The authors of this prospective study assess 12 patients who underwent hamstring ACL reconstruction with upright MRI scans, KT-1000 measurements and outcome questionnaires. They conclude that, compared with the contralateral knee as a control, the lateral tibial plateau remains anteriorly subluxed in extension and 30 degrees of flexion posto-peratively. Thus hamstring ACL reconstruction in the using their technique did not effectively correct the “pivot abnormality”, with the tibia remaining internally rotated relative to the femur in extension.
It has long been established both in biomechanical studies and in reported clinical outcomes, that ACL reconstruction does not re-establish normal knee kinematics.1 This study quantifies this concept in further detail by using a more “physiological” radiological assessment tool with the knee in a weight bearing state, at different angles of flexion. Although there are some doubts regarding using the “flexion facet centre technique”, this is a well-established method of measuring tibial translation.2
Whilst ACL reconstruction remains a relatively successful procedure in terms of patient satisfaction,3 the return to peak performance level of elite athletes remains disappointingly low.4 This may be related to the lack of restoration of normal kinematics. The challenge in ACL surgery remains in improving the clinical outcome in terms of knee stability and return to activity in high demand athletes, by restoring more normal kinematics of the knee. This “holy grail” centers around the pivot shift phenomenon,5 of which internal rotation of the tibia in extension is a part.
As with many worthwhile studies, this paper raises more questions than it answers: would bone-patellar tendon-bone reconstruction have restored the biomechanical parameters more reliably? Was the persistent internal tibial rotation caused by gradual stretching of the graft post-operatively due to viscoelasticity, or by slippage of the tibial fixation? A what angle of flexion was the graft tensioned, and was an external rotation torque applied to the tibia at the time of tensioning to counteract the internal rotation abnormality?
The authors also mention the debate about double bundled reconstruction providing more faithful restoration of kinematics.6 Double-bundled reconstruction is certainly a more anatomical procedure, but questions remain as to its clinical advantage, the risk of differential failure of bundles, and its technical demands for the non-specialist orthopaedic surgeon. Related to this is the femoral tunnel position in the single-bundled reconstruction. It could be hypothesised that a more oblique tunnel position further away from the centre of rotation of the knee may provide greater control of the tibial internal rotation.7,8 It would be interesting to assess the femoral tunnel positions in these 12 patients.
The key to restoring better knee kinematics in ACL surgery lies in understanding the structures that are damaged in addition to the ACL. There are several mechanisms that result in ACL injury,9 and it may be that different mechanisms result in injury to different secondary structures. These include the posterolateral corner, the posteromedial capsule and also the anterolateral capsular structures. The restoration or reconstruction of these additional structures may improve kinematics.
One further possibility in dealing with persistent lateral tibial anterior translation, is by augmenting the ACL reconstruction with a lateral extraarticular procedure (e.g. MacIntosh or modification thereof). This would surely provide better correction of tibial internal rotation, but has been attempted many times in the past. The literature generally does not show favourable results, with some notable exceptions.10 With newer techniques of hamstring ACL fixation and improved rehabilitation protocols, it may be worth analysing why extra-articular reconstruction failed in the past (e.g prolonged immobilisation in a cast post-operatively), and whether this technique is worth revisiting with new eyes.
The numbers of patients in this single centre study are too small to make any firm conclusions regarding hamstring ACL reconstruction as a whole, but the need for improvement in our techniques in order to better restore knee biomechanics and kinematics is highlighted well by its results.
1. Lie DTT, Bull AMJ, Amis AA. Persistence of the mini pivot shift after anatomically placed anterior cruciate ligament reconstruction. Clin Orthop 2006;457:203-9.
2. Nicholson JA, Sutherland AG, Smith FW, Kawasaki T. Upright MRI in kinematic assessment of the ACL-deficient knee. Knee. 2010 Dec 14. Epub ahead of print.
3. Mansson O, Kartus J, Sernert N. Health- related quality of life after anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc 2011;19:479-87.
4. Arden C, Webster KE, Taylor NF, Feller JA. Return to the preinjury level of competitive sports after anterior cruciate ligament reconstruction surgery: two-thirds of patients have not returned by 12 months after surgery. Am J Sports Med 2011;39:538-43.
5. Galway RD, Beaupre A, MacIntosh DL. ‘Pivot shift: a clinical sign of symptomatic anterior cruciate insufficiency.’ J Bone Joint Surg [Br] 1972;54-B:763-4.
6. Williams A. Further opinion on ‘Longo AG, King JB, Denaro V, Maffulli N. Double bundle arthroscopic reconstruction of the anterior cruciate ligament. Does the evidence add up? J Bone Joint Surg [Br] 2008; 90-B:995-9.
7. Lee MC, Seong SC, Lee S, et al. Vertical femoral tunnel placement results in rotational knee laxity after anterior cruciate ligament reconstruction. Arthroscopy 2007;23:771-8.
8. Seon JK, Park SJ, Lee KB, Seo HY, Kim MS, Song EK. In vivo stability and clinical comparison of anterior cruciate ligament reconstruction using low or high femoral tunnel positions. Am J Sports Med 2011;39:127-33.
9. Boden BP, Dean GS, Feagin JA Jr, Garrett WE Jr. Mechanisms of anterior cruciate ligament injury. Orthopedics 2000;23:573-8.
10. Ireland J, Trickey AL. MacIntosh tenodesis for anterolateral instability of the knee. J Bone Joint Surg [Br] 1980;62-B;340-5.
Mr Chinmay Gupte
Consultant Trauma and Orthopaedic Surgeon and Senior Lecturer
Imperial College NHS Trust and Imperial College London, UK