Thumb Metacarpophalangeal Joint Kinematics and Elongation of the Ulnar Collateral Ligament.

PURPOSE: The purpose of the study was to determine if the sphericity of the thumb metacarpophalangeal (MCP) joint influences the joint's rotational axis (RA) and elongation patterns of the ulnar collateral ligament (UCL). METHODS: Ulnar collateral ligament origins and attachments of 28 fresh-frozen cadaveric thumbs were marked with a radiopaque marker. Lateral radiographs were obtained in neutral and 20°, 40°, and 60° of flexion. The dorsal and palmar joint gap and the length of four different UCL portions were digitally measured in all flexion states. The RA was determined by the intersection of the midshaft axis of the proximal phalanx in neutral and flexion states. Sphericity of the MCP joint was assessed using morphometric parameters. Joints were grouped as round or flat. Differences in all measured parameters between groups were analyzed. RESULTS: During flexion, the dorsal joint gap increased by 322% in flat joints and 163% in round joints. The palmar joint gap decreased to 45% in flat joints and to 87% in round joints. The RA was at 29% of metacarpal height and 96% of metacarpal length in flat joints and at 40% of height and 86% of length in round joints. Maximum UCL elongation (111%) was noted at 40° flexion in the dorsal proper UCL in flat joints and at 60° flexion in the accessory UCL (117%) in round joints. CONCLUSIONS: In flat MCP joints, the RA is more dorsal and distal in the metacarpal head compared to round joints, resulting in a hinged flexion motion. Elongation of the UCL is highest at end flexion in round joints and highest at midflexion in flat joints. CLINICAL RELEVANCE: The different kinematics of flat and round MCP joints may contribute to the understanding of the pathophysiology of UCL ruptures. The propensity of this injury and the position in which they occur may be affected by the MCP joint morphology.

Improved restoration of biomechanical factors using a narrow-box shaped reconstruction compared to a wide one in superior capsular reconstruction for irreparable supraspinatus tendon tears: a biomechanical study using a static shoulder simulator.

HYPOTHESIS AND/OR BACKGROUND: Extensive, irreparable rotator cuff tears remain a surgical challenge and multiple treatment options are proposed and currently in use. To biomechanically compare superior glenohumeral translation, subacromial contact pressures, and area in a box-shaped reconstruction using the long head of the biceps tendon (LHBT) in an irreparable supraspinatus tendon tear model. METHODS: Seven cadaveric shoulders (mean age 61 years; range 32-84 years; standard deviation 22.3) were tested with a custom testing rig used to evaluate superior translation; subacromial contact pressures; and areas at 0°, 30°, and 60° of glenohumeral abduction. Conditions tested included the native state; a complete tear of the supraspinatus tendon; a wide box-shaped, double-bundle LHBT superior capsular reconstruction (BS-SCR); and a narrow BS-SCR. RESULTS: Compared with the wide BS-SCR, the narrow BS-SCR had statistically significantly lower median contact pressure at 30° and 60°. The subacromial contact area showed a statistically significant difference at 0° (P = .001) and 30° (P = .004) for the narrow BS-SCR compared with the wide BS-SCR. At an abduction angle of 0°, the narrow BS-SCR could restore superior translation significantly better compared with the wide construct. For all angles, the wide and narrow BS-SCR increased the median subacromial distance statistically significantly. The contact areas in 30° and 60° of abduction were higher for all scenarios, both peaking in the intact state in 30° with approximately 600 mm2. CONCLUSIONS: In comparison to a wide BS-SCR, a narrow BS-SCR using the LHBT has biomechanical advantages in regard to subacromial contact pressures, the subacromial contact areas, as well as the acromiohumeral distance. The width of the reconstruction, therefore, has a direct influence on the success of the technique.

Optimal screw orientation for fixation of coronal shear fractures: a biomechanical comparison.

