Isolated unicompartmental osteoarthritis of the knee is common. Operative treatment varies from high tibial osteotomy, unicompartmental knee replacement and total knee replacement according to the age of the patient and the level of activity . Severe osteoarthritis of one compartment in young and active patients with pre-existing deficiency of the anterior cruciate ligament (ACL) and severe functionally instability is a difficult subgroup to manage .
There is considerable debate regarding management of young patients with isolated unicompartment osteoarthritis and concomitant ACL deficiency. The aim of the treatment should be to offer a procedure that will give lasting relief of symptoms and will not compromise any future surgery. Various surgical options have been described, including arthroscopic debridement, reconstruction of the ACL, high tibial osteotomy with or without ACL reconstruction, unicompartmental knee arthroplasty and total knee replacement . None of these address the two major symptoms apart from total knee replacement.
The advantages of unicompartmental arthroplasty over total knee replacement are preservation of bone stock, less invasive surgery, minimal blood loss, faster recovery, better range of movement and more physiological function . It is also more cost-effective than total knee replacement .
Recent studies have shown that, with the proper patient selection and surgical technique, UKA can have performance and survivorship comparable with total knee arthroplasty or high tibial osteotomy .
The anterior cruciate ligament (ACL) is the primary restraint to anterior tibial translation in the native knee . It has been suggested that the ACL also plays an important role in the successful outcome of UKA [7–9]. Unicompartmental knee arthroplasty can provide disappointing long-term results when the ACL is deficient [10, 11].
Good fellow found a greater incidence of failure of mobile-bearing UKA when the ACL was deficient . A nonfunctional ACL was assumed to cause abnormal kinematics of the knee after UKA .
It may be important to divide the ACL deficient group into two subgroups. Firstly those patients with a prior, traumatic ACL tear and functional instability and second those patients with attrition of their ACL, without a concomitant capsule tear and in many instances some arthritis associated capsule stiffness. These patients do not have functional instability related to their ACL deficiency. These two separate groups may explain why some series have found poor results with ACL deficiency and other no difference
The majority of failures were because of tibial loosening, which tended to occur early, with a 21% rate of revision observed by two years . It was proposed that this loosening may have resulted from eccentric or increased loading caused by posterior femoral subluxation or instability . It was reasoned that if the posterior subluxation and instability could be prevented by reconstruction of the ACL, it might reduce the incidence of tibial loosening in this setting.
In the recent series, Pandit confirmed that the normal kinematics is restored in the ACL Deficient arthritic knee by combing ACLR and Oxford UKA. It is probably because the kinematics is restored that the patients who have had an ACLR and UKA have been able to achieve such a high level of function.
We report the early term results of fixed bearing unicompartmental knee arthroplasty in patients with isolated one compartment osteoarthritis and concomitant ACL deficiency with functional instability, in whom ligament reconstruction was undertaken as a combined procedure.