Outcomes of surgery for acromioclavicular joint dislocation using different angled hook plates: a prospective study

Purpose Hook plate fixation is widely used to treat acromioclavicular joint dislocation. However, there are many post-operative complications affecting the effect of treatment. The aim of this study is to evaluate the efficacy of the clavicular hook plate with different hook angles as a method of treatment in AC joint dislocation, and to guide the clinical application of hook plate. Methods We prospectively analysed 54 patients who were diagnosed with AC joint dislocation and treated with hook plate fixation by different hook angles. The patients were randomised into three groups: the -20A degrees A < AHP < 0A degrees group, the 20A degrees A > AHP > 0A degrees group and the 40A degrees A > AHP > 20A degrees group. All patients were required to conform to regular follow-up post-operatively. Routine imaging to the shoulder was obtained to evaluate maintenance of the dislocation and the implant. Constant-Murley criteria were used to evaluate functional results. Results There were 19 patients in the -20A degrees A < AHP < 0A degrees group, with one lost to follow-up, 22 patients in the 20A degrees A > AHP > 0A degrees group, with two male patients lost to follow-up, and one female patient excluded because of no follow-up consent, and 19 patients in the 40A degrees A > AHP > 20A degrees group, with one female and one male patient lost to follow-up. The Constant score was 61.8 +/- 12.8, 74.7 +/- 9.2 and 70.7 +/- 9.4 before implant removal, and 78.8 +/- 8.3, 87.1 +/- 6.4 and 85.0 +/- 6.1 after implant removal in the -20A degrees A < AHP < 0A degrees, 20A degrees A > AHP > 0A degrees and 40A degrees A > AHP > 20A degrees groups, respectively. The functional results of the 20A degrees A > AHP > 0A degrees and 40A degrees A > AHP > 20A degrees groups were significantly better than the -20A degrees A < AHP < 0A degrees group (P < 0.05), but the functional results of the 20A degrees A > AHP > 0A degrees and 40A degrees A > AHP > 20A degrees groups were not statistically significant. The CCD was 98.1 +/- 4.8%, 107.5 +/- 5.1% and 105.5 +/- 4.1% before implant removal, and 98.8 +/- 4.6%, 108.3 +/- 4.8% and 107.2 +/- 3.3% after implant removal in the three groups, respectively. The CCD of the 20A degrees A > AHP > 0A degrees and 40A degrees A > AHP > 20A degrees groups were statistically significantly different from the -20A degrees A < AHP < 0A degrees group (P < 0.001). However, there was no statistical difference between the 20A degrees A > AHP > 0A degrees group and the 40A degrees A > AHP > 20A degrees group. Post-operative persistent pain occurred in 18.5% of all patients, post-operative stiffness occurred in 25.9% of all patients and 24.0% of patients had subacromial erosion. Conclusions Hook plate treatment for AC joint dislocation can achieve the desired results, but the efficacy was significantly different depending on the different angles of the hook plate. AHP should be controlled within the range of 0-40A degrees as much as possible when making clinical decisions.