Why Kinematic Alignment Makes Little Sense in Valgus Osteoarthritis of the Knee: A Narrative Review.

There is a debate about the best alignment strategies in total knee arthroplasty (TKA). Mechanical alignment (MA) targets in combination with necessary soft tissue releases are the gold standard for TKA in end-stage valgus osteoarthritis. Some authors propagate kinematic alignment (KA) with the aim of restoring the patient's native alignment and minimizing the need for soft tissue releases. Our previous studies showed that MA with standardized soft tissue release produces reproducible results, and that the preoperative phenotype does not influence the results of patients with valgus osteoarthritis. These data suggest that there is no functional advantage to preserving valgus alignment in patients with valgus osteoarthritis. Many patients with valgus osteoarthritis present with a compromised medial collateral ligament and leaving the knee in valgus could increase the risk of secondary instability. The current literature supports MA TKA with soft tissue release as the gold standard. While using more sophisticated enabling technologies like robotic surgery might allow for aiming for very slight (1-2°) valgus alignment on the femoral side, any valgus alignment outside this range should be avoided. This review paper summarizes our current knowledge on the surgical techniques of TKA in patients with valgus osteoarthritis.

Pelvic Roll Back Can Trigger Functional Psoas Impingement in Total Hip Arthroplasty.

In most cases, impingement of the iliopsoas tendon after total hip arthroplasty is caused by acetabular component retroversion. The present case report describes a patient with functional iliopsoas impingement following total hip arthroplasty. With increasing flexibility of the hip joint after surgery, the functional adjustment to the stiff thoracolumbar spine in this patient with diffuse idiopathic skeletal hyperostosis resulted in progressive pelvic roll back. This roll back resulted in a functional iliopsoas impingement as the psoas tendon travels over the front of the pecten ossis pubis. Since excessive roll back is usually also addressed in primary total hip arthroplasty by decreasing anteversion of the acetabular component, surgeons should be aware to avoid the combination of roll back and decreased anteversion and their potential impact on iliopsoas impingement.

Complex periprosthetic wound coverage in patients undergoing revision total knee arthroplasty: a single plastic surgeon study.

INTRODUCTION: Options for soft tissue coverage in revision total knee arthroplasty (rTKA) range from primary wound closure to complex muscle flap reconstructions. The purpose of this study was to investigate the institutional experience of wound coverage options for complex soft tissue defects in rTKA. MATERIALS AND METHODS: 77 patients undergoing rTKA with complex wound closure by a single plastic surgeon were retrospectively reviewed. The average follow-up was 30.1 months. In 18 (23.4%) patients, an intraoperative decision for primary closure was made. Fifty-nine patients (76.6%) received either a local fasciocutaneous (N = 18), a medial gastrocnemius (N = 37), a free latissimus dorsi (N = 3) or a lateral gastrocnemius flap (N = 1). Revision-free survival and complication rates were assessed and risk factors were analyzed with Cox-regression analysis. RESULTS: Medial gastrocnemius flaps had significant lower cumulative revision-free survival rates than local fasciocutaneous flaps (P = 0.021) and primary closures (P < 0.001) (42.5% vs. 71.5% vs. 100%,respectively). Comparing the most common complex closure procedures medial gastrocnemius flaps had the highest rate of prolonged wound healing (29.7%) and infection/reinfection (40.5%). Infection-associated flap procedures had significant lower cumulative revision-free survival rates (30.5%) than non-infection associated flap procedures (62.8%,P = 0.047). A history of more than two prior surgeries (HR = 6.11,P < 0.001) and an age ≥ 65 years (HR = 0.30,P = 0.018) significantly increased the risk of revision. CONCLUSIONS: The results of this study indicate that primary closure -if possible- should be preferred to early proactive muscle flap coverage. Even in the hands of an experienced plastic surgeon muscle flaps have high revision and complication rates. The study highlights the need to clarify flap indications and to investigate alternative approaches.

Hip joint center lateralization minimally affects the biomechanics of patient-specific flanged acetabular components: A computational model.

