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Guideline-based surgical cartilage therapy for focal cartilage damage offers highly effective possibilities to sustainably reduce patients' complaints and to prevent or at least delay the development of early osteoarthritis. In the knee joint, it has the potential to reduce almost a quarter of the arthroses requiring joint replacement caused by cartilage damage. Biologically effective injection therapies could further improve these results. Based on the currently available literature and preclinical studies, intra- and postoperative injectables may have a positive effect of platelet-rich plasma/fibrin (PRP/PRF) and hyaluronic acid (HA) on cartilage regeneration and, in the case of HA injections, also on the clinical outcome can be assumed. The role of a combination therapy with use of intra-articular corticosteroids is lacking in the absence of adequate study data and cannot be defined yet. With regard to adipose tissue-based cell therapy, the current scientific data do not yet justify any recommendation for its use. Further studies also regarding application intervals, timing and differences in different joints are required., Competing Interests: Declarations Conflict of interest The authors have no potential conflict of interest., (© 2023. The Author(s).)

Purpose: The goal of this study was the assessment of long-term outcome of dorsal capsular imbrication of the distal radioulnar joint (DRUJ) in dorsal instability., Methods: The study included ten patients (mean 38.7 years of age) with a mean follow-up time of 11.2 years (9.3 years to 14.3 years). Examination parameters included Disabilities of Arm, Shoulder, and Hand (DASH) questionnaire, modified Mayo Wrist Score (MMWS), determination of range of motion in comparison with the healthy extremity, pre- and post-operative pain level assessment, and examination of DRUJ stability., Results: Eight of ten DRUJs proved to be stable after the above-mentioned follow-up. Mean MMWS was 92.5 (65-100; SD: 11.1). Mean DASH Score was 8.8 (0-60; SD: 18.4). Grip strength reached 93.5% of the contralateral unaffected hand. Range of motion did not differ significantly in comparison with the healthy contralateral extremity. Nine of ten patients regarded pain level reduction as excellent. Eight of ten patients regarded DRUJ stability as excellent after surgery., Conclusion: Dorsal capsular imbrication of the DRUJ is an efficacious surgical technique for post-traumatic dorsal instability in the long-term.

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.

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.

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.

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.

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.

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.

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.

Introduction: Fixed-bearing unicompartmental knee arthroplasty (UKA) closely replicates native knee kinematics. As few studies have assessed kinematics following mobile-bearing (MB) UKA, the current study aimed to investigate whether MB UKA preserves natural knee kinematics., Materials and Methods: Seven fresh-frozen full-leg cadaver specimens were prepared and mounted in a kinematic rig that allowed all degrees of freedom at the knee. Three motion patterns, passive flexion-extension (0°-110° flexion), open-chain extension (5°-70° flexion) and squatting (30°-100° flexion), were performed pre- and post-implantation of a medial MB UKA and compared in terms of rotational and translational knee joint kinematics in the different anatomical planes, respectively., Results: In terms of frontal plane rotational kinematics, MB UKA specimens were in a more valgus orientation for all motion patterns. In the axial plane, internal rotation of the tibia before and after UKA was consistent, regardless of motion task, with no significant differences. In terms of frontal plane, i.e., inferior-superior, translations, the FMCC was significantly higher in UKA knees in all flexion angles and motor tasks, except in early flexion during passive motion. In terms of axial plane, i.e., anteroposterior (AP), translations, during open-chain activities, the femoral medial condyle center (FMCC) tended to be more posterior following UKA relative to the native knee in mid-flexion and above. AP excursions of the FMCC were small in all tested motions, however. There was substantial AP translation of the femoral lateral condyle center during passive motion before and after UKA, which was significantly different for flexion angles > 38°., Conclusions: Our study data demonstrate that the kinematics of the unloaded knee following MB UKA closely resemble those of the native knee while relative medial overstuffing with UKA will result in the joint being more valgus. However, replacing the conforming and rigidly fixed medial meniscus with a mobile inlay may successfully prevent aberrant posterior translation of the medial femoral compartment during passive motion and squatting motion.

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.

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.

