Purposes of Study: To establish what happens, over time, to an ACL graft which is implanted in the skeletally immature knee.

Methods/Results: 5 cases of hamstring ACL reconstruction in prepubertal patients were available from the practices of 2 surgeons in which there were X-ray/MRI images taken over a period of an average of approximately 3 years from the operation. The changes in graft dimensions were measured from these images. No case of growth arrest was seen, nor of soft tissue contracture such as fixed flexion. All patients recovered to their same pre-injury level of activity, including elite level sport in 3 cases. Clinical laxity tests were always satisfactory but the senior authors have noticed that they tighten in time.

The growth of the patients was an average 17cm. The graft diameters did not change despite large changes in graft length (average 145%). Most of the length gain was in the femur.

Conclusion: Much has been written regarding potential harm to the growth plate in these patients but we are not aware of literature on the subject of the fate of the graft itself. Considerable length changes in the grafts were evident. The biological phenomena taking place in the graft are unknown. We have clearly shown an increase in the size of graft tissue due to lengthening but no change in girth. Either the graft stretches or tissue neogenesis occurs, or both. If it simply stretched then the graft would be expected to become narrower, at least in places- it did not. Nevertheless the ‘tightening’ phenomenon reported anecdotally could be due to the graft having to stretch but failing to keep up with growth. As the volume of graft increases so much then at least some neogenesis is highly likely.

Purpose of Study: To further study a group of patients with characteristic features presenting with significant, perisistent, and seemingly hard to diagnose and so treat, knee pain.

Methods/Results: 16 cases were collected. The was no association with age. 8 cases were sent as a second opinion.

Causation: 7 cases:direct trauma [5: associated with MCL tears (1 chronic overload from triple-jump),1:a blow to front of knee, 1:chronic from kneeling]

In all cases the time to make the diagnosis was prolonged. All had pain, which on close questioning was ‘neuritic’ [burning] in approximately 2/3. It was exceedingly well localized in all. Altered sensation in the appropriate distribution was noted by the patient in 3 cases, but shown in 5 cases on examination. A positive Tinel test was present in all cases.

In approximately half of cases ultrasound plus diagnostic injection of local anaesthetic [+/− steroid] was useful. However 15 of the 16 came to surgery in which a neurolysis or removal of neuroma, in 3 cases, [all confirmed on histology] was undertaken plus the underlying causative factor dealt with eg excision of osteophyte or scar. One case settled [90% better according to patient] after ultrasound-guided injection of a prepatellar bursa which was irritating the infrapatellar branch of the nerve. Of the 15 who had had surgery 12 had complete resolution of symptoms.

Conclusion: Although a relatively uncommon this scenario is worth considering as a cause of significant morbidity, with a good outcome from treatment in most cases. The presentation is of persistent very well localized troubling pain with marked tenderness, and a positive Tinel test.