Abstract. Background. Conventional TKR aims for neutral mechanical alignment which may result in a smaller lateral distal femoral condyle resection than the implant thickness. We aim to explore the mismatch between implant thickness and bone resection using 3D planning software used for Patient Specific Instrumentation (PSI) TKR. Methods. This is a retrospective anatomical study from pre-operative MRI 3D models for PSI TKR. Cartilage mapping allowed us to recreate the native anatomy, enabling us to quantify the mismatch between the distal lateral femoral condyle resection and the implant thickness. Results. We modelled 292 knees from PSI TKR performed between 2012 and 2015. There were 225 varus knees and 67 valgus knees, with mean supine hip-knee-angle of 5.6±3.1 degrees and 3.6±4.6 degrees, respectively. In varus knees, the mean cartilage loss from medial and lateral femoral condyle was 2.3±0.7mm and 1.1±0.8mm respectively; the mean overstuffing of the lateral condyle 1.9±2.2mm. In valgus knees, the mean cartilage loss from medial and lateral condyle was 1.4±0.8mm and 1.5±0.9mm respectively; the mean overstuffing of the lateral condyle was 4.1±1.9mm. Conclusions. Neutral alignment TKR often results in overstuffing of the lateral condyle. This may increase the patello-femoral pressure at the lateral facet in flexion. Anterior knee pain may be persistent even after patellar resurfacing due to tight lateral retinacular structures. An alternative method of alignment such as anatomic alignment may minimise this problem

Introduction. Oriental people habitually adopt formal sitting and squatting postures, the extreme flexion of the knees allowing of this. The influence exercised by pressure and posture are, therefore, found at the posterior side of knee joint. However, we don't have many report about articular cartilage of posterior femoral condyle. Objectives. The purpose of this study was to reveal the accurate prevalence and related factors to the presence of degenerative changing of the articular cartilage of posterior femoral condyle in cadaveric knee joints. Methods. One hundred and thirty two knees from 66 cadavers (42 male knees and 24 female knees, formalin fixed, Japanese anatomical specimens) were included in this study. The average age of the cadavers was 81.4 (56–101) years. Knees were macroscopically evaluated the depth of cartilage degeneration of the patellofemoral joint, medial and lateral femoral condyle, medial and lateral posterior femoral condyle following the Outerbridge's classification. Grading was as follows: Grade 1: normal cartilage or softening and swelling of the cartilage. Grade 2: partial-thickness defect which did not reach the subchondral bone and was less than 1.3 cm in diameter. Grade 3: partial-thickness defect which did not reach the subchondral bone and was more than 1.3 cm in diameter. Grade 4: exposed subchondral bone and visible reactive tissue formation. When there were multiple lesions of different Outerbridge's classification grades, the sizes of the lesions were added up. Lesions with degenerative changes more severe than Outerbridge's classification grade 3 were regarded as OA lesions. Statistical analysis was performed to reveal the correlation between the occurrences of cartilage degeneration of medial and lateral posterior femoral condyle and medial and lateral femoral condyle and gender. Results. The prevalence of OA-positive was 48.5% (64 knees). Analyzing in the prevalence in gender, male was 31% (26 knees) OA-positive, female was 79.2% (38knees) OA-positive. The frequency of OA-positive was significantly higher in females than in males (P < 0.001). The prevalence of OA-positive in posterior condyle was 53.1% (34 knees) in 64 knees of OA-positive. Analyzing in the prevalence in gender, male was 15.4% (4 knees) in 26 knees of OA-positive, female was 78.4% (30knees) in 38 knees of OA-positive. The frequency of OA-positive in posterior condyle was significantly higher in females than in males (P < 0.001). Conclusions. In this study, the prevalence of OA-positive in posterior condyle was evaluated in cadaveric knees. The prevalence of OA-positive in posterior condyle was 53.1% in OA-positive knees, and was significantly correlated with the gender

