Fanny Canet

Validity of Goniometric Elbow Measurements: Comparative Study with a Radiographic Method

BackgroundA universal goniometer is commonly used to measure the elbow’s ROM and carrying angle; however, some authors question its poor intertester reliability.Questions/purposesWe (1) assessed the validity of goniometric measurements as compared with radiographic measurements in the evaluation of ROM of the elbow and (2) determined the reliability of both.MethodsThe ROM and carrying angle of 51 healthy subjects (102 elbows) were measured using two methods: with a universal goniometer by one observer three times and on radiographs by two independent examiners. Paired t-test and Pearson’s correlation were used to compare and detect the relationship between mean ROM. The maximal error was calculated according to the Bland and Altman method.ResultsThe intraclass correlation coefficients (ICC) ranged from 0.945 to 0.973 for the goniometric measurements and from 0.980 to 0.991 for the radiographic measurements. The two methods correlated when measuring the total ROM in flexion and extension. The maximal errors of the goniometric measurement were 10.3° for extension, 7.0° for flexion, and 6.5° for carrying angle 95% of the time. We observed differences for maximum flexion, maximal extension, and carrying angle between the methods.ConclusionBoth measurement methods differ but they correlate. When measured with a goniometer, the elbow ROM shows a maximal error of approximately 10°.Clinical RelevanceThe goniometer is a reasonable and simple clinical tool, but for research protocols, we suggest using the radiographic method because of the higher level of precision required.

Progressive osteolysis of the radius after distal biceps tendon repair with the bioabsorbable screw

BACKGROUND Several complications have been reported with the use of the PLLA (poly-L-Lactide) bioabsorbable screw in orthopedic surgery. The hypothesis was that the use of a bioabsorbable screw in distal biceps tenodesis results in significant osteolysis of the radial bone. The correlation between osteolysis and functional and clinical outcomes was also studied. METHODS All consecutive patients who underwent anatomic repair of the distal biceps tendon with a bioabsorbable screw were included. From the x-ray taken immediately after the surgery, the ratio between the volume of the bone tunnel and the volume of the radius bone section was measured. This relation was calculated at different follow-up periods to obtain the percentage of tunnel enlargement over time. Complications, as well as functional and clinical outcomes, were also assessed. Mayo Elbow Performance Score (MEPS), the quick-Disability Arm Shoulder Hand (DASH), and the Short-Form 12 (SF-12) were used. RESULTS Nineteen consecutive patients were available for follow-up. The average initial relative volume occupied by the screw tunnel was 49% of the bone section and increased to 61% at the last follow-up at an average of 22 months (range, 3-62 months). Eight of the 19 patients presented postoperative complications. There was only 1 case of complete bone filling of the tunnel, which was observed at a 5-year and 2-months follow-up. There was no significant correlation between the volume of bone resorption and functional and clinical outcomes. DISCUSSION No correlation was found between the volume of bone tunnel and the functional outcome. However, the results indicate that the use of a bioabsorbable screw in distal biceps tendon repair results in significant bone osteolysis.

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.

Effect of force tightening on cable tension and displacement in greater trochanter reattachment

The purpose of this study was to evaluate cable tension during installation, and during loading similar to walking in a cable grip type greater trochanter (GT), reattachment system. A 4th generation Sawbones composite femur with osteotomised GT was reattached with four Cable-Ready® systems (Zimmer, Warsaw, IN). Cables were tightened at 3 different target installation forces (178, 356 and 534 N) and retightened once as recommended by the manufacturer. Cables tension was continuously monitored using in-situ load cells. To simulate walking, a custom frame was used to apply quasi static load on the head of a femoral stem implant (2340 N) and abductor pull (667 N) on the GT. GT displacement (gap and sliding) relative to the femur was measured using a 3D camera system. During installation, a drop in cable tension was observed when tightening subsequent cables: an average 40+12.2% and 11±5.9% tension loss was measured in the first and second cable. Therefore, retightening the cables, as recommended by the manufacturer, is important. During simulated walking, the second cable additionally lost up to 12.2+3.6% of tension. No difference was observed between the GT-femur gaps measured with cables tightened at different installation forces (p=0.32). The GT sliding however was significantly greater (0.9±0.3 mm) when target installation force was set to only 178 N compared to 356 N (0.2±0.1 mm); p<0.001. There were no significant changes when initial tightening force was increased to 534 N (0.3±0.1 mm); p=0.11. In conclusion, the cable tightening force should be as close as possible to that recommended by the manufacturer, because reducing it compromises the stability of the GT fragment, whereas increasing it does not improve this stability, but could lead to cable breakage.

Initial Tension Loss in Cerclage Cables

Cerclage cables, frequently used in the management of fractures and osteotomies, are associated with a high failure rate and significant loosening during surgery. This study compared the capacity to maintain tension of different types of orthopaedic cable systems. Multifilament Cobalt-Chrome (CoCr) cables with four different crimp/clamp devices (DePuy, Stryker, Zimmer and Smith&Nephew) and one non-metallic Nylon (Ny) cable from Kinamed were instrumented with a load cell to measure tension during insertion. Significant tension loss was observed with crimping for all cables (P<0.05). Removing the tensioner led to an additional unexpected tension loss (CoCr-DePuy: 18%, CoCr-Stryker: 29%, CoCr-Smith&Nephew: 33%, Ny: 46%, and CoCr-Zimmer: 52%). The simple CoCr (DePuy) cable system outperformed the more sophisticated locking devices due to its significantly better ability to prevent tension loss.

Force relaxation and sprinback of novel elastic orthopedic cables

Cerclage cables have proven to be very useful in the orthopedic field for bones stabilization and plate fixation but the initial enthusiasm for metallic cables has declined with their high complication rates. Metal materials provide limited elastic deformation compromising their ability to maintain compression. This study compares the mechanical properties of new elastic cables with cobalt-chrome and stainless-steel cables. Methods: Stainless-steel, cobalt-chrome, nylon and nickel-titanium cables were first loaded up to 356 N, then elongation was maintained for 12 hours, next unloaded and finally reloaded to failure. Initial elongation (%), Relative force relaxation (% loss of initial load after a 12h), elastic springback (%) and force to failure (N) were extracted from force-elongation curves. Findings: Initial elongation was the highest for nylon cables (9%), followed by the nickel-titanium (4%) and both metallic cables (0.3%). During 12 hours, no relaxation was observed for the nickel-titanium and the cobalt-chrome cables, whereas 28 and 45% of the tension was lost respectively for the stainless-steel and the nylon cables. The elastic springback of the nickel-titanium and nylon cables (4.4 and 4.7% respectively) was 20 times higher than that of the stainless-steel and cobalt-chrome cables (0.12 and 0.16% respectively). The force to failure of the stainless steel and cobalt-chrome cables was twice that of the nickel-titanium cables. Interpretation: Multi-braided stainless-steel and cobalt-chrome cables have a high-stiffness with limited ability to tolerate displacement, leading to early cable loosening. Novel low-stiffness cables made of nylon or nickel-titanium offer significant elastic springback improving binding stability.