The Endoscopic Treatment of Carpal Tunnel Syndrome as an Outpatient Procedure

From September 1995 to July 1996 50 patients were treated for carpal tunnel syndrome as outpatients by endoscopic release in the rooms of an orthopaedic surgeon (two-portal-technique). The average age was 51.3 years (27–61 years). The average length of symptoms was 43 months, the postoperative time off work averaged 27 days. Six months postoperatively wasting of the thenar persisted in 2 out of 16 patients, a positive Tinel's sign in 1 out of 46 patients and delayed median nerve conduction in 2 out of 48 presenting these symptoms preoperatively. At 6 months the average handgrip strength had recovered to 109% of the preoperative value. One out of 49 patients still presented paresthesia and 1 out of 50 nocturnal dysesthesia. There were minor complications in 7 patients (14%), only one patient requires further treatment. We conclude that endoscopic carpal tunnel release done on outpatients in a private surgery can be reliable, safe and cost efficient.


INTRODUCTION
The carpal tunnel syndrome (CTS) is the most common nerve compression syndrome [1] accounting for approximately 20% of all peripheral nerve lesions. In 50% of all patients it is the cause of brachialgia. The prevalence amongst women as quoted from [2] is 9.2% and amongst men 0.6%. It is therefore commonly seen in private practice. Table I summarises disorders predisposing to CTS.
The carpal tunnel syndrome can be classified into 3 stages. Stage. is defined as mainly nocturnal burning or tingling pains of the hand and/or forearm (dysesthesia nocturna). In stage 2 there is thenar wasting and hypesthesia and hypalgesia

Operation Technique
All 50 operations were done under local anesthesia. When the patient felt uncomfortable with the instruments in situ i.v.-analgesics were administered.
The patient is then positioned supine, the arm abducted 90 on an armboard. The landmarks are drawn on the skin [18] (Fig. 1). Then the arm is disinfected. Under local anesthesia [19] the proximal incision is made first at the site marked previously (Fig. 2). The palmar aponeurosis is split longitudinally exposing the fascia. A narrow dissector is advanced under the transcarpal ligament, preparing the path for the following instruments. By feeling for the rough undersurface of the carpal ligament the surgeon makes sure the dissector is positioned correctly under the ligament. At this stage of the operation the patient often feels some discomfort. Next the trocar follows the path of the dissector (see Fig. 3) with the wrist maximally hyperextended over the specially designed bolster (Fig. 4). The second skin incision is made over the tip of the trocar (Fig. 5). Now the transverse carpal ligament should be visible at the 12 o'clock position if the instrument has been placed correctly (Fig. 6). Special knives are used to dissect the ligament, the dissection should be continued for 1-1.5cm into the fascia of the forearm. Once the ligament is dissected subcutaneous fat bulges into the gutter (see Fig. 7) compromising the endoscopic view. Swabs help to improve the view.
The operation is finished by probing the boarders of the ligament. The trocar is reintroduced into the gutter and both removed from the carpal tunnel. The skin is sutured with non-resorbable 6.0 material. A well padded dressing is applied and left for three days postoperatively. The     TREATMENT OF CARPAL TUNNEL SYNDROME 189 patients receive no physiotherapy. On demand, the patients could take systemic NSAID's.

Complications
There were no intraoperative complications. Three patients developed a hematoma postoperatively. All but patient were free of symptoms at six months p.o. This patient presented with persisting paresthesia and requires revision surgery.
In 2 patients the motor latency of the median nerve hat not recovered to normal at six months postoperatively. As they are free of symptoms this cannot be considered to be a complication in the strict sense. Three patients reported sore scares for several months. All in all, 7 patients presented with minor complications. Chow described 1993 no permanent nerve or vessel damage, hematoma, tendon laceration or infection found in his series. The comparison between outpatient and hospital based inpatient shows no increase in complications rate of the outpatient procedure.

DISCUSSION
When discussing results of studies on CTS one must stress the fact that interpreting neurophysiological data is not without problems. The motor latency of the median nerve is influenced both by the investigator and by circadiem rhythm. The latency also increases with age [16] and is influenced by hormonal changes. Considering these facts, functional impairment, pain characteristics and clinical findings determine the indication for operation. Statistical analysis of the pre-and postoperative neurophysiological data therefore makes little sense. More important is the clinical outcome and the patient's satisfaction with the procedure, which was very good in this series. The only patient with persisting symptoms shows fibrosis of the epineurium of the median nerve on MRI, the aetiology of which cannot be determined.
With an average 27 days off work our series compared favourably with data reported by Agee et al. in 1992. In his series the average time off work was 25 days after unilateral endoscopic procedures. However, as the patients in this study did not receive any postoperative physiotherapy [20] we feel that routine physiotherapy could have shortened the time back to work. This question remains to be studied by further investigations. Although 4 patients presented marked wasting of the thenar and 7 moderate wasting all of them demonstrated some recovery after six months. In such cases the literature [16] favours open procedures. It is noteworthy though, that in none of the patients in this series the function of the thumb was impaired. If this had been the case more extensive procedures would have been necessary to restore the opposition movement of the thumb [21,22].
Endoscopic techniques need to be thoroughly instructed before they can be practised safely [15,21,22]. Once mastered, this technique is simple and cost efficient due to short operating times and reusable and resterilisable instruments.
We therefore conclude that the endoscopic release of the carpal ligament can be practised safely and cost efficiently as an outpatient procedure in private practice. It thus offers a valuable alternative to the open procedure performed on hospital based inpatients.