Radial Head Arthroplasty: A Radiologic Outcome Study

Transcription

1 Musculoskeletal Imaging Original Research Ha et al. Outcomes of Radial Head rthroplasty Musculoskeletal Imaging Original Research lice S. Ha 1 Jonelle M. Petscavage 1,2 Felix S. Chew 1 Ha S, Petscavage JM, Chew FS Keywords: arthroplasty, fracture, radial head DOI: /JR Received ugust 9, 2011; accepted after revision January 27, Department of Radiology, University of Washington, 4245 Roosevelt Way NE, ox , Seattle, W ddress correspondence to. S. Ha (aha1@uw.edu). 2 Present address: Penn State Hershey Medical Center, Hershey, P. CME This article is available for CME credit. JR 2012; 199: X/12/ merican Roentgen Ray Society Radial Head rthroplasty: Radiologic Outcome Study OJECTIVE. The purpose of this study is to provide a radiographic outcome assessment of radial head arthroplasty in correlation with clinical outcomes and to determine whether there is an association between certain patient factors and clinical and radiographic outcomes. MTERILS ND METHODS. 10-year retrospective review was performed to identify patients with metal radial head arthroplasty. t least two follow-up radiographs were reviewed for each patient and were correlated with clinical information. Statistical analysis included calculation of complication rates, phi coefficient for variable association with complications, and Kaplan-Meier survival. RESULTS. total of 258 radial head implants in 244 patients were reviewed. The mean patient age was 46 years, with mean follow-up time of 12.8 months. Two hundred nineteen (84.9%) implants were unipolar in design, whereas 39 implants were bipolar. The most common indication for arthroplasty was trauma (94% acute and 2% failed internal fixation). Radiographic abnormalities included nonbridging heterotopic ossification (38.0%), secondary radiocapitellar joint osteoarthritis (27.9%), loosening (19.8%), bridging heterotopic ossification (8.9%), fracture (2.3%), and hardware dislocation (2.7%). Overall, there were 62 second surgeries for either revision or removal. Reasons for second surgery included heterotopic ossification (53.2%), synovectomy or capsulectomy (43.5%), and infection (3.2%). There was a statistically significant association between radiographic complications and the presence of patient symptoms (p < 0.05). There was no association between radiographic or clinical complications with age, sex, side, or type of arthroplasty (R < 0.001). CONCLUSION. There is a positive association between radiographic findings and patient symptoms for postoperative complications after radial head arthroplasty. y 9 months, 50% of implants showed radiographic complications. R adial head fractures account for % of all fractures and 30% of fractures involving the elbow in adults [1, 2]. Using Mason classification, type 1 (nondisplaced partial fractures) are usually treated nonoperatively [1]. Type 2 (partial marginal fractures involving < 30% of the articular surface and with > 2 mm of displacement) are usually treated with open reduction and internal fixation. Type 3 (comminuted fractures of the entire radial head) and type 4 (radial head fractures with radius dislocation) continue to pose a challenge to orthopedic surgeons. Unstable comminuted radial head fractures are often part of a complex injury. The most common patterns are radial head fracture with ulnar collateral ligament tear, Essex- Lopresti fracture-dislocation (radial head fracture plus interosseous membrane rupture), posterior elbow dislocation with fractures of the radial head and coronoid process (Terrible Triad), and posterior olecranon fracturedislocation (posterior Monteggia variant) [3]. Elbow motion is complex, with the radial head moving in both flexion-extension and forearm rotation. Open reduction and internal fixation of comminuted radial head fractures in more than three fragments is associated with early failure, nonunion, and poor forearm motion [3]. Historically, Mason type 3 radial head fractures were treated with radial head excision, which showed initial pain improvement and increased range of motion in low-demand patients. However, long-term follow-up found increased pain, valgus instability, proximal radial migration and wrist pain, diminished grip strength, weak forearm rotation, and ulnohumeral osteoarthritis [4, 5]. Currently, radial head excision is reserved for patients with isolated Mason type 3 fractures without other injuries JR:199, November 2012

2 Outcomes of Radial Head rthroplasty Over the years, the radial head s importance in proper elbow function has been recognized. lthough the anterior band of the ulnar collateral ligament is the primary stabilizer to valgus stress, the radial head is the second most important stabilizer [6]. In cases of torn ulnar collateral ligament or lateral ulnar collateral ligament, the radial head acts as the primary valgus stress stabilizer [7]. In addition, the radial head is a critical conduit in transmission of axial force from the hand to the upper arm. Finally, the radiocapitellar joint is the primary restraint to proximal radial migration. lternative therapy for Mason type 3 radial head fracture is radial head replacement. The first radial head arthroplasty was performed by Speed in 1941 [8]. Silicone implants, first introduced in the late 1960s, have fallen out of favor because of high rates of implant fracture and silicone synovitis [9, 10]. Recently, metallic implants are preferred because they serve to give strength to the lateral column of elbow and allow overlying ligament healing. Contraindications to radial head arthroplasty include active infection, either local or remote. There are