Emilie Sandman

The influence of proximal ulnar morphology on elbow range of motion

BACKGROUND Physiologic dorsal apex angulation of the proximal ulna is present in 96% of the population. We hypothesize that a correlation exists between the physiologic dorsal ulnar angulation and elbow range of motion (ROM). METHODS Fifty healthy adults underwent bilateral lateral elbow radiographs in neutral forearm rotation in the following positions: terminal flexion (TF), 90° of flexion, and terminal extension (TE). The proximal ulna dorsal angulation (PUDA), TF, and TE were measured on the digital lateral radiographs by 2 independent observers. ROM was calculated as the difference between TF and TE measurements. Subjects were divided into 2 groups: those with PUDA measurements less than the median and those with PUDA measurements equal to or greater than the median. The relationship between the PUDA and TE, TF, and ROM was evaluated by use of Pearson correlation coefficients. RESULTS The mean age of the cohort was 31 ± 9 years, and there were 30 women among the 50 volunteers. The sample of 100 elbow radiographs had a mean TF of 150.8° ± 4.5°, a mean TE (ie, flexion contracture) of 11.5° ± 7.3°, and a mean ROM of 139.3° ± 8.4°. The mean PUDA was 5.2° ± 2.8°. Elbows with a greater PUDA had significantly less TE (r = 0.381, P ≤ .001) and ROM (r = -0.351, P ≤ .001). The group of elbows with a lesser PUDA had better TE (9.4° vs 13.6°, P = .004) and ROM (142.0° vs 136.7°, P = .001) than elbows with a greater PUDA. CONCLUSION The increasing magnitude of the PUDA is associated with decreased maximal elbow extension and global elbow ROM.

A biomechanical study comparing polyaxial locking screw mechanisms

OBJECTIVE Locking plates have become ubiquitous in modern fracture surgery. Recently, manufacturers have developed locking plates with polyaxial screw capabilities in order to optimise screw placement. It has already been demonstrated that inserting uniaxial locking screws off axis results in weaker loads to failure. Our hypothesis was that even implants specifically designed for polyaxial insertion would experience a drop-off in resistance when using non-perpendicular screws. METHODS Four different types (one monoaxial and three polyaxial locking plates) of readily available small fragment plates were tested. A biomechanical model was developed to test the screws until failure (defined as breakage and rapid loss of >50% force). Screws were inserted at 0, 10 and 15°. RESULTS The standard monoaxial locking mechanism sustained saw a 60% reduction in force (332N vs. 134N) when screws were inserted cross-threaded at 10°. Two polyaxial systems saw similar significant reductions in force of 45% and 34%, respectively at 15°. A third system utilizing an end cap locking mechanism showed highly variable results with large standard deviations. Polyaxial screws showed on average only limited reduction at 10 degrees of insertion angle. CONCLUSION Newer designs of locking plates have attractive properties to allow more surgical options during fixation. However this freedom comes at the price of reduced force. Our results show that the safe zone for inserting these screws is closer to 20°, rather than the 30° indicated by the manufacturers. Also, the various polyaxial locking mechanisms seem to influence the overall resistance of the screws.

Demographic and anthropometric factors affecting elbow range of motion in healthy adults

BACKGROUND To use elbow range of motion routinely as a diagnostic index, it is important to explain the normal variability among the population. Consequently, this study assessed the possible associations between age, sex, laterality, body mass index, joint laxity, level of physical activities, upper limb dimensions, and the elbow range of motion in flexion/extension. MATERIALS AND METHODS Maximal flexion and extension were measured on the lateral radiographs of 102 elbows of 51 volunteers. The difference of range of motion regarding sex and laterality was assessed with Student t tests. The Pearson correlation coefficient was used to evaluate the relationship between elbow mobility and the other factors, and a stepwise multiple regression analysis was performed. RESULTS Among the 51 volunteers, a correlation was found between flexion and body mass index, age, and midbrachial and forearm circumferences (r = -0.234 to -0.594). Age (r = 0.268) and hyperlaxity (r = -0.323) were the only factors associated with a change in elbow extension. No correlation was found between the level of physical activity or with the laterality and changes in elbow mobility. Finally, women presented with more flexion and total elbow range of motion than men. CONCLUSIONS This study confirms the association between various demographic and anthropometric factors and elbow range of motion in healthy adults. Among these, the body mass index and forearm circumference are the most likely responsible for mobility variations among the population.

