Bone dowels in anterior lumbar interbody fusion

Since the Food and Drug Administration approved the Babgy-Kuslich BAK cage for anterior lumbar interbody fusion (ALIF), various threaded interbody fusion devices have been introduced. Bone dowels offer several theoretical advantages over cages with regard to stress shielding; the purpose of this study was to assess the efficacy of bone dowels in interbody fusion. All patients undergoing ALIF performed by the senior author between 1998 and 2001 were retrospectively reviewed. Patients' preoperative and postoperative neurologic status, functional status, and both back and radicular pain were assessed according to a previously published outcome measure. Between 1998 and 2000, 23 patients underwent ALIF with cortical femoral allograft bone dowels. One patient underwent simultaneous bone dowel and titanium cage placements and was therefore excluded from further analysis. The 22 remaining patients underwent a total of 33 fused segments; of these, 21 patients were available for follow-up. Mean clinical follow-up was 30.6 months. Mean imaging follow-up was 21 months. There were 5 instances of radiographic nonunion (3 symptomatic and 2 asymptomatic). The incidence of technical failures and complications related to the bone dowels was 17%. Bone dowels failed and caused symptoms only in patients with a stand-alone ALIF. There were no clinical failures in patients treated with supplemental anterior or posterior spinal fixation. These data demonstrate that marginal fusion rates and functional success rates can be achieved using stand-alone bone dowels for ALIF. The clinical success and fusion rates are significantly higher if ALIF dowels are shielded from stress with rigid spinal instrumentation.     

Anterior lumbar interbody fusion with osteoinductive growth factors

Anterior intervertebral fusion increasingly is used as a treatment for discogenic or intersegmental pathologic diseases of the lumbar spine. This is in part attributable to the evolution and refinement of laparoscopic and minimally invasive surgical techniques that now can be used to access the anterior spinal column. It also is attributable to the availability of newer generation intervertebral fixation devices such as the threaded titanium cages or threaded allograft bone dowels, both of which are technically simpler to implant. Recently, limited clinical studies of intervertebral lumbar fusion have examined the use of these devices combined with osteoinductive growth factors as substitutes for autogenous bone graft. Early clinical results of lumbar fusion using threaded intervertebral implants filled with recombinant human bone morphogenetic protein-2 have been favorable. Higher fusion rates, shorter operative times, and shorter hospital stays have been reported in the initial series. Clinical trials involving larger cohorts with various spinal applications for osteoinductive molecules currently are in progress.     

Use of rhBMP-2 in combination with structural cortical allografts: clinical and radiographic outcomes in anterior lumbar spinal surgery

BACKGROUND: Recombinant human bone morphogenetic protein-2 soaked into an absorbable collagen sponge (rhBMP-2/ACS) has been shown in a nonhuman primate study and in a pilot study in humans to promote new bone formation and incorporation of an allograft device when implanted in patients undergoing anterior lumbar interbody arthrodesis. However, a larger series with longer follow-up is needed to demonstrate its superiority to autogenous iliac crest bone graft. METHODS: Between 1998 and 2001, a two-part, prospective, randomized, multicenter study of 131 patients was conducted to determine the safety and efficacy of the use of rhBMP-2/ACS as a replacement for autogenous iliac crest bone graft in anterior lumbar spinal arthrodesis with threaded cortical allograft dowels. Patients were randomly assigned to a study group that received rhBMP-2/ACS or to a control group that received autograft. The clinical and radiographic outcomes were determined with use of well-established instruments and radiographic assessments. RESULTS: The patients in the study group had significantly better outcomes than the control group with regard to the average length of surgery (p < 0.001), blood loss (p < 0.001), and hospital stay (p = 0.020). Fusion rates were significantly better in the study group (p < 0.001). The average Oswestry Disability Index scores, Short-Form-36 physical component summary scores, and low-back and leg-pain scores were significantly better in the study group (p < 0.05). CONCLUSIONS: In patients undergoing anterior lumbar interbody arthrodesis with threaded allograft cortical bone dowels, rhBMP-2/ACS was an effective replacement for autogenous bone graft and eliminated the morbidity associated with graft harvesting.     

