Patient-specific instrumentation (PSI) has been greatly marketed in knee endoprosthetics for the past few years. By utilising PSI, the prosthesis´ accuracy of fit should be improved. Besides, both surgical time and hospital costs should be reduced. Whether these proposed advantages are achieved in medial UKA remains unclear yet. The aim of this study was to evaluate the preoperative planning accuracy, time saving, and cost effectiveness utilising PSI in UKA.

Data from 22 patients (24 knees) with isolated medial unicompartmental knee osteoarthritis were analysed retrospectively. The sample comprised sixteen men and six women (mean age 61 ± 8 years) who were electively provided with a UKA utilising PSI between June 2012 and October 2014. For evaluation of preoperative planning accuracy (1) planned vs. implanted femoral component size, (2) planned vs. implanted tibial component size, and (3) planned vs. implanted polyethylene insert size were analysed. Since UKA is a less common, technically demanding surgery, depending in large part on the surgeon´s experience, preoperative planning reliability was also evaluated with regard to surgeon experience. Moreover, actual surgical time and cost effectiveness utilising PSI was evaluated.

Preoperative planning had to be modified intraoperatively to a wide extend for gaining an optimal outcome. The femoral component had to be adjusted in 41.7% of all cases, the tibial component in 58.3%, and the insert in 87.5%. Less experienced surgeons had to change preoperative planning more often than experienced surgeons. Utilising PSI increased surgical time regardless of experience. Linear regression revealed PSI-planning and surgeon inexperience as main predictors for increased surgical time. Additionally, PSI increased surgical costs due to e.g. enlarged surgical time, license fees and extraordinary expenditure for MRI scans.

The preoperative planning accuracy depends on many different factors. The advertised advantages of PSI could not be fully supported in case of UKA on the basis of the here presented data – especially not for the inexperienced surgeon.

Several preoperative planning tools in computer-assisted surgery in acetabular fractures have been proposed. Moreover, all these preoperative planning tools are based on geometrical repositioning with their own limitations. The aim of this study was to evaluate the value of our prototype virtual planning tool using a rigid biomechanical model to predict failure in fracture reduction.

Between November of 2015 and June of 2016, 10 patients were operated by the main author for acetabular fracture in our institution. To validate our biomechanical model planning tool, biomechanical simulation was performed for each patient immediately after the surgery. Reduction quality was assessed on post-operative CT scans. A 3D model of the acetabular fracture was build out of the CT images using the non-commercial software Itksnap. Then a biomechanical model implemented within the non-commercial Artisynth framework was used to perform virtual reduction. Surgical approach and surgical strategy according to the operative report were simulated. The simulated reductions and the surgical reductions were compared.

The same reductions were obtained during surgery and biomechanical simulation in the 10 cases. For 7 cases, reduction was achieved by anterior surgical approach and so was the simulation. For 3 cases, reduction was achieved by posterior surgical approach and so was the simulation. The biomechanical simulation found similar results using the same surgical strategy with 9 anatomical reductions (90%) and one imperfect reduction (10%). The mean duration to perform acetabular planning surgery was 24 +/− 9 min [16–38].

Our virtual planning tool using a rigid biomechanical model can predict success or failure in fracture reduction according to the surgical approach and the surgical strategy.

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.

Introduction

Surgical planning for Patient Specific Instrumentation (PSI) in total knee arthroplasty (TKA) is based on static non-functional imaging (CT or MRI). Component alignment is determined prior to any assessment of clinical soft tissue laxity. This leads to surgical planning where assumptions of correctability of preoperative deformity are false and a need for intraoperative variation or abandonment of the PSI blocks occurs. The aim of this study is to determine whether functional radiology complements pre-surgical planning by identifying non-predictable patient variation in laxity.

Introduction

The number of total hip arthroplasties has been increasing worldwide, and it is expected that revision surgeries will increase significantly in the near future. Although reconstructing normal hip biomechanics with extensive bone loss in the revision surgery remains challenging. The custom−made acetabular component produced by additive manufacturing, which can be fitted to a patient's anatomy and bone defect, is expected to be a predominant reconstruction material. However, there have been few reports on the setting precision and molding precision of this type of material. The purpose of this study was to validate the custom−made acetabular component regarding postoperative three−dimensional positioning and alignment.

