The impact of generalized joint laxity on the clinical and radiological outcomes of single-level posterior lumbar interbody fusion.

BACKGROUND CONTEXT

Recent reports have suggested that excessive motion of the lumbar spine might be associated with low back pain and accelerated disc degeneration and may negatively influence the outcome of posterior lumbar interbody fusion (PLIF) surgery. These findings suggest that generalized joint laxity (GJL) might be a negative factor affecting PLIF outcome, although this relationship has not been well studied. In addition, the impact of GJL on adjacent segment pathology (ASP) after PLIF has not been reported.

PURPOSE

To explore the relationship between GJL and the outcome of single-level PLIF, we compared fusion rates, clinical outcomes, and ASP in PLIF patients with and without GJL.

STUDY DESIGN

Retrospective comparative study.

PATIENT SAMPLE

A total of 256 patients who underwent PLIF and were followed for at least 2 years after surgery were classified into two groups: Group A (37 patients with GJL) and Group B (219 patients without GJL).

OUTCOME MEASURES

The primary outcome measure was the fusion rate on dynamic radiographs and computed tomography scans. The secondary outcome measures were pain intensity in the low back based on a visual analog scale, functional outcome based on the Oswestry Disability Index, and prevalence and severity of ASP on lumbar spine magnetic resonance imaging 2 years postoperatively compared with preoperative images.

METHODS

We compared baseline data for the two groups studied. To evaluate the effects of GJL on the outcome of PLIF, we also compared outcome measures between the two groups. No funds were received in support of this work.

RESULTS

Successful fusion 2 years after surgery was achieved in 91.9% of patients in Group A and 91.8% of patients in Group B according to dynamic radiographs (p=.85) and in 86.5% of patients in Group A and 90% of patients in Group B according to computed tomography scans (p=.14). Secondary endpoints including pain intensity (visual analog scale) and Oswestry Disability Index scores were not significantly different between the two groups (p=.71 and .86, respectively). Adjacent segment pathology was present in both the superior and inferior adjacent segments in both groups and was not significantly different (p=.07 and .06, respectively), although severe degeneration that was greater than Grade III on modified Pfirrmann classification was more frequently observed in Group A (15 of 37, 40.5%, at the superior segment and 11 of 20, 55%, at the inferior segment) than in Group B (60 of 219, 27.4%, at the superior segment and 30 of 111, 27%, at the inferior segment), which was statistically significant (p=.02 and .01, respectively). Moreover, ASP was more prominent at the superior adjacent segment compared with the inferior adjacent segment and was most commonly observed at the inferior adjacent segment (L5-S1) after L4-L5 PLIF and the superior adjacent segment (L4-L5) after L5-S1 PLIF (p=.02 and .03, respectively).

CONCLUSIONS

Generalized joint laxity at baseline does not impact fusion rate or clinical outcome with respect to pain intensity or functional status but could negatively impact ASP compared with that in patients without GJL. Consequently, GJL should be evaluated preoperatively, and patients with GJL undergoing PLIF should be informed of the potential risks of surgery.