In the 1960's Sir John Charnley introduced to clinical practice his low friction arthroplasty with a highly polished cemented femoral stem. The satisfactory long term results of this and other cemented stems support the use of polymethylmethacrylate (PMMA) for fixation. The constituents of PMMA remain virtually unchanged since the 1960s. However, in the last three decades, advances in the understanding of cement fixation, mixing techniques, application, pressurization, stem materials and design provided further improvements to the clinical results.

The beneficial changes in cementing technique include femoral preparation to diminish interface bleeding, pulsatile lavage, reduced cement porosity by vacuum mixing, the use of a cement restrictor, pre-heating of the stem and polymer, retrograde canal filling and pressurization with a cement gun, stem centralization and stem geometries that increase the intramedullary pressure and penetration of PMMA into the cancellous structure of bone. Some other changes in cementing technique proved to be detrimental and were abandoned, such as the use of Boneloc cement that polymerised at a low temperature, and roughening and pre-coating of the stem surface.

In the last two decades there has been a tendency towards an increased use of cementless femoral fixation for primary hip arthroplasty. The shift in the type of fixation followed the consistent, durable fixation obtained with uncemented acetabular cups, ease of implantation and the poor results of cemented femoral fixation of rough and pre-coated stems.

Unlike cementless femoral fixation, modern cemented femoral fixation has numerous advantages: it is versatile, durable and can be used regardless of the diagnosis, proximal femoral geometry, natural neck version, and bone quality. It can be used in combination with antibiotics in patients with a history or predisposition for infection. Intra-operative femoral fractures are rare. However, the risk may be increased in collarless polished tapered stems. Post-operative thigh pain is extremely rare. Survivorship has not been surpassed by uncemented femoral fixation and it continues to be my preferred form of fixation. However, heavy, young, male patients may exhibit a slightly higher aseptic loosening rate.

Adequate soft tissue balance at the time of total knee arthroplasty (TKA) prevents early failure. In cases of varus deformity, once the medial osteophytes have been resected, a progressive release of the medial soft tissue sleeve (MSS) from the proximal medial tibia is needed to achieve balance.

The “classic” medial soft tissue release technique, popularised by John Insall et al., consists of a sharp subperiosteal dissection from the proximal medial tibia that includes superficial and deep medial collateral ligament (MCL), semimembranosus tendon, posteromedial capsule, along with the pes anserinus tendons, if needed. However, this technique allows for little control over releases that selectively affect the flexion and extension gaps. When severe deformity is present, an extensive MSS release can cause iatrogenic medial instability and the need to use a constrained implant.

It has been suggested that the MSS can be elongated by performing selective releases. This algorithmic approach includes the resection of the posterior osteophytes as the initial balancing gesture. If additional MSS release is necessary in extension, a subperiosteal release of the posterior aspect of the MSS is performed with electrocautery, detaching the posterior aspect of the deep MCL, posteromedial capsule and semimembranosus tendon for the proximal and medial tibia. Dissection is rarely extended more than 1.5 cm distal to the joint line. If additional release is necessary in extension, the medial compartment is tensioned with a laminar spreader and multiple needle punctures (generally less than 8) are performed in the taut portion of the MSS using an 18G or 16G needle. If additional release is necessary to balance the flexion gap, multiple needle punctures in the anterior aspect of the MSS are performed.

This stepwise approach to releasing the MSS in a patient with a varus deformity allows the surgeon to target areas that selectively affect the flexion and extension gaps. Its use has resulted in diminished use of constrained TKA constructs and subsequent cost savings. We have not seen an increase in post-operative instability developing within the first post-operative year.

We recommend caution when implementing this technique. Unlike the traditional release method, pie-crusting is likely technique-dependent and failure can occur within the MCL itself. Due to the critical importance of the MCL in knee stability, further research and continuous follow up of patients undergoing TKA with this technique are warranted. Intra-operative sensing technology may be useful to quantitate the effect of pie-crusting on the compartmental loads and overall knee balance.

