Mechanical properties of bone after grafting with coralline hydroxyapatite: an experimental study

Implantable Materials Update

There are a variety of materials available for surgical reconstruction of the foot and ankle. The material that provides the best physical properties to match the mechanical stress should be chosen. Ideal implant material should be biocompatible, nontoxic, noncarcinogenic, nonpyrogenic, and nonallergenic. Key properties include strength, durability, and resistance to fatigue. The material should have ductility to provide continued strength once it has been adapted to the bone surface. The material should be readily available, affordable, and reproducible. Materials that are available for use are stainless steel, cobalt chrome alloys, titanium and titanium alloys, pyrolytic carbon, thermoplastics, and bioceramics.

Coralline hydroxyapatite and laminectomy-derived bone as adjuvant graft material for lumbar posterolateral fusion

OBJECT

The purpose of this study was to evaluate the effectiveness of coralline hydroxyapatite (CHA) and laminectomy-derived bone as an adjuvant graft material when combined with autogenous iliac bone graft (AIBG) in posterolateral fusion (PLF).

METHODS

This prospective, case-control study involved 58 patients who underwent lumbar instrumentation-augmented PLF for degenerative spinal stenosis-induced segmental instability between July 2000 and June 2001. The patients were divided into three groups. Laminectomy bone and AIBG were placed in the right intertransverse process space in Group 1 (20 patients), CHA and AIBG were placed in Group 2 (19 patients), and laminectomy bone and CHA were placed in Group 3 (19 patients). Pure autogenous iliac cancellous bone graft was placed in the left intertransverse process space in all three groups of patients. Successful fusion was determined by two spine surgeons after examining the plain, anteroposterior, bilateral oblique, and lateral flexion-extension radiographs. If the examiners did not agree on fusion status, fine-cut computerized tomography scans of the fusion mass were used to make the final decision. The chi-square test was used to compare the fusion rate at different time intervals among the three groups.

CONCLUSIONS

Pure AIBG placed in left intertransverse process space was associated with the best fusion rate. After 6 months, CHA produced a comparable result to laminectomy-derived bone when combined with AIBG. When laminectomy bone was mixed with CHA, the combination failed to yield a satisfactory fusion rate (57.9%) even 1 year after surgery if no AIBG was added.

Bone graft substitutes: osteobiologics

Future devolvement of osteobiologic materials will no doubt replace materials currently being used. As techniques to improve biointegration and manipulation of the healing environment proceed, future graft substitutes may exceed even autogenous bone in their reliability. The primary role of bone graft use in foot and ankle surgery has been to fill traumatic defects and benign tumors or to augment arthrodesis techniques. This article highlights the osteobiologics in use today, including calcium-based ceramics, hydroxyapatite, calcium phosphates and calcium composite materials, collagen composite materials, calcium sulfate, calcium cements, and allograft.

Anterior lumbar interbody fusion with processed sea coral (coralline hydroxyapatite) as part of a circumferential fusion

STUDY DESIGN

A retrospective review of 20 patients undergoing circumferential lumbar fusion with coralline hydroxyapatite blocks anteriorly and autograft with transpedicular or translaminar facet screw fixation posteriorly.

OBJECTIVES

To examine the efficacy of coralline hydroxyapatite as a bone graft substitute for anterior lumbar interbody fusion.

SUMMARY OF BACKGROUND DATA

Autograft is the gold standard for bone grafting in the anterior lumbar spine. Harvesting bone from the iliac crest leads to significant postoperative pain and morbidity. Femoral ring allograft is a widely used alternative to autograft but has some inherent problems. Coralline hydroxyapatite was shown to be 100% successful for anterior cervical fusion when combined with rigid plating.

METHODS

A retrospective review of 20 patients with low back pain and indicated for surgical intervention. A circumferential instrumented fusion was performed with coralline hydroxyapatite blocks anteriorly and transpedicular or translaminar facet fixation and autograft posteriorly. All patients reached a minimum 3-year clinical and radiologic follow-up.

RESULTS

Radiographic follow-up yielded a solid arthrodesis rate of 93.8% by level (30 of 32 disc spaces) and 90% by patient (18 of 20). Clinical follow-up generated a mean pain reduction of 61.8% with clinical success demonstrated in 80% (16 of 20) of all patients who reported good or excellent pain relief. Eight of 12 (66.7%) patients employed before surgery returned to work in some capacity.

CONCLUSIONS

Coralline hydroxyapatite is a practicable anterior lumbar interbody fusion alternative to autograft and allograft as part of a circumferential fusion with rigid posterior fixation. It is not recommended for stand-alone anterior lumbar interbody fusion without further study.

Supplementation of autogenous bone graft with coralline hydroxyapatite in posterior spine fusion for idiopathic adolescent scoliosis

Twenty-seven consecutive patients with adolescent idiopathic scoliosis underwent posterior spinal fusion with pediatric Texas Scottish Rite Hospital instrumentation. Coralline hydroxyapatite (Interpore, Irvine, Calif) was mixed with limited autograft from posterior iliac crest (an approximate 70/30 ratio of coralline hydroxyapatite to autograft). Patient evaluation was based on clinical and radiographic findings. On initial radiographic evaluation, a "snowstorm" appearance consistent with the exoskeleton of the coralline hydroxyapatite was observed. After two years, the fusion mass had a "marble-like" appearance with distinct decreased visibility of the disk spaces in the fusion mass. This latter stage of "marbilization correlated with solid fusion clinically. All patients achieved solid fusion at an average follow-up of 27 months. Coralline hydroxyapatite is safe, biocompatible, and effective in augmenting autogenous bone graft in the treatment of idiopathic adolescent scoliosis with posterior spinal fusion. In addition to decreased donor site morbidity, this may be invaluable in cases where there is insufficient autograft available.

