Imprecise prediction of implant sizes with preoperative 2D digital templating in total knee arthroplasty.

PURPOSE: To analyze the match between preoperatively determined implant size (2D templating) and intraoperatively used implant size in total knee arthroplasty (TKA). Also examined were the factors that might influence templating accuracy (gender, surgeon experience, obesity, etc.). MATERIALS AND METHODS: The study was retrospective and conducted in a specialized ENDOCERT arthroplasty center. Digital templating was done with the MediCAD software. If the planned and implanted TKA components (both femur and tibia) were the same size, the match was classified "exact." A deviation of ± one size (at the femur or tibia or both) was classified "accurate." A deviation of ± two or more sizes (at the femur or tibia or both) was classified "inaccurate." Obesity, gender, implant type and surgeon experience were investigated for potential influence on templating accuracy. Chi-square tests and Cohen's weighted kappa test were used for statistical analysis. RESULTS: A total of 482 cases [33.6% male, 66.4% female, age 69 ± 11, body mass index (BMI) 30.3 ± 5.8] were included. When the femur and tibia were taken together, exact size match was observed in 34% (95% CI 29.9-38.3%) of cases, accurate size match in 57.5% (95% CI 53-61.8%) and inaccurate size match in 8.5% (95% CI 6.3-11.2%). Inaccurate size match prolonged operative time (p = 0.028). Regarding the factors potentially influencing templating accuracy, only gender had a significant influence, with templating being more accurate in men (p = 0.004). BMI had no influence on accuracy (p = 0.87). No effect on accuracy was observed for implant type and surgeon experience. CONCLUSIONS: The accuracy of 2D size templating in TKA is low, even in a specialized ENDOCERT arthroplasty center. The study findings challenge the usefulness of preoperative 2D size templating and highlight the importance of more reliable templating methods. LEVEL OF EVIDENCE: Level III (retrospective observational study).

The clinical outcome of total knee arthroplasty is compromised by a previously implanted medial unicondylar knee arthroplasty.

OBJECTIVE: To investigate the clinical outcome of patients that underwent conversion of a medial unicondylar knee arthroplasty (UKA) to a total knee arthroplasty (TKA) and to compare that outcome to patients that underwent primary TKA. It was hypothesized that those groups would significantly differ in terms of knee score outcome and implant survival. METHODS: A retrospective-comparative study was conducted utilizing data from the Federal state's arthroplasty registry. Included were patients from our department that undergone a conversion of a medial UKA to a TKA (UKA-TKA group). The Western Ontario and MacMaster Universities Osteoarthritis Index (WOMAC) from preoperative and 1-year postoperative was used. Moreover, the implant survival was analyzed. RESULTS: In the UKA-TKA group, there were 51 cases (age 67 ± 10, 74% women), and in the TKA group, there were 2247 cases (age 69 ± 9, 66% women). The one-year postoperative WOMAC total score was 33 in the UKA-TKA group und 21 in the TKA group (p < 0.001). Similarly, the WOMAC pain, WOMAC stiffness, and WOMAC function scores were significantly worse in the UKA-TKA. After 5 years, the survival rates were 82% and 95% (p = 0.001). The 10-years prosthesis survival was 74% and 91% in the UKA-TKA and TKA groups, respectively (p < 0.001). CONCLUSIONS: Based on our findings it is concluded that patients who received a TKA after UKA have inferior results than those that directly receive a TKA. This is true for both patient-reported knee outcome and prosthesis survival. Converting UKA to TKA should not be seen as an easy operation, but should rather be done by surgeons with considerable experience in both primary and revision knee arthroplasty.

Accuracy of digital templating of uncemented total hip arthroplasty at a certified arthroplasty center: a retrospective comparative study.

