Inverse Kinematic Alignment (iKA) and Gap Balancing (GB) aim to achieve a balanced TKA via component alignment. However, iKA aims to recreate the native joint line versus resecting the tibia perpendicular to the mechanical axis. This study aims to compare how two alignment methods impact 1) gap balance and laxity throughout flexion and 2) the coronal plane alignment of the knee (CPAK). Two surgeons performed 75 robotic assisted iKA TKA's using a cruciate retaining implant. An anatomic tibial resection restored the native joint line. A digital joint tensioner measured laxity throughout flexion prior to femoral resection. Femoral component position was adjusted using predictive planning to optimize balance. After femoral resection, final joint laxity was collected. Planned GB (pGB) was simulated for all cases posthoc using a neutral tibial resection and adjusting femoral position to optimize balance. Differences in ML balance, laxity, and CPAK were compared between planned iKA (piKA) and pGB. ML balance and laxity were also compared between piKA and final (fiKA). piKA and pGB had similar ML balance and laxity, with mean differences <0.4mm. piKA more closely replicated native MPTA (Native=86.9±2.8°, piKA=87.8±1.8°, pGB=90±0°) and native LDFA (Native=87.5±2.7°, piKA=88.9±3°, pGB=90.8±3.5°). piKA planned for a more native CPAK distribution, with the most common types being II (22.7%), I (20%), III (18.7%), IV (18.7%) and V (18.7%). Most pGB knees were type V (28.4%), VII (37.8%), and III (16.2). fiKA and piKA had similar ML balance and laxity, however fiKA was more variable in midflexion and flexion (p<0.01). Although ML balance and laxity were similar between piKA and pGB, piKA better restored native joint line and CPAK type. The bulk of pGB knees were moved into types V, VII, and III due to the neutral tibial cut. Surgeons should be cognizant of how these differing alignment strategies affect knee phenotype

Background. Proper femoral component placement plays a key role in the success of a total knee replacement (TKR). Controversy exists on which technique should be used to ensure proper femoral component placement. This two-part study compares gap balancing (GB) and measured resection (MR) techniques used in TKR, investigating femoral component position and early clinical outcomes. Methods. Femoral component position was analyzed in 95 consecutive knees that underwent primary TKR. Both GB and MR cutting blocks from the same knee system were sequentially placed on the operative knee, marking the pin sits. A standardized photograph (Figure) was taken prior to making final femoral cuts. Relative rotation was determined based on measurements made from a commercially available software. Clinical comparison was made using 50 consecutive GB patients and 50 consecutive MR patients. Clinical outcome measures were Knee Society Scores (KSS), knee range of motion (ROM), functional ROM (FROM), tourniquet time, and patients having manipulations under anesthesia (MUA). Results. The GB technique resulted in relative external and internal rotation of the femoral component in 41% and 17% knees respectively. Forty 42% of knees had no relative rotation. Mean pre and 1 year post-operative knee ROM for the MR cohort was 116.4±14.3. °. and 115±12.9. °. respectively, with FROM of 103.0±17.2. °. The GB cohort had mean pre and 1 year post-operative knee ROM values of 113.9±10.8. °. and 116.8±13.6. °. respectively, with FROM of 96.0±22.5. °. Mean 1 year pain and function KSS in the MR cohort were 92.5±10.7 and 85.4±18.9. In the GB cohort, the mean 1 year KSS values were 95.7±6.7 and 84.9±19.58 for pain and function respectively. Clinical outcome measures were not statistically different. Conclusion. We found that the GB technique resulted in external rotation relative to the MR technique. Despite these intraoperative findings we found no significant clinical differences

Introduction. Valgus deformity in an end stage osteoarthritic knee can be difficult to correct with no clear consensus on case management. Dependent on if the joint can be reduced and the degree of medial laxity or distension, a surgeon must use their discretion on the correct method for adequate lateral releases. Robotic assisted (RA) technology has been shown to have three dimensional (3D) cut accuracy which could assist with addressing these complex cases. The purpose of this work was to determine the number of soft tissue releases and component orientation of valgus cases performed with RA total knee arthroplasty (TKA). Methods. This study was a retrospective chart review of 72 RATKA cases with valgus deformity pre-operatively performed by a single surgeon from July 2016 to December 2017. Initial and final 3D component alignment, knee balancing gaps, component size, and full or partial releases were collected intraoperatively. Post-operatively, radiographs, adverse events, WOMAC total and KOOS Jr scores were collected at 6 months, 1 year and 2 year post-operatively. Results. Pre-operatively, knee deformities ranged from reducible knees with less than 5mm of medial laxity to up to 12° with fixed flexion contracture. All knees were corrected within 2.5 degrees of mechanical neutral. Average femoral component position was 0.26. o. valgus, and 4.07. o. flexion. Average tibial component position was 0.37. o. valgus, and 2.96. o. slope, where all tibial components were placed in a neutral or valgus orientation. Flexion and extension gaps were within 2mm (mean 1mm) for all knees. Medial and lateral gaps were balanced 100% in extension and 93% in flexion. The average flexion gap was 18.3mm and the average extension gap was 18.7mm. For component size prediction, the surgeon achieved their planned within one size on the femur 93.8% and tibia 100% of the time. The surgeon upsized the femur in 6.2% of cases. Soft tissue releases were reported in one of the cases. At latest follow-up, radiographic evidence suggested well seated and well fixed components. Radiographs also indicated the patella components were tracking well within the trochlear groove. No revision and re-operation is reported. Mean WOMAC total scores were improved from 24±8.3 pre-op to 6.6±4.4 2-year post-op (p<0.01). Mean KOOS scores were improved from 46.8±9.7 pre-op to 88.4±13.5 2-year post-op (p<0.01). Discussion. In this retrospective case review, the surgeon was able to balance the knee with bone resections and avoid disturbing the soft tissue envelope in valgus knees with 1–12° of deformity. To achieve this balance, the femoral component was often adjusted in axial and valgus rotations. This allowed the surgeon to open lateral flexion and extension gaps. While this study has several limitations, RATKA for valgus knees should continue to be investigated. For any figures or tables, please contact authors directly

