Publications by authors named "Patrick O Zingg"

61 Publications

MRI findings of ischiofemoral impingement after total hip arthroplasty are associated with increased femoral antetorsion.

Acta Radiol 2021 Jun 7:2841851211021044. Epub 2021 Jun 7.

Department of Radiology, Balgrist University Hospital, University of Zurich, Zurich, Switzerland.

Background: Ischiofemoral impingement (IFI) is a known complication after total hip arthroplasty (THA).

Purpose: To assess if increased postoperative (FA) is associated with magnetic resonance imaging (MRI) findings of IFI.

Material And Methods: In 221 patients with THA, two independent readers measured FA, ischiofemoral space (IFS), quadratus femoris space (QFS), edema, and fatty infiltration of quadratus femoris muscle. Three sets of IFI-imaging features were defined: acute IFI (set 1): IFS ≤15 mm or QFS ≤10 mm and edema in the quadratus femoris muscle; chronic IFI (set 2): IFS ≤15 mm or QFS ≤10 mm and fatty infiltration of quadratus femoris muscle Goutallier grade ≥2; acute and chronic IFI (set 3) with both criteria applicable. For each set, FA angles were compared between positive findings of IFI and negative findings of IFI. The t-test for independent samples tested statistical significance.

Results: In 7.2% (16/221) of patients, findings of IFI (IFS ≤15 mm or QFS ≤10 mm and edema, n = 1; fatty infiltration, n = 9; or both, n = 6) were observed. In women, 11.4% (14/123) exhibited findings of IFI compared to 2.0% (2/98) in men. Comparison in set 1 (n = 7): mean antetorsion of 23.9° ± 9.8° (findings of acute IFI) compared to 14.4° ± 9.7° ( = 0.01). Comparison in set 2 (n = 15): mean antetorsion of 16.2° ± 6.3° (findings of chronic IFI) compared to 14.5° ± 9.9° ( = 0.49). Comparison in set 3 (n = 6): mean antetorsion of 20.4° ± 3.8° (findings of acute and chronic IFI) compared to 14.5° ± 9.9° ( = 0.01).

Conclusion: After THA, high postoperative FA is associated with MRI findings of acute as well as acute and chronic IFI. Findings of IFI were commonly seen in women.
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http://dx.doi.org/10.1177/02841851211021044DOI Listing
June 2021

Lack of Conclusive Evidence of the Benefit of Biologic Augmentation in Core Decompression for Nontraumatic Osteonecrosis of the Femoral Head: A Systematic Review.

Arthroscopy 2021 May 5. Epub 2021 May 5.

Department of Orthopaedics, Balgrist University Hospital, Zurich, Switzerland.

Purpose: To assess whether biologic augmentation in addition to core decompression (CD), compared with CD alone, improves clinical and radiographic outcomes in the treatment of nontraumatic osteonecrosis of the femoral head (ONFH). Our hypothesis was that biologic augmentation would reduce the progression of osteonecrosis and therefore also the rate of conversion to total hip arthroplasty (THA).

Methods: A systematic review was performed in accordance with the Preferred Reporting Items of Systematic Reviews and Meta-analysis (PRISMA) statement. Six databases were searched: Central, MEDLINE, Embase, Scopus, AMED, and Web of Science. Studies comparing outcomes of CD versus CD plus biologic augmentation (with or without structural augmentation), with a reported minimum level of evidence of III and ≥24 months of follow-up, were eligible. Procedural success was conceptualized as (1) avoidance of conversion to THA and (2) absence of radiographic disease progression. Risk of bias was assessed using the Joanna Briggs Institute critical appraisal checklists. A quantitative analysis of heterogeneity was undertaken.

Results: We included studies reporting on 560 hips in 484 patients. Biologic augmentation consisted of bone marrow stem cells in 10 studies, bone morphogenic protein in 2, and platelet-rich plasma in 1. Three studies used additional structural augmentation. The median maximum follow-up time was 45 months. Only 4 studies reported improvement in all clinical scores in the augmentation group. Seven studies observed a reduction in the rate of radiographic progression, and only 5 found reduced rates of conversion to THA when using augmentation. A high risk of bias and marked heterogeneity was found, with uncertainty about the study designs implemented, analytical approaches, and quality of reporting.

Conclusion: Current evidence is inconclusive regarding the benefit of biologic augmentation in CD for nontraumatic ONFH, because of inconsistent results with substantial heterogeneity and high risk of bias.

Level Of Evidence: III, systematic review of level I, II, and III studies.
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http://dx.doi.org/10.1016/j.arthro.2021.04.062DOI Listing
May 2021

Is the contralateral lesser trochanter a reliable reference for planning of total hip arthroplasty - a 3-dimensional analysis.

BMC Musculoskelet Disord 2021 Mar 11;22(1):268. Epub 2021 Mar 11.

Department of Orthopaedics, Balgrist University Hospital, University of Zurich, Forchstrasse 340, CH-8008, Zurich, Switzerland.

Background: Preoperative templating in total hip arthroplasty (THA) is mandatory to achieve appropriate offset and leg length equality. However, templating methods using the contralateral hip might be susceptible to errors resulting from side-differences in the femoral morphology. The distance of the lesser trochanter to the femoral head center (LTFHD) is a frequently used reference parameter for preoperative planning and intraoperative validation during THA. However, currently no three-dimensional (3D) analysis of side differences of the LTFHD exists.

Methods: Using Computer tomography (CT)-based surface models from 100 paired femora (50 cadavers), side-to-side asymmetry of the LTFHD, femoral length, femoral head diameter (FHD) and femoral antetorsion were analyzed. Univariate linear regression models were established to evaluate potential associations between sides regarding LTFHD and FHD as well as a correlation of these parameters with each other.

Results: Statistically significant side-differences were found for the LTFHD (p = 0.02) and FHD (p = 0.03) with a mean absolute side-difference of 1.6 ± 1.4mm (range 0.1-5.5mm) and 0.4mm ± 0.6mm (range 0-3mm), respectively. The ratio between the LTFHD and FHD was consistent with an average value of 1.16 ± 0.08 and reliable between sides with a correlation coefficient (r) of 0.72 (p < 0.01).

Conclusions: The LTFHD is a reliable reference parameter for preoperative templating and intraoperative validation during THA with a high correlation between sides (r = 0.93, p < 0.01). However, 8 % of the investigated specimens revealed a LTFHD of more than 4mm, which should be anticipated during THA to avoid unsatisfiable results.
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http://dx.doi.org/10.1186/s12891-021-04131-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7953689PMC
March 2021

Osseous defect of the anteroinferior femoral head: is it associated with femoroacetabular impingement (FAI)?

Skeletal Radiol 2021 Feb 4. Epub 2021 Feb 4.

Balgrist University Hospital, University of Zurich, Forchstrasse 340, 8008, Zürich, Switzerland.

Objective: To evaluate the prevalence, morphology, and clinical significance of a repeatedly observed yet not examined circumscript osseous defect at the anteroinferior aspect of the femoral head, termed femoral head defect.

Materials And Methods: Retrospective study with approval of the institutional review board. There was informed consent by all individuals. Magnetic resonance imaging (MRI) hip examinations of 970 individuals (age 15 to 55) were analyzed for femoral head defect. Patients with femoral head defect were matched for age and gender with patients without defect. Two readers independently assessed MRI images regarding presence, location, and morphology of the defect. MR images and radiographs were analyzed for findings of femoroacetabular impingement (FAI). Femoral torsion was measured. Independent t test and chi-square test were used for statistics.

