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 Future of Total Elbow Arthroplasty: A Statistical Forecast Model for Germany.

This study provides a statistical forecast for the development of total elbow arthroplasties (TEAs) in Germany until 2045. The authors used an autoregressive integrated moving average (ARIMA), Error-Trend-Seasonality (ETS), and Poisson model to forecast trends in total elbow arthroplasty based on demographic information and official procedure statistics. They predict a significant increase in total elbow joint replacements, with a higher prevalence among women than men. Comprehensive national data provided by the Federal Statistical Office of Germany (Statistisches Bundesamt) were used to quantify TEA's total number and incidence rates. Poisson regression, exponential smoothing with Error-Trend-Seasonality, and autoregressive integrated moving average models (ARIMA) were used to predict developments in the total number of surgeries until 2045. Overall, the number of TEAs is projected to increase continuously from 2021 to 2045. This will result in a total number of 982 (TEAs) in 2045 of mostly elderly patients above 80 years. Notably, female patients will receive TEAs 7.5 times more often than men. This is likely influenced by demographic and societal factors such as an ageing population, changes in healthcare access and utilization, and advancements in medical technology. Our projection emphasises the necessity for continuous improvements in surgical training, implant development, and rehabilitation protocols.

The effects of Tourniquet use in elbow surgery: A retrospective analysis.

BACKGROUND: Pneumatic tourniquets are frequently employed in extremity surgeries, aiming to enhance intraoperative visibility and minimize blood loss. While their benefits and drawbacks have been extensively studied in lower limb operations, their impact on upper limb procedures, particularly elbow surgery, remains poorly understood. This study investigates the advantages and risks associated with pneumatic tourniquet utilization in elbow surgery. METHODS: A retrospective analysis was conducted on 183 patients who underwent elbow surgery for fractures between January 2019 and September 2023. Patients were categorized into two groups: those who underwent surgery with a tourniquet (WT) and those without a tourniquet (NT). Subgroup analyses were performed based on fracture complexity. Data collected included patient characteristics, tourniquet usage, surgical duration, pre- and postoperative hemoglobin levels, C-reactive protein levels, pain assessments, opioid administration, hospital stay duration, follow-up, complications, and revisions. Statistical analyses were used to identify significant differences and correlations. RESULTS: The use of a tourniquet in elbow surgery yielded several notable outcomes. Patients in the WT group experienced significantly shorter surgical durations and hospital stays. Hemoglobin drop was lower in the WT group, indicating reduced blood loss. However, there were no significant differences in postoperative pain, opioid consumption, or complications between the WT and NT groups. Subgroup analysis revealed that the recorded differences, particularly shorter surgical durations, were more pronounced in complex fractures. CONCLUSIONS: This study shows promising results in the use of pneumatic tourniquets in elbow surgery in terms of enhanced efficiency, reduced blood loss, and overall safety, without compromising patient outcomes. However, the potential influence of perioperative decision-making on tourniquet usage underscores the need for further research to elucidate its role and optimize its application, especially in complex elbow fractures.

[Elbow hemiarthroplasty for coronal shear fractures of the distal humerus]. / Ellenbogenhemiprothese bei koronaren Abscherfrakturen des distalen Humerus.

OBJECTIVE: The aim of the operation is to replace the articular surface of the distal humerus in cases of nonreconstructible fractures of the distal humerus. INDICATIONS: Active patients with high functional requirements, in whom weight limitation of total elbow arthroplasty should be avoided. CONTRAINDICATIONS: Contraindications include fractures with irreconstructible epicondyles and/or irreconstructible collateral ligaments, as well as ulnohumeral, or radiohumeral osteoarthritis. SURGICAL TECHNIQUE: Following subcutaneous anterior transposition of the ulnar nerve, surgical dislocation of the elbow joint is achieved through a paratricipital approach with release of the soft tissue structures from the humerus. After resection of the trochlea, the intramedullary canal of the humerus is prepared using rasps in order to implant the hemiprosthesis with retrograde cementing. Finally, the medial and lateral collateral ligaments as well as the flexors and extensors are repaired. POSTOPERATIVE MANAGEMENT: Early functional rehabilitation in a hinged elbow orthosis while avoiding varus/valgus stress after wound healing is completed. RESULTS: Between 2018 and 2022, 18 patients with coronal shear fractures were treated with elbow hemiarthroplasty. The mean Mayo Elbow Performance Score (MEPS) was 79 (70-95) after a mean follow-up of 12 months. The mean range of motion was 99° (70-130°) in extension-flexion and 162° (90-180°) in pronation-supination.

