The medial patellofemoral ligament (MPFL) is a key soft tissue stabilizer of the medial patella, with deﬁciency proven to be a key contributor to patellar dislocation. Reconstruction of this ligament has become a widely employed procedure in man- aging patients with recurrent patellar dislocation, and is also gaining popularity in the setting of primary dislocation. A wide variety of techniques have been described, differing in the type of graft used, sites for ﬁxation and ﬁxation technique. A number of complications have also been reported in the literature, including post-operative stiffness, apprehension, patellar fracture and recurrence of instability and dislocation. Here we report a case of an endobutton used in MPFL reconstruction becoming displaced after minimal trauma in a young female patient, subsequently causing patellofemoral irritation, patellar cartilaginous damage and functional limitation. This complication has not been previously reported to our knowledge and is one that surgeons must be aware of. endobutton used for anterior femoral cortex graft ﬁxation INTRODUCTION becoming traumatically displaced following minimal trauma. The medial patellofemoral ligament (MPFL) acts as the primary We conclude that this complication was due to erroneous ini- medial stabilizer of the patella between full extension and 20° of tial tunnelling technique, and make suggestions how to avoid ﬂexion . Duetothisrole, incompetence of theMPFLhas been such a complication if tunnelling goes awry. widely accepted as a major factor in patellar dislocations. Open macroscopic examination of 67 knees with either acute or chronic patellar dislocation found abnormalities in all cases, varying from CASE PRESENTATION loose attachment and scar tissue formation to total absence and rupture . These ﬁndings have also been correlated via MR A 19-year-old female presented to fracture clinic 1 day after imaging . Thus, reconstruction of this ligament has become a sustaining a twisting injury to her right knee. At presentation popular technique in managing patients with patellar dislocations. the knee was mildly swollen without effusion. There was sig- A variety of techniques have been described in MPFL recon- niﬁcant tenderness on the medial patella. A longitudinal med- struction. Similarly, a variety of post-operative complications ial para patellar scar and longitudinal medial scar over the MCL have also been reported. Here, we report a unique case of an were noted. Range of motion was 0–40° actively. Received: November 19, 2017. Accepted: February 12, 2018 Published by Oxford University Press and JSCR Publishing Ltd. All rights reserved. © The Author(s) 2018. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/ licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact email@example.com Downloaded from https://academic.oup.com/jscr/article-abstract/2018/2/rjy025/4898378 by Ed 'DeepDyve' Gillespie user on 16 March 2018 2 R. Hasan and W. Jamil The patient had undergone an MPFL reconstruction 5 years medial epicondyle to the anterior cortex of the femur at the previously. At presentation there was no ligament laxity. The level of the suprapatellar fat pad. patient was given a supportive splint and advised to mobilize Based on tunnel positions, we conclude that the original as tolerated. surgeon had perforated the anterior femoral cortex when dril- The patient failed to fully improve with these measures, ling from the medial femoral condyle. Due to this an anterior continuing to experience severe pain on the medial knee, as cortex endobutton ﬁxation was used to supplement the medial well as symptoms of locking and giving way. Her extensor condylar interference screw ﬁxation. A degree of likely soft tis- mechanism was found to be intact, but range of motion in ﬂex- sue interposition in the suprapatellar region led to migration of ion was limited to 95° due to pain overlying the quadriceps ten- the endobutton, and subsequent rupture from its scar tissue don and medial aspect of the knee. A reproducible click was bed following minimal trauma. both heard and palpated between 0° and 20° of ﬂexion, a ﬁnd- At athroscopy, the endobutton was found embedded in the ing which had not been noted previously. synovium of the suprapatellar pouch. The trailing endocord CT (Fig. 1) and MR imaging showed an endobutton and was located under the medial facet of the patella, and was seen