INTRODUCTION. During total knee arthroplasty (TKA), the pursuit of accurate alignment, proper bone cuts, and good soft tissue balancing sometimes can result in the overhang of the femoral component, especially in smaller-sized Asian knees. As size and shape of the distal femur are highly variable, component designs that offer increased shape and size offerings may be desirable to fit the distal femur. This study tested the hypothesis that increased shape and size offerings in TKA femoral designs may improve their fit to the Japanese femur compared to designs that offer only one shape and limited sizes. METHODS. Five contemporary femoral component designs were evaluated (Designs A-E). Design A has multiple mediolateral (ML) size offerings for a specific component anteroposterior (AP) size, and the finest increment (2mm) in AP sizes among all the designs. Designs B-E have single ML offerings across component AP sizes. For each design, virtual TKA resections were performed on the digital surfaces of 82 Japanese distal femora, each sized by selecting the component AP size that most closely matched but did not exceed the femoral AP dimension (Fig 1A,B). The aspect ratio (ML/AP) of the resected femora was regressed against the aspect ratio of their properly sized components per design. The closeness of each design to the perfect shape match was evaluated by the root-mean-square deviation (RMSD) of the deviations between the femoral bone and components. Differences in ML dimensions (overhang/underhang) between component and resected femora were calculated (Fig1C,D). The incidence of clinically significant femoral overhang (>3mm), in which component downsizing is required, were analyzed. RESULTS. Design A captured the shape variability in the resected femur, with component aspect ratios being the closest to the anatomy of the resected femur among the five designs (RMSD=0.04) (Fig 2). In contrast, Designs B-E had greater deviation from the shape of the resected femur (RMSD=0.08–0.12), indicating higher incidence of shape mismatch that may lead to surgical compromise. Designs C and E had the highest incidence and severity for clinically significant overhang, followed by Designs B and D (Fig 3A). Design A exhibited the lowest incidence and severity of clinically significant overhang and had the least variability in ML width differences (standard deviation=2.4mm) compared to the other designs (Designs B-E, standard deviation=4.0–4.9mm). In all the designs investigated, the percentage of bones that required downsizing was the highest in Designs C (48%) and E (39%), followed by Designs B and D (17% and 22%). In contrast, minimal downsizing was required in Design A (4%). The highest incidences of downsizing were generally observed in mid-sized components (Fig 3B). DISCUSSION. The design family with multiple ML offerings per AP size (Design A) provides the closest match to the shape of the distal femur compared to those with single ML offerings (Designs B-E). Additionally, increased AP size offerings in Design A (12 sizes) further improve component fit compared to Designs B-E (7–9 sizes). Among all five design families investigated, Design A exhibited minimal incidence of downsizing due to clinically significant overhang in the Japanese patients

Aims. The aticularis genu (AG) is the least substantial and deepest muscle of the anterior compartment of the thigh and of uncertain significance. The aim of the study was to describe the anatomy of AG in cadaveric specimens, to characterize the relevance of AG in pathological distal femur specimens, and to correlate the anatomy and pathology with preoperative magnetic resonance imaging (MRI) of AG. Methods. In 24 cadaveric specimens, AG was identified, photographed, measured, and dissected including neurovascular supply. In all, 35 resected distal femur specimens were examined. AG was photographed and measured and its utility as a surgical margin examined. Preoperative MRIs of these cases were retrospectively analyzed and assessed and its utility assessed as an anterior soft tissue margin in surgery. In all cadaveric specimens, AG was identified as a substantial structure, deep and separate to vastus itermedius (VI) and separated by a clear fascial plane with a discrete neurovascular supply. Mean length of AG was 16.1 cm ( ± 1.6 cm) origin anterior aspect distal third femur and insertion into suprapatellar bursa. In 32 of 35 pathological specimens, AG was identified (mean length 12.8 cm ( ± 0.6 cm)). Where AG was used as anterior cover in pathological specimens all surgical margins were clear of disease. Of these cases, preoperative MRI identified AG in 34 of 35 cases (mean length 8.8 cm ( ± 0.4 cm)). Results. AG was best visualized with T1-weighted axial images providing sufficient cover in 25 cases confirmed by pathological findings.These results demonstrate AG as a discrete and substantial muscle of the anterior compartment of the thigh, deep to VI and useful in providing anterior soft tissue margin in distal femoral resection in bone tumours. Conclusion. Preoperative assessment of cover by AG may be useful in predicting cases where AG can be dissected, sparing the remaining quadriceps muscle, and therefore function. Cite this article: Bone Joint Open 2020;1-9:585–593

