Objectives. It has been hypothesized that patellofemoral pain, a common knee condition in adolescents and young adults, may be a precursor of degenerative joint changes and may ultimately lead to patellofemoral osteoarthritis. Since both conditions share several mechanical disease characteristics, such as altered contact area between the femur and patella and increased joint stress, we investigated whether these conditions share similar and different shape characteristics of the patella compared with normal controls. Methods. This cross-sectional study compared three different study populations: 32 patellofemoral pain subjects (mean age, 32 years (22 to 45); 72% female); 56 isolated radiological patellofemoral osteoarthritis subjects (mean age, 54 years (44 to 58); 89% female); and 80 healthy control subjects (mean age, 52 years (44 to 58); 74% female). Measurements included questionnaires, and lateral and skyline radiographs of the knee. Two separate 30-point 2D statistical shape models of the patella were created from the lateral and skyline radiographs. A general linear model was used to test for differences in standardized shape modes (a specific shape variant of the patella) between patellofemoral osteoarthritis, patellofemoral pain, and controls, using Bonferroni correction and adjustment for body mass index and gender. Results. Five shape modes showed statistically significant differences between groups: skyline modes 1 (p < 0.001), 8 (p = 0.004), and 10 (p < 0.001); and lateral modes 5 (p = 0.002) and 7 (p = 0.002). Skyline mode 8 and lateral mode 5 were similar for patellofemoral osteoarthritis and patellofemoral pain populations, while being statistically significant different from the control group. Conclusion. Our results indicate that patellofemoral pain and patellofemoral osteoarthritis share similar shape characteristics, which are different from control subjects. These findings support the proposed continuum disease model of patellofemoral pain predisposing to the development of patellofemoral osteoarthritis. Cite this article: J. F. A. Eijkenboom, J. H. Waarsing, E. H. G. Oei, S. M. A. Bierma-Zeinstra, M. van Middelkoop. Is patellofemoral pain a precursor to osteoarthritis? Patellofemoral osteoarthritis and patellofemoral pain patients share aberrant patellar shape compared with healthy controls. Bone Joint Res 2018;7:541–547. DOI: 10.1302/2046-3758.79.BJR-2018-0112.R1

Our study aims were to establish correlations between the incidence of patellofemoral pain and clinical, functional and radiographic outcomes in Total Knee Arthroplasty (TKR), using the Duracon prosthesis without patella resurfacing. A consecutive cohort of 52 patients (71 knees) were reviewed at a special follow up clinic at a mean of 29 months. All operations were carried out by a single surgeon or under his direct supervision using a standard procedure. Patients were evaluated clinically and asked directly if they had anterior knee pain. American Knee Society Scores (AKSS) and knee alignment were assessed and patients completed SF-12 and WOMAC questionnaires. Standardised 45 degree skyline and standing lateral radiographs were taken and assessed by a single blinded observer, and patella tilt and displacement measured using Gomes’ method, and patella height measured using the Insall-Salvati ratio. Knees with patellofemoral pain underwent triple phase bone scintigraphy using Technetium 99m-MDP with vascular, blood pool and static (3 hour) imaging. Significant patellofemoral pain was identified in 8 knees (11%), in 6 patients. This group had a reduced mean AKSS compared to knees without patellofemoral pain, although 50% still had a good to excellent outcome as judged by the AKSS. Only 2 knees with patellofemoral pain had abnormal alignment (2 and 12 degrees valgus). The mean SF-12 and WOMAC scores did not differ significantly between knees with patellofemoral pain and those without. Patella tilt and displacement were a common finding in this cohort, and could be as great as 17 degrees and 30% respectively without patellofemoral dysfunction. Paradoxically the mean values for these parameters were found to be reduced in knees with patellofemoral pain. Patella height did not substantially vary between knees with patellofemoral pain and those without. Bone scintigraphy of 7 of the knees with patellofemoral pain revealed a spectrum of activity from complete normality (3 knees) to tricompartmental increase in activity (2 knees). Increased activity localised to the patellofemoral articulation was evident in 2 knees. We conclude that despite favourable overall results, the Duracon prosthesis fails to eliminate patellofemoral pain without patella resurfacing. This conflicts with excellent reported results using this anatomic prosthesis with patella resurfacing. The presence of patellofemoral pain correlates well with a poor AKKS, but the role of plain radiography and bone scintigraphy as investigative tools remains unclear