Patient-specific flanged acetabular components are utilized to treat failed total hip arthroplasties with large acetabular defects. Previous clinical studies from our institution showed that these implants tend to lateralize the acetabular center of rotation. However, the clinical impact of lateralization on implant survivorship is debated. Our goal was to develop a finite element model to quantify how lateralization of the native hip center affects periprosthetic strain and implant-bone micromotion distributions in a static level gait loading condition. To build the model, we computationally created a superomedial acetabular defect in a computed tomography 3D reconstruction of a native pelvis and designed a flanged acetabular implant to address this simulated bone defect. We modeled two implants, one with ~1 cm and a second with ~2 cm of hip center lateralization. We applied the maximum hip contact force and corresponding abductor force observed during level gait. The resulting strains were compared to bone fatigue strength (0.3% strain) and the micromotions were compared to the threshold for bone ingrowth (20 µm). Overall, the model demonstrated that the additional lateralization only slightly increased the area of bone at risk of failure and decreased the areas compatible with bone ingrowth. This computational study of patient-specific acetabular implants establishes the utility of our modeling approach. Further refinement will yield a model that can explore a multitude of variables and could be used to develop a biomechanically-based acetabular bone loss classification system to guide the development of patient-specific implants in the treatment of large acetabular bone defects.

A novel quantitative grading system for implant fixation in revision total knee arthroplasty.

Aims: Obtaining solid implant fixation is crucial in revision total knee arthroplasty (rTKA) to avoid aseptic loosening, a major reason for re-revision. This study aims to validate a novel grading system that quantifies implant fixation across three anatomical zones (epiphysis, metaphysis, diaphysis). Methods: Based on pre-, intra-, and postoperative assessments, the novel grading system allocates a quantitative score (0, 0.5, or 1 point) for the quality of fixation achieved in each anatomical zone. The criteria used by the algorithm to assign the score include the bone quality, the size of the bone defect, and the type of fixation used. A consecutive cohort of 245 patients undergoing rTKA from 2012 to 2018 were evaluated using the current novel scoring system and followed prospectively. In addition, 100 first-time revision cases were assessed radiologically from the original cohort and graded by three observers to evaluate the intra- and inter-rater reliability of the novel radiological grading system. Results: At a mean follow-up of 90 months (64 to 130), only two out of 245 cases failed due to aseptic loosening. Intraoperative grading yielded mean scores of 1.87 (95% confidence interval (CI) 1.82 to 1.92) for the femur and 1.96 (95% CI 1.92 to 2.0) for the tibia. Only 3.7% of femoral and 1.7% of tibial reconstructions fell below the 1.5-point threshold, which included the two cases of aseptic loosening. Interobserver reliability for postoperative radiological grading was 0.97 for the femur and 0.85 for the tibia. Conclusion: A minimum score of 1.5 points for each skeletal segment appears to be a reasonable cut-off to define sufficient fixation in rTKA. There were no revisions for aseptic loosening at mid-term follow-up when this fixation threshold was achieved or exceeded. When assessing first-time revisions, this novel grading system has shown excellent intra- and interobserver reliability.

Reconstruction of Chronic Quadriceps Tendon Rupture: The Quadriceps Advancement and Imbrication Technique.

BACKGROUND: Chronic extensor mechanism disruption after total knee arthroplasty (TKA) is a rare but challenging condition. There are several surgical approaches for quadriceps tendon repairs. In this report, we present a modified surgical technique for quadriceps tendon repair in chronic extensor mechanism disruption without the use of allografts or mesh augmentation. METHODS: We retrospectively reviewed 12 consecutive cases of chronic extensor mechanism with complete quadriceps tendon ruptures after TKA that underwent the advancement and imbrication technique. Patient outcomes were evaluated using the Knee Injury and Osteoarthritis Outcome Score for Joint Replacement, the range of motion and extensor lag measurements, and standardized lateral radiographs were reviewed for Insall-Salvati-Ratio preoperatively and at their most recent follow-up visit. RESULTS: There were 12 knees from patients who had a mean age of 72 years (range, 62 to 81) and were evaluated with a mean follow-up of 15.9 months (range, 11.4 to 50.9). The extensor lag significantly improved from 40.8 ± 31.9° (range, 10 to 90°) to 2.9 ± 6.9° (P = .014), the Insall-Salvati-Ratio significantly changed from 0.87 to 1.07 (P = .010), and the Knee Injury and Osteoarthritis Outcome Score for Joint Replacement showed a significant difference: a raw score of 13.0 ± 5.8 versus 8.7 ± 5.6 (P = .002) and an interval score of 54.1 ± 14.0 versus 66.2 ± 15.6 (P = .001). CONCLUSIONS: Reconstruction of extensor mechanism in chronic quadriceps tendon ruptures after TKA with the advancement and imbrication technique showed excellent functional outcomes with no extensor lag and excellent restoration of motion. This technique can be combined with TKA revision surgery or used on its own. To ensure successful outcomes, the authors favor rigid immobilization for 12 weeks before starting mobilization.

