Purpose of Study. Bicondylar tibial plateau fractures are serious injuries to a major weight bearing joint. These injuries are often associated with severe soft tissue injuries that complicate the surgical management. This retrospective study evaluates the management of these high-energy injuries with the use of limited open reduction and fine wire circular external fixation. Methods. Between July 2008 and June 2012, 54 consecutive patients (19 females and 35 males) with high-energy tibial plateau fractures were treated at our tertiary level government hospital. All patients were treated with limited open reduction, and cannulated screw fixation combined with fine wire circular external fixators as the definitive management. The records of these patients were reviewed. Results. Forty-six patients met the inclusion and exclusion criteria. Thirty-six patients had Schatzker type-VI and ten patients had Schatzker type-V fractures. All fractures united without loss of operative reduction. No wound complications, osteomyelitis or septic arthritis occurred. Average Knee Society Clinical Rating Score was 81.6, translating to good clinical results. Minor pin tract infection was the most common complication encountered. Conclusion. Fine wire circular external fixation combined with limited open reduction and cannulated screw fixation consistently produced good functional results without serious complications. NO DISCLOSURES

The primary objective of implanting a total knee prosthesis is to release the patient from pain and to improve the joint mobility at the same time. This leads to an increased quality of life that is optimally kept for the patient's residual lifespan. Joint mobility and stability requires an intra-operative soft-tissue balancing. To reach the goal of a correct implant positioning and well-balanced ligaments two different operative procedures can be used: the so-called “Femur-first”-technique and the “Tibia-first” technique. Since now more than ten years the CT-free navigation is established as a routine procedure in TKA. Studies investigating this innovative technique have shown to lead to a higher precision regarding implant positioning and leg alignment. The present study compares navigated “Femur-first”-technique and “ Tibia-first”-technique. We hypothesised that, due to its better soft-tissue balance, the tibia first technique (T) would allow a flexion improvement of 10° compared to the femur first technique (F).

Between February 21, 2008, and October 10, 2009, 116 consecutive patients were implanted a Columbus® non-constrained total knee replacement (Aesculap®, Tuttlingen, Germany) using navigation; they were examined before the operation and 1 year after. The TKAs were performed by 3 surgeons experienced in knee replacement surgery. We used the femur first technique (F) in 63 patients, the tibia first technique (T) in 53 patients. We performed the final flexion measurement one year after the operation using a Goniometer and evaluated standing full-length radiographs. In addition, we took standard varus and valgus stress radiographs to evaluate the stability of the collateral ligaments and determine the relative position of the implants to one another. Finally, to compare the two patient groups, we used the following pain and function scores: Knee Society Score (KSS), Oxford Score, Knee Injury and Osteoarthritic Outcome Score (KOOS), Short Form 36 (SF 36), Tegner Lysholm Score.

Concerning maximal flexion as the main parameter, we did not find any significant difference between the F and T groups (maximal flexion in group F: 113.4± 9,8° and in group T: 113.5± 8.4°; p = 0.963); thus we could not confirm our hypothesis. Radiological evaluation of the stability of the collateral ligaments did not reveal any significant difference between the two groups both in the medial and lateral joint cavity (lateral collateral ligament in group F: 3.4± 1.4°, and in group T: 3.9± 1.7°; p = 0.850, and medial collateral ligament in group F: 4.0± 1.4°, and in group T: 4.1± 1.7°; p = 0.086). Concerning the mechanical axis on the standing full-length radiograph as part of the 1-year results, no significant difference was found between the two groups (p = 0.089). Likewise, the pain and function scores did not show any difference between the two groups.

Concerning operating time (OP time) and outliers exceeding 3° of varus/valgus deviation from the ideal mechanical axis, trends were identifiable. The number of outliers tended to be higher in the F group, the OP time in group T seemed longer.

As a conclusion, we can say that both the tibia first and the femur first techniques yield good clinical and radiological results in combination with navigation. In terms of function and patient satisfaction, we did not find any significant difference.