Results: Sixty-eight (7%) of 970 MRI examinations exhibited a femoral head defect in an anteroinferior location of the femoral head (29/400 men, 7.3%; 39/570 women, 6.8%; p = 0.8). The most frequent morphology of femoral head defect was type I, dent-like (34; 50%), followed by type II, crater-like (27; 40%), and III, cystic (7; 10%). Femoral head defect was slightly more common on the right hip (39 individuals; 57%) compared to left (29 individuals; 43%), non-significantly (p = 0.115). There was no association between FAI or its subtypes and the presence of femoral head defect (p = 0.890). Femoral antetorsion was reduced in patients with femoral head defect (12.9° ± 8.6) compared to patients without defect (15.2° ± 8.5), without statistical significance (p = 0.121).

Conclusion: The femoral head defect is a common finding in MRI examinations of the hip and is situated in the anteroinferior location. There was no association with FAI yet a non-significant trend towards lower femoral antetorsion in patients with femoral head defects.
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http://dx.doi.org/10.1007/s00256-021-03730-xDOI Listing
February 2021

Cutibacterium avidum resists surgical skin antisepsis in the groin-a potential risk factor for periprosthetic joint infection: a quality control study.

Antimicrob Resist Infect Control 2021 02 1;10(1):27. Epub 2021 Feb 1.

Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.

Background: The skin commensal Cutibacterium avidum has been recognized as an emerging pathogen for periprosthetic joint infections (PJI). One currently assumes that the early occurring PJIs are a consequence of skin commensals contaminating the peri-implant tissue during surgery. We addressed whether standard skin antisepsis with povidone-iodine/alcohol before total hip arthroplasty (THA) is effective to eliminate colonizing bacteria with focus on C. avidum.

Methods: In a single-center, prospective study, we screened all patients for skin colonizing C. avidum in the groin before THA. Only in the patients positive for C. avidum, we preoperatively repeated skin swabs after the first and third skin antisepsis and antibiotic prophylaxis. We also obtained dermis biopsies for microbiology and fluorescence in situ hybridization (FISH).

Results: Fifty-one out of 60 patients (85%) were colonized on the skin with various bacteria, in particular with C. avidum in 12 out of 60. Skin antisepsis eliminated C. avidum in eight of ten (20%) colonized patients undergoing THA. Deeper skin (dermis) biopsies were all culture negative, but FISH detected single positive ribosome-rich C. avidum in one case near sweat glands.

Conclusion: Standard skin antisepsis was not effective to completely eliminate colonizing C. avidum on the skin in the groin of patients undergoing THA. Colonizing with C. avidum might pose an increased risk for PJI when considering a THA. Novel more effective antisepsis strategies are needed. Trial registration No clinical trial.
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http://dx.doi.org/10.1186/s13756-021-00883-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7852298PMC
February 2021

Revision rate of THA in patients younger than 40 years depends on primary diagnosis - a retrospective analysis with a minimum follow-up of 10 years.

Eur J Orthop Surg Traumatol 2021 Jan 25. Epub 2021 Jan 25.

Department of Orthopaedics, Balgrist University Hospital, Forchstrasse 340, 8008, Zurich, Switzerland.

Background: Treating osteoarthritis in elderly patients with THA is very successful. However, surgeons hesitate to recommend THA in younger patients. The spectrum of etiologies for end stage hip disease in the younger population is diverse and therefore different courses may be assumed. Our objective was to evaluate THA revision rate within a minimum follow-up period of 10 years in young patients and to analyze the difference between different primary diagnoses.

Methods: We included 144 consecutive hips in 127 patients younger than 40 years, who received a primary THA from 01/1996 to 12/2007. Operative reports, clinical and radiographic documentation were reviewed to determine primary diagnosis, prior hip surgery, component specifications and revision surgery. 111 hips in 97 patients were available for outcome analysis with a minimum follow-up of 10 years.

Results: The mean age was 33 years (range 15-40 years) at the time of the index THA, 68 patients were female and 59 were male. Ten years revision rate on the prosthetic components was 13%. The most common primary diagnosis was DDH. DDH was associated with a risk of 17% for requiring a reoperation on the prosthetic components because of mechanical fatigue and therefore, significantly higher than for any other primary diagnosis (p = 0.005).

Conclusion: THA in young patients is associated with a high revision rate of 13% in 10 years. 17% of patients with DDH required revision surgery for mechanical fatigue within 10 years, which was significantly higher than for any other primary diagnosis (1.2%, OR 16.8).
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http://dx.doi.org/10.1007/s00590-021-02881-wDOI Listing
January 2021

The Lisbon Agreement on Femoroacetabular Impingement Imaging-part 3: imaging techniques.

Eur Radiol 2021 Jul 7;31(7):4652-4668. Epub 2021 Jan 7.

Universitair Ziekenhuis Brussel, Brussels, Belgium.

Objectives: Imaging diagnosis of femoroacetabular impingement (FAI) remains controversial due to a lack of high-level evidence, leading to significant variability in patient management. Optimizing protocols and technical details is essential in FAI imaging, although challenging in clinical practice. The purpose of this agreement is to establish expert-based statements on FAI imaging, using formal consensus techniques driven by relevant literature review. Recommendations on the selection and use of imaging techniques for FAI assessment, as well as guidance on relevant radiographic and MRI classifications, are provided.

Methods: The Delphi method was used to assess agreement and derive consensus among 30 panel members (musculoskeletal radiologists and orthopedic surgeons). Forty-four questions were agreed on and classified into five major topics and recent relevant literature was circulated, in order to produce answering statements. The level of evidence was assessed for all statements and panel members scored their level of agreement with each statement during 4 Delphi rounds. Either "group consensus," "group agreement," or "no agreement" was achieved.

Results: Forty-seven statements were generated and group consensus was reached for 45. Twenty-two statements pertaining to "Imaging techniques" were generated. Eight statements on "Radiographic assessment" and 12 statements on "MRI evaluation" gained consensus. No agreement was reached for the 2 "Ultrasound" related statements.

Conclusion: The first international consensus on FAI imaging was developed. Researchers and clinicians working with FAI and hip-related pain may use these recommendations to guide, develop, and implement comprehensive, evidence-based imaging protocols and classifications.

Key Points: • Radiographic evaluation is recommended for the initial assessment of FAI, while MRI with a dedicated protocol is the gold standard imaging technique for the comprehensive evaluation of this condition. • The MRI protocol for FAI evaluation should include unilateral small FOV with radial imaging, femoral torsion assessment, and a fluid sensitive sequence covering the whole pelvis. • The definite role of other imaging methods in FAI, such as ultrasound or CT, is still not well defined.
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http://dx.doi.org/10.1007/s00330-020-07501-5DOI Listing
July 2021

The Lisbon Agreement on femoroacetabular impingement imaging-part 2: general issues, parameters, and reporting.

Eur Radiol 2021 Jul 7;31(7):4634-4651. Epub 2021 Jan 7.

Universitair Ziekenhuis Brussel, Brussels, Belgium.

Objectives: Imaging assessment for the clinical management of femoroacetabular impingement (FAI) is controversial because of a paucity of evidence-based guidance and notable variability among practitioners. Hence, expert consensus is needed because standardised imaging assessment is critical for clinical practice and research. We aimed to establish expert-based statements on FAI imaging by using formal methods of consensus building.