Introduction & aims. Different racial groups show variations in femoral morphometry. Femoral anteroposterior measurement and mediolateral measurement are key variables in designing femoral implant for TKR. Their aspect ratio determines the shape and mediolateral sizing for the proper patellofemoral tracking and uniform stress distribution over the resected distal femoral surface. Method. We reviewed the current literature in December 2013 in common medical databases including the Cochrane Library, PubMed and Medline. Keywords included combinations of: Anthropometry, Knee, Arthroplasty, Femur, Morphometry, Geometry. We selected papers including femoral morphometric data collected from populations of different ethnic origins. Papers covered populations in the USA, China, Germany, Thailand, Korea, India, Japan and Malaysia. Results. We have analysed femoral morphometry variables among different ethnic groups from the available data. Gross size of the resected femur can be defined in terms of antero-posterior (AP) and medio-lateral (ML) dimensions, an in the aspect ratio of femoral medio-lateral to femoral antero-posterior dimensions (fML/fAP). The Korean population showed the least value of fAP among all the groups, followed by Thai, Japanese, Indian, Malaysian and Chinese showing the increasing order among the sub-groups of Asian Population. American population shows the next higher fAP measurements from Asian population. German follows, and Arab quantify the largest value of this femoral anthropometric variable. fML varies by huge difference among male and female data in all populations. Thai, Indian, Malaysian, Arab, Japanese, Korean, German, Chinese and American; this sequence is the increasing order of fML. More trapezoid-shaped and narrower ML, this variation in female group leads to over-hang the implant for a given fAP. Generally, the aspect ratios are measured higher in these smaller female knees, and lower in larger male knees. Conclusions. Anthropometric data measuring distal femoral segment in different ethnic groups shows that the Asian population requires custom-fit implant design based on the morphological data. It would be more appropriate to introduce several medio-lateral options in sizing the implant for given antero-posterior dimensions

Introduction. The primary purpose of Total Hip Arthroplasty (THA), aside from pain relief, is to restore hip biomechanics such that the patient experiences no discernible functional deficit, while also providing an environment conducive to implant longevity. Key factors in determining a successful THA include achieving the desired pre-operative femoral offset and leg length, as well as the restoration of range of motion (ROM). Minor leg length discrepancies (LLDs), less than a centimetre, are common after THA and usually well tolerated. However, in some patients, even these small discrepancies are a source of dissatisfaction. More significant discrepancies can be a risk factor for more serious concerns such as nerve injury, abnormal gait and chronic pain. The level of the femoral neck osteotomy is a critical step in reproducing a planned femoral stem position. Frequently the femoral osteotomy is too high and can lead to an increase in leg length and varus stem positioning. If the desired implant positions are identified from preoperative 3D templating, a planned femoral osteotomy can be used as a reference to recreate the correct leg length and offset. The aim of this study was assess the accuracy of a 3D printed patient-specific guide for delivering a pre-planned femoral neck osteotomy. Methodology. A consecutive series of 33 patients, from two surgeons at a single institution, were sent for Trinity OPS pre-operative planning (Optimized Ortho, Australia). Trinity OPS is a pre-operative, dynamic, patient-specific modelling system for acetabular and femoral implant positioning. The system requires a pre-operative CT scan which allows patient specific implant sizing as well as positioning. Once the preoperative implant positioning