Introduction. Within the reconstruction of unicondylar femoral bone defects with morselized bone grafts in revision total knee arthroplasty (TKA), a stem extension appears to be critical to obtain adequate mechanical stability. Whether the stability is still secured by this reconstruction technique in bicondylar defects has not been assessed. Long, rigid stem extensions have been advocated to maximize the stability in revision TKAs. The disadvantage of relatively stiff stem extensions is that bone resorption is promoted due to stress shielding. Therefore, we developed a relatively thin intramedullary stem which allowed for axial sliding movements of the articulating part relative to the intramedullary stem. The hypothesis behind the design is that compressive contact forces are directly transmitted to the distal femoral bone, whereas adequate stability is provided by the sliding intramedullary stem. A prototype was made of this new knee revision design and applied to the reconstruction of uncontained bicondylar femoral bone defects. Materials and Methods. Five synthetic distal femora with a bicondylar defect were reconstructed with impacted bone grafting (IBG) and this new knee revision design. A custom-made screw connection between the stem and the intercondylar box was designed to lock or initiate the sliding mechanism, another screw (dis)connected the stem. A cyclically axial load of 500 N was applied to the prosthetic condyles to assess the stability of the reconstruction. Radiostereometry was used to determine the migrations of the femoral component with a rigidly connected stem, a sliding stem and no stem extension. Results. We found a stable reconstruction of the bicondylar femoral defects with IBG in case of a rigidly connected stem. After disconnecting the stem, the femoral component showed substantially more migrations. With a sliding stem rotational migrations were similar to those of a rigidly connected stem. However, the sliding stem allowed proximal migration of the condylar component, thereby compressing the IBG. Discussion. A stable reconstruction of uncontained bicondylar femoral defects could be created with IBG and a TKA with a thin stem extension. It appeared that the presence of a functional stem extension was important for the stability of the bicondylar reconstruction. In an effort to reduce stress shielding, we developed a sliding stem mechanism. This sliding stem provided adequate stability, while compressive contact forces are still transmitted to the distal femoral bone. Clinical studies have to confirm that our sliding stem mechanism leads to long term bone maintenance after revision TKAs

Controversy exists whether a single proximal lateral tibia (PLT) locked plate is adequate for bicondylar fractures and whether the use of integral raft screws makes the use of bone graft less important. 57 consecutive patients who underwent reconstruction with a locked PLT plate were retrospectively reviewed. Radiographs were examined for operative reduction and subsequent loss of reduction. 55 patients were followed-up for an average of 27 weeks. Fractures were divided into unicondylar (Group 1, n=33) and bicondylar (Group 2, n=22). Union occurred in all patients, with no revisions or removal of metalwork at final follow-up. In 50 patients (88%), the fracture was reduced to within 2mm of anatomical. Articular surface collapse of >2mm occurred in three patients. Nine patients underwent bone grafting with no difference in outcome. A supplementary medial plate was used in three patients with a separate posteromedial fragment. Except for a separate posteromedial fragment, the use of a single locked PLT plate for bicondylar fractures allows union to occur without failure. With the use of integral raft screws, the need for bone graft is questionable. The short-term radiological results and complication rate of PLT locked plating is excellent

Purpose. Isolated fractures of femoral condyle in the coronal plane (Hoffa fracture) is rare and is surgically challenging to treat. 44 patients were operated between 2004–2014. The aim was to retrospectively assess the fracture patterns, fixation done and functional outcome. Methods. All injuries resulted from direct trauma to the knee out of which 36 were due to road traffic accidents.38 were closed injuries and the rest open.35 involved lateral condyle, 8 involved medial condyle and one was bicondylar type. All were anatomically reduced with fixation decided based on preoperative radiographs, CT scan and intra-op observation. Early passive motion and isometric exercises were started but kept non-weight bearing for 6–8 weeks. The mean follow up period was five years. Outcomes were measured using Neer's scoring system and International Knee Society Documentation Committee (IKDC) Functional Score. Results. 26 patients had excellent outcome, 14 had satisfactory and 4 had unsatisfactory outcome which corresponded with the specified fracture severity pattern. Uniformly excellent results were obtained in all simple pattern fractures, whereas comminuted fracture patterns were more challenging to treat with variable outcomes. Conclusion. In our retrospective observational study, we found that each fracture had specific pattern which dictated the treatment plan and the prognosis. Subsequently we grouped the fractures and proposed a classification system that would specify the pattern of fracture and dictate the type of fixation preferred. We conclude that therapeutic outcome is significantly affected by the amount of articular surface comminution, posterior cortex comminution, attainment of anatomical reduction and stable fixation

