Failure of metal radial head replacement

Transcription

1 Failure of metal radial head replacement R. P. van Riet, J. Sanchez-Sotelo, B. F. Morrey From Mayo Clinic, Rochester, Minnesota, United States 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. R. P. van Riet, MD, PhD, Orthopaedic Surgeon Monica Hospital SPM Deurne, Stevenslei 20, 2100 Deurne, Belgium. J. Sanchez-Sotelo, MD, PhD, Consultant, Associate Professor B. F. Morrey, MD, Professor Department of Orthopaedic Surgery Mayo Clinic, Mayo Foundation, 200 First Street SW, Rochester, Minnesota 55905, USA. Correspondence should be sent to Dr J. Sanchez-Sotelo; sanchezsotelo.joaquin@mayo. edu 2010 British Editorial Society of Bone and Joint Surgery doi: / x.92b $2.00 J Bone Joint Surg [Br] 2010;92-B: Received 9 July 2009; Accepted after revision 10 December 2009 Replacement of the head of the radius may be used to treat fractures which cannot be reconstructed. The radial head acts as a stabiliser of the elbow in valgus 1 and rotation. 2 In the presence of other lesions, commonly associated with fractures of the radial head, 3-5 replacement arthroplasty can contribute substantially to the stability of the elbow and forearm. Replacement has been shown to be superior to open reduction and internal fixation when the head is fractured into more than three displaced fragments. 6,7 Replacement prostheses may also be used in chronic conditions, 8,9 including nonunion, malunion, post-traumatic osteoarthritis, and when symptoms arise following previous resection of the head. Most reports oof replacements are in the short- or medium-term, 9-13 and there are very few long-term follow-up studies. 14 Failure of replacement leading to revision surgery is mentioned in several studies, but the specific mechanisms of failure and the results of reoperation are currently unknown. The aim of this study was to examine the mechanism of failure requiring revision surgery, and to document the findings at the time of re-operation. Patients and Methods Following approval of the institutional review board, a joint registry database search was set up to identify all patients who had a radial head replacement, or removal or revision of a replacement, at our institution between 1998 and Patients who had a failed silastic prosthesis or failure of a radial head component as part of a total elbow or radiocapitellar arthroplasty were excluded from the study. A total of 47 radial head replacements (44 patients) which had been removed for various reasons were identified and formed the basis of this study. There were 25 males and 19 females and the mean age at the time of the initial operation was 48 years (16 to 70). The dominant arm was involved in 28 patients. The most common indication for the initial operation was a fracture of the radial head in 42 patients (45 elbows). The indication was rheumatoid arthritis in one patient (one elbow), and osteoarthritis with a previous radial head resection one year earlier in one patient (one elbow). A second revision to a metal prosthesis, was performed in three patients (three elbows) due to loosening of the index prosthesis. In the 42 patients (45 elbows) requiring radial head replacement after trauma, the initial operation had been undertaken at a mean of 17 months after injury (0 to 230). It was introduced acutely (less than one week after trauma) in 13 patients (32%), subacutely (one to six weeks) in seven (17%), and in a delayed fashion (six weeks or more in 22) (52%). The mean delay between fracture and replacement in the delayed group was 32 months (6 to 230). VOL. 92-B, No. 5, MAY

2 662 R. P. VAN RIET, J. SANCHEZ-SOTELO, B. F. MORREY Table I. Details of the failed radial head replacements and the implants used for revision, as well as the mode of fixation Number Cemented Non-cemented Failed radial head replacement design * used Unipolar rhead Swanson Anatomic Modular Solar Bipolar rhead recon Judet Loose stem Evolve Total Radial head replacement design Unipolar rhead Anatomic Bipolar rhead recon Judet Loose stem Evolve Total Total elbow prosthesis Removal or replacement head component 3 NA NA Resection 18 NA NA * rhead and rhead recon (Avanta, San Diego, California); Evolve and Swanson (Wright Medical Technology, Arlington, Tennessee); Anatomic (Acumed, Hillsbro, Oregon); Judet (Tornier, Edina, Minnesota); Solar (Stryker, Rutherford, New Jersey); Modular (Ascension Orthopedics, Austin, Texas) NA, not available Table II. Clinical reasons for failure of radial head prosthesis Pain 40 