Higher satisfaction and function scores in restricted kinematic alignment versus mechanical alignment with medial pivot design total knee arthroplasty: A prospective randomised controlled trial

PURPOSE

Restricted kinematic alignment (rKA) in total knee arthroplasty (TKA) and medial pivot (MP) knee designs already showed superior outcomes in independent comparative studies. The objective of this study was to assess whether rKA with MP TKA provides better clinical and functional outcomes compared to mechanical alignment (MA) with MP TKA.

METHODS

This is a randomised, parallel two group study involving a total of 98 patients with end-stage knee osteoarthritis. Patients were randomly allocated to either rKA or MA TKA procedures conducted with a MP prothesis using patient-specific instruments between 2017 and 2020. Final follow-up was at 2 years postoperatively. Demographic data and clinical and functional scores (Oxford knee score, knee society score [KSS], Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC], forgotten joint score [FJS]) were collected and compared preoperative, 1 year postoperative and 2 years postoperative. Coronal plane alignment of the knee and functional knee phenotype classification were recorded.

RESULTS

A total of 47 patients (rKA) and 51 patients (MA) were included in final analysis. Superior joint awareness scores (FJS) were found at 1 year postoperative for rKA (62.2 vs. 52.4, p = 0.04). KSS subscores (expectation score, satisfaction score) improved with rKA with significant differences at both 1 and 2 years postoperatively. Major differences between rKA and MA were found in subgroup analysis of varus and neutral CPAK phenotypes. Both 1 year and 2 years postoperatively, FJS was significantly better in KA compared with MA in varus CPAK phenotypes (63.1 vs. 44.9, p = 0.03; 71.1 vs. 46.0, p = 0.005). Further clinical and functional scores showed improvement in the varus CPAK phenotypes with predominantly significant improvement in the expectation and satisfaction KSS subscores. No significant differences were found in the comparison of rKA and MA in neutral CPAK phenotypes.

CONCLUSION

The rKA of MP TKA design shows superior patient satisfaction and self-reported function when compared to MA MP TKA. Furthermore, rKA MP TKA shows superior joint awareness at early postoperative stage. The most important clinical relevance of this study is the clear superiority of rKA in varus phenotypes.

LEVEL OF EVIDENCE

Level II.

Radiopacity Enhancements in Polymeric Implant Biomaterials: A Comprehensive Literature Review

Polymers as biomaterials possess favorable properties, which include corrosion resistance, light weight, biocompatibility, ease of processing, low cost, and an ability to be easily tailored to meet specific applications. However, their inherent low X-ray attenuation, resulting from the low atomic numbers of their constituent elements, i.e., hydrogen (1), carbon (6), nitrogen (7), and oxygen (8), makes them difficult to visualize radiographically. Imparting radiopacity to radiolucent polymeric implants is necessary to enable noninvasive evaluation of implantable medical devices using conventional imaging methods. Numerous studies have undertaken this by blending various polymers with contrast agents consisting of heavy elements. The selection of an appropriate contrast agent is important, primarily to ensure that it does not cause detrimental effects to the relevant mechanical and physical properties of the polymer depending upon the intended application. Furthermore, its biocompatibility with adjacent tissues and its excretion from the body require thorough evaluation. We aimed to summarize the current knowledge on contrast agents incorporated into synthetic polymers in the context of implantable medical devices. While a single review was found that discussed radiopacity in polymeric biomaterials, the publication is outdated and does not address contemporary polymers employed in implant applications. Our review provides an up-to-date overview of contrast agents incorporated into synthetic medical polymers, encompassing both temporary and permanent implants. We expect that our results will significantly inform and guide the strategic selection of contrast agents, considering the specific requirements of implantable polymeric medical devices.

A 19-color single-tube full spectrum flow cytometry assay for the detection of measurable residual disease in acute myeloid leukemia

Multiparameter flow cytometry (MFC) has emerged as a standard method for quantifying measurable residual disease (MRD) in acute myeloid leukemia. However, the limited number of available channels on conventional flow cytometers requires the division of a diagnostic sample into several tubes, restricting the number of cells and the complexity of immunophenotypes that can be analyzed. Full spectrum flow cytometers overcome this limitation by enabling the simultaneous use of up to 40 fluorescent markers. Here, we used this approach to develop a good laboratory practice-conform single-tube 19-color MRD detection assay that complies with recommendations of the European LeukemiaNet Flow-MRD Working Party. We based our assay on clinically-validated antibody clones and evaluated its performance on an IVD-certified full spectrum flow cytometer. We measured MRD and normal bone marrow samples and compared the MRD data to a widely used reference MRD-MFC panel generating highly concordant results. Using our newly developed single-tube panel, we established reference values in healthy bone marrow for 28 consensus leukemia-associated immunophenotypes and introduced a semi-automated dimensionality-reduction, clustering and cell type identification approach that aids the unbiased detection of aberrant cells. In summary, we provide a comprehensive full spectrum MRD-MFC workflow with the potential for rapid implementation for routine diagnostics due to reduced cell requirements and ease of data analysis with increased reproducibility in comparison to conventional FlowMRD routines.

Drain fluid cultures can rule in but cannot rule out infection persistence after surgical treatment of periprosthetic joint infections

BACKGROUND

Periprosthetic joint infection (PJI) is one of the most common reason for implant failure in arthroplasty. Surgical therapy is essential but there is no standardized guideline to determine infection eradication in multiple-step revision surgery. To date, clinical and laboratory inflammation markers and preoperative arthrocentesis are controversial to evaluate the infection status before reimplantation and therefore are often combined. Drain fluid cultures enable a microbiological analysis without need for further invasive procedure after revision surgery. This retrospective study evaluates the diagnostic performance of drain fluid cultures in diagnosing infection persistence according to the MSIS definition of PJI.

METHODS

Drain samples have been taken after every revision surgery for microbiological testing. Afterwards, the results have been assigned to the infection status according to the diagnostic criteria of the MSIS definition of PJI.

RESULTS

1084 revision surgeries in 183 patients have been included, resulting in a total sample size of 1552 drain fluid cultures. Overall sensitivity was 36.0%, specificity was 90.7% and ROC-AUC was 0.63.

CONCLUSION

Due to a high specificity and a low sensitivity drain fluid cultures can rule in but cannot rule out infection persistence in PJI.

The prognostic significance of surgical resection margins for local recurrence, distant metastasis, and overall survival in sarcoma

BACKGROUND AND OBJECTIVES

Surgical resection with microscopically negative margins constitutes one of the key elements of a curative therapeutic approach for localized sarcomas. However, the prognostic value of quantitative margin width remains controversial. We sought to determine the prognostic significance of margin status and margin width for local recurrence (LR), distant recurrence (DR), and overall survival.

METHODS

Retrospective analysis of 210 patients undergoing resection of localized sarcoma between 1997 and 2018 at a national sarcoma reference center.

RESULTS

Logistic regression did not reveal an effect of metric margin width as a prognostic factor for LR (odds ratio [OR] = 0.98, p = 0.574), DR (OR = 1, p = 0.908), or overall survival (hazard ratio = 0.98, 95% confidence interval = 0.73-1.20, p = 0.609). Subgroup analysis revealed no differences between complete first resections (R0) and re-resections (re-R0) following unplanned R1-resections for LR (p = 0.727) and overall survival (p = 0.125), but a significantly higher DR-rate in re-R0 cases (p = 0.022).

