Importance of the posterior bundle of the medial ulnar collateral ligament

Postoperative Elbow Instability: Options for Revision Stabilization

Persistent and recurrent postoperative elbow instability includes a spectrum of pathologies ranging from joint incongruity and subluxation to dislocation. Restoration of osseous anatomy, particularly the coronoid, is a priority in restoring elbow alignment and maintaining ulnohumeral joint stability. After managing bony deficiencies, soft-tissue and ligamentous structures are typically addressed. When required, both static and dynamic adjunctive stabilization procedures have been described, which aid in maintaining a concentric reduction. In these complex procedures, both complication avoidance and early recognition of postoperative complications assist in obtaining a good result. In this review, we discuss current treatment options for revision stabilization for patients with persistent and recurrent elbow subluxation or dislocation after primary stabilization.

Dual Bracing for Ulnar Collateral Ligament Injuries Restores Native Valgus Laxity and Native Medial Joint Gapping of the Elbow

Background

Despite growing evidence on the role of the posterior ulnar collateral ligament (pUCL) in elbow stability, current ligament bracing techniques are mainly focused on the anterior ulnar collateral ligament (aUCL). A dual-bracing technique combines the repair of the pUCL and aUCL with a suture augmentation of both bundles.

Purpose

To biomechanically assess a dual-bracing approach addressing aUCL and pUCL for humeral-sided complete UCL lesions to restore medial elbow laxity without overconstraining.

Study Design

Controlled laboratory study.

Methods

A total of 21 unpaired human elbows (11 right, 10 left; 57.19 ± 11.7 years) were randomized into 3 groups to compare dual bracing with aUCL suture augmentation and aUCL graft reconstruction. Laxity testing was performed with 25 N applied 12 cm distal to the elbow joint for 30 seconds at randomized flexion angles (0°, 30°, 60°, 90°, and 120°) for the native condition and then for each surgical technique. A calibrated motion capture system was used for assessment, allowing the 3-dimensional displacement during the complete valgus stress cycle between the optical trackers to be quantified as joint gap and laxity. The repaired constructs were then cyclically tested through a materials testing machine starting with 20 N for 200 cycles at a rate of 0.5 Hz. The load was increased stepwise by 10 N for 200 cycles until displacement reached 5.0 mm or complete failure occurred.

Results

Dual bracing and aUCL bracing resulted in significantly (P = .045) less joint gapping at 120° of flexion compared with aUCL reconstruction. No significant differences in valgus laxity were found among the surgical techniques. Within each technique, there were no significant differences between the native and the postoperative state in valgus laxity and joint gapping. No significant differences between the techniques were observed in cycles to failure and failure load.

Conclusion

Dual bracing restored native valgus joint laxity and medial joint gapping without overconstraining and provided similar primary stability regarding failure outcomes as established techniques. Furthermore, it was able to restore joint gapping in 120° of flexion significantly better than aUCL reconstruction.

Clinical Relevance

This study provides biomechanical data on the dual-bracing approach that may help surgeons to consider this new method of addressing acute humeral UCL lesions.

Coronoid fixation and lateral collateral ligament repair in varus posteromedial rotatory instability of the elbow

Background

Varus posteromedial rotatory instability is a relatively rare elbow injury, that has been infrequently reported in published literature. We intended to evaluate the outcomes of surgical management of this rare injury with anteromedial coronoid fixation, and, in selected patients, lateral ulnar collateral ligament (LUCL) repair.

Methods

Between 2017 and 2020, we identified 12 patients with anteromedial coronoid fractures, and a varus posteromedial rotatory instability, who underwent surgery for fixation of the coronoid fracture, with or without LCL repair. All the included patients were either O'Driscoll subtype 2-2, or subtype 2-3. All the 12 patients were followed up for a minimum of 24 months, and their functional outcomes assessed using the Mayo Elbow Performance Score (MEPS).

