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Background: Many distal humerus nonunions are associated with bone loss, and rigid internal fixation is difficult to obtain, especially for low transcondylar nonunions and those with severe intra-articular comminution. The purpose of this study was to analyze the results of a strategy to address this challenge utilizing internal fixation using the Supracondylar Ostectomy + Shortening (S.O.S.) procedure for distal humerus nonunions. The goals of this procedure are to (1) optimize bony contact and compression through re-shaping the nonunited fragments at the supracondylar level with selective humeral metaphyseal shortening, (2) maximize fixation using parallel-plating, and (3) provide biologic and structural augmentation with bone graft., Materials and Methods: Between 1995 and 2019, 28 distal humerus nonunions underwent internal fixation using the S.O.S. procedure at a single Institution. There were 14 males and 14 females with mean age of 47 (range 14-78) years at the time of the S.O.S procedure and an average of 1.7 prior surgeries. Medical records and radiographs were reviewed to determine rates of union, reoperations, complications, and Mayo Elbow Performance Scores (MEPS). Patients were also prospectively contacted to update their MEPS and gather additional information on complications and reoperations. Mean clinical exam follow-up was 17 months, mean clinical contact follow-up was 19 months, and mean radiographic follow-up was 32 months., Results: Four patients did not have adequate follow-up to determine union. Of the remaining 24 elbows, 22 achieved union. Two elbows developed collapse of the articular surface and were converted to a total elbow arthroplasty. There were complications in 10 elbows: contracture (5), superficial infection (2), ulnar neuropathy (1), deep infection (1), and hematoma (1). Twelve elbows underwent reoperation: 4 for contracture release, 3 for hardware removal, 2 for total elbow arthroplasty, 1 for bone grafting, 1 for hematoma evacuation, and 1 for ulnar nerve neurolysis. Compared to preoperative data, there was a significant improvement in postoperative flexion, extension and pronation (P < .01). The mean range of motion was 21° of extension, 119° of flexion, 79° of pronation, and 77° of supination. The mean MEPS was 80 points (range, 25-100 points) and 19 elbows (76%) rated as excellent or good., Discussion: Stable fixation and high union rates are possible in distal humerus nonunions with bone loss using a technique that combines supracondylar humeral shortening, parallel plating, and bone grafting. Secondary procedures are commonly needed to restore function in this challenging patient population., (Copyright © 2024 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

Background: The lateral collateral ligament complex along with the capsule is likely to be at risk during arthroscopic extensor carpi radialis brevis release for lateral epicondylitis. We hypothesized that disruption of the lateral collateral ligament-capsule complex (LCL-cc) would increase the mean contact pressure on the coronoid under gravity varus., Materials and Methods: Eight cadaveric elbows were tested via gravity varus and weighted varus (2 Nm) stress tests using a custom-made machine designed to simulate muscle loads while allowing passive flexion of the elbow. Mean articular surface contact pressure data were collected and processed using intra-articular thin-film sensors and software. Sequential testing was performed on each specimen from stage 0 to stage 3 (stage 0, intact; stage 1, release of anterior one-third of LCL-cc; stage 2; release of anterior two-thirds of LCL-cc; and stage 3, release of entire LCL-cc). The mean contact pressure on the coronoid and the mean ratio of contact pressure on the medial coronoid to that on the lateral coronoid (M/L ratio) were used for comparisons among the stages and the intact elbow., Results: The overall mean contact pressure significantly increased in stage 2 (P = .0004 in gravity varus and P = .0001 in weighted varus) and stage 3 (P < .0001 in gravity varus and P < .0001 in weighted varus) compared with that in stage 0. In contrast, release of the anterior one-third of the LCL-cc (stage 1) did not significantly increase the mean contact pressure on the coronoid in any degree of flexion under gravity varus (P = .09) or weighted varus loading (P = .6). The M/L ratio difference between stage 0 and stage 1 was 1.1 ± 1.1 under gravity varus (P = .8) and 2.1 ± 1.0 under weighted varus (P = .2). The overall M/L ratios in stage 2 and stage 3 were significantly higher than those seen in stage 0 under gravity varus (P = .04 in stage 2 and P = .02 in stage 3) and weighted varus (P = .006 in stage 2 and P < .0001 in stage 3)., Conclusions: Loss of the anterior two-thirds or more of the LCL-cc significantly increases the overall mean contact pressure on the coronoid, especially the medial coronoid, under both gravity varus and weighted varus. The LCL-cc also plays a role in the distribution of coronoid contact pressure against gravity varus loads., (Copyright © 2022 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