INTRODUCTION. The Woodpecker pneumatic broaching system facilitates femoral preparation to achieve optimal primary fixation of the stem in direct anterior hip replacement using a standard operating table. The high-frequency axial impulses of the device reduce excess bone tension, intraoperative femoral fractures and overall operating time. The Woodpecker device provides uniformity and enhanced control while broaching, optimizing cortical contact between the femur and implant and thereby maximizing prosthetic axial stability and longevity. This study aims to describe a single surgeon's experience using the Woodpecker pneumatic broaching system in 649 cases of direct anterior approach (DAA) total hip arthroplasties to determine the device's safety and efficacy. METHODOLOGY. All consecutive patients undergoing elective anterior bikini total hip arthroplasties (THA) performed by a single surgeon between July 2013 and June 2018 were included. Patients undergoing a THA with the use of the Woodpecker device through a different surgical approach, revision THA or arthroplasties for a fractured neck of femur were excluded (n=219). The pneumatic device was used for broaching the femoral canal in all cases. Pre-operative and post-operative Harris Hip Scores (HHS) and post-operative radiographs were analyzed to identify femoral fractures and femoral component positioning at 6 weeks, 6 months and 12 months post-operative. Any intra-operative or post-operative surgical complications and component survivorship until most recent follow up were recorded in the clinical notes. RESULTS. A total of 649 patients (L THA=317, R THA=328 and bilateral=2) with a mean age of 69 (range 46–91yrs) and mean BMI of 28.3 (range = 18.4–44.0) underwent a DAA THA using a Woodpecker device were included in the study. Of these patients, 521 (80%) underwent uncemented and 128 (20%) underwent cemented femoral components. The time taken to broach the femur using Woodpecker broaching this system averaged 2.8 minutes (1.4 to 7.5 minutes) in both cemented and uncemented cases. In 91% of cases the templated broach size was achieved with the remaining 9% within +/− 1 size of the planned template. Radiographic analysis revealed 67.3% of the stems placed in 0–1.82 degrees of varus and 32.7% placed in 0–1.4 degrees of valgus. Average HHS were 24.4 pre-operatively, with drastic improvements shown at 6 weeks (80.95), 6 months (91.91) and 12 months (94.18) after surgery. Intraoperative femoral fractures occurred in three patients (0.4%) during trial reduction, a further three patients had periprosthetic post-operative fractures (0.4%) from falls, two patients had stem subsidence (0.3%) and a further two patients had wound infections (0.3%). At the most recent follow up, the survivorship of the acetabular component was 99.7% and the femoral component was 99.1%, with mean follow up of 2.9 years (0.5 to 5 years). No intraoperative or post-operative complications could be directly attributed to the Woodpecker broaching system. CONCLUSION. The pneumatic Woodpecker device is a safe and effective alternative tool in minimally invasive direct anterior hip replacement surgery for femoral broaching performed on a standard operating table. The skill and experience of the surgeon must be taken into consideration when utilizing new surgical devices

Arthrofibrosis remains a dominant post-operative complication and reason for returning to the OR following total knee arthroplasty. Trauma induced by ligament releases during TKA soft tissue balancing and soft tissue imbalance are thought to be contributing factors to arthrofibrosis, which is commonly treated by manipulation under anesthesia (MUA). We hypothesized that a robotic-assisted ligament balancing technique where the femoral component position is planned in 3D based on ligament gap data would result in lower MUA rates than a measured resection technique where the implants are planned based solely on boney alignment data and ligaments are released afterwards to achieve balance. We also aimed to determine the degree of mechanical axis deviation from neutral that resulted from the ligament balancing technique. Methods. We retrospectively reviewed 301 consecutive primary TKA cases performed by a single surgeon. The first 102 consecutive cases were performed with a femur-first measured resection technique using computer navigation. The femoral component was positioned in neutral mechanical alignment and at 3° of external rotation relative to the posterior condylar axis. The tibia was resected perpendicular to the mechanical axis and ligaments were released as required until the soft tissues were sufficiently balanced. The subsequent 199 consecutive cases were performed with a tibia-first ligament balancing technique using a robotic-assisted TKA system. The tibia was resected perpendicular to the mechanical axis, and the relative positions of the femur and tibia were recorded in extension and flexion by inserting a spacer block of appropriate height in the medial and lateral compartments. The position, rotation, and size of the femoral component was then planned in all planes such that the ligament gaps were symmetric and balanced to within 1mm (Figure 1). Bone resection values were used to define acceptable limits of implant rotation: Femoral component alignment was adjusted to within 2° of varus or valgus, and within 0–3° of external rotation relative to the posterior condyles. Component flexion, anteroposterior and proximal-distal positioning were also adjusted to achieve balance in the sagittal plane. A robotic-assisted femoral cutting guide was then used to resect the femur according to the plan (Figure 2). CPT billing codes were reviewed to determine how many patients in each group underwent post-operative MUA. Post-operative mechanical alignment was measured in a subset of 50 consecutive patients in the ligament balancing group on standing long-leg radiographs by an independent observer. Results. Post-operative MUA rates were significantly lower in the ligament balancing group (0.5%; 1/199) than in the measured resection group (3.9%; 4/102), p=0.051. 91.3% (42/46) of knees were within 3° and 100% (46/46) were within 4° of neutral alignment to the mechanical axis post-operatively in the ligament balancing group. Conclusions. Gap driven femoral based planning in TKA resulted in a significantly lower post-operative manipulation rate than in the measured resection approach, while maintaining acceptable overall alignment to the mechanical axis

