Influence of Patellar Tilt Angle in Merchant View on Postoperative Range of Motion in Posterior Cruciate Ligament-Substituting Fixed-Bearing Total Knee Arthroplasty.

BACKGROUND: We investigated whether the patellar tilt angle influences the maximum knee flexion after total knee arthroplasty (TKA) performed by using a posterior cruciate ligament-substituting (PS) fixed-bearing prosthesis in patients with relatively loose or tight flexion gap. METHODS: In this prospective cohort study, we followed up 169 patients for at least 2 years after TKA using PS fixed-bearing prosthesis. The patients were divided into two groups according to the flexion gap value-calculated by subtracting the thickness of the final bearing from the flexion gap measured intraoperatively under 200-cN·m force after patellar reduction and insertion of the final femoral and tibial components-into a relatively tight group (group T; 3-6.5 mm) and a relatively loose group (group L; 7-11 mm). Patellar tilt angles and maximum non-weight-bearing active knee flexion angles were assessed postoperatively. Group T was further divided into subgroup Tn if the patellar tilt angle was < 5° and subgroup Tw if the angle was ≥ 5°. Pearson correlation test was used for the correlation analysis of the flexion gap, patellar tilt angle, and postoperative flexion range. RESULTS: The mean postoperative flexion was 137.3° in group T and 137.5° in group L. The mean patellar tilt angle was 6.5° in group T and 6.9° in group L. In group T, a strong negative correlation (r = -0.78, p < 0.05) was observed between the patellar tilt and postoperative flexion range. However, further analysis revealed that only the subgroup Tw showed a strong negative correlation (r = -0.76, p < 0.05). Significant correlations were not found in the subgroup Tn and group L. CONCLUSIONS: In TKA where a relatively tight flexion gap (≤ 6.5 mm) is created because of concerns about postoperative flexion instability due to a loose flexion gap, the patellar tilt angle should be < 5° for maximal postoperative knee flexion.

Conversion of Failed Reverse Total Shoulder Arthroplasty to Hemiarthroplasty: Three Cases of Instability and Three Cases of Glenoid Loosening.

BACKGROUND: Glenoid loosening and postoperative instability are common causes of failed reverse total shoulder arthroplasty (RTSA). When soft-tissue problems or large glenoid bone defect interferes with reimplantation in revision RTSA, conversion to hemiarthroplasty can be considered. We present a case series of patients who underwent conversion to hemiarthroplasty due to glenoid loosening and early instability after RTSAs, along with clinical results. METHODS: A total of 72 primary RTSAs using the Aequalis prosthesis were performed at our institution from May 2009 to December 2016. Of these, five patients, including one with humeral neck fracture and absent rotator cuff and four with cuff tear arthropathy, underwent conversion to hemiarthroplasty. Another patient who had RTSA at a local clinic underwent hemiarthroplasty at our institution for unresolved postoperative anterior dislocation. The mean age of the six patients was 71.7 years (range, 62 to 76 years), and the mean follow-up period was 24.4 months (range, 18 to 30 months). Clinical assessments were conducted by using the visual analog scale (VAS), American Shoulder and Elbow Surgery (ASES) score, and University of California at Los Angeles (UCLA) shoulder score at the last follow-up. RESULTS: The conversion to hemiarthroplasty in the six patients dramatically improved the mean VAS score (preoperative, 8.1; postoperative, 2.5), ASES score (preoperative, 22.1; postoperative, 56.5), and UCLA score (preoperative, 12; postoperative, 18.1). However, the range of motion was almost unchanged after surgery. CONCLUSIONS: Conversion to hemiarthroplasty can be a good alternative to revision RTSA in patients with serious complications (such as unresolved instability and glenoid loosening) difficult to treat with revision RTSA.