Plain radiographs are inadequate to identify overlengthening with a radial head prosthesis

Intraoperative visualization of the posterolateral ulnohumeral joint space is reliable to indicate overlengthening in radial head arthroplasty

INTRODUCTION

Avoiding overlengthening in radial head arthroplasty (RHA) is essential for the prognosis of the elbow joint. An overlengthening from 2 mm is visible due to widening of the anterolateral ulnohumeral joint space but intraoperatively, this particular joint space is difficult to visualize. The commonly used Kocher approach allows visualization of the posterolateral joint space without additional instruments or further surgical release of the already unstable elbow. The aim of our study was to investigate whether the visualization of the posterolateral joint space is also a reliable method to indicate overlengthening in RHA.

MATERIAL AND METHODS

RHA was performed in five human cadaveric specimens with the forearm, wrist, and hand intact. The lateral ligament complex was detached and an anatomic transosseous refixation was performed. Six stages of implantation heights were documented: native joint (1), RHA at the anatomic height (2), + 2 mm (3), + 4 mm (4), + 6 mm (5) and - 2 mm (6). Macroscopic measurement and digital image analysis of the posterolateral and anterolateral ulnohumeral joint spaces were performed.

RESULTS

All stages of overlengthening showed a significant increase in posterolateral and anterolateral joint space widening (p < 0.05). The posterior and anterior joint space showed excellent intraclass correlation.

CONCLUSION

Visualization of the posterolateral aspect of the ulnohumeral joint space is a reliable indicator for overlengthening in RHA without further compromising an already unstable elbow. Correlation to the findings of the anterolateral ulnohumeral joint space in different implants leads to the assumption that visualization of either the anterior or posterior ulnohumeral joint space is universally applicable to determine overlengthening in RHA, regardless of the type of the radial head implant.

Radiographic assessment of overlengthening of the MoPyC radial head prosthesis: a cadaveric study

INTRODUCTION

The aim of this study was to evaluate a radiographic measurement method for assessment of overlengthening of the MoPyC radial head prosthesis.

MATERIALS AND METHODS

Seven cadaver specimens were studied in ten stages: native specimen (1), radial head resection (2), and implantation of the MoPyC radial head prostheses (Bioprofile, Tornier, Montbonnot-Saint-Martin, France) in four increasing length (correct length, overlengthening of 1.5 mm, 3 mm, and 5 mm) with an intact medial collateral ligament (MCL 3-6) and following transection of the MCL (7-10). The radiographic measurement method according to Athwal et al. was evaluated to detect overlengthening. Statistical analysis included calculation of the diagnostic accuracy of the radiographic method.

RESULTS

The radiographic measurement method correctly determined the size of the radial head prosthesis within ± 1 mm in 224 of 336 scenarios (67%) and within ± 2 mm in 320 of 336 scenarios (95%). With a threshold value of ≥ 1 mm, the overall diagnostic sensitivity for detecting overlengthening when it was present and was 90% and the specificity was 79%. The sensitivity was higher with increasing size of the prosthesis: in cases with overlengthening of 1.5 mm, the sensitivity was 76%, with an overlengthening of 3 mm, the sensitivity was 95%, and with an overlengthening of 5 mm, the sensitivity was 100%.

CONCLUSION

The radiographic measurement method of Athwal et al. can be used to estimate and to diagnose the magnitude overlengthening of the MoPyC radial head prosthesis. However, the sensitivity is limited (76%) in cases with a small amount of overlengthening of 1.5 mm.

Validation of a Simple Overlay Device to Assess Radial Head Implant Length

PURPOSE

A simple overlay device (SOD) was developed to measure radial head implant length. The purpose of this study was to determine the accuracy and reliability of this device for measuring experimental radial head implant length.

METHODS

Five fresh frozen cadavers were implanted with sequentially longer implants, adjusted by neck length (0, 2, 4, and 8 mm). Fluoroscopic images were obtained in 4 forearm positions: anteroposterior in supination in full extension, anteroposterior in pronation in full extension, supinated in 45° of flexion, and neutral in 45° of flexion. The SOD measurements (made by 2 observers) were compared with the native original radial head (control) to assess implant length. In addition, gapping of the ulnohumeral joint space was measured for comparison purposes.