Juvenile Osteochondritis dissecans (JOCD) in humans and subchondral cystic lesions (SCL) in horses (also termed radiolucencies) share similarities: they develop in skeletally immature individuals at the same location in the medial femoral condyle (MFC) and their etiology is only partially understood but trauma is suspected to be involved. JOCD is relatively uncommon in people whereas SCLs arise in 6% of young horses leading to lameness. Ischemic chondronecrosis is speculated to have a role in both osteochondrosis and SCL pathogenesis. We hypothesize that MFC radiolucencies develop very early in life following a focal internal trauma to the osteochondral junction. Our aims were to characterize early MFC radioluciencies in foals from 0 to 2 years old. Distal femurs (n=182) from Thoroughbred horses (n=91, 0–2 years old), presented for post-mortem examination for reasons unrelated to this study, were collected. Radiographs and clinical tomodensitometry were performed to identify lesions defined as a focal delay of ossification. Micro-tomodensitometry (m-CT) and histology was then performed on the MFCs (CT lesions and age-matched subset of controls). Images were constructed in 3D. The thawed condyles, following fixation, were sectioned within the region of interest, determined by CT lesion sites. Hematoxylin eosin phloxin and safran (HEPS) and Martius-Scarlet-Blue (MSB) stains were performed. Histological parameters assessed included presence of chondronecrosis, fibrin, fibroplasia and osteochondral fracture. An additional subset of CT control (lesion-free) MFCs (less 6 months old) were studied to identify early chondronecrosis lesions distant from the osteochondral junction. One MFC in clinical CT triages controls had a small lesion on m-CT and was placed in the lesion group. All m-CT and histologic lesions (n=23) had a focal delay of ossification located in the same site, a weight bearing area on craniomedial condyle. The youngest specimen with lesions was less than 2 months old. On m-CT 3D image analysis, the lesions seemed to progressively move in a craniolateral to caudomedial direction with advancing age and development. Seventy-four percent (n=17/23) of the lesions had bone-cartilage separation (considered to be osteochondral fractures) confirmed by the identification of fibrin/clot on MSB stains, representing an acute focal bleed. Fibroplasia, indicating chronicity, was also identified (74%, n=17/23). In four cases, the chondrocytes in the adjacent cartilage were healthy and no chondronecrosis was identified in any sections in the lesions. Nineteen cases had chondronecrosis and always on the surface adjacent to the bone, at the osteochondral junction. None of the subset of control specimens, less than 6 months old (n=44), had chondronecrosis within the growth cartilage. Early subchondral cystic lesions of the medial femoral condyle may arise secondary to focal internal trauma at the osteochondral junction. The presence of fibrin/clot is compatible with a recent focal bleed in the lesion. Medial femorotibial joint internal forces related to geometry could be the cause of repetitive trauma and lesion progression. In the juvenile horse, and potentially humans, the early diagnosis of MFC lesions and rest during the susceptible period may reduce progression and promote healing by prevention of repetitive trauma, but requires further study

Full thickness cartilage defects of the femoral condyles are frequent, can be highly symptomatic, and pose treatment challenges when encountered in middle-aged patients. A history of biological repair procedures is frequent and patient management is complex in order to delay joint replacement procedures in active patients. Focal metallic resurfacing provides a joint preserving bridging procedure with a clinical exit into primary arthroplasty. Methods. This study presents a review of several multicenter investigations exploring the clinical benefits and validity of focal resurfacing in 78 patients, ages 35–67, with a follow-up ranging from 2 to 6 years. All patients were treated with a 15 or 20 mm contoured resurfacing implant on the medial or lateral femoral condyle. Results. At 2 years follow up, average scores for WOMAC domains improved by over 100% (40 preop to 86 postop where 100 = best). At 3 year follow-up KOOS scores were within 88 to 102% of a normal aged matched population (domain range 72–91 where 100 = best). At a minimum of 5 years, the KOOS domains were close to normative reference levels on pain relief, symptoms, and activities of daily living (range 83–89% of normal). Radiographic results demonstrated solid fixation, preservation of joint space, and no change in the osteoarthritic stage. Conclusion. The procedure adds a new layer to reconstructive treatment options in the long-term management of knee arthrosis and arthritis and allows for a clinical alternative to lifestyle changes required by many patients who failed cartilage procedures and continue to have an isolated symptomatic defect precluding them from joint arthroplasty

Introduction:. Unicompartmental knee arthroplasty has been shown to have lower morbidity, quicker rehabilitation and more normal kinematics compared to conventional TKA, but subchondral defects, or severe osteoarthritic changes, of the medial compartment may complicate component positioning. Successful UKA in these patients requires proper planning and exact placement of the components to ensure adequate and stable fixation and proper postoperative kinematics. This study presents a series of three patients with spontaneous osteonecrosis of the knee receiving a UKA with CT-based haptic robotic guidance. Methods:. This series includes two females and one male with spontaneous osteonecrosis of the medial femoral condyle who underwent outpatient mini-incision medial UKA using the MAKO Surgical Rio Robotic Arm System. Pre-operatively all patients were found to have pain with weight bearing that would not improve despite non-arthroplasty treatment. Results:. The first patient was a 69 year old female (BMI of 22.85) with a left medial femur size 3, tibia size 4, bearing size 4×8 mm. The patient improved her ROM from 3–112° pre-operatively to 0–130° at 18 months post-operatively. The second patient was a 69 year old female (BMI of 25.68) with a right medial size 2 femur and 3 tibia and a 3×9 mm bearing. ROM increased from 0–120° pre-operatively to 0–145° at 2 year follow-up. The third patient was a 74 year old male (BMI of 26.5) who underwent previous knee arthroscopy with subsequent SPONK. Conclusion:. The difficulty in treatment of SPONK with UKA solutions includes planning for the full coverage of the ON lesions while also addressing alignment, tracking and balancing needs simultaneously. Using the advanced planning tools of the MAKO Rio software, full coverage of ON lesions can be safely planned and verified preoperatively. The intraoperative flexibility of the system allows surgeon to map out the lesions intraoperatively, where visible, and aid in the proper implant positioning and size adjustment as necessary

Background

High tibial osteotomy is a common procedure to treat symptomatic osteoarthritis of the medial compartment of the knee with varus alignment. This is achieved by overcorrecting the varus alignment to 2–6° of valgus. Various high tibial osteotomy techniques are currently used to this end. Common procedures are medial opening wedge and lateral closing wedge tibial osteotomies. The lateral closing wedge technique is a primary stable correction with a high rate of consolidation, but has the disadvantage of bone loss and change in tibial condylar offset. The medial opening wedge technique does not result in any bone loss but needs to be fixated with a plate and may cause tibial slope and medial collateral ligament tightening.

