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

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

Abnormal rate of intraoperative and postoperative implant positioning outliers using ``MRI-based patient-specific'' compared to ``computer assisted'' instrumentation in total knee replacement

International audienceThe aim of this study was to analyze first intraoperative alignment and reason to abandon the use of patient-specific instrumentation using intraoperative CAS measurement, secondly assess by postoperative CT analysis if CI, based on preoperative 3D-MRI data, improved postoperative component positioning (including femoral rotation) and lower limb alignment as compared with results obtained with CAS. In this randomized controlled trial, 80 consecutive patients scheduled to undergo TKA were enrolled. Eligible knees were randomized to the group of PSI-TKAs (n = 40) or to the group of CAS-TKAs (n = 40). In the CAS group, CAS determined and controlled cutting block positioning in each plane. In the PSI group, CAS allowed to measure adequacy of intraoperative alignment including femoral component rotation. At 3 months after surgery, implants position were measured and analyzed with full-weight bearing plain radiographs and CT scan. Intraoperatively, there was a significant difference concerning Sagittal Femoral mechanical, Frontal tibial mechanical angle and tibial slope between the two groups (respectively p = 0.01, p = 0.02, p = 0.046). Custom instrumentation was abandoned intraoperatively in seven knees (17.5 %). Abnormal tibial cuts were responsible of the abandon in three out of seven cases, femoral cut in 1/7 and dual abnormalities in 3/7. Postoperatively, tibial slope outliers percentage was higher in the patient specific instrumentation group with six patients (18.18 %) versus one patient (2.5 %) in the CAS group (p = 0.041). Patient specific instrumentation was associated with an important number of hazardous cut and a higher rate of outliers in our series and thus should be used with caution as related to. This study is the first to our acknowledgement to compare intra-operative ancillary and implant positioning of PSI-TKA and CAS-TKA. High rate of malposition are sustained by our findings, as such PSI-TKA should be used with caution, by surgeons capable to switch to conventional instrumentation intra-operatively. Randomized control trial, Level I

Mid-term survivorship of Mini-keel (TM) versus Standard keel in total knee replacements: Differences in the rate of revision for aseptic loosening

International audienceIntroduction: To reduce the size of the surgical incision, modular mini-keel tibial components have been developed with or without extensions for the Nexgen (TM) MIS Tibial Component. Although a smaller component could theoretically result in defective fixation, this has never been evaluated in a large comparative series. Thus, we performed the following case control study to: (1) evaluate intermediate-term survival of a modular ``mini-keel'' tibial component compared to a reference standard keel component from the same line of products (Nexgen LPS-Flex Tibial Component, Zimmer); (2) to identify any eventual associated factors if the frequency of loosening was increased. Hypothesis: The rate of revision for aseptic tibial loosening is comparable for both components. Materials and methods: This comparative, retrospective, single center series of 459 consecutive total knee arthroplasties (TKA) was performed between 2007 and 2010: with 212 modular ``mini-keel'' (MK) tibial components and 247 ``standard'' (S) components. Survival, rate of revision for aseptic tibial loosening and identification of a radiolucent line were analyzed at the final follow-up. Results: After a median follow-up of 5years, the rate of revision for tibial aseptic loosing was significantly higher in the MK group with 12 cases (5.7%) and 4 cases in the S group (1.6%) (P=0.036). The use of the MK component appears to be a prognostic factor for surgical revision (hazard ratio=3.86 (1.23-11.88), P=0.02) but not for the development of a radiolucent line (HR=1.75 (0.9-3.4), P=0.097). The mean delay before revision was 38months (8-64) in the MK group and 15.2months (8-22) in the S group (P=0.006). Individual factors, such as gender, body mass index (BMI) and pre- or postoperative alignment were not prognostic factors for revision or radiolucent lines. Conclusion: The modular ``mini-keel'' tibial component was associated with a greater risk of revision for tibial component loosening. (C) 2016 Elsevier Masson SAS. All rights reserved