Functional outcome of surgical management of degenerative lumbar canal stenosis.

BACKGROUND: The long term outcomes of decompressive surgery on relief of pain and disability in degenerative lumbar canal stenosis are unclear. The aim of our study was to evaluate the outcome of surgical management of secondary degenerative lumbar canal stenosis and to analyze the effect on outcome variables using Japanese Orthopaedic Association (JOA) score.
MATERIALS AND METHODS: Thirty-two patients of degenerative lumbar canal stenosis managed surgically were included in this study. Laminectomy (n=2), laminectomy with disectomy (n=23), laminectomy and disectomy with instrumental stabilization (n=5), and laminectomy, disectomy with posterior interbody fusion (n=2) were performed. JOA scoring system for low backache was used to assess the patients. The recovery rate was calculated as described by Hirabayashi et al. (1981). Surgical outcome was assessed based on the recovery rate and was classified using a four-grade scale: Excellent, improvement of >90%; good, 75-89% improvement; fair, 50-74% improvement; and poor, below 49% improvement. The patients were evaluated at 3 months, one year and at last followup.
RESULTS: At 3-month followup, 18.75% patients showed excellent outcome, 62.50% patients showed good outcome, and 18.75% showed fair outcome. At 1-year followup, 64% patients showed excellent outcome and 36% patients showed good outcome. At >1 year followup (average 34.2 months, range: 2-110 months), 64% patients showed excellent outcome, 28% showed good outcome, and 8% showed fair outcome. No patient had poor outcome. Outcome of the patients improved as the time after surgery increased till 1 year and was sustained thereafter till the last followup.
CONCLUSION: Operative treatment in patients of degenerative lumbar canal stenosis yields excellent results as observed on the basis of JOA scoring system. No patient got recurrence of symptoms of nerve compression.

INTRODUCTION

The classic symptom of spinal canal stenosis is pseudoclaudication or neurogenic claudication.1–6 The classification of spinal stenosis proposed by Arnoldi et al. (1976) remains useful.7 Patients typically complain of pain, paresthesia, weakness, or heaviness in the buttocks radiating into lower extremities with walking or prolonged standing, relieved with forward bending and sitting. Nonsurgical treatment is the mainstay of treatment. Patients with severe spinal canal stenosis either do not improve with conservative measures or have frequent recurrent symptoms. Surgery is indicated when there is neurological involvement. The long term outcomes of decompressive surgery for relief of pain and disability are still unclear. This study evaluates the outcome of surgical management of secondary degenerative lumbar canal stenosis and analyzes the effect on different outcome variables using the JOA score.

MATERIALS AND METHODS

This prospective study was conducted at our hospital between August 2002 to October 2010 after obtaining clearance from the institutional ethical committee. During this period, 46 patients of degenerative lumbar canal stenosis were deemed eligible for operative treatment based on the inclusion and exclusion criteria out of which 14 patients did not consent and thus a total of 32 patients underwent surgical treatment. Patients who had posture-related radicular pain with claudication distance less than 100 m and who could not carry out their routine daily activities were assessed with magnetic resonance imaging (MRI) [Figure 1A and 1B]. Surgery was performed if the central canal diameter on MRI was found to be less than or equal to 10 mm. Spinal instability was assessed using flexion and extension lateral radiographs using Posner's criteria.8 Patients with primary bony canal stenosis, traumatic lumbar canal stenosis, stenosis due to tumors and infection, and patients not medically fit for surgery due to comorbidities were excluded from the study. Patients were managed with four different surgical techniques according to pre-formulated indications. Laminectomy with decompression was done in all cases. Discectomy was done in all cases with a soft bulging disc intraoperatively. Instrumentated stabilization was done in all cases with preoperative instability and when laminectomy was done at more than one level. In addition, posterior lumbar interbody fusion was performed in cases with degenerative listhesis. All procedures were performed by senior orthopaedic surgeon. According to this protocol, laminectomy with decompression was done in 2 cases, laminectomy and disectomy was done in 23 patients, laminectomy, disectomy with instrumented stabilization was done in 5 cases, and laminectomy, disectomy with posterior lumbar interbody fusion was performed in 2 patients. Average followup period was 34.2 months (range: 3–110 months). 25 patients were followed at one year and more. Pre and posttreatment assessment of the patients was done according to JOA evaluation system for low back pain. The JOA score was determined by direct questioning to assess subjective symptoms, clinical signs, and restriction of activities of daily living. The recovery rate of the patients following treatment was calculated by using the description of Hirabayashi et al. (1981): Recovery rate (%)=(Postoperative score – Preoperative score)/(29 – Preoperative score)×100. Recovery rate was classified using a four-grade scale: Excellent, >90%; good, 75–89%; fair, 50–74%; and poor, below 49%.9