Stiffness 18 Instability 9 Infection 2 Radial head replacement was the initial treatment in 11 patients (11 elbows). The remaining 31 patients (34 elbows) underwent replacement after failure of internal fixation, resection or arthroplasty. A total of 15 patients (18 elbows) had undergone more than one previous surgical procedure. The radial head was implanted after failure of open reduction and internal fixation (ORIF) in ten patients (11 elbows), and for failure of radial head resection in 15 patients (17 elbows). Resection had been performed after failed ORIF in three of these 15 patients (17 elbows). Two patients (two elbows) had undergone ORIF for an ulnar fracture without surgery on the associated fracture of Table III. Analysis of pre-operative radiographs Radiological findings Number Implant related Loosening 31 Over-lengthening (over-stuffing) 11 Radial head subluxation 5 Component dissociation 3 Broberg and Morrey osteoarthritis grade the radial head. The radial head implant had already been revised previously in seven patients (seven elbows). The notes and radiographs of these patients (47 elbows) were reviewed retrospectively. The information obtained included the indications for and timing of the initial THE JOURNAL OF BONE AND JOINT SURGERY

3 FAILURE OF METAL RADIAL HEAD REPLACEMENT 663 Fig. 1 Lateral radiograph showing loosening of a cemented implant. Fig. 3 Lateral radiograph showing radiolucent lines around the stem of an implant revised for pain. This particular implant is designed to fit loosely in the canal. Fig. 2 Lateral radiograph showing loosening of a malpositioned uncemented implant. Fig. 4 Lateral radiograph showing maltracking of the implant and capitellar erosion. Note ulnar subluxation. operation, post-operative complications, mechanisms of failure, and the type of revision surgery. The design and fixation used in both the primary and revision procedure were also recorded. Radiographs were analysed for loosening, instability and radial over-lengthening relative to the lesser sigmoid notch of the ulna, 15 so-called joint over-stuffing leading to asymmetry of the ulnohumeral joint. If over-lengthening of the radial head replacement was suspected radiologically, it was cross-checked with the operative notes for clinical signs of over-stuffing. 18 Any degenerative changes were graded using the Broberg and Morrey osteoarthritis (OA) scale, 19 where 0 represents a normal elbow, and 1, 2 and 3 represent mild, moderate and severe degenerative changes, respectively. Statistical analysis. Separate analyses were performed on implants categorised by their design and the timing of implantation following the initial trauma. Student s t-test was used to analyse differences in range of movement, the timing of initial implantation, radiological signs of degenerative changes, and time to failure between patients who had received different prosthetic designs, as well as between those in whom the radial head had been placed in an acute, subacute or delayed fashion. Differences in the range of movement were compared between patients in whom the radiocapitellar joint had been over-stuffed, and those in whom the length of the radial head was judged to be correct. The significance level was set at p = Results Design and fixation of the index arthroplasty. The radial head was fixed with cement in nine and without in 38 elbows, including 13 uncemented polished stems. A bipolar design was used in eight elbows, four of them in seven patients who had already had their index radial heads revised prior to further revision. Details of the failed prostheses in situ, before further surgery, and designs used for revision are shown in Table I. Pre-operative evaluation and reasons for failure. Prior to revision, the mean flexion-extension arc of movement was 86 (30 to 150 ), with a mean flexion of 117 (60 to 150 ) and a mean extension deficit of 30 (0 to 65 ). A total of VOL. 92-B, No. 5, MAY 2010

