Total Knee Arthroplasty In Patients With Parkinson's Disease- A Critical Analysis of Available Evidence

Background: In this era of modern medicine, there is an increase in life expectancy and thereby an ageing population. Among this group one of the most common neurological disorder is Parkinson disease and one of the most common operation done in elderly population is a total joint arthroplasty. But total joint arthroplasty in Parkinson disease is a relatively uncommon entity. There is sparse literature available with regards to total knee arthroplasty (TKA) in Parkinson disease. This review focusses on the necessity, complications and previous experiences on TKA in PD based on the literature available. Method: The review was conducted after a series of advanced search in the following medical databases; Pub med, Biomed central, Cochrane and Google scholar for articles related to total knee replacement in patients with Parkinson’s disease. The following keywords were used; Total knee arthroplasty, Parkinson’s disease, Hoehn and Yahr, Flexion Contracture. Results: The review indicates that the functional outcome is comparable to that of controls in immediate post-operative phase, one year and three-year phase, but the long term functional outcome seems to deteriorate significantly. Conclusion: Total knee arthroplasty can serve as an effective tool in alleviating pain in short term as well as long term periods, whereas the functional outcome seems to deteriorate post operatively on a long-term basis. Nevertheless, TKA in PD is a challenging situation, thereby necessitating a holistic approach with the efforts from various specialists needed at each stage to ensure a successful operation.


INTRODUCTION
Parkinson's disease (PD) is a neurodegenerative disorder affecting approximately 4 million people worldwide. The disease is due to the decrease in the dopaminergic activity in the nigro striatal pathway leading to a dysfunction of the basal ganglia and is characterised by motor disturbances and cognitive impairments [1]. The mean age of onset is 55 years [2]. With the improvement in life expectancy, the prevalence of Parkinson's disease is projected to be on the rise and thereby a significant increase in number of total knee arthroplasty (TKA) to be performed in PD. Therefore, it is of paramount importance for the orthopaedic surgeon to have clarity and knowledge in the approach of TKA in PD amidst varying results as recorded in available literature till date. This review tries to delineate the common problems encountered, factors influencing the outcome and considerations for TKA in PD based on the available literature.

Age:
A review of epidemiology in knee arthroplasty highlights that there has been a fivefold increase in the rates of primary TKA since 1980, primarily due to an ageing population [3]. The mean age at the time of presentation varies from 70-73 years in the available literature [4 -7]. Higher age group is associated with increased mortality and ironically a decrease in revision rates [8].

Gender:
The utilisation rates of arthroplasty seems to be equal in males and females. In PD post TKA, males are seen to have an increase in mortality whereas females are associated with an increase duration of hospital stay [8].

Clinical features:
Selection of patients with a preoperative flexion contracture, dementia and medical co morbidities like cardiovascular disease are associated with increased mortality and decreased functional outcome post TKA [8].

Stage of Parkinson's disease:
A pre-operative staging of disease is essential to determine to what extent the PD symptoms can worsen postoperatively in a given time. A scoring system would help in delineating patients who can be candidates for TKA. PD patients with impaired righting reflexes and physical instability are a contraindication for TKA. Patients with a Modified Hoehn and Yahr stage of disease less than 3 can be operated upon after taking into account the associated comorbidities. Modified Hoehn and Yahr staging ( Table 1), Columbia classification (Table 1a) were used in the studies [5,6,9,10].

Bone Mineral Density:
Patients with PD have a positive correlation with reduced bone density and are prone to vitamin D deficiency. The bradykinesia and rigidity results in the lack of spontaneous activity and muscle disuse. This in turn predisposes for an increased osteoclast mediated calcium resorption. The reduced bone mass can lead to an increased risk of peri prosthetic fracture in patients with PD. Treatment with bisphosphonates and teriparatide has been tried, however there are no consensus in this regard. However, it is imperative that bone density is assessed in patients with PD and treated appropriately pre-operatively [11].
The authors feel that the indication for TKA in PD is almost similar to that of TKA in general population, mostly due to the degenerative osteoarthritis. In addition, x ray studies have shown that the medial compartment is more commonly affected than the lateral compartment [6].

Anaesthesia:
From the available studies the use of general anaesthesia is to be avoided as the chances of post-operative confusion and psychological co morbidities is higher. More specifically, the use of levodopa and bromocriptine is known to cause orthostatic hypotension and therefore it is suggested that these medications are administered at low doses. Propofol is widely used for induction in general anaesthesia for neurodegenerative conditions but it is associated with spontaneous involuntary movements in patients with Parkinson's. There occurs an increased sensitivity of the myocardium to the catecholamines when halothane is used in patients receiving levodopa. Due to the risk of exacerbation of extra pyramidal symptoms, anti-emetics like phenothiazine and metoclopramide are best avoided. Factoring in on these inherent complications of general anaesthesia in patients with PD, the use of regional anaesthesia spinal, epidural / combined has been suggested to be a safer option [11].

Implants:
Implant selection is of great importance as it can decide the functional outcome of TKA in PD. The most important consideration while selecting the implant is the role of extensor mechanism of PD patients. The extensor mechanism is prone to disruption due to rigid hamstrings or severe flexion contracture and this can lead to implant dislocation. Condylar constrained, hinged knee device or cruciate retaining device is used to overcome this [6,12]. No single design of TKA is suitable for every patient, the design should be chosen with the conditions of the patient and the comfort of the operating surgeon in mind.