BACKGROUND: Coronal shear fractures of the capitellum are rare injuries which can be challenging to treat. The aim of this study was to compare the biomechanical properties of different internal screw fixation techniques for Dubberley type IA fractures of the capitellum. METHODS: In this biomechanical study, Dubberley type IA fractures of the capitellum were created in 30 human fresh-frozen humeri. The specimens were then divided into 3 groups: fixation was either performed with 3 × 3.0 mm headless cannulated compression screws (HCCSs) in anteroposterior (AP) orientation (AP group), 3 × 3.0 mm HCCSs in posteroanterior (PA) orientation (PA group) or with 2 × 3.0 mm HCCSs in PA orientation and 1 × 3.0 mm HCCS in lateral orientation (LAT) group. Displacement under cyclic loading and ultimate load-to-failure were evaluated in all specimens. RESULTS: There was no significant difference in fragment displacement after 2000 cycles between AP and PA groups (0.8 ± 0.5 mm vs. 0.8 ± 0.6 mm; P = .987) or PA and LAT groups (0.8 ± 0.6 mm vs. 0.8 ± 0.3 mm; P = .966). LAT group showed the highest load-to-failure (548 ± 250 N) without reaching statistically significant difference to AP group (388 ± 173 N; P = .101). There was also no significant difference between AP and PA groups (388 ± 173 N vs. 422 ± 114 N; P = .649). CONCLUSIONS: Variations in screw placement had no statistically significant influence on cyclic displacement or load-to-failure in Dubberley Type IA fractures. However, fracture fixation in 2 planes-both the coronal and the sagittal plane-by adding a screw in a lateral to medial direction may be beneficial to increase primary stability.

Primary bone graft stability after Latarjet surgery: biomechanical evaluation of a fixation technique with metal-free all-suture cerclage vs. cortical screws.

BACKGROUND: To reduce hardware-related complications in coracoid graft fixation to the anterior aspect of the glenoid, a metal-free Latarjet technique was recently introduced. The aim of this study was to compare the primary stability of a classic Latarjet procedure with 2 metal screws to a novel metal-free, all-suture cerclage method. It is hypothesized that fixation of the coracoid graft with 2 malleolar screws will provide higher primary stability compared with an all-suture cerclage technique. METHODS: This biomechanical in vitro study was conducted on 12 fresh-frozen cadaveric shoulders (6 matched pairs) with a mean donor age of 80 years (range, 67-89 years). Coracoid graft fixation was performed using a recently introduced all-suture cerclage technique (group A) or a classic Latarjet technique with two 4.5-mm malleolar screws (group B). The conjoint tendon was loaded with a static force of 10 N to simulate the sling effect. Graft loading with a probe head consisted of 6 ascending load levels (10-50 N, 10-100 N, 10-150 N, 10-200 N, 10-250 N, and 10-300 N) with 100 cycles each at 1 Hz. Relative motion of the bone graft to the glenoid was measured using an optic 3-dimensional system. RESULTS: While loading the conjoint tendon with 10 N, no difference in mean displacement of the bone-graft was found between both groups (P = .144). During cyclic loading, a significant difference in relative displacement for both groups was already detected in load level 1 (group A: 2398.8 µm vs. group B: 125.7 µm; P = .024), and this trend continued with the following load levels (P < .05). DISCUSSION AND CONCLUSION: The study demonstrated that the innovative metal-free, all-suture cerclage fixation technique results in higher micromotion than the classic coracoid graft fixation with 2 malleolar screws. According to the present biomechanical investigation, shoulders treated with a metal-free all-suture cerclage technique might need adapted rehabilitation protocols to protect the construct and allow for graft healing.

Do We Need a Strictly Lateral Radiograph for Fracture Management of Forearm Buckle Fractures in Children?

OBJECTIVES: Buckle fractures of the distal forearm are a common fracture entity in children treated conservatively. Diagnostics primarily include radiographs in 2 planes. Inadequate images may occur in the mostly very young patients. Therefore, additional lateral radiographs are often obtained to assess a possible angular tilt. The aim of this study is to investigate whether a strictly lateral x-ray image has an influence on fracture management. METHODS: Seventy-three children with buckle fractures of the distal forearm were included in this retrospective analysis. All cases were analyzed by quality of radiographs, necessity to obtain an additional lateral radiograph, and what influence on fracture management resulted. Follow-up was performed 2 to 4 weeks after immobilization. RESULTS: Thirty-five girls and 38 boys with a mean age of 7.16 years were included; 40 had fractured right and 33 had fractured left arms, respectively. Isolated distal radius fractures occurred in 48 cases, isolated distal ulna fractures in 6 cases, and both bones in 19 cases. Initial radiographic images were evaluated as inadequate in 25 cases. In each of those cases, an additional lateral image was obtained by fluoroscopy without resulting in an alternated fracture management protocol, which was chosen conservatively in each case and resulted in excellent clinical outcome at follow-up examination. CONCLUSIONS: Based on our results, the acquisition of additional lateral radiographs seems to be unnecessary in the diagnostic procedure of buckle fractures of the distal forearm, in case a possible palmar or dorsal angulation cannot be entirely assessed on the initial set of radiographs. An additional lateral image had no influence on fracture management, which was chosen conservatively in every case and led to excellent clinical results.Level of evidence: level III.