Imaging in revision total knee arthroplasty: A novel 3D classification system for tibial bone defects.

PURPOSE: The primary purpose of the study was to use pre-revision total knee arthroplasty (TKA) computer-tomography (CT)-images to analyse typical tibial bone defects and create a new schematic three-dimensional (3D)-classification system. The secondary purpose was to investigate the association between defect size and implant selection at the time of revision surgery. METHODS: Eighty-four patients with preoperative CT-scans underwent revision of a primary TKA. CT-image segmentation with the 3D-Slicer Software was performed retrospectively, and a new three-dimensional classification system was used to grade tibial bone defects. The location of tibial bone defects was recorded for all cases. Volumetric 3D bone defect measurements were used to investigate the association between the bone defect volume, the indication for rTKA, and the use of modular revision components. The t-test, the Mann-Whitney-U test, and the Fisher's exact-test were used for group comparisons, and the Kruskal-Wallis test was used for multiple group comparisons. RESULTS: The most common anatomic regions for both contained and uncontained tibial bone defects were the anteromedial epiphysis (N = 50; mean epiphyseal-defect: 5.9 cm³) and metaphysis (N = 15; mean metaphyseal-defect: 9.6 cm³). A significant association was found between patients with preoperative metaphyseal defects (N = 22) and the use of tibial augments (N = 7) (p = 0.04). The use of cones/sleeves was associated with a significantly increased 3D-CT volume of the preoperative metaphyseal bone defects (p = 0.04). Patients with osteoporosis had significantly larger volumetric defects in the metaphysis (p = 0.01). CONCLUSION: Our results emphasise the importance of considering the three-dimensional nature of tibial defects in rTKA. The findings suggest that an understanding of the volume of the defect size through CT imaging can predict the need for augments and cones/sleeves and, especially in patients with osteoporosis can help the surgeon identify larger metaphyseal defects and ensure optimal metaphyseal fixation through appropriate implant selection. LEVEL OF EVIDENCE: Level III, retrospective cohort study.

The Surgical Approach Impacts Component Selection in Total Hip Arthroplasty: A Matched Cohort Study of 7,460 Hips.

BACKGROUND: A higher risk of dislocation following total hip arthroplasty (THA) has been reported for the posterior approach (PA) compared to the anterior approach (AA). Dual mobility implants, larger head sizes, and elevated or face-changing liners can reduce the risk for dislocation. It remains unclear whether the component selection is influenced by the surgical approach. METHODS: This is a retrospective study of 7,048 patients who underwent 7,460 primary THA with either AA or PA for primary hip osteoarthritis or osteonecrosis of the femoral head between 2019 and 2021. A propensity score model based on age, body mass index, height, and American Association of Anesthesiologists Score was applied. There were 2,502 AA-THA matched with 4,958 PA-THA (2,456 1:2, and 46 1:1). Groups were compared with multiple linear regression analyses/multivariate logistic regressions after controlling for American Association of Anesthesiologists Score and body mass index. In a second step, only hips operated by surgeons using both approaches were matched 1:1 (1,204 PA and AA, respectively). The same statistics were performed after controlling for "surgeon". RESULTS: The PA was associated with a more frequent use of dual mobility implants, elevated liners, face-changing liners, as well as heads with 36 mm or larger diameters, and the implanted cups were significantly larger (P < .001, respectively). These findings were consistent for both matched cohorts. CONCLUSION: The surgical approach impacts the component selection in THA. Patients undergoing PA-THA are more likely to receive implants with larger head size or stabilizing features compared to AA-THA.

Activity Following Total Hip Arthroplasty: Which Patients Are Active, and Is Being Active Safe?

