Mycobacterial periprosthetic joint infection after primary total knee arthroplasty.

PURPOSE: Mycobacterial periprosthetic joint infection (PJI) is very rare and is generally associated with an immunosuppressive environment. Few large-scale studies of this unusual PJI have been conducted. The current study was performed to assess the clinical features and outcomes following two-stage re-implantation for mycobacterial PJI after primary total knee arthroplasty (TKA). METHODS: We conducted a retrospective review of data collected from our database involving ten cases of two-stage re-implantation manifesting mycobacterial PJI. Patients were followed for at least five years or until recurrent infection. The mean follow-up duration in patients who remained free of infection was 7.5 years (range 5-9.5 years). RESULTS: Seven patients (70%) belonged to the American Society of Anesthesiologists' grade 3 or 4. The surgical protocol entailed resection arthroplasty and cement spacer insertion with vigorous debridement, followed by at least six weeks of systemic antimicrobial therapy and delayed re-implantation in all patients. The median duration from resection arthroplasty to re-implantation was 5.3 months (range 2-10.5 months). Following re-implantation, five patients with Mycobacterium fortuitum were treated with amikacin for six weeks and oral clarithromycin for three months. Five patients infected with M. tuberculosis received anti-tuberculosis medications immediately after pathogen isolation, for a period of 12 months. CONCLUSION: Mycobacterial PJI can be treated successfully via resection arthroplasty and delayed re-implantation combined with proper antimicrobial agents. Suspicious infection or loosening after primary TKA, particularly in an immunosuppressive environment, warrants the attention of an orthopedic surgeon to consider the possibility of unusual PJI.

Is further treatment necessary for patellar crepitus after total knee arthroplasty?

BACKGROUND: Patellar crepitus may occur with posterior-stabilized (PS) TKAs. Several studies have suggested numerous etiologies of patellar crepitus after PS-TKA with patellar resurfacing. However, it is unclear whether and to what degree crepitus influences pain and function without or with patellar resurfacing. QUESTIONS/PURPOSES: We therefore determined (1) the frequency of crepitus; (2) which factors predicted the occurrence of crepitus; and (3) whether crepitus influenced pain and function. METHODS: We retrospectively reviewed 41 patients (54 knees) with painful or painless patellar crepitus after primary PS-TKAs without patellar resurfacing performed from 2007 to 2008. These patients were compared with a group of 73 patients (94 knees) without patellar crepitus matched for age, sex, and BMI. The minimum followup was 2 years (mean, 2.8 years; range, 2-4.5 years). RESULTS: Five (9%) of the 54 knees with patellar crepitus also had peripatellar pain. Mean time from primary TKA to the onset of patellar crepitus was 4 months. All patients in the patellar crepitus group were asymptomatic within 1 year of onset of symptoms without additional surgical treatment. The development of patellar crepitus was associated with an Outerbridge patellar cartilage Grade 4 (odds ratio [OR], 11.9; 95% CI, 2.2-65.3) and joint line elevation (OR, 5.1; 95% CI, 1.9-8.6). CONCLUSIONS: Patellar crepitus is typically benign and self-limited. We continue not to resurface arthritic patellae and counsel patients with patellar crepitus that their symptoms will improve without intervention. LEVEL OF EVIDENCE: Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Comparison of patellar retention versus resurfacing in LCS mobile-bearing total knee arthroplasty.

PURPOSE: The aim of this retrospective study was to compare clinical outcomes of total knee arthroplasty (TKA) with and without patellar resurfacing using the Low Contact Stress (LCS) mobile-bearing prosthesis in 275 osteoarthritic knees (199 patients) after a minimum of 7 years of follow-up. METHODS: Patients were divided into a patellar retention group (132 knees) and a resurfacing group (143 knees), with median follow-up durations of 7.8 years (range, 7-8.5 years) and 8.5 years (range, 7-10.6 years), respectively. The demographics of the two groups were otherwise matched. The patelloplasty was performed for patellar retention. Patients were evaluated by a blinded, independent observer using Feller's patellar score, the Knee Society score, patient satisfaction, patellar tilt, and lateral displacement. RESULTS: Patellar resurfacing was not superior to retention with respect to any of the measured variables. Eight knees (6.1%) without and 6 (4.2%) with patellar resurfacing had anterior knee pain related to the patellofemoral joint (n.s.). The reoperation rate related to the patellofemoral joint was 0.8% (n = 1) in the retention group compared with 2.8% (n = 4) in the resurfacing group (n.s.). In the 35 patients who underwent bilateral TKA with patellar resurfacing on only one side, there were no significant differences between the two sides in subjective preference, clinical scores, or functional ability. CONCLUSIONS: The clinical and radiographic outcomes of TKA with the LCS mobile-bearing prosthesis showed no significant difference between the two groups after a minimum of 7 years of follow-up. The findings in this study suggest that patellar retention with a patelloplasty may be viable as a routine procedure, even in knees with advanced patellofemoral arthritis, if soft tissue balancing and a patella-friendly prosthetic design are properly used. LEVEL OF EVIDENCE: Therapeutic, retrospective, comparative study, Level III.

Straight tapered titanium stem with alumina bearing in cementless primary total hip arthroplasty: a minimum 5-year follow-up.

The aim of this study was to assess the midterm results of primary cementless total hip arthroplasty using a tapered stem and alumina bearing couple in active patients. After a minimum of 5 years of follow-up, 78 arthroplasties in 72 patients were reviewed retrospectively. The mean Harris hip score was 94 points, and 2 hips had thigh pain. All components radiographically demonstrated stable fixation by bone ingrowth and mild stress shielding of the proximal femur were noted in 14% of hips. There was no significant osteolysis or aseptic loosening. There was a ceramic head fracture in 1 hip and audible sounds in 2 hips. The results of total hip arthroplasty with a straight, tapered, proximally porous-coated stem and alumina-on-alumina bearing were encouraging for active patients.

