Orthopaedic Surgery Information

Medial Patella Luxation Treatment & Complications Information Sheet
  LM Veterinary Services
Dr Lyn Minhinnett BVSc MACVSc (Small Animal Surgery)
Medial patella Luxation (MPL) is a common orthopaedic condition in small breed dogs. It occurs less frequently in large breed dogs and infrequently in cats. It affects the stifle or knee joint of the dog.
Medial patella luxation is the term used to describe dislocation of the patella (knee cap) medially (i.e. towards the inside of the leg). It is most commonly associated with abnormal conformation of the knee. The patella normally tracks in a groove at the end of the femur (thigh bone). The patella tendon which attaches the patella to the top of the tibia (shin bone) is misdirected in dogs with MPL and pulls the patella out of the groove. Typically the groove is more shallow than normal which facilitates the patella’s dislocation.
MPL is often present at an early age and may cause no symptoms. Eventually the constant dislocating of the patella produces loss of cartilage on the patella and on the joint adjacent to the groove which leads to pain and osteoarthritis. MPL is graded 1-4 where Grade 1 is the mildest and Grade 4 is the most severe. Grades 1-3 usually have a good prognosis with surgical correction. Grade 4 luxations can be challenging. The most common grades that we see which require surgery are Grade 2-3.

A number of different corrective surgical procedures are utilised depending on the Grade of the luxation and the degree of deformity of the joint. Most commonly the groove is deepened and the bony attachment of the patellar tendon is moved towards the front to draw the patella in the correct direction. Small steel pins are used to stabilise the new position of the bony attachment of the patella tendon on the shin bone. The capsule around the joint may be released on the inside and tightened on the outside.

Potential Complications of Medial Patella Luxation Surgery - Fortunately after performing many of these surgeries the associated complications have been minimised and are low in overall number, but the potential for complications will always exist – just as it does with any person who has an orthopaedic procedure.

There is risk associated with general anaesthesia. This risk is extremely low but it will never be 0%. The hospital team member who is dedicated to the patient’s anaesthesia monitors multiple parameters continuously both during and after anaesthesia. Parameters that are monitored during anaesthesia include heart rate, respiratory rate, temperature, SpO2 (oxygen saturation in the blood) and blood pressure.

 The risk of infection with orthopaedic surgery is less than 1%. We take every possible precaution to prevent infection. Bathing your pet a few days prior to surgery is a helpful precaution. Surgery will not be performed if your pet has a skin infection or evidence of infection in another part of their body. Sometimes when pets have thick coats the presence of a skin infection may not be detected until after the pet’s leg has been clipped. If infection is identified then your pet will be prescribed a course of antibiotics and the surgery will be postponed for one to two weeks.

Implant failure can occur in the post operative phase. “Implant” is the name given to any non-biological item which is implanted into the patient, e.g. nylon sutures, pins, screws, plates, titanium cages, etc. Implant failure means that the implant either loosens or breaks. The risk of implant failure is low. It is usually associated with the animal being too active in the first two months after surgery. In cases where there is implant failure and healing is not yet adequate a second surgery may be required to rectify the situation.

 Fracture of the tibia is a rare complication after MPL surgery. It is usually associated with the animal being too active in the first two months after surgery.  When a fracture occurs there is often concurrent loosening of the implants. With such cases a second surgery will likely be required to repair the fracture and replace the implants.

Cruciate ligament injury can occur in the same joint concurrently with medial patella luxation. If these the case we usually perform surgical correction of both the conditions at the same time. Dogs that have a normal cruciate ligament at the time of MPL surgery may rupture their cruciate ligament weeks to years after the MPL surgery. In these situations the cruciate ligament rupture is not a complication of the MPL surgery but was destined to occur anyway.

Post Operative Care  - Regardless of the technique undertaken for your pet’s medial patella luxation, the post operative care is the same. Activity is severely restricted for the first eight weeks after the surgery. Nursing care at home is important. Your pet must be kept very quiet for the eight weeks after surgery. Running, jumping and boisterous activity are not allowed. Jumping on and off furniture is not allowed. Going up and down stairs is not allowed. The pet must be kept confined to a small room or cage with a non-slip surface and be taken to the grass on a leash to toilet every few hours. After two weeks, if his/her progress is satisfactory then he/she can start dedicated leash walks commencing at 5-10 minutes once daily The duration of the walks increases by 5 minutes each fortnight. Off leash activity is not permitted until your pet has been assessed by a veterinarian as being sufficiently recovered.

