Paul R.T. Kuzyk

Cross-linked versus conventional polyethylene for total hip replacement: A META-ANALYSIS OF RANDOMISED CONTROLLED TRIALS

We conducted a systematic review and meta-analysis of randomised controlled trials comparing cross-linked with conventional polyethylene liners for total hip replacement in order to determine whether these liners reduce rates of wear, radiological evidence of osteolysis and the need for revision. The MEDLINE, EMBASE and COCHRANE databases were searched from their inception to May 2010 for all trials involving the use of cross-linked polyethylene in total hip replacement. Eligibility for inclusion in the review included the random allocation of treatments, the use of cross-linked and conventional polyethylene, and radiological wear as an outcome measure. The pooled mean differences were calculated for bedding-in, linear wear rate, three-dimensional linear wear rate, volumetric wear rate and total linear wear. Pooled risk ratios were calculated for radiological osteolysis and revision hip replacement. A search of the literature identified 194 potential studies, of which 12 met the inclusion criteria. All reported a significant reduction in radiological wear for cross-linked polyethylene. The pooled mean differences for linear rate of wear, three-dimensional linear rate of wear, volumetric wear rate and total linear wear were all significantly reduced for cross-linked polyethylene. The risk ratio for radiological osteolysis was 0.40 (95% confidence interval 0.27 to 0.58; I(2) = 0%), favouring cross-linked polyethylene. The follow-up was not long enough to show a difference in the need for revision surgery.

The Biomechanics of Locked Plating for Repairing Proximal Humerus Fractures With or Without Medial Cortical Support

BACKGROUND Comminuted proximal humerus fracture fixation is controversial. Locked plate complications have been addressed by anatomic reduction or medial cortical support. The relative mechanical contributions of varus malalignment and lack of medial cortical support are presently assessed. METHODS Forty synthetic humeri divided into three subgroups were osteotomized and fixed at 0 degrees, 10 degrees, and 20 degrees of varus malreduction with a locking proximal humerus plate (AxSOS, Global model; Stryker, Mahwah, NJ) to simulate mechanical medial support with cortical contact retained. Axial, torsional, and shear stiffness were measured. Half of the specimens in each of the three subgroups underwent a second osteotomy to create a segmental defect simulating loss of medial support with cortex removed. Axial, torsional, and shear stiffness tests were repeated, followed by shear load to failure in 20 degrees of abduction. RESULTS For isolated malreduction with cortical contact, the construct at 0 degrees showed statistically equivalent or higher axial, torsional, and shear stiffness than other subgroups examined. Subsequent removal of cortical support in half the specimens showed a drastic effect on axial, torsional, and shear stiffness at all varus angulations. Constructs with cortical contact at 0 degrees and 10 degrees yielded mean shear failure forces of 12965.4 N and 9341.1 N, respectively, being statistically higher (p < 0.05) compared with most other subgroups tested. Specimens failed primarily by plate bending as the humeral head was pushed down medially and distally. CONCLUSIONS Anatomic reduction with the medial cortical contact was the stiffest construct after a simulated two-part fracture. This study affirms the concept of medial cortical support by fixing proximal humeral fractures in varus, if absolutely necessary. This may be preferable to fixing the fracture in anatomic alignment when there is a medial fracture gap.

Femoral head lag screw position for cephalomedullary nails: a biomechanical analysis.

Objectives: The purpose of this study was to determine if lag screw position affects the biomechanical properties of a cephalomedullary nail used to fix an unstable peritrochanteric fracture. Methods: Unstable peritrochanteric fractures were created in 30 synthetic femurs and repaired with Long Gamma 3 Nails using one of 5 lag screw positions: superior, inferior, anterior, posterior, or central. Radiographic measurements including tip-apex distance and a calcar referenced tip-apex distance were calculated from anteroposterior and lateral radiographs. Specimens were tested for axial, lateral bending, and torsional stiffness and then loaded to failure in the axial position. Analysis of variance and linear regression were used for statistical analysis. Results: The inferior lag screw position had significantly greater mean axial stiffness than superior (P < 0.01), anterior (P = 0.02), and posterior (P = 0.04) positions. Analysis revealed significantly less mean torsional stiffness for the superior lag screw position compared with other lag screw positions (P < 0.01 all 4 pairings). No statistical differences were noted for lateral bending stiffness. Superior and central lag screw positions had significantly greater mean load-to-failure than anterior (P < 0.01 and P = 0.02) and posterior (P < 0.01 and P = 0.05) positions. There were significant negative linear correlations between stiffness with distance from the calcar on anteroposterior radiographs and load-to-failure with distance from the center of femoral neck on the lateral radiographs. Conclusions: The inferior lag screw position produced the highest axial and torsional stiffness. Anterior and posterior lag screw positions produced the lowest stiffnesses and load-to-failure. Inferior placement of the lag screw on the anteroposterior radiograph and central placement on the lateral radiographs is recommended.

