Poppy was attacked four days previously by a dog and referred to VetFix with a recurrent coxofemoral luxation. Closed reduction had been attempted immediately following injury however repeat luxation of the hip had occured.
Under anaesthesia instability was felt upon closed reduction of the hip and a decision was made to proceed to surgery. Reluxation has been reported to occur in approximately 50% of cats after closed reduction1. I am not a big fan of Ehmer slings in cats and avoid them.
A standard craniolateral approach to the hip was made. The femoral head was luxated and externally rotated to check for any evidence of chip fractures or erosions to the articular cartilage. The acetabulum was visualised and cleared of haematoma, inflammatory tissue and remnants of the teres ligament which can be quite large in the cat. Reduction of the hip was then performed. The joint capsule damage was quite severe in this case and several 2-0 PDS ligatures were used to reconstruct what remained at the dorsal acetabular rim. An iliofemoral suture technique was performed holding the femur in internal rotation, adduction and ventromedial compression thus maximising acetabular coverage of the femoral head.2 0 PDS was used for the iliofemoral suture in this case. Occasionally I use transarticular pinning for hip luxation cases, especially if still unstable following internal rotation of the femur, but prefer iliofemoral sutures. Transarticular pinning requires a second surgical procedure to remove the pin and necessitates intrarticular placement of the pin. Nonetheless it is still a good technique for some cases.
Suture material was passed through the hole in the ilium from lateral to medial. It was then carefully picked up blindly with curved mosquito forceps and returned to the lateral side. This was then passed from cranial to caudal medial to the insertion of the gluteal muscles. The suture was then returned to the cranial side through the hole in the greater trochanter and tied with the femur abducted and internally rotated.
Recovery and post-operative care
A standard multimodal pain protocol was practiced. Exercise was restricted to large cage rest for 30 days. She was noted to be using the leg well at this stage with no obvious lameness but a slight inward rotation of the affected limb. On examination 60 days following the operation Poppy was doing really well with normal motion and no pain on manipulation of the hip. A gradual return to normal exercise was advised.
Coxofemoral luxation can be a common problem in small animal practice. With vehicular trauma forces are thought to transfer through the femur driving the femoral head dorsally over the acetabular rim. In this case the forces that may have caused the luxation are atypical and likely to have resulted from traction and rotation of the limb by the dog. Craniodorsal luxation is common in coxofemoral luxations accounting for 73% of feline cases in one study3.
Closed reduction and external stabilisation using an Ehmer sling has been reported as the initial treatment of choice with success rates of 47% to 65% reported3,4. However these results are mainly for dogs and the tolerance of cats to external coaptation such as an Ehmer sling can make ancillary support difficult following closed reduction. For this case open reduction was elected due to failure of initial closed reduction and instability following a second attempt at closed reduction under general anaesthesia. It has been suggested that cats function well long-term with a dislocated hip5. However although acceptable function may be achieved, 66% of 79 cats with an untreated coxofemoral joint luxation showed some kind of locomotor dysfunction and 8% were considered to be painful on examination of the limb6. Femoral head and neck ostectomy (FHNO) for treatment of chronic coxofemoral luxation would have been an option for this case. Good results following use of this procedure in the cat have been reported7. However it is desirable to retain the hip joint and to resort to excision arthroplasty only should open reduction fail. There is limited data available on treatment and longterm outcomes of coxofemoral luxations in feline patients. Most treatment options have been extrapolated from canine studies. The wide variety of options for open reduction can be broadly separated into intra-articular and extra-articular. Toggle fixation and transarticular pinning have both been reported as methods of intra-articular reduction. Of these transarticular pinning has been described for the highest number of feline patients. Of 20 cats treated with a tranarticular pin for stabilisation of coxofemoral luxation a 77% success rate was achieved8. No benefit to the application of the Ehmer sling was found in this study. Transarticular pinning was not chosen as a primary reduction method for this case as there was a concern of articular cartilage damage that could occur during placement of the pin. Two of twelve cats that had radiographs taken at least six months following pin removal had radiographic changes consistent with moderate to severe degenerative joint disease in the reduced joint. Transarticular pinning would also necessitate a second surgical procedure and has been associated with pin breakage and osteonecrosis of the femoral head in the dog9. The DeVita pinning technique was avoided due to risk of sciatic nerve impairment10. Extra-articular placement of an iliofemoral suture was chosen and good results have been reported in a limited number of cases in the cat2. In this study a 76% longterm successful reduction rate was achieved. The study found success rate strongly related to suture material with monofilament polyamide the most prone to failure. Polydioxanon was used successfully for the iliofemoral suture in one cat in this study and was chosen as the suture material for this case. The iliofemoral suture was used to support the primary capsular repair and maintain the reduction of the hip joint. Rather than drill through the ilium a technique has been used successfully in the cat whereby the suture is anchored cranially through the tendon of insertion of the rectus femoris muscle. This was not chosen for this case as despite primary capsular repair instability was still marked and bone anchorage was considered more secure. It should be noted the iliofemoral suture does carry a risk of sciatic nerve damage on drilling of the hole through the pelvis and care should be taken with suture retrieval from the medial aspect of the ilium. The effect of the suture is to internally rotate the femoral head with slight abduction of the femur which results in maximal coaptation of the acetabulum and femoral head.
- Wildgoose, WH. (1983) Hip dislocation and use of the De Vita pin in the cat. Journal of Small Animal Practice. 24: 261-268
- Mehl, NB (1988) A new method of surgical treatment of hip dislocation in dogs and cats. Journal of Small Animal Practice. 29; Pp 789-795
- Basher, AP. Walter, MC. Newton, CD. (1986) Coxofemoral luxation in the dog and cat. Veterinary Surgery. 15; Pp 356-362
- Bone, DL. Walker, M. Cantwell, HD. (1984) Traumatic coxofemoral luxation in dogs: results of repair. Veterinary Surgery. 13: Pp 263-270
- Piermattei, DL. Flo, GL. DeCamp, CE. (2006). The hip joint. In: Brinker, Piemattie and Flo’s Handbook of Small Animal Orthopaedics and Fracture Repair. 4th Edition. Saunders Elsevier, Missouri, USA. Pp 461-511
- Perez-Aparicio, FJ. Fjeld, TO. (1993) Coxofemoral luxations in cats. Journal of Small Animal Practice. 34; Pp 345-349
- Berzon, JL. Howard, PE. Covell, SJ. A retrospective study of the efficacy of femoral head and neck excisions in 94 dogs and cats. Veterinary Surgery. 9; Pp 88-92
- Sissener, TR. Whitelock, RG. Langley-Hobbs, SJ. (2009) Long-term results of transarticular pinning for surgical stabilisation of coxofemoral luxations in 20 cats. Journal of Small Animal Practice. 50; Pp 112-117
- Hunt, CA. Henry, WB. Transarticular pinning for repair of hip dislocation in the dog: A retrospective study of 40 cases. Journal of the American Veterinary Medical Association. 187: Pp 828-833
- Lewis DD. Ishio-ilial pinning for stabilisation of coxofemoral luxations: An anatomical study. Veterinary and comparative orthopaedics and traumatology. 1; Pp 31-34