RESULTS

The measured radial head and neck lengths for the specimens were 33, 39, 31, 34, and 42 mm. The difference between the actual radial head and neck lengths and those measured with the SOD template averaged less than 2 mm for all 4 collar sizes, except in 1 measurement in which the bicipital tuberosity could not be visualized. The median intraclass correlation coefficients for observer 1 compared with the SOD were 0.94 to 0.99. The median intraclass correlation coefficients between observers were 0.88 to 0.95. For both observers, elbow position, collar height, and the 2 variables combined did not significantly affect the SOD values. The other method that was evaluated, that of measurement of the ulnohumeral joint space, had higher interobserver variability versus the SOD, and allowed detection of lengthening of over 4 mm.

CONCLUSIONS

The SOD is a reliable method for simply assessing radial head length with radiographs and can accurately detect 2 mm or more of proximal radial lengthening.

CLINICAL RELEVANCE

The SOD is a simple and accurate method that can help to optimize radial head sizing.

Radial head prosthesis: surgical tips and tricks

Radial head prostheses (RHP) have been developed to decrease the complications rate following a radial head resection surgery. The aim of the RHP is to replicate the physiological radiocapitellar tracking, reproducing the mechanical function of the native radial head: to stabilize the elbow and to shear the forces passing through the elbow along with the other stabilizers. The currently used RHP models try to achieve this target with three different prosthesis' strategies: (a) loose fit stem, (b) bipolar radial head or (c) anatomical radial head. Even if the radial head fixation is the preferred technique in every possible case and the resection can be still considered a possible option, in the last years there has been a growing worldwide consensus in using the radial head replacement in patients with unfixable radial head fractures, especially if associated with complex elbow instability. However, complications after a RHP are not uncommon, and their rate is raising as long as the implants number are increasing. The main difficulties are due to the implantation technique that needs to be performed with the same attention and precision used for the replacement of all the other joints, and to the concurrent treatment of the associated lesions. A personalized postoperative rehabilitation program is essential for obtaining good results and decreasing the complications rate. Concern exists for the young age of the patients that often require a RHP: personal experience and literature analysis suggest that if the clinical and radiographic results are positive after a 6-12-month follow-up, good outcomes can be also expected at a medium- or long-term follow-up.

Is the distal radioulnar variance useful for identification of radial head prosthesis overlengthening? A cadaver study

BACKGROUND

Overlengthening by radial head prosthetic replacement leads to insufficient functionality and increased capitellar wear. It has been shown that in monopolar prostheses, the radial overlengthening by an overstuffed prosthesis leads to significant differences in the distal radioulnar variance at the wrist. This study evaluated ipsilateral ulnar variance as a predictor for overlengthening after implantation of a multipolar prosthesis.

METHODS

The radial heads of seven fresh frozen upper extremities were resected and a multipolar radial head prosthesis was implanted. Thereafter, the native radioulnar variance at the wrist was documented via fluoroscopy. The alignment of the distal radioulnar joint in neutral, pronated and supinated rotational positions of the forearm was recorded fluoroscopically, and digital image analysis was performed regarding radioulnar shifting.

RESULTS

Statistical analysis of the difference between native height and the manipulated states did not show consistent significant differences with stepwise overlengthening of +1.5, +3, +4.5 and +6 mm and with respect to rotational position of the forearm (p > 0.05). Interclass correlation coefficients showed excellent interobserver reliability (ICC 96%), as did tests for intraobserver reliability (ICC 98-99%).

CONCLUSIONS

No consistent influence of overlengthening on the alignment of the radius and ulna at the distal radioulnar joint was found after sequential overlengthening with a multipolar prosthesis. Maybe the ligamentous structures of the forearm prevent significant longitudinal dislocation of the radius, as the multipolar prosthesis gives way by at the radiocapitellar joint. According to the data of the present study, the ipsilateral wrist is not useful in diagnosing overlengthening of the radial column in multipolar prosthetic replacement of the radial head-in contrast to the reported results with monopolar prostheses.

Terrible Triad Injuries of the Elbow

The treatment of terrible triad injuries of the elbow continues to evolve. Radial head fixation and arthroplasty, coronoid process fixation, and repair of the lateral collateral ligament continue to be the mainstays of treatment. In the elbow with persistent instability after repair of these elements, application of a static external fixation, hinged external fixation, ulnohumeral joint pinning, or an internal hinge may be needed. In patients who undergo treatment after the acute injury period, the coronoid may require reconstruction using radial head autograft, iliac crest autograft, olecranon autograft, or allograft.