Knee arthroscopy is typically approached from the anterior, posteromedial and posterolateral portals. Access to the posterior compartments through these portals can cause iatrogenic cartilage damage and create difficulties in viewing the structures of the posterior compartments. The purpose of this study was to assess the feasibility of needle arthroscopy using direct posterior portals as both working and visualising portals. For workability, the needle scope was inserted advanced from anterior between the cruciate ligament bundle and the lateral wall of the medial femoral condyle until the posterior compartments were visualised. For visualisation, direct postero-lateral and -medial portals were established. The technique was performed in 9 knees by two experienced researchers. Workability and instrumentation of the posteromedial compartment and meniscus was achieved in 56%. The posterior horns could not be visualised in four specimens as the straight lens could not provide a more medial field of view. Visualisation from the direct medial posterior portal allowed a clear view of the medial meniscus, femoral condyle and posterior cruciate ligament in all specimens. Workability and instrumentation of the posterolateral compartment was not possible with the needle scope. Direct posterior approaches for the posteromedial compartment access are challenging with the current needle scope options and could only be achieved in over 50%. The postero-lateral compartment was not accessible. An angled lens or a flexible Needle scope would be better suited for developing this technique further

This study was performed at Assiut University, Assiut, Egypt. Anterior distal femoral hemiepiphysiodesis (ADFH) using intra-articular plates for the correction of paediatric fixed knee flexion deformities (FKFD) has two main documented complications: postoperative knee pain and implant loosening. This study describes a biomechanical analysis and a preliminary report of a novel extra-articular technique for ADFH. Sixteen femoral sawbones were osteotomized at the level of the distal femoral physis and fixed by rail frames to allow linear distraction simulating longitudinal growth. Each sawbone was tested twice: first using the conventional technique with medial and lateral parapatellar eight plates (group A) and then with the plates inserted in the proposed novel location at the most anterior part of the medial and lateral surfaces of the femoral condyles with screws in the coronal plane (group B). Gradual distraction was performed, and the resulting angular correction was measured. Strain gauges were attached to the plates, and the amount of strain (and equivalent stress) over the plates was recorded. This technique was then applied to 9 paediatric FKFDs of different aetiologies. The preoperative FKFD and the amount of subsequent angular correction were measured. The amount of angular correction was higher in group B at 5, 10-, and 15-mm of distraction (p<0.001). The maximum and overall stresses measured throughout the distraction process were higher in group A (p<0.001). The mean FKFD improved from 24 ± 9° preoperatively to 9 ± 7° after 10 ± 3° months (p<0.001). The correction rate was 1.81 ± 0.65° per month. During ADFH, the fixation of the eight plates in the coronal plane at the anterior part of the femoral condyles may produce greater correction and lower stresses over the implants as compared to the conventional technique. Preliminary results from our initial series seem to support the effectiveness of this technique with respect to the degree of angular correction achieved

Objectives. Articular cartilage damage is a primary outcome of pre-clinical and clinical studies evaluating meniscal and cartilage repair or replacement techniques. Recent studies have quantitatively characterized India Ink stained cartilage damage through light reflectance and the application of local or global thresholds. We develop a method for the quantitative characterisation of inked cartilage damage with improved generalisation capability, and compare its performance to the threshold-based baseline approach against gold standard labels. Methods. The Trainable WEKA Segmentation (TWS) tool (Arganda-Carreras et al., 2017) available in Fiji (Rueden et al., 2017) was used to train two separate Random Forest classifiers to automatically segment cartilage damage on ink stained cadaveric ovine stifle joints. Gold standard labels were manually annotated for the training, validation and test datasets for each of the femoral and tibial classifiers. Each dataset included a sample of medial and lateral femoral condyles and tibial plateaus from various stifle joints, selected to ensure no overlap across datasets according to ovine identifier. Training was performed on the training data with the TWS tool using edge, texture and noise reduction filters selected for their suitability and performance. The two trained classifiers were then applied to the validation data to output damage probability maps, on which a threshold value was calibrated. Model predictions on the unseen test set were evaluated against the gold standard labels using the Dice Similarity Coefficient (DSC) – an overlap-based metric, and compared with results for the baseline global threshold approach applied in Fiji as shown in Figures 1 and 2. Results. Test set results for the global threshold approach against gold standard labels were 45.0% DSC for the femoral condyle and 32.0% DSC for the tibial plateau. Results for the developed TWS classifiers on the same unseen test data were 79.0% and 72.7% DSC, showing absolute gains of 34.0% and 40.7% DSC over the global threshold baseline for the femoral and tibial classifiers. The trained TWS classifiers were then applied to an external set of unlabelled images of ink stained femoral condyles and tibial plateaus. Model results on sample images shown in Figure 3 further highlight the generalisation capability of the developed models. The most prominent classification features were Hessian filters (32.9%), Entropy (19.4%), Gaussian blur (10.1%), Gabor filters (6.3%) and Sobel filters (6.0%), with all other features contributing less than 6%. Conclusions. Our findings show that the developed segmentation method more accurately quantifies cartilage damage and provides improved generalisation capability over a range of input variations such as inconsistent orientation and lighting conditions. The developed model enables the use of articular cartilage damage as a reliable and quantitative outcome measure in studies involving large datasets, with reduced requirements for complex pre-processing and specialised equipment. For any figures or tables, please contact the authors directly