In the congenital hip dysplasia, patients treated with total hip replacement (THR) often report persistent disability and pain, with unsatisfactory function and quality of life. A major challenge is to restore the center of rotation of the hip and a satisfactory abduction function [1]. The position of the acetabular cup during THR might be crucial, as it affects abduction moment and motor function. Recently, several software systems have been developed for surgical planning of endoprostheses. Previously developed software called HipOp [2], which is routinely used in clinics, allows surgeons to properly position the prosthetic components into the 3D space of CT data. However, this software did not allow to simulate the articular range of motion and the condition of the abductor muscles. Our aim is to present HipOpCT, an advanced version of the software that includes 3D musculoskeletal planning, through the application to hip dysplasia patients to add knowledge in the diagnosis and treatment of such patients who need THR.

40 hip dysplasia patients received pre-operative CT scanning of pelvis and thighs and had their THR surgery planned using HipOpCT. The base planning includes import of CT data, positioning of prosthetic components interactively through multimodal display, as well as geometrical measurements of the implant and the host bone. The advanced planning additionally includes evaluation of femoro-acetabular impingement and calculation of leg lengths, abductor muscle lengths and lever arms through the automatic creation of a musculoskeletal model. The musculoskeletal parameters in all patients were calculated during the surgical planning, and the data were processed to evaluate pre- and post-operative differences in leg length discrepancy, length and lever arm of the abductor muscles, and how these parameters correlated.

The surgical planning led to an increase in the operated leg length of 7.6 ± 5.7 mm. The variation in abductors lever arm was −0.9% ± 4.8% and significantly correlated with the variation in the operated leg length (r = −0.49), pre-operative leg length discrepancy (r = 0.32) and variation in abductors length (r = −0.32). The variation in abductors length was 6.6% ± 5.5%, and significantly correlated with the variation in the operated leg length (r = 0.92), post-operative leg length discrepancy (r = 0.37), pre-operative abductors length (r = −0.37) and variation in abductors lever arm (r = −0.32).

The increase in the operated leg length was strongly correlated to the increase in abductor muscle length. Conversely, abductor lever arms slightly decreased on average, and were inversely correlated to leg length variation and abductors lengths. This interactive technology for surgical planning represent a powerful tool for orthopaedic surgeons to consider the best muscle reconstruction, and for rehabilitation specialists to achieve the best functional recovery based on biomechanical outcomes. In a parallel study, we are investigating how these advanced planning is reflected onto the function, pain and biomechanical outcome after a rehabilitation protocol is completed.

Revision total knee arthroplasty (TKA) can pose significant challenges. Successful reconstruction requires a systematic approach with the ultimate goal being a well fixed and balanced knee prosthesis. Careful preoperative planning is necessary for safe exposure, component removal, and appropriate management of bone loss during revision knee surgery.

Prior to surgery, the cause of failure must be understood. Revision TKA without a clear diagnosis has been shown to lead to predictable poor results. A careful history and physical examination for both intrinsic and extrinsic causes of knee pain need to be performed. An ESR and C-reactive protein should be obtained in every patient with a painful TKA and in cases of serologic abnormalities, a joint aspiration performed.

The integrity of the collateral ligaments and the degree of anticipated bone loss at the time of revision needs to be established. In cases of severe collateral ligament deficiency, the need for constrained or hinged knee implants should be anticipated. Plain radiographs are needed to evaluate present component position, loosening, and osteolysis. Oblique radiographs and advanced imaging (i.e. CT or MRI) have been shown to more accurately quantify the severity of lysis compared to standard radiographs. This careful assessment can help prepare for the need of special implants, stems, wedges, or augments.

Finally, patient risk stratification and medical co-management can help minimise complications following revision TKA. Optimization of potentially modifiable risk factors such as glycemic control, BMI, and preoperative hemoglobin can reduce perioperative morbidity and complications.

