Survivorship and Clinical Outcomes of Primary Total Knee Arthroplasty Performed in Patients 35 Years of Age and Younger.

BACKGROUND: Total knee arthroplasties (TKAs) for patients aged ≤35 years are rare but necessary for patients who have diseases such as juvenile idiopathic arthritis, osteonecrosis, osteoarthritis, and rheumatoid arthritis. Few studies have examined the 10-year and 20-year survivorship and clinical outcomes of TKAs for young patients. METHODS: A retrospective registry review identified 185 TKAs in 119 patients aged ≤ 35 years performed between 1985 and 2010 at a single institution. The primary outcome was implant survivorship free of revision. Patient-reported outcomes were assessed at 2 time points: 2011 to 2012 and 2018 to 2019. The average age was 26 years (range, 12 to 35). Mean follow-up was 17 years (range, 8 to 33). RESULTS: Survivorship decreased from 84% (95% confidence interval [CI]: 79 to 90) at 5 years to 70% (95% CI: 64 to 77) at 10 years and to 37% (95% CI: 29 to 45) at 20 years. The most common reasons for revision were aseptic loosening (6%) and infection (4%). Risk factors for revision included increasing age at time of surgery (Hazards Ratio [HR] 1.3, P = .01) and use of constrained (HR 1.7, P = .05) or hinged prostheses (HR 4.3, P = .02). There were 86% of patients reporting that their surgery resulted in "a great improvement" or better. CONCLUSION: Survivorship of TKAs in young patients is less favorable than expected. However, for the patients who responded to our surveys, TKA demonstrated substantial pain relief and improvement in function at 17-year follow-up. Revision risk increased with older age and higher levels of constraint.

Significant Difference in Antimicrobial Resistance of Coagulase Negative Periprosthetic Joint Infection in Septic Revision Total Knee Arthroplasty Between Two Major Orthopedic Centers.

BACKGROUND: Antimicrobial resistance is recognized as a major public health threat. It occurs naturally; however, an excessive antibiotic use and misuse of antibiotics accelerate the process. Periprosthetic joint infections (PJI) are becoming harder to treat as the efficacy of antibiotics is becoming lower. The aim of this study was to compare the resistance of coagulase-negative staphylococci (CNS) to antibiotics identified after revision TKAs for PJI between two major orthopedic centers. METHODS: A review of all revision TKAs, undertaken between 2006 and 2018 in two orthopedic centers, was performed, including all those meeting the consensus criteria for PJI, in which CNS were identified. There were no major differences in surgical approach and tissue sampling between both centers. Thirteen commonly used antibiotics were tested at both centers. RESULTS: The 132 strains were analyzed for their resistance to 13 different antibiotics. Staphylococcus epidermidis was identified in 70.5% cultures, followed by Staphylococcus capitis in 8.3% cultures. The comparison of antibiotic resistance between two centers was statistically significant to penicillin (P = .001), oxacillin (P = .011), cefuroxime (P = .044), levofloxacin (P = .006), moxifloxacin (P = .008), tetracycline (P < .001), rifampicin (P < .001) and vancomycin (P < .001). The difference of resistance of CNS was not statistically significant to fosfomycin, clindamycin, teicoplanin, erythromycin and ampicillin. CONCLUSIONS: The resistance of CNS to antibiotics differs significantly between two major orthopedic centers that are geographically fairly close. Monitoring of bacteriological analyses in each referral center should be continuously performed. Close monitoring is needed for more efficient antibiotic treatment of and prophylaxis against PJI.

Correlation of tibial component size and rotation with outcomes after total knee arthroplasty.