Large cartilage lesions in younger patients can be treated by fresh osteochondral allograft transplantation, a surgical technique that relies on stable initial fixation and a minimum chondrocyte viability of 70% in the donor tissue to be successful. The Missouri Osteochondral Allograft Preservation System (MOPS) may extend the time when stored osteochondral tissues remain viable. This study aimed to provide an independent evaluation of MOPS storage by evaluating chondrocyte viability, chondrocyte metabolism, and the cartilage extracellular matrix using an ovine model. Femoral condyles from twelve female Arcott sheep (6 years, 70 ± 15 kg) were assigned to storage times of 0 (control), 14, 28, or 56 days. Sheep were assigned to standard of care [SOC, Lactated Ringer's solution, cefazolin (1 g/L), bacitracin (50,000 U/L), 4°C storage] or MOPS [proprietary media, 22-25°C storage]. Samples underwent weekly media changes. Chondrocyte viability was assessed using Calcein AM/Ethidium Homodimer and reported as percent live cells and viable cell density (VCD). Metabolism was evaluated with the Alamar blue assay and reported as Relative Fluorescent Units (RFU)/mg. Electromechanical properties were measured with the Arthro-BST, a device used to non-destructively compress cartilage and calculate a quantitative parameter (QP) that is inversely proportional to stiffness. Proteoglycan content was quantified using the dimethylmethylene blue assay of digested cartilage and distribution visualized by Safranin-O/Fast Green staining of histological sections. A two-way ANOVA and Tukey's post hoc were performed. Compared to controls, MOPS samples had fewer live cells (p=0.0002) and lower VCD (p=0.0004) after 56 days of storage, while SOC samples had fewer live cells (p=0.0004, 28 days; p=0.0002, 56 days) and lower VCD (p=0.0002, 28 days; p=0.0001, 56 days) after both 28 and 56 days (Table 1). At 14 days, the percentage of viable cells in SOC samples were statistically the same as controls but VCD was lower (p=0.0197). Cell metabolism in MOPS samples remained the same over the study duration but SOC had lower RFU/mg after 28 (p=0.0005) and 56 (p=0.0001) days in storage compared to controls. These data show that MOPS maintained viability up to 28 days yet metabolism was sustained for 56 days, suggesting that the conditions provided by MOPS storage allowed fewer cells to achieve the same metabolic levels as fresh cartilage. Electromechanical QP measurements revealed no differences between storage methods at any individual time point. QP data could not be used to interpret changes over time because a mix of medial and lateral condyles were used and they have intrinsically different properties. Proteoglycan content in MOPS samples remained the same over time but SOC was significantly lower after 56 days (p=0.0086) compared to controls. Safranin-O/Fast Green showed proteoglycan diminished gradually beginning at the articular surface and progressing towards bone in SOC samples, while MOPS maintained proteoglycan over the study duration (Figure 1). MOPS exhibited superior viability, metabolic activity and proteoglycan retention compared to SOC, but did not maintain viability for 56 days. Elucidating the effects of prolonged MOPS storage on cartilage properties supports efforts to increase the supply of fresh osteochondral allografts for clinical use. For any figures or tables, please contact the authors directly

INTRODUCTION. In living normal knee the lateral femoral condyle rolls posteriorly more than the medial side to the extent that in deep flexion the lateral femoral condyle sublux from the tibial surface (Nakagawa et al). The purpose of this presentation is to study the tibiofemoral movement in patients who had full flexion after total knee replacements and to compare it with that of normal knee. MATERIALS AND METHODS. 23 knees were scanned using SIEMENS SIREMOBILE Iso-C with 3D Extension C-arm. The system is able reconstruct 3D images that can be viewed from deferent angle and precise measurements of distances between the deferent components of the implant can be made. The knee was scanned while the patient is sitting in kneeling position with the calf touching the thigh (flexion of over 150 degree). RESULTS. All the cases studied showed a variable roll back between the medial and lateral femoral condyle. In all cases the lateral roll back was much more than the medial. In 14 cases we confirmed lateral condyle subluxation similar to what is seen in normal knee. The position of the foot (internal or external rotation) during scanning did not affect the lateral femoral condyle role back. DISCUSSION. Although previous studies have shown paradoxical types of tibiofemoral movement in patients who have total knee replacements throughout the range of movement, the knees in patients who had full flexion after TKA tend to have the same tibiofemoral movement as the normal knee in deep flexion. The lateral femoral condyles spin off or subluxation could adversely affect the implant components especially if the design does not accommodate this movement. CONCLUSION. The lateral femoral condyle may sublux from the tibia during kneeling in patients who had full flexion after TKA. These findings should call for changes in the implant design to accommodate the lateral condyle roll back

