignment [Formula: see text], while 11.7% of tibial components were classified as outliers. The mean HSS Knee Score at final follow up was 89.2. Patients whose implants were mechanically aligned did not obtain better functional outcomes ([Formula: see text]). Conclusion: In our series, the use of patient-specific positioning guides resulted in a range of mechanical malalignment, similar to conventional instrumentation results reported in the literature.

Leg-Length Change After Unilateral Unicompartmental Knee Arthroplasty in Varus Knee and Its Clinical Implications

BackgroundTo explore the magnitude of leg-length change after the unilateral index unicompartmental knee arthroplasty (UKA) in varus knee and its influence on clinical outcomes. MethodsA total of 114 patients with bilateral knee osteoarthritis who underwent unilateral UKA from June 2015 to June 2017 were included and followed up for at least 2 years. The leg length and hip-knee angle were measured on full-length standing films before and after the surgery. Flexion contracture was evaluated using a goniometer with the patient in the standing position preoperatively and postoperatively. Hospital for Special Surgery scores, perceived leg-length discrepancy (pLLD), the occurrence, and the time interval of subsequent contralateral knee arthroplasty were recorded and analyzed. ResultsThe average leg length increased after UKA was 9.39 ± 11.24 mm (range −21.00 to 33.79 mm), and 90 (78.9%) patients showed an increase in the leg length. 35 patients had LLD (defined as ≥10 mm), and 25 presented pLLD preoperatively; 25 patients had LLD, and 45 were suspected with pLLD postoperatively. At the last follow-up, 26 patients underwent subsequent contralateral knee arthroplasty. Postoperative LLD and pLLD were not associated with Hospital for Special Surgery scores of UKA but associated with subsequent contralateral knee arthroplasty. ConclusionsLLD and pLLD were common in patients both before and after UKA. Most patients showed leg lengthening after UKA. Postoperative LLD and pLLD were not associated with functional scores but associated with a subsequent contralateral knee arthroplasty.

CT-based patient-specific instrumentation for total knee arthroplasty in over 700 cases: single-use instruments are as accurate as standard instruments

PurposeEfforts in total knee arthroplasty are made to improve accuracy for a correct leg axis and reduce component malpositioning using patient-specific instruments. It was hypothesized that use of patient-specific instruments (vs. computer-navigated and conventional techniques) will reduce the number of outliers. Our second hypothesis was that single-use instrumentation will lead to the same accuracy compared to patient-specific instruments made of metal.Methods708 primary total knee arthroplasties between 2014 and 2018 using computer tomography (CT)-based patient-specific cutting block technique and a preoperative planning protocol were retrospectively reviewed. Preoperative data [hip–knee–angle (HKA), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), tibial slope, femoral component flexion] was compared to postoperative performed standard radiological follow-up X-rays. Differences of > 3° between measurements were defined as outliers.ResultsOverall 500 prostheses using standard instrumentation and 208 prostheses using single-use instruments were implanted. Preoperative HKA axes (− 1.2°; p < 0.001), femoral component flexion (Δ 0.8°, p < 0.001), LDFA (Δ − 1.5°, p < 0.001), MPTA (Δ − 0.5°, p < 0.001) and tibial posterior slopes (Δ 0.5°, p < 0.001), respectively, were different from postoperative axes. More outliers occurred using standard (vs. single-use) instruments (p < 0.001) regarding postoperative HKA (ranges of standard- vs. single-use: instruments: HKA 178.0°–180.5° vs. 178.0°–180.5°, femoral component flexion 0.0°–6.0° vs. 0.0°–4.5°, LDFA 90.0°–91.0° vs. 90.0°–90.0°, MPTA 90.0°–90.0° vs. 90.0°–90.0°, tibial posterior slope − 10° to 10° vs. − 1° to 10°). No differences were seen for other angles measured. Comparing both systems, total number of outliers was higher using standard (8%) vs. single-use instruments (4.3%).ConclusionThis study shows a high accuracy of CT-based patient-specific instrumentation concerning postoperative achieved knee angles and mechanical leg axes. Single-use instruments showed a similar accuracy.Level of evidenceIII.