CONCLUSIONS

Achieving a negative margin is essential in sarcoma surgery, however, metric margin width was not associated with disease-specific outcomes. Re-resection of unplanned R1-resections should be performed to control for LR and overall survival rates. As re-R0 cases were at significantly higher risk of DR, these patients should be followed up closely in standardized surveillance protocols.

Comparable accuracy of femoral joint line reconstruction in different kinematic and functional alignment techniques

PURPOSE

A key part of kinematic alignment (KA) and functional alignment (FA) is to restore the natural femoral joint line, in particular the medial joint line. KA is known to reproduce the femoral joint line accurately; however, direct comparisons with other surgical techniques such as FA are currently lacking. The purpose of this study was to evaluate differences of alignment parameters in KA and FA techniques with a special focus given to the femoral joint line.

METHODS

We performed a retrospective radiological analysis of pre- and postoperative long leg radiographs of 221 consecutive patients with varus or neutral leg alignment, who underwent primary total knee arthroplasty (TKA) procedures from 2018 to 2020. Patients were assigned to one of four groups: (1) FA: image-based robotic-assisted TKA, (2) FA: imageless robotic-assisted TKA, (3): restricted KA: 3D cutting block-assisted (patient-specific instruments, PSI) TKA, (4): unrestricted KA: calipered technique. Patients' radiographs were (re)-analyzed for overall limb alignment, medial proximal tibial angle (MPTA), lateral distal femoral angle (LDFA), as well as medial and lateral femoral joint line alteration. Statistical significance was determined using unpaired t testing (FA vs. KA group) and one-way ANOVA (subgroup analyses).

RESULTS

Comparisons of KA vs. FA, as well as individual subgroups of KA and FA did not show any differences in the accuracy of medial joint line reconstruction (< 2 mm, p = 0.384, p = 0.744, respectively) and LDFA alteration (< 2°, p = 0.997, 0.921, respectively). Correction of MPTA (3.4° vs. 2.2°) and lateral femoral joint line (2.1 mm vs. 1.5 mm) was higher for FA and FA subgroups compared to KA and KA subgroups (both p < 0.001).

CONCLUSION

Kinematic and functional alignments showed a comparable accuracy in reconstruction of the medial femoral joint line and femoral joint line orientation. Increased correction of MPTA and lateral femoral joint line was recorded with FA techniques.

LEVEL OF EVIDENCE

III.

[Kinematic Alignment of Total Knee Arthroplasty]

Nowadays, kinematic alignment is a widely used alignment philosophy in total knee arthroplasty. The concept of kinematic alignment respects the patient's individual prearthrotic anatomy and is based on the reconstruction of the femoral anatomy and thus the axes of motion of the knee joint. Only then the alignment of the tibial component is adapted to the femoral component. By means of this technique soft tissue balancing is reduced to a minimum. Due to the risk of excessive outlier alignment technical assistance or calipered techniques are recommended for precise implementation. This article attempts to provide an understanding of the fundamentals of kinematic alignment, and it focusses on how it differs from alternative alignment strategies and the way the philosophy is implemented in different surgical techniques.

Status and future of modern technologies in arthroplasty : Results of a survey of the German Society for Orthopedics and Trauma Surgery (DGOU)

BACKGROUND

The orthopedic community is divided on the question of whether modern technologies in arthroplasty improve outcomes. Therefore, the aim of this initiative of the working group on intraoperative imaging and technology integration (Arbeitsgemeinschaft intraoperative Bildgebung und Technologieintegration, AGiTEC) is to initiate the collection of additional data for the scientific evaluation of modern technologies.

QUESTION

To what extent are modern technologies currently used and which implementations are planned? Do the members of the German Society for Orthopedics and Trauma Surgery (DGOU) consider the acquisition of additional data for scientific assessment necessary?

METHODS

Members of the DGOU were asked via an e‑mail survey about the distribution and projected introduction of modern technologies in arthroplasty. They were also asked whether sufficient data were collected for scientific evaluation and whether acquisition of additional data in studies or arthroplasty registries were considered necessary.

RESULTS

Of the 7923 probands surveyed, 428 completed the questionnaire in full (5.4%). It was found that individual implants and navigation are currently the most frequently used (31% and 29%, respectively). The largest increases in the next 2 years are projected for virtual reality and robotics (+30% and +23%, respectively), 85% of respondents indicated that insufficient data were collected for scientific evaluation, and 89% each requested initiation of multicenter studies and inclusion of technologies in the arthroplasty registry.

CONCLUSION

The results of this study should motivate the scientific community, industry, and those responsible for the arthroplasty registries to collect and analyze data for the scientific assessment of modern technologies.

[Market overview: Robotic-assisted arthroplasty : Current robotic systems, learning curve and cost analysis]

Robotic-assisted arthroplasty has been rapidly entering clinical routine in recent years. The leading endoprosthesis manufacturers have all meanwhile placed robotic systems on the market, which, however, differ significantly from one another technically. Current systems are currently classified according to the degree of autonomy (active vs. semi-active vs. passive) and the data/image source (image-based: CT vs. X‑ray, imageless). Some systems already offer the possibility of robotic-assisted or navigated implantation of hip endoprostheses. In the following review article, the currently leading robotic systems will be presented and compared with regard to their characteristics. Furthermore, the analysis of the learning curves for the different systems, currently available cost analysis models and an outlook on future developments and challenges will be given.

Improved joint line and posterior offset restoration in primary total knee replacement using a robotic-assisted surgical technique: An international multi-centre retrospective analysis of matched cohorts

Background

Accurate restoration of joint line height and posterior offset in primary Total Knee Arthroplasty (TKA) have been shown to be important factors in post-operative range of movement and function. The aim of this study was to assess the accuracy of joint line and posterior offset restoration in a group of patients that underwent robotic-assisted TKA (raTKA). A matched cohort of patients that underwent a TKA using a conventional jig-based technique was assessed for comparison. The null hypothesis was that there would be no difference between groups.

Methods

This study was a retrospective analysis of a cohort of 120 patients with end-stage knee osteoarthritis that received a TKA using the Navio Surgical System (n = 60), or Conventional manual TKA (n = 60). Procedures were performed between 1 January 2019 and 1 October 2019 at six different centres. Joint line height and posterior offset was measured pre-operatively and post-operatively on calibrated weight bearing plain radiographs of the knee. Two observers performed measurements using validated measuring tools. A BMI and age-matched cohort of patients that underwent TKA using a conventional technique in the same six centres were assessed for comparison. Mean values, standard deviations and confidence intervals are presented for change and absolute change in joint line height and posterior offset. Student’s t-test was used to compare the changes between techniques.

Results

Patients that underwent robotic-assisted TKA had joint line height and posterior offset restored more accurately than patients undergoing TKA using a conventional technique. Average change from pre-operative measurement in joint line height using raTKA was -0.38mm [95% CI: -0.79 to 0.03] vs 0.91 [0.14 to 1.68] with the conventional technique. Average absolute change in joint line height using raTKA was 1.96mm [1.74 to 2.18] vs 4.00mm [3.68 to 4.32] with the conventional technique. Average change in posterior offset using raTKA was 0.08mm [-0.40 to 0.56] vs 1.64mm [2.47 to 0.81] with the conventional technique. Average absolute change in posterior offset with raTKA was 2.19mm [1.92 to 2.46] vs 4.24mm [3.79 to 4.69] with the conventional technique. There was a significant difference when comparing absolute change in joint line height and posterior offset between groups (p<0.01).

Conclusion

Robotic-assisted primary TKA restores the joint line height and posterior offset more accurately than conventional jig-based techniques.