INTRODUCTION: Tibial component design and positioning contribute more to patient satisfaction than previously realized. A surgeon needs to decide on the size and rotation, bearing in mind that coverage should be as high as possible, whilst malrotation and overhang should be avoided. No study investigates the impact of each of these components on clinical outcomes in a single cohort. MATERIALS AND METHODS: This is a retrospective analysis of 1-year postoperative outcomes measured with the Knee Injury and Osteoarthritis Outcome (KOOS) Score, as well as a previously validated rotational CT protocol. Coverage, rotation from Insall's axis, and overhang of an asymmetric tibial baseplate were measured, and positive and negative correlations to clinical outcomes were calculated. RESULTS: A total of 499 knees were analyzed. Patient average age was 68.4 years. Rotation within 7° internal and 5° external from Insall's axis was a "safe zone". Mean coverage was 76%. A total of 429 knees (94%) had a coverage of at least 70% and 102 knees (22%) greater than 80%. Overhang was detected in 23% of the cohort. Increased coverage was correlated to increased KOOS score and overhang correlated with a decreased KOOS score (p = 0.008). CONCLUSIONS: This study demonstrates the individual role of three aspects of tibial component implantation properties in postoperative pain and short-term functional outcomes. Upsizing to the point of overhang with rotational tolerance of 7° internal and 3° external to Insall's axis demonstrates best patient reported outcomes. Overhang decreases the clinical outcome by the same margin as loss of 16% of coverage.

Differences in total blood loss and transfusion rate between different indications for shoulder arthroplasty.

PURPOSE: In this study, the total blood loss, transfusion rate and number of transfused blood units in patients with different indications for shoulder arthroplasty: primary, fracture and secondary were compared. Risk factors for bleeding and transfusion were analysed. METHODS: Medical records and the database of the institution's blood bank from 527 patients that received shoulder arthroplasty were analysed retrospectively. This study included 419 patients that were divided in three different groups: primary (n = 278), fracture (n = 110) and secondary (following prior osteosynthesis; n = 31) shoulder arthroplasty. The demographic and clinical data were collected. The total blood loss (TBL) was calculated and transfusions recorded. RESULTS: The transfusion rate and mean amount of transfused blood units (BU) were higher in fracture (32.7% and 0.69BU, p < 0.01) and secondary arthroplasty (35.5% and 0.97BU, p < 0.01) than in primary arthroplasty (12.6% and 0.28BU). The overall transfusion rate was 19.6% at a mean TBL of 370 ml. However, patients with primary arthroplasty experienced significantly higher total blood loss than those after fracture arthroplasty (p < 0.01). Longer surgery time and male sex are significant risk factors for elevated blood loss. The pre-operative use of vitamin K antagonist, cemented arthroplasty, high BMI, coronary heart disease and ASA score > 2 are relevant risk factors for blood transfusion. CONCLUSION: The most important susceptible factor that affects the TBL is the surgery time. Transfusion rates are higher in patients with fracture arthroplasty than after primary arthroplasty.

The prevalence of a prominent anterior inferior iliac spine.

INTRODUCTION: Impingement of the prominent anterior inferior iliac spine (AIIS) against the femoral neck has recently been described as another type of impingement. The purpose of this study is to provide a distribution of AIIS types using the classification proposed by Hetsroni and thus report on the prevalence of prominent types. MATERIALS AND METHODS: A total of 400 patients were included in the study with an average age 27.3 ± 6.9 years (range 18-40). All patients received a whole-body polytrauma computer tomography (CT) scan in the emergency room (ER) upon arrival. The classification of AIIS proposed by Hetsroni et al., which describes three morphological types, was used. Type II and III were grouped as prominent types. The measurements were performed in all three planes by two examiners. RESULTS: Male to female ratio was 71:29. Type I was observed in 367 (91.7%) patients. Type II was observed in 31 (7.8%) patients and type III was observed in 2 (0.5%) patients, unilaterally. Prominent types were much more prevalent in men (10.5%) than in women (2.6%). The CT assessment demonstrated excellent intra- and interreliability (overall: 0.926, I/II: 0.906, III: 1.000). CONCLUSION: A young population demonstrates a prevalence of a prominent AIIS of 11.5%. Prominent AIIS is more common in men than in women.

Biomechanical and microbiological effects of local vancomycin in anterior cruciate ligament (ACL) reconstruction: a porcine tendon model.