endocord sitting superior to the patella, with both impinging to be impinging on the medial patellar facet and femoral troch- upon the articular surface of the medial patella facet. A metal lea. Both the offending endobutton and endocord were removed. susceptibility artefact was seen at the medial femoral condyle, An osteochondral defect had also formed within the medial which was identiﬁed as an interference screw. patella facet and a chondroplasty was performed. At the time of Imaging enabled assessment of the graft tunnels (Figs 2 and 3). operation patella tracking was normal with no sign of instability, It appeared that an oblique tunnel had been drilled from the suggesting that the MPFL reconstruction had its intended thera- peutic effect. Postoperatively the patient gradually built up her activity levels and restored range of motion. At 2 months follow-up, she had no effusion and her pain and locking symptoms had entirely resolved. DISCUSSION Several techniques using an endobutton in MPFL repair exist. Use has been described for graft ﬁxation on the lateral femur [4, 5] and the lateral patella, via either a single-tunnel [6, 7]or double-tunnel technique . No reports exist of graft ﬁxation on the anterior femoral cortex. Astur et al.’s comparison of two surgical techniques reported two complications speciﬁc to endobutton patients. 3/31 (9.7%) patients reported discomfort at the lateral patellar site where the endobutton was located, which resolved with physio- therapy. One endobutton patient suffered a patellar fracture, resolved with screw ﬁxation. There was, however, no statistical difference in post-operative functional outcome scores between patients who underwent anchor ﬁxation and those who under- Figure 1: CT scan of the right knee showing the endobutton in suprapatellar went endobutton ﬁxation, with a slight tendency for better pouch (sagittal and axial view). results in the endobutton group. Figure 2: CT scan of the right knee showing entry point and oblique path of Figure 3: CT scan of the right knee showing perforation of anterior femoral cor- femoral tunnel at medial epicondyle (sagittal and axial view). tex (sagittal and axial view). Downloaded from https://academic.oup.com/jscr/article-abstract/2018/2/rjy025/4898378 by Ed 'DeepDyve' Gillespie user on 16 March 2018 Case report of a ruptured endobutton used in medial patellofemoral ligament reconstruction 3 Mae et al.  assessed the relationship between soft tissue CONSENT interposition and endobutton migration in patients who under- Written informed consent was obtained from the patient. went anatomic double-bundle ACL reconstruction. Although 25.2% showed signiﬁcant soft tissue interposition upon imme- diate post-operative radiographs and 47% showed signiﬁcant REFERENCES endobutton migration over 1-year follow-up, neither affected 1. Amis AA, Firer P, Mountney J, Senavongse W, Thomas NP. clinical outcome. This suggests that although some migration Anatomy and biomechanics of the medial patellofemoral can be expected, this should have no clinical manifestations in ligament. Knee 2003;10:215–20. https://www.ncbi.nlm.nih. ACL reconstruction. 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It is also critical to recognize the www.ncbi.nlm.nih.gov/pmc/articles/PMC4175865/. role of soft tissue interposition in causing delayed migration. 8. Nagakawa S, Arai Y, Kan H, Ueshima K, Ikoma K, Terauchi R, et al. Medial patellofemoral ligament reconstruction proced- CONFLICT OF INTEREST STATEMENT ure using a suspensory femoral ﬁxation system. Arthrosc Tech 2013;2:e491-5. https://www.ncbi.nlm.nih.gov/pmc/articles/ The authors declare that they have no competing interests. PMC4040016/. 9. Mae T, Kuroda S, Matsumoto N, Yoneda M, Nakata K, AUTHORS’ CONTRIBUTIONS Yoshikawa H, et al. Migration of endobutton after anatomic R.H. drafted the ﬁnal article. W.J. was involved in care of the double-bundle anterior cruciate ligament reconstruction. patient, conceived this case report and helped to draft the art- Arthroscopy 2011;27:1528–35. https://www.ncbi.nlm.nih.gov/ icle. All authors read and approved the ﬁnal article. pubmed/21924859. Downloaded from https://academic.oup.com/jscr/article-abstract/2018/2/rjy025/4898378 by Ed 'DeepDyve' Gillespie user on 16 March 2018
Journal of Surgical Case Reports – Oxford University Press
Published: Feb 1, 2018
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