Introduction: Total knee arthroplasty (TKA) is a successful procedure for the management of osteoarthritis (OA) of the knee. Axial plane deformities are more common than suspected in patients presenting with osteoarthritis of the knee joint. Recent research has indicated that torsional deformities could play an important role in the development of anterior knee pain (AKP)., Methods: In a narrative review of the literature, the aetiology of maltorsion deformity of the lower extremity in both, childhood and adulthood, as well as the development of postoperative femoral axial plane deformities are examined. This includes the numerous surgical interventions that have been described for the treatment of maltorsion syndrome, and the role of patient-specific instrumentation. Finally, correcting for maltorsion deformity during and its potential implications for the current clinical care pathway, in terms of both pre- and perioperative practices is discussed., Discussion and Conclusion: Axial plane alignment is considered the 'third dimension' in TKA. Correct axial alignment the lower extremity and of prosthetic components is deemed an important prerequisite for a postoperatively stable and painless knee. Identification of and, where appropriate, adjustment for any pre-existing maltorsion deformities is thought to significantly reduce the proportion of patients with residual complaints following TKA. Well-designed and well-conducted clinical studies are required to support our hypotheses.

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.

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.

Purpose: Although there are various new scaffold-based techniques for cartilage regeneration it remains unclear up to which defect size they can be used. The present study reports of a cell-free collagen type I gel matrix for the treatment of large cartilage defects of the knee after a two-year follow-up., Methods: Twenty-eight patients with a mean cartilage defect size of 3.71 ± 1.93 cm² were treated with a cell-free collagen type I gel matrix (CaReS-1S®, Arthro Kinetics AG, Krems/Donau, Austria) via a mini-arthrotomy. Clinical outcome was assessed preoperatively and six weeks as well as six, 12 and 24 months after surgery using various clinical outcome scores (IKDC, Tegner, KOOS, VAS). Cartilage regeneration was evaluated via MRI using the MOCART score., Results: Seventeen male and 11 female patients with a mean age of 34.6 years were included in this study. Significant pain reduction (VAS) could be noted after six weeks already. Patient activity (IKDC, Tegner) could be significantly improved from 12 months on and nearly reached reported pre-operative values. All subject categories of the KOOS except for symptom (swelling) showed significant improvements throughout the study. Constant significant improvements of the mean MOCART score were observed from 12 months on. MR images did not yield any signs of infection or synovitis. After 24 months a complete defect filling could be noted in 24 out of 28 cases with a mainly smooth surface, complete integration of the border zone and homogenous structure of the repaired tissue., Conclusion: Cell-free collagen type I matrices appear to be a safe and suitable treatment option even for large cartilage defects of the knee. Results of this study were comparable to the better-established findings for small cartilage defects. Mid- and long-term results will be needed to see if clinical and MR-tomographic outcome can be maintained beyond 24 months.

Background: The ideal treatment for juvenile osteochondritis dissecans of the talus (ODT) is still unclear. To determine predictors of failure of conservative treatment, children admitted for ODT were retrospectively analyzed., Methods: Patient files were analyzed to search for children treated for an ODT between 2000 and 2011. X-rays and MRI at baseline were evaluated for grading of lesions and the patient history was obtained. Final follow-up evaluation was performed via questionnaire and complementary telephone interview. Outcome was measured using the AOFAS and the Olerud/Molander scores. Conservative treatment consisted of out of sports and modification of activity under full weight-bearing. In case of persisting pain, full load removal on crutches was initiated. For further analysis, two groups were formed: (1) successful conservative treatment; (2) converted to surgical therapy. A logistic regression was used to determine potential predictors of conservative treatment failure., Results: Seventy-seven lesions in 67 children with a mean age of 11.4 years (range 4-15 years) at the time of diagnosis were identified. Every patient received conservative treatment as a first-line treatment after diagnosis of ODT except for one single patient with a grade IV lesion at time of diagnosis who received operative treatment directly after diagnosis. Sixty-one percent of the lesions failed conservative treatment. A higher age as well as a grade III lesion at time of diagnosis was predictive for failure of the conservative treatment (p = 0.03 and p = 0.02, respectively). Regarding the functional outcome, a higher grade lesion in general was predictive for an inferior outcome as measured by clinical score., Conclusion: Grade III ODT especially in older children leads significantly more often to treatment failure when treated non-surgically. No other predictors for treatment failure could be identified., Level of Evidence: Level III (retrospective comparative study).

