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  • Author or Editor: Hiroshi Moridaira x
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Makoto Ohe, Hiroshi Moridaira, Satoshi Inami, Daisaku Takeuchi, Yutaka Nohara, and Hiroshi Taneichi

OBJECTIVE

Instrumentation failure caused by the loosening of pedicle screws (PSs) in patients with osteoporosis is a serious problem after spinal surgery. The addition of a thin hydroxyapatite (HA) surface coating applied by using a sputtering process was reported recently to be a promising method for providing bone conduction around an implant without a significant risk of coating-layer breakage. In this study, the authors evaluated the biomechanical and histological features of the bone-implant interface (BII) of PSs with a thin HA coating in an in vivo porcine osteoporotic spine model.

METHODS

Three types of PSs (untreated/standard [STPS], sandblasted [BLPS], and HA-coated [HAPS] PSs) were implanted into the thoracic and lumbar spine (T9–L6) of 8 mature Clawn miniature pigs (6 ovariectomized [osteoporosis group] and 2 sham-operated [control group] pigs). The spines were harvested from the osteoporosis group at 0, 2, 4, 8, 12, or 24 weeks after PS placement and from the control group at 0 or 24 weeks. Their bone mineral density (BMD) was measured by peripheral quantitative CT. Histological evaluation of the BIIs was conducted by performing bone volume/tissue volume and bone surface/implant surface measurements. The strength of the BII was evaluated with extraction torque testing.

RESULTS

The BMD decreased significantly in the osteoporosis group (p < 0.01). HAPSs exhibited the greatest mean extraction peak torque at 8 weeks, and HAPSs and BLPSs exhibited significantly greater mean torque than the STPSs at 12 weeks (p < 0.05). The bone surface/implant surface ratio was significantly higher for HAPSs than for STPSs after 2 weeks (p < 0.05), and bonding between bone and the implant surface was maintained until 24 weeks with no detachment of the coating layer. In contrast, the bone volume/tissue volume ratio was significantly higher for HAPSs than for BLPSs or STPSs only at 4 weeks.

CONCLUSIONS

Using PSs with a thin HA coating applied using a sputtering process strengthens bonding at the BII, which might improve early implant fixation after spinal surgery for osteoporosis. However, the absence of increased bone mass around the screw remains a concern; prescribing osteoporosis treatment to improve bone quality might be necessary to prevent fractures around the screws.

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Hiroshi Taneichi, Kota Suda, Tomomichi Kajino, Akira Matsumura, Hiroshi Moridaira, and Kiyoshi Kaneda

Object

There are no published reports of unilateral transforaminal lumbar interbody fusion (TLIF) in which two Brantigan I/F cages were placed per level through a single portal to achieve bilateral anterior-column support. The authors describe such a surgical technique and evaluate the clinical outcomes of this procedure.

Methods

Data obtained in 86 (93.5%) of the first 92 consecutive patients who underwent the procedure were retrospectively reviewed; the minimum follow-up duration was 2 years. The clinical outcomes were evaluated using the Japanese Orthopaedic Association (JOA) scoring system. Disc height, disc angle, cage positioning in the axial plane, and fusion status were radiographically evaluated.

The mean follow-up period was 33.8 months. The mean improvement in the JOA score was 77.2%. Fusion was successful in 93% of the cases. According to the Farfan method, the mean anterior and posterior disc heights increased from 20.2 and 16.9% preoperatively to 35.9 and 22.7% at follow up, respectively (p < 0.01). The mean disc angle increased from 4.8° preoperatively to 7.5° at last follow-up examination (p < 0.01). Two cages were correctly placed to achieve bilateral anterior-column support in greater than 85% of the cases. The following complications occurred: hardware migration in two patients and deep infection cured by intravenous antibiotic therapy in one patient.

Conclusions

Unilateral TLIF involving the placement of two Brantigan cages per level led to good clinical results. Two Brantigan cages were adequately placed via a single portal, and reliable bilateral anterior-column support was achieved. Although the less invasive unilateral approach was used, the outcomes were as good as those in many reported series of posterior lumbar interbody fusion in which the Brantigan cages were placed via the bilateral approach.