Methods: The Delphi method was used to formally derive consensus among 30 panel members from 13 countries. Forty-four questions were agreed upon, and relevant seminal literature was circulated and classified in major topics to produce answering statements. The level of evidence was noted for all statements, and panel members were asked to score their level of agreement (0-10). This is the second part of a three-part consensus series and focuses on 'General issues' and 'Parameters and reporting'.

Results: Forty-seven statements were generated and group consensus was reached for 45. Twenty-five statements pertaining to 'General issues' (9 addressing diagnosis, differential diagnosis, and postoperative imaging) and 'Parameters and reporting' (16 addressing femoral/acetabular parameters) were produced.

Conclusions: The available evidence was reviewed critically, recommended criteria for diagnostic imaging highlighted, and the roles/values of different imaging parameters assessed. Radiographic evaluation (AP pelvis and a Dunn 45° view) is the cornerstone of hip-imaging assessment and the minimum imaging study that should be performed when evaluating adult patients for FAI. In most cases, cross-sectional imaging is warranted because MRI is the 'gold standard' imaging modality for the comprehensive evaluation, differential diagnosis assessment, and FAI surgical planning.

Key Points: • Diagnostic imaging for FAI is not standardised due to scarce evidence-based guidance on which imaging modalities and diagnostic criteria/parameters should be used. • Radiographic evaluation is the cornerstone of hip assessment and the minimum study that should be performed when assessing suspected FAI. Cross-sectional imaging is justified in most cases because MRI is the 'gold standard' modality for comprehensive FAI evaluation. • For acetabular morphology, coverage (Wiberg's angle and acetabular index) and version (crossover, posterior wall, and ischial spine signs) should be assessed routinely. On the femoral side, the head-neck junction morphology (α° and offset), neck morphology (NSA), and torsion should be assessed.
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http://dx.doi.org/10.1007/s00330-020-07432-1DOI Listing
July 2021

Mid-term results after pinning and hip arthroscopy for mild slipped capital femoral epiphysis: a minimum five-year follow-up.

J Child Orthop 2020 Dec;14(6):521-528

Department of Orthopaedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland.

Purpose: pinning of mild slipped capital femoral epiphysis (SCFE) results in an aspherical head-neck junction and arthroscopic osteochondroplasty can successfully correct the head-neck junction. However, whether the correction stays stable over at least five years remains unknown.

Methods: In a retrospective and consecutive series, 11 patients with a mean age of 12 years (range, 10 years to 15 years) were included. All patients were treated for mild SCFE with pinning and staged hip arthroscopy correcting the head-neck junction. All patients were assessed clinically and radiographically (radiograph and magnetic resonance imaging (MRI)) pre-operatively, 12 weeks and at least five years' post-operatively.

Results: The mean range of motion (ROM) for flexion and internal rotation was stable over time with 100° (sd 4) and 21° (sd 6), respectively at the last follow-up. The mean alpha angle decreased from pre-operative 64° (range 61° to 68°) to 12 weeks post-operative 49° (range 46° to 52°; p = 0.001) and stayed stable over time. New superficial cartilage damage on either the acetabular or femoral side was seen in each three patients. Progressive labral degeneration was present in two patients.

Conclusion: pinning and staged hip arthroscopy for the correction of mild SCFE is safe, restores normal alpha angles and reveals stable morphological correction at mid-term follow-up. Furthermore, the clinical results were excellent with almost normalized internal hip rotation at mid-term follow-up in patients who had reached adulthood. However, there was some joint deterioration, but without negative impact on subjective and clinical outcome after at least five years.

Level Of Evidence: IV.
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http://dx.doi.org/10.1302/1863-2548.14.200068DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7740677PMC
December 2020

Symptomatic leg length discrepancy after total hip arthroplasty is associated with new onset of lower back pain.

Orthop Traumatol Surg Res 2021 02 11;107(1):102761. Epub 2020 Dec 11.

Department of Orthopedics, Balgrist University Hospital, University of Zurich, Forchstrasse 340, 8008 Zurich, Switzerland.

Background: Leg length discrepancy (LLD) is common after total hip arthroplasty (THA) with a plethora of clinical consequences. The associations between symptomatic (sLLD; disturbing perception of anatomical leg length discrepancy), anatomical (aLLD; side difference in leg length between the center of rotation of the hip and the center of the ankle joint) and intraarticular (iLLD; side difference between the tear drop figure and the most prominent point of the trochanter minor) LLD and lower back have not yet been reported in the literature. We performed a retrospective study to answer if postoperative (1) symptomatic LLD, (2) anatomic LLD, and (3) a change in intraarticular leg length are associated with lower back pain in patients undergoing THA. Further, we aimed to answer (4) whether symptomatic LLD is associated with the magnitude of anatomical LLD and the change in intraarticular leg length.

Hypothesis: LLD after THA is associated with lower back pain.

Materials And Methods: Seventy-nine consecutive patients were retrospectively analyzed for the presence of aLLD and iLLD using EOS™ and X-rays, and were interviewed for the presence of sLLD and lower back pain using a questionnaire 5 years after primary THA.

Results: Postoperative new onset of lower back pain was reported by 9 (11%) patients. Twenty (25%) patients reported sLLD. Anatomical LLD>5mm was present in 44 (56%) (median 8.0 (IQR -3.0 to 12.0; range -22 to 22) mm) and>10mm in 17 (22%) (median 12.0 (IQR 11.0 to 16.5; range -22 to 22) mm) patients. iLLD changed>5mm in 44 (56%) (median 8.5 (IQR 7.0 to 10.0; range -8 to 18) mm) and>10mm in 10 (13%) (median 14.0 (IQR 12.5 to 14.5; range 11 to 18) mm). New onset lower back pain was associated with sLLD (p=0.002) but not with aLLD or iLLD. Patients without preoperative lower back pain had a statistically significant association between presence of sLLD and an aLLD of >10mm (p=0.01).

Conclusions: Symptomatic LLD after primary THA is associated with postoperative new onset of lower back pain irrespective of the magnitude of LLD. In patients without lower back pain prior to THA, symptomatic LLD is associated with anatomical LLD of more than 10mm.

Level Of Evidence: IV.
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http://dx.doi.org/10.1016/j.otsr.2020.102761DOI Listing
February 2021

Augmented reality-guided periacetabular osteotomy-proof of concept.

J Orthop Surg Res 2020 Nov 17;15(1):540. Epub 2020 Nov 17.

Department of Orthopaedics, Balgrist University Hospital, University of Zürich, Forchstrasse 340, 8008, Zürich, Switzerland.

Background: The Ganz' periacetabular osteotomy (PAO) consists of four technically challenging osteotomies (OT), namely, supraacetabular (saOT), pubic (pOT), ischial (iOT), and retroacetabular OT (raOT).

Purpose: We performed a proof of concept study to test (1) the feasibility of augmented reality (AR) guidance for PAO, (2) precision of the OTs guided by AR compared to the freehand technique performed by an experienced PAO surgeon, and (3) the effect of AR on performance depending on experience.

Methods: A 3D preoperative plan of a PAO was created from segmented computed tomography (CT) data of an anatomic plastic pelvis model (PPM). The plan was then embedded in a software application for an AR head-mounted device. Soft tissue coverage was imitated using foam rubber. The 3D plan was then registered onto the PPM using an anatomical landmark registration. Two surgeons (one experienced and one novice PAO surgeon) each performed 15 freehand (FH) and 15 AR-guided PAOs. The starting point distances and angulation between the planned and executed OT planes for the FH and the AR-guided PAOs were compared in post-intervention CTs.

