[Patellar tracking in knee arthroplasty]. / Patellatracking in der Knieendoprothetik.

Knee arthroplasty is a demanding procedure that, when carried out appropriately, results in significant pain relief and patient satisfaction. The success of the operation is influenced by many factors. The most important ones describe the implant design, the orientation of the components and the ligament tension. The patellofemoral joint is often neglected as an important part of the operation. Initially, complications in the area of the patellofemoral joint do not appear to be devastating, but in many cases, they lead to significant consequences for the patient, along with severe pain and limited mobility. The most common complications arise from patellar maltracking. This often occurs due to misplacement of the tibial and femoral components and the altered shape of the patella. If the placement of the components with regard to patellar tracking is considered, bony and/or soft tissue addressing measures remain to further optimize the movement of the patella. The following manuscript is dedicated to discussing causes to avoid patellar maltracking and improve clinical outcomes.

Medial Open Wedge High tibial Osteotomy (MOWHTO) does not relevantly alter patellar kinematics: a cadaveric study.

PURPOSE: The purpose of this study was to quantify the influence of medial open wedge high tibial osteotomy on patellar kinematics using optical computer navigation, as anterior knee pain infrequently occurs postoperatively and the reason is still being unknown. METHODS: Ten medial open wedge high tibial osteotomies at supratuberosity level in 5 full body specimens were performed. The effect of the surgical procedure on patellar kinematics, measured at 5 and 10 degrees of leg alignment correction angle, was analyzed and compared to native patellar kinematics during passive motion-regarding patella shift, tilt, epicondylar distance and rotation. Linear mixed models were used for statistical analysis, a two-sided p value of ≤ 0.05 was considered statistically significant. RESULTS: Tilt behavior, medial shift and epicondylar distance did not show a significant difference regarding natural patellar kinematics at both osteotomy levels. Both osteotomy correction angles showed a significant less external rotation of the patella (p < 0.001, respectively) compared to natural kinematics. CONCLUSIONS: Except less external rotation of the patella, medial open wedge high tibial osteotomy does not seem to relevantly alter patellar alignment during passive motion. Future clinical studies have to prove the effect of MOWHTO on patellar kinematics measured in this experimental setup, especially regarding its influence on anterior knee pain.

Total Knee Arthroplasty Violates the Law of Burmester-A Biomechanical Investigation.

BACKGROUND: Kinematic patterns of knees after total knee arthroplasty (TKA) are different from those of healthy knees. We hypothesised that these changes cause a relevant shift in the medial and lateral epicondyles and, consequently, the insertion sites of the collateral ligaments. Any alterations, however, violate the law of Burmester, which states a close relation between the course of the collateral and cruciate ligaments, and the articular surfaces. METHODS: Ten healthy knees of whole body cadavers were investigated. The positions of the medial and lateral epicondyles in relation to the tibia were compared before and after cruciate retaining fixed bearing TKA between 0 and 90° of flexion using a navigational device. RESULTS: After TKA, the medial and lateral epicondyles significantly shifted laterally (~3-5mm) between 0° and 40° of flexion. Additionally, the lateral epicondyle was located significantly more dorsal (~3-5mm) during 0° and 20° of flexion and significantly shifted proximally (~2.5-3mm) between 0° and 30° of flexion. CONCLUSIONS: By changing the epicondylar positions relative to the articular surfaces, the law of Burmester is violated in the present study setting. This might explain the impairment in motion, instability, or mid-flexion instability and the persistent pain in the knees after TKA.

Operative Treatment Options for Patellofemoral Arthritis: An Expert Recommendation of the AGA Patellofemoral Committee.

BACKGROUND: The operative therapy of patellofemoral arthritis requires an individual approach depending on the underlying injury. However, the literature lacks recommendations for its course of action. PURPOSE: To generate an expert recommendation of therapy for different patellofemoral abnormalities in patients suffering from isolated patellofemoral arthritis. STUDY DESIGN: Consensus statement. METHODS: To generate recommendations, the AGA Patellofemoral Committee performed a consensus process using the Delphi method based on the available literature on isolated patellofemoral arthritis. RESULTS: In most statements and recommendations, a high percentage of consensus could be found. However, also in the expert group of the AGA Patellofemoral Committee, some controversies on the treatment of patellofemoral arthritis exist. CONCLUSION: The operative therapy of isolated patellofemoral arthritis is a challenging topic that leads to controversial discussions, even in an expert group. With this consensus statement of the AGA Patellofemoral Committee, recommendations on different operative treatment options were able to be generated, which should be considered in clinical practice.

