Varus Posteromedial Instability

Internal brace augmentation in elbow varus posteromedial rotatory instability (VPMRI) allows early rehabilitation and prevents stiffness

PURPOSE

Varus posteromedial rotatory instability (VPMRI) involves anteromedial coronoid fracture (AMCF), lateral ulnar collateral ligament (LUCL), and medial collateral ligament (MCL) injury. There is no general consensus regarding the surgical treatment, but most surgeons recommend internal fixation of the coronoid along with primary ligament repair. This methodology involves postoperative immobilization to allow ligament healing, occasionally associated with stiffness. Augmentation of one/or both collateral ligaments using a non-absorbable suture tape as an internal brace in VPMRI cases was the subject of the presented study. This method allows brace-free initiation of full elbow range of motion while protecting bony and soft tissue healing.

METHODS

17 patients (13 males and four females) with VPMRI were treated in the center from 2017 to 2021 with internal brace augmentation of collateral ligament along with ORIF (Open reduction & internal fixation)/ reconstruction of the coronoid fragment. All patients were actively mobilized early after surgery. Patients who completed a minimum follow up of 24 months were included in the study. Clinical examination findings at follow-up assessment included ROM (range of motion) recording and instability testing, including special instability tests such as moving valgus stress test, lateral pivot shift test, Posterolateral rotatory drawer test, and gravity-assisted varus stress test. Disabilities of arm, shoulder and hand (DASH) score, Mayo Elbow Performance Score (MEPS), Oxford Elbow Score (OES), Visual Analogue Score (VAS), and SEV (Simple Elbow values) were assessed and noted at follow-up.

RESULTS

At 43 months of mean follow-up, none of the patients had significant postoperative contracture, and none had any clinically apparent signs of instability or suffered subluxation or re-dislocation. Postoperative radiographs showed complete fracture/graft healing with no signs of subluxation in all patients. The mean range of motion of the patients was 6.20 (1.00-11.30) to 139.10 (136.20-142.00), with a mean Oxford elbow score (OES) of 42.0 (39.9-44.7). The mean DASH (Disability of Arm, Shoulder & Hand) score was 11.4 (6.7-16.1), the mean MEPS (Mayo Elbow Performance Score) was 91.2 (86.3-96.0), the mean Visual Analogue Score (VAS) score was 0.6 (0.1-1.2), and the mean Simple Elbow value (SEV) was 85.4% (81.1-89.8%).

CONCLUSION

Internal brace augmentation with a non-absorbable suture tape in the setting of VPMRI is a safe and helpful adjunct to coronoid repair/reconstruction and primary ligament repair and allows early mobilization and recovery of elbow stability and range of motion.

Pure varus posteromedial rotatory instability of the elbow: Radiographic findings, treatment, and outcomes

INTRODUCTION

Although varus posteromedial rotatory instability (VPMRI) is a subtle elbow injury that involves anteromedial coronoid facet (AMCF) fracture and ligamentous injuries, treatment options and outcomes of VPMRI remains controversial. The aim of this study was to investigate radiographic findings, treatments, and outcomes of a large series of VPMRI.

METHODS

We retrospectively reviewed 91 pure VPMRI cases with AMCF fracture (O'Driscoll classification anteromedial type) which were treated at 6 hospitals. Clinical and radiographic outcomes were investigated with a mean follow-up period of 46.8 months using the Mayo elbow performance score (MEPS), and the Quick Disabilities of the Arm, Shoulder and Hand (Quick-DASH) score, and serial plain radiographs.

RESULTS

In AMCF fracture, there were 4 cases of subtype 1, 67 cases of subtype 2, and 20 cases of subtype 3. On MRI, complete tears of lateral collateral ligament and medial collateral ligament were observed in 83.1 % (59/71 cases) and 33.8 % (24/71 cases). Operative treatment was performed in 68 cases (74.7 %) including both side fixation in 40 cases (58.8 %), medial side fixation only in 17 cases (25.0 %), and lateral side fixation only in 11 cases (16.2 %). Nonoperative treatment was performed in 23 cases (25.3 %). The mean final MEPS and Quick-DASH scores were 93.7 and 7.9. The overall complication and reoperation rates were 22.0 % and 15.4 %. No significant differences regarding final clinical scores and range of motions were observed between the operative group and the nonoperative group, but significant differences were observed regarding number (p = 0.019) and displacement (p = 0.002) of coronoid fragment, and complication rate (p < 0.001) between the two groups.

