In all the three cases, thorough biochemical investigations did not reveal any evidence of crystal synovitis. Detailed neurological examination failed to reveal any evidence of neuropathy. Synovial biopsy during surgery failed to ascertain the cause of gross bony destruction in all the three cases.

Surgical Techniques

In all these patients, surgery was carried out using Posterior Stabilised, Kinemax plus implant, marketed by M/S Howmedica. Gap technique and modular tibial inserts were used to restore ligament balance. Standard tibial cut was taken at 9mm distal to the most prominent tibial condyle, which was the lateral condyle in these cases. The tibial defect was bone grafted using shaved femoral condyles in cases of Mr. S.and Mrs. L. While in case of Mrs. S., shaved tibial surface was used as bone graft. The bone graft was fixed to tibia with two 4mm A.O.cancellous screws, used as lag screws. A stemmed tibial base plate was fixed to the bone using standard cementing technique. Mr. S. and Mrs. L. required 10mm tibial insert, while Mrs. S required 22mm-tibial insert for ligament balance. Standard cemented femoral and patellar components were used.

Post Operative Regimen & Results

Standard postoperative regimen consisting of mobilisation with Continuous Passive Motion machine was started within 24 hours after surgery. Static and dynamic quadriceps drills were carried out. Early partial weight bearing was permitted with patient wearing a full-length knee brace, and using walker for support ambulation. Full weight bearing was delayed for six weeks, for the bone graft to consolidate. Patients are advised to use walking stick till the other knee is operated. Recovery was uneventful in all the cases. All the patients gained 100 degrees of knee flexion, and grade five-quadriceps power within 3 weeks after surgery.

Discussion

Capacity to bear pain, avoidance of surgery due to fear and lack of information about recent surgical advances drive our patients to seek pain relief by various non surgical means. One such therapy, the use of intra-articular hydrocortisone injection for relief of pain in osteoarthrotic knees is quite common. Hydrocortisone intra-articularly not only causes chemical damage to the articular cartilage, but also causes joint changes mimicking Charcot type of neuropathic arthropathy.

Gross bony deformity with erosion of weight bearing surface, imbalance of ligaments and limb length inequality pose challenges in surgical management. The options available are fusion of the joint or knee surface replacement. Though fusion gives relief of pain and stability, it does not allow mobility. If knee surface replacement is chosen, fully constrained or semi-constrained design is required because of bone loss and ligament imbalance.

In all these cases, knee surface replacement was preferred over knee fusion. The implant selected was posteriorly stabilised semi-constrained design. Stemmed tibial component was selected for proper weight distribution. The Ultrahigh Molecular Weight Polyethylene (UHMWPE) tibial inserts are available in various thickness. This helps in achieving proper ligament balance. The prosthesis was fixed to the parent bone with bone cement. Bone grafts harvested from local site during surgery, helped in reconstruction of massive tibial condylar defects, avoiding the need for custom made prosthesis or metallic wedges, both options increase the cost of implant.

Conclusion

Knee surface replacement is an excellent operation even in gross, neglected deformities presenting late. The technique of use of locally harvested bone grafts avoids the need of costly metallic wedges and custom made prosthesis. Injections of hydrocortisone must be used with great caution in non-surgical management of knee arthritis.