Unilateral versus Bilateral:
The scope of a bilateral TKA in PD is less. Duffy and Trousdale have found that a bilateral TKA is associated with a poor knee society functional score (KSFS) at 3 years and further decline in KSFS score at end of five years. With unilateral TKA there is an improvement in KSFS score after three years but a decline in KSFS score is noted at the end of five years [6].

Blood loss:
Till date there is no evidence in literature stating the blood loss and its role in TKA for PD patients.

Pain management:
Unlike pain management of TKA in general population, the use of opioids is avoided in PD. The reason for avoidance of opioids is its ability to significantly depress the CNS in an already co-existing cognitive dysfunction. Patients with neurogenerative diseases are likely to be on monoamine oxidase inhibitors (MAOI) and the use of opioids ( in conjunction with the MAOI's can lead to the development of serotonin syndrome. Hence, the opioids are contraindicated [11] and the anti-inflammatory medications are used for pain management post operatively in patients with normal renal functions [13].

Infections:
The occurrence of superficial skin infection as well as deep infection are noted in studies [6,8]. This points to a strict vigil that needs to be maintained during wound checks and sufficient antibiotic prophylaxis to be administered.

Physical therapy:
The initial studies on TKA in PD have proven that a delay in initiation in physical therapy results in flexion contracture, quadriceps rupture and a poor functional outcome. There should be a gradual increase in initiation of physical therapy as conventional post-operative TKA physical therapy protocols can result in disruption of extensor mechanism (14,15).

Musculoskeletal issues:
As noted in many of the earlier studies, the occurrence of flexion contracture, extensor mechanism disruption due to a rigid hamstring are a few musculoskeletal complications which can occur post operatively [4,5,9]. Proper rehabilitation methods are needed to be in place to check these complications [15].

Worsening of Parkinson's Disease:
Most of the studies indicate an increase in severity of the disease post operatively on a long-term basis [7,8]. This change can be detected by worsening cognition, impaired righting reflexes or an increase in muscle imbalance [16].

Thromboprophylaxis:
Vince et al [5] had reported incidence of DVT and pulmonary embolism, hence the initiation of mechanical thromboprophylaxis with incentive spirometry, chest physiotherapy, pneumatic compression devices is essential. However, it is to be noted that there are no studies specifically indicating the rates of thromboembolic episodes in patients with PD. The authors suggest that for patients with PD, DVT prophylaxis measures should be practiced just as in TKA in general population.

THE FUNCTIONAL OUTCOME OF TKA IN PD
The functional outcome was quantified in three studies. Among the three studies, the study conducted in Dundee, UK was the sole exclusive outcome analysis study [7]. This study had used the knee society score and knee society function score. The other two studies used the knee society score [5,6] (Table 2). These reports indicate that the functional outcome is comparable to that of controls in immediate post-operative phase, one year and three-year phase, but the long term functional outcome seems to deteriorate significantly. The deterioration in functional outcome can be attributed to the progression of the Parkinson's disease and not the operation per se.

COMPLICATIONS RELATED TO TKA IN PD
Some of the complications post TKA in PD based on available literature is discussed below and given in Table 3. Table 3. Complications.
Increased mortality and hospital stay [8]

Flexion Contracture
The most highlighted complication in literatures is of the development of a flexion contracture in post TKA patients. This can be viewed in two aspects; first one being a delayed initiation of physical therapy and second aspect being development of flexion contracture in PD patients who had pre-operative muscle imbalance and ataxia [4,5]. Flexion contracture post operatively was observed only in three studies (Oni and Mackenney in 1985, Insall et al 1989and Shah et al 2004. In all these three studies initiation of physical therapy was delayed by atleast a week post operatively; whereas in other studies there was prompt early mobilisation which resulted in no flexion contracture post operatively, thereby highlighting the need for early mobilisation postoperatively. A study by Shah et al [9] in 2004 demonstrated the potential role of injecting Botulinum toxin type A into the muscle to relieve flexion contracture. Presence of flexion contracture postoperatively can significantly affect the functional capacity and range of movements in patients sometimes necessitating revision in such patients [4,5].

INFECTIONS
Superficial necrosis and wound infection was seen in five patients in the study conducted by G.P.Duffy and Robert Trousdale [6] that led to a delay in the outcome process. The infection rates in PD post TKA is comparable with that of the controls as stated in the nationwide registry of Finland study [8].

CONCLUSION
Total knee Arthroplasty is not an absolute contraindication but can be a relative indication in patients with Parkinson's disease where conservative line of management has failed. Preoperative assessment, collaborated efforts of specialists from various disciplines, appropriate surgical prosthesis design, early physiotherapy aids to prevent postoperative complications and a reduced hospital stay. TKA can serve as an effective tool in alleviating pain in short term as well as long term, whereas the use of TKA for the functional outcome rather seems to decrease post operatively on a long-term basis. Further studies focussing on functional outcome in post TKA PD patients with parameters like progression of disease, severity of disease and associated medical comorbidities should be compared and studied with matched controls over a long term for better understanding of tolerance of TKA in PD. TKA in PD is a challenging situation, thereby necessitating a holistic approach with the efforts from various specialists needed at each stage to ensure a successful operation.

ETHICS APPROVAL AND CONSENT TO PARTICIPATE
Not applicable.

HUMAN AND ANIMAL RIGHTS
No Animals/Humans were used for studies that are base of this research.

CONSENT FOR PUBLICATION
Not applicable.