INTRODUCTION: Although there is increasing evidence for the successful use of local vancomycin applied by soaked compresses during ACL reconstruction, there are still little data on its microbiological and biomechanical effects. Furthermore, exact dosage of vancomycin with respect to tendon stability and microbiological effectivity is still unknown. MATERIALS AND METHODS: 63 porcine flexor digitorum profundus tendons were harvested under sterile conditions from fresh cadaver legs. After contamination with Staphylococcus epidermidis (S. epidermidis), tendons were wrapped into sterile compresses moistened with different concentrations of vancomycin for 10 or 20 min. Sterile sodium chloride was used for control. After treatment, tendons were rolled onto blood-agar plates to test for residual bacterial contamination and tested for maximum load and stiffness using a uniaxial testing device with cryo-clamps for tendon fixation. Agar plates were checked after 1 week of culture at 36 °C for signs of bacterial growth. RESULTS: When applying vancomycin for only 10 min, bacterial contamination was found in all dosage groups ranging from 28.6% contamination (n = 2 of 7 tendons) when using 10 mg/ml up to 85.7% (n = 6 of 7 tendons) when using 1 mg/ml. Applying vancomycin-soaked compresses for 20 min, bacterial contamination was still found in the groups using 1 mg/ml and 2.5 mg/ml (contamination rate 85.7 and 42.9% respectively). When using 5 mg/ml and 10 mg/ml, no bacterial contamination could be perceived after 7 days of culture. With regard to biomechanical properties, no differences were found regarding maximum load or Young's modulus between groups. CONCLUSIONS: This study showed no signs of biomechanical impairment of porcine flexor tendons after the use of vancomycin wraps with concentration ranging from 1 to 10 mg/ml for 10 or 20 min at a time zero testing. Contamination with S. epidermidis was cleansed in 100% of tendons when using at least 5 mg/ml of vancomycin for 20 min.

The effect of ankle tape on joint position sense after local muscle fatigue: a randomized controlled trial.

BACKGROUND: Ankle tape is widely used by athletes to prevent ankle sprain. Although there is growing evidence that ankle tape improve joint position sense, but yet it is not clear even if tape improve joint position sense after muscle fatigue, because fatigue impair joint position sense and raise the risk of ankle sprain. The aim of this study is to examine the effect of ankle tape on joint position sense after local muscle fatigue. METHOD: This trial is a randomized controlled trial. 34 healthy subjects participated in this trial. Subjects were randomized distributed into two groups: with tape and without tape. Active and passive absolute error and variable error mean values for two target positions of the ankle joint (15° inversions and inversion minus 5°) before and after fatigue protocol consisted of 30 consecutive maximal concentric/concentric contractions of the ankle evertors and invertors. In this trail joint position sense for all subjects was assessed using The Biodex System isokinetic dynamometer 3, this system is used also for fatigue protocol. RESULTS: For the variable error (VE), significant mean effect was found for active joint position sense in 15° of inversion after muscle fatigue (P < 0, 05). It was a significant decrease in the work in the last third of inversion detected (P < 0, 05). There was no significant main effect found for fatigue index of eversion. CONCLUSION: Ankle tape can improve joint position sense at the fatigue session when joint position sense becomes worse. As a result, ankle tape may be useful to prevent ankle sprain during playing sports. We suggest athletes and individuals at risk of ankle sprain to apply taping before high-load activity. TRIAL REGISTRATION: The study was retrospectively registered on the ISRCTN registry with study ID ISRCTN30042335 on 12th December 2017.

Expression of MMP-9 decreases metastatic potential of Chondrosarcoma: an immunohistochemical study.

