Proponents of quadriceps-sparing (QS) subvastus approach for total knee arthroplasty (TKA) suggest short-term advantages including better early functional results, less pain and shorter hospital stay. However, because of potentially reduced visibility and exposure, the QS approach may compromise component alignment – an important surgeon-controlled outcome affecting implant longevity. The purpose of this study was to determine if a QS approach resulted in compromised component alignment compared to a medial parapatellar arthrotomy (MPPA), when both were performed with contemporary minimally invasive surgery (MIS) principles including small incision (≤ 15 cm), MIS instrumentation, patellar subluxation without eversion, and in situ bone cuts. This prospective, randomized, double-blinded study enrolled 128 patients with knee osteoarthritis undergoing primary TKA using the same cemented, posterior-stabilized prosthesis. After skin incision, patients were randomized to MPPA (n = 66) or QS technique (n = 62), with all surgeries performed by two fellowship-trained arthroplasty surgeons. Using the Knee Society roentgenographic evaluation system, two reviewers blinded to the surgical approach evaluated post-operative radiographs to measure coronal and sagittal plane alignment using the standing femoral and tibial angles as well as the lateral femoral flexion and tibial angles. Inter-observer agreement was ensured by a secondary review of all x-rays where the two observers differed by more than 1 degree in their measurements of a specific radiograph. Differences in mean angles were evaluated using the general linear model and differences in proportions were evaluated using binary regression. All analyses were conducted with SAS 9.3 on the Windows Ultimate 64-bit operating system.Introduction:
Methods:
Clinical trials have generally failed to demonstrate superior clinical effectiveness of minimally invasive surgical approaches for total knee arthroplasty (TKA). The hypothesis of the current study was that avoiding incision of the quadriceps tendon would result in a significantly faster recovery of ambulatory function after total knee arthroplasty, compared to a technique that incised the quadriceps tendon. The MIKRO (Minimally Invasive Knee Replacement Outcomes) Study is a prospective, level 1 RCT that enrolled 128 patients with knee osteoarthritis who had failed non-operative treatment, and had decided to proceed with TKA. After skin incision, 64 patients each were randomized to either a subvastus (SV) or medial parapatellar arthrotomy (MPPA) approach. All surgeries were done with the same TKA implant, with anesthesia, post-operative analgesia, and physical therapy standardized for both groups. A Patient Diary methodology was used as the primary outcome measure for ambulatory function. During the first 8 weeks after TKA, a research assistant blinded to treatment assignment telephoned each patient and completed study forms that documented indoor and outdoor walking relative to use of ambulatory devices, as well as Knee Society Score (KSS) and the UCLA activity scale. The UCLA score and change in KSS from baseline at 4- and 12-week follow-up were used to begin the validation process for an Ambulatory Function Score (AFS) derived from diary indoor and outdoor scores.INTRODUCTION
METHODOLOGY
A common feature of retrieved ceramic-on-ceramic (CoC) hips is the presence of metal transfer on the femoral head. This metal transfer represents an important change in the articulating surface and can have consequences in terms of lubrication, friction, wear, and squeaking. Given the potential impact of metal transfer on the performance of CoC bearing couples, a good understanding of the factors surrounding its occurrence is warranted. This study documents the metal transfer onto a ceramic femoral head with two subluxations onto the rim of the cup which occurred during surgery. This metal transfer is compared to that on other ceramic heads retrieved for various reported reasons, including squeaking, pain and loosening. The first ten retrieved alumina heads of current ceramic technology (Ceramtec, Plochingen, Germany) submitted to our retrieval laboratory were assessed to document the phenomenon of metal transfer. Nine devices underwent in vivo service (mean duration 32 mo., range 13 to 84) and the tenth device was removed intra-operatively and serves as an instructive control case. It was impacted onto a trunnion and during final testing for stability subluxed anteriorly over the titanium lip of the cup. The metal transfer was immediately noted by the surgeon and the head was removed. All ceramic heads were examined under light microscopy (Nikon Dissecting Microscope, Tokyo, Japan) and white light optical profilometry (NewView 7300, Zygo, Middlefield, CT). The control ceramic head showed two distinct metal transfer streaks from two discrete subluxation events that were documented by the surgeon (IMT). Those streaks are aligned in a direction approximately 24o to the right (clockwise) of a line through the polar apex of the head and parallel to the axis of the femoral neck. Microscopy and profilometry indicate that they were laid down in a direction from equator-toward-pole. Seven of the retrieved ceramic heads showed streaks of metal transfer that are very similar to those on the control ceramic head in terms of: alignment (equator-toward-pole, 20 to 45o off-axis) width (tapered point growing to approximately 1.0 to 1.5 mm), depth of metal deposition (0.25 to 0.40 μm), and depositional texture. It is notable that the metal transfer streaks commonly observed on retrievals bear a close resemblance to that caused by a single intra-operative event wherein a hip abduction force pulled the head into contact with the titanium cup/liner rim. An important implication is that this demonstrates that metal transfer can occur with a single instance of rim contact, wherein the femoral head is forced against the metal cup rim. If metal transfer onto the head were to occur during final reduction of the hip, its presence may well be undetected and any deleterious in vivo impact of the metal transfer would be in effect from the day of surgery.
Antibiotic-impregnated bone cement (ABC) is infrequently used in the North America for primary total hip arthroplasty (THA) due to concerns with cost, performance, and the possible development of antibiotic resistance. The purpose of this study is to examine the cost-effectiveness of using ABC in primary THA for osteoarthritis compared to the use of cement without antibiotics. A Markov decision model was used to determine if ABC is a cost-effective strategy for primary THA in patients with osteoarthritis. The model tabulates costs and quality adjusted life years (QALYs) accumulated by each patient to evaluate the cost-effectiveness of each strategy. Rates of revision for infection and aseptic loosening were estimated from the Norwegian Arthroplasty Register, and were used to determine the probability of transitioning to a revision arthroplasty for either infection or aseptic loosening. The model was also used to evaluate the cost-effectiveness of ABC when only revisions for infection are considered. Peri-operative mortality rates, utilities, and disutilities were estimated from the arthroplasty literature. Costs were also estimated from the literature using in-hospital resource use as the method of measurement for primary THA. The additional cost of using ABC ($600) was then added to the average cost of the initial procedure ($21,654). ABC is less expensive and more effective than standard cement when all revisions are considered, making the use of ABC the dominant strategy. When only revision for infection is considered, the use of ABC has an incremental cost-effectiveness ratio (ICER) of $37.335 per QALY compared to cement without antibiotics – which compares favorably with the cost-effectiveness of accepted medical procedures. Sensitivity analyses reveal that for all revisions the additional cost of ABC would need to be greater than $1500, or the average age of patients undergoing primary THA would need to be greater than eighty-three before the use of ABC would cost more than $50,000 per QALY gained. When only revision for infection is considered, the additional cost of ABC would need to exceed $650 before the cost of ABC would exceed $50,000 per QALY gained. Use of ABC for primary THA is cost-effective over a wide range of assumptions. Notably, when all revisions are considered, ABC is less costly and more effective than use of standard cement over the life span of the patients.
