Introduction. Genu valgum is a common presentation in paediatric patients with congenital limb deformities. The aim of this study is to assess the outcome of guided growth surgery in paediatric patients referred via our physiotherapy pathway with isolated genu valgum and associated patellar instability. Materials & Methods. Patients were identified from our prospective patellar instability database. Inclusion criteria was acquired or congenital genu valgum associated with patellar instability in skeletally immature patients. The mechanical lateral-distal femoral angle was assessed on long leg alignment radiographs (mLDFA <85 degrees). Surgical treatment was the placement of a guided growth plate (PediPlate, OrthoPediatrics, USA) on the medial distal femoral physis (hemi-epiphysiodesis). KOOS-child scores were collected pre-operatively and post-operatively (minimum at 6 months). Results. Eleven patients (seven female) with mean age of 12(range 5–15) were identified. Five patients had congenital talipes equinovarus(CTEV), one fibular hemimelia, one di-George syndrome, one septic growth arrest and three had idiopathic genu valgum. Pre- and post-operative KOOS-child scores showed overall improvement: 58(range 36–68) to 88(65–99) and knee symptoms subscores: 64(43–71) to 96(68–100) p<0.01, t-test. Mean follow-up was 10 months (range 3–23). No subsequent dislocations/subluxations occurred during follow-up. Conclusions. Guided growth surgery is an effective way of treating symptomatic patellar instability in skeletally immature patients with genu valgum in the absence of other structural pathology. It was most common in our cohort in patients with unilateral CTEV. We would recommend to screen syndromic and congenital limb deformity patients for patellar instability symptoms in the presence of genu valgum

Recurrent patellar instability is a common problem and there are multiple demographic and pathoanatomic risk factors that predispose patients to dislocating their patella. The most common of these is trochlear dysplasia. In cases of severe trochlear dysplasia associated with patellar instability, a sulcus deepening trochleoplasty combined with a medial patellofemoral ligament reconstruction (MPFLR) may be indicated. Unaddressed trochlear pathology has been associated with failure and poor post-operative outcomes after stabilization. The purpose of this study is to report the clinical outcome of patients having undergone a trochleoplasty and MPFLR for recurrent lateral patellofemoral instability in the setting of high-grade trochlear dysplasia at a mean of 2 years follow-up. A prospectively collected database was used to identify 46 patients (14 bilateral) who underwent a combined primary MPFLR and trochleoplasty for recurrent patellar instability with high-grade trochlear dysplasia between August 2013 and July 2021. A single surgeon performed a thin flap trochleoplasty using a lateral para-patellar approach with lateral retinaculum lengthening in all 60 cases. A tibial tubercle osteotomy (TTO) was performed concomitantly in seven knees (11.7%) and the MPFLR was performed with a gracilis tendon autograft in 22%, an allograft tendon in 27% and a quadriceps tendon autograft in 57% of cases. Patients were assessed post-operatively at three weeks and three, six, 12 and 24 months. The primary outcome was the Banff Patellar Instability Instrument 2.0 (BPII 2.0) and secondary outcomes were incidence of recurrent instability, complications and reoperations. The mean age was 22.2 years (range, 13 to 45), 76.7% of patients were female, the mean BMI was 25.03 and the prevalence of a positive Beighton score (>4/9) was 40%. The mean follow-up was 24.3 (range, 6 to 67.7) months and only one patient was lost to follow-up before one year post-operatively. The BPII 2.0 improved significantly from a mean of 27.3 pre-operatively to 61.1 at six months (p < 0 .01) and further slight improvement to a mean of 62.1 at 12 months and 65.6 at 24 months post-operatively. Only one patient (1.6%) experienced a single event of subluxation without frank dislocation at nine months. There were three reoperations (5%): one for removal of the TTO screws and prominent chondral nail, one for second-look arthroscopy for persistent J-sign and one for mechanical symptoms associated with overgrowth of a lateral condyle cartilage repair with a bioscaffold. There were no other complications. In this patient cohort, combined MPFLR and trochleoplasty for recurrent patellar instability with severe trochlear dysplasia led to significant improvement of patient reported outcome scores and no recurrence of patellar dislocation at a mean of 2 years. Furthermore, in this series the procedure demonstrated a low rate (5%) of complications and reoperations