Two critical steps in achieving optimal results and minimizing complications (dislocation, lengthening, and intraoperative fracture) are careful preoperative planning and more recently, the option of intraoperative imaging in order to optimise accurate and reproducible total hip replacement. The important issues to ascertain are relative limb length, offset and center of rotation. It is important to start the case knowing the patient's perception of their limb length. Patient perception is equally important, if not more important, than the radiographic assessment. On the acetabular side, the teardrop should be identified and the amount of reaming necessary to place the inferior margin of the acetabular component adjacent to the tear drop should be noted. Superiorly the amount of exposed metal that is expected to be seen during surgery should be measured in millimeters. Once the key issues of limb length, offset, center of rotation, and acetabular component position relative to the native acetabulum have been confirmed along with the expected sizing of the acetabular and femoral components, it is critical that the operative plan is reproduced at the time of surgery and this can best be consistently performed with the use of intraoperative imaging. Advances in digital imaging now make efficient, cost-effective assessment of hip replacement possible. Embedded software allows accurate confirmation of the preoperative plan intraoperatively when correction of potential errors is easily possible. Such technology is now mature after years of clinical use and studies have confirmed its success in avoiding outliers and achieving optimal results.

Accurate glenoid component placement continues to be a challenge. Knowledge that glenoid loosening is affected by malpositioning of the glenoid component has led to the development of patient specific instrumentation (PSI) in an attempt to optimise glenoid positioning. The ideal PSI would be reusable, reliable, cost-effective and robust enough to tolerate the stresses applied by the surgeon in the context of difficult glenohumeral exposure. The VIP system is a CT scan-based PSI with a reusable instrument. The subtle nuances of pre-operative planning will be discussed in a separate short video.

The live surgery will incorporate use of the patient specific instrumentation during glenoid placement and the use of a short stemmed fourth generation total shoulder arthroplasty.

Introduction. In total knee arthroplasty (TKA), the setting position of component and the angle influence surgical results. 3D matching evaluation method using the CT before and after operation was a useful method as a rating system after operation. The anterior femoral cortical line (AFCL) is an anatomical landmark for determining intraoperative femoral component rotation in total knee arthroplasty (Fig.1). Our aim in this study is to evaluate the effectiveness of the JIGEN (Jig Engaged 3D Pre-Operative Planning System for TKA) (LEXI, Japan) operation support system using AFCL. Patients and methods. We performed TKA used GENUS MB (Adler, Italy) by January, 2015 from October, 2013. As for 5 male knees, 37 woman knees, the operation average age were 68 years old. The operation was based on each insertion parameter of the rod in marrow provided by a preoperative plan by the JIGEN system and at first installed a target device in the femoral front and manufactured a insertion point and inserted a rod in the marrow to plan insertion depth (Figure 1). We performed CT photography of the whole lower limbs after operation like preoperation and femoral component setting was located after operation using evaluation software (LEXI, Japan) and evaluated it. Result. In the 3D evaluation, femoral components implanted less than 3 degrees were 98% in the coronal plane, 67% in the sagittal plane, and 79% in the axial plane (Figure 2). The rotational malposition of femoral component was found in the case that the distal femoral front was round. Conclusion. The JIGEN system is useful for operation support in TKA. AFCL has the advantages of easy access and because of its extra-articular position is not affected by articular cartilage or processes that destroy the joint (such as degeneration or osteolysis). We considered that the JIGEN system using AFCL can be effective for determining intraoperative femoral component rotation in TKA

Introduction

Computed tomography (CT) based preoperative planning provides useful information for severe TKA and revision TKA cases, such as the amount of augmentation, length of stem extension and component alignment, to achieve correct alignment and joint line. In this study, we evaluated TKA alignment performed with CT preoperative planning.

We sought to assess the precision of our surgical techniques for total knee replacement in achieving the preoperative plan generated by a combination of MRI scan and long leg radiographs.

For each patient in the study, we used the Visionaire system by Smith Nephew to generate a preoperative plan and custom patient instrumentation according to our usual protocols.

We then performed on three patients a total knee replacement using three different techniques:

Total knee replacement with standard instrumentation.

During surgery we compared the actual bone cuts performed to the cuts predicted by the Visionaire preoperative plan, component sizing, and postoperatively analyzed the alignment achieved for the total knee replacement.

In each case the size used matched the size predicted in our preoperative plan, our bone cuts averaged within 0.5mm of target, and restoration of neutral mechanical alignment of the lower extremity was achieved.

We observed that careful preoperative planning improved our surgical outcomes and regardless of instrumentation used a high level of precision could be achieved.

Puropose

Three-dimensional (3D) templating based on computed tomography (CT) in total hip arthroplasty improves the accuracy of implant size. However, even when using 3D-CT preoperative planning, getting the concordance rate between planned and actual sizes to reach 100% is not easy. To increase the concordance rate, it is important to analyze the causes of mismatch; however, no such studies have been reported. This study had the following two purposes: to clarify the concordance rate in implant size between 3D-CT preoperative planning and actual size; and to analyze risk factors for mismatch.