Backgrounds. Most of in vivo kinematic studies of total knee arthroplasty (TKA) have reported on varus knee. TKA for the valgus knee deformity is a surgical challenge. The purposes of the current study are to analyze the in vivo kinematic motion and to compare kinematic patterns between weight-bearing (WB) and non-weight-bearing (NWB) knee flexion in posterior-stabilized (PS) fixed-bearing TKA with pre-operative valgus deformity. Methods. A total of sixteen valgus knees in 12 cases that underwent TKA with Scorpio NRG PS knee prosthesis operated by modified gap balancing technique were evaluated. The mean preoperative femorotibial angle (FTA) was 156°±4.2°. During the surgery, distal femur and proximal tibia was cut perpendicular to the mechanical axis of each bone. After excision of the menisci and cruciate ligaments, balancer (Stryker joint dependent kinematics balancer) was inserted into the gap between both bones for evaluation of extension gap. Lateral release was performed in extension. Iliotibial bundle (ITB) was released from Gerdy tubercle then posterolateral capsule was released at the level of the proximal tibial cut surface. If still unbalanced, pie-crust ITB from inside-out was added at 1 cm above joint line until an even lateral and medial gap had been achieved. Flexion gap balance was obtained predominantly by the bone cut of the posterior femoral condyle. Good postoperative stability in extension and flexion was confirmed by stress roentgenogram and axial radiography of the distal femur. We evaluated the in vivo kinematics of the knee using fluoroscopy and femorotibial translation relative to the tibial tray using a 2-dimentional to 3-dimensional registration technique. Results. The average flexion angle was 111.3°±7.5° in weight-bearing and 114.9°±8.4° in non-weight-bearing. The femoral component demonstrated a mean external rotation of 5.9°±5.8° in weight-bearing and 7.4°±5.2° in non-weight-bearing (Fig.1). In weight-bearing, the femoral component showed medial pivot pattern from 0° to midflexion and a bicondylar rollback pattern from midflexion to full flexion (Fig2). Medial condyle moved similarly in non-weight-bearing condition and in weight-bearing condition. Lateral condyle moved posterior in slightly earlier angle during weight-bearing condition than during non-weight-bearing condition (Fig.3). Discussion. Numerous kinematic analyses of a normal knee have demonstrated greater posterior motion of the lateral femoral condyle relative to the medial condyle, leading to a mean external rotation and a bicondylar rollback motion with progressive knee flexion. A kinematic analysis of valgus knee was reported to show a different kinematic pattern from a physiological knee motion. Many valgus knees showed paradoxical anterior translation from extension to mid-flexion and greater posterior translation in the medial condyle than in the lateral condyle. Kitagawa et al. reported that this non-physiologic pattern wasn't completely restored after TKA using medial pivot knee system. In the present study, we showed kinematic patterns of the TKA performed on the valgus knee to be similar to the normal knee for the first time, even though the magnitude of external rotation was small. Conclusions. We conclude that the medial pivot pattern followed by posterior rollback motion can be obtained in TKA with modified gap balancing technique for the preoperative valgus deformity