BACKGROUND: Younger and physically active patients demand a return to sport after total hip arthroplasty (THA). However, because of the risk of implant wear and loosening, high-impact activities are often not recommended. The current study evaluates predictive factors and revision rates in patients with higher activity levels. METHODS: This retrospective study included 4152 hips in 3828 patients aged 45-75 that underwent primary THA for primary osteoarthritis between 2009 and 2019 with a minimum follow-up of 2 years. Pain and Lower Extremity Activity Scale (LEAS) were assessed before and 2 years after surgery. Activity was classified as low (LEAS 1-6), moderate (LEAS 7-13), or high (LEAS 14-18). RESULTS: Pain and LEAS improved from preoperative to 2-years postoperative (p < 0.001). The activity level was low in 6.2%, moderate in 52.9%, and high in 40.9% of the patients. Younger age, lower BMI, ASA, and CCI, male sex, and higher preoperative LEAS correlated with higher activity at 2 years (p < 0.001). The predicted revision-free survival rates between the activity groups were better for more highly active patients (p < 0.001). CONCLUSIONS: High physical activity 2 years following THA, with participating in sports like jogging several times a week, did not increase the risk of revision surgery. THA patients should not be prevented from a highly active lifestyle.

Individual Phenotype Does Not Impact the Outcome of Mechanical Aligned Total Knee Arthroplasties for Valgus Osteoarthritis.

Background and Objectives: There is an ongoing discussion about the best alignment targets in total knee arthroplasty (TKA). Mechanical alignment has been the standard in TKA for years. Alongside the development of various classification systems to describe the native alignment of the knee (knee phenotype), kinematic alignment restoring the individual phenotype of the knee has been advocated more recently. Alignment in TKA becomes even more challenging in knees with preoperative deformities such as valgus osteoarthritis. Materials and Methods: The study retrospectively evaluated 158 knees in 135 patients who underwent TKA with a mechanical alignment target for valgus osteoarthritis. Pre- and postoperative hip knee angle, lateral distal femur angle, and medial proximal tibial angle/tibial plate angle (pre-/postoperative) were measured on standing hip-to-ankle radiographs. Knees were grouped according to the coronal plane alignment of the knee (CPAK) classification. Preoperative and postoperative range of motion and patient-related outcome measures (WOMAC, UCLA, SF-12, pain) were assessed. Results: There was no difference in outcome for mechanically aligned TKA between the different CPAK phenotypes, suggesting that mechanical alignment is an appropriate target for the different phenotypes analyzed in the study. Remaining valgus alignment was associated with decreased postoperative UCLA scores and decreased improvement in SF-12 scores (p = 0.011/p = 0.028). Within CPAK III, mechanical aligned TKA showed better postoperative UCLA Scores than TKA with valgus alignment (p = 0.015). The individual knee phenotype in patients with valgus osteoarthritis did not influence the outcome of mechanical aligned TKA operated with standardized soft-tissue release.

How safe are intra-articular corticosteroid injections to the hip?

BACKGROUND: Intra-articular corticosteroid injections (ICSI) are an effective symptomatic treatment for osteoarthritis of the hip. However, the safety of ICSI has been questioned and a relatively high risk for septic arthritis, rapidly progressive osteoarthritis (RPIO) and periprosthetic joint infections (PJI) in patients undergoing subsequent total hip arthroplasty (THA) have been suggested. METHODS: This is a retrospective evaluation of 682 hips that underwent ICSI with 40 mg of Triamcinolone for primary osteoarthritis of the hip. All ICSI were performed using sterile techniques, the number of ICSI in each hip and the cumulative corticosteroid dosage were assessed. Pre- and post-injection radiographs were compared to identify cases with RPIO. Native joint septic arthritis, surgical site infections and PJI were identified by chart review. RESULTS: 4 hips (0.6%) developed RPIO 2-4 months following ICSI. The cumulative Triamcinolone dose was not associated with the development of RPIO (p = 0.281). 1 case was diagnosed with septic arthritis and treated with staged THA, there were no signs of infection at a 5 years follow-up. 483 hips (75.7%) underwent THA, including 199 hips with THA less than 3 months following ICSI and 181 hips with > 1 ICSI prior to THA. There were 3 superficial surgical site infections/wound dehiscence and no PJI. CONCLUSION: The rate of RPIO was 0.6%. The current findings suggest that if ICSI is performed under sterile conditions, the risk for septic arthritis or PJI following THA, even in patients with multiple ICSI or ICSI within 3 months prior to surgery, is minimal.

Tibial bone defect prediction based on preoperative artefact-reduced CT imaging is superior to standard radiograph assessment.

