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

The effect of wrist flexion/extension on radiocapitellar joint kinematics during valgus extension of the elbow

BACKGROUND

Osteochondritis dissecans (OCD) of the capitellum is prevalent among youth baseball pitchers. Repetitive shear forces during pitching are contributing factors. During the acceleration phase of pitching, the wrist joint moves from extension to flexion. The interplay between wrist position and elbow joint biomechanics has not been thoroughly examined, particularly within the radiocapitellar joint. This study aims to elucidate how different wrist positions affect the displacement of compression forces within the radiocapitellar joint during elbow extension and examine the change in contact pressure during simulated active wrist flexion and extension.

METHODS

Seven fresh frozen cadaveric upper limbs were mounted in a custom testing machine and tested under simulated throwing conditions. Radial head motion was tracked using an intra-articular thin-film pressure transducer mounted on the capitellum. The contact pressure and location of the center of force (COF) in the radiocapitellar joint were measured during 3 wrist positions by loading the wrist flexors and extensors: flexion, neutral, and extension.

RESULTS

Wrist flexion, compared to the neutral wrist position, displaced the COF significantly medially between 60° and 30° of elbow flexion (P < .05). Wrist extension slightly directed the COF laterally compared to the neutral wrist, but the differences were not significant. The total horizontal displacement between the COF during active wrist flexion and extension ranged from 1.6 mm to 1.8 mm. Mean contact pressure was significantly higher with the wrist in extension from 80° to 40° of elbow flexion and significantly lower with wrist flexion only at a 90° of elbow flexion (P < .05).

DISCUSSION

This study demonstrated that simulated active wrist flexion shifts the COF medially, potentially reducing the risk of lateral OCD lesions. In contrast, wrist extension increases contact pressure, explaining the higher susceptibility to loading in the lateral compartment. These findings highlight the importance of wrist dynamics in pitching mechanics and suggest that minimizing wrist extension during practice may prevent OCD development.

CONCLUSION

Wrist positions significantly influence the biomechanical behavior of the radiocapitellar joint during elbow extension. These insights are important for developing prevention and rehabilitation strategies for throwers at risk of OCD of the capitellum.

Anterolateral rotatory instability of the elbow: a possible etiology of primary osteoarthritis

BACKGROUND

The purpose of this study is to describe anterolateral rotatory instability (ALRI) as a possible etiology of primary osteoarthritis (OA) of the elbow.

METHODS

We examined 76 fresh frozen cadaveric elbows (male:female, 56:20; mean age, 81 years) for patterns of cartilage erosion that could be due to ALRI. These included erosions on the lateral trochlear ridge (LTR) lesion, crescent rim of the radial head (RC) lesion or the ventral capitellum (VC) lesion. The extent and location of the lesions were mapped by image processing of photographs of the humeral and radial articular surfaces, and the degeneration of the articular surface was graded.

RESULTS

Ten of 76 specimens (13%) had one or more lesions consistent with ALRI. LTR lesions were most common and were seen in 10 of 10 specimens (100%), typically involving the distal 30% of the LTR. RC lesions were seen in 9 of 10 and were located on anteromedial crescent of the radial head ranging from 6 to 10 o'clock. VC lesions were seen in 8 of 10 specimens directed anteroinferiorly about 60° to the long axis of the humerus.

CONCLUSIONS

ALRI is a possible mechanism initiating primary OA of the elbow. It has a characteristic pattern of triple lesions involving the LTR, the RC, and the VC. Level of evidence: IV.

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.

Digital smart internal fixation surgery for coronal process basal fracture with normal joint spaces or radius-shortening: Occult factor of radius-ulna load sharing

BACKGROUND

Reasonable postoperative humeroradial and humeroulnar joint spaces maybe an important indicator in biomechanical stability of smart internal fixation surgery for coronoid process basal fractures (CPBF). The aim of this study is to compare elbow articular stresses and elbow-forearm stability under smart internal fixations for the CPBF between normal elbow joint spaces and radius-shortening, and to determine the occult factor of radius-ulna load sharing.

