Fracture Pattern Influences Radial Head Replacement Size Determination Among Experienced Elbow Surgeons

The role of radial head morphology in proximal radioulnar joint congruency during forearm rotation

Purpose

Congruency of the proximal radioulnar joint (PRUJ) is important in the rotation of the forearm while any compromise would significantly impair the elbow function. The purpose of this study is to determine the morphological features of the radial head and investigate its role in the congruency of the PRUJ during forearm rotation. The hypothesis is that the PRUJ is more congruent in the maximal pronation and supination positions than in the neutral position.

Methods

Thirty sets of computed tomography images of the elbow were acquired, and a three-dimensional model of the proximal radius and ulna was generated. The radius of curvature of the radial head and the radial head at the maximal pronation, neutral positions and maximal supination were calculated and compared with a one-way analysis of variance.

Results

The point on the radial head contacting the middle point of radial head at the maximal pronation and supination was located at the ends of the semi-major axis of the ellipse, while it was located at one end of the semi-minor axis at neutral position. The radii of curvature of the pronation, neutral and supination points of the radial head were 14.72 ± 1.51, 9.74 ± 1.49 and 14.58 ± 1.70 mm, respectively. The value of the neutral point was significantly smaller than that of the pronation and supination points.

Conclusions

This study quantitatively evaluated the morphology of the radial head and suggested that the best congruency of the PRUJ was achieved at maximal pronation and supination, while the neutral position was associated with the least congruency.

Level of Evidence

Basic Science Study.

Radial head arthroplasty diameter impact on elbow kinematics evaluated by dynamic radiostereometric analysis

Purpose

Radial head arthroplasty (RHA) reestablishes elbow stability after complex radial head fracture, but complication rates are high, possibly due to inappropriate implant sizing. Knowledge of impact of radial head implant diameter on elbow kinematics is limited and warranted. This study evaluated elbow kinematics of different radial head implant diameters after RHA using dynamic radiostereometric analysis (dRSA).

Methods

Eight human donor arms were examined with dRSA during elbow flexion with the forearm in unloaded neutral position, and in supinated- and pronated position without and with 10N either varus or valgus load, respectively. Elbow kinematics were examined before and after RHA with head diameters of anatomical size, -2 mm (undersized), and +2 mm (oversized). The ligaments were kept intact by use of step-cut humerus osteotomy for repeated RHA exchange. Bone models were obtained from CT, and by AutoRSA software bone models were matched with dRSA recordings. The elbow kinematics were described using anatomical coordinate systems.

Results

Compared to the native radial head during elbow flexion, the anatomical sized RHA shifted 2.0 mm in ulnar direction during unloaded pronated forearm position. The undersized RHA shifted 1.5 mm in posterior direction and 2.1 mm in ulnar direction during unloaded pronated forearm position and increased the varus angle by 2.4° during supinated loaded forearm position. The oversized RHA shifted 1.6 mm in radial direction during loaded supinated forearm position.

Conclusions

The anatomically sized RHA should be preferred as it maintained native elbow kinematics the best. The kinematic changes with oversized and undersized RHA diameters were small, suggesting forgiveness for the RHA diameter size.

Level of Evidence

Level III.

Novel Radiographic Indexes for Elbow Stability Assessment: Part A-Cadaveric Validation

INTRODUCTION

Elbow bony stability relies primarily on the high anatomic congruency between the humeral trochlea and the ulnar greater sigmoid notch. No practical tools are available to distinguish different morphotypes of the proximal ulna and herewith predict elbow stability. The aim of this study was to assess inter-observer reproducibility, evaluate diagnostic performance and determine responsiveness to change after simulated coronoid process fracture for three novel elbow radiographic indexes.

METHODS

Ten fresh-frozen cadaver specimens of upper limbs from human donors were available for this study. Three primary indexes were defined, as well as two derived angles: Trochlear Depth Index (TDI); Posterior Coverage Index (PCI); Anterior Coverage Index (ACI); radiographic coverage angle (RCA); olecranon-diaphisary angle (ODA). Each index was first measured on standardized lateral radiographs and subsequently by direct measurement after open dissection. Finally, a type II coronoid fracture (Regan and Morrey classification) was created on each specimen and both radiographic and open measurements were repeated. All measurements were conducted by two orthopaedic surgeons and two dedicated musculoskeletal radiologists.

RESULTS

All three indexes showed good or moderate inter-observer reliability and moderate accuracy and precision when compared to the gold standard (open measurement). A significant change between the radiographic TDI and ACI before and after simulated coronoid fracture was observed [TDI: decrease from 0.45 ± 0.03 to 0.39 ± 0.08 (p = 0.035); ACI: decrease from 1.90 ± 0.17 to 1.58 ± 0.21 (p = 0.001)]. As expected, no significant changes were documented for the PCI. Based on these data, a predictive model was generated, able to identify coronoid fractures with a sensitivity of 80% and a specificity of 100%.

CONCLUSION

New, simple and easily reproducible radiological indexes to describe the congruency of the greater sigmoid notch have been proposed. TDI and ACI change significantly after a simulated coronoid fracture, indicating a good responsiveness of these parameters to a pathological condition. Furthermore, combining TDI and ACI in a regression model equation allowed to identify simulated fractures with high sensitivity and specificity. The newly proposed indexes are, therefore, promising tools to improve diagnostic accuracy of coronoid fractures and show potential to enhance perioperative diagnostic also in cases of elbow instability and stiffness.