Background: The location (proximal vs. distal) of elbow medial ulnar collateral ligament (MUCL) tears impacts clinical outcomes of nonoperative treatment. The purposes of our study were to (1) determine whether selective releases of the MUCL could be performed under ultrasound (US) guidance without disrupting overlying soft tissues, (2) assess the difference in medial elbow stability for proximal and distal releases of the MUCL using stress US and a robotic testing device, and (3) elucidate the flexion angle that resulted in the greatest amount of medial elbow laxity after MUCL injury., Methods: Sixteen paired, fresh-frozen elbow specimens were used. Valgus laxity was evaluated with both US and robotic-assisted measurements before and after selective MUCL releases. A percutaneous US-guided technique was used to perform proximal MUCL releases in 8 elbows and to perform distal MUCL releases in their matched pairs. The robot was used to determine the elbow flexion angle at which the maximum valgus displacement occurred for both proximally and distally released specimens. Open dissection was then performed to assess the accuracy of the percutaneous releases., Results: Percutaneous US-guided releases were successfully performed in 15 of 16 specimens. The proximal release resulted in greater valgus angle displacement (11° ± 2°) than the distal release (8° ± 2°) between flexion angles of 30° and 70° (P < .0001 at 30°, P < .0001 at 40°, P = .001 at 50°, P = .005 at 60°, and P = .020 at 70°). Valgus displacement between release locations did not reach the level of statistical significance between 80° and 120° (P = .051 at 80°, P = .131 at 90°, P = .245 at 100°, P = .400 at 110°, and P = .532 at 120°). When we compared the values for the mean increase in US delta gap (stressed - supported state) from before to after MUCL release, the proximally released elbows had larger increases than the distally released elbows (5.0 mm proximal vs. 3.7 mm distal, P = .032). After MUCL release, maximum mean valgus displacement occurred at 49° of flexion., Conclusions: US-guided selective releases of the MUCL can be performed reliably without violating the overlying musculature. Valgus instability is not of greater magnitude for distal releases when compared with proximal releases. This findings suggests there must be alternative factors to explain the difference in clinical prognosis between distal and proximal tears. The observed flexion angle for maximum valgus laxity could have important implications for elbow positioning during US or fluoroscopic stress examination, as well as surgical repair or reconstruction of the MUCL., (Copyright © 2022 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

Background: Heterotopic ossification (HO) is a well-recognized cause of limited flexion-extension, but it can also limit pronation-supination. There is a paucity of literature concerning restriction of pronation-supination due to HO., Methods: We conducted a retrospective review of patients who had undergone elbow surgery for HO removal between January 1, 2003, and September 27, 2013. Computed tomography scans were reviewed to determine the presence of HO restricting forearm rotation and were rated independently by 4 observers. Each elbow was given 1 of 4 scores according to the likelihood that HO was restricting forearm rotation. Agreement was achieved when 3 or 4 observers thought that HO definitely or probably caused a loss of pronation-supination., Results: Of 132 post-traumatic patients undergoing HO excision for restricted elbow motion, 61 (46%) also lacked a functional arc of pronation and supination (50° and 50°, respectively). Of these 61 patients, 32 (53%) were considered to have lost forearm rotation because of HO. The remaining 29 patients (47%) were thought to have restricted forearm rotation for reasons unrelated to HO., Discussion: In this study, loss of pronation-supination affected almost half of the patients (61 of 132 [46%]) undergoing HO excision around the elbow. Of these 61 patients, 32 (52%) had HO extending into the proximal forearm and affecting rotation. From our data, one can expect that about one-quarter (24% of patients in this study, or 32 of 132) with post-traumatic HO of the elbow will have a significant functional loss of pronation-supination due to HO extending into the forearm., (Copyright © 2018 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