Complications of radial head prostheses

Radial head prostheses are indicated for treatment of complex radial head fractures not amenable for fixation. After the initial experience with silastic implants, metallic or pyrocarbon arthroplasty have been used for 20 years. Little is known about complications related to these implants. Main complications are related to loosening whether they are cemented or not cemented. Hypotheses have been proposed like inadequate stem design, insufficient cement technique, stress shielding, and foreign body reactions secondary to polyethylene wear. Pain and stiffness are other common complications often related to oversized radial head component or overstuffing of the joint with excessive lengthening of the radius. Instability can be another complication in the context of more complex trauma with lateral collateral ligament complex lesion and coronoid fracture. Fixation of the coronoid fracture, reinsertion of the lateral collateral ligament complex, and the use of monobloc radial head prosthesis are recommended to stabilize the joint. Finally, osteoarthritis is common with follow-up.

Influence of radial head prosthetic design on radiocapitellar joint contact mechanics

HYPOTHESIS

Our aim was to test whether anatomically designed metallic radial head implants could better reproduce native radiocapitellar contact pressure and areas than nonanatomic implants.

METHODS

The distal humerus and proximal radius from 6 cadaveric upper extremities were serially tested in supination with 100 N of compression force at 4 angles of flexion (0°, 30°, 60°, and 90°). By use of a thin flexible pressure transducer, contact pressures and areas were measured for the native radial head, an anatomic implant, a nonanatomic circular monopolar implant, and a bipolar nonanatomic implant. The data (mean contact pressure and mean contact area) were modeled using a 2-factor repeated-measures analysis of variance with P ≤ .05 considered to be significant.

RESULTS

The mean contact areas for the prosthetic radial heads were significantly less than those seen with the intact radial heads at every angle tested (P < .01). The mean contact pressures increased significantly with all prosthetic radial head types as compared with the native head. The mean contact pressures increased by 29% with the anatomic prosthesis, 230% with the monopolar prosthesis, and 220% with the bipolar prosthesis. Peak pressures of more than 5 MPa were more commonly observed with both the monopolar and bipolar prostheses than with the anatomic or native radial heads.

CONCLUSIONS

The geometry of radial head implants strongly influences their contact characteristics. In a direct radius-to-capitellum axial loading experiment, an anatomically designed radial head prosthesis had lower and more evenly distributed contact pressures than the nonanatomic implants that were tested.

Can ulnar variance be used to detect overstuffing after radial head arthroplasty?

BACKGROUND

Overstuffing of the radiocapitellar joint during metallic radial head arthroplasty has been reported to cause loss of elbow flexion, capitellar erosion, and early-onset osteoarthritis. Although this is known, there is no agreed-on measurement approach to determine whether overstuffing has occurred.

QUESTIONS/PURPOSES

We therefore hypothesized that overlengthening the radial head during radial head arthroplasty changes the ulnar variance in the wrist.

METHODS

Seven cadaveric radii were implanted with radial head prostheses of increasing thickness. Each specimen was implanted successively with increasingly thick radial head prostheses measuring 2, 4, and 6 mm thicker than the native radial head, and radiographs were taken after implantation of each prosthesis. The ulnar variance with each prosthesis was measured using the method of perpendiculars.

RESULTS

The ulnar variance of the native and 2-mm (p = 0.04), 4-mm (p = 0.008), and 6-mm (p = 0.008) overly thick radial head prosthesis-implanted states decreased significantly with each incremental increase in prosthetic head thickness.

CONCLUSIONS

Implantation of thicker radial head prostheses decreased the ulnar variance. Our results indicate ulnar variance could be used to detect overstuffing of radial head prostheses.

CLINICAL RELEVANCE

The simplicity and reliability of ulnar variance make it a potentially useful indicator of overlengthening after radial head arthroplasty.

Radial head replacement with unipolar and bipolar SBi system: a clinical and radiographic analysis after a 2-year mean follow-up

Radial head prosthetic replacement is indicated in case of comminuted fracture not amenable to internal fixation, especially when the radial head fracture is part of a pattern of lesions configuring a complex instability of the elbow. Thirty-one SBi radial head prostheses were implanted in 30 patients (one bilateral simultaneous fracture) over a 2 years period. In 10 patients, the mean time from trauma to surgical treatment was 2.4 days, while the remaining 20 patients were treated as "second opinion" cases presenting with elbow stiffness or instability after an average of 19 days from trauma. The implants were monopolar in 12 cases and bipolar in 19. The clinical results were evaluated through the Mayo Elbow performance scoring system. At an average follow-up of 2 years (range 13-36 months), the mean MEPS was 90 points (range 65-100). At late radiographic analysis, radiolucent lines around the stem were found in 11 of the 31 cases. Heterotopic ossifications were found in 14 cases. Bone resorption was observed in 9 cases. Two of the 31 prostheses were removed after 16 and 20 months, in one case to correct stiffness in pronation/supination, in the other one for asymptomatic aseptic mobilization. These short-term results are satisfactory, especially when considering that they were obtained in complex elbow lesions treated in many cases at a delayed stage. Our preference over time went more and more to bipolar implants, but from a comparison of the results we could find no evidence of a superiority of bipolar or monopolar implants. The evolution of these prostheses needs to be evaluated with further studies to assess mid-term and long-term follow-up results.

