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Abstracts of Higher Degree Theses

Hamstring Contraction Latency Following Anterior Cruciate Ligament Rupture, Reconstruction and Rehabi I itat ion

David John Beard DPhil MSc GradDipPhys MCSP

Course: DPhil, University of Oxford, 1996

Housed at: Worcester College, University of Oxford Contact address: Nuffield Orthopaedic Centre, Head- ington, Oxford OX3 7 L D

The outcome of individuals sustaining anterior cruciate ligament (ACL) rupture is variable. Why some patients, but not others, having torn this knee ligament are able to maintain a high functional level remains unclear. Understanding the mechanism has implications for both surgical and conservative treatment for the condition. This thesis investigates one possible factor for the varied outcome following cruciate rupture: the ability of the thigh muscles to respond and protect the unstable joint against applied perturbation.

It is well established that the hamstrings and the ACL can act in synergy to resist anterior translation of the tibia. Therefore, the objectives of this study were to develop measurement methods to test the hypothesis that contraction latency of the hamstrings muscles, in response to tibia1 displacement, is increased in the anterior cruciate ligament deficient (ACLD) knee, and then to examine the effect of surgical reconstruction and the effect of conservative treatment on hamstring contraction latency in ACLD patients.

The validity and repeatability of the instrument designed to measure hamstring contraction latency (HCI,) was established. A study of 20 normal subjects revealed no difference between limbs in HCL. A signif- icant increase in contraction latency was found in the injured limb in 54 ACLD patients and a weak positive correlation was found between HCL and functional impairment. Furthermore, the inter-limb difference in hamstring contraction latency was found to decrease following surgical reconstruction. Non-surgical treat- ment, consisting of rehabilitation exercises, was also found to reduce any deficit in HCL. The efficacy of conservative treatment was assessed using measures of both contraction latency and function in a randomised controlled trial of 51 patients. A new functional rehab- ilitation programme was found to be more effective than a traditional strengthening programme. Validity and reliability of functional scoring methods, knee

laxity measures and muscle strength were also exam- ined.

It is suggested that the ability of the hamstring muscles to respond to perturbation of an unstable joint is one of many factors responsible for the variation in outcome of patients who tear the ACL. Theoretical models for contraction latency deficit and change following inter- vention are discussed using support from further control experiments. I t is argued tha t the increased latency in the ACLD knee and changes due to interven- tion, as recorded in this study, are predominantly the effect of mechanical alterations around the knee joint on a reflex of muscle spindle origin.

Bibliography

Beard, D J (1 992). ‘An investigation into the relationship between knee joint laxity and knee function in anterior cruciate ligament deficient subjects.’ MSc thesis, King’s College, University of London. Beard, D J, Dodd, C A F, Trundle, H and Simpson, A H R W (1 994). ‘Proprioceptive enhancement for anterior cruciate ligament deficiency: A prospective randomised trial of two physiotherapy regimes’, Journal of Bone and Joint Surgery,

Beard, D J and Fergusson, C M (1992). ‘The conservative management of anterior cruciate ligament deficiency - A nation- wide survey of current practice’, Physiotherapy, 78, 181-186. Beard, D J, Kyberd, P J, Dodd, C A F, Simpson, A H R Wand O’Connor, J J (1 994). ’Proprioception in the knee’ (letter), Journal of Bone and Joint Surgery, 76-B, 992-993.

Beard, D J, Kyberd, P J, Fergusson, C M and Dodd, C A F (1993). ‘Proprioception after rupture of the anterior cruciate ligament - An objective indication of the need for surgery?’ Journal of Bone and Joint Surgery, 75-8,311-315. Beard, D J, Kyberd, P J , O’Connor, J J, Fergusson, C M and Dodd, C A F (1994). ‘Reflex hamstring contraction latency in anterior cruciate ligament deficiency’, Journal of Orfhopaedic Research, 12,219-228.

Beard, D J, Moser, J and Crawford, C (1994). ‘Management after arthroscopy’ (letter), Journal of Bone and Joint Surgery,

Beard, D J , Soundarapandian, R S, O’Connor, J J and Dodd, C A F (1996). ‘Gait and electromyographic analysis of anterior cruciate ligament deficient subjects’, Gait and Posture, 4, 83-88.

Beard, D J, Zavatsky, A B, Murray, D W, Dowdall, M J and O’Connor, J J (1994). ‘Is leg lifting in full extension safe following anterior cruciate ligament reconstruction?’ Physiotherapy, 80, 7,

Zavatsky, A B, Beard, D J and O’Connor, J J (1994). ‘Cruciate ligament loading during isometric contractions: Guidelines for rehabilitation’, American Journal of Sports Medicine, 22, 3,

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Physiotherapy, September 1996, vol 82, no 9