Results: AR guidance did not affect the performance of the expert surgeon in terms of the mean differences between the planned and executed starting points, but the raOT angle was more accurate as compared to FH PAO (p = 0.0027). AR guidance increased the accuracy of the performance of the novice surgeon for iOT (p = 0.03). An intraarticular osteotomy performed by the novice surgeon with the FH technique could be observed only once.

Conclusion: AR guidance of osteotomies for PAOs is feasible and seems to increase accuracy. The effect is more accentuated for less-experienced surgeons.

Clinical Relevance: This is the first proof of concept study documenting the feasibility of AR guidance for PAO. Based on these findings, further studies are essential for elaborating on the potential merits of AR guidance to increase the accuracy of complex surgical procedures.
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http://dx.doi.org/10.1186/s13018-020-02066-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7672946PMC
November 2020

Factors affecting outcome in the treatment of streptococcal periprosthetic joint infections: results from a single-centre retrospective cohort study.

Int Orthop 2021 01 27;45(1):57-63. Epub 2020 Aug 27.

Department of Orthopaedics, Balgrist University Hospital, University of Zurich, Forchstrasse 340, 8008, Zurich, Switzerland.

Purpose: To report and analyse factors affecting the outcome of streptococcal periprosthetic joint infections (PJIs).

Methods: A retrospective analysis of consecutive streptococcal PJIs was performed. Musculoskeletal Infection Society 2013 criteria were used. Outcome was compared with a prospective PJI cohort from the same institution.

Results: The most common isolated streptococcal species was Streptococcus dysgalactiae (9/22, 41%) among 22 patients included. Surgical treatment consisted of DAIR (debridement, antibiotics, irrigation and retention) in 12 (55%), one-stage revision arthroplasty in one (4%), two-stage revision arthroplasty in eight (37%) and implant removal in one (4%) patient. An infection free-outcome was achieved in 15 cases (68%), whilst seven (32%) patients failed initial revision and relapsed with the same pathogen, from which six were treated with DAIR and one with one-stage revision arthroplasty. No failures were observed in patients who received a two-stage revision. Failure rates did not differ in the cases treated with rifampin (1/5) from those without 6/17 (p = 0.55). There was no correlation between the length of antibiotic treatment and relapse (p = 0.723). In all failures, a persistent distant infection focus was identified at the time of relapse. Compared with our prospective PJI cohort, relapse rates were significantly higher 32% vs 12% (p < 0.05).

Conclusion: No correlation with the use of rifampin or length of antibiotic treatment was found. No failures were observed in patients who received a two-stage revision, which may be the surgical treatment of choice. A distant persisting infection focus could be the reason for PJI relapse with recurrent hematogenous seeding in the joint.
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http://dx.doi.org/10.1007/s00264-020-04722-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7801309PMC
January 2021

Subtrochanteric rotational osteotomy for young adults with hip pain due to femoral maltorsion.

Hip Int 2020 Aug 4:1120700020943811. Epub 2020 Aug 4.

Department of Orthopaedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland.

Introduction: Femoral rotational osteotomies can be a treatment option for symptomatic femoral maltorsion. This study investigated the clinical and radiological results of subtrochanteric rotational osteotomy and its potential adverse effects, particularly on patellofemoral stability and geometry.

Methods: Retrospective consecutive series of patients undergoing subtrochanteric rotational osteotomy with hip arthroscopy. 25 hips, 18 with decreased (⩽4°), 7 with increased (⩾28°) femoral torsion (FT), were analysed. Mean follow-up was 37 months. Subjective Hip value (SHV), WOMAC and Harris Hip Score (HHS), hip range of motion, asymmetries in foot position during gait as well as patellofemoral instability were the outcome measures. Femoral and tibial torsion as well as morphological signs of patella maltracking (TTTG, patellar tilt and lateralisation) were measured on MRI.

Results: SHV improved from 52% to 72% ( = 0.002), WOMAC from 3 to 1 ( < 0.001) and HHS from 68 to 86 ( < 0.001). Hips treated for reduced FT showed better internal rotation and hips treated for excessive FT less internal rotation compared to the opposite side. 1 patient demonstrated asymptomatic minor in-toeing. Objective patellofemoral instability was not found except for in 1 patient with bilateral patellofemoral apprehension. FT was normalised (mean 16° ± 9°). Tibial torsion showed normal values. Compared to the opposite side TTTG ( > 0.08), patellar tilt ( > 0.09) and lateralisation ( > 0.26) did not differ. No complications occurred.

Conclusions: Subtrochanteric rotational osteotomy with hip arthroscopy improves the hip subjectively without leading to objective patellofemoral instability nor changes in the patellofemoral geometry compared to contralateral side. The technique of subtrochanteric rotational osteotomy is safe and reliable.
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http://dx.doi.org/10.1177/1120700020943811DOI Listing
August 2020

Mal-angulation of femoral rotational osteotomies causes more postoperative sagittal mechanical leg axis deviation in supracondylar than in subtrochanteric procedures.

J Exp Orthop 2020 Jul 1;7(1):46. Epub 2020 Jul 1.

Department of Orthopedics, Balgrist University Hospital, University of Zurich, Forchstrasse 340, 8008, Zürich, Switzerland.

Purpose: Alteration of the postoperative frontal mechanical leg axis is a known problem in femoral rotational osteotomies. However, the maintenance of the sagittal mechanical leg axis seems also important. Goal of this study was to investigate the impact of femoral rotational osteotomies on the sagittal mechanical leg axis and to identify the degree of mal-angulation of the osteotomy planes that alter the postoperative sagittal alignment relevantly.

Methods: Using 3D bone models of two patients with a pathologic femoral torsion (42° antetorsion and 6° retrotorsion), subtrochanteric and supracondylar rotational osteotomies were simulated first with an osteotomy plane perpendicular to the mechanical femoral axis (baseline osteotomy plane), second with predefined mal-angulated osteotomy planes. Subsequently, five different degrees of rotation were applied and the postoperative deviations of the sagittal mechanical leg axes were analyzed.

Results: Using the baseline osteotomy plane, the sagittal mechanical leg axis changed by 0.4° ± 0.5° over both models. Using the mal-angulated osteotomy planes, maximum deviation of the sagittal mechanical leg axis of 4.0° ± 1.2° and 11.0° ± 2.0° was observed for subtrochanteric and for supracondylar procedures, respectively. Relevant changes of more than 2° were already observed with mal-angulation of 10° in the frontal plane and 15° of rotation in supracondylar procedures.

Conclusion: Relevant changes of the postoperative sagittal mechanical leg axis could be observed with just slight mal-angulation of the osteotomy planes, in particular in supracondylar procedures and in cases with higher degrees of rotation. However, osteotomies perpendicular to the femoral mechanical axis showed no relevant alterations.
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http://dx.doi.org/10.1186/s40634-020-00262-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7326744PMC
July 2020

FAI morphology increases the risk for osteoarthritis in young people with a minimum follow-up of 25 years.

Arch Orthop Trauma Surg 2021 Jul 29;141(7):1175-1181. Epub 2020 Jun 29.

Department of Orthopaedics, Balgrist University Hospital, University of Zurich, Forchstrasse 340, 8008, Zurich, Switzerland.