A prospective study was done to assess the outcome of MPFL reconstruction for patellar instability using quadriceps graft. MPFL reconstruction was done using superficial strip of quadriceps by an anteromedial incision and attached close to medial epicondyle of femur. There were 15 knees in thirteen patients with a mean age of 23.4 years. All patients had MPFL reconstruction and 5 had tibial tuberosity transfers. With a mean follow-up of 39.4 (12–57) months, the mean pre-op Kujala scores improved from 47.8 to 87.2. The mean Lysholm scores improved from 54.2 to 86.8. None of the patients had patella re-dislocations. MPFL reconstruction with quadriceps graft appears to be effective producing good results in patients with patellar instability

Background. Patellar instability is a complex, multi-factorial disorder. Radiological assessment is regarded as an important part of the management of this population. The purpose of this study was to determine the intra- and inter-rater reliability of common radiological measurements used to evaluate patellar instability. Methods. One hundred and fifty x-rays from 51 individuals were reviewed by five reviewers: two orthopaedic trainees, a radiological trainee, a consultant radiologist and an orthopaedic physiotherapist. Radiological measurements assessed included patellar shape, sulcus angle, congruence angle, lateral patellofemoral angle (LPA), lateral patellar displacement (LPD), lateral displacement measurement (LDM), boss height, and patellar height ratios (Caton-Deschamps, Blackburne-Peel, Insall-Salvati). All assessors were provided with a summary document outlining the method of assessing each measurement. Bland-Altman analyses were adopted to assess intra- and inter-rater reliability. Results. The results indicated generally low measurement error on intra-rater reliability assessment, particularly for LPD (within-subject variance 0.7mm to 3.7mm), LDM (0.7mm to 3.5mm) and boss height (0.4mm to 1.6mm) for all assessors. There was greater measurement error for the calculation of sulcus angle (0.7° to 10.6°), congruence angle (0.8° to 18.4°) and LPA (0.8° to 16.5°). Whilst the inter-rater reliability between assessors indicated a low mean difference for assessments of patellar height measurements (0.0° to 0.6°), there was greater variability for LPA (0.1° to 3.6°), LPD (0.2mm to 4.6mm) and LDM (0.1mm to 4.0mm), with wide 95% limits of agreement for all measurements indicated poor precision. Conclusions. Many of the standard measurements used to assess the patellofemoral joint on plain radiographs have poor precision. Intra-rater reliability may be related to experience but it seems likely that to achieve good inter-rater reliability, specific training may be required to calibrate observers. More formal training in the technique of radiological measurement for those who were inexperienced might have improved the inter-rater reliability

Recurrent patellar instability is common in young and active patients. Medial patellofemoral ligament (MPFL) reconstruction with a single bundle hamstring graft is one method of surgical treatment for this problem. This is a retrospective case series of patients who underwent MPFL reconstruction by a single specialist knee surgeon between January 2009 and July 2014. Data was collected prospectively for the purpose of service evaluation. Recorded data included gender, age, length of rehabilitation, complications, Knee Injury and Outcome Score (KOOS) and International Knee Documentation Score (IKDC). Data is expressed as mean (range). 108 knees (103 patients) were identified (56 female, 52 male) with a mean age of 24.5 years (12–58). Mean length of rehabilitation was 3.2 months (0–11 months). Three patients required further revision surgery for recurrent instability. KOOS and IKDC scores improved from 44 (4–86) and 38 (2–81), respectively before surgery, to 77 (49–100) and 69 (37–95) after rehabilitation. MPFL reconstruction with a single bundle hamstring graft produces a marked improvement in knee function with a low recurrence of instability

Abnormal patella height has been found to be one of the main reasons for abnormal contact between patella and trochlear groove leading to patellar instability in children. Many methods have been described to diagnose patellar instability but most of them are justified only in adults. The reason being incomplete ossification in the paediatric population. These methods have been divided into direct and indirect methods. We analysed the MRI scan of knee of 57 children between 12–14 years of age with no previous diagnosis of patellar instability. Patients with a diagnosis of patellar instability, previous surgery on the knee or trauma and poor MRI scan were excluded from the study. We used Insall -Salvati Index (ISI), Caton-Deschamp Index (CDI) and Patella-Trochlear Index (PTI) and compared the results. We found that 40% of measurements by CDI and 41% by ISI showed patella alta in patients with normal patella height. 10% of patients in PTI readings had value suggestive of abnormal patella height. We concluded that PTI is a more reliable index to be used in children as it uses the length of articular surface and does not rely on bony landmarks. Studies done show PTI is a more reliable and accurate method of measuring patella height