Introduction: Function and kinematics following unicondylar knee arthroplasty (UKA) have been reported to be close to the native knee. Gait, stair climbing and activities of daily living expose the knee joint to a combination of varus and valgus moments. Replacement of the medial compartment via UKA is likely to change the physiologic knee stability and its ability to respond to varus and valgus moments. It was hypothesized that UKA implantation would stiffen the knee and decrease range of motion in the frontal plane., Materials and Methods: Six fresh frozen cadaver knees were prepared and mounted in a six-degrees-of-freedom robot. An axial load of 200 N was applied with the knee in 15°, 45° and 90° of flexion. Varus and valgus moments were added, respectively, before and after implantation of medial UKA. Tests were than redone with a thicker polyethylene inlay to simulate overstuffing of the medial compartment. Range of motion in the frontal plane and the tibial response to moments were recorded via the industrial robot., Results: The range of motion in the frontal plane was decreased with both, balanced and overstuffed UKA and shifted towards valgus. When exposed to valgus moments, knees following UKA were stiffer in comparison with the native knee. The effect was even more pronounced with medial overstuffing., Conclusion: In UKA, the compressive anatomy is replaced by much stiffer components. This lack of medial compression and relative overstuffing leads to a tighter medial collateral ligament. This drives the trend towards a stiffer joint as documented by a decrease in frontal plane range of motion. Overstuffing should strictly be avoided when performing UKA.

Introduction: Posterior-stabilized (PS) and cruciate-retaining (CR) total knee arthroplasties (TKA) are both successfully used for treatment of end-stage osteoarthritis. The choice of constraint depends on knee deformity and stability as well as most importantly surgeon preference. The aim of this study was to compare the amount of blood loss and required transfusions following TKA with the two different designs., Materials and Methods: In a retrospective approach, 473 patients undergoing TKA were included (240 CR and 233 PS from a single manufacturer). Demographics at base line were comparable between both groups. Blood loss [red blood cell (RBC) loss] was calculated after documentation of pre- and postoperative hematocrit levels at discharge. Transfusion requirements were recorded. Statistical analysis was done using Mann-Whitney U test., Results: The calculated blood loss (RBC loss) at discharge was 548 ± 216 ml in the PS group compared with 502 ± 186 ml in the CR group (p = 0.032). There were no differences in the transfusion requirements between both groups (PS 0.41 vs. CR 0.37, p = 0.39)., Discussion: The blood loss was significantly higher in the PS group. This may be due to the box preparation that exposes more cancellous femoral bone, which may add to postoperative bleeding. The differences remain, however, small, as they did not lead to a significantly higher transfusion rate with PS TKA.

Introduction: Patient-specific instrumentation (PSI) was introduced in an attempt to reduce positional outliers of components in total knee arthroplasty (TKA). It was hypothesized that PSI could help with the positioning of tibial components in optimal rotational alignment., Methods: A magnetic resonance imaging (MRI) analysis of 58 patients following TKA was conducted. Of these, 30 operations were performed using PSI and 28 using conventional instrumentation. The rotation of the tibial components was determined in MRI using three different reference lines: a tangent to the dorsal tibial condyles, the tibial epicondylar line, and the tibial tubercle. Deviations >9° were considered outliers. Also internal rotation >1° was considered an outlier. Data were analyzed statistically for positional outliers using the Chi-squared test., Results: There was excellent inter- and intraobserver reliability with low standard deviations for the determination of tibial component rotation using the tangent to the dorsal condyles and the tibial epicondylar line as reference. Using the dorsal tangent as reference, there were eight components in excessive external rotation (28.6 %) and one component being in relative internal rotation (5.4°) in the conventional group, while there were two components in excessive external rotation in the PSI group (6.7 %). Using the tibial epicondyles as reference, there were seven components in excessive external rotation (21.4 %) and one component being in relative internal rotation (4.4°) in the conventional group; while there were two components in excessive external rotation in the PSI group (6.7 %). These differences were statistically significant (p < 0.05). Measurements based on the tibial tubercle showed poor reproducibility in terms of intra- and interobserver reliability and was of little use in the context of the research question., Discussion and Conclusion: In this setup, PSI was effective in significantly reducing outliers of optimal rotational tibial component alignment during TKA. Anatomy of the proximal tibia does not deliver clear landmarks that are prominent and consistent. This makes both, MRI analysis as well as cutting jig production and intraoperative placement a challenge.

