TKR is the most common surgical intervention, if the patient complains of severe tibiofemoral and patellofemoral pain, loss of knee joint functions mobility with severe deformity. During the past five years, the number of TKR performed in India has increased an average of 30% each year and the same growth rate is expected to continue in forthcoming decade [1]. Over the past four decades, joint replacement surgery has become the most successful surgery for patients with severe debilitating arthritis [2]. Patients who undergo TKR show marked improvements in function and reduction in pain compared with their preoperative condition [3,4]. However, recovery of functional ability is variable and not all patient experience significant improvements in pain and functions [5,6].
Therefore, rehabilitative efforts should focus on activities that help patients to improve performance of activities of daily living. The basic drawback in postoperative rehabilitation is adhering to a protocol or a “cookbook approach”. The muscle impairments following TKR varies with different surgical approaches, but till date exercises are not designed according to the postoperative needs. The guidelines for rehabilitation progression should be tailored respecting the tissue healing parameters. It is believed that certain factors would best predict long term outcomes. Identification of these factors will aid in the creation of targeted therapeutic interventions to maximize postoperative functional ability [7].
The Orthopaedic Forum, National Institutes of Health (NIH) consensus statement on TKR in 2003 revealed that the rehabilitative services are the most under studied aspect of the postoperative management [8]. Although, there are several theoretical reasons to explain the postoperative impairments such as muscle weakness, atrophy, abnormal joint mechanics but there is no evidence supporting the generalised use of any specific preoperative or postoperative rehabilitation intervention. Finally, they concluded that there is no evidence –based guidelines exist for promoting or limiting post-TKR physical activity.
Despite major advances in the field of total joint arthroplasty, a standardised postoperative management protocol currently does not exist following TKR [9]. Despite the high incidence of TKR in recent years, there is no postoperative rehabilitation approach being incorporated correctly to address the muscular and functional deficits following surgery [10] and no studies have focused on evaluating the effects of tailored rehabilitation protocols [7] and yet not analysed in Indian population too.
Hence, the current literature states a need for protocol to mitigate these impairments and ultimately result in improved functional outcomes. The proposed protocol was designed based on principles of TKR rehabilitation as proposed by Zeni JA Jr and Snyder-Mackler L in 2010 [7]. The designed protocol requires a validation process for its relevance and ease of performance.
The term validity is referred to a test/protocol measuring what it intends to measure [11]. The content validity is also quiet similar to face validity using subjective judgement. Hence, an expert opinion is sorted to test the protocol for its intensions and practicality. The present study aimed to validate the content of TKR rehabilitation protocol in Indian population.
Materials and Methods
The process of content validation involves development stage and expert judgment stage. The protocol was designed into three stages with extensive review of literature [7,12-16]. The staging of protocol is mannered in a progressive way, meeting the functional needs of patient. The staged rehabilitation of TKR protocol follows a set pattern of exercises in non weight bearing position followed by weight bearing exercises then with functional exercises. Totally ten experts were selected for the validation process but only nine experts in field of musculoskeletal physiotherapy gave consent to participate in the study. This validation study was approved by the Institutional Ethics Committee of Sri Ramachandra University, Chennai, Tamilnadu, India.
TKR Protocol
The structured rehabilitation protocol [Annexure-1] is staged into three comprising early function phase (protective phase) from day 1 to two weeks, progressive function phase (transitional phase) from three weeks to six weeks and advanced function phase (activity phase) from seven weeks to 12 weeks. Each phase has several categories including: prerequisite, goals, precautions, therapeutic exercise with frequency and duration, functional activities, criteria for progression and outcomes measured.
In phase 1, therapeutic exercise has specific components as like general exercises, mobility exercises, stretching, muscle activation and functional training. The progressive function phase and in advanced function phase has mobility, stretching, strengthening, closed chain activities, balance training, functional training and aerobic conditioning components. Phase1 is considered as inpatient phase and discharge planning is made, whereas phase 2 and 3 are home based under supervision and minimal supervision phases respectively. The TKR protocol is aimed to reduce joint pain, swelling, promote scar healing, remodelling and improve pain free knee mobility in accordance to prosthetic kinematics. Further aimed to improve key muscle strength of quadriceps muscle and hamstrings muscle in varied types of contraction, regaining a normal gait pattern and neuromuscular coordination for walking. Finally, the protocol concludes in regaining complex weight bearing activities like stair ascent, descent, proprioception, balance and coordination for complex activities.
The protocol is developed based on current literature and muscle impairments following TKR [10,12-16]. On analysis of protocol, it was found many exercises as like closed chain exercise and balance exercises are not commonly incorporated amongst TKR patients. Hence, the protocol requires content validation by experts.