Background: The interosseous membrane (IOM) and distal radioulnar joint (DRUJ) provide axial stability to the forearm. Our hypothesis was that injury to these structures alters force transmission through the elbow., Methods: A custom-designed apparatus that applies axial loads from the wrist to the elbow was used to test 10 cadaveric upper limbs under the following simulated conditions (1) intact, (2) DRUJ injury, (3) IOM injury, or (4) IOM + DRUJ injury. IOM injury was simulated by osteotomies of the IOM attachment to the radius, and DRUJ injury was simulated by distal ulnar oblique osteotomy. We applied 160 N of axial force during cyclic and functional range of forearm rotation (40 o pronation/40 o supination), and force, contact pressure, and contact area through the elbow joint were measured simultaneously., Results: The force across the radiocapitellar joint was significantly higher in the IOM + DRUJ injury and the IOM injury groups than in the intact and DRUJ injury groups. The mean force across the radiocapitellar joint was not significantly different between the intact and DRUJ injury groups or between the IOM + DRUJ injury and the IOM injury groups. Forces across the ulnohumeral joint showed an inverse pattern to those in the radiocapitellar joint., Conclusions: These findings suggest that injury to the IOM contributes more to the disruption of the normal distribution of axial loads across the elbow than injury to the DRUJ., (Copyright © 2018 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

Background: Long-term radiographic arthritis has been commonly reported after radial head excision. Concern over radial head arthroplasty may arise in certain situations including capitellar arthritis, radiocapitellar malalignment, and in young and active patients. We hypothesized that radial head excision increases coronoid contact pressures, which may at least be partially reduced by radiocapitellar Achilles tendon disc arthroplasty., Methods: Coronoid and capitellar contact pressure was measured on 6 human cadaveric elbows on a custom-designed gravity-valgus simulator under passive flexion from 0° to 90°. Sequential testing, starting with the intact specimen, resection of the radial head, and finally, radiocapitellar Achilles tendon disc arthroplasty were performed on each specimen., Results: Mean contact pressure of the coronoid significantly increased after radial head excision (P < .0001) and significantly improved after Achilles disc arthroplasty (P < .0001). The pressure difference was most pronounced on the lateral coronoid. From 15° to 85° of elbow flexion, mean contact pressures on the lateral coronoid were 291 kPa and 476 kPa before and after radial head excision, respectively (P < .0001). Achilles disc arthroplasty significantly lowered coronoid contact pressures to 385 kPa (P = .002); however, they remained significantly higher than those in the intact radial head group (P = .0009)., Conclusions: Radial head resection increases contact pressure in the coronoid, especially the lateral coronoid. This study showed that radiocapitellar Achilles disc arthroplasty significantly improves contact pressures on the coronoid after radial head resection. Achilles disc arthroplasty could be considered in patients who are not candidates for radial head arthroplasty., (Copyright © 2018 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

Background: Forearm rotation is closely associated with the axiorotational force transmission through the elbow joint. A technique has been developed to study the transmission of force across the radiocapitellar and ulnotrochlear joints during forearm rotation., Methods: Ten human cadaveric upper limbs were prepared on a custom-designed apparatus that permits the application of extrinsic axial loads across an intact cadaveric elbow joint. A force-sensitive transducer was inserted into the elbow joint of each cadaver. A 160 N axial force was applied to the specimen during cyclic forearm rotation while the force, contact pressure, and contact area through the elbow joint were measured., Results: The mean force across the radiocapitellar joint showed no significant difference between pronation and supination (P = .3547). The radiocapitellar joint showed significantly higher contact area (P = .0001) and lower contact pressure (P = .0001) in pronation than in supination. The mean values for contact pressure, area, and force across the ulnotrochlear joint were not significantly different between supination and pronation., Conclusion: The contact pressure and contact area of the radiocapitellar joint in the cadaveric model changed according to forearm rotation while the force remained constant. The mean contact pressure of the radiocapitellar joint in pronation was significantly lower than that in supination because the force across it did not change significantly and its contact area decreased significantly. These findings may suggest that the pronated elbow can play an important role in protecting the radiocapitellar joint in high-impact activities like delivering punch in martial arts or falling on an outstretched arm., (Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

