Effect of limited ischemia time on the amount and function of mitochondria within human skeletal muscle cells.

INTRODUCTION: The clinical success of total knee arthroplasty (TKA) depends substantially on the quadriceps muscle function. A frequently applied thigh tourniquet during TKA may induce ischemia related injuries to quadriceps muscle cells. Animal limb muscles subjected to 2-5 h ischemia revealed dysfunctional mitochondria, which in turn compromised the cellular bioenergetics and increased the level of reactive oxygen species. The hypothesis of the present study was that tourniquet application during TKA for 60 min (min) affects the amount and function of mitochondria within musculus vastus medialis cells. MATERIALS AND METHODS: In a randomized clinical trial, 10 patients enrolled to undergo primary TKA. The patients were randomly assigned to the tourniquet (n = 5) or non-tourniquet group (n = 5) after obtaining a written informed consent. For each of the groups, the first muscle biopsy was harvested immediately after performing the surgical approach and the second biopsy exactly 60 min later. All biopsies (5 × 5 × 5 mm) 125 mm3 were harvested from musculus vastus medialis and snap-frozen in liquid nitrogen. The biochemical analysis of the prepared muscle tissues included the measurement of activities of mitochondrial respiratory chain enzyme complexes I-III and citrate synthase. RESULTS: Tourniquet-induced 60 min ischemia time did not significantly change the activities of the mitochondrial respiratory chain enzymes complexes I-III of the skeletal muscle cells. The citrate synthase activities found to be not significantly different between both groups. CONCLUSIONS: The use of tourniquet during TKA within a limited time period of 60 min remained without substantial effects on the amount and function of mitochondria within human skeletal muscle cells.

Preservation of the PCL when performing cruciate-retaining TKA: Is the tibial tuberosity a reliable predictor of the PCL footprint location?

PURPOSE: Reconstruction of the joint line is crucial in total knee arthroplasty (TKA). A routine height of tibial cut to maintain the natural joint line may compromise the preservation of the PCL. Since the PCL footprint is not accessible prior to tibial osteotomy, it seems beneficial to identify a reliable extraarticular anatomic landmark for predicting the PCL footprint and being visible within standard TKA approach. The fibula head predicts reliably the location of PCL footprint; however, it is not accessible during TKA. The aim of this study now was to analyze whether the tibial tuberosity can serve as a reliable referencing landmark to estimate the PCL footprint height prior to tibial cut. METHODS: The first consecutive case series included 216 CR TKA. Standing postoperative lateral view radiographs were utilized to measure the vertical distance between tibial tuberosity and tibial osteotomy plane. In the second case series, 223 knee MRIs were consecutively analyzed to measure the vertical distance between tibial tuberosity and PCL footprint. The probability of partial or total PCL removal was calculated for different vertical distances between tibial tuberosity and tibial cutting surface. RESULTS: The vertical distance between the tibial tuberosity and tibial cut averaged 24.7 ± 4 mm. The average vertical distance from tibial tuberosity to proximal and to distal PCL footprint was found to be 22 ± 4.4 and 16 ± 4.4 mm, respectively. Five knees were considered at 50% risk of an entire PCL removal after CR TKA. CONCLUSIONS: Current surgical techniques of tibial preparation may result in partial or total PCL damage. Tibial tuberosity is a useful anatomical landmark to locate the PCL footprint and to predict the probability of its detachment pre-, intra-, and postoperatively. This knowledge might be useful to predict and avoid instability, consecutive pain, and dissatisfaction after TKA related to PCL insufficiency. LEVEL OF EVIDENCE: III.

Alteration of the patellar height following total knee arthroplasty.

