In 1944, Spurling et al. first described the effectiveness of p-PECD for the treatment of cervical foraminal stenosis which induced by a lateral CDH or osteophytes (32). Studies proved that p-PECD is an effective treatment for cervical diseases and its inner diameter of working cannula ranges from 3.7 mm to 6.9 mm (17, 22, 28). In our opinion, different diameters of the working cannula may lead to different surgical efficiency. However, no studies were performed to compare the clinical outcomes of keyhole technique and delta technique of p-PECD in CDH patients. In this study, we described the clinical results of 28 consecutive patients diagnosed with unilateral CDH who performed p-PECD using the keyhole or delta technique.
Anaesthesia
Studies suggested that local and general anaesthesias are the effective strategies of PECD (17, 22, 23, 33). Wan et al. (17) claimed that local anaesthesia in selected CDH patients is a promising and feasible alternative. However, local anaesthesia still has unavoidable shortcomings, such as uncomfortable and psychentonia during operation. Moreover, if the patient is awake, hearing the voice of the surgical instrument may cause elevated blood pressure, increased heart rate, and poor surgical experience (17). General anaesthesia has been described in several previous studies, which could offer patients a comfortable experience during p-PECD surgery (22, 23, 33).
In the present cohort, to minimize their intraoperative anxiety and pain and to attain their better cooperation, general anaesthesia was carried out in all patients. Besides, INM technology were used in this study to prevent iatrogenic neurological deterioration intraoperatively. The detailed method refers to Yu et al. (17, 34). No nerve compromise was observed in both groups postoperatively and we attribute this positive results to reasonable choice of anesthesia method and application of INM.
Clinical Results
The mean hospital stays of traditional posterior foraminotomy or ACDF in China usually more than seven days (23). In our study, the mean hospitalization of delta group and keyhole group were 5.1 (from 2 to 8) and 4.8 (from 3 to 6) days respectively, and both groups had an improvement compared with China average results. However, there was no significant difference between delta group and keyhole group in the average hospital stay period (P>0.05). The longer operative times were required in keyhole group (76.5 min) than delta group (61.5 min), we suggest this result may because of the small-diameter working cannula can only accommodate smaller-diameter endoscopic instruments, such as RF probe, forceps and drill, which obviously limits the efficiency of “V” point identification, overlying soft tissue removal and laminoforaminotomy.
On the basis of previous surgical experience (23, 35, 36), the average VAS score after surgery was significantly lower for both techniques, however, the difference in the average VAS scores between keyhole technique and delta technique was not significant (P>0.05). Meanwhile, considering to the modified MacNab criteria, the proportion of having a satisfied result (excellent or good recovery) improved during follow-up visit in both techniques, nevertheless, the difference between keyhole technique and delta technique was not significant (P>0.05). Therefore, the clinical outcomes of both techniques were similarly effective.
Operation Technique (Table 4)
Identification of “V” point
Identification of V-point is an extremely critical operation step, which dominates the success or failure of the p-PECD surgery. Furthermore, accuracy and rapid confirming V-point can provide sufficient confidence for the surgeon to proceed with the next step. In our study, identification of V-point was easier in the delta group than keyhole group (18.608±3.7607min vs. 11.256±2.7161min, p<0.001), which may be attributed to a large diameter of working cannula in the delta group.
Potential of spinal cord injury
In this study, neither the delta nor keyhole group had a surgical complication of spinal cord damage. However, our correspondence author argues that keyhole technology has a higher risk of spinal cord injury than delta technique. The minimal working cannula of keyhole approach has a danger of trapping into the spinal canal through the iatrogenic hole and damaging the spinal cord. Meanwhile, delta technique has a wide enough outer surface of working cannula to prevent negligently inserting into the spinal canal, which increases the safety of the operation. This idea was also agreed by Lin et al. (20), who suggested that increasing outer diameter of the working cannula can reduce the risk of spinal cord injury.
Anterior decompression
Keyhole technique is better than delta technique for anterior decompression of the intervertebral foramen due to its smaller outer diameter of working cannula which reduces the compression of the spinal cord. In contrast, through the delta working channel, which has a large inner diameter, may lead to spinal cord injury.
Table 4. Comparation of Keyhole group and Delta Group in Surgical Characteristic
|
Parameter
|
Keyhole
|
Delta
|
Incision
|
Short
|
Long
|
Identification of “V”Point
|
Slow
|
Fast
|
Removal of overlying soft tissue
|
Slow
|
Fast
|
The efficiency of laminoforaminotomy
|
Slow
|
Fast
|
Operation time
|
Slow
|
Fast
|
Anterior decompression
|
Easy
|
Hard
|
Possiblity of spinal cord injury
|
High
|
Low
|
Complications
Surgical related complications, including headache, neck pain, dural damage, nerve roots or spinal cord injury, seizures or neurological deterioration due to the highly increased cervical epidural pressure by continuous saline irrigation, intraoperative bleeding or postoperative epidural bleeding, instability caused by surgical and infections, could happen in p-PECD for CDH patients (13, 23).
In 2007, Ruetten et al. (22, 30) described a rate of 3% of complications in 89 patients in p-PECD, and in 2008 he reported three postoperatively complications of transient, dermatoma-related hypesthesia. In 2009, Joh et al. (37) demonstrated that 8 of 28 patients complained of neck pain caused by the increased pressure of continuous irrigation system in a prospective study. In 2014, Yang et al. (23) observed a transient pain of the contralateral side in one patient, which due to excessive operation of the myelon, and concluded an incidence of 4.8% (2/42) in patients underwent p-PECD. In 2018, Wu et al. (27) reported that two patients suffered the bluntness of the pupillary light reflex, loss of consciousness, muscle weakness of extremities and weak spontaneous respiration in p-PECD under local anaesthesia. C6 lamina was perforated with the spinal needle , which lead to anaesthetics went through the iatrogenic hole and entered subarachnoid space.
In the present cohort, nerve root outer membrane was torn in one case in the delta group, but there was no cerebrospinal fluid leakage during operation and no neurological deterioration postoperatively. No other surgical complications were observed in both groups. The overall incidence of surgical complication in our study was 3.7% (1/28), and this result is similar to previous studies (22) (23).
Limitation
Despite positive clinical outcomes were achieved in this study, there were still many limitations. The limitations of our study include the lack of randomization, the use of single surgeon, the deficiency of multicenter research and the comparably short term follow-up period. Therefore, multicenter randomized controlled trials with large sample size and long-term follow-up visit should be established.