Lower Limb Malrotation Is Regularly Present in Long-Leg Radiographs Resulting in Significant Measurement Errors.

Weight-bearing long-leg radiographs are commonly used in orthopaedic surgery. Measured parameters, however, change when radiographs are conducted in different rotational positions of the leg. It was hypothesized that rotational errors are regularly present in long-leg radiographs resulting in wrong measurements. In 100 consecutive long-leg radiographs conducted according to the method of Paley, rotation was assessed by fibular overlap. Angular parameters in radiographs (mechanical lateral proximal femoral angle (mLPFA), mechanical lateral distal femoral angle (mLDFA), angle between the anatomical and mechanical femoral axis (AMA), mechanical medial proximal tibia angle (mMPTA), mechanical lateral distal tibial angle (mLDTA), and the mechanical femoral and tibial axis (mFA-mTA) were measured and deviations related to malrotation calculated. An average internal rotation of 8 degrees was found in lower limbs showing a range between 29 degrees of internal and 22 degrees of external rotation. As a result, mean differences before and after rotational correction for measured parameters (mLPFA, mLDFA, AMA, mMPTA, mLDTA, mFA-mTA) ranged between 0.4 and 1.7 degrees (-2.1; 5.6 95% confidence interval [CI]). In conclusion, malrotation of lower limbs is regularly present in long-leg radiographs. As all measured parameters are influenced by malrotation, correct lower limb rotation needs to be verified.

Trochlear dysplasia relates to medial femoral condyle hypoplasia: an MRI-based study.

PURPOSE: Trochlear dysplasia is one of the most important pathomorphologies predisposing to patellofemoral instability. The development of the trochlea groove is not well understood so far. We hypothesized that the underlying pathology of trochlear dysplasia is a medial hypoplasia. METHODS: 110 magnetic resonance imaging (MRI) scans from adult knees, 55 with and 55 without trochlear dysplasia were analyzed. On the axial and sagittal T2 MRI sequences, the height (h), width (w) and depth (d) of the medial (MC) and lateral femoral condyle (LC) as well as the depth of the trochlea groove (dTG) were measured using a three-dimensional measuring algorithm. RESULTS: For all calculated values of the lateral femoral condyle, the comparison of both groups showed no significant difference (p = 0.95, p = 0.11, p = 0.07). The depth of the trochlear groove (dTG) showed significant lower values in the study group (p < 0.05). In the study group, all measurements of the medial femoral condyle were statistically significantly smaller compared to the control group (p < 0.05). CONCLUSIONS: We found that the height, the width and the depth of the medial condyle is significant smaller in patients with trochlea dysplasia than in healthy controls. The measurements of the lateral femoral condyle showed no significant difference. Patients with a dysplastic trochlea have a hypoplastic medial femoral condyle and a more medially placed trochlea groove compared to controls.

A Knee Size-Independent Parameter for Malalignment of the Distal Patellofemoral Joint in Children.

INTRODUCTION: Patellar instability (PI) is a common finding in children. Current parameters describing patellofemoral joint alignment do not account for knee size. Additionally, most parameters utilize joint-crossing tibiofemoral landmarks and are prone to errors. The aim of the present study was to develop a knee size-independent parameter that is suitable for pediatric or small knees and determines the malpositioning of the distal patellar tendon insertion solely utilizing tibial landmarks. METHODS: Sixty-one pediatric knees were included in the study. The tibial tubercle posterior cruciate ligament distance (TTPCL) was measured via magnetic resonance imaging (MRI). The tibial head diameter (THD) was utilized as a parameter for knee size. An index was calculated for the TTPCL and THD (TTPCL/THD). One-hundred adult knees were analyzed to correlate the data with a normalized cohort. RESULTS: The THD was significantly lower in healthy females than in males (69.3 mm ± 0.8 mm vs. 79.1 mm ± 0.7 mm; p < 0.001) and therefore was chosen to serve as a knee size parameter. However, no gender differences were found for the TTPCL/THD index in the healthy adult study cohort. The TTPCL/THD was significantly higher in adult PI patients than in the control group (0.301 ± 0.007 vs. 0.270 ± 0.007; p=0.005). This finding was repeated in the PI group when the pediatric cohort was analyzed (0.316 ± 0.008 vs. 0.288 ± 0.010; p=0.033). CONCLUSION: The TTPCL/THD index represents a novel knee size-independent measure describing malpositioning of the distal patellar tendon insertion determined solely by tibial landmarks.