Radiographic fusion rate after implantation of facet bone dowels

Background contextAchieving a posterolateral fusion in conjunction with performing decompressive laminectomies can prevent recurrence of stenosis or worsening of spondylolisthesis. Facet bone dowels have been introduced and marketed as a less invasive alternative to pedicle screws. Surgeons have been placing them during lumbar laminectomy surgery and coding for intervertebral biomechanical device and posterolateral fusion. These bone dowels have also been placed percutaneously in outpatient surgery centers and pain clinics for facet-mediated back pain.PurposeTo describe fusion outcomes in patients who underwent facet bone dowel placement.Study design/settingRetrospective analysis of a single center's experience.Patient sampleNinety-six patients comprise the entire cohort of patients who underwent facet bone dowel implantation at our institution with adequate postoperative imaging to determine fusion status.Outcome measuresFusion rates as determined on postoperative computed tomography (CT) scans and dynamic lumbar X-rays if CT is not available.MethodsThreaded facet bone dowels in this study were placed according to the manufacturer's recommended methods. The bone dowels were placed after open exploration of the facet complex or percutaneously through a tubular retractor on the contralateral side from a microdiscectomy or synovial cyst resection. The most recent available postoperative imaging was reviewed to determine fusion status.ResultsOf 96 patients in our series, 6 (6.3%) had a fusion seen on CT and 4 did not exhibit any movement on dynamic lumbar X-rays for a total fusion rate of 10.4% (10/96). Eighty-six (89.6%) patients were shown on imaging to not have a solid fusion either by visualizing a patent facet joint on CT or measurable movement between the flexion and the extension lumbar X-rays.ConclusionsThis article is mainly intended to question whether the implantation of facet bone dowels can produce a solid fusion radiographically. In our experience, the placement of facet bone dowels does not equal the time, skill, or attention to detail that is necessary for a posterolateral lumbar arthrodesis, and our follow-up radiographic studies clearly demonstrate an inadequate fusion rate.     

Anterior lumbar microdiscectomy and interbody fusion for the treatment of recurrent disc herniation

OBJECTIVE: To demonstrate the feasibility of anterior lumbar microdiscectomy in patients with recurrent, sequestered lumbar disc herniations. METHODS: Between 1997 and 1999, six patients underwent a muscle-sparing "minilaparotomy" approach and subsequent microscopic anterior lumbar microdiscectomy and fragmentectomy for recurrent lumbar disc extrusions at L5-S1 (n = 4) or L4-L5 (n = 2). A contralateral distraction plug permitted ipsilateral discectomy under microscopic magnification. Effective resection of the extruded disc fragments was accomplished by opening the posterior longitudinal ligament. Interbody fusion was performed by placing cylindrical threaded titanium cages (n = 4) or threaded allograft bone dowels (n = 2). RESULTS: There were no complications, and blood loss was minimal. Follow-up magnetic resonance imaging revealed complete resection of all herniated disc material. Plain x-rays revealed excellent interbody cage position. Radicular pain and neurological deficits resolved in all six patients (mean follow-up, 14 mo). CONCLUSION: Anterior lumbar microdiscectomy with interbody fusion provides a viable alternative for the treatment of recurrent lumbar disc herniations. Recurrent herniated disc fragments can be removed completely under direct microscopic visualization, and interbody fusion can be performed in the same setting.     