BACKGROUND: Chondrosarcoma is the second most common primary malignant bone tumor. Because of their heterogeneity, with differences in invasive and metastatic behavior, it is important to identify biological markers that will allow for a more accurate estimation of prognosis in patients with these tumors. Matrix metalloproteinases (MMP) play a crucial role in tumor progression, invasion and metastasis. The mechanism of tumor progression dependent of MMPs is complex and influences malignant transformation, angiogenesis and tumor growth at the primary and metastatic sites. The purpose of this study was to investigate immunohistochemicaly the influence of MMP-1, MMP-3, MMP-9 and MMP-13 expression on prognostic parameter in chondrosarcoma. METHODS: We investigated tissue samples of 28 patients with chondrosarcoma. Immunohistochemical staining to evaluate the expression of MMP-1, MMP-3, MMP-9 and MMP-13 was performed. Subsequently, the expression level was correlated with metastatic potential, histological grading and overall survival in patients with this neoplasm. RESULTS: In consideration of semi quantitative scoring 64% of chondrosarcoma were scored as positive for MMP-1, 46% for MMP-3, 61% for MMP-9. The specimens had shown no expression of MMP-13. High expression of MMP-9 was associated with better histological differentiation, decreased metastatic potential and favourable overall survival. No correlation was found for expression of MMP-1, MMP-3 or MMP-13. CONCLUSIONS: MMP-1, MMP-3 and MMP-9 are expressed in chondrosarcoma. Our findings suggest that the expression of MMP-9 is associated with clinical outcome parameters in chondrosarcoma.

Internal femoral component malrotation in TKA significantly alters tibiofemoral kinematics.

PURPOSE: Femoral component malrotation in total knee arthroplasty (TKA) is clinically proven to cause dissatisfaction and impaired function. This study is an attempt to characterize the tibiofemoral kinematics following femoral malrotation in posterior stabilized (PS) TKA. It was hypothesized that internal malrotation would introduce the most pronounced changes. METHODS: Six fresh-frozen cadaver specimens were mounted in a kinematic rig. Three motion patterns were applied with the native knee and following PS TKA (passive motion, open chain extension, and squatting) while infrared cameras recorded the trajectories of markers attached to femur and tibia. Three different femoral implants were tested: a conventional posterior stabilized component, and adapted components of the same implant with 5° of intrinsic external and internal rotation, respectively. RESULTS: The implantation of the PS TKA resulted in less tibial internal rotation (squat 33-70°, p < 0.05) and the medial femoral condyle shifted posteriorly especially in deep flexion (squat 84-111°, p < 0.05). Internal component malrotation caused internal rotation and abduction of the tibia in flexion (squat 33-111°, p < 0.05), an elevated (squat 43-111°, p < 0.05) and more anterior (passive 61-126°, p < 0.05) located medial femoral condyle and a lateral femoral condyle located more posterior and inferior (squat 73-111°, p < 0.05) than in the neutrally aligned TKA. External component malrotation caused only little changes under passive motion. Under a squat there was less internal rotation and more adduction to the tibia (33-111°, p < 0.05). The medial femoral condyle was moved more posterior (squat 59-97°, p < 0.05), the lateral femoral condyle more superior (squat 54-105°, p < 0.05) than in the neutrally aligned TKA. CONCLUSION: The greatest differences to the native tibiofemoral kinematics were introduced by internal rotation of the femoral component. Also neutrally and externally rotated femoral components introduce kinematic changes, but to a lesser extent. With respect to the alterations introduced to kinematics internal malrotation should be avoided when performing PS TKA.

The effect of surgeon's learning curve: complications and outcome after hip arthroscopy.

INTRODUCTION: The aim of the present study was to determine the incidence and type of complications during and after hip arthroscopy as well as the effect of the surgeon's learning curve on the occurrence of complications. We expect that the currently reported prevalence especially of minor complications is likely to be underreported in most retrospective series based on chart analysis. MATERIALS AND METHODS: The study included all consecutive patients who underwent hip arthroscopy between 2006 and 2014 at a minimum follow-up of 6 weeks starting with the first patient undergoing hip arthroscopy at the institution. Patient outcome was evaluated using the WOMAC score, VAS for pain, SF-36 questionnaire and the hip-outcome score. Additionally, intra- and postoperative complications were recorded via a questionnaire and additional review of patient files. RESULTS: We identified 529 patients who underwent hip arthroscopy between 2006 and 2014. Complete data could be gathered from 485 patients (91.7%). Major complications occurred in three patients (0.6%; fractures of the femoral neck requiring surgical treatment in one case). Minor complications that did not require further intervention were self-limiting postoperative temporary neurapraxia, hematoma, self-limiting dyspareunia, deep vein thrombosis and impaired wound healing, with hematoma and temporary paresthesia due to traction neurapraxia being the most common ones (22.5 and 16.4% respectively). The overall re-operation rate was 15.7% with conversion to total hip arthroplasty being the most common (11.9%). CONCLUSIONS: The overall major complication rate was low and thus hip arthroscopy can be rated as a safe procedure. But minor complications such as hematoma and temporary paresthesia due to traction neurapraxia are common and currently underreported. Surgeons' learning curves show a reduction of major complications once 60 procedures per surgeon per year is surpassed.

