Calcium phosphate cement in wrist arthrodesis: three cases

Canine ex vivo tarsal arthrodesis: fixation by using a new bone tissue glue

Introduction

Arthrodesis, performed as a salvage surgical procedure to treat intractable joint conditions in dogs and cats, is associated with a high incidence of complications intra and postoperative, proving the need for improved and new techniques in arthrodesis surgery. Adding a new resorbable bone glue to the arthrodesis could potentially add fixation strength and lower complications. The objectives of this experimental ex vivo biomechanical study were therefore to develop a biomechanical test model of partial tarsal arthrodesis and to determine whether the new resorbable bone glue (phosphoserine modified cement) produced measurable fixation strength in canine calcaneoquartal arthrodesis, without orthopedic implants.

Methods

Four biomechanical test models with a total of 35 canine tarsal joints were used. Soft tissues were dissected to 4 different test models with variable contributions from soft tissues. The calcaneoquartal joint was prepared as in vivo arthrodesis and the glue was applied to joint surfaces as a liquid/putty (0.4 cc). After curing for 24 h, a shear force was applied to the joint (1 mm per minute) and the failure strength was recorded.

Results

Calcaneoquartal joints, where all soft tissues had been completely resected and fixated with glue (1-1.5 cm2 joint surface), withstood 2-5 mm of displacement and an average of 100 ± 58 N/cm2 of shear force (Model 1). Similar adhesive fixation strengths were obtained in Model 2 and 3 with increasing contributions from soft tissues (80 ± 44 and 63 ± 23 N/cm2, p = 0.39, ANOVA).

Conclusion

The developed biomechanical model was sensitive enough to measure differences in fixation strengths between different glue formulations. The average fixation strength (60-100 N/cm2) should be strong enough to support short-term load bearing in medium sized canines (20 kg). The developed cadaver biomechanical test model is of potential use for other arthrodesis studies. The new resorbable glue can potentially contribute to stability at arthrodesis surgery, acting as a complement to today's standard fixation, metal implants.

Role for cementoplasty in intra-articular distal radius fractures: Cadaver study and application to arthroscopy

BACKGROUND

Die-punch intra-articular fractures of the distal radius raise surgical challenges. The residual articular step-off must be less than 1mm to prevent the development of radio-carpal osteoarthritis. The objectives of this cadaver study were to evaluate whether cementoplasty was effective in reducing die-punch fractures and to determine whether this technique was feasible as an arthroscopic procedure.

HYPOTHESIS

Cementoplasty performed as an arthroscopic procedure is effective in treating die-punch fractures.

MATERIAL AND METHODS

Eleven cadaver forearms collected at a laboratory were studied. In each, a depressed fracture of the lunate fossa of the radial articular surface was created using a Tinius Olsen H25K-S compression test machine. A Kyphon XPander^® balloon (Medtronic) was used to lift the depressed area, and calcium-phosphate cement was then injected to stabilise the reduction. Cementoplasty under arthroscopic guidance was performed on an additional forearm.

RESULTS

Computed tomography of the wrists after fracture induction showed a mean depression of 4.66mm (range, 4.01-5.25mm). Arthroscopic cementoplasty proved feasible with the arthroscope inserted through the 3-4 radio-carpal portal. Positioning the balloon under the depressed area ensured satisfactory reduction and allowed the injection of cement.

DISCUSSION

Cementoplasty may be useful for the treatment of die-punch fractures. Additional indications may be other types of distal radius fractures with articular surface depression.

LEVEL OF EVIDENCE

IV, cadaver study.

Self-setting calcium orthophosphate formulations

In early 1980s, researchers discovered self-setting calcium orthophosphate cements, which are bioactive and biodegradable grafting bioceramics in the form of a powder and a liquid. After mixing, both phases form pastes, which set and harden forming either a non-stoichiometric calcium deficient hydroxyapatite or brushite. Since both of them are remarkably biocompartible, bioresorbable and osteoconductive, self-setting calcium orthophosphate formulations appear to be promising bioceramics for bone grafting. Furthermore, such formulations possess excellent molding capabilities, easy manipulation and nearly perfect adaptation to the complex shapes of bone defects, followed by gradual bioresorption and new bone formation. In addition, reinforced formulations have been introduced, which might be described as calcium orthophosphate concretes. The discovery of self-setting properties opened up a new era in the medical application of calcium orthophosphates and many commercial trademarks have been introduced as a result. Currently such formulations are widely used as synthetic bone grafts, with several advantages, such as pourability and injectability. Moreover, their low-temperature setting reactions and intrinsic porosity allow loading by drugs, biomolecules and even cells for tissue engineering purposes. In this review, an insight into the self-setting calcium orthophosphate formulations, as excellent bioceramics suitable for both dental and bone grafting applications, has been provided.

Calcium Orthophosphate Cements and Concretes

In early 1980s, researchers discovered self-setting calcium orthophosphate cements, which are a bioactive and biodegradable grafting material in the form of a powder and a liquid. Both phases form after mixing a viscous paste that after being implanted, sets and hardens within the body as either a non-stoichiometric calcium deficient hydroxyapatite (CDHA) or brushite, sometimes blended with unreacted particles and other phases. As both CDHA and brushite are remarkably biocompartible and bioresorbable (therefore, in vivo they can be replaced with newly forming bone), calcium orthophosphate cements represent a good correction technique for non-weight-bearing bone fractures or defects and appear to be very promising materials for bone grafting applications. Besides, these cements possess an excellent osteoconductivity, molding capabilities and easy manipulation. Furthermore, reinforced cement formulations are available, which in a certain sense might be described as calcium orthophosphate concretes. The concepts established by calcium orthophosphate cement pioneers in the early 1980s were used as a platform to initiate a new generation of bone substitute materials for commercialization. Since then, advances have been made in the composition, performance and manufacturing; several beneficial formulations have already been introduced as a result. Many other compositions are in experimental stages. In this review, an insight into calcium orthophosphate cements and concretes, as excellent biomaterials suitable for both dental and bone grafting application, has been provided.