Contralateral elbow radiographs can reliably diagnose radial head implant overlengthening

BACKGROUND

Excessive lengthening of the radius with use of a radial head implant, a common cause of capitellar wear and clinical failure, is difficult to identify on radiographs of the injured elbow. The purpose of this study was to determine if a novel measurement technique based on radiographs of the contralateral elbow could be used to accurately estimate the magnitude of overlengthening due to the radial head implant. In part I of this study, we examined the side-to-side consistency of radiographic landmarks used in the measurement technique. In part II, the technique was validated in a cadaveric model with simulated radial head implant overlengthening.

METHODS

In part I of the study, a side-to-side comparison of elbow joint dimensions was performed with use of 100 radiographs from fifty patients. In part II, radial head prostheses of varying lengths (leading to 0, 2, 4, 6, and 8 mm of overlengthening) were implanted in four pairs of cadaveric specimens (eight elbows). Radiographic measurements were performed by two examiners blinded to the implant size to determine if radiographs of the contralateral elbow could be used to diagnose, and provide a valid estimate of the magnitude of, implant overlengthening. Intrarater and interrater reliability ratios, absolute measurement errors, and diagnostic accuracy were determined.

RESULTS

No significant side-to-side differences (p > 0.2) in radiographic measurements were identified between paired elbows. In the cadaveric model, the measurement technique involving use of radiographs of the contralateral elbow was successful in predicting the implant size (± 1 mm) in 104 (87%) of the 120 scenarios tested. The sensitivity of the technique--i.e., the ability of the test to correctly identify overlengthening (within ± 1 mm) when it was present--was 98%, with a positive likelihood ratio of 49 and a negative likelihood ratio of 0.02. The reliability of the radiographic measurements, based on repeated measurements performed by a single blinded orthopaedic surgeon on two separate occasions or based on separate measurements performed by two different orthopaedic surgeons, was excellent (intraclass correlation coefficient > 0.95).

CONCLUSIONS

A measurement technique based on radiographs of the contralateral elbow can be used to diagnose and calculate the magnitude of radial overlengthening due to the use of an incorrectly sized radial head implant.

Comminuted radial head fractures treated with pyrocarbon prosthetic replacement

PURPOSE

We had evaluated our experience in the treatment of displaced and comminuted radial head fractures with pyrocarbon radial head prosthesis.

METHODS

From May 2003 to July 2008, radial head prostheses were performed in 47 patients. There were 29 female and 18 male with mean age 51 (34-70 years). The follow-up was a mean of 48 (12-60 months). Fractures of the radial head have been classified by Hotchkiss. The indications for a radial head replacement were type III fractures in 27 cases, type IV fractures in ten cases, comminuted radial fracture associated with disruption of the medial collateral ligament in three cases, Monteggia variant in five cases, and Essex-Lopresti in two cases. Functional outcomes were assessed by visual analog scales (VAS) of pain, joint motion and stability, and using the Mayo Elbow Performance Index.

RESULTS

The mean VAS score for elbow pain was 1 (0.5-2.1). Patients showed an average arc of motion from 6° to 140°, with 75° of pronation and 67° of supination. By using the Mayo Elbow Performance Index, 42 patients had good/excellent results, with three fair and two poor outcomes. Complications were two implant dislocations, one elbow stiffness, one dissociation of the implant, one stem rupture, and two posterior interosseous nerve palsy that recovered from 5 to 8 weeks. We had not seen persistent instability, infection, synostosis, severe degenerative changes, or impingement.

CONCLUSIONS

The treatment of comminuted radial head fracture with pyrocarbon implant usually gives an optimal result depending on the severity of the initial injury and the presence of associated lesions. The size of the prosthesis is often overestimated, causing restriction in motion due to impingement, overstuffing, or dislocations.

Simple overlay device for determining radial head and neck height

BACKGROUND

The purpose of this study was to test the hypothesis that a simple overlay device can be used on radiographs to measure radial head and neck height.

