Total Hip Replacement

THR X-ray

Description

A total hip replacement is a surgical procedure in which both damaged surfaces of the hip joint are replaced with prosthetic substitutes. It was first performed in the 1960's and is said to be one of the most successful surgeries in the last few decades.[1] It was called "The operation of the century" in an article published in the Lancet in 2007, as a result of the excellent outcomes achieved with this operation.[2] According to the guideline for hip replacements at a tertiary centre in South Africa, 90-95% of hip replacements will still be functioning well after 10-15 years.[3]

During a hip replacement, the head of the femur is replaced with a prosthetic head on a shaft, and the joint surface of the acetabulum is lined with a bowl shaped synthetic joint surface. A partial replacement can also be done for neck of femur fractures (mostly displaced)[4] where only the femoral part is replaced. A lot of advances occurred in hip research over the last decade, but age, medical problems, hip disease, activity status and possible fracture characteristics should all be taken into account when considering hip replacement surgery.[5][6]

Clinically Relevant Anatomy

The hip is a ball and socket joint, meaning that the head of the femur fits into the acetabulum of the pelvis. The ball is the femoral head which fits into the socket, the acetabular part of the pelvis. This ball and socket design allows the poly-axial movement seen at the hip. The acetabulum is cup-shaped, providing the articular surface for the head of femur to move within. The head of the femur is gripped by the acetabulum beyond its maximum diameter. The head of the femur and the inside of the acetabulum are covered with a layer of hyaline cartilage.[7] Once this cartilage is worn away or damaged (usually by arthritis), the underlying bone is exposed, resulting in pain, stiffness and possibly shortening of the affected leg. By replacing these surfaces the aim is to reduce pain and stiffness to restore an active and pain-free life.

Hip.jpg

Epidemiology/Etiology

Total hip replacement is a frequently done procedure.[8][9][10][11] Although mostly done electively, it is also used to in the management of hip fractures (mostly displaced neck of femur fractures) caused by trauma (e.g. fall) or pathological processes. Osteoporosis and osteomalacia are significant factors responsible for the high incidence of hip fractures within the elderly population. Arthritis is a common degenerative process occurring in joints within this elderly population, with osteoarthritis being the most common of the varieties. Due to the high degree of success at reinstating independence and mobility of osteoarthritis sufferers, total hip replacement procedures have become a well accepted treatment modality for hip degeneration secondary to osteoarthritis[8][9][10][12][11]. It is also a treatment for juvenile rheumatoid arthritis but only if all the other options have failed[12].

Clinical Presentation

Preoperative:

  • Neck of femur fractures: Often unable to walk, complains of vague pain in the knee, thigh, groin, back or buttock and difficulty of weight bearing [13]. Impacted femur neck on X-ray.
    Neck of femur fracture
  • Osteoarthritis: Sensible or audible crepitations on movement, inability to assume the neutral anatomical position. Often also linked with painful and/or decreased range of motion. X-ray findings commonly include decreased joint space, subchondral sclerosis, cyst formation and osteophytes.[14]
    Hip osteoarthritis
  • Rheumatoid arthritis: Range of all hip movements are impaired, movement is painful, pain and stiffness when the activity is resumed after resting. [12] 
Avascular necrosis

Indications for surgery

Pain and loss of mobility are the most common preoperative complaints of patients prior to a total hip arthroplasty.[16] In advanced cases, despite full conservative management, persistent pain, limited mobility and night pain is normally present.[3] Preexisting hip disease is a valid indication for primary total hip replacement. When there are complications with the internal fixation of a fracture to the femoral neck, in particularly if articular cartilage in the acetabulum is lost or when endoprosthesis have failed in acute fractures, a total hip replacement is a good solution.[7]

Fractures of the neck of the femur caused by an underlying pathology for example Paget’s disease in older patients are generally treated with a total hip replacement.[7][17] When a patient is suffering from a rapidly destructive hip disease[16] ,a rapid destruction of the femoral head or the pubic ramus is observed on the radiographs, therefore a total hip replacement should be the only option.[12]

