Pronator and AIN Release Info Evidence Consent
Reviewed by Dr Kieran Hirpara, Specialist Orthopaedic Surgeon Last reviewed
Why this operation has been suggested
Dr Kieran Hirpara, an upper-limb surgeon at Mater Private Hospital Rockhampton, starts with the least invasive options that suit your condition. Patients are generally referred to our clinic by their GP; if a physiotherapist has suggested you see us, you will still need a referral from your GP in order to be eligible for the Medicare rebate. A clinic assessment, including your history, an examination and imaging where needed, establishes the diagnosis.
This operation releases tight tissue that is pressing on a nerve in your forearm. It is offered when simpler care has not given enough improvement. We usually begin with rest, avoiding the activities that aggravate your symptoms, and anti-inflammatory medicine. For pronator syndrome, surgery is considered when symptoms have persisted for more than 6 months. For anterior interosseous nerve syndrome, it is considered after a minimum of 12 months with no signs of motor improvement. We will talk through the options with you and decide together. The aim of the operation is to relieve the pressure on the nerve, ease your pain and let you return to your previous activities.
Before the operation
In the weeks before surgery, we will confirm the plan with you and check any imaging such as an X-ray, MRI or ultrasound. You will need to stop eating and drinking for 7 hours before your operation. We ask for 7 hours rather than a shorter time so you can be brought forward if the theatre list runs early. Some medicines may need to be paused before surgery; we will tell you which ones and when. Bring a list of your current medications with you. Arrange for someone to drive you home afterwards. Wear loose, comfortable clothing on the day. If you have other medical conditions, you may need blood tests or a review with the anaesthetist.
On the day
You will arrive at the hospital's surgical admissions unit, where you are checked in and prepared for theatre. You will then meet the anaesthetist, the doctor who puts you to sleep for the operation and looks after you during it. This operation is done under general anaesthetic. A regional nerve block is sometimes added for post-operative pain relief; the anaesthetist will discuss this with you on the day. You are then taken into the operating theatre, where the operation is performed.
Afterwards you will wake up in the recovery area, where nurses watch over you while the anaesthetic wears off. Once you are stable, you will either go to a ward or go home, depending on the procedure and how your recovery is going.
What the operation involves
The operation is called a nerve release. The surgeon makes a cut on the palm side of your forearm, over the spot where the nerve is being squeezed. Through this cut, the surgeon frees the nerve from the tight bands of tissue pressing on it. There are a few common places where this happens, including a fibrous band near the elbow and a tendinous arch partway down the forearm. The surgeon checks each of these spots and releases any that are tight.
Where possible, the surgeon uses a small or keyhole approach. This uses one or more short cuts and a thin camera to see inside, so the tissue around the nerve is disturbed less. In some cases a wider cut is needed, for example when there is scar tissue to remove or swelling is expected. If a band of tissue over the front of the elbow (the lacertus fibrosus) is part of the problem, the surgeon releases that too.
Once the nerve is free, the surgeon closes the cut with stitches and covers it with a dressing. You will go home with the dressing in place, and we will tell you how to care for it over the following days.
After the operation
You will wake up in the recovery area, where nurses keep a close eye on you while the anaesthetic wears off. Your hand and forearm will have a dressing on the wound. We will give you medicine to keep you comfortable, and we will check that your pain is well controlled before you leave. You can move your fingers, hand and arm gently as soon as you feel able; early movement helps your recovery. Someone should stay with you for the first 24 hours after you get home. Your team will tell you whether you go home the same day or stay one night in hospital. We leave the dressing on for about 10 days; please do not take it off before then unless we tell you to. We change or remove it when we see you.
Recovery
In the first days after surgery, your forearm and hand may feel sore and swollen where the nerve was released. This is normal and settles gradually. Keeping your hand raised on a pillow when resting helps the swelling go down. The medicine we give you keeps you comfortable while the worst of the soreness passes.
You can move your fingers, hand and arm gently from the start, and early movement helps your recovery. Hand therapy after surgery is with Ruby Doolan at Extend Rehabilitation. Ruby will guide your exercises and make any splint you need. Doing these exercises as directed keeps the nerve gliding and stops stiffness setting in. Around the house, you can use your hand for light tasks as comfort allows, but avoid heavy lifting, gripping hard, or anything that strains the forearm until your therapist says it is safe.