Introduction. Robotic TKA allows for quantifiable precision performing bone resections for implant realignment within acceptable final component and limb alignments. One of the early steps in this robotic technique is after initial exposure and removal of medial and lateral osteophytes, a “pose-capture” is performed with varus and valgus stress applied to the knee in near full extension and 90° of flexion to assess gaps. Component alignment adjustments can be made on the preoperative plan to balance the gaps. At this point in the procedure any posterior osteophytes will still be present, which could after removal change the flexion and extension gaps by 1–3mm. This must be taken into consideration, or changes in component alignment could result in over-correction of gaps can occur. Objective. The purpose of this study was to identify what effect the posterior osteophyte's size and location and their removal had on gap measurements between pose-capture and after bone cuts are made and gaps assessed during implant trialing. Methods. This was a retrospective, single center cohort study comparing 100 robotic-assisted TKAs. Preoperative computer tomography was assessed for the presence, size and location of posterior osteophytes. Robotic-assessed gaps at pose capture and trialing were collected. Paired t-tests, independent t-tests and Pearson's correlation were used to examine this relationship. Results. Posterior osteophytes were present in 87% of cases with 59.3% isolated to the posterior medial femoral condyle. In the sagittal plane, posterior medial femoral condyle (pMFC), posterior lateral femoral condyle (pLFC) and posterior tibial (pT) osteophytes measured 6.75 ± 2.7mm, 5.77 ± 2.8mm, and 6.52 ± 3.14mm respectively. There was a significant increase in medial (17.4 ± 2.7mm vs 19.7 ± 2.2mm, p<0.01) and lateral (19.2 ± 2.2mm vs 20.5 ± 1.9mm, p<0.01) extension gaps from pose-capture to trialing. There was no difference in the delta of medial extension gaps from pose-change to trialing for knees with pMFC osteophytes > or < 5mm (2.1 ± 2.3 mm vs 2.4 ± 2.1mm, p=0.56). Similarly, there was no difference in the change in lateral extension gaps from pose-capture to trialing for knees with lateral posterior osteophytes > or < 5mm (1.2 ± 2.0mm vs 1.73 ± 1.53mm, p = 0.37). There was no statistically significant correlation between medial or lateral osteophyte size and change in medial (r=0.12, p=0.27) or lateral (r=0.11, p=0.36) extension gaps respectively. Conclusion. While there is a significant change in robotically assessed gaps at pose-capture and trialing, this change is small, our study findings are not able to substantiate that it is solely due to the presence, size or location of posterior osteophytes. A post-hoc power analysis indicates that, in order to detect a difference in gap between pose-capture and trialing of 1mm, over 75 knees with and without posterior osteophytes would be needed

Patients undergoing revision surgery of a primary total hip arthroplasty often exhibit bone loss and poor bone quality, which make achieving stable fixation and osseointegration challenging. Implant components coated in porous metals are used clinically to improve mechanical stability and encourage bone in-growth. We compared ultra-porous titanium coatings, known commercially as Gription and Porocoat, in an intra-articular model by press-fitting coated cylindrical implants into ovine femoral condyles and evaluating bone in-growth and fixation strength 4, 8 and 16 weeks post-operatively. Bilateral surgery using a mini-arthrotomy approach was performed on twenty-four Dorset-Rideau Arcott rams (3.4 ± 0.8 years old, 84.8 ± 9.3 kg) with Institutional Animal Care Committee approval in accordance with the Canadian Council on Animal Care. Cylindrical implants, 6.2 mm in diameter by 10 mm in length with surface radius of curvature of 35 mm, were composed of a titanium substrate coated in either Porocoat or Gription and press-fit into 6 mm diameter recipient holes in the weight-bearing regions of the medial (MFC) and lateral (LFC) femoral condyles. Each sheep received 4 implants; two Gription in one stifle (knee) and two Porocoat in the contralateral joint. Biomechanical push-out tests (Instron ElectroPuls E10000) were performed on LFCs, where implants were pushed out relative to the condyle at a rate of 2 mm/min. Force and displacement data were used to calculate force and displacement at failure, stiffness, energy, stress, strain, elastic modulus, and toughness. MFCs were fixed in 70% ethanol, processed undecalcified, and polished sections, approximately 70 µm thick (Exakt Micro Grinding system) were carbon-coated. Backscattered electron images were collected on a scanning electron microscope (Hitachi SU3500) at 5 kV and working distance of 5 mm. Bone in-growth within the porous coating was quantified using software (ImageJ). Statistical comparisons were made using a two-way ANOVA and Fisher's LSD post-hoc test (Statistica v.8). Biomechanical evaluation of the bone-implant interface revealed that by 16 weeks, Gription-coated implants exhibited higher force (2455±1362 N vs. 1002±1466 N, p=0.046) and stress (12.60±6.99 MPa vs. 5.14±7.53 MPa, p=0.046) at failure, and trended towards higher stiffness (11510±7645 N/mm vs. 5010±8374 N/mm, p=.061) and modulus of elasticity (591±392 MPa vs. 256±431 MPa, p=0.61). Similarly, by 16 weeks, bone in-growth in Gription-coated implants was approximately double that measured in Porocoat (6.73±3.86 % vs. 3.22±1.52 %, p=0.045). No statistically significant differences were detected at either 4 nor 8 weeks, however, qualitative observations of the exposed bone-implant interface, made following push-out testing, showed more bony material consistently adhered to Gription compared to Porocoat at all three time points. High variability is attributed to implant placement, resulting from the small visual window afforded during surgery, unique curvatures of the condyles, and presence of the extensor digitorum longus tendon which limited access to the LFC. Ultra-porous titanium coatings, know commercially as Gription and Porocoat, were compared for the first time in a challenging intra-articular ovine model. Gription provided superior fixation strength and bone in-growth, suggesting it may be beneficial in hip replacement surgeries where bone stock quality and quantity may be compromised