Introduction: This pilot study used magnet resonance imaging (MRI) to analyse the rotation of medial unicondylar knee arthroplasty (UKA) components and assessed how accurately the results could be reproduced., Materials and Methods: Knee MRI using a special protocol to reduce metal artefact was performed in ten patients who had undergone medial UKA. Two independent investigators measured the rotation angle of femoral (zirconium) and tibial (cemented full-poly or cemented modular metal-backed) components applying different reference lines for the latter. Statistical analysis comprised tests for reliability, variance between measurement techniques, standard deviations and limits of agreement., Results: For all methods tested, there was sufficient inter- and intra-observer reliability. Lowest variances were, however, found for the femoral epicondyles, for both femoral and tibial components. A tangent to the dorsal epicondyles of the tibia also gave reproducible results with low variances for the tibial component., Discussion: Almost all applied measurement techniques were reproducible by statistical definition, although some of them resulted in substantial differences between both, observations and observers. A variance test helps to distinguish better between clinically useful and less accurate references., Conclusion: MRI allows good reproducible rotation analysis via the femoral epicondyles for both femoral and tibial UKA implants. For the tibia, the tibial tuberosity, the eminentia and the tibial epicondyles in particular were shown to be less reliable. The dorsal epicondyles seem to be most suitable for the tibial component.

Purpose: The affect of anterior cruciate ligament (ACL) integrity on the early postoperative stability of a collagen type-I gel scaffold was investigated. The value of fibrin glue for graft fixation in ACL deficient porcine knees over a simulated early postoperative period was also studied., Methods: Full-thickness articular cartilage defects (11 × 6 mm) were created on the medial femoral condyle of 80 porcine knees. The ACL was left intact or completely transected in each of 40 knees. Gel plugs were tested in each group: press-fitting only in 20 specimens and press-fitting plus fibrin glue in 20 specimens. Each knee underwent 2,000 cycles in a validated ex-vivo continuous passive motion model., Results: Press-fit-only fixation grafts in knee specimens with an intact ACL showed significantly superior stability than that in ACL deficient knees (p = 0.01). In ACL deficient knees, grafts fixed with press-fitting plus fibrin glue showed significantly superior stability than those using press-fit only fixation (p = 0.01). Press-fitting plus fibrin glue fixation showed no significant differences in worn surface area between knee specimens with intact and deficient ACL., Conclusions: ACL deficiency led to early scaffold instability in an ex-vivo porcine knee model. Fibrin glue in ACL deficient knees led to additional graft stability. These findings indicated that cartilage regenerative techniques may give optimum results in ACL intact knees.

Introduction: Unicompartmental knee arthroplasty (UKA) has been proven to be a viable procedure in case of medial osteoarthritis of the knee joint. Minimally invasive surgery (MIS) techniques have been described to facilitate recovery after surgery. The aim of this study was to rule out major failure mechanisms and to obtain clinical data for comparison between a conventional and the MIS approach., Materials and Methods: A consecutive series of 163 UKA (160 patients) were retrospectively included (83 conventional and 80 MIS interventions). Patients were invited for a clinical examination including clinical scores (KSS, Lequesne, UCLA, VAS, Feller- and Turba Patella Scores). Seven patients (4.3%) were lost to follow-up., Results: Average follow-up was 4.6 ± 1.3 (1.5-6.8) years. Average age at operation was 67.5 ± 7.9 (45-81) years. Fifteen implants had been converted to TKA (9.2%). There were seven conversions to TKA in the MIS and 8 in the conventional group. Of the applied clinical scores there were better values for the Turba patella score in the MIS group. Differences of the other scores were not statistically significant., Conclusion: Comparable functional results for both UKA procedures could be shown. There were no significant differences in terms of clinical scores or revision rates. The MIS approach in medial UKA did not show any major complications. Its use seems to be safe.