Introduction

For preoperative planning of Total Hip Arthroplasty (THA) it is paramount to choose the correct implant size to avoid subsidence with too small a component or fracture with too large a component. This planning can be done either in 2D or 3D. 2D templating from X-rays frontal images remains the gold standard technique in THA preoperative planning despite the lower accuracy with uncemented components. 3D planning techniques require a CT-Scan examination overexposing patients to radiation. Biplanar EOS^® radiographs are an alternative to obtain bone 3D reconstructions with a very low dose of radiation. The objective of this study was to evaluate the accuracy and reproducibility a novel 3D technique for THA preoperative planning based on biplanar low-dose radiographs.

Introduction

Recently, computer-aided orthopaedic surgery has enabled three dimensional (3D) preoperative planning, navigation systems and patient matched instrument, and they provide good clinical results in total knee arthroplasty. However, the preoperative planning methods and the criteria in total elbow arthroplasty (TEA) still have not sufficiently established due to the uncertainty of 3D anatomical geometry of the elbow joints. In order to clarify the 3D anatomical geometry, this study measured 3D bone models of the normal elbow joints. Additionally this study attempted to apply the 3D preoperative planning to ordinary surgery. Then the postoperative position of implant has evaluated as compared with the position in 3D preoperative planning.

Despite many new methods with preoperative or intra-operative assistance to improve the accuracy of leg alignment, traditional intramedullary (IM) method of bone cutting is still the most commonly used. Traditional TKR using IM guide has more outliers comparing to new computer aided methods, especially in bowing femur which is more prevalent in Asian population. And IM guide could not be used when there is a medullary bony pathology. Avoiding entrance of medullary cavity has been proposed as one of criteria of minimally invasive TKA.

We have designed an extramedullary (EM) guide for the distal femoral bone cutting with millimeter to millimeter increment which is compatible with all posterior referencing instrumentation systems. With mechanical line as the guide line on long leg X-ray film taking with the knee and foot facing anteriorly, the amount of distal femoral bone cutting was measured and recorded on computer screen pre-operatively. During surgery, distal femoral cutting was performed using the EM cutting jig for coronal alignment adjustment tool and anterior femoral cortex and a guide post as sagittal alignment guide.

We retrogratively compared the post-operation long leg X-ray film of two hundreds patients using IM or EM guides, the mechanical alignment of femoral components were measured in coronal and sagittal planes. The results showed no significant difference in distribution and the ratio of outliers. However, if the bowing of femur is more than 8 degree, the outlier is more in the IM group.

We have applied this technique in 8 patients having medullary pathology including plates or nails in femur. All patients got good post-operative limb alignment without the needs of computer assistance device during surgery.

In conclusion, the technique is easy and the instrument is simple. The operative time was not prolonged; the medullary cavity was not entered and compatible with the principle of MIS technique. In case of medullary cavity is obstructed, it is cost-effective by using our EM guide comparing to other methods such as CAOS or PSI.

Achieving optimal acetabular cup orientation in Total Hip Replacement (THR) remains one of the most difficult challenges in THR surgery (AAOR 2013) but very little has been added to useful understanding since Lewinnek published recommendations in 1978. This is largely due to difficulties of analysis in functional positions. The pelvis is not a static reference but rotates especially in the sagittal plane depending upon the activity being performed. These dynamic changes in pelvic rotation have a substantial effect on the functional orientation of the acetabulum, not appreciated on standard radiographs [Fig1].

Studies of groups of individuals have found the mean pelvic rotation in the sagittal plane is small but large individual variations commonly occur. Posterior rotation, with sitting, increases the functional arc of the hip and is protective of a THR in regards to both edge loading and risk of dislocation. Conversely Anterior rotation, with sitting, is potentially hazardous.

We developed a protocol using three functional positions – standing, supine and flexed seated (posture at “seat-off” from a standard chair). Lateral radiographs were used to define the pelvic tilt in the standing and flexed seated positions. Pelvic tilt was defined as the angle between a vertical reference line and the anterior pelvic plane (defined by the line joining both anterior superior iliac spines and the pubic symphysis). In the supine position pelvic tilt was defined as the angle between a horizontal reference line and the anterior pelvic plane. Supine pelvic tilt was measured from computed tomography.