4 664 R. P. VAN RIET, J. SANCHEZ-SOTELO, B. F. MORREY Fig. 5a Fig. 5b Lateral radiograph a) showing the radial head component dissociated from the stem and b) Post-operative lateral radiograph of the same elbow. The radial head component was removed. At the time of surgery both the elbow and the forearm were stable, and it was decided to simply remove the head. 18 patients (20 elbows) had a functional range of movement of more than 100, from at least 130 of flexion to < 30 fixed flexion deformity. 20 The pronation-supination arc was a mean of 110 (0 to 185 ), with a mean pronation of 58 (-15 to 95 ) and a mean supination of 52 (0 to 90 ). A total of 28 patients (30 elbows) had a functional arc of rotation from at least 50 of pronation and 50 of supination. 19 The radial head replacements had failed for a variety of reasons at a mean of 23 months (0 to 180) following insertion. The clinical reasons for failure leading to revision are listed in Table II. The most common symptom was pain, followed by stiffness. Radiological analysis. Table III summarises the radiological findings. Pre-operative radiographs showed evidence of implant loosening in 31 elbows. Only three radiologically loose implants had been fixed with cement (Fig. 1), whereas the remaining loose implants were uncemented (Fig. 2). Of the 28 loose uncemented implants, 11 had been specifically designed to be placed loose in the intramedullary canal of the radius (Fig. 3). Signs of instability were found in 11 elbows (11 patients). There was subluxation in the radial head in five (Figs 2 and 4), a complete dislocation in three, and dissociation of the radial head from the stem in three (Fig. 5). There were radiological signs of overlengthening and joint over-stuffing in 11 elbows (Fig. 6). These findings were confirmed at surgery. However, there was no significant difference in the range of flexion, extension, pronation and supination between patients in whom the radiocapitellar joint was over-stuffed and those where the prosthesis was of the correct length (student t-test; flexion p = 0.38, extension p = 0.45, pronation p = 0.79, supination p = 0.65). Further procedures. In 17 patients the radial head replacement was removed and not replaced. The radial head component from a bipolar prosthesis which had become dissociated from the stem was removed in one patient, leaving the stem in place (Fig. 6). In 23 patients (24 elbows) the radial head replacement was removed and replaced. In Fig. 6 Radial over-lengthening in relation to the sigmoid notch. Lateral ulnatrochlear opening and an asymmetric joint space are noted in this anteroposterior radiograph. Overstuffing was confirmed at operation, with the radial head articular surface clearly proximal to the proximal edge of the lesser sigmoid notch patients (18 elbows) the revision stem was cemented into place. A bipolar design was used in 17 patients (17 elbows). In two patients (two elbows) only the radial head component of a bipolar design was replaced, and the stem was left in situ. In one of these the metal radial head was replaced with a polyethylene component and a capitellar replacement was inserted at the same time. In the other patient (one elbow), the radial head component was replaced because of dissociation of this component from the stem. In three patients (three elbows) the radial head was removed and a total elbow replacement was implanted. These three patients (three elbows) are not included in the data in Table IV. Severe erosion of the articular cartilage of THE JOURNAL OF BONE AND JOINT SURGERY

5 FAILURE OF METAL RADIAL HEAD REPLACEMENT 665 Table IV. Findings categorised by the time between trauma and the initial replacement of the radial head. Results are presented as the number of patients, unless stated otherwise. Degeneration was graded according to Broberg and Morrey 19 Time between trauma and placement of the prosthesis < 1 week * 1 to 6 weeks > 6 weeks Number Implant design Fixed-stem unipolar Loose-stem unipolar Fixed-stem bipolar Clinical findings Pain Stiffness Instability Mean flexion ( ) (range) 117 (90 to 145 ) 99 (90 to 120 ) 120 (90 to 150 ) Mean extension ( ) (range) 22 (0 to 60 ) 14 (30 to 65 ) 20 (0 to 65 ) Mean pronation ( ) (range) 27 (0 to 90 ) 17 (30 to 80 ) 27 (-15 to 85 ) Mean supination ( ) (range) 28 (0 to 90 ) 38 (0 to 90 ) 26 (0 to 90 ) Radiographs Loosening Over-lengthening Radial head subluxation Component dissociation Elbow dislocation Degeneration grade Degeneration grade Degeneration grade Degeneration grade Time to failure in mths (range) 15 (3 to 65) 10 (0 to 21) 23 (1 to 65) Per-operative findings Capitellar erosion * three revisions of failed revisions performed in our institution are not included in this analysis. The radial head was replaced for rheumatoid arthritis in one patient and osteoarthritis in another. These patients were not included in this analysis significant difference (p < 0.05) the capitellum was noted at the time of further operation in 18 patients (20 elbows). Effect on failure of the design and the timing of the index replacement of the radial head. The