Purpose: Safety and efficacy of unicompartmental knee arthroplasty (UKA) in unicompartmental osteoarthritis (OA) has been shown in large patient series. It has been matter of discussion whether or not spontaneous osteonecrosis of the knee (SONK) can successfully be treated with UKA., Patients and Methods: A retrospective approach included 52 cases of UKA for SONK of the femoral condyles. Four implants were revised (7.7%), and seven patients had died. Nine patients were interviewed by telephone, 28 followed the invitation for clinical examination including clinical scores (KSS and WOMAC) and radiographs. Satisfaction of patients was recorded in four categories. Four patients (7.7%) were lost to follow-up., Results: Average follow-up was 10.9 ± 4.8 years (4-25). Average age at operation was 66.6 ± 9.7 years. The KSS score increased from a preoperative 85 ± 30 to 173 ± 27 (p < 0.0001) at latest follow-up. WOMAC was 7.7 ± 11.4 at latest follow-up. Of the patients with implants still in place, most patients were satisfied (21.6%) or very satisfied (75.7%) with the outcome of this surgical procedure. One patient was dissatisfied (2.7%). Kaplan-Meier analysis with implant revision as endpoint revealed a survival rate of 93.1% at 10 years and 90.6% at 15 years., Discussion: This study shows that spontaneous osteonecrosis of the knee (SONK) can successfully be treated with UKA at a good mid- to long-term follow-up.

Lateral unicondylar knee arthroplasty (UKA) has been utilized as a treatment for isolated lateral tibiofemoral osteoarthritis (OA) since the first description of UKA in the 1970s. To date, there remains some controversy on UKA procedures. As indications for lateral UKA are usually rare, surgeon experience seems to be the key factor for a successful intervention. Better understanding of biomechanics of the knee joint, recent developments in prosthesis design, surgical techniques and indications may add to improved outcomes of lateral UKA. Alternatives that are applied to treat lateral tibiofemoral OA include arthroscopic interventions, osteotomies and total knee arthroplasty (TKA). In comparison with TKA, potential advantages of UKA include a minimally or less invasive approach, less bone resection, preservation of the cruciate ligaments, preservation of the medial tibiofemoral and the patellofemoral compartments, shorter rehabilitation, and physiological knee kinematics. This review aims to summarize the current concepts of implant designs as well as indications and contraindications for lateral UKA. The literature will be presented and discussed as well as results and realistic expectations on both the surgeon's and the patient's side. Alternative treatments and future concepts for lateral UKA will be presented.

Introduction: Safety and efficacy of unicompartmental knee arthroplasty (UKA) has been shown in large patient series. Patellofemoral replacement (PFR) is known to be a viable solution to end-stage patellofemoral arthritis. Bicompartmental osteoarthritis (OA) affecting the medial tibio-femoral and the patello-femoral compartment (medio-patellofemoral OA) is often treated with total knee arthroplasty (TKA). It was hypothesized that medio-patellofemoral OA can successfully be treated with bicompartmental arthroplasty., Method: In a retrospective approach nine patients who had received UKA in combination with PFR were included into the study. Intact ACL and lateral compartment were conditions for the indication. Patients were clinically examined including clinical scores (KSS and WOMAC) and radiographies were evaluated. Satisfaction of patients was recorded under four categories., Results: Average follow-up after bicompartmental arthroplasty was 11.8 ± 5.4 years (4-17 years). Among the nine patients there were eight females and one male at an average age at operation of 64 ± 5 years. No surgical revisions were required following bicompartmental arthroplasty. The KSS score increased from a preoperative 68.8 ± 26.2 to 175.5 ± 22.9 at latest follow-up (p = 0.002). WOMAC was 18.3 ± 8.6 at latest follow-up. All patients included were satisfied (n = 3) or very satisfied (n = 6) with the outcome of this surgical procedure., Conclusion: This small case series shows that a bicompartmental arthroplasty can be a successful approach to prevent or postpone TKA. However, this intervention is technically demanding and requires experience in both UKA and PFR.