PURPOSE: The purpose of this study was to evaluate the accuracy of preoperative CT-based Anderson Orthopaedic Research Institute (AORI)-grading and to correlate Computed tomography (CT)-based volumetric defect measurements with intraoperative AORI findings. METHODS: 99 patients undergoing revision total knee arthroplasty (rTKA) with preoperative CT-images were identified in an institutional revision registry. CT-image segmentation with 3D-Slicer Software was used to create 3D tibial bone defects which were then graded according to the AORI-classification. The AORI classification categorizes tibial defects into three types: Type I has healthy cortical and cancellous bone near the joint line, Type II involves metaphyseal bone loss affecting one or both condyles, and Type III indicates deficient metaphyseal bone with distal defects and potential damage to the patellar tendon and collateral ligament attachments. These 3D-CT gradings were compared to preoperative X-ray and intraoperative AORI grading. The Friedman test was used to investigate differences between AORI values of each measurement method. Volumetric 3D-bone defect measurements were used to investigate the relationship between AORI classification and volumetric defect size in the three anatomic zones of the tibia. RESULTS: Substantial agreements between preoperative 3D-CT AORI and intraoperative AORI (kappa = 0.663; P < 0.01) and fair agreements between preoperative X-ray AORI and intraoperative AORI grading (kappa = 0.304; P < 0.01) were found. Moderate correlations between volume of remaining bone and intraoperative AORI grading were found in epiphysis (rS = - 0.529; P < 0.001), metaphysis (rS = - 0.557; P < 0.001) and diaphysis (rS = - 0.421; P < 0.001). Small volumetric differences between AORI I vs. AORI II defects and relatively large differences between AORI II and AORI III defects in each zone were detected. CONCLUSION: Tibial bone defect prediction based on preoperative 3D-CT segmentation showed a substantial agreement with intraoperative findings and is superior to standard radiograph assessment. The relatively small difference in defect volume between AORI I, IIa and IIb suggests that updated CT-based classifications might hold benefits for the planning of rTKA. LEVEL OF EVIDENCE: Retrospective Cohort Study; III.

Gluteus maximus transfer for wound closure and treatment of abductor deficiency: a single-plastic surgeon series.

INTRODUCTION: Due to the increasing number of total hip arthroplasties (THA), the number and complexity of revision procedures are also on the rise. For complex cases such as periprosthetic joint infections with soft tissue compromise or for abductor muscle deficiencies, one of the treatment options is a gluteus maximus flap (GMF) that covers dead space and can help restore the failed abductor mechanism. The purpose of this study is to investigate the outcomes of a single-plastic surgeon's series of GMF procedures. MATERIALS AND METHODS: This retrospective review reports on 57 patients (mean follow-up 39.2 months) undergoing GMF transfers for abductor insufficiency on native hip (N = 16), for abductor insufficiency in aseptic revision THA (rTHA) (N = 16), for soft tissue defects in aseptic rTHA (N = 8) and for soft tissue defects in septic rTHA (N = 17) by a single plastic surgeon over a 10-year period. Revision-free survival and complication rates were assessed and risk factors were analyzed with Cox-regression analysis. RESULTS: The reoperation-free survival rate of GMF for abductor insufficiency in native hips was 100%. GMF procedures for soft tissue defects in septic rTHA had the lowest cumulative revision-free survival (34.3%) and highest reinfection rates (53.9%). More than three prior surgeries (HR = 2.9, p = 0.020), presence of infection (HR = 3.2, p = 0.010) and resistant organisms (HR = 3.1, p = 0.022) significantly increased the risk of revision. CONCLUSIONS: GMF is a viable option for addressing abductor insufficiency in native hip joints. However, high revision and complication rates are reported for GMF in septic rTHA. This study highlights the need to clarify the circumstances for which the flap reconstruction will be indicated.

Predictors for activity following total and unicompartmental knee arthroplasty.