Introduction: The mechanical conflict in symptomatic femoroacetabular impingement can lead to early osteoarthritis. However, radiographic impingement morphology is often seen in asymptomatic individuals. Long-term observation regarding the risk of developing osteoarthritis in these individuals is lacking. Our study addressed the following questions: Does femoroacetabular impingement morphology increase the risk for development of osteoarthritis after at least 25 years? If yes, which radiographic parameter is the most predictive? Does the level of activity influence the risk for development of osteoarthritis? Are PROM influenced by the grade of osteoarthritis in this population?

Methods: We investigated 51 (32 male, 19 female) patients for whom AP pelvis and Dunn view radiographs were available with a minimum follow-up of 25 years. Alpha angle in AP pelvis and Dunn view radiographs, femoral torsion in Dunn view, lateral center edge angle, cross-over sign, posterior wall sign and prominence of ischial spine sign in AP pelvis radiographs were determined. On the follow-up radiographs, osteoarthritis was graded. Tegner Score for the time of the index radiograph was evaluated. Harris Hip Score and Western Ontario and McMaster Universities Osteoarthritis Index were assessed at latest follow-up.

Results: The mean follow-up was 43 years (range 25-58). Cam impingement morphology showed to increase the risk for development of osteoarthritis: Alpha angles of ≥ 55° on AP pelvis and Dunn view radiographs were associated risk factors and showed an OR of 1.05 (p = 0.002) and 1.10 (p = 0.001), respectively. Abnormal femoral torsion and acetabular retroversion were not risk factors for osteoarthritis. Tegner Score at index presentation, HHS and WOMAC Score did not correlate with the grade of osteoarthritis.

Conclusion: This study showed that cam impingement morphology in young patients raises the risk for development of hip osteoarthritis by 5-10% in a long-term follow-up with a minimum of 25 years, thus its contribution was small.
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http://dx.doi.org/10.1007/s00402-020-03522-3DOI Listing
July 2021

Impact of stem design and cementation on postoperative femoral antetorsion in 227 patients with total hip arthroplasty (THA).

Skeletal Radiol 2020 Dec 25;49(12):2001-2009. Epub 2020 Jun 25.

Department of Radiology, Balgrist University Hospital, University of Zurich, Forchstrasse 340, 8008, Zurich, Switzerland.

Objective: In total hip arthroplasty (THA), surgeons attempt to achieve a physiological antetorsion. However, postoperative antetorsion of the femoral stem is known to show large variabilities. The purpose of this study was to assess whether postoperative antetorsion is influenced by stem design or cementation.

Materials And Methods: This retrospective study included 227 patients with a hip prosthesis with five different stem designs (S1: short curved, S2 and S3: standard straight, S4: standard straight collared, S5: cemented straight), who had metal suppressed 1.5T-MRI of the hip between February 2015 and October 2019. Measurement of femoral antetorsion was done independently by two fellowship-trained radiologists on axial images by measuring the angle between the long axis of the femoral neck and the posterior condylar tangent of the knee. Measured angles in the different groups were compared using the t test for independent samples.

Results: The cementless collared stem S4 showed the highest antetorsion with 18.1° (± 10.5°; range -10°-45°), which was significantly higher than the antetorsion of the collarless S3 with 13.3° (± 8.4°; - 4°-29°) and the cemented S5 with 12.7° (± 7.7°; - 3°-27°) with p = 0.012 and p = 0.007, respectively. S1 and S2 showed an antetorsion of 14.8° (± 10.0°; 1°-37°) and 14.1° (± 12.2°; - 20°-41°). The torsional variability of the cementless stems (S1-4) was significantly higher compared with that of the cemented S5 with a combined standard deviation of 10.5° and 7.7° (p = 0.019).

Conclusion: Prosthesis design impacts the postoperative femoral antetorsion, with the cementless collared stem showing the highest antetorsion. Cemented stems demonstrated significantly lower variability, suggesting the lowest rate of inadvertent malrotation.
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http://dx.doi.org/10.1007/s00256-020-03483-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7652799PMC
December 2020

The Lisbon Agreement on Femoroacetabular Impingement Imaging-part 1: overview.

Eur Radiol 2020 Oct 17;30(10):5281-5297. Epub 2020 Jul 17.

Universitair Ziekenhuis Brussel, Brussels, Belgium.

Objectives: Imaging assessment for the clinical management of femoroacetabular impingement (FAI) syndrome remains controversial because of a paucity of evidence-based guidance and notable variability in clinical practice, ultimately requiring expert consensus. The purpose of this agreement is to establish expert-based statements on FAI imaging, using formal techniques of consensus building.

Methods: A validated Delphi method and peer-reviewed literature were used to formally derive consensus among 30 panel members (21 musculoskeletal radiologists and 9 orthopaedic surgeons) from 13 countries. Forty-four questions were agreed on, and recent relevant seminal literature was circulated and classified in five major topics ('General issues', 'Parameters and reporting', 'Radiographic assessment', 'MRI' and 'Ultrasound') in order to produce answering statements. The level of evidence was noted for all statements, and panel members were asked to score their level of agreement with each statement (0 to 10) during iterative rounds. Either 'consensus', 'agreement' or 'no agreement' was achieved.

Results: Forty-seven statements were generated, and group consensus was reached for 45 (95.7%). Seventeen of these statements were selected as most important for dissemination in advance. There was no agreement for the two statements pertaining to 'Ultrasound'.

Conclusion: Radiographic evaluation is the cornerstone of hip evaluation. An anteroposterior pelvis radiograph and a Dunn 45° view are recommended for the initial assessment of FAI although MRI with a dedicated protocol is the gold standard imaging technique in this setting. The resulting consensus can serve as a tool to reduce variability in clinical practices and guide further research for the clinical management of FAI.

Key Points: • FAI imaging literature is extensive although often of low level of evidence. • Radiographic evaluation with a reproducible technique is the cornerstone of hip imaging assessment. • MRI with a dedicated protocol is the gold standard imaging technique for FAI assessment.
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http://dx.doi.org/10.1007/s00330-020-06822-9DOI Listing
October 2020

Hip arthroscopy versus total hip arthroplasty in patients above 40 differences: outcome and residual complain.

Eur J Orthop Surg Traumatol 2020 Oct 4;30(7):1187-1192. Epub 2020 May 4.

Departments of Orthopedics, Schulthess Klinik, Lengghalde 2, 8008, Zürich, Switzerland.

This study aimed to compare patient outcomes and residual complains after hip arthroscopy (HAS) and total hip arthroplasty (THA) to improve patient counseling. It includes 140 hips/129 HAS-patients and 77 hips/62 THA-patients aged 40 to 55 years with a BMI under 30. All patients underwent primary HAS or primary THA in our hospital from 2007 until 2014. Exclusion criteria were a history of prior hip surgery or suffering sequels of childhood's hip disease, systemic inflammatory disease or avascular hip osteonecrosis. Outcome measures were WOMAC, subjective hip value, residual complains, the need of infiltrations and the complication and conversion rate. Patient data and scores were collected pre-operative, after one year and at the last follow-up. Scores indicated significant patient benefits in both groups (p < 0.0001). Variability of outcome was significantly higher and less predictable in the HAS group (HAS: 1.9 vs. THA: 0.9). While THA showed significant improvement mainly after one year, HAS showed significant improvements after one year and the latest follow-up. Residual complains were more frequent after HAS (p = 0.026). Groin pain was the main complain after HAS, limping and disturbing leg length discrepancy after THA. THA more predictably improves patient's outcome with shorter recovery time. Limping and leg length discrepancy are predominant after THA.
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http://dx.doi.org/10.1007/s00590-020-02678-3DOI Listing
October 2020

Alpha-defensin lateral flow test does not appear to be useful in predicting shoulder periprosthetic joint infections.

