Artificial total knee designs have revolutionized over time, yet 20% of the population still report dissatisfaction. The standard implants fail to replicate native knee kinematic functionality due to mismatch of condylar surfaces and non-anatomically placed implantation. (Daggett et al 2016; Saigo et al 2017). It is essential that the implant surface matches the native knee to prevent Instability and soft tissue impingement. Our goal is to use computational modeling to determine the ideal shapes and orientations of anatomically-shaped components and test the accuracy of fit of component surfaces. One hundred MRI scans of knees with early osteoarthritis were obtained from the NIH Osteoarthritis Initiative, converted into 3D meshes, and aligned via an anatomic coordinate system algorithm. Geomagic Design X software was used to determine the average anterior-posterior (AP) length. Each knee was then scaled in three dimensions to match the average AP length. Geomagic's least-squares algorithm was used to create an average surface model. This method was validated by generating a statistical shaped model using principal component analysis (PCA) to compare to the least square's method. The averaged knee surface was used to design component system sizing schemes of 1, 3, 5, and 7 (fig 1). A further fifty arthritic knees were modeled to test the accuracy of fit for all component sizing schemes. Standard deviation maps were created using Geomagic to analyze the error of fit of the implant surface compared to the native femur surface.Background
Methods
The major loss of articular cartilage in medial osteoarthritis occurs in a central band on the distal femur, and in the center of the tibial plateau (Figure). This is consistent with varus deformity due to cartilage loss and meniscal degeneration, together with the sliding regions in walking. Treatment at an early stage such as KL grade 2 or 3, has the advantages of little bone deformity and cruciate preservation, and could be accomplished by resurfacing only the arthritic areas with Early Intervention (EI) components. Such components would need to be geometrically compatible with the surrounding bearing surfaces, to preserve continuity and stability. However because of the relatively small surface area covered, compared with total knees and even unicompartmentals, it is hypothesized that EI components will be an accurate fit on a population of knees with only a small number of sizes, and that accuracy can be maintained without requiring right-left components. We examined this hypothesis using unique design and methodology. Average femur and tibia models, including cartilage, were generated from MRI scans of 20 normal males. The images were imported into Geomagic software. Surface point clouds based on least squares algorithms produced the average models. Averages were also produced from different numbers to determine method validity. Average arthritic models were also generated from 12 KL 1–2 cases, and 13 KL 2–3 cases. The 3 averages were compared by deviation mapping. Using the average from the 20 knees, femoral and tibial implant surfaces were designed using contour matching to fit the arthritic regions, maintaining right-left symmetry. A 5 size system was designed corresponding to large male, average male, small male/large female, average female, small female. For the 20 knees, the components were fitted based on the best possible matching of the contours to the surrounding bearing surfaces. For the femoral component the target was 1 mm projection at the center, matching at the ends. The accuracy of reproducing the cartilage surfaces was then determined by mapping the deviations between the implant surfaces and the cartilage surfaces.INTRODUCTION
METHODS
Our aim was to determine the effect of delay to surgery on the time to discharge, in-hospital death, the presence of major and minor medical complications and the incidence of pressure sores in patients with a fracture of the hip. All patients admitted to Vancouver General Hospital with this injury between 1998 and 2001 inclusive were identified from our trauma registry. A review of the case notes was performed to determine the delay in time from admission to surgery, age, gender, type of fracture and medical comorbidities. A time-to-event analysis was performed for length of stay. Additionally, a Cox proportional hazards model was used to determine the effect of delay to surgery on the length of stay while controlling for other pertinent confounding factors. Using logistical regression we determined the effect of delay to surgery on in-hospital death, medical complications and the presence of pressure sores, while controlling for confounding factors. Delay to surgery (p = 0.0255), comorbidity (p <
0.0001), age (p <
0.0001) and type of fracture (p = 0.0004) were all significant in the Cox proportional hazards model for increased time to discharge. Delay to surgery was not a significant predictor of in-hospital mortality. However, a delay of more than 24 hours was a significant predictor of a minor medical complication (odds ratio (OR) 1.53, 95% confidence interval (CI) 1.05 to 2.22), while a delay of more than 48 hours was associated with an increased risk of a major medical complication (OR 2.21, 95% CI 1.01 to 4.34), a minor medical complication (OR 2.27, 95% CI 1.38 to 3.72) and of pressure sores (OR 2.29, 95% CI 1.19 to 4.40). Patients with a fracture of the hip should have surgery early to lessen the time to acute-care hospital discharge and to minimise the risk of complications.
