Complications and Revisions in Metal-Backed Anatomic Total Shoulder Arthroplasty: A Comparative Study of Revision Rates Between Stemless and Stemmed Humeral Components.

BACKGROUND: The primary objective of this study was to evaluate and compare the incidence of complications and revision surgeries between in two of convertible metal-back glenoid systems in total shoulder arthroplasty (aTSA) groups over a follow-up period of up to five years. METHODS: A retrospective analysis included 69 shoulders from 65 patients with primary aTSA. Patients were divided into Group 1 (n=31), receiving convertible cementless stemmed aTSA (Lima SMR) and Group 2 (n=38), receiving humeral head replacement aTSA (Arthrex, Eclipse) both with metal-back glenoid components. Clinical and radiological assessments were conducted at 2, 5, and 10 years postoperatively. Assessments included the following: Constant Score, DASH, SPADI, SSV, Glenohumeral Distance, Critical Shoulder Angle and Lateral Acromion Index. In addition, we compared complications, revision rates and survival rates between groups using Kaplan-Maier curves and Log-Rank-test. RESULTS: Baseline demographics and preoperative outcome scores showed no significant differences between groups (p≥0.05). The overall revision rate did not significantly differ between groups (Group 1:32% vs. Group 2:24%, p=0.60), nor did the mean time to revision (p=0.27). The mean follow-up was 71±41 months (Group 1: 94±48 months, Group 2: 53±23 months, p<0.001). Kaplan-Meier analysis showed similar mid-term survival probabilities (p=0.94). Revision reasons included rotator cuff insufficiency (n=4 in Group 1, n=2 in Group 2) and glenoid wear/loosening (n=5 in Group 1, n=7 in Group 2). Interestingly, Group 1 demonstrated no occurrence of glenoid metal baseplate or humeral loosening, while complex revisions were more common in the Group 2. At 2 and 5 years, non-revised patients in both groups had similar outcome scores. CONCLUSION: Metal-backed glenoid implants in combination with both stemless and stemmed humeral components in aTSA exhibit comparable revision rates and survival probabilities. Rotator cuff insufficiency and polyethylene wear are the two most common complications leading to revision. To facilitate ongoing monitoring and optimize patient safety, we implemented a modification in the follow-up protocol, transitioning to annual appointments or earlier when necessary. This study underscores the unsolved disadvantages in metal-back components and the importance of a mid- to long-term longitudinal assessment of those patients.

[Reverse Shoulder Arthroplasty - Current Concepts]. / Inverse Schulterendoprothetik ­ aktueller Stand.

Due to first promising long term outcome data, reverse shoulder arthroplasty experienced an immense increase of usage during the past decade. Moreover, the initial Grammont concept has constantly been refined and adapted to current scientific findings. Therefore, clinical and radiological problems like scapular notching and postoperative instability were constantly addressed but do still remain an area of concern.This article summarises current concepts in reverse shoulder arthroplasty and gives an overview of actual indications like cuff tear arthropathy, severe osteoarthritis, proximal humerus fractures, tumours, fracture sequelae as well as revision surgery and their corresponding clinical and radiological results.

[Management of muscle trauma in popular sports]. / Management des Muskeltraumas im Breitensport.

Muscle injuries make up the majority of injuries in popular sports. The causes for the development are multifactorial and can be divided into functional disorders and a lack of knowledge regarding training control. Insufficient warm-up and overtraining both increase the danger of the occurrence of the injury. Knowledge of the different types of muscle injuries and their incorporation into an exact classification enable the establishment of a correct treatment plan and can have a positive influence on the healing process. In addition to acute treatment the knowledge and application of preventive programs are necessary as these can significantly reduce the prevalence of muscle injuries in sports.

Implant-dependent behavior of tunnel widening and clavicular button migration after arthroscopic-assisted treatment of acromioclavicular joint instabilities.