Introduction. Acetabular component positioning, offset, combined anteversion, leg length, and soft tissue envelope around the hip plays an important role in hip function and durability. In this paper we will focus on acetabular positioning of the cup. Technique. The axis of the pelvis is identified intra-operatively as a line drawn from the highest point of the iliac crest to the middle of the greater trochanter. Prior to reaming the acetabulum, an undersized trial acetabular component is placed parallel and inside the transverse ligament, inside the anterior column and projecting posterior to the axis of the pelvis. This direction is marked and the subsequent reaming and final component placement is performed in the same direction. The lateral opening is judged based on the 45-degree angle from the tear drop to the lateral margin of the acetabulum on anteroposterior pelvic radiographs. The final anteversion of the cup is adjusted based on increased or decreased lumbar lordosis and combined anteversion. Methods. Anteroposterior pelvic radiographs of 100 consecutive patients undergoing posterior THR between September 2010 and March 2011 with this method were evaluated for cup inclination angle and anteversion using EBRA software. Results. There were no malalignments or dislocations. The mean cup inclination angle and anteversion were 41 ± 5.1 degrees (range 37.1 – 48.4) and 22.1 ± 4.8 degrees (range 16.6 – 29.3), respectively. Conclusion. This is a reproducible method of cup positioning and with proper femoral component position and restoring leg length, offset, combined anteversion, and balance soft tissue around the hip. These factors affect the incidence of dislocation, infection, reduced wear, and durability

Introduction: Acetabular component positioning, offset, combined anteversion, leg length, and soft tissue envelope around the hip plays an important role in hip function and durability. In this paper we will focus on acetabular positioning of the cup. Technique: The axis of the pelvis is identified intra-operatively as a line drawn from the highest point of the iliac crest to the middle of the greater trochanter. Prior to reaming the acetabulum, an undersized trial acetabular component is placed parallel and inside the transverse ligament, inside the anterior column and projecting posterior to the axis of the pelvis. This direction is marked and the subsequent reaming and final component placement is performed in the same direction. The lateral opening is judged based on 45-degree angle from the tear drop to the lateral margin of the acetabulum on anteroposterior pelvic radiographs. The final anteversion of the cup is adjusted based on increase or decrease of lumbar lordosis and combined anteversion. Methods: Anteroposterior pelvic radiographs of 100 consecutive patients undergoing posterior THR between September 2010 and March 2011 with this method were evaluated for cup inclination angle and anteversion using EBRA software. Results: There were no malalignment or dislocation. The mean cup inclination angle and anteversion were 41 ± 5.1 degrees (range 37.1 – 48.4) and 22.1 ± 4.8 degrees (range 16.6 – 29.3), respectively. Conclusion: This is a reproducible method of cup positioning and with proper femoral component position, restores leg length, offset, combined anteversion, and balances soft tissue around the hip. These factors affect the incidence of dislocation, infection, reduced wear, and durability

The stem of a femoral component can be helpful in assuring proper implant orientation. However, recent interest in short femoral components with which to better accommodate smaller incisions has resulted in technical challenges to proper implant positioning. In order to avoid component malposition and potential compromise of implant longevity, surgeons may rely upon intra-operative x-rays. However this has major drawbacks: radiation exposure of the OR staff; and accommodation of x-ray equipment without compromise of operating field sterility. There has been created a simple, precise instrument which will ensure proper implant positioning in varus/valgus and flexion/extension planes without the need of intra-operative x-ray. Its reliability has been confirmed by both cadaveric and clinical studies. It has been demonstrated to be 100% accurate in providing proper short femoral component positioning