plan was confirmed by the surgeon, a patient-specific guide was designed and printed to enable the planned level of femoral neck osteotomy to be achieved, Fig 1. All patients received a Trinity cementless acetabular component (Corin, UK) and a cementless TriFit TS femoral component (Corin, UK) through a posterior approach. The achieved level of osteotomy was confirmed postoperatively by doing a 3D/2D registration, in the Mimics X-ray Module (Materialise, Belgium), of the planned 3D resected femur to the postoperative AP radiograph, Fig 2. The image was then scaled and the difference between the planned and achieved level of osteotomy was measured (imatri Medical, South Africa), Fig 2. Results. The mean absolute difference between the planned and achieved osteotomy level was 0.7mm (range 0.1mm − 6.6mm). Only 1 patient had a difference of more than 3mm, Fig 3. Of the 33 patients, 28 had a difference of less than 1mm. Conclusions. The results from this initial series of 33 patients suggest that a 3D printed patient-specific guide can be a simple and accurate way of intraoperatively reproducing a planned femoral neck osteotomy, though there was one significant outlier. Whether the 3D planning, patient-specific guide and accurate femoral osteotomy can then be used to achieve precise leg length and offset recreation is the subject of an on-going evaluation

Introduction:. Cam type femoroacetabular impingement (FAI) may lead to osteoarthritis (OA)[1]. In 2D studies, an alpha angle greater than 55° was considered abnormal however limitations of 2D alpha angle measurement have led to the development of 3D methods [2–4]. Failure to completely address the bony impingement lesions during surgery has been the most common reason for unsuccessful hip arthroscopy surgery [5]. Robotic technology has facilitated more accurate surgery in comparison to the conventional means. In this study we aim to assess the potential application of robotic technology in dealing with this technically challenging procedure of cam sculpting surgery. Methods:. CT scans of three patients' hips with severe cam deformity (A, B and C models) were obtained and used to construct 3D dry bone models. A 3D surgical plan was made in custom written software. Each 3D plan was imported into the Acrobot Sculptor robot and bone resection was carried out. In total, 42 femoral models were sculpted (14/subset), thirty of which were performed by a single operator and the remaining 12 femurs were resected by two other operators. CT of the pre/post resected specimens was segmented and a 3D alpha angle and head neck ratios were measured [3–4] and compared using Mann-Whitney U test. Coefficient of variation (CV) was used to determine the degree of variation between the mean and maximum observed alpha angles for inter and intra observer repeatability. Results:. The maximal alpha angle in cam A, B and C (90.8°, 91.3° and 87.1°). There was significant reduction (p < 0.001) in maximum alpha angles post-operatively within all three models when compared to original model (Figure 1). The HNRs for cam A, B and C prior to surgery were found to be 3.2, 3.4 and 3.1 respectively that were reduced to a mean of 3.0 ± 0.1, 3.1 ± 0.1 and 3.1 ± 0.0, following resection surgery. The results of the intra and inter-observer repeatability study found good reproducibility (CV<10%) of the maximum and mean alpha angles between the 12 resected femurs. Discussion:. In this study we evaluated the use of robotic system to perform cam correction surgery by evaluating the 3D morphology of head/neck prior to and post surgery. With existing surgical options there is a potential for under or over-resection of the cam lesion, which runs the risk of the need for further surgery or rarely neck fracture and dislocation. Based on the calculated alpha angles and HNRs we have proved that we have successfully performed the surgery by avoiding under and over resection respectively. Amore accurate bony resection performed here may minimize the complications due to over and under resection and hence will decrease the burden on the health service