Changes in knee joint line orientation after high tibial osteotomy are the result of adaptation of the lower limb to the new alignment

BackgroundChanges in knee joint line orientation (KJLO) resulting in excessive joint line obliquity are a well-known consequence of high tibial osteotomy (HTO) procedures and could lead to degenerative changes. The precise effect of the correction on final KJLO changes is poorly understood. The goal of this study was to identify radiographical parameters that could help to explain the size of KJLO changes after HTO surgery. MethodsA total 117 HTO patients were radiographically examined preoperatively and three months postoperatively. Radiographic parameters were KJLO, medial proximal tibial angle (MPTA), hip–knee angle (HKA), mechanical lateral distal femoral angle (mLDFA), lateral distal tibial angle (LDTA), knee joint line congruence angle (KJLCA), ankle joint line congruence angle (AJLCA) and ankle joint line orientation (AJLO). Four new radiographic parameters were introduced to describe knee and foot position on long-leg X-ray: malleolar distance to midline (MDTM), intermalleolar distance (IMD), condylar distance to midline (CDTM) and intercondylar distance (ICD). Correlations of these parameters and changes in KJLO were assessed. ResultsStrong correlations are found between KJLO changes and MDTM (r = 0.709), IMD (r = 0.691), CDTM (r = 0.711) and ICDM (r = 0.702), in contrast to weak correlations between changes in KJLO and MPTA (r = −0.342). These results suggest an important impact of foot and knee position changes on the final alteration of KJLO after HTO. ConclusionsThe final change of KJLO after HTO is the effect of adaptation of the lower limb, which is driven by the (maximum) alterations of foot and knee position rather than the size of correction of the procedure.

Contralateral preoperative templating of lower limbs' mechanical angles is a reasonable option.

In cases where the femur or tibia exhibits abnormal mechanical angulation due to degenerative changes or fracture, the contralateral leg is often used to complete preoperative templating. The aim of this study was to determine the degree of asymmetry between knee joints in healthy individuals and to determine whether it is affected by differing demographic parameters. A CT scan-based modelling and analysis system was used to examine the lower limb of 233 patients (102 males, 131 women; mean age 61.2 ± 15.2years, mean body mass index 24.9 ± 4.4kg/m2) The hip-knee angle (HKA), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), posterior proximal tibial angle (ppta) and posterior distal femoral angle (PDFA) were then calculated for each patient. Results were then analysed to calculate femoral symmetry based on absolute differences (AD) and percentage asymmetry (%AS) using a previously validated method. Our results do not demonstrate any considerable asymmetry (percentage of asymmetry > 2%) for all the anatomical parameters analysed: HKA (mean AD = 1.5°; mean AS% = 0.8, n.s), MPTA (AD = 1.1°; AS% = 1.3, n.s), PPTA (AD = 1.4°; AS% = 1.0, n.s), LDFA (AD = 1.2mm; AS% = 1.4, n.s) and PDFA (AD = 0.9°; AS% = 1.0, n.s). Gender and ethnicity were not associated with significantly higher AD asymmetry. A significant correlation of AD asymmetry was observed between BMI and HKA, BMI and MPTA, and between patients' age and the MPTA. This data demonstrate that there is a non-statistically significant mechanical angle asymmetry between the two lower limbs. In cases where contralateral templating is used, such asymmetry will induce minimal (if any) clinical differences. IV.

Relationship of the Posterior Condylar Line and the Transepicondylar Axis: A CT-Based Evaluation.

Posterior condylar referencing, a common method for determining femoral axial orientation during total knee arthroplasty (TKA), relies upon an assumed consistent relationship between the posterior condylar line (PCL) and the transepicondylar axis (TEA) of 3 degrees rotation. A total of 3,010 computed tomography (CT) scans and three-dimension (3D)-reconstructions for presurgical creation of patient-matched TKA instrumentation were analyzed. Demographic data and five anthropometric measurements (hip-knee angle [HKA], distal femoral angle [DFA], proximal tibial angle [PTA], tibial slope [TS], and PCL-TEA relationship) were recorded for each scan. A logistic regression model was fit to assess interaction between the PCL-TEA relationship and demographic and radiological variables. The mean (standard deviation [SD]) PCL-TEA was +2.9 degrees (0.8 degree). The range varied between +0.5 and +16.5 degrees. In 2,758 knees (91.6%), the PCL-TEA was within 3 ± 1 degrees, whereas 252 knees (8.4%) fell outside this range. There were no significant demographic or anthropometric differences between those knees with PCL-TEA relationship between 3 ± 1 degrees and those falling outside that range. The posterior condyles of diseased knees undergoing TKA can be reliably used to indirectly reference the TEA of the distal femur with an error of only 1 degree in 92% of patients.