Comparative study of intraoperative knee flexion with three different TKR designs

SummaryIntroductionSubstantial flexion after total knee arthroplasty (TKA) is required for certain categories of patients who wish to squat or kneel in their daily life. Many factors influence this postoperative flexion, including the prosthesis design. It is therefore valuable to in vivo analyze these factors on three knee prosthesis designs through a study of their intraoperative flexion.HypothesisThe posterior-stabilized (PS) knee prostheses provide better intraoperative flexion than the ultracongruent (UC) model. Of the currently available PS models, the high-flexion ones have better intraoperative flexion than standard models. Our main focus endpoint was the intraoperative flexion achieved, before soft-tissues closure, during TKA surgical procedure.Patients and methodsThis was a controlled study. Seventy-two osteoarthritic knees requiring TKA were included to compare three selected prosthesis models: the SAL ultracongruent and two PS models (the standard LPS and the LPS Flex). This was a single-operator study, with patients divided into three homogenous, comparable groups, in which intraoperative measurement of flexion was performed using computer-assisted navigation. Statistical analysis allowed comparison of the three models.ResultsIntraoperatively, after prosthesis implantation, before soft-tissues closure, the mean flexion of the LPS-Flex was 134° versus 124° for the SAL (p=0.0004); the mean flexion of the standard LPS model was 130° versus 124° for the SAL (p=0.14); the PS Flex model showed no significant difference (p=0.26) in flexion (134°) compared to the standard model (130°). The SAL ultracongruent model seemed to be a factor reducing the intraoperative flexion by 8° compared to the PS models (p<10−4).DiscussionIn this study, the PS designs (standard or Flex) provided better intraoperative flexion than the SAL ultracongruent design. However, the LPS Prosthesis did not demonstrate superiority over the standard LPS Prosthesis.Level of evidenceLevel III, low-power prospective study

Rotational positioning of the tibial tray in total knee arthroplasty: A CT evaluation

SummaryIntroductionVarious surgical techniques have been described to set the rotational alignment of the tibial baseplate during total knee arthroplasty. The self-positioning method (“self-adjustment”) aligns the tibial implant according to the rotational alignment of the femoral component which is used as a reference after performing repeated knee flexion/extension cycles. Postoperative computed tomography scanning produces accurate measurements of the tibial baseplate rotational alignment with respect to the femoral component.HypothesisThe rotational positioning of the tibial baseplate matches the rotation of the femoral component with parallel alignment to the prosthetic posterior bicondylar axis.Patients and methodsA 3-month follow-up CT scan was carried out after primary total knee arthroplasty implanted in osteoarthritic patients with a mean 7.8° varus deformity of the knee in 50 cases and a mean 8.7° valgus deformity of the knee in 44 cases. The NexGen LPS Flex (Zimmer) fixed-bearing knee prosthesis was used in all cases. An independant examiner (not part of the operating team) measured different variables: the angle between the anatomic transepicondylar axis and the posterior bicondylar axis of the femoral prosthesis (prosthetic posterior condylar angle), the angle between the posterior bicondylar axis and the posterior marginal axis of the tibial prosthesis, the angle between the posterior marginal axis of the tibial prosthesis and the posterior marginal axis of the tibial bone and finally the angle between the anatomic transepicondylar axis and the posterior marginal axis of the tibial prosthesis.ResultsFor the genu varum and genu valgum subgroups, the mean posterior condylar axis of the femoral prosthesis was 3.1° (SD: 1.91; extremes 0° to 17.5°) and 4.7° (SD: 2.7; extremes 0° to 11°) respectively. The tibial baseplate was placed in external rotation with respect to the femoral component: 0.7° (SD : 4.45; extremes –9.5° to 9.8°) and 0.9° (SD: 4.53; extremes –10.8° to 9.5°), but also to the native tibia: 6.1° (SD: 5.85; extremes –4.6° to 22.5°) and 12.5° (SD: 8.6; extremes –10° to 28.9°). The tibial component was placed in internal rotation relative to the anatomic transepicondylar axis: 1.9° (SD : 4.93; extremes –13.6° to 7°) and 3° (SD : 4.38; extremes –16.2° to 4.8°).DiscussionThe tibial component is aligned parallel to the femoral component whatever the initial frontal deformity (P≅0.7). However, a difference was observed between the rotational alignment of the tibial baseplate and the native tibia depending on the initial deformity and could be attributed to the morphological variations of the bony tibial plateau in case of genu valgum.ConclusionThe self-positioning method is a reproducible option when using this type of implant since it allows the tibial component to be positioned parallel to the posterior border of the femur.Level of evidenceLevel III. Observational prospective study