Background: Minimal micromotion is necessary for osteointegration of cementless radial head prostheses. When radial head fractures extend longitudinally, where the neck cut for prosthetic replacement should be made is uncertain. We hypothesized that complete resection of the notched portion of a radial neck confers no advantage in initial stability compared with not resecting the defect and inserting the implant into a notched radial neck., Materials and Methods: The radii of 7 cadavers underwent radial head resection and implantation with a 25-mm-long press-fit radial head stem. Before implantation, a 5-mm-long notch that was less than 1-mm wide was made in the radial neck. After the stem-bone micromotion was recorded, the proximal 5 mm of radial neck, incorporating the entire notch, was cut away, the stem was inserted 5 mm further, and the resulting micromotion was recorded., Results: The mean micromotion measured in the presence of a cortical notch was 51 ± 6 µm. After the neck was circumferentially cut and the stem was advanced, the micromotion (46 ± 9 µm) was not statistically significantly different., Discussion: Initial stability of an adequately sized cementless stem in the presence of a 5-mm-long cortical notch was well within the threshold needed for bone ingrowth (<100 µm). In addition, there was no reduction of micromotion after the notch-containing portion of the radial neck was resected and the stem was advanced. Making a neck cut distal to a 5-mm-long, 1-mm-wide cortical notch does not confer added stability. Thus, surgeons can preserve bone stock and avoid an aggressive neck cut., (Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

Hypothesis: The purposes of this study were to test the hypothesis that coronoid deficiency in the setting of posteromedial rotatory instability (PMRI) must be reconstructed to restore articular contact pressures to normal and to compare 3 different osteochondral grafts for this purpose., Methods: After creation of a anteromedial fracture, six cadaveric elbows were tested under gravity varus stress using a custom-made machine designed to simulate muscle loads and to passively flex the elbow. Mean articular surface contact pressure data were collected and processed using TekScan sensors and software. After testing of the intact specimen (intact condition), a PMRI injury was created (PMRI condition). Testing was repeated after reconstruction of the lateral collateral ligament (LCL) (LCL-only condition), followed by reconstruction of the coronoid with 3 different osteochondral graft techniques (reconstructed conditions)., Results: Contact pressure was consistently significantly higher in the PMRI elbow compared with the intact, LCL-only, and reconstructed conditions (P < .006). The LCL-only elbow contact pressure was significantly higher than that of the intact and reconstructed conditions from 5° to 55° of flexion (P = .018). The contact pressure of the intact elbow was never significantly different from that of the reconstructed elbow, except at 5° of flexion (P ≤ .008). No significant difference was detected between each of the reconstructed techniques (P ≥ .15). However, the annular surface of the radial head was the only graft that yielded contact pressures not significantly different from normal at any flexion angle., Conclusion: Isolated reconstruction of the LCL did not restore native articular surface contact pressure, and reconstruction of the coronoid using osteochondral graft was necessary. There was no difference in contact pressures among the 3 coronoid reconstruction techniques., (Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

Background: Posteromedial rotatory instability (PMRI) of the elbow consists of an anteromedial coronoid fracture with lateral collateral ligament (LCL) and posterior bundle of the medial collateral ligament (PMCL) tears. We hypothesized that the LCL tear is required for elbow subluxation/joint incongruity and that an elbow affected by an anteromedial subtype 2 coronoid fracture and a PMCL tear exhibits contact pressures different from both an intact elbow and an elbow affected by PMRI., Materials and Methods: Six cadaveric elbows were tested under gravity varus stress using a custom-made machine designed to simulate muscle loads and to passively flex the elbow from 0° to 90° and measure joint contact pressures. After testing of the intact specimen (INTACT-elbow), an anteromedial subtype 2 coronoid fracture with a PMCL tear (COR+PMCL-elbow) and a PMRI injury (PMRI-elbow), after adding an LCL tear, were tested. The highest values of mean contact pressure were used for the comparison among the 3 groups., Results: Neither subluxation nor joint incongruity was observed in the COR+PMCL-elbow. The addition of an LCL detachment consistently caused subluxation and joint incongruity. Mean contact pressures were higher in the COR+PMCL-elbow compared with the INTACT-elbow (P < .03) but lower than in the PMRI-elbow (P < .001)., Conclusions: The LCL lesion in PMRI is necessary for elbow subluxation and causes marked elevations in contact pressures. Even without subluxation, the COR+PMCL-elbow showed higher contact pressures compared with the INTACT-elbow. Treatment of PMRI should be directed toward prevention of joint incongruity, whether by surgical or nonsurgical means, to prevent high articular contact pressures., (Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

