Finite element analysis of a customized coronoid prosthesis for traumatic coronoid deficiency.

BACKGROUND: Traumatic coronoid deficiency with persistent elbow instability is a challenging condition. Autologous bone graft reconstruction is often associated with a range of additional clinical problems and the outcome is often unpredictable. The purpose of this study was to design a prosthetic device that can reconstruct coronoid deficiency of any height and to evaluate its mechanical properties using finite element analysis. MATERIALS AND METHODS: A customized coronoid prosthesis was designed based on image registration, automatic measurement, and computer-aided design. After pilot study and sample size calculation, image data collected from 6 patients who underwent bilateral complete upper extremity CT scans were reconstructed. The test was divided into 3 groups: coronoid intact, prosthesis and autograft. Regan-Morrey type II and autologous olecranon osteotomy models were established. The prosthesis and autogenous olecranon were assembled to the coronoid base. Stress was applied axially along the proximal humeral diaphysis and implant micromotion and contact mechanics of the humeroulnar joint were measured at 30°, 45°, 60° and 90° of joint flexion respectively. RESULTS: At all flexion angles, the maximum stress on the coronoid articular surface was significantly reduced in the prosthesis and autograft groups, with the reduction being more significant in the latter (P < .001). With increasing flexion, the maximum stress at the coronoid articular surface increased significantly after autograft reconstruction (7.2 to 68 MPa, P < .001), whereas the humeroulnar joint obtained a similar contact mechanics pattern to that of the control group after prosthetic reconstruction. As the flexion angle increased, the relative micromotion of both the prosthesis and autograft increased significantly (0.5-1.6 vs. 0.2-1.2, Pmeasure time < 0.001, Pgroups < 0.001). Contact pressure and center-of-force paths of the humeroulnar joint experience abrupt stress changes at approximately 60° of flexion. CONCLUSION: The contact stress pattern in the humeroulnar joint is similar in prosthesis and intact coronoid groups. Autograft reconstruction increases contact stresses at the articular surface and alters the joint center-of-force path. The "stress surge phenomenon" in the humeroulnar joint surface before and after 60° of flexion may be one of the mechanisms of traumatic elbow degeneration.

[Coronoid reconstruction with autologous iliac crest bone graft in chronic elbow instability through a medial approach]. / Coronoidaufbau mittels Beckenkammspan über einen medialen Zugang zur Therapie von chronischen Coronoiddefekten mit posteromedialer Rotationsinstabilität.

OBJECTIVE: Neutralizing a posteromedial rotatory instability (PMRI) caused by coronoid deficiency by restoration of the humeroulnar joint surface with an autologous iliac crest bone graft. INDICATIONS: Surgery is indicated in patients with chronic deficiency of the anteromedial facet of the coronoid with subsequent PMRI. CONTRAINDICATIONS: Coronoid reconstruction is not recommended in patients with advanced osteoarthritis of the elbow caused by subluxation of the humeroulnar joint. General contraindications like acute infection, pregnancy and lack of operability should also be taken into account. SURGICAL TECHNIQUE: First, a medial approach is established and the base of the coronoid is prepared. Afterwards an autologous iliac crest bone graft is placed onto the defect and secured by screws or a plate. In addition, a reconstruction of the anterior bundle of the medial collateral ligament with an autologous tendon graft is performed. POSTOPERATIVE MANAGEMENT: An elbow orthesis is worn for 6 weeks after surgery to avoid valgus or varus stress. There is no restriction in range of motion. A continuous passive motion elbow chair supports the patient in regaining elbow mobility. RESULTS: Between 2015 and 2017, we treated 10 patients suffering from chronic coronoid defects with coronoid reconstruction. Eight of the patients were available for follow-up 86 weeks after surgery. The mean age was 41.4 years. In all patients, elbow range of motion and patient-related outcome measures were improved after surgery. Plain radiographs illustrated correct centering of the elbow joint. One patient had to undergo elbow arthroplasty and was excluded. Coronoid reconstruction with an autologous iliac crest bone graft restored humeroulnar joint congruency and improved satisfaction in patients suffering from chronic coronoid deficiency.

Osteochondral reconstruction for post-traumatic coronoid deficiency.