Full-length standing radiographs can be used for determination of the Femoral neck-shaft angle but not acetabular coverage

INTRODUCTION

The exact evaluation of hip morphology is essential for surgical planning. A wide range of morphometric measures of the acetabulum is deduced from conventional anterior-posterior (ap) pelvic radiographs. Full-length weight-bearing radiographs (FLWBR) also depict the acetabulum and are commonly used for osteotomy planning of the lower limb. This study aimed to determine whether FLWBR can be used to evaluate acetabular morphology.

METHODS

Radiographs of patients receiving a hip workup that included a conventional ap pelvic X-ray and FLWBR were utilized for radiographic measurements. The following parameters were measured: extrusion index of the femoral head, anterior wall index, posterior wall index, lateral center edge angle (LCE), acetabular index, pubic arc angle (subpubic angle), and centrum-collum-diaphyseal angle (CCD).

RESULTS

FLWBR depicted a significantly reduced anterior coverage (p = 0.049) and increased posterior coverage (p < 0.001), higher acetabular index (p = 0.015), and higher pubic-arc angle (p = 0.02) compared to conventional ap pelvic radiographs. There were no significant differences regarding the CCD angle (p = 0.28), extrusion index (p = 0.31), and LCE (p = 0.16).

DISCUSSION

The CCD angle of the femur can be measured on conventional ap radiographs and full-length weight-bearing X-rays for lower limb deformity analysis. However, FLWBR will depict an anteverted acetabular morphology, rendering conventional ap radiographs necessary for planning pelvic osteotomies.

Discharging the medial knee compartment: comparison of pressure distribution and kinematic shifting after implantation of an extra-capsular absorber system (ATLAS) and open-wedge high tibial osteotomy-a biomechanical in vitro analysis

PURPOSE

Young and active patients suffering early degenerative changes of the medial compartment with an underlying straight-leg axis do face a therapeutical gap as unloading of the medial compartment cannot be achieved by high tibial osteotomy. Extracapsular absorbing implants were developed to close this existing therapeutical gap. Purpose of the present cadaveric biomechanical study was to compare the unloading effect of the knee joint after implantation of an extra-articular absorber system (ATLAS) in comparison to open-wedge high tibial osteotomy (OW-HTO) under physiological conditions. The hypothesis of the study was that implantation of an extra-capsular absorber results in an unloading effect comparable to the one achievable with OW-HTO.

METHODS

Eight fresh-frozen cadaveric knees were tested under isokinetic flexion-extension motions and physiological loading using a biomechanical knee simulator. Tibiofemoral area contact and peak contact pressures were measured using pressure-sensitive film in the untreated medial compartment. The tibiofemoral superior-inferior, latero-medial translation and varus/valgus rotation were measured with a 3D tracking system Polaris. Pressures and kinematics changes were measured after native testing, ATLAS System implantation and OW-HTO (5° and 10° correction angles) performed with an angular stable internal fixator (TomoFix).

RESULTS

The absorber device decreased the pressure in the medial compartment near full extension moments. Implantation of the ATLAS absorbing system according to the manufacturers' instruction did not result in a significant unloading effect. Deviating from the surgery manual provided by the manufacturer the implantation of a larger spring size while applying varus stress before releasing the absorber resulted in a significant pressure diminution. Contact pressure decreased significantly Δ0.20 ± 0.04 MPa p = 0.044. Performing the OW-HTO in 5° correction angle resulted in significant decreased contact pressure (Δ0.25 ± 0.10 MPa, p = 0.0036) and peak contact pressure (Δ0.39 ± 0.38 MPa, p = 0.029) compared with the native test cycle. With a 10° correction angle, OW-HTO significantly decreased area contact pressure by Δ0.32 ± 0.09 MPa, p = 0.006 and peak contact pressure by Δ0.48 ± 0.12 MPa, p = 0.0654 compared to OW-HTO 5°. Surgical treatment did not result in kinematic changes regarding the superior-inferior translation of the medial joint section. A significant difference was observed for the translation towards the lateral compartment for the ATLAS system Δ1.31 ± 0.54 MPa p = 0.022 and the osteotomy Δ3.51 ± 0.92 MPa p = 0.001. Furthermore, significant shifting varus to valgus rotation of the treated knee joint was verified for HTO 5° about Δ2.97-3.69° and for HTO 10° Δ4.11-5.23° (pHTO 5 = 0.0012; pHTO 10 = 0.0007) over the entire extension cycle.

CONCLUSION

OW-HTO results in a significant unloading of the medial compartment. Implantation of an extra-capsular absorbing device did not result in a significant unloading until the implantation technique was applied against the manufacturer's recommendation. While the clinical difficulty for young and active patients with straight-leg axis and early degenerative changes of the medial compartment persists further biomechanical research to develop sufficient unloading devices is required.

Noise exposure during robot-assisted total knee arthroplasty

The aim of the study was to examine the noise exposure for operating theater staff during total knee arthroplasty (TKA) with three different robot systems. There is already evidence that noise exposure during TKA performed manually exceeds recommended guidelines for occupational noise. Therefore, if surgical staff is exposed to it for several years, the development of noise-inducing hearing loss (NIHL) is significantly increased. To investigate the noise exposure during robot-assisted TKA, the study measured the average noise and the peak sound pressure during TKA with MAKO robot (Stryker, Kalamazoo, Michigan, United States), NAVIO robot (Smith and Nephew, London, Great Britain), and CORI robot (Smith and Nephew, London, Great Britain) using a class 1 sound level meter. Each robot system exceeds the recommended guidelines from the national institute for occupational safety and health. While the MAKO robot had the highest average sound level (93.18 dB(A)) of the three robot systems (NAVIO: 88.88 dB(A), CORI: 89.38 dB(A)), the peak sound level was the highest with the NAVIO Robot (134.48 dB(C)) compared to the MAKO Robot (128.98 dB(C)) and CORI robot (126.48 dB(C)). Robot-assisted TKA is a risk factor for NIHL, like manually performed TKA. Further research for decreasing the noise exposure during TKA is needed to minimize the hearing loss in operating theater staff.

Sports activity after pelvic osteotomy for treatment of developmental dysplasia of the hip : A comparative study between the triple pelvic and periacetabular osteotomy techniques

BACKGROUND

Symptomatic dysplasia of the hip represents an indication for a bony correction of the acetabulum. In the last decades several operative procedures were established.

OBJECTIVE

The aim of the current study was to analyze whether the level of sports activity is higher in patients after periacetabular osteotomy (PAO) according to Ganz as a technique which preserves the posterior column compared to classical triple pelvic osteotomy (TPO) for treatment of developmental hip dysplasia.

MATERIAL AND METHODS

The study group included 102 patients treated with the classical TPO with already published clinical results, who were compared to 34 patients treated with PAO between 2012 and 2016. The clinical outcome scores included the modified Harris Hip Score, the Hip Osteoarthritis Outcome Score, the University of California, Los Angeles activity score and the visual analog scale.

RESULTS

After a mean follow-up of 4.4 years the clinical parameters improved significantly after PAO (p < 0.05). In comparison to the TPO group the clinical scores of the PAO group had inferior baseline values and a tendency to inferior follow-up results in the mHHS (p < 0.05) and HOOS (p > 0.05). After surgery, the PAO group showed a shift to medium and high impact sport activities.

CONCLUSION

The shorter time of postoperative partial weight bearing after PAO due to the preservation of the posterior column seemed not to have a positive impact on the clinical results or the sports activity compared to the TPO treated patients.