Results

The mean MEPS recorded in our study was 92.08, and the mean range of elbow flexion achieved was 124.2°. The mean flexion contracture in our patients was 5.83°. Three of our twelve patients (25%) suffered from elbow stiffness even at final follow-up. The results were graded as Excellent in eight, Good in three, and Fair in one patient.

Conclusion

Coronoid fractures and LUCL disruptions associated with varus posteromedial rotatory instability can be reliably managed by employing a protocol that combines radiographic parameters, as well as intra-operative assessments of stability. While surgical intervention successfully restored stability, there is a learning curve to the management of these injuries and complications are not uncommon, particularly elbow stiffness. Hence, in addition to surgical fixation, emphasis should also be placed on intensive post-operative rehabilitation to improve outcomes.

Effectiveness and safety of a less-invasive MCL reconstruction technique for contracted or ossified ligaments in patients with elbow stiffness: An open-label, non-randomised, prospective, multicentre trial in China

BACKGROUND

The elbow joint is sensitive to trauma from accidents, sports injuries, and surgical trauma. Some patients develop ossification or contracture of the medial collateral ligament (MCL) after elbow trauma. A less invasive reconstruction of the MCL can be performed after resection of diseased MCL. The biomechanical characteristics of this technique have been demonstrated and validated. However, its clinical effectiveness and safety require further confirmation in clinical practice.

METHODS

This open-label, non-randomised, prospective, multicentre trial included consecutive patients with elbow stiffness from five orthopaedic centres in China. Patients willing to participate in the study, with elbow stiffness caused by traumatic injury, who had reached skeletal maturity, and who had a range of motion of <100° were eligible for inclusion. Patients with immunological or metabolic causes of elbow stiffness, burns, or central nervous system injuries were excluded. In addition, patients who did not require MCL release and reconstruction after intraoperative release of other structures were also excluded. All patients underwent resection of the diseased MCL part in an open arthrolysis. Medial stability of the elbow was reconstructed using a less invasive MCL reconstruction technique that uses fascia and tendon patches. In this study, the primary outcomes, including stability, Mayo Elbow Performance Score (MEPS), Amadio score, were used to comprehensively evaluate this technique. Outcomes were assessed at 6 weeks, 6 months, and 1 year postoperatively and annually thereafter. This study reports the results of one arm of the trial that has been registered with the Chinese Clinical Trial Registry (chictr.org.cn), ChiCTR-INC-16010019.

FINDINGS

Between January 1, 2017 and March 1, 2020, 104 eligible patients were enrolled. The mean follow-up time was 43·47 (95% CI, 41·45 - 45·49) months. Among all 104 patients, 100 (96%) patients who underwent MCL reconstruction retained medial stability at the last follow-up. All outcomes from the last follow-up were used for comparison with the preoperative outcomes. No differences in preoperative and postoperative stability scores were observed (P = 0·7820). Extension, flexion, pronation, and supination of the injured elbow improved significantly (P < 0·0001, P < 0·0001, P < 0·0001, P < 0·0001). The mean range of motion (ROM) and forearm rotational range of motion (FRR) increased by 71·25° (152%) (P < 0·0001) and 30·83° (25%) (P < 0·0001), respectively. Additionally, the Mayo Elbow Performance Score (MEPS) and muscle strength had increased after evaluation at follow-ups (P < 0·0001, P < 0·0001). Drastic pain relief and nerve symptom reduction were observed, as evaluated using VAS scores and Amadio scores, respectively (P < 0·0001, P < 0·0001). Seventeen (16%) patients experienced a recurrence of elbow stiffness of varying severity, but only two patients had poor or fair results. Several common and non-severe complications, including infection in one (1%) patient, new nerve symptoms in seven (7%) patients, new pain in one (1%) patient, fracture in one (1%) patient, and valgus instability in four (4%) patients, were observed and properly treated in this study.

INTERPRETATION

The less invasive MCL reconstruction technique using fascia and tendon patches is an effective method for restoring medial stability in patients with elbow stiffness after complete arthrolysis with certain safety. The technique shows prospects for elbow MCL reconstruction in clinical practice.