Many people notice relief soon after the operation because the pressure on the nerve has been taken away. For some, feeling returns steadily over time as the nerve recovers. It is also possible for symptoms to partly come back weeks or months later, especially in people over 50 who may have some neck irritation affecting the nerve. This does not always mean the problem has returned.
Recovery varies from person to person. Your timeline may differ, and your surgeon and hand therapist will guide you along the way.
What can go wrong
Most patients do well, but problems can occasionally happen. Your surgeon and the team monitor you closely to spot any issue early.
The relief you feel soon after the operation may not last. Some symptoms can partly return weeks or months later. This is more likely if you are over 50 or have some neck irritation affecting the nerve. It does not always mean the problem has come back. Bring it up at your next review so we can work out what is going on.
You may notice a deep ache in the forearm that does not fully settle, or weakness in the thumb and index finger that makes pinching hard. Some people keep a small amount of weakness or find turning the palm down slightly harder than the other side, even a long time after surgery. If this worries you, mention it at your review appointment.
With anterior interosseous nerve syndrome, the nerve often recovers on its own over time, and surgery may not change that. This is why we avoid rushing into an operation for it. If you notice new weakness or loss of movement in the thumb and index finger after any other procedure, such as shoulder surgery, tell your surgeon or call the clinic so it can be assessed promptly.
If you have both pronator syndrome and carpal tunnel syndrome, we sometimes release both nerves in the one operation. This means one anaesthetic and one recovery instead of two. We will discuss this with you beforehand if it applies to you.
Most people find their pain eases after surgery, and this is often the main gain of the operation. If your pain does not improve, or if symptoms return and interfere with daily tasks, contact the clinic. We will assess you and talk through what can be done next.
The complications table on this page lists typical rates if you want the specifics.
When to call us
Call us if your pain gets worse instead of better, or if new numbness or weakness appears in your hand or forearm. Call us if you notice increasing redness, swelling or discharge from the wound, or if you develop a fever. Go to emergency if you have sudden severe pain, calf swelling or pain, shortness of breath, or if you cannot move your arm or hand at all. These signs need urgent assessment. If you are unsure, call the clinic and we will help you decide what to do.
Evidence & references
This is the clinical evidence summary written for health professionals. It is technical, and it lists the research this page was built from. You do not need to read it to understand your treatment or to make a decision about it.
Anatomy & Pathophysiology
Bony Anatomy
- The elbow is a trocho-ginglymoid joint consisting of medial and lateral articulations that provide bony stability [3].
- The trochlea articulates with the ulna within the greater sigmoid notch to create the ulnohumeral, hinged, or trochoid portion of the elbow joint [3].
- The ulnohumeral articulation has highly congruent anatomy through almost 180° of articular contact, with the exception of the bare area of the greater sigmoid notch which is devoid of cartilage [3].
- The coronoid has a medial and lateral facet which buttresses the trochlea anteriorly [3].
- The sublime tubercle is located just distal and medial to the coronoid and provides the attachment site for the anterior bundle of the medial ulnar collateral ligament [3].
- The medial epicondyle forms the attachment site for the origins of the flexor pronator mass and is larger and more posteriorly oriented than the lateral epicondyle [3].
- The capitellum and radial head form the radiocapitellar joint [3].
- The radius is held in close approximation to the ulna at the proximal radioulnar joint by the annular ligament [3].
- The area of the ulna which articulates with the margin of the radial head at the proximal radioulnar joint is known as the lesser sigmoid notch [3].
- The radial head is a concave elliptical structure covered with articular cartilage along the radiocapitellar joint and approximately 270° of the articular margin [3].
- The radial head articulates with both the capitellum and the lesser sigmoid notch [3].
- The lateral epicondyle is the origin of the lateral extensor musculature [3].
- The origin of the lateral ulnar collateral ligamentous complex is located just distal to the lateral epicondyle at the geometric center of the radiocapitellar articulation [3].
- The distal humeral articulation is angled 30° from the longitudinal axis [3].
- The anterior humeral line should pass through the center of the axis of rotation [3].