Proprietary software (Optimized Ortho, Sydney) based on Rigid Body Dynamics then modelled the patients’ dynamics through their functional range producing a patient-specific simulation which also calculates the magnitude and direction of the dynamic force at the hip and traces the contact area between prosthetic head/liner onto a polar plot of the articulating surface, Fig 2. Given prosthesis specific information edge-loading can then be predicted based on the measured distance of the contact patch to the edge of the acetabular liner.

Delivery of desired orientation at surgery is facilitated by use of a solid 3D printed model of the acetabulum along with a patient specific guide which fits the model and the intra-operative acetabulum (with cartilage but not osteophytes removed) - an incorporated laser pointer then marks a reference point for the reamer and cup inserter to replicate the chosen orientation.

Introduction

Patient specific instrumentation (PSI) generates customized guides from an MRI- or CT-based preoperative plan for use in total knee arthroplasty (TKA). PSI software executes the preoperative planning process. Several manufacturers have developed proprietary PSI software for preoperative planning. It is possible that each proprietary software has a unique preoperative planning process, which may lead to variation in preoperative plans among manufactures and thus variation in the overall PSI technology. The purpose of this study was to determine whether different PSI software generate similar preoperative plans when applied to a single implant system and given identical MR images.

Introduction

Radiographs and computed tomography (CT) images are used for the preoperative planning in total knee arthroplasty (TKA), however, these two-dimensional (2D) measurements are affected easily by limb position and scanning direction relative to three-dimensional (3D) bone model analyses. The purpose of our study was to compare these measurements to evaluate the factors affecting the difference.

Preoperative planning is important – an ounce of prevention is worth a pound of cure. It is perhaps useful to consider the process of preoperative planning in three areas: 1) the patient, 2) the hip, and 3) the operative environment.

The Patient - The patient must first be an appropriate candidate for surgery. By this, they should have confirmed arthritis of the hip by radiograph and physical exam and should have failed conservative management. They should have pain and/or physical disability that impair their activities of daily living. They should be fit and willing to undergo surgery. Their expectations of surgical outcome should be reasonable and the anticipated net clinical benefit of the procedure should outweigh the risks.

There are several patient variables that should be optimised prior to surgery. Blood glucose control in diabetics should be tightly controlled prior to surgery as failure to do so results in an increased risk of infection. Anemia should be ascertained in the history and diagnosed with a CBC if suspected. Reasons for anemia should be addressed and hemoglobin should be optimised preoperatively. Nutrition is important to reduce the risk of infection. Be aware of paradoxical malnutrition in the obese. Understand if the patient has an allergy to penicillin and what specifically the reaction is. Patients with a history that is not characteristic of an IgE mediated response should be offered a cephalosporin. The patient's risk of bleeding or clot as well as their tolerance of specific anticoagulants should be understood and planned for regarding the postoperative anticoagulant. Assess the patient for risk of dislocation.

The Hip - Assessment of the hip is important. An AP of the pelvis and lateral of the hip should be obtained in all cases. Any pelvic obliquity should be assessed in relation to leg length discrepancy, and, if necessary, a 3-foot standing x-ray should be obtained. Leg length and offset should be assessed carefully. Beware of the patient with the operative hip presenting as the longer leg as it is difficult to shorten a hip via THA and the net effect of the intervention is most often lengthening. Patients with low offset should be planned for carefully so that low offset components are available. Patients with high offset need corresponding high offset implants in order to avoid leg lengthening. The acetabulum should be assessed for true center of rotation and orientation, as well as for dysplasia or deficiency. The femur should be assessed for shape, offset and neck angle, as well as for any proximal or distal mismatch. Be prepared to remove hardware that will be in the way.

Template all your cases. The most experienced surgeons still template for THA. Have a Plan A and a Plan B for every case

The Operative Environment - The surgeon is ultimately in control of the operative environment. Make sure that the implants anticipated and sizes are available. I personally put them in the room before the case. Ensure that qualified assistants and nurses are available. Know in advance and communicate when high BMI patients are involved. Display the radiographs and anticipated plan and make sure the team is aware of it. Ensure that antibiotics and tranexamic acid (if not contra-indicated) are administered at a timely fashion. Tell the staff in the time out that traffic flow is important and should be reduced to a minimum. Plan to close one of the doors during the case. Make sure protective covering is available and worn, such as protective eyewear and hair covers.