Ventral acetabular augmentation for management of caudoventral luxation following total hip replacement in dogs.

OBJECTIVE: To report ventral acetabular augmentation with an internal fixator for management of caudoventral luxation following total hip replacement in dogs and to report clinical outcomes. MATERIALS AND METHODS: Clinical records from three UK-based referral hospitals were reviewed retrospectively between 2010 and 2020 to identify dogs with caudoventral hip luxation managed by ventral acetabular augmentation. Hip prosthesis component orientation was radiographically assessed to identify potential risk factors associated with the luxation. Clinical and radiographic assessments were performed at short-term (≤12 weeks) and long-term (>12 months) follow-up and all complications were recorded. A standardised owner telephone questionnaire was used to assess long-term outcomes when a clinical assessment was unavailable. RESULTS: Nine dogs were included. Risk factors contributing to the luxation could not be defined. Implants used included a string-of-pearls plate (6/9), a polyaxial locking plate combined with a polyethylene implant (1/9) or a polyethylene implant alone (2/9). Complications occurred in two of nine dogs, including recurrent luxation and femoral stem loosening; both dogs had received a polyethylene implant alone, of which one received explantation of the hip prosthesis. Median long-term follow-up was 39 months (range 13.5-62). Seven dogs who received a ventral acetabular plate achieved full function of the operated limb and the overall outcome was good for eight dogs. Follow-up radiographs revealed stable hip prostheses in dogs who received a ventral plate, with the longest assessment at 37 months postoperatively. Owner satisfaction was good for all cases. CLINICAL SIGNIFICANCE: Ventral acetabular augmentation can successfully manage caudoventral luxation following total hip replacement in dogs.

Effect of Tibial Plateau Levelling Osteotomy on Cranial Tibial Subluxation in the Feline Cranial Cruciate Deficient Stifle Joint: An Ex Vivo Experimental Study.

OBJECTIVES: This study evaluated the effects of tibial plateau levelling osteotomy on cranial tibial subluxation and tibial rotation angle in a model of feline cranial cruciate ligament deficient stifle joint. METHODS: Quadriceps and gastrocnemius muscles were simulated with cables, turnbuckles and a spring in an ex vivo limb model. Cranial tibial subluxation and tibial rotation angle were measured radiographically before and after cranial cruciate ligament section, and after tibial plateau levelling osteotomy, at postoperative tibial plateau angles of +5°, 0° and -5°. RESULTS: Cranial tibial subluxation and tibial rotation angle were not significantly altered after tibial plateau levelling osteotomy with a tibial plateau angle of +5°. Additional rotation of the tibial plateau to a tibial plateau angle of 0° and -5° had no significant effect on cranial tibial subluxation and tibial rotation angle, although 2 out of 10 specimens were stabilized by a postoperative tibial plateau angle of -5°. No stabilization of the cranial cruciate ligament deficient stifle was observed in this model of the feline stifle, after tibial plateau levelling osteotomy. CLINICAL SIGNIFICANCE: Given that stabilization of the cranial cruciate ligament deficient stifle was not obtained in this model, simple transposition of the tibial plateau levelling osteotomy technique from the dog to the cat may not be appropriate.

Effect of tibial tuberosity advancement on cranial tibial subluxation in the feline cranial cruciate deficient stifle joint: An ex vivo experimental study.

The effects of Tibial Tuberosity Advancement (TTA) on Cranial Tibial Subluxation (CTS) and Tibial Rotation Angle (TRA) were evaluated in a model of feline Cranial Cruciate Ligament (CrCL)-deficient stifle joint. Ten hindlimbs of adult cats were used. Quadriceps and gastrocnemius muscles were simulated using cables, turnbuckles and a spring. An axial load of 30% body weight was applied. The stifle and talocrural joint angles were adjusted to 120°. Patellar tendon angle (PTA), CTS and TRA were measured radiographically before and after CrCL section, after TTA and after additional advancement by 1 and 2mm. CrCL section resulted in a CTS of 8.1±1.5mm and a TRA of 18.4±5.7 °. After TTA, PTA was significantly decreased from 99.1±1.7° to 89.1±0.7°; CTS and TRA did not change significantly (7.8±1.0mm and 15.9±5.7° respectively). Additional advancement of the tibial tuberosity by 1mm did not significantly affect CTS and TRA. Additional advancement of the tibial tuberosity by 2mm significantly reduced the PTA to 82.9±0.9°. A significant decrease of CTS (6.9±1.3mm) and TRA (14.7±3.6°) was also observed. A lack of stabilization of the CrCL deficient stifle was observed after TTA in this model of the feline stifle. Even though the validity of the model can be questioned, simple transposition of the technique of TTA from the cat to the dog appeared hazardous.

Biomechanical comparison of two locking plate constructs under cyclic torsional loading in a fracture gap model. Two screws versus three screws per fragment.

OBJECTIVES: The number of locking screws required per fragment during bridging osteosynthesis in the dog has not been determined. The purpose of this study was to assess the survival of two constructs, with either two or three screws per fragment, under cyclic torsion. METHODS: Ten-hole 3.5 mm stainless steel locking compression plates (LCP) were fixed 1 mm away from bone surrogates with a fracture gap of 47 mm using two bicortical locking screws (10 constructs) or three bicortical locking screws (10 constructs) per fragment, placed at the extremities of each LCP. Constructs were tested in cyclic torsion (range: 0 to +0.218 rad) until failure. RESULTS: The 3-screws constructs (29.65 ± 1.89 N.m/rad) were stiffer than the 2-screws constructs (23.73 ± 0.87 N.m/rad), and therefore, were subjected to a greater torque during cycling (6.05 ± 1.33 N.m and 4.88 ± 1.14 N.m respectively). The 3-screws constructs sustained a significantly greater number of cycles (20,700 ± 5,735 cycles) than the 2-screws constructs (15,600 ± 5,272 cycles). In most constructs, failure was due to screw damage at the junction of the shaft and head. The remaining constructs failed because of screw head unlocking, sometimes due to incomplete seating of the screw head prior to testing. CLINICAL SIGNIFICANCE: Omitting the third innermost locking screw during bridging osteosynthesis led to a reduction in fatigue life of 25% and construct stiffness by 20%. Fracture of the screws is believed to occur sequentially, starting with the innermost screw that initially shields the other screws.

A case of stifle osteochondrosis treated by osteochondral autogenous grafting. One month morphological follow-up.

OBJECTIVE: To describe the one-month morphological appearance of autogenous osteochondral grafting in a dog with stifle osteochondrosis. METHOD: Osteochondral autografting was performed in one stifle of an eight-month-old dog with spontaneously occurring bilateral osteochondrosis. RESULT: Histopathological analysis performed one month after surgery confirmed partial integration of the grafts and osteochondral survival. CLINICAL SIGNIFICANCE: Autogenous osteochondral grafting in stifle osteochondrosis results in acceptable graft survival postoperatively and is worthy of further evaluation.