INTRODUCTION: Despite ongoing discussions for the previous few decades, there is still no consensus regarding the optimal surgical technique for acromioclavicular joint instabilities. The purpose of this study was to determine the impact of various implant materials following arthroscopically assisted stabilization of acromioclavicular joint instabilities on tunnel widening and implant migration. We hypothesized an implant-dependent behavior for tunnel widening and implant migration with differences when comparing acute and chronic acromioclavicular joint instabilities. METHODS: This study compared 105 patients with acromioclavicular joint instabilities that were managed operatively with coracoclavicular double button constructs. Two of the groups containing acute cases were treated with either a double button construct with a wire (TR) or a tape (D) as a central pillar. The two groups with chronic cases were either treated with a wire (T+) or tape D+ as a central pillar and additional hamstring tendon augmentation (+). One central transclavicular-transcoracoidal drill channel was made in the acute cases, while additional medial and lateral drill channels to augment the central pillar with the hamstring tendon were made. The central drill channel in all cases and the medial/lateral drill channels in chronic cases were subsequently radiologically analyzed immediately postoperatively and at follow-up. Following this, additional radiological analysis of the implant migration of the clavicular button took place. RESULTS: All groups showed significant tunnel widening of the central drill channel at follow-up (p ≤ 0.001). The TR+ technique demonstrated significant widening in both the medial (p ≤ 0.001) and lateral (p ≤ 0.001) drill channels. The D and D+ group displayed significant higher rates of clavicular button migration to a cortical and intraosseous level (p ≤ 0.002). CONCLUSION: Tunnel widening and implant migration following arthroscopically assisted management of acromioclavicular joint instabilities are dependent on the chosen implant. The stable tape showed a significantly increased degree of tunnel widening with respect to the central drill channel in comparison with the wire. In contrast, a higher degree of load capacity of the tape ultimately favors a protected intraosseous graft healing for chronic cases, which leads to less tunnel widening of the medial and lateral drill channel. Finally, the D/D+ implant groups showed higher rates of implant migration due to lower contact surface area of the implant at the upper clavicular cortex.

Minimum 2-year results of the second-generation CFR-PEEK locking plate on the proximal humeral fracture.

PURPOSE: The aim of this study was to analyse and compare the 24-month range of motion results of patients treated with CFR-PEEK2 versus conventional titanium plate osteosyntheses (TAL-P). We hypothesized similar clinical outcomes but a better range of motion in the CFR-PEEK2 group than the TAL-P group in the 2-year follow-up. METHODS: This retrospective study analysing prospectively collected data included all patients that presented with a PHF and were treated with CFR-PEEK2 between November 2016 and April 2018. Follow-up was performed after a minimum of 24 months, evaluating the functional degree of movement functional scores, including the Subjective Shoulder Value (SSV) as well as an age- and sex-adapted Constant-Murley score (CMS). The 2-year results were compared to the results of a matched pair group comprising patients that were treated with TAL-P during the same period. RESULTS: Of the 35 patients included (mean age: 61.2 [18-78] years), 30 (86%) patients completed the 24-month follow-up in the CFR-PEEK2-group. After 24 months, the mean CMS was 89.9 points (pt) (44.5-100 pt) and the mean SSV was 86.7% (35-100%). Compared to the matched-pair TAL-P cohort, the 24-month follow-up showed similar results (CMS: 88.6 pt. (40.5-100 pt.) [p = 0.9]; SSV: 76% (30-100%) [p = 0.05]). However, significantly better degrees of forward flexion and internal rotation as well as a better range of motion in abduction was recorded in patients treated with CFR-PEEK2 plates than TAL-P. CONCLUSION: At the 24-month follow-up, patients who received treatment with CFR-PEEK2 compared to those that received TAL-P showed enhanced range of motion whilst having similar clinical scores.

Superior clinical results for early arthroscopic treatment of grade IIIb and V acromioclavicular joint instability compared to delayed operative treatment.

