VETcpd - Orthopaedics Peer Reviewed Patellar luxation in dogs Part 2: Treatment Surgical treatments for patellar luxation may be broadly categorised into those which reduce the ease with which the patella can exit the trochlear groove, and those which aim to realign the quadriceps mechanism. A number of techniques may be performed to increase the depth of the trochlear groove and implants have become available in recent years to increase the height of the trochlear ridges. Soft tissue release (medially) and imbrication (laterally) may be relied upon, only temporarily, to stabilise a luxating patella. Realignment of the quadriceps mechanism can be performed by moving the insertion of the musculo-tendinous unit (i.e. tibial tuberosity transposition) or anti-rotational suture placement. More advanced procedures to address femoral and tibial deformities may also be considered for certain cases. Phil Witte Key words: Orthopaedics, patella, patellar luxation, quadriceps muscles, surgery BSc BVSc CertAVP(GSAS) DSAS(Orth) MRCVS deepening. Arthurs and Langley-Hobbs RCVS Specialist in Small Introduction In the previous article the (2006) suggested that the frequency of Animal Surgery (Orthopaedics) author discussed the diag- re-luxation was greater without groove Philip graduated from the University of nosis of patellar luxation deepening, Linney et al. (2011) demon- Bristol in 2005. He cut his teeth with and its aetiology, with an strated a reluxation rate of 19.8% without two years in rural mixed practice prior emphasis on the influence groove deepening and Cashmore et al. to a six month stint working with Cape ©istockphoto.com of hind limb anatomy (2014) recognised a 5.1 fold reduction in buffalo in Phalaborwa, South Africa. on quadriceps mechanism alignment. In the rate of patellar luxation with groove He completed a surgical internship in this article the options for management deepening. Groove deepening in the 2009 and an orthopaedic residency at and the reported complications following absence of consideration of quadriceps Southern Counties Veterinary Specialists surgical intervention are discussed. realignment was reported in 46 stifles in a in 2013. He completed the RCVS study of Pomeranians in which 2/46 had Certificate in Advanced Veterinary Surgical treatment options recurrence of luxation within a relatively Practice in September 2013 and the Surgical stabilisation of the femoro- short period of follow-up of 16 weeks RCVS Diploma in Small Animal Surgery patellar joint should restore: (Wangdee et al. 2013). There are a few (Orthopaedics) in 2018. His interests • quadriceps function techniques for increasing trochlear groove include angular limb deformity correction depth and an increasing array of techniques and complex fracture management. (to improve limb function) for realigning the quadriceps mechanism. E: [email protected] • femoro-patellar loading (theoretically slowing the rate of To complete an evidence-based discussion progression of osteoarthritis) of treatment of PL, it should be noted that there is limited evidence that resolution Patellar luxation (PL) is a mechanical of PL has a meaningful influence on the problem with mechanical solutions. A progression of osteoarthritis, although this number of techniques and subsequent would seem intuitive. In fact, in a study of modifications have been proposed. 12 dogs with bilateral PL and unilateral Broadly, these can be divided into surgery, osteoarthritis, as detected radio- procedures that: graphically, had progressed symmetrically a 1. Reduce the ease with which the mean of 33 months following intervention patella can luxate (often involving (Roy et al. 1992). Of course, in that deepening of the trochlear groove) study the more severely affected limb was presumably selected for surgical stabilisa- Or tion, inducing bias in the interpretation of 2. Realign the quadriceps mechanism. the results. Arguably, the latter consideration is of No matter the techniques employed greater importance, however, there is suf- during surgery, the author would empha- ficient evidence to suggest that groove sise that surgeons should never finish a deepening remains an important factor surgery and perform a closure on a PL case SUBSCRIBE TO VETCPD JOURNAL in achieving a stable patella. Three studies in which the patella is not 100% stable. If document patellar luxation surgery in the patella is not stable through a full range Call us on 01225 445561 which tibial tuberosity transposition was of stifle motion on the table, the soft tissue or visit www.vetcpd.co.uk performed (to realign the quadriceps closure cannot be relied upon to prevent mechanism) with or without groove reluxation during convalescence. Page 36 - VETcpd - Vol 6 - Issue 2 VETcpd - Orthopaedics