CONCLUSION

Depending on the pattern of coronoid fragment and the degree of ligamentous injuries, operative treatment of unstable VPMRI using various fixation techniques including coronoid fixation and ligament repair yielded satisfactory final clinical outcomes. However, surgeons should be aware of the high complication and reoperation rates after operative treatment. Stable VPMRI with AMCF fracture involving minimal displacement or small number of fragments can be treated nonoperatively.

Rehabilitation following ulnar collateral ligament injury of the elbow in a female acrobatic athlete: A case report

BACKGROUND

The mechanism of injury and the conservative rehabilitation of the ulnar collateral ligament of the elbow (UCL) are well studied and reported in overhead athletes, while research on gymnastic athletes is sparse. Evidence suggests exercise as the mainstay in UCL injury rehabilitation. With this report, we aimed to provide a complete rehabilitation protocol following a partial UCL tear of an acrobatic athlete, where exercise and adjunct treatments, such as manual therapy, were used in a progressive staged rehabilitation.

CASE DESCRIPTION

A 16-year-old female acrobatic athlete was diagnosed with partial tear of the anterior band of UCL. The rehabilitation included progressive exercise loading in conjunction with manual therapy for 10 sessions in 8 weeks. Pain, UCL special tests, the Disabilities of Arm, Shoulder and Hand Score Questionnaire (DASH), and the Upper Limb Functional Index (ULFI) were assessed and administered at baseline and at 3, 6, 10 weeks, and 3 months.

RESULTS

Improvement in all outcome measures was noted at the 3-month follow-up indicating a substantial reduction in pain and disability, and an increase in stability of the elbow joint. Return to training was achieved at 8 weeks from the initial visit, while return to sport at the pre-injury level was achieved at 3 months.

CONCLUSION

Progressive exercise loading along with the addition of manual therapy is an effective intervention for the rehabilitation and return to sport following a partial UCL tear. A progressive staged rehabilitation guideline for acrobatic athletes with UCL injuries has been provided to be used and guide clinical practice.

LEVEL OF EVIDENCE

Level IV.

A systematic review of techniques for step cut osteotomy in cubitus varus: A comprehensive analysis

Background

Cubitus varus, a common post-traumatic deformity of the elbow in children, poses challenges for both patients and surgeons. Step cut osteotomy has emerged as a reasonable surgical technique to address this condition, offering multiple approaches and modifications.

Methods

We present a comprehensive systematic review of techniques for step cut osteotomy in cubitus varus, analyzing 13 studies that meet our inclusion criteria. These studies encompass diverse patient populations, including pediatric and adult cases, and span different geographical regions.

Results

Our systematic review explores three primary osteotomy techniques-Classic Step-Cut Osteotomy, Reverse V Osteotomy, and Modified Step Cut Osteotomy-along with their modifications, providing surgeons with valuable options for individualized correction. Functional outcomes showcase improvements in range of motion, functional scores, and carrying angle, highlighting the technique's efficacy in restoring elbow function and enhancing quality of life. Radiological evaluations demonstrate successful corrections of various angles and achievement of bony union, reinforcing the stability and anatomical improvements achieved through step cut osteotomy.

Conclusions

Complication rates are notably low, with transient nerve palsies being the most commonly encountered, often resolving within months. Implant failure and other complications are infrequent, underlining the safety and reliability of step cut osteotomy as a surgical intervention for cubitus varus.While the predominance of retrospective studies and heterogeneity across included studies warrant caution, our systematic review provides a robust and diverse synthesis of evidence. It underscores the significance of step cut osteotomy in managing cubitus varus deformity, emphasizing its versatility, favourable outcomes, and safety profile. Further research with rigorous designs and longer follow-up periods will enhance our understanding of step cut osteotomy's role in cubitus varus correction.

Coronoid fractures and traumatic elbow instability

The coronoid process is key to concentric elbow alignment. Malalignment can contribute to post-traumatic osteoarthritis. The aim of treatment is to keep the joint aligned while the collateral ligaments and fractures heal. The injury pattern is apparent in the shape and size of the coronoid fracture fragments: (1) coronoid tip fractures associated with terrible triad (TT) injuries; (2) anteromedial facet fractures with posteromedial varus rotational type injuries; and (3) large coronoid base fractures with anterior (trans-) or posterior olecranon fracture dislocations. Each injury pattern is associated with specific ligamentous injuries and fracture characteristics useful in planning treatment. The tip fractures associated with TT injuries are repaired with suture fixation or screw fixation in addition to repair or replacement of the radial head fracture and reattachment of the lateral collateral ligament origin. Anteromedial facet fractures are usually repaired with a medial buttress plate. If the elbow is concentrically located on computed tomography and the patient can avoid varus stress for a month, TT and anteromedial facet injuries can be treated nonoperatively. Base fractures are associated with olecranon fractures and can usually be fixed with screws through the posterior plate or with an additional medial plate. If the surgery makes elbow subluxation or dislocation unlikely, and the fracture fixation is secure, elbow motion and stretching can commence within a week when the patient is comfortable.