INTRODUCTION: To investigate the accuracy of preoperative digital templating for total hip arthroplasty (THA) at a certified arthroplasty center (EndoCert EPZmax). MATERIALS AND METHODS: In a retrospective study design, we analysed 620 uncemented primary THAs for templating accuracy by comparing the preoperatively planned THA component size and the implanted size as documented by the surgeon. Templating was determined to be a) exact if the planned and the implanted component were the same size and b) accurate if they were exact ± one size. Moreover, we investigated factors that potentially influence templating accuracy: overweight and obesity (WHO criteria), sex, implant design, surgeon experience, preoperative diagnosis. Digital templating was done with MediCAD software. The Mann-Whitney U test and the Kruskal-Wallis test were used for statistical analysis. RESULTS: Templating was exact in 52% of stems and 51% of cups and was accurate in 90% of the stems and 85% of the cups. Regarding the factors potentially influencing templating accuracy, the type of cup implant had a significant influence (p = 0.016). Moreover, greater accuracy of stem templating was achieved in female patients (p = 0.004). No such effect was determined for the other factors investigated. CONCLUSIONS: We conclude that preoperative 2D templating is accurate in 90% of the stems and 85% of the cups. Greater accuracy may be achieved in female patients. In addition to gender, the type of implant used may influence planning accuracy as well. Surgeon experience, BMI and preoperative diagnosis did not influence templating accuracy. LEVEL OF EVIDENCE: Level III (retrospective comparative study with prospective cohort).

Different wear in two highly cross-linked polyethylene liners in THA: wear analysis with EBRA.

INTRODUCTION: The purpose of this study was (1) to compare early wear rates in bedding-in periods of two highly cross-linked polyethylene liners frequently used in THA and (2) to evaluate risk factors indicating a possible higher wear rate. MATERIALS AND METHODS: 1120 patients who received a Crossfire or a Marathon highly cross-linked (HXLPE) ultra-high-molecular-weight polyethylene liner in primary THA at our Department between 2004 and 2018 were retrospectively reviewed. Patients with (1) only alumina heads on HXLPE acetabular bearings, (2) a minimum of four radiographs per patient for EBRA analysis, (3) no osteolysis around the acetabular cup and (4) no dislocations that occurred during the study period were included. RESULTS: A total of 328 patients (female: 183; male: 145; Marathon: 179; Crossfire: 149) fulfilled the inclusion criteria. Mean follow-up was 24 (range 7-51) months. With 0.22 (SD 0.27) mm mean total wear for the Marathon was three times greater than for the Crossfire, namely 0.07 (SD 0.14) mm. Mean cup migration during the investigated follow-up period was 0.7 (SD 0.8) mm for the Pinnacle and 0.5 mm (SD 0.7) for the Trident PSL cups. CONCLUSION: Initial early wear of highly cross-linked polyethylene in combination with alumina heads differs strongly between products. Long-term survivorship of these liners should be observed to determine whether early wear has an impact on aseptic loosening. LEVEL OF EVIDENCE: Level III (retrospective comparative study with prospective cohort).

[A multidimensional v-shaped distalizing osteotomy of the tibial tuberosity with a proximal buttress ("coffin-shaped" osteotomy)]. / Die multiplanare v-förmige distalisierende Tuberositasosteotomie mit proximalem Widerlager ("sargförmige" Osteotomie).

The aim of the intervention presented is a distalization of the tibial tuberosity. It is indicated in patients with symptomatic patella alta, i.e. patients with instability of the patella. It facilitates a V-shaped osteotomy. The bone gained during distalization is used as a proximal buttress. This leads to an improved mediolateral and proximal stability. The bony surface area is increased, which improves bony healing. There were no secondary dislocations in the patient group of 10 patients treated by the surgeon.

Prevailing disagreement in the treatment of complex patellar instability cases: an online expert survey of the AGA Knee-Patellofemoral Committee.