Advances in Spinal Interbody Cages

Since the late 1980s, spinal interbody cages (ICs) have been used to aid bone fusion in a variety of spinal disorders. Utilized to restore intervertebral height, enable bone graft containment for arthrodesis, and restore anterior column biomechanical stability, ICs have since evolved to become a highly successful means of achieving fusion, being associated with less postoperative pain, shorter hospital stay, fewer complications and higher rates of fusion when than bone graft only spinal fusion. IC design and materials have changed considerably over the past two decades. The threaded titanium‐alloy cylindrical screw cages, typically filled with autologous bone graft, of the mid‐1990s achieved greater fusion rates than bone grafts and non‐threaded cages. Threaded screw cages, however, were soon found to be less stable in extension and flexion; additionally, they had a high incidence of cage subsidence. As of the early 2000s, non‐threaded box‐shaped titanium or polyether ether ketone IC designs have become increasingly more common. This modern design continues to achieve greater cage stability in flexion, axial rotation and bending. However, cage stability and subsidence, bone fusion rates and surgical complications still require optimization. Thus, this review provides an update of recent research findings relevant to ICs over the past 3 years, highlighting trends in optimization of cage design, materials, alternatives to bone grafts, and coatings that may enhance fusion.     

Cervical interbody fusion using calf bone

Since 1972, Kiel Surgibone (calf bone) dowels have been inserted in the cervical intervertebral space of 221 patients. The anterior approach was used for cervical interbody fusion. Fusion occurred in every patient who survived long enough for it to occur. No complications occurred that specifically could be attributed to use of this type of grafting material. Kiel Surgibone has the advantage of eliminating the need for osteotomy when autologous bone is used or for a bone bank when homologous bone is employed. Kiel Surgibone is supplied sterile and is precisely preshaped.     

Torque load and types of fractures of threaded holes in cortical bone by lag screw. Mechanic and histological studies (author's transl)]

For the better understanding of fracture fixation by means of screws the torque load and types of fractures from threaded screw holes in cortical bone were studied. The experiments were performed on sheep tibia and femora in vitro and in vivo. We applied the 4.5 mm cortical bone screw (AISF) as lag screw. The screw was threaded in until total destruction of the thread occurred. The process of torque load was registered as a torque-angle of twist curve with 4 typical parts. Histologically in most cases shear fractures with different geometry occurred. In some cases we found conical geometric, and in others cylindrical geometric fragments in the threaded screw holes. The value of the torque at which destruction of a threaded hole occurs is a linear function of the thickness of the cortical bone. The gradient of this linear function is 6.6 kpcm/mm. In practical case, the insertional torque may be estimated by multiplying the cortical bone thickness in mm (if known) by a factor 4.     

A cost analysis of bone morphogenetic protein versus autogenous iliac crest bone graft in single-level anterior lumbar fusion

An economic model was developed to compare costs of stand-alone anterior lumbar interbody fusion with recombinant human bone morphogenetic protein 2 on an absorbable collagen sponge versus autogenous iliac crest bone graft in a tapered cylindrical cage or a threaded cortical bone dowel. The economic model was developed from clinical trial data, peer-reviewed literature, and clinical expert opinion. The upfront price of bone morphogenetic protein (3380 dollars) is likely to be offset to a significant extent by reductions in the use of other medical resources, particularly if costs incurred during the 2 year period following the index hospitalization are taken into account.     

Allograft implants for posterior lumbar interbody fusion: results comparing cylindrical dowels and impacted wedges