Evaluation of Surgical Approaches to Management of Traumatic Posteromedial Elbow Instability Syndrome: A Systematic Literature Review Protocol

Posteromedial Instability Syndrome of the Elbow (PMIE) is a condition that arises from injuries to the stabilizing structures of the elbow joint, such as the coronoid process or ulnar lateral collateral ligament. Surgical treatment is commonly performed, but there is uncertainty regarding its results. This systematic review will synthesise the available evidence regarding the efficacy of surgical approaches to PMIE. Published and unpublished primary studies that regard outcomes of patients treated for PMIE, irrespective of approach, will be considered for inclusion. Iterative searches will be performed in the PubMed/MEDLINE, EMBASE, and Cochrane CENTRAL repositories from their inception to May 2023. Grey literature repositories will also be searched. The Cochrane risk of bias tool will be used to assess the quality of eligible interventional studies, while the MINORS tool will be employed for observational studies. If possible, a meta-analysis based on the random-effects model will be conducted. Heterogeneity will be assessed using Cochrane's Q and I2 statistics, and explored through subgroup analyses and sensitivity analyses. Relevant outcomes will include elbow joint functionality as assessed by validated scales, the proportion of patients returning to usual daily life activities, the development of recurrent joint instability in the postoperative period, quality of life and the development of postoperative arthritis. This protocol has been registered in the International Prospective Register of Systematic Reviews (PROSPERO) at the University of York. Its registration number is CRD42023451516.

Results of arthroscopically assisted reduction and fixation of anteromedial facet coronoid fractures at short-term follow-up

BACKGROUND

Varus posteromedial rotatory instability is a typical pattern of elbow injury that involves fracture of the anteromedial facet (AMF) of the coronoid, as well as injuries to the lateral ligament complex and the posterior bundle of the medial collateral ligament. Some authors support the idea that subtype II AMF coronoid fractures require fixation to restore elbow stability, but this topic is still an issue in the literature. The purpose of this study was to assess the clinical and radiologic outcomes of arthroscopically assisted reduction and internal fixation (ARIF) of AMF fractures.

METHODS

This retrospective single-center trial evaluated consecutive patients who underwent ARIF of isolated subtype II AMF coronoid fractures between 2014 and 2020. At the final follow-up, the patients were examined for elbow range of motion, stability, and pain. Injury and post-treatment radiographs were reviewed to assess fracture healing and heterotopic ossification.

RESULTS

A total of 32 patients (21 male and 11 female patients) with a median age of 47 ± 16 years were included. The average follow-up period was 28 ± 12.4 months. Coronoid process fractures were fixed by cannulated screws in 26 cases (81.25%); in 2 of these cases, additional Kirschner wires were used. Two Kirschner wires were used in 1 case (3.12%), and in the remaining 5 cases (15.62%), osteosuture was used. The lateral ulnar collateral ligament was injured in 27 cases (84.4%) and was always repaired. Other associated lesions were medial collateral ligament injury, osteochondral lesion, and radial head fracture. There were no surgical complications. At the final follow-up, the average Mayo Elbow Performance Score was 98.4 ± 2.7 and the mean Oxford Elbow Score was 47.3 ± 1.4. No cases of nonunion were detected on radiographic assessment.

CONCLUSIONS

Although technically demanding, ARIF has several potential advantages in comparison to open surgery: less scarring, a decreased risk of infection, and less postoperative pain.

[Clinical treatment of dorsal avulsion fracture of the capitellum combined with medial or posterior medial dislocation of the elbow joint]

OBJECTIVE

To analyze the possible injury mechanisms in patients with dorsal avulsion fracture of the capitellum combined with medial or posterior medial dislocation of the elbow joint, and to discuss their treatment and prognosis.

