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Diagnosis and Treatment of Cauda Equina Entrapment in Lumbar Burst Fractures with Vertical Lamina Fractures

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Written by Taku Nakakohji, Satoshi Kawasaki, Gyo Murakami and Kenji Hisa

Abstract from the SRS 2003 Annual Meeting

Purpose: Dural laceration of lumbar burst fracture can result in leak of cerebrospinal fluid leading to pseudomeningocele, and trapping of herniated nerve roots cause involvement of neural elements in scar tissue. However, the predictive value of the radiological signs still remains controversial. We experienced 8 cases of lumbar burst fractures associated with vertical lamina fractures who had been treated surgically with posterior instrumentation. Of these, dural lacerations were found in 7 cases. The purpose of this study was to determine whether dural lacerations or neural damage could be detected preoperatively using CT, MRI, and myelography, and to report the outcome of the treatment in these patients.

Materials and Methods: Eight patients (5male, 3female) who had burst fractures associated with vertical lamina fractures were reviewed retrospectively, whose mean age was 34 years (range, 24 to 47). The mean follow-up period was 3 years (range, 2 to 5 years). There were 4 type B, 1 type C, and 3 type D fractures. The height of the vertebral body was measured and the percent of canal compromise by the retropulsed bone fragment was estimated by Computed tomography (CT) and digitizer (WT-4400 WACOM).

Results: On their initial physical examination all 8 patients with lamina fractures had partial neurological deficits including bowel and bladder function deficits. They were evaluated clinically using Frankel scale (Table 1). Before surgery the mean height of the vertebra was decreased to 54 percent (range 40 to 69 percent), and the mean compromise of canal by the retropulsed bone fragment was 65 percent (range 17 to 86 percent). Seven patients underwent preoperative myelography. Five patients had a complete myelographic block. In one patient, dye was seen leaking out through the dural tear. During surgery, in 7 of the 8 fractures (88%) dural lacerations were found and of these 7 dural lacerations, neural elements were injured in 6 patients (86%). Four of the 6 patients had rootlets that were extruded through the dural tear. In the other two patients, root pouches were lacerated, and spinal nerves were ruptured or amputated. (Table 2). Complete myelographic block was significantly (p<0 .005) associated with dural laceration and neural element injury. In the MRI, disappearance of epidural fat or presence hematoma was not After surgery, mean height vertebral body significantly increased to 72 % (range 56 90%) (p<0.01) compromise canal disappeared in all patients. All patients could ambulate, but 4 them needed orthosis due muscle weakness.

Conclusions: 1. Thoracolumbar burst fracture associated with vertical laminar fracture had a high probability of dural tear and extrusion of neural elements. 2: Complete myelographic block likely showed dural laceration. 3: In treating the thoracolumbar burst fracture with laminar involvement, posterior exposure and visual inspection followed by repair of dural tear and neural elements should be needed.

Table 1. Etiology of injury and pre- and postoperative clinical findings of lumbar burst fractures with lamina fractures

Case	Sex	Age	Mechanism of Injury	Level of Injury	Denis Type	Lamina Fracture	Neurologic Deficit	Frankel Preop	Scale Postop	Bladder Function
1	F	31	Suicidal fall	L1	B	Rt	Rt	C	D	•
2	F	32	Suicidal fall	L2	B	Rt	Rt	C	D	•
3	M	41	Thrown from a truck	L3	B	Rt	Rt	B	C	X
4	F	24	Suicidal fall	L1,3	B	Lt	Lt	C	D	•
5	M	27	Paraglider accident	L3	D	Lt	Lt	D	E	%
6	M	27	M.V.A.	L4,5	D	Both	Both	B	D	•
7	M	43	Fall from tree	T12	C	Rt	Rt	D	E	•
8	M	47	Fall from building	L4	D	Rt	Rt	C	D	•

M.V.A.= motor vehicle accident Frankel Scale: A=complete, B=sensory intact, C=motor useless, D=motor useful, E=intact •: return of function, X: no return of function, %: no original conus function deficit

Table 2. Pre- and postoperative radiological findings and surgical procedures of burst fractures with lamina fractures

Case	Vertebral Preop	Height Postop	Compromise of Canal	Mylelographic Findings	MRI Findings	Operative Findings	Levels Laminectomy	Instrume & Outcome	Follow (years)
1	61	66	45	incomplete block	DEF	dural laceration	T12-L2	CDI Fused
2	50	56	75		DEF,EH	dural rootlet laceration amputation	L1-3	HR Fused	2
3	54	84	83	complete block	DEF,EH	dural l rootlet laceration amputation	L2-4	CDI Fused	2
4	69	90	60	complete block	DEF	dural laceration spinal nerve rupture	T12-L4	CDI Fused	4
5	57	57	71	complete block	-	dural laceration spinal nerve rupture	L2-4	CDI Fused	2
6	52	68	86	complete block	DEF	dural laceration spinal nerve amputation	L3-5	CDI Fused	5
7	51	69	17	incomplete block	DEF	no laceration	T12-L1	TSRH Fused	3
8	40*	63*	83	complete block	DEF,EH	dural laceration rootlet eruption	L3-5	TSRH Fused	4

D.E.F.=Disappearance of epidural fat; E.H.=Epidural hematoma; E.C.E.=Extrusion of cauda equine; % = no examination CDI=Ctrel-Dubousset instrumentation; HR=Harrington rod; TSRH=Texas Scottish Rite Hospital spinal system*: p<0 .01

Table 3. Myelographic results correlated with surgical findings

Myelographic Findings	Number of cases	Torn Dura	Surgical Findings Extruded Roots	Amputated Roots
Complete Block	5	5	4	3
Incomplete Block	2	1*	0*	0