Faculty Bibliography

The number of total knee arthroplasties performed in the United States is growing, and a leading cause of failure is postoperative knee instability from suboptimal coronal or sagittal balancing. This article reviews native knee anatomy as well as several guiding principles of total knee arthroplasty such as limb axis, femoral referencing, and implant constraint. Next, techniques that can be used by the surgeon to achieve ideal sagittal balance and coronal balance are discussed in detail. Finally, due to the growing use of computer and robotic technologies in knee replacement, the impact of advanced technologies on total knee arthroplasty balancing and alignment is reviewed. An in-depth understanding of these topics will enable surgeons to optimize the outcome of their total knee arthroplasty patients.

Despite the overall successful outcomes following primary total knee arthroplasty (TKA) and the concept that a well-balanced TKA yields a more successful result, concerns still remain in the reported literature regarding the patellofemoral joint. Diminished outcomes have been associated with poorly balanced or placed patella implants. The effect of different techniques to achieve flexion-extension balance and the use of posterior stabilized (PS) versus cruciate retaining (CR) implant designs on patellofemoral balancing has not been previously studied. The purpose of this study is to utilize a validated computational analysis software to simulate the effects of varying implant positions and sizes of femoral components. The patellofemoral retinaculum (PFR) load was significantly affected by some conditions, while others did not reach significance. The proximal-distal implant position with knee flexion angle (p < 0.001), the implant size (p < 0.001), and the implant bearing type (CR/PS) (p < 0.05) were significant. For the proximal-distal implant position and knee flexion angle, a more proximal implant position (elevating the joint line) increased the PFR load from 15 to 30°, and a more proximal implant position reduced retinaculum load from 60 to 135°. However, at 45°, implant position does not affect retinaculum load. Achieving the appropriate balance between the dynamic nature of both the tibiofemoral and the patellofemoral interaction in TKA has proven to be complex and challenging to manage. Balancing of a TKA is essential to the proper functioning and overall longevity of the implant. These results demonstrate that patellofemoral balance is affected by implant size and position during flexion-extension gap balancing.

BACKGROUND:Patients with chronic hepatitis C (HCV) have had extremely high complication rates after total hip arthroplasty (THA). We sought to compare perioperative complication rates between untreated and treated HCV in THA patients and to compare these rates between patients treated with 2 different therapies (interferon vs direct antiviral agents). METHODS:A multicenter retrospective database query was used to identify patients diagnosed with HCV who underwent THA between 2006 and 2016. All patients (n = 105) identified were included and divided into 2 groups: untreated (n = 63) and treated (n = 42) HCV; treated patients were further subdivided into those receiving interferon (n = 16) or direct antiviral agent therapies (n = 26). Comparisons between the treated and untreated groups were made with respect to demographic data, comorbidities, preoperative viral load, Model for End-Stage Liver Disease score, and all surgical and medical complications; a subgroup analysis of the treated patients was also performed. Separate independent t-tests or Mann-Whitney U tests were conducted for continuous variables. Categorical variables were compared using the chi-squared test of independence. RESULTS:A greater number of untreated patients were human immunodeficiency virus infected (P = .01), while a reduced number of treated patients were either former or current smokers (P = .004). The untreated group had greater surgical complication rates (25.4% vs 4.8%; P = .007), with a higher rate of periprosthetic joint infection (14.3% vs 0%, P = .01). For treated patients, no differences were observed between treatment types for postsurgical complications. CONCLUSION/CONCLUSIONS:Treatment for HCV prior to THA appears to be associated to fewer postoperative complications, primarily periprosthetic joint infection. Although further investigation is warranted, strong consideration should be given to treating patients for HCV prior to elective THA.

Despite the development of newer preventative measures, the rate of infection continues to be approximately 1% for patients undergoing total joint arthroplasty (TJA). The extent of the infection can range from a mild superficial infection to a more serious periprosthetic joint infection (PJI). PJIs not only play a significant role in the clinical well-being of the TJA patient population, but also have substantial economic implications on the health care system. Several approaches are currently being used to mitigate the risk of PJI after TJA. The variety of prophylactic measures to prevent infection after TJA must be thoroughly discussed and evaluated.

Introduction/UNASSIGNED:Preliminary analysis of accelerometry measurements has shown physical activity may not increase significantly after total knee arthroplasty (TKA). This study evaluates the effect of TKA on physical activity accelerometry measurements and body mass index (BMI). Methods/UNASSIGNED:tests. Results/UNASSIGNED:Twenty-three patients from the OAI database were identified for the paired analysis. They were evaluated at a mean postoperative follow-up of 15 months. There were no statistically significant differences between the post-TKA group and pre-TKA group for the accelerometry variables and BMI, though patients experienced a significant improvement in knee function and pain relief measures included in this analysis. Discussion/UNASSIGNED:Although TKA can successfully restore function and relieve pain, there remains no good evidence that neither physical activity nor BMI improve postoperatively. Conclusion/UNASSIGNED:No significant differences in physical activity and BMI were observed after TKA in this study.

Interprosthetic femur fractures are a rare but serious complication following total hip and knee arthroplasty. Classification systems have focused not only on diagnosis but also on treatment algorithm. Critical to the evaluation of patients with these fractures are an assessment of fracture location, bone quality, and the presence of stemmed implants. The gold standard for fracture fixation is locked plating with bicortical and unicortical screws, supplemented with wires or cables as needed. For patients with compromised bone stock or insufficient bony area for fixation, allograft augmentation with struts or interprosthetic sleeves may be used. For fractures with severe bone loss, conversion to a megaprosthesis or total femur replacement may be warranted.

Two-stage exchange is most commonly used for treatment of prosthetic joint infections (PJI) but, this may fail to eradicate infections. C-reactive protein/albumin ratio (CAR) has been used to predict survival and operative success in other surgical subspecialties and so, we assess the association between CAR and reimplantation success during two-stage revision for PJI defined by the Musculoskeletal Infection Society following a primary total hip (THA) or knee (TKA) arthroplasty. From January, 2005 to December, 2015, two institutional databases were queried and patient demographics, antibiotic duration, C-reactive protein, and albumin were collected prior to reimplantation. Two-stage revisions were considered successful if patients were off of antibiotics and did not require a repeat surgery. CAR was available for 79 patients (34 hips and 46 knees) with 61 successful two-stage revisions and 18 failures. The average CAR for patients with successful reimplantation was 1.2 (0.2, 3.0) compared to 1.0 (0.4, 3.2) for treatment failure. However, this was not statistically significant (p=0.766). Therefore, CAR is not applicable in predicting the prognosis of two-stage revisions for PJI in total arthroplasty but other preoperative inflammatory-based prognostic scores should be explored.