METHODS

Retrospective analysis was made on the clinical data of 4 patients with dorsal avulsion fracture of the capitellum combined with medial or posterior medial dislocation of the elbow joint admitted between September 2014 and September 2020, including 3 males and 1 female with an average age of 20.7 years (range, 13-32 years). There were 2 cases of dorsal avulsion fracture of the capitellum combined with medial dislocation of the elbow joint and 2 cases of dorsal avulsion fracture of the capitellum and anterior medial fracture of the coronoid process combined with posterior medial subluxation of the elbow joint. Closed reduction was performed in 3 patients with fresh fracture combined with dislocation, then 2 cases were fixed with tension band and 1 case was fixed with tension band combined with Acumed coronoid anatomic plate. And in patient with old fracture nonunion, the coronoid process was fixed with 1 screw, then the humeral sclerotic bone mass was removed, and finally the lateral collateral ligament was repaired and a hinged external fixator was added.

RESULTS

All the incisions healed by first intention without early complications such as infection or peripheral nerve injury. The 4 patients were followed up 13-30 months (mean, 20.8 months). The fractures all healed with a healing time of 70-90 days (mean, 79.5 days). At 6 months after operation, heterotopic ossification was seen in the posterior aspect of the right elbow joint in 1 case, and the alkaline phosphatase level was normal (67 U/L); the tension band was removed to clear the heterotopic ossification and the elbow joint was released. The rest of the patients had no heterotopic ossification. At last follow-up, all patients had good functional recovery of the elbow joint, with a Mayo score of 85-100 (mean, 92.5), and the excellent and good rate was 100%. The elbow flexion range of motion was 120°-135°, the extension range of motion was 10°-20°, and the pronation and supination range of motion were all 75°-85°.

CONCLUSION

Dorsal avulsion fractures of the capitellum combined with medial or posterior medial dislocation of the elbow may be due to simple varus stress. If an anteromedial coronoid facet fracture also occurs, it may be for the varus posteromedial rotatory instability, which is the opposite mechanism to that of an Osborne-Cotterill lesion. For fresh dorsal avulsion fractures of the capitellum, tension band fixation can be used with good results.

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.

Clinical comparison of the over-the-top and flexor carpi ulnaris split approaches for the treatment of anteromedial facet fracture of the coronoid process

BACKGROUND

The flexor carpi ulnaris (FCU)-split approach and the over-the-top approach have been used frequently for the fixation of anteromedial facet (AMF) fractures of the coronoid process. Clinical studies have not compared functional recovery and complication rates associated with these approaches. This study aimed to compare the clinical effectiveness of the over-the-top and FCU-split approaches for the treatment of AMF fractures of the coronoid process.

METHODS

Thirty-two patients who underwent surgery for AMF fractures between January 2013 and August 2019 were divided into the FCU-split and over-the-top groups. The FCU-split approach was used from January 2013 to March 2016, and the over-the-top approach was used from April 2016 to August 2019. Bony union, radiographic signs of osteoarthritis (Broberg and Morrey classification), and development of heterotopic ossification were evaluated. Postoperative pain score (visual analog scale at 2 days after the operation), surgical time (minutes), range of motion of the elbow, elbow function (Mayo Elbow Performance Score [MEPS]), and the presence of postoperative ulnar neuropathy were also compared between the 2 groups.

RESULTS

The FCU-split and over-the-top approaches were performed in 15 and 17 patients, respectively. The mean age was 46 ± 13 years (range, 22-67 years), and the mean follow-up duration was 19± 6.7 months (range, 13-38 months). All coronoid fractures had a solid osseous union during the follow-up, and no subluxation or dislocation was observed in the 2 groups. The occurrence of heterotopic ossification and the grade of post-traumatic arthritis did not differ significantly between the groups (all P > .05). There were also no significant differences between the groups in terms of postoperative pain score, range of motion, and MEPS (all P > .05). However, the surgical time was shorter for the over-the-top approach than that for the FCU-split approach (79± 23 vs. 101 ± 14, P = .008), and the surgical time was significantly associated with the fracture classification and surgical approach (P = .001 and .003, respectively). In addition, postoperative ulnar neuropathy occurred less with the over-the-top approach than with the FCU-spilt approach (5.9% vs. 46%, P = .013).

CONCLUSION

Both the FCU-split and over-the-top approaches were appropriate for performing the buttress plate fixation for AMF fractures of the coronoid process and for restoring the elbow stability. The fixation of AMF fractures through the over-the-top approach was technically easier and had less incidence of postoperative ulnar neuropathy.

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.

Elbow Instability: Evaluation and Treatment

Acute elbow dislocations are commonly seen in clinical practice, and attention to management principles and strategies can help facilitate improved outcomes. Patients may present with simple elbow dislocation, in which nonoperative treatment is highly successful. Alternatively, fracture dislocations can be sometimes easily managed but frequently are associated with the need for surgical intervention and operative and postoperative challenges.

