Coronoid Fracture

The coronoid process provides anterior buttress against posterior subluxation or displacement. The radial head prevents valgus instability, and the coronoid process prevents varus instability. The coronoid process also provides attachment for the anterior bundle of the MCL and attachment to the anterior capsule. The anterior capsule attaches 6mm distal to the tip of the coronoid process. The anterior bundle of the medial collateral ligament attaches to the sublime tubercle 18mm distal to the tip of the coronoid process. You need to know the difference between the insertion of the MCL and the insertion of the brachialis as seen here. If the fracture of the coronoid process tip is small, the brachialis should insert distal to the tip of the coronoid process. There are two types for the mechanism of injury: posterolateral rotatory displacement and varus and posteromedial rotatory displacement. Posterolateral rotatory displacement is a fracture of the radial head, fracture of the coronoid process tip, and dislocation of the elbow. Varus and posteromedial rotatory displacement are associated with fracture of the anteromedial coronoid process. The LCL tears from the humerus, and the MCL may not be ruptured. In posterior elbow dislocation and posterolateral instability, the lateral side fails first with the medial side failing last. This valgus and supination can result in the terrible triad. Patient with instability after elbow fracture dislocation always has a coronoid fracture, and it can redislocate in a cast or after surgery. Elbow dislocation with Type II coronoid process fracture and non-reconstructable comminuted radial head fracture. Treated by repair of the lateral collateral ligament, do radial head arthroplasty, and do ORIF of the coronoid process. This is an example of the terrible triad (dislocation of the elbow, coronoid fracture, and radial head fracture) and you need to fix all these injuries. Address each injury to restore elbow stability. If you have an elbow dislocation with fracture of the olecranon tip fracture and a radial head fracture, the likely pattern of instability is valgus posterolateral rotatory instability. There will be rupture of the LCL from the humerus and varus force will cause medial facet fracture, and this is the malignant fracture pattern. To recognize the posteromedial facet injury, look at the AP view x-ray in addition to the lateral view x-ray (in the lateral view you may miss it). In large medial coronoid fracture and elbow dislocation, there probably will be varus posteromedial rotatory instability, and it will affect the anteromedial facet of the coronoid. In fracture of the coronoid process, the x-ray is difficult to interpret. The fracture may be mistaken for a radial head fracture. The structures overlap, and we may miss the fracture. In the lateral view radiograph, you find a chip a bone. AP view radiograph will find a nondislocated elbow with an anteromedial coronoid process fracture. if you miss the anteromedial coronoid process fracture, you will get progressive narrowing of the joint space from lateral to medial between the medial trochlea and the coronoid process. This entity (anteromedial facet fracture) that gives posteromedial instability, occurs in conjunction with lateral collateral ligament injury. When you see this fracture, suspect anteromedial coronoid fracture, especially when you cannot find a radial head fracture. You may also find narrowing of the joint space between the medial trochlea and the coronoid process. CT scan is usually very helpful. There are two known classification systems: Regan & Morrey Classification and O’Driscoll Classification. Regan & Morrey Classification is based on viewing the lateral x-ray. In Regan & Morrey Classification, there are three fracture types based on viewing the lateral x-ray. Type I is a shear fracture of the tip of the coronoid process. Type II involves up to 50% of the coronoid process. Type III involves more than 50% of the coronoid process. This is a very simple classification system, but the problem is that it does not show the malignant fracture pattern. The O’Driscoll classification is very helpful, and it will show the anteromedial facet fracture that will create posteromedial instability. The O’Driscoll classification can be the tip, anteromedial facet, or basal. The O’Driscoll classification recognized the anteromedial facet fracture caused by varus posteromedial rotatory force. This fracture could be missed on the x-ray and can cause degenerative joint disease.