BACKGROUND: Arthroscopy-assisted cortical fixation devices have been increasingly used in the operative management of both acute and chronic cases of acromioclavicular joint instability (ACJI). It has been hypothesized that delayed surgical management leads to inferior clinical and radiologic outcomes compared to acute treatment. The purpose of this study is to compare clinical and radiologic outcomes, scapula dyskinesia, and failure or revision rates of arthroscopically treated acute and chronic ACJI. METHODS: This retrospective study of prospectively collected data included all surgically treated patients with grade IIIb and V chronic ACJI between 2013 and 2017, matched 1:1 to a group of acute grade IIIb and V ACJI patients treated during the same time period. Chronic ACJI was defined as delayed surgical treatment >21 days after injury. Chronic cases received an additional hamstring autograft next to the suture pulley systems. Follow-up was obtained at an average of 3.2 years (range: 1.4-6.2). Clinical outcome scores included the Constant-Murley Score (CMS), Taft Score (TF), Nottingham Clavicle Score (NCS), ACJI Score, Sick Scapula Score (SSS), Subjective Shoulder Value (SSV), Subjective Shoulder Test (SST), American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES) score, and the visual analog scale pain score. Radiologic follow-up was obtained pre- and postoperatively and at final follow-up. The 2-year results were compared to the results of a 1:1 matched-pair group comprising patients who were treated with an acute ACJI during the same period. RESULTS: Thirty-three (80.5%) of 41 chronic ACJI cases were available for follow-up and were compared with 33 matched-pair cases of acute ACJI (of 41). The clinical scores were significantly better in the acute cohort for the CMS (92 ± 8 vs. 88 ± 8, P = .030), ASES (91 ± 13 vs. 85 ± 13, P = .002), SSS (1.4 ± 1.6 vs. 3.4 ± 2.5, P = .0004), NCS (86 ± 13 vs. 81 ± 13, P = .049), TF (9.9 ± 1.9 vs. 9.0 ± 2.1, P = .030), and ACJI (83 ± 13 vs. 75 ± 1, P = .003). In contrast to the chronic cohort, the acute cohort illustrated a significant loss of reduction at follow-up (P = .020). CONCLUSION: Based on the results of this study, early arthroscopy-assisted operative treatment of grade IIIb and V ACJIs seems superior to delayed surgical intervention of grade IIIb and V ACJIs. Furthermore, an additional autograft loop leads to less loss of reduction compared with suture pulley/suspensory loop fixation standalones.

Are Patient-Reported Outcome Scores a Reasonable Substitute for Clinical Follow-up After Surgically Managed Acromioclavicular Joint Injuries?

Background: Various clinical outcome scores have been described to evaluate postoperative shoulder function after operatively treated acromioclavicular joint (ACJ) instability. Clinical outcome scores can be divided between patient-reported outcome measures (PROMs) and examiner-dependent outcome measures (EDOMs) after a clinical examination by a physician. The correlation between PROMs and EDOMs, and thus their interchangeability with regard to operatively treated ACJ instability, has not yet been evaluated. Purpose: To investigate whether PROMs are a reasonable substitute for EDOMs. Correlations between global shoulder (GS) and ACJ-specific outcome measures were also investigated. Study Design: Cohort study (diagnosis); Level of evidence, 3. Methods: Included in this study were 131 consecutive patients with operatively treated ACJ instability between 2011 and 2017. Postoperative shoulder function was measured using PROMs, including the Subjective Shoulder Value (SSV), Subjective Shoulder Test, and Nottingham Clavicle Score (NCS), and EDOMs, including the Constant-Murley score (CMS), Taft score, ACJ instability (ACJI) score, and SICK Scapula Score (SSS). Associations between PROM and EDOM scores were calculated using the Pearson and Spearman correlation coefficients for linear and nonlinear variables, respectively, and were interpreted using the Cohen classification. The scores were further stratified into GS versus ACJ-specific measures. Results: A strong correlation was observed between several PROMs and EDOMs (CMS vs SSV [r = 0.59; P = .02] and CMS vs NCS [r = 0.79; P ≤ .001]) and between several GS and ACJ-specific scores (CMS vs NCS; CMS vs ACJI [rs = 0.69; P < .001]; and CMS vs SSS [r = -0.68; P < .001]). Conclusion: Based on the results of this study, PROMs such as the SSV (a GS measure) and the NCS (an ACJ-specific measure) can substitute for EDOMs. Clinical Relevance: PROMs that can be substituted for EDOMs can enable the conduct of clinical studies in circumstances in which in-person clinical follow-up of the patient by a physician is not possible.

Age-Independent Clinical Outcome in Proximal Humeral Fractures: 2-Year Results Using the Example of a Precontoured Locking Plate.