Aim. To determine differences in knee valgus angles produced during a single leg squat and hip muscle strength between healthy subjects and patients with patellofemoral pain (PFP). To determine correlations between variables of hip muscle strength, knee valgus angle and pain. Study design: Observational study of 20 (8 male 12 female) healthy (H) subjects, matched for age height and weight with 20 (8 male 12 female) PFP patients (mean symptom duration 46.75 weeks). All subjects fulfilled specific inclusion and exclusion criteria. Appropriate Ethical approval was obtained. Measures for both groups were Knee valgus angle during a single leg squat using 2D motion capture and SiliconCoach software for measurement of knee valgus angles, hip abduction, internal and external rotation muscle strength using hand held dynamometry, visual analogue scale for pain. Strength was reported as a percentage of body weight. All measures were taken on the affected leg for PFP subjects and matched for the equivalent leg in healthy group. SiliconCoach was determined to be reliable for intra-rater reliability of knee valgus angle (ICC.996). Results. There were no significant differences in age, height and weight (p=.59,.51,.26 respectively). Significant differences existed in hip abduction strength p=.001(PFP 19.93(9.2), H 32.22(8.26)), Hip internal rotation p=0.001 (PFP 12.94(4.35), H 19.53(6.36)), Hip external rotation p=0.001(PFP 10.00(3.07), H 16.26 (4.62)), Knee Valgus Angles p=0.001(PFP 5.31(2.59), H 2.29 (2.35)). No correlations existed between any of the variables including pain. This preliminary study shows that patients with PFP have larger knee valgus angles when doing a single leg squat and significantly weaker hip muscle strength when compared to healthy subjects. The reason for larger knee angles during single leg squat could be hypothesised as being due to weak hip abductor muscles not sufficiently controlling the alignment of the femur. However no correlations were found for these measures, nor were they found for any of the other variables including pain level. In summary the results indicate that hip musculature strengthening of the rotators and abductors and measures to reduce knee valgus angle should be included in the rehabilitation programme of patients with PFP. Further research with larger numbers of subjects should be developed to investigate this subject

Background: The role of frontal plane tibiofemoral alignment in subjects with patellofemoral pain syndrome (PFPS) is controversial and rarely discussed in the literature. As well, little research has been done on the effects of the hamstrings muscles on PFPS. The aim of the current study was to determine whether, in individuals with PFPS, frontal plane tibiofemoral alignment or muscular activity of the index knee’s crossing muscles is altered during maximum eccentric leg press exercise. Methods: This cross-sectional study involved 19 patients with PFPS and 19 control subjects who were matched according to gender, age, and physical activity. During eccentric leg press action, frontal plane tibiofemoral alignment was assessed with a motion analysis system based on skin markers. Simultaneously, surfaceelectro-myography was used to assess the activity levels of the relevant knee crossing muscles. To assess the activity under functional conditions, a leg press with a footplate having variable stability was used for barefoot testing. Findings: The PFPS subjects did not have significantly different frontal plane leg alignment compared to controls. On electromyography (EMG), PFPS patients had significantly lower levels of hamstring activity during eccentric leg exercise. The differences between the 2 groups (%; absolute differences normalized EMG) ranged from 19.57% (semitendinosus; stable footplate; p = 0.017) to 20.04% (biceps femoris; unstable foot-plate; p = 0.019) and 32.03% (semitendinosus; unstable footplate; p = 0.002). Interpretation: PFPS is not linked to altered frontal plane leg alignment during eccentric leg pressing. However, PFPS is associated with eccentric under-activation of the hamstrings, which may be a compensatory strategy that maintains patellofemoral joint pressure within bearable levels