Introduction. The most challenging aspect in rotational deformity correction is translating the pre-operative plan to an accurate intra-operative correction. Landmarks away from the osteotomy site are typically employed at pre-operative planning and this can render inadequate correction. Our proposed technique of pre-operative planning using CT scan and leg length radiographs can translate to accurate intra-operative correction. Materials and Methods. A circle was superimposed at osteotomy site with its centre serving as the centre of correction of rotation. Medio-lateral distance at osteotomy site measured and used as diameter of the circle. Circumference of the circle was calculated by multiplying diameter with Pi and used in the below formula to obtain accurate de-rotation distance;. Derotation distance = (Circumference/360) × correction value for desired ante-version. The exact site of osteotomy was measured in theatre under C-arm and exposed. Derotation distance was marked on the surface of bone as point A and point B with a flexible ruler. Osteotomy performed with saw and derotation was done till point A and point B were co-linear. Derotation distance obtained using this technique is specific for the site of chosen osteotomy and implies a specific degree of correction for every millimeter derotated. Distal femur was the chosen site of osteotomy if there was associated patellar instability and proximal femur if there was no patellar instability. Results. We have used the above technique to successfully correct rotational malalignment of femur and tibia in three patients thus far. The foot progression angle improved in all patients following surgery. One patient had post-operative CT scan of the hips which showed accurate reduction of ante-version. Conclusions. Our new technique of rotational deformity correction is simple and reproducible using commonly available tools as CT scan and leg length radiographs. This technique effectively translates the pre-operative plan to accurate intra-operative correction of rotational deformity

Abstract. Background. The primary objective of the study is to determine the function outcome and survivorship of patellofemoral replacement. The secondary aim is to find the determinants of successful/poor outcome. Methods. This retrospective study involved 45 patients who underwent AVON patellofemoral replacement between January 2015 to December 2020 with the minimal follow-up off for 12 months. The functional outcome was measured using Oxford Knee score (OKS), EuroQol five dimension (EQ-5D). IWANO and Kellgren-Lawrence classification was used to analyse radiographs. To identify determinants of outcome, the following subgroups the presence or absence of normal alignment, tibiofemoral arthritis, trochlear dysplasia and previous surgery. Complications and revision rates were also recorded. Results. The mean follow-up period was 41.7 +/− 8.3 months with no patients lost in follow-up. Patellofemoral replacement significantly improved the Oxford Knee score (OKS), EuroQol five dimension (EQ-5D) (p<0.001). Four out of 45(8.9%) patients underwent revision surgery. Patients with normal alignment preoperatively did worse than those with abnormal alignment with patellar instability. Patients with grade two tibiofemoral arthritis, history of previous surgery did significantly worse with poorer functional outcome. Conclusion. Patellofemoral arthroplasty is reliable treatment option which improves patient function and quality of life with good survivorship in isolated patellofemoral arthritis in mid-term follow-up