[Central band reconstruction in Essex-Lopresti lesions]. / Rekonstruktion des Zentralen Bandes bei Essex-Lopresti-Verletzung.

OBJECTIVE: Restoration of longitudinal forearm stability by reconstruction of the central band (CB) of the interosseous membrane (IOM) of the forearm. INDICATIONS: Acute and chronic Essex-Lopresti lesions (EL) with longitudinal forearm instability. CONTRAINDICATIONS: Absolute: acute/subacute infection. Relative: severe complex regional pain syndrome (CRPS), bony deformity/bone loss, pronounced osteoarthritis of the elbow and wrist. SURGICAL TECHNIQUE: Ulnar approach with exposure of the ulna approximately 6 cm proximal to the ulnar styloid. Creation of a 3.5 mm drill hole from ulnar-distal to radial-proximal. A Fiberloop (Fa. Arthrex, Naples, FL, USA) is fixed to one end of the LARS (Ligament Advanced Reconstruction System, Fa. Corin Group, Cirencester, UK) in a whipstitch technique, is shuttled through the drill hole from radial to ulnar and fixed over a BicepsButton (Fa. Arthrex, Naples, FL, USA). Exposure of the radius through a modified Henry approach. A 3.5 mm drill hole is made from radial-proximal to ulnar-distal approximately 12 cm proximal to the radial styloid. The graft is shuttled from the ulnar to the radial incision directly on the palmar surface of the IOM and shortened to the required length. Another Fiberloop is used to perform a whipstitch on the free end of the LARS. The final fixation of the CB reconstruction is achieved by shuttling the Fiberloop sutures through the radial drill hole with fixation over a BicepsButton. POSTOPERATIVE MANAGEMENT: Short-term immobilization in a long arm cast with subsequent early functional treatment. RESULTS: Mediocre to poor clinical results are reported in the literature for the treatment of chronic EL. Future research will tell whether the advanced surgical techniques with CB reconstruction will lead to better clinical outcomes.

[Autologous minced cartilage implantation for focal cartilage lesions of the humeral capitellum]. / Autologes Minced Cartilage bei fokalen Knorpelschäden des Capitulum humeri.

OBJECTIVE: The goal of minced cartilage implantation (MCI) is to restore an intact cartilage surface in focal osteochondral lesions of the humeral capitellum. INDICATIONS: The indications for MCI are limited osteochondral lesions at the humeral capitellum, also at the head of the radius, with intact cartilage border as well as in situ or a completely detached fragment, and free joint bodies (grade II-grade V according to Hefti). CONTRAINDICATIONS: Contraindications for MCI are already concomitant or associated cartilage damage as well as bilateral osteochondral lesions and insufficient available cartilage material. SURGICAL TECHNIQUE: After diagnostic arthroscopy to detect possible concomitant pathologies and to exclude already corresponding cartilage lesions, the arthroscope is flipped posterolaterally over the high posterolateral portal and a second portal is created under visualization via the soft spot. Initially, debridement of the focal cartilage defect, assessment of the marginal zone, and/or salvage of free joint bodies. Using a smooth shaver and the filter provided, the partially or even completely detached cartilage fragment is unidirectionally fragmented under continuous suction. The remaining defect with a stable marginal zone is cleanly curetted, and the joint is completely dried. The fragmented cartilage collected in the filter is bonded to a membrane using autologous conditioned plasma (ACP) and then arthroscopically applied to the defect via a cannula, sealed using thrombin and fibrin. POSTOPERATIVE MANAGEMENT: Postoperative immobilization in a cast for at least 24 h is required. Afterwards, free exercise of the joint is possible, but no loading should be maintained for 6 weeks. Return to sport after 3 months. RESULTS: Good to very good clinical and MRI morphologic results are already evident in the short-term course. Prospective and retrospective multicenter studies are needed to evaluate future long-term results.