Ten-year follow-up of a cemented tapered stem.

INTRODUCTION: This stem was cleared by the FDA in 2002 and has been implanted in cementless and cemented versions. Despite its long history, there are no long-term clinical  results available for the cemented version of this implant. The aim of this study was to provide such data. It was hypothesized that this implant delivers clinical success comparable to other tapered cemented stems. MATERIALS AND METHODS: A total of 113 hip replacements were performed in 106 patients between October 2007 and December 2009 using the cemented version of this stem. The mean age of the patients at operation was 74.8 years (range 50-91 years). The mean follow-up was 8.9 years with only two patients lost to follow-up. Implant survival was determined using the Kaplan-Meier analysis. RESULTS: Stem survival with revision for any reason as the endpoint was 96.4% after 10 years. Survival for stem aseptic loosening was 100%. There were no cases of osteolysis. Clinical outcomes, as shown by Harris Hip Scores, were in line with previous investigations and the rate of adverse events was very low. CONCLUSIONS: This is a modern cemented stem with an excellent survival rate and satisfactory functional outcomes. In this cohort, there were no failures related to the stem through the first decade.

Bleeding in primary shoulder arthroplasty.

INTRODUCTION: The aim of this investigation was to analyse "total blood loss" (TBL), "blood transfusion rate" (BT) and the "amount of transfused blood units" (BU) between the different primary shoulder arthroplasty (SA) types: reverse, anatomical and stemless. Only primary SA was included. Further goal was to identify risk factors for TBL, amount of BU and BT rate. METHODS: A retrospective charts analysis of patients who received primary SA for degenerative shoulder pathology in our institution between 2004 and 2016 was performed. The demographic data, co-morbidities, haemoglobin and hematocrit level, BT rate, amount of transfused BU etc. were collected. TBL was estimated. Linear regression, log-linear poisson regression and logistic regression were used to compare the outcomes TBL, amount of transfused BU and BT rate, respectively, between different prosthesis types. RESULTS: Of 278 patients included in this study 209 received reverse, 57 anatomical and 12 stemless SA. Mean TBL was 392.7 ml in reverse, 394.6 ml in anatomical and 298.3 ml in stemless SA. The BT rate and mean amount of BU were, respectively, 14.4% and 0.32 in reverse and 8.77% and 0.23 in anatomical SA. None of the patients with stemless arthroplasty received BT. Significant risk factors for elevated TBL are operation time, higher BMI, male sex. Significant risk parameters for BT and higher amount of transfused BU are low BMI, cemented arthroplasty, coronary heart disease, ASA score > 2 and previous therapy with vitamin K antagonists. CONCLUSION: Although there were little differences between the blood transfusion rates in reverse vs. anatomical arthroplasty, there was no difference in total blood loss between these different prosthesis types. None of the patients with stemless arthroplasty received blood transfusion. There are various risk factors affecting total blood loss and blood transfusion rate. However, risk parameters influencing blood transfusion may be different to them affecting total blood loss.

Balancing mobile-bearing unicondylar knee arthroplasty in vitro.