two main designs of radial head replacements [11]. Unipolar implants are designed as anatomic spacers. Implanted without cement with a smooth stem, unipolar implants can self-center on the capitellum with forearm rotation and are expected to have some motion within the radial neck, leading to less than 2 mm perihardware lucency on radiographs. This intentionally loose design is proposed to compensate for the asymmetric articular surfaces between the spherical capitellum and disclike radial head [12]. In contrast, bipolar implants are designed to simulate the normal motion at the radiocapitellar joint by creating a semiconstrained articulation at the radial head and neck, thereby reducing the stress at the implant-bone interface. Introduced by Judet et al. [13] in 1996, a bipolar implant has a fixed radial stem (cemented or press-fit) that articulates with a mobile head via a polyethylene component. There is of motion in all planes, as in a native elbow. So far, intermediate-term follow-up studies on radial head arthroplasty for both unipolar and bipolar types have concentrated on clinical outcomes, such as patient satisfaction, subjective pain level, and range of motion [14 20]. ll have reported favorable clinical outcome, with low rates of revision surgeries. Many of these studies are limited by small sample sizes, most involving fewer than 20 implants, with a study by Popovic et al. [17] being the largest, with 51 implants. With unipolar implants, asymptomatic less than 2 mm lucency about the radial stem was commonly reported; Fehringer et al. [15] reported this finding in 16 of 17 total implants. lthough this finding persisted in all 20 implants in the only long-term study of unipolar types, by Harrington et al. [20], its clinical significance is still unknown. The purpose of this study is to study the radiographic outcomes of radial head replacements and how they compare with clinical outcomes, to determine the most common types of radiographic abnormalities and to assess for patient factors associated with these radiographic complications. We hypothesize that radiography has high sensitivity for detecting clinically significant complications after radial head arthroplasty. Materials and Methods This retrospective study had institutional review board approval and was compliant with institutional HIP policies. Medical records were searched over a 10-year period for patients who received metal radial head implants. Demographic data, including age, sex, hand dominance, and indication for arthroplasty, were recorded. Initial operative reports were reviewed to confirm the types of radial head implants used. vailable elbow radiographs were interpreted for evidence of radiographic change or complication by one of four fellowship-trained musculoskeletal radiologists with range of experience from 1 to more than 20 years. One author reviewed all the original reports and radiographs again to reconfirm the findings. Postoperative radiographs were compared with preoperative radiographs for the presence of the following radiographic findings: nonbridging or bridging heterotopic ossification, secondary radiocapitellar joint osteoarthritis, perihardware fracture, hardware loosening, hardware disengagement, and joint effusion of infection. Radiocapitellar osteoarthritis was defined as joint space narrowing, and changes in the capitellum, including osteopenia, subchondral sclerosis, subchondral cyst formation, and osteophyte formation, which were new compared with preoperative and the immediate postoperative imaging studies. Hardware loosening was defined as perihardware lucency greater than 2 mm. Radiographic findings were correlated with contemporaneous clinical findings available from clinical notes from follow-up office visits. Patient symptoms, including pain scale (0 10), range of motion, stiffness, crepitus, drainage, erythema, and reasons for removal or revision of radial head implants, were noted. Operative reports for second surgeries for removal or revisions were reviewed. Statistical analysis included calculation of complication rates, logistic regression analysis for patient demographic factors associated with radiographic and clinical outcomes, Pearson chi-square test, and Kaplan-Meier survival curve analysis of radiographic and clinical survival. Results total of 258 radial head implants in 244 patients were found over a 10-year period (March 2000 to March 2010). The mean patient age was 46 years (age range, years). Sixty-seven percent (173/258) of implants were placed in men (mean age, 43 years; age range, years), and 33% (85/258) were placed in women (mean age, 50 years; age range, years). One hundred forty-two implants were implanted in the left arm, and 116 were implanted in the right arm. Two hundred nineteen (84.9%) implants were unipolar in design, whereas 39 (15.1%) were bipolar. Only three cases of concurrent capitellar resurfacing arthroplasty were seen, two in bipolar implants and one in a unipolar implant. y far, the most common indication for radial head replacement was trauma, including acute (94% [243/258]) and prior failed internal fixation (2% [6/258]). Failed radial head resection (7/258) and osteoarthritis (2/258) accounted for the rest of the population. When data were separated by implant type, epidemiologic data for bipolar or unipolar implant groups were similar to those for the overall group. Thirty-nine bipolar radial head implants were found in 38 patients, with a mean age of 45 years (range, years). There were 26 implants in men (67%) and 13 in women. Seventeen right-sided and 22 leftsided implants were performed. The mean follow-up time was 16 months (range, months). Two hundred nineteen unipolar implants were found in 206 patients, with a mean age of 51 years (range, years). There were 147 implants in men (67%) and 72 in women. Ninety-nine right-sided and 120 leftsided unipolar implants were performed. The mean radiographic follow-up time was 12.8 months (range, months); 56.7% of implants had at least 6 months of follow-up. Thirty-six patients were lost to follow-up, defined as only one postoperative radiographic study with a subsequent lack of postoperative clinical visit. Radiographic abnormalities (summarized in Table 1) included (in order from highest to lowest percentage) nonbridg- JR:199, November