Important considerations before choosing for a total hip arthroplasty are age, activity status, the patients expectations and medical conditions based on radiological disorders.[6] [7] In the end it’s the surgeon, together with the patient, decides if a total hip replacement is the best solution for the patient.[7] Hip replacement prioritisation scores (e.g. New Zealand's National Clinical Priority System) can be used to determine the need or urgency of the hip replacement. This is often used in centers where patients are put on a waiting list for surgery due to limited resources, scoring patients on need and benefit of the surgery.[18]

Common indications include:[19]

Diagnostic procedures

Diagnosis of patients requiring total hip replacement surgery is mostly symptom based. Pain, loss of range of motion and functional impairments are mostly considered here. A comprehensive differential diagnosis should also be made for patients complaining of hip pain, as it can often be referred from the spine or pelvis and have no connection to the hip joint itself.[12] An orthopaedic surgeon will guide the diagnosis and management process.

Consultation with an orthopaedic surgeon would include the following:[15] (Also see the page for hip examination)

  • Observation
  • Subjective interview:
    • Complaints of pain, deformity, stiffness and/or limp
    • Previous history linked to hip pain (congenital or childhood problems, previous trauma)
  • Physical examination:
    • Standing
    • Trendelenberg test
    • Gait
    • Supine (including leg length)
  • Objective observation (posture, deformities, muscle atrophy)
  • Range of motion

There are specific ways to diagnose osteoarthritis, rheumatoid arthritis and hip fracture but for those subjects see the links above.

Special investigations

  • X-rays: AP pelvis for hips

This would be the first and, in a lot of cases, only radiological investigations requested, as a lot of the diagnoses in need of a hip replacement can be diagnosed or confirmed by this. This will guide the need for further investigations if needed.[15]

Surgery

Surgical approaches

  • Anterior approach (Smith-Petersen)
  • Anteriolateral approach (Watson-Jones)
  • Direct lateral approach (Hardinge/Transgluteal)
Hardinge approach
  • Lateral Transtrochanteric approach
  • Lateral approach
  • Posterolateral approach
  • Posterior approach (Moore/Southern)
Posterior approach
  • Minimally Invasive Approaches (e.g. direct anterior approach)

[20]

Many surgical approaches for THR are described but we can resume them to anterior, lateral and posterior approach. These approaches determine the amount of soft tissue damage and are used to determine the major precautions following total hip replacement surgery. Posterior approach surgery is the most preferred method of total hip replacement surgery.[21] This method provides good visualisation of the femur and acetabulum and also spares the abductor muscle group.[22] Anterior approach surgery is less invasive and damaging for muscles, capsules, ligaments and nerves[23][24]. Other studies have shown a better rehabilitation time and functional outcome[25]. Because of the lowered risk of dislocation compared to a posterior approach[26], early mobilizations as well as full weight bearing exercises according to tolerance are made possible in the first postoperative days[25]. The use of minimally invasive surgery is becoming popular all around the world, due to the quicker recovery rates and reduced postoperative pain.[27] Long term follow-up and comparison studies are still needed in this field.

Prosthesis

Hip prosthesis (titanium), with a ceramic head and polyethylene acetabular cup


The articulating prostheses used by surgeons are made of metal-on-polyethylene (PE), ceramic-on-PE, metal-on-metal and ceramic-on-ceramic[28]. Important components of prosthesis are friction-coefficient, survival, stability against dislocation and fixation in bone tissue[29][30]. In some cases there can be formation of osteonecrosis due to erosion of the two components rubbing against each other[31]. Recent studies have shown that Vitamin E infused polyethylene provides 95% less wear when compared to other liners.[32][33]

Complications

2-10% of patients will develop complications during and after a total hip replacement.[34] The following are the most commonly described in literature and observed in the clinical setting:

  • Dislocation: Decreased dislocation rates when comparing anterior approach to direct posterior approach)[34]
  • Abductor insufficiency: Mostly after direct lateral approach
  • Intra-operative fracture
  • Nerve injury (associated to specific surgical approaches):[35]
    • Direct lateral approach - superior gluteal nerve, femoral nerve
    • Direct anterior approach - femoral cutaneous nerve
    • Posterior approach - sciatic nerve
  • Wound infection and/or sepsis
  • Deep-vein thrombosis or pulmonary emboli
  • Atelectasis
  • Lower respiratory tract infection
  • Leg length discrepancy
  • Prosthetic loosening and implant wear

[35][36][37]

Physiotherapy management

Precautions & contraindications

Patients are at risk of hip dislocation after replacement as a result of the trauma to the hip stabilizers of the hip (capsule, ligaments and muscles) as well as due to the size difference of the prosthesis to the bones. Reduced size of the prosthetic femur head when compared to the average human femur head makes it easier to dislocate until the stabilizing tissues have healed and adapted to this smaller size[38]. This generally takes up to 6 weeks to heal.