PURPOSE: Balancing mobile-bearing (MB) unicondylar knee arthroplasty (UKA) is challenging. If performed improperly, potential complications include pain, implant loosening, or progression of osteoarthritis in the preserved compartment. The purpose of this study was to document effects of improper balancing on knee kinematics and joint contact stress. It was hypothesized that over-stuffing would lead to more valgus and higher lateral contact force. METHODS: Seven fresh-frozen cadaver legs were mounted in a kinematic rig that applied three motion patterns to the specimens: passive flexion-extension, open chain extension, and squatting. During testing, an infrared camera system recorded the trajectories of markers rigidly attached to femur and tibia, while a pressure sensor measured contact pressure in the lateral compartment. Prior computer tomography scans allowed identification of coordinate frames of the bones and calculations of anatomical rotations and translations. Collateral ligament strains were calculated, and quadriceps forces recorded. Following testing on the native knee, a medial MB UKA was implanted in each specimen and all motion trials were repeated. Three inlay thicknesses were tested to simulate optimal balancing as well as under- (1 mm thinner) and over-stuffing (1 mm thicker) of the medial compartment relative to the optimal thickness. RESULTS: Under-stuffing of the medial compartment leads to kinematics closest to the native knee. Subjectively balanced and over-stuffed MB UKA knees were in more valgus. Lateral peak contact stress was higher from mid- to deep flexion following UKA in all three tested states; however, these results were not significant. Peak strain in the superficial medial collateral ligament (sMCL) was significantly higher in MB UKA, regardless of the inlay thickness mainly in mid-flexion. Inlay thickness had no significant impact on measured quadriceps force during squatting. CONCLUSION: The results underline the importance of optimal balancing. Over-stuffing should be avoided as it results in the largest kinematic changes relative to the native condition and induces higher strains in the sMCL. Based on the kinematic findings, it is advisable to use thinner inlays, as long as this is not compromising stability or risking inlay luxation.

Kinematics of a bicruciate-retaining total knee arthroplasty.

PURPOSE: The recently reintroduced bicruciate-retaining Total Knee Arthroplasty (BCR TKA) is an interesting approach in the quest for close replication of knee joint biomechanics and kinematics closer to the native knee. Therefore, this study aimed at providing a detailed biomechanical view on the functional resemblance of BCR TKA to the native knee joint. METHODS: Seven fresh-frozen full leg cadaver specimens (76 ± 10 year) were mounted in a 6 degrees-of-freedom kinematic rig that applied a dynamic squatting motion knee flexion. Two motion patterns were performed pre- and post-implantation of a fixed bearing BCR TKA: passive flexion-extension and squatting while an infrared camera system tracked the location of reflective markers attached to the tibia and femur. Additionally, specimen laxity was assessed using Lachman tests and varus/valgus stress tests in triplicate. RESULTS: Overall, differences in tibiofemoral kinematics between native knee and BCR TKA were small. Some minor differences appeared under the load of a squat: less internal tibial rotation and some minor paradoxical anterior translation of the medial femoral condyle during mid-flexion. BCR TKA may slightly elevate the joint line. Knee laxity as measured by the Lachman and varus/valgus tests was not significantly influenced by BCR TKA implantation. CONCLUSION: As both cruciate ligaments are preserved with BCR TKA the unloaded knee closely resembles native knee kinematics including preserving the rollback mechanism. The loss of the conforming anatomy of menisci and tibial cartilage and replacement via a relatively flat polyethylene inlay may account for the loss of tibial internal rotation and the slight paradoxical AP motion of the medial femoral condyle with BCR TKA. This phenomenon reproduces findings made earlier with fixed bearing unicondylar knee arthroplasty.

Anatomic dissection of the anterolateral ligament (ALL) in paired fresh-frozen cadaveric knee joints.