The alignment of prostheses components has a major impact on the longevity of total knee protheses as it significantly influences the biomechanics and thus also the load distribution in the knee joint. Knee joint loads depend on three factors: (1) geometrical conditions such as bone geometry and implant position/orientation, (2) passive structures such as ligaments and tendons as well as passive mechanical properties of muscles, and (3) active structures that are muscles. The complex correlation between implant position and clinical outcome of TKA and later in vivo joint loading after TKA has been investigated since 1977. These investigations predominantly focused on component alignment relative to the mechanical leg axis (Mikulicz-line) and more recently on rotational alignment perpendicular to the mechanical axis. In general four different approaches can be used to study the relationship between implant position and knee joint loads: In anatomical studies (1), the influence of the geometrical conditions and passive structures can be analyzed under the constraint that the properties of vital tissue are only approximated. This could be overcome with an intraoperative load measurement approach (2). Though, this set up does not consider the influence of active structures. Although post-operative in vivo load measurements (3) provide information about the actual loading condition including the influence of active structures, this method is not applicable to investigate the influence of different implant positions. Using mathematical approaches (4) including finite element analysis and multi-body-modeling, prostheses positions can be varied freely. However, there exists no systematical analysis of the influence of prosthesis alignment on knee loading conditions not only in axial alignment along and rotational alignment perpendicular to the mechanical axis but in all six degrees of freedom (DOF) with a validated mathematical model. Our goal was therefore to investigate the correlation between implant position and joint load in all six DOF using an adaptable biomechanical multi-body model. A model for the simulation of static single leg stance was implemented as an approximation of the phase with the highest load during walking cycle. This model is based on the AnyBody simulation software (AnyBody Technology A/S, Denmark). As an initial approach, with regard to the simulation of purely static loading the knee joint was implemented as hinge joint. The patella was realised as a deflection point, a so called “ViaNode,” for the quadriceps femoris muscle. All muscles were implemented based on Hill's muscle model. The knee model was indirectly validated by comparison of the simulation results for single and also double leg stance with in-vivo measurements from the Orthoload database (www.orthoload.de). For the investigation of the correlation between implant position and knee load, major boundary conditions were chosen as follows:. •. Flexion angle was set to 20° corresponding to the position with the highest muscle activity during gait cycle. •. Muscle lengths and thereby also muscle loads were adapted to the geometrical changes after each simulation step representing the situation after post-operative rehabilitation. As input parameters, the tibial and femoral components' positions were independently translated in a range of ±20mm in 10 equally distant steps for all three spatial directions. For the rotational alignment in adduction/abduction as well as flexion/extension the tibial and femoral components' positions were varied in the range of ±15° and for internal/external rotation within the range of ±20°, also in 10 equally angled steps. Changes in knee joint forces and torques as well as in patellar forces were recorded and compared to results of previous studies. Comparing the simulation results of single and double leg stance with the in-vivo measurements from the Orthoload database, changes in knee joint forces showed similar trends and the slope of changes in torques transmitted by the joint was equal. Against the background of unknown geometrical conditions in the Orthoload measurements and the simplification (hinge joint) of the initial multi-body-model compared to real knee joints, the developed model provides a reasonable basis for further investigations already – and will be refined in future works. As influencing parameters are very complex, a non-ambiguous interpretation of force/torque changes in the knee joint as a function of changes in component positions was in many cases hardly possible. Changes in patella force on the other hand could be traced back to geometrical and force changes in the quadriceps femoris muscle. Positional changes mostly were in good agreement with our hypotheses based on literature data when knee load and patellar forces respectively were primarily influenced by active structures, e.g. with regard to the danger of patella luxation in case of increased internal rotation of the tibial component. Whereas simulations also showed results contradicting our expectations for positional changes mainly affecting passive structures, e.g. cranial/caudal translation of the femoral component. This shows the major drawback of the implemented model: Intra-articular passive structures such as cruciate and collateral ligaments were not represented. Additionally kinematic influences on knee and patella loading were not taken into account as the simulations were made under static conditions. Implementation of relative movements of femoral, tibial and patella components and simulation under dynamic conditions might overcome this limitation. Furthermore, the boundary condition of complete muscle adaptations might be critical, as joint loads might be significantly higher shortly after operation. This could lead to a much longer and possibly ineffective rehabilitation process

Introduction. A femoral rotational alignment is one of the essential factors, affecting the postoperative knee balance and patellofemoral tracking in total knee arthroplasty (TKA). To obtain an adequate alignment, the femoral component must be implanted parallel to the surgical epicondylar axis (SEA). We have developed “a superimposable Computed Tomography (CT) scan-based template”, in which the SEA is drawn on a distal femoral cross section of the CT image at the assumed bone resection level, to determine the precise SEA. Therefore, the objective of this study was to evaluate the accuracy of the rotational alignment of the femoral component positioned with the superimposed template in TKA. Patients and methods. Twenty-six consecutive TKA patients, including 4 females with bilateral TKAs were enrolled. To prepare a template, all knees received CT scans with a 2.5 mm slice thickness preoperatively. Serial three slices of the CT images, in which the medial epicondyle and/or lateral epicondyle were visible, were selected. Then, these images were merged into a single image onto which the SEA was drawn. Thereafter, another serial two CT images, which were taken at approximately 9 mm proximal from the femoral condyles, were also selected, and the earlier drawn SEA was traced onto each of these pictures. These pictures with the SEA were then printed out onto transparent sheets to be used as potential “templates” (Fig. 1-a). In the TKA, the distal femur was resected with the modified measured resection technique. Then, one template, whichever of the two potential templates, was closer to the actual shape, was selected and its SEA was duplicated onto the distal femoral surface (Fig. 1-b). Following that, the distal femur was resected parallel to this SEA. The rotational alignment of the femoral component was evaluated with CT scan postoperatively. For convention, an external rotation of the femoral component from the SEA was given a positive numerical value, and an internal rotation was given a negative numerical value. Results. The subjects were 4 knees in 4 males and 26 knees in 22 females. A mean age (for 30 knees) at the operation was 76.7 ± 6.1 years (range from 66.4 to 88.3). The posterior condylar angle was −0.27 ± 1.43, and the outlier, more than 3 degrees, was 1 case. Discussion. Conventionally, the SEA is palpated intraoperatively, however, the sulcus of the medial condyle sometimes cannot be identified precisely in osteoarthritic degeneration at the medial condyle. Also, the SEA is determined from the posterior condylar axis (PCA) by calculating the posterior condylar angle, which is between the SEA and the PCA, with the measurements from the preoperative CT scan. However, the residual cartilage thickness is not considered in this method, and thus, the SEA is possible to be inaccurate. The simple technology of our template allowed us to determine the SEA directly on the femoral surface, without any influence from bone degeneration. The femoral components could be implanted accurately, and therefore, the superimposed template was considered to improve TKA outcomes with the accurate SEA

