Continuing Education in Physical Therapy: Low Back Pain
Anatomy and landmarks for the superior and middle cluneal nerves: application to posterior iliac crest harvest and entrapment syndromes
Tubbs RS, Levin MR, Loukas M, Potts EA, Cohen-Gadol AA. J Neurosurg Spine. 2010 Sep;13(3):356-9.
Abstracted by Pedro Castex, PT, COMT from Santiago, Chile. IAOM-US Fellowship Student
INTRODUCTION TO THE STUDY
Lumbago is a common musculoskeletal disorder affecting a significant proportion of the population. This term describes the presence of pain in the lumbar area, most likely due to the involvement of a structure in the lumbosacral spine (intervertebral disc, facet joints, neural tissue, etc.). However, a specific group of patients presents with equivocal symptoms that don’t fit with expected clinical presentations and/or lack of significant imaging findings. Among these, cluneal nerves pathology is considered an infrequent yet possible cause of low back pain. The superior cluneal nerves are formed by L1-L3 dorsal rami. These nerves provide the sensory innervation of the upper gluteal and posterior iliac crest areas. The middle cluneal nerves arise from S1-S3 dorsal rami, travelling near to the posterior superior iliac spine (PSIS). Considering the anatomical distribution of these nerves, patients with cluneal nerve pathology may present with persistent low back pain, possibly radiating to the upper gluteal area.
Figure I. Superior and Middle Cluneal Nerves
and their relationship with pelvic bone landmarks
In this study, the anatomy and landmarks for the superior and medial cluneal nerves were described, and considerations for entrapment and possible nerve injury as a consequence of surgical procedure were revised. Dissection of 10 embalmed cadavers was performed following the path of the superior and medial cluneal nerves, from origin to termination.
The results of this study demonstrated that although some specimens lacked of one superior cluneal nerve, all cadavers had at least two cluneal nerves. In cases when one cluneal nerve was absent, the other two cluneal nerves covered this territory. From their origin, these nerves passed through the psoas major and paraspinal muscles, then passing just posterior to the quadratus lumborum between this muscle and the anterior layer of the thoracolumbar fascia. The superior cluneal nerves passed an average of 5 cm, 6.5 cm and 7.3 cm from the midpoint of the PSIS, laterally on the iliac crest. Then, the nerves extended covering the area of the upper half of the gluteus maximus and medius. After these nerves passed the iliac crest, they demonstrated the tendency to anastomose with one another.
Middle cluneal nerves pierced the posterior layer of the thoracolumbar fascia and the lower inferior portion of the latissimus dorsi muscle, demonstrating no evident osteofibrous tunnels incision approximately 2.5 cm anterior to the PSIS and perpendicular to the long axis of the posterior iliac crest, which will most likely avoid injury of the superior and medial cluneal nerves. They also defined a secure zone for incision around the PSIS
Figure II. Schematic drawing of the Superior
and Middle Cluneal nerves, and the relative
safe zone to avoid these nerves during
Another cause of cluneal nerves pathology is the entrapment between the different fascial layers, especially when passing next to the iliac crest. The authors in this study noted no osteofibrous tunnels in the path of the superior and medial cluneal nerves; therefore they concluded entrapment pathology of these nerves might be less likely to occur due to lack of evidence of entrapment sites.
The iliac crest is the most common donor site for harvesting of autologous bone. It has been reported that the most common complication after this procedure is pain at the donor site1. In fact, in a 10-years follow-up study of 100 patients who underwent spinal fusion procedure using iliac crest graft, 37% complained of persistent donor site pain2. Cluneal nerves injury due to posterior iliac crest harvest is a reasonable cause of persistent pain after this procedure.
A non-surgical reason for cluneal nerve pathology is the entrapment of one of these nerves along their course. In a previous report of Maigne3, it has been suggested that entrapment of the medial superior cluneal nerve (derived from L1) may occur as the nerve runs through an osteofibrous tunnel between the thoracolumbar fascia and the rim of the posterior iliac crest. This area was invariably found 7 cm from the midline over the iliac crest. In a later study of Maigne4, the criteria for diagnosis of medial superior cluneal nerve entrapment was established as the presence of a “trigger point” of pain 7 cm from the midline over the iliac crest (corresponding to the entrapment zone), pain in the distribution of the cluneal nerve (Figure III) and relief of symptoms by local nerve block in the area of entrapment. Twenty-nine patients were selected for intervention; all of them received a series of 1-3 nerve block injection, which relieve symptoms in 8 out of 29 patients. Of the remaining 21 subjects, 19 patients underwent surgery, demonstrating an evident osteofibrous tunnel in 15 cases. Of these 15 cases, 13 reported satisfactory results from surgical procedure.
Although the results of Tubb’s study fail to confirm the presence of an osteofibrous tunnel over the posterior iliac crest, it is evident that the possibility of entrapment of the medial superior cluneal nerve cannot be overlooked
Figure III. Distribution of symptoms in the presence
of Superior Medial Cluneal nerve pathology.
Aly et al. 5 described the clinical presentation of two patients with a suspected superior medial cluneal nerve entrapment. In both cases, neurological exam, nerve tension signs or other clinical information was unremarkable. Presence of a trigger point of pain 6-7 cm lateral to the midline over the iliac crest raised the theory for a medial superior cluneal nerve entrapment. In this study, authors introduced the “hip-knee flexion test” as an alternative for diagnosis of this condition. In this test, hip and knee are fully flexed in an attempt to cause tension in the cluneal nerves without tensing other structures. The test is positive when symptoms are provoked in the distribution of the nerve (Figure III). The two cases in this study were successfully treated with local nerve blocks in the area of entrapment.