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)

Introduction. An equal knee joint height during flexion and extension is of critical importance in optimizing soft-tissue balancing following total knee arthroplasty (TKA). However, there is a paucity of data regarding the in-vivo knee joint height behavior. This study evaluated in-vivo heights and anterior-posterior (AP) translations of the medial and lateral femoral condyles before and after a cruciate-retaining (CR)-TKA using two flexion axes: surgical transepicondylar axis (sTEA) and geometric center axis (GCA). Methods. Eleven patient with advanced medial knee osteoarthritis (age: 51–73 years) who scheduled for a CR TKA and 9 knees from 8 healthy subjects (age: 23–49 years) were recruited. 3D models of the tibia and femur were created from their MR images. Dual fluoroscopic images of each knee were acquired during a weight-bearing single leg lunge. The OA knee was imaged again one year after surgery using the fluoroscopy during the same weight-bearing single leg lunge. The in vivo positions of the knee along the flexion path were determined using a 2D/3D matching technique. The GCA and sTEA were determined based on existing methods. Besides the anterior-posterior translation, the femoral condyle heights were determined using the distances from the medial and lateral epicondyle centers on the sTEA and GCA to the tibial plateau surface in coronal plane (Fig. 1). The paired t-test was applied to compare the medial and lateral condyle motion within each group (Healthy, OA, and CR-TKA). Two-way ANOVA followed post hoc Newman–Keuls test was adopted to detect significant differences among the groups. p<0.05 was considered significant. Results. The results demonstrated that following TKA, the medial and lateral femoral condyle heights were not equal at mid-flexion (15° to 45°, medial condyle lower then lateral by 2.4mm at least, p<0.01), although the knees were well-balanced at 0° and 90° (Fig. 2). While the femoral condyle heights increased from the pre-operative values (>2mm increase on average, p<0.05), they were similar to the intact knees except that the medial sTEA was lower than the intact medial condyle between 0 and 90°. At deep flexion (>90°), both condyles were significantly higher (>2mm, p <0.01) than the healthy knees. Anterior femoral translation of the TKA knee was more pronounce at mid-flexion (Fig. 3), whereas limited posterior translation was found at deep flexion. Conclusion. Femoral condyle heights and AP translations of the CR TKA knees were significantly different from the healthy knees during the weight bearing flexion activity when measured using both the sTEA and GCA, especially at mid-flexion (15° to 45°) and deep flexion (>90°). These results suggest that a well-balanced knee intra-operatively might not necessarily result in mid-flexion and deep flexion balance during functional weight-bearing motion, implying mid-flexion instability and deep flexion tightness of the knee. The data could be useful for improvement of future prostheses designs and surgical techniques in treatment of patients with end-stage medial knee OA