Intramedullary Versus Extramedullary Fixation for Subtrochanteric Femur Fractures

Objectives: Both intramedullary and extramedullary internal fixation has been advocated for the treatment of subtrochanteric femur fractures. Is there clinical evidence to recommend one method of internal fixation over the other? Data Sources: A search of MEDLINE (1950 to June 2007), CINAHL (1982 to June 2007), and EMBASE (1980 to June 2007) was performed. Results were limited to English language studies. References from eligible studies were reviewed to identify additional studies. Study Selection: Studies were selected for review based on the following criteria: comparison and observational studies examining the use of intramedullary and/or extramedullary implants for the fixation of subtrochanteric femur fractures, inclusion of intertrochanteric hip fractures with subtrochanteric extension, exclusion of pure intertrochanteric and intracapsular hip fractures, and exclusion of pathologic fractures. Data Extraction: The following outcomes were extracted from eligible studies: operative time, operative blood loss, intraoperative complications, postoperative medical complications, number of patients transfused, wound complications, failure of fixation, rate of nonunion, length of hospital stay, and functional recovery. Data Synthesis: Three level I and 9 level IV studies were identified and used in the systematic review of outcomes for intramedullary and extramedullary fixation for subtrochanteric fractures. Three level I studies were used to calculate a pooled relative risk for failure of fixation with a 95% confidence interval. An analysis of heterogeneity between pooled studies was conducted. Conclusions: There is grade B evidence that operative time is reduced and that fixation failure is reduced with the use of intramedullary implants for subtrochanteric fractures. Future studies should perform subgroup analysis according to the type of population sampled (ie, young versus elderly) and subtrochanteric fracture type.

External fixation versus open reduction with plate fixation for distal radius fractures: A meta-analysis of randomised controlled trials

BACKGROUND Both external fixation and open reduction with internal fixation (ORIF) using plates have been recommended for treatment of distal radius fractures. We conducted a systematic review and meta-analysis of randomised controlled trials comparing external fixation to ORIF. METHODS MEDLINE, EMBASE, and COCHRANE databases were searched from inception to January 2011 for all trials involving use of external fixation and ORIF for distal radius fractures. Eligibility for inclusion in the review was: use of random allocation of treatments; treatment arm receiving external fixation; and treatment arm receiving ORIF with plate fixation. Eligible studies were obtained and read in full by two co-authors who then independently applied the Checklist to Evaluate a Report of a Nonpharmacological Trial. Pooled mean differences were calculated for the following continuous outcomes: wrist range of motion; radiographic parameters; grip strength; and Disabilities of the Arm, Shoulder, and Hand (DASH) score. Pooled risk ratios were calculated for rates of complications and reoperation. RESULTS The literature search strategy identified 52 potential publications of which nine publications (10 studies) met inclusion criteria. Pooled mean difference for DASH scores was significantly less for the ORIF with plate fixation group (-5.92, 95% C.I. of -9.89 to -1.96, p < 0.01, I(2) = 39%). Pooled mean difference for ulnar variance was significantly less in the ORIF with plate fixation group (-0.70, 95% C.I. of -1.20 to -0.19, p < 0.01, I(2) = 0%), indicating better restoration of radial length for this group. Pooled risk ratio for infection was 0.37 (95% C.I. of 0.19-0.73, p < 0.01, I(2) = 0%), favouring ORIF with plate fixation. There were no significant differences in all other clinical outcomes. CONCLUSIONS ORIF with plate fixation provides lower DASH scores, better restoration of radial length and reduced infection rates as compared to external fixation for treatment of distal radius fractures.

Two-stage Revision Arthroplasty for Management of Chronic Periprosthetic Hip and Knee Infection: Techniques, Controversies, and Outcomes

In North America, two-stage revision arthroplasty is the treatment of choice for chronic periprosthetic infection of the hip and knee. Controversy exists regarding the diagnosis of persistent infection, cement spacer design, and duration of antibiotic therapy. Erythrocyte sedimentation rate and C-reactive protein tests have no clear cutoff values for detecting infection before reimplantation of hardware, and aspiration for microbial culture can yield false-negative results. Mobile spacers are as effective as static spacers for eradicating infection, but mobile spacers provide better interim function and may help to make the second stage of surgery technically easier. Some articulating spacer designs have fewer reports of spacer dislocation and fracture than do others. Although prolonged antibiotic therapy has been the standard of care for two-stage procedures, some have suggested that a short course of antibiotics is just as effective. When infection persists despite antibiotic therapy, the second stage of revision arthroplasty should be delayed until the first stage of the procedure is repeated.