- The axis of rotation is 5° to 7° angulated in the coronal plane to the epicondylar axis, with the medial side more distal than the lateral side [3].
- The angulation of the distal humeral articulation accounts for the change in a valgus carrying angle to a more varus position as the elbow is flexed [3].
- There is a high correlation between the size of the radius and capitellum on the left and right sides in the same individual [3].
- The olecranon allows for a broad attachment site of the triceps [3].
- The ulna medially bends approximately 8° at 8 cm from the tip of the olecranon [3].
- There is a slight anterior bow to the proximal ulna [3].
- The articulation to the tip of the coronoid is approximately 30° from the long axis of the ulna in the sagittal plane [3].
Ligaments and Capsule
- The medial ulnar collateral ligaments are areas of capsular thickening which provide stability to the medial side of the elbow joint [3].
- The medial ulnar collateral ligament is the primary valgus stabilizer [4, 5].
- The anterior bundle of the medial ulnar collateral ligament is the most important component for stability [4, 5].
- The posterior bundle of the medial ulnar collateral ligament has the greatest change in length and becomes taut at flexion beyond 120 degrees [4, 5].
- The lateral ulnar collateral ligament is the posterolateral stabilizer [4, 5].
- Osborne’s ligament stabilizes the ulnar nerve in the cubital tunnel [4, 5].
- The ligament of Struthers is a variant anatomy arising from the supracondylar process to attach to the medial epicondyle and is a potential site of median nerve compression [4, 5].
- The elbow capsule allows maximum distension at approximately 70 to 80 degrees of flexion [4, 5].
- The anterior capsule attaches at a point approximately 6 mm distal to the tip of the coronoid [4, 5].
- The coronoid tip is an intraarticular structure that is visualized during elbow arthroscopy [4, 5].
- Tensile forces are present at the medial elbow and compressive forces are present at the lateral elbow [4, 5].
Muscles
- The brachialis is the strongest elbow flexor and attaches to the coronoid 11 mm distal to the tip [4, 5].
- The biceps brachii inserts at the ulnar margin of the radial tuberosity, with the long head inserting proximally and the short head distally [4, 5].
- The biceps brachii is a powerful supinator of the forearm [4, 5].
- The triceps is the primary elbow extensor and inserts on the olecranon process [4, 5].
- The mobile wad consists of the brachioradialis, extensor carpi radialis longus, and extensor carpi radialis brevis [4, 5].
- The flexor-pronator mass consists of the pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, and flexor digitorum superficialis [4, 5].
Biomechanics and Motion
- The normal elbow has a range of motion from 0° to 140° from extension to flexion [1].
- The normal elbow has a range of motion of 75° in pronation and 85° in supination [1].
- A functional arc for flexion and extension is 100° [1].
- A functional arc for forearm rotation is 100° [1].
- Elbow stability is determined by primary and secondary stabilizers [1].
- The three primary stabilizers of the elbow are the ulnohumeral articulation, the medial ulnar collateral ligament, and the lateral ulnar collateral ligament complex [1].
- The secondary stabilizers of the elbow are the radiocapitellar articulation, the common flexor tendon, the common extensor tendon, and the joint capsule [1].
Investigations
History and Physical Examination
- The physical examination of the elbow is directed by the history and the location of the patient's pain in the anterior, posterior, medial, or lateral aspect of the elbow [1].
- Active and passive flexion, extension, supination, and pronation should be evaluated using a goniometer for accurate measurement [9].
- The contralateral elbow should be examined for comparison during range of motion assessment [9].
- If the elbow has less than 90° to 100° of flexion, the posterior bundle of the medial collateral ligament is contracted and must be released to restore flexion [9].
- Pain assessment during the mid-arc or at the terminal ends of motion is required, with mid-arc pain being more common with intrinsic disease [9].
- The ulnar nerve is of utmost importance in the examination due to its anatomic proximity to the elbow [9].
- Electromyography and nerve conduction velocity studies should be performed if there is any question about neurologic dysfunction [9].
- An assessment for ulnar nerve subluxation should be performed, as subluxation is a relative contraindication for arthroscopic procedures due to the risk of iatrogenic nerve injury [9].
- The status of any prior ulnar nerve transposition should be verified if there is a history of previous surgical procedures [9].