FUNDING

The study was supported by the National Key Research and Development Program of China (No. 2021YFC2400805), National Natural Science Foundation of China (No. 81830076), Young Elite Scientist Sponsorship Program by Cast (No. YESS20200153), Shanghai Sailing Program (No. 20YF1436000), Shanghai Municipal Science and Technology Commission Foundation (No.19ZR1439200), Municipal Hospital Newly-developing Cutting-edge Technologies Joint Research Program of Shanghai Shenkang Hospital Development Centre (No. SHDC12018130).

Biomechanical Evaluation of a Low-Invasive Elbow Medial Collateral Ligament Reconstruction Technique With Fascia and Tendon Patches

Background: Injury to the medial collateral ligament (MCL) of the elbow has become increasingly common in sports, and the elbow is prone to contracture and ossification in trauma. Effective reconstruction of the MCL with reduction of irritation to the elbow has rarely been reported. This study introduces a minimally invasive elbow MCL reconstruction technique and evaluates the valgus stability.

Methods: Eight fresh-frozen elbow specimens underwent reconstruction of the anterior bundle of the MCL (AMCL) first with the flexor carpi ulnaris fascia patches, followed by reconstruction of the posterior bundle of the MCL (PMCL) with the triceps tendon patches. The valgus angles of each specimen were examined in three stages as follows: intact MCL, reconstruction of the AMCL alone, and reconstruction of the MCL (including AMCL and PMCL). Finally, specimens were loaded to failure, and failure modes were recorded.

Results: AMCL reconstruction alone had similar valgus stability at all testing angles (p = 0.080, 30° flexion; p = 0.064, 60° flexion; p = 0.151, 90° flexion; p = 0.283, 120° flexion) compared with the intact MCL, as did MCL reconstruction (p = 0.951, 30° flexion; p = 0.739, 60° flexion; p = 0.841, 90° flexion; p = 0.538, 120° flexion). More importantly, a significant difference existed between the MCL reconstruction and the AMCL reconstruction alone at 30° flexion (p = 0.043) and 60° flexion (p = 0.013) but not at the 90° flexion (p = 0.369) and 120° flexion (p = 0.879). The mean maximum failure torque of MCL reconstruction was 24.02 Nm at 90° elbow flexion.

Conclusion: Both AMCL reconstruction alone and MCL reconstruction provided valgus stability comparable with the native MCL, and importantly, MCL reconstruction provided more valgus stability than AMCL reconstruction alone at 30° flexion and 60° flexion of the elbow. Therefore, the new MCL reconstruction technique might be a useful guide for the treatment of elbow MCL injuries or deficiencies.

Repair Versus Non-Repair of Lateral Ulnar Collateral Ligament in Elbow Varus Posteromedial Rotatory Instability Treatment: A Comparative Study

OBJECTIVE

To compare the effects of repairing and not repairing the lateral ulnar collateral ligament (LUCL) when surgically treating elbow varus posteromedial rotatory instability (PMRI).

METHODS

In this retrospective study spanning June 2014 to February 2019, 24 patients with elbow PMRI who were treated surgically were assigned to group RL (Repair LUCL) or group NL (Non-repair LUCL) depending on whether the LUCL was repaired. Hospitalization time, operation time, intraoperative blood loss, and related complications were reviewed. The elbow range of motion (ROM), the visual analog scale (VAS), the Mayo elbow performance score (MEPS), and the disabilities of the arm, shoulder, and hand (DASH) score were used for functional assessment.