Int Orthop 2020 06 14;44(6):1023-1029. Epub 2020 Mar 14.

Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.

Purpose: Periprosthetic joint infections (PJIs) remain a challenging complication after shoulder arthroplasty. The antimicrobial peptide α-defensin has been proposed as a new synovial fluid biomarker in diagnosing PJIs. To date, only little data are available on the diagnostic accuracy of α-defensin in shoulder PJIs; thus, we aimed to evaluate its diagnostic value in a cohort of patients with a suspected shoulder PJI.

Methods: Between June 2016 and June 2018, we prospectively enrolled patients with a diagnostic shoulder aspiration due to painful shoulder arthroplasty or planned revision surgery. PJI diagnostics were performed according to the Musculoskeletal Infection Society (MSIS) criteria. All patients with an antibiotic therapy within two  weeks before enrollment, insufficient amount of synovial aspirate, or bloody aspiration were excluded. α-Defensin was measured in the synovial fluid using the α-defensin lateral flow (ADLF) test (Synovasure®).

Results: Out of 60 patients, we could include 29 (59% female) patients with a mean age of 70 (range, 50-92) years. A shoulder PJI was detected in five cases (Staphylococcus aureus, n = 2; Staphylococcus epidermidis, n = 2; Cutibacterium acnes, n = 1). The ADLF test was positive in seven out of 29 cases. According to the MSIS criteria, the ADLF test was false-negative in two patients and false-positive in four patients, resulting in sensitivity, specificity, and positive and negative predictive value of 60%, 83%, 43%, and 91%, respectively. The overall accuracy was 79%.

Conclusion: The ALDF test does not appear to be useful in predicting shoulder PJIs but may be used as an additional diagnostic factor in rejecting these infections.
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http://dx.doi.org/10.1007/s00264-020-04532-xDOI Listing
June 2020

The impact of mal-angulated femoral rotational osteotomies on mechanical leg axis: a computer simulation model.

BMC Musculoskelet Disord 2020 Jan 23;21(1):50. Epub 2020 Jan 23.

Department of Orthopedics, Balgrist University Hospital, University of Zurich, Forchstrasse 340, 8008, Zürich, Switzerland.

Background: Subtrochanteric or supracondylar femoral rotational osteotomies are established surgical treatments for femoral rotational deformities. Unintended change of the mechanical leg axis is an identified problem. Different attempts exist to plan a correct osteotomy plane, but implementation of the preoperative planning into the surgical situation can be challenging. Goal of this study was to identify the critical threshold of mal-angulation of the osteotomy plane and of femoral rotation that leads to a relevant deviation of the postoperative mechanical leg axis using a computer simulation approach.

Methods: Three-dimensional (3D) surface models of the lower extremity of two patients (Model 1: 42° femoral antetorsion; Model 2: 6° femoral retrotorsion) were generated from computed tomography data. First, baseline subtrochanteric and supracondylar rotational osteotomies, perpendicular to the femoral mechanical axis were simulated. Afterwards, mal-angulated osteotomies in sagittal and frontal plane followed by different degrees of rotation were simulated and frontal mechanical axis was analyzed.

Results: 400 mal-angulated osteotomies have been simulated. Mal-angulation of ±30° with 30° rotation showed maximum deviation from preoperative mechanical axis in subtrochanteric osteotomies (4.0° ± 0.4°) and in supracondylar osteotomies (12.4° ± 0.8°). Minimal mal-angulation of 15° in sagittal plane in subtrochanteric osteotomies and mal-angulation of 10° in sagittal plane in supracondylar osteotomies altered the mechanical axis by > 2°. Mal-angulation in sagittal plane showed higher deviations of the mechanical axis (up to 12.4° ± 0.8°), than in frontal plane mal-angulation (up to 4.0° ± 1.9°).

Conclusion: A femoral rotational osteotomy, perpendicular to the femoral mechanical axis, has no considerable influence on the mechanical leg axis. However, mal-angulation of femoral rotational osteotomies showed relevant changes of the mechanical leg axis. In supracondylar respectively subtrochanteric procedures, mal-angulation of only 10° in combination with already 15° of femoral rotation respectively mal-angulation of 15° in combination with 30° of femoral rotation, can lead to a relevant postoperative mechanical leg axis deviation of more than 2°, wherefore these patients probably would benefit from the use of navigation aids.
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http://dx.doi.org/10.1186/s12891-020-3075-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6979061PMC
January 2020

MRI with state-of-the-art metal artifact reduction after total hip arthroplasty: periprosthetic findings in asymptomatic and symptomatic patients.

Eur Radiol 2020 Apr 20;30(4):2241-2252. Epub 2019 Dec 20.

Radiology, Balgrist University Hospital, University of Zurich, Forchstrasse 340, CH-8008, Zurich, Switzerland.

Objectives: To assess the spectrum of periprosthetic MRI findings after primary total hip arthroplasty (THA).

Methods: This multi-center cohort study analyzed 31 asymptomatic patients (65.7 ± 12.7 years) and 27 symptomatic patients (62.3 ± 11.9 years) between 6 months and 2 years after THA. 1.5-T MRI was performed using Compressed Sensing SEMAC and high-bandwidth sequences. Femoral stem and acetabular cup were assessed for bone marrow edema, osteolysis, and periosteal reaction in Gruen zones and DeLee and Charnley zones. Student t test and Fisher's exact test were performed.

Results: The asymptomatic and symptomatic groups showed different patterns of imaging findings. Bone marrow edema was seen in 19/31 (61.3%) asymptomatic and 22/27 (81.5%) symptomatic patients, most commonly in Gruen zones 1, 7, and 8 (p ≥ 0.18). Osteolysis occurred in 14/31 (45.2%) asymptomatic and 14/27 (51.9%) symptomatic patients and was significantly more common in Gruen zone 7 in the symptomatic group (8/27 (29.6%)) compared to the asymptomatic group (2/31 (6.5%)) (p = 0.03). Periosteal reaction was present in 4/31 asymptomatic (12.9%) and 9/27 symptomatic patients (33.3%) and more common in Gruen zones 5 and 6 in the symptomatic group (p = 0.04 and 0.02, respectively). In the acetabulum, bone marrow edema pattern was encountered in 3/27 (11.1%) symptomatic patients but not in asymptomatic patients (p ≥ 0.21). Patient management was altered in 8/27 (29.6%) patients based on MRI findings.

Conclusions: Periprosthetic bone marrow edema is common after THA both in asymptomatic and symptomatic patients. Osteolysis and periosteal reaction are more frequent in symptomatic patients. MRI findings led to altered patient management in 29.6% of patients.

Key Points: • Bone marrow edema pattern was frequent in both asymptomatic and symptomatic patients after THA, particularly around the proximal femoral stem in Gruen zones 1, 7, and 8. • Osteolysis was significantly more frequent in symptomatic patients in Gruen zone 7. • Periosteal reaction occurred more frequently in symptomatic patients in Gruen zones 5 and 6.
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http://dx.doi.org/10.1007/s00330-019-06554-5DOI Listing
April 2020

Periacetabular osteotomy using three-dimensional cutting and reposition guides: a cadaveric study.

J Hip Preserv Surg 2019 Dec 24;6(4):411-420. Epub 2019 Oct 24.

Department of Orthopaedics, University of Zürich, Balgrist Hospital, Zürich 8032, Switzerland.

