Introduction

While the use of stemmed implants is accepted for patients with medial ligament laxity in primary total knee arthroplasty (TKA), the role of stemmed implants in the setting of isolated lateral laxity is unclear. We present a cohort study to assess the effect of unstemmed, constrained TKA for isolated lateral laxity.

Squeaking is a rare complication of hard-on-hard hip bearings. Occasionally the noise is troublesome enough to warrant revision surgery. The purpose of this study is to contribute to the understanding of the mechanism(s) underlying squeaking.

We analyzed 10 alumina ceramic-on-ceramic bearings from squeaking hips collected at revision surgery. The reason for revision was given as squeaking (6 cases) or squeaking and pain (4 cases). Six of the 10 patients were male, average patient age was 48. Bearings were retrieved after an average of 23 months in service (11 to 61 months). There were 4 different designs of acetabular component from 2 different manufacturers. Nine have an elevated metal rim which is proud of the ceramic and one does not. Two bearings were 36mm in diameter, 6 were 32mm and 2 were 28mm.

All 10 bearings showed evidence of edge loading wear. Mean dimensions of the wear patch were 37mm by 12mm on the acetabular component and 32mm by 13mm on the femoral heads. Wear dimension was not related to bearing diameter. Seven of the 10 implants also had evidence of impingement of the femoral neck against the elevated metallic rim or the ceramic insert or both. There was no chipping or fracture of any of the ceramic components.

Squeaking is a recently recognized complication of hard on hard bearing surface. This retrieval study is the first of its kind, to our knowledge attempting to unravel the mechanism of this undesirable complication. Although impingement seems to be present in majority of cases, the latter does not seem to be necessary. Edge loading wear was the common factor in all cases and this may prove to be a critical mechanism.

Ceramic-ceramic articulations have been in used in total hip arthroplasty (THA) since 1970. Although the problems of wear were well recognised in the early days of hip replacement, early ceramic-ceramic implants were plagued by poor design, fixation problems and component fractures. Early designs were often uncemented with no biological coating to augment fixation. Loosening of one side of the joint or the other was common-place.

Improvements in ceramic manufacturing were made and included improved purity, hot isostatic pressing and proof testing. The grain size, an indicator of toughness had dropped from 4.5 um in the 1970’s to 1.8 um in the 1990’s. Ceramic ball heads were approved in both alumina and zirconia in the late 1980’s for use on polyethylene. The hardness and toughness of ceramic pieces had now reached a new level of reliability, worthy of routine use in total hip replacements. Taper technology was also enhanced, resulting in proper load transfer to the ceramic parts. Fracture rates are estimated at 4/100 000. Stem fractures occur at a rate of 35 times higher.

Wear studies label ceramic-ceramic bearings among the lowest in debris generation, up to 200 times less than metal on conventional polyethylene. Modern alumina-alumina ceramic THAs were developed and clinical trials began under the auspices of several FDA Investigational Device Exemptions (IDE). Two have been completed and await full approval from the FDA. With a much better understanding of the aspects of design coupled with successful fixation, both cemented and uncemented, ceramic components can be coupled with these implants with the potential for optimal survivorship. America, brace yourself for the next generation of THA that is truly new and improved.

Impaction grafting has been used for both femoral and acetabular defects quite successfully for over 15 years. Sloof, Ling and others have demonstrated consistent remodelling of the morselised allograft in both locations as well as long-term survivorship in a high percentage of difficult revisions. The application of this concept to the knee is somewhat novel, although there have been a few scattered reports, but bone loss in revision knee surgery can also be profound. Like its counterpart in the hip, it relies heavily on meticulous technique for success. Key aspects of the technique: the use of crushed cancellous fresh frozen allograft; tight packing of the graft; containment of the graft with mesh when necessary; and secondary packing with proper instruments to ensure stability of and load bearing on the graft. The need for polished tapered stems remains in question, as RSA techniques in the hip have indicated that motion is less commonly linked with stability. Subsidence, mechanically speaking, will not be tolerated as well at the knee as in the hip and will, in most cases, lead to loosening or gap mismatching with accompanying instability.

Patients with greater than 50% loss of cancellous bone stock volume, tibial height at or below the fibular head, and/or distal femoral loss to or beyond the epicondyle(s) are ideal candidates. Augments usually have difficulty restoring the joint line in these massive loss cases and usually add nothing that can potentially serve as a foundation for new implants should yet another revision be necessary in a patient’s lifetime. Impaction grafting at the knee has the potential to augment the bone stock in such cases substantially.