- Patients with valgus extension overload syndrome report posteromedial elbow pain that occurs during the deceleration phase of throwing as the elbow reaches terminal extension [11].
- Crepitus and tenderness over the posteromedial olecranon may be noted in patients with valgus extension overload syndrome [11].
- Pain is reproduced when the elbow is forced into extension in patients with valgus extension overload syndrome [11].
- Elbow flexion contracture may be seen in patients with valgus extension overload syndrome [11].
- Patients with osteoarthritis of the elbow typically present with loss of terminal extension and flexion and painful catching, clicking, or locking of the elbow [13].
- Pain in osteoarthritis of the elbow is typically noted at the end ranges of motion and not through the midrange [13].
- Forearm rotation is relatively preserved until later in the disease process of osteoarthritis [13].
- Ulnar neuropathy is present in up to 50% of patients with osteoarthritis of the elbow [13].
Imaging
- Plain radiographs remain the hallmark and the best screening test for elbow evaluation [1].
- AP, lateral, and oblique radiographs are standard for elbow evaluation [9].
- Serial radiography is used as follow-up when heterotopic ossification is present [9].
- Primary bony landmarks identified on radiographs include the ulnohumeral joint, coronoid process, radial head, capitellum, radiocapitellar joint, olecranon tip, coronoid/olecranon fossae, and trochlear ridge [9].
- CT is helpful when assessing for malunion architecture and the location and pattern of osteophytes and/or loose bodies [9].
- Three-dimensional CT is used to check for heterotopic ossification [9].
- CT is not necessary when elbow stiffness is entirely soft-tissue related [9].
- CT is beneficial if any joint incongruity or abnormal bony anatomy is present [9].
- MRI can be used to evaluate ligaments and tendons, but it is rarely indicated for elbow stiffness [9].
- AP, lateral, oblique, and axillary views of the elbow may reveal posteromedial olecranon osteophytes and/or loose bodies in valgus extension overload syndrome [11].
- CT with two-dimensional reconstruction and three-dimensional surface rendering best visualizes the pathology of valgus extension overload syndrome [11].
- MRI may be most helpful in evaluating associated injuries including partial or complete tears of the medial collateral ligament in valgus extension overload syndrome [11].
- Radiographs typically show osteophyte formation at the coronoid process, coronoid fossa, radial fossa, radial head, olecranon tip, and olecranon fossa in osteoarthritis [13].
- Joint spaces at the ulnohumeral joint are usually preserved in osteoarthritis [13].
- Joint spaces at the radiocapitellar joint are mildly narrowed in osteoarthritis [13].
- Loose bodies may be evident on radiographs, which typically underestimate the number present in osteoarthritis [13].
- CT may be useful for surgical planning in osteoarthritis, allowing a detailed assessment of osteophytes and the presence of loose bodies [13].
- Radiographic evaluations are essential when diagnosing an osteochondritis dissecans lesion of the elbow [12].
- Important aspects of osteochondritis dissecans lesions may be better seen with MRI [12].
References
[1] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Anatomy, Biomechanics, Physical Examination, and Imaging of the Elbow > Summary and Conclusions.
[3] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Anatomy, Biomechanics, Physical Examination, and Imaging of the Elbow > Anatomy > Bony Anatomy.
[4] Miller S Review Of Orthopaedics. SECTION 16 PATELLAR TRACKING IN TOTAL KNEE ARTHROPLASTY > TABLE 2.3 Shoulder Spaces.
[5] Miller S Review Of Orthopaedics. Genetics of musculoskeletal conditions and abnormalities are summarized in Table 1.27 > TABLE 2.3 Shoulder Spaces.
[9] Aaos Comprehensive Orthopaedic Review 3. Elbow Stiffness* > IV. Evaluation.
[11] Aaos Comprehensive Orthopaedic Review 3. Elbow Injuries in the Athlete* > III. Valgus Extension Overload Syndrome and Posterior Impingement.
[12] Orthopaedic Knowledge Update. Osteochondritis Dissecans of the Knee and Elbow* > Summary.
[13] Aaos Comprehensive Orthopaedic Review 3. Arthritis and Arthroplasty of the Elbow > I. Osteoarthritis.