Introduction. Femoral stem anteversion after total hip arthroplasty (THA) has always been assessed using CT scan in supine position. In this study, we evaluated the anteversion of the femoral prosthesis neck in functional standing position using EOS® technology with repeatability and reproducibility of the measurements. The data obtained were compared with conventional anatomic measurements. Materials and Methods. We measured the anteversion of the femoral prosthesis neck in 45 consecutive patients who had THA performed in nine hospitals. All measurements were obtained using the EOS® imaging system with patients in comfortable standing position. The orientation of the final vector representing the femoral neck was measured on 3-dimensional reconstructions. The anatomic femoral anteversion was calculated as in a transverse plane relative to the scanner and to the plane of the reconstructed bicondylar femoral segment (femoral prosthesis neck against the femoral condyles). Functional femoral anteversion (FFA) was measured in the horizontal plane relative to the frontal plane of the patient through the center of two femoral heads. FFA embodies true anteversion of the femoral prosthesis neck relative to the pelvis, representing the combined lower extremity anteversion. Results. The average anatomic anteversion was 8.7° (−42.2 to 32.8; SD 15.2). The average functional anteversion was −0.2° (−32.7 to 30.2; SD 14.3). The paired Student t test showed a significant difference between these values (p = 0.036). Discussion. In a significant number of cases, the anatomic orientation of the prosthesis in relation to the posterior bicondylar plane does not correlate with the functional orientation of the frontal plane of the standing patient. Other factors such as tibial, femoral and acetabular anatomic features determine the overall posture of the lower limb and the functional anteversion of the femoral neck prosthesis, highlighting adaptations related to hip-knee relations. EOS® technology can assess patients in functional positions of standing, sitting, squatting or bending forward at the cost of very low exposure to irradiation. These data may be useful in future studies of the orientation of the acetabulum that explore both qualitatively and quantitatively the combined functional anatomy of hip joint and, more precisely, the phenomena of instability and subluxation

Introduction. Bone loss in the distal femur and proximal tibia is frequently encountered with both complex primary and revision knee replacement surgery. Metaphyseal sleeves provide a good option for enhanced fixation in managing such defects on both the tibia and femur. We present our results in 48 patients (50 knees) with a minimum 12 month follow up (range 12 to 45). Methods. 48 patients (50 knees) who had revision knee arthroplasty for either septic or aseptic loosening. All were graded Type II or III using the Anderson Orthopaedic Research Institute (AORI) grading system of both femoral and tibial defects. A large portion of aseptic loosening revisions were for extreme osteolysis of a bicondylar knee prosthesis. Results. 52% had tibial sleeves only, 38% had both tibial and femoral sleeves and the remainder had only femoral sleeves inserted. All knee radiographs at final follow-up showed well-fixed osteointegrated components without component migration or clinically significant osteolysis. Two knees were treated with multiple arthroscopic washouts for infection. Two knees subsequently underwent manipulation under anaesthesia with good improvement in range of movement. One subsequently developed Complex Regional Pain Syndrome. No femoral or tibial components were revised. The average pre-operative Oxford Knee Score was 22 (12 to 38) and subsequently improved to 38 (12 to 45) post-operatively. Discussion and conclusions. Our early results show encouraging signs that porous titanium sleeves are a good option when managing large metaphyseal bone loss in both femur and tibia especially in revision arthroplasty. Post operative complications were low and functional outcome scores were comparable with more traditional knee revision arthroplasty techniques in the presence of bone loss

Knee laxity following anterior cruciate ligament (ACL) injury is a complex phenomenon influenced by various biomechanical and anatomical factors. The contribution of soft tissue injuries – such as ligaments, menisci, and capsule – has been previously defined, but less is known about the effects of bony morphology. (Tanaka et al, KSSTA 2012) The pivot shift test is frequently employed in the clinical setting to assess the combined rotational and translational laxity of the ACL deficient knee. In order to standardise the maneuver and allow for reproducible interpretation, the quantitative pivot shift test was developed. (Hoshino et al, KSSTA 2013) The aim of this study is to employ the quantitative pivot shift test to determine the effects of bone morphology as determined by magnetic resonance imaging (MRI) on rotatory laxity of the ACL deficient knee. Fifty-three ACL injured patients scheduled for surgical reconstruction (36 males and 17 females; 26±10 years) were prospectively enrolled in the study. Preoperative magnetic resonance imaging (MRI) scans were reviewed by two blinded observers and the following parameters were measured: medial and lateral tibial slope, tibial plateau width, femoral condyle width, bicondylar width, and notch width. (Musahl et al. KSSTA 2012). Preoperatively and under anaesthesia, a quantitative pivot shift test was performed on each patient by a single experienced examiner. An image analysis technique was used to quantify the lateral compartment translation during the maneuver. Subjects were classified as “high laxity” or “low laxity” based upon the median value of lateral compartment translation. (Hoshino et al. KSSTA 2012) Independent t-tests and univariate logistic regression were used to investigate the relationship between the pivot shift grade and various features of bone morphology. Statistical significance was set at p<0.05. A high inter-rater reliability was observed in all MRI measurements of bone morphology (ICC=0.72–0.88). The median lateral compartment translation during quantitative pivot shift testing was 2.8mm. Twenty-nine subjects were classified as “low laxity” (2.8mm). The lateral tibial plateau slope was significantly increased in “high laxity” patients (9.3+/−3.4mm versus 6.1+/−3.7mm; p<0.05). No other significant difference in bone morphology was observed between the groups. This study employed an objective assessment tool – the quantitative pivot shift test – to assess the contribution of various features of bone morphology to rotatory laxity in the ACL deficient knee. Increased lateral tibial plateau slope was shown to be a significant independent predictor of high laxity. These findings could help guide treatment strategies in patients with high grade rotatory laxity. Further research into the role of tibial osteotomies in this sub-group is warranted