Magnetic resonance imaging, magnetic resonance arthrography and ultrasonography for assessing rotator cuff tears in people with shoulder pain for whom surgery is being considered

Background Shoulder pain is a very common symptom. Disorders of the rotator cuff tendons due to wear or tear are among the most common causes of shoulder pain and disability. Magnetic resonance imaging (MRI), magnetic resonance arthrography (MRA) and ultrasound (US) are increasingly being used to assess the presence and size of rotator cuff tears to assist in planning surgical treatment. It is not known whether one imaging method is superior to any of the others.Objectives To compare the diagnostic test accuracy of MRI, MRA and US for detecting any rotator cuff tears (i.e. partial or full thickness) in people with suspected rotator cuff tears for whom surgery is being considered.Search methods We searched the Cochrane Register of Diagnostic Test Accuracy Studies, MEDLINE, EMBASE, and LILACS from inception to February 2011. We also searched trial registers, conference proceedings and reference lists of articles to identify additional studies. No language or publication restrictions were applied.Selection criteria We included all prospective diagnostic accuracy studies that assessed MRI, MRA or US against arthroscopy or open surgery as the reference standard, in people suspected of having a partial or full thickness rotator cuff tear. We excluded studies that selected a healthy control group, or participants who had been previously diagnosed with other specific causes of shoulder pain such as osteoarthritis or rheumatoid arthritis. Studies with an excessively long period (a year or longer) between the index and reference tests were also excluded.Data collection and analysis Two review authors independently extracted data on study characteristics and results of included studies, and performed quality assessment according to QUADAS criteria. Our unit of analysis was the shoulder. for each test, estimates of sensitivity and specificity from each study were plotted in ROC space and forest plots were constructed for visual examination of variation in test accuracy. Meta-analyses were performed using the bivariate model to produce summary estimates of sensitivity and specificity. We were unable to formally investigate potential sources of heterogeneity because of the small number of studies.Main results We included 20 studies of people with suspected rotator cuff tears (1147 shoulders), of which six evaluated MRI and US (252 shoulders), or MRA and US (127 shoulders) in the same people. Many studies had design flaws, with the potential for bias, thus limiting the reliability of their findings. Overall, the methodological quality of the studies was judged to be low or unclear. for each test, we observed considerable heterogeneity in study results, especially between studies that evaluated US for the detection of full thickness tears and studies that evaluated MRA for the detection of partial thickness tears. the criteria for a positive diagnostic test (index tests and reference standard) varied between studies.Meta-analyses were not possible for studies that assessed MRA for detection of any rotator cuff tears or partial thickness tears. We found no statistically significant differences in sensitivity or specificity between MRI and US for detecting any rotator cuff tears (P = 0.13), or for detecting partial thickness tears (P = 1.0). Similarly, for the comparison between MRI, MRA and US for detecting full thickness tears, there was no statistically significant difference in diagnostic performance (P = 0.7). for any rotator cuff tears, the summary sensitivity and specificity were 98% (95% CI 92% to 99%) and 79% (95% CI 68% to 87%) respectively for MRI (6 studies, 347 shoulders), and 91% (95% CI 83% to 95%) and 85% (95% CI 74% to 92%) respectively for US (13 studies, 854 shoulders). for full thickness tears, the summary sensitivity and specificity were 94% (95% CI 85% to 98%) and 93% (95% CI 83% to 97%) respectively for MRI (7 studies, 368 shoulders); 94% (95% CI 80% to 98%) and 92% (95% CI 83% to 97%) respectively for MRA (3 studies, 183 shoulders); and 92% (95% CI 82% to 96%) and 93% (95% CI 81% to 97%) respectively for US (10 studies, 729 shoulders).Because few studies were direct head-to-head comparisons, we could not perform meta-analyses restricted to these studies. the test comparisons for each of the three classifications of the target condition were therefore based on indirect comparisons which may be prone to bias due to confounding.Authors' conclusions MRI, MRA and US have good diagnostic accuracy and any of these tests could equally be used for detection of full thickness tears in people with shoulder pain for whom surgery is being considered. the diagnostic performance of MRI and US may be similar for detection of any rotator cuff tears. However, both MRI and US may have poor sensitivity for detecting partial thickness tears, and the sensitivity of US may be much lower than that of MRI. the strength of evidence for all test comparisons is limited because most studies were small, heterogeneous and methodologically flawed, and there were few comparative studies. Well designed studies that directly compare MRI, MRA and US for detection of rotator cuff tears are needed.Universidade Federal de São Paulo, BrazilParker Institute, DenmarkOak FoundationTeesside University, UKUniversidade Federal de São Paulo, Dept Orthopaed & Traumatol, BR-04038032 São Paulo, BrazilMonash Univ, Sch Publ Hlth & Prevent Med, Dept Epidemiol & Prevent Med, Monash Dept Clin Epidemiol,Cabrini Hosp, Malvern, AustraliaUniv Birmingham, Birmingham, W Midlands, EnglandUniv Teesside, Hlth & Social Care Inst, Middlesbrough, Cleveland, EnglandUniversidade Federal de São Paulo, Dept Orthopaed & Traumatol, BR-04038032 São Paulo, BrazilWeb of Scienc