Implantation of an attachment tube preserves knee extension after nonunion of Felix IV fracture: a case report

Background

While commonly utilized to fix tissue and muscles to megaprostheses to restore function and stability after tumor surgery, an attachment tube was used as a synthetic reconstruction of the knee joint’s extension mechanism after nonunion of Felix IV C fracture. Fixation of the tibial fragment, and therefore its osteointegration, is complicated after total knee arthroplasty, causing tibial tubercle dislocation.

Case presentation

A 61-year-old German patient presented to our clinic with Felix IV C fracture, persistent knee pain, and reduced knee extension strength. In this special case, mobilization and reattachment of the tibial tubercle was not possible because of necrosis and underlying tibial component. Therefore, we covered the defect with cement and used an polyethylene terephthalate tube for knee extension system augmentation. Follow-up after 10 months demonstrated a good clinical result.

Conclusion

The management of Felix IV C fractures is complicated by the underlying prosthesis resulting in redislocation of the fragment and persistent symptoms of pain and reduced functionality. We here present a new surgical technique to treat periprosthetic fracture complicated by tibial tubercle dislocation. Good clinical and radiologic results on follow-up after 10 months indicate the use of attachment tubes as a suitable surgical technique to restore knee joint extension and to reduce knee pain after dislocated Felix IV C fracture.

Detailed Revision Risk Analysis after Single- vs. Two-Stage Revision Total Knee Arthroplasty in Periprosthetic Joint Infection: A Retrospective Tertiary Center Analysis

Periprosthetic joint infection (PJI) remains one of the most common causes of revision knee arthroplasty. Controversy continues to surround the proper operative technique of PJI in knee arthroplasty with single- or two-stage replacement. Significant variations are seen in the eradication rates of PJI and in implant survival rates. This detailed retrospective analysis of a single tertiary center is intended to provide further data and insight comparing single- and two-stage revision surgery. A retrospective analysis of all revision total knee arthroplasty (TKA) surgeries from 2013 to 2019 was performed and screened with respect to single- or two-stage TKA revisions. Single- and two-stage revisions were analyzed with regard to implant survival, revision rate, microbiological spectrum, and other typical demographic characteristics. A total of 63 patients were included, with 15 patients undergoing single-stage revision and 48 patients undergoing two-stage revision. The mean follow-up time was 40.7 to 43.7 months. Statistically, no difference was found between both groups in overall survival (54.4% vs. 70.1%, p = 0.68) and implant survival with respect to reinfection (71.4% vs. 82.4%, p = 0.48). Further, high reinfection rates were found for patients with difficult-to-treat organisms and low- to semi-constrained implant types, in comparison to constrained implant types. A statistically comparable revision rate for recurrence of infection could be shown for both groups, although a tendency to higher reinfection rate for single-stage change was evident. The revision rate in this single-center study was comparably high, which could be caused by the high comorbidity and high proportion of difficult-to-treat bacteria in patients at a tertiary center. In this patient population, the expectation of implant survival should be critically discussed with patients.

[Treatment strategies for tumor-related pathological fractures of the extremities]

Pathological fractures of the extremities frequently lead to uncertainty with respect to the treatment strategy and timing. The origin of metastases is typically breast, bronchial, renal and prostate cancer and myelomas. Primary bone tumors play a subordinate role. The majority affect the femur, humerus and occasionally the tibia. Surgery is typically the first line treatment as healing under conservative treatment is unlikely. The most important goal is to relieve pain and the preservation or restoration of function. For correct assessment of indications, analysis of the fracture pattern and oncological aspects including dignity, entity, prognosis, metastatic status and the general condition of the patient need to be taken into consideration. Based on all these aspects the surgical approach can be chosen. Treatment options range from osteosynthetic stabilization and augmentation osteosynthesis up to endoprosthesis replacement. The treatment is carried out in an interdisciplinary procedure as additional measures need to be addressed in addition to the surgical treatment.

CT based PSI blocks for osteotomies around the knee provide accurate results when intraoperative imaging is used

Purpose

Correction osteotomies around the knee are common methods for the treatment of varus or valgus malalignment of the lower extremity. In recent years, patient specific instrumentation (PSI) guides were introduced in order to enhance the accuracy of these procedures. The purpose of this study was to determine the accuracy of CT based PSI guides for correction osteotomies around the knee of low volume osteotomy surgeons and to evaluate if CT based PSI blocks deliver a high degree of accuracy without using intraoperative fluoroscopy.

Methods

Two study arms with CT based PSI cutting blocks for osteotomies around the knee were conducted. Part one: A retrospective analysis of 19 osteotomies was made in order to evaluate the accuracy in the hands of a low volume surgeon on long-leg radiographs. Part two: A cadaveric study with 8 knees was performed for the purpose of analyzing the accuracy without using intraoperative fluoroscopy on pre- and postoperative CT scans. Hip-Knee-Ankle angle (HKA), lateral distal femoral angle (LDFA) and medial proximal tibial angle (MPTA) were analyzed. The mean absolute delta (∂) between the planned and postoperative parameters were calculated. The accuracy of both study arms were compared.

Results

Part one: The mean MPTA ∂, LDFA ∂ and HKA ∂ was 0.9°, 1.9° and 1.5°, respectively. Part two: The mean MPTA ∂ and LDFA ∂ was 3.5° and 2.2°, respectively. The mean ∂ of MPTA is significantly different between clinical patients with fluoroscopic control and cadaveric specimens without fluoroscopic control (P < 0.001). All surgeries were performed without complications such as a hinge fracture.

Conclusion

The clinical use of PSI guides for osteotomies around the knee in the hands of low volume surgeons is a safe procedure. The PSI guides deliver a reliable accuracy under fluoroscopic control whereas their non-use of intraoperative fluoroscopy leads to a lack of accuracy. The use of fluoroscopic control during PSI guided correction osteotomies is highly recommended.

Level of evidence

IV – Retrospective and experimental Study

Individual Revision Knee Arthroplasty Is a Safe Limb Salvage Procedure

Introduction: Revision total knee arthroplasty after multiple pre-surgeries is challenging. Due to severe bone defects, standard implants for metaphyseal and diaphyseal anchoring may no longer be suitable. The primary aim of this case series is to evaluate the early complication rate for individual knee implants with custom-made cones and stems after two-stage revision with severe bone defects. Methods: Ten patients who were treated with custom-made 3D-printed knee revision implants were included. Inclusion criteria were a two-stage revision due to late-onset or chronic periprosthetic joint infection as well as aseptic loosening. All severe bone defects were AORI type III. All procedure-related complications were evaluated. Postoperative range of motion after one year was measured. The time between the two surgeries was evaluated. Results: The mean follow-up was 21 months (range: 12–40). The mean time between the two-stage surgeries was 71.6 days. No fractures were observed intra- and postoperatively. Two patients were revised without changing metal components due to persistent hematoma (three weeks post-surgery) and persistent PJI (three months post-surgery). The mean passive postoperative range of motion was 92° (range: 80–110°). Conclusions: Individual custom-made implants for rTKA provide a safe procedure for patients with huge bone defects after several pre-surgeries. If standard knee systems with standard cones or sleeves are not suitable anymore, custom-made treatment offers the patient the last option for limb preservation. However, this is associated with increased costs.