Evaluation of interleukin-6 in synovial fluid in periprosthetic joint infection of the elbow.

PURPOSE: Searching for quick determinable biomarkers with high sensitivity and specificity is necessary to improve and optimise the early diagnosis of periprosthetic elbow infection (PEI). Therefore, this study's objective was to evaluate the diagnostic value of synovial fluid interleukin-6 (IL-6) levels for diagnosing PEI in total elbow arthroplasty. METHOD: Twelve prospective enrolled patients underwent total elbow arthroplasty revision surgery, during which synovial fluid was obtained. Between the initial implantation and the revision procedure were 33.5 ± 41 months (range, 2-144 months). Synovial fluid was collected for immediate IL-6 analysis parallel to the revision surgery. Furthermore, microbiological samples were obtained and analysed. Two groups were defined based on the microbiological results: non-infection and infection group. The ability of synovial fluid IL-6 analysis to predict infection status was explored using receiver operating characteristic curves and further statistical analysis. RESULTS: Synovial fluid IL-6 analysis had a good diagnostic accuracy of 83% for PEI with an area under the curve of 0,79 and an ideal cutoff value (determined using Youden's criterion) of 15244 pg/mL. DISCUSSION: This is the first study to clinically evaluate IL-6 as a diagnostical marker for periprosthetic joint infection (PJI) in total elbow arthroplasty. Our results suggest a good accuracy and high sensitivity for IL-6 to identify a PEI. The analysis of IL-6 can improve surgical decision-making regarding managing total elbow arthroplasty in terms of one- or two-staged revision. CONCLUSION: IL-6 can play an important role in the perioperative differentiation of infected and non-infected situations.

The temperature profile in elbow arthroscopy using radiofrequency ablation.

INTRODUCTION: Over the last decades, arthroscopic surgery has become increasingly relevant as its minimally invasive approach offers many benefits. To investigate the risks of orthoscopic surgery at the elbow, this study aimed to investigate the development of temperatures in elbow joints while performing radiofrequency ablation in arthroscopic surgery. MATERIALS AND METHODS: We performed standard arthroscopic surgeries with posterolateral, transtricipital and anterolateral approaches on seven cadaveric elbows and performed ablation on predefined locations with or without irrigation. Two temperature probes were positioned into the olecranon fossa and between the ulnar nerve and the medial joint capsule. The temperature data were recorded using a real-time data logger. A bipolar radiofrequency ablation (bRFA) device was used at the medial and lateral recess and in the fossa olecrani over a defined period. Data was then analyzed using Matlab. RESULTS: Using bRFA without irrigation results in rapidly increasing temperature within the joint. A significant temperature increase was found within only 5 s without irrigation (p = 0.0052) in the fossa olecrani. We did not observe critical temperatures above 41 °C close to the ulnar nerve within 30 s under constant irrigation (p = 0.0747). CONCLUSIONS: Radiofrequency ablation (RFA) can be safely used in elbow arthroscopy with irrigation. The continuous use without irrigation should be limited to 3 s. Despite the anatomical proximity of the ulnar nerve and capsule, we were able to show that a possible rise in temperature most likely does not affect the ulnar nerve.

Comprehensive analysis and classification of retrocondylar ulnar groove morphology using CT imaging in an average population of adults.