The outcome of 77 high energy tibial plateau fractures treated by locking or conventional plating was reviewed. The aim of the study was to determine if there was any advantage of locking plates in reducing the complication rates associated with fixation of these injuries. All patients had a high energy injury pattern (medial or bicondylar plateau fractures). There were 32 locked plates and 45 non-locking plates used. Compartment syndrome complicated 5 patients (16%) in the locked plate group and 3 (7%) in the non-locked group (p = 0.198). Superficial infection occurred in 4 (13%) patients with locked plates and 7 (16%) patients with non-locked plates. Thromboembolic complications occurred in 3 (7%) patients treated with non-locked plates. There were no thrombembolic complications in the locked plate group (p = 0.135). Overall, malunion of the plateau occurred in 10 (22%) patients treated with non-locked plates compared to 7 (22%) patients who received locked plates. This was due to residual malreduction in 4 (13%) patients in the locked plate group and 6 (13%) patients in the non-locked plate group at the time of surgery. In the remaining cases loss of reduction after fixation occurred in 4 (9%) patients who received non-locked plates and in 3 (9%) patients who were treated with locked plates. No statistically significant difference was noted in the treatment outcomes of patients managed with locked plates or non-locked plates, regardless of fracture severity. We concluded that there is no definite advantage associated with the use of locked plating for high energy tibial plateau fractures

Infection after knee arthroplasty is a devastating complication. Our aim is to present our outcomes of treating infected knee replacements at a tertiary referral centre. We performed a consecutive, retrospective case series of all revision knee arthroplasty for infection between January 2006 and December 2008. Case notes were reviewed and data collated on the date and institution of primary arthroplasty, procedures undertaken at our institution, microbiology and bone loss post first stage, serological markers (C-reactive protein, ESR) prior to second stage and outcome. During this three year period we performed 430 knee revision operations. 51 were in the presence of deep chronic infection. 90% were referred from other hospitals. Overall infection was successfully eradicated in 69%. Nineteen patients underwent repeat two-stage and overall eleven (58%) patients had successful eradication of infection with multiple two-stages. Of these 47% had F3/T3, the highest grading of Anderson Orthopaedic Research Institute bone loss indicating no metaphyseal bone. A further 12% had bicondylar deficiency on the tibia and no femoral metaphyseal bone (F3/T2b). Multidrug resistance present in 69% and 47% were infected with multiple organisms. All members of the unsuccessful outcome group had at least one multidrug resistant organism compared to 43% in the successful cohort (P=0.0002). Multiple organisms are associated with an unsuccessful outcome (P=0.056). Serological markers were not significantly different between the successful and unsuccessful outcome groups. Where the referring hospital had attempted revision and failed, the chance of eradicating infection dropped from 75% to 58% and the rate of above knee amputation was twelve times higher (3% vs. 36%). Custom constrained, rotating hinge prostheses enable aggressive soft tissue debridement including ligaments. Successful two-stage requires a multidisciplinary approach including tissue viability nurses, microbiologists and plastic surgeons. Where units lack revision expertise this series suggests early referral increases the chance of limb salvage