INTRODUCTION: The optimal treatment strategy for the proximal humeral fracture (PHF) remains controversial. The debate is centered around the correct treatment strategy in the elderly patient population. The present study investigated whether age predicts the functional outcome of locking plate osteosynthesis for this fracture entity. METHODS: A consecutive series of patients with surgically treated displaced PHF between 01/2017 and 01/2018 was retrospectively analyzed. Patients were treated by locking plate osteosynthesis. The cohort was divided into two groups: Group 1 (≥65 years) and Group 2 (<65 years). At the follow-up examination, the SSV, CMS, ASES, and Oxford Shoulder Score (OS), as well as a radiological follow-up, was obtained. The quality of fracture reduction is evaluated according to Schnetzke et al. Results: Of the 95 patients, 79 were followed up (83.1%). Group 1 consists of 42 patients (age range: 65-89 years, FU: 25 months) and Group 2 of 37 patients (28-64 years, FU: 24 months). The clinical results showed no significant differences between both groups: SSV 73.4 ± 23.4% (Group 1) vs. 80.5 ± 189% (Group 2). CMS: 79.4 ± 21 vs. 81.9 ± 16, ASES: 77.2 ± 20.4 vs. 77.5 ± 23.1, OS: 39.5 ± 9.1 vs. 40.8 ± 8.2; OS: 39.5 ± 9.1 vs. 40.8 ± 8.2. In the radiological follow-up, fractures healed in all cases. Furthermore, the quality of fracture reduction in both groups is comparable without significant differences. The revision rate was 9.5% in Group 1 vs. 16.2% in Group 2. DISCUSSION: Both age groups show comparable functional outcomes and complication rates. Thus, the locking plate osteosynthesis can be used irrespective of patient age; the treatment decision should instead be based on fracture morphology and individual patient factors.

[Arthroscopic-assisted management of intra-articular scapular fractures in a rugby player]. / Arthroskopisch assistierte Versorgung einer intraartikulären Skapulafraktur bei einem Rugbyspieler.

Scapular fractures are a rare injury entity accounting for 0,4-1 % of all fractures and 3-5 % of fractures involving the shoulder girdle. This study focuses on a 29-year-old male patient who sustained an intraarticular scapular fracture during a "Rugby Bundesliga" match after direct impact with another player. The clinical and radiological examinations showed a dislocated multifragmentary transverse scapular fracture involving the superior border, the medial border and the glenoid (Euler and Rüedi D2b/AO 14 F1.3e). The patient was subjected to arthroscopic surgery and underwent early postoperative functional rehabilitation without weight-bearing and with a limited range of motion of 90° abduction/anteversion. In the first match of the second half of the season (5 months post-operatively), the patient was available to play, and in the clinical follow-up 6 months post-operatively, he was pain-free with excellent clinical results (CS 100 pt, SSV 98 %, OSS 12 pt, ASES 100 pt). No pain or restrictions in the range of motion were reported. In conclusion, the arthroscopic-assisted management of intra-articular scapular fractures is a safe and effective choice of treatment in young and active patients.

Additional coracoclavicular augmentation reduces revision rates in the treatment of lateral clavicle fractures as compared to angle-stable plate osteosynthesis alone.

INTRODUCTION: There is no uniform approach to the management of lateral clavicle fractures. Recent studies have investigated additive coracoclavicular (CC) augmentation as a treatment option; however, it is unclear whether it is superior to conventional locking plate osteosynthesis. METHODS: We carried out a retrospective analysis of 40 patients with lateral clavicle fracture (Neer type IIb) who were treated between 2014 and 2017 with either a hybrid locking plate osteosynthesis/additive arthroscopy-assisted CC augmentation (HP) procedure or a locking plate osteosynthesis only (PO) approach to determine which strategy was more effective. At follow-up, subjective shoulder value, age- and sex-adjusted Constant-Murley score, Taft (TF) score, American Shoulder and Elbow score, Nottingham clavicle score, and Visual Analogue Scale score were compared between patient groups. A radiologic evaluation was also conducted. RESULTS: A total of 14/17 patients (83%; 9 male/5 female, mean age: 43 ± 15 years) were followed up in the PO group. The mean follow-up time was 29 ± 12.4 months. In the HP group, 17/23 patients (74%; 9 male/8 female, mean age: 43 ± 17 years) were followed up, with a mean follow-up time of 18 ± 7.1 months. There were no significant differences in clinical parameters between the HP and PO groups; notably, the shoulder girdle-specific TF score was comparable in the 2 groups (HP: 11.3 ± 1.1 points and PO: 10.9 ± 0.9 points). In the HP group, additional pathologies were identified and arthroscopically treated in 35% of cases. Radiologic examination revealed a significant difference between pre- and postoperative CC distance in the HP group (P = 0.001). CONCLUSION: Additive CC augmentation in combination with locking plate osteosynthesis seems to improve the vertical stability and reduces the revision rate in patients with a lateral clavicle fracture. Furthermore, an arthroscopy-assisted procedure allows for an intraoperative detection and single-step treatment of accompanying intraarticular pathologies.