Procedure of Validation
The primary investigator invited 10 independent experts with minimum 10 years of experience in musculoskeletal physiotherapy. As per recommendations by Lynn MR [17] a minimum of five and a maximum of 10 experts are required for the validation process. Out of 10, nine experts agreed to participate and were diversely placed in Southern parts of India. All experts were practicing musculoskeletal physiotherapy including five Professors and four senior Physiotherapists. The process of validation included rating of experts in a 5 point likert grading on two parameters namely relevance and ease of performance. The scale was scored as 1=strongly disagree, 2=mildly disagree, 3=neutral, 4=agree, 5=strongly agree. The score 4 and 5 were acceptable for calculation, if scored less than 3, experts were requested for suggestions. The key exercise components were listed in three stage manner with likert scale being measured for its relevance and ease of performance. The prepared content was sent through electronic media and basic instructions were given. Based on expert’s inputs on TKR protocol, the level of agreement, content validation index and kappa value was calculated.
The content validation index was calculated by dividing number of experts who scored 4 or 5 by total number of experts participated. The cut off level for acceptance if >0.78 as in accordance to a study [18], thus seven out of nine agree for an exercise. This further highlights that if level of agreement is greater than 78%, the exercise is considered with good agreement among experts and to be included in protocol. A modified kappa was calculated to confirm the relevance of exercise protocol. The interpretation of kappa values were proposed as: fair= 0.40 to 0.60, good= 0.60 to 0.74 and excellent= 0.75 to 1.00.
Results
Based on the reports of nine experts, the Content Validity Index (CVI) is tabulated in [Table/Fig-1]. The protocol has eight components namely general exercises, mobility, stretching, muscle activation, strengthening, closed chain activity, balance training and functional training.
Content Validity Index (CVI) and kappa (K*) of TKR protocol.
| Contents of TKR protocol | Relevance | Ease of performance |
|---|
| CVI | Kappa | CVI | Kappa |
|---|
| General |
| Chest Physiotherapy | 100 | 1.00 | 100 | 1.00 |
| Bed mobility | 100 | 1.00 | 100 | 1.00 |
| Mobility |
| Continuous passive motion | 89 | 0.89 | 67 | 0.60 |
| Heel slides in supine lying | 89 | 0.89 | 89 | 0.89 |
| Hip abduction in supine lying | 100 | 1.00 | 89 | 0.89 |
| Passive patellar glides | 89 | 0.89 | 89 | 0.89 |
| Stretching |
| Knee extension stretch | 100 | 1.00 | 100 | 1.00 |
| Scar tissue mobilization | 100 | 1.00 | 78 | 0.76 |
| Muscle Activation |
| Isometrics of key muscles | 100 | 1.00 | 100 | 1.00 |
| SLR, Short arc knee extension | 100 | 1.00 | 100 | 1.00 |
| Seated knee extension | 100 | 1.00 | 100 | 1.00 |
| Hamstring curl | 100 | 1.00 | 100 | 1.00 |
| Vastus medialis oblique activation | 89 | 0.89 | 78 | 0.76 |
| Strengthening |
| Hip abduction in side lying | 100 | 1.00 | 100 | 1.00 |
| Multi angle hip movements in standing | 100 | 1.00 | 100 | 1.00 |
| Resistance exercises to quadriceps and hamstring | 100 | 1.00 | 78 | 0.76 |
| Closed Chain Activity |
| Vastus medialis oblique contraction in standing | 89 | 0.89 | 100 | 1.00 |
| Wall slides | 100 | 1.00 | 89 | 0.89 |
| Forward and lateral step up | 89 | 0.89 | 100 | 1.00 |
| Balance Training |
| Standing-arm raise and diagonal reach | 100 | 1.00 | 100 | 1.00 |
| Standing on foam pad | 89 | 0.89 | 78 | 0.76 |
| Standing on wobble board | 89 | 0.89 | 78 | 0.76 |
| Obstacle walking | 89 | 0.89 | 100 | 1.00 |
| Functional Training |
| Full weight bearing standing | 89 | 0.89 | 89 | 0.89 |
| Symmetrical weight shift in standing | 100 | 1.00 | 89 | 0.89 |
| Unsupported ambulation | 100 | 1.00 | 78 | 0.76 |
| Stair ascent and descent | 100 | 1.00 | 100 | 1.00 |
The 29 item TKR rehabilitation protocol was graded by all experts with good agreement among them. Apart from 27 items, two exercises were rated with poor agreement namely upper extremity strength training (CVI-67%) and lap stool exercises to improve knee mobility (CVI-44%). The experts suggested that upper extremity strength training was not specific to the protocol and lap stool exercise are not commonly prescribed and it may produce more forces on replaced knee joint. Hence as per expert’s suggestion, these two exercises were excluded from protocol.
The CVI of > 78% is considered to exhibit excellent level of agreement; those exercises with CVI less than 78% are not included in the protocol as described above. Expert’s opinion in use of Continuous passive motion is CVI-89% and its ease of performance was rated 67%.