PURPOSE: Anatomical variations of the concave shaped retrocondylar ulnar groove (RUG) can contribute to ulnar nerve instability. However, there are currently limited available standardized data describing the anatomy of the RUG based on radiologic imaging, such as computed tomography (CT). This study aims to provide a comprehensive description and classification of RUG anatomy based on RUG angle measurements. METHODS: 400 CT scans of the elbows of adults showing no signs of osseous damage were evaluated. RUG angles were measured in four anatomically defined axial planes that spanned from the proximal to the distal end of the RUG. Furthermore, distance measurements at the medial epicondyle were conducted. A classification system for the RUG is proposed based on the acquired RUG angles, aiming to categorize the individual angles according to the 25th and 75th percentiles. RESULTS: RUG angles were significantly larger in males compared to females (p < 0.001) accompanied by larger distances including the off-set and height of the medial epicondyle (p < 0.001). RUG angles decreased from proximal to distal locations (p < 0.05). CONCLUSION: This study revealed that men exhibited larger RUG angles compared to women, indicating a less-concave shape of the RUG in men. Introducing an objective RUG classification system can improve our understanding of anatomical variations and potentially find application in diagnostics and preoperative planning.

Postoperative swelling after elbow surgery: influence of a negative pressure application in comparison to manual lymphatic drainage-a randomized controlled trial.

PURPOSE: Postoperative soft tissue swelling is a significant factor influencing outcomes after elbow surgery. It can crucially affect important parameters such as postoperative mobilization, pain, and subsequently the range of motion (ROM) of the affected limb. Furthermore, lymphedema is considered a significant risk factor for numerous postoperative complications. Manual lymphatic drainage is nowadays part of the standardized post-treatment concept, basing on the concept of activating the lymphatic tissue to absorb stagnated fluid from the tissue into the lymphatic system. This prospective study aims to investigate the influence of technical device-assisted negative pressure therapy (NP) on early functional outcomes after elbow surgery. NP was therefore compared to manual lymphatic drainage (MLD). Is a technical device-based NP suitable for treatment of lymphedema after elbow surgery? METHODS: A total of 50 consecutive patients undergoing elbow surgery were enrolled. The patients were randomized into 2 groups. 25 participants per group were either treated by conventional MLD or NP. The primary outcome parameter was defined as the circumference of the affected limb in cm postoperative up to seven days postoperatively. The secondary outcome parameter was a subjective perception of pain (measured via visual analogue scale, VAS). All parameters were measured on each day of postoperative inpatient care. RESULTS AND CONCLUSION: NP showed an overall equivalent influence compared to MLD in reducing upper limb swelling after surgery. Moreover, the application of NP showed a significant decrease in overall pain perception compared to manual lymphatic drainage on days 2, 4 and 5 after surgery (p < 0.05). CONCLUSION: Our findings show that NP could be a useful supplementary device in clinical routine treating postoperative swelling after elbow surgery. Its application is easy, effective and comfortable for the patient. Especially due to the shortage of healthcare workers and physical therapists, there is a need for supportive measures which NP could be.

The simulation of terrible triad injuries in fresh-frozen human cadaveric specimens with intact soft tissue envelope.

INTRODUCTION: The aim of the present study was to develop a technical process to reproducibly generate terrible triad injuries (TTI) in fresh-frozen human cadaveric specimens, while leaving the skin intact. Such "pre-fractured" specimens, used for scientific analysis and for surgical education, might help to improve current treatment, which is complex and prone to complications. MATERIALS AND METHODS: To induce the desired fractures, a custom-made fracturing unit was used to apply an axial force on the extended cadaveric elbow specimens, with the forearm pronated and under valgus load. To simulate the valgus load, a pneumatic cylinder was developed to apply valgus stress to the joint by an additional force vector from the lateral side of the joint. RESULTS: The success rate of TTI induction was 92.3% (12/13). Of the 12 radial head fractures, 3 (25%) were classified Mason type II and 9 (75%) Mason type III. The coronoid fractures were grouped in tip subtype 2 (5 fractures, 41.7%), anteromedial facet (AMF) subtype 2 (4 fractures, 33.3%), AMF subtype 3 (1 fracture, 8.3%) and basal subtype 1 (2 fractures, 16.7%). CONCLUSIONS: The present study provides an instrument for successful and reproducible production of dislocation fracture patterns with their typical accompanying soft tissue lesions. The methodology might be applied on a broad basis to be able to perform biomechanical studies regarding primary stability of fixation concepts for TTI and to educate surgeons in a fairly realistic scenario with the surgical treatment of TTI.

Locking suture repair versus ligament augmentation-a biomechanical study regarding the treatment of acute lateral collateral ligament injuries of the elbow.