Leukocyte Esterase and Glucose Reagent Test Can Rule in and Rule out Septic Arthritis

BACKGROUND/AIM

Septic arthritis (SA) requires rapid diagnosis and therapy to avoid joint damage. This study evaluated the diagnostic accuracy of leukocyte esterase (LE) and glucose (GLC) strip tests for diagnosing SA.

PATIENTS AND METHODS

Synovial fluids from 455 patients with atraumatic joint effusions were assessed prospectively over a 5-year period with LE and glucose strip tests. Results were compared to modified Newman criteria for diagnosing joint infections. Synovial fluid cultures, crystal, blood and synovial cell analyses were also performed.

RESULTS

Forty-one patients had SA and 252 non-SA. A positive LE reading combined with negative glucose reading could detect SA with 100% specificity, 85% sensitivity, 100% positive predictive value (PPV) and 98% negative predictive value (NPV). Positive synovial LE reading alone detected SA with 82% specificity, 95% sensitivity, 47% PPV, and 99% NPV.

CONCLUSION

Combined LE and glucose strip tests represent a low-cost tool for rapidly diagnosing or ruling out SA.

3D-surface scan based validated new measurement technique of femoral joint line reconstruction in total knee arthroplasty

Purpose

This study aimed to validate a new joint line measurement technique in total knee arthroplasty for separated assessment of the medial and lateral femoral joint line alteration with 3D-surface scan technology. Separate assessment of the medial and lateral joint line alteration may improve TKA alignment assessment regarding to joint line restoration in kinematic alignment and use of robotic-assisted TKA surgery.

Methods

The medial and lateral joint line difference after TKA implantation on an artificial bone model was analyzed and compared with a 3D-scan and full femoral radiographs pre- and postoperatively. Radiographic analysis included the perpendicular distance between the most distal point of the medial and lateral condyle and the reproduced preoperative lateral distal femoral angle (LDFA). For evaluation of validity and reliability, radiographs were captured initially with true anteroposterior view and subsequently with combined flexion and rotation malpositioning. Reliability of the introduced measurement technique in between three observers was tested with intraclass correlation coefficient (ICC).

Results

Radiographic measurement showed a mean difference of 0.9 mm on the medial side and 0.6 mm on the lateral side when compared to the 3D-surface scan measurement. The reliability of measurement accuracy was ≤ 1 mm in x-rays with < 10° flexion error regardless to malrotation in these images. The ICC test showed very good reliability for the medial joint line evaluation and good reliability for lateral joint line evaluation (ICC 0.92, ICC 0.86 respectively).

Conclusion

The new introduced joint line measurement method showed a sufficient reliability, accuracy and precision. It provides separated information about medial and lateral joint line alteration in TKA surgery in absolute values.

Level of evidence

V - Experimental Study

[End-of-stem pain in hip and knee arthroplasty]

End-of-stem pain after knee and hip arthroplasty with diaphyseal supportive stems is a frequently overlooked and potentially underestimated complication. A commonly recurring clinical phenome is the symptom-free interval after surgery of weeks to months, with new onset of symptoms under stress only later. The patient is often again reliant on walking sticks. End-of-stem pain is a diagnosis of exclusion. Pain is projected into the tip of the stem, and if differential diagnoses such as loosening are excluded, then the patient might be treated with a "bending-plate". Since bone cement has a similar elastic modulus to human cortical bone, a change of method to a cemented implant can also be expedient. In the primary situation, in addition to cemented stems, the use of "split-stems" could be useful. After revision surgery of any kind, a timely cessation of pain confirms the diagnosis.

Higher revision rate for posterior cruciate-retaining than posterior-stabilized total knee arthroplasty for the treatment of valgus osteoarthritis

PURPOSE

Determining the point at which a valgus deformity requires a more invasive therapy-in this case PS TKA-is surgically challenging. Retaining the posterior cruciate ligament has both advantages and disadvantages. The aim was to evaluate the failure rate and clinical outcomes.

METHODS

248 patients with valgus gonarthrosis underwent surgical treatment: 167 CR TKA cases and 81 PS TKA cases. The KOOS and the OKS were recorded, and 201 patients (133 CR, 68 PS) were recruited into the retrospective study. The influence of BMI and degree of preoperative valgus deformity on the clinical outcome was determined. The revision rate was documented and analysed.

RESULTS

Of 201 patients, 10 required revision surgery owing to instability (10/133 CR, 0/68 PS). Based on the KOOS and the OKS, no significant difference between CR TKA and PS TKA was found. BMI and degree of valgus deformity had no effect on the clinical outcome.

CONCLUSIONS

No difference in the clinical outcome between the CR and PS TKA patients was found. In the CR group, significantly more patients showed 'excellent' OKS than in the PS group. However, 8.0% of the patients in the CR group and none in the PS group underwent surgery due to instability. A higher rate of dissatisfied patients in the CR group is likely. In our clinic, we no longer perform CR TKA for valgus cases.

Noninvasive diagnostic of periprosthetic joint infection by urinary peptide markers: A preliminary study

Previous immunohistochemical analyses revealed altered protein expression in the periprosthetic membranes of patients with periprosthetic joint infection (PJI). Proteins are degraded to peptides that may pass the blood-kidney barrier depending on their size. The aim of this study was to evaluate if PJI can be diagnosed based on the urinary peptide excretion pattern. Thirty patients undergoing removal of their hip or knee prostheses due to septic or aseptic loosening were enrolled. Specimen sampling was performed according to the MusculoSkeletal Infection Society criteria. A urinary sample was analyzed before surgery using capillary electrophoresis coupled with mass spectrometry. Peptides with differential urinary excretion between groups were used to establish a multimarker model. A total of 137 peptides were differentially excreted between the septic and aseptic groups. The majority of identified peptide markers were fragments of structural extracellular matrix proteins, potentially due to their origin from the periprosthetic membrane. A marker model with 83 peptides achieved the best diagnostic performance for diagnosing PJI with a sensitivity of 95%, a specificity of 90%, and an area under the curve of 0.96. The altered protein expression pattern in the periprosthetic membrane of PJI is most likely reflected in excreted urinary peptides. Thus, the diagnosis of PJI by urinary peptide markers seems to be a reasonable approach.

Computer-Assisted Orthopedic and Trauma Surgery

BACKGROUND

There are many ways in which computer-assisted orthopedic and trauma surgery (CAOS) procedures can help surgeons to plan and execute an intervention.

METHODS

This study is based on data derived from a selective search of the literature in the PubMed database, supported by a Google Scholar search.

RESULTS

For most applications the evidence is weak. In no sector did the use of computer-assisted surgery yield any relevant clinical or functional improvement. In trauma surgery, 3D-navigated sacroiliac screw fixation has become clinically established for the treatment of pelvic fractures. One randomized controlled trial showed a reduction in the rate of screw misplacement: 0% with 3D navigation versus 20.4% with the conventional procedure und 16.6% with 2D navigation. Moreover, navigation-assisted pedicle screw stabilization lowers the misplacement rate. In joint replacements, the long-term results showed no difference in respect of clinical/functional scores, the time for which the implant remained in place, or aseptic loosening.

CONCLUSION

Computer-assisted procedures can improve the precision of certain surgical interventions. Particularly in joint replacement and spinal surgery, the research is moving away from navigation in the direction of robotic procedures. Future studies should place greater emphasis on clinical and functional results.

Three-dimensional templating in hip arthroplasty: the basis for template-directed instrumentation?

INTRODUCTION

Computed tomography-based three-dimensional models may allow the accurate determination of the center of rotation, lateral and anterior femoral offsets, and the required implant size in total hip arthroplasty. In this cadaver study, the accuracy of anatomical reconstruction was evaluated using a three-dimensional planning tool.