Introduction. We have been re-evaluating patellofemoral alignment after total knee arthroplasty (TKA) by using a weight- bearing axial radiographic view after detecting patellar maltracking (lateral tilt > 5° or lateral subluxation > 5 mm) on standard non-weight-bearing axial radiographs. However, it is unclear whether the patellar component shape affects this evaluation method. Therefore, we compared 2 differently shaped components on weight-bearing axial radiographs. Methods. From 2004 to 2013, 408 TKAs were performed with the same type of posterior-stabilized total knee implant at our hospital. All patellae were resurfaced with an all-polyethylene, three-pegged component to restore original thickness. Regarding patellar component type, an 8-mm domed component was used when the patella was so thin that a 10-mm bone cut could not be performed. Otherwise, a 10-mm medialized patellar component was selected. Twenty-five knees of 25 patients, in whom patellar maltracking was noted on standard axial radiographs at the latest follow-up, were included in this study. Knees were divided into 2 groups: 15 knees received a medialized patella (group M) while 10 received a domed patella (group D). Weight-bearing axial radiographs with patients in the semi-squatting position were recorded with the method of Baldini et al. Patellar alignment (tilt and subluxation) was measured according to the method described by Gomes et al. using both standard and weight-bearing axial views. Results. Patients’ demographic data, such as age at surgery, sex, and disease were similar for both groups. The average follow-up period was significantly longer in group D than group M (5.4 years vs. 2.5 years, respectively; p = 0.0045, Mann- Whitney U-test). The lateral tilt angle decreased significantly (p < 0.0001, paired t-test) from 6.5° ± 2.8° to 1.0° ± 1.2° with weight bearing in group M. However, this parameter in group D changed from 6.7° ± 2.7° to 4.7° ± 3.0° with weight bearing; the difference was not significant. Lateral subluxation also decreased significantly (p < 0.0001, paired t-test) from 5.1 mm ± 2.4 mm to 2.5 mm ± 1.4 mm with weight bearing in group M. However, that in group D changed from 2.8 mm ± 2.7 mm to 2.4 mm ± 2.8 mm with weight bearing, and the difference was not significant. On weight-bearing views, patellar maltracking was noted in 4 knees in group D but no knees in group M. The difference was significant (p = 0.017, Fisher's exact test). One of the 21 patients with adequate patellar tracking (4.8%) and 1 of 4 patients with maltracking (25%) complained of mild anterior knee pain. Discussion. Patellar tracking on axial radiographic views improved better in group M than in group D with weight bearing. The patellofemoral contact area was maintained with a domed patella despite tilting, but not with a medialized patella. Our results indicate that the shape difference affected the degree of radiographic improvement. Thus, the weight-bearing axial radiographic view devised by Baldini et al. is useful for evaluating patellofemoral alignment after TKA, but the shape of the patellar component should be considered for result interpretation

Kinematics of the knee change during the full range of flexion [1]. The lateral femoral condyle (LFC) rolls back progressively through the entire range of flexion. The medial femoral condyle (MFC) does not move back during the first 110 degrees, but from 110 to 160 degrees it moves back by 10mm. This dual arc makes anatomical knee design a challenging task. In medial rotation, during flexion, the MFC stays in place, but the LFC moves forward in extension and backward in flexion. In lateral rotation the LFC stays still while the MFC moves back and forward in flexion and extension. During central rotation both condyles move reciprocally. However the knee is stable against an anteriorly or posteriorly directed force. It is important that all these degrees of freedom and stability are reproduced in total knee replacement (TKR) design. Furthermore, the two femoral condyles together form a spiral. Like the threads of a screw in a nut they allow medio-lateral translation of the femur [2] in the tibial reference frame. During flexion the knee centre moves laterally nearly 20% of the width of the tibial plateau and in extension the femur translates medially. This medio-lateral translation occurs in the natural normal knee joint. This has special significance in knee design because the natural femur (along with the trochlea) moves laterally in flexion, allowing the patella to be sited laterally, while most regular TKRs drive the patella medially. In order to test this anomaly we studied patellar maltracking in vivo and in cadavers. In vivo tracking studies using a patellar tracker during total knee replacement demonstrated average patellar maltracking of 10mm with regular TKR designs. Experiments on 22 cadaveric limbs using loaded quadriceps mechanism and trackers on the femur, tibia and patella, showed that in the natural knee the patella tracked medially by an average of 5mm. In regular TKRs the patella tracked medially. Compared to a normal knee, the patella in these designs maltracked on average by 10mm. Spiral condyles applied to the same bone cuts in the cadavers allowed the patella tracking to return to the expected lateral position in flexion. This has application to total knee replacement design. Unless the spiral design is incorporated in the condyles, patellar maltracking is inevitable and is likely to cause lateral knee pain and stiffness post-operatively

Each of the seven cuts required for a total knee arthroplasty has its own science, and can affect the outcome of surgery. Distal Femur. Sets the axial alignment (along with the tibial cut), and too little or too much depth affects ligament tension in extension. Anterior Femur. Sets the rotation of the femoral component, which affects patellar tracking. Internal rotation results in patellar maltracking. External rotation will either notch the femur, or cause too large a femoral component to be selected. Anterior and posterior femoral cuts also determine femoral component size selection. Too small a femoral component causes notching, flexion instability, and mismatch to the tibial component. Too big a femoral component causes overstuffing, periarticular pain, and patellar maltracking. Posterior Femur. Posterior referencing usually works, and the typical knee requires 3 degrees of external rotation to align with the transepicondylar axis. In valgus knees, there may be significant hypoplasia of the lateral femoral condyle, and posterior referencing has to be adjusted to avoid internal rotation. Posterior chamfer. A 4-in-one block saves time. Anterior chamfer. Deeper anterior chamfer allows a deeper trochlear groove, for patellar tracking. Tibia. Sets axial alignment with distal femoral cut. Posterior slope loosens flexion gap. Oversizing results in painful medial overhang. Lateral overhang usually not a problem. Undersizing results in inadequate bone support and subsidence. Patella. Inset or onset. Central peg associated with fracture. Err to medial and superior to assist tracking and avoid impingement on the tibial insert