Background: Metallic radial head prostheses are often used in the management of comminuted radial head fractures and elbow instability. We hypothesized that during radiocapitellar subluxation, the contact pressure characteristics of an anatomic radial head prosthesis will more closely mimic those of the native radial head compared with a monopolar circular or a bipolar circular radial head design., Materials and Methods: With use of 6 fresh frozen cadaver elbows, mean radiocapitellar contact pressures, contact areas, and peak pressures of the native radial head were assessed at 0, 2, 4, and 6 mm of posterior subluxation. These assessments were repeated after the native radial head was replaced with anatomic, monopolar circular and bipolar circular prostheses., Results: The joint contact pressures increased with the native and the prosthetic radial head subluxation. The mean contact pressures for the native radial head and anatomic prosthesis increased progressively and significantly from 0 to 6 mm of subluxation (native, 0.6 ± 0.0 MPa to 1.9 ± 0.2 MPa; anatomic, 0.7 ± 0.0 MPa to 2.1 ± 0.3 MPa; P < .0001). The contact pressures with the monopolar and bipolar prostheses were significantly higher at baseline and did not change significantly further with subluxation (monopolar, 2.0 ± 0.1 MPa to 2.2 ± 0.2 MPa [P = .31]; bipolar, 1.7 ± 0.1 MPa to 1.9 ± 0.1 MPa [P = .12]). The pattern of increase in contact pressures with the anatomic prosthesis mimicked that of the native radial head. Conversely, the circular prostheses started out with higher contact pressures that stayed elevated., Conclusion: The articular surface design of a radial head prosthesis is an important determinant of joint contact pressures., (Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

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., (Copyright © 2014 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Mosby, Inc. All rights reserved.)

Background: While many design-specific features of radial head prostheses have been studied (ie, geometry and surface coating), the optimum technique for canal preparation has not been determined. We hypothesized that preparation of the radial canal with a reamer would allow for the accommodation of a larger stem diameter versus following canal preparation with a rasp, and would provide acceptable stem-bone micromotion., Methods: Paired proximal radii from 7 cadavers were prepared by a rasp on one side and a reamer on the contralateral side. Cementless radial head stems of increasing diameter were sequentially implanted up to the maximum size or until a fracture occurred and the micromotion between the stem and bone was recorded., Results: In 3 of 5 pairs, at least a 1 mm larger stem size fit into the canal after reaming versus after rasping (P = .04). 5 of 7 radii fractured secondary to intentional stem oversizing. For the optimally-sized stems, similar micromotion values were observed whether the canal was rasped (41 ± 6 μm) or reamed (44 ± 6 μm) (P = .72)., Discussion: This study investigated an aspect of radial head arthroplasty technique about which little has currently been published. It is possible that use of a reamer rather than a rasp, while providing similar initial stability, might expand the stem size options for initial press-fit stability, and decrease the risk of fracture., Conclusion: Radial canal preparation with a reamer allows for implantation of a 1 mm larger stem diameter versus rasping, while providing comparable initial stability to that achieved after rasping., (Copyright © 2013 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Mosby, Inc. All rights reserved.)

