Timo M. Ecker

Squeaking in Total Hip Replacement: No Cause for Concern

Traditional total hip arthroplasty (THA) using metalon-polyethylene bearings has been established as a reliable procedure, but polyethylene wear and wear debris–associated osteolysis are among the most frequent reasons for revision.1 Hard-bearing-surface THAs with improved tribological properties have been introduced to decrease wear and wear debris–induced osteolysis. Among the hardbearing alternatives, alumina ceramic-on-ceramic bearings have consistently shown low wear and biological reactivity to wear particles. Clinically, ceramic-on-ceramic hip arthroplasties with modern metal-backed alumina cups have demonstrated excellent clinical outcomes with low revision rates,2,3 with complications such as acetabular liner, femoral head fractures, or chipping occurring rarely.4 Curiously, after more than 30 years of clinical experience with alumina ceramic-on-ceramic bearings worldwide and with 2 closely studied longterm FDA studies in the United States,2,3 a new phenomenon of frequent, clinically reproducible squeaking was reported, primarily beginning in 2006. Further, these reports were authored by surgeons who had little, if any, experience with alumina ceramic-on-ceramic bearings during the IDE study period from 1997 to 2003. Inevitably, many theories were proposed to explain this phenomen, including mismatched ceramic bearings diameters,5 edge loading due to acetabular component malpositioning,6 disruption of fl uid fi lm lubrication with stripe wear,7 microseparation and subluxation of the femoral head,7 the use of short necks,8 and wear debris from metal-on-metal impingement in implants.9 Ultimately though, one fundamental question has remained: Why, after years of successfully using ceramic-on-ceramic THA, did this phenomenon of squeaking suddenly become frequently noted by a subset of surgeons, particularly practicing in the Unitied States? The goal of this study was to use our clinical experience with two FDA IDE studies2,3 during a period of more than 10 years to improve our understanding of this squeaking phenomenon.

Factors Affecting Bony Impingement in Hip Arthroplasty

Computer modeling of 10 patients computed tomographic scans was used to study the variables affecting hip arthroplasty range of motion before bony impingement (ROMBI) including acetabular offset and height, femoral offset, height and anteversion, and osteophyte removal. The ROMBI was compared with the ROM before component impingement and the native hip ROM. The ROMBI decreased with decreased total offset and limb shortening. Acetabular offset and height had a greater effect on ROMBI than femoral offset and height. The ROMBI lost with decreased acetabular offset was not fully recoverable with an increase in femoral offset or osteophyte removal. Bony impingement increased and component impingement decreased with decreased acetabular offset and increased head diameter.

Managing Length and Stability: The Role of the Modular Neck

Drs Steppacher, Ecker, and Murphy are from New England Baptist Hospital, Tufts University School of Medicine, Boston, Massachusetts and Dr Timmerman is from Wright Medical Technology Inc, Arlington, Tennessee. Financial Disclosure: Correspondence should be addressed to S.B. Murphy, MD, 125 Parker Hill Dr, Ste 545, Boston, MA 02146. Good results after a total hip arthroplasty (THA) depend on several critical factors including surgical exposure, implant design, and restoration of biomechanics. The goal is to achieve a stable hip joint with a well-tensioned soft tissue envelope and an impingement-free range of motion. Appropriate location of the hip joint center and correction of femoral anteversion, offset, and height are critical to any successful reconstruction. These goals are challenging since the proximal femoral anatomy in nondeformed hips shows a wide variation between individuals1,2 and these variations are likely to be even greater in arthritic hips.

Second-generation uncemented stems: excellent 5–13-year results

IntroductionThe purpose of this study was to prospectively evaluate the 5–13-year results of a cementless total hip arthroplasty with a special focus on the survivorship, occurrence of osteolysis, incidence of intraoperative femoral fractures, thigh pain, and cortical hypertrophy of the femoral stem. The femoral component used in this study was titanium fluted, slotted, symmetrical component that was prepared with intraoperative machining. The proximal third of the stem had hydroxyl-apatite coating and horizontal steps.MethodsThe clinical and radiographical results of a consecutive series of 157 total hip arthroplasties (124 patients) with this stem were investigated. Minimum follow-up was 5xa0years. The average age of the patients at the time of surgery was 47xa0years. Three patients died and ten patients were lost to follow-up, leaving 142 hips for evaluation. The clinical result was evaluated on the basis of the Merle d’Aubigné score, complications and thigh pain. A detailed radiographic analysis was performed at each follow-up visit. Kaplan–Meier survivorship analysis was performed to evaluate stem, cup, and bearing survivorship.ResultsThe mean follow-up was 8.5xa0years (range 5–13xa0years). The average Merle d’Aubigné score improved from 10.5 points preoperatively to 17.4 points postoperatively. The cumulative 10-year survival rate was 99% for the femoral component, 99% for the acetabular component, and 69% for the bearing. Thigh pain was identified in three patients (2%). There was no distal femoral osteolysis. Seventy-nine percent of all the hips had endosteal spot welds around the coated, proximal one-third of the prosthesis. 51% had radiodense lines around the distal tip of the prosthesis, and 3% had cortical hypertrophy. One undersized stem and one cup were revised for aseptic loosening, and 25 bearings were exchanged.ConclusionsUncemented, machined, fluted titanium canal-filling femoral components achieve reliable fixation in this young patient population. They have a decreased incidence of activity-related thigh pain, lower rate of intraoperative femur fractures and cortical hypertrophy with comparable bone-ingrowth in comparison to other second-generation uncemented femoral components described in literature. Bearing wear and the need for bearing exchange was the only limitation of these constructs.

Computer-Assisted Orthopedic Surgery

Surgical navigation systems have been invented to assist the surgeon during crucial parts of an intervention. Application to orthopedic surgery began with computer-assisted pedicle screw placement, acetabular cup placement, and navigation of pelvic osteotomies.