BACKGROUND: Lateral collateral ligament (LCL) tears are frequently observed in fractures and dislocations of the elbow. Recent biomechanical evidence suggests that additional ligament augmentation may improve repair stability. The aim of this biomechanical in-vitro study was to compare the resistance of a locking suture repair of the LCL with a ligament augmentation technique. MATERIAL AND METHODS: Eight fresh frozen cadaveric elbows were evaluated for stability against varus/posterolateral rotatory forces (3 Nm). A strain gauge (µm/m; negative values) was placed at the origin and insertion of the lateral ulnar collateral ligament (LUCL) and cyclic loading was performed for 1000 cycles. We analyzed three distinct scenarios: (A) native LCL, (B) locking transosseou suture repair of the LCL, (C) simple LCL repair with additional ligament augmentation of the LUCL. RESULTS: The mean measured strain was - 416.1 µm/m (A), - 618 µm/m (B) and - 288.5 µm/m (C) with the elbow flexion at 90°; the strain was significantly higher in scenario B compared to C (p = .01). During the cyclic load (1000) the mean measured strain was - 523.1 µm/m (B) and - 226.3 µm/m (C) with the elbow flexion at 60°; the strain was significantly higher in scenario B compared to C (p = .01). No significant difference between the first and the last cycles was observed (p = .09; p = .07). One failure of the LCL repair was observed after 1000 cycles; none of the ligament augmentations failed. CONCLUSION: Ligament augmentation (C) provides higher resistance compared to the native LCL (A) and to the locking suture repair technique (B). Both techniques, however, hold up during 1000 cycles. While ligament augmentation might enhance the primary stability of the repair, future clinical studies have to show whether this increase in resistance leads to negative effects like higher rates of posttraumatic elbow stiffness. LEVEL OF EVIDENCE: Basic science study, biomechanics.

Surgical arthrolysis of the stiff elbow: a systematic review.

INTRODUCTION: Stiffness after elbow injuries can severely limit daily life. If adequate conservative treatment does not result in satisfactory improvement of elbow function, surgical intervention should be considered. Whether an open or arthroscopic procedure is preferable is still a topic of debate and a systematic review of functional outcomes is lacking. MATERIALS AND METHODS: We systematically reviewed the available literature searching electronic databases, MEDLINE using the PubMed interface and EMBASE, for studies published between 2013 and 2021. Primary objective was to compare open and arthroscopic arthrolysis' functional outcomes, respectively, especially ROM and MEPS, as well as the accompanied complications. The PRISMA guidelines were applied. RESULTS: 27 studies comprising 1666 patients were included. 1059 patients (63.6%) were treated with open arthrolysis, and 607 patients (36.4%) were treated with arthroscopic arthrolysis. The results presented indicate satisfactory outcomes in open and arthroscopic arthrolysis with regard to functional outcome parameters. Treatment success, defined as excellent or good results according to the Mayo Elbow Performance Score, among the patients treated with an open procedure was 88.8%; 6.3% required revision whereas 18.1% had complications without the need for revision surgery. Within the cohort of arthroscopically treated patients, treatment success was 91.8%. Revisions and complications without further surgical intervention were significantly less frequent than in the open cohort, at 1.6% and 9.1%, respectively. CONCLUSIONS: Both open and arthroscopic arthrolysis provide good to excellent functional outcomes. Since the number of complications and revision increases with the invasiveness of the treatment, an arthroscopic procedure might be favored if feasible by indication. The role of forearm rotation and the use of a hinged external fixator remains of interest. STUDY DESIGN: Level IV; Systematic review.

Trans-fracture approach for ORIF of coronal shear fractures of the distal humerus.

