Discussion

For cases presenting with a subacute or chronic history, and relatively low grade lameness, the main principle of treatment is to try and work the horse through the problem, so that increased muscling will stabilise the sacroiliac region. Generally the pain has to be controlled before the horse will build up muscle appropriately. Any lower limb lameness must be treated. Many cases of sacroiliac joint region pain (SIJRP) associated with proximal suspensory demitis (PSD) will not require any specific treatment if the suspensory pain is definitively treated and the horse is rehabilitated appropriately. Physiotherapy/osteopathy/ chiropractic can be helpful for low grade SIJRP, as can systemic phenylbutazone. Acute onset cases with significant lameness and subluxation of the joint require a period of rest to allow healing of any soft tissue injuries and reduction of inflammation. They will normally be left with a residual lameness which will need to be worked through, as for a chronic/subacute case.
Medication of the sacroiliac region can be performed in a similar fashion to the block. If ultrasound changes are identified on the cranial or caudal margins of the sacroiliac joint, then ultrasound-guided techniques may be more appropriate. Overall, my highest success rate is with the blind technique. I normally use infiltration with either methylprednisolone (120 mg divided between 2 sides) or 'sclerosing agent' (50 ml between 2 sides; P2G Solution, Martindale Pharmaceuticals, Romford, UK). Horses are continued in the same plane of work, and improvement normally is reported within a week. The duration of response varies, and some horses do not require repeat treatments, others require treatment at approximately 6 monthly intervals. If the horse has a period of rest then there is the risk of recurrence of the problem.

Results of retrospective study:
In a series of 50 cases diagnosed with SIJRP by myself, there was an incidence of 6.1%, within a total of 864 orthopaedic cases seen over the time period. Comparing the SIJRP group to the other orthopaedic cases examined, there was no significant age or sex differences between the groups. Warmbloods and Thoroughbred crosses were over-represented and Thoroughbreds under-represented in the SIJRP group (P = 0.001). Showjumpers and dressage horses were statistically over-represented in the SIJRP group, while eventers and general-purpose horses were under-represented (P = 0.037). The majority of horses presented with poor performance rather than lameness or back pain (P<0.0001). The most common presenting problem was poor hindlimb impulsion. On clinical examination 34% of the SIJRP horses were noted to have pelvic asymmetry and 44% had pain on palpation of the overlying sacroiliac region. All horses demonstrated hindlimb lameness, 58% of them bilaterally. The lameness grades ranged from 0.5 - 5/10, with a median of 3. All
50 horses showed a positive response to analgesia of the sacroiliac region. 68% of the horses blocked out bilaterally. Scintigraphy was performed on 36 horses, 23 of which (64%) showed an increase in radionuclide uptake in the sacroiliac joint.

Ultrasonographic examination per rectum was performed in 12 horses and no significant abnormalities were detected in these horses. A number of concurrent diagnoses were made with 86% of the horses having hindlimb PSD, 38% hock pain and 26% impinging dorsal spinous processes and 20% stifle pain. Only 4 horses were diagnosed with SIJRP alone.
Long-term follow up was available on 48 horses, with 2 horses still convalescing. Thirty-six (75%) horses returned to full work, 3 (6%) were doing lower level work, 4 (8%) were retired due to other problems and 5 (10%) were retired because of either PSD or sacroiliac region pain. With conservative treatment, 1/3 cases (33%) returned to full work. Horses treated with medication of the sacroiliac region with either methylprednisolone acetate or phenol and glycerol ('sclerosing agent') led to 11/12 (85%) returning to full function. There was no significant difference in outcome between treatment with the 2 types of injection (P = 0.9) but the numbers are too small for meaningful analysis. For horses where the primary problem of HLPSD was treated by plantar metatarsal neurectomy and fasciotomy; 8/9 (89%) returned to full function with no specific treatment of the SIJRP. Of those that were treated with neurectomy and fasciotomy and subsequent sacroiliac medication, 11/17 (65%) returned to full work. Of the small number treated with medication of the sacroiliac region and of the proximal suspensory region with triamcinolone, 5/6 (83%) returned to full function.

Conclusions:
The overall success rate in this case series is good, which is considerably better than the current expectations in the literature. A large number of these cases had lower limb pathology and we would consider that treating this is important in achieving a successful outcome. The success rate is poorer in horses treated surgically for suspensory desmitis which then received medication of the sacroiliac region compared to those which had no specific treatment of the sacroiliac region. This represents the standard management of these horses whereby they would receive surgical treatment for the suspensory problem and only received medication in the sacroiliac region if pain was noted during the rehabilitation process. Thus those horses that received medication were those that were showing residual pain, indicating a greater degree of sacroiliac pathology.
The selection criteria on which the diagnosis of sacroiliac pain is made determines the apparent accuracy of the different diagnostic methods used. It was not considered diagnostically necessary for horses to have increased radionuclide uptake in the sacroiliac region if they blocked to this region.