Efficacy and Safety of an Absorbable Cervical Cage with and Without Plating: A Multicenter Case Study

Patient number

Age (years)

48.0 (range, 18–83)

Male/Female

53 / 36

Table 34.2

Operated level

	With plating	Without plating	All patients
One level	31	39	70
C2-3	1	0	1
C3-4	3	1	4
C4-5	5	4	9
C5-6	14	9	23
C6-7	6	19	25
C7-T1	1	5	6
Missing data	1	1	2
Two levels	14	3	17
C3-4, 4-5	2	0	2
C4-5, 5-6	4	2	6
C5-6, 6-7	7	1	8
C6-7, 7-T1	1	0	1
Three levels	2	0	2
C5-6, 6-7, 7-T1	2	0	2

Surgical Technique

The operative procedure was performed by an antero-lateral approach following epi and lateral X-rays. After discectomy, curettage of the disc space with preparation of the cortical structures of the vertebral endplates and a decompression of neural structures, a synthetic composite (TCP/PLLA) ceramic cervical cage (Duocage®, SBM, Lourdes, France) with suitable height and width was introduced. The cages have been placed into the interbody space, at the center of the vertebral end plates, under careful impaction. The additional plating used was a Zephir® (Medtronic, Memphis, TN, USA) in all cases.

A soft collar was used during 3 weeks after the surgery.

Procedures

The primary endpoints were the resorption (over 75 %, 25–75 %, or under 25 %) as evaluated by comparing the initial density of the implant to that of adjacent cancellous bone, and the fusion of the cervical interbody cage (Fig. 34.1). Fusion was evaluated by means of dynamic flexion extension X-rays (less than 3°), displacement (none, 1–5 mm, or over 5 mm) and loss of disc height (none, 1–3 mm, or over 3 mm) by measuring the distance of the two adjacent intact vertebral plateau to eliminate the imprecision of measure at the treated level. Prespecified secondary outcomes were clinical inflammatory reactions (no or yes), functional result (good, fair, or poor), pain (none, moderate, or acute) using VAS scale and return to physical activities, sportive and professionals (good, fair, or poor). Radiological evaluation also included the presence of a radiolucent line (none, 0–1 mm, or over 1 mm). Data were measured at 3, 6 and 12 months after the surgery and at the latest follow-up available, at least 18 months where the overall result was estimated (excellent, good, fair, or bad). All adverse events were reported.

Fig. 34.1

Resorption higher than 25 %

Migration was defined as a displacement of the cage superior to 5 mm, and subsidence was defined as a more than 3 mm loss of initial implant height. Migration, subsidence or fracture of the implant, non-union and fusion, were evaluated by means of standing lateral spinal radiographs including flexion-extension radiographs and CT scan evaluation at 1 year or latest follow up. They were taken at each follow-up, except at the first to prevent risks of non-union during bone healing.

Statistical Analysis

89 patients were enrolled, and 110 cages were implanted. The number of patients required was not based on statistical considerations. Analysis of difference between the groups with or without a plate, with separated analysis for the one-level and the multi-level operated patients, were conducted using descriptive statistics and the t-test or the Wilcoxon test to compare the calculated means at every endpoint, depending of the normality of the observed distribution. Patient’s proportions were compared by the χ [2] or the Fisher’s exact test, depending on the computed theoretical effectives. The approach was two-sided and a type I error of 5 % was chosen for declaration of statistical significance. SAS version 8.2 (Inst; Cary, NC, USA) was used for all statistical analyses.

Results

The average follow-up is 19 months (range, 1–36 months). Ten subjects were lost to follow-up: 2 died, 1 moved, 5 withdrawn their consent and 2 files were lost.

Radiological Results and Adverse Events

The radiological data of the operated patients are summarized in Table 34.3 (Fig. 34.2 and 34.3). Cervical interbody fusion with Duocage® cage was uneventful in all patients. There were no early or late implant-related complications. There were two patients with pseudarthrosis. No late inflammation was noticed. We did not observe any problems such as cage fracture.

Table 34.3

Radiological results at last follow-up

(%)	With plating	Without plating	All levels
Stable dynamic X-rays	100.0	93.8	98.0
Radiolucent line under 1 mm	100.0	88.9	97.0^*
Migration under 5 mm	100.0	88.2	97.0^*
Loss of disc height under 3 mm	100.0	88.9	97.0^*

^* P < 0.05, Fisher’s exact test, between with or without plating groups

Fig. 34.2

Fusion and resorption of the Duocage®: extension X-rays at (a) 4 months and (b) 32 months after surgery without plate

Fig. 34.3

Fusion and resorption of the Duocage®: patient with a fixation plate at (a) immediate post-operative visit and (b) 24 months after surgery

A bony bridge was observed between the two vertebrae with no mobility in every except the patients who presented a pseudarthrosis. One of these patients, operated on two levels without plate fixation, evidenced non union only on one of the two levels since fusion was achieved at the upper level.

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