Modern issues in bone graft substitutes and advances in bone tissue technology

Autogenous bone grafting is the gold standard in repair of bony defects, fracture nonunion, and promoting arthrodesis. The complications related to obtaining autogenous grafts can be significant, and numerous materials are now available for augmentation or substitution. Allograft materials are highly effective for most applications; however, the surgeon needs to be acutely aware of the source of the tissue, for some tissue banks still use unacceptable processing techniques that destroy the structural and osteoinductive capacities of the graft. DBM products are unregulated and serious concerns exist as to the distribution of inactive products as commercially available to the practicing surgeon. Pressure from the orthopedic community has caused some manufacturers to test their products for activity before distribution. Calcium-based ceramic materials are effective as osteoconductive agents and work well alone as bone void fillers; however, augmentation of these implants with osteoinductive materials should be considered for use in nonunions and arthrodesis. Composite materials that incorporate osteoinductive materials in osteoconductive scaffolds are promising. New technology in isolation and creation of recombinant human bone morphogenic proteins and growth factors, and in the application of autogenous stem cells are emerging as the future of bone grafting procedures.

Anterior lumbar interbody fusion with titanium mesh cages, coralline hydroxyapatite, and demineralized bone matrix as part of a circumferential fusion

BACKGROUND CONTEXT

Anterior lumbar interbody fusion (ALIF) has become one of the primary choices for eliminating motion between vertebral segments in patients with severe discogenic pain and other lumbar pathologies. Autograft is the gold standard for spinal fusion. However, multiple authors have reported complication and morbidity rates associated with iliac crest harvesting to be as high as 25%. Drawbacks to the use of allograft in the anterior column include slower incorporation rates, the possibility for disease transmission, increasing cost resulting from stringent processing and unavailability on a worldwide basis resulting from religious and economic concerns.

PURPOSE

To determine the clinical and arthrodesis efficacy of coralline hydroxyapatite as an osteoconductive bone graft substitute in the anterior lumbar spine using a titanium mesh cage.

STUDY DESIGN

A series of 50 patients returning for long-term prospective follow-up, implanted with titanium mesh cages filled with coralline hydroxyapatite and demineralized bone matrix for ALIF as part of a circumferential fusion.

PATIENT SAMPLE

Long-term clinical and radiographic follow-up were examined for the first 50 patients undergoing this technique by one surgeon.

OUTCOME MEASURES

Pain was measured with a visual analog scale and function was measured with the Oswestry Disability Index.

METHODS

All 50 patients underwent successful ALIF with titanium mesh cages, coralline hydroxyapatite and demineralized bone matrix, as well as an autologous posterolateral fusion with rigid posterior instrumentation. Patients filled out follow-up questionnaires and appropriate radiographs were taken.

RESULTS

A solid fusion rate of 96% was achieved. Mean pain decrease was 60% overall. A total of 70% of all patients either returned to work or to full home activities at a mean of 8 months after surgery. Ninety percent felt the surgery was successful.

CONCLUSIONS

The combination of titanium mesh cages, coralline hydroxyapatite and demineralized bone matrix is effective for anterior interbody fusion of the lumbar spine when used as part of a rigidly instrumented circumferential fusion.

Instrumented posterolateral lumbar fusion using coralline hydroxyapatite with or without demineralized bone matrix, as an adjunct to autologous bone

BACKGROUND CONTEXT

Autogenous posterolateral fusion with and without instrumentation has been reported with good results. However, difficult-to-fuse patients, such as smokers, elderly patients with poor bone quality and/or quantity, or patients with prior posterior surgeries, may have somewhat lower fusion rates.

PURPOSE

To determine the efficacy of coralline hydroxyapatite with or without demineralized bone matrix as a bone graft extender in a human clinical model with long-term follow-up.

STUDY DESIGN/SETTING

A retrospective series of 40 patients undergoing instrumented autogenous posterolateral lumbar fusion augmented with coralline hydroxyapatite with or without demineralized bone matrix.

PATIENT SAMPLE

Long-term clinical and radiographic follow-up were examined for 40 patients who underwent an instrumented posterolateral fusion only. Patients undergoing anterior lumbar interbody fusion (ALIF) procedures were not considered part of the sample.

METHODS

All patients underwent successful transpedicular fixation with autogenous posterolateral lumbar fusion. Fifteen cc of Pro Osteon 500 coralline hydroxyapatite (Interpore Cross International, Irvine, CA) was used at each level. An additional 10 cc of Grafton demineralized bone matrix gel (Osteotech, Eatontown, NJ) was used in 70% of these patients.

RESULTS

An overall fusion rate of 92.5% was achieved. Pain and function improvement were good but somewhat age dependent and correlated with the number of comorbidities. Patients with Grafton DBM gel had a lower fusion rate of 89.3%.

CONCLUSIONS

Based on this small retrospective review, coralline hydroxyapatite is an effective bone graft extender in difficult-to-fuse patients as an adjunct to autologous bone for posterolateral fusion of the lumbar spine when combined with rigid instrumentation.