Etude anatomique pour l'abord endoscopique de l'espace scapulo-thoracique (dangers des nerfs spinal accessoire, dorsal de la scapula et supra-scapulaire)

PARIS6-Bibl. St Antoine CHU (751122104) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Sectioning of the anterior intermeniscal ligament changes knee loading mechanics

International audienceIntroduction: The aim of this cadaver research project was to describe the biomechanical consequences of AIML resection on menisci function under load conditions in full extension and 60° flexion. Methods: Ten unpaired fresh frozen cadaveric knees were dissected leaving the knee joint intact with its capsular and ligamentous attachments. The femur and tibia were sectioned 15 cm from the joint line and mounted onto loading plateform. A linear motion x-y table allows the tibial part of the joint to freely translate in anterior-posterior direction. K-scan sensors, were used to define contact area, contact pressure and position of pressure center of application (PCOA). Two series of analysis were planed: before and after AIML resection, mechanical testing were performed with specimens in full extension and 60° of flexion to approximate heel strike and foot impulsion during the gait. A standard compression load of 1400 N at full extension and 700N at 60° flexion was applied. Results: Sectioning of the AIML produced mechanical variations bellow the two menisci when specimens were at full extension and loaded to 1400N: increasing of mean contact-pressure (delta 0.4+/-0.2MPa, + 15% variation p=0.008) and maximum contact-pressure (delta 1.50+/-0.8MPa, 15% variation p<0.0001), decreasing of tibio-femoral contact area (delta 71+/-51mm2,-15% variation p<0.0001) and PCOA (delta 2.1+/0.8mm). At 60° flexion, significant differences regarding lateral meniscus mechanical parameters was observed before and after AIML resection : mean contact pressure increasing (delta 0.06+/-0.1MPa, +21% variation p=0.001), maximal contact-pressure increasing (delta 0.17+/-0.9MPa, +28% variation p=0.001), mean contact area decreasing (delta 1.84+/-8mm2 4% variation p=0.3), PCOA displacement to the joint-center (mean displacement 0.6+/-0.5mm). Conclusion: The section of the intermeniscal ligament leads to substantial changes in knee's biomechanics, increasing femoro-tibial contact pressures, decreasing contact areas and finally moving force center of application which becomes more central inside of the joint