METHODS

CT images of 70 volunteers with intact elbow joints were retrospectively collected for accurate three-dimensional reconstruction to measure the longitudinal and transverse joint spaces. Two groups of ten finite element (FE) models were established prospectively between normal joint space and radius-shortening with 2.0 mm, including intact elbow joint and forearm, elbow-forearm with CPBF trauma, anterior or posterior double screws-cancellous bone fixation, mini-plate-cancellous bone fixation. Three sets of physiological loads (compression, valgus, varus) were used for FE intelligent calculation, FE model verification, and biomechanical and motion analysis.

RESULTS

The stress distribution between coronoid process and radial head, compression displacements and valgus angles of elbow-forearm in the three smart fixation models of the normal joint spaces were close to those of corresponding intact elbow model, but were significantly different from those of preoperative CPBF models and fixed radius-shortening models. The maximum stresses of three smart fixation instrument models of normal joint spaces were significantly smaller than those of the corresponding fixed radius-shortening models.

CONCLUSIONS

On the basis of the existing trauma of the elbow-forearm system in clinical practice, which is a dominant factor affecting radius-ulna load sharing, the elbow joint longitudinal space has been found to be the occult factor affecting radius-ulna load sharing. The stability and load sharing of radius and ulna after three kinds of smart fixations of the CPBF is not only related to the anatomical and biomechanical stability principles of smart internal fixations, but also closely related to postoperative elbow joint longitudinal space.

A Feasibility Study on Using Hanging Arm Test to Assess Elbow Stability During Surgical Treatment for Varus Posteromedial Rotatory Instability

Objectives

The aim of this study to investigate the safety and effectiveness of performing the hanging arm test during surgical treatment for elbow varus posteromedial rotatory instability (VPMRI) to assess elbow stability and determine whether to repair the lateral ulnar collateral ligament (LUCL).

Methods

In a retrospective study from August 2014 to March 2019, 27 patients with VPMRI who had a negative result in the hanging arm test after fixation of coronoid fracture were selected. Intraoperative bleeding, operative time, elbow range of motion (ROM), and complications were recorded. Elbow function was evaluated with the Mayo elbow performance score (MEPS) and the disabilities of the arm, shoulder, and hand (DASH) score.

Results

The operation time was 85.9 ± 11.06 min (range 65-110). The intraoperative blood loss was 70.7 ± 9.31 ml (range 60-100). At the last follow-up, the elbow joint averaged 73.8° ± 2.931° in pronation, 78.9° ± 2.941° in supination, 7.2° ± 3.207° in extension, and 123.3° ± 6.651° in flexion. The MEPS score was 90.7 ± 4.36 (range 74-95), and the DASH score was 9.8 ± 2.58 (range 6.67-13.3). One patient presented with symptoms of ulnar nerve entrapment 2 months after operation and was treated with ulnar nerve release. The symptom of numbness went away completely 1 week after operation. No complications such as wound infection, arthritis, or chronic instability of the elbow were found in the other patients.

Conclusion

Our findings suggest that not all VPMRI patients need the LUCL to be repaired, and the hanging arm test is a safe and reliable method to assess whether to repair the LUCL in the treatment of elbow VPMRI.

Level of evidence

Level IV; Retrospective studies.

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.

Comparison of buttress plate and cannulated screw in the treatment of anteromedial coronoid fracture with elbow posteromedial rotatory instability

PURPOSE

The purpose of this study is to compare the effect of buttress plate and cannulated screw in the treatment of anteromedial coronoid fracture with posteromedial rotatory instability (PMRI).

METHODS

We retrospectively evaluated patients who were diagnosed with O'Driscoll type 2 fractures combined with elbow posteromedial rotatory instability and underwent surgery for anteromedial coronoid fracture between August 2014 and March 2019. They were divided into buttress plate (n=16) and cannulated screw (n=11) groups. The elbow range of motion, visual analog scale (VAS), Mayo elbow performance score (MEPS), and disabilities of the arm, shoulder, and hand score (DASH) were used for clinical outcome assessment.

RESULT

There were no significant differences in clinical outcomes. However, the surgical time was significantly shorter in cannulated screw group (85.45±4.156) compared to the buttress plate group (93.81±8.863, P=0.008), and the surgical time was associated with internal fixation (P=0.008).

CONCLUSION

Although there was selection of cases in that small fragments were treated with buttress plate and large fragments with cannulated screw, the buttress plate and cannulated screw have comparable functional outcomes on fixation of the anteromedial coronoid fracture with elbow PMRI. The fixation of the anteromedial coronoid fracture with large fragments using the cannulated screw has a shorter operation time.