The basic science of peri-implant bone healing

Given the popularity of cementless orthopedic implants, it is imperative for orthopedic surgeons to have a basic understanding of the process of peri-implant bone healing. Contact and distance osteogenesis have been used to explain peri-implant bone healing. In contact osteogenesis, de novo bone forms on the implant surface, while in distance osteogenesis, the bone grows from the old bone surface toward the implant surface in an appositional manner. Contact osteogenesis may lead to bone bonding if the surface of the implant displays the appropriate surface topography. The early stage of peri-implant bone healing is very important and involves the body’s initial response to a foreign material: protein adsorption, platelet activation, coagulation, and inflammation. This results in the formation of a stable fibrin clot that is a depot for growth factors and allows for osteoconduction. Osteoconduction is the migration and differentiation of osteogenic cells, such as pericytes, into osteoblasts. Osteoconduction allows for contact osteogenesis to occur at the implant surface. The late stage of healing involves the remodeling of this woven bone. In many respects, this process is similar to the bone healing occurring at a fracture site.

The science of electrical stimulation therapy for fracture healing

This article is a brief review of the basic science research conducted in the field of electrical stimulation for fracture healing. Direct electrical current, capacitive coupling, and inductive coupling have been studied as potential techniques to enhance fracture healing through the proliferation and differentiation of osteogenic cells. These techniques are particularly appealing as they offer a potential minimally invasive solution to the difficult clinical problem of delayed fracture healing and nonunion. Basic science studies have shown conclusively that electrical stimulation techniques lead to bone cell proliferation and have attempted to elucidate the intracellular processes by which this bone cell proliferation occurs. Further basic science and clinical research is required to enhance the effectiveness of this therapy for the treatment of fracture nonunions.

Predictors of failure for cephalomedullary nailing of proximal femoral fractures

The purpose of this study was to identify factors that predict implant cut-out after cephalomedullary nailing of intertrochanteric and subtrochanteric hip fractures, and to test the significance of calcar referenced tip-apex distance (CalTAD) as a predictor for cut-out. We retrospectively reviewed 170 consecutive fractures that had undergone cephalomedullary nailing. Of these, 77 met the inclusion criteria of a non-pathological fracture with a minimum of 80 days radiological follow-up (mean 408 days; 81 days to 4.9 years). The overall cut-out rate was 13% (10/77). The significant parameters in the univariate analysis were tip-apex distance (TAD) (p < 0.001), CalTAD (p = 0.001), cervical angle difference (p = 0.004), and lag screw placement in the anteroposterior (AP) view (Parkers ratio index) (p = 0.003). Non-significant parameters were age (p = 0.325), gender (p = 1.000), fracture side (p = 0.507), fracture type (AO classification) (p = 0.381), Singh Osteoporosis Index (p = 0.575), lag screw placement in the lateral view (p = 0.123), and reduction quality (modified Baumgaertners method) (p = 0.575). In the multivariate analysis, CalTAD was the only significant measurement (p = 0.001). CalTAD had almost perfect inter-observer reliability (interclass correlation coefficient (ICC) 0.901). Our data provide the first reported clinical evidence that CalTAD is a predictor of cut-out. The finding of CalTAD as the only significant parameter in the multivariate analysis, along with the univariate significance of Parkers ratio index in the AP view, suggest that inferior placement of the lag screw is preferable to reduce the rate of cut-out.

Cartilage restoration of the hip using fresh osteochondral allograft: resurfacing the potholes.

Cartilage defects of the hip cause significant pain and may lead to arthritic changes that necessitate hip replacement. We propose the use of fresh osteochondral allografts as an option for the treatment of such defects in young patients. Here we present the results of fresh osteochondral allografts for cartilage defects in 17 patients in a prospective study. The underlying diagnoses for the cartilage defects were osteochondritis dissecans in eight and avascular necrosis in six. Two had Legg-Calve-Perthes and one a femoral head fracture. Pre-operatively, an MRI was used to determine the size of the cartilage defect and the femoral head diameter. All patients underwent surgical hip dislocation with a trochanteric slide osteotomy for placement of the allograft. The mean age at surgery was 25.9 years (17 to 44) and mean follow-up was 41.6 months (3 to 74). The mean Harris hip score was significantly better after surgery (p<0.01) and 13 patients had fair to good outcomes. One patient required a repeat allograft, one patient underwent hip replacement and two patients are awaiting hip replacement. Fresh osteochondral allograft is a reasonable treatment option for hip cartilage defects in young patients.