Increasing resistance of two osteotomies (a wedge of triangu- • Wangdee et al. (2015) reported a wedge to patellar luxation lar cross-section) whilst the rectangular recession which was extended proxi- Also termed ‘trochleoplasty’, a few tech- block consists of two parallel osteotomies mally as an excisional trochleoplasty in niques have been described to deepen the connected by a third osteotomy made seven Pomeranian dogs with bidirec- trochlear groove, effectively increasing the deep to the groove using an osteotome tional instability (luxation to either side resistance to luxation of the patella. Groove (Figure 2). Wedges and blocks do not of the groove). deepening has classically been performed require internal fixation, but instead rely • Kite-shield shaped wedge recession by recession of the trochlear groove (see on the frictional interface between the (Katayama et al. 2016) was reported in description below), to effectively elevate two surfaces of cancellous bone and the seven toy breed dogs (10 procedures). the trochlear ridges. More recent innova- compressive force associated with the The technique was called ‘K-wedge’ tions include permanent implants to raise reduced patella. In the case of the rectan- and consists of a wedge in the usual or replace the trochlear ridges. Soft tissue gular block recession trochleoplasty, small position with a third osteotomy made Figure 4: RidgeStop™ is a medical grade, ultra high slivers of bone may be wedged between molecular weight, polyethylene implant fixed in position techniques may aid patellar stabilisation 1A in a dorsal plane at the proximal extent with two or more screws (depending on the size of the and are also mentioned. the block and the trochlear ridge to of the groove to meet the wedge. The implant) to augment the trochlear ridge and reduce the Tibial tuberosity Patella Intercondylar notch Elevated flap of articular increase frictional stability. Johnson et al. resulting wedge/block is removed and ease with which the patella can luxate Abrasion or excisional cartilage with distal base (2001) performed ex vivo experiments recessed. In the study the K-wedge was trochleoplasty involves removal of to show that block recession (initially combined with anti-rotation sutures articular cartilage and subchondral bone, described by Talcott et al. 2000) was (see below) or tibial tuberosity trans- often using a cylindrical file. With this superior to wedge recession in terms position and re-luxation was present technique, the surface on which the patel- of deepening the groove at its proximal (grade I from a grade 3 pre-op) in 1/10. la articulates following healing is likely to extent and improving patellar stabil- • Medial ridge elevation trochleoplasty consist of fibrous and fibrocartilaginous ity with the stifle in extension (when (Fujii et al. 2013) was reported in five material with the potential for ongoing the patella is positioned at the proximal dogs (six stifles) with grade 3 medial retropatellar abrasion and discomfort. extent of the groove). For this reason, the patellar luxation. This technique aims Attempts to resurface the abraded trochlea author prefers rectangular block reces- not to recess the groove, but to elevate with free autogenous periosteal grafts 1B 1C sion (Figure 3). Bone union of a trochlear the medial trochlear ridge by rotating were met with poor results (Hulse et al. wedge was documented from eight weeks o an asymmetrical wedge through 180 . Figure 5: Intra-operative photograph of left 1986). Trochlear abrasion results in slower Figure 1: Chondroplasty performed in a five month old female entire Hungarian Puli with lateral patellar following surgery by Boone et al. (1983). luxation. (A) Articular cartilage is scored with a scalpel blade parallel with and just axial to the trochlear ridges. • Rotation of the entire femoral trochlea stifle and tibia following Kyon Patellar Groove rates of improvement in clinical function Complications specifically associated with The cartilage is elevated from the underlying bone (B) with the intact base of the flap proximal or distal (as has been reported for a single case of Replacement. The distal extent of the lateral in comparison with techniques which these techniques include migration of the femoral condyle and the intracondylar notch are in this case). Note that even in this young dog the articular cartilage is elevated with some subchondral grade 3 medial patellar luxation (Pinna preserve the articular cartilage (Boone et bone remaining adherent to the cartilage (i.e. the surgeon should not expect the articular cartilage to roll off triangular wedge during the early phase apparent distal to the prosthesis. (Distal is left) et al. 2008) in which the primary al. 1983). It is the author’s