Summary

We describe a new aetiology of AC Joint pathology, that being a traumatic tear of the intra-articular ACJ Disc, that is treated successfully with arthroscopic excision.

Abstract

Background

Injury to the acromioclavicular joint (ACJ) has been well described in the literature. Osteoarthritis remains the most common cause of pain at the ACJ with dislocation and distal clavicle osteolysis other recognised pathologies. All these are evident on radiographic imaging. A cartilaginous disc is present in the ACJ in a proportion of patients although it is not visualised on plain radiographs and difficult to observe on some low resonance MRI Scan images.

We present a case series of patients with ACJ pain and normal radiographs that underwent arthroscopic excision of the ACJ with the hypothesis of a cartilaginous disc tear being the aetiology. We propose this as a new form of ACJ injury as it has not to our knowledge been previously described in the literature.

Methods

Eight patients were prospectively recruited over a 5-year period, presenting with ACJ pain. Each had described an injury consistent with excessive load to the ACJ and each demonstrated positive clinical signs for isolated ACJ pathology on examination, i.e. tenderness to palpation over the ACJ with a positive SCARF or Lipmann-Kessel test. No patient had radiographic evidence of osteoarthritis, dislocation or distal clavicle osteolysis. Increased signal was observed in the ACJ on MRI Scan in 4 of the patients in keeping with possible disc tear with 2 having a convincing image consistent with disc tear. All patients underwent an ultrasound guided diagnostic injection which provided complete resolution of symptoms for all patients. Each subsequently proceeded to surgery with an arthroscopic excision of the ACJ. Pre-operative scores were recorded for ASES Score and Nottingham AC Joint Score. Post-operative radiographs were taken to assess the suitability of ACJ excision.

Results

The mean age of the patients was 39 years (range 27 to 56). The mean follow-up time was 22 months (range 15 to 30). At the time of surgery, the intra-articular ACJ disc was identified and was visualised and appeared to be damaged. It was excised along with the distal clavicle. Each patient described improvement following surgery with a mean improvement in ASES score from 18.3 (range 11.6 to 21.6) pre-op to 97.6 (93.3 to 99.9) post-op (p < 0.05) and Nottingham score 42.8 pre-op to 94.8 post-op (p < 0.05). Every patient had a satisfactory post-op excision seen on post-operative radiographs.

Conclusions

We have not previously seen in the literature the description of a tear of the cartilaginous disc of the ACJ. We present a series of patients that were symptomatic for this with no evidence of previously described ACJ pathologies. Each patient improved following surgical intervention at the ACJ. We suggest this diagnosis should be considered in such patients presenting with ACJ pain without any evidence of osteoarthritis, dislocation or distal clavicle osteolysis