Flexor Pronator Slide Under Local Anesthesia without a Tourniquet for Non-Ischemic Contractures of the Forearm
Authors: Jerome J. Terrence Jose 
Published: February 2024

Background:
The flexor pronator slide is an effective treatment option for ischemic contracture and contracture related to spastic cerebral palsy, but little is known about the use of the flexor pronator slide in other non-ischemic contractures. I propose a flexor pronator slide to simultaneously correct wrist and finger flexor contractures and preserve the muscle resting length. To avoid overcorrection of the deformity, I propose the use of a wide-awake local anesthesia with no tourniquet (WALANT) procedure, in which the patient is able to continually assist the surgeon in assessing the contracture release and improvement in finger movement. Additionally, the WALANT flexor pronator slide releases the specific muscles responsible for wrist and finger contractures (i.e., the flexor digitorum profundus, flexor carpi ulnaris, flexor carpi radialis, flexor digitorum superficialis, and pronator teres), sparing the intact finger functions.

Description:
The patient in the video received a WALANT injection of 1% lidocaine with 1:100,000 epinephrine and 8.4% sodium bicarbonate in the operating room, and surgery was started 30 minutes after the injection to obtain the maximum hemostatic effect
1
. The injections were performed from proximal to distal along the volar-ulnar skin markings from the distal upper arm to the distal third of the forearm. The total volume utilized in this patient was <7 mg/kg (approximately 100 mL). A 25 or 27-gauge needle was infiltrated under the skin at the medial aspect of the elbow and in the distal and proximal forearm fascia. A total of 25 to 40 mL anesthetic was injected at each site, which serves to numb the ulnar nerve. over the volar-radial and volar side of the mid-forearm and distal forearm to numb the median nerve. For the WALANT procedure, an additional 8 mg of dexamethasone was added as an adjuvant to prolong the analgesia and the duration of the nerve block. The skin incision was made over the ulnar border of the forearm, extending proximally just posterior to the medial epicondyle up to the distal third of the upper arm. The origin of the flexor carpi ulnaris was elevated first, then the flexor digitorum profundus and flexor digitorum superficialis were mobilized from the ulna and the interosseous membrane. The release continued in an ulnar-to-radial direction. The patient was awake throughout the procedure, so that the improvement in the contracture could be better assessed. Further dissection around the ulnar nerve was done to release the arcade of Struthers, the Osborne ligament, and the triceps fascia in order to prevent ulnar nerve kinking during anterior transposition. The medial epicondyle was identified, and the flexor pronator wad was released meticulously without joint capsule perforation and medial collateral ligament injury. The muscles were finally examined for contracture in full wrist and finger extension, and further release was performed if remaining contracture was observed. All released muscles were tension-free, suspended on the trunks and branches of the median nerve, ulnar nerve, and radial and ulnar arteries. The ulnar nerve was transposed anteriorly to the medial epicondyle. The subcutaneous tissues were sutured with an absorbable suture, and the skin was closed with the same suture in a subcuticular fashion with a drain.

Alternatives:
Fractional or Z-lengthening of the flexor tendons is the alternative for finger and wrist flexion contractures.

Rationale:
This patient had previously undergone multiple flexor tendon surgeries in the hand and forearm. The patient developed tight ring, middle, and little finger contractures that could not be passively extended with the wrist in neutral or dorsiflexion. This patient could not extend the proximal or distal interphalangeal joints of the middle, ring, and little finger in wrist extension. Conversely, wrist flexion extended all fingers. When the surgeon tried to extend the fingers with the wrist in extension, excessive force was required and a jog in the movement was appreciated in all small joints. This denoted contractures of the long flexors and flexor tendons of the forearm. Fractional or Z-lengthening may release the flexion contracture in such cases, but leads to loss of active flexion, disrupts the muscle resting length, and causes loss of flexion strength. Because our patient had very tight finger contractures, they were deemed not amenable to fractional or Z-lengthening. Therefore, we preferred the use of a flexor pronator slide to simultaneously correct wrist and finger flexor contractures while preserving the muscle resting length. To avoid overcorrection of the deformity, we preferred to perform a WALANT procedure, during which the patient could continually assist the surgeon in assessing the contracture release and improvement in finger movement. This patient returned to her computer job after the surgery.

Expected Outcomes:
The flexor pronator slide is an effective treatment option for ischemic contracture and contracture related to spastic cerebral palsy. In 1923, Page described the flexor pronator slide as a surgical option for the late management of compartment syndrome
2,3
. He noted that the procedure allowed extensive correction of the flexion contracture with less impact on the muscle resting length compared with alternative procedures. Sharma and Swamy noted good hand function in 14 (74%) of 19 patients and an average grip strength of 75% of the contralateral hand following a flexor pronator slide for the treatment of moderate Volkmann contracture3. A flexor pronator slide will simultaneously correct wrist and finger flexor contractures and preserve muscle resting length. To avoid overcorrection of the deformity, the flexor pronator slide can be performed as a WALANT procedure, during which the patient is able to continually assist the surgeon in assessing the contracture release and improvement in finger movement. Additionally, a WALANT flexor pronator slide releases the specific muscles responsible for wrist and finger contractures, sparing intact muscles. Good functional outcomes are expected, with a full return to work by 3 months postoperatively. Major complications, such as overcorrection of the deformity, anterior interosseous neurovascular bundle injury, ulnar nerve injury, and wound dehiscence, are unexpected for this procedure.

Important Tips:

The treatment for a non-ischemic contracture of the wrist and fingers requires flexor pronator slide surgery to simultaneously correct the deformity without losing the resting muscle length and strength.Both fractional or Z-lengthening and flexor pronator slide surgery for such contractures yield straightforward contracture release. However, maximal preservation of the flexion power and muscle resting strength when releasing these contractures is possible only by shifting the flexor pronator muscles distally without affecting its resting length, which can be achieved by flexor pronator slide.A WALANT flexor pronator slide avoids overcorrection of the deformity because the patient is able to continually assist the surgeon in assessing the contracture release and improvement in finger movement.

Acronyms and Abbreviations:

FCU = flexor carpi ulnarisFCR = flexor carpi radialisWALANT = wide-awake local anesthesia with no tourniquetFPL = flexor pollicis longusDASH = Disabilities of the Arm, Shoulder and HandFDP = flexor digitorum profundusFDS = flexor digitorum superficialis