BACKGROUND: Functional demands of patients undergoing knee arthroplasty are increasing. However, it remains unclear which patient-specific factors have an impact on postoperative activity and whether there is a difference between total and unicompartmental knee arthroplasties (TKA/UKA). MATERIALS AND METHODS: This retrospective study analyzed 1907 knees with TKA (n = 1746) or UKA (n = 161), implanted for primary osteoarthritis. Pain and activity (lower extremity activity scale, LEAS) were assessed 2 years after surgery. High activity was defined as LEAS ≥ 14. Cohorts were compared using Kruskal-Wallis or Pearson-Chi-square test. A generalized least squares model was used to predict LEAS scores between cohorts adjusted for age, sex, BMI, Charlson Comorbidity Index, ASA score, and preoperative LEAS. RESULT: There was no difference in pain 2 years after surgery between UKA and TKA (p = 0.952). Preoperative LEAS was similar for UKA and TKA (p = 0.994), and both groups showed significant (p < 0.001 respectively) and similar improvements after surgery (p = 0.068). LEAS 2 years after surgery was 11.1 (SD 3.2) for TKA and 11.9 (SD 3.5) for the UKA group (p = 0.004). After adjusting for preoperative LEAS, age, sex, BMI, CCI and ASA, the difference was not significant (p = 0.225). Male sex, lower BMI, higher preoperative LEAS, and younger age were associated with higher postoperative LEAS (p < 0.001, respectively). CONCLUSION: Patients can achieve a high level of activity following both TKA and UKA. While the postoperative activity level did not depend on the type of the procedure, younger age, male sex, lower BMI, and a higher preoperative activity level were associated with a higher postoperative activity level.

[Treatment of symptomatic pseudarthrosis following acromion fracture with a patient-specific implant customized on a 3D-printed scapula]. / Versorgung symptomatischer Pseudarthrosen nach Akromionfraktur mit patientenspezifisch am 3-D-Modell angepasstem Implantat.

OBJECTIVE: Patient-specific osteosynthesis for pseudarthrosis of the acromion. INDICATIONS: Symptomatic pseudarthrosis of the acromion at the level of a meta/mesacromion. CONTRAINDICATIONS: Infection; patient noncompliance regarding postoperative treatment protocol. SURGICAL TECHNIQUE: Preoperatively, a patient-specific three-dimensional model of the scapula is printed. A locking compression plate (LCP) is individually adapted to this model. Via a dorsal surgical approach over the scapular spine, the pseudarthrosis is refreshed and autologous cancellous bone from the iliac crest is embedded in the fracture zone. This is followed by fixed-angle osteosynthesis with the individualized plate. In addition, tension banding with tapes is performed to reduce the tensile and shear forces on the fracture caused by the muscle. POSTOPERATIVE MANAGEMENT: Consistent wearing of a shoulder-arm brace for 6 weeks postoperatively, active-assisted increase in range of motion for an additional 3 weeks, then gradual increase in weight-bearing and initiation of daily activities without additional weights until 12 weeks postoperatively. RESULTS: Treatment with the presented technique resulted in radiographic consolidation of the fracture and significant improvement in range of motion and pain at the 1­year follow-up.

Prophylactic cable prevents tapered titanium stem subsidence with 2 cm of stem-cortical engagement in a cadaveric model.

Aims: When performing revision total hip arthroplasty using diaphyseal-engaging titanium tapered stems (TTS), the recommended 3 to 4 cm of stem-cortical diaphyseal contact may not be available. In challenging cases such as these with only 2 cm of contact, can sufficient axial stability be achieved and what is the benefit of a prophylactic cable? This study sought to determine, first, whether a prophylactic cable allows for sufficient axial stability when the contact length is 2 cm, and second, if differing TTS taper angles (2° vs 3.5°) impact these results. Methods: A biomechanical matched-pair cadaveric study was designed using six matched pairs of human fresh cadaveric femora prepared so that 2 cm of diaphyseal bone engaged with 2° (right femora) or 3.5° (left femora) TTS. Before impaction, three matched pairs received a single 100 lb-tensioned prophylactic beaded cable; the remaining three matched pairs received no cable adjuncts. Specimens underwent stepwise axial loading to 2600 N or until failure, defined as stem subsidence > 5 mm. Results: All specimens without cable adjuncts (6/6 femora) failed during axial testing, while all specimens with a prophylactic cable (6/6) successfully resisted axial load, regardless of taper angle. In total, four of the failed specimens experienced proximal longitudinal fractures, three of which occurred with the higher 3.5° TTS. One fracture occurred in a 3.5° TTS with a prophylactic cable yet passed axial testing, subsiding < 5 mm. Among specimens with a prophylactic cable, the 3.5° TTS resulted in lower mean subsidence (0.5 mm (SD 0.8)) compared with the 2° TTS (2.4 mm (SD 1.8)). Conclusion: A single prophylactic beaded cable dramatically improved initial axial stability when stem-cortex contact length was 2 cm. All implants failed secondary to fracture or subsidence > 5 mm when a prophylactic cable was not used. A higher taper angle appears to decrease the magnitude of subsidence but increased the fracture risk. The fracture risk was mitigated by the use of a prophylactic cable.