PURPOSE: To evaluate the current state of knowledge and potential controversies in the treatment of patellofemoral instability among orthopaedic/trauma surgeons in the German-speaking countries. METHODS: An online survey consisting of 32 questions and three fictitious cases was sent to members of the AGA-Society for Arthroscopy and Joint Surgery. Surgeons were defined by our senior authors as high-volume or low-volume surgeons, depending on the number of their cases. The treatment of 25% of patients with patellofemoral instability and/or the performance of 50 patellofemoral instability cases per year distinguishes high- from low-volume surgeons in this study. RESULTS: The online questionnaire was completed by 541 experienced knee surgeons from Germany (78%), Austria (10.9%), Switzerland (10.4%) and other countries (0.7%). Most surgeons prefer MPFL reconstruction as surgical intervention in patients with recurrent patellar instability (64-81%). Sixty percent of high-volume surgeons as compared to 21.8% of low-volume surgeons have ever performed a trochleoplasty. Of the overall respondents, 25% would not perform any surgical treatment on adolescents with patellar instability and an open growth plate. Of all responding surgeons, 95% would not treat patellofemoral instability with an isolated lateral release. This corresponds to recent literature showing poor outcome of its strictly isolated application. CONCLUSION: This study provides an overview of the current management of acute and recurrent patellofemoral instability in the German-speaking countries. Results show the surgeons' awareness for highly demanding surgical possibilities for complex patellar instability cases. However, disagreement among surgeons still prevails when it comes to selecting individual multimodal treatment options. This highlights the need for treatment guidelines and algorithms for patellofemoral instability. LEVEL OF EVIDENCE: V.

Massive cutback in orthopaedic healthcare services due to the COVID-19 pandemic.

PURPOSE: Due to the lack of evidence, it was the aim of the study to investigate current possible cutbacks in orthopaedic healthcare due to the coronavirus disease 2019 pandemic (COVID-19). METHODS: An online survey was performed of orthopaedic surgeons in the German-speaking Arthroscopy Society (Gesellschaft für Arthroskopie und Gelenkchirurgie, AGA). The survey consisted of 20 questions concerning four topics: four questions addressed the origin and surgical experience of the participant, 12 questions dealt with potential cutbacks in orthopaedic healthcare and 4 questions addressed the influence of the pandemic on the particular surgeon. RESULTS: Of 4234 contacted orthopaedic surgeons, 1399 responded. Regarding arthroscopic procedures between 10 and 30% of the participants stated that these were still being performed-with actual percentages depending on the specific joint and procedure. Only 6.2% of the participants stated that elective total joint arthroplasty was still being performed at their centre. In addition, physical rehabilitation and surgeons' postoperative follow-ups were severely affected. CONCLUSION: Orthopaedic healthcare services in Austria, Germany, and Switzerland are suffering a drastic cutback due to COVID-19. A drastic reduction in arthroscopic procedures like rotator cuff repair and cruciate ligament reconstruction and an almost total shutdown of elective total joint arthroplasty were reported. Long-term consequences cannot be predicted yet. The described disruption in orthopaedic healthcare services has to be viewed as historic. LEVEL OF EVIDENCE: V.

Disruption of joint arthroplasty services in Europe during the COVID-19 pandemic: an online survey within the European Hip Society (EHS) and the European Knee Associates (EKA).

PURPOSE: The aim of the present study was to evaluate the impact of the coronavirus (COVID-19) pandemic on joint arthroplasty service in Europe by conducting an online survey of arthroplasty surgeons. METHODS: The survey was conducted in the European Hip Society (EHS) and the European Knee Associates (EKA). The survey consisted of 20 questions (single, multiple choice, ranked). Four topics were addressed: (1) origin and surgical experience of the participant (four questions); (2) potential disruption of arthroplasty surgeries (12 questions); (3) influence of the COVID-19 pandemic on the particular arthroplasty surgeon (four questions); (4) a matrix provided 14 different arthroplasty surgeries and the participant was asked to state whether dedicated surgery was stopped, delayed or cancelled. RESULTS: Two-hundred and seventy-two surgeons (217 EHS, 55 EKA) from 40 different countries participated. Of the respondents, 25.7% stated that all surgeries were cancelled in their departments, while 68.4% responded that elective inpatient procedures were no longer being performed. With regard to the specific surgical procedures, nearly all primary TJA were cancelled (92.6%) as well as aseptic revisions (94.7%). In most hospitals, periprosthetic fractures (87.2%), hip arthroplasty for femoral neck fractures and septic revisions for acute infections (75.8%) were still being performed. CONCLUSION: During the current 2020 COVID-19 pandemic, we are experiencing a near-total shutdown of TJA. A massive cutback was observed for primary TJA and revision TJA, even in massively failed TJA with collapse, dislocation, component failure or imminent dislocation. Only life-threatening pathologies like periprosthetic fractures and acute septic TJA are currently undergoing surgical treatment. LEVEL OF EVIDENCE: V.