Rotational positioning of the femoral component during the realisation of a total knee arthroplasty is an important part of the surgical technique and remains a topic of discussion in the literature. The challenge of this positioning is important because it determines the anatomical result and its effect on the flexion gap and clinical outcome mainly through its impact on patellofemoral alignment. The intraoperative identification of the axis transepicondylar visually or by navigation is not reliable or reproducible. The empirical setting to 3 ° of external rotation, the procedure used to cut or dependent or independent is not adapted to the individual variability of knee surgery. Indeed, the angle formed by the posterior condylar axis and trans-epicondylar axis is subject to large individual variations. The authors propose a novel technique, using the navigation of the trochlea to determine the rotation of the femoral component. The principle is to consider the rotation of the femoral implant as “ideal” when it makes a perfect superposition of the prosthetic trochlea with the native bony trochlea on patellofemoral view at 60° when planning the femur. The bottom of the prosthetic trochlea is well aligned with the trochlea groove, identified during the trochlear morphing, itself perpendicular to the trans-epicondylar axis. The authors hope to encourage centering patellofemoral joint prosthesis, thus favoring the original kinematics of the extensor apparatus. The purpose of this study is to demonstrate firstly, that the navigation of the trochlea is a reliable and reproducible method to adjust the rotation of the femoral component relative to the trans-epicondylar axis taken as reference and the other, the rotation control by this method is not done at the expense of the balance gap in flexion. It is a bi-centric study prospective, nonrandomised, including continuously recruited 145 patients in two French centers. All patients were included in the year 2010 and have all been revised three months and one year of surgery. The average age of patients was 71 years [53, 88]. It was made no selection of patients who have all been included consecutively in the study and in the two centres. In all cases, the rotation of the femoral component was determined by intraoperative navigation of the trochlea. The authors compared the alpha angle (angular divergence between the plane and the posterior bicondylar plane and trans-epicondylar axis) obtained by this method and that calculated on a pre-or postoperative scan. The authors also measured the space between femur and tibia internal and external side in flexion (90°) to assess the impact on the balance in flexion. There is excellent agreement between the results obtained by the method of CT scan and the trochlear navigation technique. In addition, this technique allows us to achieve a quadrilateral space gap in flexion. The authors found large individual variation in the distal femoral epiphyseal torsion (angle alpha). They demonstrate that the navigation of the trochlea is a reliable and reproducible method to adjust the rotation of the femoral component relative to the trans-epicondylar axis taken as reference and provides, concomitantly, a quadrilateral space gap in flexion

Rotational positioning of the femoral component during the realisation of a total knee arthroplasty is an important part of the surgical technique and remains a topic of discussion in the literature. The challenge of this positioning is important because it determines the anatomical result and its effect on the flexion gap and clinical outcome mainly through its impact on patellofemoral alignment. The intraoperative identification of the axis transepicondylar visually or by navigation is not reliable or reproducible. The empirical setting to 3 ° of external rotation, the procedure used to cut or dependent or independent is not adapted to the individual variability of knee surgery. Indeed, the angle formed by the posterior condylar axis and trans-epicondylar axis is subject to large individual variations. The authors propose a novel technique, using the navigation of the trochlea to determine the rotation of the femoral component. The principle is to consider the rotation of the femoral implant as “ideal” when it makes a perfect superposition of the prosthetic trochlea with the native bony trochlea on patellofemoral view at 60 ° when planning the femur. The bottom of the prosthetic trochlea is well aligned with the trochlea groove, identified during the trochlear morphing, itself perpendicular to the trans-epicondylar axis. The authors hope to encourage centering patellofemoral joint prosthesis, thus favouring the original kinematics of the extensor apparatus. The purpose of this study is to demonstrate firstly, that the navigation of the trochlea is a reliable and reproducible method to adjust the rotation of the femoral component relative to the trans-epicondylar axis taken as reference and the other, the rotation control by this method is not done at the expense of the balance gap in flexion. It is a bi-centric study prospective, nonrandomised, including continuously recruited 145 patients in two French centres. All patients were included in the year 2010 and have all been revised three months and one year of surgery. The average age of patients was 71 years [53, 88]. It was made no selection of patients who have all been included consecutively in the study and in the two centres. In all cases, the rotation of the femoral component was determined by intraoperative navigation of the trochlea. The authors compared the alpha angle (angular divergence between the plane and the posterior bicondylar plane and trans-epicondylar axis) obtained by this method and that calculated on a pre-or postoperative scan. The authors also measured the space between femur and tibia internal and external side in flexion (90°) to assess the impact on the balance in flexion. There is excellent agreement between the results obtained by the method of CT scan and the trochlear navigation technique. In addition, this technique allows to achieve a quadrilateral space gap in flexion. The authors found large individual variation in the distal femoral epiphyseal torsion (angle alpha). They demonstrate that the navigation of the trochlea is a reliable and reproducible method to adjust the rotation of the femoral component relative to the trans-epicondylar axis taken as reference and provides, concomitantly, a quadrilateral space gap in flexion