Malreduction of the syndesmosis is a poor prognosticator following ankle fracture and has been documented in as many as 52% of patients following fracture fixation. The current standard for assessment of reduction of the syndesmosis is bilateral computed tomography (CT) scan of the ankle. Multiple radiographic parameters are utilized to define malreduction, however, there has been limited investigation into the accuracy of these measurements to differentiate malreduction from inherent anatomical asymmetry. The purpose of this study was to identify the prevalence of positive malreduction standards within the syndesmosis of native, uninjured ankles. Bilateral lower extremity CT scans including ankles were screened. Studies were excluded if the patient was skeletally immature, had pathology below the knee or if they had congenital neuromuscular syndromes. The resulting cohort consisted of 207 patients. The indication for bilateral CT scan was femoral acetabular impingement in 110 patients (53%), rotation assessment following arthroplasty in 32 patients (15%), rotation assessment following femoral fracture in 30 patients (14%), rotational assessment for patellar instability in 30 patients (14%) and five miscellaneous indications (2%). Fifty patients were reviewed by three observers independently and to determine inter-observer reliability. A single observer repeated the measurements within the same cohort four weeks later to evaluate intra-observer reliability. Three observers then measured the anterior syndesmotic distance, posterior syndesmotic distance, central syndesmotic distance, fibular rotation and sagittal fibular translation at 1cm from the distal tibial articular surface. Overall side to side variability between the left and right ankle were assessed. Previously studied malreduction standards were evaluated. These included: anterior to posterior syndesmotic distance > 2mm, central syndesmotic difference > 1.5mm, average syndesmotic distance > 2mm, fibular rotational difference > 10o and sagittal translational difference > 2mm. The inter- and intra-observer reliability was good to excellent for anterior, posterior and central syndesmotic distance, and fibular rotation measurements. Sagittal fibular translation had an ICC of 0.583, and thus was only of fair reliability. Side to side comparison revealed statistically significant difference in only anterior syndesmotic difference (p=0.038). A difference of anterior to posterior syndesmotic distance of greater than 2mm was observed in 43 patients (20.2%). Thirty eight patients (17.8%) had a central syndesmotic difference of greater than 1.5mm. A fibular rotational difference of greater than 10o was observed in 49 patients (23%). The average difference between the anterior and posterior syndesmosis was greater than 2mm in 17 patients (8.2%). Nine patients (4.2%) had sagittal translation of greater than 2mm. Eighty one patients (39%) demonstrated at least one parameter beyond previously set standards for malreduction. Only one parameters was anomalous in 54 patients (26%), 18 patients (8%) had two positive parameters, while eight patients (4%) had three. One patient was asymmetrical in all measured parameters. In this study there was no statistically significant asymmetry between ankles. However, 39% of native syndesmoses would be classified as malreduced on CT scan using previously studied malreduction limits. Current radiographic parameters are not sufficient to differentiate mild inherent anatomical asymmetry from malreduction of the syndesmosis

Introduction. Epidemiologic studies indicate that isolated patellofemoral (PF) arthritis affects nearly 10% of the population over 40 years of age, with a predilection for females. A small percentage of patients with PF arthritis may require surgical intervention. Surgical options include non-arthroplasty procedures (arthroscopic debridement, tibial tubercle unloading procedures, cartilage restoration, and patellectomy), and patellofemoral or total knee arthroplasty (PFA or TKA). Historically, non-arthroplasty surgical treatment has provided inconsistent results, with short-term success rates of 60–70%, especially in patients with advanced arthritis. Although TKA provides reproducible results in patients with isolated PF arthritis, it may be undesirable for those interested in a more conservative, kinematic-preserving approach, particularly in younger patients, who may account for nearly 50% of patients undergoing surgery for PF arthritis. Due to these limitations, patellofemoral arthroplasty (PFA) has become utilised more frequently over the past two decades. Indications for PFA. The ideal candidate for PFA has isolated, non-inflammatory PF arthritis resulting in “anterior” pain and functional limitations. Pain should be retro- and/or peri-patellar and exacerbated by descending stairs/hills, sitting with the knee flexed, kneeling and standing from a seated position. There should be less pain when walking on level ground. Symptoms should be reproducible during physical examination with squatting and patellar inhibition testing. An abnormal Q-angle or J-sign indicate significant maltracking and/or dysplasia, particularly with a previous history of patellar dislocations. The presence of these findings may necessitate concomitant realignment surgery with PFA. Often, patients with PF arthritis will have significant quadriceps weakness, which should be treated with preoperative physical therapy to prevent prolonged postoperative pain and functional limitations. Tibiofemoral joint pain suggests additional pathology, which may not be amenable to PFA alone. Conclusion. PFA is effective for the treatment of arthritis localised to the PF compartment. Outcomes can be optimised with proper patient selection, meticulous surgical technique, and selection of an onlay-style implant that can be positioned perpendicular to the AP axis of the femur. Minimizing the risk of patellar instability by using onlay-design PFAs has enhanced mid- and long-term results, and leaves progressive tibiofemoral arthritis as the primary failure mechanism beyond 10–15 years