Scratch Collapse Test

The scratch collapse test is a provocative test for nerve entrapment or compression. This is becoming a popular test, and it is one of many examination techniques used in the diagnosis of nerve compression, entrapment, or injuries. The scratch test is a simple examination test that is similar in sensitivity to other examination tests in the diagnosis of cubital tunnel syndrome and other entrapment areas of the different nerves, such as radial tunnel syndrome, pronator teres syndrome, and other nerve entrapment areas. This test supplements, but does not replace, other information that we collect during obtaining the history and physical examination of the patient. It is really an added, helpful test that will precisely localize the site of nerve compression. Do this test if you need to. Not only can this test add or provide confirmation where entrapment of the nerve is located, but it can also precisely localize the area of the entrapment of the nerve that `is known to have different sites of entrapment, such as the ulnar nerve. If the patient has a nerve entrapment at a specific site, after the scratch, the patient will temporarily lose the ability to resist the internal rotation force to their arm. The arm will collapse in the direction of internal rotation. The mechanism is unknown, and it could be a reflex response. Because after you scratch or stroke the skin above the nerve, the arm seems to have no power, and it collapses as we test the resistance and internally rotate the arm. There might be bias from the examiner due to the subjective evaluation of the brief, temporary loss of resistance or loss of power after the scratch. To perform the test, have the patient standing or sitting with the arms at the sides and the elbows flexed to 90 degrees. Have the fingers and the wrist extended, then the examiner applies force against the patient’s forearm to internally rotate the arm and ask the patient to resist this force. The examiner and the patient will both assess the baseline resistance of the patient. The skin over the potential nerve entrapment area is scratched by the examiner, and then the examiner immediately repeats the test. The change in resistance is assessed. Positive scratch collapse test occurs when the patient has no resistance to the examiners force and the arm collapses in internal rotation. There should be no delays in retesting the patient because it may produce a false negative result. Adding ethyl chloride (the cold spray) will temporarily numb or anesthetize the skin superficial to the nerve of interest. It will freeze out a response to scratching. It also may show secondary areas of compression of the same nerve or different nerves. It also may show secondary areas of compression of the same nerve or different nerves. After you apply the cold freezing spray to the area of interest, the test is repeated. The cold spray should freeze out the response to scratching. If you suspect multiple sites of entrapment, use the freezing spray to numb the area then scratch it, and usually the patient will have strength return after scratching the area. The freezing spray can make the examiner eliminate sites or add sites of entrapment to the differential diagnosis. It could be helpful in identifying multiple areas of compression for the same nerve.

Subtalar Dislocation

When the subtalar dislocation happens, the talonavicular joint also becomes dislocated. There are two types of subtalar dislocations: medial subtalar dislocation and lateral subtalar dislocation. Medial dislocations are 4 times as common as lateral dislocations. Some of these dislocations can be open and urgent reduction is important to decrease skin necrosis and interruption of the circulation of the foot. After either closed or open reduction, the subtalar joint is usually stable. Lateral subtalar dislocation means that the foot goes lateral. As the foot goes lateral, the structure in the medial side becomes trapped. The posterior tibial tendon blocks successful closed reduction of the lateral subtalar dislocation. Lateral subtalar dislocation is a bad type. It is worse than the medial subtalar dislocation and is not as common. The foot goes lateral and as the foot goes lateral, the medial structures get pulled from also trying to go lateral. As you try to reduce the foot to its normal position, then there can be some entrapment, usually the posterior tibial tendon. This tendon will be interposed, and you will be unable to do closed reduction. This lateral subtalar dislocation will have a high incidence of fractures of the surrounding tarsal bones, and the subtalar joint could be unstable after reducing the dislocation. Lateral subtalar dislocations are more open than the medial subtalar dislocations. Open subtalar dislocations have a high incidence of infection. If the patient sustained an open injury to the foot with complete extrusion of the talus, the treatment should be to give the patient antibiotics and debride the wound, clean the talus using betadine solution or normal saline with antibiotics, and after the wound is debrided, implant the talus back into its bed. You may want tot use external fixator after that. The medial subtalar dislocation is different. Rarely the dislocation is irreducible (it usually reduces easily). Irreducible dislocation can be due to: impaction fracture of the head of the talus, interposition of the extensor digitorum brevis tendon (popular in exams), or interposition of the peroneal tendons. In medial subtalar dislocation, the foot appears supinated. In lateral dislocation, the foot appears pronated. The majority of both dislocations can be managed by closed reduction and immobilization, which the closed reduction should be done as soon as possible to decrease the risk of skin complications. Closed reduction is probably difficult in about 5-10% of medial dislocations and 15-20% of lateral dislocations. The dislocation can be reduced easily, and you will get an x-ray to evaluate and see if the dislocation is reduced or not, but you will probably also see it clinically. If you do not have a fracture or any fragments in the post-reduction x-rays, then the success rate with a splint or immobilization cast is very good. The medial dislocation has a better prognosis than the lateral dislocation. In the medial subtalar dislocation, the late instability is rare, and the duration of immobilization should be short (about 3-4 weeks). If you have a lateral subtalar dislocation, you may want to evaluate the foot by CT scan after closed reduction and splinting the patient. The reason that you get a CT scan, is to see if you have any bony fragments that need to be removed or fixed, and that can also be done for the medial subtalar dislocation if you think it is necessary. These bony fragments can cause the subtalar joint to be unstable. The lateral subtalar dislocations are a high energy injury. They are frequently associated with small osteochondral fractures. Larger fragments should be fixed, and a small fragment that is entrapped in the joint should be excised. If you think the joint is unstable after reduction, check for the presence of a large intra-articular fracture and try to reduce it and fix it. You want to start early range of motion, so immobilize the patient for a short period to avoid stiffness but try to avoid the recurrence of the dislocation or the instability. The subtalar dislocations can cause stiffness of the subtalar joint and degenerative arthritis. If you can’t do closed reduction then you need to do open reduction, and you need to know that the extensor digitorum brevis is usually the entrapped in medial subtalar dislocation, and the tibialis posterior is the one that is usually entrapped in the lateral subtalar dislocation.