The goal of periacetabular osteotomy (PAO) is to reorient the acetabulum in a more physiological position. Its realization remains challenging regarding the final position of the acetabulum. Assistance with custom cutting- and reorientation-guides would thus be very helpful. Our purpose is to present a pilot study on such guides. Eight cadaveric hemipelvis were scanned using CT. After segmentation, 3D models of each specimen were created, a PAO was virtually performed and reorientation of the acetabula were defined. A specific guide was designed aiming to assist in iliac, posterior column and superior pubic ramus cuts as well as in acetabulum reorientation. Furthermore, the acetabular position was planned. Three-dimensional printed guides were used to perform PAO using the modified Smith-Peterson approach. The post-operative CT images and virtually planned acetabulum reorientation were compared in terms of acetabular index (AC), lateral centre edge angle (LCE), acetabular anteversion angle (AcetAV). There was no intra-articular or posterior column fracture seen. Two cadavers showed very low bone quality with insufficient stability of fixation and were excluded from further analysis. Correlation between the post-operative result and planning of the six included cadavers revealed the following mean deviations: 5° (SD ±3°) for AC angle, 6° (SD ±4°) for LCE angle and 15° (SD ±11°) for AcetAV angle. The use of 3D cutting and reorientation blocks for PAO was possible through a modified Smith-Peterson approach and revealed accurate fit to bone, accurate positioning of the osteotomies and acceptable planned corrections in cadavers with good bone quality.
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http://dx.doi.org/10.1093/jhps/hnz051DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7869095PMC
December 2019

Total hip arthroplasty with accolade/trident through the direct minimally invasive anterior approach without traction table: Learning curve and results after a minimum of 5 years.

Orthop Traumatol Surg Res 2019 09 26;105(5):931-936. Epub 2019 Jun 26.

Department of Orthopaedics, Balgrist University Hospital, University of Zurich, 8008 Zurich, Switzerland.

Background: The direct minimally invasive anterior approach (DMIAA) in total hip arthroplasty (THA) is widely accepted. In our department the DMIAA according to Rachbauer together with the Trident cup and Accolade stem was introduced in 2004. The purpose of the study was to demonstrate the five-year results and to analyze the learning curve of a new introduced approach.

Patients And Methods: Between July 2004 and May 2006, a consecutive series of 151 THA in 147 patients was retrospectively analyzed. All patients were planned to received a THA with the Accolade/Trident implant system using the DMIAA without traction table. Clinical and radiographic data, complications and survivorship were documented with a follow-up of at least 5 years.

Results: Regarding cup implantation, there were 11 (7.3%) failed intentions to treat due to missing pressfit (8 cases) and acetabular floor perforation (3 cases). No failed intentions to treat occurred during stem implantation. Total implant survival after 5 years follow-up after exclusion of 11 cases with failed intention to treat (N=140) was 96.9% (SD 1.4; CI 94.3-99.6). After exclusion of the failed intentions to treat (N=140, N=4 in the first 20 cases), there was significant (p<0.001) difference between the first 16 implants with a 5 year-survival of 83.2% (SD 8.6; CI 66.4-100) and 95.7% (SD 0.9; CI 93.9-97.5) for the following 124 implants. Radiolucent lines were observed in Gruen zone 1 in 3.3% and in Gruen zone 1 and 2 in 1.1%.

Discussion: THA with Accolade/Trident using the DMIAA without traction table according to Rachbauer temporary exposed patients to a higher risk of implant revisions, which was normalized after the first 20 cases. Results of the learning curve are comparable to other techniques using an orthopaedic traction table. After the typical learning curve, the rate of 5 years implant failure is in accordance with the registry data for non-cemented implants. The Accolade stem showed minimal radiographic signs of radiolucency.

Level Of Evidence: IV, retrospective, consecutive case series.
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http://dx.doi.org/10.1016/j.otsr.2019.05.008DOI Listing
September 2019

Acetabular coverage differs between standing and supine positions: model-based assessment of low-dose biplanar radiographs and comparison with CT.

Eur Radiol 2019 Oct 22;29(10):5691-5699. Epub 2019 Mar 22.

Department of Radiology, University Hospital Balgrist, Forchstrasse 340, CH-8008, Zurich, Switzerland.

Objectives: To evaluate the feasibility of 2D and 3D acetabular coverage assessments based on low-dose biplanar radiographs (BPR) in comparison with CT, and to demonstrate the influence of weight-bearing position (WBP) on anterior and posterior acetabular coverages.

Methods: Fifty patients (21 females, 29 males) underwent standing BPR and supine CT of the pelvis. Using dedicated software, BPR-based calculations of anterior and posterior 2D coverages and anterior, posterior, and global 3D coverages were performed in standardized anterior pelvic plane (APP) and WBP. CT-based anterior and posterior 2D coverages and global 3D coverage was calculated in APP and compared with BPR-based data. Statistics included intraclass correlation coefficients (ICC) and Bland-Altman plots.

Results: Mean anterior 2D coverage was 21.2% (standard deviation, ± 7.4%) for BPR and 23.8% (± 8.4%) for CT (p = 0.226). Mean posterior 2D coverage was 54.2% (± 9.8%) for BPR and 61.7% (± 9.7%) for CT (p = 0.001). Mean global 3D coverage was 46.5% (± 3.0%) for BPR and 45.6% (± 3.6%) for CT (p = 0.215). The inter-method reliability between CT and BPR and inter-reader reliability for BPR-based measurements were very good for all measurement (all ICC > 0.8). Based on BPR, mean anterior and posterior 3D coverages were 20.5% and 26.0% in WBP and APP, while 25 patients increased anterior and 24 patients increased posterior 3D coverage from APP to WBP with a relative change of coverage of up to 11.9% and 10.0%, respectively.

Conclusions: 2D and 3D acetabular coverages can be calculated with very good reliability based on BPR. The impact of standing position on acetabular coverage can be quantified with BPR on an individual basis.

Key Points: • 2D and 3D acetabular coverages can be calculated with very good reliability based on biplanar radiographs in comparison with CT. • The impact of standing position on anterior and posterior acetabular coverages can be quantified with BPR on an individual basis.
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http://dx.doi.org/10.1007/s00330-019-06136-5DOI Listing
October 2019

Uncemented Total Hip Arthroplasty Through the Direct Anterior Approach: Analysis of a Consecutive Series of 275 Hips With a Minimum Follow-Up of 10 Years.

J Arthroplasty 2019 06 31;34(6):1132-1138. Epub 2019 Jan 31.

Department of Orthopaedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland.

Background: The purpose of this study was to document complications, outcomes, and 10-year survivorship of primary total hip arthroplasty (THA) using a direct anterior approach with an uncemented, straight, hydroxyapatite-coated stem and an uncemented cup.

Methods: A retrospective, consecutive series of 275 primary THAs through a direct anterior approach with traction table using Medacta Versafit cup and Quadra-H stem with a minimum of 10-year follow-up was identified. The cumulative 10-year survival of the implants was estimated using Kaplan-Meier estimator. All complications, reoperations, and failures were analyzed. Subjective and clinical outcomes (Subjective Hip Value, Western Ontario and McMaster Universities Osteoarthritis Index, and Harris Hip Score) were measured.

