Ž . The Knee 9 2002 7375 Case report Tibial cyst formation after anterior cruciate ligament reconstruction using a new bioabsorbable screw K. Malhan  , A. Kumar, D. Rees Robert Jones & Agnes Hunt Orthopaedic Hospital, Oswestry, Shropshire, SY10 7AG, UK Received 12 March 2001; received in revised form 23 May 2001; accepted 7 June 2001 Abstract We report a case of tibial cyst formation twelve months after anterior cruciate ligament reconstruction using hamstring graft. A composite bioabsorbable interference screw made of ‘beta tricalcium phosphate and poly L-lactide’ fixed the graft distally. The patient presented with acute symptoms of pain and swelling over the proximal tibia. Curettage of the cyst resulted in complete recovery within 3 months.  2002 Elsevier Science B.V. All rights reserved. Keywords: Tibial cyst; Bioabsorbable screw; Anterior cruciate ligament reconstruction 1. Introduction Bioabsorbable screws have been used for the fixa- tion of grafts in anterior cruciate ligament reconstruc- tion. These screws are made up of polymers that vary in their crystallinity and degradation behaviour. Bio- Ž . Lok Atlantech Medical Devices Ltd, Harrogate, UK is a composite polymer interference screw of poly-L- lactide and beta tricalcium phosphate. Complications   like screw breakage 1 , synovitis 2 and pretibial cyst  3 formation have been reported in literature with other polymer screws. We report a case of a tibial cyst formation after using BioLok screw for fixation of the hamstring graft. 2. Case report A 22-year-old lady presented with 6 months history  Corresponding author. Tel.: 44-1691-404435; fax: 44-1691- 404071. Ž . E-mail address: k.malhan@medix-uk.com K. Malhan . of right knee instability following a twisting injury. She had sustained an isolated rupture of the anterior Ž . cruciate ligament ACL . The ligament was recon- structed using hamstring graft, which was fixed proxi- mally with a transfemoral metal screw and distally with a BioLok interference screw. The patient made a satisfactory recovery and returned to pre injury level of activity in 6 months. Twelve months after the operation, the patient attended casualty with pain and swelling over the proximal tibia. On examination, there was a small tender swelling over the operative site, but the local temperature was normal. She had a full range of movements with no evidence of synovitis or instability in the knee. Routine blood investiga- tions like full blood count, ESR and CRP were within normal limits. Plain radiograph showed cystic expan- Ž . sion of the tibial tunnel Fig. 1 . An MRI scan con- firmed cystic expansion of the distal two-thirds of the tibial tunnel with increased signal intensity on T2 and STIR sequences. The cyst did not appear to commu- nicate with the joint. The screw was not seen and the Ž . graft looked intact Fig. 2 . The patient was taken to theatre for exploration of 0968-016002$ - see front matter  2002 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 9 6 8 - 0 1 6 0 01 00109-0