Background

Achieving optimal prosthesis alignment during total knee arthroplasty (TKA) is essential. Imageless computer-assisted surgery (CAS) is developed to improve knee prosthesis alignment and with CAS it is possible to perform intraoperative alignment measurements. Lower limb alignment measurements are also performed for preoperative planning and postoperative evaluation. A new stereoradiography system, called EOS, can be used to perform these measurements in 3D and thus measurement errors due to malpositioning can be eliminated. Since both CAS and EOS are based on 3D modeling, measurements should theoretically correlate well. Therefore, objective was to compare intraoperative CAS-TKA measurements with pre- and postoperative EOS 3D measurements.

Summary

Within hours after exposure to hypoxic circumstances hMSCs start producing AGFs. Initially hypoxia does not affect hMSC proliferation and metabolic activity, but after 7 days both are decreased, compared to hMSCs cultured under ambient oxygen conditions.

Summary

The EOS stereography system has been developed for the evaluation of prosthetic alignment. This new low-dose device provides reliable 2D/3D measurements of knee prosthesis alignment.

Summary

Computer assisted surgery (CAS) during total knee arthroplasty (TKA) is known to improve prosthetic alignment in coronal and sagittal plane. In this systematic review, no evidence is found that CAS also improves axial component orientation when used during TKA.

For amputated patients, direct attachment of upper leg prosthesis to the skeletal system by a percutaneous implant is an alternative solution to the traditional socket fixation. Currently available implants, the OPRA system (Integrum AB, Göteborg, Sweden) and the ISP Endo/Exo prosthesis (ESKA Implants AG, Lübeck, Germany) [1-2] allow overcoming common soft tissue problems of conventional socket fixation and provide better control of the prosthetic limb [3], higher mobility and comfort [2, 4]. However, restraining issues such as soft-tissue infections, peri-prosthetic bone fractures [3, 5–8] and considerable bone loss around the stem [9], which might lead to implant's loosening, are present. Finally, a long a residual limb is required for implant fitting.

In order to overcome the limiting biomechanical issues of the current designs, a new concept of the direct intramedullary fixation was developed. The aim was to restore the natural load transfer in the femur and allow implantations in short femur remnants (Figure 1). We hypothesize that the new design will reduce the peri-prosthetic bone failure risk and adverse bone remodeling.

Generic CT-based finite element models of an intact femoral bone and amputated bones implanted with 3 analyzed implants were created for the study. Models were loaded with two loading cases from a normal walking obtained from the experimental measurements with the OPRA device [10-11]. Periprosthetic bone failure risk was evaluated by considering the von Mises stress criterion [12-14]. Subsequently the strain adaptive bone remodeling theory was used to predict long-term changes in bone mineral density (BMD) around the implants. The bone mineral content (BMC) change was measured around implants and the results were visualized in the form of DXA scans.

The OPRA and the ISP implants induced the high stress concentration in the proximal region decreasing in the distal direction to values below physiological levels as compared with the intact bone. The stresses around the new design were more uniformly distributed along the cortex and resembled better the intact case. Consequently, the bone failure risk was reduced as compared to the OPRA and the ISP implants. The adaptive bone remodeling simulations showed high bone resorption around distal parts of the OPRA and the ISP implants in the distal end of the femur (on average −75% ISP to −78% OPRA after 60 months). The bone remodeling simulation did not reveal any bone loss around the new design, but more bone densification was seen (Figure 2). In terms of total bone mineral content (BMC) the OPRA and the ISP implants induced only a short-term bone densification in contrast to the new design, which provoked a steady increase in the BMC over the whole analyzed period (Figure 3).

In conclusion, we have seen that the new design offers much better bone maintenance and lower failure probability than the current osseointegrated trans-femoral prostheses. This positive outcome should encourage further developments of the presented concept, which in our opinion has a potential to considerably improve safety of the rehabilitation with the direct fixation implants and allow treatment of patients with short stumps.

