Using a patella reduced technique while balancing a TKA results in restored physiological strain in the collateral ligaments: an ex vivo kinematic analysis.

INTRODUCTION: Poor soft tissue balance in total knee arthroplasty (TKA) often results in patient dissatisfaction and reduced joint longevity. Patella-in-place balancing (PIPB) is a novel technique which aims to restore native collateral ligament behavior without collateral ligament release, while restoring post-operative patellar position. This study aimed to assess the effectiveness of this novel technique through a detailed ex vivo biomechanical analysis by comparing post-TKA tibiofemoral kinematics and collateral ligament behavior to the native condition. MATERIALS AND METHODS: Eight fresh-frozen cadaveric legs (89.2 ± 6 years) were tested on a validated dynamic knee simulator, following computed tomography imaging. Specimens were subjected to passive flexion (10-120°), squatting (35-100°), and varus/valgus laxity testing (10 Nm at 0°, 30°, 60°, 90° flexion). An optical motion capture system recorded markers affixed rigidly to the femur, tibia, and patella, while digital extensometers longitudinally affixed to the superficial medial collateral ligament (MCL) and lateral collateral ligament (LCL) collected synchronized strain data. Following native testing, a Stryker Triathlon CR TKA (Stryker, MI, USA) was performed on each specimen and the identical testing protocol was repeated. Statistical analyses were performed using a linear mixed model for functional motor tasks, while Wilcoxon signed-rank test was used for laxity tests (p < 0.05). RESULTS: Postoperative laxity was lower than the native condition at all flexion angles while post-operative ligament strain was lowered only for MCL at 30° (p = 0.017) and 60° (p = 0.011). Postoperative femoral rollback patterns were comparable to the native condition in passive flexion but demonstrated a more pronounced medial pivot during squatting. CONCLUSIONS: Balancing a TKA with the PIPB technique resulted in reduced joint laxity, while restoring collateral ligament strains. The technique also seemed to restore kinematics and strains, especially in passive flexion.

Influence of outpatient total knee arthroplasty compared to inpatient surgery on medical and economic outcomes.

Firstly, this study compared the rate of readmission after a total knee arthroplasty between selected out- patients (no hospitalization, directly sent home after surgery) and inpatients (3 days hospitalization) at 6 weeks. Secondly, it examined the mobility and the complications in the two groups after the same period of time. The rate of readmission, complications and knee mobility of 32 outpatients (M-age : 61 years ± 10 ; 10 females), were compared against those of 32 birth- matched inpatients (M-age : 64 years ± 8.6 ; 10 females). No patient was re-admitted in either group. Post- surgical complications included one hematoma resorbed at 6 weeks in the outpatient group and three joint effusions in the inpatient group. There were no instances of deep venous thrombosis, failure of primary fixation, infection, or wound dehiscence. Knee mobility was identical between the two groups. This is the first study to compare inpatient and outpatient total knee arthroplasty in a Belgian setting. Our study suggests that day-care total knee arthroplasty in selected patients is possible without increasing the rate of re-admission and complications, and without affecting the mobility at 6 weeks. However, the Belgian financial incentives do not seem to currently promote this surgical approach. These results should be confirmed with a larger sample to define the adequate length of stay after a total knee arthroplasty.

Improved alignment and operating room efficiency with patient-specific instrumentation for TKA.

BACKGROUND: Achieving accurate alignment in total knee arthroplasty (TKA) remains a concern. Patient-specific instrumentation (PSI) produced using preoperative 3D models was developed to offer surgeons a simplified, reliable, efficient and customised TKA procedure. METHODS: In this prospective study, 60 patients underwent TKA with conventional instrumentation and 71 patients were operated on using PSI. The primary endpoint was surgical time. Secondary endpoints included operating room (OR) time, the number of instrument trays used and postoperative radiographic limb alignment. RESULTS: Compared to conventional instrumentation, PSI significantly reduced total surgical time by 8.9 ± 3.3 min (p=0.038), OR time by 8.6 ± 4.2 min (p=0.043), and the number of instrument trays by six trays (p<0.001). Mechanical axis malalignment of the lower limb of >3° was observed in 13% of PSI patients versus 29% with conventional instrumentation (p=0.043). PSI predicted the size of the femoral and tibial components actually used in 85.9% and 78.9% of cases, respectively. CONCLUSION: PSI improves alignment, surgical and OR time, reduces the number of instruments trays used compared to conventional instrumentation in patients undergoing TKA and results in fewer outliers in overall mechanical alignment in the coronal plane. LEVEL OF EVIDENCE II: Prospective comparative therapeutic study.

Prosthetic joint infections: radionuclide state-of-the-art imaging.

Prosthetic joint replacement surgery is performed with increasing frequency. Overall the incidence of prosthetic joint infection (PJI) and subsequently prosthesis revision failure is estimated to be between 1 and 3%. Differentiating infection from aseptic mechanical loosening, which is the most common cause of prosthetic failure, is especially important because of different types of therapeutic management. Despite a thorough patient history, physical examination, multiple diagnostic tests and complex algorithms, differentiating PJI from aseptic loosening remains challenging. Among imaging modalities, radiographs are neither sensitive nor specific and cross-sectional imaging techniques, such as computed tomography and magnetic resonance imaging, are limited by hardware-induced artefacts. Radionuclide imaging reflects functional rather than anatomical changes and is not hampered by the presence of a metallic joint prosthesis. As a result scintigraphy is currently the modality of choice in the investigation of suspected PJI. Unfortunately, there is no true consensus about the gold standard technique since there are several drawbacks and limitations inherent to each modality. Bone scintigraphy (BS) is sensitive for identifying the failed joint replacement, but cannot differentiate between infection and aseptic loosening. Combined bone/gallium scintigraphy (BS/GS) offers modest improvement over BS alone for diagnosing PJI. However, due to a number of drawbacks, BS/GS has generally been superseded by other techniques but it still may have a role in neutropenic patients. Radiolabelled leucocyte scintigraphy remains the gold standard technique for diagnosing neutrophil-mediated processes. It seems to be that combined in vitro labelled leucocyte/bone marrow scintigraphy (LS/BMS), with an accuracy of about 90%, is currently the imaging modality of choice for diagnosing PJI. There are, however, significant limitations using in vitro labelled leucocytes and considerable effort has been devoted to developing alternative radiotracers, such as radiolabelled HIGs, liposomes, antigranulocyte antibodies and fragments, as well as more investigational tracers such as radiolabelled antibiotics, antimicrobial peptides, bacteriophages and thymidine kinase. On the other hand, positron emission tomography (PET) is still growing in the field of PJI imaging with radiotracers such as (18)F-fluorodeoxyglucose (FDG), (18)F-FDG white blood cells and (18)F-fluoride. But unfortunately this superb tomographic technique will only receive full acceptance when specific PET uptake patterns can be successfully developed. The emergence of hybrid modality imaging using integrated single photon emission computed tomography (SPECT) and PET with computed tomography (SPECT/CT and PET/CT) may also have a contributing role for more accurate assessment of joint replacement complications, especially combined with new radiotracers such as (68)Ga and (64)Cu. Finally, in searching for infection-specific tracers, currently there is no such diagnostic agent available.