Posterior approach:

  • No combination of the following hip movements on the operated side:
    • Flexion > 90 degrees
    • Internal rotation past neutral
    • Adduction past midline
  • Weight bearing restrictions as per surgeon (mostly partial to full weight bearing for 6 weeks after surgery)

Anterior approach:

Hip replacements following this surgical approach is generally more stable. No specific ranges are currently linked to the precaution movements, as surgeon preference should also be taken into account.

  • Patients are encouraged to avoid a) excessive ranges and b) combination of the following hip movements on the operated side:
    • Extension
    • Abduction
    • External rotation
  • Weight bearing restrictions as per surgeon (usually less strict than with posterior approach surgery and patients are able/allowed to mobilise unaided sooner)

Pre-operative

Prescribing preoperative exercise as soon as people are approved for hip surgery could play an important role towards improving preoperative quality of life, because people can wait many months for surgery and might experience further deterioration in health-related quality of life during long waits.[39] Level 2b evidence shows that physiotherapy and educational therapy may be useful for end-stage osteoarthritis.[40] A study on a 6 week education and exercise programme has shown significant and sustained improvements in pain and disability on patients wait-listed for joint replacement surgery. Further positive results included improvements in function, knowledge and psycho-social aspects.[41]

A pre-operative assessment and treatment session is very helpful in the planning of the post-operative management of patients following a total hip replacement. Benefits include decreased length of stay[42],decreased anxiety levels[43], improved self-confidence[44] and establishing a relationship of trust between the physiotherapist and patient early on. Further benefits include improved quality of life and psychological health.[43] It also helps to develop a patient-specific rehabilitation programme to follow post-operative, taking assessment findings into consideration. The main factors defining the therapy management are the surgical approach and the general state of the patient. Whether the patient desires to gain physical fitness or wishes to recover for recreational activity should also be taken into account when establishing the rehabilitation programme.

Research has shown that a combination of verbal explanation and written pamphlets is the best method for health education.[43] It is very important to incorporate this into the pre-operative physiotherapy management of patients prior to total hip replacements. Pre-operative education on precautions are liked to better post-operative adherence.[43]

Assessment:

  • Subjective history
  • Range of motion
  • Muscle power
  • Circulation
  • Mobility and function

[44]

Treatment:

  • Education and advice:
    • Patient information booklet
    • Precautions and contraindications
    • Rehabilitation process
    • Goals & expectations
    • Functional/ADL adaptions
    • Safety principles
  • Encourage to stop smoking if applicable
  • Discharge planning
  • Teach:
    • Bed exercises
    • Transfers in and out of bed (within precautions)
  • Gait re-education with mobility assestive device (crutches vs walking frame vs rollator)
  • Stair climbing

Post-operative

The aim of post-operative rehabilitation is to address the functional needs of the patient (e.g. start mobilising) and to improve strength and range of motion. This starts off as an assisted process, but the aim is to get the patient as functional as possible prior to discharge. As a result of the underlying pre-operative pathology, patients may present with muscle atrophy and loss of strength, particularly in the gluteus medius and quadriceps muscles. The result of the loss of strength is that the elderly are less independent.[8] Although the surgery will correct the joint problems, any associated muscle weakness that was present before the surgery, will remain and require post-operative rehabilitation. Research has shown hip abductor weakness after surgery is a major risk associated with joint instability and prosthetic loosening.[9] Early postoperative rehabilitation after a total hip replacement focuses on resorting mobility, strength, flexibility and reducing pain.[10] It is found that patients can achieve significant improvements through a targeted strengthening programme following total hip replacement.[45]