The IAOM-US teaches that the cluneal nerves are a possible cause of pain, especially in the upper outer quadrant of the buttock area. However, there is a high probability that the results of the basic clinical examination may not provide with all the information we need to establish a proper diagnosis. There isn’t consensus about the genesis of this condition (except when pathology occurs as a consequence of surgery), but based on the presentation of other common nerve entrapment conditions, we could assume it can develop as a result of excessive friction, traction, direct trauma, compression or any other mechanical force, either micro or macrotraumatic, that could create irritation of the nerve, local edema, scarring and possibly narrowing of the nerve space. In cases when cluneal nerve pathology is suspected, a checklist of clinical signs and symptoms could assist in the decision-making process.
PROPOSED CRITERIA FOR DIAGNOSIS OF CLUNEAL NERVE PATHOLOGY
1. Onset probably associated to mechanical stress (compression, traction, trauma, etc.) over the nerve, especially in the classic entrapment site. As well, suspect this condition in presence of persistent pain status post posterior iliac crest harvest.
2. Intolerance to sit for long periods of time.
3. Pain in the distribution of the nerve (Figure III).
4. Presence of a painful “trigger point” about 7 centimeters (2.75 inches) lateral to the midline over the posterior iliac crest.
5. Pain relieves with local nerve block injection in the entrapment site.
6. Possibly, pain provocation in the distribution of the medial superior cluneal nerve with the hip-knee flexion test.
Local nerve block injections, alcohol neurolysis and surgery have been proposed as options for treatment of cluneal nerves pathology. As advocated by IAOM-US, neural flossing could be an effective treatment option in the presence of nerve entrapment. This is not the exception for the cluneal nerves, since flossing techniques may help improve nutrition and mobility of the nerves in the entrapment site. Aly5 postulates that tension in cluneal nerves increases with trunk and/or hip flexion. This makes sense since the nerve is located “behind” the axis of rotation of these two segments.
PROPOSED TECHNIQUE FOR CLUNEAL NERVES NEURAL FLOSSING
Figure IV. Patient is positioned in sidelying, affected side up, and trunk side bent towards the affected side (decreases nerve and quadratus lumborum tension)
|| Figure V. Upside hip is positioned in neutral position in the frontal plane, and slight external rotation in the transverse plane (decreases gluteal muscles tension). Upside knee is slightly flexed to reduce tension on sacral plexus. Avoid excessive tension on anterior thigh
Figure VI. Tableside hip and knee are positioned in 90 degrees of flexion (reduces stress in lumbar spine) and held with mobilization belt or manually with the tableside hand of the patient. Upside shoulder is positioned in slight extension to decrease tension in thoracolumbar fascia
Figure VII. Therapist initiates flossing technique moving upside hip from neutral position on sagittal plane to flexion, and return to neutral. Avoid excessive pelvic movement using stabilization hand.
Movement should be performed within painfree range of motion. It is suggested to stop the technique as soon as patient reports symptoms. The goal is to gradually increase both excursion of leg movement and number of repetitions up to 120 repetitions, 1-2 times a day, without presence of symptoms during technique execution.
PROPOSED SELF-FLOSSING TECHNIQUE FOR CLUNEAL NERVES
Figure VIII. Self-flossing technique for cluneal nerves. Patient lies supine and places a towel roll around distal thigh. Both hips and knee are flexed comfortably. Patient sidebends trunk towards affected side. Patient initiates hip flexion with assistance of towel roll and returns to initial position. Patient may place a soft pillow under the affected side if contact surface is uncomfortable. It could also be performed in sidelying using the same rules.
Anatomical description derived from this study provides useful information regarding the localization of pain due to cluneal nerves injury when suspecting pathology of these nerves. Although there seems to be consensus about the entrapment site of the medial superior cluneal nerve, it is also important to consider the possible variations in the number of cluneal nerves, distribution of nerve territory, and possible anastomosis with other adjacent nerves when understanding clinical presentation and results of the clinical examination and proposed tests. Entrapment pathology, perhaps less frequent than surgical injury of the cluneal nerves, is still a plausible cause of persistent pain in the lumbosacral spine, and could be considered when other treatment options have failed to relieve symptoms, and when history and clinical presentation make sense for this condition.
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1.- Delawi D, Dhert WJ, Castelein RM, Verbout AJ, Oner FC: The incidence of donor site pain after bone graft harvesting from the posterior iliac crest may be overestimated: a study on spine fracture patients. Spine 32:1865–1868, 2007
2.- Frymoyer JW, Howe J, Kuhlmann D: The long-term effects of spinal fusion on the sacroiliac joints and ilium. Clin Orthop Relat Res 134:196–201, 1978
3.- Maigne JY, Lazareth JP, Guérin-Surville H, Maigne R. The lateral cutaneous branches of the dorsal rami of the thoracolumbar junction: A study on 37 dissections. Surg Radiol Anat 1989;11:289-93.
4.- Maigne JY, Doursounian L. Entrapment neuropathy of the medial superior cluneal nerve. Nineteen cases surgically treated, with a minimum of 2 years' follow-up. Spine (Phila Pa 1976). 1997 May 15;22(10):1156-9.
5.- Aly TA, Tanaka Y, Aizawa T, Ozawa H, Kokubun S. Medial superior cluneal nerve entrapment neuropathy in teenagers: a report of two cases. Tohoku J Exp Med. 2002 Aug;197(4):229-31.