Computed Tomographic Assessment of Block Recession Trochleoplasty and Partial Parasagittal Patellectomy in Cats

Abstract

Objective The aim of this study was to assess computed tomography (CT) images of cadaveric feline stifles and record the relationship between the patella and femoral trochlea in normal stifles; then to investigate the effect of block recession trochleoplasty (BRT) with and without partial parasagittal patellectomy (PPP) on patellofemoral contact, depth of patellar recession and size of trochlea and patella. Materials and Methods The sample population included six cat cadavers (12 stifles). Preoperative CT scans with stifles in three positions: extended (155–165°), neutral (85–95°) and flexed (35–45°). Lateral stifle arthrotomy was followed by BRT. CT scans were taken as above. PPP was performed so the width of the patella was 1 mm narrower than the BRT. CT scans were repeated and CT measurements were taken. Results The area of contact between the patella and femoral trochlea was significantly reduced after BRT and then significantly increased after PPP. The depth of patellar recession was unchanged after BRT, but then was significantly higher after PPP. The patella was wider than the trochlea preoperatively and post-BRT and narrower post-PPP. Reduction in bone volume following PPP (mean: 20%) was 50% the reduction in patella width (mean: 40%). Conclusion Block recession trochleoplasty did not improve patellar recession and decreased patellofemoral contact area. Following BRT, the patella rides the trochlear ridges and loses contact with the trochlear sulcus. Block recession trochleoplasty alone should not be performed in cats. Instead, BRT should be combined with PPP.

Comparison of Hindlimb Conformation in Cats with and without Medial Patellar Luxation

“…However, more recent publications have suggested additional techniques are required, such as a partial patellectomy, based on the unique anatomy in the cat. [4][5][6] A weak correlation with hip dysplasia and patellar luxation in cats has also been described. 3 Skeletal deformities have been reported in dogs with patellar luxation with a malalignment of the quadriceps mechanism leading to a medially directed force on the patella and consequently medial luxation.…”

Tibial tuberosity transposition advancement for treatment of concomitant cranial cruciate ligament rupture and medial patellar luxation in four feline stifles

“…Partial parasagittal patellectomy was necessary in all four surgeries described in this case series in order to establish patellar tracking in contact with the recessed sulcus and to stabilize the patella. This technique has been previously reported clinically, 24 and was shown to improve the depth of patellar recession over that achieved with block recession trochleoplasty alone in a cadaveric study using CT. 55 The feline patella is relatively wider than the feline femoral trochlear sulcus, 56 and ex vivo studies in cats have shown that following block recession trochleoplasty alone, the feline trochlea becomes too narrow to accommodate it. 55 Instead, the patella rides the trochlear ridges and loses contact with the trochlear sulcus.…”

“…This technique has been previously reported clinically, 24 and was shown to improve the depth of patellar recession over that achieved with block recession trochleoplasty alone in a cadaveric study using CT. 55 The feline patella is relatively wider than the feline femoral trochlear sulcus, 56 and ex vivo studies in cats have shown that following block recession trochleoplasty alone, the feline trochlea becomes too narrow to accommodate it. 55 Instead, the patella rides the trochlear ridges and loses contact with the trochlear sulcus. The clinical impact of partial parasagittal patellectomy long term has not been reported; however, no intra- or postoperative complications related to this procedure were encountered in our cases.…”

Patellar Groove Replacement in a Cat

“…Patella width exceeded the width of the sulcular part of the trochlear prosthesis and, as such, accurate patella-to-trochlear prosthesis fitting was deemed to be suboptimal; the patella rode on trochlear ridges rather than being in contact with prosthesis sulcus. Partial parasagittal patellectomy was performed 9 which, subjectively, improved patella fit and contact within the prosthetic trochlea.…”

“…7 Techniques reported for the correction of MPL include femoral trochlear sulcoplasty, tibial tuberosity transposition, lateral retinacular imbrication, medial soft tissue release 1 distal femoral corrective osteotomy, 8 and partial parasagittal patellectomy. 9 Patellar groove replacement (PGR) has been reported in the literature as a surgical technique for the treatment of canine patellar luxation associated with severe femoro-patellar osteoarthritis. 10 To the authors' knowledge, this is the first case of PGR in a cat in published literature.…”