INTRODUCTION: Open reduction and internal fixation (ORIF) of comminuted coronal shear fractures of the distal humerus is challenging. When a concomitant lateral condyle fracture is present, it may be used for a trans-fracture approach to facilitate exposure and fracture reduction. This study aimed to investigate the frequency of lateral condyle fractures in coronal shear fractures of the distal humerus and analyze fracture reduction, fracture union and clinical results following ORIF through a trans-fracture approach. MATERIALS AND METHODS: All adult patients who underwent treatment for an acute distal humerus fracture during a three-year period in our level-one trauma center were identified. All fractures were classified according to the Orthopaedic Trauma Association (OTA/AO) fracture classification system and all B3 fractures were classified according to the Dubberley classification. B3 fractures with a concomitant radial condyle fracture were identified. The clinical and radiological results, (Mayo Elbow Performance Score = MEPS, Visual Analogue Scale = VAS, range of motion), complications and revision surgeries were analyzed. RESULTS: 53 patients (mean age 52 ± 19 years) were identified. 13 fractures (24.5%) were B3 fractures. Four of them (30.8%) had a concomitant radial condyle fracture. All of these patients underwent ORIF with headless cannulated compression screws and a (postero-)lateral locking plate through a trans-fracture approach. At a minimum follow-up of 24 months, the MEPS was 88 ± 12 points, the VAS was 2 ± 1 and the range of motion was 118° ± 12°. All fractures showed anatomic reduction. One patient developed partial avascular necrosis and underwent arthrolysis at 6 months. One patient underwent partial hardware removal and lateral collateral ligament bracing at 6 months. CONCLUSIONS: Lateral condyle fractures are present in about one third of coronal shear fractures of the distal humerus. This injury can be used for a trans-fracture approach to facilitate exposure and to reliably achieve anatomic fracture reduction.

The effect of long calcar screws on the primary stability of 3-part, varus impacted proximal humeral fractures compared to short calcar screws: a real fracture simulation study.

BACKGROUND: Complex proximal humeral fracture ranks among the most common fracture types, especially in elderly patients. In locked plate fixation of proximal humerus fractures, the calcar is deciding for screws providing further medial column support. To date, the biomechanical effect of the length of these calcar screws is not well known. The purpose of this study was to analyze the effect of long calcar screws on fresh frozen prefractured cadaveric specimens. METHODS: In the present biomechanical study, 8 pairs of cadaveric proximal humeri were fractured identically using a custom-made fracture simulator. ORIF was performed using a locking plate (PHILOS; Fa. Synthes). The specimens were tested in a biomechanical setup under increased axial load without any calcar screws installed, with short calcar screws and long calcar screws installed. Strain gages (4-wire-120 Ohm, Fa. Vishay) mounted on the locking plate were used to evaluate the fixation strain and to give an estimate for primary stability.. RESULTS: The measured strain of the locking plate without calcar screws (804,64 µm/m) at maximum load (200 N) was significantly higher than with short (619,07 µm/m; p = 0.02) or long calcar screws (527,31 µm/m; p = 0.007). Additionally, strain with short calcar screws was noticeably higher in comparison to long calcar screws (619,07 µm/m vs. 527,31 µm/m; p = 0.03). CONCLUSION: Use of calcar screws improves the stability of realistically impacted 3-part varus humeral fractures. Long calcar screws that are positioned as close as possible to the joint provide further primary stability compared to short calcar screws. LEVEL OF EVIDENCE: Basic science study.

Influence of rotator cuff preload on fracture configuration in proximal humerus fractures: a proof of concept for fracture simulation.

INTRODUCTION: In regard of surgical training, the reproducible simulation of life-like proximal humerus fractures in human cadaveric specimens is desirable. The aim of the present study was to develop a technique that allows simulation of realistic proximal humerus fractures and to analyse the influence of rotator cuff preload on the generated lesions in regards of fracture configuration. MATERIALS AND METHODS: Ten cadaveric specimens (6 left, 4 right) were fractured using a custom-made drop-test bench, in two groups. Five specimens were fractured without rotator cuff preload, while the other five were fractured with the tendons of the rotator cuff preloaded with 2 kg each. The humeral shaft and the shortened scapula were potted. The humerus was positioned at 90° of abduction and 10° of internal rotation to simulate a fall on the elevated arm. In two specimens of each group, the emergence of the fractures was documented with high-speed video imaging. Pre-fracture radiographs were taken to evaluate the deltoid-tuberosity index as a measure of bone density. Post-fracture X-rays and CT scans were performed to define the exact fracture configurations. Neer's classification was used to analyse the fractures. RESULTS: In all ten cadaveric specimens life-like proximal humerus fractures were achieved. Two III-part and three IV-part fractures resulted in each group. The preloading of the rotator cuff muscles had no further influence on the fracture configuration. High-speed videos of the fracture simulation revealed identical fracture mechanisms for both groups. We observed a two-step fracture mechanism, with initial impaction of the head segment against the glenoid followed by fracturing of the head and the tuberosities and then with further impaction of the shaft against the acromion, which lead to separation of the tuberosities. CONCLUSION: A high energetic axial impulse can reliably induce realistic proximal humerus fractures in cadaveric specimens. The preload of the rotator cuff muscles had no influence on initial fracture configuration. Therefore, fracture simulation in the proximal humerus is less elaborate. Using the presented technique, pre-fractured specimens are available for real-life surgical education. LEVEL OF EVIDENCE: III.