OBJECTIVE: With the proliferation of implant types available for use in posterior lumbar interbody fusion (PLIF) procedures, the choices for surgeons have become increasingly complex. The goal of this study was to retrospectively review a series of 49 patients who underwent PLIF with the use of allograft cylindrical threaded cortical bone dowels (TCBDs) and allograft impacted wedges. Nerve root injury rates, fusion rates, and clinical outcomes of the allograft impacted wedge group are compared with those in the allograft cylindrical TCBD group. METHODS: We performed a retrospective chart and radiographic review of 49 patients. Twenty-seven patients underwent PLIF with impacted allograft wedges, and 22 patients underwent PLIF with allograft cylindrical TCBD. Permanent nerve root injury rates, fusion rates, and clinical outcomes were assessed on the basis of a minimum of 1 year of follow-up data in this nonconsecutive series. RESULTS: Permanent nerve root injuries in the impacted wedge and TCBD groups were documented with physical examinations conducted pre- and postoperatively. The cylindrical TCBD group showed a 13.6% rate of permanent nerve root injury, and the impacted wedge group demonstrated a 0% rate, and these rates were statistically significant (analysis of variance, P = 0.049). The fusion rate at a mean of 13.9 months of follow-up was 95.4% in patients in whom the cylindrical TCBD was implanted and 88.9% after a mean of 17.4 months of follow-up in patients in whom impacted wedges were used. The fusion rate difference between the TCBD and impacted wedge groups was not significant. The satisfactory outcome rate was 72.7% for the TCBD group and 85.1% for the impacted wedge group, and the impacted wedge group was found to have a significantly higher rate of satisfactory outcomes (P = 0.016, analysis of variance). Analysis of the patient outcomes in the TCBD and impacted wedge groups according to sex, mean length of follow-up, workman's compensation claim rate, and smoking habit yielded no significant difference. CONCLUSION: With a minimum of 1 year of follow-up in this nonconsecutive series of 49 patients, a comparison of the use of allograft TCBD versus allograft impacted wedges in PLIF procedures reveals a statistically significant increase in permanent nerve root injury rates with the use of cylindrical TCBD implants as compared with impacted allograft wedges. There is no difference between the two groups in terms of fusion rates, and clinical outcomes with the use of impacted wedges were significantly better.     

Segmental cement extraction at revision total hip arthroplasty.

Cement removal in revision total hip arthroplasty can be technically challenging. Traditional methods involve using a combination of chisels, power burrs, and drills, as well as windowing the femoral cortex to gain access to cement distally. These methods can be associated with femoral fracture or uncontrolled cortical perforation and bone loss. A new technique had been developed that permits segmental extraction of bone cement from the femoral canal. Fresh cement is introduced into the old cement mantle and a threaded rod is placed into the wet cement and held in place while the cement hardens. The thread-forming rod is then removed leaving a threaded channel in the cement. Extraction rods are then screwed 1.5 to 2.5 cm into the threaded channel. A slap hammer, which attaches to the opposite end of the extraction rod, is used to remove 1.5- to 2.5-cm segments of cement. Fifteen cases involving revision of cemented femoral components were analyzed using this system. Complete cement removal was achieved in 12 cases with much less damage to the femur when compared with conventional methods. In two cases, there was retained cement along the medial wall of the femur and, in one case, the plug could not be extracted using this system. There were no fractures or cortical perforations in this series.     

Editorial Commentary: It is Never Wrong to Perform Anterior Cruciate Ligament Revision Reconstruction as a Two-Stage Procedure

Revision anterior cruciate ligament (ACL) reconstruction can be performed in a single surgery, but in some instances, it requires 2 stages to get it right. The most common reasons for staged reconstruction include dilated bone tunnels on the tibial or femoral side (>13 mm), imperfectly placed bone tunnels that cannot be reused but cannot be avoided, and/or the need to combine the revision ACL reconstruction with meniscus and/or cartilage allograft transplantation. In my practice, we use prefabricated bone dowels, sizing up 0.5 to 1 mm relative to the size of the tunnel (after debridement) for both the femoral side and tibial side. The benefits are efficiency and reproducibility, while the challenges include cost and the potential need for multiple dowels if the prefabricated dowels are not long enough. We will occasionally add demineralized bone matrix, particularly on the tibial side, in the event that there is <5 mm of unfilled tunnel using the bone dowel. We wait ∼3 months before proceeding to the second stage using only plain radiographs to assess healing (advanced imaging such as computed tomography scan is not routinely used). We have also begun to push the limits of single-stage revision reconstruction, using dowels in a single setting. No matter what, it is never wrong to perform ACL revision reconstruction as a 2-stage procedure. When performed for the appropriate indications, outcomes tend to be good, regardless of the chosen technique.     

Accelerating lumbar fusions by combining rhBMP-2 with allograft bone: a prospective analysis of interbody fusion rates and clinical outcomes.