Double plating - surgical technique and good clinical results in complex and highly unstable proximal humeral fractures.

INTRODUCTION: A stable fixation of highly unstable proximal humerus fractures remains challenging and complication rates, especially secondary varus dislocation, remains high. Different techniques of double plate osteosynthesis have been suggested for the treatment of complex proximal humeral fractures as they are well established for other fractures. The aim of this study was to evaluate an operative technique using an angular stable lateral plate supported by a one-third tubular plate positioned anteriorly at the lesser tuberosity for unstable proximal humeral fractures. PATIENTS AND METHODS: Retrospectively, patients treated with a double plate osteosynthesis were included between January 2014 and December 2017. Out of 31, 25 patients (80.6%) with an average age of 53.1 years ± 12.5 were available for follow-up. 60% of the patients were male. The clinical evaluation consisted of a physical examination and standardised questionnaire including subjective and objective shoulder scores like the Constant-Murley Shoulder Score, Simple Shoulder Score, and Subjective Shoulder Value. RESULTS: After a mean follow-up of 30.9 months (range, 12-76 months) eighteen patients (72%) had either excellent or good results regarding the Constant-Murley Shoulder Score with a mean value of 77 points ± 17. Average Simple Shoulder Score was 76% ± 0.2 and Subjective Shoulder Value 72% ± 0.2%. Mean NSA at time of follow-up 135° ± 13°. Nine patients had an implant-removal, five in combination with arthrolysis after a mean of 7.2 months. Three patients underwent surgery for secondary arthroplasty. The study shows a complication rate of 16%. No revision-surgery because of secondary varus dislocation was reported. DISCUSSION: Arthroplasty is the less favourable treatment for a younger, active cohort of patients with highly unstable proximal humeral fractures as results are not as good and options for revision are limited. Double plate osteosynthesis can be used in addition to calcar screws, bone graft augmentation, cement augmentation and additional free screws for more multidirectional stability and shows good clinical results despite a higher rate of avascular necrosis and high primary stability with comparable complication-rates to single plate osteosynthesis. It seems to be a valid alternative to primary fracture arthroplasty and can prevent secondary varus displacement.

[Injuries of the sternoclavicular joint]. / Verletzungen des Sternoklavikulargelenks.

Injuries of the sternoclavicular joint (SCJ) are rare accounting for 3% of all injuries to the shoulder girdle and are often overlooked. The SCJ is surrounded by tight ligamentous structures, thus substantial energy with corresponding force vectors is needed to cause dislocation. Causative are mostly high-energy traumas. Anterior dislocation is most common but in rare cases potentially life-threatening posterior dislocation occurs, which requires immediate reduction. The established gold standard is 3D reconstruction in contrast-enhanced computed tomography (CT) for depiction of neurovascular structures. Low-grade instability can initially be treated conservatively. For unsuccessful attempts at reduction, high-grade instability and chronic instability various surgical techniques are established. Next to retentive augmentation with suture materials, in acute cases with chronic instability biological tendon augmentation is preferred. In cases of posttraumatic instability arthritis SCJ resection with or without additive biological augmentation can be carried out. Various study groups have shown good to very good midterm outcome.

Can low-profile double-plate osteosynthesis for olecranon fractures reduce implant removal? A retrospective multicenter study.