  Cranial Cruciate Ligament Injuries Treatment & Complications Information Sheet 

Dr Lyn Minhinnett BVSc MACVSc (Small Animal Surgery)

The cranial cruciate ligament (CrCL) is an important ligament in the stifle joint of the cat and dog. The stifle joint in animals is equivalent to theknee joint in people. The cranial cruciate ligament provides stability between the femur (thigh bone) and the tibia (shin bone). When the cranial cruciate ligament is partially or fully ruptured, biomechanical instability occurs in the joint. The biomechanical instability occurs between the femur and the tibia during walking. This results in inflammation (arthritis) in the joint which produces pain and lameness. The instability can cause damage to other structures within the stifle joint, namely the meniscus. The meniscus is a crescent-moon shaped cartilage that act as a shock absorbers and help the cruciate ligament to stabilise the joint. Each stifle joint has two menisci. When a meniscus is damaged they are painful and contribute to arthritis and lameness.
Ruptured cranial cruciate ligaments do not heal and the recommended treatment is surgery. The aim of surgery is to remove any damaged ligament and menisci and return stability to the stifle joint. Ideally we would like to replace the cranial cruciate ligament with an identical material in the identical site but as yet the technology for this does not exist.
There are several different surgical techniques for treating cranial cruciate ligament injuries. The most appropriate technique for your pet is chosen after careful consideration of your pet’s size, conformation, lifestyle (i.e. athletic or sedentary) and the amount of arthritic change already present in the stifle. The techniques can be divided into two broad categories i.e. extracapsular prosthesis techniques and osteotomy techniques. These are described below.
Extracapsular Prosthesis technique - Lateral Fabella Suture (DeAngeles) Technique - The joint is explored surgically and damaged ligament and meniscus are removed. Stability is created by placing a nylon prosthesis i.e. a thick nylon suture, across the outside of the joint (i.e. extracapsular) as shown in the diagram. The prosthesis stabilises the joint and acts as a scaffold for fibrous tissue (scar tissue) to grow around it and eventually provide all of the stabilisation. This technique is most frequently used in cats and smaller dogs (less than 20kg) but it can also be used successfully in large breed dogs.
The joint is explored surgically and damaged ligament and meniscus are removed. An osteotomy is performed. Osteotomy means “to cut the bone”. An osteotomy technique involves cutting the tibia (shin bone) to change the biomechanics of the stifle joint so that the joint is stable during weight bearing without requiring a nylon prosthesis. The technique names have been abbreviated e.g. TTA means tibial tuberosity advancement; TTAR means tibial tuberosity advancement rapid; TTO means triple tibial osteotomy, etc. The technique selected is based on the animal’s conformation and the surgeon’s preference. Osteotomy techniques are suitable for dogs of all sizes but are mostly frequently used in dogs that weigh more than 20kgs.
Potential Complications of Cruciate Surgery Fortunately after performing many of these surgeries the associated complications have been minimised and are low in overall number, but the potential for serious complications will always exist – just as it does with any person who has an orthopaedic procedure.
There is risk associated with general anaesthesia. This risk is extremely low but it will never be 0%. The hospital team member who is dedicated to the patient’s anaesthesia monitors multiple parameters continuously both during and after anaesthesia. Parameters that are monitored during anaesthesia include heart rate, respiratory rate, temperature, SpO2 (oxygen saturation in the blood) and blood pressure.
The risk of infection with orthopaedic surgery is less than 1%. We take every possible precaution to prevent infection. Bathing your pet a few days prior to surgery is a helpful precaution. Surgery will not be performed if your pet has a skin infection or evidence of infection in another part of the body. Sometimes when pets have thick coats the presence of a skin infection may not be detected until after the pet’s leg has been clipped. If infection is identified then your pet will be prescribed a course of antibiotics and the surgery will be postponed for one to two weeks.
Late meniscal injury can occur in up to 10% of cruciate surgery cases. Late meniscal injury means that the meniscus was normal at the time of surgery but subsequently develops a tear. Late meniscal injury can occur weeks to years after the original surgery. Meniscal tears cause pain in the stifle joint and lameness. If the tear is minor it may resolve with rest and anti-inflammatory drugs. If the tear is more significant then surgery is required to remove injured portion the meniscus.
 Implant failure can occur in the post operative phase. “Implant” is the name given to any non-biological item which is implanted into the patient, e.g. nylon sutures, pins, screws, plates, titanium cages, etc. Implant failure means that the implant either loosens or breaks. The risk of implant failure is low. It is almost always associated with the animal being too active in the first two months after surgery. In cases where there is significant implant failure and healing is not yet adequate a second surgery would be required to replace the implants.
Fracture of the tibia is infrequent complication after an osteotomy technique. It is usually associated with the animal being too active in the first few weeks after surgery.  When a fracture occurs there is concurrent failure of the implants. With such cases a second surgery is usually required to repair the fracture and replace the implants.
Patella (knee cap) luxation is an infrequent complication that can occur following cruciate surgery. The patella may dislocate out of its normal position. In cases where this occurs the affected animal usually has underlying anatomical abnormalities that predispose to the luxation. Surgery may be required to correct the luxation.
Post Operative Care - Regardless of the technique undertaken as treatment for your pet’s cruciate ligament rupture, the post operative care is the same. Activity is severely restricted for the first eight to ten weeks after the surgery. Nursing care at home is important.
Your pet must be kept very quiet for the eight to ten weeks after surgery. Running, jumping and boisterous activity are not allowed. Jumping on and off furniture is not allowed. Going up and down stairs is not allowed. The pet must be kept confined to a small room or cage with a non-slip surface and be taken to the grass on a leash to toilet every few hours. After two weeks, if his/her progress is satisfactory then he/she can start dedicated leash walks commencing at 5-10 minutes once daily. The duration of walks increases by 5 minutes each fortnight. Off leash activity is not permitted until your pet has been assessed by a veterinarian as being sufficiently recovered.