Is Injectable Beta-Tricalcium Phosphate Effective as Gap Filler for Medial Open Wedge High Tibial Osteotomy?

Special Article - Orthopedic Surgery

Austin J Surg. 2016; 3(2): 1088.

Is Injectable Beta-Tricalcium Phosphate Effective as Gap Filler for Medial Open Wedge High Tibial Osteotomy?

Choi WC, Kim B, Kim U and Kim JH*

Department of Orthopaedic Surgery, CHA University, Republic of Korea

*Corresponding author: Jae-Hwa Kim, Department of Orthopaedic Surgery, CHA University, Republic of Korea

Received: August 09, 2016; Accepted: September 28, 2016; Published: October 03, 2016


We aimed to evaluate whether using novel injectable gel-type beta Tricalcium Phosphate (β-TCP) as gap filler for Medial Open Wedge High Tibial Osteotomy (MOWHTO) is effective. Consecutive 28 patients who were scheduled to undergo biplanar MOWHTO for medial compartmental osteoarthritis were prospectively enrolled. The osteotomy was fixed by an anatomical locking plate and the gap was filled with novel injectable β-TCP. The degree of bone union and maturation of β-TCP was assessed by radiographs and Computed Tomography (CT) scans at postoperative 3 and 12 months. The mechanical Femoro-Tibial Angle (mFTA) was measured and compared between pre and postoperative period. Clinical outcome was evaluated by determining International Knee Documentation Committee (IKDC), Western Ontario and McMaster Universities Arthritis Index (WOMAC) and Visual Analogue Scales (VAS) for pain scores. Twenty-five patients (89.3%) were analyzed and all cases showed bony union of osteotomy site without any complication. Serial progress of bone union was found on radiographs and the mean ratio (β-TCP/ host bone) of CT attenuation values significantly changed from postoperative 3 months (12.26) to 12 months (8.37) (P=0.012), which indicates maturation of β-TCP. The average mFTA significantly changed from preoperative (4.1° varus) to 3 months (4.8° valgus) and maintained at 12 months (4.3° valgus) (P<0.001). Significant improvements of the IKDC, WOMAC and VAS pain scores were also seen (P<0.001, P=0.002 and P=0.002 respectively). We found satisfactory bone union and clinical outcome without any complication after using injectable β-TCP as gap filler for MOWHTO.

Keywords: High tibial osteotomy; Beta-tricalcium phosphate; Computed tomography


High tibial osteotomy is an established procedure for the treatment of patients with varus medial compartmental osteoarthritis of the knee, particularly in young and/or active individuals [1]. Two osteotomies; lateral closed wedge and medial open wedge; are possible surgical options. Compared to lateral closed wedge osteotomy, Medial Open Wedge High Tibial Osteotomy (MOWHTO) has advantages including relatively easier performing, preservation of bone stock, correction of the deformity close to its origin, avoidance of fibular osteotomy and predictable and adjustable correction [2]. However, previous studies concerned about risk of nonunion, early collapse or loss of correction after MOWHTO and suggested that some type of osteotomy gap filler is needed [3,4]. Using bone substitutes as gap filler for MOWHTO has been tried to avoid some pitfalls of using autogenous or allogenic bone graft [5,6]. Beta Tricalcium Phosphate (β-TCP) is well known for high biocompatibility and osteoconductivity and rigid wedge or granule type of β-TCP has been used as a bone substitute graft for MOWHTO [7-9]. In this study, we tried to evaluate the radiographic and clinical outcome of MOWHTO using novel injectable β-TCP; which consisted of 100% β-TCP and thermo sensitive hydrogel to provide injectability; as gap filler. Our hypothesis was that MOWHTO using injectable β-TCP as gap filler would result in satisfactory bone union and clinical outcome at 12 months after the surgery.

Materials and Methods

This prospective cohort series was performed according to the declaration of Helsinki for medical research involving human subjects and was organized and approved by the institutional review board of our hospital (protocol number: BD2013-014M). Consecutive patients who were scheduled to undergo MOWHTO were assessed for eligibility. Patients who had grade 3 or 4 Kellgren & Lawrence osteoarthritic changes on lateral or patellofemoral compartment of knee joint, who had valgus or less than 2° of varus limb alignment, who had more than 10° of flexion contracture or less than 90° of knee range of motion or who refused to participate were excluded from the study. We also excluded patients with heavy cigarette smoking, Body Mass Index (BMI) higher than 35 kg/m2 and exogenous steroid use.

Preoperative evaluation

Full-length double-limb standing anteroposterior radiographs, including the femoral head and ankle, were taken according to the standardized technique described by McGrory, et al. [10]. Mechanical Femoro-Tibial Angle (mFTA) was measured and amount of osteotomy to achieve target correction angle; 5° valgus of mFTA; was decided.

Surgical procedures

All surgical procedures were carried out by a single surgeon (JHK). The patient was placed in the supine position with spinal or epidural anesthesia and a thigh tourniquet was inflated during the surgery. Knee arthroscopy was performed first during which the menisci, ligaments and articular cartilage were inspected and concomitant arthroscopic procedures including partial meniscectomy or microfracture were carried out if necessary. Biplanar medial openwedge HTO was performed according to the method that previously reported under fluoroscopic control [11]. Osteotomy was performed using osteotomes and a calibrated distractor was used to open the osteotomy site in order to achieve the target mFTA; 5° valgus of mFTA; that preoperatively planned. Fixation of osteotomy was performed using an anatomical locking plate (OhtoFix; Ohtomedical Co. Ltd., Goyang, Korea). After plate fixation, 5 cc of β-TCP (EXCELOS inject; CG Bio, Seongnam, Korea) (Ca3(PO4)2) was injected into the osteotomy gap.

Characteristics of injectable β-TCP

The injectable gel-type β-TCP used in this study is pre-filled in a syringe and consisted of 100% β-TCP granules with 75% porosity and 100 to 300 μm pore size mixed with bio-degradable hydrogel. The hydrogel is highly concentrated polyoxyethylene-polyoxypropylene block co-polymer (Poloxamer 407), which ensures the injectability of β-TCP and make the sol–gel transition at 25 °C [12] (Figure 1).