3 Ha et al. TLE 1: Radiographic bnormalities fter Radial Head rthroplasty Radiographic Finding Total (n = 156) Unipolar (n = 136) ipolar (n = 20) Nonbridging heterotopic ossification Radiocapitellar osteoarthritis Loosening ridging heterotopic ossification Dislocation or disengagement Fracture Note Data are percentages of implants with complications. total of 258 radial head implants were studied; 156 patients had radiographic abnormalities. ing heterotopic ossification, secondary radiocapitellar osteoarthritis (Fig. 1), hardware loosening (Fig. 2), bridging heterotopic ossification (Fig. 1), hardware disengagement (Fig. 3), and perihardware fracture or dislocation. lthough this study was not designed to study the timing of the complications, heterotopic ossification was usually first seen 3 6 months after implant surgery. ridging heterotopic ossification was more often seen at 12 months, as was the presence of osteolysis greater than 2 mm. Findings of infection were seen between 0 3 months after surgery. For the purposes of this study, clinical symptoms included pain ( 4 on scale of 10), decreased range of motion, stiffness, signs of infection (redness, swelling, and drainage from wound), and dislocation or instability. One hundred ten of 258 (42.6%) radial head implants were associated with both abnormal radiographic findings and clinical symptoms. Forty-six implants (18%) showed radiographic abnormalities without clinical symptoms. Sixteen implants (6%) only had clinical symptoms. Eighty-six implants (33%) had normal radiographs and lacked clinical symptoms. Overall, 62 of the 258 implants (24%) required second surgeries. Thirty-eight implants were revised, and 24 implants were removed. ll 10 bipolar implants that required second surgery (five removals and five revisions) had radiographic abnormalities. Of the 52 unipolar implants with second surgery, 33 were revised and 19 were removed. ll but one of these unipolar implants had abnormal radiographic Fig year-old man with secondary radiocapitellar osteoarthritis after radial head arthroplasty, with bridging heterotopic ossification. and, nteroposterior () and lateral () radiographs of elbow after unipolar arthroplasty show narrowing of radiocapitellar joint and subchondral cystic changes and osteopenia in capitellum. Cerclage wire is noted around coronoid process. Heterotopic ossification is noted lateral to proximal radial shaft, which is bridging ventral portion of elbow joint on lateral view. findings. Reasons for second surgery included heterotopic ossification (33/62 [53.2%]); stiffness, decreased range of motion, or pain from thickened synovium or joint capsule (27/62 [43.5%]); and infection (2/62 [3.2%]). There was a statistically significant association between radiographic complications and the presence of patient symptoms for the total group and for the separated unipolar and bipolar groups (all p < 0.05). However, there was no association between age, sex, side of arthroplasty, or implant type and radiographic or clinical complications (R < 0.001). Kaplan- Meier survival curve analysis was constructed for clinical survival and radiographic abnormality (Fig. 4). Patients who were lost to follow-up were used as censored data in the data creation. Clinical failure of the implant was defined as the time to the second surgery. Radiographic failure was defined as the time to the first radiographic abnormality. t 9 months, 50% of radial head implants had radiographic abnormalities. y 36 months, only 25% were deemed to be radiographically normal. Overall, according to the Kaplan-Meier survival analysis, radiographic survival was worse than clinical survival. Discussion Radial head implants allow restoration of elbow joint stability, preservation of range of motion, and maintenance of the radial length [21] in patients with complex radial head fractures. We present a retrospective study of the largest number of radial head implant numbers to date. Our study includes both types of implants. In addition, the study uniquely identifies specific radiographic complications and their rates. lso, the radiographic complication rates are correlated with demographic factors and clinical outcome for the first time, to our knowledge. Demographic factors, such as age, sex, side of arthroplasty, or implant type, had no association with radiographic or clinical complication (R < 0.001). In contrast, radiographic findings had a statistically significant positive association with clinical symptoms after radial head arthroplasty, further validating radiography as the reference standard for postoperative imaging modality after radial head arthroplasty. Previous studies have reported some, but not all, radiographic findings [14, 15, 17, 18]. In our study, the three most common radiographic complications were heterotopic ossification, radiocapitellar osteoarthritis, and hardware loosening. high rate of heterotopic ossification (46.9% for nonbridging and bridging combined) was noteworthy and found to be much higher than in other joints, such as knee or shoulder, but similar to the hip [22 25]. We hypothesize that this may be related to the high rate of concomitant ligamentous injuries that occur with these complex radial head fractures, not necessarily to the implant surgery techniques. This raises the question for routine preventive therapy for heterotopic 1080 JR:199, November 2012