Introduction. Fifteen percent of the primary total knee arthroplasties (TKA) fails within 20 years. Among the main causes for revision surgery are instability and patellofemoral pain. Currently, the diagnostic pathway requires various diagnostic techniques to reveal the original cause for the failed knee prosthesis and is therefore time consuming and inefficient. Accordingly, there is a growing demand for a diagnostic tool that is able to simultaneously visualize soft tissue structures, bone and TKA. Magnetic resonance imaging (MRI) is capable of visualising all the structures in the knee although a trade- off needs to be made between metal artefact reducing capacities and image quality. Low-field MRI (0.25T) results in less metal artefacts and a lower image quality compared with high-field MRI (1.5T). The aim of this study is to develop a MRI imaging guide to image the problematic TKA and to evaluate this guide by comparing low-field and high-field MRI on a case study. Method. Based on literature and current differential diagnostic pathways a guide to diagnose patellofemoral pain, instability, malposition and signs of infection or fracture with MRI was developed. Therefore, methods as Insall Salvati, patellar tilt angle and visibility of fluid and soft tissues were chosen. Visibility was scored on a VAS scale from 0 to 100mm (0mm zero visibility, 100mm excellent visibility). Subsequently, this guide is used to analyse MRI scans made of a volunteer (female, 61 years, right knee) with primary TKA (Biomet, Zimmer) in sagittal, coronal and transversal direction with a FSE PD metal artefact reducing (MAR) sequence (TE/TR 12/1030ms, slice thickness 4.0mm, FOV 260×260×120mm. 3. , matrix size 224×216) on low-field MRI (Esaote G-scan Brio, 0.25T) and with a FSE T. 1. -weighted high bandwidth MAR sequence (TE/TR 6/500ms, slice thickness 3.0mm, FOV 195×195×100mm. 3. , matrix size 320×224) on high-field MRI (Avanto 1.5T, Siemens). Scans were analysed three times by one observer and the intra observer reliability was calculated with a two-way random effects model intra class correlation coefficient (ICC). Results. Due to less metal artefacts on the low-field MRI scans the angle, distance and ratio measurements were more consistent: Insall Salvati low-field 0.97–0.99, Insall Salvati high-field 1.05–1.12, patellar tilt angle low-field 2.1–2.8°, patellar tilt angle high-field 2.4–7.6°. Over all, the VAS scores are higher on the high-field MRI scans; VAS medial collateral ligament high-field 26–45, VAS medial collateral ligament low-field 24–34, VAS popliteus tendon high-field 15–27, VAS popliteus tendon low-field 2–7. The ICC values of the VAS scores, angle measurements and ratio measurements were excellent, ICC > 0.9. The ICC values of the distance measurements were moderate, ICC > 0.6. Conclusion. MRI offers possibilities to simultaneously differentiate underlying causes of the failed knee prosthesis. The structures of interest were more clearly visible on the high-field MRI scans due to higher image contrast. The angle, distance and ratio measurements were more consistent on the low-field MRI scans due to less metal artefacts. Further research should focus on a larger group of patients with complaints after TKA to verify the analysis methods

Introduction. Tibial tuberosity and trochlear groove (TT-TG) distance has been investigated for the patients with primary patellofemoral subluxation/dislocation. To date, TT-TG distance after TKA has not been evaluated, and the effect of postoperative TT-TG distance on patellar tracking is unknown. The purpose of the current study was to investigate the effect of TT-TG distance and rotational position of the femoral and tibial components on patellar tilt after TKA. Methods. Consecutive 115 knees for the diagnosis of osteoarthritis were included in the current study. TKA was performed using posterior cruciate ligament sacrificed prosthesis. A total of 17 men and 96 women with an average age of 75.3 years were included at the time of the surgery. Computed tomography (CT) was taken after TKA in full extension. Postoperative TT-TG distance was measured as a reference of surgical epicondylar axis (SEA) of the femur. Patellar tilt was defined as the angle of the patellar component relative to SEA. Femoral and tibial component rotation was measured as the angle relative to SEA and tibial antero-posterior (AP) axis. Tibial AP axis was defined as the line connecting medial one-third of the tibial tuberosity and center of medial-lateral width. Pearson correlation coefficients were calculated to determine the correlations between patellar tilt and TT-TG distance and between patellar tilt and femoral and tibial component rotation. Results. TT-TG distance had significant correlation with patellar tilt (Figure 1; r = 0.254, p = 0.006), whereas femoral component rotation (p = 0.092) and tibial component rotation (p = 0.062) were not correlated with patellar tilt. Concerning the effect on TT-TG distance, femoral component rotation (r = 0.248, p = 0.008) and tibial component rotation (r = −0.567, p < 0.001) were correlated with TT-TG distance. Conclusion. The current study investigated the effect of TT-TG distance on patellar tilt with postoperative CT scan. Greater TT-TG distance resulted in more patellar tilt, which might have negative effects on patellar tracking. In previous clinical studies, femoral component and tibial component rotation affected patellar maltracking. In the current study, however, component rotation itself did not affect patellar tilt. Postoperative TT-TG distance includes information of rotational and medial-lateral positioning of the femoral and tibial components, and can be a useful indicator to predict patellar maltracking after TKA. For any figures or tables, please contact authors directly

