Coronal malposition effects in total knee arthroplasty: a finite element analysis.

Prosthetic component malposition is not infrequent, because of technical flaws, especially without a computed navigation system. We assumed that an inclined interline of a prosthetic knee with components parallel in the coronal plane provides a better load distribution and lower contact pressure towards a varus malalignment. For that we studied, using finite element analysis, load intensity and distribution for three situations: ideal alignment of prosthetic components, tibial varus malposition of 3° and 8° leading to tibio-femoral varus malalignment (i.e. an unbalanced knee) and the same tibial varus malpositions, but with the femoral component also malpositioned in the coronal plane, so that they are parallel, and with equally tightened collateral ligaments (i.e. a balanced knee). We found that maximum contact pressure and underlying bone compression forces are higher for a balanced knee with an inclined interline than in ideal alignment, but lower than in an unbalanced knee. According to our results, 2- and 4-mm additional medial plateau resection on a proper balanced knee does not significantly affect the load distribution towards ideal alignment. Balancing is a key factor for prosthetic survival in cases when a certain degree of coronal malposition cannot be avoided.

Survival Analysis and Failure Modes of Total Hip Arthroplasty Using a Cemented Semi-Retentive Acetabular Cup.

To reduce the incidence of total hip revisions, there have been continuous efforts to enhance prosthetic materials and designs to optimize implant survival. A primary implant with a constrained acetabular component is often used to minimize the risk of dislocations even though this approach has some drawbacks as reported in the literature. To address these concerns, this study aimed to assess the survivorship and dislocation rate of a semi-retentive cemented acetabular cup when used as a primary implant. The specific cemented cup that we studied was not present in any study that we consulted, so to fill this gap, we conducted a retrospective examination of 527 cemented hip prostheses that utilized the semi-retentive cup between the years 2005 and 2012. We employed Cox multiple regression models for our statistical analysis. The revision due to dislocation occurred in 12.8% of all cases, with a lower incidence of 5% (14 cases) in age groups >70 years than in age groups <70 years (14%-32 cases) (p < 0.001). The survival rates of the semi-retentive cemented acetabular cup were 98.6% (520 cases) at 5 years and 92.2% (487 cases) at 10 years. The survival rates were significantly lower in women than men, with 1.9% (7 cases) toward 0% at 5 years and 8.1% (30 cases) toward 5% (7 cases) at 10 years (p = 0.002). The difference in failure rates between age groups over 70 years (2.3%-10 cases) and age groups under 70 years (11.5%-34 cases) was also statistically significant (p < 0.001). Our study indicates that the semi-constrained design may cause frequent damage to the polyethylene liner due to impingement and wear, which are the primary factors for failure. Also, this implant has a similar risk of revision due to dislocation as reported in studies and may be beneficial as a primary implant in elderly patients with low-demanding lifestyles, muscular insufficiency, and low compliance regarding hip prosthetic behavior, without a major effect on survivorship.

A finite element analysis for predicting outcomes of cemented total knee arthroplasty.

The study was designed to assess the validity of a finite element analysis for predicting the behavior of cemented knee implant used in total knee arthroplasty (TKA), for different mechanical loads, and correlation with clinical outcomes of this procedure. We conducted computational simulations using finite element analysis of two situations: i) The ideal prosthetic component positioning; and ii) variable varus tibial malposition, but with a balanced knee. A total of 80 cemented TKAs performed on 70 patients were divided into two groups. Patients from one group required secondary asymmetric tibial recut for balancing the prosthetic knee and patients from the other group, did not. In regards to the results, we observed no differences upon analysis of the postoperative results of the Knee Society Score (KSS), the angle between the femur and tibia, the range of motion and frontal laxity between groups. The finite element analysis showed that in a 3˚ varus inclination of the joint interline, but with a balanced knee, the maximum contact stress, measured on the tibial plateau surface, increased by 11% compared to the value of mechanical alignment. In conclusion, analysis of the computational model using finite elements showed predictable results of cemented TKA for the different situations of mechanical loads.

Giant Cell Tumor of Long Bones Outcomes of Treatment Corelating with Histopathological Grade.

INTRODUCTION: Giant cell tumor (GCT) of bone is a borderline lesion of bones, meaning that in certain conditions it could be transforming in malignant tumor. This article describes the clinical outcome of patients with giant cell tumor of bone and discusses the surgical options for this lesion corelating with histopathological grade. MATERIAL AND METHODS: From 2007 to 2015, 15 patients who met the histological criteria of giant cell tumor of bone were treated at our institution. Diagnosis and histopathological grade were established by biopsy and extemporaneous exam during surgery. Procedure to be selected was decided based on histopathological grade. Outcomes: In all cases the joint functional results were good except 3 cases (20%) where recurrence occurred. In one case the local recurrence was observed after 6 months, and in the other 2 cases, at 3, respectively 5 years after primary treatment. In all 3 cases the initial histopathological exam showed inactive lesions and were treated with curettage and bone grafting. CONCLUSION: In our series it was an early reccurence at 6 months and 2 recidives after 2 years.The histopathological exam has significant role in the management of GCT. All inactive lesions were treated by curettage and bone grafting, and active lesions, by curettage and bone cement filling no matter of Campanacci's grading system. The management is depending mostly on histopathological exam. Low rate of recurrence can be achieved if treatment is selected according to this parameter and with a properly technique.

Human gait and postural control after unilateral total knee arthroplasty.

INTRODUCTION: This study assesses the changes in human gait in the early postoperative phase of unilateral TKA, by evaluating the variability of free moment. MATERIALS AND METHOD: The study group consisted of 10 patients from the Orthopedic Department of the 'Elias' University Hospital in Bucharest who undergone unilateral knee arthroplasty with the same type of posterior cruciate ligament substituting prosthesis. For the evaluation of free moment an AMTI AccuGait force platform was used. RESULTS: Regarding the free moment peaks, for the operated and non-operated limb, increased significantly (p <0.05) in the postoperative period. The stance time was higher post-surgery for both limbs. DISCUSSION: In the early postoperative phase of unilateral TKA, free moment is higher on both the operated and the non-operated limbs, which means that the knees are subjected to higher torques. Shortly after TKA, patients tend to walk with lower speed, with small steps and reduced cadence. Stance time differences between the operated and the non-operated limbs can lead to overuse of the latter, worsening its condition. CONCLUSIONS: It is highly important to adopt a well-managed rehabilitation program in order to increase walking stability. The cost effectiveness of this procedure could be highly dependent on the rehab program. The parameters studied in this article are useful in assessing the rehabilitation protocol.

Total knee arthroplasty following high tibial osteotomy - a radiological evaluation.

The purpose of this study was to evaluate the results of total knee arthroplasty (TKA) following a closed wedge high tibial osteotomy (HTO). A total of 16 TKAs were performed in 16 pacients who had previously undergone a closed wedge (HTO) as a treatement for knee osteoarthritis. The radiographic results were evaluated with respect to the femurotibial angle (FTA), joint line height (JLH), tibial bone resection and Insall-Salvati ratio. The FTA improved in average, from 6.5 degree of varus preoperatively at 5.7 degree of valgus postoperatively. The JLH averaged 14.34 mm preop and 13.81 mm at the last follow-up. The amount of tibial bone resection averaged 5.98 mm, face to 7.5 mm for knees without HTO. The Insall-Salvati ratio was 1.127 preop and 1.172 postop. A meticulous surgical technique may lead to satisfactory results in TKA after HTO, considering the correction of the deformity, the re-estabilish of JLH and the amount of the tibial bone resection.