Anteromedial coronoid facet fractures and associated ligament lesions: A case series

INTRODUCTION

Varus posteromedial rotational injury mechanisms lead to fractures of the coronoids process' anteromedial facet. As these fractures are often unstable, rapid fracture treatment is vital to prevent progressive osteoarthritis.

MATERIALS AND METHODS

Twelve patients with a fracture of the anteromedial facet treated surgically were enrolled in the study. Computed tomography images were used to classify the fractures according to the system by O'Driscoll et al. Clinical follow-up included each patient's medical record, surgical treatment algorithm, all complications encountered during the follow-up period, Disabilities of the arm, shoulder, and hand score, subjective elbow value, and pain.

RESULTS

A total of 8 men (66.7%) and 4 women (33.3%) were treated surgically and followed-up after a mean period of 45 ± 23 months. The mean DASH score was 11.9 ± 12.9 points. One patient complained of transient neuropathy in the innervation area of the ulnar nerve, however, this existed already pre-operatively and resolved after less than three months.

CONCLUSIONS

The presented patient cohort shows that AMF fracture of the coronoid process are unstable lesions according to the bony instability and the frequently ruptured collateral ligament complexes which need to be addressed. The MCL seems to be affected more frequently than previously appreciated.

LEVEL OF EVIDENCE

Level IV; Case Series; Treatment Study.

Biomechanical impact of elbow motion in elbow stiffness

BACKGROUND

A mechanical block in the elbow due to osteophytes in the olecranon fossa is a common clinical symptom for elbow stiffness.

PURPOSE/HYPOTHESIS

This study aims to understand the biomechanical characteristics or changes in the stiff elbow in the resting (or neutral) and swing position of the arm using a cadaveric model. The hypotheses included the following: (1) a difference exists in the articular contact pressure of the elbow by comparing the non-stiff and stiff models in in vivo studies; (2) the degree of stiffness would affect the increase of the joint loading of the elbow.

STUDY DESIGN

Controlled laboratory study, cadaveric study.

METHODS

Eight fresh-frozen specimens from individuals of both sexes were included in the biomechanical study. The specimen was mounted on a custom-designed jig system with gravity-assisted muscle contracture to mimic the elbow in a standing position. The elbow was tested in two conditions (the resting and passive swing). Contact pressure was recorded for three seconds in the resting position, which was the neutral position of the humerus. By dropping the forearm from 90° of the elbow flexion, the passive swing was performed. The specimens were tested sequentially in three stages of stiffness (stage 0, no stiffness; stage 1, 30° of extension limitation; and stage 2, 60° of extension limitation). After data collection was completed in stage 0, a stiff model was sequentially created for each stage. The stiff model of the elbow was created by blocking the olecranon by inserting a 2.0 K-wire into the olecranon fossa horizontally with the intercondylar axis.

RESULTS

The mean contact pressures were 279 ± 23, 302 ± 6, and 349 ± 23 kPa in stages 0, 1, and 2, respectively. The increases in the mean contact pressure in stages 2 versus 0 were significant (P < 0.0001). The mean contact pressures were 297 ± 19, 310 ± 14, and 326 ± 13 kPa in stages 0, 1, and 2, respectively. The peak contact pressures were 420 ± 54, 448 ± 84, and 500 ± 67 kPa in stages 0, 1, and 2, respectively. The increases in mean contact pressure in stage 2 versus 0 were significant (P = 0.039). The increases in peak contact pressure in stages 0 versus 2 were significant (P = 0.007).

CONCLUSIONS

The elbow bears the load created by gravity and muscle contracture in the resting and swing motion. Moreover, extension limitation of stiff elbow increases the load bearing in the resting position and swing motion. Careful surgical management should be considered for meticulous clearance of bony spur around olecranon fossa to resolve the extension limitation of the elbow.

The role of the lateral part of the distal triceps and the anconeus in varus stability of the elbow: a biomechanical study

BACKGROUND

The role of the lateral part of the distal triceps as a stabilizer in the lateral collateral ligament-deficient elbow and whether its effect in improving the stability is independent of that of the anconeus are unclear.