MATERIALS AND METHODS

Thirty anteroposterior elbow radiographs from 30 patients with a clinical diagnosis of lateral epicondylitis were examined to measure radial head and neck height. Three methods using different points along the bicipital tuberosity as a landmark were used. Method 1 used the proximal end of the bicipital tuberosity, method 2 used the most prominent point of the bicipital tuberosity, and method 3 used a simple overlay device (SOD) template that was aligned with anatomic reference points. All measurements were performed three times by three observers to determine interobserver and intraobserver reliability.

RESULTS

Intraclass correlation coefficients revealed higher interobserver and intraobserver correlations for the SOD template method than for the other two methods. The 95% limits of agreement between observers were markedly better (-1.8 mm to +1.0 mm) for the SOD template method than for the proximal point method (-3.8 mm to +3.4 mm) or the prominent point method (-5.9 mm to +4.9 mm).

CONCLUSIONS

We found that the SOD template method was reliable for assessing radial head and neck height. It had less variability than other methods, its 95% limit of agreement being less than 2 mm. This method could be helpful for assessing whether or not the insertion of a radial head prosthesis has resulted in over-lengthening of the radius.

Failure of metal radial head replacement

There is little information available at present regarding the mechanisms of failure of modern metallic radial head implants. Between 1998 and 2008, 44 consecutive patients (47 elbows) underwent removal of a failed metallic radial head replacement. In 13 patients (13 elbows) the initial operation had been undertaken within one week of a fracture of the radial head, at one to six weeks in seven patients (seven elbows) and more than six weeks (mean of 2.5 years (2 to 65 months)) in 22 patients (25 elbows). In the remaining two elbows the replacement was inserted for non-traumatic reasons. The most common indication for further surgery was painful loosening (31 elbows). Revision was undertaken for stiffness in 18 elbows, instability in nine, and deep infection in two. There were signs of over-lengthening of the radius in 11 elbows. Degenerative changes were found in all but one. Only three loose implants had been fixed with cement. Instability was not identified in any of the bipolar implants.

Determination of correct implant size in radial head arthroplasty to avoid overlengthening

BACKGROUND

Insertion of a radial head implant that results in radial overlengthening has been associated with altered elbow kinematics, increased radiocapitellar joint forces, capitellar erosions, early-onset arthritis, and loss of elbow flexion. The purpose of this study was to identify clinical and radiographic features that may be used to diagnose overlengthening of the radius intraoperatively and on postoperative radiographs.

METHODS

Radial head implants of varying thicknesses were inserted into seven cadaver specimens, which were then assessed clinically and radiographically. Eight stages were examined: the intact specimen (stage 1); repair of the lateral collateral ligament (stage 2); radial head resection with repair of the lateral collateral ligament (stage 3); insertion of an implant of the correct thickness (stage 4); and insertion of an implant that resulted in radial overlengthening of 2 mm (stage 5), 4 mm (stage 6), 6 mm (stage 7), or 8 mm (stage 8). The specimens were tested with and without muscle loading to simulate resting muscle tone and surgical paralysis, respectively. At each stage, radiographs were made to measure the ulnohumeral joint space and the lateral ulnohumeral joint was visually assessed.

RESULTS

We identified no difference, with regard to medial ulnohumeral joint incongruity as seen radiographically, among stages 1 through 6 during the tests with muscle loading. A significant difference in medial ulnohumeral joint incongruity was found in stages 7 (p = 0.003) and 8 (p < 0.001). The clinical (visually assessed) lateral ulnohumeral joint space gap was negligible in stages 1 through 4 but increased significantly at all stages involving overlengthening (gross gap, 0.9 mm with 2 mm of overlengthening [p = 0.005], 2.3 mm with 4 mm of overlengthening [p < 0.001], 3.4 mm with 6 mm [p < 0.001], and 4.7 mm with 8 mm [p < 0.001]).

CONCLUSIONS

Incongruity of the medial ulnohumeral joint becomes apparent radiographically only after overlengthening of the radius by >or=6 mm. Intraoperative visualization of a gap in the lateral ulnohumeral joint is a reliable indicator of overlengthening following the insertion of a radial head prosthesis.

Radial head implant arthroplasty

Radial head arthroplasty has developed into a reliable procedure to address fractures of the radial head not amenable to reconstruction, particularly when associated with an unstable elbow or forearm. Good to excellent results can be anticipated when used for the correct indications and when care is taken to understand and address the concomitant injuries. This article will discuss the technique of radial head arthroplasty in the context of the injuries that often accompany radial head fractures.