Patella component diameters of 38 mm and up might be associated with higher revision rates after patella resurfacing.

PURPOSE: Patellar resurfacing is considered the standard of care for total knee arthroplasty in the USA. Complications of patella resurfacing include aseptic loosening or patella fractures and can threaten the integrity of the extensor mechanism. The goal of this study was to report on patella button revision rates in posterior stabilized total knee arthroplasty. MATERIAL AND METHODS: Between 01/2010 and 08/2016 patella buttons were implanted in 1056 patients (267 men and 550 women) as part of a posterior stabilized total knee arthroplasty. RESULTS: Of 1056 cases, 35 cases (14 women, 15 men, 5 bilateral, 3.3%) showed early loosening at a mean 52.5 months postoperatively. Patella components of 38 mm or larger diameters showed a significantly higher loosening rate than the 29, 32, 35 mm buttons (p < 0.01). Mean BMI of patients identified with aseptic loosening was 31.7 kg/m2, mean age at time of revision surgery was 63.3 years. All of the patients with loosening of the patella button required revision surgery; in 33 cases an exchange of the button was performed, in two cases a removal of the button and patellar bone grafting was indicated. No complications occurred after revision surgery. CONCLUSION: The current study reports a 3.3% patella loosening rate during this mid-term follow-up. Size 38 mm and larger patella components showed a significantly higher revision rate than smaller buttons and the authors advise caution when using large diameter patella components.

Does high activity after total and unicompartmental knee arthroplasty increase the risk for aseptic revision?

INTRODUCTION: It has been suggested that high activity might negatively impact implant survival following total and unicompartmental knee arthroplasty (TKA/UKA) and many surgeons advise their patients to only participate in moderate level sport activities. To date, it remains unclear whether such restraints are necessary to assure longevity of the implants. MATERIALS AND METHODS: We conducted a retrospective study on 1906 knees (1745 TKA, 161 UKA) in 1636 patients aged 45-75 years who underwent primary arthroplasty for primary osteoarthritis. Lower extremity activity scale (LEAS) at a two year follow-up was assessed to define the activity level. Cases were grouped in low (LEAS ≤ 6), moderate (LEAS 7-13) and high activity (LEAS ≥ 14). Cohorts were compared with Kruskal-Wallis- or Pearson-Chi2-Test. Univariate logistic regression was conducted to test for association between activity level at two years and later revisions. Odds ratio was reported and converted to predicted probability. A Kaplan-Meier curve was plotted to predict implant survival. RESULTS: The predicted implant survival for UKA was 100.0% at two years and 98.1% at five years. The predicted implant survival for TKA was 99.8% at two years, 98.1% at five years. The difference was not significant (p = 0.410). 2.5% of the UKA underwent revision, one knee in the low and three knees in the moderate activity group, differences between the moderate and high activity group were not significant (p = 0.292). The revision rate in the high activity TKA group was lower than in the low and moderate activity groups (p = 0.008). A higher LEAS two years after surgery was associated with a lower risk for future revision (p = 0.001). A one-point increase in LEAS two years after surgery lowered the odds for undergoing revision surgery by 19%. CONCLUSIONS: The study suggests that participating in sports activity following both UKA and TKA is safe and not a risk factor for revision surgery at a mid-term follow-up. Patients should not be prevented from an active lifestyle following knee replacement.

Achieving Precise Cup Positioning in Direct Anterior Total Hip Arthroplasty: A Narrative Review.

Malpositioned implants in total hip arthroplasty are associated with impingement, increased wear, and dislocations, thus precise cup positioning is crucial. However, significant deviations between targeted and actually achieved cup positions have been found even in patients operated by experienced surgeons. When aiming for higher accuracy, various methods based on freehand positioning lead by anatomic landmarks, C-arm fluoroscopy, imageless navigation, or robotic-assisted-surgery have been described. There is a constant development of new products aiming to simplify and improve intraoperative guidance. Both the literature and expert opinions on this topic are often quite controversial. This article aims to give an overview of the different methods and systems with their specific advantages and potential pitfalls while also taking a look into the future of cup positioning in anterior hip replacements.