METHODS

Seven cadaveric elbows were tested under gravity varus stress using a custom-made machine designed to simulate muscle loads while allowing passive flexion of the elbow. An injury model was created by sectioning the lateral collateral ligament and sparing the common extensor origin. The lateral part of the distal triceps tendon was loaded sequentially with 0 N, 10 N, 25 N, and 40 N. Each stage of the lateral part of the distal triceps loading was tested with the anconeus unloaded (inactive) or with a 25-N load applied (active). Articular contact pressures on the coronoid, the medial facet, and the lateral facet were collected and processed using Tekscan sensors and software.

RESULTS

A significant decrease in the mean coronoid contact pressure was seen with sequential loading of the lateral part of the distal triceps (P < .001). The ratio of medial to lateral facet contact pressures significantly decreased with sequential loading of the lateral part of the distal triceps (P < .001), indicating a better distribution of the contact pressure between the medial and lateral facets as the lateral part of the distal triceps was loaded. These effects were statistically significant, both with and without anconeus loading. There was no significant modification of the effect of the lateral part of the distal triceps loading on the contact pressure by the anconeus loading (P = .47). However, with active anconeus loading, the contact pressure and the ratio of medial to lateral facet contact pressures were significantly lower for any stage of lateral triceps loading (P < .001), indicating a synergistic effect of the anconeus.

CONCLUSIONS

In a lateral collateral ligament-deficient elbow, the lateral part of the distal triceps loading prevents the increased contact pressure on the coronoid under varus stress and improves the distribution of contact pressures on the coronoid. Anconeus loading further decreases and improves the distribution of the contact pressures; however, its effect is independent of that of the lateral part of the distal triceps. These results substantiate a role of the lateral part of the distal triceps as a dynamic constraint against elbow varus and have clinical implications for prevention and rehabilitation of elbow instability.

The role of the lateral collateral ligament-capsule complex of the elbow under gravity varus

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.

Effect of Radiocapitellar Joint Over/Under Stuffing on Elbow Joint Contact Pressure

PURPOSE

Comminuted radial head fractures are commonly treated by surgical resection or replacement with a prosthesis. A potential problem with radial head replacement is overlengthening of the radial neck ("overstuffing" of the radial head), which has been shown to affect both ulnohumeral kinematics and radiocapitellar pressures. We hypothesized that an overstuffed radial head prosthesis increases capitellar pressure and reduces coronoid pressure.

METHODS

Seven human cadaveric elbows were prepared on a custom-designed apparatus simulating stabilizing muscle loads, and passively flexed from 0° to 90° under gravity valgus torque while joint contact pressures were measured. Each elbow was tested sequentially with different neck lengths, starting with the intact specimen followed by insertion of understuffed (-2 mm), standard-height (0 mm), and overstuffed (+2 mm) radial head prostheses in neutral forearm rotation, 40° pronation, and 40° supination positions, respectively.

RESULTS

Capitellar mean contact pressures significantly increased after insertion of an overstuffed radial head prosthesis. In valgus position with neutral forearm rotation, capitellar mean contact pressure on the joint with an intact radial head averaged 227 ± 70 kPa. Insertion of understuffed, standard-height, and overstuffed radial head prostheses changed the mean contact pressures to 152 ± 76 kPa, 212 ± 68 kPa, and 491 ± 168 kPa, respectively. The overstuffed radial head group had significantly lower whole coronoid mean contact pressures (153 ± 56 kPa) compared with the intact (390 ± 138 kPa) and standard-height (376 ± 191 kPa) radial head groups.

CONCLUSIONS

An increase in radial prosthesis height significantly increases capitellar contact pressures and reduces coronoid contact pressures.

CLINICAL RELEVANCE

Restoration of the anatomic radial head height is critical when performing radial head arthroplasty to maintain normal joint biomechanics. Elevated capitellar contact pressures can potentially lead to pain and early degenerative changes.

Coronal Shear Fractures of the Distal Humerus

Coronal shear fractures of the distal humerus are rare, frequently comminuted, and are without consensus for treatment. The aim of this paper is to review the current concepts on the diagnosis, classification, treatment options, surgical approaches, and complications of capitellar and trochlear fractures. Computed Tomography (CT) scans, along with the Dubberley classification, are extremely helpful in the decision-making process. Most of the fractures necessitate open reduction and internal fixation, although elbow arthroplasty is an option for comminuted fractures in the elderly low-demand patient. Stiffness is the most common complication after fixation, although reoperation is infrequent.