MATERIALS AND METHODS

A total of eight hip arthroplasties were performed on four bilateral specimens. Based on a computed tomography scan, the position and size of the prosthesis were templated with respect to the anatomical conditions.

RESULTS

On average, all parameters were reconstructed to an accuracy of 4.5 mm and lie within the limits recommended in the literature. All prostheses were implanted with the templated size.

CONCLUSIONS

The exact anatomy of the patient and the required size and position of the prosthesis were precisely analyzed using a templating software. Based on the present findings, the development of template-directed instrumentation is conceivable using this method. However, further technical features (e.g., navigation or robot-assisted surgery) are required for improved precision for implant positioning.

Individualized alignment in total knee arthroplasty using image-based robotic assistance : Video article

Introduction

Over the past decades many innovations were introduced in total knee arthroplasty (TKA) focusing on implant longevity and higher procedural precision; however, there are still a high number of dissatisfied patients. It was reported that better anatomical alignment may result in improved patient outcome; however, current technologies have limitations to achieve this. The aim of this video article is to describe the technique of individualized alignment in TKA with the use of image-based robotic assistance.

Methods

The technology is based on an individual patient knee model computed from segmented computed tomography (CT) scans. A preoperative planning of prosthesis position is conducted following the principle of kinematic alignment. Intraoperatively the soft tissue envelope is recorded and the computer predicts the gap balance based on the virtual planning. The prosthesis position is then adapted to achieve balanced gaps and to avoid soft tissue release. This technique is shown in a cadaver operation and clinical examples of two patients are described.

Results

With the combination of anatomically oriented prosthesis positioning and minor adaptations with respect to the soft tissue, an individualized alignment is achieved with reduced need of soft tissue release. The robotic-assisted surgery guarantees a precise implementation of the planning. The initial experience showed a promising outcome in short-term follow-up.

Video online

The online version of this article (10.1007/s00132-018-3637-1) contains a video on patient individualized alignment in total knee arthroplasty. The article and video are available in the electronic full text archive at SpringerMedizin.de under http://www.springermedizin.de/der-orthopaede. The video can be found at the end of the article as supplementary material.

[Arthroplasty in patients with osteoporosis]

Arthroplasty has become a very successful operation with excellent long-term results. A dedicated diagnostic set-up to exclude osteoporosis prior to a joint replacement and the use of drugs to improve the outcome of a joint replacement are currently not recommended. Knee arthroplasty should always be cemented in patients with known osteoporosis. The same is recommended for hip joint replacement, even if the cement-free acetabular component yields good results. Rapid loading and mobilization appear beneficial also with respect to the osteoporosis and its systemic treatment.

Reverse shoulder arthroplasty for fracture sequelae: Clinical outcome and prognostic factors

BACKGROUND

The reverse total shoulder arthroplasty (RTSA) is a common therapy for the fracture sequelae (FS) of the proximal humerus. The aim of this study was to show the short and midterm clinical outcome of the RTSA for FS and to identify prognostic factors.

METHODS

Data from 46 patients with chronic FS who underwent RTSA were analysed. The clinical follow-up included the Constant score and radiographic examination. Patients were divided into groups based on the Boileau classification of FS, and the degree of metaphyseal bone loss was measured (Boileau type I 9 patients; type II 3 patients; type III 8 patients and type IV 16 patients). Scapular notching was assessed according to the classification of Sirveaux.

RESULTS

The mean postoperative Constant score was 57. Clinical outcomes were similar among the various FS groups, as defined according to the Boileau classification, but patients who had undergone revision arthroplasty had a significantly inferior mean Constant score than patients with type IV FS. There were no significant differences between patients who were initially managed with conservative therapy and those treated surgically. Patients with metaphyseal bone loss >3 cm showed inferior clinical scores. Inferior scapular notching was seen in 25 patients, and had a negative effect on the clinical outcome. Complications included five infections and one dislocation.

CONCLUSION

Metaphyseal bone loss was unfavourable prognostic factors in patients with FS treated with RTSA. However, the Boileau classification did not serve as a prognostic criterion. Previous operative or conservative treatment had no influence on the outcome and scapular notching was associated with inferior clinical results.

Fluorescence in Situ Hybridization (FISH) for the Diagnosis of Periprosthetic Joint Infection in Formalin-Fixed Paraffin-Embedded Surgical Tissues

BACKGROUND

As the number of arthroplasties performed increases, periprosthetic joint infection (PJI) represents a common and challenging problem. The Musculoskeletal Infection Society (MSIS) recommends diagnosing PJI according to its guidelines. The aim of the current study was to assess whether fluorescence in situ hybridization (FISH) analysis of formalin-fixed paraffin-embedded periprosthetic membranes can successfully improve the diagnosis of infection in patients with orthopaedic implants.

METHODS

We retrospectively analyzed 88 periprosthetic membranes of joint prostheses using FISH analysis according to a standard protocol, with a probe targeting a sequence found in most bacteria. We compared the results with routine clinical classification according to the guidelines of the MSIS, microbiological culture, and histopathological classification according to Morawietz and Krenn. We additionally performed FISH analysis using 2 species-specific probes for several culture-positive cases.

RESULTS

FISH successfully detected bacteria in 38 (95%) of 40 periprosthetic membranes that were rated positive by clinical classification. FISH results compared with clinical classification demonstrated a sensitivity of 95% (95% confidence interval [CI], 83.08% to 99.39%), a specificity of 85.42% (95% CI, 72.24% to 93.93%), a positive predictive value of 84.44% (95% CI, 70.55% to 93.50%), and a negative predictive value of 95.35% (95% CI, 84.19% to 99.43%). FISH results compared with histopathological classification demonstrated a sensitivity of 95.12% (95% CI, 83.47% to 99.40%), a specificity of 87.23% (95% CI, 74.26% to 95.17%), a positive predictive value of 86.67% (95% CI, 73.21% to 94.95%), and a negative predictive value of 95.35% (95% CI, 84.19% to 99.43%). We successfully detected Pseudomonas aeruginosa and Staphylococcus aureus with species-specific FISH probes in all cases that were positive for these respective bacteria by microbiological culture.

CONCLUSIONS

FISH-based diagnosis of PJI is feasible and can be used as an additional diagnostic criterion. FISH not only can detect bacteria in periprosthetic membranes but can also differentiate pathogens at the species level. FISH represents a fast and reliable tool for detecting PJI in periprosthetic membranes, especially in combination with clinical and histopathological classification.

LEVEL OF EVIDENCE

Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Digital templating of rotating hinge revision and primary total knee arthroplasty

Preoperative digital templating in total knee arthroplastiy (TKA) is useful in predicting implant size, the level of bone resections and the need for special implants. This study should evaluate the templating of a rotating hinge prosthesis and the realization of the preoperative plan. Two observers with different experience levels templated 40 cases which received TKA and R-TKA using digital planning on standard preoperative x-rays. The examiners templated all cases independently and were blinded to the component sizes used intraoperatively. The kappa coefficient and Pearson coefficient were determined. The accuracy in predicting the correct implant size in revision TKA varied from 67,9% to 82,1% depending on the training level of the observer. The two observers show moderate and substantial correlation. The coefficient indicates a substantial agreement in between the two observers in templating revision TKA. The accuracy depends on the experience of the observer. In the cases were the templating was incorrect, the prosthesis was implanted smaller than the preoperative plan. With this knowledge very good results can be made with this prosthesis.