BACKGROUND CONTEXT: Recombinant human bone morphogenetic protein-2 (rhBMP-2) is an osteoinductive protein approved for use in the anterior lumbar interspace. High fusion rates with rhBMP-2 have been reported with threaded interbody allograft dowels. There may be a clinical benefit for the patient by adding rhBMP-2 to the allograft. PURPOSE: To compare the fusion rates and clinical outcomes of patients treated with allograft interbody fusions with and without the addition of rhBMP-2. STUDY DESIGN: Prospective consecutive patient enrollment with minimum 24-month follow-up. PATIENT SAMPLE: Seventy-five patients with lumbar interbody fusions at 1-3 spinal segments. OUTCOMES MEASURES: Clinical: Numerical Rating Scale (NRS) and Oswestry Disability Index (ODI). Radiographic: X-ray and computed tomographic scan analysis using the Molinari-Bridwell fusion scale. METHODS: Seventy-five patients scheduled for lumbar fusion were enrolled sequentially. Group 1: 30 patients had anterior interbody allografts alone. Group 2: 45 patients had anterior interbody allograft filled with rhBMP-2. All cases had posterior pedicle screw instrumentation. A total of 165 surgical levels (62 allograft alone/103 allograft+BMP) were included. Fusion data and clinical outcomes were collected for a minimum of 2 years after surgery. RESULTS: Statistically higher fusion rates were observed in the patients with BMP at all time points compared with allograft alone. Group 2 (+ BMP) fusion rates were 94%, 100%, and 100% at 6, 12, and 24 months after surgery. Group 1 (-BMP) fusion rates were 66%, 84%, and 89% at the same time intervals. Clinical outcomes were significantly improved in Group 2 compared with Group 1 at 6 months. There were no revisions (0%) in the BMP group and 4 revision fusion surgeries (13%) in the allograft group. No untoward effects were attributable to the rhBMP-2. CONCLUSIONS: Our study confirms the efficacy of an innovative lumbar fusion technique: an interbody femoral ring allograft, combined with an osteoinductive stimulant (rhBMP-2), protected by pedicle screws. This combination of a structural interbody allograft with rhBMP-2 eliminates the insult of iliac crest harvest, allows for reliable radiographic analysis, and results in successful fusion formation in 100% of the cases in this study.     

Unilateral posterior lumbar interbody fusion: simplified dowel technique

Two hundred sixteen patients were treated by a simplified unilateral posterior lumbar interbody fusion (U-PLIF) in which the disc was removed and replaced by bone. The disc was approached far laterally by removing two-thirds of the superior facet preserving most of the ligamentum flavum, removing the disc, decorticating in a semicircular fashion the adjacent vertebral bodies unilaterally close to the midline, and packing the anterior one-fourth of the interspace with cancellous bone chips. The bone chips were covered with up to five half-thickness bone dowels. Consolidation of the fusion and stabilization of the motion segment of Junghanns from either the cephalad or caudal end of the bone grafts were verified by motion roentgenographic films, CT scans, and/or examinations during the follow-up period, which ranged from 16 years to a minimum of one year. Of the 34 cases selected for CT scan, 25 had lateral reconstruction performed, and solid unilateral fusion was confirmed in 21 cases (84%). The advantages of the unilateral approach include an intact ligamentum flavum overlying nerve roots.     

