[Subsidence and its effects on the anterior plate stabilization in the course of cervical interbody spondylodesis. Part II. Clinical evaluation. Study design].
METHODS
Subsidence is a common phenomenon in the process of interbody fusion. The paper presents a retrospective clinical and radiological evaluation of subsidence in a group of 23 patients after cervical corpectomy with mesh cage and plate stabilization. Subsidence magnitude and its impact on the stabilizing system and on the clinical and radiological outcome were estimated.


METHODS
The mesh cage and cervical plate stabilization was preformed after one- (20 cases) or two-level (3 cases) corpectomy. The patients' mean age was 35 years (age range 18-72); 9 patients were aged over 50. Indications to corpectomy were: neurological impairment due to burst body fractures in 14 cases, multilevel spondylosis in 5, and OPLL in 2 patients. One patient had a kidney cancer metastasis. The mean follow-up period was 17 months (range 12-28 mo.). The patients' clinical status was evaluated using the ASIA scale in the post-traumatic group, and the Odom criteria in spondylotic cases. In all the cases pain severity was estimated by the VAS scale. Magnitude of subsidence was measured on consecutive lateral x-rays during the follow-up. Bone fusion was confirmed after 3 months in lateral flexion-extension x-rays. Changes in the local and general cervical lordosis were evaluated during the follow-up.


RESULTS
A 72-year-old patient died after 6 weeks due to causes unrelated to the surgery. In all the remaining patients bone fusion was attained. There were no cases of the clinical status deterioration during the follow-up. Subsidence of over 1 mm was found in 19 patients (86.4%). The mean value of subsidence was 2.2 mm, but in a group of older patients (aged over 50) it amounted to 2.8 mm. In 4 cases (18.1%) with hardware complications, i.e. a screw breakage or slipping, the mean subsidence magnitude was 4.3 mm. Local and general cervical lordosis were maintained during the follow-up period, even in the group with excessive subsidence. The screw breakage site was invariably the round hole of the plate.


CONCLUSIONS
The subsidence phenomenon is seen in a majority of fused patients. Nevertheless, clinical and radiological results of the surgery are good. An excessive subsidence may result from hardware complications. In newly designed plates subsidence should be taken into account.
Hakało
Jerzy
J
Oddziału Neurochirurgii Szpitala Wojewódzkiego w Zielonej Górze. hakalo@poczta.onet.pl
Wroński
Jerzy
J
D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D001860:Bone Plates; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D005260:Female; D006801:Humans; D016268:Internal Fixators / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D009333:Neck / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D011859:Radiography; D012189:Retrospective Studies; D013123:Spinal Fusion / Q000009:adverse effects / Q000379:methods; D013130:Spinal Stenosis / Q000000981:diagnostic imaging* / Q000209:etiology*; D013526:Surgical Mesh; D013997:Time Factors; D016896:Treatment Outcome