Medial Patella Luxation

Patella Luxation refers to the small bone (knee cap) which sits at the front of the knee joint and allows the muscles to extend the knee and lower part of the leg. In some dogs there are anatomical abnormalities which allow the knee cap to luxate or ‘pop out’ of its normal groove. This causes pain and discomfort for the patient as the knee cap rubs on areas of the joints which are not covered with articulating cartilage, causing inflammation and the progression of osteoarthritis. As the disease progresses the cartilage becomes worn away and the knee cap rubs against the exposed bone causing additional pain.

Medial patella luxation generally presents in smaller breed dogs, at any age, although younger patients are most commonly presented. The condition is usually observed as an intermittent skip or even a persistent limp in one or both back legs.

The knee cap generally displaces medially (inwards) due to the abnormal alignment of the shin bone, patella tendon, knee cap and thigh bone. The groove which the knee cap sits in is often too shallow. The aim of surgery is to correct the alignment of the knee cap so that it is positioned within the groove and articulates on the normal cartilage where it should be.

Surgical correction should address the underlying factors for the condition. The main procedure for correction in the majority of cases is a tibial tuberosity transposition, which involves moving the bone and patella tendon which the knee cap attaches to. This involves cutting the bone, moving it laterally (outwards) and fixing it in position with wires. This small portion of bone then needs time to heal, usually 6-8 weeks, before returning to more normal activity. The other procedure used to correct the position of the knee cap are trochleoplasty (increasing the depth of the groove that the knee cap sits in), and soft tissue reconstruction (adjusting the tension of the soft tissues), to make it more difficult for the knee cap to pop out.

Outcomes following surgery are good, but are dependent upon the degree of damage to the joint at the time of surgery, with most patients expected to return to normal function and also delaying the inevitable progression of osteoarthritis.

Complications rates are low, with the most common complications being infection, usually less than 5%. Treatment usually only requires antibiotics in addition to the ones dispensed at the time of surgery. In a much smaller number of cases where the implants are infected or cause irritation to the soft tissues, removal of the implant via a short simple procedure performed under general anaesthesia, may be required once the bones have healed completely.

The other most common complication is related to the patient themselves, with over activity and excessive stress placed on the healing bone and implants, with either failure and breakage of the small bone the implants are anchored to. Generally, gentle lead controlled walks in incrementally increasing lengths are well tolerated in the weeks following patella surgery, however it is the short periods of high risk activity when these avoidable complications occur. Jumping, stairs, slippery floors, any off-lead activity will increase this risk and potentially cause catastrophic failure requiring repeat surgery. AS the owner you will be the brains of the recovery and be responsible for enforcing the strict rest and confinement, rehabilitation program, and lead controlled walks, prior to a return to normal activity over a 12-week period.

Image Gallery

  • Example of a TPLO and Patella Luxation Correction
  • Example of a TPLO and Patella Luxation Correction

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Kyon Patella Grove Replacement

Patello-femoral degenerative joint disease is a frequent, often ignored consequence of some of the most common conditions of the canine stifle such as patellar luxation, or cruciate ligament degeneration and rupture. Surgical treatments of patellar luxation, whether by tibial tuberosity transposition or by corrective osteotomies of the femur and/or tibia, combined with patellar groove deepening by one of several methods, seek restoration of joint stability.

Progression of arthrosis to a chronically painful joint must be expected, but that seems to be an accepted, generally ignored consequence of these surgical interventions. Replacement of the severely effected and/or worn-out patellar groove by a prosthesis presents an option worthy of serious consideration. In an effort to address this need, KYON proposed a novel prosthesis, the KYON Patellar Groove Replacement (PGR)*.

The PGR should provide a low friction, scratch resistant surface that could indefinitely tolerate the contact pressures and gliding friction generated by the bare bone of the patella. The KYON Patellar Groove Replacement (PGR)* is thus comprised of two components:

an upper anatomically shaped groove component produced from Titanium alloy (tial6v4), highly polished and treated with Amorphous Diamond-Like Coating (ADLC). ADLC shows exceptionally low friction against many solid surfaces, offering the possibility of maintaining heat generation below the threshold of thermal necrosis. ADLC is also very hard and scratch resistant when applied to a suitable substrate. It is chemically inert and thus biocompatible.

A perforated base plate produced from c.p. Titanium, coated by glow discharge anodisation with addition of calcium phosphate to promote bony integration.

Ostectomy of the patellar groove just cranially to the insertion of the tendon of the long digital extensor creates a broad, well perfused cancellous bone bed onto which the base plate is secured by titanium bone screws. The groove component is then attached to the base plate by means of 3 conical pegs fitted into receiving conical holes. The broad area of the ostectomy of the patellar groove allows for considerable freedom in medial-lateral positioning of the base plate that can be used to improve quadriceps-to-patellar tendon alignment, thus avoiding conventional tibial tuberosity transposition. Use of trial implants during surgery aids the search for an optimal position of the final implant.

Functional loading of the implant leads to compression of its interface to the bone, which is mechanically favourable to the ill-conditioned load transfer called for by conventional tuberosity transposition, where the full force of the patellar tendon is transferred to the tibia by pins and a figure eight wire.

Significant angular deformities can be treated by concurrent corrective osteotomies in addition to patellar groove replacement, should the condition of the patello-femoral joint call for it. The same is true for cruciate ligament ruptures that can be concurrently treated by, for example, Tibial Tuberosity Advancement (TTA).

Clinical application of the Kyon PGR was initiated in 2009 through a controlled clinical release with 15 surgeons (from USA, Europe and Japan) participating in this phase. By mid 2012, 35 surgeons had performed ~100 procedures. Surgical planning with templates and execution of the procedure are deemed simple and the risks as acceptable. Post-surgical recovery is rapid and, at this time, no signs of implant loosening have been observed. The procedure presents relatively low morbidity and is meeting the expectations of the early adopters in terms of clinical improvement.

Image Gallery

  • Example of Patella Groove Replacement and TPLO
  • Example of Patella Groove Replacement and TPLO