The Biomechanical Effect of Prosthetic Design on Radiocapitellar Stability in a Terrible Triad Model

Abstract

Objectives: The integrity of elbow soft tissues affects radiocapitellar joint stability in the presence of bipolar radial head (RH) prostheses. This study examined the effect on radiocapitellar stability of monopolar designs versus bipolar RH prostheses in an elbow model with a surgically controlled terrible triad injury.Methods: In each of 8 fresh-frozen elbow specimens (4 male and 4 female), a terrible triad fracture dislocation was created through soft tissue releases, coronoid fracture, and RH resection. Radiocapitellar stability was recorded under the following 3 sets of conditions: (1) surgical control (native RH), (2) RH replacement (circular monopolar or bipolar), (3) replacement with alternate circular RH not used in condition 2, and (4) replacement with the anatomic RH.Results: The type of RH used significantly impacted the mean peak force required to resist posterior subluxation (p = 0.0001). The mean peak subluxation force of the bipolar prosthesis (1 6 1 N) was significantly less than both the anatomic (16 6 1 N) and nonanatomic circular (12 6 1 N) implants (p = 0.0002). The peak subluxation force of the native RH (18 6 2 N) was not different than the anatomic implant (p = 0.09) but was greater than the nonanatomic circular design (p = 0.0006).Conclusions: Monopolar RHs confer greater radiocapitellar stability than bipolar implants in the setting of terrible triad injuries.Of the 2 monopolar designs tested, the anatomic design provided more stability than the non-anatomic RH prosthesis.

Causes for early and late surgical re-intervention after radial head arthroplasty

“…Several radial head prosthesis (RHP) designs are currently available. Bipolar implants allow for more movement of the cup with respect to the capitellum, despite suboptimal reproduction of anatomic and biomechanical properties [14,28,29]. However, studies analyzing implant characteristics have demonstrated no significant difference in clinical outcomes and report high satisfaction for various designs at both short-and long-term post-operative follow-up [30][31][32][33].…”

“…Repeated posterolateral dislocations increase the risk of hypermobility of the cup secondary to radiocapitellar instability and may lead to complete dissociation of the cup from the stem [15,26]. Monopolar prostheses are the implants of choice in cases with associated ligamentous injury because they allow for superior radiocapitellar stability thanks to increased concave compression of the implants [28,29]. Tissue integrity did not affect implant choice for each patient as only one design was available at the time of surgery for all patients in this series.…”

“…Tissue integrity did not affect implant choice for each patient as only one design was available at the time of surgery for all patients in this series. We recognize this is an inherent limitation in our study as the bipolar is clearly used only when there is malignment of the proximal radius with the capitellum [28,29].…”

Radial Head Arthroplasty

“…33 It should be noted that monopolar implants can better resist radiocapitellar subluxation in the setting of soft-tissue deficient cadaver elbows, 32 particularly in a terrible triad model.…”

Radial Head Reconstruction in Elbow Fracture-Dislocation: Monopolar or Bipolar Prosthesis?

“…Conversely, both Schneeberger et al [16] and Pomianowski et al [14] demonstrated significant improvements in ulnohumeral laxity with a monopolar implant compared with a bipolar implant in terrible triad models. The biopolar implant has been demonstrated to provide less stability in an elbow with no ligamentous structures [4,11]. The specific dependence and influence of the lateral collateral ligament has been shown to be more critical with a bipolar implant design [5].…”