Abstract. Objectives. Patella resurfacing in primary total knee arthroplasty (TKA) remains a contentious issue. Australian rates of patellar resurfacing are 66.6%, significantly higher compared to UK rates of 8–15% and Swedish rates of 2%. Resurfacing has gained popularity in Australia since registry data has shown decreased revision rates with no increase in patellar component related complications. We present for discussion an analysis of 113,694 total knee arthroplasties using commonly implanted prostheses in the UK. Methods. We included all TKA's since the Australian register's conception on 01/09/1999 for a primary diagnosis of osteoarthritis involving the use of either the Triathlon or Duracon implant with and without patellar components. The primary outcome of the study was time to revision for Triathlon's resurfaced and non-resurfaced prosthesis compared to the Duracon's equivalent data. We also analysed the reasons for revision between the 4 groups, type of revision and complication rates. We then compared minimally stabilised and posterior stabilised prostheses. Results. The cumulative revision rate for Triathlon prostheses with resurfacing after 12 years was 3.2% (95% CI, 2.9% to 3.6%) compared to 5.6% (95% CI, 5.0% to 6.2%) without resurfacing. Duracon's equivalent data was 6.3% with resurfacing and 5.9% without resurfacing. Triathlon prosthesis with resurfacing have much lower rates of revision due to loosening, patellofemoral pain, patellar erosion compared to unresurfaced Triathlon prostheses. Conclusion. Triathlon with re-surfacing has lower revision rates regardless of age or BMI. Previous concerns regarding patellofemoral loosening, tibial wear, maltracking relate to Duracon only, indicating the importance of implant specific studies. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

The October 2012 Knee Roundup. 360. looks at: autologous chondrocytes and chondromalacia patellae; drilling the femoral tunnel at ACL reconstruction; whether we repair the radially torn lateral meniscus; factors associated with patellofemoral pain; mechanoreceptors and the allografted ACL; whether high tibial osteotomy can delay the need for knee replacement; return to sport after ACL reconstruction; tissue-engineered cartilage; and the benefits of yoga

Objectives. Malrotation of the femoral component can result in post-operative complications in total knee arthroplasty (TKA), including patellar maltracking. Therefore, we used computational simulation to investigate the influence of femoral malrotation on contact stresses on the polyethylene (PE) insert and on the patellar button as well as on the forces on the collateral ligaments. Materials and Methods. Validated finite element (FE) models, for internal and external malrotations from 0° to 10° with regard to the neutral position, were developed to evaluate the effect of malrotation on the femoral component in TKA. Femoral malrotation in TKA on the knee joint was simulated in walking stance-phase gait and squat loading conditions. Results. Contact stress on the medial side of the PE insert increased with internal femoral malrotation and decreased with external femoral malrotation in both stance-phase gait and squat loading conditions. There was an opposite trend in the lateral side of the PE insert case. Contact stress on the patellar button increased with internal femoral malrotation and decreased with external femoral malrotation in both stance-phase gait and squat loading conditions. In particular, contact stress on the patellar button increased by 98% with internal malrotation of 10° in the squat loading condition. The force on the medial collateral ligament (MCL) and the lateral collateral ligament (LCL) increased with internal and external femoral malrotations, respectively. Conclusions. These findings provide support for orthopaedic surgeons to determine a more accurate femoral component alignment in order to reduce post-operative PE problems. Cite this article: K-T. Kang, Y-G. Koh, J. Son, O-R. Kwon, C. Baek, S. H. Jung, K. K. Park. Measuring the effect of femoral malrotation on knee joint biomechanics for total knee arthroplasty using computational simulation. Bone Joint Res 2016;5:552–559. DOI: 10.1302/2046-3758.511.BJR-2016-0107.R1