BACKGROUND: Because of poor soft-tissue coverage at the proximal ulna and prominent posteriorly positioned implants, hardware removal remains the most common reason for revision surgery of olecranon fractures that were operatively treated using plate osteosynthesis. We hypothesized that low-profile double-plate osteosynthesis would reduce the number of soft tissue-related hardware removals compared with single posterior plating whereas the functional results would be comparable. METHODS: This study retrospectively included patients who were treated with low-profile double-plate osteosynthesis or a posterior 2.7-/3.5-mm locking compression plate (LCP) for isolated olecranon fractures from 3 study centers. In addition to the implant removal rate, functional outcome measures (range of motion; Mayo Elbow Performance Score; Disabilities of the Arm, Shoulder and Hand score) were statistically compared. RESULTS: The study included 79 patients, with a mean follow-up period of 36 months (range, 24-77 months). Of these patients, 37 were treated with low-profile double-plate osteosynthesis and 42, with a 2.7-/3.5-mm LCP. The mean age was 57 years (range, 18-93 years). Range of motion after treatment with low-profile double-plate osteosynthesis and a 2.7-/3.5-mm LCP measured 129° (range, 80°-155°) and 139° (range, 100°-155°), respectively. The Mayo Elbow Performance Scores were 95 (range, 65-100) and 99 (range, 85-100), respectively (P = .028), and the Disabilities of the Arm, Shoulder and Hand scores were 5.0 (range, 0-49) and 4.6 (range, 0-28), respectively (P = .673). Hardware was removed in 32% and 50% of patients after treatment with double-plate osteosynthesis and a 2.7-/3.5-mm LCP, respectively (P = .11). Hardware removal owing to soft-tissue irritation was noted in 27% of patients after double-plate osteosynthesis and 38% after LCP treatment (P = .30). DISCUSSION: Low-profile double-plate osteosynthesis for treating olecranon fractures resulted in good clinical outcomes. However, the rate of hardware removal was not significantly reduced, and the functional results were comparable to those of common single-posterior plate osteosynthesis.

Corrective Osteosynthesis in Failed Proximal Humeral Fractures. / Korrekturmöglichkeiten bei fehlgeschlagener Osteosynthese ­ proximaler Humerus.

Despite implant improvement and increasing standardisation of operation techniques, the rate of therapy failure of proximal humeral fracture care with primary osteosyntheses is estimated to be 10 to 20%. Most commonly failure is precipitated by: material failure, technical error, non-anatomical repositioning, avascular necrosis, lacking medial support. An additive medial stabilisation of the so-called "calcar region" can decrease failure rates significantly. An early correction osteosynthesis with the purpose of restoring the anatomy is indicated in bony, non-consolidated "fresh" fractures. Bony consolidated fractures should be classified according to Boileau and Walch. The authors of this article advice a structured and classification-adapted approach to treatment with a correction osteosynthesis. Post-traumatic deficits can be augmented utilising the following methods: correction osteosynthesis with allogeneic/autologous bone grafts, correction osteosynthesis with hydroxyapatite grafts. For the additive stabilisation of repositioned and fixated fractures, the following are described: correction osteosynthesis with an additive ventral one-third tubular plate, correction osteosynthesis with cement-augmented screws. Based on results of endoprosthetics following fractures of the proximal humerus, the correction osteosynthesis indeed represents a real therapeutic alternative in patients that are below the age of 60, a good bone mass and with relative functional requirements.

Influence of plate material and screw design on stiffness and ultimate load of locked plating in osteoporotic proximal humeral fractures.

INTRODUCTION: The main purpose was to compare the biomechanical properties of a carbon-fibre reinforced polyetheretherketone (CF-PEEK) composite locking plate with pre-existing data of a titanium-alloy plate when used for fixation of an unstable 2-part fracture of the surgical neck of the humerus. The secondary purpose was to compare the mechanical behaviour of locking bolts and conventional locking cancellous screws. METHODS: 7 pairs of fresh frozen human humeri were allocated to two equal groups. All specimens were fixed with the CF-PEEK plate. Cancellous screws (PEEK/screw) were compared to locking bolts (PEEK/bolt) for humeral head fixation. Stiffness, fracture gap deflection and ultimate load as well as load before screw perforation of the articular surface were assessed. Results were compared between groups and with pre-existing biomechanical data of a titanium-alloy plate. RESULTS: The CF-PEEK plate featured significantly lower stiffness compared to the titanium-alloy plate (P<0.001). In ultimate load testing, 6 out of 14 CF-PEEK plates failed due to irreversible deformation and cracking. No significant difference was observed between results of groups PEEK/screw and PEEK/bolt (P>0.05). DISCUSSION: The CF-PEEK plate has more elastic properties and significantly increases movement at the fracture site of an unstable proximal humeral fracture model compared to the commonly used titanium-alloy plate. The screw design however does neither affect the constructs primary mechanical behaviour in the constellation tested nor the load before screw perforation.