Reducing Tourniquet Time In Carpal Tunnel Release

R Samuel Clinical Research Fellow
R Samarji Consultant Orthopaedic Surgeon
Dept of Orthopaedics, Manchester Royal Infirmary, Manchester, UK.

INTRODUCTION

Carpal tunnel syndrome is a common complaint seen in orthopaedic clinics. Surgical therapy involves release of the flexor retinaculum, a procedure well tolerated by patients under a local anaesthetic (1). The median nerve is at risk of iatrogenic damage during the procedure due to its close relation to the overlying ligament. So a bloodless field is preferable before any sharp dissection is performed near the nerve. To enable this it is common practice to perform the operation under tourniquet control. Use of the tourniquet often requires pressures on the arm of 250mmHg or more that can be very uncomfortable for the conscious patient. Our preferred technique for carpal tunnel release enables the procedure to be performed swiftly and safely thus minimising tourniquet time and patient discomfort.

PROCEDURE

Anaesthesia

Local anaesthesia is provided by injecting a solution consisting of 2% lignocaine into the region of the carpal tunnel. We have found that by using 2% lignocaine a total of 5ml of fluid is all that is required to provide adequate anaesthesia (Figure 1). This aids subsequent dissection and reduces the need for swabbing of the operative field. Injection of lignocaine is performed in the anaesthetic room and then the patient is immediately moved through into the operating theatre. As the patient is positioned and the operating team prepare for surgery sufficient time elapses for the solution to take effect.

Figure 1 5ml of 2% lignocaine is generally all that is required for complete analgesia

Preparation

The tourniquet is applied to the arm but not inflated immediately. Preparation with antiseptic wash involves the limb from the fingers to the elbow with appropriate draping exposing the forearm. The surgeon then checks that:
1. All surgical instruments to be used in the procedure are laid out and within easy reach
2. Suture for closure is already mounted on the needle holder
3. Dressings for the hand are already prepared (Figure 2).

Figure 2 All instruments and dressings should be laid out before commencing the procedure

4. The area for incision is fully anaesthetised
Only once all these criteria are met is the limb then elevated by the surgeon and exsanguinated. This is performed as a sterile procedure by wrapping the arm tightly in a sterile bandage (Figure 3). The tourniquet is then inflated to the required pressure and the bandage removed.

Figure 3 Exsanguination is performed by elevating the limb and tightly wrapping in a sterile bandage.

Incision and Release

A longitudinal incision extending from the distal wrist crease for approximately 5cm in line with the fourth ray ensures good access with little risk of damage to the palmar cutaneous branch of the median nerve. Dissection through the superficial tissues is aided by the use of two 'cats paws' retractors, one held by the assistant and the other by the surgeon. This provides a better field of view, we have found, than the use of self-retaining retractors. Need for haemostasis of any bleeding points should be minimal. Once the flexor retinaculum has been exposed, an initial incision is made large enough to pass a Macdonald's probe underneath the retinaculum but above the median nerve both proximally and distally (Figure 4). The probe protects the underlying nerve as complete division of the ligament ensures full decompression.

Figure 4 Cutting the retinaculum onto a Macdonald's probe protects the underlying median nerve.

Completing the Procedure

Skin edges are approximated using 4/0 non-absorbable sutures. A non-adherent dressing is applied to the wound before firmly wrapping the hand in a soft cottonwool bandage and then crepe bandage. Only after all dressings have been applied is the tourniquet deflated.

We have found that these simple techniques enable a straightforward carpal tunnel release to be performed by an experienced surgeon in approximately five minutes. If they are followed by junior staff, who often perform this procedure, we feel they will save substantial operating time thus minimising tourniquet time and discomfort to the patient.

References

1. Baguneid MS, Sochart DH, Dunlop D, Kenny NW Carpal tunnel decompression under local anaesthetic and tourniquet control. J Hand Surg (Br) 1997; 22(3): 322-4.