Patients with recurrent patella instability, who have an abnormal patellofemoral alignment (patella height or tibial tubercle-trochlear groove (TTTG) distance), benefit from tibial tubercle transfer along with medial patellofemoral ligament (MPFL) reconstruction. Between July 2008 and April 2013, 18 patients (21 knees) with recurrent patellar instability underwent combined MPFL reconstruction and tibial tubercle transfer. All patients had abnormal patellofemoral alignment in addition to MPFL insufficiency. 15 patients (16 knees) with a mean age of 24 years (16–41) had a mean follow up of 26 months (6–55). We assessed the outcome using KOOS, KUJALA, activity level and patient satisfaction scores. All patients had a stable patella. There was a significant improvement in outcome scores in 12 out of 15 patients. At final follow up KOOS score had improved from 68.25(44 to 93.9) to 77.05(48.8 to 96.4) and KUJALA score had improved from 63.3(41–88) to 78.06 (45 to 99). 9 patients showed excellent results and achieved at least a pre-injury level of activity. 4 of these had activity level better then preoperative level. 6 patients had a lower activity level than pre-injury (1 – ongoing physiotherapy, 1 – because of lack of confidence, and 4 – Life style modification). 14 patients were satisfied and happy to recommend this procedure. There were 3 postop complications, with 2 cases of stiffness and 1 case of non-union of the tibial tuberosity. Our prospective study has shown that restoration of tibial tubercle-trochlear groove index, Patella height and Medial Patellofemoral Ligament reconstruction yields good results in carefully selected patients

Clinical management of patellofemoral (PF) instability is a challenge, particularly considering the wide range of contributing variables that must be taken into consideration when determining optimal treatment. An important outcome measure to consider in this patient population is disease-specific quality of life (QOL). The purpose of this study was to factor analyse and reduce the total number of items in the Banff Patellar Instability Instrument (BPII). Subsequent to the factor analysis, the new, item-reduced BPII 2.0 was tested for validity, reliability and responsiveness. Disease-specific QOL was measured in patients with a confirmed diagnosis of PF instability (n = 223) at the initial consultation with the original BPII. Data from these BPII scores was used to employ a principal component analysis (PCA) to factor analyse and reduce the total number of items in the original BPII, to create the new BPII 2.0. The BPII 2.0 underwent content validation (Cronbach's Alpha, patient interviews and reading-level); construct validation (ANOVA comparing the initial consultation, 6, 12 and 24 month post-operative, Eta squared); convergent validation (Pearson r correlation to the original BPII); responsiveness testing (Eta squared, anchor-based distribution testing); and reliability testing (intra-class correlation coefficient (ICC) 2,k). The original BPII was successfully reduced from 32 to 23 items. The new BPII 2.0 demonstrated excellent Cronbach's Alpha values: initial consult = 0.91; 6-months = 0.96; 12-months = 0.97; and 24-months post-operative = 0.76. Grade-level reading assessment for all items in the BPII 2.0 was below grade twelve. The ANOVA determined the BPII 2.0 was able to discriminate between the initial consultation, 6, 12 and 24 months post-operative assessments, with significant differences between each time-point (p < 0.05). Eta squared was 0.40, demonstrating a medium to large effect size. Convergent validity was established with the BPII 2.0 significantly correlated to the original BPII (initial consult = 0.82, 6-month = 0.90, 12-month = 0.90, and 24-month = 0.94). Anchor-based responsiveness was established with a significant correlation between the 7-point scale of patient-perceived improvement and 24-month post-operative BPII 2.0 scores. Strong reliability was established with an ICC (2,k) = .97. The BPII has undergone a critical step in its psychometric and clinimetric evolution: structural validation. With the work completed in this study, the BPII and BPII 2.0 have completed assessment of seven of the nine Consensus-based Standards for the selection of health Measurement INstruments (COSMIN) properties including: 1) Internal consistency; 2) Reliability; 3) Standard error of measurement; 4) Content validation; 5) Structural validity; 6) Criterion validity; and, 7) Responsiveness testing. Completion of these assessments and the introduction of a structurally valid and shorter questionnaire, the BPII 2.0, provides a definitive level of credibility to this disease-specific outcome measure