Background. The Bi-Cruciate Stabilized (BCS) total knee arthroplasty (TKA) incorporates two cam-post mechanisms in order to replicate the functionality and stability provided by the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) in the native knee. Recently (2012), a second generation BCS design has introduced femur and tibial bearing modifications that are intended to delay lateral femoral condyle rollback and encourage more stable positioning of the medial femoral condyle to more closely replicate normal knee kinematics. The purpose of this study was to compare the kinematics of this TKA to the normal knee during a weight bearing flexion activity. Methods. In vivo kinematics were derived for 10 normal non-implanted knees and 40 second generation BCS TKAs all implanted by a single surgeon. Computed tomography (CT) scans were obtained for each normal patient, and 3D reconstruction of the femur, tibia/fibula, and patella was performed. Fluoroscopic images were captured at 60 Hz using a mobile fluoroscopic unit that tracked the knee while patients performed a deep knee bend (DKB) from full extension to maximum flexion. A 3D-to-2D image registration technique was used at 30° increments to determine the transformations of the segmented bones or TKA components. The anterior-posterior motion of the lateral femoral condyle contact point (LAP) and the medial femoral condyle contact point (MAP), as well as tibio-femoral axial rotation, were measured at 30° increments from full extension to maximum flexion. Statistical analysis was conducted at the 95% confidence level. Results. From full extension to 120° of knee flexion the lateral condyle contact point translated posteriorly by 14.55 mm ± 5.11 mm and 10.47 mm ± 3.14 mm in the Normal and BCS groups respectively (p=0.1984). Over the same range of motion, the anterior-posterior motion of the medial condyle contact point in the Normal and BCS groups was −5.05 mm ± 2.91 mm and −10.66 mm ± 4.46 mm respectively (p=0.0433). Significant differences in LAP and/or MAP position existed at each flexion increment from 0–120° of flexion (Figure 1). The Normal group exhibited 19.85° ± 6.92° of axial rotation from full extension to 120° of flexion, while the BCS rotated 7.36° ± 4.31° (p=0.0085). Significant differences in femoral rotation with respect to the tibia existed at full extension as well as at 30° and 60° of knee flexion (Figure 2). Conclusions. Like the normal knee, the BCS experiences larger amounts of posterior motion in the first 30 degrees of knee flexion, compared to its mid-flexion phases (30°–90°). After 90 degrees the posterior motion in the BCS continues to increase, likely in part due to posterior cam-post engagement as intended. In this sample of normal knee subjects, very little posterior motion of either femoral condyle happens between 90 and 120 degrees of knee flexion although significant amounts of rollback are expected thereafter as reported in the literature. The axial rotation experienced by the BCS group is quite less than that experienced by the Normal group, however it is quite comparable to other TKAs, if not greater

The purpose of this study was to compare intra-operative, clinical, functional, and patient-reported outcomes following revision anterior cruciate ligament reconstruction (ACL-R) with a matched cohort of primary isolated ACL-R. A secondary purpose was to compare patient-reported outcomes within revision ACL-R based on intra-operative cartilage pathology. Between January 2010 and August 2017, 396 patients underwent revision ACL-R, and were matched to primary isolated ACL-R patients using sex, age, body mass index (BMI), and Beighton score. Intra-operative assessments including meniscal and chondral pathology, and graft diameter were recorded. Lachman and pivot shift tests were completed independently on each patient at two-years post-operative by a physiotherapist and orthopaedic surgeon. A battery of functional tests was assssed including single-leg Bosu balance, and four single-leg hop tests. The Anterior Cruciate Ligament-Quality of Life Questionnaire (ACL-QOL) was completed pre-operatively and two-years post-operatively. Descriptive statistics including means (M) and standard deviations (SD), and as appropriate paired t-tests were used to compare between-groups demographics, the degree and frequency of meniscal and chondral pathology, graft diameter, rate of post-operative ACL graft laxity, the surgical failure rate, and ACL-QOL scores. Comparative assessment of operative to non-operative limb performance on the functional tests was used to assess limb symmetry indices (LSI). Revision ACL-R patients were 52.3% male, mean age 30.7 years (SD=10.2), mean BMI 25.3 kg/m2 (SD=3.79), and mean Beighton score 3.52 (SD=2.51). In the revision group, meniscal (83%) and chondral pathology (57.5%) was significantly more frequent than in the primary group (68.2% and 32.1%) respectively, (p < 0 .05). Mean graft diameter (mm) in the revision ACL-R group for hamstring (M=7.89, SD=0.99), allograft (M=8.42, SD=0.82), and patellar or quadriceps tendon (M=9.56, SD=0.69) was larger than in the primary ACL-R group (M=7.54, SD=0.76, M=8.06, SD=0.55, M=9, SD=1) respectively. The presence of combined positive Lachman and pivot shift tests was significantly more frequent in the revision (21.5%) than primary group (4.89%), (p < 0 .05). Surgical failure rate was higher in the revision (10.3%) than primary group (5.9%). Seventy-three percent of revision patients completed functional testing. No significant LSI differences were demonstrated between the revision and primary ACL-R groups on any of the functional tests. No statistically significant differences were demonstrated in mean preoperative ACL-QOL scores between the revision (M=28.5/100, SD=13.5) and primary groups (M=28.5/100, SD=14.4). Mean two-year scores demonstrated statistically significant and minimally clinically important differences between the revision (M=61.1/100, SD=20.4) and primary groups (M=76.0/100, SD=18.9), (p < 0 .05). Mean two-year scores for revision patients with repair of the medial (M=59.4/100, SD=21.7) or lateral meniscus (M=59.4/100, SD=23.6), partial medial meniscectomy (M=59.7/100, SD=20), grade three or four osteoarthritis (M=55.9/100, SD=19.5), and medial femoral condyle osteoarthritis (M=59.1/100, SD=18) were lower compared with partial lateral meniscectomy (M=67.1/100, SD=19.1), grade one or two osteoarthritis (M=63.8/100, SD=18.9), and lateral femoral condyle osteoarthritis (M=62, SD=21). Revision ACL-R patients demonstrated a greater amount of meniscal and chondral pathology at the time of surgery. Two-years post-operative these patients demonstrated higher rates of graft laxity and lower ACL-QOL scores compared with the primary ACL-R group. Higher grade and medial sided osteoarthritis was associated with inferior ACL-QOL scores in revision ACL-R