Objective of the study is to determine to what extent patients experience more limitations 1–5 years after revision total hip arthroplasty (THA) compared to patients after primary THA, and if this is accompanied by a reduction in physical activity behavior. Five hundred and six patients were included: 372 primary and 134 revision THA. Questionnaires were used to measure limitations and physical activity. Linear regression analysis showed that patients after revision surgery report significantly more, clinically relevant limitations compared with primary THA patients, but did not show a significant difference in mean total minutes of physical activity per week. Physical activity behavior appeared to be similar for primary and revision THA patients. The results stress the importance of determining different aspects of recovery after THA.

In oncological resections there is a higher risk of infection around the foot and ankle. An infection here can be difficult to treat and easily lead to an amputation due to the limited amount of soft tissue coverage of the region. In three patients an infection developed after resection of a bone tumour in the foot and ankle.

In the first case, female 34 years, an epitheloid hemangioepithelioma was excised from the anterior part of the calcaneus, cuboid and lateral os cuneiform. An iliac crest graft was initially used to fill the defect, but got infected. The antibiotic loaded bone cement spacer cured the infection and filled the dead space but was painful. A free vascularised fibula with skin-flap was used successfully to fill the defect and take away the pain. At three-year follow-up there is no pain and full weight bearing, with a nice hypertrophy of the graft. In the second case, a 14-year old girl, there was an Aneu-rismal Bone Cyst (ABC) of the distal tibia with a deep infection after ethibloc injection. The vacuum assisted closure cleaned the wound but a defect resulted. It was successfully filled with an ipsilateral free vascularised fibula with skin-flap. Follow-up shows full function and nice hypertrophy at 24 months. In the third case, male 65 years, a chondrosarcoma grade one (after biopsy) in the cuboid was curetted out. It proved grade two in the definitive histology and furthermore it got infected. The cuboid was excised and a cement spacer was placed. The soft tissues were insufficient to close it properly. A free vascularised fibula with skin-flap was used. The vascularity of the graft was insufficient and the skin-flap did not survive. A vacuum assisted closure was done. He can bear weight and has no pain. The fibula graft is shows some hypertrophy and a fistula persists for 18 months now.

We conclude that vascularised free fibula with skinflap can successfully prevent amputation in case of infection in oncological resection of foot and ankle. The fibula reconstructs the bone defect and the skin-flap the soft tissue defect.

In orthopaedic oncology surgical precision is important and intraoperative imaging is often necessary. CAS may enhance precision and provide continuous 3D imaging without radiation. The goal of this work is to report our experience with CAS.

Since 2006 we used CAS (Stryker) in 26 patients with a bone tumour: 11 chondrosarcomas, three osteosarcomas, seven osteochondromas and five miscellaneous. Twelve lesions were located in the femur, six in the pelvis, five in the lower leg and three in the upper extremity. In 18 cases a tumour was excised, in six of these a prosthesis was placed. In eight cases a curettage was done. In 23 cases the navigation was image-based (CT and/or MRI based) and in three cases image-less (no image-preparation necessary preoperatively).

CAS was successfully employed in 23 cases. In three cases the procedure was aborted. In two cases, both in the ulna, we were unable to reconstruct the exact dimensions and in one case (image-less) the tracker was to far away from the work-field. There were no complications related to CAS. Mean precision is 0.5 mm. The time CAS takes is about 15 minutes during the procedure (7–60). In the eight curettages it proved helpful. We did not measure radiation time. In the six resections were tumour-prostheses were placed it was really helpful in rotation and length determination. In three of these, image-less navigation was performed (all distal femur). In osteochondroma resections it is helpful in four of seven cases. All surgical margins were adequate in the resections; after curettage, all MRI controls at three months did not show residual tumour. Oncology follow-up is too short yet; there was one local recurrence after two years in a parosteal osteosarcoma.

We conclude that CAS can be our navigator in orthopaedic oncology; it is successful in providing precision and continuous 3D imaging. The indication area needs further study.

