Abstract
We have studied the effects of sustained local anaesthesia on postoperative mobilization of the injured hand. Small epidural catheters were placed adjacent to the peripheral nerves providing sensation to the involved part of the hand under direct vision in the distal forearm. Repeated doses of 0.5% bupivacaine were then administered during mobilization therapy to relieve pain. Fourteen out of 24 digits (60%) recorded 30° or more increases in active range of motion after bupivacaine injection. The cases that failed to improve had suffered severe injuries. Complications were few and were easily managed as the catheters were distal, superficial and accessible. This is an effective, specific and safe method of providing sustained postoperative analgesia for mobilization.
INTRODUCTION
The aim of treatment of complex hand injuries is to restore useful function. Severe crush injuries often result in tendon adhesions and joint contractures and secondary tenolyses and arthrolyses are often indicated to improve function. A motivated patient who is compliant with an aggressive rehabilitation programme is required in order to achieve a good outcome.
The hand must be mobilized in the early phases of rehabilitation in order to allow tendons to form a gliding interface with the surrounding tissues and restore useful movement. However, pain is often a major inhibitory factor to early active motion. Local anaesthetics can be used to relieve pain during rehabilitation by selectively blocking sensory nerves of the hand.
A prospective clinical study was performed to evaluate the effects of prolonged local anaesthesia in improving postoperative mobilization of the injured digits.
PATIENTS AND METHODS
Patients
This prospective clinical series involved 17 patients with 24 injured digits and was carried out between November 1999 and May 2001 in the National University Hospital, Singapore. The patients’ ages ranged from 17 to 45 years and there were 15 men and 2 women. Selection criteria included digits that required secondary procedures for stiffness, or acute injuries that were likely to result in stiffness (e.g. intraarticular fractures). The patient needed to be motivated and compliant with the therapy regime. Due to the diverse nature of injuries treated in this study, a customized injury score was devised to stratify the severity of injury for meaningful analysis (Table 1). The patient acted as his own control.
Surgical technique
Types of surgery included intraarticular bony fixation, release of scar contracture, tenolysis and joint arthrolysis. At the end of the surgical procedure, a 20 gauge epidural catheter was inserted through a small transverse incision at the wrist with direct visualization of the median or ulnar nerve. The tip of the catheter was placed adjacent to the peripheral nerve innervating the involved part of the hand and the proximal catheter was tunnelled and anchored to the skin proximally (Fig 1).
Rehabilitation protocol
Postoperatively every patient was treated by early mobilization and 2 ml of 0.5% bupivacaine was delivered via the catheter every 12 hours. Intermittent administration was chosen over continuous infusion as this allowed us to measure the total active range of motion of the digit just prior to, and 30 minutes after, the administration of bupivacaine. Hence, each patient acted as his own control. The patients were also asked to grade their pain before and after bupivacaine administration using a 0 to 10 visual analogue scale, with 10 indicating the most severe pain. They were assessed twice every week and their therapy was continued until their progress plateaued, or a minor complication such as a superficial infection or catheter leakage occurred. The duration of local anaesthetic infusion ranged from 4 days to 4 weeks (mean, 12 days) and the results are shown in Table 2.
The rehabilitation regime was similar to that used with other patients who were not treated with local anaesthetic.
RESULTS
Stratification by severity of injury allowed us to classify the digits into three broad groups (Table 3). Group I consisted of digits with a single tissue injury, namely intraarticular fractures and tendon adhesions. Group II included digits with two damaged structures, usually tendon adhesions after flexor or extensor tendon repair together with fractures or a nerve injury. Group III included digits that had suffered multiple tissue injuries and required complex surgical procedures such as tenolysis, arthrolysis or skin flaps.
Figure 2 shows the active range of motion of the involved digit on the first postoperative day before, and 30 minutes, after bupivacaine administration. A mean improvement in active range of motion of 37° (range, 6–106°) was documented. Group I patients registered an average increase of 50° in active range of motion after bupivacaine analgesia, group II cases an average improvement of 33° while group III cases only improved by a mean of 29°. Thus the degree of improvement decreased with the severity of the injury.
The catheters were removed when the difference between the active range of movement before and after bupivacaine anaesthesia was decreasing or when complications occurred. The mean improvement in motion on final assessment was 19° (range, 6–66°) (Fig 2). Group I cases improved by an average of 17°, group II cases by 26° and group III cases by an average of 13°. The effect of the bupivacaine anaesthesia decreased as the patient’s overall active range of motion improved. In most cases the improvement in range of motion was sustained.
Visual analogue scale pain scores
There was a median reduction of 2 points (range, 1–5 points) in the VAS pain score after the injection of bupivacaine. This showed that patients obtained significant pain relief with this method.