LEVEL OF EVIDENCE

Basic science study.

CLINICAL RELEVANCE

The newly proposed indexes are promising tools to improve diagnostic accuracy of coronoid fractures as well as to enhance perioperative diagnostic for elbow instability and stiffness.

Novel Radiographic Indexes for Elbow Stability Assessment: Part B-Preliminary Clinical Study

INTRODUCTION

The coronoid process plays a key-role in preserving elbow stability. Currently, there are no radiographic indexes conceived to assess the intrinsic elbow stability and the joint congruency. The aim of this study is to present new radiological parameters, which will help assess the intrinsic stability of the ulnohumeral joint and to define normal values of these indexes in a normal, healthy population.

METHODS

Four independent observers (two orthopaedic surgeons and two radiologists) selected lateral view X-rays of subjects with no history of upper limb disease or surgery. The following radiographic indexes were defined: trochlear depth index (TDI); anterior coverage index (ACI); posterior coverage index (PCI); olecranon-coronoid angle (OCA); radiographic coverage angle (RCA). Inter-observer and intra-observer reproducibility were assessed for each index.

RESULTS

126 subjects were included. Standardized lateral elbow radiographs (62 left and 64 right elbows) were obtained and analysed. The mean TDI was 0.46 ± 0.06 (0.3-1.6), the mean ACI was 2.0 ± 0.2 (1.6-3.1) and the mean PCI was 1.3 ± 0.1 (1.0-1.9). The mean RCA was 179.6 ± 8.3° (normalized RCA: 49.9 ± 2.3%) and the mean OCA was 24.6 ± 3.7°. The indexes had a high-grade of inter-observer and intra-observer reliability for each of the four observers. Significantly higher values were found for males for TDI, ACI, PCI and RCA.

CONCLUSION

The novel radiological parameters described are simple, reliable and easily reproducible. These features make them a promising tool for radiographic evaluation both for orthopaedic surgeons and for radiologists in the emergency department setting or during outpatient services.

LEVEL OF EVIDENCE

Basic Science Study (Case Series).

CLINICAL RELEVANCE

The novel radiological parameters described are reliable, easily reproducible and become handy for orthopaedic surgeons as well as radiologists in daily clinical practice.

Does Sawbone-Based Arthroscopy Module (SBAM) Can Help Elbow Surgeons?

INTRODUCTION

The use of elbow arthroscopy is becoming increasingly common in orthopaedic practice; nevertheless, it is still considered a difficult procedure with a long learning curve. The aim of the study is to evaluate the role of a new elbow Sawbone-Based Arthroscopy Module (e-SBAM) in the training of elbow surgeons.

METHODS

Fourteen surgeons were classified as "Expert" (n: 7; more than 10 years of experience in arthroscopic surgery) and "Not-expert" surgeons (n: 7; less than 10 years of experience). During a dedicated arthroscopic session, using the Sawbones Elbow model (Sawbones Europe AB®), all participants were asked to perform an arthroscopic round and to touch three specific landmarks. An independent observer measured the time that each participant needed to perform this task (Performance 1). The same measurement was repeated after two weeks of eSBAM training (Performance 2).

RESULTS

"Not-expert" surgeons needed significantly more time (41 s; range 26-120) than "Expert" ones (13 s; range 8-36) to complete Performance 1. One "Not-expert" surgeon did not complete Performance 1 and needed more than 120 s for Performance 2. The whole study group required a median of 5 s less to complete Performance 2. A tendency towards an improvement was observed in the group of the non-experienced surgeons as compared with the experienced ones.

CONCLUSIONS

The simulation training can be advantageous in the learning curve of young elbow surgeons and helpful for experienced surgeons. E-SBAM can be used as an effective tool for the current stepwise arthroscopic elbow training programs with the aim of improving arthroscopic elbow skills.

LEVEL OF EVIDENCE

Basic Science Study.

Validation of a Practical Forearm Supination Strength Measurement Technique in the Large Sample Cohort

INTRODUCTION

The strength of forearm in pronation and supination (P/S) is an important clinical assessment during pre-operative examination as well as in post-operative evaluation. Many clinical trials concerning the measurement of forearm P/S strength were performed using a dynamometer fixed on the wall. The aim of this study was to bring out a simple and reliable technique for the measurement of P/S strength using a dynamometer manually supported and stabilized by an examiner. We hypothesized that there are no differences in evaluation of elbow P/S strength using the dynamometer fixed or the dynamometer stabilized by an operator in healthy people.

METHODS

The study was performed on a cross-sectional cohort of 100 healthy subjects without any history of injuries or previous surgery of the upper limbs. Isometric forearm P/S strengths were measured on the dominant and non-dominant forearms, using the dynamometer fixed on a table, and using the same dynamometer kept by an operator. The measurements were repeated in triplicate at 45°, 90° and 120° of elbow flexion in both upper limbs for all patients.

RESULTS

A total of 100 subjects (50 females, 50 males) were included in the study group. The mean age was 46.5 years (range 25-52 years). Female and male subjects showed no significant differences concerning the mean age (F/M ratio 0.50/0.50). The mean body mass index of all participants was 24.34 ± 3.66 kg/m2.No significant statistics difference was reported between the P/S strength measured using the two detection methods in our study group (45°, 90° and 120° of elbow flexion and both upper limbs).

CONCLUSION

The manually stabilized technique is a valid and reliable technique to assess the P/S strength of the forearm. This is a simple and effective method that may be reproduced in our daily clinical practice as well as in sportive practice.