Total knee arthroplasty with the Medial-Pivot knee system: Clinical and radiological outcomes at 9.5 years' mean follow-up.

INTRODUCTION: The "ball-in-socket" design of the Medial-Pivot knee system (MicroPort Orthopedics, Arlington, Tennessee, USA) aims to reproduce normal knee kinematics by medializing its rotational axis. The goal of this study was to measure knee range of motion (ROM) with this implant after a mean follow-up of 10 years and to report the survivorship and long-term clinical and radiological outcomes. We hypothesized the prosthetic knee would have at least 120° flexion at 10 years. MATERIAL AND METHODS: This was retrospective, single-centre study of 74 Medial-Pivot knees implanted in 71 patients (average age of 69 years) between May 2005 and November 2007. All patients who received a Medial-Pivot knee were included consecutively. The mean follow-up was 10 years. Clinical and radiological assessments were performed using the Knee Society Score (KSS) and Ewald's score. Kaplan-Meir survival analysis was used to calculate survivorship. RESULTS: Seven percent of cases were lost to follow-up. The knee ROM was 110° at 10 years. The survivorship was 93% for all revision causes and 95.9% when revisions due to trauma or infection were excluded. The mean KSS score was 195. Stable radiolucent lines were found in 14% of cases. No aseptic loosening was observed. CONCLUSION: Our hypothesis was not confirmed. Knee flexion at the final follow-up was comparable to other semi-constrained implant designs but was not as large as expected. The survival of the Medial-Pivot knee at 10 years is good. Its radiological and clinical outcomes are satisfactory. LEVEL OF EVIDENCE: IV (retrospective cohort study).

Total hip arthroplasty revision by dual-mobility acetabular cup cemented in a metal reinforcement: A 62 case series at a minimum 5 years' follow-up.

INTRODUCTION: Total hip arthroplasty (THA) requires bone reconstruction in case of severe acetabular injury, with risk of dislocation, especially postoperatively. Dual-mobility cups have proved effective in preventing dislocation in THA revision for instability, but their behavior when cemented in a metal reinforcement has been little studied. OBJECTIVES: The present study assessed results for a dual-mobility cup cemented in a metal reinforcement, in terms of aseptic loosening and postoperative instability. MATERIAL AND METHODS: A single-center continuous series of 62 patients receiving such an assembly in THA revision was assessed retrospectively at a minimum 5 years' follow-up. Failure due to aseptic loosening or instability and implant survival at last follow-up were analyzed. RESULTS: Radiological and clinical analysis was performed at a mean 77 months' follow-up. Mean Merle-d'Aubigné-Postel score was 14, Harris score 73 and Oxford-12 score 23.9 at last follow-up. Complications comprised 5 cases of loosening and 2 of dislocation. Loosening risk was significantly greater in case of<2mm cement thickness between cup and reinforcement. Eight-year infection-free survival was 91.9%. DISCUSSION: The present clinical results were comparable to those in series using the same kind of assembly; the dislocation rate was low, but the rate of aseptic loosening was higher than reported elsewhere. Cement thickness between cup and reinforcement was a determining factor for stability. Cup design may also be relevant to loosening. This technique seemed to be a good option in THA revision with severe bone loss. LEVEL OF EVIDENCE: IV, retrospective study.

Reproducibility of X-rays and CT arthrography in SLAC, SNAC, SCAC wrists.

The purpose of this study was to assess the inter-observer and intra-observer reproducibility of the interpretation of CT arthrography and plain X-rays for scapholunate advanced collapse (SLAC), scaphoid non-union advanced collapse (SNAC) and scaphoid chondrocalcinosis advanced collapse (SCAC) wrist conditions, as well as the clinical relevance of these imaging modalities. The CT and X-rays images were reviewed twice in a blinded and randomized manner by two experienced orthopedic surgeons specialized in hand surgery, two orthopedic surgery residents and two experienced radiologists specialized in bone and joint imaging. Cohen's kappa and Fleiss' kappa coefficients were used to analyze the reproducibility of interpretation of the radiological examinations. With CT arthrography, the overall diagnosis was often a problem, in terms of both inter- or intra-observer reproducibility. The assessment of the joint line appeared to be fairly reproducible for each observer but was poorly reproducible between different observers. Plain X-rays are not sufficient to assess cartilage quality in degenerative wrist disease. CT arthrography is a reliable examination, but its interpretation is not always standardized. Diagnostic arthroscopy may be justified in doubtful cases.