In addition, we measured ankle and brachial pressures in a separate group of 39 patients with the limb in three different positions: flat with the knee in extension (ABPI 1), raised with the knee in extension (ABPI 2), and finally with the knee flexed to 90° (ABPI 3).
ABPI measurements were calculated in the standard fashion, the mean ABPI in each limb position being 1.17 (ABPI 1), 0.87 (ABPI 2) and 0.83 (ABPI 3) respectively.
Antegrade intramedullary nailing via a piriformis fossa start point is the treatment of choice for most femoral shaft fractures in adults. Recently alternate approaches for intramedullary nailing of the femur have been advocated, including retrograde nailing and trochanteric start point antegrade nailing. Reasons cited for considering altenative starting points to the piriformis fossa include a concern about the damage to the hip abductor muscles that may occur during access to the piriformis fossa. There is very little literature about long- term muscle function after standard antegrade intramedullary nailing and the conclusions of the available studies are conflicting. The purpose of this study was to document the hip abductor muscle strength following standard antegrade intramedullary nailing utilizing two different objective measures (KinCom and gait analysis). Objective evidence of hip abductor muscle strength will assist in planning new nailing techniques. Twenty-two patients with isolated femoral shaft fractures who were treated with standard antegrade reamed interlocking intramedullary nailing and who had a minimum one year follow-up were identified. The patients were examined for muscle strength, range of motion and limb length. All of the patients answered a questionnaire and completed the SF-36 and Musculoskeletal Functional Assessment outcome measures. All patients had isokinetic muscle testing of their hip abductors, hip extensors and knee extensors using the KinCom muscle testing machine. Ten of the patients also underwent formal gait lab analysis. Isokinetic muscle testing showed no significant difference from the uninjured contralateral side in hip abduction, hip extension or knee extension. The gait lab analysis failed to show any important changes in gait pattern. SF-36 scores were comparable to norms. MFA scores did not indicate any significant long term disability. Antegrade reamed interlocking intramedullary nailing of femoral shaft fractures utilizing a standard piri-formis fossa starting point is not associated with any significant long term hip abductor muscle strength deficit. Gait pattern returns to normal following femoral shaft fracture treated with this technique and functional outcomes are good.
Fifty-six patients, with a median fourteen years follow-up of isolated tibial shaft fracture treated with an IM nailing, underwent functional evaluation with SMFA and SF-36 questionnaires, as well as an injury specific questionnaire. Thirty-three also underwent clinical and radiological evaluation. Overall, SF-36 scores (PCS 49.9, MCS 52.0) were near normal. Five (15.2%) had physical findings of venous stasis, while a third reported symptoms A third had at least mild OA on radiographs (knee-seven, ankle-eleven). A third of patients had a loss in ankle dorsiflexion, and more than half reported knee pain that was limiting to at least one activity. We conducted a study to evaluate the long term functional outcomes and disabilities of patients with an isolated tibial shaft fracture treated with intramedullary nailing. We identified two hundred and fifty eligible patients from the VGH Orthopaedic Trauma database between 1987 and 1992. A total of fifty-six patients agreed to participate. All were evaluated with the SF-36 and SMFA functional questionnaires, as well as an injury specific questionnaire focusing on knee pain, and symptoms of venous insufficiency. A sub-group of thirty-three patients were evaluated radiographically and by physical examination. We had a median follow-up of fourteen years, with a range from twelve to seventeen years. The SF-36 scores (PCS 49.9, MCS 52.0) were comparable to population norms. Of the questionnaire group (n=56), fifteen denied knee pain with any activity, while twenty-nine had knee pain that was limiting to at least one type of activity. With respect to swelling, eighteen reported asymmetrical swelling affecting the injured limb. However, in the examination group, only five had objective evidence of venous stasis. Knee range of motion was essentially equivalent to the unaffected side, while thirteen patients had a restricted range of motion of the ankle. Radiographically, seven patients had at least mild OA of at least one knee compartment, while eleven had at least mild OA of the tibio-talar joint, despite near anatomic fracture healing. At a median fourteen years following tibial nailing of isolated tibial fractures, patients function very well, but objective and subjective evaluation shows not insignificant sequellae.