[Technical modifications to elbow interposition arthroplasty]. / Technische Modifikation der Interpositionsarthroplastik des Ellenbogens.

OBJECTIVE: Interposition arthroplasty of the elbow involves the interposition of a fascia lata or dermis autograft or allograft between the distal humerus and the ulna or radius, while preserving the original form of articulation. INDICATIONS: Interposition arthroplasty is indicated for young patients with high functional demands who suffer from end-stage elbow arthritis and associated pain or joint stiffness. CONTRAINDICATIONS: Contraindications include acute or subacute infection, skeletal immaturity, bone loss, deformity, or gross instability. SURGICAL TECHNIQUE: Once the ulnar nerve has been secured, joint access is established via a posterior approach. The radial collateral ligament (RCL) and the common extensor tendon origin (CEO) are detached, while preserving the anconeus muscle and the lateral ulnar collateral ligament (LUCL). Subsequently, a capsular release is required to maintain adequate joint exposure and address the accompanying stiffness. Three to four transosseous drill holes are placed at the level of the distal humerus to secure the graft. After the graft has been positioned successfully within the joint space using two guide sutures, it can be secured to the distal humerus using a horizontal mattress stitch. Finally, the detached tendon and ligament structures are reconstructed. POSTOPERATIVE MANAGEMENT: After initial immobilization, early functional exercise of the elbow is performed in the motion orthosis, avoiding valgus or varus stress. RESULTS: The efficacy of elbow interposition arthroplasty has been demonstrated, particularly for young and active patients with severe inflammatory or post-traumatic osteoarthritis. Despite the results in terms of postoperative function and pain reduction are satisfactory, the current literature reports high complication, subsequent treatment, and revision rates. In the event of interposition arthroplasty failure, revision with another interposition procedure or conversion to endoprosthesis may be considered.

Optimal Screw Orientation for Fixation of Coronal Shear Fractures: A Biomechanical Comparison.

OBJECTIVE: 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 three groups: fixation was either performed with 3 x 3.0 mm headless cannulated compression screws (HCCSs) in anteroposterior (AP) orientation (AP group), 3 x 3.0 mm HCCSs in posteroanterior (PA) orientation (PA group) or with 2 x 3.0 mm HCCSs in PA orientation and 1 x 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 = 0.987) or PA and LAT groups (0.8 ± 0.6 mm vs. 0.8 ± 0.3 mm; p = 0.966). LAT group showed the highest load-to-failure (548 ± 250 N) without reaching statistically significant difference to AP group (388 ± 173 N; p = 0.101). There was also no significant difference between AP and PA groups (388 ± 173 N vs. 422 ± 114 N; p = 0.649). 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 two 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.

Compression therapy after endovenous laser ablation: Patient compliance and impact on clinical outcome.

OBJECTIVES: This study aimed to investigate the impact of post-interventional compression therapy on clinical outcomes after endovenous laser ablation (EVLA) of incompetent saphenous veins. METHODS: This prospective, controlled, multicenter study in Germany involved 493 varicose vein patients followed-up for 6 months. RESULTS: Compression therapy significantly reduced symptoms compared to no compression (VCSS: 1.4 ± 1.6 vs 2.2 ± 2.2; p = .007). Post-interventional therapy duration of up to 14 days was found to be most effective for improving patient-reported disease severity (p < .001) and higher quality of life (p = .001). Patient compliance was high (82%), and non-compliance was linked to worse disease severity (VCSS 1.4 ± 1.5 vs 2.1 ± 2.3, p = .009). CONCLUSION: In conclusion, post-interventional compression therapy is beneficial by reducing symptoms and improving quality of life. High patient compliance with the therapy is observed, and non-compliance is associated with worse disease severity.

In Which Cases Do We Operate? Posterior Malleolar Fractures-Intraobserver and Interobserver Reliability of the Bartonícek/Rammelt Classification and Corresponding Surgery Rates.

