EARLY COMPLICATIONS OF UNICOMPARTMENTAL KNEE REPLACEMENT.

Abstract

Osteoarthritis of the knee usually affects the medial compartment first and may later involve the lateral compartment. In its early stages, the options for operative treatment are valgus high tibial osteotomy, unicompartmental arthroplasty, and total knee arthroplasty.

The general feeling is that UKR offers potential advantages over the more extensive total knee replacement (TKR) procedure for the management of unicompartmental disease: preservation of bone stock, retention of the anterior and posterior cruciate ligaments, and preservation of both the patellofemoral joint and half of the weight-bearing articulating surface of the knee joint.

The purpose of this paper was to review all our cases of UKR and their early complication rate and to try and determine the factors that led to the individual complications as well as an assessment of the technical difficulties experienced in managing these cases.

Over a period of 5 years, 206 UKR procedures were performed in one hundred and eighty-five patients. There were 21 bilateral cases. Eighty-three cases were left-sided and eighty-one were right-sided. There were sixty-nine female and one hundred and sixteen male patients. The age of the patients averaged 63.7 years (range, thirty-two to eighty-nine years)

Five surgeons were involved in performing the surgery. There were thirty-five cases of lateral, and one hundred and seventy-one cases of medial compartment osteoarthritis.

Due to the five-year period that this study spans, different prostheses were used

Surgical complications: Early complications requiring repeat surgery were seen in thirty-one patients. The following early complications were seen:

Dislocation of polyethylene spacer: 7 cases

Subsiden ce: 4 cases

Early loosening: 2 cases

Surgical error: Technical errors relating to the sizing and positioning of components occurred in five cases.

Perioperative fracture:

• One patient sustained a tibial fracture intra-operatively

• Three cases of tibial fracture occurred within six weeks of the operation

Other compartment problems: The oldest patient in this series (89yrs) developed a rapid progression of osteoarthritis in the lateral compartment following a medial UKR within one year from her operation.

Pain/Locking/Swelling/stiffness: This occurred in some patients necessitating surgical intervention.

Non-surgical complications:

• - One case of proximal tibia stress fracture occurred within 6 months post UKR.

• - Ongoing pain past the one-year mark occurred in five patients

• - Superficial wound sepsis occurred in one patient

Summary of management within the First year following UKR:

• - 31 (15%) Patients underwent further surgery.

• - 13 (6.3%) Patients had their UKR revised to a TKR.

• - 9 (4.4%) Patients had at least one arthroscopic procedure.

• - 7 (3.4%) Patients had a procedure to remedy an illfitting polyethylene spacer.

Conclusions:

1. Most of the failures that we had within the first year post-operatively occurred due to either surgical technical error or patient selection.

2. We concur with previous studies indicating that revision UKR to TKR should not be undertaken lightly. Adequate revision instrumentation should be available and careful planning should be carried out prior to embarking on this procedure. One should be prepared for significant bone loss in the affected compartment.

3. Arthroscopic debridement and adhesiolysis can be very successful in patients with distinct catching and clicking associated with an effusion, post UKR.

4. Some patients have unexplained pain and failing to find a causative factor, the patients can be reassured that there will be a high probability of this pain diminishing, or even disappearing.

5. Subsidence of the tibial component may occur in older patients with generalized osteopaenia, and if not severe, it can be observed. It may not cause a clinical problem.

6. It appears that the more cases one does, the less likely the chance of failure and revision.