Results: Of 256 patients (275 hips, 143 men and 113 women) with a mean age of 63 (range, 24-85) years, 48 (19%) patients (52 hips) deceased not related to the surgery after a mean time 49 months (range, 3-118) postoperatively. At >10-year follow-up, 9 THAs were revised. The overall implant survival rate was 96.8% (95% confidence interval, 94.4-98.7) at 10 years. One cup and 1 stem were revised because of aseptic loosening. At the last follow-up, the median Subjective Hip Value was 90% (range, 20-100), the Western Ontario and McMaster Universities Osteoarthritis Index score reached a median of 0.2 points (range, 0-6.3), and the median Harris Hip Score points was 99 (range, 29-100).

Conclusion: Primary THA through an anterior minimal invasive approach with the mentioned implants showed low revision rates and good to excellent clinical outcome after at least 10 years.
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http://dx.doi.org/10.1016/j.arth.2019.01.062DOI Listing
June 2019

Validation of a Virtual Reality-Based Hip Arthroscopy Simulator.

Arthroscopy 2019 03 4;35(3):789-795. Epub 2019 Feb 4.

Department of Orthopaedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland.

Purpose: To assess construct and face validity of a novel virtual reality-based hip arthroscopy simulator using the previously validated Arthroscopic Surgery Skills Evaluation Tool (ASSET), metric parameters, and a questionnaire.

Methods: Metric parameters including task completion time, camera path, and grasper path were recorded, and the ASSET score was used to assess construct validity. Face validity was evaluated using a questionnaire.

Results: Nine hip arthroscopy experts, of whom the majority performed more than 200 procedures (age, 48 ± 7.3; range, 38-61 years; 8 men, 1 woman), and 33 nonexperts (age, 33 ± 7.9; range, 26-62 years; 25 men, 8 women) performed 3 individual tasks on a virtual reality-based arthroscopy simulator of a left hip. The ASSET global rating scale showed a statistically significant difference between the hip arthroscopy expert and the nonexpert group, indicating strong construct validity (25.0 in the expert group, range, 17-34, versus 15.30 in the nonexpert group, range, 8-30 [P < .001], respectively). This also applied to most metric parameters recorded by the simulator. The simulator also demonstrated high face validity. The overall impression in terms of realism was graded "completely realistic" by 17% and "close to realistic" by 62% of participants.

Conclusions: The tested simulator demonstrated high construct and face validity.

Clinical Relevance: This study demonstrates the construct and face validity of a novel hip arthroscopy simulator. The device proved to be an adequate model for the simulation of some arthroscopic procedures of the hip.
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http://dx.doi.org/10.1016/j.arthro.2018.10.131DOI Listing
March 2019

Species Rarely Cause Orthopedic Infections.

J Clin Microbiol 2018 12 27;56(12). Epub 2018 Nov 27.

Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, University of Zurich, Zurich, Switzerland

spp. are rarely considered pathogens, but data on spp. as a cause of orthopedic infections are sparse. Therefore, we asked how often spp. caused an infection in a defined cohort of orthopedic patients with a positive culture. In addition, we aimed to determine the species variety and the susceptibility of isolated strains to define potential treatment strategies. We retrospectively assessed all bone and joint samples that were collected between 2006 and 2015 from an orthopedic ward and that were positive for spp. by culture. The isolates were considered relevant to an infection if the same sp. was present in at least two samples. We found 97 orthopedic cases with isolation of spp. (128 positive samples). These were mainly ( = 26), ( = 17), ( = 13), and ( = 11). Compared to the species found in a cohort of patients with positive blood cultures hospitalized in nonorthopedic wards, we found significantly more - and -positive cases but no -positive cases in our orthopedic cohort. Only 16 out of 66 cases (24.2%) with an available diagnostic set of at least two samples had an infection. Antibiotic susceptibility testing (AST) showed various susceptibility results for all antibiotics except vancomycin and linezolid, to which 100% of the isolates were susceptible. The rates of susceptibility of corynebacteria isolated from orthopedic samples and of isolates from blood cultures were comparable. In conclusion, our study results confirmed that a sp. is most often isolated as a contaminant in a cohort of orthopedic patients. AST is necessary to define the optimal treatment in orthopedic infections.
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http://dx.doi.org/10.1128/JCM.01200-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6258853PMC
December 2018

Do osteoarthritic subchondral bone cysts spontaneously consolidate after total hip replacement?

Hip Int 2019 Jul 26;29(4):398-404. Epub 2018 Jul 26.

2 Orthopaedic Department, Balgrist University Hospital, University of Zurich, Switzerland.

Background: During total hip replacement (THR), subchondral acetabular bone cysts are either left alone or treated by filling with autologous bone graft. We hypothesized that subchondral cysts would consolidate spontaneously over time without compromising the midterm survival of the implant.

Methods: We retrospectively screened the anteroposterior hip radiographs of 731 consecutive patients who underwent primary THR between January 2006 and April 2009. Patients were included in the current study if they had acetabular subchondral bone cysts visible radiographically that had been left alone during THR.

Results: 52 patients (54 hips) matched the inclusion criteria, with mean age of 66 ± 11 years at surgery, and a mean follow-up of 6.3 years (range 5-9 years). Among the 52 patients, there were 88 cysts, with 1.6 ± 0.83 cysts per patient and a mean cyst size of 9.3 ± 10 mm (range 0.9-57 mm). Among the 88 cysts, 71 cysts (38 hips) had disappeared by the final follow-up, whereas 17 cysts (16 hips) were still visible. Most of these persistent cysts were located in Charnley zone I and were significantly smaller at the follow-up than before surgery ( = 0.015). Overall, most cysts decreased in size ( = 0.04). All cups survived and none showed radiological signs of loosening.

Conclusions: After THR, most neglected subchondral cysts spontaneously consolidate or decrease in size. Larger cysts may persist without affecting the surgical outcome. No radiological signs of loosening or other adverse effects were observed when acetabular bone cysts are neglected during primary THR.
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http://dx.doi.org/10.1177/1120700018787108DOI Listing
July 2019

Association of Cutibacterium avidum Colonization in the Groin With Obesity: A Potential Risk Factor for Hip Periprosthetic Joint Infection.

Clin Infect Dis 2018 11;67(12):1878-1882

Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich.

Background: An increase in the incidence of hip periprosthetic joint infections caused by Cutibacterium avidum has recently been detected after hip arthroplasty with an anterior surgical approach. We raised the question of whether skin colonization with C. avidum differs between the anterior and the lateral thigh as areas of surgical incision fields.

Methods: Between February and June 2017, we analyzed skin scrapings from the groin and the anterior and lateral thigh in patients undergoing a primary hip arthroplasty. We anaerobically cultured plated swab samples for Cutibacterium spp. for ≥7 days. Univariate logistic regression analysis was used to explore associations between body mass index (BMI) and colonization rate at different sites.

Results: Twenty-one of 65 patients (32.3%) were colonized with C. avidum at any site, mainly at the groin (n = 16; 24.6%), which was significantly higher at the anterior (n = 5; 7.7%; P = .009) or lateral (n = 6; 9.2%; P = .02) thigh. Patients colonized with C. avidum did not differ from noncolonized patients in age or sex, but their BMIs were significantly higher (30.1 vs 25.6 kg/m2, respectively; P = .02). Furthermore, increased BMI was associated with colonization at the groin (odds ratio per unit BMI increase, 1.15; 95% confidence interval; 1.03-1.29; P = .01).

Conclusions: The groin, rather than the anterior thigh, showed colonization for C. avidum in obese patients. Further studies are needed to evaluate current skin disinfection and draping protocols for hip arthroplasty, particularly in obese patients.
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http://dx.doi.org/10.1093/cid/ciy379DOI Listing
November 2018