INTRODUCTION: The Bartonícek/Rammelt classification is established for posterior malleolar fractures. It subdivides the fractures into 5 types and outlines treatment recommendations. This study aims to determine the intraobserver and interobserver reliability of the Bartonícek/Rammelt classification and investigates its applicability regarding treatment recommendations. MATERIALS AND METHODS: Computed tomography (CT) scans of 80 ankle fractures with a posterior malleolar fracture were analyzed by four observers at two different time points 30 days apart (d1 and d2). Intrarater and interrater reliability was measured using kappa values. The corresponding surgery rates of the fracture subtypes were analyzed, and the surgery rates were correlated with fragment sizes and displacements. RESULTS: A moderate interobserver reliability for d1 0.41 (CI 0.35-0.47) and d2 0.42 (CI 0.36-0.48) was detected. Intraobserver reliability was documented as perfect, with a mean kappa of 0.83. Type II fractures were operated on in 50% of cases. In 50% of type II cases, a nonoperative treatment was chosen. Fragment size correlated strongly with the chosen therapy, and osteosynthesis was performed significantly more often when the fragment size exceeded 3 cm3 (P < .01). CONCLUSIONS: The Bartonícek/Rammelt classification system showed moderate interobserver reliability and perfect to substantial intraobserver reliability. In clinical practice of this study cohort, the size of the posterior malleolar fragment rather than the dislocation and joint impaction seemed to have the decision to operate on type II or III fractures. Existing treatment recommendations based on the Bartonícek/Rammelt classification correspond to the therapy algorithm carried out in this cohort of patients.Levels of Evidence: Level III: Retrospective study.

Safety of synchronous prophylactic ablation of the anterior saphenous vein in patients undergoing great saphenous vein thermal ablation- 6 months follow-up data of the SYNCHRONOUS study.

BACKGROUND: The SYNCHRONOUS-study investigates simultaneous ASV-ablation with great saphenous vein (GSV) treatment in endovenous laser ablation (EVLA) for preventing varicose vein recurrence. This sub-study examines complication rates associated with prophylactic ASV-ablation. METHODS: Among 1173 patients with refluxing GSV, 604 underwent GSV-ablation only, and 569 received additional ASV-ablation. Complication rates were compared over 6 months. RESULTS: Approximately 80% of patients were complication-free with minor bruising and dysesthesia being most common complications. After 6 months, additional prophylactic ASV-ablation did not increase the rate of complications compared to GSV-only treatment. CONCLUSION: The 6-months follow-up data suggests that prophylactic ASV-closure, alongside GSV-treatment, is safe, with similar complication rates to GSV-only EVLA.

How Preoperative Closed Reduction and Time to Surgery Impact Postoperative Palmar Inclination in Distal Radius Fractures.

Background: The anatomical reconstruction of the wrist is the aim when treating distal radius fractures. Current literature on the importance of preoperative reduction in fractures that are treated operatively is limited. Methods: This study investigated the effect of the preoperative closed reduction of distal radius fractures on the day of trauma and the time to surgery on postoperative palmar inclination. A total of eighty patients (48 females and 32 males, mean age 55.6 years) were studied retrospectively. All patients were treated with an open reduction and internal fixation. The palmar inclination angle was measured using X-rays by two investigators, and the interobservers and pre- and post-reduction parameters were compared. Results: When the surgical management of closed distal radius fractures is required, neither initial repositioning nor a delay of up to 14 days to the surgical treatment influences postoperative palmar inclination. Conclusions: The significance of preoperative reduction of distal radius fractures without neurovascular or extensive soft tissue damage is limited and is not leading to improved outcomes. When surgery is about to be performed, surgeons should carefully consider if reduction is really vital preoperatively. Level of evidence: III.

Mayo classification of olecranon fractures revisited - Assessment of intra- and interobserver reliability based on CT scans.