INTRODUCTION: Different dissection studies as well as comparative studies about the anterolateral ligament of the knee (ALL) already exist and the structure's topology and properties have been shown. However, most of the studies investigating the ligament were performed in embalmed knees, which is thought to change the structural integrity of ligaments and thus the topologic and dynamic measurements. Since the biomechanical function of the ALL is not fully understood until today and a correlation with the pivot shift phenomenon is yet speculative, further studies will have to clarify its definitive importance. Its function as a limiter of internal rotation and lateral meniscal extrusion leads to the assumption of a secondary knee stabilizer. METHODS: Twenty paired fresh-frozen cadaveric knees of ten donors have been dissected in a layerwise fashion. After identification of the ALL, topologic measurements were undertaken using a digital caliper. RESULTS: The ALL could be identified as a tender, pearly structure in front of the anterolateral joint capsule in only 60% of the dissected knee joints. Only 20% of donors had a bilateral ALL while 80% had an ALL only in one side. Mean length, thickness and width as well as topographic measurements were comparable to other available studies investigating fresh-frozen cadavers. CONCLUSION: Anatomy and topography of the ALL seem to be highly variable, but consistent within certain borders. Prevalence has to be argued though as it strongly differs between studies. The impact of an ALL absence, even if only unilateral, needs to be investigated in clinical and imaging studies to finally clarify its importance.

Balancing UKA: overstuffing leads to high medial collateral ligament strains.

PURPOSE: Balancing unicondylar knee arthroplasty (UKA) is challenging. If not performed properly, it may lead to implant loosening or progression of osteoarthritis in the preserved compartment. This study was aimed to document the biomechanical effects of improper balancing. We hypothesised that overstuffing would lead to more valgus, higher strain in the medial collateral ligament (sMCL), and higher lateral contact force. METHODS: Six fresh-frozen cadaver specimens were mounted in a kinematic rig. Three motion patterns were applied with the native knee and following medial UKA (passive motion, open-chain extension, and squatting), while infrared cameras recorded the trajectories of markers attached to femur and tibia. Three inlay thicknesses were tested (8, 9, 10 mm). RESULTS: Overstuffed knees were in more valgus and showed less tibial rotation and higher strains in the sMCL (p < 0.05). Lateral contact forces were higher in some specimens and lower in others. Stiffening of the medial compartment by UKA, even well balanced, already leads to a knee more in valgus with a more stressed sMCL. Overstuffing increases these effects. Knees with a tight sMCL may even see lower lateral contact force. Biomechanics were closest to the native knee with understuffing. CONCLUSION: The first two hypotheses were confirmed, but not the latter. This underlines the importance of optimal balancing. Overstuffing should certainly be avoided. Although kinematics is only slightly affected, contact forces and ligament strains are considerably changed and this might be of more clinical importance. It is advisable to use thinner inlays, if stability is not compromised.

Midterm follow-up after implantation of a polyurethane meniscal scaffold for segmental medial meniscus loss: maintenance of good clinical and MRI outcome.

PURPOSE: The preservation of meniscal structure and function after segmental meniscal loss is of crucial importance to prevent early development of osteoarthritis. Implantation of artificial meniscal implants has been reported as a feasible treatment option. The purpose of this study was to assess the clinical and magnetic resonance imaging (MRI) results 4 years after implantation of a polyurethane scaffold for chronic segmental medial meniscus deficiency following partial medial meniscectomy. METHODS: Eighteen patients received arthroscopic implantation of an Actifit(®) polyurethane meniscal implant (Orteq Sports Medicine, London, UK) for deficiency of the medial meniscus. Patients were followed at 6, 12, 24, and 48 months. Clinical outcome was assessed using established patient-reported outcome scores (KOOS, KSS, UCLA Activity Scale, VAS for pain). Radiological outcome was quantified by MRI scans after 6, 12, 24, and 48 months evaluating scaffold morphology, tissue integration, and status of the articular cartilage as well as signs of inflammation. RESULTS: Median patient age was 32.5 years (range 17-49 years) with a median meniscal defect size of 44.5 mm (range 35-62 mm). Continuing improvement of the VAS and KSS Knee and Function Scores could be observed after 48 months compared to baseline, whereas improvement of the activity level according to UCLA continued only up to 24 months and decreased from there on. The KOOS Score showed significant improvement in all dimensions. MRI scans showed reappearance of bone bruises in two patients with scaffold extrusion. No significant changes in the articular cartilage could be perceived. CONCLUSION: Arthroscopic treatment for patients with chronic segmental meniscal loss using a polyurethane meniscal implant can achieve sustainable midterm results regarding pain reduction and knee function. LEVEL OF EVIDENCE: IV.