RESULTS

Among the 24 patients with PMRI, 15 were assigned to group RL and nine were assigned to group NL. The mean blood loss (184.66 ± 20.3 vs 207.33 ± 19.447, P < 0.001), the operation time (98.88 ± 12.693 min vs 184.66 ± 20.3 min, P < 0.001) were significantly lower in group RL compared to group NL. There were no significant differences between the two groups in time until surgery and follow-up time (6.66 ± 1.838 vs 6.11 ± 1.900 days, 25.53 ± 2.099 vs 26.11 ± 2.891 months, P = 0.577, P = 0.486). All of the patients achieved bone union. The elbow flexion-extension ROM (122.00° ± 3.162°vs 121.11° ± 3.333° at 12 months, P = 0.520) and pronation-supination ROM (154.53° ± 3.335° vs 155.55° ± 4.639° at 12 months, P = 0.537). Both groups achieved similar results in MEPS score (90.53 ± 2.695 vs 89.77 ± 3.865, P = 0.578) and DASH (9.77 ± 1.897 vs 9.99 ± 1.550, P = 0.772) score at the final follow-up. And the MEPS score revealed excellent results (87% in group RL, 89% in group NL).The VAS scores decreased significantly in group RL (from 6.13 ± 0.990 to 1.93 ± 0.593) and group NL (from 5.77 ± 1.481 to 1.88 ± 0.781), and no significant differences in preoperative or final follow-up were observed between the two groups (P = 0.487, P = 0.876). Complications observed in group NL with one patient occurred cubital tunnel syndrome 3 months after the operation, the patient underwent ulnar nerve simple neurolysis and the symptoms were relieved after 3 weeks.

CONCLUSION

For patients with elbow PMRI, satisfactory functional outcomes can be yielded with non-repair of the LUCL as long as the stable elbow joint is performed during operation.

Posteromedial rotatory instability of the elbow: What the radiologist needs to know

Varus posteromedial rotatory instability of the elbow joint is a relatively new subject described for the first time in 2003. It occurs secondary to axial loading of the elbow with varus force and internal rotation of the forearm. There is usually a specific pattern of osseous and soft tissue injuries that can be recognized on imaging. This includes an anteromedial coronoid fracture and avulsion of the lateral collateral ligament complex from its humeral attachment. Ulnar collateral ligament complex injury is also reported, particularly its posterior bundle which plays an important role in posteromedial elbow joint stability. There is high incidence of early osteoarthritis secondary to the resultant varus instability and increased contact pressure at the ulnohumeral joint. Surgical fixation of the coronoid fracture and ligamentous reconstruction maybe indicated to prevent this recurrent instability. The article reviews the key radiological features of posteromedial rotatory instability with multiple examples from different imaging modalities. The relevant anatomy of the elbow joint stabilising structures will be illustrated, in particular the coronoid process anatomy and the O'Driscoll classification for coronoid process fractures. Radiologists should be familiar with the imaging findings of posteromedial rotatory instability.

Role of the transverse ligament of the ulnar collateral ligament of the elbow: a biomechanical study

Background

The ulnar collateral ligament (UCL) complex of the elbow plays a primary role in valgus and posteromedial stability of the elbow. The anterior oblique ligament (AOL) of the UCL is believed to provide the majority of resistance to external forces on the medial elbow. The transverse ligament (TL) of the UCL is generally thought to have minimal contribution to the elbow’s overall stability. However, recent studies have suggested a more significant role for the TL. The primary aim of this study was to identify the TL’s contribution to the stability of the elbow joint in determining the joint stiffness and neutral zone variation in internal rotation.

Methods

Twelve cadaveric elbows, set at a 90° flexion angle, were tested by applying an internal rotational force on the humerus to generate a medial opening torque at the level of the elbow. The specimens were preconditioned with 10 cycles of humeral internal rotation with sinusoidal torque ranging from 0 to 5 Nm. Elbow stiffness measures and joint neutral zone were first evaluated in its integrity during a final ramp loading. The test was subsequently repeated after cutting the TL at 33%, 66%, and 100% followed by the AOL in the same fashion.

Results

The native UCL complex joint stiffness to internal rotation measured 1.52 ± 0.51 Nm/°. The first observable change occurred with 33% sectioning of the AOL, with further sectioning of the AOL minimizing the joint stiffness to 1.26 ± 0.32 Nm/° (P = .004). A 33% resection of the TL found an initial neutral zone variation of 0.376 ± 0.23° that increased to 0.771 ± 0.41° (P < .01) at full resection. These values were marginal when compared with the full resection of the AOL for which we have found 3.69 ± 1.65° (P < .01).