Introduction: When highly conforming polyethylene inlays were introduced into total knee arthroplasty (TKA), they were characterized as adding anteroposterior stability to the reconstructed knee. The aim of this study was to examine the patellofemoral pressure with the designs of a highly conforming and a posterior stabilized inlay. The patellofemoral pressure depends among other factors on the anteroposterior stability of the knee joint., Materials and Methods: Eight fresh frozen human knee specimens underwent testing in a kinematic device. Knee motion was driven by a hydraulic cylinder at an extension moment of 31 Nm. The patellofemoral contact pressure was measured using a pressure sensitive film (Tekscan((R)), Inc., Boston, USA). First, this was assessed after implantation of a cruciate retaining (CR) TKA with a highly conforming polyethylene insert before and after resection of the posterior cruciate ligament. After that, the same measurements were performed with a similar posterior stabilized prosthesis., Results: Patellofemoral contact pressures in the CR prosthesis using the highly conforming inlay were not significantly different before and after resection of the posterior cruciate ligament. However, after implantation of a posterior stabilized prosthesis peak pressure was significantly lower [Mean: 6.12, (SD 2.37) MPa] in comparison to the highly conforming type [7.12, (SD 2.53) MPa, P < 0.01] at a preserved posterior cruciate ligament. Further to that, the mean contact pressure turned out to be lower with the posterior stabilized design (P < 0.006)., Conclusion: The results of this study suggest that a posterior stabilized prosthesis design reduces the patellofemoral peak and mean pressure in comparison with a high conforming design. The better reproducible femoral rollback with a posterior stabilized model at a tibial ventral shift could serve as a possible explanation.

Purpose: Decreased quadriceps strength and fatigue is suspected to be one of the contributing factors for anterior knee pain and malfunction after total knee arthroplasty (TKA). The purpose of this in vitro study was to investigate the amount of quadriceps force required to extend the knee isokinetically after TKA in dependence of different prosthesis designs and the state of the posterior cruciate ligament (PCL)., Materials and Methods: Eight fresh frozen human knee specimens underwent testing in a kinematic device simulating an isokinetic knee extension cycle from 120° of flexion to full extension. The quadriceps force was measured after implantation of a cruciate retaining (CR) TKA (Genesis II, Smith&Nephew, Memphis, TN, USA) applying a conventional CR (11 mm) and a highly conforming (deep dished, DD) polyethylene (PE) inlay consecutively before and after resection of the PCL. Finally, tests were repeated with a posterior-stabilized (PS) design., Results: Simulating a physiological knee extension, no significant differences in the average quadriceps force were detected between the cruciate preserving inlays (CR 1,146.57 ± 88.04 N, DD 1,150.19 ± 97.54 N, P = 0.86) as long as the PCL was intact. After resection of the PCL, the required quadriceps force increased significantly for both designs (CR 1,203.17 ± 91.51 N, P < 0.01 and DD 1,191.88 ± 80.07 N, P < 0.03). After implantation of the posterior stabilized femoral component quad force decreased to its initial levels with forces significantly lower compared to the PCL deficient knees provided with a CR or DD (PS 1,130.91 ± 107.88 N, P < 0.01) inlay. With a deficient PCL there were no statistical differences for the DD design in comparison with CR in mean quad forces (CR 1,203.17 ± 91.51 N vs. DD 1,191.88 ± 80.07 N, P = 0.50) nor in peak forces (CR 1,729.44 ± 161.86 N, DD 1,688.66 ± 123.18 N, P = 0.17)., Discussion: At intact PCL peak quad forces and mean forces beyond 70° of flexion could be shown to be significantly lower with a PS TKA design in comparison with cruciate preserving designs such as CR and DD. In the PCL deficient knee quad forces with a highly conforming implant (DD) and CR were significantly higher than with a PS TKA. The use of PS implants in all PCL deficient knees seems to be advisable