Calcium phosphate cement loaded with bupivacaine vs ropivacaine may accelerate functional recovery after bone reconstruction surgery and maintain bone-filling properties, according to an animal study published in The Journal of Pain.

Bone reconstruction surgery is often complicated by substantial postoperative pain that requires quick minimization if chronic pain is to be avoided. Alternatives to standard systemic therapies are needed to address this issue. In this study, 18 rats were randomly assigned to receive calcium phosphate cement alone, calcium phosphate cement plus 8% ropivacaine, and calcium phosphate cement plus 8% bupivacaine (n=6 for all).

All rats had critical-size defects created at the lateral femoral condyles of their right hind limbs. The gait of animals after surgery was analyzed using the CatWalk system — which assesses pain relief via print area, paw intensity, print length, and duty cycle — at 2, 4, 6, 24, 48 and 72 hours and 7 and 14 days. All surgical procedures and analyses were blinded.

In the short-term, adequate pain relief was achieved with both anesthetic-loaded and unloaded calcium phosphate cements. Calcium phosphate cements loaded with anesthetics indicated good drug release, with bupivacaine and ropivacaine providing initial bursts of 44% and 30% over 8 hours and 74% and 70% by the end of the trial period, respectively. At 24 hours, print area was reduced by 65%, 42%, and 24%, and paw intensity was lowered by 25%, 9%, and 1%, for the unloaded, ropivacaine, and bupivacaine groups, respectively, compared with baseline levels.

Print areas were significantly greater in both loaded and unloaded calcium phosphate cements at 24 hours, and differences in intensity were significant in all 3 groups (P <.01 for all). Significant differences were observed between the loaded and unloaded groups at 24 hours in terms of manual print length (ie, distance during stance between middle/third toe and heel) and duty cycle (ie, stance phase; P <.01 for both).

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Overall, bupivacaine-loaded calcium phosphate cement was found superior to ropivacaine-loaded calcium phosphate cement for pain relief, return to full function, and preoperative CatWalk levels. Both anesthetic-loaded calcium phosphate cements retained their mechanical and biological properties and displayed good safety profiles with no adverse cardiovascular effects, bone tissue reactions, neurological problems, or muscle atrophy.

The investigators are hopeful that their findings could lead to increased use of such combination products in human orthopedic surgeries, particularly for iliac crest surgery, noting, “Such bone substitutes, which can both fill the harvest site and deliver an analgesic substance in situ, could constitute a novel therapeutic approach.”

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Dupleichs M, Masson M, Gauthier O, et al. Pain management after bone reconstruction surgery using an analgesic bone cement: a functional non-invasive in vivo study using gait analysisJ Pain. May 2018. doi:10.1016/j.jpain.2018.04.014