General:
Any major surgery (not just hip replacement) carries certain risks. These are: bleeding, venous thrombo-embolism and anesthesia-related or medical-related – like disturbances of blood pressure or blood sugar, chest infection, and rarely, stroke, ischemic heart disease, etc.
Risks specific to hip replacement involve infection, limb length discrepancy, dislocation, nerve injury, stiffness, wear and aseptic loosening, etc.
The risks of hip replacement surgery are relatively low. This is because of preoperative optimization of patient’s condition (like control of diabetes, blood pressure, etc) and strict adherence to preoperative, intra-operative and post-operative care plan. In general, operations on extremities carry lesser systemic risks and permit faster post-operative recovery as compared to abdominal or cardio-vascular surgery – as there is no surgical handling of vital organs in the abdomen or chest. In addition, general anesthesia can be avoided. The rate of major complications like infection is around 1-2 percent.
Infection:
Infection of the joint can occur immediately after or at a later date. The risk of infection is higher in diabetic patients and those suffering from rheumatoid arthritis.
Preventive measures include pre-operative and post-operative antibiotics, strict discipline in operation theatre and the use of a dedicated clean operation theatre with laminar air flow facilities. Prevention of delayed infection is done by proper control of diabetes and other medical conditions and prompt treatment of infection in any part of the body like – teeth, urinary tract, etc.
Treatment of infected joint generally involves reoperation to wash the joint and remove any infected tissues. It may also be necessary to remove the prosthesis and implant a new one later. In severe or recurrent infections, resection arthroplasty (leaving the gap without re-inserting new implants) is advised. This results in shortening of the limb and a flail hip.
Limb length discrepancy:
Severe arthritis, collapse, developmental mal-formations, injuries or proir surgeries can result in severe deformities (usually shortening), soft tissue contractures and bony defects. It may not be possible to correct every aspect of the deformity by standard techniques and implants. Trying to do so may result in excessive surgical dissection, injury to muscles, weakness of stabilizing soft tissues; and tension on nerves leading to foot-drop, etc. In such situations it is preferable to accept some deformity and avoid these complications. This results in unequal leg length, which is treated by a shoe raise. Hip deformities, especially those due to congenital dysplasias or childhood diseases, can cause severe secondary deformities in the spine which are almost impossible to correct.
Dislocation:
The femoral head can slip out of the socket resulting in dislocation. Dislocation mostly occurs in early post-operative period before the soft tissues have healed. It may occur repeatedly and impair the result of the surgery. Improper alignment of the implants or imbalance or weakness of soft tissues may be responsible for this condition. Treatment of acute dislocation involves relocation of the hip (sometimes under anaesthesia) and stabilizing the limb in traction (or in a brace) till the soft tissues heal. Recurrent dislocation needs proper evaluation and may require surgical intervention to correct it.
Injury to nerves and blood vessels:
Direct injury to the nerves and blood vessels occurs very rarely. Indirect injury to the nerves is more common. The sciatic nerve can be stretched during hip replacement, especially if the patient has a severe pre-operative deformity or previous surgical scarring. This results in foot-drop deformity which usually recovers spontaneously. Persisting neurological deficit or significant injuries to blood vessels may require surgical exploration and remedial measures.
Venous Thrombo-Embolism (VTE):
Clotting of blood in leg veins can cause swelling and pain in the leg. Propagation and dislodgement of the clot can cause blockage of the blood flow in the lungs – this can range from a mild to a life-threatening event.
This is prevented by the use of medications, mechanical devices like stockings, foot pumps, etc, epidural anesthesia, proper hydration during surgery and early mobilization of the patient.
Treatment of established thrombosis and embolism involves blood thinning medications and very rarely surgery.
Stiffness and Heterotopic Ossification:
This can occur in patients who have a poor range of motion before surgery and who do not adhere to the physiotherapy/exercise regimen. Treatment is by physiotherapy or manipulation under anesthesia. It should be understood that most artificial joints give a good range, but not the full range, of movements. This is because of design factors and the anatomical peculiarities of each joint.
Sometimes, extra bone forms in the muscles around the hip. This is called heterotopic ossification. Usually this is mild and causes minimal loss of movements. Sometimes, it is excessive and results in significant restriction of motion. These cases may need surgical removal of the excess bone. Post-operatively, Indomethacin and/or low-dose radiation is advised to prevent recurrence.
Persistent pain following surgery:
This could be due to a problem in or around the joint itself like irritation of tendon (psoas tendon at the edge of the cup) or fascia. Pushing the hip to extremes of movement can also result in pain. Pain may also be due to other problems like spondylosis, diabetic neuropathy or poor circulation in the limb. Infection in the hip can also cause pain. A thorough assessment is required to determine and treat the cause.
Wear and Aseptic loosening:
Over a period of time, the plastic, metal and ceramic articulations slowly wear out. The rate of wear is very low and the implant generally lasts around 15-20 years. Polyethylene wear is strictly not a complication but is an expected outcome. It is considered to be a complication when it occurs earlier. Excessive stress like obesity, high impact activities, sports, etc. will lead to early wear.
The fixation of the implant to bone can become loose as a result of mechanical forces or as a reaction to wear debris particles. A variable amount of bone gets resorbed in the process. Wear and aseptic loosening are treated by revising the joint replacement.
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