Conclusion

The TL had no contribution to internal rotation elbow joint stiffness at a flexion angle of 90°. However, sequential sectioning of the TL was found to significantly increase the joint neutral zone when compared with the native cadaveric elbow at a flexion angle of 90°. This provides evidence toward the TL having some form of contribution to the elbow’s overall stability.

LUCL internal bracing restores posterolateral rotatory stability of the elbow

PURPOSE

Posterolateral rotatory instability (PLRI) of the elbow occurs from an insufficient lateral collateral ligament complex (LCLC). For subacute LCLC injuries, lateral ulnar collateral ligament (LUCL) internal bracing rather than reconstruction may be a viable option. The purpose of the study was to compare the stabilizing effects of LUCL internal bracing to triceps tendon graft reconstruction in simulated PLRI.

METHODS

Sixteen cadaveric elbows were assigned for either LUCL internal bracing (n = 8) or reconstruction with triceps tendon graft (n = 8). Specimen were mounted and a valgus rotational torque was applied to the ulna to test posterolateral rotatory stability. Posterolateral rotation was measured at 0°, 30°, 60°, 90° and 120° of elbow flexion. Cyclic loading was performed for 1000 cycles at 90° of elbow flexion. Three conditions were compared in each specimen: intact elbow, LUCL and radial collateral ligament (RCL) transected, and then either LUCL internal bracing or reconstruction with triceps tendon graft.

RESULTS

Transection of the LUCL and RCL significantly increased posterolateral rotation in all degrees of elbow flexion compared to the intact condition (P < 0.05). Both LUCL internal bracing and reconstruction restored posterolateral rotatory stability to the native state between 0° and 120° of elbow flexion, with no significant difference in improvement between groups. Similarly, LUCL internal bracing and reconstruction groups showed no significant difference in posterolateral rotation compared to the intact condition during cyclic loading.

CONCLUSIONS

At time zero, both LUCL internal bracing and reconstruction with triceps tendon graft restored posterolateral rotatory stability. As such, this study supports the use of internal bracing as an adjunct to primary ligament repair in subacute PLRI.

Morphological features of the posterior oblique ligament of the ulnar collateral ligament of the elbow joint

PURPOSE

The purpose of this basic research study was to clarify the morphological characteristics of the posterior oblique fibers (POL) of the ulnar collateral ligament using a large number of specimens.

METHODS

This study examined 50 arms from 25 Japanese cadavers. Type classification was performed by focusing on the positional relationship between POL morphology and the joint capsule. The morphological features measured were fiber bundle length, width, and thickness.

RESULTS

The POL was classified as follows: Type I, the POL's anterior and posterior edges are located on the surface of the joint capsule and can be separated as a single fiber bundle; Type II-a, the POL anterior edge can be separated, but the posterior edge cannot be separated; Type II-b, the POL posterior edge can be separated, but the anterior edge cannot be separated; and Type III, the POL cannot be separated from the joint capsule. Type I was seen in 23 elbows (46%), Type II-a in 6 elbows (12%), Type II-b in 7 elbows (14%), and Type III in 14 elbows (28%).

CONCLUSION

The results of this study suggested that the POL could be classified into an independent type and an unclear type, and the presence of the unclear type was one of the factors that caused morphological variation.