With the success of the medial parapatellar approach (MPA) to total knee arthroplasty (TKA), current research is aimed at reducing iatrogenic microneurovascular and soft tissues damage to the knee. In an effort to avoid disruption to the medial structures of the knee, we propose a novel quadriceps-sparing, subvastus lateralis approach (SLA) to TKA. The aim of the present study is to compare if a SLA can provide adequate exposure of the internal compartment of the knee while reducing soft tissue damage, compared to the MPA. Less disruption of these tissues could translate to better patient outcomes, such as reduced post-operative pain, increased range of motion, reduced instances of patellar maltracking or necrosis, and a shorter recovery time. To determine if adequate exposure could be achieved, the length of the skin incision and perimeter of surgical exposure was compared amongst 22 paired fresh-frozen cadaveric lower limbs (five females/six males) which underwent TKA using the SLA or MPA approach. Additionally, subjective observations which included the percent of visibility of the femoral condyles and tibial plateau, as well as the patellar tracking, were noted in order to qualify adequate exposure. All procedures were conducted by the same surgeon. Subsequently, to determine the extent of soft tissue damage associated with the approaches, an observational assessment of the dynamic and static structures of the knee was performed, in addition to an examination of the microneurovascular structures involved. Dynamic and static structures were assessed by measuring the extent of muscular and ligamentus damage during gross dissection of the internal compartment of the knee. Microneurovascular involvement was evaluated through a microscopic histological examination of the tissue harvested adjacent to the capsular incision. Comparison of the mean exposure perimeter and length of incision was not significantly different between the SLA and the MPA (p>0.05). In fact, on average, the SLA facilitated a 5 mm larger exposure perimeter to the internal compartment, with an 8 mm smaller incision, compared to the MPA, additional investigation is required to assert the clinical implications of these findings. Preliminary analysis of the total visibility of the femoral condyles were comparable between the SLA and MPA, though the tibial plateau visibility appears slightly reduced in the SLA. Analyses of differences in soft tissue damage are in progress. Adequate exposure to the internal compartment of the knee can be achieved using an incision of similar length when the SLA to TKA is performed, compared to the standard MPA. Future studies should evaluate the versatility of the SLA through an examination of specimens with a known degree of knee deformity (valgus or varus)

Purpose. To validate accuracy of transepicondylar axis as a reference for femoral component rotation in primary total knee arthroplasty. Methods. A prospective study done from dec 2010 to dec 2011 at tertiary centre. 80 knees were included (43 females and 21 males). All surgeries were carried out by one senior arthroplasty surgeon. All patients undergoing primary total knee replacement were included and all revision cases were excluded. Intraoperative assessment of TEA was done by palpating most prominent point on lateral epicondyle and sulcus on medial epicondyle and passing a k wire through it. Confirmation is done under image intensifier C arm with epicondylar view. Postoperative TEA was assessed by taking CT scan, measuring condylar twist angle and posterior condylar angle. Also correlation of femoral component rotation with postoperative anterior knee pain was assessed. Results. The mean PCA was around 4° with TEA as reference and only 10% patients required an additional lateral release of which 2% patient had preop patellar maltracking. No postoperative patellar maltracking was seen. Anterior knee pain was present in 8% patients. No postop infection is noted. Alignment ranging from 3° to 9° external rotation. Conclusion. TEA is most accurate reference for femoral component rotation even in severely deformed arthritic knees. Key words – Transepicondylar axis, total knee arthroplasty, femoral component rotation,

Purpose:. To compare accuracy of transepicondylar axis as a reference for femoral component rotation in primary navigated versus non navigated total knee arthroplasty in severely deformed knees. Methods:. A prospective study done from dec 2009 to dec 2011 at tertiary centre. 180 knees were included (124 females and 56 males). All cases were randomly allocated into 2 groups: navigated and non navigated. All surgeries were carried out by two senior arthroplasty surgeons. All patients undergoing primary total knee replacement were included and all revision cases were excluded. Intraoperative assessment of TEA was done by palpating most prominent point on lateral epicondyle and sulcus on medial epicondyle and passing a k wire through it. Confirmation is done under image intensifier C arm with epicondylar view in Non navigated knees. Postoperative TEA was assessed by taking CT scan, measuring condylar twist angle and posterior condylar angle (PCA). Results:. The mean PCA was around 4° with TEA as reference in Navigated and 6° in Non navigated knees and only 7% patients required an additional lateral release of which 2% patient had preop patellar maltracking. No postoperative patellar maltracking was seen. Anterior knee pain was present in 10% patients. No postop infection is noted. Alignment ranging from 4° to 8° external rotation. Conclusion:. Navigation is most accurate measure for TEA as reference, as compared to non navigated TKA, which can lead to excessive external rotation especially in severely deformed knees