Objective. The aim of this study was to evaluate the shape of patella relative to the femoral epicondylar axis and to find sex differences. Materials and methods. Computed tomography (CT) images of 100 knees with tibiofemoral osteoarthritis in 100 patients were prospectively collected. All patients were diagnosed as varus-type osteoarthritis with no destructive patellar deformity. Fifty patients were male and 50 female. The average male age was 70.8±14.6 (mean ± SD) years and the average female age was 73.3±6.7 years. Forty nine knees were right and 51 knees were left. The average height of males was 162.6±7.4 cm and that of females 149.6±5.7 cm. Males were significantly taller than females. The CT scan was performed with 2mm-interval slices in the vertical plane to the long axis of femoral shaft. Every CT image was examined to determine the maximum distance between the medial and lateral femoral epicondyle (inter-epicondylar distance, IED) along the epicondylar axis. The maximum patellar width and thickness were also measured at the image which had these maximum distances, while patellar cartilage thickness in anteroposterior diameter was not measured in this study. For evaluating the patellar size, each measured value was divided by IED and calculated each ratio. The ratio of patellar width to patellar thickness was also calculated. All parameters were compared between males and females. Statistical software Statview ver.5.0 (SAS Institute Inc.) was used for all analyses with significance being set at the 5% level. Results. Measured values are presented on Table 1. The average IED, patellar width and patellar thickness of males were all significantly larger than those of females. As shown in Table 2, by contrast, each ratio to IED was almost the same between the sexes and there were no significant differences. The ratio of patellar width to patellar thickness was 46.7±2.6% in males and 46.6±2.9% in females. Discussion. Although some studies have assessed the actual measurement values of patella, no prior study, to our knowledge, has morphologically evaluated the patella relative to the femur. This is the first study to investigate the configuration and location of patella relative to femoral epicondylar axis. Our results showed the configuration of patella relative to the femoral epicondylar axis was the same between sexes. The patellar width is approximately 56% and TGD is approximately 39% of IED. The most common complications after the surgery are related to patellofemoral problems. The ideal thickness of the resurfaced patella has not been clearly investigated. Patellar disabilities are associated with both decreased and increased patellar thickness— a thin patella could lead to anteroposterior patellar instability and a thick patella could increase the risk of stiffness of the knee and patellar subluxation. Therefore, it is desirable to restore the original patellar thickness during surgery. The results of current study showed that the ratio of patellar width to the patellar thickness was about 47%, which is useful to determine the thickness of patella during surgeries for severely damaged knees or revision surgeries

The aim of this study was to evaluate the functional and clinical outcome following medial patello-femoral ligament reconstruction using autogenous hamstring tendon grafts for patellar instability. Over a 4 year period the senior author operated on 35 patients for lateral instability of the patella. The predominant initiating event was a sporting injury. Each patient had either failed conservative management including physiotherapy, or failed surgical management including tibial tuberosity transfer. Post-operatively, all patients were allowed full flexion and extension. Sporting activity was restricted until 4-6 months post-operatively. Patients were evaluated clinically and functionally. The Fulkerson score was utilised pre- and post-operatively. The minimum follow-up was 6 months, the mean follow-up was 20 months. There were 18 males and 17 females. The mean age was 24.6 years. The mean pre-operative Fulkerson score was 59.3 (range 6-100). The mean post-operative Fulkerson score was 83.6 (range 25-100), the mean improvement was 24.3. 24 patients returned to sporting activities. The main complications were one patient with a patella fracture that was stabilised with internal fixation, one patient requiring exploration and reinforcing the ligament which had attenuated. Both patients finally had a good clinical outcome. Our study has shown that symptomatic lateral instability of the patella can be effectively treated with a medial patello-femoral ligament reconstruction and result in overall good clinical and functional outcome. We would recommend this technique

Purpose. Total knee arthroplasty (TKA) is the preferred treatment for those with end stage osteoarthritis (OA) and severe functional limitations. With the demographic transition in society, TKA is being offered to a younger patient population. Younger patients are generally more active requiring an increased range of motion, and place greater physiological demands on the prosthesis than typical older patients. The mobile bearing (MB) total knee prosthesis has theoretically been designed to meet these demands. We conducted a meta-analysis and systematic review of randomized controlled trials comparing outcomes of MB and fixed bearing (FB) TKA. Method. After testing for publication bias and heterogeneity, the data were aggregated by fixed effects modelling. Our searches identified 14 studies for reporting our primary outcome of Knee Society Scores (KSS). We also pooled data for post-operative range of motion (ROM) and Hospital for Special Surgery scores (HSS). Results. The standard difference in mean outcome scores for KSS and HSS demonstrated no difference between groups (p = 0.902, and p = 0.426 respectively). Similarly, the pooled data for ROM showed no difference between groups (p = 0.265). Conclusion. The results of our systematic review and meta-analysis of the literature indicate that there are no significant differences between MB and FB TKA in the outcome measures of KSS, ROM or HSS at final follow up. Only 3 of 12 studies found any benefit of MB knees in terms of patient reported pain. There were no differences found between FB and MB regarding patellar instability or stair climbing ability. Implant longevity remains the only outcome measure in which MB implants may provide an advantage