Lisfranc Dislocation

Lisfranc injury is a tarsometatarsal fracture dislocation that involves the medial cuneiform and the base of the second metatarsal. The severity of the injury can range from a mild sprain to severe dislocation or fracture dislocation. The Lisfranc dislocation can be a purely ligamentous injury, boney injury, or a combination of both. The metatarsals are usually dislocated dorsally and laterally. The condition could be missed and may result in progressive foot deformity, disfunction, chronic pain, and arthritis. The oblique interosseous ligament (Lisfranc ligament) is the strongest ligament. The region is stable because the bony architecture is connected to strong ligaments, especially the Lisfranc ligament. Osseous stability is provided by the roman arch arrangement of the metatarsals, and the Lisfranc ligament stabilizes the 2nd metatarsal to maintain the midfoot arch. The Lisfranc ligament is between the medial cuneiform and the base of the 2nd metatarsal. The keystone configuration is formed by the base of the 2nd metatarsal that fits into the mortise, which is made by the medial cuneiform and the recessed middle cuneiform. The mechanism of injury results from axial loading on a plantar flexed foot. Diagnosis is done by a combination of clinical exam and x-rays. Clinical presentation could show midfoot pain, plantar ecchymosis, and tenderness on the dorsal aspect of the midfoot. When you see that clinical situation, you need to suspect Lisfranc injury even if the x-ray is negative. The fleck sign is a small avulsion fracture at the medial base of the second metatarsal. It represents an avulsion of the Lisfranc ligament. The diastasis between the 1st and 2nd metatarsal of more than 2 mm is considered to be a Lisfranc injury. The injury may be subtle and can be missed. You will need to get standing weight bearing x-rays if the injury is suspected (compare the x-ray to the other side). If you purely ligamentous injury, the treatment will be early fusion of the 1st and 2nd tarsometatarsal joints. Ligamentous injuries to the tarsometatarsal and intermetatarsal joints resulted in a worse outcome following open reduction and internal fixation than Lisfranc injuries that involve fractures. Ligamentous Lisfranc injuries will give a better result if they are treated by primary arthrodesis. If the Lisfranc injury is treated by open reduction internal fixation, it will result in a higher rate of secondary surgery and a lower function outcome. Anatomic reduction is important if the surgeon selects open reduction and internal fixation. If you do open reduction and internal fixation for a ligamentous injury, the patient may have persistent pain and arthritis. Closed reduction and percutaneous pinning do not give a good result. Post-traumatic arthritis and altered gait is common.