clinical, radiological and pre-operative findings are shown in Tables IV and V. The radial head was replaced for osteoarthritis in one patient (one elbow) and for rheumatoid arthritis in another. These two patients were not included in the data in Tables IV and V. We found no significant difference for flexion, extension, pronation and supination excursion between designs (p > 0.05). Bipolar implants had been inserted at a significantly longer interval after trauma than the loose stem unipolar designs (p = 0.037). There was no significant difference in this interval between the loose-stem unipolar and the fixed-stem unipolar, nor between the fixed-stem unipolar and the fixed stem bipolar designs. There were no significant differences between designs for time to failure or osteoarthritis scores (p > 0.05). Loosening was less common in fixed-stem bipolar implants. Five of eight fixedstem bipolar implants had been cemented in place, and three were uncemented. Both loose fixed-stem bipolar implants had been implanted without cement. Radiocapitellar subluxation did not occur in any of the bipolar implants, but capitellar erosion was more prevalent in this group. Relatively more bipolar prostheses were used in reconstructive procedures delayed more than six weeks after trauma. The difference in the radiological osteoarthritis score was significant between patients who had acute implantation (less than one week) of the radial head replacement and those who had delayed implantation (more than six weeks) (p = 0.03). We also found a significantly increased fixed-flexion deformity in patients in whom the radial head had been implanted at between one to six weeks, compared to acutely (p = 0.03). Over-lengthening, radial head subluxation, component dissociation and instability all occurred more often in the one- to six-week group. Capitellar erosion occurred more often when the implant was inserted more than six weeks after trauma. VOL. 92-B, No. 5, MAY 2010

6 666 R. P. VAN RIET, J. SANCHEZ-SOTELO, B. F. MORREY Table V. Findings categorised by design. Osteoarthritis was graded according to Broberg and Morrey 19 Fixed-stem unipolar n = 24 * Loose-stem unipolar n = 13 Fixed-stem bipolar n = 8 Time between trauma and primary implant Mean in mths (range) 27 (0 to 230) 3 (0 to 18) 11 (0 to 32) < 1 week to 6 weeks > 6 weeks Clinical findings Pain Stiffness Instability Mean flexion ( ) (range) 118 (90 to 150 ) 112 (60 to 140 ) 118 (90 to 140 ) Mean extension ( ) (range) 31 (0 to 65 ) 32 (0 to 60 ) 29 (50 to 65 ) Mean pronation ( ) (range) 53 (-15 to 90 ) 63 (15 to 90 ) 65 (50 to 80 ) Mean supination ( ) (range) 50 (0 to 90 ) 50 (0 to 90 ) 64 (30 to 90 ) Radiographs Loosening * 2 Over-lengthening Radial head subluxation Component dissociation Elbow dislocation Degeneration grade Degeneration grade Degeneration grade Degeneration grade Mean time to failure in mths (range) 26 (3 to 180) 13 (0 to 26) 27 (4 to 71) Per-operative findings Capitellar erosion There were no significant differences in range of movement between the different designs of radial head prosthesis (p > 0.05) * designed to be placed loose in the proximal radial canal the radial head was replaced for rheumatoid arthritis in one patient and osteoarthritis in another. These two patients had received a fixed-stem unipolar implant and were not included in this analysis Discussion Replacement arthroplasty of the head of the radius is commonly used in the treatment of radiocapitellar disorders. However, there is little published information regarding the complications and rate of revision of this procedure. Painful loosening, 21 radioulnar synostosis, 21,22 dissociation of the components 23 and deep infection 24 have been reported. In this study, implant loosening was the most common radiological finding prior to further surgery in 29 patients (31 elbows). In contrast with the findings of other authors who found a high rate of radiolucent lines in asymptomatic patients, 14,21,24-27 all 29 patients (31 elbows) with a radiologically loose implant had pain, which was moderate or severe in 28 patients (29 elbows). Loosening of a fixed-stem bipolar implant was less common, possibly because the stresses at the radial head component are transmitted less, protecting the stem interface. Reduced movement was the most common indication for further surgery, which is also reflected in the literature. 11,25,28 Only 18 elbows in our group had a functional flexion arc. Stiffness may reflect the severity of the initial injury, but may also be secondary to pain and/or overstuffing of the radiocapitellar joint. 