Anterior vertebral screw strain with and without solid interspace support

STUDY DESIGN: This in vitro biomechanical study examines segmental anterior vertebral screw strain and solid rod construct stiffness with and without the addition of multilevel, threaded cortical bone dowels in a bovine model. OBJECTIVE: To determine whether strain at the bone-screw interface is higher at the end levels during physiologic range loading, and whether solid interspace support decreases segmental strain on the implant. SUMMARY OF BACKGROUND DATA: Anterior instrumentation provides greater correction and preserves distal motion segments. However, nonunion and implant failure are observed more frequently than with posterior segmental instrumentation, and when observed, loss of fixation occurs at the end levels. METHODS: Eight calf spines underwent mechanical testing in the following sequence: 1) intact condition, 2) anterior release with anterior solid rod and bicortical rib grafts, and 3) anterior release with anterior solid rod and threaded cortical bone dowels (L2-L5). Instrumented vertebral screws were used to assess strain within the vertebral body by the near cortex, whereas an anterior extensometer spanning the instrumented segments was used to measure segmental displacements to calculate construct stiffness. The protocol included axial compression (-400 N), right lateral bending (4 Nm (Newton-meter), away from the implant), and left lateral bending (4 Nm, toward the implant). Statistical analysis included a one-way analysis of variance and a Student-Newman-Keuls post hoc test. A pilot study was performed using four additional specimens loaded for 4000 cycles to investigate macroscopic loosening after fatigue loading. RESULTS: In lateral bending toward the implant, the strain was higher at both end levels, with no differences between the rib and dowel reconstructions. The stiffness values were greater than the intact values for both groups. In lateral bending away from the implant, the strain also was higher at both end screws, and the dowel group had less strain at these levels than the rib group. Both groups were stiffer than the intact condition, and the dowel group was stiffer than the rib group. Axial compressive strain also was higher at the end levels, but this difference did not reach statistical significance. The rib group did not reach intact stiffness values, whereas the dowel group was stiffer than the intact condition. The fatigue study showed gross loosening at one or both end levels in all cases. CONCLUSIONS: Higher strain was observed at the bone-screw interface in both end screws of an anterior solid rod construct during lateral bending, which correlates with the clinically observed failure location. This suggests that physiologic range loading may predispose to failure at the end levels. Disc space augmentation with solid implants increased construct stiffness in all three load paths and decreased strain at the end levels in lateral bending away from the implant. Future implant modifications should achieve better fixation at the end screws, and the current model provides a means to compare different strategies to decrease strain at these levels.     

Finite element analysis of acetabular reconstruction. Noncemented threaded cups

The load-transfer mechanism and stress patterns in the acetabulum reconstructed with a threaded cup were investigated relative to the normal hip using the Finite Element Method (FEM). Several models were applied in the analysis to investigate the effects of axisymmetric 3-D versus 2-D approaches, inclusion of the femoral head, and local stress patterns around the threads in three types of implant/bone bonding modes. It was found that the threaded ring behaves as a relatively rigid implant shielding the trabecular bone and enhancing load transfer through the cortical shells. Load transfer from ring to bone is concentrated at the first and last threads where the subchondral bone layer is penetrated. Stress peaks of up to 24 MPa occur in these regions.     

Finite element analysis of acetabular reconstruction: Noncemented threaded cups

The load-transfer mechanism and stress patterns in the acetabulum reconstructed with a threaded cup were investigated relative to the normal hip using the Finite Element Method (FEM). Several models were applied in the analysis to investigate the effects of axisymmetric 3-D versus 2-D approaches, inclusion of the femoral head, and local stress patterns around the threads in three types of implant/bone bonding modes. It was found that the threaded ring behaves as a relatively rigid implant shielding the trabecular bone and enhancing load transfer through the cortical shells. Load transfer from ring to bone is concentrated at the first and last threads where the subchondral bone layer is penetrated. Stress peaks of up to 24 MPa occur in these regions.     

Effect of surgical fit on integration of cancellous bone and implant cortical bone shear strength for a porous titanium

Porous scaffold dowels of Ti₆Al₄V were prepared and implanted into cancellous and cortical bone sites in adult sheep. Cancellous implants were examined under gap, line-to-line, and press-fit conditions, whereas line-to-line implantation was used in cortical sites. Cortical shear strength increased significantly with time and reached 26.1 ± 8.6 MPa at 12 weeks, accompanied by a concomitant increase in bone integration and remodeling. In cancellous sites, bone integration was well established at 4 and 12 weeks under conditions of press-fit and line-to-line match between implant and surgical defect. New bone growth was also found in the gap conditions, although to a lesser extent. These findings suggest that the porous Ti₆Al₄V could prove an effective scaffold material for uncemented fixation in cortical and cancellous sites.     