Biomechanical Role and Motion Contribution of Ligaments and Bony Constraints in the Elbow Stability: A Preliminary Study

In flexion–extension motion, the interaction of several ligaments and bones characterizes the elbow joint stability. The aim of this preliminary study was to quantify the relative motion of the ulna with respect to the humerus in two human upper limbs specimens and to investigate the constraints role for maintaining the elbow joint stability in different section conditions. Two clusters of four markers were fixed respectively to the ulna and humerus, and their trajectory was recorded by a motion capture system during functional orthopedic maneuver. Considering the posterior bundle of medial collateral complex (pMUCL) and the coronoid, two section sequences were executed. The orthopedic maneuver of compression, pronation and varus force was repeated at 30°, 60° and 90° flexion for the functional investigation of constraints. Ulna deflection was compared to a baseline elbow flexion condition. With respect to the intact elbow, the coronoid osteotomy influences the elbow stability at 90° (deflection = 11.49 ± 17.39 mm), while small differences occur at 30° and 60°, due to ligaments constraint. The contemporary pMUCL section and coronoid osteotomy causes elbow instability, with large deflection at 30° (deflection = 34.40 ± 9.10 mm), 60° (deflection = 45.41 ± 18.47 mm) and 90° (deflection = 52.16 ± 21.92 mm). Surgeons may consider the pMUCL reconstruction in case of unfixable coronoid fracture.

Posteromedial rotatory incongruity of the elbow: a computational kinematics study

BACKGROUND

Our objective was to analyze the effect of different anteromedial coronoid fracture patterns with different combinations of ligamentous repairs. We hypothesized that smaller fractures would be sufficiently treated with ligamentous repair alone but that larger fragments would require a combination of ligament and bony repair versus reconstruction.

METHODS

Two multibody models were created from cadaveric specimens in the ADAMS program. Four different conditions were simulated: (1) no fracture, (2) O'Driscoll anteromedial subtype I (2.5-mm) fracture, (3) subtype II 2.5-mm fracture, and (4) subtype II 5-mm fracture. In each of these conditions, 3 ligament repairs were studied: lateral ulnar collateral ligament (LUCL), posterior bundle of the medial collateral ligament (pMCL), and both LUCL and pMCL. For each condition, kinematics and articular contact areas were calculated.

RESULTS

LUCL repair alone increases whereas pMCL repair decreases internal rotation of the ulna relative to all tested posteromedial rotatory instability conditions; their rotational effects are summative when both ligaments are repaired. With a subtype I fracture and both pMCL and LUCL injuries, repairing the LUCL alone corrects angulation whereas rotational stability is satisfactory through the arc from 0° to 90°. In a subtype II 2.5-mm fracture, isolated repair of the LUCL or pMCL is not capable of restoring rotation or angulation. For a subtype II 5-mm fracture, no combination of ligamentous repairs could restore rotation or angulation.

CONCLUSIONS

This study suggests that LUCL repair alone is sufficient to restore kinematics for small subtype I fractures for an arc avoiding deep flexion; whereas nearly normal kinematics throughout the arc of motion can be achieved if the pMCL is also repaired. Larger anteromedial coronoid fractures should ideally have fragments fixed in addition to ligament repairs.

Varus posteromedial rotatory instability: a biomechanical analysis of posterior bundle of the medial ulnar collateral ligament reconstruction

BACKGROUND

Recently, there has been growing interest in the involvement of the posterior bundle of the medial ulnar collateral ligament (pMUCL) in varus posteromedial rotatory instability (PMRI). Varus PMRI has been observed clinically, but the degree of involvement of the pMUCL remains unclear. This study assessed the degree to which the pMUCL is involved in stabilizing the elbow and the feasibility of a pMUCL reconstruction to restore stability.

METHODS

Movements simulating PMRI were performed in 8 cadaveric elbows. Joint gapping values were obtained by 3-dimensional motion capture for the proximal and distal aspects of the ulnohumeral joint. Specimens were assessed at "intact," "cut coronoid + pMUCL," "reconstruction," and "cut anterior aspect MUCL + reconstruction" conditions with mechanical testing at 30°, 60°, and 90° of elbow flexion.

RESULTS

Proximal joint gapping significantly increased from intact to cut coronoid + pMUCL at 60° and 90°, and distal joint gapping significantly increased at 90°. In the reconstruction condition, joint gapping across the proximal joint at 60° and 90° significantly recovered, as did distal joint gapping at 90°. In the cut anterior aspect MUCL + reconstruction condition, no significant increase occurred in proximal or distal joint gapping.