Radial head translation measurement in healthy individuals: the radiocapitellar ratio

HYPOTHESIS We hypothesized that the radiocapitellar ratio (RCR) is a valid and reproducible method to assess radial head translation in healthy individuals and that the normal RCR of healthy individuals is 0%. MATERIALS AND METHODS Lateral radiographs of the elbow were examined in 40 healthy patients. The measurement method of the RCR was the displacement of the radial head (minimal distance between the right bisector of the radial head and the center of the capitellum) divided by the diameter of the capitellum. Intraobserver and interobserver reliability was evaluated using intraclass correlation (ICC). RESULTS The RCR was 4% ± 4% (range, -7% to 19%). The mean RCR of 4% measured in this cohort represents an anterior displacement of 1 mm in a capitellum of 25 mm. Intraobserver reliability was good (ICC, 0.72) and interobserver reliability was fair (ICC, 0.52). A significant side-to-side correlation was observed (r = 0.4, P = .009). No difference was identified between men and women, and no correlation was identified between age and the RCR. The standard deviation of the centered RCR measurements was 3%, which represented the variability of RCR measurements. CONCLUSIONS The results of this study confirm the traditional belief that in the normal elbow, the radial head is generally aligned towards the capitellum on lateral radiographs. Accordingly, a RCR observed outside the ranges of 1 mm posterior (-5%) to 3 mm anterior (13%) in a 25 mm capitellum suggests a misalignment at the RC joint of the elbow. The RCR method to assess RC joint translations has demonstrated a normal distribution in healthy individuals and good reliability.

Radial Head Subluxation After Malalignment of the Proximal Ulna: A Biomechanical Study.

Objectives: Understanding the anatomy of proximal ulna is important when treating complex injuries, since nonanatomic reconstruction may lead to malunion, arthrosis, and instability. The proximal ulna has a sagittal bow, termed the proximal ulna dorsal angulation (PUDA). The purpose of this study was to evaluate the magnitude of angular malalignment at the PUDA that would lead to radial head subluxation. Methods: This biomechanical study was conducted on 6 fresh frozen upper extremities with an elbow movement simulator. An osteotomy was performed at the PUDA and stabilized with internal fixation at 5 angles. Lateral elbow fluoroscopic images were taken in 4 elbow and 3 forearm positions, with the annular ligament intact and then released. The displacement of the radial head was quantified with the radiocapitellar ratio measurement. Results: A significant interaction exists between elbow positions, angles of malalignment, and annular ligament integrity (P < 0.001). The greatest magnitudes of radial head subluxation were with annular ligament tear, ranging from −4% to 88% (P < 0.001). Significant differences were found between the different internal fixation angles (P = 0.002) and elbow positions (P < 0.001). Anterior subluxation increased as malalignment was fixed into extension and with progressive elbow flexion. Posterior subluxation increased as malalignment advanced into flexion and decreased with elbow flexion. Conclusions: Proximal ulna malalignment combined with an annular ligament tear affect the biomechanics of the elbow and can lead to radial head subluxation. This study demonstrates the importance of an anatomic reconstruction, specifically recreation of each individuals unique PUDA. Thus, in the setting of a comminuted proximal ulna fracture with associated annular ligament insufficiency, radiographs of the contralateral elbow may assist with the restoration of the normal anatomy to limit radial head instability.