Acetabular protrusio is defined radiographically as migration of the femoral head medial to Kohler's line (a line from the lateral border of the obturator foramen to the medial border of the sciatic notch). Protrusio can develop in association with metabolic bone diseases such as osteogenesis imperfecta, Marfan's Syndrome, and Paget's disease, inflammatory arthritis or osteoarthritis, tumors, or result from prior trauma. Acetabular protrusio can cause limited hip motion due to impingement of the femoral neck against the acetabular rim. When protrusio develops in association with osteoarthritis, coxa vara is often also present. Surgical treatment of acetabular protrusio during total hip arthroplasty should lateralise the center of the hip to its anatomic position. This typically can be achieved with use of a larger, slightly oversized, rim fit cementless acetabular component and medial morselised femoral head bone autograft. In cases with more severe deformity, a reconstruction cage may be required. Alternatively a medialised acetabular shell can be used with a lateralised liner. If coxa vara is also present, standard femoral component position (approximately 1cm above the lesser trochanter) can result in an increase in leg length. Careful pre-operative templating should be performed and may require more distal placement of the femoral component to avoid overlengthening the limb

INTRODUCTION. Although the most commonly used method of femoral component alignment in total knee arthroplasty (TKA) is an intramedullary (IM) guides, this method demonstrated a limited degree of accuracy. The purpose of this study was to assess whether a portable, accelerometer-based surgical navigation system (Knee Align 2 system; Orth Align, Inc, Aliso Viejo, Calif) improve accuracy of the post-operative radiographic femoral component alignment compared to conventional IM alignment guide. MATERIALS & METHODS. Since February 2014, 44 consecutive patients (39 female, 5 male) with primary arthritis of the knee were enrolled in this prospective, randomized controlled study. 24 patients underwent TKA (Vanguard RP or PS, Biomet Japan) using the navigation device for the distal femoral resection (Navigated Group), and 20 patients with conventional femoral IM alignment guide. The proximal tibial resection was performed using an extramedullary guide. All the operation was performed by a single senior surgeon (YK) with the same gap balancing technique except for the use of the navigation system for the femur. Accuracy of femoral implant positioning was evaluated on 2 weeks postoperative standing anteroposterior (AP) hip to ankle radiographs. RESUTS. In the navigated group, 100% of patients had an alignment within 90 ± 3° to the femoral mechanical axis in the coronal plane, versus 90.0% in the IM guides cohort (Fig). The mean absolute difference between the intraoperative goal and the postoperative alignment was 0.79 ± 1.0° in the Knee Align 2 cohort, and 1.72 ± 1.6° in the IM guides cohort (P < 0.05). There was a difference in the standard deviations observed for the navigated cases and the conventional cases when femoral component position was considered. There were no technique specific complications associated with the navigation system. DISCUSSION & CONCLUSION. The distal femoral resection has been the main source of error as for the neutral mechanical axis because of the difficulty in visualization and detection of the center of the femoral head. The results in the current study have shown that a portable, accelerometer-based navigation device (Knee Align 2 system) significantly decreases outliers in femoral component alignment compared to conventional IM alignment guides in TKA

Hip resurfacing using metal-on-metal bearings has a number of purported advantages over traditional total hip replacement in the young, active patient. Males in particular can benefit from the bone preservation, stability, and higher activity levels seen with this procedure. As more is learned about the factors affecting long-term outcome of hip resurfacing, component position has emerged as one major predictor of success. Given a well-selected patient, and a well-designed device, acetabular positioning is perhaps the most important determinant of long-term survivorship in hip resurfacing. One feature of resurfacing socket design which has not been widely disseminated is the sub-hemispheric arc of the bearing surface. While the outer circumference of the socket represents a complete hemisphere, and radiographic evaluation may assume that the apparent socket angle is satisfactory, the actual bearing is less than a hemisphere, so that the true abduction of the bearing is considerably more vertical. This important fact leads to excessive bearing inclination, edge loading, and all that follows, including runaway wear, metallosis, ALVAL, and pseudotumors. Inadequate socket anteversion can expose the psoas tendon to abrasion and tendonitis. Too much acetabular anteversion, especially when combined with increased femoral neck anteversion, can result in an overall decrease in bearing contact area, and excessive wear. Femoral component positioning is critical in the prevention of femoral neck fractures, which are a chief cause of early failure. Varus placement increases the tensile stresses on the superior femoral neck. Excessive valgus threatens notching. Both increase femoral neck fractures. Sufficient malposition will ultimately result in edge loading. Edge wear is incompatible with fluid film lubrication, the key to longevity of these bearings