PURPOSE: This study aimed to evaluate the clinical outcome and graft survival following coronoid reconstruction with osteochondral bone grafts for post-traumatic coronoid deficiency treatment. We hypothesized that coronoid reconstruction using an osteochondral bone graft will provide favorable results in treating post-traumatic coronoid deficiency. METHODS: A retrospective review was performed on eight patients (mean age = 45.8 years) who underwent osteochondral bone graft reconstruction indicated for post-traumatic coronoid deficiency. The osteochondral bone grafts were obtained from the radial head remnant (four patients), olecranon tip (two patients), and iliac crest (two patients). All the injuries were terrible triad. The mean duration from injury to surgery was 79.3 weeks. The visual analog scale (VAS) for pain, motion arc, and Mayo elbow performance score (MEPS) were used to evaluate the clinical outcome. Radiologic evaluation of graft healing and integrity was performed using computed tomography at 19 months and plain elbow radiography at 24.1 months after reconstruction. The immediate graft height was measured. RESULTS: VAS and MEPS values improved from 4.1 ± 1.2 to 1.1 ± 0.3 and 34.2 ± 16.9 to 85.0 ± 7.1, respectively (p = 0.018, p = 0.018) after reconstruction. The motion arc significantly improved from 84.2° ± 16.1° to 102.1° ± 18.2° at the final follow-up of 39.1 ± 18.8 months (p = 0.048). All the osteochondral grafts survived, with nonunion in two patients (25%). The mean immediate graft height was 15.4 ± 2.6 mm. Among the eight patients, three (37.5%) developed secondary osteoarthritis of the ulnohumeral joint. CONCLUSIONS: Coronoid reconstruction with osteochondral bone graft may serve as an option to salvage post-traumatic coronoid deficiency. Sufficient graft height was required for graft survival. Secondary osteoarthritis of the ulnohumeral joint should not be underestimated during follow-up.

Management of the Posttraumatic Coronoid-Deficient Elbow.

Posttraumatic coronoid deficiency is one of the most challenging scenarios even for the most experienced elbow surgeon. Surgical options can be grouped into soft tissue reconstructions, autogenous corticocancellous bone graft reconstructions, osteochondral reconstructions, and prosthetic replacement. However, the literature is inconclusive with limited cases, short follow-up, and no conclusive clinical comparative studies of these techniques. This article provides a review of the current surgical options, and we offer the senior author's (S.W.O.) perspective after years of experience with many of these techniques.

Coronoid reconstruction using osteochondral grafts: a biomechanical study.

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.

Prosthetic replacement for coronoid deficiency: report of three cases.

BACKGROUND: Persistent elbow instability associated with coronoid deficiency is a difficult condition to treat. Several surgical techniques have been described for coronoid reconstruction, but the resulting outcomes have been unpredictable. We hypothesized that a coronoid prosthesis could restore elbow stability. METHODS: A nonanatomically shaped metallic coronoid prosthesis was custom designed for each of 3 patients. Each had a chronic fracture-subluxation with persistent instability, deficiencies of the coronoid, and compromise of the radial head. Each patient had undergone 2 to 4 prior failed operations. RESULTS: At a mean follow-up of 11 years (range, 10-12), 2 of the 3 patients were completely pain free; the third had a visual analog scale pain score not greater than 3/10. All 3 maintained a stable joint, although a functional range of motion was not able to be maintained in any. Two patients rated themselves "improved" and 1 patient rated himself "almost normal" on the Summary Outcome Determination scale. All radiographic follow-up showed the coronoid prosthesis in proper position without loosening. CONCLUSION: Prosthetic replacement of the coronoid appears successful in restoring stability in chronically unstable elbows with coronoid deficiency.

Coronoid reconstruction with an osteochondral radial head graft.

BACKGROUND: Chronic coronoid deficiency can occur subsequent to coronoid fracture malunion/nonunion or to coronoid hypoplasia or dysplasia resulting from injury during development. Several surgical options have been described to treat this difficult condition, but results are equivocal. We hypothesized that a modified coronoid reconstruction using a radial head osteochondral graft could restore elbow stability and congruity and that a technique involving rigid internal fixation would promote graft union. METHODS: The coronoid was reconstructed using an osteochondral fragment from a frozen allograft radial head in 3 young women affected by complex post-traumatic elbow instability and incongruity resulting from coronoid deficiency. To promote bone healing, the fragment was kept as large as could be fitted in place, the cut surface compressed onto the remaining coronoid was as large as possible, the medial portion of the radial head (containing dense bone) was used, and 3 lag screws were inserted in different directions. RESULTS: At a mean follow-up of 26 months, all 3 patients achieved a painless, congruent stable joint with a functional range of motion. Computed tomography scans performed 3 months after surgery showed complete union of the graft in all the patients. Each patient rated herself as "almost normal" or "greatly improved" on the Summary Outcome Determination scale. CONCLUSION: Coronoid reconstruction with a radial head osteochondral allograft was successful in restoring stability and function in chronically unstable elbows with coronoid deficiency. Strong fixation using a large segment of the medial radial head achieved rapid graft healing.