Adjustable-length loop cortical button versus interference screw fixation in quadriceps tendon anterior cruciate ligament reconstruction - A biomechanical in vitro study

BACKGROUND

This biomechanical cadaveric in vitro study aimed to evaluate and compare the dynamic elongation behavior and ultimate failure strength of tibial adjustable-length loop cortical button versus interference screw fixation in quadriceps tendon-based anterior cruciate ligament reconstruction.

METHODS

Sixteen human quadriceps tendons were harvested and fixed into porcine tibiae using either biodegradable interference screw (n = 8) or adjustable loop device (n = 8) fixation. An acrylic block was utilized for femoral adjustable loop device fixation for both groups. All constructs were precycled for 10 times at 0.5 Hz and manually retensioned before tested in position and force control mode each for 1000 cycles at 0.75 Hz according to in vitro loading conditions replicating the in vivo ACL environment. Subsequently, an ultimate failure test at 50 mm/min was performed with mode of failure noted.

FINDINGS

Tibial IS fixation showed no statistically significant differences in the initial (-0.46 vs. -0.47 mm; P = 0.9780), dynamic (2.18 mm vs. 2.89 mm; P = 0,0661), and total elongation (1.72 mm vs. 2.42 mm; P = 0,0997) compared to adjustable loop device fixation. The tibial button fixation revealed an increased ultimate failure load (743.3 N vs. 606.3 N; P = 0.0027), while stiffness was decreased in comparison to screw fixation (133.2 N/mm vs. 153.5 N/mm; P = 0,0045).

INTERPRETATION

Anterior cruciate ligament reconstruction for quadriceps tendon graft using a tibial adjustable-length loop cortical button provides for comparable dynamic stabilization of the knee with increased ultimate failure load at decreased stiffness compared to screw fixation.

Stability of supramalleolar osteotomies using different implants in a sawbone model

BACKGROUND

With ankle arthritis often affecting young patients, joint-sparing treatments instead of total joint replacement should be considered. Only a few implants were specially developed for supramalleolar osteotomies (SMOT). This study was performed to analyse the stability of different implants and their appropriateness for SMOT.

METHODS

Twenty-five bone models (Sawbone Europe, Malmö, Sweden) were used for biomechanical testing. SMOT were performed as a uniplanar osteotomy, leaving 5 mm of lateral bone intact with a standardized gap of 8 mm. Five different plates commonly used for SMOT were assessed. For axial stability, the constructs were tested during 100 cycles for each load (150N and 800N) at a rate of 0.5 Hz. For rotational stability, each construct was subject to 100 cycles of 5 Nm torque at a rate of 0.25 Hz, performing three runs with an axial preload of 0N, 150N, or 800N. Ultimate axial load was performed for one-half and ultimate rotational load was performed for the other half of the constructs. In addition, the stiffness of the different constructs after failure was tested.

RESULTS

All constructs showed high stability and could be tested until maximum cyclic load. There was no significant difference between the five plates, neither for stiffness (axial or rotational) nor for failure load (axial or rotational). One plate indicated superiority in axial failure testing without any significant difference.

CONCLUSION

All implants could be tested until maximum load. The intact hinge apparently provides enough support to compensate for lower moment of inertia of some plates.

LEVEL OF EVIDENCE

Not applicable.

Biomechanical properties of adjustable extracortical graft fixations in ACL reconstruction

Background

Reliable biomechanical data about the strength of different tibial extracortical graft fixation devices is sparse. This biomechanical study compares the properties of tibial graft fixation in ACL reconstruction with either the ACL Tight Rope™ or the Rigid Loop Adjustable™ device. The hypothesis was that both fixation devices would provide comparable results concerning gap formation during cyclic loading and ultimate failure load.

Methods

Sixteen sawbone tibiae (Sawbones™) underwent extracortical fixation of porcine flexor digitorum profundus grafts for ACL reconstruction. Either the ACL Tight Rope™ (Arthrex) or the Rigid Loop Adjustable™ (DePuy Mitek) fixation device were used, resulting in 2 groups with 8 specimens per group. Biomechanical analysis included pretensioning the constructs 10 times with 0.75 Hz, then cyclic loading of 1,000 position-controlled cycles and 1,000 force-controlled cycles applied with a servohydraulic testing machine. Elongation during cyclic loading was recorded. After this, ultimate failure load and failure mode analysis were performed.

Results

No statistically significant difference could be noted between the groups regarding gap formation during cyclic loading (4.6 ± 2.6 mm for the Rigid Loop Adjustable™ vs. 6.6 ± 1.5 mm for the ACL Tight Rope™ (p > 0.05)), and ultimate failure loads (980 ± 101.9 N for the Rigid Loop Adjustable™ vs. 861 ± 115 N ACL Tight Rope™ (p > 0.05)).

Conclusion

ACL Tight Rope™ and the Rigid Loop Adjustable™ fixation devices yield comparable biomechanical results for tibial extracortical graft fixation in ACL reconstruction. These findings may be of relevance for the future surgical decision-making in ACL reconstruction. Randomized controlled clinical trials comparing both fixation devices are desirable for the future.

Outcome of kinematic alignment using patient-specific instrumentation versus mechanical alignment in TKA: a meta-analysis and subgroup analysis of randomised trials

INTRODUCTION

Kinematic alignment (KA) in total knee arthroplasty (TKA) matches component position to the pre-arthritic anatomy of an individual patient, with the aim of improving functional outcomes. Recent randomised controlled trials (RCTs) comparing KA to traditional neutral mechanical alignment (MA) have been mixed. This collaborative study combined raw data from RCTs, aiming to compare functional outcomes between KA using patient-specific instrumentation (PSI) and MA, and whether any patient subgroups may benefit more from KA technique.

MATERIALS AND METHODS

A literature search in PubMed, EMBASE and Cochrane databases identified four randomised controlled trials comparing patients undergoing TKA using PSI-KA and MA. Unpublished data including Western Ontario McMaster Universities Arthritis Index (WOMAC) and Knee Society Score (KSS) were obtained from study authors. Meta-analysis compared MA to KA change (post-op minus pre-op) scores. Subgroup-analysis on KA patients looked for subgroups more likely to benefit from KA and the impact of PSI accuracy.

RESULTS

Meta-analyses of change scores in 229 KA patients versus 229 MA patients were no different from WOMAC (mean difference 3.4; 95% confidence interval - 0.5 to 7.3), KSS function (1.3, - 3.9 to 6.4) or KSS combined (7.2, - 0.8 to 15.2). A small advantage was seen for KSS pain in the KA group (3.6, 95% CI 0.2-7.1). Subgroup-analysis showed no difference between varus, valgus and neutral pre-operative alignment groups, and those who did and did not achieve KA plans. Pain-free patients at 1-year were more likely to achieve KA plans.

CONCLUSION

Patient-reported outcome scores following TKA using PSI-KA are similar to MA. No identifiable subgroups benefited more from KA, and long-term results remain unknown. Inaccuracy of the PSI system used in KA patients could potentially affect outcome.