29 With the numbers available there was no statistical difference between the patients in whom the radius was judged to be over-lengthened and those in whom the radial head was the correct length. Interestingly, although it was not reflected by objective measurements, a higher percentage of patients in the acutely reconstructed group complained of stiffness in their pre-operative clinical examination (Table IV). By contrast, patients in whom the radial head replacement had been inserted between one and six weeks had significantly reduced extension compared with the acute group (p = 0.03). Other technical issues, such as over-lengthening, radial head subluxation, component dissociation 23 and instability, all occurred more frequently in the one- to sixweek group, suggesting that radial head replacement during this period may be technically more challenging. Our analysis also showed that timing was the most important factor in predicting the prevalence of capitellar erosion. In 12 of 22 elbows (55%) who had a radial head replacement inserted more than six weeks after trauma there were clear signs of capitellar erosion. This constituted 63% of all 19 (21 elbows) with capitellar erosion, and may THE JOURNAL OF BONE AND JOINT SURGERY

7 FAILURE OF METAL RADIAL HEAD REPLACEMENT 667 be due to disuse osteopenia as previously suggested. 30 Only four of 11 patients (11 elbows) with an over-lengthened radial head had severe capitellar erosion at a mean of 13 months (1 to 53) following the initial replacement, suggesting that over-stuffing may be only a secondary factor. With regard to the different design philosophies, we made several observations. No radiocapitellar subluxation was found where a fixed-stem bipolar design had been used. Surprisingly, in two of 13 patients (2 of 13 elbows) where the loose-stem unipolar prosthesis was used, subluxation of the radial head relative to the capitellum was found, compared with three of 24 patients (3 of 26 elbows) in the fixed-stem unipolar group. The loose-stem unipolar replacement was designed to realign itself with the capitellum, but this suggests that it may not always be the case. Despite its improved alignment, the fixed-stem bipolar radial head replacement had the highest incidence of capitellar erosion, but this prosthesis was used more often in a reconstruction. Biomechanical studies have shown bipolar prostheses to provide less stability at the elbow. 31,32 There was no statistical evidence of this in our study, but there was a trend towards increased stability in the fixed-stem unipolar group. Clinical signs of instability were found in five of 24 patients in the fixed-stem unipolar group versus three of 13 and two of eight in the loose-stem unipolar and fixed-stem bipolar groups, respectively. This study has several weaknesses. It is retrospective and includes a heterogeneous group of patients with a wide range of indications for radial head replacement using different designs. However, we believe it provides the first in-depth analysis of failed radial head replacements in the literature. We conclude that failed radial head replacements may lead to re-operation for pain, reduced range of movement, instability or infection. Radiological loosening was prevalent in this group of failed replacements. In addition to a delay in surgical intervention, technical errors leading to over-lengthening or malpositioning appear to be the cause of some failures. Further studies are required to identify the ideal design, fixation and timing to avoid such failures. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. References 1. Morrey BF, Tanaka S, An KN. Valgus stability of the elbow: a definition of primary and secondary constraints. Clin Orthop 1991;265: Schneeberger AG, Sadowski MM, Jacob HA. Coronoid process and radial head as posterolateral rotatory stabilizers of the elbow. J Bone Joint Surg [Am] 2004;86- A: van Riet RP, Morrey BF, O Driscoll SW, Van Glabbeek F. Associated injuries complicating radial head fractures: a demographic study. Clin Orthop 2005;441: Kaas L, van Riet RP, Vroemen JP, Eygendaal D. The incidence of associated fractures of the upper limb in fractures of the radial head. Strategies Trauma Limb Reconstr 2008;3: van Riet RP, Morrey BF. Documentation of associated injuries occurring with radial head fracture. Clin Orthop 2008;466: Ring D, Quintero J, Jupiter JB. Open reduction and internal fixation of fractures of the radial