The role of patelloplasty in total knee arthroplasty.

INTRODUCTION: Anterior knee pain (AKP) is a frequent complication after total knee arthroplasty (TKA). Patelloplasty, defined as reshaping the patella for optimal tracking in the trochlea, has been proposed to reduce the rate of this complication in patellar retaining implants. Aim of this study was to analyze the available literature regarding the outcomes of patelloplasty and to assess its methodological quality. MATERIALS AND METHODS: A comprehensive review of the English literature was performed using the keywords "total knee arthroplasty", "patelloplasty" and "patellaplasty" with no limit regarding the year of publication. All the selected articles were evaluated with the Coleman score. RESULTS: Seven full text articles were retrieved. The initial cohort included 461 knees in the study groups and 465 in the control groups. At an average FU of 70.6 months 447 knees were reviewed in the study group and 447 in the control groups. The global rate of AKP after patelloplasty was 11.3 % which compared to 7.9 % in the patella resurfacing control group. No signs of specific patellar complications due to patelloplasty were reported. Average Coleman score was 66.9. CONCLUSION: Most of the literature has barely sufficient methodological quality. Patelloplasty aims at reducing patellar thickness and improve its tracking with TKA. This procedure is a safe and easy option with no reported adverse effects. In the included studies, outcome seemed to be superior in comparison with isolated osteophyte removal and denervation with a lower rate of AKP. The included studies, however, report a lower rate of AKP following TKA with patellar resurfacing. Patelloplasty may have the potential to improve the outcome of patellar retaining implants. LEVEL OF EVIDENCE: 4, systematic review.

Fixation techniques and stem dimensions in hinged total knee arthroplasty: a finite element study.

INTRODUCTION: No evidence-based guidelines are available to determine the appropriate stem length, and whether or not to cement stems in revision total knee arthroplasty (TKA). Therefore, the objective of this study was to compare stresses and relative movement of cemented and uncemented stems of different lengths using a finite element analysis. MATERIALS AND METHODS: A finite element model was created for a synthetic tibia. Two stem lengths (95 and 160 mm) and two types of fixation (cemented or press fit) of a hinged TKA were examined. The average compressive stress distribution in different regions of interest, as well as implant micromotions, was determined and compared during lunge and squat motor tasks. RESULTS: Both long and short stems in revision TKA lead to high stresses, primarily in the region around the stem tip. The presence of cement reduces the stresses in the bone in every region along the stem. Short stem configurations are less affected by the presence of cement than the long stem configuration. Press-fit stems showed higher micromotions compared to cemented stems. CONCLUSIONS: Lowest stresses and micromotion were found for long cemented stems. Cementless stems showed more micromotion and increased stress levels especially at the level of the stem tip, which may explain the clinical phenomenon of stem-end pain following revision knee arthroplasty. These findings will help the surgeon with optimal individual implant choice.

The anterolateral ligament (ALL) and its role in rotational extra-articular stability of the knee joint: a review of anatomy and surgical concepts.

The anterolateral ligament of the knee (ALL) has caused a lot of rumors in orthopaedics these days. The structure that was first described by Segond back in 1879 has experienced a long history of anatomic descriptions and speculations until its rediscovery by Claes in 2013. Its biomechanical properties and function have been examined recently, but are not yet fully understood. While the structure seems to act as a limiter of internal rotation and lateral meniscal extrusion its possible proprioceptive effect remains questionable. Its contribution to the pivot shift phenomenon has been uncovered in parts, therefore it has been recognized that a concomitant anterolateral stabilization together with ACL reconstruction may aid in prevention of postoperative instability after severe ligamentous knee damages. However, there are a lot of different methods to perform this procedure and the clinical outcome has yet to be examined. This concise review will give an overview on the present literature to outline the long history of the ALL under its different names, its anatomic variances and topography as well as on histologic examinations, imaging modalities, arthroscopic aspects and methods for a possible anterolateral stabilization of the knee joint.