Anterior-posterior glide mobile-bearing total knee arthroplasty: complications related to prosthesis design.

The aim of this study was to evaluate complications related to prosthesis design in patients managed with cemented total knee arthroplasty using anterior-posterior glide mobile-bearing prosthesis. One hundred eighty-three total knee arthroplasties were performed using this prosthesis on 146 patients, with a minimum of 7 years of follow-up. There were late dislocations of the bearing in 2 knees, anterior soft tissue impingements in 6 knees at an earlier follow-up, excessive anteroposterior translation in 5 knees, and a fracture of the femoral component induced by osteolysis in 1 knee. Design modifications in the restraint mechanisms of the anterior-posterior glide mobile-bearing prosthesis may be required to minimize the development of complications with regard to sagittal instability and to improve the prosthesis' longevity.

Patellar Impingement on Tibial Polyethylene after Primary Total Knee Arthroplasty without Patellar Resurfacing.

Patellar impingement on tibial polyethylene (PIP) is one potential complication of total knee arthroplasty (TKA). When PIP occurs, it is often related to inaccurate restoration of the joint line or due to soft-tissue contracture. We investigated the prevalence and etiology of PIP in Asian patients with deeply flexed knees following posterior stabilized (PS)-TKA. We retrospectively reviewed 54 patients (65 knees) with PIP after primary PS-TKAs without patellar resurfacing performed between 2008 and 2011. These patients were compared with a group of 124 patients (130 knees) without PIP matched for age, sex, and body mass index (BMI). The minimum follow-up was 5 years (range, 5-8.1 years). Patients were evaluated by blinded, independent observers using the Oxford knee score, the Waters score, and radiographic parameters. Impingement between the patella and the tibial polyethylene had a mean onset of 13.5 months after PS-TKA. The development of PIP was significantly associated with change in patellar tendon length (odds ratio [OR] = 11.4, 95% confidence interval [CI]: 11.2-11.6%), shorter postoperative patellar tendon length (OR = 2.1, 95% CI: 1.8-2.5%), change in the Insall-Salvati ratio (OR = 0.9, 95% CI: 0.8-1.0%), and joint line elevation (OR = 5.3, 95% CI: 4.8-5.8%) on multiple logistic regression analysis. Our findings reinforce the importance of accurate joint line restoration and the avoidance of iatrogenic injury to the patellar tendon, which can lead to shortening of the patellar tendon. This is a retrospective comparative study and its level of evidence is III.

Fluid Behavior in Nanoporous Silica.

We investigate dynamics of water (H2O) and methanol (CH3OH and CH3OD) inside mesoporous silica materials with pore diameters of 4.0, 2.5, and 1.5 nm using low-field (LF) nuclear magnetic resonance (NMR) relaxometry. Experiments were conducted to test the effects of pore size, pore volume, type of fluid, fluid/solid ratio, and temperature on fluid dynamics. Longitudinal relaxation times (T1) and transverse relaxation times (T2) were obtained for the above systems. We observe an increasing deviation in confined fluid behavior compared to that of bulk fluid with decreasing fluid-to-solid ratio. Our results show that the surface area-to-volume ratio is a critical parameter compared to pore diameter in the relaxation dynamics of confined water. An increase in temperature for the range between 25 and 50°C studied did not influence T2 times of confined water significantly. However, when the temperature was increased, T1 times of water confined in both silica-2.5 nm and silica-1.5 nm increased, while those of water in silica-4.0 nm did not change. Reductions in both T1 and T2 values as a function of fluid-to-solid ratio were independent of confined fluid species studied here. The parameter T1/T2 indicates that H2O interacts more strongly with the pore walls of silica-4.0 nm than CH3OH and CH3OD.

Extra-adrenal pheochromocytoma after operation of congenital heart disease: a case report of 18-year-old boy.

Extra-adrenal pheochromocytoma is rare and presents variable symptoms. Its difficulty to diagnosis delays appropriate treatment. We would like to report an unusual case of extra-adrenal pheochromocytoma. The patient came to the emergency room with dyspnea, palpitation, and cyanosis. He had a history of hospitalization for Fontan operation due to congenital heart disease. Despite medication, his blood pressure remained high. After additional laboratory and image exams, he was diagnosed with extra-adrenal pheochromocytoma and had surgical treatment. The final pathology report was extra-adrenal pheochromocytoma with high risk of malignancy. The postoperative course was uneventful and showed normal laboratory results even after 3 months of outpatient follow-up. Extra-adrenal pheochromocytoma presents variable symptoms. We should consider endocrinologic diseases like extra-adrenal pheochromocytoma in cases presenting with palpitation and high blood pressure, even with a past history of cardiac surgery.

A validated finite element analysis of nerve root stress in degenerative lumbar scoliosis.

Few studies have shown the relationship between the curve pattern and nerve root symptoms in degenerative lumbar scoliosis, and its mechanism remains unclear. We developed a finite element model of two patterns of scoliotic curves (isolated lateral bending curve, lateral bending combined with rotation curve). The stress on the nerve root was calculated on both sides (right and left) of the apex vertebra. In the lateral bending curves without rotation, the compressive nerve root stress on the concave side was greater than the tensile stress on the convex side at the apex vertebra. In contrast, when the segmental rotation of the vertebrae was added to the lateral bending curve, there was significantly higher tensile stress on the convex side, and lower compressive stress on the concave side. To conclude, rotatory listhesis may be an important pathomechanism in the development of neurologic symptoms on the convex side of the curve.