Assessment of progression and clinical relevance of stress-shielding around press-fit radial head arthroplasty

Introduction: This study aimed to quantitatively evaluate the effect of the trauma to surgery time interval (Tt-Ts) and the type of tendon retraction (unretracted vs. coiled) in distal biceps tendon ruptures (DBTRs) on the choice between primary tendon repair (PR) and tendon reconstruction with graft (RG). Materials and Methods: In total, 123 patients with surgically treated DBTRs were analyzed. Patients were divided into three groups: Group I—acute (75 patients with Tt-Ts < 21 days), Group II—subacute (20 patients with Tt-Ts between 21 and 45 days), and Group III—chronic (28 patients with Tt-Ts > 45 days). The type of surgical treatment (PR vs. RG) was evaluated in each group. The type of tendon retraction (unretracted vs. coiled) was analyzed in subacute and chronic lesions. A statistical analysis was performed. Results: The mean Tt-Ts interval in the overall sample was 59.3 days; in Group I, it was 9 days (range, 2–20); in Group II, it was 29 days (range, 22–42); and in Group III, it was 196 days (range, 45–1095). PR was performed in 100%, 90%, and 29% of the patients in Groups I, II, and III, respectively. Coiled tendons were found in 60% and 71% of patients in Groups II and III, respectively. Among patients with coiled tendons, 2 and 20 received RG in Groups II and III, respectively. The Tt-Ts and the type of retraction were significantly associated with the choice of surgical treatment (PR vs. RG), with statistical differences between Group III and the other two groups (p < 0.05). A cut-off of 43.5 days following injury was found to predict the need to perform RG with an accuracy, sensitivity, and specificity of 94%, 100%, and 92%, respectively. The likelihood of receiving RG rather than PR increased each day by 6%. Conclusions: Treatment delay significantly affects the choice of surgical technique in DBTRs. PR is feasible in 98% of acute and subacute ruptures, whereas RG is necessary in 70% of chronic ruptures. The type of tendon retraction affects the choice of treatment only in chronic lesions, as coiled tendons always require RG.