Introduction. Patellofemoral pain and instability can be quantified by using the tibial tuberosity to trochlea groove (TT-TG) distance with more than or equal to 20mm considered pathological requiring surgical correction. Aim of this study is to determine if knee joint rotation angle is predictive of a pathological TT-TG. Methods. One hundred limbs were imaged from the pelvis to the foot using Computer Tomography (CT) scans in 50 patients with patellofemoral pain and instability. The TT-TG distance, femoral version, tibial torsion and knee joint rotation angle ((KJRA) were measured. Limbs were separated into pathological and non-pathological TT-TG. Significant differences in the measured angles between the pathological and non-pathological groups were estimated using the t test. The inter- and intraobserver variability of the measurement was performed. Logistic regression analysis was used to find the best combination of rotational angle predictors for a pathological TT-TG. Results. The intraclass correlation coefficients for inter- and intraobserver variability of the measured parameters was higher than 0.94 for all measurements. A statistically significant difference (P=0.024) was found between the KJRA between the pathological (mean=10.6, SD=7.79 degrees) and the non-pathological group (mean=6.99, SD=5.06 degrees). Logistic regression analysis showed that both femoral version (P=0.03, OR = 0.95) and KJRA (P=0.004, OR=1.15) were, in combination, significant predictors of an abnormal TT-TG. Tibial torsion was not a significant predictor. Conclusion. The KJRA can be used as an alternative measurement when the TT-TG distance cannot be measured as in cases of severe trochlea dysplasia and may act as a surrogate for pathological TT-TG

INTRODUCTION. Over the past 40 years of knee arthroplasty, significant advances have been made in the design of knee implants, resulting in high patient satisfaction. Patellar tracking has been central to improving the patient experience, with modern designs including an optimized Q-angle, deepened trochlear groove, and thin anterior flange.[1–4] Though many of today's femoral components are specific for the left and right sides, Total Joint Orthopedics’ (TJO) Klassic® Knee System features a universal design to achieve operating room efficiencies while providing all the advancements of a modern knee. The Klassic Femur achieves this through a patented double Q-angle to provide excellent patellar tracking whether implanted in the left or the right knee (Figure 1). The present study examines a prospective cohort of 145 consecutive TKA's performed using a modern universal femur and considers patients’ pre- and post-operative Knee Society Clinical Rating System score (KSS). METHODS AND MATERIALS. 145 primary total knee arthroplasties (TKA) were performed during the study using a measured resection technique with a slope-matching tibial cut for all patients. The posterior cruciate ligament (PCL) was sacrificed to accommodate an ultra-congruent polyethylene insert. The distal femur was cut at five degrees (5°) valgus; the tibia was resected neutral (0°) alignment for valgus legs and in two degrees (2°) of varus for varus alignment. The patella was resurfaced for all patients. Patients were followed annually for up to 46 months and were evaluated using the KSS score on a 200-point scale. RESULTS. The final study group comprised 127 primary TKAs. The average age was 68 years (51–90) with 45 males and 68 females. The average weight was 110kg (range: 75–151kg) for men and 88kg (range: 50–129kg) for women. One patient deceased during the follow-up period, four required manipulation under anesthesia, and two required revision for periprosthetic joint infection. There were no failures due to patellar maltracking. No special soft tissue releases were required in any patient. Average pre-operative knee score was 107, improving to 182 at average follow-up of 41 months (36–46 months). Results are summarized in Table 1. DISCUSSION. The improvement in patient clinical experience demonstrates that a universal femoral design can achieve excellent results if it incorporates modern technologies. A double Q-angle design with a deepened trochlear groove and a thin anterior flange appears to provide excellent patellar tracking for all patients in this cohort. This study is limited to the experience of a single institution. Further study would improve the extensibility of these findings. It does show, however, that a femur using a universal design with modern patellar tracking can improve patient satisfaction with their knee following TKA. For any figures or tables, please contact the authors directly

Treatment of the young patient with medial compartment arthritis and a PCL deficient knee is a complex problem. This study evaluates the efficacy of the anteromedial opening wedge osteotomy for PCL deficient knees with medial compartment degenerative changes. Eighteen patients have undergone an anteromedial opening wedge high tibial osteotomy for the PCL deficient varus knee. Patients were evaluated prospectively pre-operatively and at one and five years post surgery by visual analogue pain scores and patellofemoral pain scores, subjective IKDC, WOMAC and SF-36. Radiographic evaluation to determine correction in the coronal plane and the degree of slope increase was performed at one-year post surgery. All patients reported and improvement in PCL instability. There was a significant improvement in visual analogue pain and patellofemoral pain sc ores, subjective IKDC, WOMAC and SF-36 and overall knee function at one and five years. Patients with less severe arthritis at the time of surgery performed better at five years. This technique shows encouraging midterm results for a complex problem. Better results are obtained with less significant arthritis at the time of surgery