head. J Bone Joint Surg [Am] 2002;84-A: Ruan HJ, Fan CY, Liu JJ, Zeng BF. A comparative study of internal fixation and prosthesis replacement for radial head fractures of Mason type III. Int Orthop 2007;33: Shore BJ, Mozzon JB, MacDermid JC, Faber KJ, King GJ. Chronic posttraumatic elbow disorders treated with metallic radial head arthroplasty. J Bone Joint Surg [Am] 2008;90-A: Brinkman JM, Rahusen FT, de Vos MJ, Eygendaal D. Treatment of sequelae of radial head fractures with a bipolar radial head prosthesis: good outcome after 1-4 years follow-up in 11 patients. Acta Orthop 2005;76: Gabrion A, Havet E, Bellot F, et al. Recent fractures of the radial head associated with elbow instability treated with floating Judet prosthesis. Rev Chir Orthop Reparatrice Appar Mot 2005;91: (in French). 11. Smets S, Govaers K, Jansen N, et al. The floating radial head prosthesis for comminuted radial head fractures: a multicentre study. Acta Orthop Belg 2000;66: Ashwood N, Bain GI, Unni R. Management of Mason type-iii radial head fractures with a titanium prosthesis, ligament repair, and early mobilization. J Bone Joint Surg [Am] 2004;86-A: Dotzis A, Cochu G, Mabit C, Charissoux JL, Arnaud JP. Comminuted fractures of the radial head treated by the Judet floating radial head prosthesis. J Bone Joint Surg [Br] 2006;88-B: Harrington IJ, Sekyi-Otu A, Barrington TW, Evans DC, Tuli V. The functional outcome with metallic radial head implants in the treatment of unstable elbow fractures: a long-term review. J Trauma 2001;50: van Riet RP, van Glabbeek F, de Weerdt W, Oemar J, Bortier H. Validation of the lesser sigmoid notch of the ulna as a reference point for accurate placement of a prosthesis for the head of the radius: a cadaver study. J Bone Joint Surg [Br] 2007;89- B: Rowland AS, Athwal GS, MacDermid JC, King GJ. Lateral ulnohumeral joint space widening is not diagnostic of radial head arthroplasty overstuffing. J Hand Surg [Am] 2007;32: Shors HC, Gannon C, Miller MC, Schmidt CC, Baratz ME. Plain radiographs are inadequate to identify overlengthening with a radial head prosthesis. J Hand Surg [Am] 2008;33: Frank SG, Grewal R, Johnson J, et al. Determination of correct implant size in radial head arthroplasty to avoid overlengthening. J Bone Joint Surg [Am] 2009;91- A: Broberg MA, Morrey BF. Results of delayed excision of the radial head after fracture. J Bone Joint Surg [Am] 1986;68-A: Morrey BF, Askew LJ, Chao EY. A biomechanical study of normal functional elbow motion. J Bone Joint Surg [Am] 1981;63-A: Knight DJ, Rymaszewski LA, Amis AA, Miller JH. Primary replacement of the fractured radial head with a metal prosthesis. J Bone Joint Surg [Br] 1993;75-B: Bimmel R, van Riet RP, Sys J. Heterotopic ossification causing proximal radioulnar synostosis after insertion of a radial head prosthesis. J Hand Surg [Br] 2006;31: Herald J, O Driscoll S. Complete dissociation of a bipolar radial head prosthesis: a case report. J Shoulder Elbow Surg 2008;17:e Doornberg JN, Parisien R, van Duijn PJ, Ring D. Radial head arthroplasty with a modular metal spacer to treat acute traumatic elbow instability. J Bone Joint Surg [Am] 2007;89-A: Wretenberg P, Ericson A, Stark A. Radial head prosthesis after fracture of radial head with associated elbow instability. Arch Orthop Trauma Surg 2006;126: Popovic N, Lemaire R, Georis P, Gillet P. Midterm results with a bipolar radial head prosthesis: radiographic evidence of loosening at the bone-cement interface. J Bone Joint Surg [Am] 2007;89-A: Lim YJ, Chan BK. Short-term to medium-term outcomes of cemented Vitallium radial head prostheses after early excision for radial head fractures. J Shoulder Elbow Surg 2008;17: Birkedal JP, Deal DN, Ruch DS. Loss of flexion after radial head replacement. J Shoulder Elbow Surg 2004;13: Van Glabbeek F, van Riet RP, Baumfield JA, et al. Detrimental effects of overstuffing or understuffing with a radial head replacement in the medial collateral-ligament deficient elbow. J Bone Joint Surg [Am] 2004;86-A: van Riet RP, van Glabbeek F, Verborgt O, Gielen J. Capitellar erosion caused by a metal radial head prosthesis: a case report. J Bone Joint Surg [Am] 2004;86-A: Pomianowski S, Morrey BF, Neale PG, et al. Contribution of monoblock and bipolar radial head prostheses to valgus stability of the elbow. J Bone Joint Surg [Am] 2001;83-A: Moon JG, Berglund LJ, Domire Z, An KN, O Driscoll SW. Radiocapitellar joint stability with bipolar versus monopolar radial head prostheses. J Shoulder Elbow Surg 2009;18: VOL. 92-B, No. 5, MAY 2010