INTRODUCTION: Patellofemoral related complications after total knee arthroplasty (TKA) remain clinically relevant. The hypothesis of the present study was that the patellar height changes more than 10% of its preoperative height after TKA. Possible influences of age, gender, side and navigation system on patellar height were evaluated separately in subgroups. MATERIALS AND METHODS: A total of 107 knees were enrolled after primary TKA. The patellar height was determined for each patient preoperatively, 1 week and 1 year postoperatively on routinely performed standing lateral view radiographs at 30° knee flexion. Insall-Salvati index (ISI), modified Insall-Salvati index (MIS) as well as Miura-Kawamura index (MKI) were determined for the whole cohort. RESULTS: One week after TKA the ISI, MIS and MKI changed by more than 10% in 24 (22%), 33 (30%) and 54 (50%) cases, respectively. Moreover, the 1 year follow-up revealed a decrease or increase of ISI in 30 (28%), MIS in 47 (44 %) and MK in 65 (61%) knees. The frequency of patella alta, norma and baja preoperatively as well as 1 week and 1 year postoperatively were not significantly different. Significant differences of patellar height changes were not noted between the defined subgroups. CONCLUSIONS: The present study demonstrates that TKA leads, at 1 week and 1 year follow-up, to patellar height alteration more than 10% in a significant number of knee joints. However, with the use of ISI and MIS the changes of patellar height did not exceed the defined thresholds to be classified as patella alta or baja.

Joint line changes after primary total knee arthroplasty: navigated versus non-navigated.

PURPOSE: Navigation has been introduced to achieve more accurate positioning of the implants after TKA. The scientific attention was mainly paid on limb alignment rather than restoration of the natural joint line. The aim of our study was to compare the accuracy of the joint line restoration in primary TKA with and without navigation. We hypothesized that joint line reconstruction in navigated TKA is more accurate. METHODS: A total of 493 primary TKAs operated in a single medical centre were consecutively selected and divided into two groups. 206 cases were performed computer assisted (BrainLab CI-System), whereas 287 knees were implanted conventionally. For both groups, the joint line position of the knee was determined on standardized calibrated standing pre- and postoperative digital radiographs in ap view by a modified method of Kawamura et al. A joint line shift of more than 8 mm was defined as outlier. RESULTS: In the conventional group, the joint line shift averaged 0.7 mm (±4.4 mm), whereas the findings in the computer-assisted cases were in average 0.6 mm (±4.5 mm). The joint line was located above 8 mm in 6 % of non-navigated versus 6.8 % of navigated primary TKAs. There were no statistically significant differences of joint line shift between the different component types. A statistically significant relation was not found between joint line shift and leg alignment changes. CONCLUSIONS: Conventional surgical technique allows a precise joint line reconstruction in primary TKA. Navigation did not improve the joint line reconstruction. LEVEL OF EVIDENCE: Diagnostic study, Level III.

Precision of Ci-navigated extension and flexion gap balancing in total knee arthroplasty and analysis of potential predictive variables.

INTRODUCTION: The aim of this study was to evaluate the accuracy of final limb alignment and flexion-extension and medial-lateral gap balancing in computer navigated total knee arthroplasty and to analyze various possible predictive variables that may affect the gaps in computer navigated knee arthroplasty. MATERIALS AND METHODS: The DePuy Ci system, a nonimage-based passive optical computer navigation system, was used in 225 patients with knee osteoarthritis to assist for the total knee arthroplasty. From the raw data the Ci-verified pre- and postoperative leg axis in extension, angle of tibia and femur resection, the flexion and extension angle, the medial and lateral extension and flexion gaps were extracted; and differences in gaps were calculated and subjected to statistical analysis. Leg alignment and implant position were determined only by the navigation system. Preoperative variables were evaluated for their impact on the final flexion/extension and medial/lateral gaps achieved. RESULTS: Though the preoperative femoro-tibial coronal alignment had a large variance, postoperatively 98.22% of the knee was found to be between -3° and +3° in the coronal limb alignment axis. The Ci-verified femoral and tibial cuts in the coronal plane showed a good accuracy. The sagittal alignment of the femoral cut ranged from 8.20° flexion to 3.20° of extension. Rectangular extension and flexion gaps were achieved with ≤3 mm of difference in gaps on medial and lateral sides in 98 and 93% of knees, respectively. Difference between extension and flexion gaps on the medial side was ≤3 mm in 83% and on the lateral side in 84% of the knees. Of all the possible predictive variables analyzed, Pearson correlation and multiple regression analysis showed significant correlation only between the medial-lateral gap difference in extension and the Ci-verified femoral cut, tibial cut and limb axis, all in the coronal plane. CONCLUSION: Computer-assisted navigated total knee replacement allows for accurate gap balancing that is not dependent on the various pre- and intraoperative factors mentioned, including age, sex, Range of motion preoperative deformity and grade of osteoarthritis. The Ci-calculated and verified tibial, and femoral cuts are the only possible factors affecting the extension gap.