Screw placement in arthroscopically assisted osteosynthesis of radial head fractures using a reference k-wire in the radiocapitellar joint: a cadaveric study.

PURPOSE: The optimal screw placement in arthroscopically assisted fixation of radial head fractures is still an issue and no guiding methods have been evaluated in the recent literature. The study hypothesis was that using a "reference k-wire" percutaneously inserted in and parallel to the radiocapitellar joint would enable to achieve a trajectory more parallel to the radial head articular surface as compared to a free-hand k-wire placement. METHODS: Arthroscopically assisted placement of a k-wire in the radial head was performed in seven fresh-frozen human cadaver specimens by three surgeons. Three different techniques were evaluated: freehand drilling (technique A), placement using a "reference" k-wire in the radiocapitellar joint as a reference without (technique B), and with the AO parallel k-wire guide (technique C). Radiographs from all procedures were obtained and the inclination angle "α" between the k-wire and the articular surface of the radial head was measured and compared among the techniques. RESULTS: Angles of 84 radiographs were obtained and showed a mean α angle of 30.1° ± 13° for technique A, 5.7° ± 4.5° for technique B, and 5.4° ± 3.7° for technique C. The angle α was significantly higher with technique A as compared to B (p < 0.0001) and C (p < 0.0001). There was no difference between methods B and C (n.s.). No difference was observed among the surgeons for all three methods (p = 0.66). CONCLUSION: With the use of an additional "reference" k-wire placed in the radiocapitellar joint, the guiding k-wire for screw drilling can be placed almost parallel to the radial head joint line with limited variability and a good reproducibility during arthroscopically assisted radial head fracture fixation. CLINICAL RELEVANCE: The here-presented method of an additional, percutaneous introduced "reference" k-wire is easily applicable and helpful to achieve parallel screw placement during arthroscopically assisted radial head fracture fixation. LEVEL OF EVIDENCE: IV, biomechanical cadaver study.

Correlation of head screw lengths in proximal humerus nailing: a CT-based study on 289 cases.

INTRODUCTION: Nailing of the proximal humerus is an established method for the treatment of proximal humerus fractures. Choice of the correct length for potentially four proximal locking screws is essential for postoperative outcome. Due to positioning of the patient, intraoperative determination of the correct length of the anteroposterior (AP) screw with the x-ray beam is particularly challenging even for experienced surgeons. We hypothesized that there would be a correlation between the projected lengths of the different proximal locking screws and therefore the length of the AP-screw could be determined based on the three lateromedial (LM) screws. MATERIALS AND METHODS: In this retrospective study (level of evidence: III) CT-scans of shoulders of 289 patients were 3D reconstructed with the program Horos. Using the manufacturer Stryker's instructions, the four proximal locking screws of the T2 Humeral Nail system were reproduced in the 3D reconstructed shoulders. The length of the AP-screw was correlated with the lengths of the LM-screws by Linear Regression and Multiple Linear Regression. RESULTS: The results of this study showed that the lengths of proximal locking screws in proximal humeral nailing correlated significantly with each other. Based on the given data, a formula could be established to calculate the length of the AP-screw based on the lengths of the LM-screws with a probability of 76.5%. CONCLUSIONS: This study was able to show that the length of the AP-screw could be determined from the intraoperatively measured lengths of the LM-screws. As our findings base on measurements performed in CT scans, clinical studies are needed to support our data.

Computed tomography-based angle measurements of the sagittal capitulum and trochlea position in relation to the humeral shaft.