The presence of retained metalwork, previou fractures or osteotomies makes TKA surgery challenging. Obstructed intramedually canals can produce difficulty with the use of IM instrumentation whilst the altered alignment can result in problematic soft tissue balancing. We present a series of 35 patients with deformity who underwent a successful TKA. Between July 2003 and January 2006 35 patients were operated on between 3 centres. All had extraarticular deformities in either the femur or tibia due to previous fractures or exposure to surgery. All underwent TKA surgery using an image free computer navigation system and extramedullary TKA instrumentation. All patients underwent pre-op and post-operative long eg alignment films. The pre-operative long eg films showed an alignment of 16 degrees varus to 18 degrees of valgus. Post-operative alignment ranged from 3 degrees varus to 4 degrees valgus. The femoral component position ranged from 88-91 degrees from the mechanical axis whilst the tibial component position ranged from 89-92 degrees from the mechanical axis of the limb. Total knee arthroplasty in the presence of extraarticular deformity is fraught with problems in regaining limb alignment and soft tissue balancing. This is the largest combined series of patients in which the same navigation system has been used to provide extramedullary alignment and cuts resulting in excellent component positioning and post-operative alignment. We recommend the routine use of computer navigation in these difficult cases

Introduction. Conventional total knee instrumentation is used for most total knee replacements. Computer-assisted total knee arthroplasty (CA-TKA) including custom guides has gained popularity due to its reported accuracy in restoring optimal alignment. CA-TKA has demonstrated increased surgical time and cost, with know risks of pin-site infection and fracture. We assessed the radiographic alignment of conventional TKA by one surgeon and determined whether preoperative alignment has an effect on postoperative alignment. Methods. A prospective series of 100 primary total knee arthroplasties (in 95 patients) from 1/2012-3/2013 were performed by the senior author, using a single conventional instrument system and a consistent methodology of 5° valgus distal femoral cut, intramedullary femoral entry-point, and minor cement balancing. Mechanical axis and component alignment were measured digitally on preoperative and postoperative lower extremity scanograms. Target alignment was set at neutral ± 3°. Knees with preoperative deformity within 0 ± 5° (non-deformed group) and those with >5° varus/valgus (deformed group) were compared using chi-square test. Results. Target mechanical axis alignment (0 ± 3°) was achieved in 79% cases, while 21% remained in varus alignment (Fig 1). The non-deformed group achieved target alignment in 93.2% cases versus 62.2% in the deformed group (p = 0.0006). The femoral component fell within target alignment (90 ± 3°) 80% of the time and most often was in 1° of varus. The tibial component achieved target alignment (90 ± 3°) 96% cases and was most often in neutral (Fig 2). Conclusion. Our results were consistent with those reported in the literature for conventional TKA, with a trend towards under-correction of varus deformity. The majority of the variability stemmed from the femoral component position and careful adjustments should be made to accommodate the individual differences of each patient. Given the significant difference in achieving target alignment between the deformed and non-deformed groups, perhaps CA-TKA could be useful in patients with preoperative deformity > ± 5°

The aim of tissue sparing surgery in total knee arthroplasty is to reduce surgical invasivity to the entire knee joint. Surgical invasion should not be limited only toward soft tissues but also toward bone. The classic technique for total knee arthroplasty implies intramedullary canal invasion for proper femoral component positioning. This phase is associated to fat embolism, activation of coagulation, and occult bleeding from the reamed canal. The purpose of our study was to validate a new extramedullary device which relies on templated data. Two-hundred patients in four different orthopaedics centres were randomized to undergo primary total knee arthroplasty either using standard intramedullary femoral instruments (IM group) or using a new extramedullary device (EM group). A new set of instruments was developed to control the sagittal and coranl plane of the distal femoral resection. The extramedullary instrument was calibrated referencing to templated data obtained from the preoperative long-limb radiograph (Fig 1, 2). Varus-valgus orientation of the resection were established by moving the two paddles according to templated data. An L-shaped sliding tool (5 centimetres long) over the anterior cortex controls the flexion-extension parameter of the resection and is intended to allow a cut flush with the anterior cortex at 0° of angulation with the distal aspect of the femoral diaphysis on the sagittal plane. Femoral component coronal alignment was within 0±3° of the mechanical axis in 86% of the IM group and 88% of the EM group. Sagittal alignment of the femoral component was 0±3° in 80% of the IM group and 94% of the EM group. There was no difference in the average operative time between the two groups. The EM group showed a trend toward less postoperative blood loss. Extramedullary reference with careful preoperative templating can be safely utilized during total knee arthroplasty