Introduction. Malrotation of the femoral component is a cause of patellofemoral maltracking after total knee arthroplasty. We have developed a balanced gap technique in posterior stabilized total knee arthroplasty using an original instrument. Patellar instability is associated with an increased the tibial tubercle and the center of the groove (TT-TG) distance > 20 mm, and TT-TG is regarded as one index of a factor influencing congruity. To assess the influence on a patellofemoral joint by a modified gap technique, the purpose of this study is to compare the TT-TG distance before surgery and after total knee arthroplasty. Material and Methods. We explored the 30 knees, 25 patients (4 male and 21 female), who underwent total knee arthroplasties (NexGen LPS-Flex, fixed surface, Zimmer; Warsaw, USA) for osteoarthritis or rheumatoid arthritis. All procedures were performed through a medial parapatellar approach and a balanced gap technique used a developed versatile tensor device. We compared the preoperative and postoperative CT at a knee flexion angle of 30 degrees. To assess the force vector of the extensor mechanism, TT-TG distance and the proximal-distal distance between the entrance of the tracheal groove and the tibial tubercle (ET-TT distance) were measured in CT. The relation of both distances (TT-TG index) that divided TT-TG in ET-TT was calculated, because the TT-TG distance was affected by the individual knee size. Three dimensional Q-angle (θ) was also calculated using TT-TG distance and ET-TT distance, sinθ = TT-TG distance/ET-TT distance. (Figure 1). Results. The mean TT-TG distance of the pre-operation and post-operation was 14.6 ± 4.9 mm and 12.4 ± 3.9 mm, respectively. The mean ET-TT distance of the pre-operation and post-operation was 68.5 ± 7.3 mm and 71.8 ± 7.5 mm, respectively. The mean TT-TG index of the pre-operation and post-operation was 0.22 ± 0.07 and 0.17 ± 0.05, respectively. The mean θ was 12.1 ± 3.96 degrees and 9.84 ± 2.98 degrees, respectively. There were statistically differences of between pre-operation and post-operation. Discussion. TT-TG distance, TT-TG index and the three dimensional Q angle decreased after total knee arthroplasty using the modified gap technique. These results indicated that patellofemoral joint was realigned and stabilized, and the force vector of the extensor mechanism was decreased by the modified gap technique

Total knee arthroplasty (TKA) has produced excellent results, but many surgeons are hesitant to perform TKA in younger patients with isolated patellofemoral arthritis. In properly selected patients, patellofemoral arthroplasty (PFA) is an effective procedure with good long-term results. Contemporary PFA prostheses have eliminated many of the patellar maltracking problems associated with older designs, and short-term results, as described here, are encouraging. Long-term outcome and prospective trials comparing TKA to PFA are needed. Incidence. Isolated patellofemoral arthritis occurs in as many as 11% of men and 24% of women older than age 55 years with symptomatic osteoarthritis (OA) of the knee; Isolated patellofemoral arthritis found in 9.2% of patients older than age 40 years; 7% to 19% of patients experience residual anterior knee pain when TKA is done for isolated patellofemoral arthritis. Imaging. Weight bearing AP radiographs as supine radiographs can underestimate the extent of tibiofemoral arthritis; Midflexion posteroanterior radiographs to rule out posterior condylar wear; Lateral radiographs to identify the presence or absence of patella alta or baja; Axial radiographs identify the presence of trochlear dysplasia, patellar tilt or subluxation, and extent of patellofemoral arthritis; Magnetic resonance imaging and arthroscopic photographs should be reviewed if available. Indications. Osteoarthritis limited to the patellofemoral joint; Symptoms affecting daily activity referable to patellofemoral joint degeneration unresponsive to lengthy nonoperative treatment; Posttraumatic osteoarthritis; Extensive Grade-III chondrosis; Failed extensor unloading surgical procedure; Patellofemoral malalignment/dysplasia-induced degeneration. Contraindications. No attempt at nonoperative care or to rule out other sources of pain; Arthritis of greater than Grade 1 involving tibiofemoral articulation; Systemic inflammatory arthropathy; Osteoarthritis/chondrosis of the patellofemoral joint of Grade 3 or less; Patella baja; Uncorrected patellofemoral instability or malalignment; Uncorrected tibiofemoral mechanical malalignment; Active infection; Evidence of chronic regional pain syndrome or evidence of psychogenic pain; Fixed loss of knee range of motion, minimum 10–110 degrees ROM. Results. Majority of failures related to patellar instability from uncorrected patellar malalignment, soft-tissue imbalance, or component malposition; With improved implant designs tibiofemoral arthritis has become the primary source of failure; Failure from component subsidence or loosening occurring in <1% of knees. Our Series. Retrospective review 34 patients, 40 knees average 30 month follow-up using Natural Knee II Patello-femoral Joint System (Zimmer, Warsaw, IN); Average age 61, ranging from 34–84 years of age; Average subset KOOS scores were 93 for pain, 94 for symptoms, 94 for ADL's, 70 for sports and recreation, 82 for quality of life; Average pre-operative Tegner score 2.6, increasing to 4.7 post-operatively; 38/40 survival over 30 months with the two failures undergoing revision for traumatic injuries; No revisions to TKA; At most recent follow-up no progression of OA to involve tibiofemoral compartments; No evidence of component loosening