Kinematic component alignment in total knee arthroplasty leads to better restoration of natural tibiofemoral kinematics compared to mechanic alignment.

PURPOSE: Kinematically aligned total knee arthroplasty is associated with superior pain relief, increased flexion and a more normal feeling knee. It was hypothesized that due to restoring the knee's natural anatomy, kinematically aligned knees show more physiological tibiofemoral kinematics than mechanically aligned knees. METHODS: Investigations were performed in nine healthy cadaveric knees of whole bodies fixed by the Thiel method. Tibiofemoral kinematics of healthy knees and after kinematically and mechanically aligned total knee arthroplasty were assessed between 0° and 90° of flexion by a navigational device. RESULTS: Regarding tibial internal rotation or femoral roll back, respectively, kinematically aligned total knee arthroplasties showed no significant differences between 0° and 70° of flexion in comparison to knees before total knee arthroplasty. In contrast, mechanically aligned total knee arthroplasties showed significant changes between 10° and 90° of flexion. Kinematically aligned knees showed a significant changed abduction/adduction between 20° and 70° of flexion, mechanically aligned knees within 20° and 90° of flexion. CONCLUSION: In the present study setting kinematically aligned total knee arthroplasties showed more natural and physiological tibiofemoral kinematic pattern with regard to tibial internal rotation or femoral rollback, respectively, and tibial adduction than mechanically aligned total knee arthroplasties. While these results may support promising early clinical results of kinematical alignment proposing a better function, long-term results especially implant survival need to be awaited.

Kinematic alignment in total knee arthroplasty leads to a better restoration of patellar kinematics compared to mechanic alignment.

PURPOSE: The influence of different implantation techniques in TKA on tibiofemoral kinematics was analysed in few investigations so far. However, the influence on patellar kinematics remain unclear. The aim of the present investigation was to compare patellar kinematics of the natural knee with those of knees after both kinematically and mechanically aligned TKAs. METHODS: Patellar kinematics of ten cadaveric knees before and after TKAs implanted using both a kinematic and mechanic alignment technique were investigated and compared using a commercial optical computer navigation system. RESULTS: There was a statistically significant difference between natural patellar kinematics and both implantation techniques analysing mediolateral shift. Patellar lateral tilt showed significant better results in the kinematically compared to the mechanically aligned TKAs. In terms of patella rotation, the patella of both mechanically and kinematically aligned TKAs showed significant higher values for external rotation compared to the natural knee. Regarding epicondylar distance again a significant better restoration of natural kinematics could be found in the kinematically aligned TKAs. CONCLUSION: Kinematically aligned TKAs showed a better overall restoration of patellar kinematics compared to a conventional mechanical alignment technique. In terms of clinical usefulness, the present study highlights the potential benefit for clinical outcome using a kinematically aligned implantation technique in TKA to achieve a better restoration of natural patellofemoral kinematics.

Reproducibility of navigation based kinematic analysis of the knee - A cadaveric investigation.