Background. Most of contemporary total knee systems address on improving of range of motion and bearing materials. Although new total knee designs in most systems accommodated the knee morphology according to gender differences, reestablishing of the same anterior offset of the distal femur during total knee arthroplasty (TKA) has not been well addressed. Furthermore, in most total knee systems, the anterior offset of the femoral component is constant regardless of the increment of the femoral size. We hypothesized that change of the anterior offset of the distal femur during TKA might affect the quadriceps strength and immediate clinical outcomes which may result in improved design of the future femoral component. Purpose. To evaluate the peak quadriceps strength and immediate clinical outcomes related to the change of anterior offset of the distal femur during TKA. Materials & Methods. We prospectively evaluated 75 patients (75 knees) who had primary osteoarthritis and underwent an uncomplicated TKA. A measured-resection technique of surgery using a single design of semi-constrained posterior-stabilized prosthesis with patellar resurfacing was used in all knees. In every TKA, the patellar resection was quantified in order to provide a similar thickness of the patellar composite to the original patellar thickness. A uniform perioperative protocol was applied. The mean thickness from the medial and lateral sides of the resected anterior femur were evaluated and compared with the mean thickness of the anterior part of the femoral component. The peak quadriceps strength and peak hip flexor strength was evaluated before surgery, and then at 2 weeks, 6 weeks and 3 months, postoperatively, using a digital dynamometer. The Difference of thickness between the resected anterior femoral bone and the anterior femoral component was defined as the change of the anterior offset of the distal femur. Clinical outcomes, including Knee Society Scores (KSS) and Western Ontario and McMaster University Arthritis Index (WOMAC) scores at 2 weeks, 6 weeks and 12 weeks were evaluated in relation of muscle strengths. Results. Patients were divided in 2 groups according to the change of the anterior offset of the distal femur during TKA. Thirty knees (group A) had similar or increased anterior offset of the distal femur and 45 knees (group B) had decreased anterior offset of the distal femur. The mean thickness of the resected anterior femoral bones in group A and B were 4.8 mm and 9.7 mm, respectively. The mean changes of anterior offset in group A and B were (+)0.7 mm and (−)4.2 mm with statistical difference (p, 0.01). There were no differences in patient's demographic data including age, sex, and body mass index (BMI). Preoperatively, both groups had similar mean peak quadriceps strength (108.04 N vs.115.52 N, p, 0.191) and mean peak hip flexor strength (105.98 N vs.108.05 N, p.0.745). At 2-week follow-up (FU), group A had significantly better peak quadriceps strength (111.53 N vs. 99.75 N, p, 0.03) and improve of total WOMAC score (32.4 points vs. 27.4 points, p, 0.03) than those of group B, The improved WOMAC score was statistical significant in subgroup of function (16.7 points vs. 12.7, p, 0.04) However, the peak hip flexor strength, KSS clinical scores and function scores were not different. At 6-week FU 12-week FU, there were no differences in all measuring parameters. Discussion and Conclusion. Biomechanical study has shown that the anterior offset of the distal femur provides role as a lever arm for a proper quadriceps function. Therefore, with maintaining of the patellar thickness during TKA in individual patient, a constant thickness of the anterior offset of the femoral component regardless of size may result in change of the anterior offset of the distal femur and may affect the function of quadriceps. The present study demonstrated that, at 2 weeks postoperatively, patients who had increased anterior offset of the distal femur could significantly gain better peak quadriceps strength and improved WOMAC function score than those who did not. In addition, change of anterior offset of the distal femur had no relation with the peak hip flexor strength. A mean 4.2-mm decreasing of anterior offset of the distal femur during TKA caused a shorter lever arm to the quadriceps and resulted in reducing the peak quadriceps strength with no gross effect on hip flexor strength. Although peak quadriceps strength in patients who had increased anterior offset of distal femur correlated with improved WOMAC function score, this marginal statistical significance provided a very short time for advantages. As there was a similar or slightly increased of anterior femoral offset in Group A, the anterior overstuff should be very minimal. At 6 weeks and 12 weeks after surgery, we found that investigated parameters, as well as clinical outcomes, were not different in both groups. We concluded that the change of femoral offset during TKA provided a short effect on quadriceps strength and clinical outcomes for few weeks which had no clinical impact on the drive to improve the prosthetic design of the femoral component which has a constant thickness of the anterior offset