Despite the successful, durable results, concern remains for using TKA in patients with isolated patello-femoral OA, as it requires an extensive surgical exposure and bone resection, a long recovery time, and a potentially more complex revision than that required for a patient with a failed patello-femoral arthroplasty (PFA).

PFA was introduced in the late 1970s. While PFA was successful in providing pain relief, the procedure did not gain widespread use because of initial design limitations that predisposed to PF maltracking, catching, and subluxation. The mechanical complications associated with first-generation PFA offset the potential advantages of maintaining the knee's native soft tissues and spurred efforts to improve implant design, and to refine surgical techniques and patient selection.

Over the past two decades, second generation PFAs incorporated changes in implant design and instrumentation and have shown promising results when used in the properly selected patient population. In addition, with improved instrumentation and robotics, adequate implant alignment and rotation can be achieved in the majority of patients, including those with severe patellofemoral dysplasia.

Our meta-analysis of TKA and PFA for the treatment of isolated patello-femoral OA showed that the rate of complications of patients undergoing PFA was 30% after a median follow up of 5.3 years, which is significantly higher than the 7% rate of complications in patients who underwent TKA. The most frequent type of complication associated with PFA was mechanical (including loosening and instability), which is consistent with the malalignment and maltracking-related failures previously reported. The incidence of re-operation after PFA (21%) was significantly higher than that seen after TKA (2%). The most frequent indication for re-operation after PFA was mechanical failure (7%), followed by progression of OA (6%), and persistent pain or stiffness (5%). The most common re-operations after PFA were conversion to TKA, revision of PFA components, lateral releases, open or arthroscopic debridement, manipulations under anesthesia, and bony and/or soft tissue extensor mechanism re-alignment procedures. In our study, 11% of patients treated with PFA underwent a revision arthroplasty, with 4% undergoing revision PFA and 7% undergoing conversion to TKA.

Our comparison of patients who were treated with second-generation PFA designs versus TKA showed no difference in the rate of complications, re-operation, or revision arthroplasty. Additionally, length of follow-up did not significantly influence any of these outcomes when comparing second-generation PFA and TKA.

These observations provide support for the use of current PFA designs. The mechanical complications and subsequent re-operations that affected first-generation PFA designs appear to be of less concern with proper patient selection, meticulous surgical technique, current implant designs and peri-operative care. While it is difficult to predict the survivorship of current PFA designs, it is our expectation that patient selection will continue to be a critical component in determining long-term results. The potential benefit of providing pain relief while preserving the tibiofemoral articulations makes PFA a promising treatment option.

Uncontained acetabular defects with loss of superior iliac and posterior column support (Paprosky 3) represent a reconstructive challenge as the deficient bone will preclude the use of a conventional hemispherical cup. Such defects can be addressed with large metallic constructs like cages with and without allograft, custom tri-flange cups, and more recently with trabecular metal augments. An underutilised alternative is impaction bone grafting, after creating a contained cavitary defect with a reinforcement mesh. This reconstructive option delivers a large volume of bone while using a small-size socket fixed with acrylic cement.

Between 2005 and 2014, 21 patients with a Paprosky 3B acetabular defect were treated with cancellous, fresh frozen impaction grafting supported by a peripheral reinforcement mesh secured to the pelvis with screws. A cemented all-polyethylene cup was used. Pre-operative diagnosis was aseptic loosening (15 cemented and 6 uncemented). The femoral component was revised in 10 patients. Post-operative course consisted of 3 months of protected weight bearing. Patients were followed clinically and radiographically.

One patient had an incomplete post-operative sciatic palsy. After a mean follow up of 47 months (13 to 128) none of the patients required re-revision of the acetabular component. One asymptomatic patient presented with aseptic loosening 9 years post-operatively. Hardware failure was not observed. All patients had radiographic signs of graft incorporation and bone remodeling. There were no dislocations.

The early and mid-term results of revisions of large acetabular defects with this technique are encouraging. Reconstitution of hip center of rotation and bone stock with the use of a small-size implant makes this technique an attractive option for large defects. Longer follow-up is needed to assess survivability.