Resuming elective hip and knee arthroplasty after the first phase of the SARS-CoV-2 pandemic: the European Hip Society and European Knee Associates recommendations.

PURPOSE: The Covid-19 pandemic has disrupted health care systems all over the world. Elective surgical procedures have been postponed and/or cancelled. Consensus is, therefore, required related to the factors that need to be in place before elective surgery, including hip and knee replacement surgery, which is restarted. Entirely new pathways and protocols need to be worked out. METHODS: A panel of experts from the European Hip Society and European Knee Association have agreed to a consensus statement on how to reintroduce elective arthroplasty surgery safely. The recommendations are based on the best available evidence and have been validated in a separate survey. RESULTS: The guidelines are based on five themes: modification and/or reorganisation of hospital wards. Restrictions on orthopaedic wards and in operation suite(s). Additional disinfection of the environment. The role of ultra-clean operation theatres. Personal protective equipment enhancement. CONCLUSION: Apart from the following national and local guidance, protocols need to be put in place in the patient pathway for primary arthroplasty to allow for a safe return.

Recommendations for resuming elective hip and knee arthroplasty in the setting of the SARS-CoV-2 pandemic: the European Hip Society and European Knee Associates Survey of Members.

PURPOSE: The COVID-19 pandemic has disrupted the health care system around the entire globe. A consensus is needed about resuming total hip and knee procedures. The European Hip Society (EHS) and the European Knee Association (EKA) formed a panel of experts that have produced a consensus statement on how the safe re-introduction of elective hip and knee arthroplasty should be undertaken. METHODS: A prospective online survey was done among members of EHS and EKA. The survey consisted of 27 questions. It includes basic information on demographics and details the participant's agreement with each recommendation. The participant could choose among three options (agree, disagree, abstain). Recommendations focussed on pre-operative, peri-operative, and post-operative handling of patients and precautions. RESULTS: A total of 681 arthroplasty surgeons participated in the survey, with 479 fully completing the survey. The participants were from 44 countries and 6 continents. Apart from adhering to National and Local Guidelines, the recommendations concerned how to make elective arthroplasty safe for patients and staff. CONCLUSION: The survey has shown good-to-excellent agreement of the participants with regards to the statements made in the recommendations for the safe return to elective arthroplasty following the first wave of the COVID-19 pandemic.

What makes patients aware of their artificial knee joint?

BACKGROUND: Joint awareness was recently introduced as a new concept for outcome assessment after total knee arthroplasty (TKA). Findings from qualitative and psychometric studies suggest that joint awareness is a distinct concept especially relevant to patients with good surgical outcome and patients at late follow-up time points. The aim of this study was to improve the understanding of the concept of joint awareness by identifying situations in which patients are aware of their artificial knee joint and to investigate what bodily sensations and psychological factors raise a patient's awareness of her/his knee. In addition, we evaluated the relative importance of patient-reported outcome parameters that are commonly assessed in orthopaedics. METHODS: Qualitative interviews were conducted with patients being at least 12 months after TKA. The interviews focused on when, where and for what reasons patients were aware of their artificial knee joint. To evaluate the relative importance of 'joint awareness' after TKA among nine commonly assessed outcome parameters (e.g. pain or stiffness), we collected importance ratings ('0' indicating no importance at all and '10' indicating high importance). RESULTS: We conducted interviews with 40 TKA patients (mean age 69.0 years; 65.0% female). Joint awareness was found to be frequently triggered by kneeling on the floor (30%), climbing stairs (25%), and starting up after resting (25%). Patients reported joint awareness to be related to activities of daily living (68%), specific movements (60%), or meteoropathy (18%). Sensations causing joint awareness included pain (45%) or stiffness (15%). Psychological factors raising a patient's awareness of his/her knee comprised for example feelings of insecurity (15%), and fears related to revision surgeries, inflammations or recurring pain (8%). Patients' importance ratings of outcome parameters were generally high and did not allow differentiating clearly among them. CONCLUSIONS: We have identified a wide range of situations, activities, movements and psychological factors contributing to patients' awareness of their artificial knee joints. This improves the understanding of the concept of joint awareness and of a patient's perception of his/her artificial knee joint. The diversity of sensations and factors raising patient's awareness of their joint encourages taking a broader perspective on outcome after TKA.