The radiologic evaluation of the sagittal angulation of the distal humerus is commonly based on standard lateral radiographs. However, lateral radiographs do not allow to examine the lateral angulation of the capitulum and the trochlea, separately. Although this problem could be approached via computed tomography, there are no data available describing the difference between the angulation of the capitulum and trochlea. Therefore, we aimed to assess sagittal angles of the capitulum and trochlea in relation to the humeral shaft based on 400 CT-scans of the elbow in healthy adults. Angles were measured in sagittal planes at the capitulum center and three anatomically defined trochlea locations and were spanned between the axis of the joint component and the humerus shaft. Angles were tested for differences between measurement locations and correlation with patient characteristics (age, sex, trans-epicondylar distance). Angles increased from lateral to medial measurement locations (107.4 ± 9.6°, 167.4 ± 8.2°, 171.8 ± 7.3°, 179.1 ± 7.0°; p < 0.05). Largest angle differences were detected between the capitulum and trochlea with smallest angles measured at the capitulum. Patient characteristics did not correlate with angles (p > 0.05). Intra-rater-reliability was r = 0.79-0.86. As CT-imaging allows to distinguish between sagittal capitulum and trochlea locations, it might benefit the radiologic diagnostic of sagittal malalignments of the distal humerus at the capitulum and trochlea, separately.

A biomechanical analysis of different meshes for reconstructions of the pelvic floor in the porcine model.

PURPOSE: Many different surgical approaches have been established for the repair of a pelvic organ prolapse. Especially in laparoscopic surgery, it is important to generate easy surgical techniques with similar stability. This study shall simplify the choice of mesh by evaluating three polypropylene meshes regarding their biomechanical properties. METHODS: Biomechanical testing was performed in the porcine model. The meshes are fixated on porcine fresh cadaver cervices after subtotal hysterectomy. The apical part of the mesh is fixated with parallel screw clamps at the testing frame. Forty-one trials were performed overall, subdivided into four subgroups. The groups differ in mesh type and fixation method. Maximum load, displacement at failure and stiffness parameters were evaluated with an Instron 5565® test frame. RESULTS: SERATEX® E11 PA (E11) showed the highest values for maximum load (199 ± 29N), failure displacement (71 ± 12 mm) and stiffness (3.93 ± 0.59 N/mm). There was no significant difference in all three evaluated parameters between SERATEX® B3 PA (B3) and SERATEX® SlimSling® with bilateral fixation (SSB). SERATEX® SlimSling® with unilateral fixation (SSU) had the lowest stiffness (0.91 ± 0.19 N/mm) and maximum load (30 ± 2 N) but no significant difference in displacement at failure. CONCLUSION: All meshes achieved a good tensile strength, but the results of maximum load show that the E11 is superior to the other meshes. Through a bilateral fixation of SERATEX® SlimSling®, a simple operating method is generated without a loss of stability.

Tacks vs. sutures: a biomechanical analysis of sacral bony fixation methods for laparoscopic apical fixations in the porcine model.

PURPOSE: There is a novel surgical procedure, called cervicosacropexy (CESA) and vaginosacropexy (VASA) to treat pelvic organ prolapse and a concomitant urgency and mixed urinary incontinence. As there is little experience with the tapes so far and literature is scanty, the aim of this study was to investigate biomechanical properties for the fixation of the PVDF-tapes with three different fixation methods in context of apical fixations. METHODS: Evaluation was performed on porcine, fresh cadaver sacral spines. A total of 40 trials, divided into 4 subgroups, was performed on the anterior longitudinal ligament. Recorded biomechanical properties were displacement at failure, maximum load and stiffness in terms of the primary endpoints. The failure mode was a secondary endpoint. Group 4 was a reference group to compare single sutures on porcine tissue with those on human tissue. Biomechanical parameters for single sutures on the human anterior longitudinal ligament were evaluated in a previous work by Hachenberg et al. RESULTS: The maximum load for group 1 (two single sutures) was 65 ± 12 N, for group 2 (three titanium tacks arranged in a row) it was 25 ± 10 N and for group 3 (three titanium tacks arranged in a triangle) it was 38 ± 12 N. There was a significant difference between all three groups. The most common failure mode was a "mesh failure" in 9/10 trials for groups 1-3. CONCLUSION: The PVDF-tape fixation with two single sutures endures 2.6 times more load than titanium tacks arranged in a row and 1.7 times more load than titanium tacks arranged in a triangle. The presacral fixation with titanium tacks reduced surgical time compared to the fixation with sutures, nevertheless sutures represent the significantly stronger and cheaper fixation method.