Factors associated with bilateral discoid lateral meniscus tear in patients with symptomatic discoid lateral meniscus tear using MRI and X-ray.

BACKGROUND: The incidence of bilateral discoid lateral meniscus (DLM) is as high as 73 to 85%, and associated contralateral meniscus tears ranged from 4 to 33% in symptomatic surgical DLM. The goal of the study was analyzing the factors that predict contralateral presence and tearing of DLM in patients who underwent surgery for symptomatic DLM. Our hypothesis was that there is a significant correlation between operative DLM properties and the incidence of bilateral DLM with associated contralateral meniscus tears. These properties include tear patterns, younger patient age, and characteristic X-ray findings. PATIENTS AND METHODS: This prospective study included 76 patients who underwent arthroscopic surgery for symptomatic DLM. The contralateral knees were evaluated with X-ray and MRI. Based on the MRI findings, DLM was categorized into three types, and tear patterns were analyzed. The characteristic X-ray findings were evaluated as follows: (1) high fibular head, (2) squared-off appearance of the lateral femoral condyle, (3) cupping of the lateral tibial plateau, (4) widened femorotibial joint space, (5) hypoplasia of the lateral intercondylar spine, (6) notching of the LFC. The number of characteristic X-ray findings (0/1/more than 2) was noted. Binary logistic analysis was performed to find the factors that predict the presence and tear of contralateral DLM. RESULTS: MRI of contralateral knees revealed 43 cases (57%) of complete DLM, 25 cases (33%) of incomplete DLM, and 8 cases (11%) of normal meniscus. Meniscus tears were found in 29 cases (38%) in the contralateral knee. X-ray of the contralateral knee revealed that 27 patients (36%) had one and 24 patients (32%) had two or more characteristic X-ray findings. On logistic regression analysis, the associations between contralateral knee meniscal tear and the presence of one or more than two characteristic X-ray findings were statistically significant (OR: 16.5, p=0.028; OR: 264.0, p=0.000, respectively). DISCUSSION: The number of characteristic X-ray findings in the contralateral knee is a significant predictive factor for contralateral DLM type and/or tear. Symptomatic DLM patients with characteristic X-ray findings should be carefully evaluated for contralateral DLM and meniscal tears. LEVEL OF EVIDENCE: III, prospective diagnostic study of consecutive patients.

High incidence of early subtrochanteric lateral cortical atrophy after hip arthroplasty using bone-conserving short stem.

PURPOSE: Load transfer to the bone is believed to be more physiological around the short stem in total hip arthroplasty (THA). However, we found unusual bony remodeling around the shortened tapered stem. This study was performed to investigate the extent and frequency of this phenomenon and to find the possible risk factors of it. METHODS: Among 121 consecutive THA using the same short stem, 80 THAs were enrolled. Radiographic measurements were made using anteroposterior (AP) radiographs taken immediately and at two years after surgery. The thickness of the lateral cortex at the level of the distal end of the coated surface and at 10, 20, 30, and 40 mm proximal to it were measured. RESULTS: Significant atrophy was noted in all regions (P < 0.001 each). In 46 cases, this presented as an intra-cortical osteolytic line (IOL). Sixty-one cases showed either an IOL or atrophy >10%. The risk of a mean reduction >20% was related to an increased operating time (odds ratio [OR] = 0.981; 0.966 < 95% confidence interval [CI] < 0.996) and lower body mass index (BMI) (OR = 1.216; 1.043 < 95% CI < 1.417). Periprosthetic fracture through the lateral cortex occurred in one case. CONCLUSION: Even with THA using a shortened stem, high incidence of proximal stress shielding was noted in the form of lateral cortical atrophy, especially for the patient with low BMI.

Dissociation of Polyethylene Liner of the Dual Mobility Acetabular Component after Closed Reduction of Dislocation: A Case Report.

A dual mobility acetabular component has a structure that combines a polyethylene liner and a femoral head, unlike the general design of acetabular cups, making the dissociation of a polyethylene liner highly unlikely. In addition, it increases the range of motion and reduces the possibility of dislocations by increasing a jump distance. A fifty-one-year-old male who had received total hip arthroplasty with the dual mobility acetabular component visited a hospital for a posterior hip dislocation 10 weeks after the operation. At the emergency room, closed reduction was performed and the dislocation was reduced. However, plain imaging test revealed polyethylene liner dissociation after the closed reduction. Revision surgery was performed. We will report a rare case of early dislocation of the dual mobility acetabular component and dissociation of polyethylene liner accompanied with a literature review.