PURPOSE: Several navigation-based kinematic studies of the knee have been published recently, but little information is available about reproducibility and reliability of the acquired data. The aim of the present study first is to determine reproducibility and reliability of kinematical measurements of healthy knees and knees after TKA (total knee arthroplasty) with regards to rotational and translational measurement parameters. Second the mathematical background, applicability, and limitations of investigating navigation-based kinematics should be compiled. METHODS: Using cadavers fixed by the Thiel method, in ten knees reproducibility of obtained angular and translational kinematic parameters were investigated before and after total knee arthroplasty. For this reason agreement of obtained data of a first and a second movement cycle and the same after a surgical intervention was assessed using a commercially available navigational device. RESULTS: For both angular and translational parameters in healthy knees and knees after total knee arthroplasty mean differences between measured parameters of the first and second movement cycle and after surgical intervention of less than 0.5° or millimeters (standard deviation 1.3 or less) or a inter class correlation of 0.92 and more, respectively, was found. DISCUSSION: Use of a commercial navigation system allows highly accurate investigations of knee kinematics in cadavers before and after TKA. This technique, which does not require any specific technical knowledge of the investigator, is in accordance with current accepted biomechanical methods.

Multicenter cohort-study of 15326 cases analyzing patient satisfaction and perioperative pain management: general, regional and combination anesthesia in knee arthroplasty.

Numbers of knee replacement surgeries have been rising over the past years. After having ameliorated operation techniques and material, pain management and anesthetic methods have come into focus. All 15326 patients included had undergone primary knee arthroplasty within this multicenter cohort-study, conducted in 46 orthopedic departments. Parameters were evaluated on first postoperative day. Primary outcome values were pain levels (activity, minimum and maximum pain, and pain management satisfaction). Pain medication necessity was analyzed. Parameters were compared between the types of anesthesia used: general, regional and combination anesthesia. Pain scores and pain management satisfaction were significantly better in the groups of either spinal or peripheral anesthesia combined with general anesthesia (p < 0.001, respectively). Patients who received the combination of general and spinal anesthesia were associated with the lowest need for opioids (p < 0.001). The use of a combined general and spinal anesthesia as well as using a combination of general and peripheral anesthesia in knee arthroplasty was associated with a highly significant advantage to other anesthetic techniques regarding perioperative pain management in daily clinical practice, but maybe below clinical relevance. Furthermore they were associated with positive tendency considering side effects and subjective well-being parameters.

Rotation of intramedullary alignment rods affects distal femoral cutting plane in total knee arthroplasty.

PURPOSE: Intramedullary rods are widely used to align the distal femoral cut in total knee arthroplasty. We hypothesised that both coronal (varus/valgus) and sagittal (extension/flexion) cutting plane are affected by rotational changes of intramedullary femoral alignment guides. METHODS: Distal femoral cuts using intramedullary alignment rods were simulated by means of a computer-aided engineering software in 4°, 6°, 8°, 10°, and 12° of valgus in relation to the femoral anatomical axis and 4° extension, neutral, as well as 4°, 8°, and 12° of flexion in relation to the femoral mechanical axis. This reflects the different angles between anatomical and mechanical axis in coronal and sagittal planes. To assess the influence of rotation of the alignment guide on the effective distal femoral cutting plane, all combinations were simulated with the rod gradually aligned from 40° of external to 40° of internal rotation. RESULTS: Rotational changes of the distal femoral alignment guides affect both the coronal and sagittal cutting planes. When alignment rods are intruded neutrally with regards to sagittal alignment, external rotation causes flexion, while internal rotation causes extension of the sagittal cutting plane. Simultaneously the coronal effect (valgus) decreases resulting in an increased varus of the cutting plane. However, when alignment rods are intruded in extension or flexion partly contradictory effects are observed. Generally the effect increases with the degree of valgus preset, rotation and flexion. CONCLUSION: As incorrect rotation of intramedullary alignment guides for distal femoral cuts causes significant cutting errors, exact rotational alignment is crucial. Coronal cutting errors in the distal femoral plane might result in overall leg malalignment, asymmetric extension gaps and subsequent sagittal cutting errors.

Postoperative pain and patient satisfaction are not influenced by daytime and duration of knee and hip arthroplasty: a prospective cohort study.