No, not my mother, but metal-on-metal (MoM) hips! My involvement in the DEFENSE side of MoM hips has allowed me the luxury of reflection and continued study on the basic and clinical science of this particular wear couple. Much of what I have learned is relevant to other articular couples, and might help you in your next THR. No amount of in vitro laboratory testing can replicate or predict in vivo behavior of a particular wear couple. (Mother Nature always has something new to teach us!) Although MoM implants went through complete pre-market evaluation and approval in both the US and EU, the process is inadequate and does not assure safety or success of new designs and materials. Two year results obtained in pre-market (IDE) studies are of insufficient follow-up for accurate evaluation of new materials or designs. Be conservative! Be neither the first, nor the last, to embrace new technology!. Clinical experience and retrieval analysis of MoM devices has revealed factors that are not as apparent for other wear couples such as metal-on-polyethylene (MoP), or ceramic-on-ceramic (CoC). For instance:. All THR's are at risk of micro-lateralization, or displacement of the femoral head from the acetabular wear couple during swing phase, resulting in edge loading. In addition, impingement or displacement related to component malposition or failure to balance the soft tissues about the hip can produce subluxation, producing edge loading and accelerated wear. In the case of MoM implants, the tribology and wear properties of MoM produce identifiable wear scars; all MoM designs appear to be subject to these phenomena. However, evidence now exists that both MoP and CoC wear couples are at similar risk for accelerated wear, although at different rates than MoM. Hard-on-hard wear couples (ceramic, metal) are less tolerant of edge loading than hard-on-soft (e.g., MoP or CoP) wear couples, and therefore require a higher degree of surgical precision in implant placement and reconstruction of the soft tissue balance of the hip. One of the previously unrecognised factors that can change relative implant position (and therefore, the risk of subluxation or edge loading) is the effect of the lumbar spine on apparent acetabular component position (e.g., changes between sitting, standing, or lying prone). This is largely due to the effect of lumbar spine flexibility, as shown in both orthogonal x-ray (“EOSr”) studies, and dynamic CAT scan studies. There is currently no validated algorithm or technique to assess these factors; however, surgeon awareness and at least clinical assessment preoperatively may result in better positioning of implants. Femoral component position can also have a major effect of the risk of impingement or subluxation of the femoral head; the combined anteversion concept of Dorr et al. should be rigorously adhered during THR. Other issues such as fretting corrosion associated with large diameter femoral heads and tissue response to wear debris may not be anticipated until a very large cohort population is available for examination and analysis. No matter how extensive in vitro testing may be, only clinical experience and retrieval analysis can provide the ultimate reassurance as to the success of a new design or material

Introduction. Proper alignment (tibial alignment, femoral alignment, and overall anatomic alignment) of the prosthesis during total knee replacement is critical in maximizing implant survival[7] and to reduce polyethylene wear[1]. Poor overall anatomic alignment of a total knee replacement was associated with a 6.9 times greater risk of failure due to tibial collapse, that varus tibial alignment is associated with a 3.2 times greater risk[2] and valgus femoral alignment is associated with a 5.1 times greater risk of failure[7]. To reduce this variability intramedullary (IM) instruments have been widely used, with increased risk of the fat emboli rate to the lungs and brain during TKA[6] and possible increase of blood loss[4, 5]. Or, alternatively, navigation has been used to achieve proper alignment and to reduce morbidity[3]. Recently, for distal femoral resection, inertial sensors have been coupled to extramedullary (EM) instruments to improve TKA surgery in terms of femoral implant alignment, with respect to femoral mechanical axis, and reduced morbidity by avoidance of IM canal violation. The purpose if this study is to compare blood loss and alignment of distal femoral cut in three cohorts of patients: 1 Operated with inertial based cutting guide; 2 Operated with navigation instruments; 3 operated with conventional IM instruments. Material and methods. From September to November 2014 30 consecutive patients, eligible for TKA, were randomly divided into three cohorts with 10 patients each:x 1 “EM Perseus”, patient operated with EM inertial based instruments (Perseus, Orthokey Italia srl, Florence, Italy); 2 “EM Nav”, operated with standard navigated technique, where bone resections were planned and verified by mean of navigation system (BLUIGS, Orthokey Italia srl, Florence, Italy); 3 “IM Conv”, operated with standard IM instrumentation. All patients were operated by the same surgical technique, implanted TKA were mobile bearing PS models, Gemini (Waldemar Link, Hamburg, Germany) and Attune (Depuy, Warsaw, Indiana). Anteroposterior, lateral, and full-limb weightbearing views preoperatively and postoperatively at discharge were obtained, taking care of neutral limb rotational positioning in all patients enrolled in the study. Angles between femoral mechanical axis and implant orientation on frontal and lateral planes were measured with a CAD software (Rhinoceros 3, McNeel Europe, Rome, Italy) by two independent persons, average value was used for statistical analysis. Haemoglobin values were recorded at three time intervals: the day before surgery, at 24h follow-up and at patients discharge. Statistical analysis. Kruskal-Wallis test was used to compare differences between the three cohorts in blood loss and femoral implant alignment. Results. All the three cohorts were comparable in terms of age, sex, preoperative limb alignment and preoperative haemoglobin values (Tab. 1). Haemoglobin ad discharge was reduced for all three cohorts (Tab. 2), no significant differences was found even if IM Conv group showed higher loss compared to EM Perseus and EM Nav groups. Femoral implant alignment deviation, considering perpendicularity with femoral mechanical axis as goal, was comparable in frontal and lateral plane for all three cohorts (Tab. 2). Discussion. The aim of the study was to compare the accuracy in femoral component positioning, on the coronal and sagittal plane obtained with a new inertial based EM instrument, with a standard IM distal femoral cutting jig and with navigation. We confirm our hypothesis that the use of inertial based EM instruments to perform the distal femoral bone cut in TKA is reliable and at least as accurate as the standard IM technique and navigation. Our study did not show a statistical decrease in blood loss when the femoral canal was not reamed (in inertial based EM, and navigated groups), even if patient operated with IM instruments had sensibly higher blood loss compared to the other two groups. This study was not exactly powered for that purpose, a study with a larger cohort and strict patient selection criteria would be required. This study demonstrates that inertial based EM instruments is accurate for femoral component alignment in TKA and compares favorably to navigation systems and standard IM techniques. Other indications for the use of inertial based EM instruments include all major femoral extraarticular deformities, the presence of ipsilateral long-stemmed hip arthroplasty, and the presence of hardware such as distal femoral plates and screws or IM nails