Validation of the German version of the Kujala score in patients with patellofemoral instability: a prospective multi-centre study.

INTRODUCTION: The Kujala score is the most frequently used questionnaire for patellofemoral disorders like pain, instability or osteoarthritis. Unfortunately, we are not aware of a validated German version of the Kujala score. The aim of our study was the translation and linguistic validation of the Kujala score in German-speaking patients with patella instability and the assessment of its measurement characteristics. MATERIALS AND METHODS: The German Kujala score was developed in several steps of translation. In addition to healthy controls, the Kujala German was assessed in consecutive patients undergoing reconstruction of the medial patellofemoral ligament for recurrent patellar dislocations. Pre-op, 6 and 12 months postop the patients completed the Kujala German score, the KOOS, the Lysholm score, a VAS Pain, and the SF-12v2 scores. In addition, there was a Kujala German Score retest preop after a 1-week interval. RESULTS: We found high reliability in terms of internal consistency for the Kujala score (Cronbach's alpha = 0.87). Convergent validity with the KOOS (symptom r = 0.65, pain r = 0.78, ADL r = 0.74, sports/recreation r = 0.84, quality of life r = 0.70), the Lysholm score (r = 0.88) and the SF-12 physical component summary score (r = 0.79) and VAS pain (r = - 0.71) was also very high. Discriminant validity in terms of correlation with the SF-12 mental component summary Score was satisfactory (r = 0.14). CONCLUSIONS: In conclusion, the German version of the Kujala score proved to be a reliable and valid instrument in the setting of a typical patellofemoral disease treated with a standard patellofemoral procedure.

Mini-midvastus total knee arthroplasty does not result in superior gait pattern.

PURPOSE: Previous studies dealing with gait after minimally invasive surgery (MIS) total knee arthroplasty (TKA) are rare and insufficient. It was the purpose of the study to determine in a prospective, comparative setting whether MIS influences the outcome of TKA in terms of typical 3D gait parameters. METHODS: Patients scheduled for TKA or MIS TKA were invited to participate. MIS TKA was defined as TKA with shorter skin incision, mini-midvastus arthrotomy, special instruments, and avoidance of tibiofemoral dislocation and patella eversion. All other intra- and perioperative aspects were identical for both groups. A 3D gait analysis was performed with a VICON system 1 month preoperative and 8 weeks post-operative. A multivariate analysis of variance was conducted including the main effects time (pre- and post-surgery) and surgical group and the group-by-time interaction effect. RESULTS: Seventeen MIS TKA patients and 20 TKA patients were eligible for the final analysis. We determined neither inter-group differences nor time × group interactions for any gait variables (temporospatial, ground reaction forces, joint angles and joint moments)­except for the varus-valgus knee kinematics. In pre- to post-operative comparison, the maximum valgus sway increased in the MIS group, whereas it decreased in the conventional group (p = 0.001). CONCLUSION: From our findings, it was concluded that MIS TKA does not result in a superior walking pattern 8 weeks post-operative. Because we previously also observed mini-midvastus MIS TKA to have equal or slightly inferior results with regard to knee scores, knee torque, radiographic outcome and tourniquet/operating time, we discontinued the procedure. LEVEL OF EVIDENCE: Prospective comparative study, Therapy, Level II.

[Arthroscopic procedure for Baker's cysts : surgical technique. Video article]. / Arthroskopische Operation der Baker-Zyste : Operationstechnik. Videobeitrag.