PURPOSE: The number of total hip and knee arthroplasties (THA and TKA) is steadily increasing. Many factors that influence pain have been reported, but little is known about the correlation between the time of day and the duration of surgery and postoperative pain. On one hand, surgical interventions are performed faster due to economic pressure; on the other hand, obtaining sound surgical skills and a thorough education are most important for young surgeons, particularly at university hospitals. Amidst these different interests, it is the patient who should be the focus of all medical efforts. Therefore, our study investigated the effects of the time of day and the duration of total knee and hip arthroplasty on postoperative pain perception and patient satisfaction. METHODS: 623 patients were analyzed 24 h after primary total knee or hip arthroplasty regarding pain, patient satisfaction, and side effects by means of the questionnaires of the German-wide project Quality Improvement in Postoperative Pain Management (QUIPS). RESULTS: The time of day and the duration of knee or hip arthroplasty were not correlated with maximum, minimum, and activity-related pain and patient satisfaction rated on a numeric rating scale (NRS). CONCLUSIONS: This study is the first to show that neither the time of day nor the duration of surgery has any influence on patient satisfaction and postoperative pain 24 h after total knee or hip arthroplasty; regarding these aspects, young orthopaedic surgeons may be trained in the operating theatre without time pressure.

The influence of varus and valgus deviation on patellar kinematics in healthy knees: An exploratory cadaver study.

BACKGROUND: Patellofemoral instability may lead to osteoarthritis, anterior knee pain, and patellar luxation. The purpose of this study was to conduct an exploratory investigation into the difference of patellar kinematics of healthy knees during extension/flexion cycles in neutral, varus and valgus alignment. METHODS: The three-dimensional patellar kinematics of 10 lower extremities of whole body cadavers were examined during passive motion, in neutral position, and under valgus and varus stress. Kinematics was recorded by means of an optical computer navigation system. RESULTS: The study samples did not significantly differ with regard to mediolateral patellar shift and epicondylar distance. Varus stress led to significantly higher external rotation than valgus stress (P=0.04) and to a significantly higher lateral patellar tilt than neutral position (P=0.016) and valgus stress (P=0.016). No difference was found between valgus stress and neutral position. CONCLUSION: Analysis of tibiofemoral alignment alone is insufficient for predicting patellar kinematics.

Stability of capsule closure and postoperative anterior knee pain after medial parapatellar approach in TKA.

PURPOSE: Anterior knee pain after total knee arthroplasty (TKA) remains a widely discussed postoperative complication. In contrast to sports traumatology, the role of the dissected medial patellofemoral ligament (MPFL) using a medial parapatellar approach in TKA has not been discussed so far. In the present study, it was hypothesized that the attempted repair of the MPFL in TKA by simple closure of the joint capsule may not be successful in some cases, causing anterior knee pain. Furthermore, it was hypothesized, that the success of repair might be influenced by femoral component rotation. METHODS: Forty patients received their TKA in a ligament-balanced and forty patients in a conventional measured-resection technique. After implantation of the TKA using a medial parapatellar approach, two titan clips were attached on both sides of the capsule incision. 3 days and 3 months after surgery, the dehiscence of the two clips was measured on skyline patella radiographs; additionally patellar tilt, shift, the Knee Society Score and the Feller Score were obtained. RESULTS: 48 patients showed an increase of capsule dehiscence. Patients with a capsule dehiscence of more than 4 mm showed significantly less improvement in the Feller score 3 months postoperatively than patients with a capsule dehiscence ≤4 mm. Regarding the radiological measurements and the clinical outcome, no significant difference between the ligament-balanced and the measured-resection group was found. CONCLUSIONS: The present results suggest that the successful repair of the MPFL after using a medial parapatellar approach in TKA could reduce the high rate of postoperative anterior knee pain. Furthermore, the appearance of capsule dehiscence and anterior knee pain does not seem to be dependent on the used operative technique.

Influence of Component Rotation in Total Knee Arthroplasty on Tibiofemoral Kinematics-A Cadaveric Investigation.