Introduction. Malrotation of the femoral component is a cause of patellofemoral maltracking after TKA. Its precise effect on the patellofemoral (PF) mechanics has not been well quantified. The aim of this study was to investigate the effect of malrotation of the femoral component on PF initial contact area, initial contact pressure and wear after 4 million full gait cycles in TKA using a knee simulator. Moreover, the influence of the counterface material (CoCr or OxZr) on PF wear was also investigated. Materials & Methods. Femoral components (FCs) were cemented onto specially designed fixtures, allowing positioning of the FC in different angles of axial rotation. Patellar buttons and FCs were then mounted in a Prosim knee simulator. Patellofemoral contact mechanics. Seven axial rotation configurations were tested: neutral (FC parallel to the epicondylar axis), 2.5° endo- and exorotation, 5° endo- and exorotation and 7.5° endo- and exorotation. Patellar contact location, contact area and contact pressure were measured dynamically during 20 gait cycles with a Tekscan sensor covering the patella collecting data at a rate of 100 frames per second. Patellofemoral wear. For three alignments (neutral, 5° endo- and exorotation), a PF wear test of 4 million cycles in bovine serum (diluted to 40%) was done with three CoCr and three OxZr components on conventional ultra-high molecular weight polyethylene (UHMWPE, density: 0.93mg/mm. 3. ). Every 0.5 million cycles the test lubricant was replaced, the patellar samples were cleaned and dried and polyethylene wear was measured gravimetrically. A linear regression model was used to calculate the wear rate of each patellar sample. Aggregate wear rates were determined for each test condition by pooling the measurements of all three patellar samples. Results. For all six endorotation and exorotation configurations, the contact area was significantly lower and the contact pressure significantly higher than the neutral position (p < 0.001, Figs 1 and 2). In the patellofemoral wear test, the highest average wear rate was found in the group of endorotated CoCr femoral components (0.54 mm. 3. /Mcycle), but this is still only 11% of a typical tibiofemoral wear rate with the same CoCr component (5 mm. 3. /Mcycle). The following trends in the average wear rates could be observed: the average wear rate for CoCr (0.34 mm. 3. /Mcycle) was higher than for OxZr (0.19 mm. 3. /Mcycle) and the average wear rate for 5° endorotation (0.35 mm. 3. /Mcycle) was higher than for 5° exorotation (0.21 mm. 3. /Mcycle) and neutral alignment (0.23 mm. 3. /Mcycle) (Figs 3 and 4). None of these differences reached statistical significance (p=0.05), though. Discussion. Our results indicate that both internally and externally malrotated femoral components significantly decrease contact areas and significantly increase contact pressures in the patellofemoral joint. These significant changes in contact pressure didn't translate in significant changes in wear, however. Overall, patellofemoral wear is very small compared to tibiofemoral wear, in all the configurations that we investigated. Based on our results, we can conclude that clinical problems with patellar maltracking after femoral component malrotation seem not to be related to increased wear, but rather to pain and patellar instability