The Effect of Lower Limb Alignment on Tibiofemoral Joint Contact Biomechanics after Medial Meniscus Posterior Root Repair: A Finite-Element Analysis.

INTRODUCTION: The purpose of this study was to determine how variations in lower limb alignment affect tibiofemoral joint contact biomechanics in the setting of medial meniscus posterior root tear (MMPRT) and associated root repair. METHODS: A finite-element model of an intact knee joint was developed. Limb alignments ranging from 4° valgus to 8° varus were simulated under a 1,000 N compression load applied to the femoral head. For the intact, MMPRT, and root repair conditions, the peak contact pressure (PCP), total contact area, mean and maximum local contact pressure (LCP) elevation, and total area of LCP elevation of the medial tibiofemoral compartment were quantified. RESULTS: The PCP and total contact area of the medial compartment in the intact knee increased from 2.43 MPa and 361 mm 2 at 4° valgus to 9.09 MPa and 508 mm 2 at 8° of varus. Compared with the intact state, in the MMPRT condition, medial compartment PCP was greater and the total contact area smaller for all alignment conditions. Root repair roughly restored PCPs in the medial compartment; however, this ability was compromised in knees with increasing varus alignment. Specifically, elevations in PCP relative to the intact state increased with increasing varus, as did the total contact area with LCP elevation. After root repair, medial compartment PCP remained elevated above the intact state at all degrees tested, ranging from 0.05 MPa at 4° valgus to 0.27 MPa at 8° of varus, with overall PCP values increasing from 2.48 to 9.09 MPa. For varus alignment greater than 4°, root repair failed to reduce the total contact area with LCP elevation relative to the MMPRT state. DISCUSSION: Greater PCPs and areas of LCP elevation in varus knees may reduce the clinical effectiveness of root repair in delaying or preventing the development of tibiofemoral osteoarthritis.

Impact of human immunodeficiency virus on 2-year revision rates following lumbar fusion for degenerative spinal conditions: a retrospective cohort study.

BACKGROUND: To our knowledge, no studies exist that evaluate the impact of human immunodeficiency virus (HIV) on long-term revision rates following lumbar fusion. This study aims to understand how HIV impacts 2-year revision rates and 90-day postoperative complication rates following primary lumbar fusion for degenerative spine conditions. METHODS: Data collection was done using PearlDiver Patient Records Database, a national insurance database from 2010-2019. Patients who underwent primary lumbar fusion for degenerative diseases were divided into a cohort of patients that are HIV positive (HIV), have asymptomatic HIV (AHIV), acquired immune deficiency syndrome (AIDS), and HIV-negative at the time of their procedure. Univariate and multivariable regression analyses were performed to determine rates of revision surgery, surgical site infection (SSI), neurological complications, sensory deficits, bowel/bladder dysfunction and myelopathies within two years of surgery as well as 90-day postoperative complications. RESULTS: In total, 216,587 patients were included in this study. Of these, 631 patients (0.29%) had HIV including 502 patients (0.23%) with asymptomatic HIV and 129 patients (0.06%) with AIDS. Relative to the control cohort, patients with HIV had no difference in odds of two-year revision surgery, SSI, neurological complications, sensory deficits, bowel/bladder dysfunction and myelopathies. Patients with HIV did have increased odds of postoperative pneumonia (OR 1.592; 95% CI: 1.048-2.314; P=0.021). AIDS patients had greater odds of respiratory complications (OR 2.585; 95% CI: 1.075-5.264; P=0.017) and septic complications (OR 2.702; 95% CI: 1.122-5.514; P=0.013) 90-day postoperatively. CONCLUSIONS: Our study found that HIV positive status did not significantly affect two-year revision rates compared to the control group. However, there is a higher rate of pneumonia and respiratory complications among HIV positive patients. Before deciding to proceed with surgical intervention in HIV positive individuals, surgeons must carefully consider each patient's specific diagnosis, comorbidities, and risk factors.