CONCLUSIONS

Transection of the pMUCL with a coronoid fracture leads to increased joint gapping, suggesting the presence of PMRI. PMRI can still occur with an intact lateral ligamentous complex. A pMUCL tendon graft reconstruction confers some elbow stability in this injury mechanism.

Outcomes following surgical management of complex terrible triad injuries of the elbow: a single surgeon case series

BACKGROUND

Terrible triad injuries of the elbow are complex injuries to treat and we report our outcomes following surgical management.

METHODS

Twenty-two consecutive patients who underwent fixation of terrible triad injuries between 2007 and 2012 were identified. Clinical outcomes were assessed by examination, visual analogue scores (VAS), Oxford Elbow Score (OES), Mayo Elbow Performance Index (MEPI) and QuickDash score (QD).

RESULTS

The mean age of patients was 47 years, with a mean follow-up of 32 months. All patients underwent lateral ligament repair, with additional medial ligament repair in four cases. Thirteen patients required repair of the coronoid and 18 patients required surgery to the radial head. The mean flexion-extension arc was 113°, with mean prono-supination of 136°. The functional elbow scores revealed good outcomes in the majority (mean OES of 37, MEPI of 79 and QD of 21). The overall complication rate was 41%. In total, 23% required reoperation, with one patient requiring fasciotomy for acute compartment syndrome and four requiring subsequent removal of metalwork as a result of stiffness.

CONCLUSIONS

Recognition of this complex injury pattern and appropriate restoration of the joint stability are the prerequisites. Systematic surgical approach is effective and can provide both stability and good function, in most cases.

Multibody modelling of ligamentous and bony stabilizers in the human elbow

The elbow ligamentous and bony structures play essential roles in the joint stability. Nevertheless, the contribution of different structures to joint stability is not yet clear and a comprehensive experimental investigation into the ligament and osseous constraints changes in relation to joint motions would be uphill and somehow unattainable, due to the impossibility of obtaining all the possible configurations on the same specimen. Therefore, a predictive tool of the joint behavior after the loss of retentive structures would be helpful in designing reconstructive surgeries and in pre-operative planning. In this work, a multibody model consisting of bones and non-linear ligamentous structures is presented and validated through comparison with experimental data. An accurate geometrical model was equipped with non-linear ligaments bundles between optimized origin and insertion points. The joint function was simulated according to maneuvers accomplished in published experimental studies which explored the posteromedial rotatory instability (PMRI) in coronoid and posterior medial collateral ligament (PB) deficient elbows. Moreover, a complete design of experiments (DOE) was explored, investigating the influence of the elbow flexion degree, of the coronoid process and of the medial collateral ligaments (MCL) structures (anterior and posterior bundles) in the elbow joint opening. The implemented computational model accurately predicted the joint behavior with intact and deficient stabilizing structures at each flexion degree, and highlighted the statistically significant influence of the MCL structures (P<0.05) on the elbow stability. The predictive ability of this multibody elbow joint model let foresee that future investigations under different loading scenarios and injured or surgically reconstructed states could be effectively simulated, helping the ligaments reconstruction optimization in terms of bone tunnel localizations and grafts pre-loading.

Level of evidence

V.

[Research progress of posteromedial rotatory instability of the elbow]

Objective

To summarize the research progress in posteromedial rotatory instability (PMRI) of the elbow joint.

Methods

The recent researches about the management of PMRI of the elbow joint from the aspects of pathological anatomy, biomechanics, diagnosis, and therapy were analyzed and summarized.

Results

The most important factors related to PMRI of the elbow joint are lateral collateral ligament complex (LCLC) lesion, posterior bundle of the medial collateral ligament complex (MCLC) lesion, and anteromedial coronoid fracture. Clinical physical examination include varus and valgus stress test of the elbow joint. X-ray examination, computed tomography, particularly three-dimensional reconstruction, are particularly useful to diagnose the fracture. Also MRI, arthroscopy, and dynamic ultrasound can assistantly evaluate the affiliated injury of the parenchyma. It is important to repair and reconstruct LCLC and MCLC and fix coronoid process fracture for recovering stability of the elbow joint. There are such ways to repair ligament injury as in situ repairation and functional reconstruction, which include direct suturation, borehole repairation, wire anchor repairation, and transplantation repairation etc. The methods for fixation of coronal fracture include screw fixation, plate fixation, unabsorbable suture fixation, and arthroscopy technology.