BACKGROUND: Physiological tibiofemoral kinematics have been shown to be important for good knee function after total knee arthroplasty (TKA). The purpose of the present study was to investigate the influence of component rotation on tibiofemoral kinematics during knee flexion. We asked which axial component alignment best reconstructs physiological tibiofemoral kinematics and which combinations should be avoided. METHODS: Ten healthy cadaveric knees were examined. By means of a navigational device, tibiofemoral kinematics between 0° and 90° of flexion were assessed before and after TKA using the following different rotational component alignment: femoral components: ligament balanced, 6° internal, 3° external rotation, and 6° external rotation in relation to the posterior condylar line; tibial components: self-adapted, 6° internal rotation, and 6° external rotation. RESULTS: Physiological tibiofemoral kinematics could be partly reconstructed by TKA. Ligament-balanced femoral rotation and 6° femoral external rotation both in combination with 6° tibial component external rotation, and 3° femoral external rotation in combination with 6° tibial component internal rotation or self-aligning tibial component were able to restore tibial longitudinal rotation. Largest kinematical differences were found for the combination femoral component internal and tibial component external rotations. CONCLUSION: From a kinematic-based view, surgeons should avoid internal rotation of femoral components. However, even often recommended combinations of rotational component alignment (3° femoral external and tibial external rotation) significantly change tibiofemoral kinematics. Self-aligning tibial components solely restored tibiofemoral kinematics with the combination of 3° femoral component of external rotation. For the future, navigational devices might help to axially align components to restore patient-specific and natural tibiofemoral kinematics.

Presence of rotational errors in long leg radiographs after total knee arthroplasty and impact on measured lower limb and component alignment.

PURPOSE: Rotation of the lower limb in weight bearing long leg radiographs has a great impact on measured component and lower limb alignment parameters. We asked which rotational errors of long leg radiographs are present in a high volume centre and which radiological and clinical consequences arise regarding measured coronal component and lower limb alignment after total knee arthroplasty. METHODS: In 100 long leg radiographs coronal femoral and tibial component alignment and hip knee ankle angle (HKA) were measured. Present rotational errors in long leg radiographs were determined by fibular overlap and its impact on alignment parameters calculated. RESULTS: A mean internal rotation of 8.1° (9.3 SD) with a range between 36° of internal and 16° of external rotation was found in long leg radiographs. This resulted in mean differences between measurements before and after rotational correction regarding femoral and tibial component alignment and HKA of 0.6-0.8° (range 3.5° valgus and 1.6° varus error). Clinically, 11 out of 100 patients were wrongly assigned to either mal- or well-alignment (neutral mechanical alignment within ±3° varus or valgus). CONCLUSION: Surgeons should be aware of potential rotational errors in long leg radiographs after total knee arthroplasty resulting in wrong measurements. In case of rotational errors, radiographs should be repeated or rotational corrections calculated. For study purposes only radiographs after rotational correction should be accepted.

Are We Subluxating Knees in Total Knee Arthroplasty? A Cadaveric Investigation.

BACKGROUND: In comparison to coronal, sagittal, and rotational alignment, translational alignment parameters have been widely neglected in total knee arthroplasty (TKA) so far. As there is a certain variable range of possible component placement in mediolateral, ventrodorsal, and proximodistal direction, we hypothesized that relative positions between the femoral and tibial bones are changed after TKA, resulting in a subluxation of knees. METHODS: In 10 knees of Thiel-embalmed whole body cadavers, the relative position between the femur and the tibia during passive flexion was measured before and after TKA by means of a navigational device. RESULTS: After TKA, in extension, femoral bones in average shifted 5.3 mm (standard deviation [SD] = 4.0, P = .002) laterally and 2.4 mm (SD = 3.1, P = .038) proximally in extension which, however, decreased throughout flexion. Furthermore, the ventrodorsal femoral position was altered, resulting in a slight relative dorsal shift (2.6 mm, SD = 4.5, P = .099) in extension, which continuously changed into a ventral shift (2.6 mm, SD = 4.3, P = .087) during flexion. CONCLUSION: The present investigation reveals changed translational parameters between the tibia and the femur after TKA. The resulting subluxation of the knee may be responsible for changed kinematic patterns. These changes in tibofemoral position should be considered in future biomechanical studies. Main reasons for this effect might be a noncentral placement of tibial and femoral implants in relation to the proximal tibial and distal femoral anatomy, obscured intraoperative articular geometry, symmetric implants, and operative techniques. Smaller steps between different component sizes, asymmetric tibial implant design, or individual (anatomic) implants could help to minimize subluxation in TKA.