Posterolateral lumbar spine fusion with INFUSE bone graft.

BACKGROUND CONTEXT: INFUSE has been proven effective in conjunction with threaded cages and bone dowels for single-level anterior lumbar interbody fusion (ALIF). The published experience with posterolateral fusion, although encouraging, utilizes a significantly higher dose and concentration of recombinant human bone morphogenic protein-2 (rhBMP-2) and a different carrier than the commercially available INFUSE. PURPOSE: To present an assessment of fusion rate for posterolateral spine fusion with INFUSE Bone Graft. STUDY DESIGN/SETTING: Retrospective review of patients treated using INFUSE in posterolateral spine fusion in a single institution. PATIENT SAMPLE: 91 patients with minimum 2-year follow-up who underwent posterolateral spine fusion using INFUSE as an iliac crest bone graft (ICBG) substitute. OUTCOME MEASURES: Fusion rate based on fine-cut computed tomographic (CT) scans with sagittal and coronal reconstructions. METHODS: Fusion was performed using one large INFUSE kit (12 mg rhBMP-2, 1.5 mg/mL), which was prepared according to the manufacturer's instructions. The INFUSE sponge was wrapped around the local bone or graft extender and placed over the decorticated surfaces in the lateral gutters. Postoperative CT scans with reconstructions were reviewed by two independent orthopedic spine surgeons. CT scans of a comparison group of 35 patients who underwent primary single-level posterolateral fusion with ICBG were also reviewed. RESULTS: The overall group had a mean 4.38 CT fusion grade and a 6.6% nonunion rate. Primary one-level fusion cases (n=48) had a mean 4.42 fusion grade a 4.2% nonunion rate. Primary multilevel fusions (n=27) had a mean 4.65 CT grade and no nonunions detected. Assessment of the 35 primary one-level ICBG control cases demonstrated a mean CT grade of 4.35 and a nonunion rate of 11.4%. In the 16 cases of revision for prior nonunion, mean CT grade was 3.81 and 4 subjects had nonunions. Additional subgroup analysis showed that smokers (n=14) had a mean 4.32 CT grade with no nonunions. Men had a mean 4.04 CT grade and an 11.1% nonunion rate compared with a mean 4.61 CT grade and 3.6% nonunion rate in women. This difference was statistically significant (p=.036). No significant differences in fusion rate were observed based upon the specific graft extender used (p=.200). CONCLUSIONS: Posterolateral spine fusion involves a more difficult healing environment with a limited surface for healing, a gap between transverse processes and the milieu of distractive forces. Historically, only ICBG has been able to overcome these challenges and reliably generate a successful posterolateral lumbar spine fusion. In contrast to prior studies, clinically available INFUSE delivers only 12 mg rhBMP-2 at a concentration of 1.5 mg/mL. Despite the lower dose and concentration of rhBMP-2, this study suggests that fusion success with INFUSE is equivalent to ICBG for posterolateral spine fusion. As with ICBG, development of solid fusion or nonunion is a multifactorial process. The use of INFUSE is not a substitute for proper surgical technique or optimization of patient-related risk factors. Additional studies are needed to determine the incremental benefit of a greater rhBMP-2 dose or use of alternative carriers for posterolateral fusion. Finally, correlation between radiographic findings and clinical outcomes, and a cost-benefit analysis are needed. Despite these issues, this study presents compelling evidence that commercially available INFUSE is an effective ICBG substitute for one- and two-level posterolateral instrumented spine fusion.     

The use of free, mainly cancellous bone grafts for reconstruction of phalanges and metacarpal bones following tumour resection

Neoplasms of the hand frequently require amputation which is associated with significant disability and disfigurement. Although reconstruction using autologous cortical bone grafts has been performed in such cases, bone resorption is a common problem and allogeneic bone may be required to fill large defects. Reconstruction using cancellous bone is an alternative technique that we have developed to overcome the limitations of cortical grafts. Here, we present five cases of bone tumours of the hand which have undergone reconstruction using a cancellous bone grafting technique.