No specific general hip replacement protocol is currently in use, as small elements of the rehabilitation process is surgeon specific. For example, in some enhanced recovery after surgery protocols, patients are mobilised out of bed within the first 6 hours post surgery. Other settings may only start mobilising patients out of bed on day 1 or 2 post surgery. Accelerated rehabilitation programmes and early mobilisation have shown to give patients more confidence in their post-operative mobilization and activities of daily living, as well as being more comfortable with earlier discharge.[46]

Evidence:

  • Physiotherapy can improve strength and gait speed after total hip replacement and help prevent complications such as subluxation and thromboembolic disease. In addition, physiotherapy increases the patient’s mobility and offers education about the exercises and precautions that are necessary during hospitalization and after discharge.[47] (level of evidence 1a)
  • Physiotherapy maximizes the patient’s function which is associated with a greater probability of earlier discharge, which is in turn associated with a lower total cost of care[48](level of evidence 2c).
  • Physiotherapy provides pain relief, promotes rehabilitation and the reintegration of patients into ADLs. It also provides a better quality of life through the patients’ reintegration into social life [49] (level of evidence 1b).
  • Level 1b evidence suggests that bed exercise following a total hip replacement does not seem to have an effect on the quality of life[50], but stays important for the effects on oedema, cardiac function and improving range of motion and muscle strength (level 4 evidence).[51]. It also allows an assessment of the physical and psychological condition of the patient right after surgery.
  • Early weight bearing and physical activity has benefits for the quality of bone tissue[31] as it improves the fixation of the prosthesis and decreases the incidence of early loosening. The amount of activity is patient specific, and clinical reasoning should be used to make adaptions where needed. Certain specific sport movements have a higher risk of injury for unskilled individuals, and should be incorporated later in the rehabilitation process under supervision of a physiotherapist or biokinetisist.

The following is a suggested protocol in the absence of complications. Surgeon preference should be taken into account, as well as any other factors that might hinder the following of the protocol. Adaptions should be made to make it more patient specific.[44][52]

Day 1 post-surgery:

  • Education and advice
  • Education of muscular relaxation
  • Revision of precautions and contraindications (provided that patient had a pre-operative session with the physiotherapist, otherwise full education will be done as mentioned in pre-operative section).
  • Bed exercises:
    • Circulation drills
    • Upper limb exercises to stimulate the cardiac function
    • Maintenance of the non-operated leg: attention should be paid to the range of motion in order to preserve controlled mobilisation on the operated hip
    • Isometric quadriceps (progressing to consentric VMO) and gluteal contractions
    • Active-assisted (progressing to active) heel slides, hip abduction/adduction
  • Bed mobilisation using unilateral bridging on the unaffected leg
  • Transfer to sit over edge of bed
  • Sit to stand with mobility assistive device (preferably a device giving more support like a walking frame or rollator)
  • Gait re-education with mobility assistive device as tolerated (weight bearing status as determined by surgeon)
  • Sitting out in chair for maximum 1 hour
  • Postioning when transferred back to bed

Day 2 post-surgery

  • Bed exercises as described above, progressing repetitions and decreasing assistance given to patient
  • Progression of distance mobilised and/or mobility assistive device
  • Incorporate balance exercises if needed
  • Sitting in chair

Day 3 post-surgery

  • Bed exercises as described above, progressing repetitions and decreasing assistance given to patient
  • Progression of distance mobilised and/or mobility assistive device
  • Stair climbing (at least 3, or as per home requirements)
  • Sitting in chair
  • Revision of precautions, contraindications and functional adaptions
  • Give 6 week progressive resistive strengthening home exercise to patient; this can include stationary cycling, as long as the patient stays within the precautions (especially posterior approach surgery)
  • Discharge from hospital

Accelerated protocol:

  • Combination of day 2 & 3 to discharge patient day 2 post surgery.
  • Only selected patients

6 weeks post surgery:

  • Patients are normally followed up by orthopaedic surgeon
  • Surgeon determine if the patient are allowed the following:
    • Full range of motion at the hip
    • Full weight bearing without mobility assistive device
    • Driving

After 6 weeks:

  • Gain of initial ROM, stabilization, and proprioception
  • Endurance
  • Flexibility
  • Balance
  • Speed, precision, neurological coordination
  • Functional exercises

Outcome measures

Take home message

Proper preoperative examination and early postoperative rehabilitation is crucial for successful outcome.

Resources

References

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