Background: Osteointegration of press-fit radial head implants is achieved by limiting micromotion between the stem and bone. Aspects of stem design that contribute to the enhancement of initial stability (ie, stem diameter and surface coating) have been investigated. The importance of total prosthesis length and level of the neck cut has not been examined., Methods: Cadaveric radii were implanted with cementless, porous-coated radial head stems. We resected 10, 12, 15, 20, and 25 mm of radial neck in each specimen. Stem-bone micromotion was measured after each cut. Values were expressed in terms of quotients (cantilever quotient)., Results: A threshold effect was observed at 15 mm of neck resection (cantilever quotient, 0.4), with a significant increase in micromotion observed between 12 mm (40 ± 10 μm) and 15 mm (80 ± 25 μm). A cantilever quotient of 0.35 or less predicted implant stability, whereas implants with a cantilever quotient of 0.6 or more were unstable. In between, the stems were "at risk" of instability., Conclusion: Initial stem stability of a porous-coated, cementless radial head implant is dependent on length of the implant stem within bone and the level of the cut (amount of bone resected). Stability may be compromised by an implant with a combined head and neck length that is too long compared with the stem length within the canal. We found a critical ratio of exposed prosthesis to total implant length (cantilever quotient of 0.4), which puts the prosthesis at risk of inadequate initial stability. These data carry important implications for implant design and use., (Copyright © 2012 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Mosby, Inc. All rights reserved.)

Background: Successful bone ingrowth around cementless implants requires adequate initial stability. Hoop stress fractures during stem insertion can potentially hinder prosthesis stability., Hypothesis: We hypothesized that an oversized radial head prosthetic stem (1 mm "too large" and causing a hoop stress fracture during insertion) would result in an unacceptable amount of micromotion., Materials and Methods: Grit-blasted radial head prosthetic stems were implanted into cadaveric radii. Rasp and stem insertion energies were measured, along with micromotion at the stem tip. The sizes were increased until a fracture developed in the radial neck., Results: Prosthetic radial head stems that were oversized by 1 mm caused small cracks in the radial neck. Micromotion of oversized stems (42 ± 7 μm) was within the threshold conducive for bone ingrowth (<100 μm) and not significantly different from that for the maximum sized stems (50 ± 12 μm) (P ≥ .4)., Discussion: Contrary to our hypothesis, hoop stress fractures caused by implantation of a stem oversized by 1 mm did not result in loss of stability. Stem micromotion remained within the range for bone ingrowth and was not significantly diminished after the fracture. This suggests that if a crack occurs during the final stages of stem insertion, it may be acceptable to leave the stem in place without adding a cerclage wire., Conclusion: A small radial neck fracture occurring during insertion of a radial head prosthetic stem oversized by 1 mm does not necessarily compromise initial stability., (Copyright © 2012 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Mosby, Inc. All rights reserved.)

Background: Radial head prosthetic stems designed for bone ingrowth are available with both plasma spray and grit blasted surfaces. A recent study comparing micromotion between the 2 demonstrated greater micromotion in the plasma spray than grit blasted stems, even though the latter had lower surface roughness. This raised the question that perhaps the size mismatch for grit-blasted radial head stems (0.5 mm) might be inadequate for plasma spray stems., Hypothesis: A tighter initial press-fit with plasma spray radial head stems may be gained by preparation with an undersized rasp., Methods: Paired cadaveric radii were implanted with plasma spray stems. The surgical control was prepared with a rasp designated for its corresponding stem size ("size-matched"), while the experimental group was prepared with a rasp 0.5 mm smaller than designated ("undersized")., Results: The micromotion for the undersized rasp group (46 ± 12 μm) was not significantly different than for the size-matched rasp group (21 ± 12 μm) (P = .1)., Discussion: Contrary to our hypothesis, no reduction in micromotion was observed when using an undersized rasp with a plasma spray stem. The micromotion results were not different from those observed when using a size-matched rasp, and actually approached significance in the opposite direction. This may be due to the rough stem surface chipping away bone fragments, rather than the bone being cut away precisely as is done with a rasp., Conclusion: The use of an undersized rasp prior to implantation of a plasma spray radial head prosthesis does not confer any added benefit in terms of initial stability., (Copyright © 2012 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Mosby, Inc. All rights reserved.)

