Effect of Posterior Cruciate Ligament Resection on Gap Balancing in Robot-assisted Total Knee Arthroplasty.

OBJECTIVE: Retention or sacrifice of the posterior cruciate ligament (PCL) is one of the most controversial issues while performing total knee arthroplasty (TKA). This study aimed to evaluate the impact of PCL resection on flexion-extension gaps, femoral component rotation, and bone resection amounts during robot-assisted TKA. METHODS: This prospective study included 40 patients with knee osteoarthritis who underwent robot-assisted posterior-stabilized (PS) TKA between September 2021 and February 2022. Of the patients, 75% were women (30/40) with a mean age and BMI of 72.6 years and 27.4 kg/m2, respectively. The guidance module and camera stand assembly were used to capture gaps before and after PCL resection. Measurements of femoral component rotation and bone resection amounts were made in cruciate-retaining (CR) TKA mode and PS-TKA mode. RESULTS: After PCL resection, the mean change in the medial and lateral compartments of flexion gaps increased by 2.0 and 0.6 mm, respectively (p < 0.001). Compared with the CR-TKA mode group, the bone resection amounts of the medial posterior condyle and the lateral posterior condyle in the PS-TKA mode group decreased by 2.0 ± 1.1 and 1.1 ± 1.1 mm, respectively, and the external rotation of the femoral prosthesis relative to the posterior condylar axis and trans-epicondylar line was reduced by 1.0° ± 1.3° and 1.2° ± 1.6°, respectively (p < 0.001). CONCLUSION: The release of the PCL did not affect the extension gap, but significantly increased the flexion gap. Moreover, the increases in the medial flexion gap were greater than those of the lateral flexion gap. After PCL resection, less external rotation of the femoral prosthesis and fewer bone cuts of the posterior femur were needed in PS-TKA.

Diagnostic Role of Metagenomic Next-Generation Sequencing in Tubercular Orthopedic Implant-Associated Infection.

Objective: The diagnosis of tubercular orthopedic implant-associated infection (TB-IAI) is challenging. This study evaluated the value of metagenomic next-generation sequencing (mNGS) for the diagnosis of TB-IAI and developed a standardized diagnostic procedure for TB-IAI. Methods: The records of all patients with TB-IAI diagnosed and treated at our institution between December 2018 and September 2022 were retrospectively reviewed. Patient demographic characteristics, medical history, laboratory test, microbial culture, histopathology, and mNGS results, and time to diagnosis were recorded. The diagnostic efficiency of mNGS for TB-IAI was assessed by comparing the results and diagnostic time with that of other diagnostic modalities. Results: Ten patients were included in the analysis, including eight with prosthetic joint infections and two with fracture-related infections. The mNGS positivity rate was 100% (10/10), which was higher than that of TB-antibody (11%, 1/9), real-time quantitative polymerase chain reaction (22%, 2/9), T-SPOT.TB (25%, 2/8), purified protein derivative (50%, 4/8), microbial culture (50%, 5/10), and histopathology (20%, 2/10). mNGS shortened the time to diagnosis of TB-IAI. A standardized diagnostic procedure for TB-IAI was developed based on the findings. Conclusion: mNGS is useful for the diagnosis of TB-IAI. mNGS is recommended in cases where it is difficult to identify a pathogen using routine diagnostic tests. The standardized diagnostic procedure might improve TB-IAI diagnosis. Importance: TB-IAI is a rare infection, which occurs after orthopedic surgery and hard to diagnose microbiologically. mNGS is a new detection technique not yet discussed in current literature as a means for TB-IAI diagnostics. Here we describe a cohort of patients with TB-IAI diagnosed by mNGS show high efficiency of mNGS for detection of this pathology and present a clinical algorithm supplementing conventional methods for TB-IAI assessment.

Use of 1.5-Stage Functional Articulating Hip Spacers for Two-Stage Treatment of Hip Infection.

BACKGROUND: A two-stage treatment is commonly used for chronic hip infections. This study compared the clinical efficacy and complications associated with 1.5-stage functional articulating hip spacers (FAHS) and handmade spacers utilized during two-stage treatment. METHODS: This retrospective study included 50 patients who had hip infections, of which 41 were periprosthetic joint infections, 3 were internal fixation infections, and 6 had septic arthritis. They were divided into two groups according to the spacer type: 23 patients treated with handmade spacers comprising 1 to 2 Kirschner wires as an endoskeleton (group A) and 27 patients treated with 1.5-stage FAHS comprising a cemented femoral stem, metal femoral head, and polyethylene acetabular liner or cemented acetabular cup (group B). Clinical characteristics, surgical data, infection control rate, spacer complications, modified Harris hip, visual analog scale, and 36-item short-form physical functioning scale scores were compared between the groups. All patients were followed up for at least 24 months after the last surgical procedure. RESULTS: No significant differences were noted in the infection eradication rate between the two groups (100 versus 96.30%, P = 1.0). The incidence of mechanical complications, especially spacer fracture, was significantly lower in group B than in group A (P = .044). Hip function and quality of life were significantly better in group B during the interim period. Group B patients had a longer interval time (median 7.40 versus 4.30 months, P = .004) and a lower reimplantation rate than group A patients (42.31 versus 82.61%, P = .004). CONCLUSIONS: The 1.5-stage FAHS surgical technique is feasible for the treatment of hip infection, with a lower mechanical complication rate, better hip function, and better quality of life during the interim period compared to that of handmade spacers. The 1.5-stage FAHS with maintained function could delay or negate the need for second-stage revision.