BACKGROUND: Baker's cysts are related to increased intra-articular pressure. The causes may be inflammatory, degenerative or traumatic disorders. Owing to the increased intra-articular pressure a cyst protrudes between the semimembranosus and the medial gastrocnemius tendons. The traditional treatment for a Baker's cyst is open resection. As an alternative, an arthroscopic procedure can be performed, which is demonstrated by the video on surgical technique that accompanies this short report. SURGICAL TECHNIQUE: From the anterolateral portal the arthroscope is advanced through the intercondylar notch (below the posterior cruciate ligament) to the posteromedial recess. Under visual control, a posteromedial portal is created followed by identification of the capsular fold separating the cyst from the joint cavity. This fold (valvular mechanism) is resected with a shaver from the posteromedial portal until a large enough connection exists between the joint and the cyst (cyst decompression). After the decompression, the arthroscope is inserted from the posteromedial portal directly into the cyst cavity. Subsequently, the inner wall of the cyst is removed with the shaver via an additional far posterior cystic portal. It is obligatory to treat the associated intra-articular pathological condition. In our video a medial meniscal lesion is treated with partial meniscectomy.

Brake response time returns to the pre-surgical level 6 weeks after unicompartmental knee arthroplasty.

PURPOSE: The objective of the study was to clarify whether driving abstinence should be recommended when patients are discharged from hospital after unicompartmental knee arthroplasty (UKA). We tested the hypotheses that there are differences in the peri-operative course of brake response time in patients undergoing right-sided (1) or left-sided (2) UKA. Additionally, we tested whether brake response time is significantly influenced by pain (3), driving experience (4) or age (5). METHODS: In 43 patients undergoing UKA, brake response time was measured with a custom-made driving simulator pre-operatively and 1 and 6 weeks after UKA. Patients' visual analogue scales for knee pain and their self-reported driving experience were also assessed. RESULTS: In patients with right-sided UKA, brake response time changed from 786 (261) ms pre-operatively to 900 (430) ms 1 week post-operatively (p = 0.029). At 6 weeks post-operatively, brake response time had returned to 712 (139) ms, which was deemed to be an insignificant change from the pre-operative reference benchmark. When surgery was performed on the contralateral left side, no effect was found onto the right side's brake response time. Knee pain and driving experience were significantly correlated with brake response time. No such correlations were found between brake response time and age. CONCLUSIONS: On the basis of the current findings, it is concluded that brake response time returns to pre-operative levels 6 weeks after UKA surgery. Therefore, it is proposed that driving be abstained from for that period.

[Operative therapy of isolated patellofemoral arthritis. Biomechanics as a guide]. / Operative Therapie der isolierten patellofemoralen Arthrose. Biomechanik als Wegweiser.

BACKGROUND: The treatment of patellofemoral arthritis places high demands on orthopedists. The exact analysis of the underlying pathobiomechanical relationships is the basis for every therapy decision. METHODS: Soft tissue procedures, such as medial patellofemoral ligament (MPFL) reconstruction for stabilization and bone interventions for alignment optimization (e.g. tuberosity transfer and corrective osteotomy) can play a role in treatment. In cases of advanced patellofemoral arthrosis these interventions can be used as well as in combination with partial joint replacement. For the choice of implant the use of anatomical prosthesis types is recommended because with these components the number of additional procedures can be reduced. CONCLUSION: The success of patellofemoral prosthetics depends mainly on the recognition of biomechanical deviations. If these can be corrected the risk of implant failure can be reduced.

Conservative versus tailored surgical treatment in patients with first time lateral patella dislocation: a randomized-controlled trial.

