Osteolytic changes around biodegradable cement restrictors in hip surgery

Abstract

Background and purposeBiodegradable cement restrictors are widely used in hip arthroplasty. Like others, we observed osteolytic reactions associated with a specific cement restrictor (SynPlug; made of PolyActive) and reviewed our patients.Patients and methodsWe identified 703 patients with suitable radiographs from our database (2007 to 2012) who underwent cemented hip arthroplasty and received a SynPlug biodegradable cement restrictor. We reviewed all available radiographs to determine the incidence, severity, and progression of osteolysis. Mean postoperative follow-up was 1.8 (1–7) yearsResults1 year after implantation, the femoral cortex showed thinning by 12% in the anterior-posterior view and by 8% in the axial view. This had increased to 14% and 12%, respectively, at the latest available follow-up postoperatively (at a mean of 4 years). Cortical thinning of less than 10% was found in 37% of patients, but cortical thinning of 10–30% was found in 56% of patients. In the remaining 7%, a reduction of more than 30% of the original cortical thickness was observed.InterpretationOsteolytic changes associated with the SynPlug biodegradable bone restrictors are inconsistent and highly variable. While some patients showed increased weakening of the femoral cortex with the potential risk of periprosthetic fracture, in others the degree of osteolysis only increased slightly or stabilized after 2 or more years. Any cortical bone loss after total hip replacement should be avoided, so the use of PolyActive biodegradable cement restrictors should be discontinued. Patients with a PolyActive cement restrictor in place should be followed up closely after surgery.

Comparison of osteolysis around 3 different cement restrictors in total hip arthroplasty

“…1 study found an average increase in cortical ratio as a measure of osteolysis of 14% after an average 1.8 year follow-up. 12 Another found that 87% had >10% cortical thinning after 1 year. 10 Both studies had a rather short follow-up and did not compare the PEG/PBT restrictor with other cement restrictors.…”

“…We assumed that the plug was located immediately underneath the inferior border of the cement mantle (Figure 1). 12 The cortical ratio was assessed on radiographs of the 1st postoperative day (T0) and at follow-up.…”

“…To categorise the degree of osteolysis around a cement restrictor a classification with 4 categories was used: <10%, 10-20%, 20-30% and ⩾30% in accordance with a recently published study. 12 An increase of 10% was considered a minimal clinical important difference (MCID).…”

“…8,9 Recent reports reveal progressive osteolysis surrounding biodegradable cement restrictors, especially restrictors with polyethylene glycol/polybutylene terephthalate (PEG/PBT) copolymer as a compound. [10][11][12] 1 case report presented a periprosthetic fracture due to excessive osteolysis surrounding the cement restrictor. 13 We are not aware of any register that records the cement restrictor as a separate component of a cemented THA, the follow-up on the cement restrictor may have been neglected.…”

Imaging in Hip Arthroplasty Management Part 2: Postoperative Diagnostic Imaging Strategy

“…In cemented femoral components, intramedullary plugs are commonly used and are available in a wide variety of materials and shapes, both biodegradable and non-resorbable. Osteolytic changes around biodegradable models have even been described [ 46 ]. Some types of restrictors have a metallic marker that can appear at the tip of the stem ( Figure 1 ).…”