Complications
Most of the complications were local and minor, the most common being leakage of anaesthetic at the entry point of the catheter into the wrist after a few days of therapy. This was often the result of movement of the catheter during therapy causing local irritation. Two patients reported entry point infection, with localized inflammation, but this resolved soon after the catheter was removed. One patient reported transient intrinsic weakness, as illustrated by an ulnar claw (ulnar nerve block) while another had difficulty with thumb opposition during therapy (median nerve block). Two patients reported inadequate analgesia in the later days of therapy, possibly as a result of tachyphylaxis to the local anaesthetic. One patient had a flexor tendon rupture after tenolysis, possibly as a result of an over-aggressive rehabilitation programme and reduced protective pain sensation.
Case study
This illustrates the natural progression of mobilization for a patient with an injury to his left index finger which was crushed by a heavy beam. He sustained an open fracture of the proximal phalanx with division of both flexor tendons and the radial digital nerve, producing an injury score of 5 (severe category). Primary treatment included stable bone fixation and tendon and nerve repair. Four months after the injury, the total AROM of his index was 126° and he underwent a flexor tenolysis and digital nerve neurolysis. A catheter was inserted adjacent to the median nerve at the wrist at surgery. On the first postoperative day, his AROM was 124° before, and 168° 30 minutes after, bupivacaine instillation (44° difference). This gradually narrowed to 26° by Day 12. Figure 3 illustrates his progress.
DISCUSSION
Early mobilization after surgery improves the mobility of digits, helps to decrease swelling, allows the formation of a gliding surface on the tendon and improves tendon and joint nutrition. A rapid decrease in the gliding of rat flexor tendons occurs within hours of tendon injury (Lane et al., 1976) and postoperative haematoma and oedema restrict gliding of the tendon long before collagenous adhesions have formed. Strickland (1997) has noted that it is rare to see a substantial improvement in the range of motion beyond what was actively achieved during the first week after tenolysis, and thus every effort must be made to regain as much movement as possible during that time. It is our experience that postoperative pain following surgical procedures significantly limits active excursion of the digits, allowing the vicious cycle of oedema and contracture to develop.
Local anaesthetics can predictably and reversibly block the proximal conduction of pain impulses along nerve fibres and cause no damage to the nerve. Bupivacaine has been in clinical use for 30 years and is a member of the amide group. It offers the clinical advantages of cost effectiveness, long duration of action, a good safety profile and a sensory-motor differential block (Duthie et al., 1968; Rubin and Lawson, 1968; Watt et al., 1968a,b). In pharmacokinetic studies, bilateral bupivacaine intercostal blocks provide sensory and motor blocks for 10±3 hrs (Kopacz et al., 1994), thus minimizing the need for frequent administration. In dose–response tests with human volunteers undergoing ulnar nerve blocks using a similar drug (ropivacaine 0.5–0.75%), only small volumes of the drug (2 ml) were required to produce maximal effect (Nolte et al., 1990). This minimizes the risk of potential side-effects due to increased volume and local oedema after infiltration and decreases patient discomfort.
An in-vivo animal experiment on the effects of prolonged bupivacaine use on the rabbit sciatic nerve was performed by the senior author (Helm et al., 1987). The anaesthetic was delivered daily through an epidural catheter over a period of 10 days, and the nerves were then harvested for histological examination. Focal damage to the sciatic nerve was found in 13% of the bupivacaine group and 25% of the normal saline control group. This was probably due to mechanical trauma from the adjacent catheter rather than the anaesthetic agents. The logical extrapolation of this is that there is no lasting disruption of the peripheral nerve as any focal demyelination should recover without sequelae.
Several authors have inserted small percutaneous catheters near an injured digit inorder to instill long acting anaesthetics for pain relief (Foucher and Padjardi, 1997; Kirchhoff et al., 2000). However, there are no published series of the results of this method of pain relief. Compared to a conventional proximal brachial plexus block, our method achieved a specific distal blockade of the peripheral nerves supplying the injured digit, hence sparing the forearm muscles whose function is critical for active mobilization. Only one-third of the daily required amount of anaesthetic for brachial plexus blocks was needed with our method, hence ensuring a higher safety margin. The open technique of precise catheter placement which we used prevents the risks of intravascular injection and pneumothorax which can occur with brachial blocks. Our technique did not require the patient to be hospitalized, and did not require the services of an anaesthetist, thus limiting the resources utilized. Some patients in this series were on the regime for up to 4 weeks and only experienced minimal complications. Furthermore, it gave the patients a sense of control over their own therapy, as they were able to control their pain levels. We did not attempt to block the dorsal sensory supply of the hand during therapy as this innervation is complex and proximal blockade would be unpredictable.
It is apparent from our results that the severity of the initial injury is the most important determinant of eventual outcome. A clear inverse relationship was demonstrated between the injury score and the early and late active ranges of motion (Fig 2). Our customized injury score was devised to describe the severity of injury and has not been validated objectively. Nonetheless, it has allowed us to analyse our results more meaningfully, by allowing us to categorise the wide variety of surgical reconstructions in the series. These were often combined fracture fixations arthrolyses and tenolyses. We consider that our postoperative bupivacaine infusions allowed us to shorten the rehabilitation time of our patients and most of them were satisfied with the outcome, having achieved improved active digital motion.