Knieprothesendesign und Kinematik: Unterschiede in Radien, Konformität und Rotation/Pivot

Mittlerweile findet sich ein schier unendliches Angebot an Knieprothesenmodellen auf dem Markt, aus denen der Chirurg für seine Versorgung wählen kann. Obwohl sich die Designs auf den ersten Blick immer weiter annähern und ähneln, betreibt die Industrie einen hohen Aufwand, unterschiedliche Designmerkmale als Alleinstellung herauszuarbeiten. Für den Anwender ist es zunehmend schwierig, den Überblick zu behalten und die tatsächliche Relevanz der Features zu bewerten. Unabhängige vergleichende wissenschaftliche Arbeiten sind Mangelware und die Evidenz entsprechend gering. Dennoch erfordern unterschiedliche Designphilosophien ein tiefgründiges konzeptionelles Verständnis und besondere Operationsalgorithmen, sodass sich der Chirurg mit der von ihm benutzten Prothese entsprechend gut auskennen muss. Interessant ist auch eine sich aus diesem Wissen ergebende indikationsbezogene Prothesenauswahl. Im Folgenden wird ein kurzer Überblick über die wesentlichen Konzepte der ungekoppelten Primärprothesen gegeben und deren klinisch relevante Unterschiede in Bezug auf die Biomechanik und den klinischen Einsatz angesprochen.

Influence of stem length on component flexion and posterior condylar offset in revision total knee arthroplasty

BACKGROUND

Hyperextension of the femoral component and excessive slope of the tibial component may delay the cam-post engagement in semi-constrained revision total knee arthroplasty (TKA). Further, it may compromise the posterior condylar offset (PCO). No prior study has determined whether a short 50-mm stem, or longer stems (100mm and 150mm) lead to less hyperextension of the femoral component or excessive slope and its influence on the posterior condylar offset.

METHODS

Flexion/extension of the femoral component with respect to the sagittal femoral anatomic axis of the distal diaphysis (SFAA) and the tibial slope were measured from rotationally controlled lateral X-rays of 126 consecutive patients with a one- or two-stage revision TKA. Stems of 50mm, 100mm and 150mm were analyzed. Further, reconstruction of the PCO with respect to stem length and component flexion was evaluated.

RESULTS

The average flexion (+) or extension (-) of the femoral component in the sagittal distal anatomical axis was -4.1°±2.8° (mean ± std) for components, which have been implanted with 50-mm stems and 1.1°±1.1° for components with 100- or 150-mm stems, respectively (P=0.0001). The average slope of the tibial was 2.6°±1.5° for tibial trays with 50-mm stems, which was more than the 1.3°±1° for trays with 100-mm stems (P=0.0001). The average PCO ratio was 0.8±1.7 for femoral components with 50-mm stems, which was less than the 1.0±1.7 for trays with 100-mm stems (P=0.0001).

CONCLUSIONS

Because 50-mm stems resulted in about three degree hyperextension of the femoral component with respect to the SFAA compared to 100-mm or 150-mm stems, the longer stems do not alter the natural femoral flexion and a delay of the cam-post engagement may be avoided. Further, a better reconstruction of the PCO may be archived with the use of longer stems.

In vivo heterotopic culturing of prefabricated tendon grafts with mechanical stimulation in a sheep model

BACKGROUND

The goal of this study is to investigate the biomechanical and histological properties of in vivo heterotopically prefabricated cruciate ligament replacement grafts with and without mechanical stimulation. The clinical goal is to heterotopically prefabricate a bone-tendon-bone graft for anterior cruciate ligament reconstruction, which allows rapid ingrowth and early full weight bearing.

METHODS

In a sheep model, eight quadriceps tendon grafts were harvested and introduced into culture chambers at their proximal and distal ends. In group S, four tendon-chamber constructs were mechanically stimulated by direct attachment to the quadriceps tendon and patella. In group NS, the same constructs were cultured without proximal attachment. All sheep were sacrificed six weeks postoperatively and the constructs were examined biomechanically and histologically. The healthy contralateral ACL and quadriceps tendon were used as controls.

RESULTS

Macroscopically, no obvious ossification could be observed at the ends of the tendon-chamber constructs six weeks postoperatively. Histologically, the tendon tissue from the mechanically stimulated constructs revealed higher counts of cells and capillaries. However, there was less regular cell distribution and collagen fiber orientation compared to the control group. In addition, osteoblasts and osteogenesis were observed in the prefabricated constructs both with and without mechanical stimulation. Biomechanically, there were no significant differences in stiffness, elongation and ultimate failure load between the groups.

CONCLUSION

In vivo heterotopic culture of prefabricated tendon grafts may have the potential to stimulate osteoblasts and induce osteogenesis. Future studies with longer follow-up and modifications of the surgical technique and culture conditions are desirable.

[Light protection for xeroderma pigmentosum]

Xeroderma pigmentosum is a rare autosomal recessive disorder which is caused by germinal mutations responsible for the repair of ultraviolet (UV) radiation-induced DNA lesions. It is characterized by hypersensitivity to UV radiation, poikiloderma, ocular surface disease, and in some patients pronounced sunburn and neurological disease. Patients have a very high risk of developing ocular and skin cancer on exposed body sites. No cure is available for these patients except complete protection from all types of UV radiation.

Arthroscopic posterior bone block stabilization-early results of an effective procedure for the recurrent posterior instability

PURPOSE

In the current study the clinical outcome of an arthroscopic posterior bone block augmentation in combination with a posterior capsular repair was investigated.

METHODS

Twenty-four shoulders (18 patients) with unidirectional posterior shoulder instability were treated with an arthroscopic posterior bone block and capsular reconstruction. The mean follow up period was 26 months. The patients were examined pre- and postoperatively using the Constant-Murley score, the Rowe score, Walch-Duplay score and Western Ontario Shoulder index.

RESULTS

At the follow up examination 21 shoulders were classified to be stable, while one patient reported a single redislocation and two further patients reported recurrent posterior subluxation or posterior apprehension. Thus, the recurrence rate was defined to be 12.5%. The Rowe-Score significantly improved from 50 points preoperatively to 75 points postoperatively (p = 0.0003). The WOSI-score significantly improved from 37% preoperatively to 66% postoperatively (p = 0.0001). Revision surgery commonly was required for screw removal.

CONCLUSION

The early clinical results of this arthroscopic bone block augmentation and capsular repair are promising.

LEVEL OF EVIDENCE

IV.

PSI kinematic versus non-PSI mechanical alignment in total knee arthroplasty: a prospective, randomized study

PURPOSE

Kinematic alignment in TKA is supposed to restore function by aligning the components to the premorbid flexion-extension axis instead of altering the joint line and natural kinematic axes of the knee. The purpose of this study was to compare mechanically aligned TKA to kinematic alignment.

METHODS

In this study, 200 patients underwent TKA and were randomly assigned to 2 groups: 100 TKAs were performed using kinematic alignment with custom-made cutting guides in order to complete cruciate-retaining TKA; the other 100 patients underwent TKA that was manually performed using mechanical alignment. The WOMAC and combined Knee Society Score (KSS), as well as radiological alignment, were determined as outcome parameters at the 12-month endpoint.

RESULTS

WOMAC and KSS significantly improved in both groups. There was a significant difference in both scores between groups in favour of kinematic alignment. Although the kinematic alignment group demonstrated significantly better overall results, more outliers with poor outcomes were also seen in this group. A correlation between post-operative alignment deviation from the initial plan and poor outcomes was also noted. The most important finding of this study is that applying kinematic alignment in TKA achieves comparable results to mechanical alignment in TKA. This study also shows that restoring the premorbid flexion-extension axis of the knee joint leads to better overall functional results.

CONCLUSION

Kinematic alignment is a favourable technique for TKA.

CLINICAL RELEVANCE

The kinematic alignment idea might be a considerable alternative to mechanical alignment in the future.

LEVEL OF EVIDENCE

II.