Introduction. Bicompartmental osteoarthritis involving the medial tibiofemoral and the patellofemoral compartments is often treated with total knee replacement. Improved implants and surgical techniques have led to renewed interest in bicompartmental arthroplasty. This study evaluates the radiographic and early clinical results of bicompartmental arthroplasty with separate unlinked components implanted with the assistance of a robotic surgical arm. In addition, we examine the amount of bone resected using unlinked bicompartmental components compared to total knee replacement. Finally, a retrospective review of total knee cases examines the applicability of this early intervention procedure. Methods. 97 patients received simultaneous but geometrically separate medial tibiofemoral and patellofemoral arthroplasties with implants specifically designed to take advantage of a new bone and tissue sparing implantation technique using haptic robotics. These patients came from four surgeons at four different hospitals. The average follow-up was 9 months. Pre- and post-operative radiographs were taken. ROM, KSS and WOMAC scores were recorded. The patients had an average age of 67 yrs (range: 45-95), BMI of 29 ± 4kg/m. 2. 47% of the patients were male. We retrospectively reviewed pre and post operative notes from 406 consecutive TKA patients from a single surgeon. Intraoperative data included the integrity of the three compartments and the ACL. Results. At only six weeks follow-up, patients recovered their pre-operative ROM (p=0.37). Knee Society Knee scores (knee and function) and WOMAC scores (pain, function and total) significantly improved from pre-operative values at every follow-up of 6 weeks, 6 months and 1 year (p<0.05). Radiographically, there was no evidence of loosening, wear or progression of OA. There were also no perioperative complications. Using computer simulation, the amount of bone removed using bicompartmental arthroplasty compared to traditional TKA was predicted. Total bone removed on the femur and the tibia using a standard TKA implant is 3.5 times the bone removed using a bicompartmental onlay implant and 4 times the bone removed when using a bicompartmental inlay implant. In the review of 406 TKA cases, the ACL was intact in 66% of these cases. Based on these data alone, 16% of these TKA patients were indicated for a unicondylar arthroplasty, 12% medial UKA, 3% lateral UKA and 1% PFA. In addition, 31% were indicated for bicompartmental arthroplasty with 4% bicondylar (medial and lateral UKA), 6% lateral UKA and PFA and 21% medial UKA and PFA. While these data don't yet account for fixed versus flexible deformities, excessive osteophytes or other contraindications, it seems clear that the disease often treated with a TKA does not actually involve all three compartments. Conclusions. Modular bicompartmental arthroplasty is an effective method for treating arthritis of the knee restricted to the medial and patellofemoral compartments. Early results using contemporary prostheses are encouraging and should prompt further mid- and long-term study. Robotic assistance of bicompartmental arthroplasty has shown good early clinical and radiographic success. In addition, bicompartmental arthroplasty removes significantly less bone than total knee arthroplasty. Also, data indicates that may total knee patients have healthy cruciates and disease in only two of the three compartments, indicating that TKA is an overtreatment of earlier stage osteoarthritis. Longer term studies will determine the clinical significance of preserving healthy cartilage and ligaments routinely resected with traditional tricompartmental TKA