Introduction. Impingement of total hip arthroplasties (THAs) has been reported to cause rim damage of polyethylene liners, and in some instances has led to dislocation and/or mechanical failure of liner locking mechanisms in modular designs. Elevated rim liners are used to improve stability and reduce the risk of dislocation, however they restrict the possible range of motion of the joint, and retrieval studies have found impingement related damage on lipped liners. The aim of this study was to develop a tool for assessing the occurrence of impingement under different activities, and use it to evaluate the effects a lipped liner and position of the lip has on the impingement-free range of motion. MATERIALS & METHOD. A geometrical model incorporated a hemi-pelvis and femur geometries of one individual with a THA (DePuy Pinnacle® acetabular cup with neutral and lipped liners; size 12 Corail® stem with 32mm diameter head) was created in SOLIDWORKS (Dassault Systèmes). Joint motions were taken from kinematic data of activities of daily living that were associated with dislocation of THA, such as stooping to pick an object off the floor and rolling over. The femoral component was positioned to conform within the geometry of the femur, and the acetabular component was orientated in a clinically acceptable position (45° inclination and 20° anteversion). Variation in orientation of the apex of the lip was investigated by rotating about the acetabular axes from the superior (0°) in increments of 45° (0°−315°), and compared to a neutral liner. Results. When a lipped liner was used, implant (neck on acetabular rim) impingement was found to occur when performing sit-to-stand from a normal seat, leg cross and pivot, whereas no impingement occurred with a neutral liner. The presence and position of the lip reduced the impingement-free range of motion, compared to the neutral liner. Impingement occurred when the lip was positioned superiorly and anteriorly, when performing most of the activities that were prone to posterior dislocation, and posteriorly, posterior-superiorly and posterior-inferiorly when performing activities prone to anterior dislocation. During sit-to-stand from a normal seat no impingement occurred when a lipped or neutral liner was used. Bone impingement was observed when the performing the roll activity with both lipped and neutral liners. DISCUSSION. Impingement was observed more with lipped liners compared to neutral liners, this agrees with the findings of some clinical studies. The results indicate that the positioning of the lip influences the possible range of impingement-free motion. Considering this and the improved joint stability of using a lipped liner, a balance is required to achieve an optimal range of motion without increasing the risk of dislocation. This tool could potentially to be used to optimise lipped liner design and position, and could assist with the liner selection for patients based on their activities

Different femoral designs in TKA have shown multiple effects on the conformity of the patella-femoral joint. Historically, this anatomical relationship may interfere with clinical results. The objective of this study was to compare the reproducibility of a correct patello-femoral conformity in patients underwent TKA utilizing modern femoral implants. MATERIALS AND METHODS. We performed 50 consecutives TKA in fifty patients affected by knee arthritis utilizing the PFC Sigma System (De Puy, Warsaw, USA) with a new femoral design, having a prolonged anterior flange and a “smoother” throclea. The surgical procedure was performed utilizing the Sigma HP instrumentation to allow 3 degrees of external rotation of the femoral component and the “balanced gaps technique” was chosen. All patellae were replaced. All patients were evaluated preoperatively and at six months follow-up both clinically with the Knee society Score as well as radiografically: standing 30x90 cm. view, Merchant view, standard lateral view and a CT-scan with two millimeters cuts (Berger Protocol) at 20 degrees of flexion were all done. Particular attention was paid to the following CT measurements: patellar tilt, patellar conformity angle, patellar lateralization, femoral component external-rotation in relation to the patellar sitting. Statistical analysis was performed utilizing the t-test e the Wilcoxon test (p<.05). RESULTS. Any patient was dropped from the study group. Femoral component positioning in relationship to the trans-epicondilar axis showed at follow-up an external rotation of 2.74° (± 2.10°) respect to a preoperative value of 5.7 ° (± 1.80°). Average patellar conformity angle was at follow-up 12.5 (range, -2.5 ° - 28.2 °) respect to an average preoperative value of 10.3° (range, 1.5 – 25.6). Average patellar tilt at follow-up was 2.8°(±7.5°) respect to a preoperative average value of 18.5° (±8.5 °). Average lateralization index was at follow-up 2.7 mm (range, - 3.4 – 7.1 mm) respect to a preoperative value of 12.2 mm (± 4.8 mm). CONCLUSION. This study highlighted that a correct utilization of a modern instrumentation and a femoral design with softer edges and a prolonged femoral groove allow for a correct reproducibility of the patello-femoral conformity. TC scan is a reliable method to evaluate the patella-femoral compartment after TKA