Amir Sternheim

Combined trabecular metal acetabular shell and augment for acetabular revision with substantial bone loss A mid-term review

Trabecular metal (TM) augments are a relatively new option for reconstructing segmental bone loss during acetabular revision. We studied 34 failed hip replacements in 34 patients that were revised between October 2003 and March 2010 using a TM acetabular shell and one or two augments. The mean age of the patients at the time of surgery was 69.3 years (46 to 86) and the mean follow-up was 64.5 months (27 to 107). In all, 18 patients had a minor column defect, 14 had a major column defect, and two were associated with pelvic discontinuity. The hip centre of rotation was restored in 27 patients (79.4%). The Oxford hip score increased from a mean of 15.4 points (6 to 25) before revision to a mean of 37.7 (29 to 47) at the final follow-up. There were three aseptic loosenings of the construct, two of them in the patients with pelvic discontinuity. One septic loosening also occurred in a patient who had previously had an infected hip replacement. The augments remained stable in two of the failed hips. Whenever there was a loose acetabular component in contact with a stable augment, progressive metal debris shedding was evident on the serial radiographs. Complications included another deep infection treated without revision surgery. Good clinical and radiological results can be expected for bone-deficient acetabula treated by a TM cup and augment, but for pelvic discontinuities this might not be a reliable option.

The effect of the setting of a positive surgical margin in soft tissue sarcoma

The objectives of this study were to evaluate the risk of local recurrence and survival after soft tissue sarcoma (STS) resection with positive margins and to evaluate the safety of sparing adjacent critical structures.

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.

Treatment of large bone defects with trabecular metal cones in revision total knee arthroplasty: short term clinical and radiographic outcomes.

The early term results of 29 cases of revision total knee arthroplasty using highly porous trabecular metal cone implants for femoral and tibial major bone deficit reconstruction (Anderson Orthopedic Research Institute classification type 2B and 3) have been prospectively analyzed. Indications for revision surgery included: aseptic loosening/wear, staged reimplantation after infection, as well as periprosthetic fracture. At an average follow-up of 33 months (range, 13-73 months) the mean Knee Society Score and functional score statistically improved. Radiological follow-up revealed no evidence of loosening or migration of the constructs. No evidence of complications was noted in correlation with the use of trabecular metal cones. This study supports evidence that trabecular metal cones are an efficient and effective option for dealing with significant bone deficits and obtaining stable biological fixation in revision total knee arthroplasty.

Distal Femoral Varus Osteotomy: Unloading the Lateral Compartment: Long-term Follow-up of 45 Medial Closing Wedge Osteotomies

Distal femoral medial closing wedge osteotomy is useful for mechanical axis realignment to unload the lateral compartment of the valgus knee. The primary indication for unloading the lateral compartment is lateral unicompartmental osteoarthritis. Alternative treatment options include lateral unicompartment or total knee arthroplasty (TKA). Prerequisites for the osteotomy include a 90° arc of motion, age younger than 60 years, and an active patient capable of an extensive period of rehabilitation. Surgery is carried out through a midline skin incision and uses a subvastus approach. The medial femoral closing wedge osteotomy is fixed with a 90° dynamic compression blade plate. A critical technical point is the need to insert the blade plate parallel to the joint line. The right angle plate corrects the tibialfemoral angle to 0°. A benefit of the closing wedge over an opening wedge osteotomy is reduced risk of nonunion. Survivorship and functional outcome of 41 patients with 45 distal femoral varus osteotomies at a mean follow-up of 13.3 years were retrospectively analyzed. Survivorship at 10, 15, and 20 years was 90%, 79%, and 21.5% respectively. Mean Modified Knee Society Score was 36.1 preoperatively, 74.4 at 1-year postoperatively, and 60.5 at last follow-up. Distal femoral varus osteotomy is effective at unloading the lateral compartment in unicompartmental arthritis in the valgus knee. It may be indicated in the young, high activity demand, and overweight patient. By 20 years after the osteotomy most patients require conversion to TKA.

Effect of patellar thickness on knee flexion in total knee arthroplasty: a biomechanical and experimental study.