Purpose: Olecranon fractures are classified using the commonly accepted Mayo classification. Its reliability has been analyzed by means of radiographs. A CT scan is often obtained due to joint involvement. Purpose of this study was to evaluate the intra- and interobserver reliability of the Mayo classification based on CT examination. Methods: Radiographic and CT images of 20 olecranon fractures were classified by four surgeons at two time points 30 days apart. Intra- and interobserver reliability were assessed using kappa coefficients. Results: Mean intraobserver reliability between X-rays was substantial and between CTs almost perfect (0.76 and 0.82, respectively). Mean interobserver reliability was fair for X-rays and moderate for CTs (0.32 and 0.44, respectively). Conclusion: Despite the more detailed imaging compared with radiography only moderate interobserver reliability was found for the classification of olecranon fractures based on CT imaging. This might lead to inconsistent fracture classification in both scientific and clinical setting.

The importance of interdigitating screw fixation of the trochlea in double plate osteosynthesis of low transcondylar distal humerus fractures: A biomechanical study.

OBJECTIVE: The trochlea is of great importance for the stability of the elbow and its fixation in low transcondylar fractures of the distal humerus is especially challenging. The aim of this study was to determine the optimal trochlea fixation in double plate osteosynthesis of intraarticular distal humerus fractures. METHODS: A low transcondylar, C3-type distal humerus fracture was created in 20 fresh-frozen human cadaveric humeri. The samples were then randomly divided into two groups of 10 specimens each. Double plate osteosynthesis was performed in both groups. In group A, the two most distal screws of the lateral plate were inserted into the trochlea fragment. In group B, these screws did not extend into the trochlea. Displacement under cyclic loading and ultimate failure loads were determined for all specimens. RESULTS: Group A showed significantly less displacement under cyclic loading in each measurement interval (0.92 mm vs. 1.53 mm after 100 cycles, p = 0 0.006; 1.10 mm vs. 1.84 mm after 1000 cycles, p = 0.007; 1.18 mm vs. 1.98 mm after 2000 cycles, p = 0.008). The ultimate failure load was significantly higher in group A than in group B (345.61 ± 120.389 N vs. 238.42 ± 131.61 N, p = 0.037). CONCLUSIONS: Fixation of the trochlea with interdigitating screws in double plate osteosynthesis of low-condylar type C distal humerus fractures results in superior construct stability. LEVEL OF EVIDENCE: not applicable (biomechanical).

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.

Unilateral Technique for Interposition Arthroplasty of the Elbow-A Technical Note.

Stiffness and pain secondary to end-stage dysfunctional osteoarthritis of the elbow can pose a therapeutic dilemma. Although total elbow arthroplasty is successful in older patients with low functional demand, alternatives to joint replacement must be found in the younger, more active individual. Interposition arthroplasty provides a salvage option for young, high-demand patients who hope to minimize functional restrictions of the affected extremity. The procedure traditionally involves release of both collateral ligaments and the joint capsule, resulting in a higher risk for postoperative instability and complications. The present unilateral technique demonstrates an approach maintaining the integrity of the medial or lateral collateral ligament while still allowing secure graft fixation. Stability can usually be preserved without ligament reconstruction or hinged external fixation if the elbow was stable before surgery.

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.

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.

Morphometrics of the coronoid process and the radial notch of the ulna: implications for fracture assessment.

PURPOSE: A comprehensive analysis of the morphology of fractures of the coronoid process (CP) can aid diagnosis and guide treatment. The involvement of the radial notch of the ulna (RN)-e.g., in anterolateral facet fractures and transverse fractures of the CP-may influence the biomechanical conditions of the proximal radioulnar joint. However, the morphometric relation between the CP and the RN and the extent to what the proximal radioulnar joint can be affected in these types of fractures is unknown. METHODS: A total of 113 embalmed, cadaveric ulnae were dissected. All soft tissue was removed. Strictly lateral, high-resolution photographs were taken and digitally analyzed. The height of the CP and its relation to the RN was measured. Sex differences and correlations between measured parameters were calculated. RESULTS: Mean height of the CP was 16 mm (range: 12-23 mm; SD: 2). Mean height of the RN was 16 mm (11-25 mm; 2.2). The 50% mark of the CP corresponded to 18% (0-56%; 11.2) of the height of the RN. No significant differences were found between male and female specimens. CONCLUSION: The RN of the ulna extends only to a small part to the CP. Transverse or anterolateral fractures of less than 50% of the coronoid process may involve only a small portion of the proximal radioulnar joint.