Transforaminal sacral approach for spinal anesthesia in orthopedic surgery: A novel approach.

Regional anesthesia is preferred world-wide for its distinct advantages. The benefits of regional anesthesia in patients with comorbid conditions are well-established. The administration of regional anesthesia can sometimes pose a challenge to the anesthesiologist due to the structural abnormalities of the spine. The most common difficulty encountered for spinal anesthesia in our hospital (Nalgonda District) is skeletal fluorosis. Apart from the midline approach, paramedian, and Taylor's approaches are advocated for difficult scenarios. This article reports two orthopedic cases, conducted under a novel spinal anesthesia technique, i.e., transforaminal sacral approach under C-arm guidance with a successful outcome. The sacral foraminal subarachnoid block is a method to access the subarachnoid space through the upper posterior sacral foramina.

INTRODUCTION

The orthopedic patients mostly belong to geriatric age group where general anesthesia would not be prudent. Regional anesthesia has always been the technique of choice for lower limb surgeries. The hemodynamic and respiratory alterations are deemed to occur with sympathetic block, but they are easily manageable. Blood loss, deep vein thrombosis and stress response to surgery are minimal. The features of fluorosis are a combination of osteosclerosis, osteomalacia, osteoporosis, limitation of joint movement, calcification of ligaments of the vertebral column, crippling deformities of the spine and major joints. The ligaments are calcified due to which there is a technical difficulty in giving regional anesthesia. There are many techniques for giving regional anesthesia under C-arm and ultrasound guidance. Goodman has reported two cases where there was an accidental dural puncture at the time of a lumbar transforaminal epidural injection.[1] Based on this we performed transforaminal sacral approach (TFS) for spinal anesthesia under C-arm guidance in patients with anticipated difficulty.

CASE REPORTS

Case 1

A 75-year-old patient had fracture neck of the left femur was posted for hemiarthroplasty. He had a history of pulmonary tuberculosis 10 years ago and received treatment for the same. On examination, patient had respiratory rate of 24/min, with depression of left hemithorax. Accessory muscles of breathing were used. On auscultation, he had decreased breath sounds with crepitations on the left side. His breath holding time was 10 s. Chest X-ray (CXR) revealed fibrocavitory lesions as shown in Figure 1. Blood biochemistry was normal. Arterial blood gas showed pH 7.2, pCO2 60, pO2 was 59, HCO3 26.1, base excess 2.3 and oxygen saturation was 96%. Serum fluoride level was 3.5 ppm which is above normal. Forced expiratory volume in 1 second (FEV1) and forced vital capacity were decreased.

Figure 1

Chest X-ray showing extensive fibrocavitory lesion in the left lung, suggestive of old Koch's

Case 2

A 55-year-old patient with fracture both bones left leg was posted for open reduction and internal fixation. Pre-operative assessment was done. Patient was a smoker and had breathlessness and cough since 10 years and was diagnosed to have chronic obstructive pulmonary disease (COPD). On examination, breath holding time was 15 s, patient had bilateral wheeze and fluorotic spine with no visible and tactile landmarks. CXR revealed signs of COPD. Blood biochemistry was normal, but for a serum fluoride level of 3.2 ppm. Electrocardiogram was normal. FEV1 <50% of predicted value.

Both cases had compromised respiratory status and hence regional anesthesia was preferred. In addition to this, they had fluorotic spine as suggested by magnetic resonance imaging and serum fluoride estimation. By virtue of anticipated difficulty in performing spinal anesthesia by conventional method we decided to proceed with the technique of “TFS” for spinal anesthesia. The patients were monitored with multiparameter monitor. Intravenous access was achieved with 18 gauge cannula.

Patient is made to sit on a pillow with anterioposterior position of the C-arm as shown in Figure 2. First or second sacral foraminae were identified 2-3 cm caudal and 3-4 cm medial to the posterior superior iliac spine. A 25 gauge spinal needle was introduced with C-arm guidance into the foramina directing cephalomedially until the loss of resistance is achieved as shown in Figure 3. After the puncture of the dura and free flow of cerebrospinal fluid 15 mg of injection bupivacaine 0.5% and injection fentanyl 25 μg were administered and patients placed in the supine position. Adequate analgesia was achieved up to T-10 level in 5-10 min. Duration of surgery was 2 h. Vital parameters were stable throughout the procedure.

Figure 2

Patient positioned for transforaminal approach under C-arm guidance

Figure 3

Spinal needle seen in the first sacral foramen in C-arm image

DISCUSSION

Fluorosis is an important public health problem in some states of India. Nalgonda is one such district in Andhra Pradesh which is endemic for fluorosis.[2] In skeletal fluorosis the stiffness of the back increases steadily until the entire spine becomes one continuous column of bone manifesting a condition referred to as “pokers back.” Lumbar transforaminal epidural steroid injections have been utilized and shown to be effective in the treatment of lumbar radiculopathy.[345] This selectively delivers the medication to the epidural space near exiting spinal nerves. Based on this, we performed spinal anesthesia by TFS.

The knowledge of sacral anatomy is essential for practicing this technique, the anatomical details are as shown in Figure 4. The sacrum is a fused bone of (five) sacral vertebrae with centrally placed sacral canal. This canal may be absent in 5-10% of population.[6] The L5-S1 inter laminar space is the widest and least likely to be affected by degenerative changes that may arise secondarily to the fused joints.[7] The “lumbosacral puncture” for spinal anesthesia was first described by Taylor and truly is a special variant of the conventional paramedian approach (PMA).[8] Similarly, TFS also is a variant of PMA. When a spinal needle is inserted through 1st or 2nd dorsal foramen of the sacrum in cranial direction, it will penetrate through skin, subcutaneous tissue, paraspinal dorsal muscle, ligamentum flavum, epidural space, dura mater, subdural space, arachnoid mater and subarachnoid space.

Figure 4

The entry of spinal needle through first sacral foramina in cephalomedial direction

In 1913, Danis[9] introduced “transsacral anesthesia” by bilateral multiple injections of local anesthetics into sacral canal through each dorsal foramen, but this difficult technique failed to gain popularity. Rabinowitz et al., revealed in their study with geriatric orthopedic patients that after the initial attempt, the PMA is associated with a success rate of 85% in comparison to midline approach of 45%.[10] Landa et al. defined two major types of cervical and lumbar spinal injections, the translaminar and transforaminal approaches.[11]

During sacral neuromodulation,[12] an electrode is placed in third dorsal foramen for the treatment of urge incontinence. Based on this, it was decided to administer spinal anesthesia through first or second dorsal foramen of the sacrum to evaluate its merits and demerits as well as to assess the feasibility of such a procedure.[13] Our patients had respiratory problems and skeletal fluorosis, so we administered spinal anesthesia by this novel approach anticipating difficulty, they did not have any complications and the recovery was uneventful. Anatomical variations of sacrum may pose a problem with this technique.

CONCLUSION

TFS for spinal anesthesia is a viable alternative to the conventional technique. This novel technique needs more research in its application in clinical practice. It continues to evolve and should be in the armamentarium available to overcome the problem of difficult spinal.