Figure 1A

(a) Preoperative AP and (b) Lateral X-rays of a 52 years old male patient who presented with secondary degenerative LCS at L3-4, L4-5 with retrolisthesis of L4 over L5. His preoperative JOA score was 5

Figure 1B

(a) Preoperative T2 sagittal MRI section of the same patient showing degenerative LCS L3-4, L4-5 with degenerated disc at L2-3, L3-4, L4-5. Discs at L3-4 and L4-5 were found to be soft and bulging intraoperatively and hence were removed along with posterior decompression, laminectomy and pedicle screw fixation from L2 to L5, (b) Preoperative T2 axial MRI section showing large herniated disc at L3-4. The patient attained JOA score of 28 at 3 months followup which was maintained till last followup of 7 months

Statistical analysis

Preoperative and postoperative JOA scores at immediate, 3 month, 6 month, and 1 year followup were compared using Wilcoxon's test for nonparametric data.

RESULTS

The average age was 45.1 years (range 17-74 years). There were 22 males and 10 females. All the patients had symptoms for more than 3 months duration at presentation. Complete data of all the 32 patients along with their JOA scores are presented [Table 1]. Distribution of patients in all the variables of JOA scoring system was assessed before and after treatment [Table 2].

Table 1

Clinical details and outcome of all patients

Table 2

Distribution of variables of JOA score in surgically managed LCS patients (Preoperative vs. Three months postoperative)

Preoperatively, 71.87% of patients (n=23) presented with continuous severe low backache, 25% (n=8) with occasional severe low backache, and 3.13% (n=1) presented with occasional mild low backache. Three months postoperatively, 62.5% patients (n=20) had no back pain and 37.5% (n=12) had occasional mild low back pain. No patient had occasional severe or continuous severe low back pain.

Most of the patients (87.5%, n=28) had presented to us with posture related severe leg pain, but postoperatively 96.87% patients (n=31) had no leg pain. All patients had preoperative claudication distance less than 100 m, but 93.75% patients (n=30) had normal gait with walking distance more than 500 m and no claudication symptoms postoperatively. The most common level of involvement was L4-L5(81.82% patients, n=27) followed by L5-S1(54.55% patients, n=18). 54.55% patients (n=18) showed involvement at more than one level.

93.74% patients (n=30) had abnormal straight leg raising test [46.87% patients (n=15) had straight leg raising positive below 30° and 46.87% patients (n=15) had between 30° and 70°], but postoperatively all patients had normal straight leg raising test. Sensations were diminished in L4 dermatome in 3 patients, L5 dermatome in 14 patients and S1 dermatome in 8 patients. More than one dermatome was involved in 5 patients. Overall, 20 patients (62.5%) had shown sensory disturbance preoperatively, but postoperatively 19 of these 20 patients recovered normal sensory function. Motor weakness was present in 15 patients (46.87%) preoperatively, but postoperatively only 6 patients (18.75%) showed motor deficit. Overall, 93.75% patients (n=30) in our study showed improvement in all variables of the JOA scoring system postoperatively.

At 3 month followup, 18.75% (n=6) patients showed excellent outcome, 62.50% (n=20) showed good outcome, and 18.75% (n=6) patients showed fair outcome [Table 3]. At 6 month followup, 38.46% patients (n=10) showed excellent outcome and 61.54% patients (n=16) showed good outcome. At 1 year followup, 64.00% patients (n=16) showed excellent outcome and 36.00% patients (n=9) showed good outcome. At final followup, 64% patients (n=16) showed excellent outcome, 28% (n=7) showed good outcome, and 8% (n=2) showed fair outcome. No patient had poor outcome. Outcome of the patients improved as the time after surgery increased till 1 year and was sustained thereafter till the last followup (only two patients showed decrease in their recovery rate which was due to prolapsed disc or canal stenosis at a different level). Statistically significant improvement was seen in all variables except running and lifting heavy weight [Table 2].

Table 3

Outcome of 32 surgically managed patients assessed by pre and posttreatment (JOA) score

On comparison of preoperative and three months postoperative JOA scores using Wilcoxon's test for nonparametric data, P value is <0.001 which meant that outcomes were extremely significant postoperatively. Further, JOA scores significantly improved even postoperatively till 1 year (P<0.05). After 1 year, the JOA scores did not change significantly with time till the last followup.