Background: Management for Mason type II radial head fractures is controversial. We hypothesized that angulation or depression of a marginal radial head fragment would affect radiocapitellar stability similarly to fragment excision., Materials and Methods: A Mason type II radial head fracture was created in 6 cadaveric elbows by excising a segment from the anterolateral quadrant that was 30% of the diameter of the articular surface. Radiocapitellar stability was recorded under 5 sets of conditions: (1) intact radial head (intact), (2) 30% surface area fragment resected (partially excised), (3) anatomic fragment fixation with screws (fixed), (4) fragment fixation with 2 mm of depression relative to the articular surface (depressed), and (5) fragment fixation after a 30° wedge resection (angulated)., Results: The forces required to subluxate the joint were greatly reduced after fragment excision (5 ± 1 N; P = .0001) and restored to normal (21 ± 1 N; P = .9) after anatomic fixation of the excised fragment. The peak forces were significantly reduced with fragment depression (4 ± 1 N) and angulation (4 ± 2 N; P = .0001)., Conclusion: A radial head fracture that is depressed 2 mm or angulated 30° may cause up to an 80% loss of concavity-compression stability of the radiocapitellar joint., (Copyright © 2012 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Mosby, Inc. All rights reserved.)

Background: A critical component of evaluating the outcomes after surgery to restore lost elbow motion is the range of motion (ROM) of the elbow. This study examined if digital photography-based goniometry is as accurate and reliable as clinical goniometry for measuring elbow ROM., Materials and Methods: Instrument validity and reliability for photography-based goniometry were evaluated for a consecutive series of 50 elbow contractures by 4 observers with different levels of elbow experience. Goniometric ROM measurements were taken with the elbows in full extension and full flexion directly in the clinic (once) and from digital photographs (twice in a blinded random manner)., Results: Instrument validity for photography-based goniometry was extremely high (intraclass correlation coefficient: extension = 0.98, flexion = 0.96). For extension and flexion measurements by the expert surgeon, systematic error was negligible (0° and 1°, respectively). Limits of agreement were 7° (95% confidence interval [CI], 5° to 9°) and -7° (95% CI, -5° to -9°) for extension and 8° (95% CI, 6° to 10°) and -7° (95% CI, -5° to -9°) for flexion. Interobserver reliability for photography-based goniometry was better than that for clinical goniometry. The least experienced observer's photographic goniometry measurements were closer to the reference measurements than the clinical goniometry measurements., Conclusions: Photography-based goniometry is accurate and reliable for measuring elbow ROM. The photography-based method relied less on observer expertise than clinical goniometry. This validates an objective measure of patient outcome without requiring doctor-patient contact at a tertiary care center, where most contracture surgeries are done., (Copyright © 2012 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Mosby, Inc. All rights reserved.)

Background: Radial head prostheses are available with multiple geometric properties. The effect of design features on radiocapitellar stability has not been investigated., Hypothesis: The shape (depth and radius of curvature) of the articulating dish of a radial head prosthesis affects radiocapitellar stability., Materials and Methods: Radiocapitellar stability due to concavity-compression was evaluated in 8 fresh frozen elbows before and after radial head replacement with 2 different designs of radial head implants (RH 1 and RH 2). Both functioned as monopolar implants. Peak forces resisting subluxation and force-displacement characteristics were compared between the 2 and to the native radial head., Results: Radial head design significantly affected radiocapitellar stability. RH 1, which had a deeper dish than RH 2, required significantly higher peak forces to subluxate the radiocapitellar joint. The peak subluxation forces and the slopes of the force-displacement curves were not significantly different from the native radial head for RH 1, but they were for RH 2., Conclusion: The shape of the articular dish (depth, radius of curvature) of a monopolar radial head implant affects its contribution to radiocapitellar stability. An implant that mimics normal anatomy is more effective than a shallow radial head implant with a radius of curvature that is longer than normal., (Copyright © 2011 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Mosby, Inc. All rights reserved.)