The three staged TKR protocol almost exhibited an excellent agreement on all stages. However, muscle activation exercises(except Vastus medialis oblique activation), stretching, strengthening program and functional training showed 100% agreement than other stages. In general group of exercises, both chest physiotherapy and bed mobility exercises, the CVI is 100%. All exercises in joint mobility program has CVI >89%, except CPM. The ease to perform scar tissue mobilization was rated as CVI 78%. All the exercises used to activate major muscles following TKR have excellent agreement of 100% except VMO activation (Relevance CVI-89% and Ease of performance-78%).
The strengthening program of major muscles of Knee joint had excellent agreement amongst experts but ease of performing resistance exercises has been rated CVI-78%. Closed chain activities relevance of performing VMO activation in standing and step up exercises is 89%. The stable base standing with arm reaches and in diagonal reaches has excellent agreement of 100%, whereas foam pad and wobble board standing balance training has 89% relevance and 78% ease to perform it. In functional training, the ease to perform full weight bearing standing, symmetrical weight shifting in standing and unsupported ambulation was rated 89%, 89% and 78% respectively.
Discussion
The main finding of the present study is that 27 exercises out of 29, exhibited excellent agreement. The process of validation includes development of protocol, initial review of few experts, expert judgment process and analysis. The proposed structured TKR rehabilitation protocol was considered to possess excellent content validity and applicable to primary TKR in Indian population.
Before the validation process, a group of experts evaluated the face validity of the protocol, in which few exercises were not considered by the members. This includes Neuromuscular Electrical Stimulation (NMES) for quadriceps, prone leg hang to encourage knee extension and strengthening of knee rotators. A Cochrane review in 2010 has concluded the use of NMES after TKR is unclear and poor evidence exists on its use [19], moreover its use for activation may be applicable in poor quadriceps strength. It was considered by the experts that adopting prone positions in acute postoperative period to perform prone leg hang was not found to be feasible. Whereas, strengthening the key stabilizers of knee joint is required rather considering knee rotators, which is not found in literature. Hence before validation process, these three exercises were excluded from the protocol.
The role of chest physiotherapy and early bed mobility exercises on postoperative day one was rated to be the most crucial step to start the rehabilitation process. Continuous passive motion is considered to be an early intervention following TKR, despite various controversies of its use, experts agreed the relevance of using CPM but not the ease of performance in acute postoperative care. Hence, the use of CPM is left out to be optional in TKR rehabilitation. This finding is in accordance to a very recent study in 2014 [20] concluded that there is no high quality studies in CPM and its use need to be reconsidered. The stretching program comprises knee extension stretch in acute postoperative days to prevent flexion contractures as it is a normal tendency for patients to maintain in minimal knee flexion to ease pain. However, the importance of scar tissue mobilization during remodeling phases was also considered to be significant in preventing tissue tightness.
The muscle activation program was considered to possess excellent agreement amongst experts. Muscle impairments are the most crucial parameter to be addressed following TKR, hence muscle activation program will address those needs [10]. Of all the muscle activation exercises, Vastus medialis Obliques muscle activation was rated less, as no studies reported its use in TKR. The protocol further explains the need for resistance exercises and methods to implement strengthening program. This stage also exhibits excellent validation index, as studies reported that resistance exercises will show better improvements if muscle impairments are resolved through muscle activation programs [12]. The optimal resistance ranges from 0.5 kg to 1 kg as prescribed in a TKR outpatient protocol, however in later stages, 60% of one Repetition Maximum (1RM) can be employed.
Closed Chain Activities (CCA) are not so commonly incorporated in TKR protocols because of its kinematic loading characteristics. The key important mechanical principle behind closed chain exercises is co-contraction of muscle groups; however lateral step up exercises will recruit/train quadriceps to a greater extent. Studies analysing the effects of CCA are sparse apart from a case report in bilateral TKR [13].
Mostly rehabilitation programs are designed to increase range of motion and strengthening muscles but measures to improve balance is neglected [15]. Even though the CVI of staged balance training was found to be excellent, careful administration of methods is required in acute stages. In this present study, basic balance training like forward arm reaches; diagonal arm reaches in standing are incorporated. This stage of training is expected to promote early return of functional activities and weaning of assistive device. Further, the balance training is progressed in standing using foam pad with eyes open and followed by eyes closed and use of wobble board is optional. The benefits of additional balance training will significantly impact early functional recovery following TKR [15].
Thus the structured, staged TKR rehabilitation protocol was well appreciated by majority of experts and the functional training and aerobic conditioning was considered to be the most integral part of rehabilitation.
Limitation
The limitations of the present study include experts were recruited only from the Southern parts of India for the validation process.
Conclusion
The structured TKR rehabilitation protocol exhibited excellent content validity to its use in Indian population. The protocol is safe and can be administered from initial postoperative day till full functional recovery. In future, the effectiveness of validated TKR protocol in Indian population to be analysed and next levels of validation testing to be carried out.