Elbow Dislocation

This article is a brief overview of the elbow dislocations focusing on updates in treatment and rehabilitation protocols. The fight between obtaining elbow stability without leading to long-term elbow stiffness has been a continued focus in field of sports medicine. This article highlights advances made to help treat the injuries appropriately and obtain optimal patient outcomes.

Anteromedial fractures of the ulnar coronoid process: correlation between surgical outcomes and radiographic findings

BACKGROUND

This study aimed to report the radiographic findings and surgical outcomes of anteromedial facet (AMF) fracture of the ulnar coronoid process and to suggest an optimal approach.

METHODS

In this retrospective study, 20 consecutive patients with unilateral AMF fracture of coronoid process were surgically treated and divided into two groups without (group A) and with (group B) additional proximal ulnar fractures in equal case number. Time from injury to surgery averaged 4.38 ± 2.56 weeks. Mayo Elbow Performance Score (MEPS) and Shortened Disability of the Arm and Shoulder and Hand (quickDASH) score were used for functional evaluation. Cohen kappa coefficient (kappa) analysis was used to determine interobserver reliability on a radiographic reading.

RESULTS

All cases had a mean follow-up of 2.3 years. MEPS at 2 years averaged 87.75 ± 12.51; quickDASH, 7.05 ± 6.19. A significantly higher MEPS was found in subtype 3 than in subtype 2 (p = 0.036) and in group B than in group A (p = 0.020). Significantly lower quickDASH cores were found in group B than in group A (p = 0.011). Kappa analysis showed moderate agreement in the O'Driscoll classification (kappa = 0.56) and substantial agreement in categorization of the additional proximal ulnar fractures (kappa = 0.76).

CONCLUSIONS

Additional proximal ulnar lesions were considered an integral part of varus posteromedial rotatory instability and required further categorization in the management of AMF fractures. Significantly better functional outcomes were achieved when those lesions were fully addressed.

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.

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.

Articular Contact Area and Pressure in Posteromedial Rotatory Instability of the Elbow

BACKGROUND

Joint incongruity in posteromedial rotatory instability (PMRI) has been theorized to determine early articular degenerative changes. Our hypothesis was that the articular contact area and contact pressure differ significantly between an intact elbow and an elbow affected by PMRI.

METHODS

Seven cadaveric elbows were tested under gravity varus stress using a custom-made machine designed to simulate muscle loads and allow passive elbow flexion (0° to 90°). The mean contact area and contact pressure data were collected and processed using the Tekscan sensor and software. After testing the intact specimen (intact elbow), a PMRI injury was simulated (PMRI elbow) and the specimen was tested again.

RESULTS

The PMRI elbows were characterized by initial joint subluxation and significantly elevated articular contact pressure. Both worsened, corresponding with a reduction in contact area, as the elbow was flexed from 0° until the joint subluxation and incongruity spontaneously reduced (at a mean [and standard error] of 60° ± 5° of flexion), at which point the mean contact pressure decreased from 870 ± 50 kPa (pre-reduction) to 440 ± 40 kPa (post-reduction) (p < 0.001) and the mean contact area increased from 80 ± 8 mm to 150 ± 58 mm (p < 0.001). This reduction of the subluxation was also followed by a shift of the contact area from the coronoid fracture edge toward the lower portion of the coronoid. At the flexion angle at which the PMRI elbows reduced, both the contact area and the contact pressure of the intact elbows differed significantly from those of the PMRI elbows, both before and after the elbow reduction (p < 0.001).

CONCLUSIONS

The reduction in contact area and increased contact pressures due to joint subluxation and incongruity could explain the progressive arthritis seen in some elbows affected by PMRI.

CLINICAL RELEVANCE

This biomechanical study suggests that the early degenerative changes associated with PMRI reported in the literature could be subsequent to joint incongruity and an increase in contact pressure between the coronoid fracture surface and the trochlea.

Role of the lateral collateral ligament in posteromedial rotatory instability of the elbow

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.

Elbow Instability: Anatomy, Biomechanics, Diagnostic Maneuvers, and Testing

The elbow comprises a complex of bony and ligamentous stabilizers that provide both primary and secondary constraints to elbow instability. Through trauma and overuse, classic instability patterns arise by loss of these important stabilizers. The diagnosis of elbow instability can made using specific examination maneuvers and testing to diagnose the clinical pattern. This article reviews the elbow's unique anatomy and biomechanical characteristics and these are applied when reviewing the maneuvers and testing used to diagnose elbow instability.