Background: Initial stability of a textured surface prosthetic stem is necessary for bone in-growth. Surfaces currently used for radial head prostheses include titanium plasma spray and grit-blasted titanium., Hypothesis: Plasma spray radial head prosthetic stems are less dependent than grit-blasted stems on a tight press fit. Good initial press-fit stability, with acceptable micro-motion, can be achieved with a greater range of stem sizes using a plasma spray than grit-blasted surface., Methods: Paired cadaveric radii were implanted with plasma spray or grit-blasted radial head prosthetic stems. Micromotion at the stem tip was measured under circumstances simulating eccentric loads., Results: Micromotion in the plasma spray (PS) stems (49 ± 37) μm was not better than that in the grit-blasted (GB) stems (28 ± 10) μm (P = .13). Micromotion of less than 100 μm was measured in all 12 GB stems that were maximum or 1 mm less than maximum size, versus 5/6, and 4/6 PS stems, respectively., Discussion: Micromotion in plasma spray prosthetic radial head stems was not better than that seen in grit-blasted stems, contrary to our initial hypothesis., Conclusion: Grit-blasted prosthetic radial head stems confer initial press-fit stability that is as good as, or slightly better than, corresponding plasma spray stems. Acceptable amounts of micromotion can be achieved with 2 grit-blasted stem sizes and probably with 2 plasma spray stem sizes., (Copyright © 2011 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Mosby, Inc. All rights reserved.)

Introduction: Radiocapitellar stability depends, in part, on concavity-compression mechanics. This study was conducted to examine the effects of the soft tissues on radiocapitellar stability with radial head prostheses., Hypothesis: Monopolar radial head implants are more effective in stabilizing the radiocapitellar joint than bipolar radial head prostheses, with the soft tissues intact or repaired., Materials and Methods: Twelve fresh frozen elbow specimens were used to evaluate radiocapitellar stability with monopolar and bipolar radial heads. The study variables focused on varying soft tissue conditions and examined the mean peak subluxation forces put forth by each prosthesis design., Results: With the soft tissues intact, the mean peak force resisting posterior subluxation depended significantly on the radial head used (P = .03). Peak force was greatest for the native radial head (32 ± 7 N) and least with the bipolar prosthesis (12 ± 3 N), with the monopolar prosthesis falling in between (21 ± 4 N). The presence of soft tissues significantly affected the bipolar implant's ability to resist subluxation, though it did not significantly impact the native or monopolar radial heads., Discussion: This study reveals the dependence of radiocapitellar stability on soft tissue integrity, particularly for bipolar prostheses. Overall, monopolar prostheses have a better capacity to resist radiocapitellar subluxation., Conclusion: From a biomechanical perspective, the enhancement of elbow stability with a monopolar radial head prosthesis is superior to that with a bipolar design. This is especially true when the integrity of the soft tissues has been compromised, such as in trauma., (Copyright © 2011 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Mosby, Inc. All rights reserved.)

Background: Compared to fully textured prosthetic stems, partial texturing lessens bone loss due to stress shielding and makes removal easier. However, initial press-fit stability is necessary for bone ingrowth., Hypothesis: There is no significant difference in the initial stability of radial head prostheses that are partially grit-blasted compared to those that are fully grit-blasted., Materials and Methods: Cadaveric radii were implanted with partial or fully grit-blasted radial head prostheses. Micromotion of the stem at the isthmus of the canal and stem tip were measured under circumstances simulating eccentric loads., Results: Micromotion was not significantly different in the fully grit-blasted stems (isthmus, 11 ± 1 μm; tip, 21 ± 2 μm) and partially grit-blasted stems (isthmus, 13 ± 2 μm; tip, 25 ± 2 μm) (P = 0.4). The direction of loading had no effect on micromotion characteristics in either the fully or partially grit-blasted stems (P = .07)., Discussion: Micromotion is comparable in partially and fully grit-blasted radial head prosthetic stems. For both stem surfaces, micromotion was well within the range that is conducive for bone ingrowth. A partially textured stem might have less bone loss due to stress shielding, making it easier to remove without destroying bone., Conclusion: The initial stability of a radial head stem that is partially grit-blasted only at the proximal end is comparable to that of a radial head stem that is grit-blasted along its entire length., (Copyright © 2011 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Mosby, Inc. All rights reserved.)