Introduction: Gait before and after total hip arthroplasty (THA) is often determined by walking at preferred speed. However gait function comprises more than just walking at preferred speed. The objective is to describe recovery of gait after THA based on the assessment of spatio-temporal gait parameters determined with an ambulatory system whereby an extended test protocol is used.

Materials and Methods: Sixty-three patients participating in a short-stay program for primary unilateral THA were assessed preoperatively and at 6 weeks and 6 months postoperatively. The spatiotemporal gait parameters walking speed, step length, step duration and variability coefficient (VC) were determined with an ambulatory system using accelerometers. The test protocol contained walking at different speeds, walking while performing an additional cognitive task, and an endurance test.

Results: Patients improved significantly over time; however, the extent and speed of recovery of gait parameters was different for each test part. The relation between walking speed and step length showed systematic improvement when analyzed over a range of speeds. At 6 months, the VC of the additional cognitive task part was comparable with the preferred walking VC. The endurance test results could be predicted from the results of preferred walking.

Conclusion: The assessment of the recovery of gait function requires more than only the assessment of ‘normal’ walking. Particularly, an analysis of walking at different speeds and walking while performing an additional cognitive task demonstrate different aspects of gait recovery after THA.

Introduction: Despite growing awareness of the beneficial effects of physical activity on health, little is known about the amount of physical activity after THA. Although the WOMAC does not give direct information about the amount of physical activity it can be hypothesized that when patients experience limitations this will have an adverse effect on the amount of physical activity they are involved in. In this way the WOMAC can be predictive for the amount of physical activity. The aim of this study is to determine the correlation between the WOMAC and the amount of physical activity and to determine the predictive value of the WOMAC on meeting the (inter-) national guidelines of health -enhancing physical activity.

Materials and Methods: 364 patients with a THA (minimal one year postoperative) were included. Self-reported physical functioning was assessed by means of the WOMAC and the amount of physical activity by means of the SQUASH. Correlations between the WOMAC and SQUASH-scores were assessed using Pearson’s correlation coefficient. Binary logistic regression modelling was used to determine to which extent the score on the WOMAC was predictive in meeting the (inter-)national guidelines.

Results: A significant, low correlation between the WOMAC and SQUASH-scores (range 0.14 – 0.24) was found. Although the WOMAC was a significant predictor to meet the (inter-) national guidelines of physical activity (p< 0.001), the odds-ratio was low (1.022, 95%CI 1.0121.033). The Nagelkerke R2 was 0.069, implicating that 6.9% of the variance could be explained.

Conclusion: The WOMAC is not suitable to predict the amount of physical activity after THA, necessitating the use of additional quantitative outcome measures.

Rat patellae were preincubated with culture medium M199 for one hour and then with either fresh culture medium or Ringer's solution, Ringer lactate, Ringer glucose, normal saline or Betadine for another hour. The rate of proteoglycan synthesis in the articular cartilage was then measured by uptake of 35SO4 for the next 16 hours. Cartilage metabolism was inhibited by all of the solutions even after a recovery time of 16 hours. The inhibition was by 5% for Ringer's solution, 10% for Ringer glucose (p < 0.01), 20% for saline and Ringer lactate (p < 0.001) and 55% for Betadine (p < 0.001). Ringer's solution is therefore the best choice for joint irrigation during arthroscopy or other procedures.

Twenty-five patients with 30 chondral lesions of the knee were treated with an autogenous strip of costal perichondrium. The graft was fixed to the subchondral bone with Tissucol (Immuno, Vienna), a human fibrin glue. The leg was then immobilised for two weeks followed by two weeks of continuous passive motion. Weight-bearing was permitted after three months. The mean knee score (Ranawat, Insall and Shine 1976) changed from 73 before operation to 90 one year after; in 14 patients evaluated after two years there was no decrease. In 28 cases the defect was completely filled with tissue resembling articular cartilage. We conclude that in most cases perichondral arthroplasty of cartilage defects of the knee gives excellent results.