Incidence of Radiolucent Lines after Cemented Total Knee Arthroplasty.

Background: Cemented Total Knee Arthroplasty (TKA) provides excellent long-term survival rates and functional results, however, radiolucent lines (RLLs) often appear during early post-operative follow-up and their incidence and clinical significance are unknown. The primary aim was to establish the incidence, location, frequency, and time taken for RLLs to appear within the first year after a primary cemented TKA with an anatomic tibial baseplate (Smith and Nephew, LEGION Total Knee System). Methods: This was a retrospective analysis of 135 primary cemented TKA in 131 patients over three years. We compared demographics, serial radiographs, and early clinical and functional outcomes. Results: There were 65 TKAs (48%) in 62 patients who had RLLs within the first year post-operatively. Most were females (58.8%). Mean age was 68.3 ± 7.9 years. There were 88 RLLs, with the most and second commonest location at the medial tibial baseplate (38%) and anterior femoral flange (23%). 89% were in the bone-cement interface. The largest average length of RLLs were at the anterior flange of the femoral component (1.98 ± 1.33 mm). The average time to development was 6.5 ± 4.1 months. None of these patients had infections nor required revision. Patients with RLLs did not do worse in functional and clinical scoring at 1-year. Conclusion: There was a 48% incidence of physiological RLLs after cemented TKA, with the highest occurrence at the medial tibial baseplate at 38%. These radiolucent lines did not affect early post-operative clinical and functional outcomes of patients.

Numbness after medial unicompartmental knee arthroplasty: Prevalence and effect on functional outcome.

BACKGROUND: The prevalence of skin sensation alteration after total knee arthroplasty is well established but less so in medial unicompartmental knee arthroplasty (MUKA). The aim of this study was to determine the prevalence, extent of numbness and its effect on mid-term functional outcomes after MUKA. METHODS: A level 2 prospective cohort study was conducted. Twenty patients (21 knees) were recruited. Demographics, length of surgical incision and the thigh-to-calf ratio was recorded. At the 1-year postoperative period, the extent of numbness was measured using a quantifiable grid-based system for both pinprick and fine touch. Preoperative, 3 months and 1 year postoperative Knee Society Scores (KSS) and 36-Item Short Form Health Survey (SF-36) scores were recorded. RESULTS: At the 1-year postoperative period, the prevalence of numbness to both fine touch and pin prick was 58% and 66%, respectively. The mean area of numbness to fine touch and pin prick was 336 mm2 and 521 mm2, respectively. The prevalence and extent of numbness was not significantly associated with surgical factors such as incision length and thigh-to-calf ratio. Prevalence and extent of numbness was not significantly associated with SF-36 scores and KSS at the 1-year postoperative period. CONCLUSIONS: There is a high prevalence of numbness around the knee 1 year after MUKA. Surgical incision length and thigh-to-calf ratio was not associated with the extent of numbness. The presence and extent of numbness did not affect functional outcomes scores at the 1-year postoperative period. This study finding allows for accurate preoperative counselling with regards to numbness and its effects for patients undergoing MUKA.

Accuracy of the α-defensin lateral flow assay for diagnosing periprosthetic joint infection in Asians.

OBJECTIVE: This study aimed to test the accuracy of the Synovasure®, α-defensin lateral flow test kit, in diagnosing periprosthetic joint infections (PJIs) in a predominantly Asian population and to evaluate whether other patient or disease factors may affect its results. METHODS: 61 Asian patients comprising 70 hip or knee prosthetic joints, performed between November 2015 and November 2018, were retrospectively evaluated. Cases were categorized as infected or not infected using Musculoskeletal Infection Society (MSIS) Criteria. Synovial fluid was tested for α-defensin using a commercially available kit. . RESULTS: The Synovasure test had a sensitivity of 73.7% (95% confidence interval (CI): 48.8-90.9%) and specificity of 92.2% (95% CI: 81.1-97.8%) in an Asian population, which was slightly lower compared to previously reported studies in a predominantly Caucasian population. The positive predictive value was 77.8% (95% CI: 56.8-90.3%) and the negative predictive value was 90.4% (95% CI: 81.5-95.2%). The test had an area under curve (AUC) of the receiver operating characteristic (ROC) graph of 0.938, which represents an accuracy that is similar to synovial white blood cells (WBCs) and almost equivalent to that of synovial polymorphonuclear cells (PMNs). The presence of diabetes ( p = 0.26), systemic inflammatory joint disease ( p = 0.33), other metallic implants ( p = 0.53), immunosuppression ( p = 0.13), prior antibiotic usage ( p = 0.99), and chronicity of symptoms ( p = 0.34) was not significantly associated with a positive test in patients with PJI. CONCLUSION: The α-defensin lateral flow test kit is highly accurate in the diagnosis of PJI but with slightly lower sensitivity and specificity in an Asian population when compared with previous studies. The test should be used in conjunction with other MSIS criteria to provide clinically relevant and meaningful results for the diagnosis of PJI.

Can preoperative scoring systems be applied to Asian hip fracture populations? Validation of the Nottingham Hip Fracture Score (NHFS) and identification of preoperative risk factors in hip fractures.

INTRODUCTION: Hip fractures in the elderly are a major cause of morbidity and mortality. Determining which patients will benefit from hip fracture surgery is crucial to reducing mortality and morbidity. Our objectives are: 1) to define the rate of index admission, 1-month and 1-year mortality in all hip fracture patients, and 2) to apply the Nottingham Hip Fracture Score (NHFS) to determine validity in an Asian population. MATERIALS AND METHODS: This is a prospective cohort study of 212 patients with hip fractures above 60 years from September 2009 to April 2010 for 1-year. Sociodemographic, prefracture comorbidity and data on functional status was collected on admission, and at intervals after discharge. The main outcome measures were mortality on index admission, 1 month and 12 months after treatment. RESULTS: In our study, the overall mortality at 1-month and 1-year after surgery was 7.3% and 14.6% respectively. Surgically treated hip fracture patients had lower odds ratio (OR) for mortality as compared to conservatively treated ones. The OR was 0.17 during index admission, 0.17 at 1-month, and 0.18 at 12-months after discharge. These were statistically significant. Adjustments for age, gender, and duration to surgery were taken into account. The NHFS was found to be a good predictor of 1-month mortality after surgery. CONCLUSION: Surgically treated hip fracture patients have a lower OR for mortality than conservatively managed ones even up to 1-year. The NHFS has shown to predict 1-month mortality accurately for surgically treated hip fracture patients, even for our Asian population. It can be used as a tool for clinicians at the individual patient level to communicate risk with patients and help plan care for fracture patients.