BackgroundThe purpose of this study was to evaluate the influence of image-free computer-assisted navigation system update on outcome in total knee arthroplasty.MethodsThirty-three knees were replaced using the Stryker 3.1 image-free navigation system and 49 knees were replaced using the Stryker 4.0 system. One surgeon took part in all procedures as chief surgeon or first assistant. All patients received the Stryker Scopio NRG CR total knee prosthesis. We compared the accuracy of component positioning measured using radiographs and CT scans, operating time and clinical outcome 1 year after surgery.ResultsThe mean hip-knee-ankle, frontal femoral and tibial component angle were 179.8° (ideally implanted 85%), 89.8° (88%), 90.4° (88%) respectively for the 3.1 group and 179.5° (96%), 90.6° (92%), 90.2° (94%) for the 4.0 group. The mean sagittal tibial component angle was 85.5° (82%) for the 3.1 group and 85.6° (92%) for the 4.0 group. The mean rotational femoral and tibial component angle were −0.5° (81%), −0.7° (73%) for the 3.1 group and 0.0° (84%), 0.4° (72%) for the 4.0 group. There were no statistically significant findings with regard to component positioning.Operating time was significantly longer in the 3.1 group (3.1 group: 137 min, 4.1group: 125 min, P < 0.01).No significant difference was detected in postoperative clinical outcome.ConclusionThe navigation system update from Stryker 3.1 to Stryker 4.0 reduced operating time by 12 min. However, there were no statistically significant findings with regard to component positioning and clinical outcome.

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Background: Lumbar bone stress injury (BSI) is a high-risk long time—loss injury for adolescent soccer players. However, the risk factors for lumbar BSI are unclear. Purpose: To identify the risk factors for bilateral lumbar BSI for adolescent soccer players. Study Design: Case-control study; Level of evidence, 3. Methods: Adolescent soccer players underwent orthopaedic examination, whole-body dual energy x-ray scan, lumbar magnetic resonance imaging (MRI), and muscle tightness testing at baseline. Lumbar lordosis (LL), sacral slope, maturity stage of lumbar vertebral body, and bone marrow edema (BME) at the L5 were examined via MRI. In addition, bone mineral density and content; trunk lean body mass via dual energy x-ray scan; and bilateral muscle tightness including the iliopsoas, hamstrings, and quadriceps were measured. Lumbar BSI was diagnosed as positive bilateral BME and extension-based lumbar pain. All participants were examined twice, one at 6 months and one at 1 year, after the baseline examination. Multivariate logistic regression analysis was performed to identify the risk factors for bilateral lumbar BSI. Results: A total of 69 (26.3%) players were diagnosed with bilateral lumbar BSI. Asymptomatic BME (odds ratio [OR], 4.260; 95% CI, 2.153-8.431), apophyseal stage of the lumbar vertebral body (OR, 3.438; 95% CI, 1.698-6.959), sacral slope relative to LL ≥5° (OR, 4.067; 95% CI, 2.021-8.181), and hamstring tightness ≥50° (OR, 3.221; 95% CI, 1.385-7.489) were significantly associated with bilateral lumbar BSI. Conclusion: The incidence of bilateral lumbar BSI was common at 26.2%. Asymptomatic BME, sacral anterior tilt relative to LL, immature lumbar epiphyses, and hamstring tightness were found to be risk factors for bilateral lumbar BSI. The results of this study suggest that regular MRI examination could facilitate the early detection of BME, and improvement in hamstring flexibility and lumbosacral alignment may prevent bilateral lumbar BSI in young athletes.

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