DISCUSSION

In our study, 40.63% (n=13) patients were in the age group 50–59 years, followed by 40–49 year age group, and the average age was 45.1 years, with similar age and sex distribution reported by others.10

64% patients showed excellent and 28% showed good outcome at the end of 1 year followup, while Ganz et al. (1990) reported almost similar result showing 86% good outcome in their series of 33 patients treated by decompressive surgery. In their patients whose preoperative symptoms were relieved by postural changes, the success rate was 96% compared to only 50% in those unchanged by postural changes.11

Weinstein et al. (2010) showed that patients with degenerative spondylolisthesis and spinal stenosis treated surgically showed substantially greater improvement in pain and function during a period of 2 years than those treated nonsurgically.12

In our study, finally, 62.5% patients had no back pain and 37.5% had occasional mild pain, 96.87% had no leg pain, 93.75% had normal gait, 100% had normal straight leg raising, and 95% had sensory improvement (i.e. 19 patients out of 20 who presented with sensory impairment). Similar findings were observed in the study of Herron et al. (1991) with average leg pain improvement of 82% and average back pain improvement of 71%.13

Weinstein et al. (2010) in their prospective multicentre SPORT study of 654 patients concluded that patients with symptomatic spinal stenosis treated surgically compared to those treated nonoperatively maintain substantially greater improvement in pain and function through 4 years. All patients in their study were surgical candidates with a history of at least 12 weeks of neurogenic claudication or radicular leg symptoms and spinal stenosis without spondylolisthesis (as confirmed on imaging). They were enrolled in either a randomized cohort (289 patients) or an observational cohort (365 patients) at 13 U.S. spine clinics and were treated by either standard decompressive laminectomy (414 patients) or usual nonsurgical care (240 patients).14

No patient in our series had poor result. This could be due to the fact that all patients underwent at least a 12 weeks trial of adequate conservative treatment and were only operated after clinicoradiological correlation of their symptoms with imaging was confirmed. Decompressive laminectomy was also adequately supplemented with pedicle screw fixation (in cases of preoperative instability or when more than one level laminectomy was performed) and/or posterior lumbar interbody fusion (in cases of degenerative listhesis) and/or discectomy (cases with a soft bulging disc). Only two patients had fair outcome. The failure of surgery to completely relieve pain in these two patients may be attributed to the widespread degeneration. Outcome was also affected due to some variables in scoring system like running and heavy weight lifting in which female patients and patients over 50 years scored less despite being free of pain.

Getty (1980) personally reviewed 31 patients (age range 18 to 75 years) who had been treated surgically for lumbar spinal stenosis between 1968 and 1978 and followed them for an average of 42 months. In 28 (90%) patients, degenerative changes in the lumbar spine had been the principal etiological factor; the other 3 had idiopathic developmental lumbar spinal stenosis. In 17 (55%) patients, the result was classified as good, although a total of 26 (84%) patients were satisfied. This compares well with our study in which 93.75% patients (n=30) were satisfied with their surgery. Good results of operation for lumbar spinal stenosis in series of Getty were characterized by rapid resolution of pain in the leg. The most important reason for failure to relieve symptoms in his series was stated to be inadequate decompression.15

Postacchini et al. (1992) noted bone regrowth in 88% of 40 patients who had laminectomy or laminotomy for spinal stenosis at an average of 8.6 years of followup. Bone regrowth was noted in all patients with associated spondylolisthesis.16 We did not observe any case of bone regrowth in our series. A possible explanation could be that interbody fusion was done in all cases of listhesis and pedicle screw fixation to supplement any case with preoperative instability or multilevel decompression in our series. Moreover, we performed a wide laminectomy with medial facetectomy in all our patients as compared to narrow laminotomy in some cases of Postacchini et al. Postacchini (1999) described that 70–80% of patients of lumbar canal stenosis had satisfactory result from surgery, but the outcome tended to deteriorate in the long term.17 Our outcomes improved postoperatively till 1 year but therafter neither showed any improvement or deterioration till last followup.

The authors are of the opinion that operative treatment in patients of degenerative lumbar canal stenosis yields excellent long term functional results as observed on the basis of JOA scoring system provided that patients are properly selected and decompressive surgery is performed simultaneously addressing the associated instability or listhesis. All activities of daily living which were assessed using JOA score showed significant improvement except for running and lifting heavy weight. No patient got recurrence of symptoms of nerve compression.