Discoid medial meniscus: Report of four cases and literature review

SummaryIntroductionDiscoid medial meniscus is a rare abnormality, with incidence estimated at 0.12%. The present study describes this congenital abnormality anatomically and reports clinical results in four symptomatic cases managed by surgery.Materials and methodA retrospective study included three patients (2 female, 1 male), one of whom had bilateral pathology. Mean age at consultation was 18.5 years (range, 13 to 28 yrs). Presenting symptoms were knee pain, associated with acute locking (1 case) or recurrent effusion (1 case). Plain X-rays were normal. MRI found discoid medial meniscus in all four cases, with intrameniscal hypersignal on T2-weighted sequences.ResultsArthroscopy confirmed the discoid abnormality of the medial menisci. Meniscal tear was systematically associated: horizontal in two cases and vertical in the other two. Three cases showed insertion defect of the anterior horn of the discoid medial meniscus. All two cases were managed by meniscoplasty, removing the central part of the meniscus and sparing its peripheral part. Meniscal repair was associated in one case. Subjective results were assessed by KOOS score. At a mean 23 months’ follow-up (range, 7 to 54 months), mean KOOS score was 82.7 (range, 77.6 to 86.4): 88±5 for pain, 89±8 for other symptoms, 98±1 for function, 69±17 for sports activity, and 69±16 for quality of life.ConclusionSymptomatic discoid medial meniscus is frequently associated with bone insertion abnormality of the anterior horn. Meniscal tear is consistently present and revelatory, indicating meniscal tissue fragility, as in the lateral meniscus. Meniscoplasty, possibly with associated meniscal repair if the remaining meniscal wall is unstable, provides satisfactory but imperfect results while avoiding total meniscectomy, which would be disabling in this age group.Level of evidenceLevel IV Type of study: retrospective

Opening-wedge high tibial osteotomy without bone grafting in severe varus osteoarthritic knee. Rate and risk factors of non-union in 41 cases

International audienc

Sectioning of the anterior intermeniscal ligament changes knee loading mechanics

International audienceIntroduction: The aim of this cadaver research project was to describe the biomechanical consequences of AIML resection on menisci function under load conditions in full extension and 60° flexion. Methods: Ten unpaired fresh frozen cadaveric knees were dissected leaving the knee joint intact with its capsular and ligamentous attachments. The femur and tibia were sectioned 15 cm from the joint line and mounted onto loading plateform. A linear motion x-y table allows the tibial part of the joint to freely translate in anterior-posterior direction. K-scan sensors, were used to define contact area, contact pressure and position of pressure center of application (PCOA). Two series of analysis were planed: before and after AIML resection, mechanical testing were performed with specimens in full extension and 60° of flexion to approximate heel strike and foot impulsion during the gait. A standard compression load of 1400 N at full extension and 700N at 60° flexion was applied. Results: Sectioning of the AIML produced mechanical variations bellow the two menisci when specimens were at full extension and loaded to 1400N: increasing of mean contact-pressure (delta 0.4+/-0.2MPa, + 15% variation p=0.008) and maximum contact-pressure (delta 1.50+/-0.8MPa, 15% variation p<0.0001), decreasing of tibio-femoral contact area (delta 71+/-51mm2,-15% variation p<0.0001) and PCOA (delta 2.1+/0.8mm). At 60° flexion, significant differences regarding lateral meniscus mechanical parameters was observed before and after AIML resection : mean contact pressure increasing (delta 0.06+/-0.1MPa, +21% variation p=0.001), maximal contact-pressure increasing (delta 0.17+/-0.9MPa, +28% variation p=0.001), mean contact area decreasing (delta 1.84+/-8mm2 4% variation p=0.3), PCOA displacement to the joint-center (mean displacement 0.6+/-0.5mm). Conclusion: The section of the intermeniscal ligament leads to substantial changes in knee's biomechanics, increasing femoro-tibial contact pressures, decreasing contact areas and finally moving force center of application which becomes more central inside of the joint