[Coronoid reconstruction with autologous iliac crest bone graft in chronic elbow instability through a medial approach]

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.

Reconstruction of the coronoid process with the olecranon tip for chronic elbow dislocation in children: A rare case report and literature review

The coronoid process of the ulna, as a key part of the elbow joint, plays an important role in maintaining elbow joint stability. Reconstruction of the coronoid process is necessary in both acute and chronic coronoid defects to restore elbow stability and avoid early joint degeneration. The olecranon tip may be a useful autologous osteochondral graft for reconstructing the same shape of the ulna coronoid process. The purpose of this report was to verify if reconstruction of the coronoid process with the olecranon tip can restore elbow stability and kinematics. Here, we report a 13-year-old boy who had undergone Kirschner-wire fixation for a left supracondylar fracture of the left humerus 9 years previously. After that, the right elbow dislocation and varus deformity gradually appeared. Imaging revealed posterolateral dislocation of the left elbow due to the absence of the coronoid process of the ulna. We reconstructed the ulnar coronoid process by intercepting the ipsilateral olecranon tip. After 22 months of follow-up, the range of motion of the left elbow joint was normal, and the cubitus varus deformity disappeared. The results of this report suggest that olecranon tip autografts are suitable to replace transverse coronoid defects. Given the patient's satisfactory clinical results, this reconstruction technique is safe and effective for the treatment of chronic elbow instability due to coronoid process defects of the ulna.

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.

Effect of incremental increase in radial neck height on coronoid and capitellar contact pressures

BACKGROUND

Over-lengthening of the radial neck has been shown to affect ulnohumeral kinematics and has been proposed to affect radiocapitellar pressures. We hypothesized that an incremental increase in radial neck height increases the capitellar contact pressure and reduces the coronoid contact pressure. Knowledge of the effects of over-lengthening is clinically important in preventing pain and degenerative changes due to overstuffing.

METHODS

Six human cadaveric elbows were prepared on a custom-designed apparatus simulating muscle loads and passive flexion from 0° to 90° under gravity valgus torque while measuring joint contact pressures in this biomechanical study. Each elbow was tested sequentially starting with the intact specimen followed by insertion of a radial head prosthesis with 0, +2, and +4 mm of radial neck height, respectively.

RESULTS

Capitellar mean contact pressures significantly increased after insertion of +2 and +4 mm radial head prostheses (p < 0.03). The capitellar mean contact pressure with a 0 mm radial head prosthesis was 97 KPa. Insertion of +2 mm and +4 mm radial heads increased mean contact pressures to 391 KPa (p = 0.001) and 619 KPa (p = 0.001), respectively, with 90° of elbow flexion.

DISCUSSION

Increasing radial prosthesis height by 2 mm significantly increases capitellar contact pressures and reduces coronoid contact pressures.

Morphological characteristics of fractures of the anteromedial facet of the coronoid in posteromedial rotatory instability of the elbow: a three-dimensional CT remodeling study

BACKGROUND

Fractures of the anteromedial facet of the coronoid in posteromedial rotatory instability of the elbow are classified into 3 subtypes based on their location. The purpose of this study was to analyze the fracture morphology of anteromedial facet fractures in their 3 subtypes (anteromedial rim, anteromedial rim + tip, and anteromedial rim + sublime tubercle [±tip]).

METHODS

Three-dimensional computed tomography remodeling was used to evaluate anteromedial facet fractures in a consecutive series of 40 patients, all of whom were affected by posteromedial rotatory instability of the elbow. Characteristics of the fractures, including the number of fragments, size of fragments, plane of the fracture line, and involvement of the sublime tubercle and radial notch, were measured for each subtype of the anteromedial facet fractures.

RESULTS

Each subtype had a typical fracture pattern and distinct size. The fracture subtype 1 showed a single-fragment fracture, subtype 2 showed either a single- or dual-fragment fracture, and subtype 3 showed either a dual- or triple-fragment fracture. The angle between the fracture line and the coronal plane was greatest in subtype 3 fractures. The surface area of the fragment was largest in subtype 3 fractures. The percentages of articular involvement of the sublime tubercle were 0% in subtype 1, 47% in subtype 2, and 79% in subtype 3. The percentages of articular involvement of the radial notch were 0% in subtype 1, 7% in subtype 2, and 8% in subtype 3.