4 Outcomes of Radial Head rthroplasty Fig year-old man with disengagement of radial head implant., In flexed position, lateral radiograph of bipolar radial head implant appears grossly normal., nteroposterior radiograph in extended position shows disengagement between head and neck components (arrow) of implant. rticular surface of head component is seen en face on anteroposterior view, abnormal orientation that should raise concern for disarticulation. Radial head is subluxed external to joint line on anteroposterior view. This image also shows abnormal valgus tilt of stem in radial neck (arrowhead), consistent with subsidence. ossification after implant surgery, such as lowdose radiation or indomethacin therapy [25]. Secondary radiocapitellar osteoarthritis is a common complication that may occur because of overstuffing or loosening of radial head implant [21]. Even with perfect fitting, interaction between the metallic radial head and the nascent capitellum seems to lead to eventual capitellar osteoarthritis. Often, these patients go on to require capitellar resurfacing arthroplasty. Our rate of radiocapitellar osteoarthritis (27.9%) is lower than that previously reported, which ranges from 47% [19] to 70% [18]. ipolar implants did show a much lower rate (5.1%) compared with unipolar implants (31.9%). This may be because of the superior ability of the bipolar implants to simulate the normal motion at the radiocapitellar joint by creating a semiconstrained articulation at the radial head and neck and by reducing the stress at the implantbone interface. However, the smaller sample size of our bipolar group (n = 39) may explain the discrepancy from previously published rate of 58% in study by Popovic et al. [17] (n = 51). Perihardware lucency around radial head implants has previously been reported to be Fig year-old man with hardware loosening after radial head arthroplasty. and, nteroposterior () and lateral () views of elbow show perihardware lucency (arrows) about bipolar radial head implant, with tilting of implant. There are two suture anchors in lateral humeral epicondyle. of little clinical consequence [14, 15, 17, 18]. However, in most of the studies, perihardware lucency was defined as 1 mm thickness, with the exception of the study by Popovic et al. [17], where balloon-like osteolysis was distinguished from 1 mm lucency. In our previous study with joint replacements in the hands, perihardware lucency less than 2 mm was not associated with clinical symptoms or second surgeries [26]. Therefore, our study defined loosening as greater than 2 mm. This more strict definition most likely explains our lower rate in lucency (19.8%) compared with prior rates of approximately 60% [14, 17, 18]. In our study, second surgery (revision or removal of implants) was considered to be the endpoint for clinical survival. Sixty-two implants (24% of total) required second surgeries. With one exception, there was a nearly complete association between radiographic findings and second surgery incidence. Previous reports vary widely in their rates of second surgeries, from as low as 2% [17] to as high as 88% [27]. Clinical reasoning for second surgery was dominated by joint stiffness, whether by heterotopic ossification (53.2%) or thickened synovium or joint capsule (43.5%). Of note, thickened synovium or joint capsule is a radiographically occult finding and therefore was not accounted for in our Kaplan-Meier survival analysis. Kaplan-Meier survival analysis shows a steep decline in radiographic survival at 9 months, where half of the implants had radiographic abnormalities. In comparison, clinical survival was approximately 75% at 9 months. Using the second surgical date as the endpoint for clinical survival instead of the first date of clinical symptoms likely explains why the radiographic survival curve is worse than the clinical curve on Kaplan-Meier analysis (Fig. 4). The first date of clinical symptoms was not used because of variability or unreliability in reporting. Limitations of our study include patient loss to radiographic follow-up at different time points, which required censoring in survival analysis. There was retrospective reliance on clinicians reporting on physical examinations and subjective reporting on patients symptoms. There were five surgeons who performed the radial head implant surgeries, also contributing to possible surgeon-dependent JR:199, November

5 Ha et al. Survival (%) Time (mo) Fig. 4 Kaplan-Meier survival analysis curve shows clinical survivorship (solid line), which is defined as time to revision or retrieval surgery, compared with radiographic survivorship (dashed line), which is defined as time of first radiographic abnormality. technique variabilities. Some patients with radiographic abnormalities may have refused second surgeries for other medical or insurance reasons. Finally, our study includes a smaller sample size of bipolar radial head implants. Overall, our study has a relatively short follow-up length (mean, 12.8 months) compared with prior long-term studies such as that by Popovic et al. (8.4 years) [17]. We have presented here a large sample size follow-up study on radial head arthroplasty with an emphasis on radiographic findings. 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