Abstract
Objectives:
To determine if UCL Reconstruction (UCLR) results in a decrease in ulnohumeral joint space gapping as measured on postoperative Stress Ultrasound (SUS) examination.
Methods:
Patients were identified from an existing IRB-approved single-blinded, prospective, randomized controlled trial designed to assess treatment outcomes after modified Jobe or Docking ulnar collateral ligament reconstructions (UCLR). This population consisted of overhead throwing athletes (any level-recreational, high school, collegiate & professional). Patients all met the following inclusion criteria: age 16-30 years of age, diagnosis of ulnar collateral ligament (UCL) instability involving either a complete UCL tear or a partial UCL tear that failed non-operative management. Any patients with a history of a previous ipsilateral elbow surgery (UCL reconstruction, ulnar nerve transposition, flexor-pronator debridement, posteromedial impingement debridement, or elbow fracture fixation) were excluded.
All patients were randomized to UCLR by either the modified Jobe or the Docking technique utilizing a uniform surgical approach and contralateral gracilis autograft. Technique allocation was disclosed to the surgeon on the morning of surgery, but the patient remained blinded. All UCLR were performed by a board-certified, Sports Medicine fellowship-trained orthopedic surgeon who performs a high volume of UCLR. All patients were treated with a uniform postoperative rehabilitation and were followed for a minimum of 2 years for clinical outcomes.
All patients underwent uniform pre- and post-operative radiographic assessment, including magnetic resonance imaging/arthrography (MRI/MRA) and stress ultrasound (SUS). All postoperative imaging was performed at a minimum of 1 year after surgery. All SUS exams were performed or directly supervised by experienced musculoskeletal radiologists well-versed in this technique. SUS provides a quantitative, dynamic assessment of ulnohumeral joint space gapping and has been previously validated. Patients who lacked any SUS data were excluded.
All SUS exams were conducted using a 13-MHz linear-array transducer measuring the magnitude of ulnohumeral joint gapping at rest and with application of a valgus stress. Patients were positioned seated with the elbow at approximately 30 degrees of flexion. Ulnohumeral joint space gapping was assessed by first orienting the probe along the longitudinal axis of the UCL such that the sublime tubercle and the trochlea could be identified, being separated by the hypoechoic shadowing of the joint space and fluid. All measurements were taken using electronic calipers from the hyperechoic peak of the trochlea to the hyperechoic peak of the proximal-most ulna at the sublime tubercle. In addition, the static resting UCL graft length was recorded, as were the presence and size of any calcifications or hypoechoic foci within the UCL substance.
Analysis was conducted using SPSS (IBM, Corp), utilizing two-tailed independent t-tests to compare population means, two-tailed paired student’s t-tests for assessments of subjects over two different time points, and two-tailed one sample t-tests to compare the impact of UCLR to a reference population mean.
Results:
Of the 80 patients that were randomized in the prospective trial, 57 patients with SUS data were available. Of the 57 UCLR, 26 were reconstructed by the Modified Jobe technique and 31 by the Docking technique. The mean age was 19.3 ± 1.8 years, and all were overhead athletes (93% baseball).
SUS findings available for the 57 patients included: 100% (57/57) preoperative baseline SUS exam, 87.8% (50/57) 1-year post-UCLR SUS exam, 40/57 (71.9%) reference preoperative SUS exam on contralateral un-injured elbow. The amount of joint space gapping as a result of the stress exam (delta) was 0.83 ± 0.53mm for the contralateral reference elbow, 2.11 ± 1.21 for pre-operative affected elbow baseline, and 0.62 ± 0.41mm for 1-year post-UCLR. Figures 1 and 2 show scatter plots of postoperative delta values compared to the preoperative baseline, and the preoperative contralateral reference, respectively.
UCLR resulted in approximately 340% decrease in the magnitude of joint gapping measured on SUS, representing a mean 1.49mm decrease. UCLR restored delta gapping to values comparable to those of the native elbow. There was significantly less delta gapping on SUS examination at 1-year post UCLR (0.61 ± 0.42mm) compared to the preoperative SUS examination time point (2.11 ± 1.21; p<0.001). This was true irrespective of the procedure, with the docking technique decreasing from 2.17 ± 1.3mm to 0.57 ± 0.39mm (p<0.001), and the Jobe technique decreasing from 1.82 ± 0.87mm to 0.67 ± 0.46mm (p<0.001) on paired analyses.
Considering all UCLR patients, two-tailed one sample t-testing found less joint gapping present in the minimum 1-year postoperative cohort (0.61 ± 0.42mm; p=0.003) compared to the reference contralateral mean (0.83mm), which was also true for the docking (p=0.007) but not Modified Jobe (p=0.193). When delta gaps for the contralateral reference were paired with post-UCLR in the same patients, there was no significant difference seen (0.61 ± 0.42mm vs 0.83 ± 0.53mm; p=0.187).
Conclusions:
UCLR returned average ulnohumeral joint gapping to normal values on postoperative SUS. UCLR results in an average decrease of joint space gapping from 2.11 ± 1.21mm to 0.61 ± 0.42mm. Regardless of technique, UCLR restored delta values comparable to those of the contralateral unaffected elbow (0.83 ± 0.53mm). Both techniques yielded mean gapping values less than 1.0mm. These findings provide surgeons with the expected change in joint gapping following UCLR as measured on SUS. By providing a reference, surgeons can better assess patients with concern for recurrent injury following previous UCLR in situations where MR alone may be challenging to interpret.