A biomechanical computer-based model was developed to simulate the influence of patellar thickness on passive knee flexion after arthroplasty. Using the computer model of a single-radius, PCL-sacrificing knee prosthesis, a range of patella-implant composite thicknesses was simulated. The biomechanical model was then replicated using two cadaveric knees. A patellar-thickness range of 15 mm was applied to each of the knees. Knee flexion was found to decrease exponentially with increased patellar thickness in both the biomechanical and experimental studies. Importantly, this flexion loss followed an exponential pattern with higher patellar thicknesses in both studies. In order to avoid adverse biomechanical and functional consequences, it is recommended to restore patellar thickness to that of the native knee during total knee arthroplasty.

Wound Healing Problems in Total Knee Arthroplasty

It is important to avoid underestimating the significance of wound complications following total knee arthroplasty (TKA). Expedient and aggressive care is recommended. Understanding the blood supply to the skin around the knee and measures to prevent wound complications are fundamental to preventing wound problems. A detailed patient history and physical examination will identify high-risk patients and any modifiable risk factors. Operative techniques such as raising full-thickness skin flaps and judicious placement of skin incisions in the presence of pre-existing scars can greatly reduce the incidence of wound problems. The first step in treating wound problems is recognizing when a problem is present and knowing when a minor problem can turn into a major one. Superficial infections or stitch abscesses can be treated with conservative treatment. However, the surgeon should have a low threshold to revert to surgical management if drainage persists. Skin necrosis or non-viable skin must be excised in the operating room, and the presence of a deep infection must be diagnosed by joint aspiration. The appropriate course of action in dealing with deep infection is dependent on the duration elapsed since the index procedure. The ability to perform a medial gastrocnemius muscle flap and skin graft is an invaluable skill in complex cases where primary wound closure cannot be achieved. Meticulous attention to detail during surgery and aggressive surgical treatment of wound complications can be the difference in saving the knee.

Can Experienced Observers Differentiate between Lipoma and Well-Differentiated Liposarcoma Using Only MRI?

Well-differentiated liposarcoma represents a radiographic diagnostic dilemma. To determine the accuracy, interrater reliability, and relationship of stranding, nodularity, and size in the MRI differentiation of lipoma and well-differentiated liposarcoma, MRI scans of 60 patients with large (>5 cm), deep, pathologically proven lipomas or well-differentiated liposarcomas were examined by 10 observers with subspecialty training blinded to diagnosis. Observers indicated whether the amount of stranding, nodularity, and size of each tumor suggested a benign or malignant diagnosis and rendered a diagnosis of lipoma or well-differentiated liposarcoma. The accuracy, reliability, and relationship of stranding, nodularity, and size to diagnosis were calculated for all samples. 69% of reader MRI diagnoses agreed with final pathology diagnosis (95% CI 65–73%). Readers tended to err choosing a diagnosis of liposarcoma, correctly identifying lipomas in 63% of cases (95% CI 58–69%) and liposarcomas in 75% of cases (95% CI 69–80%). Assessment of the relationship of stranding, nodularity, and size to correct diagnosis showed that the presence of each was associated with a decreased likelihood of a lipoma pathological diagnosis (P < 0.01). While the radiographic diagnosis of lipoma or well-differentiated liposarcoma cannot be made with 100% certainty, experienced observers have a 69% chance of rendering a correct diagnosis.

Cementless fixation in total knee arthroplasty

In this study we present our experience with four generations of uncemented total knee arthroplasty (TKA) from Smith & Nephew: Tricon M, Tricon LS, Tricon II and Profix, focusing on the failure rates correlating with each design change. Beginning in 1984, 380 Tricon M, 435 Tricon LS, 305 Tricon 2 and 588 Profix were implanted by the senior author. The rate of revision for loosening was 1.1% for the Tricon M, 1.1% for the Tricon LS, 0.5% for the Tricon 2 with a HA coated tibial component, and 1.3% for the Profix TKA. No loosening of the femoral component was seen with the Tricon M, Tricon LS or Tricon 2, with no loosening seen of the tibial component with the Profix TKA. Regarding revision for wear, the incidence was 13.1% for the Tricon M, 6.6% for the Tricon LS, 2.3% for the Tricon 2, and 0% for the Profix. These results demonstrate that improvements in the design of uncemented components, including increased polyethylene thickness, improved polyethylene quality, and the introduction of hydroxyapatite coating, has improved the outcomes of uncemented TKA over time.