Patella recurrent dislocation and patellofemoral pain syndrome instability many young people and especially athletes. In the present study we present the results of the extension mechanism realignment through the Fulkerson oblique osteotomy of the tibial tuberosity and soft tissue balancing. During the last two years 10 patients (7 men, 3 women, mean age 29.3/ range 20–39) were treated operatively for recurrent dislocation of the patella using the Fulkerson procedure. All patients underwent knee arthroscopy for the treatment of potential chondral damage or loose bodies and for lateral retinacular release. After that we performed oblique tibial tuberosity osteotomy, medialization and internal fixation with 2 cortical screws. This oblique osteotomy allows also the anteriorization of tibial tuberosity as we move it medially. In addition, we performed medial placation. All the patients used functional knee brace locked to 0° right after the operation and with gradual ROM increase till the 8th p.o. week. The patients had no initial or long term complication. During their last follow up examination had a painless knee with full ROM and marked improvement of the patella tracking. The mean Lysholm score was 90.5. No patella dislocation was referred. Our findings show that the Fulkerson osteotomy procedure, with an additional intervention on the lateral and medial patella retinacular, is an excellent option for the treatment of recurrent patella instability and relief of the patellofemoral pain

Introduction. Instability, loosening, and patellofemoral pain belong to the main causes for revision of total knee arthroplasty (TKA). Currently, the diagnostic pathway requires various diagnostic techniques such as x-rays, CT or SPECT-CT to reveal the original cause for the failed knee prosthesis, but increase radiation exposure and fail to show soft-tissue structures around TKA. There is a growing demand for a diagnostic tool that is able to simultaneously visualize soft tissue structures, bone, and TKA without radiation exposure. MRI is capable of visualising all the structures in the knee although it is still disturbed by susceptibility artefacts caused by the metal implant. Low-field MRI (0.25T) results in less metal artefacts and offers the ability to visualize the knee in weight-bearing condition. Therefore, the aim of this study is to investigate the possibilities of low field MRI to image, the patellofemoral joint and the prosthesis to evaluate the knee joint in patients with and without complaints after TKA. Method. Ten patients, eight satisfied and two unsatisfied with their primary TKA, (NexGen posterior stabilized, BiometZimmer) were included. The patients were scanned in sagittal, coronal, and transversal direction on a low field MRI scanner (G-scan Brio, 0.25T, Esaote SpA, Italy) in weight-bearing and non-weight-bearing conditions with T1, T2 and PD-weighted metal artefact reducing sequences (TE/TR 12–72/1160–7060, slice thickness 4.0mm, FOV 260×260×120m. 3. , matrix size 224×216). Scans were analysed by two observers for:. - Patellofemoral joint: Caton-Descamps index and Tibial Tuberosity-Trochlear Groove (TT-TG) distance. - Prosthesis malalignment: femoral component rotation using the posterior condylar angle (PCA) and tibial rotation using the Berger angle. Significance of differences in parameters between weight-bearing and non-weight-bearing were calculated with the Wilcoxon rank test. To assess the reliability the inter and intra observer reliability was calculated with a two-way random effects model intra class correlation coefficient (ICC). The two unsatisfied patients underwent revision arthroplasty and intra-operative findings were compared with MRI findings. Results. In the satisfied group, a significant difference was found between TT-TG distance in non-weight-bearing and weight-bearing condition (p=0.018), with a good interrater reliability ICC=0.89. Furthermore, differences between weight-bearing and non-weight-bearing were found for the CD ratio, however, not significant (p=0.093), with a good interrater reliability ICC=0.89. The Berger angle could be measured with an excellent interrater reliability (ICC=0.94). The PCA was hard to assess with a poor interrater reliability (ICC=0.48). For one unsatisfied patient a deviation was found for tibial component rotation, according to the perioperative findings as, ‘malposition of the tibial component’. For the other unsatisfied patient revision surgery was performed due to aseptic loosening in which the MRI showed a notable amount of synovitis. Conclusion. It is possible to image the patellofemoral joint and knee prosthesis with low field MRI. Patellofemoral measurements and tibial component rotation measurements can reliably be performed. For the two patients with complaints MRI findings were consistent with intra-operative findings. Further research should focus on a larger group of patients with complaints after TKA to verify the diagnostic capacity of low field MRI for peri-prosthetic knee problems. For any figures or tables, please contact authors directly