CONCLUSION

Analysis with quantitative 3-dimensional computed tomography showed the characteristic morphology of each subtype of anteromedial facet fracture. Subtype 1 comprised 1 fragment with the smallest fragment size. Subtype 2 was a single- or dual-fragment fracture, the size of which should be considered in the treatment plan. Subtype 3 was a large fragment comprising the sublime tubercle. Our findings are significant because they highlight unique fracture morphology that may help surgeons to distinguish one fracture subtype from another in clinical practice.

Coronoid process reconstruction with a distal clavicle autograft: an in silico analysis of fitting accuracy

BACKGROUND

The coronoid process plays a vital role in preserving elbow stability. In cases of acute or chronic deficiency of the coronoid process, reconstruction is warranted to restore stability and to avoid early joint degeneration. The distal clavicle might be a useful osteochondral autograft for coronoid reconstruction with low donor-site morbidity. This study evaluated the fitting accuracy of the distal clavicle as an autograft for coronoid process reconstruction.

METHODS

One hundred upper-extremity computed tomography scans of 85 body donors were available for this study (mean age, 69 ± 17 years; 46 male and 39 female donors; 15 bilateral specimens). Standardized 40% transverse defects of the coronoid process were digitally created; the distal clavicles were digitally harvested and placed onto the defects by a best-fit technique in 2 different orientations using commercially available software: (1) with the superior aspect of the articular surface of the graft oriented toward the coronoid tip and (2) with the inferior aspect of the articular surface of the graft oriented toward the coronoid tip. The fitting accuracy of the grafts to the native coronoid process was evaluated from lateral to medial using custom code.

RESULTS

Regardless of the orientation of the graft, the distal clavicle provided a good fit in the central portion of the coronoid process. In the lateral and medial aspects of the defect, however, the fitting accuracy of the graft declined significantly (P ≤ .044). No significant differences were observed between ipsilateral and contralateral grafts (P ≥ .199). The intrarater reliability was excellent.

CONCLUSION

The results of this study suggest that a distal clavicle autograft may be suitable to replace a transverse defect of the coronoid process; however, it may not fully reconstruct the anteromedial and anterolateral aspects of the coronoid.

The Effect of Ulnar Collateral Ligament Repair With Internal Brace Augmentation on Articular Contact Mechanics: A Cadaveric Study

Background:

There has been renewed interest in ulnar collateral ligament (UCL) repair in throwing athletes because of a greater understanding of UCL injuries, improvement in ligament repair technology, and potentially expedited rehabilitation time and return to play relative to UCL reconstruction.

Purpose:

To evaluate elbow articular contact and overall joint torque after UCL reconstruction and repair augmented with a collagen-coated fiber tape, InternalBrace.

Study Design:

Controlled laboratory study.

Methods:

Ten matched pairs of cadaveric arms (mean age, 41 ± 11 years) were dissected to expose the UCL. Each specimen was secured into a custom test fixture at 90°, and 1 specimen from each pair underwent either a modified Jobe UCL reconstruction or UCL repair with InternalBrace. Each specimen underwent 10 cycles of elbow valgus angular displacement between 0° and 5° at a rate of 1 deg/s in the intact state, after UCL avulsion, and then after UCL reconstruction or repair. Articular contact mechanics and overall joint torque and stiffness were recorded.

Results:

Contact mechanics of reconstructed and repaired specimens were not significantly different. Both reconstruction and repair procedures returned the overall resistance of the joint to valgus torsion to near-intact levels. UCL repair tended to restore joint torque more closely to the intact state than did reconstruction, given that reconstruction showed a nonsignificant trend toward lower torque than the intact state (P = .07).

Conclusion:

Neither UCL reconstruction nor UCL repair with InternalBrace overconstrained the elbow joint, as both groups had similar contact pressures compared with the native joint. Both procedures also restored elbow joint torque and stiffness to levels not statistically different from the intact state.