Introduction. The Bi-Cruciate Stabilized (BCS) total knee arthroplasty (TKA) incorporates two cam-post mechanisms to reproduce the functionality and stability provided by the anterior cruciate ligament and posterior cruciate ligament in the native knee. The anterior cam-post mechanism provides stability in full extension and early flexion (≤20°) while the posterior cam-post mechanism prevents anterior sliding of the femur during deeper flexion (≥60°). Recently (2012), a second generation BCS design introduced more normal shapes to the femur and tibial bearing geometries that provides delayed lateral femoral condyle rollback and encourages more stable positioning of the medial femoral condyle. The purpose of this study was to compare the in vivo kinematics exhibited by the two generations during weight bearing flexion. Methods. In vivo kinematics were derived for 126 patients. Eighty-six subjects were implanted with a first generation BCS (BCS 1) TKA and 40 with the second generation BCS (BCS 2) TKA. Fluoroscopic videos were captured for patients while they performed a deep knee bend (DKB) from full extension to maximum flexion. Anterior-posterior motion of the lateral femoral condyle (LAP) and the medial femoral condyle (MAP), as well as tibio-femoral axial rotation, were analyzed at 30° increments from full extension to maximum flexion using a 3D-to-2D image registration technique. Statistical analysis was conducted at the 95% confidence level. Results. From full extension to 120° of flexion the amount of posterior femoral rollback (PFR) for the lateral condyle was −25.8±5.87 mm and −14.4±4.75 mm for the BCS1 and BCS2 groups respectively (p=0.003). Over the same range of motion, the anterior-posterior motion of the medial condyle in the BCS1 and BCS2 groups was −15.8±3.03 mm and −8.46±2.35 mm respectively (p=0.001). Significant differences in LAP and/or MAP position existed at each flexion increment from 0–120° of flexion (Figure 1). The BCS1 group exhibited 12.1±6.57° of axial rotation from full extension to 120° of flexion, while the BCS2 rotated 7.36±4.31° (p=0.046). Significant differences in femoral rotation with respect to the tibia existed at full extension and 30°of flexion (Figure 2). Discussion and Conclusion. Compared to BCS2 subjects, those implanted with the BCS1 exhibited greater magnitudes of anterior-posterior motion and more tibio-femoral axial rotation during DKB. The guided motion of the BCS1 encouraged large translations and rotations that may have led to complications such as dislocations and anterolateral knee pain. In comparison, the BCS2 exhibits attenuated and more stable anterior-posterior motions, while still maintaining sufficient magnitudes of rollback and rotation as intended

Introduction. Many factors can influence post-operative kinematics after total knee arthroplasty (TKA). These factors include intraoperative surgical conditions such as ligament release or quantity of bone resection as well as differences in implant design. Release of the medial collateral ligament (MCL) is commonly performed to allow correction of varus knee. Precise biomechanical knowledge of the individual components of the MCL is critical for proper MCL release during TKA. The purpose of this study was to define the influences of the deep medial collateral ligament (dMCL) and the posterior oblique ligament (POL) on kinematics in TKA. Materials and Methods. This study used six fresh-frozen cadaveric knees with intact cruciate ligaments. All TKA procedures were performed by the same surgeon using CR-TKA with a CT-free navigation system. Each knee was tested at 0°, 20°, 30°, 60°, and 90° of flexion. One sequential sectioning sequence was performed on each knee, beginning with femoral arthroplasty only (S1), and thereafter sequentially; medial half tibial resection with spacer (S2), ACL cut (S3), tibial arthroplasty (S4), release of the dMCL (S5), and finally, release of the POL (S6). The same examiner applied all external loads of 10 N-m valgus and 5 N-m internal and external rotation torques at each flexion angle and for each cut state. The AP locations of medial and lateral condyles were determined as the lowest point on each femoral condyle. All data were analyzed statistically using paired t-test. A significant difference was determined to be present for P < .05. Results. All knees showed that posterior femoral translation of the lateral condyle from 0° to 90° was greater than posterior femoral translation of the medial condyle at any step or any tested angle. Posterior femoral translation of the medial femoral condyle under valgus load significantly increased after S4 compared with that at S1 at 20°, 30° and 90°, and after S5 compared with that at S1 at 20° and 30°. Thereafter, significant increase in posterior translation of the medial condyle was seen, at 30° after S6 compared with S1. Posterior femoral translation of the medial femoral condyle under external rotation torque significantly increased after S4 at 90°, and S6 at 0° compared with that at S1. Posterior femoral translation of the medial femoral condyle under internal rotation torque significantly increased after S2 at 0°, after S4 at 60° and 90°, after S5 at 0°, and after S6 at 60° compared with S1. Conclusion. From this study we concluded that retaining of the medial knee structures preserves the valgus and rotatory stability of the knee after TKA. Accordingly, to devise a surgical approach of retaining the dMCL and POL has a possibility to improve outcomes after primary TKA

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