Conclusion

It is crucial that recovering the stability of the elbow joint and early functional exercise for the treatment of PMRI. Individual treatment is favorable to protect soft tissue, reduce surgical complications, and improve the functional recovery and the quality of life.

The Posterior Bundle's Effect on Posteromedial Elbow Instability After a Transverse Coronoid Fracture: A Biomechanical Study

PURPOSE

There has been increased interest in the role of the posterior bundle of the medial collateral ligament (pMUCL) in the elbow, particularly its effects on posteromedial rotatory stability. The ligament's effect in the context of an unfixable coronoid fracture has not been the focus of any study. The purposes of this biomechanical study were to evaluate the stabilizing effect of the pMUCL with a transverse coronoid fracture and to assess the effect of graft reconstruction of the ligament.

METHODS

We simulated a varus and internal rotatory subluxation in 7 cadaveric elbows at 30°, 60°, and 90° elbow flexion. The amount of ulnar rotation and medial ulnohumeral joint gapping were assessed in the intact elbow after we created a transverse coronoid injury, after we divided the pMUCL, and finally, after we performed a graft reconstruction of the pMUCL.

RESULTS

At all angles tested, some stability was lost after cutting the pMUCL once the coronoid had been injured, because mean proximal ulnohumeral joint gapping increased afterward by 2.1, 2.2, and 1.3 mm at 90°, 60°, and 30°, respectively. Ulnar internal rotation significantly increased after pMUCL transection at 90°. At 60° and 30° elbow flexion, ulnar rotation increased after resection of the coronoid but not after pMUCL resection.

CONCLUSIONS

An uninjured pMUCL stabilizes against varus internal rotatory instability in the setting of a transverse coronoid fracture at higher flexion angles. Further research is needed to optimize graft reconstruction of the pMUCL.

CLINICAL RELEVANCE

The pMUCL is an important secondary stabilizer against posteromedial instability in the coronoid-deficient elbow. In the setting of an unfixable coronoid fracture, the surgeon should examine for posteromedial instability and consider addressing the pMUCL surgically.

The posterior bundle of the elbow medial collateral ligament: biomechanical study and proposal for a new reconstruction surgical technique

BACKGROUND

The medial collateral ligament (MCL) is one of the primary elbows stabilizers. It is composed of an anterior bundle (AB), a posterior bundle (PB) and a transverse bundle. In elbow dislocations, until today MCL reconstruction has addressed the AB only. The purpose of this paper is to understand the biomechanical role of the PB of the MCL and to propose a new surgical technique for the simultaneous reconstruction of the anterior and posterior bundles, preventing the risk of recurrent posterior dislocation or posteromedial rotational instability (PMRI).

MATERIALS AND METHODS

Sixteen cadaveric elbows were subjected to a force in compression, supination valgus and pronation varus. The residual stability was evaluated in three conditions: intact MCL, sectioned AB and sectioned AB + PB. The tests were performed in collaboration with the Department of Mechanical and Aerospace Engineering of the Politecnico di Torino. In six elbows, the MCL was then reconstructed with the new technique.

RESULTS

Complete posterior elbow dislocation does not occur until the PB is sectioned. The section of the AB alone causes elbow instability in valgus stress, but not a dislocation. The reconstruction of the AB and the PB using the described technique allows a good recovery of range of motion and joint stability.

CONCLUSIONS

The PB of the MCL has a primary role in elbow stability against valgus stress, and it prevents elbow posterior dislocation at all flexion angles. The described reconstruction technique should reduce the risk of residual PMRI.