Clinical Relevance:

Given the sound biomechanical properties of UCL repair with InternalBrace, it may have a significant role as treatment for UCL injuries.

Use of 3D-Printed Heel Support Insoles Based on Arch Lift Improves Foot Pressure Distribution in Healthy People

Background

3D-printed insoles are widely used. This study was conducted to test a customized three-dimensional (3D)-printed heel support insole based on arch lift and to investigate whether the pressure distribution on the sole was improved while maintaining foot function.

Material/Methods

The design was based on a 3D plantar contour scanning modeling technique. Thirty healthy male participants walked along a 10-m track under 3 self-controlled interventions. A customized 3D-printed heel support insole based on arch lift was inserted into the socks for the experimental condition A. For condition B, a customized 3D-printed heel-supporting insole was inserted into the socks, and a standardized pre-made heel-supporting insole was inserted into the socks as a control (condition C). We used the Footscan^® pressure plate to measure the plantar parameters in the forefoot contact and foot flange phases in each condition.

Results

Compared with condition B and the control condition, the peak pressure under the heel was significantly lower in condition A (P<0.05), and the peak pressure in the midfoot region was not significantly increased (P>0.05).

Conclusions

The biomechanical properties of the customized 3D-printed heel support are better than those of the traditional heel support insole, especially when there is a need for an additional increase in heel height. Patients do not decrease midfoot motion function while using this customized insole.

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.

The role of the posterior bundle of the medial collateral ligament in posteromedial rotatory instability of the elbow

Aims

The aim of this study was to evaluate two hypotheses. First, that disruption of posterior bundle of the medial collateral ligament (PMCL) has to occur for the elbow to subluxate in cases of posteromedial rotatory instability (PMRI) and second, that ulnohumeral contact pressures increase after disruption of the PMCL.

Materials and Methods

Six human cadaveric elbows were prepared on a custom-designed apparatus which allowed muscle loading and passive elbow motion under gravitational varus. Joint contact pressures were measured sequentially in the intact elbow (INTACT), followed by an anteromedial subtype two coronoid fracture (COR), a lateral collateral ligament (LCL) tear (COR + LCL), and a PMCL tear (COR + LCL + PMCL).

Results

There was no subluxation or joint incongruity in the INTACT, COR, and COR + LCL specimens. All specimens in the COR + LCL + PMCL group subluxated under gravity-varus loads. The mean articular contact pressure of the COR + LCL group was significantly higher than those in the INTACT and the COR groups. The mean articular contact pressure of the COR + LCL + PMCL group was significantly higher than that of the INTACT group, but not higher than that of the COR + LCL group.

Conclusion

In the presence of an anteromedial fracture and disruption of the LCL, the posterior bundle of the MCL has to be disrupted for gross subluxation of the elbow to occur. However, elevated joint contact pressures are seen after an anteromedial fracture and LCL disruption even in the absence of such subluxation. Cite this article: Bone Joint J 2018;100-B:1060–5.

Quantitative measurements of facets on the ulnar coronoid process from reformatted CT images

Background

To quantify the size and angle of the medial and lateral facets of the ulnar coronoid process by reformatted computed tomography (CT) imaging.

Methods

Elbow CT images were retrospectively selected from the picture archiving and communication system in our hospital over a 5-year period (January 2011 to December 2015). The widths, heights, gradient and tilt angles of both the medial and lateral facet of the ulnar coronoid process were measured using two-dimensional (2D) reformations of CT images.

Results

Our database research yielded 120 elbow joints (53 right, 67 left) of 120 patients (54 males, 66 females) which fulfilled our criteria. The average width of the two facets of the ulnar coronoid process were 13.34±1.85 mm for the medial facet and 8.39±1.29 mm for the lateral facet. The average height of the medial facet was 18.45±3.38 mm and the lateral facet was 17.55±3.81 mm. The average tilt angles of medial and lateral facet were 80.34°±7.71° and 98.78°±5.71° respectively. The average gradient angles of the medial and lateral facet ridge were 60.02°±8.78° and 36.97°±4.99° respectively. The length of the lateral facet ridge was longer than the medial facet ridge.

Conclusions

Reformatted CT images allow for multiple, accurate measurements of facets on the ulnar coronoid process. These measurements can be applied to guiding appropriate surgical interventions for fractures in this area.