BACKGROUND: Patellar instability has a high incidence and occurs particularly in young and female patients. If the patella dislocates for the first time, treatment is usually conservative. However, this cautious approach carries the risk of recurrence and of secondary pathologies such as osteochondral fractures. Moreover, there is also risk of continuous symptoms apparent, as recurrent patella dislocation is related to patellofemoral osteoarthritis as well. An initial surgical treatment could possibly avoid these consequences of recurrent patella dislocation. METHODS: A prospective, randomized-controlled trial design is applied. Patients with unilateral first-time patella dislocation will be considered for participation. Study participants will be randomized to either conservative treatment or to a tailored patella stabilizing treatment. In the conservative group, patients will use a knee brace and will be prescribed outpatient physical therapy. The surgical treatment will be performed in a tailored manner, addressing the pathologic anatomy that predisposes to patella dislocation. The Banff Patellofemoral Instability-Instrument 2.0, recurrence rate, apprehension test, joint degeneration, and the Patella Instability Severity Score will serve as outcome parameters. The main analysis will focus on the difference in change of the scores between the two groups within a 2-year follow-up. Statistical analysis will use linear mixed models. Power analysis was done for the comparison of the two study arms at 2-year follow-up with regard to the BPII Score. A sample size of N = 64 per study arm (128 overall) provides 80% power (alpha = 0.05, two-tailed) to detect a difference of 0.5 standard deviations in a t-test for independent samples. DISCUSSION: Although several studies have already dealt with this issue, there is still no consensus on the ideal treatment concept for primary patellar dislocation. Moreover, most of these studies show a unified surgical group, which means that all patients were treated with the same surgical procedure. This is regarded as a major limitation as surgical treatment of patella dislocation should depend on the patient's anatomic pathologies leading to patellar instability. To our knowledge, this is the first study investigating whether patients with primary patella dislocation are better treated conservatively or operatively with tailored surgery to stabilize the patella. TRIAL REGISTRATION: The study will be prospectively registered in the publicly accessible database www.ClinicalTrials.gov .

Injury of the right and left inferior epigastric artery during the implantation of a stand-alone ALIF cage through a left retroperitoneal approach: a case report.

Various perioperative vascular complications of anterior lumbar spine procedures have been described in orthopaedic literature. We report the unusual case of a perioperative bleeding from the right and left epigastric inferior artery occurring when using a stand-alone ALIF device (Synfix, Synthes, Oberdorf, Switzerland) at the L5/S1 level through an anterior left retroperitoneal approach. The primary stability of the Synfix is achieved by four divergent screws which are inserted through the anteriorly located plate into the neighbouring vertebral endplates. For the screw insertion the surrounding structures have to be mobilized more extensively than during a "standard" anterior lumbar interbody fusion (ALIF) procedure. The epigastric inferior arteries were embolized by applying polyvinyl alcohol particles and metal coils. The retroperitoneal haematoma caused herniation of the external rectus sheath. Hence revision surgery with removal of the haematoma and resuturing of the rectus sheath were performed. Insertion of divergent screws of the Synfix device may cause severe distension and rupture of the epigastric vessels. This case shows that a lesion of the right epigastric artery may be a hazard even in left retroperitoneal approaches. To the author's knowledge this is the first case describing a lesion of the right epigastric artery during an ALIF procedure through a left retroperitoneal approach.

Material modifications enhancing the antibacterial properties of two biodegradable poly(3-hydroxybutyrate) implants.

The aim of this study was to evaluate the antimicrobial efficacy of adding a gentamicin palmitate (GP) coating and zirconium dioxide (ZrO2) to biodegradable poly(3-hydroxybutyrate) (PHB) to reduce biofilm formation. Cylindrical pins with and without a coating were incubated in Müller-Hinton broth inoculated with 2 × 105 colony-forming units (CFU) ml-1 of Staphylococcus aureus for 2 d or 7 d, then sonicated to disrupt biofilms. Pure PHB (PHB + GP) and PHB pins with ZrO2 added (PHBzr + GP) were coated with GP and compared with PHB pins lacking a coating (PHB). Cells (CFU) were counted to quantify the number of bacteria in the biofilm and a cell proliferation assay was employed to evaluate metabolic activity, and scanning electron microscopy (SEM) was performed to visualize the structure of the biofilm. After 2 d of incubation there were significantly more cells in biofilms on PHB pins than PHB + GP and PHBzr + GP pins (p < 0.0001), and cells in the sonication fluid obtained from GP-coated pins exhibited significantly lower metabolic activity than cells from uncoated PHB pins (p < 0.0001). After 7 d of incubation metabolic activity was lowest for PHBzr + GP, with significant differences between PHB and PHBzr + GP (p = 0.001). SEM revealed more cells attached to the surface, and more structured biofilms, on pins without a coating. Coating pins with GP significantly reduced early biofilm formation on PHB implants. This could lower the potential risk of surgical site infections when using PHB implants. Addition of ZrO2 might further enhance the antibacterial properties. Such modification of the implant material should therefore be considered when developing new biodegradable PHB implants.