Measurement of combined glenoid and Hill–Sachs lesions in anterior shoulder instability

Background Recurrent glenohumeral anterior instability (RGAI) frequently induces combined glenoid and Hill–Sachs bone lesions and is a risk factor for soft tissue repair failure. This cohort study describes a simple preoperative quantification method for bone loss, the Clock method, the first that combines glenoid and humeral lesions. Methods Computed tomography scans of 34 shoulders with RGAI were twice reviewed by three independent observers, who measured bone lesions using the new Clock method and existing validated methods. Intra- and inter-observer reliability of the Clock method was evaluated (intraclass correlation coefficient). Pearson correlation was used to correlate Clock method with existing methods, and with function (Western Ontario Shoulder Instability, Quick-Disabilities of the Arm, Shoulder and Hand). Results Thirty-two patients met the inclusion criteria: three females and 29 males, mean age 28 years. The intra- and inter-observer reliability was excellent, with intraclass correlation coefficient ranging from 0.817 to 0.938 for the novel Clock method. Humeral Clock and Glenoid Clock strongly correlated with Humeral Ratio (r = 0.882, p < 0.001) and Glenoid Surface Area and Glenoid Ratio (r = 0.793 and 0.717, p < 0.001), respectively. The classic threshold of 25% of the glenoid diameter with the Glenoid Ratio method corresponds to 4 hours with the Glenoid Clock method. Conclusions The Clock method is quick and reliable, with more studies being needed to investigate whether it is correlated with surgical outcomes.

Involvement of the proximal radial ulnar joint in partial radial head fractures: a novel three-dimensional computed tomography scan evaluation method

Background Partial radial head fractures (PRHF) can involve the proximal radioulnar joint (PRUJ) or be restricted to the ‘safe zone’ (SZ) during forearm rotation. The objective of the present study was to develop an assessment method for PRUJ involvement in radial head fractures using axial computed tomography (CT) scans. Methods The area of the radial head in contact with the PRUJ zone was identified, and defined on 18 cadaveric elbows CT scans; the quantitative relationship between PRUJ zone and radial tuberosity was established. Then, four evaluators validated it on PRHF CT scan axial views, classifying the fractures as involving the PRUJ or not. Results Using the radial tuberosity as the 0° of a 360° circle, the SZ was within 108° to 212° clockwise for a right elbow and counter clockwise for the left elbow. Fifty-five consecutive (30 men, 25 women, mean age of 49 years) partial radial head fracture CT scans were classified: four in the SZ only, three in the PRUJ zone and 48 in both the PRUJ and SZ. The kappa for the inter- and intra-observer agreement was 0.517 and 0.881, respectively. Conclusions Ninety-three percent of partial radial head fractures will involve the PRUJ and the geometric model developed allows their classification, potentially helping surgeons decide on optimal treatment. Level of evidence Retrospective basic science study. Level III: anatomic study, imaging

Effect of elbow position on radiographic measurements of radio-capitellar alignment

AIM To evaluate the effect of different elbow and forearm positions on radiocapitellar alignment. METHODS Fifty-one healthy volunteers were recruited and bilateral elbow radiographs were taken to form a radiologic database. Lateral elbow radiographs were taken with the elbow in five different positions: Maximal extension and forearm in neutral, maximal flexion and forearm in neutral, elbow at 90° and forearm in neutral, elbow at 90° and forearm in supination and elbow at 90° and forearm in pronation. A goniometer was used to verify the accuracy of the elbows position for the radiographs at a 90° angle. The radiocapitellar ratio (RCR) measurements were then taken on the collected radiographs using the SliceOmatic software. An orthopedic resident performed the radiographic measurements on the 102 elbows, for a total of 510 lateral elbow radiographic measures. ANOVA paired t-tests and Pearson coefficients were used to assess the differences and correlations between the RCR in each position. RESULTS Mean RCR values were -2% ± 7% (maximal extension), -5% ± 9% (maximal flexion), and for elbow at 90° and forearm in neutral -2% ± 5%, supination 1% ± 6% and pronation 1% ± 5%. ANOVA analyses demonstrated significant differences between the RCR in different elbow and forearm positions. Paired t-tests confirmed significant differences between the RCR at maximal flexion and flexion at 90°, and maximal extension and flexion. The Pearson coefficient showed significant correlations between the RCR with the elbow at 90° - maximal flexion; the forearm in neutral-supination; the forearm in neutral-pronation. CONCLUSION Overall, 95% of the RCR values are included in the normal range (obtained at 90° of flexion) and a value outside this range, in any position, should raise suspicion for instability.